No. 4747.

AUGUST 22, 1914.

ABSTRACT OF

A Presidential AddressON

HEREDITY IN MAN.Delivered in Sydney on August 20th, 1914, before the

Meeting of the British Association for the Advance-ment of Science,

BY WILLIAM BATESON, M.A., F.R.S.,PRESIDENT OF THE ASSOCIATION.

[Professor Bateson commenced his address byreferring to what he had said at Melbourne in

regard to Mendelian analysis and the resulting dis-coveries. Although confession had to be made of deepignorance in regard to theoretical aspects, he saidthat enough had been learnt of the general courseof heredity within a single species to justify manypractical conclusions which could not in the mainbe shaken. He then continued :]THE FACTORIAL SYSTEM IN HUMAN INHERITANCE.

I propose now to develop some of these con-

clusions in regard to our own species-Man.In my former address I mentioned the condition

of certain animals and plants which are what wecall "polymorphic." Their populations consist ofindividuals of many types, though they breed freelytogether with perfect fertility. In cases of this kindwhich have been sufficiently investigated it has beenfound that these distinctions-sometimes very greatand affecting most diverse features of organisation-are due to the presence or absence of elements,or factors as we call them, which are treated in here-dity as separate entities. These factors and theircombinations produce the characteristics which weperceive. No individual can acquire a particularcharacteristic unless the requisite factors enteredinto the composition of that individual at fertilisa-tion, being received either from the father or from z’

the mother or from both, and consequently no indi-vidual can pass on to his offspring positivecharacters which he does not himself possess.Rules of this kind have already been traced in

operation in the human species; and though Iadmit that an assumption of some magnitude isinvolved when we extend the application of thesame system to human characteristics in general,yet the assumption is one which I believe we are

fully justified in making. With little hesitation wecan now declare that the potentialities and apti-tudes, physical as well as mental-sex, colours,powers of work or invention, liability to diseases,possible duration of life, and the other features bywhich the members of a mixed population differfrom each other-are determined from the momentof fertilisation; and by all that we know of heredityin the forms of life with which we can experimentwe are compelled to believe that these qualities arein the main distributed on a factorial system. Bychanges in the outward conditions of life theexpression of some of these powers and featuresmay be excited or restrained. For the developmentof some an external opportunity is needed, and ifthat be withheld the character is never seen, anymore than if the body be starved can the full heightbe attained; but such influences are superficial anddo not alter the genetic constitution.The factors which the individual receives from

1 THE LANCET, August 15th, 1914, p. 435.

his parents and no others are those which he cantransmit to his offspring; and if a factor was

received from one parent only, not more than halfthe offspring, on an average, will inherit it. [Thereasons why mankind had not discovered such simplefacts were considered. The individual body is adoitble structure, whereas the germ cells are single.Two germ cells unite to produce each individualbody, and the ingredients they respectively con-tribute interact in ways that leave the ultimate

product a medley in which it is difficult to identifythe several ingredients. When, however, theireffects are conspicuous the task is by no meansimpossible. If only pedigrees had been drawn theright way up, the essential truth that heredity canbe expressed in terms of presence and absence musthave at once become apparent. He continued :]Let me not, however, give the impression that

the unravelling of such descents is easy. Evenwith fairly full details, which in the case of manare very rarely to be had, many complicationsoccur, often preventing us from obtaining morethan a rough general indication of the system ofdescent. The nature of these complications wepartly understand from our experience of animalsand plants which are amenable to breeding undercareful restrictions, and we know that they aremostly referable to various effects of interactionbetween factors by which the presence of some ismasked.

EVIDENCE AFFORDED BY NORMAL AND ABNORMALCONDITIONS.

