1909. | POSTCAVAL VEIN IN MAMMALS. AQT 
that the venous system of Mammals, even as concerns the large 
trunks, is subject to considerable variation. It is, therefore, 
not without usefulness merely to record the facts alone as a con- 
tribution to this department of anatomical study. I have, how- 
ever, referred to previous work upon the subject, and have 
endeavoured to summarise the present state of our knowledge 
upon the posteaval veins of Mammals and their branches. The 
important work of Hochstetter *, and more recently of McClure? 
and others, upon the venous systems of Edentates and Marsupials 
has attracted a great deal of attention to the venous system, and 
has been productive of definite ideas as to the arrangement of 
the several trunks in these animals. Jam able to confirm, and 
in some respects to slightly extend, the work of these writers. 
In making observations and in deducing conclusions from the 
arrangement of the veins in Mammals it is requisite to bear in 
mind the variability of these vessels, which appears to be greater 
than that of the chief arterial trunks. Recently the variability 
of the postcaval and its branches has been studied by McClure 
in the Virginian Opossum (Didelphys marsupialis) £, by Wilhani 
Darrach in the common domestic cat§, and by H. von W. Schulte 
in various Marsupials||, while I myself have recorded4{[ some 
variations among the Carnivora. J am able in the present com- 
munication to note some variations as well as normal arrange- 
ments. But inasmuch as variation occurs so frequently in so 
fixed a type as the Carnivore Felis, a specialised race of a 
specialised group, it is probable that variation occurs pretty well 
everywhere. But in the centre of this variation lies a mean 
which can be derived from the study of many examples. 
§ The Postcaval Trunk and its Branches in various Orders 
of Mammals. 
The Marsupials show a very constant condition in that the 
posteava lies medianly ventral to the aorta, so that on dissection 
the aorta is not seen, being completely covered by the postcava. 
The discovery of this very nearly universal characteristic of 
Marsupials we owe, as Hochstetter has pointed out**, to Owen TT. 
After examining Macropus giganteus, M. bennetti, Phascolomys 
wombat, Phalangista vulpina, Didelphys lanigera, D. pusilla, Phas- 
cologale penicillata, Belidews sciureus, Cuscus sp., Hypsiprymnus 
sp., and two pouch-young of Petaurus taguanoides, Hochstetter 
found that this generalisation held good for all those species with 
* “Beitrage zur Entwickelungsgeschichte des Venensystems der Amnioten,’’ 
Morph. J.B. 1893; and “ Monotremen und Marsupialier,’ in Semon’s ‘ Forschungs- 
reisen in Australien,’ Bd. ii. Lief. 3, 1896. 
+ Amer. Journ. Anat. vol. ii. 1903, and vol. vy. 1906. 
{ Loe. cit. 
§ “Variations in the Postcava....in 605 Examples of the Domestic Cat,” 
Amer. Journ. Anat. vol. vi. 1907, Anat. Rec. p. 30. 
|| Ibid. p. 34. 
{| “On the Anatomy of Galidia,” P. Z.S. 1909, p. 486. 
** Toc, cit. p. 626. +t ‘The Anatomy of Vertebrates,’ vol. iil. p. 552. 
