Page:Popular Science Monthly Volume 51.djvu/108

100 considered hopeless. This involved the construction of the myograph and the application of Pouillet's method of measuring small intervals of time.

The nerves, however, are only the peripheral portions of the nervous system; the desire lay near to measure the time occupied by the brain processes. Such measurements have been (and still are at the present day) impossible by direct physiological methods. It was, however, a sufficiently settled fact that the brain processes are closely accompanied by mental processes. This consideration led to the employment of the time-methods on living human beings. The stimulus was applied to the skin, to the eye, or to the ear, and the time required for the subject to respond by a muscular movement was measured. Since the subject could tell what he experienced under different variations of the experiment it was found possible to measure the time of sensation, of action, etc. The physiological processes corresponding to these mental processes were to some extent known. It was soon discovered, however, that other mental processes—e. g., discrimination, association, etc.—could be introduced in such a way as to be measured.

Beginning with 1865, Donders made a systematic attack on the problem of psychological time-measurements, and was soon followed by Exner. Helmholtz had already directed the experiments of his pupil Exner in measuring the time of sensation, and in 1877 the work of Auerbach and von Kries appeared from his Berlin laboratory.

The interest of the physiologist lay, however, mainly in the deductions to be drawn concerning brain action. Even from the simpler forms of reaction time the amount of physiological knowledge to be obtained is small, and for the more complicated forms it is zero. It was natural, therefore, for physiology to pursue the subject not much further.

Thus the two sciences of astronomy and physiology discovered and developed the methods of investigating mental times; the further development was the task of psychology.

Another source of the new psychology is to be found in the physiological study of the sense organs. The most obvious method for determining the functions of the nerves and end organs of the skin—the nose, the ear, or the eye—is to ask the living subject what he feels when various stimuli are applied. In this way there has arisen a large body, of knowledge concerning the sensory functions of the nervous system. In this form, however, the problem is a purely psychological one. To inquire if the skin