SECRETION. 



405 



which are devoid of walls, receive from the cells some of the products 

 of their secretory activity, and hence are comparable to the lumen of 

 the alveoli of other secreting glands. At the periphery of the lobules 

 the bile capillaries communicate with larger channels which are the 

 beginnings of the hepatic or bile-ducts lying in the interlobular 

 spaces. The interlobular bile-ducts possess a distinct wall lined by 

 flattened epithelium. There is, however, no distinct line of demarca- 

 tion between the cells of the interlobular ducts and the secreting 

 cells of the liver proper, as the two blend insensibly, the one into 

 the other. As the hepatic ducts increase in size they gradually 

 acquire the structure characteristic of the main hepatic duct: viz., a 

 mucous, a muscle, and a fibrous coat. 



&hj&4$i**j?& 



FIG. 186. TRANSVERSE SECTION or A SINGLE HEPATIC LOBULE, i. Intralobular 

 vein, cut across. 2, 2, 2, 2. Afferent branches of the intralobular vein. 3, 3, 

 3' 3> 3> 3 3> 3> 3- Interlobular branches of the portal vein, with its capillary 

 branches, forming the lobular plexus, extending to the radicles of the intralobular 

 vein. (Sappey.) 



Nerves. Experimental investigations have demonstrated that 

 the liver is supplied with nerves derived from the central nerve 

 system. The route of these nerves is probably by way of the splanch- 

 nics and the vagi. Many of the nerves which enter the liver are 

 vasomotor in function; as to whether others are secretory in character 

 is yet a subject of investigation. It has been asserted that nerve 

 terminals have been demonstrated running between the cells and 

 even penetrating their substance. This fact would indicate that the 

 metabolic processes of the liver are under the control of the central 

 nerve system. 



Functions of the Liver. The anatomic and histologic pecu- 



