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I must at the outset remark that amongthe many sciences that are occupied withthe study of the living world there is noone that may properly lay exclusive claim to the name of Biology..

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BY

EDMUND BEECHER

WILSON

PROFESSOR OF ZOOLOGY COLUMBIA UNIVERSITY

New York THE COLUMBIA UNIVERSITY PRESS

1908

BIOLOGY

ALECTUREDELIVEREDAT

COLUMBIA

IN THESERIES ONSCIENCE,

PHILOSOPHYAND ARTNOVEMBER

20, 1907

BIOLOGY

BY

EDMUND BEECHER

WILSON

PROFESSOR OF ZOOLOGY COLUMBIA UNIVERSITY

New York THE COLUMBIA UNIVERSITY PRESS

1908

C OPYRIGHT , 1908,

by THE COLUMBIA UNIVERSITY PRESS Set up, and published March, 1908.

I must at the outset remark that amongthe many sciences that are occupied withthe study of the living world there is noone that may properly lay exclusive claim

to the name of Biology The word doesnot, in fact, denote any particular sciencebut is a generic term applied to a largegroup of biological sciences all of whichalike are concerned with the phenomena

of life To present in a single address,

even in rudimentary outline, the specificresults of these sciences is obviously animpossible task, and one that I have nointention of attempting I shall offer nomore than a kind of preface orintroduction to those who will speak after

me on the biological sciences ofphysiology, botany and zoology; and Ishall confine it to what seem to me themost essential and characteristic of thegeneral problems towards which all lines

of biological inquiry must sooner or laterconverge

It is the general aim of the biologicalsciences to learn something of the order ofnature in the living world Perhaps it isnot amiss to remark that the biologist maynot hope to solve the ultimate problems of

life any more than the chemist andphysicist may hope to penetrate the finalmysteries of existence in the non-livingworld What he can do is to observe,compare and experiment with phenomena,

to resolve more complex phenomena intosimpler components, and to this extent, as

he says, to "explain" them; but he knows inadvance that his explanations will never

be in the full sense of the word final orcomplete Investigation can do no morethan push forward the limits ofknowledge

The task of the biologist is a doubleone His more immediate effort is toinquire into the nature of the existingorganism, to ascertain in what measure thecomplex phenomena of life as they now

appear are capable of resolution intosimpler factors or components, and todetermine as far as he can what is therelation of these factors to other naturalphenomena It is often practicallyconvenient to consider the organism aspresenting two different aspects—astructural or morphological one, and afunctional or physiological—andbiologists often call themselvesaccordingly morphologists orphysiologists Morphologicalinvestigation has in the past largelyfollowed the method of observation andcomparison, physiological investigationthat of experiment; but it is one of the bestsigns of progress that in recent years thefact has come clearly into view thatmorphology and physiology are really

inseparable, and in consequence thedistinctions between them, in respect both

to subject matter and to method, havelargely disappeared in a greatercommunity of aim Morphology andphysiology alike were profoundlytransformed by the introduction intobiological studies of the genetic orhistorical point of view by Darwin, whodid more than any other to establish thefact, suspected by many earlier naturalists,that existing vital phenomena are theoutcome of a definite process ofevolution; and it was he who first fullybrought home to us how defective andone-sided is our view of the organism solong as we do not consider it as a product

of the past It is the second and perhapsgreater task of the biologist to study the

organism from the historical point ofview, considering it as the product of acontinuous process of evolution that hasbeen in operation since life began In itswidest scope this genetic inquiry involvesnot only the evolution of higher formsfrom lower ones, but also the still largerquestion of the primordial relation ofliving things to the non-living world Here

is involved the possibility so strikinglyexpressed many years ago by Tyndall inthat eloquent passage in the Belfastaddress, where he declared himself driven

by an intellectual necessity to cross theboundary line of the experimentalevidence and to discern in non-livingmatter, as he said, the promise andpotency of every form and quality ofterrestrial life This intellectual necessity

was created by a conviction of thecontinuity and consistency of naturalphenomena, which is almost inseparablefrom the scientific attitude towards nature.But Tyndall's words stood after all for aconfession of faith, not for a statement of

fact; and they soared far above the terra

firma of the actual evidence At the

present day we too may find ourselveslogically driven to the view that livingthings first arose as a product of non-living matter We must fully recognize theextraordinary progress that has been made

by the chemist in the artificial synthesis ofcompounds formerly known only as thedirect products of living protoplasm But

it must also be admitted that we are stillwholly without evidence of the origin ofany living thing, at any period of the

