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Recelyed for publication July 9, 1909.
Recelyed for publication July 9, 1909.
==THE PHYLOGENY OF THE FACIAL NERVE AND CHORDA TYMPAN==
RALPH EDWARD SHELDON, A88i8tant Professor of Anatomy, University of Pittsburgh.
With Six Figures.
The structure of the human nervous system is so complex and is modified in so many ways from the normal vertebrate type that the interpretation of its morphology and function often becomes a matter of serious disagreement. The situation is further complicated by the fact that experimentation, open to the student of lower animals, is necessarily barred in an investigation of the highest. It is largely owing to these considerations that the question of the innervation of the tongue for the sense of taste is even now, after seventy years of study, one of the most disputed points in human anatomy. This discussion is for the purpose of calling attention to the ease with which a careful analysis of the data furnished by phylogenetic history will elucidate the most vexed questions of human morphology.
The tongue is innervated by two sensory nerves, the glossopharyngeal and the lingual. While the former takes its course direct from the posterior part of the tongiie to the petrosal ganglion, the latter is joined shortly by the chorda tympani from the facial nerve. (Fig. 6.) It would seem that the question as to which of these nerves fur ^Address given before a joint meeting of the Chicago Neurological Society and the University of Chicago Biological Club, March .30, 1909.
(593)
D 594 Ealph Edward Sheldon.
nishes the fibers for taste could be easily settled by their dissection in the adult, by sections of embryological material or by the observations made in clinical or other pathological cases. Such studies have, however, led to the most diverse results. Since the time of the researches of Claude Bernard in 184:3 most authorities have been agreed in assigning the fibers for taste for the anterior part of the tongue (one-third to four-fifths) to the chorda tympani and denying their presence in the lingual above its junction with the chorda. Lussana, Wolf and Halban found that section of the chorda led to the loss of taste in the anterior part of the tongue while Blau obtained taste sensations by stimulation of the same nerve. Disease of the middle ear, aflFecting the chorda, after ihe observations of TJrbantschitsch, Schlichting, Kiesow and Nadoleczny and Koster, likewise causes loss of taste. Destruction of the lingual V above its junction with the chorda almost invariably is without effect on the sense of taste, although Schiff in 1887 and recently Koster, consider that a part of the taste fibers go by way of the lingual either directly into the Gasserian ganglion or into the otic and thence to the brain.
There is likewise considerable unanimity in regard to the source of the taste fibers for the posterior part of the tongue. The work of Dana, Pope, Cassirer, Zander, etc., demonstrates conclusively that these belong to the glossopharyngeal, the lingual IX. Most authors are agreed that these fibers originate from cells in the petrosal ganglion and connect directly through the sensory IXth root with the fasciculus solitarius. Some few, as noted in Fig. 5, trace the glossopharyngeal fibers, however, into the brain by way of Jacobson's nerve and the small superficial petrosal to the trigeminus. Such a view is given little weight at present. The controversy, then, centers on the course which the taste fibers from the anterior part of the tongue take after they enter the facial nerve from the chorda tympani. The earlier workers, such as Claude Bernard, Lussana, Duchenne and Vulpian, believed that these fibers took the most obvious course and entered the brain through the pars intermedia of Wrisberg. Clinicians in removal of the Gasserian ganglion or resection of the second or third ramus of the trigeminus for facial neuralgia often noted a complete loss of taste on the anterior part of the tongue of the same side.
D The Facial Nerve and Chorda Tympani. 595
Similar conditions M^ere observed in cases of lesions affecting these nerves. Many such cases have been described, notably those by Erb, Ferguson, Gowers, Salomonsohn, Turner, Senator, Ziehl, Kron, etcL These cases have been so numerous and have been supported by such a weight of authority that even now the most widely accepted course for the chorda taste fibers is by way of the fifth nerve. Men holding this view differ, however, as to whether the taste fibers enter the brain by way of the maxillaris or the mandibularis branch of the trigeminus and likewise as to the pathway by which they reach these rami from the facial trunk. That most generally accepted traces the chorda fibers into the geniculate ganglion, thence through the great superficial petrosal and Vidian nerve to the sphenopalatine ganglion and thence into the maxillaris. Another course advocated is by way of the geniculate ganglion, the anastomotic branch to the small superficial petrosal, thence to the otic ganglion to the mandibularis nerve. It should be noted that practically all these cases rest upon clinical observations of pathological cases. As Scheier ('95) observes, many of these presented chronic lesions which are rarely local and might easily affect other nerve roots or ganglia. The same is true with the operations for removal of the Gasserian ganglion particularly as performed by the Hartley-Krause method. Few of the cases, moreover, were carefully studied for a long period of time by trained observers. The importance of this will appear later.
There are many cases recorded in opposition to this interpretation and it must be argued that a large number of such cases of removal of the Gasserian ganglion without interference with taste negative any number of cases accompanied by loss of taste. If the ganglion can be removed in its entirety without loss of taste the taste fibers certainly cannot go through it. Brunns, Tooth, Thomas, Tiffany^ Frankl-Hochwart, and Fasola all note such cases. The most convincing, however, is the report of Gushing ('03) who removed the Gasserian ganglion completely in eleven cases and partially in two. Observations on the sense of taste were made in practically all the cases before operations. There was a temporary diminution or loss of taste in most of the cases, but in all but one taste returned eventually. The exception was under observation for only six days after
D 596 Ralph Edward Sheldon.
the operation. These results offer the strongest kind of evidence that the taste fibers for the anterior part of the tongue do not enter the brain by the way of the trigeminal nerve. Probably in the first cases noted other nerves were affected or else the cases were not under observation for a sufficiently long time.
Some recent experimental work on the lower vertebrates (Sheldon, '09) indicates that these discrepancies may be due to another cause: viz., that the nerves of general sensation, as found in the trigeminal nerve, for instance, react to certain kinds of chemical stimuli. Under fluch conditions, therefore, destruction of the Gasserian ganglion or of the lingual above its junction with the chorda might affect what we call the sense of taste.
Of course it is possible that the taste fibers enter the brain by way of the glossopharyngeal nerve. Such a course has been advocated by Carl, Herman, and Cassirer, for instance. The usual course advocated is by way of the chorda tympani, geniculate ganglion, ramus anastomoticus to the small superficial petrosal and thence into the plexus tympanicus and Jacobson's nerve to the petrosal ganglion. Another course su^ested is by way of the lingual nerve into the otic ganglion and thence iJirough the small superficial petrosal into Jacobson's nerve. While there is some anatomical evidence that there are fibers in the small superficial petrosal running in the direction indicated, there is little support to the view that these are taste fibers from the chorda tympani. The fibers certainly could not be derived from the geniculate ganglion as will be pointed out later, and there is no conclusive evidence that glossopharyngeal fibers enter the chorda or the lingual from the otic as Carl advocates. If the chorda fibei^ do not enter the brain through the fifth or the ninth nerve they must pass by way of the seventh. The situation here is complicated by the fact that clinicians generally find no interference with taste in lesions of the facial nerve in facial palsy, provided the lesions are centrad of the geniculate ganglion. Lesions or fractures peripherally of the ganglion in the temporal bone usually destroy taste in the anterior part of the tongue on the same side. Such evidence is presented by Wachsmuth, or more recently and fully by Koster, Rosenfeld, Kopczynski and Scheiber. It may be pointed out here, however, that the evidenceIC
The Facial Nerve and Chorda Tympani. 597
is not conclusive in these cases that the portio intermedia is involved. It might easily happen that the motor root is destroyed without injury to the sensory. This is supported by the large number of cases of destruction of the facial centrad of the ganglion involving the sense of taste on the anterior part of the tongue. Such cases are cited by Claude Bernard, Brunns, Lehman, Scheier, Panski, Donath, etc. Summarizing the clinical and other pathological cases we may say that the evidence is quite conclusive to the effect that taste fibers do not enter the brain by way of the fifth nerve, equally conclusive that the fibers from the anterior part of the tongue do not enter the ninth nerve and inconclusive so far as the pars intermedia is concerned.
So far as the innervation of the soft palate for taste is concerned there is much difference of opinion. The weight of evidence however, as Dixon points out, is to the effect that it is innervated through fibers from the geniculate ganglion through the great superficial petrosal, the sphenopalatine ganglion and the palatine nerves. Part of these fibers may, however, come from the glossopharyngeal nerve through Jacobson's nerve and the anastomotic branch from the tympanic plexus into the great superficial petrosal.
Writers who deny that the taste fibers for the chorda originate from the geniculate ganglion usually argue that the ganglion is sympathetic and may be concerned with fibers of that type found in the lingual. There is little doubt that the chorda contains sympathetic fibers for the submaxillary gland. Sympathetic fibers are also undoubtedly present in the glossopharyngeal, the superficial petrosal nerves and Jacobson's nerve. Part of these fibers are probably postganglionic with their cells of origin in some of the many sympathetic ganglia of this region ; on the other hand a large proportion of such fibers found in the chorda tympani and associated visceral nerves are without question of the preganglionic type with their origin in the brain. Such include visceral efferent fibers of the secretory or excito-glandular type and vaso-motor fibers. The presence of such fibers, common to all the visceral nerves, in the pars intermedia of Wrisberg, cannot, therefore, be sufficient ground for assuming that this root or the geniculate ganglion are exclusively sympathetic.
Embryological and histological studies give more positive results.
D 598 Ralph Edward Sheldon.
Alexander ('02) found loss of taste after degeneration of the geniculate ganglion, which would show that the chorda fibers take their origin from it From the time of His it has been known that the course of conduction in nerves can be demonstrated through knowledge of their method of growth ; that is, an efferent nerve grows out from the brain while an afferent nerve grows, both toward the brain, and peripherally from its ganglion. His, Dixon and Streeter show conclusively that the facial is a mixed nerve, motor and sensory, and that its sensory part, the pars intermedia of Wrisberg, and the geniculate ganglion are similar in structure with the sensory parts of other nerves. Retzius, Martin, von Lenhossek and Ramon y Cajal, all working on mammals, have shown that the geniculate ganglion conforms to the cerebro-spinal rather than to the sympathetic type. It possesses the same kinds of cells as do other ganglia of the central nervous system and these cells send their processes both into the brain and peripherally. Roller, Turner, Huguenin, van Gehuchten, Ramon y Cajal and many others trace these central fibers into the fasciculus solitarius, known to be the center for taste in the human brain. Alexander obtained a peripheral degeneration of both the chorda and the great superficial petrosal. Sapolini traced fibers from the geniculate ganglion into the chorda, von Lenhossek believed that such was the course of the fibers, Weigner traced part of these fibers into the great superficial petrosal, Ramon y Cajal did likewise, while Dixon and Streeter found that both this and the chorda arise as outgrowths of the geniculate ganglion. This evidence shows that the geniculate ganglion is not sympathetic but cerebro-spinal in type, that its cells join centrally the taste centers of the medulla oblongata, and that its peripheral outgrowths form the chorda tympani and the great superficial petrosal nerves. Dixon shows that at the fifth week in the human embryo this latter nerve is free from any anastomoses with the fifth and that if any fibers grow into it from the fifth they must do so at a very late date. The anatomical evidence is, therefore, conclusive that the fibers for taste for the anterior part of the tongue are derived from the geniculate ganglion and enter the brain through the pars intermedia of Wrisberg. The question now arises as to the extent to which comparative neurology will clarify the question. It has been noted that the fas
D The Facial Nerve and Chorda Tympani. 599
ciQulus solitarius, the central connection of the fibers from the geniculate ganglion, is likewise the terminus for the taste fibers of the ninth nerve and is, therefore, the center for taste in man. Comparative studies show that the facial muscles of man are derived from the musculature of the hyoid arch of the lower vertebrates ; the facial is, therefore, the nerve of the hyoid segment, just as the ninth is the nerve for the first posthyoidean segment. Such studies have also shown that although the tongue musculature has grown forward from the postbranchial segmented mesoderm that the sensory surfaces of the tongue in man belong to more rostral segments. The case is, simply, that the sensory surfaces involved retain their primitive innervation with only a slight shifting while more caudal muscles grow forward when the tongue evolves in phylogenetic history. We, therefore, find that the mucous surface of the posterior part of the tongue in man belongs to the first posthyoidean segment or that of the ninth nerve, while the anterior mucous surface of the tongue is a part of the hyoidean and mandibular segments, or the segments of the facial and trigeminal nerves. It is known also that the Eustachian tube of mammals corresponds to the spiracular cleft of fishes in a general way, although other structures also enter into the formation of the Eustachian tube. In man the chorda passes over the tympanic cavity, but underneath the auditory ossicles. It has, therefore, long been considered a pretrematic or prebranchial nerve, although Froriep held the opinion that it is postbranchial. In 1904 Emmel, however, found that at an early stage the mammalian chorda passes beneath the spiracular cleft or primitive Eustachian tube and that its pretrematic position is taken up later. The nerve is, therefore, posttrematic.
The facial nerve of the lower vertebrates, leaving out of consideration the lateral line component of the neuromasts which is only apparently a part of the facial, is in every case a mixed motor and sensory nerve. As has been noted before, it is the nerve of the hyoid segment. As the musculature of this segment is, in all lower forms, derived from the lateral mesoderm, its motor component, as in man, is visceral motor. Primitively, as Johnston has shown in the lamprey, the facial nerve contained two sensory components, that is, it possessed fil)ers for the innervation of the skin for general sensation and
