Digitized by the Internet Archive in 2015 https://archive.org/details/cyclopaediaofana2183todd THE CYCLOPAEDIA OF ANATOMY and PHYSIOLOGY. YOL. II. DIA INS 1836-1839 THE CYCLO P JE D I A OF ANATOMY and PHYSIOLOGY. EDITED EY ROBERT B. TODD, M.D. F.R.S. FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS; PHYSICIAN TO KING’S COLLEGE HOSPITAL; AND FORMERLY PROFESSOR OF PHYSIOLOGY AND OF GENERAL AND MORBID ANATOMY IN KING’S COLLEGE, LONDON, ETC. ETC. VOL. II. DIA INS 1836 — 1839 15701 LONDON LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. CONTENTS OF THE SECOND VOLUME Dr. Hart , 65 Page Diaphragm Dr. Benson 1 Digestion Dr. Bostock 6 Digestive Canal Dr. Grant 27 ^chinodermata Dr. Sharpey 30 Edentata T. Bell, Esq 46 Elasticity Dr. Brenan 55 Elbow, Region of the Dr. Hart 62 Elbow, Joint of, ) Normal Anatomy ^ Elbow, Joint of, Ab- ) ’ ’ I K. Adams, Esq. . . 67 normal Anatomy . . ’ Electricity, Animal .. Dr. Coldstream .. 81 Endosmosis Dr. Dutrochet .... 98 Entozoa R. Owen, Esq Ill Erectile Tissue Dr. Hart 144 Excretion Dr. Alison 147 Extremity Dr. Todd 151 Eye Dr. Jacob 171 Face R. Partridge, Esq. 207 Fascia ... Dr. Todd 229 Fat W.T. Brunde,Esq. 231 Femoral Artery Dr. Alcock 235 Fibrine W.T. Brande, Esq. 257 Fibro-Cartilage Dr. Todd 260 Fibrous Tissue R.D.Grainger,Esq. 263 Fibular Artery Dr. Todd 267 Fifth Pair of Nerves. . Dr. Alcock 268 Foetus Dr. Montgomery . . 316 Foot, Bones and ) T . [ Dr. Todd 338 Joints of ’ Foot, Abnormal Con- ) ’ . [A.T. S. Dodd, Esq. 347 ditions of ’ 1 Foot, Regions and ) \ A.T. S. Dodd, Esq. 350 Muscles of J ’ 1 Fore-arm, Muscles ) , r, . e < S. Solly, Esq 361 and Regions of . . ’ J J Fourth Pair of Nerves Dr. Alcock 370 Ganglion R.D. Grainger, Esq. 371 Gasteropoda T. Rymer Jones, Esq. 377 Page Gelatin W. T. Brande, Esq . 404 Generation, Organs > [ T. Rymer Jones, Esq. 406 of “ Generation Dr. Allen Thomson. . 424 Gland R.D. Grainger, Esq. 480 Glosso-Pharyngeal t . , J b > Dr. Reid 494 Nerve. 5 Glutaeal Region.... A. T. S. Dodd, Esq. 500 Groin, Region of the Dr. Todd 503 Haematosine Dr. Rees 503 Hand, Bones of the Dr. Todd 505 Hand, Abnormal ) „ , , „ r R. Adams, Esq 510 Conditions of the ’ Hand, Muscles of ) „ ,, „ ,, „ ^ F. T. ATDougall, Esq. 519 Hand, Regions oftlie F. T. M'Dougall, Esq. 523 Hearing, Organ of. . T. W. Jones , Esq. . . 529 Hearing Dr. Todd 564 Heart Dr. Reid 577 Heart, on the -v Arrangement of > H. Searle, Esq. .... 619 the Fibres of the ' Heart, Abnormal } Conditions of the ^ Heat, Animal Dr. W. F. Edwards . 648 Hermaphroditism.. Dr. Simpson 684 Hernia W. H. Porter, Esq. 738 Hibernation Dr. Marshall Hall . . 764 Hip-Joint, Normal ) ,, ,, I II. Hancock, Esq. .. 776 Anatomy ’ Hip-Joint, Abnor- ) „ , , _ ! R. Adams, Esq 780 malConditions of ' Hypersemia Dr. Todd .......... 825 Hypertrophy Dr. Todd 826 Iliac Arteries Dr. Alcock 827 Innominata Artery . H. Hancock, Esq. . . 850 Insecta G. Newport, Esq. . . 853 Insectivora T. Bell, Esq. ...... 994 Dr. Todd 630 15701 \ ' THE CYCLOPEDIA OF ANATOMY AND PHYSIOLOGY. DIAPHRAGM (in anatomy), (3i a,foa.yp.a., <$t«, inter, and , sepio, claudo ; Lat. diu- phragma ; Ital. diqframma; Fr. diaphragme ; Ger. Zwerchfell; Eng. midriff), the name given to that musculo-tendinous septum by which the cavities of the thorax and abdomen are separated from each other in the Mammalia. Nothing analogous to the diaphragm of mam- mals can be detected in the Invertebrate classes of animals ; the function of which it is a princi- pal muscular agentin the Mammalia, respiration, being effected by the skin, intestines, stigmata, tracheae, gills, &c. Most of the Vertebrata, however, exhibit something analogous to the diaphragm. Thus in Fishes the muscular sep- tum dividing the cavity of the branchial ap- pai-atus (thorax) from the abdomen bears a certain resemblance to the diaphragm. Birds have muscles which proceed obliquely upwards in the form of flat bundles of fibres from the middle of the lower ribs to the under part of the lungs, where they are lost in the pleura ^ covering these organs; and thus by their con- traction depress the lungs themselves, expand their cells, and facilitate the ingress of air into them. These muscular fibres are particu- larly developed in the parrot.* But, as has been said, it is only in Mammalia that the genuine diaphragm is to be found ; and all the animals of this class possess it. The organ, as might be expected, undergoes some modifica- tions in different families. In amphibious and cetaceous mammalia it approximates to that of birds. A very strong and fleshy diaphragm is * C. G. Carus, Comparative Anatomy. VOL. II. attached to the dorsal side of the cavity of the trunk so low down that it ascends considerably in order to be connected in a peculiar manner with the upper and anterior extremity of the abdominal muscles ; so that the lungs lie be- hind rather than above the diaphragm.* In the porpoise there is no central tendon .f The horse, elephant, rhinoceros, and other animals whose ribs approach the pelvis, have a very extensive diaphragm, which forms an elevated arch towards the thoiax.I This shape is neces- sary to accommodate the bulky contents of the abdomen, without altering the attachments of the muscle, which, as in man, are connected to the lowest ribs. Some other variations from the structure and form of the diaphragm in man might be noticed, but they are very unim- portant. We shall therefore proceed to give a detailed account of the muscle in the human subject. Diaphragm (human anatomy). — The dia- phragm in man is a muscle of great importance (post cor facile princeps, Haller), being the chief agent by which respiration is carried on, while it assists in the performance of many other im- portant processes. It is placed between the thorax and abdomen, forming a convex floor to the former, and a concave ceiling to tire latter. Although a single muscle, and situated in the median line, it is not symmetrical ; the right side of it is 'more extensive than the left. Symmetry, however, was not necessary in an * C. G. Cams, Comparative Anatomy. t Tyson. | Cuvier, Anat. Comp. vol. iv. 2 DIAPHRAGM. organ which could exert no influence on the external form ; nor was it to be expected in a muscle which is not wholly voluntary. In this article it is intended to describe, 1st, the form, structure, and organization of the diaphragm ; 2nd, its uses ; and, 3rd, its malformations and diseases. Fig. 1. A bdominal surface of the diaphragm. Fig. 2. Thoracic surface seen from behind , the vertebra' being removed. For the convenience of description the dia- phragm is usually divided into two portions — the upper, which is called the costal, or true or greater muscle ; and the lower, which is named the vertebral, or smaller, and is also well known as the crura or pillars. This division is sanc- tioned by the situation, the shape, and the uses of the two portions. The upper portion, placed tranversely, ( sep- tum transversurn,) is thin, but of great super- ficial extent, being connected by its margins to the entire circumference of the inferior outlet of the thorax. Narrow between the sternum and spine, it spreads out on each side into large wings, and its outline bears some resemblance to the figure of eight laid on the side, thus co . The centre is tendinous ; the border consists of fleshy fibres. The tendinous part (Jig. 1, T) ( centrum tendineum, s. nerveum, s. phrenicum, cordiforni tendon ) is of considerable size, and in shape resembles tbe trefoil leaf. It presents a large semicircular notch behind towards the spine, and is deeply divided on its anterior margin into three lobes, of which one points for- wards and one to each side. Of these lobes the right is usually the largest, the left the smallest; the anterior is the shortest, and sometimes the broadest; the left is the narrowest and often the longest. But these proportions will be found to vary in different individuals. The tendon is composed of fibres which pursue various courses. The greater number radiate from the vertebral notch ; these are crossed by others which run in every direction, and which seem to be continuous with the muscular fibres; and others again appear to be laid on the tendon as accessaries, rather than as con- tributing to its texture. These last are most distinctly seen in old men, and on the under surface of the right lobe. The tendinous centre forms nearly the highest part of the arch. It is less curved than the fleshy portion, and more fixed in its position. One large opening pre- sents itself here, between the right and middle lobes, through which the vena cava passes to the heart. From the anterior and lateral margins of this tendon the muscular fibres pass off in arches, to be inserted into all the base of the thorax by digitations which mix with those of the trans- versus abdominis. Beginning in front, we find two slender fasci- culi running downwards and forwards to the ensiform cartilage. These are separated from each other by a line of cellular tissue, marking the median line of the muscle; sometimes one or both of these bundles may be absent, pro- bably resulting from an arrest of formation. To the outside of these, on each side, a con- siderable triangular interval exists, where the pleura and peritoneum are separated only by cellular substance. Here some small branches of the internal mammary artery pass to the ab- domen ; and in this situation fluids might easily find their way from the cellular tissue of one cavity to that of the other. The fibres next in order, bounding these spaces externally, are much longer ; they pass outwards and down- wards to the seventh rib, and are inserted by a DIAPHRAGM. 3 broad digitation into the point of the bone and into about one half of the adjoining portion of its cartilage. The next fibres are still longer, usually the longest of all ; they run outwards, then downwards, forming the second digitation, which is attached in a similar manner to the eighth rib. The following fibres becoming shorter as they approach the spinal notch, go to the ninth and tenth ribs, and are similarly con- nected. The succeeding ones, still shorter, proceed to the eleventh and twelfth, and attach themselves to a considerable portion of their length. In the two lowest intercostal spaces the diaphragm and transversus abdominis are united by a common aponeurosis, which is very thin ; and here it is not very unusual to meet with a deficiency in the diaphragm. The thin portion of the muscle, near to the crura, has its short fleshy fibres inserted into the ligamentum arcuutum externum.* ( Fig. 1 , d.) This last appel- lation is bestowed on a thin aponeurosis which stretches from the inferior margin of the last rib to the point of the transverse process of the first lumbar vertebra. In reality it is nothing more than the anterior layer of the tendon of the transversus abdominis which lies in front of the quadratus lumborum muscle, and is connected to the lowest rib. By pulling the rib outwards the aponeurosis is projected into a fold which looks like a ligament. It is designated ex- ternum to distinguish it from another that is much stronger and more truly ligamentous, which arches over the psoas magnus muscle, is attached to the transverse process of the first lumbar vertebra (just where the former ends), and to the body of the second. The latter is known as the ligamentum nrcuatum internum f (fig. 1 ,f ;) it is also called the true, and the external the false, — names derived from their structure. The vertebral or smaller muscle of the dia- phragm is placed almost perpendicularly. The fibres pass off from the concave margin of the tendon which is turned to the spine. They run downwards and a little backwards at first, then along the lumbar vertebra, into which they are principally inserted. The shortest and most external of them go to the internal ligamentum arcuatum ; but the greater number form two large and long fasciculi, the crura, or pillars, or appendices of the diaphragm. The right crus is longer and thicker than the left, and is nearer to the middle line. It is attached by tendinous slips to the bodies of the three (often of the four) superior lumbar ver- tebra and to the intervertebral substances. The left is attached in a similar way, but never de- scends so low. Both become smaller as they pass down, the more external fibres being soonest inserted. The muscular bundles, on quitting the cordiform tendon, separate imme- diately from each other, to permit the oesopha- gus to pass into the abdomen, and unite again behind that tube. Here a crossing or inter- lacing of the fibres takes place, a considerable bundle descending from the left side of the * Arcus tendineus exterior, Senac. t Arcus tendineus interior. Id. oesophagus to the right crus, and a smaller one from the right side to the left crus. In general the latter is placed anteriorly ; and occasionally two bundles descend from each side alternating with their opposites. The fleshy fibres again separate on a level with the lower edge of the last dorsal vertebra to allow the aorta to pass, and they continue afterwards distinct. The foramina or openings which present themselves in this septum require to be noticed. Three large ones have been already mentioned ; but as the organs which they transmit are of great importance, they deserve more minute at- tention. The first is situated in the tendon of the diaphragm, toward its posterior part, a little to the right of the centre (fig. 1, c). It corre- sponds to the line of division between the middle and right lobes. Its shape is quadrangular, ( foramen quadratum,') having an anterior, a pos- terior, a right and a left edge. The right is the longest, the anterior the shortest, and these two often appear to form but one. The inferior vena cava passes through this opening and im- mediately empties itself into the right auricle of the heart. The vein is firmly connected to the foramen by means of thin aponeuroses sent off from the tendinous margins; the posterior margin sending fibres upwards, the lateral downwards, and the anterior in both directions. This is the highest opening in the diaphragm, being on a level with the lower edge of the ninth dorsal vertebra and fifth rib. As the boundaries of it are entirely tendinous they cannot act on the vein themselves, and the ac- tion of the muscular fibres only serves to keep it dilated. Some branches of the phrenic nerve accompany this vein. A little to the left of the median line, and close behind the central tendon, we find an opening of an elliptical form through which the oesophagus and pneumogastric nerves pass (fig. 1, e). Its majoraxis, two inchesin length, is di- rected obliquely downwardsand backwards. The borders are entirely muscular, at least very ge- nerally, for it sometimes happens that the ante- rior extremity is bounded by the cordiform ten- don. It results from a separation of the fibres which are descending to constitute the crura, and may be said to lie between the crura. The crossing or interlacing of the fibres which takes place just behind it must enable them to shut up this opening completely when they act strongly. This foramen is on a level with the tenth dorsal vertebra, its upper and lower an- gles corresponding to the planes of the upper and lower surfaces of that bone. About two inches below the inferior point of the oesophageal opening the aorta may be seen, coming out of the thorax, opposite the lower edge of the last dorsal vertebra (fig. 1, a.) This great vessel enters the abdomen by a canal which is formed posteriorly by bone, anteriorly by the decussating fibres, and on either side by the crura of the diaphragm. These crura, after passing along the sides of the artery, almost meet behind it by their tendinous expansions lower down. The margin of the aortic opening is bordered with tendon, and the fleshy fibres are so connected with it that their action does B 2 4 DIAPHRAGM. not ;it all diminish the size of the passage Along with the aorta and to its right side we see the vena azygos and thoracic duct passing into the thorax. Some other foramina transmit vessels and nerves, but they are very small and irregular. The sympathetic nerve usually passes with the psoas muscle under the internal ligamentum arcuatum. The right splanchnic slips out of the thorax between the fibres of the right crus, at a point internal, superior, and anterior to the sympathetic. The left splanchnic comes in the same way, or more frequently with the aorta. The lesser splanchnic passes at the outer side of the former, separated from it by a few fibres. Behind the external ligamentum arcuatum the last dorsal nerve may be seen. Filaments of the phrenic nerve pierce the muscle in several places, principally its tendinous part, and some pass through the opening for tire vena cava. And branches of the internal mammary artery creep through those cellular spaces which are left between the xiphoid cartilage and first costal attachment. The upper muscle of the diaphragm is lined for the most part of its under surface by the peritoneum, and on its upper by the pleurae and pericardium ; being thus placed between serous membranes. In some points the peri- toneum is reflected off to form ligaments for the liver, and there this last organ conies in contact with the muscle. The same thing oc- curs to a small extent in the case of the kid- neys. The upper surface too is for a little way all along its margin destitute of serous covering, and in contact with the ribs, intercostal mus- cles, quadratus lumborum, psoas, and triangu- laris sterni. Over the serous membranes on the thoracic surface we find on each side the base of the lungs, and in the centre the heart resting on the middle lobe of the tendon and on some muscular fibres to its right. The ab- dominal surface is related to the liver, stomach, spleen, and kidneys. The inferior muscle of the diaphragm has one surface turned back to the spinal column, and in contact with it and with a little of the aorta ; the other surface looks forwards, and is covered by the suprarenal capsules, the semi- lunar ganglia, and various nerves, the aorta and its principal branches, the ascending cava, the commencement of the abdominal vena porta and its tributaries, the pancreas, stomach, duo- denum, and occasionally other parts. Little or no peritoneum can touch this portion. Arteries. — A muscle of so much importance in the animal economy as the diaphragm, and so perpetually in action, requires a large supply of blood. This it receives through numerous channels and from distinct sources ; and as all its vessels inosculate freely in its substance, no failure in the supply can well occur. The phrenic and internal mammary are distributed to its middle ; the same vessels, with the in- tercostal, the lumbal, and some small aortic twigs, feed the circumference. Veins. — The veins of the diaphragm accom- pany the arteries as in other parts of the body ; each artery having one or two vena; comites. The principal veins, however, .correspond to the phrenic artery, and pour their blood into two trunks, a right and a left, which empty them- selves into the cava. They are usually seen on the under surface of the tendon, sometimes on the upper ; or there may be two above and two below. Occasionally they lie between the two surfaces, so that their entrance into the cava is not seen ; and in some cases they join the hepatic veins. Lymphatics.— The diaphragm is furnished with lymphatic vessels as other muscles, but there is nothing peculiar in them. They are not easily demonstrated, as they do not form any very distinct trunks, but join with the lymphatics of the neighbouring organs. Nerves. — The diaphragm receives a great number of nerves. The lumbar send twigs to the crura, the lower dorsal to the broad muscle, and there is a phrenic plexus sent off from the solar, which accompanies the phrenic arteries, and distributes its numerous and delicate fila- ments with extreme minuteness to the under surface of the muscle. From the plexus which the eighth pair forms on the stomach, we trace also some fine filaments. But the chief and most important nerves are the phrenic. The phrenic nerve arises from the cervical plexus ; its principal origin is from the fourth cervical nerve, to which there is usually joined a small twig from the third. It runs down along the anterior scalenus, and gets into the thorax be- tween the subclavian artery and vein. In the neck it generally receives filaments from each cervical nerve. As it enters the thorax, it com- municates with the inferior cervical ganglion, and gets a filament from the descendens noni and the pneumogastric. The nerve thus formed is conducted by the mediastinum and pericar- dium, in front of the root of the lung, to the diaphragm ; the left being a little longer than the right, and thrown somewhat further back by the position of the heart. It enters the diaphragm at the anterior edge of the tendon in six or seven branches, the largest of which pass backwards. Some go through the muscle, ramify on its under sur- face, and anastomose with the solar plexus ; and one may usually be traced tljrough the opening for the cava on to that plexus. The influence which these nerves exert on the organ will presently be adverted to. Uses. — The chief use of the diaphragm is to assist in the function of respiration, and it will be found to be the principal agent in the me- chanical part of that process. By its action the thoracic cavity is enlarged from above downwards, whilst its circumference is in- creased by the intercostal and other muscles. When the diaphragm acts, the entire muscle descends, pushing the abdominal viscera down- wards and forwards ; but its different portions descend very unequally. The tendinous centre is nearly fixed, and the crura are incapable of much change of position ; it is only in the broad lateral expansions that the motion is very apparent. The muscular fibres of these when relaxed are pressed upwards, and present arches, convex to the thorax, and rising even DIAPHRAGM. 5 above tbe tendon ; but when brought into ac- tion, each fibre approaches to a right line, which runs obliquely down from the tendon to its point of insertion. Thus, instead of a great arch we have a number of inclined planes, very short in front, very long at the sides, and of intermediate length further back, all surmount- ed by a tendinous platform. The base of the lung resting on the muscle descends with it; the liver, stomach, spleen, and all the moveable viscera of the abdomen are pressed downwards and forwards against the abdominal muscles. When the diaphragm descends, therefore, in- spiration takes place by the rush of air into the expanding thorax ; when it ascends expiration is the result, the air being forced out. In the former case the diaphragm is active ; in the latter it is completely passive, following the re- siliency of the lungs, and pressed up by the action of the abdominal muscles on the viscera beneath.'* The central tendon descends very little on account of its attachment to the peri- cardium : descent here would be useless or worse; but the lateral portions on which the broad bases of the lungs rest, freely change their place, and allow of considerable expansion of the thorax where it is most required. From viewing the insertion of the diaphragm into the lower ribs it might be thought that they would be drawn in by its action, and the capacity of the thorax thereby diminished more than increased; but the intercostals prevent this occurrence by acting at the same moment to elevate and draw out the ribs. Tiie crura, besides acting in common with the broad muscle in enlarging the thorax, serve to fix the central tendon, and prevent it from being drawn to either side by the irregular ac- tion of either half of the muscle, or forced too high up. They may also by their fibres conti- nued on each side of the oesophageal orifice, and contracting in concert with the rest of the muscle, close that opening, and thus prevent regurgitation from the stomach at the time when this viscus is pressed upon by the descent of the diaphragm. The extent to which the diaphragm descends is not great. The central tendon will not admit of much displacement in the normal state of the parts, and the shape and motions of the liver show that even the great alae do not un- dergo much alteration. Haller indeed says that he saw the diaphragm descend so much in violent inspiration as to present a convexity to- wards the abdomen.f But this is quite incre- dible. The utmost muscular effort, if there were no fixed point in its centre, could only obliterate the arch ; but even this we think im- possible on account of its attachments. We find on some occasions one side of the dia- phragm act independently of the other. The importance of the diaphragm in respira- tion is shewn by the difficulty with which that ? * Senac says the. anterior fibres assist in expira- tion by drawing the ribs inwards and backwards. Acad, des Sciences, 1729. t In violentissima respiratione omnino vidi deor- sum versus abdomen diaphragma convcxum reddi, Haller, Elem. Phys. lib. viii. sect. 1, function is performed when the actions of the muscle are interfered with. Ascites and tu- mours in the abdomen render the breathing shorter; even a full meal will have this effect, owing to the impediments to the descent of the diaphragm. If the phrenic nerves be divided in a living animal, great difficulty of breathing follows, the entire labour of respiration being thrown on the muscles which elevate the ribs. If the spina! marrow be divided above the giving off of the phrenic nerves, respiration ceases at once, but not so if divided imme- diately below that point; and in a case of fatal dyspnoea Beclard could find no cause but a tumour on one of the phrenic nerves. Besides the part which it plays in respira- tion, it is probable that the diaphragm, by its ordinaiy motions, exerts a beneficial influence on the digestive organs. The liver must be more or less affected by it in its secretion, and the gall-bladder is supposed to receive from it a compression which in some degree makes amends for the want of muscular fibres,* whilst the agitation of tbe hollow viscera will favour the transmission of their contents. The chyle in the lacteals and thoracic duct may also receive an impulse from the dia- phragm. Some anatomists were of opinion that tbe venous circulation in the abdomen was also assisted by the pressure, but the absence of valves in these vessels must prevent them from deriving any assistance from alternate compres- sion and relaxation . It acts powerfully, how- ever, on the venous circulation of the whole system by the vacuum which it has a tendency to form in the thorax. The nerves which pass through the dia- phragm, as the par vagum, sympathetics, and splanchnics, were formerly supposed to suffer compression, and the alternate transmission and interruption of the nervous influence, it was thought, could account for the pulsations of the heart and the vermicular motions of the intestines. But all this is too obviously erro- neous to require comment. The diaphragm assists, though rather as a passive instrument, in the expulsion of the urine, fasces, &c. For this purpose the thorax is filled with air, the rima glottidis is closed, and the diaphragm forms a resisting surface against which the abdominal muscles press the hollow viscera, and force out their contents wherever an exit is afforded them. The diaphragm is more or less engaged in hiccup, yawning, sighing, sobbing, groaning, which are all actions connected in various wxays with the function of respiration, and some of them more especially dependent on the dia- phragm, particularly hiccup, which is an explo- sive inspiration, in which the diaphragm acts involuntarily by a short and sudden effort, a sound being at the same time produced in the larynx. The diaphragm also performs an . important part in vomiting. A full inspiration .precedes* this act, then the glottis is. closed, and tltei ah- • ~ • * Scttac. : ‘ - •' ; v 6 DIGESTION. dorainal muscles forcibly press the stomach against the diaphragm, so as to assist the anti- peristaltic motion of that viscus. Magendie made experiments to show that unless the dia- phragm or abdominal muscles acted on the stomach, no vomiting could take place. He went too far, however, when he attributed the entire result to them. Substituting a pig’s bladder for the stomach, he injected tartar emetic into the veins, and vomiting followed. But lie forgot that pressure might readily empty a dead bladder and have little effect on a living stomach. And that such is the case we may be certain, else every cough would evacuate the stomach. Lastly, the diaphragm acts the part of a sep- tum or mediastinum to separate the two great cavities between which it is placed. When this septum is wanting, the abdominal viscera get into the thorax, and in such cases the lungs are constantly found in a rudimentary state : their further evolution being impeded by the pressure exerted on them by the intruding viscera.* It has been stated that the oesophageal open- ing may be closed by those fibres of the crura which curve round it. The other openings, as the aortic, and that for the ascending cava, can- not be diminished by the efforts of the muscle. This is plain from the tendinous margins which they present, and the manner in which the mus- cular fibres are attached to their borders. We have not mentioned some of the uses which the ancients ascribed to the diaphragm — as, that it is the seat of the passions, f that it prevented noxious vapours from rising into the thorax, that it fanned the hypochondria, and so forth. These are too fanciful to demand serious notice. Malformations and diseases. — The dia- phragm may be absent in whole or in part by congenital malformation. In the very young foetus the thorax and abdomen form one cavity, as in birds, reptiles, and fishes; and the deve- lopment of the diaphragm, as of most other organs, is by a process of growth from the cir- cumference to the centre. If, therefore, an arrest of formation occur at a very early period of foetal existence, the muscle may be entirely wanting ; if at a later period, some deficiency will be found at or near the centre. An exam- ple of the total absence of the diaphragm was dissected by Diemorbroeck. The subject lived to the age of seven years without suffering any inconvenience except a frequent cough-! Con- genital deficiencies near its middle are not very rare. They are observed oftener towards the left than the right side, and are always accom- panied with a protrusion of the abdominal viscera into the thorax, not vice versa. The development of the thoracic viscera is impeded by this intrusion, and they remain more or less rudimentary. It sometimes happens that the natural openings of the diaphragm are too large, and then protrusions or herniae are apt to occur by the sides of the tubes which they were intended alone to transmit. Openings frequently occur in consequence of disease or violence. Ulcers often make a perforation, and it is common enough to see an abscess of the liver make its way into the lung through the diaphragm. The writer lately saw an abscess, which formed in the gastrosplenic omentum, take the same course. Wounds often penetrate the diaphragm, and it is remarkable that however small they may be, a ventral phrenic hernia is sure to follow. The diaphragm has been suddenly ruptured during violent muscular efforts, vomiting, falls, &c. and instant death has usually followed. Various examples of such ruptures are recorded in the Dictionnaire des Sciences Med. art. Diaphragme. The countenance in all such cases assumes the peculiar expression or grin called risus Sardonicus. The diaphragm is subject to attacks of in- flammation, which, in almost every case, is communicated to it by the adhering pleura or peritoneum. It is indeed usually confined to one or other of these serous membranes, chiefly the pleura, and does not affect the muscular fibre. It is, notwithstanding, termed diaphrag- mitis. Hippocrates called it phrenitis, and Boerhaave changed the name to paraphrenitis , to distinguish it from a well-known cerebral affection. Gangrene, collections of pus, tumours, &c.are occasionally met with, and are of very difficult diagnosis. Cartilaginous and osseous deposits have been found on both sides of the diaphragm in the subserous cellular tissue. The diaphragm is often considerably dis- placed upwards or downwards. In ascites, and in consequence of diseases of the liver and of abdominal tumours, it may be pushed up to the second rib on one side ; in thoracic affec- tions again it has been so pushed down as to become convex, in part of its extent, towards the abdomen. Senac mentions a case of great enlargement of the heart which caused the cen- tral tendon to be buried in the abdomen, it being formed into a kind of pouch.* Dr. W. Stokes found the left ala convex towards the abdomen in emphysema of the lungs, f and it is known to yield extensively to the pressure of fluid in cases of empyema, more especially if the pleura covering it has been much engaged, as the same accurate observer has noticed and explained. For Bibliography see that of Anatomy (Intro- duction). ( Charles Benson .) * Andral’s Pathological Anatomy, tr. by Town- send and West, vol. i. t The word phrenic, used with reference to the diaphragm, as phrenic nerve, phrenic centre, &c. has its origin in this opinion, puv, mens, tanquam mentis sedes. | Diet, des Sciences Med. art. Diaphragme. DIGESTTON. (Fr. digestion; Germ. Ver- dauung ; Ital. digestionef) This term is em- ployed in Physiology to designate that func- tion by which alimentary matter is received * Acad, des Sciences, Mem. 1729. t Dublin Med. Journal, vol. ix. p. 37. DIGESTION. 7 into an appropriate organ, or set of organs, and where it is subjected to a specific action, which adapts it for the purpose of nutrition.* * * § In its original and technical sense this action was confined to the stomach, f but it is gene- rally applied more extensively, so as to include a number of distinct operations, and a suc- cession of changes, which the food experiences, after it has been received into the stomach, until a portion of its elements are separated from the mass, and are conveyed, by means of the lacteals, to the bloodvessels. In the following article we shall employ the term in its most extensive acceptation, and shall regard the whole as one function, the successive steps of which are intimately and necessarily connected together, and each of them essential to the completion of the whole.} We shall commence by a description of the organs of digestion, we shall next give an ac- count of the nature of the substances usually employed as food ; in the third place we shall trace the successive changes which the food experiences in the different parts of the pro- cess; in the fourth place we shall examine some of the hypotheses that have been pro- posed to explain these various operations, and shall conclude by some remarks on certain affections of the digestive organs, which are connected with, or dependant upon, their functions. I. Description of the organs of digestion. — The organs of digestion, taken in their most comprehensive sense, may be arranged under three divisions : the first, by which the aliment is prepared for the chemical change which it is afterwards to experience, and is conveyed into the stomach, being principally of a mechanical nature ; secondly, what have been more ex- clusively termed the proper digestive organs, where the aliment receives its appropriate chemical changes ; and lastly, those organs by which, after the nutritive substance thus elaborated has been separated from the mass, in order to be conveyed into the blood, the residuary matter is expelled from the system.§ * The term appears to have been originally bor- rowed irom the chemists, or the chemical physio- logists, who supposed that the aliment was ma- cerated in the stomach precisely in the same manner as substances are said to be digested in various operations in the laboratory. It was a term very frequently employed by Van Helmont. — See Castelli, Lexicon, “ Digestio.” t Cullen’s Physiol. § 201. t Magendie divides the process of digestion into eight distinct actions : 1, the reception of the food ; 2, mastication ; 3, insalivation ; 4, deglutition ; 5, the action of the stomach; 6, of the smaller in- testines; 7, of the large intestines; 8, expulsion of the faeces. Phys. t. ii. p. 33. Adelon and Chaussier arrange them under seven heads : appe- tition, gustation, mastication, dcglntion, chymitica- tion, chylificatiou, and defaecation. Diet. Sc. Med. t. ix. p. 357. § Adelon considers the digestive organs to con- sist of six essential parts : the mouth, the pharynx and oesophagus, the stomach, the duodenum, the small intestines, and the large intestines. Diet. Sc. Med. t. ix. p.355. In the higher orders of animals, where the functions are more numerous, and more varied in their nature, we find them to be so inti- mately connected together, and dependent on each other, that it is impossible for any one of them to be suspended without the derange- ment of the whole. But as we descend to animals of a less perfect and complicated structure, the functions are considerably re- duced in number, and seem also to be less intimately connected, so that certain of them are either altogether wanting, or are performed, although imperfectly, by other organs, which are not exclusively appropriated to them. Thus we observe that some, even of the parts which are the most essential to human ex- istence, as the brain, the heart, and the lungs, are not to be found in many very extensive classes of animals, some of the functions be- longing to these organs being entirely deficient, or being effected in a more simple or a less complete manner, by a less complicated ap- paratus. As we descend still lower in the scale, we find the functions still more restricted and simplified, until we arrive at the lowest term which would appear to be compatible with the existence of an organized being, where no functions remain but those which seem to be essential to the original formation of the animal and to its subsequent nutrition. That some apparatus of this description is abso- lutely essential may be concluded, both from the consideration, that the nutritive matter which is received into the system must un- dergo a certain change, either chemical or mechanical, before it can be employed for this purpose, as well as from the fact, that a sto- mach, or something equivalent to it, has been found to be the circumstance, which is the most characteristic of animal, as distinguished from vegetable life.'* Accordingly, with a very few exceptions, and those perhaps depending rather upon the inaccuracy of our observation, than upon the actual fact, it is generally ad- mitted, that every animal, the size and texture of which admit of its being distinctly ex- amined, is possessed of some organ appro- priated to the purposes of digestion.f Of the three orders of parts mentioned above, the second is the only indispensable one, or that which is alone essential to the due per- formance of the function. In many cases the aliment is directly received into the stomach, without any previous preparation, either che- mical or mechanical, and there are not a few instances in which the residuary matter is im- mediately rejected from the stomach, without any distinct apparatus for its removal. In the * Smith’s Introd. to Botany, p. 5 ; Grant, Cyc. of Anat. v. i. p. 107. Dr. Willis, on the other hand, remarks, in the same work, that nothing resembling a stomach has been found in any vege- table, p. 107. f Soemmering, Corp. hum. fab. t. vi. p. 229 ; Blumenbach’s Comp. Anat. § 82. Many of the exceptions which were supposed to exist to the general rule have been removed by the interesting observations of Ehrenberg ; Ann. Sc. Nat. t. ii. 2e ser.; Roget’s Bridgewater Treatise, v. ii. p. 95. DIGESTION. a following pages our main object will be to give an account of the function of digestion as it is exercised in man and in those animals which the most nearly resemble him, referring to other animals only so far as it may contribute to illustrate or explain the nature of the ope- ration in the human species. In the various divisions of the Mammalia the first order of parts may be arranged under the five heads of the mouth with its muscular appendages, the teeth, the salivary glands, the pharynx, and the oesophagus. With the exception of the salivary glands, the effect of these organs is entirely mechanical ; it con- sists in the prehension, the mastication, and the deglutition of the aliment. The first of these organs may be again subdivided into three parts, the lips, the cheeks, and the tongue ; the lips being more immediately adapted for seizing and retaining the food, and the others for conveying it, in the first instance, to the teeth, for the purpose of mas- tication, and afterwards to the pharynx, in order that it may be swallowed. In this, as in every other part of the animal frame, we perceive that adaptation of the structure of each individual organ to the general habits of the animal, which forms a constant subject of delight and admiration to the anatomist and the physiologist. In animals that feed upon succulent and luxuriant herbage the lips are capacious, strong, and pendulous, for the pur- pose of grasping and detaching their food, while in those that employ an animal diet, where their prey is to be seized and divided principally by means of the teeth, the lips are thin, membranous, and retractile. Again in the muscles that are connected with the cheeks, we find the same adaptation, although perhaps not in so obvious a degree. We observe that animals who receive large quantities of food, either in consequence of its being of a less nutritive nature, or from any other peculiarity in their habits and organization, as well as those whose food is of a harder consistence and firmer texture, have larger and more powerful muscles, both for the purpose of moving the jaws with greater force, and for acting upon the larger mass of matter which is taken into the mouth. The principle of adaptation is still more remarkable in the teeth. Among the different orders which compose the Mammalia, we ob- serve a general analogy and resemblance be- tween the teeth, both as to their number, form, and relative position, while, at the same time, there is so great a diversity in the different tribes of animals, that some of the most dis- tinguished naturalists have regarded these organs as the parts the best adapted for form- ing the basis of their systematic arrangements, inasmuch as they afford the most characteristic marks of the habits of the animals, and of the peculiarities of their other functions.* Thus, by an inspection of the teeth we can at once discover whether the individual is intended to Linnaeus, Sys. Nat. t, i. p. 16 et alibi; Shaw’s Zool. v. i. luUod. p. vii et alibi. employ animal or vegetable food, some of them being obviously adapted for seizing and lace- rating the animals which they acquire in the chace or by combat, while the teeth of others are obviously formed for the cropping of vege- tables, and for breaking down and triturating the tough and rigid parts of which they prin- cipally consist. It is with a view to this dou- ble purpose of prehension and mastication that the great division of the teeth into the incisors and the molares, the cutting and the grinding teeth, depends, the former being of course situated in the front of the mouth, the latter in the sides of the jaws. The chemical com- position and mechanical texture of the teeth is no less adapted to their office of dividing and comminuting the food than their figure and position. They are composed of nearly the same materials with the bones generally, but their texture is considerably more dense and compact, while they are covered with an ena- mel of so peculiarly firm a consistence, as to enable them, in many kinds of animals, to break down and pulverize even the hardest bones of other animals, and to reduce them to a state in which they may be swallowed, and received by the stomach, in the condition the best adapted for being acted upon by the gastric juice.'* At the same time that the alimentary matter is subjected to the mechanical action of the teeth, it is mixed with the fluids that are dis- charged from the salivary and mucous glands, which are situated in various parts of the mouth. The use of the saliva is to soften the food, and thus render it more easily masti- cated, to facilitate its passage along the pha- rynx and oesophagus, and perhaps, by a certain chemical action, to prepare it for the change which it is afterwards to experience, when it is received into the stomach. f The food, after it has been sufficiently di- vided by the teeth, and incorporated with the saliva, is transmitted, by the act of deglutition, into the stomach. There is perhaps no part of the system, which exhibits a more perfect specimen of animal mechanism than the pro- cess of deglutition. It consists in the succes- sive contraction of various muscles, that are connected with the contiguous parts, each of which contributes to form a series of mecha- nical actions, which, when connected with each other, effect the ultimate object 'in the most complete manner. The muscles of the mouth and the tongue first mould the mas- ticated aliment into the proper form, and trans- mit it to the pharynx; this part is, at the same time, by the cooperation of other muscles, placed in the most suitable position for re- ceiving the alimentary mass, and transmitting it to the (Esophagus, while another set of mus- * Hatchett, in Phil. Trans, for 1799, p. 328-9; Berzelius, View of Animal Chemistry, p. 78; Pepys, in Fox on the Teeth, p. 92 et seq ; Turner’s! Chemistry, p. 1012. t For the opinions that were entertained by the older physiologists on this point the reader is re- ferred to Baglivi, Biss. 2, circa salivam, op. p. 412 et seq.; also to Haller, El. Phys. 18. 2. 13. DIGESTION. 9 cles causes the epiglottis to dose the passage into the larynx. The muscular fibres of the oesophagus itself are now brought into play, and by their successive contraction, propel the food from the upper to the lower part of the tube, and thus convey it to its final destination. These three stages, which altogether constitute a very complicated train of actions, are so connected with each other, that the operation appears to be of the most simple kind ; it is one of the first that is performed by the newly born animal, and is exercised during the whole period of existence with the most perfect facility.* The food, after having thus experienced the action of the first order of parts, which, as we have seen above, is principally, if not entirely, of a mechanical nature, is finally deposited in the stomach. The stomach is a bag of an irregular oval form, which lies obliquely across the upper part of the abdomen, in what is termed, from the presence of this organ, the epigastric region. The structure of the sto- mach, considered in its physiological relation, is threefold. A large portion of it is composed of membranous matter, which gives it its ge- neral form, determines its bulk, and connects it with the neighbouring parts, constituting its external coat. To the interior surface of this coat are attached a number of muscular fibres, by which the various contractile actions of the stomach are performed ; these, although not capable of being exhibited as a connected or continuous structure, are considered, accord- ing to the custom of the anatomists, as com- posing the muscular coat, while its internal coat consists of a mucous membrane, which appears to be the immediate seat of the se^- ereting glands, from which the stomach de- rives its appropriate fluids. But besides this, which may be regarded as the physiological structure of the stomach, by which its parts are so arranged as to give' the organ its form and position, its contractile power, and its chemical action, the anatomists have resolved it into a greater number of mechanical divisions, depending principally upon the minuteness to which they have carried their dissections. In this way no less than six or even eight distinct strata or coats have been assigned to the sto- mach. First, the peritoneal covering, which it has in common with all the other abdominal viscera, the dense membrane which more especially gives the stomach its form, called in the language of the older writers the ner- vous coat, two muscular coats, f one composed of longitudinal and the other of circular fibres, and the innermost, or, as it has been termed, * For a minute account of the process of deglu- tition generally we may refer to Boerhaave, Prasl. t. i. $ 70. .2, Haller’s Phys. by Mihles, lect. 23; Prim. Lin. cap. 18, § 607 . . 621 ; El. Phys. xviii. 3. 21. . 5; Dumas, Physiol, t. i. p. 341. . 353, who divides the act ot deglutition into four stages, and to Magendie, Physiol, t. ii. p. 54.. 67, who reduces them to three. t Boyer, ubi supra, supposes that the muscular fibres are arranged in three layers. See also JEl- liotson’s Physiol, p. 78. the villous coat, together with three cellular coats, which are situated between the former and connect them with each other. The ner- vous coat is usually described as being the seat of the glands, as well as of the bloodvessels, nerves, and absorbents which belong to the stomach; but although they cannot perhaps be actually traced beyond this part, there is some reason to suppose that their ultimate destination is on the innermost or villous coat. The membranous part of the stomach ap- pears to be peculiarly distensible, so as readily to admit of having its capacity greatly and suddenly increased, in order to contain the large quantity of solids and fluids that are occasionally received into it, while its mus- cular fibres and nerves are possessed respec- tively of a high degree of contractility and sensibility, by which they act powerfully on its contents, propelling them, when necessary, into the duodenum, and thus reducing the bulk of the stomach to its ordinary standard. Besides the mucous fluid which the inner sur- face secretes, in common with all other mem- branes of this description, the stomach is sup- posed to possess certain glands, adapted for the formation of a specific fluid, termed the gastric juice, which acts an important part in the process of digestion ; but the presence of these glands has been rather inferred from their supposed necessity, than from any actual ob- servation of their existence.* From the peculiar form and disposition of what have been termed the muscular coats of the stomach, they not only enable the organ to contract in its whole extent and in all direc- tions, but they give to its individual parts the power of successively contracting and relaxing, so as to produce what has been termed its peristaltic or vermicular motion ,f The effect produced appears to be, in the first instance, to form in the interior of the stomach a series of folds or furrows, and at the same time to agitate the alimentary mass, so as to bring every part of it, in its turn, within the in- fluence of the gastric juice, while the whole of the mass is gradually carried forwards to- wards the pylorus, and is in due time dis- charged from that orifice. The muscular fibres of the stomach, like all those that are con- nected with membranous expansions, forming what are termed muscular coats, are not under the control of the will. In consequence of the great degree of vitality which the stomach possesses, a circumstance in which it is surpassed by scarcely any organ in the whole body, it is very plentifully provided with bloodvessels and with nerves. The arteries, according to the ordinary construction of the sys- tem, are furnished by the contiguous large trunks, * Winslow’s Anat. Sect. viii. § 63..5 ; Haller, El. Phys. xix. 1. 14; Bell’s Anat. v. iv. p.58. f Haller, El. Phys. xix. 4. 9, 0 ; Boyer, Anat. t. iv. p. 333 . . 5 ; Bertin, Mem. Acad, pour 1760, p. 58 et seq.; this writer appears to have been one of the first who gave us a correct description of the muscular coats of the stomach. 10 DIGESTION. while the veins, in common with all those that be- long to what are termed the chylopoietic viscera, terminate in the vena portae.* The nerves of the stomach are not only very numerous, but they are remarkable for the number of different sources whence they derive their origin. These are, in the first instance, threefold ; it is fur- nished with a large quantity of ganglionic nerves, in common with all the neighbouring viscera ; it likewise receives nerves directly from the spinal cord, and unlike all the other parts of the body, except what are termed the organs of sense, it has a pair of cerebral nerves in a great degree appropriated to it. The specific uses of these different nerves are not certainly ascertained, and it would scarcely fall under the immediate object of this treatise to enter upon the consideration of this point ; but we may observe, that no organ, in any part of the body, partakes more fully of what may be considered as the actions of the nervous system, or is more remarkably affected by its various changes, including not merely those of a physio- logical nature, but such likewise as are con- nected with the various mental impressions, j- The two extremities of the stomach, by which the food is received and discharged, are respec- tively termed the cardia and the pylorus. Their structure, in many respects, differs from that of the other parts of the organ. The cardia is remarkable for the great proportion of nerves which are distributed over it, and as these are principally derived from the par vagum, or the eighth pair of cerebral nerves, we may under- stand why this should be the most sensitive part of the stomach. The pylorus is remarkable for the mechanical disposition of its muscular fibres, which form an imperfect kind of sphinc- ter, by which the food is detained in the cavity until it has experienced the chemical action of the gastric juice. And besides the functions which are actually possessed by this part, many imaginary and mysterious powers were ascribed to the pylorus by the older physiologists. The sensibility of the stomach was supposed to reside more especially in this extremity ; it was selected by some of the visionary philosophers of the sixteenth and seventeenth centuries as being the seat of the soul, and even some of the moderns ascribe to it a kind of intelligence or peculiar tact, by which it is enabled to select the part of the alimentary mass, which has been sufficiently prepared to enter the duodenum, while it prevents the remainder from passing through its orifice, and retains it for the purpose of being still farther elaborated. \ On account of the form and position of the stomach it is sufficiently obvious, that a con- siderable proportion of its contents must be, at all times, below the level of the pylorus. The food is hence prevented from passing too hastily out of the organ, while we may conclude that * Winslow, sect, viii, § 2. 72. .7 ; Haller, El. Phys. xix. 1. 16. .20 ; Blumenbach, Inst. Physiol. $ 356 ; Bell’s Dissect, p. 19 . . 25. pi. 3, 4. f Winslow, ubi supra, 78, 9 ; Haller, xix. 1. 21 ; Blumenbach, § 355 ; Bell s Anat. v. iv. p. 64 ; Walter, Tab. nerv. No. 3, 4. i Richexand, Physiol. $23. § 111, 2. the transmission of the food is almost entirely effected by the contraction of its muscular fibres, aided probably by the diaphragm and the abdominal muscles, but scarcely in any degree by the mere action of gravity.* It must, however, be observed that the position of the stomach generally, with respect to the neighbour- ing organs, as well as the relation of its different parts to each other, varies considerably according to its state of repletion ; when it is the most fully distended, its large arch, which previously was pendulous, is now pushed forwards and raised upwards, so as to be nearly on the same level with the pylorus.f When the food leaves the stomach, it is re- ceived by the intestinal canal, a long and winding tube, which varies much in its diameter and its form, in the different parts of its course, but which, both in its anatomical structure and in its physiological functions, bears a consider- able resemblance to the stomach. It may be said, in the same manner, to consist of three essential parts, the membranous, the muscular, and the mucous, which respectively serve to give it its form, to enable it to propel its con- tents, and to furnish the necessary secretions. With respect to the form of its individual parts, it has been divided, in the first instance, into the large and small intestines, a division which depends upon the comparative diameter of the two portions, while each of these has been sub- divided into three parts, depending more upon their form and their position than upon their structure or functions. But although it may be supposed, that the division of the tube into the great and small in- testines refers to their difference of size alone, it is to be observed that they perform very differ- ent functions, and are subservient to very differ- ent purposes in the animal ceconomy. It is in the small intestines, and more especially in the first portion of them, termed the duodenum, that what must be considered as the most essen- tial or specific part of the function of digestion is effected, the formation of chyle, while it is almost exclusively in the duodenum and the other small intestines, the jejunum and the ileum, that the chyle thus produced is taken up by the lacteals, in order to be conveyed to the thoracic duct, and finally deposited in the bloodvessels. The use of the large intestines, and more es- pecially of the colon, which constitutes a con- siderable proportion of the whole, appears to be more of a mechanical nature, serving as a depo- sit or reservoir, in which the residuary matter is received and lodged, fora certain period, until it is finally expelled from the system. The division between the parts of the small intestines, to which the names jejunum and ileum have been applied, is entirely arbitrary, as they ap- pear to be precisely similar to each other, both in their structure and their functions. But the case is very different with respect to the duode- num, which in both these respects possesses a clearly marked and distinctive character. Of 5 Haller, ubi supra, § 2. .4. t Blumenbach, $ 353. DIGESTION. 11 this anatomists have long been well aware, and it has accordingly been made the object of par- ticular attention, and has even received the ap- pellation of the accessory stomach ; but we shall enter more particularly into the consideration of this subject when we come to treat upon the difference between chyme and chyle, and the nature of the process by which it is effected. The peculiarities of the digestive organs in the different classes of animals are interesting, not merely as affording remarkable examples of the adaptation of the animal to the situation in which it is placed, but are especially worthy of our notice on this occasion, as serving to illus- trate the nature of the operation generally, and the mode in which its various stages are related to each other. The most remarkable examples of this kind are the complicated stomachs of the rumiuant quadrupeds, and the muscular sto- machs of certain classes of birds.* The ruminant animals belong to the class of the mammalia, and are such as feed principally upon the stalks and leaves of plants. The quan- tity of food “which they take is very consider- able ; it is swallowed, in the first instance, al- most without mastication, and is received into the first stomach, a large cavity, which is termed the venter magnus, pause, or paunch. \ The food, after remaining for some time in this sto- mach, for the purpose, as it would appear, of being macerated, is next conveyed into the second stomach, a smaller cavity, the internal coat of which is drawn up into folds that lie in both directions, so as to form a number of an- gular cells, from which circumstance it has received the appellation of reticulum, bonnet, or honeycomb. The reticulum is provided with a number of strong muscular fibres, by which the food is rounded into the form of a ball, and is propelled along the oesophagus into the mouth. It is now completely masticated, after having been properly prepared for the pro- cess by its previous maceration in the paunch ; this mastication constitutes what has been termed chewing the cud, or rumination. When the food has been sufficiently com- minuted it is again swallowed, but by a pecu- liar mechanism of muscular contraction the passage into the venter magnus is closed, while an opening is left for it to pass into the third stomach, termed omasum, feuillet, or maniplies ; it is smaller than any of the other cavities, and its internal coat is formed into a series of strong ridges and furrows, but without the transverse ridges of the reticulum. From the omasum the food is finally deposited in the fourth stomach, the abomasum, caillette, or reed, a cavity consi- derably larger than either the second or third stomach, although less than the first. It is of an irregular conical form, the base being turned * For an interesting account of the comparative anatomy of the digestive organs we may refer to Carus’s Comparative Anatomy, by Gore, v. ii. p. 72 et seq. t We have selected the terms by which each of the four stomachs is usually designated in Latin, French, and English respectively; there are, how- ever, various other names which have been applied to them. to the omasum ; it is lined with a thick mucous or villous coat, which is contracted into ridges or furrows, somewhat in the manner of the oma- sum, and it appears to be that part of the diges- tive apparatus which is analogous to the single stomach of the other mammalia, where the ali- ment undergoes the process of chymification, the three first stomachs being intended to macerate and grind it down, in order to prepare it for the action of the gastric juice. (See Ruminantia.) Although we conceive that the operation of the different parts of this complicated apparatus is pretty well understood, it still remains for us to inquire into the final cause of the arrange- ment, or why the maceration and mastication of the food in certain classes of animals should be effected in a manner so different from what it is in others, which, in their general structure and functions, the most nearly resemble them. The opinion which was entertained on this subject by the older anatomists, and which may be still regarded as the popular doctrine, is, that the nature of the food of these animals, and the large quantity of it necessary for their support, requires a greater length of time for its comminution and a greater quantity of the mucous secretions than it could obtain by the ordinary process. But although there may be some foundation for this opinion, the more extended observations of modern naturalists show, that it does not apply in all cases, and that there are so many excep- tions to the general rule as to lead us to doubt the truth of the position.* It is to be ob- served, that when animals with ruminant sto- machs take in liquids, the fluid passes immedi- ately into the second stomach ,f where it is mixed with the aliment after1 it has been macerated in the venter magnus, and probably moulds it into the proper form, for its return along the oesophagus into the mouth. While the young animal is nourished by the mother’s milk, the fluid is conveyed, in the first instance, through the third stomach into the fourth, and it is not until it begins to take solid food, that the process of rumination is established. It is hence concluded, that the animal possesses the power of conveying the food at pleasure either into the first or the third stomach, and of return- ing it from the second into the mouth ;J these, like many other voluntary acts, being of the kind which are termed instinctive. The other kind of stomach which we referred to above as possessing a peculiar structure, and acting on a different principle from that of the human species, is the muscular stomach of certain classes of birds. Birds are not pro- vided with teeth, or with any apparatus which can directly serve for the process of mastica- tion ; yet many of them feed upon hard sub- stances, which cannot be acted upon by the gastric juice, until they have undergone some process, by which they may be comminuted or ground down into a pulpy mass. This is effected by the ingluvies, the craw or crop, and the ventriculus bulbosus or gizzard. The first * Blumenbach’s Comp. Anat. p. 138. note 20. f Home, ubi supra, p. 363. 1 Blumenbach, ubi supra, p. 138. note 18; Ray’s Wisdom of God, &c., p. 188. 12 DIGESTION. of these is a large membranous bag, analogous to the paunch of the ruminants, into which the food, without any previous alteration, is re- ceived from the oesophagus, and where it is macerated in the usual manner by the conjoined action of heat and moisture. The gizzard is of much smaller dimensions than the crop, composed of four muscles, two of which are of a flattened form and of very dense texture, lined internally with a firm cal- lous membrane, and capable of an extremely powerful action. These constitute the main part of the parietes, the two other muscles being much smaller, and situated at the extremities, serving, as it would appear, merely to com- plete the cavity.* The gizzard is so connected with the crop, that the food, after due macera- tion, is allowed to pass by small successive portions between the two larger muscles; by their contraction they are moved laterally and obliquely upon each other, so that whatever is placed between them is completely triturated. The force of these muscles, as w'ell as the impenetrability of their investing membrane, is almost inconceivably great, so that, according to the experiments of Spallanzani and others, not only are the hardest kinds of seeds and grains reduced to a perfect pulp, but even pieces of glass, sharp metallic instruments, and mineral substances, are broken down or flattened, while the part still remains unin- jured.f The action of both the crop and the gizzard must be regarded as at least essentially mechanical, mainly adapted for the purposes of maceration and trituration, and as compen- sating for the saliva and teeth of man and the greatest part of the mammalia. W e are able in this case to observe the connexion between the habits of the animals and the peculiarities of their organs more clearly than with regard to the ruminants, for we can always perceive an intimate relation between the food of the different kinds of birds and the structure of their stomach. II. A n account of thenatureof the substances usually employed as food. — All the articles that are employed in diet may be arranged under the two primary divisions of animal and vege- table, according to the source whence they are derived. Those in which the distinctive cha- racters are the most strongly marked differ both in their proximate principles and their ultimate elements, although in this, as in most other cases, there are many intermediate shades. The ulti- mate elements of vegetables are oxygen, hy- drogen, and carbon, to which, in some cases, a portion of nitrogen is added. Animal sub- stances contain all these four ingredients, the carbon being in less quantity than in vege- * Grew, tibi supra, p. 34 ; Bluinenbach, ubi supra, §99; Poycr, Anat. Ventr. Gall., in Man- get, Bibl. Anat. t. i. p. 172; Hunter on the Ani- mal (Economy, p. 198-9; Clift, in Phil. Trans, for 1807, pi. 5, fig. 1 ; Home’s Lect. v. ii. pi. 49, 62 ; anti the art. Aves. t Spallanzani, Dissert, i. § 5 . . 8, and 10 . . 22 ; see also Acad, del Ciinenlo, p. 268,9 ; Borelli, De motu anim. t. ii. prop. 189; lledi, Esperiense, p.89 et seq. ; Grew, ch. 8 ; 'he art. “ Birds” in Rees ; and “ Aves” by Mr. Owen, in the present work. tables, while the hydrogen, and still more the nitrogen, are generally in much greater quan- tity. There are various circumstances which seem to prove that either species of diet is alone competent to the support of life, although each of them is more especially adapted to certain classes of animals. This, it is pro- bable, depends both upon the chemical and the mechanical nature of the substances in question, but perhaps more upon the latter than the former, for we find that the processes of cookery, which act principally upon mecha- nical principles, render various substances per- fectly digestible, which the stomach could not act upon before they had undergone these operations. W e also find that animals, which, in their natural state, have the strongest in- stinctive predilection for certain kinds of food, may, by a gradual training and the necessary preparation of the articles employed, have their habits entirely changed, without their health being in any degree affected. There is, however, a circumstance in the structure of the animal, which clearly points out a natural provision for the reception of one species of food in preference to the other, viz. the comparative capacity of the digestive or- gans. It may be concluded that, in all cases, the aliment must undergo a certain change before it can serve for the purpose of nutrition, and that this change will occupy a greater length of time, and that a greater bulk of materials will be requisite, according as the nature of the food received into the stomach is more or less different from the substance into which it is to be afterwards reduced. Hence, as a very general rule, we find that the diges- tive organs of carnivorous animals are less capacious than those of the herbivorous, and that even in the latter there is a considerable difference, according as the food consists of seeds and fruits or of the leaves and stems of plants. There are indeed certain circumstances in the habits of some of the carnivora which require organs of considerable capacity, as, for ex- ample, those beasts of prey who take their food at long intervals, being supplied, as it were, in an occasional or incidental manner, so that it becomes necessary for them to lay up a considerable store of materials, and to take advantage of any opportunity which presents itself of replenishing the stomach. The anato- mical structure of the human digestive organs indicates that man was intended by nature for a mixed diet of animal and vegetable aliment, but with a preponderance towards the latter ;* and it appears in fact that, while a, suitable combination of the two seems the most condu- cive to his health, and to the due performance of all his functions, either species is alone competent to his growth and nutrition. f * Cuvier, Regne Animal, t. i. p. 86; Lawrence’s Lect. p. 217 et seq. ; see also the elaborate dis- sertation ot Richter, De victus animalis antiq. &c. f Haller, El. Pliys. xix. 3. 2 . . 4 ; these sections contain a very full account of the different kinds of diet employed by different nations or individuals. We have a number of curious facts of this kind in DIGESTION. The most important of the proximate prin- ciples employed in diet are fibrin, albumen, oil, jelly, gluten, mucilage, farina, and sugar, to which may be added some others of less frequent occurrence. They are derived, more or less, from almost all the classes of animals and vegetables, and from nearly all their indi- vidual parts, their employment being regulated, in most cases, rather by the facility with which they are procured, and reduced into a form proper to be acted upon by the stomach, than by the quantity of nutritive matter which they con- tain. This is one of those subjects in which we have to notice the remarkable effects of habit and custom, both on the functions and the sensations. We find whole tribes of people living on a diet, which, to those unaccustomed to it, would be not only in the highest degree unpalatable, but likewise altogether indiges- tible; while, by the various modes of preparing food, which have been suggested, either by luxury or by necessity, the most intractable substances are reduced into a digestible state.* The writers on dietetics have attempted to include all substances that are competent to afford nutrition under a few general principles, of which, as they exist in nature, they are supposed to be composed. Cullen, who may be considered as the first who attempted to in- troduce correct philosophical principles into this department of physiology, reduced them to two, the oily and the saccharine, and endea- voured to prove that all the animal fluids may be referred to these principles. j- Magendie, on the contrary, proceeding less upon their chemical composition than upon the forms under which they present themselves, classes alimentary substances under the nine heads of farinaceous, mucilaginous, saccharine, acidu- lous, oily, caseous, gelatinous, albuminous, and fibrinous. j Dr. Prout, whose views on this subject are marked by his characteristic acuteness, reverts to the mode of Cullen, ad- mitting only of the oily, the saccharine, and the albuminous principles, which three, he conceives, form the “ groundwork of all orga- nized bodies. ”§ Of animal compounds which are employed Stark’s works, p. 94, 5; see also Lorry, Sur les ali- mens ; Plenk, Bromatologia ; Soemmering, Corp. hum. fab. p. 241,250; Richerand, El. Phys. §3, p. 83 ; Parr’s Diet. art. Aliment; Pearson’s Syn- opsis, parti. ; Lawrence’s Lect. p. 201, 9 ; Thack- rah’s 2d Lect. on Diet, p. 54 et seq. ; Paris on Diet ; Koget’s Bridgewater Treatise, part 2, ck. 3, § 1. * Elliotson’s Physiol, p. 65, 6 ; Roget, part 2, ch. 3, § 1. t Physiol. § 211, and Mat. Med. v. i. p. 1, ch. 1, p. 218 et seq. 1 Physiol, t. ii. p.3,4; see also Fordyce on Di- gestion, p. 84 et seq. ; Paris on Diet, part 2, p. 117 et seq. ; Richerand, El. Physiol. § 3, p. 82; Dumas, Physiol, t. i. p. 187 ; Davy’s Lect. on Agric. Chem. p. 73 et seq. ; Londe, Diet, de Med. et de Chir. art. ‘ ‘ Aliment,” t. ii. p. 1 et seq ; Ros- tan. Diet, de Med. art. “ Aliment,” t. i. p. 523 et seq. ; Rullier, Ibid. Art. “Nutrition,” t. xv. p. 161 et seq. ; Kellie, in Brewster’s Encyc. Art. “ Aliment.” § Abstract of his Gulstonian Lecture, p. 5, 9. in diet milk may be regarded as holding the first place, both from its nutritive aud its digestible properties, and as such it has no doubt been provided by nature for die newly-born animal, when it requires a diet, which may be adapted to the delicacy of its organs m its novel state of existence, while, at the same time, it pro- vides for its rapid growth. We accordingly find that the three principles mentioned above are combined in milk in a manner the most proper for this double purpose, and that there is no compound, either natural or artificial, which is equally well suited to it.* Next to milk, with respect to its nutritive properties, we may class eggs of various kinds, the mus- cular fibre of animals, and their gelatinous and albuminous parts, very few of which, how- ever, are employed in diet until they have undergone the various operations of cookery. Of these operations the most important in their dietetical effect is the formation of decoctions or infusions, constituting soups of all descrip- tions, in which we retain the more soluble, and, for the most part, the more nutiitive matter, while the residue is rejected. The fish which are usually employed in diet consist of a much greater proportion of jelly and albumen than the flesh of the mammalia and of birds ; these principles are united, in most cases, with a con- siderable quantity of oil. The most nutritive of the vegetable proximate principles is gluten ; it forms a considerable proportion of certain kinds of seeds, and more especially of wheat, and we accordingly find that in all those countries which admit of the growth of this plant, and which have arrived at any considerable degree of civilization, wheaten bread forms the most important article of vegetable diet, and one which appears the best adapted for all ages and all constitutions. Next to gluten we may rank farina, both from its valuable properties and from the extent to which it is employed. It enters largely into the composition of wheat and of the other seeds of the cerealia, also of rice and maize, while it constitutes a great proportion of the whole substance of the leguminous seeds and of tubers. It also forms the principal in- gredient of the chesnut, and of the esculent algse, so that, upon the whole, we may con- sider it as entering more largely into the aliment of mankind, in all different climates and situa- tions, than any other vegetable compound. Perhaps there is no proximate principle which contains in the same bulk a larger pro- portion of nutritive matter than oil, and we accordingly find that oil, as derived either from the animal or vegetable kingdom, enters largely into the diet of all nations. But it affords an example of one of those articles, which, al- though highly nutritious, is not very digestible without a due admixture of other substances, which may in some way render it more proper for the action of the gastric juice f It may * Prout, ut supra, p. 12. t It is upon this principle, rather than to the ab- sence of azote, that we should be disposed to account for the results ot Mageridic’s experiments, in which DIGESTION. 14 indeed be received as a very general rule that a certain quantity of matter, which in itself contains but a small proportion of the princi- ples which immediately serve for nutrition, is necessary for the due performance of the func- tions of the stomach, probably in some degree for the purpose of mere dilution or mechanical division. Tire same remark applies to sugar as to oil. Sugar would appear to be one of the most nutritive of the proximate principles, but when taken alone or in too great quantity it deranges the digestive organs, and becomes incapable of supporting life.* The difference in the different kinds of ali- ment between their capacity of affording the materials from which chyme may be produced, and the facility with which they are acted upon by the stomach, or in ordinary language, be- tween their nutritive and their digestible quality, has been distinctly recognized by various phy- siologists,f although it has not always been sufficiently attended to. We have some strik- ing illustrations of the fact in a series of expe- riments which were performed by Goss,} and in those of Stark, § where the digestibility and the nutrition of various species of aliment bore no relation to each other, while they afford the most decisive proof of the advantage, or rather the necessity, of a mixture of substances, in order to produce the compound which is the best adapted for the action of the stomach. We have referred above to the difference in the digestive powers of the stomachs of diffe- rent classes of animals as depending on their peculiar organization. In many instances the difference is so strongly marked as to leave no doubt either as to its existence or as to the cause by which it is directly produced. But there are many cases where we observe the effect without being able to assign any imme- diate cause for it ; where substances, which are highly nutritive and perfectly salutary to certain individuals, are apparently incapable of being digested by others. After making all due al- lowance for the effects of habit, association, or even caprice, there still appears sufficient ground for concluding that there are original differences in the powers of the stomach, which cannot be assigned to any more general prin- ciple. This observation applies principally to the individuals of the human species, where such variations, or, as they have been termed, idiosyncrasies, of all descriptions are much more apparent than in any other kind of ani- mals. All other animals, even those which the most nearly resemble the human species, are much more uniform in this respect, being guided in the choice of their food principally by that instinctive feeling which leads them he found that animals could not be fed upon pure sugar, oil, or gum ; Physiol, t. ii. p. 390, and Ann. Cliim. et Phys. t. iii. p. 66 et seq.; see Bos- tock’s Physiol, v. ii. p. 467, 8. * Haller, El. Phys. xix. 3. 12; Stark’s Works, p. 94 et alibi; Pearson’s Synopsis, p. 104, 5. t Adelon et Chaussier, Diet. Sc. Med. Art. “ Digestion,” t. ix. 4 Spallanzani, Sur la Digestion, par Senebier, p. cxxxi...cxl. § Works, p. 89 et seq. to select the substances which are the best adapted for their organs. But even here we meet with ceitain peculiarities, where animals prefer certain kinds of aliment, and where there is no obvious anatomical or physiological cause which can explain the effect. This, however, we may regard as an exception to the general rule, for there is perhaps no one of the functions in which we are enabled more clearly to trace the adaptation of the organ to the struc- ture and habits of the animal, than in what respects the supply of nutrition, including the mode of procuring the food, and the whole of the series of changes which it experiences from the digestive organs.* Liquids of various kinds constitute an im- portant part of the diet of almost all indivi- duals. They may be arranged under the two divisions of those liquids which we employ merely for the purpose of quenching thirst, or diluting our solid food, or such as are made the vehicles of nutriment, including various kinds of decoctions and infusions. The latter are derived both from the animal and the vege- table kingdoms, and when duly prepared form a species of food, which, as containing the most soluble and the most sapid portions, is, in most cases, both highly nutritive and diges- tible. But we observe here the same kind of idiosyncrasy to which we referred above, and which it frequently becomes necessary to attend to in the directions that are given respecting diet, and more especially to invalids and to children. The liquids that are employed for the pur- pose of quenching thirst, which are more pro- perly styled drinks, may be arranged under the two heads of vegetable infusions or decoctions and fermented liquors. Of the former a great variety have been employed in different coun- tries and at different periods, but in Europe, almost the only kinds which are in common use are tea and coffee. These cannot be con- sidered as in themselves affording any nourish- ment, but they are generally employed with the addition of some nutritive substance, and if not taken in excess, would appear to promote digestion, and to exercise a favourable influence on the system at large. It has been observed that all tribes of people that have made the least advances in the arts of life, either by accidental observation or by tradition, have become acquainted with the process of fermentation, and have indulged in the use of certain species of vinous liquors. The making of wine is among the first transac- tions that are recorded of Noah after he left the ark, and the experiment which he made of its effects has been but too frequently repeated by his progeny. The basis of all vinous liquors being the saccharine principle, the grape has been naturally had recourse to in all those parts of the world which are adapted to the growth of the vine ; in the more northern regions, as in our own island, different species of grains are employed, in which the sugar is evolved by an artificial process, while in the torrid zone, * Bostock’s Physiol, v. ii. p. 469, 70. DIGESTION. 15 other saccharine juices, procured from certain tropical plants, are employed for the same pur- pose. The fermented liquors of our own coun- try generally contain a considerable quantity of mucilaginous and saccharine matter, which still remains undecomposed, and which is directly nutritive ; but fully fermented wines are only indirectly so, as aiding the digestive powers by their stimulating effect on the stomach. It is generally admitted, that the operation of alcohol, when properly diluted, and when taken in moderate quantity, is favourable to the health of most individuals who are engaged in laborious pursuits, and have occasion to exert the full powers of the system. But the almost irresistible temptation to excess, and the fatal consequences which thence ensue, both to our physical and our mental constitution, have long been the subject of deep regret and severe re- prehension, both to the physician and the mo- ralist, and it may be asserted, that of all the gifts which providence has bestowed on the human race, there is none which, according to the present state of society, would appear of such dubious advantage as the knowledge of the process by which one of the most nutritive articles of diet is converted into one of the deadliest poisons. We have now to notice a class of substances very generally employed in diet, which are not in themselves nutritive, but are added to our food, for the purpose of rendering it more agree- able to the palate. These are the various arti- cles styled condiments ; they may be classed under the two heads of salts and spices. There is so very general a disposition among all classes of people in all countries to relish sapid food, that we are led to conceive that there must be some final cause for it, independent of the mere gratification of the senses, or that this gratifica- tion is made subservient to some more import- ant purpose. With respect to what is termed common salt, the muriate of soda, we observe, in many cases, the same relish for it among the lower animals as in man. We have well au- thenticated accounts given us, by various tra- vellers and naturalists, of the extraordinary efforts which are made by the beasts of prey which inhabit the great African and American continents, to obtain it.* Wre can scarcely therefore doubt that it must be, in some way or other, essential to the well-being of the animal; but whether it directly promotes the process of chymification, or whether it be taken into the stomach, for the purpose of being transmitted to the blood, and thus furnishing to the system the portion of saline matter which is always present in the animal fluids, must be considered as entirely conjectural.f The other division of condiments, the spices, are very numerous, and are derived from vari- ous sources, but are chiefly of vegetable origin. They are generally of a stimulating nature, and * Among these we may select the account given us by Mr. Hodgson, in his interesting letters from North America, vol. i. p. 240, 1, note. t Haller, El. Phys. xix. 3, 11; Fordyce on Digestion, p. 55. such as may be supposed to act, in the first in- stance, on the nervous system. Some of them increase the action of the heart and arteries, and some of them augment the secretions or excretions, but they differ essentially from alcohol, in not producing any thing resembling intoxication and the subsequent exhaustion. Thus they are much less injurious to the con- stitution, even when taken to excess, and are seldom liable to any stronger imputation than that of being useless. They afford some of the most remarkable examples of the effect of habit on the system, in changing or modifying our original perceptions, for it is very generally found that those substances to which we be- come, in process of time, the most attached, are such as, in the first instance, were not only perfectly indifferent, but even positively dis- gusting. Before we quit this part of the subject it remains for us to say a few words respecting the class of substances which are properly termed medicaments. The medicaments are nearly related to the condiments in their action on the system, but with this difference, that they are not only disagreeable to the palate, but are, for the most part, incapable of being re- conciled to it by habit. But there is in fact no exact line of demarcation between them ; many of the articles which are usually consi- dered as condiments, being not unfrequently used in medicine, and some of what are gene- rally regarded as the most active and nauseous medicines, being employed by some individuals as agreeable condiments. Both these classes of substances appear to differ in one essential particular from what are more properly re- garded as articles of diet, that while it is essen- tial to the operation of the latter, that they should be decomposed, and probably resolved into their constituent elements, the specific effect of the former seems to depend upon their acting on the stomach in their entire state. Nearly connected to this class of substances, and indeed differing from it only in degree, are the articles that are usually termed poisons. The term may, however, be regarded as entirely a popular designation, for as there is no active medicine which may not immediately destroy life by an excessive or improper administra- tion, so there are no substances, among those which are usually considered as poisonous, which may not, under certain circumstances, prove valuable medical agents. III. An account of the changes which the food, experiences in the process of digestion. — We now proceed to the consideration of the third subject which we proposed for our in- quiry, the nature of the change which the food undergoes during the process of digestion. In prosecuting this inquiry we shall consider in succession the various processes by which the aliment, after being received into the mouth, is brought into the state of chyle. These changes may be reduced essentially to three ; the me- chanical division of the food, as effected by the operations of maceration, mastication, and tri- turation ; the conversion of the alimentary mass into chyme, by the action of the gastric juice ; 1 G DIGESTION. and lastly, the conversion of chyme into chyle in the duodenum.* After the account which we have given above of the organs of mastication, nothing further remains for us to say on the first part of the process ; we may therefore conceive that the food, after it has been mechanically divided by means of the teeth or any analogous organ, is conveyed to the stomach, in order to be acted on by the gastric juice and converted into chyme.f The process of chymification consists in a certain chemical change, by which the aliment, from whatever source it may have been derived, and whatever may have been its origi- nal constitution, is converted into a uniform pultaceous mass, having certain specific pro- perties, which are different from those of the substances from which it is formed. And we may here observe, that this kind of change, which has been frequently spoken of as something of a mysterious or inexplicable nature, is perfectly analogous to what takes place in all chemical action, where the addition of a new agent imparts new properties to the mixture. The supposed difficulty in this case has arisen from an indistinct conception in the minds of many physiologists, both of the nature of chemical action generally, and of the appro- priate powers which belong to a living orga- nized system. The essential and exclusive functions of vitality may probably be all re- duced to two great principles of sensation and motion, as depending primarily upon the action of the nerves and the muscles. Chemical affi- nity is independent of these principles, but it is, in various ways, modified by their operation, by bringing the agents into contact, by separa- ting them from each other, and thus enabling them to produce new compounds, and when the compounds are formed, by removing them from the further action of the agents, and by conveying them to the situations when they are required, for the exercise of some new function. In the present case the glands of the stomach secrete a fluid possessed of specific properties; by the act of deglutition, and by the muscular contraction of the stomach itself, the alimentary mass is conveyed to the part where it may be brought into contact and mixed with this fluid. Each portion of the aliment is successively subjected to the due action of this agent, and when the process is completed, it is carried through the pylorus out of the stomach, while a new portion of aliment takes its place and goes through the same process. In this part of our subject there are two * See on this subject Magendie, Physiol, t. ii. p.81,2; Dr. Prout’s paper in Ann. Phil. vol. xiii and xiv. and Dr. Philip’s Inquiry, ch. vii. sect. 1. f It is necessary -to remark in this place, that most of the older physiologists, and some even of a later period, have employed the terms chyme and chyle indiscriminately, or at least have not made any accurate distinction between them. The words and appear to be nearly synonymous in their original acceptation; see Castelli, Lexicon, and Stephens, Thes. in loco. The latest physiolo- gists have, however, for the most part, employed the two terms in the restricted sense which is adopted in this article. points which will require our particular atten- tion ; first, we must ascertain the properties of chyme, and secondly, those of the gastric juice. It is commonly stated, that from whatever source the chyme is derived, provided the stomach be in a healthy state, its properties are always the same,* and it must be admitted that, as a general principle, this would appear to be the case. In animals of the same species, notwithstanding the miscellaneous nature of the substances that are employed in diet, the result of the complete action of the stomach is a mass of uniform consistence, in which the peculiar sensible properties of the articles of food cannot be recognized. But this statement must be re- ceived with certain limitations, and is only ap- plicable to the ordinary diet, for we have reason to believe, not only that the chyme produced from animal matter differs from that of vegetable origin, but even that different species of vege- table aliment produce a different kind of chyme. The chyme from fruits or green vege- table matter is notoriously more disposed to pass into the acetous fermentation than chyme formed from farina or gluten, a circumstance which must depend upon a difference in their chemical constitution. We also know that the same kind of aliment is differently acted on by the gastric juice of different individuals; but this may probably depend upon some variation in the nature of the gastric juice itself, and is therefore to be referred to a different principle. Disregarding, however, for the present what may appear only exceptions to the general rule, we must inquire into the nature of the sub- stance which is found, under ordinary circum- stances, in the proper digestive stomach, after it has experienced the full operation of the gastric juice. Although many observations have been made upon the pultaceous mass which is thus produced, our information re- specting it is not very precise ; we are told little more than that the texture, odour, and flavour of the food employed are no longer perceptible, and it is said to have slightly acid properties, or rather to be disposed to pass into the acetous fermentation. As we remarked above, the change which the food undergoes is to be regarded as the result of chemical action, where not merely the mechanical texture and the physical properties of the substance are changed, but where it has acquired new chemi- cal relations. This conclusion is deduced from a number of very interesting experiments, which were performed successively by Reaumur, Stevens, and Spallanzani, and which consisted in insert- ing different kinds of alimentary matter into perforated tubes or balls, or inclosing them in pieces of porous cloth. These were introduced into the stomach, and after some time were re- moved from it and examined, when it was found that the inclosed substances bad under- gone more or less completely the process of chymification, while the enclosing body was * Haller, El. Phys. xix. 4, 31 ; see the remarks of Tiedemann and Gmelin in the third section of their researches. DIGESTION. not acted upon, thus proving decisively that the effect was not produced by a mere mecha- nical operation.* The results of these experi- ments have been confirmed by some remark- able facts, which bear still more directly upon the point under investigation, where certain in- dividuals have had preternatural openings made into the stomach, either from accident or dis- ease, while the functions of the part appear to have been but little, if at all, impaired. By this means the operation that is going forwards in this organ may be minutely watched in all its various stages, and we are enabled to ob- serve the change which the food undergoes from the time that it enters the stomach until it passes from the pylorus, and to compare the changes which the different kinds of food ex- perience during the progress of the whole mass. A case of this kind is related by Circaud, where an individual lived many years with a fistulous opening into the stomach ;f but a much more remarkable case of the same de- scription has been lately communicated by Dr. Beaumont. The individual in question was wounded, early in life, by a shot in the epigas- tric region, which perforated the stomach. After some time the wounded part healed, with the exception of an aperture two and a half inches in diameter, which communicated with the stomach. He lived many years in this state, in perfect health and vigour, so as to be capable of following a laborious occupation, while the fistulous opening still remained. Under these circumstances he was made the subject of experiment by Dr. Beaumont, who for the space of eight years continued his ob- servations, with great assiduity and minuteness, on the action of the stomach both in its ordi- nary state, and when subjected to different con- ditions, for the immediate purpose of the expe- riment. We may remark generally, that the results of the experiments confirm those of Spallanzaui in their most essential particulars, and at the same time enable us to decide upon some points which were left imperfect by that naturalist. j Among the more important points respecting the formation of chyme, which appear to be confirmed by the experiments of Dr. Beau- mont, are the following; that the different kinds of aliment all require to undergo the same process, by means of the gastric fluid, in order to be reduced into chyme ; that the rapidity of the process differs considerably according to the delicacy of their natural tex- ture or the degree of their mechanical division ; that the saliva is of no specific use in the con- version of aliment into chyme; that animal substances are more easily converted into chyme than vegetables; and that oily sub- stances, although they contain a large quantity * Reaumur, Med. Acad, pour 1752, p. 266 et seq. and p. 461 ec seq. ; Stevens, De Alim. Concoct, cap.xii. ex. 1 ... 9 and 11 . . .23; Spallanzani, Exper. sur la Digest, passim ; Blumenbach, Inst. Physiol. §358,9; Monro (Tert.) Elem. v. i. p.532. t Journ. de Phys. t. liii. p. 156, 7. t Beaumont on the Gastric Juice and on Diges- tion, sect. 1, 5. VOL. II. 17 of nutriment, are comparatively difficult of digestion.* We must next inquire into the physical and chemical properties of the gastric juice, the fluid secreted from the interior of the stomach, by which the change in the aliment, that we have been describing, is produced. Since the publication of Reaumur’s experiments, about the middle of the last century, the general opinion among physiologists and chemists has been, that the gastric juice possesses specific properties, which enable it to dissolve or com- bine with the aliment ; and many experiments have been performed for the purpose of ascer- taining the chemical nature of the secretion, so as to account for the powerful action which it appears to possess over such a great variety of substances. Besides the more general ac- count which we have of the gastric juice by Boerhaave, Haller, and Reaumur, f it was made the subject of an elaborate series of expe- riments by Spallanzani it was also analyzed by Scopoli§ and by Carminati,|| and has been lately examined by Dr. Prout,5r and by MM. Tiedemann and Gmelin.** The result is, upon the whole, rather unsatisfactory, or at least it may be said, that nothing has been detected in the fluid, which seems to account for or explain the powerful action which it exercises on the alimentary substances subjected to its influence.ff All that we learn is, that the gastric juice contains certain saline substances in small quantity, more especially the muriate of soda, in common with the other animal fluids, but that it does not differ essentially, in its chemical properties, from saliva, or from the secretions of mucous membranes gene- rally. Dr. Prout indeed informs us, that a quantity of muriatic acid is always present in the stomach during digestion but as there does not seem to be any decisive evidence of its appearance previously to the introduction of the food into the stomach, we ought probably rather to consider it as developed by the pro- cess of digestion, than as entering into the constitution of the gastric juice; nor indeed, if it were so, are we able to explain the mode in which it operates in converting aliment into chyme.§§ This apparent difficulty in account- ing for the mode in which chyme is formed by the gastric juice, and the supposed inadequacy * Beaumont, page 275 . . 8 et alibi. f Boerhaave, Prselect. § 77 et seq. ; Haller, El. Phys. xix. 1. 15. et 4. 20; Reaumur, Mem. Acad, pour 1752, p. 480, 495. t Ut supra, § 81 et seq. 145, 185, 192. § In Spallanzani, § 244. || Jour. Phys. t. xxiv. p. 168 et seq. Ann. Phil. v. xiii. p. 13. ** Recherches sur la Digestion, trad, par Jour- dan. ff Henry’s Chem. v. ii. p. 410, 1. ft Phil. Trans, for 1824, p. 45 et seq. §§ The presence of acid in the stomach, in its healthy state, has been made the subject of in- quiry by many experimentalists, and of much con- troversy ; the result is that the older physiologists generally denied its existence, except in morbid states of the stomach, while many of the most eminent modern physiologists believe it to be always present, and indeed regard it as an essem c 18 DIGESTION. of the agent to this purpose, has led to many singular theoretical opinions, which will be noticed in a subsequent part of this article* But in whatever way, or upon whatever principle we may explain the action of the gastric fluid upon the aliment, we are irre- sistibly led to the conclusion, that it is the physical agent which produces the effect, not only from those cases, where in consequence of a preternatural opening into the stomach we are able to observe the actual phenomena of digestion, but stdl more so, by the expe- riments on what has been termed artificial di- gestion, especially those of Spallanzani and Beaumont, where the gastric juice has been procured, and applied out of the stomach, and where the process of chymification has proceeded, as nearly resembling that in the stomach itself as might reasonably be ex- pected, considering the unavoidable imper- fection of the experiment. This imperfection respects both the mode of obtaining the gastric juice itself, and the mode of applying it to the aliment. We reduce the action of the stomach into somewhat of an unnatural con- dition in order to procure the secretion, and in the application of it we are deprived of the contractile motion of the organ ; yet, not- withstanding these unavoidable circumstances, the substances were reduced to a state very considerably resembling that of chyme. That this change was not produced by a mere me- chanical action is proved by the circumstance, that the change in the substances operated on bore no proportion to the hardness of their texture or other physical properties. Thus we find that the gastric fluid acts upon dense membrane, and in some cases, even upon bone, while there are other substances, of a very delicate texture, which are not affected by it. This kind of selection of certain sub- stances in preference to others bears so close an analogy to the operation of chemical affinity, that we ought not to refuse our assent to the idea of their belonging to the same class of tial agent in the process. From the first part of this remark we must, however, except Vanhelmont and Willis; Ortus Med. p. 164. .7 et alibi ; De Ferment, op. t. i. p. 25. See Haller in Boerhaave, Praeleet. not. ad j 77, and El. Phys. xix. 1. 15, and 4. 29 ; Fordyce, p. 150, 1 ; Spallanzani, § 239 . . 245; Hunter, p. 293 et seq. ; Circaud, ut supra; Dumas, El. Phys. t. i. p. 278 . . 0 ; Tiede- mann et Gmelin, Recherches, t. i. p. 166, 7. It may be proper to remark that Leuret and Lassaigne do not admit of the presence of this acid ; they, on the contrary, suppose that the gastric juice owes its acid properties to the lactic acid ; Recherches Physiol, et Chimiques, p. 114. .7; Dr. Prout has, however, as we conceive, satisfac- torily answered their objections to his experiments ; Ann. Phil. v. xii. p. 406. Dr. Carswell considers acidity to be the essential and active property of the gastric juice ; Pathol. Anat. fas. 5. * Montegre has lately performed a series of ex- periments, the results of which lead him to deny the specific action of the gastric juice ; Exper. sur la Digestion, p. 43, 4. But, notwithstanding the apparent accuracy with which they were conducted, we cannot but suspect some source of error, seeing how much they are at variance with all our other information on the subject. actions, although it occurs under circum- stances where we might not have expected to find it. There are two other properties of the gastric juice, besides its solvent power, which are at least as difficult to account for, but of which we seem to have very complete evidence, — - its property of coagulating albumen, and that of preventing putrefaction. It is the former of these properties which we employ in mak- ing cheese, cheese being essentially the albu- minous part of milk, coagulated by means of what is termed rennet, a fluid consisting of the infusion of the digestive stomach of the calf. This is unequivocally a chemical change, yet it is very difficult to explain it upon any che- mical principle, i. e. to refer this individual case to any series of facts, with which it can be connected.* We can only say in this instance, as in so many others in the physical sciences, that although the fact is clearly ascertained, its efficient cause still remains doubtful. We are compelled to make the same re- mark with regard to the other property of the gastric juice, to which we have referred above, its antiseptic power. Of the fact, however, we are well assured, both as occurring in the natural process of digestion, and in the expe- riments that have been made out of the body. It is not uncommon for carnivorous animals to take their food in a half putrid state, when it is found that the first action of the gastric juice is to remove the foetor; and an effect of precisely the same kind was noticed by Spal- lanzani in his experiments.f Here again we have a chemical change, the nature of which we cannot explain ; it is, however, a circum- stance which may appear less remarkable, with respect to the subject now under consideration, because the action of antiseptics generally is one which we find it difficult to refer to any general principles. Respecting the process of chymification it only remains for us to remark, that the con- tractile action of the stomach is admirably fitted to aid the chemical action of the secreted fluids; the vermicular motion of the organ has the effect of keeping the whole of its contents in a gradual state of progression from the cardia to the pylorus, while, at the same time, each individual portion of the aliment is com- pletely mixed together, and brought into the * This difficulty appears to be increased by the amount of effect which is produced by the very small quantity of the agent; Fordyce informs us, that a very few grains of the inner coat of the stomach, a very small proportion of which must have consisted of the secretion, was capable, when infused in water, of coagulating more than one hundred parts of milk; p. 57,9; 176 et seq.; Prout, Ann. Phil. v. xiii. p. 13 et seq. t Exper. § 250.. 2 et alibi ; see also Hunter on the Anim. CEcon. p. 204. Montegre does not admit of this property, and would appear to doubt also of the coagulating power of the gastric juice, p. 21 et alibi ; the same opinion is also maintained by Dr. Thackrah, lect. p. 14; but it would require a very powerful series of negative facts to controvert the strong evidence that we possess on this subject. DIGESTION. 19 proper state for being received into the duode- num. The undulatory motion of the stomach is more especially effected by the circular fibres, while the longitudinal fibres are more effective in the progressive motion of its contents from the cardia to the pylorus. The alimentary mass is now to undergo the last of the three changes to which we referred above, its conversion from chyme into chyle. These substances are obviously different from each other in their sensible properties, but respecting the exact nature of this difference, the change which they experience, or the mode in which it is produced, we have little certain information. The fact appears to be, that as soon as the uniform pultaceous mass, which composes the chyme, enters the duodenum, it begins to separate into two parts, a white creamy substance, which constitutes the chyle, and a residuary mass, which is gradually con- verted into faeces, and is propelled along the course of the intestine, in order to be finally expelled from the system.* * * § Although no point in physiology appears to be more clearly as- certained than that chyle, properly so called, is never found in the stomach, and that the duodenum is the appropriate organ for its pro- duction, yet owing partly to the inaccurate mode in which the terms have been employed, and partly to the inaccuracy of our obser- vation, some writers, even in our own times, f have spoken of chyle as being formed in the stomach, and have conceived that the only change which was effected in the duodenum was the separation of the chyle from the re- mainder of the mass.J With respect to the mode in which this change is brought about, or the agent by which it is effected, we have little to offer except con- jecture. The secretions of the liver and the pancreas are, each of them, conveyed into the duodenum, and it has been stated that the completion of the chyle takes place exactly at the part where the bile and the pancreatic juice enter into the intestines. Of this, however, we do not possess any direct evidence, and the fact, that in certain cases of disease or mal- formation, the process of chylification has gone on, nearly in its ordinary course, although the fluids in question have not been transmitted into the intestine, § appears to furnish a de- * Prout, ut supra, v. xiii. p. 12 et alibi. The difference between chyme and chyle, as well as the different organs in which they are elaborated, was well known to some of the older writers, although not acknowledged ; see Juncker, Conspect. Physiol, tab. 11 et 25; Vanhelmont, Ortus Med. p. 167, 8, and Baglivi, Diss. 3. circa bilem. t Home, in Phil. Trans, for 1807, p. 88, 9. t On this subject the reader is referred to the following works : Boerhaave, Praelect. § 90 . . 5 ; Haller, ibid, in notis, Prim. Lin. § 635 . . 8 et alibi, and El. Phys. xviii. 4. 24, 31 et xxiv. 2. 1 ; Hunter, Anim. CEcon. p. 213 ; Fordyce, ut supra, passim ; Bell’s Anat. v. iv. p. 65 et seq. ; Monro's (Tert.) Elem. v. i. p. 552; Richerand, El. Physiol. § 11, 25. § The experiments of Sir B. Brodie, in which the formation of chyle appears to have been sus- pended by tying the biliary duct, although inte- cisive objection to the hypothesis. Some phy- siologists have conceived that the duodenum itself secretes a specific fluid, analogous to that in the stomach, by which the process of chylification is effected ; but we have no evi- dence of the existence of this fluid, except the supposed necessity to explain the effects that are produced. In this deficiency of direct evi- dence we appear to be reduced to the sup- position, that the conversion of chyme into chyle is effected partly by the mutual action of its constituent elements on each other, aided perhaps, in some degree, by the intervention of the bile and the pancreatic juice.* We have various analyses of chyle, which appear to have been made with sufficient accu- racy. It is a white opaque substance, re- sembling cream in its appearance and phy- sical properties. When removed from the body, it shows a tendency to concrete and undergoes a change considerably resembling the coagulation of the blood, by which it se- parates into two parts, a dense white coagulum, and a transparent colourless fluid, analogous respectively to crassamentum and to serum. The chemical properties of chyle appear very similar to those of the blood, and it also re- sembles blood in the nature of its saline con- tents; but it differs from it in containing a portion of oil as one of its essential consti- tuents, while in the blood oil is only an occa- sional, and probably a morbid ingredient. f The chemical analysis of chyle was first made by Vauquelin, who employed for this purpose the contents of the thoracic duct and large lacteals of a horse. The coagulum from the duct was observed to be of a light pink colour, while the corresponding part from the lacteals was nearly white ; but it is not ascer- tained how far this difference of colour de- pended upon an accidental occurrence, or whether it is to be regarded as a uniform cir- cumstance. The coagulum contained a sub- stance which bore a considerable resemblance to fi brine, or perhaps more correctly possessed properties intermediate between fibrine and albumen. The liquid part of the chyle was found to be very similar to the serum of the blood, differing from it only in containing a quantity of an oily or fatty substance; like serum it exhibited marks of an uncombined alcali.j resting and important, cannot be regarded as con- clusive, until we are more minutely informed of every circumstance connected with them ; Quart. Journ. v. xiv. p. 341 et seq. * Dr. Prout conceives, that the bile is the prin- cipal agent in this process ; and that when it is added to the contents of the duodenum, it separates the chyle by a kind of precipitation ; it does not, however, appear very clearly what is the exact nature of the chemical action which takes place. f Fordyce, p. 121; Young’s Med. Lit. p. 516 ; Dumas, t. i. p. 379 . . 1 ; Magendie, t. ii. p. 154.. 8. Some late experiments appear indeed to prove that a certain quantity of an oily matter is always present in the blood ; but the proportion in the chyle is.at least very much more considerable. J Ann. Chim. t. Ixxxi. p. 113 et seq.; Ann. Phil, v. ii. p. 220 et seq. We have some experiments on chyle by Emmert, previous to those of Vauque- C 2 20 DIGESTION. The next experiments which we possess are those of Marcet, who operated upon the chyle as procured from dogs. One main object of his researches was to ascertain how far chyle of animal origin differs from that from vege- tables, and he had the food of the dogs regu- lated accordingly. His results with regard to the general nature and properties of chyle cor- respond very exactly with those of Vauquelin. lie found the coagulum to have a pink colour, and to contain a fibrous or filamentous sub- stance, while the liquid part contained a quan- tity of an oily matter, which floated on its surface like cream. This oily matter appeared, however, to be confined to the animal chyle, and it is remarked generally, that this bore more resemblance to blood than the chyle from vegetables. They contained the same saline ingredients, but the solid residuum of the animal chyle was considerably greater; and as the vegetable chyle, when submitted to destructive distillation, was found to contain much more carbon, it was inferred that the animal chyle must have contained proportion- ably more hydrogen and nitrogen.'*' Upon these experiments we may remark, that the difference between the animal and the vege- table chyle in this case might perhaps depend in some degree upon vegetable food being less adapted to the digestive organs of the dog ; because the chyle of the horse, as examined by Vauquelin, appeared to be more completely animalized, although it must have been derived from vegetable diet. The experiments of Dr. Prout agreed gene- rally with those of Vauquelin and Marcet; he found the coagulum and the fluid part analogous to the two components of the blood, and he likewise observed the oily matter. He compared the chyle derived from animal, with that from vegetable food, and detected the oil in both of them, and, upon the whole, he found them to differ less than was supposed by Marcet ; he remarks, however, that the latter contains more water and less albuminous matter than the former.-t We were likewise indebted to Dr. Prout for an interesting ac- count of the successive changes which the chyle experiences, from its entrance into the iacteals, until it is finally deposited in the thoracic duct, its gradual conversion into blood corresponding to the progress along the vessels.]; While the alimentary mass passes through the small intestines, the chyle, as it is separated from it, is taken up by the Iacteals, so that when it arrives at the large intestines, nothing remains but the residuary matter, whch is to be discharged from the system; this consti- lin, but they do not contain much precise informa- tion ; Ann. Chim. t. lxxx. p. 81 et seq. * Med. Chir. Trans, v. vi. p. 618 et seq. f In some late experiments which were per- formed by MM. Macaire and F. Marcet, on the origin of nitrogen in animals, they analyzed the two species of chyle, and found them to be nearly the same in their chemical composition, and espe- cially in respect to the quantity of nitrogen which they contained ; Ann. Chim. t. li. p. 371. t Ann. Phil, v, xiii. p. 22.. 5. See also Magendie, Physiol, t. ii. p. 154. . 8. tutes what has been termed the process of defecation. There can be no doubt that the principal and primary use of the large in- testines is to serve as a depository for this residuary mass, yet there are certain circum- stances in their anatomical and physiological structure, which might render it probable that some farther purpose is served by them than the mere retention of the feces. Dr. Prout, who has minutely examined the successive changes which the contents of the intestinal canal experience, observes that the secretions even of the rectum still possess the property of coagulating milk, which we noticed above as being one of the most distinguishing cha- racters of the digestive system, so that it would seem that these organs, in some way or other, still assist in the process of nutrition. We may presume, however, that this is only a secondary object, and that the primary use of the large intestines is to serve as a reservoir, in which the fecal mass might be retained, in order to be evacuated at certain intervals only* (See Intestinal Canal.) Before we dismiss this part of our subject, it may be proper to make a few remarks upon two of the abdominal viscera, which, from their anatomical position and their physiological rela- tions, are generally classed among the chylopoi- etic organs, as being supposed to contribute to the function of digestion ; these are the pancreas and the spleen. The pancreas bears a very near resemblance to the salivary glands of the mouth and fauces, both from its intimate structure and from the nature of its secretions, and it has been presumed, that it acts in the same manner upon the aliment;! it must, however, be admitted that we have little but analogy or conjecture in favour of this opinion. The spleen is an organ which, both from its size, its situation, and the number of blood- vessels belonging to it, has been supposed to serve some important purpose in the animal economy, and from its apparent connexion with the stomach to be, in some way, concerned in the process of digestion. But although many % Prout, ut supra, p. 15 . . 22 ; see also Soem- mering, Corp. Hum. Fab. t. vi. § 241. We do not perceive that there is any foundation for the hy- pothesis of Sir E. Home, that the colon is the organ in which the adipose matter is produced, lect. v. i. p. 468 et seq. and Phil. Trans, for 1821, p. 34. Dr. O’Beirne has lately published an essay on the process of defamation, to which we shall refer our readers, as containing some new views on the subject. We are indebted to Berzelius for an ana- lysis of the fames, which appears more minute than any that had been previously made. t For an account of the pancreas and its secre- tions we may refer to De Graaf, Tract. Anat. Med. as the first correct treatise on the subject ; to Boer- haave, Prtelect. § 101, cum notis ; Haller, Prim. Lin. cap. 22. and El. Phys. xxii. ; Scemmering, Corp. Hum. Fab. t. vi. p. 142.. 8; lordyce, ut supra, p. 70.. 2; Blumenbach, Inst. Physiol. $ 24 ; Santorini, tab. 13. fig. 1. Tiedemann and Gmelin- have given us the result of their examina- tion of the pancreatic juice, from which they con- clude that it differs in some respects from the saliva; Recherches, t. i. p.41,2. Leuret ana Lassaigne, on the contrary, suppose these secre- tions to be very nearly identical ; Recherches, p. 49 et seq. DIGESTION. 21 hypotheses and conjeotures have been formed on the subject, there is none which seems to have obtained any credit with physiologists, or indeed to be entitled to much consideration.* * * § The latest researches on the subject are those of Home, and of Tiedemann and Gmelin. Home examined the structure of the spleen, and, as the result of his investigation, informs us that it consists entirely of a congeries of bloodvessels and absorbents, and that there are interstices between the vessels into which the blood is effused, through certain natural orifices in the veins, when they are much distended. The conclusion which he forms respecting the use of the spleen is, that it is a reservoir for any super- fluous matter, which may exist in the stomach, after the process of digestion is completed, which is not carried off by the intestines, as serum, lymph, globules, and mucus; that these are conveyed to the spleen by certain communi- cating vessels, and are removed from it, partly by the veins and partly by the absorbents.f The account of the structure of the spleen which is given us by Tiedemann and Gmelin is considerably different from that of Home. They inform us that it essentially resembles that of the lymphatic glands, and they conceive that it is to be regarded as an appendage to the lymphatic system. They suppose its specific function to be the secretion of a fluid which is conveyed to the thoracic duct, and being united with the chyle, converts it into blood .J There are many circumstances which render it pro- bable that the spleen, in some way or other, promotes sanguification, and we have some reason to believe, that there is an immediate and a ready communication between its arterial and its absorbent systems, but we conceive that the hypothesis must still be regarded rather as a plausible conjecture, than as a deduction from facts. There is moreover a circumstance which must not be overlooked in our speculations respecting the spleen, that we have some well authenticated cases, where it has been either originally wanting, or has been removed from the body without apparent injury .§ This argu- ment cannot, however, be considered as decisive, because it is well known, that in consequence of the extraordinary compensating powers of the system, certain organs may be occasionally dis- pensed with, which, under ordinary circumstan- * See Haller, El. Phys. lib. xxi. ; Soemmering, t. vi. p. 149 et seq. t Phil. Trans, for 1808, p. 45 et seq. and p. 133 et seq,, and for 1821, p. 35 et seq. pi. 3. .8, t We have an ample and apparently correct ab- stract of the memoir of Tiedemann and Gmelin in the Ed. Med. Jotirn. v. xviii. p. 285 et seq. See also on this subject Elliotson’s Physiol, p. 108 et seq. ; also an essay by Dr. Hodgkin, appended to his translation of Edwards’s physiological work. § Baillie’s Morbid Anat., p. 260, 1 ; works, by Wardrop, v. ii. p. 235. [Dupuytren observed an in- creased voracity in dogs from which the spleen had been removed. — Assolant, Dissertation du Kate ; and Mayo has in two instances remarked a considerable obesity in dogs after the removal of the spleen, but does not say whether this may not be attribu- table to the increase in the quantity of their food. In both instances the duration of the obesity was for l«ss than a year. Mayo’s Pathol, vol. i. — Ed.] ces, appear the most essential to its existence and welfare. We may therefore conclude with respect to the pancreas and the spleen, that although there is reason to suppose that they contribute, in some way, to the function of di- gestion, we are still unable to ascertain the pre- cise mode in which they conduce to this end. Before we dismiss this part of our subject, it will be necessary to make a few observations upon a question, which has been proposed in relation to the digestive process, whether any part of the aliment passes through the stomach, and is taken up by the absorbents, without de- composition. It is obvious that this cannot be the case with vegetable substances of any des- cription, and with respect to substances of ani- mal origin, that form a part of the diet, although they approach so much nearer to the nature of chyle, yet it appears that they are not entirely identical with it, and that they must conse- quently be decomposed and assimilated to the general mass, before they can serve for the pur- poses of nutrition. There are indeed certain substances, that are received into the stomach, which would appear to form exceptions to this general principle ; these are the various saline substances, which are found in all organized bodies, as well as some others, which give their appropriate odours and flavours to the food, and also certain medical agents. There are some salts, which appear to constitute an essential part of the blood and other animal fluids, and as the same salts are introduced into the sto- mach with the food, we may conceive that they pass unchanged into the vessels. There are likewise certain substances which give their specific odour to the milk, and to other secre- tions and excretions, proving that they likewise pass into the circulating system without suffer- ing decomposition, and the same is the case with some of the medicaments.* IV. Theory of digestion. — We now enter upon the fourth branch of our inquiry, the mode in which we are to explain the action of the di- gestive organs upon the aliment. This has been one of the most fertile sources of conjecture and speculation from the earliest period, from Hip- pocrates down to our own times, and the ques- tion is one respecting which the greatest differ- ence of opinion still exists among the most intelligent physiologists f We shall not think it necessary to notice the opinions of the older writers, which were necessarily formed from very insufficient data, but shall select those hy- potheses which appear deserving of more par- ticular attention, either as havingbeen supported by men of acknowledged eminence, or as * See the remarks of Fordyce, p. 122, 3 ; the results of the experiments that have been made on this point are somewhat contradictory ; but upon the whole there seems no doubt that, under certain circumstances, various extraneous substances may be taken up by the absorbents and recognized in the blood and other fluids. See Bostock’s Physiol, v. ii. p. 569, 0, note. t For an account of the doctrines maintained by the earlier physiologists, the reader is referred to the treatise of Fernel, De Concoctionibus, Physiol, lib. vi. cap. 6 ; Boerliaave, Prielect. not. ad § 86 ; Haller, El. Phys. xix. 4 et 5 passim ; and Blu- menbacb, Instit. Physiol. §360. 22 DIGESTION. possessing in themselves the merit of consis- tency and probability. Those which we shall select are the theories of trituration, of fermen- tation, of chemical solution, and of nervous action, under one or other of which we may comprehend all the most important speculations which have engaged the attention of modern physiologists. The hypothesis of trituration may be consi- dered as having originated with the mechanical physiologists of the seventeenth century, and was apparently supported by the curious facts, which were, at that time, more particularly brought into view and minutely ascertained, of the great force exercised by the muscular sto- machs of certain tribes of birds. The facts, although perhaps in some instances rather ex- aggerated, were sufficiently curious, but the deductions from them were incorrect, first, in extending the analogy from one class of ani- mals to other classes, where it was altogether inapplicable; and secondly, in conceiving of the trituration which takes place in these mus- cular stomachs, as constituting the proper pro- cess of digestion, whereas it is merely a preli- minary process, equivalent to mastication. The aliment, after it leaves the gizzard, is in the same state of comminution into which it is re- duced by the teeth of those animals that are provided with these organs, and is then sub- jected to the action of the proper digestive stomach, and undergoes the process of ehymi- ficalion. On this point the experiments of Stevens and Spallanzani, which were referred to above, are quite decisive; they show clearly how far the agency of mechanical action is in- strumental in the process of digestion, and they also show that some other principle is essentially necessary for its completion.* While the mathematical physiologists were thus attempting to explain the theory of diges- tion upon the principles of mechanical action, their rivals the chemists, who in every point strenuously opposed them, brought forward their hypothesis of fermentation. This was originally, at least in modern times, advanced by Vanhelmont, and was embraced by a large part of his contemporaries and successors.! it may indeed be considered as having been, for some time, the prevailing theory ; a circum- stance which we may ascribe, partly to the comprehensive, or rather the indeterminate sense in which the term was employed, and partly from the actual phenomena attending the process, which were more easily referable to this operation than to any other which was then recognized. For an account of the effects of trituration, e given by some of the older physiologists, the reE der is more particularly referred to the \vork9 c I iieairn, who was one of the most learned men ( his time; Dissert, p, 72. .95; Elem. cap,v. p. 25. .7 see also Haller, El. Phys. xix. 5. 1; Hales Statical Essays, v. ii. p, 174, 5; C'heselden’s Ana p. 152..5; Fordyce, ut supra, p. 124.. 138 : an Richerand, Physiol. § 18. t See particularly his singular treatise entitle oextuplex Digestio alimenti humani,” where together, with much mysticism and false reasoning we find many acute remarks and some curious in formation. The merits, or rather the truth of this hypo- thesis rests, in some degree, upon the defini- tion of the term fermentation, or the mode in which it was employed by the writers of that period. As far as we can understand their meaning, and perhaps we may even say, as far as they themselves attached any definite idea to their own expressions, they ascribed to this process every change which the constituents of the body undergo by their action upon each other. Fermentation was therefore the cause of the morbid changes which the system expe- riences, as well as of its natural actions ; it was equally the cause of fever and inflammation, as of secretion and digestion ; and so far was this theory pushed, that even muscular contraction and nervous sensation were referred to certain fermentative processes. As our ideas on this subject became more correct, in consequence of the extension of our information, our language became more precise. The change which cer- tain vegetable infusions undergo in the forma- tion of alcohol was assumed as the type of this class of actions ; the controversy then took a new aspect, and the question at issue was, whether the change of aliment into chyme and afterwards into chyle ought to be referred to the same class of operations with that by which sugar and mucilage are converted into alcohol. This question we shall be more able to answer satisfactorily when we have taken a view of the next hypothesis, that of chemical solution. The doctrine of chemical solution, as applied to the action of the stomach upoD the aliment received into it, is, in many respects, very similar to that of fermentation, depending, as will be seen, partly upon the definition of the terms employed, and partly upon the minute obser- vation of the various steps of the process. The hypothesis owes its origin to the experiments of Reaumur, and was very much confirmed by those of Stevens and Spallanzani, so often referred to, and especially those of the latter experimen- talist, where chynufication was produced out of the body, simply by exposing the various species of aliment to the gastric juice obtained from the stomach, in a proper temperature, and under circumstances, as nearly as possible, re- sembling those of the natural digestion.* Making a due allowance for the unavoidable causes of interference, the results maybe regard- ed as satisfactory, aDd they clearly prove one part of the hypothesis, that the vital operation of the stomach consists merely in providing the agent, and in bringing the alimentary substan- ces within the sphere of its action. This con- clusion is still farther sanctioned by the power of the gastric juice in suspending or correcting putrefaction, and in coagulating milk, both which properties are observed in experiments made out of the body, apparently in as great a degree as in the stomach itself, and which can only be referred to the chemical relations of the substances employed. These considerations must be allowed to be very favourable to the hypothesis of chemical solution, but still there are many very serious difficulties which we have to encounter, before we can regard it as * We may remark that the experiments of Dr, Beaumont lead us to the same conclusion. DIGESTION. 23 fully established. Of these the most import- ant is the objection, which has been frequently urged against it, and has perhaps never been satisfactorily repelled, that it is contrary to the ordinary operations of chemical action for the same agent to be able to reduce the various and heterogeneous matters that are taken into the stomach into a uniform and homogeneous mass, and this difficulty is further increased, when we perceive this powerful effect to be produced by a substance possessed of properties apparently so little active as the gastric juice.* These objections, and others of an analogous nature, have appeared to many of the most emi- nent modern physiologists to press so powerfully upon any hypothesis of digestion which is derived from either mechanical or chemical principles, that they have conceived it necessary to abandon altogether this mode of reasoning, and have referred it entirely to the direct action of what has been termed the vital principle. It is assumed that the internal coat of the stomach is endowed with a specific property, peculiar to itself, and essentially different from any merely physical agency, by which it acts upon the food and reduces it to the state of chyme. This vital property of the stomach is supposed to be proved, both by the necessity of having recourse to this kind of power, in consequence of the in- adequacy of the ordinary properties of matter, and to be farther confirmed by certain facts that have been supposed to prove that the same substance is differently affected by the gastric juice, merely in consequence of the absence or presence of this principle. Thus it has been observed, that in cases of sudden death, the stomach itself has been partially digested by the gastric juice that was secreted during life,ff and * Tiedemann and Gmelin, as the result of their elaborate experimental researches into the nature of the digestive process, conclude that it consists essentially in the solution of the aliment by the gastric juice. Water alone, they observe, at the tem- perature of the mammalia, is capable of dissolving many of the articles employed in diet, and many which are not soluble in water are so in the acids which are found in the stomach, and to these they are disposed to refer a considerable part of the operation; Reeherches, t. i. p. 363..7. We may, however, remark, that a solution of the alimentary matters in water, or even in the acids that exist in the stomach, cannot be supposed to be identical with chyme. t This curious fact, which was first announced by Hunter, Phil. Trans, for 1772, p. 447 et seq., and afterwards more fully detailed in his Observ. on the Anim. CEcon. p. 226. ..1, has since been fully con- firmed by the observations of some of the most emi- nent modern anatomists. See particularly Baillie’s Morb. Anat. ch. 7. p. 148, 9, and works by War- drop, v. ii. p. 136, 7, and engrav. to Morb. Anat. fas. 3. pi. 7. fig. 2. ; Beck’s Med. Jurisp. by Dunlop, p. 376. .380 contains many references and good remarks. We have a valuable paper on the subject by Dr. Gairdner, Ed. Med. Chir. Trans, v. i. p. 311 et seq. and also by Dr. Carswell, Ed. Med. Jour. v. xxxiv. p. 282 et seq. ; also Archives de Med. Eev. 1830, and Amer. Jour. Med. Sc. v. vii. p. 227. .9. In the Cambridge Phil. Trans, v. i. p. 287 etseq., we have a case of this description by Dr. Haviland. Dr. Carswell has given an accurate and ample account of the appearances and effects produced by the gastric juice on the stomach, in the fifth number of his Pathol. Anat. ; it is accompanied by two excellent plates. upon this principle it has been found, that cer- tain kinds of worms, which exist in the diges- tive organs of animals, are not affected by the gastric juice as long as they remain alive, but that after death they become subject to its action. This hypothesis of the vital principle is the one which was supported by Fordyce in his elaborate treatise, and is probably that which, under certain modifications, may be regarded as the prevailing opinion of the modern physiolo- gists. To a certain extent it is correct, and the position on which it is founded, that the living body differs essentially in its powers and pro- perties from the dead body, cannot be denied. But it may still be questioned, whether the ex- planation thus offered be not rather verbal than real, or whether any actual explanation is afforded of the phenomena, or any actual diffi- culty removed by adopting this mode of ex- pression. Every one admits that a living sto- mach differs from one that is deprived of life, but still it remains for us to point out in what this difference consists ; is it a chemical or a mechanical action ? or if it be not referable to either of these actions, to what general principle can it be referred ? It is contrary to the rules of sound reasoning to invent a new agent for the urgency of the individual case, until we are able to demonstrate the absolute impossibility of employing those which were previously recognized. With respect therefore to the hypothesis of the vital principle, as maintained- by Fordyce and many of the modern physiolo- gists, we should say, that it is rather a verbal than a real explanation of the phenomena, and that it rather evades the objections than answers them. The last hypothesis of digestion which we proposed to notice, that of nervous action, although somewhat allied to the one which we have last examined, is more precise and defi- nite in its statement, and consequently more entitled to our consideration. It assumes, that the process of digestion depends upon the direct and immediate agency of the nervous system. It is founded upon the anatomical fact of the mode in which the stomach is con- nected with the nervous system, and upon the observed relations between those causes that act through the medium of this system, and the changes that take place in the action of the stomach. With respect to the anatomical ar- gument it has been urged, that there is no organ of the body, which is provided with such a number of nerves, proceeding from so many sources, and connected in so direct a way with the cerebral system. There are equally remarkable circumstances of a physiological and pathological nature, which prove the inti- mate connection between the nervous system and the action of the stomach. Not only does the stomach partake of almost every change that occurs, in any part of the corporeal frame, either natural or morbid, in a way which we must conceive can only be brought about through the intervention of the nervous sys- tem, but it is affected by our mental emo- tions, and that probably in a greater degree than any other ot our organs, except those that 24 DIGESTION. are immediately connected with the external senses. Its functions are excited or depressed by various causes, which can only act through the medium of the mind or imagination; while it is argued that in all cases its various condi- tions and the changes which its functions expe- rience can be referred to no cause, except to corresponding changes in the nervous system.* This hypothesis, like that of the vital prin- ciple, has been supported by the consideration of the inadequacy of all the other modes of explaining the phenomena, and the impossi- bility of referring them either to mechanical or to chemical principles. Butithas this clear and decided advantage, that it rests upon the co-operation of an actual agent of great and acknowledged power, one the existence of which is universally recognized, the only ques- tion being whether it is applicable to this indi- vidual case. But although we admit the facts in their full force, we must still demur to the conclusions that must be deduced from them. If we inquire upon what principle, or by what medium the nervous system can operate on the digestive functions, two modes present them- selves to the mind. We may ascribe the effect either to the general operation of the nervous energy, whatever this may be, which pervades every part of the system, and the stomach among the rest, and which gives it those powers which distinguish living from dead matter; or we may conceive that the ner- vous system is, in some way, more especially concerned in the production of the gastric juice, and that consequently whatever tends to decrease or diminish the nervous energy, may operate in the increased or diminished produc- tion of this secretion, and thus indirectly, al- though necessarily, affect the digestive func- tion. But although we may admit the truth of both these suppositions, we gain no specific answer to our inquiry. It is not enough to be informed that the stomach acts upon its con- tents because it is alive, or that whatever pre- vents the secretion of the gastric juice puts a stop to the digestion. Our inquiry embraces a farther object, and leads us to investigate the nature of the connexion between these facts and the ultimate effect produced, or to discover the reason why certain acknowledged effects are connected with certain acknowledged causes; but to this question the nervous hypothesis gives us no satisfactory answer. It indeed rather involves the theory of secretion than of digestion, for even were it to be clearly proved that the nervous power (whether, according to the hypothesis of Dr. Philip, we identify it with the galvanic influence, or we act the more cautious part of not attempting to explain its nature,) is the immediate agent in the forma- tion of the secretions, still we are left equally * It was on facts of this deser'plion that Vanhel- mont founded his hypothesis of the stomach being the immediate seat of the soul ; Orlus Med. p° 248, 49, 50. See also on the same subject the remarks of Hartley, on Man, v. i. p. 189, and Soemmering, § 179. ..4, who may be respectively considered as among the most accurate metaphysi- cians and anatomists of modem times. uninformed concerning the mode in which this fluid, when secreted, performs its appropriate function.* From this brief review of the different the- ories of digestion we may conclude, that the hypothesis of trituration is decidedly incorrect, and that those of the vital principle and the nervous energy do not resolve the question. We are therefore reduced to the two chemical hypotheses, which, although not without con- siderable difficulties, are not so palpably defec- tive or erroneous. In deciding between these two hypotheses it must he our first object to ascertain the exact sense in which the term fermentation was used by the older physio- logists, and how far, according to the modem use of the term, it is applicable to the phe- nomena in question. The word was originally employed in a very extensive, and, as may be supposed, in a somewhat vague manner, to designate every spontaneous change which took place between bodies that were placed in con- tact, and which generally manifested itself by the extrication of some gaseous or volatile matter. Thus all the spontaneous changes in the body, whether natural or morbid, were considered to be different kinds of fermen- tations, and many of the changes that take place among inorganic substances, as well as various processes in the laboratory, were dis- tinguished by the same appellation. As our knowledge of the nature of these processes was extended, and we were thus enabled to ascertain more correctly what was the change which was produced, our language became more correct and better defined, and the term fermentation was restricted to a spe- cific operation, in which certain proximate principles, derived from organized bodies, f act upon each other, and enter into new elementary combinations. The process is generally pro- moted by the addition of a substance called the ferment, which is employed to enable the bodies to act upon each in the first instance, although, when the action has commenced, its presence may be no longer necessary. The most familiar kind of fermentation is that by which a mixture of sugar and mucilage is con- verted into alcohol, and that by which the same substances, when exposed to the atmos- phere, and to a certain temperature, are con- verted into acetous acid. How far we are to extend the number of fermentations is a point respecting which chemists are not agreed, and indeed there appears to be no reason but that of convenience which can decide the point. We accordingly find that while Mr. Brande is disposed to restrict the term to the vinous and acetous fermentation, J others extend it to three, four, or with Dumas, § even to six processes. * We may refer our readers to the judicious re- marks of Dr. Prichard, in his Essay on the Vital Prin. sect. 8. t Some of the most eminent chemists confine the process of fermentation to the proximate principles derived from vegetables ; but this restriction is Dot universally adopted, nor does it appear to be neces- sary. f Ut supra. $ Ut supra. DIGESTION. 25 Among these, one which is the subject of daily observation is the panary, or that by which dough is converted into bread, a change which appears to come strictly under the definition, as a spontaneous action among the elementary constituents of the body, by which a substance is produced, essentially different from the one from which it was composed. Now we are disposed to think that the same principle will apply to the conversion of aliment into chyme, and that it is little more than a difference in the mode of expression, whether we say that digestion depends upon chemical action gene- rally, or upon that peculiar kind of chemical action which has been termed fermentation. The foregoing remarks apply immediately to the production of chyme, and it still remains for us to consider whether the same mode of reasoning can be applied to the further conver- sion of chyme into chyle. And it must be confessed that this part of our subject presents us with new difficulties, and that the analogy, which in the former case was imperfect, is apparently still more so, when we apply it to the action of chylification. Here we have a chemical change in the constituents, without the intervention of any assignable agent, at- tended with the production of a new substance, in consequence, as far as we can judge, of the spontaneous action of the elements upon each other, and with the separation of the substance thus formed from the remainder of the mass. But although the operation may be somewhat more complicated, and although we may find it less easy to assign an efficient cause for each step of the process, there will be found nothing contrary to the recognized effects of chemical affinity. And with respect to the question, how far these effects should be referred to the specific action of fermentation, we may remark that the result of the proper fermentative pro- cesses is to form a new product, and to sepa- rate the product thus formed from the residuary mass. Upon the whole therefore we may con- clude, that although there are many points in the chemical theory of digestion that are still unexplained and require to be further investi- gated, yet that we have no facts which directly oppose it, while the difficulties which we feel on certain points would appear to be princi- pally owing to the imperfect state of our know- ledge on the subject. V. Peculiar affections of the digestive or- gans.— We now proceed, in the last place, to offer some remarks on certain affections of the stomach and its appendages, which are only indirectly connected with the function of diges- tion. Of these the most important are hunger, thirst, and nausea; we shall consider in suc- cession the causes of each of them, and the relation which they bear to the animal economy in general. Hunger is a peculiar perception experienced in the stomach, depending on the want of food. Its final cause is obvious, but respecting its efficient cause there has been considerable difference of opinion among physiologists, some referring it to a mechanical, others to a chemical action, while by a third set of writers it is referred exclusively to a peculiar condition of the nervous system. Before we enter int© the respective merits of these opinions it will be necessary to remark concerning the feeling excited by hunger, that it is one of a specific nature, as essentially different from the mere perception of touch, as the sense of sight is from that of mechanical pressure made on the ball of the eye. In physiological language the stomach may be regarded as one of the organs of sense, in the same way with the eye and the ear; i. e. a part furnished with a spe- cific apparatus for producing specific impres- sions on a set of nerves appropriated to it, which convey to the mind certain perceptions, and which, by habit or by instinct,, we connect with certain conditions of the organ. In most cases we are able to point out distinctly the nature of the agent which produces these per- ceptions, as light when applied to the eye, and the undulations of the air to the ear ; in the particular case of the stomach we are not able to point out any corresponding agent of this description, and in so far the analogy between the stomach and the organs of sense must be considered as defective. The mechanical physiologists ascribed hun- ger to the friction of the different parts of the internal membrane of the stomach on each other, an opinion which, although sanctioned to a certain extent by Haller,* must be aban- doned, whether we regard the anatomical structure of the part, which shows that such friction is incompatible with its rounded form, and the disposition of its muscular fibres, or the nature of the sensation itself, which is specifically different from that produced by pressure, or any species of mechanical impulse on the surface of the body. Nor can the hy- pothesis be maintained, which supposes that the action of the gastric juice, by its tendency to decompose organized substances, exercises a degree of this eroding quality on the internal coat of the stomach, and thus produces the uneasy sensation. But in this hypothesis the great distinction, which has been so frequently referred to, between living and dead matter as to the action of the gastric juice is disregarded; besides that from every analogy which we pos- sess, it might be presumed that a substance so mild and apparently so little active as the gas- tric juice, could not produce effects, which must be attributed to a body possessed of highly acid or noxious qualities. And it may be fur- ther remarked, that in cases of the most pro- tracted privation of food, and where death has occurred after the most severe pangs of hunger, nothing like erosion of the stomach has been observed, and that conversely, in those in- stances where this effect has been produced after death, we have no reason to suppose that it was in any degree caused by the deficiency of food, or had been preceded by hunger. From what has been stated above it may be inferred that the view which we feel disposed to take of the efficient cause of hunger is to regal'd it as a specific perception, occasioned * Prim. Lin. § 368 ; El. Phys. xix. 2, 12. 26 DIGESTION. by a peculiar state induced on certain of the nerves of the stomach, in the same way that certain nerves of the eye and of the ear receive the impressions of light and of sound. There is, however, this difference between the two cases, that in the instance of the eye and the ear we are able to point out the agent by which the impression is made, whereas we are unable to do this with respect to the stomach.* The perception of thirst, although seated in the tongue and fauces, is so intimately con- nected with the state of the stomach, as to be properly referred to our consideration in this place. It is immediately produced by a defi- ciency of the mucous secretion of the part, and consequently must be regarded as ulti- mately depending on a peculiar condition of the glands which secrete this substance. Al- though the sensation of thirst has a less specific character than that of hunger, yet we conceive that it must be referred to a peculiar action induced upon the nerves of the part, in a way analogous to what we suppose to take place with respect to hunger, and like it depending on a peculiar action, the intimate nature of which we are unable to explain.f There are various circumstances, which differ much in their nature and origin, acting upon different parts of the system, which all concur in producing a peculiar sensation termed nausea, which is referred to the region of the stomach. It is usually attended with a considerable derangement of all the powers of the body, both muscular and nervous, and if continued, produces the effort to vomit. The act of vomit- ing consists in an inversion of the peristaltic motion of the stomach, commencing at the pylorus, which causes the contents to be carried towards the cardia, and to be forcibly ejected from the oesophagus. It has been generally supposed that the impression which produces nausea, and ultimately vomiting, is in the first instance made on the nerves of the stomach, that it is communicated by them to its muscu- lar fibres, that their action is transmitted, probably by the intervention of the nerves, to the muscles of the abdomen and to the dia- phragm, and that their contraction cooperates with the muscular coats of the stomach in the evacuation of its contents. It has long been a subject of controversy among physiologists in what degree the abdominal muscles assist the coats of the stomach, or how far the latter are * See the remarks of Blutnenbach, ut supra, §21; Magendie, Physiol, t. ii. p. 24 et seq. and art. “ Digestion,” in Diet. Sc. Med. t. ix. p. 370. .5. We have some valuable observations by Boerhaave, Prcelect. § 88. cum notis ; also by Soemmering, Covp. Hum. Fab. t. vi. § 149. .56. Haller describes the phenomena of long-continued fasting with his usual minute correctness; El Phys. xix. 2, 3. .7 ; we have some interesting cases of long-protracted abstinence in Dr. Copland’s Trans, of Richerand’s Physiol, p. 565 et seq. t For an account of the phenomena of thirst, and the explanations that have been offered of them, the reader is referred to Boerhaave, Pradect. §585 , 804; Haller, Prim. Lin. § 639; El. Phys. xix. 2, 9; Blumenbach, Physiol. § 330-2, cum notaB; Magendie, Physiol, t. ii. p. 31. .3; Elliot- son’s Physiol, p. 52. competent to produce the effect without the aid of the former. Ilaller supposed that the stomach alone is capable of evacuating its contents,* while Chirac, Duverney,f and other French physiologists conceived that this organ is entirely passive in the act of vomiting, and the same opinion has been lately maintained by Magendie, and supported by a series of direct experiments. He not only found that vomiting was entirely suspended, when the abdominal muscles and diaphragm were ren- dered incapable of acting upon the stomach, but he even informs us, that when the stomach was removed, and a bladder substituted in its place, vomiting was still induced. % But we are still disposed to believe that the commonly received doctrine is the correct one; that the action commences in the muscular fibres of the stomach, and is materially assisted by the diaphragm and abdominal muscles. We rest our opinion on the analogy of the other hollow viscera, the uterus, the bladder, and the intestines, where the contraction commences in the organ itself; on the ante- cedent probability, that as the agent whi h produces the effect is, in most cases, applied to the stomach, it must be supposed to act immediately upon it, and lastly on the mecha- nical nature of the act of vomiting, which appears to be produced rather by a sudden and forcible contraction of the organ itself, than by any external pressure exercised upon it. We conceive also that this view of the subject is confirmed by the effect that succeeds to the division of the par vagum ; it is asserted that when this nerve is divided vomiting can no longer take place, and as it is distributed principally over the stomach, so as to make it appear that this organ is its specific destination, we may presume that the incapacity for vomit- ing depends upon the loss of power in the stomach. § * El Phys. xix. 4. 12, 14; see also Lieutaud, Mem. Acad, pour 1752, p. 223 et seq. ; Sauvages, Nosol. Meth. t. ii. p. 337. t Miscel. Curios. Dec. ii. ant. 4, obs. 125, p. 247, 8, and Mem. Acad, pour 1700, hist. p. 27. Nearly the same opinion was maintained by Hun- ter, Anim. (Econ. p. 199, 0. J Mem. sur le vomissement, p. 19, 2, and Physiol, t. ii. p. 138. .40. § Bell's Anat. vol. iv. p. 54 et seq. Legallois and Beclard performed a series of experiments on this subject, which consisted in injecting into the veins a solution of emetic tartar. They particularly attended to the effect produced on the oesophagus, the diaphragm, the abdominal muscles, and the stomach itself; the conclusion which maybe de- duced from these experiments is, that vomiting cannot take place without the compression of some of the contiguous parts upon the stomach ; CEuvres de Legallois, t. ii. p. 91 et seq. Dr. Hall has lately investigated the nature of the connexion between the act of vomiting and the state of the organs of respiration. He conceives that the diaphragm is passive in the operation and that the larynx is closed, and he hence concludes that the muscles of expiration, by their sudden contraction, press upon the stomach and project its contents through the oesophagus ; Quart. Journ. We must conceive, however, that a state of nausea must be, in the first instance, induced, and this must take place through the intervention of the nerves of the DIGESTIVE CANAL. 27 With respect to the causes of nausea they may be reduced to two heads ; those that act immediately on the stomach, and those that act, in the first instance, on the system at large. Of the first class the most active in their opera- tion are the medicinal substances which are specifically styled emetics, from their peculiar tendency to produce nausea and subsequent vomiting. Besides these certain kinds of food, or food of any description, if it remain in an undigested state, and various substances of an acrid or stimulating nature frequently produce nausea and vomiting. In the second class of causes we have to enumerate various circum- stances, which act upon parts of the body, sometimes very remote from the stomach, but which, either by direct nervous communica- tion, by sympathy, or association, produce the effect in question. One of the most powerful of these is the motion of a vessel at sea, giving rise to the well-known and most distressing sensation of sea-sickness, certain morbid affec- tions of the brain, particular odours and flavours, renal and biliary calculi, hernias or other affec- tions of the intestinal canal, and lastly, certain causes which can act only through the medium of the mind or imagination. 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See also the art. “ Vomissement,” by Adelon, Diet, de Med. t. xxi. p. 427 et seq. ; also Blandin’s Notes on Bichat, t. iii. p. 460. * Haller, Prim. Lin. § 652, and El. Phys. xix. 4, 13; Soemmering, Corp. Hum. Fab. t. iv. $ 178; Magendie, ut supra. digestion, (2ded.) Lond. 1791. Fox on the teeth, Lond. 1803. Gairdner, in Ed. Med. Chir. Tr. vol. i. Hales’s Statical essays, (4th ed.) Lond. 1767. Hall, in Quart. Journ. Hartley on man, Lond. 1791. Hatchett, in Phil. Trans, tor 1799. Haviland, in Camb. Phil. Trans, vol. i. Hodgkin’s Trans, of EJwards, Lond. 1832. Hodgson’s Letters from North America. Home’s Lectures on compa- rative anatomy, Lond. 1814. Home, in Phil. Trans, for 1806, 7, 8, 21. Hunter on the Animal (Economy. Hunter, in Phil. Trans, for 1772. Hunter on the teeth, Lond. 1803. Juncker, Con- spect. Physiol. Kellie, in Brewster’s Encyc. Legallois, CEuvres de. Par. 1824. Leuret if Las- saigne, Recherches sur la digestion. Par. 1825. Lieutaud, in Mem. Acad, pour 1752. Linnaeus, Syst. nat. (ed. 10a) Holm. 1758. Londe, in Diet. .Med. et Chir. t. ii. Lorry, Sur les alimens. Par. 1781. Lower, De corde, Amst. 1669. Macaire ty F. Marcet, in Ann. Chim. t. ii. Magendie, in Ann. Chim. et Phys. t. iii. Magendie, in Diet. Sc. Med. t. ix. Ditto, Sur le Vomissement, Par. 1813. Marcet, in Med. Chir. Tr. vol. vi. M‘ Bride’s Essays (2d ed.) Lond. 1767. Montegre, Exper. sur la digestion. Par. 1824. Monro ( Prim.), in Ed. Med. Essays, vol. iv. Monro ( Tert.) on the gullet, Edin. 1811. O’Beirne on defalcation. Dub. 1833. Paris on diet, Lond. 1826. Parr’s Med. Diet. Lond. 1809. Pearson’s Synopsis, Lond. 1808. Peyer, Anat. Ventric., in Manget, Bibl. anat. Peyer, Mericologia, Basil. 1685. Philip’s Inquiry, (2d ed.) Lond. 1818. Pitcairn, Dissert. Edin. 1713. Pitcairn, Elem. Hagte, 1718. Plenh, Bromatologia, Vien. 1784. Prichard on the vital principle, Lond. 1829. Pringle’s Observations, (3d ed.) Lond. 1761. Prout’s Abstract of his Gulstonian Lecture. Ditto, in Ann. Phil. vol. xiii. xiv. Ditto, in Phil. Trans, for 1824. Ray’s Wisdom of God, Lond. 1717. Reaumur, in Mem. Acad, pour 1752. Redi, Experien. d.vers. cose, Firen. 1671. Richter, De Viet. Anim. Antiq. Gott. 1761. Roget’s Bridgewater Treatise, Lond. 1834. Rostan, Diet, de Med. t. i. Rousseau, Anat. comp, du syst. dentaire, Par. 1827. Rullier, Diet, de Med. t. xv. Ruysch, Opera, Amst. 1737. Santorini, Tabulas, Parm. 1775- St, Hilaire, Sys- teme dentaire, Par. 1824. Sausages, Nosol. Meth. Amst. 1678. Serves, L’anat. et physiol, des dents. Par. 1817. Serves, in Mem. Soc. d’Emul. t. viii. Smith’s Intr. to Botany, Lond. 1807. Spallanzani’s Dissertations, Lond. 1784. Spallanzani, Sur la di- gestion, Gen. 1783. Stahl, Fund. Chym. Dogmat. Norim. 1732. Stark’s Works, by Smyth, Lond. 1788. Stevens, De Aliment. Concoct., in Thes. Med. t. iii. Sylvius, Opera, Gen. 1781. Thackrah’s Lect. Lond. 1824. Tiedemann Gmelin, Recherches sur la digestion. Par. 1826, 7. Vanhelmont, Ortus Medicina?, Amst. 1652. Valsalva, Opera, Venet. 1740. Vauquelin, in Ann. Chem. t. Ixxxi. Young's Medical literature, Lond. 1813. (J. Bostock.) DIGESTIVE CANAL (Comp. Anat.) — The digestive canal is that cavity of the body which is destined to receive the food of animals and to retain it until its nutritious partitas been separated or absorbed. It is termed also the alimentary or the intestinal canal. As it is the part into which foreign matter is first conveyed for the nutriment of the system, its forms and structure are most intimately related to the kind of food, and consequently to the living habits and instincts, and the whole mechanism of animals. The most universal organs in the animal kingdom are the digestive, and most of the others may be considered as secondary or subservient to these. The lowest animals pre- sent us with no other organs than those sub- servient to digestion, and almost all the organs 28 DIGESTIVE CANAL. which are superadded to these as we ascend in the scale eithei form an extension of the nutri- tive apparatus, or are destined to regulate the kind of food admitted into the alimentary cavity. An animal, in the abstract, may almost be viewed as a moving sac, organized to con- vert foreign matter into its own likeness, and all the complex organs of animal life are but auxiliaries to this primitive digestive bag. The bones and other hard parts which form the solid frame-work of the body connected toge- ther by their various ligaments serve only as firm levers to enable the active organs, the muscles, to carry it to and fro, and the ner- vous system with its various organs of sense serve but to direct its motions in quest of food. Nature has placed the unorganized food of plants on the exterior of their body, and their vessels are sent there to seek it, which roots them through life to a fixed point; but animals place their food in their stomach and have their roots directed inwards and towards that central reservoir, so that they can move about and select what is most congenial to their nature. The organs of animal life relate to this diffe- rence between the two organized kingdoms — to this locomotion of animals and their power of selecting their food; but the organs of vege- tative life of which the alimentary canal is the first, relate merely to the assimilation of food when already within the body, and are there- fore common to animals with plants. The digestive surface of the plant is the surface of its root, ramified and fixed in the soil, which affords it a never-failing supply of food ; so that the vegetable is like an animal with its stomach turned inside out. The organs of relation are necessarily connected with the varied circumstances in which animals are placed, and are remarkable for their variable character, and even for their inconstancy in the lower tribes, where they are often entirely want- ing; but those of vegetative or organic life are more regular and constant in their character, and indeed no organ is more universal among animals than that internal digestive cavity by which they differ so much from the species of the vegetable kingdom. This primitive sac is but a development or a continuation of the mucous surface of the skin, which extends into the homogeneous cellular tissue of the body, or completely through it; and although, in the simplest conditions of animals, it per- forms alone all the assimilative functions, we find it, as we ascend in the scale, giving origin to various other systems to which distinct parts of the complex function of assimilation are entrusted. Thus the peripheral mode of nutri- tion of the plant passes insensibly into the central internal mode of the animal, and all the organs of organic life, whether they open into the digestive cavity within, or on the surface of the body without, may be considered as originating from the skin, which is itself only a portion of the primitive cellular tissue of the body, here modified by the contact of the sur- rounding element so as to assume the character of a mucous membrane. As the various tubular prolongations become more and more developed and isolated from this primitive source, they assume properties more and more peculiar, and thus form the numerous glandular appara- tus and vascular systems. An internal digestive cavity, the first element of all the organs subservient to individual nutrition, is observed in every class of animals and almost in every genus; and where this part has not yet been perceived, there can be little doubt, from analogy, of its existence. Its form and structure vary according to the kind of food on which the various tribes of animals are destined to subsist, and the extent of elabo- ration it requires to undergo to assimilate it to the animal’s body ; so that the diversities of this first part of the digestive apparatus are intimately related to all the living habits of animals, and to all the peculiarities they pre- sent in their other assimilative organs and in their organs of relation. 1. Polygastrica. In the monads a digestive apparatus is distinctly seen, and in almost all the other genera of animalcules, where, indeed, the internal cavities connected with this im- portant function are so numerous in almost all the known forms of these animals that this lowest class of animals has been termed poly- gastrica to express their common character. From the transparency of these minute animals, their digestive sacs appear, when empty or when filled with water, like portions of the common cellular substance of the body, or like animalcules which have been swallowed, or like internal gemmules ; and from not being generally recognized as alimentary cavities, many observers were led to suppose that the animalcules are nourished solely by superficial absorption like marine plants. Leuwenhoeck, however, not doubting that they possessed a sto- mach, believed that they devour each other; this wasobserved also by Ellis, and Spallanzani main- tained that they devour each other so voraciously that they are seen to become distended with this food. Goeze saw the trichoda seizing and swallowing the animalcules which were smaller than itself. Baron Gleichen, in order to dis- cover the form of their internal digestive cavi- ties, placed them in infusions coloured with carmine which they soon swallowed, and in his coloured plates he has represented this red colouring matter as filling the internal stomachs of numerous trichoda, vorticella, and other animalcules. Indeed those internal globular cavities of animalcules are represented in the plates of Muller, Bruguiere, and all the older writers on this class. But Ehrenberg, by adopting the plan of Gleichen and Trembley of employing opaque colouring matter to detect the forms of these internal cavities, and by using principally carmine, sap-green, and indigo, carefully freed from all impurities which might prevent their being swallowed, has succeeded better than all his predecessors in unfolding the structure of the digestive organs of animal- cules. Such coloured organic matter diffused as fine particles mechanically suspended in the water in which animalcules are placed, is readily swallowed by them, and renders visible through their transparent bodies the form and DIGESTIVE CANAL. 29 disposition of their alimentary cavities; but however long they remain in these coloured infusions, with their stomachs distended with the colouring matter, it is not perceived to communicate the slightest tinge to the general cellular tissue of their body. In most of the animals of this class there is an alimentary canal with an oral and an anal orifice, which traverses the body and is provided with nume- rous small round ccecal appendices, which open into its sides throughout its whole course, and which appear to perform the office of stomachs in receiving and preparing the food. In the simplest forms of animalcules however, (as in the munas atomus represented in fig. 4 A) there Fig. 4. is but one orifice ( fg . 4 A, «) to the alimen- tary cavity, and the numerous ccecal appendices (fg. 4 A, b) open into this general wide orifice placed at the anterior extremity of the body. This simpler form of the digestive apparatus is found in the monads and in about forty other known genera of polygastrica, which, from this circumstance of their having no intestine passing through their body, have been grouped together as an order under the name of anen- tera. In the monos termo, which is only about the two-thousandth of a line in diameter, four and even six of these roand stomachs have been seen filled with the colouring matter, although they did not appear to be half the number which might be contained in its body. Each of these round stomachs was about 5^ of a line in diameter, and they appear to open, as in other anentera, by a narrow neck into a wide funnel-shaped mouth surrounded with a single row of long vibratile cilia, which attract the floating organic particles or minuter invisi- ble animalcules as food. This anenterous form of the digestive sacs is found both in the lori- cated and in the naked kinds of animalcules belonging to the lowest genera of the class, many of which, however, have been found to be only the young of supposed higher genera. The intestine which traverses the interior of the body in all the higher forms of polygastric animalcules, and connects all the internal sto- machs with its cavity, presents very different appearances in different genera and even in different species of the same genus. In the vorticellu citrina (fg- 4 B) the intestine (fg. 4 B, b, c) passes downwards from the mouth, nearly of equal width throughout, and after forming a curve in the lower part of the body, it ascends to terminate at the same oral funnel- shaped ciliated aperture, ( fig. 4 B, a ,) between the two circles of cilia around the head at which it commenced, having numerous coecal stomachs communicating with its cylindrical equal canal throughout its whole course. This circular form of intestine opening at both its extremities in the same ciliated aperture, is seen also in the carchesium, zoocladium, episty- lis, ophrydium, vaginicola, and other genera, which from this character are termed cyclocccla. In some of the animalcules of this group, as in the stentor polytnorphus, (fig. 5 B,j the intes- Fig. 5. tine pursuing the same circular course through the body, is sacculated or irregularly dilated into round vesicles throughout its whole length, and from these enlarged parts the little stomachs commence by short narrow necks. In other species of the stentor the intestine is twisted in a spiral manner throughout its circular course. Many of the polygastric animalcules which ap- proach nearer to the helminthoid classes in the lengthened form of their body, have the mouth and anus placed at the opposite extremities, as in these higher classes. In the long body of the enc hells pupa, (fig. 6,) the intestine is seen passing straight and cylindri- Fig. 6. cal through the body from the wide ciliated terminal mouth (fig. 6, a) to the opposite dilated anal termi- nation (fig. 6, b ) and giving off numerous small sacs along its whole course. Such animalcules form the group termed orthoccela from this straight course of the intestine. The intestine, however, in the leucophrys patula (fig. 5 A) passes in a spiral course through the short and broad body of the animalcule, giving off small stomachs or cceca along its whole course, and such crooked forms of the alimentary canal com- pose the group of campyloccela, in the distribution of this class proposed by Ehrenberg. Thirty-five genera of polygastrica present an intestine passing through their transparent body, and developing from its parietes these minute globular cceca, which have been regarded as stomachs, from the quickness with which the animalcule conveys the food into them, and from its not accumulating or retaining its food in any other part of the digestive apparatus. More than a hundred of these stomachs have been seen in the paramxcium and aurelia filled at the same time, and there may have been many more unseen from their empty and col- lapsed state. These little sacs are contracted, 30 ECIIINODERMATA. filiform, and almost invisible, when empty; but they are susceptible of great dilatation, and are sometimes seen filled with water or dis- tended with smaller animalcules seized as food. Viewed through the microscope these minute animals present very different appearances, ac- cording to the quantity and kind of food con- tained in their ccecal appendices, and from this circumstance twelve different species of animal- cules, belonging to six supposed distinct genera, have been formed of the single vorticella con- vullaria. No glandular organs to assist in digestion have been observed in the polygastric animalcules; and notwithstanding their almost invisible minuteness and the great simplicity of their structure, they appear to be the most numerous, the most active, the most prolific, and the most voracious of all living beings. Very recently, by the aid of an improved mi- croscope made at Berlin, Ehrenberg has been able to detect a dental apparatus in the kolpoda cucullulus of Muller, one of these minute poly- gastric animalcules, which shews a further ana- logy between them and the helminthoid articu- lata. Notwithstanding the number of stomachs in this class of animals, and the infinite variety of prey which commonly surround them, we often observe them devouring animals, which from their magnitude are incapable of being conveyed into these cavities. 1 have observed a trachelius, after swallowing several monads which swarmed around it, proceed slowly to swallow down a trichoda, which appeared to be ten times the size of one of its internal sacs. It took about a minute to swallow the trichoda , after having turned it in different directions with its long transparent moveable upper lip. The prey could not be perceived to offer the slightest resistance, while the trachelius, with its upper lip spread over the small anterior end of the trichoda, gradually advanced and ex- panded the short lower lip to embrace it below. The body of the trachelius was much shortened during this prolonged act, being drawn forwards towards the lips, and the animalcule, become slower in its movements, was sensibly distended on one side by this large prey in the intestine ; but in less than half an hour it had recovered its usual lengthened form and gliding move- ments, and was seen to seize again the smaller monads around it. Ehrenberg has figured an enchelys swallowing a loxodes ten times the size of its stomachs even when filled with car- mine, and in the body of the loxodes he has represented navicula which have been swal- lowed, though several times the size of any of its stomachs distended with sap-green. In the capacious alimentary cavity of the paranuecium chrysalis I have found a constant slow revolu- tion of the whole contents, like the cyclosis in the large cells of a chara, and the round sacs appear often to be driven to and fro like loose balls in a sac. Baron Gleichen has figured some of these round sacs of Ehrenberg separate from the animalcules, as a bolus of matter which had escaped per anum. These round transparent bodies are often hurried to one end of the animalcule’s body and then to the oppo- site, or spread generally through the cavity, and they sometimes join partially in the general internal cyclosis of the abdominal cavity. In many genera of polygastric animalcules a cir- cular proboscis is seen around the mouth, composed of long parallel straight teeth closely applied to each other, which can be extended or retracted, and forms their masticating appa- ratus. (For the higher forms of the alimentary canal in all the separate classes of the animal king- dom, see the names of the several classes from the Porifera to the Mammalia, Animal Kingdom, and the preceding article Diges- tion.) ( R. E. Grant.) ECIIINODERMATA, (E%lv0;, echinus— curium,) Fr. Echinodermes. A class of invertebrate animals belonging to the di- vision Radiata or the Cycloneurose sub-king- dom. The most familiar examples of them are the common sea-urchin and star-fish. In these the skin is covered with prickles, a circumstance from which the class has received its name ; but animals of corresponding in- ternal structure, such as the Ilolothuria, are also comprehended among the Echinodermata, although the skin is destitute of prickles. They are all inhabitants of the sea, examples of them are found in all climates, and the remains of extinct species exist in a fossil state in various mineral strata. Naturalists are not agreed as to the limits of this class. Cuvier includes in it two orders of animals; the first provided with tubular retractile organs named feet, the second desti- tute of feet, but allied, he conceives, to the first in other respects. Other zoologists separate this second order of Cuvier from the Echinoder- mata. But in fact these apodous animals, comprehending the genera Molpadia, Minyas, Priapulus, and Sipunculus, are as yet so im- perfectly known, at least as regards their in- ternal structure, that naturalists seem at a loss to discover their appropriate place in the zoo- logical system. In these circumstances we shall confine ourselves to the consideration of the true or pedicellate Echinodermata, of whose systematic arrangement the following is a tabu- lar view. Order I. ASTEROIDEA or STELLE- RIDA. Body depressed, divided into rays like a star, or at least with prominent angles. Mouth inferior, generally no anus. a. Holes for the feet disposed in grooves on the inferior surface. Genus 1. Asterias, (Jigs. 298 vol. i. 7-22.) b. No grooves for the feet. Genus 2. Ophicjra. Rays simple, elon- gated, cirrhous, with lateral spines. Genus 3. Euryale. Rays long, cir- rhous, divided dichotomously. Genus 4. Comatula. Rays in two sets, dorsal and marginal. The dor- sal rays simple, filiform, cirrhous. The marginal much larger and pin- nated, their inferior pinnules turned ECUINODERMATA. 31 downwards arid surrounding the ven- tral disk. Border of the mouth formed by a prominent membranous tube. Genus 5. Encrinus. Body supported on a jointed stem. (With one ex- ception the species are all fossil.) Order II. ECHIN IDA. Body globular or ovoid, without rays ; skin containing a calcareous shell ; anus distinct. a. Regularia. Mouth and anus diametri- cally opposite in the centre of the ventral and dorsal surface respectively. Genus 1 . Echinus, (figs- 33 vol. i. 10-19.) Genus 2. Cidarites. b. Mesostoma. Mouth in the centre, anus- eccentric. Genus Anus on the ventral . surface or j the border. 3. Galerites. 4. Echinoneus. 1 -V r f 9. Rows of feet extending from the anus to the inferior opening of the shell. 5. Scutella. 6. Clypeaster. \__7. Fibularia. Anus above the border or dorsal. c. Plagyostoma. centric. Genus 10. Ananchites. Genus 11. Spatangus. Order IIL HOLOTHU RIJE. Cassidui.us. . Nucleolites. Rows of feet not extending >-to the inferior opening of the shell. Mouth and anus both ec- Body oblong, (fig. 34 vol. i.) coriaceous, with the anus (k) and mouth (a) at its opposite extremities. Mouth surrounded with retrac- tile, branched tentacula (o). Organ of re- spiration a ramified tube ( h , f, J'fi placed within the body and opening at the anus. Genus. Holotiiuria. (fig. 34 p. 109, vol. i. and fig. 20.) The genera Asterias, Echinus, and Hulo- thuria are those in which the internal struc- ture has been most frequently and fully inves- tigated ; they are therefore usually selected as the leading examples in anatomical descriptions of the Echinodermata, the peculiarities of other genera being mentioned in so far as they have been satisfactorily ascertained, and are of suffi- cient importance to demand special notice. 1. Integuments. — An incision made through the tough skin of the star-fish or shell of the sea-urchin, lays open the internal cavity of the body in which the viscera lie ; so that in these animals the integuments in a great mea- sure constitute the parietes of the body, there being little else except the peritoneum or lining membrane of the visceral cavity which is spread over their internal surface. In the Holothuria there are muscles of considerable thickness be- neath the skin. The integuments of the former animals contain imbedded pieces of calcareous substance, which constitute a kind of cutaneous skeleton. In the latter there is merely a calca- reous ring surrounding the mouth. a. In the Asterias the integuments consist of, 1st, a tough coriaceous membrane, with por- tions of calcareous substance imbedded in it, or at least connected by it ; 2d, a softer external membrane ; 3d, various appendages. The calcareous pieces form inferiorly a ring round the mouth and a series of transverse segments (from a to A, fig. 7 ; C,fig. 22,) placed in succes- segments is connected with the ring ; they de- crease in size- as they approach the point or distal end of the ray, and openings are left between them for the passage- of the feet. In the Asterias rubens, which has five rays, the central ring consists of ten larger and five smaller pieces, the former disposed in pairs opposite the commencement of the rays, the latter corresponding to the angles between the rays. The segments of the rays are symme- trical ; in the species mentioned they consist of two oblong pieces (a, fig, 8), united in the Fig. 8. Section of a ray of Asterias rubens, showiny the arrangement of the calcareous pieces. 32 ECHINODERMATA. median line, and two smaller ones (6, b,) placed laterally. On the sides of the ray the calcareous substance is disposed, as it were, in ribs (c, c, jig. 9) ; these rise from the floor at first nearly parallel with each other, and are con- nected by cross bars, but on approaching the upper part or roof of the ray they cross in all directions and form an irregular network, the intervals of which are occupied by softer inte- gument. The ribs and bars are made up of small pieces joined by plane but oblique sur- faces, a mode of construction calculated to admit of their being lengthened and shortened upon one another, and thus to allow of the ca- vity they surround being dilated and contracted. Fig. 9. Portion of a ray of Asterias rubens viewed laterally. A broad calcareous disk is situated on the upper surface of the body, in the angle be- tween two of the rays, (Jigs. 12 and 16, ?,) which is connected internally with a singular organ named by Tiedemann the sand canal, to be afterwards described. The calcareous pieces are of a homogeneous structure, without cells or fibres ; they consist, according to Hatchett’s analysis, of carbonate of lime, with a smaller proportion of phosphate of lime. The coriaceous membrane which connects the pieces of the skeleton is made up of white glistening fibres. It is contractile and irritable, for it slowly shrinks on being scratched with the point of a knife, or when it is cut through. The external membrane is much thinner and softer than that just described ; in various parts it is coloured, or in these parts there is a co- loured layer underneath it. The appendages or processes on the surface of the body are of three kinds. First, calcareous spines ; these are found over the whole surface except the grooves for the feet. They are at- tached by a moveable joint at their base to the calcareous pieces of the skin, and are invested by the external soft membrane nearly as far as their point. Those on the upper surface are solitary, short, and for the most part club- shaped, their broader summit being marked with radiating points ; whence they were named stelliform processes by Tiedemann. On each side of the groove for the feet the spines are thickly set (c, c, Jig. 7) ; these in Asterias rubens form three rows, in the middle and innermost of which they are placed three deep. On this part of the surface they are also longer and pointed. The spines are slowly moved at the will of the -animal. The appendages of the second kind are of a very singular nature ; they have the appearanc-e of pincers or crabs’ claws in miniature ( fig. 298, c, b, b, p. 615, vol. i.) and were described by Muller as parasitical animals under the name of Pedicellaria. Monro gave the name of antennae to analogous organs which are found on the sea-urchin. They probably do not exist in all species, for Tiedemann makes no mention of them in his description of A. auranliaca. In A. rubens they cover the surface generally, and form dense groups round the spines. Each consists of a soft stem bearing at its summit, or (when branched) at the point of each branch, a sort of forceps of calcareous matter not unlike a crab’s claw, except that the two blades are equal and similar. When the point of a fine needle is introduced between the blades, which are for the most part open in a fresh and vigorous specimen, they instantly close and grasp it with consi- derable force. The particular use of these prehensile organs is not apparent ; their stem, it may be remarked, is quite impervious. The third sort of appendages consists of those which are named the respiratory tubes; they will be considered afterwards. The other genera of Asteroidea have also a cutaneous skeleton presenting the same general mode of construction as that of Asterias, but with certain modifications of structure and still greater differences of form in particular cases. Of these we may here notice the crinoid echi- nodermata and the genus comatula, as the most interesting examples. The former ani- mals, comprehended by most naturalists in the genus Encrinus, are, with one exception ( the Enc. caput medusa or Pentacrinite ) found only in a fossil state, and the remains of their ske- letons constitute the fossils named encrinites, trochites, entrochites, &c. An idea of their structure may be obtained if we imagine an asterias placed with its mouth upwards on a columnar jointed stem, one end of which is connected to the dorsal surface of the animal, and the other most probably fixed at the bottom of the sea. The rays or arms extending- from the circumference of the body are much branched, and at last pinnated ; other jointed processes, named auxiliary arms, surround the stem in whorls placed at short intervals. The column is perforated in its centre with a narrow canal, down which a prolongation of the sto- mach extends, and lateral canals proceed from the central one through the verticillate auxiliary arms. The Comatula has rays spreading from the circumference of the body, branched and pinnated like those of the pentacrinite. It is not fixed on a column, but the dorsal surface of the body is elevated in the middle, and bears a number of smaller rays or arms, and this dorsal eminence with its rays has been sometimes compared to a rudiment of the column of the pentacrinite with its auxiliary arms. Besides the mouth there is an anal opening on the ventral surface, situated on an eminence near the margin* b. In the sea-urchin the calcareous matter is disposed in polygonal plates, which, being * Meckel, Vergl. Anat. ii. p, 31. ECHINODERMATA. firmly joined to one another, form by their union a shell approaching more or less to a spherical figure, (Jig. 10, A, B.) The shell is covered outside by a membranous integu- ment, spines, and other appendages; on the inside it is lined by the peritoneum. It is Fig. 10. A. the perforations for the feet. perforated above for the anal orifice of the intestine (6), and below it presents a much larger opening, which is closed by the mem- branous integument, except in the middle, where the mouth is situated (Jig. 15). The pieces composing the shell are mostly five- sided, transversely oblong, and disposed in twenty vertical rows or columns, which extend from the anus to the inferior opening. Ten of the columns are narrower, and consist of smaller pieces, (fig. 10, e, e,) which are perforated with holes for the feet ; they are thence termed ambulacral. The other ten are broader, and consist of larger pieces (f,f). The ten am- bulacral columns are disposed in five pairs, with which the ten larger columns, also dis- posed in pairs, alternate. The two columns of each pair are joined by a zigzag line. The VOL. II. upper ends of the columns are connected with ten plates, alternately larger and smaller, placed round the anus; the larger perforated for the passage of the oviducts, and named ovarial plates, the smaller also perforated by a smaller hole, which is connected with the vascular sys- tem. At its lower edge the shell sends inwards a process in form of an arch over each pair of the ambulacral columns (g, g, g). The number of plates in a row varies with the age of the animal, increasing as it grows older and larger. They are marked on the outside with tubercles or knobs, of various sizes, which support the spines. The spines themselves have a cup-like cavity at their base, which is connected with and moves on the prominent tubercle, the union being effected at the circumference of the articulation by the soft irritable integu- ment, or, according to some, by distinct mus- cular fibres. Besides the spines, there exist on the external surface of the Echinus appendages ( fig. 1 1), of the same nature as the claw-like organs of the Asterias, only that in the Echinus the sort of forceps which they bear at their extremity for the most part consists of three blades. Fig. 11. The shell of the irregularly-shaped Echinida differs considerably in structure from that of Echinus. The division into plates is less ob- vious, and in some cases disappears altogether. The series of holes or ambulacra do not extend uninterruptedly from the anus to the lower orifice. Lastly, in Clypeaster the shell is di- vided interiorly, by vertical calcareous parti- tions, into five compartments which commu- nicate together, the septa being incomplete. c. The integuments of the Holothuriae differ considerably in different species. In those species in which there is a marked distinction of the dorsal and ventral surface of the body, the integument differs in character on these two surfaces : in other cases it is pretty nearly uniform over the whole body. It in general consists of a white fibrous layer, which consti- tutes its chief thickness, and a soft coloured layer and epidermis placed more exteriorly. In some species the skin exhibits hard conical warts scattered over the dorsal surface; in others it contains imbricated calcareous scales. In H. phantapus, in addition to these scales, which are about a line in breadth, the in- tegument, according to our observation, is thickly beset with small calcareous eminences, about of an inch in diameter, resembling, except in size, the short calcareous processes on the upper surface of the Asterias. A calcareous ring, forming in many species the only hard part of the body, surrounds the D 34 ECHINODERMATA. mouth. It is made up of ten pieces alternately larger and smaller, aud gives attachment to the longitudinal muscles of the body. It is re- garded as the rudiment of a skeleton, while the addition of scales or plates in the skin forms in some species an approach to the more perfect cutaneous skeletons of the star-fish and sea-urchin. 2. Organs of motion. — The spines of some Echinodermata are employed to a certain extent as organs of locomotion ; they have been al- ready described. The star-fish has the power of slowly moving its rays; it can bend them towards the dorsal or ventral surface, or ap- proximate some of them while it separates others more widely, and thus prepare itself for creeping through narrow passages. Tiedemann ascribes these motions wholly to the contractile skin ; they are no doubt partly effected by that tissue, but Meckel describes distinct muscles passing between the calcareous plates which form the floor of the rays, and we have our- selves observed a distinct band of muscular fibres running along the roof of each ray be- tween the coriaceous skm and peritoneal mem- brane, and also transverse fibres, but less marked, lying between the same parts ; the latter are seen adhering to the external surface of the peritoneal membrane when it is stript off. The muscular system of the Ilolothuria is much more developed. Ten longitudinal mus- cles (Jig. 20, s, s, s,) arise from the calcareous ring in the vicinity of the mouth, and pass along the body in the form of broad bands to the posterior extremity; between these and the skin transverse or circular muscles ( l , l,) are situated; they extend over the whole internal surface of the skin. The principal locomotive organs of Echino- dermata are the membranous tubes named the feet. These are very numerous and are usually disposed in regular rows; they contain a clear fluid, which is conveyed to them by a peculiar system of vessels. Each foot consists of two parts, an internal and generally vesicular por- tion (Jig. 12, d ,) placed within the body, and a tubular part (c) on the outside, projecting from the surface and continuous with the first through an aperture in the skin or shell (Jig. 23,/). The tube is closed at the extremity and terminates there in a sucker, which has usually the form of a disk slightly depressed in the centre. Both parts of the foot are evidently muscular, the fibres of the tubular portion being disposed in a circular and a longitudinal layer; the cavity is lined with a transparent membrane, and the tubular part moreover receives an external covering from the epidermis. The foot is extended by the contraction of its inter- nal vesicle, which forces the fluid into the tube, or when a vesicle is wanting, by the projection of a fluid into the tube from a communicating vessel ; the tubular part is thus distended and elongated ; it retracts itself of course by its muscular fibres, and when this takes place the fluid is forced back again into the vesicular or internal part. In progression the animal extends a few of its feet in the direction in which it desires to go, attaches the suckers to rocks, stones, or other fixed objects immedi- ately in advance, then shortening its feet it draws its body in the wished-for direction. a. In the starfish the feet are disposed in rows along the under surface of the rays, di- minishing in size as they approach the extre- mity (Jig. 7, a, b, d). There are usually two sim- ple rows in each ray, (fig. 23, c,) and the vesi- cular part is for the most part deeply cleft into two lobes (as in A. aurantiaca, fig. 22, d, d ). In Fig. 12. ECHINODERMATA. 35 other cases, as A. rubens, there are two double rows (Jig. 7, b,) in every ray, and each foot has a round undivided vesicle (Jigs. 12 and 16, d). The canals or vessels which convey the fluid to and from the feet are all connected with a circular vessel situated in the vicinity of the mouth. This vessel (figs. 12 and 22, i,i,) lies immediately within the calcareous ring already described as connecting the rays at their com- mencement ; from it a straight canal proceeds along the floor of each ray in the median line, and in its progress gives off lateral branches which open into the vesicles of the feet. There are moreover connected w’ith the circular ves- sel,— first, a certain number of bodies (ten in five-rayed species) which Tiedemann com- pares to glands (figs. 12 and 22, m, m ); they are very small, brown, sacculated organs, each opening by a small orifice into the circular vessel; Tiedemann supposes them to be the source from which the fluid filling the feet is derived. Secondly, pyriform sacs; 'mA.au- rantiaca there are four groups of these (fig. 22, k); and each group consists of three or four sacs which open by a common tubular pedicle into the circular vessel. In some other species there are five simple sacs. They are muscular, and Tiedemann conceives them to be the chief agents by which the fluid is forced into the vesicles of the feet, to which they are placed in a sort of antagonism. It would seem, however, that this purpose may be accomplished by other means, for according to Meckel’s statement, and, we may add, our own observation, they are not present in all species. Lastly, the circular vessel receives the singular organ named the stone canal or sand canal by Tiedemann, (figs. 12 and 22, S,) who describes it as a membranous canal con- taining a friable mass of sandy or earthy matter, which commences by a wide origin on the inferior or internal surface of the calcareous disk (figs. 12 and 16, z ,) already described as situate on the upper part of the body, descends in a duplicature of fibrous membrane, and opens by a narrow orifice into the circular vessel, the upper or wide end being closed by the disk. Ehrenberg has correctly remarked that this organ is not filled with an amorphous mass of earthy or cretaceous matter ; he de- scribes it as exhibiting a dense network of calcareous fibres with hexagonal and penta- gonal meshes, resembling in some respects the cavernous structure of the penis. The result of our own examination in more than one species is different still. We have always found the earthy matter forming a jointed cal- careous tube. This tube, which is about the thickness of a surgeon’s probe, is composed of rings of calcareous substance connected by membrane, so that viewed externally it is not unlike the windpipe of a small animal. On cutting it across, however, it is found to be more complex in structure than appears exter- nally, for it contains within, two convoluted laminre of the same nature as its calcareous parietes (fig.\3). These laminae are rolled lon- gitudinally; they rise conjointly or as one, from Portion of the sand canal of Asterias rubens, magnified. Fig .13. the internal surface of the tube, pass inwardly a cer- tain way, then separating are rolled in opposite di- rections ; something after the same manner as the inferior turbinated bone of the ox. These internal laminae become more con- voluted towards the upper end, where at last they, as well as the more external part of the tube, join the dorsal disk, appearing gra- dually to become conti- nuous with its substance. The disk is perforated with numerous pores which open into the tube. Tiedemann con- ceives the function of the sand canal to be that of secreting the earthy matter required for the growth of the calcareous skeleton. Meckel considered this view as very improbable, and the description we have given does not tend to corroborate it. We must confess ourselves unable to offer more than mere conjecture as to the use of this singular structure. If the fluid contained in the feet and their vessels be sea- water, (either pure or with an admixture of organic particles,) which is probable from its chemical composition, may it not be intro- duced and perhaps again discharged through the pores of the disk and the calcareous tube, the porous disk serving as a sort of filter to exclude impurities ? In the Echinus the feet are disposed in ver- tical rows running from the anal orifice towards the mouth; and the corresponding rows of apertures (fig. 10, e, e,) thus diverging from a point have been compared to garden-walks, and named ambulacra. In most cases the feet extend all the way to the inferior opening of the shell, but in some genera they stop short before reaching this point. There are ten rows disposed in five pairs. The tubular part of each foot communicates with the interior of the shell by two branches which pass through two aper- tures. These branches in some species (as E. sexatalis ) communicate directly with the canals which convey the fluid to the feet ; in others (as E. esculentus ) they open into a plexus of vessels, by the intervention of which they are connected with the canals. The plex- uses of vessels alluded to are formed in leaf- like membranes (fig- 14, tf, d, representing two of them magnified,) which are of equal num- Fig. 14. ber with the feet, and of course disposed in d 2 36 ECIIINODERMATA. double rows on the inside of the shell (Jig. 10, d.) Monro describes each foot as communi- cating with two of these laminae, and conse- quently every lamina as receiving a branch from two feet; in our own dissections we have al- ways found that both branches of each foot belonged to one lamina. These branches are represented as cut at a in the annexed figure. Five longitudinal vessels run down on the inside of the shell, there being one in the middle of each double row of feet (flgs. 10 and 14, u); lateral branches go off from these either directly to the feet or to the laminar plexuses when they are present. The five longitudinal vessels descending towards the mouth rise through the dental apparatus named the lan- tern, and open into five sacs or receptacles placed on its upper part, where according to Tiedemann they terminate. Monro on the other hand describes the sacs as communicating together, and states that from them the liquor passes down the sockets of the teeth, and is discharged into the sea. The vessels and la- minae are highly irritable, and by their contrac- tion distend the feet. Ten tubular tentacula, similar in structure to the feet, are situated in the vicinity of the mouth (Jig. 15, d, d, d .) In Ech. esculentus they are attached to the small calcareous plates Fig. 15. mg of the shell ; e, e, membrane which fills it. which are imbedded in the membrane that fills up the aperture of the shell. The plates are each pierced with a hole, through which the tentacula communicate with the canals of the feet. In Holothurise the feet are sometimes scat- tered over the whole surface of the body; in other species (as H. pentodes ) they are placed in five longitudinal and tolerably regular rows ; while in others again they are confined to the ventral surface, as in H. phnntapus, where they form only three rows. The tubular part (Jig. 20, b, b,) is in general very short, and is connected with a simple vesicle inside. The vessels of the feet arise from a circular canal which surrounds the stomach near the fore part of the body. One or sometimes two large pyriform sacs (Jig. 34, b, p. 109, vol. i.) open into this canal, and a number of small brown hollow glandular-like bodies are also connected with it. Five vessels issue from it, which run forwards and terminate in a second canal situate immediately within the calcareous ring which surrounds the mouth. This se- cond circular canal is connected with the tentacula, as will be afterwards described, and it gives off five longitudinal vessels which run towards the posterior end of the body, and dis- tribute lateral branches to the vesicles of the feet. Tiedemann regards the fluid contained in this system of vessels as a secretion, and conceives that it nourishes the skin, the mus- cles, and tissue of the feet, besides supplying to the latter the mechanical means of their distension. Further observation would, how- ever, be required in order to determine its true nature, for there is much reason to suspect that the fluid of the feet in other Echinoder- mata consists at least in great part of sea-water, and it is not to be supposed that in the Holo- thuria it should be materially different. Under this head we may notice the tentacula of the Holothuria (Jig- 34, o, p. 109, vol. i.) re- tracted, as they present a great analogy in struc- ture with the feet. These organs are placed round the mouth and are twenty in number; the ex- tremity of each is formed into a circular sucker surrounded by five or six branched processes. They are hollow, and a great part of them is lodged within the body ; this internal part is long and tapering, and communicates by a small orifice with the anterior circular canal already described, from which the tentacula receive their distending fluid. In the rest of their structure and in their mode of action they resemble the feet. They seem to be very sen- sible, and are probably used as organs of touch as well as prehension. In H. pentodes the tentacula are very large, much larger than in H. tubulosa. 3. Digestive organs. — The digestive appa- ratus is very simple. The sea-urchin and Holothuria have an alimentary canal with a mouth and anus, but in the star-fish there is merely a stomach with coecal appendages and only one orifice. The cavity in which the alimentary organs and other viscera are lodged is lined with a peritoneal membrane, which being reflected upon them forms their external tunic, and attaches them by a duplicature or mesentery to the inside of the cavity. The Echinodermata are said to live chiefly on tes- taceous mollusca and Crustacea. a. In Asterius a short but dilatable gullet leads to the stomach (Jigs. 16 and 22, f), which occupies the central part of the animal, and from the stomach a pair of lobulated coeca ( g, g, and g, g', inflated,) pass into each ray. The stomach is connected at various places with the parietes of the body by ligamentous bands ; it is thin and membranous, soft and corrugated on the internal surface, receiving externally a covering of peritoneum, and con- taining muscular fibres which are more obvious towards the lower part, when it adjoins the still more muscular cesophagus. Two or more blind sacs (l), branched in some species, open ECIIINODERMATA. 37 Fig. 16. Asterias rubens: three rays opened — in the one, at A, cceca cut, short to shew the vesicles of the feet, d, d, and one ovary, o ; g, g, cceca, g‘ g' , cceca inflated. into it from above, which are probably secre- ting organs. The cceca are thin and mem- branous like the stomach; each consists of a central tube with lateral branches, which in their turn are lobed or branched, and terminate in cellular dilatations. The two coeca of a ray sometimes communicate with the stomach by a short single tube (/f); in other cases they have separate orifices. They do not reach so far as the distal end of the ray; each one is attached to the roof by what might be called a double mesentery, for the peritoneum forms here two duplicatures (figs. 12 and 16, n ,) between the ccecum and the roof of the ray. A space is inclosed between these duplicatures which opens into the central part of the body at the root of the coeca. Such is the structure in the Asterias, but in some other genera belonging to the tribe of Asteroidea it is different. In Ophiura, Eu - ryale, and Comatula, in which the rays are very long and slender, the coeca are mere cel- lular dilatations of the stomach, and do not extend into the rays. Comatula moreover dif- fers from all the tribe, inasmuch as its alimen- tary canal has two openings, a mouth and anus, situated near to each other on the ventral sur- face. The mouth of the star-fish is very dilatable, so as to admit large mollusca in their entire 38 ECIIINODERMATA. shell. The gullet and part of the stomach are usually everted, protruded, and applied round tile object to be swallowed, which is then drawn in. The hard or indigestible matters, such as the shells of mollusca, are discharged by the mouth. The star-fish is said to be very de- structive to oyster-beds, and is popularly be- lieved to suck the animals out of their shells. Bishop Sprat, in his History of the Royal Society, informs us that great penalties are laid by the Admiralty Court upon those en- gaged in the oyster-fishery who “ do not tread under their feet or throw upon the shore a fish which they call a Five-finger, resembling a spur-rowel, because that fish gets into the oysters when they gape, and sucks them out.'7 Tiedemann found the cceca to contain a grey- ish-white fluid which he supposed to be di- gested aliment ; others again, such as Meckel, regard the coeca as secreting organs, analogous to the biliary organs of many invertebrate ani- mals, with which, it must be allowed, they agree in several respects. b. The mouth of the Echinus is an orifice situated in the middle of the circular mem- brane which fills up the lower aperture of the shell (fig. 15, a.) The points of the five teeth are seen within it, and at no great distance from its circumference the ten tubular tentacula (d) are observable, which have been already described. The teeth are set in five moveable sockets or jaws which surround the commence- ment of the gullet, and with the addition of some accessory pieces form tire singular struc- ture usually named Aristotle's lantern. The lantern (figs. 10, 17, and 18) has the appearance of a five-sided pyramid placed with its apex Dental apparatus of the Sea-urchin viewed from above. downwards or towards the mouth, the gullet («) rising through its centre. It is made up of five smaller hollow pyramids ( h ,) which are the sockets of the teeth. Each lesser pyramid is three-sided ; its external side (fig- 18, h’,) which forms one of the faces of the greater pyramid, presents an opening in its upper half which is closed by membrane ; its lateral faces (fig. 18, h, h,) are applied to the cor- responding sides of the adjacent sockets, with which they are connected by short muscular fibres ( p ) ; they approach each other at the inner Fig. 18. A, two sockets with teeth, B, single socket with of Echinus esculentus . its tooth viewed on the outside. edge of the socket, but do not meet. The tooth ( t ) is prismatic, very long, and lodged in a groove formed in the external side of the socket ; its point projects beyond the apex of the socket; its opposite extremity or root rises above the base, where it is bent inwards and downwards and inclosed in a membrane. The teeth are very hard at the point, but softer towards the root, where they are easily sepa- rable into transverse scales or plates with a fine silky or asbestine lustre; they seem to grow continually at the root, and wear at the point as in the Rodentia. Ten additional pieces contribute to form the lantern. Five of these (f) are oblong and flattened, and are placed horizontally, in a ra- diating manner, on the upper surface of the lantern, occupying the intervals between the bases of the lesser pyramids. The other five (/r) are placed directly over the first; they are longer but more slender, and bent in a semi- circular form, the convexity being upwards; their central ends are articulated with the cor- responding extremities of the horizontal pieces ; the outer ends are bifid and give attachment to ligaments. The muscles and ligaments belonging to the dental apparatus partly pass between its dif- ferent pieces, and partly connect it with the border of the shell. It will be recollected that the border of the shell forms five processes (figs. 10 and 17, g,g, g,) which rise in the form of arches into its cavity round the lower aper- ture. Ten muscles (rn, m,) arise from these arches, and descending inwardly are inserted into the lesser pyramids or sockets near the point. Two of these muscles come from every arch, and diverging are inserted into different pyramids, so that each pyramid receives its two muscles in a converging manner from two adjacent arches. The muscles described draw outwards the sockets separating them and widening the mouth. Other ten muscles (it, n ,) arise in pairs from the border of the shell in the intervals of the arches, and, ascending, are inserted into the outer surface of the sockets near their base, each socket receiving a pair. These are antagonists to the last described ; they move the points of the pyramids, and consequently the teeth inwards and against each other. Five muscles composed of short ECHINODERMATA. 39 transverse fibres ( p , Jig. 1 8,) unite the lateral surfaces of the sockets, and serve to approxi- mate them, acting collectively as a sort of sphincter, and as antagonists to those first de- scribed. Lastly, five muscles (Jigs. 10 and 17, o, o, o ,) pass between the semicircular pieces on the upper part of the lantern. Besides the muscles described, there are ten very thin whitish bands (s, s,) which arise in pairs from the external forked extremities of the semi- circular pieces, and are inserted into the border of the shell in the intervals between the arches. Tiedemann describes these bands as muscles ; Meckel, on the other hand, considers them as ligaments ; in the E. esculentus they certainly seem to us to be ligamentous. Two liga- mentous filaments pass from the central end of every semicircular piece to the gullet. A co- vering of the peritoneum envelopes the dental apparatus, extending to it from the border of the shell. The oesophagus (Jig. 19, a,) rises through the lantern, to which it is connected by fine ligaments, and after a few curvatures termi- nates in a wider part of the alimentary canal, somewhat in the same way as the small intes- tine joins the great in the human body. The wider portion {b, b,) of the canal turns twice round the inside of the shell in a waving manner, and terminates at the anus (c). In Fig. 19. Internal view of Echinus sexatilis. ,A, under half; B, upper. its second or superior circuit it changes to an opposite direction, but its flexures in both cir- cuits are parallel. The tissue of the alimentary canal is very delicate, the external tunic is formed by the peritoneum, which attaches the intestine by a mesentery to the shell, lines the inside of the latter, and is reflected over the ovaries and the lantern. The inner coat of the intestine is soft and of a brownish-yellow co- lour; between it and the external, Tiedemann states that delicate longitudinal and circular muscular fibres are distinguishable. The Echini are generally believed to feed on mollusca and Crustacea, and in corroboration of this, Tiedemann states that he has found in the Echinus sexatilis small univalve and bivalve shells entire among the excrements, besides fragments of larger ones. Blainville,* on the other hand, could never find any thing else than sand in the alimentary canal, and he re- marks that the general opinion as to the carni- * Diet, des Sc. Nat. art. Oursin. vorous habits of the sea-urchin is probably more an inference from the structure of the teeth and jaws than the result of observation ; he, however, adds that M. Bose had witnessed an echinus in the act of seizing and devouring a small crustaceous animal. In the intestine of the E. esculentus we have usually found numerous small morsels of sea-weed, for the most part encrusted with a flustra. The excre- ments, which are in the form of small round pellets about the size of peppercorns, consist chiefly of sandy matter w'ith fragments of shells, but it would be difficult to say whether these are the remains of digested mollusca or merely a portion of the usual testaceous debris so abundant in sand and mud. The principal difference of the alimentary organs in the different genera of Echinida de- pends on the position of the anus and the presence or absence of teeth. In Scutella, Clypeaster, Fibularia, Echinoneus, Galerites, Ananchites, and Spatangus, the anus as well as the mouth opens on the under surface. In Echinus, Cidaris, Cassidula, and Nucleolites, it is situated on the upper surface ; in the first two exactly in the centre, in the last two at a greater or less distance from it. The teeth are wanting in Spatangus and Cassidula. c. The alimentary canal of the Holothuria is Fig. 20. Holothuria tubulosa : alimentary canal and blood- vessels. The respiratory organ, c, c, is cut short. 40 ECIIINODERMATA. veiy simple (fig. 20, e,f, g, h.) At the mouth it is surrounded by the tentacula and calcareous ring already described, it passes back- wards on the right side the whole length of the body (from e to J\) then bending forwards it returns to near the mouth (from f to g,) and at last runs back again to the posterior extremity (from g to h,) where it terminates in a short and wide cloacal cavity (d), common to it and the respiratory organ, and opening externally at the anus. The intestine is fixed by a mesentery, and the cloaca is con- nected to the parietes of the body by numerous muscular bands de- rived from the transverse muscles. The coats of the canal are thin ; Tiedemann enumerates three, an external derived from the perito- neum, a middle which is very vas- cular and contains muscular fibres, and an internal or mucous. In H. tubulosa a small part of the canal near its commencement is wider than the rest, has thicker coats, and is more decidedly mus- cular; Tiedemann regards this part as the stomach. In H. pentactes, the part immediately succeeding the oesophagus and ex- tending nearly to the first flexure, is somewhat cellular and at the same time wider, but thin- ner in its coats than the rest of the canal ; this part is considered to be the stomach by Meckel It is a singular fact, which it appears was first noticed by Redi, that several species of Holothuria, on being taken from the sea and put into a vessel of sea-water, discharge their intestine and part of the respiratory organ through the anus. This operation is effected by repeated contractions of the cutaneous muscles, and some naturalists are disposed to regard it as a voluntary act. 4. Respiratory organs. — The Echinodermata breathe through the medium of sea-water. In the star-fish and urchin the water enters the body, passing into the space in which the viscera are lodged, and this cavity, which, as already stated, is lined by a peritoneal mem- brane and occupies the greater part of the body, is generally regarded as the chief seat of the respiratory process. In the Holothuria the water is alternately drawn in and expelled from a tubular respiratory organ ramified within the body. a. In the star-fish the water is generally be- lieved to enter and issue from the body by numerous small tubes on the surface, which have accordingly been named the respiratory tubes. These are very small, membranous, and in figure somewhat conical (fig. 298, c, c, p. 615, vol. i.); they communicate at their base with the interior of the body, and are perforated at the summit by an orifice which can be very accurately closed. Most of them are placed in groups or patches, and opposite Fig. 21. each group the fibrous membrane forming the wall of the body presents on its inside a shal- low pit(fig.21, a; fig. 298, vol.i. e; fig. 16, s, s,) perforated with holes, through which the tubes communicate with the internal cavity. The tubes are formed externally of the superficial layer of the skin, and are lined in the inside by a prolongation of the peritoneal membrane. This membrane lines the parietes of the body, and is reflected over the contained parts; at least it covers the stomach and coeea, and pro- bably also the ovaries and vesicles of the feet; opposite the perforated pits it sends prolonga- tions (b, b,) through the holes into the tubes, as may be easily seen on stripping off' a portion of it. There can be no doubt that sea-water enters the peritoneal cavity. The animal slowly dis- tends itself with that fluid, and again, but at no stated interval, gives out a portion of it: this is obvious from the fact that the same animal may be seen distended at one time and flaccid at another. Naturalists are generally of opinion that the water enters and issues by the respiratory tubes, and indeed no other orifices have been discovered ; we must, however, freely own that we have never been able actually to observe its passage through these tubes. The peritoneal membrane seems to be the principal seat of respiration; spread over the viscera and the parietes of their containing cavity, and lining the respiratory tubes, it pre- sents a great extent of surface continually in contact with the surrounding medium ; and we have found that a beautiful provision exists for maintaining currents of water along the mem- brane, and thus effecting that constant reno- vation of the fluid in contact with its surface ECI1IN0DERMATA. 41 which is required in the respiratory process. These currents are produced by means of cilia ; they are more particularly described in the article Cilia, to which we refer the reader. Ciliary currents take place also on the external surface of the body, which probably partakes in the process of respiration ; we have more- over observed them within the tubular feet and on the internal surface of the stomach and cceca; in this last situation they are probably subservient to digestion, but their use is more fully considered in the article referred to. b. The respiratory system of the sea-urchin is very similar. The water enters the body through membranous respiratory tubes, which are collected into ten small bunches (Jig. 15, e, e), situated on the under surface of the animal at the border of the shell, and opening internally by ten perforated pits like those of the Asterias. The fluid being introduced into the peritoneal cavity, is moved along its parietes and over the surface of the alimentary canal, the ovaries and the vascular laminae of the feet, by the action of cilia. Ciliary currents have also been observed on the external surface of the body. c. The respiratory organ of Holothuria (Jig . 