FERMENTS. 465 



remains even after they have been isolated. E. Buchner and J. Meisen- 

 heimer * have recently succeeded, by using the acetone method of procedure, 

 in obtaining a preparation from Bacillus Delbrucki (Leichmann) which 

 produced lactic acid from grape-sugar in the same manner as the bacillus 

 itself. They also obtained preserved preparations from beer-acetic-acid 

 bacteria, using the acetone method, which converted alcohol into acetic 

 acid. 



There is evidently no sharp dividing line between the individual cell- 

 ferments and the free, unorganized ferments. There are some which are 

 undoubtedly closely related to the cell contents, and others which are more 

 loosely united to the cell contents than is the case with yeast zymase, and 

 can consequently be more easily isolated from the cells. Finally, there 

 are those ferments which are given off by the cells themselves. 



The secretion by the gland cells can be followed directly by histological 

 methods, and it is quite possible that certain visible changes of the gland 

 cells may be related to the formation of ferments. The morphological 

 changes in the cells of the pancreas have been studied in particular. 

 Although the cells of the resting gland are but slightly distinguishable 

 from one another, we observe sharp, generally double, boundary lines, at 

 the instant when activity begins. The cells, and likewise the gland itself, 

 change their form. They become filled out. We observe kernels, which 

 belong to the inner zone of the cells, migrate towards the lumen of the 

 gland, become smaller, and finally disappear. The cell-changes in the 

 salivary glands, especially the parotid, have been very carefully studied 

 during their activity. The cells decrease in size during secretion. The 

 nucleus, usually angular, becomes rounded, and shows granules very 

 distinctly. The clear, homogeneous substance, predominating when at 

 rest, decreases in amount, while the granular substance increases. It is 

 difficult to say whether the gland cells give up a part of their protoplasm 

 during the secretion, or if, as seems more probable, products are formed 

 which then go over into the secretion. It is possible that the granules 

 mentioned possess some relation to the formation of ferments. 



The fact that a great many ferments are not secreted as such, but in an 

 inactive form, must be looked upon as of the greatest significance for the 

 conception of fermentation processes. The activation results from the 

 influence of another substance which is often produced at another place, 

 and does not necessarily form a part of the ferment, and may even be of 

 simpler composition. We call the secreted inactive ferment a zymogen or 

 preferment. Thus, we know that the pepsin zymogen is activated by 

 hydrochloric acid, while the trypsin zymogen requires the enterokinase. 

 Undoubtedly there are innumerable other ferments which are secreted in 



1 Ber. 36, 634 (1903). 



