MUSCLE AND NERVE 



33 



nemius is then cut across and the muscle peeled off from the bones of 

 the leg. Next the latter are cut across near the knee-joint and dis- 

 carded, together with the foot. A thread is then tied around the end 

 of the tendon and connected with the writing lever near its center of 

 rotation. Below the tendon a slight weight is attached which is pre- 

 vented from extending the muscle by an after-loading device. The 

 electrodes are adjusted upon the upper part of the muscle (Fig. 11). 



The recording surface is formed by a sheet of glazed paper which 

 has been firmly attached to the surface of the cylinder of a kymograph 

 and has been covered with a thin layer of soot. The smoking of the 

 drum is accomplished most conveniently by suspending it in a smoking 

 rack. The drum is then revolved at the rate of about once in every 



FIG. 11. A METHOD USED TO REGISTER MUSCULAR CONTRACTION. 

 St, Stand for holding of clamp C and writing lever WL. The muscle M is attached to 

 the lever by means of a small hook and string. The lever carries weight W. The stimula- 

 tion is effected through the electrodes, S. The speed of the kymograph K may be varied 

 by fan F. 



second, while a broad gas flame is held directly underneath with its 

 outer yellow zone barely touching the paper. Smoke the paper from 

 left to right, remaining in the same place until an even brown surface 

 has been produced. Never cease rotating the drum while the flame is 

 directed against the paper, and do not overheat the latter, otherwise a 

 burned gray surface will be obtained. When properly smoked, the 

 paper should possess a velvety, chocolate-brown color (Fig. 12). 



Replace the drum upon the rotating disk of the kymograph. Adjust 

 the writing lever with the least possible friction upon the paper, and 

 take care that it writes as a tangent upon a sphere and in a straight 

 vertical line. The writing lever is provided with an after-loading device 

 consisting, as a rule, of a screw-support by means of which the lever 



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