40 THE CELL 



The following discoveries appear to afford a wider outlook. In the alco- 

 holic fermentation effected by the yeast plant, maltose dissolved in water is 

 changed under the influence of an enzyme formed by the yeast cells into grape 

 sugar, and this is split into carbon dioxide and alcohol. Until recently it 

 was supposed that the latter cleavage could only be accomplished by the vital 

 activity of the yeast cells themselves, which appeared in fact to follow from 

 a number of experiments. By trituration of the yeast cells and subsequent 

 compression with a pressure of 400-500 atmospheres, however, E. Buchner 

 (1897) succeeded in obtaining a sap, which after being filtered through steril- 

 ized " infusorial earth " and thus being freed entirely of yeast cells, was 

 still able to split sugar into alcohol and carbon dioxide. The active substance 

 contained in the sap Buchner named zymaze. 



This discovery opens up new prospects for our whole conception of the mode 

 of decomposition in the animal body. It makes possible the assumption that 

 not only the yeast cell but all other cells carry out the chemical work charac- 

 teristic of their vital activities by means of substances analogous to the enzymes 

 and capable of being- isolated which are formed within the cells and are given off 

 by them. It would be premature however from the present standpoint of science 

 to make such a generalization even hypothetically. For the substances formed 

 in the processes under consideration are so manifold, and the essence of the 

 processes is still so obscure that immediate dissimilation effected by the vital 

 activity of the cells cannot without further information on the subject be com- 

 pletely excluded. Moreover, the oxidation processes of the body are so well regu- 

 lated in relation to the amount of work to be done and the time of doing it, 

 that it is difficult to imagine how they could be brought about exclusively by 

 ferment action. 



Any dissimilation accomplished by the direct action of the cell, in contra- 

 distinction to the effect of the enzymes and zymaze, is designated as ferment 

 action, and the cells participating are known as organized ferments. Sub- 

 stances resulting from such action represent decomposition products formed 

 directly by the vital activity of the cell. Carbon dioxide which is produced 

 in every living being belongs (at least in part) in this category, as do other 

 substances which especially characterize the different organisms, e. g., the 

 peculiar metabolic products of different Bacteria (toxins). 



It is generally true for all cells that the substances produced in their 

 metabolism are harmful to the organisms themselves, and if retained in large 

 quantities they are fatal. Hence neither yeast cells nor Bacteria can live 

 continuously in the same solution, even though there is no lack of nourish- 

 ment, unless provision is made for the removal of the products of decomposi- 

 tion from the solution. 



E. THE ELIMINATION OF DECOMPOSITION PRODUCTS 



The cells of course cannot remove the waste products from the medium 

 in which they live. They can do no more than remove the products from 

 their own bodies. The indigestible residues of the solid food such as walls 

 of Alga?, cases of diatoms, the chitin of rotifers, etc., are egested from the 



