INTESTINAL DIGESTION. 65 



liver in a medium-sized horse is eleven pounds. In its ex- 

 ternal form, it is flattened before and behind, and irregu- 

 larly lengthened in an eliptical form, thick in its center, 

 and thin towards its borders, which are notched in such a 

 manner as to divide it into three principal lobes. The 

 front face is convex, smooth, and having a deep notch for 

 the passage of the large vein, called vena cava. The back 

 face is also smooth and convex, and is entered by the 

 portal vein, hepatic artery, and nerves ; and more biliary 

 ducts leave the liver. 



Viewing the liver in position, it is found that the front 

 face is applied against the diaphragm, and the back face in 

 contact with the stomach, duodenum, and colon. 



The liver secretes bile and sugar. It secretes bile from 

 the blood of the portal vein, which comes from the intes- 

 tines charged with assimilable substances. It is supposed 

 to assist in purification of the blood, in digestion and in 

 the generation of animal heat, as the elements it absorbs 

 are rich in carbon and hydrogen. The sugar formed in the 

 liver finds its way into the blood, and is carried off by the 

 veins. It is elaborated in hepatic cells by the transforma- 

 tion of starch, or a similar substance, by contact with a 

 kind of animal yeast or diastase in the interior of these cells. 

 The sugar is passed off in the veins and the bile is carried 

 away in the biliary ducts to the gall bladder for storage till 

 required. The bile is composed of soda in combination 

 with glycocholic, taurocholic and several other acids with 

 ammonia. The soda comes from the common salt of the 

 food. The action of bile in digestion is largely upon 

 the fat, which it decomposes and turns into an emulsion, 

 separating it into very minute globules, similar to butter 

 globules in milk. 



Another office it is supposed to perform, is to change the 

 undissolved starch into sugar and facilitate its absorption 

 into the circulation. It is also thought to assist in pre- 



