Chap, viii Respiration 



425 



action of an air pump a stem into which a quantity of 

 oxygen had been injected, he was unable to extract it again 

 by a diminution of pressure. In 1868 Engelmann brought 

 forward evidence of the existence of intramolecular oxygen 

 in ciliated epithelial cells. Borodin's researches in 1878, 

 which have already been alluded to, may be regarded as 

 confirmatory of the hypothesis. In 1879, and in 1883, 

 Detmer supported it in a slightly modified form, when he 

 suggested that the primary source of the energy developed 

 in living organisms consists in the splitting up of highly 

 complex labile compounds, the decomposition products of 

 which subsequently become oxidized, carbon dioxide and 

 water being the ultimate products. In 1894 Maquenne 

 held, as the result of experiments with leaves, that the 

 living substance separates from itself a material which, 

 on contact with fresh oxygen, oxidizes and gives off carbon 

 dioxide. 



The views of Pfluger were somewhat modified and 

 extended in 1894 by Verworn, who associated the action 

 with the biogen molecules to which we have referred. He 

 held that the oxygen entering into the biogen molecule 

 gives it its maximum power of decomposition, ' so that only 

 very slight impulses are required to bring about the union 

 of the atoms of oxygen with the carbon in the cyanogen. 

 The material of the non-nitrogenous groups of atoms 

 afforded by the explosive decomposition of the biogen 

 molecule can easily be regenerated by the residue of the 

 biogen molecule from the carbohydrates and fats that are 

 present in the living substance and contain such groups.' 

 He agreed with Pfluger in calling these substances ' the 

 satellites of the proteid molecule ', and in thinking this to 

 be probably their essential significance. He said further, 



' in contrast to other explosive bodies we must evidently 

 ascribe to the biogens the peculiarity that in decomposition 

 the whole molecule is not destroyed, but that certain groups 



