September 14, 1893] 



NATURE 



46; 



to the minds of those who have sought to understand the dis- 

 tinction between living and non-living. Without going back to 

 the true faiher and founder of biology, Aristotle, we may recall 

 with interest the language employed in relation to it by the 

 physiologists of three hundred years ago. It was at that time 

 expressed by the term consensus partiiim — which was defined as 

 the concurrence of parti in action, of such a nature that each 

 does qitod sutivi dt^ all combining to bring about one effect 

 "as il they had been in secret council," but at the same time 

 constanti qtiadam nahtro' Isge.^ Prof. Huxley lias made fami- 

 liar to us how a century later Descartes imagined to himself a 

 mechanism to cafry out this consensus^ based on such scanty 

 knowledge as was then available of ihe structure of the nervous 

 system. The discoveries of the early part of the present cen- 

 tury relating to reflex action and the funciions of sensory and 

 motor nerves, served to realise in a wonderful way his anticipa- 

 tions as to the channels of influence, afferent and efferent, by 

 which the ccti.'cmns is maintained ; and in recent times (as we 

 hope to learn from Prof. Horsley's lecture on the phy.>.iology of 

 the neivous system) these channels have been investigated with 

 extraordinary minuteness and success. 



Whether with the old writers we speak about ccnscnsus, with 

 Treviranus about adaftalion, or are content to take organism as 

 our point of departure, it mean; that, regarding a plant or an 

 animal as an organism, we concern ourselves primarily with 

 its nciivitie«, or, to use the word which best expresses it, its 

 energies. Now the first thing that strikes us in beginning to 

 think a'lout the activities of an organism is that they are naturally 

 distinguishable into two kinds, acc^-'rding as we consider the 

 action of the whole organism in its relation to the external 

 world or to other organisms, or the action of the parts or organs 

 in iheir relation to each other. The distinction to which we are 

 thus led between the /«/f/«a/ and ^.r^<r«a/ relations of plants 

 and animals has of course always existed, but has only lately 

 come into such prominence that it divides biologists more or less 

 completely into two camps — on the one hand those who make it 

 their aim to investigate the actions of the organism and its parts 

 by the accepted methods of physics and chemistry, carrying this 

 investigation as far as the conditions under which each process 

 manifests itself will permit ; on the other, those who interest 

 themselves rather in considering the place which each organism 

 occupies, and the part which it plays in the economy of nature. 

 It is apparent that the two lines of inquiry, although they equally 

 relate to «hat the organism does, rather than to what it is, and 

 therefore both have equal right to be included in the one great 

 science of life, or biology, yet lead in directions which are 

 scarcely even parallel. So marked, indeed, is the distinction, 

 that Prof. Ilaeckel some twenty years ago proposed to separate 

 the study of organisms with reference to their place in nature 

 under the designation of " oecologv," defining it as comprising 

 "the relations of the animal to its organic as well as to its 

 inorganic environment, particularly its friendly or hostile rela- 

 tions to those animals or plants with which it comes into direct 

 contact." - Whether this term expresses it or not, the distinc- 

 tion is a fundamentalone. Whether with the (ccologist we re- 

 gard the organism in relation to the world, or with the physiolo- 

 gist as a wonderful complex of vital energies, the two branches 

 have this in common, that both studies fix their attention, not on 

 stuffed animals, butterflies in cases, or even microscopical sec- 

 tions of the animal or plant body— all of which relate to the 

 framework of life — but on life itself. 



The conception of biology which was developed by Treviranus 

 as far as the knowledge of plants and animals which then 

 existed rendered possible, seems t > me still to express the scope 

 of Ihe science. I should have liked, had it been within my 

 power, to present to you both aspects of the subject in equal 

 fulness; but I feel that I shall best profit by the present oppor- 

 tunity if I derive my illustrations ehiefly from the division of 

 biology to which I am attached — that which concerns the 

 internal relations of the organism, it being my object not to 

 specialise in either direction, but as Treviranus desired to do, 

 to regard it as part — surely a very important part— of the great 

 science of nature. 



The origin of life, the first transition from nonliving to 



^ Bausner, Dt Consensu P art i nm Huviani Corporis, Amst., 1556, Praf. 

 ad Irctorem, p. 4. 



