104 Chittenden and Allen—Influence of various Salts 
digested, were obtained with different percentages of hydrochloric 
acid; the amount of pepsin being the same in each case. 
Per cent, MG sg see _ O05 Ol O°2 O38 O-4 
Per cent. fibrin digested 73°8 89°3 84-0 81°7 63°8 
This shows plainly, that, with the amount of pepsin employed in our 
experiments, acceleration of proteolytic action on the addition of 
neutral salts, might in some instances be due to slight diminution of 
free hydrochloric acid. That this is not the sole cause, however, is 
plain from the fact that closely related salts do not act alike. 
Potassium bromide and Potassium iodide. 
With these two potassium salts, the following results were ob- 
tained : 
Undigested Fibrin Relative proteo- 
KBr. residue. digested. lytic action. 
0 0°3837 gram. 61°63 per cent. 100°0 
0-005 per cent. 0°3205 67-95 110:2 
07025 0°3035 69°65 113°0 
0710 0°4204 57:96 94-0 
0°50 075690 43°10 70:0 
1:00 0°6203 3797 61:6 
Kl. 
0 0°2572 gram. 74°28 per cent. 100-0 
0005 per cent. 0:2755 72°45 97-5 
0025 073421 65°78 88°6 
0°10 0°2841 TONES) 96°4 
0°50 0°6367 36°33 48'9 
1:00 0°7586 24°14 32°5 
By comparison of these two series of results, we see that there is 
a very decided difference in the action of the two salts; potassium 
bromide in very small quantity, causes a decided acceleration in pro- 
teolytic action, which is wholly lacking with potassium iodide. Again, 
there is a very great difference in the amount of retardation produced 
by the two salts ; thus by comparison with their respective controls 
we see, that while 1 per cent. of potassium bromide causes retardation 
in digestive action, amounting to 38-4 per cent., the same percentage 
of iodide causes retardation amounting to 67°5 per cent. It is to be 
supposed, naturally, that in the presence of large amounts of the 
salts, the ferment must act wholly in combination with hydrobromic 
and hydriodic acid respectively; that is to say, the hydrochloric 
acid of the gastric juice must have replaced these two acids in the ° 
potassium salts, and thus new pepsin-compounds formed, of which 
pepsin-hydrobromic acid is the more active digestive agent. 
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