INTERNAL STRUCTURE OF THE MEDULLA. 459 
_ by fibres, some of which pass straight through the gray lamina, whilst others end in con- 
a 
nexion with the cells. It is only in mammals that the olivary nuclei are found well 
developed. 
As the fibres of the fillet decussate and assume a longitudinal direction they 
come to lie between the olivary nuclei of opposite sides, and hence the term inter- 
olivary stratum (stratum interolivare lemnisci) is frequently apphed to them. 
Restiform Body (corpus restiforme).—The gracile and cuneate nuclei gradually 
give place to the restiform body in the upper part of the posterior district of the 
medulla. Fibres from various quarters converge to form this great strand. It first 
takes shape as a thin superficial layer of longitudinal fibres, which are gathered 
together on the outside of the cuneate nucleus ; but after that nucleus has come 
to an end, and as the upper part of the medulla is reached, the restiform body 
is seen to have grown into a massive strand, which presents a kidney-shaped or 
oval outline on transverse section (Fig. 
341), and which ultimately enters the white — “sooy™ 
central core of the cerebellum as its inferior RCURPE re eehene Niel 
peduncle. The fibres which build up the s canoe nce, 
restiform body are the following: (1) the \ ’ 
direct cerebellar tract ; (2) the posterior super- ; 
ficial arcuate fibres; (3) the anterior super- 
ficial arcuate fibres; and (4) cerebello-olivary 
fibres. Sees 
The direct cerebellar tract extends upwards SSSpincers 200 
eke. CEREBELLAR TR.” 
from the lateral column of the cord. In the de 
lateral district of the medulla it occupies a § 
similar position; but before the olivary § 
eminence is reached it inclines backwards, a 
crosses the postero-lateral furrow, and passes RCuntE 
2 
obliquely upwards into the restiform body. 
As its fibres diverge backwards they pass over 
the tubercle’ of Rolando: and cover bes the Which shows in part the fibres which enter into 
spinal root of the trigeminal nerve and the Tate anattatontotinemectiromminoda: 
substantia Rolandi, thus shutting them out 
from the surface. The fibres of the direct cerebellar tract enter into the outer 
or superficial part of the restiform body. 
The posterior superficial arcuate fibres take origin from the gracile and cuneate 
nuclei, and enter the superficial part of the restiform body of the same side. 
The anterior superficial arcuate fibres proceed from the lower portions of the 
gracile and cuneate nuclei of the opposite side. After decussating in the middle 
line, it can easily be determined that all the deep arcuate fibres which arise from 
these nuclei do not enter the fillet. A large proportion of them gain the surface by 
sweeping round the inner aspect of the pyramid in the antero-mesial fissure. Many 
of them likewise gain the surface by piercing the pyramid or by passing out 
between it and the olive. These fibres constitute the anterior superficial arcuate 
group, and on the surface of the medulla they sweep backwards around it, forming 
a thin layer over the olivary eminence and ultimately reaching the restiform body. 
The anterior superficial arcuate fibres, as well as the direct cerebellar tract-fibres, 
cover over the trigeminal spinal root, which thus comes to take up a deeper posi- 
tion in the substance of the medulla (Figs. 340 and 541). 
Fic. 342.— DIAGRAM, 
Amongst the fibres which reach the surface of the medulla in this way Kolliker includes 
fibres from the strie acustice. If this be the case, these fibres connect the cochlear nucleus 
with the cerebellum, the path being striz acusticee, superficial arcuate fibres, and restiform 
body (vide p. 481). 
The fibres of the direct cerebellar tract, which come from the cells of the posterior vesicular 
column of the cord, and the superficial posterior arcuate fibres, which are derived from the cells 
of the gracile and cuneate nuclei, do not cross the mesial plane, but enter the restiform body of 
the same side. The anterior superficial arcuate fibres arise from the cells of the cuneate and 
gracile nuclei, and cross the mesial plane so as to gain the restiform body of the opposite side. 
The cerebello-olivary fibres are only seen in the upper part of the medulla. They 
