2 PHYSIOLOGICAL CHEMISTRY. 



nivora, upon plant-life, from which they derive the three chief 

 groups of organic nutritive matter proteids, carbohydrates, and 

 fat. These bodies, of which the protein substances and fat form 

 the chief mass of the animal body, undergo within the animal 

 organism a splitting and oxidation, and yield as final products ex- 

 actly the above-mentioned chief components of the nutrition of 

 plants, namely, carbon dioxide, water, and ammonia derivatives, 

 which are rich in oxygen and have a feeble chemical tension. The 

 chemical tension, which is partly combined with the free oxygen 

 and partly stored up in the above-mentioned more complex chemi- 

 cal compounds, is transformed into vis viva, heat, and mechanical 

 work. While in the plant reduction processes and syntheses, which 

 are active in the conversion of living force into potential energy or 

 chemical tension, are the prevailing forces, we find in the animal 

 body the reverse of this, namely, splitting and oxidation processes, 

 which convert chemical tension into living force (vis viva). 



This difference between animals and plants must not be over- 

 rated, nor must we consider that there exists a sharp boundary-line 

 between the two. This is not the case. There are not only lower 

 plants, free from chlorophyll, which in regard to chemical processes 

 represent intermediate steps between higher plants and animals, 

 but the difference existing between the higher plants and animals 

 is more of a quantitative than a qualitative kind. Plants require 

 oxygen as peremptorily as do animals. Like the animal, the plant 

 also, in the dark and by means of those parts which are free from 

 chlorophyll, takes up oxygen and eliminates carbon dioxide, while 

 in the light the oxidation processes going on in the green parts are 

 overshadowed or hidden beneath the more intense reduction pro- 

 cesses. Like the animal the vegetable ferments transform chemi- 

 cal tension into living energy and heat; and even in a few of the 

 higher plants as the aroidece when bearing fruit a considerable 

 development of heat has been observed. The reverse is found in 

 the animal organism, for, besides oxidation and splitting, reduction 

 processes and syntheses also take place. The contrast which 

 seemingly exists between animals and plants consists merely in 

 that in the animal organism the processes of oxidation and split- 

 ting are prevalent, while in the plant those of reduction and syn- 

 thesis have mostly been observed. 



