EFFECT OF SNAKE VENOM UPON THE NERVOUS SYSTEM, ETC. 125 



Stimulated, but without response. The motor column was still excitable. 

 The motor nerves were the last to become non-irritable and remained active 

 some time after the irritability of the motor column of the cord had dis- 

 appeared. They also observed that cutting off the vagus at the neck prevents 

 the occurrence of the primary acceleration of the respiration rate. This 

 they regard to be due to the blockade of stimulus from the peripheral nerves 

 to be transmitted to the nerve center, while the secondary diminution has its 

 cause in the nerve center itself — namely, a paralytic action on this part. 

 Thus they think venom has duplex effects, the irritation of the nerve-ending 

 and depression upon the centers. 



Venom globulins, except copper globuhn, act similarly to the unmodified 

 venom, but venom peptones cause much less depression of the respiration 

 than the former. 



The effects upon the nervous system of the venom of Lachesis flavoviridis 

 s. Trimeresurus riukiuanus, one of the genera belonging to Crotalinae, have 

 been studied by Ishizaka. 



In Rana esculenta o.oi gm. (subcutaneous) of the dried venom causes death 

 in from lo to 24 hours. The frog soon shows progressive paralysis, although 

 its reflexes, as well as the motor nerves, remain capable of responding to the 

 stimulus for a long time after death. There is no early paralysis of the motor 

 nerve-endings in the striated muscles, and this presents a marked contrast 

 to the effects produced by the venom of Cobra. The frequency of the heart- 

 beat gradually diminishes and is not influenced by atropin. The heart stops 

 in a semi-systolic state. Direct apphcation of a i per cent solution of the 

 venom to an isolated frog's heart brings about momentary changes. The 

 diastolism becomes restricted in width and is soon so stiff that scarcely any 

 blood flows into the relaxed ventricle, while all the peripheral vessels get 

 strongly filled. In this state the cardiac frequency remains unaltered for 

 some time. A frog's heart perfused with Ringer's solution by Williams's 

 apparatus becomes paralyzed within 6 to 12 minutes when a i per cent 

 venom dissolved in Ringer's solution is allowed to stream through the heart. 



In rabbits the venom causes an early cessation of respiration, with the 

 electric irritabihty of the phrenic nerves and other intramuscular nerves 

 unimpaired. The heart beats some time after the respiration ceases. 



A direct inoculation of the venom into the substance of the brain is re- 

 sponded to by acceleration and difficulty of respiration, the increase of reflex 

 actions, and clonic or tonic convulsions. If 0.00 1 gm. of the venom is used 

 death may occur in from i to 4 hours, with the cessation of the respiratory 

 function. 



In dogs or rabbits an intravenous injection of the venom causes a rapid 

 faU of blood pressure, but the frequency and the size of the pulse remain 

 unaffected. The fall of the blood pressure is not due to the paralysis of the 

 vasomotor center, because the pressure rises again in the later stage when 

 the artificial respiration is suspended. The irritabihty of the splanchnic 

 nerve is always diminished, but never completely lost. The maintenance of 