D 600 Ralph Edward Sheldon.
the region of the spiracle, roof and floor of the mouth for taste and other visceral sensation. In most forms above the cyclostomes the evidence is strong that the only sensory component remaining is the visceral, innervating mucous surfaces, while cutaneous sensation for the hyoid segment is served by fibers from the trigeminal or vagus nerves. J. Ramsey Hunt has, however, brought forward evidence to show that in man a part of the general sensory system of fibers still remains in the facial ; shown, for instance, by the persistence of tactile sensation on the anterior part of the tongue after section of the lingual above its junction with the chorda. In every carefully studied example among the lower vertebrates all taste buds in front of the glossopharyngeal segment are innervated through visceral sensory fibers from the facial nerve. They are likewise all derived from the geniculate ganglion and always end in the brain in the fasciculus solitarius which is, as has been noted, the center for taste in man.
Taking up the different groups of lower vertebrates more in detail the situation is made clearer. No attempt will be made, however, to consider the many mooted questions as to the comparative morphology of the different rami of the facial already ably discussed by Herrick, Cole, Coghill, etc In the selachians, as will be noted from Fig. 1 (Chlamydoselachus anguineus), the facial contains the usual motor component, the ramus hyoideus for the hyoid musculature. There is a small component for the skin, derived, however, from the trigeminus nerve in all probability, through the anastomotic rami from the Gasserian ganglion. There are several rami for the sense of taste. Close to, or else arising directly from the geniculate ganglion is the palatine nerve for the mucosa of the roof of the mouth. Either from this or from the main trunk, slightly more distad are given off prespiracular or pretrematic rami. These innervate the spiracle and occasionally a part of the floor of the mouth. Descending with the main branch of the facial, the hyomandibular, is a large sensory component for the mucosa of the floor of the mouth rostrad, the mandibularis internus. This is evidently the homologue of the chorda tympani. Practically all selachians, as is shown by Cole, Strong, Ewart, Green, Jackson and Clarke and other workers, exhibit these conditions. We may, therefore, say that in this group the
D The Facial Nerve and Chorda Tympani. 601
sensory fibers of the facial serve the sense- of taste of the roof of the mouth through the palatine rami, and the floor of the mouth rostrad through the pretrematic, and particularly the mandibularis intemus.
In teleosts (Fig. 2, Menidia; Fig. 3, the cod) conditions are quite similar. The motor nerve, the ramus hyoideus, innervates the muscles of the hyoid arch, accompanied by a cutaneous branch from the Gasserian ganglion. A visceral sensory palatine arises from cells in the geniculate ganglion for the taste buds of the roof of the mouth ; a large posttrematic ramus, the mandibularis intemus innervates the floor, including the mucosa over the bones of the hyoid arch. A few visceral sensory fibers in Menidia leave the geniculate ganglion with the maxillaris for the upper lip and mucous lining of the upper jaw. The glossopharyngeal nerve here, as in higher forms, sends a lingual branch to the taste buds of the floor of the mouth. In the cod, as shown in Fig. 3, a branch from the petrosal ganglion of the ninth nerve, Jacobson's anastomosis, joins the posterior palatine nerve which largely distributes to the mucosa of the roof of the mouth. In Pleuronectes, as shown by Cole, there is a similar anastomosis. We know, from Dixon, Streeter, Ramon y Cajal, etc., that the origin of the great superficial petrosal of man is similar to that of the palatine VII in fishes. It is interesting to note that in fishes there exists an anastomosis from the ninth quite similar to that between Jacobson's nerve and the great superficial petrosal in man. It should be emphasized, however, that such an anastomosis is absent in many cases, as in the selachians and Menidia, so that the palatine VII in fishes is actually a derivative of the facial, flacobson's anastomosis of fishes and Jacobson's nerve in man are apparently both palatine or pharyngeal rami of the ninth nerv^e carrying taste fibers for the roof of the pharynx.
An important special case is to be observed in the catfishes. Herrick has shown that the outer skin of Ameirus is covered with taste buds similar to those in the mouth. He has likewise shown, through extensive and painstaking experiments, that the fishes react to sapid substances on stimulation of these external taste buds in exactly the same way that they do when such substances come in contact with the mouth. In these fishes the external as well as the usual internal
D 602 Ealph Edward Sheldon.
taste buds are innervated through the facial nerve. Many special rami are developed for this purpose, leading to an enormous hypertrophy of the nerve and its center in the brain, the fasciculus solitarius.
In the amphibia conditions vary somewhat, but are essentially similar to those in fishes. Cutaneous fibers may be present in the Vllth but if so are derived from the Xth by way of a communicating branch. The ramus hyoideus in all amphibia is homologous with the motor facial of the fishes and man. A palatine ramus from the geniculate ganglion is always present and in the Urodela is joined by Jacobson's anastomosis, the fibers innervating taste buds in the roof of the mouth. The taste buds of the anterior part of the mouth are innervated by a nerve, called the ramus alveolaris in the Urodela and the mandibularis intemus in the frc^. It is, in both cases, derived from the geniculate ganglion as in the fishes. It is said to be, however, postspiracular or posttrematic in the Anura and pretrematic in the Urodela. (See Coghill, '02.) The origin and the region innervated are the same in both cases and it is without doubt the functional equivalent of the chorda tympani. The posterior part of the tongue is innervated by the lingual IX as in man.
In all these cases it will be noted that there are present the same three rami of the trigeminus as in man. There are, likewise, in the amphibia as in man, anastomoses between the terminal rami of the mandibularis and the nerves for taste for the rostral part of the tongue.
It is evident from the foregoing that the facial of lower vertebrates is both sensory and motor ; that its motor portion is homologous with the facial proper in man; that its sensory portion through nerves homologous with the chorda tympani of man innervates the taste buds of a region comparable to the anterior part of the human tongue and that another branch of this same sensory element of the nerve, the palatine, is homologous with the great superficial petrosal of man. The evidence of comparative neurology, therefore, offers the strongest possible confirmation of the view that the chorda tympani of man is the nerve for taste for the anterior part of the tongue and that its fibers are derived from the geniculate ganglion, entering the brain
D The Facial Nerve and Chorda TympanL 603
through the pars intermedia of Wrisberg. It also indicates that the great superficial petrosal nerve, like its homologue, the palatine, carries the fibers for taste for the roof of the mouth, and therefore innervates the taste buds of the soft palate through the palatine nerves from the sphenopalatine ganglion.
Hull Labobatobt of Anatomy, The University of Chicago.
Received for pubUcation August 16, 1909.
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Hunt, J. Ramsey
1909. The sensory system of the facial nerve, and its symptomatology. Jour. Nerv. and Mental Disease, Vol. 36, pp. 321-350, figs. 6.
Jackson, W. H., and Clabke, W. B.
1876. The brain and cranial nerves of Echlnorhinus splnosus, with notes on the other viscera. Jour, Anat. and Phys., Vol. 10, pp. 75-107, pi. 7.
Johnston, J. B.
1905. The cranial nerve components of Petromyzon. Morph. Jahrb., Bd. 34, Hf t. 2, pp. 149-203, pi. 5, figs. 18.
KlESOW, F., AND Nadoleczny, M.
1900. Zur Psychophysiologie der Chorda tympani. Zeitschr, f. Psychol, u. Physiol, d. Sinnesorgane, Bd. 23, pp. 33-59.
KOPCZYNSKI
1904. Fall von doppelseltiger traumatlscher Facialisiahmung. Mediclnlsche Gesellsch. in Warschau. 1 Mftrz, 1904. Neur. Gentralbl., Bd. 24, p. 733.
D The Facial Nerve and Chorda Tympani. 607
KOSTEB, GeOBO
1900. Klinlscher und experimenteller Beitrag zur Lehre von der Laiiniung
des Nervus facialis, zugleieb eln Beitrag zur Pbysiologie des
Geschmackes, der Schweiss-, Speicliel- und Thranenabsonderung.
Deut. Arch, f, klin. Med., Bd. 68, pp. 343-382, 3 Abb. ; pp. 505 589, 5 Abb. Ejuluse, Fedob
1896. Die Pbysiologie des Trigeminus nacb Untersucbungen an Menscben,
bel denen das Ganglion Gasseri entfemt worden ist. Munch.
Med, Wochemchr.y Jabrg. 42, No. 25, pp. 477-481, figs. 11 ; pp.
602-604; pp. 628-631. 1896. Die Neuralgie des Trigeminus. Monograpb. Leipzig, 1896. Kbon, J.
1901. Ein Beitrag zur Lebre tiber den Yerlauf der Gesebmacksfasern.
Ifeur. Centralhl., Bd. 20, pp. 549-561. Lehman, Kakl B.
1884. Eln Beitrag zur Lehre vom Gescbmackssinn. PfHiger's Arch. f. d. gesam. Physiol, Bd. 33, pp. 194-198. Lenhoss^k, Michael v.
1894. Das Ganglion geniculi Nervi facialis imd seine Yerbindungen. Beitrgge zur Histologie des Nervensystems und der Sinnesorgane. Wiesbaden, 1894.
LUBSANA, Ph.
1869. Recberches exp6rimentales et observations patbologiques sur les nerfs du gotlt. Arcfi, de physioL, T. 2, pp. 20-32.
1871. Sur les nerfs du goOt. Observations et experiences nouvelles. Ibid., T. 4, 1871-1872, pp. 150-167 ; 334-350.
Mabtin, p. 1890. Die erste Entwickelung der Kopfnerven bei der Katze. Ostcncich. Monatschr. f. Tierheilkunde.
Nobbib, H. W.
1908. Tbe cranial nerves of Ampbiuma means. Jour. Camp. yeur. and Psychol, Vol. 18, pp. 527-568, pis. 4-8. Obebsteiiveb, Heinbich
1896. Anleitung beim Studium der nervosen Centralorgane. Vierte Auf., 1901. Leipzig u. Wien.
Panski
1906. Ein Fall von Diplegia facialis. Czasopismo lekarskie, No. 10, p. 342-. Rev. Xeur. Centralbl, Bd. 26, 1907, p. 462.
Pope, Fbank M.
1889. Tbrombosis of vertebral artery pressing on glossopbaryngeal nerve ; unilateral loss of taste at back of tongue. Brit. Med. Jour., 1889, Vol. 2, pp. 1148-1149.
D 608 Ralph Edward Sheldon.
Ramon y Cajal, S.
1904. Textura del sistema nervloso del Hombre y de los Vertebrados. T. II. Madrid, 1904.
Retzius, Gustap
1880. Untersuchungen ttber die Nervenzellen der cerebrospinalen Ganglien
und der Ubrigen peripherischen Kopfganglien. Arch. f. Anat. (tt. Phys,), pp. 369-492, pis. 17-22.
Roller, C* F. W.
1881. Der centrale Verlauf des Nervus glossopbaryngeus. Der Nucleus
lateralis medius. Schultze*8 Arvh, f. mikr, Anof., Bd. 19, pp. 347-383, pis. 19-20.
ROSENFELD, M.
1903. Zur Symptomatologie der peripheren Facial islUhmung. Neur. Cen tram., Bd. 22, pp. 303-308. Salomonsohn, H.
1888. Ueber den Weg der "Geschmacksfasem" zum Gehirn. Inaugural Dissertation, Berlin. March, 1888. Rev. Neur. Centralbl, Bd. 7, pp. 295-296. Sapolimi
1884. Etudes anatomiques sur le nerf de Wrisberg et la corde du tympan ou un trezi^me nerf cranien. Jour, de m^decine de Bruxelles.
SCHEIBEB, S. H.
1904. Beitrag zur Lehre liber die Thr&nensekretion im Anschlusse von
3 FUllen von FazialislUhmung niit Tbrilnenmangel, nebst Bemerkungen tiber den Gescbmackssinn tiber Sensibilitatsstorungeu bei Fazialisiahmung. Deut. Zeitschr. f. Nervenheilk., Bd. 27, pp. 45-70. ScHEiEB, Max
1895. Beitrag zur Kenntnis der Geschmacksinnervatlon und der neuroparalytischen Augenentztindung. Zeitschr. f. klin, Med., Bd. 28, pp. 441-460.
SCHIFP
1887. Les nerfs gustatifs. Revue mMicale de la Suisse romande, 1887, No. 1, p. 51-. Rev. Neur. CentralU., Bd. 6, pp. 149-150.
SCHLICHTING, HaNS
1897. Klinische Studien tiber die Geschmacksiahmungen durch Zerstorung der Chorda tympani und des Plexus tympanicus. Zeitschr, f. Ohrenheilk., Bd. 32, pp. 388-401.
Senator, H.
1892. Ein Fall von TrigeminusafPection. Beitrag zur Kenntnis von der neuroparalytischen Ophthalmie, dem Verlauf der Geschmacksfasem der Chorda und den intermittierenden Gelenkschwellungen. Arch. f. Psychiatric, Bd. 13, pp. 590-001.
D D D The Facial Xerve and Chorda Tympani. 609
Sheldon, R. E.
1909. The reactions of the dogfish to chemical stimuli. Jowr, Comp. Neur. and Psychol, Vol. 19, No. 3, pp. 273-312, figs. 3. Stbeeteb, Geoboe L.
1908. The peripheral nervous system in the human embryo, at the end of the first mouth. Am. Jour. AnaU, Vol. 8, No. 3, pp. 285-302, Pis. 3. fig. 1. Strong, Olives S.
1895. The cranial nerves of Amphibia. Jour. Morph., Vol. 10, pp. 101 218, Pis. 7-12. 1903- The cranial nerves of Squalus acanthias. Science^ N. S., Vol. 17, pp. 254-255. Thomas, J. Lynn
1899. Notes on two recent operations upon the Gasserian ganglion and
the second and third divisions of the fifth nerve for neuralgia
by the Hartley-Krause method. Brit. Med. Jour., 1899, Vol.
2, pp. 1080-1082, figs. 3. Tiffany, Louis McLane
1894. Intracranial Neurectomy and removal of the Gasserian ganglion.
Annals of Surgery, Vol. 19, pp. 47-57, figs. 4. Tooth, H. H.
1893. Destructive lesion of the fifth nerve-trunk. 8t. Bartholomew's
Hosp. Reports, Vol. 29, pp. 215-224. Turner, W. Aldren
1894. On the central connections and relations of certain cranial nerves.
Brit. Med. Jour.^ 1894, Vol. 2, p. G43.
1895. The central connections and relations of the trigeminal, vago glossopharyngeal, vago-accessory, and hypoglossal nerves. Jour, of Anat. and Phys., Vol. 29, N. S. Vol. 9, pp. 1-15.
1896. On facial paralysis and the sense of taste. Edin. Hosp. Reports,
Vol. 4, pp. 326-342.
1897. Note on the course of the fibers of taste. Edin. Med. Jour., N. S.
Vol. 2, pp. 261-262. Urbantschitsch. Victor
1876. Beob. fiber Anomalien des Geschmacks in Erkrank. der Pauken hohle. Stuttgart. 1883. Beobachtuiig eines Fallos von Anilsthesie der peripheren Chorda tympani Fasern, bei Auslosbarkeit von Geschmacks- und GefUhlsempfindungen durch Reizung des Chorda tympaniStammes. Arch. f. Ohrenheilk., Bd. 19, p. 135. Van Gehuchten, A.
1900. Recherches sur la terminaison centrale des nerfs sensibles per ipheriques. I. Le nerf interm(^diaire de Wrisberg. Le Ncuraxe, Vol. 1, pp. 5-12, figs. 5. II. Le faisceau solitaire, ibid., pp. 173-197. 1906. Anatomic du syst^me nerveux de Thomme. 4th edit. Lou vain.
D 1
610 Ralph Edward Sheldon.
VULPIAN, A.
1878. Experiences ayant pour but de determiner la veritable orlglne de la corde tympan. Compt, rend, des stances, T. 96, pp. 1053-1057. Wachbmuth, Adolf
1834. Ueber progressive Bulbar-Paralyse (bulbus medullse) und die Diplegia facialis. Dorpat, pp. 1-114. Weigneb
1901. Ueber den Verlauf des Nervus intermedius. BuUetin International de Vacad^mie dea Sciences de Prague, Wolf
Zur Function der Chorda tympani. Zeitschr, f, Ohrenheilk,, Bd. 9, p. 152. Zakdeb, Richard
1897. Ueber das Verbreltungsgebiet der Gefflhls- und Geschmacksnerven in der Zungenschleimhaut. Anat, Anz., Bd. 14, pp. 131-145, 1 Abb.
ZlEHL, FBAITZ
1889. Ein Fall von isolirter LUhmung des ganzen dritten Trigeminusastes nebst einigen Bemerkungen fiber den Verlauf der Geschmacksfasem der Chorda tympani und die Innervation des Geschmackes tlberhaupt Virchoto's Arch, /. path, AnaU i*. Phys.^ Bd. 117, pp. 52-82.
1893. Ein neuer Fall von isolirter LS.hmung des dritten Trigeminusastes mit GeschmacksstOrungen. lUd., Bd. 130, pp. 528-529.
D The Facial Nerve and Chorda Tympani. 611
EXPLANATION OF FIGURES. It will be noted that legends accompany the figures, indicating that the rami which are crosshatched are general sensory; those in black, visceral and those blocked in, motor. The term "general sensory" as used here refers to fibers of the general somatic sensory type; "visceral," to fibers of the visceral sensory type and also to preganglionic visceral motor fibers of the sympathetic systeln while the "motor" fibers are those of the vipceral motor type specialized for the innervation of the branchiomeric striated musculature.
