292 STUDIES AV LIFE AND SENSE. 



sented by the table, and a " sensation " (of touch) is the result of the 

 contact in question. Here ends the act, we may be disposed to say ; 

 but our previous knowledge of " reflex action " and its nature forbids 

 the supposition. " How dp you know you touched the table ? " is 

 the pertinent query of physiology. The reply is, " Because I felt the 

 contact betwixt my nerves and the object in question." But, retorts 

 the physiologist, " feeling is a brain act ; it is an act wherein con- 

 sciousness or knowledge participates. The seat of knowledge is not 

 the tip of the finger, but the brain. And you must therefore reason- 

 ably assume that to the brain the sensation formed and produced in 

 the forefinger is transmitted." Thus we find logical justification for 

 the doctrine of "reflex action," in a common-sense study of the 

 results of touch. The motor impulse sent out from the brain, and, 

 putting the arm and hand in motion, is returned to the brain. It is 

 " reflected " back as a sensory impulse to the sensorium, and kindles 

 therein the knowledge we desire even whilst we are yet in mere 

 expectancy. 



But is this induction founded upon anything more than a con- 

 sistent theory of brain control and bodily action? In 1811 Sir 

 Charles Bell published his first essay on the nerves which originate 

 from the spinal cord (hence called " spinal nerves") and which 

 supply the body generally with nervous power. The spinal cord 

 itself being a direct continuation downwards of the brain, it follows 

 that impulses from the brain pass at first along the main line of the 

 spinal marrow lodged securely within the bony canal formed by 

 the spine and thereafter pass along the nerves or branch lines to 

 various stations and termini in the body. To Sir Charles Bell 

 belongs the great and lasting merit of the discovery of the difference 

 in function between the two roots by which each spinal nerve arises 

 from the spinal cord. Each nerve passing outwards to the body, 

 thus consists in reality of two sets of nerve-fibres, indistinguishable 

 by microscopic investigation, similar in appearance, but widely dif- 

 ferent in use and function. Once for all settling, by vivisection on 

 rabbits, the meaning of the double-rooted origin of the nerves, Bell 

 laid the foundation of all subsequent knowledge of nerves and their 

 functions to which in these latter days we have attained. "On 

 laying bare the roots of the spinal nerves," says Bell, " I found I 

 could cut across the posterior fasciculus (or hinder root) of nerves, 

 which took its origin from the posterior portion of the spinal 

 marrow, without convulsing the muscles of the back ; but that, on 

 touching the anterior fasciculus (or front root) with the point of the 

 knife, the muscles of the back were immediately convulsed." Thus 

 was foreshadowed the great truth that those fibres of a nerve which 

 arise from the hinder part of the spinal cord endow us with sensa- 

 tion ; whilst the front roots give us power of motion. Turn now to 



