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logical mechanisms which can influence or modify theorientation reflex.

Several letters have implied that, although the notionalbasis of the at-risk register concept is unsound, the idea is

acceptable in practice. The compiling of these registers andthe subsequent screening of those included are largely func-tions of the local-authority public-health service, and theletter from Dr. Rogers (Nov. 4, p. 988) suggests strongly thatthe concept not only is notionally unsound but in practicefails to achieve the purpose for which it was conceived.

I. D. G. RICHARDS.

Social Paediatric Research Group,23 Montrose Street,

Glasgow, C.1.

C. J. ROBERTS.

Department of Social andOccupational Medicine,

Welsh National School of Medicine,Cardiff.

WHY DEMOSTHENES MOUTHED PEBBLES?

SIR,-During a visit to the British Museum I observed that2 busts of the head of Demosthenes 1 2 seemed to show that hehad a left harelip. Subsequently, I saw on the beaches ofGreece sea-smooth shingle and pebbles which could serveadmirably as obturators. A return visit lately to the basementof the British Museum, together with the description in thecatalogue,3 confirmed my impression of the possibility of adevelopmental defect.The description 3 stated that " The expression of the lips

has been thought to indicate the infirmity of stammering ...",and that "... the lips are tightly compressed ..." in thoseexamples of heads which are most characteristic and certain. Itis possible that the author of this description was not expert inmaxillo-facial development, which might account for theunusual attribution of an anatomical expression to the infirmityof stammering; It is possible also that the sculptor tended tolessen a facial deformity in so notable a personage as

Demosthenes, the orator and statesman. There was, in both

Head of Demosthenes

heads, restoration of the nose and the right side of the head andlip. The left side appeared in one head 1 (see accompanyingfigure) to be unrestored. Thus from these heads alone it is notpossible to ascertain the original condition of the right side.A study 4 of 15 cases of unoperated unilateral cleft palateshowed that the development of facial bones was normal exceptin the region of the cleft.

1. Head of Demosthenes, Sculpture no. 1840. British Museum, London.2. Head of Demosthenes, Sculpture no. 1841. ibid.3. Smith, A. H. A Catalogue of Sculpture; vol. III, p. 136. London, 1904.4. Atherton, J. D. Cleft Palate J. 1967, 4, 18.

Recalling that Demosthenes was reputed to go down to thesea-shore, there filling his mouth with pebbles to orate abovethe roar of the waves, it occurred to me that in all likelihoodthe mission was to obtain a flat surf-smooth stone which wouldserve as an obturator for a possible cleft palate associated withthe presumed developmental lip defect. His repeated visits mayhave been to lay up a store of suitable new pebbles, whichwould have been serviceable without proper sterilisation inthose pre-listerian days.

SAUL M. BIEN.

Guggenheim Institute for Dental Research,New York University,New York 10010.

MAGNESIUM LEVELS AND THYROID DISEASE

SIR,-Previous investigations on the interrelation betweenthe thyroid gland and magnesium have included observationson the effects of both magnesium on thyroid function andthyroid on magnesium metabolism. Neguib reported thata high level of magnesium apparently caused notable diminutionin the size of the thyroid gland in patients with both toxic andnon-toxic goitre. It is, on the other hand, fairly well acceptedthat the serum-magnesium level is raised in patients withhypothyroidism and reduced in hyperthyroidism; this has beenattributed to increase or decrease in ultrafiltrable magnesium,or positive or negative balance of this ion.

ALTERATIONS IN SERUM-MAGNESIUM LEVELS IN PATIENTS WITH THYROID

DISORDERS (mEq. per litre)

Mean value of serum-magnesium concentration for normal subjects was2-23 mEq. per litre (S.D. 0-16).

In our laboratory determinations of serum-magnesium con-centrations were made before and after treatment in 9 hyper-thyroid and 3 hypothyroid patients. The patients with hyper-thyroidism were treated with methimazole, and those withhypothyroidism with lyothyronine (tri-iodothyronine, Ta). Dura-tion of the treatment ranged from 5 months to 2 years. Thetreatment of both disorders was satisfactory, and the clinicalsymptoms disappeared on return to normal of the blood-chem-istry (including serum total-cholesterol and protein-boundiodine, and basal metabolic rate). Serum-magnesium concen-trations were measured by a modification 2 of the fluorometricestimation of Schachter with’ Multiplier Fluorescence Meter,model 540 ’ (Photovolt Corporation).The results of this study are summarised in the accompanying

table. The untreated patients with hyperthyroidism had verylow levels of serum-magnesium by the standard of ourlaboratory.4 These levels increased slightly after treatment withmethimazole in 4 patients; patient no. 1 had a decreased leveldespite a satisfactory response to therapy. On the other hand,1 untreated hypothyroid patient had a raised serum-magnesium

1. Neguib, M. A. Lancet, 1963, i, 1405.2. Kobayashi, A., Shiraki, K. Archs Dis. Childh. (in the press).3. Schachter, D. J. Lab. clin. Med. 1961, 58, 495.4. Kobayashi, A. Lancet, July 8, 1967, p. 100.