256 



DR JAMES A. GUNN ON 



10,000, or sometimes 1 in 20,000. Harmaline produces rigor as rapidly and as com- 

 pletely in curarised muscle, so that the effect is probably due to an action on the muscle 

 protoplasm. In respect of this action in producing shortening and loss of excitability 

 of muscle, harmaline resembles quinine, but is more powerful. In none of the experi- 

 ments did fibrillary twitchings of the poisoned muscle occur. 



Solutions of harmaline which are too dilute to produce rigor of muscle do not 



Fig. 1. 



Fig. 2. 



markedly diminish the excitability of the muscle. Thus a gastrocnemius-sciatic 

 preparation was kept in a solution of harmaline 1 in 25,000 for eighteen hours, at the 

 end of which time the muscle reacted to direct and indirect stimulation almost as well 

 as a control preparation kept for the same time in Ringer's solution alone. This may 

 explain why, in spite of the fact that actual rigor of muscle may be produced by a 

 solution so dilute as 1 in 20,000, paralysis of the voluntary muscles plays a part 

 relatively so unimportant among the general effects of harmaline poisoning, for the 

 muscles respond to stimulation of their nerves for some hours after abolition of reflex 

 excitability. 



E. Action on the Circulation. 



(a) Heart. 



The description given of the symptoms occurring in the frog after subcutaneous injec- 

 tion of harmaline has shown that this alkaloid at an early period causes slowing of the 

 rate of the heart, but that the heart, though apparently much enfeebled, continues to beat 

 until after cessation of respiration and paralysis of reflex excitability. In mammals too 

 the rate of the heart-beats is reduced very soon after the injection of harmaline. With 

 large doses, this reduction in rate is progressive, and arrest of the heart plays a part 



