PHYSIOLOGICAL ANATOMY OF THE LIVER. 431 



CHAPTER XIII. 



FUNCTIONS OF THE LIVER. 



Physiological anatomy of the liver Distribution of the portal vein, the hepatic artery, and the hepatic duct- 

 Origin and course of the hepatic veins Structure of a lobule of the liver Arrangement of the bile-ducts in 

 the lobules Anatomy of the excretory biliary passages Nerves and lymphatics of the liver Mechanism of 

 the secretion and discharge of bile Quantity of bile Variations in the flow of the bile Discharge of bile from 

 the gall-bladder General properties of the bile Composition of the bile Origin of the biliary salts Choles- 

 terine Biliverdine Tests for bile Excretory function of the liver Origin of cholesterine Experiments show- 

 ing the passage of cholesterine into the blood as it circulates through the brain Elimination of cholesterine by 

 the liver Cholesteramia Production of sugar in the liver Evidences of a glycogenic function in the liver 

 Does the liver contain sugar during life? Mechanism of the production of sugar by the liver Glycogenic mat- 

 ter Variations in the glycogenic function Production of sugar in fetal life Influence of digestion and of differ- 

 ent kinds of food upon glycogenesis Influence of the nervous system, etc., upon glycogenesis Artificial dia- 

 betes Destination of sugar Alleged production of fat by the liver Changes in the albuminoid and the corpus- 

 cular elements of the blood in their passage through the h'ver. 



Physiological Anatomy of the Liver. 



THE liver, by far the largest gland in the body, is now known to have several entirely 

 distinct functions ; and one of the most important of these has already been fully con- 

 sidered, in connection with digestion. It is true that we know very little with regard to 

 the exact office of the bile in digestion, but that this function is essential to life, there 

 can be no doubt. We have, however, more positive information with regard to the 

 excrementitious function of the liver and the changes which the blood undergoes in pass- 

 ing through its substance ; and the study of these functions is closely connected with 

 the anatomy of the liver and the chemical constitution of the bile. 



It is unnecessary, in this connection, to dwell upon the ordinary descriptive anatomy of 

 the liver. It is sufficient to state that it is situated just below the diaphragm, in the right 

 hypochondriac region, and is the largest gland in the body, weighing, when moderately 

 filled with blood, about four and a half pounds. Its weight is somewhat variable, but it 

 is stated by Sappey that, in a person of ordinary adipose development, its proportion to 

 the weight of the body is about as one to thirty-two. In early life, the liver is relatively 

 larger, its proportion to the weight of the body, in the new-born child, being as one to 

 eighteen or twenty. 



The liver is covered externally by peritoneum, folds or duplicatures of this mem- 

 brane being formed as it passes from the surface of the liver to the adjacent parts. These 

 constitute four of the so-called ligaments that hold the liver in place. The proper coat 

 of the liver is a very thin but dense and resisting fibrous membrane, adherent to the sub- 

 stance of the organ, but detached without much difficulty, and very closely united to the 

 peritoneum. This membrane is of variable thickness at different parts of the liver, being 

 especially thin in the groove for the vena cava. At the transverse fissure, it surrounds 

 the duct, blood-vessels, and nerves, and it penetrates the substance of the organ in the 

 form of a vagina, or sheath, surrounding the vessels and branching with them. This 

 membrane, as it ramifies in the substance of the liver, is called the capsule of Glis- 

 son. It will be more fully described in connection with the arrangement of the hepatic 

 vessels. 



The substance of the liver is made up of innumerable lobules, of an irregularly ovoid 

 or rounded form, and about ^ of an inch in diameter. The space which separates these 

 lobules is about one-quarter of the diameter of the lobule and is occupied with the blood- 

 vessels, nerves, and ramifications of the hepatic duct, all enclosed in the fibrous sheath. 

 In a few animals, as, for example, the pig and the polar bear, the division of the hepatic 

 substance can be readily made out with the naked eye; but, in man and in most of the 



