1907.] AZYGOS VEINS IX MAMMALS. 197 



others [of the " Lissencephala "], and is larger than the right." 

 This does not exactly agree with what I have f onnd in an example 

 of Erinaceus cdgirus, 5 . Two az3rgos veins were present (text- 

 fig. 67) and of equal length. Each opened into the precaval of its 

 own side at a point corresponding to the interval between the 

 second and third ribs. In the case of the right azygos, the first 

 afiluent arising between the second and third ribs and the second 

 arising between ribs 5 and 6 were particulaily large. It is note- 

 worthy that posteriorly there was also an irregularity in the 

 branches of the azygos, one branch often serving two intercostal 

 spaces. The specially thick affluents were not noticeable on the 

 left azygos. 



I have also dissected one example of the Common Hedgehog 

 {Erinaceus europceits), which differs both from Owen's account of 

 that species already referred to and fi'om Erinaceus algirus as 

 dissected by myself. In this Hedgehog the right azygos alone was 

 well developed, and commenced with an afiluent from the first rib 

 space, opposite to which it entered the right precaval. On the 

 left side a very small azygos was present consisting, so far as I 

 could see, of only one branch arising from the first intercostal 

 space. It joined the left precaval at a point apparently exactly 

 opposite the right azygos. 



(4) Lemurs and Apes. 



Of this group I have examined a considerable number of species, 

 and in all of them the right azygos as a distinct vein is present, 

 and alone present. I have found this to be the case in the 

 following, viz. Lemnr catta (3 examples), L. mongoz, L. xantho- 

 mysiax, L. macaco^ L. albifrons, L. coronatus, L. varius, JVycticebus 

 ta?rligradus (3 examples), Perodicticus ])oUo, Galago crassi- 

 caudata. 



Although it is correct to say that there is only a right azygos 

 in these Lemurs as a complete vein entering the vena cava anterior 

 on its own side of the body, there are in a few forms traces of the 

 left azygos — of a hemiazygos. Thus in Galago crassicaudata there 

 is a longitudinal trunk springing from the right azygos opposite 

 to the 7th intercostal of the right side of the body. This vessel 

 runs forward, receiving intercostals from the left side and finally 

 enters the left subclavian. This vein is obviously the left superior 

 intercostal of man, but is more extensive in Galago than in Homo. 

 Furthermore, a posterior fragment of the same vein and not con- 

 tinuous with it is left in the shape of a longitudinal connection 

 between the 8th and 9t]i intercostals of the same side of the body. 



In Lemur alhifrons I found a hemiazygos arising from the right 

 azygos shortly "after the origin of the first of its intercostal 

 branches, which crossed to the left side and received the inter- 

 costal veins of that side of the body. 



Of the higher Primates I have examined a considerable number 

 of species, in all of which there is but one azygos, the i-ight, with, 



