140 Papers from the Marine Biological Laboratory at Tortugas. 



It is the purpose of the following paragraphs to indicate how far other 

 functions may be affected by NaOH before it penetrates the cell. It may 

 be stated in advance that every cell activity thus far studied is affected, 

 indeed abolished, before the NaOH enters, while a great many cell activities 

 remain entirely unaffected even after NH4OH has penetrated and turned 

 the neutral red to yellow. 



Evidence showing that the indicator method is an adequate one for 

 detecting the penetration of both strong and weak alkalies has been presented 

 in a previous paper (Amer. Jour. Physiology, vol. 31, 1913). 



EXPERIMENTAL. 

 MUSCLE AND NERVE TISSUE. 



Cassiopea xamachana. 



The only experiments on the permeability of the cells of medusae of 

 which I am aware are those of Bethe, cited above. 



The method of experimentation with Cassiopea, a scyphomedusa well 

 adapted for physiological investigation, was the same as that previously 

 used in studying the effect of temperature on the muscular contraction and 

 nerve conduction.^' The method was originally described by Mayer.^^ 

 A long strip of tissue cut from the disk of the jelly-fish is laid across three 

 dishes (a, b, and c, fig. i). Dishes a and c are filled with sea-water. Dish 



Fig. I. 



B is filled with the alkali solution to be tested. Stimuli are constantly 

 arising in the sense-organs in dish A and pass along the nerve-network of 

 the strip of tissue toward c, stimulating the muscles as they go. When the 

 nerves are so affected by the alkali in b that they no longer conduct a 

 stimulus, the muscle in c will no longer contract. In the case of some al- 

 kalies, acids, and most other substances, the muscles in b are affected before 

 the nerves. The time required to stop contraction can be determined by 

 mere inspection, since the muscles are being constantly stimulated by 

 nervous impulses carried from the sense-organs in A. 



In the case of certain of the alkalies, the nerves in b are affected before 

 the muscles. We may then determine by direct stimulation of the muscles 

 in b with the electric current when they have been so far affected as to cease 

 contracting. 



Entrance of alkali is of course detected by the color change of neutral 

 red. 



» Harvey, E. N. Carnegie Institution of Washington, Pub. No. 132, p. 27. 1911. 

 ^ Mayer, A. G. Carnegie Institution of Washington, Pub. No. 102, p. 128. 1908. 



