TEMPERATURE 79 



times a second, but is ideal for the examination of regularly 

 beating cilia with a higher frequency of beat, and permits a quick 

 and accurate measurement of the ciliary frequency. 



Valuable results have been obtained with the cine camera by 

 Gray (1930) and Lucas (1932a, b). This method has some 

 advantages and some disadvantages as compared with the strobo- 

 scopic method. If the form of beat of a cilium is to be examined, 

 the speed of the camera must be fast enough for at least ten frames 

 to be exposed in each cycle of beat if an accurate picture is to be 

 obtained. Rather slower speeds may be satisfactory for measure- 

 ments of the frequency and examination of the metachromal 

 waves. The stroboscopic method is valuable because the beating 

 of the cilia can be seen throughout — by suitable adjustment of the 

 speed of the stroboscope the cilia can be made to appear to beat 

 very slowly, so that the form of beat can be examined and the 

 metachronal waves can be studied. It is possible to photograph 

 the " flash-images " seen in the stroboscope, and from the 

 photographs to make a variety of measurements on the cilia and 

 metachronal waves. For experiments on the frequency of beat 

 and metachronism of faster cilia, the combination of stroboscope 

 and single-exposure camera undoubtedly has an advantage over 

 the cine camera in speed and ease, but the cine camera must be 

 used in the examination of slower cilia. The examination of 

 flagellar movement and sperm locomotion is usually very difficult, 

 but a cine camera can sometimes be used. 



These two methods both allow measurement of the actual 

 frequency of ciliary beat. Where the metachronal waves can be 

 clearly seen, the metachronal wavelength can be measured from 

 the films, and the metachronal wave velocity can be calculated 

 (wave velocity is frequency X wavelength). We have thus estimates 

 of both the beating activity and the rate of metachronal wave trans- 

 mission of the cilia. The amplitude of beat can be measured 

 in some cases, so can the angular velocity of the effective stroke, 

 and the speed of propagation of the bending wave along the cilium. 



2. The Effect of Temperature on Ciliary Activity 



The temperature varies quite widely in many environments, 

 and it is usual to find that the rate of a biological process is altered 

 by change in temperature. Ciliary activity is no exception, and 



