1906.] Recently- Discovered African Arrow Poison. 



47 



its lowest point and no rise of pressure resulted. Stimulation of the 

 depressor three times still caused a fall in the pressure even at this late 

 stage. The falls, however, were less marked than the former ones. 



Experiment 19. — Eabbit, weight 2400 grammes. Left vagus cut. Poison 

 1/30 gramme injected intravenously (= 0"013 gramme per kilogramme). 



Blood pressure. — After the pressure had risen the vagus was stimulated 

 at quite an early stage (strength 12). The pressure at once fell from 

 136 mm. Hg to 40 mm. Hg. The depressor was stimulated immediately 

 afterwards (strength 12) and the pressure fell from 132 to 136 mm. Hg to 

 104 to 108 mm. Hg. The vagus, aud immediately afterwards the depressor 

 were stimulated three times subsequently with the same strength of current. 

 The vagus effect became each time less marked, on the third occasion the 

 pressure only falling 10 mm. Hg. The depressor effect, however, remained 

 the same till the end. 



A second injection of poison was administered and stimulation of the 

 vagus on three occasions produced no effect whatever, although the strength 

 of the current was increased. Stimulation of the depressor, however 

 produced a fall in the blood pressure of 20 mm. Hg just before the animal 

 died. 



III. Frog Heart Experiments. 



Experiment 1. Pithed frog. — The poison was dissolved in Ringer's 

 solution (1/15 gramme to 1 c.c.) and the heart kept moist by occasionally 

 applying the solution with a brush. The rate of the heart beats before 

 the application was 42 per minute. During the application the rate finally 

 sank to 30 per minute, *the force of the ventricular systole being much 

 weaker than that of the auricle. The ventricle occasionally took on an 

 independent rhythm and its beats gradually became weaker aud weaker 

 till it finally stopped in diastole, the auricle continuing to beat after the 

 ventricle had stopped. The auricle finally stopped and washing with 

 Ringer's solution failed to restore the heart. 



Experiment 2. Pithed frog. — Poison 8 per cent in Ringer's solution. 

 When the heart had almost stopped the poison was washed off with Ringer's 

 solution and the heart kept constantly moist with it. The heart finally 

 recommenced to beat in the normal manner. 



Experiment 3. Pithed Frog. — Poison 1/5 gramme to 1 c.c. salt solution. 

 The contractions of the ventricle gradually became smaller and smaller, the 

 rate declining from 42 to 36 per minute, and it finally stopped in diastole. 

 Whilst the auricle was still contracting the sinus was stimulated with an 

 induced current. Complete standstill resulted for about 25 seconds and then 



