1! I i CD m O THE CYCLOPAEDIA \ OF ANATOMY AND PHYSIOLOGY VOL. IV,— PART II. S T A W R I 1849-1852 THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. EDITED BY ROBERT B. TODD, M.D. F.R.S. FELLOW OF THE ROTAL COLLEGE OF PHYSICIANS; PHYSICIAN TO KING'S COLLEGE HOSPITAL J AND FORMERLY PROFESSOR OF PHYSIOLOGY AND OF GENERAL AND MORBID ANATOMY IN KING'S COLLEGE, LONDON, ETC. KTC. VOL. IV.— PART II. STA WRI 1849—1852 LONDON LONGMAN, BROWN, GREEN, LONGMANS, & ROBERTS. Wf THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. VOL. IV. PLA WRI 1847-1852 THE CYCLOPAEDIA OF ANATOMY AND PHYSIOLOGY. EDITED BY 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. IV. PLA WRI 1847—1852 LONDON LONGMAN, BROWN, GREEN, LONGMANS, & HUBERTS. STATISTICS. 801 «In such instances, there is little appearance of any thing morbid beyond the increase of size. The contained blood is usually very dark, and the spleen shares the deepening of colour. By long duration, the capsule of the organ and the fibrous tissues generally, be- come somewhat thickened, but in other re- spects the texture is little altered. In the second class, in which the swelling is pro- bably produced by a peculiar state of the blood (rft/scraxia), and is certainly associated with a class of blood diseases, the texture of the organ is usually much altered. The size of the spleen is often astonishingly increased, so that it possesses a volume of from 100 to 300 cubic inches, and a weight of 10-20 Ibs. The increase includes, besides blood, a considerable quantity of a fibrinous material, the nature of which, and its relations to the healthy organ, are at present little known. The colour and consistence are of every possible gradation ; from greyish to deep brownish red, or from a soft, friable mass, to a dense, firm, and almost fibrous texture. There is a general relation of these changes to the date and duration of the swelling ; thus in acute or recent cases, the organ is usually soft and of a dark colour, while by long continuance, or in chronic diseases, its consistence is greatly increased, and its colour, as well as that of the contained blood, is much paler or greyer than natural. Atrophy of the spleen, or slow and permanent diminution of its size, is much more infrequent than the preceding converse condition. It is associated with similar varieties of colour and consistence. Inflammation of the spleen. — The peritoneal surface of the organ shares in the diseases of this structure generally, and an inflammation of this part of the serous membrane not tin- frequently accompanies the enlargements pre- viously mentioned. The exsudation and re- sults are no way peculiar. Concerning in- flammation of the parenchyma of the spleen little can at present be said. The large and numerous veins which it contains are liable to inflammation, the secondary being the more frequent form of phlebitis which affects them. As regards other morbid products, organ- ised and unorganised, the spleen otters no- thing deserving a special notice. BIBLIOGRAPHY. — M. Malpighi, De Liene, in Exercitationibus de Viscerum Struetura, Lend. IGfiD. 12. F. Ruysch, De Glandulis, Fibris, Cellu- lisque Lienalibus, Epist. Anat. Quart. Opera omnia. A. V. Leeuwenhoek, Microscopical Observations on the Structure of the Spleen, Phil. Transact. 170fi, p. 2305. T. Douglass, Observations on the Glands in the Human Spleen, Phil. Transact. 1714, p. 499. \lr. Stuckelny, Of the Spleen, its Description and llistoiy, Uses and Diseases, Lond. 1722. B. 8. Albinus, De Liene, in Anotat. Academ. lib. vii. cap. 14. p. 84. T)e Lasone, Histoire Anatomique de la Kate, Memoires de 1'Academ. de Paris, 1754. T. Lieutatid, Observation sur la Grosseur Naturdle de la Kate, Mem. de 1'Acad. de Paris, 1788. W. New- sou, Experimental Inquiries, Lond. 1776 ; et Opus Postluimum, Lngd. Bot., 1786. L. et T. P. Asso- iiuiti, Recherchcs sur la Rate, Paris, 1801. A. Sforcs- i-lii, Del vero e primario Uso della Milza nell 'L'omo vol.. iv. e in tutti gli Animali Vertebrati, Milano, . Benj. Rush, An Inquiry into the Functions of the. Spleen, &c., Philadelphia, 1806. Everard Hume, On the Structure and Uses of the Spleen, Philos. Transact, for 1808, p. 45. ; further Experiments on the Spleen, p. 133. ; Experiments, &c., ibid. 1811. C. F. Heusinger, Ueber den Ban und die VerrichtuDg der Milz, Eisenach, 1817. F. Tiedemann und L. Gmel'tn, Yersuche iiber die \Yege, auf welchen Sub - stanzen atis dem Magen und Darin im Blut gelan- gen, iiber die Verrichtung der Milz und die gehri- men Harnwege, Heidelberg, 1820. T. Hodgkin, On the Uses of the Spleen, Edinb. Med. and Surg. Journ., 1822, p. 83. Dobson, Lond. Med. and Phys. Journal, 1830, Oct. G. C. Holland, Physiology' of the Foetus, Liver, and Spleen, London, 1831. T. Milller, Ueber die Structurder eigenthiimlichen Kor- perchen in der Milz einiger pflanzenfressender Sau- gethiere, Mull. Arch., 1834. T. C. H. Giesker, Spleno- logie, oder anatomisch-physiologische Untersuchun- gen iiber die Milz, Zurich, 1835. M. T. Evans, Lond. Edinb. and Dubl. Phil. Mag., 1833. Nov. Schwager- Bardeleben, Observationes Microscopicse de Glandu- larum Ductu Excretorio carentium Struetura, &c. Berol. 1841. Th. v. Hassling, Untersuchungen iiber die weissen Korperchen der menschlichen Milz, Regenzburg, 1842. /. Reid, Lond. and Edinb. Monthly Journ., 1843. Apr. Fr. Oesterlen, Beitriige zur Physiologic des gesunden und kranken Orga- nismus, Jena, 1843, pp. 41 — 52. E. Huschhe, Lehre von den Eingeweiden und Sinnesorganen, Leipzig, 1844. Schlemm, Berliner Worterbuch der medicin. Wissenschaften, Band xxiii. Th. 435. Ch. Poehnaiui, Memoire sur la Structure et les Fonctions de la Rate, Annales et Bulletin de la Societe' de Medeeine d« Gand, 1846, Dec, C. Handheld Jones, On the Yel- low Corpuscles of the Spleen, Lond. Med. Gazette, 1847, Jan. John Simon, On the Thynms Gland, Lond. 1845. A. Kolliker, Ueber den Ban und die Verrieh- tungen der Milz, in Mittheilungen der Ziiricher naturforschenden Gesellschaft, 1847. A. Echer, Ueber die Yeriinderungen welche die Blutkorper- chen in der Milz erleiden, in Zeitschrift fiir rationelle Medicin, Band vi. 1847. C. B. Heinrich, Die Krank- heiten der Milz, Leipzig, 1847. T. Landis, Beitrage zur Lehre iiber die Verrichtungen der Milz, Zurich, 1847. Gerlach, Ueber die BlutkSrperchenhalten- den Zellen der Milz, in Zeitschrift fiir rationelle Medicin, Band vii. 1848. T. Bedard, Reeherches experimentales sur les Fonctions de la Rate et sur celles de la Yeine Porte, Archives Ge'nerales de Me'- dicine, Paris, 1848, Oct. Nov. Dec. ( Albert KolMer.} * STATISTICS, MEDICAL. — The Sta- tistical Method ; the Numerical Method. Lu Mcthode Nurnerique. — It is to be regretted that the use of numbers in any branch of scientific inquiry should have seemed to need a special name ; for the name has given rise to prejudices and misconceptions which could never have attached to the thing signified. There is no science which has not sooner or later discovered the absolute necessity of re- sorting to figures as measures and standards of comparison ; nor is there any sufficient reason why physiology and medicine should claim an exemption denied to every other branch of human knowledge. On the con- trary, they belong in an especial manner to the class of sciences which may hope to de- rive the greatest benefit from the use of imm- * The Editor is indebted to his friend Dr. Brinlon, for the translation of the article on the normal anatomy of the spleen from the German MSS. (,t' Protestor Kolliker, and for the sketch of the abnor- mal anatomy. 3 v 802 STATISTICS. bers ; and even those persons who are most given to express doubts of the necessity or expediency of resorting to them, find them- selves constrained to sanction by their own practice what they condemn in theory. This is an all-sufficient answer to those who con- tent themselves with objecting in general terms to the employment of numbers in me- dical investigations. As to more minute and detailed objections, these will be found to be anticipated and disarmed by the simple con- sideration that they apply in reality not to the use, but to the abuse of numbers. The time has long gone by, when the absolute dependence of all science on observation and experiment could admit of question or dis- pute ; and, as no one in the present day claims for physiology and medicine any im- munity from the severe conditions which the very nature of things imposes, we are spared those appeals to authority which might for- merly have been required at our hands. The absolute necessity of observation and experi- ment towards the improvement of the science and art of medicine, in the widest acceptation of those terms, may, therefore, be safely taken for granted. The only points upon which any serious difference of opinion or divergence of practice exists, are the degree of care and accuracy which should be brought to bear on individual observations and experiments, the properties which fit single facts to be thrown into groups or classes ; the language which ought to be employed in expressing the ge- neral results of such classifications ; and the number of facts which, being so grouped or classified, may be required to establish a ge- neral proposition, or to furnish an accurate test or trustworthy standard of comparison. The human mind is so constituted, that it looks forward to an occurrence with a con- fidence proportioned to the number of times that it has been previously known to happen. Hence, the universal belief that all living beings will die, and that the sun will rise and set to-morrow ; hence, the somewhat less sanguine expectation that quinine will cure ague, and that vaccination will either pre- vent or modify small-pox ; hence, the little hope we have that a severe attack of Asiatic cholera will terminate favourably, and our absolute despair of the recovery of a patient seized with hydrophobia. In these, and other analogous cases, we have either the expe- rience of all mankind in all times and places, or that of large numbers of men in addition to our own. We do not require that the in- dividual occurrences which have created our confidence, our misgiving, or our despair, should be committed to paper, arranged in columns, and embodied in sums or averages. For practical purposes we are satisfied with our own impressions. But should a doubt be expressed, and supported by a show of reason or experience, whether vaccination possess the virtue generally attributed to it ; should some new preventive measure or mode of treatment be recommended in cholera, as su- perior to other plans previously adopted ; we ask for the specific facts which have seemed to warrant the doubts of the one party, and the recommendation of the other. If these facts are few, we naturally view them with mistrust, and are disposed to attribute them, at the best, to some coincidence ; or if, being more in number, their actual amount is stated in vague and general terms, we as naturally demand the precise figures. We feel instinc- tively, that common and familiar words are altogether wanting in precision ; that they take their meaning from the character of those who use them ; that, in a word, " the sometimes of the cautious is the often of the sanguine, the always of the empiric, and the never of the sceptic ; while the numbers, 1, 10, 100, 1000, have but one meaning for all mankind." But this mistrust of vague generalities of expression, is not the only form in which the more cautious and logical spirit of modern times embodies itself. The same misgivings are felt and expressed as to the propriety of committing the facts which are to serve as the materials of our theories to the uncertain keep- ing of the memory. We feel that a science built up of such materials, bears to true science the same sort of relation which tradition bears to history. It may not be destitute of valu- able truths and sound principles, but it must fail in that precision and delicacy of discrimi- nation which forms the peculiar attribute of true science as of true history. The history of medicine abounds with examples of impor- tant principles of treatment, and valuable re- medies discovered solely by the light of experience, based upon the mere recollection of a number of individual occurrences. In this way the efficacy of bark and arsenic in ague, of mercury in syphilis, and of iodide of potassium in certain forms of secondary disease was discovered. Indeed, it may be confidently affirmed that all our knowledge of remedies is traceable to this source ; and it is probable that we shall continue to be indebted to it for all future discoveries of importance. It is the natural method of discovery, and, as such, will necessarily maintain its ground. But a very little reflection will convince us of the utter inadequacy of this method to meet the strict requirements of the science, and the ever-vary- ing exigencies of the art of medicine. We may be able by its aid to sketch the broad out- lines, and mark the salient points of a science, but we cannot hope to fill in the details with all the lights and shadows which go to make up the perfect landscape. Still less can we satisfy ourselves or others as to the real merits of disputed questions by an appeal to un- written or loosely recorded experience. We all feel that there is no solution for our doubts short of an appeal to observations carefully and faithfully recorded, and summed up in the clear and simple language of figures. The use of mercury in syphilis, supplies us with an apt illustration of this truth. An experience, founded upon unrecorded and unnumbered occurrences, first recommended this remedy for the treatment of that disease ; but it would STATISTICS. so:; appear that a counter experience of the same kind was continually leading to its disuse. Thus Morgagni tells us that, when he was quite a young man and went to Bologna, both methods of using mercury, internal and ex- ternal, were so far deserted, that he never saw any physician make use of them, or ever heard of his using them, for the whole space of eight years, during which he studied there.* It would also appear that from the beginning of the sixteenth century up to the present time, there has always been a large number of sur- geons, who have either abandoned the mer- curial treatment altogether, or have restricted the use of the mineral to certain exceptional cases.f In the difference of opinion which prevailed upon this subject, the necessity of submitting the question at issue to the test of figures made itself so strongly felt, that a series of the most elaborate inquiries was undertaken at the instigation of governments, or by private individuals. These inquiries resulted in the collection of nearly 60,000 facts, by means of which the possibility of promptly healing ve- nereal sores without mercury and with but moderate risk of a relapse, or of the occurrence of secondary symptoms, was conclusively esta- blished. £ To this same test of figures, all the questions which arise from time to time, as to the relative value of the several remedies recom- mended in the treatment of syphilis are, by common consent, submitted. A most con- vincing proof that the numerical method is, in all cases of doubt and difficulty, the means of solution to which men naturafly resort, is af- forded by the treatise of Benjamin Bell, on this very subject, published in the year 1793.§ Speaking of the treatment of incipient chancres by caustic, he notices the very important ob- jection, that the cure of the sores was often succeeded by buboes ; and he adds, that for a considerable time he was induced to suppose that the swellings of the glands, which thus take place after the cure of chancres, were more the effect of accident than of the method of treatment, and that they would have oc- curred under whatever management the sores might have been. The frequency, however, of their appearance, led him at last to suspect that he was mistaken, and further observation made it obvious that this was the case. He goes on to observe, " As experiment alone could determine the question, I was resolved to employ this test. Of the first twenty patients who occurred with incipient chancres, in ten they were destroyed by an immediate and effectual application of lunar caustic, the remedy being employed, according to my usual custom at that time, instantly on my being called ; of the other ten, five were dressed with blue mercurial ointment, and five with common wax ointment. The sores to which caustic * Morgagni's 58th Epistle. t See on this subject, the British and Foreign Medical Review, vol. v. p. 4. £ British and l^oreigii Medical Review, vol. v. p. 7. § A Treatise on Gonorrhcea Virulenta, and Lues Vencrea. By Benjamin Bell, vol. ii. p. 322. were applied healed much sooner than the others, and next to them the sores that were dressed with mercurial ointment. But of tin- ten patients to whom caustic was applied, no less than eight had buboes, whilst only one bubo occurred in all the others; and it happened in one of the patients whose chancres had been dressed with mercury. I thought also that buboes appeared to be less frequent from the application of caustic, where mercury had been previously given. This fell within my ob- servation from time to time, with patients who had taken mercury, either of their own-accord or by the advice of others ; and appearing to be of importance, I was resolved to bring it like- wise to the test of experiment, and the result was as follows : of forty-eight patients with chancres in an incipient state, and exactly as they occurred in practice, one half was treated in the manner I have mentioned, by destroy- ing the chancres with caustic immediately on my being desired to see them, while all the others were put under mercury for eight or ten days before the application of caustic. In every other circumstance the method of treat- ment was the same. The difference, however, surprised me exceedingly. Of the twenty-four treated with the immediate application of caustic, twenty wereseixed with buboes; while only three buboes occurred in an equal number to whom mercury had been previously admin- istered." The subject of the treatment of syphilis has been selected for illustration on account of the large use which has been made of figures in discussing the relative value of the two modes of treatment; and the extract from the works of Benjamin Bell as a proof that, long anterior to any discussions among me- dical men as to the value of the numerical method and the extent to which it might be applied in the solution of medical questions, men of shrewd common sense were driven to the use of numbers, as the natural and only means of solving difficult questions, and set- ting doubtful or disputed points at rest. Thus much, by way of introduction, the difference of opinion which prevails as to the value of the numerical method seemed to demand. The numerical or statistical method may be defined as the science which prescribes rules for the bringing together of scattered observ- ations, arranging them in classes, testing their sufficiency in point of number, and deducing from them, when so arranged, average and extreme results, fitted by their very condensa- tion to become standards of comparison and data for reasoning. The numerical method*, so defined and * The term, numerical method, will be used throughout this article in preference to the word statistics, or statistical method; for, properly speak- ing, statistics means the science of states (from the German word staat, a state), and is therefore syno- nymous with the terms " political economy," " po- litical science," " social science." The first use of the term statistics has boon traced to Achemvnl, Professor of History in Gottingen, who, in 17-U), published an historical work, in which the phrase scirntia statistica occurs for the first time. The use 3 V 2 804 STATISTICS. understood, comprises two distinct inquiries, the one relating to the individual facts which form the materials for the calculation of aver- age and extreme values, and the other re- ferring to the averages and extremes them- selves. This natural and convenient division of the subject it is proposed now to adopt. 1 . Of facts considered as the elements of sta- tistical inquiries. — Scientific inquiries are con- versant with two orders of facts: — namely, phenomena of varying intensity, and events brought about by a multitude of causes. The first class of facts enters very largely into the science of physiology ; the last class consti- tutes, though not to the exclusion of the first, the mass of the materials by which the prac- tical sciences of medicine and hygiene are built up. As examples of phenomena of varying inten- sity may be cited the pulse and respiration, the temperature of the body, the secretions of the skin, kidneys, and lungs, the evacuations of the bowels, the weight and stature of the body at different ages, and the muscular de- velopment and power of different nations and classes of pei>ons. These phenomena, care- fully observed and recorded by the aid of the watch, the thermometer, the measure, the balance, and other instruments adapted to special purposes, become so many numerical values, having the same relation to the aver- ages deduced from them, as the more simple events expressed in units bear to the mean results for which they furnish the materials. As an example of an event brought about by a multitude of causes may be mentioned the event of death, governed, as to the age at which it occurs, by original strength or pecu- liarity of constitution, good or bad nursing and management in infancy, sex, occupation and habits of life, climate and place of abode, skilful or unskilful treatment in sickness ; in a word, by the varied influences which make one man to differ physically from another. This is an illustration taken from the science of hygiene. The alternative of death or re- covery from a disease induced by a cause or causes of variable intensity in persons of opposite sex and of different ages, with con- stitutions modified by the several agencies just specified, and submitted to different modes of treatment, is an example from the practice of medicine. Physiology furnishes illustrations of the same kind in those func- tions of the body (such as the cutting of the teeth, and the first appearance and cessation of the catamenia) which are dependent for of numbers as a necessary means of comparison in this work of Achenwal, led men to confound the in- strument with the science. Dufau, in his Traite' de Statistique, incorrectly derives the term statistics from the Latin status. The meaning attached to the words statism and statist, in the writings of poets, essayists, and dramatists, bears out the view just put forward of the proper signification of the term statistics. Mil- ton, for instance, speaks of " statists and lawyers," and elsewhere uses the term in the sense of a man having political power and influence. Ford also uses the word in this latter sense. South speaks of persons who called our religion statinm. the period of their occurrence on peculiarity of constitution determined by the combined action of the influences already adverted to. Between these two orders of facts — phe- nomena of varying intensity, and events brought about by a multitude of causes — there is no other difference but that which is apparent on the face of each, namely, that each individual fact, in the one case, is repre- sented by a variable number, while in the other it is a simple unit. If, for example, we count the pulse of several men at the same age, we shall find that each separate observa- tion gives a different number; but, the event of death or recovery in cases of typhus fever will be recorded as a simple unit. In all other respects the two classes of facts closely re- semble each other; for the number of beats peculiar to the pulse of each individual, is as much the result of the concurrent action of several causes, as the event of death or reco- very from fever. The original and acquired constitution, towards the formation of which so many causes must have conspired, deter- mines the number of the pulse in the one case, and influences the event of the disease in the other. The two classes of facts are also equally fitted to supply the elements for the determination of average and extreme values ; for it is obvious that the mean and extreme numbers of the pulse, in males and females respectively, furnish as trustworthy standards of comparison and data for reason- ing, as the average number of men following different occupations who die before any spe- cified period of life, and the greatest age which they respectively attain. From what has been just stated, it will be seen that all the facts which form the mate- rials for our averages, are phenomena or events brought about by the concurrent action of a multitude of causes. The facts or events with which the physiologist and physician are conversant, are remarkable for the mul- tiplicity of the causes which conspire to pro- duce them. The subject of study is the hu- man frame, with its differences of sex, age, and inherited or acquired constitution, acted upon by the variable influences of climate, oc- cupation, and habits of life, and still further modified in disease by the treatment and re- gimen which may happen to be adopted. In consequence of the number and diversity of the influences brought to bear upon it, the human frame presents an object of study only less difficult than the human mind, affected by a like number and variety of moral causes, of which the true nature and force have to be unravelled by multiplied observations on the condition of mankind under different cir- cumstances ; the aggregate of such observ- ations constituting a great part of the science of statistics properly so called, and bearing to the practical science of government the same relation which pathology and therapeutics, based upon large collections of facts, do to the practice of medicine. Now this dependence of the individual facts or events with which physiology and medicine are conversant on the concurrent action of a STATISTICS. 805 multitude of causes, has been urged as an ob- jection to the introduction of the numerical method into the service of those sciences. It is admitted, that the use of numbers and averages by the astronomer who deals with the more simple relations of matter, such as magnitude and relative position, and by the engineer who avails himself of its more simple properties, such as its hardness, tenacity and elasticity, have contributed to make the science of the one perfect, and the art of the other safe ; but it is contended that the use of num- bers cannot be extended beyond such narrow limits with safety or advantage, and that medi- cine and political economy lie beyond these limits. The actual practiceof mankind, founded upon an instinctive perception of the necessity of employing figures in the service of the phy- sician and statesman, may be fairly alleged as a sufficient answer to this objection ; but a little consideration will serve to show its futility. In the first place, it is self-evident that the exclusion of figures from the service of medi- cine, does not bring about the disuse of those very facts and events which are objected to as unfit to be employed as statistical or numerical elements. The physician will still persist in stating and recording the results of his expe- rience. He will still assert that he has sometimes observed this symptom in a certain disease, that he has often found that remedy beneficial, that he has almost never known such and such a mode of treatment to fail. Those who con- tend for the use of numbers in medicine, merely insist on the necessity of reducing the sometimes, the tficn, and the almost never to a more correct and intelligible form of expres- sion ; and they argue that it is utterly incon- sistent to object to the use of facts as mate- rials or elements of numerical propositions, and yet not to censure the use of these same facts as foundations for loose and inaccurate verbal statements. From this dilemma there is obviously no escape. But, though the ob- jection itself is futile, the misgiving of which it is the exaggerated expression is natural and well founded. It cannot excite surprise that the individual facts or events which own so many concurrent causes should be regarded as requiring, on the part of the observer, a greater degree of care in verifying, recording, collecting, and arranging them than would be necessary in the more simple cases already adduced ; and that both the facts themselves, and the numerical expressions in which they are embodied, should be viewed with a pro- portionate degree of distrust. From this mo- derate and reasonable view of the case, no advocate of the numerical method will be found to dissent. On the contrary, he will seek to strengthen it by giving due promi- nence to each separate ground of misgiving, and by laying down stringent rules for the guidance and governance of the observer. Before proceeding to detail some of these rules, it may be well to advert to a probable, and, indeed, obvious cause, of the distrust with which numerical data are sometimes regarded. Indiscreet advocates of the numerical method have sought to apply the general results of collections of cases expressed in the language of figures to the treatment of individual cases of the same disease, without making allowance for those differences between case and case which confessedly existed in the collections themselves. They have used a general prin- ciple, as if it had been a rigid and unbending rule of action; forgetting that though, as the experience of assurance offices abundantly tes- tifies, the general results obtained from a large number of individual facts may be safely re- applied to an aggregate of facts of the same nature, they cannot be brought to bear on a single case, or on a small number of cases, without the greatest danger. Each case must be viewed in practice, first as a generality governed by some large law of prognosis, diagnosis, and treatment ; and secondly, as a specialty demanding a careful consideration of all its peculiarities. Among the rules which ought to govern the observer in the collection of facts destined to form the elements of averages, there are some of so simple and obvious a nature as to re- quire no discussion. Such are, the previous preparation of some simple and available form of register, by means of which the several facts may be committed to paper at the very time of observation, so that nothing may be trusted to the memory ; the careful selection of the facts themselves ; the shaping of the inquiries which may be necessary to elucidate those facts as nearly as may be in the same terms ; the avoidance as much as possible of such leading questions as would be likely to bias the respondent, when the facts in question, like most of the particulars which make up the history of diseases, are dependent upon testi- mony ; and especially the purging of the ob- server's own mind of prejudices and precon- ceptions in respect of the subject of inquiry. The careful selection of the facts which are to form the materials of our averages is by far the most important of these rules, and one which demands a little further consider- ation. If we consider the facts we are ob- serving in the light of phenomena, or events brought about by a multitude of concurrent causes, it will be obvious that care will re- quire to be exercised, not so much in verify- ing each phenomenon or event as that of which we are in search, as in ascertaining that all the concurrent causes or conditions are, or have been, in operation to bring about that phenomenon or event. The absence of a single cause or condition will vitiate the in- dividual fact, and impair or destroy the value of our average results. A few illustrations will suffice to show what is here intended. We are anxious to determine the true average frequency of the pulse in adult males, in a state of rest, and as free as possible from the influence of all disturbing causes ; but, either from ignorance or oversight, we count it in- differently in every position of the body, and at all times of the day. In this case, our facts cease to be. comparable facts ; for it is well 3r 3 806 STATISTICS. known, that both posture and time of day have a remarkable influence on the number of the pulse. Or, to take another case, we wish to ascertain the influence of some employment upon health (say that of the letter- press printer) ; but we overlook the important fact, that in every printing office, two or three very distinct occupations are carried on, of which the most important are those of the com- positor and pressman. Not being fully aware of this fact, and of the wide difference exist- ing between the two employments, we pro- ceed to extract from some mortuary register the ages at death of printers as a class, calcu- late the average age at death, and then proceed to group the whole class of printers with that large class of occupations carried on in-doors, with little bodily exertion, to which the com- positor alone properly belongs, but from which the pressman is, by the nature of his employment, excluded. In this case, we should have been misled by the common name borne by men following two really dis- tinct occupations, and our facts would again cease to be comparable facts. A third and apt illustration is afforded by the Asiatic cholera. We wish to compare two different remedies or plans of treatment ; but we administer the one remedy, or adopt the one plan, at the onset of the epidemic, and the other during its decline. Here, again, our facts are not comparable facts ; for it is one of the well- known characteristics of this disease, that it is more severe on its first occurrence than during the period of its decline. The same sort of error would be committed, if one remedy were administered in an early, and the other in an advanced, stage of the attacks themselves. The principle which these illus- trations are intended to enforce, is the ne- cessity of selecting, as the elements of the -same average, facts strictly comparable, or, in other words, brought about by the same com- bination of causes. Over the intensity with which each cause acts in individual instances, the observer can exercise no control. His province is to ascertain that the same com- bination of causes is at work to bring about each phenomenon or event. If from ignor- ance or oversight he fails in this duty, he im- pairs the value of his facts, and vitiates his inferences in proportion to the number and force of the conditions that he has overlooked or omitted. In the observation and collection, therefore, of the individual phenomena or events which are to serve as materials for our average re- sults, the first precaution to be observed i?, that those phenomena or events should be strictly comparable as regards the combination of causes by which they arc brought about ; or, as the French statists express it, we must ensure " I'invariabilttc de V ensemble des causes possibles" The frequent omission of this most necessary precaution has given birth to the dogma of Morgagni — Nan numerandcc scdpcr- pendendce sitnt. obscrvationcs — and to the most valid objections urged against the applica- tion of the numerical method in medicine. For the collection, arrangement, and classifi- cation of the facts which are to form the ma- terials of our averages, no concise rules can be laid down. The tabular forms must adapt themselves to the exigencies of each individual inquiry ; and must be more or less compli' cated as the subjects of investigation con- sist of few or many particulars. In reporting cases, for instance, and in collecting and analyzing those recorded by others, tabular forms embracing many particulars are re- quired ; and the preparation of such forms demands unusual skill and care.* The same remarks apply to the collection and classifi- cation of recorded experiences and opinions bearing on particular subjects of inquiry f ; a numerical summary of authorities favourable and adverse to particular doctrines, consti- tuting what may be not inaptly termed the statistics of opinion. 2. Of the average and extreme results de- duced from observation. — The observer having exercised all due care in the observation of his facts, having grouped together only those events which owned the same combination of antecedents or causes ; and having further correctly performed the work of enumeration, has thus obtained certain average and extreme results, which are to constitute standards of comparison and data for reasoning ; the question naturally arises — are these average and extreme results sound and trustworthy standards and data, or not ; and what are the circumstances which render them the one or the other ? Common sense and experience combine to give an authoritative answer to this question. Our average and extreme re- sults are more or less sound and trustworthy, as the individual facts from which they have been calculated are more or less numerous. Where the facts upon which it is attempted to found a general principle, or to establish a standard of comparison, are very few, we are at once conscious of their insufficiency ; and the more readily when an attempt is made to apply the principle or standard in question to some important practical purpose. A better illus- tration of the futility of such an attempt can scarcely be found than the well-known test of Ploucquet. That author proposed to deter- mine whether or not a child was still-born by referring every doubtful case to a standard of comparison, founded upon three observ- * On this subject the late Dr. Todd, of Brighton, has written a very able work, which may be safely recommended to all who desire to enter upon such complicated investigations. The title of this work is : _ The Book of Analysis, or a New Method of Experience, whereby the Induction of the Novum Organon is made easy of Application to Medicine, Physiology, Meteorology, and Natural History ; to Statistics,' Political Economy, Metaphysics, and the more complex Departments of Knowledge. By Tweedy John Todd, M. D., of the Eoyal College of Physicians of London, &c. &c. 1831. f Reference may here be made to a paper pub- lished in the 3rd volume of the Journal of the Statistical Society of London, " On the best Method of Collecting and Arranging Facts, with a proposed New Plan of Common- Place Book." By the Author of this Essav. STATISTICS. 807 ations of the relative weight of the lungs and body ; of wliich three observations, one was made upon the body of an immature infant, so that the subjects of the observations were not strictly comparable. Though Ploucquet, in this procedure, offended against two of the most obvious statistical rules, his test con- tinued to be treated with undeserved respect, till comparatively recent investigations on a larger scale had demonstrated the little re- liance to be placed upon it. The most common attention to the ordinary daily occurrences of life would suffice to caution us against such errors as that into which Ploucquet fell. Coincidences of the most .startling character are constantly happening to put us on our guard against them. One which occurred to the writer of this article deserves to be put on record. Two cases of congenital absence of the larger pectoral muscle on the same side of the body, oc- curred, on the same day, among the out- patients of the King's College Hospital. This defect he has never happened to observe within the wards of that Hospital or else- where, either before or since. A similar coincidence, though of a less striking cha- racter, presented itself in the same institution while the writer was noticing with some care and interest the complexion and physiognomy of patients suffering from pulmonary consump- tion. His own previous experience, in con- formity with the general opinion, had pointed out the fair complexion as that of the great majority of phthisical patients ; but the almost exclusive occurrence for several days together of the olive complexion, among patients labouring under that disease, had almost led him to discard his former opinion and that of the best authorities, and to embrace one which, as farther observation convinced him, would have been erroneous. Games of chance are constantly furnishing striking examples of these coincidences, in the shape of what is familiarly known as a run of good or ill-luck ; the same event, favourable or unfavourable, occurring many times in suc- cession, contrary not only to reasonable ex- pectation, but to the results of unerring cal- culation. On the other hand, the success of the bank, with only a slight calculated chance in its favour, but with a capital sufficiently large to await the inevitable change in the run of luck, vindicates the sufficiency of large numbers of facts. The great annual fluctu- ations, too, which take place in the balance of the receipts and expenditure of assurance offices, but the ultimate safety of their trans- of of in- surances, serve to enforce the same truth. The sufficiency for all practical purposes of large numbers of facts, may also be interred from the remarkable uniformity observed to take place in the annual summaries of events brought about by the continued operation of the same combination of causes. The annual reports of the Registrar-General supply many illustrations of this principle. The illustration actions, when extending over a long term years and embracing a large number best suited to our present purpose, is one drawn from an event removed, by the very nature of the case, beyond the reach of ex- ternal influences, or only very remotely and indirectly amenable to them ; namely, the proportion of male and female births in suc- cessive years. In the eighth annual report of the Registrar-General (p. Ixi.), a table is given, in which the number of males and females born, to every hundred living males and females respectively, is recorded for the seven years 1 839-45. If we substitute 100,000 for 100, the table will read thus. Year. Males. Females. Excejs of Males. 1839 6,498 6,211 287 1840 C,539 6,250 289 1841 6,580 6,289 291 1842 6,564 6,273 291 1843 6,597 6,305 292 1844 6,676 6,381 295 1845 f.,622 6,329 293 The largest excess of male over female births, therefore, in these seven years is 295, and the least 287, the average being 291 ; so that the extreme fluctuation amounts to only 8 births in about 6500, or considerably less than 1 in 800 ; while the excess or defect above or below the average of 291 is only 4 births, or less than 1 in 1600. If the causes which determine the births of males and females re- spectively could be assumed to be constant and uniform, these fractional fluctuations would express the divergences due to the insufficiency of the number of observations to express an absolutely true result. The close approximation actually obtained must be held to prove the sufficiency for every prac- tical purpose of results based upon large numbers of observations. Having thus shown, by two opposite ex- amples, the total insufficiency of small num- bers of facts, and the sufficiency, at least for practical purposes, of large numbers of ob- servations, it will be necessary to enter into a more detailed examination of the relative value of numbers of observations intermediate between these two extremes. From what has been already stated, it must be obvious that the degree of confidence to be reposed in results based upon different collections of facts must vary with the num- ber of those facts ; and that, other things being equal, the value of the results must increase with every addition made to that number. But it is only by actual observation, or by mathematical calculations based upon indisputable data, that the precise value of any particular number of facts can be deter- mined. Observation, indeed, is altogether unequal to give more than a vague and general idea of the relative values of small and large collections of facts ; so that we must ulti- mately resort to the mathematics both for authoritative decisions and safe guides. As, however, the large majority of mankind is destitute of that mathematical knowledge and 3F 4 808 STATISTICS. training which is essential to the appreciation of mathematical rules, it is desirable to show, by an appeal to the results of actual observ- ation, the increasing value of increasing col- lections of facts, as well as the rate of that increase. For this purpose, it is proposed to make use of some observations collected by the writer of this article. Having had occa- sion, a few years since, to bring together, from the pages of the Peerage and Baronetage, the ages at death of the male members of the En- glish aristocracy, dying 21 years and upwards, to the number of several hundreds, it ap- peared to be a favourable opportunity of test- ing the relative values of large and small numbers of facts, as well as of obtaining a rude approximation to a rule or measure of value. The ages at death, relating, as they do, to members of the same class in society, and taken without selection from the successive obituaries of noble families, constitute a col- lection of strictly comparable facts, well suited to the purpose in view. The following table, which embodies the results of these facts in their bearing on the question before us, has been formed in the following manner : — The several facts were first arranged in groups of 2.3 each ; two successive groups of 25 were then formed into groups of 50 ; the groups of 50, in like manner, into groups of 100, and so on, till the last totals in the table were ob- tained. The greatest and least averages ob- tained from each group of facts were then selected, and, with the range, or difference be- tween them, thrown into a tabular form. Number of Facts. Average Age at Death. Max. Min. Range. 25 50 100 200 400 800 1600 69-40 66-44 63-70 62-38 61-10 60-84 V 50-64 55-20 56-85 57-61 58-24 59-67 J 18-76 11-24 6-85 4-77 2-86 1-17 60-25 in the first column of the annexed table, we may have the errors in excess or in defect which are enumerated in the second column. These figures, then, represent the extreme error which could have been committed, in this particular case, by relying on 25, 50, 100, 200, 400, and 800 facts respectively. But it must be borne in mind, that this collection of facts is one which, from the very nature of the case, is likely to present a minimum of divergence between the averages deduced from the same number of facts ; for the several obituaries, from which the ages at death are taken, register the deaths of one and the same class, inhabitants of the same country, and split into family groups bearing a close re- semblance to each other. If, instead of a single class, exposed to similar influences, and not admitting of subdivision into smaller classes, we were to take the members of that large section of the community which is ge- nerally known as the upper and middle class, with their numerous subdivisions of employ- ment, and class them by fifties and hundreds, we should encounter a much more consider- able divergence. The results of such a com- parison for the class in question are embodied in the following table. Now; if we assume the true average duration of life among the members of the Peerage and Baronetage, who have attained their 21st year to extend to 60 years (being the mean of ]600 observations), and, for the sake of simplicity, substitute for the decimals in the table the whole numbers nearest to them in magnitude, it will follow that, in making use of the several groups of observations specified Number of Error in Excess Facts. or Defect. 25 9. 50 6* 100 8J 200 2^ 400 H 800 n Number of Facts. Average Age at Death. Max. Min. Range. 50 100 200 400 800 1600 3200 6400 84-44 76-24 73-54 69-78 68-67 67-93 66-38 v 56-78 58-25 61-50 63-51 65-07 64-84 65-82 s 27-66 17-99 12-04 6-27 3-60 3-09 0-56 66-10 If, as in the former case, we take 66 years to be the true average age attained by the entire middle class, reckoning from 21 years of age, and reduce the range in each case to the nearest whole number, we shall have the following divergences. Number of Error in Excess Facts. or Defect. 50 14 100 9 200 6 400 3 800 2 1600 li 3200 Oi In this instance, therefore, though we begin with 50 in place of 25 facts, we obtain a possible error in excess or defect of 14 years in place of 9i years. It must be obvious, then, that the errors to which averages de- duced from any given number of facts are liable, will vary with the nature of those facts ; and that the extent of possible error will bear STATISTICS. 809 a certain proportion to the number of the influences which are brought to bear on each unit of each collection of facts. It must not, however, be forgotten that the figures in these several tables represent only possible errors. It may happen that the fi>st 25 observations brought together may yield an average differing by less than a single unit from the mean of thousands of observations ; and there is always a balance of probability in favour of the average even of a small num- ber of facts approximating more closely to the true average than to the extremes. That this is the case will be evident on the most cursory inspection of the following tables, of which the first is founded upon the facts Average Age at Death. 25 Facts. 72 Groups. 50 Facts. 36 Groups. 100 Facts. 18 Groups. 200 Facts. 9 Groups. 400 Facts. 4 Groups. 800 Facts. 2 Groups. 69 1 68 0 67 0 66 3 1 65 4 0 64 9 2 I 63 3 3 1 62 3 5 3 3 61 9 6 3 0 3 1 60 9 4 3 2 0 1 59 8 5 3 3 0 58 6 5 1 1 1 57 5 1 3 56 6 3 55 1 1 54 3 53 1 52 0 51 1 Average Age at Death. 50 Facts. 128 Groups. 100 Facts. 64 Groups. 200 Facts. 32 Groups. 400 Facts. 16 Groups. 800 Facts. 8 Groups. 1600 Facts. 4 Groups. 3200 Facts. 2 Groups. 84- 1 83 0 82 0 81 0 80 0 79 0 78 0 77 0 76 J 1 • 75 1 0 74 4 1 1 73 2 1 0 72 2 1 0 71 5 0 0 70 4 4 0 1 69 7 3 2 0 1 68 13 5 3 1 0 1 67 17 9 4 4 1 0 66 20 13 14 4 2 1 2 65 5 13 2 4 3 2 64 16 6 2 2 1 63 11 1 2 62 10 4 1 61 3 1 1 60 3 0 59 0 0 58 0 1 57 3 810 STATISTICS. relating to the duration of life of the aristo- cracy, and the second on the facts relating to the duration of life of the combined upper and middle classes. For the sake of per- spicuity, the average of all the facts in either table is distinguished by a larger type. These tables speak for themselves. In the first table, for instance, the small number of 25 facts is seen to yield the same average as the total of 1800 facts in no less than 9 in- stances, or one eighth of the whole number ; while in 26 out of 72 instances, or more than one third, the average of 25 facts exceeds or falls short of the average of 1800 facts by only a single unit. In like manner, it ap- pears from the second table, that in 20 cases out of 128, or little less than one sixth, the average of 50 facts coincides with that of G400^facts; and that in 42 out of 128, or nearly one third, it differs from it only by a single unit. Without entering into a minute examination of the other columns of the two tables, it will suffice to state that the proba- bility in favour of an average of a given num- ber of observations coinciding with the true average increases with the number of observ- ations ; so that we are again brought back to the expediency of collecting large numbers of observations wherever it is practicable so to do. In using small numbers of facts to establish data for reasoning or standards of comparison, we are bound to speak with dif- fidence of their sufficiency, and we ought to regard them rather in the light of probabilities requiring to be strengthened by other pro- babilities, as weak arguments require to be supported by additional reasons, than as, in themselves, worthy of great reliance. Ac- cording to this view of the case, we are not precluded from the use of averages drawn from small numbers of facts. The employ- ment of such averages with this proviso is an absolute scientific necessity ; for in many in- stances we are prevented by causes too nu- merous to specify from bringing together facts by the hundred or the thousand, and yet, were we to reject the smaller numbers as in- admissible, we should be thrown back upon •the still more loose and less trustworthy general statements from which it is the pro- vince of statistics to rescue us. An examination of the two foregoing tables, as well as of those which display the extreme variations between the averages derived from the same numbers of facts, will serve to prove the hopelessness of any attempt to establish by observation rules for measuring the rela- tive value of averages derived from different numbers of facts. It must be equally evident that no deductions drawn from observation can enable us to state the actual liability to error of any given number of facts, considered as facts, without reference to their peculiar nature. To determine this liability to error belongs solely to the mathematics. If, on the one hand, observation is unable to supply us with the means of testing the true liability to error of conclusions based on a given number of facts, considered as facts, without reference to their peculiar nature, it must be evident, on the other hand, that ma- thematical formulae deduced from abstract reasoning can only supply us with the means of measuring the value of a given number of facts in this their abstract relation, without taking into account the varying quality of the facts themselves. But as it is of the utmost importance to be able to test the abstract sufficiency of a given number of facts to establish a principle or to supply a sound standard of comparison, it will be necessary to enter at some length into this part of our subject. The facts already adduced, must have abundantly shown that the limits of deviation from a true average result are wider or nar- rower as the number of facts from which the average is drawn is smaller or greater. Many eminent mathematicians, and M. Poisson among the number, have laboured to convert this general principle into an exact numerical expression or formula, applicable as a test of the true value of larger or smaller collections of facts, and as an exact measure of the limits of variation. M. Gavarret, in his work on Medical Statistics, contends successfully for the introduction of these formulas into the service of the medical man ; and adopting the sentiment of Laplace, " Le systeme tout entier des connaissances humaines se rattache a la theorie des probabilites," he insists that medical statistics, or, as we prefer to term it, the Numerical Method, applied to medicine, is nothing more nor less than a special appli- cation of the Calculus of Probabilities, and the Theory of large Numbers ; and that as such it is the most indispensable complement of the experimental method. In other words, he deems it incumbent on the medical man to apply to his numerical results the corrections supplied by the formulae of the pure mathe- matics ; and before he concludes that any number actually obtained by observation is a true representative of a fact or law, to deter- mine whether that number may not be com- prised within the limits of possible variation. M. Gavarret illustrates the necessity of this precaution by applying his mathematical for- mulae to a great variety of results based upon observation ; but he especially insists upon bringing the alleged efficacy of certain modes of treatment to this searching test. The most convenient course to adopt, in reference to these formulae, will be to present the calcula- tions based upon them in tabular forms, and then to apply these calculations to one or two striking examples. Tiie following table presents at one view the possible errors corresponding to average mortalities deduced from different numbers of observations. It is obvious that the table is equally applicable to other contingencies of the same kind, where one of two events is possible in every instance. The mode of using it will be presently explained and illus- trated. STATISTICS. 811 Table of the possible Errors corresponding to Average Mortalities deduced from different Numbers of Observations.* Number of Ob- serva- tions. Average Mor- tality by Observation. Number of Deaths. Number of Re- coveries. Possible Error. Number of Ob- serva- tions. Average Mor- tality by Observation. lumber of Deaths. Number of Ke- coveries. Possible Error. 25 0-200000 5 20 0-226274 500 0 300000 150 350 0-057965 50 o-iooooo 5 45 0-120000 500 O 350000 175 325 0-060333 50 0-200000 10 4O O -160000 50 0-300000 15 35 0-183302 60O o-iooooo 60 54O 0-034641 600 O-150COO 90 51O 0-041231 100 o-iooooo 10 90 0-084852 600 0 200000 120 480 O-046188 100 0-150000 15 85 0-100094 GOO 0-250000 15O 450 0-05000O 100 0-200000 20 80 0-113136 600 O -300000 180 420 0-052915 100 O-25COOO 25 75 0-122474 600 0-350000 210 390 0-055077 100 0-300000 3O 70 0-129614 100 0-350000 35 65 0-134906 700 O-10COOO 70 630 0-032071 700 0-150000 105 595 O-038173 200 0-100000 20 180 0-060000 700 0 20000O 140 560 0-042762 200 O -150000 30 170 0-071414 700 0-250000 175 525 O -046291 200 O- 200000 40 160 O -080000 700 0-300000 210 490 0-048990 200 0-250000 50 150 OO86602 700 0-350000 245 455 0-050990 200 O -300000 60 140 0-091650 200 0-350000 70 130 0-095:592 800 o-iooooo 80 7 2O 0-030000 800 O 150000 120 68O 0035707 300 o-iooooo 30 270 0-04 8 99O 800 O-20000O 16O 64O 0-04000O 300 0-170000 45 255 O 058309 800 O-25000O 200 600 0-043301 300 0-200000 60 240 0-065320 800 0-300000 24O 56O 0045826 GOO 0-250030 75 225 OO70711 SOO 0 '.550000 280 520 O-047697 300 0 300000 90 210 0-074833 300 O -3 50000 . 105 195 O-077889 900 0 100000 90 810 0 028284 90O O-l 50000 135 765 0 033665 4OO 0-100000 40 360 0-042426 900 0 200000 180 72O 0-037712 400 0-150000 60 340 0-050497 900 0-250000 225 675 0 040825 400 0-200000 80 320 0-056568 900 0-300000 270 630 0 043205 400 0-250000 100 3OO 0-061237 900 0-350000 315 585 OO44969 400 0-300000 120 280 0-064807 400 0350000 140 260 0-067454 1000 0 100000 100 90O 0 026833 1000 0 150000 150 85O 0-O.51937 500 0-100000 5O 450 0-037947 1000 0 200000 200 SOO O -03577 7 500 0-150000 75 425 0 015167 1000 O -250000 250 750 0-038730 500 0-200000 100 400 0-0505MG 1000 O -300000 30O 700 0 040988 50O 0-250000 125 375 0-054772 1000 O -3 50000 350 650 0-042661 The use of this table will be best explained by an example. Let us suppose that a me- dical man, having, for a long time, adopted a particular course of treatment in a certain malady, has arrived at the following results : 1*0 deaths, 680 recoveries, 800 cases. The average mortality in this case would ' This table is an abbreviation of one given at p. 142. of Gavarret's work, but with additional cal- culations based on the same formula, for the numbers from 25 to 200 inclusive. The formula from which the figures in the column of possible errors have been calculated is, V17 I .m.n in which ra represents tht> number of times that an event A has happened, n the number of times that an event u has happened, and fi the total number of events : so that m + n = /* ; "*. the average fre- /" quency of the events m,as obtained by observation; and m + /'2. m. wami A* /2.m.n ~JT 2V ~n* m 2V ~~t^~ the limits within which the true average,as corrected by the formula, lies. be |.£R> or 0-150000 (see the second column of the table for 800 facts and 120 deaths). At first sight the medical observer would ap- pear to be justified in asserting that under his method of treatment the mortality was at the rate of only 150,000 in 1,000,000 patients, or 15 per cent. But this assertion would be immediately met by the objection that the number of facts is not sufficient to justify this statement, that an average deduced from so small a number as 800 facts can only be re- ceived as an approximation to the truth, anil that it requires to be corrected by the aid of the figures in the table. Accordingly, on referring to the column of possible errors corresponding to 800 cases and 120 deaths, we find that the error in ex- cess and defect to which this number of facts is liable, amounts to 0'035707, which error must be added to and taken from the 0-150000, the result of actual observation. It follows, therefore, that the true result must be somewhere between the numbers 0-150000 added to 0'035707, or 0-185707, and 0 150000 dim. by 0-035707, or O'l H293. 812 STATISTICS. So that instead of asserting, as we should seem justified in doing, that the mortality under the influence of the treatment adopted amounted to 15 per cent., we could only claim a mortality comprised between the numbers 185,707 and 114,293 in 1,000,000 cases: or approximatively between the numbers, 19 and I I per cent. Uncorrected observation, therefore, would give, as the result of the treatment adopted, 15 per cent., while corrected observation would give some number between 19 and 11 per cent. The application of the formula given in the note to an actual case will be more instruc- tive than an imaginary example. M. Louis, in his Recherches sur la Ficvre Typhoide, has attempted to illustrate the treat- ment of typhus fever, by minutely analysing 140 cases. The result was as follows : — Number of deaths (m) 52 Number of recoveries (n) 88 Total O) 14.0. The mortality in these cases was therefore T\%' or 0 37143 ; and if we were to take this mortality as the strict expression of the re- sults of the treatment adopted, we should shape our proposition as follows: — The mor- tality of typhus fever, under the treatment adopted by M. Louis, amounted to 37,143 deaths in 100,000 patients ; or, in round numbers, 37 deaths in 100 patients If, now, we proceed by means of the formula referred to, to determine the possible error at- taching to this proposition (i. e. to the num- ber of facts upon which it is made to rest), we find it to be equal to 2 . m . 71 2/2.52.88 -0-11550. This being the possible error in excess and defect, the true influence of the treat- ment will be comprised between the following limits : — m , 2 / 2.m.n -+ x / — —=0-37 143+0-1 1550=0-48693 and 3— 0-11550=0-25593. Thus all that we really learn from this re- cord of experience is, that, under the treat- ment adopted, the number of deaths may vary between 48,693 and 25,593 in 100,000 patients, or approximatively between 49 and 26 in 100 patients. In other words, if we were to employ the same mode of treatment in a great number of cases of typhus fever, we might lose any number between about a fourth and a half of our patients.* The same formula is equally applicable to the solution of doubtful questions relative to the results of two or more series of facts which * Gavarret, Principes Ge'neraux de • Statistique Me'dicale, p. 284. we are desirous of comparing. It may happen that the difference between the average result of one series of facts and that of a second series, is so inconsiderable, as to leave us in doubt whether it may not be explained by a reference to the limits of error to which the number of facts in either return is liable.* It often happens, that the average results of two series of observations relating to two alternative events (such as the events of death or recovery in particular diseases, the birth of a male or female child, &c.) approxi- mate so closely, that we are at a loss whether to attribute the slight difference existing be- tween the two averages to coincidence, or to the operation of certain efficient causes. If the number of observed facts be small, the difference between the averages derived from the two series of facts may be so slight as to fall short of the difference between the limits of error in excess or defect. The same re- sult may also happen with any number of facts, however considerable. In order to solve the doubts which necessarily attach to such close approximations, a mathematical formula has been brought into requisition, and employed in the formation of tables ap- plicable to this purpose. Such a table is subjoined. The mode of applying it will be presently explained. The use of this table will be understood from the following example : — In the six years 1839-44 there occurred in England, on the average of those years, 515,478 births, of which 264,245 were males, and 251.233 fe- males. As the difference between these two numbers is not very considerable, a question might arise, whether that difference is not compatible with the error in excess to which half a million of facts is liable. The use of the formula on which the foregoing table is founded, would at once clear up this doubt. 264,245 male births in a total of 515,478, is equal to 512,904 male births in 1,000,000 births. But, on the supposition that the male and female births are really equal in number, we have the limits of variation equal to 500,000 + A /-— and 500,000— A / — ?- A/ 515478 /V 515478, or 500,000-r 000,624 and 500,000—000,624, or a maximum of 500,624, and a minimum of 499,376. The difference by the formula is, therefore, 1248 in the million, while the ob- served difference between the highest and lowest number of male births occurring in the six years 1839-44, is 514,809—511,781, or 3,028. The inference, therefore, is irresist- ible, that the excess of male births is due to some efficient cause or causes, and that it is not merely an error to which the number of half a million of facts is inevitably exposed.-]- * For illustrations of this application of the fore- going table, and of the formula fromwhich the figures are calculated, see Gavarret's Statistique Me'dicale, p. 80. et seq., and notes, p. 274. f Several applications of this table and of the formula from which the figures are derived, will be STATISTICS. 813 Table of the Limits of Variation compatible with an equal Chance relative to two observed Events.* Number of Cases. Limits of Variation. 100 0 641429 0-358571 150 0-615-170 0-38-4530 200 0-600000 0-400000 25O 0-5S9442 O-410558 300 O-581650 0-41835O 3.50 0-575593 0-424407 400 0-570711 0-429289 45O 0-566667 0-4r;3333 500 0-563246 0-436754 55O 0-560302 O-4:i9698 GOO 0557735 0-442265 650 O-55547O 0-444530 700 0-553452 0-446548 750 0-551640 0-448360 800 0-550OOO 0 450000 850 0-548507 O-451493 900 O-547140 0-452860 950 0-545883 0-4541 17 1000 0-544721 0-455279 1100 0-542640 0-457360 1200 0-540825 0-459175 1 300 0-539223 0-460777 1400 0-537796 0-462204 1500 0-536515 0-463485 KOO 0-535355 0-464645 1700 O -534300 0-465700 1800 0-533333 0-466667 1900 0-532444 0-467556 2000 0-531623 0 468377 2500 0-508284 0-471716 3000 0-525820 0-4741HO 3500 0-523905 0-476095 4000 0-522361 O-477639 Provision having been thus made by the two preceding tables for testing the suffi- ciency of average results based upon different numbers of facts relating to two alternatives, and determining the possible variation or limits of error to which the numbers of facts in question, considered simply as facts, with- out regard to their peculiar nature, are liable, provision still remains to be made for testing in like manner the value of those averages, which belong especially to the domains of physiology and hygiene, namely, the average number of the pulse and respiration, the average age at death of different classes of the community, &c. In the absence of tables specially adapted to this purpose, it must found in the work of Gavorret, so often quoted, from p. 143. onwards, and in the notes at p. 280. et seq. * The formula employed in the construction of this table is 0-50 where n, as before, represents the total of the ob- served facts. The table will be found at greater length at p. 230 of Gavarret's work on Medical Statistics. suffice to state, in general terms, that the averages derived from a given number of facts O O are not to be regarded as strict expressions of the truth, but as approximations more or less remote, as the number of facts is less or more considerable. But a very important question here arises : — To what extent, and under what restric- tions, do calculations based on mathematical formula; and derived from abstract reasoning, admit of application to the results of actual observation ? Conceding, as we may safely do, the soundness of the formulas, there is yet great room to doubt the propriety of their application to the average results of observa- tion. For if we suppose a mathematical formula to be applied successively to a long series of averages derived from the same number of facts, it must obviously administer a similar correction to those averages which happen to coincide with the true average, and to those which lie at the two extremes. This consideration is sufficient in itself to condemn the use of mathematical formulae, except as a means of exhibiting in a striking light the possible error attaching to a small number of facts, considered abstractedly as facts. From the foregoing considerations, then, it would seem to follow, that although averages derived from small numbers of facts are sub- ject to a considerable amount of possible error, there is always such a probability of their coinciding with, or not differing widely from, the true averages, as to justify their employ- ment as standards of comparison and data for reasoning. At the same time it must be con- ceded, that averages derived from small num- bers of facts stand in need of a confirmation which averages drawn from larger numbers of facts do not require, and that in using the former we are bound to speak with a reserve proportioned to the scantiness of our ma- terials. Of extreme values derived from observation, — As averages founded upon large numbers of facts are numerical expressions of true pro- babilities, so extreme values are expressions, in the same precise language, of possibilities. Both orders of facts have their scientific and practical applications ; but those applications which belong to the extreme values have been less attended to than those which pertain to averages. One obvious use of extreme values is to confirm and strengthen the conclusions drawn from averages. Thus, if we wish to ascertain the relative duration of life of two classes of persons, we may make use of the greatest age attained by either class in confirmation of the mean of all the observations ; and the coincidence of the one with the other will give increased confidence in the general result. Another important use of extreme values is as a test of numerical theories. Two apt il- lustrations of this application of figures are afforded by that practical science which i.'cals most largely in possibilities — Forensic Ali-di- cine. JM. Orfila, in his " Trait e des Exhuma- tions," states that it is possible to determine 814 SUBCLAVIAN ARTERIES. approximative^ the stature of the skeleton and of the body by measuring one of the cy- lindrical bones; but instead of testing the value of this conclusion by making use of the extreme values, he contents himself with a rough average. It appears, however, that if we take several cylindrical bones having the same length, and compare them with the cor- responding ascertained stature of the skeleton, the extreme statures are very wide apart. Of seven ulnas, for instance, having each the same length (viz. 10 inches, 8 lines), one cor- responded to a stature of 6 feet 1£ inch, and another to a stature of only 5 feet 5 inches. The difference of 8^ inches shows the possible error which might be committed by trusting to this standard of comparison, and demonstrates its futility. The other illustration is afforded by the well-known test of the absolute weight of the foetal lungs. It used to be laid down as a rough average that in still-born mature chil- dren the weight of the lungs was one ounce, and in children that were born alive two ounces. More accurate observation showed that this rough guess was very far from the truth. It was only, however, by the aid of extreme values that the utter worthlessness of this test could be proved. It resulted from the collation of a moderate number of ob- servations that the losvest weight before and after respiration were the same to an unit, while the greatest weight of the lungs of still- born children, in two instances, surpassed the greatest weight of the lungs of children born alive. Nothing could more clearly demon strate the insufficiency and invalidity of this test. The same general principle which applies to averages applies also to the extremes, namely, that the value of the extremes in- creases with the number of observations from which they are selected. It is obvious, how- ever, that a larger number of facts will be re- quired to arrive at a true extreme value than to obtain a close approximation to the true mean : 10,000 facts, for instance, may give a true mean duration of life for the inhabitants of any country ; but as many millions may not happen to embrace the greatest attainable age. The same principles, then, apply both to the mean and to the extreme values derived from observation. To obtain a correct mean or a probable extreme, we must multiply our facts. BIBLIOGRAPHY. — Gavcirrct, Jules, Principes Ge"- ncraux tie Statistique Mcdicale, ou Developpement des Regies qui doivent pre'sider a sou Emploi. De Morgan, Augustus, Ail Essay on Probabilities and their Application to Life Contingencies and In- surance Offices. Laplace, Essai Philosophique sur les Probabilites. Poisson, Kecherches sur la Proba- bilite des Jugements. Todd, Tu'eedy John, The Book of Analysis, or a new Method of Experience. Quetelet M.A. Sur 1'homme, et le Developpement de sea Facultes. (William A. Guy.) STATISTICS, VITAL. STATISTICS. See VITAL STOMACH and INTESTINAL CANAL. See SUPPLESIENT. SUBCLAVIAN ARTERIES (Arterial subclfivite, Lat. ; Artercs sous-clavieres, Fr. ; die Schlusselbein Pulsadern, Germ.). — These arteries, two in number, are the great vessels destined to supply the upper extremities with blood. Each passes to the corresponding ex- tremity as a continuous trunk, which in its course gives off numerous collateral branches to the larynx, neck, nervous centres, thorax, £c. The subclavian arteries on the right and left sides respectively differ from each other in their origin, length, direction, and in their relations to surrounding parts, — differences, however, which occur in the first stage of these vessels only : thus, on the right side, the subclavian artery is derived from the Arteria inuominata, and on the left from the arch of the aorta ; but on both sides alike the lower or outer margin of the first rib marks the termination of each vessel, which, in its further course towards the upper extremity, is designated by the name of Axillary. The course of each subclavian artery may, in general terms, be described as representing an arch, the convexity of which looks upwards towards the neck, whilst the concavity has an aspect downwards, and corresponds closely to the apex of the lung. On the right side the extremities of this arch are nearly on the same level, the outer, however, passing a little lower down than the inner; whilst on the left side the reverse obtains, the inner (or cardiac) extremity of the arch of the left subclavian artery, which springs from the aorta, being on a much lower level than the outer. Owing to the difference in the origin of these vessels, the left subclavian artery has a stage within the thorax, which does not belong to the artery of the right side. The subclavian artery on each side is ac- companied by a vein of large size ; the direction of the vein is much more transverse than that of the artery, so as to resemble in some respect, as Cruveilhier expresses it, " the cord of the arc which the artery describes:" the subclavian vein is consequently the shorter vessel of the two. The course of each subclavian artery may be divided into three stages, to which the ma- jority of anatomists agree in assigning the following limits : — A first stage comprises that portion of the vessel, from its origin, to the inner, or tracheal edge, of the scalenus anticus muscle. A second stage includes so much of the artery as is contained between the sca- leni muscles ; and the Third stage extends from the acromial edge of the scalenus anticus muscle to the lower or outer margin of the first rib : at this latter point the axillary artery commences. According to some anatomists (as Bichat), the outer margin of the scaleni muscles is the limit between the subclavian and axillary SUBCLAVIAN ARTERIES. 615 vessels ; others (as Cruveilhier) insist upon the clavicle as the line of demarcation between these two great trunks ; but the stages above assigned to the subclavian arteries are strictly in accordance with the views of British ana- tomical authorities. The subclavian vein may be divided into two stages, which correspond to the second and third stages of the artery ; at the inner edge of the scalenus anticus muscle on each side of the neck, the subclavian joins the in- ternal jugular vein to form the vena inno- minata (of Mcckel), which latter vein conse- quent/)/ corresponds to the first stage of the subclavian artery. As the right and left subclavian arteries differ from each other essentially in their first stage, it is necessary to describe them sepa- rately in this portion of their course. First stage of the right subclavian artery. — This portion of the vessel varies from one to two inches in length ; it extends from the summit of the arteria innominata to the tra- cheal edge of the anterior scalenus muscle, and passes in a direction outwards, and slightly upwards. At its commencement it lies to the right of the trachea, and is concealed by the sterno-clavicular articulation. In this stage the artery is contained in the antero-inferior triangle of the neck. The fol- lowing structures here constitute its anterior relations, and are described in the order in which they present themselves in dissection : — The skin, and subcutaneous cellular stra- tum, with one sheet of the cervical fascia, being divided, the tendon of the sterno-mas- toid muscle (sternal origin) is exposed : be- hind it is a cellular interval of constant ex- istence, though of variable extent, where anastomosing veins and small arterial twigs ramify. The outer edges of the sterno-hyoid and of the sterno-thyrcid muscles are more deeply placed ; the latter extends much fur- ther outwards than the former, and hence it more directly overhangs and conceals the subclavian artery. These muscles are con- tained in distinct sheaths (furnished by the deep cervical fascia), which isolate them, as well from the superficial as from the deeper- seated parts : the layer of fascia which forms the back of the sheath of the sterno-thyroid muscle is the deepest lamina of the cervical aponeurosis ; towards the middle line it in- vests the front of the trachea, and the deep thyroid veins; externally, it covers the carotid and subclavian arteries, with their accompany- ing veins, and is connected to the scalenus anticus muscle, whilst, interiorly, it is attached to the clavicle, to the sternum, and to the " thoracico-cervical septum," through the in- tervention of which it is connected with the fibrous layer of the pericardium. On the removal of this fascia from the region under consideration, the immediate anterior relations of the subclavian artery are exhibited ; they are as follow : — a. The right vena innominala, its satellite vein, lies anterior to the artery in the first stage of its course, but on a lower plane, and separated from it by the phrenic and vagus nerves, and by the internal mammary artery. b. The internal jiign/nr vein, which passes downwards and outwards into the subclavian vein, in order to form with it the right vena innominata, crosses the front of the artery nearly at right angles : an interval (the result of the inclination outwards of the internal jugular vein) occurs between this vein and the common carotid artery ; and here c. The vagus nerve passes over the sub- clavian artery ; whilst internal to this point the subclavian artery is enveloped ma. nervous sheath, formed of d. The cardiac filaments of the sympathetic nerve.* c. Lastly, the phrenic nerve constitutes an important anterior relation of the subclavian artery, passing anterior to the very last por- tion of the first stage of the vessel, though not in contact with it. The trajet of the nerve is external to that of the internal jugular vein, which, as before mentioned, crosses the same aspect of the artery. There is no actual contact between the phrenic nerve and the subclavian artery, because the nerve, as it leaves the inner margin of the scalenus an- ticus muscle, lies on and crosses the origin of the mammary artery, which thus separates the nerve in question from the trunk of the subclavian. The relation of f. The vertebral vein, to the subclavian ar- tery, is subject to much variety. According to the descriptions of most anatomists, it passes posterior to the artery ; but the writer has found this vein nearly as often in front of the artery as behind it ; and occasionally he has seen the vertebral vein terminate in two branches, of which one passed on the anterior, and the other on the posterior aspect of the subclavian artery, so as to encircle that vessel before they opened into the vena innominata. When the vertebral vein is single, and passes over the front of the subclavian artery, it usually lies internal and parallel to the in- ternal jugular vein. The anterior relations of the first stage of the right subclavian artery, are, therefore, the fol- lowing : — 1. Integument, subcutaneous areolar tissue, fascia. 2. Sterno-mastoid muscle, sterno-clavi- cular articulation. 3. Sterno-hyoid and thyroid muscles, iso- lated from one another, and from the last-named muscle, by layers of the cervical fascia. 4. The deep layer of the cervical aponeurosis. 5. The phrenic and vagus nerves, and the cardiac filaments of the sympathetic nerve. 6. The right innominate, and internal jugu- lar veins, and sometimes 7. The vertebral vein. The remaining relations of the artery in its first stage are the following: — Inferiorly, it corresponds to the loop of the * Vide art. NECK, vol. iii. note to p. 575. 816 SUBCLAVIAN ARTERIES. recurrent nerve, which sometimes has an an- terior relation to the artery also, in consequence of its arising from the pneumogastric at an unusual height in the neck. Superiorly, it gives off the vertebral artery opposite a triangular interval, between the scalenus anticus and longus colli muscles. Posteriorly, it corresponds from within out- wards, to the transverse process of the seventh cervical vertebra, to the inferior cardiac fila- ments and inferior cervical ganglion, of the sympathetic nerve, to the recurrent nerve, and finally, to the cone of the pleura. Nearly the outer half of the posterior sur- face of this portion of the subclavian artery is thus closely related to this serous sac, being usually that part of the vessel which is ex- ternal to the origin of the vertebral branch, and covered on its anterior surface by the internal jugular vein. First stage of the left subclavian artery. — The subclaviau artery on the left side arises within the thorax, from the termination of the second stage of the arch of the aorta, at the level of the second dorsal vertebra ; it thence assumes a direction nearly vertically upwards, to the inner margin of the scalenus anticus muscle, and lies to the left side of, and anterior to, the two upper dorsal vertebrae, from which it is but a short way distant. Whilst in the cavity of the thorax, the left subclavian artery corresponds, posteriorly, to the inferior cervical ganglion, and cord of the sympathetic nerve, to the thoracic duct, and more remotely to the longus colli muscle and spinal column. Anteriorly, it is in relation with the pleura, and more immediately with the left pneumogastric and phrenic nerves (the latter descends parallel to the artery, but the former crosses it very obliquely, from above down- wards and inwards), with the vertebral vein, the confluence of the internal jugular and left subclavian veins, and the great venous trunk which they form by their confluence, viz. the left vena innominata. Internal and posterior to the artery are placed the oesopha- gus and the left recurrent nerve ; internal and anterior to it, is the left common carotid artery ; whilst external to the artery, through- out the entire of its thoracic stage, are the left lung and pleura. After a course within the thorax of about two inches and a half, the left subclavian artery pierces the "thoracico-cervical septum," inclines outwards and a little forwards, and attains the tracheal edge of the scalenus anti- cus muscle, when it bends abruptly outwards ; this terminating portion of the first stage of the vessel (which alone belongs to the cervi- cal region) has, anterior to it, the left internal jugular vein, the vagus and phrenic nerves, and the thoracic duct, just before its termina- tion in the great subclavian vein ; in addition to these relations, the left subclavian has the same coverings as the corresponding portion of the subclavian artery on the right side. Differences between the right and the left snbclavian arteries, in their first ktage. — Lengf/i. The first stage of the left subclavian artery is much longer than that of the right, which it exceeds by about the length of the Arteria innominata. In the old subject, however, the difference is scarcely so great, for at this period of life, the part of the arch of the aorta, from which the left subclavian artery arises, is higher than that portion of it from which the innominata springs. Position. — The left subclavian artery is nearer to the spinal column, the right to the clavicle and sternum ; consequently the depth of the artery from the surface is considerably greater on the left side than on the right, a circumstance which adds greatly to the diffi- culty of the operation for securing the left subclavian artery in a ligature. Direction. — On the left side, the artery in its first stage runs almost vertically, but as it approaches the scaleni, it inclines outwards and forwards, in order to pass between these muscles; this latter part of the vessel is situ- ated in the neck, and is the only portion of its first stage found there. On the right side, the subclavian artery runs nearly horizontally outwards, and is placed throughout the whole of its first stage within the limits of the antero- inferior triangle of the neck ; for although somewhat concealed at its origin by the sterno- clavicular articulation, yet it may be removed from under cover of that joint, by extending the neck, and depressing forcibly the shoulder and clavicle. Relations. — a. Pleura. — The pleura is an anterior relation of the commencement of the left, but a posterior relation of the termina- tion of the right subclavian artery. b. Veins. — 1. The satellite vein of the right subclavian artery, in its first stage (the right vena innominata'], is parallel to the artery, though on a plane anterior and inferior to it, whilst the corresponding vein on the left side crosses the left subclavian at right angles. 2. The internal jugular vein runs parallel to the left, but intersects at right angles the front of the right subclavian artery. 3. The vertebral vein is usually anterior to the artery of the left, but posterior to the artery of the right side. c. Nerves. — The phrenic, vagi, and sympa- thetic nerves are necessarily parallel to the left subclavian artery, in the first stage of its course, in consequence of its vertical direction, whilst they run at right angles to the corresponding part of the right, by reason of its transverse course ; in other respects, however, these nerves hold the same relative position to the subclavian arteries at either side, the phrenic and vagus being anterior, and the sympathetic posterior, to the right and left subclavians respectively. Lastly, the recurrent laryngeal nerve passes behind the right subclavian artery, looping round its under surface, whilst the nerve on the left side encircles the arch of the aorta, internal to the origin of the left sub- clavian artery ; the recurrent is consequently related to the inner side of the left subclavian artery, but at no part of its course does it lie posterior to that vessel. d. The thoracic duct and oesophagus are SUBCLAVIAN ARTERIES. 817 connected with the artery of the left side, exclusively. The former holds a double relation to that vessel ; in the thorax it passes behind it, in the neck it rises high above it, and then bends downwards in front of it, to oprn into the confluence of the great veins. The oeso- phagus, as has been mentioned, lies to the right of the artery. The differences which have thus been pointed out, are of material importance with reference to the operations upon these two arteries. In the remainder of their course the sub- clavian arteries are perfectly symmetrical, and one and the same description will apply to both. Subclaman arteries in their second stage. — In its second stage each subclavian artery lies in a remarkable intermuscular space, bounded by the scaleni muscles. These muscles (sca- lenus anticus and scalenus posticus) are closely approximated to each other at their attach- ment to the tubercles of the cervical trans- verse processes ; but in descending to their insertions they diverge, leaving between them a space truly triangular, of which the base, placed inferiorly, corresponds to the first rib, and to a small portion of the second. In this space the subclavian artery, the brachial plexus of nerves, and the cone of the pleura, are situated. In front, the artery is in contact with the anterior wall of this triangle, consti- tuted by the scalenus anticus muscle ; behind, it is separated from the posterior boundary of the triangle by the summit of the cone of the pleura, which ascends thus high into the interval between the scaleni, interposing itself between the scalenus posticus and the subcla- vian artery. Towards the summit of this " scalene triangle" the nervous cords which constitute the brachial plexus are placed along the convexity of the artery, superior and external to it. A fleshy slip (Scalenus minimus, Scemmering) is often found to pass from the scalenus an- ticus to the lower, or costal extremity, of the scalenus posticus ; in this course it runs be- tween the roots of the brachial plexus, and consequently subdivides into two the scalene space. The lower compartment contains the subclavian artery, the cone of the pleura, and the inferior portion of the brachial plexus, constituted by the seventh cervical nerve, and the cord resulting from the union of the eighth cervical, with the first dorsal nerve ; whilst in the upper compartment (corresponding to the apex of the triangle), the fifth and sixth nerves of the plexus are seen to unite into a single trunk. On the front of the scalenus anticus, and separated by that muscle from the subclavian artery, are found the following parts : — Most inferiorly the subclavian vein, lying on the tendinous insertion of the muscle, and under cover of the clavicle ; above the vein the transverse branches of the thyroid axis, viz. the supra-scapular, and the transversalis colli arteries, of which the former is the more inferior, whilst the phrenic nerve descends VOL. IV. obliquely inwards towards the trachcal edge of the muscle, and intersects these two trans- verse arteries by passing behind them. Superficial to all these important structures is the clavicular origin of the sterno-cleido- mastoid muscle. In size, shape, and direction, this muscle accurately corresponds to the sca- lenus anticus, which lies deeper than it, and from which it is separated by the parts just now stated, to lie on the front of that muscle. The separation of the subclavian vein from the subclavian artery in their second stage, " constitutes one of the most remarkable fea- tures in its (anatomical) history ;" this con- dition is not, however, constant, for the vein has been found to lie with the artery between the scaleni (Blandin), and, in a few other equally rare instances, the artery has accom- panied the vein superficial to both muscles (Manec, Quain). Lastly, the artery has been seen to pass through the anterior scalenus, and hence to lie in part behind and in part in front of that muscle (Quain). It is to be understood that these deviations from the normal arrangement are remarkably infre- quent. The anterior relations of the subclavian ar- tery in its second stage, may be arranged in four orders of parts : — 1. Skin, platysma, fascia. 2. Sterno-cleido-mastoid muscle (its clavi- cular origin). 3. Subclavian vein, supra-scapular and transverse cervical arteries, phrenic nerve. 4. Scalenus anticus muscle. Subclavian artery in its third stage. — After the subclavian artery emerges from beneath the scalenus anticus muscle, it inclines down- wards and outwards, and thus completes the arch which its entire course represents. In this stage its position is marked by precise limits, which are always recognisable, even in the living subject. The artery, with the vein and brachial plexus of nerves, which still ac- company it, is here contained in the postero- infenor triangle of the neck (O mo-clavicular space, Velpeau), the several boundaries of which are constituted by the clavicle, and by the sterno-mastoid and omo-hyoid muscles. Whilst traversing this region the subclavian artery lies at first on the scalenus posticus, and then passes on the upper surface of the first rib. The subclavian vein lies inferior and in- ternal to the artery, and on a more superficial plane than it, throughout the entire of this portion of its course; it also passes with the artery over the first rib. Two superficial grooves in the adult bone mark the trajet and relative position of these great vessels ; a tu- bercle, which gives insertion to the scalenus anticus muscle, separates these grooves from each other (that for the artery is the more posterior of the two) ; it is constantly present, and serves as a guide to point out with pre- cision the situation of the artery, and so assist the operator to distinguish that vessel from the parts which surround it. Such a guide to the artery is peculiarly valuable, because, 3d 818 SUBCLAVIAN ARTERIES. in operations upon the larger blood-vessels, the touch often fails to discriminate the pro- per object, the characteristic pulsation of a large artery being, under such circumstances, often wanting. In the postero-inferior triangle of the neck the artery is covered by the integument, su- perficial fascia and platysma, descending su- perficial (supra-clavicular) twigs of the cervical plexus, and by the external jugular vein. The situation of this vein in the supra-clavicular space, is subject to much variety ; it most fre- quently runs near to the inner boundary of the triangle and parallel to the outer edge of the sterno-mastoid muscle, but frequently de- scends in the very centre of the space ; in the latter case it much embarrasses the operator in attempting to expose the subclavian artery. Next in order, a number of conglobate glands, and a plexus of anastomosing veins, principally from the scapular region, come into view; these latter usually communicate with the external jugular, or with the subclavian vein. Areolar tissue which presents a laminated arrangement encloses these glands and super- ficial vessels, and isolates them from the deeper-seated parts. These structures being removed, the sub- clavian artery appears to lie within a second triangle of smaller dimensions, bounded inter- nally by the scalenus anticus muscle, externally and superiorly by the omo-hyoid muscle, and inferiorly by the first rib; this bone represents the base of the triangle, and over it the artery is seen to pass. At this depth, two collateral arterial branches of considerable size cross the supra-clavicular space, the one, the trans- versalis colli, above, the other, the supra- scapular, below the level of this portion of the subclavian artery ; the latter is placed under cover of the clavicle, and in contact with the front of the subclavian vein. As the supra- scapular artery pursues its course towards the shoulder, it crosses in front of the subclavian artery and of the brachial plexus of nerves. Here likewise the clavicle and the subclavius muscle constitute additional anterior relations of the subclavian artery, now near its termi- nation. The nervous bundle of the brachial plexus is parallel to the subclavian artery in its third stage, and lies superior and external to the vessel ; in its descent the lower division of the plexus overhangs the artery, and one or two of the branches (anterior thoracic) cross the anterior surface of the artery, and some- times even encircle it in a nervous loop. The anterior relations of the third stage of the subclavian artery may therefore be thus arranged : — 1. Integument, superficial cutaneous nerves, platysma, fascia. 2. Areolar tissue in layers, glands, external jugular vein, an intricate plexus of smaller veins. 3. Anterior thoracic branches of the bra- chial plexus, the subclavian vein, supra-sca- pular artery, clavicle, and subclavius muscle. Anomalies in the origin of the subclavian ar- teries.— 1. The right subclavian artery some- times arises separately from the arch of the aorta, in which case there is no arteria inno- minata ; the branches that arise from the arch of the aorta are then four in number, but con- siderable variety has been observed in the relation which the right subclavian bears to the other three branches ; thus, a. It may occupy the usual position of the innominate artery, being the first in order of the branches of the arch of the aorta ; its re- lations within the thorax will then correspond with those assigned to the vessel whose place it comes to occup}'. b. It may be the second in numerical order of the branches of the arch, arising after the right carotid artery, behind which it subse- quently passes to arrive at its proper position in the neck. c. It may arise after the two carotids as the third branch of the arch ; or, • d. It may be the last branch of the aorta, and occupy the usual situation of the left sub- clavian artery. Of the varieties already men- tioned, this is the most frequently met with, and, according to the statistics of Pro- fessor Quain, it occurs once in every 250 examinations. e. Sometimes (but much more rarely) this vessel arises below the arch, from the thoracic aorta, and its position may be so low, that it will furnish some of the upper intercostal arteries. The course of the artery, when it thus arises from the left of the arch, is very remarkable ; it crosses in front of the spinal column, either behind the oesophagus, or between that tube and the trachea, and necessarily passes across the neck behind all the other branches given off from the arch of the aorta. When thus ab- normal ly situated behind the oesophagus, it has been accidentally wounded by a foreign body which had first transfixed that tube. A remarkable example of this occurrence is mentioned by Mr. Kirby, in the 2d vol. of the Dublin Hospital Reports. The irregularity in question, of the right subclavian arter}', was regarded by Dr. Bay- ford as the cause of difficult deglutition, in a case which had been accurately observed for many years, and this new disease, as he con- sidered it, he quaintly termed " Dysphagia. lusoria." * In those instances, where the right sub- clavian artery has been found to deviate thus strangely from its usual course, the inferior laryngeal nerve presented a remarkable change of direction, depending no doubt on the altered course of the artery ; in all the instances which were noted, the nerve was given off from the pneumogastric, higher up than usual, and passed directly to the larynx, so as not to be entitled to the name of " recurrent." Dr. Hart, who first directed attention to this fact, has thus clearly explained the connection be- tween the unusual position of the artery and * Memoirs of the Medical Society of London, vol. ii. 1793. SUBCLAVIAN ARTERIES. 819 the altered direction of the nerve : " In the ear- lier periods of the existence of the foetus, the rudiment of the head appears as a small pro- jection from the upper and anterior part of the trunk, the neck not being yet developed. The larynx at this time is placed behind the ascending portion of the arch of the aorta ; while the brain, as it then exists, is situated so low, as to rest on the thymus gland and front of that vessel. Hence it is that the inferior laryngeal nerves pass back to the larynx, se- parated by the ascending aorta, the left going through its arch, while the right goes below the arteria innominata. " As gestation advances, the head becomes more distinct, and the neck begins to be formed after the second month, which, as it lengthens, has the effect of removing the brain upwards to a greater distance, and of drawing out the larynx from the chest, in consequence of which the nerves of the par vagum and their recurrents become elongated, and hence the circuitous route the latter are found to take afterwards, forming loops in which the aorta and right subclavian artery are, as it were, suspended."* 2. The left subclavian artery is much less liable to vary in the mode of its origin than the right ; the varieties observed are also fewer in number, a. The origin of the left sub- clavian artery is sometimes more approximated than usual to the origin of the left carotid, and in a few instances, b. its origin is fused into that of the latter, so that these two vessels arise by a common trunk, which is a left arteria innominata, It has been observed in those instances where the arch of the aorta is reversed, so as to pass from left to right, that the same irre- gularities affect the transposed branches which then arise from it, as have been stated to occur when the arch holds its more usual po- sition. Branches of the subclavian arteries. — In the number and arrangement of the branches of the subclavian artery so much variety occurs, that no general description could, perhaps, be given, which would accurately describe their arrangement in any one instance, and hence, in works on anatomy, much discrepancy exists on this subject; the following description agrees with that of the best authorities in this country, and is strictly in accordance with the accurate statistical details of Professor Quain. In its first stage the subclavian artery usually gives origin to the following branches — the vertebral, internal mammary, and thyroid axis ; the last, after a very short course, divides in a radiating manner into the inferior thyroid, the supra-scapular (transversalis humerij, and the transverse cervical (transversalis colli) arteries ; besides, in the majority of instances, the left subclavian artery, in its first stage, furnishes (in addition to the branches already * Dr. Hart, in Edinb. Mod. and Surg. Journal, 1826. enumerated) the superior intercostal artery, a branch which, on the right side, more fre- quently arises under cover of the scalenus anticus muscle. All these branches arise nearer to the scaleni muscles, and are conse- quently more immediately covered by the internal jugular vein on the left side of the neck than on the right. The position of these branches of the .sub- clavian artery, especially on the right side, is of much interest in a surgical point of view. " The situation in which the branches arise from any large artery is an important con- sideration in its history, because of the influ- ence which their presence has on the result of an operation for the cure of aneurism. And, considering the shortness of the trunk, the size of the offsets, and the manner of their arrangement on the parent vessel, it may be confidently stated that there is no artery in which the influence alluded to is more considerable than in the subclavian."* The following statistics, derived from the author just quoted, are useful to show the average length of the subclavian artery, from its origin to the point where its first branch arises; in other words, the extent of the artery in its first stage, suitable for the appli- cation of a ligature. In sixty-five bodies examined, this distance measured — A inch and under - - - in 8 More than £ inch and not exceed- ing 1 inch - - - - „ 33 More than 1 inch and not exceed- ing 1J inch - - „ 23 If inch (the extreme length) - „ 1 Occasionally, the vertebral, or inferior thy- roid artery, has been seen to arise very close to the arteria innominata. In the second stage the subclavian artery most frequently gives off but a single branch, which soon subdivides into the cervicalis pro- funda and superior intercostal arteries. It is less usual for these two arteries to arise separately; thus, in 285 examinations, this occurred in the proportion of but 1 to 20A, whereas the former arrangement existed in 266 out of the entire number. In the majority of instances no branches arise from the subclavian artery external to the scaleni; but the posterior scapular artery (in general the continued trunk of the transver- salis colli) frequently arises from the third stage of the subclavian, and so frequently, indeed, that Cruveilhier regards it, not as a variety, but as the normal arrangement. It is computed by Professor Quain that this occurs in the proportion of 1 in 2£ cases. I. Vertebral artery. — This artery, which is the first and largest, is at the same time one of the most regular of the branches of the subclavian artery, from the upper and posterior * Anatomy of the Arteries of the Human P.ody, with its Applications to Pathology and Operative Surgery (Plates). By Prof. Quain. Part VI. 3 G 2 820 SUBCL AVIAN ARTERIES. aspect of \vhich it usually arises. There is no example on record where this branch arose either between or beneath the scaleni muscles. From its origin, the vertebral artery assumes a direction upwards, backwards, and slightly outwards to the foramen, in the transverse process of the sixth cervical vertebra; having passed through this, it is transmitted from vertebra to vertebra by the foramina which their transverse processes present, until finally it traverses the foramen magnum, where its cerebral, or cranial, stage commences. Relations. — From its origin until it enters the transverse process of the sixth cervical vertebra, the vertebral artery is placed in a muscular interspace, between the longus colli and the scalenus anticus muscles, where it is related in front to the trunk of the subclavian artery, to its own vein, and to the inferior thyroid artery ; the last of these, as it passes transversely inwards, is interposed between the vertebral vessels and the sheath of the carotid artery (in the sheath, the internal jugular vein exactly corresponds to the anterior sur- face of the vertebral artery). By its posterior surface, the vertebral artery is in relation with the inferior cervical ganglion of the sympa- thetic nerve. From the sixth to the second cervical ver- tebra inclusive, the vertebral artery is lodged in the bony foramina of the transverse pro- cesses ; in the spaces between these, it is enclosed by the pairs of intertransverse muscles, being in close contact with the anterior set, whilst from the posterior it is separated regularly by the spinal nerves in their trajet outwards. In this part of its course the artery is slightly tortuous, a provision, no doubt, to guard it against injury in the free and varied motions of this portion of the spine. For a similar reason its tortuosity increases remarkably in the subsequent stage. Having passed through the transverse pro- cess of the axis, the vertebral artery inclines outwards and slightly upwards, to reach the foramen in the transverse process of the atlas, a deviation from the former vertical course of the artery which is rendered necessary by the superior breadth of the first vertebra. Whilst engaged in the curved canal (not foramen) of the transverse process of the atlas, the artery bends abruptly backwards and inwards, so that on emerging from this bone it becomes horizontally placed on the upper surface of the posterior arch of the atlas. Between the occipital bone and the atlas the artery describes a curve, of which the concavity, looking forwards and inwards, embraces the occipito-atlantal articulation, whilst the convexity, directed backwards and outwards, is contained in a triangular space, circumscribed in the following manner by the small rotator muscles of the head. The sides of this triangle are constituted by the superior and inferior oblique muscles respectively, the apex is at the transverse process of the atlas, where both these muscles are attached ; whilst the rectus capitis posticus major (placed in- ternally) represents the base. Deeply situated in this triangular space, the vertebral artery is covered by the splenius and complexus muscles, and rests on the posterior arch of the atlas ; the bone presents a groove for the reception of the artery ; but the sub-occipital nerve, which frequently forms its ganglion in this situation, is interposed. The space which has just been described is occupied by yellow, granular-looking fatty matter, and the occi- pital artery winds along its upper boundary, freely anastomosing with the vertebral. The vertebral artery next passes beneath the lower edge of the posterior occipito-atlan- tal ligament, then perforates the dura mater, and, taking a direction upwards, forwards, and inwards, enters the cranium through the foramen magnum. The posterior occipito- atlantal ligament, by arching over the groove on the upper surface of the atlas, forms a foramen for the transmission of the artery. As the vertebral artery advances through the foramen magnum, it passes between the first and second tooth-like insertions of the ligamentum dentatum, and then ascends, lying on the anterior surface of the first of these processes, by which it is separated from the spinal accessory nerve, which latter passes upwards on the posterior surface of the liga- ment ; here the lingual nerve passes outwards to the anterior condyloid foramen, above the level of the artery. Within the cranium, the vertebral arteries, corresponding at first to the lateral aspects of the upper portion of the medulla oblongata, approximate to each other more and more as they ascend, and ultimately unite at an acute angle, opposite the inferior edge of the pons varolii ; in this manner the basilar trunk is formed. Basilar artery (Artcre meso-cepliaTique, Chaussier). — This artery, larger than either of the vertebral arteries, is yet much less capa- cious than the two vessels conjointly which unite to form it ; its length corresponds accurately to the longitudinal measurement of the pons varolii ; it runs along the median depression of the pons, lodged between that body and the upper surface of the basilar process of the occipital bone, and preserved from pressure by the double concavity of the surfaces between which it is interposed. At its commencement the basilar artery separates from each other the sixth nerves of the opposite sides ; the arachnoid membrane and the dura mater, with the transverse sinus of Haller, are interposed between the artery and the bone, whilst the pia mater alone intervenes between it and the pons. At the antero-superior edge of the pons the basilar artery usually terminates in four branches, two for the cerebrum and two for the cere- bellum. Branches of the vertebral artery. — 1. Branches to the praevertebral muscles, which anastomose with the cervicalis a^cendens and superficialis colli arteries. 2. Numerous small branches, which enter the spinal canal through the intervertebral SUBCLAVIAN ARTERIES. 821 foramina, and which are conducted by the nerves to the spinal cord, where they join and reinforce the proper spinal arteries. 3. In the space between the atlas and occi- pital bone, the vertebral artery sends several long branches down the neck, which are con- cealed by the splenius and complexus muscles. Accompanied by smaller branches of the occi- pital, these arteries keep up an important anastomosis on the back of the neck with the cervicalis profunda. 4, 5. The proper spinal arteries. These are two in number on each side, an anterior and a posterior branch from each vertebral trunk. The posterior spinal arteries arise lower down than the anterior, and pass downwards and backwards to reach the posterior surface of the medulla oblongata ; from this the artery of each side descends parallel to its fellow, to which it is connected by numerous transverse branches. Opposite the second lumbar vertebra, the posterior spinal arteries cease to exist as distinct trunks. The anterior spinal arteries are given off from the vertebral near to its termination ; these arteries in descending approximate to each other, and at last unite opposite the lower edge of the medulla oblongata ; the single trunk thus formed (anterior median artery «f the spinal cord) descends tortuously in front of the medulla spinalis, and, passing through the very centre of the fibres of the cauda equina, reaches the lowest portion of the vertebral canal, when it anastomoses with branches of the sacral arteries. The anterior and posterior spinal arteries are connected in every region of the spine with branches of arteries which enter the spinal canal through the " foramina of con- junction ;" these reinforcing branches, as they may be termed, of the spinal arteries (derived from the cervicalis ascendens and vertebral in the neck, from the intercostal in the back, and from the lumbar and sacral arteries in the lower portion of the spinal column), cause these arteries which they join to pre- serve a remarkable uniformity of size through- out their entire course. Both the spinal arteries furnish small branches to the dura mater and to the spinal cord. Branches of the basilar artery. — 1. The inferior (or posterior) ccrebcllar artery. — This artery seldom arises in precisely the same manner at opposite sides of the same subject. It most frequently springs on one side from the vertebral, and on the other from the basilar trunk. Inclining outwards and backwards, in front of the pyramidal body, the vessel in question passes (according as its origin is from the basilar, or from the vertebral artery) before or behind the sixth nerve; it then runs through the filaments going to form the ninth nerve, and between the pneumogastric and spinal accessory divi- sion of the eighth pair ; it is ultimately dis- tributed internally to the inferior vermiform process and sides of the median fissure (a branch or two may be traced into the choroid plexus of the fourth ventricle), and externally to the inferior surface and circumference of the cerebellum, where it communicates with the superior artery of the cerebellum. 2. The superior (or anterior) cercbcllar artery. — This artery arises near the antcro- superior edge of the pons varolii ; it passes in a curved direction outwards and backwards, around the line of junction of the pons with the crus cerebri. It is at first parallel to the posterior artery of the cerebrum, but separated from it by the third nerve. The fourth nerve in its trajet forwards is strictly parallel to the artery as it runs backwards on the side of the pons varolii ; the nerve, however, is contained in a canal between the layers of the tentorium, whilst the artery proceeds beneath that par- tition, and in contact with the upper surface of the cerebellum. The branches of the superior cerebellar artery are numerous ; they are distributed to the upper surface and circumference of the cerebellum, anastomosing with the inferior cerebellar artery, and also to the pons varolii, velum interpositum, superior vermiform pro- cess, and valve of Vieussens. One small branch of this artery accompanies and separates the facial and auditory nerves, entering with them into the internal auditory meatus. Lastly, some of its branches pass on the upper surface of the tentorium, and are distributed to the inferior surface of the cerebrum. 3. Posterior artery of the cerebrum. — The two posterior arteries of the cerebrum are the terminating branches of the basilar trunk ; each artery passes at first forwards, then backwards and outwards, following the course of the great cerebral fissure, and partly en- circling the crus cerebri. For a considerable portion of its course the posterior artery of the cerebrum is parallel to the posterior (or inferior) cerebellar artery; the two arteries, however, are separated from one another, at first, by the third nerve (which latter, in its further course, hooks round the posterior artery of the cerebrum), and subsequently by the tentorium. At the point where the posterior artery of the cerebrum changes its direction in order to pass backwards and outwards, it is joined by the " posterior com- municating artery," and by this means a com- munication is established between the internal carotid and basilar arteries. The posterior artery of the cerebrum is chiefly distributed by long slender branches to the inferior surface of the posterior lobe of the cerebrum, but it furnishes, in addition, the following collateral branches:—!. Nume- rous small twigs which enter the floor of the third ventricle, through the apertures in the locus perforatus medius, or are distributed to the crura cerebri, corpora albicantia, and tuber cenereum ; and 2. a choroid branch, which winds round the cms cerebri, enters the cerebral fissure, and is lost in the velum inter- positum, corpora qnaclrigemina, and choroid plexuses. 3c 3 822 SUBCLAVIAN ARTERIES. Varieties occasionally observable in the verte- bral arteries. — ]. Of origin. — n. It has already been mentioned that the vertebral artery may arise from different portions of the first stage of the subclavian artery being sometimes nearer, and sometimes further removed, from the innominata; but, independently of these varieties, the vertebral artery on the right side is b. Sometimes furnished by the common carotid artery. In all the cases where this anomaly lias been observed, the right subcla- vian artery was given off directly as a branch of the aorta. Again, c. The vertebral artery sometimes comes off from the arch of the aorta. This irre- gularity is as [infrequent on the right, as it is common on the left side. When the left vertebral artery springs from the arch of the aorta, it usually arises between the left carotid and the left subclavian arteries, though some- times its origin has been found to the left of all the other branches of the arch. d. In a few instances, more than one vessel has been found to constitute the origin of the vertebral artery; thus, it may be formed by the union of two roots, both arising from the subclavian artery, or one from the subclavian and the other from the aorta. In one exam- ple, where it was formed by three roots, two of these were derived from the subclavian, and the third from the inferior thyroid artery. These roots of the vertebral artery in some instances united before the artery had become engaged in the vertebral foramina, whilst in others the union took place subsequently. 2. Of size. — There is often a considerable difference in the size of the two vertebral arte- ries, which is stated to be most frequently in favour of that of the left side ; thus, in 98 ob- servations made by Mr. Davy, the left verte- bral artery was the larger in twenty-six, and the right in eight instances only. 3. Of course and relations. — The vertebral artery may enter the transverse process of the last cervical vertebra (though the contrary has been asserted), or it may enter one of the fo- ramina higher than that in the transverse pro- cess of the sixth, which latter it usually selects. When the artery enters any vertebra higher than the sixth cervical, it always occupies an unusually superficial position in the neck, lying external and parallel to the common carotid artery, for which, consequently, it is liable to be mistaken. (Vide CAROTID AR- TERY.) The vertebral vein corresponds to the cer- vical stage only of the artery. Its origin is found in some branches from the deep muscles at the back of the neck, joined by one from the occipital vein, and by another which passes through the posterior condyloid fo- ramen. The vertebral vein traverses the canal in the transverse process of the atlas, and descends through the same foramina by which the artery ascends ; whilst here it lies in front of the artery, and has the same relations as that vessel. Emerging from the foramen in the sixth vertebra, the vertebral vein (liable to the varieties already specified) opens into the vena innominata close to its junction with the internal jugular. II. Internal mammary artery. — This ar- tery arises (more externally than the ver- tebral) from the anterior surface of the sub- clavian, and near to the inner margin of the anterior scaknus muscle. From this origin it runs, first forwards, then downwards and inwards, and enters the thorax, lying between the pleura and the internal layer of intercostal muscles. Previous to entering the thorax, the in- ternal mammary artery is crossed anteriorly by the vena innominata and by the phrenic nerve : the latter intersects the artery ob- liquely from above and without, downwards and inwards. In the thorax, however, the nerve attains a position much posterior to the artery. The mammary artery descends on the back of the anterior parieties of the chest a little external to the junction of the costal cartilages with the sternum, and is covered posteriorly by the pleura at the line of reflexion of that membrane to form the side of the anterior mediastinum. Arrived at the cartilage of the third rib, the artery in its farther descent inclines a little outwards, and be- comes separated from the pleura by the fibres of the triangularis sterni; the vessel is now placed between that muscle, which lies behind it, and the internal layer of intercostal muscles and the cartilages of the lower true ribs, which constitute its anterior relations. Opposite the cartilage of the seventh rib the mammary artery terminates by dividing into two branches, an external and an internal. Branches of the mammary artery. — 1. Mediaslinnl branches, which are distributed to the thymus gland (thymic arteries), and the cellular issue of the anterior mediasti- num. 2. A descending muscular branch to the diaphragm (superior phrenic), also termed, from its so constantly accompanying the phrenic nerve, the comes nervi phrenici. This branch accompanies the nerve in a tortuous manner, between the pleura and the pericardium, to reach the upper surface of the diaphragm, where it anastomoses with the phrenic arte- ries from the aorta. 3. The anterior intercostal arteries. — These are distributed to the six upper intercostal spaces ; but their number is greater than that of the spaces for which they are destined, as two branches are frequently found between adjacent ribs, and this arrangement may even prevail in all of these intercostal spaces. The anterior intercostal arteries pass out- wards in the intervals between the two planes of intercostals, in which muscles some of their branches terminate ; others are lost in anasto- mosing with the intercostal arteries from the aorta, whilst many perforate the muscular fibres, and, arriving on the external surface of the thorax, dip into the pectoral muscles SUBCLAVIAN ARTERIES. 823 ami the mammary gland. In both these latter situations the arteries in question communi- cate freely with the external thoracic branches of the axillary, thus forming an important connection between the circulation of the in- terior and that of the exterior of the thorax. The terminal branches of the internal mam- mary artery are two in number, viz. internal terminal branch (Ramus abdominalis) and an external (Arteria rnnsculo-phrenica, Haller). 4. The internal, or the abdominal branch, is the smaller of the two, yet in direction it represents the parent trunk. Having communi- cated with the artery of the opposite side be- hind the xiphoid cartilage, it escapes from the thorax through a small triangular interval between the fibres of the diaphragm, and then immediately enters the sheath of the rectus abdominis, descending between the muscle and the posterior lamina of the sheath. Having arrived opposite the umbilicus, it be- comes distinctly continuous with ascending branches of the internal epigastric artery ; it likewise furnishes many branches to the sub- stance of the rectus muscle, and others which, piercing the sheath, are widely distributed to the broad muscles of the abdomen. 5. The external terminating branch (or the arteria musculo-phrenica), is larger than the internal, from which it separates nearly at right angles, passing almost transversely out- wards in a curved course along the superior line of attachment of the diaphragm to the false ribs. In this course the artery gives off, a. numerous phrenic branches of large size, which enters the diaphragm all along its cos- tal attachment ; and b. anterior intercostal branches, which supply the lower intercostal spaces in precisely the same manner as those from the mammary trunk supply the upper, and which have been already described. Varieties. — The mammary artery presents but few varieties either of origin or position ; in 290 out of 297 examinations, this artery occupied its normal position. In one in- stance it arose beneath, in six instances ex- ternal to the scalenus muscle, and in one only of the six was it derived from the axillary artery (Quain). Much more rarely still does the mammary artery deviate in the opposite direction, i.e. inwards ; it has, however, been seen to spring from the arch of the aorta, and also from the arteria innominata. Occasionally too it arises in common with the thyroid axis. Two veins (one on either side of it) accom- pany each internal mammary artery ; they are formed by branches corresponding to those given off by the artery, with the exception (according to Cruveilhier) of the vein accom- panying the arteria comes nervi phrenici, which on both sides terminates separately. ( )n the right side the mammary veins open into the commencement of the vena cava; on the left side, they are connected with the corre- sponding vena innominata. " The mammary arteries are remarkable for the number of their inosculations, and for the distant parts of the arterial system which they serve to connect : they anastomose with each other, and their inosculations with the thoracic aorta encircle the thorax. On the parieties of this cavity their branches connect the axillary and subclavian arteries ; on the diaphragm they form a link in the chain of inosculations between the subclavian artery and abdominal aorta ; and in the parieties of the abdomen they form an anastomosis most remarkable for the distance between those vessels which it serves to connect, namely, the arteries of the superior and inferior extremities."* III. Thyroid axis. — This artery springs from the anterior aspect of the subclavian trunk, close to the inner edge of the scalenus anticus muscle, and consequently from the very last portion of the artery in its first stage. The thyroid axis forms a trunk only a few lines in length, which projects forwards and a little upwards : the phrenic nerve is applied against the outer surface of this artery, and still retains the same relation to it, even where the artery arises more externally than usual, as if in such cases the nerve were drawn outwards by the artery. This arrangement was observed where the thyroid axis arose from the third stage of the subclavian. The thyroid axis usually terminates in three branches : — 1. Inferior thyroid artery. — From the thy- roid axis, this branch passes a little upwards, and then turns inwards and backwards, de- scribing a curve, of which the concavity looks forwards and downwards, corresponding to the carotid sheath. The artery next descends, but soon afterwards inclines upwards and in- wards until it reaches the thyroid body, thus forming a second curve the reverse of the former one, for the concavity of this second curve looks upwards and backwards, and is crossed anteriorly by the recurrent nerve. The anterior relations of this artery are the following : — It is crossed in its first curve, opposite the sixth cervical vertebra, by the sympathetic nerve, which more frequently on the right than on the left side however, joins the middle cervical ganglion in this situation. The inter- nal jugular vein, vagus nerve, and carotid arterv, contained in their common sheath, are the next parts which cross the artery ; and lastly, the recurrent nerve, sub-hyoid muscles, and thyroid gland, lie in front of it. The recurrent nerve lies in front of the second curve of the artery. The inferior thyroid artery is posteriorly in relation with the vertebral artery, the longns colli muscle, and the vertebral column ; and, on the left side, with the oesophagus and tho- racic duct. The thoracic duct very frequently passes up behind the inferior thyroid artery to the level of the sixth cervical vertebra, where, bending downwards and forwards, it arches over that vessel and descends in front of it, to terminate in the subclavian vein. * Harrison's Surgical Anatomy of the Arteries. 4th Edition, p. 141. Dublin. 3 u -i 821 SUBCLAVIAN ARTERIES. Branches of the inferior thyroid artery. — a. Arteria cervicalis ascendens. — This branch (arising from the upper convexity of the thy- roid, where that vessel changes its direction to pass downwards and inwards beneath the carotid sheath) passes upwards on the super- ficial surface of the scalenus anticus, parallel and internal to the phrenic nerve. The cer- vicalis ascendens (frequently as large as the thyroid itself) furnishes numerous muscular branches to the levator anguli scapulae, longus colli, rectus capitis anticus major, and to the scaleni muscles, some of which anastomose with branches of the occipital artery ; it like- wise gives off spinal branches, which enter the spinal canal along the cervical nerves, and are distributed to the cord, anastomosing both within and without the canal of the vertebra with the vertebral artery. By some anatomists the cervicalis ascen- dens is regarded as a branch of the thyroid axis, from which it not unfrequently arises ; in some rare instances it has originated di- rectly from the subclavian artery. Sometimes it is of very large size, and takes the place of the occipital artery or of the cervicalis pro- funda. b. The inferior thyroid artery furnishes se- veral descending branches, which from their destination may be termed cesophageal, tra- cheal, and bronchial. c. Terminal or thyroid branches. — The inferior thyroid artery becomes extremely tortuous as it approaches the thyroid gland ; at last it divides into two or three large branches, which enter the gland by its deep surface, and which, in the substance and around the margin of the gland, communicate freely with the corresponding artery from the oppo- site side, and with the superior thyroids of" the external carotid. The reader is now referred to the article SCAPULAR REGION, in which the remaining branches of the thyroid axis, viz. the supra- scapular and transverse cervical arteries, have already been followed to their ultimate distri- bution ; it will be only necessary in this place to describe the cervical portions of these two collateral branches. 2. Supra-scapular artery (Artcria transvcr- salis humeri). — This artery is at first directed downwards, but having reached the shelter of the clavicle, it passes nearly horizontally out- wards to the superior costa of the scapula. It crosses over the phrenic nerve, the scalenus anticus muscle, and the subclavian vein ; it then runs outwards in contact with the vein, and bound to it by cellular tissue ; it next passes across the subclavian artery and bra- chial plexus of nerves, and finally arrives at the supra-spinal fossa, which it enters by passing over the superior ligament of the scapula. The supra-scapular artery has, anterior to it, the sterno-mastoid muscle, the clavicle, and the omo-hyoid and trapczius muscles. It accu- rately corresponds to the base of the supra- clavicular space. 3. Arteria Transversals Colli. — This artery is larger than the preceding ; from its origin it passes transversely outwards over the sca- lenus anticus muscle and the phrenic nerve ; at the outer edge of this muscle, it inclines backwards and runs through the midst of the branches of the brachial plexus. The artery at this stage crosses the summit of the omo- clavicular triangle, above the level of the subclavian artery. In the space between the sterno-mastoid and the trapezius, the trans- verse cervical artery gives off a large branch, the cervicalis superficialis, which is destined for superficial structures, integuments, pla- tysma, glands, and superficial layer of mus- cles. The cervicalis superficiahs ascends in the posterior superior triangle of the neck, through a chain of conglobate glands, and through the meshes of the cervical plexus of nerves, anas- tomosing with branches of the occipital and vertebral arteries, and passing finally under cover of the trapezius, to which it distributes numerous twigs, as also to the levator anguli scapulae and splenius. After this the continued trunk of the trans- verse cervical artery is usually called posterior scapular artery, which has elsewhere been described. The posterior scapular, and the cervicalis supcrjicialis arteries, very frequently arise se- parately, instead of springing by a common trunk from the thyroid axis; in such cases the posterior scapular is usually given off by the suhclavian artery external to the scaleni. IV, Arteria Cervicalis profunda. ~| These ar- V. Superior Intercostal Artery. ] teries (as has been already mentioned) generally arise by a short trunk common to both, from the subclavian in its second stage. An analogy may thus be observed between this trunk and the aortic intercostal arteries ; for, like them, it divides into an anterior or intercostal branch (the superior intercostal artery), and a poste- rior or muscular branch (the cervicalis pro- funda). The cervicalis profunda passes from its origin backwards and upwards, between the transverse process of the last cervical ver- tebra and the first rib. When a supernumerary cervical rib exists, the artery then passes be- tween this latter and the first dorsal rib. It thus gains the posterior aspect of the neck, and ascends between the spinous and trans- verse processes of the vertebrae, separated from the laminae by the deep layer of muscles, and covered by the great complexus muscle. In this course the cervicalis profunda anas- tomoses with the large muscular branches which descend from the occipital and verte- bral arteries. The deep cervical artery sometimes passes backwards at a higher or lower level than that above specified ; these deviations must be rare, since none of them existed in 40 subjects ex- amined specially with reference to this subject by Cruveilhier. In the extensive tables col- lected by Professor Quain, and which have already been frequently alluded to in this ar- ticle, seventeen instances are given where this artery passed between the first and second rib; in a very few examples, it escaped from SUBCLAVIAN ARTERIES. 825 the thorax through the second intercostal space, and in some other equally rare cases, it has been seen to penetrate between the sixth and seventh cervical transverse pro- cesses. The superior intercostal artery passes downwards in a tortuous manner into the thorax, and gives off branches which run out- wards and supply the two or three upper intercostal spaces ; the artery of the right, usually passes to one intercostal space lower than that of the left side. The branch to the first intercostal space is in general the small- est. The trunk of the superior intercostal artery, as it descends, has the following relations: — in front, it is covered by the pleura atid lung; internal to it are placed the first dorsal gan- glion of the sympathetic nerve, and the longus colli muscle ; \vh\\st posteriorly, it corresponds to the first dorsal spinal nerve (in its ascent to join the last cervical), and to the neck of the first rib. In addition to the branches furnished to the intercostal spaces, and which are two or three in number, the superior intercostal gives off several small branches which enter the spinal canal through its lateral foramina, and also a branch which passes downwards and esta- blishes a communication with the first aortic intercostal artery. It has been already stated that the superior intercostal and the deep cervical arteries most frequently arise by a common trunk ; when they arise separately, the left superior inter- costal artery is generally derived from the first stage of the corresponding subclavian artery. Operative proceedings. — It is not intended in this place to enter into all the details con- nected with the surgical relations of the sub- clavian artery, since in the article which treats of the surgical anatomy of the neck will be found clearly described the modes of pro- cedure to be adopted by the surgeon in the operations for the ligature of this artery in different parts of its course ; the following few observations, which may be regarded as supplemental to those just alluded to, naturally follow the description which has been given of the subclavian artery in the preceding pages. First stage. — When the relations of the subclavian artery on the right side, internal to the scaleni muscles, are carefully reviewed, the inner half of this stage of the vessel will appear to be the most eligible for the applica- tion of the ligature, and the object of the operator should be to secure the artery on the cardiac side of its vertebral branch, as in that situation the pleura is comparatively little exposed to injury ; the jugular vein should lie to the outside, and the vagus nerve to the inside of the ligature, and any undue disturbance of these parts, especially of the latter, ought to be most sedulously avoided. The artery was tied, for the first time in this situation, by Mr. Colles, in the year 1813. In that instance, as in every subsequent one where the operation has been repeated, the result has proved unfavourable ; nevertheless, success has been so nearly attained in some of these cases, that few will be found to agree with Blandin in pronouncing this operation " tout a fait irrationnelle ; " nor are we to view with favour the alternative first suggested by Mr. Shaw, and lately revived and recom- mended to the profession in some recent works on surgery, viz., to remove the arm at the shoulder-joint, and to make pressure on the aneurismal tumour. In the majority of the cases in which hitherto the subclavian artery has been tied internal to the scaleni, the cause of death was referable to secondary haemorrhage ; the un- avoidable proximity of the ligature on the one hand to the heart, on the other to the aneur- ismal sac, and the small extent of this part of the subclavian artery to which a ligature can be applied, without interfering with the colla- teral branches, are probably the chief circum- stances which determine this fatal accident. If, in the desire to avoid the vertebral, thyroid, and mammary branches, the ligature be ap- plied too close to the mouth of the carotid artery, the current of blood through the latter vessel will then, with almost positive certainty, disturb those sanative processes at the seat of ligature, on which the ultimate success of the operation depends ; and hence, doubtless, has originated the proposal to secure at the same time both branches of the innominata. The incisions necessary to expose the one, would amply suffice for the ligature of the other ; the circulation through the head and upper extremity might afterwards be carried on without material injury, and the formation of a coagulum, more lengthy than that afforded by the operations hitherto performed, might lead to a favourable result. This suggestion is due to Dr. Hayden, and is mentioned in his account of the case in which he tied this artery in its first stage, so far back as the year 1835. The following brief particulars of a case which lately came under the writer's notice, may be adduced as furnishing an additional ar- gument in favour of this proposal. A woman, about 25 years of age, became the subject of an aneurism, situated at the root of the neck, which was regarded as originating from the arteria innominata. The subclavian and carotid arteries were tied at one and the same time, on the principle of Brasdor: — "On the fourteenth day after the operation, the liga- ture came away from the subclavian artery without any haemorrhage, and every thing pro- mised a favourable result, especially as the ptilsatioH in the tumour had quite disappeared. On the sixteenth' day, the patient, a woman of violent temper, had a quarrel with the nurse, when she jumped out of bed, seized a pillow and some books, and threw them at her : while making this exertion, haemorrhage set in from the carotid." A renewal of the hae- morrhage proved fatal. On examination it appeared that " jinfrrt union had lakcu place ivhcrc the //gat tire //ad been applied to the sub- 826 SUBCLAVIAN ARTERIES. daman artery, but a small opening was found in the carotid from which the haemorrhage had proceeded." In this instance the innominata was healthy ; but, a little to the left of the origin of that vessel, the aneurismal tumour, which was of a pyriform shape, sprung from the arch of the aorta, and thence passed upwards into the neck, in front of, and overlapping the arteria innominata. It is an extremely interesting circumstance connected with this case, " that the tumour was filled with a firm coagulum." This is the only instance, as far as the writer knows, in which a ligature placed on the sub- clavian artery, in its first stage, became detached without the supervention of secondary haemor- rhage. In none of the cases where this artery alone was secured did this circumstance occur, much less in any of these instances did " per- fect union," the result of adhesive inflamma- tion, follow the application of the ligature.* Until very recently it was thought that the ligature of the subclavian artery internal to the scaleni was feasible on the right side only, and this opinion of British surgeons originated perhaps in Mr. Colics' statement, that " this operation, difficult on the right, must be deemed impracticable on the left subclavian artery." Dr. Rodgers, of New York, has, however, lately succeeded in securing the left subclavian artery in its first stage. The result of this case does not verily the opinion of Velpean, that " the operation would be much less dangerous on the left side than on the right," as the patient died of secondary hae- morrhage on the fifteenth day. British anatomists will be little disposed to agree with Velpeau in such a prediction, and still less will they concur with him in thinking that it would be easier to tie the left sub- clavian artery than the right ; on the contrary, the great depth of the left subclavian trunk from the surface, the short distance to which it rises out of the thorax, and the close con- nection of the veins and nerves with its anterior surface, must entitle this operation to the distinction of being one of the most difficult, whilst the peculiar and unseen risk of wound- ing the thoracic duct must ever render it one of the most dangerous, in surgery. Second stage. — The subclavian artery has been tied between the scaleni muscles in a few instances. This operation was first per- formed by Dupuytren, in 1819, in a case of traumatic axillary aneurism ; the result was successful ; yet there is nothing in this opera- tion to recommend it, provided there be the option of tying the artery in the supra-clavi- cular space. Dupuytren did not (as some have supposed) intend it to supersede the latter operation ; he advised it in those cases only, where the depth of the vessel in its * The full details of this interesting case, which occurred in the practice of Dr. Hobart, of Cork, will be found in the forthcoming edition of " Flood's Sur- gical Anatomy of the Arteries," edited by Dr. Power, one of the lecturers at the Richmond Hospital School, to whom the writer is indebted for the facts already quoted. third stage is unusually great, in consequence of some peculiarity of development, or the unnatural elevation of the clavicle produced by an aneurismal tumour. The anatomical objections to this innovation, which is sanctioned by the authority of Dupuy- tren, are the following, and they are suffi- ciently important to justify the conclusion that, where a choice exists, the third stage of the artery should always be selected for the application of a ligature. 1st That in order to expose the subclavian artery in its second stage, the division of two muscles is required, viz., the clavicular portion of the sterno-mastoid,and the scalenus anticus. 2d. That considerable risk of injuring the phrenic nerve is incurred. 3d. That the ligature must be in close proximity to the branches usually furnished by the subclavian artery between the scaleni, viz., the cervicalis profunda, and superior intercostal; and, 4th. That from its close connection with the artery, the cone of the pleura is en- dangered. These theoretical objections to the ligature of the subclavian between the scaleni, are not the less deserving of notice because they were originally passed over in silence, and they go far to disprove the " innocuitc" of the operation, an advantage which has been claimed for it by Dupuytren.* The objections which have just been enu- merated, are not however of sufficient weight to forbid a repetition of the operation in any case where insuperable difficulties are en- countered in attempting to tie the artery in its third stage ; under such circumstances, the surgeon would evince both skill and dexterity by dividing, as far as necessary, the scalenus anticus muscle, and thus accomplishing the object of the operation ; and in so doing he would follow the example of the late Mr. Liston, who, in a parallel case, thus succeeded in securing the artery between the scaleni. Where the outer edge of the muscle alone is divided, and where proper caution is used, the safety of the phrenic nerve is not neces- sarily compromised ; but without very great caution in passing the needle, the pleura will suffer injury, as it is placed in close con- tact with the back of the artery. It should also be borne in mind, that the phrenic nerve has in a few instances been seen to pass down beneath the clavicle, lying on the outer edge of the scalenus anticus muscle ; should such an anomaly occur in a person subjected to Du- puytren's operation, the nerve could scarcely escape from injury. This irregularity in the cervical stage of the phrenic nerve, has usually been seen in connection with a variety of origin of the axis thyroideus, which has been already adverted to.-f- * Vide " Lecons Oracles," torn. iv. ; and M. Marx account of the operation in the " Repertoire Generale d' Anatomic," No. 2. t It may be presumed that the phrenic nerve was thus unusually placed in a case which occurred in the practice of Mr. 1'ranshy Cooper, and which ho SUPRA-RENAL CAPSULES. 827 In its third stage, the subclavian artery has very frequently been the subject of operation, and the ligature of the vessel in this situation, in a large number of the cases recorded, has been eminently successful. Mr. Ramsden, of St. Bartholomew's Hospital, in the year 1809, was the first who secured the artery in its third stage, and since then the operation has been successfully repeated by many surgeons, in this as well as in other countries. Although the subclavian artery, above the clavicle, is covered by no muscular fibres except those of the platysma, yet it always lies at a considerable depth, which varies much in different persons; the statement of Dupuytren will generally be found correct, viz., " that the third part of the course of the subclavian artery is placed more superficially in those who have long, slender necks, with lean and pendant shoulders, but is, on the contrary, deeply hidden in persons who have short, thick necks, and muscular shoulders."* It is an unfortunate circumstance that the disease for which the operation is usually undertaken, should so constantly be the cause of great difficulty in its performance, for an axillary aneurism of any considerable size cannot fail to elevate the clavicle con- siderably. This fact is well illustrated in the embarrassments experienced in a case where the subclavian artery was tied by the late Professor Todd, one of the surgeons of the Richmond Hospital, and which are recorded in the third volume of the Dublin Hospital Reports. So great have been the difficulties experienced in the operation, that on one occasion Sir A. Cooper was obliged to abandon the attempt, and on another (already alluded to) Mr. Listen was compelled to tie the artery between the scaleni, finding it im- practicable to expose the vessel in its third stage. (B. Gco. M'Dowel.) SUPRA-RENAL CAPSULES. (Die Ncbenniere, Germ. Capsulce suprarenales sett, atrabilaricc, Lat. Capsules suprarenales, atra- bilalrcs, Fr.) — In the bodies of Vertebrata we find a series of organs, which possess a great outward resemblance to the glands, but distinguish themselves from these by the constant absence of a duct. To this class belong the spleen, the thymus, the thyroid, thus narrates in his published lectures : " Some years ago I performed this operation (ligature of the subclavian artery in the supra-clavicular space) OH a clergyman, in the presence of the late Dr. Babing- ton and Mr. Travers ; no difficulty whatever oc- curred, but immediately after its completion the patient was seized with a constant hacking cough, as it' resulting from convulsive motion of the diaphragm. This scarcely ceased night or day until the sixth day after the operation, when he died. Xo post-mortem examination was permitted ; but there can be no doubt, in my mind, that the phrenic nerve had been injured, although it could not possibly have been included in the ligature." — Vi Med. Gazette. Lond. Vol. xlii. p. 111. July, * Le9ons Orales, torn. iv. p. 528. and the supra-renal capsules. On account of their great richness in blood-vessels, these organs have been named " blood-glands," or " glands of blood-vessels," or " vascular gang- lia." At present we are tolerably acquainted with the range of their distribution, and the differences of their form in the animal king- dom ; we have, also, some knowledge of their minute structure ; but, on the other hand, their ph>siological import remains just as ob- scure to the inquirers of the present century as it was to the physicians of ages long gone by. The supra-renal capsules, glandnlae supra- renales seu renes siicccnturiati, scu capsulic atrabilaricE, form, in the higher Vertebrata, a double organ, which is constantly placed in the neighbourhood of the kidneys; and from this situation they have received their name. So, also, in the lower Vertebrata they offen occupy the same situation ; but, not un fre- quently, they are broken up into a number of small glandular bodies. In the Invertebrate they are altogether absent. We shall successively consider, 1. The larger series constituted by the differences of form of supra-renal capsules in the animal kingdom. "I. Their structure. 3. Their de- velopment. 4. Their physiological relations. I. As already mentioned, supra-renal cap- sules occur only in the Vertebrata. But we cannot attribute them to all of these without exception. In the lowest Amphibia and Fishes, these organs have not yet been indubitably recognised. Among the Mammalia, the supra- renal capsules exhibit everywhere essentially the same structure, in spite of many differ- ences of form, size, and situation. In J\Ian they possess a half-moon shaped, or triangular and flattened form, with an an- tero-posterior slightly arched surface, and a sharp convex margin. At their bases they are deeply excavated, so that by this part they rest on the upper end of the kidney like a cap. The anterior part of the basis of the supra-renal capsule extends for a considerable distance further forwards on the kidney than the hinder part. The whole organ is included in a covering which consists of closely woven areolar tissue ; and inferiorly, it is attached by a looser areolar tissue to the kidney. At the base of the organ is also found a well- marked fissure, from out of which passes the supra-renal vein, according to Krause's state- ment.* The anterior and posterior surfaces of the supra-renal capsules exhibit an irregu- larly wrinkled appearance, caused by the nu- merous furrows of the areolar tissue. The size of the supra-renal capsules amounts in the adult to 1 — 1£ inches (German) in height, and somewhat less in breadth. The greatest antero-posterior thickness occurs in its lowest part, and amounts from 24—4 lines. In their middle the supra-renal capsules are consider- ably thinner, amounting only to ]]— 2| lines. Their absolute weight is estimated by Meckel * Vide Krause's Tlaiidbuch dtT Anatomic. 2. Autlage, Hannover, 1811. Hand 1. S. G68. 828 SUPRA-RENAL CAPSULES. to be one drachm : according to Krause * it is from 80 — 120 grains; according to Huschkef from 80 — 180 grains. The anatomist last named found that its specific weight in the newly-born infant was I '0333 ; but Krause states the supra-renal capsules of the adult to be of the somewhat lower specific gravity of 1-0163. The two supra-renal capsules of the same individual are generally of different size. Usually the right is of somewhat lesser height, but greater breadth, than the left, which has the contrary diameter the larger. The so-called accessory supra-renal capsules are often found in man. They are small round corpuscles, which, in various numbers, are attached loosely to the inner border of the supra-renal gland, or are sometimes im- bedded in an excavation on its surface. The supra-renal capsules of the Mammalia essentially correspond with this description. J They are always situated on the upper part of the kidneys ; sometimes towards the inner part, sometimes on the upper part of their border, as in man. Sometimes they are not so closely attached to the urinary organs as in man, but are somewhat more removed from them, Thus, for instance, are arranged the supra-renal capsules of the Elephant and Seal. But, in opposition to this constancy of situation of these organs, we find very considerable differences in respect of their size and form. The supra-renal capsules of Monkeys closely approach the shape seen in the human sub- ject ; but, not unfrequently, their size seems somewhat more considerable. Among the Carnivora they are, in the Dog, of an elongated cylindrical form, sometimes thicker at the margin than in the middle, and of a dense solid texture. So also in the Cat, in whom they are roundish, and somewhat flat- tened. Amongst Insectivora they have in the Mole (Talpa europeea) the form of a three- sided pyramid. In the Seal they appear very small, and Cuvicr found that their size was, to that of the kidneys, as 1 — 150. In this latter animal the whole surface of the supra-renal capsules is divided into a multitude of lobules, or acini. Amongst all the Mammalia, these blood-glands are largest in the Rodentia, their ratio to the kidneys being as 1 to 4 and 5 : this is the case, to wit, in Ccelogenys Paca, and in the Guinea-pig (Cavia cobaia). They are roundish, and somewhat flattened, in the Rabbit and the Dipus. The supra-renal cap- sules of the Mouse, the Rat, and the Myoxus Glis, have a shorter form ; while, on the other hand, in Hystrix they become more cylindrical. * Loc. cit. t Huschke, Lehre von cler Eingeweiden und Sin- nesorganen des menschlichen Korpers. Leipzig, 1844, S. 357. I Concerning the differences of form of the sirpra- renal capsules may be cousufted the well-known text-books on comparative anatomy of Cuvier and Meckel ; and, especially, Nagel in Miiller's Archiv for 1836, S. 3G5., and Ecker, Die feiuere Bau der Nebennieren, Braunschweig, 1846. Amongst the Pachydermata they have, in the Elephant, the form of an elongated cone, and their base is divided into two lobes, and turned backwards. In the Pig, their form is about midway between the cylindrical and the pris- matic. Besides this, the supra-renal capsules of this animal possess a considerable size. In the Horse they are flattened and triangular, approaching the human form. Among the Ruminantia they are, in the Rein-deer, of an oval form, which approximates to the sphe- rical. They are elongated in the Sheep. In the Ox, their shape in some degree resembles that of the kidney. Here they are almost crescentic, not unlike a horse-shoe, and their upper extremity is three-sided. Finally, the supra-renal capsules of Cetaceans are, like those of the Seal, exceedingly small, and broken up into a number of small lobes. We find a similar correspondence in the class of Birds. Their supra-renal capsules are generally small in proportion to the size of the body j sometimes spherical, sometimes oval ; and, in general, divided into lobules. They lie at the inner extremity of the anterior part of the kidney, often close to the inferior vena cava ; and they are covered by the tes- ticles, or ovaries. In the It'eplilia these organs are much less known, since only isolated (and not unfre- quently contradictory) observations have been made respecting them. Hitherto thev have not been found among the Derotremate, Pe- rennibranchiate, and Cascilian orders of this class. The supra-renal capsules of the Saurtans have been very eagerly examined, and most exactly in the genus Lacerta. In these ani- mals Nagel found them along the upper ex- tremity of the vas deferens, in the form of two long, small, lobulated bodies. Nagel's obser- vations have been recently confirmed, and added to, by Ecker. The supra-renal cap- sules, possessing the form stated by Nagel, have a length of ]i lines, with a breadth of 14. They lie closely on the vena renalis re- vehens, or on the vena cava ascendens, which is constituted by the two efferent renal veins. Since the right supra-renal capsule is usually of somewhat larger size, it is wont to lie on the vena cava itself; while the left organ is placed upon the vena renalis revehens. In the male lizard the supra-renal capsules are placed between the vein and the vas deferens ; in the female they are situated between that vessel and the ovary. Numerous blood-ves- sels convey the blood from it into the corre- sponding veins. The blind worm (Aiiguis fragilis] also possesses long, small, supra-renal capsules ; and so, probably, do the Crocodi/us Lucius and Ameiva teguixin. Nevertheless, both the latter animals are at present insuffi- ciently examined. The supra-renal capsules of the Ophidia ex- hibit a similar condition, the more exact knowledge of which we especially owe to Retzius. They form two long and small bodies, and in the Python binistatus they at- tain a length of 8 lines. The supra-renal SUPRA-RENAL CAPSULES. 829 capsules of serpents are likewise distinctly tabulated, and very vascular. In other re- spects, too, the arrangement of the vascular system exhibits much that is interesting ; but to this we shall hereafter return. They always lie closely on the venae renales abdu- centes ; and, according to the course taken by the vessels just named, they are sometimes nearer, sometimes farther from, the testicles and ovary. Batrachia. Formerly many zootomists regarded as supra-renal capsules those pecu- liar yellow finger-shaped masses of fat, which, in these animals, lie superficially to the kid- neys, and possess a connection with the sexual organs, in the periodical increase of which they take a share. Only recently have the true supra-renal capsules been recognised ; and to these the fatty bodies just mentioned have not the remotest resemblance. To Rathke*, Retziusf, Gruby J, and others, we owe the discovery and description of these organs ; the signification of which receives an additional and complete confirmation from minute anatomy, as will be hereafter shown. Here the supra-renal capsules no longer form an organ anatomically defined, but are imme- diately deposited on the abdominal surface of the substance of the kidneys. Among the tailless Batrachia, they appear in this situation as a golden-yellow streak, which does not extend the whole length of the kidney, but ceases at a distance of one line from its upper, and of two lines from its lower, end. These supra-renal organs also allow a lobular composition to be very dis- tinctly discerned ; and they do not extend along the kidney in a straight line, but usually digress into the arched form. They surround the trunks of the efferent renal veins at their exit from the substance of the kidney ; so that they seem to be, as it were, perforated by this vessel. By a more careful investiga- tion one may satisfy one's self that the glands are really imbedded in the coats of these vessels. In the tailed Batrachia, on the other hand, we no longer find the supra-ren;il capsules in the shape of this connected streak, but broken up on all sides into from twenty to thirty separate and irregular lobules. These are seated, partly in the substance of the kidney at its inner bonier, partly between the kidney and the inferior cava ; while they are also partly deposited on the coats of the latter vessel, and the gland-lobules have the same relation to the efferent renal veins as in the tailless Batrachians. Finally, amongst all the -orders of Reptilia, the supra- renal capsules are least recognised in the Chdonla. The statements formerly made by Bojanus §, that the supra-renal cap- * Beitrage zur Gcschichte der Thienvelt, Dritto Abtheilung, Halle, 1825, S. 34. t Vide the treatise of Nagel. J Annales des Sciences Naturellcs. Zoologie, Seconde Serie, torn. xvii. p. 209. § Anatorne Testudinis, Wilnte, 1819—21. Folio cum tab. sules were two long bodies, situated at the inner margin of the kidneys, and a similar statement of Nagel *, have been lately cor- rected by Ecker.f According to the last in- quirer, the supra-renal capsules of the Tcs- tudo grc nerves, therefore, are sufficiently contiguous to each other to warrant the be- lief that an irritated state of one may be pro- pagated to the other through the vesicular mutter of the centre. But it may be inquired why the irritation is limited to sensitive nerves of the shoulder ; and why movements are not excited by the stimulation of the motor fibres of the phrenic itself, or of other * Baly's Miiller, vol. i. p. 756. nerves. The limitation of the irritation to one or two nerves depends on the degree of the stimulus, ami the absence of any move- ments is due to the disposition of the phrenic nerve on the surface being unfavourable for the excitation of motions by irritation of its peripheral branches. And the experiment cited from Miiller, in the last paragraph, shows that simple irritation of the trunk of a compound nerve in connexion with the centre is not sufficient to produce motion ; which requires probably either a more prolonged and violent irritation of the nerve, or a polar state of the centre in which it is implanted. Some of the instances of sympathetic sen- sations, referred to above, do not admit of an explanation so obvious. The pain over the brow from ice or cold water in the stomach may be referred to irritation of the gastric branches of the vagus, communicated in the medulla oblongata to the fifth ; but why the irritation should be limited to the ophthalmic division of the fifth cannot be accounted for in the present state of our knowledge. In those sympathetic movements which are of ordinary and normal occurrence, two pro- visions seem to be secured, namely, a certain peripheral organisation of the excitor nerve, and a certain central relation between it and the motor nerve. But in those which are of a morbid kind, it is necessary to suppose the existence of a more or less exalted polarity of the centre in order to explain the pheno- mena fully. This polar state will continue in many instances even after the primary peri- pheral irritation has been removed, as in te- tanus, or in the convulsions from intestinal irritation ; and we learn from this fact the importance in practice of attending to the state of the nervous centre, as well as to the removal of the irritating cause. There are other sympathetic phenomena, of the physical kind, in which, however, the nervous system does not appear to take a prominent part. Such are the changes which occur in different and distant organs in con-> nexion with a particular period of life, or the development of a particular function. Among these are the phenomena of puberty in both sexes ; the enlargement of the mammae in pregnancy. Whatever part the nervous sys- tem may take in such changes, it is impos- sible to account for them by reference to that system only ; they must rather be regarded as phenomena of nutrition occurring in har- mony with the laws of growth, and there- fore affecting the vital fluid more particularly than any part of the system of solid parts. Continuity of texture disposes, as is well known, to the extension of a diseased state originating at some one point. So also docs contiguity. Phlegmonons inflammation of the areolar tissue, and erysipelas in the skin, spread with great rapidity. Inflammation arising in one of the opposed surfaces of a serous membrane readily attacks the other. These effects have been vaguely assigned to sympathy (the conlhuttnin and contiguous sym- pathy of Hunter). But it cannot be .supposed 3 i 4 856 TASTE. that the nervous system takes part in the pro- duction of such phenomena, which ought ra- ther to be ascribed, in the one case, to the continuity of blood-vessels, and, in the other, to contamination either by effused fluids or by morbid blood. (-R. B. Todd.*) SYNOVIA is that fluid which exists within the membrane lining joints, to assist motion by lubrication ; as also in the bursse. The membranes generally, which line the various cavities of the body, are lubricated by fluid. This varies in character according to circum- stances ; and among these perhaps none more tend to the requirement of especial conditions than that of active and frequent motion, in- volving friction of the surfaces so lubricated. Thus we find that the fluid of the peri- cardium differs essentially from that of the ventricles of the brain ; while again the synovia, supplying moisture to the joints, varies greatly from the fluid of the pericardium, probably in order to assist the opposed surfaces in bearing friction in an exaggerated degree. The word attrition appears, indeed, the most appropriate to the conditions relieved by the presence of synovia, placed as it is between surfaces oc- casionally s.trongly approximated either by superincumbent weight or muscular contrac- tion. Synovia was chemically examined by Mar- gueron.* The specimen he analysed was viscid, and became gelatinous soon after it was obtained. It then deposited a fibrous matter, and became clear above. Though the analysis of Margueron was not conducted on the more exact principles characterising those of the present day, it still serves to show that the specimen was peculiar as an animal fluid, and differed in one respect from the fluids generally, which lubricate surfaces. Thus it appears that as much as 1T86 per cent, was composed of fibrinous matter (fibrin), which coagulated, as stated before, soon after the fluid was obtained. Margueron's analysis is as follows : — Fibrin - Albumen - Chloride of Sodium - Soda - Phosphate of Lime .- Water - -- 11-86 .- 4-52 - 1-75 -- 071 .- 0-70 - 80-46 100- •Synovia has of late years been examined by John.-f- It is described as a viscid transparent yellowish or reddish fluid, resembling in its odour the serum of the blood. The analysis is stated as follows : — Water - - - 92-80 Albumen - 6'40 Extractive Matter, Chloride of Sodium, and Carbonate .of Soda - - 0-60 Phosphate of Lime - 0'J5 * Ann. de Chimie, xiv. f Simon's Animal Chemistry. Trans. Sydenham Society. It will be seen that these two analyses vary greatly — they were not made, it must be recollected, at the same date; and the methods of animal analysis are greatly improved since Margueron published. There is, however, an important point in which both analyses agree, viz. in stating phosphate of lime among the constituents of the fluid. John makes no mention of the existence of a coagulable fibrin- ous matter ; a fact of much importance, which it appears desirable carefully to inquire into, insomuch as it is very possible the analyst may have extracted the synovia after coagulation had occurred within the membrane, and so obtained the clear fluid only ; while Mar- gueron may have been fortunate enough to secure it before such change had taken place, and in its natural condition. With regard to this subject, on which our knowledge is but scanty, it appears still of importance to reflect on the material before us ; and it is matter of no small interest to .consider how far the results of peculiar me- chanical conditions are modified by variations in the character of lubricating fluids, know- ing, as we do, that, while the ventricles of the brain, subject to agitation only, contain no albumen in their lubricating fluid, the liquor of the pericardium contains that principle in abundance ; and that in the synovial fluid adapted to the lubrication of the joints, we have, in addition to albumen, not only a con- siderable proportion of phosphate of lime, but probably fibrin also, as a necessary consti- tuent. (G. Owen Rccs.) TASTE. — The sense by which we distin- guish the sapid properties of bodies. The term, as commonly understood, includes much more than this ; being usually employed to desig- nate the whole of that knowledge of the qualities of a body (except such as is purely tactile), which we derive through the sensory apparatus situated within the mouth. But it will be hereafter shown tnat a considerable part of this is dependent upon the assist- ance of the olfactive sense ; which is affected, through the posterior nares, by the odorous emanations of all such bodies as are capable of giving them off; and the indications of which are so combined with those of the true gustative sense, as to make an apparently •single impression upon the sensorium. More- over, there are certain sensorial impressions received through the organ of taste, which are so nearly allied in their character to those of touch, as to render it difficult to specify any fundamental difference between them : such are the pungent sensations produced by mus- tard, pepper, the essential oils, &c. ; all of which substances produce a sensation when applied for a sufficient length of time to any part of the cutaneous surface, which can scarcely be distinguished from that excited through the organ of taste, in any other way than by its inferior intensity, and by the ab- sence of the concurrent odorous emanations. The taste of such substances might, perhaps, be considered, therefore, as the composite re- TASTE. 857 suit of the impressions made upon the senso- rium through a refined and acute touch, and by the effect of their odorous emanations upon the organ of smell. After making full allow- ance, however, for all such as can be thus ac- counted for, there remains a large class of pure sapors, of which we take cognizance without the assistance of smell, and which are alto- gether dissimilar to any tactile impressions : such are the bitter of quinine, the sour of tar- taric acid, the sweet of sugar, the saline of common salt, &c. The smell can give us no assistance in distinguishing small particles of these bodies, since they are either entirely inodorous, or so nearly so as only to be recognizable through its means when in large masses ; and the most refined touch cannot afford any indication of that kind of difference among them, of which we are at once rendered cognizant by taste. Still the gustative sensa- tions scarcely differ more from the tactile than some of these last differ among each other, — the sense of heat and cold, for example, from the simple sense of contact or resistance ; and we shall find that the analogy between these two senses is so strong, both as to the con- ditions under which they are respectively ex- ercised, and the structure of the apparatus through which the impressions are received, that they must be regarded as much more nearly related to each other than either of them is to the other senses, or than the latter are amongst themselves. The seat of the sense of taste is always at the entrance to the alimentary canal ; and its purpose is obviously to afford a means of dis- crimination among the substances introduced into the mouth as food. The surface of the tongue is undoubtedly the special organ of taste in the higher animals ; but there is ade- quate evidence that the sense is not entirely restricted to that organ, even in man ; and it would seem improbable, considering the ob- vious purpose of the sense, that it should be wanting in that very large proportion of the animal kingdom in which no tongue exists, or in which the surface of that organ is so hard and horny as to forbid our attributing to it the possession of gustative sensibility. Without affirming (with Magendie) that the specific gustative sensibility extends over the teeth, the gums, the palate, and the pharynx, we feel justified in stating that in most persons it is distinctly present on the surface of the soft palate, especially in the neighbourhood of the uvula, and on that of the arches of the palate and of the fauces; and in a less degree on the surface of the anterior part of the soft palate. In making experiments upon this point, as well as upon many others connected with the sense of taste, it is important to bear in mind that if aromatic substances be em- ployed, the impressions derived through the sense of smell may confuse the result; and also that if the sensory surface be too much exposed to cold air, its sensibility will be greatly diminished. Further, it should be borne in mind that a considerable amount of individuil difference may not improbably exist, both as to the extent of the gustative surface, and the relative acuteness of the sense in different parts. Conditions of the Sc?ise of Taste. — In order that gustative impressions may be communi- cated to the sensorium, the first requisite is an afferent nerve, endowed with the power of receiving and transmitting them. The gusta- tive surface in man and the higher animals being supplied by two afferent nerves, — the glosso-pharyngeal, and the lingual branch of the fifth pair, — we shall have to inquire whether both of these are subservient to the sense of taste, as well as to that of touch ; or whether, as in the case of the organs of smell, sight, and hearing, there is one nerve of special and another of general sense. The peripheral extremities of both these nerves are in relation with a papillary apparatus, in which they are elevated above the general surface, and come into close proximity with capillary loops ; and here, as elsewhere, it appears certain that the neighbourhood of cir- culating blood is an essential condition for the reception of sensory impressions. For the gustative nerve-fibres to be impressed by the distinctive properties of sapid substances, it would further seem requisite that these sub- stances should be brought into immediate relation with them, and that they should pene- trate, in the state of solution, through the investments of the papilla?, into their sub- stance. This would seem to be proved by the two following facts : first, that every sub- stance which possesses a distinct taste is more or less soluble in the fluids of the mouth, whilst substances which are perfectly insoluble do not make their presence known in any other way than through the sense of touch ; and, second, that if the most sapid substance be applied in a dry state to the papillary sur- face, and this be also dry, no sensation of taste is excited. Hence it may be inferred that, in the reception of gustative impressions, a change is produced in the molecular condi- tion of the nerve-fibres, or, to use the lan- guage of Messrs. Todd and Bowman, their polarity is excited, by the direct agency of the sapid matter itself. This change may be in- duced, however, both by electrical and mecha- nical stimulation. If we make the tongue form part of a galvanic circuit, a peculiar sen- sation is excited, which is certainly allied rather to the gustative than to the tactile, and which does not seem to be due (as at one time supposed) to the decomposition of the salts of the saliva. And, as Dr. Baly has pointed out*, "if the end of the finger be made to strike quickly, but lightly, the surface of the tongue at its tip, or its edge near the tip, so as to affect not the substance of the organ, but merely the papillae, a taste some- times acid, sometimes saline, like the taste produced by electricity, will be distinctly per- ceived. The sensation of taste thus induced will sometimes continue several seconds after the application of the mechanical stimulus." * Translation of Miiller's Physiology, p. 1062, note. 858 TASTE. On the other hand, as Wagner has truly re- marked, if the surface of the tongue near the root be touched with a clean dry glass rod, or a drop of distilled water be placed upon it, a slightly bitterish sensation is produced ; and this, if the pressure be continued, passes into that of nausea, and if the pressure be increased even excites vomiting, The feeling of nausea may be excited by mechanical irritation of any part of the surface of the fauces and soft palate ; and this feeling is certainly much more allied to that of taste than to that of touch. Further, it has been observed by Henle, that if a small current of air be di- rected upon the tongue, it gives rise to a cool saline taste like that of saltpetre. Thus we find that the peculiar effects of sapid substances upon the nerves of taste may be imitated to a certain extent by other agencies ; and it also appears that the sensations excited by these vary according to the part of the gustative surface on which they operate; me- chanical or electrical stimulation of the front of the tongue giving rise to a kind of saline taste, whilst mechanical stimulation applied to the back of the tongue and fauces excites the feelings of bitterness and nausea. One of the conditions requisite for the clue exercise of the gustative sense, is a tempera- ture not departing far on either side from that which is natural to the body. It appears from the recent experiments of Prof. E. H. Weber *, that if the tongue be kept immersed for nearly a minute in water of about 125°, the taste of sugar brought in contact with it, either in powder or solution, is no longer perceived ; the sense of touch, usually so delicate at the t''p of the tongue, being also rendered imperfect. A similar imperfection of taste and touch was produced by immers- ing the tongue for the same length of time in a mixture of water and broken ice. Nerves of Taslc. — Much controversy has taken place upon the question whether or not there ba a special nerve of taste ; and whether the lingual branch of the fifth pair, or the glosso-pharyngcal,, possesses the best claim to this title. The principal points of this con- troversy have bcRii already noticed [See Fii'Tii PAIR and GLOSSO-PHAUYNGEAL] ; a short review of it, however, with a notice of the most recent inquiries on the subject, will be here desirable. That the glosso-pharyn- gcal is the special nerve of taste, and that its complete section on both sides destroys the sensibility to gustative impressions, was first affirmed by Panizza ; and his conclusions, adopted by Dr. M. Hall and Mr. Brouglitonf, have been since, to a certain extent, sup- ported by the experiments of Valentin! and Briins.^ The grounds on which this doc- trine rests arc briefly as follows: — After re- * Miillor's Arcliiv. 18-17, S. 342. f Sixth Report of British Association ; p. 125 of Transactions of Sections. J De Fimetionibus Xcrvorum Ccrebralium, &c., 1841), p. 41. § DC Xcrvis Cetaceormn, Tub. 183G; quoted by Midler. covering from the depression which is the immediate consequence of the operation, a clog whose glosso-pharyngeal nerves have been divided is said to eat pieces of meat rendered bitter with colocynth, and to drink milk and water dosed with the same drug, without any repugnance ; whereas if the lingual nerves be divided and the glosso-pharyngeals left entire, the bitter morsel is rejected as soon as it reaches the back of the month, although it may have been at first seized very hastily. But, on the contrary, it has been affirmed by Kornfcld *, with whom Miiller and Gurlt were associated, by Dr. Alcockf, by Dr. John ReidJ, by Guyot and Cazalis$, by Magendie||, by LongetT, and by Volkmann and Bidder **, that distinct indications may be obtained of the persistence of the sense of taste, after complete section of the glosso- pharyngeal nerves on both sides. Of a dog in which the nerve had been divided before giving off a single filament, Dr. J. Reid states : — "I have repeatedly fed that dog with morsels of animal food from my hand ; and after he had taken several morsels in this way, which he readily swallowed, I then pre- sented a morsel similar in size to the others, and with the colocynth, concealed in a way that he could not see it ; but no sooner was it taken into the mouth than it was rejected with evident symptoms of disgust. This was repeated more than once." Bidder found that although two dogs whose glosso-pharyu- gei had been divided, swallowed pieces of flesh soaked in an infusion of colocynth, which another dog whose nerves were uninjured at once rejected, yet certain movements of the lips and tongue were observed, which showed that these were not altogether relished. It is obvious that, in such an inquiry, positive evidence of the continuance of the sense of taste is more conclusive than the negative evidence from which its absence may be in- ferred. It is right to bear in mind that, as Wagner has pointed out, dogs when they are hungry will devour meat however strongly seasoned with bitter drugs, though all their nerves be entire. Dr. Reid makes the re- mark, in explanation of the results of Panizza, that one of the dogs on which he had divided the glosso-pharyngeal nerves, would eat the morsel of meat containing colocynth, rather than lose it, when very hungry ; though he refused it, if he saw any prospect of procuring another free from the bitter. Wherever any such evidence of the persistence of the sense of taste was obtained, this appeared specially to exist in the anterior portion of the mouth. * De Fnnctionibus Xervorum Linguce Experi- ment:!, lievol. IS.'Jo'. I 1 >ublin Journal of Medical and Chemical Science,. 1836. t Edinb. Med. and Surg. Journal, Jan. 1838. § Archives Genevales d'e Mc'decine, is.'i'.i. || Lemons sur les Foiictions dti Svsteme Nerveux, ISol), torn. ii. •>:>. ' * Articles Nervenphysiologie and Sclimcckcn in WagniT's Handworterbuch der Physiologic. TASTE. 859 On the other hand, it has been maintained by some physiologists (especially Mugemlie, Miiller, Gnrlt, and Kornfeld), that the lin- gual branch of the fifth pair is the special nerve of taste ; although Miiller does not altogether exclude the participation of the glosso-pha- ryngeal as having a share in the transmission of gustative impressions from the posterior part of the tongue and the fauces. The ex- periments of Dr. Alcock and others, however, appear to show that very distinct indications of gustative sensibility are presented by ani- mals in which this nerve has been divided, the sense being merely deficient in the anterior part of the tongue. On the whole, then, it may be concluded from experiment, that the glosso-pharyngeal nerve and the lingual branch of the fifth pair minister alike to the sense of taste ; the for- mer being concerned in the transmission of gustative impressions from the fauces and the posterior part of the tongue, and the latter from the anterior portion of the tongue ; and the former being the special recipient of the impressions which produce the sense of nau- sea. This inference is so completely in har- mony with the results of anatomical inquiry, that it may be considered as having a very strong claim to reception as a physiological truth. The branches of the glosso-pharyn- geal appear to constitute the sole nervous supply of that region at the base of the tongue, of which the cireumvallate papilla? form the centre, and also of the sides of the tongue near the base. As it is universally admitted that these parts are acutely endowed with gustative sensibility, we cannot help re- garding the glosso-pharyngeal nerve as its instrument. On the other hand, the middle ami anterior parts of the dorsum of the tongue appear to be solely supplied from the fifth pair, — the tip, however, receiving a branch from the glosso-pharyngeal, which runs towards it, along the under surface. It has been denied by some physiologists that the central por- tion of the upper surface possesses the proper gustative sensibility ; but we fully coincide in the statements of those who maintain the affirmative : and although it must be admitted that the sense is not so acute as it is at the base, sides, and apex of the tongue ; yet this may be fairly attributed to the greater thick- ness of the epithelial investment, and to the predominance of the conical papillae over the iiingiform in the central region. On turning to the pathological evidence which bears upon this question, we find an apparent contradiction in the phenomena re- corded by different observers ; but this is in a great degree removed by a more careful ex- amination; and the evidence on the whole preponderates in favour of the preceding con- clusions. We shall make use of the excellent summary recently put forth by Dr. J. Reid * : — " In the single cases observed and recorded by Mayo, Serres, Romberg, Mr. Bishop, and Todd and Bowman, and in the two cases by * Physiological, Pathological, and Anatomical Researches, p. 208. Mr. Dixon, both common sensation and the sense of taste were annihilated in those parts of the tongue supplied by the fifth pair ; while in one case related by Mr. Noble, and ano- ther by Vogt, common sensation was lost in the parts of the tongue supplied by the third branch of the fifth pair, yet the sense of taste remained in these parts ; and in a second case related by Mr. Noble, there was loss of taste with maintenance of feeling." In some of these cases the loss of the sense of taste ap- peared to extend to the base of the tongue ; but there was evidence that in these the glosso-pharyngeal nerve was also involved in the paralysis. " We have no proof," con- tinues Dr. Reid, " that in the cases related by Mr. Noble and Vogt, the ivhole of the fila- ments of the fifth pair sent to the tongue were affected ; and in the case of Vogt the derangement of the nerve was only tempo- rary, for the patient recovered the sensation of the part paralysed after the end of six weeks. We believe that these cases, when examined more closely, will rather be regard- ed as affording arguments in favour of the opinion, that the same nervous filaments do not convey inwards the impressions which excite pain and touch and the impressions which excite taste ; and that different fila- ments for conveying inwards the impressions that excite these sensations are bound up in the lingual branch of the fifth pair." There is believed to be no case on record, in which the whole of the fifth pair, or of the third branch of it, was found to be diseased after death, and in which, during life, the sense of taste had been retained in the anterior and middle parts of the tongue. The evidence of pathology, therefore, is in favour of that con- clusion, as to the participation of the fifth pair with the glosso-pharyngeal in the sense of taste, at which we had arrived on other grounds. The question still remains, however, as to the speciality of the nervous fibres which con- vey the gustative impressions ; that is, whether they are the common sensory fibres, whose peculiarity of function depends on the nature of the papillary apparatus at their peripheral origin ; or whether they are incapable, like the fibres of the olfactive, optic, and auditory nerves, of conveying impressions of the ordi- nary sensorial kind, being adapted exclusively to receive and transmit the peculiar impres- sions made by sapid bodies. Now, in favour of the first view, it may be urged, that the conditions of the sense of taste are so nearly allied to those required for the exercise of touch, that the two can scarcely be dis- tinguished on this ground, and that the fifth pair and the glosso-pharyngeal are both nerves of common as well as of gustative sensibility ; neither of which can be affirmed in regard to the three other senses, or of the nerves which minister to them. But, on the other hand, it must be remarked, that these nerves do not seem to be endowed with gustative and com- mon sensibility in equal proportions ; for the glosso-pharyngeal, which is decidedly more 860 TASTE. susceptible than the lingual to gustative im- pressions, far less readily excites manifesta- tions of pain when subjected to mechanical irritation. Hence, it would seem not im- probable, that there may be in each a mixture of the fibres which minister to the sense of taste with those of tactile sensibility ; and that the former may be so far special in their endowments, as to be capable of receiving only the peculiar impressions made by sapid bodies, to which the latter may be insensible. Such a view would seem to be supported by the cases of Vogt and Noble just referred to ; and it is in harmony with the views to which we are led from the consideration of the diversities manifested between the sense of heat and cold and that of simple contact. [See TOUCH.] Gustative Papilla;. — The tongue is copiously furnished with a papillary structure, bearing a close resemblance to that of the skin, but in many respects more complicated. Re- ferring to the article TONGUE for a more par- ticular anatomical description of these papilla?, we have now to inquire into their connexion with the sense of taste. According to the recent investigations of Messrs. Todd and Bowman, the lingual papillae are either simple or compound ; the former, which do not differ from those of the cutaneous surface in any other obvious character than the nature of their epithelial investment, are scattered over the whole surface of the tongue, in parts where the others do not exist, but they also par- ticipate in the formation of the compound papilla? ; the latter are of three kinds, the cir- cumvallate or cali/ciform, t\\efiingifun», and the conical. —The drcumvallate papilla?, \\hich are only eight or ten in number, and are restricted to a small space at the base of the tongue, consist merely of groups of simple papilla?, arranged in a peculiar manner, and separated from those of the adjacent mucous membrane by a circular fissure. Into these simple papillae it has not yet been found possible to trace any distinct nerve-fibres, though there can be little doubt that it is penetrated by at least the essential part of them. — The fuiigiform papilla? are scattered singly over the surface, chiefly about the sides and apex, and but very sparingly in the middle of the dorsal region, though they are abundant in front of the cir- cumvallate papilla?. These are composed of aggregations of simple papillas, which rise, however, considerably above the surface, and are covered with an epithelium so thin that they are distinguished by their blood-red colour. Fasciculi of nerve-tubes may be dis- tinctly traced into them ; but of the nature of their termination it would be unwise to give a positive statement. Some of the ap- pearances presented by them favour the idea that they form loops at their peripheral ex- tremities ; whilst, in other instances, the tu- bular portion of the fibre, with the white substance of Schwann, seems to terminate somewhat abruptly, whilst the central axis is continued onwards into the substance of the enveloping t'ssue, in which it loses itself. — The conical or filiform, which are the most numerous of the compound papillae, are dif- fused over the whole surface of the tongue, though most largely and numerously de- veloped in its central part. They consist of clusters of simple papilla? of a peculiarly elongated form, containing tubular nerve- fibres, which may frequently be seen to form distinct loops in their interior ; but their chief peculiarity consists in their epithelial invest- ment, which forms about two-thirds of their length, and gives to them their whitish tint. This investment consists of a tuft of long pointed processes, some of which present a near approach in their dense texture to hair ; whilst others may be regarded as soft or un- condensed hairs. These processes are sent off from the sides and summits of the secondary papilla?, and are usually inclined backwards, lying buried in the recesses of the mouth. The foregoing description applies, however, only to the conical papilla? of the human tongue ; and there is a considerable diversity in their structure in other animals. Thus, in the Ruminants, each conical papilla is ter- minated by a long, slender, flexible, horny filament, curving backwards ; and in the Fe- lines some of them are furnished with a brush- like tuft of slender horny filaments, like those of man*, whilst others are encased by firm horny sheaths, which are prolonged backwards as stiff spines. It is to this arrangement that the peculiar roughness of the tongue of the cat is due ; the organ being thus enabled to act as a flexible rasp, whereby the bones which they lick may be effectually cleaned of the smallest particles of flesh that may adhere to them ; and a single stroke of the tongue of a lion is said to be capable of abrading the whole thickness of the human skin. After what has been already said of the conditions essential to the exercise of the sense of taste, there is no occasion to do more than point out the evident fact, that, if some of the papilla? be covered with an epi- thelial investment so dense as to resemble horn, and offering an effectual barrier to the penetration of fluids, these cannot be sup- posed to have much participation in the sense, if they possess any. It is obvious that in the Felines the function of the spiny pa- pilla? must be purely mechanical ; and it seems probable that the brush-like papilla? which lie among them, in common with those of man, possess simple tactile sensibility, serving to direct those muscular actions of the organ, which so remarkably adapt it to deal with minute particles of food. On the other hand, the thinness of the epithelial investment on the simple papilla? which are scattered over the surface of the tongue, and which form the circumvallate and fungiform papillae by their aggregation, indicates their special adaptation to receive gustative impressions ; and this must be admitted to be more especially the case with the fungiform papillye, which often * By Cuvier these filaments are supposed to be the ultimate fasciculi of the fibres of the gustalive nerve ; but this is certainly an error. TASTE. 