THE EXPERIMENTAL STUDY OF NATURE. 375 



tion and experiment, lie brings the instrumental agency of the mind 

 as a reasoning power to bear upon them, and draws from them that 

 which adds to the store of knowledge already possessed. lie seeks for 

 facts and interprets their meaning as they come before him. This 

 was the course pursued by Harvey. Instead of giving himself up, as 

 others had done before him, to arguing out conclusions from accepted 

 axioms, he struck out into the hitherto untrodden path of inquiry — 

 that of induction — and sought knowledge by a direct appeal to Nature 

 through the medium of observation and experiment. " It were dis- 

 graceful," he says, " with this most spacious and admirable realm of 

 Nature before us, did we take the reports of others upon trust, and go 

 on coining crude problems out of these, and on them hanging knotty 

 and captious and petty disputations. Nature is herself to be ad- 

 dressed ; the paths she shows us are to be boldly trodden." 



In the discovery of the circulation, Harvey applied the principles 

 of induction, atid argued upon them in a strictly logical way. He 

 showed himself to be a good and careful observer, judged even by the 

 standard set forth in the following words of John Stuart Mill, on the 

 process of observing. "The observer," says Mill, "is not he who 

 merely sees the thing which is before his eyes, but he who sees what 

 parts that thing is composed of. To do this well is a rare talent. 

 One person, from inattention, or attending only in the wrong place, 

 overlooks half of what he sees. Another sets down much more than 

 he sees, confounding it with what he imagines or with what he infers. 

 Another takes note of the kind of all the circumstances, but, being 

 inexpert in estimating their degree, leaves the quantity of each vague 

 and uncertain. Another sees, indeed, the whole, but makes such an 

 awkward division of it into parts, throwing things into one mass 

 which require to be separated, and separating others which might more 

 conveniently be considered as one, that the result is much the same, 

 sometimes even worse, than if no analysis had been attempted at all, 

 It would be possible to point out what qualities of mind and modes of 

 mental culture fit a person for being a good observer ; that, however, 

 is a question not of logic, but of the theory of education, in the most 

 enlarged sense of the term." 



The experiments which Harvey conducted on the arteries and veins 

 to assist him in his inquiry were founded upon a well-devised plan. It 

 may be said of experiment, that it affords the means of varying the 

 circumstances, and thus aids immensely the acquirement of knowledge 

 by induction. In the application of the faculties to discovery, the 

 mind asks itself what facts are needed to assist in the establishment of 

 a correct conclusion. The fact may be looked for among the varied 

 instances presented by Nature ; or, by an artificial arrangement of cir- 

 cumstances, the required instance may be made — in other words, ex- 

 periment may be had recourse to for supplying what is wanted. In 

 the one case, we get our fact by observation from the variations in the 



