PHYSIOLOGICAL EXPERIMENTATION. 181 



I then touched the anterior division ; immediately the parts were 

 convulsed." 



" Experiment II. I now destroyed the posterior part of the spinal 

 marrow by the point of a needle ; no convulsive movement followed. 

 I injured the anterior part, and the animal was convulsed." 



The experiments thus narrated by Bell in a letter to his brother, 

 dated March 2, 1810, have been cited as proving that he had thus 

 early attributed motor functions to the anterior roots, and sensory to 

 the posterior. But the inference which he himself drew from them 

 at the time was altogether different : 



" It is almost superfluous to say that the part of the spinal marrow 

 having sensibility [i. e., the anterior column] comes from the cere- 

 brum ; the posterior and insensible port belongs to the cerebellum." 



Thus, although on the track of a great physiological discovery, 

 Bell allowed himself to be completely diverted from it by his anatom- 

 ical preconception. Of the true functional relations of the two sets of 

 nerve-roots, there is not the remotest hint in this " Idea." 



Xone the less, however, do I recognize in it what (to my mind) 

 constitutes the real basis of Bell's claim to the elucidation of the mean- 

 ing of the double origin of the spinal nerves. " Considering," he said, 

 " that the spinal nerves have a double root, and being of opinion that 

 the properties of the nerves are derived from their connections with 

 the parts of the brain, I thought that I had an opportunity of putting 

 my opinion to the test of experiment, and of proving at the same time 

 that nerves of different endowments were in the same cord and held 

 together by the same sheath." This was, unquestionably, one of the 

 most fertile suggestions that the insight of a man of genius has ever 

 put forth for the guidance of physiological inquiry ; and, even if Bell 

 had never himself pursued it further, he would clearly be entitled to a 

 very large share of any discoveries that others might make by working 

 upon it. It seems, however, as if the unsatisfactory character of the 

 results he obtained and his dislike to experimentation upon living 

 animals turned his thoughts in a different direction ; and he applied 

 himself for some years to the study of the nerves of the face, on the 

 peculiarities of whose anatomical distribution he seems to have long 

 pondered, with the idea that these might furnish him with the key of 

 which he was in search. 



Bell, as is well known, had considerable artistic ability ; and one 

 of the earliest of his publications was his very valuable "Anatomy of 

 Expression," in which he pointed out how close is the relation between 

 many of the muscular movements by which the emotions are ex- 

 pressed and those concerned in respiration. Still, as it would seem, 

 under the "dominant idea" of a special set of nerves for the "vital 

 and involuntary motions," he assigned this special motor function to the 

 seventh pair, which arises by a single root, and supplies the muscles of 

 the face generally ; while he supposed the fifth pair, which arises (like 



