1907.] 



AZYGOS VEINS IN MAMMALS. 



201 



into the thickness of the musculature. Later on this azygos 

 dilated to form a thicker vessel which lay beneath the aorta and 

 reached nearly to the iliacs. This is obviously quite comparable 

 to what I have described above in Macrojnts giganteus and other 

 species ; but in them it was the right azygos which was thus 

 pi-olonged and enlarged. I could not be certain whether in J^py- 

 prymnus rufescens there was or was not a connection with the 

 renal vein or the postcaval. In this specimen there was also on 

 the left side a superior intercostal vein flowing separately into the 

 vena cava superior. 



Text-fia-. 70. 



P-^- 



p.c. 



Azygos veins of Sahnaturiis hennettii. Lettering as in text-fig. 62. 



In a third example of J^pyprymmis rufescens, which was a 

 female, the conditions observed differed from those of either of 

 the other two. The two azygos veins were absolutely symmetrical 

 so far as I could see, and moreover this symmetry extended to 

 quite small details. On both sides of the body the last two of the 

 four intercostal affluents of each azygos joined before pouring 

 their contents into the azygos. It is curious to find here in the 

 same species all the chief varieties shown by the azygos. 



While jEjiyj^ify^nnus mfescens is an example of a Marsupial 

 in which the condition of the azygos veins varies from individual 

 to individual, the Common Phalanger [Trichosurus vulpecula) 

 offers precisely the reverse characteristic. Of this species I have 

 dissected six examples belonging to both sexes. In all of them 

 the azygos vein of the left side is fully developed and reaches back 

 as far as the diaphragm, in all of them the right azygos is present 



