Arnold Sorsby

STATISTICAL NOTE ON THE COMPONENTS OF OCULAR REFRACTION IN TWINS.

In their study on refraction and its components in twins, Sorsby, Sheridan, and Leary (I962) showed that the differences in measurements of the individual components were slight in 78 pairs of uniovular twins, in contrast to the distinctly larger differences observed in 40 pairs of binovular twins and 48 control pairs. The differences in uniovular twins were slight even when the 23 pairs with non-modal refractions (spherical refractions of ± 2-25 D. or more; or astigmatism of ± I 25 D. or more) were considered; and this pattern likewise held when only the io pairs with refraction of : 40o D. or the i8 pairs with myopia (of varying degree above o 5o D.) were studied; the binovular twins and the control pairs showed consistently larger differences in their measurements. There was also close agreement in the ocular refraction of uniovular twins, 55 pairs showing differences in refraction of less than 0o5 D. In the i8 pairs where the refraction differed by 0-5I D. to I 5 D. and the 5 pairs with a difference of more than 1.5 D.-designated here discordant refractions-the individual components still showed close values, the difference in refraction usually being determined by slight non-concordance in the axial length. In contrast, no such consistent pattern could be seen in the binovular twins and the control pairs. The general analysis thus established that there was concordance for refraction and its components in the different types of refraction in uniovular twins, a striking contrast to the lack of any such concordance in the control material. The present note attempts to evaluate statistically the findings recorded in that study. Statistical treatment has limitations where small numbers are available: this is a relevant consideration here for, as the twin material was largely a random collection representative of the general population, the higher (and unusual) refractive errors were poorly represented. There were none or but few cases in some of the refraction groups, but the material is

Modes of Inheritance of Errors of Refraction

Eighteen families in which both parents had refractions within the range of +4·0 D to −4·0 D and axial lengths seen in emmetropia (22·3-26·0 mm) showed coefficients of correlation of the order 0·5 indicative of polygenic inheritance. Such coefficients were seen for axial length (0·407) and for the cornea (0·487), but not for the lens (which is known to be yoked to the axial length). No such coefficients were seen in 19 families in which one of the parents had axial length outside the emmetropic range (nine families with long axes and 10 with short axes). The pattern of polygenic inheritance for emmetropia (completely correlated optical components) and errors of refraction up to 4·0 D (inadequately correlated components: correlation ametropia) follows that seen in stature and other measurable characters. In contrast the high refractive errors with their abnormal axial lengths (component ametropia) are—like the extremes in stature—pathological anomalies with monofactorial inheritance.

Humangenetik. Ein kurzes Handbuch in fünf Bänden

This is the seventh of the nine parts of this fivevolume encyclopaedia. The present section closes Volume I, the first section of which appeared last year (see review in this journal, Vol. 5, p. 363). It completes the discussion on normal anatomical and physiological traits, and gives an excellent summary of a very widely scattered and ill-organized literature. The largest chapter is by L. Loeffler of Hanover on the patteming of the skin in health and disease; there are nearly 600 references to an exhaustive and critical text of 200 pages. Genetically determined variations in psychological pattems are dealt with almost as extensively by v. Bracken of Marburg. Smaller chapters are devoted to the genetic variations in the iris (H. Oepen), the eye-lids (H. Ritter), the outer nose and the mouth and chin area (G. Ziegelmayer), and in taste and smell (G. Jorgenson), while the configuration of the outer ear and of the hands and feet are dealt with by F. Schwarzfischer and J. Schaeble, respectively. As in the earlier volumes, the contributors, the editor, and the publishers have done a superb job. ARNOLD SORSBY

Proceedings of a Symposium on Scoliosis

The two London symposia were held in June and in July I965, and both appear as an Action for the Crippled Child Monograph. Each runs to about IOO pages of up-to-date and authoritative accounts, going well beyond current textbook reading. In the first symposium C. 0. Carter discussed briefly the genetics of spina bifida. In the second, genetic and biochemical aspects of scoliosis were dealt with fairly exhaustively under the chairmanship of J. A. Fraser Roberts in a wide-ranging discussion, to which P. Polani, C. 0. Carter, Janet Anders, Ruth WynnDavies, and R. Ling contributed for the genetic angle. The fund sponsoring these symposia hopes to arrange for two such meetings each year dealing with different aspects of the crippled child. These two opening symposia augur well for future developments. In preparation for the meeting in October I965 the Human Genetics Unit of W.H.O. at Geneva produced an extensive summary of some 45 major studies on twins carried out at various centres. (This report is available on request from the unit.) The meeting itself concentrated on the possible use of twin material for such affections as coronary heart disease, hypertension, peptic ulcer, and diabetes. The value of a centralized agency such as W.H.O. to promote and co-ordinate international studies of such a type was recognized as was the need for acceptable criteria for the collection and analysis of the material. ARNOLD SORSBY

