1907.] 



AZYGOS VEINS IN MAMMALS. 



211 



four to seven, and there was in the same way a superior inter- 

 costal. The constancy of the first branch of the azygos of the 

 right side which supplies several branches is remarkable. It 

 seems to me to be possible that this branch is the real post- 

 cardinal, persistent here to a greater extent than in most other 

 mammals which I have dissected. In any case its relations are 

 perfectly consistent with such a view of its nature. I may 

 mention that in this example I noted an oesophageal twig arising^ 

 separately from the left jugular not in common with the azygos. 



Scl.-. 



Text-fig. 72. 

 p^. p.O. 



S.t. 



Ax. I. 



Az.r. 



A/ygos veins of Hystrix cristata. 

 oes. (Esophageal vein. Other letters as in text-fig. 62. 



In the Canadian Porcupine, Erethizon dorsattmi, the jugular, 

 contrary to what is to be found in Hystrix, is a single vessel. 

 The system of azygos veins is also single and confined to the 

 right side of the body. There is no trace that I could discover 

 of either azygos or superior intercostals on the left side. The 



U* 



