loo POPULAR SCIENCE MONTHLY. 



considered hopeless. This involved the construction of the myo- 

 graph 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 be- 

 ings. 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 muscu- 

 lar 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 pro- 

 cesses were to some extent known. It was soon discovered, how- 

 ever, that other mental processes e. g., discrimination, associa- 

 tion, 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 fol- 

 lowed by Exner. Helmholtz had already directed the experi- 

 ments 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 knowl- 

 edge 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 sub- 

 ject what he feels when various stimuli are applied. In this way 

 there has arisen a large body, of knowledge concerning the sen- 

 sory functions of the nervous system. In this form, however, the 

 problem is a purely psychological one. To inquire if the skin 



* For the historieal account of experiments on reaction time, see Buccola, La Icgge del 

 tempo nci tVnoiiieni del ])ensieio, Milano, 188:5, and Rihot, La Psychologie allemande con- 

 temporaine, Paris, 1885 ; for a summarv, with literature, see Jastrovv, Time Relations of 

 Mental Phenomena, New York, 1890. 



