INTRODUCTION 3 



able. We kno-w to-day that the causal relation between oxygen intake and 

 food consumption as accepted by Liebig does not exist, but that in the living 

 protoplasm of the cell exists the cause of the decomposition going on in the 

 organism. 



Food decomposition does not take place in the blood and fluids, as was 

 assumed at that time, but in the tissues, where the decomposition is produced 

 by the chemical activity of the cells. ^ 



The type and rate of metabolism are determined neither by the presence 

 nor by the absence of oxygen, but only the energies dormant in the protoplasm 

 of the cells — energies whose multiplicity the investigations of our own times 

 are constantly impressing upon us. 



The amount of decomposition which takes place in the cell is decided alone 

 by the energy requirement of the entire organism, so that the total consump- 

 tion of the body is made up of the metabolism of all the cells. These cells, 

 however, show a wonderful adjustment to the requirements of the organism, 

 not only quantitatively but, on account of their specific properties, qualita- 

 tively as well. 



It is not the oxygen that by its affinity to the individual constituents of the 

 body dominates the chemical processes that occur there. If oxygen ruled, the 

 readily oxidizable substances, such as uric acid, could not be so uniformly 

 present in unaltered form in the excretions, while substances which are only 

 oxidized with difficulty, such as the fats, are completely burned. It is the 

 specific force contained in the protoplasm of the cells which causes the meta- 

 bolic processes in the animal economy. 



Among these processes the splitting up of complex chemical bodies into 

 simpler bodies, while oxygen is at the same time taken up, plays an important 

 role. But besides mere splitting up, and splitting up with absorption of water 

 (hydrolytic dissociation), other processes of reduction and synthesis are 

 largely active, and occasionally all are combined in a single cell. 



Hence, as Eubner maintained, life cannot be described under the general 

 idea of a process of combustion ; we must rather say that while life exists there 

 is constantly an employment of energy and a transference of the same into 

 other forms (activity and heat). 



Physiologic and pathologic chemistry will aid us still further in analyzing 

 the chemical changes which occur during the processes of metabolism. The 

 evolution of the individual protein substances contained in the cell, and the 

 disclosure of their composition by the production of split-products, constitute 

 the one method which has been followed with success in solving the problems 

 here involved. But the protoplasm of the living cell and the proteid which 

 we have produced from it by the aid of our chemical methods are quite differ- 

 ent things. So also the products of decomposition which arise in the destruc- 

 tion of the cell protoplasm in the body are quite different from those which 

 we make by splitting up albuminous substance in a test tube. In the one case 

 dead albumin, in the other living albumin is decomposed, and as we appre- 

 ciate this great difference we seem to drift yet further from the solution of the 



1 Hofmeister, " Chemie der lebenden Zelle," Vortrag, 1901. 



