THE GENERAL TOPOGRAPHY OF THE BRAIN 



of the cerebral hemispheres. These are the cerebral peduncles and they form 

 the ventral part of the mesencephalon. At its rostral extremity each peduncle 

 is partially encircled by a flattened band, known as the optic tract, which is con- 

 tinuous through the optic chiasma with the optic nerves. A lozenge-shaped 

 depression, known as the inter peduncular fossa, is outlined by the diverging 

 cerebral peduncles and by the optic chiasma and tracts. Within the area thus 

 outlined and beginning at its caudal angle may be distinguished the following 

 parts: the inter peduncular nucleus, which is very large in the sheep and occu- 



Longitudinal fissure of cerebrum^ 



Optic nerve^ 

 Optic chiasma 

 Rhinal fissure 



Insula- 

 Lateral fissure 



Optic tract . 



Infundibulum -~ 

 Mammittary body - 



Cerebral peduncle 

 Inter peduncular fossa and 

 nucleus 



Trigeminal nerve 



Abducens nerve--- 



Acoustk( Vestibular n ~ 

 nene (Cochlearn. 

 Glossopharyngeal nerve ~-' 

 Vagus nerve 

 Hypoglossal nerve '' 

 Anterior median fissure'' 



' Olfactory bulb 



' Medial olfactory gyrus 



Anterior perforated substance 

 - Lateral olfactory stria 

 Lateral olfactory gyrus 

 -Diagonal band 

 ..- Amygdaloid nucleus 



Pyriform area 

 ; Hippocampal gyrus 

 L-- Trochlear neroe 



m,,.--Pons 

 Jn. .-'A bducens nerve 



~*?^,_-- Facial nerve 



Trapezoid body 



Cerebellum 

 '---Olive 



^Chorioid plexus 

 " Accessory nerve 

 ^Tractus later alis minor 



Fig. 83. Ventral view of the sheep's brain. 



pies an area designated in man as the substantia perforata posterior; the corpus 

 mammillare, which in man is divided by a longitudinal groove into two mam- 

 millary bodies; and also the tuber cinereum, infundibulum, and hypophysis. 

 Rostral to the optic tract there is on either side a triangular field of gray matter, 

 studded with minute pit-like depressions and known as the anterior perforated 

 substance. 



The Rhinencephalon. The olfactory bulb is situated near the rostral end 

 of the hemisphere, to the ventral surface of which it is attached by the olfactory 



