282 _ Raymond FH. Pond. 
The same point of total inhibition is found here as in the case of 
mercury and copper, The relative acidity of the reagent and control is 
different, however. The difference in acidity between the control and 
the reagent steadily increases to zero at the point of total inhibition. 
There is something of individuality in the behavior of the toxic salts 
to the protein of the enzyme solution. Since the tests for mercury, 
lead, and copper were conducted separately, the following contempo- 
raneous test for mercury and lead is given. 
Mercury and lead in contemporaneous test. — 
TABLE: XAI 
MERCURY. 
M. Control. Enzyme. Increase. 
256 0.80 0.90 0.10 
128 1.50 1.50 0.00 
64 2.60 2.60 0.00 
LEAD. 
256 0.60 0.90 0.30 
128 3.20 1.20 0.00 
64 2.00 2.00 0.00 
Enzyme, 0.25 per cent. Incubation period, 4 hours. 40° C. 
Just why the acidity of the controls in this test is so much higher 
than in the preceding separate tests is not known. . However, both the 
mercury and copper controls are higher, so that perhaps the ethylbu- 
tyrate was not quite neutral. Even so, the same relative toxicity is 
maintained in a contemporaneous test. 
DISCUSSION. 
The solutions of sodium, lithium, potassium, ammonium, barium, 
strontium, and magnesium, are all neutral, and so are the correspond- 
ing controls for the concentrations of the enzyme tried. In those 
cases there is no evidence of chemical reaction between the substance 
of the enzyme solution and the reagent. With the other reagents 
tried (Cu, Pb, Cd, Co, Zn, Hg, and Ag) there is evidence of such 
chemical action, and it seems but natural to suppose that the cause 
of toxicity is very different in the one group from that in the other. 
The latter solutions show natural acidity, and this is more or less 
affected by the substance of the enzyme solution, even though the 
latter be too dilute to coagulate upon boiling, or have any initial 
acidity. 
