1907.] AZYGOS VEINS IN MAMMALS. 199 



this Hyfena, however, the azygos is singularly short, supplyins; 

 only three intercostal spaces. It opens into the DiTctus Cuvieriby 

 a single stout branch ; this is formed by the union of three branches 

 which are of very unequal calibre. The most anterior of these is 

 a moderately stout vein running slightly forward in direction. 

 The middle vein of the three is very markedly the stouter. ^ It 

 plunges at once, after the shortest possible course, into the thick- 

 ness of the parietes. The third branch is more slender than both 

 the first and the second. It also has a very short course obliquely 

 backwards, and is very soon lost in the parietes. It gives ofi" one 

 branch to the left side and a slender short main azygos. I could 

 discover no vein upon the left side of the body. It is to be 

 remarked that we have here an abortive azygos, the first branches, 

 or pei-haps branch, only being well represented. These collectively 

 correspond, as I think, to the first branch of the azygos in some 

 other forms, which is very frequently subdivided into two or even 

 three branches. 



Text-fig. 68. 



p.C. 



Azj'gos of Hyana crocuta. Lettering as in text-fig. 62. 



It is usual for the first branch of the azygos to arise between 

 the fifth and sixth ribs in this order of mammals. I have found 

 this to be so in Procyon lotor^ Luira vulgaris (one example ; in 

 another it arose between ribs 4 and 5), Suricata tetradactyla, 

 Genetta felina. 



In Crossarchtis obscurus (text-fig. 69) the azygos entered the 

 precaval about opposite to the fifth rib. Its most anterior affluent 

 arose between the third and fourth ribs. Between the first and 

 second ribs an intercostal arose on the same side (the i-ight) and 



