Ssinuag Me ae SIL p aye fe = = ig testy : See, ae ) i “f Ne mn NA ‘ Haley fi PRN i iN ah ay on wh Wyle t i) os = S SS Ova aT Uae THE AMERICAN JOURNAL OF ANATOMY EDITORIAL CHARLES R. BARDEEN University of Wisconsin Henry H. DonAaLDSON The Wistar Institute Tuomas DwiGHtT Harvard University Simon H. GAGE Cornell University G. Cart HUBER The Wistar Institute BOARD GeEorGE 8. HUNTINGTON Columbia University FRANKLIN P. Mau Johns Hopkins University J. PuayrainR McMvurrRicH University of Toronto CHARLES 8S. Minot Harvard University GeorGE A. PIERSOL University of Pennsylvania Henry McEK. Knower, Secretary University of Cincinnati VOLUME 11 1910-1911 THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY PHILADELPHIA, PA. CONTENTS 1910-1911 No. 1. NOVEMBER, 1910 Witi1am F. Auten. Distribution of the lymphaties in the tail region of Scor- penichthys marmoratus. Twelve figures........°7..-.--.+-++-+---=--- 1 LEonARD W. WiuuiAMs. The somites of the chick. Nineteen figures....... 55 No, 2) “JANUARY; tout J. Gorpon Witson. The nerves and nerve endings in the membrana tympani SUTRA CISA Teta Mae) 0] Hol tee hg ae RS os STB Bec 6,0 ¢ b's Cieagiekes eeetcne Canny cece eae 101 FiLorence R. Sasrn. Description of a model showing the tracts of fibres medullated in a new-born baby’s brain. Nine plates................... 113 W. E. Danpy anp Emit Gortscu. The blood supply of the pituitary body. TEVSYOIE PAU SS ee ee ORME sco. c i0 b 6, 9-0 0 eG eakanie Manone” Dee 137 Jeremran S. Ferctson. The anatomy of the thyroid gland of Elasmo- branchs, with remarks upon the hypobranchial circulation in these fishes. "TR AGITIERY WEA EC'S 9 oe AD m c 0. 6 coca Sy Ciegeaa cane eee 151 No. 3. MARCH, 1911 FRANKLIN P. Maui. On the muscular architecture of the ventricles of the homanthearies Lwenty-two figures: ..:... << 2eie. eres oo dee ce 211 J. F. Gupernatscn. Hermaphroditismus verus in man. Seven figures. .... 267 Aupert Kuntz. The development of the sympathetic nervous system in FUG eee MN ATO ES Ss 2 fara tats sys). =) "> Satya alah ateenemnagetee oes ay gale «oer n 279 No. 4. MAY, 1911 Joun WarreN. The development of the paraphysis and pineal region in Reptilia. ‘Thirteen plates..:, ...e:Seaceeeeeneee ates ee eee 313 Joun Lewis Bremer. Morphology of the tubules of the human testis and epididymis. Twelve figures .. Weegee cay.« bee ok ee 393 CHARLES Russet, BARDEEN. Further studies on the variation in suscepti- bility of amphibian ova to the X-rays at different stages of develop- ment, Huighbeen frUrTes...: eee ent reer dis 4 Sai eo oo ae 419 DISTRIBUTION OF THE LYMPHATICS IN THE TAIL REGION OF SCORPANICHTHYS MARMORATUS WILLIAM F. ALLEN From the Herzstein Laboratory of the University of California, New Monterey, California TWELVE FIGURES INTRODUCTION This paper is a continuation of an earlier study. Since Scorpzenichthys differs notably in several important details from any of the many forms described by Favaro in his most compre- hensive work it seems desirable to complete the distribution of this system of vessels in this specialized species. Material and method of procedure.—Scorpenichthys marmora- tus, on which all the dissections were made, is one of the common rockfish found all along the Pacific coast. The tails of Scorpeenich- thys which were to be injected were severed a little anterior of the caudal peduncle, and were so arranged in a pan that the cut end was considerably higher than the tail end. The caudal artery was then injected with a carmine gelatin mass, after which the subcutaneous or lymphatic canals were filled with a Berlin blue gelatin mass or in one or two cases, with India ink, from the longi- tudinal neural trunk. In order to somewhat check up the work microscopically, the small tide pool cottid, Clinocottus analis, a closely related species, was sectioned. As with Scorpanznich- thys the tails of full grown adults were severed transversely a little anterior of the caudal peduncle; when they were killed, fixed, and macerated in Tellyesniczky’s potassium bichromate-acetic mixture for a period of about two weeks; after which they were embedded in paraffin, cut 10 microns, stained in Heidenhain’s THE AMERICAN JOURNAL OF ANATOMY, VOL. l11, No. 1. ~ WILLIAM F. ALLEN iron heematoxylin, and counter stained in a concentrated alcoholic solution of orange G plus a little acid fuchsin. Some microscopic observations were also made on the tail of a living Phanerodon atripes (viviparous perch) embryo. This study was made at the Herzstein Marine Laboratory of the University of California, New Monterey, California. Literature.—In addition to the bibliographical lists given in my previous papers several important works have come to my notice; among which Favaro’s monograph is of special interest. In this the author gives a detailed description of the distribu- tion of the subcutaneous vessels in the tail region of a great num- ber of species from Petromyzon to the most specialized of the Teleostomi. Furthermore he gives the development of these vessels in Acanthias vulgaris, Torpedo ocellata, Belone acus, and Squalius cavedanus. In the Cyclostomes, Selachians, and Aci- penser sturio they are portrayed as veins; while in the Teleosts they are represented as lymphatics, Favaro considering the lym- phatie system of the Teleosts as phylogenetically derived from the corresponding subcutaneous veins of the lower orders of fishes. In fig. 156 the gradual evolution of the vasa intermedia of the Selachians to the longitudinal hemal lymphatic trunk of the Teleosts is graphically shown. With Belone acus, Favaro finds an embryonic condition in the hemal canal comparable to the vasa intermedia of the Selachians. The following is a trans- lation of the last paragraph of Favaro’s paper, which is a concise summary of the authors conclusions. “‘Beyond (cephalad) the heart, likewise certain lymphatics, as for example the hemal, and indirectly to a certain extent the others, are derived from the embryonal venous system so that it is possible in fishes to recognize the close relationship, not only phylogenetic, but on- togenetic as well, between the lymphatic and venous systems.” If frequent reference to this most excellent work was not to be made later, much more would be quoted here. By a most unfortunate circumstance no note of Favaro’s mono- graph was made in my last paper, although it appeared some time prior to may publication. It is true I saw notice of Favaro’s work in the Bibliographia Zoélogica, and placed an order for it LYMPHATICS IN TAIL REGION, SCORPAANICHTHYS 3 with an European firm. It did not, however, arrive until after my paper appeared, and I was unable to gain access to another copy. A year earlier Favaro published a most interesting paper on the caudal heart of the eel, and as was the case with the previous mentioned paper I was unable to gain access to this until quite recently. The author finds the caudal heart of the eel to be a lymphatic heart situated at the posterior end of the last vertebra and to consist of two cavities. As I had long suspected the first, the atrium cordis caudalis is said to be in communication anteriorly with the longitudinal hemal trunk, tronco linfatico subvertebrale, and posteriorly with the trunk from the tail. Both openings are guarded by valves opening into the atrium. The atrium is connected mesad with the second cavity, ventriculus cordis caudalis, the orifice being guarded by valves opening into the ventricle, and anteriorly the ventricle empties into the caudal vein, the orifice, likewise having valves opening into the vein. Kellicott in his monograph on the vascular system of Ceratodus does not allude to the lymphatics or subcutaneous system further than to say that a pair of well developed lateral cutaneous veins are found beneath the skin at a level with the lateral line. Poster- iorly they are said to anastomose with the caudal vein and an- teriorly they open into the subscapular veins. Kellicott likens these veins throughout to the lateral cutaneous veins of Mustelus as described by Parker. The recent studies of Sabin, Lewis, Huntington and McClure, Hoyer, Knower, Baetjer, Heuer and Clark on the ontogeny of the lymphatic system concede that the primary or deep seated lym- phatics arise as sacs or hearts from transformed veins, and that the superficial or secondary lymphatic system originates from an endothelial sprouting from these sacs or hearts. Sala while admitting the derivation of the lymphatic hearts or sacs in the chick from the veins still holds to the old view that the ducts are formed from the mesenchyme cells. Marcus states that the segmental lymphatic hearts in the snake-like Amphibian, Hypo- geophis, are formed from the ccelom or body cavity epithelium and not from veins. 4 WILLIAM F. ALLEN Concerning the phylogeny of the lymphatics, Favaro and I have shown that considerable anatomical data supports the hypo- thesis that the lymphatic system of the higher or more special- ized orders of fishes have their homologue in veins in the lower or more generalized orders of fishes. BLOOD-VASCULAR SUPPLY FOR THE TAIL-REGION To avoid confusion it may be well to consider first the distri- bution of the blood vessels before taking up the lymphatics. Caudal artery.—As in other fishes the caudal artery in Scor- peenichthys (figs. 4, 5, 7-10, C.A.) traverses the haemal canal di- rectly below the centra. This trunk was also seen in nearly all the transverse sections of Clinocottus. In these sections it should not, however, be confused with the minor caudal artery with which it runs parallel and is a branch. Beneath the last verte- bra the caudal artery separates into a major and a minor fork. Sometimes the main stem is the left fork, but more often it is the right. The minor stem (figs. 9 and 10, R.C.A.) supplies the musculature of the side of the fin; while the major stem or caudal artery proper (figs. 4-8, 10, and 11, C.A.) continues caudad in the space between the two hypural bones to the posterior ends of these bones, where it bifurcates to form a dorsal and a ventral caudal fin artery. Immediately behind the last vertebra the posterior neural artery (figs. 6 and 7, P.Newu.A.) is given off from the major stem of the caudal artery to pass dorsad in a median line, a little in front of the superior hypural bone. In the speci- men from which fig. 7 was drawn it passed across the base of the left. side of the superior hypural and along the left side of the last interspinal bones to break up in a deep network in the con- nective tissue covering these bones, but in most of the other dis- sections it had a similar course on the opposite or right side. A little caudad of the last vertebra a pair of hypural arteries (figs. 4-7, Hyp.A.) are sent off to either side of the superior hypural bone, which they cross obliquely and break up in a capillary net work on the posterior and dorsal surfaces of the bone. These arteries may have arisen from the fusion of several of the embry- LYMPHATICS IN TAIL REGION, SCORPAINICHTHYS a onic neural arteries and if so should be considered as the posterior neural arteries instead of the hypural arteries. In the Clinocottus series the posterior neural artery was noticed, but the hypurals were not observed. The course of the caudal fin arteries (figs. 4-6, and 8, C.F.A.’ and C.F.A.’’) is either dorsad or ventrad in the basal canal of the caudal fin.! In the transverse series of Clinocottus the division of the caudal artery into the caudal fin arteries was clearly seen, and in fig. 11 the forking of the caudal artery in a 30 mm. Phane rodon embryo is shown. In Scorpzenichthys, Clinocottus, and Phanerodon a small branch, the caudal fin ray artery (figs. 4, 8, and 11, C.R.A.) is given off to the center of each ray. In Scor- penichthys and Clinocottus after continuing caudad a short distance in the center of a ray this artery forks, one branch passing along the dorsal surface of the ray and the other along the ven- tral surface, each giving off a network, to the ray and to the fin ray membrane. In the 30 mm. Phanerodon embryo (fig. 11) the first ventral caudal ray artery forked as they all do in Scorpzn- ichthys, but the remaining ones did not bifurcate within the rays; those from the dorsal half of the fin traverse the dorsal surfaces of the rays, and those from the ventral half of the fin, excepting the first, pass along the ventral surfaces of the rays. In the living Phanerodon embryo the red corpuscles could be clearly seen leav- ing these arteries to enter a network of capillaries in the fin niem- brane, and become collected on the opposite side by the caudal Tay vein. Minor caudal artery. (Figs. 5-8, 10, and 12, C.A.q)).—In the caudal peduncle region of Scorpzenichthys and in all sections of Clnocottus this vessel was found running parallel with the caudal artery, sometimes lying to the side, and again below it. At fre- quent intervals this artery gives off branches (fig. 10, C.A’.;)), which cross the lower surface of the caudal artery. Often these branches have as great a caliber as the main stem, and so far as ‘ 1 The basal canal of the caudal fin is a canal formed at the base of the caudal fin at the point where the two halves of the caudal rays separate to become attached to the hypural bones. This canal would therefore pass dorso-ventrad through the proximal ends of the caudal rays. 6 WILLIAM F. ALLEN could be ascertained they were destined to supply the blood vessels of the hemal canal. For their branches were observed going to and breaking up on the surfaces of the caudal and intersegmental arteries. In the dissection from which fig. 10 was drawn the main stem of the minor caudal artery ran along the right side of the caudal artery to the fifth vertebra from the last, when it crossed to the opposite side and continued caudad on the left side of the caudal artery to the end of the last vertebra, where it bent dorsad with the caudal artery to the interval between the two hypural bones. In the single specimen in which the origin of the minor caudal artery was traced, it was found to branch off from the left side of the dorsal aorta a few millimeters cephalad of the pos- terior end of the kidney. The main stem passed caudad along the left side of the aorta from which a short branch was given off cephalad. Shortly after leaving the body cavity the minor cau- dal artery bends to the ventral surface of the caudal artery where it separates into two forks of about equal size, the main stem trav- eling caudad on the right side of the caudal artery and the minor stem onthe left. Beside the capillary branching to the blood ves- sels, as mentioned above, there are frequent cross branches be- tween these two stems of the minor caudal artery, producing a ladder-like appearance. In some dissections of Scorpzenichtys, as in fig. 5, the minor caudal artery in traversing the hypural inter- val was situated ventrad of the caudal artery, but in other dis- sections of Scorpeenichthys and in the