OR GANGLIONAR GRAY MATTER The substantia grisea ganglionaris is found in the basal gan glia which, in their situation and relations, have already been considered. They should be re-studied in this connection. They are as follows: 1. In the hemisphere: The corpus striatum, composed of the caudate and the lentiform nucleus.
2. In the inter-brain: The thalamus, lateral and medial geniculate bodies, nu cleus hypothalamicus (Luvsi) and red nucleus.
3. In the mid-brain: The superior and inferior quadrigeminal colliculi, the sub stantia nigra, and the nucleus lateralis superior in the tegmentum.
The corpus striatum (Figs. 38, 41 and 89) is an ovoid mass of reddish-gray matter containing pigmented multipolar cell bodies of small size, the larger ones being in the globus pallidus. Many of them are spindle shaped, some are spherical and a few are stellate. The nuclei are relatively large and the cytoplasm is scanty and loaded with pigment in the nucleus caudatus and putamen. The dendritic processes of these neurones are rich; the axones are short and of small diameter. The internuncial axones, which associate one nucleus with another in the striate body, are very fine and delicate; the strio-fugal axones are of medium size, but are much finer than the adjacent cerebro spinal fibers in the internal capsule.
According to Kinnier Wilson the corpus striatum has no direct connection with the cerebral cortex. It is an independ ent, autonomous organ which exercises a steadying effect upon the lower motor neurones, preventing hypertonicity, rigidity and tremor. Its neurones are either internuncial or strio-fugal. Many afferent and efferent fibers pass through the corpus stria tum, as parts of the internal capsule; but the fibers that have genetic or terminal relations to the striate body form three groups: 1. The internuncial fibers both rise and terminate in it; 2. the strio-fugal fibers rise in the globus pallidus and end in some nucleus at a lower level; and 3. the strio-petal fibers rise in infe rior nuclei and terminate in the globus pallidus and nucleus caudatus.
i. Many delicate internuncial axones link the caudatus with the putamen and the putamen with the globus pallidus, a smaller number of axones running in the reverse direction join the putamen to the caudatus.
2. The fibers rise in the globus pallidus and descend in four fasciculi: The strio-thalamic fasciculus contains a few fibers from the caudatus in addition to those from the me dial and lateral zones of the globus pallidus; it runs medially, piercing the superior lamina of the internal capsule, and ends in the lateral nucleus and medial nucleus of the thalamus. Some of the fibers of the strio-thalamic bundle traverse the inferior lamina of the internal capsule within the ansa lenticularis. The strio-rubral fasciculus has the same origin in the globus pallidus as the strio-thalamic bundle and its fibers are of the same me dium caliber. It ends in the nucleus ruber. These two fasciculi are dorsal to the strio-hypothalamic fasciculus; and this, in turn, is dorsal to the strio-nigral fasciculus. The tracts to the hypothalamic nucleus and substantia nigra are made up of fine fibers, which issue from the base of the globus pallidus through the medullary lamina; they run through the ansa lenticularis in the inferior lamina of the internal capsule to their destination in the nuclei. The strio-nigral fasciculus has been called the intermediate bundle of the basis pedunculi.
3. The fibers received from below by the corpus striatum may be designated the thalamo-striate and hypothalamo striate fasciculi. The thalamo-striate fibers connect the thala mus chiefly to the nucleus caudatus, but partly to the globus pallidus. The hypothalamo-striate fasciculus ends wholly in the globus pallidus; it rises in the nucleus hypothalamicus and in other lower lying nuclei. Probably it contains fibers of the medial fillet and the spino-thalamic tract.
Lesions of the corpus striatum affect the internal capsule, which impales it; and may cause, if extensive, hemiplegia and partial hemianesthesia of the opposite side of the body, deafness in the opposite ear and hemianopia due to cortical isolation of the corresponding halves of both retinw.