Sept. 5, 1878] 



NATURE 



493 



untied the fowl makes no endeavour to escape, but 

 remains as it were transfixed, and refuses to move even 

 when urged to do so. Preyer observes in passing that 

 the chalk line constitutes no essential part of the con- 

 ditions, inasmuch as a fowl may be equally well thro\vn 

 into a state of hypnotism by simply holding the animal 

 for a short time upon the ground so as forcibly to prevent 

 struggUng. 



After Kircher no one seems to have investigated the 

 phenomena of hypnotism, or, as Preyer calls it, kataplexy, 

 till the years 1872-73, when some articles on the subject 

 were published by Czermak. The most striking of his 

 experiments were those which he conducted on inverte- 

 brated animals — crayfish, for instance, being made to 

 lie on their backs motionless, or even to stand up- 

 right upon their heads. Czermak endeavoured to ac- 

 count for the facts which he described by supposing 

 that in some way or other the act of fixing the eyes 

 upon a certain object, or of gazing into space, caused 

 the animals to become sleepy and stupefied.^ So vague 

 an explanation could scarcely in any case be entitled to 

 rank as a physiological hypothesis, and Preyer showed, 

 in 1873, that the act of gazing had nothing to do with 

 inducing the state of kataplexy, inasmuch as animals 

 fell into exactly the same state when their optic nerves 

 were divided, or their eyes covered with a hood — provided 

 that their bodies were at the same time held in some 

 unnatural position. Preyer therefore propounded a 

 theory of his own, which, as first published, was that the . 

 state of fear into which the animal is thrown by being 

 held in some unusual attitude serves to inhibit the power 

 of volition and so of spontaneity— the animal, therefore, 

 when released remaining statue-Hke in the position in 

 which it was placed. In order to sustain this theory 

 Preyer pointed to other cases in which fear serves to 

 inhibit spontaneity — as, for instance, the motionless 

 horror which some animals exhibit in the presence of 

 great danger, the fascination of birds by snakes, &c. 

 The theory as thus stated was very justly criticised by 

 Heubel, who, in 1876, published a paper detailing his 

 own researches on the subject, and seeking ta identify 

 the state of hypnotism with that of ordinary sleep. The 

 effect of this criticism was to make Preyer state his 

 theory with greater clearness, and as we now have it 

 (1878), it seems to be as follows. Any "sudden, strong, 

 unexpected, and unusual stimulation of centripetal 

 Herves" produces an emotion of fear, which in turn pro- 

 duces some inhibitory effect on the will, and eventually a 

 state of stupor. It may, I think, still Jbe questioned 

 whether this theory is of very much value, for even grant- 

 ing that "deathly terror" is always present — which it 

 certainly need not be when the subject of the experiment 

 is a human being — we are not acquainted with any other 

 facts which would lead us to connect the subsequent state 

 of motionless stupor with the preceding state of active 

 fear. 2 But, passing on to the facts, we soon find that an 

 important exception must be taken to the above statement 



' When we fix our eyes upon a certain object and then alter their adjust- 

 ment for some more distant point, so that the eyes endeavour, as it were, to 

 look through the object, there is no doubt that after a time a somewhat sleepy 

 feeling may be produced."^ Some persons, I find, can perform this action 

 more easily than others, and it does not seem to consist altogether in mal- 

 adjustment. At least I have observed that when the action is performed by 

 persons who can do it well the pupils dilate prodigiously, and this even when 

 the eyes are fixed upon a bright light such as the naked flame.of a moderator 

 i!f ^" ■^^ ^^ action is completely under the control of the will, cne is thus 



u- u° °''^''^* '^^ curious spectacle of the inhibition by the*%vill of a reflex 

 which under all other circumstances is beyond Ac control of the will— the 

 pupils dilaung or contracting instantly at word of command, and quite 

 irrespective of the stimulus supplied by light. 



» Indeed a ver>' remarkable experiment which is detailed further on would 

 seem to show that even in the case of animals the state of fear need have 

 nothing to do with inaugurating the state of kataplexy. The experiment in 

 question consisted in suddenly decapitating a fowl, and while the reflex con- 

 vulsions were still in progress, holding the mutilated body firmly on its back. 

