Handbook of Psychology (Philosophy in America Series)

Book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1894. Excerpt: ... state which constitutes a course a good nervous conductor. This theory is objected to both on theoretical grounds and from experiment. It makes the distinction between courses and centres too absolute and mechanical. According to it, any distinct dynamic property is taken from the nerve-tracts; while experiments show that the elementary portions of both sensor and motor nerves have a life and function of their own. The eye when removed from its socket, thus losing all connection with a centre or ganglion, still shows sensitiveness to light, and has a motor reaction in the contraction or expansion of the iris.1 Pfliiger maintains that there is an increase in intensity in the nervous disturbance as it traverses the motor nerve, and Kichet' thinks a similar increase in the sensory nerves probable. Accordingly, another theory is advanced which seems more philosophical to the present writer, as far as he ventures to have an opinion on a matter so purely physiological. This second conception of the nervous system makes it a living organism instinct with nervous force or neural properties throughout. This system is in a state of unstable equilibrium and constant change, due to stimuli through sense-organs and to spontaneous central discharge. Disturbances tend to equalize themselves everywhere in the system by a species of centrifugal and centripetal tension, which, through its greater or less effectiveness in this direction or that, upon this course or that, results in conduction or neurility. Differentiation, 1 Brown- Scquard, Proc. Roy. Soc., 1886, p. 234. Bee note of many other such facts in Lewes, Phys. Ba»is of Mind, p. 231 f. Another interpretation may be given such facts, i.e., that the stimulus acts immediately upon the muscle: but this would not damage the position in the te...