NEW VIEWS OF THE SPINAL CHORD. 379 



necessity ; " quant aiix nerfs," he says, " qui sont destines 

 aux mouvemens musculaires, ils partent vraisemblablenient 

 d'un autre foyer, et constituent, dans le systfeme nerveux, un 

 system e particulier distinct des sensations, comme ce dernier 

 est du systfeme qui sert aux actes de I'eutendenient."* In the 

 same year Alexander Walker, passing from this vague concep- 

 tion to a definite localisation of the different centres, declared 

 that the sensoiy impressions were due to the roots of the 

 nerves issuing from the anterior colmnns, and motor impres- 

 sions to the roots issuing from the posterior columns. But 

 although this was a felicitous hyj)othesis, it rested on no co- 

 ercive evidence, experunental or pathological ; and m 1811 

 Bell -f- demonstrated that it was the postei^ior root which was 

 sensitive, the anterior which was motor. This discoveiy has 

 been universally accepted. It placed Bell at once among the 

 great names in science. But this discovery, which was sup- 

 ported by ample and decisive experiments, led him and others 

 to a conclusion respecting the columns of the chord which, 

 although extremely plausible, was not fomided on decisive 

 evidence, and is now proved by Brown-Sequard to be alto- 

 gether erroneous. The roots which issue from the posterior 

 columns are sensoiy ; what more natural than to suppose that 

 the coliunns themselves must be sensory ? Natural, but 

 erroneous. While the discovery respecting the roots met 

 with Kttle opposition, the deduction respecting the columns 

 was vehemently criticised. Expermients were instituted 

 which gave a mass of conflicting testimony, cmious to consider. 



* Lamarck, PhilosopMe Zoologique, 1809, vol. ii. p. 260. 

 f Bell, An Idea of a New Anatomy of the Brain, 1811. 



