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 globulin, 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 Crotaline, have 
been studied by Ishizaka. 
In Rana esculenta 0.01 gm. (subcutaneous) of the dried venom causes death 
in from 10 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 application of a 1 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 1 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 irritability 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 o.oor gm. of the venom is used 
death may occur in from 1 to 4 hours, with the cessation of the respiratory 
function. 
In dogs or rabbits an intravenous injection of the venom causes a rapid 
fall 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 irritability of the splanchnic 
nerve is always diminished, but never completely lost. The maintenance of 
