A minute analysis (experimental) of the various movements produced by stimulating in the monkey different regions of the cortical centre for the upper limb, as defined by Professor Ferrier/ by Charles E. Beevor.

  • Beevor, Charles E.
Date:
1887
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Licence: Public Domain Mark

Credit: A minute analysis (experimental) of the various movements produced by stimulating in the monkey different regions of the cortical centre for the upper limb, as defined by Professor Ferrier/ by Charles E. Beevor. 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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    half of the area. Indeed, a glance at Table 3 will show that it is almost the only movement in the lower third of the area, in which portion of the cortex, too, the joint is very feebly represented, movement of it only being met with once in ten times on stimulating the centre 5'. (See fig. 2 and Table 3.) Adduction is the characteristic movement of the shoulder centres in the ascending parietal gyrus. Retraction (i.e., extension with rotation out and some adduction) is especially represented in the anterior half of the upper third of the ascending parietal gyrus in the centres marked 9 and 11. (See Table 3.) Circumduction was never seen. Elbow.—We need only draw especial attention to the remarkably exact manner in which representation of extension of the elbow is limited to the upper fifth of the area experimented on, while flexion is equally the function of the lower three-fifths ; and to the existence of a very important zone of cortex, where the phenomenon of confusion is represented, this forming a border-land between the regions of extension and flexion. The explanation of this zone of confusion is easy, since the representation of the elbow—the movements of which occur in only one plane-^-admits necessarily of closely limited localisation. (See Table 3 and fig. 3.) Wrist—\n tabulating the movements of this joint, it was obviously necessary to separate its two distinct functions, viz., pronation and supination, on the one hand, and flexion and extension on the other. We will first discuss the latter function, as by far the more important. On Table 3 it is seen how extremely constant is the movement of extension, and a moment's consideration will show that it is of funda- mental importance, for it is clear that the delicate movements of the fingers could not possibly be performed with any degree of accuracy and force unless the wrist be previously fixed in moderate extension, and consideration of this fact also explains why the wrist is especially provided with powerful extensor muscles which act with con- siderable independence. (See fig. 4.) In returning to the first-mentioned movements of the wrist, viz., pronation and supination, we have only to add that, as might be expected, supination is most marked in the lower two-thirds of the area, since it is here that we have also flexion of the elbow, i.e., bicipital action. The converse equally holds, viz., that pronation is associated with extension of the elbow. This association is clearly the outcome of the two great classes of action in animal life, viz., that of defence and that of feeding. The former of these is a coarse violent movement, and is naturally associated in the upper part of the region with the centres for the large trunk and leg muscles, while the latter, more delicate, is represented near to the centres for the face and mouth.* (See Table 2.) Digits.—The representation of the fingers must be considered apart from that of the thumb, the movements of which are the most highly specialized in the limb. * Similar ideas have been previously suggested by Dr. Lauder Bku^TON, F.R.S. See Brain,' vol. 4, p. 431.