146 Chittenden and Cummins—Influence of Bile 
rated with the acid, allows no proteolytic action whatewer. Further- 
more, a sufficient amount of proteid matter just saturated with 
hydrochloric acid, no free acid being present, will almost completely 
stop the action of trypsin. Proteid matter, however, only partially 
saturated with acid has a much smaller retarding action. This, 
doubtless, was the condition of the mixtures in Mays’ and Enges- 
ser’s experiments above referred to, for, as Mays states, the ferment 
could act in the presence of 0°3 per cent. hydrochloric acid only when 
a relatively large proportion of fibrin was present. 
A pancreatic juice prepared from 20 grams of dried pancreas by 
warming it at 40° C. with 200 ¢.c. 0°71 per cent. salicylic acid, etc., 
was finally made exactly neutral and diluted to 500 c.c.; 25 ¢.c. of 
this solution required 7°5 ¢.c. of a 2°0 per cent. solution of salicylic 
acid to completely saturate the proteids present,* the excess of free 
acid necessary to give the tropzolin reaction being deducted. 
Three digestive mixtures were made as follows : 
1. 25 ¢.c. of the neutral pancreatic solution + 50 ¢.c. water. 
2. 25 cc. of the same pancreatic solution+7°5 c.c. 2°0 per cent. 
salicylic acid solution +17°5 cc. water. The mixture was acid to 
test papers, but gave no reaction with tropzolin 00. It therefore 
contained no free acid, but 0°3 per cent. of combined acid. 
3. The same as No. 2, but 2°5 ¢.c. more of 2°0 per cent. salicylic 
acid, so that the solution contained, in addition to the acid proteids, 
0-1 per cent. free salicylic acid. 
One gram of fibrin was added to each of these and the mixtures 
warmed at 40° C. for 8 hours and 40 minutes. No. 1 digested 88°34 
per cent. of the fibrin, No. 2, 13°44 per cent., while No. 3 had no 
action whatever. 
Much smaller percentages of combined salicylic acid cause an 
equally diminished proteolytic action; thus, in the case of a carefully 
dialyzed juice where the proteid matter was much diminished, the 
digestive mixture, with its proteids wholly saturated, contained but 
0°060 per cent. of combined salicylic acid; yet this mixture, in 15 
hours at 40° C. digested but 17°10 per cent. of fibrin, while the same 
amount of the neutral trypsin solution digested 57°80 per cent. 
* Tested by tropzolin 00 according to the method of Danilewsky (Centralbl. med. 
Wiss., 1880). One drop of a solution containing 0-028 per cent. free salicylic acid 
gives a reddish-violet color, which is, however, not permanent as in the case of hydro- 
chloric acid, but transient. With hydrochloric acid, one drop of a 0:003 per cent. 
solution will give the reaction. 
