ii54 



NATURE 



[April 7, 192 1 



produced by a sudden dilatation of ultramicroscopic 

 pores in this membrane or membranes. I am not 

 speaking of visible pores, but of invisible pores such 

 as are postulated in theories of electrical conduction 

 and of osmotic phenomena. I imagine that these in- 

 visible pores suddenly dilate when the emotive im- 

 pulse through efferent nerves reaches the living mem- 

 brane, just as we see the pupil of the eye dilate with 

 an emotion of surprise. And with this image in my 

 mind I find it extremely interesting to recognise and 

 measure what a very long time it takes for any given 

 stimulus to produce its effect. It takes two seconds 

 before the threat of a pin-prick^or, for the matter 

 of that, an actual pin-prick — or a single induction 

 shock, brings about the sudden dilatation of pores or 

 increased permeability and the increased electrical 

 conductivity that are signified to us by the movement 



Fig. I. — This photogram is the simultaneous response of the hand and of 

 the FOOT of a normal subject, and is given as an example to illustrate 

 the method of investigation by double response. In th:s example it is 

 evident : (i) that the response occurs sooner and is of shorter duration 

 in the hand (palm) than in the foot (sole) From the time record it can 

 be seen that the lost times in the hand and in the foot are respectively 

 2 and 4 seconds (approx.), and the durations of response 15 and 40 

 seconds (approx.). A closer approximation to true time values would 

 require a quicker record to be taken for the lost times and a slower 

 record for the durations. (2) '1 hat the response is greater in the hand 

 than in the foot. This magnitude is measured by reference to the initial 

 deflections made by passing a current from ^0 volt through each of the 

 two circuits. In this example the hand response is approximately -f^, 

 and the foot response approximately -f^. The rate of movement of the 

 plate is shown (not very distinctly) in half-seconds. The portion shown 

 in the figure occupied about 45 seconds. A similar procedure by 

 simultaneous double response is required for the mapping out of the 

 body-surface. Obviously the comparison between right and left sides, 

 upper and lower extremities, distal and proximal parts, flexor and 

 extensor aspects, is to be carried out with far greater expedition and 

 certainty by double than it could be by single records. 



of the spot of light. How is this long lag of two 

 seconds to be accounted for? Does it occur on the 

 afferent side? Assuredly not. A delay of this sort 

 might be expected to amount to at most one-fifth of a 

 second. Moreover, if we miss out the afferent side 

 altogether, and bring about the response by an arti- 

 ficial explosion down efferent nerves, we shall find 

 the same long delay of two seconds between the 

 muscular movement and the emotive movement, both 

 of which are taking place at the periphery. There- 

 fore, the chief business of the long delay takes place 

 at the periphery, in the skin of the palm of the 

 hand, and its great length is a token that we have 

 to do with impulses conveyed, not along cerebro- 

 spinal, but along sympathetic nerves We may 

 find time later to discuss the question whether 



NO. 2684, VOL. 107] 



these are vasomotor or secretomotor or trophic 

 nerves. 



6. Dreams are subjective phenomena occurring in the 

 subconscious state, with which we are all familiar 

 during sleep, and during the hypnotic state, and in 

 the state called "trance." We are familiar also with 

 innumerable objective signs of such subjective pheno- 

 mena in the shape of descriptions of dreams and in 

 the behaviour of sleep-talkers and sleep-walkers, and, 

 above all, in the extraordinary cases of spiritualistic 

 mediums. These last stand highest in the scale of 

 sensitiveness. 



The relative magnitudes of response to a real pin- 

 prick and to a fictitious pin-prick vary with different 

 people under different conditions, but in general they 

 may be divided into two categories, whom we may 

 call positives and imaginatives. 



Positives — in whom little or no disturbance is 

 caused by the threat of a pin-prick, and a real pin- 

 prick is required before any response takes place. 



hnagitiatives — in whom a large response occurs to 

 the threat — larger, it may be, than the response to 

 the real fact. In not a few of this imaginative class 

 it is almost impossible to take a pure observation of 

 response to fact, for they begin to respond as soon as 

 the operator makes the slightest movement, or else 

 the response is a large one, compounded of fear fol- 

 lowed by fact. Here is a confirmatory experiment in 

 evidence of what may be characterised as a dwindling 

 fear^and its revival by fact. (Experiment.) 



All men (and, judged by their behaviour, animals 

 also) are more or less imaginative. The kind of 

 diagram you have just seen would represent the 

 responses of nine out of ten of my present hearers 

 to a series of threats with a real shock interpolated 

 in the series. Many of us had an opportunity a few 

 years ago of studying upon our friends and upon our- 

 selves the signs and symptoms of fear during German 

 air raids upon what they called the fortified city of 

 London. The noise and disturbance occasioned by 

 these raids, the false alarms and the warnings by 

 maroons and sirens, afforded a unique opportunity 

 for the exact galvanometric study of the emotions 

 aroused by various kinds of noises. From the purely 

 scientific point of view the opportunity could not be 

 neglected of studying the psychophysical phenomena 

 brought to our doors — phenomena that could not be 

 expected again within the same lifetime.. So from 

 the air raid of September 21, 1917, to the last and 

 most prolonged visit of Whitsuntide, 19 18, I enlisted 

 the services of volunteers to sit quietly, connected by- 

 wires to a galvanometer, and on two occasions I had 

 sitters arranged in connection with recording ap- 

 paratus which was set going a few minutes before 

 the noise began, so that the emotive response during 

 the Avhole affair was recorded. Let me show you 

 two or three photographs (Figs. 2 and 3). 



These photographs are not merely of interest on 

 their human side, but also have this definite scientific 

 value, that they afford measured records of the largest 

 emotive responses that I have ever witnessed. The 

 responses commonly observed in the . laboratory are 

 at most 10 per cent, changes; these air-raid 

 responses have been at least 200 per cent, changes, 

 which I cannot reproduce artificially . by any means 

 I care to employ. 



7. But to return to our different classes according to 

 sensitiveness. We classified people as positives and 

 imaginatives according as they exhibited greater 

 response to fact or to fiction. Apart from this 

 criterion, we might undertake to arrange people as 

 more or less imaginative according as they give larger 

 or smaller responses to certain standard threats, as of 



