PRACTICAL PHYSIOLOGY 37 



Action of veratrin on muscular contraction. 



The hyoglossus muscle i.e., the frog's tongue- 

 may be used. Cut away the whole of the lower 

 jaw, along with the tongue and hyoid bone. Tie 

 a thread to the tongue near its tip, and connect 

 with the muscle lever (Fig. 26). Fix the prepara- 

 tion to the myograph cork by inserting pin elec- 

 trodes on either side and immediately in front of 

 the hyoid bone so that induction shocks will stimu- 

 late all the fibres of the hyoglossus muscles. 



Take a muscle curve in the usual way. If the 

 speed of the drum is the same as before (one 

 revolution per second), the curve is more pro- 

 longed than that of the gastrocnemius i.e., the 

 contraction is slower. It is better, however, for 

 investigating the action of veratrin to use a less 

 rapid rate of cylinder, since this drug enormously 

 delays the relaxation of muscle. The cylinder 

 therefore should be arranged to revolve once in 

 about four or five seconds. A normal muscle curve 

 is first described, the point of stimulation being 

 marked in the usual way. Then inject with a 

 hypodermic syringe a few drops of veratrin acetate 

 solution (one per thousand) under the mucous 

 membrane of the tongue, so that the drug is 

 brought into contact with the fibres of the hyo- 

 glossus. After a minute or two take another mus- 

 cle curve. Describe a tuning-fork tracing below 

 the abscissa. If the preparation is excited repeat- 

 edly, it will be found that the contractions grad- 

 ually lose their prolonged character, which, how- 

 ever, returns after a period of rest. 