Necessarily the clearest evidence of regularity inthe inheritance of human characteristics has beenobtained in regard to the descent of marked abnor-malities of structure and congenital diseases. Ofthe descent of ordinary distinctions such as are metwith in the normal healthy population we knowlittle for certain. Everything points to the infer-ence that the genetics of colour and many otherfeatures in man will prove exceptionally complex.There are, however, plenty of indications of systemcomparable with those which we trace in variousanimals and plants, and we are assured that toextend and clarify such evidence is only a matterof careful analysis. For the present, in assertingalmost any general rules for human descent, we doright to make large reservations for possible excep-tions. It is tantalising to have to wait, but of theultimate result there can be no doubt.

I spoke of complications. Two of these are worthillustrating here, for probably both of them play agreat part in human genetics. It was discoveredby Nilsson-Ehle, in the course of experiments withcertain wheats, that several factors having thesame power may coexist in the same individual.These cumulative factors do not necessarily pro-duce a cumulative effect, for any one of them maysuffice to give the full result. In some cases, as in theprimulas studied by Gregory, the effect is cumulative.

: [The curious case of the mulatto was described,: Professor Bateson at present owning to a preference,

for regarding such examples as instances of imper.: feet segregation. There are many signs that in: human heredity phenomena of this kind are

common, whether they indicate a multiplicity of; cumulative factors or imperfections in segrega-- tion. Such phenomena, however, in no way

l detract from the essential truths that segrega-tion occurs, and that the organism cannot

i pass on a factor which it has not itself received.

In human heredity, he continued, we have foundsome examples, and he believed that we shall findH

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many more, in which the descent of factors islimited by sex. The classical instances are those ofcolour- blindness and haemophilia. Both these con-ditions occur with much greater frequency in malesthan in females. Such descent he considers anadmirable illustration of factorial predestination.It moreover exemplifies that parental polarity ofthe zygote to which I alluded in my first address, aphenomenon which we suspect to be at the bottomof various anomalies of heredity, and suggests thatthere may be truth in the popular notion that insome respects sons resemble their mothers and

daughters their fathers. As to the descent of

hereditary diseases and malformations, however, wehave abundant data for deciding that many are

transmitted as dominants and a few as recessives.The most remarkable collection of these data is tobe found in family histories of diseases of the eye.Neurology and dermatology have also contributedmany very instructive pedigrees. In great measurethe ophthalmological material was collected byEdward Nettleship, for whose death we so latelygrieved. Professor Bateson said that at varioustimes it has been declared that men are born equal,and that the inequality is brought about by unequal,opportunities. Acquaintance with the pedigrees ofdisease soon shows the fatuity of such fancies. Thesame conclusion, we may be sure, would result fromthe true representation of the descent of any humanfaculty. The results likely to flow from Mendel’s workby direct application to the breeding of animals andplants were alluded to. But he imagined that thegreatest practical change likely to ensue frommodern genetic discovery would be a quickening ofinterest in the true nature of man and in thebiology of races. He had spoken cautiously as tothe evidence for the operation of any simpleMendelian system in the descent of human faculty ;yet the certainty that systems which differ from thesimpler schemes only in degree of complexity areat work in the distribution of characters among thehuman population cannot fail to influence our con-ceptions of life and of ethics, leading perhaps ulti-mately to modification of social usage. Men are sofar from being born equal or similar that to thenaturalist they stand as the very type of a poly-morphic species. Even most of our local races

consist of many distinct strains and individualtypes.

DEFECTIVES AND EUGENICS.Professor Bateson then dealt with the subject of

defectives, saying that it is not for us to consider

practical measures. As men of science we observenatural events and deduce conclusions from them.He said that the remedies proposed in America, in-so far as they aim at the eugenic regulation ofmarriage on a comprehensive scale, struck him asdevised without regard to the needs either of in-dividuals or of a modern State. The spirit of

eugenic organisations almost of necessity suffersfrom a bias towards the accepted and the ordinary,and if they had power it would go hard with manyingredients of society that could be ill-spared.He proceeded:Genetic research will make it possible for a

nation to elect by what sort of beings it willbe represented not very many generations hence,much as a farmer can decide whether his byresshall be full of shorthorns or Herefords. Itwill be very surprising indeed if some nationdoes not make trial of this new power. Theymay make awful mistakes, but I think theywill try.

