PROTEIN METABOLISM 



By E. P. CATHCART, M.D. 

 Grieve Lecturer on Chemical Physiology, University of Glasgow 



In an earlier number of this journal Dr. F. Gowland Hopkins, 

 of Cambridge, in an interesting paper, drew attention to the 

 important and interesting subject of the utilisation of the 

 protein moiety of the food. As he fully discussed the subject 

 in its general bearings, I do not wish to do more than draw 

 attention to the advances which the more recent work has made 

 in our knowledge of the various changes which proteid under- 

 goes before absorption, and, in a brief fashion, to refer to the 

 probable fate of the various fractions after such absorption 

 has taken place. 



Before, however, we can gain any insight into this profound 

 problem, the question of how, and in what form, the protein 

 is absorbed must be definitely determined. 



Formerly it was universally held that protein was absorbed 

 after digestion in the form of albumoses and peptones, which 

 were immediately converted into albumen, and the whole 

 subject was then dismissed. The work of the past few years 

 has shown that this cut-and-dry statement is by no means 

 justified, and that the problem is of a much more complicated 

 nature. 



Before dealing with the absorption of the hydrolysed, i.e. 

 the digesten proteid, it would be well to consider the absorption 

 of unaltered, undigested, or native proteins, as they are called. 



The work of many investigators, both in Germany and 

 elsewhere, has demonstrated beyond cavil that native protein 

 injected into the blood stream can be utilised to a certain 

 extent — indeed, the recent work of Sollmann and Brown l has 

 shown that under favourable conditions egg albumen injected 

 intravenously can be well utilised ; in many instances only a 



1 Sollmann and Brown, Journ. of Exper. Med. 6, 407. 



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