iy fe Creatinine and Creatine in Blood 
conclusion. We therefore deemed it necessary, before publishing 
a fuller account of our work, to satisfy ourselves upon the pre- 
cise value of the analytical methods which we had employed. 
The issue of this incidental, but necessary inquiry, the details 
of which have been recorded in another paper, was such as to 
necessitate a revision of some of our original conclusions. Dur- 
ing its progress we confined our attention, in the accumulation of 
additional data, almost entirely to the fundamental points of the 
amount and the distribution of creatinine and creatine in nor- 
mal human blood. It is to the results bearing upon these points, 
and to the interpretation of them which now appears to us the 
most plausible, that the present paper is principally devoted. 
Other problems, such as the relation of blood creatine to creatinuria, 
are touched upon only in so far as incidental observations offer 
occasion. It is hoped that the opportunity may yet arise to 
carry the inquiry further along each of the lines we have proposed. 
Subjects. 
The blood specimens, which for our present purpose were 
assumed to be normal, numbered 60, and were derived from 56 
individuals, who fall into three main groups. The first, Group 
I, consists of 26 male students and instructors, all, as far as 
could be judged, in perfect health; 2 of these provided three 
specimens each of blood so that the total number of analyses 
performed within this group was 30. The second, Group II, 
includes 20 hospital patients, male and female, mostly conva- 
lescent after childbirth or purely surgical complaints, and all 
free, as far as known, from organic disease. ‘This group is di- 
vided into two subgroups; but the distinction between them is 
one of date only, Group II A having been studied several months 
earlier than II B. The fina] group, Group III, is formed by 10 
healthy women in a late stage of pregnancy, of whom 1 only was 
as yet confined to bed. 
No subject has been admitted to any of these groups in whom a 
routine examination revealed evidence of organic disease. In 
this respect all equally were normal individuals; but of course 
14 Hunter and Campbell, J. Biol. Chem., 1917, xxxii, 195. 