Whether we like it or not, extraordinary and far-reaching changes in public opinion are coming topass. Man is just beginning to know himself forwhat he is-a rather long-lived animal, with greatpowers of enjoyment if he does not deliberatelyforego them. Hitherto superstition and mythicalideas of sin have predominantly controlled thesepowers. Mysticism will not die out: for thosestrange fancies knowledge is no cure; but theirforms may change, and mysticism as a force for thesuppression of joy is happily losing its hold on themodern world. As in the decay of earlier religionsUshabti dolls were substituted for human victims,so telepathy, necromancy, and other harmless toystake the place of eschatology and the inculcationof a ferocious moral code. Among the civilisedraces of Europe we are witnessing an emancipationfrom traditional control in thought, in art, and inconduct which is likely to have prolonged andwonderful influences. Returning to freer or, if youwill, simpler conceptions of life and death, thecoming generations are determined to get more outof this world than their forefathers did. Is it thento be supposed that when science puts into theirhand means for the alleviation of suffering im-measurable, and for making this world a happierplace, they will demur to using those powers?The intenser struggle between communities is onlynow beginning, and with the approaching exhaus-tion of that capital of energy stored in the earthbefore man began it must soon become still morefierce. In England some of our great-grandchildrenwill see the end of the easily accessible coal, and,failing some miraculous discovery of availableenergy, a wholesale reduction in population. Thereare races who have shown themselves able at a wordto throw off all tradition and take into their serviceevery power that science has yet offered them. Canwe expect that they, when they see how to ridthemselves of the ever-increasing weight of a

defective population, will hesitate. The time cannotbe far distant when both individuals and com-munities will begin to think in terms of biologicalfact, and it behoves those who lead scientificthought carefully to consider whither action shouldlead. At present I ask you merely to observe thefacts. The powers of science to preserve thedefective are now enormous. Every year thesepowers increase. This course of action must reach

a limit. To the deliberate intervention of civilisa-tion for the preservation of inferior strains theremust sooner or later come an end, and beforelong nations will realise the responsibility theyhave assumed in multiplying these " cankers of acalm world and a long peace."The definitely feeble-minded we may with pro-

priety restrain, as we are beginning to do even inEngland, and we may safely prevent unions inwhich both parties are defective, for the evidenceshows that, as a rule, such marriages, though oftenprolific, commonly produce no normal children atall. The union of such social vermin we shouldno more permit than we would allow parasites tobreed on our own bodies. Further than that inrestraint of marriage we ought not to go, at leastnot yet. Something, too, may be done by a reformof medical ethics. Medical students are taughtthat it is their duty to prolong life at whatevercost in suffering. This may have been right whendiagnosis was uncertain and interference usuallyof small effect; but deliberately to interfere nowfor the preservation of an infant so gravely diseasedthat it can never be happy or come to any good is

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very like wanton cruelty. In private few mendefend such interference. Most who have seen

these cases lingering on agree that the systemis deplorable, but ask where can any line bedrawn. The biologist would reply that inall ages such decisions have been made bycivilised communities with fair success both in

regard to crime and in the closely analogous caseof lunacy. The real reason why these things aredone is because the world collectively cherishesoccult views of the nature of life, because the factsare realised by few, and because between the legalmind-to which society has become accustomed todefer-and the seeing eye there is such physio-logical antithesis that hardly can they be com-

bined in the same body. So soon as scientificknowledge becomes common property views morereasonable and, I may add, more humane are

likely to prevail.To all these great biological problems that

modern society must sooner or later face there aremany aspects besides the obvious ones.

[Infant mortality was referred to, and the

opinion was expressed that in England the limit ’,beyond which under present conditions of distribu-tion increase of population is a source of sufferingrather than of happiness has been reached already.Younger communities living in territories largelyvacant are very probably right in desiring and

encouraging more population. Increase may, forsome temporary reason, be essential to their

prosperity. Even the decline in the birth-rate ofthe intelligent and successful sections of the popula-tion (of the older communities) could not be grantedwithout qualification.

