CHAPTER VI. 



THE FERMENTS. 



I N the foregoing chapters we have considered in a general way 

 the more important characteristics of the three great classes of 

 food-stuffs, and have studied in some detail also the various decom- 

 position-products to which they give rise in their passage through 

 the animal body. We have also pointed out that with few excep- 

 tions the food-stuffs, which the animal derives either directly or 

 indirectly from the plant, cannot be utilized by the animal directly, 

 but that they must previously undergo certain changes, which vary 

 with the character of the individual substances. The native albu- 

 mins must first be transformed into albumoses and peptones ; the 

 disaccharides and polysaccharides must be inverted to monosac- 

 charides, and the fats must first be emulsified. We have seen also 

 that in the chemical laboratory these changes can, for the most part, 

 be brought about through the action of superheated steam, by boiling 

 with acids and alkalies, etc. that, is, through agencies which mani- 

 festly are not at work in the living world. The question therefore 

 suggests itself : What are the means at the disposal of living animals 

 to bring about these changes ? This question has, in a measure, 

 been answered in the introductory remarks, where it was pointed 

 out that the animal is capable of bringing about a large number of 

 analytical changes by means of certain ferments, or enzymes, which 

 are furnished by the animal cells themselves. At the same time it 

 was pointed out that the better known representatives of this class 

 are essentially hydrolytic ferments, but that there is evidence also of 

 the existence of oxidation-ferments. 



As the chemical processes which take place in the animal body 

 are essentially of the character of hydrations and oxidations, it 

 would thus appear that other factors besides the ferments would 

 be unnecessary for the functioning of the various organs. It is 

 quite possible, indeed, that this is actually the same, and that the 

 various manifestations of life may be explained upon the basis of 

 fermentative phenomena. It must be admitted, however, that with 

 the exception of those ferments which are at work in the gastro- 

 intestinal canal, and through the agency of which the ingested food- 

 stuffs are transformed into substances that can be utilized by the 

 body, our knowledge of such ferments is extremely limited ; and we 

 are scarcely in a position, as yet, to state definitely that all those 

 chemical processes which take place in the living animal arc brought 

 about in this manner. 



