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OSMOTIC PRESSURE. 11
It has been shown that those substances which are not taken up by the
cells at all or only slightly, do not lower the surface tension of the water
when dissolved therein. On the contrary, those substances which lower
the surface tension, pass into the cells. According to Gibbs those sub-
stances, which when dissolved in water lower the surface tension, occur
in greater concentration on the surface as compared with the interior.
Thus according to Traube the solution tenacity is less the lower the
surface tension of the watery solution. Otherwise the direction of
movement of a substance in the boundary between two phases (watery
solution and cells) is determined by the relationship between the solution
tenacity of the substances in the two phases. However, the solution tenac-
ity of a substance can only be directly measured in the watery solution.
Traube supports his theory. upon different experiments in which mem-
bers of the same homologous series were dissolved in water in such con-
centration #
as to have the same surface tension and also showed the
same ability to pass into the cells. The disagreement in other cases can
be explained by the unknown solution tenacity in the cell phase. As we will
show below Traube’s proposition calls to mind the accepted views as to
the origin of the adsorption phenomena or the taking up of dissolved sub-
stances by solid bodies. Lowe l
has also found, in studying the taking
up of different dissolved substances by lipoids, that the process does not
take place as called for by Overton’s theory according to Henry’s law
of absorption but rather an adsorption.
Certain substances which are of the very greatest importance for life
processes and which probably are burned to a great extent within the cells,
have according to the above experiments only a limited ability to enter
the cells. These bodies are the sugars and the amino-acids. Also the
presence of salts within the cells is not easily understood in view of the
above experiments. In consideration of this it must be remarked that
the above described experiments on the permeability of animal cells have
been carried out with cells that were removed from their attachment to
the living animal. Although these cells are not considered as physio-
logically dead cells still it is very probable that certain life functions
have been arrested. It is readily conceivable that the oxidation processes,
whereby the organic substances taken up within the cells are trans-
formed into simpler products, are at least partly brought to a standstill
(see Chapter XVI). That, nevertheless, at least salts and sugar also
attract water in the living organism and therefore only pass into the
cells in small quantities follows from the experiments of Heidenhain,
according to whom these substances are designated as lymph forming
agents of the second order (Chapter VI). This action is also explained
1
Bioch. Zeitschr., 42; 150, 190, 205, 207 (1912).
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