Clinocottus series, as shown in figs. 7 and 8, the minor caudal artery traveled for the most part dorsad of the caudal artery. In both Scorpzenichthys and Clinocottus the minor caudal artery divides into a dorsal and a ventral minor caudal fin artery (fig., 8 C.F.A.’q) and C.F.A.’’q)). As a rule these branches traverse the basal canal of the fin with, but caudad of, the corresponding caudal fin arteries, and like them, ‘send off a branch, the minor caudal ray artery (fig. 8, C.R.A.a)). These minor branches always fork before the caudal ray arteries do, and like them follow the dorsal and ,ventral surfaces of each ray, but so far as could be determined they did not extend caudad of the intrinsic muscles of the caudal fin. They appear, however, to furnish the principle supply for these muscles; while the cau- ~J LYMPHATICS IN TAIL REGION, SCORP/ENICHTHYS dal fin ray arteries supply the fin rays and the membrane connect- ing them. Favaro describes the minor caudal artery in numerous species as the arteria o arteriae longitudinales vasorum intermediorum. His fig. 156 graphically shows the evolution of this vessel. In Squalus it is represented simply as branches from the segmental arteries, which anastomose with the vasa intermedia. In Raja they also have their origin from branches of the segmental arter- ies, but run caudad in the hemal canal for a short distance before anastomosing with the vasa intermedia. In Acipenser they like- wise arise from the segmental arteries and anastomose with the vasa intermedia, and moreover by continuing in the hemal canal to anastomose with the successive segmental arteries they form a continuous trunk which runs parallel with the caudal artery and the vasa intermedia, and at regular intervals, between the intersegmental arteries it sends off anastomosing branches to the vasa intermedia; while in the Teleosts the arrangement is identi- cal to Acipenser, except that the direct connections of the vasa intermedia or longitudinal hemal lymphatic trunk with the cau- dal vein are lost. As stated above in Scorpzenichthys no connections with the intersegmental arteries were observed; hence the minor caudal artery in this species is still further differentiated ; for it is simply a vessel arising from the aorta and passing caudad with it to the tail. Caudal vein (figs. 3-6, 9 and 12, C.V.). In Scorpenichthys and Clinocottus, as in other fishes, this vein traverses the hamal canal immediately below the caudal and the minor caudal arteries. When distended its caliber is much greater than the artery, while its walls are much thinner. Unlike Lepisosteus (p. 51) it does not expand under the last vertebra in a sinus (Sinus venous cau- dalis of Favaro). As represented in Ophiodon elongatus (p. 107) the caudal vein of Scorpzenichthys and Clinocottus bifurcates below the last vertebra into a right and a left branch, which are of different lengths and different relative importance. Some- times the main stem is the right branch, but more often it is the left; while in one instance they were of equal lengths and import- ance. 8 WILLIAM F. ALLEN The minor fork of the caudal vein (figs. 3, 6, and 9, R.C.V.) curves up around the right posterior side of the last vertebra in front of the main stem of the caudal artery. When the median line is reached, it usually divides; one branch passes laterad to the periphery, and the other goes caudad a short distance between the superficial and deep muscles of the caudal fin. In one dis- section the minor fork of the caudal vein equaled the major fork in length and in caliber. It continued caudad to the caudal fin, where it penetrated the ventral basal canal of the caudal fin, and collected the blood from that half of the fin; while the blood from the dorsal half of the fin was collected by the other or main fork of the caudal vein. The main fork of the caudal vein or the caudal vein proper (figs. 4-5, C.V., and figs. 3 and 9, L.C.V.) passes up the opposite and usually the left posterior side of the last vertebra to the me- dian line; where it receives the posterior neural vein (figs.4 and 5, P.Neu.V.), which in curving around to the dorsal side of the superior hypural bone crosses directly mesad of the posterior portion of the lateral trunk, to eventually follow up the left side of the last neural spines. Meanwhile the main stem continues caudad between the fascia or superficial muscles and the deep muscles of the caudal fin. In its course between these muscles it runs parallel with and mesad to the caudal fin nerve, and re- ceives branches from these muscles. At the base of the tail this vein takes a position quite close to the periphery, in fact, it trav- els for some little distance directly mesad of the posterior por- tion of the lateral lymphatic trunk, but never communicates with the same. It then bends mesad to enter the basal canal of the caudal fin, where it soon separates into the dorsal and ven- tral caudal fin veins (figs. 4-6, and 11, C.F.V.’ and C.F.V.”). In Scorpeenichthys the bifurcation of the main trunk of the caudal vein occurs usually anterior to that of the caudal artery, nerve, or the caudal lymphatic trunk, and for the most part the caudal fin veins lie anterior to the other vessels in the basal canal of the fin. In the Phanerodon embryo (fig. 11) the caudal artery forked at the base of the tail before the caudal vein did, and the caudal fin veins were posterior in position to the caudal fin arteries in the LYMPHATICS IN TAIL REGION, SCORPAANICHTHYS 9 basal canal of the fin; while in the Clinocottus series the order of bifurcation was: first the minor acudal artery, then the caudal artery, the caudal vein, and finally the caudal lymphatic trunk. With Scorpzenichthys both caudal fin veins receive numerous caudal ray veins (fig. 4, C.R.V.) from the caudal rays. Their arrangement, however, is not so regular as the caudal ray arteries. For example, the first of the dorsal caudal ray veins (see fig. 4) in addition to receiving a branch from the dorsal and ventral surface of the first dorsal caudal ray collects a third branch which traverses the ventral surface of the second dorsal caudal ray; while the second dorsal caudal ray vein takes its source solely from one stem, which passes along the dorsal surface of the sec- ond dorsal caudal ray vein. These veins collect the capillary networks from the fin membranes and from the rays themselves. The veins arising from the intrinsic muscles of the caudal fin empty separately into both lateral sides of the caudal fin veins. In the Clinocottus series I was unable to trace the main caudal vein much beyond its branching in the basal canal of the tail, and no caudal ray veins were seen unless the caudal ray canals (fig. 3, C.R.T.) function both for lymphatics and veins. Pos- sibly the injection method would have revealed caudal ray veins emptying into the caudal fin veins. Since, the caudal ray arteries and canals are distinctly visible in all the sections through the rays, one could hardly claim the section method faulty for not showing these vessels. As stated above, the caudal fin veins in a 30 mm. Phanerodon lie posterior to the caudal fin arteries in traveling through the basal canal of the tail. Only one caudal ray vein (fig. 11, C.R.V.) was observed coming from a caudal ray. Those from the dorsal half of the fin ran along the ventral side of the rays; while those from the ventral half of the fin followed along the dorsal surface of the rays. With the exception of the first ventral caudal ray vein, none of these vessels forked; this vein, however, divided, one branch came from the dorsal side of the second ventral caudal ray, and the other from the dorsal surface of the third ventral ray. The vascular supply for the caudal fin of a young Phanerodon embryo is therefore very simple. An artery traverses one side 10 WILLIAM F. ALLEN of a ray, while a vein follows along the opposite side of the ad- jacent ray. In the membrane connecting these two rays there is a network of capillaries, through which one could readily trace corpuscles going from the caudal ray arteries to the caudal ray veins. Vogt in Salmo, Hyrtl in Esox ( = Lucius) and Leuciscus, Emery in Fierasfer, Parker in Mustelus, Hopkins in Amia { =Amiatus), and Vogt and Yung in Perea did not trace the caudal vein further caudal than the last vertebra, that is to the caudal sinus. Jones . (p.676) describes the great vein in the tail of the eel as being formed from two branches, a larger and a smaller. The larger stem is said to receive the venous radicals from the terminal parts of the tail: while the smaller stem collects the venous radicals from the dorsal part of the tail, and near the junction with the former it receives the caudal heart. Sappey (p. 46; pl. xi, fig. 6 and pl. xii, fig. 3) finds that the caudal vein in the carp and pike arises from a dorsal or superior and a ventral or inferior branch in the base of the fin. At the level of the last vertebra they unite to again divide into a right and left branches, which reunite at the end of the last vertebra in forming the caudal vein. Shortly before anastomosing, each of the above branches are said to re- ceive a papilla from the lateral lymphatic trunk. According to McKenzie the venous system of Amiurus catus takes its origin in the tail from two vessels of unequal size. Silvester (p. 109) describes and figures the caudal vein in the tile-fish as having its source from two branches from the caudal fin. Favaro in numerous Teleosts notes practically the same arrangement as described above for Scorpeenichthys. In most species he rep- resents the caudal vein as beginning as a sinus, sinus venosus caudalis, under the last vertera, which not only receives the vein from the tail, but also the caudal lymphatic sinus, ventriculus cordis caudalis. Intersegmental or intercostal vessels. (Figs. 4 and 4a, Neu. A., Neu.V., H@.A., and He.V.; figs. 9 and 10, Neu. and L.A., Neu. and L.V.,L.A.,L.V.,H@.A.,and He.V.).—Apparently these blood ves- sels are practically the same in all species of Ganoids and Teleosts. They are destined to supply the body musculature, the vertebral LYMPHATICS IN TAIL REGION, SCORPZ2NICHTHYS 11 column, the myelon, all of the fins except the caudal, and the con- nective tissue surrounding the vertebral column, the body muscles, and the periphery. Ordinarily, as shown in fig. 9, below each ver- tebra, two lateral branches and one ventral branch are given off or received by the longitudinal blood vessels of the haemal canal. One of the lateral branches is a vein and the other is an artery; while half of the ventral branches are arteries and half are veins, there being an artery for each alternate vertebra and a vein for the intermediate alternate vertebrae. Upon examining fig. 9 from cephalad to caudad it will be seen that the arteries and veins alternately shift from one side to the other. For example, under vertebra numbered 14 the artery passes to the right side and the vein to the left; while under vertebra numbered 13 the artery goes to the left and the vein to the right. Furthermore, all of the ar- teries which pass in a lateral direction, upon leaving the hemal canal curve around to the side of the centra; where one-half of them, the lateral arteries (fig. 9, L.A.), follow the intermuscular septa laterad to the periphery, and the other half (fig. 9, Neu. and L.A.) bifureate; one branch, the lateral arteries (figs. 4 and 4a, L.A.), follow the intermuscular septa laterad to the periphery, and the other branch, the neural arteries (figs. 4 and 4a, New.A.) pass dorsad along the neural spines to the periphery. The same correlation occurs with the veins that pass in a lateral direction; one-half of them (fig. 9, L.V.) to trace backward, simply pass laterad to the periphery; while the other half, (fig. 9, New. and L.V.) to trace backward, bifurcate, one branch (fig. 4a, L.V.) going lateral to the periphery, and the other (fig 4a, Neu. V.) dorsad to the periphery. The arrangement of the ventral branches of the hzemal trunks is less complicated. Below one centrum an artery (figs. 9 and 4a, H@.A.) passes ventrad along its heemal spine to the periphery, and from under the next ver- tebra to trace backward a vein (figs 9 and 4a, He. V.), passes ventrad along the hemal spine to the periphery, and so on, the veins alternating with the arteries. The outcome of this complex arrangement is, that each alter- nate dorsal intermuscular septum receives a neural artery, and from every intermedian dorsal intermuscular septa there comes 12 WILLIAM F. ALLEN a neural vein. Likewise each alternate ventral intermuscular septum receives a hemal artery, and from every intermediate ventral septa there comes a hemal vein. Furthermore each alternate lateral intermuscular septum receives a lateral artery, and from every intermedian septa there comes a lateral vein. A glance at fig. 9 demonstrates that one intermuscular septum does not, however, possess a neural, heemal, and two lateral arter- ies, but, on the contrary, that septum may receive, as shown oppo- site vertebra numbered 9 in fig. 9, a neural, a lateral, and a heemal vein and a lateral artery; while the intermuscular septum opposite vertebra numbered 8 in the same figure has a neural, a lateral and a hemal artery and a lateral vein. Occasionally, however, some irregularities may occur, as for example, opposite verte- bra numbered 10 in fig. 9 and under the posterior vertebra. Of the two classes of arteries arising from the side of the caudal artery, those designated as lateral arteries (figs. 9 and 10, L.A.; indicated but not lettered in fig. 4), after leaving the hemal canal, curve around to the side of the centra, where each bends at right angles to pass laterad in the intermuscular septum. When about half way between the vertebra and the skin it divides into a dorsal and a ventral branch. In their course these branches supply the myotome in front and the one behind, and upon arriv- ing at the surface, above and below the lateral lymphatic trunk they usually follow dorsad or ventrad a short distance on the sur- face of the intermuscular septum to give off branches to the con- nective tissue between the skin and the muscles. The other lateral branches of the caudal artery (figs. 4 and 4a, Neu.A.,; figs. 9 and 10, New. and L.A.) are larger and more im- portant vessels. Like the lateral arteries described above they curve around to the side of the centra; where each separates into a lateral and a neural artery. The former (figs. 4 and 4a, L.A.) is identical to the lateral artery described above, and the latter (figs. 4 and 4a, Neu. A.) curves around to the dorsal side of the vertebra, where it follows up along the anterior surface of the corresponding neural spine. In crossing the vertebra it gives off a myelonal artery, which presumably passes through the spinal nerve formamen, to supply the myelon or the spinal cord; this LYMPHATICS IN TAIL REGION, SCORPANICHTHYS 13 point, however, was not determined for a certainty. At the apex of the neural spine a dorsal lateral artery (figs. 4a, D.L.A.) is sent off lateral along the intermuscular septum to the periphery, supply- ing the dorsal portion of the two adjacent myotomes. At this point the neural artery makes a cephalic bend to cross the bases of the depressor and levator muscles of the adjacent dorsal! ray. After which it takes another turn to pass dorsad between this levator muscle and the next depressor muscle to the level of ex- trinsic muscles of the dorsal fin; where it divides into an anterior and a posterior branch. The main stem and these branches sup- ply the intrinsic and extrinsic muscles mentioned above, and also send off two dorsal ray arteries (fig. 4a, D.R.A.), which follow up the posterior side of their respective rays, supplying each and their fin membrane. The ventral branches of the caudal artery or the hemal arter- ies (figs. 4, 4a, 9 and 10, He. A.) after leaving the hemal canal pursue a similar course ventrad to that of the neural arteries dor- sad. At the apex of each hemal spine a ventral lateral artery (figs. 4, 4a, V.L.A.) is given off to the periphery. It passes along the intermuscular septum, between two myotomes, supply- ing each. The main stem of the hemal artery crosses a depres- sor and a levator muscle of the adjacent anal ray, and then con- tinues ventrad to the extrinsic muscles of the anal fin between the above levator muscle and the next depressor muscle. Like the corresponding neural trunks upon reaching the extrinsic muscles it separates into an anterior and a posterior branch, which sup- plies the extrinsic muscles and the levator and two depressor muscles, and sends off two anal ray arteries (figs. 4a, A.R.A.) to the posterior surfaces of two rays, supplying them and their fin membrane. Intersegmental or intercostal veins. (Figs.4 and 4a, Neu. and He. V. fig. 9, New. and L.V.; L.V., and He. V.).