RATE OF THE NERVE IMPULSE 571 



with greatest accuracy and made as long as possible. 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. 



25. Relation of Total Work to Nutrition of Muscle. Pith a frog and 

 pin it prone on a frog board. Isolate one gastrocnemius and measure its 

 total work as in experiment 7. Inject 2 cc. of one per cent, glucose in 

 Ringer into the circulation, or perfuse the heart directly with Ringer's 

 solution containing 0.2 per cent, glucose. Now repeat the measurement 

 of total work on the second gastrocnemius muscle. The experiment will 

 be more striking if the records are made parallel on the same paper with the 

 drum at constant speed. 



Variations of this demonstration can be made by comparing the work 

 of the two muscles of a frog, one while the normal circulation continues, 

 the other with the circulation tied off by ligature around the thigh. 



26. Production of Carbondioxide During Contraction. Prepare a 

 CO2-absorbing apparatus. Charge it with Ringer's solution containing 

 phenolphthalein indicator. Reduce the hydrogen iron content to a 

 constant, as indicated by the color of the solution matched against a 

 pink standard, by aerating with CC>2 free air. Prepare a small muscle 

 and attach it to the holding device. Insert in the apparatus, and accu- 

 rately measure the time until the color of the indicator is just discharged. 

 This measures the rate of CO2 production in the resting muscle. Repeat 

 until the readings are constant. 



Now make the test while stimulating the muscle to a mild tetanus. 

 The apparatus and solution are to be standardized. 



