182 
Harvey.— The Action of Poisons upon 
to within 10-15 per cent., a much greater degree of accuracy than was 
possible with lupines. In some cases, as with resorcin, the difference in the 
effects caused by a ^ per cent, and a T per cent, solution was well marked ; 
in other cases a similar difference in the concentration of the poison caused 
a much less marked effect. 
The Table shows both the very similar reactivity of widely different 
vegetable cells towards the same poison — a somewhat striking pheno- 
menon — and also a fairly constant relation between the chemical consti- 
tution of a poison and its toxic strength, since the para-derivative is in 
most cases the strongest poison of the three isomers. A close relation 
between the cessation of the power of movement of the Chlamydomonadine 
cell and its death-point is indicated. 
TABLE 1. 
Poison. 
Minimal Conct. in Gm. Molecular Wts. per Litre. 
Chlamydomonas. 
Lupinus Aldus . 1 
Bacteria. 
ortho ' 
0.0091 
o-opi25 
meta 
• dihydroxy phenol 
0*0167 
0.005 
para , 
0.000182 
0-000062 
A powerful disinfectant 1 
ortho' 
0.00316 
0*00125 
i 2 
meta 
• Cresol 
0.00125 
3 
para 
0-00159 
0*00062 
2 
ortho' 
0.0018 
1 3 
meta 
• Phthalic acid 
0.00072 
2 
para 
0*00001 2 
3 
2. The Reaction Velocity of Hydrochloric acid as a Poison . 
A small quantity of a culture of a large and actively- moving species of 
Chlamydomonas was introduced into a cylindrical glass vessel with a thin 
glass bottom. The cells swam about rapidly within a short distance from 
the bottom of the vessel, and were viewed with an inverted microscope in a 
strong red light from above. After introduction of the poison the cells 
were seen to fall one by one and rest on the bottom. The number thus 
brought to rest within the field of the microscope was counted at intervals of 
five minutes. 
If the cessation of movement of the cells in this case was a measure of 
1 Hunkel and True : Botanisches Centralblatt, B. 76, pp. 231, 289, 361. 
2 C. Frankel: Zeitsch. fiir Hygiene, 1889. The numbers give the order of increasing toxic 
strength. 
3 Order of toxic strength with Bacterium subtilis obtained in the same manner as in Frankel’s 
experiment. 
