Talk:Paper - a contribution to the anatomy and development of the venous system of didelphis marsupialis 1
A CONTRIBUTION TO THE ANATOMY AND DEVELOPMENT OF THE VENOUS SYSTEM OF DIDELPHYS MARSUPIALIS (L).— PART I, ANATOMY.
BT
CHARLES F. W. McCLURE.
Professor of Comparative Anatomy, Princeton University.
With 5 Colored Plates and 11 Text Figures.
It has been found necessary to publish this paper in two parts. The first part deals with the anatomy of the venous system of Didelphys marsupialis, while the second part, which appears later, will deal with the development of the veins.
In 1900 the writer" published a preliminary article entitled "The Variations of the Venous System in Didelphys virginiana," in which was described a set of variations that occurred in connection with the mode of origin of the postcaval vein. These variations were so unusual in character and occurred with such regularity in all of the opossums examined that a further investigation was deemed necessary. This investigation is now completed and after the examination of one hundred and one (101) opossums the writer can reiterate the statement made in the preliminary article, that the mode of origin of the postcava is so variable in Didelphys marsupialis, that it is impossible to assign any one mode of origin for this vessel that may be regarded as typical of the species.
It is astonishing how little has been published upon the anatomy of the venous system of marsupials when one considers the unique character of their postcaval vein. Previous to 1893 the writer has, with Hochstetter, 93, been able to find in the literature but one reference to the postcaval vein (Owen, 66), in which it has been described as occu 1 On the basis of priority of nomenclature tlie specific name marsupialis has been substituted for virginiana. All of the opossums made use of were captured in the neighborhood of Princeton, New Jersey.
2 The writer wishes to express his thanks to Stephen S. Palmer of New York, for his generosity in supplying the funds necessary to cover the cost of the Plates in this article. Also to his assistant C. F. Silvester thanks are due for his valuable assistance in connection with the preparation of the material used in the investigation.
372 Venous System of Didelyhijs Marsupialis
pying a })Osition ventral to the abdominal aorta, a position which is unusual in mammals.
Previous to 1893, so far as known to the writer, only the following have contributed to the anatomy of the venous system of the marsupials: Martin, 36, Owen, 35, 36, 39-47 and 66, Forbes, 81, and Cunningham. 82. From 1893 up to the present time, Hochstetter, 93, Beddard, 95, Parsons, 96, Windle and Parsons, 98, and the writer, 00, 01 and 02, Of all the above-mentioned investigators Hochstetter was the first to give an accurate and comprehensive description of the anatomy of the postcaval vein for a large number of marsupials.
In dealing with the anatomy of the venous system of Dulclphys it will be the purpose of this paper not to enter into a detailed description of all the veins, but rather to give an account of the general arrangement and principal variations of the caval veins and their chief tributaries, in order that the description may serve as a basis for comparison with the veins of other mammals. In addition to this, the main features of the heart will be discussed and a general comparison drawn between the venous system of Didelphys and that of other marsupials.
The Heart.
The heart of Didelphys presents only a few characters in which it differs from that of other mammals, and will be considered under the following topics : (1) The fetal structures; (2) the auriculoventricidar valves; (3) the pulmonary veins, and (-1) the coronary veins.
1. 2'he Fetal Structures. — A fossa ovalis, annulus ovalis and ductus arteriosus are wanting in Didelphys as in all other adult marsupials ' as hitherto described by Owen, 66, Cunningham, 82, Eose, 90, Parsons, 96, and Parsons and Windle, 98. Eose has explained the absence of the fossa and annulus ovalis in the heart of the adult marsupial on the ground that in the embryo the two auricles communicate with each other, as in birds and monotremes, by means of a number of small openings which are secondarily formed, and which close up early in correlation with the abbreviated intrauterine life of these animals.
2. The Right Aurwuloventricular Valve. — The right auriculoventricular valve of Didelphys consists of one medial or septal and two lateral membranous cusps which are continuous at their bases round the auriculoventricular orifice. The left lateral cusp is the largest, the septal next, while the right lateral is (|uite small and is only with diffi 3 With the possible exception of Peramehs in which an allantoic placenta is present.
Charles F. W. McClure
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culty to be distinguished from the left lateral cusp. The two lateral cusps are attached by means of chordae tendinege to thres musculi papillares which spring from the septal wall; the medial or septal cusp is, for the most part, attached directly to the septal wall by chordae tenilinese; a few of the latter may, however, be inserted into the smallest of the musculi papillarcs which springs from the right side of the septum.
The right auriculoventricular valve of marsu|)ials has Ijccn described by a number of investigators, and it appears from their descriptions that a considerable difference exists not only as to the number of membranous cusps, but also as to the number of musculi papillares that may be present. These differences are clearly brought out in the following table, which explains itself.
