GRNEKAL PHYSIOLOGY. 21 



filled and ready for action by putting on a screw- 

 clamp at s. Through varying the height ' of the 

 receptacle into which the siphon dips or through ad- 

 justment of the screw clamp or of the spring clamp at 

 d, the pressure and the rate of flow of gas are under 

 perfect control. Prepare a specimen of cilia for ob- 

 servation with a low power microscope. Bring a good 

 specimen into the field, focus the microscope and ob- 

 serve the rate and character of ciliary movement. 

 Remove screw clamp at s. 

 4. Observations. a. The effect of CO 2 upon ciliary activity. 



(1) While observing closely the normal action of the 

 cilia, press the spring clamp gently for a few mo- 

 ments. If after a half minute or more no noticeable 

 change takes place in the rate of movement of the 

 cilia repeat the dose of gas. 



What is the effect of CO 2 gas upon the activity 

 of cilia ? 



(2) After the effect of the gas has become apparent, 

 clamp the tube at//; disjoin at glass tube beyond and 

 gently draw air through the cell, thus ventilating it 

 and restoring practically the normal condition. Do 

 the cilia resume the normal movement ? 



(3) How many times may the cilia be narcotized to 

 the point of complete cessation of activity and then 

 by ventilation be revived again ? 



b. The effect of chloroform gas upon ciliary activity. 



(4) Clamp tube at s ; remove flask from apparatus, fill 

 flask with water to expel CO 2 ; empty ; drop into 

 the flask a pledget of cotton saturated with chloro- 

 form, replace flask as in Fig. 1. Make a new 

 preparation of cilia and observe normal movement. 



Allow the chloroform gas to flow fcr a moment 



