232 PROTEIN. 



almost Identical in composition, and, like vegetable 

 substances, they appear more or less convertible into 

 each other. A very slight alteration in the relative 

 proportion of the elements of which they consist, 

 causes very great differences in their nature and pro- 

 perties. As in consequence of the very peculiar 

 nature of nitrogen, all substances v/hich contain it 

 are exceedingly liable to change, therefore all those 

 forms of animal matter which contain any nitrogen, 

 very soon pass into a state of decomposition. 



597. On comparing together the various substances 

 which constitute animal and vegetable matter, it is 

 observed that lignin, gum, sugar, and starch, are all 

 perfectly distinct in nature and properties from any 

 of the substances usually found in the bodies of ani- 

 mals : a remarkable similarity, however, exists be- 

 tween the fibrin, albumen, legumine, and oily sub- 

 stances of plants, and certain forms of animal matters. 



598. The albumen, fibrin, and legumine of plants 

 closely resemble the albumen and fibrin of animals ; 

 indeed, some of the varieties of these substances may 

 be said to be absolutely identical ; they consist of 

 the same elements, and possess the same properties: 

 thus, for example, there is no chemical diiference be- 

 tween that variety of albumen which exists in peas, 

 beans, and other leguminous seeds, which is called 

 legumine, and that form of albumen which is found in 

 milk, cheese, &c., and called caseine (347, 569). 



599. When albumen, fibrin, or caseine, are acted 

 on by a solution of potash or soda, they soon dissolve, 