—The arrangement and distribution of these veins is identically the same as the cor- responding arteries, with this difference that they lie in the inter- mediate alternate intermuscular septa and terminate in the cau- dal vein. So that the above description of the distribution of the neural, hemal, lateral, dorsal or ventral lateral, and the dorsal 14 WILLIAM F. ALLEN or anal ray arteries would apply equally well to the distribution of the corresponding neural, hemal, lateral, dorsal or ventral lateral, and the dorsal or anal ray veins (figs. 4, 4a, 9 and 10, Neu. V., He.V.; L.V.,. Di Vay sand DV): In general with the primitive fishes, Cyclostomes and Sela- chians, but one kind of intersegmental artery or vein is portrayed by Mayer and Favaro. It is represented as forking immediately after leaving the hzemal canal into a dorsal or neural and a ven- tral or hemal vessel; both of which send out numerous branches _ to the muscles, and a mesal branch to the spinal cord. In some eases, however, the hamal or ventral vessels may arise from or empty into the main longitudinal trunks. In the Ganoid Lepisos- teus (p. 52) these intersegmental vessels: were found to be practi- eally the same as described above for Scorpzenichthys. With the Teleosts, Vogt, Sappey, Me.Kenzie, Vogt and Yung, and Favaro found the neural and hemal vessels to be entirely separated, aris- ing or emptying directly into the caudal artery or the caudal vein. They, however, portrayed incorrectly a neural and a hemal artery and a neural and a hemal vein for each intermuscular septum. Silvester, however, described the correct relationship of these vessels in the tile-fish. LYMPHATICS OF THE TAIL A transverse section, as shown by fig. 12, through the caudal peduncle of Scorpzenichthys or Clinocottus severs six great longi- tudinal lymphatic canals. Four of which are superficial or sub- cutaneous, namely, the dorsal, ventral, and lateral lymphatic trunks , and two are deep seated, namely, the longitudinal neural and heemal lymphatic trunks. These lymphatic trunks collect superficial and: deep networks, which are decidedly lymphatic in the character of their meshes, from all tissues that are supplied with blood vessels. So far as could be determined these lymphatic canals had no connection with the blood vessels, either capillary, or direct with the caudal vein.2. Nevertheless, as will be noted in * In an earlier paper on the lymphatics of the head region of Scorpznichthys it was erroneously stated that the combined trunks formed by the union of the longi- LYMPHATICS IN TAIL REGION, SCORPZNICHTHYS LS detail later on, the lymphatics came into close touch with the caudal vein, but did not anastomose. Furthermore an injection of the longitudinal neural trunk often fills the caudal vein, and conversely an injection of either the caudal artery or vein often fills the entire lymphatic system. These occurrences I attribute to an extravasation of the injection mass through the thin walls separating these vessels rather than to a direct communication. SUBCUTANEOUS SYSTEM Lateral subcutaneous lymphatic trunks. (Figs. 1-2, 4-7, and 12, L.T.).— Bo pice es Spars poh Se = DES Dopshons WQS, GEL Ge ° GES peeGnae SSO. 00S Nv e N = < — =) = = = Q font < Zi © ie) 4 THE SOMITES OF THE CHICK 97 THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, No. 1. WILLIAMS ONARD W. LE 9S 99 THE SOMITES OF THE CHICK 6 1 “@y ‘GP BY: area @ OOO, OB» On Bare OOo, Te cy WO on nee os vs Je 3 : eS Sst Ue aes 100 LEONARD W. WILLIAMS i 7: THE NERVES AND NERVE ENDINGS IN THE MEMBRANA TYMPANI OF MAN J. GORDON WILSON Department of Otology, Northwestern University Medical School SIX FIGURES! THREE PLATES The membrana tympani though recognized by the anatomist to be a structure admirably adapted to play an important part in the mechanism of sound conduction, has not, until recently, received from the neurologist the attention it would appear to merit. At present the description of the nerve distribution in this membrane in mammals, with the exception of man, may be said to be in the main satisfactory. In man the account is not only meagre but lacking in many essential details. It is con- tained in the work of Kessel published in 1872, when the technic for nerves and nerve endings was less satisfactory than it now is. So far as I know, excepting a drawing by Kessel, believed both by Jacques and myself to be inaccurate, there have not appeared any illustrations of the nerve distribution. It is difficult to ac- count for this indifference. While it may be due in some small measure to a lack of appreciation of the importance of this mem- brane, it is mainly to be accounted for by the difficulty of the technic inherent in its structure. In a former paper (’07a) I described the mode of distribution and the varieties of endings found in the membrana tympani of the rabbit, dog, cat and monkey; in this paper I propose to extend these investigations to the membrana tympani of man. 1 The drawings have been made by Herr R. Schilling of Freiburg, and Miss Hill of the University of Chicago, to whom I wish to express my sincere thanks. THE AMERICAN JOURNAL UF ANATOMY, VOL, 11, No. 2 i JANUARY, 1911 102 J. GORDON WILSON The literature of the nerve distribution in this structure in mammals is by no means voluminous. In addition to the work quoted above, it is contained in papers by Kessel, Jacques, Cala- mida and Deinike. Of these the only author who has described the nerves in the membrane of man is Kessel. Jacques’ work was done in the membrane of the cat and dog; Calamida’s investi- gations were carried out on several of the lower animals—horse, eat, goat, ete.; Deinike limited his work to the ox and horse. The papers of Jacques, Calamida and Deinike are not here re- viewed as they do not bear directly on the nerves in man and further since this has been done sufficiently in a former paper. Within the last year an article has appeared by Gemelli on the nerves in the cat, horse, dog and ape. Kessel found that in man the principal nerve, composed of medullated fibers, passes from the external auditory meatus, on to the membrane at the upper part of the posterior segment close to and behind the artery. In the onward course of the nerve branches are given off which accompany the vascular twigs. Corresponding to the forking of the artery over the manubrium the nerve divides into two branches of which one supplies the an- terior, the other the posterior and lower part of the manubrium. Besides the main trunk several smaller nerves, accompanying blood vessels, pass to the membrane from various parts of the periphery. All these nerves in their course give off branches which lie between the cutis and membrana propria forming what he calls the ground plexus. Fibers also enter the membrana tympani from the plexus tympanicus; these fibers reinforce the nerve supply which reaches the mucous membrane from the cuticular side. The ultimate distribution of these nerves is to be found: (a) around the capillaries—forming a capillary plexus, (b) under the stratum Malpighii—forming a subepithelial plexus, (ec) under the mucous membrane—forming a submucous plexus. As a result of staining with chloride of gold he describes (d) in the course of the capillaries single nerve fibers consisting of axis cylinders in which are nodal swellings, containing anucleus, NERVES IN THE MEMBRANA TYMPANI OF MAN 103 at which two or more branches may be given off; these he regarded as probably ganglion cells; (e) in the plexus under the stratum Malpighii many bi- and multipolar ganglion cells. It is no easy task to obtain good results in investigating the nerves of this membrane. Like most of the investigators— Jacques, Calamida and Deinike—I find that ordinary staining methods are inapplicable. Osmic acid, apart from its limi- tations to medullated nerves, so blackens the tissue as to make it difficult to follow the nerve. Gold and silver salts cause so great a precipitate as to make them unsuitable for satisfactory work. Methylene blue is here an ideal method. The very thin- ness of the membrane, so objectionable for the other methods, renders it for this the more suitable. It is the method I have chiefly used; at times I have found a useful substitute in a com- bination of methylene blue and osmie acid. The method employed in this research was. as follows: after removal of the brain, the petrous temporal bone was loosened from the adjacent parts by means of a small chisel and then care- fully lifted out, cutting with a knife its fibrous and muscular attachments below. It comes away easily, leaving the tympanic membrane intact in the tympanic bone with the malleus attached to it. Usually the incus remains attached to the malleus; the stapes always comes away with the petrous portion. It is of some interest from the operative point of view to note that the attachment of the foot plate of the stapes to the foramen ovale is firmer than that of the incus to the stapes. The edges of the membrana tympani and the adjacent part of the covering of the external auditory meatus are now loosened and removed leaving the malleus still attached. By this means there can be detached the whole drum membrane with as much of its mucous layer extension to the middle ear and of the cuticular layer to the external meatus as may be desired. These are im- mersed in a.weak solution of methylene blue (three to six drops of a % per cent solution in 20 cc. of normal salt solution), which has been warmed to a temperature of 37°C. The tissue in this solu- tion is placed in a thermostat at 37° C. for three to eight minutes. 104 J. GORDON WILSON This warm solution dissolves the fatty material which lies on the surface of the membrane, loosens the epithelial scales, and in- creases the action of the dye on the nerves. The effect may be increased by brushing the external surface of the membrane with asmall clean camel’s hair brush dipped in the fluid. Finally the membrane is exposed to the air on a clean glass slide with the side uppermost on which one wishes to get the better repre- sentation of the nerves, usually the external. During this process the tissue is kept moist with a solution of methlyene blue at a temperature of 37° C. of the following strength: Methylene blue (nach Ehrlich) 0.5 per cent sol..........10 ce. or 5 ce. walt solution” (0:75 percent) neeseeer eee eer eer eae 90 ce. or 95 ce. The time at which the nerves begin to appear varies with the period after death at which the tissue is obtained, the sooner after death the earlier they appear, but I have obtained results six or eight hours after death when the body has been kept in a cold chamber. If nerves do not appear within one hour it may be regarded as useless to persevere. The dye is fixed in the nerve by immersion of the tissue in an 8 per cent ammonium molybdate solution. The subsequent treatment consisting of washing in water, passing through alcohol and xylol, has been fully described in a recent paper ('10b). The membrane may be mounted entire in Canada balsam, or, the malleus being removed, it may be im- mersed in paraffin and cut. Counterstaining when required, appears to me to be best obtained by a weak alcoholic solution of orange G. acid fuchsin. I find what may be called the principal nerve of the membrana tympani, n. tympanicus major (n. t.m.), enters as a broad bundle of fibers from the posterior edge of the membrana flaccida, on the upper posterior segment of the membrana tensa (fig.1).! It has an intimate relationship to the artery of the manubrium (a. m.t.), the vessel at first lies posterior to the nerve but as the ves- ‘In a single methylene blue preparation not all the nerves take up the dye; in one a particular group will appear well, while in a second it may be a different group. This is particularly so in the human membrana tympani where the tissue is not usually obtained till some hours after death. In the preparation from which this drawing was made many of the nerves in the posterior superior and in the inferior anterior quadrant did not stain. NERVES IN THE MEMBRANA TYMPANI OF MAN 105 sel and nerve approach the manubrium the artery passes under the nerve and inthe rest of its course lies adjacent to it, but nearer, to the manubrium. As the nerve bundle passes downward it frequently gives off branches which pass outwards towards the limbus, on the anterior side passing over and external to the manu- brium. At a point inferior to the middle of the manubrium the. nerve bundle spreads out and while at first the majority of its fibers still have a downward direction, the general tendency and ultimate courseis towards the limbus. A considerable number pass over the manubrium; of these some may be traced to the anterior limbus, but the greater number break up and get lost in the plexus over the manubrium or anterior to it. At the apex of the manubrium the fibers radiate out; some curving round the apex, join fibres which have crossed the manubrium, and pass out to the anterior limbus. In