CIRCULATORY SYSTEM 57 



brates, is quite certain. All the blood from the alimentary 

 canal, however, need not reach the heart via the liver. 



In Acer'os iiipalensis the vena cava inferior receives three 

 veins from the liver, the abdominal vein (see below), and a 

 smaller twig which is compounded of branches from the 

 oesophagus. Moreover the blood from the posterior part of 

 the intestine, at any rate, may reach the system of the vena 

 cava inferior via the mesenteric vein, which, as already 

 stated, enters the iliacs at their point of junction in the 

 middle line. 



In addition to the main portal trunk a number of small 

 veins (five on the left side in Chauna chavaria) may enter the 

 liver lobes separately, a state of affairs which is precisely 

 that found in lizards. 



The umbilical vein, which is the equivalent of a part at 

 least of the anterior abdominal vein of the lower vertebrata, 

 is found in very various conditions of degeneration among 

 birds. In some it appears to be fairly well developed ; in 

 others it is practically absent altogether. In a specimen of 

 the hornbill Aceros nipalensis it was as well developed as 

 I have ever found it in birds. The vein arose near to the 

 posterior end of the abdominal cavity as a double vessel ; 

 further forward the two halves joined to form a single 

 vessel. The vein is supported by the falciform ligament, 

 and the upper of the two component vessels receives, not 

 very far from the junction of the two, a recurrent vessel 

 from the inside of the sternum. It may be that the 

 recurrent nature of this vessel is one among many hints of 

 the shortening of the sternum among birds. The anterior 

 abdominal trunk does not enter the liver, but joins the 

 hepatic vessels, and its blood is conveyed straight to the 

 heart. 



In Platalea leucorhodia I could find no trace of an 

 anterior abdominal vein in the falciform ligament. In Gni* 

 monachus it was very small ; in a large number of other 

 birds of different families the vein was present, and large, e.g. 

 Crax globicera, Spizaetus coronatus, Serpentarius, Bucorvus y 

 Chauna chavaria, Botaurus stellaris, Bernicla brenta, &c. 



