A text-book of mental diseases : with special reference to the pathological aspects of insanity / by W. Bevan Lewis.

  • Lewis, William Bevan, 1847-1929.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of mental diseases : with special reference to the pathological aspects of insanity / by W. Bevan Lewis. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    tures in the braiD, of closely aggregated cells, varying considerably in size from 5 ,a to 18 ,a. Its connection with the rest of the cerebrum is effected by means of two processes, which are directed forwards along the inner border of the thalami optici, forming a boundary between the latter and the grey matter of the third ventricle ; and descending in front in conjunc- tion with the taenia semicircularis and the pillar of the fornix : these are the two peduncles of the pineal body or habenula. These peduncles are distinctly ganglionic in structure, and together with the pineal body are probably to be regarded, as Meynert believes, as ganglia of origin for the tegmentum. The connections by medullated tracts are twofold—centric and peripheric. The former, as a connection with the cerebral hemi- spheres, takes place through the medium of the stratum zonule, already described as investing the optic thalamus. The latter or peripheric connection is effected by a large and important fasciculus, which passes down vertically from the habenula or peduncle, covered by the grey matter of the third ventricle, and towards the region (at the base) of emergence of the motor oculi nerve on the inner side of the converging crura. In this course it describes a sigmoid bend, and near the base of the mesencephalon it lies between the posterior longitudinal fasciculus, on the median aspect, and the red nucleus of the tegmentum, external to it. Some of its fibres radiate into the nucleus ruber (Meynert) ; but the larger proportion bend at this point immediately backwards at right angles to their former course, and appear to pass into the tegmental areas of the pons and medulla, in conjunction with the posterior longitudinal fasciculus. This rectan- gular bend has gained for it the appellation of the fasciculus retro- flexilS—it is often termed the Style of the peduncle of the pineal body, where it passes vertically towards the red nucleus of the tegmentum. The style or fasciculus retrofiexus may be best exposed by trans- verse vertical sections carried through the ganglion of the peduncle just in front of the quadrigeminal bodies, but it may also be traced in longitudinal vertical sections near the mesial plane of the tween and mid brain. In these sectional planes, however, owing to its sigmoid flexure, a part only of its course can be usually seen. Thus in a vertical longitudinal section of the brain of the dog, near the mesial plane, we find the lower end of this fasciculus about to bend backwards at ri<*ht angles, and on this plane it is seen to descend in front of medullated fasciculi passing downwards from the posterior commissure and the emergent roots of the third nerve. In a section carried still nearer the mesial plane, we see its course about]complete, whilst a portion of both ascending and descending pillarsof the fornix is revealed likewise.
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