July 29, 1898.] 



SCIEIWK 



135 



July; and this is interpreted to mean that there 

 is a gradual decrease in vitality as the result of 

 the continued school work. The second is the 

 remarkably close correlation between changes 

 in touch sensitiveness as tested by the sesthesi- 

 ometer and the fatigue effects of mental occupa- 

 tion. After an hour or two spent in the class 

 room the distance apart between two points 

 which can still be felt as two when applied to 

 the forehead, or the nose, distinctly increases, 

 and after a rest it again decreases. This is 

 probably to be interpreted as a modification not 

 in skin sensibility, but in the attention, for it 

 requires close attention directed to the part 

 touched to distinguish whether one feels a sin- 

 gle point or a pair of points. None the less it 

 is somewhat noteworthy that this test should , 

 yield more positive and uniform results than 

 several others in which the mental element is 

 apparently more prominent. 



In the psychological tests the pervading prin- 

 ciple is the detection of changes in the rapidity, 

 accuracy, scope and extent of mental processes 

 due to a general intellectual fatigue or to the 

 special waning of the particular group of pro- 

 cesses as the result of their prolonged exercise. 

 A good example of the latter class is the test 

 frequently applied to school children of requir- 

 ing them to perform an extended series of sim- 

 ple additions or multiplications. In a typical 

 result there is first an increase in facility due to 

 the practice or adaptation to the task, which 

 gives place to a decrease in facility from 

 quarter-hour to quarter-hour ; and the increase 

 in the number of errors furnishes a still more 

 striking evidence that fatigue is setting in. 

 Here, again, a period of rest will bring about a 

 return to a normal facility, and a rest of two 

 hours will be more effective than a rest of one 

 hour. A good example of general fatigue 

 is evidenced in the comparison of the rate and 

 accuracy of addition or dictation or memory or 

 reaction-times in the early morning hours and 

 again at the close of the morning or the day's 

 work. In a typical curve, in which time or 

 errors are tabulated, the time needed for the 

 calculations, as well as the proportion of mis- 

 takes, increase after school work, decreasing 

 again after hours given to recreation. There 

 is quite definite evidence as well that a more 



concentrated effort brings about a greater in- 

 crease in time and errors, and that the various 

 forms of test for mental fatigue — calculations, 

 dictations, reactions, memorizing and the like — 

 yield consistent although not equally definite 

 results. 



It thus appears that an appreciable advance 

 has been made in the methods of detecting the 

 nature and degree of fatigue of various types \ 

 that interesting and fairly precise means 

 of measuring these have been devised ; some 

 insight into the variety and complexity of the 

 factors involved in fatigue has been gained, 

 and some moderately successful applications to 

 the work of the school room have been offered. 

 To pursue the investigations further requires a 

 further elaboration of technique, a more com- 

 plete elimination of the sources of error, a more 

 thorough application of logical method to the 

 arrangement and interpretation of tests. One 

 very wholesome lesson of all this is that the 

 path from knowledge to practice is a long and 

 tortuous one. A suggestion arising from a slight 

 experimental investigation is not a sufiicient 

 b9,sis for raising a cry of overwork, or for re- 

 forming the school program ; nor is an off- 

 hand acquaintance with the general resvilts of 

 studies in fatigue without a detailed compre- 

 hension of the experimental conditions under 

 which such results were obtained, a proper 

 basis for either their criticism or their applica- 

 tion to pedagogical problems. The study of 

 mental fatigue is certain to become, and practi- 

 cally has become, a technical acquisition ; 

 the popular interest must be severely regu- 

 lated by scientific method and cavition ; 

 its possible practical aspect and the desire to 

 reach practical results must not be allowed to 

 interfere with a proper theoretical discussion 

 and analysis. Moreover, the road from theory 

 to practice must be by way of a quantitative 

 analysis. The determination of the. facts of 

 fatigue, however useful and indispensable, is in 

 part subservient to the determination of the de- 

 gree of fatigue ; the how much rather than the 

 how is needed for practical application, or rather 

 it is precision of nature and degree that makes 

 practice possible. The fact that many diseases 

 are of germ origin is, of course, of great impor- 

 tance, not only negatively by discountenancing 