The Bight Auriculoventricular Valve of Marsupials."
Y a m i I y — Macropodid.e.
Macropus (spec.)
(Owen, 66.) Macropus rufus.
(WiNDLE AND PaRSONS, qS.)
Dendrolagus bennetti.
(Beddard, 95.) Petrogale xanthopvu.
(Parsons, 96.) Petrogale penicillata.
(Beddard, 95 )
Fa m i ly — Phalangerid.^,
Pha.scolarctos fuscus.
(Martin, 36.) PhascoJarctos cmereus.
(Forbes, 81.) Phalarigista rulpina.
(Cunningham, 82.) Phalangista maculata.
(Cunningham, 82.) Phascoloniys wombat.
((3WEN, 36.) Phascolomijn wouibnt.
(RiisE, 90.)
No. of cusps. Not ffiven.
Not given.
Not given.
Not sriven.
Not given.
Not given.
No. of musculi papillares. 3
2 or 3
One large, one mediumsized and several small.
- Where the number of cusps is not mentioned by the author, in all probability,
the usual number, three, was observed.
In the above table as well as in the following pages of this article the writer, in order to avoid confusion, has followed the nomenclature adopted by the authors referred to.
Ot-i
Venous System of Diddphyn Marsupialis
Fa m i ly — Dasyuiud.e.
Thylacinus cijnocephalus.
(Cunningham, 82.) Thylacinus cijnocephalus.
(Rose, go.) Dasyurus viverrinus.
(Cunningham, 82.) Phascogale calura.
(Cunningham, 82)
Family — Didelphyid^.
Didelphys niarsnpkdis. (McClure.)
No. of Cusps. No. of musculi pupillares.
.5 Two groups.
3 One large, one medium sized and several small 2 3
Not given.
2
From the above table, which is supposed to represent the normal conditions, it is seen that the number of cusps that may enter into the formation of the right auriculoventricular valve of marsupials ranges between two and five, and that in one instance {Thylacinus) there appears to be a marked difference of opinion as to the number of cusps present. The question naturally arises: Do those cases in which less or more than three cusps have been observed represent the normal conditions, or do they indicate that the observers have interpreted differently as to what really constitutes a cusp ? It is well known that considerable variation exists among the higher mammals so far as their valve structure is concerned. In some mammals there is scarcely any division into a right and left lateral cusp, so that one would not be far from the mark in describing their valves as consisting of one lateral and one septal cusp. In other mammals the three cusps may be quite distinct and in some instances an extra or supernumerary cusp may be present, being formed, probably, as the result of an extra notching of the free border of one of the lateral cusps. In view of the above statements it appears to the writer that the membranous valves of marsupials must be classed with those of the higher mammals, a classification already adopted by authors of recent text-books (Beddard, 02, and Wiedersheim, 02), although they have given no reasons for so doing.
Before closing this topic it may be stated that the semi-lunar valves of the aorta and pulmonary artery, as well as the mitral or bi-cuspid valves of Didelphys and other marsupials, thus far described, agree in their structure with those of the higher mammals. .
3. The Pulmonary Veins. — There is little to be said concerning the pulmonary veins of Didelphys except that they usually unite to form a V. pulmonalis communis before opening into the left auricle. In a few eases in which a V. pulmonalis communis was not present the veins always opened into the auricle close together.
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prc.d.
As a general rule the pulmonary veins of marsupials probably present as wide a range in their method of termination as these veins do in the higher mammals. They may open into the auricle by means of a V. pulmonalis communis as in Didelphys, close together as in Petrogale (Parsons, 96), or in separate groups as in Thylacinus and the wombat (Eose, 90). Owen, 66, as opposed to Eose, states that in the wombat they may open close together or by a single trunk.
4. The Coronary Veins. — The coronary veins of Didelphys consist of a dorsal (posterior) and a ventral (anterior) group. The dorsal group consists of one large and several small veins, which, for the most part, lie upon the surface of the left ventricle and open into the left precava near its point of termination in the right auricle. The ventral group also consists of one large and several small veins. The small veins open directly into the right auricle. The large vein (V. cordis magna, V. c. m. in Text Fig. I ) , which lies in the ventral (anterior) interventricular furrow, does not, as in most mammals, on reaching the auriculoventricular groove deviate to the left and open into the left precava, but pursues a course somewhat similar to that of a coronary vein in birds, by passing dorsad between the root of the pulmonary artery (A. p.) and the left auricle and then deviating to the right over the dorsal surfaces of the roots of the pulmonary artery (A. p.) and aorta (Ao.) to open into the atrium of the right precava (pre. .1.).'