7
■^B visceral I I I motor
fig. I.
Diagram of the trigeminal, facial and glossopharyngeal nerves in Chlamydoselachus anguiueus. (Modified from O. A. Menitt Hawkes.) All of the nerves of the lateralis system have been omitted. G. G., Gasserian ganglion; G. g., geniculate ganglion; G. petr., petrosal ganglion; N. gloss., glossopharyngeal nerve; pal. IX, palatine ramus of the IX; pretrem. IX, pretrematic ramus of the IX; posttrem. IX, posttrematic ramus of the IX; R hyoideus, ramus hyoideus VII; R. mand., ramus mandibularis V; R. mand. int, ramus mandibularis internus VII ; R. max., ramus maxlllaris V ; R. ophth. prof., ramus ophthalmicus profundus V; R. ophth. sup., ramus oph-* thalmicus superficialis V ; R. palatini, palatine rami of the VII ; S., spiracle ; Tr. hyomand., truncus hyomandlbularis VII.
D 012 Ralph Edward Sheldon.
Diagram of the trigeminal, facial and glossopharyngeal nerves in Menidia. (Modified from C. Judson Herrick.) Lateralis components omitted. G. G., Gasserian ganglion ; G. g., geniculate ganglion ; G. petr., ganglion petrosum ; N. gloss., glossopharyngeal nerve; R. hyoideus, ramus hyoideus VII; R. mand., ramus mandibularis Y ; R. mand. int., ramus mandlbularis internus VII ; R. max. ramus maxillaris V ; R. ophth. sup., ramus ophthalmicus superficialis V; R. palatinus, palatine VII ramus; R. pal. post., posterior palatine VII ramus; R. recurrens fac, ramus recurrens VII. This nerve Innervates taste buds on the outer surface of the body and is the portion of the facial so enormously hypertrophled in the siluroids. Tr. hyomand., truncus hyomandibularis VII ; x, branch of the mandibularis internus for the mucosa over the bones of the hyoid arch. The general sensory fibers in the hyomandibular trunk are derived from the Gasserian ganglion.IC
The Facial Xerve and Chorda Tympani. 613
D9eneral sensorij I visceral
ind
K9.3.
Diagram showing the trigeminal-facial complex In the cod. (Modified from C. Judson Herrlck.) Lateralis and motor components omitted. The anastomosis between the petrosal ganglion and the palatine rami is to be noted especially as such an anastomosis occurs somewhat similarly in man, between Jacobson's or the tympanic nerve and the great superficial petrosal. G. G., Gasserlan ganglion; G. g., geniculate ganglion; G. petr., ganglion petrosum ; Jac. anas., Jacobson's anastomosis, the pharyngeal or palatine ramus of the IX ; R. mand., ramus mandibularis V ; R. max., ramus maxillaris V; R. ophth. sup., ramus ophthalmicus superficialis V; R. palatinus, ramus palatinus VII ; R. pal. post., ramus palatinus posterior VII ; R. recurrens fac, ramus recurrens VII. (See explanation of Fig. 2.)
D I
614
Ralph Edward Sheldon.
■general sensory ■visceral 1 mof or
H9.4
Diagram of the trigeminal, facial and glossopharyngeal nerves of Amblystoma tigrinum. (Modified from Coghill.) Lateralis component omitted; petrosal ganglion separated from the vago-glossopharyngeal complex. The general sensory fibers in the glossophar3mgeal and hyoid nerves are derived from the vagus root. G. G., Gasserian ganglion; G. g., geniculate ganglion; G. petr., ganglion petrosum ; Jac. anas., Jacobson's anastomosis. (See explanation of Fig. 3) N. glossopharyng., nervus glossopharyngeus ; R. alveolar is, ramus alveolaris VII, the functional equivalent of the chorda tympani in man; R. com., ramus communicans IX-X ad VII; R. hyoideus. ramus hyoideus VII ; excluding the vagal fibers, the homologue of the facial proper in knan; R. mand., ramus mandibularis V; R. max., ramus maxillaris V; R. ophthalmicus V; R. pretrem. IX, ramus pretrematlcus IX.
D The Facial Nerve and Chorda Tympani. 616
G.petr
f(9.5.
Diagram showing various courses advocated for the taste fibers in man. (Modified from Gushing.) The courses advocated in this article are shown by heavy black lines, other courses are indicated by dashes or dotted lines. Chorda tymp., chorda tympani ; fac. rt., motor facial root ; G. G., Gasserian ganglion ; G. g., geniculate ganglion ; G. otic, otic ganglion ; G. petr., ganglion petrosum; G. sp., sphenopalatine ganglion; g. s. p., great superficial petrosal nerve; N. fac, facial proper; N. Jac, Jacobson*s, or the tympanic nerve; N. glossopharyngeus, the lingual ramus of the IX: N. lingualis, the lingual V nerve; N. mand., mandibularis V. nerve; N. max., maxillaris V nerve; N. ophth., ophthalmicus V nerve; N. vid., vidian nerve; Pars intermed., pars intermedia of Wrisberg, the sensory root of the facial ; Rami anast., anastomotic rami between the geniculate ganglion and tympanic plexus and the small and great superficial petrosal nerves, respectively; s. s. p., small superficial petrosal nerve; Tymp., tympanum.
D I
616 Ealph Edward Sheldon.
Fig. 6. Diagram of the trlgomiDal. facial and glossopharyngeal nerves in man, from the right side. The glossopharyngeal nerve, instead of appearing in its normal position in front of the facial has been placed behind it. This Is its true morphological position and such a change makes it more easy to compare this diagram with Figs. 1-4, of the lower vertebrates. This change necessitates the lengthening of Jacobson's nerve and a slight distortion of the tympanic plexus. The postganglionic sympathetic system is unshaded. It should be noted that the visceral nerves shown in black contain not only taste fibers but also several kinds of preganglionic sympathetic fibers of the efferent vaso-dilator and excito-glandular type. Many of these nerves undoubtedly contain also postganglionic fibers from the unshaded sympathetic ganglia. The general sensory fibers of the glossopharyngeal have not been indicated in the diagram. Can. fac, canalis facialis; can. pteryg., canalis pterygoideus ; chorda tj'mp., chorda tympani ; fac. rt., motor facial root; Fiss. orb. sup., fissura orbitalis superior; For. jug., foramen jugulare; For. ov., foramen ovale; For. rot, foramen rotundum; For. stylomast., foramen stylomastoideus ; 6. 6., ganglion Qasseri ; G. g.., ganglion geniculi ; G. otic, ganglion oticum ; G. petr., ganglion petrosum ; G. sp., ganglion dphenopalatinum ; g. d. p., great deep petrosal,, from the carotid plexus to the great superficial petrosal to form the Vidian nerve; g. s. p., great superficial petrosal, from the geniculate ganglion to the sphenopalatine ganglion, probably carrying taste fibers for the soft palate through the palatine nerves; N. alv. inf., nervus alveolaris inferior; Nervi alv. sup., nervi alveola res superiores; N. front., nervus frontalis; N. infra -orb., nervus iufra-orbltalis ; N. Jac, nerve of Jacobsou or the tympanic nerve ; N. lacrim., nervus lacrimalis ; N. lingualis, nervus lingualis for the anterior part of the tongue; N. mand., nervus mandibularls V: N. max. nervus maxillaris V; N. naso-cil., nervus naso-ciliaris ; N. ophth., nervus ophthalmicus V; Nervi palatini, palatine nerves for the soft palate; N. supraorb., nervus supraorbitalis ; N. supratroch., nervus supratrochlearis ; N. vid., vidian nerve; N. zygom.. nervus zygomaticus; Pars intermed., pars intermedia of Wrisberg, the sensory root of the facial ; plex. car., plexus caroticus ; plex. tymp., plexus tympanicus ; R. anast, anastomotic rami between the geniculate ganglion and tympanic plexus and the small and great superficial petrosal nerves, respectively ; R. front., ramus frontalis ; R. pharyng., rami of the glossopharyngeal nerve for the pharyngeal plexus : R. stylopharyng., ramus stylopharyngeus IX ; s. d. p., small deep petrosal nerve from the carotid plexus to the tympanic plexus; s. s. p., small superficial petrosal, formed. by the junction of the Jacobson*s nerve through the tympanic plexus and the anastomotic branch from the geniculate ganglion ; Tymp., tympanum.
D The Facial Nerve and Chorda Tympani. 01 '
D A CONSTANT BURSA IN RELATION WITH THE BUNDLE OF HIS ; WITH STUDIES OF THE AURICULAR CONNECTIONS OF THE BUNDLE.
BY
E. J. CURRAN, M.D. From the Department of Anatomy, Harvard Medical Bchool.
With Eight Fioubes.
At the suggestion of Professor Dwight, I undertook an investigation of the anatomy of the auriculo-ventricular bundle of His. The amount of literature on the subject has reached a considerable size — beginning with the discovery by Kent (1), and also by His (2) in 1893, and growing with increasing interest to the present time. To give an adequate outline of the work which has been done by various authors would be a needless and time-consuming repetition of what is already in the literature, and this I wish to avoid as far as possible in this paper.
Perhaps no single structure in the human body has, of recent years, received more careful study and been the subject of more painstaking investigation than this one. Whether the function of the bundle of His is proved or not is not within the scope of this paper. It is sufficient to say that although the observations of anatomists, the ingenious experiments of physiologists, and the more crude ones of nature, observed by pathologists and clinicians, point convincingly to the accepted theory of its function — ^that of conducting the auricular impulse to the ventricle — ^yet they have by no means brought conclusive evidence to bear upon the subject No one will dispute, however, that a sufficient number of facts have been brought to light to make this structure of vast interest. Of all the structures of the human body — ^with perhaps the exception of some brain tracts — it stands alone as one, the existence of which was asserted on other than anatomical grounds — in fact, in opposition to the universal opinion of anatomists. On a priori evidence, deduced from certain experiments of his own, Gaskell (3) in 1883 concluded that there must be
(618)
D D D The Bundle of His. 619
a muscular connection between the auricle and ventricle in the turtle's heart. He looked for, found, and described this connection. But it was not even then thought that the mammalian heart was similar in this respect. Kent, in 1S93, discovered the muscular connection in the mammalian heart. Later in the same year. His discovered the auriculo-ventricular bundle in the human heart, and concluded that it was the sole muscular connection between the auricle and ventricle. The next notable advance in the anatomy of the bundle of His was the microscopic work of Tawara (4) and the discovery that the Purkinje fibres in the ventricle were terminal connections of the bundle and that it was distributed to all parts of the ventricles. It was partly these, facts that caused Tawara to establish the fascinating theory that it was a conducting system alone, and not contracting. I have found no experimental evidence in the literature to support the theory that it is not a contracting muscle, and histological evidence does not exclude the possibility of its being a contracting as well as a conducting muscle, as others are. In an ox's heart, which was removed quickly after death of the animal and handed to me while still beating, on opening the right ventricle I could clearly see a ridge made by the right septal branch. The endocardium being moist it presented a shining surface and any disturbance in the reflected light could easily be noticed. I observed that there was a movement along this ridge and that this movement was simultaneous with the contraction of the auricle and that it preceded that of the ventricle, which was now very feeble and giving out. The movement was a peculiar trembling or shivering, not unlike the fibrillatory movements which I have seen Professor Porter produce in the ordinary cardiac muscle by ligaturing a branch of the left coronary artery in a dog's heart, and it existed for a short time after the ventricle had ceased to contract. Whether the movement advanced from the direction of the auricle toward the ventricle, I was unable to ascertain. This would have to be investigated by physiological experiments, which I was not prepared to make at the time.
Whether the system is contracting or not, or the accepted theory of conduction is a correct one, I was led to believe that there must be friction with the surrounding parts, or some provision for lessening
D 020 E. J. Ciirran.
such friction. If the muscle contracts, it must contract before the ventricle ; and if it merely stays stationary we should have the condition of a vigorously contracting muscle by the side of, and surrounding, a comparatively stationary one, and the resulting friction would still be great. This led me to look for some protective arrangement about the bundle.
The dissecting-room subject is not suitable for studying the bundle of His ; for as a rule the natural color is lost and it is more difficult to follow in naked-eye dissections. The material used was fresh ; and in order to get the best results, Professor Dwight, whose kindly assistance and valuable suggestions have helped me greatly in this study, arranged for me to be present at a number of autopsies to examine the heart immediately on removal. For this privilege I have also to thank Dr. Oscar Kichardson, Assistant Pathologist to the Massachusetts General Hospital ; Professor Mallory, Pathologist to the Boston City Hospital; and Medical Examiners McGrath and McDonald. The number of human hearts dissected w^as ninety-six. Besides these, twenty-three were used for microscopic work, and a number of slieeps' and calves' hearts were used both for microscopic and gross work. I was unable to add anything to the histology of the auriculo-ventricular bundle, which is already well known. In all cases it was possible to dissect out the main bundle to its bifurcation. The right septal branch could be followed as far as the ridges of muscle which, in the human heart, represent the moderator band, but the left septal branch is broad, and so thin that it is usually taken off with the endocardium in the attempt to dissect it in the human heart; it can, however, be easily dissected in the sheep's or ox's heart.
I shall have to review briefly some of the anatomy of this region, for unless one is thoroughly acquainted with these parts it is most difficult to find the auriculo-ventricular bundle ; but if certain variations are known, and it is remembered that the only constant landmark is the central fibrous body, there will be very little difficulty. It is, therefore, very important to be able to locate the central fibrous l)ody, and to be aware of the other variations. If we look into the human heart from the right side, we cannot, as a rule, see the central fibrous body, but we can find it in one of the following ways: By
D The Bundle of His. 621
pulling on the Eustachian valve, we shall be able to see the origin of the fibrous band which runs along it under the endocardium; this origin is the upper left angle of the central fibrous body. If we place one finger in the left auricle and the thumb in the right, holding the interauricular septum between, and follow it up to its junction with the interventricular septum, we can thus locate it, for it is at the junction of these two septa. If the pars membranacea septi is large, we can locate the central fibrous body from the right side by holding the heart up to the light, and the central fibrous body will be in the upper left comer on the auricular side of the auriculo-ventricular fibrous band. Again, we can locate it from the left side by putting a pin through the origin of the mitral valve, near its junction with the pars membranacea septi. Lastly, sometimes we can feel it, but not often. If we insert a sharp knife at a point 2 mm. below and anterior to the central fibrous body we can cut do\^'n on the beginning of the main bundle as it enters the ventricular septum. The direction the main bundle takes is along the lower border of the pars membranacea septi, but this border is not constant, because very often the subaortic musculature comes up high, as shown in Fig. 5, and takes up the greater part of the pars membranacea septi ; and in these cases we have certain displacements of the bundle. The direction will be the same, but it will be either buried deeply in the muscle or pushed so that one may see it under the endocardium in the left ventricle. In the latter case, if we wish to expose it from the right side, it will be necessary to cut deeply in the central fibrous body. Sometimes the bundle or its branch may l)e seen on the right side, showing through the endocardium, without any more dissection than removing the end of the septal cusp. It cannot be mistaken on account of its characteristic color and size. It is a narrow, whitish band, seldom more than two or three millimeters in width, and rarely so wide, and showing distinctly from the darker ventricular muscle. The bundle runs along for about two centimeters and then divides into right and left septal branches, usually at the lower angle of the pars membranacea septi. One of these branches — the right septal branch — runs along the septum almost superficially on the right aide, and can be followed into the vestigial moderator band in the human heart. The left septal