861 undergo a kind of erection when sapid sub- stances are brought into contact with them. This inference is in complete harmony with the relative acuteness of the senses of taste and touch, in the portions of the surface on which the one or the other class of papillae is most abundant ; thus the sides and back part of the tongue are unquestionably the parts where the gustative sensibility is the greatest, and it is there that the fungiform, circumvallate, and simple papillae are most thickly set; whilst the apex and central part of the dorsum, over which the tactile sensi- bility is predominant, is that on which we meet with the largest number of filiform papillae. Whether there be any difference among the simple isolated papillae, and among those which are aggregated into the com- posite bodies that are termed fungiform and circumvallate, we are scarcely in a con- dition even to form a guess, until it shall have been determined whether the gustative and tactile nerve-fibres are identical or diverse in their endowments. If the former, it will be reasonable to suppose that every papilla through which a gustative impression can be made in virtue of the penetration of sapid matter into its tissue, may also be subservient to the reception of tactile impressions from mechanical stimulation. On the other hand, if it should be proved that the gustative sense depends on a special set of fibres, we should still have to inquire whether the same papilla may not contain fibres of both classes, so as to minister to both functions ; or whether some of the papillae are purely gustative, whilst others are purely tactile. At present there is no adequate reason to suppose that there is any essential difference of function among the papilla? covered with a soft thin epithelium, whether these be solitary or aggregate. An attempt was made by Horn * to establish some such diversity ; but the results of his experiments would rather lead to the supposition that there is a dif- ference in the gustative sensations excited by the same substance, according as it is applied to different regions of the tongue, than to different papillae. Thus he found that more than three-fourths of the substances which he applied to the circumvallate papillae excited a bitter taste, or one in which a bitter was associated with some other flavour, especi- ally an alkaline or saline ; whilst the majority of the substances applied to the filiform papillae tasted acid, or acid with a mixture of bitter and sweet. But since, as we have seen, mere mechanical stimulation produces different gustative sensations according to the part of the tongue to which it is applied, it is probable that the difference in Horn's results is not to be set down to the account of the papilla1, but rather to that of the nerves by which they are respectively supplied. Exercise of the Sense. — The simple appli- cation of a sapid1 substance to the gustative surface is usually sufficient to excite the sen- * Ueber den Geschrnacksinn des Menschen. delberg, 1825. Hei- sation ; and if this application be restricted to one particular spot, we arc able to recog- nise its place more or less distinctly. In this respect, then, the gustative impression resem- bles the tactile ; for whilst we cannot, by our own consciousness, distinguish the parts of the retina or of the auditory apparatus on which visual or auditory impressions are made, we can make this distinction in regard to the surface which is supplied by the nerves of general sense. This determination is most precise when the impression is made on the parts of the tongue of which the gus- tative sensibility is most acute ; namely, the apex, sides, and posterior part of the dorsum; being probably aided, however, near the tip, by the acuteness of its tactile sensibility. The impressibility of the middle portion of the dorsum is greatly inferior ; but still, when the gustative sensation has been excited there, it is referred to the spot on which the sapid substance was laid. The contact of sapid substances much more readily excites a gustative sensation, when it is made to press upon the papillae, or to move over them. Thus there are some substances whose taste is not perceived when they are simply applied to the central part of the dorsum of the tongue, but of whose presence we are at once rendered cognizant by pressing the tongue against the roof of the mouth. The full flavour of a sapid substance, again, is more readily perceived when it is rubbed on any part of the tongue, than when it is simply brought in contact with it or pressed against it. Even when liquids are taken into the mouth, their taste is most completely discri- minated by causing them to move over the gustative surface: thus the "wine-taster" takes a small quantity of the liquor into his mouth, carries it rapidly over every part of its lining membrane, and then ejects it. It is not improbable that this exaltation of the usual effects is simply due to mechanica causes ; the sapid particles being brought by the pressure or movement into more rapid and complete operation on the nerve-fibres, than they would be if simply placed in con- tact with the papillae. As in the case of the other senses, so do we find with regard to that of taste, that continual attention to its indications greatly increases its acuteness. Thus the " tasters '" of wine, tea, &c., acquire a power of discrimi- nation which is truly wonderful to those who have not exercised themselves in the same manner. Thus we have been informed that the "taster" to one of the extensive cellars . of sherry wines at Cadiz or Seville has not the least difficulty in distinguishing the butt from which a given sample may have been drawn, although the number of different va- rieties of the same kind of wine under his keeping may not be less than five hundred. So we are informed by Dr. Kitchener that many London epicures are capable of saying in what precise reach of the Thames the salmon on the table has been caught; and the Parisian gourmet is said to be able to distin- 862 TASTE. guish by the taste, whether the birds on which he is dining are domesticated or wild, male or female, or to give an exact determination of the spices, &c., that are combined in a parti- cular sauce. On the other hand, the power of distin- guishing sapors is for a time suspended, when several substances of very decided but dif- ferent tastes are taken into the mouth in quick succession : thus, if sweet, sour, salt, or bitter substances be applied to the tongue, or if different kinds of wine be taken, one after another, the sense is so much blunted after a short time, as to impair or destroy the power of discrimination between them until after an interval of rest. So, again, when two sub- stances of very different flavours are mingled together, the stronger will frequently mask the presence of the weaker : thus we often find it advantageous, in prescribing nauseous medicines, to combine with them aromatics, whose stronger impression shall take posses- sion (so to speak ) of the sense for a time ; and the object may be still more completely attained by giving the aromatic a moment or two previously, instead of simultaneously with the disagreeable substance. The influence of habit in blunting the sen- sibility to particular tastes, is as remarkable as it is in the case of other sensations. Still more extraordinary, however, is the degree in which the taste may be educated to approve savours which are in the first instance most disgusting. "Thus," says Dr. Dunglison*, " the Roman liquamen or garum, the most celebrated sauce of antiquity, was prepared from the half-putrid intestines of fish : and one of the varieties of the QTTOC. aiXytov, or laserpitium, is supposed to have been the assafoetida. Even at this time, certain of the Orientals are fond of the flavour of this nauseous substance. Putrid meat is the de- light of some nations ; and a rotten egg. es- pecially if accompanied with the chick, is highly esteemed by the Siamese. In civilised countries, we find game, in a putrescent state, eaten as a luxury ; this, to those unaccus- tomed to it, requires a true education. The same may be said of the pickled olive, and of several cheeses ; the fromfige de Gruyere, for example, so much esteemed by the inhabitants of continental Europe." Very extraordinary appetencies for particular flavours are some- times morbidly developed ; as in the case of chlorotic girls, pregnant women, and insane patients. The latter will sometimes even devour their own excrement. Independently of the changes produced by the education of the taste, we find great al- terations in the likes and dislikes connected with it, taking place in accordance with the development of the body, or with other changes in its physiological conditions. Thus to the infant there is obviously nothing so agreeable as milk ; in more advanced child- hood there is almost invariably a fondness for sweets ; whilst after adult age this is usually in a great degree superseded by a preference * Ilmnan Physiology, vol. i. p. 110. for other savours. It sometimes happens that articles of diet which were peculiarly agree- able to us in childhood, become positively disgusting to us in later life; whilst, on the contrary, many things to which we feel a strong distaste in childhood, are relished when we come to be men, and this by a sponta- neous change in our own appetencies. We fully believe with Wagner that these altera- tions are in some way connected with the physical condition of the nutritive functions ; for we have other examples in which this connexion is very evident. Thus, \ve may continually remark that articles of food for which we have the keenest relish when we commence a meal with a good appetite, be- come positively distasteful when we have al- ready satisfied it. Again, we have known per- sons who have a positive repugnance to fatty or oleaginous matters of almost any description, so long as they reside in temperate climates, but who eat them with avidity when exposed to the severe cold of the arctic winter. And even in our own country we may frequently remark that the taste for such articles varies with the temperature ; a cup of sweet olea- ginous cocoa, which would be almost loathed on a hot summer day, being very palatable on a cold winter night; whilst ascescent drinks, such as would be greatly relished in the former season, are altogether discarded in the latter, except when a heated atmosphere brings back the physical condition of the system which renders them palatable. So, again, we often observe in illness that an alteration in the physical conditions of the system so far affects the sense of taste, as to produce a great alteration in the usual appe- tencies. These alterations may probably be due in some instances to the depravation of the biiccal secretions, so that the gustative papillae are constantly surrounded with a sub- stance possessing a certain taste of its own, which of course affects their impressibility by other savours. But there can be little doubt that they are more commonly occasioned by alterations in the condition of the gustativi apparatus itself, which becomes the exponen! (so to speak) of the wants of the system, and which may be trusted, to a very considerable extent, as indicating what is really most de- sirable for it. Thus Dr. Holland remarks * ; — " In the majority of instances of actual illness, provided the real feelings of the pa- tient can be safely ascertained, his desires as to food and drink may be safely complied with. But undoubtedly much care is need- ful that we be not deceived as to the state of the appetites by what is merely habit or wrong impression on the part of the patient, or the effect of the solicitation of others. This class of sensations is more nurtured out of the course of nature than are those which relate to the temperature of the body. The mind becomes much more deeply engaged with them ; and though in acute illness they are generally submitted again to the natural law, there are many lesser cases where * Medical Notes and Reflections, p. 85. TASTE. 863 enough remains of the leaven of habit to render every precaution needful. With such precautions, however, which every physician who can take schooling from experience will employ, the stomach of the patient becomes a valuable guide ; whether it dictate abstinence from a recurrence to food ; whether much or little in quantity; whether what is solid or liquid; whether much drink or little; whe- ther things warm or cold ; whether sweet, acid, or saline ; whether bland or stimulating to the taste." Further, Dr. Holland remarks : " It is not wholly paradoxical to say that we are authorised to give greatest heed to the stomach when it suggests some seeming ex- travagance of diet. It may be that this is a mere depravation of the sense of taste ; but frequently it expresses an actual need of the stomach either in aid of its own functions or indirectly (under the mysterious law just re- ferred to) for the effecting of changes in the whole mass of blood. It is a good practical rule in such cases to withhold assent till we find after a certain lapse of time that the same desire continues or strongly recurs ; in which case it may generally be taken as the index of the fitness of the thing desired for the actual state of the organs. In the early stage of recovery from long gastric fevers, I recollect many curious instances of such contrariety to all rule being acquiesced in, with manifest good to the patient. Dietetics must become a much more exact branch of knowledge, before we can be justified in opposing its maxims to the natural and repeated sugges- tions of the stomach, in the state either of health or disease." In regard to the use of wine in fever, it is universally admitted by prac- tical physicians that very important indica- tions may frequently be drawn from the appe- tency or dislike manifested towards it by the patient ; this being often exhibited when there is an almost entire obtuseness of the mind in regard to all other external impressions. In such circumstances these dormant instincts seem to manifest themselves, which are kept under by the intelligence in the normal con- dition; instincts akin to those which guide the lower animals in their choice of food. There is probably not a plant, however poisonous to most, which has not one or more species of animal specially adapted to derive from it wholesome nutriment, and which is obviously drawn to it by its odour or savour ; whilst the most omnivorous feeders, such as the monkey, are usually restrained by dislikes, excited through these same senses, from touching fruits which would be noxious to them. It cannot be doubted that, in all persons of ordinary aptitude for the discrimination of flavours, there are certain natural harmonies and discords among these, as among colours and sounds ; so that particular substances of very different flavours taste agreeably in com- bination, whilst others are mutually repug- nant. Thus every body likes sugar in combi- nation with the acid of fruits ; and the sugar is popularly believed to neutralise the acid, which (as we need scarcely say) is not at all the case. On the other hand, sugar and oysters are said to form one of the most nauseous combinations possible. So, again, the flavour of many wines is improved by being tasted simultaneously with cheese, whilst it is injured by fruits. — The art of cookery is founded upon a knowledge of these facts, which have not yet perhaps received from the .scientific physiologist the systematic atten- tion they deserve. Attempts have been made by Linnaeus, Bocrhaave, and others, to form a classification of savours ; but no such clas- sification has come into general use, although there are certain savours which all agree to consider primary ; such as the aromatic, the sweet, the acid, the bitter, the saline, the astringent, and the pungent. By the first of these the sense of taste is connected with that of smell ; by the last two with that of touch. The impressions made upon the sense of taste seem to remain longer after the with- drawal of the body that excited them, than those which are received through most of our other senses. This is not surprising, when it is considered that particles of the sapid sub- stance, which have once penetrated the pa- pillsc, may linger there in contact with the sentient extremities of the nerves, for some little time after they have passed away from the external surface. In many cases, how- ever, the substance leaves an after-taste which is different from that which it first excited. It is difficult to say how much of this may be clue to the difference of the impression which is made upon the sensory papillae at the front of the tongue and upon those at its base, and also to the admixture of the olfactive sense, which will be most actively called into play as the sapid body is passing the fauces; and how much to the exhaustion of the nerves conse- quent upon their previous stimulation, so that the after-taste is complementary to that first received. It certainly appears to confirm the former explanation, that the after-taste is generally of that bitterish character which we have seen to be produced by the mere me- chanical stimulation of the papilla? at the base of the tongue. On the other hand, the fact that tannin, one of the bitterest substances known, has a sweetish after-taste, seems to favour the latter view. Probably both causes may participate in the production of the re- sult. It is not very common to find the sense of taste excited in a purely subjective manner ; since many of the tastes which are experienced in disease are probably due, as already re- marked, to the depravation of the buccal secretions. Nevertheless, we occasionally meet with instances in which some peculiar gustative sensation, usually of a disagreeable nature, is constantly experienced without being traceable to any such cause ; and in which, therefore, we must seek for its occasion in some disordered functional condition of the sensorium. The jjttr])oscof the sense of taste is obviously to serve as the guide and attraction towards 8G4 TEETH. wholesome food, and to afford pleasure in the reception of it, whilst it deters from the use of such as would be deleterious. This is more obvious in the lower animals than it is in man, who is frequently led by habit and fashion to a preference for substances which are high- flavoured over those which are most whole- some, and who is still more frequently induced to gratify his gustative sense by the reception of an amount of food which appetite alone would not incite him to take in. Of the pernicious results of such excess, this is not the place to speak. The only ulterior purposes which the sense of taste appears to perform in the economy, are to aid in exciting the flow of saliva, and in certain cases to excite the act of vomiting. Although the secretion of saliva is greatly affected by other causes, — as, for example, by the movement of the jaws, tongue, &c., — yet it is much influenced by the sapid qualities of the food introduced into the mouth, being greatly increased by the taste of savoury food. It is also augmented by the sight or odour of such food ; but it is probable that the latter sensations influence it not so much directly as indirectly, namely, through the ideas which they call up, for the idea alone, if called up with sufficient vividness, is sufficient to make " the mouth water." The sense of nausea, as already remarked, seems intermediate between taste and touch ; but it is connected most closely with the former. We experience more or less of difficulty in swallowing all substances whose taste is peculiarly repugnant to us, and we find ourselves compelled to regurgitate them when the impression becomes of a certain intensity. This is one of the auto- matic actions in which it appears requisite that a sensation, not a mere impression, should participate. (William B. Carpenter.) TEETH. — COMPARATIVE ANATOMY. (Sing. a tooth; Tunt/i,Teui.; Dens, Lat.; Dente, Ital.; Dent, Fr.; Tand, Dan. ; Tain, Old English ; Zahn, Germ. ; Dant, Welsh ; Dend, Erse ; ot>oi>e-c tWroe, Gr. ; Dantis, Lithuanic; Dantas, Sanscrit.*) A tooth is a hard body attached to the mouth or commencement of the alimentary canal, always exposed, save where its develop- ment is permanently arrested, as in the rudi- mental tusk of the Narwhal; commonly cal- cined, the exceptions being few, e. g., the horny teeth of the Lamprey and Platypus. Teetli vary not only in their tissue, but still more in number, si/e, form, structure, position, and mode of attachment, in different animals : they are principally adapted for seizing, tear- ing, dividing, pounding, or grinding the food ; in some they are modified to serve as wea- pons of offence and defence ; in others as aids in locomotion, means of anchorage, instru- * These synonyms are cited as illustrative of the coincidence in one of the primary words of a natural class of languages that prevails from the East Indies, through the west of Asia and across Europe, and as indicative of the unity of stock of the great ludo- European family of mankind. ments for uprooting or cutting down trees, or for transport and working of building materials ; they are characteristic of age and sex ; and in man they have secondary rela- tions subservient to beauty and to speech. Teeth are always most intimately related to the food and habits of the animal, and are therefore highly interesting to the physiolo- gist : they form for the same reason most important guides to the naturalist in the classification of animals ; and their value, as zoological characters, is enhanced by the facility with which, from their position, they can be examined in living or recent animals ; whilst the durability of their tissues renders them not less available to the palaeontologist in the determination of the nature and affi- nities of extinct species, of whose organisation they are often the sole remains discoverable in the deposits of former periods of the earth's history. Although there are many analogous struc- tures in the inverterbrate classes, true calcified teeth are peculiar to the Vertebrata, and may be defined as bodies primarily, if not perma- nently, distinct from the skeleton, consisting of a cellular and tubular basis of animal matter containing earthy particles, a fluid, and a vascular pulp. In general, the earth is present in such quantity as to render the tooth harder than bone, in which case the animal basis is gela- tinous, as in other hard parts where a great proportion of earth is combined with animal matter. In a very few instances among the vertebrate animals, the hardening material exists in a much smaller proportion, and the animal basis is albuminous ; the teeth here agree, in both chemical and physical qualities, with horn. True teeth consist commonly of two or more tissues, characterised by the proportions of their earthy and animal constituents, and by the size, form, and direction of the cavities in the animal basis which contain the earth, the fluid, or the vascular pulp. The tissue which forms the body of the tooth is called "dentine," (Dentinum, Lat.; Zahnbein, Zahnsnbatanz, Germ.; f Ivoire*, Fr.) The tissue which forms the outer crust of the tooth is called "cement" (ccementum, crnsta petrosa, Lat.). * The learned author of the article " Secretions," in the "Dictionnaire Universel d'Histoire Naturelle," 8vo, 1848, adopts the term " Dentine " in preference to Cuvier's name " ivoire," and after defining its properties, observes, " Sur ces divers rapports, le mot dentine, par lequel M. R. Owen les de'signe, me parait tres heureux." The term " ivory " unavoid- ably recalls the idea of the peculiar modification of " dentine," which characterises the tusks of the ele- phant, mammoth, and mastodon ; but, besides this objection to its more general application, the word is used in a still wider sense in the " Lecons d' Ana- tomic Comparee : " " Les lines (dents), en effet, out la partie enfonce'e dans 1'alveole de'nuee d'email ; cette partie, ou la racine, ne se compose ge'ne'ralement que de V ivoire interieure, reconvert tres rarement d'itioire exterieure (les dents de cachalot) ; " torn. iv. Ed. posth. 183(3, p. 200. The example cited of the tissue here denominated " ivoire exte'rieure " is the " cement." See my " Odontography," p. 355, pi. 89. TEETH. 865 The third tissue, when present, is situated between the dentine and cement, and is called "enamel" (encaustum, adamas, Lat.). "•Dentine" consists of an organised animal basis disposed in the form of extremely minute tubes and cells, and of earthy particles : these particles have a twofold arrangement, being either blended with the animal matter of the interspaces and parietes of the tubes and cells, or contained in a minutely granular state in their cavities. The density of the dentine arises principally from the proportion of earth in the first of these states of combination, the tubes and cells contain, besides the granular earth, a colourless fluid, probably transuded " plasma" or "liquor sanguinis," and thus re- late not only to the mechanical conditions of the tooth, but to the vitality and nutrition of the dentine. This typical structure of dentine is well illustrated in the article TOOTH : such " true dentine " has no canals large enough to ad- mit capillary vessels with the red particles of blood, and it has been therefore called " un- vascular dentine." The simplest modification of dentine is that in which capillary tracts of the primitive vas- cular pulp remain uncalcified, and permanently carry red blood into the substance of the tissue. These so-called " medullary canals " or " vascular canals " present various disposi- tions in the dentine which they modify, and which I have proposed to call " vaso-dentine." It is often combined with true dentine in the same tooth ; e.g. in the scalpriform incisors of certain Rodents*, the tusks of the Ele- phant f, the molars of the extinct Iguanodon.J A third modification of the fundamental tissue of the tooth is where the cellular basis of the dentine is arranged in concentric layers around the vascular canals, and contains " ra- diated cells " like those of the osseous tissue : it is called " osteo-dentine." The transition from dentine to vaso-dentine, and from this to osteo-dentine, is gradual, and the resemblance of osteo-dentine to true bone is very close. " Cement " always closely corresponds in texture with the osseous tissue of the same animal ; and wherever it occurs of sufficient thickness, as upon the teeth of the horse, sloth, or ruminant, it is also traversed, like bone, by vascular canals. In reptiles and mammals, in which the animal basis of the bones of the skeleton is excavated by minute radiated cells, forming with their contents the " corpuscles of Purkinje," these are likewise present, of similar size and form, in the " cement," and are its chief characteristic as a constituent of the tooth. The hardening ma- terial of the cement is partly segregated and combined with the parietes of the radiated cells and canals, and is partly contained in disgregated granules in the cells, which are thus rendered white and opaque, viewed by reflected light. The relative density of the dentine and cement varies according to the O * Odontosraphy, 4to, p. 405. t Ib. p. 643. J Ib. p. 251. VOL. IV. proportion of the earthy material, and chiefly of that part which is combined with the animal matter in the walls of the cavities, as compared with the size and number of the cavities themselves. In the complex grinders of the elephant, the masked boar, and the capybara, the cement, which forms nearly half the mass of the tooth, wears down sooner than the dentine. The "enamel" is the hardest constituent of a tooth, and, consequently, the hardest of animal tissues ; but it consists, like the other dental substances, of earthy matter arranged by organic forces in an animal matrix. Here, however, the earth is mainly contained in the canals of the animal membrane ; and, in mammals and reptiles, completely fills those canals, which are comparatively wide, whilst their parietes are of extreme tenuity. The hardening salts of the enamel are not only present in far greater proportion than in the other dental tissues ; but, in some animals, are peculiarly distinguished by the presence of fluate of lime. The following are characteristic examples of the above-defined tissues, and their different combinations, in different teeth. The examples are extremely few, and, as far as I know, are peculiar to the class Pisces, of calcified teeth which consist of a single tissue, and this is always a modification of dentine. The large pharyngeal teeth of the Wrasse (Labrim} consist of a very hard kind of unvascular dentine. Fig. 544. shows a ver- Fig. 544. Section of pharyngeal tooth of Labrus, magnified. ^Owen's Odantography.}\ tical section of one of these teeth, supported upon the very vascular osseous tissue of the pharyngeal bone : p is the pulp cavity. The next stage of complexity is where a portion of the dentine is modified by vascular canals. Teeth, thus composed of dentine and vaso-dentine, are very common in fishes. The hard dentine is always external, and holds the place, and performs the office, of enamel in the teeth of higher animals ; but it is only analogous to enamel, not the same 3 K 806 TEETH. tissue.* Fig. 54.5. illustrates this structure in a longitudinal section of a tooth of a shark of Fig. 515. Fig. 547. Section of tooth of Lainna, maqnijied. &'«' Oilontor/rapl/y.) the genus Lmnnn : v is the vaso-dentine ; d the hard dentine; the earthy confluent so Fig. 546. ®^feeK'5v;'%':l,i Section of tooth of Diignnrj (Halicore), magnified. * Odontography, pp. 17. 37. Section of tooth of Cachalot (Physeter). predominates that the tissue takes a polish like enamel, for which it has commonly been mistaken in the teeth of fishes : I have called it " vitro-den- tine." The molars of the Dugong are examples of teeth com- posed of dentine and cement, the latter tissue forming a thick external layer. Fig, 546. A. is a transverse section of the crown of the second molar, natural size ; and B. a magnified view of a por- tion of the section ; d the dentine, remarkable for the number of minute calcigerous cells at its periphery ; and c the cement. In the great teeth of the lower jaw of the Cachalot, the pulp-cavity of the growing tooth becomes filled up by osteo-dcntine, the result of a modified calci- fication of the dentinal pulp ; and the full- grown tooth presents three tissues, as shown TEETH. 807 in^g. 547., in which c is the thick external cement, d the hard dentine, and o the osteo- dentine ; sometimes developed in loose stalac- titic-shaped nodules. In the teeth of the Sloth, and its great extinct congener, the Megatherium, the hard dentine is reduced to a thin layer, and the chief hulk of the tooth is made up of a central body of vaso-dentine, and a thick ex- ternal crust of cement. Fig. 548. represents a F,g. 548. Section of tooth of Megatherium. longitudinal section of a lower molar of the Megatherium, of half the natural size : v is the vaso-dentine, d is the hard dentine, and c is the cement; p is the base of the wide per- sistent pulp-cavity. The hard dentine is, of course, the firmest tissue of a tooth so composed, and forms the crest of the transverse ridges of the grinding surface, like the enamel plates in the elephant's grinder. It has, consequently, been described to be enamel *, but its relation to that tissue is only one of analogy or function. The human teeth, and those of the carni- vorous mammals, appear at first sight to be composed of dentine and enamel only, as they were described to be by the Cuviers f , who * Cuvier, Ossemens Fossiles, 4to, t. v., pt. 1., p. 172. ; and Clift, Transactions of the Geological Society, 183.5, p. 438. t F. Cuvier, Dents de Mammiferes, p. 1. 8vo, 1825; G. Cuvier, Lecons d'Anat. Comp. iv. (1836), p. 199. called them, therefore, simple teeth ; but their crowns are originally, and their fangs are always, covered by a thin coat of cement. There is also commonly a small central tract of osteo-dentine in old teeth. In fig. 7, pi. 122, of my Odontography is given a longitudinal section of a human molar tooth, in which d is the dentine, c the enamel, and c the cement. The teeth, called by Cuvier compound or complex in Mammalia, differ, as regards their composition, from the preceding, only by the different proportion and disposition of the constituent tissues. Fig. 549. is a longitudinal section of the incisor of a horse ; d is the dentine, e the enamel, and c the cement ; c is the layer of cement reflected into the deep central depression of the crown ; and s is the coloured mass of tartar and particles of food which fills up tliat cavity, forming the " mark" of the horse-dealer. The characteristic struc- ture of the three tissues is shown in the uiagnified part of the section,^. 550. Fig. 549. Section of incisor of a Horse {Equus). A very complex tooth may be formed out. of two tissues by the way in which these may be interblended, as the result of an original complex disposition of the constituents of the dental matrix. Certain fishes, and a singular family of gigantic extinct Batrachians, which I have called "Labyrinthodonts,"* exhibit, as the name implies, a remarkable instance of this kind of complexity. Fig. 551. is a view of a canine tooth of the Labyrinthodon scdaman- droides, of the natural size : and Jig. 552. is a slightly magnified view of a transverse section across the part of the crown marked a. At first view, the tooth appears to be of the simple conical kind, with the exterior surface merely striated longitudinally, but every streak is a fissure into which the very thin external layer of cement (c) is reflected into the body of * Proceedings of the Geological Society, Jan 20» 1811, p. 257. 3 K 2 868 TEETH. Fig. 550. Fig. 551. Magnified portion of section of incisor of Horse ; c cement, e enamel, d dentine. the tooth, following the sinuous wavings of the lobes of dentine (d), which diverge from the central pulp-cavity, a. The inflected fold of cement c runs straight for about half a line, and then becomes wavy, the waves rapidly increasing in breadth as they recede from the periphery of the tooth ; the first two, three, or four undulations are simple ; then their contour itself becomes broken by smaller or secondary waves ; these become stronger as the fold approaches the centre of the tooth, when it increases in thickness, and finally terminates by a slight dilatation or loop close to the pulp-cavity, from which the free margin of the inflected fold of cement is separated by an extremely thin layer of dentine. The number of the inflected converging folds of dentine is about fifty at the middle of the crown of the tooth figured, but is greater at the base. All the inflected folds of cement at the base of the tooth have the same complicated disposition with increased extent; but, as they approach their termination towards the upper part of the tooth, they also gradually diminish in breadth, and consequently penetrate to a less distance into the substance of the tooth. Hence, in such a section as is delineated {fig. 552.), it will be observed that some of the convoluted folds, as those marked cc, extend near to the centre of the tooth ; others, as those marked c', reach only about half-way to the centre ; and those folds, c", which, to ,use a geological expression, are " cropping Tooth of a Labyrinthodon, natural size. out," penetrate to a very short distance into the dentine, and resemble, in their extent and Fig. 552. Transverse section of tooth of Labyrinthodon. (Magnified.') simplicity, the converging folds of cement in the fangs of the tooth of the Ichthyosnurus. The disposition of the dentine is still more complicated than that of the cement. It con- sists of a slender, central, conical column, excavated by a conical pulp-cavity for a cer- TEETH. 809 tnin distance from the base of the tooth ; and this column sends radiating outwards, from its circumference, a series of vertical plates, which divide into two once or twice before they terminate at the periphery of the tooth. Each of these diverging and dichotomising plates gives off' throughout its course smaller processes, which stand at right angles, or nearly so, to the main plate ; they are gene- rally opposite, but sometimes alternate; many of the secondary plates or processes, which are given off' near the centre of the tooth, also divide into two before they terminate; and their contour is seen, in the transverse section, to partake of all the undulations of the folds of cement which invest and divide the den- tinal plates and processes from each other. The dental pulp-cavity is reduced to a mere line about the upper third of the tooth, but throughout its whole extent fissures radiate from it, corresponding in number with the radiating plates of dentine. Each fissure is continued along the middle of each plate, dividing where this divides, and extending along the middle of each bifurcation and pro- cess to within a short distance of the line of cement. The pulp-fissure commonly dilates into a canal at the origin of the lateral pro- cesses of the radiating plates, before it divides to accompany and penetrate those processes. The main fissures or radiations of the pulp- cavity extend to within a line or half a line of the periphery of the tooth, and suddenly dilate at their terminations into spaces, which, in transverse section, are subcircular, oval, or rally smaller spaces. All these spaces, or canals, in the living tooth, must have been occupied by corresponding processes of the vascular pulp : they constitute so many cen- tres of radiation of the fine calcigerous tubes, which, with their uniting clear substance, constitute the dentine.* An analogous complexity is produced by numerous fissures radiating from a central mass of vase-dentine, which more or less fills up the pulp-cavity of the seemingly simple conical teeth of the extinct family of fishes which I have called " Dendrodonts."f Fig. 553. is one of these fossil teeth, of the natu- Fig. 553. Tooth of a Dcndrodus, natural size. ral size ; a a transverse section ; andy?g. 554* a reduced view of a portion of the same section, enlarged twenty diameters. Thus magnified, a central pulp-cavity, of Fig. 554. E Transverse section of tooth of Dendrodus. A, natural size; B, the portion c, of A, magnified 20 diameters. pyriform, p : the branches of the radiating relatively small size, and of an irregular lohu- lines, which are continued into the lateral lated form, is discerned, a portion of which secondary plates or processes of the dentinal lamellie, likewise dilate into similar, and gene- * Odontography, f lb. p. 171. - 195—217, pi. 6-lA, 64u. 3K3 870 TEETH. is shown at p; this is immediately surrounded by the transverse sections of large cylindrical medullary, or pulp-canals of different sizes; and, beyond these, there are smaller and more numerous medullary canals, which are pro- cesses of the central pulp-cavity. In the transverse section these processes are seen to be connected together by a net-work of smaller medullary canals belonging to a coarse osseous texture into which the pulp has been converted, and this structure occupies the middle half of the section. All the medullary canals were filled by the opaque matrix. From the circumference of the central net- work, straight medullary fissures radiate at pretty regular intervals to the periphery of the tooth : most of these canals divide once, rarely twice, in their course ; the division taking place sometimes at their origin, in others at different distances from their termi- nations, and the branches diverge slightly as they proceed. Each of the above medullary fissures is continued from a short process of the central structure, which is connected by a concave line with the adjoining process, so that the whole periphery of the transverse section of the central coarse reticulo-medul- lary body of the tooth presents a crenate out- line. From each ray and its primary dicho- tomous divisions, short branches are sent off at brief intervals, generally at right angles with the trunk, or slightly inclined towards the periphery of the tooth. These subdivide into a few short ramifications, like the branches of a shrub, and terminate in irregular and somewhat anguhr dilatations, simulatingleaves, but which resolve themselves into radiating fasciculi of calcigerous tubes. There are from fifteen to twenty-five or thirty- six of these short and small lateral branches on each side of the medullary rays. A third kind of complication is produced by an aggregation of many simple teeth into a single mass. The examples of these truly compound teeth* are most common in the class of Fishes, but the illustration here selected is from the Mammalian class. Each tooth of the Cape Ant-eater (Orycteropus) presents a simple form, is deeply set in the jaw, but without dividing into fangs ; its broad and flat base is porous, like the section of a com- mon cane. The canals to which these pores lead contain processes of a vascular pulp, and are the centres of radiation of as many inde- * In the " Lemons d'Anatomie Compare'e " of Cuvier, the teeth, in which folds of enamel and cement penetrate the entire substance of the crown, are called " compound : " " Nous appellous ' dent composee ' celle dont les differentes substances torment des replis tellement profonds, que dans quelque sens qu'on coupe la dent, on coupe plusieurs fois ehacune des substances qui la composent : telles sont les dents molaires de r Elephant." The teeth of the " Labyrinthodonts " would come under this definition more truly than those of the elephant, although they differ from them in having no enamel ; for a molar of an elephant might be bisected, verti- cally and transversely, without cutting the tissues across more than once. pendent series of dentinal tubules. Each tooth, in fact, consists of a congeries of long and slender prismatic denticles of dentine, which are cemented together by their ossified capsules, the columnar denticles slightly de- creasing in diameter and occasionally bifur- cating as they approach the grinding surface of the tooth. A figure of a longitudinal section of the o molar teeth is given in PL 76, fig. 10. of my " Odontography," and a magnified view of a similar section in PI. 77. ; fig. 555. gives a magnified view of a portion of the transverse Fig. 555. Part of transverse section of the tooth of the Oryc- teropus. (Magnified.) section of the fourth molar, showing c the cement ; d the dentine ; p the pulp-cavity of the denticles ; and d' a section of one or the denticles just beyond its bifurcation. The pectinated incisors of the flying Lemur of the Indian Islands (Galeopithecus) are ex- amples of teeth, the crowns of which are composed of denticles consisting of hard den- tine, with a covering of true enamel. The layer of cement over this is too thin to show its characteristic structure, and does not fill up the intervals of the denticles, which stand out as free processes from the base of the crown. Tubular prolongations of the pulp- cavity are continued up the centre of each denticle. Fig. 556. exhibits a longitudinal section, magnified, of this kind of compound tooth; d is the dentine; e the enamel; p the pulp- cavity. The originally detached summits of the crown of the human incisor are homo- logous with these columnar processes, or denticles of the incisor of the Galeopithcciis. In the compound molars of the great Afri- can wart-hogs (Phacochaerus) the columnar denticles are in three rows, and their inter- spaces are filled up by cement : each denticle consists of a slender column of hard dentine inclosed in a thick sheet of enamel, the whole being bound together by the cement ; and the TEETH. 871 denticles, as in the Gafeopithecus, blending long diameter of the tooth. When the tooth together into a common base in the fully-de- is bisected vertically and lengthwise, the three veloped tooth. substances, d dentine, e enamel, and c cement, Fig. 557. Section of lower incisor of Galeopiihecus (Magnified.) Section of molar of Elephant. are seen interblended as in Jig. 557 , in which p is the common pulp-cavity, and r one of the roots of this complex tooth. A still more complex, grinding apparatus is found in certain fishes. The lower pharyngeal A figure is given of the grinding surface of bone of the parrot-fish (Scams*), for ex- the third true molar of the Phacochcerus Pal- ample, supports a dental plate with a tri- Fig. 558. Two of (he upper pharyngeal teeth, Scarus. (Magnified.) fasii, in PI. HO, Jig. 4, of my " Odontography." turating surface like that of the compound In the elephant the denticles of the com- molars of the Phacochcerus. The interlocked pound molars are in the form of plates, vertical upper pharyngeals (Jig. 565.) support dental to the grinding surface and tranverse to the * Odontography, pi. 51., fig. 3. 3 K 4 872 TEETH. masses with a grinding surface more like that osseous tissue of the epiphyses of bones was of the compound molars of the elephant. developed differently from osseous tissue in When a vertical and longitudinal section general, e. g. by the uniform and simultaneous is made of one of these upper pharyngeal hardening or calcification, obscurely referred compound teeth, each denticle is seen to be to in the above quotation, may be questioned, composed, as in Jig. 558., of a body of very for such is not the way in which the teeth of hard and unvascular dentine d, with a thick the shark are calcified. But this is certain, sheath of enamel e, the denticles being united that the idea, whatever it might have been, together by the cement c, and supported and had no influence on the fixed belief of the further united together, and to the pharyngeal developement of the dental tissue by trans- bone, by a basal mass of vascular osteo-dentine. ndation expressed in their later and more elaborate works by Baron Cuvier and his ac- Snch are some of the prominent features complished brother ; and, in point of fact, the of a field of observation which comparative passage which I have quoted is expunged from anatomy opens out to our view ; — such the the second edition of the " Lecons d' Anatomic varied 'nature, and such the gradation of Comparee," 1835 : the successive stages of complexity of the dental tissues, which, up to calcification in the different teeth of the same December 1839*, continued, notwithstanding vertical series in the jaw of the shark, having successive approximations to the truth, to be probably been noticed in the interim by Cuvier. described in systematic works as a " pha- The author of the article " Secretions "in neros," or " a dead part or product exhaled the "Dictionnaire Universel d'Histoire Na- from the surface of a formative bulb ! " The turelle," has, however, reproduced Cuvier's ob- truth may be slowly but is surely established, scure comparison of certain fishes' teeth to subject to the usual attempts to mask or the epiphyses of bone, as evidence of the need- detract from the merit of the discovery. By lessness of any ulterior researches for the no systematic authors has the hypothesis of demonstration of the theory of dental de- the formation of dentine by transudation or velopement by conversion and calcification of secretion been more frequently or more ex- the pulp. The passage from the third vol. of the old edition (1800) of the " Lecons d'Anat. Comp.," p. 112, is cited to show that it naturally conducts to the knowledge of plicitly enunciated than by the Cuviers. Baron Cuvier repeats, in both editions of his elaborate work — the " Ossemens Fossiles " — " C'est dans ce vide conp evable que se de- such mode of developement of dentine : poseront les matieres qui doivent former la 1840 et 184-1 (the 'Comptes Rendus del' Acad. dent, savoir : la substance vulgairement ap- des Sciences' give the true date) 1'etude des pelee osscuse, qui sera transudee par des pro- dents de Squale par M. R. Owen, lui a de- ductions gelatineuses venant du fond de la montree leur accroissement par intussuscep- ' capsule, et 1'email qui sera depose par les tion, comme elle avail etc a G. Cuvier trente- cloisons membraneuses," t. ii. p. 61., ed. 1812.; cinq annees auparavant." How or why G. t. i. p. 33., ed. 1821. See, also, M. F. Cuvier, Cuvier came to abandon the theory so demon- " Dents de Mammiferes," 8vo, 1825. " L'ivoire strated, and how it happened that none of his En se depose par couches concentriques," p xxvii. ; " L' email se depose dans un sens contraire a Pivoire," ib. p. xxviii. And Baron Cuvier again, in the second edition of his "Lecons d'Anatomie Comparee/' t. iv. 1836, contemporaries adopted it, M. Duvernoy does not explain. He does give a reason for the omission, in the second edition of the " Lecons d'Anat. Comp." of the passage which he affirms to contain the demonstration : " Malheureuse- p. 214- : "L'ivoire se depose par couches, par ment, le copiste de cet ancien texte pour la 2de edition a omis ce passage, par oubli." It was natural to conclude that its obscurity illustrated the peculiarity of the teeth of and seeming contradiction to the theory of une sorte de transudation." In the first edition of this classical work, Cuvier had certain fishes, which are at first detached and afterwards united to the jaw-bone, by com- paring their growth to that of the epiphyses of the long bones : " Mais les dents qui ne tiennent qu'a la gencive seulement, comme celle des Squalci;, croissent a la maniere des epiphyses des os, c'est-a-dire que toute leur substance osseuse est d'abord tendre et po- reuse, et qu'elle se durcit uniformement, et finit par devenir entierement dure comme de 1'ivoire," t. iii. 1805, p. 112. Whether the great anatomist meant to imply that the See the Fasciculus of M. de Blainville's great dental developement, formally propounded by Cuvier, as well as to the facts shown by nature in the sharks, had been the cause of its omission ; but even had the misfortune to which M. Duvernoy now attributes that omission (for in the copious list of addenda and corrigenda to the fifth, 1837, and final, 1816, volumes it is not noticed) not occurred, the coincidence of such passages as the fol- lowing would still have been inexplicable and irreconcilable with the deductions that M. Dumeril is now enabled to draw from the comparison of the shark's tooth with the OCC LJL1C -I- ?, tooth. Inferior pharyngeal bone and teeth (Labrus). teeth of the wolf-fish, and in similar grinding and crushing teeth in other genera, whether feeders on sea-weeds, or crustaceous and testa- ceous animals. The grinding surface of these short cylindrical teeth may be convex, as in the Sheep's-head fish (Sargus) ; or flattened, as in the pharyngeal teeth of the Wrasse (La- ir«.y).§ Sometimes the hemispheric teeth are so numerous, and spread over so broad a sur- face, as to resemble a pavement, as in the pharyngeal bones of the Wrasse or Rock-fish (Labrus, fig. 564.) ; or they may be so small, as well as numerous (denies graniformes), as to give a granulated surface to the part of the mouth to which they are attached (premax- illaries of Cossyphw).\\ A progressive increase * rw«, an angle ; eHm/;, a tooth. t Vol. III., fig. 512, p. 978. art. PISCES. j Ib. fig. 51 1), 'p. 976. § Ib.fig. 513, p. 978. || Odontogrnphy, pi. 45, _/?y five vertical angular notches, penetrating in- wards through half the breadth of the sup- porting bone, and dividing the plate into six angular processes, which, from the direction and varying form and breadth of the entering notches, radiate from the posterior part of the median line or division of the tooth. The inferior dental plate is similarly notched on its outer side, but the proportions of the an- gular indentations are such, that they receive SL 882 TEETH. all the processes of the upper dental plate when the mouth is shut, whilst only the foul- anterior processes are reciprocally received into the notches of the upper dental plate, this, with the supporting arch, being anterior to the lower plate, — a position which is deci- sive in favour of its maxillary character, and against its homology with the vomer. The dental plate consists, as in the Cod and Sphyrecna, of a central mass of coarse osseous substance, traversed by large and nearly parallel medullary canals, and an ex- ternal sheath of very hard " vitro-dentine." The medullary canals are continued from a coarse reticulation of similar but wider canals in the substance of the supporting bone, and advance forwards, nearly parallel with each other and with the plane of the upper surface of the tooth ; they anastomose together by short, curved, transverse canals, which inter- cept spaces increasing in length as the canals recede from the osseous basis. The canals themselves diminish in size in the same ratio; and when they have arrived near the dense outer layer, their divisions and inosculations become 'again more frequent, the peripheral loops forming a well-marked line of demarca- tion between the coarse-tubed and the fine- tubed dentine. The interspaces of the medullary canals are occupied by a clear sub- stance, and by moss-like reticulations of fine tlentinal tubes, which appear to be more sparing in number than in the teeth of the Sphyrama or Shark. The dentinal tubes of the vitro-dentine run nearly parallel to each other, and vertically to the external surface of the dental plate through about two-thirds of the thickness of that tissue ; they then bend and cross each other in a manner very similar to those of the vitro-dentine in the teeth of the Lcpidotus, Phyllodus, &c.* In the process of attrition this external dense substance is worn away from the upper surface of the dental processes in the lower jaw, exposing the softer vaso-dentinal sub- stance of the tooth ; in this state the den- tal plate offers an analogy to the incisors of the Rodents, a posterior softer substance being sheathed by an anterior denser layer ; and an external sharp edge is similarly kept up by the unequal wearing away of the two substances. The progressive waste at the upper surface of the dental plate would appear to be met by a corresponding additon of new material to its lower part. In the structure here presented we have a condition of the dentine which has hitherto been met with only in the class of fishes. The test of the affinities of the present paradoxical genus, afforded by the micro- scopic examination of the teeth, gives addi- tional confirmation to the view to which I have been led, from arguments drawn from the rest of its organisation, that the Lcpido- siren is in every essential point a member of the class of fishes. -j- * See Odontography, pp. 70. ICO. pi. 59, fg. 4. f Linneaii Transactions, vol. xviii. 1839. p. 3oO. That the large size, or elliptical form of its blood- Dental System of Reptiles. If we compare the dental system of the foregoing Batrachoid fish with that in the true Satrackia, it is only to the larval state of the Anourans that an analogy can be found ; the tadpole of the frog having its maxilla and mandibula each sheathed with a single and continuous horny dental trenchant covering. Were this sheath actually dentinal in tissue and united to the jaw-bone, the re- semblance to the Lcpidosiren would be closer ; but in point of fact the analogy is very remote ; the horny beak of the tadpole is never calcified or anchylosed, but is shed during the progress of the metamorphosis.* The Siren alone, among the larval-like pe- rennibranchiate reptiles, retains the sheath upon the extremity of the upper and lower jaws ; it consists of a firm albuminous tissue, and becomes harder than horn. But these trenchant mandible?, which play upon one another like the blades of a pair of curved scissors, are associated with numerous small but distinct true teeth, which are grouped together to form a rasp-like surface on each half of the divided vomer, and which beset the alveolar border of the splenial element of the mandible below. In the class Reptilin, the whole order of Chelonia is edentulous, as well as the whole family of Toads (Sufomdee) in the order Batrachia; certain extinct genera of Sau- rians were likewise edentulous, e.g. the re- markable " Rhynchosaurus " of the new red sandstone of Shropshire, and some of the extinct Saurians of South Africa. In the tortoises and turtles the jaws are covered by a sheath of horn, which in some species is of considerable thickness and very dense ; its working surface is trenchant in the carnivorous species, but variously sculptured, and adapted for both cutting and bruising in the vegetable feeders ; it may be said that the transitory condition of the mandibles of the 1'atrachian larvaa is here persistent. The development of the continuous horny maxillary sheath commences, as in the parrot tribe, from a series of distinct papillae, which sink into alveolar cavities, regularly arranged (in Trtomjx) along the margins of the upper and loweV jaw-bones : these alveoli are in- dicated by the persistence of vascular canals long after the originally separate tooth-like cones have become confluent, and the horny sheath completed. The teeth of the dentigerous Saurian, discs should outweigh the cumulative evidence esta- blishing the piscine nature of the Lepidosirm could only lie surmised by those who are ignorant of the variation in size and shape which the blood-discs present in the class of fishes, and the consequent unimportance of those, particles as a character of the class. As well might the Petromyzon be deemed a mammal because its blood-discs are circular and comparatively small, as the Lc.pidasiren be held to be a Batrachian because its blood-discs are elliptical and comparatively large. * The large dental plates of Lep'ulosircn have their nearest homolognes in those of the extinct rish called Ceratodus (Odontography, pi. 22, ./H/. 2.). TEETH. 883 Ophidian, and Batrachian reptiles, are, for the most part, simple and adapted for seizing and holding, but not for dividing or masticating their food. The Siren alone combines true teeth with a horny maxillary trenchant sheath, like that of the Chelonian reptiles. With respect to number, in no existing rep- tile are the teeth reduced so low as in certain mammals and fishes ; nor, on the other hand, are they ever so multiplied as in many of the latter class. The extinct Dicynodont reptiles of South Africa had hut two teeth, which were long tusks implanted in the upper jaw.* Some species of Amphisbaina (A. alba], with fifteen teeth in the upper jaw and four- teen in the lower jaw, and certain Monitors ( farftnits], with sixteen teeth in the upper and fourteen in the lower jaw, afford examples of the smallest number of teeth amongst existing reptiles ; and certain Batrachians, with teeth " en cardes " at the roof of the mouth, or which have upwards of eighty teeth in each lateral maxillary series, present the largest number. It is rarely that the number of the teeth is fixed and determinate in any reptile so as to be characteristic of the species, and still more rarely have the individual teeth such characters as to be determined homo- logically from one species to another. With respect to situation, the teeth may be present on the jaws only, i.e. the maxillary, pre- maxillary, and mandibular bones, as in the croco- diles and many lizards : or upon the jaws and roof of the mouth ; and here either upon the pterygoid bones, as in the Iguana and Mosa- saur, or upon both palatine and pterygoid bones, as in most serpents, or upon the vomer, as in most Batrachians, or upon both vomerine and pterygoid bones, as in the Axo- lote ; or upon the vomerine and sphenoid bones, as in the Salamandra glutinosa, Maclure. With respect to the marginal or jaw teeth, these may be absent in the intermaxillary bones, as in many serpents ; or they may be present in the upper and not in the lower jaw, as in most frogs ; or in both upper and lower jaws, as in the tailed Batrachians ; and among these they may be supported, upon the lower jaw, by the premandibular or den- tary piece, as in the Salamanders, Menopome, Amphiume, Proteus ; or upon the splenial piece, as in the Siren ; or upon both splenial and premandibular bones, as in the Axolotl. The palatine and pterygoid teeth may, in the Batrachians, be arranged in several rows, like the " dents en cardes " of fishes. The sphe- noid and splenial teeth are always so ar- ranged in the few species that possess them. The intermaxillary, maxillary, and preman- dibular teeth are uniserial, or in one row, with the exception of the Caecilia and the extinct Labyrinthodonts, which have a double row of teeth at the anterior part of the lower jaw. The teeth of reptiles, with few exceptions, present a simple conical firm, with the crown more or less curved, and the apex more or * Transactions of the Geological Society, 2cl series, vol. vii., 1845, p. 59. less acute. The cone varies in length and thickness ; its transverse section is sometimes circular, but more commonly elliptical or oval, and this modification of the cone may be traced through every gradation, from' the thick, round, canine-like tooth of the croco- dile, to the sabre-shaped fang of the Varanus, the Megalosaur, and the Cladeiodon.* Some- times, as in the fully formed teeth of the Megalosaur, one of the margins of the com- pressed crown of the tooth is trenchant, sometimes both are so ; and these may be simply sharp-edged, as in the Varanus of Timor, or finely serrated, as in the great Va- ranus, the Cladeiodon, and the Megalosaur.-f- The outer surface of the crown of the tooth is usually smooth ; it may be polished, as in the Leiodon, or impressed with fine lines, as in the Labyrinthodon (jig. 551.), or raised into many narrow ridges, as in the Plciosaur and Polyptychodon, or broken by a few broad ridges, as in the Iguanodon (Jig. 571.), or grooved by a single longitudinal furrow, as in some serpents (fig. 509, A).± The cone is longest and its summit sharpest in the serpents : from these may be traced, chiefly in the lizard tribe, a progressive short- ening, expansion of the base, and blunting of the apex of the tooth, until the cone is reduced to a hemispherical tubercle, or plate, as in the Thorictes and Cyclodus (Jig. 570.). In the Pleiosaur the dental cone is three- sided, with one of the angles rounded off. The posterior subcompressed teeth of the alligator (Jig. 573.) present a new modification of form ; here they terminate in a mammillate summit, supported by a slightly constricted neck. In the tooth of the Hylceosaur the expanded summit is flattened, bent, and spear- shaped, with the edges blunted. But the expansion of the crown is greatest in the sub- compressed teeth of the extinct Cardiodon and the existing Iguanas, the teeth of which are farther complicated by having the margins notched. The great Iguanodon had the crown of the tooth expanded both in length and breadth, and combining marginal dentations with longitudinal ridges : this tooth (fig. 571.) presents the most complicated external form as yet discovered in the class of reptiles. In no reptiles does the base of the tooth ever branch into fangs. Attachment. — As a general rule, the teeth of reptiles are anchylosed to the bone which supports them. When they continue distinct, they may be lodged either in a continuous groove, as in the Ichthyosaur §, or in separate sockets, as in the Plesiosaur and Oocodilians (fig. 573.). The base of the tooth is anchy- losed to the walls of a moderately deep socket in the extinct Megalosaur and Theocodon. In the Labyrinthodonts and Caecilioe, among the Bratrachians ; in most Ophidians ; and in the Geckos, Agamians, and Varanians, among the Saurians, the base of the tooth is * Odontography, pi. 02 A, fig. 4. f lb.fg.6c. j Ib. pi. 65 ; vol. iv.,frjs. 209, 210. § Ib. pi. 13,^. 9. 3L 2 884) TEETH. imbedded in a shallow socket, and is confluent therewith. In the Scincoidians, the Safeguards (Tejns), in most Iguanians, in the Chameleons and most other Lacertian reptiles, the tooth is anchylosed by an oblique surface extending from the base more or less upon the outer side of the crown to an external alveolar plate of bone*, the inner alveolar plate not being developed. In the frogs the teeth are simi- larly but less firmly attached to an external parapet of bone. The lizards which have their teeth thus attached to the side of the jaw are termed Pleurodonts. In a few Igua- nians, as the Istiures, the teeth appear to be soldered to the margins of the jaws, these have been termed " Acrodonts." In some large extinct Lacertians, c. g. the Mosasaur and Leiodon, the tooth is fixed upon a raised conical process of bone, as shown in my " Odontography," Plate 68. Jig. }., and Plate 72. fig. 2. These modifications of the attachment of the teeth of reptiles are closely adapted to the destined application of those instruments, and relate to the habits and food of the species ; we may likewise perceive that they offer a close analogy to some of the transitory con- ditions of the human teeth. There is a period, for example -j-, when the primitive dental papillae are not defended by either an outer or an inner alveolar process, any more than their calcified homologues which are confluent with the margin of the jaw in the Rhynchocephaltis.^. There is another stage §, in which the groove containing the den- tal germs is defended by a single external cartilaginous alveolar ridge ; this condition is permanently typified in the Cyclodits (Jig. 570.) and most existing lizards. Next there is developed in the human embryo an internal alveolar plate, and the sacs and pulps of the teeth sink into a deep but continuous groove, in which traces of transverse partitions soon make their appearance ; in the ancient Ichthy- osaur the relation of the jaws to the teeth never advanced beyond this stage. Finally, the dental groove is divided by complete partitions ||, and a separate socket is formed for each tooth ; and this stage of developement is attained in the highest or- gan;sed reptiles, e.g. the crocodiles (Jig. 573.). Substance. — This may be four-fold, and a single tooth may be composed of dentine, cement, enamel, and bone ; but the dentine and cement are present in the teeth of all reptiles. In the Batrachians and Ophidians a thin layer of cement invests the central body of dentine, and, as usual, follows any in- flections or sinuosities that may characterise * Odontography, pi. 67. | At the sixth week of gestation : see Prof. Good- sir, " On the Development of the Human Teeth," Edinburgh Medical and Surgical Journal, No. 138. J See Geological Transactions, 2d series, vol. vii. pt. 2, pi. G,fgs. 5 & fi, p. 83. § At the seventh or eighth week : Ibid. II At the sixth month : Ibid. the dentine. Besides the outer coat of cement, which is thickest at the base of the teeth, a generally thin coat of enamel defends the crown of the tooth in most Saurians, and the last remains of the pulp are not unfrequently converted into a coarse bone, both in the teeth which are anchylosed to the jaw, and in some teeth, as those of the Ichthyosaur, which remain free. The only modification of the dentine, which could at all entitle it to be regarded in the light of a new or distinct substance, is that which is peculiar in the present class to the teeth of the Tguanodon, and which will be described in the following section. Structure. — The varieties of dental structure are few in the reptiles as compared with either fishes or mammals, and its most com- plicated condition arises from interblcnding of the dentinal and other substances rather than from modifications of the tissues themselves. In the teeth of most reptiles the intimate structure of the dentine corresponds with that which has been described as the type of the tissue, e.g. the hard or un vascular dentine, and which is the prevailing modification in Mammalia, viz., the radiation of a system of minute plasmatic tubes from a single pulp- cavity, at right angles to the external surface of the tooth. The most essential modification of this structure is the intermingling of cylin- drical processes of the pulp-cavity in the form of medullary canals, with the finer tubular structure.* Another modification is that in which the dentine maintains its normal struc- ture, but is folded inwardly upon itself, so as to produce a deep longitudinal indentation on one side of the tooth ; it is the expansion of the bottom of such a longitudinal deep fold that forms the central canal of the venom- fang of the serpent ; but a glance at Jig. 568. will show that, notwithstanding the singularly modified disposition of the dentine (b), its structure remains unaltered ; and although the pulp-cavity (p) is reduced to the form of a crescentic fissure, thedentinal tubes continue to radiate from it according to the usual law. By a similar inflection of many vertical longi- tudinal folds of the external cement and ex- ternal surface of the tooth at regular intervals around the entire circumference of the tooth, and by a corresponding extension of radiated processes of the pulp-cavity and dentine into the interspaces of such inflected and con- verging folds, a modification of dental struc- ture is established in certain extinct reptiles, which, by the various sinuosities of the inter- blended folds of cement and processes of dentine, with the partial dilatations of the radiated pulp-cavity, produces the compli- cated structure which is described at p. 868. and figured in cut 552. But this compli- cation is nevertheless referable to a modi- fication of form or arrangement of the dental tissues, rather than of the structure of the tissues themselves : the calcigerous tubes in each sinuous lobe of dentine, in the most * Odontography, pi. 71, Iguanoclon. TEETH. 885 complex tooth of the Labyrinthodon, exhibit the same general disposition and course as in the fang of the serpent and in the still more simple tooth of the Saurian. Development. — The teeth of reptiles are never completed, as in certain fishes, at the first or papillary stage ; but the pulp sinks into a follicle, and becomes inclosed by a cap- sule; and in certain reptiles this becomes more or less surrounded by bone ; but the process of development never offers the erup- tive stage, in the sense in which this is usually understood, as signifying the extrica- tion of the young tooth from a closed alveolus. The completion of a tooth, with the extinct exception of the Dicynodont Reptiles, is soon followed by preparation for its removal and succession : the faculty of developing new tooth-germs seems to be unlimited in the pre- sent class, and the phenomena of dental deca- dence and replacement are manifested at every period of life; the number of teeth is gene- rally the same in each successive series, and the difference of size presented by the teeth of different and distant series is considerable. The new germ is always developed, in the first instance, at the side of the base of the old tooth, never in the cavity of the base ; the crocodiles form no exception to this rule. The poison-fangs of serpents succeed each other from behind forwards ; in almost every other instance the germ of the successional tooth is developed at the inner side of the base of its predecessor. In the frog the dental germ makes its appearance in the form of a papilla developed from the bottom and towards the outer side of a small fissure in the mucous membrane or gum that fills up the shallow groove at the inner side of the alveolar parapet and its adherent teeth : the papilla is soon enveloped by a capsular pro- cess of the surrounding membrane : there is a small enamel pulp developed from the cap- sule opposite the apex of the tooth ; the de- position of the earthy salts in this mould is accompanied by ossification of the capsule, which afterwards proceeds part passu with the calcification of the dentinal papilla or pulp; so that, with the exception of its base, the surface of the uncalcified part of the pulp alone remains normally unadherent to the cap- sule. As the tooth acquires hardness and size, it presses against the base of the contiguous attached tooth, causes a progressive absorp- tion of that part, and finally undermines, dis- places, and replaces its predecessor. The number of nascent matrices of the successional teeth is so great in the frog, and they are crowded so close together, that it is not unusual to find the capsules of contiguous tooth-germs becoming adherent together, as their ossification proceeds. After a brief ma- ceration, the soft gum may be stripped from the shallow alveolar depression, and the younger tooth-germs in different stages of growth are brought away with it. The mode of development of the teeth of serpents does not differ essentially from that of the teeth of the Batrachian above described except in the relation of the papillae of the successional poison-fangs to the branch of the poison-duct that traverses the cavity of the loose mucous gum in which they are deve- loped. Batrachian modifications. — Some of the pe- culiarities of the dentition of the Batrachians have already been noticed, as in the compa- rison of the Siren with the Lepidosiren* in which the true amphibian was shown to have numerous teeth on the palate and lower jaw.* The piscine character of rasp-like teeth aggregated in numerous series, is manifested also in the Axolotl f, upon the palatal region of the mouth, and upon the splenial or oper- cular element of the lower jaw ; but the superior maxillary bones are here developed, and also support teeth. The premandibular and the premaxillary bones, instead of pre- serving the larval condition of the horny sheath, have their alveolar border armed with a single row of small, equal, fine and sharp- pointed denticles, which are continued above, along the maxillaries; thus establishing the commencement of the ordinary Batrachian condition of the marginal teeth of the buccal cavity. The dentigerous bones of the palate consist of two plates on each side, as in the Siren ; the anterior pair, or vomerine bones, converge and meet at their anterior extre- mities ; the minute denticles which they sup- port are arranged quincuncially ; the posterior pair of bones are continued backwards ac- cording to the usual disposition of the ptery- goids, to abut against the tympanic bones ; the denticles are confined to the anterior part of their oral surface, and resemble in their arrangement and anchylosed attachment those of the vomerine series, of which they form the posterior termination. The frogs (Rana^) J have no teeth on the lower jaw ; but in some species the alveolar edge of this bone is finely notched or dentated, as in the horned frogs {Ceratophrys). The in- termaxillary and maxillary bones support a long, close-set, single series of small, conical, hollow teeth, of which the apices only project beyond the external alveolar ridge to which they are attached. A short transverse row of similar but smaller teeth extends along the posterior border of each vomer, except in the slender-armed frogs (Leptobrachium), and in some of the tree frogs (e. g . Euclinemis), in which the roof of the mouth is edentulous. Amongst the most extraordinary examples of extinct reptiles are those which are charac- terised by the labyrinthic modification of the dental structure above described, and which with some affinities to Saurians, combine characters which are essentially those of the order Batrachia. I have ascertained by fossil portions of the upper jaw of the Labyrinthodon Icptognathus that the maxillary or facial divi- sion of the skull was broad, much depressed, and flattened, resembling the skull of the * Odontograpliy, pi. G'2,fys. 5 & G t Ib. pi. 02,/) with the apex extend- ing to about one-half of the implanted part of the tusk, and a linear tract is continued along the centre of the solid part of the tusk. From this central line the dentinal tubes radiate, with a gentle curve at the beginning, convex towards the point of the tusk, and then proceeding straight to the periphery of the tooth, but inclining towards the apex. They present parallel secondary curves, divide di- chotomously twice or thrice near their begin- ning, and send off numerous small lateral branches, chiefly from the side next the apex. At their primary curve the dentinal tubes are __^_-.th of an inch in diameter, and their intervals are ^^th of an inch across. The dentinal cells are most conspicuous near the periphery of the tooth, and vary in diameter from sTrir1'1 to ToVoth °f an i"ch- _ The enamel, at least at the middle of the tusk, is thinner than in the teeth of the cro- codile. It presents only a finely lamellated texture, the layers being parallel with the surface of the dentine on which it rests. There is only a fine linear trace of cement on the exterior of the sections of the implanted base of the tusks ; and here it is too thin to allow of the development of the radiated cells in its substance. There is no trace of teeth or their sockets in the lower jaw (25, 23); so much of the alveolar border as is exposed pre- sents a smooth and even edge, which seems to have played like a scissor-blade upon the inner side of the corresponding edentulous border of the upper jaw ; and it is most probable, from the analogies of similarly-shaped jaws of existing Reptilia, that the fore part of both the upper and under jaws were sheathed with horn. Until the discovery of the Rhynchosaunts*, this edentulous and horn-sheathed condition of the jaws was supposed to be peculiar to the Chelonian order among reptiles ; and it is not one of the least interesting features of the Dicynodonts of the African sandstones, that they should repeat a Chelonian character, hitherto peculiar, amongst Lacertians, to the above-cited remarkable extinct edentulous genus of the new red sandstone of Shrop- shire : but our interest rises almost to as- tonishment, when, in a Saurian skull, we find, superadded to the horn-clad mandibles * Transactions of the Cambridge Philosophical Society, vol. vii. part iii. of the Tortoise, a pair of tusks, borrowed as it were from the mammalian class, or rather foreshadowing a structure which, in the actual creation, is peculiar to certain members of the highest organised warm-blooded animals. In the other Reptilia, recent or extinct, which most nearly approach the Mammalia in the structure of their teeth, the difference characteristic of the inferior and cold-blooded class is manifested in the shape, and in the system of shedding and succession, of the teeth : the base of the implanted teeth seldom becomes consolidated, never contracted to a point, as in the fangs of the simple teeth of Mammalia, and at all periods of growth one or more germs of teeth are formed within or near the base of the tootli in use, prepared to succeed it, and progressing towards its dis- placement. The dental armature of the jaws is kept in serviceable order by uninterrupted change and succession ; but the matrix of the individual tooth is soon exhausted, and the life of the tooth itself may be said to be com- paratively short. The Dicynodonts not only manifest the higher type of free implantation of the base of the tooth in a deep and complete socket, common to Crocodilians, Megalosaurs, ami Thecodonts, but make an additional and much more important step towards the mammalian type of dentition, by maintaining the service- able state of the tusk by virtue of constant renovation of the substance of one and the same matrix, accordingly to the principle manifested in the long-lived and ever-growing tusks of the Walrus, and the scalprilorm in- cisors of the Rodentia. The genera of the typical family of the squamate Lacertians are arranged in two sub-families, the chief characteristics of which are derived from the dental system. In the first group, the teeth are solid, or without any permanent internal cavity, and are very firmly anchylosed by their base to the alveolar groove upon the inner side of the jaw ; so that the extremity of the tooth is slightly directed outwards. The species which present this character are called Pleo- donts. In the second group, the teeth are ex- cavated, or retain the pulp-cavity, and are less firmly fixed to the jaws, being applied vertically, like piles or buttresses, against the outer alveolar parapet, but not adhering by their base. This group is called Coelodonts. The Monitor Lizard of S. America is an example of the Pleodont group, in which the premaxillary teeth are ten in number. The maxillary teeth vary from ten to fifteen on each side, and increase in size as they are placed farther back : the hindmost teeth are tricuspid in young individuals, and present the form of simple tubercles in the old Mo- nitors. The mandibular teeth, fifteen to eighteen in number in each ramus, correspond in size and form with those above. In the Coelodont group, the "Swift lizards" (Tachy- dromtis) have the pterygoid bones armed with minute teeth. The teeth on both upper and TEETH. 891 lower jaws are of larger size, and the hinder ones are tricuspid. The true lizards (La- certa) have two kinds of teeth quoad form ; the anterior small, conical, and recurved ; the posterior larger, and bi- or tri-cuspid. Some species have also pterygoid teeth ; as the common Laccrta agllis. In the Gigantic fossil Monitor of Maes- tricht, the teeth combine the Pleodont with the Acrodont* characters. The true affinities of the Mosasanr, which was at least twenty-four feet in length, and the remains of which characterise the chalk- formations, were first determined by Cuvier, who places it in the Lacertian group of Saurians, between the Iguanae and Monitors. Its dentition exhibits in an eminent degree the Acrodont character; the teeth being sup- ported on expanded conical bases ancliylosed to the summit of the alveolar ridge of the . jaw : no existing Saurian exactly parallels this mode of attachment of the teeth, either in regard to the breadth of the alveolar border, or in the relative size of the osseous cones to the teeth which they support. A shallow socket is left where the tooth and its supporting base are shed. The form of the teeth is likewise different from that hitherto observed in any existing Saurian : the crown is pyramidal, with the outer side nearly plane, or slightly convex, and separated by two sharp ridges from the remaining sur- face, which forms a half-cone. All the teeth account of the Mosasaurns, " lias no true root, but it adheres strongly to that pulp which has secreted it, and it is further held in connection with it by the remains of the capsule which has furnished the enamel, and which, by becoming ossified also, and uniting itself to the maxillary bone and the ossified pulp, implants or rivets the tooth with addi- tional force." The necessity under which Cuvier felt himself compelled to regard the crown and the base of the tooth of the Mosasaur as two distinct parts, is at once banished by the recognition of the principle, that the processes of calcification are essentially the same at every part of a tooth, whether it be free or ancliylosed ; and that they are modified only, as 1 have shown in my Memoir on the Formation of the Teeth of the Shark *, ac- cording to the density of the part to be pro- duced. Scincoid Lizards. — Most of these smooth- scaled lizards have small mouths and slender sharp teeth, fitted best for insect food ; they are usually confined to the upper and lower jaws ; but the medicinal Scink of ancient pharmacy (Scincus officmalis) has four or five small obtuse teeth upon each pterygoid bone. The chief exception to the typicaf dentition of the present family is made by the large scincoid lizards of Australia, which, on that account, have received the generic name of Cycludus.^ Fig. 570. Lower jaw and teeth of Cydodus nigroluteus. are slightly recurved, and their peripheral surface is smooth. The teeth are implanted upon the premaxillary, maxillary, and pre- mandibulary bones ; a series of similarly shaped but much smaller teeth are placed upon the pterygoid bones. The gradual transition from the simple structure of the compact dentine totheosteo- dentine of the anchylosed base of the tooth was not known to Cuvier; otherwise he could not have supposed that the crown and the base of the tooth of the Mosasaurus were formed by vital processes of so dissimilar a nature as to forbid him considering them as parts of one and the same body. Cuvier had originally described the expanded base of the tooth of the Mosasaur as the root of the tooth ; but afterwards, observing that the corresponding base became anchylosed by ossification of the remains of the pulp to the jaw, he conceived it to be incorrect to regard it as a part of a body which he believed to be an inorganic product, and the result of excretion. " The tooth," he observes, in correcting his first * Oclontography, pp. 241. 258. The dentition of the Cycl. nigroluteus is exemplified in the lower jaw, fig. 570. In the upper jaw, the single premaxillary bone has depressions for twelve teeth, of which only the alternate ones are usually in place ; they are of very small size, with the fang com- pressed laterally, and the crown antero- posteriorly, so as to resemble a true incisor in form, the summit sloping to an edge from behind forwards, with the middle of the cut- ting surface a little produced. Each superior maxillary bone has depressions for fourteen teeth ; they quickly increase in size, and exchange their conical for a sub-hemispherical crown; the eighth to the thirteenth inclusive are the largest teeth ; they are set obliquely, and pretty close together. In the lower jaw there are two small incisors, at the anterior part of each premandibular bone correspond- ing with those of the premaxillary ; these are succeeded by five or six conical teeth, and the rest correspond in size and form with the tuberculate molars of the upper jaw. * Compte Rendu de 1'Academie des Sciences, Decembre, 1839. f Hound-toothed : xvxins, round ; eSoi^, tooth. 892 TEETH. All the teeth are attached, after the Pleuro- dont type, by their base and outer margin to shallow depressions on the outer side of the external alveolar parapet. The germs of the successional teeth, c. Jig. 570., are developed at the inner side of the base of their predecessors, a, which they excavate, undermine, and displace in the usual manner. Iguanas. — Certain genera of this family of lizards, e. g. Istiiirus, Lophyrus, Calotes, and Otocryptis, have the teeth soldered, like those of Mosftsaurns, to the summit of the alveolar ridge, and thence are called " Acrodonts : " in all these lizards the maxillary and mandibular teeth may be divided into anterior laniary, and posterior molary teeth. In most of the Iguaiiians the teeth are lodged in a common shallow oblique alveolar groove, and are .soldered to excavations on the inner surface of the outer wall of the groove : these are called Pleurodonts. Most of them possess pterygoid as well as maxillary teeth ; but the following genera, Jffyperanodon, Tropido- lepis, Phrynosoma, and Callisaurus, are excep- tions. In the Pleurodont Iguanians, the teeth never present the true laniary form ; and if simply conical, as at the extremes of the maxillary series, the cone is more or less obtuse ; but, in general, it is expanded, more or less trilobate, or dentated along the mar- gin of the crown. The Amblyrhynchus, a genus which is some- what remarkable for the marine habits of at least one of the species {Amblyrhynchus atcr), whose diet is sea-weed*, has the tricuspid structure well developed in the posterior teeth. The typical genus of the present family of Saurians (Iguana tubernilala), is characterised by the crenate or dentated margin of the crown of the maxillary and premandibular teeth, a few of the anterior small ones ex- cepted. The pterygoid teeth are arranged in two or three irregular rows, resembling somewhat the " dents en cardes " of fishes. In the full-grown Iguana tuberculata there are from forty-seven to forty-nine teeth in both upper and lower jaws. The number is less in young subjects. The double row of pterygoid teeth are in close order on each side. In the horned Iguana (Metopoceros cor- mdus), there are about fifty-six teeth in the upper and lower jaws, of which the four first are conical and slightly recurved. The twelve succeeding teeth are somewhat larger in size, with more compressed and expanded crowns ; the rest are triangular, compressed, with dentated margins. The inner surface of the crown of the tooth is simply convex and * This species, and probably all Ilie known Am- Uyrln/nchi, or blunt-nosed Iguana?, inhabit the islands in the Galopagos group ; their habits have been well elucidated by Mr. Danvin (Voyage of the Beagle, vol. iii. p. dGG.). In specimens which he dissected, he found the stomach loaded with minced sea-weed. smooth ; the outer surface traversed by a me- dian, longitudinal, broad, obtuse ridge. There is a single row of small teeth implanted in each pterygoid bone. No Iguanian lizard has teeth on the palatine bones. The teeth of the Iguanodon, though re- sembling those of the Iguana, do not present an exact magnified image of them, but differ in the greater relative thickness of the crown, its more complicated external surface, and, still more essentially, in a modification of the internal structure, by which the Iguanodon equally deviates from every other known reptile. As in the Iguana, the base of the tooth is elongated, contracted, and subcylindrical ; the crown expanded, and smoothly convex on the inner side. When first formed, it is acu- minated, compressed, its sloping sides ser- rated, and its external surface traversed by a median longitudinal ridge, and coated by a layer of enamel, but, beyond this point, the description of the tooth of the Iguanodon indicates characters peculiar to that genus. In most of the teeth that have hitherto been Fie. 571. Unworn tooth of Iguanodon. found, three longitudinal ridges (fg. 571.) traverse the outer surface of the crown, one on each side of the median primitive ridye ; these are separated from each other, and from the serrated margins of the crown, by four wide and smooth longitudinal grooves. The relative width of these grooves varies in different teeth ; sometimes a fourth small lon- gitudinal ridge is developed on the outer side of the crown. The marginal serrations, which, at first sight, appear to be simple notches, as in the Iguana, present, under a low magnifying power, the form of trans- verse ridges, themselves notched, so as to resemble the mammilated margins of the un- worn plates of the elephant's grinder: slight grooves lead from the interspaces of these notches upon the sides of the marginal ridges. These ridges, or dentations, do not extend beyond the expanded part of the crown : the longitudinal ridges are continued further down, especially the median ones, which do not subside till the fang of the tooth begins to assume its subcylindrical form. The tooth at first increases both in breadth and thick- ness ; it then diminishes in breadth, but its thickness goes on increasing ; in the larger and fully formed teeth, the fang de- TEETH. 893 creases in every diameter, and sometimes tapers almost to a point. The smooth un- broken surface of such fangs indicates that they did not adhere to the inner side of the maxilla?, as in the Iguana, but were placed in separate alveoli, as in the Cro- codile and Megalosaur; such support would appear, indeed, to be indispensable to teeth so worn by mastication as those of the Igu- anodon. A fracture of this tooth siiows that the pulp was not entirely solidified, but that its cavity had continued open at the thickest part of the tooth. The apex of the tooth soon begins to be worn away, and it would appear, by many specimens that have been found, that the teeth were retained until nearly the whole of the crown had yielded to the daily abrasion. In these teeth, however, the deep excavation of the remaining fang, represented in profile in the figure ./?£. 571., plainly bespeaks the pro- gress of the successional tooth prepared to supply the place of the worn-out grinder. At the earlier stages of abrasion, a sharp edge is maintained at the external part of the tooth by means of the enamel which covers that surface of the crown. The prominent ridges upon that surface give a sinuous contour to the middle of the cutting edge, whilst its sides are jagged by the lateral serrations. The adaptation of this admirable dental instrument to the cropping and com- minution of such tough vegetable food as the ClathraricE and similar plants, which are found buried with the Iguanodon, is pointed out by Dr. Buckland, with his usual felicity of il- lustration, in his " Bridgewater Treatise," vol. i. p. 246. When the crown is worn away beyond the enamel, it presents a broad and nearly hori- zontal grinding surface, and now another dental substance is brought into use to give an inequality to that surface ; this is the ossified remnant of the pulp, which, being firmer than the surrounding dentine, forms a slight transverse ridge in the middle of the grinding surface. The tooth in this stage has exchanged the functions of an incisor for that of a molar, and is prepared to give the final compression, or comminution, to the coarsely divided vegetable matters. The marginal edge of the incisive condition of the tooth and the median ridge of the molar stage are more effectually established by the introduction of a modification into the texture of the dentine, by which it is rendered softer than in the existing Iguana? and other reptiles, and more easily worn away : this is effected by an arrest of the calcifying process along certain cylindrical tracts of the pulp, which is thus continued, in the form of medullary canals, analogous to those in the soft dentine of the Megatherium's grinder, from the central cavity, at pretty regular intervals, parallel with the calcigerous tubes, nearly to the surface of the tooth. The medullary canals radiate from the internal and lateral sides of the pulp-cavity, and are confined to the dentine forming the corre- sponding walls of the tooth ; their diameter is T|5oth of an inch ; they are separated by pretty regular intervals, equal to from six to eight of their own diameters ; they some- times divide once in their course. Each medullary canal is surrounded by a clear sub- stance ; its cavity was occupied in the section described by a substance of a deeper yellow colour than the rest of the dentine. The calcigerous tubes present a diameter of •BJk>otu of an inch, with interspaces equal to about four of their diameters. At the first part of their course, near the pulp-cavity, they are bent in strong undulations, but after- wards proceed in slight and regular primary curves, or in nearly straight lines, to the periphery of the tooth. When viewed in a longitudinal section of the tooth, the concavity of the primary curvature is turned towards the base of the tooth ; the lowest tubes are inclined towards the root, the rest have a general direction at right angles to the axis of the tooth ; the few calcigerous tubes, which proceed vertically to the apex, are soon worn away, and can be seen only in a section of the apical part of the crown of an incompletely developed tooth. The secondary undulations of each tooth are regular and very minute. The branches, both primary and secondary, of the calcigerous tubes are sent off' from the concave side of the main inflections ; the minute secondary branches are remarkable at certain parts of the tooth for their flexuous ramifications, anastomoses, and dilatations into minute calcigerous cells, which take place along nearly parallel lines for a limited extent of the course of the main tubes. The ap- pearance of interruption in the course of the calcigerous tubes, occasioned by this modi- fication of their secondary branches, is repre- sented by the irregularly dotted tracts in the figure of the dental structure of this ancient reptile given in my " Odontography." This modification must contribute, with the me- dullary canals, though in a minor degree, in producing that inequality of texture and of density in the dentine, which renders the broad and thick tooth of the Jguanodon more efficient as a triturating instrument. The enamel which invests the harder dentine, forming the outer side of the tooth, presents the same peculiar dirty brown colour, when viewed by transmitted light, as in most other teeth : very minute and scarcely per- ceptible undulating fibres, running vertically to the surface of the tooth, is the only struc- ture I have been able to detect in it. The cement is simply and minutely cellular upon the crown of the tooth, but it exhibits the radiated cells at the base of the tooth. The remains of the pulp in the contracted cavity of the completely formed tooth are converted into a dense but true osseous substance, characterised by minute elliptical radiated cells, whose long axis is parallel with the plane of the concentric lamella?, which surround the few and contracted medullary canals in this substance. 894 TEETH. The microscopical examination of the struc- ture of the Iguanodon's teeth thus contributes additional evidence of the perfection of their adaptation to the offices to which their more obvious characters had indicated them to have been destined. To preserve a trenchant edge, a partial coating of enamel is applied ; and, that the thick body of the tooth might be worn away in a more regularly oblique plane, the dentine is rendered softer as it recedes from the enameled edge by the simple contrivance of arresting the calcifying process along certain tracts of the inner wall of the tooth. When attrition has at length exhausted the enamel and the tooth is limited to its functions as a grinder, a third substance has been prepared in the ossified remnant q£ the pulp to add to the efficiency of the dental instrument in its final capacity. And if the following reflections were natural and just after a review of the external characters of the dental organs of the Iguanodon, their truth and beauty be- come still more manifest as our knowledge of their subject becomes more particular and exact : " In this curious piece of animal mechanism we find a varied adjustment of all parts and proportions of the tooth, to the exercise of peculiar functions, attended by compensations adapted to shifting conditions of the in- strument, during different stages of its con- sumption. And we must estimate the works of nature by a different standard from that which we apply to the productions of human art, if we can view such examples of me- chanical contrivance, united with so much economy of expenditure, and with such anti- cipated adaptations to varying conditions in their application, without feeling a profound conviction that all this adjustment has re- sulted from design and high intelligence."* Varanians. — In the great Crocodilian Moni- tor (Varanus crocndilinus), the large fixed com- pressed teeth, of which there may be about seven in each upper maxillary bone and six in each premandibular, are anchylosed by the whole of their base and by an oblique surface leading upwards on the outer side of the tooth to a slight depression on the oblique alveolar surface, as in the Var. striatus. The base of the tooth is finely striated, the lines being produced by inflected folds of the external cement, as in the Ichthyosaur and Labyrinthodon, but they are short and straight, as in those of the former genus. The alveolar channel or groove has scarcely any depth ; but the anchylosed base of the tooth is applied to an oblique surface, terminating in a sharp edge, from which the outer side of the free crown of the tooth is directly continued. The great farauus, like the variegated species manifests its affinity to the Crocodilians in the number of successive teeth which are in progress of growth to replace each other ; but from the position in which the germs of the successional teeth are developed, the more * Buckland's Briclgewater Treatise, vol. i. p. 249. advanced teeth in this species, as in the Var. varicgatus, do not exhibit the excavations that characterise the same parts of the teeth of the Enaliosaurs and Crocodiles. Thecodonts. — We have seen that among the inferior or squamate Saurians there are two leading modifications in the mode of attach- ment of the teeth, the base of which may be either anchylosed to the summit of an alveolar ridge, or to the bottom of an alveolar groove, and supported by its lateral wall. These modifications are indicated respectively by the terms " Acrodont " and " Pleurodont." A third mode of fixation is presented by some extinct Saurians, which, in other parts of their organisation, adhere to the squamate or Lacertine division of the order, the teeth being implanted in sockets, either loosely or confluent with the bony walls of the cavity ; these I have termed the " Thecodont " * La- certians : the most ancient of all Saurians belong to this group ; viz. the Thuringian Monitor, or Protorosaurus, and the Palceo- saunts of the dolomitic conglomerates near Bristol. The compressed Varanian form of tooth, with trenchant and finely dentated margins, which characterised the ancient Pa- loeosaur and Chadeiodon, is continued in the comparatively more recent and gigantic species of terrestrial lizard, of which the remains were discovered by Dr. Buckland in the oolite of Stonesfield, by whom the peculiarities of the jaws and teeth have been accurately and gra- phically described in the following words : — " From these remains we learn that the animal was a reptile, closely allied to some of our modern lizards ; and viewing the teeth as instruments for providing food to a carni- vorous creature of enormous magnitude, they appear to have been admirably adapted to the destructive office for which they have been designed. Their form and mechanism will be best explained by reference to the figures. " The outer margin of the jaw rises nearly an inch above its inner margin, forming a continuous lateral parapet to support the teeth on the exterior side, where the greatest support was necessary, whilst the inner margin throws up a series of triangular plates of bone forming a zigzag buttress along the interior of the alveoli. From the centre of each triangular plate, a bony partition crosses to the outer parapet, thus completing the successive alveoli. The new teeth are seen in the angle between each triangular plate, rising in reserve to supply the loss of older teeth, as often as progressive growth, or ac- cidental fracture, may render such renewal necessary, and thus affording an exuberant provision for a rapid succession and resto- ration of these most essential implements. They were formed in distinct cavities, by the side of the old teeth, towards the interior surface of the jaw, and probably expelled them by the usual process of pressure and absorption, insinuating themselves into the cavities thus left vacant. This contrivance * Odontography, part ii. p. 2GG. TEETH. 893 for the renewal of teeth is strictly analogous to that which takes place in the dentition of many species of existing lizards. " In the structure of these teeth we find a combination of mechanical contrivances ana- logous to those which are adopted in the construction of the knife, the sabre, and the saw. When first protruded above the gum, the apex of each tooth presented a double cutting edge of serrated enamel. In this stage, its position and line of action were nearly vertical, and its form, like that of the two- edged point of a sabre, cutting equally on each side. As the tooth advanced in growth it became curved backwards in the form of a priming-knife, and the edge of serrated enamel was continued downwards to the base of the inner and cutting side of the tooth, whilst on the outer side a similar edge descended but a short distance from the point, and the convex portion of the tooth became blunt and thick, as the back of a knife is made thick for the purpose of producing strength. The strength of the tooth was further in- creased by the expansion of its side. Had the serrature continued along the whole of the blunt and convex portion of the tooth, it would in this position have possessed no useful cutting power ; it ceased precisely at the point beyond which it could no longer be effective. In a tooth thus formed for cutting along its concave edge, each movement of the jaw combined the power of the knife and saw ; whilst the apex, in making the first incision, acted like the two-edged point of a sabre. The backward curvature of the full-grown teeth enabled them to retain, like barbs, the prey which they had penetrated. In these adaptations we see contrivances which human ingenuity has also adopted in the preparation of various instruments of art." * The teeth of the Megctlosaur consist of a central body of dentine, with an investment of enamel upon the crown, and of cement over all, but thickest upon the fang. The marginal serrations are formed almost entirely by the enamel, and when slightly magnified are seen to be rounded, and separated by slight basal grooves ; the smooth and polished enamel upon the sides of the crown presents a finely wrinkled appearance; the remains of the pulp are converted into a coarse bone in the completely formed tooth. Enaliosaurs. — The teeth of the Ichthyo- sauri have a simple, more or less acutely conical form, with a long and, usually, ex- panded or ventricose base, or implanted fang. They are confined to the intermaxillary, max- illary, and pr eman dibular bones, in which they are arranged in a pretty close and un- interrupted series, and are of nearly equal size. They consist of a body of unvascnlar dentine, invested at the base by a thick layer of cement, and at the crown by a layer of enamel, which is itself covered by a very thin coat of cement ; the pulp-cavity is more or * Bridgewatcr Treatise, vol. i. p. 237. less occupied in fully-formed teeth by a coarse bone. The external surface of the tooth is marked by the longitudinal impressions and ridges, but the teeth vary both as to outward sculpturing and general form in the different species.* The chief peculiarity of the dental system of the Ichthyosaur is the mode of the im- plantation of the teeth ; instead of being an- chylosed to the bottom and side of a con- tinuous shallow groove, as in most Lacertians, or implanted in distinct sockets, as in the The- codon, Megalosaur, or Pterodactyle, they are lodged loosely in a long and deep continuous furrow, and retained by slight ridges between the teeth, along the sides and bottom of the furrow, and by the gum and organised mem- branes continued into the groove and upon the base of the teeth. The germs of the new teeth are developed at the inner side of the base of the old ones. Crocoddia. — The best and most readily recognisable characters by which the existing Crocodilians are grouped in appropriate genera, are derived from modifications of the dental system. In the Caimans (genus A/ligator) the teeth , 18—18 ^ 2-2—22 . vary in number from rx"iQ to — - — — ? : the fourth tooth of the lower jaw, or canine, is received into a cavity of the palatal surface of the upper jaw, where it is concealed when the mouth is shut. In old individuals the upper jaw is perforated by these large in- ferior canines, and the fossae are converted into foramina. In the Crocodiles (genus Crocodilus) the first tooth in the lower jaw perforates the palatal process of the premaxillary bone when the mouth is closed ; the fourth tooth in the lower jaw is received into a notch exca- vated in the side of the alveolar border of the upper jaw, and is visible externally when the mouth is closed. In the two preceding genera the alveolar borders of the jaw have an uneven or wavy contour, and the teeth are of an unequal size. In the Gavials (genus Gavialis) the teeth are nearly equal in size and similar in form in both jaws, and the first as well as the fourth tooth in the lower jaw, passes into a groove in the margin of the upper jaw when the mouth is closed. In the alligators and crocodiles the teeth are more unequal in size, and less regular in arrangement, and more diversified in form than in the Gavials : witness the strong thick conical laniary teeth as contrasted with the blunt mammillate summits of the posterior teeth in the alligator (fig. 573.). The teeth of the (Javial are subequal, most of them pre- sent the form of crown, shown in fig. 572., long, slender, pointed, subcompressed from before backwards, with a trenchant edge on the right and left sides, between which a few faint longitudinal ridges traverse the basal part of the enamelled crown. * Odontograpliy, pi. 73. 896 TEETH. rig. 572. Teeth in different stages of formation from one alveolus of the Gavial : a is the base partly absorbed by the pressure of b, the successional tooth ; below which is figured c, the germ of the next tooth to follow. Amongst the remains of Crocodilians which are scattered through the Tilgate strata, the most common ones are detached teeth, from the difference observable in the form of which, Dr. Mantell has observed, that " they appear referable to two kinds, the one belonging to that division of crocodiles with long slender muzzles, named Gavial, the other to a species of Crocodile, properly so-called, and resembling a fossil species found at Caen."* Dr. Mantell has obligingly communicated to me figures of well-preserved specimens of both the forms of teeth alluded to, the exact- ness of which I have recognised by a com- parison with the specimens themselves in the British Museum. The tooth which, from its more slender and acuminated form, approaches nearest to the character of those of the Gavial, presents a marked difference, however, from the teeth of any of the recent species of that sub-genus of Crocodilians, as well as from those of the long and slender-snouted extinct genera, called Teleosaurus, Sfeneosaurus, &c. I have described iff, therefore, as indicative of a distinct species, under the name of Crocodihts cultridens. The crown is laterally compressed, submcurved, with two opposite trenchant edges, one forming the concave, the other the convex, outline of the tooth. In the Gavial, the direction of the flattening of the crown and the situation of the trenchant edges are the reverse, the compression being from be- fore backwards, and the edges being lateral.^ * Wonders of Geology, 1839, vol. i. p. 386. t Odontography, pi. Ixii. A,jiys. 9, 10. J The tooth attributed by M. Deslongchamps to the Poikilopleurori) agrees in form with those of The tooth of the Crorodilus cultridens thus re- sembles in form that of the Megalosaur, and perhaps still more those of the Argenton crocodile ; but I have not observed any spe- cimens of the Wealden teeth in which the edges of the crown were serrated, as in both the reptiles just cited. The teeth of the Cro- codiliis cultridens also present a character which does not exist in the teeth of the Megalosaur, and is not attributed by Cu- vier to those of the Crocodile d'Argcnton. The sides of the crown are traversed by a few longitudinal parallel ridges, with regular intervals of about one line, in a crown of a tooth one inch and a half in length : these ridges subside before they reach the apex of the tooth, and more rapidly at the convex than at the concave side of the crown. Hitherto these teeth have not been found so associated with any part of the skeleton of the same species as to yield further cha- racters of the present extinct Crocodilian ; but from the above-mentioned well-marked differences between these teeth and those of all the existing species, it is most probable that the extinct crocodile formed the type of a distinct sub-genus, for which the term Su- chosaurus has been proposed. The second form of tooth having the gene- ric characters of those of the crocodile, which has been discovered in the Wealden and approximate strata, is as remarkable for its thick, rounded, and obtuse crown as the teeth of the preceding species are for their slender, compressed, acute, and trenchant character. It consequently approaches more nearly to the teeth which characterise the broad and comparatively short-snouted crocodiles; but it differs from these in one of the same cha- racters by which the tooth of the Suchosaurus cultridens differs from those of the Gavials, viz., in the longitudinal ridges which traverse the exterior of the crown. These are, how- ever, more numerous, more close-set, and more neatly defined than in the Suchosaurus cultridens. Two of the ridges, larger and sharper than the rest, traverse opposite sides of the tooth, from the base to the apex of the crown ; they are placed, as in the crocodile and Gavial, at the sides of the crown, midway between the convex and concave lines of the curvature of the tooth. These ridges are confined to the enamel ; the cement-covered cylindrical base of the tooth is smooth. The size of the teeth varies from a length of crown of two inches, with a basal diameter of one inch and a half to teeth of one-third of these dimensions. I have proposed to call this extinct crocodile, with biconcave vertebrae, Goniopkolis crassidcns. Development. — In the black alligator of Guiana the first fourteen teeth of the lower jaw are implanted in distinct sockets, the remaining posterior teeth are lodged close together in a continuous groove, in which the divisions for sockets are faintly indicated by vertical ridges, as in the jaws of the Ichthyo- the Gavial, and differs in the characters cited in the text from those of the Crocodilus cultridens. TEETH. 897 saurs. A thin compact, floor of bone separates this groove, and the sockets anterior to it, from the large cavity of the ram us of the jaw; it is pierced by bloodvessels for the supply of the pulps of the growing teeth and the vas- cular dentiparous membrane which lines the alveolar cavities. The tooth-germ is developed from the membrane covering the angle between the floor and the inner wall of the socket. It becomes in this situation completely enveloped by its capsule, and an enamel-organ is formed at the inner surface of the capsule before the young tooth penetrates the interior of the pulp-cavity of its predecessor. The matrix of the young growing tooth affects, by its pressure, the inner wall of the socket, as shown in Jig. 573, and forms for Fig. 573. Section of lower jaw, ii'lth four alveoli and teeth, of the black Alligator. itself a shallow recess : at the same time it attacks the side of the base of the contained tooth ; then, gaining a more extensive attach- ment by its basis and increased size, it pene- trates the large pulp-cavity of the previously formed tooth either by a circular or semi- circular perforation. The size of the calcined part of the tooth-matrix which has produced the corresponding absorption of the previously formed tooth on the one side, and of the alveolar process on the other, is represented in the second exposed alveolus of Jig. 573., the tooth « having been displaced and turned round to show the effects of the stimulus of the pressure. The size of the perforation in the tooth, and of the depression in the jaw, proves them to have been, in great part, caused by the soft matrix, which must have produced its effect by exciting vital action of the absorbents, and not by mere mechanical force. The resistance of the wall of the pulp-cavity having been thus overcome, the growing tooth and its matrix recede from the temporary alveolar depression, and sink into the substance of the pulp contained in the VOL. IV. cavity of the fully-formed tooth. As the new tooth grows, the pulp of the old one is re- moved ; the old tooth itself is next attacked, and the crown being undermined by the ab- sorption of the inner surface of its base, may be broken off' by a slight external force, when the point of the new tooth is exposed, as in thej%. 573. b. The new tooth disembarrasses itself of the cylindrical base of its predecessor, with which it is sheathed, by maintaining the excitement of the absorbent process so long as the cement of the old fang retains any vital connection with the periosteum of the socket ; but the frail remains of the old cylinder, thus re- duced, are sometimes lifted off the socket upon the crown of the new tooth, as mfig. 573. b, when they are speedily removed by the action of the jaws. This is, however, the only part of the process which is immediately produced by mechanical force : an attentive observation of the more important previous stages of growth, teaches that the pressure of the growing tooth operates upon the one to be displaced only through the medium of the vital absorbent action which it has excited. Most of the stages in the development and succession of the teeth of the crocodiles are described by Cuvier with his wonted clearness and accuracy ; but the mechanical explanation of the expulsion of the old tooth, which Cuvier adopts from M. Tenon, is opposed by the disproportionate smallness of the hard part of the new tooth to the vacuity in the old one, and by the fact that the matter im- pressing— viz. the uncalcified part of the walls of the tooth-matrix — is less dense than the part impressed. No sooner has the young tooth penetrated the interior of the old one, than another germ begins to be developed from the angle between the base of the young tooth and the inner alveolar process, or in the same relative position as that in which its immediate pre- decessor began to rise, and the processes of succession and displacement are carried on, uninterruptedly, throughout the long life of these cold-blooded carnivorous reptiles. From the period of exclusion from the egg, the teeth of the crocodile succeed each other in the vertical direction ; none are added from behind forwards, like the true molars in Mammalia. It follows, therefore, that the number of the teeth of the crocodile is as great when it first sees the light as when it has acquired its full size; and, owing to the rapidity of the succession, the cavity at the base of the fully-formed tooth is never con- solidated. The fossil jaws of the extinct Crocodilians demonstrate that the same law regulated the succession of the teeth, at the ancient epochs when those highly organised reptiles prevailed in greatest numbers, and under the most varied generic and specific modifications, as at the present period, when they are reduced to a single family, composed of so few and slightly varied species as to have constituted 3 M 898 1 in the system of Linnaeus a small fraction his genus LACERTA. TEETH. of Dental System of Mammals. The class Mammalia, like that of Beptllia and Pisces, includes a few genera and species that are devoid of teeth : the true ant-eaters (Myrmecophaga), the scaly ant-eaters or Pan- golins (Mams), and the spiny monotrematous ant-eater (Echidna), are examples of strictly edentulous Mammals. The Ornithorhynchus has horny teeth, and the whales (Eakcna and Balcenopterd) have transitory embryonic cal- cined teeth*, succeeded by whalebone sub- stitutesf in the upper jaw. Horny processes analogous to, perhaps homologous with, the lingual and palatal teeth in fishes, are present in the Echidna. The female Narwhal seems to be eden- tulous, but has the germs of two tusks in the substance of the upper jaw-bones; one of these becomes developed into a large and conspicuous weapon in the male Narwhal, and, accordingly, suggested to Linnaeus the name, for its genus, of Monodon, meaning single tooth : but the tusk is never median, like the truly single tooth on the palate of the Myxine ; and occasionally both tu.sks are developed in the Narwhal. In another Ceta- cean, the great Bottle-nose, or Hypervodon, the teeth are reduced in the adult to two in number, whence the specific name H. bidens, but they are confined to the lower jaw. The sharp-nosed dolphin (Zij)hius) has also but two teeth, one in each ramus of the lower jaw ; and this is, perhaps, a sexual character. The Delphinus grisens has five teeth on each side of the lower jaw ; but they soon become reduced to two. Amongst the marsupial ani- mals, the genus Tarsipes is remarkable for the paucity as well as minuteness of its teeth. The elephant has never more than one entire molar, or parts of two, in use on each side of the upper and lower jaws ; to which are added two tusks, more or less developed, in the upper jaw. Some Rodents, as the Australian Water- rats (Hydromys], have two grinders on each side of both jaws ; which, added to the four cutting teeth in front, make twelve in all : the common number of teeth in this order is twenty ; but the hares and rabbits have twenty- eight teeth. The sloth has eighteen teeth. The number of teeth, thirty-two, which cha- racterises man, the apes of the old world, and the true ruminants, is the average one of the class Mammalia ; but the typical number is forty-four. The examples of excessive number of teeth are presented, in the order Enda, by the Priodont Armadillo, which has ninety-eight teeth ; and, in the cetaceous order, by the Cachalot, which has upwards of sixty teeth, though most of them are confined to the lower jaw ; by the common porpoise, which has between eighty and ninety teeth ; by the * Odontography, pi. 87 a, ff/s. 1 — G. t Ib. pi. 76, Jigs'. 4. 6 ; art. CETACEA, Vol. I. p. 572, ./?, I generate ; dbmif, tooth. j tlsj twice ; fiiu and eSous • 3 w 3 902 TEETH. (herbivorous Cetacea of Cuvier) differ in has been called in question.* I have, how- many organic particulars from the Cetacea ever, discovered in specimens of the Malayan Dentition of the Dugong (Halicore inclicus). proper*, and in none, perhaps, more strikingly than in having both deciduous and permanent teeth ; this succession takes place, at least, with regard to the upper incisors of the Du- g°}lff, fig- 575. These teeth project from the gum in the male sex ; but neither upper nor lower in- cisors are visible in the female.-f- The supe- rior incisors are but two in number, in both sexes ; in the male, they are moderately long, subtriedral, slightly and equally curved, of the same diameter from the base, and deeply excavated to near the apex, which is obliquely bevelled off to a sharp edge, like the scalpriform teeth of the Rodentia. The form and extent of the persistent pulp-cavity of this tooth are shown in the figure of its longitudinal section, in my " Odontography," pi. 93. fig. 4. ; it becomes longer and more pointed than in the permanent incisor of the younger male (fig. 575, z). When fully de- veloped, only the extremity of this tusk pro- jects from the jaw, at least seven-eighths of its extent being lodged in the socket, the parietes of which are entire ; and the exterior of the great premaxillary bones presents an unbroken surface. In the female Dugong, the growth of the permanent incisive tusks of the upper jaw is arrested before they cut the gum, and they remain through life concealed in the premaxillaries ; the tusk is solid, is about an inch shorter and less bent than that of the male ; it is also irregularly cylin- drical, longitudinally indented, and it gradually diminishes to an obtuse rugged point ; the base is suddenly expanded, bent obliquely outwards, and presents a shallow excavation. These were conjectured by Home to be the " milk-tusks ; " they are, however, character- istic of sex, not of age ; and the existence of deciduous tusks at any period in the Dugong * Proceedings of the Zoological Society of London, 1838, p. 40. t Proceedings of the Zool. Society, 1838, p. 41. Dugong which I have dissected at the Zoological Society, the true deciduous in- cisors of the upper jaw (fig. 575, d i) co- existing with the permanent ones (i). They are much smaller than the permanent tusks of the female, and are loosely inserted by one extremity in conical sockets immediately an- terior to those of the permanent tusks, ad- hering by their opposite ends to the thick tegumentary gum, which presented no out- ward indication of their presence. When this gum was stripped off the bone, the deciduous tusks came away with it ; and this may account for their usual absence in dried crania of immature Dugongs, in which, nevertheless, their alveoli are generally suffi- ciently conspicuous. True permanent in- cisors are not developed in the lower jaw of the Dugong ; those which are occasionally found there are abortive remnants of the first or deciduous series, which are not destined at any time to rise above the gum (fig. 575, d i 3.). The molar teeth of the Dugong resemble those of the order Bruta in the total absence of enamel, and of any constriction defining the crown from the fangs. In the Malayan species, only five molars (fig. 575, 1, 2,3, 4, 5.) are developed on each side of both jaws : in the Australian Dugong six are developed ; i. e. the Halicore indicus is characterised by the molar formula m. - — ^=20, whilst the 5 — o Halicore australis has m. - -- = 24vf- But in 6 — b both species, the number is progressively re- duced, by the shedding of the anterior and o o smaller molars, to m. 7— 8- The struc- ture of these molar teeth is illustrated in * Dr. Ruox, Edinburgh Philosophical Transac- tions, torn. xi. p. 389. t See my appendix to Juke's " Voyage of the Fly.' TEETH. 903 jig. 546. B, their form mfig. 546. A; the last molar, when it comes into use, presents a bilobed form of grinding surface, as is shown at b,fig. 575. Owing to there being but one set of molars in the Dugong, those teeth cannot be divided into true and false molars, any more than in the Sloths or Armadillos. In the true Di- phyodonts, in which each kind of teeth have deciduous predecessors, those grinders which succeed the deciduous ones vertically, and displace them, are called "premolars," or " false molars," and those that come into place behind these, without pushing out vertically any predecessors, are the " molars proper," or " true molars." In this article, as in my " Odontography," the two sorts of grinders are called respectively " premolars " and " molars." In the Marsupial order the normal number of molars is four in each 4, 4, dental series, i. e. m. - — - ; in the placental 4 — 4 Diphyodonts their normal number is three, 3 3 i. e. m. ; the normal number of pre- 3 3 molars in the Marsupialia is r, but in the O tj ^ 4, Placentalia, it is - - : in both the numerical 4—4 character of the canines is one, i. e. 3— 3 1— I 1—1 ; that of the incisors three, i. e. * r. As regards o ~~o the latter teeth, however, the number of exceptions in the Marsupialia is considerable, and the incisors are sometimes in excess ; whilst in the placental Diphyodonts, the in- cisors never exceed the typical number, but frequently depart from it by suppression or arrest of development. In fishes and reptiles, certain teeth might be called " incisive," " laniary," or " molar" teeth, in reference to the special adaptation of their form for cutting, tearing, or bruising; but such terms, in the cold-blooded classes, imply no- thing more than those modifications of form ; they are not significative of constant and well- defined groups of teeth, and could not become the names of definite parts or organs determin- able and traceable from one species to another. In the Mammalian orders, with two sets of teeth, these organs acquire fixed individual characters, receive special denominations, and can be determined from species to species. This individualisation of the teeth is emi- nently significative of the high grade of organ- isation of the animals manifesting it ; espe- cially when we consider the great proportion of mineral substance which enters into the composition of those parts ; in the number and nature of which the principle of vegetative repetition, and the power of the general polarising forces, have been most controlled in the Mammalia. Originally, indeed, the name " incisors," "laniaries" or "canines," and "molars" were given to the teeth, in Man and certain mammals, as in reptiles, in reference merely to the shape and offices so indicated ; but they are now used as arbitrary signs, in a more fixed and determinate sense. In some Carnivora, e.g., the front teeth have broad tuberculate summits, adapted for nipping and bruising, while the principal back teeth are shaped for cutting, and work upon each other like the blades of scissors. The front teeth in the elephant project from the upper jaw, in the form, size, and direction of long pointed horns. In short, shape and size are the least constant of dental characters in the Mam- malia; and the homologous teeth are deter- mined, like other parts, by their relative position, by their connections, and by their development. Those teeth which are implanted in the premaxillary bones, and in the corresponding part of the lower jaw, are called " incisors," whatever be their shape or size. The tooth in the maxillary bone, which is situated at, or near to, the suture with the premaxillary, is the " canine," as is also that tooth in the lower jaw which, in opposing it, passes in front of its crown when the mouth is closed. The other teeth of the first set are the " de- ciduous molars ; " the teeth which displace and succeed them vertically are the " pre- molars;" the more posterior teeth, which are not displaced by vertical successors, are the " molars " properly so called. When the premolars and the molars are below their typical number, the absent teeth are missing from the fore-part of the pre- molar series and from the back part of the molar series. The most constant teeth are the fourth premolar and the first true molar ; and, these being known by their order and mode of development, the homologies of the remaining molars and premolars are deter- mined by counting the molars from before backwards, e.g. "one," " two," "three;" and the premolars from behind forwards, e. g. " four," " three," " two," " one." The incisors are counted from the median line, commonly the foremost part of both upper and lower jaws, outwards and backwards. The first in- cisor of the right side is the homotype, trans- versely, of the contiguous incisor of the left side in the same jaw, and, vertically, of its opposing tooth in the opposite jaw ; and so with regard to the canines, premolars, and molars ; just as the right arm is the homo- type of the left arm in its own segment, and also of the right leg of a succeeding segment. It suffices, therefore, to reckon and name the teeth of one side of either jaw in a species with the typical number and kinds of teeth ; e.g. the first, second, and third incisors, — the first, second, third, and fourth premolars, • — the first, second, and third molars; and of one side of both jaws in any case. The homologous teeth being thus deter- minable, they may be severally signified by a symbol as well as by a name. The incisors, e.g., by their initial letter i., and indivi- dually by an added number, i. 1, i. 2, and i. 3 ; the canines by the letter c. ; the pre- molars by the letter p. ; and the molars by 3 M 4. 904 TEETH. the letter .m. ; these also being differentiated by added numerals. Thus, the number of these teeth, on eacli side of both jaws, in any given species. Man e.g., may be expressed 2 2 by the following brief formula : — i. g— — ? I | 2 2 3 3 c- j^j, p. g^~> m. 3^3=32; and the homo- logies of the individual teeth, in relation to the typical formula, may be signified by i. 1., i. 2. ; c. ; p. 3., p. 4. ; m. 1., m. 2., m. 3. : the suppressed teeth being i. 3.*, p. 1., and p. 2. Examples of the typical dentition are ex- ceptions in the actual creation ; but it was the rule in the forms of Mammalia first introduced into this planet ; and that, too, whether the teeth were modified for animal or vegetable food. Fig. 576., e. g., shows the dental series The true molars in the one are tuberculate, indicating its tendency to vegetable diet; in the other, they are carnassial, and betoken a peculiarly destructive and bloodthirsty spe- cies. In the Quarterly Geological Journal, No. 13, 1848, p. 36. 'pi. iv., I have described and figured the entire dental series of one side of the lower jaw of an extinct hoofed quadruped, the D'n-hodon cuspidatus, from eocene or oldest tertiary strata, also mani- festing the normal number and kinds of teeth, but vvith such equality of height of crown, that no interspace is needed to lodge any of the teeth when the jaws are closed, and the series is as entire and uninterrupted as in the human subject. A great proportion of the upper jaw and teeth has been discovered, and Dentition of the Amphicyon major. Upper jaw. of the upper jaw of the Amphici/on major, a the marks of abrasion on the lower teeth mixed-feeding ferine animal, allied to the prove the series above to have been as entire Bear. Fig. 577. shows the dental series of and continuous as that below. The Anoplo- the under jaw of a more strictly carnivorous thorium (" Odontography," pi. 135. fig. 1 .), Fig. 577. Dentition of the Hytenodon. Lower jaw. beast, the Hyeenodon; the fossil remains of a species of which have been discovered in the oldest tertiary deposits of Hampshire. The symbols denote the homologies of the teeth. * I have been guided by the analogy of the hare (Odontography, p. 410, pi. 104, Jig. 5.) in this de- termination ; but a contradictor might indulge his •instinct -without liability to disproof from actual knowledge. from the gypsum quarries of Montmartre, geologically as ancient as the eocene clays of this island, long ago presented to Cuvier the same peculiar continuous dental series as is shown in the Dichodon. In his original Me- moir, Cuvier described the canines as a fourth pair of incisors, on account of their small size and their trenchant shape ; but he after- wards recognised their true homology with TEETH. 905 the larger and more lamariform canines of the PaUcotherium (" Odontography," pi. 135., fig. 4.). Tlie CfuBropotamus*, the Anthraco- therium\, the Hyopotamus^., the Hyracothe- rinm§, the Oplotherium, the Merycopotamus, the Hippohyus, and other ancient (eocene and miocene) tertiary mammalian genera presented the forty-four teeth, in number and kind according to that which is here pro- pounded as the typical or normal dentition of the placental Mammalia. Amongst the existing genera, the hog (Sits) is one of the few that retain this type. Fig. 578. shows the entire permanent series, exposed, in both molar, m. 2, has just begun to cut the gum ; p. 2, p. 3, and p. 4-, together with m. 3, are more or less incomplete and concealed in their closed alveoli. The premolars must displace deciduous molars in order to rise into place ; the molars have no such relations ; it will be observed, that the last deciduous molar, d. 4, has the same relative superiority of size to d. 3 and d. 2 which m. 3 bears to m. 2 and m. 1 ; and the crowns of p. 3 and p. 4 are of a more simple form than those of the milk- teeth which they are destined to succeed. Teeth of each of the kinds above deter- Fig. 578. Dentition of the Hog (Sus). jaws, and indicated individually by their mined, and arbitrarily named " incisors," " ca- symbols. Fig. 579. illustrates the phenomena nines," " premolars," " molars," have received of development which distinguish the pre- other special names in regard to certain pe- Fig. 579. d/, d 3 j.2 d\ Deciduous and permanent teeth (Sus). Lower jaw. molars from the molars. The first premolar, p. 1, and the first molar, in. 1, are in place and use, together with the three deciduous molars, d. 2, d. 3, and d. 4 ; the second * History of British Fossil Mammalia, p. 41 G, fig. 164. t Jobert, Annales des Sciences, t. xvii. p. 139. j Quarterly Journal of the Geological Society, May, 1848, p! 103, pi. viii. § Geological Transactions. 2nd series, vol. vi. p. 203. culiarities of form or other property ; and the ablest comparative anatomists have been led astray in determining their homologies when they have suffered themselves to be guided exclusively by morphological characters. The premolars in the human subject have been called " bicuspids." The last upper pre- molar and the first lower true molar in the Carnivora are termed, from their peculiar form, " sectorials," or " carnassial teeth," " molaires carnassieres " of Cuvier, Teeth 906 of an elongated conical form, pro- jecting considerably beyond the rest, and of uninterrupted growth, are called " tusks ; " such are the incisors of the Elephant and Dugong, the canines of the Boar and Walrus : the long and large incisors of the Rodents have been termed, from the shape and structure of their cutting edge, scalpriforrn or chisel-teeth, " denies scalprarii." The inferior in- cisors of the flying Lemurs (Galeo- fithecus] have the crown deeply notched like a comb, and are termed " denies pectinati." The canines of the Baboons are deeply grooved in front, like the poison-fangs, " denies canaliculati" of some serpents. The compressed conical crowns of the molar teeth of the small clawed seals (Sfenorhi/nchus) are divided either like a trident, into three sharp points, or like a saw, into four or five points ; the molars of the great extinct Zeuglodon had a similar form ; such teeth have been called den'es serrali. But the philosophical course of the knowledge of nature tends to explode needless terms of art, invented for unimportant vari- eties, and to establish and fix the meaning of those terms that are the signs of determinate species of things. The Cuviers divided the molar series of teeth, according to their form, into three kinds: "false mo- lars," " carnassials," and " tubercu- lar molars ; " and, in giving the ge- neric characters of Mammalia, based the dental formula? on this system : thus the genus Felis is characterised 2 2 as having <: fausses molaires TEETH. cavnassieres 1—1, 1—1 2—2 tuberculeuses 1—1 8 (3' 0—0' The uninterrupted line marked " Cuvier" in V. FELIS of fig. 580., intersects the teeth in each jaw called carnassieres ; those anterior to them being the teeth called " fausses molaires ;" the single tooth behind in the upper jaw is the " tu- berculeuse." Most Zoologists, both at home and abroad, have adopted the Cuvierian system of formalising the molar teeth. It seems a very natural one in the case of the Cat * " Les Dents cles Mammiferes consi- derees comme Caracteres zoologiqucs," 8vo. p. 77. In the original the numbers 422 are given f. in. . ; c. = ; t. -, the teeth of each side being clubbed together; they are distinguished into right and left in the text, to facilitate the comparison with the formula; used in this Article. Fig. 580. HOMO. URSUS. CANIS. MUSTELA. FELIS. MACHAIRODUS. MOSCHUS, Cuvier. De Bl Homologies of the teeth in Diphyodont Mammals. TEETH. 907 genus ; the tooth p. 4 above plays upon that, m. I, below, which has a similar remarkable carnassial modification of form ; they fit, in- deed, almost as Cuvier describes, like the blades of a pair of scissors ; the two teeth in advance of the carnassial in the upper jaw (p. 3, p. 2) in like manner are opposed to the same number of " fausses molaires " (p. 4, p. 3) in the under jaw, and the canine c. above plays upon the canine below ; all seems straightforward and symmetrical, save that the little tubercular, m. 1, above has no op- ponent in the lower jaw. And, perhaps, the close observer might notice that, whilst the upper canine, c., glides behind its homotype be- low, the first upper false molar (p. 2) passes anterior to the crown of the first false molar (p. 3) below ; and that the second false molar and carnassial of the upper jaw are also a little in advance of those teeth in the under jaw when the mouth is shut. In passing to the dentition of the Dog (Jig. 580, III. CAMS), formulised by Cuvier as: •cf l • 3— 3 - ~ fausses molaires 7 — 7, carnassieres 4—4 1—1 , tu- 2 2 12 berculeuses \ „ ; = r-r," it will be ob- £, & I Tr served that here the first upper false molar (p. 1) differs from that in Fe/is, inasmuch as, when the mouth is shut, it preserves the same relative position to its opponent below (p. 1) which the upper canine does to the lower canine, and that the same may be said of the second and the third false molars ; but that with regard to the carnassial above (p, 4) this tooth repeats the same relative position in regard to the fourth false molar below (p. 4), and not to that tooth, m. 1, which Cuvier regarded as the lower homotype of the carnassial ; and, indeed, the more back- ward position of the lower carnassial is so slight that its significance might well be over- looked, more especially as the two succeed- ing tubercular teeth above were opposed to two similar tuberculars below. Cuvier there- fore leaves us to conclude that the tooth which had no homotype or answerable op- ponent above was either the fourth " fausse molaire " below, or else the first. How un- important size and shape are, and how sig- nificant relative position is in the determina- tion of the homologies of teeth as of other parts, may be learnt before quitting the na- tural order of Carnivora ; e. g. by the condi- tion of the dental system in the Bear (Jig. 580, II. URSUS). Here the lower tooth, in. 1, instead of presenting the carnassial character, and resembling in form the upper tooth (p. 4), which is the homologue of the upper car- nassial in the dog, has a tubercular crown, and corresponds in size as well as shape with the upper tooth m. 1, to which it is almost wholly opposed, and with the same slight advance of position which we observe in the lower canine as compared with the upper one, and in the four lower premolars (p. 1, p. 2, p. 3, p. 4) as com- pared with their veritable homotypcs above. F. Cuvier divides the molar series of the 3 _ 3 genus Ursus into " fausses molaires - — r, 1 — 1 2—2 12,, carnassieres - - r, tuberculeuses - — - =• T-T. 1 1 4, - £ IT The tendency in every thinker to generalise and to recognise Nature's harmonies, has led him here to use the term " carnassiere " in an arbitrary sense, and to apply it to a tootli above (p. 4), which he owns has such a shape and diminished size as would have led him to regard it as merely a false molar, but that the upper carnassial would then have entirely dis- appeared ; and it has also led him to give the name " carnassiere " to a tooth below, m. 1, which he, nevertheless, describes as having a tubercular and not a trenchant crown. In so natural a group as the true Carnivora it was impossible to overlook the homologues of the trenchant carnassials of the lion, even when they had become tubercular in the omnivo- rous bear ; and Cuvier therefore, having de- termined and defined the teeth so called in the feline genus, felt compelled to distinguish them by the same names after they had lost their specific formal character. And if, indeed, he had succeeded in discovering the teeth which were truly answerable or homotypal in the upper and lower jaws, the term " carnassial " might have been retained as an arbitrary one for such teeth, and have been applied to their homologues in Man, the Ruminant, or the Pachyderm, where they are as certainly de- terminable as in those aberrant Carnivores, in which they have equally lost their sectorial shape. But the inconvenience of names in- dicative of such specialties of form will be very obvious when the term " tuberculeuses" comes to be applied to the three hindmost teeth in the Hyaenodon (fig. 577.), which teeth answer to the broad crushing teeth, in. 1, m. 2, and m. 3, in the bear and some other existing Car- nivora. The analogous term " molar," having a less direct or descriptive meaning, is there- fore so much the better as the requisite arbi- trary name of a determinate species of teeth. Had Cuvier been guided in his determina- tions of the teeth by their mutual opposition in the closed mouth, and had studied them with this view in the Carnivora, with the dentition most nearly approaching to the typical formula, viz. the bear, he could then have seen that the three small and inconstant lower premolars (p. 1, p. 2, p. 3) were the homotypes of the three small and similarly inconstant premolars above; that the fourth false molar (p. 4) below, which, as he observes, " alone has the normal form," * was truly the homotype of the tooth above (p. 4), which he found himself com- pelled to reject from the class of " fausses molaires," notwithstanding it presented their normal form; that the tubercular tooth, m. I, which he calls " carnassiere " in the lower jaw, was the veritable homotype of his first " molaire tuberculeuse " above (m. 1), and that the tooth in the inferior series which had no answerable one above was his second " tuber- * Dents des Mammifcrcs, p. 111. 908 TEETH. culeuse " (my m. 3), and not any of the four false molars. The true second tuber- cular above (m. 2) is, however, so much de- veloped in the bear as to oppose both JH. 2 and m. 3 in the lower jaw, and it might seem to include the homotypes of both those teeth coalesced. One sees with an interest such as only these homological researches could ex- cite, that they were distinctly developed in the ancient Amphicyon {fig. 576.), which ac- cordingly presents the typical formula. Thus, I repeat, the study of the relative position of the teeth of the bear might have led to the recognition of their real nature and homolo- gies, and have helped to raise the mask of their extreme formal modifications, by which they are adapted to the habits of the more blood- thirsty Carnivora. But the truth is plainly and satisfactorily revealed when we come to trace the course of development and succes- sion of these teeth. The weight which must ever attach itself to an opinion sanctioned by the authority of both the Cuviers, demands that a conclusion contrary to theirs, and which seems to be opposed by Nature herself in certain instances, should be supported by all the evidence of which such conclusion is susceptible. I proceed, therefore, to show how, in the bear, my determinations of the teeth are es- tablished by their development, as well as by their relative position. As the question only concerns the molar series, the remarks will be confined to these. In the jaws of the young bear, figured in cut 581 ., the first premolar, p. 1, is the only one of the permanent series in place ; similarity to p. 4 in the lower jaw (Jig. 581, URSUS), to be veritably the last of the pre- molar series, and to agree not in shape only, but in every essential character, with the three preceding teeth called by Cuvier "fausses molaires." So, likewise, in the lower jaw, we see that the primitive deciduous series, d. 1, d. 2, d. 3, and d. 4, will be displaced by the corresponding premolars,/). I, p. 2, p. 3, and p. 4 ; and that the tooth JH. 1, called car- nassiere by Cuvier, in the lower jaw, differs essentially from that p. 4, so called in the upper jaw by being developed without any vertical predecessor or deciduous tooth. The same law of development and succes- sion prevails in the genus Canis (fig. 582.). Although the tooth m. 1 in the lower jaw has exchanged the tubercular for the carnassial form, it is still developed, as in the bear, behind the deciduous series, and indepen- dently of any vertical predecessor; and the tooth p. 4 above, although acquiring a relative superiority of size to its homologue in the bear, and more decidedly a carnassial form, is not the homotype of the permanent carnas- sial below, but of that premolar (p. 4) which is destined to displace the deciduous carnassial d. 4. The symbols sufficiently indicate the relations of the other teeth, and the conclu- sions that are to be drawn from them as to their homologies. It is interesting to observe in the deciduous, as well as in the permanent series, that the lower carnassial d. 4 is not the homotype of the upper one d. 3, but of the tooth which Cuvier calls the " tuberculeuse du lait," d. 4 in the upper jaw. Fig. 581. Deciduous and permanent dentition of the Sear (Ursus). the other grinders in use are the deciduous molars, d. 2, d. 3, and d. 4; d. 2 will be displaced by p. 2, d. 3 by p. 3, and d. 4 by the tooth p. 4, which, notwithstanding its size and shape, Cuvier felt himself compelled to discard from the series of false molars, but which we now see is proved by its developmental relations to d. 4, as well as by its relative position and In the genus FcJis (Jig. 580.), the small per- manent tubercular molar of the upper jaw, JH. 1, has cut the gum before its analogue d. 4 of the deciduous series has been shed ; but though analogous in function, this is not ho- o D * mologous with, or the precedent tooth to JH. 1, but, as in the dog, to the great carnassially modified premolar, p. 4. In the lower jaw the TEETH. 909 tooth (m. I), which is functionally analogous to tition, arc m. 2 in the upper jaw, m. 2 and m. 3 the carnassial above, is also, as in the dog, the in the lower jaw ; p. \ in the upper jaw, /;. 1 Fig. 582. 7772 Deciduous and permanent teeth in the. Dog (Canis). first of the true molar series, and the homo- and p. 2 in the lower jaw ; thus illustrating the type of the little tubercular tooth (m. 1) above, rule enuntiated above, that, when the molar And the homologies of the permanent teeth series falls short of the typical number it is p. 4 above and m. 1 below, with those so from the two extremes of such series that the Fig. 583. Deciduous and permanent teeth in the Lion (Felis). symbolised in the dog (Jig. 582.), teach us teeth are taken, and that so much of the that the teeth which are wanting, in order to series as is retained is thus preserved unbroken, equal the number of those in the canine den- In the great extinct sabre-toothed tiger (Ma- 910 TEETH. cliatrodus,fig. 580, VI.*), the series is still fur- ther reduced by the loss of p. 2 in the upper jaw. That the student may test for himself the demonstration which the developmental cha- racters above defined, yield of the true nature and homologies of the feline dentition, — the most modified of all in the terrestrial Carnivora, he is recommended to compare with nature the following details of the appearance and formation of the teeth in the common cat. In this species the deciduous incisors d. i. begin to appear between two and three weeks ofd ; the canines d. c. next, and then the molars d. m. follow, the whole being iu place before the sixth week. After the seventh month they begin to fall in the same order; but the lower sectorial molar m. 1, and its tubercular homo- type above (?K. 1) appear before d. 2,d. 3, and d. 4 fall. The longitudinal grooves are very faintly marked in the deciduous canines. The first deciduous molar (d. 2), in the upper jaw is a very small and simple one-fanged tooth ; it is succeeded by the corresponding tooth of the permanent series, which answers to the second premolar ( p. 2) of the hyaena and dog. The second deciduous molar (d. 3) is the sectorial tooth; its blade is trilobate, but both the anterior and posterior smaller lobes are notched, and the internal tubercle, which is relatively larger than in the permanent sectorial, is continued from the base of the middle lobe, as in the deciduous sectorial of the dog and hyasna; it thus typifies the form of the upper sectorial, which is retained in the permanent dentition of several Viverrine and Musteline species. The third or internal fang of the deciduous sectorial is continued from the inner tubercle, and is opposite the interspace of the two outer fangs. The Musteline type is further adhered to by the young Feline in the large proportional size of its deciduous tubercular tooth, d. 4. In the lower jaw, the first milk- molar (d. 3) is succeeded by a tooth (p. 3} which answers to the third lower premolar in the clog and civet. The deciduous sectorial (d. 4), which is succeeded by the premolar (p. 4), an- swering to the fourth in the dog, has a smaller proportional anterior lobe, and a larger pos- terior talon, which is usually notched ; thereby approaching the form of the permanent lower sectorial tooth in the Mustclidae. In the article CARNIVOHA (vol. i. p. 478.), the remarks on the teeth are limited chiefly to their physiological adaptations. A description of some of their more remarkable structures will here be given, according to the idea of the nature of the teeth above developed. The dental formula of the dog, jackal, wolf, and fox, is illustrated in Jig. 580, III. CANIS. * Machairodus, from ^K^KI^K, a sabre ; and «Sols, a tooth. This generic name was imposed by Dr. Katip on the extinct animal which was armed with canine teeth, like that figured in fig. 580, VI. Such teeth, long, compressed, falciform, sharp- pointed, and with anterior and posterior finely- serrated edges, were first discovered in tertiary strata in Italy and Germany, and were ivfonvd by Cuvier to a species of bear, under the name of Ursus ciiltriilcus. Fossil canines of this genns have been found in Kent's Hole cave, Torquay. In the Megahtis, or Long-eared Fox (Oto- cyon, Licht.), the deviation from the typical dentition of the Caindce is effected by excess of development ; two additional true molars being present on each side of the upper, and one on each side of the lower jaw, in the permanent series of teeth ; and an approach is made by the modified form of the sectorial molar and of some of the other teeth to the dentition of the Vivcrridce. This family of Carnivora, which comprehends the Civets, Genets, Ichneumons, Musangs, Snrikates, and Mangues, is characterised, with few exceptions, by the following formula : — i. 5 „ ; c. T -.- ; o — o I — 1 4, _ 4, 2 _ 2 p. T T ; m. ~ ~ : = 40. It differs from that •fr" -I1 m" 5— -K •' = 3G- In the Martin cats o — o .c " • • £ (Mustela martes, L.), the little homotype of p. 1 above is present in the lower jaw ; in the bloodthirsty stoats and weasels, p. 1 is absent in both jaws ; as it is likewise in the great sea- otter (E>t/fi/dra), in which also the two middle incisors are wanting in the lower jaw. In this animal the second premolar (p. 3) has a strong obtuse conical crown, double the size of that of p. 2 ; the third premolar (p. 4) is more than twice the size of p. 3, and represents the upper carnassial or sectorial strangely modi- fied; the two lobes of the blade being hemi- spheric tubercles. The last tooth, m, 1, has a larger crown than the sectorial, and is of a similar broad crushing form. In the lower jaw the molar series are not separated bv any interspace: the first and second premolars have oblique obtuse conical crowns. The third premolar (p. 4) is more than twice the size of the second (p. 3) and supports a large anterior hemispheric protuberance with a small internal tubercle and a posterior basal ridge. The first true molar has an oblong quadrate crown with an anterior small tubercle, a larger and more prominent inner one, and the rest of the broad horizontal surface un- dulating. The second true molar has a trans- versely elliptical crown depressed in the centre. When the teeth are in apposition, the anterior third of the first true molar below is applied to the inner tubercle of the last premolar above ; the rest of its crown plays upon that of its homotype, the first true molar in the upper jaw, leaving a small part of that tooth to receive the appulse of the second true molar below, which has no corresponding tooth in the upper jaw. The MustelidcB present great constancy in regard to the number of their true molar teeth; with one exception, the Ratel (Mclli- vura), in which m. 2 is absent below, they have one true molar on each side of the upper jaw, and two on each side of the lower jaw ; the second of these has always a broad tubercular crown, like the one above. The upper true molar is supported by one inner, and sometimes by one (Pittorius, Gulo), sometimes two (Mustela, Lutra, Melphltis), outer fangs. The second true molar below is also tubercular, but has a single fang. The crown of the first true molar below offers many gradations from the sectorial type, as manifested in Putorius and Gu/o, to the tuber- cular type, as in the Taira, Ratel, and sea- otter. The principal varieties occur, as usual, in the comparatively less important premolars : in the Martins and Gluttons, they are as numerous as in the dog ; the first, in both jaws, being implanted by a single fang ; the rest by two, with the exception of VOL. IV. the last above, which has three roots. In the otter, we find the first premolar removed from the lower jaw ; and the second (now the first) shows its true homology by its double implantation, as well as by the position of its crown behind the first in the upper jaw (p. 1). In the Stoats, Skunks, and Ratels, the premolar series is further reduced by the loss of the anterior tooth (p. 1) in both jaws, and by the diminution of the size of p. 2, which thus becomes the first in both jaws, and which is also now implanted by a single fang. In a South American Skunk, the second premolar disappears in the upper jaw, leaving there only the homologues of the third and fourth of the typical formula, p. 4 being always the sectorial in the Mustelidce, as in other terrestrial Carnivora. This tooth, under all its modifications, retains the blade with the lobe, corresponding to the middle one in the feline sectoral, generally well developed and sharp-pointed ; the differences are principally manifested by the proportions of the inner tubercle, and the relative size of the third root supporting it. But the upper sectorial, being a premolar, and therefore requiring less modification of the crown to adapt it for its special functions, manifests a, more limited extent of variety than the lower sectorial, which, being a true molar, requires greater modification of the typical form of its crown to fit it for playing upon the sectorial blade of p. 4 above. Melidee. — In this sub-.family \ comprise the European Badger (Meles), the Indian Badger (Arctonyx)., and the American Badger (Taxidca) ; which, with respect to their den-, tition, stand at the opposite extreme of the Mustelidie to that occupied by the predaeeous Weasel, and manifest the most tuberculate and omnivorous character of the teeth. The 3—3 1— 1 3—3 , . . formula is:-*. c. — ] ; p. : = 30« The canines are strongly developed, well pointed, with a posterior trenchant edge ; they are more compressed in Arctonyx than in Mclcs. The first lower premolar (p. 1) is very small, single-fanged, and, generally, soon lost. The first above, corresponding with the second in the dog, is also small, and implanted by two connate fangs. The second upper premolar (p. 3) has a larger, but simple, sub-compressed conical crown, and is implanted by two fangs: the third (p. 4) re- peats the form of the second on a larger scale, with a better developed posterior talon, and with the addition of a tri-tuberculate low flat lobe, which is supported by a third fang : the outer pointed and more produced part of this tooth represents the blade of the sectorial tooth and the entire crown of the antecedent premolars. The true molar in Melcs (»/. ]) is of enormous size compared with that of any of the preceding Carnivora : it has three external tubercles, and an extensive horizontal surlare traversed longitudinally by a low 3N 914 TEETH. ridge, and bounded by an internal belt, the cingulum of Illiger: this tooth has a similarly shaped, but relatively smaller, crown in Arc- tonyx* The second premolar below (p. 2) is commonly the first, through the early loss of the minute one in front ; its fangs are usually connate, as in its homotype above. The third and fourth premolars slightly in- crease in size, have simple compressed conical crowns, and two fangs each. The first true molar below (m. 1) now retains little of its sectorial character, the blade being represented only by the two anterior small, compressed pointed lobes; behind these, the crown ex- pands into an oval grinding surface, narrower in Arctoiiyx th<™ in Meles, supporting three tubercles and a posterior tuberculate ridge: it has generally two principal roots and a small intermediate accessory fang, as in the otter. The second molar (m. 2), which ter- minates the series below, is of small size, and has a rounded flat crown, depressed in the centre, and with two small external tubercles; its two short fangs are connate. In the Labrador Badger, the last premolar has a larger relative size, the part corresponding with the blade of the sectorial, is sharper and more produced, and the internal tu- bercle has two lobes; the succeeding molar tooth is reduced in size, and its crown pre- sents a triangular form. The first true molar below has its sectorial lobes better developed : these differences give the North American badgers a more carnivorous character than is manifested by the Indian or European species. Sub-UrsidcB, — In other allied genera, which, like the badgers, have been grouped, on ac- count of the plantigrade structure of then- feet, with the bears, a progressive approxi- mation is made to the type of the dentition of the Ursine species. The first true molar below soon loses all its sectorial modification, and acquires its true tubercular character: and the last premolar above becomes more directly and completely opposed to its homo- type in the lower jaw. the Racoon ( Procyon f) and the Coati (Nasua) present good examples of these transitional modifications ; they have the complete number of premolar teeth, the 3—3 1 — 1 4—4. dental formula being, i. = — o> c- T f> P- j — 7> o — «i> 1 — i T? — ^ m. : = 40. The development of the in- ner part of the crown of the last upper pre- molar, which constitutes the tubercle of the sectorial tooth, now produces two tubercles on a level with the outer ones which represent the blade; and the opposite premolar below (p. 4), which is the true homotype of the modified sectorial above, begins to acquire a marked increase of breadth and accessory basal tu- bercles. All the lower premolars, as well as the true molars, have two fangs; the three first premolars above have two fangs, the fourth has three, like the two true molars above. The dental formula of the Indian Bentu- * See Odontography, pi. V2§,fy. 13, m. 1. f Ib. pi. 129,/gr. 7. J Ib.jfys. 8— 13. rong (Arctictis) and Kinkajou (Cercoleptei) is . 3—3 1— I 3—3 2—2 '• 3=3' c' T=T' P- 5=3' m' 2=2 = = 3G- Phocidcc. — We have seen a tendency to deviate from the ferine number of the incisors in the most aquatic and piscivorous of the Musteline quadrupeds, viz. the sea-otter (Enhydra), in which species the two middle incisors of the lower jaw are not developed in the permanent dentition. In the family of true seals, the incisive formula is further re- duced, in some species even to zero in the 3 3 lower jaw, and it never exceeds „. All the Phoc':d(E possess powerful canines ; only in the aberrant walrus ( Trichechus) are they absent in the lower jaw, but this is compensated by the singular excess of development which they manifest in the upper jaw. In the pinnigrade, as in the plantigrade, family of Carnivores we find the teeth which correspond to true mo- lars more numerous than in the digitigrade species, and even occasionally rising to the typical number, three on each side ; but this, in the seals, is manifested in the upper and not, as in the bears, in the lower jaw. The entire molar series usually includes five, rarely six teeth on each s;de of the upper jaw, and five on each side of the lower jaw, with crowns, which vary little in size or form in the same individual ; they are supported in some genera, as the Eared Seals (Oiaria?) and Elephant Seals (Cystophora*), by a single fang ; in other genera f by two fangs, which are usually connate in the first or second teeth ; the fang or fangs of both incisors, canines and molars, are always remarkable for their thickness, which commonly sur- passes the longest diameter of the crown. The crowns are most commonly compressed, conical, more or less pointed, with the " cin- gulum " and the anterior and posterior basal tubercles more or less developed; in a few of the largest species they are simple and ob- tuse, and particularly so in the walrus, in which the molar teeth are reduced to a smaller number than in the true seals. J In these the line of demarcation between the true and false molars is very indefinitely in- dicated by characters of form or position ; but, according to the instances in which a deciduous dentition has been observed, the first three permanent molars in both jaws succeed and displace the same number of milk molars, and are consequently premitlam ; occasionally, in the seals with two-rooted molars, the more simple character of the premolar teeth is manifested by their fangs being connate, and in the Stenorhynchus serri- dcns the more complex character of the true molars is manifested in the crown. There is no special modification of the crown of any tooth by which it can merit the name of a * Odontography, pi. 132, fig. 1. t Ib.fflsA—i. j The relation of Trichechus to the Phocidcc is analogous to that of Machairodus to the Fvlida; and also, in the simplification of the molars, to that of Protvks to Citnidu: TEETH. 915 "sectorial" or " carnassial ; " but we may point with certainty to the third molar above and the fourth below as answering to those teeth which manifest the sectorial character in the terrestrial Carnivora. The coadaptation of the crowns of the upper and lower teeth is more completely alternate than in any of the terrestrial Car- nivora, the lower tooth always passing into the interspace anterior to its fellow in the upper jaw. In the genus Phoca proper (Ca- locephalus, Cuv.) typified by the common seal (1'h. vitiilina), the dental formula is, i. Q — , 1—1 3—3 2—2 _ and proportions of these teeth are shown in PI. 132, fig. !., of my "Odontography." The first tooth above and below presents a complete confluence of the fangs ; they are separated from the second above ; but be- low they sometimes do not become free before the fourth, and sometimes the two roots are distinct in the third and second molars. In the Phoca ancllata Nills., the principal cusp of the molar teeth is com- plicated with anterior and posterior smaller cusps, sometimes one in number in the upper molars ; the anterior accessory cusp is some- times wanting in the first, and is rudimentary in the rest ; but usually there are two small cusps behind the principal one, and in the three or four posterior molars in the lower jaw there are sometimes two small cusps be- fore and two behind the principal one.* In the Phoca caspica the upper molars have commonly one accessory cusp before and one behind the principal lobe ; the lower molars have one accessory cusp before and two be- hind. In the Phoca gr&nlandica, the upper molars have no anterior basal cusp and only one be- hind ; the lower molars have two cusps behind and one in front, except the first, which re- sembles that above, and, like it, has connate fangs. The condition of the molar teeth is nearly the same in the Phoca barbata, but the crowns are rather thicker and stronger, and the three middle ones above have two posterior basal cusps feebly indicated, the same being more strongly marked in the four last "molars below. The following genera of seals with double- rooted molars (Pelagius and Stenorhynchus) have four incisors above as well as below, i. c. 2 9 a~ a- An upper view of the molar teeth in the Hooded Seal of the Mediterranean (Pcla- gius monachits) is given in my Odontography, PI. 132. fig. 3., as when they are worrT down in an old specimen ; the crowns are thick, obtuse, sub-compressed, with a well developed * Nillson, in Wiegmann's Archiv. 1841, 313. I notice these varieties of the crown, in connection with analogous ones in the fangs of the teeth of the same species, to show the inadequacy of such cha- racters as marks of subgeneric distinction. cingiilum, a principal lobe and an anterior and posterior accessory basal lobule ; the fangs are connate in the first tooth both above and below. The allied sub-genus (Ommatophoca) of seals of the southern hemisphere has six molar teeth on each side of the upper, and five on each side of the lower jaw, with the principal lobe of the crown more incurved. The two first molars above are closely approximated, but this may prove to be a variety. In the Stenorhynchus the jaws are more slender and produced, and the molar teeth are remarkable for the long and slender shape of the principal lobe, and of the accessory basal cusps. The incisors have sharp conical re- curved crowns, like the canines, and the ex- ternal ones in the upper jaw are intermediate in size between the canines and the middle in- cisors. In the Stenorhynchus leptonyy each molar tooth in both jaws is trilobed, the anterior and posterior accessory curving towards the principal one, which is bent slightly back- wards ; all the divisions are sharp-pointed, and the crown of each molar thus resembles the trident or fishing-spear ; the two fangs of the first molar in both jaws are connate. In Stenorhynchus serridens the three anterior mo- lars on each side of both jaws are four-lobed, there being one anterior and two posterior accessory lobes ; the remaining posterior molars (true molars) are five-lobed, the prin- cipal cusp having one small lobe in front, and three developed from its posterior margin ; the summits of the lobes are obtuse, and the posterior ones are recurved like the prin- cipal lobe. Sometimes the third molar be- low has three instead of two posterior acces- sory lobes. Occasionally, also, the second, as well as the first molar above, has it fangs con- nate ; but the essentially duplex nature of the seemingly single fang, which is unfailingly manifested within by the double pulp-cavity, is always outwardly indicated by the median longitudinal opposite indentations of the im- planted base. These slight and unessential varieties, presented by the specimens of the Saw-toothed Sterrink (Stenorhynchus serridens) brought home by the enterprising Naturalist of Sir J. Ross's Antarctic expedition, accord with the analogous varieties noticed by the best observers of the seals of our neighbour- ing seas, as, for example, Nillson. The Grey Seal (Haiichaerus gryphtis) of our own seas begins, by the extension of the connate condition of the two roots through a greater proportion of the molar series^ to manifest a transition to the family of seals with true single-rooted molars ; the formula of this genus is, i. =, c. p. 2—2 : = 34". 2—2'1' 1—1 The four middle upper in« —• 2 _ 2 cisors are close set, with pointed recurved crowns ; the lateral ones are much larger and laniariform : the canines have moderate crowns, with a sharp ridge before and behind. The* 3 N 2 916 TEETH. crowns of the molar teeth are conical, sub- compressed longitudinally and finely grooved, with an anterior and posterior edge ; those below have generally a slight notch at the fore and back part of the base. The first molars, both above and below, are the smallest, with a simple crown and a single ventricose fang ; the second and third above, and the second, third, and fourth below, have two connate roots ; the two roots are commonly distinct in the remaining posterior molars : all the roots are very thick. In the genus Otaria the dental formula is, •* c. — !, p. J . c. — , . , m. = 36. The 2—2' 1— 1 J 3—3 2—2 two middle upper incisors are small, sub-com- pressed, with the crown transversely notched ; the simple crowns of the four incisors below fit into these notches : the outer incisors above are much larger, with a long pointed conical crown, like a small canine. The true canine is twice as large as the adjoining incisor, and is rather less recurved. The molars have each a single fang ; the crown is conical, sub- compressed, pointed ; in the two last recurved, with a basal ridge or " cingulum," broadest within ; but, in the Otaria jubata, the molars have a pointed cusp developed from the fore- part, and in the last two molars also from the back part of the crown. In some species, as the Otaria lobata (Phoca lobata, Fischer), the single molar is not developed in the upper jaw, and the outer incisors above are not so large : in this species a thick plicated cingulum belts the base of each molar and developes a small tu- bercle from its fore-part in the molars of the lower jaw j the crown of the last molar above is notched. In the great proboscidian and hooded Seals (Cystopkora), the incisors and canines still more predominate in size over the molars ; but the incisors are reduced in number, the . . 2—2 1—1 3—3 formula here is : i. -, — r, c. - — r, p. ^ — - 1 — 1 1 — 1 o — o 2—2 m. ~ -- : = 30. All the molars are single- f//or!;/tcs Gorilla, adult male. (Natural sizr..) TEETH. 919 minor particulars in which it differs from the dentition of the Orang, approaches nearer the human type. In the upper jaw the middle incisors (Jig. 586, i. 1) are smaller, the lateral ones (ib. i. 2) larger than those of the Orang*; they are thus more nearly equal to each other; nevertheless the proportional superiority of the middle pair is much greater than in Man, anil the proportional size of the four incisors both to the entire skull and to the other teeth is greater. Each incisor has a prominent posterior basal ridge, and the outer angle of the lateral incisors, i. 2, is rounded off as in the Orang. The incisors incline forwards from the vertical line as much as in the great Orang. Thus the characteristics of the human incisors are, in addition to their true incisive wedge-like form, their near equality teeth " *, when the mouth is closed, is appli- cable only to the female, and does not distin- guish the Chimpanzees from the Orangs. In the male of the smaller Chimpanzee (Troglodi/- tcs niger) the upper canine is conical, pointed, but more compressed than in the Orang, and with a sharper posterior edge ; convex ante- riorly, becoming flatter at the posterior half of the outer surface, and concave on the corre- sponding part of the inner surface, which is •aversed by a shallow longitudinal impres- sion ; a feeble longitudinal rising and a second linear impression divide this from the convex anterior surface, which also bears a longitu- dinal groove at the base of the crown. The canine is rather more than twice the size of that in the female. In the male (ion/la (Jigs. 585, 586.), the crown of the canine is Fig. 5S7. Dentition of adult female, Troglodytes Gorilla. (Natural size,) of size, their vertical or nearly vertical posi- tion, and small relative size to the other teeth and to the entire skull. The diastema be- tween the incisors and the canine on each side is as well marked in the male Chim- panzee as in the male Orang.f The crown of the canine (ib. c.), passing outside the in- terspace between the lower canine and pre- molar, extends in the male Troglodytes Gorilla a little below the alveolar border of the under jaw when the mouth is shut ; the upper ca- nine of the male Troglodytes niger likewise projects a little below that border ; the seventh character, therefore, which I had formerly assigned to the genus, " apices of canines lodged in intervals of the opposite * Compare fig. 586. with pi. xxxii. (Pithecus Wtirmbii) and pi. xxxiv. (Pith. Morh\ in vol. ii. Zool. Trans. t Compare /?#. 58. 3) ; it has a subtrihedral crown, with the anterior and outer angle produced forwards, slightly indicating the peculiar fea- ture of the same tooth in the Baboons, but in a less degree than in the Orang. The summit of the crown of p. 3 terminates in two sharp trihedral cusps, the outer one rising highest, and the second cusp being feebly indicated on the ridge extending from the inner side of the first ; the crown has, also, a thick ridge at the inner and posterior part of its base. The second premolar (p. 4) has a subquad- rate crown, with the two cuf-ps developed from its anterior half, and a third smaller one from the inner angle of the posterior ridge. Each lower premolar is implanted by two antero-posteriorly compressed divergent fangs, one in front of the other, the anterior fang being the largest. The three true molars are equal in size in the Troglodytes Gorilla ; in the Troglodytes niger (fig. 588.) the first (?». 1) is a little larger than the last (m. 3), which is the Fig. 588. •Dental scries, lower jaw, adult male, Troglodytes iiigcr. (Natural Size.) TEETH. 921 only molar in the smaller Chimpanzee as large as the corresponding tooth in the black varieties of the human subject *, in most of which, especially the Australians, the true molars attain larger dimensions than in the yellow or white races. The four principal cusps, especially the two inner ones, of the first molar of both species of Chimpanzee are more pointed and prolonged than in Man ; a fifth small cusp is developed behind the outer pair, as in the Orangs and the Gibbons, but is less than that in Man. The same additional cusp is present in the second molar, which is seldom seen in Man. The crucial groove on the grinding surface is much less distinct than in Man, not being continued across the ridge connecting the anterior pair of cusps in the Chimpanzee. The crown of the third molar is longer antero-posteriorly from the greater development of the fifth posterior cusp, which, however, is rudimental in comparison with that in the Semnopitheques and Macaques. All the three true molars are supported by two distinct and well developed antero-pos- teriorly compressed divergent fangs, longitu- dinally excavated on the sides turned towards each other ; in the white and yellow races of the human subject these fangs are usually connate in m. 3, and sometimes also in m. 2. The molar series in both species of Chim- panzee forms a straight line, with a slight ten- dency in the upper jaw to bend in the opposite direction to the well-marked curve which the same series describes in the human subject. This difference of arrangement, with the more complex implantation of the premolars, the proportionally larger size of the incisors as compared with the molars ; the still greater relative magnitude of the canines ; and, above all, the sexual distinction in that respect, illus- trated by figs. 585. 587., stamp the Chimpan- zees most decisively with not merely specific but generic distinctive characters as compared with Man. For the teeth are fashioned in their shape and proportions in the dark re- cesses of their closed formative alveoli, and do not come into the sphere of operation of external modifying causes until the full size of the crowns has been acquired. The formid- able natural weapons, with which the Creator has armed the powerful males of both species of Chimpanzee, form the compensation for the want of that psychical capacity to forge destructive instruments which has been re- served as the exclusive prerogative of Man. Both Chimpanzees and Orangs differ from the human subject in the order of the de- velopment of the permanent series of teeth ; the second molar (m. 2) comes into place before either of the premolars has cut the gum, and the last molar (in. 3) is acquired before the canine. We may well suppose that the larger grinders are earlier required by the frugivorous Chimpanzees and Orangs than by the higher organised omnivorous spe- cies with more numerous and varied resources, and probably one main condition of the earlier * See my Odontography, pi. 11$, fig. 2, m. development of the canines and premolars in Man may be their smaller relative size. In the South American Quadrumana, the number of teeth is increased to thirty-six (art. QUADRUMANA, Vol. IV. p.210.; Ccbincc*], by an addition of one tooth to the molar series on each side of both jaws. It might be concluded, a priori, that as three is the typical number of true molars in the placental Mam- malia with two sets of teeth, the additional tooth in the Ccbince would be a premolar, and form one step to the resumption of the normal number (four) of that kind of teeth. The proof of the accuracy of this inference is given by the state of the dentition in the young Cebus mjig. 589., which corresponds with that of the human child in Jig. 584*., i. c. the whole of the Fig. 589. Deciduous and permanent teeth of Cebus. deciduous dentition is retained, and the first true molar (m. 1) is in place on each side of both jaws. The germs of the other teeth of the permanent series are exposed in the upper jaw ; and the crown of a premolar is found above the third molar in place, as well as above the second and first. As regards number, therefore, the molar series, in Cebux, is interme- diate between that of Mustela (fig. 580., IV.) and Felis (ib. V.) ; the little premolar p. i. in Mustela tells plainly enough which of the four is wanting to complete the typical number in the South American Monkey, and which is the additional premolar distinguishing its dental formula from that of the Old World monkeys and man. By reference to Prof. Vro- lik's article (QUADRUMANA) it wil! be seen that the eighth genus, including the little Marmoset monkeys (Hapale, Ouislili), " have only the same number of teeth as the monkeys 4 ] i of the Old World, viz. 32, i. j, c. - — »j. 'T J 1 fj £ - — -." But the difference is much greater o — o than this numerical conformity would intimate. In a young Jacchus penicillatus I find that there are three deciduous molars displaced by three premolars, as in the other South Ame- rican Quadrumana, and that it is the last true molar, »?. 3, the development of which is sup- pressed, not the premolar p. 2, and thus these diminutive squirrel-like monkeys actually differ * The dental series seems, unluckily, not to have been complete in either of the skulls represented by the distinguished author of that able article (Jit/s. 132, 133). 922 TEETH. from the Old World Quadrumana more than the Cebidce do ; i. e. they differ not only in having four teeth (p. 2 — 7), which the monkeys of the Old World do not possess, but also by wanting four teeth (m. 3 ]^T[)» which those monkeys, as well as the Cebidce, actually have. It is thus that the investigation of the exact homologies of parts leads to a recognition of the true characters indicative of zoological affinity. 3—3 Most of the Lemurincc have p. ^ „, m. 3—3 -. together with remarkable modifications • _> 7 O of their incisive and canine teeth, of which an extreme example is shown in the pectinated tooth (fig. 556.) of the Galeopithecus. The inferior incisors slope forwards in all, and the canines also, which are contiguous to them, and very similar in shape. In the Chirogaleus these canines arc entered as in- cisors in the dental formula of the genus (Vol. IV. p. 215), and the laniariform premolar (p. 2) is entered as a canine : M. Vrolik aUo describes four teeth on each side of the upper jaw, and four on each side of the lower jaw, as true tuberculated molars. They have tuber- culated crowns, but the value of shape as a character is too small to permit our accepting so great an anomaly without the requisite proof of their order of development and suc- cession. Even in the hoofed quadrupeds with toes in uneven number (Perissodactyld}, whose premolars, for the most part, repeat both the form and the complex structure of the true molars, such premolars are distinguished by the same character of development as those of the Artiodacti/la, or Ungulates with toes in even number : although in these the premolars are distinguished also by modifications of size and shape. The complex ridged and tuber- culate crowns of the second, third, and fourth grinders of the Rhinoceros, Hyrax (fg. 590.), tooth be determined, and its proper symbol applied to it. In pi. 136, _//g. 5, of my Odontography, the three posterior teeth of the almost uniform grinding series of the horse's dentition are thus proved to be the only ones entitled to the name of " true molars ;" and, if any one should doubt the certainty of the rule of count- ing, by which the symbols, p. 4*, p. 3, and p. 2, are applied to the three large anterior grinding teeth (ib. fig. 19), which are commonly the only premolars present in each lateral series of the horse's jaws, yet the occasional retention of the diminutive tooth, p. 1 (ib.fig. 6), would establish its accuracy, whether such tooth be regarded as the first of the deciduous scries unusually long retained, or the unusually small and speedily lost successor (p. 1) of an abortive d 1. The law of development, so beautiful for its instructiveness and constancy in the pla- cental Dip/iyodunts, is here illustrated in the little Hj/ra.c (fg. 591.), in which the d. 1 is Fig. 591. Deciduous mid permanent molars of the Ilyrux. normally developed and succeeded by a per- manent p. 1, differing from the rest only by a graduated inferiority of size, which, in regard to the last premolar, ceases to be a distinction between it and the first true molar. The elephant, which by its digital characters belongs to the odd-toed, or perissodactyle, group of Pachyderms, also resembles them in the close agreement in form and structure of the grinding teeth representing the premolars, Fig. 590. Molar series, upper jcai) (Ilyrnx). and horse, no more prove them to be true molars, than the trenchant shape of the lower carnassials of the lion proves them to be false molars. It is by development alone that the primary division of the series of grinding teeth can be established, and by that character only can the homologies of eacli individual with those that answer to the true molars of the Hyrax, Tapir, and Rhinoceros. The gi- gantic Proboscidian Pachyderms of Asia and Africa present, however, so many peculiarities of structure, as to have led to their being located in a particular family in the Systematic Mammalogies. And this seems to be justified TEETH. 203 by no character more than by the singular seeming exception which they present to the Diphyodont rule which governs the dentition of other hoofed quadrupeds. In fact, the elephant, like the Dugong, sheds and replaces vertically only its incisors, which are also two in number, very long, and of constant growth, forming tusks, with an analogous sexual dif- erence in this respect in the female of the Asiatic species. The molars, also, are suc- cessively lost, are not vertically replaced, and are reduced finally to one on each side of both jaws, which is larger than any of its pre- decessors. These analogies are interesting and suggestive in connection with the other approximations in the " Sirenia" to the pa- chydermal type, which I have pointed out in the " Proceedings of the Zoological Society ." * The dentition of the genus Elephas, the sole existing modification of the once numerous and varied Proboscidian family, includes two long tusks (jig. 592.), one in each of the Intermaxillary bones, and large and complex molars (ib. in. 3, 4, and 5) in both jaws : of the latter there is never more than one wholly, or two partially, in place and use on each side at any given time; for, like the molars of the Mastodons, the series is continually in progress of formation and destruction, of shedding and replacement ; and in the ele- phants all the grinders succeed one another like true molars horizontally, from behind forwards. The total number of teeth developed in the . 2—2 6—6 elephant appears to be '-/T^Ty "''fiUfi = 28< The two large permanent tusks being pre- ceded by two small deciduous ones, and the number of molar teeth which follow one another on each side of both jaws bein^ at " The socket of the permanc-.it tusk in a new-born elephant, is a round cell about three lines in diameter, situated on the inner and posterior side of the aperture of the temporary socket. The permanent tusks cut the gum when about an inch in length, a Fig. 592. least six, of which the last three may, by analogy, be regarded as answering to the true molars of other Pachyderms. I have shown in my Odontography that : — " The deciduous tusk makes its appearance beyond the gum between the fifth and seventh month ; it rarely exceeds two inches in length, and is about a third of an inch in diameter at its thickest part, where it protrudes from the socket ; the fang is solidified, and con- tracts to its termination, which is commonly a little bent, and is considerably absorbed by the time the tooth is shed, which takes place between the first and second year.f * 1838, p. 40. t See Mr. Corse's " Memoir on the Teeth of the Elephant," in Philosophical Transactions, 1700, p. 211 : a good figure of the deciduous tusk is given in plate 5. Section of cranium and tusk of the Elcphuni, month or two, usually, after the milk. tusks are shed. At this period, according to Mr. Corse *, the permanent tusks are ' black and ragged at the ends. When they become longer, and project beyond the lip, they soon are worn smooth by the motion and friction of the trunk.' Their widely open base is fixed upon a conical pulp, which, with the capsule sur- rounding the base of the tusk and the socket, continues to increase in size and depth, ob- literating all vestiges of that of the deciduous tusk, and finally extending its base close to the nasal aperture (Jig. 592.). The tusk is formed by successive calcification of layers of the pulp in contact with the inner surface of the pulp cavity ; and, being subject to no habitual attrition from an opposed tooth, but being worn only by the occasional uses to which it is applied, it arrives at an extraor- dinary length, following the curve originally * Loc. cit., p. 212. 924 TEETH. impressed upon it by the form of the socket, and gradually widening from the projecting apex to that part which was formed when the matrix and the socket had reached their full size. " These incisive teeth of the elephant not only surpass other teeth in size, as belonging to a quadruped so enormous, but they are the largest of all teeth in proportion to the size of the body; representing in a natural state those monstrous incisors of the Rodents, which are the result of accidental suppression of the wearing force of the opposite teeth." The tusks of the elephant, like those of the Mastodon, consist chiefly of that modifi- cation of dentine which is called " ivory," and which shows, on transverse fractures or sec- tions, strias proceeding in the arc of a circle from the centre to the circumference, in op- posite directions, and forming by their decus- sations curvilinear lozenges. This character is peculiar to the Proboscidian Pachyderms. In the Indian elephant the tusks are always short and straight in the female, and less deeply implanted than in the male : she thus retaining, as usual, more of the charac- ters of the immature state. In the male they have been known to acquire a length of nine feet, with a basal diameter of eight inches, nnd to weigh one hundred and fifty pounds ; hut these dimensions are rare in the Asiatic species. Mr. Corse, speaking of the variety of Indian elephant, called "Dauntelah" from its large tusks, which project almost horizontally with a slight curve upwards and outwards, says, " The largest I have known in Bengal did not exceed seventy-two pounds avoirdupois ; at Tiperah they seldom exceed fifty pounds." There are varieties of the Dauntelah in which /he large tusks of the male are nearly or quite straight ; and in a more marked breed called " Mooknah," the tusks are much smaller, are straight, and point directly downwards. These ascertained varieties in an existing species ought to weitrh with the observers of analo- • gous varieties in the teeth of fossil Probos- cidians, before they pronounce definitely on their value as characters of distinct species. More anomalous varieties occasionally pre- sent themselves in the Indian Elephant, as when one tusk is horizontal, the other ver- tical; or when, from some distortion of the alveolus, a spiral direction is impressed upon the growth of the tusk, as in that specimen figured by Grew in the " Rarities of Gresham College," Tab. 4., and which is now in the Museum of the Royal College of Surgeons, London. The tusk of the elephant is slightly moveable in its socket, and readily receives a new direction of growth from habitual pres- sure ; this often causes distorted tusks in captive elephants, and Cuvier * relates the mode in which advantage was taken of the .same impressibility, in order to rectify the growth of such tusks in an elephant kept at the Garden of Plants. The tusks of the extinct Elcphns jtriml- * Ossemens Fossiles, 4to. 1821, torn. i. p. 47. genius, or Mammoth, have a bolder and more extensive curvature than those of the Elt-phns indicus: some have been found which describe a circle ; but, the curve being oblique, they thus clear the head, and point outwards, downwards, and backwards. The numerous fossil tusks of the Mammoth which have been discovered and recorded, may be ranged under two averages of size: the larger ones at nine feet and a half, the smaller at five feet and a half in length. 1 have elsewhere * as- signed reasons for the probability of the latter belonging to the female Mammoth, which must accordingly have differed from the exist- ing elephant of India, and more resembles that of Africa in the development of her tusks ; yet manifesting an intermediate cha- racter by their smaller size. Of the tusks which are referable to the male Mammoth, one from the newer tertiary deposits in Essex, measured nine feet ten inches along the outer curve, and two feet five inches in circum- ference at its thickest part ; another from Eschscholtz Bay was nine feet two inches in length, and two feet one and a half inches in circumference, and weighed one hundred and sixty pounds. A Mammoth's tusk has been dredged up off Dungeness which measured eleven feet in length. In several of the in- stances of Mammoth's tusks from British strata, the ivory has been .so little altered as to be fit for the purposes of manufacture ; and the tusks of the Mammoth, which are still better preserved in the frozen drift of Siberia, have long been collected in great numbers as articles of commerce.-j- Cuvier J states that the elephant of Africa, at least in certain localities, has large tusks in both sexes, and that the female of this species, which lived seventeen years in the menagerie of Louis XIV., had larger tusks than those in any Indian elephant, male or female, of the same size which he had seen. The ivory of the tusks of the African ele- phant is most esteemed by the manufacturer for its density and whiteness. The molar teeth of the elephant are re- markable for their great size, even in relation to the bulk of the animal, and for the extreme complexity of their structure. The crown, of which a great proportion is buried in the socket, and very little more than the grinding surface appears above the gum, is deeply di- vided into a number of transverse perpen- dicular plates {fig. 557), consisting each of a body of dentine (d), coated by a layer of enamel (e), and this again by the less dense bone-like * History of British Fossil Mammalia, 8vo. 1844, p. 244. •f In the account of the Mammoth's bones and teeth of Siberia, published in the " Philosophical Transactions " for 1737 (No. 446), tusks are cited which weighed two hundred pounds each, and " are used as ivory, to make combs, boxes, and such other things; being but little more brittle, and easily turning yellow by weather and heat." From that time to the present there has been no inter- mission in the supply of ivory, furnished by the tusks of the extinct elephants of a former world. J Loc. cit., p. 55. TEETH. 925 substance (c) which fills the interspaces of the enamelled plates, and here more especially merits the name of " cement," since it binds together the several divisions of the crown before they are fully formed and united by the confluence of their bases into a common body of dentine. As the calcification of each plate begins at the summit, they remain de- tached from each other and like so many se- parate teeth or denticules, until their base is completed, when it becomes blended with the bases of contiguous plates to form the common body of the crown of the complex tooth from which the roots are next developed. The plates of the molar teeth of the Si- berian Mammoth (EU-phas prinrigenius) are thinner in proportion to their breadth, and are generally a little expanded at the middle ; and they are more numerous in proportion to the size of the crown than in the existing species of Asiatic Elephant. In the African Elephant, on the other hand, the lamellar divisions of the crown are fewer and thicker, and they expand more uniformly from the margins to the centre, yielding a lozenge-form when cut or worn transversely, as in masti- cation. The horizontal as well as vertical course of development of the elephant's grinder is well illustrated by the Mammoth's molar, the last of the lower jaw. The separate digital processes of the posterior plates are still distinct, and adhere only by the re- maining cement ; a little in advance we see them united to form the transverse plate ; and, at the opposite extremity of the tooth, the common base of dentine is exposed by which the plates are finally blended into one individual complex grinder*; this never takes place simultaneously along the whole course of the tooth in the larger molars of the existing Indian elephant, or its extinct congener, the Mammoth. The African ele- phant, and some of the extinct Indian species, as the El. p/anifrons, manifest their affinity to the Mastodon by the basal confluence of the hindmost plates before the foremost ones are worn out. The formation of each grinder begins with the summits of the anterior plate, and the rest are completed in succession ; the tooth is gradually advanced in position as its growth proceeds; and, in the existing Indian elephant, the anterior plates are brought into use before the posterior ones are formed. When the complex molar cuts the gum the cement is first rubbed off the digital summits: then their enamel cap is worn away, and the * Some anatomists describe the divisions of the crown of the elephant's grinder as so many " distinct teeth ; " and Mr. Corse (loc. cit. p. 213.), who iirst propounded this view, calls each complex grinder " a case of teeth," and states " that these teeth are merely joined to each other by an intermediate softer substance, acting like a cement." But this description applies only to the imperfectly-formed tooth ; and the detached eminences of the crown of any complex tooth, at that stage of growth when they are held together only by the still uncalcified supporting matrix, might with equal justice be regarded as so many distinct teeth. central dentine comes into play with a promi- nent enamel ring ; the digital processes are next ground down to their common uniting base, and a transverse tract of dentine with its wavy border of enamel is exposed ; finally, the transverse plates themselves are abraded to their common base of dentine, and a smooth and polished tract of that substance is pro- duced.* From this basis the roots of the molar are developed, and increase in length to keep the worn crown on the grinding level, until the reproductive force is exhausted. When the whole extent of a grinder has successively come into play, its last part is reduced to a long fang supporting a smooth and polished field of dentine, with, perhaps, a few remnants of the bottom of the enamel folds at its hinder part. When the complex molar has been thus worn down to a uni- form surface it becomes useless as an instru- ment for grinding the coarse vegetable sub- stances on which the elephant subsists ; it is attacked by the absorbent action, and the wasted portion of the molar is finally shed. The grinding teeth of the elephant pro- gressively increase in size, and in the number of lamellar divisions, from the first to the last ; and, as the rate of increase in both respects is nearly identical in both jaws, I shall describe them chiefly as they appear in the lower one. Thejirst molar, which cuts the gum in the course of the second week after birth, has a sub-compressed crown, nine lines in antero- posterior diameter, divided by three trans- verse clefts into four plates, the third being the broadest, and the tooth here measuring six lines across f ; the first and second plates have two mammilloid summits ; the third and fourth have three or four such ; there is a sin- gle and sometimes a double mammilloid sum- mit at the fore and back part of the crown : the base slightly contracts, and forms a neck as long as the enamelled crown, but of less breadth, and this divides into two, an anterior and posterior, long, sub-cylindrical, diverging, but mutually incurved fangs ; the total length of this tooth is one inch and a half. The corresponding upper molar, which Mr. Corse describes as cutting the gum a little earlier than the lower one, has the anterior single digital process or mammilla, and the pos- terior talon developed into a fifth plate, smaller than the fourth, with which its middle part is confluent ; the neck of this tooth is shorter, and the two fangs are shorter, larger, and more compressed than those of the lower first molar. This tooth is the homologne of the probably deciduous molar (cl. 2) in other * In the fossil specimen figured in plate 147, of my " Odontography," the left molar /, exhibits all the above-described gradations of use ; but the right molar, r, through some accident to the opposing tooth in the lower jaw, has not been so worn, but projects beyond the level of the left molar, with the mammillated margins of the plates en- tire. j1 These are also the dimensions of the first lower molar figured by Mr. Corse, loc. cit. pi. vi. ./?, and./?i/. 3; but I have seen the first lower molar of smaller dimensions. TEETH. Ungulates ; it is not a mere miniature of the great molars of the mature animal, but re- tains, agreeably with the period of life at which it is developed, a character much more nearly approaching that of the ordinary Pa- chydermal molar, manifesting the adherence to the more general type by the minor com- plexity of the crown, and by the form and relative size of the fangs. In the transverse divisions of the crown we perceive the affinity to the Tapiroid type, the different links con- necting which with the typical elephants are supplied by the extinct Lophiodons, Dino- theriums, and Mastodons. The sub-division of the summits of the primary plates recalls the character of the molars, especially the smaller ones, of the Phacochere in the Hog- tribe. As the elephant advances in age the molars rapidly acquire their more special and complex character. The first molars are completely in place, and in full use at three months, and are shed when the elephant is about two years old. The sudden increase and rapid develop- ment of the second molar may account for the non-existence of any vertical successor to the former tooth, or " premolar," in the elephant. The eight or nine plates of the crown are formed in the closed alveolus, behind the first molar by the time this cuts the gum, and they are united with the body of the tooth, and most of them in use, when the first molar is shed. The average length of the second molar is two inches and a half; ranging from two inches to two inches and nine lines. The greatest breadth, which is behind the middle of the tooth, is from one inch to one inch three lines. There are two roots : the cavity of the small anterior one expands in the crown, and is continued into that of the three anterior plates. The thicker root supports the rest of the tooth. The second molar is worn out and shed before the beginning of the sixth year. The third molar has the crown divided into from eleven to thirteen plates ; it averages four inches in length, and two inches in breadth, and has a small anterior, and a very large posterior root ; it begins to appear above the gum about the end of the second year, is in its most complete state and exten- sive use during the fifth year, and is worn out and shed in the ninth year. The last rem- nant of the third molar is shown at m. 3, fig. 592. It is probable that the three teeth above de- scribed are homologous with the deciduous mo- lars, d. 2, d.3, and d. 4. in the Hyrax and hor.se. The fourth molar presents a marked supe- riority of size over the third, and a somewhat different form : the anterior angle is more obliquely abraded, giving a pentagonal figure to the tooth in the upper jaw (Jig. 592. m. 4). The number of plates in the crown of this tooth is fifteen or sixteen : its length between seven and eight inches ; its breadth three inches. It has an anterior simple and slender root supporting the three first plates ; a second of larger size and bifid, supporting the four next plates ; and a large contracting base for the remainder. The fore-part of the grinding surface of this tooth begins to pro- trude through the gum at the sixth year : the tooth is worn away, and its last remnant shed, about the twentieth or twenty-fifth year. It may be regarded as the homologue of the first true molar of ordinary Pachyderms (in. 1). The .fifth molar, with a crown of from seventeen to twenty plates, measures between nine and ten inches in length, and about three inches and a half in breadth. The second root is more distinctly separated from the first simple root than from the large mass behind. It begins to appear above the gum about the twentieth year : its duration has not been ascertained by observation ; but it probably is not shed before the sixtieth year. The sixth molar appears to be the last, and has from twenty-two to twenty-seven plates ; its length, or antero-posterior extent, following the curvature, is from twelve to fifteen inches : the breadth of the grinding surface rarely exceeds three inches and a half. The reproductive power of the matrix in some cases surpasses that of the formative development of the cavity for lodging the tooth, and the last lamellae are obliged to be folded from behind forwards upon the side of the tooth. Fig. 99, p. 233. of my " History of British Fossil Mammals," shows this condition in the last lower molar of the Mammoth. One may reasonably conjecture that the sixth molar of the Indian elephant, if it make its appearance about the fiftieth year, would, from its superior depth and length, continue to do the work of mastication until the pon- derous Pachyderm had passed the century of its existence. Mr. Corse has figured the sixth molar, (which he calls the seventh or eighth,) with twenty-three plates, in tab. x. of his Memoir, and a small cavity, c, is marked as an in- cipient alveolus for a succeeding grinder. Had it actually been such, it might have been expected to contain some calcified portions of the anterior plates of such succeeding grinder. The molar teeth, in all the species of elephant, succeed each other from behind forwards, moving, not in a right line, but in the arc of a circle, shown by the curved line in Jig. 592. The position of the growing tooth in the closed alveolus (m. 5) is almost at right angles with that in use, the grinding surface being at first directed backwards in the upper jaw, and forwards in the lower jaw, and brought, by the revolving course, into a horizontal line in both jaws, so that they oppose each other, when developed for use. The imaginary pivot on which the grinders revolve is next their root in the upper jaw, and is next the grinding surface in the lower jaw ; in both, towards the frontal surface of the skull. Viewing both upper and lower molars as one complex whole, subject to the same revolving movement, the section dividing such whole into upper and lower portion runs TEETH. 