CHAPTER XIV. 



DIGESTION AND THE DIGESTIVE AGENTS. 



HISTORICAL. 



Our knowledge concerning the process of digestion does 

 not reach back very far. The notion of the ancients was 

 very primitive indeed. They likened the digestion in the 

 body to a kind of cooking, and in the middle ages this 

 notion was carried so far that they actually thought one 

 purpose of the animal heat of the body, especially the 

 warmth of the internal organs, was to cook the foods. It 

 was as late as the seventeenth century before definite notions 

 of digestive ferments in the stomach arose ; but these fer- 

 ments were looked upon as causing only a very fine me- 

 chanical separation of the food. However, Reaumur, in 

 1752 proved that the agent of digestion was the gastric 

 juice, and that this digestion could be accomplished with- 

 out any mechanical helps. The sour re-action which Reau- 

 mur had noticed was established by Prout in 1834, to be 

 due to free hydrochloric acid. Two years later, in 1836, 

 Schwann discovered the pepsin. In 1834 a Canadian by 

 the name of Beaumont was enabled to make a series of ob- 

 servations on a man whose stomach had been exposed by a 

 wound, and upon which the digestive processes could be 

 fairly accurately followed. In the same year Eberle suc- 

 ceeded in making artificial gastric juice, and conducted 

 experiments in digestion with the same. The sugar-forming 

 action of the saliva was discovered by Leuchs in 1831. Our 

 knowledge of the digestive processes in the intestine did 

 not begin until 1848, when Claude Bernard established the 

 fact that pancreatic juice digested fats. Nine years later, 

 in 1857, Corvisart discovered that pancreatic juice digested 



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