THE ASSOCIATION PATHS 



539 



form a compact fibre bundle, the posterior or median longitudinal 

 fasciculus. This fasciculus presents a gentle dorsal curve in its 

 passage through the medulla oblongata, in the upper part of which 



lear 

 nerve. 



Decussation 



of the Posterior 



trochlear longitudinal 

 nerve. fasciculus 

 Nucleus of the \ 

 troch- ' 

 Posterior 

 commissure- 

 Pineal gland. 



Oculo-motor 

 nucleus. ~~~A 



Facial root Hypoglossal 



(internal knee). nucleus. 



Glossopharyngeal 

 nucleus. 



Nucleus of Goll. 



Mammillary 

 body. 



Decussation 



of the 



brachium 



conjunctivum. 



Deep 

 trans- 

 verse 

 fibres 

 of the 

 pons. 



Super- 

 ficial 

 transverse 

 fibres 

 of the 

 pons. 



Mesial 

 lemniscus. 



FlG. 411. A SAGITTAL SECTION OF THE MEDULLA OBLONGATA, PONS, AND MESENCEPHALON 

 PARALLEL AND CLOSE TO THE MIDDLE LINE, FROM A CHILD AGED THREE MONTHS. 



The posterior longitudinal fasciculus and its relation to the antero-lateral ground bundle 

 of the spinal cord are particularly well shown. Weigert's stain. (After Bruce.) 



it reaches a position near the median raphe, and just in front of 

 the dorsal grey matter of the hypoglossal nucleus. Here it blends 

 with the dorsal margin of the interolivary portion of the mesial 

 fillet. 



As it enters the pons Varolii the posterior longitudinal bundle 

 separates from the fillet, thus attaining a still more dorsal position, 

 in which it continues its course through the pons. In the midbrain 

 it lies ventral to the aqueduct of Sylvius, but makes a gradual ven- 

 tral curve which corresponds to the increased depth of the grey 

 matter surrounding the aqueduct at this level. The fasciculi of 

 either side, together form a median trough in which the nuclei of 

 the oculo-motor nerve are found. 