927 parallel to the curve described by that move- ment, the upper being the central portion, or tliat nearest the pivot, the lower, the pe- ripheral portion : the grinding surface of the upper molars is consequently convex from behind forwards, and that of the lower molars concave : the upper molars are always broader than the lower ones. The bony plate forming the sockets of the growing teeth is more than usually distinct from the body of the maxillary, and participates in this re- volving course, advancing forwards with the teeth. The partition between the tooth in use and its successor is perforated near the middle ; and, in its progress forwards, that part next the grinding surface is first absorbed ; the rest disappearing with the absorption of the roots of the preceding grinder. There are few examples of organs that manifest a more striking adaptation of a highly complex and beautiful structure to the exigencies of the animal endowed with it, than the grinding teeth of the elephant. We per- ceive, for example, that the jaw is not en- cumbered with the whole weight of the mas- sive tooth at once, but that it is formed by degrees as it is required ; the division of the crown into a number of successive plates, and the subdivision of these into cylindrical pro- cesses, presenting the conditions most favour- able to progressive formation. But a more important advantage is gained by this sub- division of the tooth ; each part is formed like a perfect simple tooth, having a body of dentine, a coat of enamel, and an outer in- vestment of cement : a single digital pro- cess may be compared to the simple canine of a Carnivore ; a transverse row of these, therefore, when the work of mastication has commenced, presents, by virtue of the different densities of their constituent sub- stances, a series of cylindrical ridges of ena- mel, with as many depressions of dentine, and deeper external valleys of cement : the more advanced and more abraded part of the crown is traversed by the transverse ridges of the enamel inclosing the depressed surface of the dentine, and separated by the deeper channels of the cement : the fore-part of the tooth exhibits its least efficient con- dition for mastication ; the inequalities of the grinding surface being reduced in proportion as the enamel and cement which invested the clentinal plates have been worn away. This part of the tooth is, however, still fitted for the first coarse crushing of the branches of a tree : the transverse enamel ridges of the succeeding part of the tooth divide it into smaller fragments, and the posterior islands and tubercles of enamel pound it to the pulp fit for deglutition. The structure and pro- gressive development of the tooth not only give to the elephant's grinder the advantage of the uneven surface which adapts the mill- stone for its office, but, at the same time, secure the constant presence of thre most efficient arrangement for the finer comminu- tion of the food, at the part of the mouth which is nearest the fi.uces. With regard to the microscopic structure of the peculiar modification of dentine called " ivory," this is characterised partly by the minute size of the tubes, which, at their origin from the pulp cavity, do not exceed T7ri.__th of an inch in diameter, in their close arrangement at intervals scarcely exceeding the breadth of a single tube, and, above all, on their strong and almost angular gyrations, which are much greater than the secondary curvatures of the tubes of ordinary dentine. The dentinal tubes of ivory, as they radiate from the pulp-cavitv, incline obliquely towards the pointed end of the tusk, and describe two slight primary curves, the first convex towards that end, the second and shorter one concave ; these curves in narrow sections from near the open base of the tusk are almost obscured by the strong angular parallel secondary gyrations. The tubes divide dicho- tomously, at acute angles, and gradually de- crease in size as they approach the periphery of the tusk. The characteristic appearance of decussating curved stria?, with oblique rhomboidal spaces, so conspicuous on transverse sections or frac- tures of ivory, is due to the refraction of light caused by the parallel secondary gyrations of the tubes above described. The strong con- tour lines observed in longitudinal sections of ivory, parallel with the cone of the pulp-cavity, and which are circular and concentric when viewed in transverse slices of the tusk, are commonly caused by strata of minute opaque cellules, which are unusually numerous in the interspaces of the tubes throughout the sub- stance of the ivory, and by their very great abundance and larger size in the peripheral layers of cement. The close-set lateral branches of the calcigerous tubes unite with the tubuli of the cells. The decomposition of the fossil tusks into superimposed conical layers takes place along the strata of the opaque cellules, and directly across the course of the calci- gerous gyrating tubes. The radiated cells of the true cement are larger and more uniform in size and shape ; many of them approach nearer the circular figure than in ordinary teeth ; the long axis of the more elliptical ones is parallel with the plane of the stratum of cement ; their average diameter is ^^^th of an inch, and their interspaces sometimes do not exceed that dimension. The cemental tubuli appear from their course, and sometimes from the overlapping of the substances in the sections examined, to be directly continued from the tubuli of the ivory ; but Retzius expressly denies the continuation, and states that the cemental tubes at both the outer and the inner surface of the cement have terminations of less diameter than their middle part. This is exact with respect to the major part of the cement. In that near the base of the tusk I have seen a few vascular canals. The contour lines of the cement are usually wavy, and not parallel with the line of the outer surface of the ivory. In the tusks of the Hfrtxlwlun gigrtiilcus the 928 TEETH. outer layer of cement is relatively thicker than in the tusks of the Mammoth or in those of the Indian elephant. The general cha- racter of the microscopic structure of the ivory of the Mastodon's tusk is the same as that of the elephant. The peripheral ex- tremities of the dentinal tubes are, in some parts of the tusk, straighten than in the rest of their course ; the straighten extremities were those which were first formed in the calcification of the peripheral part of the pulp, and this first-formed ivory is accordingly, in such parts, more like the ordinary dentine, and is analogous to the thin peripheral cap of such substance in the teeth of the Sloth and of some fishes. The pulp soon, however, becomes subject to that modification of the calcifying processes by which the more tortuous disposition of the tubuli and the more frequent interposition of opaque cellules are produced ; mollifications which, in establishing the characters of ivory, present a step in the transition from true dentine to osteo-dentine. By the minuteness and close anrangement of the tubes, and especially by their strongly undulating secondary curves, a tougher and more elastic tissue is produced than results from their disposition in ordinary dentine ; and the modification which distinguishes " ivory " is doubtless essential to the due degree of coherence of so large a mass as the elephant's tusk, projecting so far from the supporting socket, and to be frequently applied in dealing hard blows and thrusts. The central part of the tusk, especially near the base of such as have reached their full size, is occupied by a slenden cylindrical tract of modified ivory, perforated by a few vascular canals, which is continued to the apex of the tusk. It is not uncommon to find processes of osteo-dentine or imperfect bone-like ivory, projecting in a stalactitic form * into the interior of the pulp-cavity, apparently the consequence of partial inflam- mation or malformation of the vascular pulp. The musket-balls and other foreign bodies which are occasionally found in ivory, are immediately surrounded by osteo-dentine in greater or less quantity. It has long ceased to be a matter of wonder how such bodies should become completely imbedded in the substance of the tusk, sometimes without any visible aperture, or how a leaden bullet may have become lodged in the solid centre of a very large tusk without having been flattened. Such a ball, aimed at the head of an elephant, may penetrate the thin bony socket and the thinner ivory parietes of the wide conical pulp-cavity occupying the inserted base of the tusk ; if the projectile force was there spent, the ball would gravitate to the opposite and lower side of the pulp-cavity, as indicated in Jig. 592.f The presence of the foreign body * Ilaller seems to have been the first to notice these irregular internal deposits in the pulp-cavity of the elephant's tusk. Elementa Physiologic, torn. viii. p. 519. t Camper, " Description Anatomiquc d'un Ele'- exciting inflammation of the pulp, an irregular course of calcification ensues, which results in the disposition around the ball of a certain thickness of osteo-dentine. The pulp then resuming its healthy state and functions, coats the inner surface of the osteo-dentine in- closing the ball, together with the rest of the conical cavity into which that mass projects, with layers of normal ivory.* The portion of the cement-forming capsule surrounding the base of the tu.sk, and the part of the pulp, which were perforated by the ball in its passage, are soon replaced by the active reparative power of these highly vascular bodies. The hole formed by the ball in the base of the tusk is then more or less completely filled up by a thick coat of cement from with- out and of osteo-dentine from within. Traces of such a cicatrix closing the entrance have been more than once noticed : and Blumen- bach deduced, therefrom, a property in the elephant's tusk to pour out bony matter in order to heal such wounds. The reparation is however effected by the calcification of the reproduced parts of the capsule and pulp. By the continued progress of growth, the ball so inclosed is carried forwards, in the course indicated by the arrow \nfig. 592., to the middle of the solidified exserted part of the tusk, as in the example in Blumenbach's collection which he considered so curious. Should the ball have penetrated the base of the tusk of a young elephant, it may be carried forwards by the uninterrupted growth of the tusk until that base has become the apex, and be finally exposed and discharged by the con- tinual abrasion to which the apex of the tusk is subjected. Yet none of these phenomena prove the absolute non-vascularity of the tusk, but only the low degree of its vascularity. Blood circulates, slowly no doubt, through the minute vascular canals which are con- tinued through the centre of the ivory to the very apex of the tusk : and it is from this source that the fine tubular structure of the ivory obtains the plasmatic colourless fluid by which its low vitality is maintained. Development. — The matrix of the tusk con- sists of a large conical pulp, which is renewed quicker than it is converted, and thus is not only preserved, but grows, up to a certain period of the animal's life : it is lodged in the cavity at the base of the tusk ; this base is surrounded by the remains of the capsule, a soft vascular membrane of moderate thickness, which is confluent with the border of the base of the pulp, where it receives its principal vessels. phant Male," fol. p. 54. Cuvier, Annalcs du Mu- se'um, torn. viii. (1806) p. 115. * Cuvier, " Annales du Museum," torn. viii. p. 115, 1806, " Sur les defenses des elephans, la structure, I'accroissement, les caraeteres distinctifs de 1'ivoire, et sur les maladies," first clearly stated that the ball or foreign body in the tusk of the elephant was immediately surrounded by a substance different from the regular ivory. The great anatomist ob- serves, " To ute la portion d'ivoire en dehors de la balle est semblable au reste ; il n'y a que ce qui 1'entoure immcdiatement qui soit irre'gulier." TEETH. 929 I had the tusk and pulp of the great ele- phant at the Zoological Gardens longitudinally divided, soon after the death of that animal iu the summer of 1847. Although the pulp could be easily detached from the inner surface of the pulp-cavity, it was not without a certain resistance, and when the edges of the co- adapted pulp and tooth were examined by a strong lens, the filamentary processes from the outer surface of the pulp could be seen stretching, as they were withdrawn from the dentinal tubes, before they broke. They are so minute that, to the naked eye, the detached surface of the pulp seems to be entire, and Cuvier was thus deceived in concluding that there was no organic connection between the pulp and the ivory.* As the learned professor who has contributed the article " PACIIYDER- MATA " adopts Cuvier's description of the formation of the teeth of the elephant by deposition and transudation of the tissues from free surfaces of the formative organs, I have the more valued the rare opportunity of testing and confirming, by examination of the recent animal, the account of the processes of conversion of those organs into the dental tissues, which I gave in my " Odontography." Each molar of the elephant is formed in the interior of a membranous sac — the capsule, the form of which partakes of that of the future tooth, being cubical in the first molar, oblong in the last, and rhomboidal in most of the intermediate teeth ; but always decreasing in vertical extent towards its posterior end, and closed at all points, save where it is penetrated by vessels and nerves. It is lodged in an osseous cavity of the same form as itself, and usually in part suspended freely in the maxillary bone ; the bony case being destined to form part of the socket of the tooth. The exterior of the membranous capsule is simple and vascular, as shown at m. 5, fg. 592. ; its internal surface gives attachment to numerous folds or processes, as in most other Ungulate animals. The dentinal pulp rises from the bottom of the capsule, or that part which lines the deepest part of the alveolus, in the form of transverse parallel plates extending towards that part of the capsule ready to escape from the socket. These plates adhere only to the bottom of the capsule ; their opposite extremity is free from all adhesion. This summit is thinner than the base ; it might be termed the edge of the plate: but it is notched, or divided into many digital processes. The tissue of these digitated plates is identical with that of the dentinal pulp of simple Mammalian teeth ; it becomes also highly vascular at the parts where the formation of the dentine is in active progress. Processes of the capsule descend from its summit into the interspaces of the dentinal pulp-plates, and consequently resemble them in form ; but they adhere not only by their * Annales du Muse'um, torn. viii. (180C), p. 94. The account is repeated verbatim in the posthumous edition of the " Ossemens Fossiles," 183G. VOL. IV. base to the surface of the capsule next the mouth, but also by their lateral margins to the sides of the capsule, and thus resemble partition-walls, confining each plate of the dentinal pulp to its proper chamber ; the margin of the partition opposite its attached base is free in the interspace of the origins of the dentinal pulp plates. The enamel organ, which Cuvier appears to have recognised under the name of the internal layer of the capsule, is distinguishable by its light blue sub- transparent colour and usual microscopic texture, adhering to the free surface of the partitions formed by the true inner layer of the capsule. Although the enamel-pulp be in close contact with the dentinal pulp prior to the commencement of the formation of the tooth, one may readily conceive a vacuity between them, which is continued uninter- ruptedly, in many foldings, between all the gelatinous plates of the dentinal pulp, and the partitions formed by the combined enamel- pulp and the folds of the capsule. According to the excretion-view, this delicate apparatus must have been immediately subjected to the violence of being compressed in the unyielding bony box, by the deposition of the dense matters of the tooth in the hypothetical vacuity between the enamel and dentinal pulps ; a process of absorption must have been con- ceived to be set on foot immediately that the altered condition of the gelatinous secreting organs took place ; and, according to Cuvier's hypothesis, the secreting function must be supposed to have proceeded, without any ir- regularity or interruption, while the process of absorption was superinduced in the same part to relieve it from the effects of pressure produced by its own secretion. The formation of the dentine commences immediately beneath the membrana jrropria of the pulp: a part which Cuvier distinctly recognised, and which he accurately traced as preserving its relative situation between the dentine and enamel throughout the whole formation of the dentine, and discernible in the completed tooth " as a very fine greyish line, which separates the enamel from the in- ternal substance " or dentine. The calcification and conversion of the cells of the dentinal pulp commence as usual at the peripheral parts of the lamelliform pro- cesses furthest from the attached base. It may readily be conceived, therefore, that, at the commencement, there is formed a little cap upon each of the processes into which the edges of the pulp-plates are divided. As the centripetal calcification proceeds the c;ips are converted into horn-shaped cones ; when it has reached the bottom of the notches of the edge of the pulp-plate all the cones be- come united together into a single transverse plate ; and, the process of conversion having reached the base of the pulp-plate, these plates coalesce to form a common base to the crown of the tooth, which would then present the same eminences and notches that charac- terised the gelatinous pulp, if, during the period of conversion, other substances had 3 o 930 TEETH. not been formed upon the surface and in the interspaces of the pulp-plates. Coincident, however, with the formation of the dentine, is the deposition of the hard- ening salts of the enamel in the extremely slender prismatic cells, which are for the most part vertical to the plane of the inner surface of the folds of the capsule to which they are attached ; these cells or moulds give a sub- transparent bluish tint to the enamel pulp. The true inner part of the capsule forms those thick transverse folds or partitions which support the enamel organ, and with it fill the interspaces of the dentinal pulps. With re- gard to the formation of the cement, Cuvier, after citing the opinion of Tenon — that it was the result of ossification of the internal layer of the capsule, and that of Blake — that it was a deposition from the opposite surface of the capsule to that which had deposited the enamel, states his own conviction to be that the cement is produced by the same layer and by the same surface as that which has produced the enamel. The proof alleged is, that so long as any space remains between the cement and the external capsule, that space is found to contain a soft internal layer of the capsule with a free surface next the cement. The phenomena could not, in fact, be otherwise explained according to the "ex- cretion theory " of dental development. To the obvious objection that the same part is made, in this explanation, to secrete two different products, Cuvier replies, that it un- dergoes a change of tissue : " Whilst it yielded enamel only it was thin and transparent ; to give cement it becomes thick, spongy, and of a reddish colour." * The external characters of the enamel organ and cement-forming cap- sule are correctly defined ; only, the one, in- stead of being converted into the other, is in fact changed into its supposed transudation : the enamel fibres being formed, and properly disposed in the direction in which their chief strength is to lie, by the assimilative proper- ties of the pre-arranged elongated prismatic non-nucleated cells, which take from the sur- rounding plasma the required salts and com- pact them in their interior. Whilst this process is on foot, and before the enamel fibres are firm in their position, the capsule begins to undergo that change which results in the formation of the thick cement ; the calcifying process commences from several points, and proceeds centrifu- gal ly, radiating therefrom, and differing from the ossification of bone chiefly in the number of these centres, which, though close to the new-formed enamel, are in the substance of the inner vascular surface of the capsular folds. The cells arrange themselves in con- centric layers around the vessels, and act * " Settlement clle change de tissue : taut qu'elle ne dounait que de 1'e'mail, elle plait mince et t/ai's- parente ; pour dormer du cortical elle devient c'paissc, spongieuse, opaque et rougeatre." — Annales du Museum, torn. viii. p. 99 ; Ossemens Fossiles, ed. ls:i I, 8vo. tom. i p. 514. Art. PACHYUEKMATA, p. 8U9. like those of the enamel pulp in receiving into their interior the bone-salts in a clear and compact state ; during this process they be- come confluent with each other, their piimi- tive distinctness being indicated only by their persistent granular nuclei, which now form the radiated Purkinjian corpuscles. The in- terspaces of the concentric series of confluent cells become filled witli the calcareous salts in a rather more opaque state, and the con- version of the capsule into cement goes on, according to the processes more particularly described in the Introduction to my " Odon- tograph y," until a continuous stratum is formed in close connection with the layer of enamel. The uncalcified part of the capsule, always much softer than cartilage, is very readily detached from the calcified part, and to the naked eye the separated surface seems entire, and might readily pass, as with Cuvier, for a secreting surface. But the fine vascular processes which have been torn from the medullary canals of the calcified part are conspicuous, and resemble viili, when the detached surface is examined, even with a moderate magnifying power, under water. Calcification extending from the numerous centres, the different portions coalesce and progressively add to the thickness of the ce- ment until all the interspaces of the coronal plates and the whole exterior of the crown is covered with the bone-like substance. The enamel-pulp ceases to be developed at the base of the crown, but the capsule continues to be formed pan passu with the partial formation of the pulp, as this continues, pro- gressively contracting, from the base of the crown, to form by its calcification the roots. The calcification of the capsule going on at the same time, a layer of cement is formed in immediate connection with the dentine. The circumscribed spaces at the bottom of the socket to which the capsule and dentinal pulp adhere, where they receive their vessels and nerves, and which are the seat of the progres- sive formation of these respective moulds of the two dental tissues, become gradually con- tracted, and subdivided by the further localis- ation of the reproductive forces to particular spots, whence the subdivision of the base into roots. The surrounding bone undergoes cor- responding modifications, growing and filling up the interspaces left by the dividing and contracting points of attachment of the re- siduary matrix. All is subordinated to one harmonious law of growth by vascular action and cell-formation, and of molecular decre- ment modifying form by absorption. Me- chanical squeezing or drawing out have no share in these changes of the pulp or capsule ; pressure at most exercises only a gentle stimulus to the vital processes. Cuvier be- lieved that there were places where the den- tinal pulp and the capsule were separate from each other. I have never found such except where the enamel-pulp was interposed be- tween them in the crown of the tooth, or where both pulp and capsule adhered to the periosteum of the socket, below the crown. TEETH. 931 Cuvier affirms that the number of fangs of an elephant's molar depends upon the number of points at which the base of the gelatinous (dentinal) pulp is attached to the bottom of the capsule; and that the interspaces of these attachments constitute the under part of the crown or body of the tooth, the attachments themselves forming the first beginnings of the fangs. True to his hypothesis of the forma- tion of the dental tissues by excretion, he says * that the elongation of the fangs is pro- duced by two circumstances : first, the pro- gressive elongation of the layers of osseous substance (dentine) which force the tooth to rise and emerge from its socket ; secondly, the thickening of the body of the tooth by the addition of successive layers to its inner sur- face, which, filling up the interior cavity, leaves scarcely room for the gelatinous pulp, and forces it down into the interior of the roots. This pulling up of the fang on the one hand, and squeezing down the pulp on the other, are forces too gross and mechanical to be admitted in actual physiology to explain the growth of the root of a tooth or of any other organised product ; such modes of explanation were, however, inevitable in adopting the excretion theory of dental development. With regard to the homologies of the com- plex molars of the Proboscidian quadrupeds, a species of insight which may come to be deemed, in the course of anatomical science, as of equal import to the knowledge of the formative processes of parts, I must admit that the mere fact of the marked and dispro- portionate increase of size of the first of the three last molars over its predecessor — the last of the first three that are developed — may appear but a feeble support to the analogical evidence on which, chiefly, I have classed the three last developed molars of the elephant, in a category distinct from that of their smaller predecessors. But the value of such indica- tion and analogy will begin to be apparent when we examine the condition of dental development in the primeval forms of Pro- boscidians. I have already shown that the typical character of the Diphyodont dentition was more closely and generally adhered to in the genera that existed during the oldest ter- tiary periods in geology than in their actual successors : it became of course highly inter- esting to inquire whether the miocene Mas- todons, the earliest of the great Proboscidian quadrupeds of which we have any cognizance, manifested any analogous closer adhesion to type than their elephantine successors, and whether they would afford any actual proof of the true deciduous nature of the first, * " Ces racines et les pedicules qui leur servent de noyaux s'alongent ensuite par deux raisons : d'abord les progres des lames de substance osseuse qui, s'alon- geant toujours, forcent la dent a s'elever et a sortir de 1'alveole ; ensuite Pe'paississement du corps de la dent par la formation des couches successives qui, en remplissant le vide inte'rieur, n'y laissent presque plus de place pour le noyau gelatineux, et le refoulunt vers 1'interieur des tubes des racines." Annnles du Museum, viii. 1807, p. 108 ; Osseui. Fossiles, 1834, p. 527. second, or third molars, by the development of a vertical successor or premolar. Cuvier first ascertained the fact, though without ap- preciating its full significance, in a specimen of the upper jaw of the Mastodon angustidetix from Dax, in which the second six-lobed deciduous molar was displaced by a four- lobed or quadricuspid premolar developed above it and succeeding it vertically.* The same important fact was subsequently con- firmed by Dr. Kaup in observations of the Mastodon longirostris of the miocene tertiary deposits of Eppelsheim.f This satisfactorily proves the true deci- duous character of the first and second molars ; and that the third molar in order of appear- ance J, is also one (the last) of the de- ciduous series, is indicated by the contrasted superiority of size of the ante-penultimate tooth, which I regard as the first of the true molar series. The great extent and activity of the pro- cesses of dental development required for the preparation of the large and complex true molar teeth would seem to exhaust the power, which, in ordinary Pachyderms, is expended in developing the vertical successors of the deci- duous teeth. In the primeval Mastodons above cited, this normal exercise of the reproductive force was not, however, wholly exhausted, anil one premolar, of more simple form than its deciduous predecessor, was developed on each side of both jaws. But even this trace of ad- herence to the archetypal dentition is lost in the more modified Proboscidians of the pre- sent day. Another and very interesting mark of adhe- sion to the archetype is shown by the deve- lopment of two incisors in the lower jaw in the young of some of the Mastodons, by the retention and development of one of these inferior tusks in the male of the Mastodon giganteus of North America, and by the reten- tion of both in the European Mastodun longi- rostris. No trace of these inferior homotypes of the great premaxillary tusks have been detected in the foetus or young of the existing elephants. In the gigantic Dinotherium the upper in- cisors were suppressed, and the two lower incisors were developed into huge tusks, which curved down from the symphvsis of the massive under jaw. Most of the grinders had two transverse ridges on the crown, as in the Tapir ; two deciduous molars, if not three, were succeeded vertically by two premolars, the second of which (p. 4 of the typical series) closely resembles the true molars, as in other Perissodactyles. The typical dentition is departed from in the existing Hippopotamus by the early loss of p. 1, and the reduction of the incisors to Q 9 ~- in both jaws : in the extinct Hippopota- mus of India p. 1 was longer retained, and the * Ossemens Fossiles, 4to. ; Divers Mastodontes, pi. iii. jffy. 2. t Ossemens Fossiles de Darmstadt, 1835, pi. 1. j Odontography, pi. 144,,/fy. 11, rf.3 3 o 2 932 TEETEI, 3—3 incisors were in normal number — - - ; whence O «3 the term Hexaproiodon proposed for this inter- esting restoration by its discoverers, Cautley and Falconer. I have before remarked that the even-toed or artiodactyle Uiigulata superadd the cha- racters of simplified form and diminished size to the more important and constant one of vertical succession in their premolars. These teeth in the Ruminants, e. g. (Jig. 580., VII., MOSCHUS, p. 2, 3, 4), represent only the moiety of the true molars, or one of the two semi-cylin- drical lobes of which those teeth consist, with at most a rudiment of the second lobe, as Cuvier very accurately describes*, and F. Cuvier figures in pi- 94. of his useful work, " Dents des Mammiferes." An analogous morphological character of the premolars will be found to distinguish them in the dentition of the genus Sits (figured in my " Odontography," pi. 140., figs. 1 and 2), in the Hippopotamus (ib. pi. 143.), and in the Pkacoc/iwrus (ib. pi. 141.), where the premolar series is greatly reduced in number : yet this instance of a natural affinity manifested in so many other parts of the organisation of the artiodactyle genera has been overlooked in F. Cuvier's work above cited, although it is expressly designed to show how such zoological relations are illus- trated by the teeth. Confiding in the accuracy of the Baron Cuvier's division of the hoofed quadrupeds into " Pachyderms " and " Rumi- nants," M. F. Cuvier separates the non ru- minant Artiodactyles from the ruminant ge- nera of the same natural division by interposing the Tapir, Hyrax, Rhinoceros and Elephant ; whilst the horse, which, in the size and com- plexity of its premolars, as well as in many other characters, agrees closely with the other perissodactyle Pachyderms, is placed in close juxtaposition with the Rumiuants.f Most of the deciduous molars of the Rumi- nants resemble in form the true molars; the last, e.g. (f. c. - — 2—2 = 18. The canines are rudimental, and are absorbed rather than shed. The deciduous incisors are shed before the young animal finally quits the pouch : when this takes place, the dentition is : — , A m — 1 9 • • i_i' a' l'2-2~ the upper incisors being i. 1, the molars d. 3 and d. 4 of the typical dentition. This stage is exemplified in the lower jaw at A, fig. 594. The next stage shows the acquisition of i. 2 in the upper jaw, and m. 1 in both jaws, and the formula is : — At one year old, the dentition is : — • 3—3 . 2—2 2—2 i. . rt.w. , m. = 24 ; 1— I 2—2' 2—2 the additional teeth being i. 3 and m. 2 (c, fig. 594. ; in which the demonstration of the true deciduous character of d. 4 and d. 3 is shown by the germ of their vertical successor, ' Odontography, p. 376, \ , signifying male and female, anil the like ; and it is time that the anatomist should avail himself of this powerful instrument of thought, instruction, and discovery, from which the chemist, the astronomer, and the mathematician have obtained such important results. (R. Owen.) TEMPERAMENT. Although all indivi- duals of the same species arc composed of the same tissues, consisting of the same elements both proximate and ultimate, and agreeing in all essential points of chemical constitution, yet there exist between certain groups of them, sometimes in the most striking degree, differences not only in the physical powers and actions of their frames, but also in their mental qualities. These differences are refer- rible only to peculiarities in the constitution of an individual, or in other words, to pecu- liarities in the quality of his solids and fluids, which are of a nature so recondite that we cannot detect them by any chemical or ana- tomical means, and we appreciate them only by the character with which they impress the physical and, to a certain extent, mental actions of the individual in which they exist. To ex- press this character in one word physiologists employ the term temperament. The use of this word is of very ancient date. We trace it as far back as the time of Galen, who broached the doctrine that the blood consisted of four humours, correspond- ing to the four elements ; these were respec- tively designated bills, saitguis, atra bilis, ph/cgma. Nunc, says Haller, ex ejusmodi quatuor humoribus sanguinem aicbant tcmpc- raii, justamque omnium principiorum commis- tionem perfectinsimum temperamenitim efficere; si vero aut sanguis supra legitimam suam quasi dosin abundaret, sive bilis, sive terra atrave bilis, sive phlegma, quatuor tune sim- plicia et praecipua temperamcnta aiebant oriri, a bilis abundautia c/iolerieiim, ah aquae uber- tate phlcgnialictini, a sanguinis aucta portione 3 o 4 936 TEMPERAMENT. sangwneum, et denique a copia atrse bills me- lancholicum.* This view of the doctrine of temperaments prevailed in the schools down to the time of Cullen, and we find that able and thoughtful physician thus expressing himself upon the subject : " The ancients very early established a distinction of temperaments which the schools of physic have almost universally adopted ever since, and appears to me to be founded on observation. I am very much of opinion, that we can perceive a combination of a particular state of the chief circumstances of the economy to take place very steadily in certain persons, and thereby to form at least two of the temperaments assigned by the an- cients." \ The temperaments, the existence of which seems most consistent with observation, are those admitted by Cnllen, namely, the sangui- neous and the melancholic, the phlegmatic being a degree or modification of the sanguineous, and the choleric of the melancholic. It is reasonable to expect an infinite variety as regards the extent to which the character- istic marks of the temperaments are manifested in various individuals. Taking examples which afford good indications, the two temperaments above referred to may be described as follows, after Cullen. Individuals of the sanguine temperament have the quantity of fluids in the body large in proportion to the solids, the habit of body soft and plump, after the period of manhood disposed to obesity, and at all times, readily sweating upon exercise, the skin smooth and white, the hair soft, generally of a pale colour or from thence passing through different shades to a red ; the complexion ruddy, the eyes com- monly blue ; the strength of the whole body- is moderate, and the mind sensible, irritable, cheerful, and unsteady. The most exquisite examples of this temperament are found in men from the time of puberty to that of man- hood, and in women. In both sexes the cha- racteristics of the temperaments are far less manifest in old age. In persons of the melancholic temperament the hain't of the body is rather hard and mea- gre, the quantity of fluids in the whole system moderate in proportion to the solids, the sim- ple solids firm and dense, the hair hard, black, with a tendency to curl, the skin coarse, of a dun colour, with a corresponding complexion, the eyes very constantly black, the strength considerable, the mind slow, disposed to gra- vity, caution and timidity, with little sensibi- lity or irritability, but tenacious of all emotions once excited, and therefore of great steadiness. This temperament is most completely formed in advanced life, hut the characters of it ap- pear often very early.']: By some writers a nervous temperament is admitted, the prominent characteristic of which consists in a great excitability of the nervous system, and a predominance of * Haller, El. Physiolog. lib. v. sect. 4. t Mat, Med. j Cullen, loc. cit. emotional impulses over the influence of the will. Individuals of this temperament are generally fidgetty and restless, take but little sleep, and are anxious about trifles ; they are called " creatures of impulse;" their emotions are easily excited, and often not readily sub- dued. In persons of this temperament, when labouring under disease, phenomena referrible to the nervous system are very apt to compli- cate and often to obscure the morbid actions. This temperament, however, cannot be s;iid to exist apart from the sanguineous or me- lancholic : it always accompanies either one or the other, most frequently the former, and the most exquisite examples of it are found in the female sex. In looking at the physical conditions of the best-marked examples of the sanguine and melancholic temperaments, it is im- portant to ascertain whether any one pro- perty or quality stands out more prominently than the rest, which might seem to give to the whole economy of the individuals its peculiar cast. It appears to me that there is no single physical property which is so closely associated with difference of temperament as variety in the quantity, and perhaps also in the kind, of colouring matter or pigment, evinced by the colour of the hair and skin, and influ- encing also the colour of the eyes, and of the blood, and of the nervous centres. Individuals of the melancholic temperament exhibit in their various tissues a considerable amount of pigment, as shown by the dark co- lour, generally black, of the hair and eyes, while on the other hand those of the san- guine temperament are deficient in colour, having light hair, blue or grey eyes, and fair or white skins. Observations are yet wanting, in sufficient number, to determine the relative amount of colouring matter in the blood of individuals of each of these temperaments, or to ascertain whether it is characterised by any peculiar chemical qualities. It seems highly probable that the amount and kind of colouring matter in the skin, hair, and eyes, as well as of that in some of the secretions, as bile, urine, &c. is influenced by the amount and kind of the haematine. The xanthous and Icucous races of man in- habiting for the most part cold or temperate climates, afford the most numerous examples of the sanguine temperament, while the me- lano-comous or dark races found chiefly in warm climates are mostly of the melancholic temperament. And those individuals of the xanthous and Icucous races, which in physical characters approach most nearly to the dark races, as by the existence of a large quantity of dark pigment in their tegumentary tissues, are of the melancholic temperament, whilst the light-coloured members of the xanthous races are prone to exhibit the characters of the sanguine temperament. If it be admitted that a constant connection exists between colour and temperament, as I think is sufficiently obvious, it would follow that the nature of the temperament is deter- mined by certain peculiarities in the physical TEMPORO-MAXILLARY ARTICULATION. 937 condition of the frame. These peculiarities react to a certain extent upon the mind, and more or less aid or clog its workings, but cer- tain powers and modes of action of the mind are by no means so constantly associated with certain states of body, as to connect the men- tal and bodily states as cause and effect. It is true that the sanguine temperament is ge- nerally accompanied by a mind exhibiting certain characters, but the exceptions to this are so numerous that we cannot assign the corporeal state as the cause of the mental — nor vice versa. Bodily peculiarities are in- finitely more frequently inherited than mental, — the powers and activity of the mind are greatly determined by education and training; but those qualities of body which give a cha- racter to its temperament are born with it ; and although they may be modified by exter- nal influences, they are yet at all times suf- ficiently distinct to prove them to be inherent physical properties of the entire organism. At the same time it seems reasonable to admit that the mind has its temperaments, as the body has, and in a great measure inde- pendently, and the terms, sanguine, melan- cholic, phlegmatic, and choleric, may be severally applied to them, according as the emotions and feelings, and the intellectual actions vary in their modes and degrees of developement, and in their rate of working. (R. B. Todd.) TEMPORO-MAXILLARY ARTICU- LATION.— Under this heading I propose to give a brief account of the jointing of the lower maxilla to the cranium. This joint can- not, of course, be identified out of the verte- brata. The mandibles and maxillae of the ar- ticiilnta are not homologous with the jaws of vertebrate animals, and the slit of their mouths is placed vertically not horizontally. In the human subject, as in all mammalia, this articulation takes place between the squamous portion of the temporal (squamosal) and the inferior maxillary bones. The description of the anatomy of the human temporo-maxillary joint comprises, therefore, that of the diarthro- dial articular surfaces of those bones, and also of the following parts : viz., the interarticuiar fibro-cartilage, the two synovial sacs, the ex- ternal and internal lateral and other liga- ments, and part of the insertion of the external pterygoid muscle. Hones. — The articular condyle of the lower jaw is sub-cylindroid in form, its length from side to side being greater than its antero-pos- terior measurement. The axis of this c} limler, however, is set neither directly from side to side, nor yet exactly level, its inner part being posterior to and below its outer; so that if the axes of the two condyles were produced inwards till they met, they would form an angle in doing so, which would point down- wards and backwards, — reaching the anterior margin of the foramen magnum. The carti- lage that encrusts this condyle extends further down behind than in front. The surface to which this condyle is (mediately) articulated forms a part of the glcnoid fossa, and is situated just below the base of the zygomatic process of the temporal bone, between its roots. It has such form as, in respect of the set of its axis, and its tranverse measurement, pretty accurately fits the condyle. It has, however, a greater antero-posterior extent, in accordance with the capability which this joint normally pos- sesses, in addition to the usual ginglymoid motion, of an antero-posterior gliding to and fro of the condyle — a kind of normal disloca- tion. The glenoid fossa of the temporal bone contains a portion of the parotid gland, as well as the condyle of the inferior maxilla ; the former occupies that portion of it which is posterior to the glasserian fissure, whilst that part which is anterior to the glasserian fissure, is lined with cartilage for the articulation of the latter. In man there is usually no bony ridge bounding this articular surface pos- teriorly, such as is generally found in the lower mammalia. The ridge that bounds it anteriorly is formed by the inferior root of the zygoma, and the cartilage is continued some way on to this ridge. Externally it is limited by a tubercle on the zygoma, which serves for the attach- ment of the external lateral ligament of the joint. Interarticuiar fibro-cartilage. — This is a thin disc or meniscus, oval or sub-oblong in form, concave below and convex above, thus capping the condyle, thicker at the edges than in the middle, where it is not unfrequently thinned away even to perforation. It differs from all the other fihro-cartilages in having muscular fibres inserted into it; namely, a portion of those of the external pterygoid. This insertion takes place along its anterior border, and by it the fibro-cartilage is made to join in that normal amount of dislocation for- wards, which as above stated, the condyle of the lower maxilla is capable of, as well as in the abnormal accidental dislocation of the jaw. It is further held in its place by the fibres of the external lateral ligament, and by the synovial bursae of the joint. Synovial Bursts, — These are two in num- ber, one above the interarticuiar fibro-carti- lage and the other below it. The upper one is the larger and slacker, for it alone is con- cerned in the antero-posterior gliding of the joint. The two sacs, of course, communicate and are reduced to one when the interarti- cuiar fibro-cartilage is perforated in the centre. Ligaments. — There is only one ligament in immediate relation with the temporo-maxil- lary joint, namely, the external lateral. This is a small ligament, broader above than below, situated at the outside of the joint; attached above to the tubercle situated at the point of divergence of the roots of the zygoma; and directed downwards and backwards to the outside of the neck that supports the condyle of the lower jaw. Midway in its passage from the one to the other it is attached by its inner aspect to the interarticuiar fibro-cartilage. 938 TEMPORO-MAXILLARY ARTICULATION. The internal lateral ligament is a long thin slip extending from the spinous process of the sphenoid, and the neighbouring parts of the temporal bone to the fore part of the lip of the inferior dental canal. It lies behind the external pterygoid muscle, by the origin of which its cranial attachment is concealed, and it is separated from the temporo-maxillary joint by a considerable space through which pa>s the internal maxillary artery and vein, giving off their middle meningeal and inferior dental branches, which indeed are conducted, the former to the foramen spinosum of the sphe- noid, the latter to the inferior dental canal, by the ligament in question. Numerous stray fibres of ligamentous tissue strengthen the synovial sacs of the temporo- maxillary joint, forming a kind of capsn/ar ligament. That process of the cervical fascia, which is called the stylo-maxillary ligament, is gene- rail}' enumerated as one of the ligaments of this joint. It extends from the styloid process to the lower part of the ram us of the jaw, separating the parotid from the submaxillary gland, and affording attachment to the stylo- glossus muscle. The condyle of the lower jaw depends for the maintenance of its normal apposition to the temporal bone much more upon the masseter, temporal and pterygoid muscles than upon these small ligaments ; by these, however, its astcro-posterior gliding is indifferently tethered. Muscles. — The external pteri/goid-muscle, proceeding backwards and outwards from its origin, is mainly inserted into the front of the neck that supports the maxillary condyle, the upper part of it, however, is inserted into the interarticular fibre-cartilage, which thereby is drawn forward along with the condyle when this muscle acts. This insertion is tendinous. Motions of the joint. — The temporo-maxil- lary joint admits o^aginglymoid motion in the vertical direction, by which the mouth is opened and shut. This motion must of ne- cessity a'ways take place in the joints of both sides at the same instant. It also admits of a horizontal antero-posterior gliding motion, in which the joint of one side only may be mainly concerned. In the human subject the front teeth of the lower jaw, in most cases, are not ex- actly opposed to those of the upper jaw — that is, the summits of the one set are not applied to the summits of the other — in the ordinary position of the month, either when at rest or engaged in mastication. The lower incisor teeth are usually posterior to the upper. But when we bite with the front teeth we bring the upper and lower set into apposition by thrusting forward the lower jaw : in this act both joints are similarly concerned. We can also execute a grinding motion from side to side, and this is done by thrusting forward one condyle whilst the other merely revolves on the axis of its neck. The jaw is elevated or closed by the tem- poral, masseter, and pterygoid muscles. The pterygoid, chiefly the external, are the agents in protruding it. These latter are antagonised by the elevating and also by the depressing muscles. The chief depressor of the lower jaw is the digastric, as is clearly shown by its comparative anatomy, but all those which ex- tend from the chin to the hyoid bone are capable of, and occasionally do assist in per- forming this act. The majority of the muscular fibres that elevate the jaw arrive at their insertion into it from before backwards ; thus the masseter has a kind of twist in the arrangement of its fibres, so that those which arise most anteriorly are inserted very conspicuously furthest back, whilst the remainder proceed directly downwards or slightly forwards ; a considerable portion of those of the temporal, namely, those which arise from the anterior part of the temporal fossa, run backwards to their insertion into the coronoid process. The use of this arrangement seems, upon a careful consideration of the mechanics of the question, to be the application of the elevating or closing force in a more favourable direc- tion, not, as might seem at first sight, the protrusion of the lower jaw — that is amply effected by the ptcrygoideus externns. ABNORMAL CONDITIONS OF THE TEMPORO- MAXILLARY JOINT. — Accidents. — The condyle of the lower jaw can only be dislocated in one direction, namely forwards. In this accident the condyle slips forward over the inferior root of the zygoma, and is then drawn somewhat upwards within the zygomatic arch. The inter- articular cartilage is carried with it, Thisusualiy happens to the joints of both sides, but occa- sionally one condyle only is dislocated. It is usually produced by the action of the muscles when the mouth is very widely opened, as in yawning, or more especially in biting a very large object, such as a large apple. When both the condi/les are dislocated, the lower jaw is thrust forwards and cannot be re- tracted. The mouth is widely open and the patient is unable to close it. The power of swallowing is lost, and the saliva, the secretion of which is probably increased, flows from the mouth involuntarily. Articulation is difficult, owing to the impossibility of making the labial sounds. There is a conspicuous depression beneath the zygoma just in front of the ear, and a flatness in the masseteric region. The coronoid process is much depressed, and forms a visible protuberance beneath the zygoma, and, as first observed by Mr. Adams of Dub- lin, there is a prominence in the temporal re- gion between the eyebrow and the ear, pro- duced by the posterior fibres of the temporal muscle being pushed up by the condyle in its new position. If this dislocation remains unreduced, the parts, as in most other dislocations, gradually accommodate themselves to their new position, so that the power of articulation and deglu- tition is re-acquired, the mouth can be closed, and a considerable amount of motion is re- gained, but the chin remains abnormally thrust forwards, and there is always a depression in the position normally occupied by the con- dyle. TEMPORO-MAXILLARY ARTICULATION. When one condyle only is dislocated, the chin is thrust forwards and towards one side — that, namely, on which the condyle remains in place. The coronoid process of the dis- located side forms a prominence even more conspicuous than when both condyles are displaced, but the mouth is not so wide open. There is, of course, the same depression in front of the ear, and the same flatness of the masseteric region. Congenital malformation. Dr. R. W. Smith of Dublin, in his Treatise on Fractures and Dislocations,* gives a detailed account of the dissection of a highly interesting case of " Con- genital luxation of the inferior maxilla." The malformation affected one side only, — the right, — and consisted mainly of an absence, or arrest of development of the condyle, the only vestige of which was a small process hooked inwards at its apex. This process did not touch the temporal bone by a quarter of an inch, and neither it nor the surface oppo- site to it presented any articular cartilage, but were both simply invested with periosteum. There was no trace of an interarticular fibro- cartilage, nor of a synovial sac, and the ex- ternal lateral ligament sloped downwards and forwards instead of downwards and backwards. The glenoid cavity did not exist, or rather the inferior root of the zygoma, which really forms the gleiioid cavity, was not developed. There was conspicuous atrophy of the whole of this side of the face in respect of the bones — temporal, right half of the body and right ramus of the inferior maxilla, malar, su- perior maxillary, and even the right half of the sphenoid, — and muscles, but the nerves •were as large as their fellows. The most re- markable of the peculiarities of the surround- ing parts, and that which clearly demonstrated the abnormal condition not to be the result of injury or disease, was an extreme shortness of the zygomatic process of the the temporal and a compensatory unusual length of that of the malar bone. The former was only half an inch long, whilst the latter was nearly twice as long as that of the other side. During the lifetime of this patient, who was an idiot, it was observed that one side of his countenance did not match the other, and that the dis- parity was much increased when he opened his mouth. He was often observed to have spasmodic twitching of the abnormal side of his face. Disease. — Chronic rheumatic arthritis occa- sionally affects this articulation. Both jointsare usually affected by it, but sometimes it attacks the joint of one side only. It is most common in elderly subjects. When it attacks the young or middle aged, it is more rapid, accompanied with more pain, and more likely to involve the neck of the condyle and the ramus of the jaw. The pain is often very severe but varia- ble, apparently influenced by meteorological changes. The lymphatic glands in the neigh- bourhood of the diseased joint are much prone * A Treatise on Fractures in the Vicinity of Joints and on Certain Forms of accidental and congenital Dislocations. Dublin, 1847. 8vo. to enlargement ; and sometimes the enlarged condyle can be felt as a bony tumour just in front of the ear. The chin is thrust forward, mesially when both joints are affected, and towards the healthy side, as well as forwards, when only one is diseased. The motion of the jaw is considerably impaired. On dissection, the condyle, in cases of this affection, is gen- erally found to be large and broad, but some- times conical, rough, and devoid of cartilage. Ivory or porcellanous deposit, so common in other joints when affected with chronic rheu- matic arthritis, is but rarely met with in this ; those abnormal ossific concretions in and around the joints, which are so constantly met with in the disease in question in other situations, have also never been found in the temporo-maxillary joint. The interarticular fibre-cartilage had disappeared in every case of this affection which lias been dissected and published. The glenoid cavity is enlarged, divested of its articular cartilage, and presents a roughened, abnormal surface. All indica- tion of the disease stops suddenly at the glas- serian fissure, and at the sphcno-temporal suture, and the enlargement of the gknoid cavity takes place at the expense of the lower root of the zygoma which generally becomes entirely absorbed. In the report of the proceedings of the Pathological Socety of London in the Medical Gazette of November 30. 1849, there is an account of a highly interesting case of necrosis of the condyle, back part of the ramus, and angle of the lower jaw in a scrofulous boy. The portion of necrosed bone, which was ex- hibited to the society, was removed many years before, by Mr. Keate, who also had examined the patient, grown to a healthy man, two years before the date of the com- munication. As far as could be ascertained by external investigation, the lost portion of bone had been perfectly restored. There was no deformity, and no impairment of motion. There are two other similar cases on record ; one by Desault, in which the whole ramus, with the condyle and coronoid process, were removed, the other by Mr. Syme, in which the condyle and ramus were necrosed. In both these cases, also, the lost bone was per- fectly restored to all external appearance, but there is no record of a dissection of such a case. In some cases which are on record, where the whole of the lower jaw, with both its condyles, has been removed, its place has been supplied by condensed fibrous tissue, but there has been no reproduction of bone. Anchylosis of the temporo-maxillary joint is a very rare occurrence. There is, however, one specimen of it in the Pathological series of the Museum of the London College of Surgeons. The fusion of the two bones is complete, as is shown in the preparation by a vertical, side to side, section through the situation of the quondam joint. This section shows that a perfectly normal-looking cancel- lous structure, shelled over by a layer of dense osseous tissue, is continued from the temporal to the inferior maxillary bone, and exhibits no 940 TEMPORO- MAXILLARY ARTICULATION. manner of trace to indicate where the joint once was. In fact this anchylosis had existed for fifty years before the death of the patient. No record is preserved of the cause of it. The joint of one side only is anchylosed, but that of the other side is much altered in form. An abnormal tubercle of bone projects down- wards from the middle of the glenoid cavity and is received into an abnormal excavation or alveolus in the middle of the condyle. The lower jaw is much wasted in size, and has lost all its teeth save the two front incisors. The upper jaw hones are thin and light. The motion of the lower jaw is often lost owing to an affection not immediately con- nected with the joint itself. When, as often happens in scarlatina, cancrum oris, &c. there is extensive sloughing of the inside of the cheeks, the cicatrices resulting from the heal- ing of the great wounds contract, and form bands, extending from the upper to the lower jaw, so strong and unyielding that the muscles which open the mouth are unable to antago- nise them. COMPARATIVE ANATOMY. — If a palasonto- logist were asked what fragment of a verte- brate skeleton, speaking generally for all ver- tebrata, would give him most information as to the status and affinities of the animal to which it belonged, he would most probably answer — the articular portion of the lower jaw or the articulation that receives it. Of the convex and concave surfaces which go to form this articulation, in all the mammalia the convexity is on the inferior maxilla, and the concavity on the squamosal bone, whilst in the three other vertebrate classes the re- verse is invariably the case — the concavity is on the interior maxilla, the convexity on the bone that articulates with it. The under jaw does not articulate with the same, or to speak more accurately, with the homologous bone in all vertebrate animals. In all the mammalia it articulates, as in man, with the squamous element of the temporal — the squamosal bone. In birds, reptiles, and osseous fishes it articulates with bones which are clearly the special homologues of the tym- panic ring of the human subject. In cartila- ginous fishes its articulation is with the ptery- goid bone, the homologue of the human internal pterygoid plate. The Lepidosiren, in which so many other characters of the osseous and cartilaginous fishes are so curi- ously blended together, in strict accord with this circumstance, presents an instance of the pterygoid and tympanic bones contributing each a part — the former the inner, the latter the outer part, of the articular surface for the reception of the lower jaw.* It is well worth while to stop here and review what is stated in the two preceding paragraphs. What is said is, really, this ; — every animal that suckles its young has a con vex articular surface to its lower jaw, whilst every vertebrate that lays eggs has a concave sur- face. Or this — every vertebrate animal that * Owen. has hair upon it, that has a diaphragm, or an epiglottis, has a convex articular surface to its lower maxilla, whilst all vertebrates that are destitute of these have a concave surface. Or, again, all animals that suckle their young, and have diaphragms, hair, and epiglottides, present their squamosal bones for the articu- lation of their inferior maxillae, whilst all in which the possession of these characters is negatived present for this articulation their tympanic, or, rarely, their pterygoid bones. Can any physiological reason be assigned for this ? Can any final purpose, holding good in all, or in the majority of, instances, be shown to be served by this difference ? I think none can. One cannot conceive but that it is a matter of perfect indifference whether the convexity is on this bone or that. Let us look once more to the facts. The bat that flies, but not the swallow, the whale that swims but not the cod-fish, the camel that walks the desert, but not the ostrich, the carnivorous lion, seal, and weasel, but not the eagle, penguin, crocodile, and shark, have convex articulations to their lower jaw and present to them their squamosal bones. Here then is a caveat for the physiologist. A character found in an animal may have no physiological signification, — no relation to external circum- stances, nor even a functional connexion with, or dependence on other characters wherewith it coexists, perhaps invariably. It may be clue to the status only of the animal. Physiolo- gically independent it may exist in an animal only because other independent characters co-exist. It may be a Syncilogy, not a Tcleo- i°gy- That certain independent characters in- variably go together, which was so elaborately illustrated by Cuvier, is a fact of a high order, perhaps the twilight of some great truth. If future investigations should prove that truth to be progressive developement, towards which hypothesis the inquirer is, even now, tempted by so many striking facts, as well as by the admirable use that can be made of it as a scaffold theory, then we should say, and as making use of a scaffolding we may say it now, that certain characters are attained to at a cer- tain stage in the chain of development, and, therefore, those are found coexisting which are proper to the degree of development to which the animal has arrived. Such characters I have been accustomed to call Syncilogies *, a word which at all events has the merit of re- ferring only to a well known fact, without in- volving any hypothesis. To the palaeontologist this " correlation of independent characters " f is, of course, invaluable, anil for the purpose of arranging natural groups in the animal kingdom, these, so to speak, useless, or Syneilogical, cha- racters are immeasurably more valuable than those modifications to meet special exigencies which are called teleologies. Afammalia. — In all mammalia, except man, the articular surface on the squamosal bone is bounded posteriorly, or, in the rodents, intcr- * a-vv, el (/.I, Xo'yofi Cuvier. TEMPORO-MAXILLARY ARTICULATION. nally, by a prominent ridge or process. This is the case in the higher Quadrumana, and there is an indication of it even in the lower races of mankind. In the Cin-nivora the con- dyle is in general extremely long, cylindroid, and its length is set, almost or quite directly from side to side, whilst the surface to which it is opposed is bounded by a very salient ridge fore and aft. This condition attains its acme in the Badger, where the salient ridges, especially the posterior, even arch over and surround the cylindroid condyle so much, that in the dry skull the lower jaw remains at- tached to the cranium without any artificial contrivance, and can be removed only by slipping each half out sideways when the sym- physis has been disjoined. With such a joint there cannot, of course, be the usual lateral motion of the jaw. In the Rodentia, on the contrary, the long diameter of the con- dyle is directed antero-posteriorly, and is ad- apted to an antero-posterior groove, mostly bounded, internally and externally, by salient ridges. Hence that nibbling, antero-posterior motion of the jaw, which is so conspicuous in these animals, and with which their teeth and masticatory muscles are in such admirable relation. This only holds good in respect of the placental rodents. In that great marsupial rodent, the Wombat, the saliently arched, cylindroid condyles have the usual side to si le and converging-behind set of their long diameters. The articular surface which is opposed to this condyle is placed, as in the plaeental rodents, on the zygomatic process, which in both runs almost directly outwards; instead, however, of being an antero-posterior groove it is a transverse convex cylindroid, describing a retreating curve ; so that in the tcmporo-maxillary joint of the wombat a cylin- droid ridge is opposed to another cylindroid ridge, the one describing a salient, the other a retreating arch.* The articular facets of the temporo-maxillary joint in the Ruminant/a approach more nearly to plane surfaces than in any other animals. The squamosal facet is bounded by a ridge posteriorly, but has no bony limitation in front. This is in re- lation with the extensive lateral movement of the jaw which these animals use in chew- ing the cud, and with the limited power of gaping which they possess. The rest of the mammalia present varieties in this joint which are extremely interesting, but an account of them would occupy more space than the limits of this work permit. Aves. — In birds, as above stated, the arti- cular surface of the lower mandible is con- cave, and is adapted to the tympanic bone, or, as the older ornithologists called it, the os quadratum.f The articular surface of the lower jaw presents two concave depressions. The tympanic bone is itself moveable, being articulated to the cranium by two diarthrodial joints, so that a bird's lower jaw is swung to the head by two moveable jointings. * See Art. MAKSUPIAI.IA, iig. f Soe Art, AVES. 94. Rcplilia. — The evenly concave articular surface of a reptile's lower jaw is often con- tributed to by more than one of the osseous pieces which compose the inferior maxilla of the oviparous vertebrates. In the crocodile by two, in some chelonia by three of these pieces. The tympanic bone is articulated with the other cranial bones by suture, and is therefore immoveable, in the Crocod/lin and Chelonia, but it is articulated with them by diarthrosis, and therefore moveable, in the Laccrtia, Op/tidia, and lialracliia. In some ophidia, as the Python, there being, properly speaking, no symphysis of the lower jaw, but instead of it an elastic ligament, holding the two halves together at the chin, one temporo- maxillary joint is capable of movement inde- pendently of the other. In the Batrachia, among their many fish-like characters is that of a dismemberment of the tympanic bone, which consists of an upper and a lower piece. Pisces. — In the majority of fishes, the tympanic bone is represented by four separate pieces called epi-, hypo-, meso-, and prae- tympanic bones. These, further, bear upon their posterior edge three opercular bones, which were considered by GeorFroy St. Hilaire to be the homologues of the ossicula auditus, but are regarded by Prof. Owen as append- ages, serially homologous with the costal appendages. The uppermost piece, the epi- tympanic, articulates by a diarthrodial joint with the mastoid, and the lowermost, hypo- tympanic, presents a diarthrodial convexity to the lower jaw. The four tympanic pieces arti- culate with one another, and with the oper- cular bones by the interposition of ligament, or rather membrane, connecting their thin ad- jacent edges together, so that the whole appa- ratus is capable of bilging outwards in the movements of respiration. In the eel tribe (Murtemdae) the number of tympanic bones is reduced to three, which is obviously an approach towards the two tympanic pieces of the Batrachia. The formation of the cranial part of the joint in question by the pterygoid and tympanic bones conjointly, in the Lepido- siren has been mentioned above. In the Sharks and Rays the tympanic pedicle descends upon that part of the pterygoid which forms the joint, but does not actually reach the articula- tion, the pterygoid being interposed. In these fishes, the super-maxillary and pterygoid pieces being confluent, and both bearing teeth, it ap- pears at first sight that the whole upper jaw is formed by the former alone, consequently that the inferior maxilla is articulated directly with the super-maxillary ; such an articulation, however, never takes place in any animal. The interarticular fibro-cartilctge is con- stantly met with in Mammalia, but in neither of the other vertebrate classes. Homology of the joint. — The joint in ques- tion is the articulation between the plcura- pojyhysis and the hcemapopliysis of the frontal vertebra. It is therefore serially homologous with the joint between the rib and the costal cartilage of mammalia, or the vertebral and sternal ribs of birds and reptiles. 942 TERATOLOGY. The joints connected with the maxillary points: 1. To the original malformation of apparatus of some of the animals belonging the germ ; 2. To the subsequent deformation to the three lower sub-kingdoms are, as was of the embryo by causes operating on its stated in the beginning, not homologous with development. this joinc, although identical in function. For I. Original ma/formation of the germ. — If, description of these parts see the articles according to the opinions generally adopted at ANNELIDA, ARACHNIDA, CEPHALOPODA, CIR- the present time, the germ may be considered RHOPEDA, CRUSTACEA, ECHINODERMATA, as a product of secretion by the female organ - ENTOZOA INSECTA, MYRIAPODA, and ROTI- ism, upon which the male sperm acts with its material and vital influence, we may suppose FERA. (S. 7?. Pittard.) that this germ may be originally malformed, owing to some influence proceeding either from the female or from the male sex. 1. Such a primitive malformation of the TERATOLOGY. — Under this name, which we owe to Geoffrey St. Hilaire, we un- derstand the doctrine of congenital deformi- germ seems to exist in those cases in which fief.* In a scientific sense, it constitutes a the same kind of monstrosity is repeatedly part of Pathological Anatomy, and demands procreated by the same parents. The cause our interest as much as the knowledge of may be ascribed : — those other deviations from the normal state, rt> To the mother. — It is a very important which is ordinarily regarded as constituting fact that, in such cases, various degrees that science. In fact, pathological anatomy of the same species of deformity are fre- comprises all the anomalies of the organiza- quently produced in successive progression, tion ; those which occur during intra-uterine so that the first born child is the most de- life are called congenital, and those which formed; and in the following children the arise during extra-uterine life acquired. We deformity progressively decreases, .and finally refer to the former the imperfections of the disappears in the last born (G. Vrolik, Vering). primitive formation, or what we call men- Sometimes a deformity of the mother is com- strosities. They are those deviations of the municated to her offspring ; for instance, con- organism which can be formed only in the genital luxation of the femur. earliest periods of gestation, or, at least, pre- £. TO the father. — Experience proves that viously to the termination of the foetal con- a well-formed man may procreate with dif- dition. ferent women children with the same mal- The opinions now held with respect to formation (Meckel, Luber), and that a cle- these malformations differ widely from the formity of the father may be transmitted to absurd notions which influence the descrip- the cliild (Burdach, Osiander). The last is tions given of them by Aldrovandi, Ambrose however rare. Pare, Licetus, Palfin, and Rueff. Formerly, 3. A second proof in support of the pro- indeed, each monstrosity was considered as bability of an original mallbrmation of the the presage of some misfortune, the warrant germ js found in hereditary deformities ex- of divine vengeance, the effect of witchcraft, tending over more than one generation, viz. &c. Lycosthenes used to go so far as to hare-lip, excessive number of fingers, hi/po- add to the description of each monster the spadias, &c. picture of some calamity which was to be its 3. A third proof may be deduced from the sequel. To that opinion they owe their name, possibility that the ovarian ova in man and derived from the Latin verb monstrare. jn the lower animals may be already inal- Their aetiology was not less strange and in- formed (Bischoff ). correct. Rueff' in 1580, devoted a whole n. Deformation of the originally well-fanned chapter to the inquiry, " An homines ex dsc- germ. — I. It is said that this may be produced monibus et rursus daemones ex hominibus in- Dy niental impression of the pregnant woman, f-intes concipere possunt ? " and ^Casparus ol- what the German authors call das Vcrsehen. Schottus treated the subject in "about the But for this opinion no positive proof can be same style.f afforded. According to the observations pnb- Theyboth give negative answers to the ques- lj,,lletl thereupon, and of which a great deal may tion, trusting to have proved by this means De found in the learned article GENERATION that monsters are not procreated by sexual of this Cyclopedia, all the supposed mental intercourse of women with the devil. Other impressions, which have been considered as wri'ers have endeavoured to explain the cause the cause of malformations, took place, with from copulation with brute animals, or with few exceptions, in the last stage of preg- pregnant or menstruating women. Notwith- nancy.* And even in those cases in which an standing our more enlightened modern ideas earlier period may be certified, we could object on this subject, the origin of monstrous births that the pout hoc must not always lead to the remains still very mysterious. The opinions conclusion crgopropter hoc. It is of some im- concerning it may be reduced to two mam portance to appreciate the correctness of this * From •«'«*?, monster ; and *»y«£, science. * See my publications in Tijdschrift v. Natuur- * From «?«?, monster ; am *°y°s, sciei • x. _ * See my publications in Ti}dschrift v. JNatuur- f I. Ruetius de Conceptu et Generatione Hommis. ]y]ic geschiedenis en Physiologic, d.iv. bl. 221, en Francof. ad M. 1580. P. Casparus Schottns e t()] ell ijamibi d. zichtch. Outlurh. d. i. bl. Societate Jesu, Physica curiosa, aucta et correcta, 33^ kJlM. - J ' n t • sive Mirabilia Natnrie et Artis. Lib. i. § xxn. TERATOLOGY. 943 reasoning, for the theory of the mental im- pressions, which was so readily adopted in the barbarous middle ages, as a mode of saving poor and innocent women from torture and stake, finds even in the present clay more ad- vocates than might have been expected. Of this I was convinced at the Congress of Naturalists at Aix-la-Chapelle in 1 847, and in the Report of the Transactions of the Sc/i wci- zerischcn Ndlurf. Gesdlschaft zu Chin; 29, 30, 31 Juli, 1844, in which the affected mind of the pregnant woman is said to produce a mysterious effect on the fetus, and that the medium by which this influence is com- municated may be the hearing as well as the sight ! To crown all these absurdities, we see mentioned in Rust, Alugasin, B. xxi. S. 261., that a woman gave birth to a child with im- perfect bones, which is attributed to her having been present, before her pregnancy, at the execution of a criminal by breaking on the wheel. To all these fantastical considera- tions I oppose the following arguments : — a. That malformations seldom, or perhaps never, agree with apprehensions or fears a priori of pregnant women (G. Vrolik, T. Zimmer, J. J. Plenck, and Burdach). On the contrary, it often happens that a woman who has once procreated a malformation, and is continually troubled by the fear of another similar sad occurrence, may become the happy mother of a second well-formed child. b. That the fetus, even when a germ, is quite independent ; transferred from the ovary into the uterus, it needs for its developement a material intercourse with the maternal body, but no organic connection ; for which reason it can be formed as well without as within the uterus, as in extra-uterine pregnancy ; that it stands in no connection, either vascular or nervous, with the body of the mother, and that therefore it is improbable that her mental condition can have any influence whatever upon the form of the fetus. c. That malformations occur likewise among the inferior animals, — insects, testaceous ani- mals, echinodermata, — in which the develope- ment of psychical life is very imperfect, and the oviparous generation of which must pre- serve the young from the influence of dis- ordered maternal imagination. (I. That in the case of twins, as the ace- phali specially show, one child may be mal- formed and the other in perfect condition, notwithstanding they were both exposed to the same influences. e. That more deeply situated organs, the very existence of which may be unknown to the pregnant woman, may be malformed ; as for instance, the heart, the intestinal tube, &c. If now, on all these grounds, I exclude the mental impressions of pregnant women from the aetiology of malformations, I do not mean to deny the influence which by her somatic condition the mother may exercise upon the fetus. Thus, if in consequence of mental agitation, her body were to suffer a violent shock, this might have a prejudicial influence on the material transmission which takes place between her and the fetus, and the latter might thereby become morbidly affected. There are instances of its being the subject of intermittent fever (P. Russell) ; of sudden death occa- sioned by frightful agitation of the mother (Wienholdt) ; of jaundice communicated by the mother (Kerckring) ; of small-pox (Jen- ner, Montgomery, Friedlander) ; of syphilis and scarlet fever (R. Lee), all derived from the mother. But all this is entirely different from the effect of mental impressions. It is a material result, easily conceived, and of which physiologists need no further explanation. 2. A second cause of malformation of the fetus is sought in external injury suffered by women during their pregnancy. Meckel goes so far as to reject this entirely. In some de- formities, for instance, in hy drops vcntriculo- ruin cerebri, the effect of external injury is easily proved. 3. A third cause is attributed to diseases of the ovurn and of the fetus. Simpson (Edinburgh Med. and Surg. Journal, No. 127., April, 1836, and Gazette Medicate de Paris, Nov. 1836, p. 393.) has described an acute and chronic form of placentitis, to which ought to be ascribed all those singular ex- udations which attach themselves to the fetus as pseudo-membranes. Fig. 595. gives a s-pe- cimen of adhesion of the placenta to the head of a fetus deformed by urania. F/g. 595. Ectopla cordis and adhesion of the Placenta. In fg. 596. a pseudo-membrane passes to TERATOLOGY. the forehead, round which is twisted the um- bilical cord. Fie/. 596. Kerckring* inveighed in a spirited and in- genious manner against the strange accounts which were formerly given of these moke. To the diseases of the placenta are referred enlargement (Kyll, Pierrard, Devilliers), con- gestion and apoplexy (J. Clarke, Dangan), calcareous concretions (Hannover). For the cetiology of malformations, this pathological anatomy of the placenta is, however, very un- productive. None of these can be explained by it, nor were any accompanied by these pla- cental diseases. Nor does the nosology of the foetus afford us much more information, notwithstanding the monograph given by J. Gmesser.f It cannot, however, be denied, that some of Us diseases may give rise to deformities ; for in- stance, chronic inflammation of the brain to hydrops vcntriculorum ccrebri, and this again to Acrania. . Perhaps also, as Rokitansky states, a morbid condition of the valves may be the cause of some congenital abnormities of the heart. Yet, notwithstanding all this, the diseases of the foetus can only, in a very limited sense, be assigned as the cause of its malformation ; and hence the opinion of Otto, who ascribes , to this source a great many malformations, In some, but very rare, cases, the coats of ou(T,n tQ be rejectet|. the ovum are destroyed, and the foetus is nn- | A fourtn) aild assuredly very general, mediately attached to the inner surface of the ^^ of maiformation, consists in impeded de- uterus ( Steinmetz). It is not to be denied, that ve|opement of tne foetus by some remote and un- through these pseudo-membranes some mal- twirt£n ^nil<5p. it is matter of dispute whether formations of the foetus may be occasioned, as Montgomery has proved, such as the truncation " ' xtremities, which he names self-ampu- tation. Further than this, however, we may not go, for the brides placentaires of Professor St. Hilaire are certainly not a universal cause of monstrosity. They are too accidental and unstable to be such. The existence of mal- formations in eggs which Geoffroy St. Hilaire coated over with varnish or wax, affords no proof of the possibility of a mechanical origin of monstrosities. The exclusion of the air pre- vents, in such a case, the necessary material change in the ovum, in consequence of which the perfect developement of the foetus is im- paired. The morbid state of the coats of the ovum may likewise cause the so-called wzote, which, according to their consistency, are divided into moles fungosa:, carnosa;, cruenta:, and tcndinosce. Valentin* distinguishes in the san- guineous mass of mola carnosa a net of vessels, from which the blood issues. It is the vas- cular net of the chorion, in which the mass of blood has been collected, in consequence of too -"" "- j through these pseudo-membranes some mal- feno^n cause- it js matter of dispute whether formations of the foetus may be occasioned, as this jeform;ng cause operates on the foetus in Montgomery has proved, such as the truncation .^ totajity> or whether it affects originally of the extremities, which he names self-ampu- Qnly Qne tenl) whjch spreads its deforming i,,i\m, Further than this, however, we may inf1uence over ail the others This last idea was embraced by Tiedemann, who at first de- duced all monstrosities from some defect of the vascular, and later from the nervous system. In opposition to this hypothesis, I suggest the following considerations. a. It is opposed to anatomical evidence. The cyclopia, whose nature consists in a more or less simplified eye and a displaced or absent external nose, is attributed by Tiede- mann to the original absence of olfactory nerves, producing the deformation of the nasal cavity, and the original fusion of the optic nerves, and of the thalami nervorum opticorum effecting the simplification of the eye. I have found, however, in cyclopes, more than once, olfactory nerves, and have likewise seen that there was no constant con- currence between the simplified form of the eye and of the optic nerve. A double optic nerve may be found with a single eye-ball (Eller, Henermann). With complete dupli- cation of the internal parts of the eye, and even with two separate eyes, I found a single optic nerve, and likewise a double, though not complete, as well as a single eye-ball, notwithstanding the entire absence of the optic nerve. Similar facts are quoted by Haller and G. F. Wolff. Hare-lip with cleft TERATOLOGY. 945 palate is attributed by Tiedemann to the original absence of olfactory nerves. G. Vrolik found them, however, in children with hare-lip. The nerves of organs may exist, although the organs themselves may be ab- sent (Seiler, W. Vrolik); and inversely, the nerves may be wanting, while the organs are present (C. G. Buttner). In anenccphali the body is very massive, notwithstanding the imperfect condition of the nervous centres. In double monsters there is no definite corre- spondence between the condition of the nerv- ous system and the duplication of the body (W. Vrolik).* b. Embryogenesis teaches that the forma- tion of the several parts of the body is not essentially the result of that of the nervous system, but that, on the contrary, each part is formed and developed independently. I refer to what I have already said, in 183t> (in my treatise on Cyclopia), and am happy to find J. Muller, Kathke, Bischoft', Burdach, and Stannius, with me on this subject. What is now proved for the nervous system, may equally be applied to the system of blood- vessels; and hence I presume to conclude, that no malformation whatever proceeds from a central system, but is occasioned merely by impeded developement, the cause of which remains concealed. This impediment may be confined to one part, or may be extended over more. This extension may sometimes stand either in causal connexion with an original malformation, as for instance the dis- placing of the nose in cyclopes ; or may take place in an entirely independent manner. In the latter case, it is a complication of mal- formation, which proves that it may extend itself to more than one region of the body, and to more than one apparatus. I have met with an instance of this, in which to acrania, cychpia, and absence of the lower jaw, was added ectopia of the intestines. If the origin of the malformation is derived from impeded developement, the so-called monstra per defectum are the result, and from excessive formation arise the monstra per excessum. The malformations occasioned by impeded developement may, for the most part, be com- pared with the natural forms through which the foetus passes in its normal developement. On this is founded the ingenious idea of Meckel, previously suggested by Wolff, that most malformations are caused by arrest of developement (btidungshemmung), for which reason they must be said, according to Bischoff, to be formed through arrested de- velopement (Jiemmungsbildungen). They, how- ever, never give us a perfect representation of the form at which the foetus has been arrested in its developement, because the in- creased growth and the progressive nutrition of the foetus cannot but make an important * On this suliject I have given copious elucida- tion in the Treatise on Cyclopia in Transactions of the First Class of the Royal Netherlaad Institute, l«:ifi, vol. v. p. 25. ; on Double Monsters, ibid. 1840, vol. ix. ; and Ilandbuch, vol. i. 1840. VOL. IV. mollification therein. As the transient, forms of the human foetus are for the most part comparable to the persistent forms of the lower animals, the malformations occasioned by impeded developement often acquire a brute appearance ; and thus a reason is at the same time given why they exhibit, in dif- ferent animals, the form of the lower, but not of the higher classes. A consequence of this mode of origin is, that they never deviate so much from the normal form as would exclude them from the rank of organized beings; and that the devia- tions from the natural form are confined within definite limits, so that they always re- remind us more or less of the regular form. Fixed laws of organization prevail in them, by which they exhibit a certain fitness of organization, and a tendency to render the capacity for life as great as possible, not- withstanding the malformation. Peculiar vi- tal relations are hereby produced adapting them for uterine life, and many are brought forth well nourished and at full time. Most, however, are unfit for life after birth, though for very different reasons. The following remarks may serve for the elucidation of these peculiar vital accommo- dations : — 1. We never see in malformed births, dis- similar parts fused or united with each other, such as the intestinal tube with the aorta, the arteries with the nerves, &c. Each part, therefore, retains, to a certain degree, its own independence, according to what Fleisch- mann denominates lex proprietatis. The gullet sometimes coalesces with the larynx, and the bladder with the rectum ; but these parts are not originally dissimilar, being developed from a common mass. 2. The malformed parts are restricted to their determinate place, according to what Fleischmann denominates lex topicorum. 3. No malformed organ loses entirely its own character, and no malformed animal loses its generic distinction. It is, therefore, justly observed by Soemmering, that nature does not deviate ad infnitum, and that even in mon- strosities a distinct gradation and natural or- der are observable. An immediate consequence of this must be, that in one and the same sort of monstrosity, there are different degrees of malformation, varying from the greatest possible degree to the very least. We might thus consider the different monstrosities as so many genera, and their varieties as so many species, where- by, according to J. T. Meckel, a new or- ganic kingdom is constituted, differing only from the others by less constancy of form. Consequently a definite type prevails in the generation of monstrosities, and they are subjected to fixed organic laws. This order appears even — 1 . In the number in which they occur within a certain space of time. In 3000 births in Paris, there occurs about one monster (J. Geoffroy St. Hilaire). 2. In the sex. In impeded developement, the mal- formed children are more frequently female, 3 p 946 TERATOLOGY. in some sorts of double monsters, male. 3. In a definite proportion between the species of the animals, and the most frequent monstrosities in them. Cyclopes, for instance, especially with a snout, occur most frequently in swine ; double monsters in man. 4. In the constant form r>f monsters, even amongst the most heteroge- neous animal's. Cyclopia, double monsters, acrania, have in Birds precisely the same cha- racters as in the Mammalia. 5. In the greater predisposition to monstrosity among some animals. This is greater among domestic than among wild animals; greater among the more perfect, than among the less perfect ; three-fourths of the monstrosities occur among Mammalia, one- fourth among Birds (J. Geoffrey St. Hi- laire). They happen seldom among Reptilia, still less frequently among Fishes, Mollusca, Articulata, and Radiata. From these premises the consequence is easily derived, that monstrosities do not take place by chance, and therefore do not by any means deserve the so very general appellation of caprices of nature (Ins us nalurce'). The result of this is, that they often present a quantitative antithesis, according to what Geoffrey St. Hilaire denominates loi de ba- lancement. According to this law, the ex- cessive developement of one part of the body is often connected with checked formation of another. To anencephalia, cyclopia, spina bifida, are often joined fingers and toes in ex- cessive number ; to sireno-mclia superfluous vertebrae and ribs ; and frequently there occur in double monsters malformations of the head. Meckel saw, in one single instance, this an- tithesis extend itself over different children of one and the same mother. A girl had on each extremity a superfluous digit, and one hand of her sister wanted four fingers, being the number of digits which her sister had in excess, reckoning the four extremities together. I have now arrived to the classification of monstrosities ; but in order to prevent all unnecessary waste of time, I shall avoid entering into a full critical examination of the systems propounded by Licetus, Huber, Wigtel, Malacarne, Buffon,Blumenbach, Bres- chet, Geoffroy St. Hilaire, Gurlt, Otto, and Bischoff. Concerning these I refer to Bis- choff*, from whom Rokitansky has chiefly borrowed what he gives in his manual. Ac- cording to my conviction, no suitable clas- sification of monstrosities can be given, and the efforts employed to this end may be re- garded as failures. I confine myself, therefore, to a simple grouping, taking embryogenesis as my basis, without presuming on any further classification, and I thus avoid a barbarous nomenclature, which, in my opinion, is at- tended with no advantage. My object is simply to make the doctrine of malformations useful for physiology and for medical practice, nearly in the same manner as was done, almost * Entwickelungs Geschichte mit besonclere Be- rilcksichtigung tier Missbildungen, in R. Wagner Haudworterbuch d. Physiologic, 13. i. g. 887. simultaneously with me, by the excellent F. A. von Ammon.* MALFORMATIONS OF THE OVUM. 1 . Mo/a botryoides or hydatica, — Hydromelra aqnatica, — is a degeneration of the chorion into vesicles of different sizes, filled with a serous liquor, which were erroneously taken for hy- datids. They cover the surface of the en- larged ovum, and are the villi of the chorion, which, as no formation of vessels took place, retained their original vesicular form (Ruysch, Albinus, Sandifort, Cruveilhier, Velpeau). Sometimes a foetus is found in it, which, how- ever, in relation to the ovum may be said to be small. The small embryo most probably dies in the early period of pregnancy, and the degenerated ovum continues to grow till a later period, when it is evacuated. In most cases abortion is the consequence of this condition of the ovum. Sometimes, nevertheless, the pregnancy lasts till the full time (Gregorini), or sometimes longer, as happened in a case observed by Lossins, in which it lasted six years. Sometimes the foetus disappears, and then this degenerated vesicular mass is evacuated alone, with ex- cessive hsemorrhage and great pain. This is the last period of what is called false preg- nancy. The vesicles are inclosed in a kind of de- cidua ; they are fixed on pedicles, from which arise other vesicles with smaller stems, so as to give to the whole the appearance of the chorion, in an earlier period of its existence, when the villi still preserve their original vesicular form. The accurate observations of Boeck show that, in most cases, these vesicles contain blood, which sometimes can be dis- placed by pressure from the one to the other vesicle, or is coagulated. The internal sur- face of the membrane which forms the vesicle is smooth, the external interwoven with fibres. A thus degenerated ovum has not the power of bringing the foetus to a state of perfect maturity. The death of the foetus and mis- carriage are its consequences. Sometimes the Mola botryoides is accompanied by malfor- mation of the foetus (Valisnieri). From this degeneration ought to be distin- guished : 1st. The vesicular degeneration of the placenta, when retained after a natural parturition in the womb (Gregorini) ; 2nd. The Polypi f u gaces or vesiculares evacuated in the anni climacteric! by elderly women (Lev- ret) ; 3rd. Those after suppressed menstrua- tion in unpregnant women (Schleierbach, Watson, Sporing, Lisfranc). As I have no ob- servations of my own of any of these cases, 1 dare not pronounce any opinion about the affinity of these vesicles to the Mola botryoides. 2. Separation of the placenta into lobes or cotyledons. — This is without doubt to be attributed to an arrest at a lower degree of developement, and it offers some resemblance * Die angeborenen Chirurgischcn KrankLeiten des Menschen. Berlin, 1842. TERATOLOGY. 947 to the placenta of the Ruminants. The smallest amount of deviation is a division into two coherent lobes, which are separated only by a small constriction (J. F. Meckel, Ebert). Such a placenta has an oblong form. Sometimes there is a single lobe adjoined to the placenta (jilacenta succenturiata) ; it is of much smaller dimensions than the placenta itself, and united to it by vessels, without a cord. The placenta may also be divided into three (Rohault, Schwencke), four (Hoboken), five (Meckel), or seven lobes (Kerckring, Wrisberg). In the observation of Kerckring, the arrest at a lower stage of development is clearly shown by the presence of the Vena omphalo-mcsenterica . 3. The vessels of the umbilical cord are sepa- rated near the placenta, and meet at a con- siderable distance from it (Sandifort, Wrisberg, Adolph). In one of the published cases, this disposition of the vessels was the cause of their rupture, which produced the child's death by haemorrhage. Sometimes they were ob- served to run separately from the placenta to Fig. 597. the abdomen of the foetus, into which they penetrated through separate openings. In most cases they meet each other just at the umbilicus (Gavel, Van Solingen). 4. The umbilical cord too long. — The com- mon length of the cord is twenty inches (Roederer, Wrisberg), but it may be forty- eight inches (Wrisberg), sometimes even five feet (Morlanne). The usual effect of such an abnormal length of the cord is a circumvolu- tion of it round the body of the foetus. An example of it is given in a very misformed foetus mfig. 597. A circumvolution of this kind may some- times become dangerous : 1. By acting as a ligature round the neck, and producing stran- gulation of the foetus (Buchanan, Hebenstreit) ; 2. By constricting one of the extremities, and producing the spontaneous amputation of Montgomery (Art. FCETUS,^/%. 157. Vol. II.) 3. By forming single or compound knots. Although these are in general not dangerous, while the vessels are sufficiently protected against pressure by the Whartonian gelatine, the}' may nevertheless in some cases be drawn so tight as to obstruct the communication between mother and child (Sandifort, Irvets, D. W. H. Busch) ; and sometimes the um- bilical cord breaks off' near the knot when the vessels have become obliterated by the pres- sure. Fig. 598. gives an example of this in an acephalus. Fig. 598. Malformed Fcetua, shnwincf the cord entwined around the neck and part of the body. {After Bonn.) 5. The umbilical cord too short. — Wrisberg gives as a minimum a measure of seven inches. It may, however, be much less. This short- ness of the cord is in general accompanied by a deformity of the foetus, usually by ectopia of the abdominal viscera, by which it indi- dicntes an arrest of developement at an earlier period of embryogenesis. In this way we should interpret' the accounts of absence of the umbilical cord. G. Absence of one of the umbilical arteries, is even observed in double monsters, but occurs principally in eclopia viscerum abdomi- 3 P 2 918 TERATOLOGY. and in defective formation of the infe- rior part of the body. Serres hence derived the conclusion, that this malformation is the con- sequence of the want of one of the umbi- lical arteries ; which is however wrong, as the evolution of the whole body may be complete, even when one of the umbilical arteries is wanting. Fig. 599. represents a specimen of this kind. - Fig. 599. a, aorta ; b, b, spermatic arteries ; c, superior mesen- teric ; d, d, common iliacs ; e, the single umbilical artery ; /, vena cava. Mende even observed in a very well formed child absence of one of the umbilical arteries, together with an unusual course of the umbi- lical vein, which, instead of communicating with the vena portae, opened immediately into the right auricle of the heart. 7. Increased number of the vessels of the cord. — A double umbilical vein is constantly to be found in the Quadrumana of the New World (Rudolphi). In Man the unusual plurality of the umbilical vessels is but ap- parent, as it is produced by the persistence of the vasa oniphalo-mescnterica. 8. Persistence of the umbilical vesicle, is a natural condition in the Onistiti (Rudolphi), and occurs as a deviation in Man. Sometimes it is only its duct that remains united with the small intestine, forming what we call a diverticulum. 9. Constriction of the umbilical cord occurs at the point where the cord penetrates into the abdomen. In the constricted part the vessels, although remarkably narrowed, still allow in some measure the circulation of the blood. The cord is thereby contorted into a spiral. The death of the foetus is its usual effect (Landsberger). Fig. 147. of the second volume of this Cyclopaedia gives a represent- ation of this constriction of the umbilical . cord. 10. The umbilical cord too thick. — Its dia- meter varies from 1* — 2£ inches. This is, in general, the consequence of an uncommon accumulation of the Whartonian gelatine, or of an oedematous conditon. In one of the recorded cases, the superior extremities were wanting, and the anus was closed. In other cases it is occasioned by an enormous quan- tity of the liquor amnii, which is usually accompanied with an abnormal developement or impeded growth of the foetus. MALFORMATIONS OF THE FCETUS. It is impossible to give in a concise article, such as is suited to a cyclopaedia, a complete description of all the various malformations of the foetus. I must refer to my manual, published in Dutch, under the title De mens- chclyke Vrucht beschouwd in hare regelmatige en onrcgelmatige ontwikkeling, Amsterdam, 1840 en 1842, and to my Tabulcs ad illustran- dam Embryo-genesin Hominis et MammaKum, where a more full and accurate description of the various kinds of malformations of the foetus is to be found. I can give here only a short description of the principal groups, as an introduction to the doctrine of the malfor- mations of the fetus. A. MONSTROSITIES PRODUCED BY AN ARREST OF DEVELOPEMKNT. I. Non-closure of the anterior Part of the Body. Embryogenesis teaches us, that the tho- racic and abdominal cavities are originally open, and close themselves by degrees at a later period of uterine life. The late ossifica- tion of the sternum and of the pubic bones is the result of this original disposition. The points of ossification are not formed in the broad cartilaginous basis of the sternum be- fore the fourth or fifth month of pregnancy ; they are in the beginning widely separated from each other by broad intervals in the middle, and approach later to fuse into one central osseous piece. This mode of formation explains some of the original malformations of the sternum; namely, its abnormal breadth, the openings which are found in it, and its separation into two parts. These two last conditions denote, that the sternum is the compound of two lateral halves fused together (Rathke). The separation of the sternum into two parts usually accompanies ectojna of the thoracic and abdominal viscera. Sometimes, although the thoracic viscera are enclosed in their cavity, the original divi- sion of the sternum remains, and is covered up by the skin (Picker, Serres, Winslow). In some rare cases, the whole or the largest part of the sternum is absent in individuals with no other deformity (Von Ammon). In most of these cases the manubrium alone is present (Wiedemann). In some, but very rare, cases the anterior wall of the thoracic and abdomi- nal cavity is only closed by the skin, and its osseous and fleshy parts are completely defi- cient (R. G. Mayne). The linea alba is, as well as the sternum, the cicatrix of a cleft existing at an earlier period. This explains its abnormal breadth, obvious in those cases in which the wall of the abdomen has been TERATOLOGY. 919 closed at a later period than usual. An ex- ample of it is given in my Tabula XXIV. Jig. 4. Sometimes the muscles of the anterior abdominal wall are wanting, in which case the convolutions of the intestines may be seen and felt through the skin (Von Animon). The thoracic and abdominal cavities being open in the first periods of embryogenesis, if this condition persists abnormally, it produces ectopia of the thoracic and abdominal viscera. The aperture through which the ectopia takes place has a constant tendency to close ; it shrinks therefore sometimes to a very small opening (Hammer). Sometimes it is closed in the middle, by a band which separates the uncovered viscera into two portions (Hiihner, Wolff). Its principal forms are : — 1. Fissure of the whole anterior Wall of the Body. a. Complete ectopia of the thoracic and abdo- minal viscera, which lie bare upon the anterior surface of the body, to which is generally added a cloaca. (Fig. GOO.) Fig. 600. Cliild with ectopia viscentm. a, liver ; b, heart ; r, c, lung ; d, stomach ; e, spleen ; /,/, intestinal canal ; , lun» liilical cicatrix; c, c, urethral orifices; d, epispa- diac penis ; f, e, scrotum. 3 p 4 952 TERATOLOGY. Fig. 604. The same Region armed with an Apparatus for the reception and evacuation of Urine. c. Ectopia vesiccE urinarice. — The smallest degree of deformity is when the urinary blad- der remains intact, but lies in an opening in the wall of the hypogastric region. It is ecto- pia vesicee urinarice, of which a representation is given in fig. 605. ; and for more details I refer to my " Tabulae ad illustrandum embryo- genesin,'' etc., Tab. xxx. Fix. 605. Hypogastric Region of a Child, which lived six years, with ectopia i-esiccc urinarice. a, part of the bladder lying on the surface of the ab- domen ; b, umbilical cicatrix ; c, penis ; d, d, pre- puce ; Ji, urethral orifice ; f, scrotum ; g, g, testes, lying at the inguinal region. d. Inversio veslcce unlnnrite. Prolapsus vc- SICCB unnaricE inverse. — If the urachns re- mains open after birth, the urinary bladder may be expelled, and thereby inverted through it. R. Froriep(C////wg. Kupfertafeln, Heft 67. Taf. cccxl.) has given an example of this malformation. It ought to be distinguished from the inversion of the bladder through the urethra, which is possible even in adult women (Voigtel). If we take a general survey of all these cases 'of non-closure of the hypogastric region, it is evident that they are intimately connected with one another. The cloacal disposition is the highest, the ectopia of the urinary bladder the lowest, de- gree of malformation, and therefore the latter is a distinct transition towards the natural con- dition. The inversion of the urinary bladder observed by Froriep has, as to its origin, no direct relation to the other forms. It is but an accidental effect of the remaining open of the urachus, through which the bladder chanced to become inverted, and the urine flowed away through the urethra if the child was held up- right. From the gradual transition of one form into the other, I conclude that the origin of this malformation cannot well be attributed to a mechanical cause, as Duncan and Bonn have asserted nearly at the same time. They both consider it the effect of a preternatural accumulation of urine, causing a violent dis- tension, and later a rupture of the bladder, of the urethra, of the hypogastric region, and of the pubic articulation. This theory had already, in the year 1816, a very strong oppo- nent in my father (Verh. d. le kl. van het Koninkl. Nederl. Instit. D. II. B. 88). His chief arguments against it, to which I add my own, are : 1 . That, if the urinary bladder bursts, as may happen in adults, the urine will be evacuated into the abdominal cavity, without fissuring the anterior wall. 2. That it is improbable that in some cases such an accumulation should fissure the whole apparatus, and in others re- strict its effect to the corpora cavernosa, penis, and the urethra, as may be seen in simple epispadias (W. Vrolik, Bosson, Sals- mann, Morgagni, and Oberteuffer). 3. That by an observation of Baillie is proved, that in fissure of the urinary bladder the posterior part of the urethra may remain intact and closed, while the corpora cavernosa are fissured at the anterior part of the penis. 4. That I have often found in the foetus atresia urethra com- plicated with an unusual expansion of the urinary bladder and of the ureters, but with- out the least sign of bursting or of producing the malformation in question. 5. Thafcectopiq of the urinary bladder demonstrates that the anterior wall of the abdomen may be open, the urinary bladder remaining intact ; or the sup- posed effect may exist, when the cause is absent. From all these and other remarks and observations I conclude that the origin of this malformation is not to be found in a mechanical cause, neither internal nor external (Roose). I am much more inclined to ascribe all its different forms to arrest of develope- ment. My chief grounds for this opinion are the frequent coexistence of: — 1. The want of artcrio: hypogastricas (G. Vrolik) ; 2. Ab- normal condition of the kidneys and the ure- ters (Pinel, Cooper, Isenflamm) ; 3. Fis- sured dorsal vertebra (Littre, Revolat, Delfin, G. Vrolik) ; and many other malformations, as labium leporinum (Dupuytren, Meckel), con- fluent toes (Saxtorph). The only question which remains is, what is the cause of this imperfect developement ? As to the cloacal TERATOLOGY. 953 formation, it is certain that it may be said to be an arrest at an earlier period of evolu- tion ; but this is not certain with regard to the vesica fissa. The origin of this can only be explained by an imperfect developement of the urinary bladder from the allantois. It is not improbable, as my drawing of the cloacal formation shows also, that the urinary bladder is formed by two half-parts, which approach each other anteriorly and posteriorly on the mesial line. If this junction does not occur, the different forms of vesica inversa will be formed. Atresia ani is, in the cloacal dis- position, without doubt, an arrest of deve- lopement at an early period of embryoge- nesis ; for previously the anus is closed. And epispadias shows that the penis is formed by two parts, which may remain separated from each other on the superior surface. Con- sequently it appears, that the name of vesica inversa is as improper as that of vesica fissa. But I shall propose no other name, because we know sufficiently the meaning of it. 5. Cervical Fissure (Fistula colli congenita), Recent observations teach us that the ori- ginal branchial fissures may persist in the neck even in adults. Hyrtl mentioned this malformation in a man of twenty, in whom the external cervical opening was small and com- municated with the pharynx close to the epi- glottis. Among 34,000 young men, Riecke found a fistula colli congcnita twice. 6. Fissure of the Face. In order to obtain a correct notion of the different forms under which fissure of the face may occur, it will be necessary to know the gradual metamorphoses of the face during its developement. Originally there is a common oral and nasal cavity. The place of the nose is occupied by two fissures, which extend from the internal angles of the eyes to the superior margin of the oral cavity. There is at this period not the least indication of a palate, so that the mouth and the nose form one common cavity. In a human fetus of less than an inch in length, Meckel found the first rudiment of a palate, in the form of an arc or a horse-shoe shape. On each side this arc is gradually completed, so as to be at first open at its posterior part, but closed afterwards, and forming a complete trans- verse plate, separating the nasal from the oral cavity. Rathke examined this more in de- tail, in fetuses of the sheep : — 1. He learned that the supermaxillary ca- vity is formed on each side from the lateral walls of the cranium. 2. That between those two parts grows out of the frontal wall of the skull a third eminence, which forms the basis for the sep- tum of the nose, that is, for the formation of the vomer, of the septum of the ethmoid bone, and of the intermaxillary bones. 3. That the two parts, quoted under No. ]., are bent inwards, and coalesce with the mesial part. 4. That the nasal cavity is at first a groove, and has originally a form which persists through their whole life in fishes. 5. That the oral and the na.sal cavity form originally a common cavity. 6. That the palate is originally a fissure. By arrest of developement in these different stages of embryogenesis, are formed the dif- ferent species of facial fissure. a. Complete fissure of the face. — The high- est degree of malformation is, when the fissure is extended from the angle of the mouth to the internal angle of the eye, the orbits, the nose, and the mouth forming but one cavity. J. S. Meckel, Van Doeveren, and myself have published examples of this malformation com- plicated with acrania. The fissure sometimes extends only over one lateral part of the face (Leuckart), and in the greatest transition to the natural condition it is but a shallow groove, as is represented in fig. 596. A fissure sometimes extends in a transverse direction over the head. C. Meyer observed this twice in new-born sheep. In both the palate had a double fissure, and the normal opening of the month reached as far as the ear, which in one of these lambs presented a trans- verse fissure. b. Double labium leporinum. — A transition to the normal condition, yet a very imper- fect one, is when the fissure is not extended over the whole surface of the face, but is re- stricted to the upper jaw. The highest de- gree of deformity is double hare-lip with fissured palate (Labium leporinum duplex cum palato fisso). On each side of the upper lip a fis- sure extends from the angles of the mouth to the alte nasi. Between these is a protube- rant tubercle, covered by a separate part of the upper lip, and consequently by the external skin and the gums. The tubercle is connected with the septum of the nose, generally obliquely distorted, and is filled up with the germs of the incisors. By the confusion ot the oral and nasal cavities, the true nasal ori- fices are wanting, the osseous palate is defec- tive, the soft palate and the uvula are fissured, and the vomer united anteriorly with the pro- tuberance, hangs in the midst of the fissure. In a lesser degree of malformation, the alveolar margin of the upper jaw is alone fissured, and in the least degree the palate is complete. c. Single hare-lip. — This name is adopted for the malformation when it is limited to one lateral part of the face. It may be complicated with fissured palate. The lip is then, on one side, fissured to the nostril, so as to form there an immediate communication between the oral and nasal cavity. The direction of the fissure is seldom accurately in the mesial line. If this occurs, it is the result of defective in- termaxillary bones. The palate offers either a simple or a double fissure. In a less degree of malformation only the alveolar ridge is cleft, and, in the least, the palate is complete. In such a case the fissure of the upper lip is merely a small incision. d. Fissure of the palate without a hare-lip. — The alveolar margin is in this case quite complete, but the palatine and the supermaxil- 954 TERATOLOGY. lary bones are largely separated from each other posteriorly, so as to form a fissure, more or less extensive, of the bony and of the soft palate. Sometimes there is only a fissure of the uvula (Von Ammon). The nearest ap- proach to the natural state is, when the planes of the palatine bones form with each other nn acute angle rising high upwards in the nasal cavity (Himly, W. Vrolik). In some cases, the palate is fissured at its anterior part, close to the foramen palatinum anticum (hiatus fora- minis palatini antici, Von Ammon). En re- sume, it appears that fissure of the palate and hare-lip are independent of each other. But it may happen that, originally, the fissure of the palate coexists with the hare-lip and closes itself later. The indentation which is ob- served in hare-lip without fissure of the palate, between the external incisive and the canine tooth, makes it probable that nature proceeds in this manner. It is also not improbable that hare-lip may sometimes be cured spontane- ously in the womb. The gradual transition of the various forms of this malformation into each other, shows that its cause is not external and accidental, and that it is produced, neither by blows which the child inflicts upon itself with its fists (Jourdain), nor by a mechanical im- pediment preventing the union of the palatine lamina? (Pinnder). Complete fissure of the face and the palate is rather to be considered as an arrest of developement at an early period of formation. Hare-lip conforms with the foetal condition in that period of develope- ment which I have called the third. If the original intermediate protuberance does not unite itself with the lateral parts, double hare- lip is formed. The protuberance obvious in it is formed by the intermaxillary bone either in its totality, or only by a part of it. If it unites itself with only one lateral part, single hare-lip is formed. The intermaxillary bone is composed of four separate parts, of which each contains an alveolus. The result of this is, that each of these parts may be united, separately, with the supermaxillary bones ; which fact explains clearly why only three or two incisive teeth are sometimes to be found in the protuberance. The fissure of the upper lip sometimes occupies the mesial line, passing through the middle of the inter- maxillary bone. This is also the case when the intermaxillary bone is wanting. In this way, all the various forms of fis- sure of the face can be reduced to an arrest of developement, which explains in the mean- time the constant tendency of the fissure to close itself, as may be observed in children having this malformation. Fissure of the palate and lip does not endanger the life of children, and union of the separated parts in hare-lip and cleft palate can be obtained by a surgical operation. e. Fissure of the under lip. — The under lip is very seldom cleft (J. F. Meckel, Von Ammon, Nicati, Bonisson). It is equally rare for the under jaw to remain after birth separated into two parts. II. Fissure of the Skull (Acrania). Many forms of this monstrosity are known, to which different names have been given, as acephalia spuria, microcephalia, ancncephalia, hcmiccphalia. But, for its shortness and ety- mological sense, I prefer the name of acrania, which was introduced by J. F. Meckel. Un- der this name I comprehend all the different forms in which this malformation occurs, and also, with Himly, the hernia ccrebri. Accord- ing to my opinion, the division into different families and genera, and the nomenclature of J. Geoffroy St. Hilaire, ought to be rejected. I, for my part, am always inclined to simplify science as much as possible, and to be succinct in its exposition; and I propose, therefore, the following types. Firbt "Type. — Want of the brain, and ex- posure of the whole basis of the skull. — The superior surface of the cranium is flat, and not formed by the bones of the skull, but only by a membrane, of which the margin is very un- equal, hard, and formed by bones. The external integuments extend over this margin, and terminate there in an unequal line, which is distinctly circumscribed by the thick hair of the head. With this cutaneous border is connected the slightly vaulted membrane, of a red, somewhat bloody colour, which imme- diately covers the periosteum that invests the more or less convex surface of the basis of the skull. The brain is wanting, but the central terminations of the cerebral nerves are in most cases present, yet sometimes these also are wanting (J. F. Meckel). The forehead is flat, and directed forwards in an oblique direction. The eyes protrude on its anterior or orbital margin, covered with swollen superior eyelids, and directed more or less upwards. The face is flat, and nearly horizontal ; the upper, and still more so the under jaw are comparatively longer than those of a well-formed subject ; the tongue is in general prominent, because the mouth cannot be shut on account of the Fig. 606. TERATOLOGY. 955 length of the under jaw. These distortions give to such monstrosities a certain brute-like aspect which induced the Germans to call them Katzenkopfe and the French tctes de crapaud. If the cervical part of the spinal column is in the meantime cleft, the cervix is so shortened, that the head seems to he fixed on the shoul- ders, and the chin rests on the breast, as is represented mjftg.606. The malformation of the bones of the skull and of the face is very great ; but as its de- scription would take too much room here, I refer the reader to my handbook and my plates, and also to Jig. 607., which will give a clear idea of it. Fig. 607. Skull of a new lorn Child with Acrania. a, a, frontals ; b, nasals ; c, c, very convex zygoma- tic bones ; d, small ensiform processes ; e, sclla turcica ; f, f, alte majores ossis sphenoidei ; g, g, petrous bones ; /(, basal part of the sphenoid bone ; it i, condyloid parts of the occipital bone ; I, I, depressed squamous parts of the occipital bone ; m, small osseous lamina:, representing the parietal bones. Second Type. — The denuded surface of the basis cranii occupied by a spongy substance, instead of brain. — In most cases vesicles, filled with a serous liquor, were observed to occur in this spongy substance, and with these occasionally also medullary corpuscles, which may be considered as rudiments of brain. There is sometimes a rudiment of the cerebellum, together with a rudiment which is continued into the spinal medulla, as though it were a medulla oblongata. The cerebral nerves are sometimes quite separated from, sometimes united with, the spongy substance. Sometimes they have the form of complete or lacerated bags, which extend along the superior surface of the skull and the posterior surface of the spinal column. The spinal co- lumn is either perfect, or partially, and some- times entirely, cleft. The last of these con- ditions is represented in Jig. 60S. Fig. G08. To this form of monstrosity GeofTroy St. Ililaire gives the name of anencephalits. Spe- cimens of it were found amongst the Egyptian mummies in the sacred sepulchres of the Cy- nocephaJi and Ibis, which is a very interesting fact as regards monstrous births in those times. Third Type. — The surface of the basis cranii only partially denuded, — a spongy tumour occupying the place of the brain. The skull may be closed at its posterior part, and remain open at its summit. A more or less malformed cerebral substance appears on the summit of the skull, just as if it were Fig. 609. Section of the Head of a Cfiild m'th Acrania, to sliaw the union of the malformed brain with the sph/al cord. a, I', cellular sars, taking tho place of (he brain; c, occipital bone ; Clltailoous fissure iu Jhe lower part of the limbs are, then, more or less completely formed parts. With exception of one, all VOL. IV. thorax; b, umbilical hernia, under which are the male external genital parts. 3 Q 962 TERATOLOGY. Fig. 619. The skeleton of the foregoing Aceplialus. a, mobile bone connected with the single cervical vertebra. always twins, and not full grown. As far as it has been mentioned by different obser- vers, there is either a common placenta, with two cords (Ponjol), or with one cord split into two (Mery) ; or there are two placentae connected together (Herhoklt); or there are two totally separate ova, with a double placenta (Moiiro). The external appear- ance differs from that of the fourth type, by greater length, and less truncated upper part of the body, in which a feeble indication of head may sometimes be visible (Ponjol, Prochaska). The integuments are as in the fourth type ; the toes are generally mal- formed ; the arms and the external genital organs are often abnormal. To the lumbar part of the spinal column is joined an imper- fect osseous thorax, sometimes with cervical vertebras (Ilevermann), but without thoracic viscera. The diaphragm exists in most cases. There are vessels without a heart, which cohere with the umbilical vessels. The viscera of the epigastric region are commonly want- ing ; Atkinson mentions only a liver. In some intestines can be recognised either as intestina tcnuia or crassa. The uropoietic organs, and the internal parts of generation are commonly pri'sent. There is in all a spinal marrow. The observations as to the nervous system are very incomplete. (Sec Jigs. 618, 619.) Sixth Type. — Acephali ivith a trunk com- posed of a thorax and an abdomen, and with two superior and two inferior limbs. — When the trunk is more developed, the thorax becomes more convex, is more distinct from the abdo- men, and supports two superior limbs. These acephali, too, are twins, at least in the greater number of the cases. They are often not full-grown, and borne by women who have frequently been pregnant. The placenta is in general common to the two foetuses, but with two cords. The thorax is more perfect than in the fifth type ; the upper part of the body terminates not in an obtuse end, but in a broad and flat surface, havii g a fissure in the midst, with an indication of a head. The sternum is often rudimentary, and the osseous frame of the superior limbs is very incom- plete. To the spinal column are added cervical vertebrae, and sometimes a confused indication of cranial bones. There is usually a dia- phragm, but neither heart nor lungs. There are commonly two vascular trunks, an arte- rial and a venous. With the venous is con- nected the umbilical vein ; and from the in- ternal iliac arteries arise the umbilical arteries. There are uropoietic organs, and an intestinal canal, with a ca?cal termination ; and some- times a liver. This latter is, however, some- times wanting, together with the spleen and the pancreas. In the intestinal tube there is no meconium, but only a mucous substance. The nervous system is very incomplete; but there is constantly a spinal marrow with the abdominal part of the sympathetic. I have observed distinct muscles, of which the pre- sence has been denied by others. Seventh Type. — Acephali in which some cranial bones are found. — This has been observed by Herhoklt, in a monster, born twin with a well-formed child, of a mo- ther who had five other children. There was an amorphous head, with an indication of eyes and nose, but without ears and mouth : the rest of the body was much de- formed. Of the cranial bones, the condyloid and vertical portions of the occipital only could be distinguished. There was no trace of facial bones. Analogous observations have been made by Curtius and Otto. Eighth Type. — Body and extremities per- fectly well developed, and having a neck, which is wanting in the other types. The neck is sur- mounted and terminated by the ears. — This is the form to which Gurlt gives the name of peroccphalns aprosopus. I have met with it in the lower animals only. The body and the limbs are perfectly well developed; on the perfect neck are placed two coalesced ears, behind which there is an imperfect cranium, composed principally of the cranial, minus the facial, bones. In all this the deformity makes a transition towards an imperfect formation of the face. (Figs. 620, 621.) Ninth Type. — Acephali which are composed of the trunk only, without the least indication of superior or inferior limbs. — Only one case of this monstrosity is known, observed by Vallis- neri. In a foetus of a very mature period of TERATOLOGY. 963 Fig. 620. The superior cervical part of a peroccphalous lamb, terminated by the ears which are coalesced with, each other. Tlie skeleton of the parts represented in fg. 620., with the trachea and the oesophagus. a, squamous part, and b, condyloid part of the occipital bone ; c, petrous ; d, squamous, part of the temporal bone ; e, parietal boue ; /, auditory bones. evolution, the head, the superior and the infe- rior limbs, were wanting. There existed only a trunk, which contained a tolerably large heart, imperfect lungs, a malformed liver, a stomach, and an intestinal canal. From this survey of the characteristics which distinguish the acephali, we learn that they are born with two, three, or four other foe- tuses at one birth. Can this quantitative multiplication of the children be the cause of the qualitative malformation of one of them? This is probable by the great fertility of the mothers of acephali, which also indicates that these monsters are produced by an arrest of developement. It is very easy to reduce their external appearance to the early periods of developement, in which the head is not yet distinct from the trunk, and in which the limbs are not yet protruded. It is worth mentioning that the abdominal cavity, with the kidneys and a part of the intestinal canal, are the most constant organs, which is very interesting with reference to the genesis of the intestinal tract. In the monstrous births of the second, third, and fourth type, there is only a colon, while in those in which a tho- rax is superadded (as in the fifth and sixth types), there is also an intestinum tenue with the coscum. I regard this as a confirmation of the statement, that the formation of the intestinal canal commences at the two ex- tremes, and proceeds from these to the mid- dle part. In the same manner the uniformity of cir- cumference of the whole intestinal tube is an arrest of developement at an early period of embryogenesis, to which may also be referred the ciecal beginning, and in many cases even theca?cal termination of the intestine. Thefre- quent deficiency of the liver is the consequence of the absence of the stomach and duode- num, and therefore a sign that the liver is a protrusion of the mucous membrane of the in- testinal tube. The connexion between the con- taining and the contained parts is also very dis- tinctly proved by the acephali. The very gene- ral presence of the lumbar part of the spine determines the existence of kidneys ; that of the pelvis, the existence of the urinary-bladder and of the genital organs. The very imper- fect condition of the thorax is in relation with the absence of the heart. The pre- sence of vessels without a heart demonstrates that the circulation of the blood can be car- ried on by these alone, and that the forma- tion of vessels is quite independent of that of the heart. The profusion of cellular tissue, by which the swollen appearance of the acephali is produced, may be formative sub- stance, which has not been employed in the production of the other parts of the body, and which has therefore grown rather abundant, In this manner many of the peculiarities of the acephali can be reduced to fixed principles. VI. Want find defective Formation of the Trunk* (2±, 625., referring for more details to my Tab. Ixxvii. 3. Limbs too short. — All their parts exist in such case, but are too short, as if they v, ere not full-grown. The malformation is however not limited to the extremities, but extends over the trunk and the head. The liead has in all the known cases the aspect of hydrocephalus. The neck is short and broad, the trunk short and swollen, and the limbs short, broad, and thick. Seemmering and Otto ascribe this to congenital rachitis. 33ut according to my opinion it ought to be attributed to defective developement, which is confirmed by the dissection, performed by C. Mayer, of such a monstrosity. 4. Limbs which seem to be truncated. — Some- times the fore-arm and the leg terminate abruptly like stumps, and present the appear- ance of cicatrices. I saw this on the four extremities of a calf, of which I have repre- sented the external form and the dissection in my Tabula? Ixxviii. and Ixxix. In many ot the known cases this defective condition of the limbs seems to be the result of arrested developement. In some others, however, it is the effect of mutilation produced by the con- striction of the umbilical cord, or by pseudo- membranes. Montgomery has given many examples of it in his article FCETUS in this Cyclopaedia. It is an interesting fact that from these stumps may grow rudiments of fingers, as Dr. Simpson showed me during the visit which I paid him at Edinburgh. 5. Diminished number of fingers and toes. — The highest degree of this malformation is the existence of but one finger or toe. Sometimes there are only the thumb and the little finger, as may be seen in a preparation in the mu- seum of Ilovius at Amsterdam. The greatest transition towards the natural condition is the presence of four fingers or four toes. 6. Coalesced fingers and toes. — In other- wise perfect limbs it is possible that hands and feet may be arrested at that inferior de- gree of developement, in which they are not yet separated into fingers and toes. The child is then born with fingers or toes, which seem to be coalesced ; but that is nothing more than a fallacious appearance. The malformation con- sists really in absence of fission. Of this there are different degrees : a, complete absence of fingers and toes, instead of which there is a common mass ; b, connection of the fingers and toes by means of a membrane ; c, the adhesion limited to the posterior parts of the fingers and the toes, while their anterior parts are completely free. All this may be seen mfigs. 62(i, 627, 628 Fig. 626. Fig. 627. Fig. 628. (sifter Otto.) 7. To all these malformations of the limbs ought to be added the abnormal direction of the foot; but this is fully considered in the TERATOLOGY. 967 article ABNORMAL CONDITIONS ov THE FOOT in this Cyclopaedia. VIII. Cyclopia. Upon this interesting malformation, which for many years was the object of my own inves- tigations, I should have much to say ; but my friend Paget has already given a succinct survey of its different forms in his learned Article NOSE, to which, therefore, I refer. I beg leave here to add to the observations which I have published in my former works upon the origin of Cychpia, a few additional remarks on the subject. Is it an arrest of clevelopement ? It cannot be denied that many deviations of the parts in Cyclopes may be referred to a previous natural form. For example, in one of my published cases the optic lobe and the brain formed one continu- ous part, which is certainly an early natu- ral condition. It is also certain that the disposition of the hemispheres of the brain in Cyclopes, which appear to be a single vesicle, accords with the vesicular state of the brain in the first period of its develope- inent, and that the unprotected situation of the ganglia of the brain, of the cerebellum, and of the medulla oblongata, may be con- sidered as a foetal condition. But, as to the eyes, it is not so certain that their single- ness is the result of an arrest of develope- ment. E. Huschke has, however, main- tained the opinion, that the eyes are formed by a single vesicle, which becomes sepa- rated into two ; but from the more recent and accurate investigations of BischofF, we must conclude that the optic lobes are from the beginning separated and double, taking their origin from the anterior cerebral vesicle, and that from an abnormal condition of this last, by which the rudiments of the eyes approach each other and fuse together, may be derived the cause of Cyclopia. If this observation is true, of which it is difficult to retain the least doubt, Cychpi-i really ap- pertains to the Verschmehungs Bildungcn of Meckel in an early period of developement. Perhaps it may be compared with the meta- morphosis of the eyes in Dap/mia, Cypris, Polypkeimts, and Cyclops, in which there are originally two vesicular bulbs, which subse- quently coalesce into one. But however this may be, it remains certain that the malforma- tion of the cranial and facial bones in Cyclopes is the consequence of the abnormal condition of the brain and of the visual and olfactive apparatus. IX. Deficiency of the Underjaw (Monotia). Want of the under jaw often coexists with Cyclopia. By this complication is formed a peculiar series of monsters, which make a gradual transition to those in which, notwith- standing the presence of two eyes, the under jaw is absent. I refer to this the following species. 1. Total defect of the opening of the mmtt/i, — as observed by me in a lamb, in which also the ears were removed to the basis of the head and coalesced. The under jaw was totally absent ; and behind the coalescent ears there was an osseous vesicular cavity, formed by the bulbous tympanic cavities, united to- gether. 2. The opening of the mouth represented by a fissure at the inferior surface of the face. — The rest of the external appearance is similar to the first species. The under jaw is want- ing, but there is a rudiment of a tongue. 3. Too short an under jnw. In man and the lower animals the under jaw is sometimes incompletely developed, and more depressed posteriorly than it ought to be. This original brevity of the under-jaw is the cause of a great many ulterior deformities. Without doubt, these three forms of mon- strosity make a continuous series. They consist, as Bischoff says, in an imperfect developement of the first visceral arc, by which the under jaw and the bones connected there- with are either wanting or defectively formed, the result of which is, that the ears are re- moved to the basis of the head, and there become fused together. The toial defect of the opening of the mouth is the highest, the too short under jaw the least degree of mal- formation. Herewith I conclude my brief account of the monstrosities resulting from arrest of de- velopement. The description of the congenital abnormal condition of the different apparatus would oblige rne to surpass the due limits of an Article for this Cyclopaedia, which already, 1 fear, may be considered rather too long ; and I think this the less necessary, because a great deal of information about them may be found in the Articles ANUS, DIAPHRAGM, FOETUS, HERMAPHRODITISBI. I therefore pass on to a succinct description of a second group of monstrosities. B. MONSTROSITIES PRODUCED BY EXCESS OK DEVELOPEMENT. I. Foetus in Fcclu. The human foetus may be included in an- other foetus, or adhere to its body. This may happen in two different manners: — 1. A fcctus more or less perfect contained in the cavity of the body of its twin-brother or sister. a. In the uterus. — The foetus would be pregnant in such a case at the moment of its birth. The observations given of it are, however, somewhat apocryphal. b. In the abdomen. — In a case recorded by Fattow, there are, in a foetus of seven months, two rudiments of foetuses contained in its abdomen. Such observations are also given by Reiter, Hemingcr, Pacini, and E. Philips. In general, the rudiments of a second foetus are very imperfect, and included in a sac. Sometimes, however, they are more complete, which was, for example, the case in an observ- ation of Young, of which the preparation is 3 Q 4. 90S TERATOLOGY. preserved in the splendid Museum of the London College of Surgeons. c. In the anterior mediastinum. — As in a case recorded by Gordon, in a female of twenty- one years. d. In the scrotum and the testes, — Such cases have been noticed by Rosenberger, I-Iartmann, D S. J. Wendt, Velpeau. Some- times the rudiments of a second foetus are found in the interior of the testis, sometimes at its exterior surface. e. In the stomach. f. In the intestinal canal. — Hiuhmore has given such a case in a youth of fifteen or six- teen years, in the gut of whom an acephalus was found. g. In the orbit. — According to Barnes, h. At the lentorium of the dura mater. 1. At the palate. — It is then in the form of a fungous excrescence, consisting of the rudiments of a second foetus (Otto, Sandi- fort, Ehrman, Stadenski). 2. The more or less developed rudiments of a fcelus adhere, in the form of a tumour, to the external surface of a second body, and ate covered by the external integu- ments. a. To the cheek. — G. Vrolik observed in a new-born male child, a sac of large circum- ference, covered by the external skin, and ad- hering to the region of the left cheek, but without communication with the mouth. In this sac there were tuberculous cartilages, os- seous nuclei, and organised parts of indefinite form and composition. b. To the neck. — According to Joube. c. To the epigastric and umbilical region. — As recorded by E. B. Gaither. d. To the sacral and perincal region. — This is the most frequent mode of adhesion, as is proved by a great many observations, among which those of Himly and of Fleischmann deserve special mention. This adhesion takes place in different manners : 1. by external cellular tissue ; 2. by internal union with the abdominal and pelvic cavity (Himly, Scliau- inann, and Stanley) ; 3. by communication with the spinal canal. There is sometimes no vascular communication between the foetus and its appendix (W. Vrolik) ; and in other cases there are large branches going from the arteria sacra media of the foetus to the sac. In general, the sac has its own integuments, over which passes the skin of the foetus. The genital parts and the anus are always quite separate from the sac, which merely lies in apposition with them. In the majority of the known cases, the rudiments of a foetus contained in the sac are but confused and ill-determined organic substances, intermin- gled with a few osseous and cartilaginous nuclei. In one case it was possible to recog- nise the cranium with the face and the naked encephalous masses (Wedemeyer) ; Mayer and Blizard found an intestinal loop: Himly saw distinct super-maxillary bones, and ru- diments of temporal, frontal, and sphenoid bones, &c. If we take a survey of all the cases which are designated as foetus in foetu, it is clear that some may be compared with parasitical dis- eases formed in the interior of the body of the foetus. 1 presume that this is the case, when the mass which is found consists only of hair, fat, teeth, and some osseous nuclei, contained in a cystic tumour. In other cases the rudiments of a foetus are included with a more or less perfect indication of an ovum in the body of a second foetus, or adhere exter- nally to' it. The large number of theories on the origin of this monstrosity have been criti- cised by Himly. It is certain that none of them can be maintained. It is most pro- bable that the foetus in foetu is an incomplete effort to form a double monster. In this sense, some cases of fcctus in fcvtu make a transition towards that form of double mon- sters which is named heterade/ph. II. Double Monsters, in which one of the Foe- tuses is more or less perfect and the other merely an Appendix to it (Heleradelphi). Under this name of heteradelphs, which we owe to Geoffroy St. Hilaire, we understand that species of double monsters of which one foetus is large and perfect, and another, or part of another, adheres to it like a para- site. They should be considered as twins, of which one has been developed at the expense of the other, which other sometimes becomes partially included in its body. According to the more or less perfect state of the appen- dix, they are reduced to different species. First Species. — Tlie appendix consisting of a head only. — This may be connected : — 1. With the epigastric region (Winslow, Hesse), 2. With the cranium (E. Home), 3. With the back (Chabelard), 4. With the palate (Hofmann), or 5. With the under-jaw of the perfect foetus (Geoffroy St. Hilaire, G. Sandifort). Second Species. — The appendix consists of more or less developed extremities only. — Supernumerary extremities, more or less deve- loped, are connected with some part of the body of a perfect foetus, as : 1. Pelvis and two inferior extremities con- nected with the epigastric region of the per- fect foetus (Serres, E. Sandifort, Trombelli, Mayer, Winslow, Reschel, Buxtorff, Cantvvell, Lycosthenes). The appendix is sometimes more, sometimes less perfect ; sometimes connected with the sternum, sometimes with the epigastric region or in communication with them by a cylin- drical cutaneous prolongation. In the appen- dix are regularly formed organs of generation, kidneys, an intestinal loop in communication with the intestinal canal of the supporting foetus, and vessels which anastomose with those of the latter. The adhering parasite is therefore one with its supporter. 2. Pelvis and the two inferior extremities connected with the lateral wall of the abdo- men of the perfect foetus (W. Vrolik). 3. Pelvis and two inferior extremities con- TERATOLOGY. 969 nected with the pelvis of the perfect foetus (Nmnan, Osiancler, Haller). 4. Separate anterior or posterior extremi- ties connected with some part of the perfect foetus (W. Vrolik, Von Baer). All these varieties are indicated under the names of gastromc/c, pygomele, and melomele. Third Species. — The appendix is an acc- phalus with four extremities, — The union has as yet been observed only at the epigastric re- gion of the supporting icetus, through which the abdominal cavity was common to the two bodies. In the appendix the genital organs existed, but the anus was closed. In many cases, the evacuation of urine has been ob- served; the appendix showed circulation of blood ; it had its own temperature, and was dependent for nutrition on the chief or perfect body. In the interior were found uropoictic organs, vessels connected with those of the chief body, and an imperfect intestinal canal (Otto, Serres). In the supporting fcetus are sometimes found traces of double organs (Otto, Serres, Kosenstiel). Fourth Species. — The appendix a com- plete body with a head and four extremilii s (Bartholinus). — This form of heteradelph makes the transition to anterior duplicity. The appendix has but to be more equally pro- portioned to the chief body, and a completely double monster is formed. The best ex- ample of this occurred in the person of a cer- tain Lazarus Colloreclo, Avho lived for some length of time. His portrait is given by Bar- tholinus. This very peculiar appendix never took food, nor had it evacuations of faeces. But the organic and the animal life appeared to be very well developed, as its cutaneous ex- halation, its movements of different parts of its body, and the fact of its sleeping, showed. The common character, by which this whole class of heteradelphs is distinguished, consists in the comparatively smaller size, and, in ge- neral, the defective developement, of the part which is termed the parasite. Imagine this difference removed by the fuller developement of the parasite, by its obtaining all its own organic apparatus, and by its growing part passu with the other, and an exact idea of complete duplicity will be formed. It will be observed also, that in the several members of this class there is a regularly graduated series, from those in which the superfluous part is only an ill-developed limb, to those in which the parasite differs from the chief in nothing but its inferior size and its depend- ence for nutrition. The cases of the last kind are, however, rare. I know but three, of which that of the said Lazarus Colloredo, de- scribed by Bartholinus, is the most remarkable. Much more commonly the parasite, even when it possesses its full numerical complement of parts, bears many signs of defective develope- ment ; it is hare-lipped, or a cyclops, or has atresia ani, or some other malformation from arrest of developement. All this seems to me to prove, that in heteradelphs there are always the rudiments of two bodies, though one or both may be defective. The beings thus formed have rarely lived man}' years after birth, and the histories of the few that have survived are, for the most part, well known in the records of medicine. Perhaps the most remarkable is that of the Chinese A-ke, of whom and his parasite little models are to be found in most of the anatomical museums of Europe. The para- site's life is, in general, only vegetative. In one of the three cases, indeed, in which it possessed all the constituent parts of a body, it moved its limbs, and appeared to have its own sensations ; but in the others, less per- fectly formed, even these signs of individual life were absent ; and in only one, that of the Chinese A-ke, had the man who bore the parasite any voluntary power over its limbs. The nutrition of the parasite appears to depend entirely on the body to which it is fixed, and through which it both receives its nutritive materials and discharges its excre- tions. The one increases and decreases in size with the other; and, of course, the para- site dies with the individual to which it is attached. The influence which, in its turn, it exercises on its supporter is not always important. In the heteradelphs that die early, death commonly ensues from the mal- formation of the main body ; if they survive, the parasite seems to do harm only, as an ordinary tumour would, by its weight, and by abstracting a certain amount of nourishment, so that those who, thus burdened, have grown up to childhood or manhood have usually been thin and delicate, like men subject to some unnatural waste. But, nevertheless, it will always be better to tolerate this evil than to risk an operation of removal, when the re- sults of all the examinations yet made prove that the parasite is deeply and by important organs connected with its supporter. The only exception which I know to the correctness of my opinion is the case in which Mr. Blizard removed, with complete success, from the sacrum of a child, a congenital tumour, which seems to have been a parasite. III. Double Monsters. 1. Anterior duplicity. It has been already said that some of the rarer kinds of hcteradelpliia approximate closely to the double monsters. In all the cases that stand nearest to the transition, the parasite has been found adherent to the epi- gastric region ; and the kind of duplicity which is most closely related to them, is therefore that in which the two bodies adhere by their anterior surfaces, or what we call anterior duplicity. The most complete examples of duplicity yet knowrr*are found in this class, whose dis- tinctive characters are, that two bodies, in a state of nearly equal developement, are placed exactly opposite to one another, with their sterna connected together, and with their abdominal cavities either partially or com- pletely coalesced. Here, however, as in all 070 TERATOLOGY. the other classes, examples are found of gra- dations towards a state of singleness. For instance, the upper parts of the body being completely double, the lower are united, so that there are but three limbs, or only two lower or posterior limbs. And, in like manner, although in many cases the bodies are alike in size and other characters, yet there are many more in which one has so far surpassed the other, both in size and in stage of develope- ment, as completely to fill up the series be- tween this class and the decided heteradelphs. Whilst in the latter case we find close approxi- mations to duplicity, there are even among the most perfect double monsters peculiarities which constantly recall to mind the parasitic attachment of the heteradelphs. With this nearly perfect external duplicity there sometimes, but not always, corresponds an equal duplicity of organs. The umbilical cord may be single (Parsons, Otto), notwith- standing the heart is perfectly double. The two umbilical arteries belong but to one child ; the umbilical vein bifurcates and enters both bodies. In another case (Cruveilhier), the single umbilical cord had two veins and four arteries, and the heart was externally single, and in its internal parts imperfectly double. In a third double monster (Otto), the umbili- cal cord had five vessels, two umbilical veins, and three arteries, and in this there were two hearts. In a fourth double monster the heart and umbilical cord were single. The bond of union, as far as the skeleton is concerned, is commonly a tough fibrous connection between the lower extremities of the sterna and the ensiform cartilages, which are set directly opposite to one another. The rest of the sterna and the ribs are usu- ally distinct, and the thoracic cavities are thereby separated. In this case there are commonly two separate and perfect hearts ; but in the cases in which the sterna are more completely fused, or (as happened in one case) entirely absent (Connn. Lift. JVo- rimberg.), only a single heart, or one partially double, with, for instance, two ventricles and four auricles, or otherwise malformed, is found. But it is particularly remarkable that in these, as in all other kinds of double monsters, there is no constant relation whatever between the respective states of the external and the in- ternal organs, for the condition of the two digestive canals, even in those which are ex- ternally almost alike, is subject to still greater varieties than the condition of the heart. The abdominal organs are always in some degree connected ; — the two livers are usually con- tinuous. A spleen, pancreas, and stomach are com- monly found in each body, and each stomach has its own duodenum, which, after some length (being continued into the jejunum) unites with the other to form a single tract of small intestine, which again divides into two canals, leading respectively to the large intestine of each body. The lungs, the urinary, and the genital systems are always double. The most remarkable example of this class was the well- known Siamese twins. When exhibited, they were not exactly opposite to each other, but stood side by side, or, rather, obliquely one by the other ; but this position, there can be little doubt, was acquired by the attempts which they had instinctively made to separate from each other in walking, or in lying and sitting down, and by the extension they had thus effected in their bond of union, which was considerably more slender than in any other yet described. It was quite impossible for them to remain always face to face; there- fore their bodies acquired an oblique direction, in which they also moved. The consequence of this was, that the right limbs of the one and the left of the other individual were the prin- cipal organs of movement ; and that the inter- mediate limbs, that is to say, the left of the one and the right of the other, remained merely passive (Dubois). The one individual was stronger than the other, and seemed to over- rule him. But, nevertheless, in organic and animal relation of life they seemed to be inde- pendent of each other. Each had his own circulation of blood, his own respiration, and digestive functions. There did not seem to be a large anastomosis of vessels between the two bodies. But, by analogy with the fore- said cases, we may conclude that these twins are connected by the ends of their sterna, and by some of their abdominal organs. Asa proof of this connection, may be adduced the result of the observations of Mr. Mayo, communicated at the Conversazione of the College of Physicians March Sth, 1831, that when either'of the youths coughed, the bond of union swelled up in its whole length, proving that they had but one peritoneal cavity, of which a trans- verse prolongation passed through the con- necting medium. And, therefore, I should conclude, that an attempt at separation could not be made with probability of success. The probability of having to cut through a piece of liver, or a peritoneal canal, must render an operation unwarrantable, unless, indeed, after the death of one of the bodies during the healthy state of the other. The case reported by Konig has scarcely authority enough to support a contrary opinion. 2. Lateral duplicity. The varieties of form in anteriorly duplex monsters are closely limited by the partial nature of the union of the sterna and the nearly complete distinctness of the thoracic cavities, and hence of the whole upper part of the body. In the next class, which I call lateral dupliciti/, there is no such limit; and between the highest degree of duplicity found in it and the lowest, or that in which the duplicity is most nearly reduced to singleness, there is a far more numerous series of intermediate forms than in any other of the types of double monsters. In lateral duplicity, the two bodies are not set opposite to one another, but are turned sideways from one another. They have a common thoracic cavity, for the forma- tion of which (at least, in the highest degree of duplicity,) the right ribs of one body, and TERATOLOGY. 971 the left of the other, proceed towards the an- terior and posterior aspects, and are there connected with an anterior and posterior sternum. The best idea of the construction of this osseous fabric may be formed by sup- posing the two complete chests of two bodies to be set one against the other, and that then the anterior extremities of the right ribs of the right body, and those of the left ribs of the left body, unite with one sternum arid pull it forwards, while, in the same manner, the left ribs of the right body, and the right of the left, unite on the posterior aspect with the other sternum, and carry it back- wards. The consequence is, that the two vertebral columns are turned away from one another, and that the parts above and below the thorax are double. By the formation of this common thorax, the lateral is distin- guished from the anterior duplicity, in which the thoraces are commonly connected only by the points of the sterna, and, as to their cavities, are separate. And with these diffe- rences of external construction, others not less important, of internal arrangement, coin- cide, which fully justify the separation of the two forms, however similar the external ap- pearances of many of the examples of either may be. The numerous varieties of lateral duplicity may be divided into two principal sets. The first begins with the complete duplicity of the whole body, and ends with its perfect sin- gleness; in the second, the duplicity of the body remains, but the head gradually becomes single. The forms included herein, of which 1 have given ample accounts elsewhere, may be briefly summed up as follows. 1. Complete duplicity: — all the external parts and sometimes the abdominal and pelvic viscera double, — one common double-sized thoracic cavity, formed in the manner just described, and containing four lungs, and (in all cases with which I have been acquainted) onl}r one heart. The examples of this form are very numerous, and are to be met with in all the large museums of Europe. 2. In the examples of this second group, which exhibits the first step towards single- ness, one of the sterna may be traced in a succession of specimens, becoming gradually narrower, and permitting a closer approxima- tion of the two corresponding upper extremi- ties, till, in some examples, they are com- pletely united, and there are found only three limbs above, with three or four below. The two juxtaposed scapulae, for example, are merged into one, or they remain separate, but have only one humerus between them, and this splits below, to articulate with two fore-arms ; or there is but one fore-arm, and this bears supernumerary fingers. In short by a great variety of modes there is a general tendency towards union of two of the upper extremities. 3. In the third group we have a repetition of the same series of changes in the lower limbs, as in the second was traced in the upper ; here, as there, presenting numerous varieties, in the last and lowest of which only three lower limbs, and the third of these ill- formed, are found. 4. The third limb has now gradually disap- peared, and, with a complete duplicity above the pelvis, there are but two limbs below it, and these well formed. In this class is placed, with many others, the Ritta-C/iristina monster, described by Serres, which lived to eight months, and the still more remarkable ex- ample mentioned by Buchanan, of a two- headed man, 28 years old, who lived in the reign of James III. of Scotland. 5. The union proceeding, and this simpli- city of the lower part of the body being re- tained, examples come next in which the upper parts also are united ; the two super- fluous upper limbs being united into one, pre- senting a single upper-arm, with a double fore-arm and hand, or a single upper-arm, fore-arm, and hand with ten fingers, or only a mal-formed limb, or a mere projection, occu- pying the place of the superfluous limbs. 6. Even this last indication of duplicity of the upper parts ceases, a scapula only remains, or this also is absent ; and next, one of the sterna having disappeared, and the vertebral columns having been connected on the corre- sponding side by their respective ribs united into single arches, these now become gradually shorter, and the columns approach each other more and more nearly, till they are connected by only a cartilaginous substance in the place of ribs, or are at some part fused together. 7. In this next group both the upper and lower parts of the body are single ; the ver- tebral column is single below the cervical region, or exhibits only a trace of duplicity (to which something similar is often presented by the sternum), but at the cervical region becomes double, and on each portion bears a head. Of this also I have published many examples. 8. In the eighth group the extent of that cervical part of the column which is double becomes less and less. 9. In the ninth group, the two heads are seated on an apparently single neck, in which all the cervical vertebrae are single, or only bear traces of duplicity, except the first two, or the first alone. 10. Hitherto the duplicity of the head was perfect ; in this group the two heads also begin to coalesce, and, in a considerable num- ber of cases, gradations are traced in which the adjacent ears are very closely approxi- mated, and the heads are united behind. Then there are cases in which one ear only is placed between the adjacent surfaces of the two heads, and this disappears gradually, and at last totally. Next in order are the cases in which the adjacent ears being lost, the two adjacent and middle eyes first become very close, and then occupying one orbit finally coalesce. Next come those case* in which there is such a union of the heads, that the two upper jaws are articulated with one lower jaw ; and, lastly, those in which the head is doubled only in individual parts or in which 972 TERATOLOGY. there is one perfect heart, with some imperfect part or parts of another attached to it. 11. The eleventh group of this division includes the cases of lateral duplicity, in which the body is single in the middle, but doubled above and below (or in brutes ante- riorly and posteriorly). In these, which are of rarer kinds, a single neck bears two more or less completely separated heads. The vertebral column is for a considerable length single, but at its lower part again divides, and bears two sets of lower extremities. 12. In the twelfth group the body is single above and doubled below. 13. In this there is a tendency towards singleness, or even complete singleness, of the head, but all parts of the trunk and all the limbs are doubled, an arrangement by which, as al- ready stated, these form a series entirely dis- tinct from the rest. In some of these cases the two heads are found coalesced below ; in others, to which the name of janiceps has been given, one face is directed backwards and the other forwards, the remainders of the two heads being merged into one ; in others, one face is perfectly, the other very dcficientli/, developed ; in others there are only the indis- tinct traces of a second head presented in the existence of one or two ears on the posterior aspect of the more perfect one ; in others, this trace of duplicity is still less evident ; and, lastly, in the remainder of the group, it is entirely lost, and one head only, which may be well or ill formed, is found upon the double body. 3. Inferior duplicity. My third division of double monsters in- cludes the cases in which there are two com- plete bodies with the lower portions of their respective trunks united, so that there is a head with upper extremities both above and below (the bodies being placed in the same straight line) and on either side of the part at which they meet two lower limbs. One may best conceive this arrangement by sup- posing two children stuck together by theii buttocks, and so fixed with wide-spreading lower limbs, as may be seen mflg. H6. of the second volume of this Cyclopaedia. A com- mon body is thus formed with a head at each end, with two upper limbs both above and below, and with two lower limbs, one belong- ing to each foetus on the right and two on the left of the united portions. A few cases only of this remarkable monstrosity are recorded ; and in these the duplicity was not always complete, but exhibited in some the same tendency towards singleness as was noticed in the others. Thus in some there were but three lower extremities ; in others there were but two, or two with a third ill-developed on the other side : and, again, in other groups there were those which have a perfect head at one end of the trunk, but an imperfect one or none at all at the other. These monsters have been known to live a considerable time, their capacity for life being probably owing to the separation of the hearts and the absence of malformation in the more important organs of the body. The umbilical cord is single, and never has a double set of vessels ; an apparent proof (confirmed by si- milar examples in other classes) that the one body is not formed of the materials of two ; a conclusion which is supported by the coinci- dent singleness of the anus and urinary blad- der, and the union of the intestinal canals. 4. Posterior duplicity. The fourth chief form is posterior duplicity, in which two bodies are united by their backs, or a part of them. The union may be at the pelvis (which is most common), and occurred in the well-known Hungarian sisters, who lived to their twenty-second year ; or at the back of the vertebral column, or at the back part of the heads. 5. Superior duplicity. The fifth is the superior duplicity, in which the two children are connected by their skulls, the bones of which are united so as to form a single skull. In these also the place of union varies greatly. The frontal bone of one coa- lesces with the parietal or the occipital of the other, or the foreheads are attached to one another, or the side of one head to the front of the other. But all these are very rare, and of each kind only one or two examples can be found on record. All these are true double monsters. Of tripled-badied monsters but one instance is known in the human subject (Atti dell' Acade- mia de Cattania, t. viii. p. 203., 1834-). To conclude the description of duplicity, those which occur in individual parts of tlie body, the rest being single, viz. in the head, chest, abdomen, and limbs, ought to be re- corded ; such as, for example, two mouths, su- pernumerary teeth and horns, two oesophagi or duodena, double hearts, or supernumerary cavities in one heart otherwise well formed, a double penis and urethra, a double clitoris, supernumerary breasts, kidneys, vertebras, ribs, fingers, toes, or whole limbs. But for all these I refer to my monograph. At present I prefer to give all those con- siderations upon the origin of double mon- sters, of which this highly interesting subject is capable. From all the facts I have published, I point out the following generalisations: — The double monsters form collectively one class of organic beings, which, however dif- ferent in their several degrees of malforma- tion, may be arranged in one continued series. As the lowest degree of duplicity, may be mentioned that of a single part of the body; for example, a double or supernumerary fin- ger ; as the highest, a complete double mon- ster with two heads, four upper and four lower limbs, and two trunks, such as the Siamese twins. And between these two ex- tremes there are different forms of duplicity, which gradually run one into the other. There is no positive or constant relation between the external and the internal organs as to their degrees or modes of duplicity. la the completes! duplicity of the exterior, for TERATOLOGY. 973 example, the heart is often single, or even shows signs of having been arrested in its developeraent ; and, on the other hand, in the more nearly single forms, the heart is usually either partially or completely double. The histories of the cases of anterior and lateral duplicity, which I have given in my mono- graph, furnish abundant proofs of this. Nor is there any closer relation between the con- dition of any other internal organ and that of the exterior, than there is between it and the heart; for in nearly complete external dupli- city any of the internal organs may be single ; when there are two trunks indeed, the urinary and genital organs are commonly double ; but as for the stomach, the liver, and the lungs, the correspondence between them and exter- nal duplicity follows no other rule than that where there are two necks there are two tracheai and two oesophagi, and as a con- sequence the lungs and stomach are also dou- bled. When in like manner the stomach is double, each has its spleen and pancreas ; but the state of the liver is very variable ; some- times there are two, sometimes but one wilh a single or double gall-bladder ; and these differences often occur in the same form of external duplicity. Parts placed on the surface of the body are more liable to multiplication than the internal organs, and duplicity of a single part is there- fore much less rare than the formation of a complete double body. The upper half of the body is more frequently doubled than the lower, probably in consequence of its earlier developement and the admitted preponderance of the upper parts of the body. The union of the two bodies takes place only between similar parts. The more each of the bodies is developed, the less is the bond of union between them, as the examples of the Siamese twins and the Hungarian sisters sufficiently prove. And with this law is connected an- other, namely, that the probability of grow- ing up is greater in the same proportion as the bond of union is smaller, and the coin- cident fusion of internal organs less, as these two and other double monsters prove. So also the further the several organs are from the situation at which the bodies are united, the more perfect they are, — one body is almost always less developed than the other: in the heteradelphs this is al- ways the case, and in others the difference between the two bodies, though less evident, is scarcely less constant than in them. There are not commonly any signs of a double monster having been at first two individuals. For except in the cases of posterior and supe- rior duplicity, and some singular examples of attachment of the umbilical cord of one foetus to the head or the body of the other, there is never more than one placenta and one cord, and the latter usually contains only a single set of vessels, which divide when they reach the abdomen. And even in the posterior and superior varieties of duplicity it is not yet certain that there are two placentae ; in some cases the placenta was positively single, and in the remainder it has very rarely been ex- amined. A last general rule is that in double monsters the twins are of the same sex. There is no well proved exception to this important rule. What explanation can be given, after all these facts, of the origin of double monsters? On this subject, three hypotheses ought to bu mentioned : 1. The double monster has been supposed to have proceeded from two distinct embryos, which have become united in the course of development ; 2. It has been held to have originated in a single germ, which has become double, or has been subdivided ; and 3. The germ has been regarded as abnormally compound from the first, implying that the organs and parts composing the double mon- ster are at once produced from this germ, without either separation or coalition of its parts other than belong to the natural process of developement. On the comparative merits of the first and second hypotheses, as parts of the general doctrine of monsters, one of the most interesting physiological discussions extant is recorded in the Mcmoires de f Aca- demic dcs Sciences de Paris, between 1724* and 1743. The chief disputants were Lemery and Winslow ; the contest lasted nineteen years ; it engaged the attention of all anato- mists, and called forth writings by Haller and a crowd of authors of less note, and was only terminated by the death of Lemery. Every argument that could be founded on the know- ledge of those days was brought forward, and the subject was, for the time, utterly exhausted ; but the facts accumulated in later years have furnished such volumes of additional evidence, that the same question, between original and acquired monstrosity, as far as it relates to double monsters, may even now claim to be discussed. It is certain that two ova may be formed in one Graafian vesicle (Von Baer, Bischoff, Bidder). The equally well-known fact, that the common fowl sometimes produces double- yolked eggs, naturally led at one time to the opinion that the formation of double monsters might be attributed to the developement and subsequent union of the embryo in each yolk ; an opinion which has been adopted by some on very insufficient grounds, as it does not appear to be warranted by any direct observ- ations made upon the result of the incubation of double-yolked eggs, and is at variance with much of what is known of the structure and mode of union of the two embryos composing a double monster.* * I have here made use of the words of Professor Allen Thompson, who, in a remarkable memoir upon double monsters, published July, 1844, in the London and Edinburgh Monthly Journal, fully entered into the topic, and illustrated the genesis of double mon- sters by some very interesting observations. I lament that he was not acquainted with my mono- graph upon the same subject, nor with the succinct account which Mr. Paget has given of it in the British and Foreign Medical Review for October, 1841. He would have found in it a great deal in corroboration of his own opinions, in which I uni- versally agree with him. 974- TERATOLOGY. C. F. Wolff has distinctly affirmed, that a double-yolked egg is equivalent to a double ovum ; that the produce of its incubation would be twins ; and that a double monster can only proceed from a single yolk contain- ing a double germ. Examples of double em- bryos of birds sometimes occur at the full period of incubation, in which both are com- plete, and there is no union, excepting at the umbilicus. It is barely possible that each of these embryos may have been developed from a separate yolk, and that in the course of incubation the two yolks have come to coa- lesce, in consequence of external pressure, or other causes. Towards the conclusion of the period of incubation, when the yolk usually enters the abdomen of the foetus, we may suppose, in the case before us, a partial en- trance of the common yolk into the abdomen of each embryo, and thus, upon the subse- quent contraction of the umbilical aperture, the union of the two embryos may be effected. We learn, from the accurately-detailed ob- servation of C. F. Wolff, previously referred to in my monograph, that two completely separate foetuses may be formed in the bird's egg upon a single yolk, and within a single germinal and vascular area. The egg, in this instance, had been incubated six days, and both the eirbryos were at once so com- plete and so distinct, that there is no reason to believe they would have been united till the period when the entrance of the yolk into the abdomen of both, and the contraction of the umbilical apertures, had brought them together. In a dozen double-yolked eggs, which Prof. Allen Thompson brought to incubation, he never succeeded in obtaining a double mon- ster, nor even two embryos, at the full period, from any of them. In several instances he found that one yolk only had been productive. All this proves that such double-yolked eggs may produce twins, but that the forma- tion of a double monster is not dependent on them. It is highly probable that in the same manner, in Mammalia, the arrival in the uterus of two impregnated ova, in close proximity with one another, will be attended with the production, not of a double monster, but of twins. The complete fusion of these twins seems to me quite impossible. One of my chief arguments against the hypothesis of fusion of originally separate germs is the important fact, which I derive from my own investi- gations and from those of others, that double monsters form one series, among whose seve- ral members the degrees and modes of devia- tion from singleness gradually increase, and pass, without one abrupt step, from the ad- dition of a Rngle ill-developed limb to the nearly complete formation of two perfect beings. Now if this be true, no hypothesis can be acceptable if it do not plausibly ex- plain the origin of the whole series of double monsters, or if, though it may suffice to ex- plain the facts in one part of the series, those in another part are opposed to it. And here is a fair objection against the hypothesis of fusion of two originally perfect and separate embryos. Grant that we might explain by it the formation of several of the more perfect instances of duplicity; still, if the same hypo- thesis is altogether opposed by the simpler forms of duplicity, it is surely not tenable. For example, it cannot account for the exist- ence on a child's sacrum of a shapeless mass, containing an isolated portion of intestine, as in Mr. Hanley's case. And still less can it explain the existence of a superfluous limb ; for the limbs are mere off-shoots, and are produced at so late a period, that if we could imagine two embryos to come in contact by their shoulders or pelvis, and a fusion of those parts to take place, we should still have to explain how one of them, leaving only an arm or a leg behind him, could for the rest of his substance, head, trunk, and all, wholly dis- appear. It was a main objection against the doctrine of Lemery, that if two germs came in contact by accident (as he supposed), they could not exhibit any regularity in their mode of attach- ment, but faces would be forced into chests, abdomens into spines, and so on. The mo- derns, who adopt the same hypothesis, sup- pose that the ova come in contact not by ac- cident, but bv an attraction de sot pour soi, of which the influence is, that the two ova being by accident set face to face or back to back, or in any other way similia similibtis, will be drawn to each other, and will unite by similar parts. But, with all respect for the authority of M. Geoffroy St. Hilaire and his disciples fas Mr. Paget elegantly said in his abstract of my monograph upon double monsters), who regard this as " la regie supreme de tons les arrangements et de toutes les mo- difications organiques chez les etres com- poses," I confess that I can find no good evidence that such an attraction exists. I can see in it nothing more than a very happy expression of a fact, which it in no wise ex- plains. The extraordinary notion of MM. Delpech and Coste, that such an attraction may be the result of electric currents, is certainly no evidence of its existence, this being entirely imaginary. And the reasoning in its favour seems no better than the facts, for I can find nothing but this kind of circle : monsters adhere by similar parts, therefore there is an attraction de soi pour soi; there is then such an attraction, and therefore double monsters so adhere. I believe, therefore, that such an attraction is hypothetical ; and if it be so, surely the hypothesis which involves it and an accident as essential elements is less probable, as well as less sufficient, than that which I maintain. It is scarcely better than Lemery's, of mere accident ; for it requires not only the accident of a particular position of the ova, but that of their being of the same sex, which has been said previously to be the general rule for double monsters. After all this, we conclude with the words of the learned Wolff, published in 1773: — " Patet, igitur, monstra composita non sic oriri, ut TERATOLOGY. 975 aliquantlo duo separati intcgri embryones fue- rint, qui dein contingentes et compress!, par- tibus eoruin nonnullis destructis, aliis coalitis et commixtis, concrescerent in unum noviun compositum corpus ; ea vero, quae vel clefectu partium vel insolita structura monstra sunt, nou ita fieri ut priiis integri et naturales em- bryones f'uerint, qui deinde per causas acci- dentales ad generationem non pertinentes inutilati vel transmutati t'uerint ; sed necesse esse, ut utraque monstroruni genera a primis suis initiis jam ejusmodi monstra f'uerint." If we are right in not admitting the exist- ence and tbe fusion of two distinct germs, we necessarily adopt the opinion that only one germ has been formed, and that in this excess of formative power lies the cause and origin of every monstrous duplicity. Mr. Allan Thompson demonstrated, in coincidence with Wolff, Von Baer, and Rcichert, as may be seen in the wood-cut {fig. 029.), that Fig. 629. Fig. G30. From a fowl's egq after sixteen or eighteen hours' in- cubation. Magnified four times. a, the germinal area of the cieatricula ; b, the transparent area, containing two primitive traces of embryos; c c, primitive grooves of the double embryonic trace, on each side of which are seen the lamina; dorsales. {After A. Thompson.} upon one yolk, and in one germinal mem- brane or blastodermatic vesicle, there may be formed, in birds, two primitive grooves, which, in their ulterior increment, shall probably form a double monster, as may be seen in a goose's egg, after five days' incubation, represented after Allan Thompson, in^. 630. By the for- mation of such a double primitive groove in a single ovum, we may explain the origin of the principal types of double monsters; and on this point a recent observation of Valentin seems particularly worthy of notice, viz. that in which an injury, inflicted on the caudal ex- tremity of an embryo on the second clay, was found, on the fifth, to have produced tbe rudiments of a double pelvis and four in- ferior extremities. But if we admit this cause for those large and principal types, we must acknowledge that it is insufficient for the heteradelphs, and for all those cases in which, the body remaining single, some parts are Double, emliri/o removed from a goose's egg after Jive days' incubation. Magnified four times, g, the common heart ; h, rudiments of the superior, i, of the inferior extremities ; k, the common ce- phalic fold of the amnios ; 7, the caudal folds. (After A. Thompson.) double. For these the excess of formative power is the only explanation we can give. We understand, under this name, not the nisus formrtliviis of the ancient physiologists, working as a Dens ex macliina, but the physical and vital metamorphoses materia?, to which tbe formation of a new being ought to be attri- buted. Those who are fond of the modern nomenclature may name it, if it pleases them, h/pical or organic power. But enough, we admit such a power, of whatever name it may be, and contend further, that different degrees or quantities of excess lie at the origin of all the cases of double monsters, the degree of excess determining in each the degree of duplicity. If a certain excess of power be admitted capable of producing any one case of duplicity, other amounts of excess may be believed capable of producing all the other cases which differ from it only in degree ; and I meant to have proved, in my monograph, and in the succinct survey I have given of double mon- sters in this Article, that all double monsters may be referred to differences in degree of deviation from the normal singleness. But in many double monsters we see excess in one part and detect in another, so that we must suppose, in our hypothesis, that in these cases the power, more or less excessive in quantity, is also wrongly distributed. Nor is this inconceivable ; for since, in the normal devclopemental power, we must imagine at least two elements, quantify and distribution, and must acknowledge that, for the attain- ment of a perfect result, the quantity must be distributed in definite proportions to each part, so it is not improbable that, in certain circumstances of fault in the ovum, a normal or an excessive power may be distributed dis- proportionately in the several parts. To sum up, therefore, our reasons for re- jecting the hypothesis of fusion of ova in 976 TESTICLE (NORMAL ANATOMY). favour of that of excess or irregular distri- bution of developemental power, for preferring to regard them as examples rather of single- ness tending to duplicity than of duplicity tending to singleness, are briefly these : that it is probable that the whole class of monsters by excess owe their origin to different de- grees of one common fault, and consequently that the explanation of their origin ought to be the same for all ; that no kind of fusion can account for the production of super- numerary individual organs, the rest of the body being single ; but that it is not impos- sible that excess of power in the ovum, which all admit can alone explain the lower degrees of duplicity, may, in proportionally higher degrees, perhaps by the formation of two primitive grooves, produce the more complete double monsters, or even two such separate individuals as are sometimes found within a single amnion. BIBLIOGRAPHY. — On account of the length of this Article, and the great number of books upon the subject, I shall omit the Bibliography, and refer to the foot-notes as well as to the manuals of Meckel, Eo- kitansky, Geoftroy St. Hilaire, von Ammon, and my own, in which the bibliography is duly noticed. (W. Vrolik.) TESTICLE. — (HUMAN ANATOMY). Gr. o(>x's 5 Latin, Testis — Testiculus ; French, Teslicule ; German, Hode ; Italian, Testkolo. The testicle is the gland by which the semen or spermatic fluid is secreted. Two in number, and contained within the scrotum, these organs are suspended at a variable and unequal distance from the abdominal rings, one testicle, generally the left, hanging a little lower than the other. This arrangement pre- vents collision between these organs when the thighs are suddenly approximated ; one tes- ticle slipping above the other, and thus elud- ing violence. In cases of transposition of the viscera and blood-vessels, it has been observed that the right testicle hangs lower than the left. The shape of the testicle of an adult is that of an oval with flattened sides. The organ has two extremities, an antero-superior, and a postero-inferior ; and two lateral surfaces. Its position in relation to the body is rather oblique, its long axis or antero-posterior di- ameter passing from above downwards and a little inwards. Its edges and sides are convex. Its upper extremity is rounded and capped by the epididymis, which rises above the body of the gland like the crest on a helmet. Ac- cording to Cruveilhier the testicle measures two inches in length, one inch in breadth, and eight lines in thickness. Sir Astley Cooper makes its long diameter two inches ; its trans- verse, an inch and a half; ami its lateral, one inch and one eighth. I have found the mean dimensions of the testicle to be one inch and three quarters in length, one inch and a quarter across or in breadth, and one inch in thirk- ness or from side to side. Meckel states its average weight to be four drachms, and Sir A. Cooper about an ounce. I have found the mean of these two estimates, viz. six drachms, to be the ordinary weight of the sound testicle of a healthy adult.* There are few organs subject to greater variations in size and weight than the testicle, even in men of the same age and constitution. The testicles also of the same individual rarely agree, the volume and weight of the left being, in general, greater than those of the right. I weighed the tes- ticles of six men, two of whom were killed by violence, and found the left gland heavier than the right in five; in neither of these instances, however, was the difference more than a drachm. The organ feels tense, compact, and slightly elastic. Its degree of consistence depends more on the tension of the tunica albuginea than on the proper substance of the gland. It is a good deal influenced by the quantity of seminal fluid contained in the tubular structure, and its state of activity or rest; the gland being tense and tumid when the organ is exercised and the tubuli are dis- tended, and soft and flaccid, when they are empty and the gland inactive. The parts composing the testicle may be described under four heads : — 1. The protective parts or tunics ; 2. The proper glandular or secreting structure ; 3. The excretory parts ; 4. The vessels and nerves. 1. The Protective Parts or Tunics. — The Tunica Vaginalis. — This is a delicate serous membrane in the form of a shut sac, which consists of two portions ; an outer one, the parietal, which is free and loose ; and an inner, reflected, visceral or testicular portion, which closely invests the gland. The two portions are connected and continuous with each other. The outer one loosely invests the whole of the testicle except its posterior edge and inferior extremity, parts where the membrane becomes attached to the gland. It is connected with the testicle at about five lines from the lower extremity, and the junc- tion of the two portions is marked by a white and rather irregular line. The uncovered por- tion of the organ corresponds to the original attachment of the gubernaculum. On the inner side of the gland the membrane, after investing the lower part of the cord to a greater or less extent, is reflected to the epi- didymis just below its head, and to the pos- terior edge of the body of the testis, being there separated from the epididymis by the vas deferens and blood-vessels of the gland. On the outer side the membrane entirely covers and closely invests the epididymis, and forms a cul-de-sac, which isolates its mid- dle from the posterior border of the testicle, and in cases of hydrocele is often distended into a pouch. At the bottom of this sac the tunica vaginalis on the two sides comes into close contact, and sometimes there is a com- munication at this spot between the two. The smooth and polished surface of the shut sac thus formed by the tunica vaginalis is lubri- ' This nearly accords •with Krause's estimate (Midler's Archiv. 1837.) — who found the mean weight in five instances to be 354-4 grains, or live drachms, two scruples and fourteen grains. TESTICLE (NORMAL ANATOMY). 977 cated by an albuminous fluid, having the ordinary properties of the secretions of the other serous membranes. The office of this membrane is to facilitate the movements of the gland, so as to enable it to elude pressure and escape violence. In some adult subjects the tunica vaginalis, •which was originally a process from the serous lining of the abdomen, still retains its con- nexion with that cavity. When the com- munication is free, the sac is very liable to receive a protrusion of some of the contents of the abdomen, and become the seat of con- genital hernia. Sometimes the communica- tion continues through a contracted tubular canal, which, though too narrow to admit the transit of any of the viscera, is open to the passage of fluid. In other cases the oblitera- tion is partial, one or more isolated serous sacs being left along the cord. It more often happens, however, that after the upper aper- ture of this process has closed a considerable part of it below remains unobliterated, so that the tunica vaginalis extends for some distance upwards in front of the cord. Frequently, also, although the obliteration is complete, remains of the prolongation may still be found in the form of a slender whitish filament, or fibrous process, which is lost in the areolar tissue in the anterior part of the cord, but may sometimes be traced as far as the tunica vaginalis. A small body of an irregular shape and variable size, and of a pale red or pinkish hue, is commonly found attached, often by a thin pedicle, either to the upper extremity of the testicle, or at the angle where the tunica vaginalis passes from the body of the gland to the epididymis. It is composed of a dupli- cature of this membrane, containing some fine areolar tissue and a number of small vessels. It occasionally contains a little fat. I have seen this little body in the testicle of the fcetus whilst in the abdomen, and, in early life, it is often of proportionally larger size, and of a deeper red colour than in the adult. It is quite distinct from the pedunculated cysts often found attached to the head of the epididymis. This little appendage to the tunica vaginalis seems to correspond with, and to be a type of, the remarkable omental process attached to the superior part of the testicle in the Rodentia and other animals. That it is an unimportant structure in the adult, is shown by its being frequently want- ing. It may be of use, however, by slightly increasing the secernent serous surface. The tunica Albuginea, or Tunica Propria, is a dense, tough, inelastic membrane, composed almost solely of white fibrous tissue, analogous to the sclerotic coat of the eye. It completely invests the body of the testicle, but not the epididymis. Its external surface is covered by the tunica vaginalis reflexa, to which it intimately adheres. This tunic is divisible into two layers, which can be separated only by a tedious dissection, but which in certain animals may be detached without difficulty. The branches of the spermatic artery and VOL. IV. veins ramify in the substance of the tunica albuginea, in canals bearing in their arrange- ment some analogy to the sinuses of the dura mater, which membrane the outer layer is supposed to resemble. The smaller vessels are chiefly distributed on the inner layer, Avhich owing to its vascularity has been com- pared to the pia mater investing the brain. At the postero-superior border of the testicle, and a little to its outer side, the tunica albu- ginea forms an internal projecting body or process, which lodges the blood-vessels and a portion of the glandular structure of the tes- ticle, called the rete testis. This body is named, after the anatomist who first'described it, the Corpus Hig/nnori. It has since, how- ever, been called by Sir A. Cooper the medi- astinum testis, and he describes it as being formed by the tunica albuginea, which at that part is divisible into three layers. The first layer turns upon the spermatic cord, and unites with the sheath which covers the ves- sels. The second layer unites with a similar layer on the opposite side, and forms a thick substance, between the fibres of which inter- stices are left for blood-vessels and absorbents, whilst the internal layer, uniting with that on the opposite side, as well as with the preced- ing layer of the tunica albuginea, forms the process called mediastinum, which projects into the testicle between the tubuli, and it is in this substance that the seminal canals of the rete are placed. The mediastinum is therefore composed of two bodies ; the upper placed towards the spermatic cord, the lower towards the centre of the testicle : in the upper are placed the blood-vessels ; in the lower, the canals of the rete. Its length varies from six to eleven lines. II. Glandular or Secreting Structure. — The glandular part of the testicle is very simple, and its tissue is more easily demonstrated than the structure of most other glands. It consists of numerous seminiferous vessels or tubes, supplied with blood-vessels, lymphatics, and nerves. Its colour is a greyish yellow or brown, more or less tinged with blood, and is paler in infants and old men than in adults. The tubes are collected into numerous lobes or lobules, invested by a fine areolar tissue, which, detached from the interior of the tunica albuginea, penetrates the gland, and sends out lateral processes forming septa, which separate and sustain the lobules. These septa at their origin partake of the fibrous character of the tunica albuginea, but as they converge towards the superior border of the testicle, occupied by the corpus Highmori, they become finer, and are gradually resolved into a delicate areolar tissue. The septa are traversed by numerous blood-vessels, which minutely divide in them before being distributed on the semi- niferous tubes. Sir A. Cooper states, that the inverted portion of the tunica albuginea, forming the mediastinum testis, sends forth numerous ligamentous cords, some of which pass to the anterior edge of the testis ; whilst others form shorter processes to support and invest the lobes, being met by similar liga- 3 R 978 TESTICLE (NORMAL ANATOMY). mentous cords from the inner surface of the tunica albuginea. I have not been able to make out any such ligamentous processes passing into the substance of the testis, as are represented in Sir A. Cooper's work (part i. pi. 2. fig. 3), which I have no doubt is an ex- aggerated view of the preparation from which it was taken. The cords described appear to me to consist chiefly of blood-vessels sup- ported by slight fibrous processes from the tunica albuginea and areolar tissue. In a well- injected testicle very little tissue of the nature of ligament can be found between the lobes. The secreting structure of the testicle, like the texture of many other glands does not possess much common sensibility. When exposed in disease it may be probed and injured with the forceps without pain. Tubuli Seminifcri. — These tubes, which form by far the greatest part of the bulk of the glandular structure of the testicle, are very numerous, and radiate from all parts of the circumference of the organ towards the mediastinum, making numberless con- volutions which progressively diminish as they approach the rete testis. Two or more of the tubuli, being collected together and invested by a common tunic of con- densed areolar tissue, form a lobe or lobule of a conical form, its apex terminating at the corpus Highmori. The lobes thus formed are Fig. 631. T7ie lobes attached to the mediastinum, but artificially separated from each other. (From a preparation in the Hunterian Museum, formerly in Sir A, Cooper's collection.) not entirely distinct, but communicate with neighbouring lobes : the processes investing them are therefore incomplete, and the lobes cannot be separated from each other without division of some of the seminiferous tubuli. Krause estimates the number of the lobes as varying from 404 to 484.