An atlas of the medulla and midbrain / Edited by H.McE.K.

  • Florence R. Sabin
Date:
1901
Catalogue details

Licence: In copyright

Credit: An atlas of the medulla and midbrain / Edited by H.McE.K. Source: Wellcome Collection.

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

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    93» (Fig. 40). The fibres of the nidix N. abducentis pass directly thruiigli tlie edge of tliis dorsal bundle, and just proximal Uj this nerve the bundle flattens out and bctMjnie.s triangular in cross sec- tion. At the beginning of the midbrain the bundles of the two sides broaden, and, at the same time, form a trough (Plate III). Tlie centre of tliis trough is deep and its floor is made, not of decus- sating fibres, but of longitudinal fibres running in the middle line (Fig. 18). The sides of the trough show shallow depressions, three on the right side and two on the left. They represent the jxtsition of the nuclei of the oculomotor and trochlear nen^es (Plate VII). Beyond these depressions is a space left in the wall for the exit of the main mass of fibres of the root of the oculomotor nerve (Plate YII). This space is artificial, the wall being in reality almost continuous. Just proximal and lateral from this space is a long groove which opens out into the proximal capsule of the nucleus ruber. This part of the capsule is a sheet of fibres placed dorsoventrally across the midln-ain. The groove contains the nucleus of Darkschewitsch and marks the junction of three different fibre masses, viz., (1) the fasciculus longitudinalis medialis, (2) the posterior commissure and (-3 )the capsule of the nucleus ruber. These relations will be more fully considered in connection with the description of the midbrain. To return to the fasciculus longi- tudinalis medialis, the sides of the trough fonned by the bundles of the two sides come into relation, in the model, with a large hollow shell which occupies the centre of the dorsal part of the midbrain. This shell is the stratum album profundum. The dorsal bundles of the two sides making u]i the fasciculi longitudinales mediales occupy the dorsal ]>art of the medulla sheets, where they form two dense bands on either side of the raphe. In the pons each band becomes broader, and in the midbrain the bundles of the two sides unite to form a deep trough. As a whole, each bundle is characterized by two curves, one in the medulla, the other in the midbrain. It is related to four nuclei, namely, the nuclei of the X. hypoglossus, X. abducens, N. trocblearis and N. oculomotorius. At the distal extremity of the medulla oblongata it is connected with the ventrolateral funiculi of the spinal cord, while at the proximal limit of the model it is related, at least in posi- tion, to three stmctures—a nucleus, a decussating bundle and a nuclear cajTsule.
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