THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 



HORIZONTAL SECTION OF THREE SUPERFICIAL 

 LOBULES, SHOWING THE TWO PRINCIPAL SYS- 

 TEMS OF BLOOD-VESSELS. 



a, a, Intra-lobular veins, terminating in the hepatic 

 veins; 6, 6, interlobular plexus, formed by 

 branches of the portal vein. 



suiTOimd the branches of the hepatic plexus, where they form the lymphatic 

 vaginfe, or canals which contain the blood-vessels. 



Connective tissue. — The intra-lobular connective tissue is scanty, the lobule 

 being almost entirely composed of cells 



or capillaries ; some trabeculae, never- ^'S- ^^^• 



theless, exist around the lymphatic 

 sheaths. There is, however, a larger 

 quantity in the interlobular spaces ; 

 and in some animals — especially the 

 Pig — Glisson's capsule sends somewhat 

 thick lamellae of connective tissue be- 

 tween these lobules.^ 



Excretory Apparatus (Fig. 

 298). — This is very simple in Solipeds, 

 and is composed of a vessel named 

 the ductus choJedochus, resulting from 

 the union of several trunks lodged in 

 the posterior fissure of the liver, and 

 which come from the three lobes. 

 Traced in the substance of the hepatic 

 tissue, these branches divide into more 

 and more attenuated vessels that arise 

 from the periphery of the lobules, and 

 are continuous with the biliary ducts 

 which envelop and penetrate these. 



Course. — At its exit from the liver, the ductus choledochus lies between the 

 layers of the gastro-hepatic omentum, and ascends to the wall of the duodenum, 

 which it passes through at about six inches from the pylorus, along with the 

 principal pancreatic duct. The 



orifices of these two canals are F'g- 297. 



surrounded by a circular mucous 

 fold (ampulla of Vater), which is 

 usually very prominent, and acts 

 as a valve in preventing the 

 entrance of alimentary substances 

 into the apertures it encircles ; 

 this office it fills so well, that it 

 will not even allow the air with 

 which the duodenum may be in- 

 flated, to pass into the ducts. 



There enter into the structure 

 of the ductus choledochus : 1. A 

 fibrous membrane, which some 

 anatomists believe contains un- 

 striped muscular fibres. 2. Sphe- 

 roidal epithelium. 3. Numerous 



* The description of the hepatic lobule has been intentionally simplified to the utmost, to 

 treatises on histology being left the task of discussing the microscopical details wliich sometimes 

 cause a lobule to be considered as a collection of tubes placed at the end of the branches of the 

 biliary ducts, at other times as a portion of a conglomerate gland full of blood-vessels. 



SECTION OF A SMALL PORTION OF THE LIVER OF A 

 RABBIT, WITH THE HEPATIC OR INTRA-LOBULAR 

 VEINS INJECTED 



