THE PERMEABILITY OF CELLS FOR ACIDS. 1 



BY E. NEWTON HARVEY. 



The results of researches on the permeability of cells for alkalies, 

 using the color change of an indicator, neutral red, within the cell as 

 a convenient method of detecting penetration of the alkali, were pub- 

 lished 2 by the present author in 1911. Bethe 3 and also Warburg 4 had 

 used the same method for certain of the alkalies, although I was un- 

 aware of their experiments at the time. Bethe likewise found that if 

 medusae (Rhyzostoma) are stained in neutral red, they become orange 

 red in color and if HC1 is then added to the sea-water the orange red 

 does not change to bright red until the tissues are killed. In the 

 meantime, loss of irritability on the part of the muscles has occurred 

 while the neutral red dye is still orange red in color. In my experience 

 neutral red has always been taken up by cells in a bright-red condition, 

 so that acid, if it entered the cell, would produce no further marked 

 color change. I have found it likewise impossible to stain living cells 

 with any other dye which will act as an indicator for acid. 



Plant cells containing blue or purple anthocyan pigments will turn 

 red in acids, and Pfeffer 5 found that purple Tradescantia or Pulmonaria 

 cells become red in an "ausserst verdiinnte" solution of HC1, H 2 SO 4 , 

 and acetic acid, and the purple color returns when the acid is washed 

 out; nor is the cell killed, as protoplasmic rotation also returns. The 

 same result has been obtained by Ruhland. 6 It is difficult to judge 

 of these results because exact molecular concentrations are not given, 

 but they seem opposed to Bethe's experiment on medusae. Plant 

 pigments are difficult to work with for two reasons: (1) The plant cell 

 is usually cuticularized and is not readily wet by the acid solution; 

 (2) anthocyan pigments are not equally sensitive to both weak and 

 strong acids. 



The experiments recorded in this paper were all made with the tissues 

 of a holothurian, Stichopus ananas, the " prickly fish" of the Beche 

 de Mer or Trepang industry. A concentrated solution of dark-red 

 pigment is found in irregular sacs or bodies of unknown nature just 

 under the epithelium of practically all the internal organs. It is 

 especially abundant on the gonads, although the eggs and sperm cells 

 are colorless. Living portions of the testis stained in Schneider's 



'Contributions from the Torres Straits Expedition of the Carnegie Institution of Washington 

 and the Physiological Laboratory of Princeton University. 



2 Journ. Exp. Zool. 10, p. 507, 1911. See also Carnegie Inst. Wash. Pub. No. 183. 

 3 Pfluger's Archiv, 127, p. 261, 1909. 

 4 Zeit. f. Physiol. Chem., 66, p. 305, 1910. 

 6 Osmotische Untersuchungen, p. 140, 1877. 

 Jahrb. f. Wiss. Bot., 46, p. 1, 1908. 



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