364 



ANATOMY OF THE RABBIT 



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

 ventricle is the most anterior space appearing in the brain, 

 the paired lateral ventricles, which are reckoned as the 

 first two without either being specifically designated as first, 

 lying laterally in the hemispheres. Each of these paired 

 ventricles is connected with the third ventricle by a narrow 

 transverse canal, the interventricular foramen (formen 

 interventriculare), situated a short distance dorsal to the 

 position of the anterior commissure (Fig. 124). 



Fig. 12-1. The brain in median section: a, anterior commissure; ac, cerebral 

 aqueduct; bo, olfactory bulb; cb, cerebellum; cc, central canal of spinal cord; 

 ccl, corpus callosum; cf, body of the fornix; cl.i, inferior coUiculus; cl.s, 

 superior colliculus; cm, mamillary body; co, optic chiasma; cp, pineal body; 

 fl.c, cervical flexure; h. habenular commissure; he, cerebral hemisphere; hp, hip- 

 pocampus; inf, infundibulum; It, laminal terminalis; mo, medulla oblongata; 

 p, posterior commissure; pc, chorioid plexus of the third ventricle; pd.c, cerebral 

 peduncle; pn, pons; sp, splenium; spl, septum pellucidum; tc, tuber cinereum; 

 th, thalamus, massa intermedia; vma, anterior medullary velum; vmp, posterior 

 medullary velum; vq, fourth ventricle; vt, third ventricle; I, olfactory nerve 

 (origin); II, optic nerve. 



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

 ventrally by the narrow transverse wall passing across 

 from one hemisphere to the other, the lamina terminalis, 

 in the dorsal portion of which is the small anterior com- 

 missure (commissura anterior), a connection between the 

 olfactory portions of the brain on one side and those on 

 the other. The ventral portion of the ventricle is projected 

 above 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 tube, narrow an- 



