494 MUSCLE-NERVE PHYSIOLOGY 



that side. Now inject under the skin of the back three drops of i per cent 

 curara, allowing twenty to thirty minutes for absorption. When the drug 

 is completely absorbed, make the following observations: 



a. Stimulate the muscles of the ligatured leg, also the muscles of the cura- 

 rized leg, both will contract. 



b. Stimulate the sciatic nerve of the ligated leg below the ligature where 

 it has not come in contact with the curara; also the sciatic of the opposite 

 side, which has come in contact with the curara. Stimulation of the first 

 nerve produces contraction of its muscle; of the second nerve does not pro- 

 duce 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. 



5. The Simple Muscle Contraction. Striated muscle responds to 

 electrical stimuli even of almost instantaneous duration. The response which 

 the muscle gives to a single stimulus is called a simple muscle contraction, 

 and is demonstrated as follows: 



Make a muscle-nerve preparation with the tendon isolated and the skin 

 removed, and mount it in a moist chamber, figure 350. Connect the tendon 



FIG. 350. Moist Chamber. 



with a recording lever by short copper-wire hooks. Lay the nerve across a 

 pair of platinum electrodes, shake a little water on the sides of the cover of 

 the moist chamber, and place it over the preparation so as to prevent drying of 

 the nerve and of the muscle. Arrange an induction coil with its keys, battery, 



