300 W. MCDOUGALL : degree of habitual exercise of the intellectual functions " <p. 5)., Fere shows also that active or passive movements of one limb, continued for some few seconds, result in an increase of the force of the maximal contraction of which the other limbs are capable by as much as 20 per cent, or more (p. 8) ; and that even the movements of speech may produce a similar effect. " When a limb is put into action, the movement, be it voluntary or passive, determines upon the cerebral motor centres of the limb an exciting action that extends itself to the neighbouring centres " (p. 12). M. Pitres is quoted as having shown that every destructive lesion of the motor region produces a muscular enfeeblement of all four limbs, and Dr. Fere asserts that in his experience "the destruction of any cerebral centre whatever produces in general a certain degree of intellectual enfeeblement " (p. 13). On page 25 we read : "All these observations taken together show us that a cerebral centre, each time that it becomes active, provokes, by a process not yet understood, an excitation of the whole organism ". Fere then goes on to confirm these conclusions by a series of experiments on hysterical and hypnotised subjects in whom corresponding effects are still more markedly displayed ; and he shows that stimuli applied to internal organs produce similar results, and he sums up thus (p. 53) : " One may say then that every peripheral excitation determines an augmentation of potential energy," and again, " les excitations pdriphtfriques dSterminent une augmentation de I'dnergie disponible, de la force utilisable " (p. 60). I have quoted thus extensively these observations and conclusions of Dr. Fere because they justify in the fullest manner, and indeed, not only justify, but imperatively de- mand that we entertain, some such conception as I am here suggesting, namely, the conception of the interconnected mass of the afferent neurones as forming a reservoir of energy to which all the afferent nerves contribute in proportion to the degree to which they are stimulated to activity, and on which all efferent channels draw when thrown into activity. 1 To put the whole matter concisely as I conceive it and in the terms I propose : The neurones of the afferent side of the nervous system constitute a common reservoir of neurin, and a variable head of pressure is kept up in it by the 1 The cerebellum which seems to consist chiefly of a mass of neurones forming relays upon sensory paths leading to the cerebrum must be regarded as constituting a principal part of the reservoir, and it is in fact frequently spoken of by physiologists as a store-house of energy.
