94 Messrs. T. L. Brunton andJ. Fayrer on the [Jan. 22, 



biting the horse-heels, so that the rider falleth backward." In this point 

 cobra-venom, when dried, appears to resemble methylconia rather than i^s 

 admixture with conia ; but it exercises numerous other actions upon the 

 blood, muscles, &c. which neither of these substances has been shown 

 to do. It is doubtful whether the cerebrum is directly affected by cobra- 

 poison, as the intelligence both in man and animals often remains almost 

 unimpaired to the last, and the stupor and drowsiness which are some- 

 times noticed may be caused indirectly, by the action of the venom on the 

 motor and vaso-motor nerves and on the functions of the cord. The re- 

 flex centres through which irritation of the fifth nerve acts, remain un- 

 affected after the reflex function of the cord is nearly gone ; and even then 

 the power of voluntary motion still exists. 



The effect of the poison upon the respiratory and vaso-motor nerves 

 will be considered under the heads of respiration and circulation. 



Action of Cobra-poiton on Motor nerves. 



As the contraction of a muscle, on irritation of the motor nerve sup- 

 plying it, is the index by which we judge of the irritability of the nerve 

 itself, the paralyzing effect of cobra-poison upon muscle renders the exact 

 determination of its action upon motor nerves much more difficult than 

 in the case of such a poison as curare, which leaves the muscular irrita- 

 bility intact. For the failure of a muscle to contract on irritation of its 

 motor nerve, can be due only to paralysis of the motor nerve in the case 

 of curare ; but in poisoning by cobra-venom it may be due to enfeeble- 

 ment of the muscles, as well as paralysis of the nerve. But if we find 

 instances in which the muscles still retain their irritability almost un- 

 altered, and respond readily to direct stimulation after they have ceased 

 to contract on irritation of their motor nerve, we are justified in saying 

 that the nerve is paralyzed ; and such is the case in Experiment XLI. 



In Experiment XXV. this action on the ends of motor nerves is all 

 the more evident from the paralysis being most complete in the part 

 where the poison was introduced. At this part, it was brought, in a con- 

 centrated state, into contact with the ends of the motor nerves, while the 

 other parts of the body received it after dilution with the blood ; and in 

 them the paralysis was much less marked. 



The paralysis of the hind legs, so often noticed in experiments, appears 

 to be due, at least in considerable measure, to the local action of the 

 poison on the ends of the motor nerves of the legs, as the injection or 

 bite is often made on the flank or thigh. 



The action of the poison on motor nerves is illustrated by the following 

 experiments, performed by Bernard's method of ligaturing one leg of a 

 frog before poisoning it. The poison is thus carried to every part of 

 the body except the ligatured limb, the motions of which indicate the 

 state of the nerve-centres after the other parts of the body have been 

 paralyzed. 



