336 A. P. MATHEWS. 



therefore, to Nef 's hypothesis, and without this the exact mechan- 

 ism of the process would be obscure, the following picture of 

 protoplasmic respiration may be formed : 



In protoplasm there is some substance (or substances) of 

 unknown nature which splits off water from itself just as the alco- 

 hol does in the above reaction or as ammonium hydrate does and 

 sets free from itself active particles having the properties of ethyl- 

 idene. The following three well known reactions are exactly 

 similar to this primary process : 



H 2 O 



For protoplasm the reaction is as follows : 



R _ CH 2 OH *^_ R CH < ; -f H,0 



In this reaction R CH 2 OH is some unknown substance. 



The nature of the substances thus reacting in protoplasm is 

 unknown. There is no evidence, however, nor is there any reason 

 for assuming that they are complex substances. It is probably 

 not a substance acting by means of a change in valence of nitrogen 

 for the reason that the nitrogen substances such as ammonia do 

 not have so great an affinity for oxygen as that required of the 

 unknown substance. We do not get for example such a decom- 

 position of ammonia as this : 



NH 3 < + OH 2 = H 3 NO + H 2 . 



On the other hand the substance possesses the powers ascribed 

 by Nef to bivalent carbon. Carbon has a powerful affinity for 

 oxygen. It ma}' well be, therefore, that the substance is a car- 

 bon compound, presumably of simple nature and derived directly 

 or indirectly from the foods so that new raw material for the 

 reaction is constantly supplied. If this is the case Nef's view 

 that bivalent carbon is at the bottom of the vital reaction would 

 be justified. 1 



1 Probably all reducing agents act in some measure in this way. For example in 

 egg white a substance is present which forms sulphuretted hydrogen in the presence 

 of sulphur. This substance is of unknown nature. The reaction probably is a 



follows : 



X CH < + OH 2 = XCHO + 2H 