earth's history, save from some otherliving thing; and after more than two

centuries Redi's aphorism omne vivum e

vivo retains to-day its full force It is my

impression therefore that the time has notyet come when hypotheses regarding adifferent origin of life can be considered

as practically useful

If I have the temerity to ask yourattention to the fundamental problemtowards which all lines of biologicalinquiry sooner or later lead us it is notwith the delusion that I can contributeanything new to the prolonged discussionsand controversies to which it has givenrise I desire only to indicate in what way

it affects the practical efforts of biologists

to gain a better understanding of the living

organism, whether regarded as a group ofexisting phenomena or as a product of theevolutionary process; and I shall speak of

it, not in any abstract or speculative way,but from the standpoint of the workingnaturalist The problem of which I speak

is that of organic mechanism and itsrelation to that of organic adaptation How

in general are the phenomena of liferelated to those of the non-living world?How far can we profitably employ thehypothesis that the living body isessentially an automaton or machine, aconfiguration of material particles, which,like an engine or a piece of clockwork,owes its mode of operation to its physicaland chemical construction? It is not open

to doubt that the living body is a machine.

It is a complex chemical engine that

applies the energy of the food-stuffs to theperformance of the work of life But is itsomething more than a machine? If wemay imagine the physico-chemicalanalysis of the body to be carried through

to the very end, may we expect to find atlast an unknown something that transcendssuch analysis and is neither a form ofphysical energy nor anything given in thephysical or chemical configuration of thebody? Shall we find anythingcorresponding to the usual popularconception—which was also along theview of physiologists—that the body is

"animated" by a specific "vital principle,"

or "vital force," a dominating "archæus"that exists only in the realm of organicnature? If such a principle exists, then themechanistic hypothesis fails and the

fundamental problem of biology becomes

a problem sui generis.

In its bearing on man's place in naturethis question is one of the most momentouswith which natural science has to deal,and it has occupied the attention ofthinking men in every age I cannot traceits history, but it will be worth our while

to place side by side the words of three ofthe great leaders of modern scientific andphilosophic thought The saying has beenattributed to Descartes, "Give me matterand I will construct the world"—meaning

by this the living world as well as thenon-living; but Descartes specificallyexcepted the human mind I do not knowwhether the great French philosopheractually used these particular words, but

they express the essence of themechanistic hypothesis that he adopted.Kant utterly repudiated such a conception

in the following well known passage: "It

is quite certain that we cannot becomeadequately acquainted with organizedcreatures and their hidden potentialities bymeans of the merely mechanical principles

of nature, much less can we explain them;and this is so certain that we may boldlyassert that it is absurd for man even tomake such an attempt or to hope that aNewton may one day arise who will makethe production of a blade of grasscomprehensible to us according to naturallaws that have not been ordered by design.Such an insight we must absolutely deny toman." Still, in another place Kant admittedthat the facts of comparative anatomy give

us "a ray of hope, however faint, thatsomething may be accomplished by the aid

of the principle of the mechanism ofnature, without which there can be noscience in general." It is interesting to turnfrom this to the bold and aggressiveassertion of Huxley: "Living matter differsfrom other matter in degree and not inkind, the microcosm repeats themacrocosm; and one chain of causationconnects the nebulous origin of suns andplanetary systems with the protoplasmicfoundations of life and organization."

Do not expect me to decide where suchlearned doctors disagree; but I will at thispoint venture on one comment which maysound the key-note of this address.Perhaps we shall find that in the long run

and in the large sense Kant was right; but

it is certain that to-day we know verymuch more about the formation of theliving body, whether a blade of grass or aman, than did the naturalists of Kant'stime; and for better or for worse thehuman mind seems to be so constitutedthat it will continue its efforts to explainsuch matters, however difficult they mayseem to be But I return to our morespecific inquiry with the remark that thehistory of physiology in the past twohundred years has been the history of aprogressive restriction of the notion of a

"vital force" or "vital principle" withinnarrower and narrower limits, until atpresent it may seem to many physiologiststhat no room for it remains within thelimits of our biological philosophy One

after another the vital activities have beenshown to be in greater or less degreeexplicable or comprehensible considered

as physico-chemical operations of variousdegrees of complexity Every physiologistwill maintain that we cannot name one ofthese activities, not even thought, that isnot carried on by a physical mechanism

