54 F. W. THYNG 



Cranial nerves 



The cranial nerves of the right side are displayed in plate 3. 

 and those of the left are shown in plates 2 and 5. Plate 6 shows 

 some of the cranial nerves on both sides. 



Nn. olfactorii. Numerous nerve fibers {Nn.olf., plate 1) ex- 

 tend from the dorsal and medial surfaces of the nasal epithelium, 

 and from the vomero-nasal organ (Org.vom.-nas.) to the olfactory 

 area {Rhin.) of the telencephalon. In plates 2 and 3 the trunk 

 formed by these nerves is represented as a stump. Among the 

 fibers are numerous groups of cells which are not represented 

 in the reconstruction. These cells perhaps have migrated from 

 the nasal epithelium along the nerve fibers. 



A^. opticus. Fibers are present, extending from the retinal 

 layer of the optic vesicle along the optic stalk to the correspond- 

 ing ridge (optic) of the brain. 



N. oculomotorius. The oculomotor nerve (iV.oc, plates 2, 3 

 and 5) issues from the ventro-lateral wall of the mesencephalon 

 (Mesen.) by numerous small rootlets. It extends ventrally and 

 cephalad, passing lateral to the posterior cerebral artery (A.cer.p.), 

 and medial to the cavernous sinus {S.cav.) and the ophthalmic 

 nerve {N.oph.). From the ophthalmic nerve it acquires a small 

 sensory branch. Caudad of the optic stalk it gives off a branch 

 to the anlage of the superior rectus muscle, but its main trunk 

 is continued to the partially differentiated anlage for the inferior 

 and medial recti and inferior oblique muscles. 



N. trochlearis. The trochlear nerve (N.troch., plates 2 and 3) 

 issues from the roof of the isthmus and extends ventrally in a 

 sinuous course to the orbit. In its course it passes just cephalad 

 of the superior cerebellar artery {A.cereh.s., plate 2) and lateral 

 to the anterior cerebral vein. In the orbital region it passes 

 dorsal to the anlage of the lateral rectus muscle, and medial to 

 the frontal ramus {N.fr., pi. 3) of the ophthalmic nerve. It 

 terminates in the anlage of the superior oblique muscle. The 

 trochlearis receives a small sensory branch from the ophthalmic 

 nerve {N.oph., pi. 3). 



