A NEW METHOD OF STUDYING PERMEABILITY 
Ss. C. Broexs 
(WITH TWO FIGURES) 
The writer™ has shown the desirability of a study of permeability 
by some method which should be entirely independent of other 
methods, and yield data the interpretation of which need not depend 
upon any unverifiable assumptions. A method is here presented 
which seems to fulfil these requirements. It has proved to be 
exceedingly reliable; and the experiments point clearly to the errors 
previously made in the interpretation of the data secured by many 
methods, and to the validity of the conclusions based on the 
evidence of certain others. 
Method 
The method depends upon diffusion of salts or other substances 
through a diaphragm of living tissue. For this purpose fronds 
of one of the common kelps of the New England coast, Laminaria 
Agardhii (formerly identified as L. saccharina), proved to be 
extremely satisfactory material because of absence of air spaces 
in the tissue, ease of manipulation, resistance to adverse conditions, 
and especially because it was possible to secure thin sheets of tissue 
in which there were no wounded surfaces in contact with the solu- 
tions. 
The method of experimentation was as follows. Sections of 
glass tubing of 18 mm. internal diameter were cut; one end of each 
piece was flared and the end ground flat. The resulting “cells” 
were either 2.5 cm. or 4 cm. in length, and were combined in pairs, 
each consisting of one long and one short cell (fig. 1, A, B)- The 
unground end of the longer cell was closed by a rubber tube and 
pinchcock (fig. 1, C, D). Disks were cut from the fronds of Lamt- 
naria of such a size as nearly to cover the ground ends of the tubes. 
Brooks, S. C., Methods of studying the permeability of protoplasm salts. 
Bor. GAz. 64:230-249. 1917. 
Botanical Gazette, vol. 64] [306 