D 622 E. J. Curran.
branch can be seen as a broad thin layer of fibres through the endocardium on the left side. Pig. 2 is a drawing of a heart which shows the left septal branch as seen through the endocardium of a fresh human heart in a good subject. Tawara has shown that these branches (right and left septal) are distributed to all parts of the ventricles, the terminals being Purkinje fibres. From the point of incision above mentioned, the bundle can be traced back to the auricle, either through the central fibrous body or more superficially, and here it is said to be lost in a reticulum which is different histologically from other parts of the bundle and from other parts of the heart. This node can be dissected out as a definite structure — at least in the human and other mammalian hearts which have come under my observation — and I propose to show in this paper that it has definite connections with the musculature proceeding to the auricular appendages of both right and left auricle, and with the musculature around the fossa ovalis and the sinus venosus.
Keith was impressed with the distinct fibrous sheath which surrounds the bundle, isolating it from the ordinary cardiac muscle, and following the branches to their terminal ramifications (7). This isolation may be considered as an indication that the system is there for the simultaneous delivery of a single co-ordinated stimulus to all parts of the ventricles. The idea appeals to one, for there is a perfect network of fibres, and each branch carries its insulating (if one might so call it) fibrous tissue with it. It is separated from , ordinary cardiac muscle cells until it has been thoroughly distributed. It was about this sheath that I looked for some protecting mechanism, and on examining it I found that it consists of two layers, more or less distinct, one around the muscle itself and the other on the wall of the muscle surrounding it. The space between is usually crossed by fine trabeculse and is well moistened with a lubricating fluid, but in some parts there are no trabeculse and only a space with the lubricating fluid. This is especially the case along the main bundle when the chordse from the valves are inserted just over it, or when the bundle at its beginning disappears behind a nodule of muscle to get to the left side, as in Pig. 6. The fluid is of greater consistency than ordinary lymph and is somewhat tenacious in character. In the
D The Bundle of His. 623
fresh heart it gives the muscle a peculiar sheen, and causes it to slip easily from under a blunt instrument, as a pencil. This fluid is to be found throughout the branches as far as they can be dissected, as well as around the main bundle, where in one case it was so abundant that on opening the bursa with the point of a sharp knife it exuded in the form of a droplet In hearts which showed atheromatous patches and thickened endocardium, I have sometimes found what I would consider an excess of this fluid, and in these cases it was more watery than usual. As a rule, the quantity is scanty and cannot be brought together to form a droplet. In two cases in which the hearts were about two days old, and had been in the freezing chamber for that time and were then thawed out, I located the bundle by seeing the fluid through the endocardium, and in it were bubbles of air which were made to move up and down the main bundle by pressing the tissue on either side. The fluid seemed more watery than it should be, and whether it filtered through or was the result of some pathological process, as bursitis, I was unable to determine. In other hearts which were subjected to the same process this did not occur.
There are several forms of this bursal space, ranging from very loose areolar tissue with lubricating fluid in the cellular spaces, which always connect with each other along the line of the bundle, to distinct cavities filled or lubricated with fluid, and no trabeculse crossing the intervening space. In the usual form there are one or two large spaces or one continuous space with very fine trabeculse crossing from the walls of the canal to the auriculo-ventricular muscle.
The size of the bursa depends on the size of the bundle of His, and the character depends upon the position of the surrounding structures. Por example, if the insertion of the chordae be over the course of bundle, in a line along the lower border of the pars membranacea septi, the character of the bursa will be open — that is, it will be a space crossed by few if any trabeculse, and the lubricating fluid will be more in evidence, probably because this condition causes extra friction by the pull of the chordae of the valves on the tissues over the bundle of His. Again, if the bundle be very small, it will not be easy to demonstrate the bursa, though in all cases its essential character can be made out by careful dissection. In hearts in which the
D 624 E. J. Curran.
subaortic musculature comes up high^ and when the main bundle lies deeply in the septum, it is not easy to demonstrate, but in this kind of septa, when the main bundle is to be dissected superficially on the left side as in Fig. 4, it can be seen under the endocardium of a healthy heart as a grayish translucent line, and fluid can occasionally be demonstrated without dissection by pressing both ends so that the bursal space bulges. In these cases also the bursa can be dissected from the right side before the bundle disappears behind the nodule of subaortic muscle, as in Fig. 5. The majority of cases are best demonstrated from the right side when the direction of the main bundle is such that it runs along the lower border of the pars membranacea septi and the chordse of the cusps are inserted into the edge just over the main bundle. If we have a large main bundle under these conditions and make a small opening with the point of a sharp knife at this position, by lifting up the edges with the forceps, or raising the edges with threads, as show^n in Fig. 3, we can easily see a dark cavity and the main bundle of His lying in it. We can now insert a blowpipe, and blow up the space to see the extent of the bursa. As a rule, such cases can be blown up as far as the reticulum, and in rare cases even beyond that into the loose tissue about the coronary sinus and the auriculo-ventricular groove. When the mouth of the blowpipe is inserted into the lower part, the right septal branch can be blown up for a distance more than half-way down the vestigial moderator band along the course of the right septal branch. If we now turn to the left ventricle, we shall probably find bubbles of air under the endocardium, showing that it has followed the branches under the endocardium of the left ventricle, and that the spaces in the loose tissue here are continuous with those of the right side. The use of the blowpipe, however, is not always successful onaccount of the difficulty of correctly inserting the end into the space and thus preventing the escape of air from it.
In the sheep's and calf s heart the bursa is always crossed by trabeculse, but it can be blown up with very slight pressure, showing continuity of the space. In the ox's heart there is a large bursa, about a centimeter in area, between the central cartilage and the bundle of His ; and this connects with the spaces along the course of
D The Bundle of His. 625
the main bundle. It is obvious that such a provision is necessary here for protection against the impact of the cartilage. On account of the larger auriculo-ventricular bundle in the sheep's and ox's heart, one might expect to find a more marked bursal space along its main trunk and branches, but since it lies deeply in the muscle it is not subjected to the pull of chordae and consequently we have, as it were, a partially developed bursa along its course, with numerous trabeculfiB and with the lubricated surface.
The purpose of the bursa is undoubtedly to lubricate and protect the bundle of His from the friction of the surrounding cardiac muscle as it contracts. It is so striking in the gross dissections that it is surprising that it has not been observed before, and this can only be explained by the fact that most of the study done on the subject has been done on microscopic sections and in these it is likely to be overlooked. Careful dissection reveals it best.
Auricular CoNisrECTiONS.
A great deal of work has been done on the ventricular connections of the bundle of His, but little information is to be found concerning the auricular side. Strangely enough the writers seemed to be content with the statement that it has its roots in the annular and septal fibres of the right auricle. This is the most I have been able to find in the literature concerning the auricular connections.
In my dissections I tried to trace the system to its ultimate ending in the auricles by following the main bundle through the central fibrous body or cartilage, keeping on the surface of it until I could dissect no further without cutting small strands of muscular tissue, which comes from the meshwork from which the bundle has been described to arise, and which Keith calls the reticulum. In the first dissections, sheep's and calves' hearts were used. As the bundle is followed up in this way, we find that we have removed the superficial layer of auricular muscle and that the fine strands mentioned above are proceeding from the reticulum to the superficial musculature of the auricle, and that they are the only connections it has with this superficial layer, the fibres of which are at right angles to the bundle of His. Therefore the bundle of His is not a continuation of this layer.
D i}2(} K. J. Curran.
The reticuliun begins on the auricular side of the central cartilage, where it spreads out immediately^ having an area of about a square centimeter. It is similar in color to the auriculo-ventricular bundle and is not so hard as the ordinary auricular or ventricular muscle. In my dissections it is flat and has a surprisingly uniform shape, somewhat like that of a nerve ganglion. It has a very thin capsule of connective tissue, which is a continuation of the sheath surrounding the bundle, but it is thinner and more delicate. If, in dissection, we get away from this sheath, which is the natural line of cleavage, it will be impossible to reveal the reticulum as a definite structure; but if we dissect carefully, not having the specimen too wet, and follow the sheath, a dissection can be made similar to the plates sho^Ti. (Figs. 6 and 8.) AMien the reticulum is dissected out, as in Figs. 6 and 8, we find that there are several well-niarked roots or branches which can be traced for a short distance into the auricles, as well as many more minute twigs not shown — all arising in this reticular mass. As these branches leave the reticulum they are distinctly pale in color like the other part of the system, but they gradually merge, in character and color, into the ordinary auricular musculature. Each part of both auricles would seem to be connected with the reticulum through these muscular bands and through smaller twigs. The largest three are shown in the drawing of the dissection of the sheep's heart, Fig. 8, and in the photograph of the dissection of the calf's heart. Fig. 6. The small twigs which wont to the surrounding muscle close by have been dissected away, leaving three large auricular connections and the main auriculoventricular bimdle going to the ventricles, and also a well-marked bundle which enters and disappears into the ventricular muscle, and into the septal cusp, just before the main bundle leaves the auricle through the central fibrous cartilage. Some of the fibres of this branch end in the septal cusp, as has been mentioned by other writers, and some pass through, under the cusp, into the mass of septal muscle which arises from the central fibrous body. These fibres have not, I Ix^lieve, been described before, excepting that they may be the second muscular connection casually mentioned by Kent (5). He speaks of a spindle-celled muscular continuity of the auricle and
D The Bundle of His. 027
ventricle, to be found in the auriculo-ventricular fibrous ring, as well as the connection now known as the bundle of His, but this has not been confirmed by other investigators. Doubtless the function of these fibres is to supply the posterior part of the septum and the adjacent ventricular muscle. It is indeed what one would expect to find, seeing that there is no backward turning branch from the main bundle of His which would supply a large part of the posterior musculature. It is well marked and easily dissected in the sheep's and calves' hearts, and can, with somewhat more careful dissection, be made out in the human heart. I have no doubt it is always present, even if at times it is obscure. I shall refer to it in this paper as the accessory septal branch of the reticulum. The existence of such a branch would probably explain the experiments of Paukel (6), in which he ligatured the main bundle and still had no incoordination in the beats of auricle with ventricle. This connection may have escaped the ligature and carried the coordinating impulse to the ventricle.
The auricular connections of the reticulum in the sheep's and calves' hearts consist chiefly of three large bands radiating from it, viz.: (1) a branch to the interauricular septum and proceeding almost as far as the superior cava, where it is lost in the auricular musculature; (2) a branch, as shown in Figs. 6 and 8, which can be traced to the pericardial surface of the right auricle, blending with the auricular muscle as it proceeds on its way to the pectinate muscles of the right auricular appendix; (3) a similar branch going to the left auricle, which can be seen as in Fig. 8 when the coronary sinus is removed, or as in Fig. 6, where it is shown giving some branches to the coronary sinus. Besides these there are numerous smaller branches radiating from the reticulum to adjacent auricular muscle. These are fine threads of muscle, and can he well seen in the human heart, in which the above-mentioned main branches are not so well marked. Fig. 1 gives a diagrammatic representation of the radiations in the human heart. The smaller radiations are also of a paler kind than the ordinary auricular musculature. The auricular connections are not so easily dissected as the ventricular bundles, owing to then* Innng no bursal space; and the sheath, if at all existing
D I
628 E. J. Curran.
