2 . ANALYSIS OP DISTURBANCES OF METABOLISM 



Baumann as by the desire to find a key to the comprehension of pathologic 

 processes. 



The practical result of these labors may he noted in the extraordinary 

 interest manifested everywhere to-day in modern dietotherapy. For this rear 

 son it is worth while to cast a retrospective glance over the long road which has 

 led to this satisfactory result. 



The scientific study of metabolism began when Lavoisier, in 1780, desig- 

 nated chemical processes in the animal economy as the source of heat accom- 

 panying all processes of life. He taught us that the food products in the 

 body utilized the oxygen breathed in with the inspired air and decomposed, 

 producing carbonic acid; that this process is therefore analogous to the 

 combustion of organic substances outside of the body, and is an oxidation 

 process which is the most important source of animal heat. 



A" long time elapsed before the discovery of the law of conservation of 

 energy also permitted new conceptions in the realm of biology (E. Meyer). In 

 opposition to the view that, besides combustion, still other independent sources 

 of heat were present in the circulation of the blood (friction, etc.), the opin- 

 ion became general that all expressions of force which" are recognized in the 

 living organism (i. e., production of heat and capacity for work) were sus- 

 ceptible of a uniform explanation. They originate from the energy which is 

 furnished the body by the food. By tireless and long-continued original 

 researches, Eubner proved conclusively that the law of the conservation of 

 energy, the correctness of which E. Meyer and Helmholtz proved in the realm 

 of physics, deserves proper recognition also in biology. The supply of energy 

 contained in the food passes through the animal iody without diminution. 



Thus the law of the permutation of forces, which had its origin in Lavoi- 

 sier's discovery of combustion as the source of energy for the organism, was 

 conclusively demonstrated by Eubner. 



It was an important epoch in the development of the laws of metabolism 

 when Justus von Liebig demonstrated the identity of the proteids of the ani- 

 mal and vegetable organisms in their chemical properties, and explained the 

 relations of the albumin products of the food to the nitrogenous products of 

 decomposition in the urine. We owe to him the knowledge that it is albumin, 

 fat, and carbohydrates which are the basis of metabolic processes. He was 

 the first to emphasize the fact of the unequal importance of the products neces- 

 sary for structural formation in the animal organism. He assumed that the 

 albumin introduced with the food alone reconstructs that which has been 

 destroyed by the activity of the body, and called albumin the plastic (tissue- 

 forming) food product, contrasting with it the F-free products (fat and 

 carbohydrates) as respiratory products. These alone, he supposed, were 

 attacked directly by the oxygen in the air, and by their combustion protected 

 the plastic products, the albumin, from oxidation. 



But this theory of a division of all food products into two opposite groups 

 could not be maintained, and the theory of Liebig that the oxygen taken up 

 in respiration caused the disintegration of the food products, and that its 

 amount decided the degree of metabolism was also later proven to be unten- 



