February 16, 1900.] 



SCIENGE. 



271 



appreciable movement indicative of pain or 

 even of sensation. 



In tlie 'additional note,' Professor Loeb 

 points out as the two chief results of the investi- 

 gation: "(1) In a great number — perhaps the 

 majority — of lower animals injuries cause no 

 reaction which might be interpreted as the ex- 

 pression of pain sensations. (2) In the limited 

 number of cases where injury is followed by 

 motions which have been considered as the ex- 

 pression of pain sensations (as in the case of 

 worms) a closer analysis shows that this inter- 

 pretation is unjustified." 



This article is noteworthy not least for what it 

 neither says nor implies, namely, that animals 

 other than those there considered probably do 

 not feel pain. Notwithstanding this most com- 

 mendable modesty of opinion on the part of its 

 author, certain considerations present them- 

 selves therefrom, which are of too great moment 

 both to psychology and to physiology to remain 

 unanswered. The problem may be properly 

 considered as insoluble— yet well worthy of de- 

 bate. It will not be maintained that these ani- 

 mals do experience pain when they are injured, 

 but only that they may for all that experiments 

 prove to the contrary. Analogy and reasonable 

 presumption are our only methods when inex- 

 perieucable sensations are in question and the 

 former of these at least works both ways. 



The lowness of the investigator's subjects in 

 the animal ' scale ' is worthy of preliminary no- 

 tice. On this account it would at first sight 

 seem that the author's and Dr. Loeb's opinion 

 was more valid, on the common supposition 

 that ' so low a grade of consciousness could not 

 include actual, stinging pain.' The nervous 

 systems of these worms and echinoderms and 

 fishes seem undoubtedly too simple to allow of 

 the presence of organs for pain such as on the 

 whole seem probable in man and his congeners. 

 The highest, highly differentiated animals re- 

 quire painful sensations as a means teleolog- 

 ieally protective of their different organs ; in 

 the lowest orders, on the other hand, this need 

 does not exist, for their relative simplicity of 

 plan makes possible the regeneration of any 

 lost part or organ or even the perfecting of an 

 individual from a part artificially cut off from 



another individual. It is therefore extremely 

 reasonable even from the pan-psychistic view- 

 point to suppose that organs of pain would be 

 undeveloped in these very lowly forms. The 

 simplicity of neural structure in these orders 

 makes it certain almost that much, present in 

 higher forms as organs correlated to conscious- 

 ness of various modes, would here be lacking. 

 The worm and the starfish, simply because they 

 are in a less degree, physiologically speaking, 

 individuals than is a dog or a man, require fewer 

 of those organs on which a continuance of in- 

 dividuality depends. But while this is so, per- 

 haps, the sort of pain under discussion is not 

 man's degree of pain, but rather that grade of 

 painful consciousness proportionate to the needs 

 of the animal in which it may or may not be 

 experienced. The difference is not one of kind 

 but one of degree, and a degree suitable to the 

 biologic needs of the particular species may be 

 present, commensurate not to the complexity of 

 a nervous system even, but perhaps only to the 

 necessity of the preservation of individuality — 

 a necessity in some of the species experimented 

 on obviously exceedingly small. 



In view of the great similarity functionally 

 between the neural structures of the higher 

 animals and those of man, no one perhaps 

 would seriously deny consciousness to, say, an 

 elephant or an ape. To damaging stimulation 

 these animals react much as does man, but it is 

 a quite gratuitous presumption that the earth- 

 worm and the flounder would react to a de- 

 structive excitation in a manner even compar- 

 able to that in which these higher forms react. 

 To suppose this would be to employ again only 

 a sort of the objectionable anthropomorphism. 

 Because the elephant or the cat with a remark- 

 ably elaborate system of innervated, muscled, 

 and jointed limbs, reacts in a characteristic 

 way to injury, there is no reason to expect the 

 Nereis or the starfish to react similarly in any 

 sense. The rabbit even, with essentially all 

 the motor mechanism which man possesses, 

 ' expresses ' pain often times only by attempts 

 to get away and by an increase in the breath- 

 rate ; indeed this dyspnoea is often the physi- 

 ologic ansesthetizer's only sign that more ether 

 is urgently demanded. It is not necessary then 

 because the lowest forms of animals do not act 



