CH. x.] MYOG&APHS. 119 



will mark a down-stroke, and if the cylinder is travelling, 

 the down-stroke will be written on a different part of the paper 

 than the up-stroke ; thus a muscle curve or myogram is ob- 

 tained. The paper may then be removed, varnished, and preserved. 



Fig. 141 shows a somewhat different arrangement. 



The muscle is fixed horizontally on a piece of cork B, one 

 end being fixed by a pin thrust through the knee-joint into the 



Fig. 141. Arrangement of the apparatus necessary for recording muscle contractions with 

 a revolving cylinder carrying smoked paper. A, revolving cylinder ; B, the muscle 

 arranged upon a cork-covered board which in capable of being raised or lowered on the 

 upright, which also can be moved along a solid triangular bar of metal attached to the 

 baae of the recording apparatus the tendon of the gastrocnemius is attached to tin- 

 wilting lever, properly weighted, by a ligature. The electrodes from the secondary coil 

 pans to the nerve being, for the sake of convenience, first of all brought to a short- 

 circuiting key, D (Du Bois Reymond's) ; C, the induction coil ; F, the battery (in thia 

 fig. a bichromate one) ; E, the key (Morse's) in the primary circuit. 



cork ; the tendo Achillis is tied to a lever which is weighted 

 near its fulcrum : the lever is so arranged that it rests on a 

 screw till the muscle begins to contract; the muscle therefore 

 does not feel the weight till it begins to contract, and gives 

 a better contraction than if it had been previously strained by 

 the weight. This arrangement is called after-loading. 



