166 Mr, Bell on the nervous circle which connects 



nerve of motion. It arises in two roots, one of these is the 

 muscular nerve, the other the sensible nerve ; on this last 

 division the Gasserian ganglion is formed. But we can trace 

 the motor nerve clear of the ganglion and onward in its 

 course to the muscles of the jaws, and so it enters the tem- 

 poral masseter pterygoid and buccinator muscles. 



If all that is necessary to the action of a muscle be a nerve 

 to excite to contraction, these branches should have been 

 unaccompanied ; but on the contrary, I found that before 

 these motor nerves entered the several muscles, they were 

 joined by branches of the nerves which came through the 

 Gasserian ganglion, and which were sensitive nerves. 



I found the same result on tracing motor nerves into the 

 orbit, and that the sensitive division of the fifth pair of nerves 

 was transmitted to the muscles of the eye, although these 

 muscles were supplied by the third, fourth, and sixth nerves. 



A circumstance observed on minute dissection remained 

 unexplained, — when motor nerves are proceeding to several 

 muscles they form a plexus ; that is, an interlacement and 

 exchange of fibres takes place. 



The muscles have no connection with each other, they are 

 combined by the nerves ; but these nerves, instead of passing 

 betwixt the muscles, interchange their fibres before their dis- 

 tribution to them, and by this means combine the muscles 

 into classes. The question therefore may thus be stated : 

 why are nerves, whose office it is to convey sensation, pro- 

 fusely given to muscles in addition to those motor nerves 

 which are given to excite their motions ? and why do both 

 classes of muscular nerves form plexus ? 



To solve this question, we must determine whether muscles 



