6 INTROD UCTOR Y. 



forced to regard the properties of compounds as the resultants of 

 the properties of their constituent elements, even though we can- 

 not well imagine how such a connection exists ; and so in the 

 long run we have to fall back upon the properties of carbon, 

 hydrogen, nitrogen, oxygen, etc., for the properties of living 

 matter. Reflections of this sort show how ignorant we are of the 

 real properties of the elements, and how important further study 

 of them is. 



Consciousness. It cannot be doubted that the living form of 

 matter alone manifests the phenomena of consciousness ; and it 

 is not generally believed to exist to any great extent, except in the 

 higher forms of animal life. Because of the purely subjective 

 nature of consciousness it is impossible to say with absolute cer- 

 tainty whether animals other than ourselves are really conscious, 

 and many of the actions commonly supposed to indicate con- 

 sciousness are simply reflex actions, even in ourselves.* We do 

 not know, therefore, how widely consciousness is distributed 

 .among living things, though there is no reason to suppose that 

 plants possess it. There is evidence, however, that it exists in 

 different degrees of intensity among animals, keeping pace in a 

 general way with the amount of organization which they ex- 

 hibit, and shading off into simpler nervous conditions. The phe- 

 nomena of consciousness are undoubtedly the least understood 

 of all biological problems. From the scientific point of view it 

 appears at present impossible to translate them into the terms 

 of physical phenomena, though they are not known to occur 

 apart from a living material basis with which they appear to 

 be in some way closely connected. 



Scope of Biology. Biology has already been defined as the 

 science which treats of matter in the living state. Whatever per- 

 tains to living matter or to living things pertains to biology. The 

 study of the forms of living things, of their habits, actions, nu- 

 trition, surroundings, distribution ; of their relations to the life- 

 less world, and to one another ; of their sensations and social re- 

 lations, their origin and their fate, -these and many other topics 



* " It is really an open question \vhether a crayfish has a mind or not. More- 

 over the problem is an absolutely insoluble one inasmuch as nothing short of 

 being a crayfish would give us positive assurance that such an animal possesses 

 consciousness." (Huxley, The Crayfish, p. bU.) 



