504 



THE BRAIN. 



from those belonging to the spinal cord. The most marked of these is 

 the olivary nucleus ; a convoluted lamina about one-third of a milli- 

 metre in thickness, occupying the interior of the olivary body on each 

 side, just below the inferior border of the pons Yarolii. 



No 



TRANSVERSE SECTION OF HUMAN MEDULLA OBLONGATA, at the lower part 

 of the fourth ventricle. No, Olivary nucleus. E, Raphe, at the median line. Ngl, Nucleus 

 of the glosso-pharyngeal nerve. Nv, Nucleus of the pneumogastric nerve. Nh, Nucleus 

 of the hypoglossal nerve. IX, Roots of the glosso-pharyngeal nerve (9th pair) at their point 

 of emergence from the medulla. XII, Roots of the hypoglossal nerve (12th pair) at their 

 point of emergence from the medulla. Magnified 8 diameters. (Henle.) 



In transverse sections, near its upper or lower extremity, the olivary 

 nucleus appears completely closed, but a section through its middle 

 shows a gap toward the median line. It forms, therefore, an ovoid 

 sac, with its long diameter parallel to the axis of the medulla, and an 

 opening at its middle directed inward. Through this opening bundles 

 of nerve fibres penetrate from the white substance of the medulla, and, 



