84 SPINAL DEPRESSANTS 



of the grey matter of the cord, they impede the trans- 

 mission of painful impressions. Sir Lauder Brunton pro- 

 pounds an explanation of the nature of inhibition. He 

 believes that nervous stimuli consist in vibrations in nerve- 

 fibres or nerve-cells, analogous to the vibrations of light or 

 sound. When two waves of light or sound fall upon each 

 other so that their crests coincide, the intensity of the light 

 or sound is increased ; but when they fall so that the crest 

 of one wave occupies the trough between the two preceding 

 or succeeding waves, such two waves of light cause dark- 

 ness, or two such waves of sound cause silence. Moving the 

 one wave forward or backward upon the other intensifies 

 or diminishes the vibrations of light or sound. ' Supposing 

 nervous stimuli to consist of vibrations like those of light 

 and sound, the action which any nerve-cell would have upon 

 the others connected with it would be stimulant or inhibi- 

 tory according to its position in relation to them.' If nerve- 

 force, as believed, consists of vibrations similar to those of 

 light or sound, the relative position of nerve-cells in action 

 will often determine a stimulant or inhibitory result. If 

 one nerve-current meets another in such a way that the 

 waves of which they consist coincide, the nervous action 

 will be doubled, but if they interfere the nervous action 

 will be abolished. If they meet so as neither completely to 

 coincide nor to interfere, the nervous action will be some- 

 what increased, or somewhat diminished, according to the 

 degree of coincidence or interference between the crests of 

 the waves. The relation of these waves to one another 

 may be affected by the distance each travels and the rate of 

 transmission. 



This hypothesis seems to explain why different doses of 

 poisons sometimes produce very different results. The 

 phenomena of strychnine poisoning thus appear to depend 

 upon the nervous vibrations being thrust crest upon crest, 

 when intense convulsions occur ; while, from one or another 

 wave dropping half a length behind, the interval of rest or 

 relaxation follows. In like manner may be explained the 

 similar effects of cold and heat. Cold retards, while heat 

 accelerates, transmission of vibrations, and either agent 

 may thus alter one of the waves, causing coincidence and 



