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with many cases of myopia are not necessarily dueto stretching of the globe, but may be regarded as asort of abiotrophic manifestation analogous to themacular degeneration which is termed senile.

These are the arguments of the modern school,ibut we agree with Mr. Sorsby in regardingthe problem of myopia as not yet solved. The.different behaviour of the hypermetropic and the

myopic eye during school life is a fact that cannotbe ignored, and although no theory of muscular

pressure during convergence, causing lengthening ofthe globe, can be considered as more than a hypo-thesis, the presumption that either from this cause orfrom the vascular engorgement due to long-continuedstooping overwork of the eyes is harmful, at any rate,to those eyes that have already shown a tendency tolengthen, is sufficiently strong to justify the hygienicmeasures usually recommended, and more particularlythe special treatment adopted for children with highmyopia in the L.C.C. schools. But in the past the’theory that myopia is a disease due to overwork ofthe eyes has certainly been pressed too far. Theincidence of high myopia among the labouring classes.and the phenomenon of monocular myopia tell againstit. Heredity is probably the main factor in the,causation of myopia as it is of hypermetropia andof astigmatism ; but to admit this is not to justifyz fatalistic attitude which would deprecate thehygienic precautions which have an influence inchecking it. ____

PROGNOSIS OF HEART-BLOCK

IT is generally held that if complete heart-block isdiscovered the outlook is necessarily bad ; but acase described by K. E. Harris shows that this isnot always so, for the patient was alive and free from.symptoms 28 years after the heart-block was recog-nised. L. B. Ellis,2 in a study of 43 cases of transient’and complete heart-block, has confirmed this view,since four of the twenty-nine patients in whom theblock was permanent lived 24, 15, 14, and 7 yearsrespectively, and it is probable that a further twohad lived for at least nine years with complete heart-block. Two important factors in assessing theprognosis in any given case are the 2etiology and the;age. This is shown by the fact that of the patientsfollowed up under 40 years of age all were living,whereas of those over 40 only 20 per cent. were aliveat the time of the inquiry. As regards setiology there- were nine cases in which the cause was either unknownor congenital, and of -these all were alive. Only onecase was found to have a definite diphtheritic setiologyand in only four others was a history of diphtheriaobtained. This is in marked contrast with the

findings of Butler and Levine,3 who obtained.a history of diphtheria in 10 out of 20 adultpatients with otherwise unexplained heart-block.In the diphtheritic case described by Ellis the blockhad persisted for 24 years without producing anydisability or symptoms. In 52 per cent. of the whole,series arterio-sclerotic changes were the probablecause of the heart-block, and of the 12 patientsfollowed, only three were still alive. Althoughsyphilis is usually regarded as an important cause ofheart-block only two cases in this series had a positiveWassermann reaction and in both of these there was.associated arterio-sclerosis. While it is unusual forpatients with heart-block to have a heart of normal

1 Heart, 1929, xiv., 289.2 Amer. Jour. Med. Sci., February, 1932, p. 225.

2 Butler, S., and Levine S. A. : Amer. Heart Jour., 1930, v.,

size, six of those followed showed no cardiac enlarge-ment and of these, five were still alive. Anotherfactor influencing prognosis is the occurrence ofStokes-Adams attacks, only one of the living patientshaving suffered from these attacks, which were,

however, common in-the -.patients who failed tosurvive. These studies show that heart-block shouldnot be considered as a disease entity but rather asa sign of cardiac damage. The severity of this damagedepends largely on the cause, since when the blockis due to arterio-sclerotic changes it is usually onlypart of a generalised myocardial lesion; whereasif the block is the result of some congenital defector of an acute infection the lesion is more likely to belocalised to the conducting tissue while the rest ofthe myocardium is spared any serious and permanentdamage. ____

A VERY YOUNG HUMAN OVUM

AT a meeting of the Anatomical Society of GreatBritain and Ireland, held at St. Mary’s Hospital onMay 6th, Prof. J. E. Frazer showed and describeda very young human ovum in situ. The specimenwas obtained post mortem, and for material of suchsort was in good condition ; the ovum itself, however,had apparently suffered in some ways from the markedtoxemia which existed for a time before the mother’’8

Ovum in situ. U.C., uterine cavity. E.V., embryonic vesicles;amnion and yolk-sac, against basal chorion.

death. We give a tracing of a section, through themiddle of this ovum, in the accompanying figure,at a magnification of approximately 16. The section.passes through the minute embryonic vesicles, whichare embedded in mesoderm on the basal chorion.The cavity in which the ovum lies is in the moresuperficial part of the stratum compactum, andcontains much blood (represented blank in the figure),and rather stumpy and short villi, with a considerableamount of cyto- and plasmodi-trophoblast. Thedecidua is very vascular, and blood is also containedin some of the glandular tubes, which have beencut through in the extension of the cavity. Nodefinite aperture of entry was apparent, nor wasthere any " closing coagulum," and the epitheliallining of the uterus was only partially destroyed overthe convexity of the capsular decidua. Implantationwas in the extreme upper part of the posterior wall.No history was obtainable, nor does there seem tohave been any menstrual irregularity or interruption,but the specimen appears to be perhaps a few hoursolder than the classical one of Peters, and is estimated

26

to be about 15 days. This seems, therefore, to be theyoungest ovum, so far described, derived from Englishsources. A full account will be published in a futurenumber of the Journal of Anatomy.

