OF THE CENTRAL MOTOR INNERVATION OP THE LARYNX. 
203 
Infernal Cajjsule. 
It will be necessary to give a slight anatomical introduction before describing 
onr results of the excitation of the internal capsule. In the first place we invariably 
have exposed the internal capsule by a horizontal section carried through the 
substance of the hemisphere from before back, after the usual preliminary ligature 
of the middle cerebral artery. In this maimer the internal capsule in its whole 
length, basal ganglia, &c,, were exposed, and readily distinguishable. The horizontal 
section before referred to passed in the Carnivora through the sub-prorean gyrus, tlie 
lower part of the orbital lobule just above the rhinal fissure, through about the middle 
of the Sylvian fissure, and so backwards through the lower end of the curved external 
convolutions and sulci, i.e., ecto-sylvian, &c. 
In the Monkey the section was carried horizontally backwards through the third 
frontal gyrus, the foot of the ascending frontal and parietal gyri respectively, across 
the Sylvian fissure, through the uppermost pai’t of the temporo-sphenoidal lobe, and 
so through the occipital lobe. The anatomical features of the cerebral sections thus 
produced, although, of course, differing considerabl}'' in the various orders of animals, 
nevertheless are not so diverse as might be anticipated (see figs. G, 7). In each case 
the section exposed both the caudate and lenticular nuclei of tlie corpus striatum as 
well as the optic thalamus. The sections in the Monkey thus correspond to 
about the level of Group 4, as described by Beevoe, and Horsley. These authors 
in their paper [ante, pp. 49—88), on the arrangement of the excitable fibres of the 
internal capsule of the Bonnet Monkey, just referred to, observed phoiiation to occur 
in one section of the capsule when these fibres were excited [ibid., p. 83), but they did 
not directly observe the laryngeal movements. 
In this connection it must be remarked that in the Carnivora the lenticular nucleus 
is relatively extremely narrow (see figs. G, 7), so that the angle made by the two lindDS 
of the capsule is a very open one, almost 150 to IGO degrees. Therefore, as will be 
seen directly, the general arrangement of the fibres, as far as the antero-posterior 
order goes, is the same in the two classes of animals, although the actual positions are 
not quite the same, owing to the non-development of the jircefrontal region in the 
Carnivora. Since the irruption of prmfrontal fibres which makes up the mass of the 
anterior limb in the Monkey and pushes the excitable fibres further backwards into 
the posterior limb does not occur in the brain of the Dog or Cat, in these animals it 
is the anterior limb which principally contains the excitable laryngeal fibres. 
In all animals the most anteriorly placed laryngeal effect observed was the accele¬ 
rated movements of the vocal cords connected with quick movements of the thorax in 
the polypnoea, wdrich we have described to be produced by excitation of the prsecrucial 
gyrus. In the Cat and in the Dog this acceleration of respiration is produced by 
excitation of a considerable number of fibres occupying the anterior half of the anterior 
limb, i.e., opposite about the anterior half of the caudate nucleus as exposed in the 
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