34,./) /', h, p. 109, vol. i.) has some resem- blance in form to that of air-breathing animals. It is a very long membranous sac, placed within the body, which opens into the cloaca near the rectum and extends forwards from thence nearly the whole length of the body, either single, or (as in Holothuria tubulosa) divided into two main branches (Jig. 20, c, c, cut short, jig. 34 , f,f, p. 109, vol. i.), which in the vicinity of the cloaca are joined by a short common stem. One of these branches is intimately connected by bloodvessels to the intestine, the other by muscular fasciculi to the parietes of the body. The sac, whether single or bifid, gives off a great many lateral branches, which after successive divisions ter- minate in shut or blind extremities. Both stem and branches contain distinct circular and longitudinal muscular fibres, and contract on being irritated. In the act of respiration sea- w’ater is drawn into and expelled from this organ, and its entrance and exit, which may be readily seen at the cloaca, occur in some species so often as once, twice, or even three times in a minute. The alternate inhalation and expulsion of the fluid are effected partly by the action of the muscular parietes of the body, but principally, it would appear, by the muscular fibres of the organ itself, for Tiede- mann observed the process still to go on, though with diminished activity, when the animal was cut open and the organ exposed. Cuvier states that the sac in some species is without branches. 5. Vascular system. — A system of vessels for the circulation of the blood exists in the animals under consideration. The tenuity of their coats, however, and pale colour of their contents render it extremely difficult to trace completely the distribution of these vessels, and we accordingly find that the descriptions of them given by Tiedemann and Delle Chiaje, the principal authorities on the subject, differ materially from each other. According to Tiedemann the proper sanguiferous system is, in its distribution, in a great measure confined to the alimentary organs and ovaries, or to these and the respiratory organ where such is present ; he therefore supposes that the canals which convey the fluid of the feet serve more- over as nutritious vessels to parts of the body also supplied by the sanguiferous system. In short he conceives that there are two systems of nutritious vessels distinct from each other, the sanguiferous system, confined to certain organs already named, and the vessels of the feet, destined to nourish another set of parts ; the vessels of the first system carrying blood, those of the second a nutritious fluid secreted from the blood. Delle Chiaje on the other hand maintains that the two orders of vessels communicate together and form but one sys- tem. From our own observations on the Asterias we are disposed to conclude that the vessels of the feet form a system apart from the bloodvessels, as is maintained by Tiede- mann ; but there seems considerable reason to doubt whether, as that author supposes, they serve as the nutritious vessels of the parts in which they run ; for even according to his own admirable description it does not appear that they ramify in the tissues, if we except, perhaps, the skin of the Holothuria. Moreover their contained liquid does not present the usual characters of blood or of a fluid adapted to nourish the textures ; it is true there are float- ing particles suspended in it, but the clear fluid when filtered yields no trace of animal matter, but agrees almost entirely in com- position with sea-water; at least such is the result of our examination of it in the Asterias. The vessels of the feet having been already de- scribed, we have here only to give an account of the proper sanguiferous system , following Tiede- mann as our leading authority, but at the same time stating the more material points in which Delle Chiaje differs from him. a. In Asterias a delicate vessel runs along the upper surface of each of the cceca. There are, of course, ten such vessels in Asterias aurantiacu (from which the description is taken) corresponding in number with the coeca (Jig. 22, v, v). They commence near the extremity of the rays, and, receiving branches from the branches and lobes of the cceca, proceed to the central part of the animal, where they terminate in a circular vessel (x) which runs round the upper part of the body on the internal surface. The circular vessel also re- ceives ten branches (y, y) from the ovaries, and five from the stomach, which before joining it unite into two ( w ). The vessels described seem to constitute the venous system, and Tiedemann further supposes that theccecal and gastric veins convey the chyle or nutritious part of the food from the alimentary organs. The circular vein opens into a vertical canal ( h , and Jig. 12, h), which descends along the prominent angle between two rays, inclosed in the same membranous sheath with the sand canal already described, and terminates in an 42 ECIIINODERMATA. Fig. 22. Asterias aurantiaea opened from above. A, ray with the coeca a, p,in their place. B, coeca removed ; vesicles of feet d, seen. C, vesicles of feet removed to shew the calcareous segments of the ray. D, skin forming roof of the body and rays A, B, C, raised ; vessels seen on its inner surface with collapsed stomach,/, &c. inferior circular vessel. The descending canal ts dilated in the middle ; its comparatively thick brown coloured parietes are smooth externally, but reticulated on the inside and composed of interlaced fibres, which Tiede- mann found to possess muscular irritability. He accordingly considers this canal as the heart. The inferior circular vessel (which must not be confounded with the circular canal connected with the feet) surrounds the mouth on the outside or inferior surface ; it sends out five branches which pass into the interior of the body, and are distributed to the stomach, coeca and ovaries. Tiedemann re- gards these branches with the circular vessel from which they proceed as arteries, and he thinks it probable that their minute ramifica- tions open into the radicles of the veins, though from their delicacy he has not been able to ascertain the fact by injection. Tiedemann’s view of the function of the respective vessels is derived solely from a con- sideration of their anatomical disposition, and while in the same way it may be inferred that the blood circulates in a direction conformable with this view, it must nevertheless be kept in mind that no direct physiological proof of such a course of the blood has been yet ob- tained. Besides the vessels described, Tiede- mann found yet another circular vessel sur- rounding the mouth on the under surface and placed more superficially than the last men- tioned ; it is of an orange colour and sends a branch along each of the rays, in the groove which is on the middle of their inferior sur- face. lie could trace no connection between ECIIINODERMATA. 43 this vessel or its branches and the rest of the vascular system, and he professes himself at a loss to conjecture what may be its function. According to Delle Chiaje the circular ves- sel (i, i, Jigs. 12 and 22,) into which the canals of the feet open receives also the veins from the up- per surface of the cceca and stomach. The same vessel, which he names the venous sinus, gives out — 1 . twenty short dental arteries; 2. the mesa- raics to the under surface of the cceca; 3. five vertebral arteries which open into the vesicles of the feet; 4. the radial to the under part of each ray ; 5. the dorsal arteries to the upper part of the ray, which extend their ramifications to the external surface of the body. b. Echinus. A circular vessel, supposed to be of a venous nature, surrounds the anal extremity of the intestine (fig- 19, at c), being situated on the internal surface of the shell. A vertical vessel (e, cut short) descends from it towards the lantern and opens into a short oval canal (h) with muscular panetes, which exhibits during life slow but distinct contrac- tions and dilatations, and which is therefore considered as a heart. The heart is situated near the commencement of the intestine ; a vessel (i, i, i, i) issues from it which first sends branches to the oesophagus and the muscles and membranes of the lantern, and then runs along the whole intestine on its inner border, first increasing somewhat in diameter, afterwards gradually diminishing as it ap- proaches the anus, where it terminates. This vessel gives off at all points of its course small branches to the intestine; it contains a dark yellow fluid coagulable by alcohol, and its parietes contract on mechanical irritation ; Tiedemann conceives it to be an artery. Ano- ther vessel (k,k,k,k) equal in length to the last described, but not directly connected with the heart, runs along the intestine on its outer or mesenteric border; it also is widest in the middle of its course, from whence it may be traced in one direction as far as the lantern, and in the other to the vicinity of the anus. Along its whole course this vessel receives small brandies from the intestine, and gives off branches from its other side, which pass along the mesentery to the internal surface of the shell, and are ramified on the lining or peritoneal membrane. Tiedemann regards this vessel as a vein ; but as it does not directly communicate with either the heart or the cir- cular vessel, he conceives that the fluid which it circulates is conveyed into it by one set of branches, and out of it by the other, the in- testinal being its entering and the mesenteric or peritoneal its issuing branches. Lastly, the circular vessel placed round the termination of the intestine receives several vessels which come from the peritoneal lining of the shell, and whose commencing branches are probably continuous with the terminations of the peri- toneal branches from the longitudinal vein. Tiedemann conceives the circulation to take place in the following manner. The blood passes from the circular vessel into the heart; it is then propelled along the artery and its branches ; from these it passes into the veins of the intestine, which also absorb the chyle, and the mixed fluid is conveyed into the great longitudinal vein ; it next passes into the branches of this vessel, which are distributed to the lining membrane of the shell, and is at last conveyed back by another set of vessels into the circular vein, from which we have supposed it to set out. That this is the course of the circulation is inferred from the anatomy of the circulating organs. On similar grounds Tiedemann with great probability supposes that the blood undergoes its respiratory change, at least chiefly, in its passage through the vessels of the peritoneal membrane, being there most effectually exposed to the influence of the water; he accordingly compares the branches of the great vein which ramify on that membrane to pulmonary or branchial arteries, and the vessels which return the blood to the circular vein, together with that vein itself, to pulmonary veins, lie found that the fluid contained in the longitudinal vein was of a yellowish white colour, from which cir- cumstance, as well as from the fact that he could discover no special chyliferous vessels, he inferred that the chyle was absorbed by its intestinal branches. This vein did not con- tract on the application of stimuli. Delle Chiaje’s description of the vessels of the Echinus is in substance as follows. An annular vessel surrounds the oesophagus ; it receives the termination of the intestinal vein, and gives out the intestinal artery, which like the vein runs along the intestine, and also five t esophageal arteries, which before ramifying on the mouth communicate (by means of a branch passing between the muscles of the teeth) with the dorsal arteries. These last are the canals of the feet; they run along the ambulacra to the anus, where, according to Delle Chiaje, they form a ring, and in their course send lateral branches into the feet. c. Holothuria. A vessel (Jig- 20, i, i, i, i,), which Tiedemann conceives to be the great artery, runs along the free border of the intes- tine. It is widest in the middle, and gradually disappears posteriorly in the neighbourhood of the cloaca, while anteriorly it forms an annular vessel (at e ) round the stomach, out of which branches proceed to the stomach, the ovaries and the sac connected with the canals of the feet and tentacula formerly described. A short but wide anastomosing branch (cut at k, k,) passes from the artery about the middle of the first portion of the intestine, to join it again at the middle of the second portion (in), that is, nearly about the middle of the arterial trunk itself. Slow contractions, followed by dilata- tions, were observed by Tiedemann in this vessel ; they commenced at the middle or widest part, and proceeded in opposite direc- tions to its two extremities, carrying on the light brown-coloured blood contained within it in a corresponding manner. The main artery, which seems thus also to serve the purpose of a heart, sends in its course numerous branches to the intestine, from these the blood is received by the commencing veins, which, uniting to- gether at the opposite or attached border of the ECIIINODERMATA. 44 intestine, form a plexus along its first portion, whose branches ultimately terminate in a large longitudinal venous trunk («, n, n, n). The blood is conveyed from this great vein to the right branch of the respiratory organ, (which lies between the first and second portions of intestine,) by a considerable number of vessels which divide like arteries into smaller ramifi- cations on the lung, and may therefore be com- ared to pulmonary arteries. The capillary ranches of these vessels transmit the blood into the commencing pulmonary veins, which, uniting into larger and larger branches, ter- minate in a third longitudinal vessel (o), situated on the second portion of intestine. This last-mentioned vessel, which may be con- sidered as the great pulmonary vein, sends branches on the intestine which open into the wide part of the main artery, and thus the blood is carried to the place whence it set out. According to Delle Chiaje, the principal vein, after diminishing in width, opens into the oblong sac which is connected with the vessels of the feet, and out of this bag six vessels issue. One of these is the great artery, which runs along the intestine; the other five are the vessels of the tentacula and feet previously described ; each of them sends four branches forwards to the tentacula, and a long one backwards between the longitudinal muscles to the vesicles of the feet. 5. Nerves. — Tiedemann discovered a nervous system in the star-fish. He describes it (in A. aurantiaca ) as consisting of a delicate white cord surrounding the mouth, in form of a ring immediately on the outside of the circular vessel into which the heart opens, and of di- verging filaments which arise from the annular cord opposite the rays. ( Fig. 23.) There are Fig. 23. c,fcel ; e,feet cut across ; f, apertures for the feet. three filaments for each ray; one runs along the under surface in the median line, and ap- pears to send small branches to the feet ; the other two, which are shorter, pass between the first and second segment of the ray into the interior of the body, and are probably distri- buted to the stomach. Tiedemann could dis- cover no ganglia, but others describe minute ganglia as existing at the points where the diverging filaments originate.* The Echinodermata have not generally been supposed to possess any other sense than that of touch. Professor Ehrenberg has how- ever recently called attention to certain parts in the Asterias, which he is disposed to re- gard as organs of vision.-)- These have the ap- pearance of small red spots, one of which is seen at the extremity of each ray. They have been long known to exist in several species of Asterias, but no one ever assigned to them any particular use till lately, when Professor Ehrenberg, struck with their resemblance in aspect to the eyes of Entomostraca and Infusoria, conjectured that they might be of the same nature. He states that he has traced the long nerve of the ray as far as the extremity, where it swells into a sort of ganglion with which the red point or supposed eye is connected. In the Echinus Tiedemann observed fine filaments on the internal surface of the mem- brane which fills the inferior opening of the shell, and on the dental apparatus and the longitudinal vessels of the feet, from which he inferred that a nervous system probably existed in the Echinus analogous in form to that of the Asterias. In the same way he was led to sus- pect the existence of such a system in the Holothuria, though by dissection he could make out nothing more than several exceedingly delicate filaments, some of which were situated in the neighbourhood of the mouth, and ap- peared to enter the tentacula, and others lay on the longitudinal muscles. Dr. Grant de- scribes a connected nervous system in the Echi- nus and Holothuria, but without mentioning on whose observations his description, which we here transcribe, is founded. “ A nervous chord,” he states, “ is seen round the ceso- phagus of the Echinus, which sends delicate white filaments to the complicated muscular and sensitive apparatus of the mouth ; other nerves are seen extending upwards from the same oesophageal ring, along the course of the vessels in the interior of the abdominal cavity. In the Holothuria the nervous sys- tem is extensively developed. Interior to the osseous apparatus of the mouth is a white nervous ring around the oesophagus, from which nerves pass outwards to the large ramified tentacula around the mouth, and others extend upwards along the course of the eight strong longitudinal muscular bands. Fine white filaments are likewise seen passing inwards to the stomach and alimentary ap- paratus.”;); In a recent notice of some obser- vations on the Echinus by M. Van Beneden, it is stated that he distinctly recognized a nervous collar surrounding the oesophagus. 6. Generative organs. — The only organs hitherto discovered in the Echinodermata, which * Grant’s Comparative Anatomy, p. 184. t Muller’s Archiv fiir Anatomie, Pkysiologie, &c, 1834. p. 577. | Comparative Anatomy, p. 184. ECHINODERMATA. 45 can with certainty be regarded as belonging to the generative system, are the ovaries, which are found in all. These animals would there- fore appear to have no distinction of sex. Whether the concurrence of two individuals is in general necessary for propagation is uncer- tain ; O. Fabricius affirms it of the star-fish, but further observation would be required satis- factorily to establish the fact ; he says “ con- greditur” (Ast. rubens) “ mense Maio, oribus arete connexis, altera supina.”* a. The ovaries of Asterias seem to vary in number according to the species. In A. rubens and aurantiaca there are ten, two being situated in each ray, above the vesicles of the feet. Each of these organs consists in the former species of an oblong cluster of ramified tubes, (Jigs.\2zxu\ 16,o, and at o', cut short), proceeding all from a single stem by which the organ is fixed, and terminating in round vesicular dila- tations. In A. aurantiaca the tubes are not all connected by a single stem, but form about twenty fasciculi, each of which has a distinct attachment (Jig. 22, o, o ). The vesicles contain a whitish pulpy sub- stance, with which they are more or less dis- tended according to the season of the year; so that the ovary, varying thus in size, is found to occupy sometimes a greater at other times a less extent of the ray, to the commencement or base of which it is attached. Tiedemann could discover no excretory duct of the ovary ; and nothing positive is known as to the way in which the ova are formed and discharged from the body. Tiedemann conjectures that they escape by openings situate in the neigh- bourhood of the mouth, in the angles between the rays. The Ophiura has also ten ovaries, which do not lie in the rays, but in the central part of the animal, and which, according to Meckel, open externally by orifices on the ventral sur- face. b. The Echinus has five ovaries, (Jig . 10, c,) attached to the inside of the shell in the upper part of the body, and occupying the spaces between the five rows of feet. They are often joined together laterally. They consist of an assemblage of small round bodies, which are the ova. Five short tubular oviducts come from the upper end of the ovaries and open externally by an equal number of orifices, pierced in five oval plates which surround the anus. The size of these organs, as in the star- fish, varies much according to the degree of maturity of the ova. The ovary, or row as it is named, is the part used as food. Mr. Pen- nant states that the E. esculentus is “ eaten by the poor in many parts of England, and by the better sort abroad in ancient Rome the Echini formed a favourite dish at the tables of the great. c. The ovary of Holothuria tubulosa (jig. 34, m, p. 109, vol. i.) is situated at the fore part of the body near the stomach and first portion of the intestine. It is a tube with many clus- tering branches, which terminate in blind and * Fauna Groenlandica, p. 368. slightly dilated extremities. The main tube or oviduct runs forwards along the stomach, and opens externally on the dorsal aspect of the body a little way behind the mouth. Between the insertion of its branches and its external orifice, eight or ten pyriform vesicles open into it, close to each other, by long tubu lar pedi- cles. The size of the ovary varies excessively at different periods ; its branches usually contain a whitish fluid ; but Tiedemann states that about the end of October he has in some in- stances found the organ enlarged to twice or three times its usual dimensions, and con- taining oblong brown-coloured bodies from half a line to a line in length, which he sup- poses were eggs or perhaps embryos. From a statement of O. Fabricius it would appear that the Hoi. pentactes is ovo-viviparous : he says, “ est vivipara : mense enim Martio in ilia versus anum pullum libere natantem, rubieundum vidi.”* The pyriform vesicles are found en- larged at the same time with the ovary itself, and Tiedemann conjectures they may be male organs, by which a fecundating fluid is produced and applied to the ova. 7. Regeneration of lost parts.— The star-fish affords an example of great regenerating power. Individuals are often found which have evi- dently sustained the loss of one or more rays, and in which new rays, as yet incomplete in their growth, occupy the place of the old. Experiments have been even purposely made which were attended with the same result; but we are not aware that the process of regeneration in these animals has been care- fully traced in its successive steps, or at least fully described. In 1741 and 42, Messrs. Bernard de Jussieu, Guettard, and Gerard de Villars made observations and experiments on this subject at various parts of the coast of France. These researches were undertaken at the request of M. de Reaumur, who thus de- scribes them. “ They (M. de Jussieu and Guettard) brought me specimens of star-fish with four large rays and a small one still growing; they found others with only three large and two extremely small rays ; others again with two large rays and three very small, and, as it seemed, very young ones. Lastly they more than once met with a single large ray from which four small ones had begun to sprout.” After remarking that the fact had been long familiarly known to the fishermen, M. Reaumur continues, “ The portions into which Messrs. Jussieu and Guet- tard had divided the animals appeared to go on well, the wounds cicatrized and consoli- dated, but the experimenters were obliged to limit their stay on the coast to about fifteen days ; too short a period to trace the progress of a reproduction which apparently is not completed till after several months, or perhaps even upwards of a year.”f Bibliography. — Kleinius, Naturalis dispositio * Fauna Groenlandica, p. 353. f Reaumur, Memoires pour servir a l’histoire des insectes, tome vi. preface, page lx. sq. 46 EDENTATA. Echinodermatum, 4to. Lips. 1778. Linkius, De stellis marinis, fob Lips. 1733. Blainville, Diet, des Sc. Nat. art. Oursin. Tiedemann, Anatomie der Rohrenholothurie, &c. Heidelberg, 1820. Eh- renherg, in Meckel’s Archiv fur Anat. & c. 1834. Delle Chiaje, Memorie sulla storia degli animali senza vertebre del regno di Napoli. ( W. Sharpey.) EDENTATA. — A group of mammiferous animals, exhibiting no very distinct general characters to indicate any close mutual affinities between them, but agreeing in the unimport- ant character of the absence of incisive teeth and the possession of long claws. They may indeed be considered as consisting of two very distinct groups ; the one exclusively vegetable feeders, the other generally insectivorous in their habits. To the first belong the Sloths ( Brady pus ), (Jig. 24), constituting the Tar- digrada of llliger ; to the second, the Ant- eaters ( Myrmecopliaga), (fig. 25), the Arma- dillos ( Dasypus ), (fig. 26), the Pangolin ( Ma- nis) (fig. 27), with their congeners, and the re- cently discovered American fossorial animal, the Chlamypltorus, forming the Edentata proper. The enormous extinct animal, the Megathe- rium (fig. 28), may be considered as an addi- tional form, and a very interesting and impor- tant one, as it certainly exhibits some charac- ters which appear to connect the Turdigrada and the true Edentata. The organization of these forms is so different as to require a se- parate description. The Ornithorynchus and the Echidna are necessarily excluded from the Edentata, with which they had been united by Cuvier and others, and form the group called Monotremata by Geoffroy. In the Sloths, the whole structure is evidently formed to enable them to pass their life in trees, amongst the branches of which they con- stantly reside, hanging with the back down- wards and creeping slowly along in this remark- able position, embracing the bough, and Fig. 24. Skeleton of the Sloth. Fig. 25. Skeleton of the Ant-eater. EDENTATA. Fig. 26. 47 Skeleton of the Armadillo. Fig. 27. Skeleton of the Mania. Fig. 28. Skeleton of the Megatherium. stretching out their hands, which in the Ai or Bradt/pus tridactylus are of great length, to enable them to lay hold of the extreme twigs, and bring them to the mouth. Their progres- sion on the ground is excessively slow and awkward, and should they be obliged to have recourse to it either from accident or from being forced by famine to seek a new tree on which to obtain their subsistence, they quit it as speedily as their peculiar organization will permit, and ascend the 'nearest tree with an awkward attempt at. alacrity. The whole of their structure is admirably adapted to these extraordinary habits ; and although upon a comparison of these slow-moving creatures with the active and intelligent and elegant ani- mals which form the more conspicuous groups of the Edentata, they may appear to possess but few advantages of structure, and little to excite interest in their habits, yet a careful investigation into the relation between their organization and their mode of life will shew that not even in the most elevated forms of the animal creation, does the wisdom of the 48 EDENTATA, Creator display itself more fully than in the construction of these contemned and apparently apathetic beings. I must refer the reader to a highly interesting paper by Professor Buck- land in the Linnsean Transactions, in which the libels of Cuvier on this maligned animal are beautifully and satisfactorily refuted. The Ant-eaters and Armadillos, on the other hand, which may be considered as the true Edentata, are constructed for very different habits, and the Chlumyphorus must be consi- dered as offering a very near affinity to the latter genus. The Ant-eaters with their thick long hair and fossorial claws, and the long ex- tensile tongue with which they are furnished, are thus enabled to scratch or dig up the ant- hills and to receive their minute but multi- tudinous inhabitants on the mucous surface of the tongue : whilst by their long dense hair they are protected from the annoyance or dan- ger which their little troublesome victims would otherwise inflict. The Armadillos and the Chlumyphorus, on the other hand, pursue their insect prey either on or beneath the sur- face of the earth, and are protected from the attacks of their enemies by the panoply of mail with which they are furnished. The osseous system. The cranium.-— The ge- neral character which at once strikes us in look- ing at the cranium of the Sloths (fig 29) is its Head of the Sloth. extreme shortness, particularly with regard to the facial portion, and the roundness of its whole contour. In the insectivorous forms the muzzle, on the contrary, is greatly elongated. The frontal bone in the Tardigrada is large, and the anterior portion convex ; it has no zygo- matic process, and the frontal and orbital por- tions pass into each other by a very obtuse angle. The parietal bone in most is of a square figure. In the Armadillos (fig. 30) and in the Fig. 30. Orycteropus the two parietals are united from an early period ; in the Ant-eaters, on the con- trary, they remain separate. In the Sloth the squamous portion of the temporal bone is of large dimensions, and the acoustic portion of but moderate size. The zygomatic process is small and does not reach the jugal bone ; a con- struction which is still more conspicuously seen in the Ant-eaters. The occipital bone is large ; the squamous portion broad and rounded, the superior part being continued to the inferior by an obtuse angle in the Sloths, and by nearly a right anglein the true Edentata. The occipital foramen is round. The jugal bone offers some remarkable peculiarities in its form. In the Ant-eaters (fig. 31) it occurs in a Fig- 31. Head of the Ant-eater. very imperfect condition, being merely an ob- long plate of bone, terminating posteriorly in a rounded point, situated in the posterior ex- tremity of the superior maxillary bone, and beneath the lachrymal, extending posteriorly scarcely beyond the latter ; consequently it is remote from the temporal bone throughout the whole length of the temporal fossa, and there is no zygomatic arch. In the Manis (fig. 32) it is absolutely wanting. In the Arma- Fig. 32. Head of the Manis. dillos it is somewhat more fully developed ; it is larger and higher and reaches the tem- poral bone by its posterior portion. In the Sloths, especially in the Bradypus diductylus, or Uriau, it attains a much greater size, and has on its inferior margin a long process extending downwards and backwards almost to the base of the lower jaw. This remarkable process is also found in the enormous fossil animal the Megatherium (fig. 33). The posterior extremity of the jugal bone is remote from the zygomatic process of the temporal in the Sloths, but in the Megatherium these bones are united, and the zygomatic arch is therefore complete. The in- ferior maxillary bone varies excessively in this order. In the Orycteropus, Manis, and Myrme- cophaga, it is extremely long and depressed ; its height does not greatly vary in the whole of its length. In the Armadillos it is much shorter, and in the Sloths it is extremely short and trun- cated. The intermaxillary bone is excessively small in the Ant-eaters and the Sloth, which are not furnished with any incisive teeth, but in Armadillos it attains a somewhat greater degree of development, especially in the genus Da- EDENTATA. 49 Fig. 33. sypus. The inferior maxillary bone varies no less in its form in the different genera of this incongruous order than the superior. It is greatly elongated and very slender in the Edentata proper, particularly in the Ant-eaters ; the ascending plate is thin and small, the right and left branches of the bone are united at the symphysis to a considerable extent, and at a very acute angle. In the Sloths this bone ex- hibits a very different structure ; it is short and deep, the ascending plate is broad and almost square, the angular process is very large, and the two branches of the jaw unite at the symphysis without an angle, the anterior por- tion of each side being curved inwards to meet its fellow. In the Megatherium the body of the bone is still higher and shorter, but the an- terior part is prolonged into a narrow and de- pressed groove somewhat similar to that of the elephant. The vertebral column. — The variation in the form and construction of the vertebrae will be found to bear an exact relation to the habits of the different genera. The cervical vertebrte of the A'i, Bradypus tridactylus, have always, until very recently, been believed to form an excep- tion to the general law, which assigns seven as the strict number of these bones in the mam- miferous animals. That this number should exist equally in the hog and the giraffe is in- deed a remarkable fact, and may be considered as a striking illustration of the law by which variations in volume in any particular system of organs are provided for rather by the differ- ence in volume or in the relative proportions of the organs themselves, than by any abrupt change in their number. The supposed excep- tion to this law which now comes under our notice consists in the fact that the neck of the animal in question, (speaking of the part rather in reference to its use than in strict ana- tomical language,) is formed of nine vertebra. Two skeletons in my own possession, however, have enabled me to demonstrate that the posterior two of these vertebrae (fig- 34) have attached to them the rudiments of two pair of ribs in the form of small elongated bones articulated to the transverse processes of these bones, which are therefore to be considered as truly dorsal ver- tebra, modified into a cervical form and func- tion, suited to the peculiar wants of the animal. The object of the increased number of ver- tebra in the neck is evidently to allow of a more extensive rotation of the head ; for as von. IJ. Fig. 34. Neclt of the Sloth. each of the bones turns to a small extent upon the succeeding one, it is clear that the degree of rotation of the extreme point will be in pro- portion to the number of moveable pieces in the whole series. When the habits of this extraordinary animal are considered, hanging as it does from the under surface of boughs with the back downwards, it is obvious that the only means by which it could look downwards towards the ground must be by rotation of the neck ; and as it was necessary, in order to effect this without diminishing the firmness of the cervical portion of the vertebral column, to add certain moveable points to the number possessed by the rest of the class, the ad- ditional motion was acquired by modifying the two superior dorsal vertebrae, and giving them the office of cervical, rather than in- fringing on a rule which is thus preserved entire without a single known exception. In the tw'o-toed Sloth there is but one pair of these rudimentary ribs, and consequently only the first dorsal vertebra enters into the compo- sition of the neck. The dorsal portion of the vertebral column is particularly long in the Ant-eaters as well as the Sloth. These vertebrae are also generally more numerous in this than in most other groups — the great Ant-eater having sixteen, the Ai fourteen, and the Unau no less than twenty-three — a larger number than is found in any other mammi- ferous animal. The ribs offer some striking peculiarities in their construction. In the Ant- eaters and Armadillos they are excessively broad with the exception of the first and second. In the Myrmecophaga jubata and M. didactyla they overlap each other in an imbricated man- ner on the upper part, — a conformation which gives great solidity to the chest. The Sloths and the Megatherium exhibit also considerable breadth of the ribs, but to a much less extent than that just described, and the latter animal, E 50 EDENTATA. at least in the remains lately described by Mr. Clift, the part joining the sternum, and answer- ing to the cartilages of the ribs, is bony and is connected to the rib itself by a moveable arti- culation. The lumbar vertebra are generally broad and furnished with strong spinous pro- cesses. The transverse processes are incon- siderable in the Sloths, but large in the Edentata proper. In the Armadillos the anterior articu- lar processes are particularly strong and larger even than the spinous. This is the case, but to a less degree, in the Ant-eaters. In the Orycte- ropus there are slight indications of inferior spinous processes on most of the lumbar verte- bra, consisting of a small longitudinal crest. The caudal vertebra vary excessively in num- ber. In the Unau and Bradypus didactylus they are very few — not more than seven or eight ; in the large Ant-eater forty, and in the African Manis forty-five. In the remains of the Megatherium lately deposited in the Mu- seum of the Royal College of Surgeons, the tail would appear, according to Mr. Clift’s computation, to consist of eighteen vertebra at least. The caudal vertebrae of the Edentata proper have inferior spinous processes of a remarkable form, being constituted of two branches meeting inferiorly in the median line. The Megatherium possesses similar V-shaped processes. In the Myrmecophaga didactyla the two branches are not united in the anterior two of them. The sternum offers a considerable developement of themanubriumot anterior bone in the whole of the Edentata, particularly in the Ant-eaters and Armadillos. It is also rather large in the Megatherium. The pelvis in the Edentata proper is much elongated, and the acetabulum rather behind the middle of the whole length of the bones. The ileum, which forms the anterior half of the pel- vis in the Armadillo, is fixed to the sacrum by its posterior portion, a surface of considerable extent. The ischium and pubis are large, the is- chiatic notch wide, and the cavity of the pelvis capacious. In the Sloths and Megatherium the pelvis is of large dimensions, the ilia very broad, especially in the latter; the cavity capa- cious, and the outlet large. The ossa pubis are joined at the symphysis in most of the Eden- tata, as is now ascertained by Mr. Clift, in the Megatherium. In the Myrmecophaga didac- tyla, it is stated by Cuvier to be open. The size of the pelvis in the Megatherium is enormous. On comparison of it with the pelvis of an elephant eleven feet in length, Mr. Clift found that in the former the ilia are 5ft. lin , and in the latter only 3ft. 8in. The anterior extremity. — The principal cha- racteristic of the bones of the arm in the Sloth is their extraordinary length. The humerus is very much elongated and cylindrical, with the elevations but slightly marked. The ulna and radius are also very long, and bowed, so that the bones are distant at the middle of their length ; the radius is very broad anteriorly. The very complete power of pronation and su- pination enjoyed by this animal is no less ob- viously suited to its habits than the great length of its anterior extremities ; both of which peculiarities are admirably subservient to the complicated objects of holding by the boughs, of advancing along their under-surface, and of reaching and bringing to the mouth the leaves on which it feeds ; and the structure of the hand (fig. 35) is no less suited to the same pur- Fig. 35. Hand of the Sloth. poses. The carpus is as long as it is broad ; it is composed of six pieces only, of which four form the first series, and two the second. The os scaphoides is the largest of the whole, and is articulated with the os semilunare by a convex articular surface : the os cuneiforme presents on its ulnar side an oblique flattened surface; the os pisiforme, which is not named by Cuvier, does however exist, though it is of small size. The inner and larger piece of the anterior series probably consists of the os trapezium, trape- zoideum, and magnum united ; and the external one solely of the os unciforme. In the Unau the os trapezdides is distinct. The metacarpal bones, to return to the A'l, consist of three per- fect and two rudimentary, the whole of which are united at their base to each other and to the inner solid carpal piece, consisting of the three bones before mentioned; so that in fact the five metacarpal bones, with the os trapezium, tra- pezoideum, and magnum, form one solid osseous piece. The fingers, which are three only, are very long, and consist each of two moveable phalanges only, the first being very small and early anchylosed to the metacarpal bone. In a very young skeleton in my possession, these bones are not yet united. There is but very little flexion between this part and the second phalanx, but between the latter and the third or ungueal phalanx the flexion is complete, the latter being bent down to the palm with perfect ease. These ungueal bones are very long, curved, laterally compressed, large at the base, at which part there is, as in the cats, a bony sheath to cover the base of the claw; and the latter envelopes the phalanx for about five-sixths of its length. Tire posterior extremity in this remarkable animal offers no less striking peculiarities. The breadth and openness of its pelvis have been already noticed. The femur is articulated to the acetabulum so as to stand obliquely outwards from the pelvis ; it has a short head, and is it- self rather short, strong, and flattened. The tibia and fibula are long and slender, and some- what curved ; the superior articular surfaces of the tibia are flat, that of the inferior extremity EDENTATA. small, triangular and slightly concave ; but the most extraordinary articulation is that of the fibula with the astragalus; its inferior extremity terminates in a conical point, which enters and plays in a corresponding cavity in the latter bone. This peculiarity of the articulation of the ankle, which was considered by Cuvier as only additional evidence of the imperfection of the animal’s structure, is no less admirably adapted to its habits than those points which have been previously noticed. The feet, it is true, are turned inwards, and there is no pos- sibility of placing the sole on the ground ; but it is the better adapted for clasping boughs, and the freedom of rotation which is provided by this curious joint allows of eveiy kind of motion required in such circumstances. The tarsus consists of the astragalus and os calcis, which are separate, and of the usual anterior series of bones, which in the aged individuals are anchylosed together as well as to the meta- tarsal bones, which are themselves united as in the carpus. The tubercle of the os calcis is very long, and so situated as to afford a sort of opposing thumb to the flexed phalanges. The latter bones very nearly resemble those of the anterior extremity. It is impossible not to be struck, even on a superficial view of the extraordinary structure of theanteriorand posterior extremities of the Sloth, with the complete adaptation of this deviation from the normal form to its peculiar mode of life. Grasping the boughs of trees on which it both feeds and reposes, crawling along with the back downwards and the belly pressed against the tree, and culling, with the long arms, the leaves at the inaccessible extre- mities of the branches, the usual construction of the members would be absolutely useless, and an incumbrance instead of an assistance. But by the great breadth of the pelvis, the di- rection of the femora, the long and curved claws, the consolidation of the tarsus, and the curious structure of the articulation of the fibula with the astragalus, every requirement of security and progression is obtained; whilst in the an- terior extremity the extensive motion of the shoulder-joint, the great length of the arms, the complete flexion of the fingers, and other peculia- rities, combine, with that security and facility of progression, the most effective means of ob- taining the animal’s peculiar food. Of the Edentata proper. — The extremities in animals of this class are, as may be con- cluded from their habits, very differently constituted from those which have just been described. In all of them the object to be obtained is facility in digging the ground, or scratching up immense nests, in search of the insects which constitute the principal food of most of these animals. The gigantic Megatherium, however, appears to have combined the phytopha- gous character of the Sloth with the fossorial habits of the Dasy- pus, and is supposed to have lived upon roots, which it 51 snatched or dug up with its enormous claws. The scapula of thejAnt-eaters and Armadillos is found nearly like that of the Sloth ; in the Myrmecophagajubata a process of bone extends from the coracoid process to the anterior margin, rendering that which is a notch in other species a complete foramen. A second spine inferior to the true one is also observed in that species, in which respect it resembles the Unau or two-toed Sloth. The scapula of the Armadillos is very high and narrow. In that of the Mega- therium there exists a large process of bone ex- tending from the coracoid process to the acro- mion,andthus completely uniting theseprocesses. The clavicle exists in many of the Edentata, as the Armadillos and Ant-eaters, but is wanting in the Man is or Pangolin. That of the Megathe- rium offers a remarkable peculiarity. It extends from the acromion, not to the sternum as in all other cases, but to the first rib. The humerus is in most of the order very short and robust, and its elevations strongly marked. In the Ant-eaters the part above the inner condyle is extremely developed, to give attachment to the powerful flexors of the claws ; and the crests for the in- sertion of the deltoid and great pectoral muscles are very prominent and angular, — a structure which is also conspicuous in the Armadillos and Manis. The humerus of the Megatherium has a similar general form; it is rude, short, and excessively strong, with abrupt and large ele- vations for the different muscular attachments ; the inferior part especially becomes suddenly larger, from the existence of a strong and ele- vated external crest. The habits of the Edentata proper demand a very different construction of the fore-arm from that of the Sloth. Requiring immense strength in digging the ground, the short ole- cranon which exists in the Sloth would be wholly inefficient. A long lever is necessary, and hence we find that in the whole' of these the olecranon is of an extraordinary length, and that in the Megatherium its more moderate length is compensated for by its immense strength. In the five-toed Armadillo this pro- cess is so extensive as to render the ulna no less than twice the length of the radius, and in the other species of the same genus it is not much less. The radius is broad, robust, and strongly marked, particularly towards the carpal extremity. The hand in the Myrmeco- phaga (fig 36) and its kindred genus Manis Fig. 36. 52 EDENTATA. offers a very remarkable structure. The ungueal phalanges, like those of the Sloth, are restricted in their motion to simple flexion, in which position they are retained during repose by strong ligaments. In the Myrmecophuga the terminal phalanges are deeply grooved in the margin ; in the latter they are bifid. The pha- langes of the fingers themselves are very une- qual in length and thickness. The middle finger is of extraordinary size, every articula- tion being very robust, and almost twice as thick as either of the others; the next on each side are nearly as long but much smaller, and the outer shorter still and very slender. The outer finger has no claw; the four others are furnished with claws. The hand in Dasypus and Oiycteropus is also of a very remarkable conformation, particularly in the gigantic spe- cies of Armadillo, Priodontu gigantea (fig 37) Fig 37. of Fr. Cuvier. Amongst the peculiarities of structure in this animal are the following. In add.tion to several remarkable anomalies in the carpal bones, the bone which results from the ossification of the flexor profundus muscle is very large, developed posteriorly into a large and irregularly formed head, articulated by large surfaces to the os semi- lunare and pis forme, presenting concave sur- faces on the side of the fore-arm, and termi- nating towards the hand by an enlargement which is compressed and smaller than the head. The metacarpals are no less extraordinary. Those of the thumb and index, as well as their phalanges, are slender, of the usual construc- tion, but that of the middle finger is irregularly rectangular and broader than it is long ; and the phalanx which it supports is of a corresponding form and size, being extraordinarily short and broad. The corresponding bones of the fourth finger are similarly formed, but somewhat smaller. The ungueal or terminal phalanx of the middle finger is enormously large and strong, curved outwards, and having at its base a large bony hood or case for the lodgement of the claw ; tiie terminal phalanx of the fourth finger is similar, but of somewhat smaller di- mensions. The fifth or little finger is much smaller, but is furnished with a claw of some size. The conformation of the hand of this animal affords a most formidable weapon, or as a powerful fossorial instrument, in the three outer claws, whilst the two inner ones are only formed for scratching or other similarly slight actions. The posterior extremity of the Edentata pi'oper offers perhaps less striking peculiarities of structure. The femur in general is of mo- derate length, but large and strong; and an elevated crest, arising from the great trochanter, extends nearly the whole length of the bone. In the Ant-eaters and the Megatherium, it is particularly broad and flattened, and the greater and lesser trochanters are not particularly pro- minent. In the genus Dasypus the great tro- chanter on the contrary is of great size, and from the middle of its outer margin arises a large process which is directed outwards. The tibia and fibula in the latter genus are extremely broad, arched, and anchylosed at both extremi- ties. In the Ant-eaters, on the other hand, these bones are of the ordinary form, and have no osseous union. In the Megatherium they are united by the superior third of their length, and closely in contact at the lower part ; they are both short and extremely thick, particularly the tibia. The tarsus is composed in the two-toed Ant-eaters of at least eight distinct bones, the largest of which is a supernumerary bone, situated at the inner part of the foot, upon the scaphoid; it extendsback- wards as far as the tuberosity of the os calcis, and thus forms a broad base to the posterior part of the sole of the foot. The Myrmecophuga jubata has also a supernumerary bone, but of smaller dimensions ; but the Armadillos and Orycteropus have but the seven or- dinary bones of the tarsus. The metatarsal bones and the toes are probably invariably five throughout the Edentata proper; the toes of the posterior extremity offer few peculiarities of any consequence. Both the anterior and poste- rior feet of the Megatherium are peculiar in their structure. In the former, those fingers which are completely formed are the three middle ones, the little finger being rudimentary, and the thumb having no claw. The ungueal pha- langes of the three former are enormously deve- loped, principally as regards the bony enve- lope for the base of the claw; the size and thickness of which indicate that the claws themselves must have been of great size and immense strength, and have afforded powerful implements for tearing up the surface of the ground in search of roots. On the hinder- foot, there is a single toe of a similar con- struction, which is the third ; the fourth and fifth, although of considerable size, bore no claws. This enormous extinct animal is cer- tainly among the most extraordinary produc- tions of the ancient world. Of dimensions the most unwieldy, and with a skeleton as solid as that of the most enormous amongst the Pachy- dermata, we find a cranium, and especially teeth, which exhibit avery near relation to those of the Sloth, and members which are no less remarkably allied to the Ant-eaters and the Ar- madillos. However the difference in bulk may appear at first sight to interfere with the idea of these affinities, and however difficult it may be at once to reconcile the relation between a small active animal like the Armadillo, or an inhabitant of trees like the Sloth, and this enormous and unwieldy tenant of the earth’s earlier surface, the affinities are neither less true nor more probable than those which subsist between the light rabbit-like hyrax Hand of the Gigantic Armadillo. EDENTATA. 53 and the ponderous rhinoceros of the present world. There is still another very interesting animal, the account of whose osteology I have not in- termixed with that of the other Edentata, be- cause it is as yet but little known, and because its peculiarities are particularly interesting. This is the Chlamyphorus truncatus (fig- 38) of Dr. Harlam, of which I have the opportunity of animals belonging to the same order. To the Echidna and Ornithorynchus it is also similar in the first bone of the sternum, and in the bony articulations as well as the dilated con- necting plates of the true and false ribs. “ In the form of the lower jaw, and in other points equally obvious, the Chlantyphorus ex- hibits characters to be found in some species of Rurninantia and Pachydermata. On Fig. 38. Skeleton of the Chlamyphorus truncatus. offering a very correct figure, for which I am indebted to the kindness of my friend Mr. Yarrell. This very remarkable animal was discovered in the interior of Chili, burrowing like the mole, and like that animal residing principally underground. The detail of its organization will be found, as given by Mr. Yarrell, in the third volume of the Zoolo- gical Journal, to which I refer. The general results of that gentleman’s observations are as follow : “ It has much less real resemblance to the mole, Talpa Europea, than its external form and subterranean habits would induce us to expect. In the shortness and great strength of the legs, and in the articulation of the claws to the first phalanges of the toes, it is similar ; but in the form of the bones of the anterior extre- mity, as well as in the compressed claws, it is perfectly different ; nor do the articulations of the bones nor the arrangement of the muscles, allow any of the lateral motion so conspicuous in the mole. The hinder extremities of the Chlamyphorus are also much more powerful. “It resembles the Bradypus tridactylus in the form of the teeth, and in the acute descending process of the zygoma, but here all comparison with the Sloth ceases. “ The skeleton of the Chlamyphorus will be found to resemble that of the Armadillo (Dasypi species plures) more than any other known quadruped. In the peculiar ossification of the cervical vertebras ; in possessing the sesamoid bones of the feet ; in the general form of all the bones, except those of the pelvis, as well as in the nature of the external covering, they are decidedly similar; they differ however in the form and appendages of the head, in the com- position and arrangement of the coat of mail, and particularly in the posterior truncated ex- tremity and tail. “ There is a resemblance to be perceived in the form of some of the bones of the Chlamy- phorus to those of the Orycteropus capensis and Mi/rmecophaga jubata, as might be expected in this sketch of its relations it is unnecessary to dilate. Its near affinity to the genera Dasy- pus and Tatusia however is so obvious that there can be no doubt of the propriety of con- sidering it as belonging to the same family of the order; whilst its relation to the mole can of course only be considered as one of analogy, in which respect it offers many interesting characters.” Digestive organs. — In the character of these organs there is no less diversity between the Tardigrada and the Edentata proper than in the osteology already described. The former, essentially herbivorous, yet living principally upon the young succulent leaves which clothe the extremities of the branches, have the teeth formed for bruising this kind of nourishment, and an articulation of the lower jaw which allows of a degree of motion commensurate with the object. The teeth consist of a cylinder of bone enclosed within a simple case of enamel, but without any of the convolutions of these two substances which characterize the structure of these organs in the Rurninantia and other graminivorous animals. They are in fact the most simple which are found in any of the Mammifera. There is a single canine on each side above and below, both in the Unau, but none in the A'i. In one form of the Armadillos, the genus Dasypus as now restricted, there are two in- cisive teeth in the upper and four in the lower jaw, and sixteen molares in each, in the allied genus Tatusia there are no incisive or canine teeth, and the molares are even rather more numerous, and in the Priodonta Gigas there are no less than fifty in the upper and forty-eight in the lower jaw. These are all simple, and formed for crushing insects. The stomach in the Sloths is very remarkably formed. In the Bradypus didactylus (fig. 39) it is double. The first is large and rounded, con- tracted posteriorly, and produced into a conical appendix, which is doubled from the left to the right, and its cavity is separated from that 54 EDENTATA. Fig. 39. of the stomach by a semilunar fold. The cardia opens very far towards the right side, leaving a very large pouch, and enters a canal which proceeds along the right side of the first stomach, giving off from its right margin a broad process, which separates the pouch of the stomach from the other cavity, which lies between the pouch and the appendix before mentioned. Thus the first stomach is divided into three cavities. The canal already described turns from the left towards the right, and enters the second stomach by a narrow opening. The second stomach is of a slender form, much smaller than the former; its parietes are very thin for the first half of its length, but much thickened towards the pylorus ; and the two portions are sepa- rated by a semilunar fold. Again, the first portion of this second stomach is itself partially divided by a beautifully indented fold, the dentated processes of which are directed towards the pylorus. There is also attached to the second stomach a small cul-de-sac, which lies between two similar ones connected with the first stomach, the internal surface of all of which appears to be glandular. In the Ai the appendix to the second stomach is much longer, and divided into three chambers by two membranous partitions. The whole of this structure, and especially the canal which extends from the cardia to the second stomach, indicates a very remarkable relation to that of the ruminants, and is evidently intended for the digestion of vege- table substances only. In the Edentata proper the stomach is, as may be expected, far more simple. In the Myrmecophaga didactyla it is of a globular form, and simple. In the Manis pentadactyla or Pangolin, it is internally divided by a fold into two cavities, of which the left, analogous to the paunch, is thin, and the pyloric, or true digestive portion, much thicker. The intestinal canal does not present the same striking distinctions between the large and small intestines which are observed in most other mammifera. There are in the Ant-eaters two ccecal appendices, which may be considered as forming the boundary between the two portions, of which the posterior is very much shorter than the anterior. It is remarkable that the entrance to these small cceca is so contracted as wholly to prevent the passage of any feeces into them. In the Manis longicauda there is not the vestige of a ccecum. In the Orycteropus it is short and oval. In the Tardigruda, the Ai for example, the large intestine is at once distinguished from the small by its sudden enlargement, and at their junction is found a slight fold, which partially separates them. The liver offers but few peculiarities of consequence in a physiological point of view. In the Ant-eaters, the Armadillos, and the Orycterope, it consists of three lobes. In the former the hepatic duct joins the cystic at a considerable distance from the neck of the gall-bladder, and, as in the Armadillo, at a very acute angle. Organs of circulation. — In a paper in the Philosophical Transactions, Sir A. Carlisle described a very remarkable peculiarity of the arrangement of the arteries of the limbs in several slow-moving animals, of which number were the Bradypus tridactylus and Bradypus didactylus. It appears that the axillary and iliac arteries, on entering the upper and lower limbs, are suddenly divided into a number of cylinders of equal size, which occasionally anastomose with each other. They are ex- clusively distributed in the muscles. Those of the other parts of the body, and even those of the limbs which supply the bones, &c. do not deviate from the usual mode of distribution. In the former species no less than forty-two of these cylinders were counted on the superficies of the brachial fasciculus, and there were probably not less than twenty concealed in the middle. In the second species they were less numerous, and deviated from the usual form. This difference in the two species is perfectly consistent with what is known of their habits ; for there can be no doubt that the peculiarity has reference to the slowness of motion of these animals, in which character the Ai far exceeds the Unau. “ The effect of this peculiar disposition of the arteries, in the limbs of these slow-moving quadrupeds, will be that of retarding the velocity of the blood. It is well known, and has been explained by various writers, that the blood moves quicker in the arteries near the heart than in the remote branches ; and also, that fluids move more rapidly through tubes which branch off suddenly from large trunks than if they had been propelled for a considerable distance through small-sized cylinders ; be- sides the frequent communications in the cylinders of the Bradypus tridactylus must produce eddies which will retard the progress of the fluid. From these and a variety of other facts, it will appear that one effect on the animal economy, connected with this ar- rangement of vessels, must be that of di- minishing the velocity of blood passing into the muscles of the limbs. It may be difficult to determine whether the slow movement of the blood sent to these muscles be a subor- dinate convenience to other primary causes of their slow contraction, or whether it be of itself the immediate and principal cause.” The integument in the Manis as well as in 55 ELASTICITY the genera Dasypus and Tatusia, comprehend- ing the Armadillos, and in Chlainyphorus, ex- hibits various modifications of a very extraordi- nary nature. The body of the Manis is co- vered with large imbricated scales, of a more or less rhomboidal form, of a horny consistence, and a reddish brown colour. The true struc- ture of these scales is undoubtedly a congeries of hairs, as is evinced in the longitudinal lines with which they are all marked. They form a very firm and complete protection to the animal when rolled up in a ball, which is its ordinary means of escaping from danger. The scales cover the whole surface, excepting the inferior part of the head and tail, the axillae, the middle of the belly, the inner surface of the thighs, and the soles of the feet, all of which parts, excepting the latter, are furnished with a few scattered hairs. In the Armadillos an osseous crust or shell envelopes the whole of the upper part of the head and the body, the outer part of the limbs, and the whole of the tail. The inferior parts of the body are not thus protected, but scantly covered with hair, intermixed with a kind of hard warts or scales. Their armour is composed of a helmet covering the upper part of the head, of a buckler over the shoulders, a similar one over the crupper, and the back has numerous imbricated bands, which move upon each other, varying in num- ber in the different species ; the tail is covered by rings, also allowing of motion It is clear that this hard bony armour is capable of afford- ing these animals the most complete protection when coiled up, which is the position usually assumed by them when in danger, or during repose. Although there is mutual motion only at the margins of the different pieces and at the commissures of the bands, there is considerable yielding at every portion of this coat of mail. Each of the larger pieces is composed of nume- rous adherent smaller ones, hexagonal, and per- fectly tessellated ; those of the shoulders are arranged in segments of concentric circles, the concavity being in front, so that the anterior series, which is the shortest, embraces the neck of the animal. The covering of the posterior part has a similar arrangement, but reversed, so that the short concave margin meets the origin of the tail. The cuirass of the Chlamy- phorus truncatus differs in many respects from that of the Armadillos, and is thus described by Dr. Harlam in the only account which we have of the details of this singular animal, with the exception of the very interesting descrip- tion of its osteology by Mr. Yarrell, in the third volume of the Zoological Journal. “ The shell which covers the body is of a consistence somewhat more dense and inflexi- ble than sole leather of equal thickness. It is composed of a series of plates of a square, rhomboidal, or cubical form ; each row sepa- rated by an epidermal or membranous produc- tion, which is reflected above and beneath, over the plates ; the rows include from fifteen to twenty-two plates; the shell being broadest at its posterior half, extending about one-half round the body ; this covering is loose through- out, excepting along the spine of the back and top of the head ; being attached to the back immediately above the spine, by a loose arti- cular production, and by two remarkable bony processes ; on the top of the os frontis, by means of two large plates, which are nearly in- corporated with the bone beneath ; but for this attachment, and the tail being firmly curved beneath the belly, the covering would be very easily detached. The number of rows of plates on the back, counting from the vertex, (where they commence,) is twenty-four; at the twenty- fourth the shell curves suddenly downwards, so as to form a right angle with the body ; this truncated surface is composed of plates nearly similar to those of the back ; they are disposed in semicircular rows, five in number ; the lower margin somewhat elliptical, presents a notch in its centre, in which is attached the free portion of tail, which makes an abrupt curvature, and runs beneath the belly parallel to the axis of the body ; the free portion of the tail consists of fourteen caudal vertebrae, surrounded by as many plates, similar to those of the body ; the extremity of the tail being depressed so as to form a paddle ; the rest of the tail compressed. The caudal vertebrae extend up to the top of the back, beneath the truncated surface, where the sacrum is bent to meet the tail. The supe- rior semicircular margin of the truncated sur- face, together with the lateral margins of the shell, are beautifully fringed with silky hair.’’ It is much to be regretted that but little is known of the generation of these animals. The dissections which have hitherto been made of the more interesting forms have been imper- fectly performed, or the subjects themselves have been in such a condition as to allow of but very incomplete observations. For Bibliography, see that of Mammalia. (T. Bell.) ELASTICITY (Germ. Sprivgkraft, Fe- derkraft ) is that property of natural bodies in virtue of which they admit of change either of size or form from the application of external force, resuming, upon the suspension of that force, their proper shape or volume. Though elasticity is a purely physical pro- perty, its investigation is scarcely less interest- ing in physiological than in mechanical science. The most cursory examination of a living body is sufficient to convince us, that nature, in regulating its varied functions, has availed herself no less of physical than of vital laws. As it is the province of the physiologist to explain and analyze the several actions whose aggregate is life, to trace each to its proper source, and to distinguish those which are truly vital from those which are merely mecha- nical, it is plain that an acquaintance with the physical properties of the material elements of living bodies becomes one of the foundations of his knowledge. Hence, in a publication, the design of which is to present a complete view of the structure and functions of living 56 ELASTICITY. beings, it would be improper to omit some notice of those properties of matter which are so frequently and so admirably employed in fitting them for their uses. In this article we shall offer, in the first place, some remarks upon elasticity generally, upon its laws, and upon the distinction between it and other forces ; we shall next advert to its existence in the organized tissues of the animal machine; and, lastly, we shall point out some important actions in the living body where elasticity plays a principal part. I. General remarks on elasticity — its laws, S)-c. — The degree of elasticity possessed by un- organized bodies is extremely variable; in some it is so great that they have obtained the name of perfectly elastic; while in others this property is so extremely small, that its very existence has been overlooked. Air is the most perfectly elastic substance with which we are acquainted ; in experiments made upon atmospheric air a portion of it has been left for years subjected to a continued pressure, upon the removal of which under the same temperature and barometric altitude, it forth- with resumed its original volume. Amongst solid bodies, the most conspicuously elastic are certain metals and metallic alloys, glass, ivory, & e.; while other solids, such as moist clay, butter, wax, and many similar substances, possess elasticity in an almost imperceptible degree. Fluids have long been considered as completely inelastic; but though it is ex- tremely difficult to demonstrate this property, yet the experiments of Canton would seem to indicate its existence ; they place at least be- yond all doubt their possession of another property, namely, compressibility, — a pro- perty somewhat allied to that we are now con- sidering. The laws which regulate the elastic force are not exactly the same in these three classes of natural bodies. In the gaseous or perfectly elastic bodies elasticity may be said to deter- mine their volume : their particles having an incessant tendency to expand into a greater space are controuled merely by the surround- ing pressure, and hence the bulk of gases is always inversely proportional to the compres- sing force. This law, at least in the case of atmospheric air, applies within all known de- grees of condensation and rarefaction. By means of accumulated pressure, air may be so reduced in volume, that upon suddenly libe- rating it, as in the air-gun, it expands with amazing force ; and in the receiver of the air- pump, even when reduced to one-thousandth Dart its original quantity, it has still elasticity enough to raise the valve. Another important law of elasticity in gases is that its power is increased by heat and diminished by cold, and this applies not only to the permanently elastic gases but to those likewise of another kind, such as the vapours of alcohol, mer- cury, nitric and muriatic acids, and water ; the elastic vapours of the nitric and muriatic acids not unfrequently burst the vessels containing them ; the vapours of mercury have broken through an iron box ; and the vapours of al- cohol have sometimes occasioned in distil- leries the most terrible explosions : the elas- ticity of steam, and the fact that we can in- crease its power to any extent by means of heat, has enabled us to construct the steam- engine, and thus armed mankind with a phy- sical power superior to every obstacle. Solid bodies are never perfectly elastic ; for although some, when acted upon by forces within a certain range, are as completely elastic as the gases themselves, yet if the disturbing force be carried beyond a certain degree, they will never res.ume their original condition. Thus, a harp-string gently drawn by the finger is thrown by its elasticity into vibratory mo- tions, returning when these have ceased to its exact original state : this may be frequently repeated and always with the same effect, as proved by the same note being repeatedly ob- tained. If, however, it be once drawn with too great a force, it no longer returns to its original condition, a differenttone is nowproduced by it : in other words, the solid substance of which it is composed exhibits a perfect elasticity, not, as the gases, under every degree of force, but only within a certain limit. Heat pro- duces very different effects upon the elasticity of gaseous and solid bodies; we have just seen that we can increase the elastic power of the former to any extent by means of heat, but the elasticity of solids is, on the contrary, usually diminished by it ; very high tempera- tures completely destroy it even in the most elastic metals. The design of this article does not permit us to enter more fully into the con- sideration of those laws, or of the experiments by which they are demonstrated. We must refer for the further investigation of this sub- ject to works which treat expressly upon physics. The various hypotheses which have been put forth to explain the nature of elasticity, though many of them extremely ingenious, do not however properly come within the pro- vince of the physical much less of the phy- siological enquirer. Indeed, while men di- rected their attention to such speculations little or no progress was made in real knowledge. The cause of elasticity, like that of life, is probably beyond the sphere of human un- derstanding; and hence, in both sciences, the method of investigation should be the same — to study the laws or conditions under which the phenomena present themselves, and to lay aside all speculations as to their causes. But in abandoning these inquiries into the nature of elasticity we must particularly advert to the necessity of the physiologist possessing a clear and definite idea of this property of matter, so as to be enabled to recognize it under every circumstance, and to distinguish it from other physical and vital forces. Ignorance upon this point has been at all times a fruitful source of error in physiological investigations. The pro- perty with which it is especially liable to be confounded is contractility : when it is re- membered that at one period of medical his- ELASTICITY. 57 tory these two propeities were looked upon as identical ; that even the illustrious Cullen has scarcely distinguished them, and that some of our most eminent living physiologists have fallen into manifest errors upon the same sub- ject, it becomes plain that we cannot be too particular in familiarizing ourselves with the distinctions between these totally independent forces. It is not enough to say that contractility is a vital and elasticity a physical property; for as we are ignorant alike of the nature of life and of elasticity, a distinction founded upon any such assumption must necessarily be futile. It is only by a diligent comparison of their respective laws that we can assign to each its proper limits. Let us then observe in con- trasting them, first, that elasticity can never act as a prime mover; it is never a source of power, but merely the reaction of a force pre- viously applied : thus, the elasticity of the spring will never of itself set the watch in motion unless some external force shall, in the first instance, have acted upon or bent it. But contractility can of itself originate motion, at least it is not essential that any mechanical force with which we are acquainted should precede its action. Again, the force of elas- ticity can never exceed that other power which has called it into existence; if, for instance, a weight of one pound be required to depress an elastic spring, the force of reaction upon the removal of that weight can never exceed the measure of a pound. But, in the case of muscular contraction, there is no such limit; there is no fixed ratio between the cause and the effect; the slightest touch of a sharp in- strument will, in an irritable muscle, such as the heart, excite the most violent contractions. Elasticity cannot manifest itself except by the removal or suspension of the cause which has called it into action: muscularity requires no such suspension of its exciting cause. The exciting cause of elasticity is always of a phy- sical nature ; but many other causes no ways allied to physical ones may excite the muscular power. Lastly, elasticity is not destroyed by death nor affected by opium or other narcotics, while contractility presents a very striking con- trast in both these respects. These facts are quite conclusive in proving that muscular and elastic contraction are go- verned by distinct laws, and cannot conse- quently be referred to the same source. But if some physiologists have erred in overlooking the distinctions between these two properties, if they have not analysed with sufficient care, others have unquestionably erred in an oppo- site direction, and by pushing analysis too far, have attributed to imaginary forces effects which are the result of elasticity alone. We feel much diffidence in controverting any doc- trine supported by the genius and authority of Bichat, but we confess that the distinction which that celebrated anatomist is so anxious throughout his various works to establish be- tween what he terms “ contractility of tissue” and elasticity, appears to us unfounded. Elas- ticity according to him is a purely physical property. Contractility of tissue, though not actually a vital one, is however found only in the animal tissues; it does not depend directly upon life, but results merely from the texture and organization of those particles which con- stitute the vital organs. The following passage from his work upon “ Life and Death'’ may, perhaps, assist us in understanding his views upon this subject. “ Most organs of our bodies are held in a state of tension by various causes ; the voluntary muscles by their anta- gonists ; the hollow muscles by the substances contained within them ; the vessels by means of their circulating Hinds; the skin of one portion of the body by that which covers the neighbouring part ; the alveolar walls by the teeth contained within them. Now, upon the suspension of the distending causes, contrac- tion takes place : divide a long muscle, — its antagonist becomes shortened; empty a hol- low muscle, it shrinks upon itself : prevent the blood from entering an artery, the vessel be- comes a ligament : cut through the integu- ments, the divided edges are separated from each other by the contraction of the adjoining skin: extract a tooth from its alveolus, that channel becomes obliterated. * * * In all these cases it is the removal of a tension naturally inherent in the tissue which determines its contraction : — in other instances it is the re- moval of a tension which does not naturally reside in the part. Thus we see the abdomen contract after parturition ; the maxillary sinus after the extirpation of a fungous growth ; the cellular tissue after the removal of an abscess • the tunica vaginalis after the operation for hydrocele; the integument of the scrotum after the removal of an enlarged testicle ; the aneurismal sac upon the emptying of its fluid.” He remarks in another place that motion when the result of elasticity is quick and sud- den, and ceases as abruptly as it has been pro- duced; but the motions which result from contractility of tissue are slow and impercep- tible, lasting frequently for hours and even days, as are seen in the retraction of muscles after amputation. The distinction laid down in these passages appears to us totally un- supported : to say, for example, that even in a dead artery there are two principles of con- traction which, though their mode of action is literally the same, should nevertheless be con- sidered distinct and referred to different sources, appears contrary to every rule of philosophic reasoning. As to the distinction drawn from the comparative quickness of these motions it is only necessary to say that upon this view’ of the subject even the movement of the watch-spring itself cannot be attributed to elas- ticity. We must then conclude that there are two and only two forces to which all the various movements of living bodies can be referred ; the one a vital force regulated by its own proper laws, the other a general physical property, whose mode of action is essentially the same in organized and unorganized bodies : the phenomena above enumerated by Bichat 58 ELASTICITY. are certainly not the result of vital action (for he admits that the contractility of tissue to which he ascribes them is not destroyed by death): they must then be owing to a physical force, and amongst the various physical agen- cies we are acquainted with, elasticity is the only one to which they can be referred. The “ vis mortua” of Haller appears like- wise to differ little if at all from elasticity. Speaking of this force he observes, that, as indeed the very name implies, it is totally in- dependent of life, and adds — “ Haec vis in partibus animalium perpetuo agere videtur, etiamsi non perpetuus effectus adparet. Vi- detur enim contractio cuique particular proprise a contraria contractione duorurn elementorum vicinorum impugnari et distrahi, ut quae breviores fieri non possunt, quin mediam par- ticulam distrahant. Id dum fit in omnibus, quies videtur, quae est summa virium contra- riarum se destruentium. Quam primum vero aliqua particula a sodalibus separatur, inflicto vulnere, tunc utique labium vulneris, nunc liberum, nec a contraria potestate retentum, se ad earn vicinam, a qua trahitur, integramque incisse membranse partem retrahit.” The facts so accurately described in this passage are easily explained by the operation of elasticity. Why then multiply causes ? Why assume the existence of another principle in order to ac- count for them ? The phenomena ascribed by Cullen and others to what he terms “ tonicity, ” are also, at least in many instances, the effects of the same physical force. (See Contrac- tility.) II. The tissues of the animal body are pos- sessed of very various degrees of elasticity; some of them are but little inferior to the most highly elastic unorganized substances, while others are endowed with this property in so very trifling a degree, that in our physiological and pathological reasonings concerning them, we may almost consider it as absent. We shall endeavour to arrange the principal organic tissues in the order of their elasticity, and shall then proceed to offer a few remarks upon each. 1. Yellow fibrous tissue. 2. Cartilage. 3. Fibro-cartilage. 4. Skin. 5. Cellular mem- brane. 6. Muscle. 7. Bone. 8. Mucous membrane. 9. Serous membrane. 10. Ner- vous matter. 1 1 . Fibrous membrane. This view of the comparative elasticity of the different tissues must not be regarded as rigorously exact : owing to the impossibility of procuring each one perfectly separate from the others, the result of our experiments can be considered merely as approximate. 1. The yellow fibrous system. — The tissues composing this system are unquestionably the most highly elastic of all : the ligamenta sub- flava which unite the laminae of the vertebrae to one another, and the ligamentum nuchae which suspends the head in some of the larger quadrupeds, are scarcely inferior to caoutchouc in this respect. The middle coat of arteries is referred by Beclard to the yellow fibrous system, perhaps from its possessing in so high a degree this characteristic property. Its exis- tence may be demonstrated by various experi- ments, and many of the physiological and pathological phenomena of the arterial tissue are modified or determined by its presence. The sudden expansion of an artery whether in the living or dead body upon the removal of a force pressing its sides together ; the gradual contraction of a divided artery, by means of which hemorrhage is so frequently arrested ; the contraction or obliteration of the vessel beyond the ligature, after it has been taken up in aneurism ; the obliteration of the umbilical arteries and of the ductus arteriosus soon after birth ; the gaping which occurs in longitudinal wounds of arteries owing to the recession of the divided edges; the power possessed by these vessels of accommodating their size to the quantity of circulating blood, (thus causing endless variations in the volume of the pulse even in the same individual) ; — all these facts have been accounted for by the transverse elasticity of the middle coat. The effects of this property in a longitudinal direction may be seen in the retraction of divided arteries during amputation ; in the sort of locomotion which these vessels undergo from the impulse of the blood, and in the enlargement of a transverse arterial wound by the retraction of its edges. The proper coat of veins, though belonging likewise to this system, is however much less elastic than that of the arteries; but we cannot agree with those who deny this property to the venous tissue. The sudden flow of blood from a portion of vein included between two ligatures ; the constantly varying size of the cutaneous veins according to the volume of their contents; the obliteration under certain circumstances of veins where circulation has been arrested, appear to us explicable only by attributing this property to them. 2. Cartilage is possessed of very great elas- ticity. On pressing the point of a scalpel into cartilage it is expelled upon the suspension of the force by the contraction of the sur- rounding substance. It may also be well de- monstrated by twisting or bending the carti- lages of the ribs, or those of the nose, eyelid, &c. The elasticity of cartilage in the adult is much greater than in the child or old person. We shall allude presently to the several impor- tant objects to which this property as connected with cartilage is applied. 3. Fibro-cartilage.- — The elasticity of this tissue may be studied in the intervertebral fibro-cartilages, in which it contributes so remarkably to the obscure movements of the spinal column and to the security of the chord : it is remarkably displayed in restoring the sub- stance to its proper condition, when pressure rather than twisting or bending has been the cause of derangement. The fibro-cartilaginous funnels through which the tendons are trans- mitted, possess likewise this property to a great extent. Bichat found, on removing a tendon in a living dog, that the funnel through which it had been transmitted became impervious, like an artery under similar circumstances. 59 ELASTICITY. 4. Skin. — The great elasticity of the cuta- neous tissue is exhibited in innumerable in- stances; the extension which it undergoes in pregnancy, in ascites, in cases of large fatty and other tumours, and the promptitude with which in these instances it returns to its proper state after the removal of the distending causes, are matters of every day observation, and are chiefly owing to its elasticity. The great re- traction of the integuments in amputation depends likewise upon the same principle. There is perhaps no tissue in the body where elasticity is more impaired by advanced age : in the young or adult subject, when, owing to disease or other causes, the subcutaneous adi- pose matter has become suddenly absorbed, the skin, owing to its great elasticity, is ena- bled to contract, and thus accommodate itself to the diminished distention ; while in old age, under the same circumstances, the power of contraction is lost, and hence it hangs in loose folds or wrinkles, so characteristic of that period of life. These remarks are meant to apply chiefly to the true skin or corion. 5. Cellular tissue ranks high among the elastic structures : many of the cases which we have just instanced as proving the elasticity of the cutaneous tissue, indicate likewise its existence in the cellular membrane; anasarca, oedema, and still more emphysema, can occur only in consequence of the distention of those filamentous threads which form the cells ; and as recession occurs immediately upon the re- moval of the distending force, it is plain that elasticity is the principle to which the change must be attributed. We may likewise remark that there is no tissue whose elasticity is so frequently and perhaps so usefully em- ployed as that which we are now considering ; for it is by this property of cellular membrane that the motion of the several muscles is per- mitted and even assisted : thus upon elevating the arm the yielding cellular tissue of the axilla permits the member to be drawn up- wards, and when the arm is again depressed the elasticity of the same tense filaments as- sists in some degree the muscles which bring it down. 6. Muscle. — Elasticity appears to belong to the muscular system in a very high degree ; it is, however, extremely difficult to estimate its extent in the muscular fibre itself, partly owing to its being the seat of two other contractile forces, the vis insita and vis nervea, and partly to the great quantity of cellular and other tis- sues which enter into the structure of muscle, and thus impart to it their physical properties. There are however many instances in which we must concede elasticity to the muscular fibre ; the contraction which occurs in the abdominal muscles even long after death, upon removing the accumulation of air or fluid contained within the peritoneum; and the recession of the cut edges which takes place upon dividing a muscle under the same circumstances, cannot be ascribed either to the vis nervea or to the vis insita, (for they have ceased to exist,) and the contraction is evidently too extensive to be attributed wholly to the cellular tissue. But we may observe the operation of this property even in the living muscles : on dividing the facial muscles of one side in a living animal the mouth is gradually drawn towards the opposite, and this takes place not by the effort, but solely by the elasticity of the un- injured muscles, which have now no coun- teracting force upon the other side to resist their contraction. So it is with all the other muscles during what is called their state of rest : the elasticity of one class is exactly ba- lanced by the same property in their antago- nists; and hence when the influence of the will is completely withdrawn, as in sleep, we may estimate the comparative quantity of elas- ticity which antagonizing muscles are possessed of : those of the face for example are exactly equal upon opposite sides in this respect, and accordingly the mouth retains its proper central position ; but in the limbs, as the elasticity of the flexors exceeds that of the extensors, we usually find these parts of the body during sleep in a semiflexed position. 7. Bone possesses considerable elasticity, though its degree is frequently underrated by the superficial observer. It is not easily demon- strable in the larger bones, but upon cutting even these into thin plates its existence becomes at once evident. There are many phenomena both healthy and diseased which depend upon the elasticity of bone ; the enlargement of the maxillary sinus from the growth of fungus within its cavity, and the collapse of its walls upon the removal of the distending matter ; the obliteration of the alveolus after the extraction of a tooth ; the narrowing of the optic hole which is found in cases of atrophy of the optic nerves, and of the carotid canal after tying the carotid artery ; the diminution of the orbital cavity which gradually takes place upon extir- pation of the eye — all these changes depend in a great degree upon the elastic qualities of bone. The great elasticity of the osseous system in the young subject, and the almost entire absence of it in the bones of old persons, is at once ex- plained by the fact that elasticity resides in the cartilaginous and not in the earthy ingredient ; the great proportion of the former in the young bone, and the accumulating deposition of earthy matter as age advances, are known to every observer. 8. Mucous membrane. — That this tissue is possessed of some degree of elasticity would appear from the well-known contraction which is found in the lower part of the intestinal canal after the establishment of an artificial anus; from the great variation of size which is observed in the stomach, and by means of which it can accomodate itself to the quantity of food con- tained within it; and from many other simi- lar instances. But in these cases it is often difficult to determine how far contraction de- pends upon the mucous membrane, or upon the other tissues with which it is associated. We should also bear in mind that the contraction of the inner coat of the stomach is much less than might in the first instance be supposed ; ELASTICITY. 60 the numerous folds or rug® into which it is thrown seem destined to compensate for its im- perfect elasticity. 9. Se7-ous membrane is still lower in the scale. In those organs whose size is subjected to frequent variation, such as the stomach, in- testines, urinary bladder, &c., we find an inter- esting provision to permit enlargement without at all stretching their serous envelope. The organ, instead of possessing a simple serous capsule, is inserted between two loosely adher- ent folds of peritoneum which permit its insinu- ation between them as soon as distension takes place. By this simple contrivance the possibi- lity of rupture or even tension of the serous coat is completely obviated, even in cases of extreme enlargement. The tunica vaginalis testis would appear to possess more elasticity than other membranes of this class: — after the ope- ration for hydrocele, a disease in which it is distended far beyond its proper limits, a sudden contraction of its tissue evidently occurs. 10. Nervous matter. — Upon the division of a nerve little or no retraction of the divided ex- tremities takes place. The brain however possesses an obscure elasticity, as may be seen upon making a horizontal section of its sub- stance : the numerous red points which there present themselves are owing to the blood forced from the divided vessels by the surrounding pressure. 11. Fibrous membrane is remarkable for its very low degree of elasticity ; hence liga- ments and tendons often give way rather than yield to a distending force. It is owing to the unyielding nature of the subcutaneous fascia in some situations that abscesses and other swel- lings occurring beneath, produce but little swel- ling upon the surface, and cause such severe pain to the patient; hence too upon dividing this fascia, no enlargement of the wound occurs as in other tissues by the elastic retraction of its edges. When the distending force however is slowly applied, there appears to exist some degree of elasticity even in fibrous membranes ; thus in hydrops articuli the structures about the joint are frequently much distended by the ac- cumulation of fluid within, upon the absorption of which they slowly resume their proper con- dition. III. We shall now proceed to point out some instances in which elasticity plays an im- portant part in the mechanism of organized beings ; but it may be necessary to remark that in doing so we by no means profess to give an anatomical description of the various structures alluded to. We shall endeavour merely to bring into one general view some of the most inter- esting cases in which elasticity plays a prominent part, and thus enable the reader to refer to the separate articles in which these details are fully discussed. Nature avails herself of this physical property in the construction of organized bodies, for several distinct ends. It is sometimes employed as a means of protecting certain delicate and important organs by bearing off or decomposing the forces to which they are exposed. It is often used to economise muscular contraction, not only in supporting depending parts, but likewise in effecting the movement of one por- tion of the body upon another. In some instan- ces it is rendered subservient to the general movement of the body, or locomotion. By elas- ticity the proper patulous condition of certain canals and outlets is secured ; and lastly, it very often serves to divide the power of particular muscles or sets of muscles, and thus to transfer the contractile force from one portion of an ap- paratus to another. 1. Elasticity is employed by nature as a means of protecting the body generally, or some of its organs more particularly, against external violence. The great elasticity of the various tissues in the young subject, and of the osseous system especially, affords at that period of life no inconsiderable security to the whole system : the bones themselves can yield in a very great degree to external impressions and thus prevent their bad effects. The frequent and apparently dangerous falls of children, and the perfect im- punity with which they are encountered, are known to every one, and can easily be accounted for by the great elasticity of the tissues at that period of life. The opposite extreme of human existence, in which we meet with the reverse of these conditions, is equally illustrative of our subject ; for then the bones, owing to the pro- gressive accumulation of earthy matter, have al- most lost their power of yielding, and hence a very slight force is sufficient to fracture them. But elasticity plays a still more important part in protecting certain organs, such as the spinal chord, whose structure is so delicate that it may be torn by the slightest violence, and whose func- tion is frequently deranged even by mere con- cussion. The mechanism of the vertebral column exhibits at every step the most admirable appli- cation of elasticity to the protection of its con- tents. An unskilful mechanic who sought to afford the greatest security to this contained or- gan might naturally enough suppose that its safety would be proportionate to the strength and density of the material which he should employ in incasing it; he would probably have thrown around it a strong cylinder of solid bone, such as we see employed for a different object in the tibia or femur. But the condition of old age again affords us a complete refutation of such reasonings ; the spinal column by the successive consolidation of its component parts is then in fact converted into one long cylinder of extraordinary strength ; it has become literally a single bone ; but now every touch upon the surface of the body, every application of the foot upon the ground, is conveyed by the solid and almost inelastic bones to the spinal cord, thus rendering even the movements of progression a source of pain ; hence repose is the natural con- dition of this period of life, as restless activity Is that of childhood. But looking at the spinal column in the active or adult age we perceive a totally different mechanism ; it now consists of no less than twenty-four distinct bones piled one upon the other and connected by twenty-four layers of fibro-cartilage, a tissue, as we have al- ELASTICITY. 61 ready seen, possessed of extraordinary elasticity. The chord, instead of filling the whole cavity, is suspended within it by means of an elastic liga- ment; and thus this delicate cylinder of nervous matter is hung loosely upon a series of elastic springs which effectually break the many jolts and concussions incident to the frame in the various movements of active life. It is owing to this extreme elasticity of the spinal column, that even after very long-continued pressure, it soon recovers its proper condition. When, for instance, from long and severe exercise the fibro- cartilages have become somewhat pressed down by the superincumbent weight, a few hours’ repose in the horizontal position is sufficient to restore the spine to its proper length. This fact has not escaped the shrewd practical observa- tion of the lower classes ; when admission into the army can be obtained only by persons of a certain stature, the candidate who apprehends he can spare nothing in that particular, usually presents himself after his night’s repose. The delicate viscera of the thoracic cavity owe like- wise their safety in a great degree to the same me- chanism. The cartilages which connect the ribs and sternum, and which, as we shall presently find, are destined to modify the movements of the thorax, tend likewise to its security by per- mitting it to yield to external forces. The ob- scure elasticity of the ribs themselves and of the ligaments connecting them to the spine contri- bute to the same end; hence we seldom find the thoracic viscera ruptured even by the greatest violence applied against their walls. It is this elasticity, aided no doubt by other still more efficient causes, which enables the mountebank to receive with impunity the blows of the weightiest sledge on an anvil laid upon his chest. 2. Elasticity is often had recourse to as a substitute for muscular contraction, and, as it would appear, with a view to economize that more important property. We find, for ex- ample, that in most animals the abdominal viscera are supported in their position chiefly by the muscles of the abdomen, and that on being forced downwards in inspiration by the descent of the diaphragm, they are again pressed upwards by the contraction of these muscles. In the large ruminating quadrupeds whose abdominal viscera are of so great a size, and in whom, owing to the horizontal position of the trunk, these organs tend directly down- wards, the quantity of muscular power requi- site to support and move them should neces- sarily have been of great amount; but instead of increasing the quantity of muscle to such an extent, nature has effected her purposes by much more simple means. Beneath the abdominal integuments there exists a mem- brane of great strength and elasticity, which not only supports the viscera but also helps to elevate them after they have been forced downwards in inspiration. The elastic liga- mentum nucha, which in these animals sup- ports the very weighty head, is a simple but complete substitute for the great mass of muscle which should have existed on the back part of the neck, in order to effect the same end. So obviously in this instance is elasticity a substitute for muscularity, that upon com- paring the structure in various animals we find the strength and elasticity of the ligament always proportionate to the weight of the head which it has to support. In the carnivora an interesting application of this property is seen in_the retractile ligament passing between the claw and the phalangeal bone ; as the claw in many genera is the chief weapon of attack, it must not be suffered to come into contact with the ground in progression, for otherwise it would become blunted, as seen in those which do not use it for the purposes mentioned; it is consequently suspended by the retractile liga- ment until drawn down at the will of the animal by means of the flexor muscles. Elasticity is here used as the means of suspension in order to save the effort of a constant muscular exer- tion. In the mo'lusca we see this property again employed to economize muscularity : the shell of the oyster admits of being opened as well as closed at the will of the animal; but muscularity is the source of the one ac- tion; elasticity residing in a strong ligament is the means of effecting the other. 3. Elasticity frequently preserves the patu- lous condition of certain outlets in the animal body, as, for example, those of the eyes and nostrils. This object is attained by the inser- tion of a rim of highly elastic cartilage into the soft parts which bound these openings. A material of greater rigidity, such as bone, would, it may be objected, have answered the purpose still better : but the rigidity of that substance would have greatly interfered with the free movements necessary for the functions of the lids, and in the nose would not only have increased the risk of injury from external violence, but would have prevented the ap- proximation of the ala which must take place in order to expel the nasal mucus. Neither would a soft and inelastic material have an- swered the purpose, for then the first effect of inspiration would be to approximate the edges of the opening, and thus Uxprevent the further entrance of air. The tracheal and bronchial canals are likewise preserved patulous by the same elastic material ; and we again meet with it performing a like office in the Eustachian tube and the external meatus of the ear. 4. Elasticity is sometimes rendered subser- vient to locomotion, or the general movement of the body. The elastic pad placed beneath the foot of the dromedary and many other ani- mals is no doubt intended to facilitate progres- sion, and to compensate in some degree for the yielding looseness of the sands upon which they tread. The same apparatus is found in very great perfection in the feet of the carni- vora, and must be of great use in enabling them to make those enormous bounds by which they spring upon their prey. But perhaps one of the most interesting examples of elasticity being rendered subservient to locomotion is met with in certain fish. The salmon, during its annual ascent to fresh-water streams for the 62 REGION OF TIIE ELBOW. purpose of depositing its spawn, often encoun- ters cataracts of great height, and which would seem to render farther progress impos- sible. By means, however, of a powerfully muscular tail and elastic spine it is enabled to surmount those obstacles ; resting one side upon a solid fulcrum, it seizes its tail between its teeth, and thus draws itself into an arch of amazing tension ; then suddenly letting go its hold, and thus freeing the elastic spring which its body represented, it is thrown into the air, often, as Twiss has seen in Ballyshannon in Ireland, to a height of twelve or fifteen feet, and falls beyond the obstacle which had op- posed it. 5. Elasticity becomes occasionally in the animal machine a means of dividing muscular force, and thus transferring it from one portion of an apparatus to another. The muscles of inspiration are, if we may use the word, too strong for their opponents, and hence it be- comes necessary to transfer a portion of their superfluous strength to the weaker set. This is effected by means of the elastic cartilages which connect the ribs and sternum. The in- spiratory muscles in enlarging the thorax act with such a force that they not only elevate the ribs, but even stretch and twist the cartilages, and hence no sooner is inspiration completed than elasticity comes into play, tending to depress the ribs and thus to assist the weaker muscles. But we must not fall into the error of suppo- sing that elasticity is in this case a substitute for muscularity, and much less that it is in itself a source of power. The only power exercised by it is that which it has just bor- rowed from the inspiratory muscles : had not the elasticity of the cartilages been set in action by this external agency, it would, like the elas- ticity of the watch-spring under the same cir- cumstances, have remained for ever dormant. In those interesting discussions which have arisen of late years relative to what is termed the suction power of the heart, we apprehend that much error has arisen from overlooking this simple law of elasticity. That doctine will of course be fully stated and examined in its proper place ; at present we shall merely observe that it was first regularly put forward in the admirable work of Dr. Wilson Philip, that it was followed up and explained by Dr. Carson, and that these views were regarded by Laennec with such respect that he pronounces their discovery the most important step made in this department of physiology since the time of Harvey. The heart, it is said, is not merely a forcing pump which by the contrac- tion of its ventricle propels the blood through- out the arteries ; it is likewise a suction pump, for by the expansion of the auricles it draws in the blood from the veins. Now this expansive force, if indeed it exist at all, is, we are quite satisfied, merely the effect of the heart’s elas- ticity; for the reasonings of those who attempt to prove it of a specific nature are evidently insufficient. In this point of view the heart’s expansion cannot be regarded as a new and independent power; if that organ be really elastic, then the muscular force of its systole must be greater than it would otherwise have been, for it has not only to propel the blood through the arterial system, but likewise to overcome the resisting elasticity of its own structure: this suction power of the heart is then merely the recoil of the surplus force; what is gained upon the one hand is lost upon the other; and hence elasticity in this instance cannot be regarded as an independent prin- ciple contributing to the blood’s motion, but merely as a means of dividing muscular power and transferring a portion of it from the begin- ning of the arterial to the end of the venous system. 6. An interesting application of elasticity in the animal machine is to convert an occasional or intermitting force into a continued one. As human ingenuity has long since discovered the application of this principle, we may see it employed in many mechanical contrivances. In the common fire-engine, for instance, we observe that though it is worked by interrupted jerks, yet the water issues from its pipe, not per saltum as we should have expected, but in one uniform and continued stream. This is effected by causing the fluid to pass, in the first instance, into a hermetically sealed vessel con- taining a portion of atmospheric air : the accu- mulation of the water presses the air into a smaller space, but in doing so it is reacted upon by the elasticity of that gas, which may thus be considered as a powerfully elastic spring exerting upon the surface of the water an uniform and continual pressure. The very same principle is employed in the mechanism of the arterial system. Upon opening one of the small arteries we perceive that the blood does not flow per saltum as in those which are nearer to the heart, but issues in an uniform and uninterrupted stream. The intermitting action of the heart has in fact been converted into a continued one by means of the elasticity of the arterial tissue. We might indeed say with truth that the blood in these small arteries is not directly propelled by the heart at all; the force of that organ is expended in distend- ing the larger elastic arteries, as the force in the fire-engine is expended in compressing the air. The immediate cause of motion is in the one case the reaction of the elastic air, and in the other the reaction of the elactic artery. For the Bibliography of this article, see that of Fibrous Tissue and Muscle. (John E. Brenan.) ELBOW, REGION OF THE ; fold or bend of the arm. (Fr. plidubras; coude.) The region of the elbow is situated at the angular union of the arm with the fore-arm, and con- tains the humero-cubital articulation and the various organs which surround it : the extent of this region may be determined, superiorly by a circular line at a finger’s breadth above the internal condyle, and inferiorlyby a similar line at two fingers’ breadth below that process : its greatest extent is m the transverse direction, and it forms an angle salient posteriorly and REGION OF THE ELBOW. 63 retiring in front, which cannot be effaced even in the utmost extension of the fore-arm. The anterior surface of this region when examined in the arm of a muscular man presents a triangular depression, in which is observed the confluence of several large subcutaneous veins ; the base of this depression is above ; the sides are formed by two prominences, of which the ex- ternal is larger and more marked than the in- ternal, and the apex of the triangle is formed inferiorly by the convergence of these pro- minences, which consist of the two masses of the muscles of the fore-arm which arise from the condyles of the humerus. This triangular depression is divided superiorly into two por- tions by a prominence formed by the tendon of the biceps ; in the external or larger portion the median cephalic vein is situated, the in- ternal is occupied by the oblique course of the median basilic vein and the trunk of the brachial artery, the pulsations of which can usually be felt and are even sometimes visible in this space : the superficial radial or cephalic vein and the two ulnar veins which contribute to form the basilic are also apparent in this region, being situated over the lateral mus- cular prominences. In the arm of a corpulent female, instead of the appearances here de- scribed, the front of the elbow presents a semilunar fold or depression, the concavity of which embraces the prominence formed by the biceps. Laterally, the region of the elbow presents two prominences formed by the condyles of the humerus, of which the internal is more marked and higher than the external : in the arms of corpulent persons, on the contrary, two depressions like dimples are placed over the condyles. Posteriorly, the olecranon forms a remark- able prominence, the situation of which varies in its relation to the condyles of the humerus according to the different motions of the fore- arm ; in complete extension it is above the level of these processes, in semiflexion it is on the same level with them, and is below them when the elbow is flexed to a right angle. On either side of the olecranon there is a depression of which that on the internal side is more marked ; pressure here produces a painful sensation which is felt in the little finger and the inner side of the ring-finger; in the depression external to the olecranon the posterior edge of the head of the radius can be felt rotating immediately below the external condyle when pronation and supination of the fore-arm are performed. An accurate know- ledge of the relations of these parts is essential to the forming an accurate diagnosis in cases of fractures and dislocations in this region. Skin and subcutaneous tissue. — The skin covering this region is thin, smooth, and de- licate in front ; it is furnished with hairs over the lateral prominences, where it also contains sebaceous follicles in greater numbers than over the anterior depression. In consequence of being very vascular and plentifully supplied with nerves, the skin here is prone to inflam- mation, and is often the seat of small phlegmo- nous abscesses and of erysipelas. Posteriorly the skin is thicker, rough on the surface, and generally thrown into transverse folds above the olecranon, particularly in extension : it abounds more in sebaceous follicles and hairs here than on the anterior surface. The sub- cutaneous cellular tissue in front consists of two layers : one of these, more deep-seated, forms a sort of fascia, between the layers of which the subcutaneous veins and nerves are situated ; the other, superficial, is principally composed of adipose tissue and varies very much in thickness. In lean persons this latter layer is often of extreme tenuity ; while the other, on the contrary, is then thicker and more closely adherent to the skin. This deeper layer is considerably thicker over the anterior angular depression than on the lateral pro- minences : it sinks in between the pronator radii teres and supinator longus in company with the deep median vein, and is continuous with the cellular tissue between the muscles and around the articulation. Posteriorly the subcutaneous cellular membrane is more loose and lamellar : adipose tissue is almost always absent in it over the condyles of the humerus, and on the smooth posterior surface of the olecranon, there is merely a subcutaneous bursa mucosa between the skin and the peri- osteum. The subcutaneous cellular tissue in front of the elbow contains some large veins, besides lymphatics and filaments of cutaneous nerves. As the subcutaneous veins in this region are those most frequently selected by surgeons for the operation of phlebotomy, and as un- toward consequences sometimes result from a want of due care or of sufficient anatomical knowledge on the part of the operator, their situation and connexions should be carefully studied. These veins are subject to much variety in their size, number, and situation : the following arrangement of them is that most uniformly adopted by authors as the normal one : three principal veins coming from the fore-arm enter the lower part of this region: 1st, the radial or cephalic on the external side courses along the external muscular prominence and ascends to the arm on the external side of the biceps ; 2d, the ulnar or basilic ascends over the in- ternal muscular prominence and the internal condyle of the humerus to the inner side of the biceps ; 3d, the median vein ascending from the front of the fore-arm enters the apex of the triangular depression of the elbow, at which point it is usually augmented by a deep branch coming from the deep radial and ulnar veins, and immediately divides at an acute angle into two branches, one of which ascends on each side of the biceps ; the internal of these, called median basilic, runs obliquely upwards and inwards over the course of the brachial artery, and joins the basilic vein above the internal condyle ; its lower extremity is external to the brachial artery, which it crosses obliquely so as to get internal to it superiorly : 04 REGION OF the other division of the median vein, called median cephalic, passes obliquely upwards and outwards, external to the prominence formed by the biceps, and joins the cephalic at an acute angle above the external condyle. The cephalic, the basilic, and the two divi- sions of the median vein joining them, form a figure which somewhat resembles the Roman capital letter M. The superficial lymphatic vessels follow the course of the veins ; those on the internal side are larger and enter small ganglions, varying in number from two to five, which are situated in the subcutaneous cellular tissue, above and in front of the internal condyle, where they are sometimes seen swollen and inflamed in consequence of inflammatory affections of the hand or fore- arm. The subcutaneous nerves are : branches of the internal cutaneous, usually three or four in number, the external cutaneous, and some twigs from the radial and ulnar nerves. The branches of the internal cutaneous pass down to the fore-arm, generally superficial to the basilic and median basilic veins, while the external cutaneous lies deeper than the ce- phalic and median cephalic, with the latter of which it is more intimately connected. Some twigs from both the internal and the external cutaneous nerves are distributed to the inte- guments behind the elbow. Aponeurosis. — The aponeurosis of the region of the elbow is continuous with the brachial aponeurosis above, and with that of the fore- arm inferiorly ; it is strong behind the elbow, where it receives an expansion from the tendon of the triceps, and has an intimate adhesion to the margin of the olecranon : on each side it is firmly attached to the condyles of the hu- merus, sending off several layers from its internal surface, which form septa between the origins of the muscles of the fore-arm which arise from these processes : anteriorly it is spread over the triangular depression, where its strength is considerably increased by ex- pansions which it receives from the tendons of the biceps and the brachiaeus anticus ; the ex- pansion from the brachiaeus anticus comes forward on the external side of the tendon of the biceps, and is lost over the external mus- cular prominence of the fore-arm in front of the external condyle ; the expansion from the biceps forms a narrow band about half an inch in breadth where it is first detached from the tendon of that muscle ; it then descends obliquely to the inner side of the fore-arm, on the aponeurosis of which it is lost about two inches below the inner condyle. Superiorly this expansion crosses over the brachial artery, and its superior margin is defined by a lunated border to which the brachial aponeurosis is attached, while its inferior margin is con- founded with the aponeurosis of the fore- arm. From the above described attachments of the tendons of the biceps and brachiaeus an- ticus to the aponeurosis of this region, it fol- lows as a necessary consequence that the con- TIIE ELBOW. tractions of these muscles must have the effect of rendering it more tense. The aponeurosis of the arm assumes the form of a very thin fascia as it approaches the superior margin of the expansion of the biceps ; at this place it often appears to degenerate into cellular tissue which covers an oval space placed obliquely, the broader extremity of which is below, being bounded by the expan- sion of the biceps externally and inferiorly, and by a sort of defined border terminating the lower margin of the brachial aponeurosis superiorly and internally : in this oval space the brachial artery and the median nerve which lies to its inner side are more thinly covered than in any other part of their course. The aponeurosis is also very weak on the external side of the expansion of the biceps, where it is pierced by the deep branch of the median vein, and by the external cutaneous nerve which comes from beneath the aponeurosis at this place. The brachial artery terminates by dividing into the radial and ulnar arteries in the tri- angular depression, which is bounded exter- nally by the supinator longus and internally by the pronator radii teres. This artery enters the region of the elbow on the internal side of the tendon of the biceps included in a common sheath with its two venre comites, one of which lies on either side of it ; it lies on the surface of the brachiaeus anticus, and, becoming deeper as it descends, it divides into the radial and ulnar arteries at about an inch below the level of the internal condyle. The median nerve lies internal to it, separated from it at first by cellular tissue ; lower down, where this nerve pierces the pro- nator teres, the external origin of that muscle arising from the coronoid process is interposed between it and the artery : the radial and ulnar arteries, while still in this region, give off their recurrent branches, which pass upwards, encir- cling the condyles of the humerus, to anasto- mose with the profundae and anastomotic branches of the brachial, as described in the article Brachial Artery. The venae comites of the brachial, radial, and ulnar arteries are double : these vessels are also accompanied by a deep set of lymphatics. The nerves which traverse this region beneath the aponeurosis are, the median on the internal side of the brachial artery; the radial, which, descending between the brachiaeus anticus and the supinator radii longus, then between the biceps and ex- tensor carpi radialis, divides into two branches, the posterior of which passes between the supi- nator brevis and extensor carpi radialis brevior to the muscles on the back part of the fore-arm, while the anterior branch or proper radial nerve descends in the fore-arm under the su- pinator radii longus. The trunk of the ulnar nerve passes behind the internal condyle, and entering between the two heads of the flexor carpi ulnaris follows that muscle down the fore-arm. Development. — In early life the condyles of the humerus are not so well marked, nor is ARTICULATION OF TIIE ELBOW. the olecranon so prominent, in consequence of which extension of the elbow can be carried farther than in the adult. At the same period the lesser sigmoid cavity of the ulna is pro- portionally smaller, and the annular ligament of the radius much more extensive. Varieties. — When a high division of the brachial artery takes place, it often happens that the radial artery takes a superficial course, sometimes under and occasionally over the aponeurosis to its usual destination. The pos- sibility of this occurrence should be constantly held in recollection in performing phlebotomy in this region, as it is evident that the vessel, when thus superficially situated, is exposed to be wounded by the lancet of the operator. In considering the relative advantages pre- sented by each of the superficial veins which may be selected for phlebotomy, it is necessary to remark that the operation may be performed on any of the veins at the bend of the arm ; on the cephalic and basilic veins it is un- attended with any danger; not so, however, when either the median basilic or median cephalic is the vessel selected. When bleed- ing in the median basilic vein about the mid- dle of its course, if the lancet should transfix the vein, there is danger of the instrument wounding the brachial artery, an accident of serious consequence ; the risk of this accident is not so great when the vein is opened near its lower part, as the brachial artery retires from it here towards the bottom of the trian- gular depression of the elbow; besides the occasional risk of wounding the radial artery, which, in consequence of a high bifurcation of the brachial, sometimes follows the super- ficial course already alluded to, the branches of the internal cutaneous nerve may be wholly or partially divided ; in which latter case sharp pains are usually felt extending along the course of these nerves. Opening the median cephalic vein may be performed without ap- prehension of injury to the brachial artery; the external cutaneous nerve however, the trunk of which lies behind this vein, may suffer a puncture, in consequence of the lancet being pushed too deeply, the consequences follow- ing which have been in many instances a pain- ful affection extending along the branches of this nerve to their terminations. In those un- fortunate cases in which the brachial artery is punctured, should the wound in the artery not be closed and united by properly regulated pressure, the consequence likely to ensue may be one of the following: 1, the blood escap- ing from the wound in the artery may become diffused through the cellular membrane of the limb extending principally upwards towards the axilla along the sheath of the vessel, (the diffused false aneurism ; ) 2, the blood which escapes from the artery may be circumscribed within a limited space by the cellular mem- brane which surrounds it becoming condensed, ( the circumscribed false aneurism ; ) 3, the wounded orifices of the artery and vein may remain in apposition, and adhere to each other, allowing the blood to pass from the artery VOL. II. 65 directly into the vein, constituting the affection called aneurismal varix ; 4, or a circum- scribed sac may be formed between the artery and vein, having a communication with both vessels, the varicose aneurism. ( J . Hart.) ELBOW (ARTICULATION OF THE), a-yicav, cubitus ; Fr. coude ; Germ, elbogen ; Ital. goinito. The elbow or humero-cubital articulation is an angular ginglymus formed by the inferior articular extremity of the os humeri and the superior articular extremities of the radius and ulna, the surfaces of which are, in the recent state, covered with a cartilaginous incrustation, and kept in apposition by an ex- tensive synovial capsule, an anterior, a poste- rior, and two strong lateral ligaments. The muscles which cover this articulation are, the brachiaeus anticus, the inferior tendon of the triceps, and some of the muscles of the fore-arm anteriorly, the triceps and anconaeus posteriorly, and the superior attachments of several of the muscles of the fore-arm laterally. Bones. — The lower part of the humerus is flattened before and behind, and curved a little forwards : an obtuse longitudinal ridge, on a line corresponding to the lesser tuberosity at its superior extremity, divides it into two slo- ping surfaces anteriorly, while posteriorly it presents a broad, flat, triangular surface : a sharp ridge on each side terminates below in a rough tuberosity, called a condyle ; the exter- nal condyle is the smaller of the two, and when the arm hangs loosely by the side, it is directed outwards and forwards : the internal condyle is much larger, more prominent, and directed inwards and backwards : a line let fall per- pendicularly from the most prominent part of the greater tuberosity above would fall upon the external condyle ; the internal condyle bears a similar relation to the centre of the superior articular head of the humerus. The inferior articular surface extends transversely, below and between the condyles, and presents a series of eminences and depressions ; begin- ning at the external side, a small spheroidal eminence, the eminenlia capitata or lesser head, situated on the front of the external condyle, directed forwards and received into the circular cavity on the head of the radius, internal to this is a small grooved depression which lodges the internal part of the border of that cavity : the remainder of this surface forms a sort of pulley, to which the greater sigmoid cavity of the ulna corresponds ; this, which is called the trochlea, presents a large depression placed be- tween two raised ridges : the depressed portion of the trochlea winds round the lower extre- mity of the humerus in an oblique direction from before backwards and a little outwards, being broader behind than in front ; its external border forms a semicircular ridge, smooth in front and sharp behind, the anterior part of which corresponds to the division between the radius and ulna; its internal margin also forms a semicircular ridge, sharper and more promi- nent than the external, and which projects half G6 ARTICULATION OF TIIE ELBOW. an inch below the internal condyle, having be- tween it and this latter process a sinuosity in which the ulnar nerve lies ; it is the prominence of this ridge which determines the obliquity in the direction of the humerus, observable when its inferior articular extremity is placed on a horizontal surface. Behind and above the trochlea a large trian- gular depression (fossa posterior ) receives the olecranon in extension of the fore-arm ; a simi- lar depression of smaller size (fossa anterior ) receives the coronoid process in flexion ; these two fossa; are separated by a plate of bone, often so thin as to be diaphanous, and some- times they communicate by an aperture, the longest diameter of which is transverse, as in the quadrumana, carnivora, glires, and pachy- dermata; Meckel is of opinion that the exist- ence of this aperture in the human subject is more frequent in the Negro and Papuas than in the Caucasian race;* however it did not exist in any one of three Negroes and four Mulattoes which I dissected, while I possess two specimens of it, and have seen several others which occurred in Europeans : a second small fossa frequently exists above in front of the eminentia capitata, into which the head of the radius is received in complete flexion. The superior extremity of the ulna presents anteriorly a deep cavity, ( the greater sigmoid cavity,) which is concave from above down- wards and convex in the transverse direction : it is bounded behind by the olecranon and in front by the coronoid process ; the surface of this cavity is smooth and covered by cartilage, with the exception of a rough transverse notch which extends from the internal side nearly the whole way across it, and the inequalities of which are effaced in the recent state by a cushion of soft adipose tissue : on the external side of the coronoid process there is a small smooth lateral surface, oval in shape, ( the lesser sigmoid cavity,) which is concave from before backwards ; this depression is covered by an extension of the cartilage of the greater sigmoid cavity, and receives the internal side of the head of the radius. The superior extremity of the radius forms a shallow circular depression which receives the lesser head of the humerus; this surface is covered by a cartilage which extends over its circumference on a circular surface applied to the lesser sigmoid cavity of the ulna internally, and embraced by the annular ligament in the rest of its extent : the articular head of the radius is supported on a cylindrical portion, called its neck, which is much smaller in its circumference, of about a finger's breadth long and curved a little outwards, its junction with the shaft of the bone being marked internally by a rough tuberosity, the tubercle of the ra- dius, into the posterior side of which the tendon of the triceps is inserted. Ligaments. — The fibrous ligaments of the elbow are four in number ; 1st, the anterior * Handbuch der menschlichen Anatomie, band ii. ligament consists of oblique and perpendicular fibres arising superiorly from the front of the condyles and the part of the humerus imme- diately above the two anterior articular fossae, and is inserted into the anterior edge of the coronoid process of the ulna inferiorly ; 2d, the posterior ligament is less distinct than the an- terior, consisting of transverse fibres extending from one condyle to the other, which become more evident when the elbow is flexed; 3d, the external lateral ligament arises from the ante- rior surface of the external condyle by a thick cord-like fasciculus of shining silvery fibres, and spreads out into a broad flat expansion, which is inserted into the whole length of the annular ligament of the radius and into the anterior and posterior margins of the lesser sig- moid cavity of the ulna ; the tendons of origin of the supinator brevis and extensor muscles of the hand are intimately connected to the exter- nal surface of this ligament, but can be easily separated from it by careful dissection ; 4th, the internal lateral ligament arises from the an- terior surface of the internal condyle of the humerus, and passing over the internal side of the synovial capsule, divides into two portions, an anterior and a posterior, the former of which is inserted into the inner side of the coronoid process, and the latter into the internal side of the olecranon : this ligament presents more of a flattened form, and is more easily separated from the tendons of the muscles which cover it than the external lateral ligament. The synovial capsule, having covered the ar- ticular surface of the humerus, ascends above this surface as high as an irregular continuous line, including the two anterior articular fossae in front, the posterior articular fossa behind, and limited by the bases of the condyles late- rally ; at the level of this line the capsule is re- flected from the humerus, and descends on the internal surfaces of the fibrous ligaments to be expanded over the articular surfaces of the radius and ulna, to the cartilaginous coverings of which it adheres in the same intimate man- ner as to that of the articular surface of the humerus ; the portion of it corresponding to the radius descends within the annular liga- ment, below which it is reflected on the neck, and thence continued over the head of that bone ; while it becomes attached to the ulna at the line which circumscribes the greater and lesser sigmoid cavities over the surfaces of which it is extended ; this capsule, which is rather tense where it lines the lateral ligaments, is flaccid and sacculated anteriorly and poste- riorly, so as not to interfere with the freedom of flexion and extension of the elbow : below the margin of the annular ligament and before it is attached to the neck of the radius, it forms a cul-de-sac so loose as to permit the rotatory motions of that bone to be executed without restraint. Several masses of adipose cellular tissue are situated around the articulation external to the synovial capsule, more especially in the articu- lar fossae at the posterior margin of the olecra- non ; between the radius and ulna and in the ABNORMAL CONDITION OF THE ELBOW-JOINT. 67 notch on the internal side of the greater sigmoid cavity, there always occurs a mass of this sub- stance from which a production extends over the rough groove described above, dividing the sigmoid cavity transversely. The synovial capsule adheres closely to the fibrous ligaments, except where masses of adi- pose tissue are interposed, to which it is but loosely connected. Motions. — The elbow is a joint remarkable for possessing great solidity, which is partly owing to the extent of its osseous surfaces and the manner in which they are locked into each other, and partly to the strong lateral ligaments and the muscles which surround it. The motions enjoyed by the elbow-joint are flexion and extension. Flexion may vary in degree so as to be com- plete or incomplete : in complete flexion the fore-arm is carried forwards and inwards in an oblique direction across the front of the thorax, so as to bring the hand towards the mouth ; the direction of the fore-arm is determined in this movement by the obliquity of the trochlea of the humerus from behind forwards and in- wards, as described above, and influenced by the clavicle preventing the falling inwards of the shoulder ; were it not for the support of the clavicle, the hand in this movement, instead of being carried to the mouth, would be direct- ed to the shoulder of the opposite side : when flexion of the elbow is carried to its greatest extent, the coronoid process and the head of the radius are received into the anterior articu- lar fossae of the humerus, displacing the adipose masses from these cavities, the olecranon is brought downwards on the trochlea so as to be placed below the level of the condyles of the humerus ; the posterior part of the synovial capsule, the posterior ligament, and the triceps and anconseus muscles are made tense, and applied to the adipose mass in the posterior articular fossa and to the posterior part of the trochlea : the anterior part of the capsule and the anterior ligament are relaxed, as are also the lateral ligaments. A dislocation is rendered impossible in this state of the articulation, L being effectually opposed by the hold which the coronoid process has on the front of the trochlea of the humerus. In partial flexion or semiflexion, the several parts of the articulation are differently circum- stanced ; the coronoid process being carried down is no longer applied to the front of the humerus, the olecranon is on a plane with the condyles, and the lateral ligaments are on the stretch : in this state of the parts a powerful force applied to the olecranon from behind might have the effect of displacing the ulna forwards, were it not for the great mobility of the limb, owing to which a force thus applied is moderated or altogether expended in increa- sing the degree of flexion ; hence a dislocation of the ulna forwards on the humerus is an acci- dent which never happens. In extension, the olecranon, ascending above the level of the condyles, is received into the posterior articular fossa, displacing the adipose substance which previously occupied that fossa, the radius is brought back on the lesser head of the humerus, over the anterior part of which and of the trochlea the capsule and the anterior ligament are stretched; the lateral ligaments, the tendon of the triceps, and the brachiasus anticus are also in a state of tension : the pos- terior part of the capsule and the posterior ligament are necessarily relaxed. It is when the elbow is in such a state of extension as here described that a dislocation of the fore-arm backwards usually occurs in consequence of a fall on the hand ; the force producing the dis- location in this case operates in the following way, the fore-arm serving as a fixed point, the humerus becomes a lever of the first order, the fulcrum of which is the point of the olecranon applied to the posterior side of its lower extre- mity, the power is represented by the weight of the trunk of the body applied to its superior extremity in front, and acting with a force pro- portioned to its remoteness from the point of resistance formed by the ligaments and muscles which are found in a state of tension in front ; when this force is such as to overcome the re- sistance, the ligaments in front are ruptured, the lower extremity of the humerus is then driven downwards in front of the bones of the fore-arm, the upper extremities of which are forced upwards behind the humerus, so that the coronoid process comes to occupy the nor- mal situation of the olecranon in the posterior articular fossa. Lateral motion. — Anatomists have been divided in opinion as to the possibility of any lateral motion being performed by the ulna on the humerus. Albinus, Boyer, Beclard, Cru- veilhier, and others, have denied the occurrence of it ; Monro and Bichat, however, have dis- tinctly noticed it : they consider that this mo- tion is possible only in the semifixed state of the elbow, when the lateral ligaments are most relaxed : in complete flexion, as well as in ex- tension, the tense state of these ligaments effec- tually opposes any such movement. In my opinion it is easy to satisfy one’s self as to the occurrence of this motion ; it consists of a slight degree of rolling of the middle prominent part of the greater sigmoid cavity in the fossa of the trochlea, produced by those fibres of the lower part of the triceps which extend from the con- dyle on each side to the olecranon, and by the action of the anconseus externally, ‘ ( J. Hart.) ELBOW-JOINT, ABNORMAL CON- DITION OF.' — Placed in the middle of the long lever which the upper extremity repre- sents, the elbow-joint is of necessity exposed to numerous accidents, the most remarkable of which are fractures and luxations. These, re- duced or unreduced, produce immediate and remote effects, to which it is our business in this place to advert. Congenital malforma- tions sometimes, though very rarely, are to be met with affecting this articulation, and require some brief consideration. The several structures too, which enter into the composition of the elbow-joint, are each and all occasionally affected by acute and f 2 68 ABNORMAL CONDITION OF THE ELBOW-JOINT. chronic inflammations, the consequences of which we cannot omit to notice, and many of these have their reputed source either in struma or syphilis, while others are attributed to an ar- thritic or to a rheumatic diathesis. I. Accident. — Fractures. — Fractures of the bones of the elbow-joint may be classed as to their situation and direction : first, as they affect the lower extremity of the humerus ; and, secondly, as they engage the upper extremities of the bones of the fore-arm. 1. Simple fractures of the humerus near the elbow-joint may be transverse or oblique. When this bone is fractured transversely at its lower part immediately above its condyles, or in young subjects through its lower epiphysis, in either case the olecranon process is pulled backwards and upwards by the triceps, while the part of the humerus superior to the fracture, that is, almost the whole of the bone, is carried forwards, and forms such a projection below as much resembles a luxation forwards of the true articular extremity of the bone ; the prominence in front is also considerably increased by the in- clination forwards of the upper extremity of the lower short fragment, which is pulled in this direction by the supinators and pronators taking their fixed point below. The prominence for- wards, formed by the angle of contact between the upper and lower fragments of the humerus, is covered in front by the brachialis anticus and biceps; and there is a projection behind formed by the olecranon process equally well marked ; so that, in comparing the posterior aspects of the two articulations, we see the ole- cranon process at the affected side exceed by its projection backwards that of the uninjured arm an inch or more : when to all this we add the observation that the antero-posterior diameter of the arm is evidently augmented, we have here many of the signs which might lead one to sus- pect the existence of the luxation of the bones of the fore-arm backwards. There is this differ- ence however, namely, that in fracture a crepitus can be felt, and the deformity is not accompa- nied with any changes of the normal relations existing between the olecranon and the con- dyles. Oblique fractures near the elbow-joint are usually prolonged into the articulation, and may be either external or internal. The frac- ture may traverse in an oblique line from without inwards, and from above downwards; and then the external condyle and capitulum of the humerus will be detached from the shaft of that bone, and will constitute the external or inferior fragment ; or the fracture may take place obliquely from above downwards, and from within outwards, so as to comprehend the trochlea of the humerus and internal con- dyle in the inner fragment. In the first case, or external fracture, the posterior muscles of the fore-arm will have a tendency to pull the condyle downwards and backwards ; and in the second, the internal fragment with the trochlea will be drawn downwards and for- wards by the pronator muscles. Oblique fractures, extending into the elbow- joint, detaching the external condyle of the os humeri, maybe detected by the following sym- ptoms. There is considerable swelling and pain upon pressure on the external condyle : and the motions of the elbow-joint, both of ex- tension and flexion, are performed with pain; but the principal diagnostic sign is the crepitus produced by communicating a rotatory motion to the fore-arm. If the portion of the frac- tured condyle be large, it is drawn a little backwards, and it carries the radius with it ; but if the portion be small, this circumstance does "not occur ; if the fracture of the external condyle take place immediately above it and within the synovial sac, it is stated by Sir A. Cooper that no union will take place except by means of ligament.* The oblique fracture of the external condyle is frequently met with in children ; a fall on the hand forwards may cause it, the impulse being transmitted along the radius to the capitulum and outer condyle of the humerus. The connexion of the radius with the ulna at this period of life is so loose that no resistance is afforded to the forcible ascent of the radius when a sudden fall for- wards on the palm of the hand occurs ; and hence in the young subject particularly an oblique fracture of the outer condyle of the humerus can readily happen : at a late period of life, the connexions between the bones of the fore-arm are so strong and unyielding, that from a similar fall forwards on the hand, it is the lower extremity of the radius which would be obliquely fractured. There is at this moment in the Richmond Hospital a young woman who met with this oblique fracture of the external condyle of the humerus near the elbow, when she was only five years of age. The outer condyle and capitulum of the humerus were detached ob- liquely from the shaft of the bone and thrown backwards, carrying with them the head and upper extremity of the radius ; she now has very good use of her arm, but in consequence of the accident much deformity exists, parti- cularly when she extends the fore-arm. The obtuse angle salient internally, which the fore- arm forms with the arm in the natural state when it is fully extended, and the hand supi- nated, does not exist. On the contrary, in this case the salient angle is external, and corres- ponds to the outer condyle and head of the radius, and the retiring angle is placed inter- nally. (See Jig. 40.) The internal condyle of the humerus is fre- quently broken obliquely from the body of the bone, and the symptoms by which the accident is known are the following : when the fore-arm is extended on the arm, the ulna projects be- hind the humerus ; the lower end of the hume- rus, too, advances on the ulna, so that it can be easily felt on the anterior part of the joint ; on flexing the fore-arm on the arm, the ulna resumes its usual position ; by grasping the condyles and bending and extending the fore- arm, a crepitus is perceived at the internal con- dyle : this accident usually occurs in youth, * See plate xxvi. fig. 1, of Sir A. Cooper’s work on Fractures and Dislocations. ABNORMAL CONDITION OF THE ELBOW-JOINT. Fig. 40. 69 Fracture and retraction of the outer condyle of the humerus. although it may be seen in those advanced in life. It is an injury very likely to be mis- taken for a dislocation. 2. Fractures which engage the upper extre- mity of the bones of the fore-arm are chiefly confined to the ulna, for the radius very seldom suffers. Sometimes the olecranon process at the ulna is broken off, and occasionally a frac- ture of the coronoid process occurs, the con- sequences of which last accident are sometimes very serious. Sir A. Cooper gives us the fol- lowing history: “A gentleman came to London for the opinion of different surgeons upon an injury he had received in his elbow. He had fallen on his hand whilst in the act of running, and on rising he found his elbow incapable of being bent, nor could he entirely extend it ; he applied to his surgeon in the country, who upon examination found that the ulna pro- jected backwards when the arm was ex- tended, but it was without much difficulty drawn forwards and bent, and the deformity was then removed. It was concluded that the coronoid process was detached from the ulna, and that thus during extension the ulna slipped back behind the inner condyle of the humerus.” A preparation of an accident, supposed to be similar, is preserved in the Museum of St. Thomas’s Hospital; the coronoid process, which had been broken off within the joint, had united by ligament only, so as to move readily upon the ulna, and thus alter the sigmoid cavity of the ulna so much as to allow in extension that bone to glide backwards upon the condyles of the humerus. Fracture of the olecranon. — This process of the ulna is not unfrequently broken off, and the accident is attended by symptoms which render the injury so evident that the nature of the case can hardly be mistaken. Pain is felt at the back of the elbow, and a soft swelling is soon produced there, through which the surgeon’s finger readily sinks into the joint ; the olecranon can be felt in a detached piece elevated sometimes to half an inch and some- times to two inches above the portion of the ulna from which it has been broken. This elevated portion of bone moves readily from side to side, but it is with great difficulty drawn downwards ; if the arm be bent, the separation between the ulna and olecranon be- comes much greater. The patient has scarcely any power to extend the fore-arm, aud the attempt produces very considerable pain, but he bends it with facility, and if the limb be left undisturbed it is prone to remain in the semiflexed position. For se- veral days after the injury has been sustained, much swelling of the elbow is produced, there is an appearance of ecchymosis to a consider- able extent, and an effusion of fluid into the joint ensues; but the extent to which these symptoms proceed depends upon the violence which produced the accident. The rotation of the radius upon the ulna is still preserved; no crepitus is felt unless the separation of the bone is extremely slight. Fractures of the upper extremity of the ulna are sometimes very com- plicated. Thus Mr. Samuel Cooper informs us that there is a preparation in the Museum of the London University, illustrating a case in which the ulna is broken at the elbow, the posterior fragment being displaced backwards by the action of the triceps ; the coronoid process is broken off ; the upper head of the radius is also dislocated from the lesser sigmoid cavity of the ulna, and drawn upwards by the action of the biceps. Luxations. — The bones of the fore-arm are liable to a great variety of luxations at the elbow-joint ; the following arrangement will pro- bably be found to comprehend most of those accidents as yet known and described. 1. Luxations of both bones backwards; 2. Luxations of both bones laterally, complete and incomplete; 3. Luxations of both bones laterally and posteriorly ; 4. Luxation of the ulna alone backwards; 5. Luxation of the radius alone forward ; 6. Luxation of the ra- dius externally and superiorly; 7. Complete luxation of the radius backwards ; 8. Sub-lux- ation of the radius backward ; 9. Congenital luxation of the radius. 1. Luxation of both bones of the fore-arm backwards. — This luxation is the most frequent of all those to which the elbow-joint is liable; it is usually produced by a fall on the palm of the hand, the fore-arm being at the time ex- tended on the arm, and carried forwards, as when a person falling forwards puts out his hand to save himself. The patient suffers at the moment of the acci- dent an acute pain in the elbow-joint, and is often conscious of something having given way in the joint. The fore-arm inclines to a state of supina- tion (fig. 41); the whole extremity is manifestly shortened ; the olecranon process rises very much above the level of the tuberosities; or, to speak more correctly, with reference to the po- sition of the limb, which is always presented to 70 ABNORMAL CONDITION OF THE ELBOW-JOINT. Fig. 41. us for examination more or less flexed, this process is placed much behind and somewhat below the plane of the condyles of the humerus. The tendon of the triceps carried back with the olecranon stands out in relief, as the tendo Achillis does from the malleoli. This part of the triceps thus standing out can be seized through the integuments by the fingers, and we perceive in front an interval between it and the back part of the humerus. Anteriorly, in the fold of the arm, through the thickness of the soft parts, we can feel a hard tumour, situated obliquely from without inwards and back- wards, formed by the lower articular extremity of the humerus. The rounded head of the radius can be seen prominent below the exter- nal condyle, and we can occasionally even sink the end of the thumb into the hollow of its cup-like extremity, and if now a movement of pronation and supination be communicated to it, the nature of the case becomes very evi- dent. The patient himself feels the arm powerless, and we find we can communicate to it but little motion. When we make the attempt to rotate or flex the arm on the fore-arm, we find our efforts resisted, and that we give the patient pain ; a little extension of the elbow-joint is allowed ; and we have invariably found that a lateral movement of abduction and adduction could be given to the fore-arm, motions this joint does not enjoy in the natural state, but which we can account for being now permitted, when we recollect the complete laceration the lateral ligaments must suffer in this injury. The transverse fracture of the lower extremity of the humerus, or a forcible separation of its lower epiphysis, are accidents most liable to be confounded with luxation of both bones backwards ; but although the elbow projects much backwards, and there is a marked prominence in front, still the relative position of the condyles of the humerus and the olecra- non process is not altered in the fracture, as they have already been described to be, in the lux- ation. Add to this, that in the fracture the sur- geon can flex the patient’s fore-arm on his arm, a movement which, in the luxation, the patient can neither himself fully perform, nor can it be communicated. In the case of the transverse fracture also, notwithstanding the apparent similitude at first with the luxation, when a steady extension is made by pulling the hand forwards, while the arm is fixed, all the marks of luxation disap- pear, to return again very shortly, when the extending force is relaxed. In fracture, too, a characteristic crepitus may be felt just above the elbow-joint, by rotating the fore-arm on the humerus. It is very true that, in some cases of luxation, the dislocated bones are very rea- dily restored to their place, and on the other hand, that a transverse fracture of the humerus may, after it is reduced, remain so for a little time, and thus we may perhaps account for the fact, that these accidents have been confounded with each other, and the mistake is a serious one. To guard against error in our diagnosis, it would be well, after the bones have been re- duced, to try the experiment of pushing the fore-arm backwards, while the arm is steadily pressed forwards ; if the accident has been a luxation, no change occurs, but if there has been a transverse fracture of the humerus, or of the coronoid process of the ulna, all appear- ances which erroneously induced a suspicion that the accident was one of luxation, are re- newed, but not so the error of attributing these appearances to a luxation, for now the exist- ence of a fracture can no longer be doubted. Lastly, after the bones, in a case of luxation, are apparently restored, it will be prudent to examine the head of the radius, and it will be right to be satisfied that this bone has also been replaced as well as the ulna, for, in the luxa- tion of both bones backwards, the connexion of the radius with the ulna by means of the coronary and oblique ligaments, may have suffered, and under such circumstances, if care be not taken, the restoration of the radius to the lesser sig- moid cavity of the ulna and capitulum of the humerus may have been forgotten, as we have known to have happened in one instance. When the luxation of both bones backwards is simple, and by mistake or neglect has been left unreduced, the case soon becomes irreme- ABNORMAL CONDITION OF THE ELBOW-JOINT. 71 diable ; the patient for ever loses the power of fully flexing the fore-arm, and the muscles of the arm become more or less atrophied ; the powers of pronation and supination also become impaired, but extension of the elbow-joint can be performed. Sir A. Cooper had an opportunity of dissect- ing a compound luxation of the elbow-joint, in which the radius and ulna were thrown back- wards, and the specimen is preserved in the Museum of St. Thomas’s Hospital, and a re- presentation given in his work on dislocations : see plate xxiii. fig. 2. The coronoid process of the ulna was thrown into the posterior fossa of the os humeri, and the olecranon projected at the back part of the elbow, above its natura 1 situation, an inch and a half. The radius was placed behind the external condyle of the os hunleri, and the humerus was thrown forwards on the anterior part of the fore-arm, where it formed a large projection. The capsular liga- ment was torn through anteriorly to a great ex- tent ; the coronary ligament remained entire. The biceps muscle was slightly put on the stretch by the radius receding, but the brachia- lis anticus was excessively stretched by the altered position of the coronoid process of the ulna. This was a recent case ; but it would ap- pear from the dissections which have been made of cases which had been left for a long time unreduced, that a new bony cavity had been made on the front of the coronoid process of the ulna, while the brachialis anticus be- came the seat of ossific depositions. An in- teresting case of this kind is recorded by Cru- veilhier, and figured by him in his Anat. Pathol, plate iv. fig. 1. Beclard also met with a simi- lar case in dissection. 2. Lateral dislocation of the hones of the fore- arm.— Lateral dislocations of the elbow-joint are rare, and this circumstance is owing to the great transverse extent of the articular surfaces, to the inequalities which the corresponding surface of the humerus presents in the transverse di- rection, to the strength of the lateral liga- ments, and the attachment to them of the tendons of those superficial muscles which pass to the anterior and posterior part of the fore-arm, which tendons almost identify themselves with the lateral ligaments, and must considerably strengthen and support the joint laterally. Again, the force which would have a tendency to luxate the bones laterally can very rarely be directed in such a manner as to produce the luxation we are now considering, nor are the muscles ever so directed as to produce them. We find in authors circumstantial accounts of the symptoms of the complete luxation outwards and also of the complete luxation inwards ; but we have not had any opportuni- ties ourselves of witnessing these complete luxa- tions as the immediate result of accidents. Indeed we can scarcely conceive any complete luxation outwards to correspond exactly to the description given ; as we imagine that when- ever the bones of the fore-arm are completely thrown outwards, these bones must be drawn * Luxation outwards of botk hones of the fore-arm, consecutive to caries of the trochlea and great sigmoid cavity of the ulna. immediately upward along the outer side of the arm. We can conceive it possible, however, that the bones of the fore-arm may be completely dislocated inwards from the trochlea of the humerus, and still be restrained from yielding to those forces which would draw them upwards and inwards, by the great pro- jection inwards of the internal condyle of the humerus, which we know is so much more prominent than the external. We could scarcely mistake the case of complete lateral luxation of the fore-arm, whether it was inwards or outwards. In the incomplete lateral luxations of the bones of the fore-arm at the elbow-joint, the articular surfaces of the bones are still in con- nexion, but the points of contact of their naturally corresponding surfaces are altered more or less as to their relative positions to each other. In these luxations the bones of the fore-arm may be thrown partially outwards or partially inwards. In the luxation outwards , the cavity of the superior extremity of the radius abandons the lesser head of the humerus, and its cup-like extremity may be felt beneath the skin, while the great sigmoid cavity of the ulna corresponds to the capitulum of the humerus from which the radius has been dis- placed. As to the anatomy of the parts under such circumstances, the ligaments must be all torn, the biceps and triceps muscles must be pulled outwards in the direction of the bones of the fore-arm, into which they are inserted, the supinator brevis muscle cannot escape lace- ration, and the musculo-spiral nerve must be more or less stretched. There must be danger of such a luxation being rendered complete or even compound. One of the most remarkable of the external signs of this injury is an increase of breadth of the fore-arm in the line of the articulation. There is a considerable projection seen at the outer side of the arm formed by the head of the radius, and an angular depression immediately above this. On the inner side of the arm we see the 72 ABNORMAL CONDITION OF THE ELBOW-JOINT. prominence formed by the inner condyle of the numerus, and its lower extremity. The fore-arm is flexed, and the patient feels it impossible to move the joint. The deviation and curved direc- tion outwards given to the biceps and triceps, and approximation of the olecranon to the outer condyle of the humerus, all taken toge- ther sufficiently characterize this rare accident. In the incomplete luxation inwards, the cavity of the superior extremity of the radius, in abandoning the small head of the humerus, may be carried more or less inwards, and be placed under the internal border of the articu- lar pulley or trochlea of this bone, while the inner edge of the great sigmoid cavity of the ulna and olecranon process must project in- wards beneath the inner condyle of the humerus. The ligaments must be all torn as well as some of the muscles arising from the internal con- dyle of the humerus, the biceps and triceps are turned from their usual direction and are curved inwards, and the ulnar nerve must be more or less stretched. The external signs of incomplete luxation inwards are what the anatomy of the parts above described would lead us to expect; there is a remarkable increase of breadth across the line of the joint, perma- nent flexion of the fore-arm, and a powerless condition of the limb, all which were noticed in the former case. We must add to these a remarkable projection below and internal to the inner condyle of the humerus, formed by the internal edge of the great sigmoid cavity of the ulna. Our attention is also attracted by the approximation of the olecranon process and inner condyle of the humerus to each other, and the distance of the olecranon from the outer condyle of the humerus, which forms a remarkable projection externally. 3. Under the head of lateral luxations of the elbow-joint, Sir A. Cooper has described accidents which might perhaps be more cor- rectly designated — a, complete luxation of the bones of the fore-arm at the elbow backwards and outwards ; h, complete luxation of the bones of the fore-arm at the elbow backwards and inwards. a. Luxation of the hones of the fore-arm backwards and outwards. — In this case the ulna, instead of being thrown into the posterior fossa of the os humeri, has its coronoid process situated on the back part of the external con- dyle of the humerus. The projection of the ulna backwards is greater in this than in the former luxation, and the radius forms a pro- tuberance behind and on the outer side of the os humeri, so as to produce a depression above it. The rotation of the head of the radius can be distinctly felt by rolling the hand. b. Luxation of the bones of the fore-arm backwards and inwards. — Sometimes the ulna is thrown on the internal condyle of the os humeri, but it still projects posteriorly, as in the external dislocation, and then the head of the radius is placed in the posterior fossa of the humerus. The external condyle of the humerus in this case projects very much out- wards, and the usual prominence of the inter- nal condyle is lost. The olecranon process approaches nearer than natural to the middle line of the body, and is pointed inwards, being thrown more posteriorly than in any other lux- ation. 4. Luxation of the ulna alone directly back- wards.— The ulna is sometimes thrown back upon the os humeri, without being followed by the radius. The appearance of the limb is much deformed by the contortion inwards of the fore-arm and hand ; the olecranon projects, and can be felt behind the os humeri. Exten- sion of the arm is impracticable but by force, which will reduce the luxation, and it cannot be bent to more than a right angle. It is an accident somewhat difficult to detect, but its distinguishing marks are the projection of the ulna, and the twist of the fore-arm inwards. A specimen of this accident is preserved in the Museum of St. Thomas’s Hospital ; the luxa- tion had existed for a length of time. The coronoid process of the ulna was thrown into the posterior fossa of the humerus, and the olecranon was found projecting behind the humerus much beyond its usual situation. The radius rested upon the external condyle, and had formed a small socket for its head, in which it was able to roll* The coronary and oblique ligaments had been torn through, and also a small part of the interosseous ligament. The brachialis anticus was stretched round the trochlea of the humerus, and the triceps had been carried backwards with the olecranon. 5. Luxations of the upper extremity of the radius from the humerus and ulna. — When we look into the best books we possess for infor- mation on this subject, we must be struck with the remarkable discrepancy of the opinions we find expressed by the authors. Tlius, upon the subject of luxation forwards of the radius, we find the celebrated Boyer stating that he doubts such a luxation can occur without being complicated with a fracture. Sanson states that this luxation forwards has never been observed, and moreover advances what he considers as anatomical and physiological explanations, to show the impossibility of such an occurrence. Sir A. Cooper, on the contrary, gives six examples of the luxation of the upper extre- mity of the radius forwards. The French writers state of the luxation of this extremity of the radius backwards, that although it is rare it has been many times witnessed, while Sir A. Cooper, alluding to this luxation back- wards, says, “ this is an accident which I have never seen in the living,” but he gives an anatomical account of the appearances found in a subject, the history of which was unknown, brought into St. Thomas’s Hospital for dissec- tion. Having thus stated the different opinions of authors upon this subject, we shall proceed to give an account of— a, the luxation of the upper extremity of the radius forwards ; b, of its luxation laterally and upwards ; c, of its luxation backwards; d, of its sub-luxation; e, of its congenital luxation backwards. * See plate xxiv.fg. 2, in Sir A. Cooper’s work. ABNORMAL CONDITION OF THE ELBOW-JOINT. 73 a. Luxation of the radius at the elbow-joint forwards. — The symptoms of this accident are as follows : the fore-arm is slightly bent, but cannot be brought to a right angle with the arm, nor can it be completely extended ; when it is suddenly bent, the head of the radius strikes against the fore part of the humerus, and pro- duces so sudden a stop to its motion as at once to convince the surgeon that one bone strikes against the other. The hand is placed in a prone position; but neither its pronation nor its supination can be completely performed, although its pronation may be nearly complete. The head of the radius may be felt on the front and upper part of the elbow-joint, and if rota- tion of the hand be attempted, the bone will be perceived to roll ; this last circumstance and the sudden stop to the bending of the arm are the best diagnostic marks of this injury. In the dissection of this case, the head of the radius is found resting in the hollow above the external condyle of the os humeri. The ulna is in its natural position. The coronary and part of the capsular ligaments as well as the oblique and a portion of the interosseous liga- ments are tom through. The laceration of the latter ligament allows of the separation of the two bones. The biceps muscle is shortened (fie- 43)- Fig. 43. Luxation of the radius forwards. We have known an instance in which this accident was produced in the following man- ner : the patient in endeavouring to protect his head from a blow aimed at him by a man who with both hands wielded a spade, received the force and weight of the spade on the edge of the ulna, which, at the same time that it pro- duced a compound fracture of this bone, also dislocated the radius forwards. This latter complication not having been discovered in time, remained ever afterwards unreduced. b. Lateral dislocation of the upper extremity of the radius. — This is an accident we find alluded to for the first time by Sir A. Cooper, in the appendix to the edition of his work on luxations. He does not adduce any recent case of it, but states that Mr. Freeman brought to his house a gentleman, aged twenty-five, whose pony having run away with him when he was twelve years old, he had struck his elbow against a tree, while his arm was bent and advanced before his head, in consequence of which the olecranon was broken, and the radius luxated upwards and outwards above the external condyle. When the arm was bent, the head of the radius passed the os humeri ; he had a useful motion of the limb, but neither the flexion nor the extension was complete. As the case here stated is the only one we are acquainted with on record of luxation of the radius upwards and outwards, we may be perhaps excused for exceeding our ordinary limits by relating the following case of this accident ; the subject of it was a very intelligent medical student, about twenty-three years old, and we shall give the case nearly in his own words : — He writes as follows : “ When I was very young, a blow was aimed at my head by a person having a heavy boat-pole in his hands. I endeavoured to save my head by parrying the blow with my left arm. I received the pole on the middle and back part of the fore-arm with a force which knocked me down, and caused a wide lacerated wound where the pole came in contact with it. Whether a luxation of the radius occurred at this time or not was not known, but ever since the accident the arm has been weak, and about seven years ago the weakness increased, and it became liable to partial luxations forwards upon the slightest causes, which luxations I reduced myself by making extension with my right arm, until at length I got a severe fall, which dislocated it to such an extent, forwards and outwards, as to defy my attempts to restore it. The arm was locked m the flexed position, and the head of the radius was to be felt high up, and pro- jecting slightly outside the external condyle of the humerus. The biceps muscle was con- tracted, and its tendon was very prominent, hard, and tense, like a bowstring. The hand was supinated. I suffered little pain, except when extension was attempted, when it became intense. Sir A. Cooper remarks, in his cases of luxation of the radius forwards, that the fore-arm is slightly bent, but cannot be bent to a right angle, nor completely extended. My arm was bent to an acute angle, and could not admit of the slightest extension. The luxation was reduced by extension, and in six weeks passive motion was begun; but I found it painful to use it, and the head of the radius would often catch in the ridge above the ex- ternal condyle, but on extending the arm it returned with a noise into its place. A month, however, did not pass before I was one morn- ing awakened in making some awkward move- ment in my bed, and my arm became luxated worse than ever. On this occasion the surgeon who heretofore had easily replaced the bone found it impracticable to effect it, and called in Mr. Colles to his assistance ; but although much force was used it was in vain. From this time the head of the radius never was 74 ABNORMAL CONDITION OF THE ELBOW-JOINT. returned back to its proper situation, but habi- tually remained dislocated completely forwards in front of the external condyle. The liga- ments seemed to have been so lacerated, and the joint felt so weak, that I was in constant terror lest the bone should be further luxated as formerly, and that it should again slip over the external condyle of the humerus. I could extend my arm, but not fully, and could rotate it, but could not flex it sufficiently to use my fork at dinner. In this state I remained for six years, and in the winter of 1834-5 the radius was again luxated laterally over the external condyle of the humerus by a fall from my bed. Now the difficulty experienced in bringing the bone back to the situation it had so long occu- pied in front of the external condyle, was ex- treme. I went to the hospital, and two sur- geons, assisted by six of my brother pupils, could not, with all their force, reduce the bone. The pulleys were also nowused,but without suc- cess. Dr. O’Beirne and the late Dr. M‘Dowel were called into consultation ; they placed me sitting on my bed, and fixing the hollow angle at the bend of the elbow against one of the bed-posts, they used great force to straighten it, in which they succeeded ; that is to say, they replaced the bone, not into its original berth, but back to the new socket, which had been formed for it in front of the external con- dyle, where it had been lodged for six years previously to the last accident, and where it now remains. At this moment it presents all the characters assigned to the luxation of the radius forwards ; the rounded head of this bone is quite prominent in front of the external con- dyle of the humerus, in which situation it seems to have worked for itself a socket, and behind the head of the radius a deep depres- sion exists. The arm has a rounded appear- ance, and the fore-arm is much wasted.” This case seems to us important as proving three circumstances: 1. that a partial luxation forwards of the radius can exist from relaxation or elongation of ligaments ; 2. that this partial luxation or weakness of the joint is readily convertible into the true luxation forwards ; and, 3. that in the case of unreduced luxation of the radius forwards the patient is still in danger of further luxation of this bone laterally, or above the capitulum and outer condyle of the humerus. c. Luxation of the upper extremity of the radius backwards. — This luxation would appear to be the most frequent the upper extremity of the radius is liable to, although it cannot be considered a common accident. When, how- ever, we consider the functions of this joint and its form, we shall not be surprised to find the luxation backwards more usual than that forwards. The articulation is less sustained posteriorly by muscular parts than in front, when the fleshy bellies of the supinators cover and support it. There is also much latitude given to the movement of pronation, and the pronators are very powerful muscles. During a forced pronation, the radius becomes very oblique, and its upper extremity has a strong tendency to pass behind the axis of the hu- merus. The motion of supination, on the contrary, is not so frequent, the muscles to effect it are not so powerful, and the oblique and interos- seous ligaments, which afford no restraint in the motion of pronation, are, on the contrary, soon rendered tense, and oppose a forced supination, which is the movement most likely to be followed by the luxation forwards. We think, therefore, we have physiological grounds for our belief that the luxation of the radius backwards ought to be the most frequent lux- ation of the radius at the elbow-joint. When the luxation of the upper extremity of the radius backward has occurred, the patient feels at the moment a severe pain in the region of the joint. The fore-arm is flexed, and the hand remains fixed in a state of pronation. Supination cannot be effected either by the voluntary action of muscles or by force ap- plied, and each effort, tending to produce this effect, is attended with a considerable augmen- tation of pain. The hand and fingers are held in a moderate state of flexion. Finally, the superior extremity of the radius forms a mani- fest prominence behind the capitulum or small head of the humerus. When the bone is left unreduced, many of the motions of the fore-arm are rendered im- perfect, particularly supination ; but the shoul- der articulation becomes somewhat more free, and in some degree this circumstance makes up for the deficiency. Sir A. Cooper, who has not seen any example of this luxation of the radius backwards in the living subject, has given us an account of a dis- section of this injury. He informs us that in the winter of 1821 a subject was brought for dis- section into the theatre of St. Thomas’s Hos- pital, in which was found this luxation, which had never been reduced. The head of the radius was thrown behind the external condyle of the humerus, and rather to the lower extre- mity of that bone. When the arm was ex- tended, the head of the radius could be seen as well as felt behind the external condyle of the humerus. On dissecting the ligaments, the coronary ligament was found to be torn through at its fore part, and the oblique ligament had also given way. The capsular ligament was partially torn, and the head of the radius would have receded much more had it not been supported by the fascia which extends over the muscles of the fore-arm. d. Sub-luxation of the upper extremity of the radius , with elongation of the coronary ligament. — While Boyer denies the possibility of any partial luxation of the upper extremity of the radius, he describes very clearly an abnormal condition of the radio-humeral joint, of which we have seen many examples, and which perhaps we may call a sub-luxation. The ligaments which connect the head of the radius to the ulna, in the cases above alluded to, undergo a gradual relaxation and elonga- tion, so that whenever an unusual effort is made to produce a strong pronation of the 75 ABNORMAL CONDITION OF THE ELBOW-JOINT. fore-arm, the head of the radius is permitted to pass backwards, somewhat behind its na- tural situation ; but as soon as the effort ceases, the radius resumes its natural position in the lesser sigmoid cavity of the ulna. A true lux- ation in these cases cannot be said to happen, unless the effort of pronation is sufficient to bring the superior extremity of the radius behind the small head of the humerus ; when- ever this has occurred, then the sub-luxation is converted into the complete luxation of the radius backwards, and presents all the cha- racters of this accident, and it cannot be re- placed without the assistance of art. It is known to anatomists that the radio-cubital joint is not advanced much in its development in infants ; that the lesser sigmoid cavity is as yet small and shallow ; and that the coronary ligament of the radius is proportionally longer and more yielding than it is destined to be in after life. This articulation, however, is fully equal, even at this earliest period of life, to sustain any efforts that its own pronator muscles can communicate to it; but it is by no means constructed so as to be able to resist those forced movements of pronation and stretching we see too frequently given to the fore-arms of infants of a tender age, by their attendants, who in lifting them from the ground usually seize them by the fore-arms, these being at the time in a full state of pro- nation. Thus we find that in delicate children the foundation is laid for that elongation of the coronary ligament, which ends in the con- dition of this joint we have denominated sub- luxation. We have usually observed that the subjects of this affection were delicate from .their youth, and that sometimes only one, and that frequently both arms were affected ; that in all cases the extremity was more or less deformed, having a bowed appearance, the convexity being external ; that a very evident protuberance could be seen and felt in the situation of the head of the radius ; and that the patient had nearly perfect use of the arm, although he could neither fully flex nor extend it. When the surgeon places his thumb on the external condyle of the humerus and head of the radius in one of these cases, and at the same time has the fore-arm supinated, the head of the radius is felt to rotate in its proper place, and on its axis, as in its perfect condition ; but if now a forced movement of pronation be given to the head of the radius, the latter will be observed to slip backwards towards the olecranon process : every time the patient him- self fully pronates the fore-arm, the sub-lux- ation occurs, and in supination the radius resumes its place again. This relaxation of the ligaments of the radio-cubital joint, no matter how produced, at all events predisposes those affected with it to the more complete luxation of the radius backwards. e. Congenital or original luxation of the superior extremity of the radius backward. — ■ Dupuytren is the first pathologist who has spoken of the congenital luxation of the radius; he met with a case of the kind in dissection, and described it in his lectures. He found that the superior extremity of each radius had abandoned its natural situation, and was found situated behind the inferior extremity of the humerus, having passed this extremity an inch at least. This disposition being absolutely the same on each side of the body, there existed no difference between these two luxations, which were probably conge- nital. It is also stated that Dupuytren had mentioned that about twenty or twenty-five years before he dissected the case now alluded to, he had seen a case nearly similar, but he was unwilling to speak positively on these cases, as the history was unknown, and acci- dent or disease might have produced similar results. Cruveilhier, in his very valuable work on Pathological Anatomy, quotes the above ob- servations from Dupuytren’s lectures, and seems to disagree entirely with the celebrated surgeon of the Hotel-Dieu, advancing it as his opinion, that it would be much more na- tural to suppose that the cases described by Dupuytren were not congenital, but rather very old luxations, a long time left unre- duced. It is very true that Dupuytren speaks with hesitation about the matter, as he appears to have met with but two cases, nor can any one speak with certainty on this subject, until ob- servation on the living, and anatomical in- vestigations, shall be combined to elucidate the matter ; but we think that already enough can be adduced to shew, that we have strong grounds for believing that such a congenital defect as luxation of the upper extremity of the radius backwards may be occasionally met with, and this is an opinion we think our- selves authorised to advance, because of the facts and reasons we can adduce to support it. In the Museum of the Royal College of Sur- geons in Ireland, there is a specimen, which the writer considers to be one of congenital lux- ation of the upper extremity of the left radius backwards ; fig. 44 is a representation of it. The outer condyle of the humerus exists, but in front of it there is no rounded head or capitulum for the radius, or any trace of the usual convex articular surface ever having existed. The coronoid process and great sig- moid cavity of the ulna are unusually large transversely, and stretch almost the whole way across the lower articular extremity of the humerus, which is entirely formed into one single trochlea wider than natural. The head of the radius, which seems never to have been adequately developed, is situated behind the plane of the outer condyle of the humerus. The tubercle of the radius is much enlarged, and leans against the lesser sigmoid cavity of the ulna, while the neck of the radius, directed somewhat backward, is twice its natural length, and instead of reaching merely to the level ot the lesser sigmoid cavity of the ulna, stretches as high up along the ulna as to reach near to the level of the summit of the olecranon pro- cess, while the carpal extremities of the radius 76 ABNORMAL CONDITION OF THE ELBOW-JOINT. . 44. I' I and ulna are, in their natural state, on an even line with each other. There is scarcely any interosseous interval, the bones seem so closely connected with each other. Indeed, from the inspec- tion of this preparation, we may justly infer that the fore-arm during life had remained much in a state of semiflexion on the arm, and of rigid pronation, and that the movement of supination was nearly impracticable. This defective formation, or atrophy of the capitu- lum and increased deve- lopement of the trochlea of the humerus, which was so formed to ac- commodate itself to the unusual breadth acquired by the coronoid process and the whole of the ulna, must not be con- sidered unprecedented. We find, by referring to the beautiful work of Sandifort, (the Museum Anatomicum, table ciii. fig. 3,) a case similar to the above delineated (Jig. 45). In referring to it, the author states that the bones of the fore-arm wereanchylosed, that the form of the ca- „ . , , p.tulum was lost, that ^ backwards( the head of the radius was luxated completely backwards, and that the ulna alone remained in articulation with the hu- merus; the parallelism between these two cases will be still more fully seen, when, speaking of the lower articular extre- mity of the humerus, we find that he says,“ Figura ergocapituliperiit.Rotula unica, sed major forma- tur;” and of the ulna, “ insignem acquisivit am- plitudinem et totam infe- _ riorem ossis humeri p Cory emtal malformation , . i of inn lit humerus — tern admittere potint. trochlea enlarged — no In examining very capitulum. lately the splendid col- lection of morbid specimens contained in the Museum of Guy’s Hospital, the writer’s attention was caught by observing a pre- paration of the radius and ulna, belonging, he is certain, to the same class of diseases now under consideration, namely, congenital luxations of the radius. In this preparation Jli'Fi Fig. 45. there is a very oblique relative position of the bones of the fore-arm to each other. While their carpal extremities are exactly upon a line with each other below, the neck of the radius is elongated upwards, and the head of this bone is displaced much backwards, and is situated behind and below the outer condyle of the humerus, and reaches nearly to the summit of the olecranon. The coronoid pro- cess and great sigmoid cavity of the ulna have acquired much breadth, and what is remark- able in this case, and in which it differs from any other we have seen, is, that a process of caries had been going on in the articulation. Cruveilhier has given four drawings of two cases of complete luxation backward of the radius, which he however does not consider to be congenital. Nor is it in our power abso- lutely to prove that they are specimens of congenital luxations backwards, although we feel persuaded that all the cases we have re- ferred to, these inclusive, are very curious specimens of this congenital deformity of the radio-humeral articulation. The previous history of all the cases we have collected is totally unknown ; it is re- corded of them all, that the arm was re- markable for its deficient development, that the fore-arm was in a state of demi-pro- nation and demi-flexion, that the movement of extension was incomplete, and of su- pination impossible. Cruveilhier, in the ac- count he has given of both his cases, states that the superior extremity of the radius was at the level of the summit lug. 46. 0f t]le olecranon process (Jig. 46), and that the infe- rior or carpal extremity of the two bones of the fore- arm were on the same pre- cise line below, and that no deformity here existed. The head of the radius and tu- bercle were deformed, or ra- ther imperfectly developed, while there was an elonga- tion of the neck of the ra- dius upwards for more than an inch. Cruveilhier can- not concur with those who consider these cases as ex- amples of congenital luxa- tions, but looks upon them as old luxations, which had been left unreduced. For our part we cannot see in these pathological ob- servations any thing to con- vince us that any one of the cases alluded to was an old luxation originally produced by accident or disease. Sup- pose, for argument sake, it be admitted that, from long disease, the form of the . , capitulum was altogether Malformation of the , . , , ■ radius, in which ost> when the radluS was n° it was found as longer in contact with it, and long as the ulna, that the acquired breadth of ABNORMAL CONDITION OF THE ELBOW-JOINT. 77 the sigmoid cavity of the ulna was the result of a natural effort to compensate for the loss of strength the joint suffered from the dislocation of the radius. Still, supposing it possible that the surface of the eapitulum of the humerus could be so completely removed, under such circumstances, as we find it was in the cases of which^gs. 44 and 45 are delineations, we may ask, is it likely, from accident or disease, that both elbow-joints should be similarly affected, as they were in Dupuytren’s cases. Another circumstance in our mind cannot be accounted for, unless by supposing these cases congenital, namely, the alteration and great elongation of the neck of the radius. “ L’ex- tremite superieure de chaque radius avait abandonne sa situation naturelle, se trouvait place derriere l’extremite inferieure de l’hu- merus, et depassait cette extremite d’un pouce au moins. Cette disposition etait ab- solument la meme de chaque cote du corps.” We know of no process which could take place in the head and neck of the radius after it had been dislocated, which could satis- factorily account for the elongation of the radius, which has been remarked in these cases. While looking on them as congenital, we need not be surprised at it ; for we have known the neck of the femur elongated and atrophied, in the case of congenital luxation of the femur, and have very frequently seen the lower extremity of the ulna exceed in length by half an inch the corresponding extremity of the radius ; and these were cases in which no doubt could be entertained that they were congenital. Disease. — Acute and chronic inflammation produces effects on the membranes, cartilages, and bones entering into the composition of the elbow-joint, which will be found nearly analo- gous to those which the same morbid action pro- duces on similar structures in other articulations. A few local peculiarities, if we may so call them, when the elbow is the seat of the acute or chronic disease, should alone occupy our atten- tion here. Synovitis of the elbow-joint, uncombined with any affection of the other structures, is rare ; it may, however, present itself either in the acute or subacute form. Increased effusion of fluid into the joint, accompanied with the usual local and sympathetic phenomena of in- flammation, is the result. Two well-marked oblong swellings at each side of the olecranon process in these cases first present themselves, which after a time, if the disease proceeds, join and form one swelling, which extends up the back of the arm, occupying the cellular in- terval existing between the back part of the humerus and the front of the triceps muscle, opposite to the outer condyle of the humerus and head of the radius; the supinators arising here are, in severe cases, occasionally elevated and thrown out from the bones by a soft tumour, which, upon examination, conveys to the fingers a distinct feeling of a fluid contained beneath. The nature of the accumulated fluid will, when the joint is cut into, be found to vary. When the effusion has followed an acute attack of in- flammation of the membrane, it will be gene- rally found to be purulent, though sometimes we have observed the quality of the synovia but little altered, except that it was more or less turbid. When the contents of the synovial sac have been washed away, the membrane will be seen to be highly vascular, and the ves- sels of the subsynovial tissue congested with blood, and its cells infiltrated with se- rum ; while, if fine injection, coloured with Vermillion, is thrown into the vascular system of these parts, the unusual redness the mem- branes assume can only be compared in height of colouring to the membrane of the eye in acute conjunctivitis. With this intense red- ness of the surrounding membranes is strongly contrasted the appearance of the cartilages of the joint; these, but little altered from their natural colour, are seldom in this articulation found covered with vascular membranes, and even when the surrounding structures are mi- nutely injected, the fluid cannot be made to penetrate the synovial investment of the carti- lages. Cartilage. — When acute inflammation has existed in the synovial membrane or bones of the elbow-joint, the articular cartilages covering these will very frequently be found to have assumed, in patches, a dull yellow colour ; in the latter discoloured points the cartilage is soft- ened, and a blunt probe slightly pressed will sink into its structure, and its subjacent surface will be found to be detached. A new vascular membrane having been interposed between the cartilage and the cancellous structure of the bone, this elevation and partial detachment of the articular cartilages from the heads of the bone, and interposition of a new organized mem- brane, are probably the usual preludes to those other changes we notice. Thus sometimes a leaf or flap of the articular cartilage, adherent only by an edge, hangs into the cavity of the joint, and again fragments of this structure completely detached are found loose in the in- terior of the articulation. In these instances there is reason to conjecture that the diseased action which detached the cartilage began on the surface of this structure contiguous to the bone. We have occasionally, however, evidence of ulcerative absorption having commenced on the free surface of the cartilage. The peculiar worm-eaten appearance which the surfaces of cartilages next the cavity of the joint occa- sionally present, and which, wherever it exists, is considered by many pathologists to be the result of a process of ulceration which had be- gun on the free surfaces of the articular carti- lages, has been occasionally though rarely seen in the elbow-joint ; much more frequently in examining elbow-joints which have been the seat of disease, the articular surfaces of the bones have been found extensively divested of their cartilages ; a few patches of them alone here and there remain ; and these, though apparently thinner than natural, are of their ordinary tex- ture, and are firmly adherent to bone. Such extensive removal of cartilage, which has exposed the cancelli of the heads of the bones, has generally been the result of some 78 ABNORMAL CONDITION OF THE ELBOW-JOINT. very violent attack of inflammation, which, no matter in what situation it had originated, ulti- mately vve find had not spared any of the tis- sues entering into the formation of the articu- lation. Bone. — The elastic white swelling (which is one of the usual external signs of this articular caries when the bones of the elbow-joint are the seat of the affection) is always situated poste- riorly, and gives a characteristic appearance and a rounded form to the back part of the elbow-joint, which cannot be mistaken nor misunderstood. The wasted appearance of the arm above and of the fore-arm below makes this swelling more conspicuous, and the whole limb remains habitually in the semiflexed posi- tion, with the fore-arm somewhat prone ; every movement of the articulation causes the patient much pain. The disease, thus arrived at its second or third stage, may remain stationary for a time or terminate in an anchylosis of the bones; commonly, however, the morbid pro- cess goes on. Luxation of one or both bones of the fore-arm occurs, symptomatic abscesses present themselves, and these after a time make their way to the surface, and discharge their contents through openings, sometimes near, and frequently at a distance from the joint; and thus, at length, we see formed direct outlets as well as sinuses and fistulous canals, which give exit to exhausting discharges. The pain and irritation attendant on the disease itself, added to all these, give rise to hectic fever, which too frequently nothing but the desperate measure of amputation will arrest. The disease, which produces such serious consequences, often be- gins very insidiously, either in the head of the radius and external condyle of the humerus, or in the trochlea of this bone and the great sig- moid cavity of the ulna. When the disease begins at the radial side, the pain runs along the course of the musculo-spiral nerve, and there is a manifest swelling externally in the situation of the radio-humeral articulation : although there is even now a marked tendency in the fore-arm to remain in a semiflexed posi- tion, still gentle flexion and limited extension are admissible ; but when the radius is pressed against the humerus, and a movement of rota- tion at the same time is given to the fore-arm, much pain is complained of. The disease may go on, confining itself chiefly to the radial side of the elbow-joint through its first stage of pain and swelling ; through its second of effu- sion of fluids and relaxation of the coronary and external lateral ligament; and, thirdly, to dislo- cation backwards of the head of the radius, and even to suppuration and discharge of mat- ter through an ulceration or slough of the inte- guments. When the caries has commenced in one of the opposed surfaces of the trochlea of the humerus or great sigmoid cavity of the ulna, the swelling and effusion are first noticed in- ternally at the side of the olecranon and inter- nal condyle. The pain extends to the wrist along the course of the ulnar nerve ; the fore- arm is in this case also in a state of semi- flexion, and any attempt to extend or increase the degree of flexion causes very severe pain, while, on the contrary, a movement of rotation of the fore-arm is permitted. If the disease pro- ceeds, the great sigmoid cavity of the ulna be- comes wider and deeper, and the humerus ad- vances on the coronoid process ; the internal lateral ligaments are relaxed, and the triceps drags back the fore-arm, so that the olecranon process projects somewhat posteriorly, and there is a tendency to a displacement backwards. Whether the disease has originated on the radial or ulnar side of the joint, it very generally spreads so as to involve the articular surfaces of the three bones, and now the disease, termed scrophulous white swelling, becomes fully esta- blished, and is easily recognized by the usual signs. Besides dislocation backwards, either of the radius or of the ulna singly, or of both these bones together, lateral displacements of the bones of the fore-arm at the elbow have been noticed as a consequence of caries ; nor need we be surprised at such variety of posi- tion being assumed by the bones, when inflam- mation has softened the strong lateral ligaments and caused their ulceration. While the patient is confined to bed or to the horizontal posture, the mere position which is given to the fore-arm on the pillow will influence the direction of the displacement that will occur. We have seen, under such circumstances, complete late- ral displacement of both bones of the fore-arm outwards. The internal condyle of the hume- rus pressing against the integuments covering it had caused a round slough, through which the internal condyle of this bone protruded, while the rounded head of the radius had on the outer side caused a similar slough and ulceration of the integuments, through which the upper cup-like extremity of this bone had protruded. This lateral displacement of both bones of the fore-arm outwards, whether occurring sud- denly from accident, or slowly from the effects of articular caries, if it be complete, must always (we imagine) be followed by a consecutive dislocation upwards. In this case of caries above alluded to, we found the whole extremity somewhat shortened, that the hand remained habitually prone, and that the fore- arm (in a state of semiflexion as to the arm) was directed with considerable obliquity in- wards. It was plain that the causes of all these external signs were, that both bones of the fore-arm having their normal relation to each other, were first carried completely out- side the inferior extremity of the humerus, and were then drawn upwards above the level of the outer condyle of this bone. The olecranon process was not thrown at all backwards, but was situated immediately above and outside the external condyle of the humerus ; the coro- noid process was in front of this bone; the inner semilunar edge of the great sigmoid ca- vity therefore corresponded to the convexity of the outer side of the humerus, and seemed, as it were, to embrace this bone here so as to for- bid any further retraction of the fore-arm. When we proceed to examine an elbow-joint which has been the seat of a scrophulous white ABNORMAL CONDITION OF THE ELBOW-JOINT. 79 swelling that had presented the usual charac- ters of this disease in its advanced form, we usually notice the surface of the skin studded over here and there with the orifices of fistulous canals ; these are found generally to have pro- ceeded by a winding course, either from the cavity of the elbow-joint or from the cancellous structure of the bones, or from both these sources. When a section is made of the bones in this advanced period of the disease, they will generally be found to be softened in the interior, and to contain a fatty or yellowish cheese-like matter in their cells ; when exam- ined in an earlier stage of this scrophulous caries, these organs are generally found to be pre- ternaturally red and vascular, and with much less proportion of earthy matter than natural, so that they admit not only of being cut with a knife without turning its edge, but yield and are crushed under very slight pressure. We have also occasionally opportunities of examining the joint when the process of caries would appear to have been arrested and to have given place to a new growth of bony vege- tations around the joint; under such circum- stances, conical granulations, several lines in length, shoot out like stalactites around the trochlea of the humerus and from the olecranon and coronoid processes of the ulna ; the bones are, however, in these specimens remarkably light, porous, and friable. In some cases, however, the caries of the bone has altogether ceased, and a process of anchylosis has been es- tablished, and the fore-arm is flexed on the arm : a section through the elbow-joint longitudinally will in such cases frequently exhibit a com- plete continuation of the cancelli through the joint from the cells of the humerus to those of the radius and ulna. Rheumatism. — The elbow-joint, like all the other articulations, is liable to attacks of acute rheumatic inflammation, the external signs of which differ hut little from those which we observe to attend an ordinary case of acute synovitis. The disease, however, seldom fixes itself for any time upon this or any one joint in particular and usually terminates favourably, so that opportunities seldom occur of ascer- taining by anatomical examination the effects of this species of inflammation in the different structures of the elbow-joint. But this articu- lation is, in the adult and in those advanced in life, affected by a disease which, for want of a better name, is termed chronic rheumatism, the anatomical characters of which are very remarkable, yet they never have received from pathologists that attention they appear to us to deserve. In these cases the elbow- joint becomes enlarged and deformed; its or- dinary movements, whether of flexion, exten- sion, or rotation, become restricted within very narrow limits ; and when we communicate to the joint any of these motions, the patient complains of much pain, and a very remarkable crepitation of rough rubbing surfaces is per- ceived : a careful external examination of the joint will in such circumstances enable us to detect foreign bodies in the articulation. Some of them are small, but others occasionally are met with of a very large size, and can easily be felt through the integuments. Sometimes the synovial membrane of the joint itself is much distended with fluid, and the bursa of the ole- cranon is likewise affected, in which small fo- reign bodies are also to be detected : sometimes, however, there would appear to exist in the in- terior of the joint even less synovia than natural. The muscles of the arm and fore-arm for want of use are more or less wasted and atrophied. As the external appearances vary, so also do we find the anatomical characters of the disease to pre- sent varieties, some of which deserve notice. W e have found the most general abnormal ap- pearance to be that the cartilages are removed from the heads of the bones which are greatly enlarged, and that these articular surfaces are covered by a smooth porcelain-like deposit, and after a time attain the polish and smooth- ness of ivory : the trochlea of the humerus, also, and corresponding surface of the great sigmoid cavity of the ulna are also marked with narrow parallel sulci or grooves in the di- rection of flexion and extension. In these cases the radio-humeral joint is likewise affected, the head of the radius becomes greatly enlarged, and it assumes quite a globular form, while the anterior and outer part of the lower extremity of the humerus will have its capitulum or con- vex head not only removed, but here the humerus will be found to be even excavated to receive the head of the radius, and to accom- modate itself to the new form it has acquired from disease. In many cases where the radius had become thus enlarged and of a globular form, the writer has found the cartilage removed altogether and its place occupied by an ivory- like enamel. In two examples he has seen a depression or dimple in this rounded head of the radius, similar to what naturally exists in the head of the femur, and in these two cases, strange to relate, a distinct bundle of ligament- ous fibres analogous to a round ligament passed from the dimple or depression alluded to, con- necting this head of the radius to the back part of the sigmoid cavity of the ulna. In some few cases, when the external signs of this chronic disease in the elbow-joint were present, we have found the bones of this articulation enlarged, hard, and presenting a rough porous appearance, while the cartilage was entirely removed; but in these specimens no ivory- deposit was formed. These were cases in which the same disease existed locally, and the same disposition prevailed in the constitution ; but from the bones having been kept in a state of quietude, the rough surfaces of the articular extremities had not been smoothed by the effects of friction, nor an ivory-like enamel formed. We believe that in such cases, were life prolonged, anchyloses would be established : in other instances the head of the radius has not been found enlarged as above described, but otherwise altered from its natural form. The superior articular extremity of this bone has been found excavated from before back- wards, its outline not being circular nor exactly oval but ovoidal, accurately representing on a small scale the glenoid cavity of the scapula. 80 ABNORMAL CONDITION OF THE ELBOW-JOINT. It may be remarked that one of our patients, a man, aged sixty, in the surgical wards of the House of Industry, who had for many years suffered from the severest forms of chronic rheumatism in all the articulations, got diarrhoea and died. The writer had previously noted in particular the condition of the right elbow- joint; the motions of Hexion and extension were very limited, attended with much crepi- tation, and caused to the patient very great pain. The exact condition of the bones described in the preceding paragraph existed, and the loss of the circular outline of the radius fully accounted for what we had in this case previously noted, viz. that to remove the hand from the state of pronation in which it habitually remained, or to communicate any movement of rotation to the radius was nearly impracticable; the glenoid-shaped surface for the head of the radius allowed of flexion and extension in the radio-humeral articulation, but any except the perfect circular form was ill- suited to permit any rotatory movement of the radius on the ulna. This then is a peculiar disease which causes a complete removal of the articular cartilage from the head of the bones of the elbow-joint, so that the porous sub- stance of the bones becomes exposed : they do not become carious, but on the contrary they are enlarged, hard, aud their surfaces seem to expand. If the joint be much used, the effects of friction become evident; if kept at rest, they are rough, and anchylosis may take place. From the phenomena we observe in the variety of cases that present themselves, we may infer that, when this disease affects the elbow-joint, in whichever bone most vitality exists and most active nutrition is going on, enlargement would appear to take place, while in the bone which is softer and in which the process of nutrition is least, the effects of fric- tion become of course most manifest. Thus, in some cases, as already mentioned, we have found the head of the radius greatly enlarged and of a globular form, and the outer condyle of the humerus excavated to adapt itself to this convexity, while on the contrary, in other cases the outer condyle of the humerus seemed to have been the seat of active nutrition, and the head of the radius to have been rendered soft and to have yielded to the effects of friction. In all these cases, there seems to be a very active cir- culation of blood in the capillary vessels of the bones and other structures of the joint. Much of the synovial membrane may be removed with the cartilages ; but the synovial folds and fimbriae (as they are called) which encircle the neck of the radius, and occupy the different fossae in front and behind the trochlea of the humerus, become unusually vascular and en- larged. In most of the cases we have examined, we have discovered what are called foreign bodies in the cavity of the joint. These we have found of all sizes, from that of a pea to that of a walnut. Some were seen hanging into the cavity of the articulation, being suspended by white slender membranous threads which seemed to be productions from the synovial sac; and some were loose in the joint: while, as to their structure, some were cartilaginous and bony. The number of these foreign bodies we have seen in the cavity of the elbow-joint we confess has astonished us, amounting in one case to twenty, in another to forty-five. In all these cases the vessels of the synovial fimbria of the joint were m a highly congested state. The co-existence, therefore, of foreign bodies with such a condition of the membranes and their capillary vessels as these dissections elicited, cannot be too fully impressed on the mind of the practical surgeon, who is some- times solicited to undertake an apparently simple operation for their removal. Lastly, instead of the few scattered fibres external to the synovial sac, which, in this joint, when in a normal state, can scarcely be said to resemble even the rudiment of a capsule, we have found in these morbid specimens the thickness and number of ligamentous fibres so considerable, that the joint seemed to possess almost a com- plete capsular ligament. In Cruveilhier’s Pathological Anatomy, li- vraison No. 9, Plate 6, Figure 1, there is a gra- phic delineation of an elbow, illustrating many of the points here alluded to : he denominates the disease usure des cartilages, but it is quite sufficient to look at one of these cases, either in the living or the dead, to be satisfied that the disease does not confine itself to the cartilages of the joint, but that the arti- cular heads of the bones are also engaged ; indeed, in many of our specimens, the bones of the elbow-joint are so much enlarged as to resemble at first sight the knee-joint; the shafts also of the ulna and radius are heavier and harder than natural, and their cancellated struc- ture no longer exists, the cells being so densely penetrated with phosphate of lime that the sections of these bones in several parts present the appearance of ivory. This account of the state of the elbow-joint produced by that slow disease called chronic rheumatism, is the result of many observations and dissections made specially by ourselves. We may also add that Mr. Smith, the able curator of the Museum of the Richmond Hospital, who has given equal attention to such investigations, has examined and preserved several specimens which verify the account here given of the anatomical cha- racters of this disease , while, under the writer’s own immediate charge in the House of Industry, are numerous living examples of, and sufferers from, this chronic disease, affecting the elbow- joint. In most of these cases, however, some of the other articulations are equally engaged.* ( K. Adams.) * [Since ihe preceding article was put to press, the Editor has been favoured with the following communication from the Author, which is too inte- resting to be omitted : “ Within these three days I met with a very singular case of congenital deformity of both elbows in a girl about eleven years of age. The radius could be felt to press forwards and backwards for the extent of an inch when it was rotated either in pronation or su- pination. These movements did not consist in a simple rotation of the radius on its longitu- ANIMAL ELECTRICITY. ELECTRICITY, ANIMAL.— A power, or imponderable agent, possessed by and evolved from certain living animals, which enables them, independently of the operations of external agents on their structures, to pro- duce several of the phenomena exhibited by common and voltaic electricity, generated in inorganic matter. The animals so endowed, with which we are at present acquainted, are all fishes; and the effect by which their power is most sensibly made known to us is the feeling of a shock, or momentary stunning, which is experienced in the hand that touches their surface. It is still doubtful whether the agent which produces this effect be absolutely identical with those which produce the various pheno- mena of common and voltaic electricity, ther- mo-electricity, &c. ; but the most recent re- searches on the subject render it probable that it is the same in its nature, although different in intensity. When Galvani discovered the possibility of exciting muscular contraction by establishing an external communication between the nerves and muscles by means of metals, he imagined that the contraction was produced by the sti- mulus of a peculiar agent (or fluid) existing in the nerves in a state of accumulation, which, being attracted by the metals, passed along them to the external surface of the muscles. The agent, which was supposed to remain latent in the nerves, was called by some “ the nervous fluid,” as it was imagined to be identical with that power which animates the nerves during life. Galvani seems to have entertained this notion. Other philosophers, avoiding a name derived from a theory, denominated the agent Galvanism. Afterwards it was called Animal dinal axis, but a real change of place of the upper extremity of the radius on the outer con- dyle of the humerus. The elbow was but slightly deformed, and all its motions were perfect ex- cept extension, which was not complete, but the girl had perfect use of both arms and fore-arms, which were exactly similarly formed. The ra- dius seemed principally in fault, and the motions of the upper head corresponded much to the de • scription given of the subluxation. (Vide p. 74.) I was afforded an opportunity of examining the joints in consequence of the child having died of scarlet fever. both joints were exactly alike. The radius was large, the great sigmoid cavity of the ulna was not half its usual size, and the coronoid process did not exist. The trochlea on the humerus, corresponding to the diminished sigmoid cavity, was one-half less than its natural size so that the lower extremity of the humerus bore so striking a resemblance to the condyles of the femur, when viewed posteriorly from the popli- teal space, that nobody could look at it without observing the striking resemblance in miniature of the humerus to the femur. There were fibious bands representing the crucial ligaments, and all the fibres around were yellow and stronger than na tural. The annular ligament of the head of the radius was wider than natural but much stronger, and accounted for the passing to and fro of this head in pronation and supination. That the deformity was congenital no one can doubt : the appearance — the history —the exis- tence of the same malformation on both sides, all prove it.” Dec. 12, 1836.] VOL. ir. Electricity. These views were supported by Valli, Carradori, Aldini, and Fowler. But, since Volta and others demonstrated that the contractions of the muscles in Galvani’s expe- riments were owing to electricity developed by the contact of the metals employed, and not to any fluid pre-existent in the nerves, the term Animal Electricity has had its meaning changed. At present, most physiologists use it in the sense which is implied in the defini- tion given above. That is not called Animal Electricity which is generated by the friction of animal sub- stances one upon the other, or by the mere contact of animal tissues of dissimilar natures. The phenomena so developed have their source in common and voltaic electricity. They are phenomena exhibited by animals in common with inorganic matter. As the study of these, however, may ultimately lead to the elucidation of some points connected with the electricity of living fishes, they shall be noticed in the course of the following article. It is in the mode of its development that the chief peculiarity of Animal Electricity consists. None of the usual excitants of elec- tricity are concerned in it. There is no che- mical action, no friction, no alterations of tem- perature, no pressure, no change of form. The exercise of the animal’s will, and the integrity of the nervous system, as well as of certain peculiar organs which exist in all the animals endowed with electrical power, seem to be alone sufficient for its evolution. The following are the systematic names of the electrical fishes at present known : — Torpedo narke. unimaculata. Risso. marmorata. Ditto. Galvanii. Ditto. Gymnotus electricus. Trichiurus electricus. Malapterurus electricus. Tetraodon electricus. The four species of Torpedo inhabit various parts of the Atlantic and Mediterranean. They were formerly regarded as constituting one species, (Raia Torpedo, of Linnaeus;) and now Dr. John Davy proposes to reduce them to two ; having satisfied himself (and in this he is supported by the opinions of Cuvier and of Rudolphi) that the T. marmorata and T. Gal- vanii are merely varieties of the same species, for which he suggests the name of T. diversi- color. It is known in Italy by the name of the Tremola. The other species (the Occhiatella of the Italians) Dr. Davy thinks would be better named T. oculata. Both pass in Malta under the term Haddayla. The first of these species (T. vulgaris, of Fleming,) occurs on the south coast of England, where it some- times attains a great size. Pennant mentions one which measured four feet in length and two and a half in breadth, and weighed fifty- three pounds. And Mr. Walsh describes an- other which was four feet six inches in length, and of the weight of seventy-three pounds.* * Phil. Trans. 1774. G 82 ANIMAL ELECTRICITY. Both species of Aristotle and Oppian) are abundant in some parts of the Mediter- ranean, and are frequently brought to the market of Rome. Off the west coasts of France, in Table-bay at the Cape of Good Hope, in the Persian Gulf and in the Pacific Ocean, the same, or at least nearly similar species are plentiful. They frequently form an article of food amongst the poorer class in the coast towns between the Loire and the Ga- ronne; but the electrical organs are carefully avoided, as they are supposed to possess some poisonous properties. The Gymnotus is found in several of the rivers of South America ; it was met with by Humboldt in the Guarapiche, the Oronoco, the Colorado, and the Amazon. The Malapterurus (Silurus, of Linnaeus) occurs in the Niger, the Senegal, and the Nile; the Trichiurus in the Indian Seas ; the Tetraodon has been met with only on the shores of Jo- hanna, one of the Comoro Isles. According to Margrav'* * * § there is a kind of ray-shark on the coasts of Brazil, which possesses the power of giving shocks. He described the fish under the name of Paraque.f It is the Rhinobatus electricus of Schneider and other modern ich- thyologists. But in an examination which Rudolphi made of the fish in question, he found no structure resembling that peculiar organ which exists in all the well-known elec- trical fishes. No other naturalist has made the same observation as Margrav, so that the elec- trical power of this fish cannot be regarded as satisfactorily ascertained. In Maxwell’s Ob- servations on Congo, mention is made of a large fish “ like a cod,” possessed of electrical powers, which was taken in the Atlantic Ocean. No such animal has yet come under the notice of any scientific observer. Certain insects seem to be possessed of some power re- sembling animal electricity in its effects, but few observations have hitherto been made on these, lleduvius serratus is one of the insects so endowed ; with regard to which an intel- ligent naturalist reports, that, on placing a living individual on the palm of his hand, he felt a kind of shock, which extended even to his shoulder; and that, immediately after- wards, he perceived on his hand red spots at the places whereon the six feet of the insect had rested. I Margrav described a species of Mantis, a native of Brazil, which, on being touched, gave a shock felt through the whole body. According to the report of Molina§ and Vidaure,|| when the Sepia hexapodia is seized with the naked hand, a degree of numb- ness is felt, which continues for a few seconds. Alcyonium bursa, a native of the German Ocean, is said to have communicated to the hand a sensation like that of an electrical shock -If It must be regarded as an extremely interest- * Hist, rerum Nat. Brasil. 