OXIDATIONS AND HYDRATIONS IN THE ANIMAL BODY. 19 



here, as in many syntheses which can artificially be brought about, 

 a relatively high temperature. In the bodies of animals and plants 

 a like temperature, of course, would destroy life, and there must 

 hence be a different mechanism at the disposal of living beings to 

 effect such a change. We know that under the influence of sun- 

 light certain plants are capable of effecting the synthesis of carbo- 

 hydrates, fats, and albumins from the carbon dioxide of the air, 

 and the water and certain mineral salts of the soil, and that the 

 ability to bring about these changes is in a large measure dependent 

 upon the presence of a chemical substance which is found in the 

 green parts of plants, and which is termed chlorophyl. We know 

 further that chlorophyl requires exposure to sunlight to effect these 

 changes, but of the mechanism through which these changes are 

 brought about we know nothing. 



Oxidations and Hydrations in the Animal Body. The oxida- 

 tion-processes which prevail in animals, and in consequence 

 of which the more complex substances which go to form the 

 various tissues and organs of the body are retransformed into 

 those simple compounds which plants require for their exist- 

 ence, we are also unable to explain. We know that the oxy- 

 gen of the air, as also that of the blood, exists in a neutral 

 molecular form, and as such is incapable of effecting the oxi- 

 dation of such complex substances as the albumins and fats. 

 The older view that oxygen exists in the body as ozone, and that 

 the various oxidation-processes take place in the animal fluids, has 

 been abandoned, and it is now generally accepted that these changes 

 occur in the individual cells. Here, then, a splitting up of the 

 neutral oxygen must take place, but of the forces which effect 

 this decomposition we know next to nothing. Whether we believe 

 with Pfliiger that the organized living albumin, in contradistinction 

 to the non-organized circulating albumin, is characterized by a 

 greater motility of its atoms, in consequence of which the neutral 

 oxygen is decomposed, or whether we accept the view that reducing- 

 substances are formed during the decomposition of the albuminous 

 molecule in consequence of the activity of a third factor, we are 

 as far removed from an adequate explanation of these phenomena 

 as in the beginning. 



Within recent years numerous observations have shown that from 

 various organs of the body certain substances can be extracted which 

 are apparently identical with or closely related to the so-called en- 

 zymes. Certain representatives of this class, such as pepsin, trypsin, 

 ptyalin, and others, are, as we shall see, formed in the cells of the 

 digestive glands of the body, and serve the purpose of transforming 

 the various food-stuffs which are furnished the animal by the plant 

 into forms which can be absorbed and built up into its tissues. The 

 chemical processes which are here involved are essentially of the 

 character of hydrations. Other bodies, however, of this order 

 which can be obtained from living tissues, and which are also 



