120 FACTORS AFFECTING CILIARY ACTIVITY 



(c) Miscellaneous chemicals. Several substances which affect the 

 action of cilia by their interference w^ith the energy supply to the 

 cilia have been mentioned earlier, as have the effects of acids, 

 alkalis and ions. The effects of methacholine (methyl ACh) and 

 camphor are show^n in Table 1 1 . Camphor seems to act directly 

 on the ciliary mechanism, according to Ishikawa and Ohzono 

 (1931), who found that the acceleration effect of ACh was inhibited 

 by atropine, but if camphor was then added the cilia were again 

 accelerated. Rajapurkar and Panjwani (1961) have found that 

 diacetylmonoxime depresses the activity of oesophagus cilia of 

 the frog at concentrations above 10~^ g/iril. 



12. Control of Ciliary Activity by the Organism 



Three types of ciliary organization have been described by Gray 

 (1928) on the basis of the way in which the cilia may be controlled. 

 Firstly, there are cilia which appear to lack any form of external 

 control and are normally in a state of continuous activity. Secondly, 

 some cilia may be controlled by activation; these are normally 

 inactive or beating feebly and are controlled by excitatory stimuli. 

 Lastly, many cilia may be under inhibitory control; these cilia are 

 normally active, but may be stopped by inhibitory stimuli. The 

 inhibitory or excitatory control is usually independent of any 

 metachronal co-ordination, since it may spread over an entire 

 ciliated area almost instantaneously, travelling much faster than the 

 metachronal waves. Where control exists, it influences the whole 

 activity of the group of cilia, so that inhibition stops the movement 

 of all the cilia, while activation may increase both the rate of beat 

 and the rate of metachronal co-ordination. 



It is not surprising that organisms have found it necessary to 

 control cilia which are used for locomotion and some other vital 

 activities. In protozoa the body cilia of a ciliate like Paramecium 

 appear to be in continuous movement, but two examples of 

 control are well known. When Paramecium performs an avoiding 

 reaction, as a result of a chemical or physical stimulus, for example, 

 the cilia are reversed for a few moments and then return to their 

 normal beating activity. The activity of the main body ciliature 

 may thus be modified in response to a stimulus. Jennings (1931) 

 has also described thigmotactic inhibition of cilia of Paramecium, 

 in which all the body cilia may cease activity when the animal 

 comes to rest in contact witft some solid body. The membranelles 



