42 



THE MEDULLA OBLONGATA AND PONS VAKOL1I. 



and those of the sixth nerve emerge in the same line with it but at the lower border 

 of the pons Varolii. In transverse sections of the medulla oblongata and pons these 

 root-bnndles may be traced back through the substance of the organ to a group or 

 column of nerve-cells situated in a portion of grey matter close to the antero-lateral 

 side of the central canal in the lower closed part of the bulb (fig. 43), and close to 

 the middle of the fourth ventricle in the upper opened-out part (figs. 44, 45). This 



/.c 



Fig. 33. SECTION ACROSS THE MKDULLA OBLONGATA A LITTLE BELOW THE POINT OF THE CALAMUS 



SCKIPTORIUS. (Lockhart Clarke.) 



c, central canal ; /, anterior median fissure ; f.g, funiculus gracilis ; f.c, funiculus cuneatus ; 

 t.R., tubercle of Rolando ; o, olivary body ; a.p.. pyramid ; XI, XII, spiral accessory and hypoglossal 

 nerves ; XI', XII', their nuclei. 



Fig. 34. VIEW OP THE MEDULLA OBLONGATA, PONS VAROLII, CRURA CEREBHI, AND CENTRAL PARTS OP 



THE ENCEPHALON FROM THE RIGHT SIDE. (Allen Thomson.) 



The corpus striatum andthalamus opticushave been preserved in connection with the central lobe and 

 crura cerebri, while the remainder of the cerebrum has been removed. 



St, upper surface of the corpus striatum ; Th, back part of the thalamus options (pulvinar) ; C. 

 placed on the middle of the five or six convolutions constituting the central lobe or island of Reil, the 

 cerebral substance being removed from its circumference ; Sy, fissure of Sylvius, from which these 

 convolutions radiate, and in which are seen the white strife of the olfactory tract ; I, the olfactory tract 

 divided and hanging down from the groove in the Convolution which lodges it ; II, optic nerves a little 

 way in front of the commissure ; a, right corpus albicans with the tuber cinereum and infundibulum in 

 front of it ; h, hypophysis or pituitary body ; e, external, and i, internal corpus geniculatum at the 

 back part of the optic tract ; P, peduncle or crus of the cerebrum ; III, right oculo-motor nerve ; p, 

 pineal gland ; q, corpora quadrigemina ; IV, trochlear nerve rising from v, the valve of Vieussens. 



The following numbers and letters refer chiefly to parts in connection with the medulla oblongata and 

 pons. V, placed on the pons Varolii above the right nervus trigeminus ; s, the superior, in, the middle, and 

 in, the inferior peduncle of the cerebellum cut short ; VI, the sixth nerve ; VII, facial nerve ; VIII. 

 auditory nerve ; IX, the glosso-pharyngeal nerve ; X, placed opposite to the cut end of the pneumo- 

 gastric nerve ; and XI, the uppermost fibres of the spinal accessory nerve ; XII, the hypoglossal nerve ; 

 p a, pyramid ; o, olive ; a r, arciform fibres ; r, restiform body ; tr, tubercle of Rolando ; c a, anterior, 

 c p, posterior, and c I, lateral columns of the spinal cord ; C I, C i, anterior and posterior roots of the 

 first cervical nerve. 



