20 WHAT IS LIFE 



the following points, at least, must be made clear. 

 In the first place whilst we can watch the move- 

 ments of and in living protoplasm under the micro- 

 scope, we cannot stain that protoplasm or still 

 more examine it chemically without killing it and 

 thus, it is highly probable, fundamentally altering 

 its characters. So that when one reads about the 

 chemistry of protoplasm, or about certain things in 

 the cell which are studied by the aid of chemical 

 re-agents, it is always important to remember that 

 it is dead protoplasm and a dead cell which we are 

 reading about, and that in that fact lies the possi- 

 bility of a fundamental fallacy. With this reserva- 

 tion then we may say that protoplasm is composed 

 of relatively few chemical elements. It contains 

 carbon, which we know of, under one of its forms, 

 as charcoal. It contains hydrogen and oxygen, 

 two gases which enter into combination to form 

 water, and it contains nitrogen, another gas which 

 with oxygen makes up most of the air which we 

 breathe. These four substances are its most im- 

 portant constituents, but in addition to this there 

 are minute quantities of other elements, notably 

 phosphorus. It is not to the number of elements 

 contained then that protoplasm owes its complexity. 

 Hasproto- But there can be no doubt that the molecule of 

 protoplasm, if indeed it is in any way correct to 

 say that protoplasm has a chemical molecule, must 



