THE FERMENTS. 99 



We do not even know in what manner the transformation of 

 albumoses and peptones into native albumins is effected, although we 

 have abundant evidence that this transformation takes place in the 

 epithelial cells which line the gastro-intestinal canal. The existence 

 of oxidation-ferments in the tissues, further, is even denied by very 

 capable observers. Then, again, we have no direct evidence that cer- 

 tain synthetic processes which occur in the animal hody, such as the 

 formation of fats from carbohydrates, are brought about through the 

 agency of ferments ; although in plants, as we have seen, this may 

 in all likelihood occur. On the other hand, we know that many 

 ferments exert their special activity within the bodies of the cells, 

 and are not secreted to the outside ; and that for this reason they are 

 'in a measure removed from observation. As a matter of fact, such 

 fVrments have been isolated from certain micro-organisms, and have 

 been shown to be capable of manifesting a certain activity even after 

 the death of the mother-cells. Experiments, however, which have 

 been undertaken for the purpose of obtaining such ferments from 

 the animal tissues have, on the whole, not yielded encouraging 

 results. Nevertheless, it must be confessed that, as our knowledge 

 of the ferments is as yet very incomplete, future investigations may 

 still show that the so-called vital forces are in reality the forces 

 which are characteristic of ferments or related bodies ; and, as has 

 been pointed out, these forces are essentially the same as those which 

 we meet with in the non-organized world. 



In the present chapter we shall deal in greater detail with the 

 ferments as a class. The ferments proper must be sharply distin- 

 guished from the so-called ferment-organisms, or organized ferments, 

 which occur widely distributed in nature and comprise the impor- 

 tant groups of bacteria, blastomycetes, and certain moulds. These 

 are living beings in themselves, and not, as the ferments proper, 

 products of life. They contain ferments, and manifest their special 

 activity, in a great measure at least, through their ferments ; but 

 they are not ferments themselves, although they are often so called. 

 In contradistinction to these organized ferments, the ferments proper 

 are also termed non-organized ferments, or enzymes. They are 

 specific products of the activity of certain cells, and occur not only 

 in the animal, but, as-we have seen, also in the vegetable Avorld. 



The activity which is manifested by the non-organized ferments, 

 so far as we can isolate them from their mother-cells, is not the same, 

 however, as that which the cell can exhibit as a whole, but only a 

 part, while, on the other hand, the cellular activity includes that of 

 its ferment. When common beer yeast is thus placed in a solution 

 of cane-sugar the cell is not only capable, through its ferment, of 

 inverting the cane-sugar into glucose and Ia3vulose, but it can of 

 itself cause the further destruction of these sugars, with the forma- 

 tion of aicohol and carbon dioxide. In this latter process the fer- 

 ment plays no part, as can be readily shown by placing some fresh 

 yeast in water to which r a t certain Amount pf chtomform has been 



