234 NEUROLOGY 



Thus, in every movement leading to exact thought and exact 

 expression, in every movement of the memory, vast numbers of 

 mental processes must cooperate, and if the outcome is to be effect- 

 ive, this cooperation must be governed from the outset by a lead- 

 ing idea as a ruling motive. The failure of this ruling idea leads to 

 the wayward flight of thoughts, so characteristic of various forms 

 of mental weakness, as has been pointed out by Liepmann. 1 The 

 psychological bearing of this principle has repeatedly been insisted 

 on by the keen psychologist, Bergson, both in his work on memory 

 and matter, 2 and in a more recent essay. 3 



The psychological researches into habit and set are likewise of 

 practical importance. The laws of habit describe the tendencies 

 under which the varied reactions of the nervous system recur under 

 forms which are really stereotyped and predetermined, although 

 simulating the purposive reaction of health, and often only with 

 difficulty to be distinguished from them. The term "set" describes 

 the process by which the reactions of every individual, beside their 

 purposive significance, receive a form and coloring, which, in a 

 measure, reflect the general characteristics of the personal life of 

 the actor, his temperament, his racial traditions, his education. 

 It indicates, as has been justly said, the "signature" in the mus- 

 ical sense, under which the movement of his life goes on. The 

 "set" of each patient must be understood before his illnesses can be 

 mastered. In the study of these important laws psychologists and 

 neurologists can lend each other mutual support. 



If a further illustration was needed of the way in which a refined 

 study of physiology and psychology can be made of the highest 

 use to supplement anatomic data, in affording a basis for clinical 

 conclusions, it could be amply furnished by a consideration of the 

 problems of fatigue, that mysterious region, daily traversed, where 

 health and sickness are so strangely mingled. 



Thanks to recent investigations, we know a good deal about the 

 anatomy, chemistry, 4 and physiology, 5 of the nervous system in 

 fatigue, as representing the primary lesions, but it needs only a 

 brief reflection to show how numerous and varied are the secondary 

 manifestations, neural and mental, involving eminently the func- 

 tions of the organism as a whole and in all its parts, that character- 

 ize the clinical outcome of acute or of prolonged exhaustion. 6 To 



1 Ueber Ideenflucht, publ. by Carl Marhold, Halle, 1904. 



2 Matibre et memoire. 



' L'effort intellectuel. Rev. Philosophique, 1902, p. 53. 



4 See especially various papers by Verworn and his pupils, which are published 

 or referred to in the recent volumes of the Zeitschrift f. Allgem. Physiologic, 1901 

 to 1904. 



6 See especially Richet, Dictionnaire de Physiologic, article "Fatigue." 



6 See "Neurasthenia," by Cowles, Shattuck Lecture, 1891, Boston Med. and 

 Surg. Jour. ; see, also, the various accounts of the Exhaustion Psychoses, and of 

 studies on the contests in the Olympian games. 