THE PROGRESS OF MAN.

In the study of history biological treatment isonly beginning to be applied. For us the causes ofthe success and failure of races are physiologicalevents, and the progress of man has depended upona chain of these events, like those which haveresulted in the

"

improvement " of the domesticatedanimals and plants. It is obvious, for example,that had the cereals never been domesticated citiescould scarcely have existed. But we may go further,and say that in temperate countries of the OldWorld (having neither rice nor maize) populationsconcentrated in large cities have been made possibleby the appearance of a

" thrashable " wheat. The

ears of the wild wheats break easily to pieces, andthe grain remains in the thick husk. Such wheatcan be used for food, but not readily. Ages beforewritten history began, in some unknown place,plants, or more likely a plant, of wheat lost thedominant factor to which this brittleness is due,and the recessive, thrashable wheat resulted. Someman noticed this wonderful novelty, and it hasbeen disseminated over the earth. The originalvariation may well have occurred once only, in asingle germ cell.

So must it have been with man. Translated intoterms of factors, how has that progress in controlof nature which we call civilisation been achieved ?By the sporadic appearance of variations, mostly,perhaps all, consisting in a loss of elements, whichinhibit the free working of the mind. The membersof civilised communities, when they think aboutsuch things at all, imagine the process a gradualone, and that they themselves are active agents init. Few, however, contribute anything but theirlabour ; and except in so far as they have freedomto adopt and imitate, their physiological composition

is that of an earlier order of beings. Annul thework of a few hundreds-I might almost sayscores-of men, and on what plane of civilisationshould we be ? We should not have advancedbeyond the mediaeval stage without printing,chemistry, steam, electricity, or surgery worthythe name. These things are the contributions ofa few excessively rare minds. Galton reckonedthose to whom the term " illustrious" might beapplied as one in a million, but in that number heis, of course, reckoning men famous in ways whichadd nothing to universal progress. To improve bysubordinate invention, to discover details missed,even to apply knowledge never before applied, allthese things need genius in some degree, and arefar beyond the powers of the average man of ourrace; but the true pioneer, the man whosepenetration creates a new world, as did thatof Newton and of Pasteur, is inconceivably rare.But for a few thousands of such men we

should perhaps be in the paleolithic era, knowingneither metale, writing, arithmetic, weaving, norpottery.

In the history of art the same is true, but withthis remarkable difference, that not only are gifts ofartistic creation very rare, but even the faculty ofartistic enjoyment, not to speak of higher powersof appreciation, is not attained without variationfrom the common type. I am speaking, of course,of the non-Semitic races of modern Europe, amongwhom the power whether of making or enjoyingworks of art is confined to an insignificant numberof individuals. Appreciation can in some degreebe simulated, but in our population there is nowidespread physiological appetite for such things.When detached from the centres where theyare made by others most of UH pass our timein great contentment, making nothing that isbeautiful, and quite unconscious of any deprivation.Musical taste is the most notable exception, for in

L certain races-for example, the Welsh and someof the Germans-it is almost universal. Otherwise

I artistic faculty is still sporadic in its occurrence.The case of music well illustrates the application

, of genetic analysis to human faculty. No one

disputes that musical ability is congenital. In itsI fuller manifestation it demands sense of rhythm,: ear, and special nervous and muscular powers.3 Each of these is separable and doubtless geneticallyI distinct. Each is the consequence of a special. departure from the common type. Teaching andi external influences are powerless to evoke these: faculties, though their development may be assisted., The only conceivable way in which the people of: England, for example, could become a musical, nation would be by the gradual rise in the: proportional numbers of a musical strain or

i strains until the present type became so rare

l as to be negligible. It by no means followsu that in any other respect the resulting population

would be distinguishable from the present one.

