4o8 Journal of Comparative Neurology. 



composed of both communis and general cutaneous fibers). 

 The communis root constitutes the " infero-medial strand " of 

 Wright, the general cutaneous root (together with the motor 

 V) the " superolateral strand." These two strands remain dis- 

 tinct until after the trunk has emerged from the cranial wall, 

 then their fibers are re-arranged so that both maxillary and 

 mandibular nerves receive general cutaneous and communis ele- 

 ments in approximately equal proportions. 



At the level of the optic nerve from its foramen, these 

 nerves are arranged ventrally of that nerve and of the great 

 levator arcus palatini muscle, mesially of the m. adductor man- 

 dibulae and dorsally of the m. adductor arcus palatini, the r. 

 mandibularis being external, the r. maxillaris internal and the 

 r. buccalis dorsally and between the other two. 



Considerable importance to phylogeny having recently 

 been attributed to the eye muscle nerves, we have carefully 

 worked them out. 



VI. The abducens arises by several rootlets and runs for- 

 ward just internal to the VIII nerve and ganglion. Continuing 

 in the same direction, it comes to lie at the ventral angle of the 

 geniculate ganglion. It now applies itself to the fiber complex 

 arising from this ganglion, the "infero-medial strand" of 

 Wright, becoming embedded in its ventral and inner edge, 

 though always clearly distinguishable by reason of the larger 

 size and heavier myelination of its fibers. As the infra-orbital 

 trunk passes through its foramen in the cranial wall, the VI 

 nerve runs up along its inner face to join the III nerve, parallel 

 with which it runs out for some distance, as mentioned by 

 Wright. It then passes directly outward close above the infra- 

 orbital trunk and under all of the other orbital structures to 

 enter the rectus externus at its posterior margin in the typical 

 way. 



IV. The trochlearis immediately upon its exit from the 

 brain applies itself to the inner face of the V + VII ganglionic 

 complex and follows the same forward, accompanying the r. 

 ophthalmicus superficialis V along its ventral edge until it has 

 emerged through its foramen into the orbit. It now lies in the 



