338 



Dr. A. J. Wall. On the 



[June 16, 



siderable difference. To this we have also to add the paralysing effect 

 on muscle, which, thongh not so great as on the nerve, is yet not un- 

 important, and would tell on the same side. Moreover, it does not 

 follow that because a nerve to which poison has had access conveys 

 electrical stimuli in a very imperfect manner, or not at all, therefore 

 the effect of that poison has been to paralyse the nerve. It is unfor- 

 tunate that the only test we have of the vitality of a nerve is its 

 power of causing contraction in a muscle when irritated by electricity 

 or mechanically. 



It would be going too far to say, therefore, that because a nerve did 

 not transmit such rude stimuli it was dead ; and when an animal loses 

 the power of withdrawing a member that is being painfully stimulated, 

 the break in the power of conducting impressions or stimuli may be 

 in any part of the nervous chain involved, or may be distributed 

 equally throughout. A poison also that produces death by totally 

 different means than paralysis may yet cause in the nerves a complete 

 deadness to stimuli. 



Experiment IV. 



The right thigh of a frog (Bana tigrina) was ligatured, so as to- 

 completely prevent circulation through the limb, the nerve being 

 included in the ligature. Two cgrms. of strychnia in solution were 

 then injected into its dorsal sac. 



12.53 p.m. Injection. 



12.56 p.m. Tetanus. 



1.10 p.m. Reflex action ceased. 



1.23 p.m. Muscles of right leg infinitely sensitive. 



1.25 p.m. Muscles of left (poisoned) leg contract with 0*75 volt. 



1.39 p.m. Right (unpoisoned) sciatic nerve infinitely sensitive,, 

 causes muscular contraction with less than "0001 volt. 



Now strychnia certainly does not kill by paralysis, and yet the- 

 difference between the poisoned and the non-poisoned sides in regard 

 to their nerves was more marked than was recorded in similar experi- 

 ments made with cobra poison. In another frog this difference was 

 very pronounced before the strychnia had ceased to produce tetanus, 

 o that it occurs long before exhaustion has taken place. The com- 

 plete interference with the vital functions produced by tetanus is the 

 real cause of death, and the deadening of the nerves is simply the 

 result of the excessive nervous discharges that have taken place 

 through them. Thus, though the trunk or extremity of a nerve may 

 be found paralysed, it does not follow that it is the direct action of a. 

 poison that may be present, or that it was the paralysis that caused 

 death. 



In cobra poisoning also it is possible to get very distinct evidence of 

 sensation long after the nervous centres of organic life have been so 



