62 THE FEEDING OF ANIMALS 



with albumin from flesh or the white of an egg, boiling 

 water converts it into a coagulima that is insoluble in 

 water and is rendered soluble only by such agents as 

 acids and alkalies upon heating. 



Dropping a soluble protein into alcohol has the same 

 effect. Globulins are, as a rule, affected in the same way. 

 The nature of this modification is not known. 



2. SECONDARY PROTEIN DERIVATIVES 



81. Proteoses, peptones. — ^When various proteins such 

 as albumin or globulin are subjected to the action of a 

 weak acid or of certain enzyms, they undergo what is 

 known as hydrolysis. This change involves a cleavage 

 (splitting) of the protein body accompanied by the taking 

 up of the elements of water. In this way are formed pro- 

 teoses and peptones, the latter being proteins that are 

 soluble in water.' A proteose is an intermediate stage 

 between the original protein and a peptone, and it receives 

 a name according to its soiu-ce, as albumose, globulose, 

 and caseose, according as an albumin, a globulin, or casein 

 is its source. 



Peptone was formerly regarded as the final product of 

 enzym action in digestion, but we now know that the 

 digestion of the proteins proceeds much farther. These 

 hydrolyzed bodies are found abundantly in the digestive 

 tract during digestion, the proteoses as stated being an 

 intermediate stage of digestion between the original pro- 

 ,.,.teins and the peptones. This means that the formation 

 of the final products of protein digestion is a progressive 

 step. Proteoses and peptones may also be obtained by 

 laboratory methods. It should be noted that commercial 

 peptones are largely proteoses. 



