THE LIVER 485 



hold from twelve to thirteen gallons of water. Its largest diameter is at 

 the commencement, from which it begins to contract, and as it crosses from 

 the right of the abdomen near the liver to the other side, where it is in close 

 proximity to the stomach, it is contracted to a comparatively small diameter, 

 but enlarges again as it lies in the left ilank. Like the CJBcum, it has 

 three longitudinal muscular bands for three-fourths of its course, but these 

 af terwai'ds are reduced to two, and as it merges in the rectum they disappear 

 altogether, the longitudinal fibres being then equally distributed. The 

 caecum and colon are supplied with blood by the posterior mesenteric artery. 

 The rectum, or straight gut, begins on the margin of the pelvis, from 

 which it extends in a straight line to the anus. It gradually expands to 

 form a considerable reservoir for the fseces, and is uncovered by peritoneum 

 after its commencement. 



THE LIVER 



This important organ is in close contact with the right side of the 

 diaphragm. It is of an irregular figure, thick in the middle and thin at the 

 edges ; divided into three lobes ; convex on its anterior surface, where it is 

 adapted to the concave aspect of the diaphragm ; concave posteriorly. The 

 colour is that which is so well known, and peculiar to itself. It is every- 

 where invested by the peritoneum, excepting the spaces occupied by the 

 large veins as they enter and pass out, and the coronary ligament which 

 suspends it, as well as the three other folds of peritoneum, which have also 

 received particular names. 



The structure of the liver is most peculiar ; but it will be impossible to 

 enter fully into its minute anatomy for Avant of space. Suffice it to observe 

 that it is composed of lobules, of an areolo-fibrous connecting medium (which 

 has received the name of the capsule of Glisson), of the ramifications of the 

 vena portse, hepatic artery, hepatic veins, hepatic duct, lymphatics and 

 nerves, enclosed in the investing peritoneal coat. The portal vein returns 

 the blood from the stomach and small intestines to be circulated through 

 the lobules, and from this the bile is secreted. It distributes its numberless 

 branches through canals which are everywhere worked out in the substance 

 of the liver, and from which the lobules are supplied. From these, which 

 are each a small gland perfect in itself, the bile is received by a network of 

 minute ducts, ultimately coalescing to form the hepatic duct, which opens 

 into the duodenum. The secretion of bile is entirely from the venous blood, 

 and the hepatic artery is solely destined to nourish the gland. The nerves 

 are chiefly from the sympathetic system, a few small branches being derived 

 from the pneumogastric through the solar plexus. The horse has no gall 

 bladder like the cow, as well as the human species. 



The function of the liver is doubtless chiefly of a depuratory natui'e ; 

 besides the separation from the blood of the compound known as bile, it 

 appears to be the manufactory in which glycogen is produced. The fluid 

 which it pours into the intestine has the quality of arresting putrefactive 

 action in the ingesta, emulsifying fats with the assistance of the pancreatic 

 and other secretions, and stimulating the walls of the intestines to perform 

 their duties. 



