GENERAL METABOLISM. 641 



ported from organs of minor importance cannot be utilized directly. Here 

 again there is a preliminary decomposition and selection of material. 



Now the only other striking phenomenon is that an increased supply of 

 albumin increases the extent of the entire metabolism; i.e., not that of 

 albumin alone. Perhaps this discovery may be accounted for by the fact 

 that the animal organism evidently has no depot for storing up the excess 

 of albumin. This is evident because it is so difficult under normal condi- 

 tions of nutrition to cause a deposition of albumin in the fully developed 

 organism. Under these circumstances it is perfectly conceivable that when 

 there is an increased supply of albumin there is a greater amount of cellular 

 transformations so that the other materials are also required. 



In this explanation we wish to call particular attention to the importance 

 that is attached to the maintenance of the perfectly specific cell construction 

 in the case of each species of animals and perhaps of every single individual. 

 Here unquestionably the proteins play the most important part by virtue 

 of the fact that they offer such a variety of forms. The abundant supply of 

 albumin guarantees to the animal organism its own individuality and that 

 of its cells as well as its own metabolism. 



We must at this place once more mention the fact that albumin 

 metabolism has been studied almost entirely from a single point of view. 

 The rapidity of the albumin decomposition has been identified with the 

 rapidity of the nitrogen elimination. We have, however, no precise reason 

 for assuming that the splitting-off of the nitrogen is, as a matter of fact, 

 the signal for the disruption of the entire molecule. After the formation 

 of urea, carbon chains remain which may be utilized in a number of different 

 ways. It is possible that the cells prefer to have so much albumin because 

 it provides them with all the different materials which they require. It is 

 perfectly thinkable that these carbon chains can be used to form sugars, 

 or they might equally well be utilized for the production of fat. 



It is, as the above discussion shows, perfectly impossible to give an 

 explanation of albumin metabolism which shall be based upon exact 

 experimentation. We can indeed formulate hypotheses, but for the 

 present there is no preference to be given to any particular one. None of 

 the present hypotheses satisfactorily unites all the known facts, in such a 

 way that in every respect all the results of experimentation are clearly 

 accounted for. We must leave these questions entirely open, and suggest 

 that new theories and new experiments can alone cause progress, and con- 

 sequently a discussion of the various attempts at explanation would be 

 scarcely worth our while. Again and again in the questions arising from 

 all sorts of different kinds of metabolism we run against the metabolism of 

 the cell, and cell activity. The conception of intermediary metabolism is 

 a very accessible one. We are constantly coming in contact with it. It 

 is here the place to state that contrary to what one might expect by reading 



