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of 35 who share the same stock. In whateverdirection his own inquiring spirit leads him heis encouraged by his masters to seek the cause ofevery mental disorder from two different motives.The patient’s family is longing to be assured ofsome cause to allay their own concern ; the Boardof Control is assiduous in the supply of forms whichthe asylum officer is required to complete. The

physician thus harassed can in some cases supplymany causes, in others none..Some of these difficulties emerge in the annual

reports of mental hospitals which we have recentlyreceived. Dr. C. C. EASTERBROOK, of the CrichtonRoyal, Dumfries, divides the causes, other thanthose of the " usual underlying and predisposingfactor of a nervous constitution," into five stresses-viz., pathological, biological, psychic, toxic,and hygienic. Many of these stresses and theireffects overlap as the figures given illustrate.Thus the physical health of 54 per cent. of theadmissions into the hospital was poor. It is

possible to speak of such conditions as stresses,but in many the physical emaciation is the resultof the psychosis and not its cause. In 46 percent. psychic stresses such as " worry, grief,aitliction, anxiety, and shock " are cited. It is amatter of no small difficulty to differentiate betweenconditions in which real anxiety has precipitatedthe illness and those in which an abnormal sensi-tiveness to anxiety has exaggerated some trivialevent. Both alcoholic excess, and insufficientrest and sleep, may be early signs of a manic-depressive episode and cannot be always heldto be exciting factors though they are certainlyintensifying causes of the severer signs. Solitarylife and want of occupation may be regarded asthe cause of mental instability when they aresometimes two of its manifestations. While Dr.EASTERBROOK finds critical periods of life partlyresponsible for 58 per cent. of his admissions,Dr. F. R. P. TAYLOR, at the East Sussex Hospital,discovers this factor in only 35 per cent. At this

hospital a family history of mental disorder wasfound in 73 per cent. of admissions, though atInverness such a history was only found in 35 percent. It is probable that the careful taking ofthe family history by the social service workerin the former hospital has something to do withthe difference.The number of possible contributory causes

being so large must raise a doubt whether thisadmirable search for the causes of mental disordermay not defeat its own ends. For the geneticistthe study of single factors is all important, andit may be that there is a place for those who willconcentrate only upon those mental patients inwhom one environmental factor, and one factoralone, seems to lie at the root of their illness.Such a quest would require more, not less, carefulsearch into the family and personal history of eachpatient, and it might well confirm the belief thatthere is never one single cause of mental disorder.But in the meantime it would necessitate the

diligent assessment of onus and this would makeboth for scientific accuracy and for great under-standing of the problem of psychotic setiology.

A PROGNOSIS SERIESON another page Dr. ROBERT HuTCHisoN

provides, from his ripe experience, an introductoryarticle to a new series which purports to offer

guidance in the difficult art of prognosis. Itis significant that these words can be used withoutfear of arousing tedious argument whether thisdivision of medicine is indeed more of an artthan a science. No one would claim scientificstatus for the basis on which medical forecastsare hazarded, whether of immediate fatality orsurvival, of probable duration of life, or of degreeof recovery of normal vigour. That some doctorsand nurses have developed an almost uncannygift of prophesy is undisputed ; but their poweris founded on a combination of diagnostic andtherapeutic skill with good judgment and, aboveall, with wide experience. It is this experiencethat we are inviting those who have watched theprogress of large numbers of cases of certain diseasesto share with their colleagues in more generalpractice. Certain crucial factors will have beensorted out as associated with if not actually deter-mining. either recovery or disaster, and criticalexamination of these over a term of years shouldhave eliminated those whose relation to prognosis,though suspected, could not in fact be established.Admittedly few trustworthy statistics on prognosisare available. They are hard both to collect andto interpret ; on the other hand, vague impressionsbased on optimism rather than on experiencecan only be misleading. It is significant, however,that many of the conclusions reached from thestatistical study of the after history of 1000 cardiaccases, on which we commented recently, wereprecisely those which were already accepted asclinical phenomena. But even should some

opinions and impressions recorded in this seriesbe subsequently disproved, their definition shouldbe of value in stimulating follow-up studies oflarge numbers of cases over many years, a branchof clinical research only now coming into its own.

It is fitting that Dr. HUTCINSON should openthe series, for he has called attention, in a lectureoriginally published in our columns and later asone of a trilogy on Some Principles of Diagnosis,Prognosis, and Treatment,2 to the meagre literatureon this most difficult subject and to the educationalvalue of attempts at accurate forecasts of thecourse of every case of serious disease, even ifthese are falsified by the result. He has remindedus aptly that in medicine there abideth faith, hope,and charity: "we have Diagnosis, which is amatter of faith ; Prognosis, which is a questionof hope ; and Treatment, which is too often anaffair of charity." And though the greatest ofthese is diagnosis, for without it one cannot eitherforecast the course and outcome of a disease, ortreat it satisfactorily, yet an error in prognosisdoes more harm to a doctor’s reputation thanan error in diagnosis. This is unjust, for, as

Dr. HUTOHISON points out, a wrong diagnosismay cost a patient his life, which a false prognosis

1 THE LANCET, March 10th, p. 524.2 Bristol : John Wright and Sons. 1928.

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can never do. Errors in prognosis, when notinevitable through lack of pathological knowledge,may be due to the attachment of too much

importance to physical signs and too little to thepatient’s general condition; to failure to allowfor possible complications ; or to refusal to face thefacts. The doctor’s own temperament, and hisage, may influence his prognosis ; the young doctorhas not yet learnt by experience how well a patientcan get on even though his organs be seriously

impaired. Subjects to be dealt with in our nextfew issues include the prognosis in enlargementof the prostate, in tuberculous laryngitis, in diabetesand in acute rheumatism in children. Next weekProf. D. P. D. WiLElE will deal with the prognosisin gall-bladder disease. The success of previousseries of short signed articles on treatment andon aids to diagnosis, contributed by invitationto this journal, justifies the hope that this serieswill meet with equal appreciation.

