FERMENTS. 479 



In this case, apparently the migrant leucocytes which are present in large 

 numbers furnish the ferment and cause a normal digestion in the lungs. 

 Some insight into the cell processes, and the ferments which come into 

 action thereby, was believed to be obtained from Salkowski's discovery 

 that organs, even when kept perfectly sterile, gradually dissolve of them- 

 selves. 1 Cleavage-products are formed at the same time which suggest 

 the presence of trypsin-like ferments. To be sure, it is generally stated 

 that the disintegration of the cell contents and especially of the albumin, 

 in this process which is known as autolysis, is not the same as that which 

 takes place in a true trypsin digestion. It is true that the same end- 

 products (amino acids, purine bases, etc.) are formed, but we do not know 

 whether the decomposition takes place in the same way, and with the 

 formation of the same intermediate products. It is questionable whether 

 we are justified at present in making deductions regarding normal cell 

 metabolism from the autolytic processes which result several days after 

 death. 2 



Thus far we have considered cell-metabolism and fermentation from 

 only one point of view. We have mentioned only the splitting ferments. 

 Now we know that extensive syntheses take place in the animal organism. 

 Since Wohler, in 1824, proved that benzoic acid administered to the animal 

 organism was neither consumed nor excreted as such, but that a nitro- 

 genous acid, richer in carbon, appeared in the urine, namely hippuric acid, 

 which is composed of glycocoll and benzoic acid, a great many other syn- 

 theses have been proved to take place. We need only to recall the fact 

 that fats are split into glycerol and fatty acid in the alimentary tract, 

 only to reappear on the other side of the intestine as fats, and also that the 

 albumins and complicated carbohydrates are disintegrated into simple 

 components only to be reconstructed, to realize that synthesis is another 

 established function of the animal cell. Although, as far as our present 

 knowledge shows, these syntheses are for the most part simple ones, and 

 usually consist of the union of two or more molecules with elimination of 

 water, we must not conclude that the animal cell is incapable of effecting 

 complicated syntheses. Certain recent results lead us to suspect that the 

 animal organism is capable of building up complicated structures. The 

 synthetic processes of the plant and animal organisms were for a long time 

 hidden in obscurity. Indeed, on purely theoretical grounds, by comparing 

 ferments with catalyzers, the conclusion was drawn that fermentations 

 must be reversible processes, and that they may be endothermic as well as 

 exothermic reactions. As a matter of fact, a whole series of syntheses has 

 been carried out by the aid of ferments. Thus we may refer to the for- 

 mation of isomaltose from concentrated d-glucose solutions by means of 



1 Z. Klin. Med. 17, Suppl. 77 (1890). 



2 Cf. Lecture XII, p. 265. 



