RATE OF THE NERVE IMPULSE 533 



30 C. automatic contractions will sometimes occur in it. Smooth muscle 

 responds like voluntary muscle to variations in temperature, to fatigue, 

 strength of stimulus, etc., etc. 



1 6. Ciliary Contractions. Ciliated Epithelium. Make a preparation 

 of ciliated epithelium by cutting out the esophagus of a terrapin or frog, 

 slitting it open longitudinally, and smoothing it out on a cork block. The 

 cilia of this membrane will drive in the direction down the esophagus. Test 

 the rate at which different loads are moved and measure the distance on the 

 preparation as follows: Cut pieces of clean white paper about 4 and 6 mm. 

 square. Select a favorable area on the ciliated surface as long as possible, 

 place the 4 mm. square paper at the beginning of the area, and measure the 

 time which it takes to travel the distance. Measure the speed in terms of 

 seconds per centimeter. Now replace the paper at the point of beginning 

 and load it with small weighed cubes of paraffin. The rate at which the 

 load is carried will slightly increase at first as the load is increased, but later 

 will sharply decrease. Elevate one end of the ciliated membrane and repeat 

 the experiment with different loads so that the cilia will now carry the load 

 uphill. Calculate the work done in terms of gramcentimeters of work per 

 square centimeter of ciliated surface acting on the load. 



17. Rate of the Nerve Impulse. Prepare a muscle-nerve with the 

 entire sciatic nerve. Sever the nerve where it leaves the cord, leaving it 

 attached to the fascia. Mount in a moist chamber using two electrodes. 

 Set one pair of electrodes on the nerve as near the muscle as possible, the 

 other at the extreme end of the sciatic. Take several pairs of simple muscle 

 contractions on the pendulum myograph stimulating, i, the long nerve, and, 

 2, the short nerve length. The difference in the time of the two latent 

 periods of each pair represents the time required for the nerve length between 

 the two pairs of electrodes. Compute the rate of the nerve impulse in meters 

 per second. Make a table of all the tests recorded and draw averages. 



