204 
DR. F. SEMON AND MR. V. HORSLEY ON AN INVESTIGATION 
section before referred to. At the same time that acceleration was produced there 
was also obtained from the most posterior bundles of these fibres, in all animals, 
abduction, this combination being concentrated in the Monkey at the genu, where the 
fibres subserving the acceleration of respiration are chiefly grouped. In the Cat and 
in the Dog these abductor fibres were found just before the genu. 
Taking the various species individually we find that, in (1) the Monkey, acceleration 
is first produced when the fibres immediately in front of the genu and exactly at the 
genu are stimulated; this is, of course, just opposite the sharp angle made by the 
middle zone of the lenticular nucleus. The fibres in the posterior limb immediately 
behind the genu when excited either give a mixed movement or simply produce on 
excitation diminution of abduction, and it is not until we get to the junction of the 
middle and posterior fourths of the capsular border of the middle zone of the lenticular 
nucleus that we get distinct adduction. There, however, the adduction is very accu¬ 
rately localised to a few bundles of fibres about 2 scpiare millimetres in area. Just 
behind this point for a short distance diminished abduction was observed on stimulat¬ 
ing the capsule in one case ; it is clear, therefore, that in the Monkey the acceleration 
of respiration is only brought about by a few fibres at the situation of the genu, while 
the phonatory adduction of the cords is subserved by a few fibres in almost exactly 
the middle of the posterior limb of the capsule. 
It may be interesting at this point to state that this is what might have been 
expected, inasmuch as it is just at this region that the observations before referred 
to"^ show that these fibres similarly subserve the movements of the tongue and 
pharynx. 
(2) . In the Dog the condition appears to prevail which is found in the Cat, about to 
be described, that is to say, that excitation of almost the whole of the anterior limb 
produces acceleration of respiration and that adduction begins to be produced at the 
genu. {(/, fig. 7.) We will therefore proceed to describe the condition as it is seen 
in the Cat, in which animal we have investigated this point closely. 
(3) . In the Cat the most anterior effect is acceleration. This commences, according 
to the level of the section, either just in front of, or just opposite to, the anterior 
extremity of the caudate nucleus, and it persists throughout the front half of the 
anterior limb of the capsule. (1-3, fig G.) At this centre point of the anterior 
limb the respirations liecome intensified, abduction much more notably marked, and 
in some cases persistent. (See fig. G.) 
Exactly at the genu, or in many cases just in front of it, i.e., opposite the posterior 
extremity of the caudate nucleus (yule figs. 6 and 7), adduction is very sharply 
marked. 
In most cases the bundle of fibres subserving this phonatory adducton is small, 
in others—possibly owing to slight difference in the obliquity of the section— 
* Beetor and Horseey, Joe. cit. 
