NERVOUS IRRITABILITY. 95 



which are intact ; this gives rise to a stimulus, which is re- 

 flected back through the motor filaments of the same nerve, 

 and the ordinary reflex movements are observed in the 

 posterior extremities. This is to be expected, inasmuch 

 as the posterior extremities arc removed from the influence 

 of the poison. If the anterior extremities, which are com- 

 pletely under the influence of the poison, be now irritated, 

 no movements are observed in these parts, but they take 

 place, as before, in the posterior extremities. The mechan- 

 ism of this action is easily understood. Reflex phenomena, 

 consisting in the movements of muscles, may be manifested 

 throughout the entire system, following irritation of a single 

 part. An impression made upon the surface is conveyed to 

 the spinal cord, and, if this be sufficiently powerful, motor 

 stimulus may be sent through all of the anterior roots com- 

 ing from the cord. The impression made upon the anterior, 

 or poisoned extremities, is conveyed by the sensory fila- 

 ments to the cord and is transmitted to the posterior ex- 

 tremities through their motor nerves, which are intact. The 

 fact of the transmission of the impression from the anterior 

 extremities to the cord shows that the poison does not affect 

 the sensory system. 1 



In the same way that the woorara-poison paralyzes the 

 motor nerves, leaving the sensory system intact, other 

 agents, as anaesthetics, will abolish the sensibility of the 

 nerves without affecting the motor filaments. This well- 

 known fact has also been experimentally illustrated by Ber- 

 nard. 3 



As we have already intimated in another connection, the 

 nerves soon lose their irritability after they have been sepa- 

 rated from the centres. 3 This loss of conducting power is 



1 BERNARD, Lemons sur la phy&iologie et la pathologie du systeme nerveuz, Paris, 

 1858, tome i., p. 203, et seq. /-and, Lefons sur les proprietes des tissiis vivants Y 

 Paris, 1866, p. 254, et seq, 



2 BERNARD, TJitorie physiologique de Tanesthesle. Rente dt& cows scienti- 

 figues, Paris, 1868-'69, tome vi., p. 383. 



3 See page 80. 



107 



