274 Studies of Acidosis. X 
dition and plasma CO, of 14 per cent. If the body weight were 
neglected in the calculation, however, and Barnett’s 0.7 »/D 
formula used, the excretion would indicate a plasma CQO, of 
46, or almost no acidosis. Similar magnification of error is 
introduced in attempting to interpret the excretion data re- 
gardless of body weight in the two patients of less than adult 
size with acidosis reported in Paper VI. These are No. 3, a 
boy of 12 with intense acidosis, and No. 5, a boy of 138 with se- 
vere acidosis. That an allowance for body size must be made 
in interpreting the rate of formation or excretion of any meta- 
bolic product is a generalization so well founded that previous 
discussion of it seemed unnecessary. 
Elimination of a third variable, the titratable acid, from the cal- 
culation, would apparently be a further step backwards. It is 
true, as exemplified by our own data, that ammonia and titratable 
acid in diabetic urine as a rule rise and fall together, the am- 
monia being usually two to three times the titratable acid. The 
aes Milla eS is by no means constant, however, varying from 
0.1 N acid ; 
0.3 to 5.0 in diabetic and normal urines, so that the titratable 
acid sometimes exceeds the ammonia. Since both. ammonia 
and titratable acid indicate excretion of acid in excess of fixed 
base, it is does not seem logical to determine the one and neglect 
the other. The result of neglecting the titratable acid is appar- 
ent, except in the case of the one diabetic who was chosen for 
continuous observation, in a decided increase in the average 
error. 
ratio 
Average Errors. Data of Paper IV. 
Table I. Table II. Table III. 
Formula. ee 11 normal 36 different | 29 observations 
persons. diabetics. on 1 diabetic. 
|D 
OOo = 80-5 eas daw a a eee 2.9 5.4 DAT 
2 Vir 
CO, = 80 — 0.9 [NH jerk 46, 74 5.7 
A practical additional reason for determining titratable acid as 
well as ammonia is that it protects against a false diagnosis of 
acidosis which might be made from the ammonia alone in urines 
