182 Creatinine and Creatine in Blood 
puscles. This conclusion, already formulated in our earlier con- 
tribution” to the subject, and later confirmed by Wilson and 
Plass,!° is not affected by the respective errors of the creatine de- 
terminations in blood and in plasma; for these are of such relative 
magnitude that existing differences are more likely to be con- 
cealed by them than exaggerated. We have shown" reason to 
suspect that the true creatine content of the blood is, roughly 
speaking, about one-half, and that of the plasma about one- 
fourth, of the amount: indicated in the colorimetric analysis. 
This estimate is not of such a precise character that it can be 
fairly applied to individual pairs of results, but it is perhaps 
not too crude to be used in a tentative correction of our averages. 
Modified accordingly, these averages vary, in the different groups 
distinguished, from 2.7 to 3.5 in the case of whole blood, and from 
0.40 to 0.62 in the case of plasma. The corrected averages for 
all cases in which creatine was determined at all are 2.97 (practi- 
cally 3.0) and 0.46. In general the proportion of whole blood to 
plasma creatine is about 6 or 7 to 1. Taking the average values 
reached along with the average plasma volumes corresponding, 
it is possible to calculate the average amount of creatine in the 
corpuscles; this appears to lie, in one group or another, between 
6 and 9, with an average for all cases of 6.7 mg. per 100 cc.” It 
may be remarked that all the figures for creatine, and especially 
those for corpuscular creatine, are higher in the female groups 
than in the male. These quantitative data are offered, as we have 
said, with due reserve and as first approximations at the best. 
3 There are no available data with which our estimates of corpuscular 
creatine can be directly compared; but Plass (Bull. Johns Hopkins Hosp., 
1917, xxviii, 297), who employs an improved analytical method, has re- 
cently published figures ranging from 5.99 to 15.29 (average, 10.8) as the 
total corpuscular creatinine of ten parturient women. He states further, 
without recording details and without indicating clearly whether he 
is dealing here with creatine or total creatinine, that non-pregnant women 
yield much lower values (6.2 to 6.5), and that in one male the corpuscular 
concentration was lower still (4.9). Our figures, it will be seen, agree 
with those of Plass in indicating a smaller proportion of creatine in the 
corpuscles of the male, and a special accumulation in those of pregnant 
women. Even with regard to the absolute amounts present there exists a 
gratifying measure of agreement between results obtained in such different 
ways. 
