192 



Anatomy of the; Rabbit. 



(e) The posterior funiculus, in passing forward from the cord, 

 is divided into medial and lateral portions. The medial 

 portion, the fasciculus gracilis, forms a narrow band ter- 

 minating forwards in a club-shaped expansion, the clava. 

 The lateral portion, the fasciculus cuneatus, passes into the 

 restiform body. 



6. The brain may be divided by a median vertical section, and one- 

 half examined from the medial surface (Fig. 56). In addition to many 

 of the features already made out on the surface the following may be 

 noted : 



(a) The deep but extremely narrow cavity formed by the third 

 ventricle is the first space appearing in the brain from the 

 anterior end, the first two (paired) ventricles lying laterally 

 in the hemispheres. They are connected with the third 

 ventricle by a narrow transverse canal, the interventricular 

 foramen (foramen interventriculare). 



Fig. 56. The brain in median section: a., anterior commissure; a.c, cerebral aque- 

 duct; b.o., olfactory bulb; cb., cerebellum; c.cl., corpus callosum; c.f., body of the 

 fornix; cl.i., inferior colliculus; cl.s., superior colliculus; cm., mammillary body; 

 CO., optic chiasma; c. p., pineal body; fl.c, cervical ftexure; h., habenular commissure; 

 h.c, cerebral hemisphere; hp. hippocampus; inf., infundibulum; l.t., laminal terminalis; 

 m.o., medulla oblongata; p., posterior commissure; p.c, chorioid plexus of the third 

 ventricle; pd.c, cerebral peduncle; pn., pons; sp., splenium; s. pi., septum pellucidum; 

 t.c, tuber cinereiim; th., thalamus, massa intermedia; v.m.a., anterior medullary 

 velum; v.m.p., posterior medullary velum; v.q., fourth ventricle; v.t., third ventricle. 

 I, olfactory nerve (origin); II, optic nerve. 



(b) The anterior boundary of the third ventricle is formed 

 ventrally by the narrow partition separating the two hemi- 

 spheres, in the dorsal portion of which is the small anterior 

 commissure (commissura anterior). The ventral portion of 

 the ventricle is projected toward the optic chiasma forming 

 the recessus opticus, and into the infundibulum, forming the 

 recessus infundibuli. 



(c) The mesencephalon contains no ventricular expansion, its 

 substance being perforated only by a narrow tube, the cere- 



