GENERAL PROPERTIES OF THE FERMENTS. 101 



the albumoses, while others are apparently globulins, and still others 

 peptone-like bodies. Whether these various substances are pro- 

 duced by the bacteria themselves or through the agency of the 

 contained ferments is not definitely known, but it is more than 

 likely that the latter are intimately concerned in their formation. 



The enzymes or ferments proper, to which we shall now return, 

 are, as has been pointed out, specific products of cellular activity, 

 and are for the most part formed in the cell-bodies from pre-existing 

 substances, the so-called proenzymes or zymogem. In the peptic 

 cells of the stomach, for example, the specific ferment pepsin does 

 not exist, but there is present the proenzyme pepsinogen, which can 

 be transformed into pepsin by means of dilute hydrochloric acid. 

 Whether this rule holds good for all ferments, however, we cannot 

 say, and in the case of those ferments which are not secreted to the 

 outside we are not in a position to put the question to the test. That 

 ferments exist which manifest their specific activity within the cell 

 is known. Such a ferment is found in a certain bacterium, the 

 Micrococcus urese. If this organism is added to fresh urine, it will 

 gradually bring about the decomposition of the urea which is present, 

 with the formation of ammonium carbonate. On filtering such de- 

 composing urine through a Chamberland filter, so as to remove the 

 bacteria, and on adding a portion of the filtrate to fresh, sterile 

 urine, no change is brought about. This shows that the ferment has 

 not passed into solution. If, on the other hand, decomposing urine 

 is precipitated with alcohol, and the bacteria which are thus thrown 

 down together with the mineral salts are now killed with absolute 

 alcohol and ether, it is possible to extract the ferment from the 

 dried cell-bodies ; and such solutions, even when filtered with the 

 utmost care, will bring about a decomposition of urea similar to 

 that caused by the bacteria themselves. 



General Properties of the Ferments. From what has been 

 said, it is clear that the ferments are capable of manifesting their 

 special activity even after the death of their mother-cells, and it is 

 noteworthy that a great many substances which are distinct proto- 

 plasmic poisons do not interfere with the ferments themselves. Such 

 substances are chloroform, ether, thymol, toluol, salicylic acid, arseni- 

 ous acid, sodium fluoride, boric acid, hydroxylamin, glycerin, etc. 

 In the study of the ferments these bodies are of great importance, as 

 we are thus enabled to exclude the protoplasmic activity of living 

 cells, and to determine whether certain chemical phenomena which 

 we observe in the tissues of the body are referable to the action of 

 ferments or not. 



Other chemicals, however, not only cause the death of the cells, 

 but also arrest or annihilate the action of the ferments. Such sub- 

 stances are the bichloride of mercury, carbolic acid, the mineral 

 acids, and to a less marked degree other metallic salts, as also 

 picric acid, tannic acid, etc. It is to be noted, however, that one 

 ferment, at least, viz., pepsin, is not destroyed by dilute acids. The 



