Cuap. VI. DIGESTION. 91 
“Quantity of fibrin digested in four hours by 10 cub. cent, 
of the liquid: 
“ Hydrochloric acid a - 02915 
Propionic acid .. a .. 0°1490 
Butyric acid .. ne - 01044 
Valerianic acid .. a .- 0°0520 
* Comparing, as before, the three last numbers with the first 
taken as 100, the digestive power of propionic acid is repre- 
sented by 168; that of butyric acid by 35°8; and that of 
valerianic by 17°8. 
“The mean of these three sets of observations (hydrochloric 
acid being taken as 100) gives for 
* Propionic acid .. a i 158 
Butyric acid... a = 32:0 
Valerianic acid .. Se af 21-4 
“7, A further experiment was madé to ascertain whether the 
digestive activity of butyric acid (which was selected as being 
apparently the most efficacious) was relatively greater at ordinary 
temperatures than at the temperature of the body. It was 
found that whereas 10 cub. cent. of a liquid containing the ordi- 
nary proportion of hydrochloric acid digested 0-1311 gramme, 
a similar liquid prepared with butyric acid digested 0:0455 
gramme of fibrin. 
“ Hence, taking the quantities digested with hydrochloric acid 
at the temperature of the body as 100, we have the digestive 
power of hydrochloric acid at the temperature of 16° to 18° 
Cent. represented by 449; that of butyric acid at the same 
temperature being 15:6.” 
We here see that at the lower of these two temperatures, 
hydrochloric acid with pepsin digests, within the same time, 
rather less than half the quantity of fibrin compared with 
what it digests at the higher temperature; and the power of 
butyric acid is reduced in the same proportion under similar 
conditions and temperatures. We have also seen that butyric 
acid, which is much more efficacious than propionic or vale- 
rianic acids, digests with pepsin at the higher temperature less 
than a third of the fibrin which is digested at the same tempera- 
ture by hydrochloric acid. 
