456 



W. J. CKOZIER 



kind has been made possible by the discovery of intracellular 

 indicators sensitive toward acids (Harvey, '14 b, Crozier, '15). 

 Measurements of cell p.enetration by acids show, so far as 

 concerns the present problem: 1) that both acetic and hydro- 

 chloric acids are able to penetrate the cell; 2) other things being 



100 



ZOO 300 400 500 600 



Dilution 

 (Liters containing one equivalent) 



Fig. 1 The average time of penetration of cells by hydrochloric, butyric, 

 and acetic acids. 



1, Acetic acid ] 



3, Butyric acid \ integument of Chromodoris zebra, a nudibranch. 

 5, Hydrochloric acid 



2, Butyric acid 



4. Hydrocloric acid 



1, 3, 5, from Crozier ('16), at 27°. 



2, 4, from Harvey ('14 c), at 28°. 



Butyric acid is introduced for comparison, since Harvey (loc. cit.) gives no 

 data for dilutions of acetic; the principle is the same for both these acids. It 

 should be noted that in Harvey's experiments the acid was dissolved in a balanced 

 salt solution, in mine in distilled water. 



testis epithelium of Stichopus ananus, a holothurij 



