THE ORIGIN OF SENSIBILITY. 391 



Wlience, then, is the Sensibility derived ? Either we must 

 admit the presence of what cannot be discovered ; or we must 

 admit that a function can act without its organ ; or, finally, 

 we must modify our conception of the relation between Sen- 

 sibility and the Nervous system. Which of these three con- 

 clusions shall we adopt ? 



Not the first : for, to admit the presence of an organ which 

 cannot be discovered, even by the very highest powers, al- 

 though easily discoverable in other animals by quite medium 

 powers, would be permissible only as the last resource of 

 hyijothesis, when no other supposition could be tenable. 



Not the second : for philosophic Biology rejects the idea of 

 a function being independent of its organ, since a function is 

 the activity of an organ. The organ is the agent, the func- 

 tion the act — a point to which we will presently recur. 



The third conclusion, therefore, seems inevitable : we must 

 modify our views. But how ? Instead of saying, "Sensibility 

 is a property of nervous tissue," we must say, " Sensibility 

 is a general 'property of the vital organism which becomes 

 specialised in the nervous tissue in proportion as the organ- 

 ism, itself becomes specialised." 



We have no difficulty in understanding how Contractility, 

 at first the property of the whole of the simple oi'ganism, 

 becomes specialised in muscular tissue. We have no diffi- 

 culty in understanding how Eespiration, at first eflected by 

 the whole sm-face of the simple organism, becomes specialised 



che vol esse ricercare nend negli animali Infusori, nei Polipi, nelle Meduse e 

 nelle Actinie." — Istituzioni di Anat. e Fisiolog. Comparaia, i. 118. He denies 

 the existence of nerves even in the Holothuriso. So likewise docs Vogt, Zoolo- 

 gische BricJ'e, with several other anatomists. 



