OXIDATIONS AND HYDRATIONS IN THE ANIMAL BODY. 19 



this is not necessarily the case, and that as a matter of fact a large 

 number of such bodies can be produced artificially in the chemical 

 laboratory. Wohler, in 1829, was the first to demonstrate this 

 possibility by preparing urea from ammonium cyanate. This he 

 accomplished by heating the substance to a temperature of 100 C., 

 when a transposition of atoms apparently takes place, and urea 

 results. The force which is necessary to effect such a change is 

 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. Of the nature of this mechanism, however, 

 we know but little, and we are forced to admit that while it is pos- 

 sible to produce chemical substances, such as those which are found 

 in the living world, by artificial means, plants and animals have 

 manifestly other forces at their command which are more or less 

 intimately associated with that peculiar phenomenon we term life. 

 We know that under the influence of sunlight certain plants are 

 capable of effecting the synthesis of carbohydrates, fats, and albu- 

 mins 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 com- 

 pounds which plants require for their existence, we are also un- 

 able to explain on the basis of simple physical laws. W T e know 

 that the oxygen of the air, as also that of the blood, exists in a 

 neutral molecular form, and is as such incapable of effecting the 

 oxidation 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 



