1917] OSTERHOUT— PERMEABILITY 319 





6 



the precipitate continues to form, while in the case of a dye which 

 is not precipitated (and which does not form a compound incap- 

 able of passing out), the absorption ceases as soon as the concen- 

 tration within the cell equals that of the solution. 



It is evident, therefore, that the temperature coefficient observed 

 by Stiles and Jorgensen may be that of a chemical process 5 

 involving the union of hydrogen ions with some constituent of the 

 cell other than the plasma membrane (or other surface), in which 

 case it would have no bearing upon the problem of the nature of 

 permeability. 



Some time ago the writer sought to throw some light on this 

 problem in ascertaining the temperature coefficient of permeability 

 by a method which is free from the objections just discussed. By 

 this method 7 the electrical conductivity of living tissue was deter- 

 mined in such a way that it may be regarded as a measure of the 

 permeability of the protoplasm. 



In these experiments a series of disks of Laminaria were packed 

 together (like a roll of coins) so as to form a solid cylinder about 2 

 inches in length. The electrical conductivity was then measured 

 at various temperatures. The temperature coefficient obtained in 

 in this way was 1 . 33. The tissue was subsequently killed, whereby 

 the conductivity was increased to practically that of sea water. 

 The temperature coefficient of the dead tissue proved to be 1 . 26, 

 which is practically the same as that of sea water. 



If most of the resistance were due to apparatus, cell walls 

 (intercellular substance), and sea water, and these had low tem- 

 perature coefficients (for example, 1 . 26), that part of the resistance 

 which is due to living protoplasm might have a high temperature 

 coefficient (for example, 2) without much raising the temperature 

 coefficient of the total resistance. The resistance of the apparatus 

 (and the sea water contained in it) was determined at each tem- 

 perature and subtracted from the total (giving what is called the 



5 Absorption may also play a part in this connection. 

 6 Cf. Biochem. Zeitschr. 67:272. 1914. 



7 Even if the hydrogen ion unites "with the plasma membrane or some part of 

 it," the temperature coefficient of this process would not necessarily be the temperature 



coefficient of permeability. 



