192 WILLIAM F. ALLEN 



A section directly peripheral to the semilunar ganglion (fig. 22) 

 shows that the motor root of the trigeminal nerve had migrated 

 laterally thi'ough the peripheral processes of the semilunar gan- 

 glion to become the motor component of the nervus masticatorius 

 (Mast.), dividing the sensory nerve processes into a cephalic 

 and a caudal portion. Also that the cephalic portion of these 

 fibers has been subdivided by connective tissue into the ner\'ns 

 ophthalmicus (Oph.) and a much larger portion, the N. maxil- 

 laris (Max.). Likewise, the caudal portion of these sensory 

 fibers has been subdivided into the N. auriculotemporalis (Aur. T.) 

 and the large N. mandibularis proper [Man.), which is situated 

 directly medial to the motor division of the trigeminal nerve, 

 namely, the N. masticatorius {Mast.). In passing between these 

 two bundles of sensory nerves, the motor root gave off a few 

 motor fibers to the N. mandibularis (fig. 29, Man.) and received 

 a few sensory fibers in return to form the buccal branch (fig. 22, 

 Buc.) of the N. masticatorius. From figure 22 and the above 

 description, the writer would maintain that, in the guinea-pig, 

 the auriculotemporal and masticator nerves are no more branches 

 of the mandibular nerve than the ophthalmic nerve is a branch 

 of the maxillary. All five nerves appear to arise separately from 

 the general complex of fibers at the distal end of the semilunar 

 ganglion. If muscle sense is eliminated, the ophthalmic, maxil- 

 lary, and auriculotemporal nerves are sensory, the mandibular 

 is sensory save for the mylohyoid, and the masticator, motor, 

 except for the buccal branch. 



It is perfectly clear from figure 22 that all of the degenerated 

 descending mesencephalic root fibers went to and were contained 

 in the masseter {Mas.), pterygoid {Pter.), and deep temporal 

 {Tern.) branches of the N. masticatorius, which were listed in 

 the previous paragraph as motor nerves. Absolutely no more 

 degenerated fibers are to be found in the N. auriculotemporahs 

 {Aur.T.), N. mandibularis proper (Man.), N. maxillaris {Max). 

 and N. ophthalmicus {Oph:) than would be found in a corre- 

 sponding section of a perfectly normal trigeminal nerve. A 

 similar section from series 67 would also demonstrate that all of 

 the degenerated descending mesencephalic root fibers are con- 



