XXXIX.] ELASTICITY AND EXTENSIBILITY OF MUSCLE. 217 



is not directly proportional to the weight, but diminishes as the 



weights increase (fig. 138). 



(c.) Repeat the same experiment with a strip of india-rubber. 



In this case equal increments of weight give an equal elongation, 

 so that a line joining the apices 

 of the vertical lines drawn 

 after each weight is a straiylit 

 line (fig. 139). 



2. The Extensibility of 

 Muscle is Increased during 

 Contraction, its Elasticity is 



FIG. 138. Curve of Diminished. FIG. x 39 . Curve of 



Elasticity of a Frogs (a) ^ ^ gastrocnein i us _ Btidty of India- 



or preferably semi-membranosus 



and gracilis in a strong clamp, connecting it to a lever to record 

 on a drum, and adjust an interrupted current to stimulate the 

 muscle, either directly or indirectly. 



(b.) Load the lever with 50 grams, and in doing so allow the 

 drum to move slowly. Remove the load and observe the curve 

 obtained. 



(c.) Tetanise the muscle, and, while it is contracted to its greatest 

 extent, again load the lever with 50 grams while the drum is in 

 motion, and remove the load. Observe the curve. 



(d.) Compare the two curves. The second curve will, of course, 

 begin higher, but notice that its absolute descent is greater than 

 the first curve, and that it does not rise to the horizontal again. 



(e.) It is better to begin the experiment with the drum stationary, 

 and then to record the tracing with the drum in motion, or it may 

 be done with a stationary drum. 



3. Blix's Myograph. Although this myograph was described 

 many years ago, it seems to be but little used in this country. 

 Personally, 1 am indebted to Prof. Fick of Wiirzburg for his 

 kindness in showing it to me. By means of it one can readily 

 record the curve of extensibility of a passive or an active muscle. 

 The following summary is based on the description given by 

 Schenk. 



In the myograph (fig. 140) the muscle-clamp and the part to which the 

 steel lever is attached form a rectangular piece, S S, which glides in a slot 

 formed by the guides, R R and R' R'. The slider, S S, carries at a the axis of 

 the lever a b, and also a lateral piece, A, placed at right angles for the attach- 

 ment of the muscle, and one end of which is fixed to the lever at b. The 

 weight is represented by P, which by means of the collar, r, presses on the 

 lever. This collar, r, moves to and fro not from side to side between two 

 pairs of fixed studs, 1 1 and ^ ^. 



