378 C. JUDSON HERRICK 



tractus bulbo-spiimlis (figs. 10 to 18, tr.b.s.) probably arises from 

 these cells. Dendrites of the large tangential neurones of the VII, 

 IX and X regions cross the meson in the ventral commissure and 

 their axones are in some cases seen to enter the fasciculus longi- 

 tudinalis medialis, some ascending and some descending. Other 

 neurones of the system of the motor tegmentum are seen in 

 figures 25, 27, 29, 30, 31, 33, 37, 38, 39, 41 and 42. 



Laterally of the motor nuclei of the VII, IX and X cranial nerves 

 is a tegmental area containing relatively small neurones in the 

 stratum griseum, whose slender dendrites spread widely through- 

 out the white substance and also in the marginal zone of the gray 

 substance among the arcuate fibers (figs. 27, 33) . These neurones, 

 whose axones are generally du'ected downward toward the 

 ventral commissure with numerous collaterals, probably are of 

 the same type as those of the formatio reticularis of higher brains. 



The VI nerve emerges from the brain by several delicate rootlets 

 some distance caudad of the motor VII roots, as stated by Coghill 

 ('02, p. 213). I have seen no Golgi impregnations of this nucleus, 

 but in Cajal preparations of the larvae its neurones do not appear 

 to differ from the small cells of the surrounding central gray. 

 In the adult, however, these neurones are considerably enlarged. 

 This nucleus closely surrounds the fasciculus longitudinalis medi- 

 alis, a special fascicle of which breaks up among its cells. This 

 fascicle is derived chiefly from the area acustico-lateralis of the 

 same side, and some of its fibers can be followed caudad as far as 

 the motor IX nucleus. 



The limits of the motor VII nucleus are fairly clear in Cajal 

 preparations, but within and around this nucleus are tegmental 

 neurones; see figures 11, 12, 13, 27, 30, 33. The motor V nucleus, 

 on the other hand, lies farther lateral than the motor VII and is 

 more clearly separated from the nucleus motorius tegmenti. 

 Medially of the motor V nucleus is a tegmental eminence which is 

 greatly enlarged farther forward as the eminentia subcerebellaris 

 tegmenti. Into this eminence are discharged ascending tracts 

 from the spinal cord (tractus spino-bulbaris) and also important 

 descending tracts from the cerebrum (figs. 4 to 7), such as the 

 tractus tecto-bulbaris (tr.t.b.), tractus thalamo-bulbaris (tr.th.b.), 