Cunningham was the first, so far as known to the writer, to notice the unusual course of this vein in marsupials (Thylacinus), and regarded its peculiarity as one of the two distinctive characters of the
cs
Fio. I. Diaai'am of vessels at base of heart. Di(lel}>luix iiKirsii iiidlig. Showing course of V. cordis rnat,^na. Ventral view. Ao., aorta; A. p., pulmonary artery; CS., crescentic notch; pre. d., rig-ht precava; pre. s.. left precava; RA., right auricle; RV., right ventricle; V. c. m., V. cordis magna.
5 In birds [Bnteo boredlis and Soirutteria molUssima) the vein iu question pursues the same course as in JJldelphys with the exception that it does not lie dorsal to the root of the aorta, as the vein opens further to the left into the sinus common to the openings of the postcava and the right precava.
oT() A'enous System of Didelphys Marsupialis
marsupial heart, the other lu-iiig the al)senee of the fossa and aniiuhis ovalis.
There is one more topic in connection with the structure of the heart that is worthy of mention, since it has been erroneously described by Owen, 66, as a constant marsupial character. I refer to the socalled bifurcated right auricular appendix. It has been described as a prominent feature of the heart by Owen in Macro pus and Phascoloiinjs; by Cunningham, 82, in Phalangista vulpina and P. maculata and by Parsons, 96, in Pelrogale. It has l)een found by Cunningham to be only slightly indicated in Pliascogale and by the writer in Didelphys (C S., Text Fig. I), and to be wanting by Cunningham in Vasyurus and. Thylacinus. The investigations of Cunningham have entirely disproved the claims of Owen as to the constancy of this character for the heart of marsupials, since he found it wanting in Dasyurus and Thylacinus.
A bifurcated right auricular appendix apparently possesses no great significance beyond the circumstance that it represents an instance in which the free margin of the appendix has become notched or invaginated as the result of its proximity to the root of the aorta. Such a notching is not uncommonly met with in the hearts of the higher mammals, as, for example, in Arctomys monax^' in which a well-defined bifurcated right auricular appendix may be .present.
The Veixs of the Head and Neck. {Text Fig. II.)
There are two precaval veins in Didelphys, and this is the rule in all marsupials with the possible exception of Belideus hreviceps, which has been described by Forbes, 81, as possessing only one. In Didelphys each precava (pre.) begins opposite the first rib and is formed through the union of three veins, the V. subclavia (V. s.), the V. Jugularis communis (V. j. c), and a vein which I have designated as the V. costovertebralis (V. cv.). The tributaries of the precaval veins are as follows: (1) A Y. mammaria interna (V. mam.) which opens into the ventral surface of each precava near its union with the subclavian vein; (2) the V. azygos {Y. a.), which opens into the left precava about opposite the head of the third rib, and (3) the posterior group of coronary veins which also open into the left precava, about opposite the head of the fifth rib. The right and left precaval veins open into the right auricle along its antero- and posterodorsal walls, respectively;
"Princeton Morphological Museum, No. 487.
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377
Ihc left precaval vein opening in common with the posteava. The internal manunary and the subclavian veins do not present any unusual characters and will not be further considered. The V. costovertebralis will be described in connection with another topic.
ol-..
y. cep
V.'cep.
Fig. II. Diagram of the veins of the head and neck of Diddphys niarsupiaUx. Tentral view.
a., small veins which collect blood from the submaxillary and sublingual glands; b., a vein which collects blood from the superficial muscles on the front of the neck; c, a vein which collects blood from the side of the larynx; cl., clavicle; do., dorsal portion of venous ring; pre, precava ; X., outer venous ring, formed by external jugular, axillary and cephalic veins ; v., ventral portion of venous ring formed exclusively by external jugular vein; V.a., V. azygos ; V.an., V. anastomotica; V.a.p., V. auricularis posterior; V.ax., V. axillaris; V.cep., V. cephalica; V.c.d., V. cervicalis descendens; V.cv., V. costovertebralis ; V.j.c, V. jugularis communis; V.j.e., V. jugularis externa ; V.j.i., V. jugularis interna; V.mam., V. mammaria interna; V.m.e., V. maxillaris externa ; V.m.i., V. maxillaris interna; V.s., V. subclavia ; V.s.max., V. subraaxillaris ; V.s.ment., V. submentalis ; V.t.s., V. transversa scapulae.
The V. jugularis communis (V. J. c.) is a short trunk and is formed, on each side, through the union of the V. jugularis externa (V. j. e.) and the V. jugularis interna (V. j. i.). The common jugular vein receives one tributary, the V. cervicalis descendens (V. c. d.), which
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378 A'^enous System of Didelphys Marsupialis
follows the course of the ascending cervical artery and opens into the dorsal surface of the common jugular near its union with the subclavian vein.
