146 THEORETICAL BIOLOGY 



Most of the lower animals are so constructed that they 

 are never in danger of injuring their own bodies. When that 

 does not occur, however, as in the sea-urchin, I have been 

 able to show that there is a special arrangement, which I 

 have called autodermophily , and this takes the place of pain. 

 The skin of these animals secretes a substance that prevents 

 the normal reflex of snapping by the pedicellariae. 



Amoebae are able to distinguish the pseudopodia of 

 their own body from those of other individuals. What this 

 depends on we cannot determine. The conditions are re- 

 versed here from what they are in other animals. Since 

 they have no framework which can be injured by their eating 

 themselves, it is quite in order for them to be perpetually 

 ingesting their own protoplasm. So that, in their case, pain 

 would make their very existence problematical. 



Pain certainly does not play the absolutely senseless role 

 usually ascribed to it, of transforming the whole living world 

 into a vale of misery and fear. Pain is present only where 

 there is a place for it in the plan of the organism, and where, 

 consequently, it is necessary and useful. 



THE INNER WORLD. — THE PHYSIOLOGICAL POINT OF VIEW 



Whosoever turns from psychology or the theory of know- 

 ledge to the physiology of the central nervous system, wiU 

 meet with very great disappointment. Here he might hope to 

 find light thrown on many unsolved problems, for the organ 

 that is generally supposed to serve as intermediary between 

 the world of the flesh and the world of the spirit, ought surely 

 to display, at any rate in its fundamental features, some 

 resemblance to the spiritual organism which the psychologist 

 and the student of the theory of knowledge thinks he can 

 recognise in the mind. On this consideration the theory of 

 psycho-physical parallelism was based, a theory which was 



