636 "Journal of Comparative Neurology and Psychology. 



the 27 and 42 cm, stages. The general conclusion may be stated 

 thus: in the human embryo of 15.5 mm. the mesencephalic root of 

 the trigeminus is connected with the sensory root and is clearly not 

 connected with the motor root or nucleus, but is widely separated 



VII 



Fig. 31. 



Fig. 32. 



Fig. 31. The second section of this series ventral to the last. X 20. The 

 motor and sensory roots of the trigeminus, the cochlearis and motor facialis 

 are shown. The outer surface of the pons is toward the left. A broken 

 line separates the motor and sensory roots. The fibers of the motor bundles 

 have a much darker and more opaque stain than those of the sensory bundles. 



Fig. 32. The sixth section of this series ventral to the last. X 20. The 

 motor and sensory roots of the trigeminus are shown near their point of exit. 

 In these last two sections there is nothing except their deeper stain to indicate 

 that bundles y and z are motor bundles. They are readily traced continuously 

 through the series as described in the text. The broken line separates the 

 motor and sensory roots. 



from them ; in the later foetus of 27, 37 and 42 cm. stages the mesen- 

 cephalic root is gradually crowded closer to the motor nucleus and 

 root and where it passes over the dorso-caudal surface of the nucleus 

 a small part of its fibers are interlaced with the decussating motor 

 fibers and with a few of the homolateral fibers ; by far the greater 



