The early development of the aortic arches of the cat with especial reference to the presence of a fifth arch.код для вставкиСкачать
THE EARLY DEVELOPMENT O F THE AORTIC ARCHES O F T H E CAT, W I T H ESPECIAL REFERENCE TO THE PRESENCE O F A FIFTH ARCH. BY CALVIN B. COULTER. From the Laboratory of Compwative Anatomy, Princeton University. WITH TWELVE FIGuBEB. 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 Blutgef bisssystems.” The history of the arches in the cat was studied by means of wax reconstructions made after the method of Born at enlargements of sixty-six and forty diameters. Twenty-six embryos were examined, from 3.5 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 t.he 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 shown in the earlier stages to illustrate the consistent relations of the blood-vessels to the branchial arches. ‘0.Hertwig, Handbuch der rergleichenden und experimentellen Entwicke lungegeschichte der Wirbeltiere, Band 111, Teil 2. (578) Aortic Arches of the Cat. 570 LIST OF MATERIALSTUDIED. 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. 5mm. 6.8 mm. 6.8 mm. 7 mm. 7 mm. 7 mm. 7.25 mm. 8 mm. 8 rnm. 9 mm. 10 mm. 11.5 mm. Series 188. Series 45. Series 93. Series 47. Series 11. Series 110. Series 84. Series 126. Series 127. Series 131. Series 30. Series 31. Series 103. Series 105. Series 137. Series 138. Series 2. Series 13. Series 3. Series 5a. Series 19. Series 101. Series 29. Columbia University Collection. Princeton University Collection. Columbia University Collection. Princeton University Collection. Princeton University Collection. Columbia University Collection. Columbia University Collection. Columbia University Collection. Columbia University Collection. Columbia University Collection. Princeton University Collection. Princeton University Collection. Columbia University Collection. Columbia University Collection. Columbia University Collection. Columbia university Collection. Princeton University Collection. Princeton University Collection. Princeton UniverGty Collection. Princeton University Collectbn. Princeton University Collection. Columbia University Collection. Princeton University Collection. In the youngest embryo examined ( 3 m.,Fig. l), 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 very 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 in 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 i 3 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 580 Calvin 13. 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 FIQ.1.-Reconstruction of the aortic arch system of a 3 mm. cnt embryo. Series 45, Princeton University Collection. Right side. X 66. Fro. 2.-Reconstruction of the aortic arches of a 4.5 mm. cnt embryo. Serles 93, Columbla University Collection. Right side. x 50. 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. 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. FIG.3.-Reconstruction of the aortic arches of a 5 rum. cat embryo. Series 47, Princeton University Collection. Right side. x 50. The dorsal anlage of the fourth aortic arch is now present on both sides, and the separation of pouches 3 and 4-5 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 aorta by means of a large cross-trunk, a peculiarity which was observed only in this embryo and in Series 31, another of the same 582 Calvin B. Coiilter. litter. The fusion of the ventral ends of the third arches has continued and now involves the bases of the fourth aortic arches. I n this embryo (Fig. 4) the sixth arch makes its first appearance, as a spur extending caudsd from the ventral portion of the fourth arch. The third pharyngeal pouch has become still farther separated from Fro. 4.-Reconstructlon of the aortic arches of a 6 mm. cat embryo. Series 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.2 Before presenting the results obtained in the cat the observations in regard to this arch in other mammals will be briefly reviewed. I n view of the differences observed in the relative development of their arches, it i s probable that the measurements of the 5 mm. embryos (Ser. 11, 30,and 31) are incorrect. Aortic Arches of the Cat. 583 Zimmermann3 (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. Tandlel." (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 arches as a fifth arch, but could not discover a fifth pouch. Lehman6 (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. Lewise (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. Lacy' (1906), commenting upon the condition of the fifth arch in the mammals, states his belief in the existence of a fifth arch. He W. Zimmermann. Ueber einen swischen Aorten und Pulmonalbogen gelegeuen Kiemenarterienbogen beim Kaninchen. Anat. Am., Bd. IV, 1889. Relionstruction einea menschlichen Embryos. Verh. Anat. Ges., 1889. J. Zur Entmickelungsgeschichte der Kopfarterien bei den Mam4Tn~~cller, malia. Xorph. Jahrb., Bd. 30, 1902. 