He will maintain further that in most casesthe vital actions are not merelyaccompanied by physico-chemicaloperations but actually consist of them;and he may go so far as definitely tomaintain that we have no evidence that lifeitself can be regarded as anything morethan their sum total He is able to bringforward cogent evidence that all modes ofvital activity are carried on by means ofenergy that is set free in protoplasm or its

products by means of definite chemicalprocesses collectively known asmetabolism When the matter is reduced toits lowest terms, life, as thus viewed,seems to have its root in chemical change;and we can understand how an eminentGerman physiologist offers us a definition

or characterization of life that runs: "Thelife-process consists in the metabolism ofproteids." I ask your particular attention tothis definition since I now wish to contrastwith it another and very different one

I shall introduce it to your attention byasking a very simple question We mayadmit that digestion, for example, is apurely chemical operation, and one thatmay be exactly imitated outside the livingbody in a glass flask My question is, how

does it come to pass that an animal has astomach?—and, pursuing the inquiry, howdoes it happen that the human stomach ispractically incapable of digestingcellulose, while the stomachs of somelower animals, such as the goat, readilydigest this substance? The earliernaturalists, such as Linnaeus, Cuvier orAgassiz, were ready with a reply whichseemed so simple, adequate and final thatthe plodding modern naturalist cannotrepress a feeling of envy In their viewplants and animals are made as they wereoriginally created, each according to itskind The biologist of to-day views thematter differently; and I shall give hisanswer in the form in which I now andthen make it to a student who may chance

to ask why an insect has six legs and a

spider eight, or why a yellowbird isyellow and a bluebird blue The answeris: "For the same reason that the elephanthas a trunk." I trust that a certain ruggedpedagogical virtue in this reply may atonefor its lack of elegance The elephant has atrunk, as the insect has six legs, for thereason that such is the specific nature ofthe animal; and we may assert with adegree of probability that amounts topractical certainty that this specific nature

is the outcome of a definite evolutionaryprocess, the nature and causes of which it

is our tremendous task to determine tosuch extent as we may be able But thisdoes not yet touch the most essential side

of the problem What is most significant isthat the clumsy, short-necked elephant hasbeen endowed—"by nature," as we say—

with precisely such an organ, the trunk, as

he needs to compensate for his lack offlexibility and agility in other respects If

we are asked why the elephant has a trunk,

we must answer because the animal needs

it But does such a reply in itself explainthe fact? Evidently not The questionwhich science must seek to answer, is

how came the elephant to have a trunk; and

we do not properly answer it by sayingthat it has developed in the course ofevolution It has been well said that eventhe most complete knowledge of thegenealogy of plants and animals wouldgive us no more than an ancestral portrait-gallery We must determine the causes andconditions that have cooperated toproduce this particular result if ouranswer is to constitute a true scientific

explanation And evidently he who adoptsthe machine-theory as a generalinterpretation of vital phenomena mustmake clear to us how the machine wasbuilt before we can admit the validity ofhis theory, even in a single case Ourapparently simple question as to why theanimal has a stomach has thus revealed to

us the full magnitude of the task withwhich the mechanist is confronted; and ithas brought us to that part of our problemthat is concerned with the nature andorigin of organic adaptations Withouttarrying to attempt a definition ofadaptation I will only emphasize the factthat many of the great naturalists, fromAristotle onward, have recognized thepurposeful or design-like quality of vitalphenomena as their most essential and

fundamental characteristic HerbertSpencer defined life as the continuous

adjustment of internal relations to

external relations It is one of the best thathas been given, though I am not sure thatProfessor Brooks has not improved upon

it when he says that life is "response to theorder of nature." This seems a long wayfrom the definition of Verworn, heretoforecited, as the "metabolism of proteids." Tothis Brooks opposes the telling epigram:

"The essence of life is not protoplasm butpurpose."

Without attempting adequately toillustrate the nature of organic adaptations,

I will direct your attention to what seems

to me one of their most striking featuresregarded from the mechanistic position

This is the fact that adaptations so oftenrun counter to direct or obviousmechanical conditions Nature is crammedwith devices to protect and maintain theorganism against the stress of theenvironment Some of these are given inthe obvious structure of the organism, such

as the tendrils by means of which theclimbing plant sustains itself against theaction of gravity or the winds, theprotective shell of the snail, the protectivecolors and shapes of animals, and the like.Any structural feature that is usefulbecause of its construction is a structuraladaptation; and when such adaptations aregiven the mechanist has for the most part arelatively easy task in his interpretation

