134 CONCERNING THE EFFECTS OF "TUBA" FISH-POISON. 



Later further changes are produced in the blood pressure, but these 

 are produced by the asphyxia. 



A dose as weak as 1 c. c. of 1 in 10,000 solution produces 

 similar changes in the respiration and blood pressure but the changes 

 are not so well marked ; the respiration is not paralysed and death 

 does not occur, the normal conditions prevailing again. 



The tissues apparently become accustomed to the poison in 

 a slight degree. Thus a dose from 1/50 gm. of the root kills if 

 injected without any previous injection being made; but if many 

 injections of weaker solutions of gradually increasing strengths 

 are first performed, a stronger dose than 1/50 gm. is required to 

 produce death. 



The poison acts upon the respiratory nervous centre in the 

 medulla and not on the vagal ending in the lungs, because the 

 same results are obtained if the vagi are cut (Fig. 2). Also if the 

 poison is injected into the carotid artery, the respiration is affected 

 in a few seconds. 



It has already been stated that the poison dilates the blood 

 vessels of the isolated limb of a monkey and that it greatly weakens 

 the tone and movements of the involuntary muscle of the intestine 

 of the same animal. The fall of blood pressure is explained by 

 these actions. Further experiments and chemical analysis are re- 

 quired to prove whether one substance causes both paralysis of 

 respiration and dilatation of the blood vessels or whether there are 

 two distinct substances for these actions. 



The previous injection of adrenalin only slightly modifies the 

 depressing influence of the poison upon the blood vessels, and the 

 fall of blood pressure is still very well marked. 



After-effects of the Poison. 



In some experiments injections were made subcutaneously into 

 monkeys, but although these injections were strong enough to pro- 

 duce very great effects on the respiration, causing a marked degree 

 of asphyxia, they were not strong enough to kill the animals. In 

 these cases the animals recover completely in a few hours and ex- 

 hibit no ill after-effects, — no paralysis, no digestive troubles and 

 no weakness of any kind. 



Discussion. 



From the results on different animals it is evident that the 

 poison affects the more highly developed members of the animal 

 kingdom more readily that it does the primitive members. This 

 is only to be expected since its action concerns the brain and one 

 particular part of this, namely the medulla oblongata. 



It could be used to destroy mosquitce larva?, but it should be 

 used in solutions not weaker than 1 in 1,000, that is just enough 



Jour. Straits Branch 



