Permeability 87 
These results show clearly that the extent to which a salt is 
absorbed by the particular tissue used depends both on the kation 
and anion of the salt. Salts having the same anion are absorbed in 
the order K, Na, Li, [Ca, Mg], Al, while salts containing the same 
kation (K) are absorbed in the order N 0 3 , Cl, S 0 4 . This means, as 
far as these results go, that salts containing two univalent ions are 
absorbed much more rapidly than salts containing a divalent or 
trivalent ion. The difference in the position of equilibrium of K, Na, 
and Li salts on the one hand, and of Ca on the other, is very striking, 
and so is the difference in the position of the equilibrium between 
chlorides and nitrates on the one side and sulphates on the other. 
The influence of the thickness of the tissue on the position of equi¬ 
librium. The only experiments of which I am aware dealing with 
this question are those of Ruhland (1909 h), who compared the 
absorption by equal weights of disks of beetroot 3 mm. and 1 mm. 
in thickness immersed in 0*4 per cent, calcium chloride, and of carrot 
disks of the same two thicknesses in 1 per cent, ammonium nitrate. 
His results are shown in Table XL. 
Table XL 
Influence of the Thickness of the Tissue on the Absorption Ratio 
Initial 
Dura¬ 
Thick¬ 
concen¬ 
tion 
ness 
Absorption ratio 
tration in 
of expt. 
of tissue 
A 
Tji 
Tissue 
Salt 
per cent. 
in days 
in mm. 
Kation 
Anion 
Carrot 
Ammonium nitrate 
1 
7 
3 
0-5276 
— 
jy 93 
y y 
1 
0-8342 
— 
Beetroot 
Calcium chloride 
0-4 
2 
3 
0-2582 
0-0354 
,, 
,, >> 
,, 
,, 
1 
0-3421 
0-0522 
,, 
,, ,, 
9 9 
4 
3 
0-3266 
0-0486 
,, 
,, 
,, 
1 > 
1 
0-5616 
0-0826 
It is clear that in these experiments the extent of absorption by 
an equal weight of tissue was considerably increased by increasing 
the surface of the tissue directly exposed to the solution. While this 
result is understandable on the view that the absorption of the salts 
examined is controlled by adsorption, yet the results are so few that 
it would be premature to elaborate an explanation of the results. 
Clearly the question is deserving of further examination. 
The Course of Absorption of Dissolved Substances 
The course of absorption of a number of salts by storage tissues 
(carrot root and potato tuber) at a fixed temperature of 20° C. has 
been determined by Stiles and Kidd (1919 a , b) by the electrical 
