EFFECT OF SNAKE VENOM UPON THE NERVOUS SYSTEM, ETC. 127 



longer transmit to the muscles of respiration the ordinary stimuli from the 

 medulla, they can still transmit those stronger impulses which proceed from 

 it when greatly stimulated by the increasing venosity of the blood, and which 

 cause the respiratory as well as the other muscles of the body to participate 

 in the general convulsions. Experiments show that the peripheral termina- 

 tions of the motor nerves are actually paralyzed by cobra venom. Here 

 special attention is drawn to the striking parallelism between the effects 

 produced by cobra venom and those by curare upon the nerve-endings. 



Brunton and Fayrer describe also the paralysis of the spinal cord by cobra 

 venom. One of the typical experiments which led these authors to demon- 

 strate the paralysis of motor-nerve endings after the injection of cobra venom 

 was made by protecting one sciatic nerve from the action of the venom (in 

 frog) by means of cutting off all its circulation, and by testing the electric 

 irritability of the protected and unprotected nerves after apparent paralysis. 

 They always found that the side which had been protected from the effects 

 of the venom gave a ready reaction to the stimulus, but that the unpro- 

 tected sciatic nerve failed to produce contraction of the muscles. Naturally 

 the irritability of the protected ^sciatic nerve did not react as strongly as 

 the control, but this was easily explained by the fact that the nerve in the 

 former frog was for some time deprived of its blood supply. The direct 

 stimulus to the muscles themselves shows that their excitability was well 

 retained both in protected and in unprotected legs. It was also seen that 

 the longer and nearer the contact of the nerve-endings with a stronger con- 

 centration, the more complete is the paralysis of the nerve-endings. 



In regard to the effects of cobra venom upon the spinal cord, both on 

 warm-blooded animals and frogs, Brunton and Fayrer concluded that the 

 gray matter is paralyzed, since there is no transmission of painful impulses; 

 but the white sensory columns are little, if at all, affected. The power of the 

 cord to conduct motor impressions from encephalic ganglia appears to be 

 little, if at all affected, until the apparent death of the animal, and they found 

 that, very shortly before respiration ceased, and when ordinary reflex action 

 from the cord was nearly gone, voluntary movements were still made. 



According to Brunton and Fayrer the sensory nerves seem to be little, if at 

 all, affected by cobra venom. In contrast to the quick paralysis of the motor 

 nerves of the poisoned limbs the irritability of the sensory nerves is long 

 retained. In an experiment the irritability of the optic nerve and the aural 

 and buccal branches of the trigeminus was seen to be present after the cord 

 had become nearly paralyzed, and in several experiments reflex actions could 

 be induced by irritation of the cornea after voluntary motion and respiration 

 had ceased. 



The effects of cobra venom upon secretory nerves have also been mentioned 

 by Brunton and Fayrer, who were uncertain as to the exact mechanism 

 effecting profuse salivation in cobra poisoning in dog. The possibilities were 

 open either to the direct or to the indirect stimulation on the secretory nerves. 

 Judging from the simultaneous occurrence of nausea and vomiting, they were 



