ON MUSCULAR ACTION. 103 



the merit of this discovery, if such it shall ulti- 

 mately prove to be. In his work on the Nervous 

 System, he endeavours to show, that one set of 

 nervous fibres conveys the mandate from the brain 

 to the muscle, and excites the contraction ; and that 

 another conveys from the muscle to the brain the 

 peculiar sense of the state of the muscle, by which 

 we judge of the fitness of the degree of contraction 

 which has been produced to accomplish the end 

 desired, and which is obviously an indispensable 

 piece of information to the mind in regulating the 

 movements of the body. Sir Charles has shown, 

 that many of the sensations supposed to be derived 

 from the sense of touch and the skin, arise from the 

 muscular sense, and are wholly imperceptible to 

 the skin, without the co-operation of muscular con- 

 traction. 



" The muscles have two nerves," says Sir Charles, 

 " which fact has not hitherto been noticed, because 

 they are commonly bound up together. But when- 

 ever the nerves, as about the head, go in a separate 

 course, we find that there is a sensitive nerve and a 

 motor nerve distributed to the muscular fibre, and 

 we have reason to conclude that those branches of 

 the spinal nerves which go to the muscles consist of 

 a motor and a sensitive filament. 



" It has been supposed hitherto, that the office of 

 a muscular nerve is only to carry out the mandate 

 of the will, and to excite the muscle to action, but 

 this betrays a very inaccurate knowledge of the 

 action of the muscular system ; for, before the mus- 

 cular svstem can be controlled under the influence 

 of the will, there must be a consciousness or know- 

 ledge of the condition of the muscle. 



*' When we admit that the various conditions of 

 the muscle must be estimated or perceived, in order 

 to be under the due control of the will, the natural 

 question arises, Is that nerve which carries out the 

 mandate of the will capable of conveying, at the 



