NITROGEN CONTENT OF BACTERIAL CELLS. 
I. METHOD. 
By HAROLD C. BRADLEY anv M. STARR NICHOLS. 
(From the Laboratory of Phystological Chemistry and the State Laboratory 
of Hygiene, University of Wisconsin, Madison.) 
(Received for publication, January 5, 1918.) — 
The production of acids, gases, and intermediate products, of 
toxins, agglutinins, and many other protein complexes serves to 
differentiate strains and groups of organisms and at the same 
time furnishes us with considerable interesting data in regard to 
bacterial metabolism. On the other hand, we have very little 
information as to the proximate and ultimate composition of 
bacteria. The difficulties attending the growth of the organism 
in sufficient quantity for accurate analysis and the difficulties of 
the analytical technique have largely prevented the development 
of this aspect of the work. 
We know that higher plants differ from each other in their 
nitrogen content, and in the compounds characteristic of each. 
Enough work has already been done to indicate that wide differ- 
ences may exist in the nitrogen content of bacteria. Nicolle and 
Alilaire (1) and Wheeler (2) give the results tabulated below for 
the nitrogen content of various organisms. 
The results show the wide variation in the nitrogen content of 
various organisms and also the great discrepancies between 
analyses of the same organism by different persons. These re- 
sults are of doubtful value, probably because of the variety of 
conditions maintained during growth, and because the technique 
allows errors of considerable magnitude where such small 
amounts of material were to be used. It was decided to apply 
the Folin method (3) to our problem and after certain adaptations. 
we arrived at the following method for determining the nitrogen. 
content of bacteria. 
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