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 King’s College London. The original may be consulted at King’s College London.

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    poSteriOPiS. A median root is described as originating from a nucleus at the level of emergence of the sensory root, in contiguity with the ascendine root and the motor nucleus. On the lateral margin of the central grey around the aqueduct, as high as the anterior quadrigemina] body, or nates, we find the cross-section of the descending root of the fifth nerve with very characteristic spherical or vesicular cells lying in the central grey upon the inner side of the root fasciculi. Both cells and descending fasciculi become more conspicuous at lower levels, and the latter extend to the level of the exit of the sensory root, where they join it to emerge from the pons. Internal to this descending root is a series of deeply pigmented nerve .cells, forming the substantia ferruginea, which is seen through the grey floor of the ventricle at the site named the loCUS COePUleuS. From these cells, according to Meyuert, pass root fibres to the opposite trigeminal root (sensory trunk), which in their course surround and traverse the pOSteriOP longitudinal faSCiCUlUS, decussate at the posterior extremity of the raphe, and thence, following out the anterior margin of the central grey, arch into tlie opposite sensory root. Associated with these latter fibres are described others which issue from the median raphe posteriorly, and after decussation terminate in the sensory root likewise. Lastly, a cePebellaP FOOt is described by some authorities. In the motor column of the central grey, lying immediately behind the posterior longitudinal fasciculus, on either side of the median line and beneath the nates, is a well-defined grouping of cells, which, however, usually presents an apparent segmentation into distinct clusters. These nerve cells, commencing as high up as the posterior commissure, are at first somewhat scattered, but assume a more compact form as they run backwards towards the upper half of the testes, in which region they appear lodged in a hollow of the posterior wall of the longitudinal fasciculus. This nuclear column represents the origin common to the OCUlo-motOP (third) and the tPOChleaPiS (fourth) nerves; the upper, scattered, segmented portion is the nucleus of the third more especially; the lower compact segment lying at the junction of the two quadrigeminal bodies is the nucleus of the fourth nerve. Both are believed to receive their centric fibres through the median raphe, those of the third nerve decussating ere they*reach their nucleus. The segmentation of the nucleus of the motor oculi nerve has been variously described by different authorities : we follow here more strictly the account given by Bruce,* which certainly accords most *'«0n the Segmentation of the Nucleus of the Third Cranial Nerve, Alex llTu 71 'i:- f^'^rve Tract, of the Mid and Hind Brain, Alex. Bruce, 1892.
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