distal to the reticulum, is not so marked. But the color of the muscle helps us greatly in the dissection, and when we are familiar with its relationship we cannot but be impressed with its morphological difference from the rest of the auricular muscle. This difference has been pointed out in the ventricular portions, where it is very striking; but the auricular connections are quite as striking in color and arrangement. In the first place, the reticulum has the naked eye appearance of a nerve ganglion, and streaming from it, or to it, are certain well-defined bundles of muscle. For descriptive purposes in this paper, I have called these bundles branches of the reticulum. If the reticulum were a fixed lx)dy, as a cartilage or the fibrous ring, we might* be inclined to call it the insei> tion of these bands, but it is quite movable — more so than any other part of the auricular muscle. It has no fixed attachment to the central fibrous body or cartilage, or to the annular fibrous ring. Therefore we cannot consider it as an insertion of a muscle in the ordinary sense. In the sheep's and in some human hearts it would seem that a pull on the reticulum would be transferred to the main bundle of His, and thence down along its branches. This would be purposeless, so far as auricular efficiency is concerned. The chief function of muscle is contractility, and any other function or quality is subservient to this. It is usual, however, for any muscle to have two attachments, or to be arranged in a circular form in order to gain any advantage of contraction. Here we have a muscle which has practically no attachment at one end. It has been suggested that the system is conductive only, and this would coincide well with anatomical findings.
The auricular parts of the system — that is, the reticulum and branches, first lie between the auricles as they turn in to form the interauricular septum and to join the ventricular septum at the central fibrous body or cartilage. If we wish to show the reticulum from either auricle, we must cut through the septal muscular wall belonging to that auricle from the inside of the heart, and we shall find it (the reticulum) lying against the septal muscular wall of the other auricle. It is thus held in between the two auricles as between two leaves of a book. If we trace the auricular septal branch, we find
D The Bundle of His. 629
that for a short distance — two or three centimeters — it still lies between the auricles, distributing itself as it proceeds along the interauricular septum, and giving a large branch to the sinus venosus, Its terminals become intimately mixed with the auricular musculature. The other branches, as has been previously pointed out, come to the pericardial surfaces (immediately under which they lie, especially in the right auricle) as they proceed to the auricular appendages. We thus have well defined branches coming from or going to the' reticulum from the great system of muscles in the auricles, viz.:' the interauricular septum and the two auricular appendages. If this is a conducting system at all, it is clear from the anatomy of the structure that the auricular impulse must begin in the reticulum and radiate to the auricles through the auricular branches, or that it begins simultaneously in both auricles and is carried through its branches to the reticulum. If this is the case, it is within the bounds of possibility that the left auricular branches control the left ventricle, that the right branches control the right ventricle, and that their meeting at the reticulum and continuing in one mainbundle to the ventricles is only an economy of space. If it is not a conducting system, how can we explain its existence? It must be admitted that it is admirably suited for conducting mechanism, and very poorly fitted for mechanical purposes. If it were a contracting system also, we would expect to find an increase in size in hypertro^ phied hearts. Keith (7) and Tawara (4) have noted that there is no such increase in size nor any diminution in atrophy; but with such a', small structure as this I do not think it possible for any one to say with certainty that there is, or is not, this change, since the size of • the muscle cell varies even in normal hearts, and there are no meansof knowing what size the muscle or its cell structure were originally. From the series of hearts which I examined I was unable to come to any such conclusion. Some of the hypertrophied heartshad large bundles. The largest bundle which I found in the human heart was in a hypertrophied heart in a case of pernicious ansemia. It was 3.5 mm. in width throughout the whole course of the main, bundle.^ The next largest is shown in Fig. 1, which was from another
This specimen and the others from which the accompanyiDg figures were* taken are now in the V^^arren Museum, Harvard Medical School.
D 1
630 E. J. Curran.
case of pernicious anaemia. On the other hand^ most of the hypertrophied hearts showed bundles which were unusually small. This may of course be due to pressure atrophy, and what was originally large may have been thus reduced in size as the hypertrophy went on. In this connection also the blood supply must be an important factor. It has recently been suggested by Monkeberg (8) that the conducting system has a blood supply unconnected with that of the surrounding muscle. He based his belief on pathological findings. Before I read his excellent paper I had been working on the blood supply and had come to the same conclusion ; but I am not quite sure that the bursa also may not have something to do with nutrition of the bundle. This work is not yet completed, but I am able to state definitely that the auriculo-ventricular bundle has a special artery which, in the human heart, arises from the right coronary, and in the sheep's and calf s heart it is a branch of the left coronary. It enters the bundle at its beginning and follows it in direction. Xot only has the bundle a special artery, but it also has special veins which follow the bundle and empty into the right (and probably left) auricle through the Thebesian openings.
Summary. The important new facts and considerations brought out in this study are the following :
1. There is a constant bursa or lubricating mechanism in relation with the auriculo-ventricular bimdle, in view of which the possibility of bursitis must be considered in connection with certain temporars' cardiac symptoms, and with conditions met with in acute febrile diseases, such as acute rheumatism, endocarditis, etc.
2. The bursa is capable of facilitating the extension of any endocardial process on account of its anatomical relationship with the endocardium, and of the fact that even small twigs of the auriculoventriclar bundle which lie immediately under the endocardium are surrounded with cellular tissue, the spaces of which are continuous with the main bursa.
' 3. The existence of the bursa proves that either the auricidoyentricular bundle does not contract at all, or that it contracts in a
D The Bundle of His. 631
different way and at a different time from the contraction of the ventricle. The observation made on the ox's heart, mentioned in the foregoing pages, supports the latter view.
4. There is a striking gross resemblance of the reticulum in the calves' and sheep's hearts to a nerve gailglion, when dissected out as shown in Figs. 6 and 8; and its connection with all parts of both auricles is through three large trunks and a number of smaller twigs, and not, as was once thought, merely arising in the right auricle only. These connections point to the possibility of the contraction wave either beginning in the reticulum and proceeding through its branches to all parts of both auricles, or to its coming from all parts of both auricles to meet at the reticulum. In this case there would be a probability of each auricle controlling the time of contraction of the corresponding ventricle, and the meeting at the reticulum of the various bundles of fibres from both auricles and proceeding thence to the ventricles as the auriculo-ventricular bundle, would merely mean an economy of space.
5. The accessory ventricular branch of the reticulum must be counted on in physiological experiments.
Received for publication, August 9, 1909.
PUBLICATIONS REFERRED TO IN THIS PAPER.
1. Kent, Journ. of Physiology, 1893, Vol. XIV, p. 233.
2. His, Arbeiten aus der medicinischen Klinik zu Leipzig, 1893.
3. Gaskell, Joum. of Physiology, 1883, Vol. IV, p. 43.
4. Taw ABA, Das ReizleltungssyRtein des SS.ugetierherzens. (Gustav Fischer,
Jena, 1906.) 6. Kent, Journ. of Physiology, 1893, Vol. XIV, p. 241.
6. E. Paukel, Soc. de biol., Paris, LXV, p. 43-45.
7. Keith and Flack. The Lancet, Aug. 11, 1906.
8. M&NCKEBEBO, Untersuchungen liber das AtrioventrikularbUndel im mensch lichen Herzen, 1908.
D Fig. 1. — This Is a drawing of a human heart opened from the right side, showing the right auricle and the right ventricular surface of the intenrentrieular septum. The great vessels are somewhat diagrammatic, as they were not saved in a suitable state for a clear drawing. The auriculo-ventricular bundle is large — ^being 3 mm. in width all along its course from the central fibrous body to its bifurcation. The central fibrous body is represented in black just to the left of the index line to the main bundle and on the auricular side. The auricular fibres of the system are shown streaming from the superior cava, the annular muscle around the fossa ovalis, the right auricular ring and the cusps. The septal artery, which gives small twigs to the reticulum and to the bundle, is also shown. The bundle Is dissected at the point of bifurcation, to show the beginning of the left septal branch. The right septal branch is dissected as far as possible into the moderator band. The index lines explain sufficiently well the other landmarks in the dissection.
Fio. 2. — This is a drawing of a human heart opened from the left side to show the left septal branch of the auriculo-ventricular bundle streaming down the interventricular septum. In this case no attempt was made to dissect it out, because it showed clearly as represented through the normal endocardium. It is always quite superficial on this side, although in a thickened endocardium it cannot usually be seen so well in the human heart. The spaces under the endocardium here can be blown up from the bursa of the main bundle. Notice the relationships of the non-coronary cusp, pars membranacea septi, and the base of the mitral valve to the course of the fibres of the auriculo-ventricular system.
D BUNDLE OF HIS. PLATE I.
E. J. COBBAN.
Main Bundle of His
FiQ. 1.
> Rt0?U Coronary Artery
I Cusp
fpfi Left Septal Branch
Fig. 2. Thb Anatomical Record. — Vol. Ill, No. 12.
ICIC
D Fio. 3. — This is a drawing of the region around the auricnlo-ventricular bundle as seen from the right side. F is position of central fibrous body where the main bundle begins to leave the auricle. JST, fossa oval is. G, coronary sinus. O, auricular appendix. E, a cut through endocardium, over the main bundle, showing the latter lying in the bursal groove or canal, and the bursal space emphasized by a pull on the threads A and B which are put through the endocardium for this purpose. D, a hollow ridge along the course of the main bundle, caused by the pull on the thread B. \
Fig. 4. — Fig. 4 is a drawing of the subaortic region In the left ventricle, showing the bursa on this side. This is a common variation from the normal, and it occurs when the subaortic musculature comes up high, invading the pars membranacea septi. It is the left side of the heart from which Fig. 5 was drawn. The subaortic musculature, as drawn in Fig. 4, shows some of the various directions which the fibres of this may tal^e. In this dissection the left septal branch first appears below the transverse fibres, about the end of the index line marlted "Left Ventricle," but they have lost their color and do not show in the drawing. The bursal space is held out by a thread inserted for the purpose, and the main bundle is seen lying at the bottom of it.
Fig. 5. — ^This is a part of the right auricle and the interventricular septum, as seen from the right ventricle of the heart from which Fig. 4 is drawn. Here a nodule of muscle grows up from the interventricular septum and invades the pars membranacea septi, malsing It very narrow. From the reticulum the main bundle can be seen for 3 or 4 mm. and It disappears between the central fibrous body and the septal muscle. At this point there is a wellmarlied bursa which does not show well in the drawing. The main bundle divides on the other side of the septum and the right septal branch, as indicated by the index line, appears on the right side, just after the division. It could be seen distinctly through the endocardium, but in the dissection this has been removed. The right septal branch then disappears into the papillary muscle, which is sometimes continuous with the moderator band. Other points in the drawing are explained by the index lines.
D J^E^i>x.E OB' nis.
Bl- J. CURBAN.
pr^TB II
«^
A B
Fig. 3
Thread
Coronary Right Coronar
Main
Cusp
fitral Cusp Bursa \fiti8culature
FlQ. 4.
Central Fibrotta Body
Fig. 5.
Auricle Mem. Septi
Septal Branch
Tub Anatomical Record. — Vol. Ill, No. 12.
D D D Fig. 6. — Fig. 6 is from a photograph of a dissection of the reticulum witli its chief auricular branches and the auriculo-ventricular bundle as seen from the right side of a calfs heart. The external walls of the right auricle and ventricle are removed. ' The septum in the region of the reticulum is made up of the septal wall of the right auricle lying against the septal wall of the left auricle, holding between them — as between two leaves of a book — the reticulum and the beginning of its branches. In order to see these, the right auricular part of the septal wall must be removed, as shown in the photograph, and on careful dissection the reticulum will appear as a mass somewhat resembling a ganglion in form. The right auricle is cut away sufficiently to show the branch going to the left auricle with its distribution to the coronary sinus, under which its course lies as it proceeds In the direction of the auricular appendix and mouths of the pulmonary veins. The large branch which goes to the right auricular appendix is pinned down to the cut edge of the right ventricular wall. The trunk of the branches to the interaurlcular septum and the superior cava Is dissected out for a short distance, sufficient to show its direction. Fibres going Into the septal cusp and right ventricle Immediately before the auriculo-ventrlcular bundle is given off, are also well shown in the photograph. Behind this pinkish pale mass (the reticulum and Its branches) can be seen the darker muscle of the left auricle, some strands of which are inserted into the auriculo-ventricular fibrous ring and some Into the central cartilage. A well-marked band of dark auricular muscle arising partly from the annular ring of the inferior cava, and also from the left auricle, can be seen disappearing between the fossa ovalis and the left auricular branch of the reticulum, under the septal branch, and again appearing In the small triangular area, as it is inserted Into the central cartilage of the heart These and other points are indicated in Fig. 7, which is a key to this photograph.
D rCJNDLE OP HIS. B. J. CUBRAN.
PLATE in.
Fig. 6.
^B Anatomical Rbcobd. — Vol. Ill, No. 12
D D i IC
T
Fig. 7. — Key to Fig. 6. A, inferior cava turned up. B, septal branch of left coronary artery, which sends twigs to the reticulum and the auriculoventrlcular bundle. (7, reticulum. D, fibres from the reticulum to ventricle and septal cusp. E, insertion of muscular band jtf, arising from left auricle and inferior cava. F, superior cava. G, Fossa ovalis. /, left auricular branch of reticulum going to mouths of pulmonary veins, auricular appendix, and coronary sinus. J, coronary sinus. K, branch of reticulum going to right auricular appendix, now pinned to the cut wall of the right ventricle. L, left ventricle. M, right auricle. ^, branch from the reticulum to the interauricular septum and mouth of superior cava. O, central fibrous cartilage. P, a twig of right septal branch to conus arteriosus of right ventricle, given off before the remaining part enters the moderator band. Q, interventricular septum seen from right ventricle.
