182 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



weight of stores. The ultimate chemical composition of 

 protoplasm, therefore, can tell us little of its real nature ; it 

 is of interest to know that its invariable constituents include 

 carbon and nitrogen, and almost universally phosphorus. It 

 will obviously be more instructive to describe it as it were by 

 stages, classifying the chemical contents into substances of 

 gradually decreasing complexity. Even then we shall only 

 have obtained a vague idea of the constituents of dead proto- 

 plasm, as we might make an inventory of the contents of 

 our hypothetical factory after business had been shut down. 

 Of the course of operations, or the economic conduct of the 

 factory, we should know little or nothing. Having obtained 

 such an inventory, however, and presuming the factory began 

 work again, by taking careful note of the material entering 

 and leaving the factory, we could form a much better idea of 

 the nature of the processes carried on therein. The task 

 which confronts the chemist is to investigate in this kind of 

 way the chemistry of protoplasm, which in other words is the 

 chemistry of life. In the present chapter an attempt will 

 be made broadly to indicate essential facts with reference to 

 the products of the activity of protoplasm. The substances 

 which have been isolated as more or less definite chemical 

 entities belong to the class known generally as albumins, 

 proteid bodies, or more recently as proteins. 



It will probably be simplest to take one or two of the 

 most characteristic of these substances and study their pro- 

 perties and products of decomposition ; afterwards will be 

 given in brief summary an account of the principal bodies of 

 this class which are known, together with their decomposition 

 products. At the same time occasion will be taken to indicate 

 certain of the main lines of investigation which are at present 

 being made use of in regard to them. 



As a typical albumin ordinary white of egg may be made use 

 of, and the following experiments carried out : 



Experiment. About 1 c.c. of white of egg may be poured 



