A text-book of physiology for medical students and physicians . luntarycontrol of the muscle is lost or im-paired permanently. It would seem,therefore, that even in an animal ashigh in the scale as the dog volun-tary control of the muscles can bemaintained through fibers otherthan those belonging to the pyra-midal system. A system such asthat found in the rubrospinal tract(p. 181) may be considered as ade-quate to fulfil such a function. Inman, however, along with the morecomplete development of the pyr-amidal system, the efficacy of thephylogenetically older motor sys-tems is correspondingly
A text-book of physiology for medical students and physicians . luntarycontrol of the muscle is lost or im-paired permanently. It would seem,therefore, that even in an animal ashigh in the scale as the dog volun-tary control of the muscles can bemaintained through fibers otherthan those belonging to the pyra-midal system. A system such asthat found in the rubrospinal tract(p. 181) may be considered as ade-quate to fulfil such a function. Inman, however, along with the morecomplete development of the pyr-amidal system, the efficacy of thephylogenetically older motor sys-tems is correspondingly reduced. The Crossed Control of theMuscles and Bilateral Represen-tation in the Cortex.—It has been known from very ancient times that an injury to the brain onone side is accompanied by a paralysis of voluntary movementon the other side of the body, a condition known as facts given above regarding the origin and course of thepyramidal system of fibers explain the crossed character ofof the paralysis quite satisfactorily. The schema thus pre-. Fig. 89.—Schema representingthe course of the fibers of the pyra-midal system: 1, Fibers to the nuclei ofthe cranial nerve ; 2, uncrossed fibersto the lateral pyramidal fasciculus;3, fibers to the anterior pyramidalfasciculus crossing in the cord ; 4 and5, fibers that cross in the pyramidaldecussation to make the lateralpyramidal tract of the opposite side. 198 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. sented to us is, however, not entirely without exception. Incases of hemiplegia in which the whole motor area of oneside is included it is known that the paralysis on the other sidedoes not involve all the muscles, and, in the second place,it is said that there is some muscular weakness on the sameside. The paralysis in hemiplegia affects but little, if at all,those muscles of the trunk which are accustomed to act inunison,—the muscles of inspiration, for instance, the diaphragm,abdominal and intercostal muscles, and the mu
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