1 86 Harvey . — The Action of Poisons upon 
obeyed when the concentration (c) is made to vary, t being the time for the 
reaction to reach completion in each case. 
In the disinfection of bacteria the same equation is obeyed, the value 
of k being dependent upon the nature of the poison and the bacterium. 1 
TABLE III. 
C = concentration 
of Resorcin in 
parts per 100,000. 
Tunes in minutes . 
t or 
average 
time . 
log c . 
logt . 
logt 
+ 1-2 I log c . 
102 
j 21 
Several hours — indefinite 
16, 18, 17, 16, 18 
1 7 
2-0828 j 
1.23 
3-75 
136 
10, 11, 10, 11, 11, 10, 10 
10.5 
2.13 
1.02 
3.60 
165 
8, 8, 8, 8, 7.5, 8, 7.5, 8 
7.8 
2.22 
0*89 
3-58 
T 95 
6-5, 7> 7 > 6.5, 6.7, 6 
6-6 
2-29 
0*82 
3-59 
224 
6, 6, 6, 6, 6 
6.0 
2-35 
0-78 
3.60 
254 
4 * 5 , 5 > 5 , 5 > 4 * 5 > 5 > 5 
4.8 
2.40 
0.68 
3*58 
278 
4 \ 5 > 4 ? 4 > 4 ’ 5 > 4*55 4 ? 4 > 4’5 
4- 2 5 
2.44 
0-63 
3-58 
4. Action of a mixture of Poisons. 
The following concentrations of poisons were each found just to cause 
cessation of movement in a culture of Chlamydomonas multifilis in ten 
minutes : — 
Hydrochloric acid 0*009 P er cen t* 
Pyrocatechin o*i per cent. 
Resorcin 0*18 per cent. 
A mixture of 0*009 per cent. HC 1 and 0*18 per cent. Resorcin caused 
cessation of movement before ten minutes, and so did a mixture of 0*009 P er 
cent. HC 1 and o-io per cent. Pyrocatechin, also a mixture of 0*18 per 
cent. Resorcin and o-io per cent. Pyrocatechin. Hence no one of these 
poisons retards the action of another to any considerable extent. 
Further experiments showed the striking fact that a mixture of the 
poisons, each slightly weaker, viz. : — 
0*007 P er cent. HC 1 
0*08 per cent. Pyrocatechin 
and 0*14 per cent. Resorcin 
does not cause cessation of movement in ten minutes, although each of the 
three poisons exceeds in strength three-quarters of the concentration which, 
by itself, will cause movement to cease. 
Here it is evident that the action of each poison is specific , and, from the 
great difference in toxic activity of isomeric modifications of the same com- 
pound, the specific action is seen to vary greatly for slight changes in 
chemical constitution. A mixture of strong acids behaves as if its toxic 
Watson : Journal of Hygiene, Oct. 1908. 
