ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OF THE BEAIN. 
309 
behind and partly on the outer side of the anterior pyramid (y), where in animals it 
forms the surface of the medulla (p", figs. 61 & 62) ; while in Man (fig. 63) it is covered 
and concealed at this point by the transverse bundles of the lower portion of the pons 
enclosing a quantity of grey substance, which consists of irregular masses of small cells 
[y" y"). This grey substance extends round the front of the anterior pyramid (y) to 
its inner side, where it forms a deep and broad layer (y'") next the raphe. The trans- 
verse bundles of the trapezium are numerous and strongly marked. Along the central 
line of the pons they decussate as usual with their fellows of the opposite side, the 
most anterior being imbedded in a mass of grey substance (y"'), which is denser, and 
contains larger cells than that which is continuous around the front of the pyramid 
to y". On the outer side the fibres of the trapezium run into and round the front of 
the superior olivary body (s"), crossing the abducens nerve (V') ; and as they reach 
the inner side of the facial nerve ( y "), they intersect each other in a complicated 
manner amongst irregular masses of grey substance consisting of granules and small 
nuclei. They then cross the facial nerve and sweep round the extremity of the grey 
tubercle (e) to the middle peduncle of the cerebellum. These bundles appear to consist 
of several sets of commissural fibres : 1, between the superior olivary body, the grey 
substance at the back of the pyramid, and the cerebellum ; 2, between the two opposite 
olivary bodies. 
(71) In Man the superior olivary body is not nearly so distinctly convoluted as in the 
Cat or the Kabbit, nor is it nearly so large in proportion to the size of the brain. It 
has the appearance, rather, of two or three ill-defined masses in continuity with each 
other. The majority of its cells are somewhat smaller than those of the inferior olivary 
body. There is one remarkable point in which this portion of the medulla, both of 
Man and the Orang Outang, differs from that of Mammalia. In figs. 62 & 63, the 
superior olivary is overlaid by the group of large multipolar cells (U) constituting the 
nucleus of the motor root of the trigeminus, and connected by numerous fibres with 
the common nucleus (Q") of the facial and abducens nerves. In Mammalia this nucleus 
of the trigeminus is not found in the same situation. 
(72) Schroder van der Kolk does not appear to have detected the existence of the 
trapezium in the human pons Varolii. Stilling described and figured this part in the 
human pons*, but he was not aware that it is homologous with the trapezium of animals ; 
and as he was not acquainted with the nucleus or superior olivary body enclosed by the 
fibres of the trapezium, he called this nucleus, in Man, “ quasi appendix nuclei inferioris 
nervi trigemini, ad formam scafi.” 
* Stillixg, Pons Varolii, tab. ii. s s. 
