No. 3655.

, SEPTEMBER 16, 1893.

ABSTRACT OF THE

Presidential AddressDelivered before the British Association for the Advance-

ment of Science at Nottingham, Sept. 13th, 1893,BY J.S. BURDON SANDERSON, M.A., M.D.EDIN.,

LL.D., D C.L, F.R.S. LOND. & EDIN.,PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OF OXFORD ; PRESIDENT

OF THE BRITISH ASSOCIATION FOR THE ADVANCEMENTOF SCIENCE.

PROFESSOR BURDON SANDERSON began his presidentialaddress by claiming for the British Association that, duringits sixty years of existence, there had been no great questionin the field of scientific inquiry which it had failed to dis-

cuss, no important investigation which it had not promoted,and no great discovery which it had not welcomed ; but he

pointed out that it had still much before it. " The wealthiest

country in the world,’’ he said, ’’ which has profited more-vastly more-by science than any other, England standsalone in the discredit of refusing the necessary expenditurefor its development, and cares not that other nations shouldreap the harvest for which her sons have laboured." A

majority of the community might be in opposition to suchviews, but he called upon all the members of the British Asso-ciation to unite in insisting that the claims of science to publicsupport,should be recognised. He announced the subject ofhis address as Biology, including the origin and first use ofthe word, and a discussion of the relations between it and- other branches of natural science. Professor Burdon Sandersonthen proceeded as follows :

ORIGIN AND MEANING OF THE TERM "BIOLOGY."

"The word ’biology,’ which is now so familiar as com-prising the sum of the knowledge which has as yet beenacquired concerning living nature, was unknown until afterthe beginning of the present century. The term was firstemployed by Treviranus, who proposed to himself, as alife-task, the development of a new science, the aim of whichshould be to study the forms and phenomena of life, its

origin and the conditions and laws of its existence. It was anew thing to regard the study of living nature as a science byitself, worthy to occupy a place by the side of naturalphilosophy, and it was therefore necessary to vindicate itsdaim to such a position. Treviranus declined to foundthis claim on its useful applications to the arts of agri-culture and medicine, but dwelt rather on its value asa discipline’ and on’its ’sùrpassing interest. Being himselfa mathematician as well as a naturalist he approached,the subject both from the side of natural philosophy andfrom that of natural history, and desired to found thenew science on the fundamental distinction between living.and non-liviing material. The difference between vital and

physical processes he accordingly found, not in the nature ofthe processes themselves, but in their coordination-that is,in their adaptedness to a given purpose and to. the,.,, peculiarand special relation in which the organism stands to theexternal world. -, The purpose which I have in view in takingyou back as..1 have done to the beginning of the century isnot merely to commemorate the work which was done by thewonderfully acute writer to whom we owe the first conceptionof the science;of life as a whole, but to show you,that this con-ception, as expressed in his ideas of the relations between vitaland physical processes, can still be accepted as true. Theysuggest the idea of organism as that to which all other

biological ideas, must relate: They-also suggest, althoughperhaps they do not express it, that action is not an attributeof the organism but 6 its essence-that if, on the one hand,protoplasm is the basis of life, life is the basis of protoplasm.Their relations to each other are reciprocal."Whether we speak with Treviranus about adaptation or are

content to take organism as our point of departure, it meansthat, regarding a plant gr an animal as an organism, we con.cern ourselves primary, with its activities or,- to use theword which best expresses, it, its energies., Now the firs1

thing that strikes us in beginning to think about the activitiesof an organism is that they are naturally distinguishable intctwo kinds, according as we consider the action of the whohorganism in its relation to the external world or to othei

