28 WONDERS OF ORGANIC LIFE. 



instinctive craving after this substance which is 

 shown by all animals." The great object of 

 the digestive apparatus, as we have shown, is 

 to prepare chyle from aliment, the general 

 character and composition of which remains 

 always the same. The stomach, therefore, is 

 endowed with the power of securing this uni- 

 formity of composition, by an appropriate action 

 upon the materials subjected to it. With re- 

 spect to albuminous and oleaginous principles, 

 the chief materials from which the chyle is 

 formed, they require to undergo but little 

 change in order to be fitted for reception into 

 the system. But the saccharine class of ali- 

 ments, as sugar, honey, starch, arrow-root, 

 (composed of carbon and water,) which, ex- 

 cepting in purely carnivorous animals, enter 

 largely into the food of mammalia and birds, 

 are by no means adapted for such speedy 

 assimilation. They have to undergo a chemical 

 change, and become converted either into albu- 

 minous or oleaginous principles, and the 

 stomach is a self-regulating apparatus, in which 

 this conversion is affected. In the conversion 

 of chyme into chyle, the pancreatic juice and 

 the bile exert a decided influence. The che- 

 mical composition of the latter is very complex ; 

 it contains a peculiar resin, fat, or colouring 

 principle, soda, salts of soda, mucus, and azotized 

 animal substances, picromel, ozmazome, and 

 cholic acid. Bile has the property of dis- 

 solving fat; and its bitter resin, which is highly 

 stimulant and antiseptic, excites the secretion 



