THE HIND-BRAIN OR RHOMBENCEPHALON 



769 



ulus. The remaining fibers i. e., those which occupy the lateral part of the 

 pyramid do not cross the middle line, but are carried downward as the anterior 

 cerebrospinal fasciculus (Fig. 680) into the anterior funiculus of the same side. 



The greater part of the anterior proper fasciculus of the medulla spinalis is con- 

 tinued upward through the medulla oblongata under the name of the medial 

 longitudinal fasciculus. 



Superior brachium Lateral geniculate body 

 Inferior brctchium / / Medial geniculate body 



4 ! I 



H: I I Optic tract 



mU. 



Pulvinar 

 Pineal body 



Superior collicul 

 Inferior colliculi Jj 



Frenulum veil 



Trochlear nerve 



Lateral lemniscus 



Superior peduncle 



Middle peduncle 

 Rhomboid fossa 



Clava 

 Glossopharyngeal and vagus nerves 



Optic commissure 



Oculomotor nerve 



Trigeminal nerve 



Acoustic nerve 

 Facial nerve 



Abducent nerve 



Bypoglossal nerve 





Accessory nerve 



FIG. 681. Hind- and mid-brains; postero-lateral view. 



The lateral district (Fig. 681) is limited in front by the antero-lateral sulcus 

 and the roots of the hypoglossal nerve, and behind by the postero-lateral sulcus 

 and the roots of the accessory, vagus, and glossopharyngeal nerves. Its upper part 

 consists of a prominent oval mass which is named the olive, while its lower part 

 is of the same width as the lateral funiculus of the medulla spinalis, and appears 

 on the surface to be a direct continuation of it. As a matter of fact, only a portion 

 of the lateral funiculus is continued upward into this district, for the lateral cerebro- 

 spinal fasciculus passes into the pyramid of the opposite side, and the dorsal 

 spinocerebellar fasciculus is carried into the inferior peduncle in the posterior 

 district. The ventral spinocerebellar fasciculus is continued upward on the lateral 

 surface of the medulla oblongata in the same relative position it occupies in the 

 spinal cord until it passes under cover of the external arcuate fibers. It passes 

 beneath these fibers just dorsal to the olive and ventral to the roots of the vagus 

 and glossopharyngeal nerves; it continues upward through the pons along the 

 dorso-lateral edge of the lateral lemniscus. The remainder of the lateral funiculus 

 consists chiefly of the lateral proper fasciculus. Most of these fibers dip beneath 

 the olive and disappear from the surface; but a small strand remains superficial to 

 the olive. In a depression at the upper end of this strand is the acoustic nerve. 



The olive (oliva; olivary body} is situated lateral to the pyramid, from which it 

 is separated by the antero-lateral sulcus, and the fibers of the hypoglossal nerve. 

 Behind, it is separated from the postero-lateral sulcus by the ventral spinocerebellar 

 fasciculus. In the depression between the upper end of the olive and the pons lies 

 the acoustic nerve. It measures about 1.25 cm. in length, and between its upper 