21n. 3RM

organisms, or the action of the parts or organs in their rela-tion to each other. The distinction to which we are thus ledbetween the internal and external relations of plants andanimals has of course always existed, but it has only latelycome into such promirlence that it divides biologists more orless completely into two camps : on the one hand, those whomake it their aim to investigate the actions of the organismand ’its parts by the accepted methods of physics andchemistry, carrying this investigation as far as the conditionsunder which each process manifests itself will permit; and, onthe other hand, those who interest themselves rather in con-sidering the place which each organism occupies and thepart which it plays in the economy of nature. This is thebranch of physiology which has been designated ’oecology’by Professor Haeckel. It is apparent that the two lines ofinquiry, although they equally relate to what the organismdoes rather than that to what it is, and therefore have equalright to be included in the one great science of life, or biology,yet lead in ’directions which are scarcely even parallel.I should have liked, had it been within my power, to presentto you both aspects of the subject in equal fulness ; but Ifeel that I shall best profit by the present opportunity if Iderive my illustrations chiefly from the’division of biology towhich I am attached-namely, - that which concerns theinternal relations of the organism—it-being my object not tospecialise in either direction, but, as Treviranus desiredto do, to regard it as part—purely a very importantpart-of the great science of nature., The origin oflife, the first transition from non-living -to- living, is aproblem which lies outside of our scope. No seriously mindedperson, however, doubts that organised nature as’ it nowpresents itself to us has become what it is by a process ofgradual perfecting or advancement, brought about ’rfyt’ theelimination of those organisms which failed to ’obey thefundamental principle of adaptation which Treviranuaindicated. Each step, therefore, in this evolution is areaction to external influences, the motive of which isessentially the same as that by which from moment tomoment the organism governs itself ; and the whole processis a necessary outcome of the fact that those organisms aremost prosperous which look best after their own welfare.From the short summary of the connexion between differentparts of our science you will see that biology naturally fallsinto three divisions, and these are even more sharply dis-tinguished by their methods than by their subjects-namely,physiology, of which the methods are eritirely experimental;morphology, the science which deals with the forms andstructure of plants and animals, and of which it may besaid that the body is anatomy and that the soul is

development ; and, finally, oecology, which uses all the

knowledge it can obtain’ from the other two, but chieflyrests on the exploration of the endless and varied pheno-mena of animal and, plant life as they manifest them-selves under natural conditions. This last branch of biologyis by far the most attractive. ’ In it those qualities of mindwhich especially distinguish the naturalist find tbeir highestexercise, and it represents more than any other branch of thesubject what Treviranus termed the ’philosophy of livingnature.’ Notwithstanding the very general interest whichseveral of its problems excite at the present moment I do notpropose to discuss any of them, but rather to limit myself tothe humbler task of showing that the fundamental ideawhich finds one form of expression in the world of livingbeings regarded as a whole-the prevalence of the best-manifests itself with equal distinctness and plays an equallyessential part in the internal’relations of the organism in thegreat science which treats’of them-namely, physiology.

ORIGIN AND SCOPE OF MODERN PHYSIOLOGY.

"Just as there was no true philosophy of living nature untilthe time of Darwin, we may with almost equal truth say thatphysiology did not exist as a science before Johannes Miiller.Muller taught in Berlin from 1833 to 1857 ; but during theperiod of his greatest activity times were changing, and he waschanging with them. During his long career as professor atBerlin he became more and more objective in his tendenciesand exercised an influence in the same direction on the menof the next generation, teaching them that it was better andmore useful to .. observe than to philosophise ; so that;although he himself is truly regarded as the last of thevitalists—for he was a vitalist to the last-his successorswere adherents of what has been very inadequately designatedthe mechanistic view of the phenomena of life. The changethus brought about just before the middle of this century

’ M

676

was a revolution. It was not a substitution of one point ofview for another, but simply a frank abandonment of theoryfor fact, of speculation for experiment. Physiologists ceasedto theorise because they had found something betterto do. May I try to give you a sketch of this era ofprogress ?

"Great discoveries as to the structure of plants and animalshad been made in the course of the previous decade, andthose especially which had resulted from the introduction ofthe microscope as an instrument of research. By its aidSchwann had been able to show that all organised structuresare built up of those particles of living substance which wenow call cells and recognise as the seats and sources of

