Mr Gray, The Effect of Ions on Ciliary Motion 313 



The Effect of Ions on Ciliary Motion. By J. Gray, M.A., 

 Fellow of King's College, Cambridge. 



[Read 10 November 1919.] 



The ciliary mechanism of the gills of Mytilus edidis has been 

 described by Orton^. There are at least four distinct sets of cilia. 

 . whose movements form a complex but highly coordinated system 

 by which food particles are filtered from the sea-water and passed 

 up to the mouth. This coordinated system is entirely free from 

 any nervous control and continues for many days in detached 

 portions of the gill. These gill fragments therefore form an 

 admirable material for the physiological study of ciliary motion. 



The effect of the hydrogen ion on ciliary action is very easily 

 studied. Normal sea- water has a Ph of about 7-8; when the con- 

 centration of hydrogen ions is increased to about 6-5 rapid cessation 

 of movement occurs. In sea-water of Ph 6-7 the rate of ciliary 

 movement is checked at first, but within f-l| hours complete 

 recovery takes place. If gill fragments whose cilia have been 

 stopped by the more acid solution are returned to normal sea- 

 water, complete recovery takes place in less than 20 minutes 

 although the cilia may have been motionless for several hours. 

 A large number of experiments have been performed from which 

 it is clear that if the concentration of hydrogen ions is only slightly 

 greater than normal, the cells can react to the environment and 

 recovery take place in the acid solution. In stronger acid, however, 

 recovery only takes place on removing the gills to a more alkaline 

 solution. In still stronger acid the cells become opaque and are 

 killed. 



Gills which are exposed to an abnormally high concentration 

 of hydroxyl ions behave in a remarkable manner. In such solu- 

 tions ciliary action is either not affected at all or proceeds at 

 an abnormally rapid rate, but the individual cells of the ciliated 

 epithelia break away from each other and move about in the 

 solution owing to the movement of their cilia. Since such cells 

 are no longer in their normal environment, it is impossible to 

 determine any upper limit of hydroxyl ions which will permit 

 normal ciliary action to go on. 



Since the hydrogen ion has a most marked effect on ciliary 

 activity,. it is necessary to adjust the hydrogen ion concentration 

 of all artificial solutions during a study of the effects of various 

 salts on ciliary action. In the case of the salts of the alkali metals 

 this is satisfactorily performed by the addition of an appropriate 



1 Journ. Marine Biol. Assoc, vol. ix, p. 444 (1912). 



