HOW TllK AMMAh LIVES 219 



glands found in the end of the stomach neart'.st 

 to the intestine. It acts on tlie nitrogenous 

 principles in the food, which are made to tak«» 

 up water, and to changi* into a nuK'h nmn- 

 stahle and ditYusible liciuid called a pcptoiM'. 



.■>I>(), Peptones of a great number of ditT<»rent 

 kinds are produced from the varied food prin- 

 ciples—from such as fibrin, albumin, glut«»n, 

 casein. The peptones all agroe in ccitain com- 

 mon characters: («) they are easily and imhh- 

 pl»'t«*ly soluble in water (fibrin, coagulalfd al- 

 bumin and casein themselves, are not soluble); 

 {h) they lilter rapidly through animal mem- 

 branes, such as a bladder (the agents from whiidi 

 they are derived do not); {<•) they are not 

 thrown down as solids by boiling or by strong 

 acids (albumin and casein are precipitated by 

 strong a<'ids, and albumin by boiling). 



3*J1. Peptones are thus easily al)sorbed into 

 the blood, while the absorption of flio original 

 principles from which they are derived would be 

 exceedingly slow and ditlicult. Pepsin acts nmch 

 more rapidly in an acid medium, so that it is 

 specially adapted to cooperate with the muriatic 

 acid. 



n!)2. The milk-curdling ferment is the product 

 of the gastric glands. It is utilized in the 

 manufacture of cheese. Like pepsin, it acts best 

 in the presence of mui*iatic acid. One part of 



