‘on the Proteolytic Action of Pepsin-hydrochloric Acid. 93 
Undigested Fibrin Relative proteo- 
FeS04+7H20. residue. digested. lytic action. 
0 0°1835 gram. 81°65 100°0 
0-001 per cent. 0'1916 80°84. 99°0 
0°005 0°2241 UT(3a8) 95:0 
0°010 071895 81°05 99°2 
0:025 0°2573 74:27 90°9 
0:050 02773 72°27 88°5 
0 0°1935 80°65 100°0 
0-1 0°3467 65°33 81°0 
0:3 0°7274. 27°26 33°8 
0°8 0°8080 19°20 23°8 
1°5 0°8447 15°53 19:2 
Here, with the ferrous salt, we find pronounced diminution of pro- 
teolytic action, commencing even with 0:001 per cent. With ferric 
chloride, the following results were obtained. 
Undigested . Fibrin Relative proteo- 
Fe2Clg. residue. digested. lytic action. 
0 0°1842 gram. 81°58 per cent. 100°0 
0-001 per cent. 0°2111 78°89 96°7 
0°005 0°2059 79°41 Sige 
0-010 0°2165 78°35 96°0 
0050 0°2332 76°68 93°9 
0 01961 80°39 100°G 
0°3 0°6526 34°74. 432 
0°5 0°8035 19°65 24-4 
0'8 08794 12:06 15:0 
30 0°9582 4°18 5:2 
A comparison of the two series of results, shows no pronounced and 
constant difference in the amount of action between the two iron 
salts; both retard proteolytic action about equally; although with 
the larger amounts, as with 0°5 per cent. and beyond, ferrie chloride 
appears the most injurious. Comparing the results with those 
obtained with the manganese salt, which of late has been recom- 
mended as a therapeutic agent where iron cannot be taken, we see 
that the manganese is throughout, far less injurious than the two salts 
of iron. 
As to the manner in which the iron salts produce their retarding 
effect on proteolytic action, it is evident that it cannot be due to a 
simple displacement of the acid of the iron salt, by which the pepsin 
is made to act with a less compatible acid, since ferric chloride acts 
similarly to the sulphate, in which case there could be no such 
injurious replacement, 
