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NATURE 



\pec. 4, 187^ 



The water grows hotter and hotter, but the brainless frog 

 never moves, till, at 56° C, it expires in a state of tetanus. 



This contrast is assuredly marked enough, and most 

 readers will be disposed to admit that if the brainless ani- 

 mal can LMidure, without manifesting even uneasiness, 

 what in the normal animal produces every sign of intense 

 pain, the conclusion that the brainless animal feels no- 

 thing, and therefore that his Spinal Chord is not a sensa- 

 tional centre, is irresistible. This conclusion I altogether 

 reject. Not that I question the facts, for I have verified 

 their accuracy ; and Mr. Foster, who has repeatedly veri- 

 fied them, only points to the new difficulty which they 

 raise, namely, why the brainless frog is not e.xcited to re- 

 flex action by the stimulus of hot water? It is, therefore, 

 the interpretation of the facts to which .attention must be 

 drawn ; and to make this complete, let me here note 

 counter facts which my experiments presented. 



The brainless frog is not insensible to the heat, sinless 

 the insensibility be gradually produced. If its foot be 

 dipped into the hot water the leg is violently retracted : 

 and if the whole or greater part of the body be immersed, 

 the frog struggles vehemently, and rapidly passes into a 

 state of tetanus. The diflerence between the behaviour 

 of a normal frog and a brainless frog when suddcnlv im- 

 mersed in very hot water is not greater than might rea- 

 sonably be anticipated between animals uninjured and 

 animals with one great sensitive centre removed. 



These facts are substantially confirmed by the facts 

 brought forward in Mr. Foster's paper. He also finds the 

 legs of a decapitated frog withdrawn by reflex action, as 

 soon as the temperature of the water reaches a little over 

 30° C. " However slowly the water be heated, the feet 

 - are always withdrawn at a temperature of 35" or earlier," 

 But he observes that when the whole body is immersed 

 and the water gradually heated, no movement, or only the 

 very slightest spasm of the muscles of the legs takes place. 



The point to which he draws attention is, that whereas 

 the stimulus of hot water applied to 'Crc foot causes re- 

 flex action, applied to the whole leg or the whole body it 

 causes none ; his explanation is that the depressing 

 influence of heat on the Spinal Cord destroys its refle.v 

 powers. This explanation seems to accord very well with 

 all his observations, but is not in accordance with the 

 fact mentioned by Goltz of the frog's wi|)ing away the acid 

 which is dropped on its back ; a fact clearly manifesting 

 the presence of reflex sensibility. 



It is this fact which 1 should urge against Goltz, and all 

 who share his views. It proves, to my mind, that although 

 the frog remains motionless in the heated water and shows 

 no sign of pain from the stimulus of heat, this is assuredly 

 not because Sensibility in general is gone, but simply 

 because Sensibility to tciitperatiire is gone. It is not 

 necessary to refer to the many well-authenticated cases of 

 analgesia without anaesthesia, of insensibility to pam or 

 temperature without insensibility to touch ; 1 will parallel 

 Goltz's case of the brainless frog suffering itself to be 

 boiled without moving, by the case of the frog with its 

 brain and other nerve centres intact, allowing its legs to 

 be burnt to a cinder without moving. In a paper read at 

 the Aberdeen Meeting of the British Association, I 

 brought forward some experiments on frogs after their 

 skins had been who'ly or partially removed. (There were 

 small patches of skin left on the head wherewith to compare 

 the effects of stimuli). These frogs assuredly had not lost 

 their .Sensibility ; they responded, as usual, to any sti- 

 mulus applied to the patches of skin which remained ; 

 and as these responses were the responses of animals in 

 possession of a brain, no one would explain them away 

 as mere reflexes. Yet these sensitive frogs allowed their 

 flayed limbs to be pinched, pricked, cut, burnt with acids, 

 and even burnt to a cinder with the flame of a wax taper, 

 yet remained motionless under all these stimuli, though a 

 touch on the patch of skin would make them wince or 

 hop away. 



I did not try the experiment of boiling one of these frogs, 

 but who can deny that the insensibility they presented 

 with their brains and without their skins, is even greater 

 than that presented by brainless frogs with their skins ? 

 The point urged is that the frog without its brain is in- 

 capable of feeling the stimulus of hot water, which, when 

 the brain is intact, is felt intensely ; and the conclusion 

 drawn is that the spinal cord is not a sensational centre. 

 But this point is blunted when we find that the frog is 

 equally insensible to the heat, when its brain is intact and 

 only the skin removed. Ought we to conclude that the 

 skin is the sensational centre ? The one conclusion would 

 be as logical as the other. 



Mr. Foster, who is only treating of the influence of 

 temperature, asks why the sensations and (Crcbral pro- 

 cesses are not dulled in the same way as he supposes the 

 spinal processes to be dulled by heat ? " The answer," 

 he says, " is that a less intense sensory impulse is needed 

 to call forth a movement of volition, that is, a movement 

 carried out by the encephalon, than an ordinary reflex ac- 

 tion, that is, a movement carried out by the spinal cord 

 alone. The water as it is being warmed suggests a move- 

 ment to the intelligent frog long before it is able to call 

 forth an unintelligent reflex action. The very first move- 

 ment of the frog, the removal of any part of his body out 

 of the water, increases the effect of the stimulus ; for the 

 return of the limb to the water already warm gives rise to 

 a stronger stimulus than contact with the water raised to 

 the same temperature while the limb is still in it ; and thus 

 one movement leads to another and the frog speedily be- 

 comes violent. It is nearly the same with the brainless 

 frog when a movement has for some reason or other been 

 started ; only in the observations we have been dealing 

 with this initial movement is wanting." 



Let us compare the energetic movements of the normal 

 frog and the absence of movement in the brainless frog, 

 with the energetic movements of a waking man in a suf- 

 focating atmosphere, and the .absence of movements in 

 the sleeping or stupefied man in the same atmosphere, 

 and all the phenomena are clear. The waking man 

 and normal frog arc alert and alarmed. The sleeping 

 man and brainless frog remain motionless. Instead of 

 our being surprised at the brainless frog manifesting so 

 little Sensibility when the gradually-increasing heat is 

 threatening its existence, we ought to be surprised at its 

 manifesting so much Sensibility as a thousand experi- 

 ments disclose ; especially when we see that if the heat 

 be suddenly applied the Sensibility is manifested as 

 equally energetic in normal and in mutilated frogs. 



In conclusion, let it be observed that unnecessary ob- 

 stacles are thrown in the way of rational interpretation 

 when connotative terms such as Spinal Soul {Riichen- 

 markseele) are adopted. It is one thing to assign a general 

 physiological Property, such as Sensibility, to the nervous 

 centres ; another thing to assign a term which is the ab- 

 stract expression of the connexus of sensibilities, to any 

 one centre. In saying that the Spinal Cord is a seat of 

 sensation, it is not meant that it is the seat, nor that the 

 sensations are speeifically like the sensations of colour, of 

 sound, of taste, of smell ; but they are as like these as 

 each of these is like the other. 



George Henry Lewes 



THE ARTISTIC REPRESENTATION OF 

 NATURE* 



nPHE late autumn of every year introduces to the public 

 -•- a large supply of gorgeous volumes, 'Vgot-up" in 

 lavish fashion with handsome plates and lightly-written 

 letter-press, which are generally spoken of as Christmas 

 Books, and are intended to be the means for the material 

 expression of the generous feelings which that season is 



• •' The Life .ind H.il.its of Wild Animals" lllustr.ited by Designi by 

 J. Wolf. (Macmillan, .87!.) 



