132 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 
is a gradual diminution, and violent convulsions repeatedly occur. This 
respiratory convulsion is interpreted by Rogers to be a sign that the 
respiratory center, which otherwise would fail, is functionally revived by the 
artificial respiration; hence convulsions. That the paralysis of the respiratory 
center is not the only cause of asphyxiation, but that paralysis of the end- 
plates of the phrenic nerves takes part in it, is experimentally shown by 
Rogers both in cold-blooded and in warm-blooded animals. In cats and 
rabbits, many times the minimal lethal doses were given intravenously, and 
then the exposed phrenic nerves at the neck were stimulated by an interrupted 
induced current at intervals of a minute. After the complete cessation of 
respiration the phrenic nerves were stimulated, but found to be completely 
paralyzed. Direct stimulation of the diaphragm gave a marked contraction. 
It was, however, found that the respiration was much reduced in frequency 
and amplitude several minutes before the weakening of the irritability of the 
phrenics. It is interesting to notice that the end-plates of the sciatic nerves 
remained excitable much longer than those of the phrenics, being still reactive 
at the time of complete cessation of circulation. 
Rogers also tested the comparative sensitiveness of the nerve-trunk and 
nerve-ending to the paralyzing action of the venom. Here, using frogs, he 
employed the venom in dilution of 1 : ro® to 10%, subjecting the nerves to its 
action for 1 to 5 minutes in strong and up to r hour in weak solution. No 
deteriorating effects on the irritability of the nerve-trunk were observed, but 
that of the nerve-ending was totally lost. Even a 1 per cent solution of the 
venom of Enhydrina acting for 5 minutes had no effect on the nerve trunk. 
In regard to its action on the reflex functions of the spinal cord, Rogers 
points out that it is slight and altogether secondary in importance to its in- 
fluence on respiration. He states that the venom of Enhydrina in 1 : 100 
solution has no appreciable effect when applied directly to the frog’s heart, 
whereas a few drops of a 1: 1000 solution are quickly fatal when given 
intravenously. This seems to present a great difference from the venoms of 
Pseudechis, Naja, and Trimeresurus. 
Fraser and Elliot,’ working with the venoms of Enhydrina valakadien and 
Enhydris curtus, mention the occurrence of motor end-plate paralysis in the 
enhydrina poisoning. They also made direct application of the venom to 
the region of the respiratory center and found it quickly fatal without affect- 
ing the circulatory system at the same time. On application of the venom 
directly to the exposed hearts (in sitw) of mammalia no effect was observed 
on the vagal cardio-inhibitory center. The vasomotor center is also un- 
affected by this venom. 

1 Fraser and Elliot. Contributions to the study of the action of sea-snake venoms. Roy. Soc. Proc., 
1904, LXXIV, 104. 
