FUNCTIONS OF THE INTERNAL CAPSULE 581 



to nerve-centers situated in the gray matter beneath the aqueduct of Sylvius, 

 in the gray matter beneath the floor of the fourth ventricle, and in the anterior 

 horns of the gray matter of the spinal cord, and which in turn are connected 

 by the cranial and spinal nerves with the muscles of the eye, head, face, 

 trunk, and limbs. The positions occupied by these different tracts are 

 shown in Fig. 240. The relation of the internal capsule to the caudate 

 nucleus and the optic thalamus internally, and to the lenticular nucleus ex- 

 ternally, is also shown in a vertical section of the cerebrum made in front of 

 the gray commissure (Fig.- 241). 



From the fact that the internal capsule contains efferent or motor tracts, 

 and afferent or sensor tracts, it is evident that a destructive lesion of the 

 motor tract would be followed by a loss of motion; and of the sensor tract, 

 by a loss of sensation on the opposite side of the body. 



FIG. 241. A TRANSVERSE SECTION OF ONE-HALF OF THE CEREBRUM. Arteries supplying 

 the lenticular nucleusLAT, the internal capsule 1C, and the caudate nucleus CN. i. The middle 

 cerebral. 2, 2. Lenticular arteries. 3. The lenticulo-striate artery passing through the ex- 

 ternal capsule. 



This condition, to a greater or less extent, frequently arises in consequence 

 of a rupture of the blood-vessels which supply the caudate nucleus, the len- 

 ticular nucleus and the internal capsule. These arteries, branches of the 

 middle cerebral, -penetrate the brain in the anterior and posterior perforated 

 spaces (Fig. 240). By reason of a diseased condition of their walls, 

 especially of the lenticulo-striate artery, the vessel ruptures and the blood 

 is extravasated into the surrounding tissues. 



If the extravasation occurs in the anterior two-thirds of the posterior 

 limb of the internal capsule, there will be a destruction of the efferent or 

 motor fibers, and a separation of the cortical motor area from the medullary 

 and spinal motor nuclei and, therefore, a loss of volitional control of the mus- 

 cles of the face, arm and leg of the opposite side. The extent of this paraly- 

 sis will depend, of course, on the extent of the extravasation. The muscles 



