84 



FACTORS AFFECTING CILIARY ACTIVITY 



frequency, metachronal wavelength and metachronal w^ave 

 velocity found in an experiment where the viscosity of the medium 

 was increased with methyl cellulose in the range up to 3*56 cP. 

 The primary effect of an increase in viscosity seems to be to slow 

 the movements of the cilia through the medium, so that the 

 frequency is decreased and the wavelength is increased, while the 

 wave velocity remains unchanged. 



Aiello (1960) has obtained similar results on the lateral cilia of 

 Mytilus gills, although at higher viscosities the metachronal wave 

 velocity shows a slight increase in average value. In experiments 



Table 6. The effect of small increases in viscosity on frequency, 



metachronal wave velocity and metachronal wavelength of 



Stentor membranelles (From Sleigh, 1956a) 



on the cilia of Modiolus and Mytilus, Gosselin (1958) used 

 polyacrylamide as the viscous agent and found that viscosities up 

 to 15 cP did not affect the frequency, or else stopped the beat 

 completely, while the metachronal wavelength and metachronal 

 wave velocity were markedly increased and the amplitude 

 consistently reduced. 



The disagreement between these findings and the results 

 quoted in Table 6 seems to have been solved by some experiments 

 (Sleigh, 1961) on the effect of higher viscosities on Stentor 

 membranelles. The results of these experiments are shown in 

 Fig. 20. The changes of metachronal wave velocity do not differ 

 significantly from zero at lower viscosities, while the frequency 

 decreases steadily, until, at a viscosity of about 3-5cP, both 

 frequency and wave velocity curves turn upwards, indicating small 

 decreases of frequency and very large increases of wave velocity 

 of up to about 100 per cent. Since the frequency is slightly lower 