short, while the main nerve is passing down- wards along the manubrium it is constantly sending off on each side branches which have a general direction towards the pe- riphery. A smaller but well marked nerve bundle which has branched off from the main trunk in the external auditory meatus enters the membrana flaccida slightly superior to the main bundle. It is directed towards the anterior superior segment, and passes sometimes directly over the processus lateralis, but always within a short distance of it. In addition to these, numerous smaller bundles pass in from the external auditory meatus not only over the membrana flaccida, but all around the periphery. At the limbus these fibers can be noted at short irregular intervals entering under the epidermal prolongation. While the general direction of their main stem is towards the center of the membrana tensa, both external and in- ternal to the limbus, branches are given off which form a well marked plexus, the zonular plexus, from which fibers radiate toward the center. The radiating fibers whether coming from the nerves entering at the membrana flaccida or from the limbus give off numerous twigs and gradually get smaller. These twigs, in the main non- medullated or with a very faint medullary sheath, after usually a long course during which they repeatedly divide, pass into: 106 J. GORDON WILSON (a) a wide meshed plexus in the fibrous tissue, through which pass most of the fibers which help to form either, (b) a subepithelial plexus under the cuticular layer, or (c) a subepithelial plexus under the mucous layer. From these plexuses the fibers can be traced to various endings, in some cases looping through the plexus they pass into another nerve stem and so reach their endings. There are fibers which enter from the tympanic cavity. These, few in number compared with those from the meatus acusticus externus, come from the plexus tympanicus. They ultimately enter the plexuses in the fibrous tissue and underthemucouslayer. (a) The wide meshed plexus, the Grundgeflecht of Kessel and Deinike, is abundantly distributed throughout the whole fibrous tissue. It consists chiefly of the ramifications and interlacings of the nerves which enter from the meatus externus though fibers also reach it from the tympanic cavity. From it fibers are dis- tributed to the subcutaneous and submucous plexuses, as well as to the endings in the connective tissue. On account of the wide meshes of which the plexus is composed it is easy to follow a single branch for a long distance. Thus in fig. 2 a branch given off from a nerve n entering from the meatus externus canbe traced through repeated dichotomus divisions till it finally ends in a sim- ple branched ending (c) in the sub-epithelial plexus. In addition to these some very complex endings are seen in the fibrous tissue consisting of an intricate interweaving of a frequently dividing nerve fiber (fig.3). Into these endings there is often seen entering a second nerve (s), very fine and varicose. I have been unable to identify in man any of the plate-like endings described and fig- ured by Deinike in the horse which lie between the radiating and circular fibers; or those endings figured by myself in the dog lying in the connective tissue in this area. In the fibrous tissue near the periphery there are seen several varieties of endings whose size, shape and poorly developed cap- sule enable one to classify as modified vater-pacinian corpuscles (figs. 4 and 5). They lie immediately under the epithelium, no papillae being present in this area or in any part of the membrana tympani. In all these capsulated endings the interlacings are so NERVES IN THE MEMBRANA TYMPANI OF MAN 107 complex and lie at such varying levels that it is impossible to give any delineation which would exactly represent what exists. To do so would only result in inextricable confusion. So it has been found advisable to draw only the most evident of these windings. Inside the capsule in fixed preparations there appears a clear space which is due to a retraction of the fine fibrils during the process of fixation. The impression given by unfixed prepar- ations is that the ending is lying in a clear semi-fluid substance enclosed within the capsule; the clear space within the capsule does not appear. The sheath of Henle blends with the capsule. At the distal end a fine twig may pierce the capsule, divide and end in the epithelium immediately above the ending (fig. 5). At times a second, very fine varicose fibril can be seen to enter the capsule. These endings are frequently to be found in man though I have failed to find similar endings in the dog, cat or monkey, nor are they described by any of the other writers. As is known modified vater-pacinian corpuscles are widely distributed in the skin. They have been chiefly described in the tela subcutanea of the genital organs and in the conjunctiva. It is interesting to note their presence in the latter where they lie immediately under the epithelium, no papillae being present, since as will be referred to later there is a close correspondence between the nerve distri- bution in the cornea and membrana tympani. The subepithelial plexus, ausseres oberflachliches Geflecht of Deinike, consists of interlacing bundles of very fine varicose fibrils lying directly under the deepest layer of the epidermis. Many of these fibrils end after a long course in the terminal part of which they run in the deeper layer of the epidermis (fig. 6.) There is thus formed an intra-epithelial plexus from which fibers pass upward towards the surface and end between the cells as fine points. These endings often appear as knobs, but it appears to me that the knob-like processes are probably artifacts produced by the dye at the terminal] point, for in the best stained and sharply defined preparations the fine points are chiefly seen, whereas in the less satisfactory preparations the bulb-like point predominates. It is no unusual thing to trace a fiber a long distance through the subepidermal plexus and even through the intra-epithelial plexus, 108 J. GORDON WILSON then back into a different nerve bundle from the one it originally eame from. These fine or bulb pointed endings are the only ones to be found in the epidermis. I have never seen any touch cor- puscles. Lying in the connective tissue under the epidermis, in close proximity to the subepithelial plexus, are the branched endings shown in fig. 2. The submucous plexus, the inneres oberflaichliches Geflecht of Deinike, consists of interlacing fibers lying in the mucous layer under the epithelial lining. In close relation to it are also branched endings similar to those shown in fig. 2. The blood vessels are abundantly supplied by non-medullated, varicose nerve fibrils. These enter along with the main vessels both over the pars flaccida (Shrapnell’s membrane) and at the periphery and can be traced to the smaller vessels, forming the well known vaso-motor plexuses. Contrary to the opinion of Kessel no ganglion cells are to be seen anywhere in the membrana tympani. Such swellings as at times appear after gold chloride impregnation are to be identi- fied as nodal points or sheath cells. The close analogy between the nerve distribution in the mem- brana tympani and the cornea was pointed out by Jacques. It will be noted that we have the zonular plexus of the former cor- responding to the annular plexus of the latter, the ground plexus to the fundamental plexus, and a subepithelial and intra-epithelial plexus in both. Ina former paper (’07b) I ventured the following remark: “One is tempted to carry the analogy further and to say that as in the cornea pain and not touch appears to be the sensa- tion evoked, so also in the membrana tympani one might expect that the slightest pressure would evoke unpleasant sensations, passing into pain, a fact well borne out by clinical observations.” Since then I have made many observations to test this hypothesis and find that it is undoubtedly true. By lightly touching the membrana tympani either witha small piece of cotton wool or a fine hair mechanical stimulation from the threshold possesses unpleasantness. My results have been briefly stated in a recent paper (’10a), as follows: “‘if this membrane be touched with a fine NERVES IN THE MEMBRANA TYMPANI OF MAN 109 hair according as the pressure stroke of the hair is increased so ‘ do we pass from unpleasantness through acute pain in the ear to pain radiating along the n. auriculo-temporalis. This it appears to me is the impress put upon the organ through its phylogenetic history that injury will entail serious results to the individual, a case illustrating what Sherrington would probably call ‘a selec- tive adaptation attached to a specific sense of its own injuries.’”’ As in the cornea so in the membrana tympani there is in the epi- thelium but one morphological variety of nerve ending, namely, free endings lying near the surface between the epithelial cells. Moreover we have in the membrana tympani one other modi- fied skin structure in which pain is the only species of sensation which can be evoked. From this it would appear that in this structure there is additional support for Sherrington’s hypothesis that the noci-ceptive organs of the skin are probably naked nerve endings. In a former paper (’07a) there were stated the experimental data on which I based my claim that the nerve supply of the membrana tympani came chiefly from the n. mandibularis through the n. auriculo-temporalis and to a less extent from the n. vagus. Briefly these were that in dogs and monkeys, after section of the n. man- dibularis at its exit from the foramen ovale and of the n. auriculo- temporalis under the mandible, degeneration was observed in the nerves of the meatus acusticus externus adjacent to the membrana tympani as well as in the nerves of that membrane. Recently it has been asserted by Hunt that the chief nerve supply comes from the ganglion geniculi of then. facialis. The chief arguments which Hunt advances in favor of this view are based on: 1. The findings of comparative anatomy that the very consid- erable afferent distribution of the facial in the lower vertebrates has “in the course of phylogenetic development undergone a considerable shrinkage and displacement by the n. trigeminus. A vestigial remnant in the mouth is still demonstrable and an important sensory innervation of facial origin still exists in the middle ear and in the external ear.’’ But there is no proof that in the lower vertebrates above the cyclostomes there are sensory 110 J. GORDON WILSON fibers from the facial to the skin except in fishes for the innerva- tion of special sense organs belonging to the gustatory or lateral line system. Herrick has frequently asserted that there is no proof that the geniculate ganglion ever sends general sensory fibers to the skin; in all eases where generalsensory fibers distribute to the skin by branches of the facialis they either have a separate root of their own (as in cyclostomes) or enter the facialis distal to the geniculate ganglion by anastomosing branches from the gas- serian ganglion of the trigeminus. 2. The experimental results of Amabolino who after cutting the n. facialis at the stylo-mastoid foramen found retrograde degener- ation in the cells of the geniculate ganglion. These results do not show as Hunt asserts that these filers “are destined for the cutaneous distribution of the facial to the external ear.” It sim- ply proves that the facial contains afferent fibers, which may be and certainly some are nerves of deep sensation. 3. Clinical observations: (a) in the loss of sensation accom- panying facial paralysis; (b) in herpes oticus with paralysis of the n. facialis. (a) Tests for anaesthesia in this area must necessarily be unsatis- factory because of the very considerable overlapping of sensory nerves. Asaresult of my own observations as well as from a study of the cases quoted by Hunt I am convinced that such evi- dence cannot give data accurate enough to decide the point at issue. (b) The frequency of the association of herpes oticus with par- alysis of the pn. facialis and with auditory symptoms appears to lend considerable weight to Hunt’s hypothesis and cannot be summarily dismissed. Although herpes oticus is comparatively rare yet Hunt has carefully collected a number of cases in which this association is a marked feature. But as he points out facial paralysis also occurs with herpes facialis and herpes occipito-col- laris. He explains this by an associated inflammation of the geniculate ganglion “based on the well recognized tendency of this affection to produce inflammatory changes in a series of spinal ganglia. The Gasserian, geniculate and upper cervical consti- NERVES IN THE MEMBRANA TYMPANI OF MAN ig tute such a serial chain” (p. 84). As the “ganglion of the audi- tory nerve may be primarily involved in zona’”’ (p. 340), and so would be embraced within this series, it only remains to explain the implication of the facial from inflammatory changes in the geniculate. I recognize the cogency of Hunt’s arguments but feel that some- thing further is required to elucidate the point in question. There are two obvious possibilities, namely, that the fibers which I have shown reach the external auditory meatus by the n. auriculo- temporalis may come from the geniculate through the n. petrosus superficialis minor and the further possibility that fibers may pass from the n. facialis to the auricular branch of the n. vagus and so reach the meatus. In order to arrive at a conclusion in this possible peripheral distribution I have recently destroyed the geniculate in dogs and monkeys so as not to involve the ninth or tenth cranial nerves nor the branches from the second and third cervical. When the series are completed I hope to publish the results. CONCLUSIONS The membrana tympani of man is chiefly supplied by nerves which enter from the external auditory meatus. These pass in (1) as one large trunk along with the principal artery; (2) as numerous small branches around the periphery. These form a plexus in the fibrous tissue from which branches are distributed to a sub-epithelial and a sub-mucous plexus. In addition there are to be distinguished a zonular and an intra-epi- thelial plexus. There are nerves, fewer in number, which enter from the tym- panic cavity. The blood vessels are well supplied by vaso-motor nerves. Only one variety of nerve ending is seen in the epithelium. In the fibrous tissue both subcutaneous and submucous there are found nerve arborisations; at the periphery modified vater-pac- inian corpuscles are present. No ganglia are to be seen. 142 J. GORDON WILSON The nerve supply comes from the n. auriculo-temporalis and the n. vagus. We have not sufficient evidence to prove that nerves reached it from the ganglion geniculi. The sensation produced by lightly touching the membrane is pain and this is to be associated with irritation of the particular nerve endings found in the epithelium. BIBLIOGRAPHY Cauamipa, U. 1901 Terminazioni nervose nella membrana timpanica. Arch. Ital. di. Otologia, vol. 11, p. 326-329. DerntkE, D. 1905 Ueber die Nerven des Trommelfells. Arch. f. mikr. Anat.» Bd. 66, 5S. 116-120. Dociet. 