462 



HISTORY OF THE HUMAN BODY 



somite the Ophthalmicus profundus represents the sensory, 

 and the Motor oculi the motor root. To the second the remain- 

 ing portion of the Trigeminus and the Trochlearis are similarly 

 related, the former with prae- and post-trematic branches about 

 the mouth. The third is supplied by the Facialis for a sensory 



rx 



Olf. CiL v vn vra ix 



' B 



G G* Gj 



FIG. 126. Two suggestions for the solution of the problem of verte- 

 brate cephalogenesis. 



(A) According to VAN WIJHE. (B) According to BEARD. 



The roman numerals enclosed in the ovals in A designate the head somites, 

 all other roman numerals refer to the cranial nerves, m, mouth; n, nasal opening; 

 sp, spiracular cleft; G v G v etc., gill-slits; Olf, olfactory nerve; Cil, ciliary nerve. 



and by the Abducens for a motor root, but for the fourth we 

 have the Acusticus alone, with the motor root wanting. The 

 remaining five possess the five elements shown in the Vagus 

 group in fishes, while two Hypoglossus roots supply motor ele- 

 ments for the last three somites. Fig. 126, B, shows a sug- 

 gestion made by another investigator, and based mainly upon 



