INTERNAL STKUCTUEE OF THE PONS. 



565 



The lateral area lies between the root fibres of the hypoglossal and those of the vagus. It 

 >ntains : (a) the inferior olivary nucleus ; (6) the dorsal accessory olivary nucleus ; (c) the nucleus 

 teralis ; (d) the nucleus ambiguus ; (e) the splanchnic efferent nucleus of the vagus and glosso- 

 liaryngeal nerves ; (/) the formatio reticularis grisea. 



The posterior area is situated behind the vagus roots, and within its limits are seen : (1) the 

 ! :stiform body ; (2) the superior part of the cuneate nucleus ; (3) to the medial side of this a crowd 

 ' transversely cut bundles of fibres, loosely arranged and forming the descending root of the 

 >,stibular part of the acoustic nerve ; (4) close to these, but placed more deeply, a round, 

 mpact, and very conspicuous bundle of transversely cut fibres, viz., the tractus solitarius, or 

 Ascending root of the vagus and glossopharyngeal nerves ; (5) the large tractus spinalis of the 

 1 igeminal nerve close to the lateral side of its nucleus composed of substantia gelatinosa. 



w 



INTERNAL STRUCTURE OF THE PONS. 



hen transverse sections are made through the pons, it is seen to be composed 

 basilar part and a dorsal or tegmental part. The latter may be regarded as 



a) -; r^5 



S W) 



3 8 : Restiform body 



fllli ! 



Nucleus of 

 tractus spinalis 

 of trigeminal 

 nerve 



Tractus spinalis 

 of trigeminal 

 nerve 



Facial nucleus 



Facial nerve 



Superior olive 



Corpus 

 trapezoideum 



Deep transverse fibres 

 of pons 



Pyramidal bundles 

 Superficial transverse fibres of pons 



-SECTION THROUGH THE LOWER PART OF THE HUMAN PONS IMMEDIATELY ABOVE THE 

 MEDULLA OBLONGATA. 



'upward prolongation of the- medulla oblongata, exclusive of the pyramids 



are drawn forward into the basilar part. 



*ars Basilaris Pontis. This constitutes the chief bulk of the pons. It is 



of: (1) transverse fibres arranged in coarse bundles, called the fibrse 



[2) longitudinal fibres, gathered together in massive bundles; and (3) a 



amount of gray matter, termed the nuclei pontis, which fills up the interstices 



t iween the intersecting bundles of fibres. 



fasciculi longitudinales, to a large extent, consist of the same fibres which, 



>wn, are gathered together in the two solid pyramidal tracts of the medulla 



ita. When the pyramids are traced upwards into the pons they are seen to 



376 