He has a far more difficult knot todisentangle in the case of the so-called

functional adaptations, where theorganism modifies its activities (and oftenalso its structure) in response to changedconditions The nature of these phenomenamay be illustrated by a few examples sochosen as to form a progressive series If

a spot on the skin be rubbed for some timethe first result is a direct and obviouslymechanical one; the skin is worn away.But if the rubbing be continued longenough, and is not too severe, an indirecteffect is produced that is precisely theopposite of the initial direct one; the skin

is replaced, becomes thicker than before,and a callus is produced that protects thespot from further injury The healing of awound involves a similar action Again,remove one kidney or one lung and theremaining one will in time enlarge to

assume, as far as it is able, the functions

of both If the leg of a salamander or alobster be amputated, the wound not onlyheals but a new leg is regenerated in place

of that which has been lost If a flatworm

be cut in two, the front piece grows out anew tail, the hind piece a new head, andtwo perfect worms result Finally, it hasbeen found in certain cases, includinganimals as highly organized assalamanders, that if the egg be separatedinto two parts at an early period ofdevelopment each part develops into aperfect embryo animal of half the usualsize, and a pair of twins results In each ofthese cases the astonishing fact is that amechanical injury sets up in the organism

a complicated adaptive response in theform of operations which in the end

counteract the initial mechanical effect It

is no doubt true that somewhat similarself-adjustments or responses may be said

to take place in certain non-livingmechanical systems, such as the spinningtop or the gyroscope; but those that occur

in the living body are of such generaloccurrence, of such complexity andvariety, and of so design-like a quality,that they may fairly be regarded as amongthe most characteristic of the vitalactivities It is precisely this characteristic

of many vital phenomena that renders theiraccurate analysis so difficult and complex

a task; and it is largely for this reason thatthe biological sciences, as a whole, stillstand far behind the physical sciences,both in precision and in completeness ofanalysis

What is the actual working attitude ofnaturalists towards the general problemthat I have endeavored to outline? Itwould be a piece of presumption for me tospeak for the body of working biologists,and I will therefore speak for only one ofthem It is my own conviction thatwhatever be the difficulties that themechanistic hypothesis has to face, it hasestablished itself as the most usefulworking hypothesis that we can at presentemploy I do not mean to assert that it isadequate, or even true I believe only that

we should make use of it as a workingprogram, because the history of biologicalresearch proves it to have been a moreeffective and fruitful means of advancingknowledge than the vitalistic hypothesis

We should therefore continue to employ it

for this purpose until it is clearly shown to

be untenable Whether we must in the endadopt it will depend on whether it provesthe simplest hypothesis in the large sense,the one most in harmony with ourknowledge of nature in general If such isthe outcome, we shall be bound by adeeply lying instinct that is almost a law

of our intellectual being to accept it, as wehave accepted the Copernican systemrather than the Ptolemaic I believe I amright in saying that the attitude I haveindicated as a more or less personal one

is also that of the body of workingbiologists, though there are someconspicuous exceptions

In endeavoring to illustrate how thisquestion actually affects research I will

offer two illustrative cases, one of whichmay indicate the fruitfulness of themechanistic conception in the analysis ofcomplex and apparently mysteriousphenomena, the other the nature of thedifficulties that have in recent years led toattempts to re-establish the vitalistic view.The first example is given by the so-calledlaw or principle of Mendel in heredity.The principle revealed by Mendel'swonderful discovery is not shown in allthe phenomena of heredity and is probably

of more or less limited application Itpossesses however a profoundsignificance because it gives almost ademonstration that a definite, and perhaps

a relatively simple, mechanism must liebehind the phenomena of heredity ingeneral Hereditary characters that

conform to this law undergo combinations,disassociations and recombinations which

in certain way suggest those that takeplace in chemical reactions; and like thelatter they conform to definite quantitativerules that are capable of arithmeticalformulation This analogy must not bepressed too far; for chemical reactions areindividually definite and fixed, whilethose of the hereditary characters involve

a fortuitous element of such a nature thatthe numerical result is not fixed orconstant in the individual case but followsthe law of probability in the aggregate ofindividuals Nevertheless, it is possible,

a nd has already become the custom, todesignate the hereditary organization bysymbols or formulas that resemble those

of the chemist in that they imply the

quantitative results of heredity that follow

the union of compounds of knowncomposition Quantitative prediction—notprecisely accurate, but in accordance withthe law of probability—has thus becomepossible to the biological experimenter onheredity I will give one example of such aprediction made by Professor Cuénot inexperimenting on the heredity of color inmice (see the following table) Theexperiment extended through threegenerations Of the four grandparents threewere pure white albinos, identical inoutward appearance, but of differenthereditary capacity, while the fourth was apure black mouse The first pair ofgrandparents consisted of an albino ofgray ancestry, AG, and one of blackancestry, AB The second pair consisted