SENSO RIM& This term is applied by physiologists to a series of ganglionic centers, each of which has the power of communicating to the mind the impressions derived from the organ with which it is connected, and of exciting automatic or involuntary muscular movements in respondence to these sensations. (See Carpenter On the Func tions of the Aereaus S.ustem to Human Physiology, Gill ed. p. 545.) These ganglionic centers, which Meat the base of the brain in man, are in direct connection with the nerves of sensation, and appear to differ entirely in their functions from the other parts of the encephalon. Anterior, there are the o/factire ganglia, or what are termed the bulbs of the olfactive nerves. The nature of these structures is more evident in many of the lower mammals. in whom the org:an of smell is highly developed, than it is in man, although even in the Imam]) subject these masses contain gray or vesicu lar nervous matter, indicating their true ganglionic nature. Behind these, we have the optic ganglia, commonly known as the corpora quadrigemina, small in man, but com paratively large in litany of the lower mammals. The auditory ganglia do not form dis tinct projecting masses, but are represented by sntall masses of vesicular matter, into which the auditory nerves may be traced, and which are imbedded in the medulla oblon gata. In fishes there is a well-developed and distinct auditory ganglion. The gustatory
ganglion is the least distinct of any. but it is supposed to be represented by a mass of vesicular matter imbedded, like the preceding ganglion, in the medulla oblongata, and into which the nerves of taste may he traced. On examining a progressive series of brains from man to the lowest mammals, we find a continuous diminution of the hemi sphere sand a corresponding development of these ganglia. or, at all events, of the olfac tory and optic ganglia; while. if we continue the investigation to the brains of birds, reptiles, and fishes, we find the same law in force, till finally, in reptiles and fishes, those ganglia form the greatest part of the brain.
It was long attempted to determine some one point in the brain where the soul is more especially located or centralized, and to this ideal point the time of Sensorium was applied in the older psychological speculations. The fancy of Descartes made it a small body near the base of the brain. called the "pineal gland." The recent views of the nervous sys'em repudiate the idea of a central point of this nature; in consciousness the brain generally is active, although under different impressions and ideas the currents may be presumed to follow different nerve tracks. no meaning is now attached to a sensorial]) in psychology, as distinct from the cerebrum at large.