Fig. 8. — Fig. 8 is a drawing of a dissection of a sheep's heart, showing a view of the auricular connections of the auriculo-ventricular bundle similar to that shown by the photograph (Fig. 6). In this case the coronary sinus is dissected away and the left auricular branch, E^ of the reticulum is shown at first as a wide band which, when it proceeds but a little distance, buries itself deeply in the left auricular musculature, only a fine strand of it showing on the surface for any considerable distance. A, trunk of left pulmonary veins. B, trunk of right pulmonary veins. (7, left auricular appendix. D, fossa ovalis. E, left auricular branch of reticulum. F, septal branch of reticulum. (?, reticulum. H, right auricular branch of the reticulum on its way to the auricular appendix. /, cut edge of the left ventricle. J, left ventricle. K, main auriculo-ventricular bundle. L, superior cava. M, right auricular appendix. ^, right auricle. O, bifurcation of main bundle. P, right septal branch. Q, moderator band cut. 22, right ventricle, septal wall. The accessory ventricular branch is also seen well in this direction.
D 3^NT>X^ OF HIS. «a- J. CUBSAN.
PLATE IV.
C D E
Fig. 8.
B8 Anatomical Rbcobd. — Vol. Ill, No. 12.
D D THE EFFECT OF CONTRACTION ON THE VOLUME OF THE SMOOTH MUSCLE NUCLEUS.
BT
CAROLINE McGILL. Instructor in Anatomy^ University of Missouri.
In a recent paper (American Journal of Anatomy, Vol. IX, No. 4, 1909) I have described the histological changes which, occur in the smooth muscle nucleus during the contraction of the tissue. Briefly these changes are as follows : The nucleus decreases markedly in length and increases in thickness. The chromatin, which is distributed uniformly through the resting nucleus in a fine reticulum, as the nucleus shortens streams towards the poles, and there forms into coarse, deeply-staining strands. The nucleus thus appears to take an active part in the process of contraction.
By most authors, contraction in smooth muscle has been assumed to be due to an increase in the volume of the myofibrillse brought about by the absorption of water from the interfibrillar substance. The observations reported in the present paper were made to determine whether there is any change in the volume of the smooth muscle nucleus during contraction, accompanying the marked changes in structure described in the preceding paragraph.
The material chosen was the intestinal muscle of Necturus. Here the nuclei are very large, in extreme extension reaching a length of eighty micra. They are large enough for fairly accurate reconstruction. Pieces of the muscle were fixed in Zenker's fluid, embedded in paraffin and cut serially. Some of the series were cut at four micra, others at five micra in thickness. The sections were stained either by Delafield's haematoxylin or in Heidenhain's iron hematoxylin.
Measurements of the volumes of a large number of nuclei, both from contracted and expanded muscle, were made. Two methods were used in determining the volume. The first method is as fol (633)
D 634
Caroline McGill.
lows : In a given area of a longitudinal section of smooth muscle, the nuclei showing the greatest size were taken as nuclei cut in median longitudinal section. These were projected and drawn by means of a camera lucida at a magnification of 1200 diameters. Assuming that the nuclei were round in cross section, the volume was calculated. This was done by breaking each nucleus up into several frustra of cones, finding the volume of each and adding the several volumes. The following table is from a series of nuclei taken as representatives from a large number of measurements. In this table the magnified size has been reduced to the actiial size. The length and w;idth of the nucleus give a fair index of the amount of contraction. The first of the series therefore represents a nucleus fully contracted, the last is fully extended.
No.
Length in Micra.
Width in
Micra.
i Volume in Cubic Mici
1.
1
28
18
2786.74
2
30
17
2447.65
3
35
15
2938.52
4
43
9
1763.30
5
55
9
1940.82
6
62
9
2537.64
7
70
7
2013.68
8
72
7
2024.72
9
76
7
2031.12
10
82
5
1766.24
In the expanded muscle the nuclei are almost round in cross section, but in contracted muscle they are often considerably flattened. This probably accounts for the apparently slightly smaller volume in the expanded muscle nucleus shown in the above table. Therefore, as a check on this first series of measurements by (probably) a more accurate method, the volumes of another series of nuclei were found by reconstruction. The size of the nucleus made it easy to do this. Thin serial sections in cross section of the muscle fibres were made from both contracted and expanded muscle.
D The Effect of Contraction.
635
Definite areas in series from these sections were projected and drawn by aid of the camera Incida at a magnification of 1500 diameters. In these series the nuclei were easily traced throughout their entire length. From the serial drawings the volumes of the nuclei were found either by means of a planimeter or by reconstruction by Bern's wax plate method (the volume in the latter case being measured by water displacement). The following table gives a few representative volumes taken from a large number of measurements by the planimeter method. As in the preceding table, the magnified size has been reduced to the actual size.
Number.
Length in Micra. 27
Volume in Cubic Micra.
1
2370.00
2
32
2400.00
3
37
2411.90
4
43
2240.00
5
47
2370.00
6
47
2434.00
7
53
2340.00
8
64
2472.00
9
70
2112.00
10
77
2408.00
_ I
The wax models of the nuclei showed very similar volumes, so a table is not given.
The above table shows little difference between the volumes of the resting and of the contracted smooth muscle nucleus. From the data it seems probable that during the contraction of the smooth muscle nucleus of Necturus there is no change in volume.
Received for publication September 9, 1009.
D A NOTE ON ORANGE G COUNTER-STAINING SUGGESTING A USEFUL METHOD IN THE MANAGEMENT OF EMBRYONIC TISSUE.
BY
JOHN T. MORRIS, From the Department of Anatomy y Columbia University,
The general value of Orange G as a means of obtaining brilliant differentiation in counter-staining is too well known to require comment. The stain, however, appears to be ill adapted to many tissues, regardless of fixation and also without reference to the length of time the tissue has been in preservation.
Finding it difficult to get a good Orange G stain in several varieties of embryonic tissues, severally fixed in Merkel's, Miiller's, Flemming's or Zenker's fluids, it was determined to use the stain experimentally with the view of finding some method by which the obstacle might be overcome. The first tissue experimented upon was a Tragulus embryo of 20 mm. which had been preserved in 85 per cent alcohol for five years. Having tried Orange G as a counter-stain to Delafield's haematoxylin in the usual manner without success, picric acid, eosin and acid picro-fuchsin were employed but failed to yield results.
Subsequently, by a reversal of the ordinary Orange G method and the introduction of an alkaline solution of the stain a decisive differentiation was obtained. A number of other tissues which were difficult as far as counter-staining was concerned have yielded entirely satisfactory results by this method ; it is now used as the routine procedure with all embryonic tissues in this laboratory and has proved the most uniformly reliable means of securing an even and clear differentiation. The solutions needed for this stain are :
1. 1 per cent solution of Orange G in 60 per cent alcohol acidulated by .25 cc concentrated HCl. to the 100 cc.
(636)
D Orange G Counterstaining. 637
2. 1 per cent solution of Orange G in 60 per cent alcohol alkalinized by saturation with lithium carbonate.
3. HflBmatoxylin solution (Delafield) full strength. The following steps should be carefully observed:
I. Acid Orange G from 10 seconds to 1 minute.
II. Wash in 60 per cent alcohol.
III. Hsematoxylin solution about 5 minutes.
IV. Wash in water.
V. Acid Orange G, about 1 minute.
VI. Wash in 60 per cent alcohol.
VII. Alkaline Orange G solution about 2 minutes.
VIII. Ascending alcohol series.
IX. Xylol.
X. Mount in Canada balsam.
Received for publication September 3, 1909.
D BOOK EEVIEWS.
Die Muskeln des Menschlighen Abmes. By Dr. Fritz Frohae and Dr. Max Frankel. With 414 pages and 154 illustrations, part in colors, forming the fifteenth section of the "Handbuch der Anatomic des Menschen," edited by Prof. Karl von Bardeleben. Gustav Fischer, Jena, 1908.
This section of von Bardeleben^s Handbook of Anatomy represents the result of an immense amount of detailed study by Dr. Fritz Frohse, of Berlin. The excellent illustrations for the most part are original, and nearly all have been drawn by Dr. Frohse and his brother, the artist, Franz Frohse. Dr. M. Frankel, surgical assistant for many years of Dr. E. von Bergmann, at the surgical clinic at Berlin, has had chiefly to do with the surgical bearings of the subject.
The book begins with a sub-section devoted to general aspects, under which the external form is first treated, numerous good pictures being given to illustrate the relations of the surface anatomy to the underlying muscles. This is followed by a brief description from Kollmann of the plastic anatomy of the arm and by a few paragraphs devoted to a classification of the muscles of the arm, which the authors state are readily divisible into four groups; those of the shoulder, upper arm, fore-arm, and hand. The muscles of these groups are treated as in part superficial and part deep. A brief classification of the muscles according to action on the joints is also given and the nerve supply is briefly summarized.
There next follows a sub-section devoted to special anatomy, in which there is given an extensive description of the structure, relations, action, practical aspects and innervation of each of the muscles of the arm. References are also made to the length of the musclebundle components, to the segmental relations of muscle innervation and to muscle variations. The illustrations in this sub-section which show the distribution of nerves within the muscles form a welcome addition to descriptive human anatomy.
(638)
D Book Eeviews. 639
Following tlie descriptive anatomy of the individual muscles of the upper extremity there is a supplemental sub-section devoted: (1) to the muscle fasciae of the upper extremity; (2) to the tendon sheaths and synovial bursse of the hand; (3) to the length of the muscles including their tendons ; (4) to the length of the muscle-bundle components of the various muscles; (5) to the weights of the various muscles; (6) to the origins and insertions of the muscles on the bones of the uppper extremity; (7) to muscle variations; (8) to neurological aspects, including relations of innervation to spinal segments, the piercing of muscle by the nerves, the double innervation of arm muscles, and electrical stimulation. Each of these sub-divisions of the supplementary sub-section contains numerous new details of value. The sub-section on the muscle fasciae contains much of value but is less happily illustrated than most other subjects treated by the authors. We need good pictures of fasciae and fascial compartments. The authors have missed an opportunity to supply this need. The subsections on the length of muscles with their tendons and on muscle bundles contain numerous important details and are well illustrated. In the sub-section on the weight of muscles there is set forth an extensive study of the weight of the muscles of the right and left arms of a muscular man and of a woman with weak muscles. In the subsection on the muscle attachments to the bones of the arm excellent illustrations are given not only of the muscle attachments but also of sub-muscular bursse. The attachments to the clavicle, scapula and humerus are illustrated on isolated bones; those to the radius and ulna are shown with these bones side by side in the position of supination* those to the bones of the wrist and hand with these bones in approximately their normal relations. Illustrations showing muscle attachments to the articulated skeleton of the entire upper extremity would add to the value of this sub-section. In the neurological subsection but little space is devoted to the relations of the muscle-nerves to the spinal segments since the authors were unable through dissection to get accurate data of their own on the subject. In the sub-section on electrical stimulation the authors follow closely the descriptions of Toby Cohn "Leitfaden der Elektrodiagnostik und Electrotherapie," the material for which was prepared by Dr. Cohn in co-operation with the anatomical studies of Erohse and Frankel.
640 The Anatomical Record.
Taking the book as a whole the anatomist will find in it many details of considerable value, but he will find comparatively few new and broad deductions drawn from these details. There is an almost entire absence of reference to embryology and comparative anatomy, the two great fields which serve to give unity and simplicity to morphology. The volume represents, however, a sincere contribution of patient labor and some real additions to descriptive human anatomy.
Charles B. Bardeen. Received for publication November 19, 1909.
D XOTES.
The Eetesement of Db. Horace Jayne.
It is a matter of deep r^et to the anatomists in this country that Doctor Horace Jayne finds it necessary to give up his active work as the head of the department of publications of the Wistar Institute. The editors of the journals for which he has worked so successfully and also his colleagues in the Wistar Institute wish to express their very keen appreciation of his untiring work and of his great generosity, both of which have made possible the bringing together the publication of the five principal anatomical and zoological journals of this country. The spirit of co-operation on the part of the Wistar Institute with the editorial boards of the various journals has led to a central publication ofiice which has definite aims along certain lines. These lines are to simplify the machinery of publication, to raise the standard of book making, to stimulate the publishing of scientific articles in our own journals, and to increase the support of our journals both at home and abroad. It is along these lines, involving the task of co-ordinating the activities of some thirty-eight different editors of the various journals, that Doctor Javne has worked for the past two years. The anatomists wish to express their gratification that the work so well begun is to go on through the- continued co-operation of the Wistar Institute.
At the University of California, Professor Eobert O. Moody, M.D., has been made acting head of the department of anatomy for the coming year.
Dr. Joseph H. Hathaway, A.M., M.D., formerly instructor in anatomy in the Cornell University Medical College, has been appointed professor of anatomy in the University of Louisville, Louisville, Ky. In the reorganization of the department microscopic anatomy and embryology are included in the chair of anatomy.
i}4:2 The Anatomical Eecord.
Dr. Wesley M. Baldwin, who has been instructor in anatomy in the Cornell University Medical College at Ithaca, has been appointed instructor in the same institution in New York City.
Dr. Henry McE. Knower, Ph.D., formerly associate in anatomy in the Johns Hopkins University, has been appointed lecturer in anatomy in the University of Toronto.
In the recent reorganization of the medical faculty of the University of Pittsburgh, Dr. Benson A. Cohoe has been appointed professor and head of the department of anatomy. The department includes gross anatomy, histology, embryology and neurology. Dr. Cohoe was formely associated with the anatomical laboratories of Toronto, Cornell, Chicago and Johns Hopkins Universities. Dr. Ealph E. Sheldon, associate in anatomy in the University of Chicago, has been appointed assistant professor of anatomy. He will have charge of histology, embryology and neurology. Dr. F. E. Gundrum, formerly house oflScer of the Johns Hopkins Hospital, has been made an assistant in anatomy.

