The diagnosis of nervous diseases.

  • Purves-Stewart, James, Sir.
Date:
1906
Catalogue details

Licence: In copyright

Credit: The diagnosis of nervous diseases. 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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    layer, whilst the posterior wall has a distinct granular layer with no giant cells. Another point to remember is that the different so-called motor areas are not sharply marked off from one another, as the diagram might indicate, but they overlap, each area signifying that stimu- lation of that point produces the maximum movement of the particular part mentioned. The chief path by which motor impulses are conducted from the cortical motor areas to the muscles, is the pyramidal tract, whose course is diagrammatically indicated in Fig. 5. From the motor cells in the cortex the fibres converge through the corona radiata into the great strand of nerve-fibres between the lenticular nucleus externally and the optic thalamus and caudate nucleus internally, namely, the internal capsule. Fig. 6 shows a horizontal section through the internal capsule, in which we notice that it has an anterior and a posterior limb, joining each other at an obtuse angle, the genu or knee. The motor fibres for the leg and arm occupy the anterior two-thirds of the posterior limb, the fibres for the tongue and mouth are at the genu, those for the face just in front. But the order in which these different strands pass through the internal capsule is not quite the same as that in which they started from the cortex. Thus we notice that immediately behind the fibres for the lips we have, from before backwards, those for the shoulder, elbow, and fingers, then for the trunk, and lastly for the hip, knee, and toes. We also notice, in passing, that the pathway of the sensory fibres traverses the posterior part of the capsule, and that behind them again are the visual fibres. The sensory fibres probably do not form a separate, compact bundle, but are partially mingled with some of the motor fibres for the leg. Before leaving Figs. 5 and 6, it is of interest to study briefly, with their help, the different effects produced by lesions of the pyramidal motor tract at various levels. A lesion in or near the motor cortex, if moderate in size, will produce, according to its situation, a monoplegia of the face, arm, or leg, on the opposite side of the body. A somewhat larger lesion will produce a brachio-facial or a brachio-crural monoplegia. (We