88 DR JAMES A. GUNN ON 
D. Action oN SKELETAL MUSCLE. 
To ascertain the effects produced by harmine on voluntary muscle, experiments were 
made on the isolated gastrocnemius muscles of the frog, one muscle being immersed in 
a solution of the alkaloid, the other muscle in Ringer’s solution. A modified Wild’s 
method was employed, and to stimulate the muscles the secondary current passed 
simultaneously through both muscles. Tracings were taken on a slowly revolving drum. 
Experiment 21 (figs. 1 and 2).—Strength of solution, 1 in 2000. Normal twitches 
resulting from stimulation with break shocks are shown at 11.28, both muscles being in 
Ringer’s solution. At 11.30 Ringer's solution was withdrawn from muscle B and 
replaced by a solution of harmine hydrochloride 1 im 2000 in Ringer's solution. 
bw 2.000 oe ‘ 
a a he Sane Ses 
renee 
a 
19-28 4-30 M32 1-34, W-36 1-33 Ue) UNLQ a4 
__ 
Fic. 1. Fic, 2. 
Muscle twitches (generally three in succession) were thereafter taken at intervals ot 
two minutes, with the secondary coil at 100 mm. throughout. 
As the tracing shows, harmine causes the muscle gradually to pass into a condition 
of rigor with diminishing excitability and extent of contraction, so that in forty minutes 
the muscle had raised the lever above the level of the summit of a single twitch and no 
longer responded to the stimulus. The control muscle was unaffected. 
This effect on muscle is always produced by solutions of harmine when not less 
dilute than 1 in 5000, sometimes even by solutions of 1 in 10,000. Results of this 
action on muscle are exemplified in the general effects of poisoning by harmine by the 
occurrence of rigidity and impaired excitability of the muscles round the seat of injec- 
tion, and also by the unusually rapid onset of rigor mortis after lethal doses. 
E. AcTION ON THE CIRCULATION. 
(a) Heart. 
A series of experiments was performed in which the isolated frog’s ventricle was 
perfused by means of Schafer’s frog-heart plethysmograph. A mixture of defibrinated 
