SENSATION AND SENSIFEROUS ORGANS. 87 



is not a little curious to observe that those who most loudly profess to 

 abstain from such commodities are all the while unconscious consumers, 

 on a great scale, of one or other of their multitudinous disguises or 

 adulterations. With mouths full of the particular kind of heavily but- 

 tered toast which they affect, they inveigh against the eating of plain 

 bread. In truth, the attempt to nourish the human intellect upon a 

 diet which contains no metaphysics is about as hopeful as that of cer- 

 tain Eastern sages to nourish their bodies without destroying life. 

 Everybody has heard the story of the pitiless microscopist, who ruined 

 the peace of mind of one of these mild enthusiasts by showing him the 

 animals moving in a drop of the water with which, in the innocency of 

 his heart, he slaked his thirst ; and the unsuspecting devotee of plain 

 common sense may look for as unexpected a shock when the magnifier 

 of severe logic reveals the germs, if not the full-grown shapes, of lively 

 metaphysical postulates rampant amid his most positive and matter- 

 of-fact notions. 



By way of escape from the metaphysical Will-o'-the-wisps gen- 

 erated in the marshes of literature and theology, the serious student is 

 sometimes bidden to betake himself to the solid ground of physical sci- 

 ence. But the fish of immortal memory, who threw himself out of the 

 frying-pan into the fire, was not more ill advised than the man who 

 seeks sanctuary from philosophical persecution within the walls of the 

 observatory or of the laboratory. It is said that " metaphysics " owe 

 their name to the fact that, in Aristotle's works, questions of pure phi- 

 losophy are dealt with immediately after those of physics. If so, the 

 accident is happily symbolical of the essential relations of things ; for 

 metaphysical speculation follows as closely upon physical theory as 

 black care upon the horseman. 



One need but mention such fundamental, and indeed indispensable, 

 conceptions of the natural philosopher as those of atoms and forces ; or 

 that of attraction considered as action at a distance ; or that of poten- 

 tial energy ; or the antinomies of a vacuum and a plenum ; to call to 

 mind the metaphysical background of plvysics and chemistry ; while, in 

 the biological sciences, the case is still worse. What is an individual 

 among the lower plants and animals ? Are genera and species realities 

 or abstractions ? Is there such a thing as Vital Force ? or does the 

 name denote a mere relic of metaphysical fetichism ? Is the doctrine 

 of final causes legitimate or illegitimate ? These are a few of the meta- 

 physical topics which are suggested by the most elementary study of 

 biological facts. But, more than this, it may be truly said that the roots 

 of every system of philosophy lie deep among the facts of physiology. 

 No one can doubt that the organs and the functions of Sensation are as 

 much a part of the province of the physiologist as are the organs and 

 functions of motion, or those of digestion ; and yet it is impossible to 

 gain an acquaintance with even the rudiments of the physiology of sen- 

 sation without being led straight to one of the most fundamental of all 



