68 DAVIDSON BLACK 



emergent fibers of the IX motor root course first dorsomediad 

 mingled with fine radicular VII motor root strands to the peri- 

 ependymal gray beneath the sulcus limitans. In this region 

 they course rostrad and, becoming separated from the more 

 medially placed VII motor root fibers, pass dorsolaterad in an 

 arched fashion through the fibrae arcuatae dorsales. At this 

 point the root fibers form a compact bundle which makes its 

 exit from the brain stem through the radix spinalis trigemini 

 in a wide curve, the convexity of which is directed rostrad. 



There is no line of demarcation between the cell groups giving 

 rise to the motor VII and IX nerves. The caudal portion of the 

 motor VII-IX nuclear complex is to be considered chiefly as 

 the source of motor IX fibers and has been so illustrated in the 

 reconstruction chart 11, C, because IX root fibers were traced 

 to this center. It is to be understood, however, that all the fibers 

 arising in this portion of the nuclear complex do not emerge 

 in the motor IX root, for undoubtedly VII motor fibers arise 

 here also. The rostral and by far the greater part of this nuclear 

 mass is apparently wholly motor facial in character. 



The motor VII root in Damonia arises in the VII-IX motor 

 nucleus and takes a characteristically indirect course to reach 

 its place of exit from the brain stem. .The fine radicular fibers 

 pass first dorsomediad and become collected upon the dorsal 

 and lateral surfaces of the fasciculus longitudinalis medialis to 

 form the ascending motor facial root. At a level somewhat 

 rostrad of the plane of its exit^ the ascending root bends laterad 

 and caudad, forming a well-marked genu. From the genu the 

 emergent fibers pass laterad and caudad and pierce the radix 

 spinalis nervi trigemini to make their exit on the lateral surface 

 of the medulla (fig. 5) . 



With regard to the origin and course of the motor VII root, 

 the relations described in Damonia correspond closely with those 

 already worked out by Kappers in Chelone, Varanus, Boa, and 

 Alligator and described by Gisi (20) in Hatteria. Such differ- 



5 In figure 12 the level at which the genu of the motor facial root is formed is 

 indicated on each reconstruction chart by the small vertical parallel lines rostrad 

 of the exit level of the root in question. 



