426 TEE DIGESTIVE APPARATUS JA MAMMALIA. 



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 

 sublumbar 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 with- 

 out going beyond our subject. Besides, there is yet much to be learned 

 respecting them. 



The liver is a biliary and glycogenetic gland. It secretes the bile at the 

 expense of the blood of the portal vein, which comes from the intestinal 

 tunics charged with the assimilable substances absorbed by the veins from 

 the villi. This fluid is submitted to modifications in the interior of the 

 liver, by which it is relieved of certain matters, while at the same time it 

 furnishes the biliary secretion. 



The bile is, therefore, in this respect an excrementitious secretion ; though 

 all its elements are not thrown off, some of them acting on the alimentary 

 substances, and others being absorbed. From the most recent researches, 

 it would appear that it has a share in the purification of the blood, in 

 digestion, and in calorification; in the latter especially, as its absorbed 

 elements are very rich in carbon and hydrogen, bodies eminently adapted 

 for the production of animal heat. 



The liver is also a glycogenetic gland, this function having been demon- 

 strated to pertain to it by Bernard. The sugar formed in the liver finds 

 its way into the blood, and leaves the organ by the suprahepatic veins. It 

 is elaborated in the hepatic cells by the transformation of the substance 

 known as " animal amidon," which is brought into contact with a kind of 

 diastase that exists with it in their interior. 



Lastly, it is also believed that tha^jver is a hcematogenetic organ, the red 

 globules being formed in its mass at nfe expense of the fibrine of the blood 

 that passes through it. .J 



It will thus be seen that the liver furnishes two very different products 

 bile and sugar. The knowledge of this fact, combined with the internal 

 arrangement of the organ, has led some anatomists to consider the organ as 

 two glands reciprocally contained within each other. But this hypothesis 

 loses its value if it be admitted that the hepatic ducts pass between the cells 

 to the centre of the lobule, and that in this portion they are destitute of 

 epithelium. It is therefore probable that the sugar and bile are produced 

 in the large hepatic cells, and that the first passes into the veins, while the 

 second is poured into the biliary ducts. 



In Solipeds, the secretion of bile, though most active during the digestive 

 period, yet goes on in a continuous manner. 



(Certain deductions of a pathological kind are based upon the foregoing 

 anatomical facts, and have an important bearing with regard to comparative 

 pathology. They have been pointed out by Wilson, and are as follows : 

 Each lobule is a perfect gland ; its structure and colour are uniform, and 

 it has the same degree of vascularity throughout. It is the seat of a double 

 venous circulation ; the vessels of the one (hepatic) being situated in the 

 centre of the lobule, and those of the other (portal) in the circumference. 

 Now the colour of the lobule, as of the entire liver, depends chiefly on the 



