1428 



A MANUAL OF ANATOMY 



Corpora Quadrigemina.— These are four rounded eminences, 

 which, as just stated, form the dorsal portion of the mesencephalon. 

 They are covered by the splenium of the corpus callosum, and are 

 arranged m pairs, upper and lower, the upper pairs (nates) being 

 larger than the lower pair (testes), but not quite so prominent. 

 The four eminences are separated from each other by two grooves, 

 longitudinal and transverse, which are arranged in a crucial manner! 

 The longitudinal groove extends upwards as far as the posterior 

 commissure, and it separates the upper and lower quadrigeminal 

 bodies of one side from those of the other side. Its upper part 

 lodges the pineal body, and from its lower part a band of white 



Middle Commissure 

 Pineal Peduncle •» Third Ventricle 



(Habenula) < 



- Optic Thalamus 



Upper Quadrigeminal Body 

 ' '"JS^— L'-'^^'' Quadrigeminal Body 

 ^i^-**\- Crus Cerebri , 



' Frenulum Veli 

 -~ Valve of Vieussens 

 ~«Superior Peduncle of 

 Cerebellum 



■■^Do., do. (cut) 



Striae Acusticse 

 "^^^NTrigonum Acusticum (base) 

 ^^^^Trigonum Hypoglossi 

 ^^ Trigonum Vagi 

 ■-^.Tubercle of Rolando 

 "xClava 

 - Funiculus Gracilis 



Funiculus Cuneatus 



Fig. 600. — The Floor of the Fourth Ventricle and Adjacent Parts. 



Eminentia Teres M^Jw ' ' 



Superior Fovea ,_S«W ^ 



Striae Acusticae.Z^T^Z^^ 

 Inferior Fovea 



Cuneate Tubercle - - 



fibres, called the frenulum veli, passes downwards to the superior 

 medullary velum or valve of Vieussens, which lies below the lower 

 pair of eminences. The transverse groove separates the upper pair of 

 quadrigeminal bodies from the lower pair. Laterally each eminence 

 is connected with a white band, called the brachium, the two 

 brachia being separated by a continuation of the transverse groove. 

 The superior brachium extends outwards and forwards from the 

 upper quadrigeminal body to the external geniculate body and 

 the outer root of the optic tract. It passes between the pulvinar 

 of the optic thalamus and the internal geniculate body. Its fibres 

 terminate within the internal geniculate body. These fibres are 

 derived from the lateral or acoustic fillet, partly directly, and partly 

 through the intervention of the lower quadrigeminal body. 



