1889-90.] Dr A. Bruce on the Inferior Olivary Body. 
23 
On the Connections of the Inferior Olivary Body. By 
Alexander Bruce, M.A., M.D., F.R.C.P.Ed., F.R.S.E. 
(With Two Plates.) 
(Read January 6, 1890.) 
The inferior olivary body or nucleus forms the ovoid projection 
which extends almost the whole length of the medulla oblongata, 
from the lower margin of the pons Varolii to within a short distance 
of the level of the decussation of the anterior pyramids. It is 
separated from the latter by a groove through which emerge the 
roots of the hypoglossal nerve. On its outer margin it is separated 
from the line of the roots of the glossopharyngeal and pneumogastric 
nerves by a shallow depression. Transverse vertical and longitu- 
dinal sections of the medulla show the olive to be a highly con- 
voluted sac of grey matter open, at its hilum, towards the mesial 
plane. (It has two accessory nuclei of smaller size, an internal and 
a posterior accessory olive, which, as they are really parts of the 
larger nucleus, do not call for special consideration here.) The 
fibres of the hypoglossal nerve pass through its substance, but do 
not become, as was at one time supposed, and as has been recently 
again affirmed by Vincenzi, connected with the olive. On its 
median aspect lies the interolivary stratum or fillet. Anteriorly 
lies the anterior pyramid, posteriorly the formatio reticularis. 
According to the experiments of Bechterew, the inferior olive is 
concerned in co-ordinating movements necessary for the maintenance 
of the equilibrium 'of the body.*^ One would naturally from this 
* Bechterew ( Neurologisches Gentralblatt , Dec. 1, 1882) states the results of 
section of the inferior olivary bodies to be as follows: — (a) Deep section of the 
olives produce forced movements, mostly rolling round the long axis of the 
body towards the injured side, and nystagmus with one eye directed upwards 
and outwards, and the other downwards and inwards. (6) Slighter lesions pro- 
duced movements in a circular or in a forward direction, or caused the animal 
to throw itself backwards, (c) Sometimes forced positions, with strong lateral 
curvature of the body, were produced, (d) There was generally, also, a tend- 
ency to fall towards the injured side, or in lesions of both olives unsteadiness 
of gait, or actual inability to stand or walk. 
In estimating the results of these experiments, it must be remembered that 
it is impossible to divide the olivary bodies without at the same time injuring 
some of the following structures, viz., the direct cerebellar tract, the arciform 
fibres of Solly (or the anterior external arcuate fibres of Edinger), the ascend- 
ing tract of Gowers, or those fibres which pass from the lateral columns of the 
