78 FACTORS AFFECTING CILIARY ACTIVITY 



information available on both beating activity and co-ordination, 

 which together make up the total ciliary activity. 



Many methods of measuring the activity of cilia have been used 

 during the last 100 years; most of these have been based on 

 measurements of the rate of doing work by the cilia, while others 

 depend on direct observations of the movements of the cilia. The 

 earlier methods have been reviewed by Gray (1928), Lucas (1932a) 

 and Nomura and Tomita (1933). Direct microscopic observation 

 with a subjective estimate of the amount of movement, in such 

 terms as " fast," " slow " or "stopped," is the first stage in most 

 investigations, and almost all workers have moved on to estimate 

 the mechanical activity of cilia. The most frequent method 

 employed for this is the measurement of the speed of movement of 

 particles of carmine, carbon or similar material (e.g. Gray, 1923, 

 and many others), of a small platinum plate (Gray, 1923), or of 

 small squares of filter paper (Parker, 1905) over the surface of a 

 ciliated epithelium. Several workers have constructed more 

 complicated devices in which they measured the rate of rotation 

 of a small cylinder (usually of glass) which was held in contact 

 with a cihated epithelium (e.g. Engelmann, 1877; Inchley, 1921). 

 In some cases it is possible to measure the rate of movement of 

 water by cilia or flagella, as in some sponges (Parker, 1914), 

 ascidians (Hecht, 1916) or kidney tubules (White, 1929). The 

 rate of movement of spermatozoa and of small ciliated or flagellated 

 organisms such as protozoa, rotifers, small flatworms and snails 

 has sometimes been used, while in much the same class comes the 

 method of Nomura and Tomita (1933) in which they measured 

 the rate of crawl of a small piece of gill lamina of a lamellibranch 

 mollusc. 



Numerical data available by these methods are usually less 

 valuable than measurements of the frequency of beat of the cilia. 

 Few cilia beat slowly enough at normal temperatures for their 

 movements to be followed by eye and counted, but two methods 

 of observing faster cilia have been used with success. The 

 stroboscope was used in studying the movement of cilia in the 

 1880's by several workers including Martins (1884); its employ- 



ent was further exploited by Gray (1930), who gives a valuable 

 account of the theory of this use of the stroboscope. This 

 apparatus can be used only on cilia which beat more than 8 or 10 