1648. t The name Puraqua is used by Cond amine in reference to the Gymnotus. 1 Kirby and Spence’s Entomol. vol. i. 110. § Naturgesch. von Chili. S. 175. jj Gesch. des K’onigr, Chili. S. 63. If Treviranus, Biologie. V. 144. ing fact that the electric fishes belong to genera widely removed from one another in structure and habits, and yet that their own structure is not so peculiar as to prevent them from being arranged along with many other fishes posses- sing no degree of the same power and no vestige of a structure analogous to their own. As the fishes enumerated above have not all been examined with the same degree of atten- tion, we are ignorant of the extent to which they exhibit phenomena exactly resembling one another. But it is well ascertained that they all agree in possessing the power of commu- nicating a sudden shock to the hand which touches them. This shock causes a certain degree of temporary numbness not only in the finger which immediately touches the fish, but also in the hand, and sometimes even in the arm. The sensation produced has been com- pared by different experimenters to the shock felt on the discharge of a Leyden phial, dif- fering from it only in force. Hence the shock caused by an electrical fish is said to be pro- duced by a discharge of its electricity. The numerous facts relating to the phenomena which accompany or are connected with this discharge, which have been collected by the industry of the many observers of the last and the present age, who have devoted their atten- tion to the subject,* maybe conveniently ar- ranged under the following heads: 1. the circumstances under which the discharge takes place: 2. the motions of the fish in the act of discharging : 3. physiological effects of the discharge : 4. magnetical effects of the discharge : 5. chemical effects of the dis- charge : 6. results of experiments on the transmission of the discharge through various conducting bodies: 7. the production of a spark and evolution of heat : 8. results of experiments in which the nerves, electrical organs, and other parts, were mutilated : 9. descriptions of the electrical organs in the several fishes which have been anatomized. I. Circumstances under which the discharge takes place. — Electrical fishes exert their pecu- liar power only occasionally, at irregular inter- vals, and chiefly when excited by the approach of some animal, or by the irritation of their surface by some foreign body. The discharge, both with regard to time and intensity, seems to be dependent on an exertion of the will. They discharge both in water and in air. Sometimes the discharge is repeated several times in close succession ; at other times, par- ticularly when the fish is languid, only one discharge follows each irritation. The inten- sity of the torpedo’s discharge is generally greater when the fish is vigorous, becomes gra- dually less as its strength fads, and is wholly imperceptible shortly before death takes place ; but Dr. Davy has met with some languid and dying fish which exerted considerable electrical * Redi, Reaumur, Walsh, Ingenhousz, John Hunter, Cavendish, Bancroft, Spallanzani, Wil- liamson, Humboldt, Gay Lussac, Geoffroy, J. T. Todd, and Dr. John Davy, have all laboured in the same field of inquiry. ANIMAL ELECTRICITY. 8a power. No irritation has ever produced a dis- charge after death. The intensity of the elec- trical power seems to bear no relation to the size of the fish, at least after it has attained mature age; small fish are almost always ac- tively electrical. The torpedo sometimes bears great irritation, even the firm grasp of a hand, without dis- charging. In these circumstances it writhes and twists itself about for some time, using strong efforts to escape, before it emits irs electricity. In a few instances it has been found impossible by any means to excite even vigorous torpedos to discharge. Both Lace- pede and Reaumur handled and irritated the most lively torpedos, even while yet in their native element, without experiencing any shock. But generally the shocks are stronger when the skin of the fish is in any way irritated. All electrical fishes soon become exhausted and die, even in sea-water, when they are excited to give a continued succession of discharges. But fishes much exhausted by frequent dis- charges recover their electrical energy after a few hours’ rest. The torpedo seems to possess electrical power even in the earliest periods of its existence. Spallanzani relates that he found within a female torpedo two living foetuses, which gave distinct shocks on being removed from their coverings. Dr. Davy, also, once received a sharp although not a strong shock, in extracting foetal fish from the uterine cavities of a dying torpedo. When the Gymnotus is grasped by the hand, the intensity of the discharge is moderate at first, but is increased if the pressure be conti- nued. The torpedo discharges whenever it is taken out of the water ; and Walsh found that a vigorous fish repeats the discharge as often as it is lifted out, and again on being re-im- mersed ; also that it gives more violent shocks in air than in water. Spallanzani found the shock to be more severe when the fish was laid on a plate of glass. The following observation, reported by Walsh, seems to prove that the Gymnotus can distinguish at some distance between substances capable of receiving and conducting its discharge, and those which can- not conduct ; and that (excepting when it is much irritated) it discharges only when con- ducting bodies are presented to it. Two wires were put into the water of the vessel in which a Gymnotus was swimming; these wires were of some length, and stretched; they termi- nated in two glasses filled with water placed at a considerable distance from each other. Whilst the apparatus remained in this state, and the circulation was of course interrupted, the animal did not prepare to exercise his power, but whenever any conducting substance filled the interval, and rendered the circle complete, it instantly approached the wires, arranged itself, and gave the shock. The same fish, according to the observations of Messrs. Humboldt and Bonpland, appears to have the power of transmitting its discharge in any direction it pleases, or towards the point where it is most sharply irritated ; and further, it seems to be able to discharge, some- times rom a single point, at other times from the whole of its surface. Dr. Davy has satis- fied himself that the Torpedo also has the power of discharging its electricity in any direction it chooses. The shock produced by the discharge of the Gymnotus is most severely felt when one hand seizes the head and the other the tail. When two persons take hold of a Gymnotus, the one by the head or by the middle of the body, and the other by the tail, both standing on the ground, shocks are felt, sometimes by one alone, sometimes by both. It has been ob- served that when metals are placed in the vessel or pond containing a Gymnotus, the fish appears much agitated, and discharges very frequently. II. Motions of the fish in the act of dis- charging.— These have been particularly ob- served only in the Torpedo and Gymnotus. At the time of discharging, according to some ob- servers, the Torpedo generally becomes some- what tumid anterior to the lateral fins, retracts its eyes within their orbits, and moves its lateral fins in a convulsive manner. When the fish begins to lose its plumpness, after having given frequent shocks, “ a little tran- sient agitation’’ is perceptible along the carti- lages which surround the electrical organs at the time of the discharge. Dr. Davy, how- ever, states that he has never seen the Torpedo of the Mediterranean retract its eyes at the time of discharging ; and that he has not been able to associate any apparent movement of the fish with the electrical discharge. The Gymnotus sometimes emits the strongest discharges without moving any part of its sur- face in the slightest perceptible degree. But, at other times, it seems to arrange itself so as to bring the side of its body into a parallel with the object of its attack before discharging. When a small fish is brought near a Gymno- tus, it swims directly up to it, as if about to seize it ; on approaching close, however, it halts, seems to view the fish for a few seconds, and then, without making the smallest move- ment discoverable by the eye, emits its dis- charge ; should the small fish not be killed by the first, the Gymnotus gives a second, and a third shock, until its object is accomplished. It continues to kill a large number in close succession, if they be supplied to it, but it eats very few. III. P hysiological effects of the discharge. — The effects of the discharge on man vary ac- cording to its intensity and the extent of the surface of the fish which is touched. A vigo- rous torpedo causes a momentary shock, which is felt through the arm even as far as the shoul- der, and leaves a degree of painful numbness in the finger and hand, continuing for a few seconds, and then going off entirely. Some observers have compared the sensation pro- duced to that felt in the arm when the elbow is struck so as to compress strongly the ulnar nerve ; and others (even such as have been much accustomed to receive electric shocks) have declared the sensation to be extremely painful ; Gay Lussac and Humboldt say that c 2 84 ANIMAL ELECTRICITY. it is more so than the shock produced by the Leyden phial ; and Configliachi compares it to that caused by the contact of two poles of the voltaic pile. Ingeuhousz thus describes his sensations under the discharge of the tor- pedo. “ I took a torpedo in my hand, so that my thumbs pressed gently on the upper surface of the lateral fin, whilst my forefingers pressed the opposite side. About one or two minutes after I felt a sudden trembling in my thumbs, which extended no further than my hands ; this lasted about two or three seconds. After some seconds more, the same trembling was felt again. Sometimes it did not return in several minutes, and then came again at very different intervals. Sometimes I felt the trem- bling both in my fingers and my thumb. These tremors gave me the same sensations as if a great number of very small electrical bottles were discharged through my hand very quickly one after the other. Sometimes the shock was very weak, at other times so strong that I was very near being obliged to quit my hold of the animal. ”* * * § Walsh ascertained that the same torpedo has the power of discharging in two different manners, so as to produce at one time the effect described by Ingenhousz as a trembling, and at another time a sharp instan- taneous shock closely resembling that produced by the discharge of a Leyden phial.f Accord- ing to Sir II. Davy, “ whoever has felt the shocks both of the voltaic battery and of the torpedo must have been convinced, as far as sensation is concerned, of their strict ana- logy.”! Sometimes the torpedo buries itself in the sand left dry at ebb-tide ; and it has occasionally happened, according to some naturalists, that persons walking across the sand, and treading upon the spot beneath which the electrical fish lay concealed, have received his discharge so fully as to be thrown down.§ The effects produced by the discharge of the Gymnotus are more severe. When it is touched with one hand, a smart shock is generally felt in the hand and fore-arm ; and, when both hands are applied, the shock passes through the breast The discharges of large fish (they grow to the length of twenty feet in their native rivers) sometimes prove sufficient to deprive * Phil. Trans. 1775, 2. f Phil. Trans. 1773, 467. t Phil. Trans. 1829, 15. § The experience of Dr. Davy would lead us to call in question the possibility of such an occurrence ; for he has always found it necessary to touch the opposite surfaces of the electrical organs or organ to receive the torpedo’s shock. He has irritated torpe- dos very frequently by pressing with the finger on different parts of the back, but however much the fish were irritated he never had any sensation re- ferrible to the passage of the electricity. In corro- boration of his opinion that the fish cannot give a shock excepting the two opposite surfaces of its electrical organs be connected by conductors, Dr.D. states that when one surface only is touched and irri- tated, the fish themselves appear to make an effort to bring, by muscular contraction, the border of the other surface into contact with the offending body. This is done even by foetal fish. Phil. Trans. 1834. men, while bathing, of sense and motion. Fermin found that a strong one had power to give a shock to fourteen persons at the same time ; and other experimenters have seen twenty- seven persons simultaneously receive its shock. Humboldt states that, having placed his feet on a fresh Gymnotus, he experienced a more dreadful shock than he ever received from a Leyden phial, and that it left a severe pain in his knees and in other parts of his body, which continued for seveial hours. Sometimes the discharge occasions strong contractions of the flexor muscles of the hand which grasps the fish, so that it cannot be immediately let go; and then, the shock being repeated still more severely, painful sensations are experienced thougliout the whole body, and headache with soreness of the legs remains for some time after.* Paralytic affections, as well as giddiness and dimness of sight, are said sometimes to have followed the reception of strong discharges.! It is stated by some observers that there are men who are as insusceptible of the shocks of electrical fishes as others are of those from the Leyden phial ; and that women affected with nervous diseases are seldom conscious of receiving the discharge. Kaempfer asserted! that, by sup- pressing respiration for a short time, any man may render himself insensible to the torpedo’s discharge; but this has been disproved by Walsh and other observers. Regarding the effects of the discharges of the other electrical fishes, we know very little. The shock given by the Malapterurusofthe Nile and Niger (Stlurus, Linn.) is said to be more feeble than that of the Torpedo, and yet very painful, attended with trembling, and followed by soreness of the limbs. In attempting to take an individual of Tetraodon electricus in his hand, Lieutenant Paterson (its discoverer) received so severe an electrical shock that he was obliged to quit his hold. The effects of the discharge of the Gymnotus on the larger animals cannot be better illustrated then by the account which Humboldt has given of the method of capturing the fish adopted by the South American Indians. This method consists in irritating the fish by driving horses into the pools which it inhabits. It directs its electricity in repeated discharges against these horses until it becomes exhausted, when it falls an easy and harmless prey into the hands of the fishermen. Humboldt saw about thirty wild horses and mules forced into a pool con- taining numerous Gymnoti. The Indians sur- rounded the banks closely, and being armed with harpoons and long reeds, effectually pre- vented the escape of the horses. Tire fishes were aroused by their trampling, and, coming to the surface, directed their electrical discharges against the bellies of the intruders. Several horses were quickly stunned, and disappeared beneath the surface of the water. Others, ex- hibiting signs of dreadful agony, hurried to the bank, with bristled mane a-nd haggard eye, but * Bryant, Trans. Amcr. Soc. ii. 167. t Flagg, do. ii. 170. f Amotn. Exot. 514. ANIMAL ELECTRICITY. 85 there they were met by the wild cries and violent menaces of the Indians, which forced them again to enter the water. And when, at last, the sur- vivors were permitted to leave the pool, they came out enfeebled to the last degree, and their benumbed limbs being unable to support them, they stretched themselves out upon the sand completely exhausted. In the course of five minutes two horses were drowned. By degrees, the discharges from the Gymnoti becoming less intense, the horses no longer manifested the same signs of agony, and the wearied fishes ap- proached the margin of the pool, almost lifeless; and then they were easily captured by means of small harpoons attached to long cords. The fishes left in a pool thus disturbed were found scarcely able to give even weak shocks at the end of two days from the time of their combat with the horses. Humboldt concluded from what he saw and heard, that the horses which are lost in the course of this singular fishery are not killed, but merely stunned, by the dis- charge. Their death is occasioned by the con- sequent submersion. In this way many mules are destroyed in at- tempting to ford rivers inhabited by the Gynmo- tus. So great a number of mules were thus lost within the last few years at a ford near Uritucu, that the road by it was entirely abandoned. When small fishes receive the discharge of a Gymnotus, they are immediately stunned, turn upon their backs, and remain motionless. They however, for the most part, recover after being removed to another vessel. Reaumur reports that he once saw a duck killed by the repeated discharges of a torpedo ; but both Ingenhousz and Dr. John Davy kept small fishes in the same vessel with torpedos, without observing that the former showed any symptoms of suffering from the shock of the latter. Humboldt saw one Gymnotus receive the discharge of anotherwith- out giving any evidence of feeling it. Galvani, having placed some frogs’ thighs, skinned, on the back of a torpedo, saw them convulsed when the fish was excited to discharge. It is said that the discharge of the torpedo is used medicinally by the Arabians of the present day, particularly in fevers. The patient is placed naked on a table, and the fish applied to all the members of the body in succession, so that each should receive, at least, one shock. This treat- ment causes rather severe suffering, but enjoys the reputation of being febrifuge. IV. Mugnetical effects of the discharge. — Schilling asserted that he had seen the magnetic needle set in motion by the discharge of a Gym- notus ;* also, that the fish was attracted by a magnet, and adhered to it ; and that it became so languid when detached from the magnet, that it gave no shock when irritated. Ingenhousz, Spallanzani, Flagg, Humboldt, and Bonpland obtained no such results in repeating the expe- riments of Schilling. Professor Hahn of Ley- den suggests that the fish examined by Schilling may have been coated with particles of ferrugi- nous sand, which frequently forms the beds of the American rivers inhabited by the Gymnotus ; * Mem. de l’Acad. de Berlin, 1770. and that these, adhering to its glutinous skin, may have given rise to the phenomena observed by Schilling. In quoting the contradictory statements of the above-mentioned observers, Treviranus remarks,* “ it is a striking circum- stance that so good an observer as Schilling was should have been convinced that he saw such magnetic phenomena in connexion with the fish, and still more remarkable is it that Humboldt and Bonpland should have found a belief in the possession of magnetic properties by the Gymnotus prevalent amongst the inhabitants of the Savannas of Caraccas.” Sir Humphry Davy passed many strong dis- charges from a torpedo through the circuit of an extremely delicate magnetic electrometer, with- out perceiving the slightest deviation of, or effect on, the needle. He explained this negative result by supposing, that the motion of the electricity in the organ of the torpedo is in no measurable time, and that a current of some continuance is necessary to produce the devia- tion of the magnetic needle.f Under more favourable circumstances than those in which Sir H. Davy investigated the properties of the electricity of the torpedo, Dr. John Davy re- sumed the enquiry at Malta, and ascertained, in the most satisfactory manner, that animal elec- tricity is capable of producing magnetic effects. He not only saw the needle of a magnetic elec- trometer very much affected by the discharge of a torpedo, but he found needles, previously free from magnetism, converted into magnets by the same. In one experiment, he placed eight needles within a spiral, formed of fine copper wire, one inch and a half long, and one tenth of an inch in diameter, containingaboutonehundred and eighty convolutions, and weighingfour grains and a half. A single discharge from a torpedo, six inches long, having been passed through this, the contained needles were all converted into magnets, each one as strong as if only one had been used. It was found that the ends of the needles which were nearest the ventral sur- face of the fish had received southern polarity, and of course the other extremities northern po- larity. The discharges from fish, only four hours after they were taken from the uterine cavities of their mother, were sufficiently strong to magne- tize needles through the medium of a spiral, al- though but feebly. The same kind of result was obtained with the multiplier; the needle of which, when subjected to a torpedo’s discharge, indicated that the electricity of the dorsal surface corresponded with that of the copperplate of the voltaic pile, and the electricity of the ventral surface with that of the zinc plate. In 1827, before Dr. Davy performed his ex- periments, similar magnetic effects were observed by means of the multiplier, by MM. De Blainville and Fleuriau, at La Rochelle. They * Biologie, v. 145. t Phil. Trans. 1829. 16. Similar experiments were made with the discharge of the Gymnotus by Messrs. Rittenhouse and Kinnersly with the same results. They saw no effect produced on the elec- trometer. Philadelphia Med. and Phys. Journal, i. 15. 86 ANIMAL ELECTRICITY. thrust into the electrical organ of a torpedo the two needles which terminate the wires of Schweigger’s multiplier, and immediately saw the magnetic needle describe more than half a revolution.* V. Chemical effects of the discharge. — It does not appear that any observer before Sir H. Davy attempted to ascertain what chemical effects the discharge from electrical fishes is capable of producing. But Sir Humphry obtained only negative results. He passed the shocks of the torpedo through the unterrupted circuit made by the silver wire through water, without being able to perceive the slightest de- composition of the water .f Dr. John Davy, however, has obtained decisive evidence of chemical agency being exerted by animal elec- tricity. The fishes which he made use of in his experiments were more recently taken from the sea, and were, consequently, more vigorous than those which were the subjects of Sir Humphry’s observations; and it was, probably, owing to this circumstance that the results which he obtained were different from those of his brother’s experiments. By means of golden wires, one of which was applied to the upper surface of the fish, and the other to its under surface, Dr. Davy passed the discharge from a torpedo through solutions of nitrate of silver, common salt, and superacetate of lead, and found that all were decomposed. The decomposition of the superacetate of lead was effected only when the fish seemed to put forth all its energy, after being much irritated.} ’ From the solution of nitrate of silver, the metal was precipitated only on the wire connected with the ventral surface of the fish. When platina wires were used, and plunged into nitric acid, gas was given off only from that in con- nexion with the dorsal surface. A solution of iodide of potassium and starch having been subjected to the discharge conveyed along the platina wires, had the iodine in combination with the starch precipitated from it on the wire from the upper surface.§ By the same dis- charges which produced these chemical effects, the needle in the galvanometer was moved, the spirit in the air-thermometer was raised, and needles in the spiral were magnetized. VI. Results of experiments on the transmis- sion of the discharge through various conduct- ing bodies. — Almost all bodies which are con- ductors of common and voltaic electricity con- duct also the discharge of electrical fishes ; and those which are non-conductors with regard to the former are the same with regard to the latter. But the discharge of the torpedo, when feeble, does not pass along even good conductors; and this circumstance has given rise to some dis- crepancy between the statements of different observers. Walsh received the torpedo’s dis- charge through iron bolts and wet hempen cords. The French fishermen declare that they sometimes receive shocks through nets, while * Bmiillet, Firm, de Phys. i. 773. + Phil. Trans. 1829. t Phil. Trans. 1832. $ Phil. Trans. 1834. the fish is twelve feet distant from their hands. But Humboldt and Gay Lussac state that they received no shock when they touched the fish with a key or any other conducting body;* further, that when they placed the fish upon a metallic plate, so that the inferior surface of its electric organ touched the metal, the hand which supported it felt no shock : and they concluded from their experiments that the torpedo could not transmit its discharge through even a thin layer of water ; although they found that when two persons applied each one hand to the fish, and completed a circuit through their own bodies by means of a pointed piece of metal held in the other hand, and plunged into a little water placed upon an insulating body, both felt the shock. In one instance Dr. Davy received the torpedo’s shock through water, but his hand was within a very short distance of the fish. Walsh transmitted the torpedo’s discharge through a chain of eight persons, who com- municated with one another only by water con- tained in basins, in which their hands were immersed. And the same observer also found that when a torpedo was touched with a single finger of one hand, while the other hand was held in the water at some distance, shocks were distinctly felt in both hands. Numerous observations made on the Gymnotus leave no doubt with regard to the passage of its discharge through water. If a person hold his finger in the water several inches (some say even ten feet) distant from the fish, and another person touch it, both receive shocks equally severe. Dr. Williamson found that a person holding his finger in a stream of water, running from a hole made in the bottom of a wooden vessel in which a Gymnotus was swimming, very dis- tinctly felt all the discharges given by the fish. The discharge from the Gymnotus passes through a chain of ten persons, so that they all seem to feel the shock in the same degree. It is con- ducted by iron rods several feet in length. It does not pass through air, interposed between metallic conductors, until these are brought within about one-hundredth of an inch of each other. So far as they have been examined, the phe- nomena presented by the discharge of the Silurus have been found to be nearly the same as those just detailed. VII. The production of a spark, and evolu- tion of heat. — No observer has hitherto seen light emitted from the body of any electrical fish at the time of the discharge ; but, by artificial arrangements, some have succeeded in pro- ducing sparks in the course of the circuit de- scribed by the discharge. In 1792, Gardini saw a spark from a torpedo’s discharge, in the course of his repeating some of Walsh’s experiments. And in 1797, Galvani obtained a small spark, visible only with the aid of a lens, from a torpedo ; but it does not appear that any other observer has been equally successful with regard to this fish. Very recently, Dr. Davy has directed his attention particularly to this point, and, although he used active fish, and took Ann. de Cliimie, t. lxv. 15. ANIMAL ELECTRICITY. 87 every possible precaution, he could neither, in the light, detect the slightest indications of the passage of electricity through even very small intervals of air, nor observe a spark in the dark. He was equally unsuccessfnl in using an elec- troscope formed on the principle of Coulomb’s, which displayed sparks when touched either with a small rod of glass slightly excited, or of sealing-wax. He varied the trials, using highly rarefied air at ordinary temperatures, and also condensed air deprived of moisture, with the same negative result. He insulated the fish on a plate of glass, wiped its margin dry, and besmeared it with oil, but no spark could be procured. Dr. Davy was more successful in obtaining indications of the evolution of heat during the torpedo’s discharge. He used Harris’s electro- meter, and saw proof of an elevation of tem- perature in the motions of the fluid in the air- thermometer ; thus corroborating the prediction of Dr. Faraday, who was previously convinced that, by means of this instrument, the evolution of heat by animal electricity would be made evident. Dr. Davy made several experiments with the view of ascertaining whether very fine platina wire might not be ignited in the passage of the electricity of the torpedo, but never witnessed the expected effect. Upon this he remarks, “ This want of ignition may, at first view, seem contrary to the effect on the ther- mometer; but perhaps it ought not to be con- sidered so, taking into account the rapid man- ner in which the heat evolved in the fine pla- tina wire must be carried off by the adjoining compound wire of platina and silver.”* From the discharge of the Gymnotus, Walsh, Fahlberg, Guisan, and other observers of the last century, obtained sparks. Walsh attached a thin sheet of pewter to a plate of glass, cut a very fine slit in it, and then passed the discharge along the metallic sheet, the fish being at the time out of the water. A spark was very dis- tinctly seen at the margins of the slit. Fahlberg of Stockholm used the same kind of apparatus, but with gold leaves instead of pewter, and placed the margins of these about a line apart. Dr. Williamson fixed two brass rods in a frame, and brought their points to within one-hundredth of an inch of each other, but, although the dis- charge of the gymnotus passed from one rod to the other through the intervening air, there was no spark. Humboldt watched an active Gym- notus for a long time during the night, and irritated it so as to obtain from it many sharp discharges, but he saw no spark. VIII. Results of experiments in which the nerves, electrical organs, and other parts were mutilated. — The general result of these experi- ments is, that destruction of the communications between the electrical organs and the nervous centres is followed by annihilation of the power of discharging. According to Mr. Todd, (whose experiments were made on the torpedo at the Cape of Good Hope,) it is necessary to cut through all the nerves going to the electrical organs to destroy their peculiar powers. He cut through all on one side, and some on the other, but still shocks were given. He also lacerated the organs themselves extensively, without destroy- ing the discharging power. Mr. Todd found that fishes in which all the electrical nerves had been cut appeared more vivacious after the operation than before it, and actually lived longer than others not so injured, but which were excited to discharge frequently.* In repeating Mr. Todd’s experiments, Dr. Davy obtained very similar results; but he mentions that “ when a small portion of brain was accidentally left, contiguous to the elec- trical nerves of one side, and with which they were connected, the fish, on being irritated, gave a shock to an assistant, who grasped the corresponding electrical organ.’’j- Spallanzani found that the torpedo loses its power of giving shocks after the aponeurotic covering of the electrical organs is removed ; but that the cutting out of the heart does not lessen this power until the animal life begins to suffer from the loss of blood. Humboldt cut a Gymnotus through the mid- dle of the body transversely, and found that the anterior portion alone continued to give shocks. Experiments of this kind have not yet been performed on the Silurus; but, judging from the structure of the organs in this fish, we have every reason to expect that the results of such experiments on it would be the same. While we would not be understood to sanction the wanton repetition of experiments such as these, which cannot but be productive of much suffer- ing to the subjects of them, we must yet repeat here the suggestion recently made by Professor Muller of Berlin with regard to future experi- ments on the Gymnotus and Silurus. He points out how very desirable it is to ascertain whether the double organs of these fishes act as opposite electromotors, which might be determined by cutting out one organ from either side, and then exciting the fish to discharge. The same dis- tinguished physiologist remarks that if he had an opportunity of experimenting on the torpedo, his first experiment should be, after having cut through the nerves going to the electrical organs, to irritate their cut extremities, still in connexion with the organs, with mechanical and galvanic stimulants, with the view of discovering whether these would excite the organs to discharge their electricity.^ IX. Anatomy of the electrical organs. — The experiments referred to in the former section sufficiently demonstrate that the manifestation of the peculiar power possessed by electrical fishes depends on the integrity of the connexion between their nervous centres and certain organs of a peculiar structure, which have been named the electrical organs. These have been particularly examined in the Torpedo, Gymnotus, and Silurus, by several anatomists, and no doubt is entertained that they, together * Phil. Trans. 1816. t Phil. Trans. 1834. 120. ( Handbuch der Physiol, des Menschen. Co- blenz, 1833. Phil. Trans. 1834. 88 ANIMAL ELECTRICITY. with their large nerves, are the sole means employed in bringing this mysterious agent under the control of the animal’s volition. They are therefore well worthy of an attentive examination. 1. The electrical organs in the torpedo. — The torpedo is a flat fish, possessing the same general appearance and structure as the rays, and classed along with them in zoological sys- tems. The electrical organs occupy a large coverings are discovered investing the electrical organs. The outer one has longitudinal fibres, which are rather loosely adherent, and, around the margins of the organs, seem to inosculate with the skin. The inner fascia is of consider- able density, forms the immediate tunic of the electric columns, and sends processes down between them to form their partitions. Through- out their whole extent, the essential part of the electrical organs is formed by a whitish soft Upper surface of electrical organ of left side. A, common integuments. B, branchial opening. C, eye. D, situation of the gills E E, skin dis- sected oft from the electrical organ, and turned outwards. F, part of the skin which covered the gills, G G, the upper surface of electrical organ. part of the broad expansions of the body, which in the other allied fishes are formed only by the lateral fins. They form two sepa- rate masses, one on either side of the head and gills, extending outwardly to the cartilaginous margins of the great fins ; and, posteriorly, to the cartilage which separates the thoracic from the abdominal cavity. Their form and the honey-comb embossments of their surfaces can be distinguished through the skin both of the dorsal and ventral aspects. The common inte- guments being removed, two strong fascial pulp, divided into numerous pentagonal prisms by the fascial processes just mentioned. These he close together, parallel with one another, and perpendicularly between the dorsal and ventral surfaces of the fish, so that their extre- mities are separated from these surfaces only by their fascial and the common integuments. When these are removed, the columns present something of the appearance of a honey-comb. The columns are longest next to the head and gills, and thence gradually diminish outwardly, until, on the external margin, they are only ANIMAL ELECTRICITY. 89 about one-sixth of the length of the internal ones. In a fish described by John Hunter,* of which the whole electrical organ was about five inches in length, the longest column was about one inch and a half, and the shortest about one-fourth of an inch in length. In the same fish the average diameter of each column was about two-tenths of an inch. In a fish from the Mediterranean, thirteen inches and a half in length, and about seven inches in breadth, (which, through the kindness of Dr. Allen Thomson, we have had an opportunity of examining in detail,) the length of the longest columns is one inch, and that of the shortest about three-tenths of an inch. Most of these columns are either irregular pentagons, or irregular hexagons ; a few are nearly tetra- gonal. They are united to one another by short but strong fibres, and by a reticular expansion of tendinous threads spread through them. Their number varies considerably ac- cording to the age of the fish. Hunter con- jectured that a few new columns are added every year to the circumference of the organ. In one of the largest fish that has yet been particularly examined, which was four feet and a half in length, the number of columns in one electrical organ was 1182. Mr. Hunter found 470 in each organ in a fish of ordinary size. Mr. Hunter described each column as being divided into numerous distinct compart- ments by delicate membranous partitions, placed horizontally, at very short distances from each other. The interstices between them appeared to him to contain a fluid. He found the partitions in several places adhering to one another by bloodvessels; and all, throughout their whole extent, attached to the inside of the column by a tine cellular membrane. In a column of one inch in length, he reckoned 150 partitions, and it appeared to him that their number is the same within the same space in all the columns. j- Hence, he thought it likely that “ the increase in the length of a column, during the growth of the animal, does not enlarge the distance between each partition in proportion to that growth, but that new partitions are formed and added to the extre- mity of the column from the fascia.” The partitions are covered with fine network of arteries, veins, and nerves. According to Hunter, “ they are very vascular.” He described the numerous arterial branches which ramify on the walls of the columns as “ sending in- wards from the circumference all around, on each partition, small arteries which anastomose upon it, and passing also from one to the other, unite with the vessels of the adjacent parti- tions.” The partitions themselves are so deli- cate as not to admit of being satisfactorily examined in tbe fresh fish : (all Hunter’s obser- vations were made upon fish that had been preserved in spirits, by which, doubtless, the delicate membranes were rendered more opaque, and therefore more easily visible.) In point * Phil. Trans 1773, 481. t Desmoulins and Majendie say that they found only seven or eight partitions in each column. Anat. des Syst. Nerv. ii. 378. of fact, Dr. Davy has never seen them in the course of the numerous dissections which he has made of the electrical organs in fish recently taken; whereas, in specimens sent hither by him, preserved in spirits, Dr. Allen Thomson and the writer of this article have satisfactorily ascertained their existence and structure as described by Hunter. Dr. Davy says, “ when I have examined with a single lens, which magnifies more than 200 times, a column of the electrical organs, it has not exhibited any regular structure ; it has appeared as a homo- geneous mass, with a few fibres passing into it in irregular directions, which were probably nervous fibres.”* However, after having im- mersed the organs in boiling water. Dr. Davy has occasionally seen something like a lami- nated structure within the column. Rudolphi satisfied himself of the division of the columns by membranous partitions, and further, that each partition is supplied with a distinct nerve.f In a memoir on the comparative anatomy of the Torpedo, Gyinnotus, and Silurus, Geoffroy described^ the columns as being filled with a semifluid matter composed of gelatine and albumen. A large quantity of fluid enters into the composition of the general mass of the elec- trical organs. Dr. Davy has found that they lose more by drying than any other part of the fish — nearly 93 per cent.; while the soft parts in general, including the electrical organs, lose only 84.5 per cent.§ He believes that the fluids of the organs hold various substances in solution, but the exact nature and proportions of them have not been ascertained. We are indebted to the same indefatigable observer for an ac- count of the specific gravity of the electrical organs. He found it to be very low compared with that of the truly muscular parts of the fish, — namely, 1.02C, to water as 1.000, while that of a part of the abdominal muscles of the same full-grown fish was 1.058, and of the dorsal muscles 1.065. In a fish eight inches long, five inches across the widest part, and which weighed 2065 grains entire, the electric organs together weighed 302 grains, the liver only 105 grains. No contraction has ever been seen in the electrical organs of living fish under the stimu- lus of the strongest excitants, not even under that of galvanism ; so that, although what appear to be tendinous threads are spread amongst and over the columns, we have no reason to suppose that any muscular tissue enters into their composition. But, in all directions, they are exposed to the pressure of * Phil. Trans. 1832. 259. f Abhandl. der Acad, der Wissensch. in Berlin. 1820. 224. f Ann. du Mus. No. 5. $ The smallest torpedo employed by Dr. Davy in his experiments weighed 410 grains, and con- tained only 48 grains of solid matter; its elec- trical organs weighed 150 grains, and contained only 14 grains of solid matter; yet this small mass gave sharp shocks, converted needles into magnets, affected distinctly the multiplier, and acted as a chemical agent. “ A priori, how inconceivable that these effects could be so produced'.” 90 ANIMAL ELECTRICITY. strong muscles, such as are plainly designed to compress them. Some of these are inserted into the marginal cartilages of the fins; and there is a set of very powerful ones, arranged in a cruci- form manner on the ventral surface, so placed as to compress the electrical organs most strongly during their contraction. Dr. Davy remarks, “ It is only necessary to compare these muscles as they exist in the torpedo with the same in any other species of ray to be convinced that they are adequate to, and designed for, the compression of the batteries.” Some observers, as John Hunter, state that a large proportion of blood circulates through the electrical organs. Giravdi found the torpedo much more full of blood than the other rays.* But Dr. Davy says, that there are very few vessels containing red blood in the organs them- selves; although their tegumentary coverings and the adjoining mucous system are highly vascular. The arteries of the organs are branches from the. arteries of the gills ; their veins run between the gills direct to the auricle. The temperature of the electrical organs is not at all higher than that of other parts of the fish. All anatomists who have examined the torpedo have had their attention much arrested by the great size of the nerves distributed to the electri- cal organs. These consist of three principal trunks, all arising immediately from the cerebro- spinal system. The two anterior trunks are re- garded by Desmoulins and Majendief as portions of the fifth pair of nerves, and the third as a branch of the eighth pair. But the first electrical nerve seems to have an origin altogether distinct from the root of what is unquestionably the main portion of the fifth pair, although it certainly is in very close proximity with it, and, in passing out of the cranium, the two nerves seem to be in some degree united for a short space. Immediately beyond this point of union, the electrical nerve sends a soft twig to a small cavity within the adjoining cartilage, (which Dr. Davy thinks is the ear,) and then divides into three small branches, and two large ones. One of the small branches goes to the gills, another to the neighbouring muscles, and the third to the mouth. The first of the large branches runs along the outer margin of the electrical organ, advancing first anteriorly, then going round to the posterior part of its circumference, and losing itself in the mucous glands of the tegu- mentary system, without sending a single twig into the electrical organ itself. The other great branch is inferior to the former in position, but much more voluminous ; it enters the electrical organ, and is ramified through its anterior third part, passing between its columns, and giving off numerous twigs for the supply of the walls of the columns, and the partitions, on which it terminates ; some of which pass even into the gelatinous matter with which the columns are filled. This branch, from its very origin, has all its fibres separated, isolated, and parallel, held together only by cellular tissue, which also forms a kind of membranous sheath around * Mem. della Soc. Ital. iii. 553. f Anat. Comp, des Syst. nerv. the nerve. Justus it reaches the organ, it is divided horizontally into two portions, one of which runs near the upper surface, the other on the plane between the lower and middle thirds of the thickness of the organ. When examined with a high magnifying power, the minute branches of the electrical nerves present a dotted appearance, showing as if the medullary substance were arranged within the sheath, not in a continuous line, but in a succession of small portions with a little space between each.* The second electrical nerve rises a little be- hind the former. After leaving the cranium, it divides into two large branches, which, with the exception of a few twigs which go to the gills, are wholly distributed in the middle third of the electrical organs, in the same manner as the first pair. The third electrical nerve arises from the brain close to the second, from which, however, it is separated by a thin cartilaginous plate. The greater portion of it goes to the electrical organ, and is distributed through its posterior third. It also supplies part of the gills, the gullet, the sto- mach, and the tail. Dr. Davy says it appeared to him that the branch ofthis nerve which goes to the stomach is the principal nerve of that organ : it is spread over its great arch.f The same observer also points out as deserving of particular attention, a very large plexusof nerves formed by a union of the anterior and posterior cervical nerves, of the former of which there are seventeen on either side, and only fourteen of the latter. This plexus presents itself as a single trunk just below the transverse cartilage that divides the thoracic from the abdominal cavity. It sends a recurrent branch to the muscles and skin of the under surface of the thorax; but the larger portion is distributed upon the pectoral fin and the neighbouring parts. The motive and sentient powers of the muscles and integuments connected with the electrical organs seem to depend on this plexus. The only other peculiarity of structure in the torpedo which can be supposed to be in any way connected with its electrical power, is in the system of mucous ducts, which is much more fully developed in it than in any other ray with which we are acquainted. It consists of numerous groups of glands arranged chiefly around the electrical organs ; and of tubes con- nected with these, having strong and dense coats, filled with a thick mucus secreted by the glands. The tubes open chiefly on the dorsal surface of the skin, and pour out the mucus, * Dr. John Davy, Phil. Trans. 1834. t On this subject. Dr. Davy remarks — “ It is an interesting fact that the nerves of the stomach aie derived from those supplying the electrical organs. Perhaps superfluous electricity, when not required for the defence of the animal, may be directed to this organ to promote digestion. In the instance of a fish which I had in my possession alive many days, and which was frequently excited to give shocks, di- gestion appeared to have been completely arrested; when it died, a small fish was found in its stomach, much in the same state as when it was swallowed — no portion of it had been dissolved.” ANIMAL ELECTRICITY. 91 Fig. 48. The right electrical organ divided horizontally at the place where the nerves enter, the upper half being turned outwards. A A, The first or anterior electrical nerve. B B, The second or middle nerve arising behind the gill. C C, The anterior branch of the third nerve arising behind the second gill. D D, The posterior branch of the third nerve arising behind the third gill. which, probably, serves as a medium of com- munication between the electrical organs ; being, apparently, a better conductor of electricity than either the naked skin or salt water.* With regard to the development of the elec- trical organs, it appears that, in the earliest stages of foetal growth, they cannot be seen. In a foetus of about seven-tenths of an inch in length, Dr. Davy found neither electrical organs nor fins. In another, more than one inch long, the organs were beginning to appear, and the roots of the electrical nerves were visible, although the brain could not be seen. In this stage, the external branchial filaments were about six-tenths of an inch in length, and pre- * Davy, Phil. Trans. 1832. Also Annales du Mus. no. v., in which E. Geoffroy endeavoured to show that the common mucous system of rays is absent in the torpedo, and that its place is supplied by the columns of the electrical organs, which he believed to be analogous to the mucous ducts. sented a very remarkable appearance. In a foetus of two inches and a half long, the electrical organs were distinctly formed, and the branchial filaments still long. These filaments Dr. Davy supposes to be destined to absorb matter for the formation of the electrical organs, and, perhaps, the gills and adjoining mucous glands. They are most numerous and of greatest length while the electrical organs are forming, appearing just before these organs begin to be developed, and being removed when they are tolerably com- plete.— In no other allied fishes is there the same “ elaborate apparatus of filaments where they do exist, they are less numerous and very much shorter. 2. The electrical organs in the Gymnotus. — This fish has a general resemblance in form to the common eel. Its electrical organs occupy nearly one-third of its whole bulk. They are formed by two series of tendinous membranes ; one of which consists of horizontal plates, run- 92 ANIMAL ELECTRICITY. ning from the abdominal cavity towards the tail, placed one above another with short distances between them ; the other of perpendicular plates, forming, along with the other series, small quad- rangular cells, which are filled with a semi-gela- tinous transparent substance. This structure is divided longitudinally into two pairs of distinct organs, one considerably larger than the other. The greater pair ( k k, jig. 49) lies above the other, and immediately beneath the long mus- cles of the tail. They are separated from one another by part of these muscles, by the air- bladder, and by a central membranous partition. They occupy a large portion of the lower and lateral parts of the body, and are covered exter- nally only by the common integuments. The smaller pair are covered also by the muscles of the caudal fin. Both pairs of organs are some- what angular in their transverse section, trun- cated anteriorly, tapering towards the tail. In the Gymnotus dissected by'John Hunter,* which was about two feet four inches long, the large Fig. 49. The surface of the electrical organs of the Gymnotus, on the right side, after removal of the integuments. a, the lower jaw. h, the abdomen, c, anus, d, pectoral fin. e, dorsal surface of fish, ff, anal fin. g g. skin turned back, h h, lateral muscles of the anal fin turned back with the skin, to expose the small electrical organ, i, part of this muscle left in its place. A A, the large electrical organ. 1 1, the small electrical organ, m m, the substance which divides the large organ from the small, n, a space from which the partition is removed. Fig. 50. A transverse section of the Gymnotus. a, the surface of the side of the fish, b, the anal fin. c c, cut ends of the dorsal muscles, d, cavity of the air-bladder. e, body of the spine, f, spinal marrow, g, aorta and vena cava, h h, cut ends of the two large electrical organs, i i, cut ends of the two small organs, k, partition between the two organs. organ of one side was about one inch and one quarter in breadth at its thickest part, and in this space there were thirty-four longitudinal septa. (In a specimen examined by Dr. Knox, there were thirty-one of these septa.j-) The smaller organ in the same fish was about half an inch in breadth, and contained fourteen septa, which were slightly waved. The per- pendicular or transverse membranes are placed much more closely toge- ther than those of the other series. John Hunter and Dr. Knox counted two hundred and forty of them in an inch. They are of a softer texture than the longitudinal plates. It ap- pears probable (as Hunter suggested) that these septa, longitudinal and transverse, answer the same purpose as the columns in the torpedo. La- cepede calculated that the discharg- ing surface of these organs in a fish four feet in length is, at least, one hundred and twenty-three square feet in extent; while in a torpedo of ordi- nary size, the discharging surface is only about fifty-eight feet square. The nerves of the electrical organs of the Gymnotus are derived from the spinal marrow alone. They are very large and numerous, and are divided into very fine twigs on the cells of the organs. Dr. Knox counted fifteen nervous blanches distributed to each inch of the organ. He describes them as being flattened like the ci- liary nerves of Mammalia. Each * Phil. Trans, lxv. 1775. t Edin. Journ. of Science, i. 96. 1824. ANIMAL ELECTRICITY. 93 nerve is, for the most part, divided into five distinct branches before entering the electrical organs; and these are again subdivided into, at least, as many branches as there are longi- tudinal septa. Rudolphi describes a nerve formed from branches of the fifth pair and sympathetic, which runs beneath the lateral line, over the surface of the electrical organs, but does not enter them. This has, by some, been supposed to be an electrical nerve, but without sufficient reason.* 3. The electrical organs in the Silurus. — The only organ that can be regarded as con- nected with the electrical function in this fish is a thick layer of dense cellular tissue, which completely surrounds the body immediately beneath the integuments. So compact is it that, at first sight, it might be mistaken for a deposit of fatty matter. But, under the mi- croscope, it appears to be composed of ten- dinous fibres, closely interwoven, the meshes of which are filled with a gelatinous substance. This organ is divided by a strong aponeurotic membrane into two circular layers, one outer, lying immediately beneath the ccrion, the other internal, placed above the muscles. Both or- gans are isolated from the surrounding parts by a dense fascia, excepting where the nerves and bloodvessels enter. The cells or meshes in the outer organ, formed by its reticulated fibres, are rhombic in shape, and very minute, so as to require a lens to see them well. The component tissue of the inner organ is some- what flaky, and also cellular. The nerves of the outer organ are branches of the fifth pair, which runs beneath the lateral line and above the aponeurotic covering of the organ. This aponeurosis is pierced by many holes for the transmission of the nerves, which are lost within the cellular tissue of the organ. The intercostals supply the inner organ : their electrical branches are numerous and remarka- bly fine.f The organs of the other known electrical fishes have not yet come under the notice of any anatomist. In taking a general view of these interesting organs, we are struck with the existence of a certain degree of analogy amongst them, and yet we fail to discover such resemblances as might be expected, and such as exist between the structures of other organs performing the same functions in different animals. Here we have tendinous membranes variously arranged, yet all so as to form a series of separate cells filled with a gelatinous matter. But how great is the difference between the large columnar cell in the torpedo full of delicate partitions, and the minute rhombic cells of the Silurus ! All, however, are equally supplied with nerves of very great size, larger than any others in the same animals; and, indeed, we may venture to say, larger than any nerve in any other ani- mal of like bulk. * Abhandl. der Acad. v. Berlin, 1820-21. 229, and Blainville, Princ. d’Anat. Comp. i. 232. t Rudolphi, (Abhandl. dcr Acad. v. Berlin. 1824.) 140. The organs vary in different fishes; first, in situation relatively to other organs. They bound the sides of the head in the torpedo ; run along the tail of the Gymnotus, and sur- round the body of the Silurus ; secondly, in having different sources of nervous energy ; and, thirdly, in the form of the cells. No other fishes have aponeuroses so extensive, or such an accumulation of gelatine and albumen in any cellular organ. Broussonet remarked that “ all the electrical fishes at present known to us, although all belonging to different classes, have yet certain characters in common. All, for instance, have the skin smooth, without scales, thick, and pierced with small holes, most numerous about the head, and which pour out a peculiar fluid. Their fins are formed of soft and flexible rays, united by means of dense membranes. Neither the Gymnotus nor torpedo has any dorsal fin ; the Silurus has only a small one, without rays, situated near the tail. All have small eyes.” * X. Analogies of animal electricity . — Setting aside the vague hypotheses of the older philo- sophers, (some of whom attributed the phe- nomena produced by the peculiar power of electrical fishes entirely to the mechanical effect of certain rapid motions of their surface, and others to the influence of currents of minute corpuscules flowing from the body of the fish in the act of discharging,) we can have no dif- ficulty in referring this very remarkable series of phenomena to the agency of some power very analogous to common or voltaic elec- tricity, which seems to stand in the same rela- tion to these as they do to electricity derived from other sources.f It was by Muschenbroek that the effects of the torpedo’s discharge were first referred to electricity. He was led to imagine that the agent producing the shock was truly electrical from the similarity of its effects to those of the discharge of the Leyden jar. Succeeding observations, however, as we have seen, have shewn that certain differences exist between the phenomena produced by Animal Electricity and those observed in con- nexion with the discharge of the Leyden jar : the chief of these are — its passage through air only to a very small distance; its producing only very slight igniting effects even when con- siderably accumulated ; and its manifesting but feebly the phenomena of attraction and repulsion. Further, it affects the multiplier more strongly than common electricity does under ordinary circumstances, and its chemical effects are more distinct. From voltaic elec- tricity it is distinguished by the comparative feebleness of its power of decomposing water; by the greater sharpness of the shock caused by the discharge, and by the weakness of its magnetizing power. Only four of the eight experimental effects enumerated by Dr. Faraday! as characteristic * Mem. de l’Acad. de Paris, 1782. 693. f It is interesting to know that the Arabic name of the torpedo (Rausch) means also lightning. t Philos. Trans. 1833. 94 ANIMAL ELECTRICITY. of common and voltaic electricity are pro- duced by animal electricity ; which appears to be sufficient to prove that the latter is as much a peculiar power distinct from these as are the agents called magneto-electricity and thermo-electricity. Perhaps, however, what we at present regard as so many powers dif- fering from one another in their natures, may be merely modifications of the same power, varied in its sensible properties by changes in the circumstances under which they are mani- fested. This latter view is that taken by Dr. Wilson Philip, who holds that Animal Elec- tricity is just common electricity modified in its properties by those of life, under the in- fluence of which it operates in the living animal. Sir Humphry Davy thought he saw a stronger analogy between common and animal electricity, than between voltaic and animal electricity, but concluded that the latter would be found by more extended researches than he was able to make to be “ of a distinctive and peculiar kind.”* Cavendish, on the other hand, believed that there is a complete identity between common electricity and that of fishes. And this he laboured to prove by imitating several of the peculiarities of the discharge of the torpedo by a particular arrangement of small Leyden jars, forming a battery, from which the electricity was discharged in large quantity but of low intensity .f Others, again, have attempted to trace a certain resemblance between the structure of the electrical organs of the torpedo and the formation of the voltaic pile, “ inasmuch as they are formed of alter- nate layers of moistened conductors of dif- ferent natures, to wit, of membranous parti- tions, and of gelatinous and albuminous fluid.” (Tiedemann.) They suppose that the nerves, being spread over one side of the transverse partitions of the cells, produce opposite states of electrical tension on the two sides of the partition. In the present imperfect state -of electrical science, all such hypotheses are un- satisfactory. The only conclusions which, in our opinion, can be legitimately drawn from the accumu- lated facts on the subject are — that the shock given by electrical fishes is caused by an agent closely allied in its nature to common elec- tricity and other like powers ;} and that the developement and discharge of this agent are strictly dependent on the integrity of the ner- vous communication between certain peculiar organs and the great nervous centres. It is evident that the nervous system plays a very important part in the electrical function. But whether its influence merely stimulates the electrical organs to do what their organic * Philos. Trans. 1829. 16. t Philos. Trans. 1776. 196. t The latest experiments on the subject, with which we are acquainted, are those of Messrs. Becquerel and Breschet, reported to the Academy of Sciences in October, 1835, (Ann. des Sciences Nat. n. s. iv. 253,) which seem to have been per- formed with great care. The experimenters com- pletely satisfied themselves that the shock of the torpedo is the result of an electrical discharge. structure renders them capable of doing, or really supplies them with a stream of the im- ponderable agent which they accumulate, and then, under voluntary impulses, discharge, is still a point for further investigation. In the structure of the electrical organs, we do not see any arrangement, such as researches in elec- tricity artificially developed lead us to believe fitted either to produce or to accumulate elec- tricity. But this is in itself no reason why we should conclude that the organs have not such powers. It seems more in accordance with what we know of the actions of other parts of the animal frame, to believe that they do possess such powers. But — if the elec- trical organs, by their organic structure, be fitted to develope and to discharge electricity under the nervous influence, just as a gland secretes its peculiar fluid and its ducts eject it, why (it may be asked) are the nerves going to these organs of so very great a size compared with the same parts in other organs of similar bulk and very energetic action ? Is their sub- jection to the will of the animal sufficient to account for the difference ? or does it indicate, as some physiologists maintain, that the ner- vous influence does more in this case than merely supply the vital stimulus such as is received by all other organs in common ? In other words — is the agent discharged by the fish as electricity first developed in the ner- vous centres, and only accumulated in the electrical organs; and is this agent identical with common nervism ? To these questions we cannot yet give a satisfactory reply. They point the way to some very interesting and im- portant fields of investigation, and cheer us with the hope of considerably extending our acquaintance with the physiology of the nerves, on the supposition that the phenomena of ani- mal electricity shall one day be proved to be owing to an accumulation and discharge of the very same agent that causes contraction of muscles, &c. Such a view appears to have been taken of this subject by Sir H. Davy when he remarked,* “ there seems a gleam of light worth pursuing in the peculiarities of animal electricity, — its connexion with so large a nervous system, — its dependence on the will of the animal, — and the instantaneous nature of its transfer, which may lead, when pursued by adequate inquirers, to results very important for physiology.” Treviranus, in 1818, suggested the likelihood of the power concerned in the ma- nifestation of electrical phenomena by animals, being one of those on which continuance of life in general depends. “Perhaps,” said he,f “ it is the same power which enables the tor- pedo to give electric shocks that is the imme- diate cause of the contraction of muscular fibres.” The same hypothesis is thus ex- pressed by Cams.} “ Numerous nerves are distributed upon the cells of the electrical organs, and as it is through the agency of * Philos. Trans. 1828. t Biologic, v. 141. | Traite element, d’anat. comp. 2d edit. i. 392. (French translation by Jourdan. j ANIMAL ELECTRICITY. these nerves that the organs act, it is not im- possible that the nervous influence itself is accumulated in these cells as in condensers, and that it is discharged at will, just as this influence is accumulated in the muscular tissue to produce contraction of its fibres.” It was reflection on the phenomena of animal elec- tricity that led Dr. Wollaston to form the hy- pothesis, which he supported with so much ability, of secretion in general being depen- dant on electricity, conveyed by the nerves, and acting on the secerning organs.* Dr. Wilson Philip, also, thinks that the circum- stances under which electrical action is mani- fested by fishes go to the support of his theory of the nervous influence being identical with common and voltaic electricity. Dr. Faraday says that, from the time that it was shewn that electricity could perform the functions of the nervous influence, he has had no doubt of their very close relation, and probably as effects of one common cause. To the numerous list of learned observers who have speculated on this interesting subject, we have to add the re- spected name of Sir John Herschel, who imagines that the present state of electrical science warrants the conjecture, that the brain and spinal marrow form an electric organ, which is spontaneously discharged along the nerves, at brief intervals, “ when the tension of the electricity reaches a certain point. ”f Meissner, again, supposes that the blood be- comes charged with electricity in the lungs, during the chemical process of respiration ; that the electricity immediately traverses the nerves of the lungs, and then the other parts of the ganglionic system ; that hence the cen- tral organs of the nervous system become charged ; and that the brain, on and through which the will acts, being charged, excites the several organs to activity through the medium of their respective nerves, along which electric currents are passed. J The facts, (in addition to those which have chiefly engaged our atten- tion in this article,) upon which such theories are built are, — (1) that the muscles of an animal recently dead contract when common electricity passes through them, just as they do when they are subject to the animal’s will; (2) that voltaic electricity acts upon secreting organs, so as to enable them in some degree to carry on their functions after their proper nerves have been cut; and (3) that the same agent appears to influence powerfully the capillary circulation. But, although these facts, taken along with what we know of the phenomena of the electricity of fishes, certainly do appear to favour the views to which we have just * Phil. Mag. xxxiii. 488. f Discourse on the Study of Nat. Phil. 343. | Syst. der Heilkunde. Wien. 1832. If hypo- theses such as these should hereafter be proved to express the true state of the case, the electrical fishes will become objects of great interest to the physiologist, as presenting him with opportunities, such as no other animals afford, of studying in accumulation the properties of that wonderful agent, which is the moving power of the animal organiza- tion, and a very important link in the chain of causes and effects by which life is manifested. 95 alluded, there are yet other facts which are so hostile to them as to make it probable that they do not express the truth. For instance, the most carefully conducted experiments have failed to demonstrate the existence of electric currents through muscles during their contrac- tion; which, from all that is known of the phenomena exhibited by electricity in other circumstances, it may be presumed would not have been the case had it been the immediate stimulant of muscular contraction. M. Per- son has applied the poles of a galvanometer to the spinal marrow without obtaining any indi- cations of the existence of electrical currents through its substance. The subjects of Per- son’s experiments were cats, dogs, rabbits, eels, and frogs. The spinal canal having been opened, the piles of the galvanometer were placed nr communication with the anterior and posterior columns of the cord. This was done at different parts, after the roots of the nerves had been cut. Small plates of platina, with which the wires of the instrument were armed, were thrust into the cerebellum and into several of the largest nerves. These experiments were repeated after the animals had been placed under the influence of strychnia. But there was no certain indication of electricity ob- tained, although the most delicate instruments were used.* Person’s experiments have been repeated by Muller with the same results. Messrs. Prevost and Dumas, however, state that, having armed the branches of their gal- vanometer with two wires of platina, exactly alike, and having plunged one of them into the muscles of a frog’s leg, while, with the other, heated to redness, they touched its nerves, they saw considerable deviations of the needle of the instrument follow the contrac- tions of the muscles.)- But seeing that the electricity made manifest in this experiment may have been developed rather by the con- tact of the hot wire and the nerves than by the nervous actions, we cannot admit that it is sufficient to prove the existence of electrical currents in muscles during their contraction. Dr. Faraday, also, has lately experimented on living muscles with the very delicate galvano- meter invented by himself, but has entirely failed to obtain indications of moving electri- city. Negative results such as these, obtained by so many practised observers, are sufficient to induce us to withhold our assent from those theories which make nervism identical with electricity, until the whole subject shall have been more fully investigated. As in some degree illustrative of the pheno- mena of animal electricity, properly so called, we must here take notice of the manifestation of common electricity in animal substances and in living animals. The mere contact of heterogeneous bodies is * Journal de Physiol, x. 217. Some years ago M. Pouillet announced that he had witnessed electrical phenomena during the operation of the acupuncture of muscles ; but lie has since con- fessed that he was deceived. f Edwards, De l’influence des agens physiques sur la Vie, in Appendix. 96 ANIMAL ELECTRICITY. sufficient for the development of electricity; and animal tissues of dissimilar natures, both living and dead, obey the same law as other sub- stances in this respect. For instance, a kind of voltaic pile has been formed by building up layers of muscle and nerve placed one above the other alternately ; (Bunlzen :) also by placing one upon another alternate layers of muscular fibre and brain, separated by a porous substance, soaked in salt-water. (Lagrave.) Another such has been made with plates of one kind of metal, fresh muscle, and salt-water, or blood, which acted on the galvanometer. When the con- ductors of a galvanometer (Schweigger’s) are armed with plates of platina, on one of which a piece of muscle of a few ounces in weight is placed, and the conductors are then plunged in blood or in a weak solution of salt, a deviation of the magnetic needle of the in- strument is perceptible., (Prevost and Dumas.) The same happens when to one conductor is applied a plate of platina moistened with mu- riate of antimony or nitric acid, to the other a piece of nerve, muscle, or brain, and both are brought into contact. (Majendie.) Dry piles of considerable electrical power may be formed of organic materials alone, without the interven- tion of metals. If concentrated extracts of organic bodies (animal or vegetable) be spread upon thin paper, and piles be built up of discs cut from this paper, so that two dissimilar layers be separated by two thicknesses of the paper, so much electricity is developed that the elec- trometer is affected. (Koemtz.) When two persons, both insulated, join hands, electricity is developed sufficiently to affect Coulomb’s electroscope. And, if the contraction of mus- cles, the nervous connexion of which with the living body has been destroyed, be considered as a proof that they are subject to the influence of electricity, there are numerous experiments on record tending to prove that electricity is evolved by the mere contact of two dissimilar animal substances. Galvani, Volta, Humboldt, Aldini, Kellie, and Muller, have all found that when the muscles and the great nerves of a frog’s limb are touched synchronously with a piece of the muscle of a warm-blooded animal, weak contractions of the frog's muscles ensue ; and that, when the crural muscles are cut and folded back so as to touch the lumbar nerves, muscular contractions are perceived in the lower part of the limb. Aldmi excited most powerful contractions by bringing the nerves of a warm- blooded animal into contact with the muscles of a cold-blooded animal, and vice versa. And Muller has further found that contractions are excited by touching the moistened skin of the leg with the nerves of the thigh dissected out and turned down upon them ; the nerves being held by means of an insulating rod.* Tiedemann thus states the general results of experiments such as these. “1. The nerves of the muscles in which it is proposed to excite convulsions must make part of the chain. 2. The nerve or portion of nerve which is to * Ilandbuch dev Physiol, des Menschen. Berlin, 1833. make part of the chain must be isolated as completely as may be, and no other conductor must produce derivation in this portion of the chain, so as to oblige the electric current, when developed in the chain, to take a course through the nerves. 3. Cceteris paribus, the convulsions are so much stronger, and are manifested over a greater extent, as the nervous portion, acting as a conductor, enters into the chain. 4. The convulsions are so much more powerful, and last the longer, as the chain is quickly formed, and the surface with which the parts consti- tuting it are in contact is extensive.”* And lastly, we now know that even the evaporation of fluids, and changes in the molecular consti- tution of both solids and fluids are always accompanied by electrical excitation. Applying these facts to our knowledge of the various processes of the animal ceconomy, we cannot but conclude that, in the course of the many interchanges that are constantly taking place amongst the component particles of all living organs, electricity (perhaps modified by the organic forces) must be developed alto- gether independently of nervous influence. It is certain, however, that electricity flowing from this source is very feebly manifested; at least it affects our best electrometers in a very incon- siderable degree. Saussure frequently ex- amined the electricity of his own body by means of Volta’s electrometer, used along with a condenser, but always failed to perceive any indications of free electricity while he was entirely naked. It was also imperceptible while lie perspired freely, and when his clothing was cold. Under other circumstances, he found the electricity of his body sometimes positive, and at other times negative ; but he could not determine the causes of these variations. Simi- lar observations were made by Ilemmer of Mannheim in 1786, both on the electricity of his own body, and on that of many other indi- viduals placed in various circumstances. lie obtained the following results. 1. Electricity is developed in all men, but varies in intensity and in nature in different individuals. 2. The character and intensity of the electricity fre- quently varies in the same person. In 2422 experiments, it was 1252 times positive, 771 negative, and 399 times imperceptible. 3. When the body is at rest and warm, its electricity is always positive. 4. When the surface is much cooled, the electricity becomes negative. 5. It is also negative when the muscular vigour is diminished. More recently this subject has been investigated by Messrs. Pfaff and Ahrens.f They used a gold-leaf electrometer; and the subjects of their observations were insulated. The collecting plate screwed on the electrometer was touched by the person experimented upon. The upper plate of the same was placed in communication with the ground by means of i conductors. The results which they thus pro- cured were as follows: — 1. The electricity of healthy men is generally positive. 2. Irritable men of sanguine temperament have more free I * Physiol, transl. by Drs. Gully and Lane, 276. t Meckel’s Archiv. iii. 161. ANIMAL ELECTRICITY. 97 electricity than those of a phlegmatic tempera- ment. 3. An increased accumulation of elec- tricity takes place in the evening. 4. Spirituous drinks augment its intensity. 5. The elec- tricity of women is more frequently negative than that of men. 6. In winter, while the body is very cold, no electricity is manifested, but it gradually reappears as the body is warmed. 7. The whole body naked, as well as every part of it, shews the same phenomena. 8. During the existence of rheumatism, the electricity is greatly diminished in intensity, but as the dis- ease declines it again increases. Gardini found that the electricity of women during menstrua- tion and pregnancy is negative. Some individuals exhibit electrical pheno- mena much more readily than others. Some persons, for instance, hardly ever pull off articles of dress worn next the skin without sparks and a crackling noise being produced. It is related of a certain monk that sparks were always emitted from his hair when it was stroked back- wards ; and of an Italian lady that her skin, when rubbed with a linen cloth, gave out sparks, attended with a crackling noise. The same phenomenon, as exhibited by the cat, and by other animals covered with a soft fur, is daily observed. But it has been stated that the cat’s electricity may be accumulated in its own body and given off suddenly, so as to produce a shock. Romer says,* “ If one take a cat in his lap, in dry weather, and apply the left hand to its breast, while with the right he strokes its back, at first he obtains only a few sparks from the hair; but, after continuing to stroke for some time, he receives a sharp shock, which is often felt above the wrists of both arms. At the same moment, the animal runs off with expressions of terror, and will seldom submit itself to a second experiment.” In repeating this experiment, we have obtained the like result. We are not aware of any other observer having met with any thing resembling an accumulation of electricity in quadrupeds, excepting Cotugno, who asserted that, in dissecting a living mouse, he felt an electric shock when its tail touched his finger.f XI. Uses of animal electricity. — The pur- pose which the electrical function is fitted to serve in the animal economy is proba- bly not single. It is very evident that the discharge from the organs frequently strikes terror into the enemies of their possessors, and thus it may be regarded as a means of defence ; while, in certain circumstances, it may be useful in enabling the fish more easily to secure its prey. But this, probably, is not all. It is very likely, as Dr. Roget has suggested,! that the electrical organs communicate to the fish perceptions of electrical states and changes in surrounding bodies, (very different from any that we can feel,) in the same way as other organs of sense convey perceptions with regard * Gilbert’s Ann. der Phys. B. xvii. t Humboldt. Ueber die gereizte Muskel-und- Nervenfaser. Berlin, 1793. i. 30. t Bridgewater Treatise, i. 31. VOL. II. to light and sound. Such perceptions we can conceive to be very useful and pleasurable to animals living in the dark abysses of the waters. Some of Dr. John Davy’s observations make it very doubtful whether the electrical function is ever subservient to that of prehensiou of food. He kept young torpedos for a period of five months or more, in large jars of salt water, during which time they ate nothing, although very small fishes, both dead and alive, were put into the water. Yet they grew, and their elec- trical energies and general activity increased.'* The small fishes seemed to have no dread of the torpedos. On one occasion, however, when a lively torpedo was placed in a small vessel along with a smelt, and excited to discharge, the smelt was evidently alarmed, and once or twice, when exposed to the shock, leaped nearly out of the vessel, but it was not injured by the electricity. It has also been frequently ob- served of the gymnotus that it eats very few of the fishes that it kills by its discharge. The electrical power of the young fish is proportionally very much greater than that of the old, and can be exerted without exhaus- tion and loss of life much more frequently. After a few shocks, most of the old fish which Dr. Davy has endeavoured to keep alive have become languid, and died in a few hours, whilst young ones, from three to six inches long, remained active during ten or fifteen days, and sometimes lived as many weeks. Hence Dr. Davy concludes that the chief use of the electrical function is to guard the fish from its enemies, rather than to enable it to destroy its prey, and so provide itself with food. He fur- ther conjectures that, besides its defensive use, the electrical function may serve also to assist in respiration by effecting the decomposition of the surrounding water, and so supplying the gills with air when the fish is lying covered with mud or sand, in which it is easy to con- ceive that pure air may be deficient. And Dr. Davy has often imagined that he saw something of this kind going on. After repeated dis- charges, he has observed, all around the margin of the pectoral fins, an appearance as if very minute bubbles of air were generated in it and confined. That this may be one purpose which the electrical function is designed to serve, is rendered still more probable by the circumstance, that the gills (in the torpedo at least) are largely supplied with twigs of the electrical nerves. In fishes in which he had cut the electrical nerves, Dr. Davy found the secretion of the cutaneous mucus considerably diminished or altogether arrested ; and hence he supposes that the electricity assists in the production of this fluid. Lastly, it has been conjectured that the elec- trical function is subservient to that of digestion. This idea was started by Mr. J. Couch some years ago.f He says, “ Without denying that the torpedo may devour that which it disables by the shock, I conceive that the principal use of this power has a reference to the functions of , * Phil. Trans. 1835. t Linn. Trans, xiv. 89. H 98 NDOSMOSIS. digestion. It is well known that an effect of lightning or the electric shock is to deprive animated bodies very suddenly of their irrita- bility ; and that thereby they are rendered more readily disposed to pass into a state of disso- lution than they would otherwise be ; in which condition the digestive powers of the stomach can be much more speedily and effectually exerted on them. If any creature may seem to require such a preparation of the food more than another, it is the torpedo, the whole intes- tinal canal of which is not more than half as long as the stomach.” These views receive some support from the fact that the nerves of the stomach are derived from those supplying the electrical organs ; and perhaps also from the fact, reported by Dr. Davy regarding a torpedo, in which, after it had been frequently excited to give shocks, diges- tion seemed to be completely arrested. The only conclusion to which, in the present state of our knowledge, we can come on this point is, that although the electrical organs form a very efficient means of defence from their enemies for the fishes which possess them, this is not the only purpose they are intended to serve ; what, however, their other uses are is at present only matter of conjecture. There remains yet unentered upon a large field of enquiry connected with the physiology of those wonderful organs, which, we doubt not, will yield to future ages very striking examples of that nice and close adaptation of means to ends which so clearly proves to us the existence and continued exercise of Wisdom Supreme, “upholding all things by the word of his power,” making the smallest of his works “ very good,” and “ to be thought upon.” Bibliography.— Volta, Memorie sull’ elettri- cita animali, 1782. Galvani, Dell’ uso e dell’ at- tivita dell’ arco conduttore nelle contrazioni dei moscoli. Bologna, 1794. Ejus. Memorie sull’ elettricita animale, Bologn. 1797. Fowler, Expe- riments and Observations relative to the influence called animal electricity. Lond. 1793. Aldini, Essai Theorique et experimental sur le Galvanisme, ct in Bulletin des sciences, an xi. No. 68. Hfaff, Ueber thierische Elettricitiit und Reizburkeit. Leipzig, 1795. Humboldt, Versuche iiber die ge- reizte Muskel und Nervenfaser. Berlin, 1797. Treviranus, Biologie. Tiedemann, Physiologie. Muller, Physiologie. Cams, A nat. Comp. French ed. t. i, Lorenzini, Osservazioni interno alle tor- pedini, Flor. 1678. Walsh, Phil. Trans. 1774. Pringle on the Torpedo, Lond. 1783. Ingenhousz, Phil. Trans. 1775. Hunter, Phil. Trans, t. Ixiii. et Ixv. Geoffrey Saint Hilaire, Ann. du Mus. t. i. Humboldt, Recueil d’observ. de zoologie et d’anat. comp. Knox, Edin. Journal of Science, 1824. Todd, Phil. Trans. 1816. Davy, Phil. Trans. 1834. Majendie and Desmoulins, Anat. des Systemes Nerv. t. ti. Rudolphi, Abhandl. der Acad, der Wissen- schaft in Berlin, 1820. Becqtierel, Traite d’Elec- tricite et Galvanism, t. iv. Par. 1836. (John Coldstream.) ENCEPHALON. In order to lay before the reader a connected view of the Anatomy of the Encephalon in conjunction with that of the Medulla Spinalis, the Anatomy of both these organs will be given under the article “ Ner- vous Centres.” ENDOSMOSIS, (ivS'oy, intus, attr^.05, im- pulsus). — Accident having made me acquainted with the fact that a small animal bladder, con- taining an organic fluid, became considerably distended by remaining for some time plunged in water, and that the water even expelled the thicker fluid contained within the bladder, when there was a hole by which it could escape, I be- thought me of the probable cause of this pheno- menon, and soon came to the conclusion that it depended on the difference of density between the included or interior fluid, and the water or exterior fluid. I found that the cceca of fowls filled with milk, thin syrup, &c.and secured with a ligature, became turgid and even excessively distended when treated in the same way. I now discovered that the fluids contained in the cceca permeated their coats, and were diffused in the surrounding water. I saw, further, that two opposite currents were established through the parietes of the cceca; the first and stronger formed by the exterior water flowing towards the fluid contained in the cceca; the second and weaker, by the thick included fluid flow- ing towards the water. To the first of these currents I gave the name of Endosmosis, and to the second that of Exosmosis. These titles, I must allow, are objectionable, and perhaps badly chosen. The first conveys the idea of an entrance and the second of an exit. Now, the phenomenon, regarded in its proper point of view, consists in a double permeation of fluids, abstracted from any idea of entrance or exit. Besides, the current of endosmosis, which, etymologically speaking, expresses an in-going current, may nevertheless be, experimentally speaking, an out-going current ; this, for exam- ple, happens when a hollow membranous organ, containing water, comes to be placed in contact exteriorly with a fluid more dense than water. There is then a current of endosmosis which goes out of the bladder, and a current of exos- mosis which enters it. Thus facts are found in contradiction to the terms, and these I should not have hesitated to change, if their general adoption did not render this change very diffi- cult, and subject to great inconvenience. I have, therefore, resolved to retain them, wishing it to be understood by naturalists that no attention is here paid to their etymological signification. To estimate the amount of endosmosis I contrived an apparatus to which I gave the name of endosmometer ; it consists of a small bottle, the bottom of which is taken out, and replaced by a piece of bladder. Into this bottle I pour some dense fluid, and close the neck with a cork, through which a glass tube, fixed upon a graduated scale, is passed. I then plunge the bottle, which I entitle the reservoir of the endosmometer , into pure water, which, by en- dosmosis, penetrates the bottle in various quan- tities through the membrane closing its bottom. The dense fluid in the bottle, increased in quan- tity by this addition, rises in the tube fitted to its neck, and the velocity of its ascent becomes the measure of the velocity of the endosmosis. To measure the strength of endosmosis, I have made use of an endosmometer in which the tube was twice bent upon itself, the as- ENDOSMOSIS. 99 cending branch containing a column of mer- cury, which was raised by the interior fluid of the endosmometer in proportion as the en- dosmosis increased the volume of this fluid.* By means of these two instruments I have found that the velocity and strength of endos- mosis follow exactly the same law. Both are in relation to the quantities which express, in two comparative experiments, the excess of density of two dense fluids contained in the endosmometer, above the density of water, which in these two experiments is exterior to the instrument. Thus, for example, in putting successively into the same endosmometer, syrup of which the density is 1.1, and syrup of which the density is 1.2, and in plunging in both cases the reservoir of the endosmometer into pure water, you obtain in the first case an en- dosmosis, of which the strength and velocity are represented by 1 , and in the second case an endosmosis, of which the strength and velocity are represented by 2 ; that is to say, by the numbers relative to the fractionals 0,1 and 0.2, which express the excesses of density of the two solutions of sugar above the density of water, which is 1 . I have ascertained by ex- periment that the strength of endosmosis is such that, with syrup of which the density is 1.11, and an endosmometer, the opening of which is closed by three pieces of bladder, one over the other, you obtain an endosmosis which raises the mercury to 1 metre 238 millimetres, or 4.5 inches 9 lines, which is equivalent to an elevation of water of 16 metres 77 centimetres, or 51 feet 8 inches. It follows from this, that in employing syrup, of which the density was 1.33, (its ordinary density,) you would obtain an endosmosis, the strength of which would be capable of raising water more than 150 feet. Fluids of a different nature have, with refer- ence to endosmosis, properties which are in no way in proportion to their respective densities. Thus sugar-water and gum-water of the same density, being put successively into the same endosmometer, which is plunged into pure water, the former produces the endosmosis with a velocity as 17, and the latter with a velocity as 8 only. I have seen, in the same manner, a solution of hydrochlorate of soda and a solution of sulphate of soda of the same density, put successively in the same endosmo- meter surrounded with pure water ; the velo- city of the endosmosis produced by the solu- tion of sulphate of soda is exactly double that of the endosmosis produced by the solution of hydrochlorate of soda. These results are inva- riable, and I am persuaded that if 1 have ever obtained a different result, the experiment has been defective. I have made several experiments since with gelatinous and albuminous waters placed suc- cessively in the same endosmometer, surround- ed with pure water, which produced endos- mosis severally in the proportion of 1 to 4 ; so that the albumen had four times more power of endosmosis than the gelatine. I have seen * See my work entitled, Nouvelles Recherches sur : l’endosmose et l’exosmose, &c. 8vo. Paris, 1828. by another experiment that the power of en- dosmosis of syrup is to the power of endos- mosis of albuminous water of the same den- sity, as 11 is to 12. All alkalies and soluble salts produce en- dosmosis; so do all acids, but each with spe- cial phenomena, which will be noticed by and by. These chemical agents in general occasion an endosmosis of short duration only, when the endosmometer is closed with a portion of an animal membrane. Organic fluids alone, which are not very sensibly either acid or alkaline, or salt, produce lasting endosmosis, which, in- deed, does not stop until the fluids are altered by putrefaction, when they become charged with sulphuretted hydrogen. I have shown that when an endosmometer is closed with a thin plate of baked clay instead of the animal mem- brane, the endosmosis which a saline solution produces, and which would have stopped in a few hours with the animal membrane, continues to go on indefinitely with the baked clay. The property of destroying endosmosis may be considered as belonging to all chemical re- agents, but merely on account of their sus- ceptibility to enter into combination with the permeable partition of the endosmometer. Thus all acids, alkalies, soluble salts, alcohol, &c. being disposed to combine with the elements of organic membranes, destroy endosmosis, al- though they had induced it before their complete combination with the elements of the membrane had taken place ; and it is not until this combi- nation is complete that endosmosis ceases. Or- ganic fluids, which have no chemical action upon the elements of the membrane of the endosmo- meter, ought not, consequently, to tend to the destruction of endosmosis, unless some change should take place which should give them a chemical action, such as they usually acquire by decomposition, when they usually become charged with sulphuretted hydrogen. My earlier experiments tended to show that carbonate of lime (chaux carbonat'ee) reduced to thin laminae, and employed to close an en- dosmometer, is totally without the power of producing endosmosis; my latter experiments have somewhat modified this conclusion. After having vainly employed laminae of carbonate of lime of greater or less thickness, I finished by making use of one of white marble, two millimetres in thickness, but with no better success. Without carrying my experiments further, I concluded that porous carbonate of lime was totally unapt to excite endosmosis. This conclusion having, notwithstanding, left some doubts in my mind, I again took the same plate of marble with the intention of measuring its permeability to water, compared with the various degrees of thickness which I could give it, and of renewing, at the same time, my at- tempts to make it produce endosmosis. Having closed an endosmometer with this plate of mar- ble, I filled the reservoir and the tube of the instrument with pure water, and suspended it over a vessel filled with water, in which the plate of marble only was immersed. If the marble had been permeable to water, the fluid con- tained in the endosmometer would have flowed h 2 100 ENDOSMOSIS. through the capillary conduits of the plate, and this flow would have become perceptible by the sinking of the water in the tube, the inte- rior of which was only two millimeters in dia- meter. The result of this experiment was that the plate of marble, which was four centimeters in diameter, did not lose by filtration, in one day, more than the small quantity of water capable, by its subtraction, of lowering its level one millimeter and a half in the tube. 1 next tried syrup in this endosmometer, the reservoir being plunged into pure water; but no endosmosis was induced. I now reduced the thickness of the plate of marble to one millimeter and a half; in this state it lost by filtration, in the course of a day, eleven mil- limeters of water measured by the tube. The permeability of this plate was, as may be per- ceived, very sensibly increased : still the en- dosmometer which it closed when filled with syrup showed no indications of endosmosis. 1 reduced the thickness of the plate of marble to one millimeter. In this state it lost by fil- tration, in the space of a day, twenty-one milli- meters of water measured in the tube. I put into the endosmometer, which this plate of marble closed, the same syrup which had been used in the preceding experiments, and the density of which was 1.12, and I now ob- tained an endosmosis which manifested itself by an ascension of seven millimeters in four- and-twenty hours. This last experiment proved to me that carbonate of lime was not, as I had hitherto found it, totally without the power to produce endosmosis. I wished to compare this plate of marble with a piece of bladder of the same surface under the double point of view, of their permeability, and their respec- tive properties of producing endosmosis. Having therefore taken off the plate of marble which closed the endosmometer, I replaced it by a piece of bladder whose permeability to water I measured in the same manner as above. I found this permeability very nearly equal to that of the plate of marble of one millimeter in thick- ness. I then put into this endosmometer some syrup similar in density to that which I had used in the same endosmometer closed with the plate of marble. The endosmosis which I obtained raised the syrup seventy-three millimeters in three hours. Thus the permea- bility to water being equal in the bladder and in the plate of marble, the endosmosis pro- duced by the first was to the endosmosis pro- duced by the second as 584 is to 7, a most extraordinary difference, and difficult to be accounted for. These experiments prove that carbonate of lime is but very little apt to pro- duce endosmosis, in which it differs singularly from baked clay, thin laminre of which are almost as apt to produce endosmosis as organic membranes. The varieties of sulphate of lime which may be employed in endosmometrical experiments are not sufficiently numerous or of sufficient variety of permeability for it to be possible to appreciate the properties of this substance in relation to endosmosis. I found that the sul- phate of lime used in the manufacture of plaster in the environs of Paris, employed in thin plates to close an endosmometer, did not produce endosmosis. But this mineral is per- haps too easily permeable. In fact it is found impossible to obtain endosmosis when the in- terior fluid of the endosmometer flows easily by filtration, in virtue of its weight, through porous plates. I should say as much of plates of freestone (grts ) which I have employed without success in these experiments, but that I recollect to have obtained the phenomenon in a very slight degree with a plate of freestone very close-grained and very little permeable to fluids. I have tried a variety of experiments shew- ing that an increase of temperature increases endosmosis. This result has been confirmed by repeated experiments. The quantity of the same fluid introduced by endosmosis, and with the same sort of per- meable partition, is generally in proportion to the extent of surface of this partition. The following experiment demonstrated this fact. I took two endosmometers, the membranes of which, taken from the same bladder, were of diameters in the relation of one to two ; I filled the reservoirs of these two endosmometers with syrup of equal density, and then plunged them into pure water. I had taken care to weigh them previously with great exactness. After continuing the experiment for two hours, I weighed the instruments afresh, and found in the large endosmometer four times as great an increase of weight as in the small one, which proved that the first had introduced, by endos- mosis, four times as much water as the second. This relation was exactly that of the extent of surface of their respective membranes, the diameters of which were as one is to two, and their surfaces consequently as one is to four. I have thus enumerated the effects ; let us now endeavour to ascertain their causes. The first idea which presented itself to my mind to explain the phenomenon of endosmosis was that it was owing to electricity. We know that effects exactly similar to those of endos- mosis are produced by means of the electricity of the voltaic pile in the experiment of M. Porret, inserted in the Annales de Chimie, vol. xi. p. 137. This naturalist having divided a vessel into two compartments by a septum of bladder, filled one of the compartments with water, and put only a small quantity in the other. Having placed the positive pole of the pile in communication with the compartment full of water, and the negative pole with the compartment containing little water, the fluid was forced through the bladder from the full compartment into the almost empty one, and there rose to a higher level than that to which it was reduced in the original full compart- ment. I varied this experiment by applying it to my own apparatus. I put pure water into an endosmometer, the membrane of which was plunged into water. I made the interior water of the endosmometer communicate with the negative pole of the pile, and the exterior ENDOSMOSIS. 101 water with the positive pole. I soon saw the water rise in the tube of the instrument : en- dostnosis had taken place. The similarity of effects led me to admit that some particular and unknown mode or form of electricity was the cause of the endosmosis produced by the heterogeneous nature of fluids. It was in vain, however, that I tried to discover signs of this electricity with the most delicate electro- meters. In reflecting afterwards upon what might be the common cause of the phenomenon pre- sented in Porret’s experiment and that of or- dinary endosmosis, I was inclined to think that electricity might not be the immediate cause of the effects exhibited, and that it only acted in the case cited by producing heteroge- neousness of quality in the two fluids subjected to the positive and negative poles. Experience seems to have confirmed my doubts on this point. I took a small endosmometer of glass, closed by a piece of bladder, and filled its re- servoir with water coloured blue with the co- louring matter of violets ; I plunged the reser- voir of this endosmometer into the same co- loured water contained in a small glass vessel ; I put this latter fluid in communication with the positive pole of the voltaic pile, and the interior fluid of the endosmometer in commu- nication with the negative pole. The exterior blue fluid soon became red, and consequently acid, and the interior blue fluid became green, and consequently alkaline. These two fluids having thus become heterogeneous, to this may be ascribed the endosmosis which manifested itself, and which increased the volume of the interior fluid at the expense of the volume of the exterior fluid. Thus electricity would not be in this case the immediate cause of endos- mosis, but the remote one ; it would only act in producing the heterogeneous quality in the two fluids, and it would be this quality which would produce the passage of fluids as in the experiments on endosmosis, the discovery of which belongs to me. But let us now inquire in what way hetero- geneousness of quality in two fluids, separated by a membranous partition, occasions the phe- nomenon of endosmosis. Upon this point opinions are greatly divided. M. Poisson and Mr. Power have each, in his own way, given an analytical explanation of the phenomenon, and ascribed it to the action of the capillary canals of the porous septum interposed be- tween the two fluids. In this explanation the phenomenon of the current of exosmosis is set aside, or regarded as occurring merely acciden- tally. Now this is entirely opposed to the fact, — we have constantly evidence of the simulta- neous existence of the two opposite and une- qual currents of endosmosis and exosmosis. Endosmosis by others has been held to be simply the effect of the viscidity of one of the fluids divided by a porous septum. This visci- dity prevents the upper fluid from permeating the interposed septum, whilst the inferior fluid, little or not at all viscid, filters readily through the septum and mingles with the upper fluid, whose volume it consequently increases. This- opinion, published by a man of distinction, de- serves to be seriously investigated. When an equal weight of gum arabic and of sugar is dissolved in two equal weights of water, the viscidity of the different solutions is by no means the same, the solution of the gum is ob- viously more viscid than that of the sugar. Now if these two solutions be divided by a piece of bladder, the current of endosmosis will be found to flow from the solution of the gum towards that of the sugar ; in other words, from the more viscid to the less viscid fluid; in this instance, consequently, we see the more viscid fluid permeating the membrane with greater facility or in greater quantity than the less viscid fluid. More than this, the same phenomenon takes place if the quantity of the gum be made double that of the sugar. I have, for instance, tried a solution of two parts of gum arabic in thirty-two parts of water, (den- sity 1.023,) and a solution of one part of sugak in the same quantity of the menstruum, (den- sity 1.014,) divided by a piece of bladder, and found that the endosmotic current was still directed from the solution of the gum towards that of the sugar. These facts suffice to prove that the endosmotic current does not always flow from the less towards the more viscid fluid. It is not, therefore, the inequality of vicosity in these two fluids which is, in this instance, the cause of their unequal permeation across the porous lamina which separates them. In order to place these facts beyond a doubt, the comparative viscidity of the gum-water and the sugar-water which were made use of in the experiments of which I have been speaking, required to be accurately measured. Such a comparative estimate of the viscidity of fluids may be obtained by observing the time which an equal quantity of each of them, at the same temperature, takes to run through a glass capil- lary tube. In this way I tried, 1st, pure water; 2d, a solution of one part of sugar in thirty-two parts of water; 3d, a solution of one part of gum-arabic in thirty-two parts of water; 4th, and lastly, a solution of two parts of gum in thirty- two of water. With a temperature of +7° cent. I found that fifteen centilitres of pure water passed through a capillary tube of glass in one hundred and fifty-seven seconds; that fifteen centilitres of the solution of one part of sugar in thirty-two of water passed through the same tube in one hundred and fifty-nine seconds and a half ; that fifteen centilitres of the solution of one part of gum in thirty-two of water passed through in two hundred and sixty-two seconds and one-third ; and that the same quantity of the solution of two parts of gum in thirty-two of water required three hundred and twenty-six seconds to pass through. From these experiments it appears that the viscidity of the solution of sugar, in the propor- tion of one to thirty-two of water, (density 1.014,) is very little above that of pure water ; that the viscidity of the solution of gum-arabic, in the proportion of one to thirty-two of water, is much greater than that of the sugared water 102 ENDOSMOSIS. just mentioned ; and finally, that the viscidity of the gum-water, containing two parts of gum to thirty-two of water, (density 1.023,) is twice as viscid as the solution of sugar employed. It seems that nothing more is wanting to these proofs of the fact that endosmosis does not depend on the mere viscidity of fluids. Nevertheless I shall cite another proof of this truth. The very singular fact I am about to mention will also prove that the septa employed exert a special influence on the direction in which endosmosis takes place. It is well known that, in separating water from alcohol by an organized animal or vege- table membrane, the endosmotic current flows from the water towards the alcohol. I employed oil-silk ( taffetas goinmc ) or silk covered with a layer of caoutchouc, which may be regarded as equivalent to a thin lamina of elastic gum, as the medium of separation between these two fluids. During the first thirty-six hours of the experiment, I observed an extremely slow en- dosmotic current from the alcohol towards the water. After this period the endosmosis, with the same direction, became very rapid. This increase in the rapidity of the endosmosis I considered due to some alteration in the caout- chouc produced by the action of the alcohol, and in consequence of which it became more readily permeable. The endosmotic current, however, let it be observed, is always from the water towards the alcohol in this experiment, instead of being from the alcohol towards the water, as is constantly the case when the septum between the spirit and the water is formed by an organic, whether animal or vegetable, tissue. We have thus a clear demonstration of the great influence possessed by the septum upon the direction of the current of endosmosis. We have, also, in the instance just quoted, a proof that the different degrees of viscidity of two liquids plays no part in the production of this phenomenon. I would remark that the endos- motic current carrying the alcohol towards the water athwart the septum of caoutchouc is ac- companied by a counter-current, which carries the water towards the alcohol through the same septum. I assured myself that the alcohol had received some addition of water; and yet it is well known that caoutchouc is impermeable to water ; which would seem to say that the latter fluid could only have passed through the sep- tum of caoutchouc by becoming mingled with the alcohol occupying the molecular interstices of that substance. Once within these intersti- ces the alcohol attracts the water by the affinity of mixture, (afjinite de mixtion) and enables it to penetrate the substance of the caoutchouc, which denies all access to water when it is pure. It is therefore to the state of commixtion within the capillary tubes of the septum that the two opposed fluids proceed the one towards the other with cross but unequal motions. The means I took to ascertain the fact of water having become mixed with the alcohol was simple enough : I set fire to a quantity of the fluid which had served for the experiment, and found that, after all the spirit had burned out, a considerable quantity of water remained, whilst the alcohol, previously to being so em- ployed, burned away entirely, leaving no water behind it. The theoretical views of Magnus in regard to endosmosis have been adopted by Berzelius in his Chemistry, and the idea upon which they are based has been reproduced by M. Poisson. To give a clear notion of this theory, let us sup- pose that a measure of salt water is separated from a measure of pure water by a permeable septum, a piece of bladder for example ; the current of endosmosis, in this instance, will be from the pure water towards the salt, and for the following reason : in the salt water there are three attractions, namely, the attraction of the molecules of the water for one another; secondly, the attraction of the molecules of the salt for one another; and thirdly, the reciprocal attraction of the molecules of the water and of the molecules of the salt. The pure water on the opposite side of the septum again has no more than a single form of attraction, to wit, that of its particles for one another. The salt water subjected to three attractions will be moved, it may be imagined, with greater diffi- culty than the pure water, the molecules of which are obedient to but one attraction. Con- sequently, in the reciprocal attraction of these two fluids, the one, the molecules of which are the least subjected to attraction among them- selves, will make its way with greatest rapidity athwart the capillary conduits of the dividing membrane. This theory has a seducing aspect, but we shall find immediately that it is inapplicable to certain endosmotic phenomena presented by 1 have shown above that it is not always to- wards the denser fluid that the endosmotic cur- rent is turned. Thus alcohol and ether are very much less dense than water, and yet it is towards these fluids of inferior density that water flows in endosmotic experiments. Alco- hol and ether have this in common with dense fluids generally, that they rise to a less height in capillary tubes than water. From this ob- servation I was led to imagine that the endos- motic current was always from the fluid having the greatest power of capillary ascension, to- wards the fluid having the least of this capa- city. It is true, indeed, as we have already seen, that alcohol proceeds by endosmosis to- wards water when the medium dividing them is caoutchouc. This would seem to say that alcohol would rise higher than water in capil- lary tubes of caoutchouc; and it is certain that caoutchouc has a greater attraction for alcohol than for water, inasmuch as the surface of India-rubber is much more readily wetted by alcohol than by water, which only adheres to it partially and imperfectly. This fact, there- fore, would not be in contradiction to my theory ; although I must confess that it is not reconcilable with certain endosmotic pheno- mena presented by the acids, as we shall imme- diately have occasion to perceive. In spite of this, however, I do not think I ought to pass ENDOSMOSIS. 103 in silence all the proofs that seem to establish this theory upon a basis of sufficient solidity ; for I cannot but perceive that it is applicable to the most general phenomena of endosmosis, phenomena, too, which the acids, like all other fluid bodies, exhibit, although they also present endosmotic phenomena in addition of a diffe- rent nature, and which belong to them exclu- sively. Inequality of density being one cause of en- dosmosis among fluids, it became a point with me first to ascertain what differences in power of capillary ascension resulted from determi- nate differences of density among fluids ; and next, to discover whether the difference in power of capillary ascent of two fluids bore any constant ratio to the difference of endos- mosis as it is proclaimed by experiment. The height to which different fluids rise in capillary tubes depends on a variety of causes, in appearance very different, but which must have some fundamental analogy. Of all fluids water is that which rises highest; and sub- stances held dissolved in it which increase its density, lessen its power of capillary ascent, which is also diminished by increase of tempe- rature : hot water ascends a less way in a capil- lary tube than cold water. Combustible fluids, such as alcohol and ether, are like dense fluids in regard to power of capillary ascent ; so that combustibility acts in the same manner as den- sity in this respect. The matter ot which ca- pillary tubes are formed is also endowed with the power of modifying the capillary ascent of fluids. Thus water, at the same temperature, will not rise to the same height in a series of equal capillary tubes made of different mate- rials. These multiplied elements, which enter into the determination of the capillary ascend- ing power of different fluids, render it an ex- tremely complicated phenomenon. To simplify the study of this phenomenon in the greatest possible degree, let us confine ourselves to the use of two fluids, namely, water and a solution of the hydrochlorate of soda. It is easy to try the latter fluid of different densities, and to compare the power of capillary ascent pos- sessed by each of these with that of pure water at like temperatures. The same glass tube will answer for these comparative experiments. Be- fore detailing these experiments, however, I have one important remark to make, which is this ; that the layer of fluid which moistens, internally, the canal of a tube is one of the elements of the capillary ascension which this tube effects. Thus, water will rise to a de- terminate height, in a tube interiorly moistened with water ; but if the interior of the tube be moistened by a saline solution, or by any other watery fluid, or by alcohol, pure water will not again rise so high in this tube as when it was moistened by water only. It will be in vain to attempt to cleanse the tube by passing water repeatedly through it; water will never detach the stratum of saline or other liquid which ad- heres to it, and which diminishes its power of producing capillary ascension. To detach this stratum of fluid you must pass a filiform body repeatedly through the tube full of water ; it is only by the rubbing of this body that the stratum can be detached. It must be evident after this observation, that in making experiments on the power of capillary ascension with various fluids and with the same tube, it is necessary to cleanse this tube with great care before each experiment; without this we should have de- fective results. We must also take care not to warm the tube by holding it between the fingers, for if the temperature be increased it will no longer exert so strong a capillary attrac- tion. Let us now pass to the detail of these experiments. I prepared a solution of hydrochlorate of soda, the density of which was 1.12, the den- sity of the water being one. I took a part of this solution and to it added an equal volume of water, which gave it a density of 1.06. I had thus two saline solutions, of which the excess of density, above the density of water, was 0.12 and 0.06. The excess was thus in the relation of two to one. From my former experiments, these two excesses ought to serve as measures of the endosmosis produced by each of these saline solutions, put successively into the same endosmometer plunged in pure water. In fact, having submitted both of the saline solutions to experiment, I obtained from the most dense solution an endosmosis exactly double of that which was produced by the least dense solution. I next inquired into the rela- tion existing between the known density of these two saline solutions and water, and the power of capillary ascension possessed by the three fluids. I took a glass tube, whose capillary action raised water to the height of 12 lines at a temperature of + 10 degrees R. (50 Fahrenh.) I found that the same tube, at the same tem- perature, raised to 6^ lines the solution of hydrochlorate of soda, the density of which was 1.12, and that it raised to 9^ lines the solution of the same salt, the density of which was 1.06. 1 . The capillary ascension of the water being .... 12 The capillary ascension of the most dense fluid being 6J The excess of the capillary ascension of water is 5 J 2. The capillary ascension of water being 12 The capillary ascension of the least dense saline solution being 9 1 The excess of the capillary ascension of water is 2 1 Thus the two excesses of the capillary ascen- sion of water above the capillary ascension of each of these saline solutions are 5^ and 2?, or 4| and 2§. numbers which are in the relation of two to one, as are the two excesses 0.12 and 0.06 of the density of the two saline solutions above the density of water. Here, then, are two saline solutions which, put separately in relation to pure water, produce endosmosis inthe relation of 2 to 1. Shall we refer this result to the 104 ENDOSMOSIS. circumstance that the excesses of density of each of these saline solutions over the density of water are in the ratio of 2 to 1, or to this, — that the excesses in the power of capillary ascent of each of these saline solutions over the power of capillary ascent of water are in the ratio of 2 to 1 ? In other words, is it the re- spective density of the two fluids which regu- lates or determines their endosmosis, or is it the respective powers of capillary ascension of the fluids severally? The following experiment will solve this question. We have seen above that a solution of sulphate of soda and a solution of hydro- chlorate of soda of equal densities being put in relation to pure water, produce endosmoses which are in the relation of two to one. Here the difference of density does not interfere with the regulation of the endosmosis ; we must then see if it be regulated by the power of capillary ascension. I prepared a solution of sulphate of soda and one of hydrochlorate of soda, having the same density 1.085, and tested their ca- pillary ascension in the same tube in which we have seen pure water raised to a height of 12 lines at a temperature of + 10 degrees R. I found that in the same tube and at the same temperature the capillary ascension of the so- lution of sulphate of soda was of 8 lines, and that of the solution of hydrochlorate of soda was of 10 lines. The excess of thecapil- lary ascension of water above that of the solu- tion of sulphate of soda is consequently 4 ; the excess of the capillary ascension of water above the solution of hydrochlorate of soda is 2. These two excesses are in the relation of two to one, a relation which also measures the endosmosis produced with the concurrence of water by each of these two solutions of equal density. The result of this is that the capillary ascension, or power of capillary ascent, of fluids governs their endosmosis, and that their density only intervenes in this case as the determining cause of their capillary ascension. But how does the capillary action operate here ? This ap- pears to be difficult to determine. The capillary action never carries fluids out of the canals in which it takes place; how then apply this action to the phenomenon of double permeation, which takes place in endosmosis and exosmosis ? This double permeation, which carries two he- terogeneous fluids towards each other, seems as though it were the result of the reciprocal attraction of the two fluids, of their tendency to associate by admixture. In experiments of endosmosis made with a dense fluid and water, the tendency to mix is favoured by the respec- tive positions of the two fluids; the dense fluid is above and the water below. This dis- position may possibly be one cause which fa- vours the reciprocal mixture of the two fluids, whose specific gravity would tend to place them in an inverse situation to that given them in the experiment. This does not take place when experiments on endosmosis are made with alcohol and water ; then the alcohol, spe- cifically lighter than water, is situated above this latter fluid, and, notwithstanding this, the endosmosis is exceedingly energetic ; we must then acknowledge that the specific gravity of two fluids has not here the degree of influence that might be supposed to belong to it at first sight. We have consequently no means left to explain the course of the two fluids towards each other athwart the capillary canals of the parti- tion which separates them, but their reciprocal attraction or tendency to admixture. In ad- mitting that such is the efficient cause of this double permeation we must also necessarily admit that this efficient cause is governed in its operation by the capillary action of the par- tition. Here another question presents itself,— do the two fluids accomplish their admixture in the capillary canals themselves, or do they cross the partition by different capillary canals, so that neither fluid mixes with its opposite fluid until the moment of its exit from the capillary canals ? On the latter hypothesis it were necessary to admit that the number and diameter of the capillary canals followed sepa- rately by each of the two fluids must be per- fectly equal, for, without that, how would the general result of this double permeation, a result which is explained by the quantity of endosmo- sis, be in exact relation with thecapillary action on the two fluids? Now it is repugnant to reason to admit any such perfect equality among all the capillary canals, or to suppose an equal number especially fitted for the transmission of each of the two fluids. It must then necessarily be allowed that the transmission of the two op- posite fluids takes place by the same capillary canals, and that consequently this double movement of transmission takes place by a reciprocal penetration of the two fluids. The preceding theory, with which I was at one time inclined to rest satisfied, and which, indeed, seemed to be based on a sufficiently firm foundation, was however brought into jeo- pardy by a discovery which I made subse- quently, in regard to the phenomena of endos- mosis exhibited by certain acids separated from pure water by a layer of animal mem- brane. In the earliest experiments I made on the endosmosis of the acids, I observed a number of anomalous phenomena, for which I felt my- self incompetent to assign any sufficient reason. I had always placed the acids above the water, from which they were separated by a layer of animal membrane. Certain acids, such as the hydrochloric, at very different degrees of den- sity, and nitric acid only at pretty high degrees of density, gave me an endosmosis, the current of which was directed from the inferior water towards the superior acid, so that the acid rose gradually in the tube of the endosmometer. On the other hand, I had always found the sulphuric acid pretty largely diluted, and the hydrosulphuric acid, under the same circum- i stances as the acids mentioned above, gradually to sink in the tube of the endosmometer. I con- cluded from this that these acids did not occasion any endosmosis, and that they passed mechani- cally, and merely in virtue of their gravity, athwart the animal membrane to mingle with the water. 1 had also found that the sulphuric ENDOSMOSIS. 105 and hydrosulphuric acids, added to gum-water, deprived it of the faculty of producing endos- mosis, and that this acidulated water fell in the tube of the endosmometer, instead of rising, as simple gum-water constantly does. These facts induced me to say metaphorically that the sul- phuric and hydrosulphuric acids were the ene- mies of endosmosis. More recent inquiries have enabled me to see the above mentioned phenomena in ano- ther light. It was the oxalic acid which led me to the conclusions I shall now lay be- fore the reader. Having poured a solution of this acid into the endosmometer closed with a piece of bladder, and placed the re- servoir in water, I found the acid fluid sink rapidly in the tube, and flow towards the inferior water, making its way by filtration through the animal membrane. I then reversed the arrangement observed in this experi- ment. I filled the endosmometer with water, and plunged the reservoir into a solution of oxalic acid. I was now surprised to find the water making its way rapidly into the endos- mometer, and the eolumn rising in the tube, so that, in opposition to all I had yet observed, here was the current of endosmosis directed from the acid towards the water. The follow- ing are the particulars of this experiment. Having poured some rain-water into the reser- voir of the endosmometer, I plunged the reser- voir, closed with a piece of bladder, into a so- lution of oxalic acid of the density of 1.045, (11.6 parts of crystallized acid in 100 of the solution,) the temperature being + 25 cent. The ascent of the water in the tube of the en- dosmometer lasted for three days, becoming gradually slower and slower. The ascent hav- ing then become almost imperceptible, I emp- tied the endosmometer, in the contents of which I found water charged with oxalic acid. The exterior fluid was reduced in density to 1.033, so that, whilst the lower acid had pene- trated the upper water by endosmosis, the water had penetrated the acid by exosmosis, and thus diminished its density ; the permea- tion of the water, however, had been less con- siderable than that of the acid ; so that the upper water, increased in volume, had risen in the tube of the endosmometer. We have thus, in the present instance, another obvious proof of the existence of two opposite and unequal currents. Having filled the reservoir of the en- dosmometer anew with rain-water, I placed it in the solution of oxalic acid already used, and of the reduced density of 1.033. The ascent in the tube which again occurred, having almost ceased at the end of two days, I tested the fluid in the endosmometer, and found it to con- tain oxalic acid, and discovered the density of the external fluid further reduced to 1.025. I re- peated the same experiment a third time, filling the reservoir of the endosmometer with rain- water, and plunging it in the old acid solution. Endosmosis went on as before, but with less celerity. Having given up the experiment, after the lapse of twenty-four hours I found the density of the exterior fluid now reduced to 1.023, and the internal fluid to contain a por- tion of oxalic acid as before. I reduced the density of the exterior acid solution to 1.01, but the included water still gave evidence of a pretty active endosmosis. I reduced the den- sity of the acid to 1.005, (1.2 of acid to 100 of the solution,) and the endosmosis was still very remarkable. In these experiments I found that the endosmosis was by so much the more rapid as the exterior acid solution was more dense, so that the capacity of oxalic acid to permeate an animal membrane would appear to increase with the density of its solution in water. In these experiments, too, we observe a fluid, more dense than water, and having a less power of capillary ascent than it, never- theless forming the stronger current, or current of endosmosis, whilst the water opposed to this fluid forms the weaker current, or counter-cur- rent of exosmosis. This is in opposition to all I had observed before ; and the theory I had raised on the different capacities of capillary ascent possessed by two opposed fluids is con- sequently shaken, or at all events proved to be no longer generally applicable. What may be the cause of this new phenomenon ? Do animal membranes give passage more readily through their meshes to solutions of oxalic acid than to water ? This point I sought to determine by the following experiments. The filtration of a fluid, by virtue of its gra- vity, through a porous lamina, the capillary canals of which are very minute, is not readily appreciable, unless the inferior or outer surface of this porous plate is kept plunged in or moistened by the same fluid. It is in this way only that the filtration of fluids through animal membranes, the texture of which is dense (a piece of bladder for example,) becomes appre- ciable. It is essential that the inferior aspect of the membrane be bathed with the same fluid as that which rests on its superior aspect, in order that no foreign cause modify its filtration. We know in fact that the heterogeneousness of two fluids, by producing endosmosis, would completely mask the effects of simple filtration. Would I, then, try the filtration of. water through a membrane, I apply this membrane to an en- dosmometer, which I fill with water to a certain height in the tube of the instrument; I next apply the lower surface of this membrane to the surface of a body of water placed below it. The water contained in the endosmometer filters through the membrane and mingles with the water in the vessel below ; the amount of this filtration in a given time is indicated by the fall of the column in the graduated tube of the instrument. Would I essay comparatively the filtration of any watery solution, I place this solution in the same endosmometer, and taking care to keep the exterior of the membranous part of the instrument in contact with a solution of the same nature, situated below it, I observe the degree to which the depression of the co- lumn in the tube takes place in a space of time equal to that which was taken by the filtration of the water. It is necessary to begin by proving the filtration of water; after this the filtration of the watery solution may be tried ; but it is always to be borne in mind that the 106 ENDOSMOSIS. membrane of the endosmometer must have been kept plunged in the watery solution about to be experimented on for at least a quarter of an hour, in order that it may become tho- roughly impregnated with the solution, and to secure that this should take the place of the water which the membrane had formerly con- tained in its pores. Without this measure of precaution, the results of the second experi- ment would be faulty. It is also indispensa- ble that the circumstances under which the two experiments are performed are in all re- spects exactly alike. It was in this way that I proceeded to ascertain comparatively the capa- city of filtration of water to that of a watery solution of oxalic acid through a piece of blad- der. I found that the filtrating power of rain- water, at the temperature of + 21 cent, being denoted by 24, the filtrating power of a watery solution of oxalic acid of no greater density than 1.005, (1.2 of acid to 100 of solution,) was denoted by 12. A solution of the same acid, of thedensity of 1.01, being tried, its filtrating power was found to be represented by 9. By these ex- periments it is therefore proved that water tra- verses an animal membrane more readily than a solution of oxalic acid. Why then does the latter solution traverse an animal membrane more readily and in greater quantity than water, when it is water which is in contact with the surface of the membrane opposite to that which is in contact with the acid ? This is a question which I find it impossible to answer in the present state of our knowledge. The discovery of this singular property of the oxalic acid to cause the endosmotic current to flow towards the water when separated from the latter fluid by a lamina of animal mem- brane, led me to imagine that all the acids would be found to possess a similar property. And this I ascertained, in the first instance, to be the case in regard to the tartaric and citric acids. Both of these acids are much more so- luble in water than oxalic acid. The saturated solution of oxalic acid at -{- 25 cent, has no higher a density than 1.045 (11.6 acid to 100 of the solution.) But the solubility of the tar- taric and citric acids is such that their watery solutions may have a density of far greater amount. I tried the endosmotic effects of the tartaric and citric acids in watery solution of various density, and I discovered, not without surprise, that very dense solutions of them and solutions of inferior density exhibited endos- motic phenomena in inverse ratios. Thus, when a solution of tartaric acid was of a den- sity above 1.05, (11 crystallized acid in 100 of solution,) and it was divided from water by an animal membrane, the temperature being + 25 cent, the endosmotic current is directed from the water towards the acid ; but when, under the same circumstances, the density of the acid solution is below 1.05, the current of endos- mosis is directed from the acid towards the water, just as we have found it to be with refe- rence to the oxalic acid. Consequently, ac- cording to its greater or less density, tartaric acid presents the phenomenon of endosmosis in two opposite directions. At the mean density of 1.05, at a temperature of + 25° cent, it exhibits no obvious endosmotic phenomena whatever ; not that there is not reciprocal pe- netration between the acid and the water, which are divided by the animal membrane ; but this reciprocal penetration takes place so equally on either side, that there is no increase of bulk of the one fluid at the cost of the other — there is no endosmosis. The citric acid exhibits pre- cisely the same phenomena ; the point of mean density, which divides its two opposed endos- motic capacities, is also very nearly the same, namely, 1 .05 at a temperature of -j- 25° cent. These facts induced me to imagine that if the oxalic acid alone presented the endosmotic cur- rent directed from the acid towards the water, this arose from the fact of its solution at + 25° cent, falling short of the density necessary to permit the acid solution to cause the endosmo- tic current to flow from the water towards the acid. The preceding observations were made during the heats of summer. The centigrade thermo- meter was standing at + 25° when I determined the mean term of density of the solution of tar- taric acid, above and short of which the endos- mosis happening between this solution and water is directed towards the acid. It was of importance to know whether a depression of temperature would cause any modification in these phenomena. I therefore repeated the same experiments when the temperature was -f- 15° cent, and I was astonished to find that the mean term of density , of which we have spoken above, was considerably altered, being made to move in the direction of the increase of density of the acid solution. Thus the mean term of density being 1.05, (11 crystallized acid to 100 solution,) at a temperature of -f- 25° cent, it came to be 1.1, (21 acid to 100 solu- tion,) at a temperature of + 15° of the same scale ; that is to say, the solution of tartaric acid, which now occupies the mean term, con- ; tains nearly twice as much acid as the solution which stood at the previous mean term, when the temperature was ten degrees of the centi- grade scale higher. This first essay was enough to lead to the inference that the mean term of 1 density, which we are now discussing, would undergo further alterations in the same sense with further depressions of temperature; and this was actually found to be the case. At a temperature of 8-g° cent, the solution of tarta- ric acid, of the density 1.1, was no longer the solution of mean density dividing the two op- posed endosmotic currents, as it was when the temperature was + 15° cent. This solution then caused the endosmotic current to flow freely towards the water. I had to increase its density to 1.15 (30 acid to 100 solution) to come to the new mean term, beyond which the current of endosmosis was directed towards the acid, and within which it was directed towards the water. W ith the temperature depressed to a quarter of a degree cent, above zero, the solution of tartaric acid, of the density of 1.15, no longer presented the mean term; this solution now occasioned endosmosis towards the water, which indicated that the mean term was to be ENDOSJVIOSIS. 107 sought for in a more dense solution of tartaric acid, and this I actually found in a solution of the density of 1.21 (40 acid to 100 solution). Every solution of this acid of greater density than 1.21, at the temperature of £th of a degree above zero cent caused the endosmotic cur- rent to flow from the water towards the acid, and every solution of the same acid, under the density of 1.21, caused the endosmotic current from the acid towards the water. From all these experiments it follows that a fall of tem- perature favours the endosmosis towards the water, and that a rise of temperature favours the endosmosis towards the acid. In fact, the same solution of tartaric acid occasions at one time endosmosis towards the acid, when the temperature is high ; at another, endosmosis towards the water when the temperature is re- latively low. It would appear from this, that a depression of temperature renders the solu- tion of tartaric acid more apt than water to permeate animal membranes, and that there is a certain concordance between this capacity of permeation and the temperature and the den- sity of the acid solution. This phenonemon, at first sight, appears analogous to that which M. Girard discovered,* in regard to the com- parative flow of a solution of nitre and of pure water through a capillary glass tube. M. Girard found that, at a temperature of -f* 1 0°, a solu- tion of one part of nitrate of potash in three parts of water flows more rapidly than pure water through a capillary glass tube, whilst the same solution flows more slowly than water when the temperature is above -(- 16°. To discover whether this apparent analogy was well founded or not, I made an experiment to ascertain the relative duration of the flow through a capillary glass tube of a given mea- sure of pure water, and a like measure of a solution of tartaric acid, the density of which was 1.05 (21.8 parts acid, 100 solution.) The temperature being + 7° cent. I found that fifteen centilitres of water flowed through a ca- pillary glass tube in 157 seconds; but the same quantity of the solution of tartaric acid required 301 seconds to pass through the same capillary tube. There is consequently no ac- tual analogy to be established between the re- sults of the experiments of M. Girard and the fact of the endosmosis towards the water, which takes place when at a temperature of +7° cent, a solution of tartaric acid of the den- sity of 1.105, is separated from a volume of pure water by a piece of an animal membrane. It may be as well if I here state that when a solution of one part of nitrate of potash in three parts of water was separated by a piece of bladder from pure water, I have always ob- served the endosmotic current directed towards the solution ; the temperature might be at zero, or + 10°, or higher, the same phenome- non always occurred. This is sufficient to prove that endosmosis is governed by laws en- tirely different from those that preside over simple capillary filtration. I add, that the solution of tartaric acid, of 1.105 density, hav- ' Mem. de l’Acad. des Sciences, 1816. ing a viscidity nearly the double of that of water, and passing, nevertheless, by endosmo- sis into the latter fluid, when it is separated from it by an animal membrane, and the tem- perature is + 7“ cent, also proves that endos- mosis does not generally depend on the visci- dity of fluids. Acid solutions are the only fluids which have yet been found to occasion the endosmotic cur- rent to flow towards water when separated from this fluid by an animal membrane. The whole of the acids, without exception, exhibit this phenomenon, which was long overlooked by me, from its having been confounded with another phenomenon, namely, the abolition of endosmosis. I have in fact shown, in a work already before the public,* that all fluids which act chemically on the membrane of the endos- mometer, put an end, with greater or less cele- rity, to the phenomenon of endosmosis, — it goes on for some time, but it never fails to cease at length. Sulphuric acid, above all the other acids, has the property of putting an end to endosmosis. This acid, poured into the en- dosmometer, sinks by virtue of its simple gravity towards the lower water, filtering mechanically through the membrane placed between it and the water. If the position of the two fluids be reversed, the endosmometer being charged with water, and the sulphuric acid placed externally and on the lower level, the water still sinks to- wards the acid, passing in its turn mechani- cally through the membranous septum of the instrument, rendered incapable of effecting en- dosmosis. From these experiments I was led at first to conclude that sulphuric acid was in- active as regards endosmosis ; in other words, was incapable of exhibiting or producing this phenomenon. I have since found, however, that the sulphuric, like all the other acids, has the faculty of exerting endosmosis in the two opposite directions, but always during a very brief space of time only. Thus the tempera- ture being -f- 10° cent., sulphuric acid, of the density of 1.093, separated from water by a piece of bladder, the endosmotic current is directed from the water towards the acid, but the phenomenon lasts only for a short time ; the current soon ceases, and if the acid be on the higher level, it then begins to sink by sim- ple mechanical filtration towards the water. At the same temperature of + 10° cent., the sulphuric acid attenuated to 1.054 being placed in the endosmometer, and the reservoir and a part of the tube being plunged in water, en- dosmosis is established, but in this case the current is from the acid towards the water, so that the acid liquor sinks in the tube ; and that this sinking is due to endosmosis is demon- strated by the fact of the acid continuing to sink in the tube of the endosmometer a consi- derable way below the level of the external water, and not stopping short when the level is obtained, as it does when the descent is owing to simple mechanical filtration. In this expe- riment, as in the one detailed immediately be- * Nouv. Reeherches sur l’Endosmose, &c. p. 25. See also my Memoir in the 49th vol. of the Annales de Chimie, p. 415. 108 ENDOSMOSIS. fore it, the endosmosis towards the water is abolished, and then the column in the endos- mometer begins to rise again slowly, until the level of the external and included fluids corre- spond. We, therefore, see that at a tempera- ture of + 10° cent., sulphuric acid, of the density of 1.093, presents the current of endos- mosis from the water towards the acid ; whilst the density being 1.054, the endosmosis is from the acid towards the water. Between these two opposite endosmotic currents there necessarily exists a mean when no phenomena of the kind occur. This mean, the tempera- ture continuing -|- 10°, I find to belong to sul- phuric acid of the density of 1.07. The two fluids, divided by the animal membrane of the endosmometer, penetrate one another athwart the septum reciprocally and in equal measure, so that the contents of the endosmometer re- main for a certain time at the same height in the tube of the instrument; subsequently the contained fluid begins to sink in consequence of the cessation of all endosmosis. These ex- periments were necessarily undertaken when the temperature was moderate or low ; the phenomena detailed would not else have been appreciable ; for in a warm atmosphere the abolition of endosmosis by sulphuric acid is accomplished so rapidly, that it is with diffi- culty the slight current established in the first instance can be observed. Sulphurous acid, of the density 1.02, sepa- rated from water by an animal membrane, only exhibits endosmosis towards the water ; this endosmosis is pretty active at first ; but after the lapse of a brief interval the current ceases, just as it does with the sulphuric acid. These results I came to after a number of experi- ments, the temperature being at one time + 5°, and at another + 25° cent. Formerly I regarded tire hydrosulphuric acid as inactive in regard to endosmosis ; I assimi- lated it, in this respect, with the sulphuric acid. The feet, however, is that, like the sulphuric acid, it has the property of producing endos- mosis. The acid I employed was of the den- sity of 1.00628. With a piece of bladder be- tween this acid and water, the endosmosis was constantly towards the water. This conclusion was not influenced by variations of tempera- ture between -j- 4° and -f 25° cent. The ac- tion was somewhat protracted, but the endos- mosis never failed to cease after a certain time, as in the case of the sulphuric acid. The nitric acid of considerable density exhi- bits endosmosis towards the acid when sepa- rated from water by a piece of animal mem- brane. Thus, at a temperature of + 10° cent, this acid (density 1.12 or higher) presents the current flowing towards the acid. Under the same circumstances, but of the density of 1.08, the endosmosis is towards the water. Of the density 1 .09, the mean term between the two opposite endosmoses is obtained. At higher temperatures the nitric acid very speedily puts an end to the phenomena of endosmosis, espe- cially when its density is not very high, so that it becomes difficult to perceive the very tran- sient currents produced in the first instance- The hydrochloric is the most potent of all the mineral acids in directing the current of endosmosis from the water towards the acid. Its density must be considerably reduced before it offers the direction of the current changed, or from the acid towards the water. At a tempe- rature of + 22° cent, for instance, the hydro- chloric acid has to be brought, by the addition of water, to a density no higher than 1.003, before it presents the endosmosis flowing to- wards the water, from which, as understood, it is divided by a layer of animal membrane. Of greater density the endosmosis is towards the acid. When the temperature is lower than + 22°, the same acid, of greater density, ac- quires the property of causing endosmosis to- wards the water. Thus, with the centigrade thermometer at -f- 10°, I found that hydro- chloric acid of 1.017 density presented the mean term between the two opposite endosmo- ses. At the same temperature hydrochloric acid, of 1 .02 density, presented endosmosis to- wards the acid, and of 1.015 density, endos- mosis towards the water. Under a higher temperature, however, and of the latter density (1.015), the endosmosis was towards the water, so that a depression of 12° cent, in tem- perature causes the mean term of the density of hydrochloric acid, which separates the two op- posed endosmoses, to rise from that of about 1.003 to that of 1.027; that is to say, the quantity of acid added to the water must be increased almost six-fold to produce the same effects. In the present state of our knowledge, we find it quite impossible to give any explanation of the remarkable phenomenon exhibited in the changes of direction of the endosmotic currents according to the degree of density of the acid and the temperature. The singularity of this phenomenon will appear the greater when the following observation is taken into the account. Hitherto it was always by a layer of animal membrane that I separated the acid from the water. Instead of the animal membrane I now tried the effect of one of vegetable origin. We have seen above that oxalic acid, whatever its density and under whatever temperature, when separated from water by an animal mem- brane, always exhibited endosmosis from the acid towards the water. I filled a pod of the colutea arborescens, which being opened at one end only and forming a little bag, was readily attached by means of a ligature to a glass tube, with a solution of oxalic acid, and having plunged it into rain-water, endosmosis was ma- nifested by the ascent of the contained acid fluid in the tube ; that is to say, the current flowed from the water towards the acid. The lower part of the leek ( allium por rum) is en- veloped or sheathed by the tubular petioles of the leaves. By slitting these cylindrical tubes down one side, vegetable membranous webs, of sufficient breadth and strength to be tied upon the reservoir of an endosmometer, are readily obtained. An endosmometer, fitted with one of these vegetable membranes, having been filled with a solution of oxalic acid, and then plunged into rain-water, the included fluid rose ENDOSMOSIS. 109 gradually in the tube of the endosmometer, so that the endosmosis was from the water towards the acid, the reverse of that which takes place when the endosmometer is furnished with an animal membrane. The tartaric and citric acids of densities below 1.05, and at a tempe- rature of + 25° cent, exhibit endosmosis to- wards the water with an animal membrane ; but with a vegetable membrane the case is altered ; the endosmosis being then directed from the water towards the acid. I have tried solutions of tartaric acid, decreasing gradually in density from 1.05 (11 tartaric acid to 100 solution) to a density so low as 1.0004, (1 tar- taric acid, 1000 solution,) and always seen the endosmosis towards the acid. A gradual fall in the temperature from -j- 25° to near zero did not affect the result. Sulphuric acid of 1.0274 density and at a temperature of + 4° centes. when separated from water by a vegetable membrane, exhibited endosmosis towards the acid ; separated by an animal membrane, however, the endosmosis was towards the water. Hydrosulphuric acid (density 1.00628) sepa- rated from water by an animal membrane, always shows endosmosis towards the water ; but separated by a vegetable membrane, the current is as uniformly towards the acid. The experiment from which I deduce this result was only performed at a temperature of -(- 5°. Sulphurous acid (density 1.02) separated from water by an animal membrane, exhibits an active endosmosis towards the water, at every temperature from zero up to -f- 25° centes. (I have made no experiments on endosmosis at higher temperatures.) When sulphurous acid, of the density of 1 .02, is separated from water by a layer of vegetable membrane, it presents neither endosmosis towards the acid nor endos- mosis towards the water ; it then appears to be under the influence of the simple laws presiding over the flow of fluids by filtration : there is abolition of endosmosis. I was anxious to see vvliat endosmotic effects it would produce with an endosmometer closed with a layer of baked clay, and it was not without surprise that I saw the current flowing vigorously towards the water. I had put the acid into the reservoir of the endosmometer; and the included fluid rose to a considerable height in the tube of the in- strument, which I had taken care to immerse in water to the place where the acid rose in the tube. The acid continued to sink in the tube of the endosmometer for four hours, and had then fallen to about 12 centimetres below the level of the external water ; it subsequently be- gan to rise slowly in the tube, and finally gained the level of the external water, where it remained. It was obvious that the sulphurous acid had sunk in the tube below the level of the water, in consequence of endosmosis towards the water, and that its subsequent rise to the level of the water was due to simple filtration through the membrane. Endosmosis had then ceased. Sulphuric acid, diluted with water to the den- sity of 1.0549, exhibits the same phenomena as sulphurous acid when separated from water by a lamina of baked clay : it first occasions en- dosmosis towards the water, but after some minutes this endosmosis ceases, and is not re- placed by endosmosis of an opposite nature ; simple filtration from the effect of gravity is all that then takes place; endosmosis of each kind is put a stop to. Hydrosulphuric acid, sepa- rated from water by a lamina of baked clay, gives the same results precisely as the sulphu- ric acid. This phenomenon is rendered still more strange by the fact of its not being general. Thus the oxalic acid exhibits endosmosis to- wards the acid when this is separated from water by a lamina of baked clay. This fact I ascertained under a variety of temperatures from + 4° to + 25° centes. and with solutions of the acid of as great density as could be ob- tained at each temperature, as well as with so- lutions of very low density. The tartaric acid also presents endosmosis towards the acid when separated from water by a lamina of baked clay. I had formerly found* that a little sul- phuric or hydrosulphuric acid added to gum- water, causes the current of endosmosis to cease flowing from the water towards the gum-water, so that the latter fluid, instead of rising in the tube of the endosmometer, begins gradually to fall. I then attributed this phenomenon to the abolition of endosmosis ; but it is evident that in certain cases it is owing to the current of en- dosmosis changing its direction and flowing from the acid towards the water. Thus, with reference to the acidulated gum-water, of which I have just spoken, when placed above water, from which it was separated by an animal membrane, it fell in the stem of the endosmo- meter and flowed towards the water, either from the abolition of endosmosis, and in virtue of its gravity, or in consequence of the establishment of an endosmotic current towards the external water. Experiment can alone determine which of these two causes is the efficient one of the descent of the acidulated fluid in the stem of the endosmometer. The whole of the acids used of such density as comports with the pro- duction of endosmosis towards water, and in sufficient quantity, are adequate to overcome the disposition which any fluid may possess to produce endosmosis in the opposite direction. Here is a case in illustration of this point. The power of sugar-water in causing endosmosis is very great, as I have shown already. Water holding no more than one-sixteenth of its weight of sugar in solution causes rapid endos- mosis from the water towards the solution. But I have found that, by adding to this sweet liquid a quantity of oxalic acid equal in weight to that of the sugar which it holds in solution, the direction of the endosmotic current is im- mediately changed ; the flow is no longer from the water towards the solution, but from the sweet-sour solution towards the water, so that the oxalic acid may be said to compel the sac- charine solution to which it is added to take the direction of the endosmotic current which is proper to it. Here it is the viscid and dense fluid, with little power of capillary ascent, which traverses the animal membrane with * Nouv. Rech. sur l’Endosmose, p. 8. 110 ENDOSMOSIS. greater ease and more rapidity than pure water. This may be added to the facts set forth already to prove, in the most decided manner, that the greater power of permeation manifested by one of the two fluids in experiments on endosmosis does not follow from any greater viscidity it may possess than the fluid opposed to it. In sixteen parts of water I dissolved two parts of sugar and one part of oxalic acid. In this so- lution I plunged the reservoir of an endosmo- meter, closed with a piece of bladder, and filled with pure water : this did not show any diffe- rence of level in the tube during the two hours that I continued the experiment. There was consequently no endosmosis. Nevertheless, I found that the water contained in the endosmo- meter contained a large quantity of oxalic acid, whether tested by the addition of lime-water or by the palate, which last also detected the presence of sugar. Thus the sweet-sour fluid, exterior to the endosmometer, had penetrated the water contained within its cavity. If this circumstance was proclaimed by no increase in the volume of the water, this undoubtedly was owing to the included water having lost by the descending counter-current an amount exactly equal to the amount it had gained by the in- ward or ascending current. There was no en- dosmosis in the sense in which I use that word, although it is certain that there were two active antagonist currents athwart the membrane which separated the two fluids. It must not be lost sight of that I only give the title of endosmosis to a stronger current opposed to a weaker counter-current, antagonists to each other, and proceeding simultaneously athwart the septum, dividing the two fluids which are made the subjects of experiment. The instant these two antagonist currents become equal, there is no accumulation of fluid on one side, and there is then no longer any effort at dilatation or im- pulsion; in a word, there is no longer any endosmosis. The opposite directions in which the endos- mosis towards water, effected by acids of deter- minate density, and the endosmosis from water occasioned by other fluids, would lead us to conclude that in placing such a fluid as gum- water or sugar-water in an endosmometer fur- nished with an animal membrane, and in con- tact externally with an acid solution of appro- priate density, we should have a much more rapid endosmosis towards the included fluid than if it were pure water in which the endos- mometer was plunged ; and this in fact is what I have found to be the case by experiment. Into an endosmometer, closed with a piece of bladder, I poured a solution of five parts of sugar in twenty-four parts of water. Having plunged the reservoir of the instrument into water, I obtained in the course of an hour an ascent of the included fluid, which may be re- presented by the number 9. The reservoir of the same endosmometer filled with a portion of the same saccharine solution, having been plunged into a solution of oxalic acid, the den- sity of which was 1.014, (3.2 parts acid to 100 solution,) I obtained in the course of an hour an ascent of the included fluid, which required to be represented by the number 27. The substitution of a solution of oxalic acid for pure water consequently caused the amount of endosmosis in the same interval of time to be tripled. 1 obtained like results with the tarta- ric and citric acids, employed of the densities required to enable them to produce endosmosis towards water. From these experiments it would appear that water, charged with a small proportion of one of the acids, of which men- tion has been made, possesses a power of pene- tration athwart animal membranes greater than that inherent in pure water. But a direct ex- periment, detailed in an earlier part of this paper, proves that this is not the case; pure water used by itself is still the fluid that pos- sesses the greatest power of penetrating through animal membranes. If, consequently, in those experiments which I have last described, the water charged with acid passed more readily and more copiously into the saccharine solu- tion than pure water, this happens undoubtedly from other causes or conditions which I cannot take upon me to explain, but which appear to be : 1st. A reciprocal action between the two heterogeneous fluids, an action which modifies, which even completely inverts the natural power of penetration possessed by each of the fluids when employed singly ; 2d. Aparticular action of the membrane upon the two fluids which penetrate it, an action which, with the animal membrane, gives the stronger current or current of endosmosis to the acid solution of due density, and the weaker current or coun- ter-current of exosmosis to the pure water. It seems to me impossible to deny this peculiar action to the animal membrane, when we see that a vegetable membrane in the same circum- stances produces endosmotic phenomena di- rectly the reverse. The peculiar influence of the membranous septum is likewise manifested in a very striking way in the experiment in which I have shown that the current of endos- mosis flows from water towards alcohol when these two fluids are divided by an animal membrane, and, on the contrary, that the cur- rent of endosmosis flows from alcohol towards water when the two fluids are separated by a membranous septum of caoutchouc. Endosmosis, in the present order of things, is a phenomenon restricted to the realm of or- ganization ; it is nowhere observed in the inor- ganic world. It is in fact only among organ- ized beings that we observe fluids of different density separated by thin septa and capillary pores ; we meet with nothing of the same kind among inorganic bodies. Endosmosis, then, is a physical phenomenon inherent exclusively in organic bodies, and observation teaches us that this phenomenon plays a part of the high- est importance in their economy. It is among vegetables especially that the importance of the phenomenon strikes us ; I have, in fact, de- monstrated that it is to endosmosis that are due, in great part, the motions of the sap, and particularly its very energetic ascending motion. I have also shown that all the spontaneous mo- tions of vegetables are referable to endosmosis. The organic vegetable tissue is composed of a ENTOZOA. Ill multitude of agglomerated cells mingled with tubes. The whole of these hollow organs, the parietes of which are extremely thin, and which contain fluids the densities of which vary, ne- cessarily make mutual exchanges of their con- tents by way of endosmosis and exosmosis. Nor can we suppose but that the same pheno- mena take place among the various cells and cavities exhibited by the organism of animals. But the effects of endosmosis, its influence on the physiological phenomena presented by ani- mals, has yet to be determined ; and here, un- doubtedly, the physiologist has an ample field before him for inquiry. I shall only say in conclusion, and with reference to this very in- teresting part of the subject, that I have satis- fied myself that it is to endosmosis that the motions of the well-known spiral spring tubes of the milt of the cuttle-fish, when put into water, are owing. ( H. Dutrocliet.) ENTOZOA, (s»to?, intus, ^uov, animal,) sTuzoSe; crTgoyyvXoi, eX^oOe? rr'ha.'rna.i, aanct- Arist. et Antiq. Vers Intestinaux, Cuv. Entelmintha, Splanchnelmintha, Zeder. The term Entozoa, like the term Infusoria, is indicative of a series of animals, associated together chiefly in consequence of a similarity of local habitation ; which in the present class is the internal parts of animals. In treating therefore of the organization of these parasites, we are compelled to consider them, not as a class of animals established on any common, exclusive, or intelligible cha- racters, but as the inhabitants of a peculiar dis- trict or country. They do not, indeed, present the types of so many distinct groups as those into which the naturalist finds it necessary to distribute the subjects of a local Fauna, yet they can as little be regarded as constituting one natural assem- blage in the system of Animated Nature. And it may be further observed that as the members of no single class of animals are con- fined to one particular country, so neither are the different natural groups of Entozoa exclu- sively represented by species parasitic in the interior of animal bodies. Few zoologists, we apprehend, would dissociate and place in sepa- rate classes, in any system professing to set forth the natural affinities of the animal king- dom, the Planaria from the Trematoda , or the Vibrionidce from the microscopic parasite of the human muscles. In the present article it is proposed to divide the various animals confounded together under the common term of Entozoa or Entelmintha into three primary groups or classes ; and, as in speaking of the traits of organization common to each, it becomes not only convenient but necessary to have terms for the groups so spoken of, they will be denominated Protel- mintha, Sterelminthu, and Ccdelmintha respec- tively. It may be observed that each of these groups, which here follow one another in the order of their respective superiority or com- plexity of organization, has been indicated, and more or less accurately defined by pre- vious zoologists. After the dismemberment of the Infusoria of Cuvier into the classes Polygastrica and Rot if era, which resulted from the researches of Professor Ehrenberg into the structure of these microscopic beings, there remained certain families of Animalcules which could not be definitely classed with either : these were the Cercariadte and Vibrio- nida. Mr. Pritchard, in his very useful work on Animalcules, has applied to the latter fa- mily the term Entozoa, from the analogy of their external form to the ordinary species of intestinal worms ; and it is somewhat singular that a species referrible to the Vibrionida should subsequently have been detected in the human body itself. Premising that the tribe Vibrionidte as at present constituted is by no means a natural group, and that some of the higher organized genera, as Anguillula, are re- ferrible to the highest rather than the lowest of the classes of Entozoa, we join the lower organ- ized genera, which have no distinct oviducts, and which, like the parasitic Trichina, resemble the foetal stage of the Nematoid worms, with the Cercariada, in which the generative apparatus is equally inconspicuous; and these families, dismembered from the Infusoria of Lamarck, constitute the class Protelmintha, the first or earliest forms of Entozoa. The second and third classes correspond to the two divisions of the class Intestinalia, in the ‘ Regne Animal’ of Cuvier, and which are there respectively denominated ‘ Vers Intesti- naux Parenchymateux,’ and ‘Vers Intestinaux Cavitaires.’ The characters of these classes will be fully considered hereafter; and in the mean- while but little apology seems necessary for in- venting names expressive of the leading distinc- tion of each group as Latin equivalents for the compound French phrases by which they have hitherto been designated. E fyov? appears to have been applied by the Greeks to the in- testinal worms generally, as Aristotle speaks of Efyuvfh; TrXaTEtai, intestinalia lata, and ttyurfiss ux^oyyv'ha.i, intestinalia teretia. In framing the terms Sterelmintha and Ccdelmin- tha, from Efyur; trre^ea, a solid or parenchy- matous worm, and e X/zo? koiXij, a hollow or cavitary worm, I follow the example of Zeder, and omit the aspirate letter. It may be ob- served by the way that Zeder’s term Splanchnel- mintha, besides including animals which are developed in other parts than the viscera, is, like the term Entozoa, open to the objection of being applied to a series of animals which, ac- cording to their organization, belong to distinct classes. The limits and object of the present article obviously forbid an extensive or very minute consideration of the anatomical details of each of these classes of animals, and we are com- pelled to confine ourselves almost exclusively to such illustrations of their respective plans of organization as are afforded by the species referrible to each which inhabit the human body. If a drop of the secretion of the testicle be expressed from the divided vas deferens in a recently killed mammiferous animal, which 112 ENTOZOA. lias arrived at maturity, and be diluted with a little pure tepid water and placed in the field of a microscope, a swarm of minute beings resembling tadpoles will be observed moving about with various degrees of velo- city, and in various directions, apparently by means of the inflexions of a filamentary caudal appendage. These are the seminal animalcules, Zoosperms, or Spermatozoa (jig. 51): and, as it is still undetermined whether they are to be regarded as analogous to the moving filaments of the pollen of plants, or as independent or- ganisms, it has been deemed more convenient to consider them zoographically in the present article as members of the class Entozoa. The body to which the tail is attached is of an oval and flattened or compressed form, so that, when viewed sideways, the Zoosperm appears to be a moving filament like a minute Vibrio. It is this compressed form of the body which principally distinguishes the Sper- matozoa or seminal Cercariec , from the true Cercaria of vegetable infusions, in which the body is ovoid or cylindrical ; the caudal ap- pendage of the Spermatozoa is also propor- tionally longer than in the Cercaria. In some species of the latter genus an oral aperture and ocelliform specks of an opake red colour have been observed on the anterior part of the body, and they manifest their sen- sibility to light by collecting towards the side of the vessel exposed to that influence. -In the Zoosperms, which are developed exclu- sively in the dark recesses of animal bodies, the simplest rudiments of a visual organ would be superfluous ; they are, in fact, devoid of ocelli, and even an oral aperture has not yet been detected in these simplest and most mi- nute of Entozoa. In neither the Zoosperms nor the Cere aria has the polygastric struc- ture been determined. On the contrary, some of the non-parasitic species, as the Cercaria Lemma, are stated to have ‘ a true alimen- tary canal, not polygastric.’ '* The Spermatozoa are not, however, the only examples of the present order of Protelmintha which have their habitat in the interior of living animals ; many of the Entozoa themselves have been observed to be infested by internal para- sites, which are referrible by their external form to the Cercariadte. Although no distinct organs of generation have been detected, there is reason to suspect that the Spermatozoa are oviparous : they are also stated to propagate by spontaneous fission ; the separation taking place between the disc of the body and the caudal appendage; each of which develope the part required to form a perfect whole. The Zoosperms of each genus of animals present differences of form or proportion, and frequently also differences of relative size as compared to the animal in which they are deve- loped ; thus, in the figures subjoined, which are all magnified in the same degree, the Zoosperm from the Rabbit is nearly as large as that from the Bull, (fig. 51.) * Pritchard’s Animalcules, p. 184. Fig. 51. Man. Bull. Rabbit. Sparrow. They appear to be formed in the seminal secretion under similar laws to those which pre- side over the develop- ment of other Entozoa in the mucous secretion of the Intestines, ike., but are more constant in their existence, and must there- fore be regarded as fulfil- ling some more important office in the economy of the animal in which they exist. They are not found in the seminal passages or glands until the full pe- riod of puberty ; and in some cases would seem to be periodically deve- loped. In the Hedgehog and Mole, which exhibit a periodical variation in the size of the testes in a well-marked degree, the Spermatozoa are not ob- servable in those glands during their state of quiescence and partial atrophy. Professor Wag- ner* examined the testes of different Passerine Birds in the winter sea- son, when those bodies are much diminished in size. (Seevol.i. p.354, fig. 183.) They then con- tained only granular sub- stances, without a trace of the Spermatozoa. When the same bodies were ex- amined in spring, they were found to contain spherical granules of dif- ferent sizes and appear- ances, (A, B, fig. 52,) which led to the suppo- sition that they were the ova of the Spermatozoa in different stages of deve- lopment, and capsules containing each a nume- rous group of Spermco- tozoa (C) were also pre- sent ; whence it would appear that many of these animalcules were deve- loped from a single ovum. In the semen contained in the vasa deferentiathe Spermatozoa (D) were in great numbers, having escaped from their cap- sules ; they exhibit a re- markable rotation on their * Muller’s Archiv. 1836, Development of Sper- P • 225. matozoa, Bunting. Silk-worm. Moth. Fig. 52. ENTOZOA. 113 axis, which continues for five or ten minutes after the death of the bird in which they are developed. Some have supposed that these animalcules were the result of a putrefactive process, but this is disproved by their presence in testicles which have been removed from living animals, and by their ceasing in fact to exist when the seminal secretion begins to undergo a decom- position. Their extraordinary number is such that a drop of semen appears as a moving mass, in which nothing can be distinguished until it has been diluted as before-mentioned, when the animalcules are seen to disengage them- selves and commence their undulatory move- ments. By means of the continual agitation thus produced the chemical elements of the fecundating fluid are probably kept in a due state of admixture. By the same movements the impregnating influence of the semen may be carried beyond the boundary which it reaches in the female organs from the expulsive actions of the coitus. It has been conjectured that from the rapid and extensive multiplication of these animalcules they may contribute to pro- duce the stimulus of the rut. But the con- sideration of the part which the Zoosperms may play in generation belongs to the Physio- logical history of that function, and would lead to discussions foreign to the present article, which treats of their form and structure simply as the parasites of animal bodies. In the human subject the form of the Zoo- sperm is accurately represented in fig. 51. Among the cold-blooded Reptiles the Zoo- sperms of the Frog (fig. 51) have been ex- amined with most attention, and have been the subject of interesting experiments in the hands of Spallanzani and Dumas. The milt or developed testicle of the osseous Fishes abounds with moving bodies of a glo- bular form. In the Shark and Ray the Zoo- sperms are of a linear and spiral form. The molluscous animals are favourable sub- jects for the examination of the present tribe of Entozoa on account of the great relative size of the parasites of the seminal secretion. They are mostly of a filamentary form, and have long been known in the Cephalopods. The Zoosperms of the Snail (Helix Pomatia) present an undulated capillary body, and move sufficiently slowly to permit their being readily followed by the eye. The Spermatozoa have been detected and described in the different classes of the Arti- culate Animals. In Insects they are of a fine capillary form, and are generally aggregated in bundles. They abound in the semen of the Anellides and Cirripeds; lastly, these parasites have been found to exist in vast numbers in the spermatic tubes of the higher organized En- tozoa themselves. The second tribe of Protelmintha includes those cylindrical, filiform, eel-like, microscopic Animalcules which abound in decayed vege- table paste, stale vinegar, &c. together with others which have attracted particular attention by the destructive waste caused by certain spe- cies which are parasitic on living vegetables. These animalcules are termed Vibrionidee from VOL. II. their darting or quivering motion. They differ from the polygastric Infusories, not only in the absence of internal stomachs but also of external cilia, which is inferred by their not exciting any currents when placed in coloured water. They present a higher grade of organi- zation than the Cercarian tribe in the presence of a straight alimentary canal, which is re- markably distinct in some of the higher forms of the group, as the Gordioides and Oxyu- roides of Bory St. Vincent. The higher organized Vibrion.es have distinct generative organs, and are ovo-viviparous. In the species of Vibrio which infests the grains of wheat and occasions the destructive disease called Ear-cockle or Purples, Mr. Bauer found the ova arranged between the alimentary canal and the integument, in a chaplet or moniliform oviduct which terminated by a bilabiate orifice at a little distance from the caudal extremity of the body. The ova are discharged at this orifice in strings of five or six, adhering to each other. Each egg is about ji^th of an inch long, and gLjth or g^jth in di- ameter: and they are sufficiently transparent to allow of the young worm being seen within : and the embryo, in about an hour and a half after the egg is laid, extricates itself from the egg-coverings. Of the numerous individuals examined by Mr. Bauer, not any exhibited external distinctions of sex, and he believes them to be hermaphrodites. In the Anguillula aceti, or common Vinegar- eel, Bory St. Vincent has distinguished indi- viduals in which a slender spiculum is pro- truded from the labiate orifice corresponding to that above described from which the ova are extruded ; these individuals he considers to be males; they are much less numerous than the females ; are considerably smaller ; and the internal chaplet of ova is not dis- cernible in them. In the female the ova are arranged in two series on each side of the alimentary canal, and the embryo worms are usually seen to escape from the egg-coverings while yet within the body of the parent, and to be born alive. Ehrenberg figures the two sexes of Anguillula fiuviatilis in his first trea- tise on the Infusoria (tab. vii. fig. 5.*) The granular testis and intromittent spiculum, which is single, are conspicuous in the male; the ova in the female are large and arranged as in Anguillula aceti. Such an organization, it is obvious, closely approximates these higher Vibrionidee to the nematoid Entozoa, as the Ascarides and Oxyuri, and further researches on this interesting group will doubtless lead to the dismemberment of the Oxyuroid family from the more simple Vibrionidee, as the genera Bacterium, Spirillum, and Vibrio, with which they are at present associated. To the group composed of the three last- named genera, the microscopic parasite of the human muscles, termed Trichina Spiralis, is referrible.f * Organisation, systematik und georaphisches Verhaltniss der Infusionthieschen, lb30. t Zool. Trans, vol. i. p. 315, and Zool. Pro- ceedings, for February, 1835. 114 ENTOZOA. This singular Entozoon I discovered in a portion of the muscles of a male subject, which was transmitted to me for examination, at the beginning of 1835, by Mr. Wormald, Demon- strator of Anatomy at St. Bartholomew’s Hos- pital, on account of a peculiar speckled ap- pearance of those parts. This state of the muscles had been noticed by that gentleman as an occasional but rare occurrence in subjects dissected at St. Bartholomew’s in several pre- vious years. The portion of muscle was beset with minute whitish specks, as represented in the subjoined cut (fig. 53) : and in fourteen subsequent instances which have Fig- 53. come to my knowledge of the presence of this entozoon in the human subject, the muscles have presented very similar appearances. The specks are produ- ced by the cysts con- taining the worm, and vary, as to their dis- tinctness, according to their degreesof opacity, whiteness, and hard- ness. The cysts are very readily detected by gently compressing a Cysts of the Trichina thin slice of theinfect- Spiralis in situ, natural ed muscle between two stxe • pieces of glass and ap- plying a magnifying power of an inch focus. They are of an elliptical figure, with the extremi- ties more or less attenuated, often unequally elongated, andalways moreopaque than thebody or intermediate part of the cyst, which is, in general, sufficiently transparent to shew that it contains a minute coiled-up worm. The cysts are always arranged with their long axis parallel to the course of the mus- cular fibres, which probably results from their yielding to the pressure of the contained worm, and becoming elongated at the two points where the separation of the muscular fasciculi most readily takes place, and offers least re- sistance ; and for the same reason one or both of the extremities of the cyst become from repeated pressure and irritation thicker and more opaque than the rest. That the adhesive process in the cellular tissue, to which I refer the for- mation of the cyst, was most active at the extremities of the cyst is also evinced by the closer adhesion which these parts have to the surroundingcellular tissue. The cysts measure generally about j'jth of an inch in their longitudinal, and ^thof an inch in their transverse diameters : like other cysts which are the result of the adhesive inflamma- tion, they have a rough exterior, and are of a laminated texture. Fig. 54. A separate Cyst of the Trichi- na. which is seen coiled up through the transparent coats , magni- The innermost layer (fig. 54), however, can sometimes be detached entire, like a distinct cyst, from the outer portion, and its contour is generally well marked when seen by trans- mitted light. By cutting off the extremity of the cyst, which may be done with a cataract needle or fine knife, and gently pressing on the opposite extremity, the Trichina and the granular secre- tion with which it is surrounded, will escape ; and it frequently starts out as soon as the cyst is opened. But this delicate operation requires some practice and familiarity with microsco- pical dissection, and many attempts may fail before the dissector succeeds in liberating the worm entire and uninjured. When first extracted, the Trichina is usually disposed in two or two and a half spiral coils : when straightened out (which is to be done with a pair of hooked needles, when the sur- rounding moisture is so far evaporated as that the adhesion of the middle of the worm to the glass it rests upon shall afford a due resistance to a pressure of the needle upon the extremi- ties), it measures ^th of an inch in length and T^th of an inch in diameter, and now requires for its satisfactory examination a magnifying power of at least 200 linear admeasurement. The worm (fig. 55) is cylindrical and fili- form, terminating obtusely at both extremities, which are of unequal sizes ; taper • ing towards one end for about one-fourth part of its length, but continuing of uniform diameter from that point to the opposite ex- tremity. Until lately it was only at the larger extremity that I have been able to distin- guish an indication of an orifice, and this is situated in many specimens in the centre of a transverse, bilabiate, linear mouth, («, fig. 54.) A recently extracted living worm, when ex- amined by a good achromatic instrument be- fore any evaporation of the surrounding fluid has affected the integument, presents a smooth transparent exterior skin, inclosing apparently a fine granular parenchyma. It is curious to watch the variety of deceptive appearances of a more complex organization which result from the wrinkling of the delicate integument. I have sometimes perceived what seemed to be a sacculated or spiral intestine ; and, as eva- poration proceeds, this has apparently been surrounded by minute tortuous tubes; but the fallacy of the latter appearance is easily de- tected. A structure, which 1 have found in more recent and better preserved specimens than those which were the subjects of my first description, is evidently real, and may pro- bably belong to the generative system of the Trichina ; it consists of a small rounded cluster of granules of a darker or more opaque nature than the rest of the body; it is situated about one-fifth of the length of the animal from the larger or anterior extremity, and extends about half-way across the body. Trichina spiralis magnified. ENTOZOA. 115 Dr. Arthur Farre, whose powers of patient and minute observation and practised skill with the microscope, are well known to those who have the pleasure of his acquaintance, discovered, by theexamination of recent Trichina; under favourable circumstances, that they pos- sess an intestinal canal with distinct parietes. He describes it as commencing at the large end of the worm, bounded by two parallel but slightly irregular lines for about one-fifth of the length of the body, and then assuming a sacculated structure which “ becomes gradually lost towards the smaller end where the canal assumes a zig-zag or perhaps spiral course, and at length terminates at the small end.”* In a recent examination of some Trichina from an aged male subject at St. Bartholomew’s Hospital, I perceived a transverse slit close to the small extremity on the concave side, which I regard as the anus. The muscles which are affected by the Tri- china are those of the voluntary class ; and the superficial ones are found to contain them in greater numbers than those which are deep- seated; the pectoralis major, latissimus dorsi, and other large flat muscles usually present them in great abundance. They have been detected in the muscles of the eye, and even in those belonging to the ossicles of the ear, and of whose actions we are wholly uncon- scious: they also occur in the diaphragm, in the muscles of the tongue, in those of the soft palate, in the constrictors of the pharynx, in the levator ani, in the external sphincter ani, and in the muscles of the urethra. But they have not yet been detected in the muscular tunic of the stomach and intestines, in the detrusor urinse, or in the heart. It is an inte- resting fact that all the muscles infested by the Trichina are characterized by the striated ap- pearance of the ultimate fasciculi : while the muscles of organic life, in which they are absent, have, with the exception of the heart, smooth fibres, not grouped into fasciculi, but reticularly united. From the instances of this parasitical affec- tion of the human body which have already been recorded, and from other unpublished cases in which I have examined the worms, it is evident that their presence in the system is unconnected with age, sex, or any particular form of disease. They have been found in the bodies of persons who have died of cancer of the penis; tubercles in the lungs; exhaustion of the vital powers by extensive external ul- ceration of the leg ; fever combined with tu- bercles in the lungs; aneurism of the aorta; sudden depression of the vital powers after a comminuted fracture of the humerus ; diar- rhoea. The cases which had occurred before the publication of the first description of this Eniozoon led me to conceive that, although the species was of so minute a size, yet the num- ber of individuals infesting the body was so immense, and their distribution through the muscular system so extensive, that they might * See Medical Gazette, December, 1835. occasion debility from the quantity of nutri- ment required for their support; and I ob- served “ that it was satisfactory to believe, that the Trichina are productive of no other con- sequences than debility of the muscular system; and it may be questioned how far they can be considered as a primary cause of debility, since an enfeebled state of the vital powers is the probable condition under which they are originally developed. No painful or incon- venient symptoms were present in any of the above-mentioned cases to lead the medical attendants to suspect the condition of the mus- cular system, which dissection afterwards dis- closed : and it is probable that in all cases the patient himself will be unconscious of the presence of the microscopic parasites which are enjoying their vitality at his expense.”* Since writing the above, a case has occurred in which the Trichinae were met with in the muscles of a man who was killed while in the apparent enjoyment of robust health by a frac- ture of the skull. I received portions of the muscles of the larynx of this individual from my friend Mr. Curling, Assistant-Surgeon to the London-Hospital, who has recorded the case in the Medical Gazette, and the worms were similar in every respect to those occurring in the diseased subjects. The deduction there- fore of the development of the Trichina being dependent on an enfeeblement of the vital powers is invalidated by this interesting ex- ample.f Leaving now the consideration of Entozoa, which from their minute size and organization would have ranked with the vast assemblage of animalcules which are collected under the head Infusoria in the Regne Animal, we come next to the consideration of the animals which form that scarcely less heterogeneous class, the Entozoa of Rudolphi. These are distributed by that Naturalist into five orders, which may be synthetically arranged and characterized as follows. Ordo I. Cystica, Rud. (jet/ern;, vesica.) Vermes vesiculares, Blasenwurmer, Cyst-worms or Hydatids. Char. Body flattened or rounded, conti- nued posteriorly into a cyst, which is sometimes common to many indivi- duals. Head provided with pits (ho- thria two or four) or suctorious pores (four), and with a circle of hooklels or with four unarmed or uncinated tentacles. No discernible organs of generation. Obs. This order is not a very natural one; the species composing it are closely allied to the Tape-worms in the structure of the head, and when this is combined with a jointed structure of the body, as in the Cyslicercus J'asciolaris common in the liver of Rats, the small caudal vesicle forms but a slight ground for a distinc- tion of ordinal importance. The Cystica of Rudolphi form part of the Order Tanioidea of Cuvier; and maybe regarded as representing * Zoological Transactions, voV, i. p. 315. t Zool. Trans, vol. i. p. 323. I 2 116 ENTOZOA. the immature states of the higher orders of Sterelmintha. Ordo II. Cestoidea, (xeo-to;, cingulum, sifrot;, forma.) Vermes tteniecformes, Bandwiirmer, Tape-worms. Char. Body elongated, flattened, soft, continuous, or articulated. Head either simply labiate, or provided with pits (bothria) or suctorious orifices (osculti suctoria ) either two or four in number, and sometimes with four retractile un- armed or uncinated tentacles. Andro- gynous generative organs. Obs. In this order Rudolphi includes the inarticulated Lignite, with simple heads un- provided with bothria or suckers; a conjunc- tion which detracts from the natural character of the group. Cuvier separates the Ligulte from the T tenia:, and they form exclusively his Order Cestoidea ; it must be observed, however, that the passage from the one to the other is rendered very gradual by the traces of bothria, and of generative organs which appear in the higher organized Ligulte found in the intestines of Birds ; and respecting which Rudolphi hazards the theory that they are the more simple Ligulte of Fishes, developed into a higher grade of structure by the warmth and abundant nutri- ment which they meet with in the intestines of Birds which have swallowed the Fishes infested by them. Ordo III. Trematoda, (y^npa., foramen, foraminosus.) Vermes suctorii, Saugwurmer, Fluke- worms. Char. Body soft, rounded, or flattened. Head indistinct, with a suctorious fo- ramen ; generally one or more suctorious cavities for adhesion in different parts of the body. Organs of both sexes in each individual. Obs. This very natural order includes, in the system of Cuvier, many species which do not infest other animals, but are found only in fresh waters ; these non-parasitic species form the greater part of the genus Planaria of Muller, (fig. 80.) Rudolphi, who seems to have sup- posed the Planarite to be of a more simple organization than they truly possess, approxi- mates them to the Ligulae or inarticulated Ces- toidea. Other naturalists, unwilling to asso- ciate the Planarite with the Entozoa, have placed them in the Class Anellida, but the absence of a ganglionic abdominal nervous chord, of a floating intestine, and of an anus, renders such an association very arbitrary. Ordo IV. Acajjthocepiiala, (uxavOa., spina, x£(pa.\vi, caput.) Vermes uncinuti, Hacken-wurmer, Hooked-worms. Char. Body elongated, round, sub-elas- tic. Head with a retractile proboscis armed with recurved spines, (Jig- 74.) Sexual Organs appropriated to distinct individuals, male and female. Obs. This natural group includes the most noxious of the internal parasites ; fortunately no species is known to infest the human body. They abound in the lower animals, and present great diversity of form, some being cylindrical and others sacciform. OrdoV. Nematoidea, ( vnp.a.,filum , mJo;, forma.) Vermes teretes, Rund-wiirmer. Round- worms. Char. Body elongated, rounded, elastic. Mouth variously organized according to the genera. A true intestinal canal terminating by a distinct anus. Sexes distinct. Ohs. The internal character which Rudolphi has introduced’in his definition of this Order,'* viz. that derived from the structure of the ali- mentary canal, its free course through the body, and its termination by a distinct anus at the extremity opposite the mouth, is one of much greater value than any of the external modifica- tions of the body which characterize the four preceding orders. It is, in fact, a trait of or- ganization which is accompanied by corre- sponding modifications of other important parts, more especially the nervous system. The Entozoa which manifest this higher type of structure form in the system of Cuvier a group equivalent to that which is constituted by the four other orders combined. The En- tozoa composing the first four orders above characterized have no distinct abdominal cavity or intestine, but the digestive function is carried on in canals without an anal outlet excavated in the parenchymatous substance of the body, and Cuvier accordingly denominates them the Vers intestinaux parenchymateux. The Ne- matoidea, with which Cuvier rightly associates the genus Pentastoma of Rudolphi, and also (but less naturally) the Vers rigidules of La- marck, or Epizoa, he denominates ‘ Vers intes- tinaux cavitaires.’ With respect to the Epizoa, or the external Lernaean parasites of Fishes, although they agree with the Nematoidea and all inferior Entozoa in the absence of distinct respiratory organs, yet the ciliated natatory members which they possess in the young state, and the exter- nal ovarian appendages of the adult, are cha- racters which raise them above the Entozoa as a distinct and higher class of animals, having intimate relations with the soft-skinned Sipho- nostomous Crustaceans. Limiting, then, the Cavitary Entozoa to the Nematoidea of Rudolphi, and the Genera Lin- guatula, Pentastoma, Porocephalus, and Syn- gamus, which, under the habit of Cestoid or Tremalode Worms, mask a higher grade of organization, we propose to regard them as a group equivalent to the Sterelmintha, and to retain for them the name of Ccdelmintha. The class of Entozoa thus constituted em- braces already the types of three different orders, of which one is formed by the Nema- toidea of Rudolphi, a second has been esta- blished by Diesing for the genus Pentastoma and its congeneric forms, under the name of * “ Corpus teres elasticum, tractus intestinalis hinc ore, illinc ano terminatus. Alia individua mascula, alia feminea.” — Synops. Entox. p. 3. ENTOZOA. nr Acanthotheca ; and the singular organization of the Syngumps of Siebold, presently to be described, clearly indicates the type of a third order of Cavitary Entozoa. As a short description has already been given of the species of Protelmintha which inhabit the human body, we shall proceed to notice those species belonging to the two di- visions of Entozoa above defined, which have a similar locality, before entering upon the organization of the class generally. The first and simplest parasite which de- mands our attention is the common globular Hydatid, which is frequently developed in the substance of the liver, kidney, or other abdo- minal viscera, and occasionally exists in prodi- gious numbers in dropsical cysts in the human subject. Considerable diversity of opinion still exists as to the nature of these ambiguous productions, to which Laennec first gave the name of Ace- phalocysts ; we shall nevertheless admit them into the category of human parasites, for reasons which are stated in the following descrip- tion. The Acephalocyst is an organized being, consisting of a globular bag, which is com- posed of condensed albuminous matter, of a laminated texture, and contains a limpid co- lourless fluid, with a little albuminous and a greater proportion of gelatinous substance. The properties by which we recognize the Acephalocyst as an independent or individual organized being are, first, growth, by intrinsic power of imbibition ; and, secondly, reproduc- tion of its species by gemmation. The young Acephalocysts are developed between the layers of the parent cyst, and thrown off either inter- nally or externally according to the species. As the best observers agree in stating that the Acephalocyst is impassive under the appli- cation of stimuli of any kind, and manifests no contractile power either partial or general, save such as evidently results from elasticity, in short, neither feels nor moves, it cannot, as the animal kingdom is at present characterized, be referred to that division of organic nature. It would then be a question how far its chemical composition forbids us to rank the Acephalocyst among vegetables. In this king- dom it would obviously take place next those simple and minute vesicles, which, in the aggregate, constitute the green matter of Priestly, ( Protococcus viridis, Agardh ;) or those equally simple but differently coloured Psychodiaria, which give rise to the red snow of the Arctic regions, ( Protococcus Ker- mesianus .) These “ first-born of Flora” con- sist in fact of a simple transparent cyst, and propagate their kind by gemmules developed from the external surface of the parent. Or shall we, from the accidental circum- stance of the Acephalocyst being developed in the interior of animal bodies, regard it, as Rudolphi would persuade, in the same light as an ulcer, or pustule, — as a mere morbid pro- duct? The reasons assigned by the learned Pro- fessor* do induce us to consider the Acephalo- cyst as a being far inferior in the scale of orga- nization to the Cysticercus ; but still not the less as an independent organized species, sharing its place of development and sphere of existence in common with the rest of the Entozoa. Acephulocystis endogena. Pill-box Hydatid of Hunter, (Jig. 56). This species is so called from the circum- stance of the gem- mules being detach- ed from the internal surface of the cyst, where they grow, and, in like man- ner, propagate then- kind, so that the successive genera- tions produce the appearance descri- bed by Hunter and other pathologists. The membrane of the cyst is thin, delicate, transparent, or with a certain pearly semi-opacity ; it tears readily and equally in every direction, and can, in large specimens, be separated into laminae. The phenomenon of endosmose is readily seen by placing the recent Acepha- locyst in a coloured liquid, little streams of which are gradually transmitted and mingle with the fluid of the parasite. The vesicles or gemmules, developed in the parietes of the cyst, may be observed of different sizes, some of microscopic dimensions, others of a line in diameter before they are cast off, see fig. 56, where a shows the laminated membrane, b the minute Acephalocysts developed between its layers. The Acephalocyst of the Ox and other Ru- minant Animals differs from that of the Hu- man Subject in excluding the gemmule from the external surface, whence the species is termed Acephulocystis exogena by Kuhl. Both kinds are contained in an adventitious cyst, com- posed of the condensed cellular substance of the organ in which they are developed. The Genus Echinococcus is admitted by Rudolphi into the Order Cystica, less on ac- count of the external globular cyst, which, like the Acephalocyst, is unprovided with a head or mouth, than from the structure of the minute bodies which it contains, and which are described as possessing the armed and suctorious head characteristic of the Ccenuri and Cysticerci. It must be ob- served that Rudolphij- does not ascribe this * Mihi, quidem, ea tandem hydatis animal vivum vocatur, quae vitam propriam degit uti Cys- ticerci, Ccenuri, &c. Quae autem organismi alieni C v. c. humani) particulnm efficit animal, me judice, dici nequit. Mortua non est, quamdiu organismi partem sistit, uti etiam ulcus, pustula, efflorescentia ; sed hasc ideo non sunt animalia. — • Synops. Entoz. p. 551. f Yermiculi globosi, subglobosi, obovati, obcor- dati, etc.; pro capite plus minus vel exserto vel retracto; postice mox obtusissimi, mox obtusi, mox acuti. Corona uncinulorwn, uti vidctur, duplex. Fig. 56. Acephalocystis endogena. 118 ENTOZOA. complicated structure to the vermiculi of the Human Echinococcus on his own authority, and speaks doubtfully respecting the coronet of hooklets and suctorious mouths of the ver- miculi contained in the cyst of the Echinococcus of the Sheep, Hog, &c. The Echinococcus hominis, (fig- 57,) which occurs in cysts in the liver, spleen, omen- tum, or mesentery, is composed ofan exter- nal yellow coriace- ous, sometimes crus- taceous tunic, and an internal transparent, firm, gelatinous membrane. The form of the contained ver- miculi is represented in the magnified view subjoined, (fig- 58,) taken from the Elminto- grafia humana of Delle Chiaje. Fig. 58. Muller'- has recently described a species of Echinococcus voided with the urine by a young man labouring under symptoms of renal disease. The tunic of the containing cyst was a thick white membrane, not naturally divided into laminae; the animalcules floating in the con- tained fluid presented a circle of hooklets and four obtuse processes round the head ; the pos- terior end of the body obtuse : some of them were inclosed in small vesicles floating in the large one ; others presented a filamentary pro- cess at their obtuse end, probably a connecting pedicle which had been broken through. Of the species entitled Echinococcus veteri- vorum we have carefully examined several in- dividuals soon after they were extracted from the recently-killed animal, (a sow, in which they existed in great abundance in cysts in the abdomen.) The containing cysts were com- posed of two layers, artificially separable, both of a gelatinous texture, nearly colourless and subtransparent, the external one being the firmest. The contained fluid was colourless and limpid, with a few granular bodies floating Oneida, suctoria quatuor ; an h cellulosa ) which occasionally infests the human subject, with an uncinated proboscis for adhering to and irritating, and four suctorious mouths for ab- sorbing the fluid secreted by, the adventitious cyst in which they are lodged. In the larger Cysticerci lateral canals may be traced from the suctorious pores extending down the body towards the terminal cyst, but they appear not to terminate in that cavity, the fluid of which is more probably the result of secretion or endosmosis. We cannot, however, partici- pate in the opinion of Rudolphi,* that the retracted head derives nutriment from the surrounding fluid of the caudal vesicle, for if that were the case, where would be the neces- sity for an armed rostellum in addition to the absorbent pores? The frequency with which the Cysticerci are found with the head so retracted, may be attributed to the in- stinctive action arising from the stimulus of diminished temperature and other changes m the surrounding parts occasioned by the death of the animal in which the hydatid has been developed. Cestoidea. — In the Cestoidea the digestive apparatus commences for the most part by two or four oral apertures, to which, in many spe- cies (the Tama armata ), a central uncinated proboscis is superadded, as in the Cysticerci. Sometimes the mouths are in the form of oblong pits or fossae, as in the Bothriocephalus tutus , and the allied species grouped under the same gene- ric name ; or they have the structure of circular suctorious discs, as in the Tania solium and othertrue Tania, j- In both genera two alimen- tary canals are continued backwards in a straight line near the lateral margins of the body ( e, e, * “ Osculis tamen canalibusque dictis omnem aqu® vim vesica caudali collectam parari potuisse vix credibile, sed hac parata vermetn eandem absorbere ideoqne semper fere caput huic immissum offerre, longe aliam vero fluid! advehendi viam dari, plurima suadent.’’— Hist. Entoz. i. p. 279. t Many beautiful preparations, showing the nutrient canals of the Teenia solium injected with coloured size and quicksilver, are preserved in the Hunterian collection, (see Nos. 843, 844, 845.) These were prepared, during the life-time of John Hunter, and were presented to that great anato- mist by Sir Anthony Carlisle, by whom they are described in the ‘ Observations upon the Struc- ture and CEconomy of Taenia;,’ in the second vo- lume of the Linnaean Transactions, (1794). fig. 90), and are united by transverse canals fig. 90) passing across the posterior margins of the segments. These connecting canals are relatively wider in the Tania solium than in the Bothriocephalus latus, their size apparently depending on the length of the segments, which is much greater in the former than the latter. Neither the transverse nor the longi- tudinal vessels undergo any partial dilatations. The chief point at issue respecting the digestive organs of the Tape-worms is, whether the nu- triment is imbibed by them through the pores which occur at the sides or margins of each joint, or whether the entire body is dependent for its nutriment upon the anterior mouths from which the lateral canals commence. The re- sults of numerous examinations, which I have made with this view, both on Bothriocephali* and Taenias, have uniformly corresponded with those of Rudolphi, and I entirely subscribe to the opinion of that experienced helminthologist, that the marginal or lateral orifices of the seg- ments are exclusively the outlets of the gene- rative organs. In some species of Tape-worm, as the Tania sphanocephalus, in which no ovaria have been detected, there has been a corresponding ab- sence both of lateral and marginal pores, while the lateral longitudinal canals have been pre- sent and of the ordinary size. In the Tania solium the generative pores being placed at one or other of the lateral margins of the seg- ments, the ducts of the ovary and testis ( g, h, fig. 90) cross the longitudinal canal of that side, and give rise to a deceptive appearance, as if a short tube were continued from the alimentary canal to the pore. But in the Bothriocephalus latus and Bothriocephalus Pythonis the generative pores open upon the middle of one of the surfaces of each segment, and in these it is plain that the lateral nu- trient vessels have no communication with the central pores. The orifices of the segments, in short, correspond with the modifications of the generative apparatus, while the nutrient canals undergo no corresponding change. Nutrition may be assisted by superficial ab- sorption ; and, as Rudolphi suggests, -f the se- parated segments may for a short time imbibe nutriment by the open orifices of the broken canals ; but setting aside cutaneous absorption and the more problematical action of the rup- * Principally on that species which infests the intestines of the large serpent commonly exhibited in this country the Python Tigris, Dand. And we invite the attention of comparative anatomists interested in this point to an injected preparation of one of these worms in the Museum of the Royal College of Surgeons, No. 846 A. f “ Al. Olfers (de veget. et anim. p. 35) articulos Teenier singulos ope absorptionis cetane® perparum, maxime autem ope osculi marginalis nutriri contendit, sed osculum hoc vere ad genitalia pertinere in capite insequente evincam. Si cl. vir absorptionem cutaneam minoris aestumat, hac de re non litigabo, sed res alio modo explicari potest. Annon enim ad vasa linearia nutrientia, utrinque longitudinaliter decurrentia, si articuius soluius est, in utroque ejus fine utrinque hiantia, absorbendi officium deferri posset.” — Synops. Entoz „ p. 585. 132 ENTOZOA. tured vessels, the head of the Tape-worm is the sole natural instrument by which it im- bibes its nutriment, and it is to the expulsion of this part that the attention of the physician should be principally directed, in his attempts to relieve a patient from these exhausting para- sites. Trematodu. — Four kinds of vessels or canals are met with in the parenchymatous body of the Trematode worms, viz. digestive, nutritive or sanguiferous, seminal, and ovigerous. In the genus Monostoma, the digestive canal is bifur- cated, each branch traverses in a serpentine direction the sides of the body, and they are united, in some species, by a transverse com- municating vessel at the caudal extremity ; in others, as Monost. mutubile, they converge and terminate in an arched vessel at the posterior part of the body. They are of small size, and not very clearly distinguishable from the sangui- ferous vessels. In the Distoma hepaticum, the digestive organs are more distinctly developed. The oesophagus is continued from the anterior pore, and forms a short wide tube, shaped like an inverted funnel. Two intestinal canals are continued from its apex, which immediately begin 10 send off from their outer sides short and wide coecal processes, and continue thus ramifying to the opposite end of the body, but have no anal outlet. Rudolphi* states that when successfully injected with mercury, more minute vessels are continued from the apices of the digestive canals, which form a net- work over the superficies of the body. A similar dendritic form of the digestive canal obtains in the singular genus Diplozoon, discovered by Nordmann in the gills of the Bream; the central canal and minified ere cal processes in this En- tozoon are represented (fig. 328, vol.i. p. 654,) on that moiety, which is opposite the left hand of the observer: on the other moiety the vascu- lar system alone is delineated. The latter is not, like the digestive canal, common to both halves of the body, but consists of two closed systems of vessels, each peculiar to its own moiety. Two principal trunks, a, a, traverse the sides of each moiety, preserving a uniform diameter throughout their entire course. In the external vessels marked a, a, Nordmann states that the blood is conveyed forwards or towards the head: in the internal ones, it passes back- wards in the opposite direction. The latter vessels commence by many minute branches which unite in the space between the oral suckers and the anterior extremity of the body, and terminate between the disc and suckers at the posterior extremity of the body. The exterior or ascending vessels begin where these disappear and pass towards the opposite end of the body : both trunks freely inter- communicate by means of superficial capil- laries. The blood moves through them with great rapidity, but without being influenced by any contraction or dilatation of the vessels themselves. The circulation continues for three or four hours to go on uninterruptedly in * Entoz. Synopsis, p. 583. each moiety of the Diplozoon, after they have been separated from one another by a division of the connecting band. The blood itself is per- fectly limpid. It should be observed, with refe- rence to the above description, that the appear- ance of circulatory movements in the vessels of the Diplozoon paradoxum is ascribed by Ehren- berg ( Weigmann s Archiven, 1835, th. ii.) and Siebold (Ibid. 1 836, th. ii.) to the motion of cilia on the inner surface of the vascular canals. In the genus Diplostomum, in which the nutritious and vascular systems characteristic of the Trematoda are peculiarly well displayed, (fig. 81,) a short and slightly dilated canal is continued from the mouth, and soon divides into two alimentary passages or intestines, e, e, which diverge, and proceed in a slightly un- dulating course, towards the hinder sacciform appendage of the body, dilating as they de- scend, and ultimately terminating each in a blind extremity, /^/'. The contents of this long bifid blind alimentary canal are of a yellowish brown colour, especially in old individuals, and consist of a finely granular substance. As there is no separate anal aperture, the crude and effete particles are probably regurgitated and cast out by the mouth, as in all other Trematoda. The posterior projection of the body, g, Nordmann compares to the posterior appen- dage in the Cercaria ; it is terminated by a posterior aperture which seems to be the ex- cretory outlet of some secerning organ ; since a milky fluid is sometimes ejected from it with force. In a species of Distoma ( Distoma clavatum, Rud.) which I recently dissected, Fig. 81. Digestive and nutrient canals, Diplostomum volvens, magnified. ENTOZOA. 133 there is a similar aperture which forms the outlet of a vertically compressed sac situ- ated between the chyle-receptacles (see Trans- actions of the Zoological Society, plate 4, p.381, pi. 41, figs. 17, 18, d, g). In the Diplostomum volvens Nordmann supposes the aperture in question, h, to be the termination of a canal continued from the oviduct. Besides this canal the posterior appendage of the body is occupied by a sac of a corresponding form containing a milky fluid, t, i, and to which the term of chyle-receptacle is given by Nord- mann, as was previously done by Laurer to a corresponding cavity in the Amphistoma coni- cum. The nutritious contents of this canal would seem to exude through the parietes of the ccecal extremities of the intestines, as no distinct aperture of communication is obvious. Two vessels, k, k, are continued on each side from the anterior and external part of the chyle receptacle ; they extend forwards to the anterior third of the body, and are there brought in to com- munication by a transverse vessel, l, l, which ex- tends across the dorsal aspect of the body. From the point of union of the transverse with the external lateral vessels, a vessel is continued for- ward on each side, appearing as the continuation of the external lateral one. These vessels, in, m, are reflected inward at the anterior angles of the body, and unite in the middle line to form the vessel, n, which may be regarded, according to Nordmann, as representing the arterial trunk, and which is continued to the posterior extremity of the body, distributing branches on each side throughout its whole length. Nord- mann observed a circulation of fluid in the vessels marked m, m, which was unaccom- panied by any pulsation, and which may there- fore be compared to the cyclosis of the nutrient fluids in the vessels of Polygas- trica, Polypi, and other Acrita, and is probably due to the action of vibratile cilia. In a few species of Pla- naria the mouth is terminal and anterior, as in the Distomata ; these form the subgenus Prostoma of Professor Dughs.* In the greater number of these non- parasitic Sterelmintha the alimentarvcanal commences from a cavity situated at the middle of the inferior sur- face of the body. A pro- boscis or suctorious tube (a, fig. 82), varying in length according to the species, is contained in this cavity, from which it can be pro- truded, and the mouth is situated in the form of a Dendritic digestive round Pore at the extremity cavity , Planaria of this proboscis. The ac- lactea. tion of this tube is well dis- * Duges, .Annales des Sciences, 1828, p. 16. played when a hungry Planaria makes an attack upon a Nats ; it then wraps its flat body around its prey (see fg. 76,) and applies to it the extre- mity of its trumpet-shaped sucker ; the red- blood of the little Anellide is seen to dis- appear from the part in contact with the sucker; and if the body of the Nais be broken in the conflict, the Planaria directs the extremity of the proboscis to the torn and bleeding surface. After a meal of this kind the digestive canals of the Planaria are displayed by the red colour of their contents, like the corresponding parts of the Liver-fluke when filled with bile, and they greatly resemble the latter in structure ; instead of two canals, however, three are con- tinued from the base of the proboscis ; one of these is central ( b ), and passes upwards to the anterior extremity of the body, distributing its wide coeca on either side ; the other two (c, c) descend, almost parallel to one another, and give off their ccecal processes chiefly from the outer margin, as in the Distoma. The Planaria: are, equally with the parasitic Trematoda, de- void of an anus : and the remains of Poly- gastric infusories swallowed by them have been seen to be regurgitated by the proboscis. Mi- nute nutrient vessels are continued from the extremities of the intestinal coeca, and form a very fine cutaneous network, which communi- cate with a mesial and dorsal canal and two lateral vessels, as in the Diplostomum. Some species of the Trematode Entozoa are infested by parasitic Polygastrica which belong to the Monads : Nordmann observed some brown corpuscles by the sides of the alimen- tary canal of a Diplostomum, which contained minute particles in continual and lively motion. On crushing the corpuscles between plates of glass an immense concourse of the moving atoms escaped : they were smaller than the Monas atomos of Muller, of an oval form, and of a clear yellow colour; their movements were very singular : they whirled rapidly round on their axis, then darted forward in a straight line, whirled round again, and again darted forward. When we consider that the Diplos- tomum itself does not exceed a quarter of a line in length, and that the aqueous humour of a single eye serves as the sphere of existence to hundreds of individuals, what views does the fact of the parasites of so minute an Ento- zoon open of the boundless and inexhaustible field of the animal creation ! Acanthocephala- — The worms of this order, although in external form, in the development of the tegumentary and muscular system, and above all in their dioecious generation, they ap- proach very closely the Nematoid Worms, yet preserve the distinguishing character of the Sterelminthoid class in the structure of the digestive organs. In the Echinorhynchus gigas the mouth is an extremely minute pore, situated on a projectile armed proboscis, the structure of which we have already described. From its posterior part are continued two long cylindrical canals (e, e, figs. 83, 84) which ad- here closely to the muscular fibres by their outer side, and project on the opposite side into the triangular cavity (A, fig. 84) left between the Fig. 82. 