38 FREAKS OF FLANT LIFE. 



stomach. It also is a fermentation, i.e.^ a chemical 

 change, efifected by the agency of a leaven or ferment 

 which is contained in the stomach juice, and can be, 

 like the ferment of saliva, easily separated and pre- 

 pared. As so separated it is called pepsin. Conse- 

 quently, having the ferment, we can easily imitate 

 digestion out of the body. For this experiment 

 there are three things necessary (i) That our liquid 

 should contain pepsin ; (2) That it should be slightly 

 acid ; (3) That it should be kept at the temperature 

 of incubation (about 97° Fahr.). We select for the 

 experiment a substance which, although nutritious 

 and containing nitrogen, is not easily digested — such, 

 for example, as boiled white of zg^. In water con- 

 taining a small percentage of hydrochloric acid, and a 

 trace of pepsin, it is gradually dissolved ; but chemical 

 examination of the liquid shows us that it has not 

 been destroyed, but merely transformed into a new 

 substance called peptone, which is afterwards ab- 

 sorbed, i.c., taken into the circulating blood." 



" Between this process and the digestion of the 

 Dionoea leaf the resemblance is complete. It digests 

 exactly the same substances in exactly the same way, 

 i.e., it digests the albuminous constituents of the 

 bodies of animals just as we digest them. In both 

 instances it is essential that the body to be digested 

 should be steeped in a liquid, which in Dionoea is 

 secreted by the red glands on the upper surface of 