Latest revision as of 22:20, 22 February 2020

The Early Development Of The Aortic Arches Of The Cat, With Especial Reference To The Presence Of A Fifth Arch

Coulter CB. The early development of the aortic arches of the cat, with especial reference to the presence of a fifth arch. (1909) Anat. Rec. 3: 578-691.

By

Calvin B. Coulter. From the Laboratory of Comparative Anatomy, Princeton JJniversity.

With Twelve Figures.

Through the investigations of Rathke, Hochstetter, and others the development of the aortic arches of the vertebrates in general is very well understood. The existence in the mammals, however, of a fifth aortic arch, lying between the systemic and pulmonic arches, has been a matter of recent discussion, and the work on this paper was begun with the view of investigating the conditions as they are in the cat. Consideration will be given to the papers dealing with a fifth arch in the mammals when this arch is dealt with in the following pages. An extensive general bibliography may be found in Hertwig's "Handbuch" following Hochstetter's article on "Die Entwickelung des Blutgefasssystems."

The history of the arches in the cat was studied by means of wax reconstructions made after the method of Bom at enlargements of sixty-six and forty diameters. Twenty-six embryos were examined, from 3.6 to 16 mm. in length, and sixteen reconstructed, of which ten are reproduced here. The reconstructions represent casts as it were of the lumina of the blood vessels and the cavity of the pharynx, and do not indicate the thickness of the walls or the character of the glandular structures developed from the branchial pouches. No attempt will be made to describe fully the development of the pouches, which are sho^\Ti in the earlier stages to illustrate the consistent relations of the blood-vessels to the branchial arches.^

0. Hertwig, Handbuch der verglelchenden und experimentellen Entwickelungsgeschichte der Wlrbeltiere, Baud III, Teil 2. (578)


D D D Aortic Arches of the Cat.


579


List of Material Studied.


3 mm. 3 mm.

4.5 mm. 5 mm.

5 mm.

5.6 mm.

6 mm. 6 mm.

6 mm. 6.5 mm. 5 mm.

5 mm . 6.8 mm. 6.8 mm.

7 mm. 7 mm.

7 mm. 7.25 mm.

8 mm.

8 mm.

9 mm. 10 mm. 11.5 mm.


Series 188. Series 45. Series 93. Series 47. Series 11. Series 110. Series 84. Scries 126. Series 127. Series 131. Series 30. Series 31. Series 103. Series 105. Series 137. Series 138. Series 2. Series 13. Series 3.

5a.

19. Series 101. Series 29.


Columbia Princeton Columbia Princeton Princeton Columbia Columbia Columbia Columbia Columbia Princeton Princeton Columbia Columbia Columbia Columbia Princeton Princeton Princeton Princeton Princeton Columbia Princeton


University University University University University University University University University University University University University University University University University University University University University University University


Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection. Collection.


In the youngest embryo examined (3 mm., Fig. 1), in which the pharyngeal membrane has not yet broken through, there is a single aortic arch, through which on each side the primitive heart communicates directly with the dorsal aorta. There are two well-defined branchial pouches on each side, which appear to be homologous with the first and second pouches of later stages. Between these two there are slight protrusions from the dorsal aorta, and an irregular outgrowth from the ventral aorta, as shown in Fig 1. This ventral outgrowth is of a verj^ indefinite character, and has the appearance of a tissue-space which has become continuous with the ventral aorta in two places. An identical condition was found Ia another embryo of this litter. Series 188. Whether or not these cavities are to be regarded as tissue-spaces that are utilized in forming the second aortic arch cannot be discussed here; at any rate, they and the dorsal buds seem to be the ventral and dorsal anlages of the second arch. Behind the second pouch also there is on each side an evagination from the dorsal aorta, the anlage of the third arch.

An embryo of 4.5 mm. (Fig. 2) shows the second and third arches completed, and the ventral anlage of the fourth arch extending caudad from the middle of the third arch. On the left side, a


D 680 Calvin B. Coulter.

dorsal as well as a ventral anlage of the fourth arch has appeared. From the distal end of the first arch a vessel has grown forward, and when this arch degenerates carries the blood directly forward from the dorsal aorta into the head region. This vessel constitutes that portion of the internal carotid artery which is developed in


Arch P<mch

Arch

Pouch Arch

Dorsal A ah

Fig. 1. — Reconstruction of the aortic arch system of a 3 mm. cat embryo. Series 45, Princeton University Collection. Right side. X 66.


iichS

P<>^^^ AarHcBulb

Archi

Pouch t ^«* *

ArdiA Pouch S

Pouch A-6 Donal Aorta

Fig. 2. — ^Reconstruction of the aortic arches of a 4.5 mm. cat embrya Series 93, Columbia University Collection. Right side. X 60.

front of the first aortic arch. A small aortic bulb has been formed by the coalescence of the ventral ends of the first and second aortic arches. Behind the third arch a large branchial evagination has made its appearance, and has already begun to divide into the third pouch and the swelling from which the fourth and fifth pouches are subsequently formed by a similar division.


D Aortic Arches of the Cat. 581

In the next stage (5 mm., Fig, 3) the first two aortic arches are reduced in size, and from the ventral portion of the first arch capillaries extend out into the mandibular region. The ventral ends of the third arches have begun to fuse together, so that the aortic bulb is enlarged and shifted caudad. This is a stage in the progressive coalescence which takes place between the ventral ends of all the aortic arches, with the .subsequent formation of a large aortic bulb.


Archl Pouch 1 ArehM

Tr. Arterio9U9 Pouch g Aortic Bulb

Arch 3 Pouch S Arch 4 Pouch 4-6

Dcraal Aorta

Fig. 3. — Reconstruction of the aortic arches of a 5 mm. cat embryo. Series 47, Princeton University Collection. Right side. X ^•

The dorsal anlage of the fourth aortic arch is now present on both sides, and the separation of pouches 3 and 4-6 more distinct.

Fig. 4, of an embryo 5 mm. in length, shows the fourth arch completed. The first arch has lost its connection with the dorsal aorta, leaving a dorsal remnant which soon disappears. Just anterior to this remnant, and to the hypophysis which lies mesial to it, there is an anastomosis, not visible in the figure, between the two dorsal aortflB by means of a large cross-trunk, a peculiarity which was observed only in this embryo and in Series 31, another of the same


D 582 Calvin B. Coulter.

litter. The fusion of the ventral ends of the third arches has continued and now involves the bases of the fourth aortic arches. In this embryo (Fig. 4) the sixth arch makes its first appearance, as a spur extending caudad from the ventral portion of the fourth arch. The third pharyngeal pouch has become still farther separated from


Archl


Pouch 1 Archg


Pouch B Arch 3 Pouch 3

Arch 6 Arch 4 Pouch 4-6


Dortal Aorta


Fio. 4. — Reconstruction of the aortic arches of a 5 mm. cat embryo. Scries 30, Princeton University Collection. Right side. X 60.


the evagination caudal to it, which is a simple rounded structure that shows no evidence of division.

