130 



THE NERVOUS SYSTEM 



groove on the medial aspect of the peduncle, through which emerge the fibers 

 of the third nerve, is known as the sulcus of the oculomotor nerve, while that on 

 the lateral aspect is called the lateral sulcus of the mesencephalon. Dorsal to 

 this latter groove the tegmentum comes to the surface and is faintly marked by 

 fine bundles of fibers which curve dorsally toward the inferior colliculus of the 

 corpora quadrigemina (Fig. 88). These fibers belong to the lateral lemniscus, 

 the central tract associated with the cochlear nerve. 



The corpora quadrigemina form the dorsal portion of the mesencephalon, 

 and consist of four rounded eminences, the quadrigeminal bodies or colliculi, 



Anterior limb of internal capsule.^ 

 Stria terminalis^ / 



Habenular commissure 

 Habenular trigone. \ 



Pineal body^ /\R 



Posterior limb of internal capsule^. )\l" 

 Superior colliculus X"<- 



Optic radiation % ?\ v ^ 

 Attachment anterior'^! 

 medullary velum -J 

 Inferior colliculus 



Superior fovea . ^ 

 Brachium conjunctivum ^v\ 

 O 



Brachium pontis 

 Restiform body 

 Dorsal cochlear nucleus. 

 Acoustic area 

 Inferior fovea and restiform body ~-~ 



Tcenia of fourth ventricle 

 Clava 



Cuneale tubercle 

 Posterior lateral sulcus 



Corona radiata 

 -Head of cattdate nucleus 

 .Stria medullaris of thalamus 

 _ .- Third ventricle 



, Thalamus 

 '\ ,, Tail of caudate nucleus 



\, Median sulcus 

 W . Trochlear nerve 



/''/Facial colliculus 

 ' ,/,' Trigeminal nerve 



'/Sulcus limitans 

 ^'Medial eminence 

 Ala cinerea 



.. Lateral recess of fourth ventricle 

 Trigone of hypoglossal nerve 

 Obex 



'--Posterior median fissure 



Posterior intermediate sulcus 



Funiculus gracilis 



Funiculus cuneatus 



Fig. 91. Dorsal view of brain stem of sheep. 



which arise from the dorsal aspect of a plate of mingled gray and white matter 

 known as the quadrigeminal lamina (Figs. 89, 91). The superior colliculi are 

 larger than the inferior, the disproportion being greater in the sheep than in 

 man. A median longitudinal groove separates the colliculi on either side. In 

 the rostral end of this groove rests the pineal body, while attached to its caudal 

 end is a band which runs to the anterior medullary velum, and is known as the 

 frenulum veli. A transverse groove runs between the superior and inferior collic- 

 uli and extends on to the lateral aspect of the mesencephalon, where it inter- 

 venes between the superior colliculus and the inferior quadrigeminal brachium 

 (Figs. 87, 89). 