every kind of vital activity. Hugo Mohl, working in anotherdirection, had given the name protoplasm’ to a certainhyaline substance which forms the lining of the cells of plants,though no one as yet knew that it was the essential constituentof all living structures--the basis of life no less in animalsthan in plants. And, finally, a new branch of study-histology-founded on observations which the microscope hadfor the first time rendered possible, had come into existence.Bowman, one of the earliest and most successful cultivatorsof this new science, called it ’physiological anatomy,’ andjustified the title by the very important inferences as to thesecreting function of epithelial cells and as to the nature ofmuscular contraction, which he deduced from his admirableanatomical researches. From structure to function, frommicroscopical observation to physiological experiment, thetransition was natural. Anatomy was able to answer somequestions, but it asked many more. Fifty years ago physio-logists had microscopes, but they had no laboratories. Englishphysiologists-Bowman, Paget, Sharpey-were at the sametime anatomists, and in Berlin Johannes Muller taught com-parative anatomy and pathology as well as anatomy andphysiology; but soon that specialisation which, howevermuch we may regret its necessity, is an essential concomitantof progress became more and more inevitable. The structuralconditions on which the processes of life depend had become,if not known, at least accessible to investigation; but very littleindeed had been ascertained of the nature of the processesthemselves-so little, indeed, that if at this moment we couldblot from the records of physiology the whole of the informa-tion which had been acquired, say, in 1840, the loss would bedifficult to trace-not that the previously known facts wereof little value, but because every fact of moment has sincebeen subjected to experimental verification. It is for thisreason that, without any hesitation, we accord to Muller andto his successors, Brucke, Du Bois Reymond and Helmholtz,who were his pupils, and Ludwig in Germany, and to ClaudeBernard 2 in France, the title of founders of our science ; forit is the work which they began at that remarkable time(1845-55), and which is now being carried on by their pupilsor their pupils’ pupils in England, America, France, Germany,Denmark, Sweden, Italy and even in that youngest contri-butor to the advancement of science, Japan, that phy-siology has been gradually built up to whatever com-

pleteness it has at present attained. What were theconditions which brought about this great advance whichcoincided with the middle of the century? There is but little

difficulty in answering the question. There was a leadingidea in the minds of those who were chiefly concerned inbringing it about that, however complicated the conditionsunder which vital energies manifest themselves, they can bedivided into processes identical in nature with those of the non-living world, and, as a corollary to this, that the analysing ofa vital process into its physical and chemical constituents, soas to bring these constituents into measurable relation withphysical or chemical standards, is the only mode of investi-gating them which can lead to satisfactory results. This newschool profited by the advances which had been made inphysics, partly by borrowing from the physical laboratoryvarious improved methods of observing the phenomena ofliving beings, but chiefly in consequence of the direct bearingof the crowning discovery of that epoch-that of the con-servation of energy-on the discussions which then took placeas to the relations between vital and physical forces. I willnot attempt even to enumerate the achievements of thatepoch of progress. I may, however, without risk of wearying

1 The first part of the "Physiological Anatomy" appeared in 1843; itwas concluded in 1856.

2 It is worthy of note that these five distinguished men were nearlycontemporaries : Ludwig graduated in 1839, Bernard in 1843, the otherthree between those dates. Three survive—Helmholtz, Ludwig andDu Bois Reymond.

you, indicate the lines along which research at first pro-ceeded and draw your attention to the contrast between thenand now. At present a young observer who is zealousto engage in research finds himself provided with themost elaborate means of investigation, the chief obstacleto his success being that the problems which have beenleft over by his predecessors are of extreme difficulty,all of the .easier questions having been worked out. Therewere then also difficulties, but of an entirely different kind.The work to be done was in itself easier, but the means fordoing it were wanting, and every investigator had to dependon his own resources. Consequently the successful men werethose who, in addition to scientific training, possessed theingenuity to devise and the skill to carry out methods forthemselves. The work by which Du Bois Reymond laid thefoundation of animal electricity would not have been possiblehad not its author, besides being a trained physicist, knownhow to do as good work in a small room in the upperfloor of the old University building at Berlin as any whichis now done in his splendid laboratory. Had Ludwig notpossessed mechanical aptitude, in addition to scientificknowledge, he would have been unable to devise theapparatus by which he measured and recorded the variations.of arterial pressure (1848), and verified the principles whichYoung had laid down thirty years before as to the mechanicsof the circulation. Nor, lastly, could Helmholtz, had he notbeen a great deal more than a mere physiologist, have madethose measurements of the time relations of muscular and’nervous responses to stimulation, which not only afford asolid foundation for all that has been done since in the same.direction, but have served as models of physiological experi.ment, and as evidence that perfect work was possible andwas done by capable men, even when there were no physio-logical laboratories. Each of these examples relates to workdone within a year or two of the middle of the century. If itwere possible to enter more fully into the scientific historyof the time, we should, I think, find the clearest evidence,firstly, that the foundation was laid in anatomical discoveries,in which it is gratifying to remember that English ana.

tomists (Allen Thomson, Bowman, Goodsir, Sharpey) tooka considerable share ; and, secondly,,that pro ress was renderedpossible by the rapid advances which, during the previousdecade, had been made in physics and chemistry, and theparticipation of physiology in the general awakening of thescientific spirit which these discoveries produced. I venture,however, to think that, notwithstanding the operation ofthese two causes, or rather combinations of causes, the

development of our science would have been delayed had itnot been for the exceptional endowments of the four or fiveyoung experimenters whose names I have mentioned, each ofwhom was capable of becoming a master in his own branchand of guiding the future progress of inquiry.

