The Mechanism of Ciliary Movement. 



Ill 



The comparative efficiency of ammonia and sodium hydroxide is also 

 seen from the following experiment. Fragments, after previous acid treat- 

 ment, were transferred to sea-water whose alkalinity had been raised to a 

 known value by jSTaOH and by ]STH 4 OH. 



Ph. 



Time in minutes for full recovery in 



NH 4 OH. 



jSTaOH. 



9-5 



2 



5 



9-2 



1 

 2 



7 



9-0 



2 



8 



8-7 



1 



8-10 



8-5 



3 



10-12 



8-4 



5 



12-15 



The above figures all apply to fragments of the same gill after precisely 

 the same acid treatment. The experiment was repeated several times with 

 identical results. 



It is therefore clear that the weak acids which enter the cell are more 

 efficient inhibitors of ciliary movement than are the strong acids which do not 

 enter readily, and conversely the weak alkalies are much more efficient restoratives 

 than the strong alkcdies. 



It is impossible to accept the suggestion that the normal activity of the 

 ciliated cells is upset by acids owing to a disturbance of the cell surface. 

 The physiological effects of both acids and alkalies depend upon the ease 

 with which these reagents penetrate to the cell interior. It may be noted 

 that another series of experiments showed that the presence of neutral 

 electrolytes in external medium has but little effect upon the efficiency 

 of either acids or alkalies. 



It is important to note that the cilia come to rest in an acid solution by a 

 gradual diminution in the rate of the vmole beat, without any reduction in its 

 amplitude. Both the effective and the recovery strokes become slower, and 

 there is often a marked pause at the beginning and end of each stroke, 

 so that a complete beat may take as long as 10 seconds. It is difficult 

 to imagine how this could occur where there is actual derangement of the 

 contractile elements — since we would expect such to be attended by a 

 gradual reduction in the amplitude of the beat. 



Again, the cilia invariably come to rest at the end of the effective stroke ; 

 that is, in that position in which the cilium itself possesses no available 

 potential energy. 



Interesting evidence is available from a study of spermatozoa which are 



