Walter Stiles 
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released on the other side of the plasma-membrane or combines or 
is adsorbed by some other cell constituent according to the molecular 
affinities of the various constituents. 
Pauli (1904) appeared to consider that salts were absorbed by 
their combining chemically in this way with the plasma-membrane, 
and the same opinion was held by Traube-Mengarini and Scala (1909) 
working with algae and protozoa. The work of Sziics (1910, 1911,1912, 
1913) appears rather to suggest adsorption as responsible for the 
intake, and Pantanelli (1915 a, b, c, 1918) also lays emphasis on the 
importance of adsorption. 
It is to be observed that this theory can be applied equally well 
to a cell surrounded by a plasma-membrane and to one in which the 
protoplasm is approximately homogeneous, and indeed Moore (1921) 
and his co-workers (Moore and Roaf, 1908; Moore, Roaf and Webster, 
1912), who deny the existence of plasma-membranes, are supporters 
of this view. 
Sziics (1912) appears to think a combination of the lipoid theory 
and adsorption theory is possible, the intake of dyes and narcotics 
being explained by their solubility in fatty substances, while salts 
enter by adsorption or chemical combination. The relation between 
external concentration and the position of the equilibrium attained 
in the absorption of salts by some plant cells can be used in support 
of this view, but it must be mentioned that at least some dyes appear 
to follow the same rule (Redfern, 1922 b). 
Electrical Theories 
The great difference between acid and basic dyes in regard to 
their penetration into cells, and the assumed influence of acids and 
alkalies in influencing the intake of these dyes, has suggested the 
possibility that the electric charge on the plasma-membrane may be 
of importance in determining whether particular ions are absorbed. 
The theories propounded ( e.g . Girard, 1914 a, 1919 a , b) are at present 
mostly vague, and the foundation of fact on which they rest insecure 
(cf. Collander, 1921) so that a discussion of such theories in the present 
state of our knowledge would be scarcely profitable. It is not at all 
clear, moreover, whether such theories in the end do not resolve 
themselves into special cases of the adsorption theory of perme¬ 
ability. 
A theory of cell permeability combining an electrical theory with 
a colloidal theory closely resembling that of Lloyd and Free, has 
recently been propounded by Miss Haynes (1921), who assumes that 