* The tubuli are of a white colour and uniform size, but their calibre differs in different subjects, and varies a good deal according to the age of the subject and the state of activity of the testicles, being larger in young adults and when distended with semen, than in old persons and when the gland is in a state of rest. The size of the ducts also often differs in the two testicles of the same subject. In general the calibre of the tubuli corresponds to the size of the tes- * Mliller, Archiv. fur Anatomic, 1837, s. 22. tide. Observers do not exactly agree in their estimates of the diameter of the tubuli. The average diameter of the uninjected canal is estimated by Miiller at -^ of a line ; by Lauth * at T|^ of an inch. Krause found the tubuli, when filled with semen, to measure about -JL. of a line, and in old men and youths •Jg-. Huschkef estimated the ordinary thick- ness of the whole tube from -^ to ^ of a line, and that of the walls from —t^ to ^y. Owing to the stoutness of the basement membrane, the thickness of the walls of the tubes is con- siderable as compared with the secreting ducts of other glands, and this accounts for the tubes being able to resist the pressure of a column of mercury in injections. Monro reckoned the number of the seminiferous tubes at 300 ; Lauth made the average num- ber 840, and he estimated the mean length of all the ducts united at 1750 feet. He found the individual ducts to vary in length, the mean being 25 inches. Krause estimated their entire length at 1015 feet. The mem- brane composing the tubuli is continuous with the mucous surface of the genito-uriuary system. It is lined with epithelium, and the spermatozoa are developed from the epi- Fig. 632. Glandular structure of the testicle, displayed by mer- curial injection. (After Lauth.) a a a, glandular substance of the testicle subdi- vided into lobes, each lobe being composed of con- voluted tubuli closely packed ; b, rete testis ; c, vasa efferentia ; d, inflected part of the vasa efferentia forming the coni vasculosi ; e, dilatations of the efferent vessels ; /, body of the epididymis ; g, tail of the epididymis ; h, vasculum aberrans ; i, in- flected part of the vas deferens ; k, straight part of the duct. * Mem. de la Societe' d'Hist. Nat. de Strasbourg, t. i. f Encyclopedic Anatoinique, t. v. p. 347. TESTICLE (NORMAL ANATOMY). thelial cells. There is no appearance of an intertubiilar substance ; the ducts are merely connected by a loose network of vessels, and consequently readily admit of being sepa- rated and unravelled. The tubes, when suc- cessfully injected with quicksilver, form a beautiful anatomical preparation. Sir A. Cooper succeeded in filling the tubes with size injection ; but he has not described the mode in which it was effected, and other anatomists have failed in similar attempts.* When the tubuli seminiferi are unravelled, they are found to divide and form numerous anastamoses, which increase in frequency to- wards the circumference of the testicle. "(See diagram, /g. 633. a1 a1). The tubuli thus form one vast network of communication, so that it is impossible to isolate completely either a duct or a lobule. The credit of making this interest- ing discovery of the anastamoses of the se- minal tubes is due to Lauth. In only one instance did he succeed in finding a duct, ter- minating in a blind pouch, and this he regarded as exceptional. Blind ends have been found, however, more frequently by Krause. The anastamoses of the tubules have been observed in the rat and other animals as well as in man. The convolutions of the seminal tubes di- minish in number as they approach the me- diastinum, and cease altogether at a distance of from one to two lines, where two or more unite to form a single straight duct, termed vas rectum, which joins the rete testis at a right angle (a~ a"). The vasa recta are very slender, and easily give way when injected : their calibre, which is greater than that of the seminal tubes, is estimated by Lauth at y^th Fig. 633. Diagram of the testicle. (After Lauth.') a a a, tubuli; a1 a1, subdivisions and anastamoses of the tubuli ; a"2 a1*, vasa recta. The other references are the same as in fig. C32. *_Sir A. Cooper's beautiful preparations of the testicle are preserved in the Museum of the Royal College of Surgeons of England. 979 of an inch. Haller reckoned their number at twenty, which is, however, too few. Rcte Testis, as its name implies, consists of a plexus of seminal tubes, which occupies the corpus Highmori, or mediastinum testis. The vasa recta, after penetrating the walls of this body, terminate in from seven to thirteen ves- sels which, running parallel to each other in a waving course, and frequently dividing and anastomosing, form the rete testis. (b). Lauth found the mean diameter of the vessels of the rete in injected preparations ^ of an inch. According to Prochaska, these vessels are supplied with valves, but such is not the case. Small dilatations, however, are often found in different parts of the plexus. III. The Excretory Parts. — The epididymis, a continuation of the testicle, is a body of a crescentic form, divided into an anterior and upper extremity, called head, or gtobus major, which is firmly attached to the testicle ; a middle part or body, which is less in size, and separated from the gland by a pouch of the tunica vaginalis ; and a tail or globus minor, connected to the testicle by areolar tissue. The volume and weight of the epididymis vary in different subjects, but are proportionate to the size of the testicle. It is longer than the testicle, measuring about two inches in length and four or five lines in width. Its name (from eVl upon, and 5i5v/j.os testis,) indi- cates its position, which is along the postero- superior border of the gland. The epiclidv- mis is chiefly made up of seminal canals connected and supported by a firm resisting areolar tissue. The ducts which spring from the upper part of the rete testis to form the epididymis are termed vasa cjfcrentia. They are usually about twelve or fourteen in num- ber, but vary from nine to thirty. The inflec- tions of each of these efferent ducts are so arranged as to form in the head of the epidi- dymis a series of elongated conical figures called coni vasculosi. These ducts, at their commencement, run straight for a distance of about one or two lines, when they form con- volutions which become more numerous and close as the ducts recede from the testicle. Their length varies, the upper being the shortest. Lauth found their average length to be seven inches four lines, and calculating their number at thirteen, he makes the united length of the vasa efferentia nearly eight fc'et. He states that the efferent ducts diminish in size from their commencement to their ter- mination in the canal of the epididymis, where they are less than the seminiferous ducts of the testicle. (Fig. 634-.) As in the rete, round dilatations of variable size are often met with in these ducts. (Fig. 632., e c.) The efferent ducts, after forming the coni vasculosi, successively join a single duct, the canal of the epididymis, at irregular distances, the intermediate portions of the duct varying in length from half an inch to six inches. The efferent ducts are more slender than the canal of the epididymis, and frequently give way under the pressure of the column of mer- cury when injected. The body and tail of the 3 R 2 980 TESTICLE (NORMAL ANATOMY). onididymis are entirely made up of the con- didymis or vas deferens. It is more corn- volutions of the single canal in which the monly attached at the angle formed by t Fig. 634. Fig- fi35- An efferent vessel and a portion of the head of the epididymis magnified, to show the progressive dimi- nution of the canal of the cone, and the calibre of this vessel, in comparison with that of the canal of the epididymis. c, vas deferens ; d, inflected portion of the duct ; e e, head of the epididymis. (After Lauth.) vasa efferentia terminate, closely connected by areolar tissue. Monro described this canal as gradually increasing in size from the head to the tail, and he estimated its calibre about its middle at J^ of an inch. Lauth states that its size is subject to great irregularities in different parts and in different subjects. This anatomist has particularly described the con- volutions of this duct, and has shown that they are regularly arranged in four series, which successively increase in size ; the first being the smallest, and the fourth the largest. The arrangement will be understood by reference to the subjoined figure. Monro estimated the length of the canal at thirty feet eleven inches. Lauth found its mean length to be nineteen feet four inches eight lines. The parietes of the canal are strong, and bear considerable resistance. The canal of the epididymis ter- minates in the excretory duct of the testicle, the vas deferens, and is usually contracted at the part where the two join, which accounts for the mercury when forced into the vas de- ferens being often arrested at this point. It was calculated by Monro that the semen, be- fore arriving at the vas deferens traverses a tube forty-two feet in length. Lauth, how- ever, makes the whole distance but little more than twenty-two feet. Vasculum aberrans. — This name was given by Haller to a blind duct or coscal appendage often found connected either to the epi- Canal of the epididymis partly unravelled, to show the four series of inflections u-liich the duct undergoes 'in the several divisions of the epididymis. o, o, first series of inflections ; p, p, second series ; q, q, third series ; r, r, fourth series. (After Lauth). termination of the former in the latter. (Figs. 632., and 633, //.) It forms a convoluted duct as large as the canal of the epididymis, which is contracted at its insertion, and ter- minates in a blind and often dilated extremity. Sometimes after being dilated for a certain distance it diminishes, and becoming very minute, is lost in the areolar tissue of the cord. It usually passes up the cord for about two or three inches, but has been found to extend as far up as the brim of the pelvis. The length of this appendage when unravelled varies from one to twelve or fourteen inches. The vasculum aberrans is not constantly pre- sent ; indeed, Monro found it only four times in sixteen ; but I believe, with Lauth, that it exists more frequently. Occasionally there is more than one, and as many as three have been found both by Lauth and Sir A. Cooper. Hunter regarded these ducts as supernumerary vasa deferentia, of a nature similar to the double ureters.* Miiller states that their office is evidently the secretion of a fluid which they pour into the epididymis. f We have no evidence, however, that the duct serves any particular office. Vas defcrens,— the excretory duct of the testicle, commences from the tail of the epidi- dymis, and terminates in one of the ejacu- latory canals behind the bladder, being in length from fifteen to sixteen inches. Arising * Works by Palmer, vol. iv. p. 24 t Physiology, trans, by Baly, vol. i. p. 45 TESTICLE (NORMAL ANATOMY). from the contracted part of the canal of the epididymis at an acute angle, it ascends along the inner side of this body, from which it is separated by areolar tissue and the spermatic arteries and veins. A right or left testicle may thus always be distinguished by the circum- stance that when the testicle is in position, the vas deferens is situated on the inner or mesial side of the organ. In this part of its course, for the distance of about an inch and a half, or more, the vas deferens forms numer- ous convolutions, (fig*. 632., and 633, z.), which gradually cease as the duct mounts above the testicle. The inflected part of the vas deferens, when unravelled, was found by Lauth to measure six inches and a half. It afterwards takes a direct course (/•.•) up the spermatic cord to the inguinal canal, passing behind anil at a short distance from the spermatic arteries and veins. On entering the abdomen at the internal ring, it quits the spermatic vessels and descends into the pelvis, passing at first by the side of, and afterwards behind and below the bladder, on the inner side of the corresponding vesicula seminalis, the excretory duct of which it joins at an acute angle, to form the ejacnlatory canal. The canal of the vas deferens is extremely fine, and its walls are nearly uniform in thick- ness until it reaches the vesicula seminalis. It is lined by a fine membrane of a mucous character, which is continuous with the urethra. This membrane forms longitudinal folds. The vas deferens is round and in- durated,— harder than any other excretory duct in the body, by which character it is easily distinguished, when handled, from the other parts constituting the spermatic cord. Many anatomists have entertained the opinion that the parietes of this duct are muscular. It is distinctly so in the bear, bull, and other animals. On careful examination, however, of sections of the human vas deferens with the microscope, I could discover nothing more than simple fibrous tissue. Huschke makes three layers of fibres ; two longitudinal, and one circular, situated between them ; the latter being the thickest. The duct has an external investment of condensed areolar tissue. IV. The Vessels and Nerves. — Spermatic Vessels. — The spermatic arteries, the chief vessels supplying the testicles, arise in pairs, at a very acute angle, from the fore-part of the aorta, immediately below the renal ar- teries. Their origin is subject to consider- able varieties. The two seldom arise at the same level, and the right is often a branch of the right renal artery. Sometimes one or both come off from the superior mesenteric. Occasionally there are two spermatic arteries on one or both sides, arising in the regular way. All these deviations are more frequently met with on the left than on the right side of the body. Each artery pursues a tortuous course downwards and outwards, passing behind the peritoneum obliquely across the psoas muscle and ureter, to which, as well as to the surrounding areolar tissue, it gives 981 off several branches. The artery then enters the inguinal canal through the internal ring, and emerging at the external, passes down the cord, being surrounded in its course by the spermatic veins. The further distribution of the artery is thus correctly described by Sir A. Cooper : " When the artery reaches from one to three inches from the epididymis, varying in different subjects, it divides into two branches, which descend to the testicle on its inner side, opposite to that on which the epididymis is placed ; one passing on the anterior and upper, the other to the posterior and lower part of the testis. From the anterior branch the vessels of the epididymis arise: first, one which passes to its caput; secondly, another to its body, and, thirdly, one to its cauda and the first convolutions of the vas deferens, communicating freely with the de- ferential artery. The spermatic artery, after giving off branches to the epididymis, enters the testis, by penetrating the outer layer of the tunica albuginea ; and dividing upon its vascular layer, they form an arch by their junction at the lower part of the testis, from which numerous vessels pass upwards ; and then descending, they supply the lobes of the tubuli serniniferi. Besides this lower arch, there is another passing in the direction of the rete, extremely convoluted in its course, and forming an anastomosis between the prin- cipal branches.'' The testis receives a further supply of blood from another vessel, the ar- tery of the vas deferens, or posterior spermatic artery, which arises from one of the vesical arteries, branches of the internal iliac. This artery divides into two sets of branches, one set descending to the vesicula seminalis and to the termination of the vas deferens ; the other, ascending upon the vas deferens, runs in a serpentine direction upon the coat of that vessel, passing through the whole length of the spermatic cord ; and when it reaches the cauda epididymis, it divides into two sets of branches, one advancing to unite with the spermatic artery to supply the testis and epi- didymis, the other passing backwards to the tunica vaginalis and cremaster. The spermatic veins spring in three sets from the testicle, one from the rete and tubuli, and another from the vascular layer of the tunica albuginea, and a third from the lower extremity of the vas deferens. The veins of the testicle pass in three courses into the beginning of the spermatic cord ; two of these quit the back of the testicle, one at its anterior and upper part, and a second at its centre ; and these, after passing from two or three inches, become united into one. The other column accompanies the vas deferens. There is also a large vein, just above the testicle, which crosses to join the three columns. The veins of the epididymis are one from the caput, another from its body ; one from its cauda, and another from its junction with the vas deferens, besides some small branches ; they terminate in the veins of the spermatic cord. The veins, after quitting the testicle, become extremely tortuous, and frequently 3 R 3 TESTICLE (NORMAL ANATOMY). 982 divide and inosculate in the cord, forming a plexus termed vasa panipiiiifurmia. These communications cease as the veins approach the ring, which they enter, and ascending along with the psoas muscle in company with the spermatic artery, unite to form a single vein which usually terminates on the right side in the vena cava inferior, and on the left, in the renal vein ; though this is subject to some variety. The left spermatic veins pass under the sigmoid flexure of the colon. Many anatomists speak of the spermatic veins as being destitute of valves, which they assign as one of the reasons for the occurrence of varicocele. I have several times injected these veins with alcohol, and on laying them open have observed valves in the larger vessels, and I have also found injections thrown into the veins arrested by the valves. They are seldom seen, however, very near the testicle, or in the smaller veins forming the plexus ; nor have I observed them within the ab- domen. Absorbents. — The absorbent vessels of the testicle are very numerous, and arise from every part of its internal structure and coats. They unite to form four or five trunks, which ascend along the cord, and traverse the in- guinal canal, without communicating with the glands in the groin, but pass upwards in front of the psoas muscle, behind the peritoneum, and terminate in the lumbar glands on the side of the aorta. Nerves. — The nerves of the testicle are derived chiefly from the renal plexus, but partly also from the superior mesenteric and aortic plexuses. These nerves descend in company with the spermatic artery to the cord, where, being joined by branches from the hypogastric plexus, which pass along the vas deterens, they form together the spermatic plexus, the branches of which are intermingled with the vessels of the cord, and ultimately terminate in the substance of the testicle. A few twigs from the external spermatic nerve may also be traced to the coverings of the gland. The Testicle in the Foetus, and its Passage into the Scrotum. — The testicles are first de- veloped and situated in the abdomen. They originate from the lower part of the corpora Wolffiana, and may be detected at an early period of foetal existence immediately below the kidneys on the forepart of the psoas muscles, to which they are attached by a reflexion of peritoneum. This membrane closely invests the testicles in the same man- ner as it covers the other abdominal viscera. The position of the testicle in the abdomen is nearly the same as it maintains after its passage into the scrotum. The epididymis, however, is relatively of a larger size than in the adult, being about one-third that of the body of the organ. Attached to each testicle whilst in the abdomen is a peculiar body, which was termed by Mr. Hunter, who first described it, the gubernaculum, as it was sup- posed to serve as a guide to the testicle in its passage. It is a soft solid projecting body of a conical form, which varies somewhat in shape and size at different periods of transi- tion of the testes, becoming shorter and thicker as the gland approaches the abdo- minal ring. It is situated in front of the psoas muscle, to which it is connected by a reflexion of peritoneum. Its upper part is attached to the inferior extremity of the testicle, lower end of the epididymis, and commencement of the vas deferens. The lower part of this process passes out of the abdomen at the abdominal ring, and diminishing in substance and spreading, terminates in three processes, each of which has a distinct attachment. The central part and bulk of the gubernaculum is composed of a soft, transparent, gelatinous substance, which, on examination by the mi- croscope, is found to consist of nucleated cells, the primitive areolar tissue : this central mass is surrounded by a layer of well-deve- loped muscular fibres, which may be distin- guished by the naked eye, and svhich can be very distinctly recognised in the microscope to be composed of striped elementary fibres. These muscular fibres, which may be traced the whole way from the ring to the testicle, are surrounded by a layer of the soft elements of the areolar tissue, similar to that composing the central mass ; and, in the same way as the testicle, the whole process, except at its pos- terior part, is invested with peritoneum. On carefully laying open the inguinal canal, and gently drawing up the gubernaculum, the muscular fibres may be traced to the three processes, which are attached as follows : the external and broadest is connected to Pou- part's ligament in the inguinal canal; the middle forms a lengthened band which escapes at the external abdominal ring, and passes to the bottom of the scrotum, where it joins the dartos ; the internal takes the direction in- wards, and has a firm attachment to the os pubis and sheath of the rectus muscle. Be- sides these, a number of muscular fibres are reflected from the internal oblique on the front of the gubernaculum. It thus appears, that the attachments of the muscle of the guber- naculum, and those of the cremaster in the adult are exactly similar. I have succeeded in tracing out the former before the testicle has moved from its original position, at dif- ferent stages of the process of transition, and immediately after its completion ; and of the identity of the two muscles no doubt can be entertained. Cams was of opinion that the cremaster does not exist before the transition of the testicle ; but that it is formed mecha- nically, by the testicle pushing before it the lower fibres of the internal oblique, so as to form the loops of this muscle.* This view which has been adopted by M. Jules Cloquet, and after him by many of the anatomists of this country, is erroneous and inaccurate.f The vessels of the testicle in the foetus * Compartive Anatomy, by Gore, vol. 2. p. 347. t Vide Obervatious on the Structure of the Gu- bernaculum, and on the Descent of the Testis in the Foetus, by the author, in Lend. Medical Gazette, April 10. 18-11, or in the Lancet, of the same date. TESTICLE (NORMAL ANATOMY). arise from" the nearest largest trunks, and enter the substance of the gland at its pos- terior part. The artery of the vas deferens, from which the gubernaculum is chiefly sup- plied, is nearly as large as the spermatic. The long course taken by the arteries and veins of the testicle when in the scrotum is thus ex- plained by the original site of the organ, to which circumstance must also be ascribed the sharp turn upwards of the vas deferens from the epididymis, the two being continuous in a direct line, whilst the testicle is in the ab- domen. Fig. 636. Diagram of the gubernaculum and testicle previous to its descent. 1, the kidney ; 2, the testicle ; 3, 3, the peritoneum ' 4, vas deferens passing down into the pelvis by the side of the bladder; 5, the bladder; 6, the abdo- minal ring ; 7, 7, Poupart's ligament ; 8, pubic por- tion of the cremaster ; 9, fibres of the cremaster arising from Poupart's ligament ; 10, portion of the guberuaculuui attached to the bottom of the scro- tum. Between the fifth and sixth month of foetal existence, sometimes later, the testicle begins to move from its situation near the kidney towards the ring, which it usually reaches about the seventh month. During the eighth month it generally traverses the inguinal canal, and by the end of the ninth arrives at the bottom of the scrotum, in which situation it is commonly found at birth. The testicle, both during its passage to the ring and through the inguinal canal, carries along with it its original peritoneal coat, adhering by the reflexion of this membrane, during the whole of its course to the parts behind, in the same manner as whilst situated below the kidney. The testicle therefore does not pass directly and abruptly into a pouch prepared to receive it, but carries the peritoneum with it, con- tinuing to be connected to the parts behind by the reflexion of the membrane, between the folds of which the vessels and nerves join the gland. In the passage of the testicle from the abdomen to the bottom of the scrotum, the gubernaculum, including its peritoneal investment and muscular fibres, undergoes the same change as that which takes place in certain of the rodcntia at the access of the season of sexual excitement ; the muscle of the testicle is gradually everted, until, when the transition is completed, it forms a mus- cular envelope external to the process of peri- toneum, which surrounds the gland and front of the cord. As the testicle approaches the bottom of the scrotum, the gubernaculum di- 983 minishes in size, owing to a change in the dis- position of its areolar elements ; the muscular fibres, however, undergo little or no diminu- tion, and are very distinct around the tunica vaginalis in the recently descended testicle. The mass composing the central part of the gubernaculum which is so soft, lax, and yield- ing, as in every way to facilitate these changes, becomes gradually diffused, and after the arrival of the testicle in the scrotum, contri- butes to form the loose areolar tissue which afterwards exists so abundantly in this part; the middle attachment of the gubernaculum, which may be traced to the dartos at the bottom of the scrotum, gradually wastes away and soon becomes indistinct, though slight traces of this process often remain to the latest period of life. Thus, after death, in dragging the testicle of an adult out of the scrotum by pulling the cord, the lower part of the gland, which is uncovered by serous membrane, is often found connected to the bottom of the scrotum by a band of firm and dense areolar tissue, which requires division with the scalpel. This band is the remains of the middle attachment of the gubernaculum. In cases in which the testicle has been re- tained in the groin, I have traced a cord of dense tissue from the gland to the lower part of the scrotum. After the arrival of the tes- ticle in the scrotum, the peritoneum with which it is closely invested, its original en- velope, becomes the inner layer of the tunica vaginalis ; whilst the pouch around, which is continuous with it, forms the outer layer, or vaginal sac. Immediately after the arrival of the testicle in the scrotum, this bag commu- nicates with the abdomen, and in quadrupeds continues to do so during life ; but in the human subject it soon begins to close, and when the foetus is ushered into the world, the abdominal orifice is often shut, and the whole canal from the ring to the upper part of the gland is, in general, completely obli- terated in the course of the first month after birth. The obliteration is effected by an intimate union of the surfaces of the serous membrane. It sometimes does not take place at all*, or is delayed or only partially com- Fig. 637. Diagram of the. testicle immediately after its arrival in the scrotum, the cremaster being everted' 1, the testicle ; 2, the shortened gubernaculum ; 3, 3, the peritoneum ; 4 , portion of the cremaster arising from Poupart's ligament ; 5 pubic portion of the nruscle. * The communication constantly remains open in quadrupeds, the chimpanzee, according to Professor 3 R 4i 984 TESTICLE (NORMAL ANATOMY). pleted. Congenital hernia, or hydrocele is the result of a failure in this process ; and other forms of hydrocele are occasioned by imperfect obliteration of the canal. Much difference of opinion exists as to the immediate cause of the transition of the tes- ticle. Hunter, Meckel, and others came to the conclusion that the muscular fibres of the cremaster are insufficient to bring the testicle further than the abdominal ring and complete the passage. They were not, however, ac- quainted with the attachment of this muscle to the pubis external to the ring, or it would be difficult to understand why Mr. Hunter, after arriving at the conviction that the cremaster passes to the testicle whilst in the abdomen, chiefly from analogy, was not induced by the same process of reasoning to conclude, that a muscle capable of changing the position of the testicle in brute animals, would be ade- quate to accomplish the same office in the human foetus. The necessity for some active agent to effect this change in the latter would appear to be greater even than in the lower animals, since, in the usual position of the foetus in utero, the passage of the testicle is contrary to gravitation,* and unaided by the movements of respiration. Now, when we consider the attachments and connec- tions of this muscle in the fcetus ; the per- fect development of its fibres, as ascertained by microscopical examination ; and the circum- stance that there are no other means, no other motive powers, by which this change can be effected, or in any way promoted, 1 think there is no reason to doubt that the cremaster ex- ecutes the same office in the human embryo, as that which it undoubtedly performs in cer- tain brute animals at a particular season. The fibres proceeding from Poupart's liga- ment, and the obliquus interims, tend to guide the gland into the inguinal canal ; those at- tached to the os pubis to draw it outside the abdominal ring ; and the process extend- ing to the bottom of the scrotum, to direct it to its final destination. As the process ap- proaches completion, the muscular fibres which perform so important a part in it gra- dually become everted, and acquire the new functions of elevating, supporting, and com- pressing the gland. The Functions of the Testicle. — The sperm or fluid secreted by the testicle has been con- sidered in the article (SEMEN). On survey- ing the structure of this gland, we cannot fail to remark the great extent of secreting surface afforded by the numerous, long, and tortuous tubuli, and the length and complexity of the excretory duct through which the seminal fluid has to pass. The extent of this duct is, indeed, so remarkable, that many physiologists have been led to suppose that the semen is Owen, being the only brute animal in which the tunica vaginalis forms a shut sac. * For this reason I have departed from the usual custom of English anatomists, and avoided describ- ing the change in the position of the testicle, as the descent. further elaborated or perfected in its passage through the convolutions constituting the epididymis. An examination of the spermatic fluid taken from the testicle and its duct both in man and in the lower animals, under all circumstances and at all periods, and the varying state of the discharge in cases of spermatic fistula, leave little room to doubt that secretion takes place actively only dur- ing the periods of sexual excitement, or under the influence of sexual feelings and desires. From birth to the period of puberty the testicles remain small, and grow but little in proportion to other parts ; but as the body, on the arrival of puberty, becomes stamped with the characters of the male sex, they rapidly enlarge, their glandular structure becomes much more developed, and, being excited, these organs begin to exercise the office of secretion, no spermatozoa being found in them until this period arrives. The age at which the testicles thus become developed varies in different climates, and in different constitutions, and is influenced by the mode of life and circumstances in which the indivi- dual is placed. The inhabitants of warm climates reach the age of puberty earlier than those of cold countries. In this part of Europe the change takes place from the age of fourteen to seventeen years, according to circumstances. Unlike the inferior ani- mals, the testicles in man are ready at all seasons to perform their office. The de- sires subside, and the secretion of semen be- comes languid as life advances, though they seldom cease entirely till the age of sixty-five or seventy. Indeed, I have several times dis- covered spermatozoa in the testicles of men upwards of seventy years of age, and once in the testicle of a tailor who died at the age of eighty-seven. There are instances on record of persons retaining the procreative faculty to the a<*e of one hundred years ; but in these cases, as in the well-known instance of old Parr, the general bodily powers were also pre- served in a very extraordinary degree.* " To the use of the sexual organs for the continuance of his race man is prompted by a powerful instinctive desire, which he shares with the lower animals. This instinct is ex- cited by sensations, and these may either ori- ginate in the sexual organs themselves or may be excited through the organs of special sen- sation. Thus in man it is most powerfully aroused by impressions conveyed through the sight or the touch : in many other animals, the auditory and olfactive organs communi- cate impressions which have an equal power ; and it is not improbable that in certain mor- bidly excited suites of feeling, the same may be the case in ourselves. That local impres- * Old Parr, who lived to the great age of 152, was dissected by the celebrated Harvey, and it is stated, " Gcnitalibus erat integris, neque retructo pene neque extenuato, neque scroto distento ramice aquoso tit in decrepitis solet, testiculis etiam inte- gris et magnis." Bettus de Ortu et Natura San- guinis, p. 320. TESTICLE (NORMAL ANATOMY). 983 sions have also very powerful effect in excit- ing sexual desire must have been within the experience of almost every one ; the fact is most remarkable, however, in cases of saty- riasis ; which disease is generally found to be connected with some obvious cause ot irrita- tion of the generative system, such as pruri- tus, active congestion," &c. * The part of the brain which is the seat of the sexual appetite is supposed by the phrenolo- gists to be the cerebellum, between which and the genital organs a close sympathy is said to exist. The grounds for this assumption, and the objections which have been fairly urged against it by sound physiologists, have been stated in a preceding article. (NERVOUS SYS- TEM, PHYSIOLOGY OF, vol. iii. p. 782. s.) No doubt, however, can be entertained that the mind is intimately connected with the procre- ative faculty, and that the brain controls and animates the desire for sexual enjoyment. An affection of the brain, or the mind, as sudden disgust, arrests the secretion of the testicles and extinguishes all desire as quickly and effectually as a strong mental impression stops the secretion of the gastric juice, and takes away all appetite for food. The influence of the brain on the reproductive function is well illustrated by the occasional effects of injuries of the head. Hildanus mentions the case of a man accused of impotency by his wife, who sued for a divorce. Nothing external was de- fective ; but the man stated that eight years previously he had received a blow on his head by a stick. From that period, " confitebatur penem erigi non posse." f Dr. Fisher relates the case of a gentleman who, while looking out of the window of a railway carriage, which at that moment encountered a violent collision, received a blow on the head and neck, by which he was stunned. On the se- cond day after the accident he complained of a numbness in his right arm, and experienced difficulty in passing his urine. In the course of two weeks he was able to leave his bed, and walk in the street ; but his vision was defective. Between the fourth and fifth week after his injury he made the discovery that he had lost the desire and physical power for sexual intercourse, and that no amorous sentiment, or the approach of a female could excite it. Under appropriate treatment the bladder gradually recovered its power, and his vision became perfect ; but the numbness of the right arm continued, and the generative functions remained partially impaired. His mental powers, particularly his memory of events, were also for a time seriously affected.^ Dr. Gall mentions that at Vienna he was con- sulted by two officers who had become im- potent in consequence of blows from fire-arms which had grazed the napes of their necks. One of the officers recovered his powers by * Dr. Carpenter's Principles of Human Physio- logy, p. 619. f Opera Observationum et Curationum Meclico- Chiriirgiearuni, p. 574. J Case by Dr. Fisher. American Journal of the Medical Sciences, Feb. 1839. p. 357. degrees, married, and became the father of several children.* When treating of Atrophy of these glands, I shall have occasion to mention cases in which the genital function has been perma- nently annihilated, and complete wasting of the testicles has resulted from injuries of the head. In respect to the mode in which these organs are called into action, they bear consi- derable analogy to the lachrymal, salivary, and mammary glands, in which secretion is excited both by the influence of the mind and by me- chanical contact or local irritation of the ex- tremity of the excretory duct, the glans penis holding the same relation to the testicle as the mucous membrane of the mouth does to the salivary glands, or as the nipple does to the mamma. The influence of the testicles and brain upon each other appears, as has been already observed, to be reciprocal ; for not only may desire be aroused by local irritation and ex- citing the testicles to secrete, but the passion itself never arises when these glands are re- moved before puberty and is extinguished by their extirpation afterwards. Nothing, indeed, illustrates more forcibly the intimate relation which the functions of the testicles bear to the mind and character of the individual, and the general organisation of the body, than the effects of castration. When it is performed in early life, the changes characteristic of puberty never ensue. There is a deficiency of the beard ; the muscles do not acquire the manly tone and vigour ; the areolar and adipose tissues abound ; the voice retains the high and clear tones of infancy ; and the mind remains deficient in energy and strength. When the testicles are removed after the period of puberty, the eunuch loses in part, though not entirely, his former masculine character. His beard grows less abundantly ; his voice becomes shrill; and there is di- minished energy and vigour in all his senti- ments and actions. These changes in the con- stitution, as well as the loss of the sexual instinct which occur in men thus degraded, do not immediately succeed the removal of the testicles, but take place gradually ; and there are well-attested cases in which desire has been experienced, and connection with emis- sion accomplished many months after the loss of these organs. This shows that the passion is not solely dependent on the secretion of semen, though it invariably declines when the power of procreation becomes lost. The emis- sions in such cases are imperfect and fruitless, consisting merely of the secretions of the vesiculae seminales and prostrate. The testi- cles not being parts essential to life, are sub- ject to different laws from those which re- gulate the actions of the vital organs. Their functions may be suspended, or they may remain in abeyance for an indefinite period without injury to the glands or any material effect on the constitution. In persons of * On the Functions of the Cwebellimi, tr. by Combe, p. -10. 986 recluse and studious habits the functions of these organs often continue dormant for years. Like the mammae in the unmarried female, though inactive, they remain sound and competent for secretion when duly ex- cited and called upon to exercise their func- tions. It often happens that the passions are excited without an opportunity being afforded for their gratification. Under these circum- stances the testicles become encumbered with secretion which would prove injurious to them were they not relieved by occasional nocturnal emission, or ejaculations of the semen under the influence of dreams during sleep, which appear to be a salutary provision to obviate the inconveniences which might result as well from ungratified desires as from an accumulation of semen in the ducts. Envelopes of the testicle. — The scrotum, or pouch of integument containing the testicles, including the dartos, has already been de- scribed. (Article SCROTUM). Superficial or external spermatic fascia. — Beneath the loose areolar tissue of the scro- tum is situated a delicate layer of fascia, which is continuous with the superficial fascia of the lower part of the abdominal parietes, and, descending so as to form a sheath to the spermatic cord and an envelope to the testicle, becomes continuous behind with the super- ficial fascia of the perineum. This fascia is usually very thick and distinct in cases of large and old scrotal hernia. Cremaster muscle — Directly beneath the superficial fascia is found the cremaster muscle (so named from Kpf/j-du to suspend), or, as it has been appropriately termed by Mr. Hunter, the musculus testis. (For description, vide, ABDOMEN, vol.i. p. 6.) The two attachments of this muscle, the external to Poupart's ligament, and the internal to the os pubis, correspond, as I have previously (p. 983.) shown, to those of the muscle of the gubernaculum, being indeed the same structure, with its relations altered. The actions of the cremaster, which, with a few exceptions, are involuntary, appear to be those of giving a tonic support to the testicles, retracting them to the abdominal rings, and compressing them during the sexual act. In some instances, in boys before the approach of puberty, this muscle has been capable of drawing the gland up into the in- guinal canal. Persons are occasionally met with who possess a voluntary power over its actions in various degrees of perfection. Some are able to elevate the testicle on one side but not on the other, whilst others can retract both testicles to the abdominal rings, and retain them there at will. A very remarkable instance of the cremaster muscle being com- pletely under the influence of volition is recorded by Mr. Hutchinson.* Deep spermatic fascia. — The tunica vagi- nalis and spermatic cord are invested by a thin delicate fascia, which is situated beneath the cremaster muscle, and forms a common * Practical Observations in Surgery, second edit. p. 180. TESTICLE (ABNORMAL ANATOMY). fibrous envelope to the testicle, and spermatic cord. It is attached to the back part of the gland. This membrane may be traced as a prolongation of the fascia transversal^, and is probably formed in the process of transition of the testicle from the abdomen to the scrotum. The spermatic cord. — The parts composing the spermatic cord, are the vas deferens, the artery of the duct, the spermatic artery and veins, the lymphatic vessels, and the spermatic nerves. These parts are connected by loose areolar tissue. A fibro-cellular process, being the remains of the process of serous membrane originally connecting the tunica vaginalis with the peritoneum, may sometimes be perceived in the front part of the cord. The spermatic cord extends from the internal abdominal ring to the back part of the testicle. Its upper portion, therefore, lies in the inguinal canal. The coverings of the cord are the same as those of the testicle : viz., the inte- guments, superficial fascia, cremaster muscle, and deep spermatic fascia. For COMPARATIVE ANATOMY, see the article ORGANS OF GENERATION. ABNORMAL ANATOMY OF THE TESTICLE. — • Congenital imperfections and malformations. — Numerical excesses and defects. — Cases of su- pernumerary testicles are mentioned in the writings of the old authors, and persons have been described with four or five of them, ac- companied with a proportionate increase in the venereal appetite. Nearly all these cases are of a fabulous character. Such must be remarked of the case of irfvr6pxos, or man with five tes- ticles, mentioned by Schaarf*, and with that of a man with four testicles alluded to by Blegny.-(- Blasius, an old writer not un- worthy of credit, has, however, given an account of the examination of a man, thirty years of age, and otherwise well formed, who had two testicles on the right side, of the same size and shape as that on the left, which is illustrated by a small engraved figure re- presenting a distinct artery from the aorta, and vein from the vena cava proceeding to each of the two testicles on the right side.J This is the only case of supernumerary testicle recorded by the old authors, which has any semblance of authenticity. Neither Morgagni, Flaller, nor Meckel met with a single exam- ple, and they questioned the existence of such a condition. Two cases have recently been recorded as examples of triple testicle, but they were not verified by examination after death. One is related by Bliimener, an army surgeon, in Rust's Magazin fiir die Gesammte Heilkunde for 1824- : the other by Dr. Macann, a British surgeon. § An epi- plocele, a fatty or fibrous tumour in the scrotum, or an encysted hydrocele of the cord, * Eph. Nat. Cur. Dec. 111. Ann. v. vi. Obs. 89. p. 175. •)• Zodiaqne Francais, Ann. 11. Most of the re- pitted cases of Triorchides are quoted by Arnaud, in his Me'moires de Ghirurgie. Mem. iii. part i. J Ger. lilasius, Obs. Med. Anat. Obs. 20. p. 60. § Provincial Medical Journal, Nov. 5. 18-12, p. 113. TESTICLE (ABNORMAL ANATOMY). 987 might readily be mistaken for an additional testicle. Morgagni mentions that he was once deceived by a portion of omentum. In the pathological collection at St. Thomas's Hos- pital is preserved the testicle of the eccentric Dr. Mousey, who appeared during life to be supplied with three of these glands. The sup- posed additional testicle consists of an in- durated fibrous tumour attached apparently to the tunica vaginalis. Many instances of monorclridcs, or persons having only a single testicle are also mentioned by the old authors ; but as the data are very imperfect, and as little was known respecting the transition of the testicle at the time these cases were recorded, they must be viewed with great suspicion. They were most pro- bably cases in which one of the glands was either retained within the abdomen, or, from some cause had been completely atrophied. I know no satisfactory reason why a defici- ency of one or both testicles should not occasionally occur without any other mal- formation ; but they are anomalies of which there are few authentic examples in the annals of medical science. Mr. Paget has published the particulars of a case in which he believes one testicle was deficient at birth.* No account of the man is attached to the particulars of the dissection, and it is open to question whether the deficiency of the gland was not the result of atrophy. Dr. Fisher, of Boston f, has recorded a more satisfactory example of absence of both testicles. The de^ ficiency was remarked from birth, and the sub- ject of the malformation was regarded as a na- tural eunuch, and died at the age of forty-five. Mr. Thurnham has published an account of the dissection of an infant who died at the age of four months. In addition to an atrophied condition of the right kidney, and a remark- able malformation of the ureters, it was found that neither of the testicles had descended. The right lay in the abdominal cavity, just above the inguinal canal. On the left side no testicle would appear to have been formed; the spermatic vessels on this side terminated in a little mass of fat ; the vas deferens, how- ever, was present, and was apparently as well developed as that of the perfect testicle. J A case of monstrosity is related by Dr. Friese in Casper's Wbchenschrift. $ The child lived only half an hour : in addition to the absence of the external genital organs, there were neither testes, vasa deferentia, nor vesiculae seminales. Cases, however, in which the whole of the genital apparatus is deficient or irregularly formed, do not come within the scope of this article. Geoffroy St. Hilaire has recorded a remarkable, and so for as I know, unique case of union of the testicles in the abdomen. || * London Medical Gazette, vol. xxviii. p. 817. f American Journal of the American Sciences, vol. xxiii. p. 352. J London Medical Gazette, vol. xx. p. 717. § Dec. 25. 1841. Quoted in the British and Fo- reign Medical Review for April 1812, p. 527. || Hist, ties Anomal. de I'Orgaa. t. i. p. 542. Deficiencies and imperfections of the vas deferens. — In Mr. Paget's case of supposed absence of the testicle it is stated, that the vas deferens terminated nearly opposite the external ring in a rounded cul-de-sac; and in Dr. Fisher's case of deficiency of both testicles, that the vasa deferentia, though properly formed and nearly of natural size, terminated in cul-de-sacs at the end of the cord. In the museum of St. Bartholomew's Hospital, there is a preparation taken from a man fifty years of age, who died of strangulated hernia. A piece of intestine was strictured by a band of adhesion connected with the mesentery, and the testicle was detained in the upper open- ing of the ring. On dissection of the parts, the vas deferens was found to terminate near the testicle in a cul-de-sac. The gland was very small, and its structure appeared granular like the undeveloped testicle of a youth. There was no trace of the epididymis. Mr. Hunter in dissecting a male subject found the vasa deferentia not only deficient near the testicles, but terminating below in a single irregularly formed vesicula seminaliss and having no com- munication with the urethra.* There are a few other cases on record, in which the vas deferens has been defective at the extremity which joins the ejaculatory canal. Thus, Tenon, in the dissection of an infant affected with extraversion of the bladder, found that the vasa deferentia terminated separately at the bottom of the pelvis, in two white tuber- cles : the scrotum, testes, and vesiculae semi- nales were in a natural state, f But besides these imperfections at its two extremities, this duct has been found wanting throughout nearly its whole extent. Brugnoni mentions, that in dissecting the parts of generation in a robust man, from twenty-six to twenty-seven years of age, he found the right epididymis almost entirely absent, the only part remaining being the head, which formed nodules filled with semen. The rest of the epididymis and the vas deferens were wanting, without any mark of disease. The testicle was perfectly sound, and nearly of the same size as the left one. On examining the corresponding vesicula seminalis he found at its anterior extremity a portion of the canal of the vas deferens about an inch in length, and properly formed. The vesicula seminalis itself was flaccid and quite empty ; whilst the left was full of semen. He remarks, that although this vicious conforma- tion was according to all appearances con- genital, nevertheless the vesicula seminalis and ejaculatory canal had preserved their natural cavities. J In a case related by Bosscha, the left vas deferens of a robust man terminated in a blind extremity near the testicle, the rest of the canal being wanting. There was the rudiment of a left vesicula seminalis in the * Works by Palmer, vol iv. p. 23. f Mem sur qnelques Vices des Voies Urinaires, &c. n Mem. de FAcad. Roy. des Sciences a Paris, 1761, p. 115. J Observ. Anat. snr les Vesicules Seminales. M('m dc 1'Acad. Roy. des Sciences a Turin, 1780, and 1787, p. G25. 988 TESTICLE (ABNORMAL ANATOMY). form of a blindly-ending canal running tor- tuously in the shape of the letter S. The left testicle was sound.* Mr. Paget has happily explained the origin of these several defects in the vas deferens, by reference to the mode of development of the special organs of generation. He observes t, after Miiller and Valentin, that, in the normal course of human development the proper ge- nital organs are in either sex developed in two distinct pieces : namely, the part for the for- mation of the generative substance, the testicle or ovary, and the part for the conveyance of that substance out of the body, the seminal duct or ovi-duct. The testicle or ovary as the case may be, (and in their earliest periods they cannot be distinguished), is formed on the inner concave side of the corpus Wolffianum, and the seminal or ovi-duct, which is originally an isolated tube closed at both extremities, passes along the outer border of that body from the level of the formative organ above to the cloaca or common sinus of the urinary, genital, and digestive systems below. The perfection of development is attained only by the conducting tube acquiring its just connec- tions at once with the formative organ, and, through the medium of the cloaca, with the exterior of the body. The sexual character is first established, when, in the male, the for- mative and conducting organs become con- nected by the development of intermediate tubes which constitute the epididymis ; or when in the female, a simple aperture is formed at the upper extremity of the conducting tube, and is placed closely adjacent to the formative organ. In both sexes alike, the lower ex- tremities of the conducting tubes first open into the common cloaca, and subsequently, when that cavity is partitioned into bladder and rec- tum, or bladder, vagina, and rectum, they ac- quireineach their just connections, and become in the male the perfect vasa deferentia, and in the female the Fallopian tubes and uterus. The inquiry is not without interest, what influence have these deficiencies and imperfec- tions in the vas deferens on the evolution and subsequent condition of the testicle ? In the case of the adult which occurred at St. Bar- tholomew's Hospital, the testicle was small, and its structure appeared granular, like the undeveloped testicle of a youth, but as it had not descended into the scrotum, and was com- bined with hernia, there may have been other causes impeding its due evolution. In Mr. Hunter's case, the testicles which were in the scrotum were very sound. In the case of the man related by Brugnone, the testicle on the side corresponding to the defective vas de- ferens was perfectly sound, and nearly of the same size as the other. So also in Bosscha's case, it is stated, that the testicle was sound. Although either of these defects in the vas deferens renders the gland an useless organ, * Diss. sistens Obs. de vesiculte seminalis sinis- traj defectu, integris testibus, vase vero deferente clause, quoted by Dr. Vrolik, Handbook der Ontleed- kundige Ziektekunde, 1st Decl. p. 210. •(• Loc. cit. p. 818. and if it occurred on both sides of the body, would necessarily cause impotency, these cases, nevertheless, tend to shew that the absence or imperfection of the excretory duct does not prevent the development of the tes- ticle at the proper period, and has no direct influence in causing it to waste; and these inferences are fully confirmed by experiments on animals, performed by Sir A. Cooper and by myself.* These cases and experiments show, then, that the testicles may be properly developed, though a physical obstacle to the elimination of their secretion is present from birth ; and that so long as the testicles exist entire, though to no purpose, the individual acquires and preserves all the marks of the male sex ; the secretory organ alone appear- ing to be that upon which the sexual charac- ters depend. The engorgement of the se- minal ducts with sperm is liable, it is true, to cause inflammation of the testicle, which may end in atrophy, but this is only a secondary and occasional effect of the interruption in the excretory duct. Imperfect transition. — It occasionally hap- pens that at birth one or both testicles have not passed into the scrotum, being detained either in the abdomen near the groin, in the inguinal canal, or in the groin, just outside the external ring. In a table of one hundred and three male infants, examined by Wrisberg at the time of birth, it appears that seventy-three had both testicles in the scrotum ; in twenty-one, one or both were in the groin. Of these, five had both, seven the right, and nine the left in the groin ; in twelve, four had both, three the right, five the left, only in the abdomen.-)- According to this table, the imperfection occurs rather more frequently on the left side than on the right, in the proportion of seven to five. In twenty-five cases examined at different ages, varying from five to sixty, — sixteen of which came under myown observation, the remainder being taken from the recorded experience of others, — in thirteen the imperfection was on the right side, and in twelve on the left. Dr. Marshall states, that in the examination of 10,800 recruits, he had found five in whom the right, and six in whom the left testicle was not apparent. In two of these cases there was inguinal hernia on the side where the tes- ticle had not descended. J He met with but one instance in which both testicles had not appeared. § The testicle sometimes remains permanently fixed in the situation in which it is placed at birth || ; but in some instances the passage, though delayed, is completed at some period previous to puberty, and often within a few weeks after birth. Mr. Hunter was of opinion that this completion most frequently * Vide Sir A. Cooper on Anatomy of the Testis, p. 51., and my Treatise on the Diseases of the Testis, p. 64, and seq. f Commentatio Soc, Eeg. Scient. Goetting. 1778. I Hints to Young Medical Officers in the Army, p. 83. § Ibid. p. 207. || Persons whose testicles had not made their ap- pearance were called xpu^opx.idis, or testicondi, by the ancients. TESTICLE (ABNORMAL ANATOMY). 989 happens between the years of two and ten.* Of the twelve cases mentioned by Wrisberg, in which one or both testicles were retained in the abdomen, in one the descent took place the day of birth, in three on the day after, in three others on the third day, in two instances on the fifth day, and in one on the twenty- first clay : in the other cases, the testicles had not appeared at the fourth or fifth week after parturition.-)- My own observations lead me to believe, that if the passage does not take place within a twelvemonth after birth, it is rarely fully and perfectly completed afterwards, without being accompanied with rupture. For the causes which operate at this late period tend as much to promote the formation of hernia as the transition of the testicle. In cases where the testicle makes no appearance before puberty, uneasiness is often experienced at that period, owing to the enlargement of the gland being restrained by the rings and parts composing the inguinal canal. At the same time also, it is often protruded outside the external ring by the movements of the abdomen in respiration. The causes of a failure in the transition of the testicle have not been much investigated, and as considerable doubt has long prevailed respecting the mode and agency by which this change is effected, no satisfactory explana- tion could 'be expected of the circumstances interrupting or preventing it. When we re- flect on the nature of that process, as my researches have led me to describe it, it is clear, that there must not only be a perfect adaptation of parts, a due relation between the body displaced and the structures which it traverses, but also corresponding power in the agent by which it is accomplished. There are few muscles in the human body whose development in different individuals varies in a greater degree than that of the cremaster. And if such be the case after birth, it is not unreasonable to presume that similar differ- ences exist in the foetus before the gland changes its position, and that a failure in the process may be the result of deficient power in the musculus tcstis to accomplish the pas- sage. It is not improbable that this muscle is sometimes paralysed, and that the faulty transition is owing to a want of a due supply of the nervous energy, which we know is often denied to other muscles during fostal exist- ence, and is the cause of deformities in the feet and other parts, with which infants are often ushered into the world. I think, indeed, we may fairly enumerate paralysis and defective development of the cremaster amongst the presumed causes of the imperfect transition of the testicle. Peritonitis occasionally at- tacks the fcetus in uteroj, and produces ad- hesions between the various abdominal viscera. It is well known that in congenital hernia the testicle is frequently united to a portion of * Lib. cit. p. 15. f Lib. cit. p. 203. j Vide Contributions to Tntra-uterine Pathology, by Dr. Simpson, Edinb. Med. and Surg. Journal, nos. cxxxvii. and cxl. intestine or omentum, and that the formation of these adhesions previous to the transition of the testicle is sometimes the cause of the displacement, the viscera being drawn, together with the gland, into the scrotum. Many facts seem to show that similar adhesions are, on the other hand, an occasional cause of the temporary and permanent retention of the testicle, the cremaster being insufficient to overcome this obstacle to its passage. In the examination of a man, age sixty, I found the right testicle just external to the abdominal ring ; it was small in size, and closely adherent to a portion of omentum. A young man was under my care for many months, on account of an imperfect transition of the testicle on the left side. The gland moved backwards and forwards through the external abdominal ring. By pressure above, it could be forced down sufficiently to admit of being examined. This testicle was much smaller than the right, which was in the scrotum, and I could distinctly make out a portion of intestine closely adherent, which accompanied the org;:n in all its movements. It is probable that the smallness of the opening in the internal abdominal ring is sometimes a cause of the detention of the testicle, especially in those cases in which the organ is retained within the inguinal canal. Mr. Wilson, an accurate anatomist, was of this opinion*, which is supported by the fact, that the testicle is oftener found in the groin than in the cavity of the abdomen. M. Dela- siauve mentions a case, in which, he states, the organ was retained by the border of the outer column of the ring, f Mr. Hunter was inclined to suspect that the fault originates in the testicles themselves. It is difficult to un- derstand how this can be, for as the gland is passive in this process, it can offer no obstacle, unless it grows too large to pass the opening in the abdominal parietes ; whereas, it is ad- mitted that the gland when retained is usually • below the natural size. Nor does it appear, that the interruption is owing to any want of proper length in the vas deferens, for in a case of imperfect transition in a boy, whose body I examined, I particularly noticed that this duct was so long as to be doubled on itself, and tortuous, a circumstance which has been remarked in other cases by Mr. Mayof , Rosen- merhel$, and others. It may be concluded then, that the causes of a failure in the pas- sage of the testicle are various ; that this imperfection may result from want of power, or paralysis of the cremaster muscle ; from adhesions retaining the gland within the ab- domen ; and from a contracted state of the opening of the external abdominal ring. Mr. Hunter states, that when one or both testicles remain through life in the belly, he believes that they are exceedingly imperfect, * Lectures on the Urinary and Genital Organs, p. 405. t Revue Me'dicale, Mars, 1840, p. 3G3. ± Human Physiology, 3d edit. p. .411. § Uebor die Kadicalcur des in der Weiche liegen- dcn Testikels. 990 TESTICLE (ABNORMAL ANATOMY). and probably incapable of performing their natural functions ; and that this imperfection prevents the disposition for descent taking place. That they are more defective even than those which are late in passing to the scrotum, he infers from the circumstance, that in quadrupeds, the testicle that has reached the scrotum is considerably larger than the one which remains in the abdomen. Mr. Hunter had seen only one case in the human subject where both testicles continued in the abdomen, but this proved an exception to the above observation, since we are led to con- clude that they were perfectly formed, as the person had all the powers and passions of a man.* Professor Owen in commenting upon these observations, states, " It seems remark- able that with this experience Mr. Hunter should have formed from inconclusive analogy, and promulgated, an opinion tending to occa- sion so much unhappiness as that which attri- butes exceeding imperfection and probable incapacity of performing their natural func- tions to testes which in the human subject are retained within the abdomen. That there is nothing in such a situation which neces- sarily tends to impair their efficiency is evident, from the number of animals in which they constantly form part of the abdominal vis- cera; and in those in which the testes na- turally pass into a scrotum, their continuance in the abdomen, ^according to our author's own observation, is accompanied only with a difference of size or shape ; now we may readily suppose that this may influence the quantity, but not necessarily the quality, of the secretion." There are very few accounts on record of the dissection of undescended testicles. In a case, in which M. Cloquet found the left testicle situated within the abdomen, the gland was well formed, and of the same size as the right, which had de- scended into the scrotum. The parts taken from an apprentice of Sir A. Cooper, who unfortunately committed suicide in conse- quence of the infirmity, are preserved in the Museum of Guy's Hospital. I have ex- amined the preparation ; and the testicles, which are both within the abdomen, close to the internal ring, appear to be nearly, if not quite, the natural size, and it is stated that the ducts contained semen. In a lad, aged nineteen, whose left testicle was found, by Dr. Bright, within the abdomen, near the brim of the pelvis, the gland was considerably smaller than natural, but the ducts and se- creting structure were quite perfect/)" These are the only cases of testicles situated within the abdomen in which we have any account of the anatomical condition of the gland. In addition to the evidence they afford of the ca- pability of testicles thus placed to exercise their functions, may be adduced the case of Mr. Hunter, just alluded to, in which a person, both of whose testicles continued in the ab- domen, had all the powers and passions of * Works by Palmer, vol. iv. p. 18. •f- Hospital Reports, vol. ii. p. 258. a man ; and a case recorded by Mr. Poland, of a man so formed, who was aged twenty- nine. He had all the signs of virility, had married twice, and was the father of two children.* On the other hand, Mr. Wilson mentions the case of a young man, twenty-five years of age, whose testicles never descended. He had some beard, and not an unmanly ap- pearance ; but although an imprudent, and in some things a dissipated person, he had never shown the least desire for women, or disposition for sexual intercourse, j" John West, a lad, aged sixteen, died in the London Hospital, in a state of universal anasarca. There was no appearance of beard, and only a few hairs were scattered over the pubes. My attention was particularly directed to the state of the genital organs, by observing that the scrotum, which was greatly distended with serous effusion, was not fully developed on the right side. I found the right testicle within the abdomen, about an inch and a half above the internal ring. It was very small, not larger than that of a child two years of age; and on cutting into it, the gland pre- sented the granular appearance usually re- marked at that early period. Passage of the Testicle into the Perineum. — Mr. Hunter first observed that the testicle in changing its situation does not always pre- serve a proper course towards the scrotum, there being instances of its taking another direction and passing into the perineum. How this is brought about, he remarks, it is difficult to say : it may possibly be occasioned by something unusual in the construction of the scrotum, or more probably, by a peculiarity in that of the perineum itself. For it is not easy to imagine how the testicle could make its way to the parts about the perineum, if these were in a perfectly natural state. He met with two instances of this imperfection. Many years ago a little boy, one of whose testicles had thus deviated from its proper course was brought to the London Hospital. The gland was lodged in the perineum at the root of the scrotum. M. Ricord met with this singular anomaly in two instances. M. Vidal (de Cassis) observed it in two brothers : their father was exempt from it. The testicle abnormally placed was smaller than the other. J The irregularity is exceedingly rare, and the above cases are all with which I am acquainted. Passage of the Testicle through the Crural King. — M. Vidal relates the case of a man, one of whose testicles, instead of passing out of the abdomen at the inguinal canal, made its exit at the crural ring. The organ was mounted upon the abdomen like a crural hernia. A portion of intestine traversed the inguinal canal, forming a rupture on that side. § I know of only one other instance of this * Guy's Hospital Reports. Second series, vol. i. pp. 162, 163. t Lectures on the Urinary and Genital Organs, p. 408. t Traite de Pathologic externe, t. v. p. 432. 2eme, edit. § Ibid p. 431. TESTICLE (ABNORMAL ANATOMY). 991 anomaly, which is reported by Eckarclt. In this case, the testicle passed out at first through the inguinal canal, but having been returned by the patient into the abdomen, it subsequently escaped at the femoral ring.* Inversion of the Testicle, — It sometimes happens that the position of the testicle in the scrotum is reversed, so that the free sur- face presents posteriorly, and the epididymis is attached to the anterior part of the gland, instead of to the posterior. The first case that I met with was that of a man who had a swelling of the right testicle, which puzzled his medical attendant. On examination 1 found this to be the epididymis thickened from chronic inflammation. I was able clearly to trace the vas deferens proceeding to it along the front of the scrotum. The body of the testicle was unaffected, and its posterior edge was quite smooth and regular. The disposition of the left testicle was normal. On visiting the Hopital de Midi in Paris, in April, 1849, M. Ricord showed me a case of epididymitis on the left side, in which the gland was thus inverted. He informed me that he had often met with this arrangement. I have since had two patients under my care, one of whose tes- ticles was thus inverted. One was a lad in the London Hospital affected with epididymitis. The other was a gentleman who consulted me for chronic orchitis confined to the body of the testicle. The epididymis being unaffected, the inversion was less perceptible than in the three preceding cases. M. Maissonneuve, in a thesis published in Paris in 1835, I believe first called attention to this irregular disposition, which he states that he had met with many times upon the dead body, and upon the living, and he mentions what I remarked myself in the four cases just noticed, that the inversion was confined to one side. Surgeons should bear in mind the liability to^this dis- position of the gland in making their diagnosis of the diseases affecting it. Atrophy of the Testicle. — The testicles, like other organs formed for the exercise of tem- porary functions, do not arrive at a perfect state of development until a certain period of life, after which their activity ceases, and they become gradually and imperceptibly diminished. Thus we find that in early life they are small in proportion to the size of the body as compared with their condition at puberty, and that as old age advances and the generative functions cease to be called into action, they undergo a diminution in size, their vessels grow less, the seminiferous tubes become small and contracted, and partially ob- literated. In the lower animals these changes are far more remarkable than in man, for as the functions of the testicle are exerted only at stated periods of the year, as the rutting or copulating season advances these organs rapidly increase in bulk, and in its decline undergo a proportionate degree of wasting. In man, it sometimes happens that the tes- * Looter's Journal fur die Chirurg. ii. Bd. 1 Stff. s. 187. tides do not acquire their proper size at the usual period, their development being from some cause or other arrested ; and also, after the organs have arrived at their full and perfect growth, that occasionally one or both suffer a premature decay. Under the head then of Atrophy of the Testicle I shall consider : 1. Arrest of Development ; and 2. Wasting. Arrest of Development. — If the congenital lesions to which the testicle is liable had not been previously treatetl of, the cases of ab- sence of the organ already described, might be correctly referred to the present head, as the deficiency in these cases was no doubt the result of an arrest in the early development of the organ. But the cases that 1 am now about to consider are those in which the sub- sequent evolution which the testicles undergo at puberty is delayed beyond the usual period, or never takes place at all. Mr. Wilson relates a curious instance of his having been consulted by a gentleman, twenty-six years of age, on the propriety of entering the marriage state, whose penis and testicles very little ex- ceeded in size those of a boy of eight years of age. He had never felt the desire for sexual intercourse until he became acquainted with his intended wife ; since that period he had experienced repeated erections, attended with nocturnal emissions. He married, be- came the father of a family ; and these parts, which at six and twenty years of age were so much smaller than usual, at twenty-eight haol increased nearly to the usual size of those of an adult man.* Mr. Wilson mentions this singular case, as it will admit of questions whether the parts alluded to became properly formed as to size, and possessed of the power of secretion, in consequence of being, although so late in life, influenced by the passions excited by attachment to a particular female ; or whether the enlargement and proper action of the parts beginning, occasioned such passion first to exist. He thinks the probability in favour of the former supposition, in which opinion I certainly concur. Lallemand men- tions having seen a man about thirty years of age, extremely fat, and without a beard or hair on the pubes, whose penis and testicle ap- peared to belong to a child of from seven to eight years : he had never experienced erec- tions or venereal desires. f A young man died in the London Hospital of disease of the heart. He was seventeen years and nine months old : the body measured five feet five inches in height, and was plump and well formed. There was no appearance of beard, or whiskers, or of hair on the pubes. The penis and testicles were very small, not larger than they are usually found in boys of three or four years of age. The testicles were about equal in size, and one of them weighed only two scruples and one grain. Both organs were normal in structure, appearing like the glands in early life, when the tubular structure * Lectures on the Urinary and Genital Organs, p. 424. t Des Pertes Se'minales Involontaires, t. ii. p. 380. 992 TESTICLE (ABNORMAL ANATOMY). is very indistinctly developed. No sperma- tozoa could be detected. These were clearly instances of arrest of development of the tes- ticles. As these organs are chiefly excited to action by an operation of the mind, it is easy to understand that they may sometimes re- main undeveloped owing to defective organi- sation of the brain, an absence of sexual desires being invariably remarked in these cases. Cases of wasting of the testicles after injuries of the head, and the frequent absence of the venereal appetite in cretins and idiots, tend to strengthen this opinion. The follow- ing are marked examples of defective develop- ment of the sexual organs, accompanied with imperfection of the brain. An idiot, aged nineteen, subject to epileptic fits, died of typhus fever in the Hackney union. The youth was of short stature, and the form of the body was not indicative of either sex, but the contour was rounded as in the female. There was no appearance of hair about the face or pubes. The abdomen and other parts were covered with a thick layer of fat. The penis and scrotum were remarkably small, not larger than they are usually found in a child two or three years of age. Both testicles were in the scrotum, but they were of very diminutive size ; the right weighed less than a drachm, and the left not more than twenty three grains. The right gland had descended a very little way below the abdominal ring. The glandular structure and epididymis of both testicles were indistinct, and the vasa deferentia also extremely small. Nothing re- markable was observed in the structure of the brain. Mr. Hovell, the surgeon of the union, also showed me another inmate of the same workhouse, a lad aged nineteen, and of weak mind, whose penis and testicles did not exceed in size those of a boy seven or eight years of age, and who had only a few scattered hairs on the pubes. In the museum at Fort Pitt, Chatham, are preserved two undeveloped testicles about the size of those of a child six months old, but healthy in structure, which were taken from a lunatic 58 years of age. His penis was small and he had never experienced any inclination for sexual inter- course. Wasting. — In investigating the alterations in the nutritive condition of the testicle, it is very desirable to fix, if possible, some standard by which they may be estimated. The size of the gland is neither uniform nor conveniently appreciated. Its weight, likewise, varies so much in different persons and in the same in- dividual at different periods, according as it has lately exercised its functions or remained inactive, and as it is full of semen or empty, that it is scarcely possible to determine on any accurate standard of this kind. (See p. 976.) I should consider the testicle of an adult weighing less than three drachms as in a state of atrophy. A testicle in an advaced state of wasting, not arising from disease of the gland, usually preserves its shape, but feels soft, having lost its elasticity and firm- ness. Its texture is pale and exhibits few- blood-vessels, the tubuli and septa dividing the lobes are indistinct, and the former cannot be so readily drawn out into shreds as before. The epididymis does not usually waste so soon nor in the same degree as the body of the testicle. It sometimes however, loses its characteristic appearance, and I have even found it reduced to a few fibrous threads. The fluid pressed out of the wasted testicle and epididymis is entirely destitute of sper- matic granules and spermatozoa. In many instances adipose tissue is deposited behind the tunica vaginalis, and encroaches on the epididymis and posterior part of the testicle. Fatty matter is also found in the glandular sub- stance of atrophied testicles, as in one taken from a man aged forty-six, who died of dropy consequent on disease of the kidneys, which was wasted to one fifth its natural size. In ad- dition to the presence of adipose tissue be- neath the visceral portion of the tunica vagin- alis, I recognised a quantity of yellow matter irregularly disposed amongst the wasted tu- buli. This matter on examination in the mi- croscope, proved to be oil globules, and readily dissolved on the application of ether. The structures composing the spermatic cord un- dergo a corresponding diminution ; the cre- master muscle disappears, the nerves shrink, and the vessels are reduced in size and num- ber. The vas deferens, though small, can ge- nerally be injected with mercury as far as the commencement of the epididymis. A testicle, atrophied from disease, is not only of dimin- ished size and weight, but is altered in shape, being uneven and irregular, and sometimes of an elongated form. The surfaces of the tunica vaginalis are adherent and its cavity is partly or entirely obliterated. There is no, or very little, trace of the proper glandular structure, the organ being converted into fibrous tissue of a firm texture. It loses its peculiar sensi- bility to pressure, but is sometimes the seat of morbid sensibility. All those causes which produce decay in other parts likewise occasion wasting of the testicle. Thus an impeded circulation, pressure, want of exercise, and loss of nervous influence, have been noticed as causes of atrophy of this gland. To these must be added certain causes which specially affect the testicle. The following case, related by Mr. Wardrop, is a good example of atrophy from defective nutrition. A person, both of whose testicles were completely absorbed, nothing being felt in the scrotum but a loose vaginal coat, died of an aneurism of the aorta, formed at the origin of the spermatic arteries, both of which were obliterated.* A ligature on the spermatic artery is sufficient to cause a total decay of the testicle, which induced the celebrated Harvey f to propose its ap- * Note to his edition of Baillie's works, vol. ii. p. 315. t Anatomical Exercitations concerning the Generation of Living Creatures. Loud. 1653, pp. 113, 114. TESTICLE (ABNORMAL ANATOMY). plication for the removal of a certain form of sarcocele ; a suggestion, the credit of which has been improperly assumed in recent years by C. J. Maunoir, of Geneva. The influ- ence of pressure in causing partial atrophy of the testicle, is somtimes remarked in old cases of hydrocele and hoematocele, in which the gland has been long subjected to com- pression from the retained fluid. It has been said that the testicles waste in those persons who strictly adhere to their monastic vows, but I am not awnre that there is sufficient authority for this remark. In persons who marry, after many years of ab- stinence from sexual intercourse, the testicles undergo a certain degree of enlargement. It is a great error to suppose that sexual connec- tion in early life is essential for the preservation of these organs. In cases of enlargement of the prostate the ejaculatory canals sometimes become completely obstructed. Under these circumstances, the semen secreted under ex- citement having no means of escape, encum- bers the testicles for a time, but afterwards becomes absorbed, and it is said that atrophy of these glands sometimes follows ; but I have never observed any instance of wasting of the organs from this cause. As examples of atrophy of the testicles from loss of nervous in- fluence, may be adduced cases of paraplegia, in which these organs have been known to waste. Portal mentions the case of a robust man, aged thirty-five, who was attacked with painter's colic, attended with great debility of the lower extremities. The testicles dimin- ished considerably ; and although he after- wards recovered from the paralysis of his limbs, these glands always remained wasted ; and the man was incapable of the act of gene- ration.* In the xxth volume of the " Medical and Physical Journal," there is an account of a case of recovery after fracture, with partial dislocation of the first and second lumbar vertebrae, followed by paraplegia, in which, three years afterwards, the testicles were found entirely obliterated. It has been stated that the testicles sometimes waste from in- juries, or from compression of the spine at the origin of the spermatic nerves. In a man who had received a blow on the lum- bar region, the testicles gradually wasted away.-j- The most common cause of atrophy of the the testicle is the disturbance in its organisa- tion consequent upon inflammation. As the inflammatory process ceases, the enlarged gland not only becomes reduced to its original size, but it sometimes slowly but steadily diminishes, till at length very little vestige of it remains Mr. Hunter has related three eases in which the testicle decayed in this way.J 1 have met with several instances of atrophy arising from this cause, and there are few surgeons of experience who have not witnessed cases of the kind. Wasting of the * Coiirs cl'Anatojnie Me'dicale, t. v. p. 434. f Baillie's Works, by Wardrop, vol ii. p. 315. | Treatise on the Venereal Disease, VOL. IV. 993 testicle has been observed to occur after an attack of orchids in mumps, arising as it is supposed from the translation of inflamma- tion from the parotid to the testicle. Two cases of cynanche parotidea in the adult, in which atrophy took place in the gland chiefly affected, are related by Dr. R. Hamilton.* I have witnessed one case, in which the patient attributed the loss of the gland to an attack of mumps in his infancy. Wasting is more liable to occur after inflammation of the body of the gland than after consecutive inflamma- tion in which the epididymis is the part chiefly affected. One or both testicles have been found to waste in persons who have indulged too much in sexual intercourse or been addicted to onanism. Baron Larrey met with several cases of atrophy from excessive venery and abuse of strong drinks amongst the soldiers of the Imperial Guard.f Sir B. Brodie has recorded two cases in which wasting was occasioned by over-excitement ; in one from onanism, in the other from sexual intercourse.^ I have also witnessed an instance of total atrophy of the left testicle in a person addicted to excessive masturbation. In this case, and probably in the others just quoted, the wasting was preceded by an attack of inflammation induced by inordinate excitement. It is a common belief that wasting of the testicle is liable to be induced by the long- continued use of iodine. I have not met with any instance of it, and there are few cases in which the evidence is such as to render it at all clear that the decay of the gland was really occasioned by the remedy. M. Cullerier has published the case of a young man who took from twenty-five to thirty drops of the tinc- ture of iodine for a period of three months for the cure of an obstinate gonorrhsea. This was followed by a state of impotency and partial wasting of the testicles, which lasted a twelvemonth, and the organs never regained their former size and vigour. M. Cullerier mentions another case of temporary loss of virile power occurring from the use of the iodine of iron.<) I feel convinced, however, that if iodine produces wasting of the testicle at all, it does so so rarely, that the liability cannot be regarded as any objection to the free and long-continued use of this valuable remedy. Atrophy of the testicle has been remarked in elephantiasis of the Greeks, a disease in which tubercles are developed in various parts of the skin. Dr. Adams, in an account of the cases of that disease observed in Maderia, states that all those who were attacked with it before the age of puberty never acquired the distinguishing marks of that change in the constitution, and their testicles diminished in size, and that in those affected later in life the testicles became * Philos. Trans. Edinb. vol. ii. art. ix. p. 59. f Me'moires de Chirurgie Militaires, vol. ii. p. Ofi. j London Medical and Physical Journal, vol. Ivi. p. 297. § Me'moires de la Societe' de Chirtirgie de Paris, t. L 3 s TESTICLE (ABNORMAL ANATOMY). 994- atrophied, and they lost the power of pro- creation.* Mr. Peacock also noticed a wasting of the testicles in several cases of elephan- tiasis in the Leper Hospital of Colombo, in Ceylon.-)- A similar condition of these glands was remarked in a case of this disease, so rare in this country, narrated by Mr. Law- rence J, and also in another case at the London Hospital, which I recorded many years ago.$ In a confirmed case however of this disease, in a boy aged thirteen, who was under my care in the year 1849, there was no diminution in the size of these glands. Wasting of the testicles is liable to occur after injuries of the head. Some years ago I saw a man who had met with an injury of this description, which had been followed by wasting of the testicles, and the development of tumours on each sicleof the chest, resembling mammae. He was about fifty- nine years of age, a married man, and the father of several children. He had belonged to the legion in the Queen of Spain's service. About two years and a half previously, in an at- tempt to jump over a trench, he fell backwards and injured the posterior part of his head. Whilst on the ground he received a bayonet wound on the side, and a sabre cut on the fore- head. He recovered from these injuries and returned to England. Since the accident he had completely lost his virility. He had no desire for sexual connection ; his penis had dwindled in size ; his right testicle had gradu- ally wasted, and was no larger than a horse bean, and the left gland was also a good deal diminished in bulk. The skull at the occiput seemed somewhat flattened. Baron Larrey records the case of a man who was wounded in the back of the neck by a mu.sket ball which grazed the inferior occipital protuber- ance. He recovered from the injury, but the testicles were reduced to a state of atrophy, and the penis shrunk and remained inactive. He also relates the case of a man of strong constitution and vigorous passions who re- ceived a sabre wound which cut off all the convex projecting part of the occipital bone, and exposed the dura mater. The patient lost the senses of sight and hearing on the right side, and his testicles sensibly diminished, and in fifteen days were reduced, especially the left, to the size of a bean.|| Lallemand had under his care a man thirty years of age, who, in the expedition to Algiers had received a sabre wound at the nape of the neck. His testicles were wasted, and venereal desire as well as erections had entirely ceased. If We cannot doubt that in these cases the loss of sexual desire, and the wasting of the testicles were the direct results of the injury to the brain, and they go far to prove the essential dependence of the functions of these glands * On Morbid Poisons, p. 265. •j- Edinb. Medical and Surgical Journal, vol. liii. p. 139. J Medico-Chirurgical Transactions, vol. vi. p. 214. § Vide Medical Gazette, vol. vii. p. 447. Memoires de Chirnrgie Militaire, p. 262. Pertes Semiuales Involontaires, t. ii. p. 41 . upon the cerebral organ. The physiologist cannot fail to notice the rapidity with which the atrophy is stated in some of the cases to have succeeded the injury and the extent to which it proceeded. The withering of the testicles, was, indeed, so remarkable, that it can only be attributed to the sudden and complete extinction of the sexual instinct resident in the brain, and (if I may so express myself) to the immediate impression on the system of the future uselessness of these organs. In old age and in lingering diseases the decay of the testicles is extremely slow and gradual, and is never carried to the extent observed in cases of injury to the brain. In fact, men have survived the power or desire of performing the sexual act many years without the testicles being materially reduced in size. We have seen, too, that in the lower animals the testicles have been rendered use- less by interrupting the vasa deferentia, with- out any such striking effect being produced on the glands as occurred in these cases of cerebral injury. Inflammation of the tunica vaginalis, or acute hydrocele. — The inflammatory changes of the tunica vaginalis resemble those of the other serous membranes. M. Roux injected a hydrocele in a middle-aged man : inflamma- tion was developed, but on the fourth day, gangrenous erysipelas attacked the scrotum, and caused the patient's death on the tenth day after the operation. On examining the tunica vaginalis, he found that it contained a large quantity of whitish serum, in the midst of which floated flakes of albumen ; other flakes of the same kind formed a thick coating over the testicle and internal surface of the membranous pouch. The serous membrane beneath appeared slightly thickened, and of a deep red colour. The epididymis and the lower part of the cord were swollen, and con- stituted the more solid part of the tumour produced by the inflammation. The body of the testicle was not increased in bulk, and it retained its natural consistence.* In the mu- seum of the College of Surgeons, there is a beautifully injected preparation of hydrocele, showing the effects of inflammation after the application of the caustic. It is represented in the annexed wood-cut, which exhibits the sac with part of it cut away to show the swollen state of the epididymis, and the aperture made by the caustic (1); the tunica vaginalis is coated with flocculi of lymph. The sac of an inguinal hernia is seen above the hydrocele. The sound state of the body of the testicle, though surrounded by an in- flamed serous tunic, whilst the epididymis partakes in the disease, has been accounted for by Gendrin. He says, when the sub- serous cellular tissue, which always partici- pates in the inflammation of a serous mem- brane penetrates into the interior of an organ, it becomes a ready means of communicating * Journal Ge'ne"ral de Medicine, &c. t. Iviii. p. 25. ; quoted from Gendrin, Histoire Anatomique des In- flammations, t. i. p. 143. TESTICLE (ABNORMAL ANATOMY). 995 the inflammatory action ; but when the con- tiguous organ or subjacent part is of a dif- Fig. 638. ferent structure from that of the cellular tissue, the extension of inflammation inwards is checked. Thus, in the case of the inflamed tunica vaginalis, the cellular tissue readily transmitted the morbid action to the epididy- mis, but the tunica albuginea arrested its progress to the body of the testicle ; and this explains the fact that after inflammation of the tunica vaginalis, excited by injection, the body of the gland is rarely found to suffer. On the other hand, the epididymis is seldom attacked with inflammation without the disease being quickly propagated to the tunica vagi- nalis. The lymph effused in inflammation very often forms adhesions between the opposed serous surfaces, and these after some time are rendered very firm and dense, and in old cases are often converted into a fibro-cartilaginous structure. In a testicle which I examined some little while after an attack of acute in- flammation, I found the lymph on both sur- faces of the tunica vaginalis presenting a honeycomb or lace-like appearance, similar to that often met with on the pericardium. In- flammation, if violent, may end in the forma- tion of pus ; suppuration is, however, a rare occurrence, unless artificially excited, for the cure of hydrocele. Inflammation of the tunica vaginalis is not only the most frequent disease of the testicle, but it is also one of the most common affections to which the body is liable. In the different disorders of the gland this membrane usually becomes inflamed at some period or other, and adhesions between its opposed surfaces are scarcely less common than those of the pleura. In examining the testicles of twenty- four adults, I found ad- hesions of greater or less extent in one or both glands in as many as nine instances. Hydrocele of the tunica vaginalis. — The sac of the tunica vaginalis, like other serous ca- vities, is liable to dropsical effusion. The fluid effused is usually transparent, and of an amber, pale yellow, citron, or straw co- lour, and resembles the serum of the blood, but is occasionally thick. According to Dr. Marcel's analysis*, 1000 grains of this fluid of the specific gravity 102. 137. about three years before. In this case, there- fore, the injurious influence of soot must have been exerted nineteen years before the ap- pearance of disease, during which long period he was entirely removed from the effects of its exciting cause. It has sometimes hap- pened, alter the morbid parts had been com- pletely extirpated, and the wound healed, the patient having avoided further contact with soot, that the disease has re-appeared as it were afresh, a second and even a third time ; not, however, in the cicatrix of the wound, but on a different part of the scrotum. These, and similar facts, lead to the conclu- sion that though abandonment of his occupa- tion may render the adult chimney -sweeper less liable to cancer, it by no means forms a satisfactory security against its occurrence. Cancer scroti chiefly extends its ravages by affecting the contiguous tissues, and has little disposition to contaminate the lymphatic glands or distant parts. An instance is on record of an old chimney-sweeper, who had been subject to this disease for forty years, and had undergone three operations for its removal, yet even then the glands in the groin were unaffected.* A man aged fifty-one who had been a chimney-sweeper ever since the age of seven years, was a patient of mine on account of this disease. He had been re- peatedly attacked with it during a period of twenty-two years, and had submitted to no less than five operations for its removal. The glands in one groin became affected only a few months previously. Ulceration took place, and the patient died from its irritative effects on the constitution. On a careful' examina- tion of the body, no trace of internal disease could be detected; The cancer was strictly limited to the groin and scrotum. Mr. B. Cooper has likewise recorded a case of chim- ney-sweeper's cancer which ended fatally; and on examination none of the glands or viscera of the interior of the body were af- fect ed.-j- These cases show that, when the inguinal glands are indurated, they may be excised with a fair hope of a successful result. j\felanosis. — Notwithstanding the dark co- lour of the skin of the scrotum, melanosis is an exceedingly rare affection of this part. Indeed, the only case of its occurrence there with which I am acquainted, is one that hap- pened in my own practice. The patient was a cabinet-maker, aged thirty-two, and the disease commenced as a small dark spot, ap- parently produced by some black deposit be- neath the epidermis, raising it a little above the surrounding surface. This spot increased until it formed a fungous growth. I excised the part, but the disease re-appeared in the scrotum and in the glands of the groin six months afterwards. It made, however, very slow progress, and did not destroy the patient for six years.J * Mr. Hawkin's Lecture on Tumours. Lond. Med. Gazette, vol. xxi. p. 842. f Lond. Med. Gazette, vol. xliii. p. 532. j Vide Report of the Case in Loud. Journal of Medicine, vol. i. p. 220. THORAX. 1016 Fibrous tumours. — A small fibrous tumour is occasionally developed in the areolar tissue of the scrotum. It may acquire the size of the and heart, and by its movements to maintain the function of respiration. Generally by the term thorax is understood testicle, and being firm and of an oval form, a cavity set apart for the respiratory organs. resembles a supernumerary gland. I have met with only one case of this form of tumour. Dr. Mott, of the United States, excised an enormous mass from the scrotum of a man about seventy-three years of age. The scrotum was twelve to fifteen times its ordinary bulk, and was filled with tumours of a stony hard- ness, from the size of a nutmeg to that of a large pea. The tumours had all a very white appearance, and the integuments over two or three of the largest, having been ulcerated for upwards of a year, poured forth a foetid discharge, together with a white substance resembling mortar. The disease was upwards of twenty years' duration. I have no doubt this disease was originally of a fibrous cha- racter. The calcareous matter and other changes resemble those occasionally observed in large fibrous tumours of the uterus. A tumour of a similar character and of great size was removed by operation from the scrotum of a man in St. Vincent's hospital, Dublin, by Dr. O'Ferrall.* BIBLIOGRAPHY. — Anatomy. — De Graaf, DeYir. Organ. Gener. Lugcl. Bat. 1668. Monro, Essays and Observations, vol. i. Edinb. 1754 ; also De Testibus et de Semine in variis Animalibus. Diss. Inaug. Smellie. Thes. Med. ii. 317. 1755. Hunter, W. Me- dical Commentaries, 17G2. Warner, An Account of the Testicles, 1774. Palletta, Nova Gubernaculi Testis Hunteriani et Tunicas Vaginalis Descriptio, 1777. Brugnoni, De Testium in Fcetu positu, &c., 178.3. John Hunter, A Description of the Situation of the Testis in the Fostus, with its Descent into the Scrotum, (Animal CEeonomy), 1786. Seiler, Observ. de Testiculorum ex Abdomine in Scrotum descensu. Lepsia?, 1817. Wilson, Lectures on the Urinary and Genital Organs, 1821. Sir Astley Cooper, Observa- tions on the Structure of the Testis, 4to., 1830. Lauth, Memoir de la Socie'te d'Hist. Nat. de Stras- bourg, t. i. 1830. Krause, Mailer, Archiv. fur An- atomic, 1837. Gulliver, Proceedings of Zoological Society, 1842. Cm-line/, Treatise on the Testis, 1843. E. Huschke, Encyclopedic Anatornique, t. T. Paris, 1845. Morbid Anatomy of the Testicle. — Pott, On Hydrocele and other Diseases of the Testicle, 1767. Bell, B. On Hydrocele and other Diseases of the Testis, Edinb. "1794. Wolf, L. De Sarcocele, Er- lang. 1799. Sir Astley Cooper, Observations en the Diseases of the Testis, 1830. Baring, Ueber den Markschwamm der Hoden, Gbtting. 1833. Ku^ill, Observations on the Testicles, 1833. Brodie, Lec- tures on Diseases of the Testicle, Lond. Med. Ga- zette, vol. xiii. 1834. Berard, Journal desConnaiss. Me'dico-Chirurgic. pour 1'anne'e 1835. Velpeau, Diet, de Me'd. t. xv. Landouzy, Du Varicocele, Paris, 1838. Curling, Treatise on the Diseases of the Testis, 1843. Maladies des Testicules — Biblio- theque du Me'dicin Practicien, t. iv. Paris, 1M6. Yidul (de Cassis), Traite de Pathologic, t. v. 1846. (T. B. Curling.) THORAX (dt&pajj from Sopw to leap, be- cause in it the heart beats). " The habitation of the breathing parts." — That part of the human body destined to contain the lungs * Dublin Hospital Gazette. Feb. 1845 Such a cavity, however, is not essential to respiration : a respiratory surface only is es- sential. This must exist in every animal, whilst a separate thorax is found perfect only in mammalia. The development of the respiratory surface may take place in three ways. 1st. Either towards the interior of the body, in the form of ramified or sacculated ca- vities ; or, 2ndly. Towards the exterior, in the form of lamellated, ramified, pectinated, tufted, cili- ated, or pinnated processes called " bronchia;" in which Nature seems to have exhausted all imaginable varieties of form ; and, 3rdly. By a system of tubes ramified to ex- treme fineness, either in an especial cavity or thorax, or in a cavity common to these organs and to others destined for the diges- tive function. The movements necessary to respiration, are modified according to the form of the re- spiratory apparatus and the nature of the medium to be respired, whether pure air or air contained in water. In some of the lowest animals, the respira- tory movements are the same as those of loco- motion, as in the monad and other infusorial animalcules. In all animals, even when the respiratory organs are contained in a true thoracic cavity, the frame-work serves other purposes besides that of drawing in and throwing out air ; it gives attachment to the largest muscles of the upper extremity, whe- ther prehensile or locomotive. In man parti- cularly, we find the respiratory muscles con- tribute to such acts as coughing, sucking, sneezing, yawning, sighing, singing, vomiting, as well as the innumerable articulate sounds of language. Distinct respiratory movements, as depen- dent upon alternate contractions and dilata- tions of a thoracic cavity, are most regular, or at least, they have been more noticed, in mammiferous animals. The thoracic cavities of mammiferous animals have much of the mechanism of respiration in common. They all possess a vertebral column or spine, and that peculiar frame-work of ribs, together with a sternum, so articulated together as to move in breathing. There is likewise a great similarity of mus- cular arrangement around the thoracic cavity; and consequently the respiratory movements closely resemble each other. Although the boundaries of the thorax are generally the parts which move in respiration, and these are generally composed of vertebrae ribs and sternum, yet some animals may have either all of these, or they may lack some of them, or, if present, they may not move in the breathing function. Frogs have a ster- num, but no ribs ; serpents have ribs, but no sternum ; tortoises have ribs, vertebrae, and 1018 THORAX. sternum in one mass, rigid and immoveable : the crocodile and lizard have perfect ribs, but their sternum is almost entirely cartilaginous ; and, lastly, in man, the components of the thoracic cavity may have a mobility to com- mand or exceed a space equal to the whole cavity allotted for the respiratory organs. The relative quantity of air which he can respire for the aeration of his blood is probably greater than in any other animal, and his movements are more under the control of his will, and are greatly influenced by mental emotions. CLASSIFICATION OF THE RESPIRATORY MOVEMENTS IN ANIMALS. — It is not easy to name any particular part in the perfect thorax of the higher vertebrata, which is equally destined for respiratory motion throughout the class. Commonly with ribs and intercostal muscles, we connect the idea of a thorax, or a breathing chamber for re- spiration ; but a fish has ribs, and likewise intercostal muscles, yet not for any of the purposes of respiration, nor do we acknow- ledge them to belong to its thorax. A frog has a thorax for respiration with internal lungs, but no ribs, nor, consequently, any intercostal muscles. Nor is a diaphragm necessary to thoracic respiration ; for it is mostly absent in birds and reptiles, and quite rudimentary in the few instances (such as the ostrich, crocodile, and cheloniaX in which it is met with. In the chelonia neither ribs, spine, nor sternum are concerned in the respiratory movements. The movements of respiration tend to bring- before some surface, air or air contained in water ; or to bring a certain surface con- tinually into a fresh medium, In whatever way this may be accomplished, whether by moving the whole body, or part of the body to and fro, such movements, likewise, are not uniformly for the mere purpose of re- spiration, i. e. the mere purpose of aeration. All reptiles take more air into their capacious lungs than they require for oxygenating the blood, particularly in the aquatic kinds (as in the turtle), where the air serves to buoy up their heavy and slow-moving bodies in the dense element they inhabit. Serpents are provided with numerous highly-moveable ribs and powerful intercostal muscles, capable of rapid and extensive inspiration and expiration. Tuey can perfectly distend their body with air. The same may be observed in the chameleon. These volumes of air cannot alone be subservient to respiration, as it cannot all come into contact with the simple undivided respiratory sacs. We see, therefore, there is no necessary rela- tion between the quantity of air an animal may inspire and the extent of respiratory surface. The long hissing sound which serpents pro- duce to alarm their prey, is effected by the expulsion of this great volume of air, by their ribs, through the narrow passages of the nos- trils. In the higher mammiferous animals, we find respiration more especially destined for the chemical purpose of oxygenating the blood. Hence a more limited quantity is taken in, and it is speedily thrown out again. Large animals make fewer respirations than small ones. Ac- cording to Scoresby*, the whale breathes four or five times a minute ; the dog, the cat, and rabbit, from twenty to thirty in the same period ; and in small birds the respirations are remarkably rapid. Whatever be the form of the aerating or- gan, "breathing" is accomplished either by, 1st, the weight of the atmosphere rushing into certain cavities, because certain parts of these cavities dilate and threaten a vacuum ; or, 2ndly, by the direct projectile or collapsing force of an organ throwing the ambient ele- ment onward. These two ways are generally more or less combined in the same animal. Nor does there appear to be any relation be- tween the grade of the animal and the order of respiratory movement obtained. We notice in the respiration of man a regular inspiration and expiration, two currents in different di- rections ; and in the lowest animal, the connecting link with the vegetable kingdom, the porifera, or sponge tribe, there are like- wise two respiratory currents by distinct channels, which are as regular as the motion of rivers from their source to the ocean, or any other movement depending upon the established order of things. In some spe- cies of medusae, there are peculiar sacs on the inferior surface of the body, which, during the expansion of the body, admit water through certain apertures, and again expel it during the succeeding contraction, re- presenting a perfect inspiratory and expi- ratory action. The complexity, therefore, of respiratory movements does not correspond with the increasing development of the breathing organs. Those animals which have an internal aacculated lung, always retain a certain quantity of the breathing element in " reserve " within their system ; whereas those animals which have external lungs, or gills, have no " reserve " respirable medium. They need none, because where there is an exter- nal lung, the ambient element answers the purpose of the "reserve"; it is always in contact with the breathing surface. Tin's " reserve," in mammalia, &c., is not, pro- bably, so necessary to aeration as for the purpose of ejecting any matter which may obstruct the air passages — or, in more po- pular language, for " coughing " up any matter out of the throat. The different kinds of respiratory move- ment may be arranged as follows ; — 1. Infusorial Animalcules Ity projectile force. 2. Insects - Uncertain. 3. Fishes - By vacuum & pro- jectile force. 4. Amphibia - - do. do. 5. Birds - do. do. 6. Mammalia - do. do. Of the First Kind of Respiratory Movement. Infusoria. — These animals breathe by a stream propelled in one direction, produced by the ra- * El. Physiol. Wagner, 8vo. 1844, p. G70. THORAX. 1019 pid vibration of hair-like organs — cilia. ( Vid. Art. CILIA.) Of Hie Second Species of Respiration. In- sects.— The breathing apparatus in insects generally reaches a high degree of develop- ment. Sometimes respiratory tubes or tra- cheae penetrate every part, in the form of mi- nute ramifying vessels conveying the included air to all the organs. The moving power or means of the renewal of the air in these tubes is at present little known. Some insects, al- though they live in water (as, for instance, the water beetles, and also water spiders), retain a bubble of air around them ; and, according to Nitzch*, they renew the air in the irtrachae by alternately elevating and depressing the an- tennae. Beetles, before flying, seem to inflate themselves with air, so as to unfold their wings, which, like other parts of their body, are supplied with air tubes. In this case an inspirative effort must be made by some cavity. Under certain circumstances, bees emit a voice, a shrill sound, which is indepen- dent of the motion of the wings, and which appears to be connected with the existence of a current of air through the respiratory tubes or tracheae ; at least, such has been observed when the animal has been irritated and im- mersed in water, the surface of which, where it was in contact with the orifice of the stig- mata at the root of the wing, evidently vibrated at the moment the sound was produced.^ In the orthoptera particularly, there are distinct respiratory movements, alternate dila- tations and contractions of the abdomen ; in fact, respiratory motions are. more distinctly perceptible in this division than in any other in- sects. In the locusta verrucivora particularly, it is easy to distinguish how the abdominal rings, which have smaller abdominal scuta between them inferiorly, are alternately elevated and depressed exactly like ribs. If we smear the great thoracic stigmata with oil, we find that numerous bubbles of air escape from it during these motions. The organs of respiratory motion, by means of which the supply of air is renewed, present many points of uncertainty. On the one hand, where large stigmata are placed opposite to each other, and connected by trachea, it is easv to see that alternate opening and shutting of their valves may produce a current capable of renewing the supply of air. It is conceiv- able also, how, in the orthoptera, lepidoptera, and others, the expansion and contraction of the body, and the elasticity of the air-sacs contained in it, may cause the ingress of air. It is less obvious, however, how the same effect is produced in caterpillars and the larvae of beetles, where a current of air cannot very easily arise from the opposite position of the stigmata, on account of the minute ramifica- tions of the tracheae ; and consequently we must look for some peculiar mechanism, pro- bably cilia, unless we are disposed to admit * On the Respiration of the Hydrophila?, in Reil's Archiv. B. x. S. 440. t Hunter, Philosophical Transactions. 1792. p. 182. the stagnation of the air in its vessels. Hence it has been conjectured that the dilatation and contraction of the dorsal vessel contributes to this purpose. This, however, appears to be scarcely possible ; and it might be asked on the contrary, if the vermicular motion of the body itself, the sliding of its segments upon each other, are not the means of keeping up the constant ingress and egress of air,* In the lowest of the molluscous class, the external tunic with which they are covered is generally so elastic, that it is capable of dilating by its own properties, when it has been greatly contracted by the muscular coat that is within ; and in forcible expirations, Dr. Grant has observed these animals to contract their muscular coat, and to retract the exterior covering, so as to propel, with considerable impetuosity, and to a distance, the water that fills their respiratory cavity. The elasticity of the tunic tends to over- come the resistance of the muscular coat, and to expand, to a certain extent, the respi- ratory cavity. Without, therefore, the existence of clastic ligaments, such as we find in ccnchi- fera, there is a partial means of enlarging the respiratory cavity given to these tunicated animals. This, however, is only in occa- sional, forced, respiration ; constant and al- ternate contraction and expansion of the ex- terior tunic is not met with in any known tu- nicated, nor in a conchiferous animal, f The streams that enter the respiratory, and pass out of the anal aperture, are smooth, regular, and incessant, and are produced by ciliary movement. Of the Third Species of Respiration. Fishes. — It may be said that the thorax of fishes usually presents four elastic cartilaginous arches, which approximate and separate, open or close the gills, at the same time increasing or diminishing the capacity of the so-formed thorax. These ribs, or branchial arches, sup- port the gills, which are covered by a great flap (operculum) on each side of the base of the skull. The respiratory current enters at the mouth, passes through the fissures on each side of the fauces, and escapes through the branchial openings, placed laterally, covered by the moveable operculum. This stream is uniformly in one direction, — from before, backwards. It might be asked, why does not the water rush in by the branchial opening when the mouth "threatens" a vacuum ? It will be observed that the margin of the oper- culum, or great lateral flap, is edged with a delicate membrane, which acts as a valve, this, by the pressure of the water, is forced close round the lateral openings : thus, the water, upon the expansion of the jaws, is prevented entering behind, and consequently rushes in towards the gills by the mouth ; the jaws now close, the operculum immediately opens by the * Reimarcus, Ueber das Athmen. in Reil's Archiv. B. xi. S. 2. ; and Nitzsch, Comment, de Respirat. p. 39. et seq. f Grant's Lecture " On the Respiratory Organs of Invcrtebrata." Lancet, Itfoo — 1, vol. i. p. 904. 1020 THORAX. force of the jaws contracting with the mouth full of water, which contraction, or expiration, forces the water through the branchial arches and ultimately out by the lateral openings. Thus the respiration is of a mixed order. The first stage by atmospheric and hydraulic pressure ; the second stage by direct muscular force, similar to that of swallowing. If we cut off the delicate fringe around the operculum the fish is suffocated, the opera- tion being analogous to puncturing the human thorax. Fishes also possess a power of regulating their respiration. We have watched fishes when in a quiescent state move their respi- ratory organs so gently that the motion was nearly imperceptible, and at times quite so ; but if at such times you alarm the animal, respiration becomes vigorous, and a compa- ratively vast body of water rushes past their respiratory organs. The same may be like- wise observed when fishes have remained long in a small quantity of water, as if the respira- tory movements became more and more vigo- rous with the deterioration of their element, but give them a fresh supply of water and re- spiration becomes quiescent again. Of the Fourth Species of Respiration. Amphi- bia.— In this class there is a gradual develop- ment of the animal formation from an aquatic to an aerial being ; so likewise is the aqueous gradually converted into aerial respiration. The respiration of some of these animals is indeed most curious, — curious as to the very limited quantity of air necessary for their well- being, and curious as to whether they have this limited quantity supplied regularly or otherwise. For instance, you may keep an aquatic turtle out of water for days, and it will keep constantly respiring air ; immerse it in water, and it will remain below the sur- face for half an hour, or an hour, without any inconvenience, and some of these animals will breathe at the surface during the day, and sleep at the bottom all night without once rising for air, while during the day the same animal cannot remain below above half an hour without showing signs of discomfort. And again, the common tortoise during hy- bernation breathes so small a quantity of air, that we have never been able to form any calculation of the quantity then respired. In frogs there are no ribs by which the lungs may be moved ; consequently there is no vacuum formed by their thorax dur- ing respiration ; they fill the lungs like the tortoise, the newt, the chameleon, &c., by the working of their jaws ; or, in other words, they swallow their air just as we swallow our food. In this respect their respiratory movements resemble those of fishes; the first process being through the agency of external pressure, by making a vacuum with the mouth ; the se- cond, that of forcing, by the operation of the pharynx. They resemble mammalia in having an internal lung, retaining the air for some time, and in expelling it through the same channel by which it entered. The respira- tion of the frog has gained attention, and is hence better understood than that of many other animals of this class. The following is the mechanism of its respiration, as described particularly by Townson *, though before no- ticed by Swammerdam and Malpighi. When the broad lingual bone which forms the floor of the mouth is drawn down from the pa- late by its muscles, the air of the mouth is rarefied, and an additional quantity enters by the nasal apertures, which admit of being closed by valves. The lingual bone is then raised, the nasal apertures are closed, and the air is now forced, or rather swallowed, through the rima glottidis into the pulmonary sacs, and can also fill the laryngeal pouches which open into the mouth. Expiration is produced partly by the pressure of the abdo- minal muscles, and partly by the peculiar mus- cular power of the pulmonary parietes. To the careless observer the frog does not appear to breathe : it is never seen to open its mouth ; there is no motion of its sides like breathing, and when it is provoked (or rather through fear), though it still keeps its mouth close shut, its sides and back rise, and it blows itself up ap- parently by some internal power. Upon observ- ing it more narrowly, that skinny and bag-like part of its mouth which is under the jaw, is seen to be in constant motion. While this bag is dilating and contracting, the mouth is never opened to take in new air, but it seems to live all the while on one mouthful of air, and seems to be playing it backwards and forwards between the mouth and lungs. If we now observe the nostrils, a twirling motion, which lets in air at each movement of the jaws, is apparent, corresponding to the quantity of air inspired. If we keep the mouth open we presently see the animal struggle for breath, for we by this means disable the forcing apparatus from pro- pelling the required air into the lungs. The newt breathes with the jaws and nos- trils like the frog. It has, like the frog, a constant motion, by short strokes of the bag under the jaw. This bag is formed by the membranes of the mouth, covered and moved by the genio-hyoid and mylo-hyoid muscles. Every minute, or less, it stops, as if intending some particular motion ; then gradually the bag swells out under the lower jaw to a great size ; the contained air is then pressed down into the lungs, .and in propor- tion as the jaws are emptied, the sides of the animal are swelled up. The toad, the chame- leon, and the green lizard breathe in the same way, propelling mouthfuls of air down into the lungs. The chameleon can force down a greater or smaller quantity of air, as its needs or fears prompt it. At times it seems to fill its body almost to bursting with air. The tortoise, like the frog, holds its jaws close, and swallows the air ; alternately depressing and elevating the hyoid bone. The first of these motions permits the air to enter the nostrils, when, tbe'tongue immediately closing their internal aperture, the second motion forces the air into the lungs. It is not un- * Tracts and Obs. on Nat, Hist., &c, London, 1799. THORAX. 1021 common to notice tortoises yawn ; but how different is their yawning from that of man, who makes, at that time, a deep inspiration, while, in the tortoise, respiration is impossible. We are not prepared exactly to say how the tortoise and turtle expire ; but probably the expiration is performed by the contraction of the abdominal muscles between the lower shield or plastron and the posterior extremi- ties ; for either of these animals can at will, when alarmed, forcibly expel air with a hiss- ing sound, although its shell is unyielding. The most remarkable respiratory move- ment we have noticed, has been in the com- mon turtle. Sometimes this animal will swell out his hard case, the sternum or plastron yielding to some internal force ; but it is diffi- cult to say by what means this is distended and kept distended. It is clear this animal can gorge itself with air until it cannot sink in water, and that at pleasure it can disgorge itself and fall to the bottom, where it lives upon only a fraction of the quantity of air it had just previously ex- pelled. Of the Fifth Species of Respiration. Birds. — Here we have a contracting and dilating thorax, with ribs and sternum. The cavity of the chest is not divided by a diaphragm, but is common to the whole digestive organs as well as the lungs; or, as is said, they are "all chest and no belly." They differ from all other animals in this respect, that the lungs do not hang in the cavity of the trunk as unat- tached sacs, but are attached in the form of flattened masses, of spongy, bright red, cellular texture, to the posterior side of the thorax, reaching to the pelvis. They have vesicles or air bags extending through the whole bod}' ; and the cancellated structure of their bones is connected with the true lungs; so that if we tie the trachea and amputate the wing, leaving the stamp of the bone exposed, the bird can inspire and expire through the humerus. In the same manner that the diffusion of air through all parts of the body in insects makes the highest extent of respiration in invertebrata, so also is it with birds among the vertebrata. The sternum and ribs, together with the immoveable range of dorsal vertebrae, all con- tribute to dilate and narrow the thorax, after the manner of a bellows movement. This di- latation and contraction draws the air through the true lungs, which never move, and imme- diately the air cells are expanded. By this means two conditions are obtained ; the air is drawn through the lungs for aeration ; and the air filling the cancellated structure, renders the bird specifically lighter. The high flying rapacious bird can thus by a respiratory movement attenuate the air in his body, when soaring in the atmosphere, and again at pleasure condense it in every inter- stice of his frame, when he drops like a can- non ball, to pounce on his prey ; but imme- diately before seizing it, again he attenu- ates the air within him to break his fall ; other- wise he would be dashed to pieces upon the pointed crag, and die along with his victim. This beautiful provision is wholly due to his respiratory movement, at one time acting as a condensing, and at another time as an exhausting syringe. Of the Sixth Species of Respiration. Ufam- tnalia. — In this class we first meet with a perfect muscular septum (diaphragm) forming the two cavities of the trunk ; the one for the lungs, and the other for the abdominal viscera. All animals which have a diaphragm, maintain respiration in a manner similar to each other ; for, indeed, it appears that the ouly use of this muscle is to maintain a movement of air — that unceasing pumping to and fro of inspi- ration and expiration. Their respiration, or at least their inspiration, is purely of the vacuum order. The diaphragm is the chief muscle of ordi- nary breathing. It can act with great power, protruding the viscera, by its descent, at each ordinary inspiration. This is strikingly seen in animals recumbent and at rest, as in the cow, horse, goat, dog, &c., when it ap- pears as if the animal was breathing with its abdomen. The ribs likewise in some degree maintain respiration in the lower mammiferous animals, particularly in disease. For instance, the respiration of the horse or dog, when the lung is emphysematous, or what is familiarly termed " broken-winded," is costal , and at such times the respiratory action of the ribs may be beautifully seen. It is most probable that in mammalian re- spiration we have the highest order of accom- modation for peculiar respiration, according to the condition of the animal ; i. e. an instinc- tive power to respire by different parts of the thoracic cavity, according to the needs of the animal, whether modified by health or disease. Nearly two hundred years ago, Lower changed the respiratory movements of the dog from diaphragmatic to costal, by paralysing the diaphragm through the medium of the phrenic nerve. (Phil. Tr. Abr., vol. i. p. 179.) The respiration of mammalia is the bellows action — inflation of the lungs by expansion of the thorax, or inspiration by vacuum, and ex- piration by propulsion. The projectile force in the respiration of mammalia is nearly all due to mere elastic contractility ; i. e. ordinary expirations are produced by the elasticity of the lungs and ribs, returning backwards, or collapsing, after their distension by the inspiratory muscles. This mere dead and involuntary force performs one half of our respiration. Man is not distinguished either by the force, extent, or complexity of his respiratory move- ments ; he is exceeded in all these particulars by inferior animals. The roar of the lion gives the idea of an overwhelming expiratory power ; nor are his lungs less complicated ; and the vibration of thousands of cilia, pro- moting currents around the monad, is more complex than the simple respiratory thoracic action of mammalia. The most striking dif- ference is th.it produced by mental influence, which appears to command the most delicate modifications of this movement, so indicative 1022 THORAX. of the passions of his mind, while in the lower animals we see none of these. OF THE THORAX IN MAN. Anatomy of the framework of the Thorax. — A portion of the spine, the ribs, the sternum, together with numerous muscles, form the wall of the human thorax. The framework of bones is so ar- ranged as to admit of free mobility in various directions, so as to increase or diminish the cubic capacity of the thoracic cavity. OfthcDorsal Vertebrce. — That portion of the spine which enters into the composition of the thorax consists of the dorsal vertebrae, which are 12 in number, intermediate in size and position, between the cervical and the lumbar vertebra. They form the main pillar of support for the whole respiratory apparatus — the great fixed point for the chief respira- tory muscles to act against or draw upon. Their general appearance is that of increasing in size from above downwards ; but when carefully examined, they are as two cones, the apices of which touch at about the fourth or fifth vertebra, from which point, in either direction, they increase in their dimensions ; their breadth laterally exceeds their depth from before backwards. Their bodies are large and project deeply into the cavity of the tho- rax, diminishing greatly the antero-posterior diameter of the chest. Out of twenty cases, the average projection is 2f of an inch, leaving little more than 4 inches for the heart and great blood-vessels. A deep sulcus is thus formed, which if a cast be taken of the cavity of the thorax, is very striking. In phthisis pulmonalis, the space between the bodies of these verte- brae and the sternum is sometimes less than one inch ! When the thorax changes its form by disease, this centre pillar is liable to wedge in or jam up the thoracic organs against the walls of the chest. The vertebras are connected to each other by ligaments, and jointed beautifully into each other, so as collectively to admit of extensive motion, while there is but little movement between any two vertebrae. Of the bonds of union, the most remarkable are the inter-vertebral disks (ligamenta inter- vcrtebra/ia — Weitbr.) — composed of fibro-car- tilage, and placed between the bodies of the vertebra;, each disk serving to unite two vertebras, and yet to permit a motion in any direction, yielding on that side towards which the column inclines, while on the contrary side it expands with the increasing intervertebral space. This substance is to the brain what the cushion or " buffer " between each railway carriage is to the traveller; it breaks a sud- den jar from being transmitted from carriage to carriage. So does this intervertebral sub- stance soften down any sudden jerk received at the lower extremity of the spine, preventing its being transmitted to the brain in the varied actions of walking, running, and leaping. Of the Sternum (os pectoris : Xiphoides), so named from artpror, the breast : is a kind of flattened bone, symmetrical in shape, which occupies the anterior and middle part of the thorax. It is supported by the ribs on either side ; it is broadest at its upper part, and then narrowed ; it widens again, and finally becomes compressed and narrow where it joins the ensiform cartilage. (Fig. 660, e.) Its direction is oblique from above down- wards and forwards. This, with the curva- ture backwards of the spine opposite to it, increases the antero-posterior diameter of the thorax, as may be seen in a lateral view of a cast of the thoracic cavity. The length of the sternum, which is pro- portionably smaller in the female than the male, varies from 5 to 1\ inches. At the upper part its breadth is from 1^ to 2 inches. Its thickness above is about 6 lines ; at its lowest part it is much thinner, never exceed- ing three lines. The ancients compared the sternum to the sword of a gladiator ; and hence have arisen the denominations given to its various parts : as the handle (inamtbrium), the body (mucro), the point, or xiphoid appendix, (ensiformis) ; but the last mention- ed part now only retains the designation grounded on this circumstance. This division of the bone into three parts has been retained by some modern anatomists, who describe the three pieces of the sternum separately, as so many distinct bones ; we shall only adhere to this in speaking of the development of the bone. In anatomical language it is said, the ster- num presents two surfaces, two borders, and two extremities. Of the anterior or cutaneous surface of the Sternum. — This is subcutaneous, slightly con- vex and affords attachment to the aponeurosis of the pectoralis major and the sterno-cleido- mastoid muscles. It presents three orfourtrans- verse projecting lines, which are traces of the original division of the bone into five pieces. The union between the 1st and 2nd pieces cor- responds to the insertion of the 2nd costal car- tilage, and is frequently cartilaginous even in the adult age. The line which marks the union of the first two pieces of the bone is the most remarkable : it causes a projection of variable size in different individuals, which has been sometimes mistaken for a fracture or exos- tosis. At the lower part we sometimes find a foramen ; sometimes in place of the foramen there is a considerable aperture, to which much importance has been attached, as afford- ing a proof of the primitive separation of the bone in the median line. (Fig. 660. (/.) The existence of this opening explains how puru- lent matter deposited behind the sternum may, in certain cases, make its way outwards without any absorption of the bone. This bone is covered by a strong interlacement of very numerous aponeurotic fibres. Of the posterior (mediastinal or cardiac) sur- face.— This is slightly concave, and parallel in direction to the anterior surface. The con- cavity is directed downwards and backwards, towards the cavity of the thorax, and gives attachment superiorly to the sterno-lit/oidcus and sterno-thyroideus muscles, inferiorly to the triangularis stemi. THORAX. J023 Along the middle line, this concavity cor- responds with the interval left by the diverg- ence of the two pleura (anterior mediasti- num). In the young subject, transverse lines are seen corresponding to those which occupy the anterior surface ; all of these, except the two between the first and second pieces of the bone, are effaced at a more advanced age. This surface is in relation with many organs contained in the chest, and especially the heart, in front of which the sternum forms a kind of shield. This is exemplified, as al- ready noticed, in the frog, which is provided with a sternum, though it has no ribs. At the lower part of the sternum are many nutritient foramina. Of the borders of the Sternum. — These are thick and marked at each side by seven an- gular depressions for the reception of the cartilages of the first seven ribs, which gives this bone a notched and serrated appear- ance. These angular cavities are separated from each other by semilunar notches, which are longer above than below, where the facettes closely approach each other. The uppermost of these seven cavities is shallow, triangular, and at an early age becomes ingrained with the cartilage of the first rib ; those which follow are deeper, angular, and situated at the ex- tremities of each of the transverse lines. When examined in the dried specimen, they appear more angular and deeper in proportion to the youth of the subject. Of the clavicular extremity. — This is slightly convex, and is the broadest and thickest part of the whole bone. It is slightly excavated from side to side, and presents at each corner a depression for the reception of the sternal end of the clavicle, which bears the name fourchcttc; this is surrounded with irregula- rities for the insertion of ligaments. It fre- quently happens that the two clavicular arti- culations are not at the same height ; a fact which was noticed by Morgagni, and which Cruveilhier attributes to the unequal wearing of the two articular surfaces. We have once seen the clavicular articulation so low as to unite with the first costal cartilage. Of the inferior extremity of the Sternum. — This is formed by the xiphoid appendix ; or emifonn cartilage, for it often remains cartilaginous to adult age. In length, shape, and direction, it presents nume- rous varieties ; it is frequently bifid, some- times pierced by a foramen, and is occasion- ally bent forwards, or to one side, and in certain cases much depressed : its summit gives attachment to an aponeurotic structure, called the linea alba; behind, it indirectly corresponds with the stomach, which rests upon it when the body is placed in a prone position. Connections. — The sternum articulates with fourteen ribs through the medium of their cartilages, and more directly with the two cla- vicles. Structure of the Sternum. — This bone con- sists of two very thin compact lamina?, with an intervening cancellated structure, the cells of which are very large and have very delicate parietes. It is one of the most spongy bones of the body, and it is more than probable that to this circumstance the frequency of disease in it may be attributed. Absorption of this bone and great displace- ment by bending inwards is very common, particularly in women who wear tight stays. Under such circumstances, or by disease, we have witnessed the sternum so depressed in- wards that the depth, including all the thoracic integuments from the spinous processes of the dorsal vertebra? to the anterior surface of this bone, did not exceed three inches, in- stead of from seven to nine inches. Of the Development or Ossification of the Sternum. — As far as the middle of foetal life or a little later, the sternum is altogether cartilaginous, as represented n.ta,Jig. 600. This Fig. 660. bone is one of the slowest in its ossification ; it exhibits no bony points or centres of os- sification up to the sixth month of foetal life. It is also of all bones the one in which the phenomena of ossification proceed with the least regularity. After the sixth month of fcetal life, ossification begins with the for- mation of osseous grannies in the middle of the intervals between the points at which the cartilages of the ribs are connected. " There are five of these granules for the sternum, exclusive of the ensiform appendage, and they form as many pieces (e, Jig. 660.). The process of ossification makes its appear- ance in the first between the fifth and sixth months ; and, soon following in the second and third, it reaches the fourth at the end of foetal life. The osseous centre of the last varies considerably in the time of its appearance. It may be found soon after birth, and may not be visible for a considerable time (one or two years) after that period." " In many cases, one or more of the divi- sions of the sternum are formed from more nuclei than one, and there are peculiarities with respect to the number and position of these additional granules which require notice." Ossification of the 1st piece. — This some- times presents a single nucleus (fg. 660, b 1.), rounded and transversely strong ; sometimes it presents two nuclei, and in this case they 1024. THORAX. may be either placed one above the other, or side by side. In the former case the up- permost nucleus is the larger ; in the latter, both may be symmetrical and of equal size, or what is more common, they may be of un- equal magnitude. It may occasionally present more than two osseous points. Albinus found three in one subject, and four in another.* Mr.Quain has a preparation in Uni- versity College, where the very unusual num- ber of six (fig. 660. c. 1'.) are to be seen. In this case, where there is a plurality of osseous points, the largest are generally situated alone; exceptions to this rule are very rare. Ossification of the body, or the 2nd, 3rd, \th, and oth pieces. — The osseous nuclei which enter into the composition of the body of the sternum have generally a rounded form when they are single, and are situated in the middle line ; where they are in pairs or are placed laterally, they are more elongated, but smaller, and appear to represent only the half of one of the single nodules. The second piece has not often more than a single granule (b. 2, c. 2'.), but the rest are frequently formed from two nuclei, which are placed laterally to one another (c 3', 4'.), and not vertically as occurs in the first piece. These different osseous points are always so arranged as to be situated between two costo-sternal articulations, so that a portion of the sternum is developed in each of the intervals comprised between the ribs. The last piece is the only exception, being com- mon to the articulation of the 6th and 7th ribs. There are, therefore, four primitive pieces of the body of the sternum (b. 1, 2, 3, 4.), and each of these is sometimes formed by one point of ossification ; at other times by two lateral points. The first piece may be formed of one or many ossific points, which may be arranged vertically as well as laterally To the centres of ossification here described, M. Brechet f has added two small epi-sternal granules, whose position is sufficiently shown by the indication of them, fig. 660. at d**. They occur only at rather advanced periods of life, but they do not appear to be constant. Union of the points of ossification of the body of the Sternum. — In considering the union of the different parts which compose the body of the sternum, it is necessary to make a distinc- tion between the lateral conjunction — that is, the union of the osseous points which are situated on each side of the median line — and the vertical conjunction, or the union of the pieces of the sternum properly so called. The lateral conjunction, or the union of these osseous germs, which form a pair in the same interval, always precedes the vertical conjunc- tion. The vertical conjunction, or the union of the different pieces of the body of the sternum * Cruveilhier, Descrip. Anat. 8vo. 1840. Lend, p. 87. f Recherches sur Differentes Pieces du Sque- lette des Aniinanx Verte'bre's, &c. in " Anr.ales des Sciences Naturelles." 2de Serie, t. 10. (Zoologie) p. 91. together, commences with the two inferior portions. After this union, the body of the bone consists only of three parts. The 2nd piece then unites with the lower: the sternal foramen is formed sometimes at the junction of these last mentioned parts, sometimes at the place where the two lateral points of the 4-th and of the 3rd portions of the bod}' are united. If the interruption to the progress of ossification should occur at the point where the lateral parts of two sternal pieces would meet, the foramen is likely to have con- siderable size ; for it may be the result of an "arrest of development" proceeding from four centres each constituting a part. (Fig. 660. d. ) The union of the divisions of the body of the sternum takes place precisely in tiie inverse order of their appearance In fact the appearance of the osseous points proceeds from above downwards, while their union proceeds from below upwards : a fact which verifies the assertion, that the order of development of osseous points is not always correlative to the order of junction. The lowest or 5th piece is joined to the 4th soon after puberty; the 4th and the 3rd are united, between 20 and 30 year* of age ; and the body of the sternum is usually not .completed by the junction of the 3rd piece to the 2nd before 35 or 40 years. Lastly, the 1st division does not in general join the rest of the sternum at any period ; but should its union happen to take place, it is only to be met with in advanced age. Of the ossification of the appendix. — This is generally accomplished by one nodule. Some- times there are two ; and then they are rarely symmetrical. The process commences in the upper part of the cartilage, and very rare'y extends through the whole. The time of ap- pearance of the osseous point is extremely variable. Sometimes it is visible towards the 3rd or 4th year; sometimes not until the 12th or even the 18th year; according to the observation of Beclard, between the 2nd and 18th years. From the 40th to the 50th year, and some- times later, the appendix becomes united to the body of the sternum. From the varieties of ossification or development of the sternum, it will be evident that it is impossible to assign to it a limited number of osseous points. OF THR RIBS. — The ribs (Coatee from cus- todcs *) extend from the dorsal portion of the vertebral column to the sternum, form- ing arches which correspond to the lateral segments of the chest. About one sixth of the ribs are cartilaginous, and the rest os- seous. The osseous portion is the rib pro- perly so called ; the cartilaginous portion is named the costal cartilage. The ribs are 24 in number, 12 on each side ; but cases occasionally occur in which this number is augmented by the addition * As if they were guardians of those principal organs of the animal machine, the heart and lungs. — Munro : The Anatomy of the Human Bones, p. 234. Eclingb. 1726. THORAX. 1025 of a pair of cervical or lumbar ribs : in this case the supernumerary ribs are formed from the anterior parts of the transverse processes of either the seventh cervical or first lumbar vertebra ; which affords a strong proof of the analogy existing between a transverse process and a rib. Sometimes the usual number is diminished to 22 : this is more rarely the case. When this occurs, we sometimes find two adjacent ribs united throughout their entire length. Sometimes the first rib is in a rudimentary state, being properly formed posteriorly, but having its an- terior extremity lost among the muscles, or united to the 2nd rib. Mr. Quain has lately seen an instance in which this diminution of the number of the ribs was accompanied with the absence of a dorsal vertebra.* Classification of the ribs. — The ribs are nu- merically designated 1st, 2nd, 3rd, and so on, counting from above downwards. In the living or in the undissected subject it is easier to count the ribs from below upwards. The seven superior ribs are united by means of their own cartilaginous prolongations (fig, 661. b, c, d, e,f, g, and h ; and Jig. 662.) Fig. 661. to the sternum, and are called true ribs or sternal ribs, or vertebra-sternal ribs ; the re- maining five are not so immediately prolonged to the sternum, and are denominated false ribs, or asternal ribs, or vertebral ribs. We think it would be more judicious to classify them otherwise, and consider the five superior ribs as sternal, true, or thoracic ribs ; the five next inferior, as diaphragmatic ribs ; the two last, being floating or false ribs. Be- cause, the first five especially encompass the cavity of the thorax ; the five next a portion only of this space, together with a large por- tion of the abdominal viscera ; and, lastly, be- cause the two last do not touch the sternum through the medium of any cartilage. The transverse shade (fig. 682.) represents the arch * Elements of Anatomy by Mr. Quain and W. Sharpey, M. D. London, Svo. 1843, p. 105. VOL. IV. of the diaphragm, or the floor of the thorax. Every rib articulates with the dorsal vertebral ; Fig. 662. Position of the ribs and spine after deep expiration. the spine is their fixed point, or centre of motion, — the main pillar upon which they act. The superior ten ribs articulate through the medium of cartilages, the first seven through the medium of their own, the next three through that of those of their superior neighbours, (fig. 661.) with the sternum. The ribs have certain general characters which distinguish them from all other bones; and likewise certain proper or special charac- ters, by which one is known from another. I. Of the general characters of the ribs. — The ribs resemble flattened bony hoops, varying in breadth from '4 to "7 of an inch, and from •! to '-t of an inch in thickness; they once at- tain a maximum, and twice a minimum length (fig. 662.) They are of a very irregular shape. Their arch or curve is neither uniform relatively to each other, nor yet relatively to itself at different parts of the bone ; moreover they are twisted in different degrees upon themselves so that the two extremities of the same bone point in different directions, and cannot simulta- neously touch an horizontal surface. Surfaces. — These bones present two sur- faces : an external or cutaneous surface, which is convex and smooth ; and an internal or pul- monary surface, which is concave and likewise smooth. The anterior end is comparatively flat, the posterior is more cylindrical and truncated, and is rough, particularly at the extremity. Borders. — The ribs have two borders, the one superior, and the other inferior. The superior border is smooth and rounded, and gives attachment to the intercostal muscles ; 3 i) 1026 THORAX. the inferior border is more thin and sharp, particularly in the middle third, or body, of the bone. This thin or blade-like appearance is caused by a groove on its inner aspect termed sulcus costalis, which is commonly said to be for the lodgment of the intercostal vessels : this border also gives attachment to the intercostal muscles. The borders are irregular in their direction corresponding with the shape of the rib ; which we shall presently notice. Fig. 663. Fourth rib. Extremities. — (a) Posterior or vertebral extremity, (fig. 663. r). — This is rougher and somewhat thicker than the other parts of the rib, and is hence denominated its head (capitulum cosies). It presents, except in in- stances to be presently stated two articular facets, a superior and an inferior one, sepa- rated by a well-defined ridge. Each of these facets articulates with a corresponding small surface on the bodies of two vertebra?, the ridge just mentioned corresponding with the intervertebral substance. The head of the rib is supported by a narrow round part, somewhat constricted — the iwck (fig. 663. /). This is flattened from before backwards and is the weakest part of the bone. Behind the neck there are some inequalities, which correspond to the trans- verse process of the dorsal vertebra below. Externally to the neck is an eminence known as the tubercle of the rib (tuberos- ity, tuberculum costce, jig. 663. g), which is smooth in one part for its articulation with the transverse process of the lower of the two vertebras to which the head is connected, and rough in the other, which is posterior, and in some ribs superior to the above, for the inser- tion of the posterior costo-transverse liga- ment. The tubercles are most prominent in the four or five superior ribs. Anterior to the tubercle the rib suddenly bends forwards, leaving this part the most convex, making what is termed its angle, (fig. 663. //) The interval which separates the tuberosity from the angle, is the thickest, roundest, and strongest part of the bone. (b) Anterior, or sternal extremity (fig. 663. cT). — The anterior extremity of the ribs is broad, flat, and deeply hollowed out at its tip into an oval pit, into which is implanted the costal cartilage. This extremity of the rib is broader and thicker than it is an inch more posteriorly. Body. — This may be described as that part intervening between the angle and the anterior extremity. We have stated that the posterior end is more round than the anterior ; the body, therefore, may be considered as of a transition form, passing from the cylindrical to the flat, blade-like, shape as it approaches towards the sternum. Curve. — The curve which the ribs follow is very irregular, and therefore not easy to describe. No doubt they are of the form best adapted to admit of a great increase of thoracic capacity at;the expense of a remark- ably small movement. They appear to encom- pass the thorax in a somewhat spiral manner (see dark lines figs. 682 and 683.) ; to accom- plish which they have three curves, one the common general arch or bend of the bone ; the others the twist of the edges near the extremities termed the curve of torsion. (A) Arch or general bend of the ribs. — This is the most remarkable feature of a rib. What- ever be the curve of the 1st rib, it may be said that each inferior rib describes a curve "one size" larger; so that one rib can be laid close within the other, like hoops of gradually increasing sizes. Two distinct curves will then be seen. It will be ob- served that the part extending between the head and the angle describes a larger cir- cle than the angle itself, which as the name im- plies, is the most acute turn in the bone. More anterior to this, the curve becomes remarkably large ; which Haller has so ex- pressively described as representing the tan- gent to the posterior curve. In connexion with the general curve of the rib should be noticed two linear measurements, viz., the chord and the versed sine. In fig. 664. is given Fig. 664. Second rib. the 2nd rib ; the line A B is the chord, and D c the versed sine, or a line extending from the chord to the most prominent part of the bend of the bone. The general curve regulates the length of the versed sine. This curve of the rib gives the sides of the chest a power of enlarging, — a lateral mobility, — according to the length of the versed sine, and quite distinct from the antero-posterior enlargement, which is according to the length of the chord. The ribs do not increase the lateral dimensions of the thorax by abduction, but solely by their rotation upon the line A B (B) Curves of torsion of the ribs. — If we take THORAX. 1027 the 7th rib and place it on a table it will be observed that the extremities cannot simul- taneously rest upon one plane, because it is twisted upon itself. This is due to what is called the curve of torsion. The rib is twisted at each end ; hence a posterior and an ante- rior torsion. The posterior torsion is most conspicuous, and is therefore more commonly noticed. («) Posterior torsion. — This torsion is marked at the angle of the rib (h,fg. 663.), particularly upon the convex surface, by an oblique line or a series of faint lines directed from above downwards and forwards. Like other features of the ribs, it passes through gradations, being scarcely perceptible in the 2nd rib, more so in the 3rd, and in- creasing to the maximum in the 8th, in the 9th and 10th it quickly decreases, until it is lost in the llth and 12th. The greater the torsion the more distinct is the angle ; where the angle is rudimentary the torsion is imper- ceptible, as in the llth and 12th ribs. The degrees of this torsion as it passes through the ribs are most distinctly seen by having the ribs separate, and placing them on a flat surface with their superior edge upper- most, arranging them so that they do not quite touch each other, when the heads of the dif- ferent ribs will stand up at different heights from the table, forming a somewhat regular wave. This is solely produced by this posterior torsion. (1)) Anterior torsion. — "Near the anterior extremity, on the convex surface, in well- developed ribs, we observe an oblique line analogous to that at the angle of the rib, but much less distinctly marked. This line may be considered as forming the anterior angle and corresponding torsion of the ribs, which, like the posterior, is intended for more favour- able muscular insertions. Although the anterior angle is comparatively feebly marked, the anterior torsion of the ribs is as well defined as the posterior torsion. It will be seen in jig. 6G7, that while the posterior extremity of the rib curls upwards, the an- terior extremity curls downwards. In like manner as we notice the posterior torsion by placing • the separate ribs on a table, so may the anterior torsion be as strikingly seen, taking care to place the ribs upon their superior edge so that the sharp inferior edge is turned upwards. The anterior ends will be seen to stand up in different degrees from the table according to their torsion, commenc- ing with the 3rd or 4th and terminating with the 10th rib. Articulations of the ribs. — The ribs are articulated behind with the dorsal vertebras, and in front with the sternum through the medium of the costal cartilages. This has alreadj' been noticed under Extremities of the ribs. Position of the ribs. — The ribs are arranged more or less obliquely, — about midway between the perpendicular and horizontal (Jigs. 662. and 083.) ; — and they somewhat diverge from each other as they approach the sternum. (Jigs. 662. 680. and 681.) Not one of them is horizontal, though commonly re- presented as if they were. Their position is given iiy%. 662. This is important to remem- ber, because we shall see that costal breathing altogether depends upon their obliquity. Structure. — The compact and spongy sub- stances are so distributed throughout the whole length of the ribs that they possess a certain degree of flexibility, with great power of resistance. In young subjects the compact substance is in excess ; in the aged, and in certain diseases, the opposite is the case ; hence the extreme fragility of these bones, which are then broken by the least effort. Development. — The ribs are amongst the earliest developed bones, ossification com- mencing in them even somewhat before it has made its appearance in the vertebrae. The deposition of osseous matter extends rapidly throughout them. Each rib (with exceptions to be noticed) is formed from one principal piece ; and two epiphyses. Of these two epiphyses, one forms the head of the rib, and the other the tubercle : their ossification commences between the sixteenth and twentieth years of age ; and they are united to the rest of the bone a few years after, — about the twenty-fifth year. II. Special characters of different ribs. — The differential characters of the ribs, when mi- nutely examined, are well marked ; for, strictly speaking, no two ribs on the same side are of the same shape and dimensions. Although the difference is very small between two con- tiguous ribs, as, for instance, between the cen- tral ribs, i. e. between the 6th, 7th, and 8th, yet it is very conspicuous between those of the top compared with those of the bottom of the thorax. Whatever be the peculiarity under examination, we find it most developed in the 6th or 7th rib ; and below this it becomes less and less marked, until, in the 12th rib, it appears rudimentary. In fact, the 12th rib may be considered little more than a prolonged transverse process ; but not so with the 1st rib, which possesses all the marks and uses necessary to the character of a rib. The ribs differ in their length, and in their chord and versed-sine measurements, and consequently in the area of thorax which they encompass. The thoracic dimensions vary considerably in different men and in the two sexes ; yet the relative measurements and weight of the ribs will be found useful to our comprehending more perfectly the res- piratory movements. These relative measurements are from a well-formed male thorax. The area-measure- ment is calculated from an internal cast of the thorax, cut up slice by slice through each intercostal space. These slices were traced upon paper and measured, giving the absolute area of thoracic cavity encompassed by each pair of ribs, their cartilages, and the sternum. (See^/zg. 668.) 3 u 2 1028 THORAX. TABLE A. — Relative Lengths and Weight of, and Area of Thoracic Space encompassed by, the respective Ribs, including the Space made up by the Sternum and Costal Cartilages. Rib. Absolute Length. Chord Length. Versed Sine Area Sq. In. Weight, Grains. 1 5-25 2-00 1-75 10- 98 2 9-00 3-75 3-00 27- 134 3 11-00 5-10 3-40 40- 181 4 12-25 6-00 3-50 51- 255 5 12-50 6-90 3-50 57- 308 6 12-60 7-10 3-50 63- 317 7 12-25 7-50 3-30 58-5 391 8 12-10 7-90 3-25 43- 363 9 11-50 7-75 3'10 27- 280 10 10-50 7-00 2-90 20- 216 11 8-25 5-90 2-25 10- 145 12 4-50 3-75 1-00 7-5 60 Fig. 665. represents the above table by curves. The perpendicular lines represent the ribs; and the curves the characters re- ferred to. By a general view it will be seen that all the lines curve upwards, and are at their highest at about from the 5th to the 9th rib. We shall not treat of particular ribs, but of certain characteristics as they run through the ribs. A knowledge of their shape is ne- cessary to comprehending the respiratory movements in diagnosing thoracic disease. 1. Length. — The length of a rib may be taken in three ways, — its absolute length, chord length, and versed-sine length. (a) Absolute length. — In the length from the anterior to the posterior extremity, (A c B, fig. 664.) the 12th rib is the shortest. The 1 1th rib is nearly double the length of the 12th rib ; likewise the 2nd rib is nearly double the length of the 1st rib ; therefore the 1st and 2nd, and the llth and 12th differ more re- markably in their length than do any of the other ribs. The length (curve a, fig. 665.) suddenly increases up to the 4th rib ; and then the difference is trifling to the 8th rib ; after this the shortening is as rapid as in the four superior ribs. (b) Chord length. — The dotted line b,fig. 665, represents this measurement. This length from tip to tip (A B, fig. 664.) of the rib is the chief modifier of the different apparent mobility of particular ribs. If we allow the range of costal movement to be the same in each rib, while each succeeding rib increases in its chord length, the apparent mobility in different ribs will increase exactly as their chord measurement increases. If a rib be three inches long, and if its free extremity by a given movement passes through one inch of space, the free extremity of a rib six inches long will, with the same absolute movement, pass through two inches. The chord length is an important element in modifying thoracic capacity. It is in this measurement that the 1st rib is the shortest and nearly one half the length of the 2nd rib, — as 2" is to 3-75. (Table A.) The chord length (line b, fig. 665, com- pare with line a,) increases and decreases less abruptly than that of the absolute length. If we were to admit that all the ribs at their fulcra possessed the same extent of mo- tion, still the antero-posterior length of the thorax would be unequally increased, and that exactly in relation to the chord measurement ; Fig. 665. Absolute length Chord 3 Versed sine Area - - fl Weight - t e \. 9 10 11 and hence the 7th, 8th, 9th, and 10th ribs advances most, somewhat representing the would advance most. It is a fact that in deep curve line b,fig. 665. inspiration the lower part of the sternum (c) Versed Sine Length (D c, fig. 664.) — THORAX. 1029 As the chord length is to the antero-posterior movement, so is this measurement to the lateral movement of the thorax. This is the most uniform measurement in the ribs. If the 1st rib be T75, the 2nd rib is to that as 3; and from this rib to the 9th rib, the versed sine never exceeds 3'5 ; hence the curve c, Jig. 665. is more horizontal than any of the other curves. So likewise it will be found that the lateral enlargement of the thorax in deep breathing is more uniform than the antero-posterior enlargement. (See dotted line, jti*s. 71 1, 712. compared with dotted line, Jigs. 713, 714.) The space gained by the ribs rotating must he strictly in relation to the length between the deepest part of the arch and the chord line. (D c,Jig. 664.) This mea- surement is greatest relatively in the 2nd rib, and absolutely smallest in the 12th rib, the curve here being very small. The versed sine of the ribs corresponds with the great curve: if a rib were not curved at all, there would be no versed sine. The versed sine does not increase after the 4th rib; and the curvature of the first four ribs forms smaller circles than the rest. The 5th and 6th ribs, although rapidly increasing in absolute length (see Table A.), yet present nearly the same versed sine; and while the chord line increases up to the 9th rib, from the 6th to the 9th the versed sine decreases, showing that the circle or arch of the rib becomes larger as we descend, until the 12th rib, which describes the greatest curve and the shortest versed sine. In fact there is little difference in the versed sine length from the 3rd to the 10th rib, as described by the double line c,fig. 665. This difference of arching of the ribs constitutes the conical form of the thorax, the smaller circles being at the apex, and the larger at the base of the cavity. (2) Weight. — The ribs increase not only in their various measurements but also in their weight up to the 7th or 8th where they attain their maximum development. The faint con- tinuous curve, e, Jig. 665. is the line of the relative weight. (3) Torsion of the ribs (special characters'). — We have already mentioned that the ribs have two torsions, an anterior and a pos- rerior. No rib is entirely free from this twist. It is incorrect to believe that the 1st rib is without any torsion, and therefore that the whole rib in its length can touch the same plane. In fact the 1st rib may in one sense be looked upon as the most twisted of all the set, inasmuch as the flat sides which are internal and external in other ribs are in this rib inferior and superior. Like other features, the degree of torsion in the different ribs is progressive towards a maximum, and then towards a minimum. The 2nd, llth, and 12th ribs are most devoid of torsion. In the last two ribs the torsion ap- pears less than it really is, because of their shortness and the large circle which they de- scribe. The two torsions in each rib are always in contrary directions, except in the 2nd rib, where they are both downwards, but the tor- sion is here very slight. In the 1st rib, as in the ten inferior ribs, they are in contrary di- rections to each other, so that its two ends cannot touch the same plane at the same time ; but its anterior and posterior torsions are respectively contrary to those of the ten in- ferior ribs ; its posterior torsion being, like that of the second rib, downwards, and its an- terior upwards. The relative torsion of the ribs maybe ex- pressed by giving the respective elevations of each extremity from the plane upon which they rest. Thus the posterior torsion is seen when the rib rests upon its inferior edge, and the anterior torsion when it rests upon its su- perior edge. In this way the following table is calculated. TABLE B. — Torsions of the Ribs. Ribs. Posterior End Torsion Upwards. Anterior End Torsion Downwards. 1 2 6-0* 2-5* 5'Of 3-0 3 3-0 3-0 4 12-5 4-25 5 13-0 12-0 6 12-25 21-5 7 18-00 29-5 8 21-25 28-0 9 21'25 25-0 10 9-50 17-5 11 1-50 5-5 12 2-00 4-5 If the posterior twist of the ribs upwards be expressed conjointly as 114, the anterior tor- sion downwards is 153 ; therefore the anterior torsion is greater than the posterior. The torsions in the 2nd, 3rd, llth, and 12th are the least ; and they are the greatest in the 7th, 8th, and 9th ribs. Moreover as the tor- sion increases at one extremity of the rib, for the most part it increases at the other like- wise. The ribs of some persons are much less twisted than those of others. This is parti- cularly the case in young subjects before the age of puberty. In infants the torsions are imperceptible ; therefore they increase as we advance to maturity. These torsions afford more favourable traction for the muscles. Where the respiratory movement is most ap- parent, as from the 4th to the 9th rib, the torsion is highest. t The posterior torsion gives the ribs, when placed in their natural position, aver}' oblique direction with reference to the spine. This is very important to remember; for the more oblique, the more favourable are they for mo- bility or for increasing the thoracic cavity. For the same reason the anterior torsion, being in a contrary direction to the posterior, increases still more the obliquity of the rib with refer- * Downwards. f Upwards. 3 u 3 1030 THORAX. lowed out for their cartilage. Fig. GGG. ence to the spine. But the relation of these lowed out for their cartilage. As the ribs torsions to the spine are different : the pos- become more perfectly developed, for in- terior torsion is relative to the spine late- stance, the 5th, 6th, 7th, and 8th, the an- rallv, while the anterior torsion relates to terior extremity is broader, but not more the" spine more in the antero-posterior direc- deeply hollowed out than some of the other tion ' they both conspire to increase the obli- ribs, which are less perfectly developed, as in quity of the rib in one given direction, — from the 2nd and 3rd, or 1 1th ribs. This extremity above downwards. is most pointed in the 12th rib. The torsion of the 1st rib, we have noticed, is directed in a contrary direction to that of other ribs ; and we have observed that the presence of torsion in general favours muscular traction: but the 1st rib is an exception to this ; here the torsion exists only between its two chief articulating pro- cesses, — the head and the tubercle : in the other ribs the torsion is between the tu- bercle and the body of the bone. The pos- terior torsion of the 1st rib appears to be merely destined to afford the head a more complete attachment to the body of the one vertebra (the 1st dorsal) to which that rib is fixed. A posterior torsion, in this short rib, is not needed for muscular traction, be- cause here the scaleni are placed in the most favourable position — nearly at an angle of 90° with reference to the body of the bone in question, while their other insertion into the cervical vertebras facilitates the most ex- tensive and favourable means for its mobility, independently of any favouring twist in the rib for that purpose. (4) Surfaces (special differences). — The thorax being conical, or somewhat barrel- shaped, it follows that the surfaces of the ribs, like the hoops of a very spherical Reiation Of the ribs to the spine in angular curvature. barrel, must gradually change their direc- tion ; thus the surfaces of the 1st rib are (b) Posterior extremity. — The posterior ex- nearly superior and inferior, this bone forming tremity of the rib is more complicated, and the lid to the thorax, while the surfaces of the has certain named parts, as the head, neck, 6th or 7th rib are external and internal, and as tubercle, and anjjle, all of which become niodi- we proceed downwards to the 10th, llth, and fied as we pass from above downwards. Their 12th ribs, the surfaces are again slightly differences may briefly be noticed, tending towards a superior and inferior po- sition, so that the internal surfaces of the 1st and 12th ribs are directed somewhat towards each other. The body of the rib, or that }sl Of the /iead.~ On the head of the rib, articulating with the vertebrae, a surface or facet is formed. The 1st, the llth, and the 12th ribs articulate each with the body of one part which covers the lung laterally, and the vertebra, and therefore they have one arti- anterior and posterior extremities, have also culating surface. All the rest articulate each their surfaces inclined in different directions. with the bodies of two vertebrae, and they Thus, take a perfect rib, say the 7th, laterally consequently have two such articulating sur- to the thorax the two surfaces are internal faces as already described. The head of the and external, while at the anterior end they ]st rib is relatively larger than that of the are directed — external surface, forwards and downwards ; internal surface, upwards and backwards ; — at the posterior end, — external surface, upwards and backwards ; internal surface, downwards and forwards. This is produced by their respective torsions. In others. For the most part, as the ribs in- crease in size, the head likewise increases, so that in the best developed rib the head and its surfaces are most perfectly formed, dege- nerating again to the 12th rib. 2nd Of the neck. — The neck being that /» _ 1 •« I i \_ . .,!_* 1 ._ 4.1 „ ,-. C some of the lower animals the ribs overlap part of the rib between the articulation of each other like the tiles of a house; this sometimes threatens in man, particularly in diseases of the spine (fig- 666.), when they closely approach each other. the rib with the bodies of the vertebra, and that with the transverse process, and these points differing but little in their distance from each other in the dorsal vertebra;, it (5) Specific differences of the extremities of follows that the absolute length of the neck the ribs. — The greatest difference is in the of the different ribs is nearly the same. The posterior end of the rib. The anterior pro necks of the ribs differ in their thickness, ac- senting little difference. cordingly as their respective ribs increase or (si) Anterior extremity. — These are all hoi- diminish iu size; therefore, in the middle THORAX. 1031 set of ribs, the necks are the thickest and strongest. In the llth and 12th ribs, the neck, according to our definition, does not exist. 3rd Of the tubercle. — As the tubercle ar- ticulates with transverse processes, those ribs which have no such articulation have no tu- bercle; this is the case in the llth and 12th ribs. The tubercles are most prominent in the superior ribs, gradually degenerating, or be- coming less apparent, down to the 10th, where it is almost rudimentary. 4rdly. With the sternum (C/iondro-stcnial articulation). — The costo-sternal articulation is between the angular extremities of the car- tilages of the ribs and the corresponding fossie in the margins of the sternum ; these ar- ticulations are covered and supported by two sets of ligaments. 1st, by an anterior set of ligamentous fibres, thin, scattered, and radi- ated (ligamenta radiatim disjecta Weitbr.), passing from the extremity of the cartilage to the anterior surface of the sternum, where they interlace with those of the op- posite side, and are blended with the apo- neurosis of the pectoralis major muscle. 2ndly, by a posterior set of fibres similarly disposed, but not so thick or numerous, con- necting the thoracic surfaces of the same parts ; together with some ligamentous fibres placed above, and others below the joint. A synovial membrane is interposed be- tween the ends of each true rib, and the sternum. These membranes can be demon- strated by slicing oft' a little of the anterior surface ot the sternum and cartilages. Cruveil- hier doubts the existence of such synovial membranes ; we are inclined to differ from him in this respect. Characters peculiar to' chondro- or costo- sternal articulations, — The 1st, 2nd, 6th, and 7th chondro-sternal articulations present the following peculiarities : — 1st, The cartilage of the 1st rib is some- THORAX. 1033 times continuous with the sternum, and is sometimes articulated like the cartilages of the other ribs. Cruveilhier found in one sub- ject the 1st rib excessively moveable, because its cartilage, instead of being continuous with the sternum, had its upper edge applied to the side of that bone to which it was united by ligaments, and was ultimately articulated by a narrow extremity immediately above the 2nd rib. 2ndly. The second cartilage is much more angular at its inner extremity than any of the others : it is received into the retreating angle formed by the union of the first two pieces of the sternum. Sometimes there is an inter- osseous ligament in this joint, running from the angle of the cartilage to the bottom of the cavity, and there are then two synovial cap- sules ; in other cases there is only one, but it is always more marked than in the other joints. The articulations of the 6th and 7th carti- lages, besides the anterior ligaments, have also a chondro- or costo-xiphoid ligament, more or less strong, which crosses with the ligament of the opposite side in front of the ensiform car- tilage, and the lower end of the sternum. Sometimes this ligament onlj' exists for the 7th cartilage ; it is intended not only to strengthen the chondro-sternal articulation, but also to maintain the xiphoid appendix in its place. Connection of the ribs with their cartilages. — The cartilages are almost immoveably united to the ribs, being received into rounded depressions on the ends of the ribs, and their union is maintained only by periosteum, which may be considered to represent their liga- ments. Articulations of the costal cartilages one with the other. — Some of the costal cartilages articulate with each other by their edges. The 1st, 2nd, 3rd, 4th, and 5th costal car- tilages do not articulate together, unless the aponeurotic lamellae, sometimes very strong, which form the continuation of the external intercostal muscles, and occupy the whole length of the cartilages, be considered as uniting media. The 6th, 7th, and 8th cartilages, frequently the 5th, and sometimes the 9th, present true articulations with one another. Cartilaginous processes arise from the neighbouring edges and come in contact with each other : there are sometimes two articular faces between the 6th and 7th cartilages. The means of union are some vertical fibres united in bundles, so as to form two ligaments, the one anterior and thicker, the other posterior and thinner. The edges of the articulating surfaces, from the 6th to the 8th or 9th, are lined by sy- novial membrane. The 7th, 8th, and 10th cartilages have not always articular surfaces, but are simply united by vertical ligaments. Ligaments of the sternum (Membranes sterni, Weitbr.). — The pieces of the sternum are connected by a layer of nbro-cartilage, placed between their contiguous borders; and, oji the anterior and posterior surfaces, liga- mentous fibres may be observed running longi- tudinally, which serve to strengthen their con- nection. They are sometimes called the anterior and posterior sternal ligaments. The longitudinal fibres are mixed with those ra- diating from the costal cartilages, especially in front of the sternum, where likewise they blend with the aponeurosis of the pectoral muscles. The anterior portion has thus most of the accessory fibres, and is rough and irre- gular ; the posterior one is smooth and pearly in its aspect. The muscles of the thorax will be more con- veniently noticed hereafter. OF THE THORAX IN GENERAL. — The ster- num, the ribs and their cartilages, together with the dorsal vertebra?, are so united to- gether as to compose the frame-work of the thorax. (_/%. 662.) Their arrangement is such as collectively to admit of great mobility, and at the same time to protect completely the or- gans of respiration and the heart. How well adapted this mechanism is for protecting those vital organs is well shown by the impunity with which the prize-fighter receives for many hours the trained blows of his antagonist. Although the range of motion between each vertebra and the ribs attached to it, is very limited, yet the whole frame-work of the chest enjoys such mobility, that, by a deep inspiration, its capacity is sometimes more than doubled. This bony frame-work is by no means destined solely to cover the respira- tory organs, for it extends considerably down- wards, composing part of the abdominal walls within which lie the liver, spleen, kidneys, stomach, duodenum, and part of the colon ; hence the distinction between thoracic and diaphragmatic ribs. In fact it will be found that about one half only of the costal surface is destined to compose the thorax. The shade running transversely across the ribs in_y%. 632. marks the bottom of the thoracic cavity. In each individual the thoracic cavity cor- responds exactly with the volume of the heart and lungs. But there is no relation between the volume of the lungs and the vigour of the constitution — nor between the size of the ca- vity of the thorax and the amount of air which can be respired, as will be hereafter shown. There is likewise no relation between the vo- lume of the thorax and that of the abdominal cavity. No doubt the vigour of aeration in the lungs is at all times exactly commensurate with the vigour of the alimentary canal, so that the one harmonises with the other; but this vigour bears no relation to space or size. A small thorax may in some individuals admit of the inspiration of a greater volume of air than a larger thorax in others. In fact it may be commonly noticed that where there is a large abdomen there is generally a small thorax, and that the volume of air which can be expelled at one effort from the lungs of those who have a large abdomen, is less than from those with a small abdomen. The alimentary canal receives at once a given quantity of food, and there it remains for an indefinite time, the thorax large o1* small, it 1031 THORAX. matters not which, aerates the blood from this food by movements, quick or slow, long or short ; therefore the respiratory movements only, need be relative to the abdominal cavity, in the same way as the volume of the blast from a pair of bellows is more dependent on their mobility than on their absolute size. The above remarks are applicable to the thorax of either male or female. I. Boundaries of the thoracic cavity. — The thoracic cavity, situated between the shoul- ders and below the neck, extends but a short way downwards, in the male about seven inches, and in the female about eight inches, below the clavicle, so that a horizontal line drawn about an inch below the axilla, corres- ponds (roughly) with its floor. The floor of the chest, therefore, is much higher up in the trunk of the body than is commonly supposed. The thorax is bounded anteriorly by the sternum and costal cartilages ; laterally by the bodies of the ribs and the intercostal muscles ; posteriorly by the vertebrae and angles of the ribs, and inferiorly by a thin tendinous and fleshy floor — the diaphragm. The su- rior aperture of the chest is about sixteen inches in circumference, this is the smaller end, and thence called the apex of the tho- rax. It is bounded laterally by the two 1st ribs, anteriorly by the upper edge of the sternum and inter-articular ligament, and posteriorly by the last cervical and first dorsal vertebrae. The inferior aperture is about thirty or thirty-one inches in circumference, and forms the base of the chest. Anatomists describe this part as bounded in front by the cartilaginous extremity of the sternum or xiphoid cartilage, and the cartilaginous extremities of the last true and false ribs, and more laterally by the 1 1th and 12th ribs, pos- teriorly by the last dorsal and first lumbar vertebrae. But as they assume to themselves the privilege of giving a bone' a surgical neck as well as an anatomical one, so may we take a similar liberty in describing the thorax for medical purposes. In the examination of the chest during life, too exclusive attention to anatomical boundary has probably led to the error, of regarding the chest as much deeper than it really is, and thence to examining for disease of the lung where really little or no lung exists. A sharp instrument, piercing the chest laterally, at the cartilaginous extremities _of the last true ribs, would most probably pene- trate no lung, for the liver, spleen, stomach, &c. are contained within these points. The bottom of the chest is so moveable and so much arched (See art. DIAPHRAGM, /g. 3.), that in the different stages of inspiration, the lung assumes different positions This may be demonstrated by percussing over the 5th rib at its junction with its cartilage, first after a deep expiration and then after a deep inspira- tion ; in the latter the sound is " clear," in the former it is strikingly " dull." Therefore, instead of taking the insertion of the dia- phragm as the bottom of the thorax, it will be found more convenient for examining the chest to take the top of the arch of this muscle as the lower thoracic boundary, or the shaded line crossing the ribs in fig. 4., for the medical base. This may be described as corres- ponding in front with the xiphoid cartilage ; laterally to different osseous portions of the 7th, 8th, 9th, 10th, llth, and sometimes the 12th rib (fig. G82.), and posteriorly to the 8th and 9th dorsal vertebras. This will place the bottom of the thorax in a very different posi- tion from what is generally supposed ; for, if we express the distance from the 1st rib, to the lowest point of the 10th rib as ]3'5, that from the 1st rib to the arch of the diaphragm or medical boundary will be only G'25, less than one half the depth of the thorax as ana- tomically described. The medical base of the thorax forms a nearly horizontal plane, which extends between the sternum and the bo- dies of the 9th or 10th dorsal vertebrae, its posterior being somewhat higher than its an- terior. But on each side of the bodies of the vertebrae there is a deep groove formed by the angles of the ribs. In that part of this groove which extends below the above-mentioned in- clined plane, a wedge-shaped process of lung is lodged, which varies in size in different sub- jects, and consequently will be found to ter- minate at different points in the dorsal re- gion, as already noticed, sometimes hanging down like a broad, thick flap, and at other times forming only an insignificant process. In examining the chest, it is of paramount importance that the student should familiarly know this medical fioor of the thorax. The sign laid down by the late Dr. Edwyn Har- rison, for marking this boundary, we have found strictly correct in every normal-shaped thorax. Namely, take the xiphoid cartilage as a point to start from, and pass the fiat hand horizontally from thence to the side of the chest, the index finger, when horizontal, will distinguish a slight depression or sulcus at the maximum lateral bulge of the thorax, then from this point slide the hand slightly upwards (perpendicularly), and it will pass over a bulge, about enough to fill the palm of the hand, into another sulcus, better defined than the former one ; this groove corresponds with the medical base of the thorax, and a probe passed in here would graze the arch of the diaphragm after passing through the moveable inferior edges of the lungs. It is necessary that the hand be kept perfectly horizontal, or it will fall into an intercostal space, which does not correspond with the groove in question. With practice, the hand falls at once into the upper sulcus, without first searching for the lower one ; indeed, latterly, Dr. Harrison allowed that the lower sulcus might be absent, and yet the upper one present. This groove is higher upon the right side than upon the left, corresponding to the height of the liver. By external observation, the medical base of the thorax may be known by the slight rota- tory motion made upon the diaphragm when a person is walking. A kind of great ball and socket-joint may be conceived to exist between the abdomen and thorax, and the THORAX. 1035 outer garments even exhibit a correspondence to this base of the thorax. II. Contents of the thorax. — Not only does the thorax contain organs proper to itself, but it lodges and protects others passing to the abdomen ; thus, the food we eat passes through the thorax to enter the stomach, while the eighth nerve both supplies the lungs and then passes onwards to the stomach. Like other cavities, the thorax is lined with a serous membrane (pleura costalis], which like- wise invests the lungs (pleura pufniona/is) (See PLEUKA). The heart and its blood- vessels, the trachea, and the lungs, almost completely fill the thorax. The remaining organs, viz., the origin of the sterno-hyoid and -thyroid muscles, remains of the thymus gland, lymphatic glands, mammary vessels, triangulares sterni muscles, the phrenic, the eighth pair, and the splanchnic nerves, the oesophagus, thoracic duct, vena azygos, and venae cavae, occupy very little space. Thus the thorax is completely filled. The older anatomists, however, even as late asBenj. lloadley's time, considered that there was a considerable space containing air, between the lungs and the walls of the thorax. Now, we know that any considerable accumulation of air in this situation would be destructive to the respiratory function. HI. Shape of the thorax. — The shape of the thorax is subject to many varieties which may be conveniently studied under the fol- lowing headings : External thorax. — The thorax in the perfect subject is somewhat conical, broader above than it is below ; but when deprived of the upper extremities and their appen- dages, the contrary obtains, for it is nar- rower above than it is below (see Jigs. 662. and 630. et seq.). Therefore the notion we commonly connect with broad shoulders or broad back, has but a feeble relation with the absolute breadth of the thorax. In fact the diameter of the neck corresponds more correctly with the diameter of the upper part or true apex of the thorax. Freeman the American giant measured 26 inches from tip to tip of his shoulders, while the diameter at the lower part of his neck, in the same direction, was only 6 inches. In women the mammae materially add to the dimensions of the chest towards the apex. We have found the measure of a female round the thorax over the mamma; 45^ inches, while the root of the neck was 15 inches. Allowing two inches for muscle, &c., the true thoracic apex would not exceed 13 inches, whilst 45^ inches was the apparent circumference of the thorax. The true apex of the thorax is loaded with large muscles, sometimes a vast quantity of fat, the upper extremities, and in the female with large maninuu besides. The true base of the chest is comparatively little covered, particularly below the axilla, where theserrati are seen. This is the weakest and thinnest part of the thorax, but it is well protected by the arms. (a) The anterior or slcrnal region of the tho- rax.— In a well-developed thorax the sternum appears to lie in a fossa formed by the pecto- rales and mamma;. This region assumes more or less of the perpendicular, according to the carriage of the person ; a perpendicular drawn to the external plane of the sternum would, however, be directed upwards. Laterally to this, the costal cartilages articulate with the sternum ; and, still more laterally, the ribs and their cartilages unite, forming an oblique ridge from above downwards. (See Jigs. 080. and 681. the line on each side of the sternum.) Still more externally, and parallel to this, may be noticed the projections formed by the anterior angles of the ribs, which bound the anterior region. (b) The posterior or vertebral region. — In the well-developed thorax the spines of the dorsal vertebrae lie in a deep groove formed by the great mass of the erector spins on either side. These masses extend outwards to about the posterior angles of the ribs, which are nearly in a plane with the spinous processes of the vertebra1, and may be easily distin- guished, bounding the posterior region. (c) The lateral or costal region is composed of the bodies of the ribs and the intercostal spaces. Much difference has prevailed amongst writers upon various points con- nected with the ribs, and the spaces be- tween the ribs. Probably this may have arisen from their having made their observa- tions upon the dead subject, wherein the ribs have collapsed to their minimum, or the thorax of a thin subject with the ribs expanded by, perhaps, 200 cubic inches of air, or the ribs when artificially articulated in the clean skele- ton, wherein they are generally arranged too wide apart and too horizontal. In the collapsed state of the ribs, i. e. after the most ample expiration by death, we no- tice 1st, That the intercostal spaces are not of a uniform width from the vertebra; to the ster- num. They are most narrow behind, and be- come wider as they approach the sternum (fig. 680.). The 1st, 2d, and 3rd spaces upon the whole are broader than the five next in- ferior, and the 10th and llth spaces are the widest (fig. 682.). 2dly, Their length differs with the length of the ribs ; thus the two first and two last spaces are the shortest. 3dly, The position of the intercostal spaces is very oblique (fig. 684.), roughly speaking, about mid-way between the horizontal and the perpendicular. 4thly, They are moveable, and in the dif- ferent stages of respiration they can assume different positions and different perpendicular widths. It has been found necessary for the con- venience of auscultation, to subdivide the thorax more minutely. The subdivision pro- posed by Laennec has been generally adopted, although some of the terms, like those of the respiratory sounds, have been modified by writers of later date. The anterior and lateral superior division, 1036 THORAX. TABLE C. — Thoracic Regions. REGION. Anterior : Clavicular (subclavian of Laennec) - Infra-clavian (anterior superior of Laennec) Mammary ------ Infra-mammary (sub-mammary of Laennec) SITUATION. Portion covered by the clavicle. Between the clavicle and 4th rib inclusive. Between the 4th and 8th ribs. From the 8th rib to the cartilaginous border of false ribs. superior, middle, inferior - - Over the respective parts of the sternum. Sternal Lateral: Axillary - Infra-axillary (lateral of Laennec) Inferior-lateral - Acromial - Posterior : Scapular, upper and lower Interscapular ------ Infra-scapular (inferior dorsal of Laennec) All the axilla to the 4th rib inclusive. Between the 4th and 8th ribs at the side. Below the 8th to the false ribs inclusive. Between the clavicle, neck of humerus, and along the upper margin of scapula, includ- ing the root of the neck. Supra-spinous fossa and infra-spin ous fossa. Between the inner margin of scapulas. Below inferior angle of scapula and border of serrati to the level of 12th vertebra. give the clearest sound upon percussion, and the back the least clear. Below Harrison's line, there is little or no evidence, from percussion, of the presence of lung, except in deep inspiration, and then the sound on per- cussion is mixed with other sounds from the abdominal organs. Only a small part of the mammary region covers lung, scarcely any being subjacent to the anterior parts of the Gth,B7th, and 8th ribs. (See fig. _4, wherein a transverse shading indicates the diaphragm. ) Internal conformation of the thorax. — To comprehend clearly the internal shape of the thorax, it is necessary to take a cast of this cavity. This may be done by making an open- ing in the sternal region, just large enough to admit the hand to remove the heart and lungs, filling up the whole of the cavity with plaster of Paris and returning the sternum, then opening the abdomen, cutting away the diaphragm, and so removing the cast, which wives us a clear knowledge of the internal conformation, and every kind of measurement correctly. (Fig. 667. is a cast from the cavity of figs. 680—685, — male subject.) We have stated that the perfect thorax viewed externally, and the same when the superficial muscles and upper extremities are removed, differ widely in their relative form. The tho- racic cavity likewise differs remarkably from either of these views. The general view is that of a cone, but broader from side to side than from before backwards : therefore the cone is somewhat flattened. (a) Anterior region. — This very closely re- sembles the anterior region of the external surface, being convex in its form, precisely corresponding with the concave sternum. The upper part, immediately behind the superior end of the sternum, is rather concave (fig. 667 ). At this part the cavity divides into two small cones, for the reception of the right and left apices of the lungs, which ascend upwards to a variable height, — an inch or an inch and a half. Both apices of the lungs are directed from below, upwards Fig. 667. Cast of the cavity of the thorax represented in figs. 1, 2, 3, 4, 5, and 6. and forwards; it is incorrect to consider them as directed backwards ( fig. 667. a, which is the left apex seen above the 1st rib.) In some cases, particularly where the lung presents a puckered appearance, the axis of the apex is inclined nearly to the horizontal, and at all times it is about per- pendicular to the sternum. These apices, throughout advancing life, are tending to in- cline forwards ; it is this portion above the 1st rib (fix- 667.), which is so vulnerable in phthisis pulmonalis. There is great difference in the precise character of these apices in different individuals ; in fact we have seen no two the same ; some are remarkably truncated, and broad from before backwards ; others are thin in this direction, and pointed ; some obtuse and low, others acute and high. They have the THORAX. 