PHYSIOLOGICAL ANATOMY OF THE SPLEEN. 413 



The liver has a glycogenic action, which consists in the constant forma- 

 tion of sugar out of the glycogen, the sugar being carried away by the blood 

 of the hepatic veins, which always contains sugar in a certain proportion. 

 This production of sugar takes place in the carnivora, as well as in those 

 animals that take sugar and starch as food ; and it is to a certain extent in- 

 dependent of the kind of food taken. 



During life the liver contains glycogen only and no sugar, because the 

 blood which is constantly passing through this organ washes out the sugar as 

 fast as it is formed ; but after death or when the circulation is interfered 

 with, the transformation of glycogen into sugar continues. The sugar is not 

 removed under these conditions, and it can then be detected in the substance 

 of the liver. 



The liver serves as a receptacle for the carbohydrates, which, under nor- 

 mal conditions of alimentation and nutrition, are all converted into glycogen. 

 The glycogen is then converted into sugar, which is supplied to the system 

 as the nutritive requirements demand. 



In addition to the varied uses of the liver which have been described, it is 

 thought that this organ either arrests or in some way influences the condition 

 of certain foreign and poisonous substances which may be absorbed from the 

 alimentary canal ; but a study of this action does not properly belong to 

 physiology. 



DUCTLESS GLANDS. 



Certain organs in the body, with a structure resembling, in some regards, 

 the true glands, but without excretory ducts, have long been the subject of 

 physiological speculation ; and the most extravagant notions concerning their 

 uses have prevailed in the early history of physiology. The discovery of the 

 action of the liver, which consists in modifications in the composition of the 

 blood passing through its substance, has foreshadowed the probable mode of 

 action of the ductless glands ; for as far as the production of glycogen is con- 

 cerned, the liver belongs to this class. Indeed, the supposition that the 

 ductless glands effect certain changes in the blood is now regarded by physi- 

 ologists as the most reasonable of the many theories that have been entertained 

 concerning their uses in the economy. Under this idea, these organs have 

 been called blood-glands or vascular glands. Under the head of ductless 

 glands, are classed the spleen, the suprarenal capsules, the thyroid gland, the 

 thymus, and sometimes the pituitary body and the pineal gland. 



PHYSIOLOGICAL ANATOMY OF THE SPLEEN. 



The spleen is situated in the left hypochondriac region, next the cardiac 

 extremity of the stomach. Its color is a dark bluish-red and its consistence 

 is rather soft and friable. It is shaped somewhat like the tongue of a dog, 

 presenting above, a rather thickened extremity, which is in relation with 

 the diaphragm, and below, a pointed extremity, in relation with the trans- 

 verse colon. Its external surface is convex. Its internal surface is concave, 

 presenting a vertical fissure, the hilum, which gives passage to the vessels and 



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