The 5 mm. embryo. Series 11 (Fig. 5), is a very important one, for it brings us to the question of a fifth aortic arch.^ Before presenting the results obtained in the cat the observations in regard to this arch in other mammals will be briefiy reviewed.

In view of the differences observed in the relative development of their arches, it is probable that the measurements of the 5 mm. embryos (Ser. 11, 30, and 31) are incorrect.


D Aortic Arches of the Cat. 683

Zimmermann^ (1889) described in the rabbit an artery arising from the truncus arteriosus and emptying into the dorsal aorta near the base of the pulmonic arch, separated from the systemic and pulmonic arches by distinct entodermal pouches. In an incomplete sheep series he found a vessel extending ventrad from the distal end of the pulmonic arch, but was unable to trace its ventral connection. The fifth arch as he described it in man represented a very different condition, as it arose from and terminated in the fourth arch, enclosing its middle third.

Tandlei^ (1902) found in two human embryos a vessel extending from the ventral aorta to the distal end of the pulmonic arch. In the rat he interpreted an anastomosis between the fourth and pulmonic ardies as a fifth arch, but could not discover a fifth pouch.

Lehman' (1905) found in the rabbit irregular vessels arising from the fourth and pulmonic arches, and in the pig a somewhat similar condition, but found in one case a complete vessel from the ventral end of the fourth arch to the dorsal aorta. This vessel was connected by a short stem with the pulmonic arch, and was separated from the fourth and sixth arches by distinct branchial pouches.

Lewis® (1906) in the rabbit and pig described only irregular vessels, and expressed the belief that none of these spurs or additional roots at the bases of the arches could be interpreted as a fifth aortic arch, and that the evagination described as postbranchial body is not serially homologous with the preceding pouches.

Locy*^ (1906), commenting upon the condition of the fifth arch in the mammals, states his belief in the existence of a fifth arch. He

•W. Zlmmermann. Ueber einen zwischen Aorten und Pulmonalbogen gelegenen Kiemenarterienbogen beim Kaninchen. Anat Anz., Bd. IV, 1889.

Rekonstruction eines menschlichen Embryos. Verb. Anat Ges., 1889.

Tandler, J. Zur Entwickelungsgescbicbte der Kopfarterien bei den Mammalia. Morph. Jahrb., Bd. 30, 1902. 'Lehmann, Harriet. On the Embryonic History of the Aortic Arches in Mammals. Anat Anz., Bd. XXVI, 1905.

•Lewis, F. T. The Fifth and Sixth Aortic Arches and the Related Pharyngeal Pouches in the Rabbit and Pig. Anat. Anz., Bd. XXVIII, 1906.

Locy, William A. The Fifth and Sixth Aortic Arches of Chick Embryos with comments on the condition of the same vessels in other Vertebrates. Anat Anz., Bd. XXIX, 1906.


D 584


Calvin B. Coulter.


thinks that its extreme variability and transitory character undonbt' edly explain the lack of definite information regarding it in some of the forms, and notes the individual differences in those forms in which a complete arch has been described.

Soulie and Bonne® (1908) in their paper on the arches of the mole describe a typical fifth aortic arch, arising separately from the


Pouch 1


Pouch 2


Pouch 3


Doraal Aorta


Archl

Arch ft

Tr. Arterioms

Aortic Bulb Arch 3

Arch 6 Arch 4 Arch 6 Right Pulm, Artery


Pouch 4-S


Fig. 5. — ^Reconstruction of the aortic arches of a 5 mm. cat embryo. II, Princeton University Collection. Right side. X 60.


Series


aortic bulb or in a common trunk with the pulmonic, and emptying in every case into the dorsal aorta in common with the pulmonic arch. This fifth vessel in the mole occupies a distinct branchial arch, which lies somewhat lateral to the fourth and sixth arches.

The typical mammalian fifth aortic arch appears thus to be a vessel which arises from the aortic bulb and empties into the pulmonic arch near its junction with the dorsal aorta. The development is

•Souli^, A., and Bonne, C. L'Appareil Branchial et les Arcs Aortiques de FEmbryon de Taupe. Journ. de TAnat et de la Phys., No. 1, 1908.


D J


Aortic Arches of the Cat. 685

most complete in man and the mole, in which an unbroken arch is the rule; in the cat, as will be described in the following pages, and in the pig, the same type of development is followed, but a perfect arch would seem not to be produced ordinarily. In the rabbit the condition is still more rudimentary, and one must agree with Lewis that evidence of a fifth aortic arch in this form is wanting.


n Thyroid

g


Arch 4 \

Arch £ .

Arch 6 ,

Arch 6 S


Dorsal Aorta


Left Pulm. Artery

FigT 6. — Reconstruction of the aortic arches of a 5.6 mm. cat embryo. Series 110, Columbia University Collection. Ventral view. X 50.

while the observations on the sheep and the rat are still incomplete, as giving evidence for a vessel of the type described above.

A condition very similar to that occurring in man and the mole, but, in general, more rudimentary, was found by the writer in the cat. In embryo Series 11 (Fig. 5) on the right side a spur extends dorsad from the aortic bulb, between the fourth and pulmonic arches (arch 6). This spur occupies the position from which a fifth arch


D I


586 Calvin B. Coulter.

would develop and resembles in all respects the anlages from which the other arches arise. The sixth arch is complete, and gives off a short pulmonary artery on the right side. In addition to the spur of the fifth aortic arch, there is a short vessel connecting the dorsal ends of the fourth and sixth arches, very similar to the anastomosis between the two arches found in the rat by Tandler and to the vessel between the fourth arch and the root of the pulmonic in the pig described by Lehmann. On the left side there was to be found no


Pouch

Arch 4

Pouch . , ^ ^ ^

iial Arch 6

Pouch

Arch 6


Fig. 7. — Photomicrograph of a transverse section through the fourth, fifth and sixth branchial arches of a 5.6 mm. cat embryo. Right side. Series 110. Columbia University Collection.

trace of a fifth aortic arch. The fourth and fifth pharyngeal pouches have not separated in this embryo and consequently the fifth branchial arch is not clearly marked out.

In an embryo of 5.6 mm. (Series 110, Fig. 6) the second aortic arches have lost their connection with the dorsal aorta, and their ventral remnants are disintegrating. There is on the right side a spur of the fifth arch from the aortic bulb similar to that shown in the preceding embryo, and in addition, a spur from the dorsal root of the pulmonic arch, with a blind vessel between them, almost con


D Aortic Arches of the Cat 587

tinuous with the ventral spur, and running parallel to the arches on either side. Each pulmonic arch joins the dorsal aorta by three distinct roots, not clearly shown in the figure. On the left side two spurs project from the dorsal end of the pulmonic arch, the larger of which is directed ventrad between the fourth and fifth branchial pouches. The fourth or most caudal pharyngeal evagination has grown out, in its dorsal portion, into two divisions, the fourth and fifth branchial pouches, which are shown in section in Fig. 7, through the right side, and Fig. 8, through the left side. The photomicrographs show also the distinct character of the fifth branchial arch, and the two ectodermal grooves in the floor of the sinus precervicalis. The ventral portion of the fourth pharyngeal evagination remains undivided and as a result the fifth branchial aich is very short This stage marks the highest development of the fifth aortic and branchial arches in the cat ; in later stages the development is retrogressive.®

In embryo Series 138, 7 mm. in length (Fig. 9), the first aortic arches have entirely disappeared, and the second arches are mere stubs which break up into capillaries. There is no fifth aortic arch, but the fifth branchial arch is very clearly marked out by the ectodermal grooves on the outside, and as in Series 110 (Figs. 7 and 8) lies to the outer side of the fourth and sixth branchial arches. The dorsal end of the sixth aortic arch is very large, and on the right side shows a peculiar grooving which is suggestive of a division into two much longer roots than found elsewhere. In this and the pre

Since the completion of this paper, Tandler has published in the Anat Hefte, 115 Heft (38 Bd., Heft 2), a careful description of the aortic arches and related pharyngeal pouches to be found in human embryos. His account agrees remarkably with mine. In man, however, the fourth and fifth pouches are derived from the ventral portion of the last pharyngeal evagination, and become more widely separated and distinct structures than in the cat. Correspondingly, the fifth aortic arch attains a more complete development. The pouches of the cat have been made the subject of a careful study by Henry Fox, whose article on "The Pharyngeal Pouches of the Mammalia*' has appeared since the completion of the present work in the Am. Jour, of Anat, Vol. VIII, No. 3. His results are entirely in accord with mine, although be makes no mention of a fifth pouch, which I interpret as a division of bis "dorsal process of the fourth pouch." An indication of this separation into two pouches Is to be seen on the left side In his Fig. 60.


D 588 Calvin B. Coulter.


Branchial Arch ^•. Branchial Arch 6^^. n , .

Branchial ArchjS-^ - '^"^^ ^


Fig. 8.— Same as Fig. 7. liCft side.


Pouch 1


^^<^ * .Aortic Bulb

Pouch $

ArchS

Pouch S

Arch 4

Arche

Right Pultn. Artmy

Pouch 4 Pouch 6

Dorgal Aorta


Fig. 9. — ^Reconstruction of the aortic arches of a 7 mm. cat embryo. Series 188, Columbia University Collection. Right side. X ^•


D Aortic Arches of the Cat. 589

ceding embryo the fourth and fifth branchial pouches are distinguishable, but their lumina are becoming obliterated, and their common connection with the pharynx cavity is being elongated and constricted off. Traces of the fourth pouch are to be found in embryos of 8 and 9 mm., but in later stages it apparently disappears completely.


Pouch


Arch

PoiuJi

Arch

Pouch

^^^ Pouch A

Right Pulm. Artery Pouch S m* '««'^

Arch Left Pvlm, Artery


DoreaiAori


Fig. 10. — Reconstruction of the aortic arches of a 9 nun. cat embryo. Series 19, Princeton University Collection. Right side, x 30.

In an embryo of 6 mm. (Series 129, not figured) the dorsal root of the sixth aortic arch is very large, as in the Series 110 (Fig. 6), and a similar but longer spur arises from the base of the left pulmonic arch and ends blindly in the substance of the fifth branchial arch.

Whatever the significance of the arterial spurs in the cat may be, it is certain that we have here, outlined by the five entodermal pouches on the inside and the corresponding ectodermal grooves on


D 590 Calvin B. Coulter.

the outside, six branchial arches. The fifth is a diminutive structure and occupies a position relatively dorsal and lateral to the other branchial arches. The facts observed point to the conclusion that Ordinarily no fifth aortic arch is completely developed in the cat; and it seems more than probable that the incomplete development and


Arch Arch

Arch


Left Pulm. Artery. Right Pulm. ArteryArch


Doreal Aori


Vertebrc Svbclavia


Fig. 11. — Reconstruction of the aortic arches of a 10 mm. cat embryo. Series 101, CJolumbla University Collection. Right side. X 28.

uncertain character of the fifth aortic arch is merely an expression of the incomplete development of the fifth branchial arch. It may well be that the anastomoses and irregular roots about the base of the pulmonic arch which have been so generally described in the mammalia are evidence of an assimilation of the fifth aortic arch into the pulmonic, beginning at their dorsal extremities.


D D D Aortic Arches of the Cat 691

The ventral anlage of the sixth aortic arch appears firsts as a bud from the ventral end of the fourth arch (Fig. 4). Somewhat later a dorsal bud grows out from the mesial side of the dorsal aorta, and the completed arch pursues a curved or bent course around the fourth anl fifth pouches. The dorsal root of the pulmonic arch in every case, from its first appearance until after the buds of the pulmonary arteries arise, was found to be pierced by two or more "islands." The significance of this has been referred to above. At


Archg

I


ArehS.

Common Carotid' Arch 4


Vertebral


Doraal Aorta

Ductus Arterionu

Subclavian

Vertebral


Arch 6 Right Pulm. Artery

Fig. 12. — ^Reconstruction of the aortic arches of an 11.5 mm. cat embryo. Series 29, Princeton University Collection. Right side. X 27.

about the time that the rudiments of the fifth aortic arch appear, (Figs, 5 and 6) the pulmonary arteries begin to develop from the middle of the sixth or pulmonic arches. Their development is very similar to that described by Bremer^^ (1901) in the rabbit. They grow caudad, following the curve of the dorsal aorta, on each side of the trachea. The aortic bulb now begins to lengthen out between the fourth and sixth arches, and to divide into the short systemic

"Bremer, J. L. On the Origin of the Pulmonary Arteries in Mammals. Am. Jour. Anat, Vol. I.


D


592 Calvin B. Coulter.

and pulmonio trunks (Figs. 9^ 10 and 11). In this process, the pulmonic trunk is twisted from right to left, and so comes to lie on the left side of the systemic trunk. At the same time the ventral ends of the two pulmonic arches are brought into contact, and they fuse together up to the point where the pulmonary arteries are given off (Figs. 11 and 12).

The later history of the aortic arch system is too well known to require any comment, and I leave the description at this point.

Recelyed for publication July 9, 1909.

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