December 6, 1889] 



SCIENCE. 



391 



epileptic seizure it was .50 of a second for louch, and .37 for sound. 

 In another patient the re-action times were .35 of a second for 

 touch and .30 for hearing three hours after an attack, as against .21 

 of a second and .16 normally. A third patient, whose normal re- 

 action times were .28 of a second (touch) and .34 of a second 

 ^sound), two hours after a seizure, re-acted in .40 of a second to 

 touch and .37 of a second to a sound. The same patient, seventy- 

 two hours after the last of fifteen successive attacks, required i.ii 

 seconds to re-act to touch, and 1.25 seconds to re-act to a sound. 

 In an independent research, M. Fere had shown that in the aver- 

 age of twenty cases the dynamometric power was reduced to 45 

 per cent of its normal value immediately after a seizure, to 33 per 

 cent after one-quarter of an hour, to 25 per cent after an interval 

 of one half-hour, and to 17 per cent after an interval of three- 

 quarters of an hour. Apart from special relations of the nature of 

 the seizure to the diminution in muscular poWer, the general thesis 

 of M. Fer^ is well borne out by these facts. 



In normal individuals the same relations can be demonstrated, 

 though the contrasts are not as sharp. Fatigue diminishes muscu- 

 lar force, and increases the times of re-action. Intelligent persons, 

 speaking generally, have a short re-action time and a high dyna- 

 mometric pressure. In order to study in closer detail the relation 

 of re action time and motor power in special motor groups, M. 

 Fer^ had constructed a dynamometer in which the pressure of each 

 finger was recorded separately. With this apparatus M. Fere was 

 able to establish that the movements of flexion were from three to 

 ten times as powerful as those of extension ; that the power of 

 •different fingers varies with different individuals, and stands in re- 

 lation to the profession of the individual, the third and fourth 

 fingers being especially strong in piano-players ; and that intel- 

 lectual persons have an especially strong thumb, an essentially 

 human movement. 



Re-FCtion Tii 

 Seconds. 



Thumb 



Forefinger... . 

 jVIiddle finger. . 

 Third finger . . 

 Little finger . . 



Thumb........ 



Forefinger 



Middle finger. 

 Third finger.. 

 Little finger . 



Thumb . .. 

 forefinger.. . 

 JMiddle finger 

 Third finger 

 Little finger. 



Thumb 



Forefinger 



Middle finger. 

 Third finger . 

 Little finger.. 



.346 

 .436 



The first three records were obtained from officials of the hospi- 

 tal, and exhibited very fairly the points in discussion, while the third 

 subject is also a pianist, and shows a remarkable power of flexion 

 of the little finger as well as a quick re-action time for both flexion 

 .and extension of this finger. The fourth record is of an intelligent 

 epileptic patient. We see, that, while the dynamometer shows 



movements of flexion far superior to those of extension, the re- 

 action times show only a slight superiority, and that exercise seems 

 to increase not only the power of flexion, but the speed of exten- 

 sion. If we make separate observations on the right and left 

 hands, we will find that the preferred hand presses more strongly 

 and re-acts more C|uickly than the other hand. 



The same method can be applied to the movement of other or- 

 gans. The energy of extension of the tongue has been measured, 

 and varies in normal subjects from 500 to 850 grams. In deaf- 

 mutes and patients afflicted with aphasia it may be as low as 100 

 grams. That the energy of this movement is related to the re-ac- 

 tion time is shown in the following results ; F (a normal subject) 

 moves the tongue with a force of S50 grams, and performs this 

 motion in .13 of a second ; L (also normal), 400 grams and .15 of a 

 second ; J (partially aphasic), 300 grams and .30 of a second ; F (a 

 stammerer), 200 grams and .33 of a second. 



That nutritive processes play an important part in these move- 

 ments is more than likely. Cold retards and heat accelerates the 

 re-action times. The following table shows the effect of warming 

 upon the re-action time in movements of flexion and extension of 

 the five fingers : — 



Thumb .... 

 Forefinger - . 

 Middle finge 

 Third finger 

 Little finger 



fited by this 



This research, though incomplete, and founded upon rather few 

 experiments with each subject, yet admirably suggests the close 

 relations that exist between the motor, sensory, and nutritive func- 

 tions of the psycho-physical organism. As our knowledge of this 

 relation becomes more and more exact, the possibilities of utilizing 

 such knowledge for making the elementary processes of knowledge 

 and action easier and quicker, become more and more real. 



Rapidity of Movements. — A pianist, in playing a presto of 

 Mendelssohn, played 5,595 notes in four minutes and three sec- 

 onds. The striking of each of these notes, it has been estimated, 

 involved two movements of the finger, and possibly more. Again, 

 the movements of the wrists, elbows, and arms can scarcely be. less 

 than one movement for each note. As twenty-four notes were 

 played each second, and each involves three movements, we would 

 have seventy-two voluntary movements per second. Again, the 

 place, the force, the time, and the duration of each of these move- 

 ments, was controlled. All these motor re-actions were conditioned 

 upon a knowledge of the position of each finger of each hand before it 

 was moved, while moving it, as well as of the auditory effect in force 

 and pitch, all of which involves at least equallv rapid sensory trans- 

 missions. If we add to this the work of the memory in placing the 

 notes in their proper position, as well as the fact that the performer 

 at the same time participates in the emotions the selection de- 

 scribes, and feels the strength and weaknesses of the performance, 

 we arrive at a truly bewildering network of afferent and efferent 

 impulses, coursing along at inconceivably rapid rates. Such esti- 

 mates show, too, that we are capable of doing many things at once. 

 The mind is not a unit, but is composed of higher and lower cen- 

 tres, the available fund of attention being distributable among 

 them. 



BOOK-REVIEWS. 



A Treatise on Linear Differeiitial Equations. By ThO.M.^S 



Craig. New York, Wiley. 8°. 



The theory of differential equa.ions has undergone within the 



last thirty years a most fundamental change. The object of the 



older theory was to integrate a given differential equation " in finite 



