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the voluntary muscles with the brain. 
have any other purpose to serve than merely to contract 
under the impulse of the motor nerves. For if they have a 
reflective influence, and if their condition is to be felt or 
perceived, it will presently appear that the motor nerves are 
not suitable internuncii betwixt them and the sensorium. 
I shall first enquire , if it be necessary to the governance of the 
muscular frame , that there be a consciousness of the state or degree 
of action of the muscles f That we have a sense of the condi- 
tion of the muscles, appears from this : that we feel the effects 
of over exertion and weariness, and are excruciated by 
spasms, and feel the irksomeness of continued position. We 
possess a power of weighing in the hand: — what is this but 
estimating the muscular force ? We are sensible of the most 
minute changes of muscular exertion, by which we know the 
position of the body and limbs, when there is no other means 
of knowledge open to us. If a rope-dancer measures his 
steps by the eye, yet on the other hand a blind man can 
balance his body. In standing, walking, and running, every 
effort of the voluntary power, which gives motion to the 
body, is directed by a sense of the condition of the muscles, 
and without this sense we could not regulate their actions. 
If it were necessary to enlarge on this subject, it would be 
easy to prove that the muscular exertions of the hand, the 
eye, the ear, and the tongue, are felt and estimated when we 
have perception through these organs of sense ; and that 
without a sense of the actions of the muscular frame, a very 
principal inlet to knowledge would be cut off. 
If it be granted, that there must be a sense of the condition 
of the muscle, we have next to show that a motor nerve is 
