THE ESSENTIALS OF HISTOLOGY. 



each lateral half of the bulb into three areas a posterior a middle, 

 and an anterior. Of these the posterior is chiefly occupied by the 

 grey matter of the floor of the fourth ventricle, and, with fibres which 

 are passing obliquely upwards and outwards towards the cerebellum, 

 forming its inferior crus (festiform body, c.r.); and in addition there 

 is the continuation upwards of the portions of grey matter forming 

 the nuclei of the funiculus gracilis (n.g.), of the funiculus cuneatus 



aunt. 



FIG. 260. SECTION ACROSS THE MEDULLA OBLONG ATA AT ABOUT THE MIDDLE OF 

 THE OLIVARY BODY. (Magnified 5 diameters.) 



r raphe;/, fillet; ar.ext.. fibre arcuatse extern* ; n.ar., nucleus arcuatus ; py, pyramid; 

 n.d.o., nucleus dentatus olivse ; h.o., hilum olivfe ; s.o., siliqua olivse ; acc.o., oliva ac- 

 cessoria; n.L, nucleus lateralis ; ri, portions of grey matter containing large cells, 



ventral nucleus of tenth nerve (nucleus ambiguus) ; n.p., nucleus posterior; s, fas- 

 ciculus solitarius (ascending root of A', and IX. nerves) ; t, tamia (attachment of ependy- 

 mal roof of fourth ventricle) ; /.r., formatio reticularis ; n.X., dorsal nucleus of tenth 

 nerve ; n.XIL, upper part of nucleus of twelfth nerve ; n.t., nucleus of funiculus teres ; 

 v.l.b., posterior or dorsal longitudinal bundle. 



(n.c.), and of the tubercle of Kolando (g). The anterior or mesial area 

 is occupied in front by the pyramid (p), and behind this by a reticular 

 formation (reticularis alba, A) composed of longitudinally coursing 

 bundles of fibres interlaced with fibres that are passing obliquely from 

 the opposite side, through the raphe, towards the nuclei of the posterior 

 columns and restiform body (figs. 260, 261). The middle area, which 

 lies between the issuing bundles of the two sets of nerve-roots, consists 





