BASE OF BRAIN 



455 



oval prominence called the olive. A distinct sulcus or groove, 

 which passes downwards anterior to this body, separates it 

 from an elongated strand, termed the pyramid of the medulla 

 oblongata. From the bottom of this sulcus and its prolonga- 

 tion downwards issue a series of nerve fila which belong to two 

 different nerves. Those which issue from the lower part of 

 the groove, below the level of the olive, belong to the anterior 

 root of the first cervical nerve ; those which emerge from the 



Optic chiasma 



Optic tract 



Corpus geniculatum 

 laterale 



Corpus geniculatum 

 mediale~~~ 



Substantia perforat 

 posterior 



Brachium pontis 



Restiform body 

 Olive 



Pyramid 



External arcuate 



fibres- 



Decussation of 



pyramids' 



Optic nerve 

 Infundibulum 

 Tuber cinereum 



Corpus mamillare 



Oculo-motor nerve 



(in.) 



Trochlear nerve (iv.) 



winding round pedun- 



culus cerebri 



Trigeminal nerve (v.) 

 Abducent nerve (vi.) 

 Facial nerve (vn.) 

 Acustic nerve (vm.) 



Vago-glosso-pharyri- 

 geal nerve (ix. and x.) 



Fila of hypoglossal 

 nerve (xn.) cut short 



Accessory nerve (xi.) 

 First cervical nerve 



FIG. 183. Anterior aspect of the Medulla oblongata, Pons, and 

 Mesencephalon of a full-time Foetus. 



upper part of the groove, in the interval between the olive 

 and the pyramid, form the hypoglossal nerve. 



Glosso-pharyngeal, Vagus, and Accessory Nerves. Posterior 

 to the olive, in the postero -lateral sulcus of the medulla 

 oblongata, is another continuous row of nerve fila. These 

 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 