The internal jugular vein (V. j. i.) presents no unusual conditions except that it is an exceedingly small vessel as compared with the size of the external jugular (V, j. e.)/
The external jugular vein (V. j. e.) begins near the angle of the lower jaw and is formed, on each side, through the union of three veins: The V. maxillaris externa (V. m. c), the V. maxillaris interna (V. m. i.) and a vein which may be designated as the V. submaxillaris (Y. s. max.). The external and internal maxillary veins often unite to form a V. maxillaris communis before joining the submaxillary vein.
The external jugular vein (V. j. e.), along most of its course, lies quite superficially and instead of passing into the thoracic cavity on the dorsal side of the clavicle, as is usually the case in mammals, it forms about it, on each side, a complete venous ring so that one part of the external jugular lies ventral (v.) and another dorsal (do.) to the clavicle (cl.).* Hochstetter, 96, has described the presence of a somewhat similar venous ring in Ornithorliynchtis and states that the portion of the ring which lies dorsal to the clavicle is much larger than the ventral and forms the main trunk of the external jugular. In Didelphys there is not much difference in size between the dorsal and ventral portions of the ring, as, in the majority of cases observed, they were found to be subequal in size.
The formation of such a venous ring about the clavicle, so far as the writer knows, has not been hitherto described for Didelphys nor for any marsupial. In a specimen of Petrogale recently examined by the w^riter no indication of such an annulus was present, so that in all probability this feature is not of common occurrence among the marsupials.
Of the veins opening into each external jugular the following are the most important: Beginning craniad, (1) one or two veins which return blood from the postauricular region (V. a. p.) ; (2) the V. transversa
' This is also the case in Petrogale (Beddard, 95, and the writer).
■^ As a matter of fact two venous rings are formed about the clavicle in Didelphys ; the one mentioned above, which is formed exclusively by the external jugular vein and another (X.), much larger, which is formed through a contluence of the cephalic vein (V.cep.) with the axillary (V.ax.) and external jugular (V.j.e.) veins. The last mentioned or outer ring (X.) is not uncommon in mammals. It is a prominent feature in the three-toed sloth (Bradnpus tridactylns) and is sometimes met with in man (Nuhnl.
Cliarle? F. W. McClure 379
scapula (Y. t. s.) ; (3) the V. cephalica (Y. cep.), which arises on the radial side of the hand and forearm (this vein also opens into the axillar}' vein); (4) two veins which may open separately or by a common trunk into the dorsal portion (do.) of the venous ring, one of which (b.) returns blood from the superficial muscles on the ventral surface of Ihe neck, while the other (c), besides uniting with the internal maxillary vein, collects blood from the side of the larynx.
In addition to the above mentioned tributaries, the external jugular veins anastomose with eacb other across the middle line of the neck. This anastomosis may be accomplished in one of two ways: Either by means of two vessels which run between the dorsal and ventral portions of the venous rings of opposite sides and fuse in the middle line of the neck (Y. an.), or by means of a single vessel whicb extends between the ventral portions of the two venous rings as in Text Fig. lY (Y. an.).
The affluent veins of each external jugular are, as mentioned above, tlie Y. submaxillaris (Y. s. max.), the Y. maxillaris externa (Y. m. e.) and the Y. maxillaris interna (Y. m. i.). The submaxillary veins are quite large and anastomose with each other on the dorsal surfaces of the geniohyoid muscles. Each submaxillary vein receives the following tributaries: Yeins from the tongue and the floor of the mouth; the Y. submentalis (Y. s. ment.) and small veins from the submaxillary and sublingual glands (a.).
The external maxillary vein collects blood from the face and the internal maxillary from the regions supplied by the internal maxillary artery.
The Yeixs of the Yektebral Canal and the Deep Lying Yeins of THE Cekvical and Thoracic Eegions." {Text Fig. III.)
Text Fig. Ill is a diagram of the veins of the vertebral canal and the deep-lying system of veins of the cervical and thoracic (first five intercostal spaces) regions. These two regions need a special description, since the relations which exist here among the veins are quite unusual.
The Y\. columnae vertebrales (Yv. c. ve.) consist of two large venous sinuses which lie ventral to the spinal cord and extend, on each side, within and along the entire length of the vertebral or spinal canal. In the region of the first thoracic vertebra they anastomose at one point dorsal to the spinal cord.
"This deep-lying system of veins was largely studied by means of corrosions.
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Venous System of Didelpliys Marsupialis
The V. eostovertebralis (V. cv.), previously mentioned as one of the tributaries of the precava, is most intimately connected with this deep-lying system of veins and may, therefore, be considered at this point.
The tributaries of the V. eostovertebralis {\. cv.) are, on each side, as follows : ( 1 ) A small superficial Y. intercostalis suprema (V. i. s. I) ; (2) two large veins, one of which lies just cranial (d.) and the other caudal (e.)
