MYOGRAM OR MUSCLE-CURVE. 



974 



its movements on a stationary glass plate, so that the muscle merely makes a vertical line or 

 ordinate instead of a curve ; it thus merely indicates the height or extent of the contraction, 

 not its duration.] 



A rapidly rotating disc was used by Valentin and Rosenthal for registering the muscle- 

 curve, while Harless used a plate which was 

 allowed to fall rapidly, the so-called " Fall- 

 myograph." In all these experiments it is 

 necessary to indicate at the same time the 

 moment of stimulation. 



Contraction Curve of Human Muscle. 

 In man, another principle is adopted, 

 viz., to measure the increase in thickness 

 during the contraction, either by means 

 of a lever or a compressible tambour, such 

 as is used in Brondgeest's pansphygmo- 

 graph (fig. 36). [The thickening of the 

 adductor muscles of the thumb may be 

 registered by means of Marey's pince 

 myographiquej 



I. Simple Contraction. If a single 



shock or stimulus of momentary duration be 



applied to a muscle, a " simple muscular 



contraction " [or shortly, a contraction or 



twitch] is the result, i.e., the muscle 



rapidly shortens and quickly returns a^ain . 



. r ; . J , , j 1 ,. J ,. & Scheme of 



to its original relaxed condition. 



Myogram or Muscle-Curve. Suppose 



a single stimulus be applied to a muscle 



attached to a light writing-lever, which 



is not " overweighted " with any weight 



Fig. 322. 



the arrangement of the pendulum 

 myograph. B, battery ; I, primary, II, 

 secondary spiral of the induction machine; 

 S, tooth ; K', key ; C, C, catches ; K' in 

 the corner, scheme of K'; K, key in primary 

 circuit. 



attached to it, then, when the muscle contracts, the following events take place : 



Fig. 323. 

 Spring myograph or " shooter." 



[(1) A period or stage of latent stimulation (figs. 324, 325). 



(2) A period of increasing energy or contraction. 



(3) A period of decreasing energy or more rapid relaxation. 



(4) A period of slow relaxation, or the elastic after-vibration.] 



