AMCEBOID AND CILIARY MOVEMENT 3 



coloured with Scharlach R., and place it gently on the surface of a 

 0*1 per cent, solution of sodium carbonate. Sketch the amoeba-like 

 changes of shape which it undergoes. With stronger solutions of 

 sodium carbonate the drop of oil becomes rapidly vacuolated and 

 tends to break up in an explosive manner. 



2. A globule of mercury is placed in a watch-glass of dilute nitric 

 acid (1 per cent.), (a) Introduce into the fluid near, but not touching, 

 the drop a small crystal of potassium bichromate ; (6) touch the 

 globule with a steel needle. Observe the movements of the mercury. 



Experiments on ciliary movement. 1. In a model consisting of a 

 thick rubber ball from which a flattened, curved rubber tube projects, 

 notice that the tube straightens out or curves over to one side according 

 to the tension of the contents of the ball. This movement, which 

 resembles that of a cilium, is thus produced by variations in tension 

 within the part representing the cell. 



2. In a frog which has just been killed, cut through the attach- 

 ments of the lower jaw and carry the incision down the oesophagus to 

 the stomach. Cut this organ across, seize the cardiac end with forceps, 

 and dissect out the oesophagus together with the pharynx and a part 

 of the mucous membrane of the mouth. Pin out the 03sophagus and 

 pharynx and adjacent parts of the buccal membrane on a flat cork 

 with the inner surface uppermost. Rinse with Ringer's solution. 

 Sprinkle a few grains of charcoal over the buccal end of the preparation, 

 and notice that the charcoal is carried down as far as the stomach by 

 the action of the cilia. In the same way, pieces of cork or wax, or 

 even small flat pieces of heavy materials such as lead, may be passed 

 over the surface. 



3. Effect of temperature on ciliary movement. Fasten with pins 

 two pieces of thread one centimetre apart across the above preparation 

 of oesophagus, and slightly raised above it. Rinse the membrane with 

 ice-cold Ringer solution. Drop a grain of charcoal on the buccal end, 

 and, with a watch, record the number of seconds which the charcoal 

 takes to pass over the interval between the threads. Again rinse the 

 membrane, but this time with warm Ringer (25 C.), and repeat the 

 experiment. Note the difference in time taken to traverse the space 

 marked off by the threads. Lastly, rinse with Ringer heated to 50 C., 

 and repeat the experiment. The ciliated cells are killed at this 

 temperature, and the charcoal is no longer carried along. 



