THE INTESTINAL ORGANS. 129 



At the point of diminution of calibre of the large intestines the 

 faeces gradually become hard, acquiring the form of small black 

 pellets, being voided in this condition when the animal is in 

 good health. 



We shall now consider the organs secreting fluids which 

 have entrance to the intestinal canal, for the purpose of 

 aiding digestion. Of these we find two, the liver and pancreas. 

 The liver is the largest and most useful solid organ of the 

 body. Having manifold functions, it secretes the bile which. is of 

 vast importance for the digestion of food; and fiirthermore, it 

 manufactures sugar, the bile is thrown into the ducts, while the 

 sugar finds immediate access to the blood vessels, to be conveyed 

 on through the system. In the sheep the weight of the liver 

 averages about l-50th part of that of the carcass, with a slightly 

 greater specific gravity than water. The structure of this organ 

 is peculiar, owing to the diversity of the functions it is called 

 upon to perform. Externally it is found to present a mottled 

 appearance due to small polygonal spaces of a rounded appear- 

 ance, in the center of which redish spots will be observed. 



These circular bodies are the lobules about l-20th of an inch 

 in diameter, separated one from the other by the polygonal 

 spaces, which are really a network of blood vessels. To explain 

 the structure of this important organ it will be only necessary to 

 examine one of the lobules. The lobule itself is separated from 

 the others and held in place by a network of blood vessels, which 

 permeate its substance, joining together in the center of the 

 lobule. An artery called the hepatic artery and a vein called the 

 portal vein convey blood to the liver, both entering the organ 

 side by side through a fissure called the transverse. 



X:hc Bile. 

 The bile is elaborated from the blood brought to the liver 

 by the portal vein, which conies direct from the intestinal mu- 

 cous surfaces, charged with assimilable substances absorbed by 

 the veins of the intestinal papillae called the villi. 



