500 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



racemose glands, opening on the surface of the epithelium by very small 

 orifices. 



Vessels and Nerves of the Liver. — The blood-vessels are the hepatic 

 artery, portal vein, and sublobular veins. 



The hepatic artery is a branch of the coeliac, and enters the gland by the 

 josterior fissure, in company with the portal vein and ductus choledochus. In 

 the liver it divides into very fine ramifications, which join the intra-lobular 

 plexus, anastomose on the surface of the biliary ducts, or are expended either on 

 the serous membrane, or in the walls of the portal vein. 



The portal rein is the functional vessel of the liver. It reaches that organ by 

 the posterior fissure, and G-lisson's capsule accompanies its ramifications as far as 

 the hepatic lobules, where they form the plexus of subhepatic veins. 



The supra-hepatic {sublobular) veins are so named because they gain the 

 antero-superior face of the viscus, to open into the posterior vena cava. They 

 carry away the blood that has been brought by the portal vein and hepatic artery. 

 Their origin is due to the union of the intra-lobular veins, which make a passage 



Fig. 298. 



EXCRETORY APPARATUS OF THE HORSE'S LIVER. 



1, left lobe of the liver ; 2, middle lobe ; 3, right lobe ; 4, lobus Spigelii (caudate lobe) ; 6, posterior 

 vena cava at its entrance into the liver ; 7, vena portse ; 8, ductus choledochus ; 9, pancreatic 

 duct; 10, common entrance of these two ducts into the small intestine. 



through the hepatic tissue with which their walls are immediately in contact, 

 gradually join each other, and enter the posterior vena cava on its way through 

 the anterior fissure of the liver. The number of trunks {hepatic) entering this 

 vessel is considerable, but the majority are very small ; the principal confluent 

 is placed at the anterior extremity of the fissure. 



The hjmphatirs form a fine superficial plexus, easy to inject ; with deeper 

 networks placed around the vessels that penetrate by the posterior fissure. In 

 the lobules they are disposed as described above. Joined to the lymphatics 

 of the stomach, they constitute a single trunk that goes to the sublmnbar 

 receptacle. 



The nerves are more particularly derived from the solar plexus, although the 

 pneumogastric and diaphragmatic also supply filaments to the liver. They 

 interlace around the hepatic artery and portal vein ; their mode of termination 

 is unknown. 



Functions. — The most important considerations are attached to the study 

 of the functions of the liver ; but we cannot enter into them in detail without 

 going beyond our subject. 