134 ENTOZOA. /- HL r - w il ovaries in the female and testes in the male. They are extremely minute at their commencement, but increase so as to be readily visible in the middle of their course. They are trans- parent and irregularly dila- ted or sacculated at inter- vals. Posteriorly they ter- minate in a cul-de-sac, and have no anal outlet. They contain a transparent in- odorous albuminous liquid, give off no visible lateral branches, and do not com- municate together in any part of their course. Be- sides these canals we find in the cavity of the body of an Echinorhynchus two long wavy tubes called lemnisci, ( d , d, jig. 83). They are attached to the lateral parts of the neck by an extremely attenuated an- terior extremity, float freely in the remainder of their extent, and terminate in an enlarged obtuse and imper- forate extremity. They are of a whitish colour, tran- sparent in the living worm, but become opake after death; they present consi- derable variety of form, and would seem to be highly irritable parts, since they are not unfrequently found fold- ed into a packet, or twisted both together, and turned to one side of the body. When examined with a high microscopic power, a tran- sparent vessel is perceived running through the centre and ramifying as it descends in the substance of the lem- niscus, which is soft, fragile, and granular. Cloquet com- pares these organs to the nutrient processes which project into the abdominal cavity of the Ascaris, and they are also regarded by Goeze, Zeder,and Rudolphi as belonging to the organs of nutrition. In the Ccdelmintha or Cavitary Entozoa, the ali- mentary canal is single and of large size, and extends nearly in a straight line from the mouth to the anus, which are at opposite extremities of the body. With regard to the existence of an anal outlet, the parasitic Entozoon, ( Syngamus /rachealis, Siebold,) which infests the windpipe of our common Gallinaceous Birds, presents an exception. It was supposed by Montague to be a single individual with two pedunculate mouths: r Digestive and gene- rative organs , Echi- norhynchus gigas , female. Fig. 84. Transverse section of Echinorhynchus gigas. and by Rudolphi was placed in the same group as Distoma Jure atum, which is a true double- necked Trematode worm. But the digestive system has the essential character of the coelel- minthic structure, the intestine floating freely in an abdominal cavity. The orifice at the extremity of the smaller or male branch leads to a muscular oesophagus, which is continuous with a somewhat broader reddish-brown intes- tine, continued in a tortuous manner down the neck, and terminating in a cul-de-sac prior to the confluence of the extremity of this branch with the body of the female. The mouth of the larger branch, which is the true continua- tion of the larger and single body, leads first to a horny basin-like cavity, which communi- cates by an opposite pore, surrounded by six horny hooks or teeth, with the oesophagus, from which a similar reddish-brown intestine is continued, but in a more tortuous manner than in the male, through the whole body, ter- minating in a cul-de-sac at the caudal extre- mity. In both intestinal canals are molecules of apparently the colouring matter of blood. Their inner surface is reticulate. In the freedom of these intestines from the muscular parietes of the body, and in the cy- lindrical form of the latter, we have a close affinity to the Nematoid type: but the intestine is blind — without an anal outlet. It is not, however, bifurcate, as in the true Trematoda. In the genus Linguatula or Pentastoma of Rudolphi, the intestine is a simple straight tube, and is surrounded by the convolutions of the oviduct : the two intestinula cceca with which Rudolphi describes the alimentary canal as being complicated,* appertain to the gene- rative system, and communicate exclusively with the oviduct : the intestine terminates by a distinct anus at the posterior extremity of the body. In the Nematoidea the intestine is also frequently concealed in a part of its extent by the coils of the genital tubes, but these are disposed in masses by the side of the alimen- tary canal, and not wound around it as in the Linguatula : in most species the alimentary canal is attached to the internal parietes of the abdominal cavity by means of numerous small laminated or filamentary processes. In the Strongylus gigas the mouth (A, jig. 71) is surrounded by six papill® ; the cesopha- * Synopsis Entoz. p. 584. ENTOZOA. 135 1 rietes of the body by means of slender, radiated filaments : its cavity is occupied by three lon- gitudinal ridges, which meet in the centre and reduce the canal to a triangular form. The oesophagus is separated by a well-marked con- striction from the second part of the digestive canal, which in the rest of its course presents no natural division into stomach and intestine. -The anterior portion of the canal is attached by filaments, as in the Strongylus , to the pro- cesses and lining membrane Fig. 87. of the abdominal cavity. Those which come off from the sides of the canal ( d , d ) communi- cate with the nutritious vessels and appendages, and in pass- ing from the intestine they diverge and leave on each side a triangular space, of which the base corresponds to the lateral line or vessel (e, fig. 86), and the apex to the side of the intestine. These lateral spaces are filled with a serous fluid, and are continuous with the common cavity contain- ing the alimentary and gene- rative tubes. About the mid- dle of the body the intestine becomes narrower, being here surrounded and compressed by the aggregated loops of the oviduct or testis, and the me- senteric processes or filaments diminish in number, and at last leave the intestine quite free, which then gradually en- larges to within a short dis- tance of its termination (h). The parietes of the intestine are thin and transparent, and easily lacerable ; they consist of a gelatinous membrane, the internal surface of which is disposed in irregular angular meshes and transverse folds, which gradually disappear to- wards the lower part of the canal. The soft obtuse processes (f f, fig ■ 86) analogous to n(-g those which project from the lining membrane of the abdo- minal cavity in the Strongylus, acquire a considerable deve- lopment in the Ascaris. They arise chiefly in the dorsal and ventral regions, and are con- tinued from numerous trans- verse bands ( e,e,fig. 88) which pass across the body from one lateral absorbent vessel to the ||, < other. In the anterior third of the body these transverse bands (vaisseaux nourriciers, f Cloquet,) are quite concealed Digestive and gene- ^ the processes in question rative tubes, Ascaris ( °PPend tees nournciers, Clo- Transverse section of Ascaris lumbricoides, magnified. lumln-icoides, male. quet), but are very conspicu- gus ( b,fig . 95) is round and slightly contorted, and suddenly dilates at the distance of about two inches from the mouth into the intestinal canal; there is no gastric portion marked off in this canal by an inferior constriction, but it is conti- nued of uniform structure, slightly enlarging in diameter to the anus. The chief pecu- liarity of the intestine in this species is that it is a square and not a cylindrical tube, and the mesenteric processes pass from the four longitudinal and nearly equidistant angles of the intestine to the abdominal parietes. These processes, when viewed by a high mag- nifying power, are partly composed of fibres and partly of strings of clear globules, which appear like moniliform vessels turning around the fibres. The whole inner surface of the abdominal cavity is beset with soft, short, obtuse, pulpy processes, which probably im- bibe the nutriment exuded from the intestine into the general cavity of the body, and carry it to the four longitudinal vessels, which tra- verse at equal distances the muscular parietes. The analogous processes are more highly de- veloped in the Ascaris lumbricoides, in which species we shall consider the digestive and nutritive apparatus more in detail. The mouth (d, fig. 87 and fig. 85) is sur- rounded with three tubercles, of which one is superior («, fg. 85), the others inferior (6, b) ; they are rounded externally, triangular inter- nally, and slightly granulated on the opposed surfaces which form the boundaries of the oral aperture (c). The longitudinal muscles of the body are attached to these tubercles; the dorsal fasciculus converges to a point to be inserted into the superior one ; the ventral fasciculus contracts and then divides to be inserted into the two which are situated below. By means of these attachments the lon- gitudinal muscles serve to produce the divarication of the tubercles and the open- ing of the mouth ; the tu- bercles are approximated by the action of a sphincter muscle. The oesophagus (e,fig. Head and month of 87) is muscular and four Ascaris lumbricoides. or five lines in length, nar- row, slightly dilated pos- teriorly, and attached to the muscular pa- Fig. 86. / 1 re Fig. 85. 3 ENTOZOA. 136 ous at the posterior part of the body. The nervous chord passes at a right angle to the transverse bands between them and the longi- tudinal muscles, and sometimes is included in loops of the former, as at d, Jig. 88. Both the pendant processes and the transverse bands are composed of a homogeneous spongy tissue, without any central cavity, and appear to form a nidus of nutrient matter like the fatty omen- tal processes in higher animals. The longitudinal lines (c, c,fig. 86, 88), which extend along each side the body of the Ascaris Lutnbricoides, and which are very conspicuous Fig. 88. externally through the transparent integument, consist each of a narrow flattened tract of opaque substance, by some anatomists considered as nervous, and a very slender vessel which ad- heres closely to the outer side of the band. The two bands become expanded at the an- terior extremity of the body, and unite in forming a circle around the oesophagus : the vessels, on the contrary, become detached from the bands, and pass transversely below the oesophagus to anastomose together, forming a simple loop or arch, the convexity of which is anterior. By pressure the reddish fluid con- tained in these vessels may be made to tra- verse them backwards and forwards. With respect to the accessory glands of the digestive system of the Entozoa, I have hi- therto met with them in two species only of the Nematoidea, in both of which they pre- sented the primitive form of simple elongated unbranched cceca. The first being developed from the commencement of the alimentary canal, and co-existing with a pair of rudimen- tal jaws, must be regarded as salivary organs. They exist in a species of worm which infests the stomach of the Tiger, and which I have recently described under the name of Gnathostoma aculeatum.* They consist of four slender elongated coeca, communi- cating with the mouth, and gradually increas- ing in size as they extend backwards into the abdominal cavity, where they end each in a cul-de-sac; they are placed at equal distances around the alimentary canal, and have no at- tachment except at their open anterior extre- mity. The length of each ccecum is about one-twentieth of the entire alimentary canal. Their parietes under a high magnifying power present a beautiful arrangement of spirally decussating fibres. Their contents when recent are clear, but become opaque when immersed in alcohol. That the Gnathostoma is not the larva of an insect is proved by the complete development of the generative system, which resembles that of the Ascarides, and by the absence of a ganglionic nervous system. The second example of an accessory digestive gland occurs in a species of Ascaris infesting the stomach of the Dugong : here a single elongated ccecum is developed from the in- testine at a distance of half an inch from the mouth ; and is continued upwards, lying by the side of the beginning of the intestine, with its blind extremity close to the mouth ; from the position where the secretion of this coecum enters the intestine, it may be regarded as re- presenting a rudimental liver.f Respiratory Organs. — The Entozoa have no distinct internal or external organs of respi- ration. The skin in many of the Trematoda and Acanthocephala is highly vascular, J and the circulating fluids in these worms may be- come oxygenated by contact with the vascular mucous membranes of the higher organized animals which they infest. In the Planariie the surrounding water is renewed upon the vascular surface of the body by means of the currents excited by the action of vibratile cilia; and the young of certain species of Distomata, which pass the first epoch of their existence under the form of Polygastric In- fusoria, freely moving in water, are pro- vided with superficial vibratile cilia arranged in longitudinal rows; but these organs of lo- comotion and adjuncts to the respiratory pro- cess are lost when the Distomata resume their position as parasites in the intestines of the Fishes from which they were originally ex- pelled. Excretory glands. — As an example of an organ of excretion, we may refer to the glan- dular sac lodged in the enlarged extremity of the Distoma clavatum, which opens externally * Proceedings of the Zoological Society, Nov. 1836. f See the Preparation, No. 429 A, Mus. Coll. Surgeons, Phys. Catalogue, p. 121. | Conf. Echinorhynchus vasculosus,Entoz.Synop. p. 581 . ENTOZOA. 137 by a small orifice in the centre of tlmt part,* and the corresponding cavities from which a clear or milky fluid is ejected by the posterior pores of some smaller species of Distomata and Diplostomata.f Organs of generation. — The generative sys- tem in the Entozoa presents great varieties in the form, structure, and combination of its several parts. Sometimes the female or productive organs alone are discernible. In many Cestoidea, and in all the Trematoda, the male gland is present and communicates with the oviduct, so that each individual is sufficient for itself in the reproductive capacity. In the Acanthocephala and Ne- matoidea the sexes are distinct, and a con- currence of two individuals is required for impregnation. No trace of a generative apparatus has hither- to been detected in the Cystic Entozoa. They would seem to be gemmiparous, and to have the reproductive power diffused over the whole cyst, at least in the Acephalocysts, in which the young are not developed from any special organ, or limited to any particular part of the cyst. The ovaries in the most simple of the Ces- toid worms, as the Ligula, are situated in the centre of each joint, where they open by a transverse aperture, from which projects a small filamentary process or lemniscus, re- garded by Rudolphi as a male organ. In the Bolhriocephali the ovaries have a similar po- sition, and in the Bothriocephalus latus (fig. 89) assume a stellated figure, with Fig. 89. the aperture in the centre, n fl which is situated in the mid- dle of each joint. In the Bothriocephalus microcephalus the ovary consists of one or two rounded corpuscles in the centre of the joints, but the generative orifices are margi- nal and irregularly alternate, and the oviducts may be dis- tinctly seen passing backwards to them. In the Tania Candelabra- ria a sacciform ovary exists in each segment, which sends off an oviduct to the marginal outlet. Besides which, ac- cording to Rudolphi, there is a longitudinal canal, uniting the different ovaries together, and undergoing a partial dila- tation at the anterior part of each joint. — May not this be the male organ ? The androgynous structure of the generative apparatus is very well displayed in the Tape- worm of this country, the Tania Solium. In each joint of this worm there is a large branched ovarium (i, fig. 90) from which a duct (h) is continued to the lateral open- Ovarian apertures and ova, Bothrio- cephalus latus. Fig. 90. Generative organs magnified, Taenia solium. ing. The ova are crowded in the ovary ; and in those situated in the posterior segments of the body, they generally present a brownish colour, which renders the form of their recep- tacle sufficiently conspicuous.* In segments which have been expelled separately, we have observed the ovary to be nearly empty, and it is in these that the male duct and gland is most easily perceived. For this purpose it is only necessary to place the segment between two slips of glass, and view it by means of a simple lens, magnifying from twenty to thirty diameters: a well-defined line (g), more slender and opake than the oviduct, may then be traced extending from the termination of the oviduct, at the lateral opening, to the middle of the joint, and inclining in a curved or * See Zool. Trans, pt. iv. vol. i. p. 381. pi. 41. fig. 18. See Nordmann, loc. cit. p. 38. t See Nordmann, loc. cit. p. 140. * The dendritic ovarian receptacles can also be injected with mercury or coloured size, and they have been regarded, but erroneously, as forming part of the nutrient apparatus. ENTOZOA. 138 slightly wavy line to rear the middle of the posterior margin of the segment, where it ter- minates in a small oval vesicle. This, as seen by transmitted light, is sub-transparent in the centre and opaque at the circumference, indi- cating its hollow or vesicular structure. The duct, or vas deferens, contains a grumous se- cretion ; it is slightly dilated just before its termination. In this species therefore, as also in Ampliis- toma conicum, the ova are impregnated in their passage outward. But in several species of Distomata, as D. clavigerum, ovatum, cirrige- rum, and in the Distoma hepaticum, the ova escape by an aperture situated near the base of the penis, and reciprocal fecundation exists. The concourse of two individuals must also take place in those species of the genus Monos- tomum , which, like the Monostomum mutabile, are viviparous, and in which the orifices of the male and female parts are distinct. All the Sterelmintha of the Trematode order are androgynous; but the generative apparatus, instead of being divided and multiplied as in the Tania, is individualized, and its several parts receive a higher degree of development. We have selected the figure which Nordmann has given of the Distoma perlatum, on account Fig. 91. of the clearness with which the several parts are delineated, but it must be observed that it deviates in some remarkable peculiarities from what may be regarded as the Trematode type of the reproductive organs. The specimen is seen from the under side, part of the parietes of the body having been removed : a is the oral aperture, 6 the oesophagus seen through the transparent integument, c d the windings of the beginning of the simple digestive cavity, c e the two intestinal prolon- gations,/'/' the dilated claviform coecal ter- minations of the intestines, g the two internal, and h the two external trunks of the vascular system proceeding to the anterior part of the body ; i is the great sacciform uterus, k ap- parently glandular bodies contained therein, l m the two testes, which are beset internally with small spines or cilia; n the projecting cirrus from which the ova are expelled, o the terminal dilatation of the oviduct which com- municates with the testes, p p p p convo- lutions of the oviduct which are filled with ova, q q the mass of ova which lies above the ovi- duct, and occupies almost the whole cavity of the body, r r the passages by which the ovaries communicate with the uterus or dilated commencement of the oviduct. The generative organs present some varieties in the Planaria, but are essentially the same as in the Distomata. In the Planaria lactea the penis and oviduct are situated below, and the two vesicular and secerning parts of the apparatus towards the upper part of the body. The male organ (a, fig. 92) consists, according Fig. 92. to the researches of Professor Dugfes, of two parts, one of which is free, smooth, semi- transparent, contractile, and always divided into two portions by a circular constriction ; it is traversed by a central canal, susceptible of being dilated into a vesicle, and is open at its free extremity, which is turned backwards ; the second division is thicker, more opaque, vesicular, adherent to the contiguous paren- chyma, and receives two flexuous spermatic canals (6, b ). The free portion of the penis is con- tained within a cylindrical muscular sheath (c), which is adherent to the circumference of the base of the intromittent organ, and serves to protrude it externally. This sheath commu- nicates with the terminal sac of the female apparatus near its outlet by a projecting orifice (c/). The oviduct (e) opens into the posterior part of the terminal sac : it is a narrow tube which passes directly backwards, and dividing into two equal branches, again subdivides and ramifies amongst the branches of the dendritic digestive organ. Besides the ovary there are two accessory vesicles (gaud//), communicating together by a narrow duct / f), and opening into the terminal generative sac. M. Baer twice witnessed the copulation of ENTOZOA. 139 Planaria in the species Planaria torva. Upon separating the individuals, he perceived a long white tube projecting from the genital pore of each, proving the reciprocity of fecundation. Notwithstanding the complicated apparatus above described, the Planaria are remark- able for their spontaneous fissiparous gene- ration, and the facility with which detached or mutilated parts assume the form and func- tions of the perfect animal. Fig. 92, o, repre- sents a P/anuria lactea, with the anterior part of the body artificially divided in the longitu- dinal direction ; fig. 92, e, shews the same in- dividual having two perfect heads, the result of the preceding operation. The female generative organs of the Lingua- tula ( Pentastoma ) tanioides present a struc- ture in some respects analogous to that of the Distoma per latum : the ovary (n,n,fig. 78) is a part distinct from the tubular oviduct, and is attached to the integument or pa- rietes of the body, extending down the middle of the dorsal aspect. It consists of a thin stratum of minute granules ; clustered in a ramified form to minute white tubes, which converge and ultimately unite to form two oviducts (o, o, fig. 78). These tubes pro- ceed from the anterior extremity of the ovary, diverge, pass on each side of the alimentary canal, and unite beneath the origins of the nerves of the body, so as to surround the oesophagus and these nerves as in a loop. The single tube (p) formed by the union of the two oviducts above described, descends, winding round the alimentary canal in numerous coils, and ter- minates at the anal extremity of the body. The single oviduct, besides receiving the ova from the two tubes (o, o), communicates at its com- mencement with two elongated pyriform sacs (»;, m), which prepare and pour into the ovi- duct an opaque white secretion. These bodies, from their analogy to the impregnating glands in the Trematoda, I was led to regard (in the description, published in the Zoological Trans- actions, of the only individual of this interesting species that I have hitherto been able to pro- cure for dissection,) as testes, and the gene- ration of the Linguatula to be androgynous, without reciprocal fecundation; individuals, however, of the male sex have since been de- scribed in this species by Miram* and Diesing. The male Linguatula is, as in dioecious Entozoa generally, much smaller than the female : the generative apparatus consists of two winding seminal tubes or testes, and a single vas deferens, which carries the semen from the testes by a very narrow tube, and afterwards grows wider. It communicates anteriorly with two capillary processes, or penes, which are connected together at their origin by a cordiform glandular body, repre- senting a prostate or vesicula seminalis. The external orifices of the male apparatus, accord- ing to Miram, are two in number, and are situated on the dorsal aspect of the body, just behind the head. Diesing, however, describes the male Pen- * Nova Acta Acad. Naturae Curios, tom. xvii. f tastoma as having only a single penis, which perforates the interspace between the second and first segments of the body, and protrudes below and behind the oral aperture. Much interest attends the consideration of the reproductive organs of the dioecious En- tozoa, since they are the first and most simple forms of the animal kingdom which present that condition of the generative function. In the Acanthocephala the structure of the generative apparatus has been ably elucidated by Cloquet in the species which commonly infests the Hog, viz. the Echinorhynchus gigas. The male organs consist of two testes, two vasa defe- rentia, which unite together to terminate in a single vesicula seminalis, and a long penis gifted with a particular muscular apparatus. The testes (f, h, fig. 93) are cylindrical bodies, pointed at both ex- Fig. 93. tremities, of nearly the same magnitude, but situated one a little anterior to the other. The anterior one is attached by a filamentary process (g) to the posterior extremity of the proboscis : the posterior gland is connected by a similar filament to the in- ternal parietes of the body. The vasa deferentia ( i ), after their union, form seve- ral irregular dilatations ( k ), which together constitute a lobulated vesicula seminalis. This reservoir is filled with a white grumous fluid like that which is found in the testes, and it is embraced posteriorly by the retractor muscles of the penis (r, r ), which form a kind of coni- cal sheath for it. A small, firm, white, and apparently glandular body ( q ) is situated at the point of union between the vesi- cula seminalis and the penis. The penis is a straight, cylindrical, firm, white or- gan, and in the retracted state is terminated by a di- lated portion (o), occupying the posterior extremity of the body, but which disap- pears when the intromittent organ is protruded. This action is produced by the muscles s, s, when the penis presents the form of a short broad cone, adhering by the apex to the caudal extremity of the body : it is retracted by the muscles r, r, above described. The female organs consist of two ovaries and one oviduct. The former are long and wide cylindrical canals, which of themselves occupy almost the whole cavity of the body extending from the proboscis to the tail (//, h, fig. 83). They are situated, one at the ventral, the other at the dorsal aspects of the body, and k H f ■ -in. T Male organs of gene- ration, Echinorhyn- chus gigas. 140 ENTOZOA. are separated in the greater part of their extent by a septum : see fig. 84, J\ g, which shows them in transverse section. They contain a prodigious quantity of ova, and adhere by their outer surfaces very firmly to the muscular parietes of the body. The dorsal ovary opens into the ventral one by an oblique valvular aperture about an inch distant from the extremity of the proboscis, anterior to which the common cavity extends forwards between the lateral lemnisci, and terminates by a conical canal (i, fig. 83), which is attached to the posterior portion of the pro- boscis. The two ovaries terminate in a dif- ferent manner posteriorly, the dorsal one end- ing in a cul-de-sac, the ventral becoming continued in a slender oviduct (/c), which opens by an extremely minute pore at the caudal extremity of the body ( l ). The tissue of the ovaries is remarkable for its trans- parency and apparent delicacy, but it pos- sesses a moderate degree of resistance. The generative organs in the Nematoidea are upon the whole more simple than in the Acanthocephala. The testis in each of the genera is a single tube, but differs in its mode and place of ter- mination, and the modifications of the intro- mittent part of the male apparatus have afforded good generic characters. Genitale masculum, spiculum simplex , is the phrase employed by Rudolphi in the formula of the genus Filaria, and this appears to be founded on an observation made on the Filaria papillosa, in which he once saw a slender spicu- lum projecting from near the apex of the tail. According to the recent observations of Dr. Leblond,'*' the male-duct in the Filaria papil- Fig. 94. Penis of Ascaris lumbricoides. * “ Quelques Materiaux pour servir a 1’Histoire des Filaires ct Strocgles, 8vo. Paris, 1836.” lusa terminates at the anterior extremity of the body close to the mouth. From this aperture the slender duct, after a slight con- tortion, is continued straight down the body to a dilated elongated sac, which represents the testis. In the Ascaris lumbricoides the penis (a, fig. 94) projects from the anterior part of the anus in the form of a slender, conical, slightly curved process, at the extremity of which a minute pore may be observed with the aid of the micro- scope. The base of the penis (t) communicates with a seminal reservoir, and is attached to several muscular fibres, destined for its re- traction and protrusion : the reservoir is about an inch in length, and gradually enlarges as it advances forwards : the testis or seminal tube is continued from the middle of the anterior truncated extremity of the reservoir; it pre- sents the form of a long, slender, cylindrical, whitish-coloured tube, extends to the anterior third of the body, forming numerous convo- lutions and loops about the intestine, and its attenuated extremity adheres intimately to the nutrient vessels of the dorsal region of the body. The total length of the seminiferous tube in an ordinary sized Ascaris lumbricoides is from two feet and a half to three feet. Its contents, when examined with a high micro- scopic power, consist of a transparent viscous fluid, in which float an innumerable quantity of round white globules, much smaller than the ova in the corresponding tubes of the female. In the genus Trichocephalus the fila- mentary testis is convoluted around the intes- tine in the enlarged posterior part of the body. The intromittent organ in the Trichocephalus dispar is inclosed in a distinct sheath, which is everted together with the penis, and then presents the form of an elongated cone (c, fig. 69), adhering by its apex to the enlarged anal extremity of the body, and having the simple filiform spiculum or penis (d,Jig. 69) projecting from the middle of its base. In the Strongylus gigas the bursa or sheath of the penis terminates the posterior extremity of the body, and is a cutaneous production, of a round, enlarged, truncated form, with the spiculum projecting from its centre, as at B, Jig. 71. In other species of Strongylus, as in the Strongylus infiexus , the bursa penis is bifid, and in the Strongylus armatus it is divided into four lobes : the obvious functions of these appendages, as of the lateral alaeform cuta- neous productions which characterize the Phy- saloplertz and Spiropterx, is to embrace the vulva of the female, and ensure an effective intromission and impregnation of the ova. In the genus Cucullunus, and in most of the smaller species of Ascaris, the intromittent organ consists of a double spiculum. This is also the case in the Syngamus tra- chealis, the parasitic worm before alluded to as infesting the trachea of the common fowl, and occasioning the disease termed the ‘ Gapes.’ In this species the male individual appears as a branch from the body of the female. The testis begins near the middle of the (esophagus by a slender blind extremity, and winds round ENTOZOA. 141 the gut, as it descends, gradually enlarging, to the lower part of the intestine, where it sud- denly contracts and runs down, as a very slender canal, to near the vulva. It is partly covered by two long slender bodies of a horny sub- stance, representing a bifurcate penis. From this comparison of different genera of the Nematoidea, it is seen that, although there are many varieties of structure in the efferent and copulative part of the male gene- rative apparatus, the essential or secerning por- tion uniformly consists of a single tube. A like uniformity of structure does not obtain in the essential parts of the female organs : in a few instances the ovary is single, correspond- ing to the testis in the male, but in the greater number of the Nematoid worms it consists of two filamentary tubes. The Strongylus gigas is an example of the more simple structure above alluded to. The single ovary commences by an obtuse blind extremity close to the anal extremity of the body, and is firmly attached to the termination of the intestine ; it passes first in a straight line towards the anterior extremity of the body, and when arrived to within a short distance from the vulva, is again Fig. 95. attached to the parietes of the body, and makes a sudden turn back- wards 95); it then forms two long loops about the mid- dle of the body and returns again forwards, suddenly dilating into an uterus (e), which is three inches in length, and from the anterior extremity of which a slender cylindrical tube, or vagina, about an inch in length, (e,d. Jig. 95) is continued, which after forming a small convolution ter- i£V« minates in the vulva, f ", at the distance of two inches from the ante- 11' RS rior extremity of the body. Rudolphi was uncertain as to the ter- mination of the ovi- duct in the Strongylus gigas, and Professor Otto, who appears to have mistaken its blind commencement for its termination, believed that theoviductopened into the rectum. The theory which had suggested itself to Rudolphi of the corre- _ lation of a simple ovi- Anterior extremity of the dimt in the female with Strongylus gigas, showing ^ lculum simplex the commencement of the c , r , , rr of digestive and the termina- tion of the generative tube . of the male, and of a double oviduct with the spiculum duplex, receives additional dis- proof from the circumstance of the uteri and oviducts being double in the Strongylus in - Jlexus and Strongylus armatus. In the former species (which infests the bronchial tubes and pulmonary vessels of the Porpesse, and which I once found in the right ventricle of the heart of that animal,) each of the two female tubular organs may be divided into ovary, oviduct, and uterus : the ovary is one inch in length, commences by a point opposite the middle of the body, and, after slightly enlarging, abruptly contracts into a capillary duct about two lines in length, which may be termed the oviduct, or Fallopian tube, and this opens into a dilated moniliform uterus three inches in length ; the divisions here described were constant in several individuals examined, and cannot, therefore, be considered to result from partial contractions. Both tubes are remark- ably short, presenting none of the convolutions characteristic of the oviducts of Ascaris and Filaria, but extend, in a straight line, (with the exception of the short twisted capillary communication between the ovaria and uteri,) to the vulva, which forms a slight projec- tion below the curved anal extremity of the body. The reason of this situation of the vulva seems to be the fixed condition of the head of this species of Strongylus. In both sexes it is commonly imbedded so tightly in a con- densed portion of the periphery of the lung as to be with difficulty extracted ; the anal extre- mity, on the contrary, hangs freely in the larger branches of the bronchi, where the coitus, in consequence of the above dispo- sition of the female organs, may readily take place. In the Strongylus armatus the two oviducts terminate in a single dilated uterus, and the vulva is situated at the anterior extremity of the body, close to the mouth. We find a similar situation of the vulva in a species of Filaria, about thirty inches in length, which infests the abdominal cavity of the Rhea, or American Ostrich. The single portion of the genital tube continued from the vulva is one inch and a quarter in length ; it then divides, and the two oviducts, after forming several interlaced convolutions in the middle third of the body, separate ; one ex- tends to the anal, the other to the oral ex- tremities of the body, where the capillary portions of the oviducts respectively com- mence. In the Ascaris Lumbricoides the female organs (Jig. 96) consist of a vulva, a vagina, a uterus, which divides into two long tortuous oviducts gradually diminishing to a capillary tube, which may be regarded as ovaries. All these parts are remarkable in the recent animal for their extreme whiteness. The vulva ( d , Jig. 72,) is situated on the ventral surface of the body at the junction of the anterior and middle thirds of the body, which is generally marked at that part by a slight constriction. The vagina is a slightly wavy canal five or six lines in length, which passes beneath the in- 142 Fig. 96. ENTOZOA. testine and dilates into the uterus (/c, jig. 96). The division of this part soon takes place, and the cornua extend with an irregularly wavy course to near the posterior extremity of the body, gradually diminish- ing in size; they are then reflected forwards and form numerous, and apparently inextricable, coils about the two posterior thirds of the intestine. Hunter has successfully unravelled these convolutions, and each of the tubes may be seen in the preparation in the Hunterian Collection to measure upwards of four feet. The generative organs contained in the female, or longer branch of the Syn- gainus trachealis, have a cor- responding structure with those of the Nematoidea. The capillary unbranched ovary and uterus are double, as in Ascaris, Spiroptera, Filaria, and most Strun- gyli. The vulva is in the form of a transverse slit, and is situated at the ante- rior third of the body, im- mediately below the attach- ment of the male branch. In the Nematoidea the male individual is always smaller, and sometimes dis- proportionately so, than the female. At the season of reproduction the anal ex- tremity of the male is at- tached to the vulva of the female by the intromission of the single or double spi- culum, and the adhesion of the surrounding tumid la- bia ; and, as the vulva of the female is generally si- tuated at a distance from either extremity of her body, the male has the appearance of a branch or young indi- vidual sent off by gemma- tion, but attached at an acute angle to the body of the female.* In the Heteroura andro- phora of Nitzch (Hersch and Gruber’s Encyclopre- die, th. vi. p. 49, and th. ix. * See Figures of Nematoid Entozoa in copulation, in Bremser, leones Heliuinthum tab. iii. fig. 8. 15. ; and Gurlt, Lehrbuch der Fatholog: Ana- tomie der Hans-Saiigethiere, tab. vi. fig. 35. taf. 3. f. 7.) the male maintains an habitual con- nexion with the female, which has a horny pre- hensile process for the purpose of retaining the male in this position. Here there is no conflu- ence of the substance of the bodies of the two sexes; the individuals are distinct in their su- perficies as in their internal organization. But this singular species offers the transitional grade to that still more extraordinary Entozoon, the Syngumus trachealis, in which the male is orga- nically blended by its caudal extremity with the female, immediately anterior to the slit-shaped aperture of the vulva, which is situated as usual near the anterior third of the body. By this union a kind of hermaphroditism is produced ; but the male apparatus is furnished with its own peculiar nutrient system ; and an indivi- dual animal is constituted distinct in every respect, save in its terminal confluence, with the body of the female. This condition of animal life, which was conceived by Hunter as within the circle of physiological possibilities, (see Anim. (Economy, p. 46,) has hitherto been only exemplified in this single species of Ento- zoon ; the discovery of the true nature of which is due to the sagacity and patient research of Dr. Charles Theodore Von Siebold. The Entozoa of the parenchymatous class are chiefly oviparous, those of the cavitary class for the most part ovoviviparous. The germinal vesicle has not yet been dis- covered in the vitelline substance of the ova of the Acanthocephala, Tremaloda, or Ces- toidea ; but it is distinctly discernible in the ova of the Nematoidea ; I have also observed and have figured it in the highly organized ovum of the Linguatula tanioides. The ova of the Tania present considerable varieties of size and form in different species ; Rudolphi has figured seven forms of these ova in the Synopsis Entozoorum, (tab. iii.)* Some are much elongated and pointed at both extremities, others elliptical: the ova of the Bothrioceplialus lotus are of the latter form, ( L ,fig 89) ; those of the Tania solium are sphe- rical, as are also the ova of Tania jili for mis. In some species the development of the em- bryo Tape-worm has been observed to have distinctly commenced in the undischarged ova, as in the Tania poli/morpha. In dissecting a Touraeo infested by the Tania jiUjornns , we found that the segments of the Trenia in which the ova were most developed had been ae- tached from the rest of the body, a process remarkably analogous to that which takes place in the Lernea and Entomostraca, where the external ovaries are cast off, when charged with mature ova. A few of the Trematode Entozoa, as the Monostoma mutabile, produce the young alive ; but these have a very different form from the parent. It would seem that they were des- tined to pass a transitional state of their ex- istence in a fluid medium permeated by light, since two coloured ocelli have been discovered on the head, and the surface of the body is beset with locomotive vibratile cilia. f * Synopsis Entoz. p. 505, pi. iii. fig. 10, 11. f See Siebold, in Weigmann’s Archiv. 1835. ENTOZOA. 143 The ova of the greater part of the Trematoda are excluded prior to the full development of the foetus ; they are generally of an oval but some- times spherical form, and many of them singu- larly resemble the seeds or capsules of certain mosses, in having a small circular portion of the outer covering separate from the rest, and closing the cavity of the egg like a lid. Nordmann has studied the development of the young of the Distoma hums, which infest the intestines of the perch. According to this excellent observer the foetus raises, in its en- deavours to slip out of the egg, the small lid, and writhes about for some time, being still attached to one point of the egg. In about six hours it succeeds in freeing itself from the egg-coverings ; and at this period it differs in every respect from the shape of the parent animal; the body, which is of a mucous con- sistence and perfectly transparent, is of an oval form ; the anterior mouth forms a small square- shaped projection, and the whole surface of the body is beset with many longitudinal rows of short cilia, which are in rapid and incessant motion, and create a vortex in the surrounding water, similar to that which the Polygastric Infusoria produce. The little animal having its anterior extremity diminish- ing to a point, is well formed for swimming, and by means of its vibratile cilia, quickly darts out of the field of vision when under the microscope. At the distance of one-third of the body from the anterior extremity there is a single coloured eye-speck, from which, when pressed between glass plates, there escapes a brilliant blue-coloured pigment. Thus orga- nized, the young of the intestinal parasite just described move to and fro in water as if this were their natural element, and approximate in form and structure most closely to the Poly- gastric Infusoria of the genus Paramecium, Ehrenb. In this state, doubtless, they are ejected by the Fish, in the intestines of which they were originally developed, into the sur- rounding water, and whenagain received into the alimentary canal undergo their metamorphosis, lose, like the Lerneae and Cirnpedes, the organ of vision which guided the movements of their young and free life, and grow and procreate at the expense of the nutrient secretions with which they are now abundantly provided. In the Ccdelmintha the young cast their in- tegument, and would seem in some species, as the Filaria Medinensis, to undergo a change in the form and proportions of the extremities of the body, but they do not possess cilia or ocelli, as in the Trematoda above-mentioned. The ova of the Linguatula are of an oval form : the germinal vesicle is situated near the superficies half-way between the two extremi- ties ; the vitelline membrane is surrounded with a strong cortical membrane : the develop- ment of the fetus takes place out of the body. In the Strongylus gigas, Strongylus injiexus, and a species of Trichosoma infesting the in- testines of the Goatsucker, we have found the foetus completely formed in the ova contained in the uterus or terminal segment of the gene- rative tube, while those in the ovary or narrow' commencement of the samepart were still occu- pied with the granular matter of the vitellus. The mature ova of the Strongylus gigas are of an elliptical form, and the embryo within is plainly seen coiled up through the trans- parent coats of the egg; the resemblance which these bear to the Trichina when inclosed in its inner cyst is very striking: the hypothesis suggested by this resemblance need only be alluded to for the purpose of exciting the at- tention of those, who may hereafter meet with the preceding minute muscular parasite, to the existence of larger Nematoid Entozoa in other parts of the body. Cloquet describes the ova in the beginning of the ovaries of the Ascaris Lumbricoides as consisting of rounded linear corpuscles, pointed at one extremity, thickened at the other; in the middle of the ovaries they as- sume an elongated triangular form, and one of their angles frequently supports a small spherical eminence ; the base of the ovum adheres to theparietes of the oviduct, the apex projects into its cavity. In the enlarged canals, which he terms the cornua of the uterus, the ova are unattached and of a conoid or irre- gularly triangular figure. In the uterus itself they have assumed an ovoid or elliptical form, are surrounded by a transparent glairy mucus, and are composed of a transparent cortical membrane, perfectly smooth on the external surface, and filled with a transparent fluid, in which floats a linear embryo, disposed either in a straight line or coiled up. Cloquet never observed the young Ascarides excluded from the egg in the interior of the uterus, and we equally searched in vain for free embryos in the generative tubes of the Strongylus and Oxyurus above-mentioned, although their de- velopment in regard to form appeared to be complete in the ovum ; the structure of the embryo resembles that of the simpler Vibriones, there being no generative tubes apparent, and the cavity of the body being occupied by a granular parenchyma. With respect to the exclusion of the ova in these and similar ovo-viviparous Nematoid Entozoa, it would appear to be very commonly accompanied with a rupture of the parietes of the body and of the generative tube. Ru- dolphi observes, with respect to the Cucullanus, “ Ovula, verme quieto, per intervalla ex vulva pullulent ; quin eodem disrupto, quod saepe accidit, ovula vel embryones ex ovariis pro- lapsis parituque ruptis vi quadam et undatim protroduntur.” The generation of the Filaria Medinensis is of the viviparous kind, and the progeny is countless,. — “ Filariae nostrse,” observes Rudol- phi, “ prole quasi farctae sunt, quod si harum longitudinem lllius vero minutiem spectas, fetuum multa millium millia singulis tnbuit.” What is most remarkable is, that these em- bryos are not, as in the Strongylus and the Nematoid genera above-mentioned, enveloped in an egg-covering, nor are they included in a special generative tube, but float freely along with a granular substance in the common mus- cular envelope of the cavity of the body. 144 ERECTILE TISSUE. M. Jacobson,* who has recently published a description and figures of the young Filaria Medinensis, compares the body of the mother to a tube or sheath inhabited by the young ones; and, after a careful examination of three individuals, we have equally failed in detecting either generative or digestive tubes within the muscular sac of the body. The external tunic of the body is a firm subtransparent elastic integument, which, examined under a high magnifying power, presents fine trans- verse striae, occasioned most probably by ad- herent muscular fibres. Within this tunic and readily separable from it are the longitu- dinal muscular fibres, which are arranged in two fasciculi, separated from each other by two well-marked intervals on opposite sides of the body, which are indicated by an impression (or furrow, as the worm dries by evaporation) on the exterior surface. When from long maceration the crisp outer integument has become separated from the longitudinal mus- cular bands, these might be mistaken for two tubes contained loosely within the cavity. 1 believe that these muscular bands are the tubes Jibrineuses, described by Dr. Le Blond f as the alimentary canal and intestine in the fragment of Filaria Medinensis, which he dissected. In a small Filaria Medinensis, containing no vermiculi, we have also failed to discover any distinct tubes for digestion or generation. It is interesting to observe that the young of the Filaria Medinensis do not resemble the parent in form ; one extremity is obtuse, the body slightly enlarges for about one-fourth of its length, then gradually diminishes to within a third of the opposite extremity, which is capillary and terminates in the finest point. The enlarged part of the worm contains a granular substance, and is coiled upon itself, and presents a distinct but minute annulation of the integument : the capillary extremity is smooth, transparent, and generally straight. The Triclwcephalus dispar closely resembles in its external form the foetus, if it be such, of the Filaria Medinensis. Bibliography. — Redi, Osservazioni intorno agli animali viventi che si trovano negli animali viventi, Firenze, 1684. Bloch , Abhand. von d. Erzeugung Eingewerdwiirmer. Berl. 1782. Goeze, Versuch einer Naturgeschichte der Eingewerdwiir- mer, nnd Nachtrag dazn. Leipz. 1782-1800. Veil- lisneri, Considerazioni ed esperienze intorno alia generazione de vermi ordinarj del corpo umano. Padova, 1782. Werner, Verrnium intestinaliuin, &c. brevis expositio. Leipz. 1782. Retxius, Lec- tiones publica; de Vermibus intestinalibus. Holm. 1786. Schrauk, Verzeuhniss der bisherigen hin- langlich. bekannten Eingeweidwiirmer, Munch, 1788. Rudolphi, Observ. circa vermes intestinales, 2 fasc. Greifsw. 1793-95. Rudolphi, Entozoorum s. vermium intestinalium historia naturalis, 2 in 3 vol. Amst. 1808-9. Rudolphi, Entozoorum Synop- sis, Berl. 1819. Treutler, Obs. pathol. anat. ad helminthologiamcorp. humani. Leipz. 1793. Zeder, Anleitung zur Naturgeschichte des Eingeweidwiir- * Nouvelles Annales du Museum d’Histoire Na- turelle, tom. iii. p. 80, pi. v. t Quelques Materiaux pour servir a 1’Histoire desFilaires et des Strongles, 8vo. 1836. mer. Bamb. 1803. Olfers, De vegetativis et ani- matis corporibus in corporibus viventibus reperiun- dis comment. Berl. 1816. Fischer, Brevis fintozo- orum s. verm, intest, expositio. Viennie, 1822. Bremser, Ueber lehende Wiirmer in lebenden Mens- chen. Wien, 1819; trad, en fran9ais, par MM. Grundler et de Blainville, Paris, 1825. Bremser, leones Helminthorum Systema Rudolphii illus- trantes, Wien. 1823. Joerdens, Entomologie und llelminthologie des Mensch. Koerpers. 2 Bde. Hof. 1801-02. Lulth de Jeude, Recueil des figures des Vers intestinaux, Leid. 1829. Cloquet, Anatomie des Vers intestinaux, Paris, 1824. Creplin, Observ. de Entozois, Greifesw. 1825-29. Schmalz, De En- tozoorum systemati nervoso, Leipz. 1827. Ejus, Tabulae anatomicse Entozoorum, Dresd. 1831. Le Blond, Quelques materiaux pour servir a l’histoire des filaires et des strongles, Paris, 1836. Mehlis, Obs. Anat. de distomate hepatico et lanceolato. Gutting. 1825. Nordmann, Mikrographische Bei- trage, 2 Bde. Berlin, 1832. Jacobson, in Nouv. Annales du Museum d’Hist. Nat. tom. iii. Klein, in Philos. Trans, for 1730. Carlisle, in Trans, of the Linnean Society, vol. ii. Laennec, in Bulletin des Sciences de l’Ecole de Medecine, An xiii. Home, in Philos. Trans, for 1793 ; Frisch, in Miscell. Berolinensia, tom. iii. ; and for further re- ferences to numerous papers on the natural history of particular families and species, vide Reuss's Repertorium, &c. Scientias Naturalis, tom. i. Zoo- logia, &c. Gotting. ; the first vol. of Rudolphi’s Entozoorum historia naturalis, and Wieqemann's Archiv fur Naturgeschichte und Vergleichende Anatomie. ( R. Owen.) ERECTILE TISSUE, (tela erect ills ; Ft. tissu erectile; Germ, das erectile, oder schwcll- bure Gewebe,) a structure composed prin- cipally of bloodvessels, intimately interwoven with nervous filaments. This tissue in its ordi- nary state is soft, flaccid, and spongy ; but when influenced by various causes of excite- ment, whether these consist of stimuli directly applied, or operating through the medium of the sensorium, it exhibits the faculty of admit- ting an influx of blood much greater in quantity than what is sufficient for its nutrition, and in virtue of which it suffers a state of turgescence giving rise to a swollen condition, with more or less of rigidity and increased sensibility of the organs into the structure of which it enters, and which state has been long known by the name of erection. From the property of under- going erection peculiar to this tissue, Dupuytren and Rullier first applied to it the term erectile, and the propriety of this distinguishing appel- lation is now very generally admitted by anato- mical authors. The erectile tissue is developed in various degrees in the several parts of the animal economy in which it occurs; it is abundant and particularly evident in the corpora caver- nosa penis, corpus spongiosum urethrae, clitoris, nymphae, plexus retiformis, the nipples of the mammary glands, less marked in the red borders of the lips, &c. ; it also enters into the structure of the papillae of the skin and the villi of the mucous membranes which possess the property of becoming erected in the per- formance of their functions, as is exemplified in the papillae of the tongue. These consist of the pulpy terminations of nerves enveloped by this tissue; in their unexcited state they appear ERECTILE TISSUE. 145 small, pale, soft, and shrunken ; but when excited to erection, they become increased in size, stiff, red, and distended with blood, at the same time that their sensibility is remark- ably exalted. The foregoing remarks apply equally to the cutaneous papillae, particularly those on the pulpy extremities of the fingers, where the sense of touch is developed in its highest degree of perfection. Erectile tissue has also been recognised in the callosities on the buttocks of some of the quadrumana, in the comb and gills of the cock, the wattles of the turkey, and in the tongue of the charnel ion.* It is not improbable that this tissue enters into the structure of the iris ; and Beclard seems disposed to consider that it exists in the spleen, as well from the appearance which that organ presents when a section of it is made, as from the different states in which it is found on opening the bodies of animals; being sometimes contracted and corrugated on the surface, and at other times plump, smooth, and swollen. In some of the situations above enumerated, the erectile tissue is enclosed in a fibrous sheath which limits its extent and determines the form of the organs in which it occurs ; while in other situations it is deployed superficially, as in the tegumentary organs. It is in the corpora cavernosa penis and corpus spongiosum urethrae, however, that the erectile tissue has been more especially made the subject of anatomical and physiological research ; and the results of the investigations instituted in these organs have been rather inferred from analogy than directly proved as equally applicable to it in all other situations in which its existence has been indicated. According to De Graaf, Ruysch, Duverney, Boerhaave, Haller, and Bichat, the cavernous bodies of the penis and urethra consist of a loose and elastic spongy tissue formed of in- numerable cells, into which, during erection, blood is poured from the arteries, and from which it is afterwards removed by an absorbing power of the veins. Such an opinion would accord with the appearances observed by examining sections of this structure after having been inflated and dried, but careful examina- tion of it when previously prepared by injec- tion, proves the foregoing opinion to be founded in error. Vesalius, who appears to have directed his attention to the particular nature of this struc- ture in the penis, describes it as composed of innumerable fasciculi of arteries and veins closely interwoven, and included in an invest- ing sheath. Malpighi considered it as composed of diver- ticula or appendices of veins. Mascagni, who at one time believed in the existence of cells interposed between the veins and arteries, in consequence of subsequent researches abandoned that opinion, and de- monstrated the fact, that a plexus of veins with arteries corresponding, but smaller and less * On the structure and mechanism of the tongue of the chamelion, by J. Houston, in Transactions of the Royal Irish Academy, vol. xv. VOL. II. numerous, formed the corpus spongiosum urethrae, glans, and plexus retiformis, and that the arteries entering this substance terminated in the commencement of veins. Mr. Hunter remarked that the corpus spon- giosum urethrae and glans penis were not spongy or cellular, but made up of a plexus of veins, and that this structure is discernible in the human subject, but much more distinctly seen in many animals, as the horse, &c. Subsequent researches respecting the struc- ture of the penis and clitoris of man, the horse, elephant, ram, &c. have been instituted by Duverney, Mascagni, Baron Cuvier, Tiede- mann, liibes, Moreschi, Panizza, Beclard, Weber, &c, and the result has been a con- firmation of the views developed by Vesalius, Malpighi, and Hunter. Moreschi, in particular, has shewn that the corpora cavernosa penis, corpus spongiosum urethra, and glans consist of a congeries of fine vessels in all animals, whether covered by skin, hairs, spines, or scales ; and that these vessels, which are principally veins, are characterized by their abundance, tenuity, and softness, which distinguish them from the veins in the muscles and other parts of the body. The annexed figure (fig. 97) from Moreschi Fig. 97. 14G ERECTILE TISSUE. represents the plexiform arrangement of the veins apparent on the surface of the glans, and which empty themselves into the superficial veins of the penis. M idler having more recently investigated the structure of the penis, has announced the discovery of two sets of arteries in that organ, differing from one another in their size, their mode of termination, and their use ; the first he calls nourishing twigs (raminutritii), which are distributed upon the walls of the veins and throughout the spongy substance, differing in no respect from the nutritive arteries of other parts ; they anastomose with each other freely, and end in the general capillary network. The second set of arteries he calls arteria heli- cina. In order to see these vessels, an injection of size and vermilion should be thrown into a separated penis through the arteria profunda : when the injection has become cold, the corpora cavernosa should be cut open longitu- dinally, and that portion of the injection which has escaped into the cells carefully washed out. If the tissue of the corpora cavernosa be now examined at its posterior third with a lens, it will be seen that, in addition to the nutritious arteries, there is another class of vessels of different form, size, and distribution. These branches are short, being about a line in length and a fifth of a millimetre in diameter; they are given off from the larger branches as well as from the finest twigs of the artery. Although fine, they are still easily recognised with the naked eye ; most of them come off at a right angle, and projecting into the cavities of the spongy substance, either terminate abruptly or swell out into a club-like process without again subdividing. These vessels appear most obvious and are most easily examined in the penis of man, to which the following description refers. These twigs branch off from place to place, sometimes alone, and sometimes in little bundles of from three to ten in number; these, as well as the former, project constantly into the cells or venous cavities of the corpora cavernosa penis. When the arteries thus form a bundle, they arise by a common stem. Sometimes such a vessel, whether it proceeds from the artery as a single branch or as part of a cluster, divides into two or three parallel branches, which also either terminate abruptly, or else swell out near their extremity. Almost all these arteries have this character, that they are bent like a horn, so that the end describes half a circle, or somewhat more. When such a branch so divides itself, there are formed doubly bent twigs inclined one to the other. Many of these arteries enlarge towards their end; this enlargement is gradual, and is greatest at some little distance from the extremity, so that the end is somewhat conical, terminating immediately in a rounded point without giving off any branches. The diameter of these arte- rial twigs, in their middle, is from one-fifth to one-sixth of a millimetre : those which branch off from the trunk of the arteria profunda penis are no larger than those which arise from its finest twigs. It is by no means unusual to Fig. 99. observe the finest twigs of the arteria profunda giving off branches of this kind which seem much thicker than the twig from which they arose. The annexed figure (fig. 98) (from Muller’s Archiv.) repre- sents a portion of the arteria profunda penis of man, with its arteria helicinse somewhat mag- nified. These remarkable arte- ries have a great resem- blance to the tendrils of the vine, only that they are so much shorter in proportion to their thick- ness, whence they have received the name arteria helicinte. Their termi- nations may also be com- pared to a crosier. By a more minute examination of these vessels either with the lens or with the microscope, it will be seen that, although they at all times project into the venous cavities of the corpora cavernosa, yet they are not entirely naked, but are covered with a delicate mem- brane, which under the microscope appears granular (Jig. 99). After a more forcible in- jection this envelope is no longer visible. When the arteries form a bundle, the whole is covered by a slight gauze-like membrane. With respect to this in- vesting membrane, Profes- sor Miiller appears to con- sider it as performing an important part in producing the phenomena of erection. These tendril-like arteries have neither on their surface nor their extremities any openings discoverable with the aid of the microscope ; and when the blood, as it is probable, escapes from them in large masses into the cells of the corpora cavernosa during erection, it must either traverse invisible openings, or pass through small openings which become en- larged by the dilatation of these arteries. If the great number of the tendril-like branches of the arteria profunda be compared with the very fine nutritious twigs of the same vessel, it is evident that when the former are filled they must take up the greater part of the blood of the arteria profunda; the diameter of the profunda therefore not only includes its nu- tritious twigs, but also the tendril-like branches, which derive their blood from it, yet pro- bably allow none to pass except during erec- tion ; therefore the blood in the unerected state only traverses the nutritive branches and ar- rives at the commencement of the venous cells in smaller quantities, while during erection it probably passes in considerable quantity into the cells through these tendril-like vessels. Professor Miiller, after pointing out the dif- ference between the tendril-shaped vessels and the looped vessels discovered by Weber in the EXCRETION. 147 villi of the placenta, observes : our vessels are simple ; they bend themselves at the end, but do not return to their trunk as a loop, being simply blood-containing processes of the ar- teries which project freely into the cellular cavities of the veins of the corpora cavernosa. These vessels are most numerous in the pos- terior part of the corpora cavernosa ; they occur but seldom in the middle and anterior parts : they are also present in the corpus spongiosum urethrae, especially in the bulb; here also they become less frequent anteriorly, and as yet they have not been perceived in the glans. They are much more difficult of detection in the corpus spongiosum urethrae than in the corpora cavernosa, where they are very easily exhibited, especially in the human penis. In no other animal have they been found so dis- tinct, or so uniform in their existence as in man. The greater development of these arteries, adds Professor Muller, in the posterior parts of the organ corresponds with the fact of erection being always earlier evident there, as if the blood distributed itself from thence into the venous cells. During erection blood is accumulated in large quantity in the erectile tissue, but the cause and mechanism of this accumulation are but imperfectly known. Ilebenstreit ascribes it to a living power, named turgor vitalis , which exists in different degrees in almost all the textures of the animal body, but most dis- tinctly in the erectile tissue. It still remains, however, to be proved how far erection de- pends on mechanical pressure affecting the veins which convey blood from this structure, and consequent retardation of the venous circu- lation ; and how far it may depend upon an increased flow of blood to its arteries accompa- nied, or perhaps more correctly, occasioned by an increase of sensibility,* or whether it may not depend upon the influence of both these causes combined. Erectile tissue appears sometimes to be de- veloped as a morbid production, which has been described under the names of varicose tumour, aneurism by anastomosis, naevus raa- ternus, telangiectasis, &c. Its anatomical cha- racters are of the same kind as those of the [* Ii must be obvious that the discovery of the arterial helicinae by Professor Muller favours this theory of erection, as proving the existence of ves- sels distinct from the ordinary ones, which receive and transmit the increased supply cf blood to the venous cells. What, in other organs, is effected by a diminished tonicity in the arteries, and a con- sequent enlargement of them, ultimately giving rise to the tortuosity so striking in some cases, is here effected by means of a very peculiar set of arterial processes superadded to the ordinary nutri- tious arteries of the organ. In the pregnant uterus the increased supply of blood is provided for by the enlargement and consequent tortuosity of its ordi- nary arteries ; there are no sinuous veins here to receive the new supply of blood, and consequently erection is not present ; but in the case of the penis this phenomenon occurs in consequence of the existence of the sinuous veins which constitute so large a proportion of the corpora cavernosa. It will be interesting to inquire whether any similar or analogous arrangement of arterial processes exists in other erectile organs. — Ed.] normal erectile tissue ; it varies in size, being more or less circumscribed, sometimes sur- rounded by a thin fibrous envelope; presenting internally an appearance of cells or spongy cavities, but consisting, in reality, of an in- extricable congeries of arteries and veins which communicate by innumerable anastomoses like capillary vessels, but much larger, espe- cially the veins. It is difficult to inject it from the arteries, more easy from the neighbouring veins, which are sometimes much enlarged. This alteration most commonly exists in the substance of the skin, where it sometimes re- sembles the comb and other analogous parts of the gallinaceae. The skin of the face, espe- cially that of the lips, is frequently its seat. It has been observed in the subcutaneous cel- lular tissue in masses of various dimensions, sometimes so large as to occupy an entire limb. It rarely affects the internal organs; sometimes it extends beneath the mucous membrane of the mouth, mostly in the vicinity of the red borders of the lips. This production is occa- sionally affected by a vibratory motion amount- ing sometimes to a pulsation resembling that of ananeurismal tumour, which is increased by all the causes which excite the activity of the general circulation ; it cannot be properly said that this structure has the property of under- going erection. It is often congenital, some- times it appears to have been produced by accidental causes ; it sometimes remains un- altered ; but it more usually continues to in- crease in size until some of its cavities burst, when haemorrhage of a troublesome description ensues. Beclard considers the haemorrhoidal tumours which occur round the anus as constituting a variety of anormal erectile tissue. Bibliography. — Vesalius de corp. humani fabrica, lib. v. cap. xiv. Venet. 1564. De Graaf Regner, De virorum organis, &c. p. 99 et seq. Lugd. Bat. 1668. Malpighi Udarcelli opera omnia, tom. ii. p. 221. London, 1686. Ruysch Frid., Observatio, C. Amstel. 1691. Haller, Ele- menta, lib. ii. sect. i. § 24, et lib. xxvii. sect. iii. $ 10. Mascagni, Prodromo della grande anatomia, Firenze, 1819. Hunter John, On certain parts of the animal economy. Bond. 1786. Moreschi Alex. Comment, de urethra; corporis glandisque structura, Mediolani, 1817. Dmernay, in comment. Petro- polit. tom. ii. p. 200. Cuvier, Lemons d’anatomie comparee, tom. iv. Paris, 1799 — 1805. Tiedemann, in Journal complementaire, tom. iv. p. 282. Hebenstreit, G. De turgore vitali in Brera Sylloge, tom. ii. Duverney, CEuvres anatomiques, tom. ii. Paris, 1761. Mascagni, P. Hist, vasorum lymphat. sect. ii. Senis, 1787. Beclard, A nat. generale, Paris, 1823. Weber, H. E. Allgemeine anatomie, p. 415. Braunschweig, 1830. Craigie David, M.D. Elements of general and pathological anatomy, Edin. 1828. Muller, in Archiv fur Physiologie, Jahr 1835, p. 202. The paper of Professor Muller has been very ably translated in the London Me- dical Gazette, No. 423. ( J. Hart.) EXCRETION. — This term is applied to the formation of those fluids in'- the animal economy, which are destined to no useful purpose in the system, but are intended to be discharged from it, and the retention of which is injurious or l 2 148 EXCRETION. even fatal. The term used by the older phy- siologists was excrementitious secretions. Some general observations may be made on these ex- cretions, with the view both of stating the pre- sent extent of our knowledge on this mysterious subject, and of pointing out the importance of an arrangement and combination of facts re- lating to it, which are usually treated, perhaps, in too unconnected a manner, but the con- nexion of which is already perceptible, and can hardly fail to be satisfactorily elucidated in the progress of physiology. When we shall have more precise informa- tion as to the peculiar, and hitherto obscure principles, which regulate the chemical changes continually taking place in living bodies, it does not seem unreasonable to anticipate, that a dis- covery will be made, connecting the excretions of the body with the assimilation of the food, and with the nourishment of the different tex- tures, a discovery which may be equally as important in illustrating the chemical phenome- na of the living body, as that of the circulation was in explaining those changes which come more immediately under our observation. In the mean time, we can point out a great deal of contrivance, connected with the general function of excretion, and can state what are the general injurious results, when this contrivance fails of its intended effect; but we are unable to explain how the contrivance effects its purpose, or to point out any general law, by which these in- jurious results are determined. I. We may state, in the first place, that the necessity for some kind of excretion, or dis- charge of certain matter from the organized frame, corresponding to the acts of nutrition, or of reception and assimilation of external matter, is a law of vital action, applicable to all organized beings without exception. The uni- versality of the excretion of carbon, (whether pure, or in the form of carbonic acid, we need not now inquire,) has been established by the inquiries of Mr. Ellis and others, and the poi- sonous influence of the carbonic acid, in an un- diluted state, to all living beings, is an equally general fact. In all animals, which possess organs of such size and distinctness as to make their economy matter of observation, other excre- tions are likewise observed; and in vegetables, it is not only certain that various excretions, besides the exhalation of water and of carbonic acid, take place, but it is even believed by De Candolle, that all the peculiar products of vital action, excepting only gum, sugar, starch, and lignine, (which have nearly the same elementary composition, and are convertible into one another,) and, perhaps, fixed oils, are applied to no useful purpose in the economy, and are poisonous to the plants in which they are formed, if taken in by their roots and com- bined with their sap; so that, although often long retained in individual portions of the plants, they all possess the essential characters of excretions.* And it appears to be well ascer- tained by the observations of De Candolle and of Macaire, that at least great part of the proper * Physiol. Veget. p. 217. juices of vegetables, which descend chiefly by their bark, and are expelled into the soil, are destined to excretion only, and are noxious to plants of the same species, or even of the same families, if growing in that soil (although often useful to the growth of plants of different fami- lies); and this principle has been happily ap- plied by the former author to explain the neces- sity of rotation of crops of different natural families, to prevent deterioration of the produce.* As this necessity of excretion appears to be so general an accompaniment of the vital action of all organized beings, it seems obvious that there must be some general law, which deter- mines the noxious quality of these products of that action, and imposes the necessity of their expulsion. Yet it is certain that the chemi- cal demerits which pass off in the excretions, are the same which are found in the textures of the animal body, and in the nourishment, which is essential to animal life. It would appear, therefore, that the noxious property belongs to certain combinations only of these elements, which are formed in the course of the chemical changes in living beings, and which, when once formed, must either be ex- pelled from the body, or else laid up in cells appropriated for the purpose, (as in the case of the resins and volatile oils in vegetables, and of the bile in the gall-bladder in animals,) and kept out of the mass of the nourishing fluid. There is one general fact, on which much stress has been justly laid by Dr. Prout, which is confirmed by M. Iiaspail, and which may, perhaps, be concerned in determining the noxious qualities of certain compounds, in liv- ing beings, viz. that although the elements which enter into the composition of organized bodies, readily combine, in other circumstances, so as to form crystals, yet the peculiar combi- nations which they form in all the textures which are essential constituents of those organic structures are never crystalline. When a crystal occurs in an organized body, according to Dr. Prout, f it is always either the result of disease, or of some artificial process, or it is part of an excretion, separated from the nourishing fluid and from the useful textures. 1 Every one of these textures contains, even in its minutest particles, saline and earthy, as well as animal or vegetable matter ;§ but the combinations arc always so arranged, by the powers of life, that these saline and earthy particles are always dif- fused through membranes, fibres, or cells, never concentrated in crystals. On the other hand, the elements constituting the peculiar matters of the excretions are generally in such a state of combination as readily to assume the crystalline form, either alone, or in the simplest farther combinations of which they are susceptible ; and it seems possible, that this circumstance may be part at least of the cause which necessi- tates their expulsion. This is only matter of * Ibid. p. 249, and p. 1496. t Lectures in Medical Gazette, vol. viii. f “ Jamais je n’ai aper9U,” says Raspail, " de cristaux dans le sein d’une cellule vivante et d’ac- croisement,” Raspail, Chimie Organique, § 1378. § Ibid. § 1390. EXCRETION. 149 speculation, but that some such general prin- ciple determines the incompatibility of the mat- ters of the excretions with the life of the struc- tures in which they are formed, can hardly be doubted. II. Although the necessity of various excre- tions is obvious, there is a difficulty, both in the case of animals and vegetables, in fixing on those products of vital action which come exclu- sively under this denomination ; and it appears certain, that some of the organs of excretion (such as the lungs) are at the same time de- stined to other purposes, particularly absorption ; and even that part of certain excreted fluids (such as the bile) is employed likewise in the work of assimilation. But it is certain that the lungs or gills, the skin, the intestines, and the kidneys, are the outlets for excreted matters in all vertebrated animals. 1. There can be no doubt that the watery vapour and carbonic acid which are exhaled from the lungs, are strictly excretions, although it is still doubted by some physiologists, whe- ther the latter substance is truly exhaled, or rather formed at the lungs; on the latter sup- position we should say, that the excretions of the lungs are water and carbon. It appears certain, from some experiments of Dr. Gordon, that no animal or saline matter escapes by this outlet. The total amount of loss by this excretion in twenty-four hours, in a middle-sized man, has been stated by Lavoisier and Seguiti as aver- aging about fifteen ounces; and it must be re- membered, that as we have good evidence of very considerable absorption at the lungs, the whole quantity of matter excreted must consi- derably exceed this weight. Indeed, Mr. Dal- ton estimates the exhalation of watery vapour only from the lungs at twenty-four ounces in the day. Some have estimated the quantity of carbon alone escaping in this way in the day at eleven ounces ; but this estimate is probably exaggerated. It seems to be ascertained by the experiments of Dr. Edwards, of Despretz, and Collard de Martigny, that there is at times an obvious exhalation of azote by the lungs; and Dr. Edwards expresses an opinion that there is probably, at all times, both an exhalation and absorption of that gas, but that these processes in general nearly compensate one another. According to Dr. Prout’s views, re- cently, though briefly, announced, we may, per- haps, state the source and cause of the forma- tion of the carbonic acid, and assign the use of the excretion of the water, which escapes by the lungs, with more precision. He supposes the acid to be evolved in the course of the circula- tion, by that “ process of reduction,” by which the gelatin of the animal textures is formed from the albumen of the blood ; and the water to be given off chiefly from tlieweak albuminous matters of the chyle, and to be an essential part of the “process of completion,” by which this is converted into the strong albumen of the blood * 2. The excretion by the skin is chiefly * See 13 ridge water Treatise, p. 524. watery vapour; the escape of carbon, or carbonic acid, by this outlet appears to be to a very small amount, and to be very variable. In the sen- sible perspiration or sweat there is an excess of lactic acid, a small quantity of the same animal and saline matters as are contained in the serum of the blood, and a little oily or fatty matter, probably from the sebaceous glands ; the whole loss by this excretion in the human adult has been stated as averaging about thirty ounces in the day, but is evidently liable to very great variety. Many experiments prove that there is much less compensating absorption by this tex- ture than by the lungs. 3. The excretions by the bowels are, properly speaking, only those parts of the alvine evacua- tions, which are secreted within the body itself, and mixed with the residue of the food. It is probable that part of the secretions from a!) parts of the primse viae are thus excreted, but the only one of which it has been ascertained that it is, in part at least, destined necessarily for excretion, is the bile. It is certain that the peculiar animal matter of this secretion, (re- garded by some as of pretty simple and by others as of very complicated composition) is never found in the healthy slate in the lacteal vessels or thoracic duct — that it is found in full quantity along with the residue of the aliments in the lower intestines,- — that it is increased in quantity when the excretion of urine is sup- pressed in animals by extirpation of the kid- neys ; and again, that when this secretion is sup- pressed, the urine is increased and altered ; and we can therefore have no difficulty about regard- ing this part of the bile as strictly an excretion, notwithstanding that we have good evidence, that at least the alkali of the bile is of use in the digestion and assimilation of the food. Of the quantity of matter strictly excreted from the intestines in the day it must of course be very difficult to judge. The chemical elements that escape in the biliary matter must be chiefly carbon and hydrogen. 4. The urine is the most complex of the ex- cretions, particularly as to saline impregnation, containing not only the salts which are detected in the blood, but a portion of every earthy and saline matter that can be found in any part of the body, besides the peculiar and highly azo- tised animal matters, lithic acid and urea. The average quantity of urine passed in twenty-four hours may be about forty ounces, but is very liable to variation, particularly by temperature, being generally greater, as the excretion by the skin is less. The quantity of solid matter, animal, earthy, and saline, that passes oft’ in this way has been stated at about fifteen drachms on an average, and is evidently much less liable to change, the density of urine, in the healthy state, always diminishing as its quantity increases, and vice versa. The milk, and the semen, although destined to no useful office in the system in which they are formed, are rather to be called recrementitious secretions than excretions. Yet the former has this property in common with excretions, that its retention within the body, when the conditions of its formation exist, is EXCRETION. 150 hurtful. The menstrual discharge may be regarded as strictly an excretion, though one which is required only in the human species and for a limited time. Berzelius stated several distinctions, which he thought important, between the excremen- titious and recrementitious secretions in the animal body, particularly that the former are always acid, that each of them contains more than one animal matter, and that their salts are more numerous and varied than those in the blood, while the latter have an excess of alkali from the same saline ingredients as the serum of the blood, and each contains only a single animal principle, substituted for the albumen of the serum. But these distinctions are cer- tainly inapplicable in several instances, and the only one of them which appears to be a general fact, is the more complex saline impregnation of the excreted fluids. III. It is unnecessary to dwell on the well- known injurious effects, on the animal oeconomy, of the suppression of any of these excretions. It may, indeed, reasonably be doubted, whether the rapidly fatal effects of obstructing the ex- posure of the blood to the air at the lungs are owing to the retention of carbon, or carbonic acid ; it seems much more probable that the cause which stops the circulation at the lungs in asphyxia, is the suspension of the absorption of free oxygen into the blood, rather than the suspension of the evolution of carbon or car- bonic acid. But even if the circulation could be maintained, after the exposure of the blood to the air is suspended, we know that the carbonic acid which we have good reason to believe would soon be in excess in the blood, would then act as a narcotic poison. Of the effects of suspension of the excretion by the skin we can- not speak with certainty, because that is a case which probably hardly ever occurs ; and if it were to occur, the lungs and kidneys would probably act as perfect succedanea. But it is worthy of notice that at a time when the skin is known to be nearly unfit for its usual functions — during the desquamation that succeeds exan- thematous diseases, and especially scarlatina, — the lungs and the kidneys, on which an unusual burden may thereby be supposed to be thrown, are remarkably prone to disease. The effect of suppression of the excretion of urine (i. e. of ischuria renalis), whether occurring as a disease in man, or produced by extirpation of the kid- neys in animals, is uniformly more or less of febrile symptoms quickly followed by coma and death; and in these circumstances it is now known, that the urea may be detected in the blood. A variety of morbid affections, and particularly an affection of the nervous system marked by inaptitude for muscular or mental exertion, always follows the obstruction of the excretion of bile, and absorption of bile into the blood constituting jaundice. There are a few cases of intense jaundice which terminate in coma and death as rapidly as the ischuria renalis does, and with as little morbid appearance in the brain to explain this kind of fatal termination ; and in several such cases the remarkable phenomenon has been observed after death, that the bile-ducts have been pervious and empty.* It is obvious, that it is this last circumstance only, that can make a case of jaundice analogous to cases of the ischuria renalis. If it shall appear to be a general fact, that the cases of jaundice presenting this remarkable appearance on dissection are those which terminate with unusual rapidity in the way of coma, the analogy will appear to be complete ; and when such cases are compared with those, much more frequently occurring, where the excretion of bile is only obstructed, not suppressed, and where months frequently elapse without any bad symptom occurring, — it appears a reason- able conjecture, that the retention in the blood of matters destined for excretion, is more rapidly and certainly injurious than the re- absorption of matters which have been excreted from the blood at their ordinary outlet, but not expelled from the body. Although there is still much obscurity in regard to the intention of the menstrual dis- charge, yet it may be stated as a general fact, that the suppression of this evacuation is more frequently followed by injurious effects (particu- larly affections of the nervous system, or vica- rious haemorrhage) than the stopping of an equal amount of haemorrhage, going on equally slowly, would be ; so that the general principle applicable to other excretions is exemplified here likewise. IV. The next question in regard to the ex- cretions is, in what manner they are effected ; and on this question, although we must profess ignorance in the last result, yet it is instructive to observe, what seems now to be well ascer- tained, that the large size, and apparently com- plex structure, of several of the organs of excre- tion, appear to be no part of the contrivance for the formation of these fluids from the blood. It is stated by Cuvier, as the result of a general review of the structure of glandular organs indifferent classes of animals, that pro- ducts very nearly resembling each other, and evidently answering the same ends, are formed in organs where the structure, and the disposi- tion of vessels are very various ; and again, that substances the most widely different are formed in organs that are in these respects ex- tremely similar;! and that this should be the case will not appear surprising when we consider the result of the most minute and accurate observations on the ultimate structure even of those secreting organs, which form substances the most dissimilar to the general nourishing fluid, either of animals or vegetables. “ Chaquc cellule de la structure vegetale,” says De Candolle, “ peut etre consideree comme une vesicule organique et vivante, qui est entouree, ou de cavites dans lesquelles abordent des liquides, ou de cellules remplies elles-memes de * See Marsh in Dublin Hospital Reports, vol. iii Two cases of exactly the same description have oc- curred within these few years in the Edinburgh Clinical wards. t Leyons d’Anat, Comp. t. v. p. 214. EXCRETION. 151 liquides. Cette vesicule, par sa vitalite propre, absorbe une partie du fluide qui l’entoure; ce fluide est ou de l’eau prfesque pure, et alors elle en est simplement impregnee et lubrifiee ; ou de l’eau plus ou moins chargee de cetle matiere gommeuse, elaboree dans les feuilles, et d’autres matieres alimentaires qui peuvent se trouver portees avec la seve dans les diverses parties. La vesicule qui V a absorbce lui fait subir une action cleterminee d’apres sa propre nature, et cette action modifie les materiaux contenus dans la cellule, de mantere a en faire, ou l’une des matiferes communes que nous avons considerees, ou l’une des matieres que nous aurons bieutot a examiner, telles que les huiles volatiles, les resines, &c. Certains vaisseaux analogues a la nature des cellules jouent le meme role sous ce rapport. Les matieres ainsi localement elaborees peuvent, ou rester dans les cellules ou les vaisseaux qui leur ont donne naissance, ou s’extravaser au dehors et donner lieu, soit a des excretions, soit a des transports des matieres d’une partie a l’autre du tissu.”* The description given by Dutrochet of the act of secretion as it may almost be detected in the glands of the lower classes of animals, is exactly similar. “ Entre les vesicules qui composent le tissu organique des animaux ram pent les vaisseaux sanguins, chezles animaux a circulation : ces vesicules sont appliquees sur les parois des vaisseaux; et il est certain que la cavite des vesicules ne communique point immediatement avec la cavite des vais- seaux, puisque le meme fluide n’existe point dans leurs cavites. Ce fait est tres facile a verifier, en examinant au microscope le tissu d’un organe secretive chez un mollusque gas- teropode, celui de la foie par example : on voit toutes les vesicules de cet organe remplies par la bile, que Ton distingue a sa couleur, tandisque les vaisseaux sanguins qui cotoient ces vesicules n’ont que la diaphaniete que leur donne l’etat incolore du sang qui les remplit. Ainsi, les vaisseaux sanguins n ’existent que comme des moyens d’irrigation pour les vesi- cules qu’ils cotoient, et ce n’est peut-etre que par filtration que le fluide sanguin penetre, en si modifiant, j usque dans ces vesicules elemen- taires. Le systeme sanguin, eonsidere dans son entier, forme une cavite sans issue, dans laquelle rien ne peut entrer, et de laquelle l ien ne peut sortir, autrement que par filtration." f Any one who is acquainted with the elabo- rate “ Vasorum Lymphaticorum Ilistoria” of Mascagni, will recognize the perfect accordance of this statement with the result of his careful and minute investigation of the structure of the secreting organs in the higher animals.! We may consider, then, the act of secretion, en dermere analyse,” as consisting simply in * Physiol. Vegetale, p. 215. t L’agent immediat du mouvement vital devoile, &c. p. 192. t It must not be considered as ascertained, that the files or tracks of globules of blood seen under the microscope, and usually called capillaries, have really, in all animals, and all parts of these, vascular coats. It seems pretty certain, that in the passage of certain portions of a compound fluid through a thin living membrane, and the exclusion of others; or, according to the for- tunate expression of Dutrochet, as a chemical filtration. “ All that is necessary for any kind of secretion in a living animal,” says Mr. Mayo, “ is a vascular membrane, and all the arrangements of the glands appear to be merely contrivances for conveniently packing a great extent of such a surface in a small compass.” And if we are asked, to what cause we can ascribe this escape of certain matters from the circulating fluid through one portion of mem- brane, and of others through another, we can only answer, in the words of this last author, that it depends on the exercise of certain “ vital affinities,’ ’ peculiar to the living state, and the existence of which will always bean ultimate fact in Physiology, although we may attain to a knowledge of the laws according to which they operate. V. One principle may already be laid down, almost with certainty, as to the exercise of these powers in the present instance, viz. that the peculiar matters characterizing the excretions are not actually formed from the blood at the parts where they appear, but only separated from the blood at these parts, — their formation, if not actually completed, having been at least considerably advanced, in the blood itself which reaches these parts. Of this we are well assured, chiefly by the following facts. 1. The experiments already mentioned, first made by Prevost and Dumas, have proved that within a short time after the extirpation of the kidneys in animals, urea may be detected in the blood, showing clearly that the existence of these glands is not necessary to the forma- tion of this very peculiar excrementitious matter, and giving us reason to conjecture that the office of the kidneys is, not to form the urea, but to attract it out of the blood as fast as it is formed there. The same existence of urea in the blood has been ascertained in the human body, both in cases of diseased kidneys, when the excretion there was much impeded, and in cases of malignant cholera, when the excretion was suppressed. The cases of rapidly fatal jaun- dice already mentioned , where the bile-ducts were pervious and empty, would seem to have been cases where the peculiar matter of the bile has been in like manner formed in the blood, without finding the usual vent at the liver. And it will appear under the head of Respira- tion, particularly from the experiments of Dr. Edwards, and of Collard de Martigny, that there is good reason to believe the carbonic acid of expired air to be formed in the course of the circulation, and only exchanged for oxygen at the lungs. 2. There are various instances in disease, of substances generally found in the secretions of certain glands only, being deposited in situa- tions quite unusual, and where no texture similar to these glands exists ; e. g. cholesterine, many cases they are only lines or membranes, or channels in a solid parenchyma ; but still the obser- vation in the text applies strictly to the escape of any particles of the circulating fluid from them. 152 EXCRETION. which in the natural state is found only in the bile, has been found deposited in diseased structures in the brain, kidneys, pelvis, scro- tum, &c. ; and lithic acid, naturally existing only in the urine, is deposited in cases of chalk- stone in the textures immediately surrounding the joints of the fingers and toes. It seems to be nearly in like manner that purulent matter, when mixed in unusual quantity with the blood, as by inflammation of a vein, is fre- quently deposited in individual parts of the body, with little or none of the usual sym- ptoms, or of the other accompaniments, of in- flammation at these parts. 3. There are a considerable number of cases recorded on unexceptionable evidence, where excretions have passed off per uliena cola, i. e. by organs which in the natural state yield no such products, and the structure of which is widely different from that of the glands where they are usually secreted. This has been most frequently observed of the milk and of the urine, and of the latter, both in cases where the secretion at the kidneys had been sup- pressed, and in cases where its discharge by the urinary passages has been obstructed, so as to occasion its re-absorption. In both cases it is obvious that the peculiar matter of this excretion must have been first mixed generally with the blood, and then deposited in indivi- dual parts of the system, widely different as well as distant from those where it usually appears. In cases of this kind collected by Haller,* the vicarious discharge of urine is stated to have occurred from the skin, from the stomach, from the intestines, and from the nipples; and in cases recorded by Dr. Arnold and Dr. Sen- ter in America, it is stated to have been passed by vomiting, by stool, from the nose and from the mamma, as well as other parts.f Both in cases given by Haller, and in one recorded in Magendie’s Journal de Physiologie, (vol. vii.) milk is stated to have been evacuated in quan- tity from pustules that formed on the thigh ; and among the former are instances of its hav- ing passed off from the salivary glands, the kidneys, and the uterus. Such statements were formerly considered as fabulous, but since the facts already mentioned (and particularly the appearance of urea in the blood after ex- tirpation of the kidneys) have been ascertained, this scepticism seems no longer reasonable. It must be here observed, that the healthy blood is easily shown to contain in itself mat- ters more nearly akin to all the solid textures and to the other secreted fluids of the body, than to the bile and the urine ; and hence, if we are satisfied that the elaboration of these latter fluids is effected in the blood itself, and does not essentially require any special action of the organs in which they usually appear, there can be little hesitation about extending this inference to other acts of secretion and to nutrition. It appears, therefore, at least highly probable, that the whole processes of as- similation and elaboration of the fluids in the * Klein. Phys. lib. vii. ch. 1. t London Med. and Phys. Journal, 1828. living body are carried on, as other chemical changes on fluids are, in the interior of these fluids themselves, and that the solids of the body are concerned in these changes only in two ways : first, by securing the complete sub- division and intimate intermixture of the fluids necessary to their chemical changes ; and second- ly, by determining the parts of the body where peculiar matters, already existing in the blood, shall be deposited from it, or attracted out of it. VI. We may next enquire, what is the most probable original source of the matters which are thrown out of the body in the way of ex- cretion. As it is generally believed, and on strong grounds, that the solid textures, as well as prepared fluids of the body, are liable to continual decay and renovation, it has long been the general belief, that the materials for the ex- cretions are supplied chiefly from those sub- stances which have formed part of the textures, and, after fulfilling their office there, have been taken back into the circulation with a view to their discharge from the body. And it has been conjectured, certainly with much probabi- lity, by Berzelius and by Autenrieth, that the animal matters thus mixed with the blood on their way to the excretories, are distinguishable from the albuminous or nutritious parts of the blood, by their solubility both in hot and cold water, and constitute the animal matter of the serosity, or uncoagulable animal matter of the blood. This is supported by the observation, that, when the kidneys are extirpated, this part of the blood is first observed to increase in amount, and afterwards it is here that the urea is detected.* And the connexion of the excretions with absorption from all parts of the body seems farther illustrated by the pheno- mena of diabetes, which may be held to be the disease in which there is the strongest evidence of increased absorption in all parts of the body, from the rapid digestion, the rapid recurrence of thirst after drinking, the dryness of the sur- face, and the progressive emaciation notwith- standing the excessive amount of ingesta ; and in which the quantity of the urine is often ten times, and the solid contents of the urine often twenty times, the average quantity in health.) But it should not be too hastily concluded, that all the solid constituents of the animal body are liable to continual absorption and renova- tion. The permanence of coloured marks on the skin, noticed by Magendie, is sufficient evidence, that, in some of the textures, any such change must go on very slowly ; and some of the best observers doubt whether any such pro- cess of alternate deposition and absorption takes place in vegetables, in which, nevertheless, as we have seen, excretion is a necessary process. * Prevost et Dumas in Ann. de Chimie, t. xxiii. p. 97. f The change of nature of the animal part of this solid matter, (viz. the disappearance of part of the urea, and substitution of an excessive quantity of sugar,) is evidently connected with the singular fact ascertained by Dr. Prout, that sugar differs from urea simply in containing no azote, and a dou- ble quantity of carbon and oxygen : a discovery which will, probably, acquire a greatly increased importance in the progress of organic chemistry. EXCRETION. 153 Dr. Prout has lately stated strong reasons for thinking, that great part of the contents of the lymphatic vessels are not excrementitious, but destined for useful purposes in the animal eco- nomy ; remarking particularly on the way in which hybernating animals appear to be nou- rished by absorption of their own fat .* And it is obviously possible, that the excre- tions may be required to purify the blood of matters taken in from without, or evolved in the course of the circulation and its abundant changes, as well as to purify it of what has been absorbed from the system itself. Now that we know, that great part of the ingesta into the stomach are taken up by the veins, and pass through the liver on their way to the heart ; and, likewise, that the venous blood is the chief source of the excretions of bile, it seems pro- bable, that one important use of this excretion is, to subject a part of the ingesta to a second filtration, or rejection of part of their ingre- dients, subsidiary to that which they undergo in the prim* vi*. This may also be probably one principal reason why the great mass of the chyle, and other products of absorption in the body, should be mixed with the blood just before its concentration at the heart, and subsequent dif- fusion through the lungs ; and thus participate in a purification, by the rejection of water and carbonic acid, before they are applied to the purposes of nutrition. We know, that in birds, reptiles, and fishes, there is a venous circulation similar to that of the vena port*, through the substance of the kidneys, of most of the blood coming from the lower half of the body ; a part of the ingredients of that blood will, there- fore, be evolved with the urine; and, in the case of the reptiles, it has been lately ascertained, that this venous blood receives, before entering the kidneys, the contents of numerous and large lymphatics.j- At all events, if we are right in supposing, that, in the higher animals, all the great chemi- cal changes which are wrought on the blood, even the formation of the excretions, are effected during its circulation in the bloodvessels them- selves, we can thereby acquire a general notion of the intention of several contrivances, the use of which is otherwise very obscure. We can understand, that the object of the concentration of the blood at the heart may be not merely mechanical, but, partly, also chemical ; and we can see the intention of the heart being so ad- mirably adapted, by the articulated structure of its internal surfaces, not only to receive and propel, but also most effectually to intermix, all the component particles of the blood, both be- fore and after its exposure to the air ; the most perfect illustration of which power of the heart is afforded by the effect it produces on any com- pressible and elastic fluid which is received in a mass of any considerable volume into its cavi- ties, and which is necessarily subdivided into so many minute globules, and compressed in so many directions, that it cannot escape from the heart, and so stops the circulation. * Bridgewater Treatise, p. 515, ot seq. t Muller, in Phil. Transactions, 1833. Again, when we attend to the manner in which substances foreign to the circulation are absorbed into it, whether from the system itself, or from without, we see a great deal of contri- vance, evidently adapted, and probably intended, to secure the most gradual introduction, and the most perfect intermixture possible, and to allow the escape of certain parts of the compound fluid formed. Thus of the contents of the prim* vi*, part are absorbed into the veins, and sent through the capillaries of the liver and those of the lungs, (both admitting of excretion,) before they are admitted into the arteries. What is taken up by the lacteals has already undergone much elaboration by living fluids ; this portion passes through the mesenteric glands, and is, probably, so far intermixed with the blood there, and partly received into the veins passing from them to the liver;* and the rest is mixed with much matter flowing from other parts of the system by the lymphatics; and, according to the views of Dr. Proutf as to the nature of absorption, is so far assimilated by this mixture also, before it is poured into the great veins in the state of chyle, to undergo the thorough agitation at both sides of the heart, and to participate in the changes at the lungs. What is absorbed from other parts of the body seems to be partly taken up by the veins, partly also by lymphatics which immediately convey it into adjacent veins; the remainder passes through lymphatic glands, and is there pretty certainly subjected to an intermixture and an interchange of particles with blood; after which it has necessarily much further admix- ture, and two thorough agitations at the heart, as well as the exposure at the lungs, to undergo, before arriving at the left side of the heart. In those of the vertebrated animals which have no lymphatic glands, the thorough inter- mixture of the fluids contained in the lymphatic vessels is provided for by numerous plexuses,); and, in the case of reptiles, by distinct lympha- tic hearts communicating with veins ;§ and we are sure, that much of the matters absorbed in these animals, whether by veins or lymphatics, passes through the capillaries of the kidneys or liver, as well as the lungs, before reaching the arteries. When we see so much contrivance, evidently adapted for giving every facility to the gradual operation of the vital affinities subsisting among the constituents of the blood, before it reaches the scene of any of the acts of nutrition, secre- tion, or excretion, we cannot be surprised to find, that these acts themselves should appear to be so simple as the observations already quoted would seem to indicate. It must be admitted, that if we consider these contrivances in the higher animals as important agents in the elaboration of the blood, and con- sequent formation of the textures and prepared fluids of the body, there is a difficulty in under- standing how these objects can be accomplished * Tiedemann et Gmelin, Rccherchcs, & c. f Bridgewater Treatise, ubi supra. t Cuvier, Lemons, &c. t. iv. p. 98. § Muller, ubi supra. 154 EXTREMITY. in the lowest classes, particularly the insects and zoophyta, where the nourishment of various textures, and formation of secretions and excre- tions, has been thought to be merely in the way of imbibition from a central cavity.* But it is to be observed, that in several of these tribes, in insects, and even in the infusory animals, recent observations have disclosed a much more com- plex apparatus for the movement of the fluids, than was previously suspected. And, in regard to the lowest zoophyta, it may be said in general, that if there is little apparent provision for the elaboration of the fluids, there is also little occasion for it, — first, because there is little variety of textures to be nourished, and secondly , because the simplicity of their structure is such, that all the particles of their nourishing fluid, — admitted into a central cavity, flowing thence towards their surface, and acted on by the air at all parts of that surface, — are similarly situate in regard to all the agents by which they can be affected, and must be equally fitted for the changes which the vital affinities there acting on them can produce, so that the same necessity for gradual intermixture, and repeated agitation, of heterogeneous mate- rials, does not probably exist in them, as in the animals of more complex structure. The analogy of their economy, therefore, is not a serious objection to the inference we have drawn from so many other facts, as to the numerous changes which are wrought in the blood of the higher animals, while circulating in the vessels, and as to the function of excre- tion being a necessary accompaniment of the assimilation of aliment, and nutrition of tex- tures, even independently of their renovation by processes of ultimate deposition and absorption . ( IV. P. Alison.) EXTREMITY, (in human anatomy), mem- brum, artus; Gr. p.aAo?, kuXov ; Fr. extremitc, membra ; Germ. Gliedmassen ; Ital. membro. This term is used to denote certain appendages most manifest in the vertebrated classes of animals, employed as instruments of prehen- sion, or support, or motion, also occasionally employed for other purposes sufficiently in- dicated by the habits of the animal. In fa- miliar language we apply the word, limb, synonymously, and the superior and inferior limbs of man, or the anterior and posterior ones of the Mammiferous Quadrupeds, are the best examples by which we can illustrate our de- finition. When these appendages exist in their complete number, i. e. four, they are distin- guished either by the appellatives already mentioned, anterior and posterior, or superior and inferior, or more precisely pectoral, and pelvic or ventral, or again atlantal and sacral. In Fishes we find that in most instances the anterior limbs (pectoral fins) are larger than the posterior (ventral fins) : and sometimes the posterior are absent altogether, as in the com- mon eel. In Fishes we look for the simplest form of the skeleton of the more highly de- veloped limbs in Man and Mammalia : and * Cuvier, Le9ons, &c. 27. here we find, more or less obviously in differ- ent instances, the same elements which sub- sequently appear in a more distinct and com- plete form. Thus, in the case of the Lophius piscatorius, we find very distinctly the scapula and clavicle forming the bond of connection of the other bones of the limb to the trunk. We can also recognize the radius and ulna, what seems to be a very rudimentary humerus, and the bones of the carpus, as well as the phalanges, which generally greatly exceed in number any arrangement that is to be found in the higher classes. The ventral fins, how- ever, the analogues of the posterior extremities, are not so developed : while bones analogous to the phalanges of tire feet are found in it, we meet no trace of the femur, tibia, or fibula In all the other Vertebrata we find the an- terior and posterior extremities developed on a plan similar to that in man, with such vari- ations as the manner of life of the animal requires. We must, however, notice an excep- tion in the case of serpents and Cetacea. In the former there are no limbs, or at least the merest trace of them; in the latter the pos- terior are absent, although the anterior exhibit very perfectly all the elements of the human upper extremity. We propose to devote the present article to the detail of the descriptive anatomy of the osseous system of the extremities in Man, in whom, by reason of his erect attitude, the terms superior and inferior are substituted for anterior and posterior, as applied to the ex- tremities of the lower animals. Superior extremity. — The superior extremity is connected to the trunk through the medium of two bones, which, as being intimately con- nected with the motions of the limb, first de- mand attention. These bones are the clavicle and scapula, and are commonly called the bones of the shoulder. Clavicle (from clavis, a key;) collar-bone; syn. ligula, jugulum, os furcale; Germ. Schlus- selbein. This bone is situated at the upper and anterior part of the thorax, and forms the anterior part of the shoulder: its direction is from within outwards, so that its external end, which is articulated with the scapula, is pos- terior, and on a plane superior to its internal end, which is articulated with the sternum. It thus constitutes the key to the bony arch formed at the shoulder, and hence its integrity is especially necessary to the integrity of the motions of the shoulder. The clavicle is a long bone, cylindrical, and so curved as to resemble the italic f placed horizontally. Its internal extremity is thick and rounded, while its external one is flat- tened ; of its two curves one is internal, with its convexity directed forwards ; the other ex- ternal, with its convexity directed backwards. The internal extremity, also called sternal, is formed by a gradual expansion of the shaft of the bone, which, however, still preserves the general cylindrical form, but is flattened a little on its superior surface : in size this ex- ceeds all other parts of the bone. The inner surface of this extremity of the clavicle is EXTREMITY. 155 destined for articulation with the sternum, and accordingly we find on it a considerable arti- cular facet, which is convex from above down- wards, and concave from before backwards. The outline of this surface is triangular, and each angle is easily distinguishable by the degree of its prominence : thus, one angle is situated anteriorly and inferiorly, it is the least prominent ; a second is posterior and inferior, it is the most prominent; and the third is su- perior, and may easily be felt under the inte- guments in the different motions of the bone. The external or acromial end of the clavicle is at once distinguished by its flattened appear- ance; it is flattened on its superior and in- ferior surfaces. At its extremity we find an elliptical articular surface adapted to a similar one upon the acromion process ; this surface is nearly plane, its long axis is directed horizon- tally from before backwards. The body or shaft of the bone presents se- veral points deserving of notice. The superior surface is smooth and rounded, expanding to- wards the sternal end, where it affords attach- ment to the clavicular portion of the sterno- mastoid muscle. It expands likewise towards the acromial end, but loses the cylindrical form and becomes flattened : the central part is the most contracted and the most cylindrical; here the bone is almost subcutaneous, being co- vered only by the common integument, some fibres of the platysma, and crossed by the supra-clavicular filaments from the cervical plexus of nerves. On the inferior surface of the clavicle we notice towards its sternal end a rough surface for the insertion of the costo-clavicular or rhom- boid ligament : external to this and extending outwards is a superficial excavation along the inferior surface of the bone, which lodges the subclavius muscle. This groove terminates at the commencement of the external fourth of the bone, where we notice a rough and promi- nent surface for the insertion of the coraco-cla- vicular or conoid and trapezoid ligaments; in the articulated skeleton this surface corresponds to the root of the coracoid process, immediately over which it lies. On the inferior surface, near its middle, is the orifice of the canal for the transmission of the nutritious artery, the direction of which is outwards. The anterior edge is thicker and more rounded towards the inner than towards the outer end, where it partakes of the general flattened ap- pearance of the bone at that part; in the former situation it affords attachment to the pectoralis major muscle — in the latter to the deltoid. The two internal thirds of this edge are convex, its external third is concave. The posterior edge is smooth and thin upon its two internal thirds, thicker and rougher at its external third, where the trapezius muscle is inserted into it ; in the former situation this edge is convex, in the latter it is concave. The relations of the clavicle in this situation are in- teresting : it forms the anterior boundary of a space somewhat triangular in form, through which a communication is formed between the axilla and the neck. The posterior boundary of this opening is formed by the superior border of the scapula, and the internal by the inferior vertebra of the cervical region of the spine, while the first rib constitutes a sort of floor, over which pass the various vessels, nerves, and other parts which enter the cavity of the axilla. Tire anterior third of the first rib passes beneath the sternal end of the clavicle, but its two posterior thirds lie on a plane superior to it. Consequently we find that the cone of the pleura passes up behind this end of the clavicle so as to be on a level with it, hence the so- noriety elicited by percussion of the clavicle, and hence likewise the possibility in many instances, where embonpoint does not interfere, of hearing the respiratory murmur in the supra- clavicular region. The great importance of the clavicle in the motions of the upper extremity is rendered abundantly evident by observing how com- pletely synchronous are its movements with even the slightest change of position in the arm. But this is illustrated in a more striking man- ner by reference to the comparative anatomy of this bone. Those animals only possess a well- developed clavicle whose habits of life require extensive and varied movements of the shoul- der. Where the anterior extremity is employed merely as an instrument of progressive motion on a plane surface, we have no clavicle ; hence this bone is absent from the skeletons of Pa- chydermata, Ruminantia, Solipeda, and the mo- tions of the shoulders are only such as are required for the flexion and extension of the limb. In the Carnivora, where there is a slight increase in the range of motion of the anterior extremities, a rudimentary clavicle exists, and in this class we observe that the size of the bone in the different orders bears a direct relation to the extent of motion enjoyed by the limb. Thus it is smallest in the Dogs and largest in the Cats; in these animals it has no attachment to either the sternum or the scapula, but is enclosed in the flesh, and does not occupy much more than half the space between the two bones last named. “ But, however imperfect,” says Sir C. Bell, “ it marks a correspondence in the bones of the shoulder to those of the arm and paw, and the extent of the motion enjoyed. When the bear stands up, we perceive, by his ungainly attitude and the motion of his paws, that there must be a wide difference in the bones of his upper extremity from those of the ruminant or solipede. He can take the keeper’s hat from his head and hold it; he can hug an animal to death. The ant-bear especially, as he is defi- cient in teeth, possesses extraordinary powers of hugging with his great paws; and, although harmless in disposition, he can squeeze his enemy the jaguar to death. These actions and the power of climbing result from the structure of the shoulder, or from possessing a collar-bone however imperfect.”* In those Mammalia that dig and burrow in the ground, or whose anterior extremities are so modified as to aid them in flight, or who are skilful in seizing upon and holding objects * Bridgewater Treatise, p. 48. 156 EXTREMITY. with their paws, the clavicle is fully developed, and extends the whole way from the scapula to the sternum. Thus in the Rodentia this bone is very perfect, as, for example, the Squirrel, the Beaver, the Rabbit, the Rat, &c. The Bat affords an example of a very strong and long clavicle, as also the Mole and the Hedgehog among the Insectivora. Among the Edentata those tribes possess a clavicle whose habits are fossorial, as the Ant- eater, the Armadillos, and even the Gigantic Megatherium, in which animal, however, the clavicle presented the peculiarity of being arti- culated with the first rib instead of with the sternum. In the Quadrumana the clavicles are strong and curved as in the human subject. In Birds, the bone which is analogous to the clavicle presents similar variations in its developement, according to the range of motion required in the anterior extremity, or in other words, in proportion to the extent to which the powers of flight are enjoyed. Thus, in some these bones are anchylosed along the mesial line, and constitute the furculum ; in others they are cartilaginous internally; and in others they do not reach the sternum.* I n women the clavicle is in general less curved than in men ; the diminution in the incurvation is most manifest in the external portion. Accord- ing to Cruveilhier, the clavicles are often une- qually developed in the same individual accord- ing as one limb is more used than the other, and sometimes the difference is sufficiently obvious to enable one to ascertain from the relative size of the clavicles, whether the individual is right or left-handed. Structure . — The clavicle contains a conside- rable proportion of compact tissue in its shaft, and a cylindrical medullary canal ; at the ex- tremities the compact tissue greatly diminishes, and is replaced by the reticular, which likewise fills up the bone and obliterates the medullary cavity. Developement. — A strong argument as to the great importance of this bone to the motions of the shoulder, is derived from its precocious de- velopement ; for although the cartilaginous nidus of the vertebra; as well as that of the ribs appear before that of the clavicle, yet the latter bone begins to ossify sooner and is completed more rapidly than any other bone in the body, ex- cepting perhaps the lower jaw, which some- times takes the precedence in the process of ossification. It is remarkable loo for the diver- sity in its proportional size, which it presents at different periods; thus, according to Meckel, about the middle of the second month of pregnancy, the clavicle is four times longer than the humerus or femur, and it is not until the fourth month that the humerus exceeds it in length. The clavicle has but one primitive point of ossification: a supplementary point is developed under the form of a very thin lamella at the anterior part of the sternal extremity. f Scapula, scapulum, omoplata, hume- rus, vrAarv;, latus.) Fr. omoplate; Germ, das Schulterblatt. — This bone forms the posterior * See Avls, p. 285, vol. i. t Cruveilhier, Anat. Desc. t. i. p. 219. and principal portion of the shoulder; it is placed on the posterior and outer part of the thorax, and occupies a space which extends from the second to the seventh rib. The scapula is very thin in the greatest part of its extent, quite papyraceous in some places. It is triangular in form, and anatomists com- monly describe its sides or borders, its angles, and its surfaces. The borders, or costa, of the scapula are three in number, and are named according to the position they occupy or the relation they bear: thus there are the superior border or cervical, the posterior or vertebral, and the anterior or axillary. The cervical border (also called the coracoid ) is the shortest, being some- what less than a fourth of the length of the vertebral border; it is connected posteriorly with the vertebral at an angle the apex of which is rounded off'; it is slightly concave, and the bone for some way below it is very thin, and the bor- der itself is acute. Anteriorly it terminates in a notch which is bounded in front by one root of the coracoid process, ( incisura semilunaris, lunula, coracoid notch.) This notch is converted into a foramen by a ligament which is often ossi- fied, and thus the suprascapular nerve, which is lodged in the notch, is separated from the artery of the same name, which passes over the ligament. The extent, therefore, of the cervical border is from the posterior superior angle to this notch. The levator anguli sca- pula; and the omo-hyoid muscles are attached to this border. The vertebral border, also called the base of the scapula, is the longest, being in an ave- rage-sized bone from seven to eight inches in length ; it is sharp in its whole extent, which is limited above by the posterior superior angle, and below by the inferior angle. At the junc- tion of the superior fourth with the remaining portion there is an inclined surface, triangular in form, the base confounded with the margin of the bone, the apex continued to the spine. This surface is smooth, and the ascending fibres of the trapezius muscle glide over it. To that part of this edge, which is above the surface, the levator anguli scapula; is attached, and below it the rhomboidei. The anterior or axillary border is limited above by the glenoid cavity, and below by the inferior angle of the scapula. It is much thicker than either of the others, and its thick- ness increases towards its upper extremity, where, close to the glenoid cavity, there is a rough surface which gives attachment to the long head of the triceps muscle; inferior to this, the edge affords insertion to the teres minor muscle, and still lower down to the teres major. The superior and posterior angle is formed by thejunction of the cervical and vertebral bor- ders; it is a little less than a right angle, and is chiefly remarkable for affording insertion to the levator anguli scapula; muscle. The inferior angle, formed by the union of the axillary and vertebral borders, is very acute; the bone here is very thick and spongy ; part of the latissimus dorsi glides over this angle, and sometimes some of its fibres are inserted into it. It is EXTREMITY, 157 only this portion of the muscle which separates this part of the scapula from the common inte- guments, and to this superficial position is at- tributed the more frequent occurrence of frac- tures from direct violence in this than in any other portion of the bone. The angle between the cervical and axillary borders is truncated, and presents many points of great interest. We here notice an articular concavity, destined to contribute to the for- mation of the shoulder-joint, commonly known under the name of the glenoid cavity, ( sinus articularis.J This cavity, which is a very superficial one, is oval ; the long axis of the oval being vertical in its direction, the acute extremity of the oval is situated superiorly, and here the edge of the bone is cut and rounded oflT towards the posterior part, where is inserted the tendon of the biceps. The cavity is surrounded by a thick lip of bone, to which in the recent state the fibro-cartilage, called glenoid ligament, is applied. At the internal or anterior part of this border, is a notch for the passage of the tendon of the sub- scapularis muscle. The aspect of the glenoid cavity when the scapula is quiescent is outwards and slightly upwards and forwards. This cavity is connected with the rest of the bone by a thick but contracted portion denominated the neck of the scapula. The neck of the scapula is surmounted by a remarkable curved process, called the coracoid process, {y.ofoc^, corvus.) This process, well compared to a semiflexed finger, is directed forwards and outwards, it is connected to the scapula by a thick portion, which seems to arise by two roots, one posterior, thick and rough, lying immediately in front of the notch in the cervical border, the other anterior and thin, and connected with the apex of the glenoid cavity. The concave surface of the coracoid process is directed downwards and outwards, and in the recent state projects over the upper and internal part of the shoul- der-joint : its convex surface is rough, and has inserted into it the ligaments by which the clavicle is tied to it. The coracoid process affords attachment by its internal edge to the pectoralis minor muscle; to its outer edge is affixed the ligament which, with the acromion process, completes the osseo-ligamentous arch over the shoulder-joint, and by its summit it gives insertion to the short head of the biceps and to the coraco-brachialis. It remains only to examine the surfaces of this bone. The anterior surface forms in the greatest part of its extent a shallow fossa, fossa subscapularis, which is limited above and be- hind by the superior and posterior margins of the bone, and in front by a smooth and rounded ridge, which extends from the glenoid cavity to the inferior angle. This fossa is frequently intersected in various directions by bony ridges. Cruveilhier remarks, that in a well-formed per- son, this surface ought to be exactly adapted to the thorax; but when the chest is contracted, as in phthisical patients, the scapula not par- ticipating to a proportionate extent in the con- traction, there follows such a change of re- lation that the scapulae become very prominent behind, and are in some degree detached from the ribs like wings, whence the expression scapula alata, applied to the projection of the shoulders in phthisical patients. The whole fossa has lodged in and inserted into it the subscapularis muscle, whence its name. At the superior posterior angle and the inferior one, are rough surfaces into which are inserted the superior and inferior fibres of the serratus magnus muscle. The posterior surface is remarkable for its division into two portions by a large process which projects from it nearly horizontally back- wards and slightly upwards. This process, called the spine of the scapula, is fixed to the bone at the line of union of its superior and mid- dle thirds; it commences at the triangular surface already noticed at the termination of the superior fourth of the vertebral border of the scapula, thence it proceeds outwards, in- clining a little upwards, and just where the neck of the scapula is united with the rest of the bone, this spine ceases to be connected with the scapula, and is continued outwards in a slightly arched form, as a broad and flattened process, denominated the acromion process, (a>t£o;, summus, up.o<;, humerus.') The spine presents posteriorly a thick and rough edge, which by its superior border gives attachment to the trapezius muscle, and by its inferior to the deltoid, the intervening space being covered by the aponeurotic expansion which connects the muscles last-named. The superior surface of the spine looks nearly directly upwards ; it is concave, and contributes to form the fossa supra-spinala. The inferior surface, on the other hand, forming part of the fossa supra- spinata, is convex anteriorly and slightly con- cave posteriorly, and looks downwards and backwards ; on each surface we observe a large nutritious foramen. The posterior edge of the spine is quite subcutaneous, and the physician often finds it desirable to practise percussion upon it. Above the spine of the scapula is thefossa supra-spinata, which lodges the muscle of the same name, formed in front by the scapula, behind by the spine, both surfaces being slightly concave. Below the spine is the fossa supra-spinata much larger than the preceding, slightly convex, except towards its anterior part. This fossa is formed by the scapula below and the inferior surface of the spine above ; it is limited in front by a ridge which proceeds downwards and backwards, from the glenoid cavity to the inferior angle, and bounds behind a surface which gives attachment to the teres major and minor muscles. Into this ridge itself is inserted a fibrous fascia, which separates the attachment of the last-named muscles from the fossa infra-spinata and the insertion of the muscle of the same name. The two fossae, thus separated by the spine, com- municate through a channel formed on the posterior part of the neck of the scapula and bounded behind by the spine ; through this channel pass the arterial and nervous ramifica- tions from the superior to the inferior fossa. The acromion process is evidently continu- 158 EXTREMITY. ous with the posterior thick edge of the spine of the scapula, and viewed from above ap- pears to be merely an expansion of it. The narrowest part of the process is where it seems to spring from the spine, forming a sort of pedicle. Its posterior surface is convex, rough, covered with fibrous tissue in the recent state ; its aspect is upwards and backwards. Here the process is quite subcutaneous as the pos- terior part of the spine of the scapula. The anterior surface is concave, smooth, looks downwards and forwards to the posterior and superior part of the shoulder-joint. The posterior or inferior edge of the process con- tinuous with the corresponding edge of the spine of the scapula forms a curve, convex downwards and outwards, and terminates in the pointed extremity or apex of the pro- cess; all this edge affords attachment to the deltoid muscle. The superior edge is con- cave ; near the apex we observe upon it a plane oval articular surface to which the acromial extremity of the clavicle is articulated ; into this edge the trapezius muscle is inserted. The apex of the acromion, which is imme- diately in front of the articular surface for the clavicle, gives insertion to the apex of the liga- ment, whose base is attached to the outer edge of the coracoid process. The scapula isconnected to the trunk through its articulation with the clavicle, but chiefly through the intervention of muscles, so that muscles are inserted into all its edges, and its surfaces are “ cushioned with muscles.” It is, then, as might be anticipated, a very moveable bone, and its motions consist in more or less extensive revolutions round an axis through its centre. This bone, then, being the medium of connexion between the pectoral extremity and the trunk, it is evident that the great move- ments of the former must depend upon the movements produced in the scapula by the muscles which pass to it from the trunk; more- over, when some of these muscles fix the scapula, it becomes the point whence the others act in producing the motions of the ribs. The scapula, then, is an essential element in the upper extremity, and it exists wherever we find that limb in a perfectly developed state, but it experiences various modifications in position and shape according to the uses to which the upper extremity is applied. In quadrupeds the position of the scapula is more forwards and on the side of the chest, for in them the anterior extremity is employed as an instrument of support. It is interesting to observe the variation in the aspect of the glenoid cavity, according to the oblique or upright position of the scapula, indicating whether the pectoral extremities are used chiefly as instruments of support or as instruments of prehension, &c. When freedom and rapidity of motion are required conjoined with strength, we find the scapula placed obliquely over the ribs, and a corresponding obliquity between the humerus and scapula. “ In the horse, as in most quadrupeds, the speed results from the strength of the loins and hinder extremities, for it is the muscles there which propel the animal. But were the anterior extremities joined to the trunk firmly and by bone, they could not withstand the shock from the descent of the whole weight thrown forwards ; even though they were as powerful as the posterior extremities they would suffer fracture or dis- location. We cannot but admire, therefore, the provision in all quadrupeds whose speed is great, and whose spring is extensive, that, from the structure of their bones, they have an elastic resistance by which the shock of descend- ing is diminished. “ If we observe the bones of the anterior extremity in the horse, we shall see that the scapula is oblique to the chest, the humerus oblique to the scapula, and the bones of the fore-arm at an angle with the humerus. Were these bones connected together in a straight line, end to end, the shock of alighting would be conveyed through a solid column, and the bones of the foot or the joints would suffer from the concussion. When the rider is thrown forwards on his hands, and more certainly when he is pitched on his shoulder, the collar-bone is broken, because in man this bone forms a link of connexion between the shoulder and the trunk, so as to receive the whole shock; and the same would happen in the horse, the stag, and all quadrupeds of great strength and swiftness, were not the scapula sustained by muscles and not by bone, and did not the bones recoil and fold up.” “ The horse-jockey runs his hand down the horse’s neck in a knowing way and says, ‘ this horse has got a heavy shoulder, he is a slow horse.’ He is right, but he does not under- stand the matter; it is not possible that the shoulder can be too much loaded with muscle, for muscle is the source of motion and bestows power. What the jockey feels and forms his judgement on is the abrupt transition from the neck to the shoulder, which, in a horse for the turf, ought to be a smooth undulating surface. This abruptness or prominence of the shoulder is a consequence of the upright position of the scapula ; the sloping and light shoulder results from its obliquity. An upright shoulder is the mark of a stumbling horse — it does not revolve easily to throw forward the foot.”* A comparison between the skeleton of the anterior extremity in the elephant and in one of the stag kind illustrates how the oblique position of the scapula is favourable to rapidity of motion, while the upright position is that most calculated for supporting weight. In the elephant the glenoid cavity of the scapula is placed vertically over the head of the humerus, and all the other component parts of the limb are similarly disposed, so as to form a complete pillar of support for the trunk. Hence the attitude of standing in the elephant requires but slight muscular effort, and in this position he is in such complete repose as often to obtain sleep. In this animal, then, the angle between the scapula and humerus is nearly obliterated, but in the stag it approaches closely to a right angle, the scapula is oblique to the ribs, and * Sir Charles Hell, Bridgewater Treatise. EXTREMITY. 159 the humerus to the scapula. The rule seems to be that where the pectoral extremity is chiefly a pillar of support, the aspect of the glenoid cavity is nearly vertically downwards. If free- dom and rapidity of motion be required in addition to strength as a member of support, the trunk being lighter, the scapula is oblique, and consequently the glenoid cavity looks downwards and forwards; or if the limb be not used to support the trunk, then the aspect of the glenoid cavity is no longer downwards but outwards, as in man. Structure. — The greatest part of the scapula is composed of very thin almost papyraceous compact substance ; but its processes, and the enlargements at its edges and angles, contain reticular tissue. Developement. — This bone is developed by six points of ossification ; one for the body, and five supplementary ones, viz. one for the coracoid process, two for the acromion, one for the posterior border of the bone, and one for its inferior angle. The ossification of the body commences about the second month, and the spine appears in the third month as a growth from the posterior surface of the scapula. The union of the several epiphyses is not completed till late, and it is not until after the fifteenth year that the ossification is finished. The bones of the upper extremity, properly so called, are the humerus, radius, ulna, and bones of the hand. Humerus, (os brachii; Fr. Vos du bras; Germ, das Oberarmbein). This is the longest bone of the upper extremity; it is situated between the scapula and forearm, being, as it were, suspended by muscle and ligament from the former. Like all long bones, the humerus consists of a shaft and two extremities. The superior extremity is formed by a smooth and rounded convexity, rather less than half a sphere ; a slight depression in, or constriction of, the bone, most manifest above, marks the limit of this articular eminence. The eminence is called the head of the humerus ; the constric- tion indicates what is denominated the anato- mical neck of the bone, being that portion which connects the head to the shaft, and analogous to the more developed neck of the thigh-bone. The axis of the neck is but a continuation of that of the head, and passes in a direction from within outwards and down- wards, forming an obtuse angle with the axis of the shaft. The head of the humerus is entirely covered by articular cartilage, and arti- culates with the glenoid cavity of the scapula, to which, however, it obviously does not at all correspond in dimensions. The inferior part of the anatomical neck of the humerus is very slightly marked, and is continued in a smooth declivity slightly con- cave from above downwards, into the shaft of the bone. Its superior part is more distinct, and the depth of the groove here seems in a great degree owing to the prominence of two bony protuberances, one situated anteriorly, called the lesser tuberosity, and the other pos- teriorly, denominated the greater tuberosity. The lesser tuberosity of the humerus ( tuber- culum minus) is somewhat conical in shape, and inferiorly it ends in a smooth, rounded bony ridge (spina tuberculi minoris ), which extends downwards and inwards, gradually diminishing in prominence till it is lost in the shaft of the bone at the inner part of its ante- rior surface. The lesser tuberosity gives in- sertion to the tendon of the subscapularis muscle, and the ridge or spine last described forms the anterior and internal boundary of the bicipital groove. The greater tuberosity ( tuberculum majus, externum s. posterius) forms a considerable prominence on the upper and outer part of the humerus, being the most external part in that situation and easily to be felt under the integuments. Superiorly the constriction cor- responding to the anatomical neck separates it from the head of the humerus ; inferiorly it is continued into and gradually lost in the shaft of the bone at its outer part. A very distinct and prominent ridge ( spina tuberculi majoris) is continued from its anterior extremity down- wards and inclining very slightly inwards, which terminates about the middle of the an- terior surface of the bone, just internal to the deltoid ridge. This ridge is most prominent but smooth in its upper third, in its inferior two-thirds it is less prominent but rough; it forms the posterior boundary of the bicipital groove. On the greater tuberosity three dis- tinct surfaces are marked, to the anterior of which the supra-spinatus muscle is attached, to the middle the infra-spinatus, and to the posterior the teres minor. The bicipital groove commences above be- tween the two tuberosities, and passes down- wards and slightly inwards, bounded before and behind by the spines which proceed from those tubercles. This groove, very distinct at its commencement, ceases to be so a little above the termination of the superior third ; in the recent state it is lined by the tendinous expansion of the latissimus dorsi and teres major muscles, and lodges the tendon of the biceps muscle, whence its name. From the anatomical neck the bone gra- dually tapers down and becomes more cylin- drical in its form ; this upper portion is, for the convenience of description, distinguished by the name of surgical neck of the humerus. The middle third of the shaft of the bone is prismatic in form ; the external spine which commences at the greater tuberosity is continued down, forming a prominent ridge all down the front of the bone to the termination of its flattened inferior third. The outer part of the middle third of the humerus is remarkable for the rough surface into which the deltoid muscle is inserted, the deltoid ridge, situated nearer the upper than the lower part of this portion, and directed downwards and very slightly forwards. The inner part of the middle third presents a smooth, flattened, and inclined surface, which is continued down in this form to within a very short distance of the inferior extremity of the bone. The posterior surface is rounded and very smooth. ICO EXTREMITY. At the junction of the middle and inferior thirds we notice a very slight and superficial groove passing downwards and inwards, and very much resembling what one would ima- gine might be produced by an attempt to twist the bone while yet in a yielding condition, the inferior third having been twisted inwards and the two superior thirds outwards. This groove indicates the spiral course from above down- wards and from without inwards of the musculo- spiral or radial nerve. Below this groove is the inferior third of the humerus, the anatomical characters of which are very distinct from those of the remaining parts of the bone. A pro- minent and rounded ridge, continuous with that already noticed in connexion with the greater tuberosity, passes vertically down in front of it; from each side of this ridge a smooth surface inclines backwards, forming an inclined plane on each side of it, the ex- ternal being larger and more distinct than the internal. The posterior surface of the upper part of this portion is flat and very smooth. As the bone descends it expands considerably late- rally, so as to present in front a broad surface slightly convex from side to side, bounded on either side by prominent edges, continued from the edges of the inclined planes above de- scribed. Each edge terminates in a pro- minence, the inner one being the largest; the inner edge itself being thicker, more pro- minent, and describing a slight curve as it descends. The posterior surface is limited below by a deep depression, to be further de- scribed hereafter. Thus, by its gradual expan- sion laterally, the inferior portion of the hu- merus, being about one fifth of the entire length of the bone, has a triangular figure, the base being formed by the inferior articular ex- tremity of the bone. The whole shaft of the humerus is com- pletely clothed with muscle. We have already indicated the place of insertion of the deltoid muscle on the outer surface of the bone; all that portion of the outer and anterior surface below the deltoid ridge, and for a little way on each side of its inferior extremity, is co- vered by the brachiaeus anticus muscle. In- ternal to the bicipital groove, on the inner surface of the humerus, about its middle, the coraco-brachialis muscle is inserted. The ex- ternal edge below the spiral groove affords attachment to the brachiaeus anticus, supinator longus, extensor carpi radialis longior, and the triceps muscles. The internal edge below the insertion of the coraco-brachialis has the brachiaeus anticus and triceps muscles inserted into it, and both edges afford insertion to intermuscular apo- neuroses, which separate the muscles con- nected with the anterior from those on the posterior part of the bone. The posterior sur- face is completely covered by the triceps mus- cle, excepting in the line which corresponds to the groove already referred to, in which the radial nerve and musculo-spiral artery pass. The foramen for the nutritious artery is found upon the internal surface at the inferior ex- tremity of its middle third ; the direction of the canal is downwards; sometimes this fora- men exists upon the external, or upon the in- ternal surface. The inferior extremity of the humerus is terminated by an articular cylinder, which pro- jects into a plane anterior to that of the shaft of the bone, (processus cubitalis). This cy- linder is placed transversely, but in transverse extent it falls short of the widest part of the inferior third of the humerus. Various de- pressions and elevations are marked upon the surface of this cylinder. Proceeding from without inwards, we notice a convexity or rounded head, limited externally by the mar- gin of the cylinder and internally by a groove, which passes in a curved direction from before backwards, the concavity of the curve corres- ponding to the rounded head. This head is properly denominated the external condyle of tile humerus ; it articulates with a cavity on the head of the radius ; the anatomist should notice that the axis of this head passes in a direction downwards and forwards. On the anterior surface of the humerus immediately above this head, we observe a slight and very superficial depression which receives the edge or lip of the cavity of the radius, when the forearm is in a state of complete flexion. Internal to the groove which bounds the con- dyle on the inner side, we have a pulley-like surface, which is destined for articulation with the ulna. The concavity which forms the cen- tral part of this pulley is deep, but deeper and wider behind than before; its anterior ex- tremity terminates in communicating with an oval depression on the anterior surface of the bone (fovea anterior minor), which in flexion of the forearm receives the anterior projecting angle of the coronoid process of the ulna ; the posterior extremity terminates in a similar depression, (fovea posterior v. sinus maximus,) but a much deeper one, and of greater dimen- sions generally, occupying, in short, nearly the whole posterior surface of the bone ; this de- pression receives the olecranon process of the ulna, when the elbow-joint is in extension. The trochlear concavity, in passing from before backwards, takes a curved direction, so that its posterior extremity is much nearer the external part of the articular cylinder than the anteriot This has an important influence on the direc- tion of the motions of the forearm. These two depressions are separated from each other by a thin osseous lamina, almost transparent We sometimes meet with instances in which this lamina is perforated in consequence of a defect of ossification; and Meckel states that he has found this perforation more frequently in the bones of Negroes and Papuas than in those of the superior races of mankind. It is the permanent condition of many pachydermata, rodentia, carnivora, and quadrumana. On the inside the trochlear concavity is bounded by a thick and projecting lip, which, when the bone is placed at right angles with a horizontal plane surface, descends lower down than any other part, so that this part comes in contact with the plane surface, while the remaining EXTREMITY. 161 portion of the articular cylinder is raised con- siderably above it. This arrangement accounts for the hollow angle manifest on the outer side of the elbow-joint when the forearm is extended. We have yet to describe two processes which are connected in great measure with the outer and inner extremities of the articular cy- linder, and to which we have already referred, as being the points in which the margins of the bone terminate. The external one is trian- gular and thick, rough upon its surface, and projects slightly. It is improperly called the external condyle — more correctly it should be designated epicondyle, being applied to the outer surface of what is properly the external condyle. This process affords attachment to the external lateral ligament of the elbow- joint and to the principal supinator and ex- tensor muscles on the forearm, whence it has been called condylun extenxorius. The inter- nal process is very prominent, distinctly trian- gular, terminating the inner edge of the hu- merus and connected with the trochlea; it is more correctly denominated epitrochlea. It affords insertion to the internal lateral ligament, and to the pronator and flexor muscles of the forearm. Its posterior surface is slightly hol- lowed at the line of its junction with the rest of the bone; the ulnar nerve passes behind it. The humerus is the principal lever of the pectoral extremity ; hence in all animals its strength is proportionate to the force and power which is required in the limb. In the ele- phant it is a massive pillar of support ; and here we may notice a variety following the same law which influences the difference in the aspect of the glenoid cavity of the scapula, already noticed ; namely, that the angle be- tween the axes of the head and shaft of the humerus, is at its maximum when the arm- bone is mainly an instrument of support, and diminishes as that bone is more used for pre- hension and other purposes ; and as this use is found for this bone chiefly in the human sub- ject, we may presume that in man the angle in question is the least removed from a right angle. When this limb is used mainly for support and progression, a considerable range of motion in the shoulder-joint is not required, the tuberosities at the upper extremity of the hone project and limit the motions of the joint. When, however, a considerable motion is ne- cessary, these tubercles are depressed as in man, so as not to interfere with these motions. The lower extremity of the humerus likewise affords marks indicative of the mobility of the fore- arm and hand ; thus, in the one case one or both of the edges of the bone which terminate m the epitrochlea and epicondyle are promi- nent and strong in proportion as the muscles which arise from it are frequently called into play, as when the pronating and supinating motions of the forearm are extensive : in the other case this ridge is imperfectly developed, and the principal modification of the lower end of the bone is to be seen in the articular cy- linder, where greater depth is given to the trochlea, in order to afford increased strength and security to the elbow-joint. VOL. II. One of the most singular instances of the developement of bony processes in accordance with muscular power is in the case of the mole. In this little animal the whole anterior ex- tremity is constructed entirely with reference to its burrowing habits; its short, thick, and almost square clavicle and its elongated lever- like scapula tend to the same end, as its amaz- ingly strong humerus. The upper extremity of this latter bone is extremely broad ; it pre- sents two articular surfaces, being articulated with the clavicle as well as with the scapula, and the tuberosities which give insertion to the muscles of rotation are enormously de- veloped. The body of the bone is short, thick, and strong ; the inferior extremity is nearly as large as the superior ; both the epicondyle and epitrochlea are very highly developed, especially the latter, which is accounted for by the fact that the muscles of pronation are those most called into action, in order to enable the animal to employ the accessory bone on the radial side of the hand, in scraping up the earth. This large size of the humerus, and great develope- ment of its muscular eminences, is found in all fossorial animals, as the megatherium, the pan- golins, beavers, ant-eaters, moles, and mono- tremata. In the two last the developement is the most remarkable. In the class of Birds, the humerus is de- veloped as regards the prominence of its mus- cular protuberances, in proportion to the powers of flight. In birds which fly, those eminences are strong and prominent, and the bone itself is proportionally strong; but in those which do not fly, the bone is weak and gene- rally short. In the common pigeon, for ex- ample, the enlargement of the scapular ex- tremity of the humerus, and the developement of the tubercles is very manifest, as well as the strength and thickness of the shaft of the bone. Structure. — The structure of the humerus is characteristic of that of long bones in general. In a vertical section we observe that the re- ticular texture is chiefly accumulated towards the extremities; the shaft being mainly formed of compact tissue. At the upper extremity we notice the mark of union of the epiphysis of the head, which corresponds to the line of the anatomical neck of the bone. The canal, when a transverse section of it is viewed, appears somewhat quadrilateral in form. Its walls are formed of very dense compact tissue. Developement. — The ossification of the hu- merus begins in its shaft, and that very early, according to Meckel about the second month ; the shaft goes on enlarging, but the extremities are still cartilaginous during the whole of in- tra-uterine life, and for the first year after birth. The superior extremity is developed by two points of ossification, one for the head, the other for the great tuberosity ; about the be- ginning of the second year the ossification of the head of the bone commences, and from the four-and-twentieth to the thirtieth month the ossification of the great tuberosity begins. According to Beclard, a small ossific point for the lesser tuberosity is visible in the fifth or M 1G2 EXTREMITY. sixth year ; from the eighth to the ninth year tiie ossific elements of the head of the hume- rus become united and the head is com- pleted. The inferior extremity of die humerus, accord- ing to Cruveilhier, begins to ossify later than the superior. The first point of ossification noticed in it is for the external condyle: this appears at the age of two years and a half ; at seven years a second point of ossification commences for the epitrochlea; at twelve a third point appears for the internal edge of the trochlea; and at sixteen years a fourth point for the epicondyle. These four points of ossification, Cruveilhier states, are united in the following order: first, in the second year, the two points of the trochlea are united ; and, secondly, at sixteen years the trochlea, epicondyle, and the condyle form a a single piece.* The union of the extremities with the shaft of the bone takes place from the eighteenth to the twentieth year; and all ob- servers agree in stating that the union of the inferior extremity with the shaft always pre- cedes that of the superior extremity, although the ossification of the latter is prior. Forearm.- — -The bones of the forearm are the ulna and radius, of which the former con- stitutes the second essential element in the elbow-joint, the radius being chiefly an acces- sory bone to provide for the wider range of motion of the band. The ulna therefore is the principal lever of the forearm, and the motions of flexion and extension of that segment of the limb upon the arm depend upon it ; at its superior extremity it forms a very firm hinge- joint with the trochlea of the humerus, but m- feriorly its connexion with the carpus at the wrist-joint is very slight, and it forms by no means an essential element of that joint On the other hand, the radius at its inferior ex- tremity forms a very important part of the wrist-joint, but at its superior its connection with the elbow-joint is due to its necessary articulation with the outer side of the ulna. Ulna {y.vfi iror, cubitus; Fr. os clu coude ; Germ, das Ellenbogenbein.-f) This bone is situated on the inner side of the forearm. It is the longest and the largest bone of that region, and in the vertical position of the limb it is directed downwards and a little outwards, the obliquity being occasioned by the greater pro- jection downwards of the inner lip of the trochlea of the humerus, as already alluded to in describing that bone. The upper or humeral extremity of the ulna is at once distinguished by its great size from the inferior extremity. It consists of two pro- cesses joined to each other at a right angle, and so that that angle opens forwards. One of these processes is vertical, and is continued in '* Cruveilhier, Anat. Descr. tom. i. p. 231. t The term facile was applied lo this bone as well as to the radius by some of the ancient anatomists, in imitation of the Arabians, who used the word mend, sc. an instrument analogous to our tinder-box, which consisted of two sticks, similar in appear- ance and proportions to the bones of the forearm. Focile majus was the ulna, focile minus the radius. Blumcnbach, Beschreibung der Knochen, p. 395. the direction of the long axis of the bone, and is little else than a continuation of the shaft; this is the olecranon : the other is horizontal, anterior to the olecranon, as it were placed upon the superior extremity of the bone, so as to project considerably beyond the plane of its anterior surface : tins is the curonoid process. The olecranon, (ahiVY), cubitus, xgavov, caput,) also called processus anconaus, may be said to begin from the angle of junction of the coro- noid process with it ; there the bone appears slightly constricted, for above that point it ex- pands. We notice five surfaces upon it. The superior surface is horizontal ; it presents pos- teriorly a muscular impression affording inser- tion to the triceps extensor, and anteriorly it ends in a remarkable beak, which, in the state of complete extension, is received into the ole- cranon cavity of the humerus. The posterior surface is rough with a very obviously trian- gular outline ; this surface gives insertion to the triceps muscle. The internal surface is also rough, and covered by the fibrous ex- pansion from the tendon of the triceps, and at its anterior margin affords insertion to the superior fibres of the internal lateral ligament. The external surface is smooth, and also is covered by the fibrous expansion from the ten- don of the triceps. The anterior surface is articular ; it presents the appearance of having been covered by articular cartilage ; it is divided by a rounded vertical ridge into two unequal portions, of which the internal is larger than the external. This surface is limited below by a transverse depression, non-articular, in which some fatty matter is deposited in the recent state. The surface is convex from side to side in the centre, and each of its lateral portions is concave ; the whole surface is concave from above downwards. In the extended state of the forearm this articular surface of the olecra- non is applied to the posterior part of the trochlea of the humerus ; it forms the posterior part of the great sigmoid cavity of the ulna. The coronoid process is wedge-shaped, at- tached by its base to the anterior surface of the ulna, the sharper edge projecting forwards and free. This edge is convex, and sometimes forms a point ; it is received into the coronoid cavity of the humerus. On the external sur- face of the coronoid process is an oval articular facet, concave from behind forwards, whose long axis is horizontal ; this is the lesser sigmoid cavity, and is articulated with the inner side of the head of the radius ; the internal surface is rough, and has a projecting lip, which affords attachment to the anterior fibres of the internal lateral ligament. The anterior surface is in- clined from above downwards and from before backwards, so that its aspect is downwards and forwards ; it is slightly hollowed transversely, and is rough, the roughness being continued down for a little way in front of the bone, thus forming a rough surface triangular in form, the base corresponding to the anterior edge of the coronoid process ; this surface affords insertion to the brachireus anticus muscle. The superior surface forms the anterior portion of the great EXTREMITY. sigmoid cavity ; like the similar surface on the olecranon, it is divided by an obtuse ridge directed from before backwards, into two une- qual portions ; these portions correspond in shape and size with those already noticed on the olecranon. The shaft of the ulna gradually tapers from above downwards ; it is triangular in its entire extent, excepting for about an inch above the inferior extremity, where the bone is distinctly cylindrical. On the shaft anatomists commonly describe three surfaces. The anterior surface is broader in the middle than at its extremities; it is slightly concave in the transverse direction in its middle third ; on this surface, at its upper part, we notice the orifice of the nutritious canal, which is directed upwards towards the coro- noid and olecranon. By its three superior fourths this surface affords attachments to the flexor digitorum profundus, and by its inferior fourth to the pronator quadratus ; the place of attachment of this latter muscle is limited above by an oblique line which passes from without inwards and from above downwards. The in- ternal surface is smooth, and convex in its en- tire extent; widest above, it gradually tapers to the inferior extremity. In its inferior fourth it is subcutaneous, and to its three superior fourths is attached the deep flexor muscle of the fingers ; the aspect of this surface is back- wards as well as inwards. The third surface is posterior. The two in- ferior thirds of this surface are smooth, the mid- dle being flat and the lowest rounded ; here are attached the extensor muscles of the thumb and that of the index finger. In the superior third we distinctly notice two surfaces, easily distinguishable by the difference of aspect ; the internal one, which is continued up on the olecranon process, looks backwards and slightly outwards; to it the anconaeus muscle is attached superiorly, and inferiorly the extensor carpi ulnaris. The external of these two surfaces looks directly outwards, and is separated from that last described by a line which passes ob- liquely downwards and inwards ; to this sur- face, which commences just below the lesser sigmoid cavity, the supinator brevis is attached, and below it, commences the line of attachment of the extensor muscles already alluded to. Three edges separate the surfaces above de- scribed ; of these the external is at once distin- guished by its greater prominence ; it is sharp in nearly its two inferior thirds, and superiorly is lost on the surface to which the supinator brevis is attached ; all that part of this edge which is prominent and sharp gives insertion to the interosseous ligament. The anterior edge commences just below the coronoid pro- cess, and terminates, inclining a little back- wards, in front of the styloid process of the ulna : it is rounded and smooth in its entire extent, and has the deep flexor of the fingers and the pronator quadratus inserted into it. The posterior edge commences at the apex of the posterior surface of the olecranon, and ter- minates insensibly towards the inferior fourth of the bone. The inferior or carpal ex tremity of the ulna 163 is very small ; it forms a slightly rounded head; on its posterior and internal part is a small process, projecting vertically downwards and ending in a point, to which the internal lateral ligament of the wrist-joint is attached : this process is the styloid process ; external to this is a depression or pit, into which is inserted the triangular cartilage of the wrist-joint, and external to this depression is the rounded head, which is smooth on its inferior surface, covered with cartilage in the recent state; the triangular cartilage glides upon this surface. On the outer side of the head is an articular convexity which articulates with a concave surface on the inner side of the carpal extremity of the radius. On the posterior surface of the head, imme- diately external to the styloid process, there is a slight channel, in which is lodged the tendon of the extensor carpi ulnaris. Structure. — The olecranon and coronoid processes are completely cellular in structure, excepting the external cortex of compact tissue. The inferior extremity of the ulna is likewise cellular, but the shaft is mainly composed of compact tissue, hollowed by a medullary canal, which commences a little below the coronoid process, and terminates just above the inferior extremity. Radius , (Germ, die Speiche,) so called from its being compared to the spoke of a wheel ; it is the shorter of the two bones of the forearm ; its proportion to the ulna being as 11 to 12. The superior extremity or head of the radius is a cylindrical head excavated on its superior surface so as to form a superficial cavity, cavitas glenoidea, which is articulated with the external condyle of the humerus. The circumference of this head consists of a deep lip of bone present- ing a smooth surface covered by cartilage in the recent state, the depth of which, measured verti- cally, is greatest on the inner side, so as there to form an oval convex articular facet which is adapted to the lesser sigmoid cavity of the ulna ; the remainder of the circumference is embraced by the annular ligament of the radius. The head of the radius is connected to the shaft by a short and cylindrical neck, which passes obliquely downwards and inwards; the neck of the radius is limited inferiorly and on the ulnar side by a rounded tubercular process, into the internal posterior and rough part of which the biceps mus- cle is inserted, the bicipital tuberosity or tubercle of the radius ; the anterior part of this tubercle, over which the tendon of the biceps glides, is smooth. For about an inch below this process the bone retains the cylindrical form, being here embraced by the inferior fibres of the su- pinator brevis muscle ; but below this the bone becomes distinctly prismatic in its form, and begins to expand to its inferior or carpal extre- mity. We here describe three surfaces as in the ulna : the anterior is inclined inwards, its aspect is forwards and inwards ; about its middle this surface is slightly hollowed from above downwards; at the junction of its middle and inferior third it is convex, and in its inferior third, where it attains its greatest lateral expan- sion, it is concave again. At the superior third of the bone we notice on this surface the nutri- m 2 164 EXTREMITY. tious foramen, the canal following the same direction as that of the ulna, namely upwards. The muscles attached to the anterior surface of the radius are the flexor pollicis proprius, con- nected with the two superior thirds of the bone, and the pronator quadratus occupying the in- ferior third. The posterior surface of the radius is likewise inclined, and looks backwards and inwards, very narrow in its whole extent, but broadest at its inferior extremity, convex in its superior and inferior thirds, and slightly con- cave from above downwards in its middle third. This last portion of the bone affords attachment to the two inferior extensor muscles of the thumb ; the superior third is embraced by the supinator brevis, and the inferior third has applied to it the tendon of the common extensor of the fingers, the indicator, and the extensor tertii internodii pollicis. The external surface is convex in its whole extent, and like the others expands inferiorly; about its middle we observe a rough surface, which gives insertion to the pronator quadratus ; in its upper portion the surface is embraced by the supinator brevis, and inferiorly the radial extensors of the wrist are applied to it. Of the three edges which separate these sur- faces, the internal is sharp, and extends from about an inch below the bicipital tuberosity to about the same distance above the carpal extre- mity of the radius; at this latter point the edge seems to bifurcate and form a plane triangular surface above the inferior extremity of the ra- dius. This edge gives attachment in its entire extent to the interosseous ligament. The an- terior edge is rounded ; it distinctly originates from the bicipital tuberosity, and terminates at the outer side of the carpal extremity of the radius in front of the styloid process. The su- pinator brevis, the proper flexor of the thumb, and the flexor sublimis of the fingers, have attachments to this edge above, and below the pronator quadratus and supinator longus are inserted into it. The posterior edge is very imperfectly defined, being distinct only in its middle. The inferior or carpal extremity of the radius is the largest part of the bone ; it is irregularly quadrilateral in form. Its inferior surface forms an articular excavation, the outline of which is triangular, the apex being external and the base internal ; this surface is divided into two by a slightly prominent line which passes from before backwards ; the outer of these two portions retains the triangular form, and is articulated with the scaphoid bone of the carpus ; the internal is quadrilateral, and articulated with the lunar bone. At its inner margin, this surface is continuous with a slightly excavated articular facet on the ulnar side of the inferior extremity of the bone, which is articulated with the convex surface on the cor- responding part of the ulna. The inferior ex- tremity of the radius presents, at its outer part, a pyramidal process projecting downwards and slightly outwards ; this is the styloid process, which by its apex gives attachment to the ex- ternal lateral ligament of the wrist-joint. The anterior margin of the inferior extremity is slightly concave from side to side ; it gives at- tachment to the anterior ligament of the wrist- joint, and the tendons of the flexor muscles of the fingers pass over it into the palm of the hand. On the posterior margin of this extremity we observe two grooves: the internal one, wide and very superficial, lodges the tendons of the com- mon extensor of the fingers and the indicator ; the external, deeper and oblique, lodges the extensor tertii internodii pollicis. Externally we notice likewise two superficial grooves, of which the posterior lodges the radial extensors of the wrist, and the anterior is traversed by the extensores primi et secundi internodii pollicis. Structure. — The central canal extends up- wards into the neck of the bone; it is cylin- drical at the extremities, and prismatic in the centre. Both extremities are composed of can- cellated structure. Developement of the bones of the fore-arm. — Both bones appear about the same time, and if not synchronously with the humerus, at least a very little later. With both bones the ossifi- cation begins on the shafts, which are very early completed ; the ossific point of the shaft of the radius is said, by Beclard and Cruveil- hier, to begin some days before that of the ulna. In the radius the inferior extremity begins to ossify before the superior, about the end of the second year. The ossification of the superior extremity begins between the seventh and ninth year; it is united to the shaft about the twelfth year, whilst the inferior extremity, whose ossification begins earlier, is not united till the eighteenth or twentieth year. The progress of the ossification of the ulna is very similar. The inferior extremity developed by a single point of ossification begins first about the sixth year. A little later the olecra- non begins to ossify; the coronoid is formed by an extension of ossification from the shaft. The union of the superior extremity of the ulna with the shaft takes place about the fifteenth or sixteenth year ; that of the inferior about the eighteenth or twentieth. It is important to observe that the articula- tion of the radius with the ulna, in the manner in which it is effected in man, has reference to the motions of the hand. Pronation and supi- nation of the hand are effected by the rotation of the head of the radius within the coronary ligament and on the lesser sigmoid cavity of the ulna. The hand is so connected with the radius that it follows the motions of that bone; when, therefore, the radius rotates in such a direction that its inferior part crosses the ulna, the posterior edge is directed outwards, and its anterior surface inwards and backwards ; the palm of the hand is turned backwards and the dorsum forwards; the forearm and hand are then said to be in pronation. On the contrary, when the rotation is such that the ulna and ra- dius are placed on the same plane, the dorsum of the hand is directed backwards and the palm forwards ; this is supination. In the lower animals we never find this mode of articulation of the radius with the ulna, unless there be also present the motions of su- pination and pronation of the hand. In such EXTREMITY. animals, evidence of the existence of these motions is afforded by certain points in the conformation of the radius and ulna them- selves, such as the peculiar form of the head of the radius, and the concave articular sur- face on the ulnar side of its lower extremity, as well as the lesser sigmoid cavity of the ulna, and the convexity on the radial side of the head of the same bone. This is found in many of the Carnivora, but chiefly in the Quadru- mana. In the Ruminants and Solipeds the radius and ulna are consolidated together so as to form one bone; they can, however, be distin- guished at the humeral end, where the latter bone is conspicuous by its elongated olecranon, which not only affords insertion to the extensor muscles of the arm, but also increases the secu- rity of the elbow-joint. The radius, which is the principal bone of the fore-arm, is so arti- culated with the humerus as to admit of free flexion and extension, but it is fixed in the state of pronation. In many of the other Mam- malia the radius and ulna are distinct through- out, but do not admit of the rotation of the one on the other; this is the case in liodentia, many Carnivora, Pachydermata, Edentata, In- sectivora, and Cetacea. In the Sloth, how- ever, among the Edentata, the motions of pro- nation and supination are conspicuous, and the olecranon is imperfectly developed ; on the contrary, in the Edentata proper, as the Arma- dillo, Megatherium, &c. these motions do not exist, and the olecranon is very much deve- loped. In the Cheiroptera the radius is the principal bone of the fore-arm, the ulna being developed only as to its humeral extremity consisting sometimes of little more than its olecranon ; and in some, as the Vespertilio vam- pyrus, the olecranon exists in the form of a pa- tella, connected with the upper extremity of the ulna. In Birds the radius and ulna are distinct throughout, but do not admit of motion between them; they are fixed in a state intermediate be- tween pronation and supination. The. Hand. — The third division of the upper extremity is the hand : for the description of the bones which compose it, we refer to the article Hand. Inferior extremity. — The bones which form the skeleton of the inferior or pelvic extremity are the femur, tibia, fibula, and the bones of the foot, occupying subdivisions of this mem- ber, which correspond to the arm, forearm, and hand in the pectoral extremity. Femur ( thigh-bone , os femoris v. cruris, os coxa. Fr. os de la cuisse, le femur. Germ, das Schenketbein.) This is the largest and longest bone of the skeleton ; it constitutes the upper part of the inferior extremity, and is articulated with the pelvis above and the tibia inferiorly. The femur exhibits very obviously the characteristic marks of the class of long bones in its elonga- ted and cylindrical shaft, and its swollen extre- mities. The superior extremity of the femur consists of a spherical head, connected to the shaft of the bone by a neck. The head is very regu- 165 larly spheroidal, being nearly two-thirds of a sphere ; it is limited towards the neck by a waving line which passes all round, and corre- sponds to the margin of the acetabulum. The whole head of the femur is incrusted in the recent state with articular cartilage, excepting at one point, where there is a depression or pit, varying in depth in different subjects. The precise situation of this depression is just infe- rior and posterior to the point at which the axis of the head of the femur would pass out : into this depression the ligamentum teres is in- serted. From the head of the femur is prolonged outwards and downwards to the upper end of the shaft the neck ( cervix v. collum femoris ). This portion of bone, cylindrical where it is connected to the head, gradually expands as it proceeds outwards, and is flattened in front and behind. That portion of the neck of the femur which is connected with the shaft may be called its base; here we observe two lines, by which the demarcation between the neck and shaft is indicated ; one of these lines is anterior, being simply a rough line extending from the great trochanter obliquely downwards, inwards, and slightly backwards to the lesser trochanter, and thence called the anterior inter- trochanteric line, into which the capsular liga- ment of the hip-joint is inserted; the other line may be more correctly designated a prominent ridge ; it is situated at the posterior part of the base of the neck, and extended also between the trochanters, the posterior inter-trochanteric line. The anterior surface of the neck of the femur is for the most part plane, but slightly concave just external to the line of junction of the head. The superior surface of the neck is concave, being limited on the outside by the great tro- chanter ; the posterior surface is likewise con- cave, being, as it were, hollowed from within outwards. The inferior surface is slightly con- cave from above downwards, but rounded from before backwards : this surface inclines down- wards and outwards, and at its termination is connected with the trochanter minor behind, and the inner side of the shaft of the bone in front ; in length it exceeds all the rest ; the su- perior surface is the shortest, and the posterior is longer than the anterior. On all the surfaces of the neck we observe numerous foramina for the transmission of vessels into the substance of the bone ; these foramina are largest and most numerous on the superior surface. At the superior angle of the base of the neck of the femur, and at the upper and outer part of the shaft of the bone, we observe a large and thick process, the trochanter major, (from t epyjn.01, roto,) processus exterior femoris ; it is a prolongation upwards of the shaft of the bone, but its most elevated point is below the level of the head of the bone, corresponding to the upper part of the line of junction of the head with the neck. “ This eminence,” says Cruveilhier, “ whose size is considerable, and which makes a very manifest prominence under the skin, ought to be studied with care in its relations as to its relative position ; first, with the crista ilii, beyond which it projects exter- 166 EXTREMITY. nally ; secondly, with the external condyle of the femur; thirdly, with the malleolus exter- nus, because these relations are constantly va- luable guides, as well in the diagnosis as in the reduction, of the luxations of the femur and of the fractures of the neck or shaft of the bone.” The external surface of the great trochanter is convex and rough, and the tendon of the glutceus maximus muscle covers it in the recent condition; this surface is terminated below by a projecting line, into which is inserted the upper extremity of the vastus externus muscle. The internal surface is of much less extent : it is placed at right angles with the superior sur- face of the neck of the bone, and at its posterior part it is excavated so as to form a deep pit or depression, the digital cavity or fossa trochante- rica, into which are inserted the tendon of the pyriformis, the gemelli, and the obturatores internus and externus. The anterior edge is thick and irregular; the glutoei medius and minimus are inserted into it, the former into its inferior, the latter into its superior part. Superiorly the trochanter forms a thin edge, more or less pointed, into the interior half of which the glutceus minimus is inserted, and into its posterior or pointed portion the glutoeus medius; it may in general be observed, that the size of this pointed part of the superior edge of the great trochanter is proportionate to the developement of the glutoeus medius mus- cle. The posterior edge is convex and thick, and gives attachment to the quadratus femoris muscle. At the inferior angle of the base of the cervix femoris, and on the internal and posterior part, we notice a short conical process, trochanter minor , ( processus interior femoris,) attached to the bone by its base, its apex directed downwards, inwards, and backwards, smooth on its whole surface. This process affords insertion to the tendon of the psoas and iliacus muscles. In the male adult, theaxisof the head and neck of the femur passes downwards, outwards, and slightly backwards, and forms an obtuse angle with the shaft, an angle of about 135 degrees. In the female this angle is somewhat smaller, and approaches more nearly to a right angle, which contributes with the greater lateral dimensions of the pelvis, to increase the distance of the trochanters of opposite sides from each other, and to cause that projection of these processes which form., a peculiarity of the female form. In early age, when the neck of the femur is imperfectly developed, the angle between the neck and shaft is not defined ; in the earliest condition the connexion of the head and shaft very much resembles the permanent condition of the corresponding parts in the humerus ; as the neck becomes developed, the angle is ren- dered apparent, at first, however, little removed from a right angle, but subsequently it in- creases up to the adult period ; after that time we often find that the neck of the bone dimi- nishes in its dimensions, and the angle is con- sequently altered, so as to approximate to a right angle. The following may be given as the mean measurements of the different parts of the neck of the femur. In the centre it measures about one inch, its posterior surface about fifteen lines, its inferior edge about twenty lines, and its superior about eleven lines ; its vertical diameter, in its most contracted part, is about seventeen lines, and its antero-posterior about ten. The shaft of the femur forms a slight curve from above downwards, convex anteriorly and concave posteriorly, the excavation thus formed behind being filled up by tjie powerful muscles on the back of the thigh. It likewise presents the appearance as if it had been twisted, like that which we have noticed in the humerus, the inferior extremity being twisted inwards, the superior in the contrary direction. Cru- veilhier remarks, that this curvature of torsion is in relation with the disposition of the femoral artery, which in its spiral course passes from the anterior to the posterior surface of the bone. In the greater part of its extent the shaft of the femur is prismatic ; at the superior extre- mity it is expanded laterally and flattened ; at the inferior it is likewise very considerably ex- panded. The anterior surface of the shaft is smooth and rounded ; at the upper part it is a little rough : this surface is covered completely by the triceps extensor muscle. The posterior surface is divided along the middle into two, which are inclined, the one forwards and in- wards, the other forwards and outwards ; the external surface is covered by the vastus exter- nus, the internal by the vastus internus. In the middle, separating these two surfaces, is a rough ridge, linea aspera, which occupies two- fifths of the shaft of the bone about its middle, but is bifurcated above and below. Superiorly the bifurcation takes place about the termina- tion of the superior fifth ; two lines proceed, the external, rough and prominent, to the great trochanter; the internal, rather indistinct, to the lesser trochanter. The external line gives in- sertion to the vastus externus, the adductor magnus, and the glutceus maximus ; the pecti- j nreus and the vastus internus are inserted into the internal line. Interiorly, the bifurcation takes place at a point corresponding to the I commencement of the two inferior fifths ; each line proceeds down to the corresponding con- dyle, and a triangular space is thus enclosed, the base of which is formed by the posterior extremities of the condyles, and the apex is at the point of bifurcation of the linea aspera. This space, which presents a smooth surface, slightly concave in both the vertical and trans- verse directions, forms the floor of the popliteal region. The external line, from the inferior bifurcation, is more prominent than the inter- nal, and gives insertion to the vastus externus and to the short head of the biceps. The in- ternal is very faint superiorly where the femoral artery passes over it, and interiorly the vastus internus and the adductor magnus are inserted into it. The nutritious foramen of the femur is found either upon, or on one side of, the linea aspera. EXTREMITY. 167 The direction of the canal is upwards towards the head of the femur. The inferior extremity of the femur is much more considerable than the superior. We no- tice upon it two articular processes of large size, united in front, but separated by a deep depression posteriorly. These processes are the external and internal condyles ; at the point of union of these two condyles in front, we ob- serve a transversely concave surface, which ex- tends for a little distance upwards upon the anterior surface of the bone ; this is the trochlea of-tlie femur, on which the patella moves. The deep notch which separates the condyles poste- riorly is denominated the intercondyloid notch. Each condyle is ovoidal in its outline and convex. The external condyle is placed di- rectly under the external part of the femur ; it projects more forwards than the internal con- dyle ; its antero-posterior diameter is less than that of the internal condyle, but its trans- verse is greater. On the other hand, the in- ternal condyle projects inwards out of the plane of the internal surface of the bone; its posterior extremity extends much further backwards than that of the external, and if the bone be placed at right angles with a plane surface, it will be seen that this condyle alone touches that surface, a circumstauce which arises from the internal condyle project- ing downwards more than the external. It is also worthy of notice, as resulting from this conformation of the internal condyle, that in order to bring both condyles in contact with a plane surface, the bone must be made to in- cline with the inferior extremity inwards. Above the posterior extremity of each condyle there is a depression for the insertion of the two heads of the gastrocnemius muscle. The external surface of the external condyle is continuous with the outer surface of the shaft; it is rough and convex, and is called by some anatomists the external tuberosity. At its posterior part there is a prominent tubercle to which the external lateral ligament is attached, and below and a little posterior to this is a de- pression into which the tendon of the popliteus is inserted. The internal surface of this con- dyle forms the outer wall of the depression which separates the condyles behind ; it is concave, and has the anterior crucial ligament inserted into it. The inner wall of this notch is formed by the external surface of the in- ternal condyle, which is likewise concave, and into it tire implanted the fibres of the pos- terior crucial ligament. The internal surface of this condyle, or the internal tuberosity, is rough, much more convex than the external tuberosity; the internal lateral ligament and tendon of the adductor magnus are inserted into it. Both the tuberosities are perforated by a number of minute foramina for the trans- mission of vessels to the cancellated texture. Structure. — A vertical section of the femur demonstrates its structure to be the same as that of all the long bones, composed of can- cellated texture at the extremities and com- pact in the shaft, which is bored by a cylin- drical canal. Posteriorly the compact tissue is of great density and hardness, especially where it forms the linea aspera or spine of the bone. When the section of the femur is made so as to divide the neck vertically in its long axis into two equal portions, we observe how ad- mirably the arrangement of the osseous texture in this part is adapted to the function which it has to perform. The head is entirely composed of reticular texture surrounded by a thin cortex ; this cortex gradually increases in thickness on the upper surface of the neck till it reaches the great trochanter. On the inferior surface of the neck, however, the compact tissue, although thin near the head, becomes very much in- creased in thickness as it curves downwards and outwards to the lesser trochanter. We observe, moreover, that although the principal portion of the head and neck are composed of reticular texture, in certain parts this texture is more loose than in others. From the upper part of the head to the thick part of the compact tissue on the inferior surface of the neck, a series of parallel fibres proceed in an oblique course, and closely applied to one another; these fibres receive and transmit the weight to the arch of the neck. Again, the reticular texture is loose and rare, external to these fibres and in all the inferior part of the head of the bone where no stress is laid upon the bone. Developement.- — According to Beclajd, the femur begins to ossify before the humerus; its ossification commences about the thirtieth day by a point for the shaft. A second point of ossification is for the inferior extremity, and this consists in a single osseous nucleus which is formed within the last month of foetal ex- istence, and is situated between the two con- dyles, occupying the centre of the cartilage. According to Cruveilhier this osseous nucleus appears during the last fifteen days of intra- uterine life. “ The constant presence,” adds this author, “ of this osseous point in the inferior extremity of the femur is a fact of great im- portance in legal medicine ; because from the knowledge of this circumstance alone, namely, that this nucleus exists in the epiphysis of the inferior extremity of the femur of a foetus, we can pronounce that foetus to have arrived at its full period.” The neck of the femur is formed by an ex- tension from the body. The head has a distinct point of ossification which begins to form at the end of the first year. The trochanters have each a separate point of ossification ; that of the great trochanter is formed about the third or fourth year, that of the lesser from the thir- teenth to the fourteenth year. These several osseous points are united to the shaft about the period of puberty in the following order ; first, the trochanter minor, next the head and trochan- ter major, and lastly the inferior extremity. In the skeleton the femur is articulated so that its inferior extremity approximates the corresponding part of the bone of the op- posite side, while the superior extremities are separated from each other to a considerable extent. One object of this oblique position of the femora has been already referred to, namely, to bring both condyles of each femur in con- 168 EXTREMITY. tact with the articular surfaces of the vertical tibiae. In women, in consequence of the more horizontal position of the neck of the femur and the greater width of the pelvis, the ob- liquity is more manifest, and hence they are naturally more in-kneed, than men, as from the greater projection of the internal condyle that surface alone would come in contact with the tibia if the position of the femur were vertical. The separation above is ef- fected by the neck of the bone, and the ad- vantage of this arrangement is to give a more favourable insertion to the muscles of rotation ; they thus acquire a lever power proportionate to the length of the neck, a fact which is abundantly manifest by comparing the relative powers of rotation in the shoulder and hip joints ; in the former these motions are more extensive, because, from the peculiar form of the joint, the obstacles to extent of motion are fewer; in the latter they are effected with greater power at a less expense of muscular force. In comparing the femur of man with that of the lower mammalia, we notice the imperfect developement or the non-developement of the cervix in the latter, the head in some being placed nearly vertically over the shaft of the bone, and also the small size of the trochanters, and the magnitude of the trochanter major in some classes. The curved form of the shaft of the femur is much less in the lower mammalia than in man ; in some the femur is perfectly straight, and as a consequence the linea aspera or spine is indistinctly marked. The propor- tionate length of the femur to the other bones of the inferior extremity differs also : in man it exceeds that of the tibia ; in the inferior mammalia, although in most cases the strongest bone, the femur is shorter than the tibia, and shorter even than the foot, although longer than each segment of this portion of the limb. The trochlea in the inferior extremity is deeper, and the transverse dimensions of the condyles are less than in man. Patella, (rotula, knee-pan, os sesamoideurn maximum, Bertin ; Fr. la rotule ; Germ, die Knitscheibe ). This bone, although belonging to the class of sesamoid bones, is yet so fully developed in the adult human subject, and is so essential to the integrity of the knee-joint, that it is usual to examine its anatomical characters along with those of the other bones of the in- ferior extremity. Its developement in the tendon of the rectus femoris leads to its being classed among the sesamoid bones. The pateila is of a triangular form, the apex being directed downwards and the base up- wards ; the former is connected with the tibia by the continued tendon of the rectus, under the name of ligamentum patella;; the tendon of the rectus and the tendinous expansions of the triceps extensor are inserted into the base, which expansions are likewise implanted into the margins of the bone, so that the whole circumference and anterior surface of the pa- tella are invested with tendinous fibres. The anterior surface of the patella is very slightly convex, and exhibits a fibrous ap- pearance produced by vertical and parallel fibres, with narrow fissures between, into which the fibrous expansion which invests this surface is implanted. The posterior surface is articular and adapted to the trochlea of the femur. A vertical ridge, which inclines a little outwards in its descent, divides this sur- face into two lateral portions ; each of these por- tions is a concave articular facet for adaptation to the anterior part of each condyle of the femur, and consequently there is between these surfaces the same inequality which exists be- tween the condyles. In the recent condition these surfaces are covered by a soft and very elastic cartilage. Structure and developement. — The patella is entirely composed of cancellated texture, the anterior surface being covered by a thin lamella of very fibrous compact tissue already referred to. This bone is developed by a single point of ossification, which commences about the second year. The patella exists pretty generally among Mammalia, also among Birds. It is most de- veloped in the Pachydermata and the Solipeds, and also in the Monotremata; and least so in the Carnivora and Quadrumana. It is absent in Cheiroptera and Marsupiata.* Leg.- — The bones that form the second segment of the inferior extremity are the Tibia and Fibula. Tibia, (shin-bone ; Germ, das Schienbein.) This bone is situated between the inferior ex- tremity of the femur and the astragalus. Its length is to that of the femur as five to six. It forms the principal support of the leg, on the inside of which it is placed, and its volume is five times that of the fibula. After the femur, it is the longest bone in the body, being longer than the humerus. The upper or femoral extremity of the tibia is thicker and broader than the remaining parts of the bone, and is properly the head of the bone. Its transverse extent is much greater than its antero-posterior. Its superior surface presents two bony processes lying on the same plane, denominated condyles of the tibia. Each of these has upon its superior surface a superficial concave articular facet, oval with long axis from before backwards; to these surfaces the term condyle has been improperly applied ; but they are more correctly called the glenoid cavities of the tibia, ( cavitates glenoi.dc/e, ex- terna et interna). These cavities correspond to the condyles of the femur, having the semi- lunar cartilages interposed ; the outer cavity approaches more to the circular form than the internal one ; it is likewise much less deep, and at its posterior part it is even convex. The internal one, on the other hand, is uniformly concave, and its antero-posterior axis greatly exceeds its transverse. These sur- faces are separated in the centre by a pyra- midal eminence whose apex appears bifurcated, the subdivisions of which are separated by a narrow rough space. This is the spine of the tibia, ( acclivitas intercondyloidea ) ; it corres- ponds to the intercondyloid fossa of the femur * Meckel, Anat. Compar. EXTREMITY. 169 where the crucial ligaments are attached. Anterior and posterior to this spine are two rougli depressions, the posterior more hollowed than the anterior : into the former the posterior crucial ligament is inserted, and the latter re- ceives the anterior crucial ligament. The circumference of the head is rough and perforated by a vast number of minute vas- cular foramina. Each condyle projects late- rally beyond the plane of the corresponding surface of the shaft, the internal to a greater extent than the external. These lateral pro- jections are distinguished by the name of Tu- berosities. The internal tuberosity gives in- sertion at its lower part to the internal lateral ligament of the knee-joint; posteriorly this tuberosity is grooved, and one of the tendons of the semi-membranosus is inserted into the groove, and separates the internal lateral ligament from the bone in this situation. At the pos- terior part of the external tuberosity there is a small articular facet, nearly circular and plane, with which the fibula is articulated. In front of the head of the tibia there is a rough triangular surface, the apex of which is directed downwards and forms a promi- nence, which is smooth at its superior part, but rough inferiorly. The ligamentum pate 1 he is inserted in the latter situation ; the smooth portion indicates the position of a bursa which intervenes between the ligament and the bone. This prominence is called the anterior tube- rosity, and by some anatomists the spine. From the inferior rough portion of this tube- rosity there passes upwards and outwards a prominent line, most prominent at its ter- mination, where the tibialis anticus muscle has one of its attachments. The shaft of the tibia has the form of a triangular prism in almost its whole extent ; at its inferior third this form is less distinct, in consequence of the angles being rounded oil'. Of the three surfaces the anterior is that which presents the greatest dimensions : it is smooth and slightly convex in its entire extent, in- clined backwards and inwards, subcutaneous, except at its upper part, where an aponeurotic expansion connected with the tendons of the semi-tendinosus,sartorius, and gracilis muscles. The inferior fourth of this surface is much more convex than the upper portion, and looks directly inwards. The external surface is in- clined backwards and outwards, and is con- cave in its three superior fifths, convex in the rest of its extent. The depth of the superior concave portion is proportionate to the de- velopement of the tibialis anticus muscle, to which it gives insertion. The inferior con- vex portion is of less extent than the superior, and as it descends it experiences a change of aspect, so as to look directly forwards. This change is in accordance with the altered di- rection of the tendons of the tibialis anticus and extensor muscles of the toes, which lie in contact with the bone in this situation. The posterior surface is expanded at its extremities and contracted in the centre. At its superior part a triangular surface is marked of!' from the rest, towards the upper extremity by an oblique line, which proceeds from below up- wards, and from within outwards ; into this line are inserted the poplitaeus, solceus, tibialis posticus, and the long flexor muscle of the toes. The space which intervenes between this line and the posterior margin of the head of the bone is covered by the poplitaeus muscle and forms part of the floor of the popliteal space. Immediately below this oblique line, the orifice of the nutritious canal is situated, penetrating the bone obliquely downwards ; this canal is the largest of the medullary canals of the long bones ; and Cruveilhier states that he has traced a nervous filament passing into it in company with its artery. All that portion of the posterior surface which is below the oblique line is smooth and divided by a ver- tical line, which is variously developed indif- ferent subjects; the tibialis posticus muscle and the long flexor of the toes are attached to this surface. Three distinct edges separate these surfaces. The anterior edge ( crista tibia) is very promi- nent and sharp in its three superior fourths, but rounded oft' below ; in its upper part it is quite subcutaneous, and may be felt under the skin. The external edge forms a very distinct line of demarcation between the internal and posterior surfaces ; it gives attachment to the interosseous ligament, and at its inferior extremity it bifur- cates and encloses a concave triangular surface, in which the fibula rests. The internal edge is more rounded than either of the others ; more distinct inferiorly than superiorly. At its up- per end it gives insertion to the internal lateral ligament of the knee-joint and the popliteus muscle, and lower down to the solceus and the common flexor of the toes. The inferior or tarsal extremity of the tibia is of larger dimensions than the shaft, although much smaller than the superior. On its infe- rior surface we notice a quadrilateral articular cavity, of greater dimensions transversely than from before backwards, concave in this latter direction, and slightly convex transversely, in consequence of the existence of a slight ridge in the centre, which passes from before backwards. This surface is for articulation with the supe- rior part of the body of the astragalus to form the ankle-joint. The anterior surface of the inferior extremity of the tibia is convex and rough ; it gives in- sertion to the anterior ligamentous fibres of the ankle-joint, and the tendons of the extensor muscles pass over it. The posterior surface is very slightly convex ; sometimes a very super- ficial groove exists upon it for lodging the ten- don of the flexor pollicis longus ; and internal to that, and lying behind the internal malleolus, a more distinct and constant groove, which passes obliquely downwards and inwards, and lodges the tendons of the tibialis posticus and flexor communis. On the inside of the inferior extremity, we observe that the bone is prolonged downwards and slightly inwards, forming a thick and flat- tened process, quadrilateral in form, called malleolus internus. The internal surface of this process is rough and convex; it is quite 170 EXTREMITY. subcutaneous; its external surface is smooth, and exhibits a triangular articular facet, which is united at a little more than a right angle with the articular surface on the inferior extremity of the tibia; by this facet the internal malleolus moves on the inner surface of the body of the astragalus. The apex of the mal- leolus has the internal lateral ligament of the ankle-joint inserted into it ; the anterior edge gives insertion to ligamentous fibres, and the posterior edge, much thicker than the anterior, is closely connected with the posterior surface of the inferior extremity of the tibia, and has upon it the oblique groove already referred to. In comparing the position of the malleolus in- ternus with that of the internal tuberosity of the tibia, (which may best be done by laying the bone on its posterior surface on a horizontal plane,) it will be observed that the malleolus is considerably anterior to the tuberosity, a fact which is attributable to the same cause which occasions the change of aspect in the inferior part of each of the three surfaces of the shaft, namely, a torsion of the bone similar to that already noticed in the other long bones of the extremities. This torsion is manifest at the junction of the inferior and middle thirds, the lower part having the appearance of being twisted inwards, and the upper part outwards. The outer side of the tarsal extremity of the tibia is excavated so as to form a triangular surface, rough in its entire extent, to which the fibula is applied, and into which are implanted the strong ligamentous fibres by which that bone is tied to the tibia. Structure. — The cancellated texture is accu- mulated in large quantity at the extremities, where, especially at the superior, a line is very frequently apparent on the whole circumference, indicating the place of junction of the epiphysis and shaft. The medullary canal is large, ap- proaching the cylindrical form, and surrounded by a dense compact tissue. Fibula (I’r. perone ; Germ. Wadenbein). — This bone is situated on the outer and posterior part of the tibia. It is about the same length as that bone, but as its upper extremity is ap- plied to the under surface of the external tube- rosity, its inferior extremity projects below that of the tibia. There is a slight obliquity in its direction, and in consequence, its inferior extre- mity advances more forwards than its superior. The fibula is a very slender bone in its entire extent, however its extremities are a little enlarged. The superior extremity or head of the fibula (capitulum) is somewhat rounded on its inner side, flattened on its external surface, terminating superiorly in a point into which the external lateral ligament of the knee-joint is inserted, anterior and posterior to which the edge of the bone receives the tendon of the biceps muscle. At the upper and anterior part of its internal surface there is a small sur- face nearly plane, which is articulated with a similar one on the external tuberosity of the tibia. On the shaft of the fibula we may dis- tinguish three surfaces, but in consequence of the great extent to which the fibula appears to have undergone torsion, it is at first difficult to detect the lines of demarcation between these surfaces. The external surface is very narrow and convex in its upper third, gradually ex- pands as it descends, and becomes hollowed out in its middle third, where it receives the peroncei muscles ; in both these portions the aspect of this surface is outwards and slightly forwards. In the inferior third it is quite flat, and its aspect is outwards and backwards. The internal surface has a longitudinal sharp ridge upon it, which gives insertion to the interosse- ous ligament. This crest divides the internal surface into two portions ; the anterior, very small, in some cases not exceeding two or three lines, gives attachment to the extensor muscles of the toes and the peronaeus tertius ; the pos- terior, much more considerable and slightly concave longitudinally for about its two supe- rior thirds, has the tibialis posticus inserted into it. This surface, which above looks nearly directly inwards, looks forwards in its inferior third. The posterior surface is also very nar- row above, and expands as it descends ; upon it the twist in the bone is very obvious. In its superior third this surface looks outwards and backwards ; in its middle third, where it is much more expanded, it looks directly back- wards ; and in its inferior third its aspect is inwards, and here it terminates in forming a rough surface which is adapted to the similar one on the fibular side of the inferior extremity of the tibia. Superiorly the posterior surface of the tibia gives attachment to the soloeus muscle, and lower down to the flexor pollicis proprius. The orifice of the nutritious canal, directed down- wards and forwards, is found here. A knowledge of the edges which separate these surfaces will assist the student in understanding the position of the surfaces themselves. The anterior edge begins just below the head, passes down in front of the bone as far as the middle, then becomes exter- nal and bifurcates, enclosing a triangular sur- face on the outside of the inferior extremity of the bone, which is quite subcutaneous. The external edge is at first external, and about the commencement of the inferior third it begins to wind round so as ultimately to become posterior. The internal edge , which is the most acute, and is more prominent in the centre than at its extremities, passes forwards inferiorly, and terminates in front of the inferior extre- mity of the bone : below it gives attachment to the interosseous ligament. The inferior extremity is long and flat, and terminates in a point; it extends entirely below the inferior articular surface on the tibia, and, as Cruveilhier aptly remarks, it forms exter- nally the pendant to the malleolus interims, which it exceeds in length and thickness; it is consequently called the malleolus externus. The internal surface of the external malleolus presents in its anterior two-thirds a plane triangular surface for articulation with the astragalus ; behind this surface there is an excavation, which is rough, and gives insertion to the posterior external lateral ligament. The external surface is convex and subcutaneous, and the posterior surface is grooved for the EYE. in passage of the tendons of the peronsei muscles. The apex of the malleolus is directed down- wards, and is the point of attachment of the middle external lateral ligament. Structure. — This bone is very light and elastic, a property rendered necessary by the antagonist muscles which are inserted into its opposite surfaces. Its extremities are composed of cancellated structure, which extends some way to the shaft of the bone. The medullary canal, very narrow and irregular, is found only in its middle third. Developement of the hones of the leg. — The tibia begins to ossify somewhat earlier than the fibula. Both bones begin to ossify in their shafts ; the ossific point of the shaft of the tibia appears about the middle of the second month. According to Meckel, in the embryo of ten weeks, the fibula is not above half the length of the tibia; after the third month the two bones are nearly equal. Both bones have an ossific point for each extremity. The superior extremity of the tibia begins to ossify towards the termination of the first year after birth. The inferior extre- mity is ossified in the course of the second year: the external malleolus is a prolongation of the inferior extremity. The union of the extremities with the shaft commences by the inferior, and is completed from the eighteenth to the twenty-fifth year. The ossification of the fibula follows nearly the same course, excepting that the superior extremity does not begin to ossify till the fifth year. The tibia constitutes the principal pillar of support to the leg. It is placed perpendicu- larly under the femur, and as the latter bone is inclined inwards, it follows that there must be an angle formed between these two bones at the knee-joint, a very obtuse one, with its apex inwards.* It is then by the strength and direction of the tibia that the leg firmly sup- ports the body in the erect attitude ; the fibula seems not to contribute at all to the solidity of the limb, but is chiefly employed to increase the surface of attachment for the muscles of the leg. The developement of the tibia and fibula in the inferior mammalia is pretty similar to that of the radius and ulna. The tibia is always fully developed, and, as in man, is the prin- cipal bone of the leg, its size being pro- portionate to the weight and strength of the animal. Admitting the fibula to be the ana- logue of the latter bone, we find that, as it is rudimentary in the Solipeds and Ruminants, so the fibula is in a similar condition in these animals. In the former animals this bone is applied to the external side of the head ox the tibia in the form of an elongated stilet, termi- nating less than half way down in a fine point. On the other hand, in Ruminants it is only the inferior part of the fibula that is developed ; it appears under the form of a small narrow bone, extending a very little way upwards, and form- ing the external malleolus. * A preternatural obliquity of the femur causes a corresponding divergence of the tibia from the perpendicular. When the femur is directed un- usually inwards, the tibia is directed downwards and outwards. In Pachydermata the fibula is fully deve- loped and quite distinct from the tibia, and very small in proportion. In Edentata the two bones are fully developed, and in the Sloths the inferior extremity of the fibula con- tributes to form the articular surface for the astragalus. In Rodentia the two bones are united together in the inferior half, as also with the Insectivora, particularly in the Mole. In many Carnivora these bones are fully developed and detached : this is particularly manifest in the Phocidm and the Felidae. In the Dogs, however, the fibula is attached to the posterior part of the tibia. For the description of the bones composing the foot, we refer to the article under that head ; and for further details on the osseous system of the extremities, we refer to the articles Osseous System (Comp. Anat.) and Skeleton. Abnormal condition of the hones of the extre- mities.— A congenital malformation of one or more of the extremities is classed by Isidore Geoffroy St. Hilaire among what he denomi- nates “ Monstres Ectromeliens,” of which he has three subdivisions: 1st, where the hands or feet appear to exist alone, and seem to be connected with the trunk without the inter- vention of all or some of the intermediate segments; these he denominates Phocomeles , (tpuy.y, Phoca, and jj-eXog, membrum,) from their resemblance to the permanent condition of the aquatic mammalia : 2d, cases in which there are one or more incomplete limbs terminating in the form of stumps : to these he gives the name Hemimeles: and, lastly, where the limb or limbs are wholly absent or scarcely at all developed. An interesting case of Phoco- melia is recorded by Dumeril ; all the limbs were in this condition, owing to the absence of the humerus, and forearm bones in the upper extremity, and the presence of a very imperfect femur, developed only as to the head and tro- chanters, and a very imperfect tibia in the lower extremity. The clavicle and scapula were pre- sent, but presented some irregularities of form.* The congenital absence of these last bones is rare excepting where the other bones of the limb are also absent. It would be inconsistent with the objects of this article to prosecute this subject further; we therefore refer for further details to the article Monstrosity. For Bibliography, see that of Anatomy (Introduction). ( R. B. Todd.) EYE, (in human anatomy), oipfiafytos, orga- non visus ; oculus. Fr. (Eil; Germ .dasAuge; Ital.Occhio. — The human eye is a hollow sphere, about one inch in diameter, with a circular aperture in the anterior part about one-fifth of this sphere in breadth, filled by a transparent convex portion called the cornea, through which the light is transmitted. Within this hollow * Bull, de la Soc. Philomath, t. iii., quoted in Geoff. St. Hilaire’s Anom, de l’Orgauization, t. ii. p. 211. 