PATHS OF THE CRANIAL NERVES 



553 



with each other and with the posterior longitudinal fasciculus. 

 Through this fasciculus they are placed in intimate relation with 

 the ocular centers of the lower cranial nerves. 



The second or optic nerves differ markedly in their arrangement 

 from the lower cranial nerves. From the standpoint of embryology 

 and comparative anatomy the retina of the eye represents, in part, 



OF THE HUMAN B11A1N STEM, AT THE LEVEL OF THE SUPERIOR 

 CORPORA QUADRIGEMINA. 



Aq, aqueductus Fallopii ; Brga, arm of the anterior corpora quadrigemina ; Brgp, arm 

 or peduncle of the inferior corpora quadrigemina ; Cgl, lateral geniculate body ; Cgm, 

 mesial geniculate body; Cgma, accessory nucleus of same; Coqa, commissure of the su- 

 perior corpora quadrigemina ; Fcop, bundle to the posterior commissure ; Flp, posterior 

 longitudinal bundle; Fpl, lateral pontine bundle ; Fprd, predorsal bundle; <?/, Gil, and 

 6r//7, superficial, middle, and deep grey layer; Gml, lateral ganglion of the mid brain; 

 ///, oculomotor nerve; IH, lateral bundle of the tegmentum ; ZTO, lateral lemniscus ; 

 Lmp, bundle from the fillet to the crusta ; Ndtg\ accessory dorsal nucleus of the teg- 

 mentum ; JV7//, lateral oculomotor nucleus ; Nlllm, mesial oculomotor nucleus ; N(Ja, 

 nucleus of the anterior corpora quadrigemina ; Pcm, peduncle of the mammillary body ; 

 Pp, crusta; Pal, pulvinar; SnS, substantia nigra; Stri, intermediate layer; Strl, layer 

 of the fillet; Stro, layer of the optic nerve; i$trz', stratum zonale of the corpora quadri- 

 gemina; tM, deep medullary layer; TVs, rubro-spinal tract; Tst, spino-tectal and thal- 

 amic tract; Fc, cerebral root of the trigeminus. Weigert's stain, x 2. (After Marburg.) 



at least, a detached portion of the cerebrum. The optic nerves are 

 therefore properly considered as central paths or tracts, and as such 

 must contain sensory neurones of the higher orders. 



Adopting this view, the true peripheral ganglion of the optic 

 nerve would be formed by the inner nuclear layer of the retina 



