1917] BROOKS—PERMEABILITY 241 
solution will withdraw water from the cells, and consequently 
reduce the turgidity and the degree of curvature, while a hypotonic 
solution will have the opposite effect. The penetration of the 
protoplasm by a salt with whose solution such a tissue had come 
into osmotic equilibrium would lead to an increase in the turgidity, 
and hence in the curvature of the tissue. Dr Vries (67), in the 
investigation of the isotonic coefficients of various substances by 
this method, .observed such a secondary increase in curvature. 
Such tissue curvatures have not since been used in quantitative 
researches on the permeability of the protoplasm. The writer, 
however, has found it possible to make use of this method for 
quantitative determinations of permeability (BRooks 1a). 
Changes in the volume or weight of animal cells or tissues have 
been used by many investigators to determine the rate of penetra- 
tion of electrolytes. Red blood corpuscles and striated muscle 
have been the most frequently used materials.s As an example of 
the former, the work of Kozawa (19) may be quoted. This 
investigator added to 1 cc. of corpuscles centrifuged from defibri- 
nated blood of various mammals 2 cc. of various solutions of equal 
osmotic pressure (as judged by the freezing point depression). 
corpuscles were again centrifuged after a time varying from 
15 minutes to 23 hours, and the volume of the mass of corpuscles t 
noted.® Increase of volume was c oe 
of the solute. Sodium salts were not observed ne “cause. any = 
increase in volume. nutes (8) made similar observations. oe 
In some animals gl penetrate; in others it t did ae 
‘not. It was found to be Sebi to influence the ermeability ne 
to glucose by various agents, cone certain inorganic salts. 
These conclusions agree with t ; is 
corpuscles by su 
unable to influence oa gee y - siden 
