COUESE OF FIBEES. 



507 



white substance ; and then passing radiately through the grey capsule, 

 turn backwards to the restiform body and lateral column, those of them, 

 which pierce the anterior wall of the capsule arching round it to reach 

 their destination. Other fibres pass behind the olivary into the resti- 

 form bodies, and seem to terminate in the grey substance of the floor of 

 the fourth ventricle. 



Origin of Nerves. — From the surface of the medulla certain of the 

 cranial nerves arise, namely, the sixth fi-om the anterior pyramids close 

 to the pons, the facial and auditory from the restiform body close to the 

 pons, the giosso-pharyngeal, pneumo-gastric, and spinal accessory from 

 the lateral portion of tlie medulla, the hypoglossal from the groove between 

 the anterior pyramid and oKvary body. Their fibres may be traced to 

 grey matter in or near the floor of the fourth ventricle (see p. 510 and 

 568). 



J 



Fig. 356. — DiAGKAMMATic Repkesknta- Kg. S56. 



TION OF THE PASSAGE OP THE CoLUilNS 



OF THE Medulla Oblongata upwards 



AND DOWNWARDS. 



A, the specimen, wliicli is seen from 

 before, inclixdes the medulla oblongata and 

 the pons Varolii, with a small portion of 

 the spinal marro^y. The left lateral column 

 (that to the reader's right) has been lifted 

 out of its place to the side, and the ante- 

 rior and posterior columns of that side 

 remain undisturbed : the right anterior and 

 posterior columns have been removed, and 

 the lateral column remains in its place. 

 The upper part of the right pyramid is 

 removed. The transverse fibres of the pons 

 Varolii have been divided in circumscribed 

 portions to diiferent depths corresponding 

 with the several places of passage of the 

 columns of the medulla. 



P, pons Varolii, part of the anterior sur- 

 face, where it has been left entire ; p, the 

 right and left pyramids, the upper part of 

 the right has been cut away ; p', the fibres 

 of the left pyramid, as they ascend through 

 the pons, exposed by the removal of the 

 superficial transverse fibres ; 2^", placed on 



the deeper transverse fibres of the pons on the right side, below the divided fibres of the 

 pyramid (these transverse fibres a little lower down constitute the part known as the "tra- 

 pezium ") ; a, left anterior column of the cord, passing upwards into the undecussated part 

 of the anterior pyramid, and into a', the olivary column ; 0, olivaiy body ; o', the continua- 

 tion of the olivary column ascending deeply through the pons and exposed by the removal 

 of a small portion of the deeper transverse fibres ; o", the same fibres divided by a deeper 

 incision on the right side ; /, the right lateral column, passing upwards into the following 

 parts, viz., x , the deeper pait passing by decussation into the left pyramid ; r, the part 

 passing into the restiform body ; ft, the part ascending in the back of the fourth ventricle 

 as the fasciculus teres ; to the outer side of this are seen the ascending fibres of the posterior 

 pyramid ; I', the left latei-al column drawn aside from its place in the spinal cord ; the 

 fasciculus teres, ft, and the part to the restiform body, r, cut short ; x , the deeper part 

 passing by decussation into the right pyramid ; r', the part of the restiform body derived 

 from the anterior column of the spinal cord ; pc, the posterior column of the left side 

 exposed by the removal of the lateral column, and shown ascending to the restiform body 

 as the fasciculus cuneatus, fc : on the right side the posterior column being removed, fc, 

 points to this fasciculus cuneatus cut short below. 



B, explanatory outline of the section of the spinal cord, a, anterior columns ; j?, 

 posterior ; l^ lateraL 



