178 PHYSIOLOGY AT THE FARM. 



sue a separate course, and end between the liver and the dorsal 

 spine in the posterior vena cava. Their great size is easily 

 understood when it is considered that they return to the vena 

 cava the whole of the blood carried out from the aorta by the 

 three great azygous trunks before mentioned namely, the 

 cseliac axis, the anterior mesenteric, the posterior mesenteric, 

 to which these hepatic venous trunks really correspond. 



The lobules of the liver in the dog are of the same structure 

 as in other mammals. Each lobule rests on a minute vein ; a 

 still more minute vein descends through the base of the lobule 

 to join the first, these belong to the hepatic system of veins ; 

 the latter minute vein receives its blood from a capillary of the 

 portal system after it has secreted bile, and that capillary has 

 derived its blood, in part, from the venous blood of the abdo- 

 minal chylopoetic organs, partly from the capillaries of the 

 hepatic artery. A minute duct carries away the secretion 

 from the lobule, pursuing the same course by which the cor- 

 responding subdivision of the portal vein and of the hepatic 

 artery had reached the lobule. 



The hepatic duct unites in the dog with the cystic duct sent 

 out by the gall-bladder to form a common duct like the ductus 

 communis choledochus in man. This common bile-duct ter- 

 minates in the duodenum, having first received one of the 

 ducts of the pancreas. The coats of the gall-bladder are very 

 thick in the dog, and the internal has a villus-like surface. 

 Some ducts termed hepatico-cystic, in the dog as in some other 

 animals, pass straight from the liver to the gall-bladder. 



Of the general character of the bile some account has al- 

 ready been given (p. 116). The bile in the dog conforms to that 

 common character of the two resinoid acids combined with 

 soda which seem to constitute the usual composition of bile 

 namely, the glycocholic and the taurocholic ; the latter ap- 

 pears in particular to belong to the bile in the dog. In short, 