172 EYE. sphere, and at a short distance behind the trans- parent convex portion or cornea, is fixed a doable convex lens, called the crystalline lens or crystalline humour; and between this cor- nea and crystalline lens is interposed a parti- tion or screen called the iris, with a circular aperture in its centre called the pupil. The inner surface of this hollow sphere, as well as the back of the iris or screen, are covered or stained with a black material. The space be- tween the cornea and crystalline lens, in which the iris is placed, is filled with a transparent fluid, called the aqueous humour, and the space between the crystalline lens and the bot- tom of the sphere is filled with a similar fluid, called the vitreous humour. The annexed figure represents a section of this simple piece of opti- cal mechanism, much larger than natural to render the parts more distinct. Fig. 100. An acquaintance with the laws which regu- late the transmission of the rays of light through transparent bodies, and with the manner in which the lenticular form changes the direction of these rays, teaches that a correct image of ex- ternal objects is formed in the bottom of the eye in consequence of the above adjustment of its parts. First, the rays of light acquire a con- vergence in their passage through the cornea and aqueous humour, then the central portion of the pencd of rays is transmitted through the pupil, and, finally, the rays in their passage through the crystalline lens acquire such addi- tional convergence, that they are brought to a focus on the bottom as represented in the an- nexed diagram. Such are the essential component parts of the eye, considered as a piece of optical me- chanism, but viewed as a piece of anatomical mechanism, its construction is much more com- plicated, and the materials of which it is com- posed are necessarily totally different from those of any human contrivance of a similar nature. It lives in common with the body of which it forms a part, it grows and is repaired ; conse- quently, the animal organisation destined for such functions must constitute an essential part of its construction. The organ derives its permanent spherical form, its external strength, and the support of the delicate parts within it, from a strong opaque membrane called the sclerotic coat; while the convex portion, called cornea, in front, equally strong, being transparent, allows the rays of light to pass without interruption. The interior of the portion of the sphere formed by the sclerotic coat is lined throughout by a soft membrane called the choroid, necessarily con- stituting another hollow sphere, accurately adapted and adhering to the inside of the for- mer. This also has its circular aperture ante- riorly, into which is fitted the screen called iris, as the cornea is fitted into the aperture in the sclerotic. While the external surface of this choroid coat is comparatively rough and coarse in its organization, as it adheres to the equally coarse surface of the sclerotic, the interior is exquisitely smooth and soft, being destined to embrace the retina, another spherically dis- posed membrane of extreme delicacy. The screen called iris, which is fitted into the cir- cular aperture anteriorly, is as different from the choroid coat in its organization as the cor- nea is from the sclerotic: it is perfectly plane, and therefore forms with the concave surface of the cornea a cavity of the shape of a plano- convex lens, called the anterior chamber. In or on the choroid coat the principal vessels and nerves, destined to supply the interior of the organ, are distributed, and in its texture and upon its inner surface is deposited the black material, which in this part of the chamber, as well as on the back of the iris, is so essential a provision. At the anterior margin the choroid is more firmly united to the corresponding mar- gin of the sclerotic by a circular band of pecu- liar structure called the ciliary ligament, and on I its inner surface, in the same place, it is fur- Fig. 101. EYE. 173 nished with a circle of prominent folds called ciliary processes, by means of which it is united to the corresponding surface of the hyaloid membrane of the vitreous humour. The an- nexed figure represents a section of this hollow sphere lodged within the sclerotic sphere. The external circle, a a, between the two black lines represents a section of the strong opaque membrane called the sclerotic, which consti- tutes the case or resisting sides of the organ ; l is the transparent lenticular window called cornea, which fills the aperture left in the ante- rior part of the sclerotic for its reception ; d d is the place of union between the sclerotic and cornea, to which the ciliary ligament on the outside of the anterior margin of the choroid sphere corresponds ; e e the circle bounded by the line marking the inner surface of the sclerotic externally, and by the shaded part in- ternally, represents a section of the hollow sphere called choroid. At the point d d, cor- responding to the place of union between the sclerotic and cornea, this choroid projects exter- nally, encroaching upon the sclerotic in a pecu- liar manner, to be presently described as the ciliary ligament; while at the same point it projects internally in the shape of a series of folds, to be described as the ciliary processes. The white productions extending from the same points in a vertical direction into the chamber of the aqueous humour, between the cornea and crystalline lens, represent a section of the screen called the iris, f is a section of the crystalline lens. Fig. 102. ed by the cornea being very small, and that behind bounded by the retina being very large. This large posterior chamber is distended by a spherical transparent mass, called the vitreous humour, which does not, however, fill this pos- terior chamber completely, but is discontinued or compressed at a short distance behind the iris, leaving a narrow space between it and that membrane, called the posterior chamber of the aqueous humour. This spherical mass is of ex- tremely soft consistence, and is composed of a delicate transparent cellular membrane called the hyaloid membrane, the cells of which are distended with a ransparent fluid. In the small space between the anterior part of the vitreous humour and the back of the iris, called the posterior chamber of the aqueous humour, and lodged, in a depression formed for its re- ception in the vitreous humour, is placed the double convex lens called the crystalline lens. The relation of these parts to each other may be seen in the last figure, and the one below represents the optic nerve expanded in the form of a spherical membrane over the sphere of vitreous humour, with the crystalline lens lodged in a depression on the anterior part of that sphere, and surrounded by a circle of radiating lines, which are delicate folds corres- ponding to the folds of the choroid, called the ciliary processes. Fig. 103. Through a small aperture in the sclerotic and choroid membranes in the bottom of the eye, the optic nerve is transmitted, and imme- diately expands into a texture of the most ex- quisite delicacy, called the retina. This con- stitutes a third spherically disposed membrane, not however of the same extent as the sclerotic or choroid, being discontinued at a distance of about an eighth of an inch from the anterior margins of these membranes. This is the ner- vous expansion endowed with the peculiar description of sensibility which renders the ani- mal conscious of the presence of light. The globe of the eye, as above described, is ob- viously divided by the iris into two chambers of very unequal dimensions; that in front bound- The piece of animal optical mechanism thus constructed is lodged in an open cavity of the skull called the orbit, and is furnished with six small muscles for its motions inserted into the outside of the sclerotic coat. The transparent cornea through which the light is transmitted is necessarily exposed, and not being in its nature suited to such exposure, is covered with a membrane called conjunctiva, which also extends over the sclerotic, where that membrane con- stitutes the anterior part of the globe, and then being reflected, lines the eyelids, and finally be- comes continuous with the skin of the face. The human eye is, as has been stated above, probably a sphere of about one inch in diameter. Petit, however, who appears to have first made the attempt to determine the proportions of the organ accurately, describes the axis to be to the diameter as 135 to 136, and the younger Som- merring, apparently from his own observations, as 10 to 9.5. This belief in a slight differ- ence in dimension may, however, have been 174 EYE. adopted from not making allowance for the projection of the cornea, which is a portion of a smaller sphere than the globe itself, and con- sequently projects beyond its circumference. From the flaccid state of the eye even shortly after death, it must be very difficult to measure it accurately. The question is, however, for- tunately of little practical importance. The eyeball of the male is generally a little larger than that of the female; and if a close inquiry be made into the matter, much difference in this respect might probably be detected in different individuals. I have seen the eyeball in an adult of full size not larger than that of a child of five years old ; and there is much apparent difference in consequence of the difference in the depth of the orbit, and in the gape of the eyelids. Although the human eyeball is nearly a perfect sphere, that precise form is obviously not an essential requisite in the construction of a perfect organ of vision. In all the vertebral animals the bottom of the eye, where the retina is expanded, is probably a portion of a correct sphere, but in many the anterior part is com- pressed, or in other words the sphere is trun- cated, to adapt it to the form and dimensions of the head, or to bring the cornea and lens nearer to the retina. In the mysticete whale the axis is to the diameter as 20 to 29 ; in the swan as 7 to 10 ; in the turtle as about 8 to 10 ; and in the cod as 14 to 17. This deviation from the spherical form demands a corresponding provi- sion in the construction of the sclerotic, to be noticed when describing that membrane. For a fuller account of the comparative proportional measurements of the eye, the student is referred to the works of Cuvier and D. W. Sommer- ring, as quoted at the end of this article ; the limits of which do not admit of a greater detail of facts derived from comparative anatomy than the illustration of the description of the human organ absolutely demands. Having attempted to give a general notion of the mechanism of the eye in the preceding paragraphs, it remains to consider each com- ponent part separately, and to determine its organization, properties, and application, as well as the changes to which it is liable from age, disease, or other circumstances. Of the sclerotic membrane. — This, as has been stated, constitutes, with the transpa- rent cornea, the external case upon which the integrity of the more delicate inter- nal parts of the organ depends, otherwise in- capable of preserving their precise relations to each other • without such support the compo- nent structures must fall to pieces, or be crushed by external pressure. The name is derived from the Greek o-kM^ou, and it has also been called cornea and cornea opaca in contradistinc- tion to the true or transparent cornea, a structure to which it bears no resemblance whatsoever ; it is the same animal material which exists in all parts of the body where strength with flexi- bility is required, the material which in modern times has been denominated fibrous mem- brane. When carefully freed from all ex- traneous matter by clipping with a pair of scissors under water, it presents the brilliant silvery-white appearance so characteristic of the fibrous membranes. The white streaks which give the fibrous appearance appear ar- ranged concentrically as the lines on imper- fectly polished metallic surfaces. It is inelastic as other fibrous membranes, and so strong that it does not tear or yield unless exposed to the greatest violence. Although penetrated by the vessels going into and returning from the in- ternal parts of the eye, it does not appear to have much more red blood circulating through its texture than other tendinous expansions distinguished for their whiteness. The vas- cularity of the anterior part, however, where it is exposed in the living body, constituting the tunica albuginea, or white of the eye, is different from that of the rest of the mem- brane. The four straight muscles are pene- trated by small branches of the ophthalmic artery, the delicate ramifications of which con- verge to the circumference of the cornea, for the nutrition of which membrane they appear to be destined. In the natural state they can scarcely be detected, but when enlarged by in- flammation, present a remarkable appearance, considered by practical writers one of the most characteristic symptoms of inflammation of the eyeball, or, as it is called, iritis. They then appear as numerous distinct vessels, and as they approach the margin of the cornea, become so minute and subdivided, that they can no longer be distinguished as separate vessels, but merely present a uniform red tint, described as a pink zone. The colour of this inflammatory vascula- rity is also characteristic. Whether from the vessels being more arterial than venous, or from their distribution in so white a structure, they present a brilliant pink appearance very different from the deep red of conjunctival in- flammation, which often enables the practi- tioner to pronounce an opinion as to the nature of the disease before he makes a close examin- ation. The inner surface of the sclerotic where it is in contact with the choroid, does not present the same brilliant silver-white appearance that it does externally, being stained with the black colouring matter; it is also obscured by a thin layer of cellular membrane, by means of which it is united to the external surface of the cho- roid.*' This layer of cellular membrane was described by Le Cat, and more particularly by Zinn, as a distinct membrane, and considered to be a continuation of the pia mater ; it is, how- ever, obviously nothing more than the connect- ing material applied here as in other parts of the body where union is requisite. The thickness of the sclerotic is greater in the bottom of the eye than at its anterior part, where it is so thin that hallows the black colour of the choroid to appear through it, giving to this part of the eye a blue tint, particularly remark- able in young persons of delicate frame. The at- tachments of the four straight muscles, how- ever, appear to increase the thickness in this * [Arnold and others describe and figure a serous membrane in this situation ( Spinnwebenhaut , arach- noidea ocul.i ). See the figure of a vertical section of the eye in Arnold iiber das Auge, tab. iii. fig. 2, and copied into Mr. Mackenzie’s work on the Eye. — Ed.J EYE. 175 situation ; but that there is no general thick- ening in tliis part from this cause is proved by the thinness of the membrane in the inter- vals between and beneath these tendons. The consequence of this greater thinness of the membrane anteriorly is, that when the eyeball is ruptured by a blow, the laceration takes place at a short distance from the cornea. In animals in whom the eyeball deviates much from a true sphere, as in the horse, ox, sheep, and above all, in the whale, the sclerotic is much thicker posteriorly than anteriorly, being in the latter animal from three quarters to an inch in thickness, while it is not more than a line at its junction with the cornea. The rea- son for the existence of this provision is, that the form of the perfect sphere is preserved by the uniform resistance of the contents, but when these contents are spherical in one part, and flattened in another, the external case must pos- sess strength sufficient to preserve this irregu- larity of form. It is remarkable that this strength is conferred in the class mammalia by giving to the sclerotic increase of thickness, the fibrous structure remaining nearly the same in its nature, while in birds, reptiles, and fishes, the requisite strength is derived from the pre- sence of a cartilaginous cup or portion of sphere, disposed within a very thin fibrous sclerotic. This cartilaginous sclerotic, as it is often called in the books, exists, as far as 1 have been able to ascertain, in these three classes, and is in some individuals very remarkable. In birds it is thin and flexible, giving a degree of elasticity, which distinguishes the eyeball in this class. In fishes, as has been observed by Cuvier and others, the cartilage is always present, and is particularly thick in the sturgeon ; it is even osseous in some, as the sea-bream, from the eye of which animal I have often obtained it in the form of a hard crust by putrefactive maceration. Among the reptiles the turtle presents a good example of this structure. Where the deviation from the spherical form is very great, as in birds, additional provision is made to sustain the form of the organ. This consists of a series of small osseous plates ar- ranged in a circle round the margin of the cor- nea, lapping over each other at the edges, and intimately connected with the fibrous and car- tilaginous layers of the sclerotic. A similar provision exists in the turtle, and also in the chameleon, and many other lizards, but not perhaps so neatly and perfectly arranged as in birds. It is found in the great fossil reptiles Ichthyosaurus and Plesiosaurus. The sclerotic, like other fibrous membranes, being inelastic and unyielding, does not be- come stretched when fluids accumulate in the eyeball in consequence of inflammation, or in other words, the eyeball does not become en- larged from effusion of serum or secretion of purulent matter into its chambers. To this probably may be attributed the intolerable torture and sense of tension experienced when the eyeball suppurates, as well as the severe pain extending to the temple in some forms of inflammation. The pain in such cases must not, however, be wholly attributed to this dis- tension of an unyielding membrane. The fibrous membranes in general, when affected by rheumatic or arthritic inflammation, become acutely sensible, and the cause of much suffer- ing ; and the sclerotic, when similarly affected, acquires the same description of painful sen- sibility, apparently independent of distension from effusion. In certain forms of inflam- mation and other morbid changes of the eyeball, the sclerotic appears to yield to distension, as in scrofulous inflammation and hydrophthalmia ; but this is not a mechanical stretching, but an alteration in structure at- tended with a thinning of the membrane, and consequent alteration in the shape of the globe. It appears that the cornea and sclerotic are peculiarly, if not in many instances almost ex- clusively, the seat of the disease in chronic scrofulous inflammation of the eyeball. This inference may, I think, be justly drawn from the fact, that in such cases the sclerotic becomes so much thinned that the dark choroid projects in the form of a tumour, and the eye loses its spherical form ; yet the pupil remains regular, the lens transparent, and the retina sensible to light. When the cornea is destroyed by slough or ulceration in severe ophthalmia, allowing the lens and more or less of the vitreous hu- mour to escape, the sclerotic does not accom- modate itself to the diminished contents by a uniform contraction, but merely falls in ; and when the eye has been completely emptied, it is found many years after the injury folded up into a small irregular mass in the bottom of the orbit. When the organization of the eye is completely destroyed by idiopathic, rheumatic, or syphilitic inflammation, the sclerotic becomes flaccid, and the whole eyeball soft, allowing the contraction of the four straight muscles to produce corresponding depressions, and thus convert the sphere into a form somewhat cu- bical. Of the cornea. — This is the transparent body which fills the circular aperture in the anterior part of the spherical sclerotic ; it is called cornea from its supposed resemblance to transparent horn, and cornea transparens in contradistinction to the sclerotic, which, as has been stated, is called cornea opaca. It is generally described as a transparent structure, serving to the eye the same purpose as the crystal to the watch ; but this is not a correct comparison : the crystal merely transmits the light without changing the direction of the rays ; the cornea, whether it be considered in itself a lens, or as the sphe- rical surface of the aqueous humour, refracts the rays and causes them to converge to a focus. Haller, although he does not directly say that it is a lens, yet states that if held over a book it magnifies the letters, which of course results from its lenticular form ; and Cuvier and Biot distinctly call it a meniscus. On the other hand, the Sdmmerrings, both father and son, describe it as a mere segment of a sphere, the curve of the convexity corresponding to that of the concavity, as in the watch crystal. I consider it to be a lens and a meniscus. If it be removed from the eye a short time after death with a portion of the sclerotic, and dipped in water to smooth its surfaces, it magnifies ob- jects when held between them and the eye, as 176 EYE. stated by Haller ; and sections of the cornea of the eye of the horse, ox, sheep, or other large animals, shew that the part is much thicker in the centre than at the circumference. It is also to be observed that it has the same provi- sion for the preservation of its lenticular form in a correct state as the crystalline lens, as will presently be explained. The statements made by authors respecting the measurements of the curvatures of the surface of the cornea can be considered only as an approximation to the truth. It is obvious that there must be much difficulty in accurately ascertaining the matter during life, and after death the form is so speedily altered by evaporation that the curve cannot remain the same as during life, hence the measurements differ. Haller says it is a portion of a sphere seven lines and a half in diameter; Wintringham that the chord is equal to 1.05 of an inch, the versed sine of this chord 0.29, and consequently the radius is equal to 0.620215 of an inch. Mr. Lloyd, in his Optics, states, on the authority of Chossat, that the surface of the cornea is not spherical but spheroidical. He says, “ the bounding surfaces of the refracting media, however, are not spherical but spheroidical. This remark- able fact was long since suspected by M. Petit, but of late has been placed on the clearest evidence by the accurate measurements of Chossat. This author has found that the cornea of the eye of the ox is an ellipsoid of revolution round the greater axis, this axis being inclined inwards about 10°. The ratio of the major axis to the distance between the foci in the generating ellipse he found to be 1.3; and this agreeing very nearly with 1.337, the index of refraction of the aqueous humour, it follows that parallel rays will be refracted to a focus by the surface of this humour with ma- thematical accuracy.” Whether we consider the cornea as a distinct lens, or as constituting the spherical surface of the aqueous humour, there can be no doubt of its importance as an agent in causing the convergence of the rays of light to a focus on the retina in conjunction with the crystalline lens. If other proof were wanted, it is afforded by the comparatively perfect optical mechanism of the eye after the crystalline lens has been removed by the opera- tion for cataract. The vision in such cases, especially in young persons, is often so good that individuals are satisfied with it for the common purposes of life, and do not resort to the use of the usual convex glasses. The cir- cumference of the cornea is not perfectly cir- cular externally, although it is internally; the sclerotic laps a little over it both superiorly and mferiorly, so that it appears a little wider than it is deep, the vertical being to the horizontal diameter as fifteen to sixteen. Although the cornea is in general description considered a simple and uniform membrane, it is undoubtedly composed of three forms of animal structure, as different from each other as any other three in the animal. These are the conjunctiva, which constitutes the exposed sur- face ; the proper cornea, upon which the strength of the part depends; and the elastic cornea, which lines the inner concave surface. The conjunctiva is evidently a continuation of the skin, which, reflected in the form of a vas- cular membrane, lines the eyelids, from which it is continued as a delicate transparent mem- brane over the anterior part of the globe, ad- hering loosely to the sclerotic, and closely to the cornea. The existence of conjunctiva on the surface of the cornea proper admits of easy demonstration, and its identity of character with the rest of the conjunctiva and skin of satisfactory proof. If the surface, shortly after death, be scraped with the point of a needle, the soft texture of the conjunctiva is easily torn and detached, and the tough, firm, polished surface of the cornea proper exposed ; and if the eye be allowed to remain for forty-eight hours in water, the whole layer may by a little care be turned off in the form of a distinct membrane. During life, patches of the con- junctiva are frequently scraped oft’ by accident, or by the point of the needle of the surgeon as he attempts to remove foreign bodies implanted in the cornea proper; it is also occasionally ac- cidentally removed by lime or other escharotics. When the vessels of the conjunctiva over the sclerotic become enlarged, and filled with red blood in consequence of preceding inflamma- tion, that over the cornea at length becomes equally red, and has its transparency greatly impaired by the vascular ramifications. In pustular ophthalmia, the pustules form on the conjunctiva over the cornea as well as on that over the sclerotic ; and in small-pox, vision is frequently destroyed by this part of the tegu- mentary membrane participating in the general disease. In cases where the surface is con- stantly exposed to tlie atmosphere in conse- quence of prominent staphyloma or destruc- tion or eversion of the eyelids, the conjunctiva of the cornea occasionally becomes covered with cuticle in common with the rest of the membrane; In animals over whose eyes the skin is continued without forming eyelids, the continuity of it over the cornea is obvious. In the mole-rat ( Aspalax zemni.), where the skin is uninterruptedly continued over the eye, the hairs grow from the part over the cornea as well as from the rest. When snakes cast their covering, the cuticle is detached from the cornea as well as from the rest of the body; and when the skin is drawn off the body of an eel, it is detached with equal ease from the cornea as from the rest of the eye. The cornea proper, upon which the strength of this part of the eye depends, is the structure to which the appellation cornea is generally exclusively applied ; it is, as might very rea- sonably be expected from the office which it performs, a material of peculiar nature and organization, not identical with any other of the simple membranes. During life, and before it becomes altered by the changes which take place after death, it is perfectly trans- parent, colourless, and apparently homoge- neous. This perfect transparency, however, depends upon the peculiar relation of the component parts of its texture, for if the eye- ball of an animal recently dead be firmly squeezed, the cornea is rendered completely opaque, by altering that relation of parts, and EYE. 177 as speedily recovers its transparency upon the removal of the pressure. The chemical com- position of the cornea is similar to that of the fibrous membranes in general and the sclerotic in particular: like the latter structure, it is con- verted into gelatine by boiling; but Berzelius states that it contains also a small quantity of fibrine or coagulated albumen, as proved by the formation of a precipitate upon adding the cyanuret of ferro-prussiate of potass to acetic acid, in which the membrane has been digested. The cornea possesses great strength, being seldom or never ruptured by blows on the eye- ball, which frequently tear the sclerotic exten- sively. It does not yield to distension from increased secretion, effusion, or suppuration within the eyeball in consequence of inflam- mation, but it becomes extended and altered by growth both in shape and dimensions, as may be observed in prominent staphyloma, hydrophthalmia, and that peculiar alteration called staphyloma pellucidum, in which the spherical form of the membrane degenerates into a cone, but retains its transparency. The cornea is destitute of red vessels, yet it affords a signal example of colourless and transparent texture possessing vital powers inferior to no other. No structure in the body appears more capable of uniting by the first intention. The wound inflicted in extracting a cataract is often healed in forty-eight hours, yet the lips are bathed internally with the aqueous humour, and externally with the tears. Ulcers fill up and cicatrize upon its surface ; and al- though the vessels, under such circumstances, frequently become so much enlarged as to admit red blood, yet there can be no doubt that ulcers do heal without a single red vessel making its appearance. Abscesses form in the cornea, and contain purulent matter of the same appearance as elsewhere ; they are gene- rally said to be between the layers of the cornea, but they are evidently distinct cavities circumscribed by the inflammatory process as in other cases; occasionally, however, the whole texture of the cornea becomes infil- trated with purulent matter, as the cellular membrane in erysipelas. The rapidity with which this membrane is destroyed by the ul- cerative process is another proof of its superior vitality. In a few days a mere speck of ulce- ration, the consequence of a pustule, extends through the entire thickness, and permits the iris to protrude; and in gonorrhoeal and infantile purulent ophthalmia, the process is much more rapid and extensive. It is true that in the latter case the destruction is attributed to gan- grene or sloughing, and to a certain extent correctly; but an accurate observer must admit that the two processes co-operate in the pro- duction of the lamentable consequences which result from these diseases. Ulcers of the cornea fill up by granulation and cicatrize as in other parts of the body, but the repaired part does not possess the original organization, and is consequently destitute of that transparency and regularity of surface so essential for its func- tions ; hence the various forms and degrees of VOL. II. opacity enumerated under the technical titles of albugo, leucoma , margarita, nebula, &c. which are probably never remedied, however minute they may be, notwithstanding the ge- neral reliance placed in the various stimulating applications made for this purpose. Slight opacities, or nebula as they are called, if con- fined to the conjunctival covering of the cornea, gradually disappear after the inflammation sub- sides, as does also diffused opacity of the cornea itself, the consequence of scrofulous inflammation; but I believe opacities from ulceration and cicatrix are seldom if ever re- moved. The effect of acute inflammation is to render this, and perhaps all transparent and colourless membranes, white and opaque with- out producing redness; this may be seen in wounds, where the edges speedily become gray; and in the white circle which frequently occupies the margin of the cornea in the in- flammations of the eyeball commonly called iritis. The cornea in a state of health is destitute of sensibility. Of this I have frequently sa- tisfied myself by actual experiment in cases of injury of the eye, where the texture of the part is exposed. When foreign bodies, such as specks of steel or other metals, are lodged in its structure, the surgeon experiences much dif- ficulty in his attempts to remove them, from the extremely painful sensibility of the con- junctiva as he touches it with his needle ; but the moment he strikes the point of the instru- ment beneath the foreign body into the cornea itself, the eye becomes steady, and he may touch, scrape, or cut any part of the membrane uncovered by conjunctiva without complaint. It has already been stated that the cornea, as it constitutes the transparent medium for the passage of the rays of light, is composed of three distinct forms of structure altogether dif- ferent from each other, the conjunctiva, the cornea proper, and the elastic cornea. The latter membrane is now to be described. In many of our books this membrane is vaguely alluded to as the membrane of the aqueous humour ; but with this it must not for a mo- ment be confounded. It is a distinct provision for a specific purpose, totally different from that for which the other is provided. It was known to and described by Duddell, Decemet, Demours, and latterly by Mr. Sawrey ; but all these authors having unfortunately published their accounts in separate and probably small treatises, not preserved in any journal, I have not been able to consult them. It is, however, distinctly recognized by Clemens, D. W. Sdmmerring, Blainville, and Ilegar ; and in a paper on the anatomy of the eye in the Me- dico-Chirurgical Transactions, I endeavoured to direct attention to it without effect. The struc- ture here alluded to is a firm, elastic, exqui- sitely transparent membrane, exactly applied to the inner surface of the cornea proper, and se- parating it from the aqueous humour. When the eye has been macerated for a week or ten days in water, by which the cornea proper is rendered completely opaque, this membrane re- N 178 EYE. tains its transparency perfectly ; it also retains its transparency after long-continued immersion in alcohol, or even in boiling water. When detached, it curls up and does not fall flaccid or float loosely in water, as other delicate mem- branes. It also presents a peculiar sparkling appearance in water, depending upon its greater refractive power; in fact it presents all the characters of cartilage, and is evidently of pre- cisely the same nature as the capsule of the crystalline lens. When the cornea proper is penetrated by ulceration, a small vesicular trans- parent prominence has been repeatedly ob- served in die bottom of the ulcer, confining for a time the aqueous humour, but ultimately giving way, and allowing that fluid to escape, and the iris to prolapse ; there can be little doubt that it is this membrane which presents this appearance. In syphilitic iritis, this mem- brane becomes partially opaque, appearing dusted or speckled over with small dots altogether different in appearance from any form of opacity observed on the conjunctiva or cornea proper. When it has been touched by the point of the needle in breaking up a cataract, an opacity is produced closely resembling cap- sular cataract. There is no difficulty in pre- paring and demonstrating this membrane in the eye of the sheep, ox, and especially the horse, and it may with a little care be exhibited in the human and other smaller eyes. The eye of a horse having been macerated in water for six or eight days, or until the cornea proper be- comes white, should be grasped in the left hand so as to render the anterior part plump, and then inserting the point of a sharp knife into the structure of the cornea at its junction with the sclerotic, layer after layer should be gra- dually divided by repeated touches round the circumference, until the whole thickness is cut through and the transparent elastic cornea ap- pears, after which the cornea proper may be turned off by pulling it gently with the forceps. The use of the elastic cornea does not appear to me doubtful. The crystalline lens is lodged in a capsule of precisely the same nature, evi- dently destined to preserve correctly the curva- ture of each surface of that body, a condition obviously necessary to secure the perfection of the optical mechanism of the organ. The elastic cornea in the same way, by its firmness, resistance, and elasticity, preserves the requi- site permanent correct curvature of the flaccid cornea proper. The cornea proper is closely and intimately connected to the sclerotic at its circumference. There does not appear to be any mechanical adaptation resembling the fitting of a watch-glass into the bezel, as stated in books ; but a ming- ling of texture, as in many other instances in the body. The two structures cannot be separated without anatomical artifice and much vio- lence. If the eye be macerated in water for a month, and then plunged into boiling water, the cornea may be torn from the sclerotic ; but these destructive processes prove little with re- gard to animal organization. The conjunctival covering of the cornea is, as has been already stated, continuous with the rest of the con ju ncti va, and the elastic cornea is continued for a short distance beneath the sclerotic, as if slipped in between it and the ciliary ligament. The cornea, thus composed of three different structures, varies in appearance at different periods of life. In the foetus at birth it is slightly cloudy, and even of a pinkish tint, as if it contained some red particles in its blood ; this is, however, more apparent on examination after death than during life ; it is also thicker in its centre. In old age it is harder, tougher, and less transparent than in youth, and fre- quently becomes completely opaque at its cir- cumference, presenting the appearance denomi- nated in the books arcus senilis. How far the alteration in the power of adaptation to distance, which occurs in advanced life, is to be attri- buted to change in curvature of the cornea, is not settled. If the foregoing account be correct, the ap- parently simple transparent body which fills the aperture in the anterior part of the sclerotic, is composed of three distinct varieties of organic structure, liable to changes from disease equally distinct and varied. When the aqueous hu- mour becomes the subject of description, I will endeavour to shew that there is good rea- son for believing that a fourth may be added to these three, the membrane which lines the chamber in which this fluid is lodged, and by which it is secreted. Let it not be supposed that this division of an apparently simple piece of organization into so many distinct parts, is merely an exhibition of minute anatomical re- finement. The distinction is essentially neces- sary to enable the surgeon to account for the appearances produced by disease in this part, and to guide him in the diagnosis and treat- ment. Of the choroid coat. — This membrane has been so called from its supposed resem- blance to the chorion of the gravid uterus; it has also sometimes been called uvea from its resemblance to a grape, a term, however, which is now more frequently applied to the iris. It has already been stated that the spherical external case of the eye called the sclerotic embraces another spherically disposed membrane, called the choroid coat, accurately fitted and adhering to it throughout. This spherically disposed membrane has also its cir- cular aperture anteriorly, into which is fitted the screen or diaphragm called the iris. This choroid membrane cannot be considered essen- tial to the perfection of the organ considered merely as a piece of optical mechanism, as a spherical camera obscura, but is obviously ail important part of its anatomical organization, and an essential provision for the perfection of its vital functions. It appears to be destined to secure the requisite mechanical connexion be- tween the coarser and more rigid sclerotic case and the parts within, as well as to secure these delicate parts in their situation, and preserve their form, at the same time affording a me- dium for the distribution and support of the vessels and nerves. EYE. 179 This membrane is of a deep brown or black colour, being stained with the colouring matter called the black pigment; but when this is removed, it exhibits a high degree of arterial and venous vascularity. Its external surface is comparatively rough, coarse, and flocculent, and obscured by the cellular membrane which connects it to the sclerotic. The inner surface, which is in contact with the retina, presents a very different appearance. It is soft and smooth, and when minutely injected, resembles the more delicate mucous membranes, and exhibits a remarkable degree of minute villous vascu- larity. The external surface being composed of the larger branches of arteries, veins, and nerves, may be torn away from the soft, smooth, and more closely interwoven inner layer, or the inner layer may be partially dissected up from it, with some care, especially in the eyes of the larger quadrupeds. This manoeuvre having been executed hy Ruysch, and prepara- tions so formed displayed by him, the inner layer has been denominated the tunica Ruys- chiana. But this is a mere anatomical artifice. There is no natural division into two layers, the soft, smooth, and highly vascular inner surface being formed by the ultimate subdivi- sion and distribution of the larger branches of vessels, which exhibit themselves separately on the outside. It is a condition somewhat analo- gous to that of the skin, where the soft, smooth, villous external surface presents so remarkable a contrast to the rough internal surface with its layer of cellular membrane uniting it to the subjacent parts. The choroid is supplied with blood from the ophthalmic artery by the short ciliary arteries, which penetrate the sclerotic at a short distance from the entrance of the optic nerve, and are distributed to it in nearly twenty small branches. These branches ramify and inosculate freely on the outside of the membrane, and are visible as distinct vessels, especially on the posterior part of the sphere. They finally terminate on the inner surface, forming a beautiful vascular expansion. The long ciliary arteries give scarcely any twig to the choroid, being distri- buted to the iris, and the anterior branches furnished to the sclerotic, as described in speaking of that membrane, do not penetrate to the choroid. The veins of the choroid pre- sent a peculiar appearance. The ramifications are arranged in the form of arches or portions of a circle, bending round to a common trunk like those of certain trees with pendulous branches. They discharge their blood into four or five larger branches which penetrate the sclerotic at nearly equal distances from each other behind the middle of the eyeball. On account of this peculiar arrangement they have received the name of vasa vorticosa. They lie external to the ciliary arteries, but the ultimate ramifications pervade the inner surface in the same manner as the arteries ; and if the venous system of the eye be minutely injected, the same beautiful uniform villous vascularity is displayed as in the arterial injections. The annexed figure is a copy of Zinn’s re- presentation of the vasa vorticosa. Fig. 104. The numerous nerves which pierce the scle- rotic and run forward between that membrane and the choroid, called ciliary nerves, being distributed almost exclusively to the iris, are to be noticed when that organ is described ; small branches of them are, however, probably distributed to the choroid and its appendages, and possibly even to the retina and hyaloid membrane. The inner villous surface of the choroid, which in man is stained with the black pig- ment, in several other animals presents a bril- liant colour and metallic lustre. This is called the tapetum. It is not a superadded material nor dependent on any imposed or separable colour- ing matter, but is merely a different condition of the surface of the choroid or tunica Ruys- chiana, by means of which rays of light of a certain colour only are reflected. It exists in the form of a large irregular patch, occupying the bottom of the eye toward the outside of the entrance of the optic nerve. It is of a beautiful blue, green, or yellow colour, with splendid metallic lustre, and sometimes white as silver. It is not obscured by the black pigment which covers the rest of the surface and even encroaches a little on its margin, and consequently it acts most perfectly as a concave reflector, causing the rays of light previously concentrated on the bottom of the eye by the lens to be returned, and to produce that re- markable luminous appearance observed in the eyes of cats and other animals when seen in obscure situations. This provision is absent in man, the quadrumanous animals, bats, the insectivorous order, perhaps all the rodentia, the sloths and many other of the class mammalia ; while it is present in the majority if not all of the ruminants, as well as in the horse, the cetacea, and most of the carnivorous tribe. It does not appear to exist in birds or reptiles, and is absent in the osseous, although present in the cartilaginous fishes. I must here, how- ever, state that I am obliged to speak loosely respecting this matter, as the subject has not yet been thoroughly investigated. The use of this tapetum has not been ascertained, or the reason why it exists in some and is absent in other animals explained. It is obvious that where it is present the rays of light are trans- mitted through the retina, and again when reflected by the tapetum are returned through the same retina, thus twice pervading that structure. n 2 180 EYE. On the outside and anterior part of the choroid, where the margin of that membrane corresponds to the place of union between the sclerotic and cornea, a peculiar and distinct formation exists apparently for the purpose of securing a firm union between the two mem- branes. It is commonly called the ciliary liga- ment, also orbiculus ciliaris, circulus ciliaris, by Lieutaud plexus ciliaris, by Zinn annulus cellu/usus, and by Sbmmerring gangliform ring. It is a gray circle of soft cellular membrane about two lines broad, applied like a band round the margin of the aperture into which the iris is fitted. It adheres closely to the choroid, and almost equally closely to the scle- rotic, especially in the groove where the cornea joins that membrane. It contains few red vessels, and is not stained by the black pig- ment; consequently it is of a whitish colour. The ciliary nerves penetrate it and subdivide in its structure. Hence it has been considered by Sbmmerring as a ganglion, and had been previously described by Lieutaud as a nervous plexus. The ciliary nerves, however, merely pass through, and may easily be traced on to the iris. It is evidently a mere band of cellular membrane serving to bind the choroid and sclerotic together at this point, and is obviously a provision essentiady necessary for the perfec- tion of the anatomical mechanism of the eye, as without it the aqueous humour must, from pressure on the eyeball, be forced back be- tween the two membranes. In man it is broader in proportion than in the larger quadrupeds, and in birds it is particularly large and dense, adhering more closely to the circle of osseous plates than to the choroid, and consequently presents a very remarkable appearance when the latter membrane is pulled off with the ciliary processes and iris, an appearance to which the attention of anatomists was first drawn by Mr. Crampton. From its position and appearance the ciliary ligament has often been suspected to be a muscular organ, destined by its contraction to alter the form of the cornea, and thus adapt the eye to distance. There is not, however, sufficient evidence to sustain such an opinion. The plate introduced to represent the ciliary nerves, as well as that which represents the iris, exhibit this part of the organization of the eyeball in connexion with the choroid. On the inside of the choroid, surrounding the aperture into which the iris is fitted, and corresponding in position within to the ciliary ligament without, exists another peculiar pro- vision destined to establish a connexion between this part and the hyaloid membrane of the vitreous humour, as the ciliary ligament esta- blishes a similar connexion between the sclerotic and choroid. This is the corpus ciliare or ciliary processes, called sometimes incorrectly ciliary ligament, and by Sbmmerring corona ciliaris. It is composed of a number of dis- tinct folds or productions of the choroid, having their anterior extremities extended to the back of the iris, while the posterior gradually dimi- nish until lost in the membrane from which they originate. Each fold or ciliary process is a production or continuation of the choroid, and cannot be separated from it unless clipped off by the scissors. They appear to be com- posed altogether of a remarkable interlacement of arteries and veins derived from those of the choroid, and exhibit no appearance whatsoever of muscular organization, although considered by Porterfield and others as endowed with that function. These are sixty or seventy in num- ber, fifty-seven being enumerated by Sbmmer- ring, and seventy by Zinn. They are about two lines in length, but are not equally so, every alternate one being shorter than the next to it. The free internal margin of each ciliary process is buried in the hyaloid membrane of the vitreous humour at its anterior part, round the circumference of the crystalline lens, and a corresponding production of the hyaloid mem- brane projects into the space between these processes so as to establish a most perfect bond of union between the two structures. The ciliary processes appear to be attached to the circumference of the lens, and are often de- scribed as having such connexion. This, how- ever, is not the case. The anterior extremities do not touch the circumference of the lens ; they project into the posterior chamber of the aqueous humour up to the back of the iris, and consequently constitute the circumferen- tial boundary of that cavity. When the eye becomes flaccid from evaporation after death, the ciliary processes fall down to the margin of the lens and appear to adhere ; but if the cornea and iris be removed from the eye of a subject recently dead, a circle of hyaloid membrane may distinctly be seen occupying the space between the ciliary processes and lens, through which the observer can see to the bottom of the eye. This space is represented and pointed out in Sbmmerring’s plates. The annexed figure from Zinn’s work represents the corpus ciliare or circle of ciliary processes on a large scale. Fig. 105. The choroid, in common with several other parts of the eye and its appendages, is stained by a black colouring matter secreted in and upon different textures. In man it is of a dark- brown colour, but in other animals is generally EYE. 181 black, and so loosely connected with the struc- ture in which it is deposited, that in dissecting the eyes of our common graminivorous animals under water it becomes diffused, and colours the fluid as the ink of the cuttle-fish obscures the water into which it is shed. It is not confined to any one particular structure, but is deposited in every situation where it is necessary for the purpose for which it is destined. It is found in considerable quantity on the inner surface of the choroid, where it appears as if laid on in the form of a paint, and is frequently so described ; but it is much more probable that it is deposited in the interstices of the exqui- sitely fine cellular membrane which connects the choroid with the delicate covering of the retina. In this situation it often, especially in infants, presents the appearance of a perfectly distinct black membrane, which may be peeled off in flakes or allowed to remain on the retina in patches, as noticed by Haller. It also per- vades the structure of the choroid, at least in the adult, and even stains the inner surface of the sclerotic and the cellular layer which con- nects these two membranes. It is deposited in larger quantity in the ciliary processes and upon the back and in the texture of the iris. In many animals it is found forming a black ring round the margin of the cornea and in the edge of the third eye-lid, as well as in the pecten or marsupium nigrum in birds. It is even sometimes found scattered, as if acci- dentally, as in the texture of the sclerotic in hogs, and within the sheaths of the optic nerve in oxen; it is obvious that it does not require any special form of organization for its produc- tion, but is merely secreted into the cellular membrane, where necessary, as the colouring matter is secreted with cuticle on the skin. It is darker in the earlier periods of life, and in the infant is more confined to the inner sur- face of the choroid and to the posterior surface of the iris, than pervading the texture of either of these membranes. In old age it evidently fades, and even appears as if absorbed in patches. It is sometimes altogether absent, as in those animals called albinos, where all the parts usually coloured are unstained. Its use is obviously to prevent the rays of light from being reflected from surfaces where they should be absorbed, a provision as essential to the perfection of the animal eye as to the artificial optical instrument. It is also applied to give complete opacity to prevent the transmission of light, and hence is deposited in large quantity in and on the iris, as well as in the ciliary pro- cesses which correspond in situation to the exposed part of the sclerotic, through which the light might otherwise pass to the bottom of the eye, and disturb correct vision. The layer of black pigment on the inner surface of the choroid has undergone a careful microscopic investigation, especially by Mr. T. W. Jones, the results of which are stated in a short account of the anatomy of the eye prefixed to the second edition of Mr. M‘Kenzie’s work on Diseases of the Eye. He says that it possesses organization and constitutes a veal membrane, and when examined with the miscroscope “ is seen to consist of very minute flat bodies of a hexagonal form, joined together at their edges. These bodies, which are about -^th of an inch in diameter, consist of a central transparent nucleus, surrounded by an envelope of colour- ing matter, which is most accumulated at their edges. The centre, indeed, of each hexa- gonal plate is a transparent point, and appears somewhat elevated, the elevations on the inner surface corresponding to depressions to be described in the membrane of Jacob. That part of the membrane of the pigment situated on the pars non plicata of the ciliary body around the ciliary processes, and on the poste- rior surface of the iris, is composed of irregu- larly rounded bodies, analogous to the hexa- gonal plates. In albinos the same membrane exists, but contains no pigment. The bodies composing it are but little deve- Fig. 106. loped, being nothing but the central A nuclei separated from each other by SlPffi. large intervals, and not hexagonal, but circular, or even globular.” The annexed figure represents this mem- brane of the pigment as described. Sometimes the black pigment is totally or partially deficient, not only in inferior animals, but also in man, constituting the variety deno- minated albino, of which the white rabbit affords a good example. The circumstance has attracted considerable attention, and has been the subject of particular observation by Mr. Hunter, Blumenbach, and many others. Dr. Sachs has given a curiously elaborate account of himself and his sister, who are both albinos. The eye in such cases appears of a beauti- fully brilliant red, in consequence of the blood being seen circulating through the transparent textures unobscured by the pigment, but the individual suffers from the defect in conse- quence of the light being transmitted through all the exposed part of the organ ; proving that the covering of black pigment is deposited on the back of the iris and in the ciliary pro- cesses to obviate this injurious consequence. In human albinos the eyes have often a tremu- lous oscillating motion, and the individual is unable to bear strong light. The colour of the black pigment does not ap- pear to depend on the presence of carbon or other dark material, and the minute quantity of oxide of iron contained in it is obviously insufficient for the production of so deep a tint. It is insoluble in water, either hot or cold, or in dilute sulphuric acid ; but strong nitric or sulphuric acids decompose it, and are decom- posed by it. Caustic potash is said to dissolve it, though with difficulty, but as ammonia is evolved during the process, and the nature of the pigment necessarily altered, it cannot be considered a case of simple solution. By destructive distillation it affords an empyreu- matic oil, inflammable gases, and carbonate of ammonia. It is, therefore, obviously an ani- mal principle sui generis, its elements being oxygen, hydrogen, carbon, and nitrogen. One hundred parts in a dry state leave, when incinerated, 4.46 of a calx, consisting of chlo- ride of calcium, carbonate of lime, phosphate 182 EYE. of lime, and peroxide of iron. For these par- ticulars I am indebted to Dr. Apjohn. Of the iris. — This is the circular partition or screen interposed between the cornea and crys- talline lens, filling up the aperture in the ante- rior part of the sphere of the choroid, and conse- quently exactly fitted to the place of union of the ciliary ligament and choroid with the sclerotic round the cornea. It has an aperture in the centre called thepupil, through which the central portion of the pencil of rays incident upon the cornea is transmitted, while the extreme rays are intercepted ; and appears to answer the same purpose as the diaphragm or eye-stop in the telescope, but with this advantage, that it is enlarged or diminished according to the quantity of light, the distance of objects, or even the will of the individual. The iris is frequently called uvea , a term also applied to the spherical choroid ; or the anterior part is called iris, and the posterior uvea. To avoid confusion the term should be discarded alto- gether, and that of iris alone retained to designate this important part of the organ. The surface of the iris is flat or plane, al- though it appears convex when seen through the cornea, or when in dissecting the eye it falls on the convex surface of the crystalline lens. It is remarkable that the aperture or pupil is not exactly in the centre of the disc, but a little towards the inside. The anterior surface presents a very peculiar and remarkable appearance, evidently not depending on or arising from vascular ramifications or nervous distribution. This appearance is described with precision and accuracy both by Zinn and Haller, although unnoticed or only briefly al- luded to in many of the slovenly compilations which have appeared since they wrote. It is, however, described by Meckel, who saw what he describes, and read what he quotes. Haller’s words are as follow : — “ In anteriori lamina iridis eminet natura flocculenta, vane in flam- mulas quasdam introrsum euntes disposita, quibus aliqua est similitudo rotundorum ar- cuum, ad centrum pupillse convexorum. Qui- vis flocculus est serpentmarum striarum intror- sum convergentium, et intermistarum macu- larum fuscarum congeries : conjuncti vero flocculenti fasciculi arcum quasi serratum, emi- nentem, ad aliquam a papilla distantiam efti- ciunt, qui convexus eminet, quasi antrorsum, supra reliquum planum pupillaeelatus. Fabric® pulchritudinem nulla icon expressit.” (Ele- menta Physiologi®, tom. v. p. 369.) Zinn’s description is equally accurate and precise. In the 12th volume of the Medico-Chirurgical Transactions I have noticed this structure in the following words: “ If the iris be attentively examined in the living subject, or under water after the cornea has been removed, a number of irregularly shaped masses may be seen pro- jecting from the middle space between the circumference and the pupil. From the con- vexities of these masses, a number of elevated lines, equally irregular in size and number, proceed toward the pupil, and attach them- selves at the distance of about a twentieth part of an inch from its margin, and from this point of attachment a number of much smaller stria: converge to the edge of the central open- ing. It is quite impossible for words to give an adequate idea of this appearance. If I ventured to compare it witb any other with which I am acquainted, I should say that it resembled strongly the carnea columns: and cord a tendinea of the heart, both in form, arrangement, and irregularity of conformation. This structure is more strongly marked in the hazel than in the blue iris ; and in many cases the fleshy projections coalesce, by which they appear less distinct; but the loops or cords which arise from them always exist, and often project so much from the plane of the iris as to admit of having a small probe or bristle passed beneath them. That this appearance of the iris does not depend on any particular disposition of its vessels, is, I think, obvious, from the thickness of these cords or striae being so much greater than the vessels of the iris, from their being arranged in a manner altogether different from vascular inosculation, and finally, because the iris when successfully injected and expanded does not present that interlacement of branches surrounding the pupil which has so often been described from observation of its uninjected state.” The anterior surface of the iris is of a light blue colour in persons of fair skin and light hair, of a blue grey in others, sometimes of a mixture of tints called a hazel iris ; and in neeroes and others, where the skin is stained by the usual colouring matter, the iris is of a deep brown, and is commonly described as a black eye, being pervaded by the black pigment throughout its texture, as well as coated with it on its posterior surface. In animals altogether destitute of the usual colouring matter on the surface, called albinos, the iris has no other colour than that of the blood which circulates in its vessels. The annexed engraving is a copy of a most accu- rately executed representation of the face of the iris, shewing the carnea columns and cords tendinea much magnified. Fig. 107. The posterior surface of the iris is as remark- able as the anterior, but altogether different in its nature. I have given the following des- cription of it in the paper to which I allude in EYE. 183 the Medico-Chirurgical Transactions. “ In order to obtain a correct view of the posterior surface of the iris, a transverse vertical section of the eye should be made at the distance of about an eighth of an inch behind the cornea, and the lens, and portion of vitreous humour attached to it, removed : the iris now appears covered by a thick layer of black pigment, marked by a number of converging lines ; these lines on close inspection are found to be channels or hollows, as if resulting from a puckering or folding of the membrane. The pigment is secured from being detached, and diffused in the aqueous humour, by a fine transparent membrane, which is closely attached to the margin of the pupil, from whence it is continued over the back of the iris, and anterior extremities of the ciliary processes, to the cir- cumference of the lens, over the front of the capsule of which it is also probably extended, if it be, as may be supposed, the membrane of the aqueous humour. This delicate membrane may be turned down by the point of a needle ; as it is connected to the iris by loose cellular structure only, in the interstices of which the black pigment is deposited. It is at first black, but by gentle agitation in water the colouring matter is removed, and the membrane remains transparent. When the membrane and pig- ment have been removed, the back of the iris appears free from colour, and marked by a number of delicate elevated folds, converging from the ciliary processes to within a short distance of the pupil ; they are permanent and essential, and seem of the same nature as the ciliary processes. The pupil is immediately surrounded by a well-defined distinct circle, about the twentieth part of an inch in diameter, of a denser structure than the rest of the iris : this is what has been long described as the orbicular muscle, or constrictor of the pupil. If the iris be treated, as I before mentioned, by maceration and extension, this appearance still preserves its integrity, and retains its original character.” Haller and Zinn describe these converging radiating folds, but the former de- nies the existence of the circular arrangement round the margin of the pupil, of the presence of which I do not entertain the slightest doubt, but which is sometimes so slightly marked, that I am not surprized to find its existence doubted if the part has not been examined in a variety of examples. This circle, or orbicular muscle, is sometimes equally visible on the anterior surface, but is generally obscured by the converging cords above described. The folds or elevations on the back of the iris, con- verging toward the pupil, have been considered the muscular agents for dilating the pupil, but if examined in the eyes of the larger quadru- peds, it is obvious that they are destined to give this part of the organ the requisite degree of opacity, and to afford an appropriate place for the deposit of the black pigment, in this res- pect closely resembling the ciliary processes, and the pecten in the eye of birds, so much so, that I think they might be appropriately called the ciliary processes of the iris. The iris is most plentifully supplied with bloodvessels and nerves. The two long ciliary arteries which penetrate the sclerotic posteri- orly advance horizontally, about the middle of the eyeball, between that membrane and the choriod, to the iris, where each divides into two branches, which proceed round the circumfer- ence and inosculate with each other, thus form- ing an arterial circle, from which numberless blanches converge to the pupil. Much impor- tance has been attached by anatomists to the manner in which these radiating vessels are disposed, in consequence of the representation of Ruysch, who exhibited them as forming a series of inosculations at a short distance from the pupil, since called the lesser circle of the iris. I do not deny that the vessels of the iris inosculate as in other parts of the body, but I do not believe that they present this very re- markable appearance, and I suspect that Ruysch exaggerated what he had seen, or de- scribed from an iris in which the injection had been extravasated and entangled in the tendi- nous cords, which I have described as extend- ing from the fleshy bodies to the margin of the pupil. The question is fortunately of no importance. It is sufficient to know that the organ is amply supplied with arterial blood. The iris is plentifully furnished with nerves : they are derived from the third and fifth pairs, with communications from the sym- pathetic, and consequently having connexions with the sixth. They penetrate the sclerotic posteriorly, and advance towards the iris be- tween the sclerotic and choroid, about fifteen or twenty in number: arrived at the ciliary ligament, they divide at acute angles, and may be traced through this structure until they are finally lost in the iris, as seen in the annexed figure. Fig. 108. From the foregoing description, it appears that the iris is eminently distinguished for the perfection of its organization ; and endowed as it is with the power of enlarging or diminishing the aperture in its centre, there can be little doubt that it is a beautiful application of mus- cular structure and function to the perfection of this most elaborately constructed organ. The authority of Haller operates to the pre- sent day to throw a doubt upon the muscula- rity of the iris ; but Haller, strange as it may appear, was not correctly informed in many particulars respecting this structure. He de- nies the existence of the orbicular muscle ; he doubts the irritability of the organ, and he even 184 EYE. considers it destitute of sensibility, and as- sumes that the pupil is dilated after death. Any anatomist may, however, demonstrate the orbicular muscle; any surgeon breaking up a cataract, may elicit the irritability, and see the pupil contract, as the fragments of the lens or the side of the needle touch its margin. The pain produced by pinching or cutting the iris in operations for cataract and artificial pupil is no longer matter of doubt, and the assumption that the pupil dilates when death takes place is disproved by daily observation. The pupil contracts to exclude light when too abundant, and dilates to admit it when deficient in quan- tity ; the heart contracts to expel the blood, and dilates to receive it; the diaphragm con- tracts to fill the lungs, and relaxes to assist in emptying them. I can see no material differ- ence between the phenomena exhibited by the actions of the iris, and those displayed by the muscular system generally. I believe that when the pupil contracts to intercept light, that con- traction is accomplished by the orbicular mus- cle, which operates as any other sphincter ; and that when the pupil is dilated to admit light, the dilatation is accomplished by the con- traction of the structure, which I have said re- sembles the carnere columruc and cordce tendlnett in the heart. During foetal life the aperture in the centre is closed by a membrane, hence technically called membrana pupillaris. The discovery of this membrane was first announced by W achendorf, but was subsequently claimed by Albinus, and still later by Dr. Hunter for a person of the name of Sandys. It is usually described as existing from the earliest period of foetal life to the seventh month, when it disappears. In the paper communicated by me to the Medico- Chi rurgical Society, I have endeavoured to shew that this description is not correct, but that this membrane continues to the ninth month. The account there given is as follows : “ If the eye be examined about the fifth month, the membrana pupillaris is found in great perfec- tion, extended across a very large pupil ; the vessels presenting that singular looped arrange- ment, (with a small irregular transparent por- tion in the centre,) well depicted by Wrisberg, Bluinenbach, Albinus, Sdmmerring, Cloquet, and others. About the sixth month it is equally perfect; the pupil is however smaller, the iris being more developed. Subsequently to this date the vesseis begin to diminish in size and number, and a larger transparent portion occu- pies the centre. At the approach of the eighth month, a few vessels cross the pupil, or ramify through the membrane at a short distance from the margin, without at all presenting the looped appearance of the previous period, but ad- mitting a free communication between the ves- sels of the opposite side of the iris. The pupil is now still more diminished in size, and the iris has assumed its characteristic coloured ap- pearance ; notwithstanding the absence of ves- sels, the membrane still preserves its integrity, though perfectly transparent. The period now approaches when it is to disappear; this occur- rence takes place, according to my observations, a short time previous or subsequent to birth. In every instance where I have made the exa- mination, I have found the membrana pupillaris existing in a greater or less degree of perfection in the new-born infant; frequently perfect without the smallest breach, sometimes pre- senting ragged apertures in several places, and, in other instances, nothing existing but a rem- nant hanging across the pupil like a cobweb. I have even succeeded in injecting a single ves- sel in the membrana pupillaris of the ninth month. Where I have examined it in subjects who have lived for a week or fortnight after birth, as proved by the umbilicus being healed, I have uniformly found a few shreds still re- maining. It is obvious from the preceding observations, that the membrane does not dis- appear by a rent taking place in the centre, and retraction of the vessels to the iris, as sup- posed by Bluinenbach, but that it at first loses its vascularity, then becomes exceedingly thin and delicate, and is finally absorbed. The de- monstration of what I have advanced respect- ing this delicate part is attended with much difficulty, and requires great patience. The display of the membrana pupillaris of the seventh month is comparatively easy ; but at the ninth month, or subsequently, it can only be accom- plished by particular management. The eye, together with the appendages, should be care- fully removed from the head; it should then be freed from all extraneous parts by the scis- sors, under water, and a careful section made at a short distance behind the cornea; taking care to include the vitreous humour in the divi- sion, in order that the lens may remain in its proper situation. The portion to be examined should now be removed into a shallow vessel of water, to the bottom of which a piece of wax has been secured. The operator should be provided with fine dissecting forceps and nee- dles in light handles; with one needle he should pin the sclerotic down to the wax, and with the other raise the lens, and portion of vitreous humour attached to it, from the ciliary processes, and separate the ciliary ligament from the sclerotic. lie may now expect to dis- cover the membrana pupillaris, but its perfect transparency renders it completely invisible; he may, however, ascertain the existence, by taking a minute particle of the retina and dropping it into the centre of the pupil, where it remains suspended if this membrane exist. The preparation should now be takpn up in a watch-glass, and placed in a weak mix- ture of spirit and water, and a little pow- 1 dered alum raised on the point of a needle dropped upon it. After a day or two it may be examined; and if the membrane be pre sent, it has become sufficiently opaque to be visible, and may now be suspended in a bottle of very dilute spirit.” In the annexed engravings, A represents the membrana pu- pillaris of about the fifth month, present- ing the peculiar looped arrangement of the vessels. B represents the membrane about the eighth month, not presenting the looped ar- rangement. C represents the membrane with a red vessel in its structure at the ninth month. D EYE. 185 shews a few shreds of the membrane remaining a week or more after birth. Fig. 109. The pupil is closed bv this membrane during foetal life in order to preserve its dimensions, and secure a correct growth of the iris while the organ is in darkness. If the membrane disap- peared about the seventh month, the pupil should become dilated and remain so during the two succeeding months, unless the muscu- lar power be undeveloped, which is not proba- ble, as it may be seen to operate shortly after birth. Of the retina. — This is the third spheri- cally disposed membrane entering into the structure of the eye, and may be considered the most essential of all, being that which is endowed with the peculiar description of sensibility which renders the individual con- scious of the presence of light. It is as exactly fitted to the inside of the choroid as that membrane is to the sclerotic, but does not extend to the anterior margin of the choroid as that structure extends to the anterior margin of the sclerotic. The retina is destined to be penetrated by the rays of light, which, reflected from surrounding objects, are collected to form images on the bottom of the eye, consequently its extension as far forward as the choroid or sclerotic is unnecessary, and nature makes no- thing superfluous. It is discontinued at the posterior extremities of the ciliary processes of the choroid, at the distance of about an eighth of an inch from the anterior margin of that membrane. The retina is evidently the optic nerve ex- panded in the bottom of the eye in the form of a segment of a sphere. That nerve differs, in some respects, in construction from the other nerves of the body. In its course from the hole in the bone through which it enters the orbit until it enters the eye, it is of a cylindrical form, and proceeds in a waving line to its desti- nation. The medullary fibres are involved in a tough strong material, not separable into cords or bundles as in other nerves, but constituting a cylinder of collected tubes, from the divided extremity of which the medullary matter may be squeezed in as soft and pulpy a form as it exists in the brain. It is not easy to determine by anatomical investigation, whether the medullary material is disposed in tubes or in a cellular structure, but as that material is universally disposed in a fibrous form, both in brain and nerve, it is more than probable that it is so ar- ranged here. These cerebral fibres involved thus in a cylindrical bundle of tubes, techni- cally called neurilema by modern anatomists, is covered externally by a fine transparent membrane, adhering to it so closely that it re- quires some care to separate it; and this is again covered by a tube of strong fibrous mem- brane, the sheath of the optic nerve continued from the dura mater to the sclerotic, to which membrane it adheres so firmly, that it cannot be separated except by the knife. Formerly the sclerotic was considered to be a continuation of the dura mater, and much importance, in a pathological point of view, was attached to the circumstance, but although both structures are of the fibrous class, the sclerotic is very different in texture, and the adhesion between them is not more remarkable than any other of the numerous adhesions which occur between fi- brous membranes. Where the optic nerve enters the eye, it is contracted in diameter, as if a string had been tied round it, and then passes through a hole in the sclerotic, to which it adheres. When seen from the inside, after removing the retina and choroid, it appears in the form of a circu- lar spot, perforated with small holes, from which the medullary material may be expressed. This is the lamina cribrosa of Albinus, consi- dered to be a part of the sclerotic, but which is really nothing more than the terminating ex- tremity of the nerve. The optic nerve does not enter the eye in the centre of the globe, but about an eighth of an inch to the side of it, assuming the centre to correspond to the extremity of a line passing from the middle of the cornea, through the centre of the eyeball to its back. The nerve is generally described and represented as pro- jecting in the form of a round prominence, as it enters the eye ; but this is not, I believe, the state of the part duiing life, but is produced by the contraction of the neurilema pressing out the medullary matter in this form. As the nerve enters the eye, it immediately expands into and constitutes the retina, the medullary fibres separating and spreading out on the sphe- rical vitreous humour. The expansion of the nerve in separate fibres cannot be distinctly seen in the human eye, but may be recognized with some care in the eye of the ox, and with- out difficulty in that of the hare and rabbit, where it divides into two bundles, as has been well described by Zinn in the Gottingen Com- mentaries. The retina does not consist of medullary or cerebral fibrous matter alone. As the brain has its pia muter and arachnoid membrane, and the nerve its neurilema, this nervous struc- ture has its appropriate provision for its sup- port and the distribution of its vessels. This is the vascular layer, first accurately described by Albinus. It is a delicate transparent mem- 186 EYE. brane, of such strength, that when detached, it may be moved about in water, and freely ex- amined without breaking. It adheres so firmly to the hyaloid membrane of the vitreous hu- mour in the fresh eye, that it cannot be sepa- rated entire, and the medullary fibres adhere so closely to its external surface, that they can- not be detached at all in the form of a distinct membrane. To demonstrate the vascular layer, the sclerotic should be carefully removed, leav- ing a portion of the optic nerve freed from its sheath ; the choroid should then also be re- moved under water, by tearing it asunder with a pair of forceps in each hand. The vitreous humour, covered by the retina only, should then be allowed to remain about two days in the water, at the end of which time the me- dullary layer softens and separates into flakes, which may be scraped from the vascular layer beneath by passing the edge of a knife gently over it, after which the vascular layer may be detached by careful management, and sus- pended in a bottle from the optic nerve. The retina is supplied with blood from the ophthalmic artery, a small branch of which penetrates the optic nerve at a short distance from the back of the eye, and proceeds through its centre until it arrives at the retina. The bole in the centre of the nerve, through which it passes, was formerly called the porus opticus. Arrived at the retina, the vessel, under the name of the central artery of the retina, divides into two branches, which surround the foramen of Sbmmerring, and sending ramifications in every direction, terminate by encircling the an- terior margin. Besides the branches which carry red blood, the central artery probably furnishes a transparent branch to the centre of the vitreous humour, as such a branch running on to the back of the crystalline lens, may be injected in the eye of the foetus, and a transpa- rent production from the central artery into the vitreous humour may be observed in the eyes of oxen and other large animals. The arteries of the retina supply the vitreous, humour with blood, as no other source exists, except from the ciliary processes of the choroid, which, being buried in the hyaloid membrane, most probably furnish vessels to the anterior part, and in dissecting the vascular layer above de- scribed, in which the vessels ramify, it is found to adhere to the hyaloid membrane by points along the course of the vessels, which points, it is reasonable to believe, are small branches. As the medullary or cerebral fibres of the retina are sustained on the inside by the vascu- lar layer above described, they are also protected on the outside by another membrane, which separates them from the inner surface of the choroid. This is the membrane which I des- cribed in a communication in the Philosophical Transactions in 1819, and as I cannot give a more intelligible account of it than that there contained, 1 venture to introduce it here. “ Anatomists describe the retina as consisting of two portions, the medullary expansion of the nerve, and a membranous or vascular layer. The former externally, next to the choroid coat, and the latter internally, next to the vitreous humour. All, however, except Albinus and some of his disciples, agree, that the nervous layer cannot be separated so as to present the appearance of a distinct membrane, though it may be scraped off, leaving the vascular layer perfect. That the medullary expansion of the optic nerve is supported by a vascular layer, does not, I think, admit of doubt ; but it does not appear that Albinus was right in supposing that the nervous layer can be separated in form of a distinct membrane, though shreds of a considerable size may be detached, especially if hardened by acid or spirit. “ Exclusive of these two layers, I find that the retina is covered on its external surface by a delicate transparent membrane, united to it by cellular substance and vessels. This struc- ture, not hitherto noticed by anatomists, I first observed in the spring of the last year, and have since so frequently demonstrated, as to leave no doubt on my mind of its existence as a distinct and perfect membrane, apparently of the same nature as that which lines serous cavi- ties. I cannot describe it better, than by detailing the method to be adopted for examining and dis- playing it. Having procured a human eye, within forty-eight hours after death, a thread should be passed through the layers of the cor- nea, by which the eye may be secured under water, by attaching it to a piece of wax, previ- ously fastened to the bottom of the vessel, the posterior half of the sclerotic having been first removed. With a pair of dissecting forceps in each hand, the choroid coat should be gently tom open and turned down. If the exposed surface be now carefully examined, an ex- perienced eye may perceive, that this is not the appearance usually presented by the retina ; instead of the blue-white reticulated surface of that membrane, a uniform villous structure, more or less tinged by the black pigment, pre- sents itself. If the extremity of the ivory handle of a dissecting knife be pushed against this surface, a breach is made in it, and a mem- brane of great delicacy may be separated and turned down in folds over the choroid coat, presenting the most beautiful specimen of a delicate tissue which the human body affords. If a small opening be made in the membrane, and the blunt end of a probe introduced be- neath, it may be separated throughout, without being turned down, remaining loose over the retina ; in which state if a small particle of paper or globule of air be introduced under it, it is raised so as to be seen against the light, and is thus displayed to great advantage ; or it is sometimes so strong as to support small glo- bules of quicksilver dropped between it and the retina, which renders its membranous na- ture still more evident. If a few drops of acid be added to the water after the membrane has been separated, it becomes opaque and much firmer, and may thus be preserved for several days, even without being immersed in spirit. “That it is not the nervous layer which I de- tach, is proved by the most superficial exa- mination ; first, because it is impossible to separate that part of the retina, so as to present the appearance I mention ; and, secondly, be- EYE. 187 cause I leave the retina uninjured, and present- ing the appearance described by anatomists, especially the yellow spot of Sbemmerring, which is never seen to advantage until this membrane be removed : and hence it is that conformation, as well as the fibrous structure of the retina in some animals, become better marked from remaining some time in water, by which the membrane I speak of is de- tached. “ The extent and connections of this mem- brane are sufficiently explained by saying, that it covers the retina from the optic nerve to the ciliary processes. To enter into farther inves- tigation on this subject would lead to a dis- cussion respecting the structure of the optic nerve, and the termination of the retina an- teriorly, to which it is my intention to return at a future period. “The appearance of this part I find to vary in the different classes of animals and in man, according to age and other circumstances. In the foetus of nine months it is exceedingly de- licate, and with difficulty displayed. In youth it is transparent, and scarcely tinged by the black pigment. In the adult it is firmer, and more deeply stained by the pigment, which sometimes adheres to it so closely as to colour it almost as deeply as the choroid coat itself ; and to those who have seen it in this state, it mustappear extraordinary that it should not have been before observed. In one subject, aged fifty, it possessed so great a degree of strength as to allow me to pass a probe under it, and thus convey the vitreous humour covered by it and the retina from one side of the basin to the other ; and in a younger subject I have seen it partially separated from the retina by an effused fluid. In the sheep, ox, horse, or any other individual of the class mammalia which I have had an opportunity of examining, it presents the same character as in man ; but is not so much tinged by the black pigment, adheres more firmly to the retina, is more uniform in its structure, and presents a more elegant appear- ance when turned down over the black choroid coat. In the bird it presents a rich yellow brown tint, and when raised, the blue retina presents it- self beneath ; in animals of this class, however, it is difficult to separate it to any extent, though I can detach it in small portions. In fishes, the struc- ture of this membrane is peculiar and curious. It has been already described as the medullary layer of the retina by Haller and Cuvier, but I think incorrectly, as it does not present any of the characters of nervous structure, and the retina is found perfect beneath it. if the scle- rotic coat be removed behind, with the choroid coat and gland so called, the black pigment is found resting upon, and attached to, a soft friable thick fleecy structure, which can only be detached in small portions, as it breaks when turned down in large quantity. Or if the cornea and iris be removed anteriorly, and the vitreous humour and lens withdrawn, the retina may be pulled from the membrane, which re- mains attached to the choroid coat, its inner surface not tinged by the black pigment, but presenting a clear white, not unaptly compared by Haller to snow. “ Besides being connected to the retina, I find that the membrane is also attached to the cho- roid coat, apparently by fine cellular substance and vessels ; but its connection with the retina being stronger, it generally remains attached to that membrane, though small portions are sometimes pulled off with the choroid coat. From this fact I think it follows, that the accounts hitherto given of the anatomy of these parts are incorrect. The best anatomists de- scribe the external surface of the retina as being merely in contact with the choroid coat, as the internal with the vitreous humour, but both totally unconnected by cellular mem- brane, or vessels, and even having a fluid secreted between them : some indeed speak loosely and generally of vessels passing from the choroid to the retina, but obviously not from actual observation, as I believe no one has ever seen vessels passing from the one membrane to the other. My observations lead me to conclude, that wherever the different parts of the eye are in contact, they are con- nected to each other by cellular substance, and, consequently, by vessels ; for I consider the failure of injections no proof of the want of vascularity in transparent and delicate parts, though some anatomists lay it down as a cri- terion. Undoubtedly the connection between these parts is exceedingly delicate, and, hence, is destroyed by the common method of ex- amining this organ ; but I think it is proved in the following way. I have before me the eye of a sheep killed this day, the cornea secured to a piece of wax fastened under water, and the posterior half of the sclerotic coat carefully removed. I thrust the point of the blade of a pair of sharp scissors through the choroid coat into the vitreous humour, to the depth of about an eighth of an inch, and divide all, so as to insulate a square portion of each membrane, leaving the edges free, and consequently no connection except by surface ; yet the choroid does not recede from the mem- brane I describe, the membrane from the retina, nor the retina from the vitreous humour. I take the end of the portion of choroid in the forceps, turn it half down, and pass a pin through the edge, the weight of which is in- sufficient to pull it from its connection. I se- parate the membrane in like manner, but the retina I can scarcely detach from the vitreous humour, so strong is the connection. The same fact may be ascertained by making a transverse vertical section of the eye, removing the vitreous humour from the posterior seg- ment, and taking the retina in the forceps, pulling it gently from the choroid, when it will appear beyond a doubt that there is a connec- tion between them. “ Let us contrast this account of the matter with the common one. The retina, a mem- brane of such delicacy, is described as being extended between the vitreous humour and choroid, from the optic nerve to the ciliary processes, being merely laid between them, 188 EYE. without any connection, and the medullary fibres in contact with a coloured mucus re- tained in its situation by its consistence alone. This account is totally at variance with the general laws of the animal economy ; in no instance have we parts, so dissimilar in nature, in actual contact: wherever contact without connection exists, each surface is covered by a membrane, from which a fluid is secreted ; and wherever parts are united, it is by the medium of cellular membrane, of which se- rous membrane may be considered as a mo- dification. If the retina be merely in contact with the vitreous humour and choroid, we argue from analogy, that a cavity lined by serous membrane exists both on its internal and external surface : but this is not the fact. In the eye a distinction of parts was necessary, but to accomplish this a serous membrane was not required ; it is only demanded where great precision in the motion of parts was indis- pensable, as in the head, thorax, and abdo- men ; a single membrane, with the interpo- sition of cellular substance, answers the pur- pose here. By this explanation we surmount another difficulty, the unphilosophical idea of the colouring matter being laid on the choroid, and retained in its situation by its viscidity, is discarded ; as it follows, if this account be correct, that it is secreted into the interstices of fine cellular membrane here, as it is upon the ciliary processes, back of the iris, and pecten, under the conjunctiva, round the cornea, and in the edge of the membrana nictitans and sheath of the optic nerve in many animals. Dissections are recorded where fluids have been found collected between the choroid and retina, by which the structure of the latter membrane was destroyed ; the ex- planation here given is as sufficient to account for the existence of this fluid, as that which attributes it to the increased secretion of a serous membrane.” The membrane is represented as it exists in the eye of the sheep, in the annexed figure, from my paper in the Medico-Chirurgical Transactions. Fig. 111. Mr. Dalrymple, in his valuable work on the anatomy of the eye, takes a different view of the arrangement of this part of the retina: he says : — “ From observations made on the human eye, in connection with other expe- riments on the eyes of animal, I am induced to consider it as a double reflected serous mem- brane. I was first led to take up this opinion in the year 1827, by the accidental observation of a very delicate membrane, which lined and was adherent to the entire choroid. Having minutely injected the eye of a sheep, I made a vertical transverse section through the sclero- tic, choroid, and retina, which last membrane, with Jacob’s tunic, properly so called, and the vitreous body I removed. I then placed the remaining portion of the eye in dilute spirits of wine, intending to preserve it for the ex- hibition of the tapetum, which in this instance was remarkably beautiful. A few minutes after its immersion the tapetum lost to a con- siderable extent its brilliant hue, and I re- moved it from the glass to wash from its sur- face some deposit, which I thought might have obscured its polish. In doing this, how- ever, I detached a delicate membrane, mi- nutely filled with injection, and this membrane it was which on being placed in the spirit, became slightly opaque and produced the effect alluded to ; for the tapetum thus denuded in- stantly recovered, and still retains its bril- liancy.” The inference that the membrane in ques- tion is a double reflected serous membrane is certainly more in conformity with analogy than the assumption that it is a single layer, but this uniformity in nature’s operations has been too much insisted upon. I have above stated my reasons for considering it a single layer, and not a double serous membrane ; and I should be inclined to think that the layer which Mr. Dal- rymple found adhering to the choroid was the membrane itself, which had not come away with the retina and vitreous humour, as I have found sometimes to happen, did not Mr. Dal- rymple further state that he has “ in his pos- session a preparation, which does most dis- tinctly shew the double portions of this mem- brane ; one lining the choroid, the other reflected over the pulpy structure of the retina.” Mr. Jones, in the work formerly alluded to, gives the annexed representation of the mem- brane as it appears when 112. highly magnified. Fig. 113 is a representation of the membrane by Mr. Bauer, magnified fifty diameters, from the Philosophical Transactions for 1822. In the centre of the retina, and consequently in the axis of vision, about an eighth of an inch from the entrance of the optic nerve, a very remarkable condition of structure exists. This is a small point destitute of cerebral or medullary fibres, appearing like a hole in the membrane, and hence called the foramen of Sdmmerring, from the distinguished anatomist who discovered it. This point is surrounded by a yellow margin, and the retina is here also puckered into a peculiar form of fold. Sdm- merring, in the Commentationes Societatis EYE. 189 Fig. 113. this hole, that there can be no doubt that it is a real aperture, which being situated in the centre of the retina may be appro- priately termed the foramen centrale. Sur- rounding this foramen centrale the remark- able yellow colour resembling that of gum gutta is so disposed that it appears much deeper toward the margin, and totally dis- appears at a distance of a line. This colour varies much according to the age of the individual, being very faint in infants, much deeper at puberty, on account of tire thickness and whiteness of the retina at that period, appearing of a deep yellow brownish or crocus colour. In more ad- vanced age the colour is less intense, prin- cipally on account of the diminished whiteness of the retina, which also appears extenuated at that period. Even the choroid, where it corresponds to this fora- men, sometimes appears a little deeper- coloured.” In the paper above alluded to, published in the Medico-Chirurgical Transactions, I have given the result of some careful in- quiries into the structure of this part, from which the following observations are ex- tracted. “ Summerring describes it as a hole in the retina with a yellow margin, mentioning as accidental a fold which occupies the situation of this hole and tends to conceal it, and thus accounting for its remaining so long unnoticed. This appearance is so constant and remarkable, that its existence may be very rationally considered essential to correct vision, and it therefore becomes an interesting object of speculation. The circumstances which it seems important to ascertain, are, whe- ther it is actually a hole in the retina with a yellow margin ; whether, in addition IRegiae Gottingenses, gives the following to this hole, the retina is folded or puckered in at account of the discovery. “ On the 27th of this part; or whether the appearance of a hole January, 1791, while I examined the eyes of a arises from a deficiency of the medullary layer of very fine and healthy young man, a few hours the retina without any orifice in its vascular layer, previously drowned in the Rhine, being per- Both Sbmmerring himself and many others seem fectly fresh, transparent, and full, and sup- to consider that the fold is accidental and the ported in an appropriate fluid, with the in- consequences of changes occurring after death, tention of exhibiting a perfect specimen of the It is here necessary to call to mind what those retina to my pupils in the anatomical theatre, changes are with respect to the retina. If the I so clearly detected in the posterior part of eye had become flaccid previous to dissection, the retina, which was expanded without a the retina on being exposed presents an irre- single fold, on account of the perfect state gular surface, arising from a number of folds of the eye, a round yellow spot, that I diverging from the optic nerve as from a centre, was convinced it was a natural appearance, and evidently produced by the loss of support and not a colour produced by any method of from the partial evaporation of the fluid of the preparation. In examining this spot more vitreous Humour. These folds, however, never accurately, I perceived in its centre a little observe any regular form, or preserve precise hole occupying the situation of the true centre situations, and may be obliterated by changing of the retina. With the same care I examined the position of the eye in the water. They the other eye and found it exactly similar, disappear altogether after the part has remained I then communicated the discovery to my some time in water, in consequence of the pupils in the public demonstrations.” “ In this vitreous humour becoming again distended precise spot, or in the very centre of the re- from imbibing the fluid in which it is im- tina, is found an actual deficiency of the me- mersed. It However requires no very great dullary layer, or a real hole perfectly round, care or experience to distinguish between those with a defined margin a fourth of a line in accidental folds and the peculiar one in ques- diameter.” “ The transparent vitreous humour tion. If the examination be made from with- and black pigment are so clearly seen through out, removing the sclerotic and choroid behind, 190 EYE. the retina appears to be forced or drawn at this point into the vitreous humour to the depth of about a twelfth of an inch, the entire fold being something more than an eighth in length. At first there is little or no appearance of a hole, but after the eye has remained for some time in the water, the fold begins to give way, and a small slit makes its appearance, which gradually, widens, and assumes the appearance of a round hole. This hole is large in pro- portion to the degree to which the fold has yielded ; and when the fold totally disappears, as it sometimes does, the transparent point gives the appearance which Sdmmerring re- presents, of a hole with a yellow margin. If, instead of making the examination in this way from the outside, we view this part through the vitreous humour, the appearance of the hole is more remarkable ; but still that part of the retina is evidently projected forward be- yond the level of the rest of that membrane. In the eye of a young man, which I had an opportunity of examining under peculiarly favourable circumstances, within five hours after death, I noticed the following appear- ances. The cornea and iris having been cut away, and the lens removed from its situation, I placed the part in water, beneath one of the globular glasses, and held it so as to allow the strong light of a mid-day sun to fall directly upon it ; when the retina to the outside of the optic nerve presented unequivocally the ap- pearance of being drawn or folded into the form of a cross or star, with a dark speck in the centre, surrounded by a pale yellow areola. I further satisfied myself of the prominence of the fold by holding a needle opposite to it, while the light shone full upon it, a shadow being thus cast upon the retina which deviated from the straight line when passed over the situation of the fold. To ascertain whether there is actually a hole in the retina, or merely a deficiency of nervous matter at this point, I allowed the eye to remain for some days in water, until the connexions of the parts began to give way. I then introduced a small probe between the retina and vitreous humour, the part still remaining in water, and bringing the blunt point of the instrument opposite the transparent spot, attempted to pass it through, but found I could not do so without force sufficient to tear the membrane. 1 also re- moved the nervous matter by maceration and agitation in water, and on floating the vascular layer, found that I could no longer ascertain where the spot had originally existed, there being no hole in the situation previously occu- pied by the transparent speck.” It is remarkable that the foramen of Sommer- ring has not been found in the eyes of any of the mammalia except those of the quadrumana, in some of whom it has been detected by Home, Cuvier, and others, but the extent to which it may be traced in this tribe has not been satis- factorily ascertained. Dr. Knox, in a paper in the Memoirs of the Wernerian Natural History Society, announces the discovery of its existence in certain lizards. In the lacerta supercitiosa he says, “ the retina is very thick, and somewhat firm and opaque. Where the optic nerve enters the interior of the eye-ball, there is a distinct tmirsupium or black circular body, proceeding forwards apparently through the centre of the vitreous humour. Anteriorly, somewhat supe- riorly and towards the mesial line or plane, we perceive, on looking over the surface of the retina which regards the vitreous humour, a comparatively large transparent, nearly circular spot, through which may be distinguished the dark-coloured choroid. Close to this is gene- rally placed a fold or reduplication of the retina, which is in general remarkably distinct. This fold or folds, (for there are more than one) either proceed from the transparent point towards the insertion of the optic nerve, or close to it. Sometimes the fold seems, as it were, to lie over the transparent point, and partly to conceal it from view ; or the point is formed in the edge of the fold itself, as in apes, but in general the fold runs directly from the insertion of the optic nerve upwards and inwards, pressing very close to the edge of the foramen centrale." The foramen was also seen in the lacerta striata, lacerta calutes, and others, while it was not to be detected in the gecko, crocodile, and some others. It was also subsequently discovered in the chameleon. The annexed figures represent the foramen of Sdmmerring in the human eye. A, shews the retina expanded over the vitreous humour : on the right is the place from which the optic nerve was cut away, and from which the ves- sels branch out : on the left is the foramen of Sdmmerring, represented by a black dot sur- rounded by a dark shade. B, shews the retina with a portion of the optic nerve. The exter- nal membrane is turned down as in the pre- ceding representation of the same structure in the sheep’s eye, and the foramen of Summer- ring, instead of a distinct hole, presents the appearance of a fold or depression with elevated sides. The wood-engraving does not admit of the delicacy of finish necessary to express per- fectly this condition of the part. Fig. 114. A. B. There is no part of the anatomy of the eye respecting which there has been so much diver- sity of opinion as the anterior termination of the retina. It has already been stated that it extends to the posterior extremities of the ciliary processes, where it is discontinued, pie- senting an undulating edge corresponding to the indented margin of this part of the corpus ciliare. Some assert that it extends to the mar- gin of the lens, others that it is the vascular EYE. 191 layer only which extends so far, and others that the vascular layer extends over the lens. No one however at present, who describes from observation, denies the termination of the ner- vous layer at the posterior margin of the ciliary body, although many insist upon the extension of the vascular layer to the circumference of the lens. The subject has received more attention than it deserves, as it involves no consideration of importance, either physiological or anato- mical ; but I am convinced from a very care- ful scrutiny that no such layer extends between the ciliary processes of the choroid and those of the hyaloid membrane ; these two parts being mutually inserted into each other, as will pre- sently be explained. In the paper above quoted in the Medico-Chirurgical Transactions I have explained what appears to me to be the arrangement of this part in the following words : “ On removing the choroid, ciliary processes, and iris, we see the retina terminating with a defined dentated margin, about a quarter of an inch from the circumference of the lens : be- tween this line of termination and the lens, the vitreous humour retains upon its surface part of the black pigment which covered the ciliary processes. If the eye be examined shortly after death, removing the black pigment from this part of the vitreous humour with a camel- hair pencil, there is an appearance of, at least, the vascular layer being continued to the lens ; this part not being so transparent as the rest of the hyaloid membrane, or so opaque as the retina. From such an examination I was led to con- clude that the vascular layer was continued to the margin of the lens, this part not being so transparent as the rest of the hyaloid membrane, or so opaque as the retina. From such an examination I was led to conclude that the vascular layer was continued to the margin of the lens, but I adopted a con- trary opinion after I had witnessed the change which took place when the part had remained twenty-four hours in water : the retina then separating with a slight force, and frequently detached by the disturbance given in making the examination. If, after removing the choroid without disturbing the retina, the part be al- lowed to remain in water for some days, the medullary part of the retina begins to give way, and may be altogether detached by agita- tion in water, leaving the vascular layer firmly attached at the line of termination just de- scribed. With all the care I could bestow, I have, however, never succeeded in separating this layer from the vitreous humour further. If the maceration be continued for a few days longer, the vascular layer of the retina gives way, the larger vessels alone remaining attached at the original line of termination of the retina, and appearing to enter the hyaloid membrane at this part ; the appearance which at first so much resembled the vascular layer proceeding towards the lens remaining unchanged, being in fact part of the vitreous humour itself. The circumstance which has most strengthened the notion of the retina being continued forward to the lens is, that often on raising the choroid and ciliary processes from the vitreous humour, we find those processes covered in several places by a fine semi-transparent membrane insinuated between the folds ; this is supposed to be the vascular layer of the retina, but is really the corresponding part of the hyaloid membrane which is torn up, being firmly united to this part of the choroid.” After this article had been prepared for press, I received an admirable monograph upon the retina by B. C. R. Langenbeck, son of the celebrated professor of that name in the Uni- versity of Gottingen, in which the nature, structure, and relations of this most important and interesting part of the organ are subjected to a critical and elaborate inquiry. He advo- cates the membranous nature of the black pig- ment on the inner surface of the choroid, and gives an engraving of its organization as ascer- tained by the microscope, resembling that given from the essay of Mr. Jones in the preceding pages. He devotes several pages to the de- scription of the membrane which I found covering the medullary layer of the retina, and adds the testimony of a skilful anatomist in support of my description, sufficient to coun- terbalance the convenient scepticism of certain writers better skilled in making plausible books than difficult dissections. The fibrous struc- ture of the medullary layer of the retina is established, and a plate given of the peculiar nodulated condition of these fibres. The work concludes with an account of the morbid changes of structure observed in the retina, a subject which, notwithstanding its manfest importance, has not hitherto attracted the atten- tion which it deserves. I am indebted to Dr. Graves for the following abstract of some recent investigations of Treviranus on the same subject. “ From microscopical examinations Treviranus demonstrates that the cerebral mass, both medullary and cortical, consists of hollow cylinders containing a soft matter. These cylinders, extremely minute in the cortical substance, are somewhat larger in the medul- lary, and still larger in the nerves. In the retina he finds, that after the optic nerve has penetrated the sclerotic and choroid, its cylin- ders or nervous tubes spread themselves out on every side either singly or collected into bundles, each cylinder or collection of tubes bending inwards through the vascular layer, and terminating in the form of a papilla on the vitreous humour.” Of the vitreous humour. — It has already been stated that the globe of the eye is divided into two chambers by the iris, the posterior of which is distended by a spherical transparent mass called the vitreous humour, which does not completely fill this chamber between the back of the iris and the hollow sphere of the retina, but is discontinued or compressed at a short distance from the back of the iris, having a narrow space between it and that membrane, called the posterior chamber of the aqueous humour. This trans- parent mass is composed of water containing certain saline and animal ingredients, deposited in exquisitely delicate and perfectly transparent cellular membrane ; hence it is capable of sus- 192 EYE. taining its own weight and preserving its form when placed in water, and in air presents the appearance of a gelatinous mass, scarcely de- serving the name of solid. The cellular struc- ture, in which the watery fluid is lodged, has been called the hyaloid membrane, and the whole mass denominated the vitreous humour. The fluid of the vitreous humour, according to Berzelius, is composed of water, containing about one and a half per cent, of animal and saline ingredients ; it has a saline taste, and acquires a slight opaline tint by being boiled. It consists of water 98.40, chloruret of soda with a little extractive matter 1.42, a substance solu- ble in water 0.02, and albumen 0.16. Its specific gravity is 1.059. When the hyaloid membrane is examined in its natural state, its cellular organization can scarcely be ascertained on account of its transparency; but if it be suspended on the point of a pin until the fluid is allowed to drop out, it may be inflated with a fine blowpipe and dried, or if the whole be placed in strong spirit or weak acid, the mem- brane becomes opaque, and its organization obvious. It has been supposed that the cells in which the fluid is lodged present a determi- nate form, and attempts have been made to prove this by freezing the eye and examining the frozen fragments ; but any one who has seen the hyaloid membrane rendered opaque by acid must allow that the cells are too minute to admit of such investigation, and that the frozen masses, supposed to be the contents of cells, are merely fragments of the hyaloid membrane with their contained fluid. Although the hyaloid membrane is perfectly transparent, and the red particles of the blood do not circu- late in its vessels, there can be little doubt that its growth and nutrition are effected by the circulation of a transparent fluid in vessels continuous with those conveying red blood. It is an established fact that transparent tex- tures which in a natural state do not exhibit a trace of coloured fluid, when excited or inflamed, become filled with red vessels, as may be seen in the conjunctiva. It is there- fore reasonable to admit that tbe hyaloid mem- brane does not present a deviation from this general law. The fluid of the vitreous humour, it is to be presumed from analogy, is secreted by the vessels of the hyaloid membrane, and if no red vessels can be detected, the secretion must be accomplished by transparent ones. It has already been stated that the vascular layer of the retina adheres to the surface of the vitreous humour, and that the points of adhe- sion are stronger along the course of the vessels than in the intermediate spaces ; it is therefore most probable that the more superficial part of the sphere is supplied with transparent blood from the arteries of the retina, while a branch directly from the central artery, as it penetrates the porws opticus, enters behind, and extends to the back of the lens : such a branch can be injected in the foetus, and is found to ramify on the back of the capsule of the lens ; and in the eyes of large quadrupeds a transparent production, probably vascular, has been ob- served proceeding from the entrance of the optic nerve into the mass of the vitreous humour. It is also probable that the ciliary processes of the choroid, which are buried in the hyaloid membrane anteriorly, supply blood to that part of tbe sphere. That the vitreous humour undergoes changes analogous to those which take place in textures supplied with red blood, is proved by its hyaloid membrane being found opaque and thickened in eyes which have been destroyed by internal inflam- mation. A total disorganization of the vitreous humour is a frequent occurrence, the hyaloid membrane losing its cohesion to such a degree that the fluid escapes from the eye as freely as the aqueous humour when the cornea is divided in the operation of extraction; and after the lens and its capsule have been removed by operations with the needle, opacity of the hyaloid membrane is occasionally, although rarely, observed. Allusion has frequently been made in books to an appearance in the eye denominated glaucoma, attributed, rather vaguely, to opacity of the vitreous humour ; it appears, however, to be nothing more than the usual opacity of the lens which occurs in advanced life, seen through a dilated pupil. As an additional proof of the vascularity of the vitreous humour may be adduced the fact, that in the eyes of sheep, injured by blows in driving to the shambles, the vitreous humour is deeply tinged with red blood. The spherical mass of vitreous humour, it has already been stated, is exactly fitted into and adheres to the inner surface of the retina. From the anterior termination of the retina to the posterior chamber of the aqueous humour, it is in contact with, and adhering to, the ciliary processes of the choroid. Where it is truncated or compressed on its anterior part to form the posterior chamber of the aqueous humour, it has the crystalline lens fitted into a depression in its centre, while a narrow circle of it appears between the circumference of the lens and the anterior extremities of the ciliary processes of the choroid, forming part of the boundaries of this chamber of aqueous humour. If the eye be allowed to remain for a day or two in water in order to destroy by maceration the delicate connexions between the hyaloid membrane and the choroid, and then the vitreous humour with the lens attached care- fully separated, the point of a fine blowpipe may be introduced under the surface of the hyaloid membrane at the circumference of the lens, and a series of cells encircling the lens inflated. This is the canal of Petit, or canal godronn'c. It is thus described by the dis- coverer in the Histoire de l’Academie aes Sciences for 1726. “ I have discovered a small canal surrounding the crystalline, which I call the circular canal godronne; it can be seen only by inflating it, and when filled with air it forms itself into folds similar to the ornaments on silver plate, called for this reason Vaisetle godronne. It is formed by the doubling of the hyaloid membrane, which is contracted into cells at equal distances by little canals which traverse it, and which do not admit of the same degree of extension as the membrane, EYE. 193 which is very feeble; it thus becomes godronne. If the crystalline be removed from its capsule withou injuring the membrane which forms this canal, these godronne folds are not formed by inflation or only in a very slight degree, but the canal becomes larger. It is in man commonly a line and a quarter, a line and a half or two lines in breadth, and not larger in the ox.” An- nexed is a representation of this canal of Petit on a large scale. Fig. 115. As the nature of the connection between the choroid and the hyaloid membrane, the formation of the posterior chamber of the aqueous humour, and the structure of this canal of Petit, have been the subject of contro- versy, I venture to introduce here an extract on this subject from the paper published by me in the Medico-Chirurgical Transactions. “ If the sclerotic, choroid, iris, and retina be removed one or two days after death, leaving the vitreous humour with the lens embedded on its anterior part, we observe a number of stria on the vitreous humour, converging towards the circumference of the lens, cor- responding in number, size, and form to the ciliary processes, giving the same appearance collectively that the circle of ciliary processes or corpus ciliure does on the choroid, and nar- rowed towards the nasal side as the corpus ciliure is. This appearance has been noticed by most authors, but some describe it as arising merely from the marks left by the ciliary processes, while others consider these stria of the same nature as those productions of the choroid, and call them the ciliary pro- cesses of the vitreous humour ; it is the corona ciliaris of Camper and Ziun. If we remove the black pigment with a camel-hair pencil, we leave those productions on the vitreous humour more distinctly marked than when covered by the colouring matter, and presenting all the characters above stated, commencing behind with a well-defined margin, and terminating anteriorly by attachment to the capsule of the lens, the furrows between them capable of receiving the ciliary processes of the choroid, and the folds calculated to be lodged in the corresponding furrows of these processes. The annexed figure is a representation of the vitreous humour of the human eye thus treated. VOL. II. Fig. 116, “If the cornea and iris be removed from a human eye within a few hours after death, a dark circle surrounding the lens, between it and the anterior extremities of the ciliary pro- cesses, may be observed : this is the part of the corona ciliaris of the vitreous humour to which the ciliary processes of the choroid do not extend, which appears dark on account of its perfect transparency ; the converging stria are evident, even on this part where the ciliary processes are not insinuated, interrupting the view if we attempt to look into the bottom of the eye by the side of the lens. It is, in my opiuion, therefore certain, that part of the vitreo-us humour enters into the formation of the posterior chamber of the aqueous humour. The demonstration of this fact is, however, attended with difficulty, because the flaccidity arising from even slight evaporation of the fluids of the eye permits the ends of the ciliary processes which present themselves in the posterior chamber of the aqueous humour to fall towards the circumference of the lens, and appear attached there. For myself I can say that having made the dissection in the way just pointed out, the eye of course in water, and beneath one of those globular vessels which I formerly described, I could see to the bottom of the eye through the space in front of the vitreous humour, between the ciliary processes and the margin of the lens ; this space is, however, perhaps larger in some individuals than in others. Each fold of the corona ciliaris of the vitreous humour seems to consist of two layers of hyaloid membrane, capable of being- separated one from the other byinflation, and ad- mitting of communication with each other round the lens. It appears to me that the canal of Petit or canal godronne is formed in consequence of these folds receiving the injected air one from the other ; it is, however, generally described as being formed by the membrane of the vitreous humour splitting at the circumference of the lens, one layer going before and the other behind that body, the canal existing between these two layers and the capsule of the lens. That the capsule of the lens has no share in the formation of the canal of Petit, I conclude from filling this canal with air, and allowing the part to remain for some days in water, and then with great care removing the lens included in its capsule ; this I do not find, however, causes the air to escape from the cells, but leaves them presenting nearly the original appearance ; and after the air has escaped, I can pass a small probe all round in this canal, o 194 EYE. raising by this means the folds from the hyaloid membrane. It is difficult, however, to pre- serve the air in these folds for any length of time under water, because the tendency of the air to ascend causes the rupture of the membrane, by which it is allowed to escape. After the lens, included in its proper capsule, has been detached from its situation on the vitreous humour, the space it occupied pre- sents the appearance of a circular depression, surrounded by those productions of the hyaloid membrane of which I have just spoken ; the vitreous humour remaining in every respect perfect, notwithstanding this abstraction of the lens.” M. Ribes, in the Memoires de la Societd Medicale d’Emulation for 1816, describes the ciliary processes of the vitreous humour as follows. “ At the anterior part of the vitreous humour, and at a short distance from the cir- cumference of the crystalline, may be seen a ciliary body almost altogether similar to that of the choroid, and which has been named by anatomists corona ciliaris, but no writer has hitherto pointed out its structure, or the impor- tant office it appears to perform. Each of these processes has a margin adherent to the vitreous humour, and encroaches a little on the circumference of the lens. It appears to me impossible to ascertain whether the surfaces are reticulated, but they are villous. The free margin is obviously fringed, and presents nearly the variety of appearance observed in the fringes of ciliary processes (of the choroid) of different animals examined by me, except that the summits are black ; the interval which separates each process of the vitreous humour is a species of depressed transparent gutter. The black colour of the free margins and the transparency of the space which separates each ciliary process adorns the anterior part of the vitreous humour with a circle remarkable for its agreeable effect, and which has been com- pared to the disc of a radiated flower.” Dr. Knox, in a communication made to the Royal Society of Edinburgh, at the same time that mine was made to the Medico-Chirurgical Society, describes the ciliary processes of the choroid as follows : “ In whatever way, the membrane or assemblage of membranes pro- ceeds forwards to be inserted into the circum- ference of the capsule of the lens, forming in its passage numerous longitudinal folds, and small projecting fimbriated bodies, by which, in a natural state, the transparent humours are connected with the superjacent ciliary body (of the choroid) ; when examined with a good glass, these folds are remarkably distinct, and the whole bears the closest resemblance in its distribution to the true ciliary body and pro- cesses. I have, therefore, ventured to call them the internal or transparent ciliary body, or the ciliary body of the hyaloid membrane, in contradistinction to that of the choroid.” It must not be forgotten that these ciliary pro- cesses of the hyaloid membrane were described by Monro in his Treatise on the Eye, and are strongly marked in a coarsely executed plate. He considered that the retina was continued to the lens, and describes its course under the ciliary processes of the choroid ; thus “ on ex- amining the retina with still greater accuracy, it appears that it has exactly the same number of folds or doublings that the choroid coat has; for it enters double between the ciliary pro- cesses, nearly in the same way that the pia mater enters into the coats of the brain. The furrows and doublings of the retina, which, if we are to use the favourite term ciliary, may be called its ciliary processes, make an impres- sion on the anterior part of the vitreous hu- mour.” The structure alluded to was also observed by Ilovius nearly an hundred years before. From the preceding observations respecting the ciliary processes of the vitreous humour, it may justly be inferred that the ciliary pro- cesses of the choroid, and these ciliary pro- cesses of the vitreous humour, are of the same nature, differing only in those of the choroid receiving red blood, while those of the vitreous humour receive a transparent fluid by their bloodvessels. The adaptation of these two circles of folds to each other appears to be a most beautiful example of mechanical con- struction occurring in soft parts : it is a species of dovetailing of the one structure into the other, by which an intimate union is secured between one part of considerable strength and another of extreme delicacy. A connexion equally perfect is established between the ex- ternal surface of the choroid at its margin, and the corresponding margin of the sclerotic, by means of the ciliary ligament; in fact, with- out these two provisions of ciliary ligament and ciliary processes, and their application between the sclerotic, choroid, and vitreous humour, the chambers of the eye must be imperfectly constructed, and the optical me- chanism of the organ defective. It is the mechanical bond between these dissimilar parts which perfects the chamber of aqueous humour, and prevents that fluid from escaping, either between the sclerotic and choroid, or between the choroid and vitreous humour. Of the crystalline lens. — It has been al- ready stated, that there is a double convex lens within the sphere of the eye, at a short distance behind the external lens or cornea. This is the crystalline lens or crystalline humour, which gives additional convergence to the rays of light transmitted through the pupil. It is placed in a depression, formed for its reception on the anterior, compressed, or truncated portion of the vitreous humour, where that body approaches the back of the iris, and constitutes part of the boundaries of the posterior chamber of the aqueous humour. In this depression it adheres firmly to the hya- loid membrane, and from the vessels of that structure derives its nutriment. This double convex lens does not present the same curvature on both surfaces, the anterior being less curved than the posterior, in the ratio of about 4 to 3. Attempts have been made to determine with accuracy the nature of these curvatures, first by Petit, and subsequently by Wintringham, Chossat, and others. The re- EYE. 195 suits of the numerous experiments of Petit lead to the conclusion, that the anterior curvature is that of a portion of a sphere from six to seven lines and a half in diameter, the posterior that of a sphere of from five to six lines and a quarter. From the same source it appears that the dia- meter is from four lines to four lines and a half, the axis or thickness about two lines, and the weight three or four grains. I am, however, inclined to agree with the observation of Porter- field, that, “ as it is scarce possible to measure the crystalline and the other parts of the eye with that exactness that may be depended on, all nice calculations founded on such measures must be fallacious and uncertain, and, therefore, should, for the most part, be looked on rather as illustrations than strict demonstrations of the points in question.” The method by which Petit arrived at these results must render them of doubtful value, the curvatures having been determined by the application of brass plates cut to the requisite form. The results of Chossat’s experiments, conducted with great care, and with the assistance of the megascope, are thus stated by Mr. Lloyd in his Treatise on Optics : “ This author has found that the cornea of the eye of the ox is an ellipsoid of revolution round the greater axis, this axis being inclined inwards about 10°. The ratio of the major axis to the distance between the foci in the generating ellipse he found to be 1.3 ; and this agreeing very nearly with -1.337, the index of refraction of the aqueous humour, it follows that parallel rays will be refracted to a focus, by the surface of this humour, with mathemathical accuracy. The same author found likewise that the two surfaces of the crystalline lens are ellip- soids of revolution round the lesser axis ; and itis somewhat remarkable thatthe axes of these sur- faces do not coincide in direction either with each other, or with the axis of the cornea, these axes being both inclined outwards, and containing with each other, in the horizontal section in which they lie, an angle of about 5°.” It must not be forgotten that these observations apply to the crystalline of the ox, not to that of man, and also that, as Chossat himself admits, the evaporation of the fluid part of the lens, or the absorption or imbibition of the water in which it is immersed, may materially alter the curva- ture. I cannot myself believe it possible to separate a fresh lens in its capsule perfectly from the hyaloid membrane without injuring its structure, and endangering an alteration in its form. Haller states that Kepler considered the anterior convexity to approach to a sphe- roid, and the posterior to a hyperbolic cone. Wintrmgham states the results of his inquiries as to this matter as follows : — “ In order to take the dimensions of the eye of an ox, I placed it on a horizontal board and applied three moveable silks, which were kept extended by small plummets, so as to be exact tangents to the arch of the cornea, as well at each can- tlius, as at the vertex ; then applying a very exactly divided scale, I found that the chord of the cornea was equal to 1 .05 of an inch, the versed sine of this chord to be 0.29, and con- sequently the radius of the cornea was equal to 0.620215 of an inch. 1 then carefully took off the cornea, and replaced the eye as before, and found, by applying one of the threads as a tan- gent to the vertex of the crystalline, that the distance between this and the vertex of the cor- nea was 0.355 of an inch. Afterwards I took the crystalline out without injuring its figure, or displacing the capsula, and then applying the threads to each surface of this humour, as was done before to the arch of the cornea, I found that the chord of the crystalline was 0.74 of an inch, and its versed sine, with respect to the anterior surface, to be 0.189 of an inch, and consequently the radius of this surface was 0.45665 of the same. In like manner the versed sine to the same chord, with respect to the posterior surface of the crystalline, I found to be equal to 0.38845 of an inch. Lastly, I found the axis of the crystalline and that of the whole eye from the cornea to the retina to be 0.574, 2.21 respectively.’” Whatever doubts may be entertained respecting the accuracy of the measurements of the lens, there can be none that the form is different at different periods of life, in the human subject. It also appears to differ in different individuals at the same period of life, and probably the curvature is not the same in both eyes. In other animals the dif- ference in form is most remarkable. In the human foetus, even up to the ninth month, it is almost spherical. Petit states that he found the anterior curvature in a foetus of seven months, a portion of a sphere of three lines diameter, and the posterior of two and a half, and the same in a new-born infant. In an in- fant eight days old, the anterior convexity was a portion of a sphere of four lines, and the posterior of three. All anatomists concur in considering the lens to approach more to a sphere at this period. In childhood the curva- tures still continue much greater than in ad- vanced life; from ten to twenty probably de- crease, and from that period to forty, forty-five, or fifty, remain stationary, when they become much less ; being, according to the tables of Petit, portions of spheres from seven to even twelve lines in diameter, and on the posterior of six or eight. Every day’s observation proves that the lens becomes flattened, and its curva- tures diminished as persons advance in life. It is seen in dissection, when extracted by opera- tion, and even during life; the distance between its anterior surface and the back of the iris be- ing so great in some old persons, that the sha- dow of the pupil may be seen upon it, while at an earlier period it actually touches that part of the membrane. This diminution of the curva- tures of the lens commences about the age of forty-five. Petit found the anterior convexity varying from a sphere of about seven to twelve lines diameter, and the posterior from five to eight in persons from fifty to sixty-five years of age. The alteration in power of adaptation, and the indistinctness of vision of near objects which takes place at this period, is probably to be attributed to this cause, although a diminu- tion of the muscular power of the iris, and con- sequent inactivity of the pupil, may contribute to the defect. It is also to be recollected that the density of the lens is much increased at this period, and that the young person whose lens o 2 19G EYE. presents greater curvatures does not require concave glasses, as the old person requires con- vex ones. The state of the eye, after the re- moval of the lens by operation for cataract, proves that it is a part of the organ essentially necessary for correct vision. When the eye is in other respects perfect, without any shred of opaque capsule, any irregularity or adhesion of the pupil, or any alteration in the curvature of the cornea, as in young persons who have had the lens properly broken up with a fine needle through the cornea, vision is so good for distant objects, that such persons are able to pursue their common occupations, and walk with safety through crowded streets, but they require the use of a convex lens, of from three and a half to five inches focus, for reading or vision of near; old persons, however, generally require convex glasses on all occasions after the removal of the lens. That the curvatures of the lens are fre- quently different in different individuals may be inferred from the frequency of short sight, or defective power of adaptation, not attributa- ble to any peculiarity of the cornea. Petit states that he found lenses of which the two convexities were equal, and others of which the anterior was greater than the posterior, and more than once, one more convex on its ante- rior surface in one eye, while that in the other eye was in a natural state. He also occasion- ally found the lens as convex in the advanced period of life as in youth. I have repeatedly observed the perfection of vision and power of adaptation much greater in one eye than the other in the same individual, without any defect of the cornea, pupil, or retina ; and occasionally have found young persons requiring the com- mon convex glasses used by persons advanced in life, and old persons becoming near-sighted, and requiring concaves. The annexed letters shew the difference of curvature at the different periods of life, as represented by Sbmmerring. A is the lens of the fcetus; B, that of a child of six years of age ; and C, that of an adult. Fig. 117. The colour of the lens is also different at different periods of life. In the foetus it is often of a reddish colour; at birth and in in- fancy it appears slightly opaque or opaline ; in youth it is perfectly transparent; and in the more advanced periods of life acquires a yel- lowish or amber tint. These varieties in colour are not visible, unless the lens be removed from the eye, until the colour becomes so deep in old age as to diminish the transparency, when it appears opaque or milky, or resembling the semitransparent horn used for lanterns. The hard lenticular cataract of advanced life appears to be nothing more than the extreme of this change of colour, at least when extracted and placed on white paper it presents no other disorganization ; but the lens of old persons, when seen in a good light and with a dilated pupil, always appears more or less opaque, al- though vision remains perfect. The depth of colour is sometimes so great, without any milkiness or opacity, that the pupil appears quite transparent although vision is lost. This is perhaps the state of lens vaguely alluded to by authors under the name of black cataract. The consistence of the lens varies as much as its colour. In infancy it is soft and pulpy, in youth firmer, but still so soft that it may be crushed between the finger and thumb, and in old age becomes tough and firm. Hence it is that in the earlier periods of life cataracts may be broken up completely into a pulp, and absorbed with certainty, while in old persons they adhere to the needle, unless very deli- cately touched, and are very liable to be de- tached from the capsule and thrown upon the iris, causing the destruction of the organ. On this account, therefore, the operation of extrac- tion must generally be resorted to in old per- sons labouring under this form of cataraci, while the complete division of it with the needle and exposure of the fragments to the contact of the aqueous humour secures its removal by absorption in young persons. It must not, however, be forgotten that the softer lenticular cataract occasionally occurs in ad- vanced life. The crystalline lens is a little heavier than water. Porterfield, from the experiments of Bryan Robinson, infers that the specific gra- vity of the human lens is to that of the other humours as eleven to ten, the latter being nearly the same as water; and Wintringham, from his experiments, concludes that the den- sity of the crystalline is to that of the vitreous humour in the ratio of nine to ten; the spe- cific gravity of the latter being to water as 10024 to 10000. The density of the lens is not the same throughout, the surface being nearly fluid, while the centre scarcely yields to the pressure of the finger and thumb, especially in advanced life. Wintringham found the spe- cific gravity of the centre of the lens of the ox to exceed that of the entire lens in the propor- tion of twenty-seven to twenty-six. The re- fractive power is consequently greater than that of the other humours. On this head Mr. Lloyd, in his Optics, says, “ In their refrac- tive power, the aqueous and vitreous humours differ very little from that of water. The re- fractive index of the aqueous humour is 1.337, and that of the vitreous humour 1.339; that of water being 1.336. The refractive power of the crystalline is greater, its mean refracting index being 1.384. The density of the crystal- line, however, is not uniform, but increases gradually from the outside to the centre. This increase of density serves to correct the aber- ration by increasing the convergence of the central rays more than that of the extreme parts of the pencil.” Dr. Brewster, in his Treatise on Optics, says, “ I have found the following to be the refractive powers of the different humours of the eye, the ray of light being incident upon them from the eye : aqueous humour 1.336; crystalline, surface 1.3767, centre 1.3990, mean 1.3839; vitreous humour 1.3394. But as the rays refracted by the aqueous humour pass into the crystalline, and EYE. 197 those from the crystalline into the vitreous humour, the indices of refraction of the sepa- rating surface of these humours will be, from the aqueous humour to the outer coat of the crystalline 1.046G, from the aqueous humour to the crystalline, using the mean index, 1.0353, from the vitreous to the outer coat of the cry- stalline 1.0445, from the vitreous to the crystal- line, using the mean index, 1.0332.” Dr. Young says, “ On the whole it is probable that the refractive power of the centre of the human crystalline, in its living state, is to that of water nearly as 18 to 7; that the water im- bibed after death reduces it to the ratio of 21 to 20 ; but that on account of the unequable den- sity, its effect in the eye is equivalent to a refraction of 14 to 13 for its whole size.” Respecting the chemical composition of the lens, Berzelius observes, that “ the liquid in its cells is more concentrated than any other in the body. It is completely diaphanous and colourless, holding in solution a particular animal matter belonging evidently to the class of albuminous substances, but differing from fibrine in not coagulating spontaneously, and from albumen, inasmuch as the concentrated solution, instead of becoming a coherent mass on the application of heat, becomes granulated exactly as the colouring matter of the blood when coagulated, from which it only differs in the absence of colour. All those chemical properties are the same as those of the co- louring matter of the blood. The following are the principles of which the lens is com- posed: peculiar coagulable albuminous matter 35.9, alcoholic extract with salts 2.4, watery extract with traces of salts 1.3, membrane form- ing the cells 2.4, water 58.0. From the preceding observations it might reasonably be supposed that the lens is com- posed of a homogeneous material, such as al- bumen or gelatine, more consolidated in the centre than at the circumference ; but this is not the case ; on the contrary, it exhibits as much of elaborate organization as any other structure in the animal economy. It consists of an outer case or capsule, so totally different from the solid body contained within it, that they must be separately investigated and de- scribed. The body of the lens, it has been already stated, consists of certain saline and animal ingredients combined with more than their weight of water, and when perfectly transparent presents the appearance of a tena- cious unorganized mass ; but when rendered opaque by disease, loss of vitality, heat, or im- mersion in certain fluids, its intimate structure becomes visible. If the lens with the capsule attached to the hyaloid membrane be removed from the eye and placed in water, the following day it is found slightly opaque or opaline, and spirt into several portions by fissures extending from the centre to the circumference, as seen in Jig. 118. This appearance is rendered still more obvious by immersion in spirit, or the addition of a few drops of acid to the water. If a lens thus circumstanced be al- lowed to remain some days in water, it con- tinues to expand and unfold itself, and if delicately touched and opened by the point of a needle, and carefully transferred to spirit, and as it hardens is still more unravelled by dissection, it ultimately presents a remarkable fibrous or tufted appearance, as represented in the figure below, drawn by me some years ago from a preparation of the lens of a fish thus treated (the Lophius piscatorius). The three annexed figures represent the structure of the lens above alluded to: A is the human crystal- line in its natural state; B, the same split up into its component plates ; and C, unravelled in the fish. Fig. 118. This very remarkable structure of the body of the lens appears to have been first accu- rately described by Leeuwenhoek, subse- quently by Dr. Young, and still more recently by Sir David Brewster. Leeuwenhoek says, “ It may be compared to a small globe or sphere, made up of thin pieces of paper laid one on another, and supposing each paper to be composed of particles or lines placed some- what' in the position of the meridian lines on a globe, extending from one pole to the other.” Again he says, “ With regard to the before- mentioned scales or coats, I found them so exceedingly thin, that, measuring them by my eye, I must say that there were more than two thousand of them lying one upon another.” “ And, lastly, I saw that each of these coats or scales was formed of filaments or threads placed in regular order, side by side, each coat being the thickness of one such filament.” The peculiar arrangement of these fibres he describes as follows : “ Hence we may collect how ex- cessively thin these filaments are; and we shall be struck with admiration in viewing the won- derful manner they take their course, not in a regular circle round the ball of the crystalline humour, as I first thought, but by three dif- ferent circuits proceeding from the point L, which point I will call their axis or centre. They do not on the other side of the sphere approach each other in a centre like this at L, but return in a short or sudden turn or bend, where they are the shortest, so that the filaments of which each coat is composed have not in reality any termination or end. To explain this more particularly, the shortest filaments, M K, H N, and O F, which fill the space on the other side of the sphere, constitute a kind of axis or centre, similar to this at L, so that the fila- ments M K, having gone their extent, and filled up the space on the other side, in like manner as is here shewn by the lines ELI, return back and become the shortest filaments H N. These filaments H N, passing on the other side 198 EYE. of the sphere, again form another axis or centre, and return in the direction O F, and the fila- ments O F, again on the other side of the sphere, collect round a third centre, and thence return in the direction KM; so that the fila- ments which are on this side of the sphere collect round a third centre, and thence return in the direction KM; so that the filaments which are on this side the shortest, on the other side are the longest, and those which there are the shortest are here the longest.” Annexed is Leeuwenhoek’s representation (Jig. 119). Fig. 119. G Dr. Young differs from Leeuwenhoek as to the arrangement of the fibres and other parti- culars, and in his last paper corrects the de- scription given by himself in a former one ; he says, “ The number of radiations (of the fibres) is of little consequence, but I find that in the human crystalline there are ten on each side, not three, as I once from a hasty observation concluded.” “ In quadrupeds the fibres at their angular meeting are certainly not conti- nued as Leeuwenhoek imagined.” Beneath is Dr. Young’s last view of the arrangement of the fibres, which Dr. Brewster has shown to be incorrect, but the introduction of which is jus- tified by the source from which it is derived. Fig. 120. Sir David Brewster says that the direction of the fibres is different in different animals; the simplest arrangement being that of birds, and the cod, haddock, and several other fishes. In it the fibres, like the meridians of a globe, con- verge to two opposite points of a spheroidal or lenticular solid, as in the annexed figure. Fig. 121. The second or next simplest structure he detected in the salmon, shark, trout, and other fishes ; as well as in the hare, rabbit, and por- poise among the mammalia; and in the alli- gator, gecko, and others among reptiles. Such lenses have two septa at each pole, as in the annexed figure. Fig. 122. The third or more complex structure exists in mammalia in general, “ in which three septa diverge from each pole of the lens, at angles of 120°, the septa of the posterior surface bisect- ing the angles formed by the septa of the ante- rior surface, as in the annexed figure (fig 'i 2 3)- EYE. 199 Fig. 123. The mode in which these fibres are laterally united to each other is equally curious. Sir David Brewster says that he ascertained this in looking at a bright light through a thin lamina of the lens of a cod, when he observed two faint and broad prismatic images, situated in a line exactly perpendicular to that which joined the common coloured images. Their angular distance from the central image was nearly five times greater than that of the first ordinary prismatic images, and no doubt whatsoever could be entertained that they were owing to a number of minute lines perpendicular to the direction of the fibres, and whose distance did not exceed the j^jdth of an inch. Upon ap- plying a good microscope to a well-prepared lamina, the two fibres were found united by a series of teeth exactly like those of rack work, the projecting teeth of one fibre entering into the hollows between the teeth of the adjacent one, as in Jig. 124. Fig. 124. I have said that the lens consists of an outer case or capsule totally different from the solid body contained within it. This capsule is strong, elastic, and perfectly transparent. In the paper to which I have alluded in the Me- dico-Chirurgical Transactions, I gave the fol- lowing detailed description of its nature and properties : — “ The real nature of the capsule of the lens has not, I think, been sufficiently attended to; its thickness, strength, and elasticity, have cer- tainly been noticed, but have not attracted that attention which a fact so interesting, both in a physiological and pathological point of view, deserves. That its structure is cartilaginous, I should conclude, first, from its elasticity, which causes it to assume a peculiar appearance when the lens has been removed, not falling loose into folds as other membranes, but coiled in different directions ; or if the lens be removed by opening the capsule behind, and with- drawing it through the vitreous humour, allow- ing the water in which the part is immersed to replace the lens, the capsule preserves in a great degree its original form, especially in the eye of the fish ; secondly , from the density and firmness of its texture, which may be ascer- tained by attempting to wound it by a cataract needle, by cutting it upon a solid body, or compressing it between the teeth ; thirdly, from its permanent transparency, which it does not lose except on the application of very strong acid or boiling water, and then only in a slight degree ; maceration in water for some months, or immersion in spirit of strength sufficient to preserve anatomical preparations, having little or no effect upon it. If the lens be removed from the eye of a fish dressed for the table, the capsule may be raised by the point of a pin, and be still found almost perfectly transparent. This combination of density and transparency gives the capsule a peculiar sparkling appear- ance in water, in consequence of the reflection of light from its surface, resembling a portion of thin glass which had assumed an irregular form while soft ; this sparkling I consider very characteristic of this structure. The properties just enumerated appear to me to distinguish it from every other texture but cartilage ; still, however, it may be said that cartilage is not transparent, but even the cartilage of the joints is semi-transparent, and, if divided into very thin portions, is sufficiently pellucid to permit the perception of dark objects placed behind it, and we obtain it almost perfectly transparent where it gives form to the globe of the eye, as in the sclerotic of birds and fishes. If the soft consistence, almost approaching to fluidity, of the external part of the lens, be considered, the necessity of a capsule capable itself of pre- serving a determinate form is obvious. If the lens were enclosed in a capsule such as that which envelopes the vitreous humour, its sur- face could not be expected to present the ne- cessary regular and permanent curvature ; nor could we expect that if the form of the lens were changed, it could be restored without this provision of an elastic capsule.” The capsule is liable to become opaque and constitute cataract, as the body of tire lens is. These capsular cataracts are easily distinguished 2U0 EY E. from the lenticular. They never present the stellated appearance frequently observed when the texture of the opaque lens opens in the cap- sule as it does when macerated in water, nor the uniform horny or the milky blue appearance of common lenticular cataract. The opacity in capsular cataract exists in the shape of irregular dots or patches, of an opaque paper-white ap- pearance, and when touched with the needle are found hard and elastic, like indurated cartilage, the spaces between the specks of opacity fre- quently remaining perfectly transparent. It appears to be generally assumed by writers on anatomy that a watery fluid is interposed between the body of the lens and its capsule, from an incidental observation of Morgagni when discussing the difference in density be- tween the surface and centre of the lens ; hence it has been called the aqua Morgagni. The observation of this celebrated anatomist, in his Adversaria Anatumica, which has led to the universal adoption of this notion, is, however, merely that upon opening the capsule he had frequently found a fluid to escape. “ Deinde eadem tunica in vitulis etiam, bobusque sive recens, sive non ita recens occisis perforata, pluries animadverti, illico humorem quendam aqueum prod ire : quod et in homine observare visus sum, atque adeo credidi, lrujus humoris secretione prohibita, crystallinum siccum, et opacum fieri ferh ut in extracto exsiccatoque crystallino contingit.” He does not, however, subsequently dwell upon or insist upon the point. I do not believe that any such fluid exists in a natural state, but that its accumula- tion is a consequence of loss of vitality; the water combined with the solid parts of the lens escaping to the surface and being detained by the capsule, as occurs in the pericardium and other parts of the body. In the eyes of sheep and oxen, when examined a few hours after death, not a trace of any such fluid can be detected, but after about twenty-four hours it is found in considerable quantity. In the human eye a fluid sometimes accumulates in the capsule, constituting a particular form of cataract, which presses against the iris, and almost touches the cornea ; but such eyes are, I believe, always unsound. From this erro- neous notion of an interposed fluid between the lens and its capsule has arisen the adop- tion of an unsustained and improbable conclu- sion, that the lens has no vital connexion with its capsule, and consequently must be produced and preserved by some process analogous to secretion. Respecting this matter I have ob- served, in the paper above alluded to, u The lens has been considered by some as having no connexion with its capsule, and consequently that its formation and growth is accomplished without the assistance of vessels; such a notion is so completely at variance with the known laws of the animal economy, that we are justi- fied in rejecting it, unless supported by un- questionable proof. The only reasons which have been advanced in support of this conclu- sion are, the failure of attempts to inject its vessels, and the ease with which it may be separated from its capsule when that mem- brane is opened. These reasons are far from being satisfactory; it does not necessarily follow that parts do not contain vessels, be- cause we cannot inject them ; we frequently fail when thete can be no doubt of their exist- ence, especially where they do not carry red blood. I have not myself succeeded in in- jecting the vessels of the lens, but I have not repeated the trial so often as to make me despair of accomplishing it, more especially as Albinus, an anatomist whose accuracy is universally acknowledged, asserts, that after a successful injection of the capsule of the lens, he could see a vessel passing into the centre of the lens itself. Lobe, who was his pupil, bears testimony to this. The assertion that the lens is not connected with its capsule, I think I can show to be incorrect; it has been made from want of care in pursuing the inves- tigation, and from a notion that a fluid exists throughout between the lens and its capsule. When the capsule is opened, its elasticity causes it to separate from the lens; especially if the eye be examined some days after death, or has been kept in water, as then the lens swells, and often even bursts the capsule and protrudes through the opening, by which the connexion is destroyed. I have however satis- fied myself that the lens is connected with its capsule (and that connexion by no means slight) by the following method. I remove the cornea and iris from an eye, within a few hours after death, and place it in water, then with a pair of sharp-pointed scissors I divide the capsule all round at the circumference of the lens, taking care that the division is made behind the anterior convexity, so that the lens cannot be retained by any portion of the cap- sule supporting it in front. I next invert the eye, holding it by the optic nerve, when I find that the lens cannot be displaced by agitation, if the eye be sufficiently fresh. In the eye of a young man about six hours dead, I found that, on pushing a cataract needle into the lens, after the anterior part of the capsule had been removed, I could raise the eye from the bottom of the vessel, and even half way out of the 1 water, by the connexion between the lens and its capsule. It afterwards required consider- j able force to separate them, by passing the needle beneath the lens, and raising it from its situation. I believe those who have been in the habit of performing the operation of ex- traction, have occasionally encountered consi- derable difficulty in detaching the lens from its situation after the capsule had been freely opened, this difficulty I consider fairly refer- able to the natural connexion just noticed.” When the lens enclosed in its capsule is de- j tached from the hyaloid membrane, the con- nexion between it and the capsule is destroyed by the handling, and, in consequence, it moves freely within that covering, affording to those j who believe that there is no union between the two surfaces fallacious evidence in support of that opinion, which, if not sustained by better proof, should be abandoned. Dr. Young in- sists upon the existence of the natural con- j nexion by vessels and even by nerves between the lens and its capsule; he says, “ The cap- sule adheres to the ciliary substance, and the lens to the capsule, principally in two or three points ; but I confess I have not been able to observe that these points are exactly opposite to the trunks of nerves; so that probably the adhesion is chiefly caused by those vessels which are sometimes seen passing to the cap- sule in injected eyes. We may, however, dis- cover ramifications from some of these points upon and within the substance of the lens, generally following a direction near to that of the fibres, and sometimes proceeding from a point opposite to one of the radiating lines of the same surface. But the principal vessels of the lens appear to be derived from the central artery, by two or three branches at some little distance from the posterior vortex, which I conceive to be the cause of the frequent adhe- sion of a portion of a cataract to the capsule about this point ; they follow nearly the course of the radiations and then of the fibres ; but there is often a superficial subdivision of one of the radii at the spot where one of them enters.” The great size of the vessels distri- buted on the back of the capsule in the foetus strengthens the conclusion that the lens is fur- nished with vessels as the rest of the body. When the eye of a fetus of seven or eight months is finely injected, a branch from the central artery of the retina is filled and may be traced through the centre of the vitreous hu- mour to the back of the capsule, where it ramifies in a remarkably beautiful manner, assuming, according to Sbmmerring, a stellated or radiating arrangement. Zinn declares that he found branches from this vessel penetrating the lens : “ Optime autem placet observatio arteriol* lentis, in oculo infantis, cujus vasa cera optime erant repleta, summa voluptate mihi visas, quam prope marginem ad convexi- tatem posteriorem dilatam, duobus ramulis perforata capsula in ipsam substantiam lentis profunde se immergentem cortissime con- spexi.” He also quotes the authority of Ruysch, Moeller, Albinus, and Winslow, as favouring the same view. Against such au- thority I find that of the French systematic writer Bichat advanced ; but on such a point his opinion is of little value. Annexed is Zinn’s representa- tion of the distribu- tion of the branch of the central artery on the back of the capsule, from a preparation in Lieberkuhn’s mu- seum. Similar fi- gures have been given by Albinus, Sbmmerring, and Sir Charles Bell. Of the aqueous humour. — In the preliminary observations at the commencement of this article, I stated that a cavity or space filled with water exists between the cornea and crys- talline lens, in which space the iris is extended, with its aperture or pupil, to moderate the quantity of light, and interrupt the passage of the extreme rays. It is bounded anteriorly by the concave inner surface of the cornea, and posteriorly by the crystalline lens and other parts, and is necessarily divided into two spaces or chambers by the iris. That in front of the iris, called the anterior chamber, is bounded by the concave inner surface of the cornea anteriorly, and by the flat surface of the iris posteriorly, which, I have already stated, is a plane, not a convex surface, as represented in the plates of Zinn and others. The size of this space is necessarily small, and varies in different individuals according to the convexity of the cornea, which also frequently varies. It is always, however, sufficiently large to allow the surgeon to introduce a needle to break up a cataract without wounding the iris or cornea. The posterior chamber is bounded in front by the back of the iris, and behind by the crys- talline lens; with that portion of the hyaloid membrane of the vitreous humour, which is between the anterior termination of the ciliary processes of the choroid and the circumference of the lens. The circumference of the pos- terior chamber is bounded by the anterior ex- tremities of the ciliary processes of the choroid, as they extend from the vitreous humour to the back of the iris. It does not appear to be generally admitted or well understood that any part of the hyaloid membrane of the vitreous humour enters into the composition of the posterior chamber of the aqueous hu- mour, notwithstanding the decisive opinion and accurate representation of the celebrated Sbmmerring, in which I entirely concur, as I have stated above in describing the vitreous humour. The size of the posterior chamber has been the subject of much discussion and contro- versy, and various attempts have been made by freezing the eye and other means to deter- mine the matter. Petit, after a careful inves- tigation, considered that the distance between the lens and iris was less than a quarter or half a line, in which Haller appears to concur. Winslow, in the Memoirs of the French Aca- demy for 1721, insists that the iris is in contact with the lens. Lieutaud, in his Essais Ana- tomiques, is equally positive on this point, and even denies altogether the existence of a posterior chamber. The question is not an indifferent one, inasmuch as it involves impor- tant considerations as to operations for cataract and inflammations of the iris. Modern ana- tomists appear, generally, to consider the dis- tance between the lens and iris to be greater than it really is. Although 1 cannot agree with Winslow and Lieutaud that the margin of the pupil is always in contact with the lens, I believe it frequently is so, especially in the earlier periods of life, when the curvatures of the lens are considerable. In iritis adhesions generally take place between the margin of the pupil and the capsule of the lens, a conse- quence not easily accounted for, if the parts be not in contact. In old age the lens be- comes much flattened, and therefore retreats from the pupil, to such a degree that the sha- Fig. 125. 202 EYE. dow of the iris may often be seen in a crescentic form on a cataract ; and in such persons, whe- ther from this cause or from the inflammation not being of the adhesive character, blindness is more frequently attended with dilated pupil. In breaking up cataracts through the cornea, I have repeatedly satisfied myself of the con- tact or close vicinity of the two surfaces by placing the needle between them. The an- nexed outline section, from the work of Sdm- merring, shews how small he considered the space between the iris and lens, and displays accurately how the posterior chamber is formed by the iris an- teriorly, the lens pos- teriorly, and the cili- ary processes at the circumference, with the small circular portion of the hyaloid mem- brane of the vitreous humour between the ciiliary processes of the choroid and the circumference of the lens. It appears to me unaccountable why sur- geons, with these anatomical facts before them, still continue to introduce the needle into the posterior chamber, to break up cataracts, in- stead of passing it through the cornea into the anterior chamber, where ample space exists, and a full view is obtained of all the steps of the operation. In doing so the needle is thrust through opaque parts among delicate structures, into a narrow cavity, where, hidden by the iris, it can be used with little certainty of correct application. At the same time, instead of penetrating the simple structure of the cornea, which bears injury as well as any other struc- ture of the body, the instrument pervades the fibrous sclerotic, a structure impatient of in- jury and prone to inflammation, punctures the ciliary ligament at the imminent risk of in- juring one of the ciliary nerves or even wound- ing the long ciliary artery, and finally passes through one of the most vascular parts in the body, the corpus ciliare. The practice appears a signal instance of the influence of education, habit, and authority in setting improvement at defiance. The proofs afforded of the close vicinity of the margin of the pupil to the cap- sule of the lens, should remind the surgeon that one of the greatest dangers to be ap- prehended in iritis is the adhesion of these two parts, and that one of the first steps in the treatment should be to separate them by the application of belladonna, which, by its pecu- liar influence on the pupil, dilates that aper- ture, and, consequently, brings its margin more opposite the circumference of the lens and at a greater distance from the prominent central portion. The aqueous humour, although constituting so essential a part of the optical mechanism of the eye, is but small in quantity ; according to Petit not more than four or five grains. Its specific gravity and refractive power scarcely differ from that of water; and according to Berzelius, 100 parts contain 98.10 of water, 1.15 of chloruret of soda with a slight trace of alcoholic extract, 0.75 of extractive matter soluble in water only, and a mere trace of albumen. It is perfectly transparent, but is said to be milky in the foetus. The source from which this fluid is derived has been the subject of controversy in con- sequence of Nuck, a professor of anatomy at Leyden, having asserted that he had discovered certain ducts through which it was transmitted, and published a small treatise to that effect, which ducts were proved to be vesssels by a cotemporary writer, Chrouet, in which deci- sion subsequent authors have concurred. In the present day this fluid is generally believed to be secreted by a membrane lining the cavity, as the fluid which lubricates the serous cavities is secreted by their lining membranes. Al- though this is in all probability the fact, the circumstances are not exactly the same in both cases. In the serous cavities, merely as much fluid as moistens the surface is poured out, while in the chamber of the aqueous humour sufficient to distend the cavity is secreted. In the serous cavities the membrane from which they derive their name can be demonstrated ; in the chamber of aqueous humour this can scarcely be accomplished. I have resorted to various methods to enable me to demonstrate the existence of the membrane of the aqueous humour on the back of the elastic cornea, such as maceration, immersion in hot water, soaking in alcohol, and treating with acids, alkalis, and various salts, but without effect. In describing the structure of the cornea, I have shewn that the elastic cornea itself can- not for a moment be considered the membrane in question, on account of its strength, thick- ness, elasticity, and abrupt termination; and I do not think that the demonstration of a serous membrane expanded on such a struc- ture as transparent cartilage is to be expected, inasmuch as the demonstration of the synovia! membrane on the cartilages of incrustation in the joints is attended with much difficulty. The pathological fact which tends most to prove the existence of such a membrane here, is, that in iritis, especially that of a syphilitic character, the aqueous humour appears often very muddy, especially in the inferior half of the chamber; this, however, in the latter stages may be found to arise from a delicate speckled opacity on the back of the cornea, which re- mains permanently, and injures vision con- siderably. Analogy also favours the inference that the whole cavity of the chamber must be lined by serous membrane, inasmuch as all structures, of whatsoever nature they may be, in the serous or synovial cavities, are so covered or lined. This provision is so universal, that if such various structure, as the elastic cornea, iris, capsule of the lens, ciliary processes, and hyaloid membrane, which enter into the con- struction of the chamber of aqueous humour, be exposed to the contact of the fluid without Fig. 126. EYE. 203 any intervening membrane, it constitutes an unexpected anomaly in the animal ceconomy. The consequences of inflammation greatly strengthen the conclusion that the cavity is lined by a membrane of the serous character. The slightest injuries or even small ulcers of the cornea are frequently accompanied by effu- sion of purulent matter into the anterior chamber, from the extension of the inflam- mation into that cavity, constituting the hy- popion or onyx of the books ; and the yellow masses which appear on the iris in syphilitic iritis, whether they are abscesses, or as they are called, globules of lymph, are effusions beneath a delicate membrane, as vessels may be seen with a magnifying glass, ramifying over them. In iritis the rapidity with which adhesions are formed between the margin of the pupil and the capsule, proves that these two structures are covered by a membrane of this nature. In addition to all these facts the still more conclusive one is to be adduced, namely, that the membrane can without diffi- culty be demonstrated on the back of the iris, as I have stated in speaking of that part of the organ, and as it is represented in Jig. 127, where the fold of membrane stained with black pigment is seen turned down from that structure. In the preceding pages I have availed my- self of whatever valuable and appropriate facts in comparative anatomy I found calculated to illustrate or explain the structure of the human eye. There are, however, two organs in other animals which do not exist even in the most imperfect or rudimental state in the human subject — the pecten or marsupium nigrum in birds, and the choroid gland or choroid muscle in fishes. Of the pecten. — This organ is called pecten from its folded form bearing some resemblance to a comb, and marsupium nigrum from its resemblance in the eye of the ostrich to a black purse, according to the anatomists of the French Academy, who compiled the collection of memoirs on comparative anatomy. The organ is obviously a screen projected from the bottom of the eye forward toward the crys- talline lens, and, consequently, received into a corresponding notch or wedge-shaped hollow in the vitreous humour; it appears to be of the same vascular structure as the choroid, and is deeply stained with the black pigment, which renders it perfectly opaque and imper- vious to light. The annexed figure, from the work of D. W. Sommerring, represents it in the eye of the golden eagle. Fig. 128. It is composed of a delicate membrane, highly vascular, folded exactly like the plaits of a fan, and when removed with sharp scissors from the bottom of the eye, and its free margin cut along the edge so as to allow the folds to be pulled open, it may be spread out into a strip of continuous riband-shaped membrane, as seen in jig. 129, from a paper of Sir E. Home’s in the Philosophical Transactions for 1822. Fig 127. Fig. 129. The first account I find of it is by Petit in the Mem. de 1’Acad. Roy. 1735. He says it is a trapezium or trapezoid, five lines long at the base, and three lines and a half deep, com- posed of parallel fibres, and that a fine trans- parent filament runs from the anterior superior angle to the capsule of the crystalline lens, not easily seen on account of its transparency, and that sometimes the angle itself is attached to the capsule near its margin. Haller, in his work “ Sur la formation du cceur dans le poulet,” describes it as follows : — “ It is a black membrane folded at very acute angles, as the paper of a fan, upon which transparent vessels are expanded ; it generally resembles the ciliary processes. It originates from the sclerotic in the posterior part of the eye by a serrated line, pierces the choroid, retina, and vitreous humour to attach itself to the side of the capsule of the crystalline, very near the corona ciliaris. The posterior extremity is broad, and the anterior narrows till it becomes 204 EYE. adherent to the capsule of the lens by an inser- tion a little narrower. This insertion appears to be effected by the intervention of the hyaloid membrane, to which this fan is attached. I have not had time to establish this con- nexion to my satisfaction, and I still entertain doubts respecting it. I have seen a red artery accompany this feather-like production and run to the crystalline. It would be very convenient for physiology that this folded membrane should prove muscular ; we should then have the organ sought after, which would retract the crystalline to the bottom of the eye.” In the Elementa Physiologic, t. v. p. 390, he says it originates from the entrance of the optic nerve, but that you may remove the retina and leave the pecten. He says again, “ it advances for- ward to the posterior part of the capsule, to which it sometimes adheres by a thread, and sometimes the lens is merely drawn toward it.” An artery and vein is supplied to each fold, and perhaps to the capsule of the lens. In the Opera Minora he says that there are two red vessels to each fold in the kite, and no cord runs to the lens ; that in the heron a branch of artery runs to each fold, and it adheres so closely to the lens that it cannot be ascertained whether a red vessel runs from it to the lens or not; that in the duck it is contracted toward the lens, and adheres to it by a thread contain- ing a red vessel. He also says that in the wild duck it arises from the margin of the linea alba, which terminates the entrance of the optic nerve, contains numerous vessels, and adheres to the lens ; and in the pie it is large and adheres to the lens, so as to pull it. D. W. Sbmmerring says, that in the pecten of the golden eagle, of which Jig. 128 is a representation, there are fourteen folds like ciliary processes, and that it adheres by a transparent filament to the capsule of the lens ; that in the great horned owl it is short and thick, with eight folds, and adhering to the lens by an hyaloid filament, although at a great distance from it; and that in the macaw it is longer than broad, has seven folds, and adheres to the lens. In the ostrich he says it is shaped like a patella at its base, which is white, oval, and thick; eight lines long and five broad, distinctly separate from the choroid, above which it rises, the retina being interposed. From the longer diameter of this patella (or base) a white plane or lamina projects even up to the lens, and sends out on each side seven small plaits, the lower ones partly double, the upper ones simple, black, and delicate. This conical body, something like a black purse, tapers toward the lens, and by its apex is attached to the capsule by a short semi-pellucid ligament. The white substance of the base and partition of the pecten should not be con- founded with the medullary part of the optic nerve, which, emerging on all sides from be- neath the base, expands into a great, ample, and tender retina, terminating behind the ciliary processes with a defined margin. Cuvier, in his Lectures on Comparative Anatomy, says, “ It appears of the same nature as the choroid, although it has no connexion with it ; it is like- wise very delicate, very vascular, and imbued with black pigment. Its vessels are derived from a particular branch of the ophthalmic artery, different from two which belong to the choroid ; they descend on the folds of the black membrane and form ramifications there of great beauty when injected. This mem- brane penetrates directly into the vitreous humour, as if a wedge had been driven into it ; it is in a vertical plane directed obliquely forward. The angle nearest the cornea in those species in which it is very broad, and all its anterior margin in those in which it is narrow, comes nearly to the inferior boundary of the capsule of the crystalline. In some species it approaches so near that it is difficult to say whether or not it is attached to it ; such is the case in the swan, the heron, the turkey, &c. according to Petit ; but there are other birds in which it remains at some distance, and in which it does not appear to attach itself except to some of the numerous plates which divide the vitreous humour into cells. In the swan, heron, and turkey, this membrane is broader in the direction parallel to the produced extre- mity of the optic nerve than in the contrary direction. In the ostrich, cassowary, and owl the reverse is observed. It is folded like a sleeve in a direction perpendicular to the caudal termination of the optic nerve. The folds are rounded in most species ; in the ostrich and cassowary they are compressed and sharp, and so high perpendicular to the plane of the membrane that at first sight it resembles a black purse. The folds vary in number, there being sixteen in the swan, ten or twelve in the duck and vulture, fifteen in the ostrich, and seven in the grand duke or great horned owl. The purpose for which the pecten exists in the eyes of birds does not appear to be fully ascertained. Petit says, “ when a bird views an object with both eyes, the rays enter oblique- ly in consequence of the situation of the cornea and crystalline lens, and proceed to the bottom of the eye ; but as they enter in lines parallel to the membrane, they do not encounter it. The rays which enter the eye in lines perpen- dicular to the plane of the cornea encounter this membrane, and are absorbed by it as well as those which come from the posterior side ; the subject is, however, a difficult one.” Haller supposed that it was merely destined to afford a medium through which vessels might pass to carry blood to the crystalline. Cuvier says, “ It is difficult to assign the real use of this membrane. Its position should cause part of the rays which come from objects at the side of the bird to fall upon it. Petit believed that it was destined to absorb these rays and prevent their disturbing distinct Vision of objects placed in front. Others thought, and the opinion has been lately reiterated by Home, that it possesses muscular power, and that its use is to approach the lens to the retina when the bird wishes to see distant objects. Never- theless, muscular fibre cannot be detected in it, and the experiments intended to prove its muscularity after death are not absolutely con- clusive ; moreover, as it is attached to the side EYE. 205 of the crystalline, it could move it only obliquely.” The experiments and inferences contained in Sir E. Home’s paper in the Phi- losophical Transactions for 1796, do not appear to me worthy of any attention. A pecten in an imperfect or rudimentary state appears to exist in fishes and reptiles, and has been noticed by Haller, W. Sbmmerring, and Dr. Knox. In the article Aves of this work Mr. Owen has also described the pecten, and to that arti- cle I refer the reader for additional information. Of the choroid gland or choroid muscle. — - The eyes of fishes present several remarkable peculiarities, to be accounted for perhaps from their occasional residence in the obscurity of the deep, and at other times near the surface, exposed to the full blaze of sunshine ; they must also be frequently exposed to great pres- sure at considerable depths. The sclerotic is not merely a fibrous membrane, but is strength- ened by a cartilaginous cup, and sometimes even by one composed of bone ; the cornea is generally flat or presenting little of lenticular character; the crystalline lens is spherical, and so dense that its central part is a hard solid; and the choroid presents the remarkable pecu- liarity which I have now to describe. On cutting through the cartilaginous sclerotic, a fluid is found generally interposed between this and the choroid; at least it is so in the genus gadus, (cod, haddock, &c.) The external part of the choroid is formed by a most beau- tiful membrane of a brilliant silver aspect, scarcely to be distinguished from that metal when rough and recently cleaned. On tearing this membrane away, the vascular choroid is exposed, and a red horse-shoe-shaped promi- nent mass, encircling the entrance of the optic nerve, appears. This is the choroid gland or choroid muscle. The veins of the choroid, apparently commencing from the iris, ascend in tortuous inosculating branches, of enormous size compared with the dimensions of the part, and appear to terminate by entering this horse- shoe-shaped organ, but this is not their distri- bution, as it is not hollow. The area enclosed by the organ round the optic nerve does not exhibit the same extreme vascularity. On pulling away a delicate film which covers the organ, it appears composed of lamina or plates divisible into fibres, which run transversely from within outwards, confined into a compact body by the delicate film just spoken of, and a concave depression in the structure beneath. The annexed plate, made from an accurate drawing of a careful dissection, represents the general form and vascularity remarkably well. Fig. 130. Haller, speaking of the choroid in fishes, says, “ this organ is a fleshy pulp, composed of short columns densely consolidated, resembling red gelatine.” Cuvier says, “ its colour is com- monly a vivid red, its substance is soft and more glandular than muscular; at least fibres cannot be distinguished on it, although the bloodvessels form more deeply coloured pa- rallel lines on its surface. Its form is com- monly that of a small cylinder bent like a ring round the nerve, which ring is not, however, complete; a segment of greater or less length is always deficient. Sometimes, as in the Perea lahrax, it is composed of two pieces, one on each side of the optic nerve. In other cases it is not in a circle but an irregular curve, as in the Salmon, Tetradon mola, and Cod ; but in the carps and most other fishes it approaches to to a circle. Those who suppose that the eye changes its figure according to the distance of objects, think that this muscle is destined to produce this effect by contracting the choroid ; but it appears to me that the numerous vessels passing out of it should rather lead to its being considered a gland destined to secrete some of the humours of the eye. These vessels are wdfite, fine, very tortuous, and appear to traverse the tunica Ruyschiana; they are well seen in the Te- tradon mola and Perea labrax. In the Cod they are very large, anastomose together, and are covered by a white and opaque mucus. This gland does not exist in the cartilaginous fishes, as the Rays and Sharks, in which it approaches more to the character of the eye in the Mam- malia, as has already been observed in speak- ing of the tapetum and ciliary processes.” D. W. Summering says, “ Around the insertion of the nerve is seen a peculiar red, thick, soft body of a horse-shoe shape, respecting which it is doubted whether it be muscular, glandular, or merely vascular. It is undoubtedly ex- tremely vascular, and contains many large, branching, inosculating vessels, forming a proper membrane gradually becoming thin, and terminating at the iris. This vascular membrane constitutes the second or middle layer of the choroid.” This description applies to the eye of the Cod. Sir E. Home, in a Croonian lecture published in the Philoso- phical Transactions for 1796, says that Mr. Hunter considered the organ in question to be muscular, and proceeds to state that “ this muscle has a tendinous centre round the optic nerve, at which part it is attached to the scle- rotic coat; the muscular fibres are short, and go off from the central tendon in all directions : the shape of the muscle is nearly that of a horse-shoe; anteriorly it is attached to the choroid coat, and by means of that to the sclerotic. Its action tends evidently to bring the retina forwards ; and in general the optic nerve in fishes makes a bend where it enters the eye, to admit of this motion without the nerve being stretched. In those fishes that have the sclerotic coat completely covered with bone, the whole adjustment to great dis- tances must be produced by the action of the choroid muscle; but in the others, which are by far the greater number, this effect will be 206 EYE. much assisted by the action of the straight muscles pulling the eye-ball against the socket, and compressing the posterior part, which, as it is the only membranous part in many fishes, would appear to be formed so for that pur- pose ” Although it must be admitted that these conclusions of Sir E. Home are derived from insufficient data, and are probably incor- rect in many particulars, yet it is not very im- probable that the part in question may be mus- cular, and, if so, may be instrumental in adapt- ing the eye to distance by pushing up the retina toward the lens. The organization of the part is certainly not merely vascular, as stated by Cuvier, and undoubtedly bears a stronger resemblance to muscular than any other structure; it also retains the peculiar colour of red muscle after all the rest of the eye has been blanched by continued macera- tion in water. I think, however, Sir E. Home goes too far when he describes a central tendon without reservation. For further information on the subject of this article, see Vision, and Vision, Organ of. BIBLIOGRAPHY. — In pursuit of information re- specting the anatomy of the eye, the student need scarcely go farther back than Zinn’s work, or the article on the same subject in Haller’s Elementa Physiologi®. The older anatomical writers were, generally speaking, uninformed on the subject. Ruysch’s works contain some observations worthy of attention at the time he wrote, but now scarcely worth recording ; especially as he was a vain man, and wrote for present fame and character rather than truth. In Albinus’s Annotationes Academiccd a few facts are recorded, upon the accuracy of which the student may place reliance, as he was an anatomist. Morgagni also added to the existing information of the period at which he wrote, but has left little more than noies or cursory remarks. Petit’s papers in the Memoires de l’Academie Royale des Sciences contain much original and valuable matter. In this earlier period the con- tributions of Nuck, Hovius, Briggs, and Leeuwen- hoek should not be overlooked. Cotemporary with or immediately following Haller and Zinn, Porter- field, Le Cat, Lieutaud, the second Monro, Blu- menbach, Sommerring, and many others made valuable additions to our information on this subject. The annexed list contains the titles of those works which I have consulted ; some of the more modern German monographs I have been obliged to quote or consult from those who copied from them, having endeavoured in vain to procure them : such are those of Dollenger, Chelius, Huschke, Jacob- son, Kieser, Weber, and some others. Nuck , Lialographia et duetuum aquosorum ana- tome nova, Lugd. Bat. 1695. Warner Chrouet , De tribus humoribus oculi, 1691. Hovius , De circu- lari humorum motu in oculis, Ludg. Bat. 1716. Briggs , Ophthalmograpliia, Lugd. Bat. 1686. Leuwenhoek, Arcana naturae detecta, Del phis, 1695 ; or in the Philosophical Transactions, or in the translation of his select works by Hoole, Lond. 1816. Ruyschii Thesaurus, Amstel. 1729. Al- binus , Annotationes academicae. Morgagni , Ad- versaria anatomica, Ludg. Bat. 1723, and Epistol®, Venetiis, 1750. Haller , Elementa physiologiae corporis humani, tom. v. Lausanne, 1763 ; also in Opera minora, and Formation du coeur dans le poulet. Zinn, Descriptio anatomica oculi humani, Gotting. 1780, and also in Coramentarii Societatis Regia Scientiarum Gottingenses, t. iv. 1754. Petit, in Memoires de l’Academie Royale des Sciences, 1723, 25, 26, &c. Winslow, Mem. de l’Acad. 1721. Moeller, Observations circa retinam, in Halleri Disputations anatomicae select, t. vii. Camper , De quibusdam oculi partibus, in Halleri Disp. anat. Lobe, De oculo humano, in same. Wintringham , On animal structure, London, 1740. Le Cat , Traite des Sens, Rouen, L740. Bertrandi, Dissertatio de oculo, in Opere anatomische e cerusiche. Porterfield , On the eye, Edinburgh, 1759. Lieutaud , Essais anatomiques, Paris, 1766. Dud- dell. Treatise on the diseases of the horny coat in the eye, Lond. 1729. Descemet, An sola lens crystallina cataract® sedes, Paris, 1758. Demours, Letire a M. Petit, Paris, 1767. Brendel, De fabrica oculi in foetibus abortivis. Got. 1752. Blumenbach, De oculis leuccethiopum et iridis motu, Gott. 1786. Wachendorf, Commercium litterarinm, 1744. Fon- tana, Traite sur le venin de la vipere, Florence, 1781. Walther, J. G. Epistola anat. ad Wilhelm Hunter, Berolin, 1758. Sommering, Abbildungen des menschlichen Auges, or leones oculi humani ; or translated into French by Demours. Sommering , also in Commentarii Soc. Reg. Gotting. Monro, On the brain, the eye, and the ear, Edin. 1797. Camparetti, Observationes dioptric® et anatomic® de coloribus, visu et oculo, Patavii, 1798. Sattig , Lentis crys- tallin® structura fibrosa, Hal®, 1794. Mauchart, De cornea, in Haller’s Disputationes chirurgic®, or in Reuss Dissertationes Tubingenses. Dr, Young , in the Philosophical Tansactions, 1793 et seq. Home, in several papers in the Philosophical Tiansactions, see Index. Beil, De structura ner- vorum, Hal®, 1796. Rosenthal, De oculi quibus- dam partibus, 1801. Angely, De oculo organisque lachrymalibus, Erlang. 1803 ; or, again, Schreger vergleichenden Anatomie des Auges, Leipzig, 1810. Baerens, Systematis lentis crystallina monographia. Tubing®, 1819, and in Radius Scriptores oph- thalmologici minores. Clemens , Tunic® come® et humoris aquei monographia, Gott. 1816, and in Radius, S. O. M. Sachs, Historia duorum leu- cuthiopum, Solisbaci, 1812. Maunoir, Sur l’or- ganisation de l’iris, Paris, 1812. Ribes, in Me- moires de la Societe Med. d’Emulation, an 8ieme, Paris, 1817. Chelius, Ueber die durchsichtige Hornhaut des auges, Carlsruhe, 1818. Voit, Oculi humani anatomia et pathologia, Norimberg®, 1810. Hegar, De oculi partibus quibusdam, Gott. 1818. Cuvier, Le9ons d anat. comp. Bell's Anatomy. Meckel's Handbuch d. menschl. anatomie, or the French translation. Sommer ing , D ,W . De oculorum hominis animaliumque sectione horizontale, Gott, 1818. Knox, Comparative anatomy of the eye, Trans. Royal Society of Edinburgh, 1823. Cloquet, J. Sur la membrane pupillaire, Paris, 1818, «7ac0&$cm,Siipplementa ad ophthalmiatriam.Havni®, 1821. Dollenger, Illustratio ichnographica oculi, Werceburg, 1817. Weber, De motu iridis, Lipsi®, 1828. Jacob, in Philosophical Transactions, 1819. Martegiani, Nov® observationes de oculo human., Napoli, 1812. Sawrey, An account of a newly- discovered membrane in the human eye, Lond. 1807. Husche, Commentatio de pectinis in oculo avium potestate, Jen®, 1827. Schneider, Das ende der nervenhaut in menslichen auges, Munchen, 1827. Kieser , De anamorphosi oculi, Gott. 1804. Jacob, in Medico-Chirurgical Transactions, vol. xii. Lond. 1823. F, A. ab Ammon, De genesi et usu macul® lutr®, Vinari®, 1830. Dieterich, F. C. Uber die verwundengen des linsensystems. Tubing. 1824. Dollenger, Uber das Strahlenblaitchen im menschlichen auges in Acta Ph. Med. Acad. C®sar- Leop. Car. nat. cur. t. ix. Horrebow, M. Tractatus de oculo humano, Havni®, 1792. Jacob Imans, Dissertatio inaug. de oculo, Lugd. Bat. 1820. Lieblien, V. Bemerkungen fiber das system der krystalliense bei Saugthieren und. vogeln. Wurz- burg, 1821. Muller , F. Anatomische und physio- logische darstellung des menschlichen auges, Wien. 1819. J. Muller, Zur vergliechenden physiologie des gesichtssines des menschen und der Thiere, Leipsig, 1826. G. R. Treviranus, Beitrage zur anatomic und physiologie der Sinneswcrkezeuge des FACE. 20? Menschen und der Thiere, 1 Heft. Bremen, 1828. Wardrop’s Morbid anatomy of the eye. Dalrymple’s Anatomy of the eye, Lond. 1834. Mackenzie , On diseases of the eye, Lond. 1834. Lloyd, On light and vision, Lond. 1831. Biot, Precis elementaire de physique, Paris, 1824. Langenbeck, B. C. R. De retina, Gott. 1836. Berzelius, Traitede chimie, Paris, 1833. Ammon, Zeitschrift fur die oph- thalmologie. Radius, Scriptores ophihalmologici minores. Reils, Archiv. fur die physiologie. Meckel’s Arehiv. F. Arnold, Untersuchungen liber das auge des menschen, Heidelberg, 1832. Giralde, Sur [’organization de l’oeil, Paris, 1836. For the latest observations on the retina, see Ehrenberg, Beobachtung iiber Structur des Seelenorgans, Ber- lin, 1836. For the comparative anatomy of the eye, which is still imperfect, I refer the student to the paper of Zinn in the Gottingen Commentaries, as above quoted ; Bidloo, De oculis et visu ; the article on the eye in Haller’s Elementa Physiologiae ; Cam- paretti’s observations ; Home’s papers in the Philo- sophical Transactions; Knox’s Comparative ana- tomy of the eye ; Cuvier’s Comparative anatomy ; J. Muller, Vergleichende Physiologie des Gesicht- sinnes ; and, above all, to D. W. Sommering’s book. For perfect systematic treatises on the anatomy of the eye, the student is referred to Zinn’s well-known and highly valuable work, Arnold’s work just quoted, and, in English, Mr, Dalrymple’s treatise. (Arthur Jacob.) FACE (in anatomy) (Gr. rr^oaurrov ; Lat. facies, vultus, os; Fr . face; Germ. Antlitz, Gesicht ; Ital. faccia ). — In vertebrated animals this term is applied to denote the anterior part of the head, with which most of the organs of the senses are connected ; while the cranium is destined to contain and protect the encephalic organs, the face is the seat of the organs of sight, smell, and taste, and in some animals of a special organ of touch. The relative sizes of cranium and face depend, therefore, in a great measure on the relative development of those important organs which belong to each. For the characters of the face in the different classes of animals, we refer to the articles devoted to the anatomy of them, and to the article Osseous System. Face (in human anatomy). The face is situated before and below the cranium, which bounds it above ; on the sides, it is limited by the zygomatic arches, behind by the ears and the depression which corresponds to the upper region of the pharynx, and below by the base of the lower jaw and the chin. The disposition of the face is symmetrical ; its anterior surface is trapezoidal, the largest side being above ; and its vertical section is triangular. It pre- sents an assemblage of organs which serve dif- ferent purposes, and which by their configura- tion and proportions constitute what are called th o features; individually the face presents many varieties, not only in the form and degree of development of its several parts, as the nose, mouth, &c., but also in the condition of its bones, muscles, skin, and adipose tissue. The varieties of form presented by the face afford some of the most distinctive characters of the different races of mankind. It differs also ac- cording to the age and sex of the individual ; in the infant, the peculiarities depend princi- pally upon the disposition of the bones, and in particular on the absence of the teeth ; but the soft parts have also their distinctions at this age, for while the fat is abundant, the muscles are but little developed, and hence the slightly marked features and the plump cheeks of infancy. In old age, again, the aspect of the face is the reverse of this, for not only do its thinness and the predominance of the muscles throw out the features, but the skin is covered with folds and wrinkles, from its own relaxation and the absence of fat, aided perhaps by the action of the muscles. The loss of the teeth, moreover, allows the lower jaw (when the mouth is closed) to be thrown in front of the upper, and thus the length of the face is dimi- nished, and a peculiar expression is imparted to the countenance. In women, (from the delicacy of the features and the abundance of the cellular tissue,) the face preserves the roundness of form, and something of the characteristics of childhood. Bones of the Face. — The bones of the face comprise all those of the skull which do not contribute to form the cavity for the brain ; they inclose, either by themselves or in con- junction with the adjacent bones of the cranium, 1. the organs of three senses, viz. sight, smelling, and taste ; 2. the organs of mastica- tion and the orifices of the respiratory and digestive canals ; 3. they give attachment to most of the muscles of expression. The face is divided into the upper or the fixed, and the lower or the moveable jaw, both of which are provided with teeth. The lower jaw is a single and symmetrical bone; the upper jaw, though formed of thirteen bones, consists principally of two, viz. the ossa maxillaria superiora, to which the others may be considered as additions, being attached to them immoveably, and forming altogether one large, irregular, and symmetrical piece, which constitutes the upper jaw. Of the fourteen bones which contribute to the face, two only are single or median ; the others are double, and form six pairs, viz. 2 ossa maxilla superioris ; 2 ossa palati ; 2 ossa nasi ; 2 ossa mala ; 2 ossa lachrymalia ; 2 ossa turbinata inferiora. The two single bones are, the vomer and the os maxilla in- serioris. The superior maxillary bones, ( ossa maxil- laria superiora ; Germ, die Obern Kinnbacken- beine oder Oberkiefer.) These bones, situated in the middle and front of the face, are of a very irregular figure ; they are united below along the median line, and form together, the greater part of the upper jaw. Each has four surfaces, viz. 1. a facial or anterior; 2. a posterior or zygomatic; 3. an internal or naso- palatine; 4. a superior or orbitur. The borders are three; 1. an anterior or naso-maxillary ; 2. a posterior or pterygoid ; 3. an inferior or alveolar. The facial surface presents from before backwards, 1 . the fossa myrtiformis, a depres- sion situated above the incisor teeth, which gives attachment to the depressor labii superi- oris ; 2. the canine ridge, which corresponds to the socket of the canine tooth, and which sepa- rates the myrtiform from, 3. the canine (or the FACE. 208 infra-orbitar) fossa, which gives attachment to the levator anguli oris, and at the upper part of which is seen the infra-orbitar foramen, giving exit to the vessels and nerves of the same name ; 4. the malar ridge, a semicircular crest which descends vertically from the malar pro- cess to the alveolar border of the bone, and divides its facial from its zygomatic surface, which is prominent behind, where it forms the maxillary tuberosity, most conspicuous before the exit of the last molar tooth, which in the child is lodged within it. On this surface are several small holes, (posterior dental fora- mina,) which are the orifices of canals for the posterior and superior dental vessels and nerves. From the upper and front part of the ante- rior surface of the bone a long vertical process ( the nasal process ) ascends between the nasal and lachrymal bones to be united with the frontal ; its external surface is rough, presenting small irregular holes, which transmit vessels to the cancellous interior of the bone and to the nose, and giving attachment to the levator labii superioris alaeque nasi muscle. The internal sur- face of this process is marked with some minute grooves and holes for vessels, and, tracing it from below upwards, by a transverse ridge or crest ( the inferior turbinated ridge ) for the lower spongy bone ; above this by a depres- sion corresponding to the middle meatus ; next by a crest ( the superior turbinated ridge ) for the upper spongy bone of the ethmoid ; and above this by a surface which receives and completes some of the anterior ethmoid cells. The nasal process has three borders: 1. an anterior, thin and inclined from above downwards and forwards; above, it is cut obliquely from the internal towards the external surface of the bone, and below in the contrary direction, so that this edge of the nasal process and the corresponding border of the nasal bone with which it is united, mutu- ally overlap each other. 2. A posterior border, or surface, thick and divided into two margins by a deep vertical groove (the lachry mo-nasal canal ) which contributes to lodge the lachrymal sac above, and the nasal duct below. The direction of the lachrymo-nasal canal is curved from above downwards and outwards ; so that its convexity looks forwards and inwards, and its concavity in the contrary direction. The inner margin of this groove is thin, and is united above to the anterior border of the os unguis, and below to the inferior spongy bone. The outer margin is bounded and gives attach- ment to the tendon and to some of the fibres of the orbicularis palpebrarum ; it commonly ter- minates below in a little tubercle (the lachrymal tubercle). 3- The upper boi'dcr of the nasal process, which is short, thick, and irregular, is articulated with the internal angular process of the frontal bone. The orbitar surface of the bone is the small- est; it is quadrilateral, smooth, and slightly concave, with an inclination from above down- wards and from within outwards ; it forms the greater part of the floor of the orbit. Along the middle of its posterior half runs, in a direc- tion forwards and outwards, the infra-orbitar groove, which anteriorly becomes a complete canal ( the infra-orbitar canal ), and finally divides into an internal or larger canal, which terminates at the infra-orbitar hole in the canine fossa, and into an external or small conduit, which runs in the anterior wall of the antrum, and conveys the superior anterior den- tal nerves to the incisor and canine teeth ; this outer subdivision of the canal presents several varieties in different individuals. The orbitar surface (or plate) has four borders: 1. The posterior, which, free and notched in the mid- dle by the commencement of the infra-orbitar canal, forms with the orbitar plate of the sphe- noid and palate bones the inferior orbitar or the spheno-maxillary fissure. 2. The internal, which articulates from behind forwards succes- sively with the palate, the ethmoid, and the lachrymal bones. 3. The anterior, short and smooth, separates the orbitar from the facial surfaces of the bone; at its inner extremity is the nasal process already described. 4. The external is united to the malar bone; on the outer side of this border is a rough triangular projecting surface (the malar process ) which receives the os malae, and which forms an angle of union between the anterior, posterior, and superior surfaces of the upper maxillary bone. The internal or naso-palatine surface is di- vided along the anterior three-fourths into two unequal parts by an horizontal plate of bone ( the palatine process ) : above this is the nasal portion forming the upper three-fourths of this surface, and below it, is the palatine part which forms the remaining fourth. The palatine process forms the anterior three- fourths of the floor of the nose, and roof of the mouth; it presents a smooth upper surface, concave transversely, and nearly flat in the op- posite direction : it is broad behind and narrow in front, where there is placed the orifice of the anterior palatine canal, which takes a direction downwards, forwards, and inwards, unites with the corresponding canal in the opposite bone at the median plane, and forms a common canal {the canalis incisivus), which opens below by a hole {the foramen incisivum ) on the roof of the mouth, immediately behind the middle incisor teeth. The anterior palatine canals and the incisive canal, which are often included to- gether under a common name, form a tube re- sembling the letter Y, being bifid above and single below. The inferior surface of the pa- latine process is rough and concave, and forms the anterior and larger part of the roof of the mouth ; its internal border is long and rough, thick in front, narrow behind, and united with the corresponding border of the opposite bene forms the maxillary suture : this border is sur- mounted by a half-furrow which, with that of its fellow bone, forms a groove for the reception of a partof the vomer. The posterior border isshorl and cut obliquely at the expense of the upper surface ; it supports the anterior margin of the horizontal part of the palate-bone. The pala- tine division of the internal surface of the upper maxillary bone is narrow, and forms part of the arched roof of the mouth ; along its junc- tion with the palatine process is a broad shal- FACE. 209 low groove for lodging the posterior palatine nerves and vessels. The nasal portion of the internal surface is placed above the palatine process, and is lined on its anterior three-fourths by the pituitary membrane. Tracing this sur- face from before backwards we observe, 1. the lower aperture of the naso-lachrymal canal, situate just behind the inferior turbinated crest of the nasal process; 2. posterior to this, the orifice of the maxillary sinus, or antrum of Highmore, which in the sepaiated bone is a large opening, but is contracted in the united face by the lachrymal, the ethmoid, the palate, and the inferior turbinated bones, which are attached around its margin. Above this aper- ture are seen some cells which unite with those of the ethmoid, and its lower edge presents a fissure in which is received the maxillary pro- cess of the palate-bone. Below the inferior turbinated crest, the naso-lachrymal canal and the orifice of the antrum, the bone is concave and smooth, and forms a part of the inferior meatus of the nose; behind this smooth surface and the orifice of the antrum, the bone is rough for the attachment of the vertical plate of the os palati, and it presents a groove, which, descending obliquely forwards to the palatine division of this surface, forms a part of the posterior palatine canal. The maxillary sinus (sinus maxillaris, antrum Highmori ; Germ, die Oberkiefer/mhle) oc- cupies in the adult the whole body of the bone : its form is triangular, wuh the base directed internally towards the orifice which has been already described, and the apex out- wards towards the malar process. Its superior wall is formed by the orbitar plate; the pos- terior corresponds to the maxillary tuberosity ; and the anterior to the canine fossa. All these walls present ridges or crests, which lodge canals for the passage of nerves. The posterior and anterior walls contain the su- perior, anterior, and posterior dental canals, which lodge nerves of the same name. The upper wall contains the infra-orbitar groove and canal, which gives passage to the upper maxillary nerve. Borders. — 1. The anterior or naso-maxillary border is united above along the nasal process to the nasal bone. Below this it is thin and presents a deep semicircular notch, which forms the lateral and inferior portions of the anterior aperture of the nose. At the lower extremity of this notch the bone projects, and forms with its fellow of the opposite side the anterior nasal spine. The remainder of this border proceeds downwards and a little forwards to terminate on the alveolar border of the bone between the two middle incisor teeth. 2. The posterior or pterygo-palatine border, thick, rounded, and vertical, is united below to the palate bone, and above it forms, with the palate bone, the anterior border of the pterygo-maxillary fissure. 3. The inferior or alveolar border is thick and broad, especially behind, and forms about the fourth of an oval. It is perforated with conical cavities (alveoli ) for the reception of the roots of eight teeth. These cavities are VOL. II. separated by thin transverse lamina. Tracing them backwards from the anterior extremity of the border, the orifices of the two first are nearly circular, and receive the incisors ; they are the largest, and are placed below the nasal notch. The third, in form transversely oval, receives the canine tooth, is of great depth, and ascends in front of the canine fossa. The fourth and fifth, also transversely oval, but not so deep, receive the lesser molar teeth ; they generally present ridges in their septa which correspond to grooves in the fangs of the teeth which are implanted into them. The orifices of the three last cavities are quadrilateral, and receive the molar teeth. The sixth and seventh are subdivided into three lesser cavities, of which the two external are smaller than the inner one. Sometimes one of the molar teeth has four fangs, and then we find its socket subdivided into a cor- responding number of cavities. The eighth alveolus, which receives the last molar tooth or dens sapienti®, is not so distinctly divided into subordinate cavities, but presents ridges like the lesser molar. The outline of the alveolar border is waving, convex where it corresponds to the alveoli, and depressed op- posite their septa. The whole of this border is covered by the gums, and presents innu- merable pores for the nutritious vessels. The surfaces of the alveoli are also similarly marked. Connexions. — The upper maxillary articu- lates with two bones of the cranium, viz. the ethmoid and frontal, and sometimes with the sphenoid by its pterygoid processes, or by an union of the orbitar plates of both bones at the outer extremity of the spheno-maxillary fissure. In this case the malar bone does not enter into the formation of this fissure. The upper maxillary articulates with its fellow and with all the bones of the face. The me- dian and lateral cartilages of the nose are at- tached to it. It receives the upper teeth, and gives attachment to eight muscles, viz. the orbicularis palpebrarum, the inferior oblique of the eye, the levator labii superioris alsque nasi, the levator labii proprius, the depressor alse nasi, the compressor narium, the levator anguli oris, and the buccinator; often also to some of the fibres of the temporal and the external pterygoid muscles. It lodges the naso-palatine ganglion, and gives passage to the infra-orbitar and to the anterior and pos- terior palatine and dental vessels and nerves. It forms the greater part of the sides of the nose, and of the floor of that cavity, and of the orbit, as well as of the roof of the mouth. It contains the maxillary sinus and the nasal duct. Structure. — This bone is lighter than might be expected from its size, being occupied by the large antrum maxillare. It is cancellous only at the tuberosity, along the alveolar border, and at the malar and palatine processes. Developement. — The ossification of this bone commences as early as the thirtieth or thirty- fifth day of foetal life, near its alveolar border, and it is complete at birth. It presents at p 210 FACE. this period, and often much later, two remark- able fissures. 1. The incisive fissure,, which may be traced from the alveolar border be- tween the canine and lateral incisor tooth backwards and upwards, along the incisive canal towards the nasal process : it is sel- dom observable on the facial surface of the bone. The part of the bone circumscribed by this fissure appears to correspond to the inter- maxillary bone of animals, and is probably developed as a separate piece : it supports the incisor teeth. 2. A fissure is often found ex- tending from the infra-orbitar groove forwards to the orifice of the canal. The existence of these fissures has led some anatomists to sup- pose that the bone is developed by these ossific points. At birth and in infancy the bone presents a much greater proportion from before back- wards than vertically : its nasal process is long, its orbitar plate large, the antrum is already distinct, the tuberosity prominent, and there are some remarkable holes behind the incisor teeth, which are said to have an important connexion with the development of the second set of teeth. In the adult the increase in the vertical di- mensions corresponds with the developement of the antrum and alveolar border. In old age the alveoli are obliterated, the border con- tracts, and the jaw diminishes in height. In the small vertical diameter the senile and in- fantile upper jaw bear a resemblance to each other. In the inferior mammalia, the maxillary bones are separated anteriorly in the middle line by a bone called os intermaxillare or incisivum, which contains the superior incisor teeth when they are present; sometimes this bone is distinctly divisible into two by suture. This bone is present, although the superior incisors be absent, as in Ruminants and Eden- tata, but in such cases is very small: on the other hand, when the incisor teeth are largely developed, it is of considerable size, as in the Rodentia. In the mature human foetus no sign of this bone exists, but in examining the skulls of foetuses about the third or fourth month of pregnancy, we observe it perfectly distinct from the maxillary bone. It sometimes happens that at more advanced periods, whether of in- tra or extra-uterine life, evidence of the separa- tion of the intermaxillary bone exists, and as Meckel says, we often find a transverse narrow “ lacuna" on the vault of the palate, extending from the external incisor tooth to the anterior palatine foramen. According to Weber, how- ever, who examined the extensive collection of foetal skeletons belonging to Professor Ilg in Prague, the intermaxillary bone was distinct only in those that had a double hare-lip. lie considers, however, that the intermaxillary bone readily separates when the skull of a child of one or two years old is placed for some time in dilute muriatic acid.* The palate bones, (ossa palutina ; Germ. * See Weber in Froriep’s Notizen, 1820, quoted inHildebrandt’s Anatomie, 15. ii. S. 95. die Saumenbeine,) situated at the back part of the nose and roof of the mouth, locked be- tween the maxillary bones and pterygoid pro- cesses of the sphenoid, consist of two thin plates, one short and horizontal, the palatine ; the other long and vertical, the nasal. The palatine process, or plate, has two surfaces and four borders. The upper surface, or the nasal, is smooth and concave, and forms the posterior fourth of the floor of the nose. The lower sur- face, the palatine, rough, and slightly concave anteriorly, has on its posterior and outer part a transverse crest with a depression behind it for the attachment of tbecircumflexus palatimuscle. In front and to the outer side of this is the inferior orifice of the posterior palatine canal, behind which are two or three small openings called accessory palatine holes, and in front of it is the commencement of the groove which lodges the posterior palatine vessels and nerves. The anterior border is cut obliquely from below upwards and forwards, and rests on the posterior border of the palatine plate of the upper maxillary bone, forming with it the transverse palato-maxillary suture. The pos- terior border, thin and concave, gives attach- ment to the soft palate. The internal border, rough and thick, is united to its fellow of the opposite side ; above, it forms a grooved crest, which receives a part of the vomer, and is continuous with a similar crest formed on the internal border of the palatine plate of the upper maxillary bone. Behind, this border terminates in a sharp point, which, in conjunction with the corres- ponding projection of the opposite bone, forms the posterior nasal spine, to which the levator uvulae muscle is attached. The external border is continuous with the vertical plate. The nasal process, or plate, has two surfaces and four borders. The internal or nasal pre- sents, tracing it from below upwards, 1. a smooth concave surface, which forms part of the inferior meatus: 2. a horizontal crest, the inferior turbinated crest, for the attach- ment of the inferior turbinated bone : 3. ano- ther concave surface forming part of the mid- dle meatus : 4. another horizontal crest (the superior turbinated crest ), shorter than the former, for the attachment of the middle tur- binated bone of the ethmoid. This surface is covered with the pituitary membrane. The external or zygomato-maxillary surface is rough in front, where it rests against the upper maxillary bone ; behind this the lower two-thirds are marked by a groove, which, in conjunction with one on the upper maxillary bone, forms the posterior palatine canal. Above this, the bone is smooth, and forms the inner and deep part of the pterygo-maxillary fissure. The anterior border, thin and projecting, forms a process (the maxillary ) which is re- ceived into the fissure in the lower edge of the orifice of the maxillary sinus. The posterior or pterygoid border is united to the anterior border of the pterygoid process of the sphenoid : below, it becomes broad and is continued along a process which stands FACE. 211 downwards, outwards, and backwards, from the angle of union of the posterior borders of the vertical and horizontal plates of the bone. This process is the pterygoid or pyramidal, and presents three grooves behind, viz. one internal and one external, (of which the rnner rs the deeper,) for the reception of the anterior borders of the lower extremity of the pterygoid plates ; and a middle triangular groove extending high up, and which forms a part of the pterygoid fossa. The outer surface of this process is rough, and is articulated with the upper maxillary bone : its apex is continuous with the external pterygoid plate. The inferior border is united to the horizon- tal plate. The superior border presents a deep semi- circular notch (sometimes a hole), which with the sphenoid bone above forms the spheno- palatine foramen. This notch divides the upper border into two processes, 1 . the posterior (the sphenoidal); 2. the anterior (the orbitar). The sphenoidal process is curved inwards and back- wards, and has three surfaces, 1. an internal or nasal, forming part of the cavity of the nose; 2. an external, which forms below the spheno- palatine foramen the deep wall of the pterygo- maxillary fissure ; 3. an upper, which is con- cave and rests against the body of the sphenoid bone, and contributes to the pterygo-palatine canal. The orbitar process stands upwards and outwards on a narrow neck, and presents five surfaces. 1. The anterior (or maxillary) arti- culates with the upper maxillary bone. 2. The internal (or ethmoidal) forms a cell which unites with those of the ethmoid. 3. A posterior (or sphenoidal) presents a cell uniting with the sphenoid, and communicating with its sinuses. 4. The superior (or orbitar), which is smooth and contributes to form the floor of the orbit : its posterior border forms a part of the spheno- maxillary fissure, and separates the orbitar sur- face from, 5. the external or zygomatic, which looks into the pterygo-maxillary fissure. Connexions. — Each palate bone articulates with five bones, viz. two of the cranium, the sphenoid and the ethmoid ; and with three of the face, the upper maxillary, the inferior turbi- nated, and the vomer, besides its fellow bone of the opposite side. It is lined with the buccal and pituitary membrane. It contributes to form the cavities of the mouth, nose, and orbit ; the pterygo-maxillary fissure, and the zygomatic and pterygoid fossae. It gives attachment to the soft palate, and passage to the spheno-palatine, pterygo-palatine, and posterior palatine vessels and nerves ; also to the two pterygoid muscles, the circumflexus palati, the levator uvulae, the palato-glossus, and the palato-pharyngeus. The structure is compact, except at its pte- rygoid process, where it is cancellous. Developement. — It is complete at birth, ex- cept that the vertical plate is short to corre- spond with the short vertical diameter of the upper maxillary. About the third month ossification appears in a single point, at the junction of the two plates with the pyramidal process. Malar bones (ossa mala: v. malaria v. zygo- matica ; Fr. os de la pommette ; Germ, die Jochbeine oder Backenbeme). — These bones, corresponding in situation to the prominence of the cheeks, are somewhat of a quadrilateral figure. Each presents three surfaces; 1. an external ox facial; 2. an internal or temporo- zygomatic; 3. a superior or orbitar. There are besides four borders and four angles. The facial surface forms the eminence of the cheek, looks outwards and forwards, is smooth and slightly convex in front, and is marked by one or more small holes (malar foramina), which give passage to vessels and nerves. It is covered above by the integuments and the orbi- cularis palpebrarum, and below and externally it gives attachment to the zygomatic muscles. The temporo-zygomatic surface is smooth and concave below ; and internally there is a rough surface which rests on the malar process of the upper maxillary : about the centre or to- wards the upper part of this surface is observed the internal orifice of a malar canal or a malar hole. The temporal muscle is attached to this surface. The orbitar surface is smooth, concave, and is formed upon a plate of bone ( the orbitar process ), which stands inwards, and contributes to the outer wall and floor of the orbit : its op- posite surface above makes part of the tempo- ral fossa. On the orbitar surface we observe the orifice of a malar canal. The orbitar pro- cess has an irregular summit, which receives the frontal bone ; below, it is articulated with the outer border of the orbitar plate of the sphenoid ; in the middle it corresponds to the extremity of the spheno-maxillary fissure ; and inferiorly it is united to the outer border of the orbitar plate of the upper maxillary bone. Of the four borders two are anterior and two posterior. The anterior superior, or the orbi- tar, is smooth, concave, and forms the outer and lower third of the base of the orbit. The anterior inferior, or the maxillary, rests upon the malar process of the upper maxilla from its extremity to the inferior orbitar foramen. The posterior superior, or temporal border, is waved like the letter S, and gives attachment to the temporal fascia. The posterior inferior, or masseteric border, is thick, and gives attach- ment to a muscle of the same name. The four angles are, 1 . thick, rough, superior or frontal, which receives the external angular process of the frontal bone; 2. the interior or orbitar, which is pointed; and, 3. the inferior or malar, which is round, and forms the extremities of the maxillary border, and which rests on the malar process of that bone. The posterior or zygomatic is cut obliquely from above down- wards and backwards, and supports the zygo- matic process of the temporal bone. Connexions. — The malar is connected with and locked between four bones, viz. the frontal, the sphenoid, the upper maxillary, and the temporal. It contributes to form the orbit, the temporal, and the zygomatic fossre. It gives attachment to four muscles, viz. the temporal, the masseter, and the two zygomatic ; and it gives passage to malar vessels and nerves. p 2 ■212 FACE. The structure is compact, except near its upper and lower angles, where there is some cancellous tissue. Developernent. — Its ossification commences in one piece about the fiftieth day, and is com- pleted at birth, when the bone appears thicker, and its orbitar plate larger in proportion than in the adult : its vertical diameter is, however, narrow, and the malar holes are large. The nasal bones (ossa nasi; Germ, die Nasenbeine ) form the upper part of the nose, and are placed between the nasal pro- cesses of the upper maxillary and below the frontal bones, inclining from above downwards and forwards. They have two surfaces, and their form is quadrilateral, the vertical exceed- ing the transverse diameter. They are stout and narrow above, and thin and broader below. The anterior or cutaneous surface is smooth, covered by the integuments and pyramidalis muscle, concave from above downwards, con- vex transversely. An oblique hole for the passage of vessels is usually found above the centre of one or both nasal bones, and some smaller foramina are scattered over the surface. The posterior or pituitary surface is concave, narrow, especially above, and lined by the olfactory membrane, presenting grooves for vessels and the internal orifice of the canal (or hole) mentioned above. The borders are four : a superior, short, thick, dentated, inclined from above down- wards and backwards, and resting on the nasal notch of the frontal bone between its two in- ternal angular processes : the inferior border, longer than the preceding, thin, jagged, in- clining from the median line downwards and outwards, and generally presenting about its centre a slight notch for the passage for a fila- ment of the nasal nerve. This border forms the upper and front part of the anterior opening of the nasal fossse, and gives attachment to the lateral cartilages of the nose. The external border is the longest, and is cut obliquely for its articulation with the nasal process of the upper maxillary bone. The internal border is shorter, thick and rough above, and thin be- low : it forms, on the inner aspect of the bone, in conjunction with the corresponding part of the bone of the opposite side, a ridge and groove for the reception of the nasal process or spine of the frontal bone, and for the upper and anterior border of the perpendicular plate of the ethmoid. Connexions. — The nasal bones articulate with each other, with the frontal, ethmoid, and upper maxillary bones, and with the lateral cartilages of the nose : they form a part of the cavity of the nose. Their structure is cancellous and thick above, thin and compact below. Developernent. — They are perfectly ossified at birth, when they are proportionally longer than in the adult, corresponding in this respect with the depth of the orbit and the smallness of the anterior aperture of the nose. The ossifica- tion of each nasal bone commences by a single point about the beginning of the third month. The lachrymal bones ( ossa unguis v. lachry- malia ; Germ, die Thranenbeine) are qua- drilateral in form, thin, semitransparent, and are situated on the anterior part of the inner wall of the orbit between the ethmoid, frontal, and upper maxillary bones ; they derive one of their names from the resemblance which they bear to a finger-nail. Each bone presents two surfaces and four borders. The external or orbitar surface is divided at its anterior third by a vertical crest, terminating below in a little curved process which forms the outer wall of the upper orifice of the nasal canal ; in front of this crest the bone is per- forated with numerous little holes, and its sur- face is concave and forms with that of the nasal process of the upper maxilla the canal for the lachrymal sac. The posterior part of this surface is smooth, nearly flat, and is continuous with that of the os planum of the ethmoid, which lies immediately behind it. The internal or ethmoidal surface is rough, and is divided by a vertical groove, which corresponds to the crest on the orbitar aspect of the bone ; the anterior division is convex and forms part of the middle meatus; the pos- terior division is in contact with the ethmoid and contributes to close its cells. Of the four borders, the superior is the shortest and thickest; it is irregular and arti- culates with the inner border of the orbitar plate of the os frontis. The inferior is divided into two parts by the lower extremity of the crest already described on the anterior surface of the bone ; in front of this the border de- scends along a thin process or angle of the bone, which is articulated with the inferior turbinated bone, and contributes to form the inner wall of the canal for the nasal duct; behind, this border is broad, and rests on the inner margin of the orbitar plate of the upper maxillary bone. The anterior border is slightly grooved for the reception of the inner margin of the posterior border of the nasal process belonging to the upper maxilla. The posterior border is thin and articulates with the anterior edge of the os planum. The os unguis has four angles, of which the anterior inferior is remarkable for its length. Connexions. — This bone articulates with the frontal, the upper maxillary, the ethmoid, and the inferior turbinated ; it contributes to foim part of the orbit of the cavity of the nose and of the groove for the lachrymo-nasal duct. It gives attachment to the reflected portion of the tendon of the orbicularis palpebrarum, and to the tendon of the tensor tarsi muscles. In structure it is thin and compact. Development.