1037 same characters in both sexes. There is little difference in the height of the two apices. The elevation of the liver on the right side does not necessarily cause the right apex to be the higher. The right lung is more shallow than the left; but this is not because it is " pushed up," but because, in order to ac- commodate the liver, there is less lung- substance on the right side. If the mean of a series of observations represents the right side of the thoracic cavity as equal to 151, the left may be given as 182. The same may be said of both sexes. (b) Posterior region. — If we examine this region upon a cast of the thoracic cavity, we observe in the middle line a deep fossa, formed by the projection, to the very centre of the thoracic cavity, of the bodies of the dorsal vertebrae. This fossa is wider towards the base of the thorax, as may be seen by comparing the dif- ferent sections of the cast (compare the notches, 10, 11, and 12, with those of 3,4, and 5 \nfig. 668.). Fig. 668. ' Sections of a cast of the thorax showing the space encompassed by each pair of ribs respectively. The bodies of the thoracic vertebra, form almost a complete septum ; they are certainly a central column of support for the whole trunk of the body, bearing an equal distri- bution of the superincumbent weight in all directions. There is no part of the skeleton which more strikingly demonstrates that man was destined for the erect posture, than this central position, together with the increasing dimensions from above downwards, of the vertebral column. These conditions exist only in the human subject. The groove in the cast formed by the dorsal vertebra; is directed upwards and forwards, so that at the apex of the thoracic cavity it completely divides the lungs, producing two little cones laterally for the lungs, forming the right and left apex. At the base of the thorax this perpendicular column again completely divides the lower lobes of the two lungs. The shape of the posterior part of the cast is that of a curve directed upwards, and sharply forwards, near the apex (fig. 667.). This curve near the apex is, like the form of the apices, ,very various. An inflated lung assumes the same shape as this cast, giving even the marks of the ribs. The student, in order to have a correct idea of the lungs, should remove them from the body with the heart attached ; then inflate them to their utmost, when their shape, their lobes, and relative mass before and behind, are clearly seen. If now we inspect the cavity of the thorax itself, we find that the bodies of the vertebrae by their projection as above described, divide the posterior portion of the chest into two vast lateral grooves, which lodge the posterior portions of the lungs; these two grooves, partaking of the form of the thorax, are consequently conical in their configuration. They lodge fully one half of the entire lungs. This is worthy of remembering in reference to diagnosis, particularly when pneumonia is sus- pected; in such cases auscultation of the dorsal region demands as much attention as that of the anterior region. Though less vulnerable to phthisis pulmonalis, yet it may lodge disease in parts comparatively remote, 'and where in- flammation may insidiously gain serious ground upon the patient, particularly in children. (c) Lateral region. — This precisely corre- sponds with the external lateral view of the thorax (compare fg. 667. with Jig. 680.); it presents indentation of the ribs, resembling a diagonal, curved, grate. (d) The base of the thoracic cavity has been described above. Conformation as affected by age and sex. — Age alters the conformation of the chest. In the earlier periods of existence the thorax is the smallest of the three great cavities, probably from the inactivity of the lungs. In the foetal thorax the antero-posterior dia- meter exceeds the transverse diameter, the sternum projecting forwards, and the heart and thymus gland filling up the middle of the cavity. The ribs in foetal life are less curved, and conse- quently those deep grooves, seen in the interior of the chest on each side the spine, formed by the angle of the ribs, so conspicuous in after life, are almost wanting ; the vertical depth also is much less at this period, because the lungs are unexpanded and unemployed, while the abdominal viscera, particularly the 1038 THORAX. large liver, are in activity and pushing up the diaphragm. The superior opening or true apex is greater from before backwards than trans- versely, which is the very contrary to the adult conformation. The inferior or true base of the thorax is extremely wide in every direction, from the encroachment of the ab- dominal viscera. At birth the thorax sud- denly enlarges, by the air expanding the lungs to two or three times their previous cubic dimensions. As age increases, the curvatures of the ribs increase, and, with the vertebrae, running up through the very centre of the tho- rax, form the two great lateral grooves, peculiar to man, for lodging the chief bulk of the lungs. The depth of the thorax is diminished, while its breadth is increased, and this participates in that more perfect development of the system at the age of puberty. It is at this time that malformation of the chest fre- quently becomes obvious, particularly in females. In the adult age the thorax still grows, but in a degree less apparent, until it assumes the form of what is termed an open chest, capable of expanding in any di- rection, supplying us with air under violent exercise, and resisting severe blows. As age advances, through the decline of life, the thorax has a tendency to collapse ; the bony framework threatens to unite into one rigid cage, the true apex droops forward, the shoul- ders appear higher, and the round back of old age becomes apparent, so that we may make a tolerable guess at the age of an individual by the conformation of the back. The erect thorax is absolutely necessary to healthy vigour, while the drooping-forward chest is always accompanied with proportionate feeble- ness. Sex. — The chief difference of external conformation between the sexes is due to the largeness of the mammae, and the less width across the shoulders in women than in men. There is no distinguishing the sexes by the internal form of the thorax, they so perfectly resemble each other. The chest of the female is only absolutely smaller, but not al- ways that, certainly not relatively so. The nipples are not uniformly in the same posi- tion ; those of the female are generally closer together than those of the male. ^Conformation of the thorax affected ly disease and occupation. — The conformation of the thorax chiefly depends upon the healthy condition of the main pillar of support, the spine ; but not always so, for that deformity called " chicken breast" appears to be inde- pendent of the condition of the spine. And, again, emphysema of the lungs tends to pro- trude the ribs and advance the sternum. Disease, as caries of the vertebrae, or an atonic condition of the thoracic muscles, owing to which the spinal column may yield, either laterally, producing " lateral curvature," or an- teriorly, giving " angular curvature," produces the most marked distortion of this pillar of support, and consequently of the whole thorax. In youth, particularly in females, (from the pre- sent system of education,) the spinal column, which is at all times sufficiently flexible, bends under the weight of the head and arms ; and for want of proper exercise the muscles of the back become enfeebled, and unable to restore it to the erect position. When " rickets" attack the spine, it may curve in any direction, com- pressing the ribs and projecting the sternum. It is surprising to witness to what an extent of deformity the thorax may attain, and yet life still remain (see fig. 666., where costal respiration conld not exist ; and where all the abdominal viscera must have been forced up into the cavity of the thorax, for the 10th rib is nearly touching the crista of the ilium). We have noticed a case where such was the effort of nature to pre- serve the thoracic and spinal cavities, that life was maintained in a boy 14« years of age, though 7 bodies of dorsal vertebrae were com- pletely absorbed. In emphysema of the lungs, the sternum is protruded, and the antero-poyterior diameter of the thorax is increased sometimes by an inch, the shoulders are raised, and the person assumes always the form of a man who has made the deepest inspiration. In phthisis pulmonalis, the thorax changes its form, which is manifested by the shoulders inclining forwards, the anterior and superior parts bending in the same direction ; the otherwise round full apex becomes flattened, collapsing upon itself; and there is an in- capacity to extend the apex ; this is a sure and delicate test of that disease threatening, before any symptoms can be detected by au- scultation. In other stages there is a loss of symmetry in the sides. In pleuritic effusion or in empyema, one side may be full and immov- able, whilst the other has to perform the respiratory functions. In fact, disease of the respiratory organs may produced change in the form of the thorax, either downwards, upwards, or outwards, or by collapse of the apex. Frequently repeated or permanent compres- sion, may produce many varieties of conforma- tion of the thorax. Cruveilhier observes that infants, in whom the thorax was perfectly well formed at birth, have become deformed and flattened on the sides of the thorax, by pres- sure from the hands of the nurse. Slight ex- ternal pressure in early life may be productive of permanent deformity of the thorax, The effect of strong and permanent constriction, as from tight stays, occasions a distortion in the form of the chest. This kind of com- pression principally affects the lower part of the thorax ; so that the 5th, 6th, 7th, 8th, 9th, and 10th ribs are pressed forwards and in- wards, because the length of their cartilages allow them to yield readily : and the viscera corresponding to these ribs, also undergo alteration in their position and figure, en- croaching upon the thoracic cavity, com- pressing the lungs upwards, into the apices of the chest. The imprudent custom of females wearing a hard unyielding piece of wood, steel, or whalebone up the front of their corset, commonly produces a compression inwards of THORAX. 1039 the sternum. We once noticed a case where the sternum was forced inwards to such an ex- tent, that the entire depth of the thorax, by external measurement, from the middle of the sternum to the corresponding part of the back, only measured 2 inches instead of 8 or 9 inches ! Occupation likewise modifies the form of -the thorax. The clerk who writes many hours at the desk, carries himself dif- ferently to the soldier. Coal-miners have stooping chests when they work in districts where the coal seam is thin, and the roof consequently low, as in the north of Eng- land. In fact, all trades or occupations which require stooping for many hours to- gether, tend to injure and malfonn the chest. Pigeon- or chicken-breast. — This is a mal- formation quite distinct from any of the above mentioned, always affecting the sternal region in particular. An explanation of this curious disease has attracted the attention of Mr. Shaw, to whom we are indebted for the following remarks.* He noticed the effects produced upon the thorax by violent efforts of breathing in a child with croup. If we watch, says Mr. Shaw, the motions of the thorax in a young patient who is in danger of suffocation from an obstruction in the wind-pipe, we shall perceive that at each inspiration, while the superior ribs and sternum are raised and protruded as in com- mon costal breathing, the lower ribs are, at first, flattened, and then drawn inwards, so as to produce a deep indentation on both sides. The depression is greatest in the line of junction of the ribs with their cartilages ; it is as if a band had been tied tightly round the waist, or resembles the indentation near the margin of the chest, often seen in women from tight lacing. The constriction lasts during inspiration ; in expiration, the ribs by their elasticity flap out and recover their form. That the lower ribs should be drawn inwards in the act of inspiration, diminishing the area of the chest at a time when their natural motion should enlarge it, will be un- derstood b}' considering the relative conditions of the thorax and the lungs in the laboured respiration which arises from obstruction in the wind-pipe. Under the sense of impend- ing suffocation, the young patient instinctively struggles to enlarge the cavity of the chest to its greatest capacity ; but, while that effort is making, the quantity of air that passes into the lungs is very small, because of the obstruction in the larynx or trachea : a portion of air may reach the air-cells at the apex where the bronchial tubes are short, but little or none penetrates so far as the base of the lungs ; consequently the lungs are imperfectly dilated. If the child succeed in enlarging the area of the chest in proportion to its powerful efforts, \\hile the lungs were at the same time but partially dilated, it would follow that a vacuum would be produced in the space between the * Deformity of the Chest from Dyspnoea, Oct. 1841. Load. Med. Gaz. New Series, vol. i. 1842. parietes of the thorax and lungs. But owing to the great flexibility of the ribs near the lower margin of the thorax in childhood, the atmospheric pressure overcomes the action of the muscles, and thrusts in the sides so as to preserve the balance of the air within and that without : in common language, the walls of the chest on each side are " sucked " inwards, like the valve in a pair of bellows. When we look at the general shape of the chest during the continuation of the con- striction, we perceive at once a resemblance to the pigeon-breast deformity ; there is in both the same protrusion of the sternum, and the same depression of the cartilages on each side. The question therefore arises, can the de- formity have a similar origin to the change in the figure of the chest which is caused by difficult respiration ? Dupuytren wrote a memoir upon this form of distortion, and he has shown that difficult respiration and pigeon- breast deformity are frequently associated to- gether, so that he has almost constantly found that patients who are pigeon-breasted have at the same time enlargement of the tonsils ; but Dupuytren does not profess to explain why the two complaints should go together. Some years ago Mr. Shaw had under his care a little boy with greatly enlarged tonsils, which were very low down in the throat, owing, as it appeared, to their having got within the grasp of the constrictor muscles of the pharynx. He had constant dyspnoea, and occasional fits of suffocation, in one of which Mr. Shaw performed laryngotomy: on his admission into the hospital, and for several weeks afterwards, it was observed that he had the " pigeon-breast " form of chest ; but after his tonsils were excised, and his breathing had been perfectly free for some time, the sternum subsided to its proper level, and the thorax recovered its natural shape. These facts prove that a connection, like cause and effect, exists between obstruction of the air passages and pigeon-breast de- formity. It is not necessary that such impe- diments should be so great as to produce strongly marked symptoms of dyspnoea ; for, while the distortion is being produced the child is growing, — both the size and shape of the chest are undergoing a natural change. Mr. Shaw justly considers it quite possible that a cause which may have very slight in- fluence in changing the figure of the thorax, if operating only for a week or a month, will, if continued longer, disturb and modify the pro- cess of growth ; so that after intervals of half- years or years, a decided effect will be exhibited in the form of the chest. It is not impossible that continued disease in the air passages of children, which may fail to attract much at- tention, or at least may not be thought capa- ble of producing distortion, may nevertheless gradually and insidiously give rise to the per- manent deformity of "pigeon-breast." Mr. Shaw particularly refers to enlargement of the tonsils, attended even with slight incon- venience ; to enlargement of the lymphatic 1040 THORAX. glands in the course of the trachea or bronchi ; to pressure upon the trachea hy the thymus gland, when later than natural in being ab- sorbed, or when hypertrophied ; and to mor- bid thickening of the mucous membrane of the larynx, or of the trachea and bronchi succeeding croup or cynanche pharyngea. We concur with these views upon this sub- ject, the more so as we likewise have noticed the pigeon-breast in children where enlarged tonsils have been present. We must not imagine from this that, where there is dyspnoea, there we shall always find the deformity in question; for difficult breathing may be caused by other circumstances than those which dis- turb the counter-pressure of the atmosphere in the thorax. IV. Dimensions of the thorax. — The mea- surement of the thorax may be considered externally and internally; and, what is most remarkable, the one class of measurements may not have any relation to the other class. Moreover, the external measurements bear a certain proportion to the whole frame, whilst the internal do not. (a) External measurements of the thorax. — The external dimensions of the thorax differ much in different men ; this is obvious to all. There is the broad-chested and the nar- row-chested man. Mr. Brent has calculated, from an extensive number of observations, the following proportions, which we arrange thus : — TABLE D. — Relation of the External Chest to the Height, measured over the Nipples. Minimum chest : \ of the stature — JT of the stature = circumference of chest. Medium chest : -* of the stature -4- Jg- of the stature = circumference of chest. • Maximum chest : \ of the stature = circumference of chest. For example, let us suppose a height of 61 inches, as follows, — Minimum chest : height 61 in., \ = 30'5 in. — JT = 29'5 in. circumference of chest. Medium chest: height 61 in., 1 = 30'5 in. -f- ^ (= 4'07) = 34'57 in. circumference of chest. Maximum chest : height 61 in., f = 40'7 in. = circumference of chest. Thus, by taking the most perfectly propor- tioned chests, either from living figures or from the classical athlette of ancient sculptures, the following is the result. TABLE E. — External Thoracic Dimensions, (in three classes according to weight) in rela- tion to the height, obtained from calculation. MALES : CIRCUMFERENCE OF THORAX. Height. Minimum Weight. Medium Weight. Maximum Weight. Ft. In. Inches. Inches. Inches. 5 0 29J 3* 371 5 I 30^ 34| 37| 5 2 30£ 35^ 38f 5 3 si* 351 39 5 4 31£ 36J 39| 5 5 32^ 37 40^ 5 6 32| 37i 401 5 7 33^ 381 4H 5 8 33f S8f 421 5 9 3H 391 42f 5 10 34f 39f 43i 5 11 35^- 40^ 44 -6 0 35| 40$ 445. •±•^8 From this the minimum chests increase on an average nearly f (3'9), the medium chests rather more than f (4'2), and the maximum •f of an inch for every increasing inch of stature. We have found from observation, upon 1276 cases of all various classes conjoined, a re- gular arithmetical progression of the thoracic circumference over the nipples in relation to weight. By the total mean of our observations the chest increases exactly one inch for every 10 Ibs. increase of weight, sinking the effect of height, which, however, cannot well be omitted, because, as a general rule, the height increases with the weight. Mr. Brent has found that twice the breadth of the shoulders equals the circumference of the thorax over the nipples — i. e. from point to point, or the caliber of the broadest part of the shoulders. Thus, if the caliber be 18 inches, the thorax will be 36 inches in circumference. Four times the distance between the nipples is equal to the circum- ference. Four times the antero-posterior diameter is equal to the circumference : there- fore the distance between the nipples is equal to the depth from before backwards of the ex- ternal thorax. At the height of 5 feet 9 inches this antero-posterior diameter varies from 7£ inch, to 12^ inches. (b) Internal measurement of the thoracic cavity. — Before entering into details we may observe, that the thoracic cavity is much smaller than we might, perhaps, be led to expect ; that the depth from above down- wards is, when compared with the body, very shallow. It is, however, capable of enormous dilatation or mobility, even to 100 per cent ; 80 per cent is common. The absolute dimensions of the thoracic ca- vity of females are obviously smaller than those of males, because they are altogether of smaller conformation, both in stature and weight ; but, relatively, the difference is probably little, Although the proportion of some of the diameters may differ, yet that of the total cubic measurements appears not to do so. A certain rude relation of necessity must exist between the size of a man and the dimensions of his thoracic cavity. A man 7 feet high will have a larger chest than one 5 feet or 6 feet high. But there is no constant and uniform relation of the size of the chest, either to the height or weight of THORAX. 104.1 the body. The function of the chest, how- ever, as indicated by the quantity of air which we can expel, is in strict relation to the mi- nute difference of a single inch of stature, or to lOlbs. of weight. It appears probable that the function of an organ may be exactly re- lative to the size of the body, increasing or decreasing with it, while the organ itself bears no visible relation of volume either to its own activity or to the dimensions of the body. The greatest perpendicular depth of the thoracic cavity, nearly corresponds with the greatest lateral measurement ; or if the depth be 8-7 the breadth is 9*7, and allowing for the mobility of the base of the thorax, the depth may yet more closely correspond to the breadth. The average perpendicular depth of the female thorax exactly corresponds with the average breadth, being 8'] inches in both measure- ments. The greatest antero-posterior dia- meter in both sexes, i. e. from the sternum to the deepest part of the great lateral groove at the angle of the rib, is always less than the greatest lateral breadth, being as 6 to 9 in the male, and as 6 to 8 in the female. These diameters, however, in no way cor- respond to the stature. A man, 5 feet 4 inches high, measured from the apex of the chest to the base 10£ inches, whilst' a man of 5 feet 10 inches, only measured 7 finches in the same direction, or the shorter man exceeded the taller by 3 inches in the per- pendicular depth of his thoracic cavity: — but the taller man could exceed the shorter by a volume of 77 cubic inches of air at one deep expiration. In fact, the whole of the Fig. 669. FEMALE. MALE. Area in Height. Sup. in. ft. in. 36 5 4 50 5 10 Height, Area in ft. in. Sup. in. 5 6 36 5 10 63 FEMALE. MALE. Sections of the Chest at the base. TABLE F. — Average Measurements of the Thorax. (The mean of the measurements of fourteen males and six females, — given in detail in Med. Chirurg. Trans. 1846. Vol.29, p. 176.) MALES. FEMALES. Age - ...... 51 years 40 years Height --._.- 66 in. 62 in. Weight (without clothes) ..... HOlbs. 94 Ibs. Weight of heart ---.--- 13 oz. 11 oz. Weight of right lung - 30 „ 19 „ Weight of left lung ------- 25 „ 17 „ External circumference over nipples - 32 in. 30 in. Internal circumference (maximum) ... 32 „ 24 „ Internal circumference of right half ... 15 „ 13 „ Internal circumference of left half 15 „ 13 „ Greatest depth, from before backwards, of thorax - 6-5 „ 6 „ Distance between sternum and bodies of dorsal vertebra; - 4 „ 4 „ Projection of dorsal vertebrae into thoracic cavity - 2'5 „ 2-5 „ Greatest breadth of cavity of thorax .... 9 „ 8 ., Internal superficies of costal walls of thorax ... 258 sq. in. 212 sq. in. Superficies of diaphragm ------ 49 „ 35 „ Superficies of entire boundaries (diaphragm and costal — ) - 307 „ 247 „ Volume of right half of thorax - 151 cub. in. 109 cub. in. Volume of left half of thorax -,.-.. 182 „ 141 „ Volume of entire cavity ------ 333 „ 250 „ Depth of right lung from apex to arch of diaphragm 7 in. 7 in. Depth of left lung from apex to arch of diaphragm 9 „ 8 „ Depth from between apices to diaphragm 8 „ 7 „ Depth from before backwards — right lung (maximum) - c „ 5-5 „ Depth from before backwards — left lung (maximum) 6-5 „ 5-5 „ Distance between centre of apices of lung - - - 2-5 „ 2-3 „ Vital capacity - - .... 205 cub. in. 187 cub. in. In the males the left apex was highest in 6, the right in 6, and in 2 the summits of the apices were on the same level ; in the females, the left apex was highest in 2, and the right in 4. VOL. iv. 3 x 1042 THORAX. internal measurements (cubic or diameter) clearly bear no relation to the height or weight of the man, whilst vital capacity * does so in an exact ratio. If we take a cast of the thoracic cavity and view the base, it presents the shape of the figures in diagram 'fig. 669. which gives a mean measurement, in the males of forty-six, and in females of thirty-five, superficial inches. In the diagram (reduced by scale), we affix the height of each case, and the area in su- perficial inches of such section. But the base of the thorax presents another measurement, that of the absolute area of the diaphragm. By the Jigs. 2. and 3., art. DIA- PHRAGM, this muscle will be noticed as a large muscle of a vaulted form. C.Jig. 670. repre- ents a section of a thorax, the measurement of Fig. 670. 101 outside. 74 inside Dimensions of the diaphragm in three stages. C, ordinary stage. B, spread out A, completely extended. D, relative difference between expiration and inspiration. which is forty superficial inches; the figure B, next above, is the diaphragm of the same per- son spread out, which is extended to 1 10 square inches, being nearly three times the area of the former figure ; even in this con- dition the centre is quite free, and not upon the stretch, though the circumference is so. The full measurement is nearly obtained, by slitting up the sides, as shown in figure A. and this condition gives it an increase of twenty-two superficial inches, making alto- gether 133 square inches ; but even in this con- dition the entire arched muscle is not perfectly spread out. This was the diaphragm of a man five feet six inches high, with an exceedingly * By "vital capacity "is meant the measure of the mobility of the chest, as more fully explained hereafter. (P. 1056.) small chest, only twenty-nine inches in ex- ternal circumference, and whose vital capacity was 188 cubic inches. The section, therefore, of the thorax to the area of the diaphragm is as 40 to 133, or 1 to 3'3. This renders the base of the thorax highly mobile. There is, perhaps invariably, a difference in the dimensions of the two sides of the thorax, in favour of the left side. The least difference which we observed was one cubic inch, but we think there must have been some error in this observation. Passing this over, we may say that the difference between the two sides varies from 10 to 77 cubic inches, and that, in all cases examined by us, the left side was larger than the right. Tin's difference, also, we have found not to bear any relation to sex or stature. One female of 5 feet 4 inches iu height had a difference of 77 cubic inches, which exceeds by 10 inches any of the males which we examined, up to 5 feet 10 -inches high. OF THE RESPIRATORY MUSCLES. — There are certain muscles especially destined to expand and contract the thoracic cavity, and there are others which act in different degrees as ac- cessories, they may be classed as direct and indirect respiratory muscles. The direct respiratory muscles are, inter- costales externi and interni, levatores costarum, infra costales, triangularis sterni, and the dia- phragm. The indirect respiratory muscles are all those which straighten the spine or aid in fixing the whole body for the thoracic mus- cles to act from as a fixed point, whilst by their other attachment they elevate or depress the ribs ; these are particularly the muscles of the neck and upper extremities, and those composing the walls of the abdo- men. More indirectly still, the muscles of the limbs assist in respiration; — in difficult respiration, the patient seizes hold of any fixed object, whilst he employs his whole muscular force to assist in inspiration, or, as Boerhaave has expressed it, " scarcely any particle remains in the body which is not more or less concerned in the business of respiration."* The indirect respiratory mus- cles, in fact, comprise nearly all the muscles of the body; therefore we shall only no- tice the direct respiratory muscles. The di- aphragm has already been described (art. DIAPHRAGM), 1. The intercostal muscles are arranged as two thin laminae between the ribs ; one lamella is external to the other, hence they are named external and internal. The fibres of each layer are oblique in their direction in reference to the ribs, and each layer has its fibres disposed in a contrary direction to those of the other ; thus they are said to decussate. The twelve ribs form eleven intercostal spaces, conse- quently there are eleven such decussating lamellae on each side of the thorax, and twenty- two in all. Their attachments are to the in- ferior border of one rib, and to the superior * Prelect, ad Instit. G01. Morgagni. By Alex- ander, vol. i. p. 357. THORAX. 104-3 border of the next below. They do not ac- company each other throughout the entire intercostal space. These muscles, therefore, differ from each other in two ways, in the direction of their fibres, and in the extent of their attachment, for neither set are prolonged throughout the entire length of an intercostal space. (a) Intcrcostales cxterni. — These have their fibres running obliquely downwards and for- wards ; they are continued throughout the whole osseous intercostal space, i. e. from the tubercles of the ribs, to where the cartilages commence ; here they terminate. Haller once noticed these fibres " continued without interruption to the sternum, filling up the in- tercartilaginous spaces."* A thin aponeurosis is prolonged from the free anterior margin of this layer, up to the sternum, Tin's muscular layer is thicker than the internal layer. Fig. 671. represents the anterior extremity of this Fig. 671. 072. External intercostals. — Anterior view. layer, where it terminates with the osseous part of the rib, and^zg. 672. the posterior view, commencing at the vertebrae. (b) Intercostales interni. — These, as their name implies, are internal to the above layer. Their fibres are likewise oblique, and have a contrary direction, downwards and backwards crossing the former layer. They commence at the sternum, fill up the intercartilaginous spaces, and part of the interosseous spaces, and terminate at the angles of the ribs. Fig. 671. represents them commencing at the sternum, and disappearing behind the ex- ternal layer. Figs. 673. and 674. show them for the remainder of their course ; in fig. 673. they will be seen to terminate short of the verte- bral column. A thin aponeurosis is pro- longed from their free margin backwards, to the end of the intercostal spaces. All the intercostal fibres are oblique in their direction, with reference to the spine and ster- num. The fibres of one intercostal space differ * El. Phvs. lorn. iii. p. 29. External intercostals. — Posterior view. in their degree of obliquity relatively to those of other intercostal spaces Thus, broadly, it may is. 673. Internal intercostals. — Posterior view.' be stated that the external intercostal fibres in- crease in the degree of their obliquity as they Fig. 674. Internal intercostals. — Anterior view. proceed from the first to the last intercostal bpace i and that the internal intercostal fibres, 3x2 1044 THORAX. on the contrary, decrease in the degree of their obliquity as they proceed in the same direc- tion. Moreover, for the most part the ex- ternal fibres increase in their obliquity in the same intercostal space as you proceed from the vertebrae towards the sternum, and the internal intercostal fibres, on the contrary, increase their obliquity from the sternum towards the vertebra?, therefore they seldom decussate at right angles to each other, or form a perfect cross like the letter X. This is their general relative position at death, but, during life, in every stage of respiration, their degree of obliquity varies. The obliquity of the intercostal fibres should be viewed more with reference to the spine than to the ribs, because we shall show that their action is relative to the spine, and not to the ribs and that they may be perpendicular to two ribs, while they are oblique to the spine, because the ribs are themselves oblique. We have never seen any of the external intercostal fibres perpendicular to a rib, but we may see that arrangement in the internal layer of the lower intercostal spaces (fig. 673.). The omission of the relative posi- tion of the spine with reference to the ob- liquity of these muscles has led to many false conclusions as to their action in respiration. Let E E (Jig. 675.) represent a spine or a rigid Fig. 675. dicular to the two bars ; now move the bars up to p 3, also at an angle of 45° with E E, and the fibre L K becomes more oblique than at the position p 2. Therefore a tension may change from the oblique to the perpen- dicular relatively to the ribs ; but it can never so change its relation to the spine. Thus L" K." and i/ K' between the bars at P 3 cross each other, in the same direc~ tion, but in different degrees of obliquity; when the bars are at p 4., they decussate in directions contrary with reference to the bars, but not with reference to the body E E. The position of the ribs is similar to the bars at p 4, therefore the decussation of the inter- costal muscles must be viewed with reference to the spine. The intercostal fibres never cross each other like the lines L'K' and I/'K" (fig- 675.), nor can they, by any change of movement, ever assume thatposition ; i. e. if they do not decussate in a direction con- trary with relation to the spine, in no change of position, throughout the range of a semi- circle, can they ever become directly decus- sating fibres but when they directly cross each other as v D and V'B (fig. 676.) relative to E E, in every other position to which the bars \ body, and A c, B D two levers representing ribs, allowing of free rotation at their centres of motion A and B. These two bars are per- pendicular, or at 90°, with reference to the body E E ; let L K represent a connecting tension or elastic fibre of any kind, this is oblique with reference to the two bars A c and B D, but move these bars down to the position of P 4, at an angle of 45° to the body E E, and the fibre L K becomes perpen- can be moved, they will be seen still to main- tain the same decussation. Action of the intercostal muscles. — There is, probably, no subject in the whole range of science which has excited more violent con- tention and acrimonious dispute, than that of the action of the intercostal muscles. The illustrious and learned Haller could not enter this field of inquiry without pausing to ob- serve : " Let it be allowed me to deplore, THORAX. 1045 among the miseries of human life, that such anger and bitter quarrels should be forced upon us on account of matters wherein we are so little personally concerned."* Yet, strange to say, Haller opposed with extreme violence his contemporary Hamber- ger, whose investigations on this subject, though still extant, fell, consequently, into oblivion. We know not who discovered the two sets of intercostals. There appears to be no ac- count of them prior to Galen, A. D. 131. He observes, " the intercostal muscles help the midriff, that they might draw the chest in- ward."f Albinus (A.D. 1770) considered that both the internal and external layers " raise the ribs." f H. Cooke, a learned compiler of 1651, believed, they " constrained and dilated the chest," — " that the external layers bear down the ribs, and that the internal separate the ribs, so enlarging the thoracic cavity." § Strange to say, after this Cooke divests these muscles of all thoracic motion whatever. In 1685 it was the received opinion that the external layer dilated, and that the inter- nal layer contracted the thorax. j| John Al- phonso Borelli led the way to a different opinion, which prevailed amongst most phy- siological writers. He believed, from mathe- matical reasoning, that " the fibres crossing each other produced only one effect, viz., the drawing of the ribs together," — acting in the diagonal of the decussation. It is curious that he never considered the proba- bility of the two forces acting separately, as other antagonising muscles can do. ^[ W. Cheselden believed that both these muscles dilated the thorax, acting as elevators of the ribs, when the 1st rib was fixed by the scaleni and serratus posticus posterior.** Cooke follows the views of Cheselden and Borelli.-f-f Benjamin Hoadly takes another view ; and, in so doing, illustrates the subject with diagrams, and comes to the conclusion that the external layers elevate, and that the internal depress the ribs ; and that their com- bined action is to arrest the respiratory move- ment at will. He also says, " neither range can by their action push the ribs asunder." JJ Winslow agrees with Borelli : presupposing, as usual, that the first rib is fixed. §§ Still the subject continued to be warmly dis- puted, when Haller published a controversial paper in 174-6. In his " Elements" he treats the * El. Phys. vol. iii. p. 36. t De Usu Resp., ch. 15., 5 lib., De Usu Partiiun. J Tr., fol, ed. 1777. Tab. xvii. 9, 10, et seq. § Cooke's Descrip. Anat, fol., 1651., p. 257. || Samuel Collins's System of Anat., fol., 1685, vol. ii. p. 825. ^[ De Motu Animalium, pars secunda. Lugcluni Batavorum, 1710, p. 106., Prop. 84., Tab. xviii. Fig. 2. * Anatomy of the Humane Body, 3rd ed. 8vo., Lond. 1726, p. 117. tf Cook's Anat. and Mechanical Essays, Lond. 1730, vol. i. p. 282. et seq. JJ Gulstonian Lect. on Eesp. 4to., Lond. 1740, p. 6. §§ Anatomical Exposition, 4to,. Loud. 1749, vol. i. p. 318. subject at length, siding with those whom he thinks are right, and confirming the same by many direct experiments.* Haller's view is, that the external layers elevate the ribs, be- cause their superior attachment is nearer the vertebra? than their inferior one. Franciscus Boissier de Sauvages agrees with him ; and the same is held by the majority, yet some doubt it. His opinion touching the internal layer is, that they likewise act as associates and ele- vators of the ribs with the external layer, be- cause " their superior attachment is nearer the sternum, and further from that bone in the lower ones ;" likewise, that " that por- tion of the internal layer placed between the bony parts of the ribs, cannot have a diffe- rent action from that portion placed between the cartilages." Joh. Swammerdam, Francis Bayle, J. Wilhelmus Pauli, Christianus Vater, Francis Nicholls, J. Fredericus Schreiber, differ from this, believing that the internal layers draw down the ribs. Now follows a sharp antagonist to Haller, viz. Hamberger, whose disputes with Haller we gather from Haller's writings, and not from Hamberger's writings. Hamberger breaks out with an entirely new view, which excites Haller to controversy.! Hamberger, says Haller J, believes that the external intercostal muscles have one action, — that they would raise the sternum: " that the internal layer would depress it." Ham- berger makes a machine " to demonstrate, that when the ribs are raised by these muscles their intervals are dilated ; when depressed, on the contrary, they are diminished." He furthermore gives, as his own discovery, that " the internal intercostals conjoining the os- seous portions of the ribs, and that portion which is between the cartilages, will raise them, and are therefore associated in action with the external layer." Hamberger was the first to assign a double action to the same class of muscles : he likewise believed that the whole ribs were lifted simultaneously^ Haller disputes the validity of Hamberger's experiments, upon the ground of his not con- sidering the relative mobility of the first and second rib ; because, says Haller, if the de- pressing power of the intercostal muscles is to the first rib as 20, the elevating power on the second rib, by reason of the difference of length and mobility, is as 380, nearly nine- teen times greater ; and the lower rib is to each superior rib, as far as the seventh, more moveable, in the ratio of 109 to 79. || We cannot see, with Haller, how the ten- * Vide Elementa Physiol. Corporis Humani, torn, iii., p. 28., et seq. Lausan. 4 to., 1766. f Hamberger was born 1697, and died in 1755. Haller's first anatomical paper upon respiration appeared in 1746, and his Elementa Physiol. Cor- poris Humani, in 1757-66, J El. Phys. ib. p. 37. § Hamberger's writings on this subject were an essay De Respirationis Mechanismo, Jena?, 1727, and also Physiologia Medica, Jenae, 1751. — ED. || Loc. cit. p. 39. et seq. 3x3 1016 THORAX. dency of action of a muscle can be affected by the degree of mobility of a joint ; for it is not necessary to the direction of the action of a muscle that a bone should move. Haller also denies that the two crossing fibres lengthen and shorten inversely to each other ; or that the intercostal spaces widen by their action. Haller performed many experiments ; he ap- plied strings to the ribs of a wet preparation, representing the muscles, and pulled the strings, and the intercostal spaces diminished. By vivisections he determined, that in inspir- ation the internal intercostals, " simultane- ously with the external layer, contract, swell, and wrinkle, become perpendicular and hard, with united lifting of the ribs in rotation, the turning of the lower border forwards, the protrusion of the sternum, the descent of the diaphragm," &c. On the other hand, he observed in " expiration, relaxation of the whole series of intercostal muscles, increased lensth and obliquity, increased distance be- tween the spaces, relaxation of the diaphragm, repression of the sternum, the descent of the ribs, narrowing of the chest," &c.* It is curious to see that he makes the cubic space of the thorax diminish with the inter- costal spaces widening. Nor do we wonder at his observing, in his vivisections, a contrac- tion of both sets of these muscles, for he not only skinned his animals, but " cut down and destroyed the external layers of intercostals, to lay bare the internal layer.' "Besides lap- plied (says Haller) pain and fear, being more efficient than mere pain itself," by puncturing the diaphragm to cause dyspncea ! Under such circumstances — an animal tied down, divested of all superficial muscles, with a pierced chest, • — in '" pain and fear," — and writhing under the scalpel, — producing tetanic convulsions, and then a death-like relaxation from syncope, — surely in such a condition the action of the respiratory muscles, so sensitive to the least mental emotion, could not well be determined. Although Haller appears positive, yet he concludes his controversy with a brilliant question, — a vivid picture of his master mind, — " Why has nature made two, rather than one set of intercostal muscles, if, indeed, the function of each is the same?"-]- Haller' s views have, however, prevailed to this day, and are still taught in our schools. _ Some authors have assigned but little to these muscles, counting them as mere associate muscles; others, that they are "wholly and solely " to form the thoracic parietes ; others that they are rather movers of the spine. Dr. John Barclay, a standing authority, observes, that the supposition of the two sets being antagonists in their actionr " is now ob- solete," and must " have been formed by the very witchcraft of imagination, in defiance of all observation and experiment." J Lastly, Dr. Sibson has made a commu- * El. Phys. ib. p. 43. t Ib. p. 44. j Barclay " On Muscular Motion," 8vo. Ed. 1808, pp. 533, 534. nication upon this subject. He observes, that " the scaleni invariably act during the whole time of inspiration ;" and that the function of the intercostal muscles is complicated ; thus, " the external intercostals, between the thoracic set of ribs, are throughout inspiratory ; those portions between their cartilages are expiratory, between the diaphragmatic set of ribs they are inspiratory behind, expiratory to the side and in front, and between their cartilages they are inspiratory ; between the intermediate set of ribs they are for the most part slightly in- spiratory between the ribs, and expiratory in front between the cartilages." " The internal intercostals of the thoracic ribs are expiratory behind and inspiralory in front, if the ribs approach there, and are in- spiratory between the costal cartilages. Be- tween the diaphragmatic and intermediate set of ribs, and between the cartilages, they are thought expiratory"* From this view" of Dr. Sibson's, we venture to gather, that different fibres of the same layer of intercostal muscle have diametrically opposite actions. We do not understand upon what ground it can be demonstrated that one muscle having a given action between two ribs, shall, between the same ribs, and observing the same obliquity and same attachments, present a directly con- trary action ; the conditions are the same, and therefore the action must be the same. These views, however, of Dr. Sibson, in the paper in question, are not borne out by the narra- tion of any experimental facts. Insufflation on the dead body is not the movement of inspiration in the living subject. It is better to assign to these muscles the terms of ele- vators or depressors of the ribs, instead of inspiratory and expiratory muscles. All these observers, as far as we have seen, pre-suppose that the 1st rib is fixed by the scaleni (this is the view now taught) ; and that according to the fixing of the 1st rib, all the intercostal muscles are either elevators or depressors of the ribs. It is curious to contemplate that, out of elements so few, two ribs and two muscles, opinions so contrary should be held with regard to the action of these muscles. They have nevertheless an action as definite as any other muscle in the body. We may here observe, that, although the chest is conical, the ribs segments of circles, and the spine mobile, yet treating them as planes and lines will not lead to error. Two parallel bars, rotating on a centre, will increase and decrease the perpendicular distance be- tween them ; so they will, if curved like the ribs. This we have determined by experiment. Although the rib has two movements, ele- vation and rotation, yet these are associates, and do not obstruct each other. We shall employ the same diagrams as used by Dr. Barclay, when describing the same muscles. The intercostal muscles act as a force be- tween two moveable ribs or levers ; therefore let us consider — TF-. Phil., Pt. 4, 1846, pp. 543, 544. \ THORAX. 1047 1st. The movement of such levers, when rotating. 2nd. The effect of forces, oblique, perpen- dicular, and decussating, upon such levers. 1st. The movement of the levers. — Let fig. 677. A represent a series of parallel bars, Fig. 677. Fig. 678. Diagram representing the position of the ribs affected by the position of the spine. simultaneously, the first four would approxi- mate, whilst all the rest would recede from each other. Therefore the positions of the different parts representing the spine in fig. 679. command and regulate these changes. allowing of free rotation upon a rigid per- pendicular body A a ; let the free extremities of these bars be kept apart, so that the bars may at all times be parallel to each other. In this condition a certain distance exists between the bars, and a certain distance be- tween their free extremities and the perpen- dicular body A a. Let B represent the same bars moved into another position, resembling that of the ribs ; in this position, the two conditions seen at A are altered. The perpendicular distances between the bars are diminished, and the distance between the free extremities of the bars and the body B b is likewise diminished. If the direction of this motion were still continued, the bars would ultimately touch each other, and their free extremities would be still nearer to the body B b. But let the bars be elevated, as in c c, and the same condition obtains as in the bars at B b, viz., they approximate each other, and the free ends come nearer to the body, c c. In this case the bars only have moved ; but the same effect can be obtained without moving the bars. Let A B (fig. 678.) be two bars at their maximum distance, while horizontal ; at a b, and a' b' ', they have nearly attained their minimum perpendicular distances, though still hori- zontal, because the rigid bodies c c arid c' c' have been moved respectively. Now, if we join these hree last figures into one, as in fig. 679., an then move the bars simulta- neously, some bars will approximate each other, whilst others will recede. The superior four are at their maximum perpendicular dis- tance from each other ; while the 4th, 5th, and 6th are at a medium perpendicular dis- tance, and the 6th, 7th, and 8th bars at their minimum distance. The distances of these bars are regulated by the position of the rigid body representing the spine. If all of them were moved upwards Fig. 679. Diagram as in fig. 678. with the three portions conjoined f From this we learn, that the bars cannot rotate without changing their distances, and that when they are at 90° with reference to the body A a (fig. 677.), they are at their maximum distance from each other, and as they pass this position on either side, this dis- tance diminishes. In the human body the spine may represent the body to which the bars are attached (fig. 677.). The movement of the ribs will obey the same law in receding or approaching each other, and whether they increase or diminish their intercostal spaces, will depend upon the relation they bear to the spine. Fig. 682. is a cast, from a dissection of the thorax of a male subject, weight 1071bs., height 5ft. 4in. This correctly represents the natural position of the ribs, when the thorax is in a state of complete expiration, or with only the residual air in the lungs. The position of the 3x4 1048 THORAX. ribs is very oblique"; the spine is curved ; therefore the relation of the ribs to the spine is different according to the curve, as are the bars to the body representing the spine (fig. 679.). It will be seen that the inferior six or seven ribs are at a more oblique angle to the spine than the superior ribs. The spine does not curve sufficiently to bring the upper ribs to an angle of 90° with the spine; there- fore, if all the ribs were raised simultane- ously, they would all increase the breadth of their intercostal spaces, whilst their sternal end would recede from the vertebrae, and thus, by their elevation, the thoracic cavity would be enlarged, until they attained the angle of 90° to the spine. But if the elevation were carried beyond this point, the intercostal spaces would diminish, and thus the thoracic cavity would decrease. Fig. 684. is a pos- terior view showing the sloping position of the ribs more clearly. Now, if the spine were perfectly erect, the ribs would have a greater range, and consequently the upper ribs could be elevated higher, and thus still more increase the thoracic cavity. A man Fig. 680. Tlwrax as at death. can expire a greater volume of air when perfectly erect, than in any other position. On the other hand, if we curve the spine, we limit the divergence of the ribs, because then we bring the ribs more into the po- sition of a b and a' b' (fig. 678.). Thus, in diseases of the spine, when angular cur- vature is extensive, the ribs are materially limited in their capability of increasing the perpendicular depth of their intercostal spaces, and consequently the perpendicular depth of the thorax. Fig. 666. is an instance of angular spine, reducing the ribs to their minimum distances without their moving. We have found by ex- periment, that the greatest volume of air which persons with angular spine can expire, is little more than equal to the volume of air of an ordinary respiration ; i. e. from 20 to 40 cubic inches, instead of 180 to 200 cubic inches. The following experiment proves that the ribs are all elevated when the chest is inflated, and that the spine is straightened. Into the thorax (fig- 680. et seq.) we insufflated, or forced into the lungs 310 cubic inches of air, and a second cast was taken. The changed position of the ribs and spine is represented in figs. 681. 683. and 685. where it will be seen that all the ribs are raised ; their perpendicu- lar distances or intercostal spaces are all increased, and the spine is more erect. This experiment, therefore, demonstrates two things : 1st, that by artificially inflating the chest, the intercostal spaces are widened, and 2dly, that the spine becomes more erect. It is an experiment most unfavour- able for showing these two points, because the altered shape of the thorax by insufflation is not to be compared with the exceedingly enlarged condition produced by vital inspira- tion ; in which case the spine becomes more erect, and the intercostal spaces consequently wider. By placing the fingers in the inter- costal spaces of a living subject during deep inspiration and expiration, it may easily be perceived that in the former they widen, Fig. 681. Thorax artificially inflated with air. . and in the latter they collapse. From 3000 observations we have found that, in deep in- spiration, the body becomes more erect, and less so in expiration. Insufflation is not the same, in effect, as inspiration. In the former we force air into the chest, until the parts most yielding, as the diaphragm and abdominal parietes, are rendered so tense that their tension is suffi- cient to overcome the elastic force of the ribs, their cartilages, and the lungs ; then, and not until then, do we move the costal part of the thorax. On the other hand, in the living and deep inspiration, we lift the ribs and sternum, the most unyielding portions, first. These solely produce the threatened vacuum which inflates the lungs, whilst very little, if any, is accomplished by the diaphragm. The following table shows the measure- ments of the thorax, when expanded by in- spiration and insufflation. THORAX. 1049 Fig. 682. Thorax as at death. Fig. 68-t. Thorax as at death. Fit} 683. Thorax artificially inflated with air. Fig. 685. Thorax artificially inflated with air. TABLE G. — Table of the Dimensions of the Thorax and Abdomen, in the Dead and Living Sub- ject, with the same Quantity of Air distending them. Thorax. Abdomen. Conditions at the time of observation. Circum over nipples. Diam. lateral. Diam. ant. .post. Circum. Diam. lateral. Diam. ant.-post. in. in. in. in. in. in. DEAD — Natural collapse 29J 10 8 29 1 8* 7| Insufflated si* 104- 8| SH 10 9| ALIVE — Expiration 32 1U 9f 25 10* 7| Inspiration 37 JH Hf 25} 11 8J Difference — By insufflation, dead H 1 3 5 H If H By inspiration, alive 5 1 O.I -% * * f 1050 THORAX. These facts show that we should be guarded in determining the living respiratory move- ments by experiments upon the dead subject. It should be constantly borne in mind, that to increase or diminish an intercostal space is to elevate or depress the ribs, and that to elevate or depress the ribs is to increase or diminish their intercostal spaces : the one cannot be accomplished without the other. Some au- thors have spoken of these as distinct ; thus, that in inspiration the superior ribs ap- proximate each other, whilst they are raised, or that their rising or falling does not neces- sarily involve an increase or diminishing of the intercostal spaces ; but these two changes are simultaneous and cannot be done sepa- rately. 2nd. TJie effect of tensions, oblique, perpen- dicular, and decussating, between the moveable levers or ribs. — We employ a strip of vul- canised Indian- rubber for a force representing muscular contraction. A strip of this sub- stance, of uniform thickness, \ of an inch broad and 10 inches long, increased its length, with an increasing weight, as follows : — Fig. 686. Weight in ounces. 2 4 8 16 32 64 the pan holding the weight = 850gr. = do. do. do. do. do. do. = 1725 = 2600 = 4350 = 7850 = 14850 = 28850 Increased length of Indian rubber, gr. inches. a 1287^ I H 4 Although not exactly in accordance with the law of perfect elasticity, yet it is roughly so and enough for our purpose, viz. the tension is greatest when most stretched, and weakest when least stretched, corresponding with muscular contraction. Let E E (Jig. 686.) be fixed, A B and c i>two moveable bars as before, t an oblique tension ; if t shortens, it has been supposed that the two bars would assume the position of A B' and c D ; but not so : they both rise like A B" and c D" until the two bars touch each other.* If we prevent this touching of the two bars by a rigid link, like that on parallel rulers, placed as at s fig. 687., then the tension will still raise the bars to o o'. In this experiment three circumstances may be noticed. 1st, that the bars have been elevated ; 2dly, that the perpendicular distance between them has been diminished ; and 3dly, that the tension t has been shortened in attaining the position o o'. Place the tension in a contrary direc- tion, as between the bars A' B' and c' D', and the bars are brought into a contrary position, — drawn downwards to o' o'". This can be * This appears to have been known to Hamberger ; but the author of this article was not aware of it until four years after he first introduced this move- ment to notice. (See Med. Chirurg. Trans, vol. 29, p. 213.) It is certain that Hamberger's views were not taught in any physiological school in this coun- try, Germany, or France, nor noticed in any of our philosophical works. A Effect of oblique tension on separate bars. demonstrated by a model, using a spring or Indian-rubber as the tension, and may be Fig. 687. explained as follows. Let A B, fig. 688., repre- sent one bar, c D the perpendicular fixed body ; B is the free extremity of the bar ; K an axis from which a parallel bar has been re- moved. Let e, i, and o be other fixed points ; connect e to B by an elastic tension, and the bar B will be moved towards e. Let the ten- sion be fixed at i or o, still the bar B will be raised towards the respective points. Let the tension be fixed at K (the centre of mo- tion of the bar which we suppose is removed), and still the bar A B will be raised upwards towards K, and assume the position of A B, K L (fig. 689.) at M. But it is not necessary to this that the elastic force should extend from THORAX. 1051 Fig. 688. K to L in order to produce this motion : half of it might be wood, bone, or iron, provided the other half retained its elastic power. The effect would be the same, and the bar A B at N would be elevated by the tension between T L, Fig. 689. connecting the fixed point K with L by the rigid body K T. It is the omission of the fulcrum K, in calculating such oblique forces, which has hitherto obscured the explanation of the intercostal muscles. This may be illustrated in another way (fig. 690.). Let AB and c D represent bars as before upon A c ; t' the tension ; let c D and A c be fixed ; withdraw the pin at A, and the bar A B is drawn fonvards into the position B', and the tension t becomes perpendicular to the two bars. On the other hand, reverse the experiment, as in Jig. 691.; supposing c D and the perpendicular body c A fixed, withdraw the pin at A, and the bar A B is drawn backwards to B'. This presupposes the bars kept apart, Fig. 690. B' otherwise the free bar would approximate the fixed bare D. Therefore, one fulcrum is pushed upon by one bar, and pulled upon by the other. If the bars were kept fixed, and the body re- presenting the spine was left free, the tension would draw this last mentioned body into the Fis. 691. t B; position of c c and cf c' fig. 678. Therefore, the element of the two fulcra is the chief agent for directing their upward or downward move- ment, under an oblique tension. If we arrange two bars with one fulcrum {fig. 692.), and allow Fig. 692. a £ the tension to act as before, then the effect is only to draw the two bars together, as o b and o' d(fig. 693.). If we have an arrange- ment to substitute two fulcra at a a' fig. 692. and withdraw the centre fulcrum, then the two bars rise as before. Fig. 693. Now we shall suppose the bars at an angle of 90° to the body representing the spine. A perpendicular tension (L o,fig. 69-t.) ad- mits, of course, of no variation ; oblique ten- sions admit of two variations : 1052 THORAX. a, obliquity in contrary directions. b, degrees of obliquity in each direction. Fig. 694. AG- BG- The perpendicular tension (L o, fig. 694.) produces but one effect, that of approxi- mating the two bars A c and B D, because the force of L o is acting upon A L and B o, levers of the same length, their movements being the same they would meet in the middle dis- tance at s. But if the bars are kept parallel by a rigid link like s,fig. 687. the perpendicular ten- sion would produce no apparent effect upon the two bars. They might be rotated in any direc- tion, and the tension would remain of the same length ; for example, in Jig. 695. let t 2 be the perpendicular tension between the bars A B c D, move the bars to s or s', and the ten- Jig. 695. sion is the same length, k k k, &c., may represent different places in the rotation, at each of which the tension t or k is the same length, although the bars at s, t 2, and s' are at different perpendicular distances from each other. A rigid connective, as wood or wire, may be substituted for the tension, an- this will equally allow of the bars being rod tated, and consequently changing their per- pendicular distances to each other. Hence it will be seen, that each of the lines k k k, are of the same length, although the two se- micircular lines describing the revolution of the bars are constantly changing in their re- lative distance to each othe We then seer, the possibility of having a rigid body connect- ing two bars, which shall nevertheless recede and approximate each other. From this we may gather, that though the sternum is rigid, and the cartilages, perhaps, ossified, the ribs may nevertheless maintain the capability of altering the breadth of their intercostal spaces. Perpendicular tension, therefore, like L o, (parallel to A B,) cannot rotate the bars, be- cause they never change their length. All tensions are oblique which have one of their attachments nearer to the spine than the other, therefore, in fig. 694., L K and L T are oblique tensions. An oblique tension, hence, is acting on bars at dissimilar distances from their fulcra ; thus in fig. 696., Fig. 696. x.M. Diagram showing that perpendicular fibres neve} alter their length. E tension t' is oblique to the line a A, and the points on the lines a B, AD, to which the tension t' is attached, is represented by the lines a m and A »r. And the law of action of such tension is, that it tends to move both bars or ribs towards that fulcrum which is near- est to one of its attachments. Therefore ten- sion L K (fig. 694.) would rotate the bars towards B, and tension L T towards A. The force of a given oblique tension between such bars is modified by two circumstances, — by the degree of obliquity, and by the obliquity of the bars in reference to the body which re- presents the spine. Of the degree of obliquity of a tension. — Let fig. 697. A B, c D, represent bars as before, the different connecting lines tensions of different degrees of obliquity, but of the same power of tension. L K is perpendicular, and has no rotating power. L K' possesses a certain amount of power, L K2 more power, and L A the maximum power, or the power of rotating THORAX. 1053 Fig. 697. Angle of tension. Tensi At 90° 2-5 „ 75° 2'5 „ 46° 2'5 „ 15° 2'5 7° 2-5 the bars increases with the increasing obliquity of these tensions. By experiment we found that equal tensions at the following angles, pro- duced the following difference of power in rotating the bars : — TABLE H. — Power gained by a given Tension, as an intercostal Muscle, in relation to its Obliquity. Resistance. 0 1-50 2-25 4-25 5-50 The power descreases as the tension ap- proaches the perpendicular L K', and increases as it approaches L A ; this is the maximum point : if the tension be attached to the body E E, either above A or below it, the system is changed into that of a single lever. From this we gather, that the power of an intercostal muscle, as an elevator and depressor of the ribs, increases with its obliquity ; and that this movement entirely depends upon its obliquity. This is the only instance in the body where the power of a muscle increases with its obliquity. Of the obliquity of the ribs or bars with re- ference to the spine. — A given tension, say at the angle of 45°, will, when the lever is at 90° to the spine act more powerfully than when the lever is at an angle similar to that of the ribs. We found by experiment, that the bars in the following positions required an increased power to sustain them. The tension being uniform, and the resistance to be overcome acting from the same point. This gain of power is dependent upon the obliquity of the bars and change in the direc- tion of the tension, for in each of these posi- tions the tension was maintained the same. But if the tension be not kept uniform, still the resistance is increased as the bars rise ; thus, if the bars are at the angle of 50° (fig. 699. »i") somewhat similar to the position of the ribs, and these under a certain tension allowed to resist a power of 4, when they are moved upwards to 90°, through which revolution the tension has kept diminishing (because it has kept shortening), it will resist a power of 5. In this we see a beautiful compensation to the muscular contraction, viz. that while an in- tercostal muscle is losing power as it con- tracts, this loss is made up by the change in position of the ribs. We feel conscious that we can exert a retaining power at the ter- mination of a deep inspiration as great, if not greater, than at any other intermediate posi- tion of the ribs, at all of which the muscular power actually exerted is greater. All these remarks apply equally if the spine be curved ; for change of obliquity of the ribs, or change of curvature of the spine to the ribs, is the same thing. TABLE I. — Change of Power, from the Obli- quity of Bars or Ribs to the Spine. Angles of the Bars with the Body representing the Spine. Tension. Resistance. 30° 2'5 4 60° 2-5 12 90° 2-5 22 120° 2-5 33 Of oblique tensions in contrary directions. — We have shown that an oblique tension between parallel levers moves them in a cer- tain course. Now it is evident that tension in a contrary direction (all other things remain- ing the same) must likewise move such levers in a contrary direction. This is so clear that although Haller asserted absolutely that cross- ing muscles have the same action, yet he was not comfortable under such an opinion, " for,' ' says he, " why do they cross?" We have shown that a tension in the di- rection of L T fig. 694., will raise the bars, and one in the direction of L K will depress them ; they are, therefore, antagonistic forces, and when the tensions are similar, they pro- duce an equilibrium of contrary force. If the bars A B, c D, (fig. 676.) be rotated, the lines will have directions contrary to each other, and will lengthen and shorten inversely to each other. Thus of the crossing tensions (fig. 676.) v D and v' B, v' B becomes short- ened to n b', and v D, on the contrary, becomes lengthened to n b' ; and on the other side of 90°, v D is shortened to * d, and v' B lengthened to s' b. Therefore muscles circum- stanced like the intercostals and crossing each other, or observing contrary directions to each other, cannot be associates in action, for when one contracts, the other must relax, as the ribs move. We represent this more clearly in fig. 698. where A B and c D represent bars as before, rotating upon E, E, and t t' two ten- sions in contrary directions. As the bars are raised towards m, t' lengthens, and if depressed towards in' it shortens, while t lengthens to- wards n, and shortens towards n'. We re- present the tensions t t, &c., and t' t', &c., by the white lines, in the different positions they would assume if the two bars were rotated to those places in the half cir- cle. It will likewise be observed, that while either tension gradually lengthens or shortens, the two bars pass through their maximum perpendicular distance from each other at B D, on either side of which they attain their minimum distance. Therefore, if we examine tension t at n', the bars would there be closer to each other than they are at B D ; nevertheless, this tension in ascending must contract while the bars are increasing their perpendicular distances as they move to B D ; beyond which the tension still 1054. THORAX. shortens, while the bars now decrease their perpendicular distance. Therefore it is per- fectly compatible for an intercostal fibre to separate the two ribs, between which it is at- tached, by its contracting ; and, if above a certain point (90° to the spine), to approxi- mate the same ribs by its further contraction. Fig. 698. In deep inspiration it will be found that the ribs increase the breadth of their intercostal spaces (as was mentioned years ago by Ham- berger) ; and that by the contraction of an intercostal fibre. The bars (fig. 698.) in ro- tating, twice attain a minimum, and once a maximum, distance from each other; while the oblique tension in that revolution once attains its maximum, and once its minimum length. Of tensions at different parts of the bars or ribs. — Parallel tensions of equal power pro- duce the same effect, whether near the ful- crum or more distant from it ; an intercostal fibre near the vertebrae, has the same power as a fibre near the anterior extremity of the ribs. Let Fig. 696. represent ribs as before, with two parallel tensions at different distances from the bod}', E E, then t'+A-M — t' +am=t'+x'(A.w — am)=t'+A o t + A N — t-\-a ?z=t+(A N — a n) = t + A O. Therefore the tension L T (fig. 69i.) acts with the same power as tensions p p', which is much nearer to the fulcra A B. Knowing now the effect of a single oblique tension, it is easy to consider an indefinite number of tensions, for they follow the same law of action. lnfig.699. the tensions x acting on A c, /j/i Fig. 699. the bars to m', and, by the same reason, ten- tions observing a contrary direction and acting upon A' c' lift the bars to m'". Therefore tensions, although observing contrary direc- tions, may be made to conspire to the same action, and may therefore be associates when acting upon different fulcra. We have shown that tensions in contrary directions, but acting upon the same fulcra, are antagonists. If we join the levers ( fig. 699.) and increase their number, we may represent the thorax as in fig. 700., kk representing the spine, b b the sternum, the bars a a the ribs, and the bars a' of the costal cartilages united to the bars representing ribs by a movable joint ; let r represent the external intercostals, these, we know, will act as elevators, while those at h, representing the internal intercostals, are asso- ciates in action, although they observe a con- trary direction, because they act upon the fulcra in b b ; in fact, they are elevators of the levers representing the cartilages. What now is the combined action of a series of two such tensions ? The whole body of levers will be raised, and the part b b re- presenting the sternum will have two motions : it will be raised and moved forwards into the position of b' b'. This is precisely the mo- tion of the sternum in deep inspiration. In a model of this kind, certain means must be used to limit the motion, or the movement is continued until the tensions are at rest. Or, if the bars representing the ribs a a (fig. 700.) be fixed, then the tensions representing the internal intercostals h would depress the short bars representing the car- tilages, because b b is free, and k k is fixed. And were either set of tensions continued over the joints representing the union of the cartilages with the ribs, such fibres would THORAX. 1055 antagonise each other. In nature the external intercostals are not continued over to the in- tercartilaginous spaces. Fig. 700. In this model all the ribs are elevated with- out the first bar being drawn up by any ten- sion representing the scalenii muscles. In fact the fulcra are the fixed points ; therefore there are here six fixed points for the tensions to act upon, and hence each row of oblique tensions acts quite independently. This application of force and disposition of the bars representing the ribs is after the manner of that great engine of power the "genou lever." (Vide Potter's Mechanics.) Tensions in the first space (fig. 700.) act with a greater power in pushing out the body b than do the tensions in the 5th space ; but, on the other hand, the motion is less in the 1st than in the 5th space. It will also be seen that these six bars, though moving all equally, will produce an unequal effect upon the body b b, forcing out the lower end more than the upper end. The ribs of man, in the same manner, increase in their length from the 1st to the 8th, and, therefore, by an equal mobility, an unequal protrusion of the sternum is produced, advancing the lower end more than the upper end. We have reason to believe that the mobility of all the ribs is the same, and that it is by their different lengths that the different degrees of protrusion of the anterior part of the thorax may be accounted for. Having investigated the effect of artificial tensions acting on bars made to represent the ribs, we can now return to the consider- ation of the action of the direct respiratory muscles. Action of the intercostal muscles (resumed). — The intercostales cxterni are all elevators of the ribs. Inspiratory muscles. They separate the ribs in the act, and they can do this indepen- dently of any other muscle fixing the first rib. The intercostales interni have a double action. All those portions between the ribs depress the ribs and are expiratory muscles; they also approximate the ribs and in every way an- tagonise the external intercostal muscles. Those portions between the costal cartilages are elevators of the cartilages, and associates with the external intercos.dls, and, thence, in- spiratory muscles. These muscles also can act independently of any other muscle fixing the first or last rib. The intercostal muscles being antagonists, they yield to each other, the same as any other flexor yields to an extensor muscle. We possess a perfect and definite command over the ribs, and can stop their respiratory movements at any stage of breathing, more readily than we can those of the diaphragm. It is necessary to healthy breathing that we should raise all the ribs ; they are there- fore all mobile, and all their intercostal spaces are increased in their perpendicular distance during inspiration, and diminished during ex- piration. II. Levatores costarum (Levatores breviores costarum, Alb.). — These are narrow, tendinous, and fleshy fasciculi (fig. 672.) covering the pos- terior end of the rib, and extending obliquely downwards and forwards, in the same di- rection as the external intercostals. Their superior attachment is to the extremities of the transverse processes of the dorsal ver- tebrae ; their inferior to the margins of the ribs between their angles and tubercles. These fibres spread out and become flat at their insertion. Each rib receives one from the vertebra next above; there are therefore twelve muscles on each side ; and that for the first rib is derived from the last cervical vertebra. The inferior muscles of this series divide into two parts ; one of which is distri- buted as above stated ; but the other, consist- ing of longer fibres, passes over one rib and te-r minates on the second below ; and thus each of the lower ribs receives muscular fibres from the transverse processes of two vertebrae. The long bands have been described as separate muscles under the name levatores longiores costarum (Albinus). Action. — The same as the external inter- costals. Elevators of the ribs and inspi- ratory muscles. Acting directly upon their fulcra, the transverse processes of the ver- tebrae. III. Triangularis sterni (Sterno-costalis, Ver- heyen). — A thin flat plane of muscular and tendinous fibres (fig. 674.) placed within the thorax, immediately behind the costal carti- lages. This muscle is attached to the inner surface of the ensiform cartilage, lower part of the sternum, and the cartilages of the lower true ribs. From these origins its fibres pass laterally along the inner walls of the thorax, diverging upwards, horizontally, and down- wards, and are attached by dictations (which give to the outer margin a serrated appear- ance) into the cartilages, lower border, and inner surface, of each of the true ribs, from the 5th to the 2nd inclusive. Action. — This muscle varies considerably in the extent and points of its attachment in different bodies, and even in the opposite sides of the same body. Hence, it aids in drawing down and drawing up (according to the di- 1056 THORAX. rection of its fibres) the ribs. It may be said to be both inspiratory and expiratory. IV. Infra- costales (Verheyen). — In connec- tion with the inner surface of the ribs (fig. 673.) several small bundles of fleshy and tendinous fibres, which are thus named, will be found ex- tending over two, and in some instances over three, intercostal spaces. They have the same direction with the internal intercostals, and are (properly) often described as parts of those muscles. The fasciculi vary in size and number, and may be found on any of the intercostal spaces, except, perhaps, the first ; but they are most constant on the lower ribs. Action. — The same as the costal portion of the internal intercostals, depressors of the ribs and expiratory muscles. OF THE ELASTICITY OF THE RIBS. Elasticity depends upon reaction, and restores in a contrary direction the force which have been impressed ; the effect produced is com- mensurate with the amount of the cause, and the reaction can never take place so long as the cause continues to be applied ; but immedi- ately that cause ceases, the elasticity comes into action. Inspiration is performed by the true inspi- ratory muscles, and expiration, by the expira- tory muscles, and the elasticity of the ribs and their cartilages, together with the elasticity of the lungs. We find a broad difference manifested between the inspiratory and ex- piratory power (TABLE R.), the latter exceed- ing former by about one third. This differ- ence is due to the elasticity of the ribs and lungs associating their power with the ex- piratory muscles. The combined elastic power is very great ; we have examined it in two fa- vourable cases, an hour after death, when the bodies had not fallen one degree in temperature. X. H., a young man, slightly built, erect and well formed, set. 22, weight 9ist., height 5ft. lOin., vital capacity 235 cubic inches. The absolute capacity of his chest was 248 cubic inches ; internal area 256in.; circumfe- rence of the chest, over the nipples, in the or- dinary state, alive 33 inches, dead 30^ inches. After death we forced air into his lungs, whilst the temperature of the body was still at 97°. The force resisting the introduction of this air must havebeen due to the elasticity of the ribs and their cartilages, together with that of the lungs. By an arrangement, we could force in different quantities of air, and measure the collapsing power of the elastic parts, through the medium of the confined air pressing upon a column of mercury : the following was the result : — TABLE K. — Costal clastic Collapse. X H. Inch of cub. in. mercury. Air forced in 70 Resisting elasticity 1'20 Ditto 90 ditto 1'25 Ditto 160 ditto 2'50 We could not force in more air, for with this pressure it was impossible to prevent the air escaping with great rapidity through the ne- cessary wounds. This experiment was re- peated three times with the same result. It will be remembered that X. H. had drawn into his lungs, when alive, 75 cubic inches of air more than we could force in, after death. If, therefore, 160 cubic inches pro- duced a collapsing elastic force equal to 2'5 we may suppose that 235 cubic inches would produce an elastic force equal to not less than 3'9 in. of mercury. This chest, mea- suring 256 superficial square inches, it fol- lows that X. H., in breathing out 235 cubic inches of air, with no more sensible effort than that of a mere sigh, had to overcome with his inspiratory muscles a gross elas- tic resistance of about 499lbs., and with a force equal to this weight would the thoracic walls recoil for expiration upon the air in his lungs. N. C., height 5ft. 8in., weight lOst. lOlb., set. 21: vital capacity, 200 cubic inches; ab- solute capacity, 24-5 cubic inches; superficial measurement of the entire thoracic cavity, 256 square inches ; circumference of the chest, alive, 33 inches, dead, 34£. Temperature of the body, when examined, 97° F. Tempera- ture of the air forced into the lungs, 63° F. This man was what is termed " thick set," firm, erect, and well built, a porter by trade, a very different case from the former. The fol- lowing was the elastic power of his ribs : — TABLE L Costal Collapse in N. C. Inch of cub. in. mercury. Air forced in 70 Resisting elasticity TOO Ditto 90 ditto 1-50 Ditto 180 ditto 3'25 Ditto 200 ditto 4'50 The first ninety inches of air introduced ruptured the lungs ; therefore the elasticity of the lungs did not interfere with our experi- ments. In both cases this resistance must be referred only to the ribs, their cartilages and ligamentous attachments ; also, in both cases, the bodies were kept erect, or in the sitting posture ; this should be attended to, for the mere weight of the body upon the ribs when recumbent would increase their collapsing power. These tables express a dead power al- ways in reserve, equally powerful whether we are in robust health, or emaciated by age or disease. Dead or alive, this is ready to be put into force ; and, in fact, it is never at rest, never at zero, until death ; we may even go farther, and say, not until de- composition has weakened the collapsing ten- sion of these parts. Cut through a costal cartilage, or take out a small portion of the sternum, say corresponding to the 3rd, 4th, and 5th intercostal spaces, and the opening by the elasticity of parts will retract, and we never can restore them again to their original fit, because the thoracic parietes are still not at rest. The bony cage-work of the chest is THORAX. 1057 so tightly knitted together, that at its mini- mum contraction there still remains an elastic force in operation. In fact we might expect this, because the respiratory movements are so small that it is necessary that an extensive elastic power should be ready at all the re- spiratory stages ; and therefore the parts are upon the stretch before we begin to inspire in order to increase to the geometrical degree re- quired, of two, three, or four pounds to the inch, by a very limited movement, which would not be the case did we begin to in- spire when the thoracic boundaries were at zero, at least, if it did, the walls, &c., would have to be much stronger. Supposing inspiration to be the result of muscular force equally distributed over the whole thorax, the inspiratory power is easily calculated. Taking the walls of the chest at 206 superficial inches, and the area of the diaphragm as 5 1 superficial inches, and placing them separately, it would appear as follows: — TABLE M. — Inspiratory Muscular Power re- quired to overcome Costal Elasticity, mea- sured by the Insufflation of 200 Cubic Inches of Air. (Case, N. C.) "• of water. liesidual vol. lieserve vol. ( + 90 cubic inches) Breathing vol. ( + 20 ditto) Vital capacity (+25 ditto +150 ditto - 7-2 8'2 Cfe. o BM O i .2 •3 !s § 4d ,C es +5 % a 3 .J o « +1 •C «j be tuu '£ c H u 3 >. o 1-8 -g 0 .c's; D C C M 0 C. a £ u-g •S.J >'S >u £ * PQ 01 ft. in. St. Ibs in. Ibs. in. in. in. H. 5 10 11 10 30i — 240 30 7 C. 5 8 10 10 341 16| 200 60 1-5 M. 5 9 11 0 36 36 238 45 12-5 - 17-0 M. M., female; sudden death; temperature of body 97-5° Fahr. ; aet. 28 ; height 5 ft. 9 in. ; circumference of chest over nipples 37 in. ; below 32* ; lungs healthy. TABLE P.— Elasticity of Lungs (fern., aet. 28.). Elastic col- lapsing power, Volumes of air. in. of water, liesidual vol. - .0'7 Reserve vol. (+ 100 cubic inches) 5-5 Breathing vol. (+100 ditto) - lO'O Vital capacity (+ 90 ditto) 20'0 At the commencement of "ordinary breath- ing" the collapsing power of the lungs in our experiment was 7'2 in., or nearly £ of a Ib. per superficial square inch. This is a very notable power, not less in the gross, oftentimes, than 100 Ibs. of dead uncounter- balanced resistance to the respiratory mus- cles. In the female, with nearly an arith- metical increase of 100 cubic inches per vo- lume, the collapsing power increases 5 to 10 and 20. The insufflated volume in the male being less regular, the collapsing power ma- nifested is also less regular. But, taking the mean resistance of the reserve and breathing volumes in the male combined (160 cub. in.), the power of collapse was 7'7 inches. In the female, the mean of nearly the same quantity of air in the lungs (within 10 cubic inches) allowing for little or no residual volume at the starting point when we inflated, is likewise 7-7 inches. We believe that the elastic power of the lungs in the two sexes is the same; — indeed why should it not be so? because the office of the elastic tissue is to drive out of the lungs volumes of air no longer required ; and it is probable that the resistance given by the air, against the sides of the air tubes, in both sexes, is the same; and unless the number and calibre of the air tubes are different, the resistance, by friction, to the elastic collapse of the lungs, from the trans- mission of similar volumes of air in the two sexes, must be the same. In three experiments we found the elastic collapse of the lungs cease at different degrees ; i. e. different volumes of residual air were displaced when the elastic force had come to its minimum. * For definition of these terms see p. 10G5. There is no order in the numbers 30, 60, and 45, relative to the other measurements. We do not know what quantity of air remained after these volumes were displaced. When we ex- hausted the remainder of the residual volume, which is not affected by the elastic collapse of the lungs, the sides of the air tubes themselves collapsed by the atmospheric pressure. They likewise are elastic, but in a contrary direc- tion; an expanding elasticity keeping them open. We found that the expanding elasticity acted so as to draw or suck inwards the air with the different powers represented by 7, 1'5 and 12'5 inches of water in the haemadynamo- meter, when we attempted to withdraw out of the lungs more air than the lungs themselves naturalfy displace by their collapsing elasticity. Therefore these figures may represent the ex- panding elasticity of the air tubes. In these cases there is no apparent order ; but we learn the fact that such elasticity exists. In the case C there was a tubercular condition of lung, in the milliary form, in one apex ; in H there was extensive pleuritic adhesions ; but in the case of M the lungs were remarkably healthy. It is interesting to notice that there are here two elasticities in contrary direc- tions,— an elastic collapse which has its limit at a certain point, and an elastic expansion of the air tubes, which likewise have their limit of expansion at the same point, protecting the calibre of the air tubes from any further collapse. In the case of M the expansion of the air tubes was equal to 12'5 inches of water ; by calculation it appears that the col/apse of the elastic tissue upon the vital capacity volume would be about 14 inches. These antago- nistic forces are quite independent of the will, or any nervous stimuli : one is for maintain- ing an expiratory current of air, and the other for preserving an open channel in the lungs for inspiration. The lungs are very delicate organs, and can resist but little artificial force ; for, if once inflated to the ordinary state of either the breathing volume or vital capacity volume, they do not appear able to collapse again to their original size ; — probably intra-lobular emphysema is produced. In our experiments we forced air into the lungs; they were expanded because we inflated them We now think it would be better to 3 v 2 10GO THORAX. inflate them by expanding them (removing the external atmospheric pressure), and allow the air to drop into the air vesicles by its own gravitation (as in living respiration), when they would in all probability collapse freely to their original position. When they are in- flated by expansion (the natural way of life) the delicate cells of the lungs can safely resist a force of from 3 to 9 inches of mercury, or from 40 to 121 inches of water (see next column) ; but when expanded by inflation, their collapsing power was damaged so that it could sustain only 17 or 20 inches of water. This is worthy of notice in resuscitating the apparently asphyxiated person, at which times we have long been of opinion that bellows and pumps are highly dangerous instruments to use for maintaining artificial respiration. Of the muscular contractility of the lungs. — In the trachea transverse muscular fibres extend across posteriorly, connecting the tips of the incomplete rings of cartilage. In the smaller bronchi they encircle the whole tubes, and there appears to be little doubt but that these circular fibres are to be found in every part of the air tubes as far as the terminal air vesicles. Physiologists have disputed whether these fibres are muscular or not ; if muscular, they are important agents in respiration, acting as a series of little expiratory muscles. Dr. C. J. B. Williams lately read a paper at the meeting of Glasgow (September 1840), upon the subject.* He experimented upon the lungs of some of the lower animals, — several dogs, a rabbit, a bullock, a horse, &c., — as soon as possible after death, submitting their lungs to galvanic stimuli, and securing a haemadynamometer with a stop-cork to the trachea. He found that, upon applying this stimulus, the fluid in the bent tube rose from 1 to 2 inches, and it immediately fell on break- ing contact. This effect could only be pro- duced by muscular contraction. Kolliker, a very accurate observer, confirms these views.-}- He found in man, in the larger and finer bronchial tubes, a coat formed of annular fibres, in one or more layers according to the size of the tube, consisting of unstriped muscular fibres ; and over this coat a thin layer of fibro-cellular tissue with nucleus-fibres. He found no mus- cular fibres directed longitudinally. He ob- serves, " In former observations I thought I had convinced myself of the existence of unstriped muscular fibres in the air-cells; but in my resumed examination of the lungs of man and mammalia, I can with certainty see nothing distinctly characteristic as such mus- cular tissue." Our knowledge of these cir- cular muscular fibres was first chiefly derived from the researches of Reisseissen. Laennec considered spasmodic asthma to be assignable * The Pathology and Diagnosis of Diseases of the Chest, 8vo. by Dr. C. J. B. Williams, 1840, Lon- don, p. 320. \ Beitrage zur Kenntniss der glatten Muskeln in the Zeitsehrift fur Wissenschaftliche Zoologie, H. i. S. 40. 8vo, 1848. to a spasm of these circular fibres. We are as yet ignorant of the possible extent of contrac- tion of these fibres. The discharge of air is paramount, and that from the most remote vesi- cle ; and we know that by no mechanial means can we obtain this, and therefore a molecular power is necessary, which we readily imagine can be obtained by these tissues acting so as to give a peristaltic motion, and thus dis- placing from every individual vesicle the de- licate stream of air necessary to be dis- charged. We do not need these tissues for inspiration, because the atmosphere, by its mere weight, can penetrate into the most remote air-cell, overcoming all the friction against the sides of the air-tubes. The in- spiratory volumes of air are but for one pur- pose, to aerate the blood ; but the expiratory volumes are for the voice and other purposes sometimes requiring great force to aid in cer- tain expulsive efforts. OF RESPIRATORY MUSCULAR POWER. — Young falls into an error in supposing " that in muscles of the same kind the strength must be as the number of fibres, or as the extent of the surface which would be formed by cutting the muscle across ; and it is not improbable that the contractile force of the muscles of a healthy man is equivalent to about 500 Ibs. for every square inch of the section."* When we examine men we find no such calculations are to be relied upon. It is very common to find two men of cor- responding dimensions produce very different effects upon any dynamic instrument. The respiratory power may or may not cor- respond with the general development of mus- cular force. We have submitted 1.500 men of various classes to an experiment upon the inspiratory and expiratory power. The resistance to this power was a column of mercury, — thehcsmacfy- namometer, or bent tube, first used by Dr. Hales. He observes, " A man, by a peculiar action of his mouth and tongue, may suck mercury 22 inches, and some men 27 or 28 inches, high ; yet I have found by experience that, by the bare inspiring action of the dia- phragm and dilating thorax, I could scarcely raise the mercury 2 inches." f Hales appa- rently never tested the expiratory power. We connected the column of mercury witli the index on a dial plate, which represented the inches and tenths of inches of mercury lifted. A tube was adapted to fit the nostrils through which the inspiratory or expiratory effort was made. By the former the index was moved in one direction, and by the latter in the con- trary direction ; each half of the dial plate representing, respectively, inspiratory and ex- piratory power, with expressive words at- tached, as follow : — (See top of next page.) It will be observed that the figures on each side of the same word differ in their value, those of the expiratory side ranging about one- third higher than those on the inspiratory side. * See Nat. Phil. Lond. 8vo, 1845, p. 99. t Stat., vol. i. p. 267. THORAX. 1061 Power of Inspiratory Muscles. 1'5 in. 2-0,, 3-5,, 4-5,, 5-5,, 6-0, TABLE R. Weak - Ordinary Strong Very strong Remarkable Very remarkable Extraordinary - Power of Expiratory Muscles. - 2-0 in. - 2-5 „ - 3-5,, - 4-5,, - 5-8,, - 8-5 " 7'0 „ Very extraordinary - lO'O „ Indeed when these powers are the same, it indicates disease. We subjoin the following table of the result of these cases. (Table S.) To illustrate one of the points so striking in these experiments (viz., the difference be- tween the inspiratory and expiratory power), we refer to diagram 701., which represents by curves their relative position. The upper line is the expiratory power, and the double line below, the inspiratory power. The per- pendicular lines are the different heights of the cases examined. The position of these curved lines indicates the power they re- present, — the higher the curve the greater the power. The two rows of figures at the bottom are the inches and tenths of inches of mercury elevated. (I. for inspiration, and E. for expiration.) According to this, at the height of 5 feet 7 inches, and 5 feet 8 inches, the inspiratory power is greatest, and thence the inspiratory power gradually decreases as the stature increases. The men of 5 feet 7 inches and 8 inches elevate a column of 3 inches of mercury : this may be considered a healthy power ; and the men of 6 feet high elevate about 2^ inches of mercury as their healthy power. Fig. 701. ft. in. ft. in. ft. in. ft. in. ft. in. ft in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. In. 505152535465565768595 10 5 11 606 + Expiratory. Inspiratory. E. 3-28 3-?fi I. 2-55 2-0 3-23 3-15 4-32 2-52 2-31 2-70 4'33 2-84 3-«7 2-70 4-13 3-07 4-13 4'28 2-96 2-91 3-94 3'63 4-48 2-83 2-77 2-65 4-41 2-67 Inspiratory and expiratory power in healthy cases. It may be asked, why connect this with the height ? Because it was found in six collateral observations that this was the only physical condition which presented a relation so as to throw the experiments into an or- derly position.* By TABLE S we see that the respiratory power varies in different classes. The "gentlemen," for instance, are below most of the other classes : at the height of 5 feet 8 inches, they elevate by inspiration 2'35 inches of mercury. This may account for the fact why Dr. Hales could only raise 2 inches of mercury by this effort. The expiratory power is normally more irregular — more apt to vary — than the inspi- ratory power. The expiratory muscles par- ticipate in other duties besides that of mere expiration ; the vocation of the glass-blower, the trumpeter, the wrestler, the jeweller (blow-pipe), and the sailor, especially call these muscles into use, increasing their na- tural power. They thus oftentimes become excessively strong. The inspiratory muscles are exclusively for supplying us with air, in which act they have only to oppose the uniform resistance of elasticity. The inspira- tory power is therefore the best indication of the "health"— the "vis vita." As an instance of the effect of vocation chang- * For the other observations, see p. 1068, and Med. Chir. Trans. 1846. Vol. 39. p. 14.3 et seq. ing one of the respiratory powers and not the other, we may notice the Metropolitan po- lice anil the Thames police. The inspiratory power of these two classes is nearly equal, whilst the expiratory power of the Thames police exceeds that of the Metropolitan police, — the former using their upper extre- mities, whilst the latter use their lower ex- tremities most : — the former chase the thief by the use of the oar ; the latter by the swiftness of their legs. Compositors and pressmen stand low the former are the lowest in their respiratory power ; the pressmen are much higher. The order in which some of these classes come is as follows : — the most powerful are the Thames police ; next, the sailors ; the pau- pers and the gentlemen are nearly equal ; and lastly, diseased cases. The two last lines is the mean of the four healthiest classes, — the seamen, firemen, Thames police, and pugilists : their maximum is 3 inches ; the mean of the whole classes together is little more than 2£ inches. The measure of this power when expressed by inches of mercury appears small, yet, when hydrostatically con- sidered, it is very great. Men have wondered that they could not elevate more mercury in the tube; but all surprise vanishes when it is recollected, that, by the law of hydrostatics, when a column of 3 inches height of mer- 3 Y 3 1062 THORAX. to o o •S9SB3 --co «••?««£..•: : " * o CO a •dxa O O Is* O £^ T O tO (NO oooi— — . GO to o to ; • ; o Ji l- T* CM CO TPCO^ib^ • ^ £, •dsui 1^ to q C-l 0 o 2 •saseg ,0 CM £ — CM CM C* « ^ „ _ ~ ic •n1 or •dxa — oo en o r~ c* ~* oor-ci 5 CM ci 00 ^ 4r i> co co co -^ co «r fe »« ^ CM T-. •dsni tO tD CO — C> CM O ,t-» tD iO ,-.--_ CM CO CM CM ^- CO CM CM A- ^-i *!* 0 CO in CM in o o in •S3SC3 £J ~ « fOX^ ^ ^ 0 01 : O O j-^ Ol ^* J ^D to 00 CO s t^ o o m •S3SC3 co o co 10 tc oo CN ro ^^ CN co *o ?o r» — i CM •— « — 8 c •dxa rrlco S c5to CTioOCO SSa^ ^° OCi Cl 00 c CO •4*1 COCTi W TP.— « COOOO tOO»C 1-^ COt C*1 Cfl CQ C3 M CJ Cl O1 C*l O C*J 1 s in 2 00 in !_-,.„__ _, K s •dx3 CiO tDOd*rto CO-H« at o cc CM cr. CO •dsui — o So-o^ SSco coQoS CM co? Oi ? COCO CM COCM CMCOCM ^HC^Ai (N «O) 00 0 •S8s«3 I '-•^-«CO'-l n —i « •dsui §^- f^» t-— r-~ , o o u7 ire o f^* o *n ^ o cico ;c^oo Tj* o — . o r>-co o CO tc (NCO« OJ(NINO>OC> to o in •S39BO 3 a>to««~ OJ^GO^C,- en CM o •dxa f llllf iill!l OO CO 00 CO -dsui ™* CO O O tO O CO *O ^J" l«3« in ^"1 O ao *o*rr-»ooco dtoooocMCjJ .it-» 0 CM m m 0 m •S3SE3 oo cnco-co o^co'^— i- s £ •dxg CN OO^— CM COO—^'OO*— CO CO 1C CO •dsui 'JO 4 s * OP: B-i Q K M (ii (j £ Sc.53 O J-) ® " "™* M 4. a; "(3 J2 i I ^CO g iii X w THORAX. 10G3 cury is sustained, the force exerted by the diaphragm alone is equal to the weight of as much mercury as it would take to cover a space of the same area as the diaphragm, three inches deep. The column of mercury raised, therefore, will not safely serve to compare the respiratory power of men of different dimensions, for the area of the thorax must also be considered. For instance, we examined a man, 4 feet 74 inches high (circum- ference of the chest 29 inches), who raised 3' 15 inches; and another man, 7 feet high (chest 50 inches in circumference), who could only elevate 3 inches of mercury : but the dissimilarity between the area of the dia- phragm in the dwarf and giant was such, that the latter in reality lifted about 500 Ibs., and the former only about 39 Ibs. Suppose the base of his chest to be 57 superficial square inches ; had this man raised 3 inches of mercury by his inspiratory muscles, his diaphragm alone must have opposed a resist- ance equal to more than 23 oz. on every inch of that muscle, and a total weight of more than 83 Ibs. Moreover, the sides of the chest, by attenuating the air within, resist an atmospheric pressure equal to the weight of a covering of mercury 3 inches in thick- ness, or more than 23 oz. upon every inch surface, which, if we take at 318 square inches, the chest would be found to resist a pressure of 713 Ibs. ; and, allowing the elastic resistance of the ribs as l.f inch of mercury, this will bring the weight resisted by the inspiratory muscles of the thorax as follows : — Diaphragm - Walls of the chest Costal resistance (elastic) Lung - 1146 Ibs. Or, in round numbers, we may say, that the inspiratory muscles of such a man of ordinary dimensions resisted 1000 Ibs. This is a re- sistance not counterbalanced ; for were it counterbalanced, it would only be mere dis- placement. We have made a safe addition for the elasticity of the lungs. We think it may be confidently stated that nine-tenths of the thoracic surface conspire to this act, allowing the remainder to lie dormant. Although the difference between the in- spiratory and expiratory powers, when tested to their utmost, is so great, }et it must not be thought that these two powers aie in their ordinary action so dissimilar; and indeed, when all things are considered, the question may still be asked, is the inspiratory or ex- piratory act the strongest ? In the last table (TABLE S.) there is uniformly a difference, because the two powers are unequally taxed with resistance. All elastic force is co-ope- rating with the expiratory power, whilst it antagonises the inspiratory power; therefore all the power manifested in inspiration is muscu- lar ; but in expiration it is partly muscular and partly elastic power. This probably causes the great apparent difference between inspira- tion and expiration ; at least, if we separate the resistance we assign to the elasticity of the ribs and lungs from the expiratory power, we shall nearly equalise the two. This can be easily proved upon one's own person : — partially empty the chest of air ; then forcibly test your expiration upon the haemadynamometer: pro- bably you can only elevate the mercury IA inch; then inspire deeply, completely filling the lungs, and now test your expiratory power, — instead of 1£ inch, it will probably be 5 inches. This difference appears due to two causes. 1st. In the deep inspiration the ribs are put more upon the stretch than in the moderate inspiration. 2d. The chest, when distended with air, presents points of attach- ment for muscular traction, to a greater me- chanical advantage. The most remarkable respiratory power, as tested by the hEemadynamometcr, was in the case of a Chatham recruit, who was fre- quently examined by Dr. Andrew Smith, on whose accuracy we place implicit confidence. The man's age was 18; height, 5 feet 6 inches, weight, 10 stones 5 Ibs. ; circumference of his chest, 35 inches; vital capacity, 230; — hi3 inspiratory power was equal to 7 inches of mercury, and his expiratory power to 9 inches ! The thoracic power of this man, according to our last calculation, was equal to a gross weight of 2200 Ibs. This was the amount manifested, and we may safely consider 50 per cent, of muscular power to be lost by the obliquity of the respiratory muscles ; so that this man possessed a vital power equal ta nearly 2 tons! He exhibited in no other respect any remarkable feature of strength. A dynamic instrument like the haemady- namometer would be useful to those whose duty it is to examine men for certain public services, as for the army,, navy, police, fire- brigade, &c. With care, it would often detect disease. The efforts required to move the mercury test the whole trunk of the body.. The inspiratory test produces a rarefaction of the air within the thorax, causing an extra (unbalanced) atmospheric pressure upon the body from without. In this way we have de- tected rupture of the membrana tympani; for the air rushing in by this opening equalised the difference otherwise produced. The ex- piratory test is of a contrary order, increasing the pressure from within ; in this way we have detected hernia. The difference between the healthy and dis- eased respiratory powers is broadly marked. — It is shown in the annexed diagram (fig- 702.) ; the lower curve is the power manifested by diseased, and the upper curve that of healthy persons. The difference is about 50 per cent., because weakness is the most prominent symptom of disease. We do not compare the expiratory power for the reason already assigned. We affix at the bottom of the diagram the relative powers in figures, 3 Y 4 1061 THORAX. Fig. 702. ft. in. ft.-in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. 'ft. in. ft. in. ft. in. ft. in. ft. in. ..... too 5051 525354 5556 57 58 5 95 10 511 60 Heights. £ 5 o 5152 5354555657 58 59 5 10 5 11 606 + Healthy Diseased. Healthy. 2- Diseased. . / / ^ \ \ \ ,/" \ -^ /' ^-^-. — N 1 1 3.5 2-00 2-52 2'31 2'70 2'84 2'70 3'07 2'96 '2'9I 2'83 2'77 S'f\r> 2 f *2 1-30 M6 1-00 1-34 -74 1'25 '79 1'67 1'32 -93 -88 '40 M Inspiratory power of the healthy and diseased compared. OF THE RESPIRATORY VOLUMES. — For 1500 years, from the time of Galen to Robert Boyle, naturalists, physicians, and philoso- phers disputed the simple operation of draw- ing air into the thorax. There were three explanations given : — First, " That by the dila- tations of the chest the contiguous air is thrust away, and that, pressing upon the next air to it, and so onwards, the propulsion is continued till the air be driven into the lungs, and so dilate them." Secondly, That the chest is like a pair of common bellows, " which comes therefore to be filled because it was dilated." Thirdly, That the lungs are like a bladder " which is therefore dilated because it is filled." The great philosopher Boyle adopts the bel- lows' action viz., that the lungs are filled with air, because the chest is dilated, and that with- out the motions of the thorax they could not be filled. " Indeed," says Boyle, " the dia- phragm forms the principal instrument of ordinary and gentle respiration, although to restrained respiration, if I may so call it, the intercostal muscles, and perhaps some others, may be allowed eminently to concur." * Co- temporary with Boyle, we find Richard Lower f (1667) correctly understanding the respiratory action; he makes a dog breathe like a broken-winded horse, by dividing the phrenic nerve. What Boyle and Lower demon- strated, every one nowbelieves withoutdispute; yet it took 100 years' disputation, through a number of unfounded hypothetical and contra- dictory speculations, before the truths which Boyle and Lower promulgated were received. As late as the eighteenth century, little more than one hundred years ago (A. D. 1737), it was stated in the Gulstonian Lectures before the Royal College of Physicians that there was air between the pleura; J, — a con- dition which we now know is almost instant * Boyle's Life and Works, fol., Loud. 1744, vol. i. p. 64. f Phil. Tr. Abr., vol. i. p. 179. j Hoadly, Lee. on Resp., 4to, 1740, Lond., p. 11, et seq. death. The first great epoch in the history of respiration was at the time of Harvey (1628), when he published his first work on the circulation of the blood, though at this time he did not stand commended for his discovery ; for most persons opposed it ; others said it was old ; and the epithet " cir- culatory' in its Latin invidious signification, was applied to him. We know respiration depends upon the weight of the air; and at a very remote period air was known to possess the quality of weight. Aristotle and other ancient philosophers expressly speak of the weight of the air. The process of re- spiration is attributed by an ancient writer to the pressure of the atmosphere forcing air into the lungs.* Galileo was therefore fully aware that the atmosphere possessed this pro- perty ; yet when his attention was so immedi- ately directed to one of the most striking effects of it, he did not see its connection with respira- tion. It was reserved for his pupil, Torricelli, to discover (1643) the true law of atmo- spheric pressure ; and as we can find no phi- losophical reason assigned, prior to this date, why air enters the lungs in inspiration, we may date this as a first step in the advance of knowledge upon our subject. Nevertheless, no less an authority than Swammerdam adopted, for upwards of twenty years after this, the unphilosophical reasoning of Des- cartes, that the air was forced into the lungs by its increased density around the breast, oc- casioned by the dilatations of the thorax, in consequence of the elevation of the ribs. In 1667 some attention was paid to respira- tion being maintained by distinct volumes of air ; for Hook kept a dog alive with common bellows by artificial respiration, f Fabricius, in the beginning of the 17th century, cor- rectly explained the action of the diaphragm. J Borelli is the earliest physiologist (1679) who * Lardncr's Cyclop. Nat. Phil. Hydr. and Pneum. p. 247. t Phil. Tr. Abr. vol. i. p. 194. j De Resp. ii. c. viii. THORAX. 1065 established an experimental inquiry into the quantity of air received by a single inspiration.* Jurin improves upon Borelli. About this time (1708) Dr. James Keile made some correct measurements of the volume of air breathed, f Then followed Dr. Hales, who threw more light upon the doctrine of air, the power of respiration, and the power of the heart, than all his predecessors ; yet he was quite ignorant of the use of respiration ; and at this period (1733) really very little was known upon the subject. In 1757 and fol- lowing years, Black, Rutherford, Lavoisier, Priestley, and Scheele, the chemists of the age, threw light upon the matter by discover- ing the composition of the atmosphere, and consequently the composition of respired air. It is since the time of Black that the most valuable mass of our knowledge upon respir- ation has been discovered. The functions of the thorax maybe divided into two great heads, — the chemical and the physical ; for an account of the former see RESPIRATION. Every point of the thorax can move for the purpose of respiration; and hencehas followed a. division of these movements, nominated after the parts which respectively carry on their functions, viz. costal breathing, and ab- dominal or diaphragmic breathing. These motions are, in health, symmetrical, constant, regular, sensitive, and precisely the same ; otherwise disease must exist. The breathing movements are also expres- sive of mental emotions. The tragedian imi- tates them to give force to the character he represents, whether it be the stealthy breathing of the Roman conspirator sharpen- ing his knife, or the deep swelling inspiration of Ajax defying the lightning; these repre- sentations, without such movements, would be but dull pictures of the mind of the authors who left such characters on record. It is much easier to become delicately fa- miliar with these movements and their cha- racteristic differences, than it is to describe them. The latitude of movement, performed by the walls and floor of the thorax, admits of three common degrees of division : — First, extreme expansion or enlargement. Second, extreme contraction or diminution ; and Third, an intermediate condition, — an or- dinary or quiescent state. These three divisions necessarily displace volumes of air of different magnitude. Were the respiratory movements but two in number, extreme expansion and extreme contraction, the quantity of air moved, and the character of the movement, would be easy of calculation and expression; but the interme- diate breathing or quiescent movement being so limited, so perfectly under the control of the will, so readily affected by mental emo- tions and by the animal functions, renders * De Motu Animaliiun, p. 2. prop 81. f Tentaui. Med. Phys. p. 80. the calculation of the volume of air ordinarily passing through the lungs a very difficult question. The quantity of air in the thorax, together with those portions which can be added at will, may be arranged and denominated thus : — First, residual air. Second, reserve air. Third, breathing air. Fourth, complemental air. Fifth, vital capacity. 1st. Of residual air. — After death the lungs contain air, which is not displaced by the last expiration ; this quantity remains in the thorax as long as the lungs maintain their natural structure; therefore we have no control over this volume of air : to it we assign the term " residual air" 2nd. Reserve air is that portion which re- mains in the chest after the gentle ordinary expiration, but which may be displaced at will. 3rd. Breathing air is that volume which is displaced by the constant gentle inspiration and expiration. 4th. The complemental air is that volume which can at will be drawn into the lungs by a violent exertion above the moderate effort of ordinary breathing, constituting the deepest possible inspiration. It is only occasionally demanded. 5th. The vital capacity is these last three divisions combined, being the greatest vo- luntary expiration, following the deepest inspi- ration.* This division of thoracic movements for commanding these different volumes of air may be more clearly illustrated by diagram 703. Fig. 703. rCornplcmontnl air. Vital capacity, •{ Breathing air. city. •{ l_ Reserve air. Residual air. The division of the thoracic movements. Let that portion marked H represent the resi- dual volume, or air left in the lungs, after a complete voluntary expiration ; the part next * According to physiological nomenclature, perhaps the term "vital capacity" may be objec- tionable; but we adopt it, for want of a better term, to signify a capacity or volume of air which can only be displaced by living movements, and may therefore he termed a " living volume," or " vital capacity." 1066 THORAX. anteriorly, left white, — the reserve volume, or latitude of movement appropriated for dis- placing that air left in the lungs at the end of an ordinary expiration ; the black stripe next anteriorly represents the mobi- lity for commanding the volume of breathing air ; and lastly, beyond this another white stripe shows the extreme limit of inspiration or thoracic mobility commanding the com- plemental volume of air. These last three — viz. the complemental, breathing, and reserve volumes conjointly — we style vital capacity. The absolute capacity may be considered as all the divisions combined in one. Whatever limits the mobility of the thorax must modify the volume of air respired. This applies to any or all of the above movements. Therefore the measure of the volume of air displaced becomes a measure of the thoracic mobility ; anil as disease affects the mobility of the chest, the measure of the volume of respired air becomes a measure of disease. The residual volume is entirely independ- ent of the will, and always present in the chest. The reserve volume, to use a simile, is a " tenant at will." The breathing volume is constantly passing out and in, many times a minute. The complemental volume is seldom in the chest, and then only for a very brief period. Whatever be the breathing volume ne- cessary for our well-being, the mobility demanded to maintain it is an intermediate mobility, just as the dark stripe mfg. 703. is intermediate between the white stripes ; so that at both ends of the ordinary breathing mobility there exists a spare mobility, which we can command into action according to the necessities required. This reserve and com- plemental mobility may be looked upon as a broad, spare margin which encompasses our breathing ; so that any sudden exertion may not (as it otherwise would) produce painful dyspnoea and premature death. This spare mobility, therefore, is always ready to admit of irregularities in the ordinary breathing, such as frequent or infrequent, quick or slow, regular or irregular, great or small, equal or unequal, easy or difficult, complete or incomplete, long or short, abdominal or costal; as in coughing, running, laughing, crying, sing- ing, sighing, and vociferating, many of which are but extensions or modifications of the or- dinary mobility, infringing upon this margin — the complemental or reserved mobility. This spare mobility is not only ready for such exigencies as above mentioned, but it becomes a reservoir for "times of need." Thus a man can take from 230 to 300 cubic inches of fresh air into his lungs, and live upon it without inconvenience for two minutes with- out breathing.* The knowledge of this fact * It is better to inspire and expire forcibly five or six times, cleansing the lungs of the old air, and then give one deep inspiration, and there hold. For the first 15 seconds a giddiness will be ex- perienced ; but when this leaves us, we feel not the would be of much use towards rescuing a fellow creature from suffering amidst dense smoke or in an irrespirable atmosphere, as is found sometimes in mines and wells. A variation of this condition was once wit- nessed when Mr. Brunei descended to ex- amine the breach which the river had made in the Thames Tunnel. Having lowered the diving-bell nearly 30 feet to the mouth of the opening, this was found too narrow to admit the bell ; so that no further observation could be made upon the workings, which were about 8 feet or 10 feet deeper: Mr. Brunei, therefore, laying hold of a rope, left the bell, and dived himself down the opening. His companions in the bell, being alarmed at the length of his stay, now about two minutes, gave the signal for pulling up ; and the diver, unprepared for the signal, had hardly time to catch the rope, which he had let go, and was surprised to find, on coining into the bell, that he had remained below so long. On descending again, he found that he could with ease remain fully two minutes under water. In this case the atmosphere, under a pressure of 30 feet of water, charged the lungs with nearly a double volume of air compressed into the same bulk as one volume at the surface of the water. Our ordinary breathing volume can only supply us for from three to five seconds ; for if we suddenly stop breathing for that time, we experience a degree of inconvenience. Of the volumes of air expelled from the lungs. — A knowledge of this is of incalcu- lable value to the physician and to the surgeon ; for disease cannot attack the lungs or the thoracic boundaries, without diminishing the respiratory volume, which change ultimately leads to the variations of the respiratory murmurs, first noticed as a diagnostic sign of disease by Laennec. Many experimenters have measured the different volumes of re- spired air, not primarily in reference to disease, but merely as collateral to the ob- servations of the chemist : hence experiments have been few, and deductions highly dis- crepant. (a) Residual volume. — Dr. Hales notices this volume, but assigns no measure for it*; Allen and Pep}s estimate it at 108 cubic inches in stout men of 5 feet 10 inches f; Davy at 41 cubic inches J ; Goodwyn, by the mean of seven experiments, at 108 cubic inches ; Kite, who writes expressly upon submersion, is obscure upon this point § ; Dr. Bostock allows 120 cubic inches || ; Dunglison gives Menzie's estimate of 179 cubic inches ; Jurin estimates it at 220 cubic inches ; Fontana at 40; and Cuvier at from slightest inconvenience for want of air; and two minutes of time can be passed through without breathing. The most expert pearl-divers cannot re- main under water for a longer time. * Stat, vol. i., p. 239. f Phil. Tr., 1809., vol. xcix. pp. 404. 428. | Chem. and Phil. Remarks, p. 410. § Essays and Obs. Physical and Med. 1795, p. 8. II E . Phys. 3d. Ed. p/318. THORAX. 1067 100 to 60 ; Mechli at 52 and 40 * ; Dr. Herbert, of Gottingen concludes tbis volume to be "very little." f We have fbuml it to vary from 75 to 100 cubic inches. It must be relative to the absolute capacity of the chest, which varies from 248 to 457 cubic inches. The mean absolute capacity is 312 cubic inches. Allowing 100 cubic inches for the heart and large blood vessels, and 100 cubic inches for the parenchymatic structure of the lungs, will leave a little more than 100 cubic inches for the residual air; therefore Allen and Pepys's opinion may be relied upon as very near the truth. (l>) Reserve volume. — Gooclwyn omits this volume altogether ; and this omission was pointed out forty years ago by a phy- siologist who himself omitted any notice of the complemcntat air. Kite estimates this at 87 cubic inches; Davy, by an experiment upon himself, at 77 cubic inches J ; Dr. Bos- tock, from trials upon himself, at 160 or 170$; Mechel at 110 cubic inches. || It averages about 100 cubic inches ; our obser- vations range from 70 to 110 cubic inches. It is regulated by the point at which the or- dinary breathing movement commences, (c) Breathing volume. — This has attracted most attention ; but the discrepancies of opinion are nearly commensurate with the number of observations. It would require years of labour to determine this volume by direct experiment, in a manner to be avail- able to the physician ; and it would re- quire a long time to perfect the observation of it upon a single patient, because these movements are so delicately affected by the mind, so perfectly uncontrollable, and the volume is so small, that a little error would seriously damage the value of the observation. The volume assigned by observers, varying from 3 to 100 cubic inches, is as follows : — Cub. in. Abildgaard - - - - 3 .Abernethy - - - - 12 Keutsch - - - 6 to 12 Gooclwyn - - - 3 and 14 Lavoisier and Seguin - - 13 Wurzer and Lametheria - 8 or 1 0 Kite - - - -17 Davy - - - 13 and 17 Allen and Pepys - - ;i6'5 Hetbst - - - 16 to 25 Jurin - - - - 20 Borelli - - - 15 to 40 Herdolt - - - 25 to 29 Dalton - - - 30 Fontana - - - - 35 . Hicheraiul, Poland, Gordon, and Ca- vallo - 30 to 40 Hales, Jurin, Sauvages, Haller, Ellis, Sommering, Thomson, Sprengel, * Mcchli's Manual Descrip. and Pathological Anat, vol. ii. p. 448. . f Bostock, Op. Git, p. 31G ; and Archives Ge'n. de Me'rt., t. xxi. p. 412. et seq. { Op. Cit, pp. 47, 48. § Op. Cit. p. 316. |] Manual of Descrip. Anat,, vol. ii. p. 447. Cub. in. Bostock, Chaptal, Bell, Monro, and Blumenbach - - 40 Menzies - - - 42 to 46 Reil - 40 to 100 upon an average, it varies from 16 to 20, though we have occasionally found it vary from 7 to 77 cubic inches. Though our ob- servations upon this point are but scanty com- pared with those we made on the vital capa- city, yet from about 80 experiments we con- clude that man in a perfectly quiet state, as when sitting, reading, &c., breathes much less than he does under the ordinary excitement of moving about. We think the perfectly quiet breathing, when we can scarcely perceive any movement (which is by no means uncommon), may be from 7 to 12 cubic inches, and when under ordinary excitement and exercise, from 16 to 20 cubic inches ; we have known it in one case as high as 77 cubic inches. It is probable that the quantity is relative to the volume of blood to be aerated. Herbert found that adults of smaller stature breathed less than those who were taller.* It is proba- ble that phthisical patients breathe very little, — from 2 to 4 cubic inches ; but the number of their breathing movements is greater, which compensates for this small quantity. (d) Complemental volume. — Davy, from a single experiment (upon himself}, calcu- lates this at 119 cubic inches f ; Kite, at nearly 200 cubic inches.f It is regulated by the position of the ordinary breathing movement, which is intermediate between it and the reserve air. It averages, from direct experiment, rather higher than the reserve volume, — about 105 or 110 cubic inches. Taking the mean height at 5 ft. 8 in. the vital capacity is 230 cubic inches, that is to say — cub. in. Reserve air - - - 100 Ordinary breathing - 20 Complemental - - 110 230 (r) Vital capacity volume. — Jurin and Hales correspond in stating this at 220 cubic inches § ; Davy at 213 cubic inches |j ; and he remarks in a note, " this capacity is pro- bably below the medium. My chest is nar- row, measuring in circumference but 29 inches, and my neck rather long and slender." It is probable the figures 29 are a misprint for 2 feet 9 inches round the chest. Dr. Thomson, from the mean of twelve experi- ments, upon men from fourteen to thirty- three years of age, states it at 186.V cubic inches. Dr. Thomson himself could expel 193 cubic inches. He mentions that this volume is constant when once determined. * Miiller, El. Phys., 1st ed. 8vo., Lond. p. 294> vol. i., 1847. f Op. Cit. p. 410. j Op. Cit. p. 47. § Hales's Sat,, 1732, vol. i. p. 239. || Op. Cit. p. 410. 10G8 THORAX. The temperature of the respired air is not mentioned.* Goodwyn states it at 200 cubic inchesf ; Kite, at 300 cubic inches:]; ; Menzies at 200 § ; Bostock||, corroborated by Dun- glison^T, omitting the complemental volume, at 2 10 cubic inches; lastly, Thackral, who takes this volume as the measure of health ; ex- amines some soldiers, who give the mean of 217 cubic inches, and some shoemakers, who average 182 cubic inches ; and he re- marks, " a tall young cornet threw out 295 cubic inches ; this was the greatest quantity 1 ever witnessed."** According to this evidence, the respective volumes are, — Cub. in. Residual volume, from 40 to 260 Reserve ,, ,,77 „ 170 Breathing „ „ 3 „ 100 Complemental „ „ 119 „ 200 Vital Capacity „ „ 100 „ 300 The apparent discrepancies of the breathing volumes are entirely due to the want of col- lateral observations ; for there is no distinction between the sexes, nor age, nor stature, nor weight. We have determined the vital capa- city in one man as 80 cubic inches, in another 464 cubic inches ; therefore we might say this volume varies from 80 to 460 cubic inches ; but this discrepancy is cleared up, when we add that the height of the former was 3 feet 9 inches, and his weight 4 stone 9 Ibs., while the latter measured 7 feet, with a weight of 22 stone ; and that if we arithmetically reduce the one to the other, the vital capa- city of a dwarf is within half an inch of what it actually was, viz. 79'56 cubic inches by cal- culation, and 80 cubic inches by direct expe- riment. Collateral observations clear up the experiment ; thus Kite was probably a tall man, and therefore he states the vital capacity as 300 cubic inches; Davy at 213 cubic inches, because he was of shorter stature, probably about 5 feet 7 inches ; Hales, Jurin, and Goodwyn about 5 feet 8 inches. We come to this conclusion, because we find this vo- lume bear a strict relation to stature. There- fore, probably, all the observations already mentioned are correct, and only wanted an- other combination to remove the apparent discrepancies. We have especially directed our attention to one of these volumes of air, the vital capacity. VITAL CAPACITY. — There are two ways of measuring the permeability of the lungs, or the volumes of air which they can displace, viz. by measuring the actual movement or mobility of the thoracic boundaries, or by directly measuring the absolute cubic inches of the volume of air expired. The former is open to an error, but the latter is not. * Thomson's Anim. Chem., 1843, p. G10. et seq. •j- Op. Cit. p. 32. note. \ Op. Cit. p. 48. § Mayo's Outlines of Phys., p. 76. || Op. Cit. p. 321, If Ibid. vol. ii. p. 91. ** Thackral on the Effects of Arts, Trades, &c. upon Health, p. 21. et seq. If we take the movement as an index to the permeability of the lungs, we obtain an evidence only of movement, and not of the permeability of the lungs for air, for we may move the thoracic boundaries, and yet not breathe. But when we measure the volume of air, it is self-evident that this must be the measure of both the permeability of the lungs and of mobility of the thoracic bound- aries, because we cannot breathe without moving. The classes of persons we examined were as follow : — No. Sailors (Merchant Service) - - 121 Fire Brigade of London - - - 82 Metropolitan Police - - - - 144 Thames Police - - 76 Paupers - - - - - - 129 Mixed Class (Artisans) ... 370 First Battalion Grenadier Guards - - 87 Royal Horse Guards (Blue) - - 59 Chatham Recruits - - - - 185 Woolwich Marines - 573 Pugilists and Wrestlers - - - 24 Giants and Dwarfs .... 4, •n . . f Pressmen 30 1 Printers -{ r, .. ,0 r - - 73 L Compositors 43 J Draymen ------ 20 Girls 26 Gentlemen - - - - - 97 Diseased Cases ----- 360 Total - - 2430 Each individual was subjected to the fol- lowing observations : — 1st. The number of cubic inches given by the deepest expiration, following the deepest inspiration. This was taken three times, and the highest observation was noticed. 2nd. The inspiratory power. 3rd. The expiratory power. 4th. Circumference of the chest over the nipples. 5th. Mobility of the chest with a tape- measure. 6th. The height. 7th. The weight. 8th. The pulse (sitting). 9th. The number of ordinary respirations per minute (sitting). 10th. The age llth. Temperature of the air expired. To determine these points, we constructed an air receiver, denominated " Spirometer." We used a bent tube (haemadynamometer) for ascertaining the respiratory power, scales and stand for the height and weight, and a com- mon tape-measure for measuring the mobility of the chest. We rarely exceeded three consecutive ob- servations with the spirometer, because after this the volume of respired air diminishes from mere fatigue. To measure the vital capacity volume. — The SPIROMKTER (fig. 704.), consists of a vessel containing water, out of which a re- ceiver is raised by breathing into it through a THORAX. 1069 tube ; the height to which the receiver is raised, indicates the volume of the vital capacity . To Prepare the Spirometer for Use : — 1st. Place the spirometer about three feet from the ground, upon a firm, level table. 2nd. Turn off the water-tap 4, and open the air- tap 1. Fig. 704. sufficient to bring the water down to the edge of the index. 5th. Pour a little coloured spirit into the bent tube 5, until it stands about 3£ inches, as at 6. 6th. Turn off the air-tap 1, then suspend the counterbalance weights, 11,11, from the cord over the pullies. The spirometer is now ready for an observa- tion. The flexible tube, terminated with a glass mouth-piece, is held by the person about to be examined, and the tap 1 is to be kept open by the operator while the deep expira- tion is being made. To discharge the air out of the receiver. — It will be seen that if the tap 1 be opened, the receiver will rise out of the reservoir by the power of the counterbalance weights, until it touches the cross-head 9. To return the receiver into its original position, the con- tained air must be discharged ; this can be done by slowly depressing the receiver down into the reservoir, and so pressing the air out by the way it entered, — through the air-tube. But, in order to do so more rapidly, a large valve at 14 admits of an instantaneous escape of the air. Therefore, to discharge the air, remove the plug 15 out of the socket 14 with one hand, while the other returns the receiver into its original position. Let the person to be examined loose his vest, and any other tight garment — for the least pressure from dress affects the mobility — stand perfectly erect (fg. 705.), with the head Fig. 705. Spirometer. 3rd. Pour into the spout, behind, clear cold water, until it is seen to rise behind the slip of glass 3 (above the air-tube). 4th. Slide the moveable index 2, opposite 0 on the graduated scale 13, and add more water until it is ex actly on a level with the straight edge of this index ; if too much water be poured jn, draw off, by the tap 4, thrown well back ; then slowly and effectually fill his chest with air, or inspire as deeply as possible, and then he must lift the mouth- piece of the spirometer 12 to his lips, still standing in the same erect position, and place the glass mouth-piece between the lips, holding it there sufficiently tight so as not to allow any breath to escape, he then sloivly makes the deepest expiration, displacing all the air he can out of his lungs through the mouth-piece into the spirometer, where it is measured to cubic inches, and confined there by a stop-cock, until examined. This ob- servation should be taken three times. The operator, while the experiment is going on should place his left hand upon the shoulder of the person being examined ; in this way he can determine as to the perfect inflation of the lungs and expulsion of air from them as well as the character of the thoracic expansion. The thumb of the operator should cross the clavicle, while the fingers rest on the upper 1070 THORAX. edge of the scapula, then he feels the expand- ing effect of inspiration, the swelling up of the apex of the thorax. To determine the volume of air in the spi- romcter. — The graduated scale 13 is attached to the receiver, and made to extend down- wards on the outside of the reservoir, so as always to he in relation with the index 2. On this scale 0 corresponds with the top of the receiver, or rather with the highest point to which the water can be made to rise within it. The number of cubic inches is shown by the degree upon the scale pointed to by the index 2, which corresponds with the level of the water in the receiver. But the water in the reservoir seen behind the slip of glass may not be level with the water within the receiver, just as the level of the water in a pneumatic trough may be higher or lower than the level of the water contained in a glass receiver standing upon the shelf. To know when these are level, depress the receiver until the coloured fluid in one leg of the bent tube, or inverted syphon, 5, stands level with that in the other leg, as at 6 ; then the water contained in the receiver, and that external to it, are level to each other ; and the air within the receiver is of the same density as that without. Immediately the plug 15 is replaced, and the hands withdrawn from the receiver, the latter will be seen to ascend some half-inch, the water behind the slip of glass to fall, and the coloured fluid in the bent tube to be unequal. This is caused by the excess of weight in the counterbalance (1 1, 11,), which is what necessitates the observation of the coloured fluid in the bent tubes and the cor- rection above directed. The scale is gra- duated to degrees, each of which measures two cubic inches. To correct the respired volume for tem- perature. — The table of the vital capacity- volume is calculated at 60° Fahr. The tempe- rature of a volume of air displaced out of the lungs into the spirometer is reduced at once to the temperature of the water in the spiro- meter. This, according to the season of the year, may be 50° or 80°. Now 330 cubic inches at 50° would occupy 337 cubic inches at 60°, and 330 at 80°, would be 317 at 60°. For eight months out of the year there needs no correction. But a correction is necessary, when a thermometer in the room stands much above or below 60°. We may estimate the change in the bulk of air as ¥7Vo f°r every degree (Fahr.) of variation of temperature ; thus if a man breathe, in winter, 295 cubic inches of air into the spirometer, when the thermometer in the room stands at 55°, being 5 degrees below 60°, then -^ = 2'95, must be added to the 295 cubic inches, making 297'95, or, in round numbers, 298 cubic inches. On the other hand, if the vital ca- pacity be determined at 215 cubic inches, when the thermometer stands at 72°, which is 12° above 60°, ^- = 5 must be deducted; making the corrected observation 210, instead of 215 cubic inches. In the absence of the spirometer, the mea- sure of the mobility of the ribs, by means of a common tape measure is of much value.* To measure the mobility of the thorax with a tape measure, pass the tape measure round the chest under the waistcoat, over the region of the nipples, request the person to in- spire deeply, and note that circumference, then to expire deeply, and again note the circumference, the difference is what we term the mobility. This is a rough measure- ment, but of no little value in doubtful cases of chest disease. This difference, or mobility, in men of all statures should be about 3 inches, if it is found only 2i inches the examination should be carried further ; sometimes the mobility extends to 5£ inches, but this is excessively rare. As a general rule, when we find the mobility three inches, we find the vital capacity volume correspond with our table. Sometimes the mobility may be good, and the vital capacity bad, because, as we have already noticed, we may move* the walls of the chest without breathing. The vital capacity is a constant quantity ; habit will not increase it. But this volume is disturbed directly, and modified by five circum- stances : 1st, by height ; 2nd, by position ; 3rd, by weight ; 4th, by age ; 5th, by disease. 1st. Of the effect of height. The vital capacity volume bears a striking relation to the height of the individual exa- mined ; so that, if we take a man's height, we can tell the volume of his vital capacity. We show this by a curve in^/zg. 710., as before ; let the perpendicular lines represent the heights increasing inch by inch from the left towards the right ; the single continuous line is the curve of the vital capacity, which gradually ascends as it passes over the perpendicular lines. The heights extend from 5 feet to 6 feet ; above six feet the observations are few. Whe- ther the vital capacity volume maintains the same regular progression beyond this point remains to be determined. If we draw a line in a perfect arithmetical ascent of eight units for every increasing height, the line of vital capacity will be observed to run nearly pa- rallel with it; therefore this volume increases with the increase of stature. The figures at the bottom represent the vital capacity in cubic inches, being the mean of the observa- tions under each height. The following table (TAIILE T.) places the subject more in detail : — A cursory inspection of the table shows that the vital capacity increases with the height ; this is without any consideration as to age, weight, or circumference of the chest. For clearness, we arrange it in a more re- duced form, as in TAKLE U. * Dr. Sibson and Dr. Quain have invented some ingenious instruments for measuring the thoracic movements externally. THORAX. 1071 rs °3i O u C 01 s <*- o o o oT ». 3 a C o o E j3 "o « W to o x S2d s-S tc — SO CM «5 O ^1 CO !O (O X t- 00 to l^ CM CM CN . C-I CM CM CN • TT 5O O 10 « «s : IN CM CM . l^ •* CM S .5 •S3SE3 00<«CNlO'-'f n f-H O CM d"d iO »C II OOt^OOOCMOO"O5iO^OCO •oOTrfiTr^M-^rcoM^Mt^ ; CM CM CM CM CM CN CM CM CN C-l CN CM . vo to to o TT to T Ol CM CM CM CM to T CM .= .s •S3SUO rtO^OOOlDCMWi-H'^^O^l : r-c CN T M I— " 1— 1 CM •— 1 . t1 CM O CO tD CM CO n O) CM 00 . *J . « e to o 11 o — C5— i — O O CM «5 ^ CO CM CM CM CM r~ 00 CM .£ .S •S3SEO iotoMt^ocot^aot^eooor-1 ; i— i CN M i— i CN i— i • CM X CM O) t- CO O> i-H r-H •* . — « « £ tO *C $4 3 C o — C)'-KOC100aO x O tO O. n to X CM d*"d »o »o w „; S"3 a-s wio^fCMOO r^Tr^oor- ci — co O) ^ — . jo-io^ow ; CM CM CN CM O* CM . o 1— 1 l-H P— 1 T iO ai"^ m m || t~ 00 OOOlCMOIOOCnCMOlt^ — i — 'Q-IOOOOOOOOC-H • CM CM I W — i rt -i CM CM r- ' 1-1 CM . SCO CO to 00 CM O) CM CM CM — •* CM .5 .S •S3S80 O1CM ;ff)O^ ; CM — i x ; co •* t^ •0 X . •** . C it! IO »O s-S 3 C v>"" «00 ^O — • 1-1 00 80 « t- — — O • o Oi a> i x -H ;t--i : CM CM : CM f-i — i CM •-! CN . -H C-l . x to o O '—ix CM I CM n o CN .S .£ •S3SB3 o •— i : i— it^;io 1 1~ •1 : 1-1 t ^ CM I-H . . X n ; f to : CO t^ *-" ,*^ •— '— o -o l-s 3-s XO r~'TllO «5 COX — i f-c • x t- oo • O5 ; »o 1-1 ; O-)CM :-i-,^ in . — CM : CO OJ X 01 x : oi CO 0) CH .S .£ •sasEg n • • : o u> M d :- 1^ O «5 m £ in a^ 3-s I-H I-H . l— • l-H •sasB3 rH . . • • — 1 <=>£ *^ 1C £•3 n X — O *o co : : • «5 CO SI ^^ • • • »-H •' . • i height.. : : ~A •:: TS :::::: :. o :.!-::..: 1 Jl a> •— .p u rt 0) i. HI T3 : §• S : S : : : : j ^ ojj-ip r^t/j-''5t- •§.•89 8 • u S o 1 ^k-H-C S fc *S r^ *^ S •» " .SP§ H«"--^Sgp^O SStfrfS^'g.g.gBj^. p i 0 O ZL. Hi c ~ f, >. -^ •- <5 | g '-5 .5 i .2 2 § g £ g |p S ccfapHOPHSOOP^Qd^K Mean of first s Chatham recri Woolwich mai Miscellaneous S C C3 O S *rt "o H 1072 THORAX. TABLE U. — Progression of the Vital Capacity Volume, with the Stature — from the above. e a o o 2 « >» § c % O H Q) "rt c o.g.2 u o 3 5 3 » 5 4 5 4 » 5 5 5 5 „ ^ 6 5 6 » 5 7 5 7 „ 5 8 5 8 „ 5 9 5 9 „ 5 10 5 10 ,, 5 11 5 11 » 0 0 TABLE V. — Vital Capacity Volume (temp. 60° F.) necessary to Health at the Middle Period of Life. Vital capacity. 174 182 190 198 206 214 222 230 238 246 254 262 8 in. the vital capacity is 230, we can recollect the rest by adding or subtracting eight to or from this number, for every inch of stature above or below 5 feet 8 in., between 5 and 6 feet. These numbers may betaken as expressions of certain conditions of the thorax, an expression of mobility relative to breathing, and conse- quently an expression of the permeability of the lung. It therefore follows that whatever affects the mobility of the thoracic bound- aries, or the permeability of the lungs, the amount of that cause it expressed by the volume of the vital capacity. Incipient disease is quick in affecting the vital capacity ; the amount of the injury therefore is readily measured. We are at a loss to assign any just reason why the vital capacity is rela- tive to the height, which is regulated by the length of the limbs, and not by the length of the trunk of the body. We have found by experiment, that whatever be the standing height, the sitting height is nearly the same in all persons of between 5ft. and 6ft., and if not actually the same, yet it is not a rule that the tallest men sit the highest ; for in- stance, one man standing 6ft. O^in. measured from his seat 2ft. 11-fin., whlie another who stood 5ft. 6in., sat 3ft. high ; therefore the length of the trunk bears no constant propor- tion to the length of the legs. And we found that men who stood low, breathed less than men who stood higher, but who sat the same height. Thus Jig. 706. represents two men ; A. stood 4ft. 4£in., B. 5ft. 9^in. ; they were of the same age and circumference of the chest. The weight of the short man was 7st. 2^1b., that of the taller man lOst. 3lb. Yet their sitting height was precisely the same, as is shown in ^g. 707. Nevertheless, the vital capacity volume of the shorter man was 152, and that of the taller man 236 cubic inches; so that the man who stood the shorter, but who sat as tall, if not taller, breathed eighty- four cubic inches less than the man who stood seventeen inches higher. The mobility of the chest of the taller man was nearly four inches, that of the shorter man three inches. We ex- amined several such cases with similar results. The average vital capacity volume at all heights is about 230 cubic inches. The greatest THORAX. 1073 we have examined was Randall's; height 7ft. inches. The highest height of 5ft. Sin. was weight 22 st. ; vital capacity 464 cubic inches. The smallest was Don Francisco; height 29 in., about 40lbs. ; vital capacity 46 cubic weight Fig. 706. A Relative height of two persona standing. vital capacity at the 330 cubic inches. A question arises, are the lungs and tho- racic parietes at their maximum stretch when they contain the appropriate vital capacity volume ? We believe not. The vital capa- city of the person from whom the preparations figured above (figs. 680. el seq.) were taken, whose height was 5jft. 4 in., weight 107 lb., was 198 cubic inches ; yet, after death, we forced 300 cubic inches of air into his lungs without rupturing them, being 102 cubic inches more than he could expire during life. There- fore there is still a spare mobility of parts, probably in reserve, to be exercised when dis- ease attacks the lungs. 2nd. Vital capacity affected by the posi- tion of the body. — We have said a man must hold himself erect to breathe out a good vo- lume of air ; because the mobility of the ribs is affected by the uprightness of the spine ; and, more than this, whatever touches the ribs affects their mobility, and consequently the vital capacity. Thus, standing, we have produced a vital capacity of 260 cubic inches ; sitting erect 255 cubic inches; recumbent — supine 230, prone 220 cubic inches ; position making a difference of 40 cubic inches. This may explain why patients with emphysematous lungs sit up in bed, and why for them to lie recumbent, is "suffocating;" because they thereby diminish the thoracic mobility. It may be well to recollect this effect upon respi- ration, in treatment of diseases of the spine, particularly at the present time, when they are Fig. 707. The relative Jieight of the same persons sitting. treated by laying the patient on the anterior pacity from 260 to 220 cubic inches. part of the chest for weeks and months to- 3rd. Vital capacity affected by weight. — gether, which position reduced our vital ca- The weight affects the vital capacity ; but VOL. IV. 3 Z 107* THORAX. as yet the relation does not appear so regular as that of the height. We are scarcely in a position, at present, safely to say much upon this point. As a general rule we find the weight increases with the height ; so that it is not easy to separate the effect of one from that of the other. Suppose we take two men of the same stature, say 5 feet 8 inches, the one 10 stone, the other 14- stone in weight; one of them above par, the other may be either at, or below par. If 10 stone be considered par, the 14 stone man is 4 stone in excess, or corpulent to 40 per cent. This excess weight blocks up the range of mobility, and thus, mechanically, diminishes the vital capacity volume. But let us suppose men of dissimilar heigths, one 5 feet 8 inches and the other 6 feet ; the 6 foot man should be heavier than the shorter man ; — say 3 stone heavier. This is not excess weight with him, and does not interfere with his thoracic mobility ; therefore there is an inseparable relation between the height and •weight. If, in a series of experiments, we sink the height entirely, and keep the mere weight in view, we shall find that the result as to the vital capacity volume is without order. TABLE W. — Vital Capacity Volume in Relation to Weight. Weight. Vital capacity. Difference. St. St. cub. in. 7 to 8 166 8 to 9 187 21 + 9 to 10 199 12 + 10 to 11 222 23 + 11 to 12 233 11 + 12 to 13 238 5 + 13 to 14 237 1 — 14 to 15 278 41 + From this there is seen to be a rude increase of the vital capacity with the increase of the weight, but it is quite irregular, as 21., 12., 23., &c. We have also found the mean vital capa- city of 147 men of 1 1 stone as 225 cubic inches, and that of 32 men of 14 stone, only 233 cubic inches, an increase of 8 cubic inches for an increase of 42 Ibs., or 3 stone. The over- whelming effect of height disturbs the above observation ; therefore the height must be kept in view. We have calculated the weights in relation to height, with reference to the res- piratory function, upon a number of men at the middle period of life. Besides the three classes mentioned above, we have included 1554 cases of healthy men in the prime of life, oblig- ingly furnished by Mr. Brent, viz. the Oxford and Cambridge rowers, London watermen, cricketers, pedestrians, and gentlemen (TABLE X). The weight now appears more regular, increasing with the height, as from 92 Ibs. to 218 Ibs. We may make this progression ap- pear more regular, as in TABLE Y, which is calculated by adding the mean weight, from the last table, of the men from 5 feet to 5 feet 2 inches (the mean of which is of course 5 ft. 1 in.), together, and taking the mean of that, which will be found J 19'9 Ibs.; and the next from 5 feet 1 inch to 5 feet 3 inches, taking their mean as 126-] Ibs., and so on. TABLE X. — Weight to Height, upon 3000 cases. Height. No. of Cases. Gross Weight in Ibs. Mean Wt. in Ibs. Ft. In. Ft. In. 4 6 to 5 0 26 2,399 92-26 5 0 „ 5 1 17 1,964 115-52 5 1 „ 5 2 36 4,476 124-33 5 2 „ 5 3 43 5,497 127-86 5 3 „ 5 4 88 12,145 138-01 5 4 „ 5 5 126 17,537 139-17 5 5 „ 5 6 214 31,016 144-93 5 6 „ 5 7 316 45,598 144-29 5 7 „ 5 8 379 57,822 152-59 5 8 „ 5 9 468 73,835 157-76 5 9 „ 5 10 368 61,238 166-40 5 10 „ 5 11 348 59,460 170-86 5 11 „ 6 0 245 43,475 177-45 6 0 „ G + 326 71,283 218-66 Total - - 3000 487,745 147-86 It thence follows, the range of stature from 5 feet 1 inch to 5 feet 1 1 inches is 10 inches ; and the weight rises from 1199 Ibs. to TABLE Y. — Difference of Weight to Stature on 2648 males, from the last table. Exact Stature. Weight Ibs. Weight more exactly, Ibs. Difference of Weight in Ibs. Ft. In. In. 5 1 or 61 120 119-9 + 6-2 5 2 „ 62 126 126-1 + 6'8 53,, 63 133 1329 + 5-7 5 4 „ 64 139 138-6 + 3-5 55,, 65 142 142 1 + 2-5 5 6 „ 66 145 144-6 + 3-8 5 7 „ 67 148 148-4 + 6-8 5 8 „ 68 155 155-2 + 6-9 5 9 „ 69 162 162-1 + 6-5 5 10 „ 70 169 168-6 + 5-6 5 11 „ 71 174 174-2 174-2 Ibs., or 54'3 Ibs.; or 5'43 Ibs. with every inch of stature. To subdivide the range of height it may be said : — Ibs. ft. in. ft. in. Their rise is 6'2 from 5 1 to 5 4 3-3 — 5 4 „ 5 7 6-5 — 5 7 „ 5 11 There is an inequality from 5 feet 4 inches to 5 feet 7 inches in the weight ; but this would in all probability disappear if the ob- servations were more extended ; at present it may be stated generally that the weight in- creases 6'5 Ibs. (or 6i Ibs.) for every inch of stature from 5 feet 7 inches to 6 feet, and 6*2 Ibs. for every inch of stature from 5 feet 1 inch to 5 feet 4 inches, and 3-3 Ibs. for every inch from 5 feet 4 inches to 5 feet 7 inches. At 5 feet 8 inches, or 68 inches of stature, the weight is 155'2 Ibs., or nearly 11 stone ; THORAX. 1075 from this as a starting point the weight at any height may (so far as our limited ob- servations warrant) be readily calculated. For instance, the weight is, at the height of 5 feet 155"2 8 inches, — - = 2-282 Ibs. for every inch of bo stature, or 27'38 Ibs. for every foot of stature. The bulk or weight of bodies having the same relative proportions, is as the third power (cubes) of either of their diameters : thus, if a person 67 inches high weighs 148'44 Ibs., a person 69 inches high ,. . ,/69\3 69X69 X 69 should weigh (-) x 148-44= Taking the height from 67 to 71 inches, we have as follows : — TABLE Z. — The calculated Weight compared with the observed Weight, according to the above Form. X l48-44= 67 x u? x 6? x 148-44= 162-14 Ibs. The Height in Inches. Weight deter- mined by Cal- culation. Weight deter- mined by Ob- servation. in. Ibs. Ibs. 67 148-8 148-4 68 155-5 155-2 69 162-1 162-1 70 169-3 168'6 71 176-6 174-2 33 weight at that height, from observation, was 162-08 Ibs., a similarity too close to be acci- dental. The weights vary as the 2'75th power of the height, and not as the 3rd power. The rela- tion between the two is quite close enough to show, that there is a very intimate connec- tion between the height and the weight. The observation is made upon 1276 men at the middle period of life. We have found that the vital capacity in- creases 42 cubic inches with the weight from 100 Ibs. to 155lbs., and from 155 Ibs. to 200 Ibs. the effect is balanced by minus 5 and plus 5 cubic inches. In the first division there is an increase of 42 cubic inches ; the weight then comes into power, and disturbs the regular progression for the next division ; therefore we may say there is in the second division a de- crease of 42 cubic inches in the vital capacity volume from the effect of weight. We repre- Fig. 708. no 120 120 130 130 140 170 170 180 180 190 190 200 Vital capacity. Circumference of the chests. The Effect of Weight on the Vital Capacity. sent this by a curve, fig. 708. The continuous curve is the line of vital capacity crossing the perpendicular lines of progressive weights. The curve of volume ascends, and attains its highest at 160 Ibs., and from thence it is nearly horizontal to 200 Ibs. According to this, the vital capacity increases nearly in the ratio of 1 cubic inch per Ib. from 105 to 155 Ibs., and from 155 to 200 Ibs. there is no increase. This illustration of the effect of weight is cal- culated at one height, viz. 5 feet 6 inches ; therefore to this height only these points of weight (from Hi to 14 stone) refer. We have noticed that the weight increases in a certain ratio with the height, and that the weight at 5 feet 6 inches affects the vital capacity in the relation just mentioned, com- mencing when the weight exceeds 7 per cent upon the average weight. We may, perhaps, connect this same relation with the other heights through the arithmetical progression of inch by inch. For example : — the weight of men of 5 feet 1 inch is 199'9 Ibs. ; to this add 7 per cent (8'395 Ibs.), making 128'2 Ibs. ; again, the tallest men, 5 feet 11 inches, weigh 174-2 Ibs. ; to this add 7 per cent'(12'2 Ibs.), making 186-4 Ibs. : therefore, at the height of 5 feet 1 inch a man must exceed 128 Ibs., or 9 stone 2 Ibs., and the 5 feet 1 1 inches' man 186 Ibs., or 13 stone 4 Ibs., before weight may be expected to diminish the vital capa- city volume in the relation of 1 cubic inch per Ib. for the next 25 Ibs., 2| stone being the limit of our calculation. When the man exceeds the mean weight (at each height) by 7 per cent, the vital capacity decreases 1 cubic inch per Ib. for the next 35 Ibs. above this weight. Beyond this it is not improbable but that the decrease of the vital capacity is in some geometrical progression. Below the mean weight we have never found by experiment, that the vital capacity is affected by weight. The cause of the difference of weight between men is involved in much obscu- rity.* We may in fact consider the usual weight of a man as his mean weight and * See Chambers, Gulstonian Lect. 1850. *3z 2 1076 THORAX. 0) 6X) •3 05 & O o o 4-1 O W w ij pq •S3SBJ3 I : • * CO 01 •* V) >c 1C o 1— 1 1C CO •sjsaqa : : : CTl CO Oi CO O) CO Oi CO 00 CO r—t •* Cl CO Cl CO . 0 O 0) Cl O :2 •"• °' .5 o : • : T1 oo f— 1 O) 00 rH o 01 Ol •* rH O) 1> co 01 CO CO 01 1C t^ Ol r~t Ol 01 •S8SBQ — • CN Ol Ol UO G> f- X o CO I-H Ol CD •sjsaqg O •* 00 CO 0^ 5 CO CO CO oc CO oo CO °° CO CO CO 00 CO . O 0 01 CO Cl 3 " " 1 CD oo r-l 0) I— I 00 Ol § 01 * o! CO Ol CO f Ol s Ol CO Ol •* t^ Ol CD 01 Ol •S8SB3 I— * : J^ n >o O5 CO >c CO Tf CO l^ l-H Ol I-H •S}s3q3 t- co i g §§ 00 CO CO CO 1- CO CO CO CO CO l- co l^ CO (^ CO . O O 01 t> CO := — — C • r-l O O 1C : 01 CO CO t~ t— ( ci * I— 1 01 00 OJ 01 •* t- 01 CO •* Ol 1C Ol CO Ol Cl t—t o» •S3SB[) rH I— < CO 0 f-H CO 1— 1 01 CO >c * Ol CO CO 1— 1 CO 1 — 1 1— 1 Ol oo 1— 1 •sisaqQ t> co K co CO CO CO CO CO CO CO CO CO CO >c co CO CO Cl CO CD 00 . 0 O <5 (O t- i — ~ 2 O •* t^ IO •* oo Ol o Ol CO Ol Ol r~ Ol Ol Ol •* Ol •* •*• 01 t^ Ol 0> 1C Ol Cl t^ Ol r~ M •S3SB3 Ol Ol 0 o Ol »c Ol 1 — I •* o •* o CO o CM CD 1—* * o Ol •sjsaqg r- co c- CO •* CO IO CO f CO >c CO "C CO CO CO co n CO CO 1C CO 1C CO . O O 03 ic CD — ^ — j 't1 co 0) 1-- Ol Ol t^ o Ol oo o Ol •* Ol Ol CM Ol CD CO Ol 00 CO 01 "t1 CO 01 co 1C 01 CO Ol Ol •S3SB3 r-l Ol CO "H g t> CO o CO •* J> o 1C Ol Ol CO 1C 01 * c-. Ol •sisaqo •* CO CO w ^ 00 $ •»" CO •* CO •* CO »0 CO •* CO •* CO 1C CO CO CO •* CO . O O Ol Tf 1C ~ ~~ — c u to O) O) r- 1— 1 f— * o 01 <£> o Cl CO 0 Ol 00 OJ Ol Ol « o O) Ol 1— 1 ^ 01 s Ol 7t> ^- Ol % Ol Cl 01 •S3SBQ O) •* CO £ C) d CO o •* 01 01 CO 01 0 f— ' Ol Ol 01 o Ol •sjsaijQ M co CO CO •* CO 1 CO CO CO CO CO CO •* CO CO CO CO CO CO CO CO CO CO co CO co . 0 O Jo 2 ~ £§ •* c~ §5 •* 00 o o oo oo CO l> os CO 1C w oc o CO ^ o CD § O •S3SB3 Ol 01 <0 1> I> I-H CO 1— < CO 01 C5 CO Ol h- ~H •S}saq3 •* « 01 CO i 01 co Ol CO CO CO Ol CO Ol CO £ Ol CO t—( c^ 0-1 CO . O O t/l c-1 CO •5 rr O 00 b5 tfj r~ Ol co CD Ol CTl 1C o o •T •c 00 CD Cl O •S9SB3 CO CD ^ CO 01 1 — 1 •^ CO u; | ^ ~ ¥ •sjsaqn CO 01 co CO C) CO M CO CO [ CO 1 CO co CO CO CO o CO CO . O O 01 i— i O! j r- •~ CO CO 10 02 0 0 l> VO o 00 »c 0 o 1C 0 o >c o r— t 1C 0 o CO 0 + CD 0 mean... •i-* 0) ffi .s° vi !C 1C Ol 1C CO IT) ^' US 1C 1C CO «5 t^ •c 00 >c C5 "C o 1— 1 1C 1C o CD ~a 4-» o H the term "gained weight" should be under- stood as weight superadded to his usual weight, or mean weight in the above Table. Thus, if a man may lose weight below his usual weight, he should gain above his usual weight before he can be said to have gained weight. The effect of weight in diminishing the re- spiratory volume, need not in the least disturb the observer, when testing the lungs through the measurement of the vital capacity, with re- ference to phthisis or any other chest disease. For collateral observations and the history of the case, will sufficiently protect him'from such difficulty. We see that the weight increases at so much per inch ; we have no doubt that by extended observations it will be found to be regular through the whole series of heights, and that it will be found to increase 1 Ibs. for every inch of stature. We know that the respiratory power increases in a similar arithmetical relation. We do not mean that THORAX. 1077 the Ib. will correspond to the inch, for that is accidental, merely depending upon the units employed, but that the increase of each will be found in an arithmetical progression, and hence, probably, the reason why tall men breathe more than short men. But the weight can never be the sure guide that the height is, because the former varies at any time in life, even in a few days ; where- as the latter varies only at the extremes of life. 4th. Relation of vital capacity to the circum- ference of the thorax. — We notice this here, because the question is so natural, " Has the size of the chest no relation to the vital capacity?" We do not find that there exists any direct relation between the cir- cumference of the chest and the vital capa- city. We have found — Height. Circura. Vital Men. ft. in. in. capacity. 11 58 35 235 10 58 38 226 Therefore, the men with chests 3 inches larger, breathed 9 cubic inches less, or 21 men of the same height, but of different-sized chests, breathed a mean vital capacity of 230 (the due quantity according to TABLE T). We have consolidated the following result upon 994 cases, the height is kept in view, calcu- lated at 5 feet 6i inches. TABLE B B. — Circumference of the Chest,'in Re- lation to the Vital Capacity Volume, in 99-t cases (Males). Circumference of Chest. Vital Capacity. Number of Cases. Cubic In. Difference. 30 to 301 200 14 — 13 301 „ 31 187 20 + 18 31 „ 3H 206 21 — 10 3H „ 32" 196 35 + 1 32 „ 32i 197 32 — 7 32 \- „ 33 204 50 9 33" „ 331 202 44 0 33i „ 34 202 63 + 63 34 „ 34i 213 70 + 4 34i „ 35 217 78 — 2 35 „ 351 215 71 + 14 351 „ 36" 229 74 — 10 36 „ 36i 219 59 + 2 36i „ 37 221 97 + 18 37 „ 37i 239 59 — 4 371 „ 38 235 57 — 13 38 ., 38i 222 41 + 8 38i „ 39 230 40 — 6 39 „ 391 224 18 + 2 39i „ 40 228 37 — 11 40 „ 40i 217 14 0 There is nothing in this table to confirm that which we had thought would be the main guide to the vital capacity volume ; thus, compare together the first and last 14 men whose chests differ 10 inches, and their vital capacity only 17 inches ; or compare together the first and last columns, the one is perfectly regular and the other most irregular. There is a certain rude relation between the thoracic dimensions and the vital capacity ; if, for in- stance, one man has a chest 35 inches in cir- cumference, and 3 inches mobility, and another man has a chest 40 inches in circumference, and 4 inches mobility, then the latter will surely displace a larger volume of air than the former, but omitting this, we expect as large a vital capacity from a man with a thin and narrow thorax, as from a man with a broad and deep thorax. In fact, aeration need have no re- lation to the thoracic dimension ; and, for the same reason, the size of the chest no relation to the vigour of the whole man. Indeed we incline to the contrary, viz. that it is most likely the respiration is most vigorous in the narrow-chested man, when the mobility is greatest. The vigour of the lungs, like every other organ in the body, we believe, has no relation to the dimensions. One person may have a brain 1 Ib. lighter, or 1 less than an- other person, and yet their capacity and men- tal qualities shall not appear different. 5th. Vital capacity affected by age. — Age affects the breathing movements, but less re- markably than the height and weight. Indeed the influence of age was not apparent in the first calculation upon 1012 cases, nor until we took a basis of 19^3 cases. Time affects life in two ways, first bringing it to perfection, and then determining that perfection. TABLE C C. — Effect of Age, from Observations on 1775 healthy Men. the Height being kept in View. O> u C 'o o . qj • §« >* U c Age. tubic Inches. Cases. oU h. u 01 ^- > «1 .ti «-. oj 0) 1 0 o >£>• 6 15 to 20 20 „ 25 220 220 283 491 341 34 j 220 + 5 25 „ 30 30 „ 35 222 228 347 242 34 1 35 J 225 — 19 35 „ 40 40 „ 45 212 201 171 93 341 35 J 206 — 11 45 „ 50 50 „ 55 197 193 55 37 351 36 j 195 — 13 55 „ 60 60 „ 66 182 183 30 26 361 35 j 182 Mean of all ages 205-8 1775 35 The column of "difference" exhibits the effect of time upon the breathing volumes. From 15 to 35 years of age the vital ca- pacity is increased, and from 35 to 65 years of age it is decreased in the progression of 19, 11, and 13 cubic inches. We illustrate this by a curve mfig. 709. The curve of the vital capacity will be seen to rise slightly as it passes the perpendicular lines of years until it conies to 35 years of age, after which it keeps declining as it cuts all the succeeding lines of quinquennial periods down to 65 years. We may say, therefore, that the vital capacity increases with the age up to 3 z 3 1078 THORAX. Fig. 709. Yp,,, f IS 20 25 30 35 40 45 50 55 « i20 25 30 35 40 45 50 55 60 6i Vital capacity. — The Effect of Age on the Vital Capacity. 30 years, and from 30 to 60 it decreases 43 cubic inches, or 1'43 (nearly 1-J- cubic inches) per year, or 7 cubic inches in 5 years, or 14^ cubic inches in 10 years. Al- though this appears by calculation, yet we do not strictly follow this ratio, as we find by experience that the effect of age may be more diminished, as follows : — TABLE D D. — Vital Capacity at three Periods of Life, from 4800 cases (males). Height. Vital Capa- city. Age from 15 to 55. Vital Capa- city. Age from 55 to 65. Vital Capa- city. Age from 65 to 75. ft. in. ft. in. 5 0 to 5 1 174 163 161 5 1 „ 5 2 182 173 168 5 2 „ 5 3 190 181 175 5 3 „ 5 4 198 188 182 5 4 „ 5 5 206 F96 190 5 5 „ 5 6 214 203 197 5 6 „ 5 7 222 211 204 5 7 „ 5 8 230 219 212 5 8 „ 5 9 238 226 219 5 9 „ 5 10 246 234 226 5 10 „ 5 11 254 242 234 5 11 „ 6 0 262 249 241 From 55 to 65 we have deducted 5 cubic inches per cent, and from 65 to 75 years of age 8 cubic inches per cent. We have not brought in the effect of time before the age of 55 years. This is supposed to be at the mean weight. The first column is derived from observation, the two second are derived from calculation. 6th. Of the effect of disease upon the vital capacity. — The effect of disease upon re- spiration was well known to Boerhaave and Morgagni, they considered that the disturb- ance of any organ in the body would dis- order the whole function of respiration. Morgagni devotes more than one-sixth of his celebrated work, the " Seats and Causes of Disease," " to diseases which affect respiration." We may safely say all thoracic and abdominal diseases, as tumours, abscesses, and acute in- flammations, will affect the respiration. Of the different respiratory volumes, we select that one which requires the most extended mo- bility, viz. the vital capacity, which becomes altered to an extent commensurate with that of any disease physically affecting our respiration, it is therefore a test of the pre- sence and extent of such diseases. Such movements as command this volume, extend from the neck to the plantar muscles of the feet. One condition which we have been accus- tomed to look upon as affecting our breathing, does not affect it, viz. old pleuritic adhesions. Fig. 710. Heights. [Sfl ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in ft. in. !t. in. !t. in. ft. in. ft. in 50 51 52 53 54 55 .56 57 5 8 5 9 5 II) 5 1160 51 5 ii 53 54 55 56 57 58 595 10 5 11 606 + Healthy- Diseased. ^ — • — . — . — — ' -—" __ — — ,--^" \ s „ / \ •*v s xs. e' v"x. / \ / / / \ / /' 13 r VJ If 5 r/ 0 K 7 H 1 K '2 l( ':) 7 1 21 8 U 4 2£ 0 ! 9 22 8 13 5 23 0 11 7 24 1 9 ; 24 ) 13 7 25 J 11 9 27f 1. lOf Vital Capacity of the healthy and diseased Cases compared. THORAX. 1079 We met with a case in which the lungs could not, in consequence of pleuritic adhe- sions, be removed from out of the thorax; in- deed there was not one square inch of pleura which was not firmly adherent. The lungs had to be torn out by little pieces, and so strong was the adhesion to the diaphragm, that in removing them this muscle was ruptured, yet the living respiratory mobility of the thoracic walls exceeded by three inches the whole thoracic space allotted for the heart and lungs, as measured after death. This space to the mobility was as 248 to 251. In other respects the lungs were healthy. Of all diseases, phthisis pulmonalis most readily affects the vital capacity, not only when the lunijs are beginning to be infiltrated o o o with tubercular matter, but probably before this. This is shown in fg. 710. Taking all the cases together, the difference is about 50 per cent. The effect of this disease upon the vital capacity in the case of Freeman was very remarkable. This man came from America in 1842 "trained for a prize fight." He was examined when in his "best condition," and his vital capacity measured 434 cub. in. (temp. 00°) ; height, 6 ft. 1 If in. ; weight, 19st. 5 Ibs. ; circumference of the chest, 47 in.; inspiratory power, 5*0 in. ; expiratory power, 6'5 in. Freeman fought his buttle, and for the sub- sequent two years lived a rambling and dissolute life. In November, 1844, exact!}' two years afterwards, he came to town in ill health. At this time there was no ausculta- tory evidence of phthisis pulmonalis ; but the following difference appeared in his vital capacity-volume : Nov. 1842 - Vital Capacity. Weight. Inspiratory Power. Expiratory Power. cub. in. 434 st. Ibs. J9 5 5-0 6-5 Nov. 1844 - 390 17 5 4-0 5'0 Dec. 1844 - 360 16 0 3-5 4-0 99 320 15 5 — — In October, 1845, he died at the Winches- ter hospital ; and Mr. Paul, surgeon to that charity, stated that Freeman died of extreme exhaustion and debility, expectorating pus ; and that his lung was throughout studded with tubercles ; his weight at death was 10 st. 1 Ib. ; height, 6 ft. 7£ in. Another remark- able case was that of a man of perfectly healthy appearance, and in whom there was no auscultatory or general sign of organic disease, but whose vital capacity was deficient by 47 cub. in.; and it was found, within three days of the time when he was examined, that the left lung at the apex was studded with miliary tubercles, the whole not extending beyond a square inch. In diseases of the spine, particularly in angular curvature, the mobility is changed sometimes to such a degree that the vital capacity is diminished to 20 cub. in. A full meal will even make a difference in the thora- cic mobility, of from 12 to 20 cubic inches. If the vital capacity is deficient, there must be some cause producing the t'ffcct. It may or may not be in the thoracic cavity. Collateral observations must point more definitely to the diseased part. The spirometer is only a gauge to measure the mobility and perme- ability of the lung; other circumstances must point out the cause of the mobility and per- meability being affected. Taking the observa- tions upon the diseased cases by calculation, the vital capacity volume may be arranged for all heights as follows : * TABLE E E, — Effect of Phthisis Pulmonalis upon the Vital Capacity. j- QJ J3 „ & o)2 '- C bo Ot oi 00 . c Height. 1 £ !•?=' --(CO W£ " o. "?5 to •3 O) * >. "" O s — ft. in. ft. in. I 5 0 to 5 1 174 146 117 82 99 5 1 „ 5 2 183 153 122 86 102 5 2 „ 5 3 190 160 127 89 108 5 3 „ 5 4 198 166 133 93 t!3 5 4 „ 5 5 206 173 138 97J 117 5 5 „ 5 6 214 180 143 100 122 5 6 „ 5 7 222 187 149 104 127 5 7 ,,58 230 193 154 108 131 5 8 „ 5 9 238 200 159 112 136 5 9 „ 5 10 246 207 165 116 140 5 10 „ 5 11 254 213 170 119 145 5 11 „ 6 0 262 220 176 123 149 The question naturally arises, How far defi- cient of the standard may be the vital capacity without indicating disease ? It has been found that ten cubic inches below the due quantity, i. e. 220 instead of 230 inches, need not excite alarm ; but there is a point of deficiency in the breathing volume at which it is difficult to say whether it is merely one of those physiological differences dependent on a certain irregularity in all such observations, or deficiency indicative of disease. A deficiency of 16 per cent, is sus- picious. A man below 55 years of age breath- ing 193 cub. in. instead of 230 cub. in., unless he is excessively fat, is probably the subject of disease. In phthisis pulmonalis the deficiency may amount to 90 per cent., and yet life be main- tained. The vital capacity volume is likewise a measure of improvement. A phthisical patient may improve so as to gain 40 upon 220 cub. in. OF THE RESPIRATORY MOVEMENTS. — The breathing volumes have been divided into three kinds ; so likewise the breathing move- ments admit of a similar division, — one ordi- nary and two extraordinary movements. By the independent action of the intercostal muscles, every intercostal lamella can act sepa- rately, therefore we have the thorax furnished with 22 spaces by which it can enlarge; and * See " Spirometer Observations," First Report of tin- Hospital for Consumption, p. 23. ct seq. Loud. 3 z 4 1080 THORAX. the diaphragm acting as one muscle, makes 23 mobile regions for respiration. The respiratory movements of health may be classed as costal and abdominal. The cha- racter should be established by the order in which they follow each other. In health the walls of the thorax and the floor do not dilate simultaneously but consecutively. The character of " the breatliing'" cannot always be told by the eye, but it can always be deter- mined by the touch. If we stand behind a patient, when seated and leaning against the back of the chair or against our person, and pass the right arm over the shoulder, extending it over the anterior part of the chest, until the hand rests upon the abdomen over the umbilical region, we command a delicate index of the breathing movements. It will then be found, that in ordinary male breathing the ab- domen first bulges outwards ; the ribs and sternum nearest the abdomen gently follow this movement, until the motion, like a wave, is lost over the thoracic region. The undu- lation commences at the abdomen. This is aoaomina, or diaphragmatic respiration. We here have costal motion, but as the ribs moved second it is not called costal breathing. In costal breathing the upper ribs move first, and the abdomen second. This is the ordinary breathing in women. All difficult, sudden, and extraordinary breathing is costal ; we at such times direct all our power towards the apex of the thorax, first expanding that region, and gradually those below it. When we determine the order of breathing by the sight, we must be careful to take the position of the body into account. If the pa- tient be recumbent (supine), we may notice extensive costal motion, and, indeed, it may be true costal breathing ; but place the pa- tient erect, and the breathing may be diaphrag- matic. When recumbent, all the motion is thrown forwards, the natural backward and lateral motion of the ribs being prevented ; and so sensitive are the breathing movements to impediments, that they may either take a reverse action, or all the motion being thrown forwards, will give a preternatural movement of the ribs, which may be mistaken for costal respiration. Profile vieiv of the breathing movements — (a) Ordinary breathing (Male). — Fig. 71 1 was obtained by tracing the shadow of a man on paper. The back was fixed, so as to throw all the movement forwards. The anterior black, continuous line represents the ordinary breathing. This line is thicker over the ab- domen than elsewhere. The anterior margin of this line indicates the boundary of the ordi- nary inspiration, and the posterior margin the boundary of the ordinary expiration. (Female). — This is represented by the anterior continuous line \njig.7l2., in the same manner as shown in the male. This line in the female is broadest over the sternum, and narrow over the abdomen. The movement over the abdomen of the female is so small, that the number of the respirations cannot Fig. 711. Respiratory Movements. Male. Deep inspiration, dotted line ; ordinary state, continuous line; deep expiration, anterior margin of the shade. be counted by the hand resting on that region as it can be on the male. The question of why women breathe costal, and men abdo- minal, we cannot pretend to answer. We doubt its being caused by any tight costume, for we found the same to exist in twenty-four girls between the ages of eleven and four- teen, none of whom had ever worn any tight dress. This peculiarity may be a reservation Fig. 712. Respiratory Movements. Female. Inspiration, dotted line. Ordinary, continuous line. Expiration, anterior margin. THORAX. 1081 against the period of gestation, when the ab- domen cannot allow of so free a descent of the diaphragm. Fig. 713. Respiratory Movements. Male, Front view. Inspiration, broken line. Ordinary, continuous line. Expiration, dotted line. The lateral movement of ordinary breathing is too limited to be represented by a line of varying thickness : the position is given by the continuous line,^g.s. 713. and 714. Fig. 714. enlargement of the thoracic cavity in both sexes is made by the ribs, and not by the diaphragm, as is generally believed. It appears very questionable whether the dia- phragm is any thing more than flattened and that without descending. Of the position of the diaphragm. — It is clear that all that space between the line of ordinary breathing and deep inspiration (Jig- 711.), below the ensiform cartilage, where the two lines cut each other, may be considered as just so much space deducted from the abdominal cavity ; and therefore the abdominal cavity, by deep breathing, is just so much less than it was in the posi- tion of ordinary breathing. Now, if the dia- phragm descends at this moment, whilst the abdominal parietes are being constringed on all sides, what becomes of the abdominal vis- cera? We know that in ordinary breathing the abdomen advances because the diaphragm descends, and recedes because the diaphragm ascends. We may suppose the same accom- modating movement between the diaphragm and abdominal parietes, to take place in deep breathing. There can be no doubt that the cir- cumference of the thorax is increased, as shown in D.Jig. 670., and that the diaphragm must extend its borders, and consequently the arch must be flattened ; but this may be without descending. We see (Jig. 670.) that the sec- tion of the thorax to the area of the diaphragm is as 40 to 133 — the concavity of the dia- phragm is enough to admit of its circumfe- rence expanding without its descending. Fig. 715. is a diagram of sections of the base of the living chest in three stages, u is the chest in ordinary : A, as in extreme expiration ; c, as in extreme inspiration. In this case the vital ca- pacity was 305 cubic inches, and the mobility of the chest was 5 inches, a range by no means common. The area of the chest varied 27 superficial inches between extreme inspiration and expiration.* In the sitting posture the same relations Fis. 715. Respiratory Movements. Female. Front view. Inspiration, broken line. Ordinary, continuous line. Expiration, dotted line. (/;) Deep inspiratory* — In Jig. 711. the dotted line shows this position, as when a man is just ready to displace his vital ca- pacity-volume. The sternum is protruded and the abdomen is drawn in. This is the same in the female (Jig. 712.), the dotted line is most advanced over the sternum, while over the abdomen it is drawn inwards. So much is the abdomen drawn in- wards by deep inspiration, that the portion of the continuous line (Jigs. 711, and 712.), representing the ordinary breathing is (over the abdominal region) external to the dotted line of deep inspiration. Therefore the greatest Ordinary 30 inches. Expiration Inspiration 74 inches. 101 inches. Sections of the base of thorax in the three stages of respiration, in t/ie living subject. * This is the chest of Jig. 711. 1082 THORAX. exist in the breathing movements ; the only difference being that these movements are more limited. (c) Of the deep expiratory position. — In figs. 711. and 712. the margin of the shade is the position of the thoracic boundaries in deep expiration. We have supposed the figures above men- tioned as standing with the back fixed, for the purpose of making clearly manifest the relative position of these several breathing movements, \nfig. 716. the body is quite free, and wholly alters its position in performing expiration and inspiration. This should al- ways be considered in noticing the breathing movements in diagnosis. Fig. 716. Respiratory Movements. Male, standing. Expiration, dotted line. Inspiration, continuous line. (rf) Of the change of position by extreme breathing. — In expiration the head is pro- truded and lowered (see Jigs. 713. and 714.). Therefore, by inspiration the body is raised, and the more erect the more can be inspired ; by expiration it is lowered, so much so that we have seen men when displacing their vital capacity volume stoop themselves to one-half their natural height, to one-sixth frequently : we speak from a large number of cases, — nearly 4000. Physiologists have reasoned that, as upon the principle of a bladder becom- ing longer when empty than when inflated, so the chest is shorter when inflated than when empty. But this example in no way corresponds. The bladder expands, because it is inflated ; the chest is inflated because it expands. We have given the position of the breath- ing parts (the body fixed) : we shall describe the movement of these parts relatively in time and order to each other, and " the peculiar character of these movements in health, and some of their modifications by disease. Ordinary breathing. — In men this is sym- metrical, and very limited, and commences with an advancing and receding of the abdo- men at and above the umbilical region, accom- panied with a slight lateral enlargement, and immediately followed by a bulging outwards at the cartilages of the 7th, 8th, 9th, and 10th ribs, and that part of the abdomen contiguous to them, with a slight advance of the lower third of the sternum. This is abdominal breathing, because the abdomen moves first ; and is confined to motion of the base of the thorax. In women it is likewise symmetrical, commencing with a gentle heaving of the upper part of the thorax, more or less apparent ac- cording to the fulness of the mammae. This expansion commences with the 1st and next three ribs following each other in succession, accompanied with a slight elevation of the shoulders and a slight lateral enlargement of the chest, which is immediately followed by a bulging outwards of the abdomen. So quick is this motion of the diaphragm after the mo- tion of the ribs, that at times they appear to be synchronous, especially when the individual examined is .conscious of the observation, though it is only an accommodating movement of the diaphragm. This is costal breathing, because the ribs move first, and the motion is chiefly confined to the apex of the thorax. Therefore that which is a healthy respiratory movement in women is pathological in men. Of the extraordinary breathing in both sexes {Inspiration). — This, like ordinary breathing, is symmetrical: the clavicles, shoulders, sca- pula, and superior ribs are raised, the sternum advances, the infra-clavicular region swells re- markably upwards and outwards (particularly in females) like a rolling wave, the supra-cla- vicular region is raised but this sometimes ap- pears comparatively deepened (merely bv the action of the sterno-cleido-mastoideus), the whole apex of the thorax is rendered more ob- tuse, particularly in the antero-posterior dia- meter. The lower ribs, at their cartilaginous extremities, spread outwards, increasing both the lateral and the antero-posterior diameter of the base of the thorax, the cartilaginous (go- thic) arch formed by the junction of the 6th, 7t,h. 8th, 9th, and 10th ribs below the sternum, becomes more obtuse by their lateral motion, the abdominal space within this arch, down to the umbilicus, sinks inwards. Therefore this breathing is costal, commencing with the superior ribs, and terminating over the ab- domen. The peculiar character of healthy breathing (and it is impossible to lay too much stress upon the movements of deep inspira- tion, because they are so indicative of thoracic disease) is that the ribs expand in succession. There is an indescribable undulating roll, pro- duced by the consecutive action of the re- spective ribs, which always commences with a superior rib ; — in costal breathing, a lower THORAX. 1083 rib never moves first. In fact when we inspire deeply we feel as if we directed all our power to the four or five superior ribs, giving the greatest expansion to the very apex of the lungs, — that most vulnerable part in phthisis piilmonalis. When we look at the thoracic cavity we see why this great power and mo- bility is given to the upper part of the chest. We see that the six superior ribs encompass more space than the six inferior ribs. (See fig. 668.) So that where we command most movement, there is the greatest portion ot" lung to be expanded. The hand can measure most delicately this healthy characteristic swelling or fi lling up of the apex better than any instrument, because the band covers a large field oi the chest, and can distinguish the undulating movement. Standing behind the person to be examined, the fingers of both hands should be placed over the clavicles, so that the tips rest on the infra-clavicular regions, and the thumbs over the inner borders of the scapulae. When a deep inspiration is taken the fingers and thumb of each hand diverge from each other, and we thus gain a perfect knowledge of the healthy "swelling expansion." If the deep respiratory movement is good, the ordinary movement is sure to be good likewise. The mere flat hand on the anterior and upper part of the chest (facing the patient) will likewise give the character, though less delicately. This movement or swelling of the apex by deep inspiration, is more distinctly marked on the female than on the male subject. If this fine swelling motion in deep breathing is absent disease is present. Pathological respiratory movements. — We now speak of another class of breathing move- ments, which are peculiar in this respect, that the "undulating swell" of the chest is wanting. The twelve intercostal mus- cles move in every combination, as if to meet impending difficulties, — tenacious of life, and yielding only by compulsion to the ad- vance of disease. Throughout the long list of diseases which attack man these instinctive movements have to contend, — shifting about, or growing less and less. We have noticed a man with lung disease, commence with costal respiration of the lower ribs, and, as disease advanced, he breathed with ribs higher and higher up, so that at last he said, " I breathe with my neck;" and in truth it appeared so. His 1st, 2nd, and 3rd ribs only appeared to move. He passed through almost every variety of respiration before he died. The breathing movements are quick to change, and the inquiry is interesting, what causes the change ? One great cause is the existence of dyspnoea, a disproportion between . the air passages and the volume of air to be displaced, which may be caused by an obli- terated state of lung, by tubercles, fluid in the pleurae, hypertrophy of the heart, aneu- rism of the great blood vessels, tumours of various kinds, the pain of local inflammation, pressure from the abdomen, whether ascites, obesity, distended stomach, gravid uterus, or any morbid growth bordering on the thoracic cavity, or lesion of nervous integrity'requisite for maintaining the respiratory movements. Such conditions of themselves would oc- casion deranged breathing movements. But again there are reasons for thinking that these movements may be changed from other causes not so purely physical ; because sometimes no dyspnoea is to be perceived, and yet the movements are deranged, or they may change backwards and forwards as if aerating specific portions of the lungs, acting as a curative re- medy to some incipient form of lung disease. In complicated diseases of the chest a know- ledge of the breathing movements is highly useful. There is one condition in the "res- piratory act, which is indicative of a certain state of chest, which, if not useful as a po- sitive, is at least so as a negative evidence of some existing state of things in the lungs. The condition we allude to is a sinking in and bulging out of portions of integuments which cover the thoracic cavity. If we close both nostrils and make a violent inspiratoiy effort, the integuments between the sterno- cleido-mastoidei immediately above the ster- num, will be seen to sink inward from atmo- spheric pressure. If we open one nostril, the same is less apparent. If both are open and the passages are free, it is not perceptible. In expiration (with the same obstruction) there is a bulging outwards of these integu- ments. Sometimes, particularly in thin per- sons, this may be seen on the integuments covering the intercostal spaces. This sinking inwards is an evidence of attenuated air, and the bulging outwards of condensed air in the lungs, near to the part. It is therefore an evi- dence of some obstruction in the air passage. Difficult breathing may be attended with this feature, or not ; therefore it is an evi- dence of something existing in one state of dyspnoea which does not exist in another. Dyspnoea without this " sinking or bulging" is a proof that there is no obstruction between the air cells and the external air. But, on the contrary, dyspnoea with this " sinking and bulging," is a proof that there exists some obstruction either as a direct diminution in caliber of the air tube, or that more air is drawn through certain tubes than is natural; that this obstruction must have air on both sides of it, and that the air on one side is more attenuated than on the other. For instance, when an aneurism on one of the large vessels of a well-developed chest is pressing upon one of the large bronchi, the respira- tory sounds, and those elicited by percussion, may be good, but respiration becomes la- boured,— the case is obscure, but if there is alternate sinking and fulness of the lower part of the throat, we may be sure that there is some definite obstruction in the air passages. This, in connection with the history of the case, may lead to the detection of the cause and seat of the disease ; but dyspnoea without this feature could not be caused by an aneurism or tumour. In emphysema of the lung this sinking and bulging is very manifest. This circumstance 1084 THORAX. proves simply that there is air in the chest of different density to the external air ; and if so, there must be some impediment in the air tubes, preventing the restoration of at- mospheric equilibrium. Disease of the thoracic viscera affects the breathing movements, causing them to be more limited, or non-symmetrical, reversed, massive, interrupted, partial, quick, slow, ir- regular, or double. (a) Of limited breathing movement. — The mobility of parts when disease attacks the chest may be surprisingly drawn forth. Haller allows scarcely any mobility to the first rib; Magendie asserts that the lower ribs are immovable, because they either reasoned from the healthy body, or anatomically : but it is not uncommon in phthisical patients to see strong and well-marked respiration kept up by the 1st, 2nd, and 3rd ribs, or by the 10th, llth and 12th; — these ribs are movable, but it requires disease to bring their mo- bility forth. We are satisfied that there is a latent respiratory mobility during health, which is manifested only by disease. In disease particular parts take up ex- aggerated movements, but the sum of these movements is more limited than in health. In the earliest cognisable stage of phthisis pulmonalis the expansion of the thoracic apex is diminished ; the shoulders incline forwards and inwards, and become rounded j the spine is less erect ; the apex cannot ex- pand. The mobility of the inferior ribs does not so diminish, but sometimes maintains life to the last. With an exaggerated move- ment, the respiration is frequently costal and abdominal at the same time, as if no part could afford to be unemployed. In 233 cases of phthisis pulmonalis (males) in the first stage we noticed that the breathing of 46 was costal, of 96 abdominal, and of 91 costal and abdominal. The mobility by tape measure was, instead of 3 inches and upwards, as follows' — TABLE F F. — Diminished Mobility over the Nipples on '23:3 Phthisical Males. Difference between Inspiration and Expiration. Number of cases. iin. - 3 f 5 1 ... 54 H ... 13 i| ... 44 2 ... 53 2* 12 2J - - - 25 1 (b) Qf non-symmetrical brcatliing move- ments. — In advanced stages of phthisis pul- monalis non-symmetrical movements are no- ticed ; but this may exist without a cavity or effusion of fluid in the lung ; or a cavity may exist with symmetrical movements (but a cavity never exists without extensive dimi- nution of mobility). Generally a cavity is at- tended with non-symmetrical movements, or a dragging up of one side of the chest; and in extreme cases there is no movement at all in the region of the cavity. That symmetrical movements may coexist with extensive disor- ganisation or solidification of one lung is con- trary to the opinion of many persons. It may be explained by the fact of our having so much spare lung. It has been found by experiment that 310 cubic inches of air could be forced into the lungs taken from a man with a healthy chest (height, 5 feet 4 inches ; weight, 107 Ibs. ; vital capacity, 198 cubic inches), the absolute capacity of whose thorax at death, was 245 cubic inches : therefore there was spare lung for more than 100 cubic inches — a space which he could not command during life. May it not be possible that when a part of the lung is consolidated or disabled, this spare portion may come more completely into use, and allow of the symmetrical movement ? (c) Of reversed breathing movements. — A man's breathing may be costal or abdominal for a month, a week, a day, an hour, a minute, and change again, — every possible alternation may occur. This may take place with or without a cavity in the lungs, with or without phthisis pulmonalis, as if a specific motion drew in air to certain parts of the lungs to excite some local change of condition. Al- though costal respiration is maintained at a greater expense of vital force, yet we see when the vital power is fast ebbing the re- spiration is always costal, and the last breath is a deep costal inspiration followed by the last expiration. (d) Of massive breathing movements. — Massive breathing is a marked feature of the presence of emphysema in the lungs. There is a total absence of that undulating, rolling, and consecutive motion of the ribs. The breathing is always costal, though it may be conjoined with abdominal breathing, and the ribs are elevated in the mass, sometimes together with the shoulders clavicle and sca- pula. Massive costal breathing is indicative of emphysema of the lungs or pneumo- thorax. In all other forms of dyspnoea the undulating movement is more or less pre- sent, though limited. (e) Of interrupted breathing movements. — In those diseases termed " nervous," parti- cularly in young women, the breathing, espe- cially the expiration, is sometimes interrupted and jerking. This appears to be merely a functional derangement ; it may sound to the ear like deficient respiration, for the intensity of the " murmur" is generally diminished, as if the jerking "eased away" the expiring air. This is sometimes the case in men. It is very seldom combined with organic disease of the lungs. (f ) Of partial breathing movements. — By this we mean independent movement of cer- tain ribs, or of some two or three of the res- piratory regions. All the ribs may move as in emphyscmatous breathing, or none of them may move, or the lower, the upper, or the THORAX. 1085 intermediate set may maintain the respiratory function. Anclral observes, " The partial immobility of the ribs is not without interest in a physio- logical point of view. Does not this fact prove that, in inspiration, the ribs can move independently of each other, and that they have not merely a common movement ? If," says he, " as we have often seen in phthisical patients, the lower ribs can still move when the upper ones remain motionless, it proves that independently of the action of the scaleni, the intercostal muscles are capable of taking, an active part in the act of respiration."* In this way respiration may be separately car- ried on by any of the twelve costal regions. We have seen a man ill of rheumatism, lying on his back, breathe solely with the diaphragm, and not present the slightest motion of any one of the ribs. And we have seen the con- trary, viz., costal breathing, without the slightest movement of the diaphragm. They can act quite independently of each other. (g) Of quick and slow breathing move- ments. — Not only thoracic disease, but most ill nesses, particularly febrile conditions, quicken the respiration. In health the number of respi- rations average twenty per minute (TABLE G G), and it has been found that in 244 phthisical cases (males), the average number was from twenty-four to twenty-eight per minute (sitting)" (TABLE II), the highest number was forty-four per minute. There is every reason to believe that the che- mical quality of expired air is the same whether we are in health or in advanced disease, though our requirements at these two times may be very different ; just as the quality of smoke from a fire is the same whether it burns briskly or slowly. — The quality is con- stant, and the required modifications are ob- tained by the difference of quantity in a given time. Quick breathing is short, and slow breathing is long, respiration. The natural time of breathing may change by habit. We have seen a man in health, whose ordinary respirations were six per minute. This extra- ordinary slowness was induced by an attack of asthma, during which attack (lasting about six years), his character of breathing changed from eighteen short, to six long and deep, respirations per minute ; though the asthma entirely left him the character of the re- spiration remained as first changed by the dyspnoea. In this case the return of eighteen respirations per minute, would be to him the rapid respiration of fever, although formerly the respiration of health. Time and volume, in respiration, are the great modifiers of the energy of aeration. (h) Irregular breathing. — Irregular breath- ing movements are less common when organic disease is present. A nervous person, as well as a phthisical person, may have every form of irregular breathing, but in the phthisical per- son the change is less frequent, and is probably due to some change in the disease ; in the * Andral, Cliiiiquc Me'dicale, torn. iv. 3d ed. 8vo. Paris, ISU-i. nervous person the change is frequent, some- times once or twice during an examination of the chest, Nervous breathing is generally well marked in hysteria. (i) Double breathing. — By this is meant cos- tal and diaphragmatic breathing synchronous with each other ; this is not uncommon in severe cases of emphysema, when the mobility of the ribs is much diminished. It is fre- quently met with in phthisis pulmonalis ; — in ninety-one cases out of 233. We have no voluntary power to command this form of breathing in health. It is to be looked upon as a serious modification of respira- tion. All the modifications of the respira- tory movements, induced by disease, may return to healthy breathing again, if the derangement has not been kept up too long. As a general rule, the respiratory movements become natural soon after restoration of the diseased parts to health. Of the number of respirations in a given time. — The ordinary respirations should be counted without the individual being con- scious of the observation ; otherwise they be- come disturbed in number, and sometimes in character. TABLE GG Number of Respirationsper Minute (sitting) in 1897 males. Respirations per minute. From 9 to 16 16 17 ... 18 19 20 21 22 23 24 24 to 40 Number of cases. 79 239 105 195 74 561 129 143 42 243 87 Out of 1897 cases, 1731 of them breathed from sixteen to twenty-four times, and nearly one-third of them twenty times a minute. The mean relative velocity of the breathing and the pulse is about one respiration to four pulsations of the heart (twenty to eighty), and the variation in health in the number of respirations is from sixteen to twenty-four, and of the pulse from sixty-four to eighty- eight per minute. TABLE H H. — Relation between the Respiration and the Pulse (sitting) 1407 males. Number of Respirations per Minute. Pulse. Number of Cases. 16 - - 64 - - 218 17 - - 82 - - 102 18 - - 70 - - 176 20 - - 82 - - 546 22 - - 83 - - 135 24 - - 88 - - 230 From TABLE I I, phthisis pulmonalis in- creases the velocity of the breathing move- ments from twenty (the healthy mean) to twenty-eight, and cases are numerous up to thirty-six respirations per minute. 