 The convulsions forthwith ceased, and the headless animal became for a 

 time kataplectic. Unless, tlierefore, we suppose that the spinal cord is 

 capable of suffering fear, and that it is more alarmed by Being held firmly 

 down than by being severed from the brain, we must conclude that a state 

 of fear is no essential antecedent to that of hypnotism. 



as to the conditions under which hypnotism occurs, for 

 various experiments proved that "sudden, strong, unex- 

 pected, and unusual stimulation" of any of those "cen- 

 tripetal nerves" which minister to the special senses, so 

 far from inducing a state of hypnotism, instantly aroused 

 an animal which had been previously thrown into that 

 state. So that, in point of fact, as we are afterwards told, 

 we may more correctly state the conditions which 

 produce kataplexy in animals, by substituting for the 

 words "centripetal nerves " in the above^quoted proposi- 

 tion, the words "nerves of tactile sensation." But here 

 I may observe that, so far as the experiments go, there is 

 nothing to prove that special stimulation of .even the cuta- 

 neous nerves is necessary (indeed thermal and chemical 

 stimidation of the skin was specially tried and produced no 

 results); and therefore, it seems to me, the possitfility is not 

 excluded that the special stimulus in qufestion may really 

 have reference only to the "muscular sense." At any 

 rate, all these experiments go to prove that kataplexy can 

 only be produced in animals, either by suspending them 

 in the air, or by forcibly holding them in some unusual 

 position. Most animals recover their normal state after 

 a few minutes, but frogs when suspended in the air will 

 continue kataplectic until they die. Horses become 

 kataplectic while they are being swung from wharves to 

 ships, as shown by the fact that they remain passive so 

 long as they are suspended in the air, but again begin to 

 struggle so soon as their feet touch the deck. Preyer has 

 succeeded in rendering kataplectic various species of 

 toads, newts, frogs, ducks, poultry, pea-fowl, partridge, 

 Sparrows, mice, guinea-pigs, rabbits, &c. ; but has uni- 

 formly failed in the case of many other animals. On the 

 whole he concludes that while among sundry species of 

 reptiles,^ batrachians, birds, rodents, and ruminantSj the 

 phenomena of kataplexy may be more or less easily pro- 

 duced, such is not the case with fish and the more intelli- 

 gent mammals. Nevertheless in another part of his 

 memoir he attributes to a state of partial kataplexy the 

 period of motionless delay which is observable in children 

 after they unexpectedly fall and before they begin to cry. 

 He also states, on the authority of Dr. Genzmer, that a 

 squalling child (not a young baby) may often be quieted 

 by laying it upon its stomach, or by gently pressing its 

 face with the hand — care being taken in neither case to 

 interfere with the breathing. 



Our author further maintains that the so-called 

 " shamming-dead " of certain species of Articulata -viii&a. 

 in the presence of danger is probably to be attributed to 

 kataplexy. But here, I think, it is difficult to agree with 

 him. That the action in question is not a properly 

 so-called intelligent one, no competent person at the 

 present day is likely to dispute ; but for my own part I 

 cannot see any evidence to show that it is not of the 

 nature of an instinctive action which has been developed 

 in the way to which Preyer alludes. It being for the bene- 

 fit of some animals that they should remain motionless, 

 and thus be comparatively inconspicuous in the presence 

 of danger, those individuals which endeavoured to escape 

 would be destroyed, while those which ceased to move 

 would survive. Natural selection would therefore soon fix 

 the artifice of "shamming-dead" as an inherited instinct. 

 To this view Preyer objects that, if we accept it, the 

 origift of the instinct is difficult to explain ; while on the 

 supposition of the action not being instinctive, but purely 

 kataplectic, there is no difficulty to surmount. But to 

 this it may be answered that there is no more difficulty 

 in explaining the origin of the instinct to remain passive 

 in the presence of danger than there is in explaining the 



I Preyer does not appear to have himself experimented on any species of 

 reptile, but in another part of his monograph refers in this connection to a very 

 old authority, viz., Moses, whose power of causing serpents to appear like 

 rods he supposes to have been probably due to the sagacious Israelite having 

 known something about the phenomena of kataple.xy. But considering the 

 number, variety, and general quality of the experiments which Moses is ssdd 

 to have performed, it would surely be desirable to repeat the one in questioa 

 before accepting the result as a fact of modem physiology. 