- — It is complete at birth, ex- cept at its posterior superior angle, where there is a deficiency between it and the frontal and ethmoid bones, and where a separate piece is sometimes formed. It is broader from back to front in proportion, at this period of life, than in the adult, and its lachrymal groove is larger. Its ossification commences by a single point between the third and sixth months. A small lachrymal bone has been described as sometimes found at the lower part of the os unguis; and not unfrequently some separate FACE. 213 pieces are found at its angles, formed either from the ethmoid or from the orbitar plate of the upper maxillary bone. The inferior turbinated bones, ( ossa spongiosa v. turbinata infima; Germ, die untern Muschel- beine ) of an oval form, thin and spongy in their appearance, are placed horizontally along the lower part of the outer wall of the nasal cavities, separating the middle from the inferior meatus, and contributing to increase the surface of the nose. Each bone presents two surfaces, two borders, and two extremities. The internal surface is rough, convex, and looks towards the septum of the nose, which it sometimes touches on one side when that partition inclines more than usually to the right or left. The external surface is concave, exhibiting many small fossee or pits ; it looks towards the upper maxilla and forms a part of the inferior meatus. Both surfaces are very irregular or spongy and are pitted by vessels, but especially by veins, which ramify abundantly upon them. The inferior border is convex and thick, particu- larly at its centre, where it descends towards the floor of the nose. The upper border is thin and irregular, and presents from before backwards, 1. a thin edge, which is attached to the inferior turbinated crest on the nasal process of the upper maxilla; 2. a process (the lachrymal) which ascends towards the curved process of the os unguis, with which and with the adjacent part of the upper jaw-bone it unites to complete the canal for the nasal duct ; 3. some irregular projections (ethmoidal pro- cesses) which ascend and unite with the ethmoid ; 4. a thin, curled, dog’s-ear-looking process (the auricular or maxillary ), which, descending and overhanging the internal sur- face of the bone, is attached to the lower part of the opening of the antrum, which it con- tributes to circumscribe; 5. an edge which is articulated with the inferior turbinated crest of the palate-bone. The orifice of the antrum is situated just above the centre of this border, and opens consequently into the middle mea- tus. The extremities or angles are formed by the union of the two borders ; the posterior extre- mity is more pointed than the anterior. Connexions. — Each inferior turbinated is united with four other bones, viz. the upper maxillary, the lachrymal, the ethmoid, and the palate. It is covered with the pituitary mem- brane ; it contributes to enlarge the surface of the nasal cavity, and to form a part of the nasal canal and middle and lower meatus. Its structure is compact. Its development commences at the fifth month by a single point of ossification. The vomer (Germ, das Pflugscharbein ) is of a quadrilateral figure, and resembles a ploughshare ; it is a single and symmetrical bone, situated in the median plane, and forming the posterior and inferior part of the septum nasi. It has two lateral surfaces and four borders. The surfaces, which are right and left, are smooth, flat, and lined by the pitui- tary membrane ; sometimes, when the bone inclines much to either side of the nose, one of these surfaces is convex and the other concave ; they present an oblique groove or grooves for the naso-palatine nerves and vessels. The superior border (or surface) is broad, and may be -termed the base of the bone ; it presents a deep groove in the middle, which receives the rostrum of the sphenoid, and on each side of this are two plates or laminae (sometimes called the alee) which are received into fissures of the sphenoid on each side of the rostrum, and which contribute to form a longitudinal canal for the ethmoidal vessels. The anterior border is oblique from above downwards and forwards ; above it presents a deep groove, which is a continuation of that on the upper border, and which receives the perpendicular plate of the ethmoid : below, this border is nearly flat, where it is united to the middle cartilage of the nose. The inferior border is the longest, and is received into the grooved crest formed by the united palatine plates of the superior maxillary and palate bones ; in front this border extends as far as the anterior nasal spine. The posterior border, thick above, thin be- low, is oblique, slightly curved, and forms the partition between the two posterior openings of the nose. Connexions. — The vomer is connected with four bones, viz. the sphenoid and ethmoid above, the superior maxillary and palate below: it is covered with the pituitary membrane, and forms, with the perpendicular plate of the ethmoid and the middle cartilage, the septum of the nose. Its structure is compact, and it is formed of two thin lateral plates, which are distinct above, but united inferiorly. Its development occurs by a single ossific point about the third month, and at birth it is completely ossified. The os maxillare inferius (Germ, das untere Kinnbackenbein, oder der Unterkiefer ). This single bone, which alone forms the lower jaw, occupies the lower and lateral parts of the face ; it is a flat, symmetrical bone, and bears some resemblance in shape to a horse-shoe. It con- sists of a middleor horizontal portion (the body ), and of two lateral ascending branches (the rami), which are connected with the body nearly at right angles. The body is curved, nearly horizontal, in- clining from before backwards, and a little upwards, and presents Uvo surfaces and two borders. The anterior surface is convex, and has in the centre a vertical line ( crista mentalis ex- terna ), which marks the union of the two halves of which the bone consists in the young subject : this line terminates below in a tri- angular eminence (the mental process). The vertical direction of the lower jaw at the sym- physis, and its curved figure anteriorly, form- ing what is termed the chin, are both charac- teristic of the human race. From the angles of the mental process arises on each side the external oblique line, faintly marked in front, but becoming distinct as it ascends diagonally 214 FACE. along this surface of the bone to terminate at the anterior border of the ramus of the jaw; it gives attachment to muscles and separates the external surface of the bone into two parts, viz. an anterior superior, which presents, ex- ternal to the symphysis, 1. a depression (the fossa mentalis ) for the attachment of a muscle; 2. to the outer side of this the mental foramen, which is directed obliquely upwards and out- wards; it is the lower orifice of the inferior dental canal, which conveys nerves and vessels to the teeth of the lower jaw; 3. a number of ridges and grooves near the alveolar border of the jaw, which correspond to the sockets of the teeth and to the septa which divide them : this part of the bone is covered by the gums. The surface below and behind the oblique line is smooth, or only faintly marked with irre- gular lines for the attachment of the platysma myoides. The internal surface of the body of the lower jaw is concave, and presents in the median line, at the symphysis, a vertical crest (crista mentalis interna), which is not so distinct as the corresponding ridge on the outer surface of the bone : at its lower extremity is a tubercle having four summits ( the genial processes, yrmor, chin, spina interna,) which give attachment to two pairs of muscles, viz. the two superior genial processes to the genio- hyo-glossi, the two inferior to the genio- hyoidei : below and to the outer side of these processes, on the lower border of the bone, are two oval rough depressions, one on each side of the symphysis, for the attachment of the anterior bellies of the digastric muscles. From the genial processes proceeds obliquely upwards and backwards, to join the anterior border of the ramus of the jaw, the internal oblique line, or the mylo-hyoid ridge. It is distinctly marked and very prominent oppo- site the last molar tooth ; like the external oblique line it divides the bone diagonally into two triangular portions, the anterior of which, situated above and in front of the ridge, is smooth, concave, and to the outer side of the genial processes presents a depression (sublingual fossa ) for the reception of the sub- lingual gland : elsewhere this surface is lined by the gums, and forms the inner wall of the alveolar cavities; but it is destitute of the ridges and depressions which are seen on the outer surface ot the bone. The triangular surface below the oblique line is marked by numerous small holes for the passage of nu- tritious vessels, and by a large depression ( the submaxillary fossa ) for the reception of the submaxillary gland. The two oblique maxillary lines which have been just described divide the body of the jaw into two portions, one superior or alveolar, the other inferior or basilar : in the foetus the former predominates considerably ; in the adult they are nearly equal, and in the edentulous jaw of old age the body almost entirely consists of the basilar portion. The upper or alveolar border forms a lesser curve than that of the alveolar border of the superior maxilla : like it, however, it presents sockets for the reception of sixteen teeth, which vary also in form and depth in correspondence with the fangs of the teeth which they lodge. The orifices of the sockets, however, take a direction different from those of the upper jaw, for while the sockets of the upper incisors look downwards and forwards, those of the lower are directed upwards and backwards; and again the alveoli of the upper canine and molar teeth look downwards and outwards, whereas those of the lower are directed up- wards and inwards: hence, from this different inclination of the teeth in the two jaws, and from the larger curve described by the alveolar border of the superior maxilla, we find that when the mouth is closed the upper front teeth cover the lower and at the sides overhang them a little. This arrangement is favourable to the division and mastication of the food. The lower border or base is smooth and thick, and forms a larger curve than the upper, so that the surfaces of this jaw have an in- clination from above downwards and forwards: it forms the oval border of the lower part of the face, and is the strongest portion of the bone. The rami are flat, quadrilateral processes, which stand up from the body of the jaw at almost a right angle: in the child and old person this angle is much more obtuse. Each ramus presents two surfaces and four borders. The external or masseteric surface has an inclination from above downwards and more or less outwards : it is rough, especially below, where it presents some irregular oblique ridges and depressions for the attachment of the masseter: in front of these marks, near the lower border of the bone, there is often a slight groove, which indicates the course of the facial vessels. The internal or pterygoid surface is also rough below for the attachment of the internal pterygoid muscle. In its centre is the spreading superior orifice (superior dental foramen) of the lower dental canal, marked and partly hidden internally by a spine, which gives attachment to the internal lateral ligament of the temporo-maxillary articulation : from this hole, taking a direction downwards and for- wards is a groove (the mylo-hyoid groove), which lodges the branch of the inferior dental artery and nerve. The borders of the rami are, an anterior or buccal, grooved below, where it corre- sponds with the alveolar border of the bone; the margins of this groove, which are con- tinuous with the oblique lines of the bone, unite above and form a sharp convex edge. The posterior or parotid border is round and thick above, and narrow below, and is em- braced by the parotid gland : inferiorly and internally it gives attachment to the stylo- maxillary ligament. The superior or zygomatic border is sharp and concave, forming a notch ( the sigmoid notch), which looks upwards. The inferior border is rounded, and is con- tinuous with the lower border of the body. The angles of the lower jaw are formed by the union of the body and rami ; each FACE. 215 is turned a little outwards, and in the adult forms nearly a right angle; in the infant and in the old person it is obtuse. This part of the bone is prominent and separates the in- sertion of the masseter and internal pterygoid muscles. On the upper part of each ramus stand two processes, which are separated by the sigmoid notch ; the anterior is the coronoid, which is of a triangular form, flattened laterally, and sharp in front and behind ; its summit is somewhat rounded : this process gives at- tachment to the temporal muscles. The con- dyloid process is situated behind the sigmoid notch, and arises from the ramus by a narrow neck, which is directed upwards and a little inwards, swelling above into an oval head or condyle, that has an articular surface on its summit. This articular surface is trans- versely oval, convex, covered in the recent subject with cartilage, and inclines from within outwards and a little forwards. The condyle, from the direction of its neck, somewhat over- hangs the internal surface of the ramus ; it is articulated with the anterior division of the glenoid cavity of the temporal bone. The direction and form of its articular surfaces are calculated to facilitate the rotatory move- ments of the lower jaw during mastication. In front the neck of the condyle presents a depression for the attachment of the external pterygoid muscle. Structure. — The lower jaw is formed of two complete plates, united by cancellous tissue, which is traversed by a long curved canal (the inferior dented canal ), which conveys the vessels and nerves that supply the teeth. This canal commences in a groove just above the superior dental foramen, which is situated on the internal surface of the ramus ; it then enters the substance of the bone, taking the course of the internal oblique line below, and parallel to which it runs as far as the second bicuspid tooth, where it divides into two canals, one short and wide, which terminates on the external surface of the bone at the inferior dental foramen ; and another smaller one, which continues onwards as far as the middle incisor tooth, where it ceases. From the upper side of this dental canal small tubes arise, which proceed to the alveoli ; they convey vessels and nerves to the fangs of the teeth. The situation and size of the dental canal vary according to the age of the individual. At birth it runs near the lower border of the bone, and is of considerable magnitude; after the second dentition it becomes placed just, below the mylo-hyoid ridge ; in the edentulous jaw it runs along the alveolar border of the bone, its size is much diminished, and the mental foramen is found close upon the upper border of the bone. Connexions and uses.- — The lower jaw is arti- culated with the temporal bones, and receives the sixteen inferior teeth. It gives attachment to fourteen pairs of muscles, viz. the temporal, the masseter, the two pterygoids, the bucci- nator, the superior constrictor of the pharynx, the depressor anguli oris, the depressor labii inferioris, the levator menti, the platysma, the genio-hyo-glossus, the genio-hyoideus, the mylo-hyoideus, and the digastric. Four pairs of ligaments are attached to it, viz. the external and the internal lateral ligaments of the tem- poro-maxillary articulation, the pterygo-maxil- lary (or intermaxillary) ligament, and the stylo- maxillary ligament. It forms the lower part of the face and the cavity of the mouth ; it protects the tongue, salivary gland, and pharynx ; it differs from the upper jaw and from all the other bones of the head in its remarkable mobility ; and it contributes essentially to mastication as well as to deglutition and articulation. Development.- — The lower jaw at birth con- sists of two lateral halves, which are united vertically in front along the median line by a piece of cartilage, forming what has been improperly called a symphysis. A few months after birth the removal of this cartilage com- mences, and the two halves of the bone become united below; but not unfrequently a fissure remains above for several months. At this period the alveolar border is, like that of the upper jaw, very thick, and contains some large irregular cavities which lodge the first set of teeth. Besides the superior dental foramen there is found in the foetus another, which leads to a temporary canal that supplies the first set of teeth, and behind the alveoli of the incisors may be observed a row of holes which are said to be connected with the de- velopment of the second set of teeth. Some authors maintain that each side of the lower jaw is developed by four separate points of ossification ; but this assertion wants confirma- tion. It is certain that this bone is among those which are the most early developed, and in the embryo of two months it is already of considerable size. Its alveolar border is at first a mere groove, of which the internal margin is defective, and which gradually be- comes hollowed into separate sockets as the teeth are developed. The changes of form which the lower jaw undergoes from birth till old age depend chiefly upon the development and decay of the teeth. Some of these changes have been already noticed, and will be found to correspond with those which occur in the alveolar border of the upper maxilla ; the varying form and direction of the rami and angles of the lower jaw we have noticed, and for the more detailed account of the de- velopment of this bone as connected with dentition, we refer to the article Teeth. Of the face in general. — Dimensions.- — The vertical diameter of the face is the greatest, and extends in front from the nasal eminences of the frontal bone to the lower border of the symphysis menti; this diameter decreases as we trace it backwards. The transverse dia- meter is next in length if measured at the level of the malar bone, where it is most con- siderable ; below and above this it gradually diminishes. The antero-posterior diameter is greatest at the level of the cheek-bones, where it extends from the cuneiform process of the occi- pital bone to the anterior nasal spine of the upper 216 FACE. maxilla ; this diameter also diminishes both above and below, but more especially below, where it comprises merely the thickness of the mental portion of the lower jaw. The bones which form the upper jaw are united with those of the cranium above by a very irregular surface; below they are on a level with the occipital foramen, and hence that part of the face which descends below the cranium is formed exclusively by the lower jaw. The area of the face, as presented by a vertical longitudinal section of the skull, is of a triangular figure, and forms (the lower jaw excepted) in the European about one- fifth of the whole area of the skull ; in the Negro the area of the face increases in propor- tion, and forms two-fifths of the whole. The bones of the face form, when united, a pyramid with four irregular surfaces or regions, and presenting a base above, which is connected with the cranium, an apex below at the chin. The anterior surface or facial region presents many varieties of form and proportion in different individuals, as well as others more important, which characterise the various races of mankind : (see the article Man.) This region is bounded above by the lower border of the frontal bone, extended between its two external angular processes: laterally it is limited by lines drawn from these processes to the anterior inferior angles of the malar bones : below this it follows the curve of the malar ridge of the upper maxilla, and it terminates at the outer * extremity of the base of the lower jaw. This surface presents from above downwards along the median line, the fronto-nasal suture, which is continued laterally into the fronto-maxillary and fronto-ethmoidal sutures, all contributing to form the common transverse facial suture which unites the bones of the cranium and face. Below the fronto-nasal suture the nasal bones, united by the nasal suture, form the prominent arch of the nose in conjunction with the nasal processes of the upper maxillary bones, with which the ossa nasi articulate on each side by the naso-maxillary suture. Below the nasal bones is the anterior orifice of the nasal fossre, of a pyriform shape, narrow above, broad inferiorly, where it terminates in the projecting anterior nasal spine : the margins of this orifice are sharp, and are formed by the nasal and upper maxillary bones. Below the nasal spine is the intermaxillary suture, which terminates on the alveolar border of the upper jaw between the middle incisor teeth : on each side of this suture is the myrtiform fossa. On the lower jaw is observed, in the median line, the mental ridge and process, and on each side of it a depression for muscles. The facial region presents from above down- wards, on each side, the aperture or base of the orbit, of a quadilateral form, and in- clining from within outwards and a little back- wards. The margin of this opening is formed above by the supra-ciliary ridge of the frontal bone, in which is observed the supra-orbitar notch or foramen. At the outer extremity of this ridge is the fronto-jugal suture, uniting the external angular process of the frontal bone with the frontal process of the malar : below this is the prominence of the cheek and the curved orbital' border of the malar bone, forming the outer and lower part of the margin of the orbit. Internal to this we find the short orbitar border of the upper maxillary bone, which presents at its nasal end the groove for the lachrymal sac. Below the inferior border of the orbit is the infra- orbitar foramen, to the outer side of which is the oblique jugo-maxillary suture, and below it the canine fossa, bounded exter- nally by the malar ridge, in front by the canine ridge and the anterior orifice of the nose, and below by the alveolar border of the jaw and by the teeth. On the lower jaw we find the teeth, the alveolar ridges and depressions, the mental foramen, and the ex- ternal oblique line. The posterior or guttural surface consists of three parts, two of which, the upper and lower, are vertical ; the middle is horizontal. The upper vertical portion presents along the median line the oblique posterior border of the vomer, which divides the posterior apertures of the nasal fossae ; above is the articulation formed by the base of the vomer and the sphenoid ; below is the posterior nasal spine formed by the united palate bones. At the sides of the vomer are the oval posterior orifices of the nose, greatest in their vertical diameter, and bounded superiorly by the sphenoid and sphenoidal processes of the palate bones, inferiorly by the palatine plates of the same bones, internally by the vomer, and externally by the pterygoid processes. On the outside of these apertures are placed the pterygoid fossae, formed by the pterygoid plates of the sphenoid and by the pyramidal process of the palate bone. External to these are the large zygomatic fossae or spaces, which belong to the lateral regions of the face. The horizontal portion of this surface is oval, concave, rough, and forms the roof of the mouth, consisting of the palatine plates of the palate and upper maxillary bones, on which is seen a crucial suture, formed by the longitudinal and transverse palatine sutures. At the posterior and outer angles of this hori- zontal portion are situated the posterior palatine canals and the grooves which proceed from them along the roof of the mouth ; on the inferior surface of the palate bones are ridges and depressions for the attachment of muscles, while behind the middle incisor teeth is placed the anterior palatine foramen. At the sides and in front the palatine arch is bounded by the alveolar border and teeth of the upper jaw, behind which descend the pterygoid pro- cesses of the sphenoid and palate bones. The inferior vertical division of this region is formed by the inner surface of the lower jaw and teeth; it presents in front, along the median line, the inner mental ridge, and the genial processes ; external to these the internal oblique lines, the sublingual and submaxillary fossa?, the superior dental foramen, its groove FACE. 217 and process ; the condyles and angles of the jaw, its alveolar border and its base, which terminates it below, and near which, at the chin, are seen the depressions for the digastric muscles. The lateral or zygomatic surfaces on each side are bounded above by the temporal border of the malar bone and by the zygomatic arch ; in front by a line extended vertically from the external angular process of the frontal bone to the base of the lower jaw, and behind and below by the free border of the body and ramus of the inferior maxilla. This region presents a superficial and a deep portion : the former comprises the lateral aspect of the malar bone, the zygomatic arch, and the external surface of the ramus of the jaw. On it we may remark, proceeding from above downwards, the temporal border of the malar bone and zygoma, forming the outer boundary of the temporal fossa; the external malar holes, the zygoma and its suture, which unites the malar and temporal bones; the inferior or masseteric border of the zygoma, the sigmoid notch of the lower jaw and the outer surface of its ramus, coronoid and condyloid processes and angle. The deeper division of this region presents the large zygomatic fossa, and is situated internal to the ramus of the jaw, which forms its outer boundary, and which must be removed to expose it completely : this done, the fossa is brought into view, bounded in front by the posterior surface of the upper jaw and part of the malar bone ; superiorly by the inferior surface of the great wing of the sphe- noid below its temporal ridge ; at this part of the fossa are seen the spheno-temporal suture, the spinous process, and the spinous and oval foramina of the sphenoid bone. The narrow inner boundary is formed by the external ptery- goid plate of the sphenoid; behind and below the fossa is open. At the bottom of the zygo- matic fossa is situated the pterygo-maxillary fissure, forming the external orifice of the spheno-maxillary fossa, which is a cavity situated between the tuberosity of the upper jaw in front, and the pterygoid process and palate bone behind : in this fossa are five holes, viz. three which open into it from behind, the foramen rotundum, the vidian or pterygoid, and the pterygo-palatine ; one opening inter- nally at the upper part ; the spheno-palatine ; one below, the upper orifice of the posterior palatine canal. The zygomatic fossa presents also at its upper and anterior part, the spheno- maxillary fissure, which is directed from within outwards and forwards, and is formed inter- nally by the orbitar processes of the palate and upper maxillary bones, externally by the orbitar plate of the sphenoid, and at its outer extremity, which is large, by the malar bone ; it forms a communication between the orbit and the zygo- matic fossa. Its inner end joins the sphenoidal and the pterygo-maxillary fissures, with the former of which it forms an acute, and with the latter, a right angle: thus these three fissures may be considered as branching from a common centre at the back of the orbit; they give passage to a number of vessels and nerves, and establish communications between the cavi. ties of the face and cranium. The superior or cranial region is very irregu- lar, and is immoveably united to the cranium. It presents along the median line, from before backwards, the articulation of the nasal bone, with the nasal spine of the frontal, the union of this spine with the perpendicular plate of the ethmoid, the articulation of this plate with the vomer, the articulation of the vomer with the sphenoid. Along the sides, from within outwards, are seen the arched roof of the nasal fossae formed in front of the nasal bones, in the middle by the cribriform plate of the ethmoid, and behind by the body of the sphenoid. External to these parts are found the base of the pterygoid process, the articulation of the palate with the body of the sphenoid bone, the pterygo-palatine canal, the spheno-palatine foramen ; next the spongy masses of the ethmoid united behind with the sphenoid, and anteriorly with the os frontis; and still more forwards are seen the articula- tions of this bone with the lachrymal, upper maxillary, and nasal. To the outer side of these articulations is the triangular roof of the orbit, limited externally by the sphenoid and malar bones and by the sphenoidal fissure. Next may be observed the orbitar plates of the sphenoid, forming the greater part of the outer wall of the orbit, and lastly the zygoma. The inner border of the orbitar plate of the frontal bone presents the fronto-lachrymal and the frontal-ethmoidal sutures ; the outer border the spheno-frontal and fronto-jugal sutures. The internal structure of the face appears to be very complex, presenting several cavities and divisions which give it at the same time strength and lightness. The arrangement of these parts may be understood by observing, 1. the perpendicular septum formed by the ethmoid and vomer, which divides the upper part of the face into two equal halves; 2. in each half three horizontal divisions, viz. an upper or frontal, which separates the cranium from the orbit ; a middle or maxillary, placed between the orbit and the cavity of the nose, and an inferior or palatine situated between the nose and mouth; 3. three outer divisions, viz. an upper or spheno-jugal, forming the outer wall of the orbit, and separating that cavity from the temporal fossa ; a middle, formed by the maxillary tuberosity which separates the cavity of the nose from the spheno-maxillary and zygomatic fossae ; an inferior, formed by the ramus of the jaw; 4. above and at the centre the ethmoid and lachrymal bones sepa- rate the orbits from each other and from the cavities of the nose. The principal cavities of the face are the orbits, the nasal fossae, and the mouth ; and with these all the rest are more or less con- nected. These cavities will be described under the several articles, Orbit, Nose, Mouth. Mechanism of the face. — The face forms a structure which combines both strength and lightness ; the former quality is owing to the arched form of its exterior and to the strong pillars of supports (to be presently described) FACE. 218 which connect its different parts to each other and to the cranium. The lightness of the face depends upon the thinness of some of its bones, and the large cavities which it com- prises. The two upper tnaxillary bones form by their alveolar border and palatine arch a strong platform, from which ascend five osseous pillars; one median, formed by the vomer and the perpendicular plate of the ethmoid; two at the sides of the nose, formed by the nasal process of the superior maxilla ; and at the lateral parts of the face two others, formed by the malar processes of the upper jaw and the malar bones. All these pillars connect the upper jaw with the bones of the cranium, and contribute by their form, strength, or extent of articulation to resist or diffuse the concussion of violent blows applied to the face. The strength of the lower jaw depends upon its arched form and upon its mobility, but, from its exposed situation, it is notwithstand- ing frequently broken. Development of the face.- — The development of the face consists not merely in its general increase, but in the relative proportion of its several parts at different periods of life. As the face contains the organs of sight, smell, and taste, together with those of mastication, we shall not expect to find it much deve- loped in the foetus and infant while these parts are scarcely called into action ; accord- ingly, we observe the vertical diameter of the face (strictly so called) to be very short, which is owing to the slight elevation of the ethmoid, the lachrymal, the upper and the lower maxil- lary bones, consequent on the imperfect deve- lopment of the nasal cavities, the maxillary sinuses, and the teeth; see fig. 131. The Fig. 131. orbits, indeed, are remarkably large, but this depends upon the great development of the cranium and the breadth of the orbital' plates of the frontal bones, for in their vertical dia- meters the orbits are not remarkable at this period of life. The transverse diameter of the face in the feetus is considerable across the orbits, but below these it is narrower in proportion than in the adult. The other chief peculiarities of the foetal face are, the small size of the nasal cavi- ties, the absence of the canine fossae, depend- ing partly on the small vertical diameter of the upper jaw, and partly upon the teeth being still lodged within it; the prominence and shortness of the alveolar borders of both jaws, the vertical direction of the symphysis menti, which even inclines from above downwards and a little backwards; the remarkable con- vexity of the maxillary tuberosities, owing to the teeth being lodged within them ; and the great obliquity from above downwards and forwards of the posterior apertures of the nose, arising from the smallness of the maxillary sinuses ; the small antero-posterior diameter of the palatine arch, which depends upon the same cause; and, finally, the oblique direction of the rami of the lower jaw : see fig. 377, vol. i. p. 742. In the adult, as the ethmoid and turbinated bones together with the maxillary sinuses become developed, the nasal cavities enlarge, especially in their vertical diameter; above, they communicate with the frontal sinuses, which are now fully formed and projecting; the jaws have become deeper from the protru- Fig. 132. sion of the teeth, which cause a considerable addition to the vertical diameter of the face; below, the palatine arch has extended back- wards with the development of the maxillary sinuses, and the posterior apertures of the nose have become in consequence nearly vertical : the rami of the lower jaw form also nearly a right angle with its body. In old age the vertical diameter of the face decreases in consequence of the loss of the teeth and the contraction of the alveolar borders of the jaws, which touch each other when the mouth is closed; the rami of the jaw resume the oblique direction of childhood, (fig. 133;) Fig. 133. FACE. and the symphysis inclines from the shrunken alveolar border downwards and forwards to the base of the bone, and gives to the chin the projecting appearance which is So character- istic of this period of life. The articulations of the face comprise those of the upper and that of the lower jaw. The articulations of the bones of the upper jaw with each other and with those of the cra- nium are all of the kind called suture, but they present considerable variety in the extent, form, and adaptation of their articular surfaces. Those bones of the face which contribute to form its columns of support, and to which this part of the head owes its strength and resistance to violence, have their articular surfaces for the most part broad and rough, presenting emi- nences and depressions which are adapted to those of the contiguous bone; examples of this firm articulation are seen, 1. at the anterior part of the intermaxillary suture, where the two palatine plates unite and form the horizontal column or base of the upper jaw; 2. at the nasal columns, where the nasal bones and the nasal processes of the upper maxillae unite with the frontal ; 3. on the sides of the face, or where the bones form their lateral or malar columns, viz. at the jugo-maxillary and jugo- frontal articulations. The spheno-jugal articu- lation, seen within the orbit, and the zygomatic or temporo-jugal, though formed by the union of comparatively narrow surfaces or borders, derive strength from their irregularity, and, in the case of the zygomatic suture, from its in- dented form, which maintains its security from vertical blows, as the curved direction of the zygoma protects it from lateral injury. Those sutures of the face which are, strictly speaking, harmonic, are such as are not exposed to any considerable pressure ; they present, nevertheless, some varieties in their mode of juxta-position. In some the adaptation is direct, as in the pterygo-palatine. In others one border or surface is received by another (schindylesis), as in the articulations of the vomer with the sphenoid above, and with the groove in the palatine plates of the upper max- illary and palate bone inferiorly. Sometimes the surfaces are simply applied against each other, as the nasal plate of the palate bone on the nasal surface of the upper maxillary. Lastly, the edges may alternately overlap each other, as those of the nasal and upper maxillary bones. In all the sutures of the face, whatever may be the adaptation of the osseous surfaces, we find interposed a thin layer of cartilage uniting the contiguous surfaces of the bones. This is easily shown in some of the sutures by mace- ration, and only disappears in places as some of the bones become united with advancing age. The great number of pieces of which the upper jaw consists, and the varying form and direction of the sutures, all contribute, with the figure of the bones themselves, to give strength to this part of the skull, and to break the force of blows by diffusing them over a widely ex- tended surface. 219 The sutures of the face derive their names from the bones which contribute to form them; thus we have between the orbits the fronto- nasal, fronto-maxillary, and fronto-lachrymal sutures, all contributing to form part of the transverse suture. (See Cranium.) Lower down we find the nasal, the naso-maxillary, and the laehrymo-maxillary, which turns at right angles backwards along the inner wall of the orbit into the ethmoido-maxillary and pa- Jato-orbitar sutures. On the outer side of the orbit may be observed the fronto-jugal and spheno-jugal sutures ; on the zygomatic arch the temporo-jugal suture ; and below the pro- minence of the cheek, the jugo-maxillary suture, which is seen both on the anterior and posterior surface of the upper jaw. On the roof of the mouth are seen the longitudinal and the transverse palatine sutures, the former formed by the intermaxillary in front, and by the inter-palatine suture behind : the latter is often termed the transverse or horizontal palato- maxillary suture. There are some other sutures within the nose which it is unnecessary to enu- merate. The lower jaw articulates with the cranium by diarthrosis : this important joint will be particularly described in the article Temporo- MAXILLARY ARTICULATION. The bones of the face are invested with periosteum or a fibrous membrane, which is variously modified and arranged in the orbits, nose and mouth, &e. ABNORMAL CONDITIONS OF THE BONES OF THE FACE. In the true acephalous fcEtus the bones of the face as well as those of the cranium are of course wanting, but the former are generally found in what are termed the false Acephalia (see Abnormal Conditions of the Cranium); it sometimes happens, not- withstanding, that the bones of the face are but imperfectly developed, presenting a variety of conformations which it is unnecessary to parti- cularise. The bones of the face, in some cases alone, and in others in conjunction with those of the cranium, not unfrequently acquire a de- gree of development quite disproportionate with the rest of the skeleton. In Corvisart’s Journal de Medecine the case of a Moor is cited, whose head and face were so enormous that he could not stir abroad without being followed by the populace. It is related that the nose of this man, who was half an idiot, was four inches long, and his mouth so large that he would bite a melon in the proportion that an ordinary per- son would eat an apple. I have now before me the skull of a native of Shields, who was remarkable during life for the length of his face ; the entire head is large, but the bones of the face, and particularly the lower jaw, are enormously long. The abnormal development of the facial bones generally affects one jaw only, and more frequently the lower, as in the example just mentioned. Other cases, but they are much more rare, have been related in which the lower jaw was disproportionately small. When, from either of the circumstances 220 FACE. which have been just mentioned, the develop- ment of the two jaws is unequal, the corre- spondence of their alveolar borders is lost, and mastication becomes in proportion imperfect : in mammiferous animals the unequal size of the lower jaw, by preventing suckling, is often a cause of death. The bones of the face are much more symmetrical than those of the cra- nium, and rarely present the disproportion in their lateral development which is observed in the latter. Under the head of defect or arrest of deve- lopment may be noticed, 1 . the occasional ab- sence of some of the bones, as for example, the lachrymal or the vomer; 2. the existence of fissures, or non-union of the upper maxillary bones, and, as a more rare case, the separation of the two halves of the lower jaw. Fissures of the upper jaw may exist in various degrees, and tnay occur with or without a corresponding cleft in the soft palate and lip ; it may appear as a mere slit along the middle of the roof of the mouth, forming a narrow communication between that cavity and one side of the nose; or it may extend along the whole of the pala- tine arch, and be continuous behind with a similar division of the soft palate, without, at the same time, being accompanied with hare- lip. Sometimes the aperture is very wide, and the palatine plates of the upper maxillary and palate bones are almost entirely wanting ; in this case the vomer and middle cartilage of the nose are also partially or entirely absent ; and there is both hare-lip and cleft of the soft palate, so that the mouth, both sides of the nose, and the pharynx are laid into one great cavity. When the fissure exists at the anterior part of the palate only, it almost invariably occurs at the suture which has been described between the maxillary and intermaxillary bones, so that the cleft separates the canine from the lateral incisor tooth ; when the fissure occurs on both sides of the face, the four incisor teeth are separated from the others and lodged in an alveolar border, which usually in this case projects more or less towards the lip, in which there is also commonly a single or double cleft or hare-lip. Sometimes the fissure occurs in the intermaxillary bone itself between the lateral and middle incisor teeth, and then we find a single incisor on one side and three on the op- posite : it is very rarely that the cleft exists in the median line between the two intermaxillary bones. Among the arrests of development which occur in the bones of the face may be enume- rated a fissure which occasionally extends across the lower border of the orbit, and a suture which' sometimes divides the os jugum into two pieces. The union which not unfrequently takes place between the bones of the upper jaw by the obliteration of their sutures, is commonly the effect of age, and usually occurs between the bones of the nose, between the vomer and sphenoid, and between the inferior turbinated and upper maxillary bones. Wounds and frac- tures of the bones of the face readily unite. Those most subject to these injuries are such as are the most prominent, viz. those of the nose, cheek, and lower jaw ; the last is the most frequently broken. The alveolar pro- cesses and the delicate bones in the orbit and nose are also liable to injury. The bones of the face are subject, like the rest, (though not so commonly as those of the cranium,) to hy- pertrophy and atrophy. Exostosis appears most frequently on the upper jaw, in the orbit, or along the alveolar border on the outer surface of the bones ; on the lower jaw it is situated usually along the alveolar border, at the angle or on the body of the bone. Inflammation of the periosteum and bones of the face occurs spontaneously or as the result of injuries or disease, and presents the usual phenomena. Abscesses also take place either within the cancellous structure of the more solid bones, or in the cavities which they contain ; when matter forms within the antrum, it may be evacuated by extracting the canine or the large molar tooth, which often projects into this ca- vity, and then piercing through the bottom of their sockets. When necrosis affects the bones of the face, its ravages are seldom repaired (as in the case of cylindrical bones) by the pro- duction of new osseous matter ; some attempts at reparation after the separation of a seques- trum have been, however, observed in the lower jaw. Caries, either simple or connected with syphilitic or strumous disease, may attack nearly all the bones of the face, but it more particularly affects the alveolar borders of the jaws and the delicate bones about the nose and palate ; it is often attended with partial ne- crosis. Caries of the face may occur as the re- sult of malignant ulcerations, of lupus, or of the various forms of cancer which affect the soft parts. Both the upper and lower jaw are sub- ject to osteo-sarcoma, commencing either on the surface or in the interior of the bones, and ac- quiring sometimes an enormous size, so as to encroach on the orbit, nose, and mouth, and materially to impede the motions of the lower jaw. For these growths and others more sim- ple, of a fibrous or Jibro-cartilaginous structure, large portions (sometimes amounting to nearly the whole) of the upper or lower jaw have been removed with success. Cyst-like tumours, con- taining a serous fluid, have been found in the lower jaw. The more intractable diseases of medullary sarcoma and J'ungous growths of va- rious kinds also- attack the bones of the face. A few cases of hydatids (the acephalo-cystus) have been met with in the upper jaw. THE MUSCLES OF THE FACE are arranged around the orifices of the eyelids, the nose, and the mouth, and may be divided into constrictors and dilators of these apertures. The nostrils, however, undergo but little vari- ation in their dimensions, being maintained permanently open by the elastic cartilages which form them. The eyelids also contain elastic cartilages, which are moulded upon the front of the globe over which they glide in obedience to the muscles which dilate or con- tract the orifice between them. The mouth, which is the most mobile of the facial aper- FACE. ‘221 tures, is also furnished with its contractor or sphincter muscle, and with many dilators which radiate from it at various angles. All the muscles of the face are superficially situated, and most of them are subcutaneous. In the palpebral regions, or about the eye- lids on each side, are placed, 1 . a constrictor, or the orbicularis palpebrarum, of which the corrugator supercilii is an associate; 2. the levator pulpebrte and the occipitofrontalis, which are dilators, and antagonists of the two former muscles. The orbicularis palpebrarum, ( naso-palpebrul, Chauss.) is a flat oval muscle, situated im- mediately underneath the skin, to which it adheres, and covering the base of the orbit and the superficial surface of the eyelids ; in the middle it presents a transverse aperture, which is the orifice of the palpebrse, varying in size according to the individual, and giving apparently a greater or less magnitude to the globe itself, which, however, is of nearly uni- form dimensions in different persons. The orbicularis, like the other sphincter muscles, consists of concentric fibres, but it is peculiar in having a fixed tendon on one side, from which a great part of the fibres arise; this tendon of the orbicularis, or ligamentum pal- pebrse, which is situated horizontally at the inner corner of the eye, is about two and a half lines in length, and half a line in breadth; it arises from the anterior border of the lachry- mal groove in the nasal process of the upper maxillary bone, and passing horizontally out- wards in front of the lachrymal sac, divides into a superior and an inferior slip, which are attached to the inner extremities of the corres- ponding eyelids. The tendon at first is flat- tened anteriorly and posteriorly, but afterwards becomes twisted so as to present horizontal surfaces. From its posterior part is detached a slip of fibres (the reflected tendon of the orbicularis), which proceeds backwards to- wards the os unguis, and forms the outer wall of the lachrymal canal. The orbicularis arises, 1. from the borders and surfaces of this tendon and from its reflected slip; 2. from the internal angular process of the frontal bone and from the fronto- maxillary suture ; 3. from the nasal process of the upper maxillary bone ; and, 4. by short tendinous slips from the inner third of the lower border of the orbit. From these origins the upper and lower fibres of the muscle take a curved direction outwards, their concavity look- ing towards the aperture of the lids, and fol- lowing the course of the upper and lower borders of the orbit, which they overlap. They unite at the outer side ; not, however, by a tendinous raphe or septum, as some have described, but simply by the mingling of their fibres. Each half (the upper and lower) of the orbicularis consists really of two sets of fibres ; one, which covers the margins of the orbits, and forms the circumference of the muscles, is strong, tense, and of the usual reddish colour ; it arises from the direct ten- don, and from the frontal or upper maxillary bone. These form the orbicularis properly so called. The other set, which is pale and thin, covers the lids and proceeds almost in a hori- zontal direction outwards from the palpebral bifurcation of the orbicular tendon : this forms the ciliary or palpebrales. These two sets of fibres, as we shall presently see, are distin- guished as much by their functions as by their appearance. Relations. — The superficial surface of that part of the muscle which covers the lids (the palpebrales) is connected to the skin bv delicate loose cellular tissue entirely destitute of fat. The stronger fibres which form the outer part of the muscles are closely adherent to the integument by cellular tissue more densely woven, and presenting more or less fat. The posterior surface covers, above, the lower part of the frontalis and the corrugator supercilii, with whose fibres it is connected ; internally the corresponding part of the fibro- cartilages of the lids, the lachrymal sac, and the inner border of the orbit externally, the outer border of the orbit and part of the tem- poral fascia inferiorlv, the upper part of the malar bone, the origins of the levator labii superioris proprius, the part of the levator labii superioris alseque nasi, and the inferior border of the orbit. At its circumference this muscle corresponds, by its upper half, to the frontal, which it slightly overlaps, and inter- nally to the border of the pyramidalis, with which it is connected; externally it is free. Below its border is free, covering the origin, and giving some fibres to the lesser zygomatic ; and internally it is separated from the levator labii superioris ateque nasi by cellular tissue, in which runs the facial vein. The central fibres cover the palpebral fascia and the lids, which separate them from the conjunctiva. Action. — The action of this muscle resem- bles that of other sphincters, the curved fibres in contraction approaching the centre; but as in the orbicularis palpebrarum these fibres are fixed at the inner side, it follows that the skin to which the muscle is attached by its anterior surface is drawn towards the nose, and when the muscle is in strong action, becomes cor- rugated, presenting folds which converge to- wards the inuer angle of the eye; above, where the effect of the muscle on the skin is most marked in consequence of its closer connec- tion with the integuments, the brow and the skin of the forehead are drawn down by it and its associate the corrugator; the lower fibres when in strong action, draw the cheeks upwards and inwards. Like the other sphinc- ters, also, this is a mixed muscle. Those fibres which may be supposed to be voluntary, are the larger and outer ones, which corres- pond to the border of the orbit, and are of a red colour. The involuntary fibres are those thin ones which cover the lids, are of a pale colour, like the muscles of organic life, and arise from the palpebral subdivisions of the horizontal tendon. They contract involuntarily while we are awake, in the action of winking, and during sleep in maintaining the lids closed; they also act under the will in closing the lids, particularly the upper. It appears then 222 FACE. that the orbicularis may be divided both ana- tomically and physiologically into two sets of fibres; an outer, or orbicularis proper, which is entirely a voluntary muscle, and an inner (the palpebralis) which is both voluntary and involuntary in its action. These fibres may act independently of each other, for in wink- ing and during sleep the palpebralis contracts, while the orbicularis is quiescent ; and the orbicularis may contract even strongly, as when we peer with the eyes under the influence of a strong light, while the fibres of the pal- pebrales are relaxed. It has been supposed, however, by some, that during sleep the lid is closed simply by the weight of the upper palpebra, and the relaxation of its proper elevator muscle, but this seems in contra- diction to the fact that we meet with resistance in endeavouring to unclose the lids of a sleep- ing person. Corrugator supercilii, which is the associate of the orbicularis palpebrarum, has been al- ready described, together with the occipito- frontalis, which is the antagonist of those muscles. See Cranium, muscles of the, vol. i. p. 747. Levator palpebra superior is ( orbito-palpe - bral ), though situated within the orbit, is nevertheless the direct antagonist of the palbe- bralis, and is therefore properly described with these muscles of the face. It iS a thin trian- gular muscle, which arises by a narrow slen- der tendon at the back of the orbit from the inferior surface of the lesser wing of the sphe- noid bone, above and in front of the optic foramen ; from this origin the fibres proceed almost horizontally forwards under the roof of the orbit, and gradually spreading and be- coming thinner as they advance, curve over the globe of the eye, and are inserted into the upper border and anterior surface of the upper lid. Relations. — Its upper surface is in contact, behind, with the frontal branch of the ophthal- mic nerve, which with some cellular tissue alone separates it from the periosteum of the roof of the orbit; anteriorly with cellular tissue and the palpebral fascia, which separate it from the orbicularis. The lower surface behind rests upon the superior rectus oculi, with which it is connected by cellular tissue, and anteriorly on the conjunctiva and upper lid. Its action is to raise the upper lid, and to draw it backwards over the globe and under the supra-ciliary ridge. There is no separate muscle to effect the depression of the lower lid, that action being occasioned, as Sir C. Bell ingeniously suggested, by the protrusion of the eyeball. Nasal region. — The muscles of this region, some of which are common to the upper lip, are, 1. the pyramidalis ; 2. the levator labii super ioris alaque nasi; 3. the triangularis nasi; 4. the depressor alee nasi. Pyramidalis is situated between the brows, and may be considered as a prolongation of the inner fibres of the frontalis : it is of a triangular form ; its base above is continuous with the fibres of the frontalis; below it con- tracts and is inserted into the aponeurotic ex- pansion of the triangularis nasi. It is sepa- rated from its fellow slip of the opposite side by a groove of cellular tissue. Relations. — Its superficial surface adheres to the skin; its deep one rests on the nasal eminence of the frontal bone, the nasal bones, and part of the lateral cartilage of the nose. Use. — If this muscle acts at all on the nose, it is by drawing up the skin when the occipito- frontalis is in action. Its more probable use is to give a fixed point to the frontalis, and to draw down the inner extremity of the brows and the skin between them. Levator labii superioris alaque nasi. — (l', fig. 134.) This is a thin, long, triangular Fig. 134. muscle, placed nearly vertically on each side of the nose. It arises narrow from the outer surface of the nasal process of the upper max- illary bone, immediately beneath the tendon of the orbicularis palpebrarum. It descends obliquely outwards, becoming broader, and terminates inferiorly by two slips, an internal short one, which is attached to the cartilage of the ala nasi, or to the fibrous membrane which invests it ; and an outer longer slip, which is attached to the skin of the upper lip near the nose, and mingles its fibres with the transversalis nasi, the levator labii superioris proprius, and the orbicularis oris. Relations. — Covered by the skin, and over- lapped a little above by the orbicularis pal- pebrarum, this muscle covers the nasal process of the upper maxillary bone, the triangularis nasi, and the depressor alae nasi. Its inner border above corresponds to the pyramidalis. Its action is to raise the ala of the nose and the adjacent part of the upper lip; in so doing it dilates also the nostril and becomes a muscle of inspiration. When strongly thrown into action, it corrugates the skin of the nose trans- versely. FACE. 223 Triangularis nasi ( transversalis nasi, com- pressor nuris, Albin.) (n, jig. 134), is a very thin triangular muscle, placed transversely on the middle of the side of the nose. To expose its origin, the levators of the upper lip must be turned aside, and the skin of the nose very carefully dissected off. Its origin is then seen as a narrow slip from the inner part of the canine fossa, below the ala nasi ; from this point the fibres radiate inwards and upwards, and expand into a very thin aponeurosis, which crosses the ala nasi and the lateral car- tilage of the nose to be confounded along the median line with that of the opposite muscle, and with the pyramidalis. Bourgery describes two other origins, one superficial, attached to the skin below and to the outside of the ala nasi, and a middle one crossing and connected with the fibres of the levator of the upper lip. Relations. — It is covered at its origin by the levator labii superioris alaeque nasi, and inter- nally by the integuments to which it super- ficially adheres ; it rests on part of the upper jaw, on the cartilages of the ala, and on the lateral cartilage. Its action is yet undetermined by anato- mists, some considering it a compressor or constrictor of the nose, others as a dilator or elevator. Cruveilhier thinks that its action varies with the form of the ala, which, when convex, makes it a compressor, when concave a dilator. Perhaps, as M. Bourgery suggests, its action depends upon which extremity is fixed, and that, when its base is fixed, its superficial fibres dilate the nostrils and draw the lip upwards and inwards, and that, when the muscle acts towards its maxillary attach- ment, it compresses the nostril. Depressor ala riasi ( musculus myrtiformis ), (jig. 134.) To expose this muscle the upper lip should be reversed, and the mucous mem- brane divided on each side of the fraenum labii. It is a short flat muscle, radiating upwards from the myrtiform fossa of the upper jaw, where it arises towards the ala of the nose, into the posterior part of which it is inserted below and internal to the dilator nasi. This muscle really consists of two sets of fibres, one which has been just described, the other which is in front of this and is attached above to the ala and septum of the nose, below to the inner surface of the orbicular fibres. The first set, or the naso-maxillary fibres, are de- pressors of the alae and contractors of the nostrils; the second, or naso-labial fibres, are elevators of the upper lip. Relations. — It is covered by the mucous membrane of the upper lip, by the orbicularis oris, and by the levator labii superioris alreque nasi; it covers the myrtiform fossa of the upper jaw : its inner border is separated from its fellow by the fraenum. A dilator ala nasi is described by Bourgery as a little triangular muscle, consisting of fibres placed underneath the skin lying on the outside of the ala nasi, from the posterior part of whose cartilages the fibres arise by a narrow point, and then radiate upwards, outwards, Fig. 135. and downwards, to be mingled with the fibres of the elevators of the lip, the orbicularis, and the naso-labial, all being attached to the skin. This muscle, according to Bourgery, directly draws the ala outwards, and is consequently a dilator of the nostril. The labial region presents in the centre, 1 . a sphincter (the orbicularis oris), with which are associated two muscles on each side, the depressor labii superioris and the levator labii inferioris: all these are contractors or com- pressors of the lips : 2. a number of anta- gonist muscles or dilators, which comprise many muscles, which on each side radiate from the lips, or from their commissure at different angles. They are, above, the levator labii superioris proprius and the zygomaticus minor; below, the depressor labii inferioris at the commissure, the buccinator, the levator anguli oris, and the depressor anguli oris. By some anatomists the muscles of this region of the face are divided into, 1. the sphincter, and, 2. the elevators and depressors of the lips. Orbicularis or sphincter oris (labial, Chauss. and Dum.) (o o, jig. 134) is a thick oval muscle, placed transversely around the aper- ture of the mouth, which varies in size in dif- ferent persons, but bears no relation to the size of the buccal cavity. It extends above from the free border of the upper lip to the nostrils, and inferiorly from the free border of the lower lip to the depression above the chin. Its fibres, arranged in successive layers, consist of two semi-elliptical halves, one superior, the other inferior, which are on each side united externally to the commissure of the lips by decussating each other, and mingle also at their circumference with the dilators which are attached to it. These fibres are concentric, with their curve towards the lips ; the most central run nearly in a horizontal direction along the borders of the lips, and take a di- rection forwards, which gives the prominence to the lips which is so remarkable in the Negro. The outer fibres are more curved, and receive between their layers the extensors of the lips, which are attached around them. This is the only muscle of the face which has no attachment to bone. Relations. — The anterior surface is closely FACE. 224 connected with the thick skin which covers it. The posterior surface and free border is covered with the mucous membrane of the mouth, from which it is only separated in places by the labial glands, by the coronary vessels, and by numerous nerves. Its outer border or circum- ference receives the antagonist muscles which are attached around it. Actions.- — The orbicularis enjoys a very va- ried and extensive motion, and possesses the remarkable power of either acting as a whole or in parts. Its simple use is to close the mouth, in correspondence with the elevation of the lower jaw, by bringing the red borders of the lips in contact, or by pressing them to- gether firmly. But the upper or lower labial fibres can act separately, or the fibres at either commissure, or the fibres of one side may con- tract, while the others are quiescent, so that different parts of the lips may be moved by different portions of the muscle, which is made in this way to antagonize in turn the different muscles which are attached around. The lips may be thrown forward by the con- traction of the labial and commissural fibres forming in strong action a circular projection, as in the action of whistling, or, when more relaxed, in blowing. By the contraction of the inner labial fibres the lips may, on the contrary, be turned inwards so as to cover the teeth. The play of the mouth, however, which contributes in so eminent a degree to the expression of the face, depends not only on the orbicularis, but upon its association with the different muscles which are attached around it. Naso-labiulis is a small subcutaneous slip of fibres, only distinctly seen in strong muscular lips. It is situated on each side of the median depression of the upper lip, and arises from the lower septum of the nose at the back part of the nostril ; it proceeds downwards and out- wards, and is soon lost in the fibres of the or- bicularis. It is an elevator of the middle part of the upper lip, and is considered by some as an attachment of the orbicularis. Levator labii superioris (l'} Jig. 134) is a thin, flat, quadrilateral muscle, situated about the middle of the face, and nearly on the same plane with the levator labii superioris ateque nasi. It arises from the malar and upper maxillary bones where they form three-fourths of the lower border of the orbit, by short ten- dinous slips ; from this origin the fibres, con- verging a little, take a direction downwards and inwards, and are inserted partly super- ficially into the skin of the upper lip, and partly into the fibres of the orbicularis, between the insertion of the levator labii superioris ateque nasi and the lesser zygomatic, with which its fibres are partly covered and con- founded. Relations. — Its anterior surface is covered above by the orbicularis palpebrarum, below by the skin and by the muscles with which its fibres are mingled at its insertion. Its posterior surface covers the infra-orbitar vessels and nerves at their exit from the infra-orbitar fo- ramen, which, with some fat and cellular tissue, separates it from the upper part of the levator anguli oris. It covers also part of the trian- gularis nasi. Its action is to raise and draw a little out- wards the upper lip. Zygomatic us minor (3', Jig. 134) is a narrow rounded muscle, often wanting It arises from the external surface of the os mate, and fre- quently also from the deep fibres of the orbicu- laris palpebrarum, by which its origin is co- vered ; it proceeds downwards and inwards, and is attached to the skin and orbicularis pal- pebrarum above the commissure of the lips, where its fibres are also confounded with those of the levator labii superioris proprius. Relations — This muscle is covered in front by the orbicularis palpebrarum and skin ; its posterior surface conceals a part of the levator anguli oris and of the labial vein. Action. — It is an associate of the levator labii superioris, and contributes to raise the upper lip and draw it a little outwards. Zygomaticus major (3, Jig. 134), placed to the outer side and a little below the preceding muscle, is of a rounded form, and arises by short tendinous slips from a depression on the posterior part of the outer surface of the os mate, near its lower border. Its fibres proceed downwards and inwards, nearly parallel with those of the lesser zygomatic, but much longer; and expanding a little below, they become con- founded with the fibres of the orbicularis oris at their commissure, and with those of the levator labii superioris, levator anguli oris, and depiessor anguli oris. Its superficial fibres are attached to the skin. Relations. — This muscle is surrounded by fat, which separates it from the skin. By its deep surface it rests above on the os mate' and the masseter; below, it is separated by fat from the buccinator and the levator labii supe- rioris : it crosses also the labial vein. Its action carries the commissure of the lips upwards and outwards, and is intermediate between the action of the levator and the buc- cinator: it is the antagonist of the levator an- guli oris in drawing the lip outwards; its associate in raising it. When both these mus- cles act, the commissure of the lips is directly raised. Levator anguli oris ( musculus caninus ): (r, Jig. 136). — To expose this, the levator labii superioris must be removed. It is a flat qua- drilateral muscle, which arises from the middle of the canine fossa of the upper jaw, and be- coming somewhat narrower takes a direction downwards and a little outwards and forwards, to terminate at the commissure of the bps, where its fibres mingle with those of the orbi- cularis, the buccinator, and the depressor anguli oris. Relations. — Deeply placed above, its ante- rior surface is covered by the infra-orbitar ves- sels and nerves, and by fat, which separate it from the levator labii superioris and the lesser zygomatic. Below it is covered by the zygo- maticus major and the integument. The pos- terior surface of this muscle rests on the upper FACE. 225 maxillary bone, on the mucous membrane of the mouth, and on the buccinator. Its action is to raise the commissure of the lips, and draw it a little inwards. Its action when as- sociated with that of the zygomatics has been already explained. Depressor anguli oris ( triangularis oris ) (t, Jig. 134) is a thin, triangular, subcutaneous muscle, situated at the lower part of the face. It arises by a broad base from the lower border of the inferior maxilla, and from the surface of the bone between this border and the external oblique line, extending from the chin to within half an inch of the masseter. The fibres con- verge and ascend towards the commissure of the lips, the posterior fibres taking a direction upwards and forwards, the middle nearly ver- tical, and the anterior describing a curve up- wards and backwards: they all terminate at the commissure of the lips, where they become united with those of the orbicularis and of the buccinator, and more superficially with the great zygomatic and levator anguli oris. Relations.- — Its superficial surface is covered by the skin and by the fibres of the platysma, with which it is mingled. Its deep surface rests upon part of the depressor labii inferioris and buccinator: above it is connected with all the muscles of the commissure and with the skin. Action. — This muscle draws down the angle of the mouth, and in this respect is the anta- gonist of the great zygomatic and levator an- guli oris. Depressor labii inferioris (quadratus menti ), ( d, Jig. 136, 137) flat and of a square form, is placed internal to the preceding, which partly conceals it. It arises from the inner half of the external oblique line of the lower jaw, and also from the platysma, with whose fibres it is continuous. Its fibres, which are parallel, pro- ceed upwards and inwards to be attached to the lip ; the deep fibres mingle with those of the orbicularis; the superficial pass in front of that muscle, and are fixed in the skin of the lip. The inner fibres decussate above with those of the muscle on the opposite side; below, with those of the levator menti. Fig. 136. VOL. II. Relations. — At its origin this muscle is co- vered by the triangularis, and elsewhere by the skin, to which it adheres intimately above. Its deep surface covers part of the lower jaw, the mental vessels and nerves, part of the orbicu- laris oris and levator menti. Through the an- gular interval between the two depressors of the lower lip, the levatores menti pass to their insertion. Its action is to draw downwards and out- wards one side of the lower lip; if the muscles on both sides act, the lip is drawn downwards and extended transversely. The stronger ac- tions of this muscle are usually accompanied by those of the platysma, with whose fibres, as we have seen, it is continuous. Levator menti ( houppe du menton) ( e, fig. 136,137) may be exposed by everting the lip and dividing the mucous membrane : it is a small round muscle, situated at the lower part of the face, and forming on each side a great part of the prominence of the chin. It arises in the incisive fossa below the incisor teeth of the lower jaw, external to the symphysis, and pro- ceeds downwards and forwards: it passes under the lower border of the orbicularis oris, and emerging between the depressor labii inferioris, expands a little to be inserted into the skin of the chin. Its fibres below are mingled with fat ; internally they are confounded with those of the fellow muscle, and externally with the fibres of the quadratus menti. In its action this muscle raises and corru- gates the chin, and by so doing raises also the lower lip and throws it forward. Fig. 137. Buccinator ( b,Jig . 136, 137). This muscle is situated on the side of the cheek, and to ex- pose it completely it is necessary to divide the muscles attached to the angle of the mouth, and to remove the ramus of the jaw and the muscle attached to it. The buccinator is a broad flat muscle, and arises, 1. behind and in the middle from an aponeurotic line, the pterygo-maxillary ligament or inter-maxillary ligament, which is common to it and the su- perior constrictor of the pharynx, and which is Q 22G FACE. extended between the lower extremity of the internal pterygoid plate of the sphenoid bone and the posterior extremity of the internal ob- lique line of the lower. Above, the buccinator arises, 2. from the outer surface of the upper alveolar process, between the first malar tooth and the tuberosity ; 3. below from the outer side of the alveolar border opposite the three last malar teeth. From these three origins the fibres proceed forwards, the superior curving a little downwards, the inferior upwards, and the middle passing horizontally towards the angle of the mouth, where they mingle with the fibres of the orbicularis and the elevators and depressors of the commissure. The infe- rior and superior fibres become shorter as we trace them forwards, and some of them decus- sate at the angle of the mouth to unite with the opposite labial half of the orbicularis. The fibres of the buccinator are wavy, over- lapping each other, so that they admit of great distention, which is, however, limited by a buccal fascia, which is given off from the pterygo-maxillary ligament. Relations. — The buccinator is deeply situated behind, where it is covered by the ramus of the jaw and the edge of the masseter, from which it is separated by a quantity of fat, which projects beyond the mass, fills up the hollow in front of the masseter, and is always found even in thin subjects. In the middle it corresponds to the buccal vessels and nerves and to the transverse facial artery, which runs nearly parallel to its fibres, and to the duct of the parotid gland, which, resting at first upon its fibres, pierces them opposite the second molar tooth of the upper jaw, and opens obliquely into the mouth. A buccal fascia covers the posterior half of the muscle. At the commissure the buccinator is covered by the muscles which are attached to the angle of the mouth, and is crossed at right angles by the external maxillary artery and vein. By its internal surface this muscle covers the mucous membrane of the mouth, from which it is only separated by a layer of buccal glands. Action. — This muscle, being fixed behind, above, and below, acts principally in front on the commissure of the lips, which it draws horizontally backwards, elongating the aperture of the mouth transversely, and throwing the cheek into the vertical folds which are so re- markable in old age. In this respect it is the direct antagonist of the orbicularis oris : if both these muscles act together, the lips are extended and pressed against the teeth. When the cavity of the mouth is distended with air or liquids, this muscle is protruded at the cheeks, and its fibres become separated and curved. If now the muscle acts, the fibres become straightened, and the fluid is expelled from the mouth either abruptly or gradually according to the resistance of the orbicularis. This action of the orbicularis is exemplified either in spirting fluids from the mouth, or in playing on wind instruments. In mastica- tion the buccinator presses the food from between the cheek and gums into the cavity of the mouth. It assists also in deglutition when the mouth is closed, by pressing the food backwards towards the pharynx. Among the muscles of the face, it is ne- cessary to allude to some parts of the platysma, which are not only seen in this region, but which contribute materially to the motion and expression of the face. The platysma (p,p,p, fig. 138) is a large, broad, membranous layer of fibres, which extend from the upper and an- terior part of the chest, where they commence in the subcutaneous tissue, upwards over the anterior and lateral part of the neck, to the jaw and lower part of the face, where they are inserted above. The whole superficial surface of the muscle is subcutaneous, but less firmly attached to the integument just under the jaw than elsewhere. The under surface of its cervical portion is in relation with numerous important parts on the face: it covers from before backwards the lower part of the chin, the quadralus menti, the triangularis oris, the base of the lower jaw, the facial vessels, and part of the masseter. The arrangement of its facial portion is all that need be described here. Fig. 138. As the fibres of the muscle incline upwards towards the median line, they meet below the symphysis of the chin, and some ascend as high as the levator menti. Externally the fibres seem to split to enclose the depressor anguli oris, and to proceed upwards and for- wards with that muscle and the quadratus menti to the lower lip and its angle. The middle fibres are attached to the base of the jaw, and posteriorly they mount over the FACE. angle, and are lost on the fascia of the masseter. A curious slip crosses these transversely, de- scending a little from the fascia covering the parotid gland towards the angle of the mouth. It is the risorius Santorini, which is, however, often wanting. The platysma draws down the whole of the lower part of the face, or, acting more slightly, depresses the lower lip and the commissure in conjunction with their proper depressors. The slip called risorius, on the contrary, raises the angle of the mouth. The only fasene of the face are, 1. a pal- pebral fascia, which connects the convex edges of the tarsal cartilages to the border of the orbit; and, 2. a buccal fascia, which, ex- tending forward from the intermaxillary liga- ment, covers the posterior half of the buccinator muscle : anterior to this it becomes lost in the surrounding cellular tissue. General review of the muscles of the face. — With one exception, all the muscles of the face are attached at one part to bone, and at another either to the skin or to some other muscle : their fibres are also red and firm at their fixed attachment, pale and thinner at their moveable extremity. With the exception of the orbicularis oris, which is a symmetrical muscle, all the others are arranged in pairs, one on each side of the face. The mouth being the most moveable, has by far the greatest number grouped around it. It pos- sesses, 1. a sphincter, the orbicularis oris, the important action of which on the lips in suction, respiration, whistling, blowing, and playing on wind instruments, in speech and in expression, has already been partly spoken of. The associate of this muscle is the levator menti. 2. The antagonist of this are, a, the naso-labialis, the transversalis nasi, the levator labii superioris, both proper and common to it and the nose, and which raise the upper lip ; b, the depressor labii inferioris and pla- tysma, which draw down the lower lip ; c, the buccinator, which extends the aperture of the mouth transversely ; d, the zygomatics, the risorius Santorini, and the levator anguli oris, which draw the commissure upwards ; and, e, the depressor anguli oris and platysma, which draw it downwards. About the eyes there are on each side, 1. a sphincter, the orbicularis palpebrae and pal- pebralis, with the associate, the corrugator supercilii; 2, the dilators, the occipato- frontalis and levator palpebrae. About the nose there are, 1, a constrictor, the depressor alse nasi; 2. the dilators, levator labii superioris ateque nasi and the dilator nasi; 3. the triangularis nasi, which probably both dilates and contracts the orifice of the nostrils according to the attachment, which is fixed. The muscles of the face, including the pyramidalis, the levator palpebrte, the naso- labialis, and the dilator ate nasi, are sixteen pairs in number; if we add the occipito- frontalis, the corrugator supercilii, and the platysma, nineteen pairs, and one symmetrical, the orbicularis oris. Of these, four pairs belong to the eye, three pairs to the nose, ten pairs and one single one to the mouth : two 227 pairs are common to the mouth and the nose. The use of the muscles of the face with respect to expression is a subject of so much interest, and involves so many collateral facts, that it will be better considered under the separate article Physiognomy. It will be sufficient to observe here that the muscles which express lively feeling and the gay passions, such as the occipito-frontalis, the levator pal- pebrarum, the levators and dilators of the lips and their commissure, do for the most part either raise or draw the parts from the median line; and that those muscles which manifest the sadder feelings and the darker passions, as the corrugator supercilii, the pyramidalis, the levator menti, the depressors of the lower lip and its commissure, either depress the parts or draw them from the median line. The constant and habitual exercise of either of these sets of muscles leaves corresponding permanent folds in the skin, which are in- dicative of the habitual feelings and passions of the individual. The integuments of the face. — The skin of the face is, with the exception of some parts, remarkable for its tenuity, for its abundant supply of vessels, nerves, and follicles ; for the growth of hair, which covers some parts of it; and for its attachment to the subjacent muscles. The vascularity of the skin in some parts is even beautiful, tinting the cheek and lips, as in the act of blushing, assisting in the expression of the feelings and passions. The subcutaneous cellular tissue is, in general, very dense in this region, and is mingled with more or less fat, except on the eyelids, where it is loose, delicate, and quite destitute of adipose tissue. Generally speaking, the skin of the face is more adherent, and the subjacent cel- lular tissue is more dense and less fatty, along the median line than at the lateral parts ; the nose and lips offer examples of this fact. At the sides the cellular tissue is looser below, near the base of the jaw, than higher up on the cheeks. Most of the muscles are more or less surrounded with fat, which, however, par- ticularly abounds on the cheeks and between the masseter and buccinator muscles. Vessels of the face. — The arteries are de- rived chiefly from the external carotid, viz. 1 . the external maxillary or the facial artery, and its branches; 2. branches from the tem- poral, particularly the transverse facial artery ; 3. branches from the internal maxillary, more particularly the infra-orbitar, the buccal, and the superior and inferior dental arteries ; 4. some arteries which emerge from the orbit and are derived from the ophthalmic branch of the internal carotid. These vessels communicate very freely with each other, and form with their accompanying veins an intricate vascular network over the face. See Carotid Ar- tery/’ The veins are principally branches of the external jugular, viz. 1. the facial vein with its branches, which correspond generally to the trunk and branches of the facial artery, except that the facial vein is rather more superficial Q 2 228 FACE. and further from the median line than the artery; 2. the transverse facial vein and some other small branches of the temporal; 3. veins corresponding to the branches of the internal maxillary artery already mentioned ; and, lastly, some veins about the nose and brow, which are connected with the ophthalmic vein within the orbit. Both arteries and veins are imbedded in the adipose tissue, and are often remarkably tortuous, more especially the ar- teries, in old persons. Their trunks and branches open in a direction towards the me- dian line, particularly at the upper part of the face. The lymphatics are much more numerous than those of the cranium, and follow prin- cipally the course of the bloodvessels, and terminate in the submaxillary and parotid lym- phatic ganglions ; in their course they traverse some ganglions, which are situated on the buc- cinator. The superficial lymphatics arise from all parts of the face, and, accompanying the su- perficial vessels, end in the submaxillary gan- glions; some of them traverse the smaller buccal ganglions. The deep lymphatics are situated in the zy- gomatic and pterygo-maxillary fossae ; they also accompany the bloodvessels, and ter- minate in the deep parotid and submaxillary ganglions. The lymphatic ganglions of the face are prin- cipally situated along the base of the jaw, and are termed the submaxillary ganglions. Others are placed on the jaw and buccinator, in front of the masseter (the buccal ganglions), and follow the facial vessels. Some lymphatic ganglions are situated underneath the zygoma (the zygomatic ganglions) ; and others, more numerous, are placed upon, within, or under- neath the parotid gland, and are termed the parotid ganglions. The deep lymphatics of the orbits, nose, and mouth, will be described with those cavities. The nerves (f the face are derived from the three divisions of the fifth and from the portio dura of the seventh cerebral nerves. The branches from the fifth emerge on the face, 1 . from the orbit ; these come from the oph- thalmic or first division of the fifth, and are the frontal, the supra-trochlear, the infra- trochlear, and the lachrymal : 2. from the infra-orbitar foramen escape the infra-orbitar nerve, from the second division of the fifth or superior maxillary, and from the same source, emerging from underneath the ramus of the jaw, the buccal nerves : 3. from the mental foramen emerge branches of the inferior den- tal nerve, derived from the third division of the fifth or the inferior maxillary ; and from the same source, piercing the masseter, the masseteric nerves. The portio dura, after turn- ing over the posterior border of the lower jaw, forms a plexus (the pes anserinus) within the parotid gland, and divides into a great num- ber of branches, which are distributed on the face, and which have received various names corresponding to the regions where they run. The branches of the fifth nerve which are dis- tributed to the face principally supply the in- teguments, and those of the portio dura the muscles. Some filaments, however, of the fifth, such as the buccal branch, derived from the ganglionous portion, supply muscles ; and, on the other hand, some cutaneous twigs are sent from the portio dura of the seventh to the commissure of the lips. Both nerves freely anastomose with each other on the face. For a more particular account of these nerves and of their functions, see Fifth pair of Nerves, Seventh pair of Cerebral Nerves, and Physiognomy. Abnormal conditions of the soft parts of the face. — The muscles of the face offer nothing very remarkable in their abnormal conditions ; like others, they become much developed by constant exercise, and on the other hand, when paralytic, they waste and lose both their colour and consistence; their fibres have been ob- served occasionally to have degenerated into a fatty substance, and the trichina spiralis has also been found among them as among those of other voluntary muscles. The bloodvessels of the face are subject to no anomalies in their course which call for notice in this place. It may be remarked, however, that they vary in size in different individuals, and are sometimes superficially and sometimes more deeply situated among the soft parts around ; their tortuosity in old age has already been adverted to. Vascular navi are not unfrequently found on the face, in some cases deeply situated within the cavities or underneath the bones; in others, and more commonly, they lie superficially in the skin and subcutaneous tissues. They occur of the venous, arterial, or mixed kinds. The first sometimes attain a considerable magni- tude, as I have witnessed in the case of an old woman, in whom such a nsevus grew on one cheek and lip, and exceeded in size the whole face. Such swellings are easily compressed, and often produce no other inconvenience than that of their deformity and weight. The arte- rial nrevus, however, and more especially when deeply seated, is sometimes a formidable dis- ease, which may involve all the surrounding structures and ultimately prove fatal. The cu- taneous capillaries of the cheeks, and about the tip and alse of the nose, often become enlarged and varicose, presenting a peculiar appearance, which is not uncommon in hard drinkers. The lymphatic glands of the face are particu- larly liable to inflammation, enlargement, and suppuration. In scrofula they often form im- mense swellings along the base of the jaw and about the parotid gland, sometimes remaining permanently enlarged, and sometimes suppura- ting and terminating in abscesses difficult to heal. The nerves of the face are liable to be pressed upon and irritated by the enlarged glands and by the tumours in this part of the body. The face is also subject to a most distressing com- plaint, termed tic douloureux, which may arise spontaneously or from injury, and which ap- pears to affect particularly, if not exclusively, the branches of the fifth pair of nerves, and FASCIA. more especially the infra-orbitar. Neuralgia of the lower part of the face seems, however, in some instances to follow the course of those branches of the cervical plexus which proceed toward this region. Division of the nerves, though it sometimes checks, seldom cures this painful affection, for the divided nerves spee- dily reunite, and the complaint returns ; and this takes place even after a portion of the nerve has been removed. Spasmodic affections of the face are connected with the branches of the portio dura : both nerves are of course sub- ject to palsy. The cellular tissue of the face is abundant, vascular, mingled generally with more or less fat, and in some places, as on the eyelids, is so lax as to be peculiarly liable to infiltration with fluids. Sometimes it becomes emphyse- matous, in cases of wounds of the frontal sinuses and larynx. It is easily affected by erysipelas, and is the common seat of abscesses, which, however, as there is no fascia to confine the matter, rarely attain any considerable size, but soon make their way towards the surface of the skin. When, indeed, the pus forms on the forehead between the muscles and the pericra- nium, or beneath the fascia covering the parotid gland, or beneath that investing the masseter and posterior part of the buccinator muscles, the matter being more confined is longer in arriving at the surface, and is productive of more pain than in the former instance. En- cysted tumours are not unfrequently formed in this structure of the face. The skin of the face, from its vascularity and the almost homogeneous mass which it forms with the subjacent tissues, readily unites after incised wounds, and hence the success which has attended the attempts at reparation of some parts of this region, such as the nose, cheek, and lips ; the extensibility of the skin also favours such operations. Punctured and con- tused wounds of the face are apt to produce erysipelas when they affect those parts where the cellular tissue is most dense, as on the nose and the prominence of the cheek. Abscesses are the more common result where the cellular tissue is looser. The skin of the face becomes swollen and thickened in some complaints which attack it, such as scrofula, which produ- ces enlargement of the lips and nose, and ele- phantiasis, cancer, and a few other diseases which affect it more permanently. It is sub- ject also to freckles, stains, and discolorations of various kinds, enlargement, inflammation, and induration of its follicles ; to a variety of cutaneous eruptions; to ulcerations from scro- fula, scirrhus, lupus, &c. which frequently make great ravages not only in the soft parts of the face, but even in the bones; to tubercles, warts, tumours, and auomalous growths of various kinds; and finally to boils. Its vas- cularity renders it more liable than in other parts of the body to receive the impression of small-pox pustules. Like the bones, the soft parts of the face are subject to congenital mal- formation. 1. Its apertures may be closed more or less firmly ; this happens with the eye- lids, nostrils, and lips. 2. There may be de- fects of growth, as fissures in the lips, or hare- lip, which may be single or double, and exist alone or in combination with fissures of the palate. The fissure may vary in depth, some- times, in the upper lip, extending into one of the nostrils, and at others only affecting the border of the lip. Congenital cleft of the lower lip is very rare, and is never combined with fissure of the bone. The nose is sometimes fissured, presenting no cartilaginous septum, and but one large orifice or nostril. Occasion- ally a congenital fissure has been observed in the cheek. The abnormal conditions of the teeth, the orbits and their contents, of the lachrymal apparatus, and of the cavities of the nose and mouth, will be found under the seve- ral articles on these subjects. For the BIBLIOGRAPHY of this article, see Anatomy (Introduction). ( R. Partridge.) FASCIA, (in general anatomy,) (Birule, sehinge Scheide, Flechsenhdute, Germ.) This term is applied to certain membranous expan- sions, existing in various regions of the body, and forming coverings to particular parts. These expansions are composed either of cellu- lar tissue, more or less condensed, or of fibrous tissue, the former being the cellular fascia, the latter the aponeuroses or aponeurotic fascia. The structure and connexions of a considerable number of the fascia; are highly interesting, as well with reference to correct diagnosis and prognosis in surgical disease, as in regard to the mode of proceeding in various operations. 1. Cellular fascia.— These are lamellae of cellular membrane of variable density, some- times loaded with fat, at other times totally devoid of it The best example of this form of fascia is the layer of cellular membrane which is immediately subjacent to the subcutaneous cellular tissue all over the body, and in most places so intimately connected with it as to be inseparable ; these in fact form but one mem- brane, which, although essentially the same everywhere, yet exhibits characters peculiar almost to each region of the body; it is gene- rally known under the name of the superficial fascia. Although this fascia is universal, there are, nevertheless, certain regions where, from its greater importance, it has been more care- fully examined than in others, and to which we may best refer in order to investigate its pecu- liar characters. Of these regions those of the abdomen and the neck stand pre-eminent ; here this fascia constitutes a distinct membraniform expansion, and the principal variety it pre- sents in different subjects is as regards the greater or less quantity of fat deposited in it. Where a tendinous or fibrous expansion does not lie immediately under it, this fascia sends processes from its deep surface to invest the subjacent muscles and other parts; this is very manifest in the case of the fascia of the neck ; and in general it may be stated that the super- ficial fascia has a more or less intimate connec- tion with the proper cellular covering of sub- jacent organs, whether muscles or tendons. 230 FASCIA. The arrangement to which we allude in the fascia of the neck may be satisfactorily traced from the median line on the anterior surface of the neck, proceeding outwards on each side. On the median line the fasciae of opposite sides are intimately united so as to form a dense line, called by some anatomists linea alba cervicalis; thence on each side the fascia divides into laminae, investing the sterno-hyoid and thyroid muscles, the carotid artery and jugular vein, the sterno-mastoid, and other muscles ; and thus anatomists come to describe a superficial and a deep layer of the cervical fascia; the former being continuous with the superficial fascia covering the muscles on the anterior part of the thorax, the latter, intimately con- nected with all the deep-seated structures in the neck, may be traced outwards behind the sterno-mastoid muscle, along the posterior edge of which it becomes again united with the su- perficial layer ; the fascia, thus re-constructed, passes through the triangular space which in- tervenes between the muscle last-named and the trapezius, and may be traced over that muscle to become continuous with the superfi- cial fascia on the back. It is the deep layer of this fascia which was described by Godman of Philadelphia* as passing downwards behind the sternum to be continuous with the fibrous pericardium. This description has been sub- sequently confirmed by more than one anato- mist in France, although denied by Cru- veilhier, and in this country by Sir Astley Cooper, f who has described it in the same manner, apparently without being acquainted with the previously recorded statements of the anatomists above referred to ; I may add that I have myself in many instances proved the accuracy of Godman’s description. The cer- vical fascia is continuous superiorly with the superficial fascia on the face ; and inferiorly, besides tracing it into the pectoral region, we can follow it over the shoulder into the arm. The cervical fascia, in a great part of its extent, is not, as the superficial fascia elsewhere, in intimate connexion with the subcutaneous cel- lular tissue, but is separated from it on each side of the neck by the fibres of the platysma myoides. From this brief account of the cervi- cal fascia, (we refer for the more particular description to the article on the surgical ana- tomy of the Neck,) we learn one characteristic of the superficial fascia, namely, its continuity all over the body. The superficial fascia of the abdomen has attracted the attention of anatomists and sur- geons from its connexion with all herniary tumours in that region. In its arrangement it is much less complex than the cervical fascia, being a uniform membranous expansion spread over the superficial muscular and aponeurotic structures of the abomen, continuous on either side and posteriorly with the superficial fascia of the lumbar regions, and inferiorly with that of the inferior extremities. See the description of it in the article Abdomen. * Anatomical Investigations, Pliiladelph. 1824. t On the thymus gland. The superficial fascia of the limbs is com- pletely confounded with the subcutaneous cel- lular tissue, and wants that condensation by which on the trunk generally, but particularly in the neck and abdomen, it is distinguished. There can be no doubt that the superficial fascia is no more than condensed cellular mem- brane, and its variety of appearance in different regions depends in a great measure upon pecu- liarities in the motions and arrangement of the parts contained in those regions, e.g. wherever the muscles of a part are in very frequent ac- tion, and at the same time the fascia is com- pressed between the integument and the mus- cles, it suffers condensation ; this is conspicuous in the abdomen, where there is almost incessant muscular action in consequence of the respi- ratory movements, and where the weight of the viscera, thrown forwards in the erect posture, occasions a considerable pressure upon the an- terior and lateral portions of the abdominal parietes. The deposition of adeps to any great extent is unfavourable to the existence of a distinct fascia superficialis, which is thereby, as it were, decomposed, and hence this fascia is not distinct from the subcutaneous cellular tissue in those regions where, either habitually or preternaturally, this substance is largely de- posited. The superficial fascia is identified with the subcutaneous cellular membrane in the cranial regions, a circumstance which seems attributa- ble to the firm adhesion of the aponeurotic ex- pansion of the occipito-frontalis muscle to the subcutaneous tissue, and also the cutaneous insertion of other muscles ; to a similar cause we may ascribe the indistinctness of this fascia in the face also, as likewise to the great depo- sition of fat in some parts of this region. In the pectoral region it is attenuated, and is more intimately connected with the proper cellular covering of the great muscles than with the subcutaneous cellular tissue. Where the superficial fascia has suffered condensation to a considerable extent, and there is a complete absence of adipose sub- stance, it assumes an appearance which has given rise to the designation “ fibro-cellular,’'' in consequence of the existence of thick, white, and opaque bundles intersecting the membrane in various directions; these bundles seem to be produced by the close application of the walls of the cells to each other, and the conse- quent obliteration of their cavities. This, how- ever, I believe is the nearest approach that the superficial fascia makes to fibrous membrane ; and I am strongly disposed to question the accuracy of Velpeau’s assertion, that it is some- times transformed into the yellow fibrous or into muscular tissue. The elastic abdominal ex- pansion, described by Girard, is certainly not a conversion of the superficial fascia, but of the muscular aponeurosis. Among the cellular fasciae, Velpeau* de- scribes a layer of cellular membrane, pretty uniform in its characters, and in some localities of great practical importance, and gives it the * Anat. Chiiurg. t. i. p. 42. FAT. 231 name fascia superficialis interim. It is in contact with the serous membranes of the prin- cipal cavities in the body, with those of the abdomen, thorax, and pelvis in particular ; in the former of which it has attracted most atten- tion under the denomination of the fascia pro- pria. This cellular layer lies between the serous membrane and the fibrous layer which lines the parietes of the cavities, as for instance the fascia transversalis in the abdomen ; and consequently in this last cavity, when any viscus is protruded, carrying a peritoneal sac before it, this cellular layer uniformly forms the immediate investment of the sac, and is there- fore called fascia propria, a hernial covering which every practical surgeon well knows is often of considerable density and thickness, and to which indeed is attributable the so-called thickening of the sac itself. 2. Aponeuroses or aponeurotic fascia-. — This appellation should be confined to those textures which are purely fibrous, and belong to either the white fibrous tissue or the yellow. In man, they belong entirely to the former class, but we see some interesting examples among the lower animals, where, while the same characters as to intimate texture are preserved, they assume a yellow colour, and exhibit most manifestly the property of elasticity. The greatest number of the fibrous aponeu- roses are connected with muscular fibres, and in fact serve as tendons to them, and are de- scribed as such. Of these we have the best examples in the fibrous aponeuroses of the ab- dominal muscles, by which a considerable por- tion of the paries of this cavity is constructed of a resisting inelastic material, which is at the same time under the control and regulation of muscular fibre. These expansions are com- posed of silvery white parallel fibres, in many places strengthened by bundles which cross and interlace with the fibres last named, e. g. the intercolumnar bands at the apex of the ex- ternal abdominal ring. It is interesting to notice that in the larger quadrupeds, when the weight of the viscera is imposed on these aponeuroses, they are composed of the yellow elastic fibrous tissue. I have also seen the fascia lata thus converted. A second class of these aponeuroses consists of those which cover the soft parts in particular regions. In general we find that where there are many muscles covered, the aponeurosis sends in processes by which each muscle is separately invested, these processes being ulti- mately inserted into the periosteum of the bone. Thus the fascia lata of the thigh separates by means of processes prolonged from its deep surface, the various muscles to which it forms an external envelope, in such a manner that, if the muscles be carefully dissected away from a thigh, without opening the fascia more than is sufficient for their removal, it will appear to form a series of channels in which the muscles are lodged. A similar arrangement is found in the leg and foot, and in each of the segments of the upper extremity. The fascia lata has the peculiarity of being in a great degree influenced in its tension by a muscle, called from that office, tensor vagina femoris, and the fascia which covers the palm of the hand is likewise governed by the palmaris longus, the connec- tion of which, however, with the fascia seems to have reference, not to the functions of the fascia, but to the power of the muscle, in aid of the other flexors of the wrist; the fasciae of the leg and arm too receive the terminal expan- sion of the tendons of muscles. The strength of these aponeurotic sheaths is proportionate to the strength of the muscles they cover; this is apparent, by comparing the fasciae of the arm and of the thigh ; the strength of the latter greatly exceeds that of the former, and in the thigh itself the vastus externus muscle is covered by a portion of the fascia lata, much stronger than those which cover the muscles on its posterior and inner aspects. In a third class of aponeuroses are enume- rated simple lamellae of fibrous membrane, which are found for the most part in connexion with the walls of cavities : such are the fascia transversalis, connected with the abdomen ; the fascia iliaca and pelvica, connected with the pelvis ; and the fibrous expansion lining the thorax, which has not received a name. The aponeurotic fascia; are most valuable in their power of resistance, and thus efficacious in maintaining organs in their proper situa- tions ; that they exert a considerable degree of compression upon the muscles is rendered evident by the hernia of the muscular fibres which takes place when an incision is made into the fascia lata of the thigh ; they thus re- gulate the combined action of muscles and render more complete their isolated action. It is incumbent on the surgeon to remember how they confine purulent collections and oppose their progress to the surface, a property which is likewise observable in the cellular fasciae, whose power of resistance is, however, much less, but their elasticity much greater. Such is a brief notice of the generalities con- nected with the fasciae of the body : the situa- tion, connections, and structure of many of them are of great interest to the surgical anato- mist, and will be found fully detailed in the articles devoted to the surgical anatomy of the regions. The subject is also very com- prehensively treated in the following works, Godman, Anatomical Investigations, Phila- delph. 1824; Velpeau, Anat. Chirurgicale, t. i. ed. 2de ; Vuillard, Description complete des Membranes fibreuses, Par. 1827 ; Cruveilhier, Anat. Descript, t. ii. Aponeurologie, Par. 1834; Bourgery, Anatomie de l’homme, t. ii. ( R ■ B. Todd.) FAT. (trr£a£, 7rtfj.e\Yi, adeps, pinguedo; Fr. graisse; Germ. Fett; Ith.grasso.) Under this term we include a variety of animal pro- ducts which bear a general resemblance to each other, and to a series of corresponding substances in the vegetable kingdom ; the fats of animals being, like the vegetable oils, ternary compounds of carbon, hydrogen, and oxygen, and not, apparently in any instance, containino- nitrogen, except as an adventitious or acciden- tal ingredient. 232 FAT. Fat is a deposition in the cellular membrane of certain parts of the body, especially under the skin, in the omentum, in the region of the kidneys, and within the cylindrical bones: it also occurs here and there among the muscles, and sometimes is accumulated to an extent so unnatural as to form a species of disease. In birds it is chiefly seated immediately below the skin, and in water-fowl it is largely secreted by the glands of the rump : in the whale and other warm-blooded inhabitants of the deep, it is chiefly contained in the head and jaw-bones, and abundantly interposed between the skin and the flesh ; in fish it abounds in the liver, as in the shark, cod, and ling, or is distributed over the whole body, as in the pilchard, herring, and sprat. Various opinions have been entertained re- specting the J'ormation of fat, and its insolu- bility in water has led to the idea of its produc- tion in the places in which it occurs ; but as it is found in the blood and in some other of the fluids of the body, it is probably partly received with the food, and partly formed by the process of secretion. Its remarkable absorption in cer- tain cases of disease of the chylopoietic viscera, and of deficiency of proper food, seems to point it out as a source of nutriment of which the ani- mal economy may avail itself on emergency ; and accordingly in cases of emaciation or atro- phy, it is the first substance which disappears. It varies in consistency and characters in the diffe- rent tribes of animals, and in the greater num- ber of amphibia and fishes it is usually liquid at ordinary temperatures. (See AdiposeTissue.) The general chemical characters of fat have been long known, as well as its important pro- perty of saponification by means of the alkalis; but the real nature of the changes which it un- dergoes in this process, and the essential dis- tinctive characters of its varieties, were first satisfactorily investigated by Chevreul,* whose essay upon the subject has been justly cited as a model of chemical research. It is chiefly from this source, and from the abstract of its contents given by Berzelius, f that we have taken the following details. All the varieties of fat are resolvable into mixtures of stearin and elain, (from cr tag, suet, and tA aiov, oil,) that is, into a solid and liquid ; but there are peculiar differences be- longing to these products in each individual species, which sometimes seem to depend upon very trifling causes, and at others to be con- nected with distinct ultimate composition. There are two modes by which die stearin and elain of fat may be separated : the one consists in subjecting it to pressure, (having previously softened it by heat, if necessary;) and the other, by the action of boiling alcohol, which, on cooling, deposits the stearin, and retains the elain in solution ; the latter separates on the addition of water, still however retaining a little stearin ; they may be ultimately separated by digestion in cold alcohol, sp. gr. .835, which * Recherches chimiques sur les corps gras d’ori- gitie animale. Paris, 1823. t Lelirbuch der Chemie. B. 3 and 4. Dresden, 1827. takes up the elain, and leaves it after careful distillation ; the stearin remains undissolved. Fat may be separated from its associated cellular texture, by cutting it into small pieces and melting it in boiling water ; it collects upon the surface, and when cold is removed, and again fused in a water-bath, and strained through fine cambric. Many varieties of fat, when dissolved in boiling alcohol and precipi- tated by water, leave a peculiar and slightly acid and saline extract in solution, apparently derived from the enveloping membranes. 1. The softer kinds of fat are termed lard, of which hog’s-lard furnishes a good example: it is white, fusible at a temperature between 75° and 85°, and of a specific gravity = about 0.938. When cooled to 32°, and pressed between folds of bibulous paper, it gives out 62 per cent, of colourless elain, which remains fluid at very low temperatures, has a sp. gr. = .915, and is soluble in less than its weight of boiling alco- hol, the solution becoming turbid when cooled to about 140°. The residuary stearin is ino- dorous, hard, and granular: when fused, it remains liquid at the temperature of 100°, but, on congealing, it rises to 130°, and assumes a crystalline appearance. When hog’s-lard becomes rancid, a pecu- liar volatile acid forms in it, which has not been examined. 100 parts of hog’s-lard yield, when saponified, 94.65 margaric and oleic acid, which when fused concrete at 150°; and 9. of glycerine. According to Chevreul’s analysis, the ultimate elements of hog’s-lard are — Carbon 79.098 Hydrogen 11.146 Oxygen 9.756 100.000 2. Human fat is another species of lard ; but it differs in different parts of the body. The fat from the kidney, when melted, is yellow, inodorous, begins to concrete at 77°, and is solid at about 60°. It requires 40 parts of boiling alcohol of 0.841 for solution, and this deposits stearin as it cools, which, when puri- fied by pressure between folds of filtering paper at 77°, is colourless, fusible at 122°, and may then be cooled down to 105°, before it concretes ; in the act of concreting its tempera- ture rises to 120°, and it becomes crystalline, and soluble in about four parts of boiling alco- hol, the greater part being deposited in acicular crystals as the solution cools. The elain of human fat, obtained by the action of hot water upon the paper by which it had been absorbed, is colourless, remains fluid at 40°, and con- cretes at a lower temperature. Its specific gravity at 60° is .913; it is inodorous, and has a sweetish taste. It is soluble in less than its weight of boiling alcohol, and the solution be- comes turbid when cooled to about 62°. 100 parts of human fat yield, when saponified, about 96 of margaric and oleic acids fusible at about 90°, and from 9 to 10 of glycerin. According to Chevreul, human fat and its elain are composed as follows : — 233 FAT. FAT. ELAIN. Carbon... 79.000 78 566 Hydrogen 11.416 11.447 Oxygen 9.584 9.987 100.000 100.000 3. The fat of beef when melted begins to concrete ait 100°: it requires for solution 40 parts of boiling alcohol, and contains about three-fourths its weight of stearin, which is obtained by stirring the melted fat whilst it is concreting, and then pressing it in woollen cloths at a temperature of about 95°, by which the elain is squeezed out, together with a por- tion of stearin, which is deposited at a lower temperature, for the elain does not congeal at 32°. The stearin is white, granularly crystal- line, fusible at 112°, and may be cooled to 100° before it congeals, when its temperature rises to 112°. It looks and burns like wax. 100 parts of alcohol dissolve 15 of this stearin : when saponified, it yields 0.95 of fat acids, which fuse at 130°. The elain of beef fat is colour- less and almost inodorous, and soluble in less than its weight of boiling alcohol. Candles made of the stearin of this fat, with a small addition of wax to destroy its brittle and crys- talline texture, are little inferior to wax candles. 4. Neat's foot oil is obtained by boiling the lower ends of the shin-bones of the ox, after the removal of the hair and hoofs, in water. This oil remains fluid below 32°, and after the sepa- ration of the stearin, is used for greasing turret- clocks, which are often so exposed to cold as to freeze other oils. 5. Goat's fat is characterized by its peculiar colour, which seems to depend upon the pre- sence of a distinct fatty matter, which, in the separation of the stearin and elain, is asso- ciated with the latter, and which Chevreul has called hircin. When the elain is saponified, a liquid volatile acid is formed, which may be separated as follows : four parts of the fat are made into soap with one of hydrate of potassa dissolved in four of water : the soap is after- wards diluted, and decomposed by phosphoric or tartaric acid, by which the fat acids are sepa- rated : these are distilled with water, taking care that the contents of the retort do not boil over : the distilled liquid is saturated with hydrate of baryta, evaporated to dryness, and decomposed by distillation with sulphuric acid diluted with its weight of water : the acid is separated in the form of a colourless volatile oil which floats upon the distilled liquid ; Chevreul terms it hircic acid: it congeals at 32° : it has the odour of the goat, blended with that of acetic acid ; it reddens litmus, dissolves difficultly in water, and readily in alcohol : it forms distinct salts with the bases : the salt of ammonia has a strong hircine odour : that of potassa is deliquescent, and that of baryta difficultly soluble in water. 6. Mutton fat is whiter than that of beef, and acquires a peculiar odour by exposure to air; when melted it begins to concrete at about 100°. It requires 44 parts of boiling alcohol for solution. Its stearin, when fused, begins to congeal at 100°, and its temperature rises on solidification to 113°. 100 parts of alcohol dissolve 16 of it. Its elain is colourless, slightly odorous, sp. gr. 0.913, and 80 parts of it are soluble in 100 of boiling alcohol. When saponified, it yields a very small quantity of hircic acid. This species of fat, together with its stearin and elain, are composed as fol- lows : — FAT. STEARIN. ELAIN. Carbon . ...78.996 78.776 79.354 Hydrogen ..11.700 11.770 11.090 Oxygen . ... 9.304 9.454 9.556 100.000 100.000 100.000 7. Whale oil, or train oil, (from whale blub- ber,) sp. gr. .927, when cooled to 32°, deposits stearin; the filtered oil is then soluble in 0.82 of boiling alcohol. Aided by heat it dissolves arsenious acid, oxide of copper, and oxide of lead ; sulphuric and muriatic acids render the latter combination turbid, nitric acid tinges it dark brown with effervescence ; and it is coa- gulated by potassa and soda. This oil is easily saponified when mixed with 0.6 its weight of hydrated potassa, and five parts of water ; the soap is brown, soluble in water, and when de- composed by tartaric acid and the sour liquid distilled, it yields traces of phocenic acid, also glycerine, and oleic and margaric, but no stearic acid : these acids are accompanied by a greasy substance which has the odour of the oil. The stearic portion of train oil, when freed from adhering elain by washing with weak alcohol, concretes, after having been fused, at a temperature between 70° and 80°; it is soluble in 1.8 parts of boiling alcohol, and is deposited in crystals as it cools, leaving a dark thick mother-liquor. When saponified, 100 parts yield 85 of margaric and oleic acids, 4 of a brown substance infusible at 2 1 2°, and per- fectly soluble in boiling alcohol, 7 of bitterish glycerine, and traces of phocenic acid. 8. Spermaceti oil, the produce of the sper- maceti whale,* is lodged in the cartilaginous cells of a bony cavity on the upper part of the head ; as it cools, it deposits its peculiar stearic portion in the form of spermaceti; this sub- stance is further separated by pressure in wool- len bags from the oil, and is then washed with a weak solution of caustic potassa, melted in boiling water, and strained ; it is commonly cast into oblong blocks, and if the interior liquid portion is drawn off when the exterior has concreted, the cavity exhibits upon its sur- faces a beautiful crystalline texture. Sperma- ceti, as it occurs in commerce, is in semi-trans- parent brittle masses of a foliated fracture, and soapy to the touch ; it has a slight odour and a greasy taste, and when long kept becomes yel- lowish and rancid. Its specific gravity is .943; it fuses at about 114°. 100 parts of boiling alcohol, sp. gr. .823, dissolve 3.5 spermaceti, and about 0.9 is deposited on cooling. Warm ether dissolves it so copiously, that the solution concretes on cooling; by the aid of heat, it * Physeter macrocephalus, or Cachalot. 234 FAT. dissolves in the fat and volatile oils, and is in part deposited as the solution cools. Alcohol always extracts a small portion of oil from the spermaceti of commerce ; as the boiling alco- holic solution cools, it deposits the purified spermaceti in white crystalline scales, and in this state, Chevreul terms it cetine. Cetine does not fuse under 120° ; it forms, on cooling, a lamellar, shining, inodorous, and insipid mass, which is volatile at high temperatures, and may be distdled without decomposition. It burns with a brilliant white flame, and dis- solves in about four parts of absolute alcohol ; it is very difficultly saponified ; digested for several days at a temperature between 120° and 190°, with its weight of caustic potassa and two parts of water, it yields margaiate and oleate of potassa, and a peculiar fatty matter, which Chevreul calls ethal,* and which amounts to about 40 per cent, of the cetine used. To ob- tain it in an insulated state the results of the saponification of cetine are decomposed by tartaric acid, which separates the margaric and oleic acid, together with the ethal ; the fat acids are saturated with hydrate of baryta, and the resulting mixture well washed with water to separate all excess of base ; it is then well dried, and digested in cold alcohol or ether, which takes up the ethal and leaves the barytic salts ; the former is then obtained by evapora- tion of the solvent. Ethal is a solid, transpa- rent, crystalline, fatty matter, without smell or taste; when melted alone it congeals at 120° into a crystalline cake; it is so volatile that it passes over in vapour when distilled with water. It burns like wax, and is soluble in all propor- tions in pure alcohol at a temperature below 140°. It readily unites by fusion with fat and the fat acids, and when pure is not acted upon by a solution of caustic potassa; but if mixed with a little soap it then forms a flexible yel- lowish compound, fusible at about 145°, and yielding an emulsive hydrate with boiling water. The ultimate composition of train oil, sper- maceti oil, spermaceti, cetine, and ethal, are shewn in the following tables : — TRAIN OIL. SPERMACETI OIL. Berard. Ure. Carbon . . . . 76.1 79.0 Hydrogen. . 12.4 10.5 Oxygen. . . . . 11.5 10.5 100.0 100.0 SPERMACETI. CETINE. Berard. Chevreul. Carbon . . . . 79.5 81.660 Hydrogen. . 11.6 12.862 Oxygen ... 8.9 5.478 100.0 100.000 * From the first syllables of the words ether and alcohol, in consequence of a resemblance in ultimate composition to those liquids. ethal. ( Chevreul.) Atoms. Equivalents . Theory. Experiment. Carbon. . 17 102 79.69 79.766 Hydrogen 18 18 14.06 13.945 Oxygen. . 1 8 6.25 6.289 1 128 100.00 100.000 9. Phocenine is a peculiar fatty substance contained in the oil of certain species of por- poise ( Delphinus plwcena and globiceps ). When this oil is saponified, it yields margaric and oleic acid and cetine, and a peculiar vola- tile acid obtained by a process similar to that for separating hircic acid, and which has been termed phocenic acid.* It is a thin, colourless, strong-smelling oil, of a peculiar acrid, acid, and aromatic taste; its specific gravity is .932 ; it does not congeal when cooled down to 14°. Its boiling point is above 212°. In this state it is an hydrate, containing 9 per cent, of water, from which it has not been freed. It is solu- ble in all proportions in pure alcohol. The neutral salts of this acid ( plwcenates ) are inodorous, but any free acid, even the car- bonic, in a gentle heat, evolves the odour of the phocenic acid. Heated in the air they exhale an aromatic odour, dependent upon the forma- tion of a peculiar product. By dry distillation they blacken, evolve olefiant gas and carbonic acid, and a thin, odorous, yellow oil, insoluble in potassa. The phocenates of potassa, soda, and ammonia, are deliquescent ; the phocenate of baryta forms efflorescent prismatic crystals ; and that of lime, small acicular prisms. The neutral phocenate of lead, evaporated in vacuo, yields flexible lamellar crystals, which are fusible and easily become basic when heated; the subphocenate of lead is difficultly soluble and crystallisable, and decomposed by the car- bonic acid of the air. According to Chevreul, the anhydrous pho- cenic acid (as existing in its anhydrous salts) consists of Atoms. Equivalents . Theory. Experiment . Carbon . . 10 60 65.93 65.00 Hydrogen 7 7 7.69 8 25 Oxygen . . 3 24 26.38 26.75 1 91 100.00 100.00 And the oily hydrated acid is a compound of 1 atom of dry acid and 1 atom of water, or 91 + 9 = 100. 10. The fat of birds has been but little exa- mined ; Chevreul states that the fat of geese concretes after fusion at about 80° into a gra- nular mass of the consistency of butter. Ac- cording to Braconnot it yields by pressure at. 32°, 0.68 of yellowish elain, having the odour and taste peculiar to this kind of fat, and 0.32 of stearin, fusible at 1 10°, and soluble in rather more than three parts of anhydrous alcohol. When saponified, it yields margaric and oleic acid and glycerine. * The same acid is contained, according to Chevreul, in the ripe berries of the Viburnum opulus. FEMORAL ARTERY. 235 The fat of the duck and the turkey nearly resembles the above. 11. Among insects, peculiar kinds of fat have been obtained from ants, and from the cochineal insect. The latter has been examined by Pelletier and Caventou. (Ann. de Ch. et Phys. viii. 271.) It is obtained by digesting bruised cochineal in ether, evaporating and re- dissolving the residue in alcohol, till it remains upon evaporation in the form of colourless pearly scales, insipid and inodorous, and fusible at 104°. 12. Under the term adipocere, we have else- where described a species of fatty matter which appears to result from the slow decomposition of fibrine ; and in some diseased states of the body, a large proportion of the flesh occasion- ally puts on the appearance of fat. In the former case, it has been supposed that the pro- duct is the fat originally existing in the body, which, during the putrefaction of the other parts, has become acidified, that is, converted into margaric, stearic, and oleic acids; and that these acids are more or less saturated by the ammonia which is at the same time gene- rated, and by small quantities of lime and magnesia resulting from the decomposition of certain salts of those earths pre-existing in the animal matter. This view of the nature of adi- pocere appears so far correct ; but the quantity of the altered fatty matter which was found in the cases alluded to, and in others where heaps of refuse flesh have been exposed to humid pu- trefaction, is sometimes such as to render it highly probable that a portion of the fatty matter is an actual product of the decay, and not merely an educt or residue. In regard to the apparent morbid conver- sion of muscle into fat in the living body, Berzelius observes that, because the muscles become white, it has been assumed that they are actually converted into fat, but that the appearance depends solely upon the absence of red blood, for the muscles under such circumstances do not lose their power of mo- tion. The truth is that, in these cases, the accumulation of fat goes on to such an extent in the interstitial cellular membrane of the muscular fibre, as gradually to occasion its almost entire absorption, and such of the mus- cles as undergo this change gradually lose their contractile powers. Two mutton-chops, which have undergone this change, and in which the altered muscle and the ordinary ex- ternal layer of adipose membrane are quite dis- tinct, are preserved in the Museum of the College of Surgeons, and there is a printed pamphlet giving an account of the symptoms under which the sheep laboured. What may be the chemical peculiarities of the fat depo- sited among the fibres, as compared with the ordinary fat, has not been ascertained. The above is an enumeration of such of the varieties of animal fat as have been chemically examined. In their general characters they closely resemble the corresponding compounds of the vegetable kingdom ; and, with the excep- tions specified, the process of saponification effects upon them very similar changes : they are also similarly acted on by the acids. Some of them seem to afford distinct products when subjected to destructive distillation, and during the decomposition of whale oil for the produc- tion of carburetted hydrogen for the purposes of gas illumination, a variety of binary com- pounds of hydrogen and carbon, with some other products, are obtained, the nature of which has been ably investigated by Professor Faraday.* ( IV. T. Brande.) FEMORAL ARTERY ( arteria cruralis; Germ, die Sclienkelarterie). The femoral ar- tery is the main channel through which the lower extremity is supplied with blood : in an extended sense it might, with propriety, be understood to comprehend so much of the artery of the extremity as is contained within the thigh, intermediate to those of the abdo- men and the leg; but the variety in the situ- ation and relations of that vessel in different stages of its course is so great that it has been distinguished into two, the proper femoral and the popliteal ; the former appellation being applied to so much of the vessel as is situate in the superior part of the limb, and the latter to that portion which is contained in the lower, in the popliteal region. The comparative ex- tent of the two divisions of the artery differs considerably, the femoral predominating much in this respect, and occupying two-thirds of the thigh, while the popliteal occupies but one; hence the particular extent of each may be exactly defined by dividing the thigh, longi- tudinally, into three equal parts, of which the two superior will appertain to the former, and the inferior to the latter. The proper femoral artery, then, engages the two superior thirds of the main artery of the thigh, continued from the external iliac artery above, and into the popliteal below. It emerges from beneath Poupart’s ligament into the thigh, external to the femoral vein, and on the outside of the ilio-pectineal eminence of the os innominatum, and it passes into the popliteal region below through an aperture cir- cumscribed by the tendons of the adductor magnus and vastus internus muscles. Its course is oblique from above downward, and from before backward, corresponding to a line reaching from a point midway between the anterior superior spinous process of the ilium, and the symphysis pubis upon the front of the limb above, to another midway between the two condyles of the femur, on the posterior aspect of the bone below. Its mean direction is straight, or nearly so, corresponding to the line which has been mentioned, or, according to Harrison,-)' to a line drawn from the centre of Poupart’s ligament to the inner edge of the patella; but its course is, for the most part, more or less serpentine, the vessel forming as it descends curvatures directed inward and outward. The presence and degree of these curvatures, however, are influenced very much * Phil. Trans. 1825. t Surgical Anatomy of the Arteries, vol. ii. p. 137. FEMORAL ARTERY. 236 by the state of the vessel and by the position of the limb ; when the artery is empty, they are less marked than when it is full ; and when the limb is extended, they are removed ; when flexed, they are reproduced ; while in some subjects again, they appear to be absent, the line of the vessel’s course being almost direct. The degree to which the artery passes back- ward is not equally great at all parts of its course: in its upper half, i. e. from Poupart’s ligament until it lies upon the adductor longus muscle, the vessel inclines much more back- ward than in the remainder, and at the same time describes a curve concave forward, but both the latter particulars are more remarkable when the thigh is flexed, and in thin subjects, than when the limb is extended and in sub- jects which are in good condition ; iri the last case the vessel is supported and held forward by the deep fat of the groin situate behind it. In its lower half the artery inclines less back- ward, being supported by the muscles against which it rests. The femoral artery is also described as in- clining inward* during its descent; but this statement requires correction, or at least ex- planation. The vessel certainly does incline inward at some parts of its course, and for the most part it does so as it descends from the os innominatum into the inguinal space, form- ing thereby the curvatures which have been mentioned ; but the general direction of it is either slightly outward, or at the most directly downward, not inward : the opinion that it is inward has arisen, it is to be supposed, from a partial view of its course, which, in conse- quence of its serpentine direction, is likely to mislead, and is at variance with that of the popliteal artery, (the lower part of the same vessel,) which is decidedly outward. In order to be assured of the true direction of the vessel, the writer has tested it carefully by means of the plumb-line, and he has always found that it inclined somewhat outward from the perpendicular : the degree, however, to which the proper femoral artery does so, is not considerable, though sufficient to place the matter beyond doubt. It is to be borne in mind that, in determin- ing the direction of the vessel’s course, the limb must be placed in the bearing which it holds naturally in the erect posture, inasmuch as an inclination to either side will influence materially the direction of the artery : thus an inclination of the limb inward will at once give it the same tendency, and render it spiral, both which conditions are removed by placing the limb in its ordinary position. In consequence of the course which the vessel pursues, and of the oblique position of the femur conjointly, the femoral and popliteal arteries hold very different relations to the shaft of that bone ; the former, in the first stage of its course, being in a plane anterior to the femur, and in the middle of the limb being upon its inside ; while the latter is situate be- hind the bone, and at the inferior part of the * Boyer, Cloquet, Harrison. popliteal region corresponds to the axis of its shaft: hence the artery is said* to pass some- what in a spiral manner in reference to the thigh bone; but this is incorrect, the spiral course being only apparent and resulting from the combined effect of the obliquity of the artery itself backward and outward, and of the shaft of the femur inward and forward : that this is so may be satisfactorily shewn by the application of the plumb-line to the course of the artery, upon the different aspects of the limb; from which it will appear that, allow- ance being made for the serpentine deviations already adverted to, the general course of the vessel is, quam proximi, straight, and that it cannot, at all with propriety, be said to be spiral, this being not a real but an apparent direction, the result of the circumstances which have been mentioned. The point at which the femoral artery com- mences is referred by most writers to Poupart’s ligament; this method of demarcation is at- tended with the inconvenience, that during life the exact situation of the ligament is difficult to determine, inasmuch as it does not run direct from one attachment to the other, and that in dissection its position is immediately altered on the division of its connections with the adjoining fascire : hence the student, not having a fixed point of reference, is often at a loss to distinguish between the iliac and femo- ral arteries, and mistakes affecting the relations of the most important branches of those vessels are liable to be made. For those reasons it appears to me that it would be much pre- ferable to select some fixed and unchanging point to which to refer the commencement of the artery ; and for this purpose I would suggest the llio-pectineal eminence of the os innominatum, which, to the student at least, if not to the practical surgeon, will afford an unerring guide to the distinction of the one vessel from the other; the femoral artery, at its entrance into the thigh, being situate im- mediately external to the inferior part of that prominence, f with which point the middle of the line connecting the anterior superior spi- nous process of the ilium and the symphysis of the pubis will also be found to correspond. The precise situation of the vessel is referred by some to the centre of Poupart’s ligament, or a point midway between the anterior supe- rior spinous process of the ilium and the spinous process of the pubes; by others to a point midway between the spinous process of the ilium and the symphysis of the pubes. Witli regard to this question it is to be ob- served that the relation of the artery to the points between which it is situate is not strictly the same in all instances ; that in some it will be found to correspond to the former, and in others to the latter account; but that the latter relation appears to prevail in so much the greater number, that it ought to be adopted as the rule. According to Velpeau it is distant two inches and a quarter from the spinous pro- * Harrison, op. cit. p. 137. t This point will be discussed again. FEMORAL cess of the pubes, and from two and a half to two and three quarters from the superior an- terior spinous process of the ilium. The femoral artery is attended through its entire course by the femoral vein, the two vessels lying in apposition and inclosed within a fibro-cellular investment, to which the ap- pellation femoral sheath will be applied. It is also related to the crural nerve or its branches, and it is contained, together with the vein, in a canal of fascia, which will be denominated the femoral canal. It is necessary to dwell here, for a little, upon the distinction between the two appel- lations femoral canal and femoral sheath, that a confusion of the one with the other may not arise. The vessels have in fact, throughout their course, two distinct sheaths, which may be considered peculiar to them, contained the one within the other : the external is formed by the fascia lata in a manner to be presently explained, and is in all respects analogous to the canal furnished by the cervical fascia to the carotid artery and jugular vein. This outer sheath, which many may regard as the sheath of the vessels, extends from Poupart’s liga- ment to the aperture by which they escape into the popliteal region, and will, for reasons which will appear more fully by-and-bye, be here called the femoral canal. The second or internal sheath is situate within the former, is of variable thickness, according to the point at which it may be examined, being for the most part very thin; adheres in general closely to the vessels, in which particular it differs from the outer one, within which they are com- paratively free ; and not only covers, but also separates them by a thin internal process, which by its density and intimate adhesion to the vessels connects them straitly to each other; it is further not confined, as the other is, to the vessels, while called femoral, but is prolonged upon them into the popliteal region, where in like manner it invests and connects them : to this investment the denomination femoral sheath will be applied. A distinction between the two structures is necessary in a description of the relations of the femoral artery, were it only to mark their existence, but that which I have adopted is rendered imperative by the use already made of the latter appellation with reference to the anatomy of hernia, in the history of which it is ap- plied not to the canal as formed by the fascia lata, but to that, through which the femoral vessels escape from the abdomen, and as formed by the fasciae transversalis and iliaca; and the prolongation of the former of these two fasciae being, m my opinion, con- tinued into the internal and immediate in- vestment of the vessels, it has appeared to me justifiable to extend the signification of the title femoral sheath, and to apply it to that investment throughout their entire course, as well below as above the saphenic opening of the fascia lata; while his application of the former appellation, femoral canal, is sanc- tioned by Cloquet, by whom it is used in the same sense. ARTERY. 237 Beside those which have been already mentioned, the femoral artery has also, during its course, the following general re- lations : — posteriorly it corresponds in suc- cession to the psoas magnus, the pectinalis, the adductor brevis, adductor longus and ad- ductor magnus muscles ; anteriorly it is, in the first part of its course, not covered by any muscle and is comparatively superficial ; and through the remainder and more exten- sive portion it is covered by the sartorius. Externally it corresponds to the psoas and iliacus, to the sartorius, the rectus, and lastly to the vastus internus muscles ; the latter of which is interposed between it and the inside of the femur : internally it corresponds to the pectinalis and the adductor longus mus- cles ; and lastly it is overlapped by the sar- torius. It is contained, through its upper half, in the inguinal region. This region is of a triangular prismatic form, the base of the triangle represented by it being above formed by Poupart’s ligament, or by a line connecting the anterior superior spinous process of the ilium and the symphysis pubis; its apex below by the meeting of the sartorius and the adductor longus muscles. The sides of the prism are external and internal, inclined, the former backward and inward, the latter backward and outward, and meeting each other along the internal and posterior side of the femur; they are formed, the external by the iliacus and psoas, the rectus, the vastus internus and the sartorius muscles, and the internal by the pectinalis and the adductors. The base of the prism is in front, consisting of the coverings of the space. During its descent from the os innominatum into the inguinal region, the artery generally inclines inward, describing a curve convex out- ward ; and hence, as it seems to me, the entire course of the vessel has been assumed to be inward ; but this first curve, when present, is soon compensated by another in the opposite direction. In its lower half the artery is enclosed between muscles, the vastus internus upon its outside, the adductors longus and magnus behind it, and the sartorius in front. The course of the femoral artery may be advantageously divided into three parts or stages, to be distinguished as first, second, and third, or as superior, middle, and inferior thirds ; in each of which will be found such peculiarities in the relations of the vessel as will justify the number of subdivisions. They may be defined with sufficient precision by dividing the two superior thirds of the thigh into three equal parts, and they will occupy each, according to the stature, from three to rive inches. The superior stage reaches from Poupart’s ligament to the point at which the artery is first covered by the sartorius : during this, its upper third, the vessel is not covered by muscle, except at its termination, where it is overlapped by the inner margin of the sartorius : it is therefore comparatively super- 238 FEMORAL ARTERY. ficial, and its pulsations can be felt during life with greater or less facility according to circumstances, to be explained. It has, how- ever, four structures interposed between it and the surface, and forming its coverings ; viz. the skin, the subcutaneous cellular stratum, the anterior wall of the femoral canal, and the prolongation of the fascia transversalis or the femoral sheath. The subcutaneous cellular structure pre- sents a remarkable difference according to the condition of the subject or certain other cir- cumstances. When the body is devoid of fat or emaciated, this structure appears a thin, condensed, dry and lamelliform stratum, con- tinued from the abdomen downward upon the lower extremity, and generally denominated the superficial 'fascia of the thigh; but when, on the contrary, the body is in good condition, and the quantity of superficial adeps is con- siderable, the appearance of a membranous expansion is removed, and in its stead a thick and uniform stratum of fat is found in- terposed between the skin and the fascia lata. In other cases presenting a medium condition, the stratum of fat and the membranous expan- sion may be both observed : in such case the former is generally superficial, and the latter underneath ; but when the accumulation of adeps in the subcutaneous structure is more considerable, e. g. in the healthy infant or in many adults, particularly among females, no trace of superficial fascia is to be found. So much for the varieties which the subcutaneous cellular structure presents naturally. It is also found frequently in abnormal conditions deserving of attention : at times it is divisible to a greater or less extent into a succession of expansions, having each the appearances of fasciae and being of indeterminate number : this disposition, which occurs not unfrequently, and is of considerable importance in a practical point of view, appears due to the influence of pressure exerted by tumours, e. g. that of hernia. Again, in anasarca the subcutaneous structure becomes greatly increased in depth, and loses all appearance of membrane, seeming then a deep gelatinous stratum, consisting of the cellular structure and the effused serum. The depth, therefore, of the femoral artery from the surface, and the number of coverings which it may have in individual cases, must be materially influenced by those several con- ditions of the subcutaneous cellular structure when present, and they should never be lost sight of; else uncertainty and embarrassment must arise in the conduct of operations. It is further to be borne in mind that the account of the coverings of the artery given in this description has reference to the natural and most simple arrangement of those structures. The subcutaneous structure also encloses within it the superficial vessels, nerves, and glands, the relation of some of which to the artery requires notice. The superficial vessels are the saphena vein, the superficial femoral veins, and those veins and arteries by which the inguinal glands are supplied. The saphena vein ascends, from the inner and back part of the knee, along the inner and an- terior aspects of the thigh to its upper extre- mity, where it joins the femoral vein upon its anterior and internal side, at the distance of from one inch to an inch and a half below Poupart’s ligament. During its ascent the vein passes forward and outward, and is situate internal to the femoral artery : at the lower extremity of the middle third of the thigh, (the point at which the artery is about to pass into the ham,) it is placed superficial to the vessel, between it and the internal surface of the limb, near to the inner, or at this part the posterior margin of the sartorius muscle ; but as the vein ascends, the distance between the vessels increases, partly because of the greater width of the thigh at its upper part, and partly because the course of the vein describes a curve convex inward ; and at the termination of the latter it amounts to the width of the femoral vein or somewhat more; lower down it is still greater in consequence of the curve formed by the saphena. Hence, in operations upon the superior part of the artery, the saphena ought to be exempt from danger ; while at the lower part it must be very much exposed, if the inner margin of the sartorius be cut upon as the guide to the vessel. The superficial femoral veins next claim attention : they are very irregular in their course and destination, and therefore are the more likely to prove a source of embarrass- ment in operation. They are smaller than the saphena, but yet are in many cases of con- siderable size : they present, according to the subject, two dispositions ; either they join the saphena during its ascent at variable points in the course of the thigh, and in such case cross the limb and the artery obliquely from without inward, at different heights ; or they form one or two considerable vessels, which ascend external to the saphena, and open into the femoral vein in front, at the same time with the former vessel, passing through the superficial lamina of the fascia lata in the same manner as it does. When there are two such veins, the inner one is generally situate internal to the artery, between it and the saphena, and consequently very near to it; while the external one, or the vein, if there be but one, runs upward and inward, and crosses the artery in its upper third, between the point at which the saphena joins the femoral vein and that at which the artery is overlapped by the sartorius : the last-de- scribed vein, when present, must obviously be much endangered in exposing the femoral artery at this part of its course, and perhaps is the vessel which has given rise to the idea, that the saphena itself may be encountered in cutting upon the artery in this situation. The superficial inguinal glands are distin- guished into two sets, a superior and an in- ferior : those of the former are more numerous, and nearer to the integuments than the latter. They are ranged immediately below Poupart’s ligament, having their longer diameter parallel to it, and in greatest number superficial to that part of the iliac portion of the fascia lata, FEMORAL ARTERY. 239 which is called its cribriform portion, and over the course of the femoral artery, across which they are placed obliquely : they are separated from the vessel by the superficial lamina of the iliac portion of the fascia, and by the prolongation of the fascia transversalis, with the interposed cellular structure ; and they derive numerous arterial and venous branches from the main trunks beneath : those branches, which are given off partly by the vessels themselves, and partly by their super- ficial pudic, superficial epigastric, and su- perficial anterior iliac branches, pass through the interposed structures in order to reach the glands ; in doing so they carry with them sheaths from the fascia lata, which is prolonged upon each as it escapes, and thus they become the means of establishing that connection be- tween the fascia in the groin and the subcu- taneous stratum, in which the glands are enveloped, which is considered to influence so remarkably the course of femoral hernia. The glands of the second set are less nu- merous, are situate farther from Poupart’s ligament than the former, being below the entrance of the saphena ; they are also deeper seated, lying upon the fascia lata, and they are placed with their longer diameter parallel, or nearly so, to the femur and to the course of the artery. Their relation to the artery is not in all cases the same, inasmuch as the disposition of neither part is strictly uniform, but usually one or two of them lie over the vessel, or immediately on either side of its course; their relation to it, however, is, in the natural condition of the parts, not of great consequence; for in such case they may be easily held aside during operation if necessary, and thus both they and their lymphatic vessels be saved from injury. The relation of the inguinal glands, more particularly the superior, to the femoral artery suggests several inferences. 1st, That the very commencement of the artery’s course, although the situation in which the vessel is nearest to the surface, and that in which it can be most easily distinguished by its pulsa- tion, is yet not the most eligible part at which to expose it, since the glands and their vessels cannot, by any precaution of the surgeon, be protected certainly from injury. 2dly, That phagedenic ulceration of the glands of the groin must be attended with great danger from the vicinity of the great vessels. 3dly, That hemorrhage consequent upon such ulceration does not necessarily proceed from those vessels themselves ; but that it may, and in the ma- jority of cases in the first instance probably does arise from the branches supplying the glands ; and, 4th, That the groin is likely to be the seal of pulsating tumours requiring to be distinguished from aneurism. The third covering of the artery is the superficial lamina of the iliac portion of the fascia lata. This portion having covered the an- terior surface of the iliacus and psoas muscles as far as the middle of Poupart’s ligament, along which it is attached from without inward, divides at that point into two laminae, a deep one and a superficial one ; the former passes inward and backward from the ligament, upon the psoas muscle, to the ilio-pectineal eminence of the os innominatum, into which it is in- serted, continued thence upward, upon the inside of the muscle, along the brim of the pelvis into the fascia lliaca, and downward across the capsule of the ilio-femoral articula- tion, to which it is also attached : it is in fact that part of the fascia iliaca, (for the fascia iliaca and the iliac portion of the fascia lata are one and the same expansion, distinguished from each other only by Poupart’s ligament,) which is situate upon the inside of the psoas magnus, and which forms the outer wall of the femoral canal, being interposed between the femoral artery and the muscle. At the ilio- pectineal eminence it also meets and is iden- tified with the pubic portion of the fascia lata, which is attached to the pectineal line of the pubis, in continuation with this deep lamina of the iliac portion, covers the pectinalis muscle, and is situated immediately behind the vessels. When that part of the deep lamina of the iliac portion of the fascia lata which extends from Poupart’s ligament to the ilio-pectineal eminence has had the prolonga- tion of the fascia downward detached from it, it appears as an oblique partition dividing the crural arch into two parts, an external containing the iliacus and psoas muscles with the crural nerve, and an internal containing the femoral vessels. The second lamina of the iliac portion of the fascia lata— the superficial one — passes inward across the femoral vessels, superficial to them and to the prolongation of the fascia transversalis, until it has reached the inside of the vessels : it is at the same time attached above, in front of the vessels, and in con- tinuation with the iliac portion itself, to the inferior margin of Poupart’s ligament, from its middle to the base of its third insertion — Gimbernat’s ligament, and upon their inside along the base of the latter ligament as far as the pectineal line of the pubis, into which it is finally inserted, external to the base of Gimbernat, between it and the insertion of the fascia transversalis upon the inside of the aperture of the femoral sheath, and where it is also identified with the pubic portion of the fascia attached along the same line : from thence it is united to the anterior surface of the pubic portion of the fascia lata, down- ward along the inside of the vessels. The superficial lamina of the iliac portion is thus thrown across the front of the vessels, and by the disposition, which has been detailed, the fascia lata encloses the vessels between the two laminae, and forms, by means of them and their connection at either side, a canal, within which are contained the vessels and the prolongation of the fascia transversalis covering them in front. The constitution of the canal, as described, may be considered to extend from Poupart’s ligament until the artery is about to be covered by the sartorius, from whence its anterior wall is formed, through the remainder of the vessel’s course, by another 240 FEMORAL ARTERY. and deeper layer of the fascia. The canal thus formed, to which the author would apply, with Cloquet, the term femoral canal, is widest at its upper extremity, i. e. at Poupart’s ligament; from whence, as it descends, it contracts in width until it has passed the entrance of the saphena, beyond which it continues of nearly uniform capacity to its termination. The diminution in the transverse extent of the canal is due to the direction of the line of union between the superficial lamina of the iliac portion and the pubic portion of the fascia, which, as has been already stated, inclines outward as it descends from the pectineal line of the pubis to the point at which the saphena joins the femoral vein. In the interval between Poupart’s ligament and the junction of the two veins the superficial lamina is thinner, less aponeu- rotic, and more of a cellular character than other parts of the fascia ; but it is subject to much variety in this respect : in all cases it is thinner and weaker internally than externally, but in some it is throughout distinct and un- broken, unless by the passage of vessels, and presents aponeurotic characters as decidedly as many other parts of the expansion ; while in others it is cellular, indistinct, and even fatty, not easily distinguishable from the subcuta- neous structure, and so thin as to seem de- ficient toward its inner part, or to have its line of union with the pubic portion inter- rupted at one or more points. The extent and connections of this portion of the fascia will be most satisfactorily displayed by first detaching Poupart’s ligament, upon its abdo- minal side, from the fascia transversalis as it descends beneath the ligament, and then care- fully insinuating the handle of a knife down- ward beneath the ligament and the superficial lamina of the iliac portion of the fascia lata, between them and the prolongation of the fascia transversalis : this done, the superficial lamina may, with the guidance of the instru- ment beueath it, be satisfactorily traced. The fourth structure, by which the femoral artery is covered in the first stage of its course, is the prolongation of the fascia transversalis. The two abdominal fascia;, the transversalis and the iliaca, which are, at every other part of the crural arch, either identified and united, or inserted into bone, are separated in the in- terval between the middle of Poupart’s and the base of Gimbernat’s ligament, and de- scend into the thigh, the former in front of or superficial to the femoral vessels, beneath Pou- part’s ligament and the superficial lamina of the iliac portion of the fascia lata ; the latter behind or deeper than the vessels, between them and the psoas and pectinalis muscles, constituting or continued into the pubic or deep portion of the fascia lata. The two fasciae thus leave an aperture beneath Poupart’s liga- ment, through which the vessels escape from the abdomen, and at the same time inclose them between them ; the prolongation of the transversalis covering them in front, the iliac and pubic portion of the fascia lata situate behind them. As it descends upon the vessels, the prolongation from the transversalis is united to the fascia iliaca and iliac portion of the fascia lata upon theiroutside ; and to the pubic portion upon their inside, in the same manner as the superficial lamina of the iliac portion, and within it in reference to the femoral canal : it may therefore be viewed in one of two lights with regard to that canal, viz. either as de- scending into it superficial to the vessels, and entering into the constitution of its anterior wall, or as concurring with the other fascia; to form, beneath the superficial lamina of the iliac portion of the fascia lata, a sheath, in which the vessels are immediately contained. The latter is the view which has been adopted by anatomists, and the appellation femoral has been given to the sheath so formed. Like the superficial lamina of the iliac portion of the fascia lata, the prolongation of the fascia trans- versalis is wider at Poupart’s ligament, and diminishes in width as it descends to the junc- tion of the saphena and femoral veins: hence the femoral sheath is considerably larger supe- riorly than inferiorly, does not embrace the vessels closely at their entrance into the thigh, and but for the aponeurotic expansion described by Colles, and termed by Cloquet the crural septum, would be open toward the abdomen ; but in proportion as they descend, it invests them more closely until it reaches the entrance of the saphena, at which point its connection to them is intimate, and from whence the prolon- gation seems to the author to be continued down- ward into the dense thin cellular or fibro-cellular investment, by which the artery and vein are surrounded and connected together within the femoral canal during the remainder of their course through the thigh. From Sir A. Coo- per's account of the prolongation it would appear that it terminated, or cannot be traced further than two inches below Poupart’s liga- ment. Sir Astley says, “ these vessels pass down within the sheath for about two inches, after which they carry with them a closely investing fascia derived from the fascia lata.” By the “ closely investing fascia,” the author understands the proper sheath of the vessels, which has been adverted to, and with which the prolongation of the fascia transversalis appears to him to be identified. According to Professor Harrison,* “ it soon becomes thin and indistinct, and is lost in the cribriform part of the fascia lata;” but in this view of its termination the author cannot concur ; the pro- longation is doubtless connected to the cribri- form fascia (the superficial lamina of the iliac portion of the fascia lata) by the vessels, which traverse both structures, but it is notwith- standing separable, without much difficulty, from it, by means of the proceeding already recommended for the display of that part — a proceeding equally applicable to that of the distinct existence and the connections of the expansion in question ; the superficial lamina being at the same time, as directed by Colles, divided from above downward, and its parts held to either side, inasmuch as a thin cellular * Dublin Dissector, p. 153. FEMORAL ARTERY. 241 or adipose stratum is interposed between them. The last particular in the disposition of the prolongation of the fascia transversalis, having reference to the femoral artery, is, that it is connected to the back of the femoral canal (the pubic portion of the fascia lata posterior to the vessels) by two septa or partitions, placed, one between the artery and vein, upon the inside of the former; the other internal to the latter, between it and the femoral ring: by those the abdominal aperture of the femoral sheath is divided into three compartments : an external one occupied by the artery, a mid- dle one by the vein, and an internal by the lymphatics, and at times by a gland. The two former are so protected that the occurrence of hernia through them is rare ; in the case of the first probably impossible; but the internal, whether from weakness or deficiency of pro- tecting provisions, allows its protrusion, and hence the relation of the femoral vessels, and more particularly of the artery to the neck of the sac of femoral hernia, upon the outer side of which it is always situate, separated from it by the vein. At the lower part of the first stage the artery is crossed obliquely by the most internal of the deep branches of the crural nerve, which for distinction sake might be called internal geni- cular : it enters the femoral canal on the out- side of the vessels above, at a variable distance from Poupart’s ligament; descends from without inward upon the front of the artery within the canal ; and escapes from it below on the inside of the vessel under cover of the sartorius. Situate, as the nerve is, within the femoral canal, upon the front of the artery, and closely connected to it by the femoral sheath, it is very likely, unless care be taken to avoid it, to be included in a ligature at the same time with the vessel : it will not, how- ever, be always encountered, inasmuch as it crosses the artery, and at a point higher or lower in different subjects. At times a second branch of the crural nerve crosses the artery in like manner as the former and lower down, but it is not to be always observed. Posteriorly in its first stage the artery rests, first upon the inner margin of the psoas magnus, from which it is separated by the deep lamina of the iliac portion of the fascia lata : while so related, it is situate over the anterior surface of the os innominatum, external to the iliopec- tineal eminence, having the two structures, already mentioned, interposed.* Below the * In this the author has ventured to differ from the account usually given of the relation of the artery to the os innominatum, according to which ( Boyer, Cloquet,) the vessel must be understood to be situate internal to the point mentioned, being said to lie upon the os pubis ; but in his opinion this is not correct. The artery lies on the psoas, which is not internal to the eminence, and upon the deep lamina of the iliac portion of the fascia lata covering the muscle, which at its most internal part is inserted into the eminence ; consequently the vessel, which lies on the lamina, must be ex- ternal to that point of bone, and observation will be found to confirm this view. VOL, IX. • os innominatum it is placed over the head of the femur, from which it is separated by the same parts, and also by the capsular ligament of the articulation, and the synovial bursa, which exists between the front of the capsule, and the psoas and iliacus muscles. There are then in this situation two resisting surfaces against which compression of the vessel may be effected ; and here also, as observed by Harrison, a tumour with pulsation may occur in case of effusion either into the bursa simply, or into the joint, when a communication exists between the former and the synovial membrane of the latter. Having passed the margin of the psoas and the head of the femur, the artery corresponds to the tendon of the psoas and iliacus, to the pectinalis, and to a small portion of the ad- ductor brevis, which parts it crosses obliquely in its descent : it is not, however, in contact with them, but is separated from them by a space of some depth occupied by cellular structure and vessels. The distance of the artery from the muscles varies according to circumstances : when the thigh is extended or rotated inward, it is increased; when, on the other hand, it is flexed or rotated outward,* it is diminished : in the former case, the artery is brought nearer to the anterior surface of the thigh by the extension, and by the rotation the lesser trochanter, which is in the middle and deepest part of the space, is carried back- ward from that surface. The vessels which occupy the interval be- tween the artery and the muscles are the pro- funda vein, the circumflex veins, and the femoral vein in part, they being next to the artery and immediately behind it ; posterior to them are, at times, the profunda artery, and at the upper part, according to circumstances, one or other of the circumflex arteries, when arising, as in ordinary, from it. External to the artery in its first stage are the psoas and iliacus muscles, the sartorius, the rectus, and the upper extremity of the vastus internus muscles ; from all which it is separated by the wall of the femoral canal. At the entrance of the artery into the thigh, and for about an inch below Poupart’s liga- ment, the crural portion of the genito-crural nerve is contained within the femoral canal in immediate apposition with the vessel upon its outer side. External to it are situate also the crural nerve above,and its saphena branch below. Except in rare instances, the profunda arterv lies on the outer side of the femoral during a greater or less extent of its first stage ; but it is, unless occasionally near to its origin, at the same time posterior to it, and is subject to varieties in its relation which will be more particularly detailed in the description of that vessel. Internally the artery corresponds, though at a distance, to the pectinalis and adductor mus- cles. The femoral vein at the upper part is very nearly upon the same level ; the artery, however, is somewhat anterior to it, probably * Harrison. B 242 FEMORAL ARTERY. from resting upon the psoas, while the vein corresponds to the pubes between that muscle and the pectinalis: hence the two vessels at their entrance into the thigh, allowance being made for the trifling difference which has been mentioned, lie side by side, the vein internal to the artery; but as the former descends from the pubes, it recedes from the surface more than the artery, and at the same time inclines outward, and thus it becomes posterior to it at the lower part of the stage, so as to be con- cealed by the artery by the time it has reached its termination. It is included with the artery in the femoral sheath, and is separated from it by the external of the two septa, which have been described. In its second stage the relations of the artery differ considerably from those in its first. In the first place it is covered throughout by the sartorius, the muscle crossing it obliquely from without inward, and thence first overlapping it by its inner edge, and gradually extending over it until the vessel is directly covered by it. Secondly, it is in consequence covered by two lamina: of the fascia lata enclosing the muscle; one superficial to it, the other beneath it, form- ing the front of the femoral canal ; it has then two new coverings, the muscle and the second lamina of the fascia. Thirdly, the femoral vein, which is very closely connected to the artery, is directly behind it, between it and the adduc- tor longus muscle, to which the artery corre- sponds posteriorly. Fourthly, it has no part deserving of attention upon its inside ; and, lastly, the saphenus nerve is within the femoral canal, along the outer side of the artery and anterior to it. The inferior third of the artery also presents some peculiarities of relation. The vessel is still covered by the sartorius; but here the muscle is more to the inner, as in the second stage it is more to the outer side of the vessel, not only connecting it in front, but also lying against its inner side, and the more so the nearer we approach the termination of the stage ; so much so indeed, that at its termina- tion, the artery, when injected, may be felt beneath the outer margin of the muscle ; and hence the difference between the mode of pro- ceeding with regard to the sartorius recom- mended generally to be adopted, when occasion arises for seeking the artery in its inferior third, and that to be pursued when the vessel is to be exposed in its second stage ; it being ad- vised, in the latter case, to displace the inner edge of the muscle outward, and in the former the outer inward, in order to reach the vessel with the greatest ease and certainty. The ves- sel is also covered by the same two laminae of the fascia; but the deep one presents at this part remarkable features : it increases in thick- ness and is more aponeurotic in proportion as it descends, and hence it is stronger the nearer we approach the termination of the course of the artery ; but in the inferior third its thick- ness is stdl further augmented by numerous tendinous fibres, which pass from the tendons of the adductors longus and magnus to that of the vastus internus, add very much to the thickness of the fascia, and give to it the ap- pearance of a tendinous expansion of great strength, connecting the tendons of the mus- cles, which have been mentioned, and covering the artery upon its anterior and internal sides. It is also to be observed that this accession of fibres from the tendons exists only in the infe- rior third of the artery’s course, and not in its middle stage, and hence the covering of the vessel beneath the sartorius, or the anterior wall of the canal, is much thicker and stronger in the former than in the latter ; and hence also one of the difficulties encountered in getting at the vessel in the third stage. The artery in this third stage is situate upon the inside of the shaft of the femur, crossing it ob- liquely from before backward : it is not, how- ever, in contact with the bone, but is separated from it by the vastus internus muscle : it is enclosed, as before stated, between muscles ; the sartorius before and internal to it, the ad- ductors longus and magnus behind it, and the vastus internus on its outside. The other relations of the vessel in this stage are to the saphena vein, the saphenus nerve, the femoral vein, and the superficial superior internal articular artery. The first is situate between the femoral artery and the internal face of the thigh, for the most part along the inner margin of the sartorius, but varying some- what in this respect, lying at times upon the muscle, from its middle to its inner edge, and at others posterior to it. The saphenus nerve is placed at first, as in the second stage, exter- nal and anterior to the artery, but it crosses it at its termination and escapes from the canal, upon its inside, in company with the superficial articular artery, as the vessel is about to pass into the popliteal space. The femoral vein is behind the artery and somewhat external to it : the latter relation of the vein is expressly de- nied by Velpeau,* but after careful examina- tion the author does not hesitate to affirm it. The superficial superior internal articular artery, a branch of the femoral, is given off by the artery immediately before its termination ; it arises from the front of the vessel, descends nearly in the course of it, escapes from the femoral canal in company with the saphenus nerve, and, holding generally the same relation to that nerve which the femoral itself does, may hence be mistaken for that artery at the inferior pait of its course. Thus the relations of the vessel are here in several particulars the reverse of those in its former stages, and the methods most eligible for adoption in operation ought to be varied accordingly. Operation in its last stage is seldom required, but it may be necessary, as in wounds of the artery at that part, in which case the mode of proceeding with regard to the sartorius and to the artery should be the reverse of that recommended for the upper stage, the muscle being to be displaced inward in order to expose the artery, and the separation of the latter from the vein to be effected in the same direction. * Anatomie des Regions, t. ii. p. 485. ed. 1. FEMORAL ARTERY. 243 At the termination of its third stage the arteiy passes into the ham and there receives the name of popliteal : it enters the popliteal region through an elliptical aperture situate to the inside of the femur at the junction of its middle and inferior thirds, and upon a plane with its posterior face, the longer diameter of which corresponds to the course of the arteiy, and which is circumscribed by the lower mar- gin of the united tendons of the adductor longus and the adductor magnus above, by the connection between the tendon of the adductor magnus and that of the vastus internus below ; by the tendon of the adductor magnus inter- nally, and by that of the vastus internus exter- nally : in passing through, the artery carries with it a prolongation of the femoral sheath, by which the popliteal vessels become invested and connected. Varieties. — The superficial femoral arteiy sel- dom presents a variation from itsaccustomed dis- position, so much so that it may almost be held to be uniform in this respect : however two forms of deviation have been observed, rare in occur- rence, but of great importance in a practical point of view. Two instances of the first ab- normal arrangement are recorded, one of which occurred to Sir Charles Bell, and has been pub- lished by him in Anderson’s Quarterly Journal for the year 1826 : the second is preserved in the Museum of the College of Surgeons, and has been described in the fourth volume of the Dublin Hospital Reports by Dr. Houston, Conservator to the Museum. In these cases the femoral arteiy divided into two vessels of nearly equal size, which pursued the usual course of the artery side by side and very close together, not, however, in contact, but contained in distinct compartments of the sheath and separated by a septum : hence the existence of the second artery might in operation easily pass unobserved, it not being brought into view by opening the sheath of the other. One was also larger than the other, and situate internal and on a plane posterior to it. In Bell’s case the discovery was the consequence of the un- fortunate event of an operation for popliteal aneurism ; the operation was performed in the middle third of the thigh. The pulsation of the aneurism, which was arrested on the appli- cation of the ligature, returned after an interval of some seconds, and became nearly as distinct as before : it ceased again upon the third day, but the patient was carried off on the sixth day by an erysipelatous inflammation of the thigh. On examination after death, it was ascertained that the disposition, which has been described, was present, and that but one of the two vessels had been tied. The second form of deviation is a high bifurcation into the posterior tibial and peroneal arteries: of this an instance* has been recorded by Sandifort, in which the division took place immediately below Poupart’s ligament ; and Porta If states that the crural artery has been seen to divide into two large branches shortly * Green on the Varieties in the Arterial System, and Sandifort, Observ. Anat. Pathol, iv. 97. t Anatomie Medicale, t. iii. p. 326. after its escape from the abdomen, and then there were two popliteal arteries : he further states that among individuals, in which the brachial artery was bifurcated higher than usual, the crural artery was so also in a remarkable proportion.* A division of the femoral artery into two trunks of equal size, running parallel and so near together, that they might be conveniently included in one ligature, is recorded by Gooch in the Philosophical Transactions for the year 1775, it being the third instance in amputations of the thigh, in which he had observed such a lusus nature in the arterial system ; but it is not mentioned whether they were instances of the first or of the second kind of variety : he himself, whether from examination or from in- ference, appears to have concluded that both trunks were prolonged into the lower part of the limb. Those deviations have been accounted repe- titions of similar irregularities in the brachial artery, than which, however, they are far less frequent. It is a matter to be regretted that neither in the case of Bell, nor in that of Houston, has any account been given of the disposition of the artery of the upper extremi- ties or of the other thigh. Branches of the femoral artery. — The branches given off by the femoral artery are numerous ; but the trunk of the vessel being itself intended for the supply of the leg and foot, the branches which it gives to the thigh are, with the exception of one intended speci- ally for the nutrition of that part, inconsider- able in size. The artery gives branches to the integuments of the abdomen, to the glands and other structures in the groin, to the external organs of generation, to the muscles in the vicinity of which it passes, to the inner side of the knee ; and, lastly, it gives the large branch, adverted to, for the supply of the thigh, and by which those inosculations with other arteries are formed, by means of which chiefly an in- terruption in the course of the main vessel is compensated. Those which have received names are five, viz. 1. the superficial epigas- tric ; 2. the superficial or external pudic ; 3. the superficial anterior iliac ; 4. the profunda; and 5. the superficial superior interrial articular arteries. Of those the first four arise from the artery within its first stage ; the epigastric, iliac, and pudic being given off immediately or at a very short distance below Poupart’s ligament ; and the profunda at a greater although a variable distance from that part. 1 . The superficial epigastric artery ( art'ere sous-cutanee abdominale, Cloquet ; inguinale, Chaussier;) ordinarily arises from the front of the femoral, immediately below Poupart’s liga- ment. Sometimes it is given off from a branch common to it and either one or both the ex- ternal pudics ; or it may proceed from the pro- funda.f It first comes forward through the fascia lata, and then ascends over Poupart’s * Ibid. p. 239. t Boyer. R 2 2-44 FEMORAL ARTERY. ligament upon the inferior part of the abdomen, superficial to the aponeurosis of the external oblique muscle, and enclosed in the subcuta- neous cellular stratum. Its course is irregular, at times nearly parallel* to that of the deep epigastric within the abdominal wall ; at others ascending directly upon the abdomen ; in ge- neral it pursues the latter course. It is consi- derably smaller than the deep epigastric artery, and is concerned altogether in the supply of superficial parts, and in establishing commu- nications with other vessels. Its first branches are distributed to the inguinal glands and co- verings : during its ascent upon the abdomen it gives to either side branches which supply the superficial structures, and inosculate through the ventral foramina with branches of the inter- nal epigastric from within ; and it terminates by communicating with the same and with those of the internal mammary, and of the inferior intercostals. It is, unless in case of disease, a small vessel, and of consequence only from being exposed to be divided in cer- tain operations, viz. that for inguinal hernia, or that for tying the external iliac artery. 2. The superficial or external pudic arteries (scrotales ou vulvaires, Chauss.) are generally two, distinguished into superficial f and deep, or superior l and inferior: of those distinc- tions the latter seems preferable, inasmuch as they are both equally superficial in their dis- tribution, and the difference between them in this particular amounts to no more than that the second continues longer beneath the fascia lata than the first. They arise in general either directly from the femoral, or from a trunk com- mon to them with the superficial epigastric, with which they are of nearly equal size. The superior is given off immediately below Poupart’s ligament; comes through the fascia lata, and at the same time gives branches to the inguinal glands; runs, superficial to the fascia, inward and also upward toward the pubes; and either divides into two, one of which as- cends above, the other, the more considerable, continues below that part; or, as it proceeds, it gives off small branches which ascend above the pubis, and supply the superficial struc- tures upon the inferior middle part of the ab- dominal wall; while it is itself continued to the scrotum and side of the penis, the coverings of which it supplies; or into the labium in the female. Its branches communicate with those, which the external organs of generation receive also from the internal pudic artery, and with branches of the epigastric arteries. This branch is usually divided in the operations for either inguinal or femoral hernia. The inferior external pudic artery arises from the femoral at a greater distance from Poupart’s ligament than the former: at times it is given off by the profunda§ artery, or from the in- ternal circumflex, || or from the superior branch :1[ at others it is absent.** It is situate beneath the * Harrison. f Cloquet. I Harrison. S Boyer, Cloquet, Tiedemann, H Harrison. 11 Ibid. ** Ibid. fascia lata through a greater extent of its course than the superior; runs inward across the pec- tinalis muscle, covered hy the fascia; passes then through the fascia, and gains the scrotum or the labium and the perineum, in which it is distributed, communicating with the inferior branch of the former and with the perineal artery. Its course is at times so far from Pou- part’s ligament that it crosses behind the sa- phena vein. Occasionally a third* external pudic artery is present, arising either from the femoral itself, the profunda, or the internal circumflex artery. 3. The superficial anterior iliac artery (ar- teria circumfiexa ilii superficialis, Harrison ; external cutaneous, Scarpa ; artcre musculaire superficiclle, Cloquet ;) arises from the outer side of the femoral artery, or at times from the profunda :f it runs outward in front of the crural nerve, and after a short course divides into three branches. Its first comes from within the fascia lata and is distributed to the superfi- cial inguinal glands : its second branch also comes through the fascia, runs round the ante- rior and outer side of the thigh, below the spinous process of the ilium, and is distri- buted superficially: and its third runs outward and upward, beneath the fascia lata, toward the superior anterior spinous process of the ilium ; supplies the sartorius and tensor vaginae muscles at their origin, and also gives branches to the iliacus interims. This artery communi- cates with branches of the gluteal, the deep anterior iliac, and the external circumflex arteries. 4. The profunda artery (arteria profunda femoris; intermusculaire, Chauss.) is the vessel by which the muscles and other structures of the thigh are for the greater part supplied, whence it may be regarded as in strictness the femoral artery, the trunk of the femoral, in its general acceptation, being distributed to the leg and foot : it is also the channel through which the communications between the femoral artery and the main arteries of the trunk on the one hand, and of the lower part of the limb on the other, are established, and by which, in case of interruption of the first vessel, either below or above the origin of the profunda, the circulation is to be restored : it is therefore an artery of great importance, and also of great size, being nearly equal to, though for the most part somewhat smaller than, the femoral itself, while in many cases it is fully equal to it. Hence, probably, it has received the name profunda femoris, deep femoral artery; and by many the femoral artery is distinguished into the common femoral and the superficial and deep femora Is ; the first extending from the entrance of the vessel into the thigh to the origin of the pro- funda ; the second being the vessel from the point last mentioned to that at which it becomes popliteal ; and the third the artery which is at present under consideration. The profunda artery for the most part arises from the posterior and outer side of the femoral * Scarpa, Boyer. f Cloquet, Scarpa. FEMORAL at a distance, varying from one to two inches, below Poupart’s ligament : it descends thence backward into the inguinal region, posterior to the femoral artery, and corresponding to the muscles situate behind them in the same order as the femoral itself until it reaches the adductor longus : it then passes behind that muscle and continues its descent between it and the adductor magnus, until after it has given off its last perforating branch, when it also perforates the magnus at the lower part of the middle third of the thigh, and finally is distributed to the short head of the biceps and the vastus externus, gives to the femur its in- ferior nutritious artery, and anastomoses with the descending branches of the external cir- cumflex artery, and with branches of the pop- liteal. During its descent the profunda recedes from the surface more than the femoral artery, so that it lies nearer to the bottom of the in- guinal space, and when placed directly behind it, is separated from that vessel by an interval, which is occupied by the femoral, the pro- funda, and the circumflex veins. It is accom- panied by a corresponding single vein of con- siderable size, the profunda vein, which in the upper part of the thigh is situate before the artery, intervening, as has been mentioned, between it and the femoral artery. It is con- tained at first within the same sheath with the femoral; but it is presently received into a proper sheath, an offset from the back of that which encloses the other vessel. It has not an immediate relation to any nerve. Such are the general relations of the pro- funda artery ; but it presents frequent varieties, which derive importance from the practical connections of the femoral vessels. The par- ticulars, in which it is subject to diversity, are the precise situation and relation of its point of origin, and the relation of its course to that of the femoral artery. The profunda arises generally, as has been stated, from the posterior and outer side of the femoral ; but at times its origin is directly behind that vessel, at others directly from its outer side, and occasionally again from its inner side, as may be seen from fig. 3, tab. xxxiii. of Tiedemann. The situation of its origin also is variable, at times being close to Poupart’s ligament, at others at some distance from it. According to Boyer* it corresponds to “ the middle of the space comprised be- tween the pubis and the little trochanter ; sometimes higher, but rarely lower.” Accord- ing to Scarpa.f the division of the femoral artery takes place “ at the distance of one inch, or one and a half, very rarely two inches, below the crural arch in a well-formed adult, of the ordinary stature.” According to Har- rison, J the profunda arises “ in general about two inches below Poupart’s ligament, some- times an inch or two lower down, and some- times much nearer to this ligament.” Of those * Traite complet d’Anatomie, tom. iii. p. 150. t Treatise on Aneurism, Wishart’s translation, p. 3. } Op. cit. vol. ii. p. 144. ARTERY. 245 three accounts that of Scarpa appears pre- ferable : the “ distance between the pubis and the lesser trochanter” is variable, and affords no guide for the living subject, and the author has never witnessed the origin of the vessel by any means so far from Poupart’s ligament as the statement of Harrison would imply : a distance of four inches, which may be un- derstood from it sometimes to occur, would bring the origin down to the point at which the sartorius generally commences to overlap the femoral artery, and this is manifestly alto- gether too low ; while on the other hand Scarpa* states expressly that it is never below the maximum point which he has laid down, viz. two inches from the ligament, and Hodg- sonf asserts that “ it very rarely arises so low as two inches.” The maximum distance im- plied in the description of Harrison is that which has been laid down by Bell as the me- dium point of origin, on which Burns J re- marks, “ I infer that Mr. Bell has described this artery from dried preparations, in which, from the retraction of Poupart’s ligament, the origin of the profunda seems to take place lower than on the recent subject.” The only objection which can be made to the view of Scarpa, is that the vessel not unfrequently arises nearer to the ligament than one inch from it, its origin being at times abso- lutely at it, and having been in some few instances observed even above the ligament, before the femoral had escaped from the ab- domen, or more properly from the external iliac artery : of this extraordinarily high origin four instances have been recorded by Burns, § and Tiedemann || has met with it in a female, upon both sides. Tiedemann^! has also in- ferred from his researches that the profunda arises nearer than usual to Poupart’s ligament more frequently in females and in subjects of small stature than in others. The relation of the course of the profunda to that of the femoral is the next point of variety. The main course of the former is external to that of the latter ; in arriving at its destination, however, it does not at all times pursue an uniform course, but presents diversities in this respect, which affect very much its relation to the femoral artery. Its general direction is downward, backward, and outward ; still more outward than the femoral : it is seldom how- ever direct, but describes one or more inflec- tions, by which its course is made at times to cross once or oftener that of the other vessel ; and hence the diversities in its relation to the femoral which have been adverted to. When the course of the vessel is direct or little tor- tuous, the profunda is situate throughout, external to the femoral, and this relation would appear to prevail at least as frequently as any * Op. cit. p. 328. f Treatise on Diseases of Arteries and Veins, p. 434. $ On Diseases of the Heart, &c. p. 319, 20. £ Ibid. [| Explicatio Tabularum Arteriarum, p.323. H Ibid. 246 FEMORAL ARTERY. other, or to be the most prevalent, for such is the view of the course of the artery given by Haller,* * * § in two of three views in which the relative course of the two vessels is repre- sented, and by Tiedemann + in two of four views. But at other times, when the artery is more tortuous, after descending for a little way external to the femoral, it makes a turn, and passes inward behind it, and thus fre- quently gains the inner side of that vessel before it reaches the adductor longus, after which it again inclines outward toward its destination. Such is the view given of its course by Scarpa, J with which the description of Harrison coincides : it is similarly repre- sented by Tiedemann in fig. 4, tab. xxxiii., and also by Haller § in one instance ; but the author is disposed to regard this as a less common disposition, as well from the fre- quency with which he has observed the former one to occur, as from the weight of the autho- rities which have been adduced in favour of that opinion. In other but rare instances the profunda, arising from the inside of the femo- ral, inclines at first inward and becomes in- ternal to it, and then bending outward crosses behind the femoral to its outer side : of this arrangement an instance is furnished by Tiede- mann in fig. 3, tab. xxxiii. And in others the artery does not in the first instance incline sensibly to either side; but arising from the back of the femoral it descends behind that vessel, and does not gain its outer side until it has reached the lower part of the inguinal region. When the profunda artery arises very near to or above Poupart’s ligament, and from the outer side of the femoral, is large and pursues its ordinary course, two arteries of equal or nearly equal size may be found, at the upper part of the inguinal region, side by side, and upon the same level, and thence liable to be taken, either of them, for the femoral artery. When such an arrangement occurs, the ex- ternal|| of the two vessels will almost certainly be found to be the profunda, for if that artery have once passed inward behind the femoral, it cannot afterward gain the same level with it, so as to be situate at the same time internal to and on the same plane with it : further, as the profunda descends, it recedes from the an- terior surface more than the femoral, in order to pass behind the adductor longus, and thus it gains at the lower part of the region a deeper situation than the other. But inasmuch as the profunda occasionally arises from the inside of the femoral artery, it may be possible for it, in case of high origin, to be the inner of the two vessels adverted to. Such a circumstance, however, if it ever occur, must be extremely rare, but in order to guard against it, the pre- * leones Anatomic*. t Tabulae Arteriarum. Tab. xxxi. and fig. 2. tab. xxxiii. t Reflexions et Observations Anatomico-chirur- gicales sur l’Aneurisme, tab, lere. § Op. cit. || Harrison, op. cit. vol. ii. p. 165. Hargrave, System of Operative Surgery, caution recommended of alternately compres- sing the vessels and ascertaining the effect previous to the application of a ligature, should never be neglected. Brunches of the profunda artery. — The pro- funda gives off a considerable number of branches, some of which being distributed to the muscles, by which the artery passes, and not being remarkable either for their size or their communications, have not received par- ticular names. Those which are most de- serving of attention, whether for their size, the extent and peculiarity of their course, or the anastomoses which they form with other arteries, are five or six in number, viz. two circumflex arteries, and three or at times four perforating arteries. The circumflex arteries are so named because they wind round the upper extremity of the femur, and form an arterial circle around it : they are distinguished by the epithets externul and internal, being destined, one to the outer, the other to the inner side of the limb : they are vessels of considerable size and importance because both of the extent of parts which they supply, and of the communications which are established through them between the femoral, the arteries of the pelvis, and those of the lower parts of the limb. 1. The external circumflex artery at times is the first branch of the profunda ; at others it is preceded by the internal circumflex : it is given off from the profunda while it lies on the outside of the femoral at a variable dis- tance from Poupart’s ligament, and arises from the outer side of the artery : occasionally it is given off by the femoral itself; it runs directly outward, or outward and downward, in front of the psoas and iliacus muscles; beneath the sartorius and rectus, and either between or behind the divisions of the crural nerve ; and divides after a short course into three branches, viz. an ascending, a descending, and a circum- flex. a. The first, the ascending branch, runs up- ward and outward toward the superior anterior spinous process of the ilium, between the iliacus internus and the glutoeus medius mus- cles, and concealed by the tensor vaginae fernoris : as it proceeds, it gives branches to those muscles; and having reached the outer and back part of the spinous process, it ter- minates in an anastomosis with a branch of the glutceal, and also with the deep cir- cumflex ilii arteries. The anastomosis with the glutceal artery becomes remarkably en- larged when the main vessel is interrupted above the origin of the profunda, as may be seen from Sir A. Cooper’s case of femoral aneurism.* b. The second, the descending branch, runs downward and outward beneath the rectus muscle, between it and the triceps crural, and divides after a short course for the most part into several branches of considerable size and great length for the supply of those muscles and for establishing communications : the branches are * Guy’s Hospital Reports, Jan. 1836, pi. 1. FEMORAL ARTERY. 247 at times so many as five or six, and are dis- tributed one or more to the rectus, entering the muscle upon its deep surface, and pro- longed to a great length within its substance ; one to the vastus interims, one to the cruroeus, and one or two to the vastus externus : they are accompanied, several of them, by branches of the crural nerve, and they run for a con- siderable distance, particularly the infe- rior branch to the vastus externus, between the divisions of the triceps crural muscle, before entering their substance : they are pro- longed very low down, and may be followed some of them to near the knee, where they anastomose with branches of the femoral in the vastus internus, and with the superior articular arteries. But the branches of the descending division of the external circum- flex artery are by no means uniform in number or destination, more or fewer of the arteries just described being at times branches of the profunda itself; thus, at times that to the vastus internus, that to the crureeus, and that to the rectus, arise from the profunda below the circumflex, and in such case the descend- ing branch of the latter consists solely of the branch or branches destined to the vastus ex- ternus muscle. c. The third, the circumflex branch, pursues at first the course of the original vessel, and runs outward across the upper extremity of the shaft of the femur below the great trochanter, beneath the rectus and tensor vagina muscles, and superficial to the cruraeus. It gives, in this situation, branches to the cruraus, the iliacus, the rectus and tensor muscles. It then passes backward upon the outside of the femur to its posterior part, and thus surrounds the bone upon its anterior and external sides. In the latter part of its course it traverses the upper extremity of the vastus externus, and gives off, 1. branches upward and downward into the muscle; 2. a branch or branches which run between the vastus and the bone, and supply the periosteum; 3. a branch to the gluteus maximus at its insertion, which, after furnishing it branches, perforates the muscle and becomes superficial. The circumflex divi- sion of the external circumflex anastomoses with the internal circumflex, the glutceal, the sciatic, and the perforating arteries. The ex- ternal circumflex artery is accompanied by a large vein, which crosses between the femoral and profunda arteries, superficial to the latter, in order to join the femoral or the profunda vein. 2. The internal circumflex artery is a larger vessel than the external : it is given off by the profunda usually after the external, and arises from the inner side of the artery, but at times it arises before the external. According to Harrison it “ very frequently proceeds from the femoral artery, prior to the origin of the pro- funda;” it has been found by Burns* arising from the external iliac artery, and also from the femoral artery a little below the crural arch. In the former case “ it ran along the front of * Op. cit. p. 319. the lymphatic sheath and in the second “ it traversed the front of the common sheath of the great vein and also of the lymphatics ;” and in either case, as observed by Burns, it must be exposed to great danger in operation for femoral hernia. According to Green,* both circumflex arteries sometimes are furnished from a common trunk. It runs inward, back- ward, and downward toward the lesser tro- chanter into the deepest part of the inguinal region, and escapes from that space posteriorly between the tendon of the psoas and the pecti- nalis muscles ; continues its course backward, on the inside of the neck of the femur and the capsular ligament, below the obturator exter- nus, behind the pectinalis, and anterior to the adductor magnus and the quadratus muscles, until it has got behind the neck of the bone ; and lastly, it passes through the internal, which separates the inferior margin of the quadratus femoris from the upper margin of the adductor magnus, and thus gains the posterior region of the thigh, where it terminates as will be de- scribed. The internal circumflex artery is the vessel which gains the deepest situation in the groin : it is internal and posterior to the profunda, and when it arises from that artery, while external to the femoral, it crosses the latter vessel poste- riorly in its course. While within the inguinal region the internal circumflex artery gives off first a branch to the iliacus and psoas muscles: then a considerable branch, denominated by Tiedemann superficial circumflex branch, which contributes to supply the pectinalis, the adduc- tor longus, and the adductor brevis : it runs upward and inward upon the pectinalis, at the same time giving branches to it and to the ad- ductor longus, until it reaches the interval be- tween these muscles : it then divides into two, of which one ascends in the course of the original branch, between the muscles men- tioned, toward the origin of the adductor longus, supplying the two muscles, and ultimately anastomosing with branches of the obturator artery : small branches of it traverse the adduc- tor, and become cutaneous upon the upper and inner part of the thigh. The second branch passes downward and backward, also between the pectinalis and the adductor longus, gains the anterior surface of the adductor brevis, and there meets the obturator vessels and nerves : it divides into several branches, of which some are distributed to the last muscle, some anas- tomose with the obturator artery, and others with the upper perforating artery. Behind the pectinalis the internal circumflex artery gives several branches. Downward it gives a considerable one to the adductor mag- nus, which descends into that muscle, supplies it and anastomoses with the perforating arteries. Upward and forward it gives to the adductor brevis and the obturator externus branches which communicate freely with the obturator artery after its escape from the pelvis. Out- ward it gives the articular artery of the hip a branch, small, but remarkable for its course and * Op. cit. p. 31. 248 FEMORAL ARTERY. destination ; it enters the articulation beneath the transverse ligament, through the notch at the internal and inferior part of the margin of the acetabulum, over which the ligament is thrown ; supplies the adipose structure which occupies the bottom of the socket, and is con- ducted by the ligamentum teres to the head of the femur, in which it is ultimately distributed. That part of the artery which reaches the head of the femur is of very inconsiderable size, and is the source upon which the nutrition of that part depends in fracture of the neck of the bone within the capsule. Lastly, upward and back- ward the artery sends off a considerable and regular branch which is usually described as one of its terminating branches, but which, in the opinion of the author, may with more pro- priety be considered as belonging to its middle stage. It passes upward and outward between the obturator externus and the quadratus mus- cles to the trochanteric fossa, where it is dis- tributed to the muscles inserted behind the trochanter, viz. to those which have been just mentioned ; to the obturator internus, the gemelli, the pyriformis, the glutoei medius and minimus, and to the back of the ilio-femoral articulation, and where it inosculates with the glutmal, sciatic, and external circumflex arte- ries. It may be appropriately called the poste- rior trochanteric * branch. After its passage between the quadratus and the adductor magnus, the circumflex artery divides, in the posterior region of the thigh, into an ascending and a descending branch. The former passes upward to the origin of the biceps, semi - membranosus and tendinosus muscles, and to the glutceus maximus ; the latter downward to the former muscles, to the adductor magnus, and to the sciatic nerve. They communicate with the sciatic, the exter- nal circumflex, and superior perforating arte- ries. The perforating arteries are three or four in number. They are given off backward by the profunda, below the origin of the circumflex arteries, and are denominated numerically first, second, third, &c. They all pass from the an- terior to the posterior region of the thigh by perforating the adductor magnus, and at times also the adductor brevis, whence their name ; they divide for the most part into ascending and descending branches, and are consumed partly in the supply of that region, and partly in establishing a chain of communications be- tween the arteries of the trunk and the main artery at the upper and the lower parts of the thigh. 3. The first perforating artery arises from the profunda immediately below the lesser trochan- ter, nearly opposite the lower margin of the pectinalis : it passes backward, descending a little below the lower margin of the pectinalis, either between it and the upper one of the ad- ductor brevis, or through an aperture in the latter muscle : it next perforates the adductor magnus close to the linea aspera, and so gains the posterior region of the thigh, where it * Scarpa, op. cit. divides into two or three large branches, of which one ascends and is distributed to the glutceus maximus, communicating with the glutoeal, sciatic, and circumflex arteries; ano- ther descends, supplies the long head of the biceps, the semi-membranosus and semi-tendi- nosus, and communicates with the inferior per- forating arteries ; and the third runs downward and outward into the vastus externus, through which it descends, communicating at the same time with the external circumflex artery. The artery also gives branches to the sciatic nerve, and, during its passage from the front to the back of the thigh, to the pectinalis and the ad- ductors. According to Harrison, “ this artery is sometimes a branch of the internal circum- flex; its course is nearly parallel to that vessel, and is separated from it by the tendon of the pectinaeus muscle, the first perforating artery passing below that tendon, while the circumflex artery runs superior to it.” 4. The second per foruling artery is generally the largest of those vessels : it arises a short distance below the first, and passes through both the adductors brevis and magnus ; it then divides, like the former, into ascending and de- scending branches : the former are distributed to the glutceus maximus, the vastus externus, and the tensor vaginae, likewise anastomosing with the first perforating, the glutoeal, sciatic, and circumflex arteries : the latter are distri- buted to the biceps, semi-membranosus, and semi-tendinosus, the vastus externus, and the integuments of the back of the thigh, and in- osculate with the inferior perforating and with branches of the popliteal artery. The artery also gives branches to the adductor muscles and to the sciatic nerve and the nutritious artery of the femur, which enters a canal to be ob- served in the linea aspera, at the junction of the first and second thirds of the thigh, leading obliquely upward into the bone. The second perforating artery at times does not pass through the adductor brevis, but when the first does so, it generally runs inferior to it, perfora- ting the adductor magnus only. 5. The third perforating artery is smaller than either of the former, and arises lower down; according to Harrison, at the upper edge of the adductor longus muscles, it passes through the adductor magnus, and divides in the same manner as the others : its branches are also similarly distributed, and anastomose with the second perforating artery from above, and with branches of the popliteal from below. When a fourth perforating artery exists, it pursues a similar course and is distributed similarly to the last. The perforating branches of the profunda are subject to much variety with regard to number, size, and precise course and distribution ; so much so that they hardly admit a definite description : the preceding ac- count has been taken from a comparison of the most approved authorities with the subject, in order, as far as possible, to embrace their nu- merous irregularities. Beside those branches, which have been enumerated, to which proper name have been given, the profunda artery gives off during its FEMORAL ARTERY. 249 course others less regular and less considerable, which are distributed to the muscles in its vicinity. Those are a branch to the pectinalis and adductor muscles, and one or more to the vastus internus and crurseus muscles : it has been elsewhere stated that the descending branches of the external circumflex, destined to the last-named muscles, and one of those to the vastus externus, at times also arise from the profunda itself. After having given off the last perforating artery, the profunda, very much reduced in size, continues its descent behind the adductor longus muscle, inclining at the same time outward, and external to the femoral artery : it passes through the adductor magnus a little above the passage of the femoral into the ham, giving it small branches; then tra- verses the origin of the short head of the biceps, giving it also branches; and, lastly, enters into the outer part of the vastus externus, through which it descends frequently to near the knee, distributing branches to the muscle, and anasto- mosing with the descending branches of the external circumflex and with the external arti- cular artery. The termination of the profunda is by some* called the fourth perforating artery. The profunda resembles very much in its course and termination the superior profunda or musculo-spiral branch of the brachial artery, to which it may be considered analogous. Immediately before the femoral artery passes into the popliteal space, it gives off its fifth and lowest branch. This is usually called the anastomotica magna artery, but there being no more reason to apply the epithet anastomotic to it than to the other branches of the femora, and the great anastomotic artery of the thigh being in reality the profunda, the name given to it by Tiedemann seems much to be preferred, viz. superficial superior internal articular. It arises from the front of the femoral at the inferior part of its last stage, and immediately escapes from within the femoral canal, passing- through its anterior wall at the same time with the saphenus nerve, as the femoral itself is about to pass into the ham. Having come through the aponeurosis forming the wall of the canal, it descends for some distance toward the inside of the knee parallel to the tendon of the adductor magnus and anterior to it in company with the saphenus nerve, and covered by the sartorius muscle. After a short course it divides into two branches. One of these runs down- ward and forward, in front of the adductor magnus, toward the patella ; enters the vastus internus and traverses it in its course ; divides within it into two branches, of which one runs between the muscle and the bone, and supplies the periosteum of the femur and the capsule of the articulation, anastomosing at the same time with the deep articulars ; the other continues its course through the vastus, supplying the muscle, until it reaches the side of rue tendon of the extensors : it then becomes superficial to the tendon, and descends upon the front of the patella, ramifying freely upon it, supplies the * Scarpa, op. cit. p. 17, 18. integuments and other superficial structures of the articulation on its anterior part, and com- municates freely with the other articular arte- ries. The second branch, into which the superfi- cial articular divides, descends posterior to the tendon of the adductor, in company with the saphenus nerve, and covered by the sartorius : as it descends, it gives branches to the ham- string muscles, the semi-membranosusandsemi- tendinosus, and also to the sartorius : when it has reached the inner side of the knee, it divides into two, of which one passes forward beneath the aponeurosis, upon the internal condyle of the femur, divides into branches which supply the superficial structures of the joint upon its inside, can be traced forward beneath the pa- tella, and form free communications with the other articular arteries, more particularly with the inferior internal one : the second descends to the leg, escapes from beneath the tendon of the sartorius, and then, turning forward, rami- fies over the internal surface of the tibia below its tubercle, supplies the insertions of the mus- cles and the coverings, and communicates with branches of the internal articular and of the tibial recurrent arteries. The superficial supe- rior internal articular artery is variable in size : at times it is of very considerable magnitude ; at others it is small, or even absent altogether, its place being supplied by a branch of the popliteal artery. Its distribution also varies with its size, the extent of the former being proportioned to the latter. The course of the artery diverges but little from that of the femoral, and the relation of the saphenus nerve to it is almost the same as that which the nerve holds to the latter vessel : hence, when the branch is large, it is liable to be mistaken in the operation of tying the main vessel, particularly in case of wound of the artery, for the femoral itself. The description of the articular artery here given has been taken from the plate of Tiedemann, in which the vessel is represented with its most extended distribution. The femoral artery also gives off, during its descent through the thigh, beside the branches which have been described, several others to the muscles which are in its vicinity ; above, it sends branches to the sartorius, lliacus, and pectinalis ; and in the middle of the thigh to the vastus internus on the one hand, and to the adductor muscles on the other. Those branches are for the most part inconsiderable in size, and have not received names, but they are de- serving of attention, inasmuch as they coope- rate in the collateral circulation, more particu- larly the second set, through which the femoral artery is generally preserved pervious, after ligature below the origin of the profunda, during a greater or less extent of the interval between the ligature and the popliteal artery, by means of the anastomoses between the branches in question and the circumflex arteries. The adequacy of the collateral circulation in the thigh to the maintenance and nutrition of the limb after the interruption of the femoral artery, has been so long established that it is 250 FEMORAL ARTERY. at present unnecessary to insist upon it. But the channels through which the circulation of the blood becomes in such cases restored, as well as the relations of the new circulation, are deserving of attention. The collateral connections of the femoral artery are distinguishable into those between it and the arteries of the trunk, those between it and the popliteal and arteries of the leg, and those between different parts of its own course. The communication of the femoral artery with the arteries of the trunk are established between it and both the internal and the external iliacs. Those with the internal iliac are formed, 1. by means of the inosculations of the branches of the profunda, the circumflex and perforating arteries with the obturator, glutceal, and sciatic arteries, all branches of the latter; 2. by those between the internal and external pudics ; and, 3. by the communications of the ilio-lumbar artery with the deep anterior iliac, by which the blood may be transferred to the superficial an- terior iliac or the external circumflex. F rom the obturator artery the blood is transmit- ted through theascending branches of the internal circumflex : this channel of communication be- comes, iri cases of interruption of the external iliac artery, remarkably free, the branches esta- blishing it being much enlarged and tortuous : instances and representations of it may be found in the Medico-Chirurgical Transactions, vol. iv. and in Guy’s Hospital Reports, No. 1, Jan. 1836, from the experience of Sir Astley Cooper. Through the glutaal artery the femoral com- municates with the internal iliac by the inoscu- lations between that vessel, the posterior tro- chanteric and the ascending terminal branches of the internal circumflex, and by those between it and the ascending and circumflex branches of the external circumflex artery : those connec- tions are displayed also in the works just referred to. The communication of the femoral with the internal iliac through the sciatic artery is esta- blished by the anastomosis of that vessel with the internal circumflex and the perforating arte- ries, for which also see the same works. The alteration in the condition of the sciatic artery or its branches caused by ligature of the femoral or of the external iliac artery presents one of the most remarkable results of that cir- cumstance : its branch to the sciatic nerve be- comes greatly enlarged, very tortuous, and so much elongated as to form at times a commu- nication between the sciatic artery and the posterior tibial. The connections established through the pudic and ilio-lumhar arteries are set forth, in the event of a case of ligature of the external iliac artery published in the Medico- Chirurgical Transactions, vol. xx. by Mr. Norman. The femoral artery communicates with the external iliac through means of the anastomoses between the anterior iliac arteries, internal and external, between the internal anterior iliac and the external circumflex ; and also by those be- tween the superficial and internal epigastrics. By the communications, which have been mentioned, the transmission of blood through the femoral artery may be restored, after the interruption of the external iliac artery, or of the femoral above the origin of the profunda, with sufficient freedom for the perfect nutrition of the limb ; of which numerous instances have been observed by different writers. The upper and lower parts of the femoral artery are also connected by collateral channels. Those are established by the communications which exist between the branches of the pro- funda artery arising from the upper extremity of the femoral, and branches of the latter given off during its course or from its lower extre- mity; thus the blood may pass from the femo- ral artery above into the middle part of the vessel through the anastomosis existing between the descending branches of the external circum- flex artery, and the branches given by the femo- ral to the vastus internus muscle about the middle of the thigh. A similar communication exists upon the internal side of the femoral by means of the anastomoses by which descending branches of the internal circumflex are connected with those given by the femoral itself to the adductors. The collateral connection of the femoral with the popliteal artery is established through two channels: 1. through the anastomoses between the branches of the profunda, as well the ex- ternal circumflex as the perforating arteries, with the branches of the popliteal ; whence the femoral may be interrupted at any part below the origin of the profunda, and the blood thus find a ready passage from it into the popliteal : 2. through those of the branches given by the femoral to the vastus internus and the superficial superior internal articular with the same. To the channels of communication which have been described are to be added, as pointed out by Scarpa, those established, by the arteries of the periosteum and of the in- ternal structure of the femur, between the main arteries above and below. The former are well represented by Scarpa,* and are formed by anastomoses between branches of the external circumflex, the profunda, the femoral and the popliteal distributed to the periosteum. Upon a review of the anastomotic con- nections of the femoral artery, its course pre- sents two stations at which communications are established, on the one hand with the main artery above, and on the other with that below, while in the interval they are connected the one with the other. Those are, 1. the first part of the vessel’s course from its commence- ment to below the origin of the profunda; and, 2. its lower part for so much of it as includes the origins of the branches to the triceps crural and adductor muscles, and the superficial superior internal articular. Again, it appears that through the first station, not only is the femoral connected with the arteries of the trunk and with the lower part of the vessel, but also it is connected Reflexions sur l'Aneurisme, tab. ii. FEMORAL ARTERY. 