Nervous and mental diseases . le groups 168 DISEASES OF THE BRAIN PROPER. are represented. Such outlines must be taken as suggestive rather thanactual. There is no sharp boundary between the adjoining centers, andthese fields overlap. The dippings of the sulci also serve to interferewith sharp limitations of the cortical areas and obstruct the experimentalstimulation of individual movements. Every muscular movement, ap-parently, has a locus of principal or major representation in the cortex,but such a movement is so wrapped up with other coordinate movements,and so widely related functionally,
Nervous and mental diseases . le groups 168 DISEASES OF THE BRAIN PROPER. are represented. Such outlines must be taken as suggestive rather thanactual. There is no sharp boundary between the adjoining centers, andthese fields overlap. The dippings of the sulci also serve to interferewith sharp limitations of the cortical areas and obstruct the experimentalstimulation of individual movements. Every muscular movement, ap-parently, has a locus of principal or major representation in the cortex,but such a movement is so wrapped up with other coordinate movements,and so widely related functionally, that its representation in a minor de-gree may spread over great areas. The thumb, for instance, is princi-pally represented in a given small cortical center, but the prehensileaction of the thumb is related to the grasp of the fingers, the fixationof the wrist, the rigidity of the whole upper extremity, and even toaction of the trunk and lower limbs in strongest efforts, during whichthe opposite members also come into Fig. 67.—Functional areas of the cerebral cortex of the left side (after Campbell). The most recent investigation of cortical localization in anthropoidsby Sherrington and Griinbaum, and the histological studies of A. ,1 indicate that the true motor region of the cortex is much lessextensive than was formerly thought. The functional groups of skeletalmuscles are represented in the precentral or ascending frontal convolu-tion from the lower end of Rolandos fissure up to the midline of the brain,and to a slight extent on the mesial surface of the hemisphere, in a con-tinuous narrow zone. The bottom of the fissure of Rolando sharplybounds the motor area behind, and it extends forward not to exceed thewidth of the precentral gyre. Liepman2 and Wilson3 have shown conclusively that the ability toperform skilled movements with the limbs resides in the first and second 1 Histological Studies of the Localization of Cerebral Functions, 1905. 2 Monatssch
Size: 2058px × 1215px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookid, booksubjectnervoussystem
