124 FACTORS AFFECTING CILIARY ACTIVITY 



In no case can we be certain of the means by which the control 

 of ciUa is exerted. The suggested activation mechanism of lateral 

 cilia of Mytilus by serotonin is perhaps the nearest so far, although 

 we do not know how serotonin may act on the ciliary mechanism. 

 Electrical and membrane effects on the reversal of protozoan 

 cilia may also be useful clues to the methods of control, but here 

 again we have not yet got to the roots of the problem (see pp. 93 

 and 195). 



13. Microdissection Studies on Ciliated Tissues 



The technique of microdissection has been used in several ways 

 in the study of ciliary activity. Most commonly it has been 

 employed in experiments on the co-ordination of cilia, in order to 

 find out if conduction was upset by cuts into the cells carrying the 

 cilia. Similar experiments have been carried out to find out how 

 much of the cell is necessary to maintain the beat of the cilia, 

 and to determine whether the normal polarity of beat can be 

 changed by re-orientation of the tissues carrying the cilia. 



Verworn (1889) observed that a single cilium that had been 

 isolated with a small piece of its basal cytoplasm was capable of 

 continued beating, and Lepsi (1926) removed the cytoplasm of 

 Glaucoma to leave an empty pellicle on which the cilia continued 

 to beat for a short time. From these findings it appears that only 

 part of the cell is necessary for beating activity. 



Rather more refined studies were made by Worley (1941) on 

 the epithelial cells of the intestine of some lamellibranch molluscs. 

 He cut across the cells parallel to the ciliated surface at various 

 levels in order to find the effect on beating and co-ordination. 

 While cuts through, or immediately below, the basal bodies 

 resulted in a complete stoppage of beating, cuts at deeper levels 

 allowed the beating to continue, but prevented normal co- 

 ordination unless the cuts were internal to the nucleus and ciliary 

 roots. 



Cuts through a row of cilia at right angles to the surface were 

 found by Verworn (1889) to interrupt the metachronal co-ordina- 

 tion of the cilia in the row, e.g. the membranelles of Stentor, 

 Spirostomum and Euplotes. Coonfield (1934) found a similar state 

 of affairs in Mneniiopsis. More recently it has been shown (Sleigh, 

 1957) that a cut across the membranelle row of Stentor prevents 



