222 MUSCLE. 



Lay U on a plate and attach the muscle by its tendon to 

 the hook, fasten the fine copper wire to the fragment of the 

 femur by wrapping it firmly several times round the bone 

 and then twisting the wire upon itself. Straighten the wire 

 in line with the muscle, so that the latter may pull directly 

 when attached to the recording arm' (aluminium). 



Then holding U by each end and the copper wire so as to 

 keep the muscle in position, replace and fix U in the well of 

 the cylinder. Secure the free end of the wire to the 

 recording arm, adjust the counterpoise (10 g ) at R so as to 

 take up any slackness of the muscle. Cover the well with 

 the vulcanite lid. 



See that the recorder has a fine point, and that the latter 

 rests lightly against the drum surface when the pillar arm 

 touches the stop. 



In carrying out the experiments attend to the following : 



(a) Each time a change of temperature is established in the 

 cylinder ensure that the same is effected in the muscle by 

 allowing one minute to elapse after the mercury in the ther- 

 mometer comes to rest. 



(b) Mark the temperature against each curve as soon as 

 it has been drawn. 



(c) Observe in each case changes in the height and in the 

 duration of the muscle curve, and note in the latter case if 

 the contraction or the relaxation is most affected. 



(d) If the temperature of the muscle be too suddenly and 

 largely changed, the muscle may pass into continued twitch- 

 ings ; these will pass off. The suddenness of the change acts 

 as a stimulus. 



1. Take a tracing at the temperature of the room as 

 a control experiment. 



