III. An Ex'pevimental Investigation into the Arrangement of the Excitable Eibres of 
the Internal Capsule of the Bonnet Monhey (Macacus Sinicus).'" 
By Charles E. Beevor, M.D., E.R.C.P., and Victor Horsley, B.S., E.R.S. 
[From the Laboratory of the Brown Institution.) 
Received Dec. 4,—Read Dec. 12, 1889. 
[Plates 5-11.] 
CoNTE^iTS. 
Page. 
Introduction.49 
Historical Introduction.50 
Anatomy.55 
Method of Investigation.68 
Physiological Relation of the Basal Ganglia to the Internal Ca.psule.72 
Analysis of Results.7.3 
Movements of Muscles of the same side as that iStimulated.73 
Lateral Arrangement of Fibres of Internal Capsule.77 
Character of the Movements of the parts represented in the Fibres of the Internal 
Capsule.79 
Conclusions. .86 
Introduction. 
In the following paper we propose to give the results of a research on which we have 
been engaged nearly three years, and by which we hoped to elucidate the arrange¬ 
ment of the motor fibres in the internal capsule. 
The fibres which connect the excitable areas in the cortex cerebri with the bulbo¬ 
spinal grey matter in the medulla oblongata and spinal cord are commonly spoken of 
as forming the pyramidal tract. 
These fibres course downwards between the caudate and lenticular portions of the 
corpus striatum and the optic thalamus. In passing through this region they enter 
into the composition of the bundles of white fibres, which received from the older 
anatomists the unfortunately misleading title of the internal capside. It is obvious 
* The e.vpenses of this investigation bave been defrayed by a grant partly from the Royal Society, 
and partly from the British Medical Association. 
MDCCCXC.—B. H 
25.8.90 
