STUDY OF CILIA IN ACTION. 



35 



effectually the slide must be heated and some sealing-wax melted on to it 

 and allowed to cool. The glass tube is then made hot and applied to the 

 slide, embedding itself as it does so in the sealing-wax. On this put a ring 

 of putty or modelling wax (half an inch in diameter and rising above the 

 glass tube) so as to include the end of the tube. Make a deep notch in the 

 ring opposite the tube. Place a small drop of water within the ring (fig. 36). 



Put a bar from the gill upon a cover-glass in the least possible quantity of 

 sea- water ; invert the cover-glass over the putty ring, and press it gently 

 down. The preparation hangs in a moist chamber within which it can be 

 studied through the cover-glass, and into which gases or vapours can be passed 

 and their effects observed. 



Pass CO-2 through the chamber, and after observing the effect replace it by 

 air (see fig. 37). Repeat with chloroform vapour instead of CO;). 



The movement of cilia. When in motion a cilium is bent quickly 

 over in one direction with a lashing whip-like movement, immediately 

 recovering itself. When vigorous the action is so rapid, and the 

 rhythm so frequent (ten or more times in a second) that it is impossible 

 to follow the motion with the eye. All the cilia upon a ciliated surface 

 are not in action at the same instant, but the movement travels in 



FIG. 37. METHOD OF SUBJECTING A PREPARATION TO A STREAM OF CARBONIC 



ANHYDRIDE. 



b, bottle containing marble and hydrochloric acid ; &', wash-bottle, connected by indiarubber 

 tube, t, with the moist chamber, s. 



waves over the surface. If a cell is detached from the general surface, 

 its cilia continue to act for a while, but at once cease if they are 

 detached from the cell. 



The rhythm is slowed by cold, quickened by warmth, but heat 

 beyond a certain point kills the cells. The movement will continue 

 for some time in water deprived of oxygen. Both C0 2 gas and chloro- 

 form vapour arrest the action, but it recommences on restoring air. 



