44 GRAY SUBSTANCE OF THE TRAPEZIUM, 



nucleus. Both portions of the auditory nucleus, as AveU as the caput cornu, contain 

 many scattered cells, mostly small.^ 



Numerous bundles of fibres proceed from the anterior portion of the nucleus 

 near the raphe, taking the same direction as those noticed in the lower part of the 

 medulla, serving to connect the olivary bodies with the motor nuclei ; these fibres 

 are also connected with the few remaining cells which are the uppermost of the 

 lower olivary column (Plate XIV, Fig. 8", e). The upper olivary bodies (0') are 

 now quite distinct, consisting of large and numerous multipolar cells, the processes 

 from which in connection with transverse and arciform fibres, form a rather open 

 network, inclosing numerous longitudinal bundles in its meshes. 



(2.) Higher up (Figs. 8, 8", and 33), the nucleus of the glossopharyngeal becomes 

 distinctly fused with that of the auditory, the apex of the anterior auditory nucleus 

 projecting into the caput. The j)osterior portion of the nucleus (Fig. 8", A') is very 

 large and distinct, and has already absorbed nearly, if not quite, the whole of the resti- 

 form nucleus. It is connected with the longitudinal fibres of the restiform body (r) 

 by numerous curved and radiating bundles (/•'), and is entered at .its apex by the 

 anterior division of the auditory root ( VIII), which is at first a small bundle, pass- 

 ing through and apparently connected to some extent with the arciform fibres. The 

 posterior auditory root { VIIl') is very large and well defined, and is connected with 

 the posterior portion of both divisions of the nucleus. 



TRAPEZIUM 



(3.) As we approach the trapezium the plexus of external arciform fibres which 

 has gradually diminished in the sections below, till it appears as a very thin band 

 at times hardly distinguishable beyond the extremity of the caput (Fig. 8"), quite 

 suddenly enlarges (Fig. 9"), and is now seen as a very thick and constantly increas- 

 ing marginal band of fibres, which, as Clarke has pointed out, " proceed out of the 

 restiform bodies and auditory ganglia, and sweep round the extremity of the caput 

 cornu to the back of the anterior pyramids, to decussate across the raphe. As they 

 pass the ganglion, or auditory nerve, they receive fibres from it."^ In Figs. 8", 9", 

 the course and origin of these fibres may be plainly seen, as well as their connec- 

 tion with both auditory roots. 



(4.) In Plate XIV, Fig. 9", from a section just above the commencement of the 

 trapezium, the posterior auditory root ( VIIT) has reached its greatest development, 

 and sends out from its substance numerous radiating bundles into the restiform body. 

 Some of these apparently pass out" with or join the anterior root ; the majority, 

 however, cross the root and become external arciform fibres, the number of which 

 constantly increases as we ascend towards the pons Varolii, forming a very -thick 

 and compact marginal band, completely bounding the antero-lateral and anterior 



' My observations on the formation and development of the auditory nucleus agree so entirely with 

 the description given by Clarke (Proceedings of the Royal Society, 1861), as to appear almost like a 

 direct quotation of the particulars ho has there given. 



" Proceedings of the Royal Society, June, 18G1 