ARGUING FROM WATER TO MILK

IN his report for 19311 Sir Alexander Houston dealsincidentally with the pasteurisation of milk. At firstsight this might appear a digression on the part ofthe Director of Water Examination, but it is actuallyvery much to the point. Not only is the problem ofmilk pasteurisation analogous to that of water chlor-ination, but the milk-borne epidemic of paratyphoidfever in Epping last February cost the Water Boarda large sum in safeguarding the water-supply to wellover a million persons. An investigation, he tells us,showed that an enormous amount of highly patho-genic bacteria from a sewage farm were enteringCobbins Brook, a tributary of the Lea, above theBoard’s intakes. Chlorination of this watercourse,among other expensive precautions, removed the

danger. Presumably the organisms got into the milk,not because the cows drank the polluted water, butbecause they waded in it and wetted their hides andudders and became splashed with mud from the banks ;milk utensils, moreover, are sometimes washed andrinsed with polluted water, and occasionally, thoughrarely, water is used to adulterate milk. Sir Alexanderholds that while dangers of this sort exist, all milkshould be pasteurised. He then asks why the ordinarybacteriological standards for milk and -water shouldbe so startlingly different. Most waterworks author-ities, he says, aim at producing water a majority ofsamples of which contain no Bacillus coli in 100 c.cm.and only five microbes per c.cm. on agar at 37° C.The standards applied to the special grades of milksold under licence granted by the Ministry bf Healthor a local authority are nothing like so strict: certifiedmilk must not contain more than 30,000 bacteria perc.cm. or any B. coli in 0- 1 c.cm. ; Grade A must notcontain more than 200,000 bacteria per c.cm. or anyB. coli in 0-01 c.cm. Sir Alexander answers his ownquestion by quoting a passage he wrote 25 years ago,pointing out that some degree of coliform pollution ofmilk is almost unavoidable and that B. coli can onlybe kept within reasonable limits by refrigeration orsterilisation, whereas -impure water can be purifiedby storage and filtration. Secondly, B. coli in milkusually come from non-human and those in waterfrom human sources. Thirdly, B. coli multiply soquickly in milk that the count gives no indication ofthe original amount of pollution; s in water theirnumber remains stationary or diminishes. It istherefore impossible to obtain, even in graded milks,the cleanliness demanded of public drinking wateras a matter of course, and for this reason he believes

that the further precaution of heating is desirable.

THE SEX-RATIO IN MIGRAINE

IT has frequently been stated that the incidenceof migraine is considerably higher in females than ,in males, the ratio being variously placed between, !roughly, the limits of 2 to 1 and 5 to 1. On theother hand such authorities as W. R. Gowers andF. G. Crookshank believe that the preponderanceof females has been greatly exaggerated, and thatpossibly in true migraine there is no sex difference

in incidence. In a series of 545 cases reported by1 Animal Report to the Metropolitan Water Board for 1931.

London: P. S. King and Son, Ltd. 10s. 6d.

Dr. William Allan (North Carolina),l women out-numbered men in the ratio of 2’5 to 1. Less than10 per cent. of these failed to give a history of head-aches in the father or mother or both, but there was noevidence (as has been suggested) that the maladyis inherited as a sex-linked trait. Possibly, Dr.Allan suggests, an explanation may lie in the inclusionof many types of headache in women which were nottrue , migraine. Therefore, considering flitteringscotoma to be a definite indication of true migraine,he analyses 402 case-histories in which its presenceor absence was noted. Of the 122 men 74 had

flittering scotoma (60 per cent.) as compared with127 of the 280 women (45 per cent.). If this criterionis accepted, a lower percentage of the female casesreferred to true migraine, but the female to maleratio still remains at about 1.7 to 1. In the casesdealt with in this study, the duration of headachediffers significantly between the sexes. Of the men87 per cent., compared with 67 per cent. of the women,record -a duration of one day or less, while in only4-4 per cent. of the men is the duration as much asthree days, compared with 13-6 per cent. of thewomen. There is some evidence that in womenan accompanying nausea and vomiting is more

frequent, though the sex differences are slight andnot statistically significant. The actual incidenceof migraine in the general population Dr. Allanendeavours to measure by means of a supplementaryinvestigation amongst the members of the Mecklen-burg County Medical Society. Among 103 men hefound that 54 per cent. gave a history of periodicheadaches that could be clinically classified as definitemigraine, while amongst the 92 wives 63 per cent.gave similar histories. The proportions with hemi-crania and flittering scotoma were approximatelyequal in the sexes, while both groups gave a parentalhistory in 90 per cent. of the cases. These resultslead him to the conclusion that the incidence . of

migraine is the same in men as in women but thatclinically more women than men are seen owing to thegreater severity of the headache in women. Althoughin a previous paper the author concluded thatoccupation plays no part in the incidence of migrainein either sex, it would obviously seem more thana little rash to generalise -from these results, whichare based upon a small sample of a distinct occupa-tional and social class, ’of which as many as one-halfare classified as suffering from the complaint. Migrainein one of its multiple forms is doubtless commonerthan is generally recognised, but anything approaching50 per cent. of the general population seems anunbelievably high figure.

THE COMPARATIVE STUDY OF CANCER

’1’z3E statement that malignant neoplasms are rare inanimals, or at any rate in certain species of animals, isrepeated even in quite recent-literature and in books byacknowledged authorities on cancer. Not infrequentlysuch a statement is made in order to prove a pettheory. Thus one argues that cancer is due to diet,because it is alleged to be rare in herbivorous andfrequent in carnivorous animals. Another arguesthat cancer is a disease of civilisation because wildanimals living in their natural habitat are said tobe free from it. Abundant evidence has accumulatedduring the last 25 years or more that there is no

justification for statements of this kind. Unfor-

tunately the information is scattered through theliterature and much of it is to be found in journals

1 Archives of Neurology and Psychiatry, June, 1932, p. 1436.