14 
Walter Stiles 
an untreated collodion membrane separates water and a solution of 
an acid in concentration less than M /16, positive osmosis occurs, the 
more rapidly the higher the valency of the anion. When, however, 
a similar membrane treated with gelatine is used, negative osmosis 
takes place. Similar results were observed with membranes treated 
with casein, edestin, egg-albumin and serum albumin, but not with 
peptone, alanine or starch. These results are attributed to electrical 
forces which in concentrations of solutions below M/16 mainly deter¬ 
mine the osmotic effects. In passing through the untreated collodion 
membrane the water is positively charged; on treating the membrane 
with gelatine the charge on the water becomes negative, so that the 
electrical forces will tend to send the water in the opposite direction. 
Further evidence for, and elaboration of, this view is contained in a 
series of papers by Loeb (1920 b, c, d, e,f,g, 1921) to which further 
reference may be made. Enough has already been said here to 
indicate the importance in connection with osmosis of electrical 
phenomena associated with membranes. That such phenomena are 
present in the living animal cell has already been indicated by Girard 
(1919) and Girard and Morax (1920). 
[To be continued) 
