A textbook of mental diseases.

  • Lewis, W. Bevan.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of mental diseases. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    80/749 (page 44)
    peduncle, already alluded to as the third layer of the ansa pedun- ciilaris, connected with the cortex of the temporal lobe, passes from beneath the lenticular nucleus up into the thalamus, expanding also in brush-like manner chiefly along its internal portion, and forming the inner boundary of the thalamus. It also decussates at the middle and posterior commissure to pass down as tegmental fasciculi of the eras. Both these peduncular expansions are interrupted by the nerve cells in the grey intercalated layers of the thalamus ere they decussate at the commissures. The superior peduncle takes a still more com- plicated course ; its centric connection is with the cortex of the gyrus fornicatus—appearing first in the two fimbriae or posterior pillars of the fornix arising from the cornu Ammonis ; and ascending as the body of the fornix connected by the transverse fibres of the lyra upon the thalamus, it arches forwards at the front end of this body, and thence passes downwards as the two descending pillars of the fornix. These latter pass back to the corpora albicautia, around which they form a distinct loop, and again turn upwards as the ascending^ pillars or bundles of Vicq D'Azyr to terminate within and around the anterior tubercle of the thalamus. Whilst forming this loop around the COrpuS albicans, a portion of its fibres is interrupted by nerve cells within this body, and a fasciculus starts from this site and passes directly backwards into the tegmentum. Whilst the frontal, insular, and median cortex is thus connected by the thalamic peduncles to the anterior end of the ganglia, the posterior or hinder half of the thalamus receives along its outer margin coronal radiations from the occipital and mid-regions of the hemisphere. These fasciculi radiate from the upper and outer border of the thala- mus to corresponding regions of the brain opposite them ; the middle section spreading towards the mid-regions ; and the posterior arching backwards towards the occipital pole. These latter, as they pass outwards and backwards to the occiput, are associated with similar radiations proceeding in like direction from the geniculate bodies and the brachia of the nates and testes. This system of fibres arches around the outer wall of the posterior cornu of the ventricle, and has long been known as the optic radiations of Gratiolet. In their course they are brought into close association with the sensory fibres of the cord destined for the occipital and temporal lobes; and, as we have previously seen (fig. 7, S), occupying the outer fourth of the crusta. This peduncular sensory tract, it must be remembered, has no con- nection with the optic thalamus, but runs directly into the occipital and temporal regions of the cortex. The coronal radiations which enter this outer border of the thalamus, pass through its structure as arched fasciculi towards the median line-?.e, across the long axis