ALBUMEN, AND CASEINE. 107 



Now, although it cannot be demonstrated that 

 proteine exists ready formed in these vegetable and 

 animal products, and although the difference in 

 their properties seems to indicate that their ele- 

 ments are not arranged in the same manner, yet 

 the hypothesis of the pre-existence of proteine, as 

 a point of departure in developing and comparing 

 their properties, is exceedingly convenient. At all 

 events, it is certain that the elements of these com- 

 pounds assume the same arrangement when acted 

 on by potash at a high temperature. 



All the organic nitrogenised constituents of the 

 body, how different soever they may be in composi- 

 tion, are derived from proteine. They are formed 

 from it, by the addition or subtraction of the ele- 

 ments of water or of oxygen, and by resolution 

 into two or more compounds. 



5. This proposition must be received as an un- 

 deniable truth, when we reflect on the develope- 

 ment of the young animal in the egg of a fowl. 

 The egg can be shewn to contain no other nitro- 

 genised compound except albumen. The albumen 

 of the yolk is identical with that of the white ; (23) 

 the yolk contains, besides, only a yellow fat, in 

 which cholesterine and iron may be detected. Yet 

 we see, in the process of incubation, during which 

 no food and no foreign matter, except the oxygen 

 of the air, is introduced, or can take part in the 

 developement of the animal, that out of the albu- 

 men, feathers, claws, globules of the blood, fibrme, 



