EXPLANATION OF THE PLATES. 



75 



r, r — restiform nucleus. 



s — great pyramidal nucleus (Stilling). 



i^tractus intermedio-lateralis. 



V — cell-group at foot of facial root. 



w.^fourth ventricle. 



X — cell group pushed out from the restiform 

 nucleus. 



y — -lower stem of olivary body. 



z — cell group at foot of the posterior auditory 

 root. 



r' — fibres radiating through the restiform 

 nucleus. 



A — inner jiortion of the auditory nucleus. 



A' — outer " " " " " 



VIII — anterior auditory root. 



VIII' — posterior " " 



B — antero-lateral nucleus. 



— lower olivary bodies. 



0' — upper olivary bodies. 



H — hypoglossal nucleus. 



X/J— hypoglossal roots. XII' — roots cut oif 

 by plane of section. 



S — spinal accessory nucleus. XI — spinal ac- 

 cessory roots. 



V — vagus nucleus. X — vagus roots. 



G — glossopharyngeal nucleus. IX — glosso- 

 pharyngeal roots. 



T — fasciculus teres, nucleus of sixth and sev- 

 enth pairs of nerves. 



VII — facial roots. VI — abducens roots. 



i? — raphfe. P — anterior pyramids. 



P' — fibres decussating to form the raphe. 



-D — flocculus. K — lingula or linguetta lami- 

 nosa. 



F- — fibres of the pons Varolii. 



PLATE XVI. 



Fig. 44. Transverse section from the medulla of the sheep, from a preparation hardened by chromic 

 acid, magnified about 11 diameters, some details being added by the use of higher powers, showing 

 the course of the fibres constituting the roots of the facial, abducentes and auditory nerves within their 

 respective nuclei. The location of the different cells has been omitted to avoid confusion, this being 

 sufficiently shown in the smaller outlines, especially Fig. 12°' from about the same height. VI, roots 

 of the abducens nerve : VII, facial roots : VIII, anterior division of the auditory roots : VIII', poste- 

 rior division of the same roots : a, external arciform fibres : h, caput cornu : D, a fold of the flocculus : 

 B, bundles derived partly from the flocculus and partly from the posterior division of the auditory root, 

 on their way around the restiform body towards the nucleus : r, restiform body : A, bundles derived 

 from the cerebellum passing down into the nucleus : t, fasciculus teres or nucleus of the abducens and 

 facial : B, raphe. 



Fig. 45. Epithelial cells from the fourth ventricle of the sheep, from the same preparation, a, 

 rounded cells, from the side walls of the ventricle, h, cells near the calamus scriptorius, just behind 

 the raphe, c, cells at the apex of the ventricle, exactly behind the raphe, magnified 450 diameters. 



Fig. 12\ Outline of Figs. 11, 12, Plate III. W, W, fibres radiating towards the cerebellum, 

 some of which overarch the fourth ventricle, while others pass back towards the corpus dentatum and 

 outwards towards the flocculus : M, fibres connecting the back of the auditory nucleus with the flocculus. 

 The remaining lettering of this figure is the same as that used for Plates XIII, XIV, XV. 



Each division of the scales annexed to the preceding figures represents the j^-^ or ju^o of an inch. 



PUBLISHED BY THE SMITHSONIAN INSTITUTION, 

 WASHINGTON, D. C. 



FEBRn ARY, 1 SG4. 