251 without the intermedium of the second with the popliteal artery, the latter forming by much the more free channel of communication be- tween the two vessels, whence the circulation of the lower part of the limb may be pre- served independent of the communication be- tween the upper and lower parts of the femoral artery, as has been exemplified in the case of Sir A. Cooper given in the Medico-Chirur- gical Transactions, vol. ii . ; and, lastly, a com- munication exists by which the blood may be conveyed from the arteries of the trunk into the popliteal artery and the arteries of the leg, independent of the femoral and without trans- mission through any part of its canal. Hence varieties may be expected in the con- dition of the femoral artery in cases of inter- ruption, according to the situation of the interruption, and the influence of it or other circumstances in determining the course which the circulation is to take. When the artery is obstructed above the origin of the profunda independent of aneu- rism, the origin of that vessel being free from disease, it would appear that the trunk of the femoral does not undergo any alteration in its capacity, at least from the origin of the pro- funda downward : when an interval exists between the point of interruption and the origin of that vessel, the trunk may be di- minished for so much, while again it may continue unaltered ; thus in Sir A. Cooper’s case* already referred to, the vessel was found reduced to about half its natural size between the origins of the epigastric and circumflex ilii arteries and that of the profunda, and from the latter it preserved its ordinary size through the remainder of its course : in Mr. Norman’s casef on the other hand, it was of its natural size in the interval adverted to, but inasmuch as the origin of the profunda was obstructed in the latter case, it cannot be considered so fair an instance of the influence of the simple interruption at the part specified as the former, in which the femoral artery remained pervious after the cure of the aneurism. It is hence to be inferred, 1 . that interruption of the femoral above the origin of the profunda or of the external iliac artery is not necessarily followed by obliteration of the former, unless it be of so much of the femoral as might intervene between the interruption and the origin of the profunda, where the ligature has been applied to the former: 2. that in such case the internal iliac is thenceforward the principal source from which the supply of blood to the lower extremity is to be derived; and that the profunda artery through its inosculations with the branches of the internal iliac, constitutes the chief channel through which the transmission of the blood to the trunk of the femoral and the limb takes place: 3. that the external iliac artery con- tributes, but in an inferior degree, to the sup- ply of the limb, when the interruption is in the femoral itself : 4. that the femoral artery and its branches thenceforward are to be con- * Guy’s Hospital Reports. t Med.-Chir. Trans, vol. xx. sidered branches of the iliac arteries, rather of the internal than of the external, the trunk of the femoral itself being secondary to its own branches, by which the blood is transmitted into it from the iliacs. When the interruption of the femoral occurs below the origin of the profunda, the oblitera- tion of the trunk is no farther necessary than between the interruption and the origin of the profunda on the one hand, if no other branch intervene, and that of the next considerable branch upon the other. In such case the pro- funda artery becomes the main channel of the circulation through the lower extremity from its origin downward, and the femoral with its branches thenceforth are to be regarded as branches of it. But when the interruption arises from aneu- rism and the operation necessary for its cure, obliteration of the femoral, to a greater or less extent according to the case, for the most part ensues : this appears to depend upon the in- fluence, which the mode of cure of the disease exerts upon the circulation through the vessel, for the coagulation of the contents of the sac being generally produced by the interruption of the current of blood, the passage through the sac becomes obstructed, and along with it an extent of the artery upon both sides of the seat of the aneurism greater or less according to the disposition of the adjoining branches. The extent to which the obliteration of the artery has been found to proceed, has been different in different cases, but the varieties observed have been the following : 1 . As re- gards that part of the vessel which is above the ligature, when the femoral artery has been tied below the origin of the profunda for po- pliteal aneurism, the vessel has been found, when the ligature has been applied to the lower part of the artery, either obliterated from the ligature to the origin of the pro- funda, as occurred in the first subject upon whom Mr. Hunter* operated for popliteal aneu- rism according to his method, or obliterated upward only as far as the origin of those mus- cular branches of the artery, which arise below the profunda and anastomose with the articular arteries. 2. When the ligature has been ap- plied near to the origin of the profunda, as in the operation of Scarpa, between it and the origin of the branches alluded to, the artery has been found obliterated from the point of interruption to the origin of the profunda. The condition of the artery below the seat of the ligature is equally subject to variety according to circumstances, and is still more deserving of attention than the former : it has been found in one of three states, either ob- literated throughout from the origin of the profunda down to the extremity of the popli- teal artery, as occurred in the case reported by Sir A. Cooper in the Medico-Chirurgical Transactions, vol. ii., or pervious throughout from the point of application of the ligature to the seat of the aneurism, where it was * Transactions of a Society for the improve- ment of Medical and Chirurgical Knowledge, vol. i. FEMORAL ARTERY. 2.52 obliterated. Of this condition several in- stances are cited by Hodgson,* and a most remarkable one is in the possession of Mr. Adams of this city, through whose liberality the author is permitted to introduce a notice of it. It was obtained from a patient who had been operated on by the late Professor Todd, and is remarkable, 1. because the operation had been performed upon both limbs, and the condition of both is, as nearly as may be, the same; 2. because the obliteration at the seat of the ligature does not on either side exceed an inch, on one not being more than half that length ; and, 3. because the artery is pervious on both sides from the obliteration of the ligature to the lower part of the popliteal artery, the obliteration at the seat of the dis- ease appearing not to have extended beyond it; and being, on both sides, about two inches long. Thirdly, the artery has been found par- tially and irregularly obliterated, the vessel being closed at and for some distance below the seat of the ligature ; being then pervious, the blood being conveyed into it by the in- osculations between the minor branches of the artery arising below the interruption and those of the profunda from above; and again im- pervious below, the blood being conveyed from it by similar branches anastomosing with the articular arteries. The effect of ligature of the external iliac upon the femoral artery, independent of the influence of aneurism, has been already ad- verted to. That effect is liable to be modified by the presence of the disease; thus in a case related by Sir A. Cooper in the fourth volume of the Medieo-Chirurgical Transactions, in which the iliac was tied for aneurism of the femoral artery at the middle of the thigh, the latter vessel was obliterated from the origin of the profunda downward. The case, re- corded by Mr. Norman, already referred to, in which the external iliac was also tied, presents another remarkable modification : in it the femoral remained pervious, but the root of the profunda was obliterated, while its branches were open. Operative relations of the femoral artery.- — The femoral artery may be the subject of ope- ration at any part of its course, there being nothing either in its situation or relations to forbid the exposure of it at any point, if cir- cumstances should require it. All parts, how- ever, are not equally eligible, the vessel being in some situations more deeply situate, covered by a greater number and depth of parts, and its relations more complicated than at others. It has been taken up in each of the three stages into which its course has been divided, and the operations, which may according to circumstances be performed upon it, may with advantage be referred to those. The propriety of thus distinguishing them will appear in a strong light, when those modifications, which the anatomical relations of the vessel may justify, shall have been discussed, as also from the history of the operations, which have been * Op. cit. 278, 9. and are proposed to be performed upon the femoral artery. In its first stage the vessel may be tied at two points, viz. either above or below the origin of the profunda artery : the operation at the former point, being performed under circumstances different from those in which that at the latter is admissible, may be con- sidered apart from the others, and the de- tail of it be postponed until they have been disposed of; while the operation in the second case, and those in the second and third stages have been at different times performed for the same purpose— the cure of popliteal aneurism — and therefore a comparison of their several details and advantages merits attention. The situation in which the femoral artery was first taken up for popliteal aneurism is the third stage of its course : here it was tied, as is generally known, by J. Hunter. In his ope- ration Hunter made “ an incision on the an- terior and inner part of the thigh rather below its middle;” i.e.m the third stage ; “ which in- cision was continued obliquely across the inner edge of the sartorius muscle and made large the other steps of his operation it is not neces- sary at present to particularize ; the author would only remark, as a matter of history, that Hunter’s application of ligatures has been mis- understood : he applied in his first operation four ligatures to the artery, and it is com- monly, if not generally, said that they were drawn with various degrees of tightness ; but such was not the case, they were tied all equally tight : the account given in the report of the operation being, “ the artery was now tied by both these ligatures,” viz. the two upper, “ but so slightly as only to compress the sides together. A similar application of ligatures was made a little lower. The reason for hav- ing four ligatures was to compress such a length of artery, as might make up for the want of tightness, it being wished to avoid great pressure on the vessel at any one part.” The artery may be and has been frequently taken up in the middle stage, and the ope- ration, as described in several surgical works, will be found to belong to, if not to be in- tended for, that stage. During its two latter stages the artery is covered by the sartorius : in its uppermost it is not covered by the muscle, and consequently if it be necessary to displace the muscle to bring the artery into view above the last stage, it must be in the middle one, and in the account of the operation given by some of the highest authorities, the displace- ment of the sartorius is stated as one of the steps. This the author refers to not in a spirit of criticism, but in order to mark more strongly the distinction between the operations at the several stages, and to direct attention to the advantages possessed by that in the first over the others; more particularly since de- scriptions, which in strictness apply to the operation in the middle stage, and at a part of the aitery’s course below the first, may be found so put forward that the operations at the two points must be confounded; and thus the advantages contemplated by the proposer of FEMORAL ARTERY. 253 the latter be lost. It will be recollected that in the two inferior stages the artery is covered by the sartorius and by two laminae of the fascia lata, between which the muscle is situate: the vessel is, therefore, similarly cir- cumstanced in this particular throughout both, but in some other important respects the re- lations of the artery are different. 1. In its middle stage the vessel is nearer to the anterior plane of the limb. 2. The deep layer of fascia, by which it is covered, is far less thick and strong, particularly at its upper part. 3. The artery is not so completely covered by the sar- torius; and for those reasons the vessel may be more easily reached from before. These constitute the principal anatomical conside- rations why the middle stage should be pre- ferred to the lower for operation, but, since it is at times requisite to tie the vessel in its last stage, it is necessary to examine the influence which its anatomical relations may have upon the conduct of the operation at that part. 1. The greater depth of the artery from the anterior surface of the limb renders a more extended incision necessary : in cutting upon arteries “ the centre of the incision should be,” as directed by Guthrie, “ if possible directly over that part of the artery on which it is in- tended to apply the ligature.” In the case of the femoral artery in its third stage, the length of the incision should not be less than from four to five inches according to the volume of the limb ; its direction should correspond to that of the sartorius, but it must be varied somewhat according to the side of the muscle upon which the operator may purpose to seek the vessel. It should commence somewhat below the middle of the thigh, and be con- tinued as much upon the lower as upon the middle third of the limb. 2. The artery is situate, in its third stage, nearer to the outer than the inner margin of the sartorius, and the more so the nearer to its termination ; hence it may be exposed with greater ease and cer- tainty by cutting upon the outer edge of the muscle and displacing it inward. Hunter, in his operations, selected the inner margin, and displaced it forward and outward; but this proceeding is attended with disadvantages. 1. The saphena vein is more in the way and exposed to danger of being divided since it lies at this part, along or near the inner mar- gin of the sartorius. 2. The muscle lying more to the inner than the outer side of the artery must be more displaced, and the depth of the wound for the same reason greater when the vessel is sought from its inside.* 3. The ope- ration must be more inconvenient and em- barrassing, as well because of the former difficulties as because it must be performed more from the inside of the limb, and from within outward, than in the method by the * The contrary is maintained by Lisfranc and others ; but, according to the experience of the author, without sufficient reason. He has care- fully compared the depth of the wounds as made upon the opposite sides of the muscle, and in the subjects of examination that by the inside appeared to him the deeper. outer margin of the sartorius. Those objec- tions are avoided by cutting upon the outer edge of the muscle, against which, however, it has been advanced that in that method the vastus internus may be mistaken for the sar- torius, and that the wound being made from before, there is not a depending and ready outlet afforded to matter should it form, while by the other there is. The former of these objections cannot carry much weight, and for the second the best plan for obviating the dangers of inflammation and suppuration is, as much as possible, to render them unneces- sary, which is best accomplished by selecting that method by which the artery may be ex- posed most easily, and with least disturbance to the parts in its vicinity. To the writer, therefore, it seems that the method by the outer margin of the sartorius, which appears to have been suggested by Hutchison, is the more eligible in the operation for taking up the femoral in its third stage. 2. The great thickness and strength of the anterior wall of the femoral canal both increase the dif- ficulty of opening the canal, and render it desirable that that structure should he freely divided for the double purpose of facilitating the taking up of the artery, and preventing the injurious effect which must be produced by the confinement caused by the structure in question in the event of inflammation extend- ing along the vessel. 3. The relation of the vein to the artery at this part, viz. posterior and external, will make it more safe to pass the needle round the latter from without than from the outside ; this, however, is a rule which cannot be strictly adhered to, for the direction in which the instrument shall be passed must be varied according to circum- stances ; it would be difficult to pass it from the outside in case the artery were exposed from the inside of the sartorius ; but attention to the caution demanded by the position of the vein is, for this reason, only the more necessary. 4. The saphenus nerve being here within the femoral canal is to be carefully avoided ; it will be so with certainty, if the needle be carried from the outside. 5. The mistake of confounding the superficial supe- rior internal articular artery with the femoral must be also avoided.* This mistake, which has occurred, ought not however to occur again in the hands of a well-informed surgeon, for the possibility of it ought not to be lost sight of in operations at the lower part of the thigh ; and it may be easily avoided by re- collecting, first, that the femoral itself is within the femoral canal, and therefore that any vessel, which presents before the division of the anterior wall of the canal, which is so remarkably thick in this situation that it can hardly be overlooked, cannot be the one which is sought for; and, secondly, that the course of the branch within the canal, after its origin, is very short, and therefore that in case of doubt the vessel which presents, must, if the arti- cular, conduct us directly to the trunk itself, See that vessel. 254 FEMORAL ARTERY. when followed upward for a very short dis- tance. Lastly, the structures to be divided or put aside in order to expose the artery are, — 1. the skin; 2. the subcutaneous cellular stratum; 3. the superficial lamina of the fascia lata, forming the anterior wall of the sheath of the sartorius; 4. the sartorius itself; 5. the deep lamina of the fascia forming the posterior wall of the sheath of the sartorius, and the anterior wall of the femoral canal ; and, 6. the proper sheath of the vessels. The difference between the anatomical re- lations of the operation in the middle and inferior stages of the artery depends upon the modifications to be observed in the relations of the vessel at the two points, and also in some of the parts concerned. The number and order of the structures interposed between the surface and the artery are the same as in the third, but their disposition and relations differ in some important particulars so much as to authorize a difference in the proceedings to be adopted, and to justify a preference in favour of the former. 1 . The artery is nearer to the anterior surface of the limb, and the more so the nearer to the commencement of the stage : it is therefore more easily reached and in the same proportion. 2. It is nearer to the inner than the outer margin of the sar- torius, and, in like manner, the more so, the nearer to its upper extremity ; and hence it may be brought into view with more ease and with less disturbance of the muscle by dis- placing its inner margin outward, than its outer inward. The latter proceeding is advocated by Hut- chison for the purpose of avoiding the sa- phena vein and the lymphatics. That the vein will be effectually secured from danger by cutting upon the outside of the sartorius will be at once admitted ; but it appears to the author that the advantage contemplated will be more than counterbalanced by the dis- advantages attending it, and on the other hand that the proceeding is not necessary : for, 1 . if the outer margin of the muscle be cut upon in the middle of the vessel, the incision must be made considerably external to the line of the artery’s course, and thereby the guide to the vessel otherwise afforded by that line must be lost, and uncertainty and consequently embarrassment be likely to ensue in seeking for the artery after having displaced the muscle. 2. Much more disturbance and violence are likely to be inflicted upon the artery and the adjoining parts by the plan in question, in- asmuch as the vessel is so much nearer to the inner than the outer margin of the muscle ; in consequence of which the muscle must be displaced to a much greater extent in proceed- ing from without inward, and the obstruction offered by it to the performance of the other steps of the operation must lead to greater violence either to the artery or to the muscle ; and afterward a valvular wound must be left, a circumstance very unfavourable in the event of the occurrence of inflammation and sup- puration in the vicinity of the track of the vessel, and those objections are the stronger because the artery is usually sought at the upper part of the stage, where it is but little overlapped by the muscle. On the other hand the saphena vein ought not to be endangered in the operation, for it is situate so far internal to the artery that the incision ought not to fall upon it. The case is different from that of cut- ting upon the inner margin of the sartorius during the third stage of the vessel ; for there the vein is for the most part close to the edge of the muscle, and the wound must be in- clined in depth from within outward, by which direction the vein is interposed between the surface and the artery ; whereas, in the second stage, whether the operator, in proceeding by the inner margin of the muscle, cut directly upon the artery’s course or upon the edge of the sartorius, there is sufficient space between it and the vein to leave the latter safe. The course of the artery may be crossed at any part by the superficial femoral veins, as has been explained, and they, if they present, will be in danger of division ; but this inconvenience would not be removed by the plan in question, whereas both it and the danger to the saphena may be avoided by an easier and less ob- jectionable proceeding than that of cutting upon the outer edge of the sartorius, viz. 1. by ascertaining, through means of pressure, the situation and course of the veins ; and, 2. by proceeding with somewhat more caution, where there is reason to expect their presence, dividing first only the skin and continuing the incision through the subcutaneous structure, not by a single stroke, by which the vein if in the way must necessarily be divided, but gra- dually, until the vessel has been exposed and drawn aside. It seems therefore to the author not only unnecessary, but very objectionable to cut upon the outer margin of the sartorius, in exposing the femoral artery above the mid- dle of the thigh. 3. The anterior wall of the femoral canal is much thinner than in the third stage, and therefore more easily ma- naged. 4. The vein is directly behind the artery, and therefore the needle may be passed with equal safety from either side, according to circumstances : in operating by the inner margin of the sartorius it will be more easily done from the inside : the position of the vein and its close connection to the artery render it especially necessary that the extremity of the needle be kept in contact with the artery in being carried behind it. The saphenus nerve requires the same attention as in the third stage. But the situation in which it is at present generally considered most eligible to expose the artery for the application of a ligature, when circumstances do not forbid a choice, is that recommended by Scarpa, viz. in the upper third of the thigh, and in the first stage of the artery’s course as described in the account of the anatomical relations of the vessel. In his description of the details of the operation, Scarpa directs thus : “ The surgeon pressing with his fore-finger will explore the course of the superficial femoral artery, from the crural FEMORAL ARTERY. arch downward, and when he comes to the place where he does not feel any more, or very confusedly, the vibration of the artery, he will there fix with his eye the inferior angle or ex- tremity of the incision which he proposes to make for bringing the artery into view. This lower angle of the incision will fall nearly on the internal margin of the sartorius muscle, just where this muscle crosses the course of the femoral artery. A little more than three inches above the place pointed out, the surgeon will begin his incision and carry it along the thigh in a slightly oblique line from without inwards, following the course of the femoral artery as far as the point fixed with the eye.” By this incision the skin and cellular substance are to be divided, and the fascia lata exposed, “ then with another stroke of the bistoury, with his hand free and unsupported, or upon a furrowed probe, he will divide along the thigh, and in the same direction as the external wound the fascia, and introducing the fore-finger of his left hand into the bottom of the incision, he will imme- diately feel the strong beating of the artery, and this without the necessity of removing the in- ternal margin of the sartorius from its position, or at least very little. With the point of the fore-finger of the left hand already touching the artery, the surgeon will separate it from its lateral connexions and from the vein;” after which the ligature is to be carried round it by means of a blunt aneurism-needle. The author has introduced the preceding account in order to fix the precise situation of the operation as performed by Scarpa, because it appears to him that it has been to a certain degree lost sight of, and also to direct attention more strongly to the advantage proposed by that distin- guished surgeon in the adoption of the method which he has recommended. A very brief consideration of the descriptions given by se- veral writers* of the proceedings to be adopted in the operation of taking up the artery in the upper part of the thigh will suffice to shew either that Scarpa’s method has been con- founded more or less with the operation at a lower point, or that its advantages have been disregarded: thus, while it is stated that the part of the limb in which the femoral artery can be tied with the greatest facility is between four and five inches below Poupart’s ligament, and which is Scarpa’s point, f the displacement of the sartorius is accounted a part of the ope- ration, and it has even been debated whether the incision should not be made on the outer edge of the sartorius, and the artery exposed by drawing the muscle inward ; but the dis- placement of the sartorius is not only not a necessary part of Scarpa’s plan, but is that particular the avoidance of which he proposed to himself by the method he selected ; from whence it will appear that the operation, as described in the accounts alluded to, refers, strictly speaking, to the second and not to the first third of the vessel's course, within the latter of which it must be performed in order * Hodgson, &c. t The distance at which the sartorius crosses the artery varies according to the stature. 255 to avoid the sartorius. The structures to be divided in this operation are, 1. the skin, 2. the subcutaneous cellular structure, 3. the fascia lata, forming the anterior wall of the femoral canal. The extent of the superficial incisions need not exceed three inches, com- mencing above either according to the rule of Scarpa or about two inches below Poupart’s ligament : the direction in which they should be made ought to correspond as nearly as pos- sible with the course of the artery. The extent to which the fascia lata is to be divided is stated differently by different writers : by some it is directed to be divided to the extent of about an inch : the direction of Scarpa is not precise upon the point in the text, though it is plain that he intended it should be divided to a much greater length than an inch, but in a note it is strongly insisted that the division of the fascia should correspond in extent to that of the external wound. Two reasons present for this : 1 . greater facility in the performance of the operation, and less disturbance in con- sequence to the artery; 2. the avoiding the injurious effects which must be produced by the confinement consequent upon too limited a division of the fascia in the event of the supervention of inflammation. It cannot be doubted that a division of an inch is altogether too short to meet those considerations, and that the fascia ought to be divided to a greater ex- tent ; on the other hand it does not appear that advantage would be gained by so free a divi- sion as that recommended by Scarpa; and the rule of Guthrie seems the best calculated to ac- complish the ends in view : he advises the fascia to be divided for the space of two inches. The division may be effected either with or without the assistance of the director. It will be well to recollect here that, at the point at which the sartorius is about to overlap the artery, a du- plicature of the fascia takes place in order to enclose the muscle, and hence that, if the opening of the canal be attempted at the lower extremity of the stage, and close to the muscle, two layers of the fascia may require to be di- vided before this purpose can be accomplished. The femoral canal having been opened by the division of the fascia lata, the next step in the operation is the division of the proper sheath of the vessels and the insulation of the artery. Previous to this, should the internal genicular nerve be found to cross the canal superficial to the artery at the part, at which the vessel is to be detached from the contiguous parts, it should be separated and drawn outward. The insulation of the artery Scarpa recommends to be effected with the finger, raising the vessel from the wound even along with the vein if necessaiy; such a proceeding, however, must be very objectionable, as inflicting great dis- turbance and violence upon the artery. It is to be recollected that in order to insulate the artery it is necessary to divide or lacerate the investment, which immediately encloses the two vessels and connects them to each other, and which has been elsewhere denominated the femoral sheath ; this, though thin, is dense, and is to be expected to offer resistance to the 256 FEMORAL ARTERY. separation of the artery from the vein : the best method of effecting this, as it seems to the author, will be, after having opened the sheath directly over the centre of the artery either by a touch of the knife or first nipping up a part of it with the forceps ; making an aperture into it with the blade of the knife held horizon- tally, and extending the opening upon a di- rector to the length of “ three-quarters or an inch,” as recommended by Guthrie ; then with the forceps to take hold of each portion of the sheath in turn and drawing it to its own side, outward or inward as the case may be, to de- tach the artery from it with the extremity of a director or of the aneurism-needle, moving the extiemity of the instrument gently upward and downward at the same time that the vessel is carried, by means of it, in the opposite direc- tion from the side of the sheath which is in the forceps ; by this proceeding the artery may be easily and safely insulated almost, if not quite, round, and with little if any disturbance to it. That done, the needle and ligature may be carried round the artery : the performance of this, which is the most delicate step in the operation, will be found much facilitated by the separation of the artery as recommended ; in fact, little more will then remain than to pass the needle, the passage having been al- ready opened. In doing so it will be well to hold the inner portion of the sheath, with the forceps, inward and backward, by which the vein will be drawn away from the artery, and at the same time to insinuate the blunt extre- mity of the aneurism-needle round the artery from within outward, because of the situation of the vein, moving it, if any obstruction be encountered, upward and downward, while it is also carried forward, and bearing the artery somewhat outward with it at the same time ; when the extremity of the needle has appeared on the outside of the artery it may be liberated, if necessary, by a touch of the scalpel upon it. In the execution of this manoeuvre two acci- dents are to be avoided, viz. injury of the vein, and inclusion of the saphenus nerve: the close juxta-position and attachment of the former to the artery render much care neces- sary to leave it uninjured ; but the proceeding recommended will, if carefully executed, cer- tainly preserve it from being wounded. The saphenus nerve is here on the outside of the artery, and might be included within the liga- ture if the extremity of the needle were carried too far outward ; the operator should therefore assure himself, before tying the ligature, that the nerve has not been included ; but the risk of this accident ought not to be great at this part of the artery’s course, certainly not so much so as at a lower point, inasmuch as the nerve has as yet hardly entered the femoral canal, and is therefore separated from the ar- tery by more or less of its outer wall; and with the precautions recommended in insulating the vessel and passing the ligature it will almost certainly be excluded at every part : the possi- bility of the accident is, however, not to be lost sight of. The needle having been carried round the artery, the ligature is to be taken hold of with the forceps, and one end drawn out, after which the needle is to be withdrawn. The advantages of the part chosen by Scarpa for this operation are numerous and obvious : 1. the artery is nearer to the surface and has fewer coverings; there is therefore less to be divided in order to bring it into view; 2. the vessel being more superficial, its pulsations can be more distinctly felt and its course ascer- tained previous to operation, a guide wanting in the lower parts of the thigh ; 3. “ the ope- ration is done,” as Guthrie observes, “ on that part of the artery which is not covered by muscle, and all interference with the sartorius is avoided: this method obviates all discussion as to placing the ligature on the outside of the muscle.” The plan of cutting upon the out- side of the sartorius in the upper stage of the artery must be, if contemplated by any, a pro- ceeding hardly defensible in the ordinary dis- position of the muscle, for all the reasons ad- vanced already against its use in the second stage apply with much greater force to it in the former case ; but it is at the same time to be observed that the distance of the point at which the muscle crosses the femoral artery is not ab- solutely regular, and that great deviation in this respect might render it necessary even to cut upon the outer margin of the muscle in order to expose the artery in the first third of its course. The distance from Poupart’s liga- ment at which the muscle ordinarily crosses is, according to the stature, from three and a half to five inches, but it may in certain cases be found to cross so much sooner that the artery could not be exposed below the origin of the profunda without displacing the muscle ; thus Burns* mentions that he has seen, in conse- quence of malformation of the pelvis, the artery covered by the muscle, before it had reached two inches below the ligament, and the author has witnessed the same from retraction of the thighs, consequent apparently upon long con- finement to bed ; in the latter case it would certainly have been more easy to expose the vessel from the outer than from the inner side of the muscle; but such cases are to be re- garded only as exceptions to be borne in mind, but not to influence our general conduct. 4. The performance of the last and most deli- cate parts of the operation must be much more easy and less embarrassed, the interference of the sartorius being avoided; while, on the other hand, all apprehension on account of the pro- funda is removed, since that vessel seldom, if ever, arises farther than two inches from Pou- part’s ligament, and the course of the case after operation is more likely to be favourable and exempt from untoward occurrences, since much less violence must be done, and the superven- tion of injurious inflammation or its conse- quences thereby prevented. The operation for taking up the femoral ar- tery above the origin of the profunda is not often required, and, except in case of wound, may pro- bably give place altogether to that of tying the external iliac : it presents no advantage over * Op. cit. p. 321. FIBRINE. 257 tire latter, it does not promise more successful results: should secondary hemorrhage succeed to it, there is little prospect that the ligature of the iliac would afterward succeed, and the uncertainty existing with regard to the point of origin of the profunda raises a very strong ob- jection against it, inasmuch as we cannot know whether the origin of that vessel be above, below, or at the point at which the ligature is to be applied : it is further exposed to the difficulty, before adverted to, which is likely to arise in cases of high origin of the profunda, in which that vessel may be taken for the femoral, and thus another source of embar- rassment be encountered. In the performance of it the following struc- tures will present : 1. the skin ; 2. the subcu- taneous cellular stratum along with the inguinal glands and the superficial inguinal vessels of the latter : those which are most exposed to be divided are the superficial epigastric and its branches ; the superficial anterior iliac and the superficial pudics may be encountered, but they are less likely; 3. the superficial lamina of the iliac portion of the fascia lata; and 4. the prolongation of the fascia transversalis, which forms the front of the femoral sheath. An incision three inches long will suffice ; it should commence above Poupart’s ligament, and be continued in the line of the vessel for two inches below it. If the superficial vessels bleed, on division, so much as to interfere with the course of the operation, they should be at once secured ; otherwise they will probably cease themselves, and give no further trouble. The lymphatic glands, if in the way of the incisions, may be either held aside or removed. The fascia lata and sheath may be treated in the same manner as in the other operations described ; they can be easily distinguished in consequence of the thin stratum of fat which is usually interposed. The insulation of the artery and the passage of the needle require the same precautions as in the operations at other parts of the vessel’s course. The vein being placed along the inside of the artery the needle should be passed from that side. The crural nerve and its branches are here altogether safe, as they lie without the femoral canal, but, as has been before pointed out, the crural branch of the genito-crural nerve may be included in the ligature; it will be most certainly avoided by the careful insulation of the artery : the operator should also assure himself, before tying the ligature, that no fila- ment is enclosed. Should two arteries present, as described in the anatomy of the profunda, and a question arise as to which is the femoral, the criteria pointed out will enable the operator to decide (see profunda artery ) ; and the difficulty will, almost certainly, be altogether avoided by cut- ting directly upon the centre line of the femoral as ascertained by its pulsations. Operation on the profunda artery. — From the anatomical details it follows that in the ma- jority of cases the profunda is situate, in the VOL. II. first stage of its course at least, at the outer or iliac side of tire femoral artery, though upon a plane posterior to that vessel : it has also, at the same time, the same coverings, differing only in being contained in a sheath proper to itself; and hence, if necessary, the profunda might be reached in that situation by an opera- tion similar to that for exposing the femoral itself at the same place, in which much advan- tage would be obtained by first exposing the latter vessel, and following it as a guide to the origin of the former ; which, if in its usual situation, will be exposed by displacing the femoral inward, and then the proper sheath of the profunda should be opened to a certain ex- tent, in order to allow the application of the ligature at a sufficient distance from the origin of the vessel. But in the inferior stages of its course it may be laid down, as a general rule, that it cannot be reached from the front of the thigh, inasmuch as, with the exception of those cases in which it is throughout external to the femoral, and in which, from its deep position and the want of a guide to its exact situation, the rule will yet equally apply, it is not only more deeply seated, but it is separated from the anterior surface of the limb by the super- ficial femoral artery, and by the femoral, pro- funda, and circumflex veins, as well as by the coverings of the femoral vessels, and lastly by the adductor longus muscle. In any case, did circumstances render necessary the attempt to tie the profunda, it would be an operation in which much uncertainty and difficulty must be anticipated, in consequence of the varieties presented by that artery in its origin and course. For Bibliography see ANATOMY (INTRODUC- TION), and ARTERY. ( B. Alcock.) FIBRINE, (Yx. fibrine ; Germ. Faserstofif.) Under this name physiologists and chemists have generally described the animal proximate principle constituting that part of muscular fibre which is insoluble in cold water, and that portion of the coagulum of blood which re- mains after the removal of its colouring matter. The fibrine of blood is best obtained by stirring a quantity of fresh-drawn blood with a piece of wood, to which the coagulum adheres, and may afterwards be washed in large and repeated portions of water till it loses its co- louring particles, and remains in the form of a buff-coloured, fibrous, and somewhat elastic substance; this may then be partially dried by pressure between folds of blotting-paper, di- gested in alcohol to remove fat, and then care- fully dried, during which process it loses about three-fourths of its weight, and becomes brittle and of a yellowish colour: it is insipid and in- odorous. In cold water it slowly resumes its original appearance but does not dissolve: when, however, it is subjected to the long- continued action of boiling water it shrinks and becomes friable, and a portion of a newly- formed substance is at the same time taken up by the water, which gives it a yellowish colour and the smell and taste of boiled meat, and s 258 FIBRINE. which, when obtained by evaporation, is brittle, yellow, and again soluble in water: this solu- tion is rendered turbid by infusion of galls, but the precipitate differs from that yielded by gelatin, and appears to be a distinct product. The insoluble residue has lost its original cha- racters; it no longer gelatinises with acids or alkalies, and is insoluble in acetic acid and in caustic ammonia. The action of acids and alkalies upon the fibrine of blood has been studied in detail by Berzelius and others ; the following is an ab- stract of their results.* All the acids, except the nitric, render fibrine transparent and gelatinous : the diluted acids cause it to shrink up. In sulphuric acid it acquires the appearance of a bulky yellow jelly, which immediately shrinks upon the addition of water, and is a combination of the acid and fibrine ; when well washed upon a filter it gra- dually becomes transparent and soluble, and in that state is a neutral sulphite of fibrine. It is again rendered opaque by dilute sulphuric acid, and is precipitated from its aqueous solu- tion by that acid in the form of white flakes, which appear to be a supersulphate. When fibrine is heated in sulphuric acid, both are decomposed, the mass blackens, and sulphu- rous acid is evolved. If the colouring matter has not been entirely washed out of the fibrine, the sulphuric solution is of a brown or purple colour. Nitric acid communicates a yellow colour to fibrine, and, if cold and dilute, combines with it to form a neutral nitrate, analogous to the sulphate When fibrine is digested in nitric acid, nitrogen is evolved, and its composition considerably changed, as we shall more parti- cularly mention in describing the action of this acid on muscular fibre. Muriatic acid gelatinises fibrine and then gradually dissolves it, forming a dark blue liquid, or purple and violet, if retaining any haematosin. This solution, when diluted with water, deposits a white muriate of fibrine, which, like the sulphate, gelatinises when the excess of acid is washed away, and becomes soluble, and is again thrown down from its aqueous solution by excess of acid. The blue liquid, after the separation of the precipitate by dilution, retains its colour, but loses it when saturated with ammonia, and with excess of ammonia becomes yellow. Fibrine digested in dilute muriatic acid is converted into the same white compound as that precipitated by water from the concentrated muriatic solu- tion. When boiled in the acid, nitrogen is evolved, and a solution is obtained, which, after the saturation of the acid, is precipitated by infusion of galls, but not by alkali or ferrocy- anuret of potassium ; on evaporating the solution to dryness a dark brown saline mass remains, so that the fibrine appears to have undergone some decomposition. * Berzelius, Lehrbuch der Thier-Chemie, Woh- ler’s Gprman translation. Dresden, 1831. See also Medico-Chirurgjcal Transactions, vol. iii. p. 201. A solution of recently-fused phosphoric acid acts upon fibrine in the same way as the sul- phuric acid ; but if the acid solution has been kept for some weeks, the fibrine then forms with it a soluble jelly, which is not precipitated by excess of acid. Concentrated acetic acid converts fibrine into a jelly easily soluble in warm water. When this solution is boiled, a little nitrogen is evolved, but nothing is precipitated ; when gently eva- porated, it gelatinises, and leaves, on desic- cation, an opaque insoluble residue. The other acids added to this acetic solution produce precipitates which are compounds of fibrine with the added acid. Fibrine is also preci- pitated from the acetic solution by caustic pot- assa, but is redissolved by excess of alkali. The acetic solution of fibrine is precipitated in white flakes by ferrocyanuret of potassium : this precipitate, when dried, appears to be a compound of fibrine with cyanuret of iron and hydrocyanic acid ; it is insoluble in dilute acids, but is decomposed by caustic alkalis, which abstract the cyanuret of iron and hydro- cyanic acid, and the remaining fibrine first gelatinises and then dissolves. 100 parts of this compound, carefully dried at 167°, and then incinerated in a weighed platinum cru- cible, gave 2.8 red oxide of iron, —7. 8 of the combination of cyanuret of iron with hydro- cyanic acid; whence it follows that 92.2 of fibrine were contained in the white precipitated compound. Caustic potassa, even much diluted, dissolves fibrine. If the solution is very dilute, the fibrine gradually forms a bulky jelly, which, heated in a close vessel to about 130°, dissolves into a pale yellow liquid, not quite transparent, and which soon clogs a filter. The yellow tint appears to arise from the presence of a small portion of adhering hsematosin. When this alkaline solution is saturated by muriatic or acetic acid, it exhales a peculiar fetid odour and blackens silver, announcing the presence of sulphur, so that the animal matter seems to have suffered some slight change. It is stated by Berzelius that fibrine is capable of neutral- izing the alkali, and that such neutral com- pound may be obtained by dissolving the fibrine in the alkaline solution, and adding acetic acid till it begins to occasion a precipi- tate ; the filtered liquid is then perfectly neu- tral, but the potassa bears a very small propor- tion to the fibrine. This neutral solution, he says, much resembles white of egg, and is coagulated by alcohol and acids, though not by heat. Gently evaporated, it gelatinises, and, when dry, assumes the appearance of albumen dried without coagulation. In this state it dissolves in warm water, and is first thrown down, and then redissolved by the acids when added in excess. Alcohol throws down nearly the whole of the fibrine from its neutral alkaline solution : if there be excess of alkali, much of the fibrine is retained. Mr. Hatchett found that fibrine, when digested in strong caustic potassa, evolved ammonia and yielded a species of soap; acids occasion a precipitate in this solution which is altered fibrine, for it neither gelati- FIBRINE. 259 nises nor dissolves in acetic acid: ammonia acts as potassa, but less energetically. When fibrine is digested in solution of per- sulphate of iron, or of copper, or of perchlo- ride of mercury, it combines with those salts, shrinks up, and loses all tendency to putre- faction. When the alkaline solution of fibrine is decomposed by metallic salts, the precipitate consists of the fibrine in combination with the metallic oxide; some of these compounds are soluble in caustic potassa. Tannin combines with fibrine, and occasions a precipitate both in its alkaline and acid solu- tions: the tanned fibrine resists putrefaction. The ultimate composition of fibrine has been determined by Gay Lussac and Thenard, and by Michaelis, who made a comparative ana- lysis of that of arterial and venous blood : the following are their results: — Gay Lussac Michaelis. and Thenard. Arterial. Venous. Nitrogen ..19.934 17.587 17.267 Carbon ..53.360 51.374 50.440 Hydrogen 7-021 7.254 8.228 Oxygen ..19.685 23.785 24.065 100.000 100.000 100.000 The mean of these results gives nearly the fol- lowing atomic composition : — Atoms. Equivalents. Theory. Nitrogen 1 14 19.72 Carbon 6 .36 50.70 Hydrogen 5 ....... . 5 7.04 Oxygen 2 16 22.54 1 71 10000 In reference to this atomic estimate, which is suggested by Leopold Gmelin,* Berzelius observes, that from the feeble saturating power of fibrine, its equivalent number is probably very high, that is, that it includes a larger number of simple atoms; but as we have at present no accurate means of determining its combining proportion or saturating power, its atomic constitution cannot be satisfactorily determined. Moreover, it appears that in the above analyses the fat was not separated, nor is any notice taken of the minute portion of sul- phur, the presence of which has been above adverted to. When Berzelius first obtained fat from fibrine by digesting it in alcohol and in ether, he con- cluded that it arose from the decomposition of a portion of the fibrine by those agents ; that it was a product and not an educt ; but the sub- sequent experiments of Chevreul leave no doubt that the fat exists ready formed in the blood. This fat is very soluble in alcohol, and the solution is slightly acid; when it is burned, the ash, instead of being acid, like that of the fatty matter of the brain, is alkaline, whence it appears that it existed saponified, or partly so, in the blood. Another important variety of fibrine is that which constitutes muscular fibre, but it is so interwoven with the nerves and vessels and cellular and adipose membrane, that its pro- perties are probably always more or less modi- * Handbuch der Theoretischen Chemie. fied by foreign matters. The colour of muscles appears to depend upon that of the blood in their capillary vessels ; and their moisture is referable to water, which may be expelled by drying them upon a water-bath, when they lose upon an average 75 per cent. If muscular fibre in thin slices is washed with water till all soluble matters are removed, the residue, when carefully dried, does not exceed 17 or 18 per cent, of the original weight. To obtain the fibrine of a muscle, it must be finely minced and washed in repeated portions of water at 60° or 70°, till all colouring and soluble substances are withdrawn, and till the residue is colourless, insipid, and inodorous; it is then strongly pressed between folds of linen, which renders it semitransparent and pulverulent. Berzelius observes that in this state it becomes so strongly electro-positive when triturated, that the particles repel each other and adhere to the mortar, and that it stil retains fat which is separable by alcohol or ether. When long boiled in water, it shrinks, hardens, and yields a portion of gelatine de- rived from the insterstitial cellular membrane; the fibrine itself is also modified by the con- tinued action of boiling water, and loses its solubility in acetic acid, which, when digested with it in its previous state, forms a gelatinous mass soluble in water, but slightly turbid from the presence of fat and a portion of insoluble membrane, derived apparently from the vessels which pervaded the original muscle. It is soluble in diluted caustic potassa, and precipi- tated by excess of muriatic acid, the precipitate being a compound of fibrine with excess of muriatic acid, and which, when washed with distilled water, becomes gelatinous and soluble, being reduced to the state of a neutral muriate of fibrine.* When the fibrine of muscle is mixed with its weight of sulphuric acid, it swells and dis- solves, and, when gently heated, a little fat rises to the surface and may be separated : if the mass is then diluted with twice its weight of water and boiled for nine hours, (occasion- ally replacing the loss by evaporation,) am- monia is formed, which combines with the acid, and on saturating it with carbonate of lime, filtering, and evaporating to dryness, a yellow residue remains, consisting of three distinct products : two of these are taken up by digestion in boiling alcohol of the specific gravity of .845, and are obtained upon evapo- ration ; this residue, treated with alcohol of the specific gravity of .830, communicates to it (1) a portion of a peculiar extractive matter, and the insoluble remainder (2) is white, soluble in water and crystallisable, and has been called by Braconnot leucine. f It fuses at 212°, ex- * It will be observed, by reference to the article ALBUMEN, that that principle and fibrine, if not identical, are very closely allied, and appear rather to differ in organization than in essential chemical characters : accordingly the fibrine of the blood may be considered as a modification of seralbumen, and that of muscular fibre as little differing from the fibrine of the blood. t Ann. de Chim. et Phys. xiii. 119. s 2 160 FIB 110 -C' AIITI LAG E. baling the odour of roasted meat, and partly sublimes: it is difficultly soluble in alcohol. It dissolves in nitric acid, and yields on eva- poration a white crystalline compound, the nitro-leucic acid. The portion of the original residue which is insoluble in alcohol (3) is yellow, and its aqueous solution is precipi- tated by infusion of galls, subacetate of lead, nitrate of mercury, and persulphate of iron. Jt appears therefore that the products of the action of sulphuric acid upon the fibrine of muscle, are, 1, an extractive matter soluble in alcohol ; 2. leucine ; and 3. extractive, inso- luble in alcohol but soluble in water. ( W. T. Brande.) FIBRO-CARTILAGE, (Cartilago liga- mentosa \. fibrosa ; F r. Tissu fibrocartilagineux ; Germ. Baser- Knorpel oder Band-Knorpel ). — ■ As early as the time of Galen we find certain organs distinguished by the appellation vevgo- j^ov^uciet; c’ercS'Ecr^/.oi, and Fallopius uses a similar term, namely, chondrosyndesmos, as denoting a substance distinct from true carti- lage. Haase* also, who wrote in 1747, speaks of two structures different from true cartilage, under the names of cartilagines ligamentoste and cartilagin.es mixta. Bichat likewise recog- nised a class of tissues distinct from pure cartilage, and by him it would appear that the name fibro-cart iluge was first employed. It is evident that no organ should be classed under the head of Jibro-curliluge unless it con- sist distinctly of fibrous tissue and cartilage intermixed, and thus combine not only the structure but the properties of both, the strength and power of resistance of the one, and the elas- ticity of the other; nevertheless, we shall find, in examining the various structures which are admitted by anatomists to be fibro-cartilaginous, that the fibrous tissue predominates in such a manner as to justify Beclard in regarding fibro- eartilage as a portion of the ligamentous struc- ture, which might be designated cartilaginiform ligamentous organs. Tne distinction was fully admitted too by Mr. Hunter in reference to the texture of the so-called inter-articular car- tilages. Speaking of that of the temporo- maxillary articulation, he says, “ its texture is ]igamento-cartilaginous.”f The classification of fibro-cartilages adopted by Meckel seems to me to be the best ; he arranges them under three classes:— 1. Those whose two surfaces are free wholly or at least in great part, and whose edges are united to the synovial capsules, dhe moveable jibro-car - tilages of articulation. 2. Those which are free by one of their surfaces, and which adhere to bone or tendon by the other : these aie the fibro-cartilages of tendinous sheaths, or those which limit the articular cavities, and may be called Jibro-cartilages of circumference or cylindrical jibro-cartilages. 3. Those whose two surfaces are adherent in their entire extent to the bones between which they are placed. * l)e falrica cartilag’mum, Lipsiae, 1747. t Hunter on the Teeth. Of these classes the first and third and some of those which come under the second belong to the articulations. Their forms and structure have already been described in the article Articulation. I may here, however, notice the statement of Weber* in regard to the discs interposed between the vertebrae, which have been generally regarded as fibro-cartilaginous. This anatomist denies that they exhibit any intermixture of cartilaginous substance, and considers that this is rendered manifest by stretching the intervertebral substance, by which it becomes reduced to a fibrous expansion ( sehnighautige Masse ) ; he consequently places these intervertebral discs among the fibrous tissues. There can be no doubt that the cir- cumference of each disc is purely fibrous, and that the concentric vertical lamellae of fibrous tissue extend for some distance towards the centre of the disc ; but I am at a loss to per- ceive any resemblance to fibrous tissues in the soft and elastic, and yielding substance which forms the centre. It seems to me that this texture can only be regarded as a modified form of cartilage, differing in its want of density from the ordinary cartilage, whether permanent or temporary. The intervertebral substance, however, to whatever texture it may ultimately be decided to belong, does present very striking differences from the other organs which are placed among the fibro-cartilages. It is in the fibro-cartilages of the second class that we see most uniformly the inter- mixture of the fibrous and cartilaginous texture, although here, likewise, the fibrous tissue pre- dominates over the cartilaginous. The fibro-cartilages are remarkable for their great flexibility, in virtue of which they are enabled to resist fracture, and this property is no doubt owing to the intermixture of fibrous tissue; cartilaginous laminae, on the other hand, are easily broken by bending, and many of them exhibit a fibrous appearance on the surface of the fracture, which, however, arises from the irregular fracture and not from the existence of fibres. Fibro-cartilages are of a dull white colour and quite opaque; they have no perichon- drium, but are either in immediate connexion with bone, being inserted into it by their fibrous bundles, or are covered by the synovial mem- brane of the joint in which they are enclosed. Their physical and vital properties are those which belong to pure cartilage and to fibrous tissue. Their force of cohesion is very great and surpasses even that of bones. They are more vascular than pure cartilage, but in the natural state they admit very few vessels carry- ing red blood. Bichat examined the fibro- cartilages in an animal which died asphyxiated, and found these organs not injected. The remarkable manner in which fibro-cartilages resist the influence of a compressing tumour, as a pulsating aneurism, is well known ; while by such means the bodies of the vertebrae are completely destroyed, the intervertebral discs will remain quite uninjured. 6 Einige Beobachtungen iiber das Structur der Knorpel und Faser-Knorpel, in Meckel s Archiv for 1827. FIBRO-CAIITILAGE. 261 Fibro-cartilages dry readily when exposed to_the air and become of a deep yellow colour ; they resist for a very long time, many months, the influence of maceration, and by long-con- tinued boiling they become converted into a gelatinous substance. Their chemical compo- sition is said to be made up of albumen, phos- phate of lime, chlorurets of sodium and of potassium, sulphate of lime and other salts, usually found in animal textures. The microscopic characters of fibro-cartilage do not seem to have been investigated with the same care as those of many other textures. I have examined by transmitted light very thin slices of the fibro-cartilages in the knee and temporo-maxillary joint, and the appearance presented was uniformly that of a very compli- cated cellular structure, composed of minute meshes, very irregular in size and shape. In examining the intervertebral substance I have distinctly seen, towards the circumference of the disc, those fine and uniform cylindrical fibres with wave-like bendings described and figured by Jordan ;* * * § but towards the centre the texture exhibited the cellular appearance with larger meshes, similar to that seen in the fibro- cartilages of the knee and joint of the lower jaw.f Of the structures placed by Bichat among the fibro-cartilages, some have been considered by Meckel, Beclard, Weber, and other anato- mists to be pure cartilage, and as it seems to me with much justice. These are the membra- niform cartilages of the external ear, Eustachian tube, nose, larynx, trachea, and eyelids. The cartilaginous nature of most of these textures is very apparent upon carefully dissecting oft’ the dense perichondrium which invests them, and to which, doubtless, they owe their flexi- bility, or more correctly, by which they are prevented from being fractured under the influence of a bending force. Careful micro- scopic observation may assist materially in affording marks indicative of pure cartilage ; and as the observations of Purkinje, Muller, and Miescher approach in some degree to this object, I have thought it not foreign to the subject of this article to introduce here some account of these researches. The results of x'urkinje’s examinations of the minute structure of bone as well as cartilage were published in the year 1834 in an inaugural dissertation by Deutseh.J Muller and Miescher have further investigated the subject and confirmed the statements of Purkinje.§ In examining thin slices of cartilage under * Uber das Gewebe der Tunica Dartos, &< Muller's Archiv, 1834. t Miescher states that in infants this part of th intervertebral substance is composed of a pelluci mucus, which, under the microscope, sometimi exhibits some of the cartilaginous corpuscles to t noticed in a subsequent part of this article, but i adults it is composed of adipose tissue! t De penitiori ossium structura. Diss. inaus Vratisl. 1834. § Vid. Muller, Vergleichende Anatomie dt Myxinoiden, Berlin, 1835, and Miescher, de ossiui genes , structura, et vita. Diss. inaug. Bero 1836. 6 the microscope by transmitted light, Purkinje observed numerous little bodies irregularly dis- persed through its texture, of a round or oval form, and somewhat less transparent than the intervening substance. The annexed figure, taken from Miiller’s work Fig. 139. already referred to, gives a representation of these bodies : they are deno- minated by Purkinje cartilaginous corpuscles ( Knorpel Kdrperchen ). In some cases, as in tem- porary cartilage, they ap- peared to consist of mi- nute granules ; they pre- sented this appearance likewise in the cartilagi- nous part of the cranium of a frog. In the costal cartilages they were solid, and in the cartilaginous fishes, as in the lamprey, their contents were of a soft or fluid consistence. According to Purkinje, these corpuscles are found in the temporary cartilages, in permanent cartilage, in cartilage which becomes ossified in old age, as that of the ribs and larynx, in the cartilages of the nose and septum narium. According to Miescher there are two kinds of permanent cartilage, differing from each other as well by external characters as by in- ternal structure; one of these scarcely differs at all from the temporary cartilage, the other is very dissimilar in structure. The first class is at once distinguished by its azure whiteness and by its pellucid brightness, not unlike that of mother-of-pearl, from the second, which is yellowish in colour, not pellucid, and spongy in texture. To the former class belong all articular cartilages, those of the ribs,* that of the ensiform cartilage of the sternum, the thy- roid, cricoid, and arytenoid cartilages, and those of the septum narium and alae nasi. All the cartilages of this class are characterized by containing the microscopic corpuscles above described, variously arranged in each form of cartilage, in some placed in clusters, in others closely aggregated together in one part and separated in another. It is interesting to ob- serve that the temporary cartilage universally contains these corpuscles, and as all the carti- lages we have described are more or less prone to ossification in advanced age, we are led to the inference, that these corpuscles thus de- posited are characteristic of cartilage which admits of becoming ossified.f * Sic Miescher. t The cartilages most liable to ossify by the pro- gress of age in man, are those which most fre- quently exhibit, after a certain period, a per- manently ossified condition in some of the inferior classes of animals. Thus, in birds, and among mammals, in monotremata, cheiroptera, and cetacea* the cartilages of the ribs show a very early dis- position to ossify. In birds the laryngeal cartilages are very apt to ossify, and in swine and oxen par- tial ossifications of the same cartilages, are nut. 262 FIBRO-CARTILAGE. To the second class of cartilages belong those of the external ear, of the epiglottis, and the capitula of Santorini, connected with the apices of the arytenoid cartilages, which in the ruminants, the hog tribe, and others, are of con- siderable size. Besides the characters already mentioned which distinguish this class of car- tilage from the former, the microscope dis- closes some further differences. “ Placed under the microscope,” says Miescher, “ the cartilages of this class present a very delicate network, opaque, composed of small round meshes which are filled by a uniform, pellucid substance, and each generally contains a single corpuscle somewhat roundish or oblong.” The cartilages that belong to this class are con- trasted with those of the former, as being never transformed into bone. I may add, that in my own examinations of pure cartilage, from the skeletons of cartila- ginous fishes, and from the human subject, I have found the foregoing descriptions correct. The cartilaginous corpuscles may be always seen under the compound microscope, with an object glass of a quarter of an inch or an eighth of an inch focus. In man and the mammalia, the following structures may be enumerated as belonging to the class of fibro-cartilages : 1. The so-called inter-articular cartilages in the knee, sterno- clavicular, and temporo-maxillary joints ; that in the wrist-joint seems to me to be purely cartilaginous. 2. The fibro-cartilages of cir- cumference, as in the hip and shoulder-joints. 3. The fibro-cartilages of tendons, which ulti- timately form sesamoid bones, and those of tendinous sheaths. 4. According to Miescher, the tarsal cartilages. 5. The inter-osseous laminae, as those between the pubes, pieces of the sacrum and coccyx, and, in a modified form, the intervertebral substance. In the inferior vertebrate and in the inver- tebrata fibro-cartilage gradually disappears : in the former, the intervertebral substance seems to be the only remnant of it, excepting perhaps the sclerotic coat of the eye in some fishes. In the invertebrata, Blainville considers the three tubercular teeth of the leech as being fibro-cartilaginous. Morbid conditions of fibro-cartilage. — As fibro-cartilage in its physical and vital pro- perties so nearly approaches pure cartilage, it is reasonable to expect a great similarity in the phenomena of disease as they are manifested in the two tissues. Fibro-cartilage appears to be susceptible of reparation in the same man- ner as pure cartilage. (See Cartilage.) A substance bearing some resemblance to fibro- cartilage sometimes forms the connecting me- dium between the fractured portions of a bone, where bony union cannot be obtained. The phenomena of inflammation and ulce- ration in fibro-cartilages are very similar to unfrequently found. Ossification of the nasal cartilages is extremely rave, but in the hog tribe two bones extend from the intermaxillary bone into the cartilage of the proboscis. — Vide Miescher, loc. cit. p. 27. those in pure cartilage : in the joints these morbid changes are generally complicated with similar diseased conditions of the other tex- tures, either cartilages or bones, whence they are propagated to the fibro-cartilages. It is well known that a condition of the interverte- bral discs, which is commonly spoken of under the name of ulceration, is frequently coin- cident with caries of the vertebrae, having in some instances preceded the vertebral disease, and in others followed it. To Sir Benjamin Brodie we are indebted for the observation that the diseased state of the intervertebral substance has sometimes the precedence of that of the bones; in one case, related by him, where ulceration of the articular cartilages had begun in several other parts, those between the bodies of some of the dorsal vertebrae were found to have been very much altered from their natural structure. He adds, “ I had an opportunity of noticing a similar morbid condition of two of the intervertebral cartilages in a patient who, some time after having received a blow on the loins, was affected with such symptoms as in- duced Mr. Keate to consider ■“this case as one of incipient caries of the spine, and to treat it, accordingly, with caustic issues; and who under these circumstances died of another complaint. Opportunities of examining the morbid appearances in this very early stage of disease in the spine are of very rare occur- rence, but they are sufficiently frequent when the disease has made a greater progress; and in such cases I have, in some instances, found the intervertebral cartilages in a state of ulce- ration while the bones were either in a perfectly healthy state, or merely affected with chronic inflammation, without having lost their natural texture and hardness.”* Otto mentions that he has several times satisfied himself that the destruction of the spine may originally spring from the intervertebral substance ; but he has never found suppuration, unless when at the same time the bones and neighbouring cellular tissue were inflamed.f The anatomical cha- racters of this condition to which we have been alluding consist in an erosion and soften- ing of the fibro-cartilage, frequently attended with the effusion on the surface of a dirty puriform and often fetid fluid. Fibro-cartilage is not prone to become ossi- fied ; in very old subjects the superficial portion of the intervertebral substances is often ossi- fied, but this is an extension of ossification from the bone or from the anterior common ligament : it is very rare to find any of the inter-articular fibro-cartilages ossified. The ossification of the interpubic fibro-cartilage in advanced age seems to be of a similar nature to that of the intervertebral substances. Masses of a substance very similar to fibro- cartilage are sometimes met with accidentally developed ; we find them in or connected with the uterus, in tumours, and in serous or sy- novial membranes. ( R . B. Todd.) * Brodie on (he Joints, edit. 2d, p. 231. t Pathol. Anat. by South. FIBROUS TISSUE. 263 FIBROUS TISSUE,* tela fibrosa, v el ten- dinea ; Germ, das sehnige Gewebe. The parts comprised in the fibrous system may with propriety be referred to two separate and distinct classes. I. Wuite fibrous organs. — Under this head the following structures, distinguished by their whitish colour, their fibrous organization, and their great power of resistance, are in- cluded : — a, the periosteum and perichondrium ; 6, fasciae or muscular aponeuroses ; c, sheaths of the tendons ; d, fibrous coverings of certain organs ; e, ligaments ; f, tendons. II. Yellow elastic fibrous organs. — There are certain organs, ex. gr. the yellow ligaments ( ligamenta subfiava ) of the spine, which resemble those of the former class by their fibrous structure, but which present so many important peculiarities in their texture and properties, that it is necessary to consider them apart from the preceding. All these organs resemble each other by possessing more or less a yellow colour, and a remarkable de- gree of elasticity. I. White fibrous organs. — Organiza- tion. This consists of a union of white or grayish fibres more or less distinct accord- ing to the part in which they are examined ; thus they are very apparent in most of the ligaments, in the fasciae, in the periosteum, and in many tendons, as in those of the obliquus abdominis externus, pectoralis major, &c. In other structures, on the contrary, as in the greater number of tendons, the fibres are so small and so closely united that they cannot be perceived but with difficulty, although they be- come more evident on maceration. In most parts of the body they observe a parallel direc- tion, whilst in other places they pass in an irre- gular manner, so as to cross and interlace with each other, occasionally constituting, as in the instance of the dura mater and of the tendinous centre of the diaphragm, a very intricate net- work of fibres. The result of a careful examination proves that the remarkably firm and resisting threads which constitute the basis of the various fibrous organs, are composed of condensed cellular tissue. In certain regions we may perceive the gradual transformation of the cellular tissue into a fibrous organ, as in the formation of the superficial fascia of the abdomen ; whilst by prolonged maceration the most dense tendon or ligament may be reduced into a pulpy cellu- lar substance : this opinion is corroborated by Isenflamm, who conceives that this tissue is formed by cellular fibres impregnated with gluten and albumen ; and also by Beclard, who regards it as being composed of cellular texture very much condensed. We may therefore conclude that the ideas of Professor Chaussier, * The expression fibrous tissue is by no means well chosen, as it is equally applicable to other and dissimilar organs, such as muscles, nerves, &c. all of which are eminently distinguished by a fibrous structure. It is, however, preferable to retain a received though inaccurate term, than to add to that multitude of names which already so much encumbers the science of anatomy. as to the existence of an elementary organic solid, called by him the albugineous fibre, and which is supposed to form the basis of all the ligamentous and tendinous parts of the body, are erroneous. The individual fibres are surrounded by pro- cesses of a more lax membrane, which pene- trates between them, and which is rendered particularly apparent by maceration and in cer- tain diseases. The differences that are observed in contrasting the various fibrous organs with each other, a ligament for example with a ten- don, seem principally to result from the larger or smaller proportion of the interfibrous cellu- lar substance and on the degree of its conden- sation. This combination of the common cel- lular tissue with the ligamentous fibres allows the fibrous organs to yield in a very slight de- gree when extended by the elasticity which is thus bestowed, and also slightly to contract on themselves on the removal of the extending force. ,1, ■-'iA°0rssels. — The proper fibrous tissue re- Ci c a small quantity of blood, the arteries l rd'-ute in size, and principally carrying a To/mrless fluid. The great vascularity of the dura mater and periosteum is no exception to this remark, because the vessels of these membranes are not proper to them, but to the veins they cover. Absorbents. — The ravages of disease in the neighbourhood of joints, involving the liga- ments in ulceration ; the sloughing of tendons, the destruction of the periosteum by the pres- sure of aneurism, of the tunica albuginea in scrofulous or malignant fungus of the testis, are abundant proofs of the existence of absor- bent vessels. Nerves. — According to Monro, nervous fila- ments may be traced to some of the fibrous organs ; and other anatomists, Cruveilhier for instance, speak of nerves being furnished to the joints; in general, however, none are to be seen ; but as sensibility becomes developed in disease, we must presume that communications do exist with the encephalon. Chemical properties. — The principal sub- stances that have been detected in the fibrous as in the cellular tissue consist of coagulated albumen and gelatine ; a small quantity of mucus and saline matter has also been disco- vered. The effects of desiccation are well known, tendons and ligaments becoming hard, transparent, yellowish, and fragile. This tissue resists maceration for a long time, but at length it is rendered soft and flocculent, so that the fibres can be separated and unravelled ; ulti- mately it is converted into a pulpy and fila- mentous cellular mass. Properties.— The offices which these organs are designed to fulfil in the economy being, with the exception of the periosteum and its analogous membrane the dura mater, of a me- chanical character, the properties by which they are distinguished are almost entirely of a physical nature. They offer great resistance to rupture, and thus the ligaments are capable of opposing the shocks to which, in the violent movements of the joints, they are so frequently 264 FIBROUS TISSUE. exposed; whilst the same cohesive property enables the tendons, under all ordinary circum- stances, to bear the immense force of muscular contraction. Having considered the general characters of these organs, I shall proceed to describe the most essential properties of each individual class. 1. Of the periosteum. — This may be regard- ed as the most important of the fibrous tissues ; indeed so universal are its connexions, that if any common centre of this system were sought for, we should certainly coincide with Bichat in considering this to be the periosteum. Dis- carding the erroneous ideas of the ancients and Arabian physicians, who imagined that the membranes of the body were all continued from those of the head, we shall find that, with the exception of the perichondrium of the larynx and the fibrous tunics of some glandular bodies, all the fibrous organs are in connexion with the periosteum. The inner surface of the perigsteiifn final y adheres to the several bones by a multitude > f delicate processes passing into the bpeninds observed on their external surface. These pro- cesses convey into the bones an amazing num- ber of fine arteries and veins, called therefore periosteal, and which may be regarded as the principal, or as some anatomists contend, the only proper vessels of the osseous tissue. The outer surface is rough, and is united by the cellular tissue to the surrounding muscles, tendons, ligaments, and fasciae ; in the nostrils, sinuses, and tympanum, the periosteum is, however, joined to the mucous membranes, and in the skull the surface unattached to the bones is lined by the arachnoid. The periosteum constitutes the nutrient membrane of the bones, and thus bears an im- portant part in the process of ossification and in the reparation of fractured and diseased bones; it also serves as a medium for the attachment of the ligaments, tendons, and fasciae to the skeleton. 2. Fascia.- — The fibrous fasciae or aponeu- roses not only invest the surface of the limbs, but also furnish a number of processes, which, penetrating deeply ?mong the several muscles, form sheaths to those organs, by which they as well as the bloodvessels and nerves are main- tained in their proper situation. It is evident that these partitions must exert a great influence on the growth of various kinds of tumours, on effusion of blood, on the extravasation of urine, and on the formation of matter; so that their relations form an important branch of surgical anatomy. In order to give to these muscular envelopes the necessary degree of tension, they are either provided with special muscles, as in the case of the tensor vaginae femoris and the palmaris longus, or they receive processes from the neighbouring tendons, as from the biceps cubiti, semi-tendinosus, and so forth. The aponeuroses thus braced afford a firm support to the parts they cover, and in this manner they increase the powers of the muscu- lar system ; whilst by their resistance they efficiently protect the vessels and nerves from external violence, and at the same time proba- bly assist in the circulation of the blood and lymph, and so prevent varicose enlargement of the deep-seated veins and oedema of the extre- mities. See Fascia. 3. Tendinous sheaths.- — These are in their office analogous with the last, excepting that, instead of fixing the muscles, they secure the tendons during muscular action. The thecal ligaments of the hand and foot, the annular ligaments of the wrist and ankle, and the fascial sheaths around the knee are of this character. They are distinguished by their great strength, and as they are internally lined by synovial membrane, they facilitate the play of the ten- dons ; and in many instances, as in the trochlea of the os frontis and the sulci of the carpal extre- mity of the radius, they also modify the action of the muscles whose tendons they transmit. 4. Fibrous coverings. — Certain organs are provided, for the purpose of protection, with dense ligamentous coverings ; of this order are the dura mater, the sclerotic coat of the eye, the loose portion of the pericardium, the proper covering of the kidney, of the salivary glands, mamma, spleen, thyroid gland, thymus, lym- phatic glands, of the prostate, testicle and ovary ; probably the exterior investment of the nervous ganglia is of the same character. Some of these envelopes, as the dura mater, pericar- dium, and tunica albuginea testis, are lined on one surface by a serous membrane, and thus constitute Jibro-serous membranes, or as they are called by Beclard, compound fibrous mem- branes. 5. Ligaments. — These bodies possess in an eminent degree those properties by which the whole fibrous system is distinguished; and consequently the term ligamentous is often em- ployed to designate the whole of the fibrous organs. The ligaments fulfil a very important office in the animal economy by binding together the various bones of the skeleton, an object which they are enabled to effect in consequence of their fibres being very firmly attached, and as it were consolidated with the osseous system through the medium of the periosteum. It is stated by Portal, that after the bones have been softened by the influence of an acid, the liga- ments are observed to send processes into their substance, which cause the ligaments to adhere so firmly that, although by very great force they may be torn, yet they cannot be separated from the bones. Although these organs are dissimilar in shape, yet there are three forms among them which predominate: 1. the capsular, 2. the funicular, 3. what, for want of a better ex- pression, may be called laminated. The true fibrous capsules which consist of cylindrical bags lined internally by synovial membrane, are confined to the shoulder and hip-joints, although imperfect capsules exist in many other articulations. The funicular and la- minated ligaments are much more universally diffused, assisting in fact in the formation of every joint in the skeleton. FIBROUS TISSUE. 265 6. Tendons. — These organs, which serve td connect the muscles to the osseous system, are composed of fibres so closely disposed that some anatomists, but erroneously, doubt their identity with the other fibrous organs. This compactness is owing to the extreme con- densation of the intervening cellular tissue, which is also the cause of these bodies re- sisting for a longer period than the ligamen- tous or fascial structures, the influence of ma- ceration. Every tendon is united by one of its ex- tremities to the fibres of the muscle to which it belongs, and by the other it is connected with the bone or other part on which the muscle is destined to act. The exact mode of connexion between the tendinous and mus- cular tissues is difficult to determine. Ocular and microscopical inspection seem to prove that the tendinous fibres result from the con- tinuation and condensation of those cellular sheaths, which inclose and in part form the muscular fibrils. It has, however, been stated that there is an intermediate substance between the muscle and the tendon, different from both of them, and serving to connect them together. The details relative to the mecha- nical disposition of these organs belong to the consideration of the muscular system. — See Muscle. II. Yellow elastic fibrous organs. — ( Tela elastica.) It was justly observed by Bichat that the ligaments placed between the arches of the vertebrae differ in their nature from the other ligaments of the body ; and modem anatomists, admitting this distinction, have enumerated the following structures as a separate class of the fibrous organs : the yellow ligaments of the spine ; the external and espe- cially the middle or proper membrane of the arteries, the fibrous covering of the excretory ducts; the ligamentous tissue joining the carti- lages of the air-passages; the fibrous envelope of the cavernous bodies of the penis and clitoris, and of the vesiculae seminales. Although the highest authorities consider that the middle tunic of the arteries is com- posed of this tissue, yet the correctness of this opinion is very doubtful. It is true that, as rar as colour is concerned, the similarity is well founded ; but the arterial fibrous coat is endowed with a power of contraction, evi- dently distinct from mere elastic contraction, which is totally wanting in the true yellow fibrous tissue. In addition to the parts above named, it is necessary to add that in certain organs where great elasticity is requisite there is a peculiar yellow cellular substance, which, although it does not present the dense and fibrous cha- racter, appears to belong essentially to the organs under consideration. This texture is particularly distinct in the mucous folds which constitute the superior boundary of the glottis, a part that is remarkable for its extra- ordinary elasticity.* * It is stated by Sir E. Home ( Eect. on Comp. Anat. vol. ii. p. 49,) that this tissue enters into the It occasionally happens, as in the forma- tion of the intervertebral substance, that the yellow fibrous tissue and the common liga- mentous are combined. A more striking instance of this combination is seen in the construction of the connecting ligament which forms the hinge in bivalve shells, in which one part, the external, is composed of ligamentous matter, whilst another, the internal, consists of a highly elastic fibrous tissue. Organization and properties. — If the yellow ligament of the spine or the ligamentum nu- cha in ruminants be examined, it will be seen that each is smooth on its surface, and is made up of a great number of longitudinal and highly elastic fibres, which, in the latter in- stance, are readily separated and unravelled by the finger. This texture is, I believe, sui generis, and is altogether distinct from the common ligamentous structures. In a recent publication,* M. Laurent conceives that this tissue is intermediate in its characters to the tissus scltreux (under which term he proposes to class the white fibrous organs, the cartilages and bones,) and the muscular tissue; he there- fore calls it tissu sclero-sarceux. Although it is very doubtful if the elastic fibrous structures have any thing in their organization similar to the muscular fibre, yet it is certain that in function they are intermediate between the common ligaments and the muscles, a fact which is kept in view in theHunterian Museum, in which the elastic ligaments are placed next to the muscles. The resistance and elasticity of these organs enable them firmly to connect together the parts to which they are attached, and at the same time allow them to yield to double their length on the application of an extending force. In this manner they economise mus- cular action, by substituting for that force the power of elasticity. This employment of an elastic rather than a muscular power is evinced in the yellow ligaments of the spine, which pull the vertebras towards each other, and thus assist the muscles in maintaining the upright posture. The same thing is also seen in many of the lower ani- mals; as in the support of the head by the ligamentum nuchas — the retraction of the claws in the feline carnivora by an elastic ligament — and the support of the abdominal organs in many large quadrupeds by the elastic super- ficial fascia. But the most interesting ex- ample of this economy of muscular action is displayed in the bivalve shell of the oyster and other acephalous mollusca. in which in- stance not only is the shell kept open by the elastic ligament of the hinge for the purpose of admitting the nutriment of the animal ; but formation of muscle ; but this is probably erro- neous, as the elasticity of muscles depends on the large proportion of elastic cellular membrane which they contain. Lobstein has also published some observations in the Jour. Univer. des Sc. Med. on the tissue of the uterus, which he regards as ana- logous to the so-called yellow tissue of the middle arterial coat. * Annales Fram;aises et Eirangercs d’Anat. et de Physiol. Jan. 1837. P. 59. 266 FIBROUS TISSUE. as the valves are designed by nature to be separated only to a limited extent, an elastic ligamentous structure is placed between them towards their centre, and in this manner all undue separation is prevented without any demand being made on the force of the ad- ductor muscle.* Morbid anatomy. I. Inflammation. — The low degree of organization possessed by this tissue modifies the inflammatory process, which is usually chronic in its nature, and often extremely insidious in its progress ; occa- sionally, however, as in sprains, acute rheu- matism, &c., the fibrous organs are the seat of very active disease. Owing to their great density, but little swelling takes place unless there be chronic and prolonged inflammation ; in which case, as is particularly observed in disease of the joints, a quantity of jelly-like fluid is poured into the interstitial cellular tissue, the proper fibres become massed toge- ther and with the surrounding parts, till in the advanced stage all traces of the original for- mation being lost in the diseased mass, it be- comes reduced to the pulpy consistence of diseased cellular membrane, of which the healthy structure is a modification. This deposit and thickening are the most common products of inflammation in liga- mentous parts ; but it occasionally happens that a true abscess is formed, as when pus is thrown out between the dura mater and cra- nium. I have known one case connected with disease of the bone, in which matter was de- posited in the substance of the dura mater, and in which the operation of trephining was ultimately required for the relief of the patient. Ulceration is a frequent result of scrophu- lous disease of the joints, causing great ravages in the ligaments and neighbouring parts. Mortification of ligament is not a common occurrence, whilst in the acute inflammation of tendon, especially in neglected thecal ab- scess, and of fascia in consequence of large abscess under it, sloughing is not unfrequently witnessed. There are of course certain modifications in the effects of inflammation according to the part attacked. Thus, in ligament, there is a great tendency to ulceration ; in tendon to mortification ; in the periosteum to great in- duration ; and, as we see in the formation of a node and of callus, to a transformation into cartilage and even bone. When fascia is the seat of disease, the consolidation arising from effusion often gives rise to a retraction of the affected part; a result which has been observed, for example, in inflammation of the aponeu- * Leach, Bullet, des Sciences, 1818. P. 14. [Mr. Hunter fully recognised the value of this elastic tissue, and in his Museum he set apart a series for its illustration under two classes — 1st, as an antagonist to muscle, and 2d, in aid of mus- cular action. In the former class he places such examples as that of the oyster alluded to in the text, in the latter the ligamenta nuchae and the elastic fibrous expansion on the abdomen of the elephant and other larger quadrupeds. See the Descriptive and Illustrated Catalogue of the Hun- terian Museum, vol. i. — Ed.] rosis of the fore-arm, and in that affection of the palmar fascia called by Boyer and other writers crispatura tendinum .* II. Cartilaginous tranflormation and ossi- fication. — Many parts of the fibrous system not unfrequently become cartilaginous or even osseous. The cartilaginous transformation is often observed in the ligaments of diseased and anchylosed joints; in the periosteum after fractures and in the formation of nodes ; in tendons, especially those which are exposed to great friction in the fibrous covering of the spleen. I have had opportunities of seeing many specimens of cartilaginous deposit taking place between the periosteum and the bone, and evidently arising from the former. The valuable collection of my friend Mr. Liston contains a very fine specimen of a large carti- laginous tumour proceeding from the peri- osteum. Ossification, although extremely common, occurs much more frequently in some than in other classes of these organs : thus it is often met with in the dura mater, in which structure, as far as I have observed, the bony excres- cence always proceeds from the inner layer or that towards the arachnoid, and consequently presses against the brain. In one very re- markable specimen in my possession, nearly the whole of the falx, and a large extent of the membrane attached to the vault of the cranium, are completely ossified. In an instance, ob- served I believe by Dr. Barlow (Southwark), the heart was completely encased in bone, owing to the entire ossification of the peri- cardium. The cicatrix of a wounded tendon is often osseous. III. Fungus. — The dura mater, the peri- osteum, the fascia, &c., are subject to excres- cences having a fungoid appearance, which vary in their nature, often consisting of a chronic, indolent growth, whilst at other times they are evidently scrophulous, and occasion- ally they are malignant. In the progress of those cases where the disease is situated near the bones, these organs are implicated, and some doubt has conse- quently arisen concerning the first seat of the disease ; it is, however, proved by examination that in the fungus of the dura mater and other fibrous parts, the bones are only secondarily affected. A good illustration of this fact is afforded by a preparation consisting of an extensive fungus arising from the periosteum covering the tibia, in which it is evident, al- * Boyer, Traite des Malad. Chir. tom. v. p. 55. This peculiar affection was some years since pointed out by Sir A. Cooper, and has since been more fully described by Baron Dupuytren, (Le$ons Orales de Chir. Clin. tom. i. p. 2). The tension and contrac- tion of the palmar fascia, which are usually caused by continued pressure, give rise to aretraction of one or more of the fingers, and may be removed by transversely and freely dividing the aponeurosis opposite to the metacarpo phalangean joint. I have known one case of similar induration of the fibrous sheath of the. corpus cavernosum penis ; and I have learnt from Sir A. Cooper that he has seen several such cases, occurring in persons who had freely indulged in sexual intercourse. Boyer has made a similar observation. FIBULAR ARTERY. though the subjacent bone has been partly absorbed, that the fungoid disease entirely originated from the periosteum* Malignant fungus occasionally arises from the periosteum. I have seen one case of this disease connected with the tibia, in which amputation was performed, but with an un- favourable result, the patient sinking rapidly from mortification. In medullary sarcoma that membrane is often involved. Osteo - sarcoma, according to Howship, Ciaigie, and Meckel, occasionally has its ori- gin in the periosteum. ( It. D. Grainger.) FIBULAR ARTERY, (arteria peronaa ; Fr. artere peroniere ; Germ, die Wadenbein- arterie ). — This artery is commonly described as a branch of the posterior tibial, or it may be said to be one of the branches resulting from the bifurcation of a short trunk which has its origin immediately from the popliteal, and which has been described under the name of the tibio-peroneal artery, the other branch of the bifurcation being what is ordinarily considered as the continued posterior tibial trunk. The origin of the fibular artery is situated about an inch below the inferior margin of the popliteus muscle, thence the artery extends downwards and with a very gradual inclination outwards, and terminates in the region of the external ankle, just above the os calcis and behind the fibula. It is a vessel of smaller size than the posterior tibial, and about equal to the anterior tibial, and it is interesting to ob- serve that the varieties in its calibre are in the inverse ratio of the calibre of the anterior aud posterior tibial, but more especially of the former. To expose the fibular artery in dissection the gastrocnemius and soleus muscles must be raised, and the deep fascia of the leg dissected away. The artery is then seen resting at first for a very short distance upon the tibialis posti- cus muscle, and from it getting upon the pos- terior surface of the fibula near its tibial edge, where the vessel is imbedded in the flexor pol- licis proprius and encased between that muscle and the bone. Inferiorly it passes between the flexor pollicis proprius and tibialis posticus, and is applied to the posterior surface of the interosseous ligament. The fibular artery is sometimes altogether absent, and then its place is supplied by rami- fications of the posterior tibial. Sometimes the fibular artery takes its rise higher up than the point we have indicated ; but more frequently it has a lower origin, in which case it presents a calibre smaller than that which may be con- sidered as usual ; the vessel, indeed, is found to be smaller the lower down its origin is. It is in these cases that the anterior tibial especially and the posterior tibial occur of a larger size than * The result of dissection induces me to suppose that in many old and intractable ulcers, the fun- goid excrescences seen on the surface arise either from the fascia of the leg or from the periosteum, according as they are placed on the outer or inner part of the limb. 267 natural, as it were to compensate for the de- ficiency of the fibular. Branches. — The first branches the fibular artery gives off are small muscular ones on either side to the soleus, tibialis posticus, flexor pollicis proprius, to which in its whole course it gives a liberal supply; also to the fibula and the peronaei muscles. From its inner side, according to Cruveilhier, it gives an anasto- motic branch to the posterior tibial, which passes transversely or obliquely from one artery to the other. This branch sometimes attains a considerable size, and in such cases after its communication with the posterior tibial, that artery also becomes considerably enlarged. The fibular artery divides into its two termi- nal arteries in the inferior third of the leg; these are the anterior and posterior peronaeal arteries. Anterior peroneal artery, (arteria peronaa anterior and perforans peronaa.) This branch gains the anterior surface of the leg by piercing the interosseous ligament, where it is covered by the peronseus tertius muscle. The situation at which this perforation takes place is stated by Harrison to be about two inches above the external ankle; it then inclines downwards upon the outer side of the tibia, anastomoses by a transverse branch with the anti-tibial, com- municates with the external malleolar artery from the anterior tibial, giving off numerous branches both before and after the anastomosis, which pass down to the tarsus and communi- cate with the tarsal arteries. This artery is generally smaller than the posterior, some- times so small that the ordinary injection fails to penetrate it. If there be any anomaly in the size of the anterior tibial artery, this branch is generally large in proportion as that artery is small, and in such a case it might exceed the posterior peroneal in calibre. The arteries of the dorsum of the foot spring from the anterior peroneal when the anterior tibial exhibits this deficiency. Posterior peroneal artery, (A. peronaa pos- terior; calcanienne externe, Cruveilhier). This branch continues the course of the fibular artery behind the external malleolus to the outer side of the os calcis; it runs parallel to the outer edge of the tendo Achillis, being immediately covered by the continuation of the fascia of the leg. A transverse branch from the inner side of this artery establishes its communication with the posterior tibial, and inferiorly it distributes its terminal branches to the muscles and other parts on the outside of the os calcis to anasto- mose with the external tarsal and plantar arteries ; some small vessels proceed round the tendo Achillis to effect a further communication with the posterior tibial. This may be considered as the terminal branch of the fibular artery ; it is absent only when the fibular artery passes entirely forwards, or vi hen it directly opens into the posterior tibial without having any further communica- tion with the arteries of the ankle. The fibular artery is evidently a valuable anastomotic trunk to both the tibial arteries, a deficiency in either of which it is prepared to 268 riFTII PAIR OF NERVES. supply. Deriving its origin from the same source, and anastomosing freely with both in all parts of their respective courses, it is pre- pared to take the place of either, one might say, at a moment’s warning, and the freedom of this communication affords a sufficient indica- tion to surgeons how ineffectual in cases of wounds a single ligature would be; in short, here as in other places where arterial communi- cations are so free, the rule of practice is so clearly pointed out by the anatomy as almost to render it superfluous to appeal to experience. The relations of this artery to operations being very similar to those of the posterior tibial, we refer on this head to the article Tibial Ar- teries. (R. B. Todd.) FIFTH PAIR OF NERVES.— This title is derived from the relation which the nerve bears numerically to the other encephalic pairs; it is the fifth nerve met with on the base of the brain counting from before backwards. The fifth is also called the trigeminal (Winslow) and the trifacial (Chaussier) nerve. It is the nerve upon which the general and tactile sensi- bility of the face and its cavities, as well as the voluntary power of certain muscles of these parts, depends. The following account of this nerve is meant to apply especially to the human subject; but as a knowledge of its structure and distribution in other animals must contribute very much to enlighten us in regard to its true character and properties in man, occasion has been taken to mention those particulars by which it is dis- tinguished throughout the animal series. The fifth nerve is connected at its one ex- tremity with the medulla oblongata, whilst its other end is distributed to the eye and its appendages, to the nostrils, to the palate, the mouth and tongue, to the salivary glands, to the ear, to the integuments and muscles of the face, forehead, and temple, and to the muscles which move the lower jaw in mas- tication, the temporal, pterygoid, and mas- seter muscles. The general distribution of the nerve throughout the animal series corres- ponds to that in man ; but, in certain animals and classes, varieties are presented, which claim our attention equally, whether as matters of curiosity or of physiological interest. In some individuals of the class Mammalia, the eyes possess a very inferior degree of develop- ment; a distinct optic nerve either does not exist or its existence is a matter of doubt, and its place is supplied, in part or alto- gether, by a branch of the second division of the fifth nerve: thus, in the Mole, accord- ing to M. Serres,* the optic is altogether absent, and its place is supplied by a branch of the fifth ; but, according to Treviranus,f that animal is provided with an optic nerve, as large as a human hair, and according to Cams}; ^ joins an optic branch from the fifth, and the two concur to form the retina. In * Anatomie Comparee dti Cerveau, &c. t Journal Cotnplementaire. } Journal Compl. other animals of the same class the optic seems decidedly absent, and its place is supplied al- together by the fifth. Among Reptiles also in- stances occur, in which the optic nerve is wanting. According to both Treviranus* and Serres, f the fifth nerve takes the place of the optic in the Proteus Anguinus. A va- riety in distribution, still more remarkable, is presented in the disposition of the fifth nerve in Fishes. Among the Rays the audi- tory appears to be, not a distinct nerve, but a branch of the fifth:! the special organs, with which they are provided, likewise, in many instances, derive their nerves from the fifth pair; thus, in some the electrical § organs are supplied by that nerve, and also the albu- mino-gelatinous organs : lastly, in many the nerve is distributed || in a manner and to an extent for which there is no analogy among other animals, the fins being throughout fur- nished with branches from the fifth. Hence in Fish, in which the distribution of the nerve is so much more extended than in other animals, both the size of it is propor- tionally greater, and it consists of a greater^ number of divisions; these, which in the three other classes of vertebrate animals are only three, amounting with them to from three to six. See sketch of nerves in the Ray and Cod. ( Figs. 1 44, 145.) 1 he size of the fifth nerve is very great, it being by far the largest of those proceeding from the medulla oblongata. In this respect it pre- sents much variety according to the animal or its class. M. Serres states that, the nerves being proportioned always to the volume of the organs from whence they proceed, the extent of the face and of the organs of the senses taken together gives the size of this nerve in the different classes of vertebrate animals. Among the Mammalia the extent of the face and of the organs of the senses increases pro- gressively from Man to Apes, the Carnivora, the Ruminantia, and the Rodentia, and, ac- cording to him, the size of the fifth nerves follows in a general manner the same pro- gression. Birds are remarkable for the atrophy of the muscles of the face and of several of the organs of the senses, and their fifth nerve is far from presenting the developement to be observed in the inferior Mammalia. Reptiles are still lower than Birds with regard to the dimensions of the nerves of the fifth pair; while in Fish** the size of the nerve is very great, and even surpasses in some the volume it presents in the other classes.ft However just the estimate of the comparative volume of the nerve in different animals, as here stated, may ® Op. cit. t Op. cit. t Desmoulins, Journal tie Physiologie, t. ii. Serres, op. cit. § Desmoulins, Anatomie ties Systemes Nerveux, &c. Carus, Rudolphi. || Desmoulins, op. cit. If Desmoulins, op. cit. ** See Sketches of Nerve in the Ray and Cod, fiys. 144, 145. tt Serres, Anatomic Comparee du Cerveau, dans les quatre classes des Animaux Vertebres. FIFTH PAIR OF NERVES. 209 be, the data, from which it is professedly drawn, may be reasonably objected to. In the first place the volume of the organ cannot be assumed as being alone the measure of that of the nerve supplying it • the degree of ner- vous endowment, whether general or special, which the organ enjoys, must be also taken into account ; and in the second, the extent of the organs of the senses cannot be admitted as a measure of the volume of the fifth nerve, which is not connected with them all ; thus the greater part of the organs of touch is inde- pendent of that nerve. It appears to me that the extent of distribution and amount of endowment conjointly determine the volume of the nerve, and that the latter cannot be inferred a priori. Each nerve is composed of two portions, which are remarkable for particular characters, and have received distinct names; they differ from each other in size, in anatomical disposi- tion, and in function ; one of them, larger than the other, is provided with a ganglion, and dif- fers in its distribution ; it also differs in proper- ties, being subservient to sensation ; the other is small, has no ganglion, and is destined to volition ; they are hence denominated, the former the larger, the ganglionic or the sentient portion, the latter the smaller, the non-ganglio- nic or the voluntary portion. The distinction of the nerve into two por- tions appears to prevail uniformly throughout the animal series. According to M.Serres, it is to be observed in all the classes of the ver- tebrate animals except the Reptiles; but in them, according to him, th e lateral fasciculi* are wanting. The latter assertion, however, is incorrect, the distinction being to be observed as satisfactorily in that class as in any other.f Again, the distinction is not equally remarkable in all ; in some it is still more so than in man ; in others it is less ; and according to the same authority, it is to be observed among Mam- malia the more easily as we pass from Man to the Rodentia. Among the Cetacea it is divi- ded throughout into two separate fasciculi.^ Each of the two portions of which the nerve consists is a packet containing numerous fas- ciculi, which are again divisible into filaments. The fasciculi, of which the packets are com- posed, are differently circumstanced in different stages of the course of the nerve ; in one part they are bound up so closely together that they cannot without difficulty be separated from each other and disentangled, while in another they are but loosely connected and are easily sepa- rated. The two packets are associated together more or less intimately throughout their course ; but inasmuch as they present remarkable varieties in their disposition and mutual relations at dif- ferent parts, it may be advantageous to divide the nerve, through its course, into three por- tions or stages ; one from the ganglion to the connexion of the nerve with the brain, which * The name by which he designates the lesser portion of the nerve. t See sketch of filth nerve in the Turtle, _/?y. 143. t Op. cit. may be denominated its internal or encephalic portion; a second from the ganglion to its ulti- mate distribution, its external or peripheric portion ; and, thirdly, its ganglion. Such a distinction may not be free from objection, but being adopted for the convenience of descrip- tion, it possesses at least the recommendation that there exist well-defined points of demar- cation, whether there exist or not any difference in the properties of those several portions. The nerve, in its encephalic portion, is partly within and partly superficial to the substance of the brain. The superficial part is from one-half to three-fourths of an inch in length, of a flattened form, and of very considerable size. It presents a loose fascicular texture, and is enclosed within a prolongation of the arachnoid membrane sent off upon it from the surface of the brain ; this prolongation is, as in the case of all those sent upon the vessels or nerves, in their passage from that organ to the parietes of the cranium, a cylindrical sheath, within which the nerve is enclosed ; it is at first remarkably loose, but as the nerve recedes from the brain, the membrane invests it more closely, and is continued upon it as far as the ganglion, from which it is reflected to the surface of the canal in which the nerve is contained. In the last particular the disposition of the membrane is subject to variety, for it is at times continued beneath the ganglion, and partially invests the trunks proceeding from this body before it is reflected to line the canal. Throughout this part of the nerve the two packets composing it are connected by cellular structure and vessels, and are enclosed within the prolongation of arachnoid membrane just described ; but there does not appear to be any interchange of nervous filaments between them, and they are connected so loosely that they can be separated from each other with great facility. They consist each of numerous fasciculi held together, like the packets themselves, so loosely that the latter can be easily opened out and decomposed. The fasciculi of both packets are irregular in size, some large, others small ; those of the larger are for the most part some- what smaller than those of the lesser, but they are much more numerous, amounting, accord- ing to J. F. Meckel,* to thirty or forty; while those of the lesser amount, according to the same authority, only to from nine to fourteen. The fasciculi again are composed of numerous and delicate filaments. The number of the fila- ments is very great, but differently estimated by different author.ties ; according to Meckel those of the greater packet amount to about one hundred, collected into thirty or forty fasciculi; while, according to Cloquet, f the total number of filaments contained by both packets varies from seventy to one hundred, of which he allots five or six to the smaller, and the remainder to the larger packet. This difference of opinion Meckel explains by sup- posing that fasciculi have been taken for fila- ments and not decomposed, and this appears * Manuel d’Anatomie. t Anatomie Descriptive. 270 FIFTH PAIR OF NERVES. very probable, inasmuch as Cloquet takes no account of fasciculi, and in his description of the smaller packet it is manifest that he has assumed the fasciculi, of which it is composed, to be filaments, for he does not attribute to it a greater number of filaments than it contains of fasciculi. But if Cloquet have underrated the filaments of the larger packet, Meckel junior has certainly overrated the fasciculi of the smaller one. From his account of the latter, it is to be concluded that it contains from three to fourteen fasciculi, but either of those numbers is too great, as will be seen from an examination of the subject, from which it will appear that they do not exceed the number attributed to them by Cloquet. The ultimate number of filaments, however, would seem to be somewhat uncertain, for it appears to depend very much upon the delicacy with which the separation of them may be effected ; and after all it is not a matter of any great importance. According to Wrisberg* and Scemmerringd the number of fibres contained in the greater packet is always less in the foetus than in the adult. The filaments of the smaller are stated by Cloquet to be larger, softer, and whiter than those of the other; but with regard to the difference of size it is probable that this opinion has arisen also from his having assumed the fasciculi to be filaments, inas- much as, when the fasciculi have been decom- posed, the filaments seem to be equally fine in both packets ; and for the other points of sup- posed difference the author has not been able satisfactorily to observe any in man. In other animals, however, — in some fish at least — a remarkable difference may be observed between the characters of the ganglionic and non-gan- glionic portions, the latter of which, in the Cod, is much softer, and of a darker, not whiter, colour than the other. The fascicular and filamentous disposition which has been described, is not, however, presented by the encephalic portion of the nerve through its entire extent, but only in that part of it which is superficial to the brain ; nor is it acquired by it until after it has emerged one or two lines from the substance of the organ, and then it does not assume it through- out at once, but at first superficially and later internally. The appearance of distinct fila- ments and fasciculi in one part and their ab- sence in the other appears owing to the exist- ence of neurilema in the former, for in one as in the other the nervous matter appears to be arranged in longitudinal tracts, which pre- sent in one case the form of expansions, and in the other are divided by the neurilema into separate cords ; and again the occurrence of the filamentous disposition earlier upon the surface than internally, is attributed to the superficial substance of the nerve being pro- vided with neurilema sooner than the inter- nal ; hence the length of the substance of the nerve without neurilema is greater internally * Observationes Anatomic® de quinto pari ner- vorum, &c. t In Ludwig, Script. Neurol. Min. Ueber das Organ der Seele. than externally, and when the nerve has been pulled away from its attachment to the brain, the rupture occurring at the point at which the neurilema commences, the part which is left projects in the middle, and presents a conical eminence of white matter: this, as Cloquet justly remarks, is but an incidental appearance, and not entitled to be considered, as it was by Bichat,'* a real tubercle, from which the nerve arose. In neither packet are the fasciculi laid simply in apposition ; in both, but more remarkably in the larger, they are connected by frequent interchanges of filaments, and that to such a degree that the nerve when opened out appears to form an inextricable plexus, in which it is not improbable that every filament of it is connected directly or indirectly with all the others; this plexiform arrangement diminishes as the nerve approaches the gan- glion, before reaching which the fasciculi be- come more distinct. The fifth nerve is attached to the surface of the brain on either side of the pons Varolii, at a distance of three-fourths of an inch from its middle line. It is attached to the middle crus of the cerebellum, on its anterior inferior surface, about one-fourth of an inch from its superior, and half an inch from its inferior margin. The place of the attachment of the nerve to the exterior of the brain varies greatly in dif- ferent classes of animals ; in man, it is, as has been mentioned, the crus cerebelli on either side of the pons; in the other orders of the Mammalia it is either, as in the human sub- ject, the crus cerebelli, or, when the pons is less developed than in man, the nerve is at- tached behind that part between it and the trapezium of the medulla oblongata; in the other three classes of vertebrate animals, in which the pons and trapezium are both want- ing, the nerve is uniformly attached to the la- teral parts of the spinal bulb. This contrast is equally curious and important; it affords us a natural analysis, which will throw much light on the next step in our inquiry, viz. the origin of the nerve, or its ultimate connexion with the brain. It furnishes also, as has been sug- gested by Gall and Spurzheim,f an explana- tion of the complication which exists in the human being, in whom the great developement and the situation of the pons render it neces- sary that the nerve should traverse it, in order to reach the surface of the brain. At the attachment of the nerve to the crus cerebelli in the human subject, the non-gan- glionic portion or lesser packet is situate above and to the inner side of the greater. At that place it is separated or separable into two parts, while the greater continues undivided, and hence the nerve is described as having three roots, one for the greater and two for the lesser packet. The existence of two roots for the lesser packet had been announced by Santorini,! but they have been more parti- * Anatomie Descriptive. f Anatomie et Physiologie du Systeme Nerveux. } Observationes Anatomic®. FIFTH PAIR OF NERVES. 271 cularly and accurately described by Palletta.* They are distinguished by the latter into supe- rior and inferior, being attached to the crus cerebelli, one above and behind the other, and they are frequently separated from each other at their attachment by an interval of one or two lines or more. In such case the superior root is superior and parallel to the inner side of the greater packet, while the inferior is in- ternal to it, and, it may be, on a level with its inferior surface; hence, in such instances, the greater packet corresponds to the interval be- tween the roots of the lesser, and the inferior root of the lesser, in its course from the brain, is placed at first along the inner side of the greater packet, while the superior descends internal to the greater packet, and joins the inferior beneath it to constitute the lesser packet. This is not, however, uniformly the relation of the roots of the nerve at their at- tachment to the crus, for the distance at which they are placed from each other varies very much ; in some instances the roots of the lesser packet are perfectly distinct and separated by the interval mentioned, the inferior being either in immediate contact with the greater packet, and even entering the crus through the same aperture, or being separated from it by an interval varying, according to J. F. Meckel, from a quarter of a line to a line; while in others the roots of the lesser packet are not manifestly distinct, but the fasciculi of which they consist are attached to the crus in an un- interrupted series reaching, from the attachment of the greater packet, to within a line or less of the posterior face of the crus, and separated the one from the other by trifling intervals ; in the latter case the lesser packet is, for the most part, altogether superior to the greater at their attachment. But even in this the lesser is still distinguishable into two sets of fasciculi, which take different routes through the substance of the crus, one traversing it nearer to its ante- rior, the other to its posterior surface. It has been already stated that the lesser packet of the nerve is characterized by the absence of a ganglion ; it also has no connexion with the ganglion of the larger packet, but passes it without entering into it, and then becomes attached to one of the trunks proceeding from it ; it is further maintained to be distributed ultimately into those branches which are given by the third division of the fifth to the muscles ot mastication. Palletta f concluded from these circumstances that it was a nerve distinct from the remainder of the fifth ; and observing that the superior root was principally consumed in the temporal muscle, and the inferior in the buccinator, forming the long buccal nerve, he called the former the “ crotaphitic,” and the latter the “ buccinator” nerves. The distri- bution of the lesser packet to the muscles of mastication has been confirmed by Mayoj from * Palletta, De Nervis crotaphitico et buccina- torio, an. 1784. Script. Neurol. Min. Select. Lud- wig. t Op. cit. t Commentaries, and Physiology. the dissection of the nerve in the ass. lie differs, however, from Valletta with regard to its distribution to the buccinator, which he denies : this point will come under considera- tion again. It has been proposed by Eschricht* to denominate it the masticatory nerve. The place at which the nerve is attached to the surface of the brain in the human subject is to be regarded only as the point at which it enters or emerges from the substance of the organ, inasmuch as it can be, without difficulty, followed to a much deeper part, and the fibres of the crus, which are transverse to those of the nerve, manifestly separate from each other, at the entrance of the nerve, to allow it a passage. The larger packet of the nerve is that whose course into the brain can be most easily traced; this circumstance depends partly upon the greater size of the packet, and partly upon the fact that, for the most part, its tracts are not separated from each other by those of the crus, but traverse that part in a body, the fibres of the crus seeming to be simply laid in apposi- tion with it, and connected to it by some deli- cate medium ; while those of the lesser are, in the greater number of instances, separated from each other, or even interlaced with those of the crus; hence the fibres of the crus may be easily raised, without injury to the nerve, from the larger packet, and its course be displayed, while the lesser cannot be followed but with difficulty. The larger is, however, subject to variety in the latter respect ; in many instances the fasciculi of the crus do traverse and divide it, and very frequently near its ultimate attach- ment, and this circumstance, when it occurs, renders the pursuit of its course more difficult ; but even here the fasciculus merely traverses it, and its tracts are not permanently separated, but reunite after the fasciculus has passed. The course of the packet may be exposed to a considerable extent even in the recent brain ; but for the satisfactory determination of the point, it is necessary that the brain be prepared by some of the methods recommended for that purpose, of which immersion in strong spirit is by far the best, nor does it require much time, for the substance will be found to separate more easily when it has acquired only a certain degree of firmness, than when hardened to the degree which long immersion produces; the plan which the author has found most success- ful has been to commence the dissection early, to return to it frequently, and at each time to pursue it so far and so far only as it was satis- factory. The course of the larger packet is also beneath and before that of the lesser, and hence, in the usual mode of dissection, in which the brain is reversed, it presents itself first. Its direction is backward, downward, and in- ward, toward the upper extremity of the spinal bulb; in its course the packet first traverses the middle crus of the cerebellum from its an- terior toward its posterior surface, and from its superior toward its inferior margin ; it pursues this course until it has reached the back of the crus, and descended so low as its inferior mar- * Journal dc Physiologie, t. vi. 272 FIFTH FAIR OF NERVES. gin ; it is then situate in the angle formed by the three peduncles of the cerebellum at their junction with the hemisphere; behind the middle, beneath the superior and above the in- ferior, and before, or in common language, be- neath the floor of the fourth ventricle. Thus far the course of the nerve may be ascertained without much difficulty; it is probably the same point to which Santorini had traced it, as described in his ‘ Observationes Anatomic®,’ in 1724, and from which Soemmerring has more expressly stated it to be derived, in his work ‘ De corporis humani fabrica,’ pub- lished 1798, in which he states “that it ap- pears to arise almost from the very floor of the fourth ventricle.” * At the point last described Fig. 140. Lateral view of the pons, spinal bulb, and course of the Fifth Nerve in man. 1 Pons Varolii. 2 Spina] bulb. 3 Olivary body. 4 Spinal cord. 5 Superior peduncle of cerebellum. 6 Cut surfaces of middle ditto. 7 Inferior peduncle of cerebellum. 8 Cut surface of crus cerebri. 9 Ganglion of Fifth Nerve reversed. 10 Ganglionic portion of the nerve. 1 1 Non-ganglionic portion of Fifth Nerve. 11 Roots of non-ganglionic portion. 12 Eminence at the insertion of both portions of the Fifth Nerve. 13 Fasciculus to anterior column of spinal cord. 14 Fasciculus to posterior column. 15 Auditory nerve. 16 Portio dura. 17 Posterior roots of superior cervical nerves. * Santorini, however, appears to have followed the nerve out into the spinal bulb, though, as will be seen, he did not succeed in determining its real and ultimate connection. the greater packet is attached to the side of the medulla oblongata. The point of attachment is very close to the interior of the fourth ven- tricle, being separated from it only by a thin lamina, which is little, if any thing, more than the “ epithelium” of Reil : it is situate in the angle formed by the peduncles of the cerebel- lum, behind the middle one, by the outer margin of the pons, and posterior to it, and above its lower one : it is also superior to the attachment of the auditory nerve, separated from it by an interval of some lines. We shall, in the next place, direct attention to the course and connection of the lesser packet of the nerve. In none of the authorities which the author has had an opportunity of consulting, has he found a particular origin assigned to the lesser packet. By most anatomical writers it is over- looked; J. F\ Meckel states that it can be traced a certain way into the crus, but he goes no further; Mayo asserts that the lesser portion arises close upon the greater, and, in a sketch of the origins of the nerves given by him in his Physiology, it is represented traversing the crus cerebelli, as a single fasciculus, above and behind the greater, and attached to some part above that from which the greater is re- presented to arise: but still the origin is not defined, and it is manifestly intended to be distinct from that of the greater packet. The author has succeeded, as it appears to him, satisfactorily in tracing both the roots of the lesser packet to a destination for which he was not prepared ; at setting out he expected to have found the origin of the lesser different from that of the greater packet, and to have followed it to a prolongation of the anterior columns of the spinal cord, as has been stated by Harrison it was therefore with surprise that, after a patient dissection, he succeeded in tracing both its roots to the same point, to which the greater packet is attached, behind the middle crus of the cerebellum (see Jig. 140, 12); both the roots traverse the crus, as the greater does, the inferior very frequently in company with and internal to the greater packet, or separated from it by a very thin stratum of the substance of the crus, the superior near to the superior surface of that part, and separated from the greater packet by an interposed stratum of two or more lines; the course of the latter is so near to the surface of the crus, that it can frequently he traced for a considerable way by the eye without dissect, tion : they present, in their mode of traversing the crus, two remarkable varieties; in some in- stances the fasciculi, of which they are com- posed, are separated from each other and even interlaced with those of the crus, and in such the pursuit of them is intricate and difficult ; in others they pass in two distinct packets, and in these they are more easily followed. As they proceed they approach the greater packet, so that the interval between them and it gradu- ally diminishes, and having traversed the crus, they are both attached below and behind it to * Dublin Dissector. 273 FIFTH PAIR the same part as the greater packet, and poste- rior to it. (S eefg. 140). This view of the con- nection of the lesser packet, if confirmed, must lead to interesting results with regard to the rela- tions of the two portions of the fifth nerve at least ; it will at all events decide the question as yet in dispute, whether they are to be regarded as distinct nerves, or parts of the same ; upon this point further light will be thrown by the disposition of the same part in fish, in which the source of the uncertainty prevailing with regard to the nerve in the higher classes does not exist to the same amount ; inasmuch as the ganglionic and non-ganglionic divisions of the nerve seem for the greater part associated in their distribution. Fig. 141. Back view of pons, bulb, and course of the Fifth Nerve in man. 18 Tubercula quadrigemina. 19 Continuation upward of the tract from which the Fifth Nerve arises. The other references indicate the same parts as in the preceding figure. When the adjoining matter has been care- fully cleared away from the part to which the packets of the nerve are attached, that part ap- pears to be a longitudinal tract of a yellowish- white colour, composed of fibres running in the same direction, and capable of being followed both upward and downward : upward this tract seems continued beneath the superior peduncle of the cerebellum;'* downward it descends from * Of the nature of the structure continued up- ward from the attachment of the nerve the author is not satisfied : it presents, when cleared, the ap- pearance given to it in fig. 141 , 19, but it is very cine- ritious in character, and he is not prepared to say whether it be a continuation of the tract from which the nerve appears to arise, or a part of the floor of the fourth ventricle at its upper extremity, con- nected to the attachment of the nerve : the mode in which the nerve arises in the bird and the turtle appears to the author opposed to the opinion that the tract to which the nerve is attached is, in them at least, any thing more than a continuation or VOL. ll. OF NERVES. behind the pons into the spinal bulb, and after a short course divides into two cords, one for each column of the spinal marrow (see Jigs. 140, 141). At the entrance of the tract into the bulb it is situate deep, before the floor of the fourth ventricle and behind the superficial attachment of the two portions of the seventh pair, which must be separated from each other and displaced in order that it may be ex- posed : externally the tract corresponds to the peduncles of the cerebellum, and is united in- ternally to the cineritious matter of the floor of the ventricle. At the point of attachment the tract presents a somewhat prominent en- largement, (Jigs. 140, 141, 12,) which the au- thor will venture to call an eminence, though with hesitation, lest it be considered an ex- aggeration, from which the nerve may be held to arise. It is said that the nerve may be held to arise from this tract, because, though it be certainly not its ultimate connection with the brain, and though cords can be traced from it to more remote parts, yet the union of the cords at the point, and the attachment of both portions of the nerve to it, seem to mark it as the origin of the nerve ; the change of character too which will be described as occurring at the attach- ment of the nerve, countenances the opinion that the tract is not simply a continuation of the nerve. It may be doubted whether the eminence really exist, or whether it be not merely the result of dissection : the author will not insist upon it, but several considerations induce him to consider it real : in the first place, he almost uniformly finds it,* and secondly, it seems to be a common point to the two portions of the nerve and to the other cords, which form part of its encephalic connections ; and lastly, this view is corroborated by the disposition of the same part in other animals ; for a similar ap- pearance will be found, at the attachment of the nerve behind the pons, in other mammalia as well as in man after the separation of the adjoining matter, e. g. in the horse ; and it is even asserted by Desmoulins that an eminence may be observed naturally upon the floor of the fourth ventricle, in some animals, at the attachment of the nerve. His statement is : “ on observe meme dans les rongeurs, les taupes, et les herissons, un petit mamelon ou tubercle sur l’extremite anterieure du bord du ventricule ; mamelon, dans lequel se continuent les fibres posterieures de la cinquieme paire, et de l’acoustique.” When the tract has reached the point at which the inferior peduncle of the cerebellum first inclines outward toward the hemisphere, it separates, as has been stated, into two parts or cords, (see Jigs. 140, 141,) destined, one, as is already known, to the posterior, the other, according to the author’s belief, to the an- terior column of the spinal cord. The course and disposition of these cords are remarkable and root of the nerve, but admitting this, he cannot satisfy himself that it is to be regarded in the same light in the Mammalia. * The attachment of both the packets must be made out, else the enlargement will not appear. T 274 FIFTH PAIR OF NERVES. apparently contrary to analogy ; they are dis- tinguishable into anterior and posterior, but they descend, the anterior to the posterior, and the posterior to the anterior columns. The an- terior cord is by much the larger, and is pro- longed through the inferior peduncle of the cerebellum, until at the inferior extremity of the bulb it is continued into the longitudinal fasciculi of the corresponding posterior column of the spinal marrow ; it is situate along the outer side of the olivary body, but separated from it by a slight interval, nor does it seem to have any connection with that body : it is imbedded in the substance of the superior part of the peduncle, situate, however, nearer to its anterior than its posterior surface, and laid obliquely across its fibres as they pass outward toward the hemisphere of the cerebellum ; but as it proceeds it becomes gradually more super- ficial, gains the outer side of the peduncle, and at the lower extremity of the bulb is actually at its surface almost immediately behind the lateral fissure of the cord and the posterior roots of the superior cervical nerves. The existence and course of this cord have been first established and described by Rolando in his “Saggio sopra la vera Struttura del Cervello,” and also in a memoir upon the Anatomy of the Medulla oblongata, published in the fourth volume of the Journal of Physiology. The posterior cord is much smaller than the former ; it descends behind the inferior pedun- cle of the cerebellum, as it passes outward into the hemisphere, and upon the posterior aspect of the spinal bulb ; enters the posterior fissure of the bulb, between the posterior py- ramids, and can be traced some way down- ward, in the bottom of the fissure, along the back of the anterior column of the same side, into which it appears to be ultimately con- tinued. (Figs. 140, 141, 13.) The preceding account of the encephalic connections of the fifth nerve differs very much from that adopted by some of the highest modern authorities. It is not necessary to allude to the opinions entertained upon the point, before the course of the nerve had been particularly inquired into ; but, accord- ing to some of the most recent, the nerve arises from the groove between the restiform and olivary bodies, and from the olivary bodies themselves. Such is the view given of the origin of the nerve by Gall and Spurzheim in their fifth plate of the brain, in which the nerve is represented breaking up, on the out- side of the olivary body, into several fasciculi, which plunge obliquely into it. In their account* of the course of the nerve into the brain they state, “ on peut aisement suivre son cours entier jusq’au dessous du cote exterieur des corps olivaires this might be, perhaps, interpreted to mean beyond the olivaries, reference being had to the relations of those bodies in the erect posture ; but from the representation given it is obvious that the in- tended meaning is, that the nerve can be fol- * Anatomie et Physiologie du Systeme Ner- veux, tom. i. p. 107. lowed to beneath, i. e. underneath, their outer side, the brain being placed in the manner ordinarily adopted for dissection, in which the anterior aspect of the olivaries is rendered superior; indeed their representation is alto- gether incompatible with the opinion that they had traced the nerve beyond the bodies. Such also is the opinion of J. F. Meckel,* according to whom the nerve “ passes under the posterior peduncle of the cerebellum, along the outer side of the pons, toward the groove between the olivary and restiform bo- dies, where it arises in part from the groove and in part from the olivary eminences." CloquetJ likewise states the nerve to arise between the olivary and restiform bodies, and has adopted and copied, in his late work,J the view given of its origin by Gall and Spurz- heim. Further, the discovery of this origin of the nerve has been attributed by Meckel§ and others to Santorini. It is a hardy thing to contradict such au- thorities as have been quoted, and the influence which they justly carry with them has made the author hesitate before adopting a contrary opinion : but if reference be made to the work|| of Santorini on the point, it will be found that he nowhere, in his account of the origin of the nerve, assigns the groove between the restiform and olivary bodies as its situation in the spinal bulb, as will appear from the following extract, the only paragraph of his account in which he particularizes it, and in which he supposes it to be situate between the olivary and pyramidal bodies : “ Unde in interiorem medullae ob- longatae caudicem conjectus, fere inter olivaria et pyramidalia corpora locatus, quo demum pergat, cum tenuium fibrarum implexus, turn earumdem mollitudo, ne consequerer, omnino prohibuere;" from which it is plain, as has been stated, that he supposed the nerve to be between the two latter bodies ; and also that he had not been able to trace it to any particular destination, although, in a succeeding para- graph, he conjectures the olivary body to be its source : hence there is reason to conclude that succeeding anatomists have assumed his conjecture to be an established fact, and have modelled their accounts and representations accordingly. Moreover, since the olivary bodies do not exist in the lower classes of animals, it is not likely that they should be points of origin or attachment for nerves ; in fine, the author has so uniformly succeeded in tracing the nerve to the destination which has been described, that he is satisfied of the accuracy of it, in which he is confirmed by the fact that the account here given accords with the opinions of Santorini, Scemmerring, and Rolando, so far as that of the first has been determined to be accurate, or as those of the others extend : the particulars in which it differs from, or rather in which it goes beyond these, rest upon the author’s authority and remain to be confirmed, * Manuel d’Anatomie, French edit. t Traite d* Anatomie descriptive. J Anatomie de l’Homme. § See note 5, p. 82, op. cit. vol. ii. i| Observationes Anatoruicae. FIFTH PAIR OF NERVES. 275 viz. the attachment of the two packets to thesame point, the existence of the eminence at the inser- tion, and that of a cord of communication with the anterior column of the spinal marrow. The encephalic connections of the nerve, as detailed, are corroborated by those to be observed in inferior animals. In those Mam- malia in which the pons is but little deve- loped, the nerve is attached between that part and the trapezium ; in those instances in which the pons is more so, the nerve is attached, superficially, not actually behind that part, but near to its posterior margin; with little trouble it can be followed to the back of the pons, where it is attached, as in Man, to the medulla oblongata, the point of attachment presenting here also, after the separation of the adjoining matter, the appearance of an emi- nence or tubercle, from whence a cord de- scends beneath the trapezium into the lateral column of the spinal bulb. This cord is of great size in many animals ; and in some can be seen distinctly, without dissection, upon the surface of the spinal bulb, in consequence of the degree to which it projects : it is well expressed in the delineation of the brain of the calf in the third plate of Gall and Spurzheim, and in that of the brain of the horse in fig. 275 of M. Serres’ Illustrations of the Comparative Anatomy of the Brain. In Birds, Reptiles, and Fish, neither pons, trapezium, nor olivary bodies exist, and the nerve is attached to the lateral part of the spinal bulb at its superior or anterior extremity, and to its lateral column — the prolongation of the superior column of the spinal cord. In all three the point of attachment is situate a little way from the back of the bulb and be- neath the floor of the ventricle, the cineritious stratum, of which the latter consists, being directly connected to the back of the nerve. In Birds (fig. 142) the continuation of the nerve Fig. 142. ’Brain and Fifth Nerves of the Goose. 1 Inferior surface of cerebrum. 2 Spinal bulb. 3 Ganglia of fifth nerves. 4 Root of nerve from lateral column of the bulb exposed by turning aside the superficial stratum of that part. 5 First division of the fifth. 6 Second do. 7 Third do. 8 Auditory nerve. On one side (the reader’s right) the non-gan- glionic fasciculus has been traced beneath the gan- glion into the third division of the nerve. can be traced downward along the side of the bulb toward the spinal cord, and without diffi- culty, inasmuch as it is superficial and is not crossed by a trapezium, as in the Mammalia. In the Turtle the nerve can be traced in like manner from the point of attachment down- ward into the lateral column ; and in Fish the Fig. 143. Origin of nerve in Turtle . 1 Spinal bulb. 2 Fifth nerves. The pin is passed between the ganglionic and non-ganglionic fasciculi, the latter being continued into the third division. 3 Ganglion. 4 First division of the nerve. 5 Second do. 6 Third do. attachment is in all essentials similar : the com- parative smallness of the bulb and the direc- tion which the nerve takes in its course out- ward, make it resemble the spinal nerves more than in the other classes ; but its encephalic connection is strictly the same, namely, to the lateral column of the bulb beneath the floor of the ventricle. In the Cod, after the removal of the floor of the ventricle from the back of the nerve, the latter may be followed for some way into the column, though neither to the same extent nor so satisfactorily as in the bird or the Turtle; and in the Ray, while the two inferior fasciculi of the nerve— for in this fish it consists originally of three — are connected in the usual mode to the lateral column, the superior is attached to a convolution formed by the floor, in consequence of a greater developement of its margin. In the Cod the convolution adverted to does not exist, but the floor of the ventricle cannot be raised from the nerve without destroy- ing a connection of some kind between them. In the latter fish the fifth nerve is attached before and rather superior to the auditory nerve, and the two nerves are quite distinct as far as the point of attachment, but there they are in t 2 276 FIFTH PAIR OF NERVES. Fig. 144. ' Brain and Fifth Nerves of the Cod. 1 Non-ganglionic portions (on the reader’s left side) separated from the ganglionic and thrown bach. 2 Ganglionic portion. a First branches of both portions. h Second do. " immediatP apposition and appear to have the same source. In the Ray it is different; in it the auditory seems merely a branch of the fifth (fig. 145, 7) given off from its posterior c Third do. d Fourth branch derived from both. e Fifth branch derived only from the ganglionic. The third division has been removed on the left side. ganglionic fasciculus about three lines from its attachment to the spinal bulb, and before the formation of its ganglion. After the preceding details it must seem Fig. 145. a Anterior ganglionic portion of the fifth nerve. b Posterior do. c Non-ganglionic portion. On the reader’s left it is laid back to display its connexion with the posterior ganglionic ; on the right it is in situ. e First branches of the two portions. f Second do. 7 Auditory nerves. extraordinary if the nerve in the higher ani- the brain, so very much from that in the in- itials differed, in its ultimate connection with ferior, as it is represented by some to do. FIFTH PAIR OF NERVES. 277 Vet it is asserted by M. Serres,* who has founded his opinion upon the observations which he has made upon the successive de- velopement of the brain and nerves in the embryo of vertebrate animals, that in the Mammalia the nerve is implanted upon the trapezium. Such is the form of expression by which he intends, as the author understands, the ultimate connection of the nerve with the brain. Now, in the first place, we have al- ready seen where that connection is in those animals in which the trapezium does not exist, and it appears to the author reasonable to con- clude that similar nerves have similar or ana- logous attachments in the several classes of animals, however the parts with which they are connected may be complicated or ob- scured by superadded structures. In the second place the trapezium can be regarded only as a superadded structure, and is not among those parts from which nerves are likely to arise, being itself but a commissure : and, thirdly, the situation and connections of the part to which the nerve is attached, are altogether in- compatible with the opinion that it is the tra- pezium, inasmuch as the latter is situate be- fore the cords, which ascend from the anterior columns of the spinal cord to the crura cerebri, while the structure with which the nerve is connected is posterior to them. For these reasons the author concludes that M. Serres has mistaken the place of the nerve’s attach- ment in the Mammalia. In conclusion, the representation of the ori- gin of the nerve, which appears to the writer to be the most remote of all from the real one, is that given by Swan, in his plates of the nerves lately published, in which the fifth is re- flected into the auditory nerve : such a con- nection is merely artificial and does not really exist ; it can be produced only by stopping short in the pursuit of the fifth nerve, and mould- ing it into the anterior root of the auditory, which is in contact with it. This view of its encephalic attachment has probably originated in the intimate connection known to exist between the two nerves in in- ferior animals. The complication of the cere- bral connection of the nerve in the higher animals may be now better understood. In those, in which the pons and trapezium do not exist, the nerve emerges directly from the spinal bulb, in a manner similar to the ad- joining nerves ; but in those, in which the bodies alluded to are present, inasmuch as the attachment of the nerve is behind them, it can reach the surface only by either passing be- tween them, or traversing their substance. Hence, if the nerve simply traverse them, it ought not to receive any accession of fibres from them, and such, according to- the writer’s experience, is the case. As it emerges from the pons, the lesser packet receives an epithe- lium from its surface ; but he has not been able to detect any fibres originating within the substance of that part. The structural arrangement, which the ence- * Op. cit. phalic portion of the nerve presents within the brain, is different from that, for which it is remarkable, while superficial to it. Exter- nally it is, as has been stated, of a fascicular texture; but, within, that appearance is not to be observed : there the larger portion is a white, soft, homogeneous, flattened cord, the delicacy of which, in the natural state, forbids the separation of it into distinct parts ; but when sufficiently hardened, it may be divided into numerous thin strata, and these again into delicate fibrils. That such an arrangement is a natural, and not an artificial appearance, is manifest from the circumstance, that the sepa- ration into fibrils can be effected only in one direction, the length of the nerve, and that they break off when it is attempted in the other. The nerve retains those characters as far as its attachment behind the crus, but there they cease ; the pure white colour suddenly disappears ; the point of attachment and the cords descending from it present a cineritious tint ; and they are not absolutely distinct from the surrounding substance, as the nerve had previously been, but immersed in it ; they are, however, still manifestly composed of fila- ments, which may be rent either toward or from the point of attachment ; and after im- mersion in spirit they become nearly white. The course of the nerve, from its attachment to the surface of the brain, is forward and out- ward toward the internal anterior extremity of the petrous portion of the temporal bone ; it next passes over the superior margin of that portion, and descends upon its anterior surface into the middle fossa of the base of the cra- nium, where it reaches the Gasserian ganglion.. During its short course, from its attachment to the brain, to the ganglion, it is at first contained within the proper cerebral cavity, by the side of the pons Varolii, and beneath the internal anterior angle of the tentorium cerebelli ; in the second place, in the middle fossa, it is not within the cerebral cavity of the cranium, but beneath it, separated fro n it by a lamina of dura mater; it is there contained in a canal- or chamber, formed by a separation of the dura mater into two layers, between which the nerve and its ganglion are inclosed, one be- neath them attached to the bone, another above- separating them from the brain. This chamber is situate immediately external to, and lower than the cavernous sinus, but separated from it by the inferior lamina of the dura mater just described, which ascends from the bone to join the superior, and in so doing forms a septum between the two chambers ; it is about three-fourths of an inch long,, reaching from the superior margin of the petrous bone to the anterior margin of the depression upon its anterior surface, in which the ganglion rests. In front this chamber is wide, containing at that part the ganglion, and sends fibrous offsets upon the nervous trunks proceeding from it; poste- riorly it is narrow, and presents an oval aperture, about one-third of an inch long, situate ex- ternal and inferior to the posterior clinoid pro- cess of the sphenoid bone beneath the attach- ment of the tentorium cerebelli to that process* 2?8 FIFTH PAIR OF NERVES. and also beneath the superior petrous sinus : by this aperture the chamber communicates with the cerebral cavity and the nerve enters. The chamber is lined by the arachnoid mem- brane, as far as the posterior margin of the gan- glion, but along this the membrane is reflected from the interior of the chamber to the nerve, and returns upon it into the cranium : hence the nerve is free within the chamber, while the dura mater is attached to the surfaces of the ganglion, and so closely that it requires care to separate it from them. The cham- ber presents a remarkable variety in its con- struction in some animals : in the horse, for instance, its parietes are not simply fibrous, as in man, but, frequently at least, in great part osseous, being at the same time lined by the membrane. The passage of the nerve over the margin of the petrous bone is marked by an inter- ruption in the sharp edge, which the bone presents external to that point, and its site upon its anterior surface, as also that of the ganglion by a corresponding shallow depres- sion. Throughout the course of this portion of the nerve, the relation of the two packets to each other varies ; at the attachment of the nerve to the crus cerebelli, the smaller packet, allowance being made for those varieties pre- sented by it in its mode of attachment, is superior and internal to the larger; in the in- terval between the crus and the margin of the petrous bone, the smaller packet gradually descends along the inner side of the larger, until it has reached the same level, so that the two packets are placed immediately side by side upon the margin of the bone, the lesser internal to the greater ; but as the nerve pro- ceeds into the middle fossa, the smaller, at the same time, passes from within outward beneath the larger, and also beneath the gan- glion, toward its outer and posterior extremity; during this course it has no communication with the ganglion, but is quite distinct from it, though inclosed in common in the chamber formed by the dura mater, and connected with it by a dense cellular or fibrous structure; but having thus passed the ganglion, the lesser packet is united to the third trunk proceeding from that body, and with it constitutes the third cjivision of the nerve. The larger packet, on the contrary, is at- tached to the ganglion. It has been before stated that the plexiform arrangement, which it presents, becomes less, as it approaches that body; its fasciculi become more distinct; they separate from each other, so that the width of the packet is greatly increased, and having reached the posterior margin of the ganglion they are received into the channel which it presents ; in which they are ranged, in series, from one extremity of the body to the other, overlapped by its edges, and enter abruptly into the substance of the ganglion. External portion of the nerve. — The external OKperipheric portion of the nerve consists of three large trunks or divisions, which are connected, on the one hand by their ramifications, with the organs to which the nerve is distributed, and on the other, with the ganglion and the brain. They are distributed, generally speaking, to three different regions of the head and face, one to the uppermost, another to the middle or superior maxillary, and the third to the lowest or inferior maxillary regions, and they are denominated, either numerically, first, second, and third, as by the first Meckel; or, according to the parts to which they are dis- tributed, the first the ophthalmic, by Willis; the second the superior maxillary, and the third the inferior maxillary, by Winslow. These methods of distinction have their several advantages. Could we select names which would give adequate ideas of the distribution of the trunks, the latter would certainly be preferable; but inasmuch as those which have been selected do not at all adequately express that distribution, and are attended, therefore, with the inconvenience of not giving a suffi- ciently enlarged idea thereof, it would probably have been better, had the former been from the first adopted and adhered to, for such names could not create any incorrect impression with regard to the distribution of the several divisions of the nerve ; in fact, the epithets ophthalmic, superior, and inferior maxillarics ought to be altogether discarded, for, beside the objection to their use already stated, it will be found, upon reference to the anatomy of other animals, that they are by no means dis- tinctly appropriate, and that the circumstances upon which they are founded are purely inci- dental, associated with the peculiarities of the animal; for the proof of which, see the com- parative disposition of the fifth nerve in the several classes. The three trunks differ from each other in size. The first, the ophthalmic, is the smallest; the second, the superior maxillary, is inter- mediate in size; and the third, the inferior maxillary, is by much the largest. They are connected to the anterior convex margin of the ganglion, — the first to its superior internal extremity, the second to its middle, and the third to its inferior external extremity. At their attachment they are wide, flattened, and of a cineritious tint ; but as they proceed they become contracted in width, cylindrical or oval in form, and of a white colour. Their texture is fascicular and compact, the fasciculi of which they are composed being bound up closely together, and they differ remarkably in com- position, the two first, the ophthalmic and superior maxillary, being derived altogether from the ganglion, and thus being, in anato- mical constitution, simple ; whereas the third is composed of two parts, one derived from the ganglion, and another formed by the lesser packet of the nerve, which does not join that body, and hence that division is compound. The trunks rest partly against the outer side of the cavernous sinus and in part upon the base of the cranium in its middle fossa, and they are enclosed in offsets from the fibrous chamber, in which the ganglion is contained. Their relative position corresponds to the posi- tion of the ganglion ; the first is superior and FIFTH PAIR OF NERVES. 279 internal to the other two, the second is inferior and external to the first, and the third is exter- nal, posterior, and inferior to both the others. They go off from the ganglion at different inclinations, the first forward and slightly upward, the second directly forward, and the third almost directly downward; hence the first and second form a very acute angle with each other, while that between the second and third is much greater. First or ophthalmic division. — This division is distributed to the eye and its appendages, to the nostril, and to the forehead. It is the smallest of the three trunks proceeding from the ganglion, and is situate superior and inter- nal to the other two. It is about three-fourths of an inch long from the ganglion to its division into branches, and is contained thus far within the cranium. Its course is forward, upward, and slightly outward toward the upper part of the foramen lacerum of the orbit. It is laid against the outer side of the cavernous sinus, in company with the third and fourth nerves, and is contained in the external wall of the sinus, being separated from the interior of that chamber by a thin septum, which is a prolon- gation of the inferior internal wall of the canal in which the nerve and ganglion are contained. The septum is dense, but at the same time so thin and transparent that the nerve can be seen through it from the side of the sinus, while the lamina of the dura mater, by which it is sepa- rated from the interior of the cranium, is so thick and opaque, that the course of the nerve is altogether concealed from that side. At its outset the nerve is beneath, and external to the third and fourth nerves, and external and some- what superior to the sixth, which is within the sinus; but ascending as it proceeds, it gains, about the middle of the sinus, the same level with the third, placed still at its outer side, and inferior to the fourth, and then terminates by dividing into branches. Presently after its origin from the ganglion the nerve is joined by one or more very fine filaments from the sympathetic : this is ex- pressly denied by the first Meckel, but he was certainly mistaken ; they are very faithfully represented by Arnold. In order to display them the sixth nerve may be separated carefully from the carotid artery in the cavernous sinus, after which it will be found that branches of the sympathetic ascend upon the artery internal to that nerve, and distinct from those which are connected with it. Having surmounted it they branch off, some upon the artery as it passes to the brain, others to other destinations, and of the latter some incline outward above the sixth nerve and are connected to the first division of the fifth: they are short and very delicate. The first division of the fifth gives off no branch from its outset to its final division, except an extraordinary filament described by Arnold, and denominated by him the recurrent branch of the first division of the fifth. It arises from the upper side of the trunk immediately after it leaves the ganglion, runs backward above this body at a very acute angle, enters the struc- ture of the tentorium cerebelli, and divides be- tween its laminae into several very delicate fila- ments. The branches into which the first division of the fifth ultimately divides are either two orthree; according to the elder Meckel and the greater number of authorities they are three; according to others they are sometimes three, but are more frequently only two. The three branches are the frontal, the nasal, and the lachrymal. When the branches are but two, they are, according to J. F. Meckel, the nasal and the frontal, the latter in such case giving off that, which in the other mode of distribution is the third, the lachrymal. The elder Meckel attributes the difference of opinion which prevails with re- gard to this point to the fact that the lachrymal nerve frequently has a second root derived from the frontal, which in such cases has been assumed to be the origin of the nerve. The names which have been applied to those branches have been taken either from their destination or from their relative course ; thus the frontal, so called from its distribution to the forehead, is also called the superior or middle branch; the nasal, so called because finally distributed to the nostril, the internal or inferior, and the lachrymal, which derives its name from the lachrymal gland, the external. The three branches differ in size; the frontal is considerably larger than either of the others, the nasal is second, and the lachrymal is much the smallest. They all three traverse the orbit, but they pursue different routes, and have, at entering, very different relations. 1 . The frontal nerve appears in the human subject, both from its size and its direction, to be the continuation of the original trunk. In other animals, however, it is otherwise : in them the predominance of the frontal nerve diminishes along with that of the superior region of the face, until in some it ceases to exist as a pri- mary branch of the first division of the fifth, and its place is supplied by a secondary branch of another, while the nasal branch increases in the same proportion, and seems ultimately to constitute itself the first division of the fifth.* The frontal nerve passes upward and forward toward the highest part of the foramen lacerum of the orbit, and enters that region through it. It then continues its course through the orbit to the superciliary foramen and escapes through it to the forehead. During this course it is placed, before it has entered the orbit, at the outer side of the third nerve ; it then rises above the third and crosses over it to its inner side. In doing so it is accompanied by the fourth nerve, to which it is external and in- ferior; it enters the orbit in company with the fourth and nearly on the same level, but still external to and somewhat beneath it. In entering, it passes above the origin of the superior rectus muscle, and all the other parts transmitted through the foramen lacerum, with the exception of the fourth nerve. At the en- trance of the frontal nerve into the orbit and during its course from its origin thereto it is * See comparative distribution of the fifth nerve. 200 I-IFTII PAIR OF NERVES. closely attached to the fourth nerve, but pre- sently after separates from it, the fourth in- clining inward, is continued forward to the superciliary foramen, lying upon the superior surface of the superior rectus and levator palpe- br* muscles, being through its whole course within the orbit immediately beneath its roof. Having reached the foramen it passes through it, and changing its direction, ascends round the superciliary arch, upon the forehead, be- neath the orbicularis palpebrarum and frontalis muscles, and is thenceforth called by some the external frontal nerve in contradistinction to a branch from itself, the supra-trochlear,or internal frontal. In its mode of escape from the orbit the frontal nerve is subject to some variety, consequent in part upon the mode in which the superciliary foramen is formed, that being in some instances altogether osseous, in others osseous only at its superior part and completed by ligament below; in this case the nerve escapes through an osseous notch, and not a foramen. In other instances, again, when the nerve divides previous to its escape it is some- times transmitted through two apertures. The distribution of the frontal nerve, as well as that of most of the secondary branches, is subject to varieties, which the author has en- deavoured to embrace in the following account. In the first place the frontal, at its entrance into the orbit, anastomoses with the fourth nerve. Next it gives off, some time after its entrance and previous to its division, a long and slender branch, which runs forwaid and inward toward the trochlea of the superior oblique. Then it divides into two branches, a larger one, the continuation of the nerve, which escapes through the superciliary foramen, and a smaller, the supra-trochlear or internal frontal. The latter passes forward and at the same time inward toward the trochlea of the oblique muscle, escapes from the orbit internal to the continued trunk of the frontal nerve, and ascending upon the forehead beneath the corrugator supercilii, orbicularis, and frontalis muscles, it has received the name of internal frontal, in contradistinction to the continued trunk, which is at the same time called external frontal. The point at which the frontal divides is variable; for the most part the division takes place about midway in the orbit. In some instances it occurs before the nerve has reached that point, and in others, again, not until it has approached nearer to the anterior margin of the orbit. The distance of the division from the margin of the orbit appears to modify the course of the internal branch : when it is far back, the nerve escapes from the orbit above the trochlea, and hence the name supra-tro- chlear, given to rt by Meckel ; and when near the margin it escapes external to the trochlea, be- tween it and the superciliary foramen ; while in the latter case a branch of the nerve is transmitted above the trochlea, in the usual course of the nerve itself. Nor is the size of the two branches into which the frontal divides equal or uni- form; for the most part the external branch is the larger, but in some instances the two are of equal size. In its course forward the supra- trochlear nerve gives off first, occasionally a delicate branch, which frequently arises from the frontal itself prior to its division, the course and destination of which have been already described. Next it gives off, in some instances before, in others not till after it has escaped from the orbit, a branch which passes inward toward the internal canthus, and, uniting with either the infra-trochlear itself or a branch of it, concurs in forming a small plexus, from which filaments are distributed to the structures of the upper eyelid, toward its internal part, and to the eyebrow. Having escaped from the orbit, the supra-trochlear nerve divides into two sets of branches, denominated palpebral and frontal; the first descend into the superior eyelid, and are distributed to the structures of that part; the filaments communicating exter- nally with those of the frontal, and internally with those of the infra-trochlear. The frontal branches ascend round the superciliary arch, beneath the orbicularis palpebrarum and the corrugator supercilii muscles, upon the fore- head, and these are disposed of in a manner similar to that in which the branches of the proper or external frontal are. Some are dis- tributed to the orbicularis, corrugator, and fron- talis muscles ; other, long branches, ascend beneath the frontalis, traverse it, and become subcutaneous, and are distributed to the inte- guments of the scalp upon the forehead. Of these the external unites with the internal branch of the external frontal, and forms with it a common branch, which has the same destination as the others. The external larger branch of the frontal, called, in contrast with the last, the external frontal nerve, also divides into two sets of Dranches, palpebral and frontal. The nerve in some instances emerges from the orbit a single trunk, in others it divides be- fore it escapes from that region, for the most part into two branches, which are transmitted sometimes through the same, at others through distinct apertures, and from which the several ramifications arise, they themselves becoming ultimately the long frontal branches. Immediately after their escape the frontal branches give off externally slender filaments, which run outward toward the external can- thus, one beneath the eyebrow, through the upper eyelid, and one or more through the brow itself ; these ramify as they proceed, sup- ply the lid and brow at their outer part, and anastomose with filaments of the portio dura, and of the superficial temporal nerve. The frontal branches are arranged into super- ficial and deep ; those epithets have been diffe- rently applied by different writers; thus those which the elder Meckel terms the superficial, Boyer and Cloquet denominate the deep branches ; nor is this to be wondered at, inas- much as both sets become ultimately superficial; it were better, perhaps, to arrange them into short and long branches. The short branches are distributed to the orbicularis muscle, the corrugator, and the frontalis, and having sup- plied those muscles, they or others of them be- come subcutaneous, and terminate in the inte- FIFTH PAIR OF NERVES. 281 guments of the eyebrow and forehead : one of these branches, as described by Meckel, runs outward, through the orbicularis, toward the external canthus, and establishes anasto- moses with filaments of the facial portio dura nerve. The long branches are two, an external and an internal ; of those the external is, for the most part, the larger ; they ascend beneath the frontalis and the frontal aponeurosis, the former inclining outward, the latter inward, as they ascend ; they distribute in their course ramifications to the muscle, and to the deeper structures of the scalp, as well as some- times, according to Meckel, to the pericra- nium, and traversing the frontal aponeurosis, they become subcutaneous, and terminate in the structure and integument of the scalp. The external communicates with the superficial temporal nerves ; the internal with the internal frontal, the supra-trochlear. They are said both to anastomose with the branches of the sub- occipital nerve ; but Meckel states that he has pursued them until they have escaped his sight, and yet he could not discover any anastomoses between them and the branches of that nerve. 2. The nasal nerve is in size the second branch of the first division of the fifth, and arises always separately from the original trunk. Its course is inferior and internal to those of the other two, and hence the nerve is called by some the inferior, by others the internal branch. It is distributed partly to the eye and its appen- dages and partly to the nostril, and hence it is also called naso-oculur by Scemmerring. The direction of its course is forward and very much inward ; it passes through the foramen lacerum into the orbit ; then traverses that re- gion from without inward toward its internal wall, and having reached it at the foramen or- bitarium internum anterius, it escapes from the orbit through that foramen, and passes into the cranium ; it emerges into the cranium from beneath the margin of the orbitar process of the frontal bone, and crosses the cribriform plate of the ethmoid obliquely forward and inward, contained in a channel in the bone, and in- vested by the dura mater, until it reaches the crista galli ; it then descends from the cranium into the nostril, through the cleft, which exists at either side of the crista galli at the anterior part of the cribriform plate, and having reached the roof of the nostril, it divides into its final branches.* The nasal branch is concealed at its origin by the frontal, which is situate external and superior to it. Before its entrance into the orbit it is placed by the outer side of and closely ap- plied to the third nerve. In entering the orbit * The nasal is usually described as terminating by dividing within the orbit into two branches, the ethmoidal or internal nasal, and the infra-trochlear or external nasal : the author has preferred considering the former as the continuation of the nerve, be- cause in inferior animals both the nasal is the prin- cipal portion of the first division of the fifth, or alone constitutes it, and it is manifestly prolonged, as such, into the nostril and the beak. See Com- parative Distribution. it passes between the two posterior attachments of the external rectus muscle, in company with the third and sixth nerves, external to the former and between its two divisions, and internal and somewhat superior to the latter. In its course across the orbit the nasal nerve passes above the optic nerve, immersed in fat, and accompanied by the ophthalmic artery, being at the same time beneath the levator palpebrts, the superior oblique, and superior rectus muscles, and in crossing the optic nerve, it is placed between it and the last mentioned muscle. Through the foramen or- bitarium the nerve is accompanied by the an- terior ethmoidal artery, and within the cra- nium is situate beneath but not in contact with the olfactory bulb, being separated from it by the dura mater. The course of the nerve from the orbit to the nostril is liable to be modified by the developement of the frontal sinuses ; when they are very large, and extend, as they not unfrequently do, into the orbitar processes of the frontal bone and the horizontal plate of the ethmoid, the nerve may cross to the side of the crista galli without entering the cranium, being contained in a lamella of the ethmoidal bone. The nasal branch, before entering the orbit, receives, according to Bock, J. F. Meckel, and Cloquet, a filament from the sympathetic. The branches which the nasal gives off, are the lenticular, the ciliary, the infra-trochlear, and the nasal. The lenticular branch is given off as the nasal enters the orbit, and on the outer side of the optic nerve ; it is a delicate branch, about half an inch long; it first anastomoses with the supe- rior division of the third nerve ; then runs for- ward along the outer side of the optic nerve, and terminates by joining the superior and pos- terior part of the lenticular ganglion. Accord- ing to Bock and Meckel junior, it occasionally gives off a ciliary nerve, and according to Meckel senior it is, in rare instances, derived from the third nerve. To the latter statement, however, the author hesitates to assent : it ap- pears to him, that it should rather be said in such cases to be wanting. The ophthalmic, lenticular or ciliary ganglion, according to Cloquet, is of an oblong form — its greater length from behind forward ; it is one of the smallest ganglia of the body, being, however, variable in size ; its colour is reddish, at times white; it exists constantly in the human subject : it is situate between the external rectus muscle and the optic nerve, laid against the outer side of the nerve, at a little distance from its entrance into the orbit ; its external surface convex, corresponding to the muscle ; its internal, concave, to the nerve ; to its superior posterior angle is attached the len- ticular twig of the nasal branch of the first division of the fifth ; this filament constituting its long root ; to its inferior posterior angle a filament from the inferior division of the third nerve is attached, constituting its short root. To the posterior part of the ganglion are also attached two filaments derived, one from the cavernous ganglion or the carotid plexus ; the other, the constant existence of which has not 282 FIFTH PAIR OF NERVES. been yet established, from the spheno-palatine ganglion. The ganglion gives off from its anterior ex- tremity a considerable number of very delicate filaments, denominated from their distribution ciliary : they amount to from twelve to sixteen ; are reddish and tortuous; and run forward along the optic nerve to the back of the eye, which they enter at a short distance from the nerve. They are distinguished into two fasci- culi, superior and inferior ; which are attached, one to the superior anterior, the other to the inferior anterior angles of the ganglion : the former is the smaller ; contains at first but three filaments, which, as they proceed, divide so as to produce six, and run parallel to each other above the optic nerve : the second fasciculus is situate on the outside of and beneath the optic nerve, and contains from six to ten filaments col- lected at their origin into six branches: they pass beneath the nerve and incline inward, so as to gain, some of them, its inner side : one of them runs outward and joins one of the ciliary branches of the nasal nerve. The ciliary nerves all penetrate the sclerotic coat of the eye sepa- rately and obliquely ; then run forward between the sclerotic and choroid coats, without giving filaments to either, lodged in channels upon the inner surface of the former: as they ap- proach the ciliary circle they divide, each into two or three filaments, which enter the circle and are lost in it : some of them pierce the choroid at the anterior part of the eye, and go to the ciliary processes. The ciliary branches are two or three in number ; they are very delicate, and are given off, while the nasal is crossing the optic nerve ; they run forward along the optic, imbedded in fat, penetrate the sclerotic coat of the eye pos- teriorly, and then continue forward between the sclerotic and choroid coats, in like manner as the other ciliary nerves, to the ciliary circle. The infra-trochlear branch, so called by the elder Meckel, because it escapes from the orbit beneath the trochlea of the oblique mus- cle, is also called external nasal. It is given off when the nasal has reached the inner wall of the orbit, and as it is about to enter the fora- men orbitarium ; it is a branch comparatively considerable, at times longer, at others smaller decidedly than the continuation of the nasal ; it runs directly forward along the inner wall, beneath the superior oblique muscle, toward its trochlea, and having reached that, escapes from the orbit beneath it. It then divides, in the internal canthus of the eye, into two branches, a superior and an inferior. The infra-trochlear, while within the orbit, gives off occasionally, soon after its origin, a small branch, which returns and joins the nasal before it enters the foramen orbitarium ;* also a delicate branch, which joins a corre- sponding branch given off either by the supra- trochlear or the frontal. The distribution of the nerve resulting from their junction has been already described under the frontal nerve. Of its ultimate branches, the superior joins and forms a plexus with a branch of the supra-tro- chlear nerve, already described, given off either immediately before or after that nerve has escaped from the orbit. From the junction of the two, numerous delicate ramifications are distributed to the upper eyelid and to the eye- brow. The inferiorgives off several ramifications, which are distributed to the origin of the cor- rugator, the orbicularis, and the pyramidalis nasi muscles; to the conjunctiva, at the inter- nal canthus; the carunculalachrymalis and the lachrymal sac. Of those ramifications, one de- scends before the tendon of the orbicularis, and communicates with a branch of the portio dura: another communicates with a branch of the infra-orbital ; but the latter anastomosis is uncertain.* The nasal nerve having entered the nostril di- vides at the roof of the cavity into two branches, an external and an internal: of these the former descends behind the nasal process of the frontal and the corresponding nasal bones, contained in the groove or canal observable upon their posterior surface. It. escapes from beneath them at their inferior margin, emerging between it and the lateral cartilage of the nose, and then descends along the corresponding ala, superfi- cial to the cartilage, and covered by the mus- cles of the ala, toward the tip : as it approaches the tip, it divides into two filaments, one of which is distributed to that part, and the other to the ala. During its descent along the side of the nose it also gives off some delicate fila- ments, and anastomoses with the ramifications of the nasal branches of the infra-orbital nerve and with the portio dura. It is called by Chaussier the naso-lobar : it is also generally known as the nerve of Cotunnius. The second branch, as it proceeds, divides presently into two, of which one attaches itself to the septum, and descends, between the pituitary membrane and the periosteum, parallel and near to its an- terior margin, as the naso-palatine of Scarpa does to its posterior : as it proceeds, it furnishes ramifications to the membrane of the septum. The second attaches itself to the outer wall of the nostril, and descends, in like manner be- tween the mucous membrane and the perios- teum, along its anterior part, in front of the middle turbinate bone, until it reaches the an- terior extremity of the inferior one: it then breaks up into branches, of which some are distributed to the convex surface of the latter bone in front, and others beneath it to the an- terior part of the inferior meatus. The distri- bution of the branch is very happily represented in Arnold’s leones. The nasal nerve is described as giving also, in some instances, but not uniformly, a branch to the membrane of the superior turbinate bone, at the superior part of the nostril. 3. The third branch of the first division of the fifth is the lachrymal: it has been so called by Winslow from its distribution to the lachrymal gland : it is the smallest of the three branches : its course is external to that of the others, and hence it is also called the external branch. It * J. F. Meckel. * The elder Meckel. 283 FIFTH PAIR OF NERVES. arises, for the most part, from the ophthalmic at the same time with its other branches ; J. F. Meckel asserts that it arises more fre- quently from a trunk common to it and the frontal ; but the contrary is maintained by the elder Meckel ; he, however, states that it arises frequently by two roots, one from the ophthalmic, and a second from the frontal, and once he has seen it derive a root from the tem- poro-malar branch of the superior maxillary nerve.* When it arises from the ophthalmic, it is at its origin, inferior to the frontal, and exter- nal to the nasal. Its course is forward and outward at a very acute angle with the frontal ; it enters the orbit through the foramen lacerum, and from its origin until its entrance it is con- tained in the dura mater lining the inner side of the middle fossa of the base of the cranium, beneath the lesser wing of the sphenoid bone : in entering it passes above the origins of the external rectus muscle, between it and the pe- riosteum, and pursues its course along the outer wall of the orbit, external to the superior rectus and superior to the external, until it reaches the lachrymal gland : it then passes between the gland and the eyeball, and then divides into branches. It is accompanied through its course by the lachrymal artery. The branches into which it divides are, for the most part, three ; they enter the gland on its ocular surface, traverse it and again escape from it on its external aspect; in their course through the gland they divide and commu- nicate with each other, and thus form within it a plexus, from which numerous ramifications are distributed to its substance. After having supplied the gland the branches of the lachry- mal emerge from it, and pursue two destina- tions : one of them, which is for the most part the first branch of the nerve, and is frequently given off before it has reached the gland, de- scends backward toward thespheno-maxillary cleft, and joins the temporal branch of the temporo-malar branch of the second division of the fifth. In its course this branch passes first between the external rectus muscle and the outer wall of the orbit, then becomes attached to the wall, and is either simply inclosed in the periosteum, or contained in a groove or canal in the orbitar process of the malar, or some- times of the sphenoid bone; in this canal it meets the branch of the temporo-malar, and from the junction of the two results a filament, the des- tination of which will be described under that of the temporo-malar. This branch of the lachrymal nerve is called the posterior or sphe- no-maxillary ; it might from its destination be appropriately termed temporal : it frequently gives off in its descent a filament, which passes forward, escapes from the orbit beneath the ex- ternal canthus, and is distributed as the other branches of the lachrymal are. The remaining branches of the lachrymal escape from the orbit into the upper eyelid, beneath the exter- * [According to Cruveilhier the lachrymal nerve very often arises by two filaments, one from the ophthalmic, the other from the fourth nerve, and Swan describes this as the normal condition. — Cruveilhier, Anat. Descr. t. iv. p. 911. — Ed.] nal part of the superciliary arch. They give off numerous filaments, which are distributed to the structures of the lid, the conjunctiva, the orbicular muscle, and the integument : the ex- ternal of them, which are the largest, not only supply branches to the upper, but descend be- hind the external commissure of the lids into the lower one, which they supply at its outer part; they are also distributed to the superfi- cial parts on the malar region. They anasto- mose with the frontal nerve, the superficial temporal, the facial, the temporo-malar, and the infra-orbital nerves. The second division of the fifth. — This has been called also by Winslow, in consequence of its distribution, the superior maxillary nerve. It is the second trunk connected with the Gasserian ganglion, and is intermediate to the others, both in size and situation ; larger than the first, and placed beneath and external to it; smaller than the third, and situate internal, superior and anterior to it ; it is attached to the middle of the anterior convex margin of the ganglion ; at first it is flattened, wide, and of a cineritious tint ; but, as it proceeds, it becomes contracted in width, of a cylindrical form, and presents a white colour. At leaving the gan- glion it is joined by a filament of the sympa- thetic. This has been seen by Munniks* and Laumonier,f and is stated by Meckel junior, on the authority of the latter. The communi- cation between the sympathetic and the second and third divisions is called in question by Arnold.J That with the third the author has not yet made out, but that with the second he has found satisfactorily established by a fila- ment from the branch of the sympathetic which joins the sixth nerve : this filament connects the sixth to the second division of the fifth, and is short, but grosser than those which join the first : in consequence of the irregularity which pre- vails in the arrangement of the sympathetic system, the description here given may not apply in other instances. The course of the second division of the fifth within the cranium is short; it is directed for- ward, slightly outward and downward, toward the superior maxillary or the foramen rotund um of the sphenoid bone ; having reached that foramen it enters the canal, of which it is the aperture, and escapes through it from the cranium. While within the latter the nerve is contained in a sheath of dura mater, and rests in a shallow channel on the body of the sphenoid bone, at its junction with the great ala. From the cranium it enters the spheno-maxillary fossa, and crosses that fossa at its superior extremity, from behind forward, inclining still downward and outward, though but slightly ; its course across the fossa is also very short, extended between the root of the pterygoid process behind and the highest part of the posterior wall of the maxillary antrum before; having traversed the superior part of the fossa it enters the infra-orbital canal, through * De Origine nervi intercostalis. f Roux, Journ. de Med. t. xciii. f Journ. Comp. t. xxiv. FIFTH PAIR OF NERVES. 264 which it is transmitted, in company with the in- fra-orbital artery, to the face. In the canal it is situate in the floor of the orbit or the roof of the antrum, separated from each cavity, more or less perfectly, by a thin lamina of bone ; its course within the canal is by much its longest stage; as the nerve approaches the anterior extremity of the canal, it inclines inward, and thus its course is rendered a curve, convex outward. In this respect, however, it pre- sents varieties, dependant upon the transverse dimensions of the face, which being great, the course of the nerve is more curved and vice versa, it being sometimes nearly straight. From the time that the nerve enters the canal, it has been called infra-orbital ; but, inasmuch as that part of it is manifestly but the con- tinuation of the trunk, and names are already rather too numerous than otherwise, it would be better if that one were discarded. From the infra-orbital canal the nerve escapes through its anterior aperture into the face ; that aperture corresponds, for the most part, to the point of junction of the two external with the internal third of the inferior margin of the orbit, and is from a quarter to half an inch below it ; its situation, however, is not uniform ; in some skeletons it will be found to correspond nearly to the middle of the margin, and this circum- stance is worthy of attention, in consequence of its relation to the operation for the division of the nerve. At its escape from the canal the nerve is concealed by the lower margin of the orbicu- laris palpebrarum and by the levator labii supe- riors muscle, beneath which it is placed, and it is above the upper extremity of the origin of the levator anguli oris : immediately after its escape it separates into a number of branches, which go off in different directions to their several destinations, but principally downward. The branches which the second division gives off are the temporo-malar, the spheno- palatine, the posterior superior dental, the an- terior superior dental, and the facial branches. While within the cranium the nerve gives off no branch. 1 . The first branch given off' by the second division, the temporo-malar, has been called cutaneous malar by the elder Meckel ; it has been also called orbitar, but without good reason ; the name temporo-malar fully expresses its distribution. This branch is given off by the nerve, either while yet within the canal, through which it escapes from the cranium, or after it has entered the spheno-maxillary fossa ; it is one of its smallest branches ; it passes for- ward through the fossa, toward the spheno- maxillary cleft, enters the orbit through the cleft, and then pursues its course forward and outward, along the floor of that region, beneath the inferior rectus muscle, and about the mid- dle of it divides into two branches ; an exter- nal, the temporal, and an anterior, the malar. Before entering the orbit it sometimes gives off a small branch, which enters that cavity through the periosteum of the posterior part of the orbitar process of the sphenoid bone, arid joins the lachrymal branch of the first division, presenting one of the instances of a second root to that branch, as described by the elder Meckel. The external temporal branch passes toward the outer wall of the orbit, ascends between it and the external rectus muscle ; then becomes attached to the wall, and continues its course either through the periosteum, or in a groove, or at times through a canal in the orbitar pro- cess of the malar, or occasionally of the sphe- noid bone ; here it is joined by the posterior temporal branch of the lachrymal nerve, the third branch of the first division : the conjoined branch is then transmitted into the temporal fossa, through an aperture on the temporal sur- face of the orbitar process of the malar bone ; there it is joined by a small branch of the an- terior deep temporal branch of the inferior maxillary or third division of the fifth, and plunging among the fibres of the temporal muscle, it is distributed to them in common with the filaments of the deep temporal ; a filament or filaments of it gain the superficial surface of the muscle, perforate its aponeurosis, become subcutaneous, and are distributed su- perficially upon the temple, communicating with filaments of the portio dura, and of the superficial temporal branch of the third divi- sion. The temporal branch of the temporo- malar is sometimes double, or divides into two, one communicating with the branch of the lachrymal, the other transmitted to the temple. The malar branch pursues the course of the original nerve, until it has reached nearly to the anterior margin of the orbit, at its inferior external angle ; then it enters, either single or divided into two, the corresponding canal or canals, by which the malar bone is perforated, and through them is transmitted outward and forward to the malar region of the face. Its ramifications are distributed to the inferior ex- ternal part of the orbicularis palpebrarum, and to the integuments of the malar region ; they communicate with those of the portio dura, of the superficial temporal and lachrymal nerves, and of the palpebral branches of the second division. Before reaching the malar canals, the malar branch frequently gives off one or more filaments, which ascend to the lachrymal gland, unite with those of the lachrymal nerve, and follow a similar distribution. 2. The branches, which are given off next by the second division of the fifth, are those by which the nerve is connected to the spheno- palatine ganglion ; they are hence denominated the splieno-palutine ; the ramifications derived from them, or from the ganglion with which they are connected, are distributed to the nos- tril and the palate, and they may hence with more propriety be termed the naso-palatine, an appellation which is the more appropriate, since it is already applied to the corresponding branch of the second division of the fifth in other animals. It is at the same time to be borne in mind that a difficulty has been created in this matter by the application of the epithet in question to certain secondary branches, to be mentioned by and-by ; but the latter use of the term ought to be discarded. They are irregular in number? there being sometimes but one, at FIFTH PAIR OF NERVES. 285 others two or three : they are short and of con- siderable size, and arise from the inferior side of the nerve, immediately after it has entered the spheno-maxillary fossa ; they descend from it, almost perpendicularly, into the fossa, pos- terior to the internal maxillary artery, and im- mersed in fat, and after a very short course they are connected to the ganglion, from which they may seem to ascend to the nerve. They are thus described by Cloquet, but this view is not sanctioned either by comparative anatomy, or by the result of experiments, both which prove that they are to be considered branches of the nerve, with which the ganglion is con- nected. The ganglion has been first described by the elder Meckel,* and hence has also received the title of Meckel's ganglion ; it is very small, of a grey colour, and firm consistence ; its shape is triangular or cordiform, one surface directed outward, the other inward; it is situate immediately external to the spheno-palatine foramen, its internal surface, which is flat, cor- responding to the foramen, its external, which is convex, to the zygomatic fossa. It is subject to variety ; in some instances it is wanting, and then the spheno-palatine nerve gives off those branches which otherwise arise from the ganglion : in other rare cases, according to Meckel, the two principal branches, which arise from the ganglion when present, or from the spheno-palatine when single, viz. the Vidian and the palatine, proceed separately from the trunk of the second division of the fifth ; in others again the author has observed a cineri- tious soft enlargement upon the Vidian nerve at its junction with the spheno-palatine, but not involving that nerve or the branches pro- ceeding from it ; and this, it is worth remark- ing, is precisely the disposition of the ganglion in the dog and some other animals. Different views have been taken of the nature and rela- tions of this ganglion : the Meckels, by the elder of whom it was discovered, Bichat, Boyer, and others, have regarded it as belonging pro- perly to the fifth nerve, and formed by the branches which have been mentioned : Cloquet, on the other hand, considers and describes it as a part of the ganglionic or sympathetic system, and all the nerves connected with it, as well the original spheno-palatine branches as the others, to be branches from it : Cruveil- hier again, while he admits the existence of ganglionic structure, yet leaves it uncertain whether he regards it as a sympathetic or a cerebro-spinal ganglion, but he differs from Cloquet in maintaining that “ the nerves,” which seem to arise from it, “ are not detached from the ganglion itself, and come directly from the superior maxillary.” The opinions of Cloquet and Cruveilhier appear to the author to be both, to a certain degree, well-founded. The ganglion would seem not to be properly a part of the fifth nerve, because, 1 . it is not, as he believes, present in animals below the mam- malia ; 2. it is not always present even in them, and in neither case is the general distribution of the part of the fifth nerve, with which it is connected, influenced by its absence ; 3. it is manifestly different in its characters from the fifth nerve and from the branches of the nerve to which it is attached, nor does it resemble the cerebro-spinal ganglia, the peculiar appear- ance of these bodies, viz. white filaments enter- ing and emerging, their continuity being appa- rently interrupted by an interposed mass of cineritious matter, not being observable; while, on the other hand, it resembles the ganglia of the sympathetic, and is actually connected with that nerve by a branch having precisely the same qualities with those which proceed from it, viz. by the inferior branch of the Vidian nerve : for those reasons the author would adopt the opinion of Cloquet, that the ganglion is properly a part of the ganglionic system, and that it is only accessory to the fifth nerve. On the other hand, it appears to him that Cloquet is mistaken in considering the ganglion as the source of all the nervous filaments connected with it, and more particularly of the spheno- palatine branches of the second division of the fifth, to which in man the ganglion is attached, for, as has been already stated, the general dis- tribution and existence of these branches are not at all influenced by the absence of the gan- glion, and when present it allows in general, as Cruveilhier has observed, the nerves to be fol- lowed up and down from the swelling, and lastly, any obscurity existing with regard to this point in the human subject will be at once removed by reference to the disposition of the ganglion in other .animals, in none of which that the author has examined does it involve the nerve, but is merely connected to it either by filaments or by one extremity, the continuity of the nerve being altogether uninterrupted, and a marked contrast being to be observed between the characters of the two parts : thus in the dog, the ganglion is an oblong dark- grey swelling, with the posterior extremity of which the Vidian nerve is united, while its an- terior is attached to the naso-palatine nerve. The author, therefore, concurs in the opinion of Cruveilhier, so far as to regard the nerves con- nected with the ganglion, for the greater part, as branches of the fifth nerve and not of the ganglion ; but he would exclude from this view the Vidian nerve, or at least its carotidean branch, which appears to him to belong to the sympathetic system. (See posterior branch of ganglion.) The disposition of this ganglion throughout the animal series is an object of interest. The author cannot assert its existence in the mam- malia universally, but from indirect considera- tions it appears to him likely that it does exist, generally at least, in animals of that class. It is asserted in the work* of Desmoulins and Majendie on the Anatomy of the Nervous Sys- tem in vertebrate Animals, that “ there does not exist any trace of it in cats, dogs, the rumi- nantia, the rodentia, the horse, &c. ;” and it is reasonable to infer that they had found it in others. Now their statement with regard to Mem. de l’Acad. de Berlin, 1794. * Tom. ii. p. 396. FIFTH PAIR OF NERVES; 286 its absence is, in the majority of the instances which they have selected, positively incorrect, for the author has ascertained its existence most satisfactorily in the dog, the horse, the cat, the cow, and the rabbit. Nor is any ex- ception to its existence mentioned by Cuvier, and hence he thinks it likely that it does exist generally, if not universally, throughout the class. It is not however similarly disposed in all ; in some it is connected with the primitive naso-palatine nerve; in others with its nasal; and in others again with its palatine division : in some it gives off few filaments ; in others, the horse, e. g. they are numerous beyond de- scription. The ganglion does not appear to exist in the inferior classes. From the spheno-palatine ganglion or nerve, according to the view of their source adopted, there is given off a considerable number of branches, which run in different directions and have different destinations : they have been distinguished into four sets, viz. superior, infe- rior, internal, and posterior. The superior branches are very delicate and, in some in- stances at least, numerous. Among them are described and represented by Arnold two long slender filaments, which join the optic : ano- ther is also mentioned by him to be sometimes found connected with the ophthalmic ganglion. The discovery of this connection between the two ganglia is due to Tiedemann, who found, upon the left side of a man, an anastomosis between them, established by a filament, of tolerable size, which, arising from the innerface of the spheno-palatine, entered the orbit and passing above the inferior branch of the motor- oculi nerve, where it gives off the short root, went in company with the last to gain the in- ferior and posterior part of the ophthalmic gan- glion ;* and beside those there may be found, in favourable subjects, others, which seem destined to the posterior ethmoidal cells. The inferior branch is the largest given off by the ganglion ; it is distributed principally to the palate, and hence is called “ the palatine ;” but it supplies the nostril also in part, and hence it has been suggested by J. F. Meckel, that it might be appropriately called the “ naso-palatine:” this appellation has, however, been applied by Scarpa to one of the internal branches, and it has been already explained that it belongs more properly to the original branch before its junction with the ganglion. The palatine nerve descends from the ganglion into the spheno-maxillary fossa, posterior to the internal maxillary artery and toward the pterygo-palatine canals, and after a short course divides into three branches; an anterior, larger one, denominated “ the great palatine,” and two posterior smaller branches, “ the lesser palatine nerves.” These branches continue to descend in com- pany until they reach the superior apertures of the canals ; they then enter the canals and are transmitted downward through them to the palate and fauces. The great palatine descends through the anterior pterygo-palatine canal, * Journal Compl. vol. xxiv. Arnold. in company with a branch of the palatine artery, at the same time inclining forward ■ during its descent it gives off, in some in- stances before, in others after it has entered the canal, either one or two filaments, which descend inward, pass through the nasal process of the palate bone, and enter the nostril at the back part of the middle meatus, between the posterior extremities of the middle and in- ferior turbinate bones : one of them is dis- tributed to the membrane of the middle bone and of the middle meatus ; the other to that of the convex surface of the inferior bone : when a single branch arises from the palatine it divides into two, which follow a similar distribution; these branches are denominated by the elder Meckel inferior nasal nerves in con- tradistinction to the superior nasal, to be de- scribed, given off by the ganglion and by the Vidian nerve. Another filament is described by Cloquet arising from the palatine shortly before it escapes from the canal, entering the nostril through the perpendicular plate of the palate bone, running along the margin of the inferior turbinate bone, and lost upon the ascending process of the superior maxillary bone, often also contained in an osseous canal. The great palatine nerve, then, for the most part divides into three branches, of which one, the smallest, descends through an accessory.' canal, in the pterygoid process of the palate- bone, leading from the anterior, and escapes from it inferiorly into the soft palate in which it is consumed. The other two escape from the pterygo- palatine canal, through the posterior palatine foramen, into the palate : at emerging from the foramen they are situate very far back, in the posterior angle of the hard palate on either side, and behind the last molar tooth of the upper jaw; they are immediately super- ficial to the periosteum, and above the other structures of the palate ; they are lodged, along with the branches of the accompanying artery, in channels upon the inferior surface of the palatine processes of the palate and the superior maxillary bones; they pass forward, one along the alveolar arch, the other toward the middle line of the palate, and subdivide, each, into several branches, which are dis- tributed to the structures of the hard palate, the mucous glands and membrane, and to the gums, and communicate in frontwith branches of the naso-palatine ganglion. In some instances the palatine nerve does not divide into those ultimate branches until after it has escaped from the palatine canal ; but their disposition in such cases is in other respects the same. The lesser palatine nerves are posterior to the greater; they are transmitted also through the pterygo-palatine canals, the first through the posterior, the second through the external. The first, the larger of the two, and called middle palatine nerve, escapes from the canal inferiorly in front of the hamular process of the sphenoid bone, and divides into filaments, which are distributed to the soft palate and its muscles. FIFTH PAIR OF NERVES. 287 The second, the posterior, little palatine nerve, descends at first between the external pterygoid muscle and the posterior wall of the antrum, then enters the canal, and escapes inferiorly external to the former ; it divides into two filaments, one of which is distributed to the soft palate, the other to the tonsils and arches of the palate. Those branches are accompanied by minute branches of the palatine artery. The internal branches vary in number from three to five ; they arise from the inner surface of the ganglion, run directly inward, posterior to the nasal branch of the internal maxillary artery, toward the spheno-palatine foramen, which they immediately reach ; pass through the foramen, perforating the structure by which it is closed, and enter the nostril, and thus attach the ganglion closely to the foramen : at their entrance into the nostril they are situate before and beneath the anterior wall of the sphenoidal sinus, at the back part of the su- perior meatus, and immediately above the posterior extremity of the middle turbinate bone. They are distinguishable, according to the majority of descriptions, into two sets ; one destined to the outer wall of the nostril and denominated by Meckel anterior superior vasal, in contradistinction to branches of the Vidian nerve, which he has designated “ posterior superior nasal,” and another con- nected with the septum. A third destination has been assigned to them by Arnold, accord- ing to whom a branch derived either from one of the nerves of the septum, or originally from the ganglion itself, is distributed to the supe- rior part of the pharynx, corresponding to the pharyngeal branch of Bock. The anterior superior nasal branches are either one or two in number; when but one, it divides into branches corresponding to the two ; it is so expressed in Arnold’s fifth plate ; one of the two divides into filaments, which are distributed to the posterior ethmoidal cells, to the posterior part of the superior turbinate bone, and to the superior meatus, to the mem- brane of those parts. The second distributes its filaments to the convex surface of the mid- dle turbinate bone ; according to Cloquet they in part perforate the bone, and thus gain its concave surface : they all run between the periosteum and the mucous membrane, and are distributed finally to the latter. The branches connected with the septum are two, a short and a long one ; they both pass across the anterior wall of the sphenoidal sinus from without inward, and thus reach the posterior part of the septum nasi, become attached to it, and changing their direction descend forward along it, between the perios- teum and mucous membrane. The short, lesser, branch is situate very near to the posterior margin of the septum, to which it is parallel in its course, and distri- butes its filaments to the membrane of the posterior part of it : one of them is repre- sented by Arnold as constituting the phar geal branch. The long branch descends to the superior aperture of the anterior palatine canal, enters the canal, and in it the nerves of the two sides are united to a small ganglion denominated the naso -palatine ; from it filaments descend to the anterior part of the palate, in which they are distributed and communicate with filaments of the palatine nerves. Each nerve, during its course along the septum, is situate nearer to its position inferior than to its supe- rior anterior margins : it is said not to give any filaments during its descent, but this is incorrect, as is well represented by Arnold ; those, which it gives offj are distributed to the membrane of the septum about its middle; at times also it divides into two filaments, which are afterwards reunited. Each nerve is received inferiorly in a separate canal, which inclining inward is soon united to the other in the palatine, and in it the nerve or the naso-palatine ganglion receives a filament of communication from the anterior superior den- tal branch of the second division of the fifth, as described by Cloquet. This branch has been particularly described, first by Scarpa,* and by him denominated the naso-palatine ; it has been also described by J. Hunter, f between whom and Scarpa appears to lie the merit of having first ob- served it ; it is also known as “ the nerve of the septum,” but the latter appellation is ma- nifestly incorrect ; nor is the former free from objection, inasmuch as the same title has been applied, and with reason, in the inferior Mam- malia, to the original branch given off by the second division of the fifth for the supply of the nostril and palate, with which the spheno- palatine ganglion is connected, and which in man has received the name of spheno-palatine branch. The branch of the ganglion in ques- tion is called by some the nerve of Cotunnius, but incorrectly ; having been first described by Scarpa, it cannot with justice be attributed to the former. The posterior branch of the ganglion is de- scribed and represented by the majority of authorities as arising single and in its course dividing into two filaments; but Bock, J. F. Meckel, and Hirzel state that the two fila- ments at times are throughout distinct and connected separately to the ganglion ; and Arnold represents, in like manner, two fila- ments arising from the ganglion, corresponding to the two into which the single nerve divides. The posterior branch arises from the back of the ganglion, passes directly backward from it, and is received immediately into the pterygoid or Vidian canal, along with the corresponding branch of the internal maxillary artery: it is transmitted through the canal backward and slightly outward, beneath the course of the second division of the fifth itself, and external to, or in many instances beneath the sphenoidal sinus ; having traversed the canal, * Annotationes Academicas, in which, is also con- tained a good representation of the nerve as a single branch. * Animal (Economy, 288 FIFTH PAIR OF NERVES. it escapes from its posterior aperture into the foramen lacerum anterius basis cranii : in this it is contained in the fibrous structure by which the foramen is closed, and is situate at the outer side of and beneath the internal carotid artery, as that vessel ascends, from the aperture of its canal in the petrous bone, into the cavernous sinus. Flere also, or even before it has escaped from the Vidian canal, it receives, when single, a filament of com- munication from the superior cervical ganglion of the sympathetic : this filament had been long regarded as arising from the posterior branch itself, and— though at present gene- rally* considered a branch from the sympa- thetic— it has been for the most part described, in systematic works, as such under the name of the inferior, deep, sympathic, or carotidean branch of the Vidian nerve. In its direction it certainly resembles a branch of that nerve ; but in that particular it is equally entitled to be regarded one from the sympathetic to the spheno-palatine ganglion, it being either from before backward and from above downward, or from behind forward and from below up- ward. Further, in sensible qualities it strictly resembles other branches of the latter nerve ; it is, as has been stated, at times separate from the proper Vidian, and connected directly with the spheno-palatine ganglion ; and it is, in fact, but one of the branches which ascend into the cranium from the superior cervical ganglion along the internal carotid artery, so that it would be equally correct to describe that fila- ment which is connected with the sixth nerve as a branch of that nerve, as to style the fila- ment in question a branch of the Vidian nerve. The view of the nature of this filament here advanced is, however, not universally admitted. Cruveilhier objects to it because the cranial branch of the Vidian nerve appears to him to resemble in all respects the carotidean : this, however, cannot be considered a valid objec- tion, it can only prove that one branch may be as much allied to the ganglionic system as the other, but the validity of the assertion may be questioned ; however it may be in man, the characters of the two branches in the larger quadrupeds, the horse e. g. are sufficiently distinct, the cranial branch being of a pure white colour, and the carotidean having a gan- glionic enlargement upon it at its junction with the cranial. While traversing the pterygoid canal, soon after it has entered that canal, and in some cases even before, the posterior branch of the gan- glion gives off from its inner side two or three filaments, denominated by the elder Meckel posterior superior nasal : these enter the poste- rior superior part of the nostril, in one case by passing through the spheno-palatine foramen, in the other by perforating the inner wall of the pterygoid canal, and are distributed to the posterior part of the lateral wall of the nostril, to the root of the septum, to the sphenoidal sinus and to the lateral wall of the pharynx in the vicinity of the orifice of the Eustachian L * Bock, Cloquet, Hirzel, J. F. Meckel. tube. These branches frequently arise from the ganglion itself by a single filament, de- nominated by Bock the pharyngeal nerve, and represented by Arnold among the internal branches of the ganglion : it divides into fila- ments distributed to the several parts men- tioned. After the junction of the sympathetic fila- ment, the posterior branch is continued through the fibrous structure already mentioned, ex- ternal to the internal carotid artery, and thus enters the cranium. It then passes out- ward, backward, and upward, upon the ante- rior surface of the petrous bone, beneath the third division of the fifth, very near its attachment to the Gasserian ganglion, and enclosed in the dura mater : it is at the same time lodged in a channel upon the sur- face of the bone. It is stated by Cloquet that it here sends into the cavity of the tympanum by two canals, the orifices of which are to be seen in the channel one above the other, two filaments of extreme delicacy, which go to anastomose together upon the promontory, and to communicate with a filament of the supe- rior cervical ganglion, and with the glosso- pharyngeal nerve. According to Iiirzel,* this connection between the superficial branch of the Vidian and the tympanic branch of the glosso-pharyngeal nerve on the nerve of Jacob- son, takes place in the vicinity of the junction of the former with the facial nerve. Accord- ing to Arnold, f the superficial branch of the Vidian nerve is, as proved by the researches of others and his own, not simple, but composed of two or of several filaments, and is accom- panied by one or more very delicate filaments from the carotid plexus. In one instance he found the petrous nerve composed of four filaments on the right, and three on the left. The existence of several distinct filaments in the Vidian nerve may be easily observed in the larger animals. It pursues the course men- tioned, until it has reached the hiatus Fallopii, through which it is transmitted to the aqueduct of Fallopius, where it meets and becomes in- timately connected with the facial portio dura nerve. At their junction the facial nerve pre- sents a gangliform swelling, from which two very delicate filaments proceed to the auditory nerve, j; From the time that the posterior branch of the ganglion enters the cranium until it has joined the facial nerve, it is called the cranial or superfciul petrous branch of the Vidian nerve ; by Arnold petrosus superficialis major in contradistinction to another nervous filament, which connects his ‘ otic’ ganglion to the tym- panic branch of the glosso-pharyngeal nerve ; but the application of either of these epithets would be rendered unnecessary by ceasing to consider the filament by which the posterior branch of the ganglion is connected to the sympathetic, a branch of the former. The posterior branch is also known by other * Journ. Compl. t. xxii. t Journ. Compl. t. xxiv. | Arnold. See lingual branch of third division and chorda tympani. FIFTH PAIR OF NERVES. 