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, ze. 
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! 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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