i8 W. J. MCGEE 



changes; and the idea grew, until it wrought, within a quarter 

 century, the most profound revolution in the history of human 

 thought. This effect was not due alone to Darwin's wealth 

 of facts and uprightness of record, nor was it due in more than 

 partial measure to Huxley's eloquent and aggressive advo- 

 cacy. The discovery of the conservation of energy by Joule 

 and Grove, and its exposition by Tyndall, contributed much; 

 Lyell's doctrine of uniformism strengthened the movement 

 in many circles; the extension of chemistry to organic com- 

 pounds was a potent factor; the enlargement of the known 

 universe by the spectroscope had its effect; while all these 

 combined with the habit of thought established through larger 

 associations of thinkers with practical men and with mechan- 

 ical devices, so that the formula ''the uniformity of nature" 

 won common assent. The wide and ready acceptance of the 

 Darwinian doctrine was but the co-ordination of knowledge 

 already gained. Yet the revolution would have been long 

 delayed had Englishmen alone contributed to it, or even men 

 of continental Europe; for, with a half dozen exceptions, the 

 earhest and strongest apostles were Americans, with Asa Gray 

 and Morse among the leaders. The free, vigorous, and 

 trenchant American mind was peculiarly hospitable to the 

 tenets of the new law; and it was accepted here as the founda- 

 tion for the cult of science years before it was similarly ac- 

 cepted in Great Britain. Seen in the perspective now possible, 

 Darwin's doctrine is but the extension into the organic realm 

 of the laws of action and sequence which form the basis of all 

 definite thought, and find their highest expression in that 

 power of invention which enables man to dominate duller 

 nature for his own behoof. Thus, the rise of the doctrine 

 merely marked a normal and necessary stage in the develop- 

 ment of knowledge concerning the several realms of nature. 



Made definite by the recognition of action and sequence, 

 biology has advanced apace during the last quarter century. 

 The causes of most ills to which flesh is heir have been traced 

 to germs and microbes, and modes of prevention and cure 

 have resulted; the nature of sepsis has been found out, and 

 anti-sepsis has been perfected with such rapidity that its 

 leader (Lord Lister) has Uved to see the average civilized 