Teach Yourself Genetics

This is a detailed study of the incidence of 7 malformations (anencephaly, spina bifida, hydrocephalus, cleft-lip, with and without cleft-palate, cleft-palate alone, and polydactyly). The reasons for including polydactyly are not adequately given: a condition that is so heterogeneous seems somewhat unsuited for statistical treatment. In each of these malformations a detailed breakdown by parental age, year, month, region, and town or country is given. There is no breakdown by both age and parity, and the statistical treatment is most confusing; significance tests, usually preceded by cumbrous explanations, abound, but many, such as dichotomizing parental age differences rather than giving the difference, are unnecessarily crude. Consequently, though a few of the many tests have passed the arbitrary threshold of statistical significance, the proportion is not significantly high, and the reader is left wondering whether the associations strained out by this sieve are of greater biological validity than those that slipped through. We have a meticulously drawn map of the incidence of these conditions in time and space, but we are left with the problem of what to do with it. When one is lost, as we are in the study of malformations, drawing a map may seem the first course of action; however, historically, incidence maps have been of little use in unravelling the background of malformations, the major discoveries being made from new laboratory techniques, as in mongolism, or the explosive development of unusual syndromes, as in infective embryopathies and phocomelia. The reasons for this are fairly simple-to pursue the analogy further the standard error of the contour lines exceeds the height of most of the hills and some of the mountains, so that every time the map is redrawn it is difficult to relate the movements of the contour lines to any changes in the underlying structure. Firmer contours require more malformations, which require increasing the sampling over both space and time, and this not only involves far more work, but also increases the chances of types of heterogeneity which distort or blur the final picture without adding any useful information. Whether we need more extensive maps from which smaller deviations can be charted with speed, or whether map-making will continue to be distressingly nonproductive, only the future can tell. Dr. Tunt has drawn his map as accurately as is possible, and, if it does not show the way, this is no criticism of the thoroughness of his surveying. J. H. EDWARDS

Fortschritte der allegemeinen und klinischen Humangenetik

6 months, and 10 months. Analysis of the results shows that the poor muscle tone in such infants improves with age, as judged by palpation, resistance to passive movement, the traction responses, and the effect of tone on posture in prone, sitting, and horizontal suspension. Significant positive correlations existed between marked hypotonia and strabismus at all three examinations. The Moro and primary stepping responses persisted longer than in normal infants: lower limb placing responses, absent in all mongols during the early months, appeared in some 200% by 10 to 12 months. The methods of eliciting and scoring these responses are described concisely, and supported by 55 illustrations with a useful selection of references. This book is a welcome addition to our knowledge of Downs syndrome, and will be of value to physicians and psychologists undertaking developmental studies on select groups of children. PETER ROBSON

Advances in Blood Gouping II

answering the above questions, in so far as it can be regarded as consisting of 8 inbred populations and all possible F 1 crosses between these. The records available are extremely comprehensive and provide effective environmental control, thus compensating as far as possible for the lack of experimental randomization of error. Consequently, the population can be analysed as a dialled cross. Great care has been taken in detailing the collection of the data and their reliability, and the general discussion pertinent to this results in an absorbing account of the history and sociological structure of Hawaii itself. The conclusions reached are: (1) First generation hybrids between races in man are intermediate in size, mortality, and morbidity between the parental groups. (2) At the present time, human populations do not represent co-adapted genetic combinations which are disrupted by outcrossing. It is unfortunate, however, that the authors have not seen fit to describe in greater detail the statistical methods applied, and that many of the conclusions reached appear to be dominated by a personal controversy. MICHAEL OAKES

The Living Races of Man

Under the general title of intersexu considers all states of abnormal sex and adaptation, whether related to , anomalies or not. The first part deals br consideration of clinical cytogenetics, in and with a review of the chromosoma many clinical variants of deviant sex c have been described. In the second presents a series of cases from the Derr ment of the Charite in B.rlin, and chromosomal and other findings in eig] These deal with I4 cases with ch Klinefelters syndrome, a lactating ( sexual male, a pituitary dwarf, and a ma syndrome without webbing of the ne gonadal dysgenesis in females, a comp some mosaic with a triple-X cell line a dysgenesis, testicular feminization, an hermaphroditism, transvestism, and tra congenital and acquired adrenogenital s The cytological and clinical illustrat quality, and insufficint cytological distribution) and at times clinical data are a number of inaccuracies in the spe names and in the literature quoted, an errors have crept in (page 43, first lines