200 A MANUAL OF ANATOMY. 



The cortical centre of smell is located in the uncinate 

 convolution, hippocampus major, and the pes hippocampi. 



2. The Optic Nerve. Figs. 21, 28, 29, 38, 53, 54, 10, 



I I, 12. 



This passes forward from the optic commissure or chiasm 

 to enter the optic foramen in company with the ophthalmic 

 artery, the latter being external and inferior to the nerve. 

 See page 57. 



The optic chiasm is the junction of the two optic tracts at 

 the middle of the base of the brain ; it lies in front of the 

 tuber cinereum and rests upon the optic groove of the 

 sphenoid bone. 



The optic tracts extend backward and outward from the 

 optic chiasm, winding around the crura cerebri and under 

 cover of the temporal lobes. At a later stage of the dis- 

 section the optic tracts will be found to arise from the 

 external geniculate body, the pulvinar of the optic thala- 

 mus, and the anterior of the corpora quadrigemina (the ex- 

 ternal arm) ; and from the internal geniculate body and the 

 posterior of the corpora quadrigemina (the internal root). 

 The cortical centre of sight is in the cuneate convolution 

 of the occipital lobe. 



3. The Motor Oculi. Figs. 21, 29, 38, 10, n. 



This nerve issues from the inner side of a crus cerebri, 

 close to the pons, passes forward through the cavernous 

 sinus, and leaves the skull through the sphenoidal fissure. 

 See page 57. 



(Its deep origin is from a nucleus in the floor of the 

 aqueduct of Sylvius, and its cortical representation is in the 

 convolutions about the lower extremity of the fissure of 

 Rolando.) 



