266 



THE NERVOUS SYSTEM 



olfactory fibers of the second order connecting the bulb with the secondary ol- 

 factory centers in the hemisphere. At its point of insertion into the hemisphere 

 the olfactory tract forms a triangular enlargement, the olfactory trigone. 



From the point of insertion of the olfactory bulb or tract a band of gray 

 matter, the medial olfactory gyrus, can be seen extending toward the medial 

 surf ace of the hemisphere (Figs. 159, 197, 198). A similar gray band, the lateral 

 olfactory gyrus, runs caudalward on the basal surface of the sheep's brain. Along 



Longitudinal fissure of cerebrum^ 



Optic nerve 

 Optic chiasma 

 Rhinal fissure 



Insula 

 Lateral fissure- 

 Optic tract - 



Infundibulum - 

 Mammillary body -. 



Cerebral peduncle 

 Inter peduncular fossa and 

 nucleus 



Trigeminal nerve 

 A bducens nerve 



Acoustici Vestibular n - 

 nerve \Cochlearn. - 

 Glossopharyngeal nerve ~-~ 

 Vagus nerve' 

 Hypo glossal nerve---' 

 Anterior median fissure 



^V' Olfactory bulb 



\ \' Medial olfactory gyrus 



^^t, V 



Anterior perforated substance 

 'Lateral olfactory stria 



--'Lateral olfactory gyrus 



^-Diagonal band 



Amygdaloid nucleus 



i ~ Pyriform area 



-- Trochlear nerve 



-~ Abducens nerve 

 ~ Facial nerve 



---- Trapezoid body 

 Cerebellum 

 - -Olive 



^Chorioid plexus 

 " Accessory nerve 

 * Tractus later alls minor 



Fig. 197. Ventral view of the sheep's brain. 



its lateral border it is separated from the neopallium by the rhinal fissure; while 

 its medial border contains a band of fibers, the stria olfactoria lateralis (Fig. 197). 

 The same gyrus is seen in the brain of the human fetus, but here it is directed 

 outward toward the insula (Fig. 198). In the adult human brain these olfactory 

 convolutions are very inconspicuous, and with the fibers from the olfactory tract 

 which accompany them are usually designated as the medial and lateral olfactory 

 s tries. 



