MESENCEPHALIC ROOT 193 



fined to the motor branches of the N? masticatorius. Figure 29 

 shows that all of the degenerated fibers, representing both de- 

 scending mesencephalic root fibers and trigeminal motor fibers, 

 are present in the N. mandibularis proper (a few motor fibers for 

 the mylohyoid nerve), masseter, pterygoid and deep temporal 

 branches of the N. masticatorius. Likewise, a similar section 

 from series 68 ^yould show a few degenerated fibers, probably 

 motor, in the N. mandibularis proper. The great bulk of degen- 

 erated fibers are in the so-called purely motor branches of the N. 

 masticatorius. 



A more peripheral section from this series (fig. 23) exhibits 

 the five main branches of the trigeminal nerve more widely 

 separated, and a portion of this section is sufficiently magnified 

 in figure 24 so that every particle of degenerated myelin of any 

 size could- be accurately represented. This figure includes the 

 nervus auriculotemporalis (Aur.T.), the main portion of the N. 

 mandibularis (Man.), the N. masticatorius (Mast.), and repre- 

 sentative bundles (a) and (b) from the N. ophthalmicus and N. 

 maxillaris. As in figure 22, the degenerated descending mesen- 

 cephalic root fibers are confined solely to the masseter (Mas.), 

 pterygoid (Pter.), and deep temporal (Tern.) branches of the N. 

 masticatorius. Absolutely no more degenerated fibers are to be 

 found in the N. auriculotemporalis, the main trunk of the N. 

 mandibularis, the buccal (sensory) branch of the N. mastica- 

 torius, and bundles (a) and (b) from the N. ophthalmicus and N. 

 maxillaris than would appear in a section of a perfectly normal 

 trigeminal nerve. Since the N. masticatorius has given off but 

 one small branch to the temporal muscle, there are apparently 

 fully as many normal and degenerated nerve fibers in the motor 

 branches of the N. masticatorius as there were in more central 

 sections. Also about the same ratio of normal to degenerated 

 fibers persists. Of the various motor nerves in the N. mastica- 

 torius shown in figure 24", the deep temporal {Tern.) is much the 

 smallest and the masseter (Mas.) is a little larger than the 

 pterygoid (Pter.). All possess relatively about the same number 

 of degenerated descending mesencephalic root fibers. If there is 

 any difference, the N. pterygoideus has the greatest number in 

 proportion to its size. 



