230 PIONEERS OF EVOLUTION. 



the Contemporary Review, 1871, and it may be sup- 

 plemented by a quotation from the chapter on The 

 Mental Phenomena of Animals in his Hume. " It 

 seems hard to assign any good reason for denying 

 to the higher animals any mental state or process 

 in which the employment of the vocal or visual 

 symbols of which language is composed is not in- 

 volved; and comparative psychology confirms the 

 position in relation to the rest of the animal world 

 assigned to man by comparative anatomy. As com- 

 parative anatomy is easily able to show that, physi- 

 'cally, man is but the last term of a long series of 

 forms, which lead, by slow gradations, from the high- 

 est mammal to the almost formless speck of living 

 protoplasm, which lies on the shadowy boundary 

 between animal and vegetable life; so, comparative 

 psychology, though but a young science, and far 

 short of her elder sister's growth, points to the same 

 conclusion." 



Within recent years the psychologists are doing 

 remarkable work in attacking the problem of the 

 mechanics of mental operations, and already in Eu- 

 rope and America some thirty laboratories have been 

 started for experimental work. The subject is some- 

 what abstruse for detailed reference here, and it must 

 sufifice to say that the psychologist, beginning with 

 observations upon himself, measuring, for example, 

 " the degree of sensibility of his own eye to luminous 

 irritations, or of his own skin to pricking, passes on 

 to like inquiry into the numerical relations between 