ANNOTATIONSLATENT BRUCELLA INFECTIONS

THE question is often asked why it is that, with20 to 30 per cent. of the raw market milk infectedwith Brucella abortus, undulant fever is not morecommon. It is less frequently asked why, with6 to 7 per cent. of the same type of milk infectedwith the tubercle bacillus, tuberculosis of bovine

origin is not more common. Yet the two questionshang together closely. Underlying them both is thetacit assumption that the presence of the infectingorganism is alone sufficient to give rise to overtdisease. This assumption arose in the very earlydays of bacteriology, when the rapid discovery of onepathogenic organism after another seemed to be

affording a complete answer to the mystery ofinfection. The first warning note was struck when,as the result of experiments on human volunteers,it was found that the mere ingestion of the choleravibrio was not always sufficient to give rise to cholera.Koch, who was thinking very much more deeplythan many of his colleagues, realised the significanceof this fact-namely, that in the pathogenesis ofdisease the specific micro-organism is but one ofthe factors involved. The next important stage in therealisation of this truth was the discovery of healthycarriers. Of recent years attention has been con-

centrated on the occurrence of latent infections andon mild atypical infections. It is now clear thatthe resistance of the host, determined probablyby a multitude of genetic, physiological, and environ-mental factors, plays a very large part in determiningwhether a given pathogenic organism gaining accessto the body shall be rapidly destroyed, shall give riseto a latent inactive or a latent active infection, orto a mild atypical or a fully developed typical case ofdisease. With some organisms, such as the typhusvirus, the proportion of typical cases to latentinfections appears to be high ; with other organisms,such as the meningococcus, the typical cases formonly a small fraction of the total number of infections.The fallacy of attributing all power to the infectiveagent alone is being gradually realised, and a wide fieldof research now lies open to those who wish to studythe factors determining the resistance of the host.Work, both in Europe and in America, goes to show

that Br. abortus is an organism endowed with a fairlyhigh infectivity but a relatively low pathogenicityfor man. A considerable proportion of those whocome into contact with it become latently infected,as revealed by the appearance of antibodies in theserum, but only a small proportion manifest actualsymptoms of disease. Sometimes typical undulantpyrexia is the predominating feature ; probably moreoften irregular fever, with sometimes bronchial,intestinal, or bone and joint symptoms, is met with.In regard to the incidence of overt disease due toBr. abortus there is a remarkable similarity betweendifferent countries having similarly infected bovine

populations. Russ 1 has just reported figures for twoof the Austrian states-Lower Austria and Burgen-land. During the years 1929 to July, 1933, sera wereexamined from 7406 patients with undiagnosedpyrexia, most of whom were suspected of sufferingfrom enteric fever. Of 6428 sera tested againstorganisms of the typhoid-paratyphoid group, 1907(29-7 per cent.) reacted to an apparently significanttitre, while 164 (2-2 per cent.) of all sera agglu-tinated Br. abortus to 1/100 or over. Theseproportions may be compared with the figuresfor yVidal sera in this country-namely, 21 percent. agglutinating organisms of the typhoid-para-typhoid group and 3-5 per cent. agglutinatingBr. abortus. In other states of Austria the proportionof sera agglutinating Br. abortus appears to be evenhigher. The occurrence of latent infections in personsbrought into contact with Br. abortus has been demon-strated by numerous workers, and is again referred toby three workers in Armenia who found 2 that8.7 per cent. of sera from 399 veterinary and agri.cultural students in contact with infected cattle

agglutinated Br. abortus to 1/100 or over, whereasof 268 sera from medical and other students who werenot specially exposed to contact infection only 1.9

per cent. reacted positively. Studying the history of42 reactors, they found that 11 were ill at the time,15 had a history of undulant fever, while 16 werewell and had no history of this disease. It is note-

worthy that only one of the 15 cases of undulantfever had been correctly diagnosed. The authorsconsider the term " undulant fever" unfortunate,because the characteristic pyrexia is frequentlyabsent, and suspicion of the true nature of the diseaseoften never arises.Latent brucella infections are by no means confined

to man. Recent work by a number of authors hasrevealed their frequency in animals. It has been shown,for instance, that cows may excrete abortus bacilliin their milk without ever having aborted or shownany manifest symptoms of disease. Van der Hoeden 3has infected horses, dogs, and goats with Br. abortus,and has recovered the infecting organism after sometime from the blood or the internal organs ; yet none ofthese animals showed any clinical evidence of illness.

THE DENTAL BOARD

WHILE six members of the Dental Board of theUnited Kingdom are chosen directly by dental prac-titioners, the non-dental members of Board, includingthe chairman, outnumber the dental representatives.The qualified dentists in England and Wales electtwo members, in Scotland and Ireland one each;dentists registered without qualification under theDentists Act of 1921 elect the other two. Four of

1 Russ, V. : Wien. klin. Woch., March 9th, p. 289.2Herrmann, O., Mirsabekjan, A., and Megrabjan, R.: Zeits.

f. Immunitätsforsch., 1934, lxxxi., 500.3 Van der Hoeden,.J. : J. Comp. Path. and Ther., 1933, xlvi., 232.