CERTAIN CHARACTERISTICS OF THE CORTICAL INFLUENCE OVER THE SYMPATHETIC NERVOUS SYSTEM IN MAN

Abstract

Two patients with hemi-plegia are described in whom the experiencing of an emotion produces exaggerated pilomotor phenomena on the hemiplegic side. The simple pilomotor reflex in the same zone is normal. The behavior of the pilomotor system in these 2 cases is contrasted with that in one of partial section of the spinal cord, in which, while the simple reflex is exaggerated, there are no abnormal phenomena in response to an emotional stimulus. The human cortex is probably the site of the origin of a neurone which exercises a definite influence over, and is a part of, the sympathetic nervous system. This neurone (I) probably terminates in the hypothalamus and in parts of the thalamus, from where the 2nd one (II) descends to the intraspinal cells of the first peripheral sympathetic neurone. In the hemiplegia cases there is interruption of neurone I and in the spinal cord case, of neurone II. Both neurones I and II are probably anatomically associated with the pyramidal tract and may decussate with it. The release phenomenon is a general principle, and applies to the sympathetic as well as to the other parts of the nervous system. When neurone I is interrupted, hyperfunction of neurone II is exhibited upon stimulation; destruction of neurone II causes exaggeration of the activity of the peripheral sympathetic neurones. Because of their arrangement, the sympathetic tracts are suitable for a study of certain properties of the phenomenon of inhibition, which leads to the following conclusions A. The ability of any neurone to inhibit is an inherent part of the function of that particular neurone, independent of the activities of neurones situated higher up. B. The inhibitory power is not of such a nature as to be transmissible from one neurone to another.