Diseases of the nervous system / edited by Archibald Church.

Date:
1908
Catalogue details

Licence: In copyright

Credit: Diseases of the nervous system / edited by Archibald Church. Source: Wellcome Collection.

    48/1256 (page 20)
    externus and the pulvinar. v. Monakow’s investigations, which have recently been absolutely confirmed by Probst in another way, therefore show that the thalamus opticus is a receptacle for the fibers coming from deeper portions of the brain and from other trunk ganglia, also for the corticifugal fibers, while the structure sends comparatively few fibers downward. It is chiefly an organ of transmission between the periphery and the cerebrum, but our knowledge of its minute physiologic and pathologic function is extremely limited. The space between the two optic thalami, the third ventricle, is bordered above by the plexus chorioideus, at its posterior end by the pineal gland or the epiphysis, close to the anterior division of the corpora quadrigemina. Im- mediately in front of it and equidistant at each side from the posterior region of the thalamus is the small ganglion habenulae. The epiphysis consists of solid, very vascular, epithelial tubules which contain peculiarly layered calcium concretions, the brain sand. We know nothing of the importance of the epiphysis in man; comparative anatomy, however, teaches us that this is a rudimentary organ which, in the lower vertebrate animals, extends forward as a long tube, its frontal end forming externally the frontal spot which is perceptible on the skull between the orbital spaces; a few saurians also con- tain a second frontal “ parietal organ,” the terminal vesicles situated within one of the spaces of the parietal bone, its structure closely resembling an eye with cornea, lens and retina. In its lower portion the third ventricle shows the tuber cincreum which extends to the base of the skull, the cavity of which is called the in- fundibulum. The structures below the thalamus opticu§ compose the subthalamic region; but this area has been but little in- vestigated microscopically and seldom gives opportunity for macroscopic examination. Immediately below the optic thalamus is the nucleus ruber tegmenti which a little lower passes into the corpora quadrigemina, and outside of this is the corpus sub- thalamicum, Luys’s body. At the base of the brain the cerebral peduncles run to the pons; here is situated the pes pedunculi which receives the fibers from the internal capsule in the form of an accumulation of markedly pigmented ganglion cells, the substantia nigra Soemmeringi, which are distinct from the fibers of the lemniscus situated above. We now reach the region of the mid- brain, the principal structure of which is the corpora quadrigemina, so called be- cause here, immediately behind the third ventricle and the epiphysis, four small eminences are recognizable, two in front and two behind; each of these structures possesses an arm, the anterior and posterior superior peduncle which passes to the inter-brain. The ante- Fig. 13.—Diagram of the Cerebral Peduncles. (After Obersteiner.) Qa, Anterior corpora quadrigemina; AÄ, aqueduct of Sylvius; Flu, pos- terior longitudinal bundle; Tg, teg- mentum; Nt, red nucleus; SnS, sub- stantia nigra Soemmeringi; 1, frontal pontal tract'; 2, tract of the motor cranial, nerves; 3, pyramidal tract; 4, tract of muscle sense; 5, sensory portion of the fibers of the cerebral peduncle; 6, bundle from the lem- niscus to the foot; 7, stratum inter- medium.