80 PRINCIPLES OF PHYSIOLOGY 



protoplasm. It must be observed that a 

 chemical analysis of living matter is not 

 possible, because, in the processes to which it 

 must be subjected, the condition we associate 

 with life disappears. The living matter is 

 killed by the attempt at analysis, so that what 

 we are able to analyse is dead matter that 

 was once alive. Suppose a chemist is asked to 

 reveal to us the chemical constituents of a 

 muscle, he might be able to enumerate the 

 elements of which it was composed. This 

 would teach us very little. But during the 

 analysis it would be found that numerous 

 more or less complicated chemical substances 

 appeared, and that these could be arranged 

 into groups, the members of which showed 

 certain characters in common. In this 

 way we learn that organic matter is built 

 up of certain compounds called proximate 

 constituents, or principles, already referred to 

 These are proteins, carbo-hydrates, and fats, 

 and along with these we find many other 

 substances which are derivatives of these three, 

 along with various saline substances and water. 

 39. The proteins are bodies of highly 



