Stiles and Jergensen. — Studies in Permeability. IV. 65 
Fig. 1 1 shows the relation between time and exosmosis for a variety of con- 
centrations of chloral hydrate. It will be observed that the general course 
of events is similar to that in the case of the alcohols, and that here also it is 
impossible to find a definite critical concentration above which exosmosis 
takes place and below which it does not. Chloroform, ether, and urethane 
give similar results, and it is unnecessary to reproduce the curves here. 
According to Czapek the surface tension of o-i m. chloral hydrate solution 
is about 0-96. There is no question of the surface-tension rule holding in 
this case. 
As regards Czapek’s theory of a specific toxic action in chloral hydrate 
and chloroform which does not exist in the case of the monohydric alcohols, 
such a view simply resolves itself into the assumption that in the case of the 
monohydric alcohols surface tension is the essential factor in producing 
exosmosis, in the case of chloral hydrate and chloroform it is some other 
factor. The theory that exosmosis is dependent on one physical factor, and 
one only, actually breaks down under the test of its author’s own observa- 
tions. We shall discuss this matter more fully in the theoretical part 
of this paper. 
III. Acetone . 
Experiments with acetone produced results similar to those already 
recorded for other organic substances. In the case of acetone more than in 
Time in hours. 
Fig. 12. Exosmosis of electrolytes from potato in solutions of acetone of various concentrations. 
any other might it be suggested that there exists a critical concentration 
with regard to exosmosis between m. and 1-5 m. (cf. Fig. 12). But it will 
be observed that even here exosmosis continually rises in the lower strengths 
of solution, and in 0-5 m., the lowest concentration examined, the exosmosis 
