1906.] Recently-Discovered African Arrow Poison. 21 



the blood pressure is falling towards the end of life the effect of excitation 

 of the depressor is liable to be less marked. 



In the early stages of poisoning the depression in blood pressure may not 

 be so marked with the same strength of stimulus as it was before the poison 

 was injected. This result might be expected to occur as the irritability of 

 the heart is increased. The fact that the depressor nerve will produce an 

 effect at all stages of the poisoning shows that the central and peripheral 

 vaso-motor nervous mechanisms are acting normally and that there is no 

 central or peripheral nervous paralysis. 



Section of the Spinal Cord. 



It was found that after section of the spinal cord in the upper cervical 

 region, the blood pressure still rose on injection of the poison to the same 

 extent relatively as it did in the experiments with the spinal cord intact. 

 The vaso-constriction, therefore, is obviously not of central origin. 



This rise of pressure is, however, due to constriction of the peripheral 

 vessels chiefly, because the heart by stimulation can only cause an insignificant 

 rise of arterial pressure when the peripheral resistance is greatly diminished, 

 as when the spinal cord is divided. 



Section of the Splanchnic Nerves. 



The result of section of the splanchnics is the same as that obtained in the 

 case of section of the spinal cord. The pressure goes up as much relatively 

 as when the splanchnics are undivided. This is confirmatory evidence of the 

 observation that the vaso-motor action is not central. 



^Excitation of Splanchnic Nerve. 



Stimulation of the splanchnic nerve even at a late stage of the poisoning, 

 when the blood pressure is following, still causes a rise in the blood pressure, 

 thus showing that the peripheral ends of the vaso-motor nerves are not 

 paralysed. 



Previous Injection of Apocodein. 



Apocodein, as is well known, brings about a fall of arterial blood pressure 

 by paralysing the terminations of the vaso-motor nerves. 



After the injection of apocodein the central end of the sciatic nerve was 

 stimulated to make certain that no rise of arterial blood pressure occurred, 

 thus showing that the apocodein had acted upon the nerve endings. Under 

 these circumstances, when the blood pressure had fallen as the result of the 

 injection of apocodein, the subsequent injection of the poison still produced a 



