414 Dr. N. H. Alcock. On the Rapidity of the [Oct. 2 



" On the Eapidity of the Nervous Impulse in Tall and Short 

 Individuals." By N. H. ALCOCK, M.D. Communicated by 

 A. D. WALLER, M.D., F.RS. Eeceived October 20, Read 

 November 19, 1903. 



(From the Physiological Laboratory, University of London.) 



Introduction. 



While the effect of varying conditions on the rapidity of trans- 

 mission of the nervous impulse has been fully studied, no research has 

 yet been made as to whether the stature of the individual and the 

 corresponding difference in the lengths of homologous nerves has or 

 has not any influence on this rapidity, and as recent work has rendered 

 it desirable that the question should be considered, the research here 

 recorded was undertaken to this end. 



Two series of observations were made: (1) On the frog; (2) on 

 man. 



Series I. ON FROGS' NERVES. 



The following plan was adopted after several preliminary trials : 

 Two frogs differing in size were taken, and measurements made of 

 the length from nose to anus, and of the sciatic from the emergence 

 of the last nerve root to the gastrocnemius muscle. Gastrocnemius- 

 sciatic preparations were then made, and placed side by side so that the 

 nerves rested on a little hollow metal platform which was covered with 

 thin sheet indiarubber, while the muscles were fixed just outside this. 

 Crossing this platform were two pairs of electrodes, 20 mm. apart, and 

 the two nerves lay across these, so that each nerve could be simultaneously 

 excited at either pair of electrodes. The platform was covered by a 

 hollow lid, and iced water was passed through both lid and platform, 

 so that the nerves were equally cooled to about C., while the 

 muscles remained at room temperature (17 19 C.). The muscle 

 twitch was recorded on a rapidly moving drum in the usual way. 

 This method presents the advantage that while the nervous impulse 

 is equally reduced in both nerves to an easily measureable speed, the 

 delay due to the end-plates and muscles remains at its normal figure, 

 any alteration in this latter factor bears, therefore, a lesser ratio to 

 the total " latent period " than in experiments where both nerve and 

 muscle are at ordinary temperature. The excitation was maximal 

 throughout. 



