114 



Scientific Proceedings (119). 



restricted conditions. One such condition is the reaction of the 

 medium which in the presence of plant tissue may be made to 

 vary over a much wider zone without retarding growth; another 

 condition is oxygen tension which similarly seems to require for 

 sensitive organisms much less accurate control in the presence of 

 plant tissue than in its absence. 



The exact nature of the substances contained in plant tissue 

 upon which these properties depend is not yet determined, but 

 the studies so far made suggest that they are related to the presence 

 of certain oxidizing and reducing enzymes in fresh plant tissues 

 as well as to the presence of so-called accessory food substances. 



55 (1802) 



The diffusion of sodium chloride through a " lecithin "-collodion 



membrane. 



By HAROLD A. ABRAMSON and SAMUEL H. GRAY. 



[From the Department of Pathology, College of Physicians and 

 Surgeons, Columbia University, New York City.] 



A study of the diffusion of sodium chloride through: (a) 

 membranes prepared from collodion ; and (b) membranes prepared 

 from collodion which contained approximately four grams of 

 commercial "lecithin from eggs" per hundred cubic centimeters, 

 was made under the following conditions. 



1. The collodion (Eimer and Amend's, U.S. P. IX) contained 

 about four grams of guncotton per hundred cubic centimeters. 

 The membranes, therefore, which contained "Lecithin" were 

 approximately fifty per cent, lipoid by weight. 



2. The membranes were made with as nearly uniform tech- 

 nique as possible. The viscousness of the collodion and of the 

 lecithin-collodion solution was kept constant and the same. The 

 volume of the membranes, which were shaped inside of Erlenmeyer 

 flasks, varied between fifty and sixty cubic centimeters. 



3. The only factor experimentally varied was the drying time 

 which was terminated by fixation with tap-water. 



4. In every determination of permeability, the membranes 

 were filled with one fourth molar sodium chloride and immersed 