- These he identifies with "those compl Gated mutual relations which 

 Parw^nd.-signates ascondiuuns of the struggle for existence." ,Mong with 

 choroloity— the dislribution of animals- oecology constitutes what he calls 

 Relationsf'hysiologie. H.ieckel, " Entw.ckelungsgang u. Aufgaben der 

 Z(Ki\o%\t," Jenaische Zeilsc/ir. vol. v. i86g, p. 353. 



NO T246, VOX,. 48] 



living, is a riddle which lies outside of our scope. No seriously- 

 minded person, however, doubts that organised nature as it row 

 presents itself to us has become what it is by a process of 

 gradual perfecting or advancement, brought about by the 

 elimination of those organisms which failed to obey the funda- 

 mental principle of adaptation which Treviranus indicated. 

 Each step, therefore, in this evolution is a reaction to external 

 influences, the motive of which is essentially the same as that by 

 which from moment to moment the organism governs iiself. 

 And the whole process is a necessary outcome of the fact that 

 those organisms are most prosperous which look best after iheir 

 own welfare. As in that part of biology which deals with the 

 internal relations of the organism, the interest of the individual 

 is in like manner the sole motive by which every energy is 

 guided. We may take what Treviranus called selfish ailai'ta- 

 tion — Ziveckmdssigkcit Jiir sih s.lbei — as a connecting link 

 between the two branches of biological study. Out of this rela- 

 tion springs another which I need not say was not recognised 

 until after the Darwinian epoch — that I mean, which subsists 

 between the two evolutions, that of the race and that of the 

 individual. Treviranus, no less distinctly than his great con- 

 temporary Lamarck, was well aware that the affinities of plants 

 and animals must be estimated according to their devetopiiieMal 

 value, and consequently that classification must be found, d on 

 development ; but it occurred to no one what the real link was 

 between descent and development ; nor was it, indeed, until 

 several years after the publication of the " Origin " that Ilaeckel 

 enunciated that "biogenetic law," according to which the de- 

 velopment of any individual organism is but a memory, a reca- 

 pitulation by the individual of the development of the race — of 

 the process for which Fritz Miiller had coined the excellent 

 word " phylogenesis " ; and that each stage of Ihe former is but 

 a transitory reappearance of a bygone epoch in its ancestral his- 

 tory. If, therefore, we are right in regarding ontogenesis as 

 dependent on phylogenesis the origin of the former must corre- 

 spond with that of the latter ; that is, on the power which the 

 race or the organism at every stage of its existence possesses of 

 profiting by every condition or circumstance for its own 

 advancement. 



From the short summary of the connection between diilferent 

 paits of our science you will see that biology naturally falls 

 into three divisions, and these are even mote sharply distin- 

 guished by their methods than by their subjects ; namely, 

 Physiology, of which the methods are entirely experimental; 

 Morphology, the science which deals with the forms and struc- 

 ture of plants and animals, and of which it may be said that 

 the body is anatomy, the soul, development ; and finally, 

 Qicology, which uses all the knowledge it can obtain from the 

 other two, but chiefly rests on the exploration of the endless varied 

 phenomena of animal and plant life as they manifest themselves 

 under naluial conditions. This last branch of biology — ■ 

 the science which concerns itself with the external relations of 

 plants and animals to each other, and to the past and present 

 conditions of their existence — is by far the most attractive. In 

 it those qualities of mind which especially distinguish the 

 naturalist find their highest exercise, and it represents more than 

 any other branch of the subject what Treviranus termed the 

 "philosophy of living nature." Notwithstanding the very 

 general interest which several of its problems excite at the pre- 

 sent moment I do not propose to discuss any of them, but rather 

 to limit myself to the humbler task of showing that the funda- 

 mental idea which finds one form of expression in the world of 

 living beings regarded as a whole — the prevalence of the best — 

 manifests itself with equal distinctness, and plays an equally 

 essential part in the internal relations of the organism in the 

 great science which treats of them — Physiology. 



Origin and Scope of Modern Physiology. 



Just as there was no true philosophy of living nature until 

 Darwin, we may with almost equal truth say that physiology 

 did not exist as a science before Johannes Miiller. For although 

 the sum of his numerous achievements in comparative anatomy 

 and physiologv, notwithstanding tlieir extraordinary number 

 and importance, could not be compared for merit and fruit- 

 fulness with the one discovery which furnished the key to so 

 many riddles, he, no less than Darwin, by his influence on his 

 successors was the beginner of a new era. 



Miiller taught in Herlin from 1833 to 1857. During that 

 time a gradual change was in progress in the way in which bio- 

 logists regarded the fundamental problem of life. Miiiler him- 