289 names, viz. the recurrent, the pterygoid, the ‘ Vidian, the anastomotic, or sympathic. 3. The next branch or branches of the su- perior maxillary nerve are the posterior supe- rior dental. These arise from the nerve in front of the internal maxillary artery, between it and the back of the antrum, and are sepa- rated from the artery by the spheno-palatine ; they are very irregular as to their number and precise place of origin ; at times there is but one branch, at others there are two or three : they are distributed to the buccinator muscle and the mucous membrane of the posterior lateral part of the mouth, to the roots of the posterior teeth, the membrane of the maxil- lary antrum, and the gum of the upper jaw. When but one branch is present, its sub- divisions supply the place of the others. It descends into the fossa, behind the superior maxillary bone, and before the internal maxil- lary artery, and after a certain way divides into two branches or sets of branches, posterior and anterior. The posterior consists of several long slen- der filaments, which continue to descend im- mersed in the fat of the zygomatic fossa, until they reach the surface of the buccinator muscle; they then in part are distributed to it, but in greater number pass between the fibres of the muscle and are lost in the mucous membrane of the mouth. The anterior branch descends for some time, until it reaches the back of the maxilla; it then enters a canal in the bone, within which it is transmitted forward through the wall of the antrum ; after a short way it escapes from the canal and continues its course forward within the wall, between it and the lining membrane, describing a curve convex down- ward ; having reached the front of the antrum it ascends and terminates by joining either the anterior superior dental or a branch of that nerve. During its course around the antrum the anterior branch of the nerve gives off down- ward numerous delicate filaments, which de- scend toward the teeth, traverse the structure of the alveolar arch, and in part are distributed to the roots of the posterior superior teeth in a manner analogous to that of the inferior dental nerves : in part they escape inferiorly from the alveolar arch between the sockets of the teeth, and are consumed in the gums. The nerve is also stated to give filaments to the membrane of the maxillary antrum. 4. Shortly before its escape from the infra- orbital canal, but at a distance somewhat variable from it, the second division of the fifth gives off its next regular branch, the anterior superior dental : this descends, from the infraorbital canal, through one of its own name in the anterior wall of the antrum to- ward the canine tooth ; it next runs inward above the root of that tooth, and then again descends through the perpendicular process of the maxillary bone, until it reaches the floor of the nostril, and is continued inward through the horizontal process of the bone above the roots of the incisor teeth. VOL. II. While descending through the wall of the antrum the anterior superior dental nerve either is joined by the termination of the anterior- branch of the posterior dental, or it divides into two, one of which inclines outward and joins that branch, the other pursues the course of the nerve. It supplies the anterior teedi of the upper jaw in the same manner as the pos- terior nerve does the posterior teeth ; it also gives at its termination filaments to the mem- brane of the nostril, and one to the naso- palatine ganglion or nerve. Besides the regular dental nerves, others at times arise from the second division of the fifth within the infraorbital canal, and take the place of branches of the regular nerves. 5. The facial branches of the second division of the fifth are from five to seven in number ; they differ from each other in size, and branch off in different directions; they are distin- guished, according to the direction in which they run and their destination, into three sets ; a superior or palpebral, an inferior or labial, and an internal or nasal. For the most part there is but one superior or palpebral branch, though sometimes there are two. This branch is destined to supply the lower eyelid, and is denominated the inferior palpebral nerve ; it presents some variety in its mode of origin and its course ; most frequently it does not separate from the trunk till after the latter has escaped from the infraorbital foramen; but in some instances it does so within the in- fraorbital canal, is transmitted through a dis- tinct canal, and escapes into the face through a separate foramen, situate internal to the infra- orbital ; it ascends inward toward the lower lid, in front of the inferior margin of the orbit ; in its ascent it is situate beneath the orbicularis palpebrarum, to which it gives filaments, which after supplying the muscle become cutaneous, and it is frequently contained in a superficial groove on the superior maxilla ; having reached the lid it divides into two branches, an external and an internal. The external runs outward, through the lid, toward the external angle, supplies its structures on that side, and anasto- moses with filaments of the portio dura, and of the inferior palpebral branches of the lachrymal nerve. The internal ascends in the course of the original nerve toward the internal canthus of the eye, gives a filament to the side of the nose, which communicates with the naso-lobar branch of the nasal nerve, supplies the lower lid at its internal part, is also distributed to the carun- cula and lachrymal sac, and anastomoses with a filament of the inferior branch of the infra- trochlear nerve described in the account of that nerve. It sometimes anastomoses also with the portio dura. When there is a second palpebral branch, it takes the place of the external branch of the former, which in such case is denominated the internal inferior palpebral, and the second the external. It perforates the levator labii supe- rioris muscle ; ascends toward the external angle of the eye, beneath the orbicularis palpe- brarum ; and, like the external branch of the inferior palpebral, already described, supplies u 290 FIFTH PAIR OF NERVES. the structure of the lid, and anastomoses with the portio dura, lachrymal, and malar nerves, as also with the internal palpebral. The descending or labial branches are the largest and the most numerous ; for the most part they are three, at times four. They de- scend to the upper lip, one toward its middle, the second toward its intermediate, and the third toward its outer part, the commissure of the lips, and are denominated internal, mid- dle, and external ; they are situate, all at first, beneath the levator labii superioris, between it and the levator anguli oris or canine muscle; as they descend, they give filaments to these muscles and to the parts superficial to them ; and they pass to their several destinations, the internal between the levator labii and the de- pressor alae nasi ; the middle between the same muscles ; and the external superficial to the levator anguli, and uncovered by the levator labii ; as they approach the lip they divide each into branches, which are distributed to the structures of the part at their several situa- tions ; to the orbicularis oris, and the insertions of the other muscles of the lip, to the integu- ment of the bp, internal and external, and also to the labial glands ; they all communicate to- gether, and with branches of the portio dura; the external more particularly with the latter, as also with the neighbouring branches of the fifth ; the internal with the inferior nasal ; the external with the inferior labial and buccal nerves. In the infraorbital region, the branches of the superior maxillary are crossed by and interlaced with those of the portio dura; the latter running from without inward, and for the most part superficial to the former ; but also beneath and among them, and even forming- loops about them; while the former run from above downward, and are principally deeply seated. In consequence of this diversity in their directions and the numerous anastomoses which they hold with each other, the branches of the two nerves form a very intricate mesh in that region. In some Carnivora filaments of the facial branches of the fifth nerve have been traced into the bulbs of the hairs of the whiskers and the tufts with which they are furnished ; this is remarkably so in the seal, as described by Andral : they are strongly expressed by Rapp.* The internal or nasal branches are, for the most part, two ; they are termed superficial nasal by the elder Meckel, and distinguished into supe- rior and inferior; they pass, both, inward toward the nose, beneath the levator labii superioris, the inferior at the same time descending, and having reached the side of the nostril they sub- divide. The superior is the smaller of the two, and arises frequently from a branch common to it and the internal inferior palpebral ; it divides into three, of which the first, the uppermost, is distributed to the origin of the levator labii alseque nasi, to the compressor naris, and to the integuments on the dorsum of the nose; the * Die Vevriclitungen des fiinften Hirnnerven- paars. second, the middle, to the compressor naris and also to the integuments of the nostril, and the third, the inferior, to the compressor naris, to the depressor alee nasi, and to the integu- ments of the ala. The inferior superficial nasal, the larger of the two, first gives occasionally a branch, which ascends to the eyelid ; then communicates with the superior, and having reached the ala of the nose, it gives off numerous ramifications which are distributed to the levator and depressor alte, to the integuments of the inferior part of the ala, of the tip, and of the septum, and also to the upper lip ; it communicates with the rami- fications of the naso-lobar branch of the nasal nerve, of the internal labial, and of the portio dura. The third division of the fifth. — This trunk has been denominated by Winslow, on account of its general distribution, the inferior maxillary nerve, and it is generally known by that appel- lation ; yet it appears to the writer that it would have been much belter had that title been applied only to that portion of the nerve which enters the lower jaw. Such is the opinion of the elder Meckel, who observes that this use of the epithet leads to the inconveni- ence that the branch alluded to and the trunk of the nerve may be easily confounded. It is much the largest of the three divisions, and differs remarkably from the other two in its composition ; they are both single, and derived altogether from the Gasserian ganglion ; it on the contrary is composed and made up of two portions, one derived from the ganglion, the other not connected with it ; the former is the largest of the three trunks connected with the ganglion ; it is attached to its posterior external extremity ; at its attachment it is cineritious and very wide, but as it proceeds it loses that tint, and acquires a compressed cylindrical form. It is situate external, posterior, and in- ferior to the others, and its course within the cranium is very short or none, for from the ganglion it enters at once the inferior maxillary or foramen ovale of the sphenoid bone, and escapes from the cavity, passing downward, for- ward, and outward, nearly at right angles with the second division of the fifth. Before leaving the cranium it is joined, as the first and second divisions are, by a filament from the sympa- thetic, according to Munniks, Laumonier, and Bock.* The second portion, of which the third division is composed, is the lesser packet of the fifth itself; this, it has been already stated, does not join the ganglion, but passing out- ward, beneath that body, is united to the former portion posteriorly, in the foramen ovale ; it forms, however, but a small proportion of the nerve, that part which is attached to the gan- glion exceeding it very much in size. At its junction, it is placed posterior to the other, but it immediately spreads out, and increases very much in width, and at the same time is lapped round the inner side of the ganglionic portion so as to get before it, and to form the * Op. cit. ami Journ. Compl. FIFTH PAIR OF NERVES. 291 anterior part of the nerve by the time it has escaped from the cranium. The third division of the fifth nerve, after its escape from the cranium, is situate in the superior, posterior, and internal part of the zygomatic fossa ; it is placed immediately be- hind the external pterygoid muscle, before and somewhat internal to the styloid process of the sphenoid bone, internal to and on a line with the anterior margin of the temporo-maxillary articulation, and external to the Eustachian tube. So soon as the inferior maxillary nerve has entered the fossa, it gives off, immediately beneath the superior wall of that fossa, a set of branches remarkable for their source and destination ; they proceed from the front of the nerve; their regular number is five, but they present variety in this respect, being in some instances not so many at their origin, in others amounting to six ; they vary also in the mode in which they arise; for the most part they are given off separately and branch off, as rays, from the nerve, but at times the nerve divides into two branches, a smaller anterior one, and a larger posterior; in such case the anterior divides immediately into the branches, which otherwise arise from the nerve itself. These branches are the masseteric, the deep temporals, the buccal, and the pterygoid nerves, and they are ranged in succession from behind forward, and from without inward ; the first is external and posterior ; to it succeed the tempo- rals, then the buccal, and lastly the pterygoid. 1 . The masseteric branch proceeds from the anteriorand outer part of the nerve; it passes out- ward, nearly transversely, beneath the superior wall of the temporal fossa, and in front of the articular surface of the temporal bone ; it crosses obliquely over the external pterygoid muscle, at its outer extremity, between the muscle and the wall of the fossa, and then inclines down- ward through the sigmoid notch of the lower jaw, in front of its neck, and of the insertion of the external pterygoid muscle, and posterior to the coronoid process and the tendon of the temporal muscle. Having traversed the notch it descends forward, external to the ramus of the jaw, and passing between the two portions of the masseter, divides into numerous ramifica- tions, which are distributed altogether to that muscle : while between the portions of the masseter, it inclines from its posterior toward its anterior margin, and its terminating filament can be traced to the latter at the inferior part of the muscle. This branch gives off, during its course, some minor branches ; while in front of the articulation of the jaw it gives one or more filaments to the articulation ; in the next place it gives a small branch to the posterior part of the temporal muscle, and lastly it fre- quently gives off the external or posterior deep temporal nerve. 2. The deep temporal branches are two; they are distinguished into posterior and anterior or external and internal. The anterior is the larger. They present varieties in their num- ber and mode of origin ; at times there is but one, at others there are three ; in some instances they arise by a common origin ; in others, and for the most part, separately, and in others again the posterior or lesser branch is given off either by the masseteric or the buccal nerve. They both pass outward, in front of the tem- poro-maxillary articulation, between the exter- nal pterygoid muscle and the superior wall of the zygomatic fossa; they then change their direction and ascend in the temporal fossa, be- tween the muscle and the surface of the fossa, and divide into branches, which attach them- selves to the temporal muscle, on its deep sur- face, and are distributed, those of the posterior to its posterior, and those of the anterior to its middle and anterior parts. The two branches frequently anastomose with each other as they leave the zygomatic fossa. The anterior also frequently communicates with or receives a branch from the buccal nerve, and by one of its anterior filaments it anastomoses with the nerve resulting from the junction of the tempo- ral branches of the lachrymal nerve and the temporo-malar branch of the second division of the fifth. This communication between the three divisions of the fifth is however, accord- ing to the elder Meckel, subject to variety; he states that he has seen the communicating branch of the anterior deep temporal at times enter the orbit either through the malar bone, or through the spheno-maxillary fissure, and there unite with the conjoined branch of the other two. 3. The buccal nerve is the largest and the principal of these branches ; it arises from the front of the inferior maxillary nerve, next in or- der after the anterior deep temporal, for the most part a distinct and single branch ; but it is not unusual to find the buccal nerve give off one or both of the deep temporals, or in rare cases all the three former branches : in some instances also it arises double, the two filaments, of which it is then composed, being separated by a portion of the external pterygoid muscle. It runs downward and forward, passing at first either and for the most part through the exter- nal or between the two pterygoid muscles, be- neath the external and external to the internal ; having traversed the pterygoid it descends in front of its inferior part, internal to the coronoid process of the lower jaw, and the inferior part of the temporal muscle, next between the ten- don of the temporal and the buccinator, then between the anterior margin of the masseter and the latter muscle, and finally emerging from between them it inclines toward the angle of the mouth, superficial to the buccinator and beneath the dense expansion by which that muscle is covered. During its descent it is immersed in the fat which occupies the lower part of the zygomatic fossa. The ramifications which it gives off are numerous ; first while traversing and immediately after escaping from the pterygoid it gives branches to the muscle; at the same time it gives off a fasciculus of branches which pass outward, in front of the external pterygoid to the internal surface of the temporal muscle, at its inferior part; some of these descend with the muscle xi 2 292 FIFTH PAIR OF NERVES. toward its insertion, and are distributed to it at that point, others ascend in the temporal fossa, between the muscle and the bone, penetrate the muscle, and are distributed, along with the branches of the anterior deep temporal, with which they anastomose freely, to the muscle at its inferior anterior part. In the next place, while between the masseterand the buccinator, the nerve gives off backward several branches, three or four, which are distributed to the buc- cinator at its origin, to the buccal glands, and to the membrane of the mouth ; as it lies upon the last-named muscle, between the ramus of the jaw and the angle of the mouth, it gives filaments to it at its middle and anterior part, which, like the former, both supply the muscle, pass through its fibres, and are distributed also to the buccal glands and membrane. Finally, as the nerve approaches the angle of the mouth, it divides into two, occasionally three, branches; these two branches pursue the direction of the nerve toward the angle, passing beneath the facial vein and inclining, one upward, the other downward ; after a short course they are united both to branches of the portio dura, the inferior to a branch of the inferior or cervico-facial divi- sion, the superior to one of the superior or tem- poro-facial division of that nerve. By their union they form conjoined branches or loops, from each of which are given off several fila- ments to the muscles of the mouth at their in- sertion into the angle; from the superior, more particularly, to the buccinator, the zygomatic, and levator anguli ; and from the inferior to the buccinator and depressor anguli oris. 4. The fifth and last of these branches is the •pterygoid; it is the smallest of them, and arises from the anterior internal part of the trunk; it passes inward and downward, be- hind the external pterygoid, and then between the internal pterygoid and circumflexus palati muscles ; it gives a filament of some size to the latter muscle, and then entering into the internal pterygoid at its upper extremity, it is consumed altogether in that muscle. The external pterygoid also, at times, but not uniformly, receives a distinct filament from the trunk ; when present it arises from the front of the nerve, beneath the buccal branch, and passes forward directly to the muscle, in which it is consumed. The constitution of these branches is peculiar, and is a matter of much interest: involving physiological ques- tions, this subject is deferred to another oc- casion. In consequence of its connection with the third division of the fifth, and more particularly with the lesser packet of the nerve, this seems a fit place to advert to the ganglion discovered by Arnold, and by him denominated Otic or auricular, of which the following sketch has been taken from his own account. It is situate at the inner side of the third branch of the fifth, some lines beneath the foramen ovale, at the part where the deep temporal, the masseteric, and the buccal nerves are de- tached from the same side, and a little above the origin of the superficial temporal nerve : its posterior part touches the middle meningeal artery, and the internal the internal pterygoid muscle : an abundant adipose tissue surrounds it : its form is not altogether regular, however it approaches to an oval, flattened internally and externally. It is united to the trunk of the third division not merely by cellular tissue, but by many filaments, which enter into the formation of the ganglion ; these filaments, which come solely from the lesser portion of the nerve, are mostly extremely short, and can only be observed when we try to separate the ganglion from the trunk ; but in cases where the ganglion is situate rather distant from the nerve, the filaments are of course longer and can be more easily observed. With regard to the branches of the third division, the pterygoid nerve espe- cially is in very intimate connection with the otic ganglion, so that in a superficial examina- tion it appears as if it arose from it; but, in a more accurate investigation, it is clear that this nerve soon after its origin penetrates through a part of the substance of the ganglion and takes up some of it: the slender branch, which ramifies in the tensor palati, is likewise in very intimate relation with this ganglion, and distinguishes itself from the other branches by its reddish appearance. The ganglion thus communicates with the lesser packet of the fifth : it also communicates with the glosso- pharyngeal and with the facial and auditory nerves by means of the nervus tympanicus. But, the ganglion being a body which is to be regarded as distinct from the fifth nerve, and not part of it, a further pursuit of its connections and properties would be here out of place. See Svmpathetic Nerve. The third division of the fifth descends from the foramen ovale, outward into the zygomatic fossa, posterior to the external pterygoid muscle, before the superior part of the levator palati, and internal and parallel to the middle me- ningeal artery. After a course of half an inch from the foramen, it divides for the most part into two large branches, an anterior internal one destined to the tongue, denominated the lingual branch, and an external posterior one, which is transmitted through the inferior max- illary canal, and, escaping from this, through the mental foramen, is distributed finally to the muscles and integuments of the chin ; this second branch is called inferior dental, or inferior maxillary nerve ; the latter, as has been already intimated, appears much the more appropriate appellation. The first branch bears, very generally, the name of gustatory nerve from its presumed connection with the sense of taste; but, since the opinion that it is the nerve in which the sense of taste resides has been brought into question, and since, as will appear by-and- bye, it is at least certainly not the sole nerve of that sense, it is obvious that that name should be discontinued. The manner in which the third division finally divides is not always such as has been described : in some instances it separates fairly FIFTH PAIR OF NERVES. 293 into three branches, viz. the lingual, the inferior maxillary, and the superficial temporal, and such is the mode of division mentioned by the elder Meckel. The writer has before him an instance of another mode ; the inferior maxillary arises by two roots, and the original trunk divides into two parts ; one common to the lingual, and one root of the maxillary; the other to the superficial temporal and the other root: the superficial temporal is thus, in this instance, equally an original branch as the others, and is connected to the maxillary by a filament, which it gives off soon after its origin, while the maxillary is also connected in the usual mode to the lingual : the maxillary artery, however, passes through the loop formed by the two roots of the former nerve. The length of the third division from the ganglion to its bifurcation is about three fourths of an inch, one fourth contained within the bone during its escape from the cranium, and the other two between the aperture externally and the division. When it divides into two, the branches are, at times, of the same size, but for the most part the inferior maxillary is the larger; they descend at first in close apposition with each other, but as they proceed they gradually separate, the lingual branch inclining inward and forward, the inferior maxillary outward, in the course of the original nerve, in order to gain the aperture of the dental canal ; they thus leave between them an angular interval, acute above, through which the internal maxillary artery for the most part passes. In their descent they cross, at right angles, the artery internal to the origin of the middle meningeal branch : in doing so either they pass both behind the vessel, or the lingual branch passes before, and the inferior maxillary behind it. The two nerves are most frequently connected, soon after their origin, by a short and delicate branch, which passes from the inferior maxillary to the lingual, and forms, with the nerves, a triangle, through which the artery passes in those instances in which the lingual descends before it. The nerves are situate internal to the neck and ramus of the jaw, between the pterygoid muscles, posterior and inferior to the external, external and anterior to the internal ; and they are contained in a triangular space included between the two muscles and the jaw, bounded superiorly by the external, beneath and in- ternally by the internal pterygoid, and externally by the jaw; through this space they pass from above downward, the lingual from behind forward, and from without inward, the maxil- lary from within outward, toward the aperture of the dental canal, and holding the mutual relation already indicated, — the lingual anterior and internal, the maxillary posterior and ex- ternal. Before pursuing these branches of the third division further, it will be well to describe the superficial temporal nerve. This branch has been viewed differently by different autho- rities ; by some it is accounted one of the former set, the superior anterior branches of the third division ; by Meckel it is described as one of three, into which the continuation of the nerve divides. It arises for the most part by two, and in some instances by three, roots ; a larger one from the inferior dental nerve, and a smaller from the trunk of the third division itself, given off at the same time with its superior branches, and deri- ved from the same source ; the two roots forming together a loop, through which the middle meningeal artery ascends : in conse- quence of this mode of origin it appears better to describe it thus separately, and not to refer it to either of the sets described. It has, however, been already explained that in some cases it appears to be an original branch of the third division, one of three into which it finally divides. The nerve runs outward, backward, and somewhat upward, behind the external ptery- goid muscle, toward the back of the neck of the lower jaw ; it then passes behind it and the condyle, between them and the auditory canal, traversing the posterior part of the glenoidal cavity of the temporal bone, and imbedded in the process of the parotid gland, which occupies it. The superficial temporal nerve, while within the ramus of the jaw, pursues a course nearly the reverse of that of the trunk of the internal maxillary artery in the first part of its course. At first it is situate before the tensor palati muscle, between it and the external pterygoid ; then it passes between the internal lateral ligament of the maxillary articulation and the neck of the jaw, situate at the same time above and in contact with the artery ; and lastly, it is situate behind the condyle of the jaw, between it and the meatus auditorius, and involved in the parotid. The nerve gives off numerous branches ; when it has reached the situation last described, it breaks up at once into a leash of branches, which pass off in different directions : of these two, at times only one, are destined for the interior of the meatus auditorius ; they ascend toward the canal, become attached to its ex- terior, and pass through the fibrous structure of the tube, close to its connection with the osseous portion : having thus gained its interior, they are distributed to its lining membrane, its sebaceous follicles, and the membrane of the tympanum. Before entering the tube they give some delicate filaments to its exterior; these branches may be called the internal auricular. Others, the smallest which the nerve gives off, descend along the external carotid artery, are in part distributed to the parotid gland, and establish upon the artery a manifest com- munication with branches of the sympathetic. Its next branches, two in number, pass out- ward through the substance of the parotid, behind the neck of the jaw; one external or superficial, the other internal to the temporal artery; and turning forward round the posterior margin of the javv, either they both, having given some fine ramifications to the gland, join the temporo-facial branch of the portio dura, immediately before its division, or one of them joins the facial branch of the tem- 294 FIFTH PAIR OF NERVES. poro-facial, while the other continues forward, upon the face, below the zygoma, and deeper than the branches of the temporo-facial : it divides into numerous long filaments, of which some join both branches of the temporo-facial ; others are distributed superficially upon the side of the face beneath the zygoma and upon the malar region, and, ascending over the former part, to the inferior anterior part of the temple, as far forward as the margin of the orbit. These may be called the commu- nicating branches, in consequence of the re- markable and important communication which they establish with the portio dura. The next may be called external auricular ; they ascend to the anterior part of the car- tilaginous tube of the ear, concealed by the temporal artery, attach themselves to the tube in front, and are distributed to the integuments of the concha. Lastly, the superficial temporal nerve emerges from the parotid gland, beneath the root of the zygoma, between the condyle of the jaw and the cartilaginous tube of the ear, in company with the temporal artery, and concealed by it : it then changes its course and ascends with the artery behind the zygoma and in front of the ear, upon the temple : there it emerges from beneath the artery, posterior to it, and divides into branches, which become subcutaneous, run superficial to the fascia and the artery beneath the subcutaneous cellular structure, and are ultimately distributed to the integument of the temple : their number is two or three; they maybe distinguished into anterior, middle, and posterior, and they are destined to the corresponding parts of the temple : they correspond in their course, but by no means regularly or strictly so, to the branches of the temporal artery, from which they are separated by the fascia. Of the two terminal branches of the third division, the larger one, the inferior maxil- lary or dental, descends outward to the upper orifice of the inferior maxillary canal. In its course it passes always behind the inter- nal maxillary artery, and soon glides between the internal lateral ligament of the temporo- maxillary articulation, and the ramus of the jaw, descending in front of the anterior margin of the ligament, which thus becomes interposed between it and the lingual branch, and also be- tween it and the internal pterygoid muscle, from the pressure of which the ligament is considered to protect it. In that situation it is joined by the inferior dental artery, a branch of the internal maxillary given off between the ligament and the jaw, which accompanies it through its further course. It next enters the canal, and is trans- mitted through it downward, forward, and inward toward the chin, beneath the sockets of the teeth ; having reached the termination of the canal, it is reflected upward and outward through the mental foramen, and escapes from the canal upon the lateral and superficial surface of the jaw, at either side of the chin ; at its exit it is beneath the second bicuspid tooth of the lower jaw, and covered by the muscles of the lip : it then terminates by dividing into two branches, called inferior labial nerves, external and internal. The branches of the inferior maxillary are as follow: — presently after its origin it gives off the branch by which the lingual branch and the inferior maxillary are connected, and which completes the loop through which the internal maxillary artery passes; also the branch which forms a root of the superficial temporal nerve. Next, imme- diately before entering the dental canal, it gives off a long slender branch, denominated mylo- hyoid nerve ; this branch descends forward and inward along the inside of the ramus of the jaw, between it and the internal pterygoid muscle, and lodged in a groove upon the sur- face of the bone, which leads in the same direction, and is occasionally in part a bony canal ; it is covered in the groove by a prolon- gation of the internal lateral ligament, and escapes from it inferiorly in front of the insertion of the internal pterygoid muscle and beneath the lingual branch ; it then passes beneath or external to the mylohyoid muscle, between the submaxillary gland and the internal surface of the jaw, gains the surface of the muscle itself and runs forward and inward above the super- ficial portion of the gland, between it and the muscle, and accompanied by the submental artery; finally, it divides into a leash of branches. Of these one is sometimes destined to the sub- maxillary gland ; two or three are distributed to the mylohyoid muscle; another to the anterior belly of the digastric, and the last passes first between the anterior belly of the digastric and the mylohyoid, gives filaments to the muscles in its passage, then ascends upon the chin internal to the belly of the digastric, and is consumed in the depressor labii muscle. The next branches of the nerve are those which are given off by it while within the inferior maxillary canal : they have two desti- nations, viz. the roots and periosteum of the teeth and the gum of the lower jaw. During its course through the canal the nerve gives off several long, slender branches, which run for some distance within the canal, ascend thence through the bone beneath and on either side of the roots of the teeth, ramify as they proceed, and distribute their ramifications to the desti- nations which have been mentioned. The author has never found these branches as they are for the most part represented, viz. short single filaments ascending almost directly into the several fangs of the teeth : they are deci- dedly less remarkable and less numerous in the old subject after the fall of the teeth than in the young. Again, at the mental foramen, and immediately before its escape from the canal, the nerve gives off a more considerable branch, denominated by Cruveilhier dentaire incisif, which is continued through the jaw toward the symphysis beneath the canine and incisor teeth, and distributed to them. The former set supplies the posterior molar teeth. Accord- ing to the general opinion the nerves of the teeth enter the fangs through the apertures in their extremities, and are transmitted through them into the bodies of the teeth, to be con- sumed in the pulp and the structure of the FIFTH PAIR OF NERVES. 295 teeth themselves. J. Hunter, however, lias stated in his work on the teeth, that he has never succeeded in tracing nerves into the fangs, and the experience of the writer, so far as it extends, tends to confirm the doubt thus ex- pressed; he has frequently traced the filaments to the structure at the root of the fang, but never into the fang, and in the jaw of the fcetal calf they may be found distributed in number upon the membrane of the pulp, but he has not been able to follow them into the pulp itself. The filaments sent into the gums from the dental nerves, superior as well as inferior, traverse the alveolar arch, escape from the bone upon its gingival aspect, and at once enter the gum : they are well represented by Arnold. The final branches of the inferior maxillary nerve are the inferior labial, internal and exter- nal. Of these the internal is the larger; it ascends toward the mouth, inclining inward, and breaks up into a great number of ramifica- tions, which are distributed to the depressor labii inferioris, the depressor anguli oris, the orbicularis, and the levator menti, also to the integument and internal membrane of the lip, and to the labial glands; they anastomose with branches of the inferior division of the portio dura. The external inclines toward the angle of the mouth ; it also gives off a great number of ramifications, distributed to the depressor anguli, the orbicularis, and the insertion of the muscles at the angle, the integument, and internal membrane of the lip, and the labial glands ; it also anastomoses with branches of the portio dura. The lingual branch of the third division. — The situation and relative size and position of the lingual and inferior maxillary branches in the first part of their course, have been already described Having crossed the internal maxil- lary artery, the lingual branch pursues its course downward, forward, and inward, passing first between the pterygoid muscles in the manner described, and then between the internal ptery- goid and the ramus of the jaw, until it has reached the anterior margin of that muscle ; during this part of its course it is at first separated from the inferior maxillary nerve by the internal lateral ligament, which is placed between them, the lingual branch internal, the maxillary external to it, and afterward it is situate anterior and superior to the mylohyoid branch of the maxillary. Having reached the margin of the pterygoid it emerges from between the muscle and the jaw, immediately behind the posterior extremity of the mylohyoid ridge, and enters into the digastric or submaxillary space, in which it is among the parts most deeply situate; within this space it continues to run forward and inward, until, at the anterior extremity, it attaches itself to the under surface of the tongue, and is prolonged by one of its' branches to the extremity of that organ. During its course through the digastric space, it is at first left uncovered by the muscles inferiorly, and in the interval between the margin of the pterygoid and that of the mylohyoid, where it is situate between the mucous membrane of the mouth and the posterior extremity of the submaxillary gland ; it then passes internal to the mylohyoid muscle, between it and the stylo-glossus, hyo-glossus, and genio-glossus, and is at the same time contained in a triangu- lar or wedge-shaped space, the base of which is above and the apex below; this space is bounded above by the mucous membrane of the mouth, externally by the mylohyoid muscle, and internally by the hyo-glossus, stylo-glossus, and genio-glossus muscles. In it are contained the sublingual gland, the deep process of the submaxillary and the duct of that gland with the lingual branch of the fifth and the ninth nerves; in the anterior part and superiorly, immediately beneath the mucous membrane, is situate the sublingual gland; at the posterior and rather inferiorly the deep process of the submaxillary; while the nerves and the duct are placed at the posterior or external part of the lingual branch of the fifth above, imme- diately beneath the mucous membrane; the ninth below, along, and above the cornu of the os hyoides, and the duct betweeu the nerves ; but as the three parts pass forward, the duct and lingual branch cross each other, the nerve descending, the duct ascending be- tween the nerve and the hyo-glossus, and in consequence of this circumstance, at the ante- rior part of the space, the duct is superior, the lingual branch is intermediate, and the ninth nerve is below. At first the lingual branch is above the deep process of the submaxillary gland, then it is situate internal and superior to it, external and inferior to the duct; as it pro- ceeds, it is beneath the sublingual gland, and, lastly, it ascends internal to that gland, between it and the genio-glossus, in order to reach the tongue. At the posterior part of the space, the nerve is immediately beneath the mucous membrane ; as it proceeds it descends from, but toward the anterior part again ascends, and is in con- tact with the membrane as it becomes attached to the tongue. Having reached the anterior margin of the hyo-glossus the nerve breaks up into three branches, posterior, middle, and anterior. Of these the posterior is the shortest, and ascends almost directly ; the middle runs upward and forward, and the anterior, which is much longer than, and at the same time inferior to the others, almost directly forward, along the under surface of the tongue, between the genio- glossus and the stylo-glossus ; the former muscle internal, the latter external to it. In its course beneath the tongue it is accompanied by the ranine artery, which joins it at the anterior margin of the hyo-glossus, and is situate inferior to it, immediately above the mucous membrane. The lingual nerve does not give off many branches in the first part of its course : soon after its origin it receives the branch of com- munication, by which the inferior dental nerve is connected to it. About the same point or presently after it is also joined by the chorda tympani. The uncertainty which has prevailed with regard to the source of this nerve renders 296 FIFTH PAIR OF NERVES. a more particular account of it necessary than would otherwise be required. Tire chorda tym- pani— a delicate filament — is given oti'from the portio dura shortly before that nerve escapes from the aqueduct of Fallopius, behind and be- low the tympanum : it passes upward and for- ward toward the tympanum, contained in a spe- cial canal of the bone, and having reached the back of the chamber it emerges from its posterior wall through a small aperture beneath the base of the pyramid ; it then attaches itself to the outer wall of the tympanum and crosses it toward the anterior, having first received* a delicate filament from the sympathetic, and running forward, upward, and outward. During its course from the posterior to the anterior wall it is situate at first beneath the short crus of the incus, then between the long crus of the incus and the superior part of the handle of the malleus, to which it is connected by the lining membrane of the tympanum. Having ascended above the internal muscle of the malleus it changes its direction and runs down- ward, forward, and inward along the superior anterior part of the circumference of the mem- brana tympani, until it has reached the anterior wall of the chamber, from which it goes out through the Glaserian fissure, along the tendon of the anterior muscle of the malleus. It is throughout excluded from the interior of the tympanum by the lining membrane, which is connected to it upon that side ; it is therefore incorrect to say that it crosses the chamber. After its escape from the tympanum the nerve continues to descend forward and inward in front of the levator palati muscle, and after a course from three-fourths of an inch to an inch long it is attached at a very acute angle to the back of the lingual branch, becomes inclosed in the same sheath with the nerve, and con- tinues connected with it altogether until the nerve has reached the posterior extremity of the submaxillary gland : at that point the chorda tympani divides into two parts, one of which is despatched to the submaxillary gan- glion, and the other continued along with the lingual branch. By somef it is stated that it separates from the nerve at the ganglion, and is altogether ununited to it; this, however, is incorrect. During its descent in company with the lingual branch there may be observed, upon particular examination of the conjoined trunk, a communication and identification be- tween the nervous matter of the two nerves. Originally the chorda tympani was regarded as either a recurrent filament of the lingual branch of the fifth or a branch of the portio dura : afterwards the opinion was adopted that it was not a branch of the portio dura, but the cranial superficial petrous branch of the Vidian nerve, which, instead of uniting and being iden- tified with the portio dura, descended through the aqueduct merely in apposition with it or within the same sheath, separated from it again before the nerve escaped from the aqueduct, and constituted the chorda tympani. This view * Bock, Meckel junior, Cloquet. t Cloquet. of the nature of the chord, suggested first, as it would appear, by J. Hunter, has been advo- cated also by Cloquet and Hirzel, and is at present entertained by many in this country at least; it has been objected to by Arnold, and another has been advanced by him from obser- vations made upon the calf and the human subject. Hunter’s account of the connection of the nerves is as follows : “ This nerve com- posed of portio dura and the branch of the fifth pair sends off, in the adult, the chorda tympani before its exit from the skull, and in the foetus, immediately after. The termination of the branch called chorda tympani I shall not de- scribe, yet I am almost certain it is not a branch of the seventh pair of nerves, but the last-described branch from the fifth pair,” i. e. the Vidian, “ for I think I have been able to separate this branch from the portio dura, and have found it lead to the chorda tympani ; per- haps is continued into it ; but this is a point very difficult to determine, as the portio dura is a compact nerve, and not so fasciculated as some others are.”* According to Arnold, nei- ther of the previous opinions is correct ; but the petrous nerve anastomoses with filaments of the facial nerve, principally the external, with which it forms a gangliform swelling at the place at which the nerve receives it ; and the branch which forms the corda tympani arises from the gangliform swelling of the facial nerve, and holds in an intimate manner to the petrous nerve; however it is not to be consi- dered a continuation of the latter : it is united, during its course, to the facial nerve by several filaments, and consequently the chorda tympani ought to be regarded neither as a branch of the facial nerve nor as a continuation of the petrous nerve, but as one composed of both.j- Cru- veilhierf maintains that the chorda tympani is not a prolongation of the Vidian nerve, but he assigns no reason for his opinion. The ques- tion at issue probably cannot be decided from the human subject: the impediment opposed to its satisfactory determination by the density of the facial nerve, as admitted by Hunter, and by the manner in which the facial and the Vidian nerves are in it blended together at their junction, will hardly permit the point being accurately ascertained ; but the same diffi- culty does not exist in other animals, and if the disposition of the Vidian nerve at its junction with the facial be examined, in the horse e.g., no doubt will remain that, i. the Vidian nerve certainly does not run simply in apposition with the facial nerve, and, 2. the chorda tympani is certainly not a mere conti- nuation of the Vidian nerve. In the horse the facial nerve is much less dense, and more easily analyzed than in man, and at the point of junc- tion with the Vidian its filaments are so free and so loosely connected, that little more is re- quired than to open the packet without violence in order to display satisfactorily the disposition of the Vidian at its junction with the facial : the * Animal (Economy, p. 267. t Journ. Coinpl. t. xxiv. p. 339, 341. | Anatomie Descriptive. FIFTH PAIR OF NF.RVES. 297 Vidian passes into the interior of the packet, crossing its fasciculi nearly at right angles, but rather in a reflex direction, and then spreads out and breaks up into a number of very delicate fila- ments with which cmeritious matter is inter- mixed, and thus a ganglionic structure is pro- duced, which is in some instances more mani- fest than in others, and is at the same time connected with fasciculi of the facial nerve. The filaments into which the Vidian separates can be followed in both directions, some re- trograde, and some along with the facial : the former appear to pass partly to the auditory nerve, as stated by Arnold, and partly to the facial between the point at which the Vidian joins it and the brain : they can be rent from the one into the other, and indeed look more like filaments from the facial to the Vidian than from the latter to the former. The latter fila- ments of the Vidian are dispersed among the fasciculi of the facial, with which they become united, and can be followed by means of a careful dissection for some distance : their number the writer is not prepared to state : the fasciculus of the facial from which the chorda tympani more particularly arises, appears deci- dedly to receive one or it may be more. Fur- ther, the chorda tympani does not arise by a single root, but is formed by two or three de- rived from different parts of the facial. The opinion that the chorda tympani is a continu- ation of the Vidian nerve appears, therefore, to the writer altogether unfounded, and while he admits that the conclusion of Arnold may proba- bly be well-founded, with regard to its compound nature, he yet must dissent from the opinion that the branch which forms it arises immediately from the gangliform swelling of the facial • the fasciculus, from which its principal root pro- ceeds, existing distinctly upon both sides of, and consequently not arising from the swelling, however it may receive an accession from, or be affected by its connection with this part. The author cannot refrain from regarding the chord as a branch of the facial nerve in the same sense with any other branch arising within the limits of the influence of the Vidian nerve. Magendie maintains that the chord is a continuation of the Vidian, because the section of the fifth nerve itself deprives the ear of all sensibility, but whatever part the chord may play in the sensi- bility of the ear, and it is doubtful that it plays any, the result of the experiment will be easily explained by the doctrine of Eschricht, that the facial nerve owes its sensibility to the fifth nerve, the division of which must in such case influence through the Vidian nerve any branch of the facial arising within the range of its in- fluence. After the junction of the chorda tympani with the lingual branch, the latter gives at times a small branch to the internal pterygoid mus- cle : during its descent along the ramus of the jaw, it also gives filaments to the arches of the palate, to the mucous membrane of the cheek, and to the gum of the lower jaw. While the nerve is situate between the mucous membrane of the mouth and the submaxillary gland, it is connected by means of two, three, or four fila- ments with the submaxillary ganglion. This ganglion is a small reddish body resembling the spheno-palatine ganglion in size, colour, and consistence, situate above the posterior extre- mity of the submaxillary gland, and connected superiorly with the lingual branch by the fila- ments mentioned ; inferiorly there arises from it a considerable number of very delicate nerves, which descend through the divisions of the gland, anastomose with each other, and are distributed for the most part to the substance of the gland ; one of them descends upon the hyoglossus, anastomoses with a filament from the ninth, and enters into the genioglossus muscle, and another long one accompanies the duct of the gland. A filament of communi- cation also from the superior cervical ganglion of the sympathetic reaches the submaxillary ganglion by following the course of the facial artery, and is represented by Arnold. The filaments by which the ganglion is con- nected to the lingual branch, are, as has been stated, two, three, or four ; they are not attached to the nerve all together, but one or two some lines before the others, and they are remarkable for the circumstance, that the posterior descend forward, while the anterior descend backward ; on attentive examination it is found that the posterior are derived one from the chorda tym- pani, and the other from the lingual branch itself ; it also appears that the filament derived from the former source is but a part of the cord, the remainder being continued on with the trunk of the lingual, and again that the anterior filament or filaments, which descend backward to the ganglion, are continuations of the poste- rior, which, after having been connected to the ganglion, ascend forward from it again to the trunk of the nerve. The course of those fila- ments of connection is well described and re- presented by the elder Meckel, and a very accu- rate delineation of them is given by Treviranus and Arnold. To this connection probably it is, that we are to attribute the influence which impressions on the organs of taste, or even sounds exert upon the salivary apparatus ; let us, when hungry, only hear a sound associated in our minds, in any way, with the gratification of our appetite, and at once that apparatus is roused into activity. Next, while lying between the mylohyoid and the hyoglossus muscles, the lingual nerve sends off from its inferior side some branches, which descend upon the hyoglossus, and anastomose with filaments ascending from the ninth nerve. At the same time, from its superior side, it gives filaments ; some of which, the posterior, are distributed to the mucous membrane and to the gum of the lower jaw ; others, the ante- rior, to the sublingual gland, and by some of their ramifications to the membrane and the gum. Lastly, the nerve divides at the anterior margin of the hyoglossus into its lingual branches ; these are, at first, three, poste- rior, middle, and anterior ; they pass up- ward and forward, and divide, each into two or three branches, which altogether di- verge from the nerve, and are ranged in suc- cession from behind forward, along the line 298 FIFTH PAIR OF NERVES. of separation between the stylo-glossus and the genio-glossus ; they traverse the substance of the tongue toward its superior surface and mar- gin, and run along its inferior surface, above the mucous membrane, toward its extremity ; as they proceed they subdivide, and thus re- sults a great number of filaments, the course of which through the tongue is remarkable ; they appear not to terminate, any of them, in the substance of it, but they traverse it as long, slender, single filaments, unconnected with its structure until they approach its superior sur- face, when they break up into pencils (to adopt the phrase used) of still more delicate filaments, which may be followed into the mu- cous membrane ; the posterior filaments of the posterior branch insinuate themselves internal to the hyoglossus, and reach as far back as the foramen coecum ; the filaments of the anterior are distributed to the extremity of the tongue, and are continued between the under surface of it and the mucous membrane very near to the tip, the substance of which they then tra- verse in order to reach its superior aspect and margin : they thus supply the mucous mem- brane of the organ upon its superior and lateral parts, from the foramen coecum to its point. Ganglion of the fifth nerve ( Ganglion semilunare Gasseri). See fig. 140, 9. — The ganglion of the fifth nerve is a body of crescentic form, a cineritious colour, and firm consistence. It presents two surfaces, two margins, and two extremities : its surfaces are both slightly pro- minent, and are directed one upward, outward, and forward, the other downward, inward, and backward ; they are also, the former con- cave and the latter convex longitudinally, the ganglion being somewhat curved upon itself in the same direction : they are both for the most part adherent to the iaminaj of dura mater, which form the chamber m which the gan- glion is contained ; but it is not uncommon to find the arachnoid membrane prolonged beneath it, so that its inferior surface in such instances is free ; the superior corresponds to the cranial cavity in its middle fossa, being excluded from it only by the dura mater; the inferior rests, with the intervention of dura mater also, upon the petrous portion of the temporal bone, the great ala of the sphenoid, and against the outer side of the cavernous sinus. The margins of the ganglion are di- rected one forward and downward, the other backward and upward ; the anterior is convex, and to it are attached the three great trunks, which compose the ganglionic portion of the nerve in its third stage; the posterior is con- cave and presents through its entire length a deep groove, into which the fasciculi of the ganglionic packet of the nerve are received. The extremities are obtuse, and project beyond the packet at either side; they are situate re- latively, one superior, internal, and anterior to the other. When the ganglion is in situ, the chord of the arch which it forms is six or seven lines long ; Niemeyer has sometimes found it amount to from nine to ten its width * Dc origiue paris quinti nervorum cerebri mono- graphia, Hal®, 1812. is about two lines, and its thickness, according to the part, from half a line to a line. Its colour and appearance vary much according to the subject : the former is always of a cine- ritious tint of different degrees of intensity ; when the subject is wasted, flabby, or anasar- cous, it is pale or grey, while, if the subject have been robust and corpulent, it is of a deep brown colour : in the former case also a plexi- forrn arrangement is more perceptible, whereas in the latter the ganglion seems composed of two concentric arcs, an anterior of lighter colour and manifestly plexiform character, and a posterior of very deep colour and apparently homogeneous indeterminate texture, devoid al- together of the plexiform appearance. A particular inquiry into the structure and probable function of the ganglion of the fifth nerve would involve that of the cerebro-spinal ganglia in general, and will be better post- poned to another occasion : it will suffice for the present to state that according to both Monro and Scarpa, they are composed in part of nervous chords, and in part by a soft grey or brown substance, which fills the intervals between the nervous filaments, and which according to the former resembles the cortical matter of the brain, while in the opinion of the latter it is a cellular texture filled by a matter, which varies in character according to the subject; thus he states that he has found it fatty in fat and watery in anasar- cous subjects. 2. That nervous filaments can be traced through them without interruption from the nerves situate above to those situate below the ganglion, which opinion is objected to by Niemeyer, who compares the connection of the former with the ganglion to that of the fcetal and maternal portions of the placenta ; but inspection suffices to satisfy one that this idea of Niemeyer is incorrect; for whether additional filaments be furnished or not by the ganglion, the continuity of filaments above and below it is evident even in the human subject, and is still more manifest in other animals : in the horse it is easily seen, par- ticularly after a section of the ganglion. The question whether the ganglion receives filaments from the sympathetic system has been a subject of dispute among anatomists. The elder Meckel* denies the existence of any filaments of connection between the sympa- thetic and the fifth nerve, while within the fibrous chamber or while situate by the cavern- ous sinus ; and others also, among whom are Eustachius, Haller, Albinus, and Morgagni, are of the same opinion ; but later investiga- tions have put it beyond doubt that such a communication does exist. Bockf has de- scribed filaments of the sympathetic united to the trunk of the fifth, before the formation of the Gasserian ganglion, and which join chiefly the fasciculi of the trunk, from which the ophthalmic nerve originates. And Arnold * Scriptores Neurologic! Minores, tom. i. t Beschreibung ties funften Nervenpaares und seiner Verbindung mit andern Nerven, vorziiglich mit dem Gangliensystem, 1817. FIFTH PAIR OF NERVES. 299 states “ that several very delicate filaments go from the carotid plexus to the semilunar gan- glion, particularly to the first and third branches of the nerve, and upon those points the gan- glionic matter is accumulated in greater abun- dance.”* Besides this connection between the sympathetic and the ganglion, others exist between it and the branches of the ganglion. The ganglion appears to constitute an essen- tial part of the fifth nerve throughout verte- brate animals, and to be uniformly present. It also presents in all the common character of being composed both of white and cineri- tious matter, though the comparative amount of the two constituents varies according to the class, the order, or even the individual. The presence of the two structures the author would regard as essential to the constitution of cerebro-spinal ganglia, and he would ex- clude from such those enlargements presented by nerves in certain situations, but from which cineritious matter appears to be absent. In Mammalia, Birds, and Reptiles, the fifth nerve is provided with a single ganglion, but in Fish and in both orders of that class it possesses for the most part two ganglia and two gan- glionic fasciculi; this however is not uniformly so, for in some, e. g. the lophius piscatorius, the ganglion is single. Vital Properties of the Fifth Pair of Nerves. — The discussion of the vital properties of the fifth nerve the writer pro- poses may be fitly arranged under the following heads: 1. its sensibility ; 2. its influence upon the faculties of sensation and volition, as also upon the ordinary sensibility of the parts to which it is distributed ; 3. its relation to the special senses and connection with the function of nutrition. 1. Sensibility.- — Numerous experiments per- formed and repeated by different physiologists have established the fact, that the fifth nerve enjoys exquisite sensibility. Bell appears to have been the first who directed attention particularly to this point: in his paper, pub- lished in the Philosophical Transactions for the year 1821, it is stated that, touching the su- perior maxillary branch of the fifth nerve, when exposed in an ass, “ gave acute pain.” In the first of Mayo’s experiments upon the fifth nerve, published in his Commentaries in 1822, it was also found that “ on pinching the opposite extremities” (those connected with the brain) “ of the infraorbital and inferior maxillary nerves in an ass, the animal struggled violently as at the moment of dividing the nerves: these latter results uniformly attend the division of the nerves above-mentioned, and of that branch of the fifth which joins the portio dura.”f Similar results were obtained by the writer last quoted from experiments of the same description upon the dog and the rabbit, and upon the pigeon, in regard to the first division of the fifth. lie also found “ that on pinching the gustatory nerves in living rabbits pain was evinced.” Magendie * Journ. Compl. tom. xxiv. t Commentaries, No. 1, p. 110. carried the inquiry farther, and in the fourth volume* of the Journal of Physiology, has related an experiment in which he exposed the fifth nerve within the cranium in the rabbit and dog, and found that the slightest touch produced signs of acute sensibility. From the preceding facts we infer that the ganglionic portion of the nerve at least is exquisitely sensitive, and that it is endowed with sen- sibility through its entire extent : further, the experiment of Magendie indicates that the sen- sibility of the nerve is proper and independent of the influence of other nerves, he having ex- perimented upon it at a point prior to its junction with any other. With regard to the non-ganglionic portion of the nerve, our data are at present altogether analogical : it is so situated that satisfactory experiments upon it separately are hardly to be accomplished, so that we are left to infer of it as probable what has been ascertained of other non-ganglionic nervous cords, viz. the anterior roots of the spinal nerves. The question in regard to the functions of the different portions of the spinal nerves has been inquired into by Magendie, by whom the endowments of both sets of roots have been tested in various modes, and who has inferred that the anterior roots are not devoid of sen- sibility, and if they be sensitive it is probable that the lesser packet of the fifth is sensitive also.f 2. Influence of the fifth nerve upon sensation and volition. — It is hardly necessary to remark that this point lias been the subject of much dispute, as well with regard to the fact itself as to the relative claims of the several inquirers to whom w'e are indebted for the investigation of the matter : however, physiologists now seem to be generally agreed that the nerve is one of compound function, being subservient to both the faculties of sensation and volition, and that the faculty of sensation is dependent upon its ganglionic, that of voluntary motion upon its non-ganglionic portion, and that it thus resembles the spinal nerves. That the nerve is one of compound function, and sub- servient to the two faculties, was announced by Bell in the paper already alluded to. He there distinguishes the nerves into two classes ; one original and symmetrical, the other super- added and irregular. To the former class he refers the spinal nerves, the suboccipital, and the fifth nerve, and assigns to them the fol- lowing characters, namely, they have all double origins ; they have all ganglia on one of their roots; they go out laterally to certain divisions of the body ; they do not interfere to unite the divisions of the frame; they are all mus- cular nerves, ordering the voluntary motions of the frame ; they are all exquisitely sensible, and the source of the common sensibility of the surfaces of the body : to it he refers the nerves of the spine, the suboccipital, and the fifth nerve. \ It has been already stated that * P. 314. t Journal de Physiologic, t. ii. p. 368. X Philosophical Transactions, 1821, p. 404. 300 FIFTH FAIR he had ascertained by experiment that the fifth nerve was exquisitely sensitive ; that it is the source of the sensibility of the parts to which it is distributed, he has also determined, for in allusion to the fifth he says, “ if the nerve of this original class be divided, the skin and common substance is deprived of sensibility;”* and “ by an experiment made on the 16th of March, it was found that, on cutting the infra-orbitary branch of the fifth on the left side, the sensibility of that side was completely destroyed.” -j- The experiments of Bell were repeated by Magendie, and a similar result, so far as regards the sentient properties of the fifth, obtained, as mentioned in the Journal de Physiologie, Octobre 1821. A similar result has been obtained also by Mayo in his experiments upon the fifth nerve, as detailed in his Commentaries for August 1822, more than a year after the publication of Bell’s paper. In his first experiment the infra-orbital and inferior maxillary branches were divided on either side in an ass, where they emerge from their canals, and the sensibility of the lips seemed to be destroyed : and, in a second experiment, the frontal nerve was divided on one side of the forehead of an ass, when the neighbouring surface appeared to lose its sen- sibility : the same effect was produced by the division of that branch of the fifth which joins the portio dura, inasmuch as the cheek loses sensation upon its division. From these ex- periments Mayo concluded that the facial branches of the fifth are nerves of sensation. The experiments upon the influence of the nerve on sensation have been carried still further by Magendie ; he divided the nerves within the cranium, where they lie against the cavernous sinus, and also between the pons Varolii and the petrous portion of the temporal bone, and in both instances he obtained the same result with regard to the sensibility of the parts to which the nerves are distributed, viz. total loss of sensibility on one or both sides of the face, according as one or both nerves were divided ; this extended not only to the integuments as in the former trials, but also to the lining membrane of the nostrils, to the conjunctiva, to the tongue and the interior of the mouth. The effect upon the nostril was so remarkable that the most active effluvia, even those of ammonia and acetic acid, pro- duced no impression upon it: in like manner neither piercing instruments nor ammonia ex- cited any sensation when applied to the con- junctiva, and the tongue was insensible to the action of sapid bodies at its anterior part. From such accumulated evidence but one conclusion can be drawn, viz. that the fifth is the nerve of general and tactile sensation to the face and its cavities, or to the parts upon which it is distributed. With regard to the influence of the fifth nerve upon volition, it has been already stated that Bell had announced it, as one of his regular or symmetrical nerves, to be “ a muscular * Philosophical Transactions, 1821, p. 405. t Ibicl. p. 417. OF NERVES. nerve ordering the voluntary motions.” This conclusion with regard to the fifth nerve he adopted in consequence of the following ex- periment, and of the result, which, as he conceived, he obtained from it. “ An ass being tied and thrown, the superior maxillary branch of the fifth nerve was exposed. Touching this nerve gave acute pain. It was divided, but no change took place in the motion of the nostril ; the cartilages continued to expand regularly in time with the other parts which combine in the act of respiration ; but the side of the lip was observed to hang low, and it was dragged to the other side. ITie same branch of the fifth was divided on the opposite side, and the animal let loose. He could no longer pick up his corn ; the power of elevating and projecting the lip, as in gathering food, was lost. To open the lips the animal pressed the mouth against the ground, and at length licked the oats from the ground with his tongue. The loss of motion of the lips in eating was so obvious, that it was thought a useless cruelty to cut the other branches of the fifth.” The inference here indicated is obvious, viz. that the motion of the lips in eating depends upon the superior maxillary branches of the fifth pair, so far at least as the distribution of those branches extends; and what he conceived he had thus established with regard to one branch he inferred analogically of the rest. The opinion that the fifth is a muscular nerve as well as one of sensibility Bell also maintains in later writings, and supports by additional experiments : thus, in his Exposition of the Natural System of the Nerves, published in 1824, he says, “ to confirm this opinion by experiment, the nerve of the fifth pair was exposed at its root, in an ass, the moment the animal was killed; and on irritating the nerve the muscles of the jaw acted, and the jaw was closed with a snap. On dividing the root of the nerve in a living animal, the jaw fell relaxed.” That the fifth is to a certain extent a nerve of voluntary motion is univer- sally admitted, but then a question arises of equal interest and delicacy ; of interest for its own nature, and of delicacy because of the personal claims and feelings involved in it. The question is, — it being admitted that the nerve is one of double function, — is such function enjoyed equally by all its branches and by both its portions ; and if otherwise, upon which do they severally depend ? From the extracts quoted it is evident that no dis- tinction in function between the different branches of the nerve was contemplated by Bell at the time the first was written, in 1821, and that he regarded them as being all alike nerves of compound function, — nerves both of voluntary motion and sensation; and, such being the case, either that he had not recognised a difference between the properties of the gan- glionic and the non-ganglionic portions of the nerve, or that he was then not aware of the peculiar distribution of the latter ; nor is any express information afforded us upon the subject in his earlier writings, or antecedent to 1823. The conclusion to which he had arrived with FIFTH PAIR OF NERVES. 301 regard to the nerve generally and its superior maxillary branch in particular, in the year 1821, has been stated ; in his communication to the Royal Society in 1823, he adds, “ all the nerves, without a single exception, which bestow sensibility from the top of the head to the toe have ganglia on their roots ; and those which have no ganglia are not nerves of sensation, but are for the purpose of or- dering the muscular frame:” from this, when applied to the fifth nerve, it might be inferred that sensation depended upon its ganglionic, and muscular action upon its non-ganglionic portion. But between the years 1821 and 1823 additions had been made by others to the knowledge of the functions of the fifth nerve which require notice. It is to be borne in mind that Bell inferred from his first ex- periment, published in 1821, that the superior maxillary nerve is one both of sensation and voluntary motion to the lips (see the preceding page): to this conclusion Magendie was the first to object, for in the Journal of Physiology for October of the same year (1821), he says, “ we have repeated these experiments along with Messrs. Shaw and Dupuy, and the result which we have obtained agrees perfectly with that which we have just related, with the ex- ception always of the influence of the section of the infra-orhital upon mastication , an in- fluence which I have never been able to perceive.” In August 1822 Mayo published, in his Com- mentaries, his “ experiments to determine the influence of the portio dura of the seventh, and of the facial branches of the fifth pair of nerves.” Those relating to the latter point, which have been already alluded to, are as follow. 1. The infra-orbital and inferior max- illary branches of the fifth were divided on either side, where they emerge from their re- spective canals ; the lips did not lose their tone or customary apposition to each other and to the teeth ; but their sensibility seemed destroyed : when oats were offered it, the animal pressed its lips against the vessel which contained the food, and finally raised the latter with its tongue and teeth. On pinching with a forceps the extremities nearest the lips of the divided nerves, no movement whatever of the lips ensued : on pinching the opposite extremities of the nerves, the animal struggled violently, as at the moment of dividing the nerves. Some days afterwards, though the animal did not raise its food with its lips, the latter seemed to be moved during mastica- tion by their own muscles.” 2. “ Some days after, the frontal nerve was divided on one side of the forehead of the same ass, when the neighbouring surface appeared to have lost sensation, but its muscles were not paralysed.” 4, 5, and 6. The branch of the fifth, that joins the portio dura, was divided on either side : in the fourth experi- ment, the under lip at first appeared to fall away from the teeth ; at times the lips were just closed : in the fifth and sixth, the under lip did not hang down, and no difference was observed between the action of the muscles of either side; but, he observes in a later publi- cation, “ the cheek loses sensation upon its division.” The results of these experiments, while they confirm fully the inference drawn by Bell with regard to the influence of the nerve over sensation, are altogether at variance with that of his experiment relating to the con- trol of the superior maxillary nerve over mus- cular motion, and are equally incompatible with the doctrine that the branches of the nerve, which were the subjects of experiment, have any direct connexion with muscular contrac- tion ; for while, on the one hand, the division of the nerves was followed by total loss of sensibility in the lips, on the other, the latter did not fall away either from each other or from the teeth, nor did irritation of the portions of the nerves connected with the lips excite any movement whatever of those parts, but they seemed afterwards to be moved during mastication by their own muscles. Mayo in- ferred accordingly from his experiments, “ that the frontal, infra-orbital, and inferior maxillary are nerves of sensation only, to which office that branch of the fifth which joins the portio dura probably contributes.” A circumstance in the first experiment doubtless seems at variance with the conclusion which Mayo has drawn, and demands consideration here, be- cause, unless unexplained, the fact is inconsis- tent with the inference. It has been stated that both in Bell’s and Mayo’s experiment, the animal ceased to take up its food with its lips after the division of the facial branches of tiie fifth, and from that circumstance chiefly the former appears to have inferred that the motions of the lips in eating depended on these nerves ; but the inference is objected to by Mayo as “ a theoretical account of the fact that the animal did not elevate and project its lip ; this fact,” he says, “ was noticed in my own expe- riments, but appeared to me from the first equally consistent with the hypothesis, that the lip had merely lost its sensibility, as with Mr. Bell’s explanation,” that it had lost its muscu- lar power. The fact may be obviously ex- plained by either of the two suppositions, and it is very remarkable that it should occur equally in one case as in the other. In the one, the muscles of the lips having been de- prived of tbeir power of voluntary contraction, the lips themselves cannot, of course, be made use of to take hold of an object ; and in the other, the animal not being made aware of the contact of the food in consequence of the loss of sensation, volition is not exerted, nor are the muscles called into action in order to take hold of it. To the latter cause it is attributed by Mayo, after the division of the branches of the fifth, and he confirms this view of its pro- duction by reference to the effect of ansesthesia in the human subject : “ in that disease the sensation of the extremities is wholly lost, while their muscular power remains. Now it is remarkable that in persons thus affected the muscles of the insensible part can only be exerted efficiently when another sense is em- ployed to guide them, and to supply the place of that which has been lost: a person afflicted with anaesthesia is described in a case quoted FIFTH PAIR OF NERVES. 302 by Dr. Yelloly, as liable on turning her eyes aside to drop glasses, plates, &c. which she held in safety so long as she looked at them ;” but that the absence of motion in the lips on the division of the fifth is due to the loss of sensation merely, and not of voluntary power, is positively proved by the effect of the division of the portio dura on the two sides, an experi- ment performed for the first time by Mayo : in it the voluntary motion of the lips is altogether lost, while sensation continues unaffected,* and hence the division of the fifth cannot deprive them of voluntary power, but only of sensation. The explanation of Mayo has been admitted and adopted by Bell himself in his “ Exposi- tion,” 1824, in which he has added to the detail of his experiment, as already related, the following note : “ what I attributed to the effect of the loss of motion by the division of the fifth, was in fact produced by loss of sen- sation ; ” and he corroborates this by the case of a gentleman in whom loss of sensation in the lip had been produced by extraction of a tooth. “ On putting a tumbler of water to his lips, he said, ‘ Why, you have given me a broken glass he thought that he put half a glass to his lips, because the lip had been de- prived of sensation in one half of its extent ; he retained the power of moving the lip, but not of feeling with the lip.” The last particu- lar noted is of great value, as demonstrating satisfactorily the separation of the two faculties, and, taken in connexion with anatomical con- siderations, renders it necessary to refer them to separate sources. It is manifest, then, that the circumstance of the animal not taking up the food by means of the lips, after the divi- sion of the fifth nerve, is not proof that it had lost the voluntary muscular power of them, but only that it did exert it, not having been, as it were, apprised of the necessity of doing so. It is also stated by Bell, that on the division of the nerve upon one side, “ the side of the lip was observed to hang low, and it was dragged to the other side.” This result also is objected to by Mayo, first, as contrary to his observation, for in his first experiment, after the division of the infra-orbital and inferior maxillary nerves, “ the lips did not lose their tone or customary apposition to each other and to the teeth;” and secondly, as being the effect of an extensive division of the muscular fibres, a cause quite adequate certainly to explain the fall of the lip, independent of the influence of the nerves. The difficulty, there- fore, which these circumstances appear at first to present is removed, and we are left to deter- * It will be satisfactory to those interested in this question to know, that the result of Mayo’s experiment has received full confirmation from those of others ; and first from Shaw, who has bestowed so much labour to establish the respiratory connexion of the portio dura. In the Medical and Physical Journal for December, 1822, he writes, “ immediately on cutting the nerve (the portio dura) on both sides, the lips became so paralyzed that the animal could no longer use them in raising its food.” The same result has been obtained by Mr. Broughton in experiments upon the horse, as detailed in the same Journal, June, 1823. mine the question by other means, and they are abundantly furnished from other sources. In the first place, the division of the nerves completely destroys the sensation of the parts to which they are distributed, without pro- ducing any effect upon the tone or contractile power of those parts, nor does irritation of the divided nerves excite muscular contractions. Secondly, were these nerves the source of the voluntary powers of the parts they supply, the division of every other nerve must fail to affect that power while the former remain entire; but Mayo, in several instances, divided the portio dura alone on both sides, and the result was, that “ the lips immediately fell away from the teeth, and hung flaccid,” and could not be used by the animal to take hold of food, and consequently had lost all volun- tary power ; while, “ when the extremity, nearest the lips, of either divided nerve was pinched, the muscles of the lips and nostrils on that side were convulsed.” Bell doubtless asserts that after the division of the portio dura nerve on one side, the animal “ ate without the slightest impediment;” to this Mayo objects that “ the experiment is inconclusive, because the nerve was not divided on both sides;” but in truth the experiment is quite conclusive, for though the animal can eat, and without impediment, his eating is far from perfect, and the imperfection is not the less obvious because confined to one side. When an animal which has had the portio dura divided upon one side only takes food, the lips remain motionless upon that side; and when it masticates, the lips continue in the same state, while on the other side they ac- tively co-operate, the food and saliva escaping on the side at which the nerve has been cut, and on the other being confined within the mouth. Now, if any action of the lips be voluntary, it is assuredly that by which they co-operate in the prehension and mastication of food ; and since no action of their muscles can be excited by irritation of the branches of the fifth nerve, while such action can be ex- cited by that of the portio dura, and all volun- tary action is destroyed by the division of that nerve, but one inference remains, that of Mayo already adverted to, viz. — that those branches of the fifth in question possess no influence upon the voluntary faculty of the muscles ; that they are exclusively sentient ; and that the contractile power of the muscles of the face, whether voluntary or involuntary, is to be attri- buted to another source. After what has been stated, we must admit that Mayo has been the first expressly to an- nounce that the function of these nerves is restricted to sensation. Beyond that, however, he has not gone, in reference to the question of sensation, in the publication alluded to, though it must be admitted that little remained to be added in order to complete the conclu- sion, that the ganglionic portion of the nerve is exclusively sentient. At the same time he inferred, “ from the preceding anatomical details,” — viz. their exclusive distribution to muscles, — “ that other branches of the third FIFTH PAIR OF NERVES. S03 division of the fifth are voluntary nerves to the pterygoid, the masseter, the temporal, and buccinator muscles.’7 Here again he has not reached the conclusion, though he has fallen but little short of it, and though, as in the former instance with regard to sensation, he has been the first to announce a restriction of the motor properties of the nerve to particular branches. The opinion expressed by Bell, in June 1823, has been already quoted, and from it we are bound to admit, that then at least he recognised the distinction at present acknow- ledged with reference to the appropriate function of the ganglionic and non-ganglionic portions. But in Mayo’s Commentaries for July 1823, the conclusion is for the first time expressly stated thus : — “ In the last paper of the preceding number, I mentioned that the division of the supra-orbital, infra-orbital, and inferior max- illary nerves, at the points where they emerge from their canals upon the face, produces loss of sensation, and of that alone, in the corres- ponding parts or the face. I have since, after the division of the fourth branch which emerges on the face, — namely, that which joins the portio dura, — ascertained that this branch like- wise is a nerve of sensation, inasmuch as the cheek loses sensation upon its division. I mentioned in addition that I concluded that other branches of the fifth nerve, from their distribution, are voluntary nerves. Now it is well known that the fifth nerve at its origin consists of two portions ; a larger part, which alone enters the Gasserian ganglion, and ano- ther smaller, which does not enter, but passes below the ganglion to join itself with the third division of the fifth. Towards the close of last summer 1 endeavoured to trace the final distribution of this small portion in the ass, and succeeded in making out that it furnishes those branches, which are distributed exclu- sively to muscles : I have since ascertained that in the human body precisely the same distribution exists. But the lemaining branches of the fifth are proved to be nerves of sensation ; thus it appears that the fifth nerve consists of two portions, one of which has no ganglion, and is a nerve of voluntary motion (and pro- bably of muscular sensation) ; and another, which passes through a ganglion, and furnishes branches, which are exclusively nerves of the special senses.” We return now to the question of the pro- perties of the non-ganglionic portion of the fifth nerve. It has been stated that Mayo was the first to announce the restriction of the voluntary influence of the fifth to certain branches, and that he was led to this conclu- sion from the observation of the fact that certain branches of the nerve are distributed exclusively to muscles. These muscles he has stated, in the first part of his Commentaries, to be the pterygoid, the masseter, the temporal, and buccinator; to which he has added, in his second part, the circumflexus palati ; by dis- section he ascertained that as well in man as in the ass, the lesser portion of the nerve “ fur- nishes those branches which are distributed ex- clusively to muscles;” and having already determined that the ganglionic portions of the nerve are destined exclusively to sensation, he came to the conclusion that the non-ganglionic portion is a nerve of voluntary motion. His first conclusion upon this point he himself states to have “ involved a trifling error : the pterygoid, masseter, and temporal muscles are indeed exclusively supplied by the fifth, and therefore, without doubt, the branches so dis- tributed are voluntary nerves, but the bucci- nator receives branches from the portio dura as well, and I have found subsequently, that pinching the branch of the fifth that perforates the muscle, produces no action in it : and in accordance with this view he writes in his Physiology,* “ I was led to observe that there were muscles which received no branches from any nerve but the fifth ; these muscles are the masseter, the temporal, the two pterygoids, and the circumflexus palati. After some care- ful dissection, I made out that the smaller fasciculus of the fifth is entirely consumed upon the supply of the muscles I have named.” The determination of the constitution and function of the buccal branch of the inferior maxillary nerve has become a matter of greater importance since the publication of Bell’s work on the Nervous System in 1830. In it he says, “ I am particular in re-stating this, because from time to time it has been reported that I had abandoned my original opinions, whereas every thing has tended to confirm them.” Now, it will be remembered that Bell’s original opinion is, that the muscles of the face are endowed with two powers, a volun- tary one, dependent on the fifth nerve, and an involuntary respiratory one, dependent on the portio dura ; also, that in the first instance he attributed the voluntary power of these muscles to the facial branches of the fifth, but that he had abandoned that idea, and acknowledged that what he had attributed to loss of motion was in fact due to loss of sensation. In the work adverted to he has taken new ground, and at the same time reiterates his first opinion with regard to the existence of the two distinct contractile powers in the muscles of the face, and attributes to the buccal nerve that influence over their voluntary motion which he had before referred to the infra-orbital, &c. Thus, “ but finding that the connexion between the motor root and the superior maxillary nerve proved to be only by cellular texture, and con- sidering the affirmation of M. Magendie and those who followed him, that the infra-orbitary branch had no influence upon the lips, I pro- secuted with more interest the ramus buccinalis labialis,”— the buccal nerve, — “ and nobody, I presume, will doubt that the distribution of this division confirms the notions drawn from the anatomy of the trunk, not only that the fifth nerve is the manducatory nerve as it belongs to the muscles of the jaws, but also that it is distributed to the muscles of the cheek and lips to bring them into correspondence with the motions of the jaws.” To the point at issue the writer has directed particular atten- * 1833, P. 261. 304 FIFTH PAIR OF NERVES. tion : he has made repeated dissections of the distribution of the lesser packet of the nerve both in the horse and in man, and after a care- ful examination, it appears to him that Mayo is essentially right, though the view given by him does not exactly agree with the arrange- ment of the nerve as found by the author either in the horse or in man. In the former the masseteric branch arises from the lesser packet by two fasciculi, one of which runs round the ganglionic portion of the third division of the nerve, and joins the other and larger fasciculus before it : the facial portion of the buccal nerve appears to the author to be purely gan- glionic, but the root of the nerve in part appears to be derived from the non-ganglionic portion and is not ; and in part may or may not be considered to proceed from it. It is entangled at its origin with fasciculi of that por- tion, more or fewer of the filaments which it derives from the ganglionic packet passing be- tween and even interlacing with fasciculi of the non-ganglionic ; but by a patient proceeding these may be traced to their proper source, and the nerve be extricated from this connexion. It is, however, difficult to accomplish it at times, at others it is sufficiently easy. Again, one or more branches of the non-ganglionic portion accompany the buccal nerve for some distance, connected to it more or less intimately, but apparently not enclosed within the same sheath, though communicating with the nerve by fila- ments from a ganglionic fasciculus and separa- ble without injury to either. These branches, however, separate from the nerve again for dis- tribution before it leaves the zygomatic fossa ; they may be considered, or not, to belong to the nerve, but they do not affect the question with regard to its facial portion ; and the author believes that the arrangement described is not uniform, the branches adverted to not always accompanying the buccal nerve. Again, on the one hand it has been already shewn that division of the portio dura on both sides deprives the facial muscles of all inde- pendent* contractile power, whether voluntary or involuntary ; and on the other, Mayo has found that irritation of the buccal nerve does not excite contraction in those muscles : the author has taken occasion several times to repeat the experiment of Mayo upon the latter nerve after it had emerged upon the face, and he has not succeeded in obtaining contraction of the facial muscles thereby, while the strug- gles of the animal, excited by the irritation of the nerve, proved it to be one of exquisite sen- sibility. It appears then to the author impos- sible to admit that the facial muscles either possess two contractile powers dependent on distinct nerves, or that they derive any volun- tary power from the fifth. It is extraordinary that Magendie, who was the first to detect the eixor into which Bell had fallen with regard to the influence of the infra- orbital nerve over the motions of the muscles * This expression has been used because the muscles may be still excited to contraction by irri- tation of the portion of the nerve connected with them. of the face, and has, according to his own report, divided the portio dura on animals, should, notwithstanding all that has been written upon the subject, have adopted the opinion that the muscles of the face are en- dowed with the two distinct faculties of motion, one of which is derived from the fifth. His view will be found at page 703-4, Anatomie des Systemes Nerveux, &c., and the opinion there expressed is implied in a note at page 191, Journal de Physiologie, t. x. In the former he says, “ Now Mr. Charles Bell in England and M. Magendie in France by cutting the facial nerve have paralyzed the respiratory motions of all the side of the face correspond- ing to the nerve cut. But the muscles which receive at once filaments from the facial nerve and from the fifth pair were paralyzed only in their action relative to respiration and to the expression of the physiognomy.” The influence of the fifth nerve upon the tac- tile sensibility of the parts with which it is con- nected has been discussed : its influence upon their ordinary sensibility also requires notice. From the preceding details it appears esta- blished that it is to the same nerve that this property also of the parts in general is due; but there is reason to believe that the nerve exerts a more extended control over this faculty than was at first supposed. At the commence- ment of the inquiries into the functions of the nerves of the face, the opinion generally held was that the facial nerve — portio dura of the seventh pair — was devoid of sensibility. Fur- ther observations, however, showed that this conclusion was erroneous, and that the insen- sibility to any injury done to the nerve in question manifested by the subjects of experi- ment, and from which the inference had been drawn, was only apparent, and to be referred to the constitution of the individual animal or of its species. The sensibility of the facial nerve having been established, a question arose, whether that property was independent and proper to it, or whether it was conferred by ! another ? Those who first observed the sensi- bility of the nerve adopted the former opinion ; but considerations entitled certainly to much weight led Eschricht to suspect that the facial nerve is not endowed with independent sensi- bility, and that the sensibility which is manifested when it is injured is conferred on it by the fifth nerve. In order to determine the question he performed a series of experiments in which he divided the fifth nerve within the cranium upon one side after having opened the cavity and removed so much of the corresponding hemi- sphere of the brain as was necessary for the accomplishment of his purpose : the facial nerve of the same side was then exposed, and its properties tested. The faculties of the animal are so little affected by the removal of the brain, that the result of the experiment. [ seems free from objection, while all influence of the fifth nerve upon the sensibility of the facial or other parts must be destroyed. In his first successful experiment irritation of the facial excited spasms of the lips, and also in- dications of suffering so decided that a doubt FIFTH PAIR OF NERVES. 305 could not be entertained : the fifth nerve had also been fairly divided : thus far, therefore, his conjecture was disproved. Pursuing his inquiry still further, he found in his next experiment that no indication whatever of pain was manifested by the animal on irritation of the facial on the side on which the fifth nerve had been cut ; but in two succeeding experi- ments he ascertained that while irritation of the nerve anterior to the meatus auditorius pro- duced no other effect but spasms of the nasal and labial muscles, when exerted posterior to that point it excited manifest evidence of suf- fering : this latter circumstance he accounts for by the communications of the posterior part of the facial with other sentient nerves besides the fifth, and he has come to the conclusion that the former nerve is not endowed with independent sensibility, but that it derives the property from the fifth and other sentient nerves : this ques- tion, however, requires further investigation.* Relation of the fif th pair of nerves to the special senses. — The organs of the special senses are in the higher classes and in the case of smell, sight, and hearing, each supplied with nerves from at least two sources. Besides the particular nerves, which are generally consi- dered to be the source or medium of tire spe- cial sense, they are furnished with branches from the fifth pair; and a question must, at the outset, be asked in regard to the two nerves derived from these different sources, as to which is to be considered the proper nerve of the peculiar sense enjoyed ? In connexion with the two separate nervous supplies, it is also to be observed that each organ enjoys two kinds of sensibility, viz. the special sensibility, through which sensations of the particular sense are received, and the general sensibility, in which the several organs of the body partici- pate, and which is the medium through which impressions of contact are conveyed. The exis- tence of the special sense, the coincidence of the particular nerve, the impairment or loss of the special function uniformly consequent upon the injury or destruction, whether by disease or otherwise, of that nerve ; and the community both of function and distribution, displayed by the nerve from which the organs of the senses are in common supplied, have led physiologists generally to the conclusion that in each case the particular nerve is the medium of the special sense, and that the fifth nerve confers upon the organs of the spe- cial senses general sensibility only. The con- clusion thus commonly adopted has been at different times called in question : thus Mery and Brunet, in 1697, denied to the nerves of the first pair the function of smell, and attri- * Eschricht, de functionibus nervorum faciei et olfactus organi, Hafn. 1825. [ The superficial tem- poral nerve doubtless contributes mainly to supply sensibility to the posterior twigs of the facial : but so much difficulty do some see in satisfactorily accounting for the sensibility of the portio dura, that they find it convenient to discover two roots of origin, and a ganglion on one, thus reducing it to the class of compound nerves. See Arnold, leones capitis nervorum ; also Gaedechens, nervi facialis physiologia et pathologia. — El).] VOL. II. buted this sense to the fifth nerve.* The ques- tion of the connexion between the fifth nerve and the special senses is one of much difficulty, and probably we are not as yet in possession of sufficient data from which to draw a positive conclusion upon it when viewed in all its bear- ings. It resolves itself into three: 1. how far the nerve may be concerned in the perception of special sensations in those cases in which nerves, considered to be specially intended for their perception, exist: 2. how far its co- operation or influence may be necessary to enable the special nerves to fulfil their func- tions: 3. how far it may be capable of taking the place of those special nerves, and of be- coming, under certain conditions, media of perception to sensations, for which, in other- cases, peculiar nerves are conferred. We shall review the relation of the nerve to the several senses in succession, bearing in mind the three points to which our attention is to be directed. That it is a medium of perception in the case of two senses, viz. touch and taste, is already so universally acknowledged that it is unneces- * sary to dwell upon the point. The importance of the fifth nerve in the three other senses of smell, sight, and hearing, has been advocated by several physiologists, and more particularly by Magendie, who ap- pears disposed to view the fifth nerve as the source or medium of all the three. Ilis appli- cation of this doctrine, however, has reference more particularly to the sense of smelling, upon which he has performed a series of expe- riments, of which the following is a summary: he destroyed entirely the olfactory nerves within the cranium, and he found the animal still sensible to strong odours, such as ammonia, acetic acid, essential oil of lavender. The sen- sibility of the interior of the nasal cavity had lost nothing of its energy ; the introduction of a stylet had the same effect as upon a dog which had not been touched. This experiment he performed several times, and always with the same results. He next divided the fifth nerves within the cranium, of course before they had given branches to the nostrils, and found all trace of the action of strong odours to disappear. He hence concluded that smell, in so far as pungent smells are con- cerned, is exercised by the branches of the fifth pair, and that the first is not concerned in the function. To this conclusion he himself starts the objection that the agents used are not odours, properly speaking, but chemical, pun- gent, irritating vapours, and that by the section of the fifth we destroy not the sense of smell, but only the sensibility of the membrane of the nose to these irritating vapours, and he admits the force of the objection with respect to some of the vapours alluded to ; but he denies that it will apply to the oil of lavender or that of Dippel, the effect of which in the experiments is the same. In order to remove the difficulty he destroyed the olfactory nerves of a dog of particularly fine nose, and then enclosing por- tions of food of various kinds in paper, he * See Jcmmal Complementaire, v. 20. X 306 FIFTH PAIR OF NERVES. presented them to the animal, and it always undid the paper and possessed itself of the food ; but. lie adds, “ I do not regard this ex- periment as satisfactory, because in other cir- cumstances it appeared to me to want smell to discover food which I put near him without his knowledge” (a son insu). However, the latter circumstance is overlooked by Magendie, and his conclusion is, “ une fois le nerf trifa- cial coupe, toute trace de sensibilite disparait, aucun corps odorant a distance on en contact, les corrosifs memes n’afifectent plus en aucune facon la pituitaire.”*' Doubtless this conclu- sion is qualified by another immediately suc- ceeding, “ that does not prove that the seat of smell is in the branches of the fifth pair; but it proves at least that the olfactory nerve has an indispensable need of the branches of the fifth pair to be able to enter into action ; that it is devoid of general sensibility, and that it can have only a special sensibility relative to odorous bodies. ”f The latter must be ad- mitted to come, if not quite, at least very near to the general opinion, but it is altogether at variance with the former, and one is rather at fault for the author’s precise meaning. Refe- rence to later writings, however, leaves no doubt upon that point. In the conjoint work of Desmoulins and Magendie (1825) upon the nervous system of the vertebrata, besides other similar passages, will be found the following: “ La cinquibme paire, par ses branches nasales dans les mammifbres, et par ses branches pro- pres a la caviffl pre-oculaire des trigonocephales et des serpents a sonnettes, est done l’organe de l’odorat.”! Notwithstanding the weight of Magendie’s authority, a careful review of the matter will not permit us to assent to this con- clusion, and compels us to avow not only that it is not proved, but that the premises justify a contrary one. In the first place it is not war- rantable to call the effluvia of ammonia or acetic acid odours : they are no more odours than the fumes of muriatic or nitric acid ; and, though aware of the objection, he still calls them odeurs fortes, and bases his inference upon their operation. But he says the objec- tion does not apply to oil of lavender or the animal oil of Dippel : this, however, is but an assumption at variance with fact; in the human subject these agents may act feebly upon the sensibility of the membrane of the nostrils, and may not appear to possess irritating properties; but this will not prove that they act similarly upon animals, whose organ of smell is more sensitive than that of man, and accordingly Dr. Eschricht,§ who combats the opinion of Magendie, has found that, on application to the nostrils of those animals upon which the experiments of Magendie have been performed, they produce all the same effects which am- monia or nitric acid does. In the second place his experiment of presenting food to a dog, whose olfactories had been destroyed, enclosed * Journal de Physiologie, t. iv. p. 306. t Ibid. j T. ii. p. 712. § Journal de Physiologie, t. vi. p. 350. in paper, and in which the animal undid the paper, upon his own showing not only does not justify his inference, but, so far as it reaches, proves the contrary. To establish his position the animal must have discovered the food by smell, without knowing that it was in the paper ; but it is manifest, from Magendie’s own relation, that when the animal undid the paper, it knew, or was led by some circum- stance to expect the food to be in it; but that when it was not already aware or in expecta- tion that the food was near it, it did not dis- cover it. To the writer it seems that the na- tural inference from the experiment, as related, is that the animal’s proper sense of smell de- pended upon the olfactory nerves, inasmuch as it did not display fair evidence of its presence after their destruction, and that the sensibility displayed by the membrane of the nostrils after the destruction of these nerves, and dependent upon the fifth, has reference only to those im- pressions which are objects of tactile or general sensation, but not of the special sense. At the same time, however, that we express our dissent from Magendie with regard to the nervous connexion of the proper sense of smell, it must be admitted that his researches posi- tively indicate a distinction between the media of perception in the case of different agents operating on the olfactory organ, which it has been too much the habit to regard as pro- ducing their impressions all through the olfac- tory nerves : they have gone a considerable way in demonstrating the separation of those media; a result which is made complete by the conti- nuance of the simple sense after the loss of the influence of the fifth nerve consequent upon disease : further, they indicate that sensations derived through the organ of smell are less simple than they are usually accounted ; that they may be, and probably are for the most part, compound, resulting from the combina- tion of impressions made upon the two senses thus shewn to be enjoyed by the organ. Magendie’s view has been adopted, and an endeavour made to corroborate and establish it by Desmoulins in ‘ Reflexions’ upon a case communicated by Beclard, and published in the fifth volume of the Journal of Physiology. The case is that of a patient, in whom the olfactory nerves and their bulbs were de- stroyed by the growth of a tubercular disease from the anterior lobes of the brain ; “ yet he took snuff with pleasure, appeared to distin- guish its different qualities, and was affected disagreeably by the smell of the suppuration of an abscess with which one of his neighbours was afflicted.” From this case, from that of Serres, related elsewhere, and the experiments of Magendie viewed in connexion, Desmoulins has adopted the opinion that “ the nerves and lobes called olfactory are alien to the sense of smell, or at all events co-operate so little in it, that the sense continues to be exerted without them ; that, on the contrary, this sense resides essentially in the branches of the fifth pair, which are distributed to the nostrils.” Serres’ case has been discussed elsewhere ; that of Beclard appears at first unanswerable ; but FIFTH PAIR OF NERVES. 307 how will it appear after the qualification by which it is followed has been perused ? “ I owe it to truth,” he says, “ to add that these last statements were not collected till after the dissection, and that they were gathered from the patients of the ward.” Such an admission manifestly destroys the value of the case : evi- dence obtained only after the individual’s death, so little marked as during his lifetime to have been overlooked, and relating to a question at once so obscure and delicate, can hardly fail to be imperfect ; but admitting that the patient did relish and distinguish between different kinds of snuff, and that he was disagreeably affected by his neighbour’s ailment, what then? The chief property of common, if not of every snuff, is pungency and not odour, and the per- ception of pungency is not the function of the olfactory nerve ; and one may be as disagree- ably affected by a disgusting sight as by a dis- gusting smell, and the patients of the ward not make any distinction between the senses af- fected, until taught by the inquiries made that it must have been that of smell. And if the case just quoted prove the existence in the organ of smell of a sensibility to the impres- sion of volatile agents independent of the ol- factory, and conferred by the fifth nerve, the existence of another equally independent of the latter is satisfactorily established by the continuance of smell in those cases in which the faculty conferred by the fifth nerve has been lost through disease. This may be seen from reference to the case furnished by Beclard, and advanced by the very advocates of Magendie’s doctrine in support of it; but the fact is still more strongly established by the case some time since published by Mr. Bishop, in which, though the fifth nerve was completely destroyed by the pressure of a tumour within the cra- nium, and both the ordinary and tactile sensi- bility of the same side of the face and its cavi- ties was in consequence altogether lost, the sense of smell continued unimpaired. In a case of disease of the fifth nerve which the writer has witnessed, the patient did acknow- ledge the perception of certain odoriferous agents; but judging from it alone, he could not say that smell was not impaired ; on the contrary it seemed very much so, inasmuch as the patient denied at first any perception of the impression of several agents accounted odorous, and when he did say that he smelt these, it was not of himself, nor until he had been particularly questioned, and then he said it was ‘ up in his head’ that he felt the sensa- tion, and positive must take precedence of nega- tive evidence. Further, it is very likely that in the case of sensations, themselves neither dis- agreeable nor acute, the vividness of which may depend very much upon association with other and more acute ones, the former may be disregarded where the latter have been lost, and hence the rashness of inferring that brutes have lost certain faculties, because in the course of experiments they do not by the exercise of these give evidence of their existence. The fact of the absence of olfactory nerves in the Cetacea as established by Cuvier, has also led some to the conclusion that the proper faculty of smell may be capable of being transferred at least to the fifth ; but until the faculty has been proved to exist in such case, the inference is manifestly not warranted by the premises. It appears then that there is a distinct per- ceptive faculty enjoyed by the nostrils, inde- pendent of the fifth and dependent on the olfactory nerve; that we possess no positive evidence of the latter nerves being in any case the media by which this peculiar perception is recognized, but that they serve for the recogni- tion only of impressions of contact, pungency, or irritation. 2. Relation of the fifth- nerves to vision. — That in all animals having at once the faculty of vision and an optic nerve, the latter is in- dispensably necessary to the exercise of the former cannot be denied : — disease or division of the nerve is uniformly attended by loss of the function ; but some circumstances coun- tenance the opinion that the fifth nerve pos- sesses a more important connection with vision than may at first appear. 1. Injury of the frontal and certain other branches of the fifth nerve has been long accounted among the causes of amaurosis. 2. Magendie has found that “ on division of the two ‘ fifth ’ nerves upon an animal it seems blind.” 3. The fact which countenances most strongly the opinion that the fifth nerve is concerned directly in the function of vision is derived from com- parative anatomy. It has been stated that in certain animals a special optic nerve is wanting, and the ocular nerve is derived from the fifth pair. Of this it appears universally admitted that the proteus anguinus is an instance ; its eyes are situate immediately beneath the epi- dermis, which is transparent* in front of them ; the optic nerve is wanting, f and the only nerve received by the eye is a branch of the second division of the fifth.;); Whatever vision, there- fore, may be enjoyed by this animal, and according to Carus§ it is considerable, must be exerted through the medium of the fifth nerve. Among the mammalia also are several animals which appear to be in the same, or nearly the same state ; but anatomists are not agreed on the point : the abseuce of a special optic nerve in the mole was announced by Zinn,|| who shewed that its place was taken by a branch of the fifth. Carus and Treviranus, however, maintain that the optic does exist in the animal, but that it is very minute, grey, and capillary ; that in the same proportion the fifth nerve is large, and that its second division at its exit from the cranium gives off a branch, which enters the globe of the eye, and according to the former concurs in forming the retina.^j Serres again positively denies the existence of the optic nerve in the mole, and maintains that these anatomists are mistaken ; he states that he has sought the * Sevres. t Treviranus, Serres. X Ibid. § Comparative Anatomy. j| De differentia fabrics oculi humani et brutorum. tT Journal Complementaire, vol. xv. X 2 308 FIFTH PAIR. OF NERVES. nerve with the greatest care in thirty or forty of these animals, and never succeeded in finding it; and also in confirmation thereof that the optic foramen is wanting in the sphenoid bone. According to him several other of the mammalia are similarly constituted, viz. the mus typhlus, the mus capensis, the clnysochlore, and the sorex araneus. Of these the mole, the mus capensis, and the sorex arensis decidedly enjoy vision, the first ac- cording to the observations of Geoffroy St. Hilaire and Cuvier; the second according to those of Delalande, and the third according to Serres himself ; and if his view of the anatomical disposition of their ocular nerve be correct, the fifth nerve must in them also take the place of the optic and serve as the medium of sight. Treviranus, though he maintains the existence of a special nerve in the mole, yet says, from the disproportion of the optic and the ocular branch of the fifth, that in that animal the latter ought or must have to fulfil in vision more important functions than the optic nerve.* When to these facts we add the view of the nervous connections of the senses in invertebrate animals advocated by Treviranus, viz. that the nerves of the senses in them are all branches of the fifth pair, the general proposition seems sufficiently probable, viz. that the fifth nerve is capable of acting as a medium of perception to impressions of light. But on the one hand, until it be proved what the exact nature of the optic faculty is which animals devoid of a special optic nerve possess, the question must be held to be undecided. It may be that the faculty is different in the two cases ; that where the special nerve is absent, the faculty may amount, as suggested by Treviranus, to no more than a mere perception of light, and that the im- pression is then not visual, but only one of ordinary sensibility. Such a distinction, in the sense in which that term is understood in reference to the higher animals, is easily conceived, and indeed is demonstrable from the influence of light upon an inflamed or irritable eye, and if such a distinction do naturally exist, the apparent anomaly presented by animals being sensible of light and seeming to enjoy vision without a special optic nerve will be removed, while such a faculty may suffice fully for the condition of the animal. Again, the evidence in favour of the opinion that the fifth is directly concerned in vision where a special nerve exists, seems altogether insufficient. In the first place, though in- juries involving the frontal or other branches of the fifth nerve may induce amaurosis, it remains to be proved that the injury of the nerve is the cause of the disease, and that this did not rather arise from the effect of the injury upon other parts concerned in vision; a view which is greatly confirmed by the fact that the mere section of the nerve has not been found to occasion any such affection of vision. In the second place the experiments of Magendie are far from satisfactory. In * Ibid. vol. xv. p. 210. order to determine the influence of the fifth nerve upon vision, he performed the following experiments, from which he inferred that the section of the fifth nerve destroys sight without abolishing entirely all sensibility of the eye for light, and suggests in explanation either that the fifth is the medium of perception, or that it is necessary to enable the optic to act. After having divided the fifth pair on one side in rabbits, he threw suddenly upon the eye the light of a wax candle, and no effect was produced ; the same being tried upon the sound eye, the only effect produced was move- ments of the iris. Under the impression that this was not sufficiently intense, he tried that of a powerful lamp, but, even with the as- sistance of a lens, the result was the same. He then tried the experiment with solar light, and by making the eye pass suddenly from the shade to the direct light of the sun, an impression was produced and the animal im- mediately closed its eyelids. Such data cannot be admitted as sufficient to justify the inference that vision is destroyed by the section of the fifth nerve. In the first place it is to be recollected that the experiment was made upon rabbits, in which Magendie has elsewhere told 11s that section of the fifth nerve produces strong con- traction of the iris, consequently great dimi- nution of the size of the pupil : and of what value, then, is the result that, under the in- fluence of the light of a candle or a lamp, an impression was not made sufficiently powerful to cause the animal to give evidence of it ? In the second place the animal did, under all the disadvantages, give sufficient evidence that its vision was not destroyed ; there is, therefore, no reason for the conclusion drawn from the experiment related. On the other hand, Mayo has found that the fifth nerve may be divided within the cranium in the cat and pigeon, and vision continue unaffected ; which circumstance shows that the apparent loss of vision in the rabbit W’as owing to the great contraction of the pupil, while according to Magendie’s statement there does not remain any trace whatever of sensi- bdity to the impression of light in the eye after the section of the optic nerve. We must, then, conclude that the optic nerve is the proper medium of perception to visual im- pressions, and that the co-operation of the fifth nerve is not even necessary to enable the optic nerve to fulfil its function. As the instrument of the general sensibility of the structures of the eye, however, the fifth nerve may be the channel through which impressions not visual, though perhaps excited by an agent of vision, viz. light, may be conveyed. The conclusion thus drawn from experimental physiology is fully confirmed in man by the history of those cases in which the influence of the fifth nerve has been lost from disease : of these two have been adduced by Bell in the Philosophical Transactions for 1823, one from the observation of Mr. Crampton, the other from that of Dr. Macmichael, in which the surface of the eye was totally insensible, whilst vision was entire ; and another, still FIFTH PAIR OF NERVES. 309 more remarkable, has been reported by Mr. Bishop,* * * § in which the functions of the fifth nerve seemed altogether obliterated by the pressure of a diseased growth within the cranium, and yet the patient saw distinctly to the last, the only derangement which oc- curred in the function of vision being the loss of the power of distinguishing colours, which appears sufficiently accounted for by a certain degree of pressure exerted by the tumour upon the optic nerve. Magendie endeavours to support his views upon this and other points connected with the properties of the nerve by reference to a case reported by Serres, which appears very inadequate, and will be discussed by-and-bye. Influence of the fifth nerve on hearing. — The great affinity between the sense of hearing and that of touch renders it more easy to conceive how hearing might be excited through the medium of the fifth nerve. As we have seen that the ocular nerve in certain animals is a branch of the fifth nerve, so is the auditory. Among the cartilaginous fishes there are several instances in which this occurs. The origin of the auditory nerve from the fifth in fishes was first announced by Scarpa, f and by him sup- posed to apply to fish generally. This view is combated by Treviranus : + it is admitted in part by Serres ; he states that in osseous fishes the auditory nerve is united at its in- sertion with the fifth; in cartilaginous fishes, that the auditory is sometimes confounded with the fifth, sometimes separated distinctly enough, as in the raia clavata. From his own observations the writer would say, that in the bony fishes the two nerves cannot be said to be united or to arise the one from the other, but only to have a common superficial attach- ment to the medulla oblongata; and from the analogy of the same nerves in the higher classes of animals, he would not admit, without further proof, a common superficial attachment as establishing identity of ultimate connection with the encephalon. As to the cartilaginous fishes, it appears to him that Serres has fallen into an error with regard to the connection of the auditory nerve. It appears to the writer that the fifth and the auditory are con- founded in the raia clavata as plainly as in any other individual of the class ; the posterior ganglionic fasciculus of the fifth and the auditory nerve form one trunk for a distance of some lines after leaving the medulla ob- longata ; they are at all events enclosed within the same sheath : § but whether they are to be regarded as branches of a common trunk or not, it is difficult to decide. The weight of naalogy is certainly opposed to a conclusion * Medical Gazette, vol. xvii. t De Auditu et Olfactu. t Journ. Compl. § Serres seems to have overlooked the fact that there exist two ganglionic fasciculi in the raia clavata ; that he has assumed the anterior fasci- culus to be the fifth, and described the posterior, with which the auditory is connected, as the auditory and facial jierves : the error will be manifest upon tracing the distribution of the fasciculus. in the affirmative ; and, though this were ad- mitted, a difference between the auditory and the other branches of the fifth (as supposed) must still be admitted, inasmuch as the auditory separates from the nerve before the occurrence of the ganglion, and has not itself a ganglion. On the other hand the auditory may be se- parated from the rest of the nerve, after the division of the common investing membrane, with little or no laceration of fibres. Still it may be asked why, if they be distinct nerves, are they united into one trunk 1 The opinion that the fifth nerve holds an important in- fluence over the sense of hearing derives support from the circumstance, that in most, if not all, the cases of disease of the nerve, the sense of hearing becomes impaired, though not obliterated. The last question proposed to be considered with reference to the functions of the fifth nerve is its connection with nutrition. The opinion that the nerve controls the nutrition of the parts which it supplies has been advocated by Magendie, more particularly with regard to the eye. It has been already stated that we are indebted to this writer for information in regard to results of the division of the entire trunk of the nerve within the cranium. Of these the most prominent is the entire loss of sensibility on the same side of the face, and in regard to the eye especially, loss of sensibility in the conjunc- tiva, upon which the most irritating chemical agents then produce no impression. These immediate effects of the section were followed by others not less remarkable : on the next day the sound eye was found inflamed by the ammonia, which had been applied to it, while the other presented no trace of inflam- mation. Other changes, however, supervene. The cornea of the eye of the side on which the section is made, twenty-four hours after- wards begins to become opaque; after seventy- two it is much more so ; and five or six days after it is as white as alabaster. On the second day the conjunctiva becomes red, inflames, and secretes a puriform matter. About the second day the iris also becomes red and in- flames, and false membranes are formed upon its surface. Finally the cornea ulcerates, the humours of the eye escape, and the globe contracts into a small tubercle. In endeavouring to ascertain the cause of these changes, Ma- gendie, on the supposition that they might be owing either to the continued exposure of the eye to the air or to the want of the lachrymal secretion, divided the portio dura in one rabbit, the effect of which is to destroy the power of closing the eyelids ; and from others he cut out the lachrymal gland; but in neither case did opacity of the cornea suc- ceed. The sequence of the effects mentioned after the section of the nerve might naturally lead us to infer that the loss of nervous in- fluence gives rise to them. But such is not the inference drawn by Magendie, nor indeed can it be admitted : absence or subtraction of an influence cannot be directly the cause of an alteration in the condition of an object 310 FIFTH PAIR OF NERVES. otherwise than by allowing it to come or return to a state from which it is preserved by the presence of the influence; and there is no good reason, either theoretical or experimental, for believing that the state induced in the case under consideration is one in which the eye would necessarily be, which, in fact, would be natural to the organ but for the restraining influence exerted through the fifth nerve. It is easy to imagine that the absence of such an influence should render a part slow to take on any vital action ; though even this, until proved, is an assumption — an assumption which we are induced to adopt from the fre- quency with which sensation and pain are found associated with the establishment of cer- tain vital processes, more particularly inflam- mation, but which is, on the other hand, con- tradicted by the readiness with which inflam- mation and its consequences are excited in parts whose nervous faculties are impaired or destroyed by agencies which make little or no impression when those faculties are retained, and which must be demonstrated before admit- ted, since it is manifest from the occurrence of that process after the destruction of all trans- mitted influence at least, that the principle — the main-spring of it must reside elsewhere ; and hence that, if in the natural state the nerve influence the process at all by means of such a property, it can be only in the character of a secondary and controlling power. It does, however, seem proved by the result of Magen- die’s experiment, that the interruption of the influence did retard the inflammatory process, inasmuch as the eye, on the side of the undi- vided nerve, was very actively inflamed the day after the application of ammonia to it, whilst the other eye did not present any trace of in- flammation ; a circumstance by the way diffi- cult, if not impossible, to reconcile with the doctrine that the process of inflammation is directly influenced in either way, whether posi- tively or negatively, by the power of the nerve; and further, that the division of the nerve should diminish the vital powers of the eye, and thereby render it less able to resist the effects which inflammatory action tends to pro- duce. But indeed there does not appear any reason for admitting that the alterations which took place in the condition of the eye were produced directly by the loss of nervous influ- ence. Having, as he conceived, disproved, by the experiment related, the idea that the alte- rations were owing to the continued exposure of the eye to the air, or to the want of the lachrymal secretion, — the only other causes which appear to have occurred to him, — Ma- gendie arrived at a conclusion the opposite of that just mentioned, and adopted the opinion that the phenomena “ depend upon an influ- ence purely nervous”* exerted by the fifth nerve upon the eye, — “ an influence independent of the connection of the nerve with the spinal mar- row,”!-— an influence “ proper to the nerve, * Anatomie des Systemes nerveux, &c. t. ii. p. 716. t Journal dc Physiologic, p. 304. which has not its source in the cerehro-spinal system, and which is even the more energetic, the farther we remove from that system to a certain distance,” of which the following is his proof. “ Alterations of nutrition in the eye are the less complete, the less rapid, as we remove farther from the point of branching of the nerves of the fifth pair, and as we cut, within the cra- nium, the fasciculus of origin the nearer to its insertion ; finally, the section of the nerve on the margin of the fourth ventricle no longer produces any alteration in the state of the eye.” * In this view there are plainly two posi- tions advanced, viz. that the nerve does itself exert a proper and independent influence upon the nutrition of the eye, and that it is the sec- tion of the nerve which causes the exercise of that influence, or, to use his own words, which is the cause of the inflammation, &c. That the occurrence of the alterations in the eye, in the case in question, is not due to an influence exerted by the brain through the nerve, and that it must proceed from another cause, and that not dependent upon the connection be- tween them, is manifest, since it is consequent upon the interruption of that connection ; and therefore, if the nerve do possess the supposed influence, it must be a proper and independent one : but are we, therefore, to infer that the nerve does exert such an influence upon the organ ? It appears to the writer that we cannot : for can we suppose that the nerve is endowed with a property to be displayed expressly under cir- cumstances, which it is fair to say were not contemplated in the establishment of natural laws, viz. in cases of mutilation? or is it possi- ble that a separate influence can exist in the nerve and increase in energy in proportion as the nerve is curtailed ; for the nearer the section is made to the eye, the more remarkable are the effects ; or if any other proof that the nerve does not possess such an influence be wanting, can we suppose that it is possessed for the eye and not for the other parts to which the branches of the nerve are distributed ? Why does not inflammation forthwith assail the nostrils, the mouth, and cheeks upon the mere section of the nerve, f as well as the eye ? Manifestly be- * Op. cit. ibid. t It is stated by Professor Alison, Outlines of Physiology, p. 147, that inflammation, ulceration, and sloughing are produced sometimes on the mem- brane of the nose and on the gums by section of the fifth nerve, “ as was first ascertained by Magendie.” The only passages approaching at all to this state- ment, which the author has found in Magendie’s writings, are at page 181, Journal de Physiologie, t. iv, and page 717, Anatomie des Systemes Ner- veux, &c. Desmoulins et Magendie, t. ii. In the first he says, “ when a single nerve is cut, there appear alterations in the nostrils, the mouth, the surface of the tongue on that side ; the half of the tongue becomes whitish, its epidermis is thickened, the gums quit the teeth ; the alimentary matters sink into the intervals which are formed ; probably because the animals having no longer their atten- tion attracted by the sensation of the tendency of the matters to pass between the teeth and the gums, push them thither without perceiving it;’ and in the second, “ a part of the broken food re- mains on that side, between the teeth and the check, and its contact terminates hy ulcerating the FIFTH PAIR OF NERVES. 311 cause no such influence exists; and indeed the data upon which it has been assumed, instead of proving the position, leave it precisely as it was ; for insomuch as the occurrence of the phenomena upon the section prove the exist- ence of the influence of the nerve, in the same degree does the absence of the phenomena upon the section of the nerve disprove it. But was the inflammation caused by the section of the nerve ? This question, which cer- tainly ought to have been determined satisfac- torily before a theory had been founded upon the assumption, appears to the writer to have been decided too hastily in the affirmative. If the section were the cause, no sufficient reason can be assigned why it should occasion inflam- mation in one part, to which the nerve is distri- buted, and not in another, yet such is the case; the eye is the only part in which inflammation supervenes, either so uniformly or so quickly as to afford any ground for attributing the pro- cess to the section. In the second place, were the section the real and essential cause, it can- not be supposed either on the one hand that non-essential circumstances could influence, or at all events prevent the effect, or on the other, that they could produce it. Now it will pre- sently appear that both the one and the other may take place; and a comparison of Magen- die’s experiments and their results would alone suffice to shew that the real cause is to be sought elsewhere than in the section of the nerve. Magendie divided the nerve in three different situations ; first, through the temporal fossa ; secondly, within the cranium, between the Gasserian ganglion and the pons Varolii ; and thirdly, at the margin of the fourth ventri- cle ; and his own general account of the results, which has been already cited, is as follows : “ those alterations in the nutrition of the eye are the less complete, the less rapid, as we recede more from the point of branching of the nerves of the fifth pair, and as we cut, within the cra- nium, its fasciculus of origin the nearer to its insertion ; finally, the section on the margin of the fourth ventricle no longer produces any alteration.” It is plain, then, that the nerve may be cut, and the changes in the eye ensue or not, according to circumstances to be yet explained. On the other hand, that effects similar in kind, if not equal in degree, may be produced by circumstances not essential to their production, — according to the doctrine main- tained, but incidentally associated with the supposed cause, — that such effects may be pro- buccal membrane.” In neither of those extracts is there mention of inflammation or sloughing ; and the ulceration which is mentioned, is attributed to another cause than the section of the nerve. On the other hand, the writer has frequently divided the lingual branches of the fifth nerve and pre- served the animals for months afterward, and he has been unable to detect any change in the condi- tion of the tongue, except this, that in some the tip of the organ, from being allowed to remain between the teeth, and thus to be exposed to injury, ulce- rated, and this continued until the tip was re- moved, when the extremity of the organ healed, and it appeared to be in all other respects as before. duced by such circumstances, when dissociated from the other and operating separately, the author feels justified in asserting, from the re- sult of some experiments lately made by him- self, which lead to the conclusion that similar effects may be produced without the section of the nerve at all, and that an injury in the vici- nity of the orbit may excite them though nei- ther the trunk of the fifth itself, nor its ophthal- mic division have been divided. In an endea- vour to determine the nerves of taste, he under- took the removal of the ganglion of Meckel from the dog ; in order to accomplish this it was necessary to displace the zygoma and the coro- noid process of the jaw ; he attempted it seve- ral times before he succeeded, and failed at different stages of the operation ; but in almost every instance the eye of the same side became bleared within the next two days. The animal kept it nearly closed : a whitish puriform mat- ter was discharged from it, in quantity propor- tioned to the case, which concreted between the lids ; and the animal made no attempt to remove the matter or cleanse the eye : the affec- tion of the eye was always proportioned to the violence done, and abated with the inflamma- tion of the wound ; and in one of the instances in which the ganglion was removed, it actually produced opacity of the cornea, and ulceration in that structure, which continued after the lapse of more than a month from the operation ; yet most assuredly neither infra-orbital nor ophthalmic nerves had been divided. Thus, if, on the one hand, the nerve may be cut and the changes not ensue, on the other it may be left uncut, and the changes may occur. It may be objected that the effects here de- scribed fall very far short of those which took place in the experiments of Magendie. That they fall short of those which occurred on the division of the nerve in the temporal fossa is quite true, but it is equally so that they far ex- ceed those consequent upon the section at the margin of the fourth ventricle. The objection, therefore, would be devoid of weight, and if we suppose superadded to the violence already done when the nerves are not divided, the ad- ditional violence necessarily inflicted in the division of them, we shall have a ready expla- nation furnished of the higher degree to which the effects produced amount in one case than in the other. From the preceding considerations it appears to the author necessary to infer, that the changes which supervene in the eye after the section of the fifth nerve in certain cases, take place inde- pendently of the section, as the primary, imme- diate, or proper cause ; for were it otherwise, .it cannot be supposed either that the difference of half an inch to one side or the other, as re- gards the point of section, could so influence the cause as to prevent or allow these changes, or that they could occur, even in degree, without it. How, then, are the phenomena to be ex- plained? It has been said by Magendie that they are less marked the more we recede from the point of branching of the nerve; but it is to be further observed, that, as we recede from the point of branching of the nerve, we recede 312 FIFTH PAIR OF NERVES. also from the orbit, the eye and its appendages, and in our operation for the division of the nerve we do less violence either in their vicinity or actually to them, until the operation is per- formed at such a distance from those parts, that they are not involved in the injury inflicted. Thus the nerve cannot be divided through the temporal fossa without great violence done to the parts in the vicinity of the orbit, and con- nected with the eye as well as the fifth nerve, as is evident from the result, and as has been explained elsewhere.* In the section be- tween the ganglion and the pons, the violence is inflicted at a part more remote than the former, from the orbit, &c., and here, according to his own account, the effect upon the eye was much less considerable. But the most re- markable fact is, that the alterations of nutrition are much less marked than in the former mode of experiment; there forms only a partial in- flammation at the superior part of the eye, and the opacity which ensues occupies but a small segment upon the circumference of the cornea at the superior part; and in the third case the parts injured are so far removed from the eye, — (in dividing the nerve on the margin of the fourth ventricle, Magendie exposed the parts by “ opening the spinal envelopes between the occiput and the first vertebra,”) — that the effects of the injury could not, under ordinary circum- stances, extend to it, and accordingly in it no alteration occurred. It would seem, then, that the great violence! inflicted, either in the vici- nity of the eye or actually to its appendages, constitutes the primary and immediate cause of the alterations which took place in the eye in the experiments under consideration. But it is likely they were the result of more causes than one, for there were also engaged in the experi- ments other agencies, the influence of which must have enhanced greatly that of the violence inflicted by the operation ; thus, in the first place, in some of the instances at least, — and we have no evidence that it was not so in all, — • * It is hardly possible to conceive the section effected at the point and in the mode adopted, without a division of most of the nerves’ and vessels supplying the eye and its appendages. t A better idea of the injury likely to be inflicted in the experiment will be formed from a brief ac- count of the mode of conducting it. A lancet- pointed style is driven into the cranium through the temporal fossa and through its base, and when carried in to such depth as the experience of the operator teaches him to be sufficient, its point is moved upward and downward, until the lossof sensa- tion in the superficial paits assures him that the fifth nerve has been divided. After such a proceeding the question should rather he, what mischief has not been done than what has. There cannot be any assurance that, in the division of the fifth, the third, fourth, and sixth nerves with the branches of the sympathetic — nay, the optic itself — have not been involved : and if to this he added the almost cer- tainty of dividing the internal carotid artery, from which the supply of blood to the internal structures of the eye is directly derived, and the division of which causes the death of the greater number of the subjects of experiment, an amount of injury will be made out, quite adequate to account for the total loss of the eye, and which must reduce the influence ot the fifth in producing it to a low degree indeed. a highly irritating agent was introduced, and, in consequence of the insensibility of the organ, probably in considerable quantity, into the eye; and in the second the eye was left under cir- cumstances more than enough to excite inflam- mation and to produce serious injury to it, though the organ had remained in full posses- sion of all those safeguards with which its sen- sibility and the sympathetic action established thereby between its several protecting appen- dages naturally endow it ; for “ the eye was dry;” and “ the eyelids were either widely open and immoveable, or else they were glued together by the puriform matters, which were dried between their margins ;” and an organ so circumstanced has abundant cause for inflamma- tion, independently either of nervous influence or of its absence. It may be said that Magen- die has proved that neither the open state of the eyelids nor the want of the lachrymal secre- tion is adequate to the effect. Admitting for a moment that he has, he certainly has not shewn that the combined influence of the two is inad- equate to produce it ; but the first position is by no means satisfactorily established : his mode of determining the question, whether the inflammation was excited by the eye remaining constantly open or not, was by the division of the portio dura, and his experiment has certainly proved that the effect of the section of that nerve will not excite inflammation in the eye, but no more; inasmuch as such section does not produce a permanently open state of the eye : an eye so circumstanced will be closed during sleep, and even during the waking state it requires attention and experience in such observations to discover that the animal has lost the power of closing the lids by a muscular effort of those parts themselves ; for by the sud- den exertion of the power of retracting the eye, which inferior animals possess to a remarkable degree, the lids become nearly, if not quite, closed, and the animal appears to wink as well as before, while by rolling the eye the different parts of its surface are in turn brought beneath the lids, and thus no one part is ever left long absolutely uncovered. So great indeed is the power which brutes possess in this respect, that the author has seen a dog in which the portio dura had been divided on one side, presented for observation, and persons aware that the nerve had been divided, yet not able to disco- ver on which side it had been done, and even deny that the lids were paralyzed on either side, until something was approximated to each eye successively, when the uninjured eye was at once closed, but the other remained open, and the animal appeared looking at the object, which it was unable to exclude. It is obvious, then, that the question has not been and cannot be determined in this way. To the causes already enumerated must lie added the loss of the nervous influence, for it is not intended, in what has preceded, to assert that the section of the fifth has no share in the production of the changes in the eye, but only that it is not the primary or essential cause of them. Indirectly it must contribute powerfully to produce and aggravate, or it may even excite 313 FIFTH PAIR OF NERVES. them ; for by destroying the sensation of the organ, it must leave it exposed to the unin- terrupted influence of many irritating agents, which naturally would excite inflammation, were it not that we are warned through the sensibility of the organ to avoid or to remove them, but in every such case they are the im- mediate, and the insensibility only the mediate cause of the effects produced, and such, it ap- pears to the author, is the part played by the section of the fifth in giving rise to inflamma- tion in the eye. It is further to be observed that the occurrence of inflammation in the eye in cases in which the influence of the fifth nerve upon it had been lost, had been noticed and given to the public by Bell prior to the publication of it by Magendie. In the Philo- sophical Transactions for 1823, (Magendie’s memoir dates 1824,) Sir C. Bell reports the case of a patient under the care of his colleague Dr. Macmichael, in which the surface of the eye was totally insensible, and the eye re- mained fixed and directed straightforward, while the vision was entire. “ The outward apparatus being without sensibility and mo- tion, and the surface not cleared of irritating particles, inflammation has taken place, and the cornea is becoming opaque; thus proving the necessity of the motions of the eye to the preservation of the organ.” And in the same volume he reports also a case from the expe- rience of Air. Crampton of Dublin, bearing strongly upon the question, because it shews satisfactorily that the sensation of the organ, and consequently the influence of the nerve, may be obliterated, and inflammation not ensue until a stimulus have been applied, though the conjunctiva manifestly retained its susceptibility to the impression of that sti- mulus. Air. Crampton’s account of the case is as follows: “ When she told me her eye was dead, as she expressed it, to be certain I drew my finger over its surface, and so far was this from giving her pain, that she assured me she could not feel that I was touching it at all. The eyelids made no effort to close, while I was doing this; but the conjunctiva appeared sen- sible to the stimulus, as a number of vessels on the surface of the eye became immediately in- jected with blood.” Another circumstance may be advanced in fa- vour of the opinion that the nerve influences the nutrition of the parts, to which it is necessary to allude, viz. the wasting of the muscles of masti- cation in cases of the loss of the nerve’s influence. This fact may be otherwise explained ; the de- velopment of muscles is always influenced by their exercise, which being lost they waste, and it is neutralized by the counter-fact that, though these masticatory muscles waste, the muscles of the face and its other structures do not. In fine there appears to the writer to be no good reason for attributing to the fifth nerve a direct influence upon the nutrition of the structures to which it is distributed; the existence of such an influence would be incompatible with the simplicity of natural laws, for in such case there must be two such influences in existence, one in the nerve directing the nutrition of the parts with which it is connected, and another elsewhere to direct that of the nerve. Alagendie confirms his view of the influence exerted by the fifth nerve upon the functions and nutrition of the eye, by reference to a case published by Serres in the fifth volume of the Journal of Physiology, which “ presented all the phenomena attending section of the fifth pair,” and in which there existed complete alteration of the trunk of the nerve in its sen- sible portion ; “ followed by loss of sight, of smell, of hearing, and of taste on the same side.” Before detailing this case, the writer cannot refrain from observing that in such cases none but unquestionable evidence can be admitted if we would arrive at a certain and unquestionable conclusion. Whether the case of Serres be such, it rests with the reader to decide; and first, what was the condition of the patient in other respects ? Serres replies : “ His air was dull ; his physiognomy gave, at first sight, the idea of imbecility; he seemed to conceive slowly and to comprehend with difficulty, the questions which were put to him. When he wished to reply, it was evi- dent that he experienced difficulty in express- ing himself; he pronounced with difficulty, and the little that he said seemed to require, on his part, a considerable effort : his cranium was voluminous compared to the rest of his body ; some pupils suspecting a commencing hydrocephalus, thought that they observed a separation between the parietal and temporal bones, but the prominence of the eyes made me reject that conjecture ; the maxillary and malar bones were a little separated, which had produced a flattening of the nose ; the pa- tient had some difficulty in moving the tongue; the motions and sensibility of the limbs were not affected, only he moved the lower extre- mities less freely than the upper ; he had been for some time subject to epilepsy; he had a sister deaf and dumb.” A case so complicated as this, in which there manifestly existed ex- tended disease of the encephalon, must be rejected as altogether inconclusive. But to proceed, the patient was admitted into hospital in September 1823 : at his admission he had a chronic ophthalmia of his right eye, which was considered scrofulous. In the course of De- cember he was attacked by an acute ophthalmia of the same eye, attended by ccdema of the lids, and commencing opacity of the cornea; the ophthalmia was dispersed after ten or twelve days ; but the cornea was rendered altogether opaque throughout its whole extent; of course the loss of vision on that side was the neces- sary result. In the course of January 1824 it was observed that the right eye was insensible, and soon after that the eyelid and nostril of the same side were also insensible, and likewise the tongue on that side, while all was natural on the other; soon after the gums inflamed upon the right; they were red, some white places existed here and there, they were swollen at the circumference of the sockets ; the tongue moved always with difficulty; the hearing was not then affected; in July the affection of the gums extended to the left side, but the right 314 FIFTH PAIR OF NERVES. was always more affected than the left. During August the gums became separated on the right from the necks of the teeth ; there existed between the latter and the gums spaces into which tartar and portions of food had pene- trated ; the patient suffered from the epileptic paroxysms with variable degrees of severity : lie next fell into a general cachexy, with extreme debility, impeded respiration, small frequent pulse, great alteration of countenance, and un- usual taciturnity. It is stated that in August he acknowledged deafness on the right, which diminished and again increased; the sensibility was perfectly preserved in all the extent of the right side of the face ; the patient died on the 12th of August. Both the brain and the fifth nerve were found after death much diseased, the brain on the left and the nerve on the right side. The details of the case have been given more at length than may perhaps seem necessary, but the question is interesting, and as the bearing of the case upon it could not be determined otherwise, the writer has endeavoured to give them faithfully. The difficulty of obtain- ing precise knowledge from so complicated a case has been already adverted to. We come next to inquire how far it substantiates the writer’s views, or how far it can be considered to establish the opinion of Magendie. Serres, as has been already stated, announces it as an instance of disease of the fifth nerve followed by loss of smell, sight, hearing, &c. Surely the loss of these several functions, thus an- nounced, should have been satisfactorily esta- blished, before asserted ; but such does not appear to have been the case. For the first, notwithstanding the announcement, we find Serres himself, after the patient’s death, ac- knowledging, “ toutefois l’odorat n’avait pas completement disparu, puisque,”* &c. The sense of smell then plainly was not lost. In the next place there was loss of vision, but from what cause? from opacity of the cornea, and, so far as we have data for forming a judgment, from it alone. We have no reason to think that any alteration had been pro- duced in the power of the eye to receive sensations of light, any disturbance in the function of the retina, or any other change than the occurrence of a physical impediment to the exercise of a function, which the organ may have retained in full vigour, had it only been allowed to exert it: the evidence, there- fore, afforded by the case, is too imperfect to be of value. Let us next inquire how far it bears out the opinion that the fifth nerve possesses a proper and direct influence upon the nutrition of the eye : here we shall find ourselves equally at fault for the resemblance which it has been sought to establish. In Magendie’s experi- ments the section of the nerve preceded the occurrence of the phenomena, and it is reason- able to expect, that, here, the loss of sensibi- lity, which we are to regard as the analogue of the section, should have preceded the oc- * Journ. de Phys, t. v. p. 245. currence of the inflammation of the eye ; but no. The patient had a chronic ophthalmia, con- sidered scrofulous at the time of his admission; (he was admitted in September, and in De- cember he was attacked by acute ophthalmia, attended by oedema of the lids ; a circumstance not noticed in any of Magendie’s experiments;) the inflammation was dispersed, and in the course of January, and not till then, (i.e. four months after his admission and about one after the occurrence of the second inflammation,) the insensibility of the eye was for the first time observed. Surely we have no reasonable grounds here for attributing the inflammation of the eye and the opacity of the cornea to the disease of the nerve, or for supposing that there existed any connexion, in the relation of cause and effect, between them. If we seek for a resemblance in other points, we shall be equally disappointed. It has been already remarked that oedema of the eyelids, which occurred in this case, is not one of the phenomena of Magendie’s experiments. Again, the affection of the gums related is altogether unlike : in Serres’ case they are stated to have become inflamed, and to have been affected on both sides, only more on the right than on the left ; in Magendie’s it is simply stated that they separated from the teeth and only on the side on which the nerve had been divided ; and, lastly, the continuance of sensibility upon the right side of the face throughout casts an im- pervious obscurity over the entire. Besides those effects of the section of the trunk of the nerve which have been discus- sed, there are others, for which we are in- debted also to Magendie, and which deserve notice. lie found after the section of the nerve that the eye was dry, and the motion of winking had ceased ; the globe of the eye itself seemed to have lost all its motions ; the iris was strongly contracted and immoveable. The loss of sensibility in the conjunctiva, and the sus- pension of the secretion of the tears, he refers to the loss of the influence of the fifth nerve upon the former part and upon the lachrymal gland : the explanation of the first is in accor- dance with the previously established proper- ties of the nerve as already ascertained by Mayo, but it is not equally so that the secretion of the lachrymal gland is directly controlled by the same influence, and it remains to be deter- mined whether the effect in this case was not an indirect one, consequent upon the previous insensibility of the conjunctiva. The other re- sults of the section — the immobility of the eyelids, that of the eye, and the permanent contraction of the pupil — he has not satisfac- torily explained : the immobility of the lids may, it appears to the author, be attributed with much probability to the insensibility of the conjunctiva or of the internal structures of the eye, and seems a likely consequence there- of : the ordinary action of winking would seem to be called into play through the sensations of those structures, and the cessation of that action upon the loss of their sensibility is as natural an effect as the immobility of the lips FIFTH PAIR OF NERVES. 315 on the contact of food consequent upon the division of the infra-orbital and inferior maxil- lary nerves : and this view derives confirmation from the circumstance that in the instance under consideration the immobility of the lids is not the consequence of paralysis, for on the sudden admission of solar light into the eye, the action of the muscle was excited, and the eyelids were closed. The immobility of the eye itself the author cannot but regard as an incidental circumstance, caused by the com- plication to which Magendie himself refers, viz. the division of the motor nerves of the eye along with the fifth, and this explanation is rendered more likely, if not confirmed, by the effect of the section when made between the ganglion and the brain, in which case the motor nerves are not involved, nor the motion of the eye affected. It is to be regretted that Magendie has not given a report of a dissec- tion after death of some of the animals upon which the former experiment had been per- formed, by which the question might have been determined. The permanent contraction of the iris is an extraordinary and as yet unex- plained effect : it occurred only when the experiment was made upon rabbits, and is at variance with the results of similar experi- ments upon other animals, performed both by Mayo and by Magendie himself. In Mayo’s'6 experiments, which were done upon pigeons, in no instance was contraction of the pupil caused by division of the nerves connected with the eye or its appendages. When the optic nerve was divided, the pupil became fully dilated. When the third nerve was divided, the same result ensued ; and when the fifth was divided, the iris contracted as usual on the admission of light; in Magendie’s experiments again upon cats and dogs the pupil was en- larged.-)- The fact is, however, confirmed by Mayo, who found that when the fifth nerve was compressed in a rabbit after death, the pupil became contracted slowly and gradually, and then slowly dilated ; and when the nerve was divided, the pupil became contracted to the utmost, and remained so. A correspond- ing difference between the conditions of the pupil after death in the subjects of experi- ment has been observed by Mayo, according to whom in the pigeon and cat it is naturally dilated, but in the rabbit, on the contrary, contracted.); It has been already stated that Magendie divided the nerve within the cranium both after and before the occurrence of the ganglion : in the latter case — when the section is made between the ganglion and the brain — the re- sults are different in some remarkable respects from those attending the section in the former : the effect upon the senses is equally marked ; but the motions of the globe of the eye are preserved almost always, from which the author would infer that the loss of those motions in the former must have been caused by the divi- * Comment, part ii, p. 4, 5. t Journal, t. iv. *p. 309. t Physiology. sion of the motor nerves along with the fifth, by the side of the cavernous sinus ; and also the changes which occur in the tissues of the eye are much less considerable ; the inflamma- tion and opacity ensue, but not to the same extent. Another very remarkable result of the sec- tion is displayed in the animal’s mode of pro- gression as related by Magendie : “ when the two nerves are cut upon an animal it seems blind, and its mode of progression is most sin- gular ; it advances only with the chin leant strongly upon the ground, pushing thus its head before it, and using it as a guide as the blind does his staff : the progression of an animal in this state differs altogether from that of an animal simply deprived of sight ; the latter guides itself easily by means of its whiskers, and by the sensibility of the skin of its face ; it stops at hollows, feels obstacles, and, in fine, it would be difficult to know whether it is blind or not ; while the animal whose fifth nerves have been cut has but one mode of moving, and instead of avoiding obstacles, it persists often in pushing against them for several hours, so as finally to exco- riate the skin of the anterior part of the head.”* This account, which is well calculated to excite at first extreme surprise, is after all strictly consistent, and illustrates strongly the importance of the nerves in question : in fact to the animal so circumstanced the head and face must be as a part which it does not possess, or rather of which it has been suddenly deprived, and which it yet believes itself to retain ; it can have no consciousness of their existence, while from habit, memory, and ignorance of the real condition of the parts, it yet believes them to be present, and to exercise all their usual func- tions. Thus the human being whose limb has been removed without any knowledge of what has actually occurred believes that he still pos- sesses it, acts as if he did, and is only con- vinced of his loss by the evidence of the senses of sight and touch. In like manner the ani- mal acts under the impression that it still possesses its ordinary faculties, and being altogether unconscious of the contact of ob- stacles in consequence of its loss of sensation in the part which encounters them, it acts as if it were not in contact with them, and endeavours still to advance, while it is unable to make use of sight, if this faculty be retained, as a a guide, because it has lost the correcting and regulating assistance of the sensation of its face as exercised through its whiskers ; and hence it does not appear to the author that the apparent blindness of the animal proves real blindness. Unassisted sight cannot teach us the distance of objects ; and the animal sud- denly deprived of the faculty of sensation may see the object, but not being made aware of its contact, must suppose that it has not reached it, inasmuch as the usual notice of its presence is not given by the sensibility of the face. Lastly, when the nerves have been divided * Journ. de Phys. t. iv. p. 181. 310 FCETUS. upon both sides, the lower jaw ceases to be supported by its muscles, and falls.* Influence of disease on the functions of the nerve. — The inferences drawn from the anatomy of the nerve and from physiological experiment conjointly have been confirmed in a remarkable manner by the effect of disease of the nerve upon the functions of the parts to which it is distributed: several instances have been pub- lished exemplifying either partially or com- pletely that effect, when, whether from disease of the trunk of the nerve itself or from pressure upon it, its office has been interrupted, all the parts supplied by it are deprived altogether of both their tactile and ordinary sensibility: this loss of sensibility extends to the whole of the corresponding side of the head so Jar as the distribution of the nerve reaches to the fore- head, temple, ear, surface of the eye and its appendages, cheek, nostril externally and inter- nally, lower part of the face, lips, and mouth, the corresponding half of the tongue, of the palate, and the fauces ; upon all these parts the roughest contact produces no perceptible im- pression ; inflammation is not attended by pain, the most pungent or irritating effluvia do not affect the nostril or the conjunctiva, and the sense of taste is altogether lost in the ante- rior part of the same side of the tongue : at the same time the muscles of mastication— the ex- ternal ones at least— lose their contractile power, remain inactive during the process and waste, whence are produced a flattening and depres- sion in the site of the temporal and masseter, with prominence of the adjoining points of bone : however the special senses continue un- affected apparently, unless in so far as the sense of contact may be necessary to the perfect or ordinary fulfilment of their function, the olfac- tory function seems much impaired ; the pa- tient is insensible to the impression of ammo- nia, snuff, or other pungent agent, but still ac- knowledges a perception of odour. Vision continues throughout, and appears unaf- fected, unless from the supervention of in- flammation, by which the eye may be spoiled, or from the extension of the disease to the optic nerve or the brain : in the case before alluded to, which the author has witnessed, vision re- mained perfect for a considerable time ; amau- rotic symptoms supervened during the course of the disease ; but even after the occurrence of opacity of the cornea in consequence of in- flammation, the patient could still distinguish light. Hearing appears to have been affected in most, if not all the cases, in which the dis- ease had attained a considerable degree; it was so in the case seen by the author; the sense of contact would seem associated with the perfect exercise of the sense. The facial muscles re- tain their contractile power ; in the instance alluded to, though the temporal and masseter seemed quite paralyzed, the buccinator acted with energy as ascertained by holding the cheek between the finger and thumb during its con- tractions ; the slight want of adjustment, which may occur about the mouth, seems caused by * Magendie, Bell. the want of sensation in the lips. Lastly, in all such cases the eye of the affected side is liable to have inflammation excited in it by incidental causes ; for the most part this occurs at an advanced stage of the disease, and can be referred to some exciting cause ; it is attended by but little, if any pain, and opacity of the cornea is an usual result.* (For the Bibliography see Nerve.) ( B. Alcock.) FCETUS, Gr. xtnj/za ; Fr .foetus; Germ. die Frucht ; (normal anatomy). See Ovum. FGlTUS (abnormal anatomy). Considering the peculiar circumstances of the fetus in utero, we would, at first sight, be inclined to suppose that, although of course exposed to the risk of injury from accidents or diseases occurring to the mother, it would not be liable to many or serious accidents of its own ; nevertheless, ob- servation and experience soon reveal to us a very different state of facts, and force upon us the sad truth that the seeds of life are often sown adulterated with those of infirmity and decay, that disease may mutilate, and death destroy, even before our entrance into life ; for as far as investigation has enabled us to reach, we have reason to believe that the child before birth is not only liable to certain affections which may be considered peculiarly its own, but is also subject to almost all those which affect the adult. Of these affections some appear to be, 1. strictly innate in the constitution of the fetus; 2. some communicated by infection from the mother’s system ; 3. some from the father’s sys- tem, or perhaps through that of the mother, she herself not being the subject of the affection entailed, as in certain forms of syphilis, scrofula, and small-pox ; 4. some, from strong mental impressions on the mother; 5. some, arising from morbid alterations in the envelopes of the ovum, the placenta, and cord, or in the uterus itself ; 6. some, from the influence of external agents, as falls, blows, pressure, &c. The investigation of these abnormal con- ditions is invested with a deep interest, not only as an important pathological inquiry, but as conducive to the adoption of mea- sures calculaled to be beneficial to both mo- ther and child ; to the child, by suggesting the strong necessity for preventing the exposure of the mother to influences likely to affect the welfare of her unborn offspring, as well as for removing their effects by proper remedial means : and to the mother, by affording us occasionally information of the existence of diseased taints in her system, of which we might otherwise long remain ignorant ; or by guarding her against the ill effects of unhealthy states of the child ; for, although each indivi- dual has a separate existence, there is at the * Mayo, Commentaries and Physiology ; Bell, Philosoph. Transactions and on Nerves, 1830 ; Serres, Journal de Physiologie, t. viii ; Noble, Medical Gazette; Bishop, Medical Gazette, vol. xvii. FCETUS. 317 same time a very close and intimate mutual dependence of the one on the other; and, con- trary to what we would at first expect, the health of the mother is more apt to suffer from morbid conditions of the fcetus in utero than is the latter to be injured in its developement by the state of the mother’s system. Thus we see how great a disturbance is often caused in the maternal system by a blighted ovum, or a dead and putrid fcetus ; while, on the other hand, we frequently observe that women in states of the most infirm health,* both mental and bo- dily, nay even when sinking under the ravages of some wasting disease, or depressed and worn out by mental suffering, by want of food or ex- cessive fatigue, give birth to full-grown and well-thriven children. The affections to which the fcetus is liable vary not a little according to the period of its existence at which we consider it ; during the earlier periods, when the formative process is in most active operation, and the developement of the different organs is proceeding rapidly, many important and remarkable organic altera- tions take place ; some from arrest of develop- ment caused by imperfection in or morbid alteration of the structures of the ovum ; some by destruction of parts already formed, by atrophy or inflammation, or both conjoined ; some by the effects of excessive secretion and the consequent unnatural distension, &c.; while those affections, to which more strictly belong the name of diseases, affect the more matured foetus, whose organization approaches more closely that of the new-born child. In order to give a full account of the morbid and abnormal conditions of the fcetus, we should embrace also those of its appendages or surrounding structures of the ovum ; these, however, will be alluded to at present only so far as is absolutely unavoidable, as they will receive full consideration in the articles Ovum and Placenta : and in like manner several varieties of malformation will be with more propriety described under the head of Mon- strosity, while others will be found under the account of the different organs concerned. The germ, even before its vivification in the ovary, may have a morbid taint communicated to it from the system of the female in whom it resides, or from that of the man with whom she cohabits, so that the tendency to disease or malformation sometimes precedes the first im- pulse that leads to the establishment of life. Another source of abnormal conditions in the foetus occurs in the cohesion or intus-susception of germs, in consequence of more than one ovulum being contained within the same vesi- cle ; under which circumstances unnatural union may take place between two foetuses, and give rise to the production of such anoma- lies in organization as the Siamese twins, or to other forms of fuetal duplicity, more or less re- sembling the remarkable instance represented in the annexed sketch of two children born a * See several instances recorded by Mauriceau, Malad. des femmes grosses, vol. ii. obs. 439, 497, 530 , 622, 629, 656. few years since at Boyle, in the county of Ros- common. Fig. 146. They were bom alive, and lived for more than a week ; after death they were sold to the College of Surgeons in Dublin, in whose mag- nificent Museum a preparation of their skeleton is preserved.* The writer lately received from the President of the College of Physicians, Dr. Croker, two hen’s eggs united at their end by a connecting stalk as thick as one’s little finger, which, in common with the two eggs, was covered by a tough white membrane. From intus-susception of one germ within another, arise also some very singular pheno- mena, such as the existence of perfect teeth set in bony sockets, long hair, &c. in situations far remote from those in which such structures are naturally formed ; and the still more extra- ordinary fact of foetuses being found within the bodies of males facts which, in the opinion of the writer, can be explained only on the supposition of original intus-susception of germs, constituting that abnormal condition which has been called monstrosity by inclu- sion an accident which appears to be by no means confined to the germs of the mammalia nor even of the animal kingdom. The writer has in his museum a small egg about as large as a gooseberry, which was found within ano- ther egg of the common hen, which also oc- curred to Harvey ,§ who says, “ I have seen an exceeding small egge, which had a shell of its own, and yet was contained within another egge, greater and fairer than it, which egge also had a shell too. And this egge I shewed King Charles my most gracious master in presence * See also case by Dr. Alcock in Dublin Medical Essays, vol. ii. p. 33, and Hall on the Cesarean operation, p. 470. t Med. Chir. Trans, vol. i. p. 234, case of a fcetus found in a young man, by Nathaniel High- more, 1815. t See Archives Generales de Medecine, tom. vii. p. 355. § Exercitation xi. pp. 50, 51 ; Ent’s translation. 318 FCETUS. of many others ; and that very year cutting up a large lemon, I found another, small, but yet a perfect lemon in it, which had also a yellow rind.” Many other instances of anomalies resulting from cohesion and intus-susception,'* might be referred to, but they will find their place with more propriety under the article Monstrosity. Mislocation of the germ during its growth and development is well known to be produc- tive of serious consequences, not only to the foetus, but unfortunately involves great danger to the mother also, as in those instances in which it has been developed in the ovary, f the Fallopian tube, the cavity of the abdomen, or in the substance of the uterus constituting in- terstitial pregnancy. I Atrophy. — A very common occurrence to the foetus in utero is atrophy, or a complete arrest of growth from disease attacking its en- velopes, especially the placenta or cord; in which case, a deficient and unhealthy supply of nutrition is furnished to the child, which either perishes completely or has its develop- ment retarded to such a degree, as not to pre- sent dimensions or characters corresponding to perhaps half the period that has really elapsed since conception ; as happened in the follow- ing case: a lady who menstruated in the last week of July, began about the middle of August to exhibit unequivocal symptoms of pregnancy, which proceeded regularly till the middle of October, when indications of threat- ened abortion appeared, with pain, and the re- peated expulsion of large coagula and sub- stances of various appearances. After this, the previously existing symptoms of pregnancy en- tirely disappeared, and it was supposed that miscarriage had occurred and that the ovum had escaped, unnoticed, amidst the masses of coagula. The lady resumed her ordinary habits and went into society as usual, without expe- riencing any uneasiness or unhealthy symptom, except irregular uterine discharges, which were supposed to be menstrual : so matters proceed- ed until the 7th January, when, after a long drive, she was seized with periodical pains ac- companied by smart uterine haemorrhage, in consequence of which I was sent for. I found the os uteri open and an ovum partly protruded through it, this I succeeded in disengaging and bringing away ; on examination it presented the general appearances as to size, form, and growth of the foetus, of an ovum of less than two months, but the placenta was as large and as much formed as it should be at three months, and was moreover quite unhealthy, being throughout affected with what is usually called the tubercular state of that organ ; the foetus seemed perfectly healthy, but very small ; and the umbilical cord was only about half an inch in length, much hypertrophied, being sud- denly enlarged on leaving the placenta, to three * See Dublin Journal of Medical Science, vol.iv. p. 294, and as before note f. t See Dub. Med. Journ. vol. ii. p. 195. f See a full account of this subject in Memoires by Breschet and Geoffroy St. Hilaire ; Repertoire Generate d’Anatomie, &c. No. 1. pp. 72, 75,91. or four times its natural diameter, and again as suddenly contracted almost to a thread, where it joined the abdomen of the foetus. See sub- joined sketch, of the natural size. Fig. 14 7. Cruveilhier* relates the particulars of a case in which the effect of disease of the placenta in producing atrophy of the foetus was strikingly shewn in twins at the sixth month, one of whom possessed the full development and characters belonging to that period, but the other, whose portion of thejoined placentae was thin and un- vascular, presented a size corresponding to not more than three months, as shewn inj fig. 148. In another case, formerly under the writer’s care, the foetus expelled at the ninth month had only grown during the first three.f Such cases as the above possess an interest and a demand on our attention of a very im- portant kind, as illustrative of the necessity for carefully examining into the state of the foetal appendages as to their healthy condition or otherwise, before we venture to pronounce an opinion on the time that has elapsed since con- ception, merely from the size or general ap- pearance of an ovum or foetus shewn to us ; for here we have, in one instance, an ovum, the size of which and that of the contained foetus, would indicate a period of two months ’ preg- nancy only, whereas five months had really elapsed from the time of conception, for the parties had not cohabited since the time of the threatened abortion ; and in the other case an ovum of three months' growth is expelled nine months after conception. Now, in either case, had the husband happened to die, or to have * Anatomie Patbologique, liv. vi. pi. vi ; see also Graetzer, die Krankbeiten des foetus, p. 83. t See my Exposition of the Signs of Pregnancy, Sec. pp. 96, 7, and also pp. 210, 11, and 259, 60, of same work. FOETUS. 319 Fig. 148. gone from home, shortly after the time of con- ception, and the accident to have occurred in the same way, the female might have sustained, though most unjustly, a severe injury to her reputation. Hernia. — Hernia is a very frequent occur- rence in the fcetus, especially at the umbilicus, where, in the earlier periods of foetal life, the anterior wall of the abdomen is deficient and the intestines covered by the expansion of the sheath of the cord, into which they project, in some instances considerably; of this there are several specimens in the writer’s museum ; not unfrequently this natural deficiency remains up to the time of birth, and congenital umbi- lical hernia is found in the child. In the simpler forms of this affection the her- nial sac contains intestine only, but in other instances which have occurred to the writer, some of which also he has preserved, it con- tains the liver and stomach in addition to almost the whole tract of intestines : such ag- gravated forms are in general connected with other malformations, such as spina bifida, spon- taneous amputation, &c. which combinations are noticed under their respective heads in the present article. In a specimen which occurred recently in the writer’s practice the liver was protruded into the sheath of the cord, but all the rest of the abdominal viscera were con- tained in the natural cavity. Inguinal hernia sometimes exists before birth, but is rare. Her- nia cerebri is noticed elsewhere. Diaphragmatic hernia, or protrusion of the intestines through the diaphragm into the ca- vity of the thorax is of rather rare occurrence, or perhaps, more properly speaking, is less frequently observed, because it presents no external physical alteration of form to attract attention. Like umbilical hernia in the fcetus, it is the result of incomplete developement, because in the earlier periods of foetal life the diaphragm does not exist, and the thoracic and abdominal cavities are one ; and as the muscle afterwards becomes developed from its circumference to- wards the centre, there occurs occasionally an arrest of formation, and in consequence an aperture is left, through which the intestines and other abdominal viscera, as they increase in size, pass into the cavity of the thorax, dis- placing the heart and lungs, the latter of which organs are thereby frequently so pressed upon that their developement is prevented, and there is sometimes but a very small portion of them discoverable, especially of the one at the side where the hernia principally exists; which, in a vast majority of the cases which have been met with, has been the left, and then the heart has been pushed over to the right side, where its pulsations in children born alive have some- times given the first intimation of the existence of the lesion under consideration. In general, children so affected in utero have been either still-born, or have died very soon after birth, a consequence which it appears reasonable to suppose results from the state of the lungs. But in some instances the children have sur- vived under such circumstances. Becker saw one that lived five years; and in a case re- corded by Diemerbroeck, where the diaphragm was entirely absent, the child lived seven years, annoyed only with a frequent cough. Riviere and J. L. Petit mention instances of life much more prolonged, in the same condition. The writer has before him a beautiful speci- men of this abnormal condition, for the oppor- tunity of examining which he is indebted to Dr. E.W. Murphy, as well as for permission to have a drawing taken from the preparation in his possession. (See fig. 149.) The opening in the diaphragm in this case is at the left side, rather anterior to and to the left of that which naturally transmits the oesophagus, and appears to arise in this case from separation of the fibres of the muscle ; a very large quantity of the small intestine is lodged in the left side of the thorax, from which the heart is pushed away over to the right ; the right lung, which lies behind the heart, is natural in structure, but the left does not equal in size half the kernel of an almond, and does not possess the natural pulmonary structure, but appears nearly as solid as the liver. The stomach, spleen, and liver were in their natural situation. The child had also a spina bifida tumour which covered the whole of the sacrum, and deformity of one hand, the thumb of which was attached by a small pedicle to the side of the index finger. In a case related by M. le Docteur Anthony,* which occurred in his practice, the child, which lived * See Journal Hebdomadaire. Fevrier, 1835. 320 FCETUS. Fig. 149. Diaphragmatic Hernia. a. The heart, b, b. The intestines which had passed through the diaphragm and occupy the left side of the thorax, displacing the heart, c, c. Por- tions of intestine below the diaphragm. iXs®. t Yj/po?, moist ; i^iXeib. § Pecten, -inis, a comb. || Si^oiv, a canal. Claijj.a, operculum-, o-ro/xa, mouth. GASTEROPODA. 379 Order VII. SCUTIBRANCHIATA * (Cuv.) Syn. Cervicobranches, Blain. ; Chismo- branches, Blain. ; Gast. Dermobranches, Dum. ; G. Trachelipodes, Lam. Fig. 176. In this order the structure of the branchial is analogous to what has been described in the Pectinibranchiata ; but the shell, which in the latter was always turbinated, in the Scutibran- ehiata is a mere shield, in which the indications of a spire are very slight or totally deficient. There is never an operculum. The organs of both sexes are united in every individual, but there is no necessity for copulation, each ani- mal being self-impregnating. The species are all aquatic. 1st Sub-order, Anthophora.f 1st Earn. Haliotis, Jig. 176. 2d Sub-order, Calyptracidre.,% Lam. * Scutum , a shield, t A vQo(, a fewer ; , to carry, ) $ KaXUTTTpa, a covering. 2d Fam. Capulus.* 3d Sub-order, Heteropoda \ Nucleobranches , Blainville. ' 3d Fam. Fterotrachea, Jig. 177. Order VIII. C YCLOBRANCHIATA, (Cuv.) Syn. Dermobranches, Dum.; Gast. Phylli- diens, Lam.; Gast. Chismobranches, Blain. In this order the branchiae are arranged under the margin of the mantle around the circumference of the body ; the shell is a simple shield, either composed of one piece, which is never turbinated, or else made up of several divisions. They are all hermaphrodite and self-impregnating. 1st Sub-order, Chismobranchiata , Blain.; Cy- clobranchiata, Goldfuss. 1st Fam. Patella. 2d Sub-order, Polyplaxiphora,X Blain. 2d Fam. Oscabrion. Cuvier detaches the genera Vermetus, Magi- lus, and Siliquaria from the Pectinibranchiata on account of the irregular form of their shell, which is only spiral at its commencement, and is usually firmly attached to some foreign body, a circumstance which involves as a necessary consequence the hermaphrodite type of the sexual organs, so that these genera are self- impregnating. He has, therefore, arranged them in a separate order, to which he applies the name of Tubulibranchiata. Tegumentary system. — The skin which in- vests the Gasteropoda varies exceedingly in texture, not only in different species but in dif- ferent parts of the same animal ; its structure being modified by a variety of circumstances connected with the habits of the creature, the presence or absence of a calcareous covering, or the mode of respiration. In the naked Gaste- ropods, especially in the terrestrial species, it is thick and rugose, serving as a protection against the vicissitudes consequent upon the changeable medium which they inhabit. In such as are aquatic the integument is proportionably thin- ner, and its surface more smooth and even ; in both, however, it differs much in texture in dif- ferent parts of the body; thus in the dermo- branchiate species it becomes attenuated into a thin film, where it invests the vascular appen- dages subservient to respiration, and such por- tions as cover the organs of sense assume a transparency and delicacy adapted to the sen- sibility of the parts beneath. In those orders which are provided with shells, the integument which protects such parts of the body as are exposed when the animal partially emerges from its abode, is thick and spongy, and very different from the thin fibrous membrane which invests the mass of viscera contained within the shell. We are led by various circum- stances to presume that the skin of all the Gasteropods is in structure essentially ana- logous to that of higher animals, and in de- * Many of the Capuloid Gasteropods are thought by Cuvier to be dioecious. t ETspo;, different ; vrovt, foot. } UoXvi, many ; rr\a^, a scale ; epov, to carry. 2 C 2 GASTEROPODA. 3.80 scribing it we shall avoid obscurity by applying to its different parts the names ordinarily made use of by anatomists to distinguish the tissues enumerated as composing the human integu- ment. The dermis is an extremely lax and cellular texture, eminently elastic, and so intimately blended with the contractile layers beneath it, that it is difficult to recognise it as a distinct structure : its great peculiarity consists in the power which it possesses of secreting calcareous matter, which being deposited either in a cavity within its substance, or as is more frequently the case, upon its outer surface, forms a con- cealed or external shell : from this circum- stance, and from the abundant quantity of mucus which it constantly furnishes, we may infer its great vascularity, while the high degree of sensibdity which it evidently possesses une- quivocally demonstrates that it is plentifully supplied with nerves, although the existence of a true papillary structure cannot be satisfac- torily distinguished. The colouring pigment likewise exists, as is evident from the brdliant markings which are often met with in some of the more highly coloured species ; but there is a circumstance in connection with this rete mucosum which requires particular mention, as it will enable us afterwards more clearly to ex- plain the formation of shells ; the pigment is not merely a layer which serves to paint the surface of the body generally, but appears ra- ther to be an infiltration of the lax tissue of the cutis with coloured fluid, which is poured out in great abundance at particular points, espe- cially around the margin of the shell, and there being mixed up with the calcareous matter se- creted by the collar, its tints are transferred to the exterior of the shell itself, tinging it with similar hues. The epidermis is evidently defi- cient, its place being supplied by the viscid matter with which the surface of the body is continually lubricated. The muciparous crypts destined to furnish the copious supply of glairy fluid with which the skin is so largely moist- ened, have not been detected, but the pores through which it exudes are sufficiently distinct. It is in connexion with the needful diffusion of this secretion over the entire animal, that the skin of the terrestrial species, as the Slugs and Snails, is observed to be deeply furrowed by large anastomosing channels, formed by the rugae of the surface, and serving as canals for its conveyance by a species of irrigation to every point. No pilous system, properly so called, exists in any of the Gasteropods, the hairy covering of many shells being, as we shall presently see, of a widely different nature. From the modifications observable in the structure of the integument, it is. not to be won- dered at that names have been applied to diffe- rent portions, which it will be useful to notice, especially as they are not unfrequently used in a confused and unprecise manner. That por- tion o.f the skin which is more immediately connected with the secretion of the shell, in such Gasteropoda as are provided with a de- fence of that description, has been termed the mantle , and in certain instances, from the mode in which it seems to form a special cot ering to a part of the body, it has some claim to the name ; the mantle is, however, extremely varia ble, both in position and arrangement. In the Nudibranchiata, which have no shell, it cannot be said to exist, as no fold of the integument or defined margin indicating a portion deserving of a distinct appellation can be detected. In the Tectibranchiata the mantle is a small trian- gular fold of the integument on the right side of the body, inclosing a rudimentary shell, and serving as a covering to the subjacent branchiae. In the Inferobranchiata it invests the whole of the back, and forms a fold around the margins of the body, beneath which the branchiae are found ; whilst in all the conchiferous Gastero- pods it lines the interior of the shell, whatever its shape, forming a distinct fold or thickened rim around its aperture, to which when much developed, as in Helix, the name of collar is not improperly applied. In the naked terrestrial species the mantle consists of a thickened portion, occupying a variable position on the back, and more or less defined by a distinct margin ; it is here not un- frequently termed the corselet, and generally contains a calcareous plate. In Vaginula it covers the whole of the back ; in Limax it occu- pies only its anterior portion; in Parmacella it is found in the middle of the dorsal region, whilst in Testacella it is placed quite poste- riorly in the vicinity of the tail; yet whatever its situation, shape, or size, it is the immediate agent in the formation of the shell, and as such we have deemed it necessary to be thus precise in describing the different aspects which it assumes. Growth of shell.- — The varied and beautiful shells that form so important a part of the inte- gument of many individuals belonging to this order, however they may differ in external form and apparent complication, are essentially simi- lar in composition and in the manner of their growth. These calcareous defences, although serving in many cases as a support to the ani- ma1, from which important muscles take their origin, differ widely from the internal skeletons of vertebrate animals, being mere excretions from the surface of the body, absolutely extra- vital and extra-vascular, their growth being en- tirely carried on by the addition of calcareous particles deposited in consecutive layers. The dermis or vascular portion of the integument is the secreting organ which furnishes the earthy matter, pouring it out apparently from any part of the surface of the body, although the thicker portion, distinguished by the appellation of the mantle, is more especially adapted to its pro- duction. The calcareous matter is never depo- sited in the areolae of the dermis itself, but ex- udes from the surface, suspended in the mucus which is so copiously poured out from the mu- ciparous pores, and gradually hardening by ex- posure; this calciferous fluid forms a layer of shell, coating the inner surface of the pre-exist- ent layers to increase the size of the original shell, or else is furnished at particular points for the reparation of injuries which accident may have occasioned. It is to the investiga- GASTEROPODA. 381 tions of Reaumur that we are indebted for our knowledge concerning this interesting process, and subsequent writers have added little to the information derived from his researches ; in order, however, to lay before the reader the principal facts connected with this subject, we shall commence with the simplest forms of the process, and gradually advance towards such as are more complicated and less easily under- stood. The shells of the Gasteropoda are of two kinds, some being entirely concealed within the substance of the mantle, and consequently internal, whilst others are placed upon the sur- face of the body external to the soft integument. In the former case the shell is uniform in tex- ture and colourless ; in the latter, its develope- ment is much more elaborate, and it is not un- frequently moulded into a great diversity of forms, and painted with various tints, which are sometimes of great brilliancy. The internal or dermic shells are found in many of the pulmo- nary and iectibranchiate orders, and possess but little solidity ; although inclosed in the substance cf the mantle, they are so little adhe- rent, that when exposed by an incision they readily fall out of the cavity in which they are lodged, and from which they are apparently quite detached. Their substance is generally calcareous, but in many instances, as in Aplysia, the shell is of a horny texture, being transpa- rent, flexible, and elastic, as is the gladius of many of the Cephalopod Mollusca. In all cases horny or calcareous plates of this descrip- tion are found to be composed of superposed lamellae, which are successively secreted by the floor of the cavity in which they are contained, the inferior layer being always the largest and most recent. These shells, therefore, may be con- sidered as merely formed by the deposition of successive coats of varnish, which become indu- rated, and the simple manner of their growth will best exemplify the mode in which more compli- cated shells, whatever be their form, are con- structed. External shells present an endless di- versity of figure, and some classification of their principal forms will facilitate our contemplation of the peculiarity observable in each. The con- cealed shells, which are merely the rudiments of what weare now considering, are so small in com- parison with the size of the body, that they can only be looked upon as serving for the protec- tion of the more important organs, namely, the heartand respiratory apparatus, which are placed beneath them, but the external shells, from their great developement, are not merely a partial protection to the animal, but in most cases constitute an abode into which the creature can retract its whole body. The external shell consists generally of one piece, the form of which may be symmetrical, in which case it is a cone or disc simply covering the back of the animal ; or, as is generally the case, the shell may be more or less twisted around a central axis, forming a convoluted, turbinated, or spiri— valve shell. In one genus only, Chiton, Lin., the shell is formed of several pieces articulated with each other, and covering the surface of the back. The shell of the Patella, a section of which is represented in fig. 178, is a simple cone placed upon the back of the creature, which it com- pletely covers, and upon which it is evidently moulded. On making a section of the animal, as in the figure, the shell is found to be entirely lined by the mantle a, b, by which it is secreted. Fig- 178. That the whole surface of the mantle is capable of secreting the calcifying fluid from which the shell is formed, is distinctly proved by the manner in which a fracture or perforation in any part is speedily repaired by the deposition of a patch of calcareous matter beneath it, but in the ordinary growth of the animal the differ- ent portions of the mantle execute different functions. It is obvious that the enlargement of the body of the patella, as its age increases, must necessitate a corresponding enlargement of its habitation, and this is principally effected by additions of calcareous matter in succes- sively larger rings around the mouth of the shell only ; the great agent therefore in forming the shell is the margin of the mantle, b, b. This hangs loosely as a fringe near the mouth of the shell, and being moveable at the will of the animal, the calcareous matter which it pre- eminently furnishes may be laid on in succes- sive layers to extend the mouth of its abode ; and these consecutive additions are indicated externally by concentric lines running parallel with the circumference of the shell, the num- ber of which necessarily increases with age. Whilst the abode of the creature is thus en- larged by the deposition of shell from the vas- cular and spongy margins of the mantle, the office of the rest of that membrane is reduced to the increase of its thickness, depositing succes- sive coatings of calcareous particles, which are laid on to its inner surface, and when a section of the shell is made (f J, these last-formed strata are readily distinguishable by their whiteness and different arrangement. So far the produc- tion of an external shell is entirely similar to what we have met with in the formation of the internal defences of the naked Gasteropoda, yet in other respects the former are much more ela- borately organised. In the first place many of them are adorned externally with colours, not unfrequently arranged with great regularity and beauty ; these tints belong exclusively to the outer layers of the shell, that is, to those formed by the margins of the mantle, and are produced by a glandular structure appropriated to the secretion of the colouring matter, which only exists in the vascular circumference of the cal- 382 GASTEROPODA. ciferous membrane. The colouring matter becomes thus incorporated at definite points, with the cement by which the shell is extended, and is arranged in various manners according to the position of the secreting organs which furnish it. Another peculiarity which distin- guishes external shells is that their outer sur- face is often invested with a membranous layer, called the epidermis, which having been re- garded by some authors as a part of the true integument of the body, has given rise to the supposition that all shells being placed between two layers of the skin were in fact internal, the difference between the one and the other con- sisting merely in the extent of development. In support of this opinion reference has been made to the great thickness of this epidermic coat, which not unfrequently is such as to give to the surface of the shell a felted or pilous ap- pearance ; but if such an idea were correct, it is evident that the epidermis must be formed prior to the deposit of calcareous matter be- neath it, which observation has disproved, in- asmuch as those shells in which the epidermic covering is most dense and shaggy are found whilst in ovo to be without such an investment. The so-called epidermis, therefore, whatever may be the aspect which it presents, whether it be, as is usually the case, a brittle lamella en- crusting the shell, or a flocculent and pilous covering, is evidently inorganic, being merely a crust of inspissated mucus, originally secreted with the calcareous particles, and forming when dry a layer encrusting the surface of the shell. There is yet another structure common to shells of this class, of which it remains to speak, namely, the enamel or pearl, wh ich lines such por- tions of them as are immediately in contact with the body of the animal ; this polished material may be likened to the glazing of an earthen- ware vessel, and is a varnish produced from the general surface of the mantle, by some mo- dification of its secretion the nature of which is unknown, and spread in successive coatings over the more coarse calcareous matter, where- ever such a polish becomes needful. Having thus briefly described the origin of the different parts of a shell in the simple form which we have chosen as an example, we shall now proceed to examine the structure and mode of growth in others of a more complicated aspect. The majority of the Gasteropoda are furnished with a shell which has been denominated spiri- valve. Let the reader imagine the shell of the Patella to be lengthened into a long cone, which, instead of preserving its symmetrical form, is twisted around a central axis, and he will imme- diately understand the general arrangement of the parts in shells of this description. The cause of such an arrangement is owing to the shape of the body of the animal inhabiting the shell, which, as it grows, principally enlarges its shell in one direction, thus of course making it form a spire modified in shape according to the de- gree in which each successive turn surpasses in bulk that which preceded it. The axis around which the spire revolves is called the columella, and the mode of revolution around this centre gives rise to endless diversity in the external form. In the spirivalve-shelled Gasteropoda, as in those last described, we find a difference in structure between that part of the mantle which envelopes the viscera, and is always concealed within the cavity of the shell, and the more vascular portion placed around its aperture : the former is thin and membranous, its office being merely that of thickening the shell by the deposition of successive calcareous strata applied to its inner side, and of producing the pearly lining which smooths and polishes the interior ; the latter part of the mantle is thick, spongy, and coloured, secreting largely the cal- careous particles with which the progressive amplification of the shell is effected : this por- tion (Jig. 179, c,) from its thickness, and the Fig. 179. manner in which it usually surrounds the en- trance to the shell, is generally termed the col- lar. In such species as inhabit coloured shells we may observe upon the surface of the collar (Jig. 179, d,) patches of different colours corres- ponding in tint with the various hues seen upon the exterior. These spots supply the pigment, which being mixed up with the earthy cement serving for the enlargement of the shell stains it with a corresponding tint. In many instances, as in the figure, the colours are continually secreted by the dark spaces, d, causing the painted bands which they produce to wind un- interruptedly in the direction of the convolu- tions of the spire, and they may be seen gra- dually to increase in breadth as the size of the animal enlarges : but more frequently it happens that the colouring matter is only furnished at stated periods, and in such cases of course the shell will be marked with spots, the intervals be- tween which will be regulated by the frequency of the supply. It will be seen that by a combina- tion of these circumstances it is easy to explain how every variety of marking may be produced. The most conspicuous exception to the gene- ral process by which shells are painted, is met with in the porcellaneous Couries (Cyprcea), which at various periods of their growth could scarcely be recognised as belonging to the same genus. In the young animal the enlargement of the shell is effected in the ordinary manner, and its colours are supplied from the surface of the collar : in the mature state, however, these shells are coloured in a very different manner, and acquire at the same time a great increase of thickness ; this is effected by the enormous de- velopment of the alse of the mantle, which in the full-grown animal become so much ex- tended, that when the creature is in motion they are laid over the external surface of the shell so as entirely to conceal it. These alee contain patches of pigment which secrete colours en- tirely different from those contained in the collar, and from their whole surface exudes a GASTEROPODA. 383 calcareous varnish, which being laid over the exterior of the old shell completely conceals the original markings ; these, however, may be again exposed on removing with a file the outer crust : a line, which is generally very distinctly seen running longitudinally along the back of the shell, indicates the spot where the edges of the two ate of the mantle met during the com- pletion of this singular process. Such shells are therefore remarkable from the circumstance of having their thickness increased by additions to the outer as well as to the internal surface. In terrestrial shells it is only when they have arrived at their full growth that a rim or margin is formed around the aperture, which serves to strengthen the whole fabric; but in marine shells, which attain to much larger dimensions, the growth is effected at distinct periods, each of which is indicated by a well-defined margin, and these ridges remaining permanent, the suc- cessive stages of increase may be readily seen. At each suspension of development, it is not unusual to find spines or fringes, sometimes differently coloured from the rest of the shell, and not unfrequently of considerable length. In fig. 180, which represents the shell of Murex Fig. 180. cornutus, the nature and arrangement of such spines is well exemplified. They are all formed by the margin of the mantle which shoots out into long fringes, encrusting themselves with a shelly covering ; each spine therefore is at first hollow, and if in many species they are found solid, it is because the original cavity has been gradually filled up by the deposition of earthy matter within it. The syphon with which many Conchiferous Gasteropoda are provided is pro- duced in precisely the same manner, and its identity in form with the other spines covering the surface of the shell is in the annexed figure sufficiently obvious. In many species, as in the beautiful Turbo scalaris, (fig. 181,) the epocha of growth are only indicated by ridges surrounding the shell at regular intervals, each of which originally terminated a fresh augmen- tation of its size. It is difficult to imagine by what influence these creatures are induced to enlarge their habitations at such regular inter- vals, terminating each operation by a similar margin ; some authors imagine that each time the creature emerges from its abode a fresh addition is made ; others that it is dependent upon the temperature or state of the seasons, but without sufficient grounds for either of these assertions ; it seems more probable therefore that the growth of the body gradually rendering the former dimensions of the shell incommo- dious from time to time renders these pe- riodical enlargements necessary. Although shells are evidently inorga- nic and extra-vascu- lar structures, it is now universally con- ceded that their in- habitants have the power of removing portions which may obstruct their growth, or needlessly infringe upon the limits of their abode. In the Murices we have in- disputable evidence of this fact in the removal of such spines as would interfere with the revolutions of the shell around the columella, and in Conus and similar genera a like faculty enables the animals to thin the walls which bound the inner whirls when their original thickness is rendered un- necessary by the accession of new turns. Such a solvent power indeed is not only exer- cised upon their own habitations, but many Gasteropods are able gradually to bore holes in other shells, or perforate the rocks upon which they reside to a considerable depth. The mode in which this is effected is, however, still a mystery ; some authors ascribe it to a power of absorbing their shells, an expression the vagueness of which is sufficiently evident; others ascribe it to some acid secretion at the disposal of the animal ; yet although this ex- planation is certainly plausible, when we reflect that the very structure which secretes this sup- posed acid is itself the matrix of such abundant alkaline products, it is not easy to imagine how the same structure can at the same time furnish such opposite materials. As we should expect from the mode of its growth, the shell throughout all the Conchi- ferous class is composed of earthy matter, cemented together by an animal substance easily separable by the action of acids. In the porcellaneous shells the animal matter exists in much less quantity than in those of a fibrous texture; in the former, indeed, Mr. Hatchett found that when the carbonate of lime, of which the earthy portion is almost entirely formed, is dissolved even by very feeble acids, little or no vestige of any membranous struc- ture could be perceived, nor indeed could any be detected, but by the small portion of animal coal which was formed when these shells had been exposed for a short time to a low red heat; in others however, as the Patelte, a sub- stance was left untouched by the acids which had the appearance of a yellowish transparent jelly, by means of which the earthy matter had been, as it were, cemented together. On examining minutely the mechanical ai- rangement of the layers of which these shells are composed, it is found to vary in different kinds, and from this circumstance the fossil Fig. 181. 304 GASTEROPODA. conchologist may derive important information in examining mutilated remnants sometimes so plentifully met with in calcareous strata. The simpler shells (Patella, Fissurella) are formed of very thin, compact, and parallel layers, whilst in others three distinct strata of fibres, each of which assumes a different direction, may be observed. The fibres composing the external layer are disposed perpendicularly to the axis of the shell. In the middle stratum the fibres are placed obliquely and are slightly twisted, but so arranged that each meets at an obtuse angle the extremity of one of the fibres composing the outer layer, and in the internal stratum they again assume a perpendicular direction. Such a disposition of the fibres, which is met with in all Siphonibranchiate shells, is eminently calculated to resist ex- ternal violence in whatever direction it may act, and greatly contributes to the solidity of the whole fabric. Operculum. — Many of the spirivalve Gaste- ropoda, especially such as are aquatic, are provided with a calcareous plate, which is placed upon the posterior surface of the body, and closes accurately the mouth of the shell, when the animal is retracted within it. The texture of the operculum is sometimes horny, but it is more frequently calcareous and of a stony hardness, its contour being accurately adapted to the orifice. It is composed of parallel fibres disposed perpendicularly to the base of the shell, and deposited in successive layers around an axis, so as to give to the whole structure the appearance of a solid spirivalve, as may readily be seen on removing it from the animal and examining its inner surface. This has been looked upon by some zoologists as analogous to the second valve of bivalve Mollusea, to which, but for its want of a ligamentous attachment, it certainly bears a distant resemblance. The deciduous operculum of terrestrial Gasteropoda, or epiphrugma, as it is usually called, is a widely different structure, being merely an inspissated secretion, with which, during the period of hybernation, the entrance to the shell is closed ; and on removing the outer plate, not unfrequently a second or even a third similar membrane will be found within, forming additional safeguards against intrusion or the vicissitudes of temperature. During the progressive growth of the shell the animal contained within it necessarily changes its original position, advancing gra- dually as the body enlarges from the earliest formed spires towards the aperture, as may easily be proved by sawing off the apex of a spirivalve shell containing the living animal. This circumstance is remarkably conspicuous in some of the Bulimi ( Bulimus decollatus ) , enabling the occupant, as it grows, to break off the turns of its spire which first contained it, so that at the latter period of its life it does not retain any part of its original shell. The mode in which this advancement is effected is a subject of much curiosity, as it involves a power of detaching the muscles connecting the creature with its abode, from the place where they were originally fixed, and forming a new connexion with the shell ; but whether this is effected by the removal of the original fibres and the production of others more ante- riorly, as is believed by some, or whether, as is more probably the case, the creature has a power of changing the attachment of its re- tractor muscle at pleasure, is still a matter of uncertainty. Organs of digestion. — We shall not be sur- prised to find that in a class so extensive, and composed of individuals living in such diver- sified circumstances, the alimentary organs are much modified in form in different species, according to the nature of the food with which they are nourished. Mouth. — In most instances the mouth pre- sents the appearance of a retractile proboscis, which can be protruded or shortened at the will of the animal, but unprovided with jaws or any apparatus for mastication ; it is in such cases a muscular tube, formed of longitudinal fibres prolonged from the common parietes of the body, and of circular muscles, the former serving for the retraction of the organ, the latter causing its elongation by their successive action ; by means of this simple structure every movement requisite for the prehension of food is effected. At the bottom of the tube is a narrow vertical aperture, the edges of which are slightly cartilaginous, and behind this is the tongue armed with spines variously dis- posed ; the aliment therefore, having been forced by the contractions of the proboscis through the aperture at its termination, is re- ceived by the tongue, and by the aid of the latter organ is propelled into the oesophagus without mastication or any preparatory change. In Buccinum and other syphoniferous ge- nera, the structure of the proboscis is much more complicated and curious, (fig. 182.) “ The proboscis, which carries with it the oesophagus in its different states of protrusion, is organised with wonderful artifice, being not only capable of flexion in every direction com- bined with limited power of retraction or elongation, but it can be entirely lodged in the interior of the body, folded within itself, so that that half which is nearest the base en- closes the other portion : from this position it is protruded by unfolding itself like the finger of a glove or the tentacle of a snail, only it is never completely inverted. We may repre- sent it as composed of two flexible cylinders (fig. 182, «, b,) one inclosed within the other, the upper borders of which join, so that by drawing outwards the inner cylinder, it is elongated at the expense of the other, and on the contrary, by pushing it back, the internal cylinder becomes lengthened by its shortening. These cylinders are acted upon by a number of longitudinal muscles (c, c), all very much divided at each extremity, the internal or su- perior divisions being fixed to the parietes of the body, whilst at the other end they are attached to the inner wall of the internal tube (i a ) of the proboscis, along its whole length, extending even to its extremity ; their action is obviously to draw the inner cylinder, and con- GASTEROPODA. 385 Fig. 182. sequently the entire proboscis inward. This being done, a great part of the inner sur- face of the inner cy- linder becomes a part of the external surface of the outer cylinder, ■whilst the contrary oc- curs when the pro- boscis is elongated and protruded. The elongation of the inner cylinder by the unfolding of the outer, or what is the same thing, the pro- trusion of the probos- cis, is effected by the intrinsic annular mus- cles which assist in forming the organ ; they surround it throughout its whole length, and by their suc- cessive contractions force it outwards; one espe- cially, seen at b, placed near the junction of the extremity of the outer cylinder with the inte- guments of the head, which is stronger than the rest. When the proboscis is protruded, its retractor muscles acting separately, bend it in every direction, being in this case antago- nists to each other. The internal cylinder incloses the tongue (f), the salivary canals (e), and the greater part of the oesophagus (