1826.] Philosophical Transacfipm for 1826, Parts L andIL 22% 



two classes of nerves going to the muscles of the face, and 

 divided the motor nerve, and when the muscles were deprived of 

 motion by this experiment, the natural question suggested 

 itself — of what use are the nerves that remain entire ? 



" For a time I believed that the fifth nerve, which is the sen?^ 

 sitive nerve of the head and face, did not terminate in the 

 substance of the muscles, but only passed through them to the 

 skin ; and I was the more inclined to this belief on observing, 

 that the muscular parts when exposed in surgical operations did 

 not possess that exquisite sensibility which the profusion of the 

 sensitive nerves would imply, or which the skin really pos- 

 sesses. 



" Still dissection did not authorise this conclusion. I traced 

 the sensitive nerves into the substance of the muscles : I found 

 that the fifth pair was distributed more profusely to the muscles 

 than to the skin ; and that estimating all the nerves given to the 

 muscles, the greater proportion belonged to the fifth or sensitive 

 nerve, and the smaller proportion to the seventh or motor nerve. 

 On referring to the best authorities, as Meckel,^ and my excel- 

 lent preceptor Monro, the extremities of the fifth were described 

 by them as going into the muscles, so that of this fact there 

 cannot be a doubt. 



" Having in a former paper demonstrated that the portio dura 

 of the seventh nerve was the motor of the face, and that it run 

 distinct from the sensitive nerve, the fifth, and observing that 

 they joined at their extremities, or plunged together into the 

 muscles, I was nevertheless unwilling to draw a conclusion from 

 a single instance ; and therefore cast about for other examples 

 of the distribution of the muscular nerves. It was easy to find 

 motor nerves in combination with sensitive nerves, for all the 

 spinal nerves are thus composed ; but we wanted a muscular 

 nerve clear in its course, to see what alliance it would form in its 

 ultimate distribution in the muscle. I found in the low^er max* 

 illary nerve the example I required. 



" The fifth pair, from which this lower maxillary nerve comes, 

 as I have elsewhere explained, is a compound nerve ; that is to 

 say, it is composed of a nerve of sensation, and a 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 

 Gasseriau ganghon 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 temporal 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 unac- 

 companied; but on the contrary, I found that before these 



" * Meckel de quinto pare nervorum cerebri." 



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