386 Venous System of Didelphys Marsupialis 
cranial of the intercostal spaces are, in part, drained by a deep-lying 
vein similar in its relations to the posterior vertebral vein 
of the sauropsida instead of by tributaries of the azygos, or by a 
a more superficially situated superior intercostal vein, as is commonly the 
case In marsupials. 
THE PoOsTCAVAL VEIN AND ITS TRIBUTARIES. 
For convenience of description the posteaval vein of Didelphys will be 
described under the following divisions: (1) The prehepatic division ; 
(2) the hepatic division; (3) the renal division; (4) the postrenal 
division. 
The first three divisions do not 
present any unusual characters 
and can be briefly considered ; the 
fourth or postrenal division, how- 
ever, is most variable in character 
and will be dealt with at length. 
1. The prehepatic division of 
the postcava is that portion of the 
vein which extends between the 
right auricle and the most cranial 
of the hepatic veins (PH., Text 
Mes Vi): 
The only tributaries which this 
division receives are the Vy. phre- 
nice, which collect blood from 
the diaphragm and open into the 
Fie. V. Photograph of a corrosion of the 
eranial end of the postcava and hepatic and 
renal veins of Didelphys marsupialis. Ventral 
view. Princeton Morphological Museum, No. 
153. 
H., hepatic division of the postcava; K., veins 
of right kidney; PH., prehepatic division of 
the postcava; PR., postrenal division of the 
postcava (only a very small portion of this di- 
vision is shown in the photograph); R., renal 
division of posteava. 
postcava in its passage through 
the diaphragm. ‘These veins are 
not shown in the photograph. 
Owen, 66, has stated that when 
the posterior extremities are 
smaller or not larger than the 
anterior ones, as in the ursine 
ee a 
eh) 
dasyure and wombat, the postcava is somewhat less than the left precava 
and they appear to terminate by separate apertures in the auricle; but 
in the kangaroo the proportions of the two veins are reversed, and the 
postcava more obviously receives the left precava before it terminates. 
In comparing the conditions in Petrogale with those in Didelphys the 
writer is unable to draw any such distinctions as those indicated by 
