Permeability of the Cell 



73 



Kite 1 injected cells by the Barber pipette method 2 and claimed 

 to have proved that semi-permeability is a property of all por- 

 tions of protoplasm. His conclusions are open to criticism ow- 

 ing to the extreme difficulty of the method and to his having 

 overlooked the extraordinary ability of protoplasm to form sur- 

 face films over cut surfaces. The results which I 3 obtained are 

 directly opposed to Kite's conclusions. Recently I have devised 4 

 a micro injection apparatus with which one can, with remarkable 

 ease and accuracy, inject living cells by means of pipettes with 

 a bore less than one micron in diameter. 



A half molecular ammonium chloride solution in sea water 

 is acid to neutral red. Starfish eggs stained with neutral red 

 and immersed in this acid solution turn yellow, owing to the 

 penetration of only the alkaline group of the dissociated salt. 

 If, however, stained eggs be placed in an alkaline sodium bi- 

 carbonate solution, they give evidence of the penetration of 

 only the carbonic acid group. These findings are being reported 

 by Jacobs in the Journal of General Physiology. ' They confirm 

 the observations of previous investigators that weak acids and 

 bases freely penetrate living cells whereas strong acids and bases 

 do not. 



My experiments, described in a forthcoming number of the 

 Journal of General Physiology, consisted in the injection of 

 NH4CI and NaHC0 3 into starfish eggs stained with neutral 

 red. In the case where NH 4 C1 was used. the injected area im- 

 mediately changed to a red color and then underwent cytolysis. 

 The color change and accompanying cytolysis spread from this 

 area till it reached the cortex of the egg which disintegrated from 

 within outward. In some cases this spread was arrested by the 

 formation of a surface film which converted the injected and dis- 

 integrated area into a vacuole. This experiment demonstrates 

 that V2 M NH4CI, which causes an alkaline color change within 

 eggs when its effect is transmitted only through the surface 

 film, will, when injected into the interior of the eggs, produce 



1 Amer. Jour. Physiol., 1915, xxxvii, 282. 

 2Philipp, Jour. Sc., Sec. B., Trop. Med., 1914, ix, 307. 

 zjour. Pharmacol. Exp. Therap., 1919, xiv, 75; Proc. Soc. Exp. Biol, 

 and Med., 1920, xviii, 66. 

 * Anat. Bee, 1922, xxxiv, 1. 