1086 THORAX. TABLE II. — Number of Respirations, of 255 Phthisical Patients, per Minute (sitting). Respirations per Minute. Number of Cases. 12 to 14 41 41 14 „ 16 0 J 1 16 „ 18 ,. IS 20 - 131 - 4J 17j 21 20 „ 22 „ 24 „ 26 „ 22 26 28 I ft} - 491 6J 551 55J 110 28 „ 30 „ 32 „ 34 „ 30 32 34 36 - 391 • 3j n 42 J 90 36 „ 38 16 1 171 171 38 „ 40 1 J 40 „ 42 1 1 17J 34 4-2 „ 44 * J, I j A sudden change in atmospheric pressure affects the number of breathing movements in a given time. We found the following limited but sudden increase of atmospheric pressure increase them as follows. In South- Hetton coal-mine in the county of Durham, — Depth of the mine 1488 feet. Bavom. Thermom. At the level of the sea 28'72 - - 39° At the bottom of the mine 30-26 - - 49° Difference 1-54 10C The additional pressure of the ^ of an atmosphere increased the ordinary breathing from one to three times per minute. This difference was purely the effect of pressure, and not that of fatigue or mental emotion. It might only be temporary. Aeronauts inform us that diminished pres- TABLE KK. — Effect of increased Atmospheric Pressure on the "ordinary" Respirations upon six healthy men. ON THE SURFACE. IN THE MINE. Respira Respira- Pulse. tions. Pulse. tions. M. P. 56 15 50 16 — S. 98 20 98 24 — H. 72 16 68 19 — L. 90 14 88 15 — W. 89 185 93 22 — T. 85 18 100 20 Mean - 83 16-9 84-3 19-3 sure increases the number of respirations ; but with them there is this difference, that with diminished pressure there is a sensation of a want of air. When the barometer is low •we feel lassitude, and call the " day heavy," when in truth the air is lighter, and we ourselves are heavier ; -when the barometer is high, we o-enerally experience an indescribable sensation of pleasure — the vital energies seem doubled. With a sudden and considerable fall of the barometer there is a transient plethora. The blood-vessels become distended, owing to which, together with certain hygrometric changes in the air, we feel listless, and the least exertion produces perspiration. Du- hamel observed that, in the month of De- cember, 1747, the barometer in less than two clays fell 1^ in., producing a change of pressure on the body of a man, of 1400 Ibs. ; this he ob- serves was accompanied with many sudden deaths. It is evident that with an increased pressure we get more air into the lungs with a given mobility; for, cceteris paribus, air, with the barometer at 30 in. must be more dense than the same air with the barometer at 29 in. In the mine in question, we experienced a sensa- tion of lightness and vigour. The number of respirations are always increased when there is a preternatural increase in the temperature of the body. OF THE SOUNDS OF RESPIRATION. — The breaking up of the air into minute streams was discovered by Laennec to produce certain sounds, named "breathing sounds:" which sounds are now made available in detecting organic disease in the lungs. As the air penetrates the lungs, it is divided and sub- divided until it enters the minute air vesi- cles. The air passes, 1st, through the trachea, producing " tracheal sounds," — a hollow rough blowing ; 2nd, through the next divi- sion of vessels (bronchial), producing " bron- chial sounds," less hollow and termed " whiff- ing or tubular ;" and, 3rd, into the air vesicles, producing " vesicular sound," — a soft, silky murmur like a gentle breeze among the leaves of trees. Dr. Jackson discovered that which Laennec overlooked : — this murmur is not heard in expiration, while the other two sounds are. Hence the expiratory murmur is a morbid sign, and if heard on the left side below the acromial end of the clavicle, is a sure sign of some altered condition of the air tubes, not compatible with a healthy lung. This expiratory mur- mur may sometimes be heard faintly on the right side, and not be a morbid sound ; but if strongly heard there, it is a morbid sign. A question now arises : Why is there a murmur- ing sound with inspiration and not with expira- tion ? First, let us inquire what is the dif- ference between the inspiratory and the expiratory act ? They differ in two ways : 1st. In Inspiration the lungs are passive ; the chest threatens a vacuum, and the air enters a rarefied space. In Expiration the lungs are active ; there is no rarefied space ; the air is squeezed out into the atmosphere. This does not affect our question. 2diy. In Inspiration a volume of air is broken up into smaller and smaller streams. In Expiration these small streams are collected up into the original volume by larger and larger streams. This answers the question. The hollow blowing sound in the trachea is caused by the friction of the air against the sides of the tube. The relation of the friction THORAX. 1087 to the stream is the same whether the air passes into or out of the lungs, therefore the tra- cheal sounds are equally heard in expiration and in inspiration. But not so in the lungs ; here, as the stream of air proceeds it is subdivided, and with every subdivision the friction is increased ; so that with every advance of the stream into the substance of the lung the sound is increased, and becom- ing more and more buried in the substance of the lung is heard as in a continual murmur. In expiration the very contrary happens. The friction is as quickly diminished, until the substance of the lung entirely masks what remains. In the larger vessels when the volume of the returning air becomes great, and the diameter of the tube more uniform, the friction is the same whichever way the air passes, and here tracheal and bronchial ex- piration are audible, during inspiration as well as expiration. If we take a sheep's lung and inflate it, we hear the inspiratory murmur ; let go the air and we do not hear it ; but contract part of the lung, say with the edge of a paper knife, and you hear the mur- mur during the lung's collapsing, showing that by increasing the friction you produce the expiratory murmur. When any disease thickens or diminishes the diameter of the air tubes, or when one part of the lung is obliterated and another part has to do double work, then the friction is increased, and thus expiratory murmur is a true sign of some change in the minute air tubes of the lungs. Sometimes the breathing murmur is so gentle and the thickness of the muscles so great that we have even in health known the inspiratory murmur quite inaudible. In organic change of the lung these sounds become changed in their intensity, rhythm, and character. The cause of the change of sound is yet involved in much obscurity ; hence some persons have been said to have had tubercular lungs, when such has not been the case; or even extensive cavities, &c., yetstime has shown that there never had been cavities. All the morbid true sounds yet require to be verified as to their cause. As we have natural changes in the character of breathing, so are there changes in the sounds of breathing, as follows : — I. IN ITS INTENSITY II. IN ITS RHYTHM 1. Frequency 2. Duration III. IN ITS CHARACTER When there is fluid or disorganisation in the substance of the lung, there are certain crack- lings, crepitations, and gurglings, causing certain other sounds not included in the above list. Unfortunately authors differ in the ap- plication of the names for these sounds. They may be all classed under two heads, the dry and the moist, whether the tubes be large or small in which the sounds are pro- duced. For the BIBLIOGRAPHY see that of art. " RESPIRATION," p. 3G6. (J. Hutchinson.) THYMUS GLAND.— (French, Lc thynnis; Italian, Timo; German, Die Bntstdnise ; Lat., Thymus; Greek, eiyicH-. )— It is proposed in this article to adopt the following arrange- ment : First, to treat of the gland as it exists in the human subject, comprehending its ordi- nary and structural anatomy, and its develop- ment. Secondly, to give a sketch of the comparative anatomical history of the organ. Thirdly, to treat of its physiology. Fourthly, to mention what has been observed of morbid changes occurring in it. HUMAN ANATOMY. — Sir A. Cooper's de- scription of the gland in t.he human subject is as f Strong or exaggerated. j Feeble. I Absent or suppressed. f Quick. \ Slow. Jerking or interrupted. Long. Short. Expiration prolonged. Harsh. Bronchial or tubular. Cavernous. Amphoric. follows: — "This gland is formed of a tho- racic and cervical portion on each side. The former is situated in the anterior mediastinum, and the latter is placed in the neck, just above the first bone of the sternum, and behind the sterno-hyoidei and sterno-thyroiclei muscles." " .Between two and three months of foetal life, as will be seen in the plate (fig- 717.), it is so Fig. 717. Ttte thymits, heart, lanjnx, §•<;., of the human fatug at rather more than two months. {After Sir A. Cooper.) small as to be but just perceptible. At three months (Jig. 718.) its increase is in propor- tion to the relative magnitude of the foetus, and thus it continues to grow gradually and equally (fig. 719.) to the seventh month, when it en- larges out of proportion to its former growth. At'eiglit months it is large, but at the ninth 1088 THYMUS GLAND. Fig. 718. Thymus, §• consisting of coarse granular matter not surrounded by any distinct envelope, and of an opaque dead white colour. These were perhaps ab- normal formations ; yet in a tortoise, where the gland was quite healthy, similar corpuscles, and more numerous, were observed. The clear fluid material, contained within the glandular cavities, is generally spoken of as of an albuminous nature. This opinion seems con- firmed by two analyses of the gland, made by my friend Mr. Beale, which may be regarded (lifter allowance is made for the areolar tissue, vessels, envelopes, and epithelium) as express- ing pretty correctly the chemical nature of the secretion which forms so large a part of the whole bulk. These analyses I will presently quote, but will first detail a few observations of my own, as to the effects of certain re- agents on the fluid in question. Liq. Potasses, added to a thin section pre- pared for the microscope, rendered it much more transparent, partially dissolving the epi- thelium, and leaving a quantity of oily matter diffused throughout it. Acetic acid now added to the specimen pretty nearly restored it to its former appearance, but did not bring into view any precipitated protein. Acetic acid, alone, dissolves in part the epithelium of the vesicles, and renders the fibrous tissue more transparent. Liq. Ammonite dissolves the epithelium in great part, but does not alter the transparent contents of the cavities ; nor does liq. potassa? or acetic acid. Solution of iodine does not materially affect the epithe- lium of the cavities, but renders it more opaque. Strong nitric acid at first renders the epithelium more opaque and granular, but does not manifestly affect the contained secretion. After a time it colours this material bright green or yellowish green, and disengages a great many bubbles of gas. A saturated solution of bichloride of mercury, even after long maceration, does not seem materially to affect the secreted contents of the vesicles ; it makes their peripheral stratum of epithelium quite opaque ; but the interior still appears transparent and glistening. The chief conclusion deducible from the above results is, that the secreted material of the o-landular cavities of the thyroid is not ordinary fluid albumen ; as otherwise it would certainly be coagulated by the agents em- ployed. The effect produced by nitric acid is also worthy of notice, though I cannot ex- plain the meaning of it. Analysis of thyroid gland. Human. Ox. Water - - - 70'6 71'3* Solid matter - - 29'4 28'66 Solid matter. Animal (fibrinous and albuminous) matter, Human. vessels and fat - - 26-384- Extractive matter Extractive matter gelatine Alkaline salts Earthy salts - 1"7 with Ox. 24--G28 2-888 0-642 0-502 29-400 28-660 100 100 The analyses given above testify to the presence of a large quantity of fibrinous and albuminous matters in the gland, and leave no doubt that its secretion is a protein com- pound; it is, however, unfortunately impos- sible to procure a sufficient quantity apart from other substances to analyze correctly ; and the exact nature of the thyroideal secre- tion consequently still remains unknown. Thus much, however, seems to be ascertained, or rendered very probable. (1) That the secreted material is of an albuminoid nature. (2) That it is not in the state of ordinary fluid albumen. (3) That gelatine is sometimes an ingredient of the secretion ; (it was found in the gland of an ox, but not in that of the human subject, and consequently could not have been derived from the fibrous tissue). (4) That though crystals of triple phosphate and of oxalate of lime occur in the cavities, no urea nor lithic acid, nor in fact any special organic compound, can be detected.* Vessels. — The vascular supply of the thy- roid is very abundant, and completely justifies Cruveilhier's opinion, that more than a mere process of nutrition is carried on in the gland. The arteries which are distributed chiefly to this organ are very constant in their number, and tolerably so I think in their respective dimensions, though in this respect they vary inversely with regard to each other. They ordinarily arise, as has been well remarked by Mr. Simon, just beyond the points where the arteries to the brain are given off from the large trunks, — a circumstance which he con- ceives to be very significant of the function of the gland which they supply; — the two superior thyroideal arising one on each side from the external carotids, almost immediately after the bifurcation of the common carotids, and the inferior thyroideals from the intra- scalenal portion of the subclavian, almost opposite the point where the vertebrals are given off. A fifth thyroideal artery occa- sionally exists, — that named after Venbauer; taking "its origin from the arch of the aorta or t\\earter. innominata. The superior thyroid not unfrequently takes origin a little lower down from the division of the common carotid, or even from its trunk ; or it may arise higher up from a common trunk with the lingual. It courses first forward and inward, when it is * I would not omit to express here my obligations to Mr. Beale for undertaking the analyses, and for the care and skill with which he has performed them. THYROID GLAND. 1,07 covered only by the deep fascia and platysma ; but it soon turns vertically downwards, and runs beneath the sub-hyoidean muscles to the upper extremity of the gland, where it divides into three branches; one of these runs be- tween the thyroid gland and the trachea, a second skirts the external border of the lateral lobe, while the third, running along the inter- nal border, forms an anastomosis with the cor- responding branch of the opposite side. The inferior thyroid is noticed by Cruveil- hier as one of the arterial branches most liable to vary in its origin, — an opinion which, emanating from a less high authority, I should have been inclined to question. It may arise, acccording to him, from the common carotid, the arch of the aorta, or the arlcria iiinmmn- fitn. (The supra-scapular often, less commonly the posterior scapular, and sometimes even the internal mammary, spring from the com- mencement of the inferior thyroid, which is therefore called the thyroid axis.) Its course is peculiar ; it runs at first straight upwards, then comes downward, and again ascends to reach the inferior extremity of the lateral lobe of the gland. It passes in front of the trachea, and behind the great vessels and vagus nerve : the connecting cord of the sympathetic descends behind it to the middle cervical ganglion when it exists, which is then almost constantly found, as it were, seated astride upon the vessel, exactly on the convexity of its first curve. Like the superior thyroid, it has three terminal branches, one running along the in- ferior border of the gland, another breaking up over the posterior face of the lateral lobe, and a third which penetrates between the gland and the trachea, and anastomoses with the one of the opposite side along the upper border of the isthmus. (Cruveilhier). The capillary plexus, in which the minute branches of these arteries terminate, is dis- posed in the form of hollow spheres around the glandular cavities, closely applied upon the limitary membrane and forming a continuous network throughout the gland. It is tolera- bly close-meshed, but not nearly so much so as that of the liver or kidney. The diameter of the capillaries, in a recent injected specimen, varied from ^_^i-L- inch, and the interspaces were, I think, two or three times as large. There are corresponding vence comites to the superior and inferior thyroideal arteries. The superior thyroid or thyro-laryngeal returns its blood either into the internal jugular vein, or into the common trunk of the facial and lingual, before it joins either of the jugulars. The middle thyroideal runs down and turns aside, crossing the common carotid to enter the internal jugular. Besides these there exist constantly another pair of veins, which run down in front of the trachea involved in the deepest layer of cervical fascia, and terminate either by opening both into the vena transvcrsa, or the left into this trunk, and the right into the junction of it with the right brachio-cephalic. These veins run down, gradually diverging from each other ; so that, from being at their origin no more than one third of an inch apart, they are separated at the lower part of their course by an interval of about an inch, or rather more. In this situation they are often united by a transverse branch, and are said, by Cruveilhier, to form, with the tracheal and laryngeal veins proceeding to unite with them, a considerable plexus, which it is impossible to avoid in the operation of tracheotomy. These veins correspond in some measure with the thyroideal artery of Venbauer, but are much more constant, and are sometimes three or four in number; so that the blood they re- turn is not proportioned to that conveyed by the arteiy. The lymphatics, originating probably in a closed network, proceed to enter the deep cervical glands. They may sometimes be seen filled with a concrete albuminous substance, which they have probably taken up from the glandular cavities. Nerves. — The recurrent laryngeal, shortly before it passes under the margin of the in- ferior constrictor muscle of the pharynx, gives off some filaments to the thyroid gland ; some are also furnished by the external laryngeal ; while a plexus, derived from the middle cervical ganglion, proceeds along the inferior thyroid artery, and is distributed to the gland along with its branches, forming communications with the preceding. In thin sections of the thyroid treated with acetic acid, I have seen the nucleated bands of the sympathetic, con- taining one or two caclio-spinal tubules, running for some distance in the interspaces of the vesicles ; they probably terminate by forming a looping plexus ; but I have not been able to ascertain anything certain on this head respecting either these or the tubular fibres. Development. — The thyroid is said by Cruveilhier to be developed by two lateral halves, which are subsequently united by means of the isthmus. This statement seems to be confirmed by the condition of the gland in several of the lower animals, where the lateral lobes continue separate, lying on each side of the trachea ; and is also supported by the occasional occurrence of a similar dispo- sition in the human subject. In my own researches it has not occurred to me to observe this mode of development, perhaps because I have not examined spe- cimens at a sufficiently early period ; however, in an embryonic sheep only two inches long, where the thyroid was distinctly visible, it presented the usual appearance — the lateral lobes being connected by a narrow isthmus ; the same was the case in a human foetus of 4>£ months ; the isthmus, however, being wider, and not appearing to be of at all more recent development than the lateral lobes. In the embryo of the sheep just mentioned, the gland was of an opaque whitish aspect, differing materially from its natural reddish colour ; it consisted principally of nuclei, with a small quantity of granular matter. Scarce any trace of a vesicular arrangement existed ; but the whole mass was surrounded by an investing membrane very nearly homo- geneous in texture. In another embryonic 4u 2 1108 THYROID GLAND. sheep, three inches long, the thyroid was much more of its natural reddish, semi-trans- lucent colour ; still there was scarcely any vesicular arrangement, the mass consisting almost entirely of nuclei aggregated together. The thyroid of the human foetus just men- tioned was of the same grayish aspect, as that of the smallest of the embryonic sheep. It also consisted chiefly of nuclei, but these were to some extent collected together so as to form solid globular masses (fig. 74 1.), not Fig. 74-1. Incipient vesicle from thyroid of human fcetus, at about mid-period. It is a solid mass of iiuclei, not enclosed in a distinct envelope. yet, however, quite definitely isolated, nor surrounded by homogeneous envelopes. This, however, seems to be the way in which the vesicular cavities are developed ; the limitary envelopes being formed around the primitive nuclei, which assume the arrangement of epi- thelium. The thyroid is of larger relative magnitude during intra-uterine existence and infancy than in after life, — a fact which seems rather opposed to the view which regards this gland as alternating its action with that of the brain. COMPARATIVE ANATOMY OF THYROID. — The existence of a thyroid gland in all the Mam- malian orders seems to be undoubted ; and though it is probable that, by a close and ex- tended survey of the various families, some interesting and perhaps instructive peculiarities might be detected, yet I have not the oppor- tunities necessary for undertaking such an inquiry, and can only record one observation where some deviation from the ordinary con- dition was discovered. This was in a Rabbit, in which the organ presented the vesicular arrangement much less manifestly than is usually the case. The epithelium consisted of small imperfect celloid particles, disposed so as to form hollow spheres ; but there was scarce any appearance of secretion in the included cavities, which were small, and might at first have escaped observation. For the following summary of the compa- rative anatomy of the thyroid in birds and rep- tiles, I am principally indebted to Mr. Simon's paper in the Philosophical Transactions. In Birds, there are found, in all the va- rious orders, two glands, situated one on each side of the trachea, very near the lower larynx, and frequently attached to the jugular veins. They possess the characteristic struc- ture of the thyroid body, consisting of a dense aggregation of closed vesicles, which contain a kind of epithelium, and are invested by a close capillary network applied over their homogeneous envelope. The position of these glands with respect to the larynx seems to be neither essential nor constant ; it is however stated by Mr. Simon, that it " always corre- sponds to a particular spot of the vascular system, viz., that it lies on the cervical vessels, and receives its supply of blood just opposite to the point at which the vertebral or carotid arteries diverge to their respective destina- tions." The following are the details of a mi- croscopic examination which I made of these glands in a Pigeon. They consist of closed vesicles about" ^^ inch diameter, having their homogeneous envelope lined by a rather thick layer of epithelium, so that the cavity is proportionably contracted, sometimes not being more than -n-nVo mcn diameter The epithelium consists, for the most part, of nuclei and granular matter. Some of the nuclei are very perfect, and show a distinct vesicular struc- ture, with a well marked peripheral nucleolus. Others are more like granules, solid and opaque, and not above half the size. The nuclei are imbedded in granular matter, which for the most part is diffused freely about, but occa- sionally, though very rarely, constitutes the contents of a cell. In some cavities the epi- thelium assumes the form of non-nucleated delicate vesicles, of rather large size (Jjg.H2. b.). No secretion, capable of being recognised by the eye, exists in the glandular cavities. Fig. 742. From the tltyroid of a Pigeon. a, b, Two vesicles. The epithelium of a consists of nuclei and granular matter; that of b of rather large, delicate, pellucid vesicles. The central cavity is small, especially in a. c, The two varieties of nuclei, and — d, A complete nucleated cell. Reptiles. — In the order Chclonia the organ, which is demonstrated by the microscope to be really the thyroid, is found occu- pying a definite and uniform position. It lies in the median plane of the body, immediately above the base of the heart, between the two carotid arteries, a ndis overlapped and con- cealed by the pericardia! lobes of the thymus. The structure of the gland in a young Tor- toise I found extremely well marked ; the ve- THYROID GLAND. J109 sides were large, ^ to ^ inch diameter, closely aggregated together, and very variously altered from the spherical form by mutual pressure. There was very little investing areolar tissue. The epithelium consisted of a single row of nuclei imbedded in granular matter, which was more abundant than usually is the case. In some parts this had almost disappeared, and was replaced by delicate vesicles larger than the nuclei which lay closely together in contact with each other. Whichever of these forms the epithelium assumed, it did not en- croach much on the cavities of the vesicles, which were large and filled with some trans- parent non-refracting fluid. Most of the cavities also contained one to three yellowish coarsely granular globules, _j__ to -gi-tf in. diameter ; these existed in va- rious stages of development. A fine large octohedral crystal was also seen in one of the cavities ; but there were no prisms of triple phosphate (fig. 743.). Among the various families of the Saurians the thyroid is found to occupy different posi- Fig. 743. One side of a vesicle from thyroid of Tortoise. The epithelial stratum consists of a single row of nuclei, imbedded in a more abundant quantity of granular matter than usual. tions ; in some being single and mesial, in others double ; in some it lies high in the neck, in others low. Even in the same family its arrangement is not always uniform ; thus among the Lacertida: the gland is single, and of considerable breadth in the true lizards while in the Monitor it is double. Among the IguanidtE, likewise, a similar variety prevails. The Crec/iotidcs, ChameeleonideB, and Scincidce present the same general form as the true lizard. In the Chamaeleon it is rather higher (nearer the os hyoides) than in the other families, and is overhung by the sacciform dilatation of the larynx. In the Amphisbania and Opliidia "'the gland lies just above the base of the heart, between the right and left carotid arteries. It is a little hidden by the thymus of each side ; and in those genera which possess a fat body this large organ lies conspicuously in front of both the thymus and thyroid." In the Batrachian order there has been found, in the common Frog, on each side a small glandular body, which Mr. Simon de- clares is unquestionably possessed of true thyroid structure. They are situated on the carotid arteries, just beside the cornua of the hyoid bone. Huschke conceived these bodies to have their origin in the shrinking of the branchiae, and endeavoured to establish that the thyroid generally had its origin in the transformation of the branchial arches in the early embryo. This hypothesis, however, Mr. Simon well remarks, appears refuted by the existence of the gland in a pcrcnni-branchiate animal, the Menobranchus, where it consists of two symmetrical portions connected with the inferior border of the os hyoides, one on each side. In the class of Fia/ics there seems yet some doubt whether a true thyroid gland really exists. Mr. Simon believes that he has discovered the organ in many fishes, enumerating the Carp (Cyprinus), Pike (Eso.r), Cod (Gaff us), Had- dock ( Morr/ma), Whiting (Merlangus), Eel (AnguiUa), Sturgeon (Accipenser'), Shark (Syua/us), and Skate (Rnia); — it seems also to be present in the Anableps, Exoccetus, Cal- lorhynchus, and Lamprey (Petromyzon), but the evidence for its existence is less conclusive. It may occupy, he states, either of three posi- tions ; (l)as a single organ situated in the median line in connection with the basibran- chials, and supplied with blood from the first branchial vein while yet within the gills. (2) " In the Gadidae the gland is double. One portion lies on each side, not, as in the last case, at the anterior extremity of the first branchial arch, but near its posterior or ver- tebral end. Here it occupies part of a recess which is bounded by the gill below, and above by the outer extremity of that transverse fold of mucous membrane which limits the extent of the palate. It is merely covered by mucous membrane, which leaves it apparent to the eye without need of any express dissection. Its vascular supply is reflected to it from the ophthalmic artery, which arises before the formation'of the systemic aorta from the first branchial vein close to the origin of the pro- per encephalic artery." (3) " In the carp, anableps, pike, and exoccetus, the gland is placed at the inner extremity of the same duplicatufe of mucous membrane, and more toward the palate, so as to lie upon the fibres of the pterygoid muscle." Though there is this variety of situation, yet Mr. Simon re- gards these several organs as constantly agree- ing in one point, viz., in deriving their vascular supply from the first branchial vein, and thus being brought into connection with the ence- phalic nervous centre, by their nutrient streams having origin from a common source. Pro- fessor Owen dissents from the view that the pseudobranchioe are the analogues of the thy- roid gland. He states that in osseous fishes they are not diverticular to the cerebral circu- lation, but only to the ophthalmic, and in most cases are subsidiary, in this respect, to the cho- roid vaso-ganglion. The sublingual gland of Retzius is the organ which Professor Owen considers as most nearly representing the thyroid, though he suggests a doubt as to whether, by reason of its relations to the heart and great vessels, it may not more properly be regarded as the analogue of the thymus. It is with some hesitation that I proceed to mention the results of my own examination of some specimens from the three classes pointed out by Mr. Simon, in which he seems to regard the presence of a thyroid as un- doubtedly ascertained. I have, however, care- fully examined the structure with the micro- scope in every instance, and I believe I may 4u 3 1110 THYROID GLAND. refer to the observations, so far as they go, as free from any material error. In the Skate I have found the organ described by Retzius as a salivary gland, and by Mr. Simon as a thy- roid, occupying the situation well described by the latter, and lying exactly upon the terminal division of the branchial aorta. It was of a faint reddish gray tint, and presented to the unaided eye the appearance of a conglomerate gland. No excretory duct, however, was ob- served proceeding from it. In structure it consisted of numerous vesicles aggregated to- gether. The form of these was mostly circular ; some were elongated, and many variously altered by mutual pressure. Their diameter was about Ti^ to JT inch (fig. 744-. A). The limiting envelope of the vesicles presented a Fig. 745. Fig. 744. From thyroid of Skate. A. Vesicle, -f'y in. in diameter. B. Several of the nuclei imbedded in diffused mottled substance. good example of homogeneous membrane. It was lined internally by a pretty thick stratum of epithelial substance, which in some instances was so abundant as almost to fill up the cavity. The epithelium consisted of nuclei and a very large quantity of rather coarse granular ma- terial, which quite obscured the nuclei them- selves (fig. 744. B.) There were also a few granular cells, and, in the interior of many of the vesicles, imperfect prismatic or octohedral crystals could be discerned. I could not discover, among the glandular structure, any tubes resembling excretory ducts ; so that I am much inclined to believe it has no relation to the salivary organs, but belongs to the class of ductless glands. A gland, however, it assuredly is, and not a mere vaso-ganglion. Besides this body I discovered at some dis- tance behind it, just at the junction of the branchial arches anteriorly, a small light red- dish mass, which was covered in by a thin fascia, and by the mucous membrane, and could not be seen till the latter was dissected off. Its structure was almost exactly similar to that of the organ just described, con- sisting of vesicles about -j-i^ to -^-^ inch diameter (fis,. 745.), with a thick interior stratum of epithelium resting on a beautiful homogeneous limitary membrane. The pseu- A. vesicle from sublingual gland of Skate, diam. gp in. It contains abundance of nuclei and granular matter, with delicate vesicles. dobranchia, situated on the anterior wall of the spiracular canal, is manifestly of entirely different structure to the organs described. It consists of small plicae of mucous membrane, covered by a kind of pavement epithelium. In a Dog-fish (Spinax] the pseudobranchia was very small, but distinct, 1 could discover no trace of the sublingual gland, or of the small one behind it which 1 found in the skate. In the cod and luhiling the pseudobranchia is situated, as Mr. Simon has described it, near the upper extremity of the first branchial arch on each side. It lies in a recess which is bounded by the gill below, and above by the outer extremity of that transverse fold of mucous membrane which limits the extent of the palate. Its structure is peculiar; Mr. Simon regards it as a thyroid ; but from this opinion I feel obliged to differ. The following description is taken from examination of the organ in the Cod, but applies equally to that in the Whiting. It is a body of light red colour, semi-transparent aspect, flattened so as to present two faces, about one line and a half in thickness, and having two borders, one convex and slightly notched, the other somewhat concave. The surface is slightly uneven or nodulated. It is enclosed in a cap- sule, through which some large vessels are seen ramifying. Its general aspect is that of "glandular flesh," and certainly not of a mere congeries of vessels. In structure it appears to consist of parallel folds of homogeneous membrane, beneath which is spread a vascular plexus, and which are covered by an unusually developed epithelium. This epithelium appears under the form of granular cells of an oval, circular, or irregular form, not distinctly nu- cleated, and having a diameter of -.. 11UUO inch. These do not appear to constitute a mere in- vestment, but to form a layer of some thick- ness, filling up the intervals between the adjacent processes or folds of homogeneous membrane. These organs, manifestly con- structed after the type of gills, evince thus a tendency to assume a glandular structure; yet I can see no sufficient reason for sup- posing them to represent the thyroid, from which they differ so entirely in structural characters. In the whiting I could detect no trace of a sublingual gland, nor of the small posterior one; but in the Eel, where the THYROID GLAND. 1111 pseudobranchia was absent, I found, by the aid of the microscope, between the first and second basibranchials, a small mass, which consisted in great part of fat, but contained also some large vesicles closely resembling those of a real thyroid. Their diameter varied from yi^ to ^ inch. They had an ho- mogeneous envelope lined by an epithelium, consisting of small non-nucleated pellucid cor- puscles, and surrounding a cavity filled by a transparent somewhat refracting fluid. In &Pleuronectid I found the pseudobranchia quite free, uncovered by mucous membrane, and projecting a series of small distinct leaf- lets into the branchial cavity. It differs essen- tially from that of the cod or whiting, and showed no tendency to assume a solid glan- dular form, but was manifestly a real though minute gill. In a Carp I found the pseudobranchia with some difficulty. It was situated very deeply between the anterior part of the upper ex- tremity of the first branchial arch, and the posterior border of the pterygoid muscle. Its structure was entirely that of a gill, consisting of parallel folds of a membrane, arranged transversely to a median axis, and overlaying a vascular plexus. These folds were covered with a kind of sc;i!y epithelium, which was often detached in large pieces, and mingled with some circular cells, closely resembling mucous globules. I could find no trace of the sublingual nor of other adjacent gland. From the few facts now detailed I think it may be concluded, (1) That there is no evi- dence from their structural characters to prove that the pseudobranchia? are the representa- tive of the thyroid. (2) That in some in- stances organs which seem to be of a totally different kind are found, which resemble very closely the structure of the thyroid when it unquestionably exists. Mr. Simon lays stress upon the circumstance, that the pseudobranchise and the sublingual gland re- ceive their vascular supply from the same source, viz. the 1st branchial vein ; this, how- ever, is not constantly the case, the pseudo- branchise in osseous nshes, according to Pro- fessor Owen, serving only as diverticula to the ophthalmic, and not to the cerebral circulation; so that on this ground they cannot be sup- posed to have similar functions. For a philo- sophical discussion, however, of the analogy and homology of the pseudobranchia to the thyroid, I would refer to Professor Owen's Lectures, vol. ii. p. 270. note. MORPHOLOGY. — The preceding details are abundantly sufficient to prove the glandular nature of the thyroid. This truth, which elder anatomists saw clearly, though rather afar off, we, by more intimate and minute scrutiny, are enabled to confirm and establish in every par- ticular. Let us take in order the several parts of the secretory apparatus of the thyroid as we have described them, and see whether they do not exactly correspond to homologous parts in any undoubted gland. The recep- tacular cavities, enclosed by envelopes of homogeneous membrane, manifestly represent the tubes of the kidney or testis, or the ter- minal vesicles of the salivary gland. The limitary tissue is identical in appearance in each ; but disposed in the one so as to form shut sacs ; in the others to ensure a pervious canal or outlet, for the secretion. In the true glands the limitary tissue or basement membrane supports, on its interior, a layer of epithelium, essentially consisting of nuclei and granular matter. The same tissue in the thyroid is lined internally by a similar layer, which differs only in the smaller quantity of granular matter interposed among the nuclei, and in both cases the formation of perfect cells (i. e. with envelopes) is uncom- mon. The exterior of the limitary tissue is ill contact, in all the true glands, with a capillary plexus, from which the materials for the nutrition and growth of the epithelium are furnished. The same disposition exists in the thyroid. A certain amount of fibrous tissue, or some modification of it, penetrates more or less extensively among the elementary parts of the true glands, and serves to pack and unite their component parts together ; this also we have had occasion to describe in the thyroid. With respect to a supply of lym- phatic vessels and nerves, it is sufficient to state, that as far as ordinary dissection can go, the thyroid is similarly circumstanced with the other glands ; and there is no reason to doubt that the actual arrangement of these parts in all is the same. The parallel, thus exactly sustained in every particular, warrants us in regarding the thyroid as the T?apa?eiyi.ia of the class of ductless glands, and it maybe not without advantage, if we take occasion to note, in the other organs belonging to the same class, how gradually the strongly marked characters are laid aside, till the glandiform organ passes into a modification of vascular structure. In the supra-renal capsules the limitary membrane, though described by an eminent anatomist as usually forming tubes of various length, enclosing celloid epithelial particles, is, according to my observation (which is however but limited), very faint, or entirely absent. I have never been able to discover it in the human adult or foetal sub- ject ; and in the sheep the cortical structure has seemed to consist simply of rows of celloid nucleated particles, without any enclosing membrane. Conceding, however,, that in these organs the limitary tissue does exist,, there can be no doubt that it is much more feebly de- veloped than in the thyroid, while, as a set off, the epithelial particles are more perfectly formed. In the case of the thymus the limitary tissue is well marked, and resembles very much, in its arrangement, that of the con- glomerate salivary gland ; but the epithelium is remarkably modified. The nuclei exist, but almost alone. No granular matter of any pecu- liar properties is formed around them, prepa- rative to, and evidencing the existence of, secretory action. In the spleen both these alterations coincide. The epithelium is reduced to mere nuclei aggregated in masses round prodigiously developed venous radicles, and 4 B 4 1112 THYROID GLAND. the limitary tissue is discoverable nowhere, not even surrounding those curious spherical masses of nuclei the white corpuscles of Mal- pighi. The only circumstance I know of, which seems to indicate that even in the spleen a kind of secretory action does occasionally take place, is, that there frequently occur, in the parenchyma, some peculiar yellow cor- puscles, which are most abundant in fishes, and of which I gave a detailed account some years ago. The very presence, however, of these (for they are by no means constant), as well as their condition, argue strongly that secretion is not the appointed function of the splenic parenchyma. From this, the last and lowest of the ductless glands, we descend to erectile tissue, in which the venous portion of the sanguiferous system is even more highly de- veloped than in the spleen, and where the intervening parenchyma is still further reduced in quantity; yet, from the phenomenon of afflux of blood to the part, it must be regarded, I think, as exerting an attractive force, as is unquestionably the case in the spleen.* Returning from this digression to the con- sideration of the thyroid, we may lay it down as fully established, that it is a gland whose secretion is formed, and collects, in closed cavities. Now from this fact we are able easily to deduce another, vi/., that the secre- tion when formed is capable of being absorbed from the receptacuiar cavities ; for otherwise these would go on enlarging and distending themselves indefinitely, as in fact they do under certain morbid conditions. But, though there may be various causes concerned in the production of bronchocele, yet I think it must be regarded as proved, by Mr. M'Clellan's inquiries, that certain waters are adequate of themselves to produce this disease ; — it would appear that when they are drunk, some in- gredient or principle is supplied to the blood, which, being in excess, is straightway elimi- mated by the epithelium of the glandular cavities of the thyroid, and thus collects in, and distends them. If a patient in whom this has occurred be removed from using this unwholesome water, and if the natural ab- sorbing power be aided by the influence of iodine, then, the supply of the substance for which the thyroid has a special attraction being cut oft', the excess collected in the receptacuiar cavities returns speedily to the circulating current, which now, being in a minus condition as to this principle, readily resumes it. In such cases there seems, in fact, to take place a very analogous process to that which occurs in ordinary fattening and emaciation ; if an excess of oily matter exist in the blood, old fat vesicles enlarge, and new ones are formed ; if the reverse is the * The well marked variation in size of the spleen at different times proves, I think beyond doubt, that it exerts an actively attracting force on the blood which traverses it ; else what possible reason can be given for its containing much more blood at one time than at another ? No contractile tissue exists here which can be supposed to obstruct the returning current by the splenic vein. case, the oil in the fat cells is readily absorbed into the blood circulating in the capillary loops around them. The condition in which the epithelium of the thyroideal cavities is usually found is worth observing, and seems susceptible of a probable interpretation. It may be stated as a pretty well established fact, that the nucleus of a cell is the essential part, that in it resides that influence, or is developed that force, which produces all the phenomena of growth and assimilation ; that, so long as the nucleus persists, the energy of the cell, if one has been formed, continues to be manifested ; but, if it has disappeared, the active life of the cell is at an end. It is also certain that the comple- tion of a cell, i.e. its being surrounded by an envelope, is by no mea*is an essential circum- stance ; that all the purposes of cell life may be effected by the mere aggregation of granular matter around a nucleus ; that, in fact, the cell wall or envelope is of no importance, or but very little, in the metabolic changes which are produced, and that its presence, when it exists, seems merely to denote a certain per- manence of duration in the particle. Many examples of the correctness of these state- ments, will occur to every one who is in the habit of examining the glandular organs in man or the lower animals. I believe we may also advance a step beyond these doc- trines, and regard it as very probable that, when we find an epithelial structure con- sisting principally of bare nuclei, with but a scanty interposed quantity of granular matter, the secreting action there effected is of a rapid and simple kind ; the destined pro- duct being quickly formed and thrown off, and not slowly evolved within the chamber of a cell. The following instances may be re- ferred to, as illustrating the extreme varieties of secretory action in reference to this par- ticular. The cells in which the spermatozoa are formed must be of considerable per- manence, the development of the filaments taking place gradually, and in one instance, as Mr. Goodsir has shown, only being completed in the spermatheca of the female. The biliary cells of various annelida are at first filled with pale granular contents ; but gradually these are replaced by the characteristic molecules with which the cell becomes at last distended, and thus remains, often for a long time. The cells of the kidney of the common snail, which are very perfectly formed, enclose, within a well marked envelope, an opaque white mass of uric acid, which, after a long time, may increase to such a degree as com- pletely to fill the cell. These cells are very permanent.* In contrast to these instances, wherein complex and elaborate products are formed in complete cells by a secretory action of a slow and deliberate character, we may refer to (1) * I preserved some snails in a box for about a year — they remained in a perfectly torpid state, and took no food. The renal cells at the end of that time were almost all fully distended with uric acid, while usually they are not more than half full. THYROID GLAND. 1113 the absorbent glands, which doubtless produce some change in the fluid which traverses them ; this, however, must necessarily be a rapid process, and, accordingly, scarce any cells are formed ; the mass of the glandular paren- chyma consisting of very perfect nuclei; (2), the terminal hepatic ducts, whose walls, as I have shown, consist almost entirely of nuclei set close together, and which, by means of these effective agents, eliminate the actual biliary secretion from the varying, partly biliary, partly oily, fluid formed by the hepatic cells on their exterior ; this process of elimi- nation is, I believe, continually going on, and is not so much of a metabolic as of an ab- sorbing nature; the essential change being probably effected by the hepatic cells of the lobules; (3) the nucleated tissue forming the principal part of the villi, which scarce ever developes cells,* but is constantly attracting the chylous fluid through the basement mem- brane from the cavity of the gut, and permit- ting it to pass off by the efferent lacteals (here scarce any chemical change appears to take place) ; (-t) the cineritious matter of the cerebral hemispheres, which, amid the rapid alternations of sensation, thought, and volition, must be undergoing incessant change, consists, in by far the greater part, of nuclei and granular matter, the fully formed vesicles being few and far between. Applying, now, these views to the case of the thyroid, there seems reason to believe that the ordinary condition of its epithelium is such as to adapt it for rapid and transitory action ; so that a large amount of secretion may be quickly thrown into its cavities on any sudden occasion ; which again would easily transude through the thin epithelial layer and homo- geneous tunic, when the time of action had passed by. It may also be remarked, as consonant with the views above stated, that as respects its chemical nature the secretion of the thy- roideal cavities is of a simple kind, not appa- rently requiring much elaboration. It seems, in fact, to be a mere modification of albuminous matter containing, it may be, some gelatine, but strongly contrasting with the highly wrought products of the renal and hepatic laboratories. This implies that the change effected by the thyroideal epithelium on the liquor sanguinis supplied to it is by no means considerable. USE. — Cruveilhier, writing about fifteen years ago, briefly says, " the use of the secre- tion of the thyroid is unknown ; " nor can the anatomist of the present day give a much more satisfactory account. So en- veloped in mystery the use of the gland seems to have been always regarded, that inquirers have been more willing simply to confess their ignorance than is usually the case, and fewer speculations and hypotheses have been broached respecting this than regarding other points which promised at first sight to be of easier solution. It is scarcely worth while * I venture herein to differ from Professor Good- sir) not without repeated and careful observations. to mention the opinion, which supposes the thyroid to have any essential connexion with the larynx, either as pouring into it, through supposed ducts, a fluid fitted to lubricate the lining membrane, or, as Sir A. Carlisle sup- posed, forming a protection to the delicate organs of the voice, against the variations in temperature of the external air. There seems no doubt that the relative position of the thyroid to the larynx is quite unimportant, so far as the function of the organ is con- cerned. This is borne out by the variations of its site which occur in birds, and by the results of morbid action ; since prodigious goitre does not induce disease of the larynx, except in a mechanical way, i. c. by injurious pressure. Passing over more crude conceptions, we come to consider a theory which has been propounded by Mr. Simon, and which has certainly every claim to our careful attention, both from the character of its author, and as it is the only one yet promulgated which can be said to be even probable. He considers that the thyroid acts as a diverticulum to the cerebral circulation ; exercising, at the same time, its secretory function in an alternating manner with the encephalic nervous mass. His words are, " What diversion is to the stream of blood viewed quantitatively, alter- native secretion would be to the composition of blood viewed qualitatively ; and I should conceive that the use of the thyroid gland, in its highest development, may depend on the joint exercise of these two analogous func- tions. I should suspect not only that the thyroid receives, under certain circumstances, a large share of the blood which would other- wise have supplied the brain, but also that the secretion of the former organ bears some essential relation (which chemistry may here- after elucidate) to the specific nutrition of the latter ; that the gland, — whether or not it appropriates its elements in the same proxi- mate combination as the brain does, — may, at all events, affect, in a precisely similar degree, the chemical constitution of the blood tra- versing it ; so that the respective contents of the thyroid and cerebral veins would present exactly similar alterations from the characters of aortic blood. Finally, I should suppose that these actions occur only, or chiefly, during the quiescence of the brain, and that when this organ resumes its activity the thyroid may probably render up again from its vesicles to the blood, in a still applicable form, those materials which it had previously diverted from their destination." This theory mainly rests on the circum- stance that the thyroideal arteries arise in close proximity to the cerebral, and this is I think sufficiently constantly the case to form a strong argument in its favour. It must be remembered, however, that variations in the place of origin of the arteries both of the brain and thyroid, do occur without, as far as we know, any interference with the full discharge of the functions of the gland ; and it may also be considered probable that the purpose of a diverticular stream would have been better 1114 THYROID GLAND. attained, if the origin of the vessels had been below instead of above the point of giving off of the arteries to the brain. Besides, however, this argument, two others may be mentioned which at least favour the same view. One is, that no special characteristic principle appears to exist in the secretion of the thyroid, but that it is a mere modification of albuminous matter, — this seeming to imply that no special use is served by the secretion of the gland, that it is not elaborated for the sake of pro- ducing any peculiar effect on some other part, but that it is simply secerned from the circu- lating current for a time, to return and mingle with it again in a condition but little altered from its primitive one of blood-plasma. The other argument is drawn from the con- dition of the epithelium, which, as we have before remarked, seems adapted for rapid and transitory action, so that it might quickly secrete a large amount of material on any diminution of the nutrient processes in the brain. These arguments may be allowed to possess some weight. Before, however, this theory can be regarded as at all established, a more sure and discriminating chemistry must prove some relation of composition to exist between the secretion of the thyroid and the grey nervous matter. Till this is done we can but deal with the question afar off, without bringing it to an exact issue. MORBID ANATOMY. — The following morbid changes have been observed to occur in the thyroid; (1) It maybe affected with com- mon inflammation. (2) It may be variously altered by unhealthy or perverted action of its own glandular structure. (3) It may be the seat of adventitious formations. (4) Its vessels may become remarkably enlarged, as in the so called aneurism by anastomosis. Inflammation. — Professor Hasse gives the following description of inflammation occur- ring in the thyroid. " It is rare, but may at- tack the organ either when healthy, or when enlarged by previous disease. Its course is more frequently chronic than acute. Within a very brief interval the gland often swells considerably, becomes very bloodshot, tense, and painful, its texture softened and friable, assuming at first a brown red, and ultimately a dingy gray colour. The morbid anatomy of this grade of inflammation is but imper- fectly known ; that of the suppurative stage has been more frequently observed, and more fully described. Either separate ab- scesses form, or else the entire gland is converted into pus. Under favourable cir- cumstances the abscess opens externally through the skin. There are, however, ex- amples of its obtaining vent through the oesophagus, and determining a protracted fistula of the gullet,* or of its discharging itself into the trachea, and producing death by suffocation. f After evacuation of the pus, together with numerous shreds of dead cellular tissue, the tumour collapses ; the gland on the * linger, Bcitrage zur Kliuik der Cliirurg. vol. i. f Mcokel. side affected shrivels into a hard, cellule- filamentous knot, which adheres firmly to the skin and to the surrounding parts. Some- times the shrivelling of the one gradually brings on wasting of the other lobe." Alterations of Structure. — Under the se- cond head may be included hypertrophy of the thyroid, or some enlargement without appreciable change of texture. •' This variety," Prof. Hasse states, " is frequent, and for the most part inconsiderable." It probably depends merely on distension of the glan- dular cavities by their accumulated secre- tion. This change is almost wholly " confined to youth, and is frequent about the age of puberty in both sexes, — more so, however, in the female." " Alternatives of increase and decrease are especially apparent in this kind of bronchocele, enlargement being most con- spicuous at the approach of the menstrual period." This form, though it may be called hypertrophy, is not quite strictly so desig- nated, as there is no formation of new glandu- lar tissue, but only distension of the original cavities, by an increased quantity of secretion. " Melicerous degeneration of the thyroid is one of the most frequent forms. It occurs at all ages, and is uniformly attended with intu- mescence. It may involve the organ in whole or in part. In the former case the component granules (or vesicles) are found unusually and unequally enlarged, and transformed into sepa- rate cells filled with a tenacious, viscous, jelly- like substance, of the colour of honey. The entire part is hard, nearly bloodless, and but loosely coherent with the surrounding parts. Where, as frequently happens, only certain portions are disorganized, these form spherical tumours varying in size, and imbedded clearly in the healthy structure. They present a brownish or yellow colour, and the consistency of jelly or of melted glue. Sometimes they appear as an opaque, reddish, soft, or even lardaceous, swelling. In general but few blood vessels are visible in this goitre, although it may now and then be associated with ex- uberant vascular growth." The foregoing description is quoted from the translation by the Sydenham Society of Professor Hasse's work. He does not, how- ever, seem to notice sufficiently, under this head, the variety of matters which are found in the enlarged glandular cavities. Cretaceous matter, either in a pulverulent state, or form- ing hard ossiform masses, I believe often occurs, and in Prep. 1498, of the Patholo- gical collection in the Museum of the College of Surgeons, there is seen a quantity of solid white substance, either opaque and soft, or transparent, firm and chondroid, which oc- cupies the larger cavities, the majority being filled with a transparent jelly-like material ; some also with cretaceous matter. One in- teresting instance, probably belonging to this class, is quoted in the Cyclop, of Pract. Medi- cine from De Haen : — " In cadavere horren- dam mole thyroideam nactus, publice dissecui. Mecum auditores mirabantur, nullum feregenus tumorum dari, quin in hac sola thyroidea in- THYROID GLAND. 1115 vcniretiir. Hie enim steatoma, ibi atheroma, alio in loco purulentus tumor, in alio hyda- trius, in alio erat coagulatns sangnis, fl nidus fere in alio, imo hinc glutine loculus plenus erat, alibi calce cum sebo inista." I may mention here the results of micro- scopic examination of a specimen of this form of enlarged thyroid, for the opportunity of making which I am indebted to the kind- ness of the medical officers of St. George's Hospital. The gland was greatly enlarged ; its surface somewhat nodulated. A sec- tion displayed a number of cavities visible to the naked eye, some of which were circular, others elongated, and as it were compressed. Many of them were about the size of a large pin's head; some however, much more capa- cious. The majority were filled with a slightly opaque, firm, gelatinous material ; but some (the larger) with cretaceous or ossiform matter, and some also with a reddish material. The intervening structure in several places appeared tolerably natural ; but even in this, on close in- spection, enlarged vesicles were perceptible. The areolar tissue separating the lobes of the gland was hypertrophied, and formed whitish septal bands. Under the microscope it was seen that the vesicles were generally enlarged. They were found of all sizes, from those that were distinctly visible to the naked eye, or still larger, down to the natural size. Their walls were somewhat but not uniformly or very greatly thickened. The homogeneous envelopes presented, generally, somewhat of a fibrous appearance. The greater number of the cavities were distended with a transparent, feebly refracting, structureless, material, in which were numerous small irregularly shaped particles of higher refracting power. This material resembled, almost exactly, the normal secretion in appearance, and, like it, was free in the cavity of the vesicles. In these vesicles there was very little trace of epithelium, only some small, and few, non-nucleated corpuscles ; but in other vesicles the epithelium was so abundant, that it completely occupied the cavity. It was in no respect different, except as to quantity, from its healthy condition, con- sisting of mere nuclei and interposed granular matter in no great abundance. In some of the vesicles there were large and beautiful crystals of more or less perfect octohedral form. These were either oxalate of lime or triple phosphate. One prodigiously enlarged vesi- cle contained a mass of calcareous matter, very firm and dense throughout, but most in its central and peripheral parts. In the latter situation there were numerous masses of ossi- form substance, of yellowish semi-transparent aspect. On crushing these, no bone lacunae could be discerned in the fragments. They dis- solved freely with strong effervescence in nitric acid, leaving an homogeneo-fibrous basis substance, which often exhibited a greenish yellow tint. The material, thus proved to be of cretaceous nature, contained, mingled with it, numerous tablets of cholesterine. One small reddish mass, occupying the cavity of a vesicle, was found to consist almost wholly of blood globules and their detritus, and thus seemed to be the result of haemorrhage. Another opaque whitish mass did not effervesce with nitric acid, and was therefore not cretaceous; it consisted of epithelial nuclei mingled with peculiar, and rather abundant, granular matter. In the above account it is worth noticing that no cells were found ; the epithelium retained its natural appearance ; also the matter distend- ing the greater number of the cavities resem- bled exactly, so far as the eye could judge, the natural secretion ; and lastly, that in some in- stances there was an accumulation of unaltered epithelium and not of the secretion. This last fact is of some importance with respect to the exact nature of the function discharged by the epithelium. Owing to the kindness of my friend, Mr. H. Gray, 1 have recently had the opportunity of examining a remarkable specimen of Bron- chocele. The gland was greatly enlarged, — to five or six times its natural magnitude, — and altered in form, one lateral lobe being raised up higher than the other, and the surface being somewhat uneven and nodulated. On a section being made, the exposed surface presented a reddish glossy aspect, somewhat resembling that of certain forms of malignant disease which are undergoing softening: there was no appearance of distended cavities ; in fact, the structure to the eye exhibited less of the cellular arrangement than is usual. Micro- scopic examination confirmed the impression derived from simple inspection. — But little of the natural secreting structure remained, the vesicles being destroyed, and their secretion, though still present in some quantity, being certainly diminished. Some traces of the epithelium of the cavities were perceptible ; but there was no special cell growth indicative of any adventitious formation ; a few large cells or globules only, varying in size from •e i. n. to T7Vo' 'm' diameter, existed in some of the remaining cavities : these evidently consisted of aggregations of oily molecules and drops not manifestly enclosed by any en- velope. The blood-vessels were prodigiously and universally enlarged ; some of those which were capillaries in structure were from two to three times their normal diameter, and irre- gularly dilated and varicose; they were every where clustered over with minute oil drops ; which formed so thick a coating to many of them, that they appeared as white cylinders by direct light. Some parts of the gland pre- sented to the naked eye a whiter aspect than others ; and in them it was seen that the de- posit of oily matter along the vessels, and the destruction of the glandular tissue, had pro- ceeded to the greatest extent. In some places there were masses of ossiform deposit. The morbid alteration now described ap- proaches most nearly, I think, to the vascular and aneurismatic bronchocelc ; but the exten- sive destruction of the glandular tissue, and the copious deposit of oily matter, show that there must have been some grave derangement of the nutrition of the gland. The case oc- curred in a female (aet. 75.), who died with U1G THYROID GLAND. cirrhosis of the liver and ascites ; the kidneys contained numerous small cysts, and there were two fibrinous blocks in the spleen. Adventitious formations. — Cystic formation within the thyroid is next described by Pro- fessor Hasse ; and regarding it as depending on the development of new cysts within the gland, and not on the perverted or ex- cessive action of its own natural vesicular cavities, it will fall under our third head. I am, however, rather in doubt whether most cases of cystic formation in the thy- roid do not belong to the second category, and are not dependent on the development of any adventitious structure. Prof. Hasse says, " cystic formation within the thyroid gland is one of the most frequent causes of goitre. It occurs both by itself, and in con- junction with other kinds of degeneration, and constitutes the largest and most unsightly of all tumours. Cysts of every variety and size, either solitary or in congeries, are en- countered in every part of the thyroid gland ; an entire lobe, nay, the greater portion of the whole organ, being sometimes engaged in cystic development. The surrounding tex- ture is seldom healthy, being generally com- pressed, flabby, and bloodless. The cysts are, for the most part, isolated. Occasionally, how- ever, they abut one upon another, so as to form a single multilocular capsule. Here, as elsewhere, they are composed of two mem- branes ; namely, an external filamentous, and an inner serous, one. The external membrane is either smooth, or sends forth bands which attach it closely to the rest of the texture ; in many instances it partially, if not wholly, ossifies. The sac contains a limpid fluid, or a number of secondary hydatids *, or, again, a jelly-like substance, but more commonly a yellowish or whitish crystalline pulp, consist- ing almost wholly of cholesterine crystals with phosphate and carbonate of lime. In some instances the cyst accidentally inflames and becomes atrophied ; in others it gradually fills with earthy matter, and is transformed into a hard calcareous nodule. Cysts occur in the thyroid gland, in both sexes, and nearly at all ages ; more frequently, however, in females after the prime of life." A remarkable case of cystic formation in the thyroid is mentioned by Andral. He states that the whole onjan was converted into a cyst with bony walls filled with a honey-like fluid. He seems to recognise both the cystic and melicerous degeneration as further stages of the per- verted or excessive action which occurs in simple hypertrophy, and justly refers to the case of the ovary *as exactly analogous, the cysts of which, filled with various products, originate, in all probability, in Graafian vesicles, which undergo an abnormal development. Prof. Ilasse has never met with tubercles occurring in the thyroid. Prof. Louis makes no mention of such an occurrence, nor does M. Papavoine in a table which he gives of * Lieutnud uifntions a c:iso where the trachea was perforated by one of these ucephalo-cysts. the seat of tubercle in various degrees, drawn up from the examination of the bodies of fifty children. Sauten has observed that persons affected with extensive bronchocele seldom or never become subjects of phthisis. Carcinomatous growths rarely affect the thy- roid. Eight cases in 8289 of deaths occur- ring from cancer in Paris, are ascribed to this part. * The disease is sometimes primary, sometimes secondary, or the result of invasion from some neighbouring affected part. Encephaloid or scirrhus in several of their varieties have been known to occur in the organ, but no example of colloid in it has yet been detected : of course cysts filled with melicerous contents must not be confounded with the loculi of real colloid, to which they bear some resemblance. Primary cancer in the thyroid usually exhibits the characters of scirrhus, secondary those of encephaloid : in the first case the disease is usually infiltrated, in the second of the tuberous form. Ence- phaloid here, as elsewhere, often grows rapidly, and attains a large size. It seems to ob- literate entirely the natural appearance of the gland. It is often of the //(cmatoid variety, in which there is sometimes softening in the centre of the mass, causing rupture of vessels and extravasation of blood. Occasionally black pigment is accumulated within its texture in varying amount, " Medullary cancer of this gland must not be confounded with that of the lymphatic glands of the neck, which often simulates goitre." Enlargement of the Vessels. — The last kind of morbid degeneration, which the thy- roid has been observed to undergo, is that to which the term vascular or aneurismatic bronchocele has been applied. It is de- scribed as follows by Professor Hasse, — " All the blood vessels are much amplified, the veins in particular forming very dense, capacious, often knotted, plexuses, and the whole texture consisting apparently of a dense coil of vessels. The substance of the gland has almost en- tirely lost its granular character ; it is flabby and dark red. After death the tumour col- lapses considerably, and can only be restored to its original size by artificial injection. The walls of the arteries and veins are attenuated, the dilated membranes of the vessels contain considerable clots, and capacious cavities are found filled with black coagulated blood. Vascular bronchocele affects the entire gland; principally, however, one or other lobe. It occurs most frequently in females after the prime of life, and is, like simple hypertrophy, marked by periodical augmentation and de- crease. This general dilatation of blood-vessels must not be confounded with the exuberant vascular (malignant) growth termed fungus haematodes, to which the thyroid gland is also subject." In the foregoing description we have clearly set forth the condition of an organ, the walls of whose vessels have, from loss of their natural tonicity, yielded to the * Walshe on cancer. THYROID GLAND. 1117 impetus of the current of blood, and being thus enlarged and distended, have pressed upon the essential structure of the gland, and caused it to become atrophied. It may not be amiss to observe, after this review, that the disease of the thyroid, which is of by far the most frequent occurrence, viz. enlargement of its magnitude from excessive or perverted secretory action, is just of the kind we should, from our knowledge of its actual structure, expect would be most liable to occur. For when once the nicely arranged balance of secretion and absorption, with its moderate alternating oscillations in either direction, is permanently deranged, the closed cavities of the glandular vesicles afford no exit to the accumulating matters. Thus does minute anatomy explain, and thus is it con- firmed by, the changes wrought by disease. HISTORY OF INVESTIGATIONS. — The fol- lowing is not presented as a complete history of the thyroid, but as a sketch which it is hoped contains the principal facts relative to the advance of our knowledge respecting it. In examining the works of Aristotle, I find he makes no mention of the thyroid in two places, where he describes the organs situated in the neck, and speaks especially of the trachea. Galen does not give any very dis- tinct account of the thyroid, so far as I have been able to discover ; but certainly seems to allude to it in a passage in his book " On the Use of the Parts of the Human Body," where he speaks of the glands of the larynx, " which are always found more loose and spongy than others, and which, by the common consent of anatomists have been created for the purpose of moistening and bathing all the parts of the larynx and the passage of the throat." The following passage, quoted also in a note by Morgagni *, seems to prove that he was aware of the main peculiarity of the thyroid. " Now the neck has two glands, in which a moisture is generated. But from the two glands which are in the neck there come forth no vessels by which the moisture may flow out, as those do from the glands of the tongue." Vesalius, who wrote about A.D. 1542, dis- tinctly recognises the existence of the thyroid in the following passage from his work, " De corporis humani fabrica." -j- "And this dissec- tion also shows two glands, adhering one on each side, to the root of the larynx, which are of large size, and very fungous, and nearly of the colour of flesh, but darker, and covered over with very conspicuous vessels." In the second book he describes their appearance in oxen, in whom they resemble muscular tissue, he says, very much, while in man their aspect is more truly glandular. Jacobus Sylvius, who wrote a little later than Vesalius, enumerates, in his list of glands, " duoe item ad laryngis radicem asperaeque arterioe initium utrinque una quae interdum ob magnitudinem in unam abire videntur." Wharton, in his Adenographia, published about 1G56, gives a very full and good description of the thyroid ; he notices * Advers. Anat. i. c. 26. Lib. vi. cap. 4. its situation, figure, magnitude, texture (sub- stantiam), and consistence (soliditatem) ; and remarks " that it is much more full of blood than any other gland, also more viscid and solid, and more resembling muscular flesh. This is the only difference, that it is not of a fibrous structure, but rather of a glutinous nature." He assigns four uses to the gland, which it may be worth while to quote, as affording an example of the speculations then in vogue, the last perhaps being not the least real and important of those he mentions! "(1) The first and principal use of these glands appears to be to take up certain superfluous moistures from the recurrent nerve, and to bring them back again into the vascular system by their own lymph channels. (2) To cherish the cartilages to which it is fixed, which are rather of a chilly nature, by its own heat ; for it is copiously supplied with arteries, and abounds with blood, from whence it may conveniently impart heat to the neighbouring parts. (3) To conduce by its exhalations to the lubri- cation of the larynx, and so to render the voice smoother, more melodious, and sweeter. (4) To contribute much to the rounded con- tour and beauty of the neck; for they fill up the empty spaces about the larynx, and make its protuberant parts almost to subside and become smooth, especially in the female sex, to whom on this account a larger gland has been assigned, which renders their necks more even and beautiful." Verheyen, writing about 1720, describes the thyroid as deriving its name from the cartilage so called, and states that it is con- sidered by some as double, i, e. consisting of two glands. He says, "this gland, beyond doubt, serves also to moisten the neighbour- ing parts ; but, because it is very large, there is an apparent reason why it should have rather large excretory ducts, or one at least very conspicuous, which yet hitherto has not been discovered." About 1708, Evertzen wrote an inaugural dissertation on the thyroid gland, noticing its structure, some diseases to which it is liable, and their treatment. Morgagni, in his Advers. Anat. (1723) dis- cusses two questions respecting the thyroid ; one as to whether the gland is double or single, i. e. whether the lobes are connected by an isthmus or not ; this he •''< ,s, as re- spects man, positively in the affirmative. The other vexata qucstio, as to whether the thyroid be provided with a duct or not, he confesses to be yet undetermined. He notices the ex- istence of vesicular cavities in enlarged thy- roids, which he justly supposes to be the natural cavities (nativi acini) dilated by their accumulated secretion. From his examina- tion of the secretion of the thyroid, " mollein quendam, et obliniendo lubricandoque ido- neum, succum communi isti amygdalarum oleo longe consimilem;" and from observing the thyroid to be exposed to the pressure of contracting muscles, as is the case with some other undoubted glands, he inclines to con- sider it probable that the gland has some duct 1118 THYROID GLAND. opening into the pharynx, the oesophagus, or into the top of the trachea. Santorini (Observ. Anat. 175-i), recognizes the thyroid as a single gland, and makes men- tion of its median column as previously known to Morgagni, though it was probably dis- covered by Bidloo or Lalonette. He details the failure of his efforts to discover a duct, though he had several times detected an orifice at the anterior angle of the glottis, into which a bristle could be passed ; and yet re- marks that the thyroid gland may be urged to expel its secretion by the pressure of the sub-hyoidean muscles, the throbbings of the carotids, and the contractions of the oeso- phagus. Haller (Element. Physiolog. 1766), in his account of the thyroid, gives a good descrip- tion of the median column, and of the several varieties which it presents ; four times only has he found it absent ; most frequently existing on the left side ; sometimes, however, on the right. He relates some experiments of Lalonette, in which it appeared as if the glandular cavities had been distended by inflation with air, and also the lymphatic vessels proceeding from them. The result of this coarse proceeding he explains, and probably cor- rectly, by supposing that the distended cavities were those of the areolar texture, and not the secreting vesicles. He remarks that, even according to Lalonette' s testimony, no secre- tion can ever be pressed out of the thyroid gland into the cavity of the larynx ; or if any appear it seems to be nothing more than the contents of some mucous follicles. After detailing the struggles and efforts of various anatomists to discover an efferent duct, he states at last that several inquirers, among whom he mentions Ruysch in particular, had adopted the only possible remaining opinion, that a peculiar fluid was elaborated in the gland, which being received into the radicles of the veins, was returned into the blood. This view, which laborious, and thoughtful, and sagacious men were then slow to entertain, is now universally adopted ; and it seems cer- tainly a matter of wonder that it was not sooner arrived at. May we not, however, question whether, in regard to other glands, a process somewhat similar does not also occur, — whether certain complementary products of secretory action are not formed in the gland, and afterwards absorbed and carried off by venous and lymphatic radicles ? Meek el's description of the thyroid is as complete as could be accomplished by the most consummate anatomical skill, while un- aided by the achromatic lens. I need not refer to his well known pages, further than to notice a suggestion which he offers, viz., that as the median column is much more deve- loped in the infant than in the adult, the excretory duct may exist at that period (in the median column), and become obliterated as age advances. In proceeding beyond this period, we come to the anatomists of our own day ; several of whom have advanced our knowledge con- siderably respecting the thyroid and other ductless glands. To none, however, are we more indebted than to Mr. Simon ; whose musterly and philosophical Essay on the Thymus contains the best account of the anatomy and physiology of these organs that has yet been given. BIBLIOGRAPHY. — Wharton, Adenographia. Mor- gagni, Adversaria Anatomka. Hailer, Elemeita Physiologies. Meckel and Cruveilhier's works on Descriptive Anatomy. Quain and Sharpey's Ana- tomy. Todd and Bowman, Physiological Anatomy. Simon's paper in Pliilos. Transact. 1844, on Com- parative Anatomy of Thyroid. Various parts of the essay of the same author on the Thymus gland. Henle, Allgemeine Anatomic. CEster'len, Beitra'ge zur Physiologie. ( C. Handfield Jones. ) TIBIO-FIBULAR ARTICULATIONS. — The bones of the leg, throughout the greater part of their length parallel and con- tiguous to each other only, are in contact by their extremities. At the points of contact the two tibio-fibular articulations, a superior and an inferior, are situated. SUPERIOR TIBIO-FIBULAR ARTICULATION. — The head of the fibula is in contact with the external tuberosity of the tibia. The for- mer is furnished with an articulating surface which has an aspect upwards, forwards, and in- wards, whilst the articular facet on the latter is placed rather towards the posterior part of the tuberosity of the tibia, and is directed downwards, backwards, and outwards. Both surfaces are almost perfectly plane, their form is circular, and they are encrusted with arti- cular cartilage ; hence this articulation is to be referred to the class arthrodia. a. The ligaments of this joint are two in number, named, from their relative positions, anterior and posterior ligaments. 1. The anterior ligament of the superior tibio-fibular articulation, is composed of a fas- ciculus of white fibrous bands, which are all parallel to each other. It passes from the tibia downwards and outwards to the head of the fibula, running in front of the synovial membrane of the articulation which it defends. The extensor digitorum communis muscle covers this ligament anteriorly. 2. The posterior ligament follows a similar direction on the posterior aspect of the joint; but the fibres which compose it are neither so numerous nor so strong as those of the pre- ceding; this ligament is covered posteriorly by the poplitaeus muscle. Lastly, the tendon of the biceps (flexor cnirin), by its attachment to the head of the fibula, contributes, in no inconsiderable de- gree, to the security of the articulation. b. Synovial membrane. — There is nothing, in the anatomical disposition of the synovial membrane of this articulation, which requires any particular notice ; but the surgeon should remember that it is always in close proximity to the serous sac of the knee joint, and that in many instances the two synovial membranes communicate with each other. The synovial TIBIO-FIBULAR ARTICULATIONS. 1119 membrane of the knee joint is brought into this close relationship with that of the tibio- fibular articulation, by means of a prolonga- tion which passes downwards from the former around the tendon of the poplitaeus muscle ; and when a communication does exist between the two articulations, it will therefore be found at the posterior aspect of the head of the fibula. This anatomical arrangement has an import- ant bearing on a disputed point of practice, viz. the extirpation of the head of the fibula in amputations of the leg near the knee joint. This proceeding, recommended originally by Larrey and Garriques, and subsequently re- vived by Mr. Guthrie, has been opposed by Mr. Adams of Dublin, who, appealing to the anatomical peculiarities just described, makes them the grounds for rejecting altogether the innovation in question. (Vide "ABNORMAL CONDITION OF THE KNEE JOINT," vol. iii. p. 50.) INFERIOR TIBIO-FIBULAR ARTICULATION. — This articulation is intimately connected with that of the ankle, from which, although anatomically distinct, it cannot virtually be separated. The tibia and the fibula, at the lower part of the leg, are closely connected for a consider- able portion of their extent. The tibia pre- sents, on its external aspect and inferiorly, a triangular-shaped surface, two inches in verti- cal height, and concave from side to side : superiorly, or towards the apex of this space, it presents a rough and scabrous surface ; but inferiorly it is smooth and encrusted, in the recent state, with articular cartilage. The inner surface of the lower end of the fibula is of similar shape, but convex ; it is rough su- periorly, and smooth inferiorly. Here the two bones form an arthrodial articulation. a. The cartilage, which in this situation in- vests the opposed surfaces of the tibia and fibula, is continuous with that which covers the inferior surface of the tibia. It is also lined by — b. — synovia! membrane prolonged upwards from the ankle joint, and which forms a small cul-de-sac in the tibio-fibular articulation. The rough irregular surfaces, on the bones above the line of reflexion of the synovial membrane, have the fibres of a strong inter- osseous ligament implanted into them. c. The ligaments of the inferior tibio-fibular articulation are three in number ; 1. an ante- rior, 2. a posterior, and 3. an inter osseous. 1 , Anterior tibio-fibular ligament. — The fibres of this ligament pursue a direction downwards and outwards, from the anterior margin of the small articulating surface on the tibia to the outer malleolus ; and as the lower margin of this ligament projects below the level of the tibia, it deepens somewhat the cavity for the reception of the astragalus. The tendon of the peronaeus tertius muscle covers this liga- ment in front. 2. Posterior tibio-fibular ligament. — This is a strong, round, fibre-cartilaginous cord, which passes from one malleolus to the other in an arched manner, having a concavity directed downwards, and connected with the posterior ligament of the ankle joint, and a convexity which adheres uniformly to the posterior arti- cular margins of the tibia and fibula. This ligament not only connects the two bones to each other, but it also, like circumferential fibro-cartilages elsewhere, serves the purpose of deepening the mortice-shaped cavity of the ankle joint which it borders. It likewise pre- vents the immediate contact of the osseous surfaces in forced extension of the foot, being interposed between the bones as an elastic cushion. 3. Interosseous tibio-fibular ligament. — This is composed of short transverse bands firmly implanted, at right angles, into the opposed rough surfaces on the bones already described. Superiorly, the fibres of this ligament extend nearly as far as the lower margin of the inter- osseous membrane, (separated from it bv a small interval, through which passes a branch of the fibular artery), whilst inferiorly they are limited by the direct contact of the two bones of the leg, which they serve to bind firmly together. In order to exhibit this structure, either of two methods may be adopted ; the bones of the leg may be sawn across about their centres, and then forcibly torn asunder, (in this way the ligament may be seen, and its powers of resistance appreciated), or the ligament may be exhibited in situ, by making a vertical, transverse, section of both bones, traversing the two malleoli, and also the joint of the ankle.* Mechanism of the tibio-fibular articulations. — The movements of the fibula on the tibia are extremely limited ; this is in accordance with the general plan on which the skeleton of the lower extremity is formed, its use being to serve as an organ of support, and of locomo- tion, only. The bones of the leg are connected together by the intervention of ligaments, (not consolidated together as in the arrangement met with in a few of the Mammalia), and thus a greater degree of elasticity is obtained without any sacrifice of strength ; and it may be pre- sumed that the slight degree of yielding and of gliding motion, which is permitted in the tibio- fibular articulations, may occasionally serve to diffuse, and to lessen the intensity of shocks applied to the lower extremity, and may thus diminish its liability to injury, especially to fracture. Dislocation of the fibula, at the upper tibio-fibular articulation, has occasionally, but rarely, been met with as the result of injury. Sir A. Cooper mentions a case of compound fracture of the tibia, where this complication was observed ; but the rarity of dislocations in this situation, is accounted for by the cir- cumstance, that the fibula, owing to its com- parative slightness, almost invariably breaks, on the application of a force far short of what suffices to rupture its ligamentoua connections with the tibia. The mechanism of the inferior tibio-fibular articulation is inseparably connected with * See fig. 61. p. 163. vol. i. 11-20 TONGUE. that of the neighbouring articulation of the ankle. In fact, on the perfect adaptation of the bones of the leg, at their lower extremities, essentially depends the integrity of the ankle joint itself. By the union of the tibia with the fibula the " mortice shaped" cavity, which receives the pulley of the astragalus, is formed, and any injuries which disturb the natural rela- tions of these two bones interfere propor- tionally with the functions of the ankle, which is a perfect angular ginglymus. Hence it is, that in some cases of fracture of the lower end of the fibula, a widening of the mortice is produced, from which more or less of permanent deformity and inconve- nience results, abnormal lateral motion being then permitted. The connecting media be- tween the tibia and the fibula interiorly are of extreme strength ; so much so, that no ordinary violence seems capable of rupturing them ; the bones being bound together, not only by the special ligaments of the inferior tibio-fibular articulation already described, but by the annular ligaments and fascia; of the leg also. Hence, as we might infer, the separation of these bones by injury has never been observed, except when the fibula has first been broken. In the " complete dislocation of the 'foot up- wards and outwards, we are furnished with an illustration of the immense strength of the interosseous ligament ; as it is found that even in this severe injury the fibres of this ligament are not usually torn ; but the rough surface of the tibia into which they are implanted is broken off, and carried upwards and outwards with the lower end of the fibula, to which the interosseous ligament still binds it." (See b. fig. 54<. vol. i. page 157 ; article " ABNORMAL CONDITIONS OF THE ANKLE JOINT.") {Ben. George M' Dowel.) TONGUE. (rX(JfT.). Within this and surrounded by it as by a border, is an area of a more or less oval form, of a paler colour, less dense, and showing a distinctly fibrous character. The fibres appear for the most part transverse (fig. 747. c.}, horizontal in the centre, but curved up a little on each side. They are bounded on all sides by the cortical portion. Entering the centre of the bottom of the section, passing vertically up- wards, crossing the last-mentioned fibres at right angles, and terminating in the superior surface of the cortical portion, are seen the two genioglossi muscles (fig. 747. d.}. These, therefore, constitute a vertical, set of fibres ; but they are not the only vertical fibres ; at each side of them, especially at the inferior portion of the section, other vertical fibres are seen passing upwards and a little inwards, and intersecting the more lateral portions of 4 c 3 1126 TONGUE. the transverse at right angles.* Cruveilhier has erroneously described them as passing downwards and inwards: their divergence as they pass downwards is very conspicuous. The central area — the lingual nucleus (not/au lingual') of Bauer, — is therefore constituted of two sets of fibres, a ventrical and trans- verse ; the transverse being entirely intrinsic, and the vertical in part intrinsic and in part derived from the genioglossus. A section made anterior to the free margin of this last-mentioned muscle, shows the cor- tical portion continued completely round the tongue, without the break on its inferior sur- face, occasioned, in the previous section, by the entrance of the genioglossi muscles ; it is also of greater thickness in proportion to the central part, which is comparatively small, and the transverse fibres have a less marked upward curvature at their extremities. Thirdly, a section made near the base of the tongue shows the cortical portion nearly lost at the upper surface, greatly accumulated at the sides, but not of so compact a nature as in more anterior situations ; the obliquely ver- tical fibres tolerably abundant, but the trans- verse nearly lost, and the greater part of the inferior surface occupied by the expanded genioglossi. Transverse vertical sections, therefore, dis- plav two sets of fibres, a vertical and a trans- verse, and shew their situation and quantity ; let us now see what additional light will be fur- nished by a longitudinal vertical section. It shews that the cortical portion consists of lon- gitudinal fibres, and thus supplies a third set. If the section be made in the middle line, or near it, the whole cut surface is occupied by the vertical fibres of the geniohyoglossus, at first directed backwards, but curving upwards so as to enter the tongue vertically, in which vertical direction they are continued up through its entire thickness, and are lost in the 1 ngi- tudinal fibres of the cortical portion ; if the section is made in the lateral portions, it shows the vertical striation occasioned hy the in- trinsic vertical fibres, and the cortical portion, as in the other. Having ascertained the si- tuation and direction of the three sorts of fibres, we may, by making transverse sections at all points from the apex to the base, and longitudinal ones at various distances from the vertical median plane, and also by tracing the extrinsic longitudinal muscles into the intrinsic, and seeing what part of the one the other fur- nishes, get an exact interpretation of them. We should then find the tongue to consist of the following muscles. a. A transverse lingual^, altogether intrinsic, * Theile denies the existence of the intrinsic vertical fibres ; he says that those seen in longi- tudinal section are the ascending libres of the genio- glossus, and those seen besides them in trans- verse sections are the most oblique of the transverse ; — a misconception of which the microscopical ex- amination of sections at once shows the fallacy. f The adoption of the word lingual for all the intrinsic muscles of the tongue, from the French writers on this subject, has no objection against it, and has the advantage of brevity. inserted on each side into the submucous fibrous tissue or cutis, continued from apex to base, more abundant anteriorly, where it is horizontal, becoming more curved upwards as we proceed backwards, and being lost at the base. £. A vertical lingual, in part intrinsic ; in part the lingual portion of an extrinsic muscle, the genioglossus, existing from apex to base, in all parts vertical to the surface, and there- fore, from the curved direction of the tongue, arranged in a more or less radiating or fan- like manner. 7. A superior lingual, longitudinal, in- trinsic, thin behind, thicker in the middle, and thinner again at the apex, arising from the hyoglossal membrane and cutis at the base of the tongue in a gradual way, and having a similar cutaneous insertion on the upper surface of the tip and neighbouring parts. 5. A lateral lingual, longitudinal, altogether extrinsic in its origin ; derived from two prin- cipal sources ; one, its upper and most super- ficial portion from the fibres of the stylo- glossus, which pass forward on the side of the tongue after the insertion of that muscle into it, the other from the anterior fibres of the hyoglossus which have a similar distribution : to this may be added a slender fasciculus of fibres interposed between the styloglossus ami hyoglossus, which many modern anatomists * have described as the lingual muscle. The muscle thus formed constitutes the accumula- tion of longitudinal fibres before referred to as seen at the sides of a transverse vertical section of the base ; passing forwards they become fused together and spread out so as to constitute a thin layer, merging above by converging towards the medial plane of the dorsum, in the superior lingual, below in that next to be described, and forming with them a sheath of longitudinal fibres, investing the whole surface of the tongue. e. An inferior lingual, a stout fasciculus of longitudinal muscular fibres entirely intrinsic, arising at the base of the tongue between the hyoglossus and genioglossus, and passing forwards between these two muscles to be inserted gradually into the cutis of the tongue on the inferior surface near the apex. This is the true lingual muscle of Douglas and Al- binus, and of anatomists of the present day. I am doubtful whether or not the most an- terior fibres of the genioglossus bend for- wards so much as to become longitudinal, but I think not (though Cruveilhier says they do): if they do, the longitudinal sheath in front of the free margin of the genioglossus would consist of four sets, behind it of three. Since the longitudinal fibres invest the whole of the free surface as a sheath ; since they are, most of them, not directly, but obliquely, longitudinal ; and since many of the central spread out to the sides, while the lateral converge to the centre, the division of the longitudinal lingiia/s into superior, lateral, * Bichat, Traite' d'Anatomie, t. ii. p. 43. TONGUE. 1127 and inferior must be to some extent arbitrary : however, most of those on the upper surface are intrinsic in their origin, those at the sides are extrinsic in their origin, while those on the inferior surface are sufficiently individual and distinct : some subdivision appears ne- cessaiy, and the one adopted will at any rate assist in remembering these facts. The microscopical examination of linn sections, On making a thin transverse vertical section of the human tongue, and examining it with the microscope*, we see that the appearances indicated by a similar section, viewed with the naked eye, are correct, namely, that the in- trinsic muscular fibres assume three principal directions, a vertical, a transverse, and a lon- gitudinal ; and that the longitudinal are con- fined to the neighbourhood of the surface. But we see more; we see a very curious and artificial arrangement of the fibres very much contributing to facilitate their package, and by which they mutually support one another Fig. 74-8. Transverse vertical section of the left half of the human tonrpie at the most posterior part of the free portion. (Magnified 10 diameters.) a, a, cutis; b, b, cortical portion, consisting of the three orders of fibres; c, central portion, con- sisting only of two; d, discs of longitudinal fibres, seen in section; /, horizontal median plane; g, line of emergence of the vertical from the transverse fibres ; i, i', the most superior and inferior of the transverse curving up and down; k, It, the most lateral of the vertical curving outwards. * The best method to adopt in making these the sections with some very thin flat knife. Place investigations is to keep a fresh human tongue two the sections on a glass slide with a drop or two of or three days in spirit, and then boil it about an water, cover them with a piece of thin glass, and hour. On being first put into the boiling water it view them with an inch, or, if a very large field contracts and becomes very hard. When sufficiently is wanted, a two-inch object-glass, boiled, let it dry in the air for a clav, and then make 4 c 4 1128 TONGUE. and act with the greatest advantage. This arrangement I shall now proceed to describe. Suppose the section made at a point just in front of the anterior free border of the genioglossi {fig. 748.). Immediately beneath the papillae (which may be very well dis- played by this method), the condensed sub- mucous areolar tissue or cutis of the tongue is seen, of considerable thickness, being thickest on the upper surface, especially towards the middle(art). Immediately beneath this, around the whole circumference of the tongue, is seen a very curious areolated or fenestrated ap- pearance, consisting of cross bars, branching and interlacing irregularly at various angles, leaving interspaces that are filled up by groups of discs (del). The cross bars are at once seen to be small fasciculi of the vertical or trans- verse fibres, or both, according to the part looked at, and the groups of discs are seen to be transverse sections of the longitudinal fibres passing through the meshes formed by the vertical and transverse, which they more or less completely fill, and with whose shape they more or less exactly correspond (Jigs. 748. and 751.)- The fasciculi of the longitudinal fibres are in most situations much larger than those of the vertical and transverse, among which they are contained ; indeed, the lon- gitudinal being confined to the surface, it would naturally be expected that they would preponderate there. The vertical fibres are most abundant in the vertical median plane and the horizontal in the horizontal median plane (f), the vertical not existing near the lateral surfaces, nor the transverse near the superior and inferior surface (figs. 749. a, a) ; and from this fact result almost all the pe- culiarities of arrangement of the fibres that we see. In the first place it results from this, that the vertical and horizontal fibres cross each other in the centre, which they entirely occupy, and therefore exclude the longitudinal ; ac- cordingly no discs are seen in the central part of the tongue. Secondly, that at a cer- tain line (fig. 748. g.) the vertical emerge from the transverse, and are continued up or down, to the superior or inferior surface, alone; and similarly at the lateral regions the transverse emerge from the vertical, and are continued on alone to the cutis at the sides ; hence the fibres near the middle of the upper and under surface, and at the borders of the tongue, do not interlace but pass to the surface with something of parallelism; and hence the fasciculi of longitudinal fibres here are arranged, not as in the mesh of a network, but in parallel rows at right angles to the surface ; an arrangement very charac- teristic of these situations. Thirdly, it would result from this absence of vertical fibres at the sides, and of the transverse above and below, that there would be four situations (b, b, b, b, fig. 749. A .) in the neutral ground between the upper and under surfaces and the borders respectively, where there would be no cross fibres of any sort, and where the lon- gitudinal fibres would exist alone, unsupported and unseparated. Moreover, the vertical fibres at the upper and under surface, and the trans- Fig. 749. A a a Plan of the intrinsic muscles of the tongue as seen in transverse section. a, a, a, a, Superior, inferior, right and left lateral regions ; I, b, b, b, right and left supra and sub-lateral regions. (Compare with fig. 4.). verse at the sides, would be so dense and numerous that they would hardly admit of any longitudinal fibres in their interspaces. Now the support and separation of the longitudinal fasciculi, and the admission of a sufficient number of them at all the superficial parts of the tongue (especially the two surfaces and the two edges, which may be called the cardinal points of the tongue with regard to its move- ments), are the two things that are especially to be brought about. To achieve this double object, the vertical and horizontal fibres, as they approach their respective surfaces, spread out in a sort of fan-like manner ; the most lateral of the vertical fibres spreading out to- wards the sides (fig. 748. k, k), and the most superior and inferior of the transverse spread- ing up and down towards the surfaces (fig.l^S. i, i,fi,g. 749. B.). The two sets thus cross each other and fill the otherwise empty space with a network of considerable regularity and beauty, which is characteristic of these four situations, as the parallel fasciculi at right angles to the surface are characteristic of the four inter- mediate ones. For the sake of convenience I shall call the situations where the transverse and vertical fibres approach the surface in pa- rallel bundles, the superior, the inferior, and the right and left lateral regions (fig. 749. A,B. a, a, a, a) : those in which they decussate as they approach the surface, I shall call the right and left supra-lateral, and the right and left sub-lateral (/g.749. B.b,b, b,b.). Fourthly, the mesial vertical and mesial horizontal plane are the situations where the vertical and hori- zontal fibres respectively would act with the greatest power on the form of the tongue, and where also they would admit of being the TONGUE. 1129 longest ; hence we see the fasciculi in these situations much larger and more densely packed than in the intermediate positions, so that they more than equal the longi- tudinal fibres that they transmit. The ex- treme lateral fibres, on the other hand, that spread out and interlace, having little more for their office than to support the longitudi- nal fibres, are very small and scanty, many of them consisting of only a single fibre, and hence at these points the preponderance of the longitudinal over the vertical and hori- zontal fibres is the greatest. Fifthly, the most deep-seated of the longitudinal fibres of the upper and under surface are underlaid by a definite floor of transverse fibres, and simi- larly the deepest of those at the side are under- laid by a floor of vertical fibres; therefore in these situations there is a strong line of de- marcation, the discs are abundant down to the bottom of the cortical layer, and there they terminate suddenly (fig. 751.); but in the in- termediate positions there is no definite floor, no line of demarcation, but the discs of lon- gitudinal fibres dip down at irregular distances (figs. 748, 749, 750.). This is the general plan and rationale of the arrangement, but it is rather an exposition than a description, and it must be understood as merely referring to a transverse vertical section of the tongue, made at the most pos- terior part of the free portion of the tongue : there are often irregularities that make it difficult tc recognise the plan, and, in some situations, certain disturbing forces, and su- peradded parts that quite upset its symmetry. For example, behind the anterior third of the tongue, the genioglossus is seen entering its inferior surface, and displacing all longi- tudinal fibres (fig. 747. d) ; further back, this displacement is more considerable, and we have similar infringements from other muscles; and the intermixture of fat towards the base of the tongue tends materially to upset the regularity of the muscular arrange- ment. Yet, in spite of this, it may always be detected, and the average of appearances will be such as I have described. The muscular fibres are neither straight nor parallel ; those of each system maintain their general direction, but their course is wavy and tortuous, and characterised by the utmost irregularity ; as the fibres pass out- wards they branch and sometimes re-unite (figs. 750, 751.), though their branchings are much more frequent than their re-unions, and hence the fasciculi are smaller and more numerous near the periphery than towards the centre (fig. 751.) ; by these branchings of the fasciculi each set of fibres, the vertical or transverse, possesses what may be called an intrinsic network, imperfectly marked cer- tainly, but sufficient in some parts to mask their parallelism and to break up the rows of longitudinal fibres that are packed between them. The number of fibres in each of the vertical or transverse fasciculi, varies according to the part of the section viewed, and the situation in the tongue irom which it is taken ; some- times one single fibre constitutes the fasci- culus, if one may say so, sometimes many dozen. Some of the largest are the most superior of the horizontal, — those that curve up on each side towards the upper surface (fig. 750.). The same variety of size exists in Fig. 750. li a. Portion of cortical layer of the right supra-lateral region of the tongue, showing the interlacement of a, «, the horizontal with b, b, the vertical fibres, the longitudinal fibres filling the intervals having been removed. Magnified 30 diameters. the discs of longitudinal fibres cut across; the number of fibres in them may be counted, from two or three to thirty or forty : those nearest the surface are certainly the smallest, and they do not completely fill the meshes of the muscular network through which they pass (fig. 751.), but a certain quantity of fibrous tissue dips down among them : this, however, only for a little way. The shape of the longi- tudinal bundles is as various as their size — circular, polygonal, triangular, elliptical, in fact, every conceivable shape (fig. 751.); they seem moulded by the fibres among which they lie, or, more correctly, they and the others among which they lie, mutually regu- late each other's shape and direction. The peculiarity, then, of the arrangement of the intrinsic muscles of the tongue is this : — that there are three sets of fibres passing through the same area, and acting in three different directions ; that these three direc- tions are, in the main, at right angles the one to the other, in fact, that they coincide with 1130 TONGUE. the three axes of the cube ; that to facilitate this arrangement, a beautiful system of pack- Fie. 751. Cortical layer from upper surface. (Magnified 30 diameters.) a, vertical fibres ; b, topmost stratum of the horizontal ; c, longitudinal, in section, occupying the interspaces between the vertical. age is adopted, whereby each of these is enabled to pass in a straight line to its destin- ation without being interfered with by the other two ; whereby the individual bundles of each set are isolated from their fellows ; whereby the whole of them are contained in the smallest possible compass ; whereby they not only admit the passage of, but mutually support and conduct each other ; whereby, in consequence of this, they are enabled to dis- pense with the support of cellular tissue, which accordingly we find absent ; whereby, lastly, the tongue contains the greatest amount of muscular tissue possible for its bulk. This system of package consists of this — that the crossing of the fibres of any two sets forms a lattice work, or mesh, through which the third shall pass, and that the successive layers of the crossing fibres shall be so arranged that the areola? shall form continuous channels for the transmission of the perforating ones. In whatever plane we look at the fibres, we find that this is the case — that two sets are crossing fibres and one set perforating — that two are seen in profile, one in section ; but, as we vary the plane, so do we vary the ap- pearance of the fibres, one set alone remain- ing the same and two interchanging. Thus, in a transverse vertical section the transverse and vertical fibres are seen in profile, and the longitudinal in section ; in a longitudinal ver- tical section the vertical and longitudinal are in profile, and the transverse in section ; while again, in the horizontal section, the trans- verse and longitudinal are seen in profile, and the vertical in section. So, no set can be called a perforating set or a crossing set, — they are all equally so. Again, we see that the office of the longi- tudinal fibres requires that they should have that special superficial arrangement which is the only one left them by the necessary dis- position of the other two. The chief office of the longitudinal fibres is to alter the direction of the tongue longitudinally, to twist it from side to side, or up and down ; any thing but a superficial distribution would render them powerless for this act. For if the longitu- dinal fibres were placed in the centre, it is evident that they could only shorten the tongue; but, being arranged superficially, when a portion of them contracts, that side of the tongue on which the contracting ones are is shortened more than the rest ; in other words, the tongue is turned towards that side ; and it is only when the whole sheath of longi- tudinal fibres acts equally that the tongue is contracted directly backwards. Having premised this general description, I shall now proceed to give a particular ac- count of the microscopical appearances of successive sections made in the three prin- cipal planes — the transverse, the longitudinal, and the horizontal. I shall begin with the transverse as being the clearest and the most illustrative. The first transverse vertical sections, made at the tip of the tongue, of course remove successive portions of the papillary structure : we next come to the cuds — the dense areolar tissue subtending the papillae — and many sections are made before the appearance of any muscle ; we have in fact to get through the thickness of the cutis. The first muscular fibres that make their appearance are the transverse, consisting of a single slender bundle of fibres in that direction, occupying nearly a middle plane between the upper and under surfaces, lying horizontally, collected into a single bundle in the centre, but breaking up at each end into smaller fasciculi, which diverge as they pass to their insertion into the cutis at the sides of the tongue, so as to gain a more extended attachment. The sections following this display an increasing quantity of this muscle, the diameter of the unbroken bundle in the centre being greater, and the fasciculi into which it divides at the sides more numerous ; but as yet no other system of fibres has appeared. The next addition, as we proceed backwards, is that of vertical fibres, which are at first very few and scanty, and placed not in the centre, but in two sets, one on each side of the centre ; they converge a little as they pass upwards, and are rather curved, presenting their concavity outwards. The succeeding sections show them increasing in numbers and spread- TONGUE, ing towards the centre, where the)' finally meet, and then the central part of the tongue is con- stituted in the same way as it is throughout the whole succeeding length of the organ, namely* by decussating vertical and transverse fibres ; but as yet no longitudinal fibres have appeared, and they are not seen till after the transverse area of the tongue has been entirely occupied by the vertical and hori- zontal fibres as above described. They first appear at the inferior surface, then at the sublateral and lateral regions ; next they are seen at the centre of the upper surface in a small definite cluster, from which they spread out, and so complete the circumference of the tongue. We see from this that the fibres that occupy the extreme point of the tongue are the transverse; that the next met with are the vertical ; and that the longitudinal do not extend so far forward as either of the other two. This is what might be expected. The chief muscular requisition at the extremity of the tongue is the power of pointing it : the shape of a tactile part is eminently subservient to its power of touch, because exact localisation, which is a most impor- tant element in touch (if it is not the very essence of it), depends on the smallness of the touching part. Now the extremity of the tongue, of its ordinary broad, flat shape when at rest, would be a very poor tactile instrument, and very far removed from a form that would capacitate it for the minute ap- preciation of distance and form. In what way, then, is the desired pointed shape of the tip of the tongue to be produced ? Manifestly by transverse contraction, for it is by the spread of the tongue in this direction that it departs from the pointed form ; and so we see the transverse fibres continued beyond either of the others, and occupying at the extreme tip the whole of the space assigned to the muscular structure. Furthermore, the longi- tudinal fibres are not necessary at the extreme point, either to flatten or shorten the tip, which is brought about by its own elasticity immediately on the cessation of the con- traction of the transverse fibres, or to move it in any direction, which is done rather by the movements of the parts coming immediately next the tip than of the tip itself. Thus, both negatively and positively, we see a reason for the continuation of the transverse fibres further forwards than either of the other two sets. The section last described completes what may be called the theoretical structure of the tongue (it is shown in Jig. 7y/hu/s)t the smallest of these muscles, constitutes the connection between the soft palate and the sides of the tongue. At its origin in the soft palate its fibres are mingled witli those of the palatopharyngeus ; as it descends to the tongue it becomes much narrower, constitut- TONGUE. 1133 ing the anterior pillar of the fauces ; and arrived at the sides of the tongue, it again spreads out, and its fibres mingle with those of the styloglossus, some of them passing transversely into the medullary structure. It lies immediately beneath the mucous mem- brane, and in front of the tonsil. Action : To constrict the fauces (hence its name, con- strictor isthmi ffiiicinm) by depressing the soft palate and raising the sides of the tongue. The styloglossus. — A small slender muscle arising by a pointed tendinous origin from the inferior half of the styloid process of the tem- poral bone, and also slightly from the stylo- maxillary ligament. It passes downwards and inwards to the base of the tongue, opposite to •which it expands and becomes flattened; a few of its fibres bend inwards, the majority being continued longitudinally along the side of the tongue, where they may be traced to near the apex, contributing to the formation of the lateral lingual muscle. As they pass forward, they mingle with those fibres of the hyoglossus that have a similar direction, and with the inferior lingual. Relations : Ex- ternally, with the parotid and submaxillary glands, the external carotid artery, the facial artery, the Whartonian duct, the lingual branch of the fifth nerve, and the stylomax- illary ligament ; internally, with the stylo- hyoid ligament, internal carotid, superior constrictor of the pharynx, the jugular vein, and hyoglossus muscle. Action: To retract the tongue, to raise and expand its base, and to render it concave from side to side by rais- ing its borders. The hyoglossus. — Flat, thin, and ascending nearly vertically, this muscle approaches a quadrilateral form ; but, from the dorsuin of the tongue ascending as it passes forwards, its anterior border is much larger than its posterior. It arises from the posterior ex- tremity, and from the superior border and outer surface of the greater cornua of the os hyoides, and from the body in their immediate neighbourhood. From this double origin the fibres ascend in two distinct sets. Those from the greater cornua, passing up nearly parallel to one another, are inserted into the sides of the tongue; those from the body expand as they ascend, arch forwards, and, gaining the side of the tongue at a point su- perior and anterior to the other, pass forward along the border of the tongue, and unite with Jthe styloglossus to form the lateral lingual. These two portions are separated below by a cellular interval ; and above a few fibres of the styloglossus pass in between them. Al- binus has described these as three distinct muscles : one, the cerato-glossus, arising from the greater cornua ; another, the basio-glossits, from the body : and a third, intermediate, the choiidro-gtossus, taking its origin from the lesser cornua. Relations : The external relations of this muscle are, — from above downwards, with the suomaxillary gland, the hypoglossal nerve, the mylohyoid, stylo- hyoid, and digastric muscles ; internally, it covers the glosso-pharyngeal nerve, the middle constrictor of the pharynx, the lingual ar- tery, the stylohyoid ligament, the geniohyo- glossus, and, at its attachment to the tongue, the inferior lingualis, which separates it from the last mentioned. Bichat erroneously states that the lingual artery ordinarily passes be- tween its two origins. Action : To depress the sides of the tongue and render its dorsuin convex ; to retract the tongue and draw it downwards. It is more frequently associated with other muscles than isolated in its action ; and accordingly as it acts alone or together with other muscles, either as concurring with them or antagonising them, so its actions vary. The genioglossus, the largest of all the mus- cles of the tongue, which it connects to the lower jaw, is of a radiated or fan-shape, and is placed vertically in immediate contact with its fellow of the opposite side. It arises from the superior genial tubercle of the lower jaw by a tendinous tuft from which the muscular fibres radiate to their different destinations. The most anterior, the shortest, forming the anterior free margin of the muscle, pass up- wards and forwards to the tongue, having reached the under surface of which, they are continued, according to Cruveilhier, on that surface to the tip ; but in all the specimens that I have examined they appeared to con- tinue an oblique course to the dorsum. The succeeding fibres pass more and more back- wards, and having reached the inferior surface of the tongue, are directed vertically to the dorsum, into the middle line of the whole of which they are inserted, from apex to base. The two muscles may be separated up to the point of their immergence into the tongue, but beyond that line their separation is no longer possible ; for, having entered the tongue, they come into relation with the transverse intrinsic fibres, which they cut at right angles, and interlacing with which they pass to the cutis of the dorsum, forming part of the vertical intrinsic muscle, from the rest of which they are not to be dis- tinguished except by their mesial situation. The fibres do not curve outwards, as sup- posed by Marjolin, to form part of the transverse lingual ; nor do they expand at all at their insertion, as stated by Cru- veilhier ; there is no disposition to lateral divergence in any part of their course ; on the contrary, their direction is rather upwards and inwards throughout, and their insertion extremely narrow — a mere line — as it might be imagined it would be, when its great longitudinal extent is remembered. The longitudinal furrow is, I think, mainly produced by the traction of this muscle in the median line. The most inferior fibres pass backwards and downwards, and are inserted into the hyoglossal ligament. Some of the fibres immediately above pass backwards, ac- cording to some authors, to the sides of the pharynx, where, uniting with the middle con- strictor, they form the genio-pharyngiens of Winslow. Relations: Internally with its fellow, being separated merely by areolar tissue con- 1134. TONGUE. taining some fat, particularly at its inferior part and the median fibrous lamina, when the in- termuscular areolar tissue is sufficiently dense to deserve that name ; anteriorly, with the froe- num, to which it is subjacent; inferiorly, with the geniohyoid; and externally, with the sub- lingual gland, the mylohyoid, hyoglossus, and inferior lingualis muscles, the ranine artery, and the gustatory nerve. The hypoglossal nerve threads its fibres, and passes forwards among them. Action : To raise and draw forwards the tongue ; to assist in constricting the pharynx ; to protrude, retract, or depress the tongue in the mouth, according as all or part of the fibres are employed ; to depress the centre of the tongue, and render it concave, from side to side. c. Accessory extrinsic muscles. — These are, in short, all the muscles that move the os hyoides without being attached to the tongue, for whatever moves the hyoid bone must move the tongue, which is fixed to it. They are accessory to the proper extrinsic muscles in two ways, either by acting in con- cert with them, or by facilitating their action on the tongue by rendering the hyoid bone a fixed point. Thus, in the first method, the stylohyoid and posterior belly of the digas- tricus concur with the styloglossus in draw- ing the tongue upwards and backwards. In the same way, the anterior belly of the digas- tricus, the mylohyoid, and geniohyoid, con- cur with the inferior portion of the genio- glossus in raising and drawing forwards the hyoid bone, and facilitating the protrusion of the tongue from the mouth. By the second method the muscles from the styloid process to the hyoid bone assist the longitudinal in- trinsic muscles of the tongue by rendering the base a fixed point from which they can ad- vantageously act on its length, and in the same way the inferior set of hyoidean muscles are accessory to the hyoglossus by fixing the hyoid bone down. More might be said on this subject, but enough has been stated to indicate the important relation of these muscles to the proper muscles of the tongue, and for the sake of brevity that may suffice. Movements of the tongue. — All the infinite variety of movements by which the tongue is, by virtue of its complex muscular organisa- tion, susceptible, may be arranged under two heads, — its extrinsic and intrinsic move- ments ; sometimes dissociated, more fre- quently concurrent : for the sake of clearness I shall consider them separately, and then group them. First, the intrinsic movements of the tongue are of two sorts ; those affecting its length, and those affecting its direction. a. As affecting its length. The elongation of the tongue is provided for, like all in- trinsic elongation, by diminution of calibre ; in the tongue this is produced by transverse and vertical contraction, especially the transverse, whereby the tongue becomes at once elon- gated and pointed ; by this means the tip of the tongue can be protruded beyond the teeth without any movement of the organ en masse, or any assistance of the extrinsic muscles. From this elongated state it is restored to its original position and shape by the contraction of all the longitudinal fibres composing the cortical portion, which draw it directly back, the transverse and vertical fibres at the same time ceasing to act. Thus we see that the central and cortical portions of the intrinsic muscles are antagonistic ; but they are capable of association : tor instance, when the tongue is to be flattened and its sides pressed against the teeth without any elongation, an action very frequent in mastication and in the pro- nunciation of some letters, this is done by the contraction of the vertical fibres associ- ated svith the longitudinal, the one diminishing the vertical thickness, and so spreading the tongue out, the other preventing the elonga-. tion which the diminution of vertical thick- ness would otherwise be attended with. b. As affecting its direction. The direction of the tongue is entirely regulated, as far as the intrinsic muscles go, by the longitudinal fibres, and their power of modifying the direc- tion of the tongue, as well as shortening it, depends on their power of partial action : thus the lateral lingual of one side can act, or of the other ; the superior or the inferior, and the point of the tongue is of course moved to the side of the acting muscle. This modi- fication of the direction of the tongue is, per- haps, the most complete movement that it possesses; it is certainly the most extensive : by it the tip of the tongue may be depressed deep below the incisor teeth, or reflected back on the soft palate, so as nearly to touch the uvula; or laterally, from the pillars of the fauces on one side it may be carried round the cheeks and alveolar arches to the same position on the other side : these are the cardinal points, up and down, right and left; they may be united in any proportions, so as to carry the extremity of the tongue to any intermediate position. Moreover, the movements affecting the length of the tongue may concur with those affecting its direction ; for instance, on apply- ing the tip of the tongue to the root of a canine tooth of the upper jaw, on the outer surface of the alveolus, the tongue is elon- gated, and vertico-laterally flexed ; on apply- ing it to the last molar tooth of the lower jaw it is laterally flexed and shortened. Secondly, the extrinsic movements of the tongue admit of the same division as the intrinsic, into those regulating its length, and those regulating its direction or shape. a. Thus the tongue is carried upwards and backwards by the styloglossus, assisted by the other styloid muscles, downwards and backwards by the hyoglossus, directly back- wards when these both concur; and it is carried forwards and protruded from the mouth by the genioglossus. These move- ments, en masse, almost always concur with the intrinsic movements, the whole organ following to a certain extent the direction of the extremity. b. But the extrinsic muscles affect very TONGUE. 11.3.3 materially the direction and shape of the tongue : the styloglossi raise and expand the sides, the palatoglossi raise and approximate them, and the hyoglossi depress them ; the one set makes the dorsuni of the tongue transversely concave, the other convex : moreover, the posterior fibres of the genio- glossus draw the centre of the tongue for- wards and downwards, so that they also render the tongue transversely concave. The action of the genioglossus is peculiar ; the most posterior fibres draw forwards the base of the tongue, and are those chiefly concerned in the protrusion of the organ ; the most anterior concur in replacing the tongue when thus protruded ; when the whole muscle acts it compresses the tongue into a sort of button, and carries it deep closvn in the arch of the lower jaw. The relations of the hyoglossus and genioglossus are worthy of remark : they arc congeners, inasmuch as they both tend to draw the tongue downwards ; they are antagonists, inasmuch as the one tends to draw the tongue principally forwards, the other principally backwards ; when all four muscles act, the tongue is depressed deep in the jaw, but further back than when the genioglossi act alone ; when the two muscles of one side act, that side alone is depressed, and a certain torsion is given to the tongue which enables it to 'apply the tip advantageously to parts that it would otherwise be very difficult to reach. If the movement of the tongue in transferring the tip from the last inferior molar tooth of one side to that of the other be watched, with the mouth open, at a glass, it will be seen to be collected in a globe at the back of the mouth, and to rotate horizontally, as it were on a pivot. The only way in which I can conceive this movement to be brought about, is by the consentaneous action of the hyo- glo.ssus of the one side with the genioglossus of the other, — the one right with the other left, then the one left with the other right, and so on, the styloglossi and palatoglossi at the same time preventing the depression of the tongue. But it would be vain to attempt to describe in words the endless variety of movements of which the tongue is susceptible; and if it were possible to give an idea of them, space could not be afforded: so, dismissing this part of my subject, I will proceed to the next. S.'Tegumcntary system. — The tegumentary system of the tongue is formed by the mucous membrane of the mouth passing on to it from neighbouring parts, and undergoing special modifications according to the part that it invests. A superficial glance shows it at once to admit of a triple division, into, first, a really or apparently plane portion, situated in front of the epiglottis, beneath the borders, and on the free portion of the under surface ; secondly, a papillary portion, covering the anterior two-thirds of the upper surface, the free borders, and the tip ; and, thirdly, a glandular portion, occupying the posterior third of the upper surface, where it is folded into little crypts and raised in nodules over small mucous glands: these glands exist also along the sides and beneath the tip: they will be reserved for future description. The mucous membrane here, as elsewhere, consists of three portions, — a basement or limitary membrane, underlaid by a submucous areolar tissue, and surmounted by an epithe- lium. a. Cutis. — The sub-basement areolar tissue of the tongue exists in sufficient quantity and density to deserve the name of a true chorion or cutis. It is thickest at the upper surface, where it underlays the papillae, espe- cially towards the median line; its density too is the greatest here, sometimes amounting to almost a cartilaginous hardness, and the pro- portion of white fibrous tissue to the yellow is the greatest; it is thinnest on the under surface and edges, where it contains more ot the elastic element, especially in the neigh- bourhood of the epiglottis ; at the line where the attached and free portions of the tongue meet, it gradually merges off into the loose elastic web that underlays the mucous surface in these situations. Its inner surface receives the insertion of all the intrinsic muscles of the tongue, among which for a short distance it dips, and it sends processes into the folds that attach the tongue to neighbouring parts, as the glosso-epiglottidean and fraenum. It is the medium in which the nerves and vessels destined to the surface break up previous to their ultimate distribution : the vascular rami- fications form a plane network, coincident with the surface, from which, at regular intervals, the papillary vessels ascend. b. The basement membrane is variously modified in the three situations above indi- cated; it is either continued plane, projected into papillae, or folded into mucous crypts, from which its further involution constitutes the minute ducts and ultimate follicles of the mucous glands opening into these crypts : its description will be involved in the particular consideration of these structures. c. Epithelium. — This very nearly approaches in character the cuticle of the skin, which it resembles in being of the scaly variety, in the amount to which it exists, and in its being divisible into two laj'ers, a deep one closely adherent to the basement membrane, consist- ing of more recent cells, retaining much of the cellular form (Jig. 753., c.), and a superficial one, readily desquamating, the cells of which are older and flattened into scales ( fig. 753.. d.). It exists in very different quantity in different parts, being most abundant where it invests the papillary structures. The shape of the in- dividual cells is very various ; where they are flattened their area is much extended (fig. 753., a.), and they look four or five times as large as the deep-seated ones; but probably there is no increase in size, their lateral extension resulting from their greater thinness: viewed in profile they appear quite filamentary ; some of them are not flattened but elongated, so that they appear linear in all aspects, and are really so. In spite of all these modifications 1136 TONGUE. Fig. 753. Epithelium of the tongue. a, a single flattened superficial cell, viewed super- ficially and edgewise ; b, from the horse, showing the filamentary prolongation of a part only of each cell ; d, superficial ; c, deep layer. a small single circular nucleus may generally be seen very plainly occupying a central posi- tion in the cell, and unchanged in form and size by any of the changes that the cell under- goes. Certainly the epithelium, covering most parts of the tongue, does not contain any pigment ; but I think that covering the filiform papillae in the centre of the dorsum very frequently does ; and for these reasons, — because, first, the growth of the epithelium here is very abundant, and it seems a general rule that pigment should be associated with an abundantly nourished or rapidly developed epidermis, as is seen in hair, in the colour of those spots that are called moles, and the hair that proceeds from them, which, instead of being invisible, as in neighbouring parts, is dark and rank, and in the change of colour which the cuticle and hair covering the parts of genera- tion undergo at the increase of the nutrition of the parts that accompanies the accession of the generative function ; secondly, because we see that the epithelium does undergo great changes of colour, being generally dark- est when most abundant ; thirdly, because, in two cases that I have seen, in which the only diseased condition was an enormous develop- ment of the filiform processes which the epi- thelium forms in the centre of the tongue, the colour of the fur was a dark sepia or Vandyke brown, almost black, exactly that of pigment in other situations : we see too, when the epithelium has been rendered opaque by soaking the tongue in alcohol, that all the other papillae are whiter than the fili- form occupying the centre of the dorsum, which retain their tawny colour. The epithe- lium of the tongue differs from the dermic cuticle chiefly in its moisture, and the delicacy and softness of its structure. Papillary structure of the tongue. — The pa- pillae of the tongue are generally contrasted with those of the skin, in that while the latter are covered over with an even layer of epi- derni's, and therefore not visible to the naked eye, the latter stand out free from the surface of the epithelium, dipping down between them. But viewed by the light of recent researches, this is seen to be only the appa- rent difference, the real difference being that while the papilla? of the skin are sessile, the papillae of the tongue are arranged in groups on proper pedicles or supports, whose tops and sides they cover, and which elevate them above the general surface. For it has been recently shown by Professors Todd and Bow- man *, that the papillas, heretofore considered simple, are really compound organs, and that they are covered by other smaller papillae, whose form and whose method of nervous and vascular supply, show their true analogy to the papilla of the skin. In physiological exactness, and to carry out the analogy insti- tuted by these anatomists, we may say that these large papillae, so called, are no more true papillae, than the long processes in the intes- tine of the rhinoceros are true villi. Now, these secondary, or true physiological papilla-, are covered in by an even layer of epithelium, in just the same way as the papillae of the skin ; hence we see that the distinction gene- rally laid down ceases. It would, however, be too great an innovation to reject the name of papillae for those organs that have so long possessed it, and as the value and office of their different parts will be implied in their description, no misconception can arise. I shall, therefore, continue the old nomen- clature. There are three principal forms under which the papillae, visible to the naked eye, exist on the surface of the tongue. 1st. The drcumvallate (caliciform, Cuv.), the largest and fewest in number, and the most conspicuous, situated at the junction of the middle and posterior third of the tongue, where, by their arrangement in two lines, having a direction backwards and inwards, which meet in the centre, they form a V-shaped ridge, with the base directed forwards ; 2nd. The fungiform, more numerous than the last mentioned, and smaller, irregularly scattered over the centre, sides, and apex of the tongue ; and, 3rd, The conical or Ji/iform, by far the most numerous and smallest, arranged in a dense pile over the whole anterior two-thirds of the upper surface, among which the last-mentioned are im- planted. To these may be added a fourth class of simple sessile papillae, first pointed out by Professors Todd and Bowman as existing on the apparently non-papillary surface im- mediately behind the circumvallate papillae, and which I have found also to exist on the whole of the under surface of the free portion of the tongue. The circumvallate papilla? are of the most complex form, and may be considered as con- sisting of two parts — a central, button-like projection, flattened or truncated at its free surface, and a raised border surrounding it in the form of a ring, of nearly equal elevation with the central part, the two portions being separated by a circumvallation, or fossa (b). When a vertical section is made of one of these papillae (_/?#. 754*.), the central portion is seen to be in the form of an inverted cone, and the surrounding fold is seen to constitute a cup, at the bottom of which the apex of the Physiological Anatomy, vol. i. p. 435. TONGUE. 1137 Fig. 754. Circumvallate papilla seen in vertical section. a, Truncated surface, or base of the cone ; b, cir- cumvallation ; c, raised border. (Mag. 1C diam.) cone is attached. At the attached portion the nerves and vessels enter, and the free trun- cated surface, or base, of the cone is covered with small secondary papillas, concealed by the epithelium (fig. 754. a) ; the free border is also surmounted by secondary papilla?, so that it is, in fact, a circular compound papilla (c). The circumvallate papillae possess the utmost irregularity as to size, number, shape, and arrangement. Their number has been much overstated by some anatomists ; Cruveilhier gives it as from sixteen to twenty, Marjolin from nine to fifteen, Scemmering from twelve to fourteen, and Meckel from three to twenty. I think the number given by Messrs. Todd and Bowman, as from eight to ten, is much nearer the truth ; certainly, if ten can be counted, they must be considered well deve- loped ; frequently the number is below this — I have seen as few as five, or even four. In size they vary from that of an ordinary fungi- form papilla to upwards of £th of an inch in diameter. They always assume more or less of the V-shaped arrangement, but the per- fection with which the linear series is main- tained, the straightness of the lines that form the angle, and the size of the angle so forme;!, all vary very much; I have seen them stretch- ing across from side to side of the tongue, almost in a straight line, with a third arm projecting back from the centre, something like the form of a tripod ; it is not uncommon to find a stray one or two scattered to a great distance beyond the prescribed line ; the cen- tral one is frequently thrown back half an inch, and sometimes a lateral one is found quite at the edge of the tongue. In shape, the varieties are chiefly owing to the relative size and development of the central tubercle and the circular ridge surrounding it. Sometimes one of these parts is suppressed, and then you either get what appears to be a large fungiform papilla, or a set of ridges having something of a circular or quadrilateral ar- rangement, not to be distinguished from the fused rows of conical papillae which surround the circumvallate on all sides, and which are, in fact, continuations and prolongations of their calices. Haller mentions having seen the circumvallate papilla; in two rows on each side ; I have met with a similar arrange- ment on one side. This appearance may in some degree be accounted for by the supposi- tion that the rows of conical papilla?, among which the large fungiform immediately in front of the circumvallate are planted, have attained a circular or calyx-like arrangement around them ; for a large fungiform papillae, situated in a calyx so formed, would produce a very perfect papilla circumvallata. This change is just the reverse of that which reduces a cir- cumvallate papilla to a fungiform by the sup- pression of its surrounding ridge, and both, no doubt, are sources of irregularity. These papilla? are supplied by branches from the glosso-pharyngeal nerve, which may be dis- tinctly traced to them ; their vascular supply is abundant, and their epithelium thin and fine, so that during life, and when injected, they appear very red. The fungiform papillce, as their name indi- cates, have more or less of the form of a sphere supported on a pedicle ; this is their typical form, but they often deviate from it ; in size they vary from ^nth to a'^th of an inch. They are scattered over the sides and tip of the tongue, and on the clorsum in front of the circumvallate. They may be dis- tinguished from the filiform, among which they are implanted, by their red colour, in which, in the thinness and smooth- ness of the epithelium investing them, and in the abundance of their vascular and nervous supply, they resemble those last de- scribed. When examined microscopically, they are seen to be covered on their sides and summit with secondary papillce (Jig. 75.5. A), to A, Fungiform papilla, showing the secondary papillae on its surface, and at a the epithelium covering them over. (Mag. 35 diam.) B, Another, with the capillary loops of its simple papillae injected, a, artery ; v, vein. The groove around the base of some of the fungiform papilla? is here represented, as well as the capillary loops, c c, of some neighbouring simple papilla?. (Mag. 18 diam.) (After Todd and Bowman.) 4 D 1138 TONGUE. which, in injected specimens, the individual loops of capillaries may be seen projecting with great regularity and beauty (B). The fungiform papillae are largest about the centre of the tongue, smallest along the edges, and most numerous at the sides of the tip, but they are liable to the greatest variety in their size and distribution ; I have seen them HO large about the centre of the tongue, as almost to equal in size the circumvallate ; I have seen them so numerous at the tip, as nearly to equal in number the filiform among which they were scattered ; again, in the same region, I have seen them so scanty, that they could hardly be said to exist there.* The conical or filiform papillae, the third class, constitute the great mass of the papillary structure; they cover, in a close-set pile, the whole of the anterior two-thirds of the tongue, being limited behind by the circum- vallate, and having the fungiform scattered among them : it is their structure that imparts the rough coriaceous character to the papil- lary surface, and they constitute the fur in the centre. They are altogether smaller, but in length they exceed, at least in the centre, the other two forms, and they exhibit greater di- versity of structure and a more complete ab- sence of typical shape than either of the other varieties. They affect in some situations a Fig. 756. A filiform papilla taken from the dorsum of a tongue in which the fur was much developed. (Mag. 30 diam.) a, imbricated scaly epithelium investing the cylin- drical portion of the papilla ; b, the commence- ment of its breaking up ; c, its separation into its ultimate filamentary processes ; d, the deep layer of epithelium exposed by the removal of the more scaly superficial one. * May not these varieties explain the correspond- ing diversities in the acuteness of the sense of taste, •which we so often find in different individuals? linear arrangement, principally at their con- fines, that is, in front of and around the caliciform papillae, where they are continuous with the elevations that surround these pa- pilla3, of which they are the continuations forwards and outwards, and along the whole free margin of the tongue, except at the tip, where the linear arrangement cannot be traced. In the first-mentioned situation their rows run forwards and outwards, coinciding with the arms of the V-shaped figure that the cir- cumvallate papillae assume ; in the last-men- tioned, they are placed vertically along the sides (fig. 745. i i) : they have been well de- scribed and figured by Scemmering.* Along the centre of the tongue, in the neighbourhood of the median furrow, the conical papillae often assume a cracked and fissured appearance ; but the linear arrangement is less marked here, and the fissures have no determinate direc- tion, but can be made and effaced according to the movements of the tongue. The conical papillae are largest in the neighbourhood of the circumvallate, where they are truncated, and where some of them assume almost a fungiform shape : they are longest about the centre of the tongue, near the median line, and smallest in the anterior part, near the side and tip. The form of the projections of base- ment membrane, on which the epithelium is Fig. 757. Vertical section of conical papilla. (Mag. 25 diam.~) a, basement surface ; b, conical papilla of ordinary- shape; c, more nearly approaching the simple form ; 17, one quite simple ; e, deep cellular layer of epithelium; f, superficial scaly portion; h h, points from which the filamentary prolongations would have passed up. placed, constituting the mould of the true papillary structure, is generally something of a cylindrical shape, the top supporting second- ary papillae, or it is conical, the secondary papillae being continued more or less down the sides : or the base is small, and supports a more expanded portion, and thus the conical is seen to pass into the fungiform shape. But it is in the epithelium that the characteristic difference between these and the other papillae * Icones Organoruin humanorum gustus et vocis. Francofurti, 1808. TONGUE 1139 is to be found. In the other forms we saw it continued over the whole compound organ as a thin indusium, covering in and concealing the secondary papillae under its smooth invest- ment, the scales being arranged parallel to the surface; but in the conical and filiform papillas we not only see the epithelium exist- ing in much greater quantity, but over each secondary papilla assuming a vertical arrange- ment, and, after continuing compact for some little distance, breaking up into a brush of hair-like processes (fig. 756.), the number coinciding with that of the secondary papillae Where the secondary papillas are few the hairs are few, where they are many the hairs are many, and each hair may be traced down, by following the line in which the epithelium is vertical, to each papilla. In fact, these pro- cesses are true hairs, and only differ from other hairs in being short, uncompact, imperfectly elaborated, and in having the imbrication retroverse instead of directed forwards ; and the secondary papillae from which they spring are true hair papillee, differing only from ordi- nary hair papillae in being raised and grouped on a common pedicle instead of sunk in a proper follicle. In some cases the resemblance of these filaments to ordinary hair is very close indeed, as seen in Jig. 758, ; indeed in c Fig. 758. Hair-like processes of filiform papilla, a, Mag. 150, b and c, 100 diameters. the chief difference is in the direction of the imbrication : in some morbid specimens I have seen it even closer. Now this difference in the arrangement of the epithelium on the different papillae in- dicates, I think, a very important physiolo- gical distinction ; in one case we see the sen- tient papilla? covered by a thin layer of a fine epithelium, thinner over them than in the in- tervals between them ; in the other case we see each secondary papilla the seat of a rapid generation of epithelium that clothes the whole compound organ with a dense impene- trable brush of hairs this latter arrangement seems as inconsistent with the possession of sensibility as the former seems adapted to it, and the difference would suggest to me the division of the papillae into "sentient" and "protective ;" among the former I would class the circumvallate and the fungiform, among the latter the filiform and, with a certain qua- lification, the conical : but I shall return to this presently in speaking of the functions of these papillas. The great difference between the filiform and conical forms is in the amount of the epithelium : in the filiform it is such as has just been described j in the conical, the hairs are very short and thick, and terminate in an even plane almost as soon as they be- come separate, so that they have not at all a filamentary character. This epithelium is being constantly generated and as constantly thrown off, as is shown by the variation in the quantity of fur on the tongue from day to day. It is in these papillae that the separation into two layers is best seen (Jig. 757. a' cases, however, as m the locusts and dragon £ Retracted proboscis of Buccinum undatum. a, flies, it is tree. 1ms process Cuvier con- mouth; b, tongue; c, oesophagus. sidered merely as a part of the labium, and accordingly called it labium ; Fabricius and , . B, single row of tongue-teeth of B. undatum. accordingly called it laoium ; J?aL>ncius and _,. . Latreille gave it the name of ligula. In shape f ihls. membrane is covered on its upper sur- it is generally short, but in bees it is long; it , Wlth transverse rows of minute teeth, or is frequently simple, but in the wasp its apex ralner plates with tubercular or toothlike pro- is trifid, the same in Melolontha stigma ; in ce^se.s l'P°n tliem. The number of rows is Canabus it possesses three short teeth ; in cons.lderable, and very variable, the terrestrial Elaphras it terminates in a single tooth or sPecies averaging, probably, about eighty, and point. In substance it generally approaches marine possessing often many more ; the to a cartilaginous consistence, but in the Ort'io- number °f plates in each row is subject to still greater variation : the common whelk ptera and Libellulcs it is much more fleshy: and in the predaceous beetles it is as hard and horny as the integument. In some cases it is immovable, in others projectile and re- tractile within the mouth ; in some cases smooth, in others covered with hairs, as is the case in the common hive-bee ; in Melo- luntha stigma the hairs are incurved In the undalum) has but three (fig. 759. B), the large garden slug (Limax maximus) has 180. The shape of die plates in terres- trial gasteropoda is usually irregularly qua- drangular, slightly longer than broad, while in some fluviatile and marine species they as- sume most complicated and elegant forms /• _^? . •.•,/-! T-» \ m i O I'M*.* HCMIO €.11 ^ Jill- LI 1 V tl.1 • JL11 ItPIC / j£? T»\ hive-bee the upper part of the tongue is car- 'f^- '59< B'' .The centre plate of the row is tilaginous, and remarkable for a number of alwa)'s symmetrical, and its denticular projec- transverse rings : below the middle it consists *lon!? P°int m tlle dll'ection of the closed end, of a membrane longitudinally folded in in- '• e~ backwards, and nearly horizontally. The action, but capable of being inflated to a con- p j1168 on elth.er Slde of .this central plate usu- siderable size : this membranous ba<>- receives T, y assumf m terrestrial gasteropods much the honey which the toncue, as it were laps t?e ^am.e form and direction, while some of from the flowers, and 'conveys it to the e fluviatlle and most of the marine species pharynx.f present such an endless variety of forms, that Mollusca.— Gasteropoda. In the acephalous fhe most that can be said of them, generally, mollusca there is, of course, no tongue. But 1^,that the dental processes point backwards, the Gasteropoda are provided with a very sin- f' 7o9' B represents a row of the denti- gular apparatus, which, since it is usually called gerous tongue-plates of the Buccinum undo- the tongue, cannot be allowed to pass obser- tun\ : there are sef n to be onl>' three ; the cen- vation here, though its right to such an ap- t,ra one symmetncal, the lateral ones of very pellation is somewhat questionable. Its form dlfferent, form, individually non-symmetrical, is subject to much variation, but it may be having an exact correspondence to one described generally as a thin membrane. 'ion- anoth-er; The tongue itself (Jig. 759. A, 2) is ._ i , i r> i • i . fifturh pn PQ Korrti-A ofofo,-) t^4-U^. ^_u,_ generally , and narrow, the greater extent of which is rolled into a tube. This tubular part (fg. 759. A, 6), occupies the posterior portion °of the attached, as before stated, to the oesophagus near its anterior extremity, and lies beneath it. In the Helices and Limaces it is enveloped , , e membrane, the end being closed, while its an- '"_ £ne muscular head of the gasteropod (fig. terior extremity is open and in connection • /, '\ lts Posterior Dl'"d end being just with the oesophagus ; in front of the tubular vlslble at the back part of the head, some dis- part of the tongue is a continuation of the ,tance , ow the Pomt where the oesophagus same membrane, which is here flat, and in many .es that Part and passes into the abdominal cavity. In the whelk tribe it lies beneath, and . n ,, ,', ,. parallel to, the oesophasrus, and is free, though * Ce qu on a nomine langue dans les coleopteres !.,,..,.,->,,„ J« i i i • ? et les orthoptcres, ou 1'extremite membraneuse 'de la sunoilldf.d b3' strong muscular bands, the levre infe'rieure, en me'rite & eine le nom. Guv. general direction of which is also parallel to , levre infe'rieure, en me'rite & peine le nom. Guv., Le9ons d'Auat. Comp., t. iii. p. 347. f Kirby and Spence, vol. iii. p. 453 genera irection o wic is aso par It is in this tribe that the an- terior end of the tongue is curved downward, TONGUE. 1143 while its posterior extremity unlike terrestrial species, is furnished with a strong retractile muscle. In some other marine gasteropoda, as the limpet, a very small portion only of the tongue is included in the head, whilst the rest of it lies folded up in the abdominal cavity, between the intestines and the muscular foot, but perfectly free ; and in some cases it is nearly twice as long as the entire length of the animal. Of the uses of this curious apparatus it is difficult to speak with certainty. The short thick tube of the terrestrial gasteropoda ap- pears adapted for the trituration of food pre- paratory to its passing into the oesophagus : these species are furnished with a large, strong, horny plate, fixed in the mouth at the upper part of the head, and, consequently, the flat end of the tongue acts as an under jaw working against this horny plate. It is not easy, however, to imagine that the long nar- row tube of the whelk tribe can be used in the same way for triturating food, though the envelope of strong muscles would fa- vour that idea, while the consideration of the still longer and perfectly free tube of the limpet renders this use of the tongue among the marine gasteropoda still more improbable. It is well known that the Buccinum widatum and its allies use the flat- tened portion of the tongue as a file, with which they bore holes through the shells of other species and then feed upon them, and the muscular apparatus by which this is ef- fected is an admirable piece of mechanism. It consists of a protractor muscle, over the anterior extremity of which the curved por- tion of the tongue is flexed, which, by its self-elongation, probably by intrinsic trans- verse contraction, projects this recurved por- tion of the tongue from the mouth, and keeps it there ; when the tongue is thus pro- truded, the retractor muscle, already alluded to, attached to its posterior blind extremity, contracts rhythmically, and so pulls the re- curved portion with a sawing motion over the extremity of the protractor muscle, which acts as a pulley for it: thus the teeth which cover the outer or free surface of this reflected portion are brought into the relation, with the objects on which they are to act, the most ad- vantageous for filing them away. But this gives us no clue to the determination of the manner in which the tubular part of the tongue is employed, nor am I aware of any probable conjecture having been advanced upon the subject. Professor Loven, of Stockholm, has pro- posed a system of classification of gasteropoda founded upon the forms of the tongue-plates and their arrangement ; and it is probable that conchologists will find the suggestion a valu- able one, not so much for the sole foundation of an arrangement as for a check upon classi- fication on other bases.* * For much of the above detail I am indebted to Mr. Thomson, of King's College, as well as for the specimens from which the drawings were made. Cephalopoda. Hitherto, in the insects among the Articulata, and the gasteropods among the Mollusca, we have only seen in the tongue an instrument for facilitating, mediately or immediately, the prehension of food : in the Cephalopoda we have the first structural indication of the sense of taste, and apparently in a perfection consistent with the high orga- nisation of the animal in other particulars. In both the tetrabranchiate and dibranchiate or- ders of cephalopods we meet with tongues of very similar structure, possessing in both an anterior and posterior soft papillose part, and an intermediate portion invested with a horny lamina, beset with rows of recurved spines. It is hardly possible to help seeing in this dis- tribution of parts the strong analogy it pre- sents to the mammalian tongue, in which the gustatory papillae are situated near the tip and base, while the centre of the clorsum is occu- pied by a rough indusium, subserving the same double office as the spiny lamina of the cephalopod, protecting the organ and facili- tating deglutition. In the Nautilus the tongue is supported by an oblong horny substance, probably analogous to the basis of the hyoid bone, free at its posterior extremity, but em- braced anteriorly by two retrabent muscles which arise from the posterior margins of the lower mandible. The anterior free extremity of the tongue itself is divided into three soft, fleshy, papillar caruncles, of which the central or anterior one is the largest. Behind them the surface is invested with a thin horny plate, on which are set four longitudinal rows of recurved spines, twelve in each row, each spine being about two lines in length. Be- hind this the tongue is again soft and sensory, but the papillae are coarser ; a fleshy fold pro- jects forward from each side of the fauces, likewise covered with papilla?. In the di- branchiate order the papillary structure is less perfectly developed, and the central horny lamina, instead of being in one plane, is bent at right angles into a vertical and horizontal portion, the incurved spines being set only on the vertical part. The rows of spines are seven throughout, but in the Onyc/iotctcthis, as they descend towards the base of the plate, the outer rows merge in those next them to- wards the centre till there are only three rows. The method in which the cephalopods appro- priate their food, by tearing off piecemeal, by means of their strong and sharp mandibles, portions of the prey they have seized and are holding in contact with their mouth, renders the possession of the sense of taste of high importance to them, as the immediate contact of their food prevents their testing its nature by the sense of sight : at the same time, the full enjoyment of this sense is permitted by the nature of their food, its partially commi- nuted condition, and their protracted method of taking it. Vertebrata. — In the Invertebrata the defini- tion of a tongue depends, with few exceptions, on little more than locality and function — the requisitions of a tongue and the possession of an organ of any sort that fulfils those requi- 4 n 4 1144 TONGUE. sitions, constitute its possession, or any oral process, to which no other name can be assigned, is called a tongue. But when we enter the Vertebrata we find an organ of characteristic structure, conforming to a general type, pos- sessing many common characters, of a form whose varieties are not so great as to prevent its being the name of a particular shape, and always constituted of those three systems previously enumerated as essential to the tongue of Vertebrata. I shall first consider the comparative anatomy of the bony system of the tongue in all Vertebrata, and then briefly refer to some of the principal characters of the organ itself in the four classes into which that subkingdom is divided. Hyoid apparatus. — The comparative ana- tomy of the hyoid apparatus is a subject of high interest, as it enables us, by its reflected light, to read successfully the true nature and value of the different elements of the structure as met with in man and other mammalia. It shows us, with the certainty of a demonstra- tion, and the contrariety almost of a paradox, that the hyoid bone in man, which we are ac- customed to look upon as a single bone whose dismemberment depends merely on late ossi- fication, is, in reality, a composite structure — a contribution from two distinct systems of bones ; that while the body and lesser cornua form part of the true endoskeleton, and are congeneric with the bony framework of the trunk and limbs, the greater cornua form part of the visceral or splanchno-skeleton, and are congeneric with the maxilliform supports of the teeth of the stomach of the lobster, or the bony pieces situated in the auriculo-ventricular ring, in the hearts of ruminants, or with other similar structures ; and that, as we must look upon these in regard to the function they sub- serve, as respectively digestive and circulatory bones, so we must regard the greater cornua of the hyoid as respiratory. To prove the truth of this proposition, it will be necessary to examine the state of the hyoid apparatus in water-breathing animals, and to connect its condition as found in these with what we find it in air-breathers, by tra- cing the modifications which its different parts undergo in those animals, part of whose ex- istence is destined to the respiration of water, and part to that of air ; we shall thus gain a clear insight into their homologies, and be able to refer part to part without the chance of fallacy, inasmuch as the link of their con- nection is lodged not in different individuals, but in different parts of the life of one. I shall describe it, 1st., in fish. Professor Owen has shown that the different segments of the true hyoid arch are so many elements of the inverted or haemal arch of the third cranial vertebra. The centre of this arch in fishes {Jig. 760. A) is formed by four small, subcubical bones, the bnsi-hyals (b '//) (two only are represented in the figure, being seen in profile), from the sides of which extend upwards, backwards, and outwards, two long and stout cylindrical pieces, the cerato-hyals (c //) ; the summit of each of these is surmounted by a small trian- gular piece, the epiJiyal (ep Ji), and the arch thus constituted is suspended on each side, to the base of the skull, by a small, slender ossicle, the stylo-hyal (st /;), which may be considered either as the entire proximal piece of the hyoid arch, or a dismemberment of that piece, according as the posterior division of the epitympanic, to which it is attached, is looked upon as the displaced proximal piece of the next arch in advance, the tym- pano-mandibular, or as itself the proximal element of the hyoid. This completes the hyoid arch: in most fishes, however, there are two more bones attached to the centre of the apparatus, one stiliform, projecting forwards, appended to the anterior surface of the median symphysis of the basi-hyals, the glosso-h i/al (g fi), the true lingual or tongue-bone; the other, the uro-hi/al(uh), a vertically-expanded, triangular piece, extending backwards from the posterior surface of the basi-hyals. There are generally appended to the posterior and lateral surface of the cerato-hyals and epihyals a series of slender, slightly curved rays, varying in number from three to thirty, but generally about seven, as in the cod (Gadus Morrhua) {fig. 7GO. A) ; their office is to sup- port the membrane that covers in the branchial chamber, whence they are called branchio- stegft/s (6, b). Immediately behind the hyoidean arch, we meet with a system of arches, the branchial, whose office is to support the gills, and whose structure, position, development, and con- nections prove them to have no relation with the true skeleton : they are generally five in number; the four anterior being branchial, the last, which is dentigerous and guards the gullet, pharyngeal. Each arch rises laterally from a median chain of ossicles attached to the basi-hyal, or uro-hyal when ossified, and consists of a short inferior piece, the hypo- branc/iiaf, surmounted by a long, curved piece, the cerato-bmnchial, bending first outwards and upwards, then forwards and inwards, under the base of the cranium. Now, these arches are what were just now stated to be homologous with the posterior or greater cornua of the hyoid apparatus, in all vertebrate forms, whenever they exist ; that they are so, will best be shown by tracing the modifica- tions they undergo in the metamorphoses of the anourous batrachians. Fig. 760. B, 1. re- presents the hyoid and branchial apparatus in the water-breathing tadpole ; B, 2, where the same animal has become the air-breathing frog. In the full-gilled tadpole (B, 1), a simple basi-hyal (b h) supports laterally two cerato- hyals (c h), and posteriorly two short hypo- branchials (h b), to each of which are attached four cerato-branchials (c b). The second stage is marked by the divergence and growth of the extremities of the hypo-branchials and the pro- gressive absorption of the cerato-branchials. At the third stage, the cerato-branchials have disappeared, and the hypo-branchials have assumed the character of true greater hyoidean cornua (B, 2, h b). In the fourth stage they TONGUE. Fig. 760. 1145 Comparative anatomy of the hyoid apparatus. (After Gcoffroy and Owen.) A, Fish (Cod). 13, Reptile (Frog : 1, tadpole ; 2, adult). C," D, Bird (C, Crane; D, Woodpecker). E, Mammal (Horse). became ossified, and, together with the cerato- hyal, coalesce with the basi-hyal. As in their previous condition they subserved to respira- tion, so now they do the same — as they before supported the branchiae, so now they support the trachea and larynx : they may be always recognized by this relation, — they always embrace the commencement of the air-passages in their fork, being especially connected with the first segment of the carti- laginous framework of those passages, namely, the thyroid cartilage ; the universality of this relation has induced Professor Owen to name them, in air-breathing vertebrata, thyro-hyah (fig. 760. C,D,E,A6, cb). In birds (Jlg.lGO.C and D), the elements of the true hyoid arch are either rudimentary or suppressed, while the hypo- and cerato- branchialu (h b, c b) are enormously deve- loped. The basi-hyal (b h) is generally elongated proportionately to the shape of the tongue, and to its anterior extremity is usually attached a glosso-hyal (g h), to its posterior a stiliform uro-hyal (u h) which is prolonged be- neath the trachea. In C, which represents the hyoid apparatus of the crane ( Grus cinerca), the glosso-hyal is seen to be wanting, and two rudimentary cerato-hyals (c h), lesser cornita, to be attached to the anterior extremity of the basi-hyal. In D is represented the hyoid apparatus of the woodpecker (Picus); the parts are seen to be very long and slender, furnishing the means for the lengthened pro- trusion of the tongue in pursuit of food. All the bones are seen to be linear ; there is a long basi-hyal (b It), surmounted by an arrow- shaped glosso-hyal (g h), while two slender hypo-branchials (h b,) (greater cornita) are 1146 TONGUE. surmounted by two cerato-branchials (c b) of extreme length and tenuity, which, curving round the bird's occiput and vertex, are inserted by their cartilaginous extremities into a canal in the upper mandible, the orifice of which is placed to the inside of the right nos- tril ; the true hyoid arch is here entirely sup- pressed. And, indeed, birds' tongues are not attached, they are slung ; now, tongues are attached by the osseous or fibrous continuity of the hyoid arch ; they are slung by the loose, unattached hypo- and cerato-branchials ; and accordingly as either of these methods of con- nection with the body is most consistent with the tongue's functions, so the one or the other of these systems of bones preponde- rates. In mammalia we find the hyoid apparatus recurring in its original completeness ; the three pieces, the stylo-hyal, epi-hyal, and cerato-hyal, composing the lateral arms of the arch in the fish, have each their representa- tive : the proportion of these parts, the com- pleteness of their ossification, and their anchy- losis, or separateness one from another, are liable to great variety, but either in the bony or ligamentous condition, fused or separate, the parts may be always traced. The cerato- hyals are represented by the lesser cornua ; the stylo-hyals have their homologue in the sty- loid process of the temporal ; and the epi- hyal, or intervening portion of bone, is a cylin- drical ossicle connecting the two : these are seen in their greatest completeness in the true carnivora. In man the epi-hyal is not normally ossified, but remains in a permanently liga- mentous condition, as the stylo-hyoid liga- ment. In some rare instances, this ligament has been ossified, and then the typical condi- tion of the hyoid arch is restored ; two or three of these instances have been recorded and figured by Geoffrey. In fig. 760. E is shown the condition of the hyoid apparatus in the horse ; the stylo-hyals are seen to be very large, and approximate so nearly to the cerato- hyals, that the intervening bone, corresponding to the stylo-hyoid ligament in man, is seen to be a mere pisiform nodule (ep h) ; the hypo- branchials, or posterior cornua (li b), are of much the same shape as in man, while the basi-hyal projects forwards in a rostrum, to which is attached a glosso-hyal in two pieces (g //). In the ox the condition is much the same as in the horse, but the epi-hyals are longer, and the stylo-hyals shorter. I will now briefly advert to the general characters of the tongue itself, as met with in the four classes of Vertebrata, — Pisces, Rep- tilia, Aves, and Mammalia. Pisces. — The tongue in fish is very rudi- mentary ; in some it cannot be said to exist at all ; in others it is a thin, fleshy investment, that barely covers the glosso-hyal bone pro- jecting into the mouth. In the herring (Clupca Harengus], it seems to be represented by a small muscle passing along the floor of the mouth to be inserted into the symphysis of the lower jaw, to depress and open which seems to be its function. In the cod it is round and thick, and seems to act as a sort of cushion. In the conger (Murcena Conger}, in which it is very large, it seems to possess a hyo-glossus muscle, which, arising from the inferior portion of the hyoid arch, passes for- ward on either side of the tongue, which, by the action of one of these muscles, can thus have a lateral deflexion imparted to it. The structure of the investments of the tongue is not such as to imply the possession of taste in any degree, or any thing but a very low sensi- bility. In some species, as, for instance, in the sole (Solea vulgarix), the surface is regularly rugose, and might, at first sight, appear to be papillary, but no true papillae are to be met with in any fish's tongue ; their only repre- sentatives are the calcigerous processes, or teeth, with which the tongues of some species are more or less densely set, and which assist in prehension and deglutition. Whether the vascular, erectile tissue, situated on the palate of the Cyprinoids, has any connection with the sense of taste, is doubtful — probably not. Reptilia. — The tongues of Reptilia possess a very wide diversity ; some are immovable, others the most remarkable for their protrac- tility that we find in any organism ; some are long, some so short as to have been described as wanting; some are broad and thick, some slender ; some present the development of papilla? in great perfection, some are quite smooth ; the extremes of all these charac- ters we find in the reptiles, and their oppo- site conditions in those the most closely allied. For example, among the Saurians, the tongue of the crocodile is so immovable, as to have been described by Aristotle as want- ing ; while the chameleon presents us with the most complete protractility of the organ that the animal kingdom furnishes. I think the teleologists have not a greater strong hold than that furnished them by the tongues of reptilia. Almost the only thing in common that can be assigned to them is this, that pre- hension is their principal function, and that the sense of taste is very subordinate. a. Batrachia. — All the Batrachia, in their perfect state, feed on living prey*, and in many of them the arrangement of the tongue, to enable them to secure it, is remarkably curious. In the//-og, which presents a good example, we see the tongue reversed, as it were, the base or attached end being in front, the apex or free extremity behind : its mus- cular constitution explains this arrangement. It consists essentially of two muscles, a genio- glossus and hyo-glossus, invested by the mucous membrane. The genio-glossus arises from the inferior maxillary symphysis, and, directed backwards towards the throat, spreads out, and, together with its fellow, constitutes the upper of the two muscular strata. The hyoglossi arise from the lower surface of the posterior hyoid cornua, are directed forwards * In speaking of the frog Roesel says, " Prajdam vix venatur eamdem potius prsestolans, nee ullura iinquam devorabit insectum mutu destitutum." Hist. Eauar., p. 16. TONGUE. 1H7 umler the flattened cartilaginous plate of the body of the hyoicl bone, over the anterior bor- der of which they are reflected as over a pul- ley, where, coming in contact with the under surface of the last-mentioned muscles, they curve backwards, radiate in a fan-like manner, and form the under of the two muscular layers. This is the position in a state of rest, the hyo- glossus lying under the genioglossus, and the extremity of the tongue pointing down the throat in contact with the fauces, and forming a plug with which to close the posterior nares, and prevent the regress of air every time it is swallowed. But when the animal would seize its prey, the position of the tongue is sud- denly reversed ; the genioglossus contracts, and moving on its genial attachment as on a centre, the tongue is thrown forwards, the ge- nioglossus now being below, the hyoglossus above. The apex of the tongue having come in contact with the prey to be seized, and se- cured it by its viscid secretion, the organ is instantly retracted and restored to its original position by the contraction of the hyoglossus. In many of the batrachians (as in the Triton) the tongue is fixed in its entire extent, and is of very various shapes, oblong, rhomboidal, heart-shaped, &c., affording generic and spe- cific distinctions, of which zoologists have availed themselves in classification. The tongues of Batrachia are invariably soft, and, in some of them, as the frog, covered with well-developed papilla?, containing all the es- sential elements of organs of taste and touch ; that they are the seat of an acute sense of taste is, however, highly improbable, not from any thing in their structure, but from the fact that these animals swallow their prey whole, without any subdivision, frequently alive, bolt- ing it as soon as seized. b. Ophidia. — In the ophidians the tongue is very much elongated, straight, flat or cylin- drical, fleshy, highly protractile, and deeply cleft at the apex into two tapering points which are in a state of constant vibration when the tongue is protruded. These points are the extremities of two muscular cylinders, which form the substance of the tongue, and by their close apposition constitute that part of it that seems to be undivided : they may be traced a long way down in front of the tra- chea. When the mouth is opened the tongue very frequently cannot be seen, from its being drawn within a sheath which contains it, the orifice of which is placed in front of the aper- ture of the glottis. From this sheath, and from the mouth, it is being constantly pro- jected, with a sort of vibratile darting move- ment, and, from a deficiency in the plates at the symphysis of the jaws, it can be protruded from the mouth without the jaws being sepa- rated : the character of this movement, and the pointed slender shape of the tongue, have given rise to the vulgar belief that it is the animal's weapon of offence, a sort of dart con- taining the poison that it instils into the wounds it inflicts. From the nature of the food of this order, from the disposition of the parts of the mouth, and from the short so- journ that the food makes in it, the perception of savours is probably very slight. c. Chelonia. — In Chelonia the tongue is not elongable, and its muscular structure is very simple, consisting only of two pair of muscles, the genioglossus and hyoglossus. In the tur- tles the surface is smooth ; in most of the tortoises it is clothed with very large and well- developed papillae, long, soft, and flexible, arranged with great regularity in a close pile : the structure of these papillae, together with the masticatory apparatus possessed by these animals, would imply their possession of a true sense of taste. d. Sauria. — Among the saurians we find in the Crocodile a fixed tongue projecting so little from the floor of the mouth, that Aris- totle, as has been stated, described it as want- ing; it is covered with a coriaceous integu- ment, and is remarkable chiefly for a valve-like process at its base, formed by a reduplication of the integument over the vertical ridge of the body of the hyoid bone, which, at the will of the animal, is capable of being applied to a similar one descending from the palate, and shutting off the mouth from the posterior nares and larynx, so that the animal can breathe when its mouth is under the water or engaged with its prey, and its nostrils only above the surface. In the Lizard we find a tongue, in shape very much like that of the Ophidians. In the Chameleon we find an apparatus which, for its remarkable structure and powers, has always excited the attention and curiosity of zootomists : Perrault, Hunter, Cuvier, Vallis- nieri, Vrolick, Houston, Milne Edwards, Spittal, Duvernoy, have all given their con- tributions to the subject ; the connection of the mechanism with the resulting phenomena, as given by these authors, has been very di- verse, and all, in the opinion of bibron, un- satisfactory. " It is easy," says this author*, " to conceive and explain a part of these movements, by the structure of this tongue in the chameleons, because the hyoid bone and the muscles have been perfectly described, and because it is easy to isolate them by dis- section ; yet, by the very aid of this anatomy we perceive that the movements which this mechanism should effect would not suffice for the production of such an excessive elongation, that the animal, without using any violent exer- tion, can lance from its mouth, by a sort of ex- puition, a fleshy pipe of a length nearly equal to that of its whole trunk, and that it can retract it again within its throat with the same swiftness, and without one's perceiving any apparent movement in the rest of its body." The dif- ficulty that Bibron felt was that of accounting for the very great intrinsic elongation of the tongue, and it appears to me to be a difficulty that exists ; various authors account for it variously; in my own dissections I have not met clear evidence of anything that satisfac- torily explains it to me. I shall first describe the tongue itself, and then the hyoidean appa- * Erpetologie Gi'nerale, ou Histoire Naturelle complete des Keptiles, Paris, 1830, t. iii. p. 174. 1148 TONGUE. mouth, it is seen to be a whitish, fleshy, ru- ratus and muscles, and from the description of the two deduce the most probable explanation of the movements. When a portion of the integument and lower jaw on one side is removed, so as to expose the tongue when retracted within the gous mass, about an inch and a half long, fill- ing the buccal cavity, so as to depress the floor of the mouth and throat, in shape some- thing of a cone with the base in front : the posterior half, or smaller part, is seen to be thrown into deep and numerous transverse rugae (fig. 761. A, b, and C.) which extend Fig. 7G1. Tongue of the Chameleon. A, retracted. B, elongated. C, seen from beneath, in situ, by incision and separation of the integument. quite up to the hyoid bone, and give to this part the appearance of an earth-worm, a simile suggested by Belorr. When the tongue is drawn out it is seen to be capable of great extension (B), the extension taking place in the posterior or rugose portion, and being effected by the obliteration of the transverse rugae, which one by one are smoothed or flattened out as the extension is continued, so that when it is stretched as far as it will go by moderate traction, the tongue, instead of being an inch and a half long, of which only half is occupied by the extensible portion, is five inches long, the extensible part occupying about six-sevenths of the entire extent, and being much attenuated (B, 6), while the an- terior portion retains its original size and shape (a). The tongue is thus seen to be composed of two parts, a club-shaped ex- tremity and a highly extensible medium of connection between this extremity and the hyoid bone : these two parts I shall now describe. The anterior club-shaped extremity is about three quarters of an inch long, and three lines in diameter, and in shape reminds one of the corolla of a labiate flower ; in fact it is bilabi- ate : it has a sort of dome above (a), termi- nated in front by an upper lip (c), which is opposed by a more projecting lower lip (d), and between them is situated a funnel-shaped mouth, which, when closed, as in A, forms a horizontal cleft, but is capable of being opened as shown in B, (and to an extent greater than that represented in the figure,) and closed on any object at the will of the animal, so as to assist in the prehension of food. These lips are furnished with a sort of orbicularis, and, no doubt, too, with muscles that shall raise the upper and depress the lower ; but I have been unable to detect any fibres going in such a direction as to produce these movements. This part, as well as the whole of the tongue, is invested with the mucous membrane of the mouth, and the upper surface of the dome and lower lip, are covered with minute papilla?, invested with a fine epithelium, and disposed, in the former situation, in rows, indicated by the lines (A, «). The part which covers in the infundibular cavity, and which, after the analogous part in a labiate flower, I have called the dome, Bibron has not ill compared to a tongue reversed. The second portion consists essentially of a membranous tube, threaded, as it were, by the long cartilaginous stilet, or tongue bone, of the hyoid apparatus (the glosso-hyal). This cartilaginous stilet, which has been errone- ously described as bony, is about an inch and a half long, and consequently passes through the entire length of the tongue when re- tracted, its anterior extremity being received into the lower lip of the club-shaped portion : it threads the tongue much in the same way as a bodkin threads a bag when furnishing it with a running string, and it is by the pucker- ing of the membranous portion upon this basis that the transverse rugae are formed. The membranous tube itself (which has been compared to a pipe, a piece of intestine, a TONGUE. 1140 worm, &c.) is very complex in its structure : it consists, first, of an investment of mucous membrane, very thin and extensible, covered, apparently, by a single layer of epithelium, and a good deal of bluish-grey pigment, and underlaid by fibrous tissue disposed at right angles, transversely and longitudinally. When the sheath, thus composed, is cut open, it is seen to contain another fibrous sheath, smooth, dense, white, and shining, the proper sheath of the stilet, which it closely invests, and which smoothly glides in it. Between these two sheaths is a cavity which is occupied, first, by a longitudinal muscle on each side (essentially a hyoglossus), a very fine and slender fascicle, •which runs the entire length of the tongue, and retracts it when protruded ; secondly, by a nerve on each side, disposed, when the tongue is retracted, in regular sinuosities, and, when drawn out, about five inches long ; it does not appear to give oft' any branches to the muscle, and does not diminish in size as it advances, so that it is probably distributed to the extremity, and is sensitive ; thirdly, by some cellular tissue loosely connecting the mucous investment with the fibrous sheath ot the stilet ; fourthly, no doubt, arteries and veins. The proper sheath of the stilet does not contain a canal, but is attached to the surface of the stilet, which glides in it not by its movement on the sheath, but by the move- ment of the parts of the sheath on itself. When the stilet is retracted it is seen to be cylindrical throughout, but as it advances its sheath accumulates on its anterior extremity, and it seems gradually to become club-shaped, so that when the tongue is completely re- tracted the under lip is filled not only with the extremity of the stilet, but with the sheath accumulated on it. Cuvier has described an annular muscle existing throughout the entire length of the membranous portion, which he describes as the proper muscle of the tongue, and to which he attributes its self-elongation. If such a muscle exists, which I will not posi- tively deny, it would fulfil all the required conditions, and leave nothing to be explained ; but I confess that, after careful microscopical research, I have been unable to find any mus- cular fibres having a transverse or circular dis- position, all being referable to the longitudinal bundles already referred to. Hunter has de- scribed what he considered to be two coils of some firm substance, wound in opposite di- rections, which by their approximation would become straightened, and so lengthen the tongue ; — this is an ingenious hypothesis, but no more : there is nothing that will bear such an interpretation. Perrault, in speaking of the lungs of chameleons *, expresses an opi- nion that the tongue is driven, or, as it were, coughed out by the sudden expulsion of the air which the lungs contain. The hyoid apparatus consists of the hori- zontal projecting portion — the stilet already referred to, and four cornua, two short ante- rior ones, and two long vertical posterior ones (_/%. 761. A and B). These parts can move * Essais de Physique, t. iii freely on each other, the articulation between the stilet and the greater cornua is particularly free. These cornua ascend, and are suspended loosely behind the jaws ; they are about three quarters of an inch long, and are clothed with the muscles that are attached to them. These muscles are, 1st, the gcniohyoid (e. A B and 6'.), arising from the inner surface of the symphysis menti in contact with its fellow, and inserted into the inferior extremity of the vertical cornua, sending up a slip which is attached to its whole anterior border. 2dly, a distinct, small fasciculus, the cerato-mamllary (/), arising from the inner surface of the lower jaw, and inserted into the apex of the vertical cornua. 3dly, the stcrnohyoid (g), arising from the inner surface of the sternal extremity of the fourth and fifth rib, and inserted into the junction of the cornua and glossal portion of the hyoid. 4thly, the ceralo-stemal (//), more slender and flattened than the last, the antagonist of the cerato-maxillary, arising from the outer surface of the sternal extremity of the second rib, and inserted, just opposite the cerato-maxillary, into the apex of the greater cornua. 5th ly, the omo-hyoid (i), inserted with the sterno-hyoid. This complicated arrange- ment of muscles, which I have drawn from na- ture* in Jig. 761. A, is the mechanism for the direction and extrinsic propulsion of the tongue ; by it the lower extremities of the greater cornua are drawn forward, and the summits depressed, so that, instead of being vertical, they are horizontal and advanced (B). The advance of the whole tongue thus gained is nearly an inch, and since the muscles that principally effect it, the genio-hyoid (c), are very strong, and the movement quick and forcible, the question may arise — Is this projectile movement suf- ficient to send the rest of the tongue forward, and effect its elongation, after the hyoid ap- paratus has come to a stop, in the same manner as the arrow flies from the string of a bow, though the string itself is suddenly arrested ? I think not. I think that some such muscular arrangement as that described by Cuvier must exist ; and possibly, some transverse bundles of fibres of not very cha- racteristic appearance, which, from the absence of transverse striae, I rejected as muscle, might have been of a muscular nature. The retrac- tion of the tongue is easily accounted for ; it is simply drawn back on the stilet by the lon- gitudinal muscles. The use of the stilet appears to be, partly as a support to the tongue when in a state of rest, and partly to direct its move- ments ; for aim is seen to be taken while the tongue is still retracted : the animal first places itself in such a position that its head shall be turned directly to the object to be seized ; it then fixes its head still more accurately, then slowly opens its mouth to a sufficient distance to allow the free egress of the tongue ; it then seems to fix it with a sort of tremulous rigid * It may be well to state that not only these, but all the figures illustrating this article (with one or two exceptions, which I have acknowledged), are original, and have been drawn by myself from na- ture, so that I can vouch for their correctness. 1150 TONGUE. movement, and, in an instant, the tongue has been shot out, has again disappeared, and with it its prey has disappeared too, the whole being performed with a velocity that startles one afresh every time it is witnessed. Aves. — The tongue of birds may be stated, in general, to be, like that of reptiles, prehensile and non-gustatory. Taste and mastication, or, at any rate, taste and some delay of the food in the mouth, always go together; in birds the food experiences no delay in the mouth, but, in almost all cases, is bolted at once. In most instances, true prehension, or the seizing of the food, is performed by the bill, in soine few by the tongue ; in nearly all, however, the securing of it when in the mouth is effected b> the tongue, which is armed near the base with numerous spines, directed back- wards (fig. 763. ABD), that prevent the regress of the prey, whether alive or dead, and which, with a similar structure at the roof of mouth and throat, must greatly assist the first stage of deglutition. The structure of the tongue of birds is generally such as not to acimit of intrinsic elongation ; its protrusion therefore can only be effected by the move- ment of the organ en masse ; and this is pro- duced to a surprising extent by a particular arrangement of the hyoid bone and its muscles, which I will now describe. The general cha- racter of the hyoid bone of birds, as already stated, is elongation — longitudinal extension, and to this add the fact of the suppression, entire or partial, of osseous or ligamentous attachment of the hyoid elements to the skull, such attachment being inconsistent with the required free movements of the organ. From the posterior part of the body of the hyoid bone project back the slender posterior cor- nua forming, by their divergence, an acute angle, embracing in its apex the upper part of the larynx : as they pass beneath the occiput they curve upwards, and are surmounted by slender pieces, frequently cartilaginous (cerato- branchial), having a still greater curvature; so that the whole greater cornua, as thus consti- tuted, embrace the back of the skull, to the shape of which their curve is moulded, and on which they are made to glide backwards and forwards by the muscles that regulate the protrusion and retraction of the tongue. The principal of these muscles are two pair ; the first the analogue of the stylo hyoid, which retracts the tongue, and the second pair which Cuvier has called the analogue of the genio hyoid — the conical muscle of Vicq d'Azyr, — which draws the tongue forwards : the obliquity and length of these muscles, and the free unattached suspension of the hyoid apparatus, render the movements of the tongue very free, and their range exten- sive. The retrahent muscle, the stylo-hyoid (fig. 762. a.), arises from the posterior part of the lower jaw, and passes forward to be in- serted into the upper surface of the junction of the cornua and body of the hyoid : in some birds it is more voluminous than in the species figured, and has a more extended insertion ; it retracts the tongue. The pro- trusor ( &.), which Cuvier has named, with apparently insufficient reason, the analogue of the genio hyoid, arises from the inner Fig. 762. Muscles of the Tongue of the FieIdfare(T\irAus pilaris). a, retractor; b, protrusor; c, cerato-glossal. side of the lower mandible, passes downwards and a little backwards to the posterior cor- nua, which it embraces in its fibres from the point where it comes in contact with it to its extremity : the fibres become increasingly oblique as they pass back, and embrace the cornua in a muscular cone, which, by its con- traction, causes the cornua to slide forwards in it, and so protrude the tongue . in the wood- pecker, in which the hyoid cornua pass com- pletely round -the head and into the upper mandible, this muscle is of proportionate length. Besides these, there is a mylo hyoid, a thin layer passing from the lower mandible to a median fibrous line, and a cerato-hyoid pass- ing from the posterior cornua to the uro-hyal, approximating these, and so directing the apex of the tongue to the opposite side. Fig. 7 62. c. is a small muscle, which I cannot find de- scribed ; it passes from the under surface of the basi- or glosso-hyal to the greater cornua, into which it is inserted within the sheath of the conical muscle. I would suggest the name of cerato glossal for it ; its action is to in- crease the curvature of the cornua, and there- by draw the tongue back. Fig. 763. represents some different forms of Fig. 7G3. TONGUE. 