418 ANATOMY AND PHYSIOLOGY OF THE BRAIN. 



gemina. The middle peduncles pass directly downward to 

 join the lateral parts of the pons Varolii. The posterior 

 peduncles pass downward and backward to become con- 

 tinuous with the restiform bodies. 



In passing from the spinal cord to the medulla oblongata, 

 the grey matter is met with more abundantly, becoming 

 mixed up with all parts save the anterior pyramids. The 

 superior horns become enlarged, diffused, and extended in 

 a more lateral direction. Special grey nuclei likewise 

 appear near the superior aspect of the medulla, and give 

 origin to the roots of the nerves, such as the glosso-pharyn- 

 geal, hypoglossal, vagus, auditory, and spinal accessory. 

 The posterior of these are imbedded in the substance of the 

 medulla, but more anteriorly they stand out as rounded 

 grey masses on the floor of the fourth ventricle. Two pairs 

 of the nuclei lodged in the restiform bodies demand especial 

 mention. These are the olivary bodies. They consist ex- 

 ternally of a white material containing a grey nucleus 

 thrown into folds or indentations, and in this, in turn, is a 

 central white matter thrown into diverging branches. These 

 bodies, which are extremely rudimentary, are connected 

 respectively with the roots of the facial and hypoglossal 

 nerves. 



The fibres of the posterior columns are generally held to 

 enter the substance of the restiform bodies, and proceed 

 directly to the cerebellum. Van der Kolk, however, affirms 

 that they terminate in the medulla in those nuclei which 

 form the seat of sensation, while the fibres of the posterior 

 peduncles of the cerebellum which join the restiform bodies 

 become transverse, and either pass directly to the same 

 pillars on the other side, or terminate in grey nuclei within 

 the medulla. 



Of the lateral column some fibres join the restiform 



