46 GRAY SUBSTANCE OF THE TRAPEZIUM, 



of which are of large size, and are connected by their processes with the arciform 

 fibres decussating at the raphe. Scattered cells are also found at various points in 

 the substance of the raphe. 



(5.) In the sections just above (Figs. 10, 10"), the cells representing the lower 

 olivary column are reduced to a little group in the immediate neighborhood of the 

 r^he. The upper olivary bodies in the sheep, are now seen as compact masses, 

 resembling those found in the carnivora, though not quite so large proportionally 

 or so distinctly convoluted. The cells have diminished in size, but the arrangement 

 of fibres is much more distinct and orderly. In the cat, the large ceUs found in the 

 lower part of the upper olivary column soon disappear, the open network being cut 

 in upon more and more by the wavy bundles of the trapezium, and are replaced by 

 smaller cells arranged in a distinctly convoluted lamina. 



The roots of the abducens or sixth pair of nerves (Fig. 10"", VI), are now quite 

 easily distinguishable, running inwards in two or three tolerably thick bundles to the 

 nucleus, which is more distinctly seen a little higher vip, the course pursued by the 

 roots of the abducens as well as by those of the facial being slightly ascending. The 

 commencement of the nucleus may, however, be seen in Fig. 10", 2\ partly separated 

 from the anterior portion of the auditory nucleus, in a position exactly correspond- 

 ing to the upward extension of the hypoglossal nucleus. The roots of the sixth form 

 a remarkable exception to the usual course of the nerve-roots, bending backward to 

 enter their nucleus just before they reach the floor of the fourth ventricle, instead 

 of running toioards tlie median line as do the roots of all the other nerves. 



The facial first makes its appearance as a somewhat wavy band of fibres, running 

 directly inwards towards that portion of the auditory nucleus which is close to the 

 caput, and then bending forwards towards the fasciculus teres, which constitutes the 

 common nucleus of the sixth and seventh pairs. It rapidly increases in size till it is 

 seen as a thick and broad band of fibres (Figs. 10, 10", 11, 12, 13 and 36), running 

 inwards towards the nucleus, and crossed, as it passes along the anterior margin of 

 the auditory nucleus, by very numerous wavy bundles of fibres passing out into the 

 antero-lateral columns (Plates XIV and XVI, Figs. 10", 12", and 44). The entire 

 space between the fibres of the sixth and seventh nerves is studded with little cells 

 (Figs. 10", 12"), which are also frequently found throughout the entire antero-lateral 

 network, serving to unite all the various nuclei, by means of the arciform and trans- 

 verse fibres with which their processes are connected. Not unfrequently little 

 groups of cells are found at the foot of the facial (Fig. 10", v), and at various points 

 among the external arciform fibres, the latter being the first appearance of the 

 numerous cell-groups from which the fibres of the pons Varolii are subsequently 

 developed. 



The auditory nucleus contains many very large, multipolar cells, especially in the 

 network and postero-lateral portion. In the cat (Plate IX, Fig. 35), the network 

 of the outer nucleus is very much developed, the restiform body being often quite 

 hidden beneath the fibres of the network, which is crowded with very large cells 

 reaching forward into the substance of the anterior part of the nucleus, and baclovards 

 in a straight line into the substance of the cerebellum. Large bundles of fibres 

 following the course of the posterior root may be traced from the /hccidus towards 