THE SPECIFIC ENERGIES OF THE ORGANISMS.

"In its more extended sense the specific energy’ of apartor organ-whether that part be a secreting cell, a motor cellof the brain or spinal cord, or one of the photogenous cellswhich produce the light of the glowworm, or the protoplasmicplate which generates the discharge of the torpedo-is simplythe special action which it normally performs, its norma orrule of action being in each instance the interest of theorganism as a whole of which it forms part, and the excitingcause some influence outside of the excited structure, techni-cally called a stimulus. It thus stands for a characteristic ofliving structures which seems to be universal. It cannotwell be doubted that, as every living cell or tissue is calledupon to act in the interest of the whole, the organism mustbe capable of influencing every part so as to regulate itsaction. May I now ask you to consider in detail one or twoillustrations of physiological reaction-of the letting off’of specific energy ?

"Probably everyone is acquainted with some of the familiarproofs that an object is seen for a much longer period than itis actually exposed to view ; that the visual reaction last’much longer than its cause. More precise observations teachus that this response is regulated according to laws which ithas in common with all the higher functions of an organism.If, for example, the cells in the brain of the torpedo are. let off ’-that is, awakened by an external stimulus-the

electrical discharge, which, as in the case of vision, followsafter a certain interval, lasts a certain time, first rapidlyincreasing to a maximum of intensity, and then more slowlydiminishing. In like manner, as regards the visual apparatus,we have, in the response to a sudden invasion of the eye by

677

Ught, a rise and fall of a similar character. In the case of’the electrical organ, and in many analogous instances, it is.easy to investigate the time relations of the successivephenomena, so as to represent them graphically. Again, itus found that in many physiological reactions the period of.rising ’energy’ (as Helmholtz has called it) is followed byperiod during which the responding structure is not

only inactive, but its capacity for energising is so com-

pletely lost that the same exciting cause which a moment3efore let off’ the characteristic response is now with-out effect. As regards vision, it has long been believedthat these general characteristics of physiological reactionjave their counterpart in the visual process, the most strikingevidence being that in the contemplation of a lightninglash-or, better, of an instantaneously illuminated whitedisc--the eye seems to receive a double stroke, indicatingthat, although the stimulus is single and instantaneous, theiresponse is reduplicated. The most precise of the methodswe until lately possessed for investigating the waxing and wan-ing of the visual reaction were not only difficult to carry out"jut left a large margin of uncertainty. It was therefore par-ticularly satisfactory when M. Charpentier of Nancy, whosemerits as an investigator are perhaps less known thanthey deserve to be, devised an experiment of extreme

simplicity which enables us not only to observe but tomeasure with great facility both phases of the reaction.From the results of this experiment he has been enabled tomake out another fact in relation to the visual reaction whichis, 1 think, of equal importance. In all the instances,excepting the retina, in which the physiological response tostimulus has a definite time limitation, and in so far resemblesan explosion, it can be shown experimentally that the pro-cess is propagated from the part first directly acted on toother contiguous parts of similar endowment. M. Charpentierhas now been able by a method, which, although simple, Imust not attempt to describe, not only to prove the existence,at such propagation, but to measure its rate of progress overthe visual field.

