ELEMENTAEY EXPERIMENTAL PHYSIOLOGY 31 



be rapidly absorbed it is important not to ' pith ' the frog, but to 

 destroy its cerebrum with a pair of Spencer- Wells pressure forceps. 

 In about ten minutes it will be observed that the hind legs are very 

 slowly and imperfectly flexed after a jump, and a few minutes later 

 the frog will be seized by a spasm when it jumps. As soon as these 



FIG. 86. Contraction of the hyoglossus muscle. Time marker, 100 per second. (A.P.B.) 



symptoms appear the remaining portions of the central nervous system 

 are destroyed, and a sciatic and gastrocnemius preparation made. 



In the meantime the action of veratrine may be studied on the 

 hyoglossus preparation used in the previous experiment. Five 

 minims of the veratrine solution are injected into the lymph sac 

 in which the muscle lies. The drum is arranged to revolve at a slow 

 rate of about 2 cm. in 10 sees., and a simple key instead of the 

 " striker " of the drum is placed in the primary circuit. After waiting 

 a few minutes the muscle is stimulated by a single maximal induction- 



Fio. 37. Contraction of the gastrocnemius muscle of a frog. The effect of vera- 

 trine. The first two contractions show the characteristic effect of the drug ; further 

 stimulation produced twitches without the prolonged contraction. The curve has 

 been reduced to one-half the actual size. The time is marked in seconds. (Pembrey 

 and Phillips.) 



shock, and its contraction recorded. The curve shows that the response 

 is a single slow contraction with an enormously prolonged relaxation* 

 Replace the hyoglossus by the gastrocnemius and sciatic preparation 

 and stimulate it in the same way. As soon as the first contraction 

 is over, the muscle is stimulated again, and so on for half a dozen 

 contractions. It will be seen that the first contraction (Fig. 36) con- 

 sists of a smart initial twitch followed by a much longer contraction, 

 and an even more prolonged relaxation. The second contraction 

 shows the same characters to a less extent, and the subsequent con- 

 tractions become of shorter and shorter duration until they reach the 