1904 Zeitschrift. f. Wissenschaft. Zool., v. 45, 8. 61. Gemewu, A. 1909 Les nerfs et les terminaisons nerveuses de la membrane du tympan. La Cellula, t. 25, fase. 1. Hunt, T. Ramsay. 1907 The sensory system of the facial nerve and its systemat- ology. Jour. of Nerv. and Ment. Dis., vol. 36, p. 321-349, 1909; and vol. 34. Jacques, P. 1900 De la fine innervation dela membrane du tympan. 13 Cong. internat. du medicin. Sect. d’Otologie, p. 46, Paris. Kessex, J. 1872 Das fiussere Ohr. Handbuch der Lehre von den Geweben des Menschen; herausgeben von S. Stricker, Bd. 2, 8. 853, Leipsig. SHERRINGTON, ©. 8S. 1906 The integrative action of the nervous system. Pp. 227 and 319, New York. Witson, J. G. 1907a Thenerves and nerve endings in the membrana tympani. Jour. Comp. Neur. Psych., vol. 17, p. 459-468. 1907b Jour. Comp. Neurol. Psych., vol. Fe p. 466. 19102 Pain in the ear and its diagnostic significance. Quarterly Bull., N. W. U. M: S., vol. 11, pp. 211. 1910b Intravitan staining with methylene blue. The Anatomical Record, vol. 4, p. 267-277. PLATE 1 EXPLANATION OF FIGURE 1 Nerve distribution in the right membrana tympani of man. The pars flaccida with the head of the malleus has been removed. The nerves were stained with methylene blue and the specimen was mounted in Canada balsam. During the process of mounting the manubrim mallei was twisted so that the processus later- alis (p./.) is tilted posteriorly. The main nerve trunk (n.t.m.) together with the artery (a.m.t.) is seen entering over the posterior superior quadrant. Not all the peripheral nerves (p.n.) took up the dye but a sufficient number to give an ade- quate representation of their mode of distribution at the limbus. /. a.—limbus membranae tympani anterior l. p.—limbus membranae tympani posterior NERVES IN THE MEMBRANA TYMPANI IN MAN J, GORDON WILSON THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, No. 2 PLATE 1 PLATE 2 EXPLANATION OF FIGURES 2 Course of a nerve passing in from the periphery to end in the sub-epi- thelial plexus. From the peripheral medullated nerve (7) a branch (b) is given off near the hmbus. From (6) numerous twigs branch off in the fibrous tissue with a common direction towards the sub-epithelial plexus. In the course of division the medullary sheath gets fainter and finally disappears. Terminal branches (c) were seen breaking up in the sub-epithelial plexus. Zeiss comp. oc. 4, obj. 8 mm. and obj. 2 mm. 3 A branched non-capsulated ending in the fibrous tissue of the membrana tympani. The nerve (n) breaks up into a dense mesh work of fibers from which off-shoots go forward into the adjacent connective tissue. < 210. Ao., aorta; M.C., path of cells migrating into sympathetic anlage; M.P., muscle plate ; Nc., notochord; Sp.G., spinal ganglion; Sy., anlage of symphathetic trunk. arise may be distinguished from the cells of the mesenchyme by their slightly deeper stain and by the characteristic chromatin structure of their nuclei. The cells in these tracts leading from the spinal ganglia into the cell-aggregates constituting the anlagen of the sympathetic trunks are not closely aggregated nor is there any evidence that they are embraced in syncytia. Although mitotic figures in their various phases occur frequently along SYMPATHETIC SYSTEM IN TURTLES 283 these paths, the peripheral advancement of the cells cannot be accounted for by the pressure due to mitotic division. These elements are too loosely aggregated to permit of being pushed forward by the pressure which might be exerted by the mere crowding due to the multiplication of cells. Neither is there any apparent line of weakness in the mesenchyme which might deter- mine the path of these migrant nervous elements. The course taken by them is approximately the most direct course from the distal ends of the spinal ganglia into the regions in which the an- lagen of the sympathetic trunks arise (fig. 1, M. C.). At the close of the ninth day of incubation the anlagen of the sympathetic trunks are present from the cervical to the sacral region. The cell-aggregates constituting the anlagen of the sym- pathetic ganglia appear in tranverse sections as oval or elongated cell-masses lying along the lateral surfaces of the aorta and along the dorsal surfaces of the carotid arteries. These cell-aggregates are best developed in the thoracic and in the dorsal region, 2. e., in the regions in which the sympathetic anlagen first arise. The spinal ganglia are now well differentiated and the fibers of the spinal nerves may be traced peripherally for some distance beyond the level of the aorta. The anlagen of the ganglia of the sympathetic trunks are connected with their respective nerves by cellular tracts. In some sections fibers appear in the proximal parts of these cellular tracts, constituting the earliest fibers of the communicating rami. The cellular tracts extending from the distal ends of the spinal ganglia into the anlagen of the sym- pathetic trunks, which were so conspicuous in the previous stage, no longer appear. The cells which become separated from the cerebro-spinal nervous system in the region of the trunk now migrate peripherally along the paths of the spinal nerves and of the communicating rami (fig. 2). At this stage, cells apparently become separated from the spinal ganglia in considerable numbers. At the same time cells may be traced from the mantle layer in the ventral part of the neural tube, across the marginal veil, into the proximal parts of the ven- tral nerve-roots. That cells migrate from the neural tube into the ventral nerve-roots cannot be doubted. In many sections THE AMERICAN JOURNAL OF ANATOMY, VOL. ll, NO. 3 284 ALBERT KUNTZ Fig. 2 Transverse section through the trunk region of a nine-day embryo of Thalassochelys caretta. XX 210. Ao., aorta; M.P., muscle plate; Ne., notochord; Sp.G., spinal ganglion; Sp.N., spinal nerve; Sy., anlage of symphathetie trunk; V.N.R., ventral nerve-root. continuous lines of cells may be traced from the mantle layer into the proximal parts of the ventral nerve-roots, and occasionally one of these cells may be observed half in and half out of the neu- ral tube. These cells obviously advance peripherally along the fibers of the ventral nerve-roots. After they have advanced beyond the point of union of the dorsal and the ventral nerve- roots it is no longer possible to distinguish between the cells which have their origin in the ventral part of the neural tube and wander SYMPATHETIC SYSTEM IN TURTLES 285 out along the ventral nerve-roots and those which wander down from the spinal ganglia. As the cells advancing peripherally along the paths of the spinal nerves reach the origin of the com- municating rami many of them deviate from the course of the spinal nerves and enter the anlagen of the sympathetic trunks (fig. 2, Sy.). The cells which wander into the anlagen of the sympathetic trunks along the paths of the communicating rami are, doubtless, derived in part from the spinal ganglia and in part from the ventral part of the neural tube. The great majority of the cells present in the spinal nerves are still undifferentiated and there is no reason to suppose that cells advancing peripherally from the spinal ganglia enter the sympathetic anlagen while those advancing peripherally from the ventral part of the neural tube do not. Furthermore, the fibers growing peripherally into the communicating rami are primarily ventral root fibers. If the growing nerve-fibers exert any guiding influence on the peri- pherally advancing cells, as, doubtless, they do, it is highly prob- able that many of the cells which wander out along the fibers of the ventral nerve-roots wander along these fibers into the anlagen of the sympathetic trunks. In his work on the development of the head of Gymnophion, Marcus (’10) described light areas in contact with and partly surrounding the anlagen of the sympathetic trunks in the early stages. These areas he interpreted as lymph spaces and ex- pressed the opinion that the anlagen of the ganglia of the sym- pathetic trunks grow mesially from the spinal nervesin these lymph spaces or at least are surrounded by them. To quote: ‘Der Zellstrang der Sympathicusanlage waichst medianwarts vor, gegen die Dorsalseite der Aorta zustrebend. Dabei kann ich mich des Eindrucks nicht erwehren, dass der Sympathicus in einem Lymph- raum seitlich der Aorta hineinwichst oder dochjedenfalls, dass er von Lymphgefiszen umspielt ist.’’ In the early stages in embryos of the turtle, narrow spaces simi- lar to those described by Marcus in embryos of Gymnophion may be observed in contact with and in some cases almost sur- rounding the anlagen of the sympathetic trunks as they appear in transverse sections. Such spaces, however, are not present 286 ALBERT KUNTZ in all sections, while in some sections they appear on the lateral sides of the sympathetic anlagen and are not apparent on the mesial sides. It may be noted at this point that while in the eight-day stage such light areas sometimes appear in contact with the loose cell- ageregates constituting the anlagen of the sympathetic trunks, there is no evidence of such areas of weakness in the mesenchyme along the paths of migration of the cells which wander from the distal ends of the spinal ganglia into the anlagen of the sympa- thetic trunks before the spinal nerves may be traced peripherally. In view of this fact and in view of the fact that the connections of the anlagen of the sympathetic trunks with the spinal nerves along the paths of the communicating rami arise after the anlagen of the sympathetic trunks are already present, it does not seem probable that in embryos of the turtle the anlagen of the sympa- thetic trunks grow peripherally in lymph spaces, but rather that lymph spaces are formed in contact with the sympathetic anlagen. My observations on embryos of Thalassochelys and on embryos of Chelydra are in full agreement on this point. Lymph spaces in contact with the anlagen of the sympathetic trunks cannot be satisfactorily traced in the later stages in embryos of the tur- tle because, as will be shown presently, the anlagen of the sympa- thetic trunks soon become more or less scattered and no longer appear as compact cell-aggregates. At the close of the eleventh day of incubation the anlagen of the sympathetic trunks have become somewhat larger and more conspicuous. They now lie in closer proximity with the aorta and are connected with the spinal nerves by comparatively thick fibrous communicating rami (fig. 3, C. R.). The anlagen of the sympathetic trunks no longer appear as definitely limited cell- aggregates, but are becoming somewhat scattered. In trans- verse sections they appear to be made up of several irregular cell- groups more or less closely associated with each other (fig. 3, Sy.). Such scattering of the anlagen of the sympathetic trunks is less apparent in the anterior than in the posterior region of the body. In the anterior region the anlagen of the sympathetic trunks appear in transverse sections as somewhat transversely = | SYMPATHETIC SYSTEM IN TURTLES 287 elongated cell-aggregates lying along the dorsal surfaces of the carotid arteries. Farther posteriorly the sympathetic anlagen lie close to the dorso-lateral aspects of the aorta. From the region of the suprarenals posteriorly scattered cell-groups may be found as far ventrally as the ventral level of the aorta. The spinal nerves are at this stage large and conspicuous fiber-tracts containing numerous accompanying cells which are apparently migrating peripherally. Migration of medullary cells into the ventral nerve-roots has probably reached its maximum at about this stage. In nearly every section which passes through Fig. 3 Transverse section through the anlage of the sympathetic trunk in an eleven-day embryo of Thalassochelys caretta. X 210. Ao., aorta; C.R., communi- cating ramus; Sp.N., spinal nerve; Sy. anlage of sympathetic trunk. the origin of a ventral nerve-root cells may be observed in the mar- ginal veil, while in many sections complete lines of cells may be traced from the mantle layer into the proximal part of the ventral nerve-root. It may be of interest to note that in embryos of Thalasso- chelys caretta cells may be traced from the ventral part of the neural tube into the ventral nerve-roots more readily than in embryos of Chelydra serpentina. This is probably due to the fact that the former develop more slowly than the latter and that, therefore, the migrant medullary cells linger for a longer period at the point of exit from the neural tube. Fibers are now present in the dorsal nerve-roots connecting the spinal ganglia with the neural tube. In a few sections cells 288 ALBERT KUNTZ could be observed apparently on their way from the dorsal part of the neural tube into the dorsal nerve-roots. It is not probable, however, that many cells wander out from the dorsal region of the neural tube along the fibers of the dorsal nerve-roots. Migra- tion of cells from this region of the neural tube is probably only a transient process which may play some part in the development of the spinal ganglia. At the close of the thirteenth day of incubation the anlagen of the sympathetic trunks appear to be somewhat more widely scat- tered than in the preceding stage. The communicating rami have assumed no greater prominence and their fibers cannot yet be traced beyond the anlagen of the sympathetic trunks. In many sections cell-strands may be observed pushing out from the spinal nerves proximal to the origin of the communicating rami toward the anlagen of the sympathetic trunks. These cell-strands are similar to those described by Held (09) in embryo of Emys europea. From the region of the suprarenals posteriorly cells move ventrally from the anlagen of the sympathetic trunks and build up cell-aggregates along the ventro-lateral aspects of the aorta which, as will be shown later, constitute the anlagen of the pre- vertebral plexuses. Cells still migrate peripherally both from the spinal ganglia and from the ventral part of the neural tube along the paths of the spinal nerves. The marginal veil in the neural tube, however, is becoming wider and cells are apparently migrating into the ven- tral nerve-roots less rapidly than in the preceding stages. During the seventeenth day of incubation the anlagen of the sympathetic trunks are still more widely scattered than in the preceding stage (fig. 4, Sy.). The communicating rami have not increased in size appreciably nor is there much evidence that cells still continue to wander along their paths into the sympathetic anlagen. The cell-strands which at the close of the thirteenth day were observed pushing out from the spinal nerves proxi- mal to the origin of the communicating rami now appear as irreg- ular cellular tracts extending diagonally through the mesenchyme toward the dorso-lateral aspects of the aorta where they become SYMPATHETIC SYSTEM IN TURTLES 289 merged with the anlagenof the sympathetic trunks (fig. 4, S.C. R.). In a few sections these cellular tracts were observed to unite with the communicating rami just proximal to the point at which the latter enter the sympathetic anlagen. The cellular tracts above described apparently have their ori- gin in the spinal nerves. In a few instances at this stage fibers were Fig. 4 Transverse section through the anlage of the sympathetic trunk in a sixteen-day embryo of Thalassochelys caretta. X 210. Ao., aorta; C.R.,°com- municating ramus; S.C.R., secondary cellular tract extending from the spinal nerve into the anlage of the sympathetic trunk; Sp.N., spinal nerve; Sy., anlage of sympathetic trunk. observed to deviate from the spinal nerves along these cellular tracts. These fibers may usually be recognized as ventral root fibers. They deviate from the spinal nerves at a point so near the union of the dorsal and the ventral nerve-roots that they may readily be traced proximally as fibers of the ventral roots. 