'Lehiuniin, Harriet. On the Embryonic History of the Aortic Arches in Mamuials. Anat. Am., Bd. XXVI, 1905. *Lewis, F. T. The Fifth and Sixth Aortic Arches and the Related Pharyngeal Pouches in the Rabbit and Pig. Anat. Am., 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. Am., Bd. S S I X , 1906. 584 Calvin B. Coulter. thinks that its extreme variability and transitory character undoubtedly 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. Souli6 and Bonnes (1908) in their paper on the arches of the mole describe a typical fifth aortic arch, arising separately from the FIQ.5.-Reconstruction of the nortic arches of a 5 mm. cat embryo. - Series 11, Princeton University Collection. Right side. x 50. 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 B t h 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 ‘Souli6, A.. and Bonne, C. L’Appareil Branchial et les Arcs Aortiques de I’Embryon de Taupe. Journ. de 1’Anat. et de In Phys., No. 1, 1908. Aortic Arches of the Cat. 585 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, Fro. 6.-Reconstruction of the aortic arches of a 5.6 mm. cat embryo. Serles 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. I n 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 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. I n 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 FIG.7.-Photomicrograph of n transverse section through the fourth, fifth and sixth branchial arches of a 6.6 mm. cat embryo. Right side. Series 110. Columbia University Collection. trace of a fifth aortic arch. The fourth and fifth pharyngeal ponches have not separated in this embryo and consequently the fifth branchial arch is not clearly marked out. I n an embryo of 5.6 mm. ,(Series 110, Fig. 6) the second aortic arches have lost their connection with the dorsal aorta, and their ~ e n t r a lremnants 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, r i t h a blind vessel between them, almost con- 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 arch 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.0 I n embryo Series 138, 7 mm. in length (Fig. 9), the first aortio 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. I n 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 flfth pouches a r e 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 Mammnlia” has appeared since the completion of the present work in the Am. Jour. of Anat., Vol. VIII, No. 3. Hie results are entirely in accord with mine, although he makes no mention of a fifth pouch, which I interpret as a division of his “dorsal process of tho fourth pouch.” An indication of this separation into two pouches is to be Been on the left side in his Fig. 60. Calvin €3. Coulter. 588 Fro. S.-Sarne FIG.g.-Reconstructlon as Fig. 7. Left side. of the aortic arches of a 7 mm. cat embryo. Seriea 138, Columbia University Collection. Right aide. x 50. 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. . Fro. 10.-Reconstruction of the aortic arches of a 9 mm. 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. S), and a similar but longer spur arises from the base of the left pulmonk 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 590 Calvin B. Coulter. the outside, six branchial arches. The fifth is a diminutive structure and occupies a p i t i o n relatively dorsal and lateral to the other branchial arches. The facts observed point to the conclusion that ordinarily no B t h aortic arch is completely developed in the cat; and it seems more than probable that the incomplete development and FIG.11.-Reconstruction of the aortic arches of a 10 mm. cat embryo. Series 101, Columbla University Collection. Right side. X 28. uncertain character of the fifth aortic arch is merely an expressiun 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. Aortic Arches of the Cat. 591 The ventral anlage of the sixth aortic arch appears first, 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 an1 H t h 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. .4t FIQ. 12.-Reconstruction of the aortic arches of an 11.6 mm. cat embryo. Series 29, Princeton University Collection. Right sida 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’O (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 UBremer, J. L. On the Origin of the Pulmonary Arteriea in Mammala Am. Jonr. Anat., Vol. I. 592 Calvin .B. Coulter. and pulmonic 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. Received for publication July 9, 1909.