MESENCEPHALIC ROOT 195 



containing both degenerated descending mesencephalic and motor 

 root fibers, will be seen going to a bundle of masseter muscle 

 fibers (M.F.). The excess number of degenerated fibers in the 

 masseter nerves in figure 30 over figure 27 represent trigeminal 

 motor fibers destroyed by the lesion in experiment no. 65. 

 Sections of the trigeminal nerves in series no. 68 are almost 

 identical to series 64 and 67, except that a few degenerated 

 fibers, probably trigeminal motor fibers, appear in the main 

 mandibular trunk. 



It can be stated for experiments 64, 65, 67, and 68 that no 

 descending mesencephalic root fibers were found outside the 

 mandibular division of the trigeminal nerve. Also from experi- 

 ments 64 and 67, where the mesencephalic root was severed with 

 absolutely no damage to the trigeminal motor nucleus or to the 

 roots of the trigeminal nerve, it is perfectly clear that the de- 

 scending mesencephalic root fibers are confined solely to the 

 so-called purely motor branches of the nervus masticatorius, 

 namely, the masseter, pterygoid, and deep temporal nerves. 



Returning again to the results of the experiments in which 

 the trigeminal roots were severed centrally to the semilunar 

 ganglion, where it was found that a considerable part of the 

 mesencephalic root was composed of sensory fibers taking origin 

 from the semilunar ganglion cells and also to experiment 51, 

 where no degenerated ascending sensory fibers were found in the 

 mensencephalic root after a lesion of the dorsal part of the tri- 

 geminal sensory root, which fibers were undoubtedly from the 

 ophthalmic and maxillary branches of the trigeminus (purely 

 'sensory nerves\ it is fair to assume that the so-called ascending 

 feensoryi mesencephalic root fibers, like the descending mesen- 

 cephalic root fibers, were distributed to the masticator muscle 

 nerves. Since no decending mesencephalic root fibers went to 

 the mylo-hyoid and digastric nerves, it is quite probable that the 

 ascending sensory fibers of the mesencephalic root supply the 

 mylo-hyoid and digastric muscles. 



So far as I am aware muscle sense from the masseter muscle 

 could not reach the trigeminal nerve by any other way than the 

 N. masticatorius, and it has been demonstrated that no fibers 



