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HANDBOOK OF PHYSIOLOGY. 



dyles of the femur. The femur is now fixed to a board covered with cork, 

 and the ligature attached to the tendon is tied to the upright of a piece of 

 metal bent at right angles (fig. 825, B) , which is capable of movement about a 

 pivot at its knee, the horizontal portion carrying a writing lever (myograph). 

 When the muscle contracts, the lever is raised. It is necessary to attach a 

 small weight to the lever. In this arrangement the muscle is in situ, and the 

 nerve disturbed from its relations as little as possible. 



The muscle may, however, be detached from the body with the lower end of 

 the femur irom which it arises, and the nerve going to it may be taken away 

 with it. The femur is divided at about the lower third. The bone is held in a 

 firm clamp, the nerve is placed upon two electrodes connected with an induc- 

 tion apparatus, and the lower end of the muscle is connected by means of a 

 ligature attached to its tendon with a lever which can write on a recording 

 apparatus. 



To prevent evaporation this so-called nerve-muscle preparation is placed under 



Fi;*. 327. Simple form of pendulum myograph and accessory parts. A, Pivot upon which 

 pendulum swings: B, catch on lower end of myograph opening the key, C, in its swing: U, a 

 spring-catch which retains myograph, as indicated by dotted lines, and on pressing down the 

 handle of which the pendulum swings along the arc to D on the left of figure, and is caught by 

 its spring. 



a glass shade (moist chamber, fig. 32(5), the air in which is kept moist by means 

 of blotting paper saturated with saline solution. 



Effects of a Single Induction Shock. With a nerve-muscle preparation 

 arranged in either of the above ways, on closing or opening the key in the pri- 

 mary circuit, we obtain and can record a contraction, and if we use the clock 

 work apparatus revolving rapidly, a curve is traced such as is shown in fig. o-io 



Another way of recording the contraction is by the use of the pendulum 

 myograph (fig. 327). Here the movement of the pendulum along a certain arc- 

 is substituted for the clockwork movement of the other apparatus. The pen- 



