304 



STRUCTURE OF THE LIVER. 



bladder (fig. 168), which serves to retain all the fluid that is 

 poured forth by the gland during a considerable length of 

 time, and thus prevents the necessity for its being continually 

 passed out of the body. 



Characters of Particular Secretions. 



363. In nearly all animals, the Liver holds the first rank 

 among Glands or secreting organs, in regard both to its size 

 and to the obvious importance of its function. The principal 

 varieties of its plan of structure in the Invertebrated classes 

 having been already noticed ( 356), we shall here limit 

 ourselves to a sketch of that peculiar arrangement of its 

 elementary parts, which presents itself in Man and other 

 Yertebrata. The position of this organ in the abdominal 

 cavity is shown in fig. 30. It is chiefly composed of a mass 

 of cells of a flattened spheroidal form (fig. 169, B), the dia- 

 meter of which is usually from l-800th to 1-1 600th of an inch ; 

 each cell presents a distinct nucleus, which is surrounded by 

 yellow biliary matter in a finely granular condition ; and in 

 the midst of this there are usually one or two large fatty 

 globules, or five or six small ones. The quantity of fat in 

 the liver is very liable to increase, however, when there is a 

 large amount of oily or fatty matter in the food, or when the 

 respiratory function is not performed with sufficient activity. 



The hepatic cells are 

 clustered together into 

 lobules of irregular form, 

 but about the average 

 size of a millet-seed; 

 these lobules are disposed 

 upon the ramifications of 

 the hepatic vein (fig. 

 169, A), like leaves upon 

 the branches of a tree j 

 and they are separated 

 from one another by the 

 peculiar distribution of 

 the " portal " vessels and 

 of the hepatic ducts. 

 The Vena Portce, it will be remembered, collects the blood 

 that has been distributed to the alimentary canal, and conveys 



Fig. 169. PORTION OF THE HUMAN LIVER. 



A, Showing the manner in which the substance 

 of its lobules is disposed around the branches 

 of the hepatic vein a ; B, cells of which the 

 lobules are composed, more highly magnified. 



