ENZYMES. 39 



animal body, undergo within the animal organism a cleavage and oxi- 

 dation, and yield as final products exactly the above-mentioned chief 

 components in the nutrition of plants, namely, carbon dioxide, water, 

 and ammonia derivatives, which are rich in oxygen and have little energy. 

 The chemical energy, which is partly represented by the free oxygen 

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

 compounds, is transformed into other forms of energy, principally heat 

 and mechanical work. While in the plant we find chiefly reduction 

 processes and syntheses, which by the introduction of energy from 

 without produce complex compounds having a greater content of energy, 

 we find in the animal body the reverse of this, namely, cleavage and oxi- 

 dation processes, which, as we used to state, convert chemical tension 

 into living force. 



This difference between animals and plants must not be overrated, 

 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 inter- 

 mediate steps between higher plants and animals, but the difference 

 existing between the higher plants and animals is more of a quantitative 

 than of 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 processes. As in the animal, we also find a heat production 

 in fermentation produced by plant organisms; and even in a few of the 

 higher plants as the aroideoe when bearing fruit a considerable develop- 

 ment of heat has been observed. On the other hand, in the animal 

 organism, besides oxidation and splitting, reduction processes and syn- 

 theses 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 splitting are predominant, while in the plant 

 chiefly those of reduction and synthesis have thus far been studied. 



WOHLER 1 in 1824 was the first to observe an example of the SYN- 

 THETICAL PROCESSES within the animal organism. He showed that 

 when benzoic acid is introduced into the stomach, it reappears as hippuric 

 acid in the urine after combining with glycocoll (aminoacetic acid). 

 Since the discovery of this synthesis, which may be expressed by the 

 following equation : 



Benzoic acid Glycocoll Hippuric acid 



1 Berzelius, Lehrb. d. Chemie, ubersetzt von Wohler, 4, p. 356, Abt. 1, Dresden 

 (1831). 



