. A text-book of human physiology . ig. 2:2). Special observations as to theconnections of the two sides ofthe oculo motor nucleus affordsome grounds for believing thatthe nuclei of the two sphincters(pupil and accommodation) aswell as the nuclei of those ex-trinsic muscles which take partin synergic movements of theeyes, are united. The latter isshown by the fact that synergic movements cease when the paired nuclear region is split in two by a median sagittal section. Complete division of the brain at the anterior end of the midbrain pro-duces a remarkable state of inertness in the muscles, w
. A text-book of human physiology . ig. 2:2). Special observations as to theconnections of the two sides ofthe oculo motor nucleus affordsome grounds for believing thatthe nuclei of the two sphincters(pupil and accommodation) aswell as the nuclei of those ex-trinsic muscles which take partin synergic movements of theeyes, are united. The latter isshown by the fact that synergic movements cease when the paired nuclear region is split in two by a median sagittal section. Complete division of the brain at the anterior end of the midbrain pro-duces a remarkable state of inertness in the muscles, which is described bySherrington under the name of acerebraJ rigidity. It is recognized by thefact that certain muscles become stiff: the elbows and knees, for example,are rigidly extended, the tail is inflexible, etc. This condition appears to bedue to the influence of the afferent nerves from the regions affected, for thestiffness in the arm muscles, for example, entirely disappears after sectionof the posterior roots for the Fig. 273.—Schematic representation of the nucleus ofoculo motor nerves, after Bernheimer. Tlie red linesindicate the direct, and the black the crossed rootfibers. , intrinsic muscles of the eje; Lev.,levator palpebrse sup.; , superior rectus; ,internal rectus; , inferior obliquus; ,inferior rectus; Tr., superior oblique. THE DIEXCEPHALON OR TWEENBRAIN 617 Reflex stimulation of an animal in this condition produces certain coor-dinated movements which are unmistakably related to the movements of loco-motion. For example, the left anterior and the right posterior extremitiesbecome flexed, while the right anterior and the left posterior are extendedat the same time, and vice versa. Xot infrequently these reflexes alternate,beginning regularly with flexion of the extremity directly stimulated. Atthe same time the head and neck are twisted toward the stimulated side; themouth is opened, the lips and the tongue are retracted,
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