EFFECT OF TEMPERATURE 43 



Lower the drum, adjust the 4th speed. (Steel spring 

 in upper groove, cord on large pulley on shaft and on 

 small pulley on drum.) Set the drum in motion, pour 

 Ringer's fluid at 40 C. into the muscle chamber, and 

 renew it when it cools; the muscle will slowly shrink, 

 and become opaque. (Heat rigor.) Open and close the 

 key, there will be no contraction. In frog's muscle heat 

 rigor sets in at 39 40 C., in mammalian muscle at 

 about 47 C. 



DEMONSTRATIONS. 



1. Action of curari on muscle and nerve. 



a. Two sciatic-gastrocnemius preparations are made.* 

 Two watch-glasses are put close together, one contain- 

 ing saline solution and the other curari -025 p.c. The 

 muscle of one preparation is placed in the saline solu- 

 tion and the nerve in curari ; the nerve of the other pre- 

 paration is placed in saline solution and the muscle in 

 curari, and left for an hour or longer. Then both nerves 

 are stimulated with Faradic currents. The former causes 

 contraction as usual, the latter does not cause contrac- 

 tion. Direct stimulation of each muscle causes contrac- 

 tion, but it is less widespread in the curarised one. Thus 

 curari does not abolish the irritability and conductivity 

 of the nerve, but prevents the impulse affecting the 

 muscle^an action which is commonly spoken of as a 

 paralysis of nerve -endings. 



The slow action of curari in this case is due to its slow diffusion 

 through the thick muscle; in the sartorius, the nerve is paralysed 

 in a quarter of an hour by curari of one-tenth of the percentage 

 used above. When curari is injected into an animal, the nerves are 

 not all paralysed at the same time, thus in the frog the nerves to 

 the hind limbs are paralysed before those to the fore limbs. 