1151 the tongue in birds. A, is that of, the snipe (ScoUupax gallinago'), which is seen to be linear; B, of the fieldfare (Turdus pilaris), the epithelium breaking up into a leash of filaments at its extremity ; C, that of the king-fisher (Al- cedo isjrida),$o short that it hardly projects from the surface at the bottom of its long bill ; D, is the tongue of the common goose, furnished with a linear series of spines on each side, forming a serrate margin, which, with a corre- sponding serration in the upper mandible, con- stitutes a sort of sieve, through which the bird sifts and strains, as it were, the mud and water which it palpates in search of food. In the back part of the tongue, both in this and in the other figures, there is seen to be a peculiar armature of recurved spines, whose arrange- ment in the different species is constant and characteristic. Some good representations of different varieties of tongues are given in the article AVES. Mammalia. — The tongue of mammals differs not in any material point from that of man. The proportion of the different parts of its muscular structure differ more or less widely from the human type, and we find certain muscles that have no place in the tongue of man: to enter into the minutiae of these diver- sities would not, however, comport with the scope of the present article ; they must be sought in monographs especially devoted to this part of the subject. The coincidence of the -size and form of the tongue with that of the inferior maxillary arch is very general ; in the rodents this is very conspicuous, the tongue being of the same wedge shape as their cuneiform jaw. In some animals, as in the ant-eater and giraffe, the tongue admits of great elongation, and becomes an important organ of prehension. The different elements of the tegumentary sys- tem are merely modifications of those found in man : the three orders of papillae are gene- rally sufficiently conspicuous, and in most in- stances they are more regularly arranged, and their structure is more typical than in the human subject; for instance, the circumvallate papillae are symmetrical, they present a greater contrast to the rest in number, being fewer than in man, and none of the fungiform ap- proach them in form; the shape of the fungi- form too is not liable to any variety, and they are implanted with great regularity among the conical. The conical papillae are generally true cones, and are arranged with mathemati- cal precision in lines in different directions, accordingly as they are viewed. All these papillae may be well seen in the dog. In the felidcB the conical papillfE of the centre of the dorsum are converted into recurved spines of great size and strength, which the animal uses in scraping the meat from the bones when feeding, and in combing its fur. FUNCTIONS OF THE TONGUE. — The phy- siology of the tongue, like its organisation, is double, all its functions being referable either to those sensory or muscular endow- ments which it possesses in so remarkable a degree. Naturally, these are intimately associated, its sensibility being necessary for the direction of its muscular action, and its movements necessary for the perfection of its sensibility; a systematic consideration of them, however, necessitates their separation, and those functions that are referable to the tongue as an organ of sensibility, have already been treated of in the articles TASTE and TOUCH, to which the reader is referred ; it only remains for me to consider those that it possesses as an organ of motion. These are prehension, mastication, insaliva- tion, deglutition, speech, and one or two unim- portant and non-essential offices in which it is engaged, which may be called the accidents of its physiology, as despuilion or spitting, ivhistimg, &c. Of these the four first-men- tioned belong to the tongue as an organ of digestion ; they are, in fact, the first four stages of that process; all four exist in all mammalia, the first and the last in all vertebrata ; speech and the other non-digestive motor functions are peculiar to man. Prehension. — The tongue is not, properly speaking, in man, an organ for the prehension of solid food, that office being performed by the hand, for which the opponent arrange- ment of thumb and fingers eminently fits it, so that the human tongue has not those ad- ditional qualifications which we find in other animals to adapt it for an organ of pre- hension. And this, I may remark, is an in- stance of a very general law — that the ascent in the animal scale is not a passage from animals with simple organs to animals with complex organs, but from simple individuals with organs of complex function, to complex individuals with organs of simple function, the addition as we ascend being, not of functions, but of parts to discharge those functions, and the advantage gained, not another thing done, but the same thing done better. Thus in man, instead of having one office more, the tongue has one office less than in many animals below him ; and the delicate and extended prehen- sion supplied by his hands, diminishes by one item the complexity of function, and, there- fore, of organisation of his tongue. So that in judging of the elevation of animals by their individual organs, supposing such a method to be admissible, we must not look to complex- ity of structure of those organs, but to the perfection of the resulting function. But to return. In the prehension of liquids, or suction, the tongue in man is engaged ; constituting a movable wall of the oral cavity, it acts as a piston, and draws the liquid into the mouth by the formation of a temporary vacuum. Bichat enumerates three methods of the pre- hension of liquids, by suction, by drinking from a vessel, and by infusion into the throat; in the first two the tongue is concerned ; in the last, which seems to me hardly to deserve the name of prehension, it is not. In suction, which is peculiar to the infant, the nipple is seized by the lips, which are compressed around it by the orbicularis oris ; the velum palati is elevated so as to close the posterior nares : the tongue forms, by the contraction H52 TONGUE. of the middle fibres of the genio-glossus, which depress its centre, a longitudinal channel, which receives the nipple, and transmits the milk to the pharynx as long as a vacuum con- tinues to be formed. In drinking liquids from a vessel the tongue forms a channel for its transmission, but it flows down to the pharynx by its own proper gravity. Mastication. — As far as relates to the tongue, which here, however, is only subsidiary to the teeth, the mechanism of mastication may be divided into three stages: — first, that of placing the food in an advantageous position with regard to the teeth; secondly, affecting the position of the food in a definite manner when under the action of the teeth ; thirdly, collecting the scattered portions of masticated aliment prior to deglutition. Immediately on the introduction of a morsel of food into the mouth, either bitten by the incisors or other- wise, it is at once transferred to the molars, so that it shall project beyond them, outwards, against the cheek ; the cheek is then pushed against it by the action of the buccinator, and the food is slowly driven across the teeth, which are rhythmically opened and closed, the tongue at the same time pushing moderately against it on the inside and so regulating the movement imparted to it by the cheek. Thus we see that the food under mastication is sub- jected to an equable and regulated motion ; that it is placed, as it were, between two movable walls, and that by the even lateral movements of these walls, and the rhythmical vertical action of the teeth, its perfect masti- cation is secured. As soon as the cheek has pushed it inwards as far as it can, an interval in the rhythmical closure of .the teeth takes place, and the tongue restores it to its former position, again to be pushed inwards, and so on. The equable mastication of the food is secured much in the same way as the even motion of a rod of timber, under the blade of a circular saw, secures the cutting oft' of pieces of equal thickness. Any one who watches himself whilst eating will at once observe the sets of rhythmical action, interrupted by short interval, in which the food is restored to its necessary position between the teeth. The third stage, that of collecting the food from all parts of the mouth, admits of no particular description. Insalivation. — There is no separate or super- added process forinsalivation; it proceeds con- temporaneously with mastication, the motions which are necessary for the one supplying equally the required conditions of the other ; while the food is being comminuted by the teeth, dispersed by their action to different parts of the mouth, recollected by the tongue to be again dispersed, and so on, the salivary secretion is freely mixed with it, and reduces it to a homogeneous pulp : thus mastication facilitates insalivation by breaking up the food, and insalivation facilitates mastication by softening it. As one set of acts performs the two processes, of course there are not any additional movements of the tongue to describe. Deglutition. — When the food has attained a sufficient moisture and softness, which is ap- preciated by the tongue's sense of touch, it is collected into a mass, and the process of deglutition commences. Physiologists have divided this process, and the division is a good one, into three stages, which may be distin- guished respectively as the oral, tiiepharyngeaf, and the aesophageal; the first conducts it past the anterior pillars of the fauces, the second in- cludes its transmission from that point through the pharynx into the oesophagus, and the third commences with its arrival at the eso- phagus, and terminates with its entrance into the stomach. The first is entirely voluntary ; the second is of a mixed nature, engaging partly voluntary and parti)' involuntary muscles, and, though practicable at will, is yet impres- sible on the transference to the back part of the tongue of the material to be swallowed ; the third is wholly involuntary. With the two first alone the tongue is engaged, and, there- fore, of these alone I shall speak. The first stage is merely the reference of the ball of alimentary matter to a point on the back of the tongue, posterior to the anterior pillars of the fauces. This is effected by the pressure of the tongue against the palate, whereby the food is forced back between the two. The second stage is a much more complex process, involving a more varied mechanism, and engaging in it different parts, the tongue, the pillars of the fauces, the soft palate, the larynx, and all the muscles of the pharynx. As soon as the food has passed the anterior palatine arch, that arch contracts, and by its constriction entirely prevents the regression of the food into the mouth ; at the same time the base of the tongue, and with it the food, is carried further back, and a second closure takes place from the approximation of the posterior pillars of the fauces, produced by the contraction of the palato-pharyngeal muscles that form them: this part of the mechanism requires a little explanation. The contraction of the anterior pillars of the fauces closes the entrance into the mouth by a constriction or sphincter-like action : this is due to the general circular form of the constrictor isthmi fau- cium occasioned by the inward curvature of the upper and lower extremities of each palato- glossns muscle. The contraction of the palato- pharyngei is not of this nature; they have not the same inward curvature above and below, and their inferior attachments to the pos- terior borders of the thyroid cartilage are capable of very little approximation ; when, therefore, they contract, the soft palate being fixed, they approach one another laterally like two curtains, leaving a narrow chink in the middle, wider below than above. As soon as the food has passed this point, this contraction takes place, so that the two muscles of the opposite sides almost touch, the chink between them being occupied bv the relaxed uvula ; the passage into the posterior nares and upper part of the pharynx is thus cut off", which has induced Dzondi to call the posterior palatine TONGUE. arch the velum palati posterius. At the same time that this is taking place, the base of the tongue is thrown back upon the epiglottis*, the larynx being drawn upwards and forwards to meet it, so that the rima glottidis is com- pletely closed, and the food glides safely down, over the inclined plane thus formed, into the pharynx raised and diluted to receive it : the food then comes within the grip of the constrictors of the pharynx, which successively pass it downwards to the oesophagus. This process takes place so rapidly that it is difficult to trace its parts in succession, and indeed some of them, which apparently succeed one another, are in reality contemporaneous : thus, the first stage — the raising of the dorsum of the tongue to the palate — is that which mainly contributes to the inclined plane of the second stage ; and the raising and carrying forwards of the larynx under the tongue is that which principally dilates the pharynx.-j- The third stage, or the oesophageal, conducts the food to the stomach ; it is of that peri- staltic or vermicular nature that characterises all the succeeding movements of the alimentary canal ; the muscles concerned are entirely involuntary, and the nature of the act purely reflex. The tongue is not concerned in it. Speech. — The tongue is the instrument principally engaged in those modifications of the oral passages which give rise to articulate sounds, which, definitely grouped and com- bined by man, and taken as the representa- tives of certain objects, actions, qualities, and relations, constitute Language. The con- sideration of this interesting subject, however, will more appropriately fall under the article VOICE, to which the reader is referred. MORBID ANATOMY OF THE TONGUE. — The tongue is obnoxious to a variety of morbid changes, which might naturally be expected from the number and nature of the elementary tissues which enter into its formation, as well as from the diversity of the functions it has to perform, and the exposure to injury in which it is placed ; — changes which may consist either in some increase, decrease, or disproportion of its normal ele- ments, in some lesion or morbid change in those elements, or else in the superaddition of some adventitious growth. The tongue may be affected with inflam- mation, hypertrophy, atrophy, induration ; with ulceration, numerous morbid changes in the conditions of the papillae ; with tumours, cancer, aphthae ; and the organ, moreover, is subject to be displaced, — there is prolapsus of the tongue, the tongue may be inverted * It would seem that the epiglottis is not abso- lutely necessary for the protection of the rima glot- tidis, but that the pressure of the base of the tongue over it is sufficient ; as there are authentic cases on record, in which the epiglottis was quite destroyed by syphilis, and yet deglutition was never attended with any inconvenience. t For a detailed account of this process, see Dzondi, die Functionen des weichcn Gauniens. Halle, 1831. VOL. IV. and embraced by the pharynx — swallowed; and the tongue may be unnaturally fixed by an unusual extent of frenum, the individual thus circumstanced being tongue-tied. Inflammation of the tongue. — The morbid changes caused by inflammation of the tongue are modified by the structure of the organ. There is one form of this disease in which, from the extreme vascularity of the tongue and the distensibility of its covering, it swells to an enormous size with great rapidity, and subsequently recedes without suppuration : this I have ventured to call erectile. In other cases the tongue suppurates. The constitu- tional action of mercury is another cause of glossitis. I therefore divide glossitis, for its more complete consideration, into — I. Idio- pathic (1. Suppurative i 2. Erectile) ; and II. Mercurial. Suppurative glossitis. — This is an extremely uncommon affection. It commences with heat, swelling, induration, and some fever; matter presents itself at various lengths of time, forming a more or less circumscribed abscess. It generally occurs on one side, and points just beneath the edge of the tongue. According to Dr. Moller, of Zealand, scrofu- lous persons are most liable to this affection. Instances are recorded by Mr. A. Smee, Dr. Graves, Dr. Moller, and one example occurred in the practice of the author's father. This latter patient was a lady, recovering from an attack of influenza. Her tongue, which was affected principally on one side, became swollen, tender, hard, stiff, and incapable of movement. She could not speak, and swal- lowed with great difficulty. At length the pus was evacuated, and the tongue healed, and recovered all its functions immediately. This lady now possesses a remarkably good use of the organ. Erectile glossitis. — This malady, though less rare than the preceding, is still quite un- common. The morbid condition of the tongue in this disease appears to consist in an enor- mous and rapid distension of the organ by blood, rendering it very large, hard, and stiff. In the majority of cases it occurs in people in perfect health, and seems to be a purely idio- pathic inflammation : in some cases it seems to have followed exposure to cold, and in others it was associated with febrile disorders. In this disease the first change which occurs is a perceptible enlargement of the tongue, which feels rather stiff, painful, and tender with a little difficulty in speaking, the patient being in other respects well. The case gene- rally proceeds rapidly; in two or three hours the tongue is much larger; there is a good deal of distressing burning felt in it. Sy- nocha, symptomatic of the local inflammation, now occurs, and goes on increasing with the glossitis, and the patient becomes anxious and alarmed. The tongue occupies now the whole cavity of the mouth, or even protrudes, and the jaws are kept apart. Mr. Martin thus describes the condition of the tongue at this stage ; — " On examining the tongue, I found that it occupied a large proportion of the 1151 TONGUE. cavity of the mouth ; and I could with diffi- culty introduce my little finger between it and the upper jaw. It felt smooth and hard to the touch, and had a thick coating of viscid mucus : from the high degree of tension, the point presented a glistening appearance." (Edinburgh Mcd. and Surg. Journal, vol. xxviii. p. 76.) As the case advances the tongue increases still further in size, the patient can- not perform the first part of the act of deglu- tition, and the liquid food is obliged to be conveyed by some mechanism into the pha- rynx ; respiration through the mouth ceases, and that through the nares is impeded : the patient is now almost on the verge of suffoca- tion, ami his distress and anxiety become extreme. Mr. Martin remarks: — "At this period respiration through the mouth was totally suspended ; and he could not breathe, even through the nostrils, but with difficulty. His countenance was flushed and anxious, the pulse was fluttering, his breathing offensive : in short, he was threatened with immediate suffocation." (Loc. cit., p. 77.) The condition of the tongue sometimes approaches gangrene. Mr. Hayes, in describing a similar case at an advanced stage, observes : — "It now began to look of a dark black colour, or rather as if it had been broiled over a smoky fire ; indeed, I expected it would mortify." (Memoirs of the Medical Society of London, vol. ii. p. 193.) I am not aware that mortification has ever resulted in these cases ; neither does abscess appear to be thus produced,* which, however, may be accounted for by the fact, that these urgent cases almost always render it necessary that the organ should be freely incised on the dorsum to evacuate the distending blood, and this would prevent the formation of abscess ; though in some very severe instances, where incision has not been practised, no abscess has resulted. When the inflammatory action ceases, which is immediate when the before- mentioned operation is performed, the tongue rapidly recovers, and the fever vanishes. When the tongue is incised, the quantity of blood discharged is very great. The morbid change in the tongue does not always go to the extent above described, and then milder symptoms are produced. Dr. England mentions two mild cases, in both of which the left half of the tongue alone was affected. Dr. Graves relates a severe case, also confined to the left side, in which he says the part " appeared on the verge of gan- grene." (Dublin Hospital Reports, vol. iv. p. 43.) De Lamalle narrates an example, in which the patient was almost suffocated in five hours from the first appearance of the malady. The tongue was more than three times its natural size ; it filled the whole mouth, and protruded between the teeth. Free incisions saved the organ and the patient. Trincavcllius mentions a case where it oc- * Since the above has been in type, a case occur- ring to Dr. Schneider has been published, where tin-; form of inflammation terminated in abscess. (Casper's Wbchenschrift, No. 23.) curred in Variola ; Mr. Hayes an instance, where an individual, licking an urticarious eruption, had this effect produced to a slight extent on her tongue ; and the same thing, to a small degree, I have known occur from a person eating mussels. Collier, Taynton, Job a. Mekren, Paletta, Elbuig, Frank, and Orgill, also enumerate ex- amples of this condition. Dr. Craigie has described a peculiar form of glossitis, under the name of Lingual Quinsy, which is an extension of ordinary quinsy, or tonsillitis. The portion of the tongue involved is that bounded in front by the circumvallate papillae, behind by the epi- glottis, and at the sides by the mucous mem- brane passing off' upon the pharynx and rami of the lower jaw. The inflammation extends down the puiato-glossus muscle from the ton- sils to the .':•-• se of the tongue, and seems to involve the r/.ucous, submucous, and muscular tissues. The parts are swollen, infiltrated, and stiff; t. iowe~ ' w cannot be depressed, and attempts at delation are not only diffi- cult, but the completion of the act is impos- sible. There is an abundant secretion of ropy mucus. Dr. Craigie had one fatal case, in which he found after death, that " the base of the tongue was tumid, hard, and much distended with blood and serum infiltrated into its cellular tissue, and the parts between that and the angle of the jaw were in like manner infiltrated." (Edin. Med. and Surg. Journal, vol. xlii. p. 26.) Mercurial glossitis. — Inflammation of the tongue, the result of the mercurial action, is but one symptom of the constitutional influ- ence of that drug. The tongue in this case becomes large, soft, painful, white and furred, and much indented by the teeth along its edges : the ••pithelium is soft and readily re- moved, and the surface is apt to ulcerate. The swelling is sometimes very great and rapid. Slegel and Trincavellius each mention such a case. I believe it has never caused suppuration of the organ ; but the discon- tinuance of the mercury is followed by com- plete resolution. Ulceration of the tongue. — This is the most frequent of the morbid changes occurring in the tongue, and of it there are several species and varieties. The different species may be enumerated as, I. The Dyspeptic ulceration, or that arising from disorder of the prim a; vise; II. Indurated non-malignant ulceration; III. Gangrenous ulceration ; and IV. Syphi- litic ulceration. Dyspeptic ulceration is met with in three principal forms. 1. Small circular ulcerations at the tip and along the edge of the tongue ; 2. Severe and deeper ulcerations of the body of the tongue ; and, 3. Aphthous ulceration. The small circular ulcers of the tongue are extremely common, and have been personally experienced by almost every individual. They consist of small, circular, generally regular and well defined ulcers, which are superficial and look as if a piece of mucous membrane hail been punched out ; the edges are sharp and TONGUE. 1155 well defined : these ulcers vary in size from that of a pin's head to that of a split-pea, or larger ; they are almost constantly situated at the tip, or edges of the tongue ; they are sometimes grey, at others red ; when touched against the teeth they are acutely painful, and their presence causes an abundant and con- stant secretion of saliva. In the commence- ment, however, there is no ulceration, but the malady begins by an affection of a papilla, consisting in an effusion of lymph into a fungiform papilla (hereafter to be described), and this terminates in ulceration : the papilla is at first large, yellow, and distended with lymph ; in a few hours it has disappeared, and its site is occupied by an ulcer, which after- wards more or less spreads in a regular, cen- trifugal manner. I believe this process has never before been properly described, — per- sons not being aware that any thing has hap- pened until the ulcer exists, and consequently never seeing or exhibiting the malady in the first stage; but any one, subject to these little infirmities, may satisfy himself of the truth of what I have said by carefully watching the state of his tongue from day to day. The severe and deep-seated ulcerations of the tongue, arising from mere disorder of the alimentary canal, may consist of an extension of the already-described variety, or it may commence by a vesication, or an excoriation of the surface ; it generally occurs in people who are debilitated from some cause or another. Mr. Lawrence relates the following characteristic case : — "A lady, between fifty and sixty, of unhealthy appearance, with a red pimply face, who had often suffered from dis- order of the digestive organs, consulted me for a disease of the tongue of formidable ap- pearance. The middle and upper part of the organ was swollen, and occupied by a deep ulcer of irregular figure and foul aspect. It was very painful, interfering with mastication and articulation. The digestive organs were much disturbed. The complaint yielded speedily and effectually to simple measures — regulation of diet, and the digestive organs, small doses of extract of henbane, and sooth- ing local means." (Clinical Lecture, Medical Gazette, vol. xxxvi. p. 800.) Mr. Lawrence mentions an instance in which rawness and severe excoriation of the tongue often repeated, the result of periodic and long-continued dyspepsia, appear to have induced true scirrhus of the organ. Aphthous iilccrat'um. — The ulceration is merely one stage of a peculiar morbid change, to which the tongue, in common with some other portions of the gastro-intestinal mucous membrane, is liable. The tongue, however, suffers more severely than most other parts. It is eminently the result of disordered diges- tion, and is accompanied with more or less fever of an atonic character. An aphthous tongue is rather swollen, tender, and furred, and has a sensation of burning heat : on its surface, scattered about irregularly, are small white bodies, resembling little masses of curd, varying in size from a split pea to a pin's- head, attached pretty firmly ; these bodies, as well as the swollen state of the tongue, cause the subject of them pain and inconvenience : alter a variable time these little white masses fall off, leaving the membrane on which they rested in an altered condition, — it is either raw and excoriated at these spots, the epithelium being peeled oft' and leaving the papilla? naked, exposed, and red ; or else, the deeper ele- ments of the membrane being affected, an ulcer is formed. These ulcers are generally more or less circular and superficial, and are in no way to be distinguished, at this stage, from the little circular ulcers already described, but aphthae on the neighbouring portions of the tongue disclose their true nature. The white aphthous mass itself has been variously de- scribed as a slough, concrete mucus, and albu- mino-Jibrin, but it consists in reality of a mi- nute parasitic fungus, which attaches itself to the mucous membrane and burrows among its epithelial cells. Seen under the microscope, it is found to be composed of threads matted together like felt, and intertwining among the epithelium. Accompanying aphthas are gene- rally to be seen on the surface of the tongue, small vesicae, spots of epithelium raised with a little serum underneath, and also some of the papillae distended with fibrinous exuda- tion — conditions to be described presently. Indurated non-malignant ulceration. — Indu- rated ulcers, which are neither syphilitic nor malignant, but closely resembling scirrhus, are occasionally met with, and their doubtful character gives the surgeon not a little trouble. Mr. Lane narrates the following formidable example : — " Mr. G. B., aged 33, came to me in the month of June, 1813, with a very foul ulcer beneath the tongue, and said that he some time before had had one on the upper part of it, which he said was healed ; but on examination there was a deep irregular fissure, with raised, jagged, hardened edges, commu- nicating with the ulcer under the tongue, which, on examining with a probe, I found not only communicated with the fissure on the upper surface, but the instrument passed through the substance of the tongue, into a deep seated ulcer at the root of it, and thence into the throat. The general appearance of the disease was most alarming, bearing a very strong character of carcinoma. He experienced great pain and difficulty in deglutition, and complained that the pain had of late extended behind the ears, to the back of the head and neck." (Medico-Chirur. Trans., vol.viii.p. 20:-?.) The case, however, was not one of carcinoma, for the patient completely recovered under alterative treatment. About two years since an instance came under my own notice. A man of about 45, had been a sailor ; had never had syphilis ; for about six years had been labouring under a disease of the tongue, with little improvement, or permanent change, in its condition. When I saw him, the right half of the tongue was enlarged and much indu- rated ; the left was of natural size and soft, but with few papilla? ; on the right side no pa- pilla; were to be seen, and the surface was ex- 4 E 2 115G TONGUE. coriated, chapped, ami in parts superficially ulcerated. He told me that at one time the left side had been diseased in a similar way. The lymphatic glands behind and beneath the jaw and down the neck were enlarged and indurated, and had been so from the first. The free application of lunar caustic to the tongue lessened the affection, and the lymphatic glands became smaller and softer ; but the other side became afterwards diseased, and was relieved by the same treatment ; the tongue was, however, never restored to a healthy state, though, when I last saw him, there was no ulceration. There was profuse secretion of saliva ; but, with this exception, the man was remarkably healthy. Mr. Lawrence, in his Clinical Lecture, al- ready referred to, describes this condition of tongue. (Lor. cit., p. 799, case ii.) Gangrenous ulceration. — The tongue is liable to a peculiar gangrenous ulceration, called " Glossantlirax " or " Malignant pustule." It commences as a vesicle containing bloody serum ; it gradually becomes black and bursts, and the lingual tissues beneath and around it are seen to be gangrenous ; this may proceed till the whole tongue is in a state of mortifi- cation : when it exists to this degree, there is fever of a profound typhoid character, with delirium, and the patient soon dies. Auclral has given an account of this disease in his Pathological Anatomy. Heyfelder narrates the case of a Prussian butcher, who, when slaughtering a diseased sheep, put the knife and held it for some time between his teeth. In two or three clays the margin of his tongue was covered with black pustules. The part swelled alarmingly, and most painfully ; vio- lent fever set in, and the patient was carried oft' in the course of sixty hours. I once saw a patient in low fever, who had enormous sloughing of the dorsum of the tongue, which proceeded in successive por- tions till a large deep excavation, that would have received half a walnut, was produced. Syphilitic ulceration, — Hunter* strangely fell into the error of thinking that venereal ulcer- ations of the tongue are uncommon, whereas they are the most common to which the organ is liable ; and the tongue, next to the tonsils, is more frequently attacked, in the constitu- tional forms of this disease, than any other portion of the mucous surface. A small, circular, superficial ulcer \s the most common syphilitic affection of the tongue ; it begins exactly like the little ulcers of dyspep- tics, from which it cannot be distinguished. These ulcers are situated principally at the tip and along the edges of the tongue. As in almost all instances of ulceration of the tongue, the ulcer is the second part of the process, and follows the deposition of fibrinous matter under the basement membrane ; in this case in a single papilla, or a few contiguous ones, as I have already described. These ul- * Speaking of ulceration of the tongue. Hunter observes, " these are commonly supposed to be vene- real ; but I believe they seldom arc." ( lln>ifi-r\i Trea- tise on theVenereal Disease. Page 837. 2nd Ed. 4to.) cers generally do not extend, but yield to the most simple treatment ; sometimes, however, they do extend, and form various sized un- healthy ulcers, deep in proportion to their extent, cupped and indurated at the base. At other times they show a tendency to run in one direction, and remain superficial : I saw an example of this in a patient who had a very narrow superficial ulcer an inch in length, originating in a small circular ulcer, and ex- tending along the under surface of the tongue, on the left side, just at the point where the mucous membrane is reflected from that organ to the jaw : it was very superficial, and, as it progressed, it attacked the healthy membrane in its course. Rhagades or fissures in the tongue are not uncommon : they are ulcerated clefts, which extend down, often to a considerable depth, into the substance of the tongue. Mr. Lawrence describes one three quarters of an inch deep ; though sometimes they only form a chap in the mucous membrane : he also describes one extending the whole length of the tongue, just in its centre, in the long axis j this was deep, and with irregular ulcerated edges. When seen in the fore part of the organ, they are generally in the middle line, or nearly so ; but those further back are scattered about, and just in front of the circumvallate papillae, which is their most usual situation. They are commonly associated with an indurated and irregularly tuberculated surface of tongue — these tubercular lumps being sometimes like large fissured warts, at others glossy and smooth. The rhagades are generally red, while the surrounding tubercles are grey, or whitish, or, at other times, red and excoriated. The glossy tubercle, to which I have re- ferred, is a remarkable disease : it often forms with great rapidity, and as quickly disappears. It seems to consist in an effusion of lymph into the cellular tissue underlying the mucous membrane ; this effusion is very dense, and raises and distends the surface of the tongue at the affected part above the surrounding por- tions ; the effect is, that the complications of the membrane, which constitute the papillss, become unfolded, and the papillae are, as it were, opened out, — they form now one smooth extent, and stretch over a large surface, the faintest indications only of the papilla; being apparent, and sometimes they are totally ob- literated. That this is the true explanation of these smooth tubercles is evident from the fact, that as they form, and in proportion to the distension of the membrane, the papillae diminish and shorten ; and as, under the influ- ence of medicines, the swelling decreases, they reappear exactly in the same ratio. These tubercles have little sensation or pain, unless the surface be excoriated ; they are dense, almost as hard as schirrus ; their base is felt pretty deep in the substance of the tongue ; their surface is polished, glossy, and whitish — they remind me of the tongue of a fish ; they are generally oval or round, when smallish ami single, and they are most frequently situated on the dorsum of the tongue, about half an TONGUE. 1157 inch or an inch in front of the circumvnllate papilla1, and on one side of the mesial line. Sometimes they form over tlie whole surface of the tongue. I am acquainted with a gen- tleman who, at the time he was suffering from syphilitic psoriasis, got an attack of dyspepsia ; in less than thirty-six hours the whole of his tongue was one mass of these tubercles, and not a papilla was to be seen ; in a few days (under the influence of iodide of potassium) every papilla had reappeared, and the tongue was in every way natural. This influence of disordered stomach being the immediate and exciting cause of the manifestation of the syphilitic poison on the tongue, I have fre- quently noticed ; a person who has a taint of lues venerea can scarcely sustain the least dis- order of the stomach or bowels without its showing itself upon the tongue. These tu- bercles of the tongue, when left to themselves, are very apt to become fissured and form rhagades ; the space between two of them is liable to be the seat of an ulcerated fissure. Deep circular ulcers sometimes form on these tubercles. Phagedixnic syphilitic ulcers are seen occa- sionally on the tongues of feeble debilitated people. All these forms occur as the result of the constitutional taint of lues venerea, at various periods after the primary symptoms. I have known the glossy tubercle and rhagades occur fifteen years after the primary sore. Cancer of the tongue. — The tongue is liable to be affected with scirrhus, having all the properties of genuine cancer. Mr. Travers has given a very graphic description of cancer of the tongue, which I .shall take the liberty of quoting in extcnso. — " This is not a smooth and firm rounded tubercle, such as is often met with in this organ, but an irregular rugged knob in its first stage, generally situated in the anterior third, and midway between the raphe and one edge. It sometimes, but seldom, extends across the middle line, although it often extends alongside of it. The hardness is unyielding, inelastic, and the mucous surface puckered and rigid. It also gives to the finger and thumb of the surgeon the sensation of solidity, or of its penetrating the entire mus- cular substance, being perceived equally on either surface. Sharp shoots of pain are felt through the side of the affected organ, towards the angle of the jaw and ear. "The disease tends to run backwards towards the base or posterior edge. It sometimes acquires great bulk before ulceration takes place, so as to project the tongue from the mouth. In this state a female patient of minn was seen some time ago in St. Thomas's Hospital, in whom the permanent projection of the diseased organ, beyond the widely distended lips, was from three to four inches. The ulceration often extends from the edge of the tongue to the membrane of the mouth and gums, when the elevated and distended membrane at length gives way, and ulceration is rapid. The sur- face of the ulcer is very uneven ; clean an_l bright granulations appearing in parts, and in others deep and sloughy hollows. The dart- ing pain is very acute, but only occasional. There is a dull aching alwajs present, and as constant a spitting as in deep salivation. It happens to strong and hitherto healthy per- sons, for the most part males from the age of forty onwards. There is generally an evening paroxysm of pain, and the nights are much disturbed by the secretion accumulating in the throat, which excites cough. Often the patient is roused by a painful compression of the tongue falling between the jaws. Speech is much affected and painful. " Towards the fatal termination of the dis- ease, occasional profuse haemorrhages take place at shortening intervals, and alarm and weaken the patient, who ultimately dies tabid and exhausted, generally with symptoms of more extensive disease of the mucous mem- brane in other parts. " The period at which the sublingual and contiguous lymphatic glands become affected, and the extent of their change, are very vari- able. I have known them form the base of the tumor, the cauliflower fungus occupying half the tongue, i. e. two or three inches long and one broad ; after death the jaw was found covered with fungus." (Medico-Chirurgical Transactions, vol. xv. part i. p. 245.) The scirrhus is not infrequently at the very margin of the tongue. Louis mentions a case where there was a little circumscribed tubercle of scirrhus, about the size of a filbert, at the edge of the tongue : it was ulcerated. It occasionally shows itself early in life : Arnott mentions a case where it was present in a girl of fifteen. In a subject who died of lingual cancer, dissected by myself, I found that the whole of the right side of the tongue, right tonsil, the upper part of the pharynx on the right side, and the mucous membrane, extending from the tongue to the epiglottis on the same side, were removed by ulceration, and the inner surface of the lower maxilla laid bare. The other half of the tongue was healthy, and only the ulcerated edge was scirrhous. The lymphatics were enlarged, and of a greenish-yellow colour : they con- ained pus. Tumours of the tongue. — A variety of tu- mours have been met with in the tongue. Fatty tumours have been found by Mr. Lis- ton on the under surface of the tongue. Mr. Hale Thomson exhibited to the Westminster Medical Society, in 18o9, a fatty tumour which he removed from the side of the tongue. It consisted of fat contained in a cyst. Encysted tumours. — Many of the so-called instances of ranula* have been abundantly proved by Dupuytren, Breschet, and Malgaine to be simply serous cysts, and not obstructed salivary ducts. They consist of dense mem- branous cysts, containing a thick albuminous ' The consideration of ranula belongs to the mor- bid anatomy of tli'j alivary glands, and not of t! •„• tongue. 4 E 3 1158 TONGUE. fluid, and not inspissated saliva. They are situated in the cellular tissue immediately under the mucous membrane, where they sometimes grow to an enormous size. Mr. Earle has described curious little vesicular tumours, which he found in the tongue of a boy : — " Clusters of very minute semitrans- parent vesicles pervaded the whole thickness of the tongue, occupying nearly one-half, and projected considerably both above and below that organ. The slightest injury caused these to bleed profusely, and in some places the clusters were separated by deep clefts, which discharged a fetid, irritating sanies." (Jlfcdico- Chirur. Trans., vol. xii. pt. ii.) The tongue was quite restored by the use of internal medicine. A mulberry-like tumour has been described by Mr. Probart. It formed on the tip of the tongue of a boy four years of age. It was of a peculiar granulated appearance, resembling a half-ripe mulberry, feeling hard and free from pain. It grew gradually : at two months it was the size of a nutmeg; but after that, in five weeks, it rapidly increased till it was of the bigness of a hen's egg, protruding nearly two inches beyond the lips, which were sepa- rated widely by it, preventing the little patient taking any thing but spoon meat, and that with difficulty. It was highly vascular, and bled profusely from innumerable vessels, which nothing but the cautery would arrest, when amputated. There was no return of the disease. Polypus-like tumours have been met with on the tongue, consisting of a fleshy mass, like the rest of the organ, attached to it by a pedicle. Louis mentions one of these about the size of a nutmeg, which he removed from the tongue of a young man eighteen years of age ; it was situated on the middle of the dorsum of the tongue. A more remarkable example is described by Dr. Huie. The case was that of an old maiden lady, in whom a tumour formed, about three months after a catarrh and inflammation of the fauces, upon the root of the tongue, and gradually increased for twelve months, when " the smooth rounded form of the tumour conveyed, at first sight, the idea that it was of an encysted kind ; but, upon examination with the finger, it was found to be as hard and unyielding as the substance of the tongue itself, and evi- dently of the nature of polypus." (Edinb. Med.-Chlrur. Trans., vol. iii. p. 72.) It filled nearly the whole pharynx, and moved with the tongue, to which it was attached by a pedicle. Ligature was subsequently applied, by which it was removed. " The tumour, which is in the Museum of the Royal College of Surgeons (of Edinburgh), was of an oval form, weighed exactly an ounce, and mea- sured five inches in its long, ami four in its short, circumference. It was broadest op- posite the insertion of the pedicle, which entered at the distance of an inch from the upper part of the tumour. A longitudinal incision, which lias been made into it, displays a firm cartilaginous nucleus, as large as a chestnut, surrounded by a fibre-cartilaginous structure, forming the rest of the tumour." (Loc. cit., p. 7fi.) I strongly suspect that all these pedunculated tumours of the tongue are hypertrophied fungiform or circumvallate papillae. Hypertrophy and prolajisus of the tongue. — This is a singular affection, which usually commences in infancy, and is sometimes con- genital. It generally begins and progresses slowly by an enlargement of the organ within the mouth ; it afterwards projects perma- nently between the lips, and then advances more rapidly, and the tongue, which was before of normal, though hypertrophied, struc- ture, becomes parched and fissured on the upper surface, and ulcerated beneath. Some- times the amount of tongue that is protruded is enormous. The os hyoides and larynx are drawn up, whilst the jaw is depressed, and the incisors are pushed out in a horizontal direction. Dr. Wells, of Columbia, has given a good case, of which the following is a condensed description. The patient was a little girl, six years old, with an enormous enlargement of the tongue ; otherwise she was in good health, and a fine robust girl. The following are the dimensions and state of the tongue at the time : — length, as it remained at rest and hung down over the chin, from the superior incisors to the apex, two and a half inches ; circumference just in front of the lips, six inches ; breadth, from one angle of the mouth to the other, a little more than two inches. It had undergone a very considerable change in structure, was much more dense than na- tural, and not subject to change in its dimen- sions by the action of its own muscles, or, if at all, very slightly so. Its motions other- wise were sufficiently free : upper surface smooth ; inferior covered with the cicatrices of old ulcers, several of which, where the tongue rested upon the alveolar processes of the lower jaw, were but imperfectly healed ; colour darker than natural. Within the mouth the tongue had undergone no apparent change except a moderate increase in width and thickness. The front teeth had been dis- placed from the lower jaw by the long-con- tinued pressure of the tongue. The lower lip was folded downwards. The anterior por- tion of the superior maxillary bone had under- gone a slight curve upwards ; the inferior a much greater curve downwards; so that when the back teeth came in contact, the front were an inch asunder, or, rather, the space between the upper teeth and the corresponding alveolar processes below was something more than an inch. This condition of tongue commenced by an attack of glossitis in infancy. A portion of the organ was removed by ligature, and she completely recovered. Mr. Crosse mentions a girl of six years old, in whom the tongue was prolapsed three or four inches ; and this was completely reduced by pressure and leeching. Mr. Listen has described an instance in which the tongue projected three or four TONGUE. 1159 inches from the lips of a young man, nineteen years of age, the disease having been con- genital. It was of a brown and livid colour, rough, granulated, and fissured, and beneath the mucous membrane were abundant venous plexuses. This tongue was liable to periodic intumescence, when it became much larger, was very painful, and bled profusely. Mr. Liston has stated his belief, that, from the periodical enlargement and diminution of the tongue, and the erectile tissue being evident in many parts of its surface, the mass was partly composed of a structure resembling aneurism by anastomosis. These hypertrophied tongues, when cur- tailed by the knife or ligature sufficiently to be taken within the teeth, generally soon Accommodate themselves to the form and dimensions of the oral cavity. Professor Lassus has given instances, where this has been accomplished by means of ban- daging and compressing the tongue. Atrophy of the tongue. — I am not ac- quainted with any instance of atrophy of the entire organ, nor with any unassociated with paralysis. It generally shows itself in cases of hemiplegia, when the tongue does not im- mediately recover, and results from diminished nutrition, the consequence of want of ex- ercise, being confined to the paralysed half, just as the arm and leg of the affected side become atrophied under the like circum- stances. It is more obvious, however, when the hypoglossal nerve alone is the seat of injury or disease. Professor Budd mentions, in his lectures, an instance which fell under the care of his brother, Dr. William Budd, of a man who sustained a stab in the neck, dividing the external carotid artery and hypo- glossal nerve on the left side. The artery was secured, and the man recovered with palsy of the left side of the tongue. At the end of some weeks that half of the tongue was much wasted, and all the movements of the organ were perform' ' by the other half. The atrophy was confi... :1 to he muscular element of the organ : taste aud touch re- mained uninjured. — (M5. Notes of Lecture.') Dupuytren mentions an example of atrophy and paralysis* of the left half of the tongue caused by the pressure, upon the hypoglossal nerve, of an hydatid cyst in the anterior con- dyloid foramen. In this condition, as well as in hemiplegia, the state of the tongue is remarkable from one part of the organ being passive, while the other is active. As long as it is at rest, the diminished size of the affected si'.'e is all that is observable. When the tongue is extruded, it is thrust over towards the affected side, — it emerges from the mouth obliquely, because the extruding muscles of the sound side have no antagonists. The paralysis of the intrinsic transverse muscular fibres gives rise to another phenomenon, which I have never seen de- * In both these cases the muscular motion was the only function implicated, which, as Dupuytren ob- serves, is interesting physiologically; taste and or- dinary sensation not being in the least affected. scribed, — it is the curved form of the tongue itself ; the raphe in the middle of the tongue is not straight, but curved, and the concavity looks towards the affected side. These fibres, whose function it is to make narrow, and, by that, to lengthen the tongue, only act on one side, and only half the tongue is thus elon- gated ; and this, being adherent to the other half which sustains no elongation, is thrown into an arch, on the same principle as the curving of the compound wire in a Breguet's thermometer. Diseases of the papilla;. — In considering the diseases of the surface of the tongue, authors have not taken sufficient care to consider the true anatomy of the papillary membrane, and their descriptions are consequently loose and ill-defined. It is of the utmost importance to state where the morbid changes are situated ; whether above or beneath the basement mem- brane; whether it is the epithelium, or the vessels and sub-basement areolar tissue that have undergone the alteration. The papilla; are liable to hypertrophy, atro- phy, effusion of blood or of fibrine into their interior ; they may be denuded of their epi- thelium, or that covering may be stained or rendered opaque, producing what is called /«r. Hypertrophy of 'papilla; . — The circumvallatc papillae are liable to be enlarged, the central portion forming a little tumour, rising above the surrounding ring of membrane. Dr. An- drew Ferguson has described them as increas- ing to the size of peas. There are generally several affected at once. I have seen them increased to this size, as well as some of the fungiform papillae at the back of the tongue, in an individual suffering from scrofulous enlarge- ment of the tonsils. The polypoid tumours (retaining the same form and proportions as these papillae, though greatly enlarged), I believe to be nothing more than hypertrophied fungiform, or circumvallate papillae. The conical or filiform papillae are liable to a peculiar change, which has, to the best of my knowledge, never been described. It consists in an enormous increase in their epithelial element, forming long cylindrical rods; in fact, hairs: the only apparent change in these organs being superficial to the base- ment membrane. I am in possession of the notes of two examples of this malady. For the first I am indebted to my brother, Dr. James Salter. He observes, " My patient was an old gentleman, impoverished by in- temperance ; his general health was good, and he was now temperate : for some years he had suffered from the peculiar affection of the tongue under which he now laboured. This affection was a great elongation of the conical and filiform papilla3, in all parts of the tongue where these abound : they were eight or ten times their natural length, and over-lapped each other, like the pile of plush, or long velvet. The hypertrophy appeared to be en- tirely in the long axis ; there was no increase in circumference, and they were little larger at their base than the apex. They were soft, and lay over lapping each other on the sui - 4 E i 1160 TONGUE. face ; and by smoothing the finger over the tongue they could be brushed from one side to the other. Their colour was deep Van- dyke-brown, and they were most numerous in the centre of the tongue. They looked ex- actly like little brown hairs. Sensation and taste were both a good deal damaged." To my friend, Dr. Joseph Bullar, I am indebted for the other instance. His patient was an old lady of sixty-five ; she had been subject to constipation, for which she was in the habit of taking strong purgatives. The tongue was large, vascular, and the papillae of all kinds prominently marked. It looked in an irritable condition, as if sympathising with a congested mucous membrane. On the middle and back of the dorsum was a patch of hypertrophied filiform papillae, of a dark sepia colour, or rather of the brown colour of a dark typhoid tongue. These filamentous growths were re- moved by forceps, and some were sent to me, from which I made the accompanying draw- ings. The specimens that I received were very dark, almost black : I have some of them in my possession now, nearly or quite half an inch long ; their texture was very compact, and their shape cylindrical, with hardly any trace of tapering. They all, as seen by the Fig. 764. microscope, possessed a retrorse imbrication of the same character as ordinary filiform pa- pillae (Jig. 764.). The epithelium did not con- tain any granular pigment, but the colour appeared to pervade the whole cell, which was evenly stained and semi-transparent. In fig. 7C4. is seen a papilla, or hair, at full length, and mfig. 765. a portion of another, showing the imbrication of the epithelium. The Scarlatina tongue contrasts remarkably with the preceding ; for here the deeper ele- ments of the papilla? are principally the seat of change. In scarlet fever the capillaries of the papilla?, in common with the sub-basement vascular system of so large a portion both of the internal and external surfaces of the body, become turgid, and the papillae themselves — not so much their epithelium — become en- Fig 765. R A portion of hypertrophied papilla, showing well the retrorse imbrication of its epithelium. Blag. 200 diameters. larged and red. In the early stages of the fever this change is concealed by the fur (which is a sodden and opaque condition of epithelium), as it regards the filiform papilla-, — fur being, in all cases I believe, confined to these and the papilla? conicas. Not so the fungiform papilla? ; for these are exaggerated and bright red. The result is, that the surface is a combination of thick white cream-like fur and red projected spots, the former being most conspicuous where the filiform papillae abound — the central portions of the tongue, — and the latter in the regions of the papilla? fungiforma? — the edges and tip of the tongue. These fungiform papilla? look like theacha?nia scattered on the surface of the fruit of the strawberry. As the disease advances, the epithelial covering is shed, and only a thin transparent epithelium remains : the papilla? are consequently red and bright all over the surface, which is clean, rough, red, and raw- looking in every part. Atrophy of the papilla? is occasionally met ,, , , . , j-Tf .„ , with. Mr. Lawrence mentions the case of a A portion of hypertrophiea filiform papilla, show- . „ , . . . . , . , ing its length and true hair character. Mag. 25 person in whom, from habitual drinking the and 80 diameters. tongue was, for the greater part of its surface, TONGUE. 1IG1 destitute of papillae : it was white, smooth and op;u]ue on the surface. I have already men- tioned the obliteration of the papilke in the glossy tubercle of syphilis, and it also occa- sionally occurs in lues venerea, independent of the tubercle. I have seen the tongues of old people re- markably bald, especially as it regards the filiform papilla? : as a general rule, these pa- pilla; are less prominent in the aged. Effusions into papilla. — The fungiform pa- pilla: are liable to be the seat of little extrava- sations of blood. I am acquainted with a medi- cal gentleman who has himself frequently had this trivial affection. It has always occurred to him in the night, and is indicated by a sharp pain, as though the tongue were stabbed by a red-hot needle, caused, doubtless, by the pres- sure of the blood upon the nerves in the papilla. Upon examining the tongue a papilla is seen to be distended into a minute capsule of blood, at first red, and afterwards black. The coagu- lum is absorbed in a few days, and the papilla resumes its former appearance. Lymph of a grey or ash-colour is apt to be deposited in and under the papilla?, in the tongues of persons tainted with syphilis. When this occurs on the dorsum, it gives a grey speckled appearance to the patch, some of the papilla? in the spot being unaffected. It looks as though this circumscribed surface had been rubbed with chalk. The patches vary in size from a split pea to a fourpenny piece. Occurring under the tip and along the under edge of the tongue, the appearance is a whitish even spot, of gristly texture, and not presenting a speckled appearance, the papilla? here being invisible, and covered up uniformly with epithelium. This is the most common situation for these spots, which after a time become fissured, and ulcerate. Lyrnph, effused into a fungiforni papilla, is the commencement of the common little cir- cular ulcer on the tip and edge of the tongue. I have snipped off, and examined under the microscope, one of these papillae. It was filled with a yellow, opaque, granular, sub-fibrous mass. The papilla is not only enlarged by this effusion of lymph, but is altered in form ; its pedicle is elongated, and its head flattened. When the papilla does not ulcerate, but returns to a healthy state, its contents are absorbed, it diminishes in size, and the summit of the papilla becomes pitted in the centre. It then gradually assumes its natural size, shape, and colour. This may be easily seen by watching, every few hours, a patient's tongue through an ordinary pocket lens. Denuded papillce. — The papillae are occa- sionally denuded by the effusion of serum be- tween the basement membrane and epithelium, by which this latter is raised into a blister, and is subsequently rubbed off by the motions of the tongue, leaving the red naked papilla? beneath. This denuded surface is red as com- pared with the surrounding, and smooth, but when viewed through a magnifier the small naked papilla? are seen to be regular and per- fect. This surface is not ulcerated, but feels sore when touched. I have lately seen a patch, the size of a shilling, thus denuded in a patient suffering from diarrhoea. Fur. — The/Mr of the tongue is the epithe- lium, principally of the conical and filiform papilla?, variously altered. It is most abund- ant where these papilla? are most plentiful, and it will be found, by inspecting minutely a furred tongue, that the fungiform papilla? have undergone very little, if any, change. I be- lieve, with M. Piorry, that the fur of the tongue is chiefly dependent upon the con- dition of the saliva and mucus of the mouth : and, holding this view, it is easy to understand how it is that the filiform and conical papilla? are principally affected ; they hang among the fluids of the mouth, exposing a large super- ficies in proportion to their bulk ; their sur- face is uneven and broken, and this, with the imbricated state of the epithelial particles, make them quickly and thoroughly imbibe, and become saturated with, any fluid into which they are immersed. In all this they contrast with the fungiform papilla?, whose surface, in proportion to bulk, is small, and whose epithe- lium is spread in a thin, even sheet, smoothly over their surface. It must have been ob- served by every one, that the colour of the papilla? of a brown typhoid tongue is identical with that of the sordes around the teeth, which is nothing more than the saliva and mucus, in which these papilla? have been bathed, inspis- sated, and is doubtless the source of their colour. The white fur consists of a white, opaque, soft, sodden epithelium, which, when viewed under the microscope, differs from the epithelium in its ordinary state, in no other particular than its opacity. When the fur is brown, the epithelium presents the appearance of being simply and evenly stained. There are no opaque pigmentary particles in the cavity of the cell. The various amounts and characters of the fur ; the different arrangements of it in dif- ferent diseases and at different stages ; the al- terations, form, and size of the tongue, &c. ; all symptomatic of morbid changes elsewhere, and belonging rather to the physician than the morbid anatomist, I shall not stop to describe. But it must not be forgotten that, in health, many of these conditions are natural to some persons : in some, the tongue is habitually furred, in others it is chapped, ragged, and irregular. The healing and reparation of the papillary surface of the tongue is not a little remark- able. I have known the surface of the tongue, after it has been immensely disfigured, es- pecially in syphilitic cases, by tubercles, and rhagades, and ulcers, restored almost to its former condition. After ulceration it would seem that the cicatrix contracts to a mere line, while the surrounding mucous membrane becomes extended, and cither fresh papilla? form, or else the minute simple papilla? in- crease in dimensions, anil become complicated, for the papillary surface is ultimately quite restored. I shall conclude these observations on the 1162 TONGUE. morbid anatomy of the tongue with some re- marks on faulty positions which the organ oc- casionally obtains. 1 have already spoken of 2)rolapsus of the tongue, and there now re- main for consideration — tongue-tie, tojigue- swa/towing, and adhesion of the tongue to ad- jacent parts. Tongue-tic. — This is a congenital malform- ation, consisting in the fraenum extending too far forwards and being short, thus tying down the tongue behind the incisor teeth of the lower jaw. This may occur to any degree, from an amount that is scarcely observable, to the complete tying down the tip of the tongue behind the necks of the middle incisors of the lower jaw. The frasnum generally con- sists simply of a small amount of fibrous tissue contained in the fold of mucous membrane; but it sometimes contains fibres of the genio- glossus, which occasionally extend a con- siderable way forwards : in the former case the frsenum is thin, in the latter it may be of some thickness. When left to nature the tie gradually lengthens, and, at the same time, recedes, and any unusual thickness arising from the presence of muscular fibres gra- dually lessens. This condition, to a slight extent, is very frequent, and appears to be hereditary. The cases are, however, extremely rare where the fra;num is so short as to inter- fere with sucking, mastication, deglutition, or articulation. Tongue-swallowing. — This arises from the opposite of the last condition : the move- ments of the tongue are too free ; it can be inverted, and its apex thrown back into the pharynx, which embraces it, and thus closes the aperture leading to the lungs, and symp- toms of suffocation are the result. It most frequently happens to infants. It is enume- rated by writers on Medical Jurisprudence, as one of the modes of suicide among negroes. Dr. Gordon Smith, Majendie, and Beck refer to cases of it. Mr. Crosse tells of an instance, where it could be performed at pleasure with- out the slightest inconvenience. Adhesions of the tongue. — Bernard relates an instance, in which adhesions, of the thick- ness of two lines and a half, had agglutinated the lateral parts of the tongue to the internal surface of the cheeks, to the extent of more than an inch on each side. These adhesions had succeeded an inflammation in the inside of the mouth and tongue, the circumference of which had ulcerated ; they interrupted the functions of speech and mastication. M. Ber- nard divided them by a single clip of the scissors. Necrosis of the hyoid bone. — The only in- stance of disease of the hyoid bone with which I am acquainted, is one related by Mr. Spry. The disease was necrosis, the result of ex- tended ulceration, which commenced in the throat, and continued till the bone was laid bare and dead. It was then expectorated en- tire. The patient died several weeks after- wards. The bone was entirely deprived of periosteum, irregular on its surface, and in a perfect state of necrosis. [Since this Article has been in the press I have become acquainted with a discovery of Prof. Kolliker's, that the muscular fibres iu certain situations are bifurcated and branched. In a letter to Prof. Bowman he says, that this is brilliantly exhibited by the muscles of the tongue, and he gives a pen and ink illustration of the method of branching. There can be no doubt about a fact so detailed by such an au- thority, but I must confess that I have not recognised the appearances described.] BIBLIOGRAPHY. — Albinus, De Periglottide et Corpore reticulari Linguaj ; in Aunot. Acad. t. i. Alcock, Med. Gazette, Nov. 1836. Andral, Anat. Pathol. sect. ii. Arnott, Med. Gazette, vol. xxiii. Beck, Medical Jurisprudence, 1842. Bellini, Gus- tiis Organon novissime detectum. Bologna, 1665. Bibroii, Erpetologie Ge'ne'rale, on Histoire Xaturelle complete des Reptiles. Paris, 18-44. Bicluit, Traite d' Anatomic Descrip. t. ii. Paris, 1802. Blandin, Mem. sur la Structure cle la Langue, Archives Gen. de Me'd. t. i. Paris, 1823. Breidenstein, De Morbis Linguae. Erlangen, 1791. Breschet, Repertoire d' Anatomic ; Journ. Univers. des Sciences Me'dicales, 1817. Collier, Med. Gazette, vol. xii. Craigie, Edin. Med. and Sur. Journ. vol. xlii. Crosse, Trans. Prov. Med. and Sur. Assoc. 1837. Cruveilkier, Anat. De- scrip. Cuvier, Le9ons cl'Anat. Comp. t. iii. 1805. De Lamalle, Mein. de 1'Acad. de Gliir. t. v. Du- puytren, Chirur. Clinique, t. iii. Uzondi, Die Functionen des weichen Gauuiens. Halle, 1831. Earle, Med. Cliir. Transact, vol. xii. England, Provincial Med. and Surg. Journal, 1846. Ferguson (A.), Med. and Phys. Journal, 18U2. Frascati, De Lingua. Bologna, 1665. Gerdy, Mem. sur la Struct. de la Langue ; Archiv. Gen. de Med. t. vii. Paris, 1825. Idem. Discus, et Propos d' Anat. Paris, 1825. Art. " Glossite," Diet, de Med. Graves, Med. Gazette, 1841-2. Dublin Hosp. Rep. vol. iv. Hal- Icr, lib. ix. and xiii. Hayes, Mem. of Med. Soc. of Loud. vol. ii. lleister, De Lingua sana et zegrota. Altdorf. 1716. Heyfelder, Med. Vereins-Zeitung, 1834. Hildebrandt, Handbuch der Anatomic dc.s Menschen. Brunswick, 1832. Home (Sir -ft1.), On the Structure of the Tongue and removal of Parts by Ligature, in Phil. Trans. 1805. Pract. Obs. on Cancer, 1805. Horn, Ueber den Geschmacksinn des Menschen. Heidelberg, 1825. Hide, Edin. Med. Chir. Trans, vol. iii. Hunter, On Venereal. Lond. 1788. IseujJamm, De Motu Linguae. Erlangen, 1792. Kempelen, Mechauismus der Menschlichen Sprache. Wien, 1791. Kirby and Spence, In- troduction to Entomology, vol. iii. Louis, Mem. Physiol. et Path, sur la Langue ; Mem. de 1'Acad. de Chir. t. v. Malphjhi, De Lingua. Bologna, 1665. Marjolin, Manuel d'Anatomie, t. ii. Paris, 1815. Meckel (J. F.), Manuel d'Anatomie Ge- nerale, t. iii. Paris, 1825. Miil/er, Physiology, by Baily. Owen, Lectures on Comparative Anatomy, vol. i. and ii. Archetype and Homologies of the Ver- tebrate Skeleton. Dissection of the Pearly Nautilus, 4to. 1832. Paletta, Journal of Foreign Medicine, No. xix. Panizza, in Edinb. Med. and Surg. Journ. Jan. 1836, and Med. Gazette, Sep. 1835. Ridge, Glossology. Lond. 1844. Minder, De Linguaj In- volucris. Strasb. 1778. Rowland, Aglossostouio- graphie, on Description d'une Bouche sans Langue, &c. Saumur, 1630. Roy en, De Fabrica et Usu Lingua;. Leydeu, 1742. Scemmerring, Icoues Organ- oruni Humanorum Gustus et Vocis. Frankf. 1808. Todd and Bowman, Physiological Anatomy, vol. i. Treviranus, Biologie, t. iv. Van Laer, De Struct. Capillorum Humanorum. 1841. Waller, Philoso- phical Transact. 1849, part 1. Walter (A. /'.), DC Lingua Humana. Leipsig, 1724. Wells, American Journ. of Med. Science, 1833. Willis, in Trans, of Phil. Soc. of Cambridge, vol. iii. (H. Hyde Saltcr.) TOUCH. 1163 TOUCH. — The sense through which we take cognisance of the palpable properties of bodies. The term is used, however, in two meanings, between which it is requisite to maintain a due discrimination. In its ex- tended acceptation, it implies our conscious- ness of all those sensory impressions, which are neither olfactive, visual, auditory, nor gustative ; and it is therefore designated as the general sense, in contradistinction to those, which are considered as special senses. In its most limited application, on the other hand, it is used to designate that modification of the general sensibility, which is restricted to the tegumeiitary surface, or to some special portion of it, and which serves to excite definite ideas in our minds respecting the form, size, number, configuration, weight, tem- perature, hardness, softness, &c,, of objects brought within its cognisance. The use of the sense of Touch, in the acquirement of these ideas, is, as we shall see hereafter, a very complex process ; involving not merely the discriminating employment of the proper organs of touch, but also the assistance of muscular action, and of the information de- rived from it by the " muscular sense." General Sensibility. — The most universal of all the qualities or properties of matter (that, in fact, upon which our notion of it is founded) is resistance; and it is of this quality that we find the power of cog- nisance most extensively diffused through the body, and most universally possessed by all beings endowed with consciousness. It would seem to require nothing else than the presence of nerves connected (directly or indirectly) with sensorial centres ; for there does not appear to be a need of any special organisation, surrounding the peripheral ex- tremities of these nerves, in order that they may receive and transmit impressions. Thus any unusual pressure on a nerve in its course is at once perceived by the mind, — not, however, as pressure, but as a disagreeable or painful sensation, which gives no indication of the mode in which it was excited. The nerves of smell, sight, and hearing, are not thus affected by mechanical irritation, no manifestations of pain being exhibited when they are pinched, torn, lacerated, &c. ; and the general sensibility winch these organs of sense possess is dependent upon other nerves. The nerves of taste, however, exhibit the same susceptibility to tactile impressions, as do those of touch ; and hence we have an additional proof of the very close affinity of these two senses (See TASTE). The only condition requisite for the ex- ercise of " general sensibility," beyond the integrity of the nervous apparatus, is the adequate supply of oxygenated blood. Wher- ever sensory nerves exist, we find them ac- companied by blood-vessels ; and no non- vascular tissue possesses in itself the least degree of sensibility. Thus, in the epidermis, hair, nails, cartilage, and tooth-substance, nei- ther nerves nor blood-vessels exist, and we find these tissues completely insensible. In tendons, ligaments, fibrous membranes, ami in other parts whose function is purely me- chanical, we find very little vascularity, and extremely little sensitiveness to ordinary im- pressions ; it is remarkable, however, that although the tissues, whose function it is to re- sist tension, are scarcely impressible by cutting, burning, &c., they cannot be unduly stretched without considerable pain. So, also, the serous and synovial membranes are not in the least susceptible of ordinary tactile impressions in their healthy state ; but they become acutely- sensitive when inflamed. It does not at all follow, however, that the sensibility of a part should increase with its vascularity ; for we find that some of the most vascular organs in the body are the least sensitive, the supply of blood which they receive having some pur- pose entirely different. Thus the sensibility of the muscles is by no means proportionate to the large amount of blood which they re- ceive ; and even the substance of the brain (like that of the nerves of special sensation) is destitute of this property. So, again, the mucous membranes lining the interior of the several viscera, though supplied with blood even more copiously than the skin, are very far inferior to it in sensibility. The depend- ence of this endowment, however, wherever it exists, upon the continued circulation of the blood, is at once made apparent by the results of its suspension ; thus, when the main artery of a limb is tied, there is a dimi- nution of the sensibility both of its surface and of its substance, which is so exactly proportioned to the degree in which the sup- ply of blood is diminished, and the reco- very from which takes place so precisely in accordance with the establishment of the col- lateral circulation, that we cannot doubt that, if the supply of blood were completely cut off', sensibility would be entirely suspended. The numbness produced by cold, in like manner, is partly due to the stagnation which it occasions in the capillary circulation in the skin ; though it is doubtless in part attributable to the immediate depressing influence of the cold upon the vital endowments of the ner- vous apparatus itself. The general sensibility of the body may be called into activity by impressions received from objects external to it, or by causes ori- ginating in itself ; and the consequent sensa- tions are sometimes distinguished as " ex- ternal" and "internal." These designations are by no means logically correct ; for all sensations must originate in causes external to the recipient mind; whilst, on the other hand, in order that any sensation may be felt, a certain condition of the corporeal organism must first be produced ; and this condition may be precisely the same, whether it be immediately dependent upon changes ori- ginating in the body itself, or upon changes impressed upon it from some agency external to it. Still, however, the terms " external " and " internal " sensations are sufficiently con- venient, and sufficiently free from the pro- bability of misconception, to justify the phy- 1161 TOUCH. siologist in the employment of them ; and they will be accordingly employed in our present enquiry. The external sensations received through this medium all require the absolute contact* of the body which excites them, with the im- pressible part ; and in this respect, therefore, there is an exact correspondence between the general sensibility and the sense of taste. The force with which the impression is made, is judged of by the intensity of the sen- sation and the depth to which it is felt; whilst the size of the object is in some degree es- timated by the extent of surface over which its contact is perceived. Both these estimates, however, are extremely vague, when they depend only upon the general sensibility of the body ; we shall hereafter see how much more precise they become, when the impressions are received through the skin, which is the special organ of touch, and when they are aided and corrected by the muscular sense. Still we find that the different modes in which external objects affect even the general sensibility, produce a very marked diversity in the character of the sensations. Thus the feeling called forth by a prick is of a very different kind from that which arises from a bloiv; both, again, are very distinct from that produced by a steady uniform pressure; and all these are very different from the sensation of stretc'/ing or tearing. In the case of a prick, we have an intense impression made on the sensible part ; but this is limited to a very small spot ; whilst the impression of a blow is made with a like intensity over a much larger area.f In the case of steady pressure, on the other hand, the impression is made over a large surface, but is less in- tense ; whilst in stretching and tearing, the mechanical condition of the nerves of the part operated on is affected in a manner pre- cisely opposite to that in which it is acted on by pressure. The sense of shock, derived from a blow extending over a large surface, is very distinct from that of the mere blow, and may be experienced when little or no pain is "felt, as from the "wind "of a shot; and nearly allied to this is the peculiar jar which is experienced, when the shock is transmitted in such a manner as especially to affect the solid casing of the nervous centres, — as when we jump from a height, without sufficient care to alight in such a * There might seem to be an exception to this statement in regard to heat and cold, which are perceived when their source is at any distance that allows its radiations to affect the temperature of the body itself. But, as will presently be shown, it does not appear that the sense of temperature forms part of the general sensibility of the body; the power of appreciating heat or cold, as such, being limited to the special organs of touch. f There can be no doubt that a multitude of pricks made at the same moment, in sufficiently close proximity to prevent them from being separately distinguished, would be felt as a blow; this being the only sensation which is received from the numerous incisions simultaneously made by the scariiicator used in cupping, when it is applied to the parts of the •kin endowed with the least discriminating power. manner as to deaden the concussion by the elasticity of the feet, &c. A succession of slight impulses rapidly following one another, gives rise to the peculiar sensation of thrill ; which, though most readily excited when the impressions are made upon the skin, may be received through the internal organs also as when we hold a vibrating body between the teeth. These and other well-marked differences in the kind of information received through the general sensibility of the body, seem ob- viously attributable rather to diversities in the mode in which the impressions are made, than to any differences in the nature of the impressions themselves, the character of the fibres receiving them, or the endowments of the ganglionic centres in which these fibres terminate. And hence we seem to have a greater right to conclude, that the various affections of general sensibility, which are usually ranked under the common head of internal sensations, however unlike they may be one to another, are really derived from impressions which do not mutually differ so essentially as do those of the special senses from each other and from the general sense. Of this kind are the sensations of hunger and thirst, the "besoin de respirer," the genital sense, the sensation which calls for the expul- sion of the urine and fasces, nausea, the feelings of oppression and of" sinking" at the stomach, burning, itching, tingling, formication, and others. However different these are from each other, when but slightly or moderately excited, they all merge, when more strongly called forth, into the simple consciousness of pain ; and it is further common to them all, that the nerves through which they are ex- cited are the same as those which commu- nicate the impressions that excite tactile sensations, and that mechanical irritation of any of these nerves occasions pain. To the foregoing may be added the " muscular sense," whereby we are informed of the degree of effort put forth by a muscle ; and the sense of " fatigue," which seems to be a modifica- tion of this. We are not conscious either of effort or fatigue in the actions of any of the muscles over which the will has no control, such as the heart, the muscular walls of the intestinal canal, &c. ; nor in the case of those whose actions are purely rhythmical, as those of respiration. It is, in fact, only when the will is exerted, either in increasing the force of their contractions, or in antagonising them by the operation of some other muscles, that we become conscious of effort ; and we shall hereafter see that this sense is most important, in enabling us to proportion the amount of force we exert to the resistance to be over- come, and in guiding us with regard to the direction in which exertion is required. A sense of effort and of fatigue seems also to be excited in the sensorium by the mental opera- tions of which the cerebrum is the instrument; especially \\hen these mental operations are no longer spontaneous, or carried on with facility, but when they require a more or less TOUCH. 11G5 potent exertion of the will to keep them in activity. As we have every reason to believe that all mental exertion, like muscular force, involves (in our present state of being) a dis- integration of the substance of its instrument — the brain, — there is no difficulty in under- standing that this disintegration, when carried beyond a certain point, may excite the sense of fatigue (see SLEEP), just as the " besoin de respirer" is felt after we have withheld our respiratory movements for a. few seconds, or hunger when there is a deficiency of nu- tritious matter in the circulating current. It has been said by Mr. Mayo, " that the frame is in the completes! health and condition, when the internal sensations are not excited ; the healthiest self-feeling being an absence of all inward sensation." This, however, is scarcely a sufficient account of the fact ; for, in the highest condition of health, there is not only an absence of all uneasy feeling, but a general sense of buoyancy and resiliency, dif- ficult to describe in words, which may be characterised as the positive sense of well- being. So, on the other hand, without any positive or distinct sensation, there may be a consciousness of general discomfort, which has been expressively termed by the French malaise. These two sensations may probably be considered as originating in the condition of the blood ; the first being an indication of its purity, and of its perfect adaptation to the wants of the system ; whilst the second would seem to proceed from a slight depravation of its quality, resulting not unfrequently from the imperfect elimination of excretory matters, such as is not sufficient in itself to constitute an actual disease. Having thus passed in review the principal manifestations of the general sensibility of the body, and the conditions under which they occur, we have now to proceed to the investigation of the sense of touch, as exer- cised by the organs specially adapted for the reception of tactile impressions. SENSE OF TOUCH. Special Organs of Touch. — The peculiar endowments of the tegumentary surface, which enable us to draw from the impres- sions received through it, information of so much more varied and definite a character than we can derive through any of the struc- tures which it invests, appear to consist prin- cipally, so far as the organ itself is concerned, in its greater sensibility (that is, in its greater aptitude for being affected by slight impres- sions), and in its greater power of commu- nicating distinct impressions from points in close proximity ; but a large part of our in- formation is dependent upon our power of giving motion to the tactile organ, and thus of increasing the force and variety of the impres- sions which we derive through its surface, as well as of receiving impressions of an entirely different kind, from the action of the muscles by which that motion is given. Thus, if we simply bring a solid body into contact with the point of the finger, we gain but little information of the nature of its surface, whether rough, smooth, or polished ; and we can judge nothing of its form, except in regard to that part of it in actual contact with the fingers ; and even this is but vaguely ap- preciated. This information may be rendered somewhat more precise by pressing the object against the finger ; as we shall then feel the impression made by elevations, points, or roughnesses, if they be sufficiently prominent and wide apart from each other; whilst from the degree of muscular force we exert, and from the amount of yielding of which we are conscious in the object itself, we judge of its hardness, softness, elasticity, &c. But our power of discrimination is immensely in- creased, when we move the tactile surface on the body to be examined, or vice versa ; for, from the succession of impressions then made, we obtain our best idea of the character of the surface of the object ; whilst by the combination of the tactile impressions with the muscular sense, we judge of the relative positions and connections of its different parts, and of the form of the whole. But besides this, we find that impressions may be derived through the skin, which are not re- ferable to a mere exaltation of its common sensibility, being apparently of a different cha- racter from any of which we become con- scious through other structures; such, espe- cially, are sensations of temperature. Still there would seem no sufficient cause for rank- ing even these in a distinct category from the ordinary tactile impressions ; for the feeling of heat or cold does not differ more from that of roughness or smoothness, than does the colour of the object, as seen by the eye, from its form as distinguished by the same organ. The different parts of the cutaneous sur- face are endowed with tactile sensibility in very different degrees ; and this variation seems closely to correspond with the degree of development of that papillary structure, which may be regarded as the special organ of touch, strictly so called. These papilUc are most elevated and numerous on the tip of the tongue and the points of the fingers ; are less so on the palms of the hands and the soles of the feet ; are comparatively small and few on the integument of the limbs, and on several parts of the trunk can scarcely be dis- covered at all. They are described by Messrs. Todd and Bowman* as having an average length in man of T^th of an inch ; and a diameter at their base, where they spring from the cuticle, of about ^ioth of an inch. Their form is somewhat conical, tapering off to a slightly rounded point. Their surface (after the removal of the epidermis) appears to be composed of the basement membrane of the cuds itself ; and their interior is composed of fibrous tissue, vessels, and nerves. In each papilla we find a small arterial twig, derived from the arterial plexus of the cutis ; this, advancing towards the apex of the papilla, subdivides into two or more capillary ves- * Physiological Anatomy, vol. i. p. 410. 116G TOUCH. sels; and these, forming loops whose con- vexity lies in the summit of the papilla, re- unite into venous radicles, which discharge their blood into the venous plexus of the cutis. " The vascularity of the papillae," as Messrs. Todd and Bowman correctly remark, (loc. cit.'), " is such, that their presence and relative size may be determined simply by the depth of the colour imparted to the skin by a good injection of its vessels ; the vascularity of the integument is, therefore, in general terms, proportioned to its perfection as an organ of touch." With regard to the nervous supply of these papillae, however, it is less easy to speak with confidence. It is derived, like the sanguiferous, from the plexus in the substance of the cutis, lying parallel to the surface ; the tubular fibres ascend, to all ap- pearance singly, from this plexus into the papillae ; but their mode of termination or return are not distinguishable with certainty. The following are the results of the in- quiries of Messrs. Todd and Bowman on this point. " In regard to the presence of nerves in the papilla? themselves, we can affirm that we have distinctly traced solitary tubules ascending among the other tissues of the papillae about half-way to their summits, but then becoming lost to sight, either by simply ending, or else by losing the white substance of Schwann, which alone enables us to dis- tinguish them in such situations from other textures We have in numerous in- stances failed to detect any nerves at all within the papillae, when such were plainly visible at their base, and when, consequently, the che- mical agent employed could scarcely have destroyed their characteristic structure had they been present. We incline to the belief that the tubules, either entirely or in great measure, lose the white substance when within the papilla."* With these statements, so far as they go, the writer's own observa- tions are in entire accordance ; but he thinks that from the appearances presented by sec- tions examined by reflected instead of by transmitted light, it may be inferred that the nervous tubules in the tactile papilla? undergo a change somewhat similar to that which is said by Wagner to take place in the nervous tubuli of muscle ; namely, that whilst the white substance of Schwann is not traceable beyond a certain point, the central axis is continued further, and that this breaks up into minuter fibrillae, which form loops, like those of the capillary blood vessels, returning into the tubular fibre itself. In the lower animals, as in man, it may be observed that the papillary structure is espe- cially developed on those parts of the tegu- mentary surface which are especially endowed with tactile sensibility, and the impressions received through which are of important use in finding the movements of the instruments of locomotion. Thus in the quadrumana generally, both the hands and feet are thickly set with papillae ; and in those which have a * Op. cit. p. 412. prehensile tail, the surface of this organ pos- sesses them in abundance. In the carnivorous and herbivorous mammalia, whose extremi- ties are furnished with claws or encased in hoofs, we find the lips and the parts sur- rounding the nostrils to be the chief seat of tactile sensibility, and to be copiously furnished with papillae ; this is especially the case with those which have the lips or nos- trils prolonged into a snout or proboscis, as in the pig, the rhinoceros, the tapir, and the elephant. In the mole, too, the papillary structure is remarkably developed at the ex- tremity of the snout. The only part of the skin of birds on which tactile papillae have been discovered is on the under surface of the toes, and on the web of the palmipedes, where they obviously receive impressions, which guide the prehensile and other move- ments of the feet. It is probable, however, that the very sensitive skin which covers the greater part of the mandibles in the duck tribe, is furnished with papillae ; the tactile impressions received through this part, when the bill is plunged into mud &c., being the chief means by which the presence of food is discovered. In many lizards a papillary struc- ture is found on the under surface of the toes ; and in the chameleon it exists, also, on the integuments of its prehensile tail. In the soft skinned batrachia, an imperfect papillary structure is more extensively diffused over the surface ; but on the thumb of the male frog, and probably on that of other batrachia, there is an extraordinary development of pa- pillary tissue at the season of sexual excite- ment, large papillae being formed all over it. This organisation is obviously connected with the extraordinary prehensile propensity which is then displayed by the animal, and which enables him to keep the female in his grasp during the whole period of the discharge of the ova, in a manner which no voluntary effort could effect. In serpents and chelonians, no papillary apparatus has yet been detected ; and in fishes and invertebrata its presence has not been ascertained, although it would ap- pear that certain parts, especially the tenta- cula around the oral orifice, are endowed with a high degree of tactile sensibility.* But it is not only on the tegumentary sur- face of the exterior of the body, that tactile sensibility is particularly acute ; nor is the pa- pillary apparatus restricted to it alone. In the tongue of man, we find the sense of touch remarkably developed, especially at its tip ; and of the papillae with which its surface is beset, it is probable that some are the instru- ments of tactile sensibility ; whilst others minister to the gustative sense. (See TASTE.) So it is probable that in all animals which have a soft fleshy tongue, furnished with pa- pillae, and serving as the organ of taste, this organ is the instrument of tactile sensibility also. * The movements of these organs, or such as are excited through contact with them, can scarce!}' be in themselves regarded as a sufficient indication of their tactile sensibility, as they may be purely reflex, without involving consciousness of the impression. TOUCH. 11G7 Besides the papillary apparatus, however, we find certain animals endowed with special organs of touch, which are constructed upon a very different plan ; consisting of a rod or filament, whicli is in itself insensible, but which is connected at its base with nervous fibres, in such a manner that any motion or vibration communicated to it must be transmitted to them. Such are the long stiff hairs which are known as the " whiskers" of the feline tribe, and which are so particularly large in the seal ; these are also highly deve- loped in many of the rodentia, such as the hare and rabbit ; and it has been proved by experiment, that if they be cut off, the animal loses in great degree its power of guiding its movements in the dark. Thus Mr. Broughton found that whilst a kitten whose whiskers were entire was capable of threading its way blindfold out of a labyrinth in which it was designedly placed, it was totally unable to do so when its whiskers were cut off; for it then struck its head repeatedly against the sides, ran against all the corners, and tumbled over steps placed in its way, instead of avoiding them as it did prior to the loss of its whis- kers.* In animals whose hairs are their im- portant instruments of touch, a true papilla, copiously furnished with nerves and blood- vessels, is found to project into the bulb of each hair. The jointed appendages to the head, known as antennae and palpi, which are possessed by most articulated animals, are un- doubtedly instruments of touch, whatever sensory impressions they may receive in addi- tion. The antenns, when prolonged, serve to guide the movements of the animal ; the impressions which they receive at their ex- tremities being communicated to the nerves at their base, just as a blind man judges by the stick held in his hand of the proximity of obstacles to his progress.-)- On the other hand, the palpi appear to minister to the cognisance of objects brought into the neighbourhood of the mouth, and to have for their chief office to guide in the selection of food. But while there are many facts which seem to indicate that the antennae minister to the sense of hearing, there are others which appear to point to the palpi as the special instruments of that of smell. Conditions of the Sense of Touch. — The sense of touch, strictly so called, is exercised under conditions essentially the same as those through which the general sensibility of the * London Medical and Physical Journal, 1823. f The author is acquainted with a blind gentle- man who exhibits a remarkable dexterity in the use of his stick in guiding his movements ; and he has been informed by him, that much of his power of discrimination depends upon the flexibility, elasti- city, &c. of this instrument, so that, when he has chanced to lose or break the one to which he has been accustomed, it is often long before he can ob- tain another that shall suit him so well. This cir- cumstance seems to throw some light upon the re- makable varieties of conformation in the antenna} of insects ; as it may well be imagined that each is adapted to receive and to communicate impressions of a particular class, adapted to the wants of the species. body is affected. It is requisite, in the first place, that the bodies, of whoseTpresence it takes cognisance, should be brought into actual contact with the tactile surface ; the only exception being in regard to the tempe- rature of objects, the influence of which may be communicated by radiations from a distance. This difference, however, does not indicate any fundamental diversity such as some have imagined to exist, between the sense of tem- perature and that of resistance ; for, in each case, that which is perceived by the mind is the impression made upon the sensory organ ; and the change in this is excited in the one case by pressure, and in the other by heat or cold. The same organ appears to be adapted to take cognisance of both classes of impres- sions ; a feeling of one kind being excited, when its condition is altered by pressure ; and a feeling of a different kind, when its tempe- rature has undergone a change under the in- fluence of calorific radiations. And the dif- ference between these classes of sensations is not greater than that which exists among others, — whether of a general or a special kind, — which we know to be transmitted by the same nerve-fibres. Yet it would seem that, whilst there is no sufficient reason for supposing impressions of contact and of tem- perature to be transmitted by different nerve- fibres, we must admit that some of these fibres, either in virtue of their own constitu- tion, of the locality of their central termina- tion, or of the apparatus with which they are furnished at their peripheral origin, are" en- dowed with a greater readiness to receive and transmit one or the other class of impressions. For we find that the parts whose tactile sen- sibility is the most discriminating, are not always those by which the keenest apprecia- tion of changes of temperature is obtained. And, in like manner, the occasional occur- rence of cases of paralysis, in which there is a total loss of one kind of sensation, whilst the other is preserved, or in which one is di- minished beyond all proportion to the other, seems to show that such a change may take place in the nerve-fibres, as may indispose them to the reception and transmission of one class of impressions, whilst they are still capable of actively responding to the other. After what has been said of the necessity of the supply of blood, for the active exercise of common or general sensibility, and of the vas- cularity of the special tactile organs, it is not requisite to lay any further stress on this point, in relation to the sense of touch, strictly so called. Another important condition, which is probably common to the whole sensory apparatus of the warm-blooded animal, and which has been already noticed under the head of Taste, is a temperature not too far removed from that which is natural to the body. It has been shown by Professor E. II. Weber, that if the fingers or the lips be im- mersed for half a minute or a minute in water heated to 125°, or cooled to 32°, the power of tactile discrimination is so much impaired, that the power of distinguishing between a 1168 TOUCH. hot or cold fluid or solid body is for the time completely lost, a feeling of pain alone being experienced, which is the same whether the body be hot or cold. This, too, he found to be the case, when, instead of applying the heat or cold to the peripheral extremities of the nerve, he acted on its trunk. For this ex- periment the ulnar nerve was selected, as its trunk, at the elbow, lies immediately beneath the surface. After immersing the elbow in a mixture of ice and water for about six- teen seconds, Professor Weber observed that a peculiar painful sensation was experienced along the under side of the fore-arm, the wrist, the little finger, and the inner side of the ring-finger. This pain had no resemblance to that of cold. On continuing the immersion, the pain increased considerably, and eventu- ally became almost intolerable ; then it gra- dually diminished, and the middle and ring- fingers became numb, as if " asleep," had no longer the power of distinguishing between heat and cold, and could only imperfectly per- ceive the contact and pressure of bodies. * The exercise of the sense of touch may be first considered under its simplest mode, namely, that in which the object is simply ap- plied to the tactile organ ; and in this we have specially to consider the power of Tactile Discrimination, and the Sense of Temperature. Tactile Discrimination. — A very ingenious method was devised by Professor Weber f, for determining the relative power of tactile dis- crimination in different parts of the skin, which is by no means accordant with their general sensibility. His mode of ascertaining this, was to touch the surface with the points of a pair of compasses, guarded by bits of cork or seal- ing-wax ; the eyes being closed at the same time, the legs of the compasses were approxi^ mated to each other; until they were brought so near that the points could be no longer felt to be distinct from each other. The smallest distance at which this can be perceived (en- titled "the limit of confusion," by Dr. Graves), is found to differ remarkably on different parts of the cutaneous surface ; and the com- parison of these diversities affords us the means of estimating, — not their relative tactile sensibility (for this it cannot measure), — but their relative discriminating power. The figures in the first column ot the following TABLE represent thesedistances,as determined by Professor Weber on his own person, stated in Paris lines. The inquiry has been more re- cently pursued by Professor Valentin j, whose results on the whole correspond very closely with those of Weber. He found, however, a considerable extent of individual variation ; some persons being able to distinguish the points at half, or even one-third of the dis- tances required by others. In the following table, the second column expresses the maxima * Mailer's Archiv. 1847, p. 342. f I)e Pulsu, Eespiratione, Auditu, ct Tactu, An- notationes Anatomic-re et Physiologies. Auct. H. E. Welter. Lipsise, 1834. t Lelirbuch tier Physiologic des Mcnschcn, Band ii. S. L>(J(J. of the "limit of confusion," the third column the minima, and the fourth column the mean of all the observations made by Professor Valen- tin ; it will be observed that his maxima cor- respond almost exactly with the measure- ments of Professor Weber on his own person. In the fifth and sixth columns are shown the relative acuteness and relative obtuseness of the discriminating sense in different parts, calculated from the mean results ; " the limit of confusion " (0'483) at the tip of the tongue being taken as I'OOO. Thus the co-efficient of the acuteness of the discriminating sense in the palm of the hand, calculated by this standard, is O126 ; that of its obtuseness is 7'930. The co-efficient of acuteness for the crown of the head, is 0'050 ; that of obtuse- ness, for the same part, is 19-827. The co- efficient of acuteness for the middle of the dorsal spine is 0'020 ; that of its obtuseness is 50'OS6. Or, in other words, its acuteness is only T§gnths that of the tip of the tongue ; its obtuseness fifty times as great. Similar experiments, with the like results, have been made by M. H. Belfield-Lefevre*^ and from all these, the following general pro- positions may be laid down : — 1. On almost any part of the integument, the interval between the two points is more clearly dis- tinguished, when the line which joins them is transverse (i. e. perpendicular to the axis of the body or member), than when it is longitudinal, or parallel to that axis. According to Weber, however, the tips of the fingers and of the tongue constitute an exception to this rule; the discriminating power being greatest in them, when the line joining the points of the com- passes is longitudinally directed. 2. When two points, applied simultaneously to any part of the integument, are clearly distin- guished, the distance which separates them seems to be greater, in proportion to the acute- ness of the discriminating sense in the part of the surface which is the subject of examina- tion. Thus, as Weber remarks, if the points of the compasses, set at a distance of two or three lines, be applied to the cheek just before the ear, and be then moved gradually towards the angle of the mouth, the points will seem to recede from one another, in consequence of the increase of the discriminating sense in the parts to which they are applied. 3. When the two points are successively brought into contact with the skin, they seem to be at a greater distance from each other than if they are simultaneously applied ; and, in general, the distance will seem greater in proportion to the interval between their application. 4. Two points applied on different sides of the median line, seem more remote from one another than two points equally distant, but applied on one and the same side of the median line ; in other words, the power of discrimination is greater when the two points are applied on the two sides of the median line, than when they are both applied on the same side. 5. If two parts of the tegumentary surface be * Eccherches sur la Nature, la Distribution, ct 1'Orgaiis du Sens Tactile. Paris, 1837. TOUCH. 1169 TABLE. Part of Surface. • Weber's mea- surements. Valentin's Measurements. Rela- tive acute- ness. Rela- tive obtuse- ness. Max. Min. Mean. I. II. III. IV. V. VI. Tip of the Tongue - 2 0-50 0-40 0-483 1-000 1-000 Palmar surface of 3rd phalanx of fore finger 1 TOO 0-50 0 603 0-802 1-248 Do. do. middle finger - * » • 1-00 0-37 O-706 0-685 1-461 Do. do. ring-finger . . . 1-00 0-60 0-723 0-669 1'496 Do. do. thumb - • • • 1-00 0-50 0-725 0-667 1-500 Do. do. little finger . . . 1-00 0-50 0-733 0-659 1-517 Red surface of under lip - 2 2-00 0-50 1-500 0-322 3-130 Do. upper lip - . . . 2-00 0-50 1-520 0-318 3-145 Palmar surface of 2nd phalanges of the fingers - 2 2-00 1-25 1-558 0-310 3 -223 1 "t 1 '75 1-50 1 -6.50 0-293 3-414 Middle of the dorsum of the tongue - 4 4-00 1-50 1-916 0-252 5-964 Dorsal surface of the 3rd phalanges of the fingers 3 3-00 1-75 2-125 0-227 4-397 Portion of the lips not red - 4 4-00 1-50 2-208 0-219 4-568 Tip of the nose - 3 3-00 0-50 2-250 O-215 4-655 Edge of the tongue an inch from the tip ... 400 1-50 2-478 0-195 5-127 Lateral surface of the dorsum of the tongue ... 4-00 1-50 2-500 0-193 5-172 Palmar surface of the metacarpus 3 3-00 1-75 2-625 0-184 5-431 End of the great toe 5 5-00 3 00 3-250 0-149 6-724 Metacarpal joint of the thumb - 4 4-50 2-00 3-333 0-145 6-896 External surface of the eyelids - - - - 5 5-00 2-50 3-833 0-126 7-930 Palm of the hand 5 5-00 3-00 3-833 0-126 7-930 Dorsal surface of 2nd phalanx of thumb 5 5-50 2-75 3-893 0-124 8 -054 Do. do. fore finger . . . 5-50 2-75 3 893 0-124 8-054 Do. do. middle finger - • • • 5-50 2 75 3-900 0-124 8-069 Do. do. little finger ... 5-50 2-50 3-943 0-122 8 • 1 58 Do. do. ring-finger * • * 5-50 2-75 3-971 0-121 8-216 Centre of the hard palate - - - 6 6-00 2-00 4042 0-120 8-363 Mucous membrane of lips close to the gum 9 9-00 2-00 4-125 0-117 8-535 Skin of cheek over buccinator - 5 5-00 3-25 4-541 0-106 9-395 Skin of cheek over anterior part of malar bone - 7 7-00 3-00 4-620 0-105 9-559 Dorsal surface of the Jst phalanges of the fingers 7 7-00 400 4-917 0-098 10-173 Prepuce _---.-_ *•• 6-00 4-00 5-100 0095 10-552 Dorsal surface over the heads of metacarpal bones 8 8-00 3-25 5-250 0-092 1O-862 Skin of cheek over posterior part of malar bone - 10 10-00 3-OO 5 286 0-091 10-936 Plantar surface of metacarpal bone of great toe - ... 7-00 5-00 5-875 0-082 12-155 10 10 '00 4-00 6'000 0-081 12-414 Back of the hand - - - 14 14-00 3-50 6-966 0-069 14-412 Lower part of hairy scalp in occipital region 12 12-00 6-00 8-292 0-058 17-156 Surface of the throat beneath lower jaw 15 15-00 3-00 8-292 0-058 17-156 Back of the heel ------ 10 10 00 8-00 9-000 0-054 18-621 Pubes - - ... 14-00 3-00 9-200 0-052 19-035 Crown of the head - 15 15-00 5-50 9-583 0-050 19-827 Patella and neighbouring part of thigh 16 16-00 6-00 10-208 0-047 21-120 Areola around nipple - . , , 20-00 9-50 12-066 0-040 24-964 Dorsum of foot near the toes - - 18 18-00 7-50 12-525 0-039 25-914 Axilla - ... 14-00 12-00 13-000 0-037 26-897 Upper and lower extremities of fore arm 18 18-00 7-00 13-292 0-036 27-501 Back of the neck near the occiput 24 24-00 8-OO 13-292 0-036 27 501 Upper and lower extremities of leg - 18 18-00 9-00 13-708 ! 0 035 28-361 Penis - - - - 18 18-00 10-00 13-850 0034 28-655 Acromion and upper part of arm 18 18-00 6-00 13-866 0-034 28 688 Sacral region - - - 18 18-00 7-50 14-958 0-032 30-948 Sternum - - - 20 20-00 8-00 15-875 0030 32-845 Gluteal region and neighbouring part of thigh - 18 18-00 10-50 16-625 0-029 34-397 Middle of fore arm, where its circumference is~| greatest - - J 30 30-00 8-75 17-083 0-028 35-344 Middle of thigh, do. - 30 30-00 9-00 17-633 0-027 36-482 Middle of cervical vertebrae - 30 30-00 7-00 18-542 0-026 38-362 Five upper dorsal vertebrae - 24 24-00 11-00 19000 0-025 39-310 Lower part of thorax, and over lumbar vertebrae 24 24-00 11-50 19-912 0-022 44-758 Middle of the dorsal vertebras - 30 30-00 11-00 24-208 0-020 50-086 VOL. IV. 4 F 1170 TOUCH. selected, whose relative position is subject to variation (such as the two eyelids, the two lips, &c.), and the two points of the pair of compasses be applied respectively to these two surfaces, the distance which separates them will seem to be much greater than if the two points rest at the same time on one or the other surface. 6. The same holds good, ac- cording to Weber, when the two points are applied to parts of the surface, which, though in continuity with each other, differ remark- ably, either in structure, in function, or in the use habitually made of them ; thus, the points will be more clearly distinguishable, and will therefore seem to be more distant from each other, when one is applied to the inner surface and the other to the red outer surface of the lips, than when they are both applied to the latter, although its discriminating power is much greater than that of the former; and the same holds good of the margin and dorsmn of the tongue, the palmar and dorsal surfaces of the last phalanges of the fingers, &c. 7. The discriminating sense is more acute in the in- teguments of the head, than in those of the trunk ; and on the face, its acutencss di- minishes as the distance from the mouth in- creases. 8. The tactile discrimination of the integuments of the limbs augments with the distance of the part from the axis of the body ; it is less in the integuments of the trunk, than in those of the members. The power of tactile discrimination may be conceived to depend in part upon the mode in which the ultimate nerve-fibres are dis- tributed in the skin, being greater in propor- tion as contiguous parts are supplied from distinct central sources, and less when the central terminations of their nerve-tubes are the same. Thus, if two impressions be made along the course of the same nerve-tube, they will not be felt as two, but as one , and this probably holds good of the parts of the in- tegument supplied with branches from the central axis of any one tube. On the other hand, whenever two impressions be made upon two distinct nerve-tubes, or on the branches proceeding from them, they will probably be felt to be double ; and the dis- tance at which these impressions seem to the tactile sense to be, appears to have a relation to the distinctness of the central connections of these nerve-tubes, as appears from the fact that the " limit of confusion " is less across the median line than on either side of it ; that it is less between two parts (such as the lips and eyelids) whose nervous supply is knoivn to be distinct, than on either part separately ; and that it is less between two parts whose nervous supply may be jircsumed, from their difference of function, to be dis- tinct (as the inner and outer surfaces of the lips), than on either part separately. More- ever, it would not seem to be improbable that one use of the plexuses from which the limbs are supplied, is to produce such an inter- mingling of the fibres from different gan- glionic centres, that contiguous portions of the integument shall be connected with cen- tres very remote from each other, and their discriminating power thus augmented. No such intermingling takes place in the nerves which supply the trunk, and the tactile dis- crimination of its integument is (as we have seen) vastly inferior to that of the extremities. Thus it may happen that the common sensi- bility of two parts may be the same, whilst their power of tactile discrimination may differ considerably ; and we may even have the common sensibility greatest where the tactile discrimination is least, — as we experience, for example, on the integument of the face, which is far more sensitive to a blow, and especially to a " fillip," than is the integument of the palmar surface of the fingers, although greatly inferior to them in discriminating power. The actual nervous supply, and the conse- quent sensibility, of a part, may be greater in such cases ; but the unity, or close approxi- mation, of the source from which this pro- ceeds, may prevent its discriminating power from augmenting in the same proportion. In like manner, we find that the tactile dis- crimination of different parts bears no relation whatever to that peculiar modification of common sensibility (which yet appears the exclusive attribute of the external integuments) through which the feeling of " tickling " is excited. For the parts which are most sus- ceptible to this feeling, such as the axilla; and the soles of the feet, are possessed of a very low degree of discriminating power, and those which possess this power in the highest degree (such as the tips of the fingers) are the least " ticklish." Further, it is worthy of notice that the parts through which that peculiar sensation, which we have termed the genital sense, is specially excited, — namely, the penis and the mammary areola, — are remark- able rather for the obtuseness than for the acuteness of their power of tactile discrimina- tion . That it is only through the skin and those parts of its internal reflexions which are in closest proximity with it (especially the lining of the mouth and nostrils), that we can dis- criminate tactile impressions, appears from this ; that although the internal mucous and serous surfaces, the fibrous membranes, and the parenchyma of many organs, &c. &c., are all capable of becoming acutely sensible to pain when irritated or inflamed, yet no foreign substance is ever distinctly felt by the touch through these parts. Thus, although a sensation of a pleasing or a painful nature is excited by certain substances immediately upon being swallowed, all consciousness of their presence (so far as it is dependent upon the sense of touch) soon ceases, and cannot be again recalled by the utmost exertion of the will. Further, a foreign substance, lodged in the alimentary canal, or in the trachea, may give rise to the greatest possible distress, through the irritation it produces ; but though it thus acts upon the nerves of the parts im- mediately in contact with it, these nerves convey no idea to the sufferer of the shape or size of the body, or of any other of its TOUCH. 1171 physical qualities, concerning which we re- ceive information through the sense of touch. Sense of Temperature. — This sense is called into action when there is a difference between the temperature of the sensory organ and that of the surrounding medium, or of substances with which it is specially brought into contact. It is one of which the intensity is determined, more perhaps than that of any other sensation, rather by the relative than by the absolute condition of the body which excites it. Thus, if one hand be immersed for a time in hot water, and the other in cold, and both then be plunged into tepid water, this will seem cool to the former and warm to the latter. So, again, a person coming out of cold air into an atmosphere of moderate tem- perature, derives from it the feeling of genial warmth, whilst another, coming into the very same atmosphere from one much hotter, com- plains of its chillness. Again, when the tem- perature of different substances is compared by the hand, the sense is not so much influ- enced by the absolute amount of caloric possessed by each, as by their power of imparting cold or heat to the sensory organ. Hence substances which are good conductors (such as metals or marble) are felt to be colder than those which conduct heat badly (such as wood), although really of the same temperature, because they draw off the heat of the sensory surface more rapidly ; whilst, on the other hand, it" both be warmer than the sensory surface, the best conductors will seem to be the hottest, because their caloric is most readily imparted. Further, the sense of temperature is influenced in a remarkable degree by the extent of surface on which the impression is made. Every one is familiar with the fact that hot water in which a single finger may be held without inconvenience, will be felt intolerably scalding when the whole hand is immersed in it. And it has been shown by Professor Weber, that if one vessel of water be heated to 98° and another to 1040, and the whole of the hand be im- mersed in the former, while the finger alone is immersed in the latter, a wrong judgment of their relative temperatures will be probably given, that which is really the cooler being pronounced the hotter, on account of the larger extent of surface on which it acts. This mistake was made in some of his experi- ments, when the difference was as much as eight degrees ; the cooler water being at 98°, and the hotter at 106°, and yet the former being esteemed the hotter. So, again, the immersion of the entire hand enables minute differences of temperature to be detected, which could not be recognised by the immer- sion of a single finger. By the former method, a difference of only one-third of a degree may be distinguished ; the entire hand being im- mersed, repeatedly and successively, in two vessels of water, differing only that much in their relative warmth. But it is remarked by Professor Weber, that these minute differ- ences are best detected when the medium examined does not fall short of, or exceed very considerably, the usual temperature of the body ; just as the ear can best perceive a difference of tone in sounds which are neither very acute or very grave.* It is a remarkable fact, discovered by Pro- fessor Weber, that the left hand is in most persons more sensible to variations of tem- perature than the right. Thus, when the hands of a person lying in bed, and having exactby the same temperature, are plunged each in a separate vessel of hot water, the left hand is believed to be in the hotter medium, although the water in which it is immersed is really one or two degrees colder than the other. This difference is the more remarkable, as the power of tactile discrimina- tion is usually greater in the right hand ; and it is attributed by Professor Weber to a difference in the thickness of the epidermis, the left hand usually having a thinner epi- dermis than the right, especially in the palm, because it is less used. But this will only apply to the hand ; and since (as will be presently shown) we possess a greater power of discriminating pressures through the entire surface of the left side than through that of the right, it would seem much more pro- bable that there is an original difference in the tactile endowments of the two sides respectively. There is certainly a strongly marked difference between different parts of the trunk in regard to their sensibility to tem- perature, as is experienced by those who sponge themselves over with cold water im- mediately on leaving their bed in the morning. In the writer's case, the parts most sensitive to the cold are in the centre of the dorsal region behind ; in front, between the lower end of the sternum and the umbilicus ; and the corresponding portions of the flanks. These spots are among the parts of the in- tegument least possessed of tactile discrimi- nation ; and yet the cold sponge passing over them seems to be much lower in temperature than when it is applied to other parts. Some further experiments have recently been made by Professor Weber, to determine whether the sense of temperature is received through any other channel than the sensory apparatus contained in the integuments.f The first means of which he availed himself for deciding this question, was that afforded by the results of accident or surgical operations, in which a portion of skin has been left defi- cient. Thus, in three cases in which a large portion of the skin had been destroyed by a burn, and in which healing had not advanced so far as to renew the organ of touch, it was found that no correct discrimination could be made between two spatulas, one of them at a temperature of from 48° to 54°, the other of from 113° to 122°, which were brought into * He further remarks, that the comparison be- tween two temperatures can be best made when the impressions are not simultaneously made upon two different parts, but are made in quick succession upon the same part ; as mentioned hereafter to be the case in regard to weights. t MUller's Archiv. 18-19. Heft, iv. s. 273—283. 4F 2 1172 TOUCH. contact with the denuded surface ; so that one of these patients thrice affirmed that he was being touched with the cold body when it was the warm, and the reverse. But when the spatula was in one instance made some- what warmer, and was brought into contact with the uuskinned surface, the patient felt, not heat but pain. Another means of gaining information on this point is afforded by the ingestion or injection of a large quantity of warm or cold fluid into the stomach or intes- tinal canal. Thus Professor Weber states, that after drinking a tumbler of water at 32°, he felt the cold water in the mouth, in the palate, and in the pharynx, as far as the limits of the sense of touch ; but that the gradual passage of the cold water into the stomach could not be perceived. There was, it is true, a slight sensation of cold in the gastric region ; but as it only occupied the situation of the anterior wall of the stomach, it was at- tributable to the abstraction of heat from the abdominal integuments in contact with this. In an opposite experiment, the author drank quickly three glasses of milk, the temperature of the first of which was 158°, that of the second 14<5°, whilst that of the third was in- termediate between the two. The sensation of heat could not be traced lower down than that of the cold in the previous experiment. At the moment when the fluid entered the stomach, there was a feeling which remained for some time, but which could not be dis- tinguished as heat, being mistakeable for cold. In order to ascertain the sensations produced in the large intestine by cold water, an in- jection of 1-iozs. of water of the temperature of 65° was thrown up the rectum, but scarcely any sensation of cold could be perceived from it. In another instance, 21 ozs. of water at the same temperature was thrown up, without any resulting sensation of cold. In both these cases, on the return of the enema a few mi- nutes afterwards, a distinct feeling of cold was experienced at the anus. When water of so low a temperature as 45J° was injected, the first feeling excited was a sensation of cold in the immediate neighbourhood of the anus, and then a feeble movement in the bowels ; but a little time afterwards, there was a faint sensa- tion of cold, especially in the anterior wall of the abdomen. This sensation, however, re- mained after the return of the water ; and may hence be attributed to the abstraction of warmth from the abdominal integuments, which was proved to take place, the temper- ature of the surface being lowered .3 degrees. So, again, if the cavity of the nose be filled with cold water, the coldness is only perceived in the parts of the cavity which are most en- dowed with the proper tactile sense, namely, the neighbourhood of the nostrils and of the pharynx ; and it is not at all discernible in the higher part of the cavity, which is espe- cially subservient to the olfactive sense. [See SMELL.] But when the water injected is very cold (e. g. 41°), a peculiar pain is felt in the upper part of the nasal fossae, extending to the regions of the forehead and lachrymal canals ; this pain, however, is altogether dif- ferent from the sense of coldness. From the foregoing experiments it appears fair to conclude, that the sensory nerves have no power of receiving impressions arising from difference of temperature, unless those im- pressions are communicated through a special organ ; but they afford no adequate ground for the supposition, that a set of nerve-fibres is provided for their transmission, distinct from those which minister to common sensation. This conclusion is confirmed by the fact, that we cannot excite impressions of heat or cold by direct application to the trunks of nerves which we know must conduct such impres- sions. Thus the parts of the skin immediately beneath which lie large nerve-trunks, are not more sensitive to moderate heat or cold than any other part ; whilst a greater degree of either is felt as pain, not as a change of tem- perature. Tims, as we have already seen, a mixture of ice and water, applied over the ulnar nerve, affects it in fifteen seconds, and produces severe pain, having no resemblance to cold, such as cannot be excited by the same cold applied to any other region. So the nerve of the tooth-pulp is equally and similarly affected by water of 43° and of 112°; either application causing a pain exactly similar to that excited by the other, or that produced by pressure.* We have now to consider those more com- plex modes of exercise of the sense of touch which require the conjoint exercise of the " muscular sense;" and as this is a modifi- cation of the general sensibilitv, which may perhaps be regarded as being as special or peculiar in its relations to the muscular sys- tem as the sense of touch (properly so called) is to that of the skin,jit will be desirable to examine, in the first instance, into its modus operandi. Muscular Sense. — It may be stated as a general fact, that all voluntary muscular con- traction must be guided and controlled by sen- sation ; and in the majority of cases, the con- trolling sensation is derived from the muscles themselves, of whose condition we are ren- dered cognisant by the sensory nerves with which they are furnished. The proof of this necessity is furnished by the entire want of power to make or sustain voluntary efforts, when the guiding sensation is deficient. Thus, in complete anassthcsia of the lower extre- mities, without loss of muscular power, the patient is as completely unable to walk, as if the motor nerves had also been paralysed, unless the deficient sensorial guidance be re- placed by some other ; and in similar affections of the upper extremities, there is a like in- ability to raise the limb or to sustain a weight. But in such cases, the deficiency of the " mus- * It is remarkable that the same should be true of the impressions received through the skin itself, when they pass beyond certain limits of intensity ; thus, the sensation produced by touching frozen mercury is said to be not distinguishable from that which results from touching a red-hot iron. TOUCH. 1173 cular sense" maybe made good by the visual; thus, the patient who cannot walk, because he cannot feel either the contact of his foot with the ground, or the muscular effort he is mak- ing, can do so if he looks at his limbs ; and the woman who cannot feel the pressure of her child upon her arms, can yet sustain it as long as she keeps her eyes fixed upon it, but no longer, — the muscles ceasing to contract, and the limb dropping powerless, the moment that the eyes are withdrawn from it. There are two groups of muscular actions, however, which, although as voluntary in their character as the foregoing, are yet habitually guided by other sensations than those derived from the muscles themselves. These are, the move- ments of the eyeball, and those of the vocal apparatus. The former are directed (as Dr. Alison has well shown*) by the visual sense, by which the action of the muscles is guided and controlled in the same manner as that of other muscles is directed by their own " mus- cular sense ;" and hence it happens that, when we close our eyes, we cannot move them in any required direction, without an etlbrt that strongly culls forth the muscular sense, by which the action is then guided. In persons who have become blind after having once enjoyed sight, an association is formed by habit between the muscular sense and the con- tractile action, that enables the former to serve as the guide after the loss of the visual sense ; but in those who are born perfectly blind, or who have become so in early infancy, this association is never formed, and the eyes of such persons exhibit a continued indefinite movement, and cannot by any amount of effort be steadily fixed in one spot, or be turned in any definite direction. A very small amount of the visual sense, however, such as serves merely to indicate the direction of light, is sufficient for the government of the move- ments of the eye-ball. In the production of vocal sounds, again, that nice adjustment of the muscles of the larynx, which is requisite to give forth deter- minate tones, is ordinarily directed by the auditory sense; being learned in the first instance under the guidance of the sounds actually produced ; but being subsequently effected voluntarily, in accordance with the mental conception (a sort of inward sensa- tion) of the tone to be uttered, which concep- tion cannot be formed, unless the sense of hearing has previously brought similar tones to the mind. Hence it is that persons who are born deaf, are also dumb. They may have no malformation of the organs of speech ; but they are incapable of uttering distinct vocal sounds or musical tones, because they have not the guiding conception, or recalled sensation, of the nature of these. By long training, however, and by imitative efforts directed by the muscular sense of the larynx itself, some persons thus circumstanced have acquired the power of speech ; but the want * Anatomical and Physiological Inferences from the Study of the Xerves of the Orbit, in Trails, of Roy. Soc. Edinb., vol. xv. of a sufficiently definite control over the vocal muscles is always very evident in their use of the organ. It is very rarely that a person who has once enjoyed the sense of hearing, afterwards becomes so completely deaf, as to lose all auditory control over his vocal organs. An example of this kind, however, has been made known to the public by a well known author, as having occurred in himself; and the record of his experiences * contains many points of much interest. The deafness was the result of an accident occurring in child- hood, which left him for some time in a state of extreme debility ; and when he made the attempt to speak, it was with considerable pain in the vocal organs. This pain probably resulted from the unaccustomed effort which it was necessary to make, when the usual guidance was wanting ; being analogous to the uneasiness which we experience when we attempt to move our eyes with the lids closed. His voice at that time is described as being very similar to that of a person born deaf and dumb, but who has been taught to speak. With the uneasiness in the use of the vocal organs was associated an extreme mental in- disposition to their employment; and thus, for some years, the voice was very little ex- ercised. Circumstances afterwards forced it, however, into constant employment; and great improvement has subsequently taken place in the power of vocalisation, evidently by atten- tion to the indications of the muscular sense. It is a curious circumstance, fully confirming this view, that the words which had been in use previously to the supervention of the deafness, are still pronounced (such of them, at least, as are kept in employment) as they were in childhood ; the muscular movements concerned in their articulation being still guided by the original auditory conception, in spite of the knowledge derived from the in- formation of others, that their pronunciation is erroneous. On the other hand, all the words subsequently learned are pronounced according to their spelling; the acquired as- sociations between the muscular sensations and the written signs being in this case the obvious guide. The perception of "effort" which we derive through the impressions made on the muscular sense, is one which, as we shall presently see, is of immense value, in com- bination with simple tactile sensation, in informing us of the sensible properties of external objects. In its simplest exercise, however, it enables us to appreciate the degree of muscular force which is being exerted ; and excites in our minds our most definite idea of power. It is true that we might, by the exercise of our other senses, have arrived at the conception of a tendency in bodies to attract one another, or to com- municate motion one to another ; but the notion of the force with which they do so is entirely founded, directly or indirectly, upon * See the " Lost Senses," by Dr. Kitto ; vol. i. chapters 2 and 3. 4 F 3 1174 TOUCH. the conception of the muscular exertion which would be required to produce or to antagonise the movement. Thus it is, too. that when we are about to make a muscular effort, the amount of force which we put forth is governed by the mental conception of that which will be required, as indicated by the experience of former sensations ; just as the contractions of the muscles of vocalisa- tion are regulated by the conception of the sound to be produced. Hence if the weight be unknown to us, and it prove either much heavier or much lighter than was expected, we find that we have put forth too little or too great a muscular effort. It is through the " muscular sense," in combination with the visual and tactile, that those movements are regulated, which are concerned alike in ordinary progression, and in the maintenance of the equilibrium of the body. That the visual sense has, in most persons, a large share in this regulation, is evident from the simple fact that no one who has not been accustomed [to the deprivation of it can continue to walk straightforwards, when blind-folded, or in absolute darkness, towards any point in the direction of which he may have been at first guided. But the blind man, who has been accustomed to rely exclusively upon his muscular sense, has no difficulty in keeping to a straight path ; and moves onwards with a confidence which is in remarkable contrast with the gait of a man who has been deprived of sight for the oc- casion only. In fact, as Mr. Mayo has well remarked *, in our ordinary movements, " we lean upon our eyesight as upon crutches." And when our vision, instead of aiding and guiding us, brings to the mind sensations of an antagonistic character, our movements become uncertain, from the loss of that power of guidance and control over them which the harmony of the two sensations usually gives. Thus a person unaccustomed to look down heights feels insecure at the top of a tower or a precipice, although he knows that his body is properly supported ; for the void which he sees below him contradicts (so to speak) the tactile sensations by which he is made conscious of the due equilibrium of his body. So, again, any one can walk along a narrow plank which forms part of the floor of a room, or which is elevated but a little above it, without the least difficulty, and even without any consciousness of effort. But let that plank extend across a chasm, the bottom of which is so far removed from the eye that the visual sense gives no assistance ; and even those who have braced their nerves against all emotional distraction feel that an effort is requisite to maintain the equilibrium during the passage over it; — that effort being aided by the withdrawal of the eyes from the abyss below, and the fixation of them on a point beyond, which at the same time helps to give steadiness to the move- ments, and distracts the mind from the sense of its clanger. The degree in which the muscular sense is alone sufficient for the guidance of such movements, when the mind has no consciousness of the danger, and when the visual sense neither affords aid nor contributes to distract the attention, is re- markably illustrated by the phenomena of Somnambulism; for the sleep-walker traverses, without the least hesitation, the narrow para- pet of a house, and crosses narrow and insecure planks, chambers, roofs, &c., under circum- stances that clearly indicate the nature of the guidance by which they are directed (see SLEEP, p. 694). The dependence of our ordinary power of maintaining our equili- brium upon the combination of the guiding sensations derived through the sight and the touch, is further well illustrated, as Mr. Mayo has pointed out *, by what happens to a landsman on first going to sea. " It is long before the passenger acquires his ' sea legs.' At first, as the ship moves, he can hardly keep his feet ; the shifting lines of the vessel and surface of the water unsettle his visual stability ; the different inclinations of the planks he stands on, his muscular sense. In a short time, he learns to disregard the shift- ing images and changing motions, or acquires facility in adapting himself (like one on horseback) to the different alterations in the line of direction in his frame." Before this power, however, has been gained, the pas- senger has usually to experience most dis- tressingly that peculiar feeling of want of support, which is consequent upon the pitch- ing and rolling of the ship, but more par- ticularly upon the former. As the part of the vessel on which he is standing, sitting, or lying, rises beneath him, there is a comfortable sense of support ; but as it sinks, the want of support is most disagreeably felt ; and the continual repetition of this sensation gives rise to nausea and vomiting. The tendency is increased by the sight of continually shifting lines and surfaces, which of itself, with many individuals, disposes to the same state; and hence it is that the sickness may often be kept at bay by simply closing the eyes, so as to exclude these objects ; whilst, on the other hand, the effort to stand or walk only serves to augment the distress, by increasing the sense of instability. — The giddiness and nausea produced by rapidly turning round, are the results of the same sensations. They are usually excited more through the visual than through the tactile sense ; but that the latter is of itself quite sufficient to produce them, is obvious from the fact that they are experienced when the eyes are closed, as well as by blind persons. The feeling of disturbed equilibrium is more persistent than most other sensations ; thus when a person has turned round quickly several times in suc- cession, and then suddenly stops, he feels a whirling sensation, which excites a disposition to continued motion in his limbs, and the surrounding objects appear to move before Outlines of Physiology, p. 355. * Loc. cit. TOUCH. 1175 his eyes. But if, as Mr. Whcatstonc has pointed out, the person who is turning round holds a large sheet of paper before and near his face, so as to exclude all sight of the room, and fixes his eyes upon a point — a letter, for instance, in the middle of the paper, — when he stops, he finds his head perfectly steady, and the surrounding objects have no apparent motion ; but his legs feel unsteady, as if they continued actually turn- ing round. And it is thus clearly proved that the cause of the giddiness lies in the affection of the senses, and not (as is usually imagined) in disturbed cerebral action. Sense of Weight. — This is usually derived from a double source; namely, the impression made upon the cutaneous surface by the sim- ple pressure of the body: and the conscious- ness of the muscular effort employed to re- sist that pressure. The latter enables us to compare the weights of different bodies much more accurately than the former, which is li- able to excite fallacious ideas. The extent of surface, for example, which is in contact with the skin, greatly modifies the estimate of the pressure of a heavy body ; the body feeling lightest when its pressure is distributed over a larger surface, and vice versa. Thus, a trun- cated cone seems heavier when it rests (with- out any effort being made to raise or support it) upon its small extremity, than when it rests upon its large extremity on the same part of the surface. At first sight this fact appears altogether antagonistic to the one just stated with regard to the sense of temperature, the impressions on which are more powerful when they are made over a large than over a small surface. But it is to be borne in mind, that in the latter case an absolutely larger amount of calorific influence is exerted, when the large surface is exposed to the action of heat ; whilst in the former, the amount of pressure is really the same, whether it be distributed over a larger or a smaller area. The experi- ments of Weber on the relative information derived from the mere sense of pressure, and from the sense of muscular effort, in the ap- preciation of weights, are very instructive. He found that if the two hands of the same individual be placed upon cushions, and un- equal weights be placed upon the right and left hands respectively, the eyes being kept shut, it will not be possible to say on which hand the heavier weigltt lies, unless the dif- ference be very considerable ; but a compara- tively small amount of difference is at once dis- criminated, when a muscular effort is made to lift the hands from the cushions. This power of comparison is capable of being rendered more exact by practice ; so that men accus- tomed to estimate weights by poising them in their hands, will readily distinguish between two which differ only by one-thirtieth part. It is found that the power of comparison is much greater (as in the estimation of tempe- rature) when the impressions are successively, than when they are simultaneously made, pro- vided that the interval be not too long. Thus in the comparison of two weights, the greatest nicety is attained by poising the one, and immediately afterwards the other, in the same hand ; but the intervention of a few seconds between the poising of the first and that of the second does not prevent their accurate com- parison. The interval may amount to twenty seconds, and yet a just estimate may still be made ; but when it amounts to forty seconds all accuracy is lost. Professor Weber has further ascertained, that, in the estimation of weights by their simple pressure on the sur- face, the left side and extremities have usually a more acute perception than the right ; for out of fourteen individuals, he found this to be the case in eleven ; in two, the contrary was observed ; whilst in one, no difference was perceptible. Sense of Direction. — The combination of the muscular with the simply tactile sense enables us also to judge in some degree of the direction of the pressure. Of this we gain no information whatever from the tactile sense alone, which always suggests the idea that the pressure is made vertically to the surface, when it is not corrected by the sense of mus- cular effort called forth to antagonise it. The following example, given by Weber, shows how completely involuntary may be this effort, yet how large a share it has in communicating to us the information we derive from an im- pression, of whose direction we are rendered cognisant. When a hair of the head is pulled, he remarks, we can judge perfectly well of the direction of the traction ; this power of discrimination is not, however, derived (as might at first be supposed) through the sen- sation originating in the bulb of the hair, but from the sense of the muscular effort which is called forth to antagonise the traction, and to keep the head steady during its continuance. If we prevent these muscles from being called into play, by steadily holding between the hands the head of the person operated on, and if we also prevent the traction from call- ing forth the muscular action of the scalp, by surrounding the point from which the hair is pulled with a firm pressure by the fingers, we find that the discriminating power is completely lost ; the subject of the experi- ment being totally unable to distinguish the direction from which the hair is pulled. It is by this combination, too, that we judge of the rate and direction of the passive motion of our bodies, when we have no other means of guidance. If, for example, a person be seated in a carriage, with his eyes closed, and the carriage be suddenly put in motion, the inertia of his body causes it to be thrown in the contrary direction ; and, in order to re- cover and sustain its equilibrium, a muscular effort is required, which is greater in propor- tion to the rate of motion. If the motion continue uniform, however, this effort becomes so habitual that he ceases to be conscious of it ; and he only becomes cognisant of the mo- tion by its cessation, the equilibrium of the body being then again disturbed by its inertia, which tends to impel it in the direction in which it was previously moving, so as to re- 4 F 4 1176 TOUCH. quire the effort of a contrary set of muscles for the maintenance of the erect position. Mental Phenomena connected with the Sense. — The interpretation which the mind puts upon the impressions made by external ob- jects upon the tactile organs, is partly the re- sult of intuition, partly of experience. Thus we intuitively refer an impression made upon any part of a sensory nerve in its course, to the peripheral extremities of that nerve, or (as in cases of amputation) to the part from which they should normally arise. So, again, if a part of the body be removed from its usual position and connections (as in the Taliacotian and various other operations of plastic surgery), impressions made upon it continue to be referred to its original seat, so long as it retains any nervous connection with it, and until new connections have been formed with the nerves of the part to which it has been transferred. So, again, when our members are in an unaccustomed position, we still, unless our attention be directed to the fact, interpret impressions made upon them as if they were in their ordinary relation to each other, and may thus be altogether misled : — as in the experiment mentioned by Aristotle, of rolling a pea or other globular body between two fingers of one hand, which are crossed instead of lying parallel, so that the surfaces that are usually most distant are brought into proximity with each other ; the sensation then received is that of a dis- tinct convex body opposed to each of these surfaces, so that the single body seems to be double; whereas, if the pea were rolled be- tween the two surfaces which are usually and normally approximated, it is felt but as a single globe. This intuitive reference is obviously analogous to that by which we judge of the relative situations of visual objects, from the direction in which their rays impinge upon the retina, or from the muscular sensations re- ceived from the muscles of the orbit. In a large proportion of other cases, how- ever, our interpretation of our tactile sensa- tions, especially of all those which relate to the configuration, density, &c. of external ob- jects, is based on experience ; and those who watch the eagerness with which the infant grasps and examines by its touch every attrac- tive object within its reach, are at no loss to perceive how the experience thus early inter- woven (as it were) \vith the mind, in combin- ation with that derived through the visual sense, comes to supply the place of the con- genital intuitions of the lower animals, and to cause the tactile and visual perceptions to be henceforth so indelibly associated, that each is continually suggesting the other. Thus, the notion of projection, which we derive through the sight, comes to be associated with that of solidity, which we receive through the touch ; and the visual notion of polish is so closely connected with the tactile notion of smoothness, that the one almost necessarily suggests the other. There is abundant evi- dence, however, that there is no necessary or intuitive connection between the ideas which we derive through these two senses respec- tively ; but that this connection is acquired by the consentaneous exercise of them. Thus, from observations made upon persons born blind, when visual power has been first ob- tained, it is certain that the notions of form previously acquired by the touch do not aid in the visual discrimination or recognition of objects : so that, for example, if any such person had previously learned to distinguish a sphere, a cube, and a pyramid, by the touch, he would not be able to say which was which by looking at them, until he had learned by experience to associate the two classes of per- ceptions : and, conversely, we cannot but be- lieve that the same result would occur, if a person whose notions of the external world were derived from the sight alone, were sud- denly and for the first time to become en- dowed with the sense of touch. It is, in fact, no less clear in regard to the sense of touch than it is in regard to vision, that it is not the sentient organ (as we are accustomed to term it), but the mind, which really perceives ; and that all the notions which we derive through this sense with re- spect to external objects, whether they be of the most general kind or of a more particular nature, are altogether distinct from the sensa- tions themselves. It has been well remarked by Professor Alison, that " one decisive proof of this being the true representation of this part of our mental constitution is obtained by attending to the idea of extension or space, which is undoubtedly formed during the exer- cise of the sense of touch, but which is no sooner formed than it ' swells in the human mind to infinity,' to which, certainly, no human sensation can bear any resemblance."* So, again, the elementary notion of an ex- ternal universe as something distinct from the individual self, is altogether distinct from the sensations which excites it. All that the mind is conscious of, is a change in the condi- tion of the corporeal organism ; and the re- ference of the source of this change to some external agency is a mental process in which the action of the purely sensorial apparatus has no concern. It has been thought by some that the notion of an external world depends more upon the sensations received through the touch, than upon those of any other kind. But there does not seem to the author to be any reason for considering that simply tactile impressions are more necessarily or intuitively recognised as proceeding from an external source than are the visual, olfactive, auditory, or gustative. But, as already shown, it is from the muscular sense that we derive the idea of force, involv- ing resistance to our own voluntary efforts ; and it would seem to the writer to be on this notion that our belief in the existence of an universe external to ourselves most securely rests. The active co-operation of the mind is re- quired, not only for the formation of the * Outlines of Physiology, 3rd ed. p. 290. TOUCH. 1177 notions so immediately springing from sensa- tions as to be often confounded with them, but also for the reception of the sensory impres- sions themselves. Until, in fact, the mind has been affected by these impressions, no sensation can be said to exist ; and that of which the mind takes cognisance is not the external object but the impression produced by it, and not the direct or immediate impres- sion produced by it upon the organ which first receives it, but the change in the senso- rium consequent upon this. (See SENSA- TION.) That this is the true account of the process is now universally admitted both by the psychologist and the physiologist ; and it is placed beyond all reasonable question by the occurrence of those subjective sensations, which, until their indications are corrected by experience, may suggest the idea of an external source, with such vividness and de- finiteness, that the objective unreality can scarcely be credited. In some instances the excitement of these subjective sensations ap- pears due to the occurrence of a change in the part in which they are felt, which simu- lates that which would be produced by an external impression ; as in the case of the sen- sation of extreme heat, which is often expe- rienced in inflammation to a degree far beyond that which the actual exaltation of tempera- ture would account for ; and the pain, of va- rious kinds, often resembling that inflicted by external injuries, which is the result of morbid changes in the part to which it is referred. But in other cases they are clearly referable to changes taking place in the course of the nerve-trunk to the sensorium, which simulate those which would naturally occur in it when it is the conductor of an external impression ; of this several examples have already been given. Or, again, they may be due to a change purely sensorial ; as in the various cases of " radiation of sensations " elsewhere alluded to (see SENSATION); or, as in the sensations of nausea, of shuddering, of tickling, of pain, &c., which are frequently excited by changes purely mental. The degree of intensity, again, with which actual sensations are felt, depends as much upon the state of the mind as upon that of the corporeal organism. Thus, if we experience a slight itching in the skin, and direct our thoughts to it, we are speedily annoyed by its increase ; whilst, if we steadily fix our thoughts upon some other object, we are soon unconscious of the irritation. On the other hand, the complete absorption of the mind in some train of thought which engrosses its attention, may render the individual unconscious of impres- sions that would ordinarily induce severe pain. This is remarkably seen in cases of natural and artificial somnambulism (see SLEEP) ; and it is probable that in many of the cases in which insane patients have in- flicted severe wounds upon themselves, with- out appearing to feel pain, the cause of the immunity from suffering is to be found in the entire possession which some dominant feel- ing or idea has of their consciousness, so that they are not cognizant of any external im- pressions but such as harmonize with it. Even in ordinary cases, it is well known that a severe injury suddenly inflicted, is much less felt at the moment than a far slighter injury of which the mind has been in expec- tation ; thus, a limb has been carried away by a cannon-ball, or the chest traversed by a bullet, with far less consciousness of pain than is produced by the trivial incision made in ordinary venesection. Improvcabiiiti/ of the Sense of Touch. — The mental participation in the phenomena of tactile sensation is further rendered obvious by the improvement in discriminating power which results from continual attention to its indications. Of this we have examples in the case of certain artisans, whose employments re- quire them to cultivate their tactile discrimina- tion ; thus, the female silk-throwsters of Bengal are said to be able to distinguish by the touch alone twenty different degrees of fineness in the unwound cocoons, which are sorted ac- cordingly ; and the Indian muslin-weaver con- trives, by the delicacy of his touch, to make the finest cambric in a loom of such simple construction, that European fingers could at best propose to make a piece of canvas in it. The improvement in tactile discrimination is more especially seen, however, in those indi- viduals whose dependence upon it is increased by the loss or deficiency of other senses ; and especially by blindness, congenital or ac- quired. Whilst it is doubtless to be attri- buted, in great part, to the concentration of the attention and of the powers of recollec- tion and comparison upon the sensations which are brought (as it were) to the mind, it may not seem altogether improbable that the improvement may in part depend upon an increased development of the tactile organs themselves ; resulting from that augmented nutrition which would be the natural con- sequence of the frequent use of them, and of the increased flow of blood that seems to take place towards any part on which the attention is continually fixed. Certain it is, that many blind persons can not merely obtain as defi- nite and accurate conceptions of the form, surface, &c., of objects over which they ra- pidly pass their hands, as others could only derive from the long and painstaking examin- ation of them by their tactile organs ; but the}' can discriminate minute differences, of which those who have not specially cultivated this faculty remain quite unconscious, even when their attention is pointedly directed to their discovery. The process by which the blind learn to read from books printed in an ele- vated type for their special use, affords an interesting illustration of the nature of the improveability of the proper sense of touch. On first making the attempt, the learner needs to use a large type; and even although (to a person who has previously enjoyed his sight), the visual form of each letter may be well known, yet considerable experience is required for the ready recognition of the tactile form of each separate letter. After this step has been 1178 TOUCH. gained, the individual becomes able, by a fur- ther period of diligent application, to recog- nise the combination of letters in syllables and words, without forming a separate idea of each letter, just as we see to take place in the child learning to read by eyesight ; and the pupil in time acquires the power of read- ing line after line, by passing the point of the finger consecutively over each, with consider- able rapidity. Now when this power has once been thoroughly acquired, it is found that the size of the type may be gradually diminished, so that at last it may be reduced to one but little larger than that of an ordi- nary folio Bible, which is read at least as rapidly as the words can be spoken.* As an instance of the readiness and nicety of dis- crimination which is frequently acquired by those who are chiefly dependent upon this sense for their knowledge of the outward world, we may advert to the well-known case of Laura Bridgman ; who, though destitute of sight, hearing, and smell, is able to recognise individuals with whom she has once been well acquainted, by feeling their hands, even after a long distance of time. It is related of Carolan,the celebrated blind Irish bard, that on accidentally grasping, at an interval of some years, the hand of a female to whom he had been formerly attached, he at once exclaimed, with strong emotion, " This is the hand of Bridget Cruise." A lady, who became blind, and soon afterwards deaf and dumb, in conse- quence of an attack of confluent small-pox, and whose case is recorded in the Annual Register for 1758, seems to have very speedily acquired a remarkable exaltation of the sensibility she retained. Like James Mitchell (see SMELL, p. 702.), she could distinguish strangers from acquaintance by the smell ; but she required the further help of the touch to distinguish one friend from another. " When they came in, they used to present their hands to her as a means for making themselves known. The form and the warmth of the hand generally furnished the differences which she distin- guished ; but sometimes she would span the wrist and measure the fingers. A lady with whom she was well acquainted, coming in upon a very hot day after having walked a mile, presented her hand as usual ; she examined it longer than ordinary, and seemed to doubt to whom it belonged; but at length she said, — ' I think it is Mrs. M. ; but she is warmer to-day than I ever felt her before.1" " •}• * It is worthy of remark, that, when the idea of teaching the blind to read from raised characters •was first being carried into practice, it was thought requisite by many to adopt a new alphabet of sim- pler forms, instead of the ordinary letters, in order that they might be more readily discriminated. This plan, however, was subject to the disadvantage that the teacher as well as the pupil was compelled to learn this new alphabet ; and as it was soon found that the ordinary Koman capitals, reduced to their simplest forms, could be discriminated by the blind with very little more trouble than the best set of new signs that could be devised, the idea of a spe- cial alphabet for their use has been given up. f " Lost Senses," vol. ii. p. 81. Of this lady it is positively affirmed that she was able to distinguish colours by the touch. " A lady, who was nearly related to the sufferer, having an apron on, which ac- cording to the fashion of the time, was em- broidered with silk of different colours, asked her if she could tell her what colour it was ; and after applying her fingers attentively to the figures of the embroidery, she replied that it was red, blue, and green ; but whether there were other colours in the apron, the writer of the account does not remember. The same lady having a pink ribbon on her head, and being desirous still further to satisfy her curiosity and her doubts, asked her what colour that was ? After feeling it for some time, her cousin answered that it was a pink colour. This answer was the more surprising, as it showed that she was not only capable of distinguishing different colours, but different shades of the same colour."* It is probable that in this and similar cases, the difference of hue is indicated by some diffe- rence of surface, which becomes appreciable to a refined touch. Of course, it can only be to a person who has once enjoyed sight, and who can therefore form ideas of colour, that such ideas could be suggested by the sense of touch ; and a new set of associations must be formed by habit between the tactile qualities of the surface, and the visual conception called up by its designation. Those who have been born blind must be utterly incapable of forming any such conceptions, and distinc- tions of colour can be to them nothing more than names ; yet even such have been able to discriminate by the touch between stuffs of different hues, which were similar in other respects. That such a power should be attained seems the less difficult of belief, when it is borne in mind that all colour depends upon the molecular arrangement of the par- ticles of the surfaces of bodies ; so that there is no great improbability — much less an im- possibility— in the asserted discrimination of these by a touch rendered delicate by con- stant practice, and by the habit of attending to its minutest indications. It is well known that Dr. Saunderson, the celebrated blind pro- fessor of mathematics at Cambridge, not only acquired a very accurate knowledge of medals", but could even distinguish genuine medals from imitations, more certainly than most connoisseurs in full possession of their senses ; and this power must have depended on pecu- liarities of their surface, too minute to be ap- preciated by an ordinary touch, and not dis- tinguished by the sight. _ Not only does the sense of touch, in its simplest form, undergo this remarkable exalta- tion, but also the muscular sense, which is em- ployed in combination with it in the acquire- ment of information respecting the forms, di- mensions, distances, &c. of objects. Of this, the case of the lady just cited affords an apt illustration ; " To amuse herself in the mourn- ful solitude and darkness to which she had * Op. cit. p. 79. TOUCH. 1179 been reduced, the sufferer took to working with her needle; and it is remarked that her needlework was uncommonly neat and exact. Among many other pieces of needlework pre- served in her family, was a pincushion which could scarcely be equalled. She used also sometimes to write ; and her writing was executed with the same neatness and precision as her needlework ; the characters were very pretty, the lines were all even, and the letters placed at equal distances from each other : — but the most extraordinary circumstance was, that she could by some means discover where a letter or a word had been omitted, and would place the caret under and the word over, in the right place." * This fact is obviously analogous to those formerly related, in refer- ence to the exaltation of the muscular sense in the state of somnambulism. (See SLEEP, p. 69-t.) It is by the accurate estimates which they are thus enabled to form, that we find the blind able to learn various handicraft arts, performance on musical instruments, &c. &c., which they practice with great success ; cabi- net-making, turning, and even watch-making, seem to be within the capacity of such as have a mechanical turn ; but the greatest perfec- tion of this sense is shown by those who have succeeded in modelling and sculpture. Of these, Giovanni Gonelli, sometimes called Gambasia, from the place of his birth, deserves special mention. He lost his sight at the age of twenty, and remained for ten years in that state, ignorant of the very elements of sculp- ture. But, on a sudden, the desire of making a statue came upon him ; and having handled in every way a marble figure representing Cosmo de Medici, he formed one of clay so extremely like, that it astonished all who saw it. His talent for statuary soon developed itself to such a degree, that the Grand Duke Ferdinand of Tuscany sent him to Rome to model a statue of Pope Urban VIII., which he also rendered a very striking likeness of the original. He afterwards executed many others with equal success ; amongst these, a marble statue of our Charles I. It is re- lated that the Duke of Bracciano, who had seen him at work, doubted much that he was completely blind, — and in order to set the matter at rest, he caused the artist to model his head in a dark cellar. It proved a striking * Op. cit. p. 81. It is worthy of remark, that in consequence of the strangeness of these facts to those who observed them, it was long doubted whether some faint remains of sight or hearing did not exist. Many experiments were tried to settle this matter ; but in this great caution was necessary; for some of these being accidentally discovered, she fell into violent convulsions, — these being appar- ently induced by the mental agitation she expe- rienced at the thought of being suspected of insin- cerity, or of being supposed capable of acting so wicked a part, as to feign such infirmities. Sir Plans Sloane, who attended this patient, long entertained doubts respecting the facts related of her; but having been permitted to satisfy himself by what- ever experiments he thought proper, he at length declared his conviction that she was totally blind, deaf, and dumb. likeness. Some, however, objecting that the duke's beard, which was of patriarchal ampli- tude, had made the operation of producing a seeming likeness too easy, the artist offered to model one of the duke's daughters, which he accordingly did ; and this also proved an ad- mirable likeness. Dr. Guillee, who details the preceding case in his " Essai sur 1'Instruc- tion des Aveugles," mentions also the more recent case of M. Buret, whom he calls '' one of the most able sculptors of the academy; " who became blind at the age of twenty-five, but was not thereby deterred from pursuing with much success, the course of life which he had previously chosen. It is easy to be con- ceived that a blind man might thus model or chisel accurately under the guidance of his touch, so far as mere form is concerned ; but it has been thought difficult to understand how he could thus discriminate and embody that expression, which has been supposed to be intangible* When it is remembered, how- ever, that expression must at last depend upon niceties of form, and can only be imitated by the sculptor who is under the guidance of his sight, by a minute attention to these niceties, the difficulty altogether disappears. The blind sculptor cannot form an idea of the expres- sion of his model, as seen by the eyes of others; but he may reproduce that expression with complete success, by perfectly imitating the form which exhibits it ; just as he may study and understand the laws of optics, without having ever seen the faintest ray of light. The study of natural history might have been supposed to be beyond the reach of the blind, in consequence of the difficulty of distinguish- ing specimens by the touch alone ; yet there have been examples of complete success in this pursuit. Thus of John Gough it is re- lated, that " from an early age he showed a very decided taste for zoology ; and in time he began to enlarge his knowledge of organic bodies by extending his researches from the animal to the vegetable kingdom. To bo- tanical pursuits all the time he could spare from the necessary studies of the school was most assiduously devoted ; and as his ardour in cultivating this branch of science was never relaxed, he soon conquered most of the dif- ficulties which the want of sight opposed to the gratification of this taste, and was even- tually able to discriminate and arrange with great accuracy the plants that came under his notice. His usual method of examining a plant was by applying the tip of his tongue to its several parts. Ordinary plants he could easily and readily distinguish by the touch of his fingers. To evince the power of discri- mination and strength of memory, which could alone have enabled him to take an interest in this pursuit, it is mentioned, that towards the end of his life a rare plant was put into his bands, which he very soon called by its name, observing that he had never met with more than one specimen of it, and that was fifty • " Lost Senses," vol. ii. p. 224. 1180 TOUCH. years ago."* A case of tlie same kind has been long under the writer's observation ; the subject of it being a gentleman who became blind from amaurosis soon after the age of twenty. His attention having been directed to geology and conchology, he gradually acquired a very complete knowledge of shells both recent and fossil ; being not only able to re- cognise every one of the numerous specimens in his own cabinet, but also to mention the nearest alliances of a shell previously unknown to him. He has occupied himself, moreover, in freeing his fossil shells from their matrix, with a hammer and chisel, knife, &c. ; and has frequently done this with a perfection that could scarcely be surpassed, rarely injuring the specimen with his tools, and generally clearing it completely from its incrustation, where this was practicable. In this way he has succeeded in forming a very valuable col- lection of the fossils of the interesting locality in which he resides, A similar exaltation may manifest itself, under the like circumstances, in the general tactile sensibility, both of the surface and in- terior of the body, especially as affected by the vibrations transmitted through solid sub- stances ; whereby a deficiency in the sense of hearing is in some degree supplied. Thus the visitor to a school for the deaf and dumb remarks with surprise that a slight rap given by the master on the table or floor is sufficient to excite the attention of the pupils ; and finds on examination that this is not heard, but is felt by them. A minute account of his personal experience on this head is given by Dr. Kitto ; and as it involves several interest- ing physiological considerations, the principal facts mentioned by him will be here brought under the notice of the reader. — " In the state of entire deafness," he remarks, " a peculiar susceptibility of the whole frame to tangible percussions supplies the only intimations which have the slightest approximation to those which hearing affords. I was about to call this a peculiar susceptibility of the sense of touch ; but this would unduly limit a kind of vibration, which, in certain of its develop- ments, seems to pervade the whole frame, to the very bones and marrow. I do not at all imagine that there is in this anything essen- tially different from that which is experienced by those who are in possession of their hear- ing ; but it would seem that the absence of that sense concentrates the attention more exclusively upon the sensation which is through this medium obtained; and the in- timation of which, being no longer checked and verified by the information of higher organs, assume an importance which does not naturally belong to them." This sense of percussion is but little excited in the human body by the vibrations of air ; obviously be- cause there is no expanded surface adapted to receive their influence. Thus Dr. Kitto mentions that the loudest thunder makes no impression upon him, unless it shakes * " Lost Senses," vol. ii. p. 215. the house in which he is ; in which case it communicates a sensation resembling that produced by the removal of a piece of fur- niture in an adjoining room.* In like man- ner, he is utterly unconscious alike of the sound of bells, and of the vibration produced by their percussion, unless the latter be pro- pagated through solid bodies, as when he places himself in direct contact with a tower in which a powerful peal is being rung. " I re- member," he says, " that once when I was showing a young friend from the country over St. Paul's, we happened to be up examining the great clock, at the very time it began to strike. The sensation which this occasioned was that of very heavy blows upon the fabric in which I stood, communicated to my feet by contact with the floor, and by the feet diffused over the whole body. So," he con- tinues, " guns — even powerful cannon — make no impression upon this sense, unless I happen to be very near when they are fired ; in that case, I can compare the effect to no- thing better than the sensation produced by a heavy blow upon the head from a fist co- vered with a boxing glove. This effect could only be produced by the tangible percussion of the air, and by the percussion upon the ground transmitted by the feet." So, again, Dr. Kitto states that he is not conscious of even a very loud knock at the door of the room in which he is, unless the door be in such connection with the floor that the per- cussion is communicated through the latter, or unless he be himself in contact with some part of the wall to which it is hung. But, on the other hand, he states, — " The drawing of furniture, as tables and sofas, over the floor above or below me, the shutting of doors, and the feet of children at play, distress me far more than the same causes would do if I were in actual possession of my hearing. By being to me unattended by any circumstances or preliminaries, they startle dreadfully ; and by the vibration being diffused from the feet over the whole body, they shake the whole nervous system, in a way which even long use has not enabled me to bear. The moving of a table is to me more than to the reader would be the com- bined noise and vibration of a mail coach drawn over a wooden floor ; the feet of children, like the tramp of horses upon the same floor ; and the shutting of a door like a thunder-clap, shaking the very house. It is by having once heard, that I am enabled to make such comparisons as these, for the illustration of a sensation which one who has never heard, and one who is not deaf, would be alike unable to describe." The fact that the shutting of a door is felt with painful distinctness (as Dr. Kitto elsewhere mentions), even when upon a different floor, whilst the loudest ordinary knocking at the same door is not perceived, very curiously * The writer of this article, residing near a rail- way tunnel, has frequently noticed that the emer- gence of a train is indicated by the succussion of the windows of his house, before it becomes audible. TOUCH. 1181 illustrates the necessity for the transmission of the vibrations along a solid medium. "The valve of the door on which the percussion is made by knocking, is a detached frame of wood hung upon hinges, and the vibration is therefore comparatively isolated and not pro- pagated throughout the frame of the house, as is the case when, in shutting the door, the valve itself strikes the door-post, which is identified with the framework of the build- ing." In illustration of the acuteness of this sense in his own person, Dr. Kitto states that the lightest footfall upon the same floor is quite sufficient to attract his attention, or even to arouse him from sleep. " If any small article," he continues, " such as a thimble, a pencil, a penknife, or even a more minute object, falls from the table to the floor, I am often aware of it, even when other persons sitting at the same table have not been apprised of it by the ear. The greater the number of my points of contact with the floor, the stronger are the impres- sions I receive : hence they are more vivid and distinct when I sit than when I stand ; be- cause, in the former case, not only my own two legs, but the four legs of my chair, are concerned in conveying the percussion to my sensorium. And when the chair itself on which I am seated has been subject to the percussion, the sensation is such as baffles description. For instance, a few days since, when I was seated with the back of my chair facing a chiffoniere, the door of this re- ceptacle was opened by some one, and swung back so as to touch my chair. The touch could not but have been slight, but to me the concussion was dreadful, and almost made me scream with the surprise and pain, the sensa- tion being very similar to that which a heavy person feels on touching the ground, when he has jumped from a higher place than he ought. Eve'n this concussion, to me so violent and distressing, had not been noticed by any one in the room but myself. * * * If these per- ceptions are so acute in carpeted rooms, it will be easily understood by how much more intense they become upon a naked wooden floor. The sensation then amounts to torture — as every movement or concussion, in any part of the room, then comes with an in- tensity of effect, far more than proportioned to the difference in the impression which would, under the same circumstances, be pro- duced upon the auditory sense." It is interesting to remark that, notwith- standing this acuteness of the sense in ques- tion, it does not seem to convey (in Dr. K.'s case at least) any information of the direction or distance of the percussions, except such as is afforded by their relative intensity. Thus he says ; — "I am unable to determine from the information of the sensation itself, whether it has occurred upon the floor above, or in that below me, or in the passage or room ad- joining that in which I may be at the time. I am not aware that the impression is more distinct from the floor above than from that below ; but it certainly is more distinct in another room of the same floor, than from either the one above or below; whence I am much in the habit of referring to the next room the percussions which make the strongest impression on me. In this I am not seldom mistaken. * * * The information is equally defective, even in the very room I may happen to occupy. If a book or other object falls in any part of the room, the sen- sation is painfully distinct, the percussion being upon the very boards on which I stand ; but even in this case, 1 am at a loss for the quarter in which the circumstance has oc- curred, and generally look for it in the wrong direction, and have to scan the whole room with my eye before I can make it out." It is probable that the want of power to estimate direction arises from the circumstance that the communication of the percussions takes place, in this ami similar cases, through the same channel (the floor) to the same parts of the solid mass of the body, through which the vibrations immediately spread in every direction. It can easily be conceived that if the percussions were transmitted through a liquid medium, its vibrations, being propagated in a more determinate direction, might affect one or another part of the surface in such a manner as to suggest the direction of their source ; and that in this mode aquatic animals endowed with a nervous apparatus at their surface, specially adapted to be impressed by such vibrations, might communicate with each other through great distances. This appears to be the case with regard to the Spermaceti Whale, and probably others of the Cetacea. It has been observed by the whale-fishers, that when a straggler from a " school " is attacked, even at a distance of several miles from it, a number of its fellows bear down to its assistance, in an almost incredibly short space of time. It can scarcely be doubted that this communication must be made through the medium of the vibrations of the water, excited by the struggles of the animal, or per- haps by some peculiar instinctive movements especially adapted for this purpose, and pro- pagated through the liquid medium to the large cutaneous surface of the distant whales. And this idea is confirmed by the fact, that the nerves which proceed to the surface of the body pass through the layers of blubber (which form the inner part of the true skin) with scarcely any division, and then spread out into a network of extreme minuteness as soon as they approach the exterior of the in- tegument. The expanse of such a network over a thick layer of elastic tissue, whose meshes are distended with oleaginous fluid, obviously affords a condition peculiarly fa- vourable to the reception of impressions ori- ginating in percussion. After the details which have been given in proof of the degree of exaltation of which the general tactile sensibility is capable in the human subject, we shall have less difficulty in understanding that even the vibrations of air, 1182 TOUCH. excited by percussion, may become the chief means of guidance to animals possessed of a special apparatus for taking cognisance of them. Such appears to be the case in the Sat tribe, and especially in those species whose habits are most exclusively nocturnal, and whose dwellings admit the smallest quan- tity of light. " The whole surface of their wings, on both sides, may be considered as an enormously-expanded organ of touch, of the most exquisite sensibility to the peculiar sen- sation for which it is intended ; and it is, therefore, by the varied modifications of the impulsion of the atmosphere upon this sur- face, that the knowledge of the propinquity of foreign bodies is communicated."* It would not seem improbable, however, that the remarkable cutaneous expansions with which the nose and ear are furnished in many bats, are subservi- ent to this function. The enormous exten- sion of the external ear may doubtless aug- ment the intensity of the sense of hearing ; but it is scarcely accordant with our know- ledge of the conditions under which the sense of smell is exercised, to suppose that the extraordinary " nose-leaf" of the Rlnnolopludce should be in any great degree subservient to olfactive purposes. The bats of this group (to which belong the greater and lesser horse- shoe bats of our own country) " are more completely lucifugous and retired in their ha- bits than any others ; they are found in the darkest penetralia of caverns, and other places where there is not even the imperfect light which the other genera of bats enjoy." -f- Some approach to this power of guidance, de- rived either from the impressions made by the air upon the cutaneous surface, or from the radiation of heat, is occasionally seen in blind persons; who can thus distinguish '' by the hands, and even by the face, the proximity of solid bodies (as in approaching a wall, a door, or a piece of furniture) without actually touching them. The sense of temperature, also, appears to be capable of considerable improvement, when its indications are habitually and discrimi- natingly attended to, or when the mind is intensely and exclusively fixed upon them. Thus it is related of Dr. Saunderson, that when some of his pupils were taking the sun's altitude, he was able to tell, by the slight alteration in the temperature of the air, when very light clouds were passing over the sun's disk. MORBID CONDITIONS OF THE SENSE OF TOUCH. Like most other vital functions, the sense of touch may become disordered in the way of deficiency, excess, or depravation. The state of complete deficiency is known as Anaesthesia; a term which, strictly speaking, designates the absence of all sensation, but which is more commonly employed as re- ferring to the sense of touch alone. This * See CHEIROPTERA, vol. i. p. 599. •j- Loc. cit. state, which may be either general or local, may arise from an interruption in the func- tional activity of any part of the nervous ap- paratus concerned in the reception of sensory impressions ; and thus may be due to causes acting either (1) at the peripheral origins of the sensory nerves, or (2) on the nerves in their course, or (3) on the sensorial centres ; as well as to such as act on the whole nervous system at once. The causes which act at the peripheral origins of the nerves may be such as affect either the nerves themselves, the capillary circulation, or both. Of the first we have a typical example in the " anaesthetic agents," ether, chloroform, &c. ; the applica- tion of whose vapour for any length of time to the cutaneous surface, entirely suspends its power of receiving sensory impressions ; and that this results from the direct action of the substances on the peripheral nervous ex- pansion, appears from the fact of the suspen- sion being precisely limited to the part to which the vapour is applied. But anaesthesia may be induced, also, by the stagnation of the capillary circulation in a part, without any more direct affection of its nervous endow- ments ; as we see when the main artery of a limb has been tied, previously to the re- establishment of the supply of blood by the collateral circulation, or when the flow of blood through it has been impeded by tem- porary pressure. It is probable that cold operates in producing local anaesthesia in both these modes ; namely, by its direct sedative action upon the peripheral nerves ; and by the stagnation which it produces in the capillary circulation. That the local anaesthesia, which is a not unfrequent result of the presence of poisonous substances in the blood, is due to the special action of these substances upon the peripheral nerves of the particular locality, would not seem an improbable supposition -f when it is remembered how frequently poisons of various kinds single out some particular part of a structure apparently homogeneous, for the production of their peculiar effects, — lead, for example, in whatever way introduced into the system, acting first on the muscular fibres of the alimentary canal, and afterwards most commonly on the extensor muscles of the forearm, in which its presence has been detected by chemical analysis. Of the anaesthesia induced by causes acting upon the sensory nerves in their course from the periphery to the centre, our most frequent examples are those in which it is produced by pressure on these trunks, whereby the con- veyance of the sensory impressions to the encephalon is effectually checked. Anaesthesia may also arise, however, from diseased con- ditions of these trunks, brought about by perverted nutrition ; and there is a form of paraplegia, in which the lesion of sensibility (which is more completely lost than the motor power) appears to commence in the peripheral expansions of the nerves, and to extend along the trunks to the central organs.* This is * Graves's Clinical Medicine, vol. i. p. 503. TOUCH. 1183 usually referrible, in the first place, to the influence of cold and damp; and it is especi- ally liable to occur in persons of a rheumatic or gouty diathesis. That even the sedative influence of cold may be propagated along the nerve-trunks, and that its anaesthetic effect is not due to its peripheral influence alone, appears from the circumstance remarked by Dr. Graves (loc. cit.), that the paralysis induced by handling snow, or by immersing the hands in freezing mixtures for some little time, is not confined to the hands and fingers, but extends to the muscles and surface of the fore-arms. And it was also remarked by the same eminent physician, that in a case in which the inside of the ring finger had been wounded by a blunt needle, and a partial anaesthesia induced, the same effect was per- ceived in the little finger (alike supplied by the ulnar nerve), obviously through the extension of the paralysing influence towards the centre, so as to affect the trunk higher up than the point at which its branch to the little finger was given off. Dr. Graves further cites, as an example of anaesthesia having its seat in disordered nutrition of the peripheral nerves, and gradually advancing along their trunks towards the centres, the curious Epidemic de Paris, which occurred in the spring and sum- mer of 1828. " It began (frequently in per- sons of good constitution) with sensations of pricking and severe pain in the integuments of the hands and feet, accompanied by so acute a degree of sensibility, that the patients could not bear these parts to be touched by the bed-clothes. After some time, a few days, or even a few hours, a diminution, or even abolition of sensation took place in the affected members ; they became incapable of distin- guishing the shape, texture, or temperature of bodies, the power of motion declined, and finally they were observed to become al- together paralytic. The injury was not con- fined to the hands and feet alone, but, ad- vancing with progressive pace, extended over the whole of both extremities. Persons lay in bed powerless and helpless, and continued in this state for weeks and months. Every remedy which the ingenuity of the French practitioners could suggest was tried, and proved ineffectual. In some, the stomach and bowels were deranged, and this affection terminated in a bad state of health, and even in death ; in others, the vital organs, cerebral, respiratory, and digestive, were in the same state as before their illness, and their appetites were good, but still they remained paralvtics. At last, at some period of the disease, motion and sensation gradually returned, anil a re- covery generally took place, although, in some instances, the paralysis was very capricious, vanishing and again re-appearing. In the fatal cases, no evidence could be obtained, from the most diligent search, of any lesion, functional or organic, in the brain, cerebellum, or spinal marrow."* These phenomena are * Op. Cit. p. 504. scarcely explicable on any other hypothesis than that of some general cause (probably a morbid matter circulating in the blood) affect- ing the nutrition and functional activity of the nerve-trunks, rather than of their centres. That anaesthesia may proceed from various causes whose operation is limited to the sen- sorial centres, is a matter of every-day ex- perience. It is, however, where they have suffered from some obvious lesion of a com- paratively restricted character, that the proof of this is most complete ; for although there is strong ground for believing that the ordi- nary operation of anaesthetic agents and nar- cotic poisons is confined to the cerebrum and sensorium, yet we could not positively affirm such to be the case, since, when taken into the blood, they may act not only on the sen- sorial centres, but on the entire nervous system. All the phemomena of narcotftic poisoning, however, indicate that opium, al- cohol, &c., single out the cerebrum and sen- sory ganglia for their special action, just as strychnia singles out the spinal cord ; the suspension of the functional activity of the former being usually complete, before there is the slightest affection of the latter. That a failure of the circulation in the encephalon produces complete and universal anaesthesia while it lasts, was fully proved by Sir A. Cooper's well-known experiment; and it seems probable that many of the structural lesions which manifest themselves in paralysis of motion and sensation produce this suspen- sion of functional power in parts not them- selves affected by disease, chiefly in virtue of the derangement of the intra-cranial circula- tion which they invole. There is one of the phenomena of the anaes- thesia produced by the accidental or inten- tional introduction of poisonous substances into the blood, which seems deserving of more special notice ; viz., the suspension of the power of receiving painful impressions, with- out the obliteration of the ordinary tactile sensibility. This is a frequent result of the exhibition of ether and chloroform ; and does not seem to depend upon a mere blunting of the ordinary sensibility. It has been especi- ally noticed, also, in cases of lead poisoning, in which state it seems to be more frequent than complete anaesthesia. According to M. Beau, the insensibility to pain, which he terms analgesia, may be observed in a large propor- tion of cases of " saturnine intoxication." " We must not confine ourselves," he remarks, " to asking the patient whether he feels, but limit our question to the sensation of pain. Parts which are thus insensible to pain are so also to tickling. This form of anaesthesia may affect the entire surface, being, however, most remarkable in the extremities, and especially the upper ones. It may extend even to the mucous membranes, and especially those which are normally endowed with great sen- sibility, — as the uvula, isthmus faucium, nares, or conjunctiva, — any of which parts may be tickled without tiie u:-ual conse- 1181 TOUCH. quences, the patient still being quite con- scious of the mere contact."* Reference has been already made to the influence of the attention on the acuteness of sensations; and to the slight degree in which they are felt, when the mind is completely engrossed in some other feeling or idea. This is sometimes seen in spontaneous reverie ; and there are individuals who can exert such a power of mental abstraction, as voluntarily to concentrate their attention on some ex- ternal object, or internal idea, so as to escape all suffering from a severe operation. This, however, is much better seen in some of those cases of somnambulism (see SLEEP) in which the mind is completely under the guidance of the suggestions received from without, its whole spontaneous directing power being suspended. For it is frequently possible, in such cases, to withdraw the patient's atten- tion from any part of the body, to such an extent that the anaesthesia is complete as regards that part, whilst every other portion enjoys the ordinary sensibility. Thus a tern- porary loss of sensation on the whole of one side may be induced, or a single limb may be rendered anaesthetic ; and the sensibility of the parts may be instantaneously restored, merely by directing the patient's attention towards them. With regard to hypercesthesia, or increased sensibility, we have much less definite in- formation. There can be no doubt, however, that it, too, may proceed from changes either in the periphery, or in the central organs, and perhaps also from an alteration in the trunks of the nerves in their course. The acute sensibility of an inflamed or irritated part is an example of the first of these conditions ; and the extraordinary exaltation of sensibility in the incipient stage of phrenitis may serve as an illustration of the second. In some cases the entire nervous system would seem to partake of this undue excitability ; this we especially see in hysterical subjects, in whom the slightest contact frequently occasions in- tense suffering, so that even the mere pointing of a finger at any part of the body will cause a scream of alarm. The sufferings of such persons are not rightly designated as ima- ginary; they are as real to them as are those proceeding from far more serious causes to persons of less excitable temperament. The fault partly lies in the habitual attention which they pay to the most trivial feelings ; but in part also, it may be surmised, to an abnormal state of nutrition of the entire nervous system, — both centres and trunks, — from depravation of the blood. This view harmonizes well with the fact just now stated, that in the Epidemic dc Paris, a temporary hyperaesthesia (afterwards giving place to an- aesthesia) was commonly among the earliest symptoms. And it is not a little curious that in the remarkable series of cases of lead- poisoning which recently occurred in the ex- royal family of France, during their residence * Archives Generales, torn. xvi. pp. 5—24. at Claremont, the same symptom presented itself, and was in some instances the only symptom which indicated the morbid con- tamination of the blood.