CILIAEY MOVEMENTS. 441 



seventy-five to one hundred and fifty per minute. In the 

 fresh water polyp the movements are more rapid, being from 

 two hundred and fifty to three hundred per minute. 1 There 

 is no reliable estimate of the rapidity of the ciliary currents 

 in man, but they are probably more active than in animals 

 low in the scale. a 



The movements of cilia, like those observed in fully de- 

 veloped spermatozoids, seem to be entirely independent of 

 nervous influence, and are affected only by purely local con- 

 ditions. They will continue, under favorable circumstances, 

 for more than twenty-four hours after death, and can be seen 

 in cells entirely detached from the body when they are moist- 

 ened with proper fluids. Beclard states that in the tortoise, 

 the movement may be preserved for several weeks after the 

 death of the animal. 3 When the cells are moistened with 

 pure water, the activity of the movement is at first increased ; 

 but it soon disappears as the cells become swollen. Acids 

 arrest the movement, but it may be excited by feeble alka- 

 line solutions. All abnormal conditions have a tendency 

 either to retard or to abridge the duration of the ciliary mo- 

 tion. It is true that when the movement is becoming feeble, 

 it may be temporarily restored by very dilute alkaline solu- 

 tions, but the ordinary stimuli, such as are capable of exciting 

 muscular contraction, are without effect. Purkinje and 

 Valentin, Sharpey, and others have attempted to excite 

 the movements of cilia by galvanic stimulus, but without 

 success. 4 Anaesthetics and narcotics, which have such a 

 decided effect upon muscular action, have no influence upon 

 the cilia. 



It is useless to follow the speculations that have been 



1 BECLARD, Traite elementaire de physiologic, Paris, 1859, p. 498. 



8 A pupil of M. Bernard, M. Calliburces, has devised a very ingenious in- 

 strument for measuring the rapidity of the ciliary motion (BERNARD, Lemons sur 

 les proprietes &s tissus vivants, Paris, 1866, p. 139, et seg.). 



3 Zoo. cit. 



4 SHARPEY, Cyclopaedia of Anatomy and Physiology, London, 1835-'36, vol. i., 

 p. 634, Article, Cilia. 



