GRAPHIC REGISTRATION OF MUSCULAR CONTRACTION 53 



the needle of this instrument. The above results clearly show that 

 the curare has destroyed the connection between the nerve and the 

 muscle substance. In other words, this agent has paralyzed the 

 motor plate, so that the centrifugal impulses can no longer reach 

 their destination. On the side on which the curare has been prevented 

 from producing its characteristic effect by the ligature, the impulses 

 pursue as before a perfectly straight course into the muscle. The latter 

 fact may also be demonstrated by stimulating the central end of the 

 sciatic nerve on the curarized side. The impulses here generated now 

 travel in a centripetal direction into the cord, whence they attain the 

 opposite gastrocnemius muscle by the sciatic nerve of the non-cura- 

 rized side. Clearly, therefore, the normal muscle may also be stimu- 

 lated reflexly. 



The chief conclusion to be derived from this experiment, is this: 

 Inasmuch as the nervous elements in the muscle have been rendered 

 functionally useless by the curare without destroying the susceptibility 

 of the muscle substance to direct stimulation, it must necessarily 

 follow that the myoplasm is independently irritable. In other words, 

 normal myoplasm is capable of receiving stimuli and of reacting even 

 without the aid of nervous tissue. This conclusion may be substan- 

 tiated by other facts. Thus it has been observed that the hearts of 

 embryos possess rhythmical activity long before any nerve tissue can 

 be recognized within them. Moreover, if the motor nerve of a 

 muscle is cut, it undergoes degenerative changes and finally becomes 

 functionally useless. At this time, however, it is still receptive to direct 

 stimulation. Ktihne, moreover, has observed that the sartorius 

 muscle of the frog reacts even if stimulated at its very end, in spite 

 of the fact that its ends are devoid of nerve fibers. In addition, Schiff 

 has shown that dying muscle reacts toward mechanical impacts by 

 a local contraction, i.e., the fibers near the seat of the irritation are 

 drawn together into a nodular swelling. 



CHAPTER IV 



THE GRAPHIC REGISTRATION OF MUSCULAR CONTRACTION 

 METHODS OF STIMULATION OF MUSCLE AND NERVE 



A. Muscle-nerve Preparation. — While no serious objection can 

 be raised against the use of almost any muscle, our knowledge regard- 

 ing the behavior of this tissue has been gathered chiefly from prepara- 

 tions of the gastrocnemius and sartorius muscles of the frog, owing to 

 the relative ease with which they may be isolated and rendered ac- 

 cessible to the recording apparatus. It is also true that the muscles 

 of cold-blooded animals retain their irritability after their removal from 



