NERVOUS CENTRES. (HUMAN ANATOMY. THE ENCEPHALON.) 



683 



emergence of the posterior roots of the spinal 

 nerves, indicates the distinction of these two 

 sets of fibres. If the posterior column be sepa- 

 rated from the antero-lateral in the spinal cord, 

 the separation may be easily carried upwards 

 along this line, in a specimen which has been 

 sufficiently hardened. 



From the description now given, the res- 

 tiform bodies may be regarded as the con- 

 necting fibres between the cerebellum and the 

 spinal cord. They may be designated the ce- 

 rebellar fibres of the medulla oblongata in con- 

 tradistinction to the others, which are entirely 

 connected with the mesocephale and with the 

 cerebrum. 



Rolando describes the restiform body as con- 

 taining grey matter the grey tubercle of Ro- 

 lando. This grey matter, however, may be more 

 correctly regarded as a portion of the central 

 nucleus of the medulla, from which very pro- 

 bably some fibres of the restiform body emerge. 

 The posterior pyramidal columns. On each 

 side of the posterior fissure we find a narrow 

 column, sufficiently distinct from the restiform 

 columns. These may be traced downwards 

 through the cervical region of the cord, and 

 even into the dorsal or lumbar, according to 

 Foville. They taper gradually to a fine point, 

 the situation of which varies in different sub- 

 jects. Superiorly they form the inferior and 

 part of the lateral boundary of the fourth ven- 

 tricle. Their innermost fibres end abruptly in 

 a blunt extremity, whilst the external ones are 

 continued upwards on each side of the ven- 

 tricle (fig. 386, Y). 



Olivary columns. The oval bodies, which 

 form a relief upon the surface of the medulla 

 oblongata, have been long known by the names 

 corpora olivaria, olivcc. They occupy the in- 

 terval between the anterior pyramids and the 

 restiform bodies, separated, however, from the 

 latter by the narrow band of fibrous matter 

 above described. 



The surface of each olivary body is crossed 

 to a greater or less extent by the arciform fibres, 

 as already described. Sometimes it is neces- 

 sary to remove these fibres, in order to expose 

 the proper texture of the olives. 



The superficial layer of each olivary body is 

 evidently fibrous, and the constituent fibres seem 

 to take a longitudinal course. If a section be 

 made so as to remove the prominent convexity 

 of this body, it will be seen that the white 

 matter of which it principally consists en- 

 closes a layer of vesicular or grey matter dis- 

 posed in a peculiar manner. This grey layer 

 presents the appearance of a waving line en- 

 closing white matter. If the section of the 

 olivary body be made transversely, the grey 

 waving line is still present, but it presents a 

 convex border outwards, and is open within, 

 being evidently continuous with the central 

 and less definitely disposed grey matter of the 

 medulla. And when the section is vertical, 

 and so as to divide the olivary body in its entire 

 length, the convex border of the grey line is 

 still external, but it is open towards the interior 

 of the medulla. 



This grey layer, contained within the olivary 



Fig. 387. 



Transverse sections of the medulla oblongata. 



A, anterior. P, posterior. 



o, olivary bodies, in which are seen the undula- 

 ting line of grey matter which forms the corpus 

 dentatum. 



body, is called the corpus dentatum (corps 

 Jestonne, Fr.) It is evidently a capsule of ve- 

 sicular matter continuous below with that of 

 the cord, internally with that of the central 

 substance of the medulla oblongata, and supe- 

 riorly with that of the mesocephale (o, Jig. 

 387). Its disposition, in a convoluted form, 

 has doubtless reference to the packing of a 

 certain quantity of this matter into a given 

 space, and to the important object of bringing 

 the vesicular and fibrous matter into connec- 

 tion as extensively as possible. 



It has been very commonly supposed that 

 the olivary bodies are mere gangliform masses 

 laid upon certain ascending fibres of the me- 

 dulia, and that they may be readily removed 

 without injury to the deeper-seated parts. 

 Either of the two following modes of dissec- 

 tion will, however, serve to point out the 

 erroneousness of this view. If the anterior 

 pyramids be removed, a concave surface is left 

 between the two olivary bodies, in which their 

 continuity with the central substance of the 

 medulla is distinctly seen. This central sub- 

 stance, which forms a substratum on which 

 the anterior pyramids rest, and from which it 

 is not improbable that some of the fibres of the 

 pyramids emerge, is of considerable density. 

 Each olivary body appears gradually to merge 

 into it; or, adopting another mode of descrip- 

 tion, it seems to protrude, forming a relief on 

 the exterior, in the interval between the pyra- 

 midal and restiform bodies on each side. Or a 

 transverse section, as in fig. 387, will exhibit a 

 similar continuity between the olivary bodies 

 and the central substance of the medulla. 



According to this view, then, the existence 

 of the olivary bodies in the human brain and 

 that of the Quadrumana indicates a high de- 

 velopement of the central substance of the 

 medulla oblongata as compared with its other 

 nervous columns. In all the vertebrate ani- 

 mals below man, the medulla oblongata in- 

 creases with the bulk of the body, and like 

 the spinal cord evidently bears a direct relation 

 to it. This high developement appears, how- 

 ever, to affect more especially the restiform and 

 pyramidal bodies, and their connecting fibres, 

 the trapezium. The former do not leave any 



