98 FACTORS AFFECTING CILIARY ACTIVITY 



below 5 '8, but retain motility for several hours at pH up to 9 -5 or 

 10; alkali may be used to restore motility to spermatozoa stopped 

 by acid, provided the exposure to acid is short. 



The difficulties of studying the effects of other ions on ciliary 

 activity have been emphasized by Gray (1928). Many ionic 

 changes upset the stability of the ciliated epithelium and may lead 

 to breakdown of the intercellular matrix, so that only changes 

 which aifect the ciliary mechanism without damage to the 

 epithelium are of interest here. Also, most media contain a 

 complex balance of ions, and it is difficult to make changes which 

 do not upset the whole balance. Thus it is not enough simply to 

 remove one type of ion completely, for this may upset the osmotic 

 equilibrium, while, if one ion is replaced by another, it is difficult 

 to decide whether the changes which result are caused by the 

 lack of one ion or the excess of the other. Many of the earlier 

 workers were not sufficiently cautious about these things, e.g. 

 Gray (1928) attributes most of the eifects of anions on ciliated 

 tissues reported by Lillie (1904) to effects on tissue stability and 

 not on the cilia themselves. 



Ciliary activity of Mytilus gill is largely unaffected by changes in 

 the concentration of anions, provided that the normal balance of 

 cations is maintained in the medium. Gray (1922b) made up 

 artificial sea waters in which the normal balance of Na+, K+, Ca++, 

 and Mg++, was provided, but in which only one anion was 

 present. Frontal cilia of Mytilus gills beat normally in such media 

 containing only one of the following: Cl~, NOg", I~, Br~, 

 CHgCOO", and SO4 — , but not in tartrate and citrate. The 

 divalent metals form unionized salts with these last two anions, so 

 that they effectively destroy the cation balance of the medium. The 

 cilia of protozoa seem to show a similar indifference to the relative 

 concentrations of anions. 



Studies on the effects of cations on protozoan cilia have mainly 

 centred around the reversal of the ciliary beat of the body cilia 

 of some ciliates; we have already seen (p. 90) that this is closely 

 bound up with membrane potential. Merton (1923) found that a 

 sudden increase in the concentrations of Na+ or K+ induced 

 reversed swimming in Steiitor, while similar increases of Ca++ or 

 Mg++ did not. Investigations on Paramecium by Mast and 

 Nadler (1926) and Oliphant (1938) both showed that the mono- 