"There is another aspect of the visual response to thestimulus of light which, if I am not trespassing too long onyour patience, may, I think, be interesting to consider. Asthe relations between the sensations of colour and the physicalproperties of the light which excites them are amongst themost certain and invariable in the whole range of vital reac-tions, it is obvious that they afford as fruitful a field for physio-logical investigation as those in which white light is concerned.It has been lately assumed by some that vision, like everyother specific energy, having been developed progressively,objects were seen by the most elementary forms of eye onlyin chiaroscuro, that afterwards some colours were distin-guished, and eventually all. As regards hearing it is so. Theorgan which, on structural grounds, we consider to representthat of hearing in animals low in the scale of organisationhas nothing to do with sound. As regards vision evidence iswanting. There is, so far as I know, no proof that visualorgans which are so imperfect as to be incapable of dis-tinguishing the forms of objects may not be affected differentlyby their colours. Even if it could be shown that the least

perfect forms of eye possess only the power of discriminatingbetween light and darkness, the question whether in our ownsuch a faculty exists separately from that of distinguishing’colours is one which can only be settled by experiment.There is a German proverb which says, Bei Nacht sindalle Katzen grau ’ [All cats are grey at night]. The factwhich this proverb expresses presents itself experimentallytvhen a spectrum projected on a white surface is watched,,vhilst the intensity of the light is gradually diminished.As the colours fade away they become indistinguishableas such, the last seen being the primary red and green.Finally they also disappear, but a grey band of lightstill remains, of which the most luminous part is that whichbefore was greeny Without entering into details, let usconsider what this tells us of the specific energy of the visualapparatus. Whether or not the faculty by which we seegrey in the dark is one which we possess in common with.animals of imperfectly developed vision, there seems to be littledoubt that there are individuals of our own species who, inthe fullest sense of the expression, have no eye for colour,in whom all colour sense is absent-persons who inhabit aworld of grey, seeing all things as they might have done hadthey and their ancestors always lived nocturnal lives. In the

3 Hering: "Untersuchung eines total Farbenblinden "; Pfülger’sArchiv, vol. xlix., 1891, p. 563.

theory of colour vision, as it is commonly stated, no referenceis made to such a faculty as we are now discussing.

EXPERIMENTAL PSYCHOLOGY.

"Resisting the temptation to pursue this subject further, Iwill now ask you to follow me into a region which, althoughclosely connected with the subjects we have been con-

sidering, is beset with greater difficulties-the subject in

which, under the name of physiological’ or experimentalpsychology,’ physiologists and psychologists have of late

years taken a common interest-a borderland not betweenfact and fancy, but between two methods of investigation ofquestions which are closely related, which here, though theydo not overlap, at least interdigitate. It is manifest that,quite irrespectively of any foregone conclusion as to the

dependence of mind on processes of which the biologist isaccustomed to take cognisance, mind must be regarded as oneof the specific energies’ of the organism, and should on thatground be included in the subject-matter of physiology. As,however, our science, like other sciences, is limited not merelyby its subject but also by its method, it actually takes in onlyso much of psychology as is experimental. Thus sensation,although it is psychological, and the investigation of itsrelation to the special structures by which the mind keepsitself informed of what goes on in the outside world havealways been considered to be in the physiological sphere ;and it is by anatomical researches relating to the minutestructure and to the development of the brain, by observationof the facts of disease, and, above all, by physiologicalexperiment that those changes in the ganglion cells of thebrain and spinal cord which are the immediate antecedentsof every kind of bodily action have been traced. Betweenthe two-that is, between sensation and the beginning ofaction-there is an intervening region which the physiologisthas hitherto willingly resigned to psychology, feeling hisincompetence to use the only instrument by which it can beexplored-that of introspection. This consideration enablesus to understand the course which the new study (I will notclaim for it the title of a new science, regarding it asmerely a part of the great science of life) has hithertofollowed and why physiologists have been unwilling to enteron it.

"I will make no attempt even to enumerate the special linesof inquiry which during the last decade have been conductedwith such vigour in all parts of the world, all of them beingtraceable to the influence of the Leipsic school, but will contentmyself by saying that the general purpose of these investiga-tions has been to determine with the utmost attainable pre-cision the nature of psychical relations. Some of these

investigations begin with those simpler reactions which moreor less resemble those of an automatic mechanism, proceed-ing to those in which the resulting action or movement ismodified by the influence of auxiliary or antagonistic con-ditions, or changed by the simultaneous or antecedentaction on the reagent of other stimuli, in all of whichcases the effect can be expressed quantitatively ; otherslead to results which do not so readily admit of measure-ment. In pursuing this course of inquiry the physiologistfinds himself as he proceeds more and more the coadjutorof the psychologist, less and less his director; for, whateveradvantage the former may have in the mere technique ofobservation, the things with which he has to do are revealedonly to introspection, and can be studied only by methodswhich lie outside of his sphere. I might in illustration ofthis refer to many recent experimental researches-such, forexample, as those by which it has been sought to obtainexact data as to the physiological concomitants of pleasureand of pain, or as to the influence of weariness and re-

