280 Raymond FH. Pond. 
TABLE XVII (continued). 
ZINC. 
32 6.70 Y 6.76 0.00 
64 3-30 3.60 0.30 
Enzyme, 0.125 per cent. Incubation period, 5 hours. 40° C. 
This shows the approximately equal toxicity of these metals under 
these conditions. If the concentration of the enzyme is reduced, but 
not so much as in Table IV, it is seen that the greater toxicity of zinc 
reappears. 
Cadmium and zinc in contemporaneous test. — ~ 
TABLE XVIIL. 
CADMIUM. 
M. Control. Enzyme. Increase. 
128 0.20 0.50 
64 0.50 0.50 0.00 
ZINC. 
128 1.80 1.80 0.00 
64 3.30 3-30 0.00 
Enzyme, 0.02 per cent. Incubation period, 17 hours. ao"-C: 
Here, in spite of the long incubation period, the greater toxicity of 
zinc is apparent. 
Mercury, copper, and lead show the same tendency to be of a 
toxicity with i increasing concentration of the enzyme. 
TABLE XIX. 
Mercury (CHLORID). 
M. Reagent. Control. Enzyme. Increase. 
32768 0.00 ' 0.15 1.10 0.95 
16384 0.00 0.15 0.90 0.75 
81g2 0.00 0.15 0.80 0.65 
4096 0.05 0.15 0.60 0.45 
2048 0.108 0.15 0.50 0.35 
1024 0.20 0.20 0.60 0.40 
512 0.35 0.30 0.60 0.30 
256 0.65 O70 0.80 0.10 
128 130° a 1.10 0.00 
64 2.50 * 2.20 2.20 9.00 
Water 0.15 1.10 0.95 
Enzyme, 0.25 per cent. Inewbation period, 4 hours. 40° 4. 
* A red precipitate. 
