338 PHYSIOLOGY CHAP. 



But these and other more detailed mechanical explanations of 

 co-ordinated reflexes adapted to stimuli seem inadequate to account 

 for the variety of the modes in which a brainless frog reacts to 

 different forms of stimulation. Some authors have maintained, 

 on the strength of these observations, that the spinal cord itself, 

 as the continuation of the brain, is also a seat of psychical 

 functions, and look upon these complex reactions as the expression 

 of a rudimentary consciousness and volition in the cord, persisting 

 even after it has been severed from the cerebrum. 



This doctrine is contrary to the old metaphysical axiom of 

 the absolute unity and immateriality, and consequent indivisi- 

 bility of the ego or soul. This axiom, which the earlier spiritual- 

 istic philosophy accepted as dogma, is, however, easily controverted 

 by experimental physiology. The divisibility of the " ego " as 

 a sentient principle is demonstrated by the fact that a numerous 

 class of the lower animals are propagated by fission, and are able 

 to multiply by division into the segments or metameres of which 

 they consist (Vol. I. p. 84). Each segment is capable of forming an 

 entity with the same sensorial capacity as the complete individual 

 of which it was a part. Hence it is not only legitimate, but 

 scientifically necessary, to inquire whether, on dividing the 

 cerebrospinal axis in the higher animals, consciousness can be 

 divided also. The answer to this difficult and possibly still 

 insoluble problem lies in arguments from analogy, based on the 

 experimental facts that indirectly witness to the psychical 

 capacity of the spinal cord. 



We conclude that a living being is capable of awareness of 

 itself and of the world without it ; of controlling its own actions 

 by will, of having, in fact, a " soul," only from the resemblance 

 between our own conscious actions and those that it presents. 

 Thus from the cogito ergo sum, which is the direct intuitive proof 

 of our own consciousness, we recognise the same in our fellow-men, 

 then by induction in the higher animals, and lastly in the lower 

 animals also. 



Is the adaptation to end which characterises the movements 

 of decapitated animals enough to convince us that their spinal 

 cord is capable of feeling and volition ? Evidently not, because 

 all the mechanisms of the animal economy are adapted to obvious 

 ends ; coughing cleanses the air passages ; vomiting empties the 

 stomach of injurious matters ; contraction of the pupil modifies 

 the effects of light ; winking of the eyelids removes dust particles 

 from the cornea ; intestinal peristalsis sends on the faeces, etc. etc. 

 These co-ordinated mechanisms have come about by a slow process 

 of natural selection, according to Darwin; by an evolutionary 

 automatic process of unknown character, according to Nageli; 

 more simply, they represent fossilisation of psychical functions, 

 having been built up step by step from voluntary actions, which 



