1906.] Recently -Discovered African Arrow Poison. 



23 



system. It paralyses the voluntary muscles and brings about death by a 

 direct action upon the muscular tissue of the heart. 



The first effect of the poison is to stimulate directly the muscular coats of 

 the arterioles and thus to cause a rise of arterial pressure. 



The raised arterial pressure excites the vagus centre in the medulla, and 

 brings about a slowing of the rhythm of the heart, together with a slight 

 fall in the arterial blood pressure. The irritability of the heart muscle is 

 greatly increased and soon the vagus fails to hold it in check, with the 

 result that the rhythm of the heart is accelerated and the blood pressure 

 therefore rises to a higher level as the inhibition of the vagus is overcome. 

 It is, however, probable that the chief factor in maintaining the high blood 

 pressure is the constriction of the peripheral vessels. 



The rhythm of the heart becomes more rapid and irregularity appears, the 

 heart finally passing into delirium cordis and ceasing in diastole. 



As the heart fails, the blood pressure falls more or less rapidly, and the 

 fall is interrupted by rises in which the heart temporarily recovers itself. 

 The final fall of blood pressure is due entirely to heart failure, the muscular 

 coats of the arteries being capable of response to stimulation till the very 

 end. Any effect upon the respiration is secondary to the effect upon the 

 vascular system. The final convulsion is also secondary and not due to any 

 direct action of the poison. 



In the case of the frog the action of the poison is also directed towards 

 the muscular tissue of the heart and the voluntary muscles leading to a 

 gradual paralysis. With regard to the action on the heart, all that can be 

 said is that the poison acts atonically on the muscular tissue like lactic acid 

 and potash salts, and that its conductivity is diminished. 



In conclusion, my best thanks are due to Professor Sidney Martin, F.E.S., 

 for his kindness in giving me this work to do, and also in allowing me the 

 use of his laboratory and apparatus. 



7. Protocol of Experiments. 



I. Experiments to Determine Symptoms, Fatal Dose, and Post-Mortem 



Lesions. 



Experiment 1. — Kabbit, weight 2125 grammes. Injection of 1/5 gramme 

 of poison dissolved in 2 c.c. salt solution ( = 0*094 gramme per kilogramme), 

 into the marginal vein of left ear. The solution was unfiltered. Almost 

 immediately the animal began to open its mouth during inspiration, which 

 was slow and laboured, the dyspnoea being inspiratory. The alae nasi 

 twitched. The animal tried to hop, but staggered and swayed. The limbs 



