the voluntary muscles with the brain. 171 



We have noticed, that there is a plexus formed both on 

 the nerves which convey the will to the muscles, and on the 

 nerves which give the sense of the condition of the muscles. 

 The reason of this I apprehend to be that the nerves must 

 correspond with the muscles, and consequently with one 

 another. If the motor nerve has to arrange the action of 

 several muscles so as to produce a variety of motions, the 

 combinations must be formed by the interchange of filaments 

 among the nerves before they enter the muscles, as there is 

 no connection between the muscles themselves. As the 

 various combinations of the muscles have a relation with the 

 motor nerves, the same relations must be established by 

 those nerves which convey the impression of their combina- 

 tions, and a similar plexus or interchange of filaments there- 

 fore characterizes both. 



We have seen that the returning muscular nerves are 

 associated with the nerves of sensibility to the skin, but they 

 are probably very distinct in their endowments, since there 

 is a great difference between conveying the sense of external 

 impressions, and that of muscular action. 



In surgical operations the fact is forced upon our attention 

 that the pain of cutting the skin is exquisite, compared with 

 that of the muscles ; but we must remember that pain is a 

 modification of the endowment of a nerve, serving as a guard 

 to the surface, and to the deeper parts consequently. This 



has been some days separated from the brain, the muscle is excited as when the 

 nerve was first divided. The property, however it may be defined, is therefore in 

 the nerve. Our language might perhaps be made more precise if we used terms 

 which implied the course of nervous influence, whether from or towards the brain ; 

 but it will be difficult to express this without the aid of hypothesis. 



