CHAPTER XII. 
EFFECT OF SNAKE VENOM UPON THE NERVOUS SYSTEM 
AND EFFECT OF THE SEQUELAE UPON THE RESPIRATORY 
AND CIRCULATORY FUNCTIONS. 
CROTALINZ. 
S. Weir Mitchell demonstrated as early as 1861 that the toxication of frogs 
and rabbits by the bite of the rattlesnake quickly stops all motion, volun- 
tary or reflex, within a short time after the bite. In frogs it was found that 
no reflex acts respond to the stimulation of the sciatic nerves, although the 
galvanization is followed by the movements of the muscles of the same leg. 
On the other hand, the electric stimuli to the sciatic nerves, from which the 
vicious effect of the poison had been excluded by cutting off all of its cir- 
culation, produced contraction of the muscles. The loss of the motion was 
then thought to be caused either by the incapability of the sensory nerves 
to transmit the stimulus to the nervous centers or by the destruction of the 
nerve centers themselves. In order to ascertain this point he poisoned a 
frog to a state of total paralysis, then cut the spinal cord across and thrust a 
probe up and down. No motion resulted. The irritability of the sciatic 
nerves when directly tested was found to be nearly perfect. Thus the dis- 
appearance of motion seems to have been caused by the paralysis of the 
spinal cord. 
In rabbits it was necessary to keep up the circulation and cardiac activity 
after the cessation of respiration by means of artificial respiration, which 
seems to sustain the heart’s action for about 12 minutes. During this stage 
the spinal cord was cut across; no motion resulted. A probe being thrust up 
and down the spine, feeble quivering of the nearer spinal muscles took place, 
but the limbs did not move. On dividing the sciatic nerves free motion was 
observed, and the phrenic trunk was likewise excitable. 
In 1886 Weir Mitchell and Reichert made further detailed observations 
on the effects of Crotalus adamanteus, Ancistrodon piscivorus, and Naja 
tripudians. Their experiments chiefly concern the effects of the crotaline 
venoms. In administering a dose of these venoms — just enough to cause 
acute or subacute poisoning in rabbits— into the jugular vein, they always 
noticed the increase in the respiration rate, which, however, was quickly 
followed by a diminution far below the normal. Corneal reflex disappeared 
before the cessation of respiration, which occurred first. In testing the 
electric excitability of the respiratory muscles they found them responsive 
to the stimulus. After exposing the spinal cord the sensory column was 
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