474 



NEUROLOGY. 



expands into the posterior part of the fourth ventricle, while the 

 inferior terminates in a small depression, the foramen ccecum, at 

 the posterior part of the pons Varolii. On each half of the 

 medulla the following objects can be distinguished viz., the 

 inferior pyramids, the olivary bodies, the restiform bodies, the 

 intermediate fasciculi, and the superior pyramids. 



The inferior pyramids are bundles of white fibres, placed on 

 each side of the inferior median fissure, and continuous with por- 

 tions of both the inferior and lateral columns of the cord. They 

 are constructed of three sets of fibres, the innermost of which 



decussate with those of the oppo- 

 site pyramid ; the second pass 

 in a direct manner from the cord; 

 and the third, the arciforrn fibres, 

 form a series of curves which 

 wind round the olivary body, to 

 join the restiform body. 



The corpora olivaria, very 

 rudimentary, are two elongated, 

 oval-shaped bodies, on the outside 

 of the inferior pyramids. They 

 are separated from the pons 

 Varolii by a slight depression, 

 and are partly covered by the 

 arciform fibres. A section shows 

 the corpus olivarium to be a mass 

 of white matter, in which is a 

 hollow indented capsule of grey 

 matter (corpus dentatum). This 

 capsule has an anterior opening, 

 and contains a nucleus of white 

 matter, from which a bundle of fibres springs. These fibres pass 

 through the opening, and, joining the fibres from the inferior 

 pyramids, constitute the olivary columns, which become con- 

 tinuous with the thalami optici and corpora quadrigemina. 



The restiform bodies constitute the lateral, and greater part 

 of the superior portion of the medulla, and form the connecting 

 link between the cord and cerebellum. They are composed 

 chiefly of white longitudinal fibres, derived from the superior and 

 lateral columns of the cord, and the arciform fibres, and they 

 increase in thickness as they pass forwards and upwards to form 



FIG. 177. 



Base of the brain. a a, Crura cerebri ; 

 6, Corpus .ilbicans ; c, Infuudibulum ; d, 

 Pituitary body ; e, Mammillary eminence ; 

 /, Tuber cinereum ; g, pons Varolii ; g' </', 

 Middle peduncles of the cerebellum ; h, 

 Medulla oblongata ; i i, Inferior pyra- 

 mids ; k k, Olivary bodies ; I I, Restiform 

 bodies. 



