174 EXPERIMENTAL PHYSIOLOGY. 



LESSON XXXIII. 



INFLUENCE OF TEMPERATURE, LOAD, 



VERATRIA ON MUSCULAR 



CONTRACTION. 



1. Influence of Temperature on Muscular Contraction. 



(a.) Arrange the experiment with a crank-myograph as 

 in Lesson XXXI., 10, but do not remove the skin of the leg. 

 Take a tracing at the normal temperature. 



(6.) Alter the height of the drum or that of the myograph. 

 Place ice upon the skin over the gastrocnemius for some 

 time, and then take another tracing, noting the differences in 

 the result, the contraction being much longer. 



(c.) Adjust a piece of wire gauze over the leg, and allow 

 it to project beyond the end of the plate of the myograph. 

 Heat the gauze with a spirit-lamp. Take a tracing. The 

 contraction is shorter than in 1 (6.) Do not overheat the 

 muscle. 



(d.) A piece of thin gas piping can be bent, and the 

 muscle laid on it. Water of various temperatures can then 

 be passed through it. 



(e.) The muscle may be attached to an ordinary horizontal 

 writing-lever. Surround the muscle with a double-walled 

 box, with an inflow and outflow tube, through which 

 water at different temperatures can be passed. A delicate 

 thermometer is placed in the chamber with the muscle. 



(f.) Perhaps for the purpose of the student the most 

 convenient method is to allow the muscle to rest on a small 

 circular brass box, fitted into the wooden plate of the crank- 

 myograph. The box ( B, B) is provided with an inflow and 

 an outflow tube, through which water of the desired tem- 

 perature can be passed (Fig. 62). 



