420 THE POPULAR SmENCE MONTHLY, 



live affinities of organic elemmts^ the equilihrization of organs — such 

 are the designations of the leading . doctrines which are unfolded in 

 the preliminary discourse of his " (St.-Hilaire's) " 'Anatomical Philoso- 

 phy.' Elective affinities of organic elements are the forces by "vvhich 

 the vital structures and varied forms of living things are produced ; 

 and the principles of connection and equilibrium of the forces of the 

 various parts of the organisation prescribe limits and conditions to the 

 variety and development of such forms." * Now for the first time we 

 hear such phrases, as "unity of plan," and (more significant still) 

 "unity of composition.". Then came Von Baer's law of progression 

 of structural development from the general to the special, afterward 

 extended to functional developmentj and giving rise to the conception 

 of the specialization of functions. Out of this, too, arose the term 

 "evolution," and, though confined to organic development, implied an 

 advance in generalization. The mere mention of such further ad- 

 vances as are implied in the establishment of the functional identity 

 between the contractile tissues of plants and those of the higher ani- 

 mals ; in the use of the phrase "psychical powers" to designate the 

 sensorial and mental endowments of animals; in the proof of the ab- 

 sence of specialized sensibility among the lower tribes of animals, 

 and of the hereditary transmission of certain characters acquired 

 under the influence of external circumstances ; in the parallel traced 

 Between the progressive complication of the psychical manifestations 

 during the early life of a human being, and the gradual increase in 

 mental endowment to be observed in ascending the animal scale "^ — 

 may serve, to indicate the conceptions forming the matrix in which a 

 philosophically constructed Psychology was to be moulded. How 

 great a revolution had taken place in biology, and how far we have 

 now got from the natural history method, may appear from Prof. 

 Huxley's definition of " zoological physiology," which, though made 

 some years after the first publication of the " Principles of Psycholo- 

 gy," at least points out tlie direction in which thought had been mov- 

 ing. He says : 



" It regards animal hodies as machines impelled by certain forces, and per- 

 forming an amount of work, which can be expressed in terms of the ordinary 

 forces of N'ature. The final object of physiology is to deduce the facts of mor- 

 phology, on the one hand, and those of distribution on the other, from the laws 

 of the molecular forces of matter." ^ 



With a prescient insight into the future of science which has prob- 

 ably few parallels, Mr. Spencer founded his Psychology on the hypothe- 

 sis of development. To all but a few deep-thinking observers there 

 can have seemed few signs in 1855 that that hotly-disputed theory 

 was ever likely to be in the ascendant. The exposition of none of the 



^ " History of Inductive Sciences," iii., 504. 



^ See Carpenter, " Comparative Physiology,'' passim. 



8 " Lay Sermons," pp. 106, lOY. 



