49S 



Mr. K. Lucas. 



[June 6, 



region before it can reach the muscle. The results obtained from the 

 application of this method are of two kinds, appearing successively at 

 different stages of narcosis. The earlier stage (first described by 

 Grunhagen)* is that whereas the stimulus applied within the narcotised 

 region has to be strengthened, a stimulus applied in the unaffected region 

 need be no stronger than before. Apparently, then, the propagated 

 disturbance can pass through the narcotised region without difficulty, but 

 is not easily initiated there ; the narcotic has altered excitability, but not 

 conductivity. The later stage (first noticed by Szpilman and Luchsinger)t 

 is that the stimulus inside the narcotised region may still make the muscle 

 contract if made very strong, whereas no strength of stimulus applied to the 

 normal part will produce any effect on the muscle whatever. Apparently it 

 has now become impossible for a disturbance to be propagated through the 

 whole length of the narcotised region, though one can still be set up within it. 



These facts, which have been verified repeatedly, have been taken as 

 evidence that, in the ordinary physiological terms, " excitability " and 

 " conductivity " can be differently affected, and that, consequently, excitation 

 by an external stimulus must involve a process which is not involved in 

 the propagated disturbance. Is this result to be accepted for our purpose ? 

 It is clear from the work of Werigo,} Frohlich § and Boruttau|| that the 

 later stage of narcosis certainly will not bear any such interpretation. 

 These observers have made it clear that the diminution of a propagated 

 disturbance in a narcotised nerve increases with the length of the narcotised 

 region traversed. The explanation of the second stage of narcosis would 

 therefore seem to be that the propagated disturbance set up in the normal 

 part of the nerve has to traverse the whole length of the narcotised region, 

 and consequently gets wiped out of existence, whereas that set up within 

 the narcotised region has a shorter length of narcotised nerve to traverse, 

 and therefore succeeds. But there still remains the earlier stage of 

 narcosis, in which apparently the excitability is altered, while the con- 

 ductivity is still normal. Here, again, it is probable that the apparent 

 dissociation of the two processes is illusory. Wedenskyt found that, though 

 a single disturbance appears to get through the narcotised region without 

 diminution at a time when excitability is already obviously altered, yet the 

 attempt to send a rapid succession of disturbances along a nerve in this 



* Loc. cit. 



t ' Arch. f. d. ges. Physiol.,' 1881, vol. 24, p. 347. 

 % Werigo, 'Arch. f. d. ges. Physiol.,' 1899, vol. 76, p. 552. 

 § Frohlich, 1 Zeitschr. f. allg. Physiol.,' vol. 3, p. 148. 

 || Borutt.au and Frohlich, ' Zeitschr. f. allg. Physiol.,' vol. 4, p. 153. 

 IT Wedensky, 'Arch. f. d. ges. Physiol.,' 1900, vol. 82, p. 134. 