) Difficulties of this kind beset the efforts of anthro-L pologists to trace racial origins. It must continually’ be remembered that most characters are inde-, pendently transmitted and capable of such recom-l bination. In the light of Mendelian knowledge; the discussion whether a race is pure or mixedj loses almost all significance. A race is pureL if it breeds pure and not otherwise. Historicallyl we may know that a race like our own was,: as a matter of fact, of mixed origin. But a

l character may have been introduced by a singlei individual, though subsequently it becomes common

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to the race. This is merely a variant on thefamiliar paradox that in the course of time if

registration is accurate we shall all have the samesurname. In the case of music, for instance, thegift, originally perhaps from a Welsh source, mightpermeate the nation, and the question would thenarise whether the nation, so changed, was the

English nation or not.

THE RACIAL CHARACTERISTICS OF THE GREEKS.Such a problem is raised in a striking form by

the population of modern Greece, and especially ofAthens. The racial characteristics of the Athenianof the fifth century B.C. are vividly described byGalton in " Hereditary Genius." The fact that inthat period a population, numbering manythousands, should have existed, capable of followingthe great plays at a first hearing, revelling insubtleties of speech, and thrilling with passionatedelight in beautiful things, is physiologically amost singular phenomenon. On the basis of thenumber of illustrious men produced by that ageGalton estimated the average intelligence as atleast two of his degrees above our own, differingfrom us as much as we do from the negro. A fewgenerations later the display was over. The originof that constellation of human genius which thenblazed out is as yet beyond all biological analysis,but I think we are not altogether without suspicionof the sequence of the biological events. If I visita poultry breeder who has a fine stock of thorough-bred game fowls breeding true, and ten years later-that is to say, ten fowl generations later-I goagain and find scarcely a recognisable game-fowlon the place, I know exactly what has happened.One or two birds of some other or of no breed musthave strayed in and their progeny been left unde-

stroyed. Now in Athens we have many indicationsthat up to the beginning of the fifth century solong as the phratries and gentes were maintainedin their integrity there was rather close

endogamy, a condition giving the best chance ofproducing a homogeneous population. There wasno lack of material from which intelligence andartistic power might be derived. Sporadicallythese qualities existed throughout the ancientGreek world from the dawn of history, and, forexample, the vase-painters, the makers of the

Tanagra figurines, and the gem-cutters were pre-sumably pursuing family crafts, much as are theactor families" of England or the professionalfamilies of Germany at the present day. How theintellectual strains should have acquired pre-dominance we cannot tell, but in an in-breedingcommunity homogeneity at least is not surprising.At the end of the sixth century came the "reforms"of Cleisthenes (507 B.C.), which sanctioned foreignmarriages and admitted to citizenship a numbernot only of resident aliens but also of manumittedslaves. As Aristotle says, Cleisthenes legislatedwith the deliberate purpose of breaking up thephratries and gentes, in order that the varioussections of the population might be mixed up asmuch as possible and the old tribal associationsabolished. The " reform " was probably a recogni-tion and extension of a process already begun ; butis it too much to suppose that we have here theeffective beginning of a series of genetic changeswhich in a few generations so greatly altered thecharacter of the people ? Under Pericles the oldlaw was restored (451 B.C.), but losses in the great

2 For tables of these families, see the Supplement to Who’s Who inhe Theatre.

wars led to further laxity in practice, and thoughat the end of the fifth century the strict rule wasre-enacted that a citizen must be of citizen-birth onboth sides, the population by that time may wellhave become largely mongrelised.Let me not be construed as arguing that mixture

of races is an evil: far from it. A population likeour own, indeed, owes much of its strength to.the extreme diversity of its components, for theycontribute a corresponding abundance of aptitudes.Everything turns on the nature of the ingredients.brought in, and I am concerned solely with the-observation that these genetic disturbances leadultimately to great and usually unforeseen changesin the nature of the population. Some experimentsof this kind are going on at the present time. [Inillustration of this, reference was made to theUnited States and to Japan, as also to our own