290 ALBERT KUNTZ As development advances these cellular tracts assume greater prominence and gradually become more fibrous. ‘The interval along the spinal nerve separating the origin of the primary com- municating ramus from the origin of this secondary tract gradu- ally decreases until the two tracts come into close proximity and finally fuse with each other. The secondary tract is not carried forward along the spinal nerve-trunk, but the primary communi- cating ramus is crowded backward somewhat. This is probably due to the formation of the coelom and of the Wolffian bodies. The angle between the primary communicating ramus and the proximal part of the spinal nerve, which in the early stages is an obtuse angle, has now become an acute angle. At the close of the twentieth day of incubation the primary communicating ramus and this secondary tract have come to lie in such close proximity with each other that in some instances they can no longer be dis- tinguished as separate tracts. That the origin of the communicating ramus 1s actually shifted proximally along the spinal nerve-trunk is shown bythe curve in the accompanying figure (fig. 5). This curve is based on actual measurements of the interval between the origin of the ventral nerve-root and the origin of the primary communicating ramus in successive stages ranging from the thirteenth to the twenty- eighth day of incubation. The curve is based on the averages of five independent measurements. The figures in the horizontal line indicate the number of days of incubation of the embryos; the figures in the vertical line indicate the relative length of the intervals between the origin of the ventral nerve-roots and the origin of the primary communicating rami in embryos at succes- sive stages of incubation. This curve shows that the interval between the origin of the ventral nerve-root and the origin of the primary communicating ramus increases until the close of the twentieth day of incubation; then decreases until the close of the twenty-second day of incubation, after which it again increases. The somewhat abrupt descent in this curve which occurs between the twentieth and the twenty-third day of incubation, doubtless, indicates an actual proximal displacement of the origin of the pri- mary communicating ramus along the spinal nerve-trunk. SYMPATHETIC SYSTEM IN TURTLES 291 The accompanying diagrams (figs. 6 and 7) have been intro- duced to illustrate successive stages in the process by which the primary communicating rami are shifted proximally along the spinal nerve-trunks until they fuse with the secondary tracts growing mesially from the proximal parts of the spinal nerves. After the twenty-fourth day of incubation but a single tract may be recognized connecting the sympathetic anlage with the Fig. 5 Curve designed to indicate the relative length of the intervals between the origin of the ventral nerve-root and the origin of the primary communicating ramus in embryos of Thalassochelys caretta in successive stages of development. For explanation see text. spinal nerve. This tract is distinctly fibrous, but still contains numerous accompanying cells. Most of the cells present in the communicating rami in these later stages, doubtless, have wan- dered out from the spinal ganglia. There is no longer any evi- dence of the peripheral migration of cells from the ventral part of the neural tube, except as an individual cell occasionally passes through the external limiting membrane. The development of the sympathetic trunks in embryos of the turtle proceeds comparatively slowly. After cells cease to 292 ALBERT KUNTZ migrate peripherally from the cerebro-spinal nervous system the anlagen of the sympathetic trunks assume more definite propor- ee 2. Fig. 6 Diagrammatic transverse section through the trunk region of a twenty- day embryo of Thalassochelys caretta. Ao., aorta; C.R., communicating ramus; Ne., notochord; S.C.R., secondary cellular tract from spinal nerve to sympathetic anlage; Sp.G., spinal ganglion; Sp.N., spinal nerve; Sy., anlage of sympathetic trunk; V.N.R., ventral nerve-root. Fig. 7 Diagrammatic transverse section through the trunk region of a twenty- four day embryo of Thalassochelys caretta. Ao., aorta; C.R., communicating ramus; Ne., notochord; S.C.R., secondary cellular tract from spinal nerve to sympathetic anlage; Sp. G., spinal ganglion; Sy., anlage of sympathetic trunk; V.N.R., ventral nerve-root. tions, but the sympathetic ganglia do not appear as compact and definitely limited cell-aggregates until development has advanced for a considerable period after this stage is reached. SYMPATHETIC SYSTEM IN TURTLES 293 The breaking up of the anlagen of the sympathetic trunks, the formation of secondary cellular tracts extending from the proxi- mal parts of the spinal nerves into the sympathetic anlagen, and the proximal shifting of the origin of the communicating rami along the spinal nerve-trunks above described, which are so con- spicuous in embryos of the turtle, in all probability, represent a condition which is characteristic of reptiles and which has phylo- genetic significance. His, Jr., (97) called attention to the fact that in the chick two pairs of sympathetic trunks arise in the course of ontogeny. These he has designated as the ‘primary’ and the ‘secondary’ sym- pathetic trunks. In my work on the development of the sympa- thetic nervous system in birds,’ I was able to substantiate this observation of His, Jr. The primary sympathetic trunks in the chick arise about the beginning of the fourth day of incubation, as a pair of cell-columns lying along the sides of the aorta and along the dorsal surfaces of the carotid arteries. The anlagen of the secondary sympathetic trunks arise about the beginning of the sixth day of incubation, as ganglionic enlargements on the median sides of the spinal nerves. The cells giving rise to both the pri- mary and the secondary sympathetic trunks migrate peripher- ally from the spinal ganglia and from the ventral part of the neural tube along the paths of the spinal nerves. In the early stages some of the cells advancing peripherally along the paths of the spinal nerves deviate from the course of the latter and wander toward the lateral surfaces of the aorta where they become aggregated to give rise to the primary sympathetic trunks. A little later the cells advancing peripherally no longer wander toward the aorta, but become aggregated at the median sides of the spinal nerves to give rise to the anlagen of the secondary sympathetic trunks. As development advanees and the communicating rami grow mesially the entire cell-aggregates constituting the anlagen of the secondary sympathetic trunks are displaced toward the aorta at the distal ends of the growing communicatingrami. Asthesecond- > The development of the sympathetic nervous system in birds. Jour. Comp. Neur. Psych., vol. 20, no. 4, pp. 283-308. 294 ALBERT KUNTZ ary sympathetic trunks increase in size and prominence the pri- mary sympathetic trunks decrease until they finally disappear. The phenomena above described in embryos of the turtle are of peculiar interest in view of the phenomena involved in the devel- opment of the sympathetic trunks in the chick. In embryos of the turtle, as in the chick, the earliest traces of the sympathetic trunks are found along the lateral surfaces of the aorta. In em- bryos of the turtle these formations do not give way completely to secondary formations, as is the case in the chick, but early break up to become aggregated once more during the later stages of development. Again, in embryos of the turtle, cells do not become aggregated at the median sides of the spinal nerves to form ganglionic enlargements, as is the case in the chick, but deviate from the course of the spinal nerves proximal to the origin of the communicating rami and advance in irregular cellular tracts toward the anlagen of the sympathetic trunks. In short, the phe- nomena involved in the development of the sympathetic trunks in the turtle seem to represent a generalized prototype of what has become a highly specialized condition in birds. This does not mean, however, that the sympathetic nervous system in turtles is the direct ancestral type of the highly specialized sympathetic nervous system in birds. The sympathetic nervous system in turtles is, doubtless, a specialization of a still more generalized type in the ancient reptiles. The points of correspondence which have been pointed out, however, seem to warrant the conclusion that the sympathetic nervous system in birds bears a more or less direct phylogenetic relationship to the sympathetic nervous sys- tem in the ancestral type of reptiles. b. Histogenetic relationships. In my earlier papers I have shown that the cells which migrate peripherally from the cere- bro-spinal nervous system in embryos of mammals and of birds are the descendants of the ‘germinal’ cells (Keimzellen) of His; viz, the ‘indifferent’ cells and the ‘neuroblasts’ of Schaper. They have the same genetic relationships, therefore, as the cells which give rise to the neurones and to the neuroglia cells in the central nervous system. The great majority of the cells which migrate peripherally from the spinal ganglia and from the ventral SYMPATHETIC SYSTEM IN TURTLES 295 part of the neural tube in embryos of the turtle also answer to the description of the ‘indifferent’ cells of Schaper. They are char- acterized by very little cytoplasm and by large rounded or elon- gated nuclei showing a delicate chromatin structure. In the sym- pathetic anlagen some of these cells early develop protoplasmic processes and may, therefore, be recognized as neuroblasts. Although neuroblasts have not infrequently been observed in the spinal and in certain of the cranial nerves in vertebrate embryos, I was not able to observe cells with distinct protoplasmic processes along the paths of migration of the cells giving rise to the sympa- thetic nervous system in embryos of the turtle. The great majority of the cells present in the mantle layer in the neural tube in embryos of the turtle answer to the description given above for the cells which migrate peripherally. There can be no doubt, therefore, that the cells which take part in the devel- opment of the sympathetic trunks have the same genetic relation- ships as the cells which give rise to the neurones and to the neu- rolgia cells in the central nervous system. Mitotic figures in their various phases occur frequently all along the paths of migration and in the sympathetic anlagen. We are not to sup- pose, therefore, that all the cells taking part in the development of the sympathetic trunks actually migrate as such from their sources in the cerebro-spinal nervous system. Doubtless, many arise bythe mitotic division of ‘indifferent’ cells along the course of migration as well as in the sympathetic anlagen. Prevertebral plexuses At the close of the eleventh day of incubation of embryos of Thalassochelys caretta, after the anlagen of the sympathetic trunks have begun to break up and to become somewhat scat- tered, cells may be observed wandering ventrally from the anla- gen of the sympathetic trunks in the entire region from the suprarenals posteriorly. At the close of the thirteenth day, these cells have become aggregated into groups of considerable size lying along the ventro-lateral aspects of the aorta. These cell-groups constitute the anlagen of the prevertebral plexuses. 296 ALBERT KUNTZ At the close of the sixteenth day of incubation the anlagen of the prevertebral plexuses have become more conspicuous, but, like the anlagen of the sympathetic trunks, they are composed of cell-aggregates which are more or less scattered (fig. 8, P.V.). The limits of the anlagen of the several prevertebral plexuses eannot be determined at this stage. The cell-aggregates com- posing them are scattered to such an extent that traces of one or the other of these plexuses are not wanting in any transverse section in the entire region from the suprarenals to the poster limits of the hypogastric plexus. From the seventeenth to the twentieth day of incubation the anlagen of the prevertebral plexuses assume more definite pro- portions, but many lesser cell-groups still remain more or less scattered. In the region of the origin of the iliac arteries, cells wander mesially from the anlagen of the sympathetic trunks and descend between the iliac arteries to give rise to a wedge shaped cell-aggregate lying in the median plane of the body just dorsal to the mesentery (fig. 9, S.C. G. ). Insome sections the ventral angle of this cell-aggregate projects slightly into the mesentery, while a few cells apparently become separated from it and wander ventrally toward the rectum. Continuous lines of sympathetic cells could not be traced ventrally in the mesen- tery, but in many sections in this region groups of nervous ele- ments may be observed in the tissues associated with the walls of the rectum (fig. 9,8. C.R.). This process of migration of cells from the anlagen of the prevertebral plexuses in the posterior region of the body toward the rectum, doubtless, begins at an earlier stage. I was not able, however, to observe distinct groups of nervous elements associated with the rectum until about the nineteenth or the twentieth day of incubation. In the earlier paper referred to above the writer traced the origin of the ganglion of Remak in the chick to cells which mi- grate ventrally from the anlagen of the hypogastric plexus. The ganglion of Remak in the chick is a conspicuous cell-column more or less circular in transverse section lying in the mesentery just dorsal to the rectum. Furthermore, the suggestion was offered that the ganglion of Remak may have its prototype in SYMPATHETIC SYSTEM IN TURTLES 297 Fig. 8 Transverse section through the anlage of the sympathetic trunk and the genital ridge in an embryo of Chelydra serpentina 10 mm. in length. X 210. Ao., aorta; G.P., anlage of genital plexus; G.R., genital ridge; P.V., anlage of prevertebral plexus; Sy., anlage of sympathetic trunk. 