128 



Mr. J. Gray. 



against the erosive power of potassium, whereas calcium has a well-marked 

 action. It is conceivable that this fact may ultimately be correlated with 

 the observation that calcium and potassium are mutually inhibitory in the 

 case of certain tissues ; also, if tbe cell surface be normally maintained by 

 magnesium, then it is possible that potassium may be able to penetrate 

 under normal conditions whereas sodium does not. 



Since we can control the destructive effects of the monovalent salts by 

 means of magnesium and calcium, it is interesting to note that the direct 

 action of the different monovalent ions upon the ciliary mechanism forms a 

 well-marked series. 



In the following experiment the monovalent salts were present in the 

 molecular concentration of the sodium in normal sea-water ; the divalent 

 salts were in the same concentration as they normally occur in sea-water : — 



Solution. 



Ph. 



Movement of terminal cilia. 



2'. 



5 . 



10'. 



20'. 



30'. 



60'. 



LiCl, MgCl,, CaCL 



7-0 



o 























jS'cCl, MgCL, CaCL 



7-2 



+ + 



+ +• 



+ + 



+ + 



+ + 



+ + 



NH^Cl, MgCL, CaCL. 



7 -0 



+ +© 



+ +6 



+ +S 









KC1, MgCL CaCL 



7 2 



+ + + 



+ + + 



+ + + 



+ + + 



+ + + 



+ + + 



Sea-water (HC1) 



7 2 



+ + 



+ + 



+ + . 



+ + 



+ + 



+ + 



= no moTement. 

 + + = normal rate of beat. 

 + + ^ = quicker than normal. 

 + + + = very rapid beat. 



Apart, therefore, from their action on the cell-wall, the monovalent ions 

 exert a definite effect on the rate of beat of the cilia. The order in which 

 the various ions increase the rate of beat is well marked, and is as follows : — 



Li < Na < NH 4 < K. 



The stoppage of the cilia in the lithium mixture is of the same nature as 

 that observed in acids (Gray (5)), and it is not surprising to find that by 

 raising the alkalinity of the lithium mixture, a rapid and well-maintaiued 

 beat takes place. 



The fact that the presence of potassium induces a more rapid rate of 

 beat than a corresponding amount of sodium enables us to test whether the 

 normal semipermeability of the cell membrane is essential to ciliary activity 

 or not. The experiment can be performed as follows : — Grill fragments are 

 placed in an isotonic solution of sodium citrate until all movement has 

 ceased. Individual pieces are now placed in the following solutions and 

 their behaviour noted. 



