METABOLISM IN THE CELLS. 19 



the circulation, and they are gradually consumed by this action. The 

 part injured undergoes solution, while the healthy part remains 

 unattacked. By this solvent action as well as by the formation of bacter- 

 icidal bodies, as observed by CoNRADi, 1 and of antitoxins (BLUM 2 ) 

 by means of autolysis, we can consider this autolysis as a remedy and 

 perhaps also as a protective agent for the animal body. 



For the present it is impossible to judge of the importance of the 

 enzymes active in autolysis for physiological conditions, but this does 

 not exclude the possibility that in normal cell life the enzymes play a 

 very important idle. Numerous observations show this to be true, and 

 we tend more and more toward the view that the chemical transforma- 

 tions in the living cells are brought about by enzymes, and that these 

 latter are to be considered as the chemical tools of the cells (HOFMEISTER 

 and others 3 ) . 



From this standpoint the enzymes are of especial interest because 

 to-day it is the general belief that nearly all chemical processes of great 

 importance do not occur in the animal fluids, but on the contraiy in the 

 cells, which are the real chemical workshops of the organism. It is also 

 chiefly the cells, which by their more or less active efficiency regulate 

 the extent of the chemical processes and thereby also the intensity of the 

 general metabolism. 



The researches into the chemical composition of the cells must there- 

 fore be of the greatest importance, but the difficulties which such investi- 

 gations entail are very striking. The chemical investigations of animal 

 cells must in most cases be connected with the study of those tissues 

 whose chief part they represent. Only in a few cases, such for example 

 as the investigation of pus or tissues very rich in cells, can the cells be 

 directly or by relatively simple manipulation, be isolated in a rather 

 pure form from the other parts of the tissues. Even in these cases the 

 chemical investigation does not give any positive results as to the cfln- 

 stituents of the living uninjured cells. If the physiological conditions 

 of life of the cells are removed, or injurious external influences such as the 

 action of high temperatures or of chemical agents are applied, then the 

 protoplasm dies. The protoplasm, which in the generative cell during 

 life forms a semi-solid mass which is contractile under certain conditions 

 and which readily changes, consists, with the exception of the water, 

 chiefly of protein substances, namely of colloids. On the death of the 

 cell these proteins coagulate, at least in part, and other chemical trans- 

 formations also occur in the cell. The alkaline reaction of the cells to 



1 Hofmeister's Beitrage, 1. 



2 Ibid., 5, p. 142. 



3 F. Hofmeister, Die chemische Organisation der Zelle, Braunschweig, 1901. 



