METHODS OF STUDYING PERMEABILITY OF 
PROTOPLASM TO SALTS 
S.C. BRooKs 
Investigation of the permeability of protoplasm to electrolytes 
has led to many apparent conflicts between evidence secured by 
different methods and between the theoretical conclusions based 
thereon. An intensive study of the evidence, and of the methods 
themselves, has shown that these apparent conflicts are in large 
_ measure due to an imperfect understanding of the limitations of the 
methods or to unwarranted assumptions as to the nature and 
reactions of living matter. It is therefore of interest to consider 
critically the methods heretofore employed in the study of perme- 
_ ability in order to determine which of these methods may be con- 
sidered most reliable, and thus to acquire a broader understanding — 
__ of the problem, and to lay the foundation for further investigation. 
a _ The methods employed i in the investigation of the permeability 
8 tes fall into 4 general categories, in which 
a we criteria employed are: (1) chemical pase igh of tissue extracts 
or of solutions bathing the tissues, (2) visible « es within the 
= - (3) turgidity of cells or tissues, and (4) decesisl ‘conducts S 
f tissues or of masses of cells. To these ‘may = added a diffusion 
oS s ca 
__ ANALYSIS OF TIssu 
Chance mt by Js (0). " Filaments of a “species <3 
