Stiles and J0rgensen.—Studies in Permeability. /. 353 
The tissue used in these experiments consisted of discs of potato tuber 
(Solanum tuberosum , var. King Edward VII). Potato was selected as it 
yields a very uniform tissue. Discs were cut having a diameter of a centi¬ 
metre and a weight of about \ grm. Twenty of such discs were washed 
in distilled water, dried on filter-paper, placed in 100 c.c. of solution in 
a stoppered bottle, and the electrical conductivity of the solution was 
measured from time to time by Kohlrausch’s method. As different sets 
of tissue vary somewhat, the experiments with potato were done in dupli¬ 
cate ; this gave an approximation to accuracy near enough for our purpose. 
In some cases living plants of bean (Vicia Faba) were used. They 
were grown in water-culture for some time in order that plants might be 
obtained with uninjured roots. Plants with as equal a root development as 
possible were then selected, and each one placed with its roots immersed in 
100 c.c. of solution, and the conductivity of this measured as before. With 
careful selection of equally developed plants it was found that duplicating 
the experiments yielded results of sufficient accuracy. The curves which 
follow were plotted from these results, the increase in the electrical con¬ 
ductivity being taken as ordinates, and the time as abscissae. 
The preliminary measurements were made in the Department of 
Physical Chemistry of this University. We would thank Dr. H. M. Dawson 
for putting at our disposal the resources of his laboratory. 
Experiments. 
Series 1. In this series various substances were used as external 
N 
medium in a concentration of The substances employed comprised 
both undoubted poisonous substances and salts of nutritive metals. The 
following substances were used : 
Copper sulphate £ Kahlbaum, with certificate of guarantee ’ 
Mercuric chloride „ „ „ „ 
Quinine hydrochloride ‘ Kahlbaum * 
Calcium chloride ‘ Kahlbaum, with certificate of guarantee’ 
Sodium chloride „ „ „ „ 
Magnesium chloride ,. ,, „ „ 
Potassium chloride „ „ „ „ 
Aluminium chloride ‘ Kahlbaum ’. 
As the accompanying curves show, in all these cases exosmosis of the 
electrolytes in the cell-sap takes place, as indicated by a very definite rise 
in the electrical conductivity. This rise is on a much greater scale in the 
case of undoubted toxic substances, than in the case of salts of nutrient 
metals. The obvious explanation is that the toxicity of the poisonous 