298 ALBERT KUNTZ the aggregates of sympathetic cells associated with the rectum in embryos of reptiles. In view of the probable phylogenetic relationship which has already been pointed out between the Fig.9 Diagrammatic transverse section through the iliac arteries and the rec- tum in a wenty-day embryo of Thalassochelys caretta. J.A., iliac arteries; Mes., mesentery; #., rectum; S.C.G., sympathetic cell-aggregate dorsal to the mesen- tery; S.C.R., sympathetic cells associated with the rectum. Sy., anlage of sym- pathetic trunks; P.V., anlage of prevertebral plexus. sympathetic nervous system in reptiles and in birds, it is highly probable that the sympathetic cell-aggregates associated with the rectum in turtles are not far removed from the ances- SYMPATHETIC SYSTEM IN TURTLES 299 tral type of the ganglion of Remak which is so enormously de- veloped in the avian branch of the vertebrate series. Genital plexuses In embryos of Thalassochelys caretta from the sixteenth to the twentieth day of incubation or in embryos of Chelydra ser- pentina about 10 mm. in length, cells may be traced ventrally along the median sides of the Wolffian bodies to the lateral sur- faces of the genital ridges (fig. 8, G. P.), where they become aggre- gated to give rise to the genital plexuses. The conditions here described agree with the conditions described by Held in embryos of Emys europea. Vagal sympathetic plexuses a. Introductory. In my earlier papers I have shown that in mammals and in birds the sympathetic plexuses related to the vagi; viz., the cardiac plexus and the sympathetic plexuses in the walls of the visceral organs, do not arise from cells which migrate ventrally from the sympathetic trunks and from the pre- vertebral plexuses, as the earlier investigators believed, but have their origin in cells which migrate from the vagus ganglia and from the walls of the hind-brain along the paths of the vagi. Be- cause of the genetic relationship of these plexuses to the vagi, I have designated them as the ‘vagal sympathetic’ plexuses.‘ More recently I have traced the cells giving rise to the sympathetic plexuses in the walls of the digestive tube in fishes to the same sources. The present series of observations will show that in the turtles also the cardiac plexus and the sympathetic plexuses in the walls of the visceral organs arise from cells which have their origin in the vagus ganglia and in the walls of the hind-brain and migrate peripherally along the paths of the vagi. b. Myenteric and submucous plexuses. In transverse sections through the anterior region of the cesophagus in embryos of 'Thal- 4The development of the sympathetic nervous system in mammals, p. 230. Jour. Comp. Neur. Psych., vol. 20, no. 3, pp. 211-258. THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, NO. 3 300 ALBERT KUNTZ assochelys caretta during the twelfth or the thirteenth day of incubation, the vagus trunks appear as conspicuous fiber-bundles lying a little above the level of the trachea. In some sections short fibrous branches may be traced from the vagus trunks. Cells become separated from the vagus trunks and wandering out along these fibrous branches escape from their growing tips and become arranged in a broken ring encircling the cesophagus (fig. 10, M.S.P.). Cells may be observed apparently wandering out from the vagus trunks also in sections in which fibrous branches Fig. 10 Transverse section through the cesophagus of a thirteen-day embryo of Thalassochelys caretta. x 140. M.S.P., anlagen of myenteric and submucous plexuses; Oe., cesophagus; 7’., trachea; Vag., vagus nerves. are not apparent. At this stage small groups of sympathetic cells may be traced completely round the cesophagus dorsally, while on the ventral side similar cell-groups may be traced mes- ially from the vagus trunks into the area between the cesophagus and the trachea where they become lost in the deeply staining tissues in that area. The vagus trunks may be traced poste- riorly nearly to the stomach, and as far as they may be traced SYMPATHETIC SYSTEM IN TURTLES 301 cells wander out from them and become arranged in a broken ring encircling the cesophagus. At the close of the seventeenth day of incubation the cell-aggre- gates in the walls of the cesophagus have become more conspicu- ous and the cells composing them more numerous. They are no as Fig. 11 Transverse section through the region of the heart in a seventeen- day embryo of Thalassochelys caretta. < 110. B., bronchi; C.P., anlage of cardiac plexus; D.W.A., dorsal wall of atria; Mes., mesentery; M.S.P., anlagen of myen- teric and submucous plexuses; Oe., cesophagus; Vag., vagus nerves. longer arranged in a single broken ring, but the anlagen of the myenteric and the submucous plexuses are becoming more dis- tinct (fig. 11, M.S. P.). Branches of the vagi may now be traced along the walls of the stomach. From these branches cells may be traced laterally in the walls of the stomach until the latter is completely encircled by groups of sympathetic cells. 302 ALBERT KUNTZ The exact course of the development of the myenteric and the submucous plexuses in the walls of the intestine is not easily deter- mined. Cells apparently migrate posteriorly in the walls of the intestine from the anlagen of the myenteric and the submucous plexuses in the anterior region of the digestive tube. On the other hand, as already indicated, cells migrate ventrally from the an- lagen of the prevertebral plexuses in the posterior region of the body and become aggregated along the walls of the rectum. There is no evidence of the migration of cells from the anlagen of the prevertebral plexuses into the walls of the digestive tube farther anteriorly until the anlagen of the myenteric and the submucous plexuses have become well established. The evidence at hand seems to indicate that in the anterior region of the intestine the myenteric and the submucous plexuses arise from cells which migrate peripherally along the paths of the vagi, while in the pos- terior region at least some of the cells taking part in the develop- ment of the sympathetic plexuses in the walls of the intestine wander down from anlagen of the prevertebral plexuses. c. Pulmonary plexuses. In transverse sections through the region of the lungs of embryos of Thalassochelys caretta at about the fifteenth day of incubation branches of the vagi appear to be closely associated with the bronchi as the latter enter the tissues of the lungs. Cells wander in along these branches and give rise to the anlagen of the pulmonary plexuses. d. Cardiac plexus. In transverse sections through the anterior region of the heart of embryos at about the seventeenth day of incubation the mesocardium lies far to the left. In this region a fibrous branch accompanied by numerous cells may be traced ventrally from the left vagus trunk into the dorsal wall of the left atrium where many of the accompanying cells become aggregated to form the anlagen of the cardiac plexus in this region (fig. 12, C.P.). Intransverse sections a little farther posteriorly inembryos of the same stage the mesocardium lies ventral to the oesophagus. In this region fibrous branches accompanied by numerous cells may be traced from both the right and the left vagus trunks into the dorsal wall of the heart where cells become aggregated to give rise to the anlagen of the cardiac plexus in this region (fig. 11, C. P.). SYMPATHETIC SYSTEM IN TURTLES 303 e. Histogenetic relationships. The above observations on the development of the myenteric and the submucous plexuses, the pulmonary plexuses, and the cardiac plexus in embryos of the turtle agree essentially with the writer’s observations on the devel- opment of these plexuses in embryos of mammals and of birds. These plexuses arise from cells which have their origin in the hind- brain and in the vagus ganglia and migrate peripherally along the paths of the vagi. In sections passing through the vagus rootlets in is Fig. 12 Transverse section through the anterior region of the heart in the same embryo as fig. 1]. x 140. B., left bronchus; C.P., anlage of cardiac plexus; L.A., left atrium; D.Vazg., left vagus nerve. embryos at about the tenth or the eleventh day of incubation medullary cells may be traced from the walls of the hind-brain into the rootlets of the vagi (fig. 13, Vag. R.). That such cells wander into the vagus rootlets in considerable numbers cannot be doubted. In many sections medullary cells are drawn out into cone-shaped heaps in the vagus rootlets as they traverse the mar- ginal veil. Occasionally one of these cells may be observed half in and half out of the external limiting membrane, while numerous cells are present in the vagus rootlets just outside the external 304 ALBERT KUNTZ limiting membrane. The vagus ganglia at this stage appear as elongated cell-masses which are not sharply limited distally. Cells apparently become separated from their distal ends and migrate peripherally along the paths of the vagi. As far as the latter may be traced peripherally they are accompanied by numerous cells many of which become separated from the vagus trunks and become distributed in the walls of the digestive tube to give rise to the myenteric and the submucous plexuses, or wander into the an- lagen of the other vagal sympathetic plexuses. Fig. 13 Sections through vagus rootlets in an eleven-day embryo taken at different levels. X 350. E.L.M., external limiting membrane; Vag.R., vagus rootlets. It may be of interest to note at this point that embryos of the turtle afford exceedingly satisfactory preparations for the study of the development of the vagal sympathetic plexuses. The cells constituting the anlagen of these plexuses are exceedingly numer- ous and respond readily to differential stains. In well stained preparations the cells giving rise to these plexuses can be traced from the vagus trunks with such certainty that there can be no doubt as to their genetic relationship. Furthermore, cells can- not be traced into the anlagen of these plexuses, except in the posterior region of the intestine, from any other source until they have become well established. These observations do not pre- clude the possibility that a few cells may be transferred from SYMPATHETIC SYSTEM IN TURTLES 305 the sympathetic trunks into the anlagen of these plexuses after the latter have become connected wih the former by sympathetic nerves. Such connections of the vagal sympathetic plexuses with the sympathetic trunks must, however, be looked upon as of only secondary importance in their development. The cells which migrate peripherally from the walls of the hind- brain and from the vagus ganglia along the paths of the vagi in embryos of the turtle, like the cells which migrate peripherally from the cerebro-spinal nervous system in the trunk region, are characterized by very little cytoplasm and by large rounded or elongated nuclei showing a delicate chromatin structure. They are, therefore, cells of the same character; viz., the ‘indifferent’ cells of Schaper. Inasmuch as thses cells give rise to the vagal sympathetic plexuses, these plexuses also bear a direct genetic relationship to the cerebro-spinal nervous system. Mitotic figures occur frequently along the paths of the vagi and in the anlagen of the vagal sympathetic plexuses. We are nottosuppose, therefore, that all the cells which take part in the development of the vagal sympathetic plexuses actually migrate as such from their sources in the hind-brain and in the vagus ganglia. As in the case of the sympathetic trunks, doubtless, many of these cells arise by the mitotic division of ‘indifferent’ cells along the course of migration. DISCUSSION The observations set forth in the preceding pages have shown that in turtles the sympathetic nervous system bears a direct genetic relationship to the central nervous system. The cells giving rise to the anlagen of the sympathetic trunks and of the prevertebral plexuses have their origin in the spinal ganglia or the neural crest and in the ventral part of the neural tube and mi- grate peripherally either through the mesenchyme or along the paths of the spinal nerves and of the communicating rami. The vagal sympathetic plexuses; viz., the cardiac plexus and the sym- pathetic plexuses in the walls of the visceral organs, are not de- rived from the same sources, but arise from cells which have their 306 ALBERT KUNTZ origin in the hind-brain and in the vagus ganglia and migrate peripherally along the paths of the vagi. These findings agree essentially, in regard to the sources of the cells giving rise to the sympathetic nervous system, with the writer’s observations on the histogenesis of the sympathetic nervous system in mammals, birds, and fishes. They disagree widely with all the observations hitherto recorded on the development of the sympathetic nervous system in reptiles. They disagree also with the observations of the earlier investigators on the development of the sympathetic ner- vous system in the other classes of vertebrates primarily in two particulars: (1) some of the cells which enter the anlagen of the sympathetic trunks are found to have their origin in the ventral part of the neural tube and to wander out along the paths of the motor nerve-roots; (this fact was observed by Froriep (’07) in embryos of Torpedo and of the rabbit) ; (2) the vagal sympathetic plexuses are found to bear no direct genetic relationship to the sympathetic trunks, as the earlier investigators supposed, but arise from cells which have their origin in the hind-brain and in the vagus ganglia and migrate peripherally along the paths of the vagi. The phenomena presented in embryos of the turtle may throw some new light on the problems involved in the peripheral migra- tion of embryonic nervous elements. Among the more recent investigators, Froriep (’07) has sug- gested that the nerve-fibers constitute the vehicles by means of which nervous elements are carried peripherally. According to his view the peripheral displacement of these cells is accomplished either by the growth of the axones alone or by the growth of the axones coupled with the active migration of the cells along the fibers. Held (09) advanced the theory that the ‘so called’ wandering of the sympathetic anlagen is brought about by the pressure which is exerted by the mitotic division of proliferating elements in an elongating cell-column, coupled with the formation of peripheral protoplasmic processes which are endowed with the