268 Formulas of Acid Exeretion 
that it holds “‘more consistently than any other expression which 
could be found in the literature or devised.”’ In their develop-: 
ment they noté, for instance, that the fourth root of C has been 
retained because the square root gave too much and the sixth root 
too little influence to the factor C. Now since it does not appear 
from any ordinary inspection of the values of C given that it 
can have any appreciable influence, it would seem logical to re- 
vise the formula, replacing C by a constant. Thus it is possible 
to arrive at the formula 
iD 
PI CO, = 80 —5 @/=; 
asma 2 Viv 
whose calculated values for plasma CO, for the 76 observations 
given show an average deviation from the found values of 5.45 
volumes per cent compared with 6.99 volumes per cent by the 
original formula. That is to say, the results average 1.5 volumes 
per cent better if instead of using the fourth root of C we use the 
figure 5. Therefore we must conclude that the “influence” of C 
in this formula is negligible, and that consequently the corollary 
statement made by the authors that “‘ other factors being the same, 
the amount of acid excreted in excess of mineral bases is increased, 
on the average, as the square root of the volume of urine’”’ must 
also be revised; for it is apparent that as far as we may con- 
clude from this equation the acid excretion is quite independent 
of the volume of urine. 
We may further omit W, and devise the form 
Plasma CO, = 80 — 0.7 4/ D 
which will also give results more closely approximating the found 
values of CO, than those derived from the Ambard type of 
formula. 
Or if we wish to make use of the ammonia excretion rate only, 
it will be found that from the equation 
Plasma CO, = 80 — 0.9 \/ NH; 
(where NH; is the amount of 0.1N ammonia excreted per 24 
hours) we can likewise calculate the index of blood bicarbonate 
with considerably greater precision and with much less mathe- 
