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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    curve, (:!) the lju'k of (litfcrciitiation of its fibres, except in the last section wiiicii sliows the niicldie fibres disappearing in a nucleus. 'i'lie ventral portion of the sheet will be recognized in the sections of the new-born child as the stratum interolivare lemnisci. Jn a section of adult tissue so many more fibres are crowded into this portion that it forms a triangle in cross-section, with the base against the ijyraraid. The fibres of the stratmii interolivare lemnisci, or ventral part of the medulla sheet, have been traced in the model from this sheet (1) through the corpus traiJezoideum, (2) through the pontal sheet and (3) through the central part of the midbrain sheet. Here the lemniscus medialis, now deflected far to the side, lies lateral to the nucleus ruber. The model takes the bundle only as far as the hypothalmic region (Plate I). Thus far I have not discussed the origin of these fibres. There are three groups of fibres to be considered with reference to the stratum interolivare lemnisci. (1) In Plate IV will be seen a small bundle of fibres connected with the lateral funiculus of the cord. It passes toward the middle line and appears to end blindly against the root of the hypoglossal nerve. In reality, its fibres pass on between the root bundles of the nerve adjacent to the stratum interolivare lemnisci. From the Weigert specimens alone I cannot say that these fibres enter the stratiun interolivare lemnisci, but the model shows the possibility of an uncrossed path from the lateral funiculus of the cord to the main sensory path toward the cortex (Fig. 11)). (2) By far the thickest bundles of fibres entering the lemniscus in the medulla are the bundles of internal arcuate fibres from the nucleus funiculi gracilis and the nucleus funiculi cuneati. These arcitates form two principal groups, one of which lies just distal to the root of the ]S[. hypoglossus, while tbe other lies opposite the proximal third of the nucleus funiculi cuneati (Plate V). In sections the two groups show in Figs. 28 and 31. These bundles can be described best in connection with the dorsal funiculi of the spinal cord. (3) As a further source of fibres for the lemniscus are the arcuates from the nuclei of termination of tlie cerebral sensory nerr^es. These arcuates are too diffuse and scattered to be modeled as bundles. A series of transverse sections corres])onding to the proximal portion of the central fibre mass illustrate the region well (Figs. .'^8 to 4'.i). The first two sections pass through the trapezoid body; the second, taken where that body is widest, shows that all of the fibres of the lemniscus
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