property of contractility and must, therefore, exert a pull in a longitudinal direction as soon as osmotic influences act upon their growing substance. SYMPATHETIC SYSTEM IN TURTLES 307 In a recent paper on the development of the sympathetic nervous system in certain fishes,’ I have shown that neither of these theories are adequate to account for the phenomena observed. Furthermore, I have presented evidence in support of the view that the peripheral migration of cells from the cerebro-spinal ner- vous system into the sympathetic anlagen is probably determined by the influence ofsubstances, hormones, which are produced by the cells in the richly nourished regions which are to become their ultimate destination. As already indicated, before the spinal nerves may be traced peripherally in embryos of the turtle cells become separated from the distal ends of the spinal ganglia and migrate diagonally through the mesenchyme toward the lateral surfaces of the aorta. Fibers are not present along these paths nor are the cells closely aggre- gated. Thereseemstobeno purely mechanical means, therefore, by which these cells could be carried forward or by which they could be guided in their course. During the later stages of development, as has also been shown, cells deviate from the course of the spinal nerves before reaching the origin of the communicating rami and advance by a more direct course toward the anlagen of the sym- pathetictrunks. In thiscase the cells are usually more or less closely aggregated, thus forming distinct cellular tracts which advance mesially from the spinal nerves. Mitotic figures occur along these tracts, but they are not sufficiently numerous to account either for the rapid increase in the number of cells present or for their advancement toward the sympathetic anlagen. We must con- clude, therefore, that cells are actually displaced from the spinal nerves toward the sympathetic anlagen along these cellular tracts. In these later stages, as in the stages in which the spinal nerves can not yet be traced peripherally, there is apparently nothing in the structure of the mesenchyme which might determine the course of the peripherally advancing nervous elements. The phenomena above described seem to support the view that the peripherally advancing nervous elements are attracted toward the regions in which the sympathetic anlagen arise by the influ- 5 Jour. Comp. Neur. Psych., vol. 21. 308 ALBERT KUNTZ ence of substances, hormones, which are produced in those regions. Furthermore, the form-changes of the nuclei of the migrant cells indicate that these elements play more than a passive role in their peripheral advancement. All along the paths of migration, both in the nerve-trunks and in the cellular tracts passing through the mesenchyme, many of the nuclei are distinctly elongated, while in the sympathetic anlagen they resume a more rounded outline. Not infrequently these migrant cells present evidence of amoeboid movement. In some instances the nuclei are irregular in outline, while in still others they are distinctly pyriform with the broader end directed peripherally. These variations in the form of the nuclei of these migrant nervous elements, doubtless, indicate the presence of processes going on within the cells which play a part in their peripheral advancement and which are probably stimulated by the influence of the same agents which determine the direction of migration. The phenomena observed in the development of the vagal! sym- pathetic plexuses indicate that the peripheral migration of the cells giving rise to these plexuses is determined by the same in- fluences which determine the peripheral migration of the cells giving rise to the sympathetic trunks. The cells which become distributed in the walls of the digestive tube to give rise to the anlagen of the myenteric and the submucous plexuses wander out from the vagus trunks and become aggregated into small cell- groups which are more or less closely associated with each other, but many of which, in the early stages, are quite free from nerve- fibers. The distribution of these cells cannot be explained by the purely mechanical processes involved in growth or by osmotic influences. If, however, we assume that the location of these cell-groups is determined by the influence of hormones which are produced by the cells in the walls of the digestive tube the problem becomes very simple. Likewise, the cells which wander into the walls of the heart to give rise to the cardiac plexus are not com- pactly aggregated in the early stages, nor are they always found in contact with nerve-fibers. Here again the problem becomes simple if we assume that sympathetic cells are attracted toward the heart by the influence of hormones which are produced in that region. SYMPATHETIC SYSTEM IN TURTLES 309 It may be pointed out, furthermore, that the theory advanced above may be applied to the peripheral migration of the cells giving rise to the vagal sympathetic plexuses as well as of the cells giving rise to the sympathetic trunks. In either case the direction of migration is toward a region in which there is an abundant food supply and which is the seat of primary vegetative processes. In- asmuch as the sympathetic nervous system is concerned primarily with the control of the purely vegetative functions we may suppose that the sympathetic elements respond primarily to the influence of hormones which are produced in these regions. As has already been pointed out, the cells which migrate pe- ripherally from the cerebro-spinal nervous system have the same genetic relationships as the cells which give rise to the neurones and to the neurogla cells in the central nervous system. The sym- pathetic nervous system is, therefore, homologous with the other functional divisions of the peripheral nervous system and the sym- pathetic neurones are homologous with their afferent and their efferent components. SUMMARY 1. In embryos of the turtle the anlagen of the sympathetic trunks arise as cell-aggregates lying along the lateral surfaces of the aorta and along the dorsal surfaces of the carotid arteries. The cells which give rise to the anlagen of the sympathetic trunks have their origin (a) in the spinal ganglia or in the neural crest and (b) in the neural tube. Before the spinal nerves may be traced peripherally, cells advance from the distal ends of the spinal ganglia, directly through the mesenchyme, into the anlagen of the sympathetic trunks. After the spinal nerves have grown peripher- ally, cells migrate from the spinal ganglia and from the ventral part of the neural tube along the paths of the spinal nerves and of the communicating rami into the anlagen of the sympathetic trunks. These findings agree, in regard to the sources of the cells giving rise to the sympathetic trunks, with the writer’s observa- tions on the histogenesis of the sympathetic trunks in mammals, birds, and fishes. They disagree with the findings of the earlier investigators, except those of Froriep, primarily in the fact that 310 ALBERT KUNTZ cells which wander out from the ventral part of the neural tube take part in the development of the sympathetic trunks. 2. About the eleventh day of incubation the anlagen of the sympathetic trunks begin to break up and to become more or less scattered. This scattering continues for a considerable period until the cell-groups again become aggregated into compact ganglia. 3. About the thirteenth day of incubation cell-strands push out from the spinal nerves proximal to the origin of the communi- cating rami and advance toward the aorta. These cell-strands increase in size and advance mesially until at the close of the six- teenth day they appear as irregular cellular tracts extending from the spinal nerves into the anlagen of the sympathetic trunks. 4. As development advances, the primary communicating rami are shifted proximally along the spinal nerve-trunks until they fuse with the cellular tracts extending from the proximal part of the spinal nerves into the anlagen of the sympathetic trunks. 5. A comparative study of the development of the sympathetic trunks in embryos of the turtle and in the chick strongly suggests a more or less direct phylogenetic relationship between the sympa- thetic nervous system in birds and in the ancestral type of reptiles. 6. The prevertebral plexuses arise as cell-aggregates lying along the ventro-lateral aspects of the aorta. They are derived from cells which migrate ventrally from the anlagen of the sym- pathetic trunks. 7. In the sacral region, cells may be traced ventrally from the anlagen of the prevertebral plexuses into the mesentery where they become aggregated into small cell-groups associated with the rectum. These sympathetic cell-groups probably represent the prototype of the ganglion of Remak in birds. 8. In the region of the genital ridges cells migrate ventrally from the anlagen of the prevertebral plexuses and become aggre- gated at the lateral surfaces of the former to give rise to the genital plexuses. 9. The vagal sympathetic plexuses; viz., the cardiac plexus and the sympathetic plexuses in the walls of the visceral organs, arise, SYMPATHETIC SYSTEM IN TURTLES ok not from cell which migrate ventrally from the sympathetic trunks, as earlier workers supposed, but from cells which have their origin in the hind-brain and in the vagus ganglia and mi- grate peripherally along the paths of the vagi. The results here recorded agree with the writer’s observations on embryos of mam- mals, birds, and fishes. 10. The phenomena presented in embryos of the turtle afford evidence in favor of the view advanced by the writer in an earlier paper, according to which the peripheral displacement of the cells taking part in the developmentof thesympathetic nervous system is probably determined by the influence of hormones. 11. In turtles, as in the higher vertebrates, the cells which migrate peripherally from the cerebro-spinal nervous system into the sympathetic anlagen have the same genetic relationships as the cells which give rise to the neurones and to the the neuroglia cells in the central nervous system. The sympathetic nervous system is, therefore, homologous with the other functional divi- sions of the peripheral nervous system, and the sympathetic neurones are homologous with their afferent and their efferent components. Ske ALBERT KUNTZ BIBLIOGRAPHY Froriep, A. 1907 Die Entwickelung und Bau des autonomen Nervensystems. Med. naturwiss. Archiv, vol. 1, pp. 301-321. Heup, H. 1909 Die Entwickelung des Nervengewebes bei den Wirbeltieren. Leipzig. Die Entstehung der sympathischen Nerven, pp. 212-242. Horrmann, C. K. 1890 Sympathisches Nervensystem. Bronn’s Klassen und Ordnungen des Thier-Reichs, pp. 1961-1962. Kuntz, A. 1909 A contribution to the histogenesis of the sympathetic nervous system. Anat. Rec., vol. 3, pp. 158-165. 1909 The rdéle of the vagi in the development of the sympathetic nerv-- ous system. Anatomischer Anzeiger, vol. 35, pp. 381-390. 1910 The development of the sympathetic nervous system in mam- mals. Jour. Comp. Neur. Psych., vol. 20, no. 3, pp. 211-258. - 1910 The development of the sympathetic nervous system in birds. Jour. Comp. Neur. Psych., vol. 20, no. 4, pp. 284-308. 1911 The development of the sympathetic nervous system in certain fishes. Jour. Comp. Neur. Psych., vol. 21. Marcus, H. 1910 Beitrage zur Kenntnis der Gymnophionen. IV. Zur En- twickelungsgeschichte des Kopfes. II. Teil. Sympathicus, pp. 419- 424. Festschrift fiir R. Hertwig, Bd. 2 .1910. Neumayer, L. 1906 Histogenese und Morphogenese des peripheren Nerven- systems, der Spinaiganglien und des Nervus Sympathicus. Handbuch der vergl. und exper. Entwickelungslehre der wirbeltiere, pp. 513-626. His, Jr. 1897 Ueber die Entwickelung des Bauchsympathicus beim Hithnchen und Menschen. Archiv Anat. u. Entwg. Supplement. THE DEVELOPMENT OF THE PARAPHYSIS AND PINEAL REGION IN REPTILIA JOHN WARREN From the Anatomical Department, Harvard Medical School THIRTY-NINE FIGURES THIRTEEN PLATES CONTENTS ThaeROC ROOST er BP on odo oddone GMA tne SEO 313 ID GRUNT UO Sace sae hee ee ee eer fe ILS - oot nang harman Oh o coe ae 314 TL ewerescriail 4a. sare inte ee a ee PN i adie Sete ete lees: aaa rne a 347 Mehmmandspostrvelar Arch. ..2. 02:5 oc < «(sides Hoes sala seas eee la 351 GOTO Ciel gO LERUES OS) loys ts ait. vc bis wid clan Sie + 2a ec RE ee Rep eee see 357 GOMMISSUMES EAE cles acetals dons wala A ede ore ee ee Oe eet 360 SME ROMEOMIMIUISSUTE ....5)-)oi2. <' oi cc cn g's soe 2 eee eee ere eee eee 362 TEipetierdiie Carne Oboe eee eed eee IA. 3 SIA Nee 6 Sune Gen ic oo OEE 363 eaiaAIsEAMCLPINCAl, CYC. ....2 cc << 04 acc -c15 +5) see Poets ees ny ee eee cl 365 SUTTER Y RANT OMEOMCISUOIM ... vs e°< v0 dace « 2+ su sky 2 REL Ae uel orsay seater pea ema cree 368 PES MEIN Oy eRe eL EIEN eA NPM oy oes ay ALE GA. 3 ev a ena cv alse se Rs fale Succes ee Rae ae oer Se 371 INTRODUCTION The term ‘pineal region’ is used here in the same sense in which it was introduced by Minot in the morphology of this region in Acanthias, and refers to those structures arising from the roof of the prosencephalon and diencephalon, particularly the paraphysis, velum transversum, epiphysis, superior and poster- ior commissures and the choroid plexuses. This paper is the fifth one on this region based on studies from material in the Har- vard Embryological Collection and the observations were made THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, NO. 4 MAY, 1911 314 JOHN WARREN on various forms of lizards, Lacerta muralis, agilis and viridis, and also on the turtle, Chrysemys marginata. The other papers were the following: 1. C. 8. Minot. The Morphology of the Pineal Region based on its Development in Acanthias, 1901. 2. F. Dexter. The Development of the Paraphysis in the Common Fowl, 1902. 3. J. Warren. The Development of the Paraphysis and Pineal Region in Necturus maculatus, 1905. 4. R. J. Terry. The Morphology of the Pineal Region in Teleosts, 1910. As a great deal has been written on the details of this region, especially in the lacertilia, it seemed desirable to consider the growth of the structures arising from this part of the brain rather from the standpoint of topographical development, and with this end in view wax reconstructions of the fore and mid brain of each stage have been made. Owing to the amount of material available in the Harvard Embryological Collection, a more complete series of stages of the complicated development of this region can be shown than has been described heretofore. The reconstructions display the structure of this region better than ordinary sections and also demonstrate more clearly the topography of this part of the brain. DESCRIPTION Lacertilia The observations were made on specimens of Lacerta muralis agilis, and viridis. The models are magnified 110 diameters. Fig. 1 is a model of a part of the brain of an embryo of Lacerta muralis of 1.8 mm.