486 REPORTS ON THE STATE OF SCIENCE. 



The conception towards which the study of the organism as a whole 

 points is that the neurones of the afferent side of the nervous system 

 (including the cerebellum) constitute a great common resers'oir of free 

 energy, in which the head of pressure varies from moment to moment with 

 the ratio of the in-fiow to the out-flow, and on which all efferent paths 

 may draw in turn when they come into activity. 



As to the sources from which this reservoir of free energy is supplied, 

 no doubt every one of its constituent neurones is capable of making its 

 contribution, and especially all those directly connected with, and stimu- 

 lated through, the sense-organs. 



But we shall never understand the problems of fatigue, or any other 

 of the great problems of the brain, until we adequately recognise certain 

 special sources of supply. And the study of fatigue serves to bring into 

 prominence the importance of these special sources of energy. 



In psychology we speak of instincts or innate dispositions to action, 

 and WR recognise that the constitution of every human being comprises 

 a certain number of such instinctive dispositions, and that when any one 

 of these is awakened, whether by sense impression or idea, the subject 

 experiences a state of emotional excitement, and an impulse, a desire or 

 aversion, a strong conation or felt tendency towards some kind of action. 

 We recognise that under the driving power of such an impulse the subject 

 can achieve tasks, can put forth quantities of energy, such as are 

 impossible for him in the absence of any such conative-affective excite- 

 ment.' 



It is for the physiologist to discover if possible the neural seats and 

 bases of these innate dispositions. Recent work by Pagano seems to 

 indicate that they may perhaps be found in the basal ganglio of the 

 brain. '^ 



But however that may be, it seems safe to assume that these powerful 

 impulses, which we experience in conjunction with our emotional excite- 

 ments, and which enable us to energise in a way quite impossible in 

 their absence, have nervous correlates, and that the physiological correlate 

 of such an impulse is a great liberation of energy in some centre or part 

 of the central nervous system, which energy augmenting greatly the 

 disposable free energy of the brain, can be utilised in the performance of 

 any kind of action undertaken for securing the satisfaction of the im- 

 pulse ; and it seems that such an accession of energy can overcome the 

 increased resistances obtaining in a state of moderate general fatigue, 

 abolishing more or less completely in so doing both the objective and the 

 subjective symptoms of fatigue, because the great accession of energy 

 lowers the ratio of resistance to energy. 



It is the possibility of these sudden accessions of energy that has 

 rendered well nigh futile all the many attempts hitherto made to obtain 

 I'eliable objective measures of degrees of fatigue of the organism as a 



as 188G by Dr. Hale White (^Lancet, vol. ii. 1886, p. 161 ; see also Brit. Med. Journ., 

 October 17, 1908), who proposed to use the word ' neurorrheuma' to denote nervous 

 energy so conceived. Among many others who have approved of this conception 

 are Sir Victor Horsley (Hughling's Jaclisoa Lecture, Brain, vol. xxix. p. 448) 

 and Dr. S. G. Sharkey (Presidential Address to the Neurological Society, Brain, 

 vol. ssvii. p. 12). 



' For a fuller discussion of the role of these innate dispositions in the maintenance 

 of human activities, I may refer to my 1 ntrodiiction to Social Psycholnf/y. 



■ Arckircs Italictines de Biologic, 1906. 



