VII 



THE MEDULLA OBLONGATA 



383 



Certain bundles of nerve-fibres from the spinal columns pass 

 through the medulla and pons, and on reaching the ventral part 



cl 



Fio. 201. View from before of medulla oblongata, pons Varolii, crura cerebri, and other central 

 portions of the encephalon. (Allen Thomson.) Natural size. On right side the convolutions 

 of the central lobe or island of Reil have been left, with a small part of the anterior cerebral 

 convolutions ; on left side these have been removed by an incision carried between the thalamus 

 options and the cerebral hemisphere. I', olfactory tract cut short and lying in its groove ; 

 II, left optic nerve in front of the commissure; II', right optic tract; Th, cut surface 

 of the left thalamus options; C, central lobe or island of Reil; Sy, fissure of Sylviusi; 

 X, X, anterior perforated space ; e, external, i, internal corpus geniculatum ; h, hypophysis 

 cerebri or pituitary body ; to, tuber cinereum with infundibulum ; a, one of the corpora 

 albicantia ; P, cerebral peduncle or crus ; III, close to left oculomotor nerve; X, posterior 

 perforated space. The following letters and numbers refer to parts in connection with 

 the medulla oblongata and pops: PV, pons Varolii; V, greater root of 5th neive; +, lesser 

 or motor root ; VI, 6th nerve ; VII, facial ; VIII, auditory nerve ; IX, glossopharyngeal ; 

 X, pneumogastric ; XI, spinal accessory; XII, hypoglossal ; Cl, suboccipital or 1st cervical 

 nerve ; pa, pyramid ; o, olive ; d, ventral median fissure of spinal cord, above which the 

 decussation of the pyramids is represented ; ca, ventral column of cord ; r, lateral tract of 

 bulb continuous with cl, the lateral column of the spinal cord. 



of the mid -brain divide into two large bundles the cerebral 

 peduncles which penetrate into both hemispheres. On this 



