2l6 



ELEMENTS OF MAMMALIAN ANATOMY 



A number of cross-sections of the cerebral hemispheres should 

 also be studied. 



Each ventricle is composed of a body from which projects 

 an anterior cornu and a middle or descending cornu. The 

 former extends into the frontal lobe and thence into the olfac- 

 tory lobe, and the latter descends into the temporal lobe. The 



Fig. io6. — Sagittal Section of the Brain. 



ac. Anterior commissure; av, arbor vitce; c, habena; cc, canalis centralis; cb, 

 cerebellum; cm, middle commissure or massa intermedia; cr, sulcus crucialis; 

 cpq, corpus quadrigemina; ex, choroid plexus of third ventricle — the dark line 

 dorsad of ex is the velum interpositum; /, sulcus splenialis; /r, frontal lobe of 

 cerebrum; /w, anterior pillars of the fornix; in, infundibulum; it, iter, or aqueduct 

 of cerebrum; k, genu of corpus callosum; bnx, lamina terminalis; m, splenium; ma, 

 corpus niamillare; mr, sulcus marginalis; med, medulla; op, optic chiasm; oe, 

 occipital lobe; ol, olfactory lobe; pn, pineal gland; po, pons Varolii; pe, posterior 

 commissure; pv, inferior medullary velum; pvv, superior medullary velum or valve 

 of Vieussens; 3 and 4, third and fourth ventricles. 



roof of the body of the lateral ventricle is formed by the cor- 

 pus callosum (Figs. io6, 107 and 108) and the medial wall by 

 the septum pellucidum, a mass of gray matter lying between the 

 fornix and the corpus callosum. A fringe of pia mater pro- 

 jects through the interventricular foramen of Monro into the 

 lateral ventricle, where it forms the choroid plexus. The 

 lateral ventricles are lined with the epithelial layer common 

 to the other ventricles. 



