MUSCLE-NERVE PHYSIOLOGY 



b. Stimulate the sciatic nerve of the ligated leg above the ligature; 

 also the sciatic of the opposite side, both of which have come in contact 

 with the curara. Stimulation of the first nerve produces contraction of its 

 muscle; of the second nerve does not produce contraction of its muscle. 



From this experiment of Claude Bernard's it is evident that the curara 

 does not destroy the irritability of nerve fiber nor the irritability of the 

 muscle fiber, yet it does destroy the influence of the nerve over the muscle, 

 probably acting as a specific poison for the motor end-plates. If the motor 

 end-plates are destroyed, then forms of stimuli which produce contractions 

 of the muscle must act directly on muscle substance, proving that muscle 

 substance, as such, is irritable. 



FIG. 351. Moist Chamber. 



6. The Relation of the Contraction to the Strength of the Stimu- 

 lus. Minimal and Maximal Stimuli. a. Prepare a recording cylinder for 

 making vertical records of the contractions. Adjust the writing point of the 

 muscle lever to the drum and set the drum to be moved by hand i cm. after 

 each succeeding contraction. Set the secondary coil of the induction ap- 

 paratus so that it will be too weak to produce a stimulus. 



b. Prepare a muscle nerve of the frog and mount in the moist chamber 

 and arrange for stimulating the muscle directly by means of the secondary 

 current of the induction coil, stimulating apparatus adjusted as in fig. 350. 



c. Now attempt to stimulate the muscle, then move the induction coil 

 toward the primary i cm. at a time and repeat until the first slight contraction 

 appears. Continue to slide the secondary coil toward the primary, stimulate 

 at each new position, moving the drum forward for each stimulus as directed, 

 until a series of contractions is obtained through the range of variation of 

 induction of which the apparatus is capable, usually twenty or thirty con- 

 tractions. 



