CYTOLOGY 



31 



drop are more readily focused with a high-power objective; (2) if 

 the drop is small, vapors penetrate more readily to the organisms. 

 Focus upon the drop through 



the cover-glass. If you find FIG. 10 



active protozoa, study their 

 movements and note the de- 

 gree of activity of these move- 

 ments. 



Prepare a little roll of ab- 

 sorbent cotton about as large 

 as a pea, saturate it with 50 

 per cent, alcohol and place 

 it in the bottom of the cell, 

 at one side in order not to 

 interrupt the light. 



Replace the cover-glass 

 and focus again upon the or- 

 ganisms which you studied 

 a few moments before. Note 

 carefully whether or not 

 there is any change of ac- 

 tivity; if so, describe min- 

 utely what you have ob- 

 served. 



(6) If a change in activity 

 is noticed, remove the cover- 

 glass, expose it to the air for 

 two or three minutes, then 

 invert it over a clean, dry 

 cell, and note whether there 

 is a partial or complete return 

 to the normal activity. 



(7) Repeat this experiment, 

 using fresh protozoa and 

 ether (50 per cent.) instead 

 of alcohol. 



(8) Repeat, using dilute ammonia or oil of peppermint. 



Vorticella. A, expanded condition; n, nucleus; Vc, 

 vacuole; w, peristome; Vs, vestibule; g, gemma; 

 p, pedicle; B, contracted condition. The pedicle is 

 thrown into a spiral coil, drawing the body to the 

 point of attachment. 



IV. NORMAL CILIARY MOTION. 



1. Appliances. Microscope, cell slide, and cover-glass; physio- 

 logical operating case (see Appendix, 3); normal saline solution; 

 frog or clam; camel's-hair brush or absorbent cotton; frog board 

 (see Appendix, 2) and cork board. 



2. Preparation. To Pith a Frog. (1) Grasp it with the left hand, 

 holding the legs extended, one on either side of the little finger, in 



