MAMMALIAN. 65 



In the rabbit the upper olivary body is represented by a very complete convolu- 

 tion, presenting three or four turns, entered and penetrated by the arciform fibres 

 both external and internal as well as by numerous transverse and radiating fibres. 

 In the mouse the upper olivaries consist of a wavy mass of quite large and numer- 

 ous cells. 



The structure of the upper olivary body is especially distinct in the cat, and I 

 have, therefore, given an accurate representation of the entire mass, the outline 

 being drawn by a power of about 20 diameters, to which some details were added 

 as seen by higher powers (Plate XII, Fig. 42). 



In this figure it will be noticed that the lamina is convoluted, and arranged 

 much on the same general plan as in the lower olivary bodies of the same animal 

 or of man. The bundles which surround the entire mass and radiate among the 

 foldings of the lamina, are principally derived from the external and internal 

 fibres of the arciform plexus. These bundles surround the outside of the olivary 

 body pursuing a beautiful wavy course, and turn off at varying angles to enter 

 difi"erent portions of the lamina, the cells of which are everywhere brought into 

 connection with the fibres. As these bundles approach the inner or posterior side 

 of the mass, they are joined by other bimdles derived from the radiating fibres 

 proceeding from the posterior gray substance, some of which seem to connect 

 the olivaries with the fasciculus teres or nucleus of the facial and abducens. The'se 

 bundles sometimes form quite large stems (Plate XII, Fig. 42, D), and are well 

 seen in Plate IX, Fig. 36, where the general situation and relations of the olivary 

 body to the surrounding parts is also weU. sho'wn. The course of the fibres within 

 the folds of the lamina bears much resemblance to that in the lower olivaries in 

 man ; in the cat it may be briefly described as follows : — 



1st. The entire mass is surrounded by a broad marginal band (Plate XII, Fig. 

 42, B, B), principally derived from the arciform plexus (A, A), from which, however, 

 single fibres and sometimes considerable bundles constantly pass off, penetrating 

 the lamina, and either entering cells, or passing onward to join deeper lying bundles 

 with some of the fibres of which they appear to be continuous, or else entering stiU 

 more distant folds of the lamina (some of these fibres are seen at C, C). In its 

 course around the margin of the olivary body the band is frequently joined, 

 especially on the upper side, by fibres derived from the posterior gray substance. 



2d. Traced from within outwards their course is as follows: (1). The fibres 

 from the centre of one of the bundles {D) penetrating the lamina, proceed forwards, 

 either joining cells or passing directly across the lamina, often curving around and 

 joining the marginal band or crossing its fibres nearly at right angles, soon becoming 

 lost among the fibres of the arciform plexus. (2). Those fibres forming the external 

 portion of the bundle (Z>), penetrate the lamina and diverge more and more, radiat- 

 ing in all directions among the cells, some of which they enter, the remaining fibres 

 passing outward into more distant folds of the lamina, or into the parts surrounding 

 the olivary body, usually joining ultfrnately the bundles of the arciform plexus. 

 From the anterior part of the olivary body numerous fibres radiate transversely into 

 the trapezium, crossing its wavy bundles at right angles, and often forming quite a 