Peerage.]Historians commonly ascribe such changes a&

occurred in Athens, and will almost certainly cometo pass in the United States, to conditions of lifeand especially to political institutions. Theseagencies, however, do little unless they are such as.to change the breed. External changes may indeedgive an opportunity to special strains, which thenacquire ascendency. The industrial developmentswhich began at the end of the eighteenth century,for instance, gave a chance to strains till thensubmerged, and their success involved the decay ofmost of the old aristocratic families. But thedemagogue who would argue from the rise of theone and the fall of the other that the originalrelative positions were not justifiable altogethermistakes the facts. Conditions give opportunitiesbut cause no variations. For example, in Athens,to which I just referred, the universality of culti-vated discernment could never have come to passbut for the institution of slavery which providedthe opportunity, but slavery was in no sense a causeof that development, for many other populationshave lived on slaves and remained altogetherinconspicuous.

[The long-standing controversy as to the relativeimportance of nature and nurture, to use Galton’s"

convenient jingle of words," is, said ProfessorBateson, drawing to an end, and of the over-

whelmingly greater significance of nature there isno longer any possibility of doubt. It is faith,not evidence, which encourages educationists andeconomists to hope so greatly in the amelioratingeffects of the conditions of life.]

BIOLOGY AND SCHEMES FOR REFOH,1L-

In all practical-schemes for social reform the con-genital diversity, the essential polymorphism of allcivilised communities must be recognised as a,

fundamental fact, and reformers should ratherdirect their efforts to facilitating and rectifyingclass-distinctions than to any futile attempt toabolish them. The teaching of biology is perfectlyclear. We are what we are by virtue of our

differentiation. The value of civilisation has in allages been doubted. Since, however, the firstvariations were not strangled in their birth, we arelaunched on that course of variability of whichcivilisation is the consequence. We cannot go backto homogeneity again, and differentiated we arelikely to continue. For a period measures designedto create a spurious homogeneity may be applied.Such attempts will, I anticipate, be made when thepresent unstable social state reaches a climax of

instability, which may not be long hence. Their

485

.effects can be but evanescent. The instability is,due not to inequality, which is inherent and con-

genital, but rather to the fact that in periods ofrapid change like the present, convection currentsare set up such that the elements of the strata getintermixed and the apparent stratification corre-

sponds only roughly with the genetic. In a few

generations under uniform conditions these ele-ments settle in their true levels once more.

In such equilibrium is content most surely to beexpected. To the naturalist the broad lines ofsolution of the problems of social discontent areevident. They lie neither in vain dreams of a

mystical and disintegrating equality, nor in the

promotion of that malignant individualism whichin older civilisations has threatened mortifica-tion of the humbler organs, but rather ina physiological coordination of the constituent

parts of the social organism. The rewardsof commerce are grossly out of proportion tothose attainable by intellect or industry. Even

xegarded as compensation for a dull life, theytar exceed the value of the services rendered to the- community. Such disparity is an incident of theabnormally rapid growth of population and is quiteindefensible as a permanent social condition.Nevertheless, capital, distinguished as a provisionfor offspring, is a eugenic institution; and unlesshuman instinct undergoes some profound and im-probable variation, abolition of capital means the.abolition of effort; but as in the body the power ofindependent growth of the parts is limited andsubordinated to the whole, similarly in the com-munity we may limit the powers of capital,preserving so much inequality of privilege as

corresponds with physiological fact.At every turn the student of political science is

confronted with problems that demand biologicalknowledge for their solution. Most obviously isthis true in regard to education, the criminal law,.and all those numerous branches of policy andadministration which are directly concerned withthe physiological capacities of mankind. Assump-tions as to what can be done and what cannot bedone to modify individuals and races have con-tinually to be made, and the basis of fact on whichsuch decisions are founded can be drawn only frombiological study.A knowledge of the facts of nature is not yet

deemed an essential part of the mental equipmentof politicians ; but as the priest, who began in otherages as medicine-man, has been obliged to abandonthe medical parts of his practice, so will the futurebehold the schoolmaster, the magistrate, the lawyer,and ultimately the statesman, compelled to sharewith the naturalist those functions which are

concerned with the physiology of race.