cuperation as modifiers of psychological reactions. Anotheroutwork of the mental citadel which has been invaded bythe experimental method is that of memory. Even here itcan be shown that in the comparison of transitory as com-pared with permanent memory-as, for example, in the

learning by heart of a wholly uninteresting series of words,with subsequent oblivion and reacquisition-the labourof acquiring and reacquiring may be measured, and conse-quently the relation between them; and that this ratio variesaccording to a simple numerical law. I think it not unlikelythat the only effect of what I have said may be to suggest tosome of my hearers the question, What is the use of suchinquiries ? 7 Experimental psychology has, to the best of myknowledge, no technical application. The only satisfactoryanswer I can give is that it has exercised, and will exercisein future, a helpful influence on the science of life.

678

t PHOTOTAXIS AND CHEMIOTAXI9.

" Considering that every organism must have sprung froma unicellular ancestor, some have thought that unless weare prepared to admit a deferred epigenesis of mind we Imust look for psychical manifestations even amongst thelowest animals, and that as in the protozoon all thevital activities are blended together, mind should be

present amongst them not merely potentially but actually,though in diminished degree. Such a hypothesis in-volves ultimate questions which it is unnecessary toenter upon. It will, however, be of interest in connexionwith our present subject to discuss the phenomena whichserved as a basis for it-those which relate to what may betermed the behaviour of unicellular organisms and of indi-vidual cells, in so far as these last are capable of reacting toexternal influences. The observations which afford us mostinformation are those in which the stimuli employed can beeasily measured, such as electrical currents, light, or chemicalagents in solution. A single instance, or at most two, mustsaffice to illustrate the influence of light in directing themovements of freely moving cells, or, as it is termed, photo-taxis. The rod-like purple organism cal’ed by Engelmannbacterium photometricum 4 is such a light-lover that if

you place a drop of water containing these organisms under ’,the microscope, and focus the. smallest possible beamof light on a particular spot in the field, the spot acts z’ias a light trap and becomes so crowded with the little ’irodlets as to acquire a deep port-wine colour. If, instead ofmaking his trap of white light, he projected on the field amicroscopic spectrum, Engelmann found that the rodlets- showed their preference for a spectral colour which isabsorbed when transmitted through their bodies. Bv theaid of a light trap of the same kind the very well-knownspindle-shaped and flagellate cell of Euglena can be shown tohave a similar power of discriminating colour, but its pre-ference is different. This familiar organism advances withits flagellum forwards, the sharp end of the spindle having ared or orange eye-point. Accordingly, the light it loves is

again that which is most absorbed-viz., the blue of thespectrum (line F)., These, examples may serve’ as an’ intro-duction to a similar one in which the directing cause

of movement is not physical’ but chemical. ’The spectrallight trap is used in the way already described; the

organisms to be observed are not coloured, but bacteria ofthat common sort which twenty years ago we used to callbacterium termo, and which is recognised as the ordinarydetermining cause of putrefaction. These organisms do notcare for light, but are great oxygen lovers: Consequently,if you illuminate with your spectrum a - filament offa con-fervoid alga, placed in water containing bacteria, the assimilh-tion of carbon and consequent disengagement, of oxygen ismost active in the part of the filament which receives the redrays (B to c). To this part, therefore, where there is a darkband of absorption, the bacteria which want oxygen areattracted in crowds. The motive which brings them togetheris their desire for oxygen. Let us compare other instancesin which the source of attraction is food.’ The plasmodia ofthe myxomycetes, particularly one which has been recentlyinvestigated by Mr. Arthur Lister, may be taken as a typicalinstance of what may be called the chemical allurement ofliving protoplasm. ’ < 1 .

