DIGESTION. 73 



wholesome. Meat, for instance, can be kept pure for days in 

 gastric juice. The germs which are known to be the causes 

 of typhoid and cholera are destroyed by this acid. 



The pepsin acts as a ferment, that is, it converts a sub- 

 stance into more simple elements, so that it is more readily 

 dissolved and easily taken up by the system. Besides the 

 pepsin, there is another ferment in the gastric juice, called 

 rennet. It has the property of curdling milk, as the good 

 housewife knows who uses the dried stomach of the calf for 

 curdling the milk in cheese-making. Milk curdles in the 

 stomach as a natural process of digestion, and afterwards 

 breaks down and is dissolved. 



It will be seen that the bulk of the food is changed in the 

 stomach. What is not digested is broken down and divided, 

 and passes on with the rest into the intestine, as a grayish, 

 pulpy mass. It is not probable that all those portions of the 

 food which are digested in the stomach pass into the intes- 

 tine. A certain amount is immediately taken up by the 

 absorbents in the walls of the stomach and enters the system 

 directly. This explains why soup, beef-tea, and other liquid 

 foods satisfy the appetite so readily. 



23. Intestinal Digestion. Here the food again enters 

 an alkaline medium, and the final work of digestion is com- 

 pleted. The starch that was not acted upon by the saliva, 

 meeting with the pancreatic juice, is converted into sugar. 

 This juice has also the property of splitting up the oils, and 

 rendering it possible for them, in the presence of the bile, to 

 mix more readily with the watery fluid in the intestine, and 

 to be sucked up by the villi. The pancreatic juice also con- 

 tinues the digestion of the partly changed albumens from the 

 stomach. This juice seems, indeed, to be the most useful 

 of all the digestive fluids, being capable of affecting all the 

 elements of food, and bringing them into a form fit to enter 

 the lacteals, and thence into the blood. 



