112 Chittenden and Cummins—Influence of various Substances 
pancreas. They find that arsenious acid is without influence on the 
action of the ferment. We do not know whether they added arsen- 
ious acid to a neutral or alkaline solution of the ferment, as we have’ 
seen only an abstract of their paper, but we find that the addition 
of very small amounts of arsenious oxide to a neutral solution of 
trypsin, does produce a slight retardation in the proteolytic action — 
of the ferment. Owing to the comparative insolubility of arsenious — 
oxide in water, only small percentages could be employed, but these — 
show, as might be expected from the acid character of the substance, — 
a decrease in proteolytic action. 
Undigested Fibrin Relative proteo- 
As203, residue. digested. lytic action. 
0 0°4598 gram. 54°02 per cent. 100°0 
0-001 per cent. 0-4630 53-70 99-4 
0-005 04513 5487 101°5 
0°025 0:4710 52°90 97-9 
0°050 0°4723 52°17 97°6 
4 
Arsenic acid. 
This substance, in conformity with its more decided acid character, 
causes greater retardation than arsenious acid; which fact tends, by — 
analogy, to make the retarding action of the latter still more proba- 
ble. The results are as follows: 
Undigested Fibrin Relative proteo- 
H3AsOq. residue. - digested. lytic action. 
0 0°4598 gram. 54:02 per cent. 100°0 
0°005 per cent. 0°4563 54°37 100°6 
0°025 0°4887 51°13 94°6 
0°050 075264 47°36 87:4 
0°100 0°6340 36°60 67:7 
Ammonium arsenate. 
This salt in small amount, appears to increase the proteolytic action 
of the ferment, which fact would indicate that the retarding action 
of the two preceding arsenic compounds is due more to their acid — 
character than to the arsenic contained in them. 
Undigested Fibrin Relative proteo- 
(NH4)3A804q4. residue, digested. lytic action. 
0 0°4598 gram. 54°02 per cent. 100°0 
0°050 per cent. 0°4620 53°80 99°6 
0°100 0°4442 55°58 102°8 
0 0°3675 63°25 100°0 
0°5 0°4071 59°29 931 