ISOLATION ACCOMMODATION IN BRIDGEND.-Themedical officer of health of the urban district of Bridgend,in Glamorgan, Mr. Wyndham Randall, once more in hisannual report.draws attention to the wholly inadequateaccommodation available for the isolation of infectiousdisease in the district. Six years ago an isolation hospitalwas erected with accommodation for 12 patients to serveBridgend and adjoining districts with a present populationof about 44,000. During 1913 there were treated in thewards 35 cases from Bridgend alone, and on many occasionsthe number of patients greatly exceeded the normal accom-modation. At one time 11 patients were in a six-bed wardand on another occasion several little girls had to be placedin a ward in which there were also men and boys. Fivepatients were for a short time in a two-bed ward andchildren had to be isolated in the kitchen and bathroom.

THE DIAGNOSTIC VALUE OF THE COM-PLEMENT FIXATION REACTION IN

TUBERCULOSIS.

PART I.—IN GENERAL HOSPITAL PRACTICE.

BY JAMES MCINTOSH, M.D. ABERD.,BEIT MEMORIAL RESEARCH FELLOW ; LATE RESEARCH SCHOLAR OF THE

GROCERS’ COMPANY ;

AND

PAUL FILDES, M.B., B.C. CANTAB.,ASSISTANT BACTERIOLOGIST TO THE LONDON HOSPITAL.

(From the Bacteriological Laboratory of the London Hospital.)PART II.—IN SANATORIUM PRACTICE.

BY J. A. D. RADCLIFFE, M.B., B.CH. R.U.I.,PATHOLOGIST TO KING EDWARD VII. SANATORIUM, MIDHURST.

PART I.-IN GENERAL HOSPITAL PRACTICE.

To make a certain diagnosis of tuberculosis is inmany instances a very difficult task, and for thisreason numerous attempts have been made to pro-cure a reliable biological test. The expectationraised by Koch’s discovery of the tubercle bacillushas not been fully realised, since some patientswith pulmonary tuberculosis have no bacilli in theirsputum, and, again, the lesion is not always suitedto direct examination. The tuberculin test in itsvarious forms has proved very unreliable underthe usual conditions of practice, while the agglu-tination and precipitin reactions are so frequentlyabsent as to make them of no diagnostic value.From a study of the literature dealing with com-

plement fixation in tuberculosis it is clear that

great diversity has been obtained in the results,while few have published series of cases of suffi-cient magnitude or sufficiently controlled to allowof exact deductions. The chief cause for the

diversity in the results is the composition of theantigen used. It was not appreciated by the earlierwriters that an antigen consisting of old tuber-culin was not analogous to an emulsion of tuberclebacilli. In fact, the antisubstances to these

antigens are entirely different (Bauer).Bordet and Gengou in 1903 demonstrated that

antibodies capable of uniting with tubercle bacilliand fixing complement were present in the sera oftuberculous animals. Wassermann and Bruck in1906, after a series of experiments, stated that thesera of tuberculous patients who had been treatedwith tuberculin contained an antibody capable offixing complement in the presence of tuberculin;they, however, only examined 13 cases of pulmonarytuberculosis. Citron shortly afterwards stated thatantituberculin was present in the sera of tuber-culous individuals who had not been treated withtuberculin. The results of Wassermann and hispupils must not be accepted with too much con-fidence owing to the crudeness of the technique andto the tendency of organ extracts to give non-specific reactions. Morgenroth and Rabinowitsch,and Meyer, using the technique described byWassermann, were unable to confirm his results.With tuberculin as antigen and a more elaborate

technique Bermbach, Wolff and Muhsam, and othersfound antituberculin substances present in thesera of tuberculous patients. Wolff and Miihsamobtained 78 positive results in 105 cases of phthisis.Cohn obtained 15 out of 57 and Koch about one-thirdof positive results. These were all in cases of

phthisis which had not been treated with tuber-culin. Fua and H. Koch in tuberculous children