The nervous apparatus designated by this name is formed, as we know, by the sensitive and motor filaments coming from the cranial nerves, or from the roots of the spinal nerves. That is, its ramifications are, at the same time, sensitive and motor. The movements excited by the great sympathetic are not under the influence of the will The motor impulse springing from this system diners also from that which determines voluntary movements, in that it travels less rapidly. Experiments upon animals also prove that the ganglia and ramifications of the great sympathetic continue their functions some time after they cease to be in communication with the nervous centre: The movements they induce are then executed under the influence of the nervous force pre-existing, and stored up in their substance. The great sympathetic gives motion and sensation to the machinery of organic life; it controls the nutritive functions, the circulation, the secretions, etc.
Besides the voluntary movements which result from the transmission of impressions by the nerves of sensation, and from the perception of these impressions, others are produced in which the will has no part, and which result from the impulse directly reflected upon the motor nerves, without any sensation having necessarily taken place, or at least without our having any consciousness of it These are called reflex movements, and the force which determines them, and is considered as peculiar to the nervous centre, is called reflex power or the excito-motor faculty. Several physiologists have considered the phenomena classed under the name of recurrent sensibility as belonging to this reflex action, but upon the origin of this sensibility authors are not agreed.
Lastly, there is another reflex action which gives rise to sympathy, that is the particular influence which certain organs exercise upon others, such as the sensation called setting the teeth on edge, produced by the grinding of metal against stone or glass, and the sneezing provoked by tickling the pituitary membrane, or by snuff, etc. (See Movements, p. 59).