"Another example is also derived from the physiology ofplants. Very shortly after the publication of Engelmann’sobservations of the attraction of bacteria by oxygen; Pfeffermade the remarkable discovery that the movements of thea4therozoids of ferns and of mosses are guided by impres-sions derived from chemical sources, by the allurementexercised upon them by ceitain chemical substances in solu-tion-in one of the instances mentioned by sugar, in theother, by an organic acid. The method consisted in intro-ducing the substance to be tested, in any required strength,into a minute capillary tube closed at one end, and placing itunder the microscope in water inhabited by antherozoids,which thereupon showed their predilection for the substance,or the contrary, by its effect on their movements. In accord-ance with the principle followed in experimental psychology,Pfeffer-6 made it his, object to determine, not the relative

4 Engelmann : " Bacterium photometricum." Onderzoekingen Physiol.Lab., Utrecht, vol. vii., p 200 ; also, Ueber Licht und Farbenperceptionniederster Organismen, Pfl&uuml;ger’s Archiv, vol. xxix., p 387

5 Lister: On the Plasmodium of Badhamia Auricularis, &c , Annals ofBotany, No. 5, June, 1888.

6 Pfeffer: Untersuchungen aus dem Botanischen Institute zu

Tubingen, vol. i., part 3, 1884.

effects of different doses, but the smallest perceptible increase-of dose which the organism was able to detect, with theresult that, just as’ in measurements of the relation betweenstimulus and reaction in ourselves we find that the sensationalvalue of a ’stimulus depends, not on its absolute intensity,but on the ratio between ’that intensity and the previous.excitation, so in ’this simplest of vital reagents the same-so-called psycho-physical law manifests itself. It is not,however, with a view to’ this interesting relation that I havereferred to Pfeffer’s discovery, but because it serves as acentre around which other phenomena, observed alike inplants and animals, have been grouped. As a general designa-tion of reactions of this kind Pfeffer devised the term ’chemo-taxis,’ or, as we in England prefer to call it, ’chemiotaxis,’’and as a constituent phenomenon of the process of infamma-tion it was familiar in pathology long before it was under-stood. Cohnheim himself attributed it to changes in thechannels along which the cells moved, and this explanation:was generally accepted, though some writers, at all events,recognised its incompleteness. But no sooner was Pfeffer’s;discovery known than Leber, who for years had been work--ing at the subject from the pathological side, at once sawthat the two processes were of similar nature." ’ ’ ’

’

Finally, after referring to the discreditable position occu-pied by England in relation to the scientific study of thecauses and mode of prevention of infectious diseases, Pro-.fessor Burdon Sanderson said that the purpose that he hadhad in view in his address was to show that there was butone principle-that of adaptation-separating biology fromthe exact sciences ; and he concluded as follows :

I It may perhaps be thought that their way of putting it istoo teleological, and that in taking, as it were, as my textthis evening so old-fashioned a biologist as Treviranus, I am..yielding to a retrogressive tendency. It is not so. What Ihave desired to insist on is that organism is a fact whichencounters the biologist at every step in his investigations:that in referring it to any general’biological principle, suchas adaptation, we are only referring it to itself, not explain-ing it and that no explanation will be attainable until theconditions of its coming into existence can be subjected toexperimental investigation so as to correlate them with those-of processes in the non-living world."

An AddressON THE

SURGERY OF THE AIR PASSAGES ANDTHORAX IN CHILDREN.

Delivered at the Royal College of Surgeons of England.BY BERNARD PITTS, M.A., M.C.CANTAB.,

SURGEON TO THE HOSPITAL FOR SICK CHILDREN, GREAT ORMOND-STREET.

(Continued from p. 618.)

Papillomata oj the Larynx.IN the history of a fair proportion of cases of papillomata of

the larynx a little difficulty of breathing will be found to haveexisted from birth or to have developed in very early life. Notinfrequently, however, little is noticed about the child

beyond some loss of voice until serious interference with

respiration occurs, calling for immediate relief. Tracheotomyhas then to be performed and the diagnosis is not arrived ’at until the cause of the difficulty in leaving out the tube is,investigated. Before considering further, these cases of

papillomata of the larynx I will refer to an interesting con-dition. which is occasionally to be met with in newly borninfants-where -inspiration is accompanied by a curiouscroaking noise, the cry. sound being, however, quite clear.The ’croak continues dufing sleep and even when an

anesthetic is, given.’ . It is,. however, variable in degree andoccasionally the distress in breathing is considerable and isaccompanied by sbmetecession above the sternum. These con-ditions,appear to depend upon an overcurved and rigid state

7 Leber: Die Anh&auml;ufung der Leucocyten am Orte des Entzundungs .

reizes &c. Die Entstehung dei Entz&uuml;ndung &c., pp. 423-464. Leipzigs.1891.