THE BASE OF THE BRAIN 



393 



prominence called the olive. Medial to the olive is a large 

 elongated strand of the medulla oblongata, termed the 

 pyramid ; it is separated from the olive by a groove or sulcus 

 which is prolonged downwards for some distance beyond the 

 olive. From the part of the sulcus between the olive and the 

 pyramid spring the fila of the hypoglossal nerve (Figs. 149, 

 150) ; and from the lower part of the sulcus some of the fila 

 of the anterior root of the first cervical nerve issue. 



Optic chiasma 



Optic tract- 

 Corpus geniculatum/d: 



Corpus geniculati 



mediale 



Substantia perforata 

 posterior 



Junction of pons and 

 brachium pontis 



Restiform body 

 Olive 



Pyramid 

 External arcuate 

 fib 



Decussation of 

 pyramids' 



Optic nerve 

 Infundibulum 

 Tuber cinereum 



Corpus mamillare 



Oculo-motor nerve 



(in.) 



Trochlear nerve 



(iv.) winding round 



pedunculus cerebri 



Trigeminal nerve (v.) 

 Abducens nerve (vi.) 

 Facial nerve (vn.) 

 Acoustic nerve (vm.) 



Vago-glosso-pharyn- 

 geal nerve (x. and ix.) 



Fila of hypoglossal 

 nerve (xn.) cut short 



Accessory nerve (xi.) 



Anterior root of 

 first cervical nerve 



FIG. 150. Anterior aspect of the Medulla Oblongata, Pons, and 

 Mesencephalon of a full-time Foetus. 



Nervi Glossopharyngeus et Vagus et Accessorius. Pos- 

 terior to the olive is the post-olivary sulcus, and a little more 

 dorsally lies the postero-lateral sulcus of the medulla oblongata, 

 in which a continuous row of nerve fila is attached. The fila 

 in question extend downwards, beyond the level of the olive, 

 and are attached to the whole length of the medulla oblongata 

 in linear order. They belong to three nerves, but it is im- 

 possible at present (seeing that the nerve-trunks which they 

 build up are divided) to determine precisely the number of 



