186 



Capt. E. H. Elliot. A Contribution to the [Jar. 18, 



Summary of Conclusions. 



1. Cobra venom acts directly on the muscular tissue of the blood- 

 vessels, or through their vaso-motor nerve-endings, constricting the 

 arterioles, and thus raising the arterial blood pressure. It probably 

 affects all organs alike. In the frog vessels the action can be traced 

 down to dilutions of 1 : 10,000,000. In a Cobra-bitten man, the con- 

 centration of venom in the blood is probably at least thirty times as 

 great as this. 



2. Cobra venom also acts directly on the isolated frog ventricle, 

 killing it in a position of firm systole, if the solution be concentrated, 

 and stimulating it if a weaker strength be employed. The limit of the 

 speedy lethal action on the isolated heart is reached at a concentration 

 of about 1/500,000. The stimulating action can be traced down to a 

 dilution of 1/10,000,000. This action of Cobra venom brings it into 

 line with the glucosides of the strophanthin group. Its action is more 

 rapid than that of strophanthin, and is certainly not inferior to it in 

 strength. Atropine sulphate and Cobra venom, when acting in the 

 same solution, intensify each other's action, and produce more summa- 

 tion of effect than one would have anticipated. This detracts from the 

 value of the atropine salt in the treatment of cobraism, and makes it a 

 dangerous remedy. The blood-pressure work has confirmed this view 

 of the case. 



3. Cobra venom powerfully affects the isolated mammalian heart, 

 when solutions of it are perfused through the coronary circulation. 

 The action appears to be a dual one, viz. (1) a direct action on the 

 muscular fibre, or on the nerve endings, closely resembling that which 

 is produced on the isolated frog ventricle ; and (2) an action on the 

 intracardiac vagal mechanism, which makes for inhibition. The result 

 is that, in strong solutions, we find an irregular and extreme excitation 

 of the heart, followed by early death in a position or systolic tone. If 

 the concentration be less, the early stage of excitement yields to a 

 prolonged phase, in which the tonic action of the poison on the heart 

 is most pronounced : the beat is regular, steady, and strong. Cobra 

 venom interferes with the circulation through the heart in a marked 

 manner; this is probably due (1) to a constriction of the coronary 

 vessels, brought about by the direct action of the venom on the vessel 

 walls, and (2) to the condition of tonus into which the heart is tending 

 to pass. 



4. When given subcutaneously in low lethal doses, Cobra venom kills 

 by paralysing the respiratory centre. Such a paralysis is under these 

 circumstances gradually evolved, and in the early stages of the process 

 there is often evidence of a phase of stimulation preceding the paretic 

 phase. 



There is a gradually increasing venosity of the blood, and in 



