PHYSIOLOGICAL ACTION OF VENOM OF BLACK SNAKE. 243 
and disinclined to move. If made to walk its gait is unsteady, 
and accompanied by incoordination of movement. At the same 
time it responds less readily to any form of stimulation, and its 
senses appear dulled. Later it is quite unable to stand, the 
pupils become dilated and insensible to light, and the breathing 
shallow and slowed. In this condition it responds sluggishly to 
painful stimulation, although the skin and corneal reflexes, and 
movements evoked by stimulation of the sensitive hair of the snout, 
are still rapidly produced. Eventually no response can be evoked 
by stimulation from any of the surfaces, and the corneal reflex 
disappears last. By this time the respiratory movements have 
become very sluggish, and with the exception of occasional long 
inspiratory gasps, greatly diminished in extent. The respiration 
ultimately ceases when with or without a few feeble convulsive 
movements, the animal succumbs. 
[ have already shown that the venom paralyses the heart, and 
thereby gradually depresses the circulation, and it is quite con- 
ceivable that all these nervous symptoms could be produced by a 
gradually diminished blood supply to the central nervous system. 
Accordingly, before we can draw any conclusions as to how far 
these results are due to a direct interference with the function of 
the nervous system, it will be necessary to eliminate the operation 
of this factor. 
By varying the conditions of the experiment, it is however easy 
to show that, although in many cases the circulatory depression 
contributes to the gradual extinction of function of the nervous 
system, the venom does itself exert a very powerful action upon 
the medulla and cord, and more especially upon the respiratory 
centre, 
When the venom reaches the circulation in a considerable 
quantity at one time, the heart is the more affected, whereas the 
respiratory centre is sensitive in a higher degree to the continuous 
°peration of the poison in small concentration. This conclusion 
as arrived ut from the fact that in those cases where the poison 
'S rapidly introduced into the circulation, as when small quantities 