* In most cases of this form of hyperaesthesia, the exaltation of sensibility seems confined to the surface, being much more excited by a slight touch than by hard pressure ; and this difference will frequently serve to distinguish the " hys- terical" tenderness from that of inflammation, in which the pain is augmented the more severe the pressure. The writer has had opportunities of noticing an extreme sensi- tiveness to changes of temperature in certain cases of somnambulism, both natural and artificial ; and he believes that this fact affords a ready solution of various marvels which have been narrated touching the power of "mesmerized" subjects to distinguish a piece of money which had been held in the mes- menzer's hands, or a glass of water in which his finger had been immersed. It has recently been proposed to apply Prof. Weber's method of estimating the re- lative acuteness of the tactile sense in dif- ferent parts of the body, to the determination of the degree of anaesthesia or of hyper- aesthesia, in patients affected with these dis- orders. Thus it was found by M. Brown- Sequard that in one case of nearly complete anaesthesia of the lower extremities, the pa- tient only felt a single impression on the skin of his legs, when the points of the com- passes were from 10 to 20 centim. apart ; the normal "limit of confusion" for this portion of the surface being from 3 to 5 centim. In another case of slighter anaesthesia, the " limit of confusion" in the same part was from 9 to 15 centim. And in a third case of very slight anaesthesia, it was from 6 to 7 centim. In a case of hyperaesthesia, on the other hand, which accompanied paralysis of the motor power, the patient could perceive the distinctness of the two points on the foot, when they were separated to the distance of only 5 millim., although the normal " limit of confusion" in that part was from 25 to 30 millim. The sensibility to pain, in this case, was as much exaggerated as was the tactile sensibility. Of the depravation of tactile sensibility, manifested in a variety of morbid phenomena, — such as the sense of heat or even of burning (without any real elevation of temperature), of formication, of tickling, of itching, &c., — it must suffice here to remark, that this, like the preceding affections, may be due to causes acting on the peripheral nerves, or on the nervous centres, or on the connecting trunks. Of the latter we have a good example in the formication which generally succeeds complete anaesthesia, when a nerve has been pressed upon for a time, and the pressure is then re- moved. W. B. Carpenter. * See Dr. Gueneau de Mussy's Cases of Poisoning by Lead at Claremont, in Dublin Quarterly Medical Journal, May, 1849. TUNICATA. 1185 TUNICATA. (Tuniciert, Fr.; Nackt- Mitschelcr and See-Scheiden, Germ.) — The Tunica t a are molluscous animals, having no calcified shell, but a more or less coriaceous envelope or fume, whence their name. This external coat or test is either bag-shaped and provided with two apertures, or is tube-shaped and open at the ends. They have no distinct head, and no organs serving as arms or feet ; they are provided with a muscular and a nervous system ; and with well-defined or- gans of respiration, digestion, circulation, and generation. They are exclusively marine, and are widely spread from the arctic to the tropical seas. Sessile or foot-stalked on the rock, or in- crusting seaweed and other bodies, their external form is seldom of graceful contour ; yet the arrangement of the individuals in the compound masses often exhibits curious and elegant designs. The floating forms, however, with their lengthened, sinuous chain, or tapering tubes, pellucid, rainbow-tinted, or, by night, brightly phosphorescent, are sur- passed by no terrestrial object. The other, fixed, forms, not altogether destitute of ele- gance of colour in the northern seas, become in warmer climates more and more rich in variegated hues, and in the tropics are amongst the most resplendent living gems of ocean's parterres. The earliest notice of the tunicate animals is made by Aristotle, who gives a very cor- rect account of the anatomical and zoological characters of a simple Ascidian, which he calls TtQvov* They, however, attracted no further notice until comparatively late times. Ron- deletf gives indifferent figures and descriptions. Gesner and Aldrovandus, uniting Rondelet's Tethya with those given byBeloni, which are Alcyonia, were among the first who gave rise to the confusion that long existed in the history of these animals. Linnaeus in the 4th edition of his Systema Naturae placed a Tcthi/um in his system, under the appellation of Tethys ; he pointed out at the same time that the animal of bivalve Molluscs was a Tcthys, showing that he was aware of the analogy of the Bivalves with the Tunicates. In other respects, however, he added to the confusion. After that Bohatsch § and Plancus || figured and described some species. Basterf describes a species, and gives it the name of Ascidium (from CIUKOC, a skin- bottle), at the same time adding a very just remark on the analogy of its internal struc- ture with that of the oyster. This analogy was noticed also by Pallas, who proposed ' the union of the Tetliyum and Ascidinm **, which Linnaeus carried out in the 12th edit, of his Systema Natnra?, uniting the species, noticed by Bohatsch and Koenig, under the * Hist. Anim. lib. iv. c. vi., and De Part. Anim. lib. vi. c. v. f De Piscibus, 1554. J De Aquat. 1553. § De quibusd. Aiiim. Marin. 1761. || Conchis minus notis, pi. v. & vii. 1739. *f Opusc. subseciv. ii. x. 5. 1764. * Miscell. Zoolog. 74. 1767. VOL. IV. name of Ascidia, and confining the name Tethys to the inhabitants of the Bivalves. Subsequently, O.F. Miiller*, O. Fabriciusf, Dicquemare j, Pallas §, and others, described and figured several Ascidice, which Brugiere |j and Gmelin f collected -together in their re- spective works, without adding much to the knowledge of the group. Cnvier's first ob- servations on the simple Ascidians were begun in 1797, and his memoir on their anatomy was published in 1815.** About the same time were published the researches of Schalkf f on the anatomy, and of Carus J j on the anatomy and development of the Ascidians. The memoirs of Peron and Lesueur §$ on the Pt/rosowa, Desmarest and Lesueur || || on the Botryllus, and particularly the elaborate work of Savignyflf on the simple and compound Ascidians, enabled naturalists to make rapid advances in the knowledge of this family. With respect to the Salpians, Brown***, For- skahlff-f, and TilesiusJJJ were the first to figure and describe any forms of this group. Considerable confusion with regard to these forms existed in the classifications of Linnaeus, Pallas, Brugiere, and Bosc, and indeed in the earlier writings of Lamarck and Cuvier, until the latter had an opportunity of work- ing out the anatomical characters of these animals. The earlier works on the various branches of this subject have been succeeded by the publication of the researches of many dis- tinguished naturalists. We are chiefly in- debted to the labours of Cuvier, Savigny, Carus, MacLeay, and Van Beneden, for in- formation on the structure and development of the simple Ascidians ; to the researches of Cuvier, Kuhl and Van Hasselt, Chamisso, Eschricht, and Krohn, for the history of the. Salpians ; and to Lesueur, Desmarest, Sa- vigny, Lister, Sars, Milne-Edwards, Atidouin, and Forbes, for our knowledge of the com- pound ascidian forms. And, indeed, since the commencement of the present century, the organisation of this group has been studied with great care, rewarding the labours of naturalists with discoveries of the highest interest. " It was in the animal of the Salpa" says Van Beneden, "that Van Hasselt discovered a heart of such extraordinary character, changing incessantly its auricle to ventricle and its ventricle to auricle, its ar-. * Zool. Dan. Prodromus, 1766. f Fauna Greenland, 1780. j Journal de Physique, 1777. § Spicilegia Zoologica, 1774, and Mem. de Pe'- tersbourg. || Encyclope'die Me'thodique ; Vers Mollusques. *H Systema Naturae, edit. 13. * Memoires du Museum, torn. ii. tt De Aseidiarum Structure, Halle, 1814. jj Meckel's Archiv, torn. ii. and Acta Cur. Nat. Bonn, vol. x. §§ Annales du Museum, torn. iv. || || Bull. Nouv. Soc. Philoni. 1815, and Journal de Physique, torn. Ixxx. ^[ Mem. Anim. sans Vertebres, 2C part. * Natural History of Jamaica. tft Descript. Animalium, &c. 1770. Ill Ann. Hist. Nat. Leipzig, 1802. 4 G 1186 TUNICATA. teries to veins and its veins to arteries. The Ascidians, too, furnish the first examples of complete metamorphosis in the lower ranks of the animal kingdom. The honour of this discovery is due to MM. Audouin and Milne-Edwards. From the late discoveries of M. Sars, these metamorphoses increase in interest, and appear to be still more remarkable. And, lastly, the Ascidians have contributed very considerably to our knowledge of the cir- culatory apparatus of the Mollusca generally." The term Tunicata was first used by La- marck ; its synonyms are Tethya, Auct. ; Soft- shcllcd Molluscs, Hunter ; les Acepltalcs sans coquilles, Cuvier ; Acephalophora hettrobran- chiata, Blainville ; Tunicaries, Kirby ; Gymna- aephala, Bronn. The CLASS of animals to which it is applied may be zoologically de- fined as consisting of acephalous Molluscs ; with a soft shell or test, organised, coriaceous or gelatinous, frequently destitute of mineral constituents, having a large proportion of cellulose in its composition : animals single or aggregate ; the test of each animal provided with two apertures, one bran- chial, the other anal ; the mantle forming an interior coat ; the branchiae attached wholly or in part to the internal surface of the mantle ; the mouth, without labial ten- tacles, placed below the branchial apparatus ; animals hermaphrodite, undergoing metamor- phosis in their young state. The cavity, whether of single or compound Tunicates, is occupied by a more or less muscular sac, provided, like the external tunic, with two orifices. This sac, identical with the " mantle " of the Acephalans, is attached to the inner surface of the test, generally only at the orifices, and contains the viscera. The di- gestive, reproductive, and circulatory organs are disposed at the base of the sac, and its upper and larger portion, lined with, or traversed by, the branchiae, forms the branchial cavity. This is placed at the commencement of the alimen- tary canal, of which it forms as it were the antechamber. The branchiae have generally the form of ridges, more or less complicated, and seldom symmetrical. The alimentary canal is simple, and barely distinguishable into gullet, stomach, and intestine. It is always convoluted or folded once on itself. The liver adheres to the stomach, and in many species is divided into distinct lobes. The heart consists of a slightly bent, contractile tube, and is situated near to or within the in- testinal loop. The reproductive organs, con- sisting of ovary and testicle, are often lodged in the fold of the intestine. The animal of these "soft-shelled" Mol- luscs has very close affinities with that of the other Acephalans, especially the lamellibran- chiates. And " were the test of an Ascidian converted into a hard shell, symmetrically divided into two plates, connected together dorsally by cartilage, and capable of separation so as to expose the mantle along a ventral mesial line, whilst the orifices protruded at one extremity, it would present the closest similarity with many bivalve Molluscs."* (Forbes.) All the Tunicata are free during the earlier periods of their existence ; some remain per- manently free, floating in the water (Salpce, &c.), but the generality (£otrylli,Ascidi^,&c.) become fixed to shells, seaweeds, and other marine bodies. Some exist as distinct indivi- duals (Ascidia, Cynthia, &c.), whilst various degrees of combination are affected by others (Botryllus, Cluvcll'ma, Pyrosoma, &c.) ; and some are simple in one generation and com- bined in the next (Salpa). From the above-mentioned various con- ditions of individualism or aggregation under which these animals exist, the family is divisible into two groups — the simple and the aggregate. Such forms of the latter group as were known to the earlier natu- ralists were, from a general similarity of appearance, classed by them with Alcyonia. In the former group have been placed, until a late date, the numerous species of the Sal- pidae, which now however, like the above- mentioned groups, have been separately treated of and illustrated in memoirs and monographs devoted to them. Indeed, although the ex- pressions, simple and aggregate, as will be seen hereafter, are very convenient in describing the physiology of the Tunicata, yet late re- searches have shown that the conditions to which they refer have but a subordinate value in reference to the natural grouping of the class. As may naturally be inferred from what is stated above, the Tunicata have been sub- divided in various manners. The arrangement we are inclined to adopt is as follows : — TUNICATA « Dichitonida, Fleming. Inner sac more or less detached from the external tunic ; united to it at the two ori- fices. Branchiae, large, equal, spread on the inner surface of this sac. Branchial orifice with an inner membranaceous ring and circle of tentacles. J Monochitonida, Fleming. Inner sac adhering throughout to the external tunic. Orifices " without tentacular fringes. Fixed. Branchial and anal"| orifices not opposite to I each other. Brancbias [ conjoined. Floating. Branchial andl anal orifices opposite to I each other. Branchiae J disjoined. Branchial and anal orifices "|_ opposite to each other. J Branchial and anal orifices! not opposite to each > other. Ascicliadce. Cluvellinidae. Botryllidae. Pyrosomidae. Salpidae. Pelonaiadae. * We may particularly mention the DIy(t, Pliolwks, &c. TUNICATA. 1187 DICHITONIDA. — Family ASCIDIAD^E, E. Forbes. Synonyms : Tethyes simples, Savigny ; Ascididfc, MacLeay ; Tuniciers libres on As- cidienx, Lamarck; Ascidiaria, Stark; " lex Iso- lees" Cuvier ; Ascidiacea, pars, Blainville ; tliis family : — Ascidiens simples, Milne Edwards ; Ascidicnx, Van Beneden. Body simple, fixed ; animals isolated or gregarious ; not united into groups by a com- mon integument ; oviparous, not gemmipa- rous. The following genera are members of ASCIDIAD^E, vel ASCIDI/E SIMl'MCES Branchiae not plicated Branchiae plicated - Genus Ascidia, Baster and Linnaeus. — " Rarely," says Professor E. Forbes, " is the dredge drawn up from any sea bed at all pro- lific in submarine creatures, without contain- ing few or man)' irregularly shaped leathery bodies, fixed to sea-weed, rock, or shell, by one extremity or by one side, free at the other, and presenting two more or less pro- minent orifices, from which, on the slightest pressure, the sea-water is ejected with great force. On the sea shore, when the tide is out, we find similar bodies attached to the under surface of rough stones. They are variously, often splendidly, coloured ; but otherwise are unattractive, or even repulsive, Fig. 766. Ascidia mammillata. (Original.) a, branchial orifice, open ; b, anal orifice, closed. in aspect. These creatures are Ascidia;, pro- perly so called. Numbers of them are often found clustering among tangles, like bunches of some strange semitransparent fruit." Some species (in France, vu/go " le vichet ") on the f Sessile 1 Pedunculated f Ascidia.* " { Molgula. f Cynthia. - -J Dendrodoa. [ Chfhosoma. (Bo tenia. Cystingia. Bipapillaria. coasts of the Channel -j- and the Mediterra- nean, and in the Chinese Seas, are valued as articles of food In this genus (fig. 766.) the body is sessile ; test, coriaceous or gelati- nous ; branchial orifice eight and six-lobed; branchial sac not plicated, surmounted by a circle of simple tentacular filaments. Genus Molgtila, E. Forbes ; synonym, As- cidia, Auct. — Body more or less globular, attached or free ff ; test membranous, usually invested with extraneous matter ; orifices on very contractile and naked tubes, the bran- chial six-lobed, the anal four-lobed. Genus Cynthia, Savigny ; synonym, Ascidia, Auct. — Body sessile, fixed or unattached; test coriaceous ; branchial and anal orifices open- ing in four rays or lobes ; branchial sac lon- gitudinally plicated, surmounted by a circle of tentacular filaments. Genus Dcndrodoa, MacLeay. — Body sub- cylindrical, fixed, sessile ; test coriaceous, smooth ; orifices terminal, minute, indistinctly quadrifid ; branchial sac plicated ; tentacula * Some very good observations on the subdi- visions of the Ascidiai have been made by M. Sa- vigny, Dr. Fleming, and Mr. MacLeay. But we must not here enter further into details. The fol- lowing classification is that adopted wholly or iu part by the above authors respectively : — I Pyrena. Phallusiae - - < Phallusia. (_ Cioua. ASCIDI-E - 'I f Cynthia. I Caesira. Cynthia} - -^ Styela. I Pandocia. (_Dcndrodoa. •)• " At Cette," says Van Beneden, " Ascidia are taken regularly to market ; and Cynthia microscomus, although so repulsive externally, furnishes a very delicate morsel, much sought after by some." J Individuals of several species of Ascidians, viz. of the following genera, Mokjida, Cynthia, Cystingia, 13'ipiipUlaria, and Pelonaia, are found unattached. These animals, however, cannot be said to have an entirely free existence, their tests, whether pe- dmicled or otherwise, being usually more or less imbedded in sand or mud, and frequently held to their anchorage by the agglutination of the sur- rounding sand-grains to their outer surface. But from such a position they are easily disturbed, unless when they are lodged within the mud-filled cavities of old shells and of water- worn stoues, as is the case with the Pdvnaia. 4c 2 1188 TUNICATA. simple (fig. 778). Dendrodoa closely agrees with Cynthia in its branchial reticulations and its digestive apparatus ; but, as Mr. Mac Leay has observed, of the two ovaries possessed by Cynthia, only one, and that the left, is found in Dendrodoa, whilst the right ovary alone is present in Pandocia. Genus Chelyosoma, Broderip and Sowerby. — Body depressed, oblong, fixed, sessile ; test coriaceous, its upper surface consisting of eight somewhat horny, angular plates ; ori- fices small, prominent, perforating the plated surface, each surrounded by six triangular valvules (Jig. 767.) ; branchiae plicated ; ten- tacles simple. Fig. 767. Clielyosoma Macleayanum. (After Broderip and Sowerby.) a, branchial orifice ; b, anal orifice ; c, coriaceous envelope of the sides ; d, stone to which the animal is fixed. To the Ascidiada; we may provisionally join the following obscure form, occurring on the coasts of South America: Genus Fodia, Bosc. — Body oval, mammil- lated, divided throughout its length by a vertical partition, which contains the stomach, into two unequal tubes open at each end by an orifice, the superior aperture rather depressed and ir- regularly toothed, the inferior bordered by a circular collar forming a sucker, and serving to attach the animal to extraneous objects. Genus Boltcnia, Savigny ; synonym, Ascidia, Auct. — Body more or less globular, fixed, pe- dunculated, attached sometimes to the stem of another individual; test coriaceous; ori- fices lateral, and each cleft into four rays ; branchial sac longitudinally plicated ; sur- mounted by a circle of compound tentacula. Genus Cystingia, MacLeay. — Body glo- bular, fixed, pedunculated ; test subcoriaceous; branchial orifice quadrifid, lateral ; anal irre- gular, terminal ; branchial sac plicated ; tenta- cula compound. Genus Bipapillaria, Lamarck. — Body more or less globular, free, pedunculated ; test mem- branous ; the extremity of the body opposite to the attachment of the peduncle bearing two equal, conical papillae, having their apices per- forate ; each orifice furnished with three very short, stiff, setaceous, retractile tentacles.* * This obscure genus was established by Lamarck from a description aud figure in Peron's MSS. Family CLAVELLINIDJE, E. Forbes. Syno- nyms : Ascidice, Auct. ; Tcthyes simples, pars, Savigny ; Ascidiens sociales, Milne-Edwards ; Perophoriens, Van Beneden. Body compound, fixed ; animals connected by creeping, tubular prolongations of the com- mon tunic, through which the blood circu- lates. This family comprises two genera: — Genus Clavellma, Savigny ; synonym, As- cidia, Auct. — Body elongated, erect, more or less pedunculated ; test smooth and trans- parent ; branchial and anal orifices without rays ; thorax usually marked with coloured lines (fig. 768.). Fig. 768. Clavellma producta. Group of two adult and se- veral young individuals, magnified about five times. (After Milne- Edwards.) c, branchial orifice ; e, branchiae ; h, cloaca ; i, anal orifice ; k, inner tunic or mantle ; /, stomach ; m, intestine ; n, termination of the anus and oviduct in the cloaca ; o, the heart ; p, ovary ; p", ova ready to pass into the cloaca ; u, u', u1', reproductive buds, in different degrees of development, springing from the abdomen of the adults. Genus Pcrophora, Wiegmann.* — Individuals pedunculated, suborbicular, compressed ; tho- rax not lineated by granular bands. * This curious little social Ascidian was first described and illustrated by Mr. 3. Lister, in a paper " On the Structure and Functions of tubular and cellular Polypi and of the Ascidiae," Philos. Trans. 1834. Lister gave no name to the animal, TUNICATA. 1189 Family BOTRYLLID^E, MacLeay. Syno- nyms : Alcyonia, Auct. prior. ; Tethyes com- posees, Savigny ; les Reunis ou BotryUaires, Lamarck ; les Agreges, Cuvier ; Ascidiacea, pars, Blainville ; Aacidies composces, Milne- Edwards; Polyascidiens, Van Beneden. Body compound, fixed ; animals associated; the tests fused together, forming a common mass in which the animals are imbedded in one or more groups or " systems ; " the indi- viduals not connected by any internal union ; oviparous and gemmiparous. " If, when walking on the sea-shore, about low-water mark," says the distinguished na- turalist previously quoted, " we turn over large stones, or look under projecting eaves of rock, we are almost sure to see translucent jelly-like masses of various hues of orange, purple, yellow, blue, grey, and green, some- times nearly uniform in tint, sometimes beau- tifully variegated, and very frequently pen- cilled as if with stars of gorgeous device ; now encrusting the surface of the rock, now descending from it in icicle-like projections. These are compound Ascidians. A tangle or broad-leaved fucus, torn from its rocky bed, or gathered on the sand, where the waves have cast it after storms, will show us similar rPolyclinina - bodies, mostly those star-figured, investing its stalks, winding among the intricacies of its roots, or clothing with a glairy coat the ex- panse of its foliated extremities. ... In examining these bodies, we find that it is not a single animal which lies before us, but a commonwealth of beings, bound together by common and vital ties. Each star is a family, each group of stars a community. Individuals are linked together in systems, systems com- bined into masses. . . . Indeed, few bo- dies among the forms of animal life exhibit such exquisite and kaleidoscopic figures as those which we see displayed in the combina- tions of the compound Ascidians." Previous to the researches of Savigny, the Botryllidce were regarded as Alcyonia; Gaert- ner (1774) and Renieri (1793) being the only naturalists who had suspected their compound nature and true affinities.* " The Memoir of Savigny, published in 1816, however, threw entirely new and unanticipated light on their nature. He showed that they were essentially Ascidians, differing from the simple forms only in being united into more or less complicated systems." f In the arrangement of Professor Milne- Edwards the family is subdivided as follows : BoTRYLLID-a!, vel ASCIDIJE COMPOSITE Didemnina ^Botryllina The tribe PolycUmna (les Polycliniens, Milne-Edwards) is characterised principally by the division of the body into three distinct portions, viz. a thorax, a superior abdomen, and a post-abdomen. It has, however, other anatomical peculiarities, such as the great de- velopment of the organs of generation, and the position of the heart at the inferior extremity of the body. This group comprehends nu- merous species, and is divisible into two natural sections, recognised by the external conformation of the anal orifice. In one di- vision (P. bistellafa) this orifice is surrounded with a regular circlet of rays or marginal lobules, and is exactly similar to the branchial orifice. In the other division (P. unisiel/ata) the anal differs from the branchial orifice in not being rayed, or at least in having merely irregular marginal lobules. Genus Sigillina, Savigny. — Common body a solid, elongated, erect cone ; gelatinous, pedunculated, isolated or attached to similar cones, consisting of a single system of many but Professor Wiegmann subsequently (Jahresbe- richt in Archiv. 1835) gave it the appellation of Perophora Listeri. Bistellata Unistellata - r Bistellata I Unistellata - - Sigillina. {Polyclinum. Aplidium. Sidnyum. Synoicum. Amaroucium.-]- f Distomus " \ Diazona. fDidemnum. --! Eucaslium. l^ Leptoclinum. f Botryllus. " \ Botrylloides. individuals disposed one above another in irregular circles ; branchial and anal orifices each with six rays ; abdomen larger than thorax ; post -abdomen long and slender (fig. 769.). Genus Polyclinum, Savigny. — Common body gelatinous or cartilaginous, polymorphous, sessile or slightly pedunculate ; systems nu- merous, convex, somewhat stellate, with cen- tral cloacal cavities ; individuals (10 to 150) placed at very unequal distances from their common centre ; the cavity in the common tegument occupied by each animal is divided into three chambers one above another by contractions of its calibre ; abdomen much smaller than the thorax ; post-abdomen pe- dunculate. Genus Aplidium, Savigny ; synonym, Al- cyonium, Auct. — Common body gelatinous or cartilaginous, sessile ; systems very nume- * For the early history of this genus, consult the Memoir on Botryllus stellatus by MM. Desmarest and Lesueur, Journal do Physique, torn. Ixxx. 1815. fin the latest ("commemorative") edition of Cuvier's Kegne Animal, M. Milne-Edwards has established a new subgenus, Parascidia, which has eight marginal teeth on the buccal orifice. 4 u 3 1190 TUNICATA. rons, slightly prominent, annular or subellip- tical, without central cavities; the animals (3 to 25) are placed in a single row, at Fin. 769. Siglllina australis. (After A. Vertical section of a cone, or " system," showing the distribution of the animals, •mai/nlfied. ]!. Isolated individual, magnified. C. Natural size of isolated individual. a, test, or external envelope ; b, branchial orifice ; c, anal orifice ; d, thorax ; c, abdomen ; f, oeso- phagus ; g, stomach ; h, intestine ; j, thoracic sinus ; k, intestinal loop ; /, ovary ; m, oviduct. equal distances from their common centre ; branchial orifice six-rayed ; division of the thorax and abdomen not always distinctly marked. Genus Sidin/um, Savigny. — Common body gelatinous, presenting a series of closely grouped cones, truncated and starred at the summit, rising from a common incrusting base ; each cone composed of a fascicle of indi- viduals, varying in number from five or six to ten or twelve, and forming a margin around a depressed centre. The animals partake of the characters of those of Synoicum and Aplidium, resembling the former in the struc- ture of their stomach, and the latter in their branchial sac. Each has an eight-toothed branchial orifice and a simple tubular vent folded against the thorax. The ovary is pe- duncled, and very conspicuous at the ex- tremity of the animal. (Forbes.) Genus Synoicum, Phipps.* — Common body semicartilaginous, cylindrical, peduucled, iso- lated or attached to similar cylindrical bodies ; system single, circular, comprising six to nine animals, terminal; branchial orifice six- rayed; anal orifice having six very unequal rays, the three largest forming the exterior margin of the central star ; post-abdomen sessile. Genus Amaroucium, Milne-Edwards. — Com- mon body fleshy or coriaceous, polymorphous, subpedunculate or sessile, and incrusting ; systems numerous ; individuals arranged irre- gularly around common cloacal apertures ; divisions of the thorax and abdomina faintly marked. This genus resembles Aplidium and Synoicum in the general form of the animal, and Polyclinum in the presence of a central common cavity to each system (fg. 782 ). The tribe Didemnina (Its Didemniens, Milne- Edwards) is formed of all the compound Ascidians whose body is distinctly divided into two parts, thorax and abdomen. These closely approach the C/avd/inec, and are dis- tinguished from the Ifolycliirina by the absence of the post-abdomen and by the position of the organs of generation and the liearr, which are raised up by the side of the intestine. This tribe, like the Polydinina, is divided into two groups, according to the presence or ab- sence of marginal rays around the anai orifice. M. Milne-Edwards observes that the bistellate group (Diitomus and Diazona) forms a con- necting link between the Clavcllince and the Botryllidce. Genus Dlslomus, Gacrtnert ; synonyms, Alcyonium, Auct., Pvlyzona, Fleming. — Com- mon body semi-cartilaginous, polymorphous, sessile; systems numerous, usually circular; individuals placed in one or two ranks at un- equal distances from their common centre. Both orifices six-rayed. Genus Diazona, Savigny. — Common body gelatinous, orbicular, sessile or subpedunculate ; system single, expanded into a disc, compara- ble to that of a flower or of an Actinia; animals very prominent, arranged in con- centric circles (.fig. 770.) ; branchial and anal orifices six-rayed ; abdomen peduncled ; ovary enclosed in the intestinal loop. Genus Dulcnnntm, Savigny. — Common body coriaceous, polymorphous, sessile and incrust- ing ; systems numerous, compressed, without central cavities or distinct circumscription ; animals without any appreciable order of arrangement; abdomen peduncled; ovary placed by the side of the intestinal loop, in- creasing in length when the eggs are fully developed. Genus JEuca-liitin, Savigny. Common body gelatinous, sessile and incrusting ; sy.stems numerous, without central cavities or distinct * Voyage towards the North role, 1773, p. 199, pi. 13. f Gaertner, apud Pallas, Spicilegia Zoologica, 1774. TUN 1C AT A. FIG. 770. 1191 Dlazona vlolacea, magnified. (After Savigny.) circumscription ; animals sometimes scat- tered, sometimes arranged in a quincunx ; branchial orifice circular, without distinct rays ; anal orifice very minute and indistinct ; abdominal viscera pushed up by the side of the thorax. Genus Leptoclinum, Milne-Edwards. — Com- mon body sometimes coriaceous, sometimes gelatinous, thin, sessile and incrusting ; sys- tems few ; individuals arranged irregularly around common cloacal cavities ; abdomen peduncled, short, smaller than the thorax. The tribe Botryllina (Ics BotryUiens, Milne- Edwards) comprises those compound Asci- dians that are united in systems around common excretory cavities or cloacae, and whose bodies are not divided into a distinct thorax and abdomen, the viscera being pushed forward on the side of the branchial cavity, and form- ing with the thorax an ovoid mass. Genus Butryllus, Gaertner ; synonyms, Al- cyonium, Auct., Polycyclus, Lamarck. — Com- mon body gelatinous or cartilaginous, sessile and incrusting ; systems numerous, pro- minent, round or star- shaped, with central cavities; individuals, six to twenty in each system, lying horizontally with the vent far from the branchial orifice; branchial orifice simple (fig. 771.). Genus Botrylloides, Milne-Edwards. — This genus resembles the foregoing in most respects, except that the stars formed by the systems of animals are irregular and ramifying ; the cloacae being prolonged into the common mass as irregular internal channels, on each side of which the individuals are placed in linear series, instead of having a simple star- like arrangement around the cloacae, as in Botryttut. The animals of Botrylloides, more- over, have a nearly vertical position, and their orifices are closely approximate (Jig. 783.). We should perhaps also refer to the group of the Bolryllidic, an obscure form, first no- ticed by Molina*, and subsequently named Pyura by Blainville, and considered by the latter to form a link between the simple and compound Ascidians. M. Blainville gives the following characteristics. Fig. 771. Botryllus vlofaceus. Two of the star-like systems, mag- nified. (After Milne- Edwards.) a, a, common test ; b, b, t>, some of the branchial ori- fices ; c, the common anal orifice of one of the systems. Genus Pyura, Blainville. — A pyriform body, with two small short tubes, occupying a cell in the external envelope, and forming, by its union with 10 to 12 individuals, a kind of poly- morphous mass somewhat resembling honey- comb, apparently without any external orifice. * Saggio sulla Tlistoria natnrale del Chili, logna, 1782, 4to. 4c 4- Bo- 1192 TUNICATA. Family PYROSOMIDJE. Synonyms : Lucies composees, Savigny ; Tuniciers reunis, pars, Lamarck ; " les agreges,'" pars, Cuvier ; Sal- piens agreges, Blainville; Lucidee, MacLeay; Pi/rosomiens, Milne-Edwards and Van Bene- den. The Pyrosomians are represented by three or four species of the single genus Pyrosoma. They inhabit the Mediterranean and the warmer parts of the ocean ; in the former at times their abundance is a source of dread to the fishermen, sometimes even completely clogging their nets ; and in certain oceanic regions they are met with in almost incredible profusion. Their delicate and transparent forms, their elegant tints, and their unrivalled phosphorescence render them the most beau- tiful of Molluscs, and objects of admiration to the naturalist and the voyager. Mr. Bennett relates that, during a voyage to India, the ship, proceeding at a rapid rate, continued during an entire night to pass through distinct but extensive fields of these Molluscs, float- ing, and glowing as they floated, on all sides of her course. Enveloped in a flame of bright phosphorescent light, and gleaming with a greenish lustre, the Pyrosomes, seen at night, in vast shoals upwards of a mile in breadth, and stretching out till lost in the distance, present a spectacle the glory of which may be easily imagined. The vessel, as it cleaves the gleaming mass, throws up strong flashes of light, as if ploughing through liquid fire, which illuminates the hull, the sails, and the ropes with a strange unearthly radiance. Genus Pyrosoma, Peron. — Common body semi-cartilaginous, floating, cylindrical, 2 to 14? inches long, | to 3 inches in circumference ; bearing externally numerous pointed pro- cesses, hollow and mammillated within, and open at one of its extremities only. Animals associated in a verticillate arrangement, having two orifices, one at each extremity ; elongated, fusiform, tapering at the outer, and obtuse at the inner extremity ; united at the circum- ference of the middle portion, by the fusion of the tests to one another into rings, more or less regular, and varying in number accord- ing to species, so that the whole forms the long cylinder above described. MONOCHITONIDA. — Family SALPID^E, Forbes. Synonyms : Salpce, Auct. ; TJialides, pars, and Lucies simples, Savigny ; Siphores, Brugiere ; Biphondee, Mac Leay ; Tuniciers libres, pars, Lamarck ; " les isolees," pars, Cuvier; Safpacea, pars, and Saljriens simples, Blainville ; Salpiens, Van Beneden. The Salpians are free, swimming in the ocean ; plentiful in the Me- diterranean and the warm parts of the ocean ; occurring also occasionally in the Norwegian and North British seas. In shape they re- semble a short and wide tube, sometimes oval or cylindrical, sometimes more or less square in its transverse section, and varying consi- derably in size according to species, from half an inch to 8 or 10 inches in length. The test is thin and transparent, open at the ends and often supplied with terminal and lateral processes. The mantle lines the test, and is more or less adherent throughout ; its interior constitutes the branchial cavity ; it is provided at one of the terminal openings with a more or less perfect valvular apparatus; and contains a branchial fold traversing it obliquely. Near one extremity the chief viscera are grouped together into a conspicuous mass (the " visceral nucleus" of authors), to which the brilliant tints of the liver usually impart an orange, brown, or reddish hue (fig. 772.). Fig. 772. •f ^ SalpcE, isolated and associated. A. S. runcinata, solitary; B. /!?. runcinata, asso- ciated ; c. $. zonaria, aggregated. This family is of considerable interest on account of their singular mode of reproduc- tion, discovered by Chamisso, and on account of the philosophical generalisations partly founded thereon by Steenstrup. These ani- mals occur under two distinct conditions, being at one time solitary, and at another as- sociated into circular or lengthened groups — termed garlands, cordons, ribands, and chains (..fig- 772. B and c). The Salpa-chains, vary- ing in length from a few inches to many feet, swim through the tranquil water with a regular serpentine movement, and are often regarded by sailors as sea-serpents ; but when taken from the water the individuals of the group are easily detached. Thus, in conse- quence of accidents, separate members of these chains are often met with in seas abounding with these Molluscs ; but other, separate, SalpcB are also met with that have never been united to others, and differ considerably in form from the associated ones (fig. 772. A). Chamisso, however, discovered that such permanently solitary Sa/pcs do not belong to species distinct from those united in chains, however dissimilar (and they are usually so dissimilar as to appear even generically dis- tinct), but are either the parents or the pro- geny, as the case may be, of the aggregate forms ; and that chained SalpcE do not produce chained Salpcet but solitary SalpcE, which in their turn do not produce solitary, but chained Salpce. Consequently, as Chamisso graphi- cally observed, "a iSa/pa-mother is not like its daughter or its own mother, but resembles its sister, its grand- daughter, and its grand- mother."* This family is mainly represented by the * Forbes, British Molluscs, p. 48. TUNICATA. 1193 genus Salpa, Forskahl ; synonyms Thalia, Brown ; Holothuria, Linneand Pallas ; Dagysa, Banks and Solander ; Biphora, Brugiere ; Tethis, Tilesius ; Pegca and lasts, Savigny. The characteristic features of this genus are detailed above. Quoy and Gaimard * established for some animals nearly allied to the Salpes and inha- biting the coasts of Amboina, the genus Do- lio/ium, the characters of which are, its having the form of a little cask open at the ends; from two to ten lines in length ; the anterior extremity a little prominent ; marked with circles in relief on the external surface ; and having internal branchia, divided into two branches; and a heart and a dorsal vessel, si- tuated near the union of these branches. This name had also been previously given by Otto -f- to a genus established by him on a Mediterra- nean Salpa, mutilated by a crustacean of the genus Phronymc, that had made it its habita- tion. This form, like Salpa triangufaris and S. polymorpha (by Quoy and Gaimard, and Bory de Vincent), has been erroneously regarded as belonging to the family of Diphydes. MM. Lowig and Kb'lliker, however, who found the tissue of Doliolium to be identical with the pe- culiar substance of the test of other Tunicate, have pointed out its true affinities, and placed it with the Salpidce. Family PELONAIAD.E, Forbes. — This fa- mily is represented by two rare animals, both inhabitants of the Scottish seas, constituting two species of a single genus, Pelonaia, esta- blished by Professor E. Forbes and Professor Goodsir.j We have derived our description of the general and anatomical characters of these interesting Molluscs from the detailed account given of them by the original dis- coverers. Genus Pelonaia, Forbes and Goodsir. — Animal simple, unattached. Test more or less cartilaginous, smooth or wrinkled, elon- gated, and cylindrical ; anterior extremity bearing two orifices, four-cleft, without ten- tacles, and placed on the same plane, on two equal, approximate, papillose eminences ; posterior extremity ending in a blunt point ; mantle adherent to the test. The Pelonaia: live buried in mud, quite unattached to any other body, and are extremely apathetic ani- mals, presenting scarcely any appearance of motion. ANATOMY AND PHYSIOLOGY OF THE TUNI- CATA. It will be most convenient to describe the test generally for the whole tunicate class, and the rest of their anatomy under the heading of each of the families. Test or Shell. — The test or external enve- lope of the AscidiadfE is subject to considerable variation of shape ; from the bottle-like form of the Ascidia (fg. 766.), to the flat, patella- like form ofChclyosoma (Jig. 767.) ; it is elastic, * Voyage de 1' Astrolabe, Zoologie, torn. iii. f Nova Acta Academ. Nat. Curios, t. xi. j Jameson's Edinb. New Philosoph. Journal, vol. xxxi. 1841. varying very much in its thickness and con- sistence in different species. In colour it varies considerably, being occasionally nearly black, sometimes red, orange, yellow, or milky white. Its surface is sometimes smooth, often tuberculated, covered with hairs or spines, or otherwise roughened. Sometimes minute patches of horny tissue or hardened epidermis rise up irregularly on the surface of the test ; in other cases these are placed in a tessellated arrangement. In the peculiar and unique form, Chelyosoma, first noticed by Messrs. Broderip and Sowerby, and since more fully described by Professor Eschricht, the upper surface of the test is occupied by eight large, horny, polygonal plates arranged some- what like the shell-plates of a tortoise, and by several smaller triangular plates, which form two circles, one around the branchial, and the other round the anal aperture of the animal (Jig. 767.). The large plates are so disposed that the branchial orifice is surrounded by three plates, and the anal by four, besides that which is intermediate and abuts upon both : this latter plate is hexagonal, the sides in con- tact with the orificial valvules are lunated. The three plates near the branchial orifice are much larger than the four which are near to the anal orifice. Each of the plates is marked with three or four elevated striae, which are near to the edges of the plate, and parallel with them, leaving an area in the centre, and giving rise to a general resemblance to the external plates of the shell of a land tortoise. The orifices are very small, and are surrounded by six triangular valvules, each transversely stri- ated, and, when shut, rising from the sur- rounding surface in the form of a cone. The lower or adherent part of the test of Chely- osoma is coriaceous, with occasional slight traces of separation into plates. The test of Ascid'ns is frequently covered with innumerable smaller animals and their spawn. Modiolas and Annelids burrow in it ; Cirrhipeds, naked Molluscs, and Actiniae lodge upon it ; and Corallines cover it sometimes with a little forest ; a condition fully justify- ing the denomination of " microcosmus," be- stowed by Redi * on a Mediterranean species. Occasionally, as in Ascidia conchilega and Mol- gula oculata, the animal works up extraneous matter, as gravel, fragmentary shells, &c., with the external surface of the test. It is by this shell or test that the animal fixes itself. In the sessile species, the tissue of the base or the side of the test interlaces with the stems of sea weeds and corallines, or closely adheres to the surface of another ascidian sac, or of a stone, a shell, a crab, or other object. In the peduncled forms this tunic is at one point pro- longed into a tubular process or stem, the dis- tal extremity of which is attached to marine bodies in the same manner as the base of the sessile tests. In Cystingia and Bipapittaria, however, this process or stalk appears to be less perfectly developed, and not to be al- * Opuscula varia Physiologica, 3 vols. 12mo. Lugd. Batav. 1725. 1194 TUNICATA. together adapted to maintain a permanent attachment to a fixed body. The external envelope of the Ascidiadts is always perforated by the two apertures characteristic of the Tunicnta, and analogous to the prolonged respiratory orifices of the CardktceoE and other Acephala. One of these apertures*, nearly always placed at the .sum- mit of the test, receives the sea-water, and admits it into the branchial cavity. The second aperture f is placed a little lower than the first, and is in communication with the rectum and oviduct. In Boltenia the ori- fices are lateral ; in Cystingia the branchial orifice is lateral, and the anal terminal ; the oral orifice being always the highest in relative position, and nearest to the insertion of the pedicle by which the animal is suspended. In Chclyosoma and Dendrodoa the orifices are placed on the same plane ; in the former, on the nearly flat superior surface of the animal, and in the latter they are terminal. The edges of the orifices are more or less crenulate or divided. The branchial orifice is 8-9 rayed, and the anal 6 rayed, in Plial- iusia ; both orifices are 4-fid in Cynthia, Bol- tenia, and Dendrodoa. When contracted, they are thrown into longitudinal folds ; this is the more observable when the orifices are somewhat prolonged into tubes. The test receives from the body blood- vessels, which its semitransparency in some species allows the eye to follow to the extreme ramifications. In the thinner tests the vessels are but few, and sometimes altogether escape observation ; but in the thick pellucid test of Ascidia mammillata the eye can discern an extensive network of vascular ramifications. The bloodvessels enter the test near the base. The internal surface of the test has often a glistening and pearly appearance, and is always lined with an epithelium. In Boltenia reni- formis this is a loose tissue, and forms a slight attachment to the external surface of the mus- cular sac or mantle of the body. In A. innmmillata a thin vertical septum traverses a part of the cavity of the test. The test of the ClavclUmdce is very similar in consistence and general appearance to that of some of the more delicate species of the AscidiadcB, but differs materially in having tu- bular prolongations running from its base, which are traversed by vessels continuous from one individual to another, and from which root-like processes young individuals are continually being produced by the process of gemmiparous reproduction (fig. 768.). The tube-like test of the Salpida: is " semicar- tilaginous, or gelatinous, seeming as if carved in crystal," its transparency rendering conspi- cuous the brilliant hues of the liver of the contained animal. It is usually more or less angular, bearing elongated crests, denticles, and other processes, by means of which the cohesion of the aggregated individuals is maintained (fig. 772.). * The first, oral, buccal, branchial, or respiratory, f The second, anal, ventral, or the funnel. The tests of the little animals of which the cylindrical body of the Pyrusoma is composed, are intimately connected by their lateral sur- faces, leaving their terminal orifices free (fig. 786. A). The tissue of the whole common envelope is semicartilaginoiis, transparent, tinted with azure and other colours. In the liotryllidcE the external tunic is re- presented by the tegumentary tissue com- mon to the whole association of animals, and which may perhaps be compared to the polypary of aggregated Polyps. The close aggregation of the animals causes a fusion, as it were, of the tests of the whole into a coriaceous or gelatinous mass, coated with a tough epidermic membrane, and more or less regularly beset with individuals or groups of individuals (systems) ; or, rather, the soft test of the originally isolated indivi- dual, or single system, increasing in bulk and producing within itself more and more embryos of individuals and systems, becomes an ex- tended, homogeneous mass, in which nu- merous individuals are lodged (fig. 771.). This mass is irregular, fungous, jelly-like, spongy, or coriaceous, incrusting other sessile Tuni- cates and a variety of marine bodies. Structure and chemical composition of the test. — We are indebted to the labours of MM. L6- wig and Kolliker* for considerable information on the subject of the constituent elements and the growth of the test of the simple and the compound Ascidians. These researches were undertaken with the view of examining into Dr. Schmidt's statement of the existence of the vegetable element " cellulose" in the tissue of the ascidian envelope. This they found to be correct (as the following state- ments will show), and they have also offered a lucid explanation of the fact, to which we shall subsequently refer. Cellulose forms the cell walls of vegetables, and is unaffected either by soda or hydrochloric acid. The cartilaginous envelope of Phallusia mammillaris (Fam. Ascidiadte), examined in specimens preserved in spirit, is composed of three layers of different thicknesses (fig. 773.). The internal layer, formed simply of polygonal, nucleated, epithelial cells, measuring 0'005'", covers all the interior surface of the test ; at the two external orifices, and at the points where it receives the nutrient vessels of the test, it is united with another epithelial tissue covering the mantle. The second layer is con- siderably thicker, and is composed of a homo- geneous substance, containing crystals and nuclei. The former are not present every- where, and are, perhaps, quite absent in the recent animals ; when present they are visible to the naked eye, and appear like white stria; ; seen under a moderately magnifying power, they have the form of crystals united in the form of a star, or of irregular and polymor- phous concretions. The nuclei are present in considerable numbers and under different forms ; those situated towards the interior are round, O'OOlo'"— 0'002'", with one or two * Annales des Sciences Nature-lies, 3 ser. torn. vi. 1846. TUNICATA. 1193 opaque nucleoli, similar to fat-granules. The external nuclei are larger, round or more or less produced, and contain clear or granular substance, and usually some opaque granules. Fig. 773. Test of Phallusia mammilhtris. A. Transverse sectimi, magnified 30 times. 1, inter- nal layer of epithelial cells ; 2, the second or inter- mediate layer, consisting of a homogeneous mass, thickly strewn with nuclei ; 3, the external layer, composed of a fundamental mass and cells of cellu- lose, with dispersed nuclei (c), and having pigment- cells and acicular crystals in the upper part; 4, vessels. B. A portion of the same, magnified 350 times, a, fundamental mass ; b, cellulose cells ; c, nuclei, some round, others star-shaped; d, acicular crystals of carbonate of lime ; e, the extremity of a vessel ; /, pigment-cells. The third layer forms the principal mass of the test of this species. It is the seat of the numerous and large arteries, which, arising from the heart, traverse it in every direction, having brush-like ramifications, that penetrate almost to the exterior surface, and then ap- pear to pass into other vessels that accom- pany them in their course. This layer is formed of large cells, besides a clear homo- geneous substance, which is a continuation of the principal substance of the second layer ; besides these there are locally distributed crys- tals, nuclei, and pigment-cells. The large cells, which R.Wagner previously thought to be cartilaginous, are of a peculiar nature, and resemble no other animal cell hitherto known, except perhaps those of the chorda dorsalis of some animals. The most re- markable character of these cells is their size, which varies from O'OOS"' to 0'05'", the aver- age being 0-02'" to 0'03'". Their form is spherical, pyriform, or elliptical ; their con- tents diaphanous and quite destitute of nucleus or granules : and their membrane delicate, smooth, and of an equal thickness throughout. The smallest cells are irregularly dispersed in the homogeneous fundamental mass that is common to the second and third layers. The larger cells are arranged closely together to- wards the exterior surface of the layer, pre- senting a very regular cellular tissue with very little intermediate substance; but, immediately beneath the external surface of the envelope, the cells are rather more distant one from another, and the intermediate tissue more visible. The crystals and pigment-cells before mentioned, are present only in the outer part of this third layer ; the former are acicular, about O'OO 15'" in length, occupying in com- pact masses the intercellular intervals ; the latter are yellow, and filled with somewhat large granules, and surround in particular the extreme ramifications of the vessels. The nuclei, lastly, are similar to the large nuclei of the second or intermediate layer, and are everywhere present between the large cells in considerable numbers. When slices of the test are treated with hy- drochloric acid, the crystals of the second and third layers quickly disappear ; treated with a solution of soda, the epithelial cells, the nuclei, the pigment-cells, and the vessels are dissolved. The fundamental homogeneous sub- stance of the second and third layers and the large cells are not dissolved, nor do they suffer any modification. In Phallusia monachus the large cells mea- sure from O'Ol'" to O'OS'", and are more dis- tinctly separated from one another than in the preceding example. The nuclei of the homo- geneous substance are few, and generally fusi- form or even ramified ; at the external surface of the envelope they are mixed up with a great number of minute yellow pigment-cells and pigmentary granules, as well as with acicu- lar crystals and very minute crystalline concre- tions ; all of these being in the greatest num- bers in the neighbourhood of the extremities of the vessels. In one specimen of this spe- cies MM. Lowig and Kolliker observed, that in the interior of the third layer no cells could be distinguished ; ultimately, however, they distinctly saw well defined cavities or lacunae, which were evidently vestiges of cells that had been more or less completely fused with the intermediate homogeneous substance ; and the traces of these lost cells were found to be more and more distinct towards the band of perfect cells in the surface of the test. In Phallusia sulcata the large round or ellip- tical cells, without nuclei, have a diameter of 0-01'"— 0-1#"'. In Phallusia gelatlnosa a very peculiar forma- tion was observed by the experimenters. In one specimen the soft, gelatinous substance of the envelope exhibited no trace of cells throughout its thickness, but its mass was principally composed of a homogeneous sub- stance similar to that of the other Ascidice. In another individual they observed some few and indefinite remains of cells. In both spe- cimens they found, as in the other species, vessels and nuclei, the latter for the most part round and measuring 0'002'", in the homo- geneous substance. In the individual desti- tute of cells, there was also in the exterior part a very large quantity of acicular crystals and yellow granules, the latter frequently re- sembling the nuclei with large coloured nu- cleoli. The tissue in all the Asridicc examined, when chemically treated, behaved in a similar manner to that of Pliallmia mammillaris. We have observed that the test of Boltcnia rcnifvr'iiis (preserved in spirit) presents a ho- 1196 TUNICATA. mogeneous structure crowded with " nuclei " and bloodvessels, and only occasionally does any trace of cellular tissue present itself, in which case the cells are very minute, poly- gonal, and compressed. Mr. J. Quekett has detected calcareous spiculae in the test of this species. They are situated towards the ex- terior, and are very numerous and excessively minute. Their form is usually cylindrical, with triradiate or 4-5-fid extremities.* The composition of the test of Clave/Una lepadiformis corresponds in all respects to that of the above mentioned Ascidice ; certain parts in the same individual having a more particular resemblance to one species, and others to another. The test, however, is quite destitute of bloodvessels. Transverse sections of the stalk of the Clavellina and of the excrescences that spring from it, exhibit a tissue composed of round or elongated non-nucleated cells, O'O I"'— 0-014'", almost destitute of inter- mediate tissue, and arranged very close to one another. It is only towards the upper extremity of the stalk that the cells become more and more separate, and even disappear little by little, as happens in some Ascidice, and give place to an intermediate homogeneous substance, bear- ing a quantity of nuclei. In the largest and superior moiety of the test a peculiar structure is found. Externally is a dense, but not thick, layer of delicate cells, which are very difficult to recognise, and measure about O'O^'". Be- tween the cells, and immediately at the surface, are crystals of carbonate of lime, scattered nuclei (measuring G'002"'), and large round fatty granules. Interiorly to this occurs a still thinner lamina, composed of a trans- parent, colourless, homogeneous substance, with infinitely minute pale granules. Next, there is a layer of round granules or vesicles. These are spherical, measuring 0-0005'", 0-0004/", and even O'OOS'"; their surface is smooth or granulated ; the largest are placed in the middle, the smallest at the exterior; they appear opaque, and like starch or fat granules. With solution of iodine, the}' be- come yellowish, without presenting any trace of blue, and are probably fat grains. Succeeding to these, a thick layer presents itself, homogeneous, diaphanous, with some few minute spherical nuclei, which, the nearer they approach towards the interior, contain more and more colourless granules. Lastly, quite at the interior surface, is a thinnish, com- pletely diaphanous substance, of equal thick- ness throughout, with spherical granular nuclei, measuring about O'OOS'". Treated with soda and with hydrochloric acid, the crystals, nuclei, and fat granules of the test of the Clave/Una disappear ; the large cells, on the contrary, and the homogeneous substance, with its scattered granules, remain perfectly unaffected, proving the identity of the chemical composition in Ascidia and Cla- vellina, * Several specimens are figured by Mr. Quekett in the Descript. and Illustr. Catal. of the Histological Series in the Mus. Royal Coll. Surgeons, 1849, plate xvii. fig. 13. The Salpa maxima does not contain, in its gelatinous envelope, any trace of cells similar to those of the Phallusia and Clavellina. It is for the most part composed of a homogeneous, clear, diaphanous substance. Towards the interior surface, the several elements are not so clearly arranged as in the middle and external layers. In the innermost layers, a multitude of very minute granules are pre- sent; in the others there are little round nuclei, nucleated cells, and spherical or star- shaped crystalline concretions. These latter are very regular, and formed of 3— 7 straight rays, springing from a centre (jig. 774. c). They Fig. 774. A. Incrnsted cells of the fundamental mass of Didemnum candidum. a, unaltered cells ; b, a cell the lime of which has been nearly extracted by means of hydrochloric acid. (-After Lowig and Kolliker). B. Incrusted cells of Botryllus violaceiis. a, sphe- rical cell ; b, cell with two colourless prolongations ; c, with three ; d, with four ; and e, with only one such prolongation. C. Siliceous concretions from the test of SaJpa maxi- ma, magnified 350 times. (After Lowig and Kdlliher). D. Calcareous concretion from test of Leptoclinium maculosum. (After Milne-Edn'ards.} are composed of a single or manifold series of granules, which, as they approach the exterior, increase or lessen in number, but always di- minish in size. These do not appear to be car- bonate of lime, not being soluble in hydro- chloric acid ; and their behaviour with muriate of barytes shows that they are not formed of sulphate of lime ; probably they are siliceous. The granules and nuclei are dissolved by boil- ing in solution of soda ; but the homogeneous substance, composing the mass of the tunic, remains unchanged. The test of Salpa bicaudata is essentially the same, in the nature of its composition, as that TUNICATA. 1197 of the Salpa maxima, the fundamental mass of the gelatinous envelope being composed of the homogeneous substance. It differs, however, in the elements contained in this tissue, and by the presence of a simple layer of epithelial cells, covering it on the interior surface of the test. In the interior layer of the homoge- neous substance there are granulated vesi- cles, having a diameter of O'OOS"' to 0-004/", sometimes having the appearance of nuclei, and sometimes that of cells. In the middle part, here and there, are scattered round or fusiform nuclei ; and in the exterior layer are little crystals, round nuclei, and peculiar concretions, similar to those of Salpa maxima. Some of these concretions are small, elegantly ramified, and disposed horizontally ; others are larger, ramified in a brush-like form, and appearing to the naked eye as white tufcs. These latter commence at the surface, descend vertically towards the interior, and ultimately form a tuft of fine ramified rays (Jig- lib. d). Transverse section of the test of Salpa bicaudata, magnified 30 times. (After Lowig and Kolliker.} 1, epithelial layer; 2, homogeneous mass, with nucleoli ; b, fusiform and ramified concretions ; c, nuclei ; d, brush-like concretions. Magnified 350 times, these two sorts of con- cretions are seen to be composed of opaque granules of different sizes. The chemical composition of the test of this Salpa is iden- tical with that of the preceding species. In the Pyrosoma giganteum, the common en- velope of the individuals is also formed of a homogeneous and structureless substance. In its interior are scattered here and there round nuclei, and some ramified cells, similar to those of the loose cellular tissue of the em- bryos of Mammifers, for example, to that of the gelatine of Wharton. Both of these latter elements disappear when treated with soda ; but the homogeneous substance al- together resists the action of the soda, and remains intact. The Diazona violacea (Fam. Botryllidce) possesses, in the gelatinous mass of the com- mon test, a diaphanous, structureless sub- stance, quite destitute of cells. In the ex- terior layers are crystals and concretions of carbonate of lime, vesicles with violet-coloured granules, fat granules, and, particularly to- wards the interior, a great quantity of minute round vesicles (nuclei). Treated with hy- drochloric acid and with soda, the crystals, nuclei, and pigment-cells are dissolved, but the homogeneous substance remains un- changed. Moreover, after having been a long time exposed to the influence of the alkali, and although the pigment-cells have disap- peared, some portions of the exterior parts retain a pale violet tint, giving evidence of the presence of undissolved colouring particles, and of an amorphous colouring matter per- vading the mass. The structure of the test of Didemnum can- didum (Fam. Boti'yllidfz) is quite different from that met with in any of the Tunicates before mentioned. The white substance in which the individual animals are lodged, which has been figured also by Savigny, apparently pre- sents only some white star-shaped bodies (Jig. 774.. A), measuring O'OOG'" to O'OIS'", similar to those found by M. Milne-Edwards, in Leptoclinum stellatum and L. maculosum (fig. 774. D), except only that the former are of a more rounded form, and are provided with shorter and more numerous points.* But, on being treated with hydrochloric acid, this substance has quite another appearance. The white colour quickly disappears, bubbles of gas being freely given off; and. on ex- amination with the microscope, there is seen in the yellowish, transparent membrane that remains, a fundamental homogeneous sub- stance, in which are scattered round and elongated cells, of O'OOS'"— O'OIS'" in di- ameter, and some minute granular masses. At first sight these cells appear to be analo- gous to the large cells found in the tests of Ascidia and Clavellina, being, like those of the latter, non-nucleated, indistinctly marked by a pale, delicate contour, and having perfectly liquid contents. But by boiling with soda they are quite dissolved, whereas the homo- geneous substance remains unchanged. MM. Lowig and Kolliker found also, that under the influence of hydrochloric acid each of the star- like corpuscles showed itself not to be a simple concretion, but, losing its rays little by little, became a cell filled with lime, and ultimately appeared as a colourless, empty cell, quite similar to those above described. They add that they could not discover how these curious cells, filled with lime, and fur- nished with calcareous rays externally, were formed ; but they thought it probable that they were originally large cells, full of liquid, which became gradually occupied with lime, until ultimately the membrane of the cell became incrustecl, and the lime deposited on its external surface. * We have been favoured by Mr. Bowerbank with an opportunity of examining his valuable series of microscopical preparations of ascidian tis- sues, including several kinds of the spiculse entering into the composition of the tests. The spicuhr of Didemnum are spherical bodies, closely invested with short, thick, blunt spines, and nearly resemble the globular spieulaj of Tethea, except that the invest- ing spines of the latter are more numerous and much finer. The tissue occupied by these closely set spiculaj in the Didmnimm is seen in the trans- parent portions of Mr. Bowerbank's beautifully mounted specimens to be composed of diaphanous, contiguous, irregularly hexagonal cells, the measure- ments of which we have not had time to cH'crt. Numerous nucleoli are disseminated throughout the tissue. 1198 TUN1CATA. The common test of ApUdium gibbnlosum presents a homogeneous substance with some scattered nuclei, and a great quantity of round cells, with very delicate membranes, measur- ing 0-005'" to 0-0 13'", and even to 0-02"'. Those in the interior contain only a liquid ; but the nearer they approach the exterior, the more are they found to contain calcareous concretions; and, lastly, there are cells per- fectly incrusted, but without appendages. Acted upon by soda and by hydrochloric acid, the homogeneous substance alone remains, the rest is dissolved. In the "common body" of Botrylhts vio- laceus are some remarkably incrusted cells, similar in some respects to those of Didcmnum. Some of these are perfectly round, with a diameter of O'OOO"', and, as those of Aplidium, are filled with calcareous concretions ; others, for the most part pyriform or fusiform, have one or two pointed, colourless prolongations, 0-006'"— 0-009'" in length, and are organic in substance ; others, lastly, round or tetra- hedral, have even three or four of these prolongations, which are often of a similar length, and are regularly disposed, but just as often are of different sizes, and without sym- metry (Jig.ll^. B).* These prolonged cells are probably analogous to the round cells in Didcmnum, that have lime in their interior and calcareous deposits externally, and may even be compared with vegetable cells (pollen- granules, spores, &c.), bearing external de- posits. Were these cells incrusted, they would form star-like bodies, similar to those of the Didetnnum. Professor M. Edwards observes, that in Lep- toclinum the substance of the tissue is crowded with calcareous granules, which, seen with an ordinary lens, appear to be little spherical con- cretions, but which are aggregations of little pyramidal crystals, united by their base, so as to represent a many-rayed star, surmounted on each of its faces by a group of other similar, but smaller, rays (see^-g. 774. D). The structure of the common test of the Botryllus polycyclus is peculiar and quite dif- ferent from those described above. In the exterior parts of the common mass the struc- ture resembles that ordinarily found in com- pound Ascidians, being of a clear and homo- geneous substance, with some nuclei and crys- tals ; but in the interior distinct fibres are found, by the side of the nuclei. These fibres are of two kinds ; some, the least numerous, are long, extremely pale and delicate, too fine to be measured, and, crossing one another in all directions, form elegant sinuosities ; others, less immerous,are short, O'Ol,'" toO'03'" in length, larger, opaque, and variously curved ; in a word, they resemble certain nuclei transformed into fibres (A'enifascrn). Like the homoge- neous substance of the exterior and interior parts, these fibres resist the action of hydro- chloric acid and of soda ; and consequently, since they are incontestably organic, they are composed of non-azotised substance. There are also some round points, visible to the naked eye, dispersed in the common in- tegument of this BotryUus. Some are white, generally situated towards the interior of the test, and appear under the microscope as groups of granules or spiculse ; they are in- soluble in a solution of soda, or in hydro- chloric acid, and are probably siliceous, like the concretions in Sa/pa. The other spots are violet-coloured, or reddish, and are most abundant in the external layers near the groups of individuals, yet sometimes also they are present in the interior parts of the common mass. Seen under the microscope, they appear as pj'riform, round, or elongated vesicles, bearing a reddish colouring matter, contained probably in the cells, and are at- tached to the extremities of the ramifying canals that traverse the mass in every direc- tion. These vesicles are the germs of new individuals.* The coriaceous test of the Cynthife (Fam. Ascidiadae) presents a composition still more remarkable than that of the Bolrylli. In Cynthia papillata, the fibres that constitute a large proportion of the test, are in some parts so much developed, that they may bear compari- son with the fibrils of any fibrous tissue found in vertebrate animals. In examining the structure of the test, where it is of no great thickness, we find a simple lamina, quite on the interior surface, consist- ing of an epithelium, with polygonal cells, which is united to the mantle by scattered, crossing, muscular fibres. A thick layer of fibres suc- ceeds, having cells and nuclei disseminated in it. The fibres themselves are colourless, un- dulating, resembling the fibrils of the fibrous tissue of vertebrate animals, but narrower ; they measure 0-0002'"— 0-000-t'" in thick- ness; they are never ramified, nor united inlo bundles. In their direction they are in part parallel to the axis of the animal, as in the interior lamina? ; and in part differently in- terlaced, so that some are disposed longi- tudinally, and others transversely (circular and longitudinal fibres) ; hence, from the disposition of the two kinds of layers, the test can very easily be split into, sometimes very delicate, lamina. There is apparently no intermediate substance accompanying the fibres, but the laminae formed by their diver- gences are occupied by a quantity of granules and vesicles of different forms. Firstly, there are minute colourless molecules, in some parts so abundant as to render the fibres in- distinct, and to give to some of the thicker layers a finely granular aspect; secondly, crystals, which are present only in the ex- terior layers ; thirdly, nuclei, measuring O'OOl'" to 0-003'", often with large granules, apparently of fat ; fourthly, cells of different forms. Some of these cells, containing nuclei * Specimens of these spicula in Mr. Bowerbank's * The epiderm covering the common gelatinous histological collection exhibit much more coarsely test of Botryllus steUatus is very tough, closely ad- granulated centres than those here figured. herent, and presents distinct cellular structure. TUNICATA. 1199 and brown pigment-granules, are round, having a diameter of O'OOS'" to O'Ol'", or elon- gated, with a diameter of O'OOG'" to 0-008'" ; others are of a pule colour, and, from the double nuclei and the included cells (2 to 7) seen in some of them, strongly resemble the cartilage-cells of the superior animals. This resemblance is rendered the more strik- ing by the round or elongate form of these cells, by the peculiar arrangement of the en- closed cells, and by the union of some of the mother-cells, in this case generally round and smaller, into groups of two or four. This resemblance, however, is only external, and due only to the fact that the cells increase by formation in the interior, as in cartilage ; because more exact observations show that these cells, by further transitions, become identical with the simpler pigment- cells described above, and are only the more developed forms of the latter, the pigment having disappeared by degrees on account of the condition of their growth. The third layer is formed of a yellowish, horny epidermis. The thin hairs which cover the surface of the Cynthia papillata are formed by this and the exterior fibrous layer. At certain spots a bundle of fibres springs up from the plane surface of the latter, which, being coated with the horny epidermis, rises on the surface as small needle-shaped bodies. Where the test of the Cynthia attains a thick- ness of i to \\'" and more, its composition often changes in a remarkable manner {fig. 776.). In this case the epithelium is succeeded Fig. 776. Transverse section of Cynthia paplllses externally into an irregular fibrous tissue, covered with a horny epidermis. Where this peculiar stratification of fibres exists, the test is not separable into lamina;, because the radiating fibres firmly connect the thin layers of circular fibres. Treated with hydrochloric acid and with soda, the test of Cynthia is rendered quite white. The pigment-cells, the coloured epi- dermis, the mother-cells, the crystals, the epithelium, the nuclei, and the granules are dissolved, and there remain only the fibres and the homogeneous substance that exists here and there. These two elements, then, are composed of cellulose. The structure of the thick test of the Cynthia Canopus is very similar to the above. Interiorly there is an epithelium, then a thick layer of longitudinal and circular fibres, some- what indistinctly stratified, in which, towards the exterior, crystals and largish round bodies, composed apparently of groups of cells, are disseminated ; lastly, a thin layer of solid, whitish epidermis, with little conical papillae, usually accompanied by processes from the fibrous layer. The thick fibrous layer, only, resists the action of hydrochloric acid and of soda ; all the rest is dissolved without any residue. Cynthia pomaria presents, as the chief ma- terial of its test, a layer of fibres similar to those previously described, having chiefly a longitudinal direction. Between the fibres are crystals, round pigment-cells, measuring O-OO^'to 0-006'", and further, here and there, peculiar elongated cells, filled with yellow granules, measuring O'OOS'" and more. In- ternally, and adhering to the fibrous layer, is a simple epithelium, with polygonal cells that have diameters of Q'006"' to O'OOS'". This adheres to the inner tunic by means of mus- cular fibres. Externally the fibrous layer is covered by a yellowish, solid layer of unde- termined structure. In the interior parts of the fibrous layer occurs a somewhat large number of peculiar cells, apparently not ana- logous to any other of animal or vegetable structure. These cells are primitively similar to pigment-cells, and round, but possessing a thicker membrane, and without any apparent nucleus. Subsequently they grow, preserving their shape, to the size of O'Ol'". The mem- brane at the same time continues to thicken, so much so that the cavity of the cell increas- ing but slightly, the membrane attains a thick- ness of 0-004/". Lastly, the size of the cell increases to 0'02'" and the thickness of the membrane to 0'006'". Whilst this develop- ment is going on, fine lines are observable in the thickened cell-membrane, and ultimately the membrane is transformed into fibres, so that one may see the moderately sized cells in their cavities, and yet occupied by pigment 1200 TUNICATA. or by pale granules, enveloped with an elegant skein of fine, cylindrical, opaque fibres, which can be isolated by compression. Whether the fibres have a spiral arrangement is uncertain. MM. Lowig and Kolliker, who discovered these remarkable fibre-coated cells, remark that, as to the manner in which this curious trans- formation of the pigment-cells is brought about, the increase of thickness in the cell- membrane would take place by growth, or by a development similar to that which occurs in many vegetable cells, the membrane of which consists of several layers, or by the de- position of a substance applied externally. As there is no appearance of any internal or external deposit, and as the cell-cavity is not diminished during the thickening of its walls, they consider the first to be the more likely cause of the above conditions, but, neverthe- less, not sufficient alone to account for the circumstances. It is difficult, perhaps, to say how these fibres are formed, but it may be that the cell-walls, by partial solidification, ultimately become separable into fibres. The fibrous tissue of the Cynthia pomaria is insoluble in hydrochloric acid, or in solution of soda ; the other elements of the test, sub- mitted to these agents, disappear. The following clever abstract of the facts connected with the subject has been drawn up by Professor Edward Forbes : — " MM. Lowig and Kolliker found cellulose undoubtedly present in the envelopes of many Tunicata, both simple and compound, in- cluding the genera Phallusia, Cynthia, Cla- vellina, Diazona, Botryllus, Pyrosoma, and Sal-pa ; but they sought in vain for cellulose in animals of inferior organisation, although in some of the above-named creatures it formed a very considerable part of the animal tissues. " The Memoir of MM. Lowig and Kolliker was examined by a committee of the French Institute, consistingofDumas,Milne-Ed wards, Boussingault, and Payen ; the last-named eminent philosopher drew up the report. In it he gives the following formula of the com- position of the envelopes of the Tunicata : — Cellulose Azotised substance Inorganic matter - 60-34< 27-00 12-66 lOO'OO " He remarks that the establishment of the existence of cellulose in the Tunicata is a 'fait capital' in science, very important in its bearing on future researches into the com- parative physiology of the two kingdoms. " The explanation offered by Lowig and Kolliker of these very anomalous facts is ex- tremely ingenious, and probably very near the truth. It is to the following effect: — Tuni- cata live entirely upon vegetable organisms. The contents of the stomachs of the Phal- lusia;, ClavcllinfE, and Diazona;, examined, con- sisted of particles of florideous algae, which had probably found their way there by chance, and a great quantity of microscopic plants of low position in the series, species of Navicula, Frustulia, Baccilaria, Clostcrium, &c. These minute vegetable organisms have been shown by Nageli and Schmidt to contain cellulose. " This is probably dissolved by the gastric juice, that is to say, changed into sugar or gum, in which state it circulates with the blood, and is afterwards introduced into the tunics, either directly by the sanguiferous canals (as in Phallusia), or by their prolonga- tions ramified in the walls of the common body (as in Diazona and Botryllus), which thus, as Milne Edwards has shown, contain also blood in their cavity, probably pene- trating by imbibition when the envelopes have no bloodvessels. The presence of cellulose in the tunics of the ascidian Molluscs, then, cannot be taken as an evidence of an ap- proach to a vegetable nature in those bodies. It affords us, however, a wholesome warning against the placing of confidence in asserted chemical distinctions between the great king- doms of Nature." * From the observations made by MM. Lowig and Kolliker on the histological characters of the embryos of certain compound Ascidians, they arrived at two important results. Firstly, that the external structureless envelope of the embryos, which, apparently, is identical with the external envelope of the adults, is, according to their analysis, composed of cellulose ; that this envelope is formed only when the division of the yolk is accomplished, and even when the exterior form of the embryo is indicated. Secondly, that this envelope, subsequently containing, as in Botryllus and in Aptidium, another structureless substance, fibres, nuclei, and crystals, is primitively altogether homo- geneous and unorganised. Hence it appears that the test of the Tuni- cates is a product of the activity of cells formed subsequently to the process of the division of the vitellus, and that primitively it is only a mass secreted by these cells. Its ulterior organisation is not yet understood, but remains an open field for much interesting and im- portant research. ANATOMY OF THE ASCIDIAD^E. — We have already referred to the external envelope of the Tunicates as being analogous to the cal- ciferous shells ortests of the other Acephalans; and the muscular sac enclosed within it, as the analogue of the mantle; and the membranous sac lining the mantle as analogous to the branchiae of the Acephalans. f The rest of the viscera of the Ascidians are enveloped in a peritoneum J, and the heart has, besides, its own membranous sac or pericar- dium. Thus the body, properly so called, appears as if divided into three cavities ; that of the branchiae, communicating with the exterior by the superior opening of the sac, * Hist. Brit. Molluscs, vol. i. p. 6. t According to Van Beneden, the longitudinal vessels of the branchije of the Ascidia; are more par- ticularly the analogues of the ciliated tentacles of the Bryozoa. J The peritoneum of Ascidia intestinalis offers a good example, being of firm consistence, circum- scribing and protecting the abdomen. TUSICATA. 1201 and in the base of which opens the mouth ; that of the peritoneum, which does not com- municate with the exterior by itself, but is traversed by the intestinal tube, which, arising in the branchial cavity, communicates with the exterior by the rectum and the anal aper- ture of the test ; and, lastly, that of the peri- cardium, which has no direct communication with the exterior. The position of the animal is always such, that of the two orifices the branchial is always the highest ; the entrance into the branchial sac being generally placed at or near the superior extremity of the body, and the oeso- phageal opening, at the base of the branchial sac, having an upward direction. In Boltenia and Cystingia the flexible peduncle, which is attached at the summit of the body, above the branchial orifice, allows the body to droop, thus giving the animal its normal position. In the ClavellinidfE, which have rigid peduncles continuous with the base of the test, the same normal relation of the internal parts is pre- served ; and although the intestinal loop in Boltcnia and Clavcllina is always directed to- wards the pedicle, yet this arises from the loop having, in the former an ascending, and in the latter a descending, direction. The muscular sac or mantle, enclosed in the external envelope, is attached to the in- ternal surface of the latter by an adhesion of the external surface of the extremities of its two tubular processes, which correspond to the two external orifices of the test, to the inner borders of these outer orifices {fig. 780.). In Ascidia there is often no in- timate cohesion at these points, merely an adaptation easily disturbed after death. In Cynthia, Boltenia, &c., on the contrary, the test and the tubular prolongations are strongly adherent. Beside this mode of attachment, there is sometimes a general loose adhesion formed by the epithelial tissue between the surfaces of the test and mantle ; and in Cynthia papillata there is a partial transmission of mus- cular fibres from the latter to the former ; and, lastly, there is the very slight attachment arising from the passage of bloodvessels from the body to the test. This free condition of the mantle within the external sac occurs throughout the Asci- diadcE, ClaveUinidcB, Botryllidce, and Pyroso- mid(E. In the Salpides and the Pelonaiadez, on the other hand, the mantle and the test are connected at very many points, or even throughout the extent of their contiguous surfaces. The mantle in Chelyosoma is more closely attached to the internal surface of the test than in other Ascidians ; its muscular tissue forming intimate connections between the various plates of the external envelope, and not only supplying the valvular pieces of the apertures, but also edging each of the larger plates with interlacing connecting fibres. Ex- cept at these muscular spaces the mantle ap- pears as a thin serous membrane. The interval between these two sacs is, during life, filled with some fluid; possibly a VOL. IV. secretion, or transudation through the one or the other of these envelopes ; for, except iu the case of those Ascidians whose mantle- tubes are not intimately connected with the test, the sea-water cannot be directly admitted into this cavity. The mantle is reflected upon the body, properly so called, and covers it externally, just as the peritoneum, after having coated the walls of the abdomen, is reflected upon the intestines ; with this difference, however, that it has no mesentery, and that the con- nection is only at the two orifices. It has an external serous layer, continuous with the internal membrane of the test, a muscular tissue more or less extensive, and an internal serous layer. It has also numerous ramifica- tions of nerves and bloodvessels. In Boltenia, Cystingia, and probably Bipapillaria, a tubu- lar prolongation of the mantle traverses the peduncle. The two tubes on the superior aspect of the mantle, which are directed towards, and protruding into, the two somewhat tubular orifices of the test, are more muscular than the rest of the sac, being surrounded with, generally very distinct, sphincters in addition to the fascicles of muscles that traverse them longitudinally, and are continued diagonally across the sac (fig. 780.). When open, the margins of these tubes are crenulate. The free extremity of the branchial orifice is some- times quite entire, but occasionally terminates in a circle of regular tooth-like processes, which are regarded by Dr. A. Farre as the ana- logues of the tentacles of the Bryozoa. By con- traction, the tubes are thrown into 5 or G folds. At the exterior angles of these folds in some Ascidians (A. intestinalis, Cynthia ampulla, &c.) there is a minute red spot ; in A. mammillata, the edges of the folds are more or less red- dened by an increase and diffusion, as it were, of these little red granules. Internally each tube has frequently at its base some slight valve-like prominences or folds; and the in- ner extremity of the branchial tube is always fringed with a circlet of simple or compound tentacular filaments. These, however, may more properly be said to belong to the bran- chial sac. The mantle becomes dusky and opaque, and its muscular tissue more distinctly seen, in preserved specimens. In its recent state it is more or less diaphanous, and usually of a sober tint ; but occasionally, in Ascidice, it is of a fine crimson (A. venosa), or variegated with crimson and white (A. virgi- nca), or spotted with red (//. aspersa) ; and in A. parallelogram ma it is ornamented with rectangular reticulating white lines and occa- sional bright yellow or crimson spots. In A. conckilega it is white, passing to blue ; and in A. arachnoidea it is dark blue. The branchiae of the Ascidiadac is a large bag of fine vascular network furnished with vibratile cilia, contained within the mantle of the animal, and lining the walls of that cavity (fig. 778.). Sometimes the branchial sac is oblong, oval, or rectangular ; and then 1202 TUNICATA. it occupies all the length and one of the sides of the cavity of the mantle (Cynthia). In Ascidia mammillata and A. monacha it is very long; and, after having descended to the bottom of the mantle.it is bent upwards upon itself, extending half way up the cavity again. A tube, differing in size in various species, which has its analogue, perhaps, in the retrac- tile operculum of the Bryozoa, conducts the water from the buccal aperture to the respira- tory sac. This tube or process of the mantle encloses the neck of the branchial sac. At the inner extremity of the tube, where it widens into, and is continuous with, the bran- chial sac, are frequently observed about five small valvular folds ; and below these there is always a circle of fleshy filaments or tentacular appendages (fig- 778. arid fig. 39 d. Vol. I. page 1 12. ANIMAL KINGDOM*). These are present also in the Clavellimdcc and the Botryllidce. They vary from 6 to 26 in number, and are either simple, as in Pkallufiia, or branched, as in Cynthia, Bol- tenia, &c. By detaching the anterior part of the respiratory sac of Cynthia, or others, and examining it from its inner and inferior aspect, one may perceive, at the inner mar- gin of the tube, several arboriform append- ages, somewhat large at the base, and having the branches either swollen at their extremi- ties, or finely laciniate and almost plumiform : in Cynthia Dione they are somewhat bipinnate. The number of the tentacles is difficult to be arrived at, as smaller filaments appear amongst the six or seven larger ones. The branches are generally directed downwards, towards the bottom of the sac, but sometimes are slightly curled upwards. Seen under the rni- croscope, these filaments are hollow ; and the extremities and swellings of the branches are cul-de-sacs. The several tentacles intercom- municate with each other by their hollow bases, and with the vascular network of the respiratory sac. The walls of these tubular organs are very thin and transparent ; traces of muscular fibre have been detected in their substance, and a circulation ; hue no trace of vibratile cilia, either on their outside or within their cavity. Van Beneden observes that a fluid traverses their cavity in a similar manner to the blood in the branchiae of the Doris. In Actinia and Holothuria simple and ramified filaments occur, that offer considerable analo- gies to the arborescent tentacles of Ascidiae. They are all hollow; and the fluid moving in their interior comes directly from the peri- intestinal cavity ; this great cavity, commu- nicating as in Bryozoa, with the tentacular appendages. The internal surface of the respiratory sac is sometimes uniform (in Ascidia, Pha/litsia, &c.), and frequently longitudinally plicated and disposed in deep and regular folds, all following the curve of the cavity, and termi- * This figure represents a Cynthia canopus cut open ; a, oesophagus ; b, stomach ; c, anus ; d, external anal orifice, closed ; e, branchial orifice, laid open ; f, branchial tentacles; g, nerve-ganglion; h, dorsal sinus; ft, ovary (?); i, I, indeterminate bodies. nating at a little smooth area above the pha- rynx (Cynthia, Boltenia, £c.). The folds are from 8 to 18 in number, and form the first indication of the four branchial laminae of the bivalve Acephalans. The structure of the membrane consists of an infinity of small, anastomosing vessels, generally cross- ing each other at right angles, anil forming quadrangular interspaces, which, under the microscope, are seen to be still more mi- nutely subdivided in the same manner. Milne- Edwards observes that in Pka/tusiaeiich of the meshes of the respiratory membrane is occu- pied by a minute spiracle, that allows of a communication between the interior of the branchial sac and the cavity of the mantle (the " thoracic chamber" of Milne-Edwards), the dorsal portion of this chamber being the cloaca, the base of which is occupied by the orifices of the digestive and generative tubes, and the summit of which opens externally by the anal aperture. In Cynthia ampulla the meshes are very irregular and almost inextri- cable, some of the minute vessels having apparently a spiral arrangement ; and the vessels are rather more numerously disposed around the cesophageal orifice. A somewhat spiral or vermicular arrangement of the ex- tremities of the branchial vessels exists also in Chelyosoma, as figured by Eschricht ; * and as seen in a very minute sessile Ascidia, from South America, in the collection of Mr. Bower- bank. In the respiratory network of Cynthia the large longitudinal vessels are seen to be the most prominent of all. They form, with the large transverse vessels, square meshes, which three other shorter vessels subdivide into four transverse meshes ; and these are further intercepted by extremely fine longitudinal vessels. The vertical vessels of this quadran- gular network may be said to arise from the transverse vessels, which communicate by each extremity with two vertical trunks, placed at opposite sides of the sac, and representing respectively the branchial artery and vein. The latter, in C. microcosm us and other As- cidians, bears a longitudinal series of small transverse tentacular filaments. Similar ten- tacles we shall have to describe as belonging to Chelyosoma (fig. 777. i). The angles of the meshes of the branchial O . tissue bear papillae, more or less prominent, in some genera (Ascidia, Chelyosoma, &c.) ; but in others they are not papillated ( Cynthia, &c.). These papillae, or minute pouches, are, according to Savigny, analogous to the fila- ments that border the branchial vein, in most of the simple and compound Ascidians, indi- cating the junction of the transverse vessels with that vein. The appearance of the reticu- lation is large and coarse in Cynthia, minute in Ascidia, and indistinct in Cyxtingia. Each mesh of this respiratory network is thickly fringed with vibratile cilia, as in the rest of the Tunicates and Acephalans ; and Van Beneden points out that this ciliated ex- terior of the branchial vessels is analogous to the ciliated tentacles of the Bryozoa. By the * Hoy. Danish Transact, vol. ix. pi. 1. fig. 6 & 7. TUNICATA. 1203 action of the cilia the currents arc sent in the direction of the oesophageal aperture. In Ascidia papillosa and Cynthia microcosm us, a little soft tubercle is situated on the interior of the branchial sac, not far from the orifice, between the two branchial veins, not observed in other Ascidians, but seen in all the Botryl- lians. On the internal surface of the sac are also seen several prominent lines, 12-15 in A. mammillaris and A. papillaris, 5-6 in C. am- pulla, more or less distant from one another according to their length. These are folds forming gutters converging towards the mouth, and having also transverse channels leading from one to another. Above they appear to terminate in culs-de-sac. The vibratile cilia covering them are very long and numerous. Van Beneden found that, on placing for a short time a living Ascidian in water coloured with carmine, the particles of the colouring matter quickly filled these little ducts, making them appear like injected vessels. This dis- tinguished naturalist considered them to be somehow connected with the digestive appa- ratus, moulding, perhaps, the particles of food into cord-like masses before entering the stomach. In Chclyosoma (jig. 777. z) there is a remark- Fig. 111. A.nair,my of Clielyosoma Macleayanum. (After Eschrieht.) The inner or under side of the superior plated surface of the animal is shown, the branchial cavity being split open, and the abdominal viscera re- moved, a, branchial orifice, partly closed by a membrane, and surrounded by its hexagonal sphincter muscle and the accompanying six fan- shaped muscles; b, anal orifice, similarly provided with muscles; e, f, muscles bordering the carapace- plates ; el, the central hexagonal plate ; e, e, e, e, the surrounding plates; f, the nerve-ganglion and nerve-fibres ; a Griffiths® de- scribed by him. In a unique specimen of P. Tiircica, examined by M. Savigny, the intestine lay to the left instead of the right of the bran- chial sac, and was found bending backwards and embracing the stomach from below, in- stead of bending forwards at some distance from the pylorus, approaching the superior border of the stomach, and then terminating in the rectum. In a specimen of C. Momus, the alimentary canal was also found on the left-hand side ; but, by a very peculiar intro- version, the pharynx was placed at the pos- terior instead of the anterior extremity of the branchial sac. The intestine descended as far as the bottom of the mantle, folded it- self forward, and ascending parallel to itself, terminated opposite to the pharynx ; so that the anus and the cesophageal aperture both opened into the branchial orifice. The ex- ternal communication through the anal orifice existed as usual. Both of these malformed individuals had their ovaries full of egi^s, but were not, apparently, in strong health, and were more than usually infested with ento- mostraca. In the catalogue of the Hunterian Museum (vol.i. pi. 5. fig. 2.), a dissection of an Ascidian is figured after a drawing by John Hunter (the original specimen, however, has not been found), in which there is, apparently, an abnormal elongation of the oviduct, which is accompanied by a slight granular line, both lying on a large tapering tube having much the appearance of intestine ; the anus, how- ever, shows itself projecting from the side of this tubular body some way lower down, in its usual place. The oviduct, and, apparently, the accompanying elongated tube, terminate externally at a minute aperture placed in the sulcus between the two projecting terminal orifices of the test. The oviduct, however, barely reaches this aperture ; and its accom- panying granular line terminates still lower down. Organs of circulation. — In the Ascidiadez there are two large vessels or sinuses, the dorsal and ventral, to which the branchial capillaries, on the one hand, and the heart and peri-intestinal cavity, on the other, are intermediate. The circulation is of the mixed or reptilian type ; both sinuses being in con- nection with systemic and respiratory capil- laries, and the blood, consequently, being sent by one impulse both to the system and to the branchia?, and ultimately returning from both by the same channel. We are prevented from calling either of these sinuses arterial or venous, on account of the periodic reversal of the circulation, mentioned incidentally above, and more fully detailed hereafter, whereby they are alternately changed from vein to artery and from artery to vein. One of the branchial trunks, terminating at the heart, however, answers to the branchial veins of the Gastero- pods and Bivalves ; the opposite, and often double, trunk may therefore be looked upon as the branchial artery, and is connected with the veins of the body. The Ascidia, like the rest of the Acephala, has but a left or aortic ventricle, and no ventricle at the union of the vena cava and the pulmonary artery. This aortic heart or ventricle is not always easy to be seen. When the branchial sac is simply oblong, it is situated towards its base ; and consequently, when the branchial sac is as long as the body, it is situated towards the base of the mantle ; and when the sac is shorter than the body, it is placed near the centre of the mantle. When the branchial sac is bent upon itself, the heart is situated at the. curve, and then it is always near the middle of the body. In general its position, according to Cuvier, appears to be deter- mined rather by that of the mouth, than that of the rectum ; but M. Milne-Edwards and Van Beneden consider that it follows in its displacement the organs of generation rather than the mouth. The heart in the Tunicata is never traversed by the rectum, as in other Accphala. In the Ascidians the form of the heart is oblong, and thin at the two ends, or more or less tubular. Its substance is contractile, but extremely thin and transparent, so that it is scarcely distinguishable in the cavity of its highly pellucid pericardium. Cuvier ob- served that, in the species in which the branchial sac is bent upwards, he was not able clearly to discern a dilatation sufficiently marked to deserve the name of a heart, and was inclined to think that possibly in this case the heart's function was performed by the artery. Here, however, we may notice that specimens preserved in spirit generally afford but very indistinct traces of this organ ; and Cuvier does not appear to have had the opportunity of studying transparent specimens of the living animal, in which the heart can be detected by its pulsating movements. In Ascidia inteslinalis the heart, which is very long, and extended under the ventral border of the respiratory sac, communicates with the great thoracic sinus by a longitudinal slit situated at a little distance from its an- terior extremity ; and when the peristaltic movements of the heart advance from behind forwards nearly all the blood contained in its cavity passes into this sinus, penetrating the vascular network of the branchial sac, and passing into the dorsal sinus, whence it is spread amongst the viscera, and returns to the posterior extremity of the heart not far from the anus. During this time the heart consequently performs the functions of a branchial ventricle, and the great thoracic TUNIC AT A. 1207 sinus is a kind of pulmonary artery. But when this state of things has lasted some minutes, the direction of the peristaltic move- ment of the heart is inverted, and the blood, instead of traversing the branchial network from below upwards as previously, moves from above downwards, and passes from the great thoracic sinus into the heart. The latter is then an aortic ventricle, and the sinus a branchial vein or aortic auricle. In a very fresh and uninjured individual, of Cynthia am- pulla, Van Beneden counted 45 contractions in one direction ; and then, after a rest during the space of two pulsations, he counted 160 to 170 in the other, the pulsations being about 70 per minute. In injecting the vascular system of the simple Ascidians, M. Delle Chiaje thought he found certain valvules so disposed as to hinder the return of the blood from the aorta into the cavity of the heart, or from passing again from the heart into the vessels through which it had arrived there. But by careful observa- tions on living specimens, both Milne Edwards and Van Beneden have established the fact, that, as in the Botryllida:, the Salpidcc, and the other Ascidian families, the blood of the Asciclifidfs, after having flowed for some time in one direction, traverses the same circle in an opposite direction; a condition that would be impossible were any valvular hindrances to return currents of the blood present. In Chelyosoma* , the heart is very distinctly seen in the animal when dissected ; it lies near the resophagus, and has two distinct chambers. The aorta rising from its anterior part is a stoutish vessel, and at first lies close to the in- testine : it afterwards runs in the space within the intestinal loop, ultimately breaking up into largish branches, distributed on every side. The ramifications divide some 4? or 5 times, and terminate somewhat abruptly, the extre- mities appearing as if closed. Throughout the surrounding generative organs there is a very fine network of vessels, but whether they are arteries, veins, or gland-ducts is un- decided. A largish vessel running along the left side of the stomach and duodenum ap- pears to return the blood to the branchial sac. Mr. MacLeay describes the heart of Cys- tingia as being large, ovoidal, and of a lobular appearance ; and having four vertical, lateral openings, capable of considerable dilatation. In Cynthia ampulla the heart is placed a little within the great intestinal loop, and near the middle of the body : it is fixed on an oblong vesicle, enclosing calcareous concre- tions. This vesicle is situated exterior to and above the first or principal bend of the intestine. Its colour is a greenish yellow, and it has apparently no aperture, or commu- nication with other organs. The heart itself is a slightly bent tube, with very elastic walls : it has two openings ; a single large aperture on one part, and opposite to it three ves- * Described by Esehricht (Royal Danish Trans. vol. ix. p. 12.), to whom we are indebted fur much valuable information, both with respect to this genus and the Salpians. sels that carry oft' the blood in different di- rections.* " The circulation of the Ascidians," says Van Beneden, " differs but little from that of i\\eBryozoa; and is transitional between that of the Polypes and of the Molluscs. If we re- move the heart of the Ascidian, the disposi- tion of parts is very similar, and the simpli- fication of an apparatus cannot more visibly take place. The Ascidia is but a digestive canal suspended in the midst of external mem- branes, with a liquid moving in the peri- intestinal space. A colourless liquid (blood) occupies this cavity ; but it is only in the branchial network and tentacles that it can be said to be contained in vessels. All around the intestinal tube this fluid is alter- nately moved from right to left, and vice versa. In the vessels composing the vascular net- work, and in the respiratory tentacles, the same movement of the nutrient fluid takes place. This blood contains somewhat regular globules, white as the containing liquid, that indicate the course of the fluid. In some in- dividuals the blood is yellowish. M. Milne- Edwards has observed an Ascidia with red blood."-]- Mr. Lister observed that in a sessile Ascidian half an inch long, the blood-globules were about the same size as those of the minute Perophora, viz. from '00025 to '0002 inch in diameter. Van Beneden, to whom we are indebted for so much information with regard to simple Ascidians in general and Cynthia ampulla in particular, has observed in living specimens of this species, that the blood is distributed to each branchial trunk at the same time, and with the same direction, ascending and de- scending alternately. According to this, the heart, contracting in one direction, sends blood towards the branchise, filling all the vessels at one time, and recalls it by contract- ing in an opposite direction. That a series of contractions in one direction, during a certain time, may take place without engorgement, there must be a direct communication between thebranchias and the peri-intestinal cavity; and this is afforded, according to Van Benedcu, by the respiratory tentacles, see p. 1202. Seen under the microscope, the contractile tissue of the heart affords no trace of mus- cular fibre. The contractility remains some time after the removal of this organ from the body ; and that without being irritated. Nervous system. — A single ganglion, oval, soft, consisting of a saclike neurilemma, enclos- ing nerve-cells or neurine, placed in the sub- stance of the mantle, and between its two tubu- lar orifices, gives off' four branches, two of the branches forming a loop around either tube, and other lesser filaments distributed about * In the Physiological Series of the Hunterian Museum there is a highly illustrative dissection of ,C. tulerculata (No. 898." B.), prepared by I'rof. Owen, that beautifully exhibits the heart and its pericardium, the branchial vessels, partially in • jected, and other organs. f Recherches Zoologiques faites pendant un Voyage en Sicile. Comptes Eeudus, 23 Nov. IS i 1. 4 H 4 1208 TUNICATA. the mantle. Besides these, Meckel* found in the Ascidia gelatinosa one larger and two smaller ganglia between the stomach and the branchial sac. Cuvier considered the large ganglion to be the analogue of the " inferior " ganglion of Molluscs, found in the Bivalves between the branchiae and towards the origin of the tube that admits the water ; and ob- served that he had not seen any nerves ter- minating at a brain, nor the brain itself, which must be situated by the mouth at the base of the branchiae. The great nerve-ganglion in Chelyosoma, ^"' long and £'" broad, cylindrical, and jellow- coluured, lies near the middle of the inferior surface of the plated test, and a little to the left (fig. 777. f). From its anterior angle it sends four branches, two of which form a half- circle around the star-shaped muscular ap- paratus of the branchial orifice, the other two losing themselves in the muscles bordering the nearest plates. From the posterior angle arise eight nerves, four going to the anal orifice, and four to the lateral muscles of the plates (/#. 777. d, g). Special senses. — In the last-named genus there are two remarkable bodies found in connection with the nerve-ganglion, which Professor Eschricht, to whom we are indebted for a careful anatomical description of Clie- lijosoma, considers probably to appertain to the function of hearing (Jig. 777. g, }i). One of these bodies has the appearance of a minute bladder, filled with a whitish substance. It measures V" long, and ^'" broad, and lies to the left of, and quite close to, the ganglion, being at its posterior extremity strongly ad- herent to it, or to the base of one of the nerves proceeding from it, by means of a stalk-like attachment. Through its diaphanous walls a row of arched transverse stria? are discernible, which are either folds of the parietes, or a par- tition. The other body is pear-shaped, about ^•" long, lying anterior to the ganglion and the little bladder-like body, and, like them, be- tween the serous membrane and the respira- tory sac ; its stijm is placed between these two bodies, and its head advances up to the hindmost muscle of the branchial orifice. It seems to be of tolerably firm consistence, but it is not at all bony or horny. Its thick, an- terior portion is barely \'" broad, and has anteriorly a deep hole, which seems to lead into a large cavity ; the border on all sides of this pit is prominent, gently declining to a blackish little body within. The Ascidia; have frequently around the ex- tremity of each process of the mantle, i.e. the branchial and anal tubes, a row of coloured points or ocelli, similar to the imperfect organs of sight present in the majority of the bivalve Acephalans, where they are arranged along the margin of the mantle, or dotting the edges of the siphonal orifices. The number of these oculifonn points correspond with the number of processes or folds that the margins of the tubes respectively bear ; about eight in the branchial, and six in the anal tube. They are usually red, as in A. vitrea, A. virginea, A. pru- num, and others; in A. mcntula they are yellow, with a central red spot. M. Milne-Edwards has observed similar eye- like points around the oral tubes of Amanroii- rium and Parascidia, belonging to the botryl- lian group of Tunicates. Some of the Salpce also have ocular spots. Besides these oculifonn points in the adult animals, Van Beneden has observed in the larvae of Cynthia ampulla, on the side of the gibbous or anterior portion representing the head, some black points that he regards as true eyes. Speaking of the development of the young Ascidian in the egg, Van Beneden describes the separation of the contents of the incubated ovum into an external layer, to form the skin and the tail of the young animal, and a second layer, of which subsequently the walls of the alimentary canal are formed; and, thirdly, an internal vitelline mass. " In the thickness of the external layer," says Van Beneden, " there appears towards the middle of the body, and rather inferiorly, a cell filled with black pigment, which must be regarded as the organ of vision. It persists during the whole term of the animal's locomotive exist- ence, and disappears after it becomes fixed. These organs," he adds, " which we may well call eyes, although so simple, are constant ; sometimes two are discernible on one side." M. Milne-Edwards has also seen in the larvae of the compound Ascidians one or two blackish points, but towards the posterior extremity of the body ; he merely notices them, without assigning for them any function. " We consider ourselves," says Van Beneden, " sufficiently authorised, by all that we have seen in the embryos of the free inferior ani- mals, to elevate these pigment-cells to the dignity of an organ of special sense. To say that the presence of an eye implies that of an optic nerve and of a brain does not appear to us to be more just than to say that there are muscles when there is movement. We have the example of the Hydrcc, that, without mus- cles, without nerves, without brain, and with- out a special organ of feeling, are sensible to light, and avoid or approach at will bodies whereby they are affected. And if the Hydra, without special apparatus, is sensible to light, we do not see why a cell of pigment may not be the first rudiment of the organ of sight. The appearance of the eye and the ear, in the animal series, takes place in similarly simple rudimentary forms." * Generation. — The AscidiadcE are all herma- phrodites. Between the fold of the intestine, and close to the liver, when the latter exists, there is observed a whitish glandular organ; this is the ovary. An undnlatory duct passes from it, which, following the rectum, opens near its extremity into the cloaca. Opposite to the opening of the oviduct, Carus noticed the orifice of another glandular organ, which he thought to be either a male organ, or serving * Schalk, De Ascidiarum Structura, Halle, 1814. * Van Beneden, Mem. Brux. Acad. vol. xx. p. -10. TUNICATA. 1209 to furnish the gelatinous covering of the ova. The ova of Axc'idics, instead of passing from the ovary to the branchiae, there to be deve- loped as in a uterus, are emitted externally, by the oviduct conveying them into the cloacal cavity, whence they are carried outwardly by the current of water through the external anal aperture, or through the communicating lateral opening into the branchial sac, and thence through the branchial aperture. Cuvier says that he found some minute egg-like bodies between the branchial sac and the mantle ; a position very analogous to that held by the ova of the bivalve Molluscs ; and he thought it probable that ova so placed were fecundated by seminal fluid emitted by the same duct that leads from the ovary. These granules, however, M. Savigny appa- rently regards as little glands. The generative organs are sometimes single and sometimes double ; in the latter case, the two halves, right and left, are completely se- parate, as in other Acephalans, and emit their products separately into the cloaca, which serves as a kind of incubational or marsupial pouch. The ovary is single in P/iallusia, Pandocia, and Dendrodoa ; it is usually double in Bol- teniri, &c. In Cynthia the ovary is either single or multiple, sometimes very large, form- ing long groups of clustered globules, each globule being crowded with ova. The single ovary is sometimes enclosed within the intestinal loop, without adhering to it, and sometimes, as in C. papiliata, &c., it lies against, and is adherent to, the rectum. In C. papiliata the ovary is bent on itself and terminates by an oviduct at each end. In C. canopus there are 2 — 4* or more ovaries ; those on the right side are placed against the rectum, and all terminate, as usual, by oviducts. In C. microcosmus there are two ovaries on the left side. They are composed of separate gelatinous lobes, having the appearance of a bunch of grapes. In C. mytiligera the ovary has the form of a membranous pouch, which furnishes points of attachment to the exterior of the branchial sac, and is fixed to the mantle and to the inner part of the intestinal loop. Its duct is very thin, and follows the usual course by the side of the rectum. In C. polycarpa and C. pomaria, Saviguy describes certain numerous hemispherical or conical bodies adhering to the mantle, almost fifty in number, and disposed in rows, somewhat cor- responding to the six branchial folds, as being possibly the ovaries of these species. These bodies are without ducts ; they are formed of a mass of granules resembling the eggs of some other Ascidians ; they are much com- pressed, and resemble a compound berry held in a 5-fid cup ; they have apparently no com- munication with each other or externally, and are accompanied at their base with gelatinous, transparent, subpedunculated vesicles, appa- rently empty. In C. papiliata, which has other generative organs, there are many rows of isolated, gelatinous, semitransparent, wrinkled vesicles, corresponding to the arrangement of the branchial folds, attached to the mantle, and receiving bloodvessels from it. The lobes of the ovary in C. microcosmus, after the emis- sion of the eggs, wither into wrinkled vesicles closely resembling these sessile vesicles in C. papiliata. Certain soft bodies observed in C. microcosmus, and somewhat similar to the above, Cuvier regarded as fat, serving as stores of nutritive matter ; but with this Savigny cannot agree. Savigny also points out the occurrence of various irregular, but somewhat .similar fungous or fleshy excrescences on the mantle (Jig. 39. i,l, Vol. I. p. 1 12.), ovaries, and intestines, sometimes even quite investing the latter; but these are quite distinct from the ovary-like bodies above described. In Soltenia reniformis the ovaries are double, unequal in size, elongate, formed of coarse subcubical lobes, situated one on each side of the body, and directed towards the anal orifice; the right or smaller ovary, straight, claviform, fitting closely into the ascending loop formed by the stomach and intestine. The left ovary, larger and less lobulated, is on the opposite side, between the mantle and the branchial sac ; it is undulating, and extends downwards behind the branchial vein. The tissue of these ovaries is a yellowish membrane of distinctly cellular structure, containing groups of large opaque ova and smaller clusters of exceedingly minute diapha- nous granules. The ovaries of Cystingia are two free racemes composed of globular bodies, as in Cynthia, arranged on the two sides of the body with the branchial sac and stomach between them. In Dendrodoa (fig. 778. k) the ovary is single and branched, consisting of a trifurcate, cylindrical stem, bearing at its base on one side a forked branch, and on the other a simple one, all of the same thickness ; it is situated on the left side of the body between the mantle and the branchial sac. In Chclyosoma, Professor Eschricht de- scribes as an ovary two darkish bodies, filled with vascular ramifications ; placed, one be- tween the liver and the rectum, and the other around the fold of the intestine. Another somewhat similar organ, traversed by rami- fying vessels, and placed at the anterior ex- tremity of the body, is apparently the testicle. Connected with this organ, a distinct sigmoid duct runs to the right posterior angle of the body, from whence a filamentous tube passes along to the left posterior corner.* In Cynthia ampulla the generative organs are situated in the intestinal fold, and appear at first sight to form a single organ ; but by the aid of the mi- croscope two distinct organs, male and female, are easily recognised (fig. 779. A). The testicle forms a sort of framework around the ovary ; it is of a milky white colour, and is composed of an infinite number of short, twisted cosca, visible to the naked eye, and somewhat ana- logous to the seminiferous canals composing the testicles of higher animals. Three or four mammillary processes rise from the anterior * Eoyal Danish Transact, vol. ix. p. 13. 1210 TUNICATA. surface of this organ : they are hollow in the centre, and emit a milky fluid, which is shed Fig. 779. A, generative organs of Cynthia ampulla, situated in the fold of the intestine. (After Van Buneden.} a, stomach and its aperture (destitute of ceso - phagus) ;. b, rectum and anus ; c, ovary, with its outlet into the cloaca ; d, testicle, enveloping the edges of the ovary. B, magnified portion of the reproductive organs of Ascidia grossidaria. (After Van Beneden. ) a, testicle ; b, ovary and ova. into the cloaca, and contains, or rather is almost composed of, spermatozoa, with dis- ciform heads and filamentous tails. The ovary is blackish, and is situated in the midst of the testicle. Its situation corresponds to that of the ovary of the Limaces among the Gasteropods, •which is surrounded by the liver. It is easily distinguished from the testicle by its colour and by the appearance of its contained eggs. The oviduct opens into the cloaca by the side of the anus. In Ascidia grossitlaria the eggs, seen through the walls of the ovary, are of a fine red colour, and are contained in separate sacs, the ovary appearing like a bunch of grapes (fig. 779. B). Van Beneden has distinctly seen in all of these ova the two germinal vesi- cles. The vitellus is at first white, but during development it becomes of a deep red. Bv the side of the ovary is another series of sacs without ova, and some free cells containing a great number of other more minute cells moving about in their interior, and which when shed swarm about like spermatozoa. These appear to constitute the male organ, and its disposition accords with that of the Amaroucium argus, and with that of the Bri/ozoa (Van Beneden). There remains much to be elucidated with regard to the generative functions of the Asci- dians. The male and female organs are always associated together, and are apparently each provided with efferent ducts. It appears, however, doubtful whether or not occasion- ally the ova and the spermatozoa may not be brought into contact either in the organs them- selves or in the ducts, as well as in the cloaca. We may notice that the disposition of the sexual organs in the Bryozoa, to which in so many respects the Tunicata bear reference, appears to be, from Van Beneclen's observa- tions, as follows. A male and a female organ are separately developed in the peri-intestinal cavity. Each is formed of cells, and in these cells are formed others, which become either vitellus or spermatozoa. When the latter cells are matured, the walls of the ex- terior or mother-cells are burst, and their con- tents are shed into the fluid filling the cavity around the intestine. It is here the male and female elements come into contact, and the ova are subsequently discharged by an orifice at the side of the anus. In some compound Ascidians the peduncle- like post-abdomen forms a receptacle for the ova ; and so does the pedicle of Clavel- lina, as in Cirrhipeds ; but the pedicle of Boltenia and similar forms does not appear to be used for that purpose. Muscular system. — The Astidiadce being fixed in their adult state, have no muscles of general locomotion ; but they have numerous muscular bands by which they can effect cer- tain movements of contraction and extension. The muscles do not consist, as in Bryozoa, of isolated fibres folding themselves irregularly during contraction ; but each muscle is com- posed of many fibres united. They make their appearance in the young individuals contem- poraneously with the appearance of the respi- ratory sac. The muscular fibre of Tunicata, like that of the whole of the Acephala, is of the organic or unstriped type. In the Asddiadce, as in other Tunicates, the muscular tissue is chiefly developed in the mantle ; the muscles of the heart and in- tesinal canal (if present) have not been observed. The muscles of the mantle are very thin and narrow bands, generally at considerable distances from one another, sur- rounding all the body of the animal from the anterior to the posterior extremity, and uniting in part with one another on the median line of the dorsal walls (Jig. 780.). Fig. 780. Muscular sac or mantle of Boltenia ren'formis. ( Original.') In Ascidice the mantle is more muscular on the anterior and largest part, and more membranous posteriorly. Externally there is a layer of longitudinal muscular bands, and internally of transverse bands. In some TUNICATA. 1211 (A. infestinalis, £c.) the exterior layer is much the thickest, and is composed of about twelve distinct fascicles, the fibres of which are somewhat separated from one another, insensi- bly disappearing on the anterior and superior borders. In others (Cynthia microcosmus, &c,), this external layer is very slight, and formed of distinct fibres, whilst the internal fibres are stronger, transversely oblique, and interlacing. Circular bands of muscles generally surround the tube of each orifice, and are rather stronger towards its base. The fibres forming these collars of the two tubes occasionally in- terlace with each other at the interval between the tubes, in a figure-of-eight pattern. Some- times these muscular collars or sphincters are very indistinct, and not so apparent as another set of fascicles, which run in a diagonally transverse direction across the sac, and pass up the sides of the tubes, converging at the orifices. The latter bands diverge from the two orifices in two sets, which in part cross each other obliquely, and form an open net- work. In Chclyosoma (fig.lll.a,b) each of the six triangular valvules that surround either orifice is furnished with a fan-shaped set of muscular fibres, adhering at one end to the inner sur- face of the test, and at the other extremity to a small papillary process on the valvule. Be- sides this set of muscles, and within them, is another set which passes laterally from one papilla to another, forming a sphincter, the base of which is hexagonal. There are other strong subcutaneous muscular fibres passing from the edge of the upper part of the tunic to that of the lower, and also from the edge of each of the coriaceous plates forming the upper surface (c, c). Bv the action of these muscles, the body or inner sac of the animal is transversely con- tracted and somewhat lengthened; the tubular processes also of the mantle are closed, and more or less retracted. When the animal is alarmed, the contraction takes place rapidly, causing the water contained in the respiratory and cloacal cavities to be ejected by one or other of the orifices to the height of even three feet. There is considerable analogy between the muscular system of the AsddlcB and that of the Bryozoa. In the latter there are retractor muscles of the sheath and the intestinal tube ; and in the interior of the cells there exist also transverse oblique cords, traversing the peri- intestinal cavity, and attached to one or the other surface of the skin. These transverse muscles contribute to open the tentacular circlet; and in the Asridue, by their contraction, produce the jet that escapes from each of the two apertures. Embryo-genesis of the Simple Ascidians. — In examining under the microscope a portion of the ovary of a recent Ascidia, eggs in all stages of development may often be observed. In describing the various conditions and modifi- cations of the ova of this family in course of development, we shall borrow largely from the careful and extensive researches given to the world by Professor Van Beneden, to whom naturalists are so deeply indebted for much valuable information on the subject of the em- bryo-genesis of many of the Polypifcra* and other groups of animals. The earliest form of the ovum is a simple vesicle; it next appears as a vesicle with an inner vesicle, which is evidently " the vesicle of Purkinje ; " and, thirdly, with a second, still smaller vesicle, " the vesicle of Wagner ;" these latter vesicles, one within the other, being enveloped in the outer or vitelline membntne (fig- 781. A). The space between the external membrane and Purkinje's vesicle is occupied by a sub- stance, at first clear and probably fluid, but soon appearing granulated, constituting the vitellus. This yolk increases rapidly, soon oc- cupying the whole ovum : at the periphery its granules or cells become organised (fig. 781. B), uniting among themselves, and forming a continuous sacciform membrane. The mode of growth of the vitellus is by new cells being formed in the interior of the large older cells, and subsequently producing others in their own interior. The growth of the whole ovum is evidently carried on by this process. The whole surface of the vitellus soon after- wards becomes embossed, presenting a mul- berry-like appearance (fig. 781. c). The ger- minal vesicles disappear. At the centre of each lif.tle mammilla of the surface a trans- parent vesicle becomes distinctlj' visible, and the whole appear like so many ova each with the vesicle of Purkinje. These mammillae in- crease, and their peripheral substance rapidly becomes granulated, in a similar manner to the change that took place in the whole vi- tellus. The mammillated appearance is now soon lost from the growth of the granules, and the surface becomes uniform, the mam- millae of the periphery uniting into a mem- brane, which constitutes the blastoderm. Ac- cording to Milne-Edwards, the blastoderm in the BotryUidce is formed at a determinate point only ; but in Cynthia ampulla (the species in which Van Beneden watched the modifica- tions of the ovum) the latter observer feels assured that it is formed simultaneously all over the yolk, as in all the inferior animals. At this period a number of vesicles become somewhat regularly arranged over the exterior of the ovum, which by their union with one another form a new enveloping membrane. Beneath this membrane a space, occupied by fluid, soon becomes apparent. All over the exterior of this new membrane are distributed white, transparent vesicles, having much the appearance of oil globules. This envelope soon becomes more and more extended by the increase of the contained albuminous fluid, and a second membrane appears beneath it, on the surface of which also oil-like globules become apparent, as on the external mem- brane (fig. 781. D). The ovum is now com- posed of an external membrane, of a white * See POLYPIFEIIA ; also Papers by Prof. Van Beneden on Campanulai-ia, Tubularia, and Bryozoa, Mem. iirux. Acad. torn. xvii. xviii. and xix. 1212 TUNICATA. fluid layer, another thin transparent membrane, an organised layer forming the periphery of the vitellus, and lastly of the soft yolk in the centre, the vitelline membrane and the blas- toderm forming one with the vitelline mass. The external membrane and the albuminous layer beneath it appear to be formed exter- nally to the ovum by the oviduct or the ovary; and as they envelop the ovum after its com- plete development, they may be considered only as accessory parts. It being uncertain whether the ova in which these changes take place, have been subjected to fecundation whilst still in the ovary or ovi- duct, there arises the interesting question as to what extent of modification, even to the disappearance of Purkinje's vesicle, and the mulberry-like condition of the vitellus, can take place before the ovum has received the stimulus of the seminal element. During the changes of the ovum in this first period of its development, the colour of the egg is occasionally subject to certain modifica- tions. In Ascidia grossularia, the ova become of a bright red colour, and in some species no change of colour takes place. In Amaroucium, a compound Ascidian, the ova change from a pale to a deep yellow. The second period of development is marked by the prolongation of one side of the yolk to form the caudal appendage. The ovum has now a chorion, albumen, and yolk, the two latter being separated by a fine membrane. The vitelline or embryonic mass becomes con- tracted about its middle, and is somewhat bean-shaped. From this time there are ob- servable two extremities, one lengthening it- self, as the other becomes more and more globular; and respectively representing the caudal appendage and the body (Jig. 781. E). f \ a Development of Cynthia ampulla. (After Van Beneden.~) A, ovum, with the vesicles of Purkinje and Wagner. B, the same further advanced, with surrounding vitelline globules, c, the central vesicles have disappeared, owing to the development of the vitellus ; the ovum presents the appearance of an agglomeration of ova, or the mulberry-like aspect. D, further developed ovum, with double external membrane and intervening transparent liquid. E, the yolk elongated, partially divided in the middle ; the larger portion becoming the trunk, and the narrow portion the tail, of the larva. F, the embryo at the full term of incubation : a, anterior process; b, eye; c, integu- ment. G, the same, further advanced ; the caudal portion entirely absorbed, leaving the tegumentary elongation empty; a, anterior process. H, the same, further advanced; superficial apfiendages still present; internal organs more distinct, i, embryo nearly perfect; a, branchial orifice with tentacles; b, anal orifice ; c, eye ; d, oesophageal collar ; e, ( ?) ; ff, ciliated circles, rudiments of respiratory organs ; <;, , vas dcferens, and its opening in the cloaca. The separate anal orifices are frequently destitute of the crenulated or denticulated margin that surrounds the branchial tube. This condition has afforded a distinguishing character for some of the minor groups in Milne Edwards' classification of the Bo- tryllida:. In Polyclinum, Amaroucium, Bo- tryllus, and other genera, the anus, instead of opening directly outwards, empties itself into a common cloacal cavity, that belongs to a number of individuals, and is in the form of a large canal hollowed out of the common tegumentary mass. This is frequently rami- fied interiorly, as in Botrylloides, and termi- nates at the opposite extremity by a simple TUNICATA. 1219 excretory orifice, not occupying the centre of the " system," but placed nearly at one of the extremities, and communicating with the in- dividuals situated at the other end of the group by means of the interior canal. In Amnroucium the fascal or anal orifices, by which the common cloacae open externally, are wide open during life, and easily per- ceived ; their form is round and their border thick ; but after death they contract, and are so much sunk in that they are demonstrated with difficulty. The anal orifice in some genera is sur- mounted by a membranous languet, either simple or trifid (Jig. 783. i'). Fig. 783. Anatomy of BotrylJoides rotlfem. (After Milne- Edwards.) Lateral view of an isolated individual magnified. c, branchial orifice; e, branchial stigmata; /, thoracic sinus ; h, cloaca ; i, anal orifice ; V, supra- aual languet ; j, nerve-ganglion ; k, oesophagus, /, stomach ; m, first portion of intestine, or duo- denum; m>, second portion, or chylific ventricle; m", third portion, or rectum ; n, anus, opening into the cloaca; q, testicle; r, vas deferens ; t, radiciform appendage, or proliferous stolon ; t', reproductive germs ; x, liver ( ?) ; a-', its excretory duct. In pointing out the natural groups of the associated Ascidians we have spoken of the division of the body into distinct portions, as the thorax, and super- and post-abdomen in Amaroucium (Jig. 782.), and in Polydinum, where they correspond to the three vertical chambers of the animal's cell ; and into the thorax and abdomen in Didemnum. The latter arrangement resembles that of the Cla- vellinee; but in the Botryllians, on the other hand, no distinct separation is observable, the viscera being pushed up by the side of the branchial sac, as in the Perophorce and the simple Ascidians (jig. 783.). The thorax is generally more or less cylindrical, sometimes hemispherical (jig. 769.) or subglobose, and contains the branchial organs. In Botryllus violaceus there are two little glandular tuber- cles, one on the right and one on the left of the buccal orifice, and situated at a nearly equal distance from the superior extremity of the ventral sinus and the dorsal nucleus or nerve-ganglion. The branchial sac of the BotrylKd The nerve-ganglion between the two orifices, or rather on the dorsal side of the buccal orifice, is generally more or less distinct in the Botryllidce. The circii/afion of the Botryllidce does not materially differ from that of the other Asci- dians, and has the same peculiar periodical change in the direction of the blood-currents. In the Polyclinina the heart is placed quite at the inferior extremity of the post-abdomen. It is invested with a thin, transparent pericar- dium, and has the form of a large contractile tube, bent on itself, and tapering at the ex- tremities. In the Didemnina the heart is shorter, and instead of being situated beneath the ovary, it is lodged with that organ, by the side of the intestinal loop, this condition approaching that existing in the Clavellinides. Lastly, in the Botryllina, it ascends still higher, being seated near the stomach, nearly at the base of the branchial sac. Milne-Edwards, to whom we are indebted for the preceding facts, remarks that these different positions of the heart always coincide with analogous changes in the position of the ovarium. It is also the same, says he, in the simple Asci- dians ; and Cuvier was, without sufficient reasons, led to consider that the heart fol- lowed in its position that of the mouth. If, says M. Edwards, we separate from the common test of any of the Polyclinian species a lively individual, and place it under the mi- croscope with a little sea-water, the move- ments of the heart may be easily studied. The heart's contractions succeed each other somewhat regularly, but they are not brisk and extending at once through the organ, as in the generality of animals. The contraction commences at one of its extremities, and the narrowing of the tube is propagated in an undulatory manner towards the opposite ex- tremity, in a manner somewhat similar to the peristaltic movements of the intestines in the higher animals. For some time the contrac- TUNICATA. 1221 tions follow each other somewhat rapidly, and have all the same direction ; but suddenly they are arrested, and then recommence in a con- trary direction. The blood thus sent sometimes from behind forwards, and sometimes vice versa, ascends towards the thorax ; but does not appear to be conducted thither by vessels. It is poured out between the inner tunic of the abdomen and the viscera lodged in that cavity ; and here it forms currents, which vary in their position according as the movements of the animal, or any other mechanical causes, op- pose their passage. In general, however, the chief portion of the blood ascends by the dorsal or the ventral surface of the abdomen ; and after having bathed the surface of the viscera, it gains the base of the branchial sac. When the heart's contraction is from behind forward, the ascending current passes along the anterior side of the abdomen, and the blood enters a large vertical canal, on the front of the respiratory cavity, termed by Milne-Edwards the great thoracic or ventral sinus. This median sinus gives rise on each side to a series of large transverse vessels, which intercommunicate by means of a num- ber of minute vertical vessels, and which, after having formed a kind of vascular net- work, spread over the walls of the branchial cavity, and terminate in another vertical canal parallel to the ventral sinus, but situated on the opposite side of the thorax. A portion of the blood arrives at the same time in this dorsal sinus without having traversed the branchial net-work, by means of a vessel that arises from the superior extremity of the great ventral sinus and surrounds the base of the branchial orifice. Lastly the blood spreads out between the viscera and the internal tunic of the body, descends along the dorsal side of the abdomen, and again reaches the heart. If the circulation were constant in the above direction, it would somewhat resemble that of the other Acephalans. The heart might then be compared to an aortic ventricle, the tho- racic sinus to a great branchial artery, and the dorsal sinus to a branchial vein. But owing to the contrary directions of the blood-cur- rents, from the periodically varying impulses of the heart, the vessels that fulfil at one time the functions of veins, at another become arteries, and vice versa. This peculiar extra-vascular circulation, so well described by Milne-Edwards, is also very distinctly seen in the ClavcIlincE. The learned professor especially notices C. nana as highly illustrative of this phenomenon, the inter- abdominal space being in this case very large, and the currents of the nutritive fluid, with its suspended spherical globules, being easily discernible through the transparent integu- ments. Mr. Bowerbank has favoured me with an account of some observations made by him on the circulation in the common tegumentary mass of Botryllus. Under the microscope, the more transparent portion of the test ex- hibited a reticulated arrangement of sangui- ferous channels or vessels ; perhaps the true " marginal vessels " of Savigny ; each mesh, formed by the anastomosing currents, being occupied by one of the star-like " systems " of animals. No communication could be traced between the circulation and that of the ani- mals themselves ; the former appearing to be analogous to the peculiar stem-circulation of the polypifera, to which also the circulation of the nutrient fluid in the budless stems of Pcrophora, noticed by Mr. Lister, vide supra, has reference. Embryogenesis of the Botri/llidcc. — In the de- velopment of the ova of the compound Asci- dians, there are certain striking differences from the conditions that take place during the em- bryo-genesis oftheAscidiadce. These, however, are chiefly confined to the composition of the egg, the formation of the Blastoderm, the mode of growth of the caudal appendage, the organs of vision, and the anterior appendages. From the elaborate observations of this family, given by Professor Milne-Edwards in his Paper before referred to *, it appears that the ova of several species of the PolycUmna. are, whilst still enclosed in the ovary, and before that their development is much ad- vanced, of an ellipsoid form, and are com- posed of a very thin external membrane, a subgelatinous whitish and granular inner mass, and a minute central vesicle filled with a watery fluid. The internal vesicle is the vesicle of Purkinje, or the proligerous vesicle ; the granular substance surrounding the ve- sicle is the imperfect vitellus, the vitelline membrane being the external envelope. Whilst these ova are still enclosed in the upper part of the post-abdomen, they grow rapidly and become spherical. But the most remarkable change that takes place consists in the colour of the vitellus, which is at first a pale, and afterwards a deep yellow. The vesicle of Purkinje is still visible at the com- mencement of this period of the development, but it soon disappears, and there then appears on the surface of the vitellus a nebulose spot of pale yellow, which appears to be the blasto- derm or proligerous layer destined to become the embryo of the young Asciclian. The ova arrive in the cloaca, and sometimes are even lodged in the lateral portions of the thoracic chamber, without having undergone any other appreciable modification. M. Milne- Edwards considers it probable that the fecun- dation of the ova takes place in the interior of this cavity. They are here brought into contact with the spermatozoa, and very shortly after having arrived here, they exhibit evi- dences of active internal changes. The granules composing the vitelline mass become grouped into clusters, forming them- selves, as it were, into balls, and giving the surface an embossed or mulberry-like aspect. At the same time there is formed between the yolk and the external membrane of the ovum, a gelatinous, transparent, and nearly colourless layer, which apparently becomes the external tunic or test of the young animal. * Observations sur Ics Ascidies composes. 4i 3 1222 TUNICATA. When the ova, lodged in the marsupial pouch or cloaca, have arrived at a rather more advanced period of their development, the vi- tellus loses the mulberry appearance it had but lately put on, and, if compressed between two slips ofglass.it is seen to be wholly com- posed of minute globules or granules of dif- ferent sizes. The ovum is soon a little flat- tened, and the yolk appears to be concentrated Fig. towards the middle, forming an ovoid mass of a deep yellow colour, surrounded by a some- what large border of a clearer tint. This mar- ginal portion of the yolk is condensed in its turn, and although at first sight appearing to constitute a sort of ring, becomes a long taper- ing prolongation, which encircles the central part of the yolk, adhering by its base, and having its pointed extremity free (/g. 784. A). 784. t c* Ill mm BftH !"-f 77(e Development of the Larva of Amaroucium proliferum. (After Milne- Edwards.) A. An ovum the inclination of which is far advanced, magnified about 30 times. The tail, (6') is becoming distinct from the trunk (i) ; and two lobules begin to appear on the anterior extremity of the latter (l>n). B. An ovum arrived at the full term of incubation, magnified about 30 times, a, the tegumentaiy portion ; b1, caudal portion ; b", b111, anterior appendages. c. Larval ascidia lately born, magnified about 25 times, a, tegumentary portion ; b, sac enclosing the yolk and forming the proper tunic of the body of the larva ; b11, processes terminating in suckers, and serving to fix the animal ; a, tail formed by a prolongation, of the integuments, and enclosing a tubular ap- pendage of the vitelline sac. D. The same larva, observed some hours after having fixed itself, magnified about 20 times, b11, traces of the anterior processes ; b1, vitelline prolongation of tail nearly absorbed, and the central sac, enclosing vi- tellus, is spherically contracted. E. The same larva about 20 hours after fixing, magnified about 25 times. The caudal elongation of the internal tunic (containing the vitelline matter) has entirely disappeared, and this tunic (6) has taken the form of an ovoid sac, slightly contracted in the middle ; a pale yellow circle (rf) at the anterior ex- tremity surrounds a spot that will become the mouth, and posteriorly another, clear, spot (c) appears, in which the heart will be developed. F. The same larva seen at the end of the second day of its sedentary state, magnified about 25 times, b. tunic proper ; c, pericardium spot ; e, branchial sac, beginning to be developed ; f, thoracic sinus ; g, cloaca ; /, stomach ; m, intestine, full of ftecal matter ; a, vestige of tail, of which a part only is figured. The external orifices are not yet formed. The development of this individual was much more rapid than usually is the case. G. Another individual, about 8 days old, magnified. Animal completely reversed in the interior of the tegumentary envelope ; d, oral orifice ; i, anal orifice ; I, stomach ; m, intestine ; o, heart. H. Individual about 20 days old, magnified (lying with its anterior extremity to the right), a, tegu- mentary envelope ; m, frocal matter in the intestine. In the course of incubation, the ovum in- creases in size, becoming flatter and more oval. The vitelline mass becomes more com- pact, and its surface denser; and the latter seems to be organised into a membrane, dis- tinct from the yolk beneath. The two por- tions of the ovum, before described, become more and more separate; that which occupies the centre of the ovum becomes ovoid, and knotty at one of its extremities; near the other extremity, which is continuous with the mar- which also it is distinctly divided a little in front. Lastly, the whitish substance sur- rounding the vitellus, and constituting the tegumentary mass, increases considerably in thickness. When the ova more nearly approach ma- turity, the tail-part of the vitellus is shortened, and its central part, or body of the embryo, is more and more condensed. Its anterior ex- tremity becomes lobulated and encircled with a series of five cylindrical processes, which have ginal portion, are seen one or two blackish a divergent arrangement, and advance towards • • , mi • • 1.1 ._i! * ^1 l 1 _/*.<_ l rpt „£* iU „ minute points. This ring- like portion is now seen to be a caudal prolongation, too short completely to encircle the central part, from the border of the egg. Three of these ap- pendages terminate in a kind of button, and the intervening two are tapering anteriorly. TUNICATA. 1223 At each side of the base of the group of ten- tacles, a little prominent lobular process is present. Lastly, the side of the body, opposite to that on which the tail is placed, becomes somewhat strongly embossed near its pos- terior extremity, and towards the space where the above-mentioned black points occur {Jig. 784. B). The ovum ready for exclusion differs ap- parently little from the foregoing state. The two anterior styliform appendages have almost entirely disappeared, and the three obtuse processes are further developed. The trunk is contracted towards its anterior extremity, and the yolk-mass still further condensed at the centre of the ovum. The external membrane of the ovum becomes excessively thin, and then breaks and allows the embryo to escape. Generally this ex- clusion takes place in the interior of the cloaca, but sometimes not until the ova have passed out by the anal orifice. However that may be, the young animal, free from its envelopes, soon extends its tail, and swims in the ambient fluid by the aid of its undulatory movements. In its general form the young Ascidian re- sembles somewhat that of a newly born tad- pole (fig. 784. c) ; but it still more resembles a Cercaria. The trunk or body of the larval Poly- cl'mum is oval and rather depressed. The whitish tissue of the future integument occupies all the surface, and is considerably developed at the margins ; its substance is granular and apparently subgelatinous ; its consistence is greatest at the surface; and it does not appear to possess a membranous investment. To- wards the centre of the trunk is a large ellip- tical membranous sac, the internal tunic of Milne-Edwards; this is filled with the yellow substance of the vitellus, and is continuous anteriorly with the three tubes dilated at the end, and terminating at the anterior wall of the egg in a sort of sucker. By means of gentle graduated pressure, some of the yolk may be easily made to pass from the principal sac into these appendages, and vice versa ; the little capsule, also, terminating each of these appendages can be made to protrude exter- nally by the same means. At the base of these three processes the vestiges of the others formerly occupying the intervening spaces may be observed. The yellow substance contained in the internal tunic appears to be separated into two portions; the one is clear, and situated near the wall of this sac, and the other, denser and of a deeper tint, occupies the centre. Pos- teriorly a little marginal space, clearer than the neighbouring parts, is also visible, and on one of the sides the above-mentioned minute black spots are visible. The tail is very large, and, like the trunk, is composed of two distinct parts ; the one superficial, colourless, diapha- nous, gelatinous, and much resembling the al- bumen of the eggs of frogs ; the other, central and yellow. This latter part is continuous anteriorly with the central sac of the trunk, and is also composed of a membranous tunic, enclosing a yellow granular and semi-fluid substance. It sometimes appeared to have a central canal. The larva?, after swimming about with an active wriggling motion for a few hours, attach themselves to the surface of a solid body, and, if disturbed from their position, swim about as before until they meet with a similar situation. Their activity having ceased, they become permanently fixed, and are then about the size of the head of a very small pin. They appear to affix themselves to their rest- ing place by means of one of the little suckers with which their anterior extremity is fur- nished. The larva has now lost all power of loco- motion, and quickly undergoes further changes of form. The anterior extremity of the trunk is widened, and the prolongations of the in- ternal tunic quickly disappear. The central portion of the tail becomes at the same time empty, its contents being returned to the cen- tral yolk-mass of the body. The sac or internal tunic enclosing the yolk becomes much con- tracted and spherical ; lastly, the yellow matter, which was unequally divided, seems again to be rearranged. The tail, which during the early period of the existence of the larva per- formed so important a part, being the only instrument of locomotion, is now reduced to its gelatinous or tegumentary portion ; and this, after becoming more and more trans- parent, withers, and finally is detached, or falls away in shreds at a more advanced period of the growth of the animal. The trunk, on the other hand, is the seat of important and active changes. The tegumentary portion of the body is much widened, taking an oval out- line, and is visibly augmented in bulk. The interior tunic continues at first to lessen, and becomes quite spherical, and many large patches of a lighter yellow than the rest are apparent, one of which occupies the anterior, and two others the posterior portions of the tunic {fig. 784. D). M. Milne-Edwards further remarks, that the modifications already noticed ordinarily occupy the space of from ten to twelve hours ; and if the larva; are again examined towards the end of the first day of their sedentary existence, further changes in the interior tunic may be observed. In a speci- men carefully watched by him, the follow- ing changes were noted. Instead of being spherical, the large yellow sac became oval, and its anterior part much thinned. It soon afterwards again became elongated, and a circular contraction divided it into two por- tions {fig. 784-. E). The anterior portion, smaller and lighter coloured than the pos- terior, was rounded in front, and presented at that part a large annular patch of a deep yel- low, vaguely circumscribing a central paler portion. The posterior part was swollen and of a deeper yellow than the anterior, and quite behind there was observable a minute patch of a very clear yellow. This latter spot sub- sequently became the heart, and the annular spot on the other extremity of the body was developed into the thorax of the animal. The following day all these parts grew still more distinct. The anterior portion of the inter- 4 i 4 1224 TUNICATA. nal tunic or the thorax, which had been smaller than the abdominal or posterior por- tion, was much increased, and far more dia- phanous, and the part occupied by the whitish anterior spot was somewhat elevated in the form of a nipple, marking the future position of the mouth. The obscure circle that sur- rounded the base of the buccal region was now replaced by a very narrow yellow band ; and on the inferior part of this thoracic portion of the body there were observed two yellow lines, vertically dividing it into three nearly equal lobes. The abdominal portion of the internal tunic was, on the contrary, much straitened ; the pericardial spot was more dis- tinct; and another less distinctly limited spot, situated more in front, presented apparently the first indication of the stomach. Towards the middle of the second day, the middle lobe of the thorax was much enlarged, and in certain positions of the animal appeared to be formed by a new interior cylindrical sac, which in front united with the anterior wall of the thorax at the point occupied by the yellow ring before described, whilst laterally it was separated from the internal tunic by the spaces corresponding to the lateral lobes already men- tioned. One of these lobes became very much narrowed, and seemed destined to form the great vascular sinus: subsequently, traversing the anterior surface of the thorax, the other lateral lobe appeared to correspond to the future cloaca ; and the middle lobe was evi- dently the branchial sac, from the base of which arises the digestive tube. A few hours after, the anterior nipple-like prominence was more salient, and seemed to be contractile. The situation of the stomach and the course of intestine were also distin- guishable in the abdomen (fig. 784. F). The yellow substance had now in a great degree disappeared, but it was still present in a pretty considerable quantity in the alimentary tube, and appeared to pervade all the interior parts of the young animal. Towards the end of the second day, the bran- chial orifice was easily distinguished at the summit of the thorax, and its margin began to be somewhat crenulated. This orifice, how- ever, was present only in the internal tunic, the tegumentary substance being continued over it without interruption. The nerve -ganglion appeared in the form of a minute tubercle. The yellow line encircling the summit of the thorax appeared as the superior margin of the branchial sac. All the thoracic portion of the body contracted itself from time to time. Lastly, the anal orifice began to be visible. On the third day, the heart was seen to pulsate, and pellets of faecal matter were visi- ble in the intestine. The following day, the mouth opened externally, and the water passed through it to the branchial cavity. About the same time, the integument was perforated also by the anal orifice, from which faecal matter was discharged, provided without doubt by the digestion of nutritive matter furnished by the vitelline mass (fig. 784. G). On the following days, the growth of the young animal was more rapid, its organs became more distinct, and soon afterwards the spiracles of the branchial sac, disposed in transverse rows, were visible, as well as the vibratile movements of the cilia, with which the stigmata are fringed. The number of these rows, however, was but four, the adult animal having ten. The young Amaroucium was now provided with all its necessary organs except those of generation, of which no trace was yet visible, and the future situation of which was occupied by other organs, the heart being close up to the intestinal tube. The general form of the body resembled more that ofaDidemnian than of a Polycliuian, for it had as yet no post- abdomen, and the loop of the intestine was folded up against the inferior extremity of the thorax. Lastly, during the succeeding days, the abdomen very much lengthened itself (fig. 784. H), and at the end of the second week there was present, between the heart and the intestine, a granular mass, which by its ap- pearance and position could readily be re- cognised as the generative organs. With regard to the development of the integument of this, at first solitary, but sub- sequently compound, Ascidian, and which is evidently the analogue of the polypary of the Polypifera, we have mentioned that at first it is a gelatinous layer, surrounding the yolk. An inner membrane, immediately in- vesting the yolk, and regarded as the blasto- derm, becomes the internal tunic of the animal. Whilst the larva goes through its early changes, there appears no connection at all between the inner tunic and the integu- ment. Indeed, says M. Milne-Edwards, the larva may be seen sometimes to be entirely turned round in the cavity of the tegumentary envelope ; and sometimes, when it abandons its original position, it forms a kind of hernia on the exterior of this envelope, by distending it at a weak spot (fig. 784. G). The learned professor does not, however, regard this en- velope as being either a deposit produced by secretion, or as an organised body that had ceased to live since it had ceased to be attached to the interior parts of the animal ; because, as he observes, it continues to grow and gives un- mistakable signs of vitality. Thus, not only does its bulk rapidly increase, but it frequently gives rise, as in Amaroucium Nordmanni, to lobe-like expansions, frequently changing their form, contracting and dilating very gently, and appearing to have some analogy to the proteiform expansions of the Amcebee and other inferior animals. Of these changes Professor Milne-Edwards has given an inte- resting series of figures. It is only when the mouth and the anus open externally, that an attachment is estab- lished between the integument and the inter- nal tunic of the animal ; and then, as through- out its future existence, it is around the two orifices only that organic continuity exists be- tween the two parts, one only of which is in direct relation with the organs of animal life. It is consequently probable that the nutrition TUNICATA 1225 of the test is carried on by imbibition only ; and M. Milne-Edwards points out the fact of the independence of these two portions of the body of these Ascidians daring the early periods of their life, as worthy the considera- tion of physiologists ; and he adds, that proba- bly this kind of vitality of the integument of the larval Ascidians has some analogy with what obtains in Sponges, and may, perhaps, throw some light on the peculiar existence of the basilar portion of the Sertularke and other Polyps, that continue to live for some time after the loss of the soft parts that are generally, but wrongly, regarded as constitut- ing the entire animal. From observations made by the same natu- ralist on the development of the ova and larvae of other species of the Polyclinina, and of the Didemnina and ClavellincE, it appears that very similar modifications take place ; the time occupied in the development being of course variable according to specific and external conditions. The larvae of Clave/Una have the internal tunic strongly lobed in front, very tumid behind, and destitute of the pecu- liar appendages observed in the PolycKnina. These appendages exist in the Didemnina, but are very short ; and at their base are seen a row of pyriform lobules, which might easily be taken for the germs of young individuals, but all of which really belong to one individual. The observations made by MM. Lowig and Kolliker on the embryogeny of some of these animals are generally in accordance with those of M. Milne-Edwards, but on some points, and especially with regard to the develop- ment of the Botrylli, there exists considerable discordance of opinion. The points involved being not only of interest, but of no slight im- portance, it is necessary to give in detail some of the most important observations recorded by the above-named naturalists. In Botryllus violaceus, B. aureus, Apli- dium gibbulosiim, and Amaroucium Nordmanni, MM. Lowig and Kolliker observed, in the first stages of development, a division of the yolk similar to that taking place in the eggs of frogs, and described also by M. Milne-Ed- wards, and established also in the case of the simple Ascidians by Van Beneden. This divi- sion takes place as in the intestinal worms ; that is to say, the simple nuclei, contained in the globules, which, as everywhere, are only aggregations of granules, always become double before the globules are divided in two. As soon as the division has arrived at a certain degree, the spherical form of the mass of glo- bules becomes elongated, and takes more and more the form of an embryo, its tail making a semicircle about its body. The tail is distinct before any other part, and this, according to these observers, is evidently formed, not by an elongation of the embryo, but by the separa- tion of a portion of the globules from the sur- face. In Amaroucium and Ajj/idium, at the same time as the exterior form of the embryo, and at a very early period, the two ocular points, remarked by Milne-Edwards, make their ap- pearance; presenting as yet no trace of an envelope or of anterior processes. At a later period only is there formed around the em- bryo a transparent, colourless border, which, in Amaroucium and Aplidium, increasing more and more, especially at the thick end of the body, appears as a very strong lamina, but remains without structure all the time the embryos are contained in the membranes of the egg. Cotemporaneously with the forma- tion of the envelopes, the embryos themselves commence also to undergo a series of changes. Firstly, towards the anterior extremity, there appear the three appendages of peculiar form ; secondly, the yellowish substance in the in- terior of the body separates into two laminae ; the one, external, remains diaphanous ; the other, internal, becomes opaque, and divides, in the Botrylli, into eight conical corpuscles, which surround a somewhat large, round, perforated nipple ; lastly, a great number of structural modifications take place. The mature embryos of B. aureus are formed of a spherical body, 0-28'" broad and 0-38'" long, possessing an orifice surrounded anteriorly with three lobules, and posteriorly bearing a thin, tapering tail, 0'72'" long. These em- bryos present exteriorly the thin, transparent, structureless layer (tegumentary layer) before referred to, from which almost solely the lobes, or lanceolate appendages of the head, are formed, and which terminate at the opposite extremity in a prolongation exceeding in length those parts of the tail enclosed within it. In- terior to this, in the anterior part of the bod}', is a second delicate envelope, formed of cells either round or changed into fibres, which does not enter into the composition of the lobes of the head, but encases the mammil- lated prominence before described, and also the eight spherical bodies surrounding it, and is attached at one end to the edge of the nipple, and at the other to the interior part of the tail. The internal substance, constituting the chief mass of the embryos, is, according to MM. Lowig and Kolliker, evidently a group of individuals, as M. Sars, who discovered those curious embryos of the Botrylli, has already shown. The eight spherical corpuscles, united at their bases, and provided with a kind of common stem, are so many individuals, and the prominent nipple situated in their centre represents the common excretory tube. This salient tube at its extremity has three lobules, which project into the base of the lobes of the exterior envelope : from its base three filaments (nerves ?) arise, which passing upwards bifurcate each into two, one of which terminates at the orifice of the tube ; the second reaches the summits of the lo- bules, and, passing beyond them, spread into five or six branches, extending almost to the edge of the lobes of the exterior envelope. In the eight embryos no orifice is perceptible, nor any other organs, except some canals (intestine) indistinctly rolled up. Their mi- croscopic elements, however, are very dis- tinct ; namely, various-sized nucleated cells, filled with pale red granules and fibres in 1226 TUNICATA. process of formation ; the former constitutes the principal mass of the excretory tube. The internal part of the tail, which is apparently a direct continuation of the substance of the embryo, possesses an interior cavity, and its walls are composed of two layers of cells. The internal layer is formed of cells of 0'012/// diameter, rectangular, with the angles slightly rounded, distinctly nucleated, and containing fine yellowish granules. They are very regularly arranged side by side in transverse series, so that the cavity of the tail is always surrounded by 10 — 12 cells. The external layer is composed of a continuous, simple layer, formed of minute cells, measur- ing 0-003'"— 0-00-i'", without any distinct ar- rangement. It is to be observed that this tail, formed simply of cells and a homogeneous envelope, exhibits very active movements, affording a new proof of the contractility of parts composed merely of simple cells. The body of the embryos of Aplidium and Amaroucium is formed (at an early stage) of a thick, homogeneous, external layer, and a yellowish mass enclosed within it. In the spherical portion of the body, this mass is ap- parently wholly composed of round cells, of different sizes, and containing nuclei, and, towards the interior, probably unaltered glo- bules produced by the division of the vitellus. These two elements do not compose any dis- tinct organ ; but only form two layers, one internal and opaque, and the other external and diaphanous. In Amaroucium Nordmanni there is no canal within the tail, but its centre is occupied by a simple series of large rectan- gular nucleated cells, producing a transversely radiated appearance, visible even when mode- rately magnified ; the tail has also an external simple layer of minute cells, as in Botryllus, Savigny, also, was led by his researches to regard both the ovum of Bolryllus and that of Pyrosoma as giving birth to several individuals having already a certain order of arrangement. This view, in the case of the Botryllus, is, as we have seen, supported by Lowig, Kolliker, and Sars, and is considered by Van Beneden as founded on fact and supported by analogy. Milne-Edwards, however, is not disposed to admit this conclusion ; for, in his opinion, the existence of the four embryos united in a circle in the Pi/rosoma, and the development of a single star of germs in the larval Botryl- lus, do not sufficiently account for the associa- tion of many such groups in the adult age ; there being, for instance, in the adult Pyrosoma, many hundred individuals of different de- grees of development. Van Beneden thinks it probable that the presumed aggregate larvae produce colonies similar to themselves by fis- siparous reproduction; but Milne-Edwards gives it as his confirmed opinion that, from the single product of the ovum, the other asso- ciated individuals arise by gemmiparcws repro- duction only. Of this mode of generation in the Botryllidce we will now proceed to give a slight sketch, again acknowledging the labours of the learned Professor of the Garden of Plants as the chief source of our information. In Diazona, Didcmnum, Botryllus, and Bo- trylloidcs, the common test is traversed by numerous ramifying prolongations of the inner tunic of the individual animals, terminating either simply in culs-de-sac, or swelling out into germs (fig. 785.). Savigny figured these Fig. 785. Vertical Section halfway through a 3fass of Botryllus, magnified about 6 diameters. (Original). a, animals on one of the exterior surfaces of the mass ; b, proliferous stolons, traversing the mass, and bearing reproductive germs. tubular bodies, and vaguely described them under the name of " marginal tubes " and "vascular branches." And Delle Chiaje*, in treating of Polyclinium, figures and describes " vessels " which are probably these ramifying canals. These membranous tubes, with their terminal vesicular enlargements, are readily seen during life in those species that possess a semitransparent test. Milne-Edwards ob- serves that in Botryllus and Botrylloides, (figs. 785 and 783, /, t'), each of these interior ap- pendages appears at first as a little tubercle on the surface of the abdominal portion of the inner tunic of the adult animal. The tubercle then becomes elongated, forming a tube, the free extremity of which is closed, its cavity communicating with the abdominal cavity of the animal from which it springs. The blood from the abdominal cavity circulates through- out this csecal tube, with a very active double current. As the tubes lengthen, they generally become ramified, and soon present swollen or claviform extremities. The circulation con- tinues active, and before long there is visible towards the summit of each terminal swelling a minute granular mass, the colour of which approaches that of the thorax of the adult animals situated close by. A little later this organised mass begins to present the form of a little Ascidian, and soon afterwards becomes a young animal, similar to those already occu- * Memoirs, second edition, torn. i. p. 34 tabl. 83. figs. 13. and 15. TUNICATA. 1227 pying the common mass, of which it becomes a new inhabitant. The communication be- tween the mother and the young animal be- comes obliterated ; but tor some time yet, all the young individuals growing from the same branch remain united by their pedicle, and it is this union, apparently, that determines their mode of grouping into " systems."* In Di- demnum gelatinosum, the buds growing on these proliferous stolons are very different in appearance from the ova expelled by the animals ; for not only did they differ in aspect and form, but their bulk is at first twenty or thirty times less than that of the vitelline mass of the ova. In the Amaroucium prolifcrum, Milne-Edwards has frequently found on the surface of a rounded mass, formed by a colony of these animals, many little filiform twigs, simple or branched, formed by a prolongation of the common tegumentary substance, and consisting of a tube closed at the end, and enclosing, in its interior, one or more embryos in different states of develop- ment. These young individuals terminated inferiorly by a peduncle, prolonged in form of a slender tube into the common mass, and springing apparently from the abdominal tunic of an adult individual. This mode of propa- gation by buds, which the compound Ascidians possess in common with the Polypifera, is, as we have above described, found in the Clavcl- linidcs ; the only important difference being, that in the latter the tegumentary envelope of the young is not so largely developed as in the Botryllida:, and does not become fused with that of the adults; whence it results that the individuals springing from the same stem remain isolated, instead of being united into a common mass. ANATOMY OF PVROSOMA. — The common tegumentary mass of Pyrosoma is semitrans- parent, subcartilaginous, toughish, and some- what extensile. The exterior of the hollow, conical, or cylindrical body, formed by the ag- gregation of the individual Pyrosomata, is co- vered with numerous elongated tubercles, of a rather firmer consistence than the rest of the mass. Each of these constitutes one extremity of an individual member of the living group. The opposite extremity opens into the cavity of the cylinder, and is not free, but, like the trunk of the individual's body, is closely connected by the common mass with the similar parts of other individuals lying above, below, and on * M. Savigny figures a nascent system, originated apparently by this grouping of the buds ; and Professor Van Beneden coincides with M. Milne- Edwards in the above view of the subject, but M. Steenstrup expresses his opinion that the mode in which the colonies and systems of the Botrijllida are formed, is not sufficiently explained by this hypo- thesis; and, although (following Milne-Edwards) he considers M. Sars to have been misled in re- garding the ova of the Botrylli as producing groups of animals, yet he is inclined to consider this grouping to be really a foetal condition, but occur- ring in some hitherto unnoticed " aggregate " form of animal, produced from the "solitary" larvie de- scribed by Milne-Edwards, just as the solitary Salpcc bring forth Salpa-chains. either side of it. In some species the animals are arranged much more regularly than in others, and appear to form piled-up rings or circles of individuals, more or less analogous to the otherwise disposed circular systems of some of the Botryllidce. In Pyrosoma atlan- ticum the tubercles are simply conical, and are perforated terminally. In P. elegans, also, the external orifice of the individual opens at the extremity of the tubercle, and through it the water contained in the great cylinder has been seen to escape freely in little jets, when the Pyrosome has been taken out of the sea. In P. giganteum the tubercles are of various sizes, some being short and indistinct, anil others, on the contrary, very much deve- loped. The largest are conico-cylindrical flat, and lanceolate at the extremity, with the minute branchial orifice on the inferior aspect. This lanceolate extremity is crenulated on its sharp edges, and presents on its inferior aspect, between its point and the aperture, a slightly prominent keel. The branchial orifice is sometimes surrounded by a slight, free, crenu- lated membrane. The interior of the great cavity is generally smooth. Its walls are perforated by the numerous minute anal orifices of the com- ponent individuals ; and, at a slight depth, its surface is studded with a great number of yellowish, rose-coloured, or carmine spots, which are the hepatic and other visceral organs of the numerous animals. The ter- minal aperture of the large, conical, compound body of the Pyrosoma has, according to Le- sueur and Savigny, a membranous border, which can be sometimes drawn together so as to close the cavity ; and Mr. F. D. Bennett observed that, when first removed from the sea, the broader extremity of the cylinder pre- sented a wide and circular orifice, forming nearly a continuous surface with the central tube ; but when the animal was kept in a vessel of sea-water, or much handled, this orifice was closed by the contraction of a smooth, dense membrane at its margin, and which either obliterated the aperture, or left but a minute central orifice; water at the same time being contained in the barrel or tube of the body. Besides the common envelope or test, each individual animal has an inner tunic or man- tle. This is a very thin, delicate membrane, attached apparently at four points only, two of which are at the extremities; that is, at the branchial and anal orifices ; and the other two are at two rounded, compressed bodies, one on either side, just beyond the anterior mar- gin of the branchiae, and regarded by Savigny as ovaries. The bronchia; line the inner surface of this inner tunic. They are oval in form, and their dorsal borders meet each other, and are at- tached along the dorsal aspect of the mantle ; but they are separated, at their anterior and ventral borders, by a considerable space, which is partly occupied by the ventral sinus (Jig. 786. i, i). The branchial tissue is traversed by numerous vessels anastomosing with each 1228 TUNICATA. other at right angles. The transverse vessels, varying from 18 to 25 in number, are the Fig. 786. \ Anatomy of Pyrosoma giganteum, magnified. A. A portion of the common mass with animals im- bedded in its substance. (After Savigny.~) a, a, a, a, the liver ; b, b, b, ova in the posterior cavity ; c, ovum in the substance of the common test ; d, d, d, full- grown individuals ; e, e, e, undeveloped individuals. B. A single individual cut out of the common test, with a portion of the latter surrounding it, seen from below. (After Lesueur.) a, branchial or external ori- fice ; b, anal or internal orifice ; c, c, delicate fibres traversing the test ; d, stomach ; e, liver ; /, /, bran- chiae ; g, oviduct ( ?) ; h, ovary ; i, ventral sinus ; j, nerve-ganglion. C. The viscera of an individual Pyrosome. (After Lesueur.) d, e, g, h, i, j, as in Jig. B ; k, ovum. largest and most distinct, and are folded back on themselves at the free edges of the tissue. The longitudinal vessels are from 11 to 17 in number. " Nothing is more curious," says Milne-Edwards*, "than the respiratory ap- paratus of these little animals, when the vi- bratile cilia, with which each of the branchial stigmata is furnished, are simultaneously ef- fecting their vorticiform movements with ra- pidity and perfect harmony." The oesophagus is curved, and is of a bright red colour. The stomach is subglo- bular, yellowish, and opaque. The intestine is short, and strongly bent on itself ; the anus is directed backwards towards the posterior * Annales des Sciences Naturelles, sec. se'r. torn, xii. p. 375. 1835. orifice. The liver is a globular body, which is but slightly developed in young individuals ; its postero-inferior portion is formed of several sections united by a centre, around which they converge, presenting the appearance of a flower with many petals, or a calyx with, most usually, 7, 8. or 10 divisions. The sec- tions are not always equal. Their centre is occupied by a somewhat solid, granular sub- stance, which they more or less perfectly enclose. Its colour is generally whitish, or of a light pink. It lies free in a cavity hol- lowed out of the test, and is attached by a membranous peduncle to the stomach, or rather to the intestinal loop (Jig> 786. A, a, a, B and c e, e). These viscera are si- tuated posteriorly to the branchial sac. By their disposition they leave a free passage to the water which traverses the branchial ca- vity. The nerve-ganglion is present at the anterior extremity of the dorsal border of the branchial sac. From it there proceed filiform branches towards the neck of the external tubercle and in other directions. The vessel or sinus that runs between the two free edges of the branchiae is of considerable length, and has a slight general curve. It is divided, as it were, into four, towards its largest and an- terior portion, or rather seems to be com- posed of two contiguous vessels bent upon themselves. These diminish in calibre as they run backwards, and, passing into a delicate filiform vessel, are lost near the stomach. Two arching vessels, one on either side, pass from near the nerve-ganglion to the com- pressed oval bodies on the anterior lateral points of the branchiae, and a similar pair of vessels unite these latter bodies with the extremity of the loop formed by the vessel that lies between the free ventral margins of the branchiae. These four arched vessels form therefore a circlet around the anterior ex- tremity of the branchial sac (Jig. 786. B, h). The heart is placed at the posterior part of the body, at the side of, and below, the visceral mass. Its character is perfectly analogous to that of the heart of other Ascidians. It con- tracts with the usual peristaltic ^ movement, and changes periodically the direction of this vermicular movement, the vessels alternately playing the part of artery and vein. With regard to the generation of the Pyroso- midcE, very Jittle has yet been observed. Sa- vigny describes as "oviduct" and "siphon- canal" the vessels that occupy the usual position of the dorsal sinus, running along the dorsal or superior surface of the branchial sac (Jig. 786. g, g). They have, however, no apparent connection either with the pre- sumed oviferous bodies situated at the an- terior points of the branchiae, or with the cavity posterior to the abdominal viscera occupied by the ova in Savigny's specimens (Jig. 786. A, b). Lesueur discovered and described cer- tain globular, transparent bodies in Pyrosoma, situated near the liver (Jig. 786. c, k), which he regarded as ova ; these were noticed also by Savigny. Each enclosed four minute Py- rosornes, symmetrically disposed, and readily TUNICATA. 1229 recognised by the form and arrangement of their double branchiae. Whether the ova of Pyrosoma be always composed of four, or a greater or less number of young individuals, or whether they ge- nerally contain but a single one, it is still highly probable that gemmiparous reproduc- tion obtains with these animals ; the fissi- parous mode, however, imagined by Peron as possibly occurring in the adult Pyrosome, is totally unsupported by evidence. The several stages of development in which the individual animals are found to exist in the common mass of the test, as noticed by Savigny, point to this conclusion ; and possibly the delicate filaments regarded as muscular fibres by Sa- vigny, first pointed out by the acute observer of these creatures, Lesueur, as traversing the test in a line with the abdominal cavities of the adult animals (fig. 786. B, c), may be the proliferous stolons as yet untraced throughout their course. Phosphorescence of Pyrosoma. — M. Peron, who first discovered and established the genus, has given a lively description of the circum- stances under which the P. atlanticum were first met with by him, in his Memoire sur le Pyrosome. * " We had," says he, " for a long time been detained by calms in the equatorial regions, between 19° and 20° long, west of Paris, and 3° and 4° north lat., the temperature of the sea being at the surface 22° Reaumur ; and we could make no progress except by the aid of the short-lived storms peculiar to these climates. In the evening of the 13th Frimaire we experienced one of the strongest of these squalls ; the sky was on all sides loaded with heavy clouds ; all around the obscurity was profound ; the wind blew violently; and the ship cut her way with rapidity. Suddenly we discovered, at some distance, a great phos- phorescent band stretched across the waves, and occupying an immense tract in advance of the ship. Heightened by the surrounding circumstances, the effect of this spectacle was romantic, imposing, sublime, rivetting the at- tention of all on board. Soon we reached the illuminated tract, and perceived that the prodigious brightness was certainly and only attributable to the presence of an innumerable multitude of largish animals floating with the waves. From their swimming at different depths they took apparently different forms ; those at the greatest depth were very inde- finite, presenting much the appearance of great masses of fire, or rather of enormous red- hot cannon-balls ; whilst those more distinctly seen near the surface perfectly resembled in- candescent cylinders of iron. " Taken from the water, these animals per- fectly resembled each other in form, colour, substance, and the property of phosphores- cence, differing only in their sizes, which varied from 3 to 7 inches. The large, longish tubercles with which the exterior of the Pyro- somes was bristled were of a firmer substance and more transparent than the rest of the * Annales du Museum el' Hist. Nat. tome iv. 1804. body, and were brilliant and polished like diamonds. These were the principal seat of phosphorescence. Between these large tu- bercles, smaller ones, shorter anel more ob- tuse, could be distinguished ; these also were phosphorescent. Lastly, in the interior of the substance of the animal, could be seen, by the aid of the transparency, a number of little, elongated, narrow bodies (viscera), about a millimetre in length, which also participated in a high degree in the possession of the phosphoric light. " The colour of the animals, when at rest or when moribund, was observed to be of an opaline yellow, mingled with a disagreeable green ; but during the spontaneous contrac- tions of the animals, and which were also easily excited at the pleasure of the observer, the body seemed to burn, becoming instantly like molten iron, with an extremely bright light ; but, as the phosphorescence again ceased, the colour of the animal passed suc- cessively through a number of extremely agreeable, light, and varied tints, such as red, yellow, orange, green, and azure blue, the last shade being extremely lively and pure. "Left to itself in a glass of sea- water, the Pyrosome exhibited at regular intervals of time a slight alternating movement of con- traction and dilatation. In these movements, the phosphorescence was seen to be deve- loped during the contraction, then to grow insensibly feebler, and entirely disappear, until in the next contractile movement it was quickly re-established. " By often irritating the animal, either by touching it or by shaking the water in which it floated, the phosphorescence could be ex- cited and maintained for a much longer time. Evidently dependent on the organisation and the life of the individual, after death, as is the case with all other phosphorescent marine animals, it could not be reproduced." We may remark that the observations made by Mr. F. D. Bennett*, who more than once met with shoals of P. atlanticum in lat. 1° 41' N., long. 11°56'W., and lat. 4° S., long. 18° W., differ but slightly from M. Peron's notices of the same animal. The former observed, that when the specimens were taken in the hand from a vessel of sea- water, the whole mass of the animal became instantly illuminated by myriads of bright dots, much resembling in hue the points on the wing-cases of the diamond-beetle ; and that the small specks of a brown or red colour, that were imbedded in the general tissue, and in- termingled with the prominent, rigid, pearly tubercles, appeared to him to be the chief seat of the phosphoric light, frequently re- maining bright, whilst the remainder of the body exhibited only its naturally white or yellowish hue — a hue which changed after death into a red tinge. In making a close examination of the animal, Mr. Bennett re- marked that no luminous matter was com- municated from the surface of the animal to * Proceedings of the Zoological Society, 1833 and 1837. 1230 TUNICATA. any fluid or solid in contact with it. But if the Pyrosoma were cut open and immersed in water, the brown particles that escaped diffused themselves through the fluid, and shone as numerous scintillations, independent of the perfect structure. General friction or contact was not essential to elicit the perfect light of the Pyrosome, since touching one small portion of the body was sufficient to produce a brilliant glow throughout the whole. Mr. Bennett at the same time made the following observations on the effect of fresh water on phosphorescent marine animals. " Fresh water appears to act as a powerful and permanent stimulus on marine NoctiluceB. Those that have intervals of repose from their phosphorescence immediately emit light when brought into contact with fresh water ; and this fact was strikingly exhibited in the Pyrosomata. When placed in a vessel of sea- water and permitted to remain quiet, these Molluscs afforded no light, and, when touched, gleamed forth only as long as the irritating cause remained, and then gradually returned to their original state. When, however, the same creatures were placed in a vessel of fresh water, they never ceased glowing with their brightest refulgence until life was extinct, which was not until the lapse of several hours. When also the same Molluscs were mutilated, or so near death as to refuse to emit light upon irritation in sea-water, immersing them in fresh water produced at least a temporary revival of their brightest gleam." ANATOMY OF SALPJE. — The subcartilagi- nous test of Salpce is more or less cylindrical and flexible, and when taken out of the sea, often collapses into an amorphous mass. Float- ing in the water, it is iridescent or opaline, reflecting the sun's rays in beautiful rainbow tints, and hence has been derived its name of " sun-fish." The test and its lining membrane are so diaphanous, that the whole structure of the animal can be seen through them. The exterior of the test is generally smooth, but sometimes bears minute shiny protuberances of a tissue similar to its own, as in S. Tilesii. The integument over the viscera is thicker and often of a firmer consistence than the rest of the test. Its form varies considerably, not only in different species, but in the conditions of isolation and aggregation, in which each species alternately exists, and also in the different stages of growth of the individual, especially in an associated state. The test is usually either oval or oblong, but various terminal and lateral processes considerably affect its general contour. Each of its extremities is open by an orifice ; and, in the aggregated individuals, it is perfo- rated by other much smaller apertures at the points of contact between the neighbour- ing individuals of a group. The internal surface of the test is lined by the mantle, a thin, toughish membrane, which is often more conspicuous than the highly transparent external envelope. The mantle is furnished with large, generally transverse, muscular bands, the arrangement of which differs according to the species and according to the separate or associated state of existence. Its inner surface is lined with a soft mucous coat of fine epithelial tissue. The mantle is more or less closely attached to the inner sur- face of the test, especially at the two orifices (being, indeed, continuous with the test at these points), at the protuberances that arise from the test, and along the inner surfaces of the longitudinal furrows that sometimes tra- verse its external surface, as in S. cordiformis, where, on the superior and inferior surfaces, the test is depressed into broad, deep sulci. In specimens preserved in spirit, and even in some recent specimens, this membrane will sometimes separate itself, together with the viscera and vessels, from the outer tunic, and fall through one of the external orifices. SalpcB have been met with floating in the sea, and executing, in some degree, their usual movements of contraction and dilatation; in which, from mutilations caused by parasites or other accidents, little remained except a few muscular bands of the mantle. Considerable confusion has existed among naturalists as to which is the anterior extre- mity, and which the superior surface of the Sal-pa. We shall regard, as the anterior or branchial orifice, that in the neighbourhood of which the stomach and heart are usually found (fig. 787.); and as the posterior or anal orifice, that which points in the direction of the ani- mal's retrograde motion ; and as the superior or dorsal surface, that on which the nerve- ganglion is present; and as the inferior or ventral, that in close contact with which the viscera and heart, forming the " nucleus " or " paqnet " of authors, are placed. The orifices are either terminal, or are situ- ated at the base of the terminal prolongations of the test. The anterior orifice is destitute of tentacular appendages ; it is furnished with sphincter muscles ; it is simple and tubular in S. cristata, S. Tilesii, and S. scutigera, &c., and transverse in S. cordiformis, S. zonaria, &c. When the dilatation of the animal is drawing water into the cavity of the body, the sphincters of this orifice are brought into action and close it, so that the water enters by the opposite extremity. The posterior orifice is a transverse slit, furnished with a few muscular fascicles, and is larger than the opposite orifice. In S. ciis- tata its superior lip is simple and thin ; its inferior lip is externally a rounded ridge, formed by a fold of the test, which, within its inner border, constitutes a semilunar valve. This allows the water to enter easily, but pre- vents its escape when the animal contracts itself. The constrictor muscles of the mantle are often subannular, interrupted on one or the other surface, decussating in some, connected in others. The following are a few examples of the disposition of these muscular bands. In S. cristata, around the tubular anterior ori- fice, are 4- — 5 sphincter muscles ; the first of which, as well as the last two, are continuous TUNICATA. 1231 around the tube. The last two sent! lateral processes backwards, forming, with the suc- ceeding band, the first on the trunk, and also annular, large rhomboidal meshes ; two other annular bands succeed and form large meshes by intercommunications on the upper and lower surfaces. From these last muscles two intercommunicating processes are sent off on each side to the crestlike prominence of the test. From the last band several branches run backwards to be distributed to the upper and lower lips of the posterior orifices. In S. Tilesii the anterior orifice is provided •with two lateral penniform muscles. The other muscles form six bands nearly parallel with each other, interrupted along the me- dian line of the superior surface, and not reaching further than halfway down the sides of the body. The most anterior band is somewhat forked, and the most posterior gives some branches to the superior lip of the posterior orifice, and joins, at the an£>le of the lips, a radiating group of other fascicles, that are distributed to the inferior lip. In S. scutigera the muscular bands are few. On the superior surface, two pairs of decus- sating muscles are seen, and other smaller bands occur near the extremities. In S. cy- lindnca there are eleven transverse bands, interrupted and separated by a considerable space on the inferior surface of the body ; the first six of which are parallel one to another, whilst the four following are bent towards each other on the median line of the body ; the last band, and some short lateral fascicles, are arranged close by the posterior ex- tremity. In S. fusiformis there are seven transverse bands ; some of which are parallel with, and approaching others on the sides of the animal, and others are more or less obliquely arranged. In S. cordiformis there are six broad transverse muscles on each side of the animal, not meeting on either surface. Two narrow, looplike fascicles, one above and one below, arising from the last branchial bands, and two short, transverse, lateral slips, act as sphincters to the posterior orifice. A pair of narrow muscular fascicles are sent off from the first of the branchial muscles to the anterior orifice. In S. zonaria (the aggregate form or "proles" of S. cordiformis) there are also six transverse bands interrupted only on one surface, and differing consider- ably from those of S. cordiformis, as do the distinct sets of muscles distributed to the two orifices. In S.runcinata (solitary) ( _fig.772. A) the muscular bands are nine in number, placed on the dorsal surface ; three anterior and three posterior, approximated at their centres, and three parallel bands in the middle. In S. runcinata (aggregate) (Jtg.772.ii) there are six muscles, besides those of the orifices ; four anterior and two posterior, approximating on the median lines. The bronchia is single, in the form of a riband-like tube, stretched, on a vertical plane, obliquely across the central or branchial cavity of the body, so that it is constantly bathed by the water traversing this cavity. It consists of a double membrane formed by a fold of the internal tunic or mantle, and springs anteriorly from the visceral nucleus between the ceso- phageal opening and the orifice of the rectum ; it then becomes free, and ultimately terminates on the superior part of the thoracic cavity, below the point where the nerve-ganglion and the oculiform organ are found. It thus di- vides the branchial cavity into two portions — the antero-dorsal or pharyngeal, and the postero-ventral or cloacal. The inferior border of the branchia exhibits an infinite number of minute transverse ves- sels, all parallel to each other. There is usually only a single row of these transverse vessels on each side of the foliole of the bran- chia ; but sometimes there are many rows, which indicate the presence of many longi- tudinal vessels, and thereby approach the character of the branchial tissue of the As- cidians. Savigny observed in S. octofora another small branchia near the anterior insertion of the large branchia. The whole inner surface of the branchial sac of the Salpae seems, from its high degree of vascularity, to be subservient to the purposes of respiration. The vascular tissue of the bran- chia, consisting of longitudinal and transverse vessels, is equivalent to the x vertical bran- chial network dividing transversely the respi- ratory cavity of the ClaveUince. The single branchial lamina of Salpcc ap- pears to constitute the transition from the Ascidice to the Teredines; in the latter there are two elongated branchial laminae above the intestine, and within the tubular mantle, to which the water has access and egress by means of two tubes placed at the posterioi extremity of the body. The intestinal canal is opaque, fuscous, or variously tinted, generally closely folded or convolute, and sometimes enveloped in the liver, forming altogether the " visceral nucleus." This, together with the heart, lies external to the mantle, between it and the test. The cesophageal aperture is in the antero-inferior part of the body, behind the heart, more or less conspicuous and variously modified ; dissimilar in the alternate " proles " of the same species. In the solitary " proles" of S. pinnata and S. affinis it is stretched above the branchia. In the aggregate " pro- les " of S. pinnata it is opened out longwise, and of a violet colour in the living specimen. In