18 THE BODY AT WORK 



by heating them, in solution, to the temperature at which 

 albumin coagulates a little over 50 C. Although they are 

 not alive, their behaviour very closely resembles that of living 

 matter. They can be obtained only from living things. They 

 produce their effects even though they are present in almost 

 infinitely small quantity. It is impracticable to make a chemical 

 analysis of a ferment, owing, in the first place, to the very small 

 amount available for analysis, and, in the second place, be- 

 cause of the impossibility, with existing methods, of obtaining 

 a ferment pure. The amount of ferment present in even a great 

 mass of yeast, or in many pounds of salivary gland or pancreas, 

 is extremely small. However prepared, it is always accom- 

 panied with proteid substances. It is impossible to say 

 whether ferments, like proteins, have heavy nitrogen-contain- 

 ing molecules. The fact that they are not diffusible suggests 

 that they have. 



It would be straining language to term fermentation a phe- 

 nomenon of life ; worse, to define life as a sequence of fermen- 

 tations. Yet it is safe to say that all the chemical changes 

 carried out by living organisms are fermentations. Fermenta- 

 tion and the chemistry of life are almost synonymous terms. 



A very large number of ferments are already known. Each 

 has its own specific work to do : "To every fermentable sub- 

 stance is fitted a ferment, as a key to a lock." It will be under- 

 stood, from what has been already said regarding our inability 

 to determine the composition of any ferment, that we cannot 

 say whether or not these various ferments differ one from 

 another in chemical constitution. They are classified according 

 to their action, and not according to their nature. Those which 

 build up are termed " synaptases " (a-waTrra), I unite) ; those 

 which decompose, or hydrolyse, " diastases " (&acrra<m, separa- 

 tion). The termination " ase " is added to the name of the sub- 

 stance upon which the ferment acts, except in cases in which 

 other terms have already become so general as not to be dis- 

 placeable : amylase, hydrolysing starch ; sucrase, inverting cane- 

 sugar ; protease, hydrolysing proteins. Unfortunately, there 

 is little uniformity in this nomenclature ; amylopsin, invertin, 

 pepsin, are terms used as often as those terminating in "ase." 

 As a distinguishing termination, " in " or " sin " is less desirable 

 than " ase," owing to the fact that it has been appropriated 



