THE GENERAL CONDITIONS OF LIFE 305 



atmosphere of nitrogen and yet constantly expire carbonic acid. 

 Why the addition of oxygen will transform a more stable 

 molecule into a more labile condition becomes clear when it is 

 borne in mind that, as Keklile has shown, in all organic 

 chemistry there is no single molecule that contains enough oxygen 

 to oxidise all the hydrogen-atoms of the molecule to water and 

 all the carbon-atoms to carbonic acid. For this reason molecules 

 are more or less stable and not inclined to dissociation, unless 

 other chemical causes bring in some lability. If, however, suffi- 

 cient oxygen be introduced to ensure the possibility of the 

 oxidation of the atoms of carbon and of hydrogen into the stable 

 molecules, carbonic acid and water, by intramolecular rearrange- 

 ment, the power of decomposition must become increased, for the 

 affinity of carbon and hydrogen for oxygen is very great. Thus, 

 the great inclination of living substance to decomposition is con- 

 ditioned essentially by the intramolecular oxygen. 



A comparison of the decomposition-products of living proteid 

 and those obtained by the artificial oxidation of dead proteid is of 

 great importance. The significant fact here appears, that the 

 non-nitrogenous products of the latter agree essentially with those 

 of the former, but that " the great majority of the nitrogenous pro- 

 ducts [of the latter] have not even a remote similarity to the 

 majority of those arising in the living body." It follows that, as 

 regards its non-nitrogenous groups of atoms, its hydrocarbon 

 radicals, living proteid cannot be essentially different from dead 

 proteid, but that a fundamental difference must exist as regards 

 the nitrogenous radicals. Here a starting-point for further con- 

 sideration is afforded by the fact that of the nitrogenous decom- 

 position-products of living proteid, such as uric acid, creatin, and, 

 moreover, the nuclein bases, guanin, xanthin, hypoxanthin, and 

 adenin, a part contain cyanogen, CN, as a radical, and a part, like 

 urea, the most important of all the nitrogenous decomposition- 

 products of living proteid, can be produced artificially from 

 cyanogen compounds by a rearrangement of the atoms. This 

 points strongly to the probability that living proteid contains 

 the radical cyanogen, and thus differs fundamentally from dead 

 or food-proteid. Pfliiger thereupon says: "In the formation 

 of cell-substance, i.e., of living proteid, out of food-proteid, a 

 change of the latter takes place, the atoms of nitrogen going 

 into a cyanogen-like relation with the atoms of carbon, probably 

 with the absorption of considerable heat." That considerable 

 heat is absorbed in the formation of cyanogen follows from the 

 fact that, as calorimetric investigations show, cyanogen is a 

 radical possessing a great quantity of internal energy. By the 

 addition of cyanogen to the living molecule, therefore, there is 

 " introduced into the living matter energetic internal motion." 

 Accordingly, the great property of decomposition possessed by 



