PORTAL VEIN IN THE DOG. 177 



drium, bounded by the diaphragm, stomach, duodenum, 

 colon, and right kidney. In the dog it appears to have no 

 fewer than eight lobes. More correctly, however, it has 

 a principal lobe, a right lobe, a left lobe, a right lobule, a 

 left lobule, besides some other prominences elevated to the rank 

 of lobules. The fissures in the principal lobes are deep; the 

 right fissure of the middle lobe receives the gall-bladder, the 

 left fissure the umbilical ligament. The liver in the dog is 

 said to have about one twenty-seventh part of the weight of 

 the body. 



The portal vein is formed in the dog after the same model 

 as in other mammals namely, by the union of the veins be- 

 longing to the several chylopoetic and assistant chylopoetic 

 viscera, or, what is the same thing, from all the veins which 

 bring back the blood carried out from the posterior aorta by 

 the three great azygous trunks namely, the cseliac axis, the 

 anterior mesenteric, and the posterior mesenteric. It is dis- 

 tributed in the same manner, like an artery, in the substance 

 of the liver ; and before its capillaries terminate in the radicles 

 of the hepatic veins, these are joined by the capillaries of the 

 hepatic artery, so as to receive the only part of the venous 

 blood derived from the cseliac axis which is not poured into 

 the portal trunk before it enters the liver. So strict is the 

 rule as to the blood carried out from the aorta by the three 

 great azygous trunks just referred to, that even the veins of the 

 gall-bladder terminate in the trunk of the portal vein. The 

 subdivisions of the portal vein pass throughout the liver in 

 the portal canals formed by the fibrous coat reflected into 

 the interior of the organ, under the name of the capsule of 

 Glisson. The branches of the hepatic artery, the nerves, and 

 lymphatics, follow the same course in their distribution, being 

 contained, like the subdivisions of the portal vein, in the portal 

 canals. The trunks of the hepatic veins, on the contrary, pur- 



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