October 2, 1899.] 



KNOWLEDGE. 



221 



Of all the varions branches of science, none, perhaps, is 

 to-day, none for these many years past has been, so well 

 known to, even if not understanded by, most people as 

 that of geology. Its practical lessons have brought wealth 

 to many ; its fairy tales have brought delight to more : and 

 round it hovers the charm of danger, for the conclusions 

 to which it leads touch on the nature of man's beginning. 

 In 1799 the science of geology, as we now know it, was 

 struggling into birth. There had been ft-om of old 

 cosmogonies, theories as to how the world had taken 

 shape out of primeval chaos. The brilliant Stenson, 

 in Italy, and Hooke, in our own coimtry, had laid 

 hold of some of the problems presented by fossil remains, \ 

 and Woodward with others, had laboured in the same 

 field. In the eighteenth century, especially in its \ 

 latter half, men's minds were busy about the physical j 

 agencies determining or modifying the features of the 

 earth's crust ; water and fire, subsidence from a primeval 

 ocean and transformation by outbursts of the central heat, 

 Neptune and Pluto, were being appealed to, by Werner on 

 the one hand, and by Desmarest on the other, in explana- 

 tion of the earth's phenomena. In 178H, .Tames Hutton • 

 put forward in a brief memoir his " Theory of the Earth," 

 which in 1795, two years before his death, he expanded 

 into a book ; but his ideas failed to lay hold of men's minds 

 until the century had passed away, when, in 1802 they 

 found an able expositor in -John Playfair. The very same 

 year that Hutton published his theory, Cuvier came to 

 Paris and almost forthwith began, with Brongniart, his 

 immortal researches into the fossils of Paris and its neigh- 

 bourhood. And four years later, in the year 1799 itself, 

 William Smith's tabular list of strata and fossils saw the 

 light. It is, I believe, not too much to say that out of 

 these geology, as we now know it, sprang. 



In another branch of science, in that which deals with 

 the problems presented by living beings, the thoughts of 

 men in 1799 were also different from the thoughts of men 

 to-day. It is a very old quest, the quest after the know- 

 ledge of the nature of living beings, one of the earliest on 

 which man set out ; for it promised to lead him to a 

 knowledge of himself, a promise which, perhaps, is still 

 before us, but the fulfilment of which is as yet far off. Yet 

 in the past hundred years, the biologic sciences, as we now 

 call them, have marched rapidly onward. We may look upon 

 a living body as a machine doing work in accordance with 

 certain laws, and may seek to trace out the working of the 

 inner wheels, how these raise up the lifeless dust into living 

 matter, and let the living matter fall away again into dust, 

 giving out movement and heat. Or we may look upon the 

 individual life as a link in the long chain, joining some- 

 thing which went before to something about to come, a 

 chain whose beginning lies hid in the furthest past, and 

 may seek to know the ties which bind one life to another. 

 As we call up to view the long series of living forms, living 

 now, or flitting like shadows on the screen of the past, we 

 may strive to lay hold of the influences which fashion the 

 garment of life. Whether the problems of life are looked 

 upon from the one point of view or the other, we to-day, 

 not biologists only, but all of us, have gained a knowledge 

 hidden even from the philosophers of a hundred years ago. 

 Of the problems presented by the human body viewed as a 

 machine, some may be spoken of as mechanical, others as 

 physical, yet others as chemical, while some are, apparently 

 at least, none of these. In the seventeenth century, William 

 Harvey, laying hold of the central mechanism of the blood 

 stream, opened up a path of inquiry which his own age and 

 the century which followed trod with marked success. The 

 philosopher of 1799, when he discussed the functions of 

 the animal or of the plant involving chemical changes, was 



fain for the most part, as were his predecessors in the 

 century before, to have recourse to such vague terms as 

 "fermentation " and the like; to-day our treatises on 

 physiology are largely made up of precise and exact ex- 

 positions of the play of physical agencies and chemical 

 bodies in the living organism. He made use of the words 

 " vital force " or •' vital principle " not as an occasional, 

 but as a common explanation of the phenomena of the 

 living body. During the present century, especially during 

 its latter half, the idea embodied in those words has been 

 driven away from one seat after another ; if we use it now 

 when we are dealing with the chemical and physical events 

 of life we use it with reluctance, as a ilfiis e.v machina to be 

 appealed to only when everything else has failed. 



During the latter part of the present century, and 

 especially during its last quarter, the analysis of the 

 mysterious processes in the nervous system, and especially 

 in the brain, which issue as feeling, thought, and the power 

 to move, has been pushed forward with a success con- 

 spicuous in its practical, and full of promise in its theo- 

 retical, gains. AVe now know that what takes place along 

 a tiny thread which we call a nerve-fibre differs from that 

 which takes place along its fellow-threads, that differing 

 nervous impulses travel along different nerve-fibres, and 

 that nervous and psychical events are the outcome of the 

 clashing of nervous impulses as they sweep along the 

 closely-woven web of living threads of which the brain is 

 made. We have learnt by experiment and observation 

 that the pattern of the web determines the play of the 

 impulses, and we can already explain many of the obscure 

 problems not only of nervous disease, but of nervous life, 

 by an analysis which is a tracking out the devious and 

 linked paths of nervous threads. The very beginning of 

 this analysis was unknown in 1799. Men knew that 

 nerves were the agents of feeling and of the movements of 

 muscles ; they had learnt much about what this part or 

 that part of the brain could do ; but they did not know 

 that one nerve fibre differed from another in very essence 

 of its work. 



If we pass from the problems of the living organism 

 viewed as a machine to those presented by the varied 

 features of the different creatures who have lived or who 

 still live on the earth, we at once call to mind that the 

 middle years of the present century mark an epoch in 

 biologic thought such as never came before, for it was then 

 that Charles Darwin gave to the world the " Origin of 

 Species." That work, however, with all the far-reaching 

 eii'eets which it has had, could have had little or no effect, or, 

 rather, could not have come into existence, had not the 

 earlier half of the century been in travail preparing for its 

 coming. For the germinal idea of Darwin appeals, as to 

 witnesses, to the results of two lines of biologic investi- 

 gation which were almost unknown to the men of the 

 eighteenth century. Darwin, as we know, appealed to the 

 geological record ; and we also know how that record, 

 imperfect as it was then, and imperfect as it must always 

 remain, has since his time yielded the most striking proofs 

 of, at least, one part of his general conception. In 1799 

 there was, as we have seen, no geological record at all. 

 All or nearly all the exact knowledge of the laboured way 

 in which each living creature puts on its proper shape and 

 structure is the heritage of the present century. Although 

 the way in which the chick is moulded in the egg was not 

 wholly unknown, even to the ancients, and in later years 

 had been told, first in the sixteenth century by Fabricius, 

 then in the seventeenth century in a more clear and 

 striking manner by the great Italian naturalist Malpighi, 

 the teaching thus ofi'ered had been neglected or mis- 

 interpreted. At the close of the eighteenth century the 



