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were subsequently recorded over the popliteal, thigh, and,in some cases, femoral veins. The proximal extension ofthrombi from the calf to the popliteal and then the thighveins was inferred from the observation that sequentialcounting at contiguous points showed a progressive increasein counts from below up over the counting period. This

suggestion is supported by the isotopic and venographicstudies of others. This point has already been discussedin the correspondence columns of this journal.9-11 Al-

though we may have given an incorrect emphasis to whatGibbs 12 wrote on this, he does conclude that " thrombosisof the thigh veins... may be derived from two sources:(a) by propagation from thrombus in the leg veins and(b) by primary thrombosis of the veins of the thigh occur-ring independently of leg vein thrombosis ". Althoughhis own work suggested that most thigh-vein thrombi origi-nated independently of calf-vein thrombosis, his extensivereview of the literature compelled him to draw the con-clusions we have quoted.

M.R.C. Cardiovascular Unit,Royal Postgraduate Medical School,

Ducane Road, London W.12.

B. J. MAURERR. WRAY

J. P. SHILLINGFORD.

REHABILITATION AFTER MYOCARDIALINFARCTION

SIR,-The article by Dr. Harpur and her colleagues(Dec. 18, p. 1331) is of great importance because of the estab-lished practice of keeping patients with myocardial infarc-tion in bed for from three to six weeks. The other import-ant point after discharge from hospital is the patient’srehabilitation, which should be under the supervision ofthe family doctor.

It has been my custom for the past ten to twelve years to

keep " uncomplicated " coronary cases, with or withoutmyocardial infarction, at home, and mobilise them withindays, and certainly not more than seven days after the lastepisode or after the pain has subsided. Once the patientshave been mobilised, and are beyond the stage of justgetting up for toilet, my practice is to give strict instruc-tions what to do during all the time they are awake.These instructions include exercises, however light:

moving the fingers, moving the forearm, moving the upperarm, or the toes, the knees, the thighs, whether they arestill in bed or sitting out of bed. I closely describe anddemonstrate the exercises. I give them an outline of how towhile the time away.When they are fully dressed and walk out of the house,

I apply the following principles: (1) they should walk bythe clock without consideration of distance; (2) they shouldat no time sit in a chair longer than about an hour, withoutgetting out of it for more exercises, even to walk around itand sit down again; (3) they should never feel tired doingany of the exercises or walking (if they feel tired that is asign that they have done more than they should havedone).

Considering these three points, I advise them to startwith a five-minute walk each way in the morning and inthe afternoon. This to be extended gradually after two orthree days by another five-minute walk, say twenty minutesmorning and afternoon. All these walks should be onlevel ground, and if stairs have to be mounted, it shouldbe done only once a day until the half-hour stage has beenreached.

I apply the same methods to those with major myo-cardial episodes after discharge from hospital, because the

9. Sevitt, S. ibid. p. 593.10. Negus, D., Pinto, D. J. ibid. p. 645.11. Kakkar, V. V. ibid. p. 930.12. Gibbs, N. M. Br. J. Surg. 1957, 45, 217.

effort expended is controlled by the feeling of lassitude.By the time the patient is able to walk an hour in themorning and an hour in the afternoon, without feelingtired, he is fit for almost any job, except heavy manuallabour.To discharge a patient from hospital without detailed

and adequate instructions on rehabilitation has alwaysseemed to me like rescuing a man from the seas, resuscitat-ing him, and putting him back on his raft without even apaddle to get himself to safety.

70 Lowfield Street,Dartford, Kent. E. GANCZ.

PREVENTION OF MENTAL SUBNORMALITYDUE TO HYPOTHYROIDISM

SIR,-I would agree wholeheartedly with your editorial(Dec. 18, p. 1363) that early diagnosis and treatment ofhypothyroidism is of paramount importance. However,there was no mention in your excellent discussion of thesubject that, in the newborn, protein-bound iodine levels(P.B.I.) are raised and are often well outside the range ofadult normal-values for several weeks of life.!,2 Thus,babies with hypothyroidism might be found to have P.B.i.levels within the accepted adult range of normal values, andconsequently an early diagnosis of the condition mightbe missed.More valuable tests at this time would be estimation of

the tri-iodothyronine resin uptake test (Tg) or the (TJtest, since estimation of the protein-bound iodine levelalone during the early weeks of life could result in thediagnosis of hypothyroidism being missed.Department of Child Health,

Cardiff Royal Infirmary,Cardiff, Glam. M. A. CHADD.

VITAMIN A AND CHRONIC LARYNGITIS

SIR,-Squamous metaplasia has been found in the

larynx of patients with chronic laryngitis 3; since one ofthe causes of squamous metaplasia of the respiratory tractis deficiency of vitamin A,4 we measured the serum-vitamin-A levels in 50 patients with chronic laryngitis,to examine the significance of hypovitaminosis A in itsaetiology. These 50 patients, of equal sex-distributionand an average age of 45, had been hoarse for an averageperiod of eleven months and had been shown by clinicalexamination, including examination under anxsthesia, tohave diffuse inflammation of the larynx with no otherpathological changes (diffuse hyperplastic laryngitis).The serum-vitamin-A level was estimated by a modi-

fication of the technique of van den Bergh and Muller.5 5The vitamin was leached out of serum into heptane etherand the fluorescence estimated before and after denaturingthe vitamin A with ultraviolet light; we took the normallevel to be 19-45 g. per 100 ml. Of the 50 patients, 9(18%) had a serum-vitamin-A level below the normallimit; although these results were not compared withthose from normal controls, it seems unlikely that thisnumber is much greater than that to be expected amongthe normal population, and it seems improbable that

hypovitaminosis A is a very important factor in the causeof chronic laryngitis.Of considerably more interest are a further 10 patients

1. Chadd, M. A., Davies, D. F., Gray, O. P. Archs Dis. Childh. 1968,43, 217.

2. Chadd, M. A., Gray, O. P., Davies, D. F. ibid. 1970, 45, 374.3. Kleinsasser, O. Microlaryngoscopy and Endolaryngeal Microsurgery;

p. 32. Philadelphia, 1968.4. Boyd, W. Pathology; p. 441. London, 1970.5. van den Bergh, A. A. H., Muller, P. Biochem. Z. 1920, 109, 279.