Mastication, Digestion and Assimilation. 17 



tion in the tme stomacli of the ox and sheep is more perfect than 

 in that of the horse and pig. In suckling ruminants the first 

 three stomachs are less developed than in grown animals. Colin 

 found that the rumen of a calf held 2.6 pounds, the reticulum 

 .22, the manyplies .35 pounds, and the abomasum, or true 

 stomach, 7.7 pounds. As the diet of the animal is changed to 

 solid food, grass, hay and grains, the first stomach gradually in- 

 creases in size, and attains the proportionate volume which it 

 has in grown-up animals. It then holds nine times as much as 

 the other three stomachs combined. 



29. Bile. — Passing into the small intestine, the food is subjected 

 bo the action of three other secretions, — bile, pancreatic juice 

 and intestinal secretion. 



The bile is a greenish fluid of a neutral or alkaline reaction 

 secreted by the liver, the largest single organ of the body. The 

 composition of bUe is given as follows: 



Ox. Pig. 



\Yater 90.4 88.8 



Solids 9.6 11.2 



Bile salts ~) 



Lecithin, cholesterin. . V 8.0 9.5 



Fats, soaps ) 



Mucin and coloring matter 0.3 0.6 



Inorganic salts 1.3 ' 1.1 



According to Colin the liver of the horse forms over 13 poimds 

 of bUe, the ox 5.7, and the sheep .75 pounds each 24 hours. The 

 flow of bile is continuous, increasing somewhat as the food passes 

 into the smaU intestine. Bile contains a ferment in small amount, 

 capable of converting starch into sugar. Its main use is to aid 

 in the absorption of fats. In the small intestine some of the fat 

 of the food is broken up into glycerin and fatty acids; the latter 

 unite with the alkalies of the bile and pancreatic juice and form 

 soaps. These soaps aid in forming and holding the remaining 

 fat in permanent emulsion. BUe facilitates the passage of the 

 emulsified fat through the membranes of the intestines, thus 

 aiding in its absorption. It is not only a secretion in aid of 

 digestion, but also an excretion or waste product. It prevents 

 putrefaction and decomposition of the food in the intestinal canal. 

 2 



