SURFACES. 



145 



the anterior surface at an acute angle. Its inclination is that of 

 the posterior end of the floor of the third ventricle. External to 

 the floor of the ventricle, it is attached to the thalami and internal 

 capsules. The blending of it with the thalami forms the structures 

 of the tegmental hypothalamic regions, and the continuations 

 of the extreme lateral portions, the bases pedunculi, enter into 

 the internal capsules of the hemispheres. In the median line 



Fig. 42. Transverse section of brain, cutting corpora mammillaria. 

 (After Toldt, Morris's Anatomy.) 



a. Lateral ventricle (central portion), b. Chorioid plexus of lateral ventricle, c. Caudate 

 nucleus, d. Massa intermedia, e. Internal capsule. Lenticular nucleus: f, Putamen; 

 gh. Zones, globus pallidus. i. External capsule, j. Claustrum. k. Ansa penduncularis. 1. Optic 

 tract, m. Inferior peduncle of thalamus. n. Inferior cornu of lateral ventricle, o. Hippo- 

 campus, p. Digitations. q. Oculomotor nerve, r. Corpus callosum. s. Fornix. t. Third 

 ventricle, u. Thalamus. v. Thalamo-mammillary fasciculus, w. Ansa lenticularis. x. Hy- 

 pothalamic nucleus (corpus Luysi). y. Substantia nigra. z. Basis of cerebral peduncle. 

 aa. Corpus mammillare. bb. Interpeduncular fossa, cc. Pons (varolii.) 



behind the third ventricle it is attached to the posterior commis- 

 sure. The superior surface is an inch and a half broad. 



The inferior surface joins the upper surface of the pons. It 

 is a little narrower than the superior surface. It is about one 

 inch and a quarter broad and measures an inch dorso-ventrally. 



The anterior surface (ventral) of the mid-brain looks forward 

 and downward (Figs. 45, 47 and 48). It is deeply grooved longit- 



