176 EXPERIMENTAL PHYSIOLOGY. 



(6.) Arrange the induction machine for single shocks. 



(c.) Make a nerve-muscle preparation, fix it in a moist 

 chamber, and arrange the muscle lever to record its move- 

 ments on a slowly revolving drum. Take a tracing, observ- 

 ing the long drawn-out form of the curve, and how long the 

 muscle takes to relax. 



(d.) The direct action of veratria on muscular tissue may 

 also be studied by the apparatus described in Lesson 

 XXXVII., and by this method it is easy to compare the 

 form of the curve before and after the action of the poison 

 (Fig. 70). 



LESSON XXXIV. 



ELASTICITY AND EXTENSIBILITY 

 OF MUSCLE. 



1. Elasticity of Muscle. 



(a.) Dissect out the gastrocnemius of a frog with the 

 femur attached, clamp the femur, attach the tendon to the 

 light writing muscle lever of the moist chamber, and fix a 

 scale pan to the lever. Neglect the weight of the pan, and 

 see that the lever writes horizontally on a stationary drum. 



(b.) Place in the scale pan successively different weights 

 (10, 20, 30, 40 ... 100 grammes). On placing in 10 grammes 

 the lever will descend, remove the weight and the lever 

 will ascend. Move the drum a certain distance, and add 

 20 grammes to the scale pan. This time the vertical line 

 drawn is longer, indicating greater extension of the muscle 

 by a greater weight, but nevertheless the muscle lever will 

 rise to its original height on removing the weight. Repeat 

 this with other weights. With the heavier weights care 

 must be taken that everything is securely clamped. If 

 the apices of all the lines obtained be joined, they form a 

 hyperbola. The muscle therefore has not a large amount 

 of elasticity, i.e., it is easily extended by light weights, 

 and on removal of the weight it regains its original 



