the teeth; thin enamel permits the normally yellow dentine to be seen. Such enamel hypoplasia has been chronologically assessed as being of neonatal origin. It would be interesting to learn from Dr. Davies the incidence of yellow-brown teeth in all the children they examined and whether enamel hypoplasia was present in the teeth which they examined under an ultraviolet lamp. Department of Preventive Dentistry, University of Manchester.
BLOOD-GROUPS AND SUSCEPTIBILITY TO DISEASE: A REQUEST FOR INFORMATION SiR,-The vaccination of relatively large numbers of persons for the first time presents an opportunity to test the hypothesis that blood-group-A substance and vaccinia virus possess antigenic affinities as suggested by Pettenkofer and Bickerich,1 and referred to by Dr. Harris and his colleagues (March 24). I am collecting information on the blood-groups of those patients with atopic eczema who develop eczema vaccinatum (Kaposi’s varicelliform eruption) when exposed to the vaccinia virus, either through direct vaccination or through contact with a vaccinated person. It would be of interest too to know the blood-groups of those individuals, whether atopic subjects or not, who develop generalised vaccinia. I would be grateful if any of your readers could let me have the following details of any case under his care: age, sex, whether the vaccination was primary or not, diagnosis
(eczema vaccinatum or generalised vaccinia or both), whether the skin eruption was present at the time of exposure to the virus and, if not, how long had the skin been clear, blood-group, and outcome. Hospital for Sick Children, Great Ormond Street, London, W.C.1.
MENTAL DISORDERS AND EXTERNAL STRESS
SIR,-In his letter of March 31, Dr. Neville rightly criticised Dr. Atkins (March 17) for treating so lightly the fear of nuclear annihilation as a possible factor in the aetiology of mental illness. I think Dr. Atkins is also wrong in referring to this fear as a " new stress ", since the fear of annihilation has presented itself under different guises to every generation. At the present day, this fear has assumed far greater dimensions with the development of nuclear weapons. The possibility of killing on such a vast scale has, in my opinion, disrupted man’s conventional attitudes towards death; and Freud’s thoughts on the impact of warfare on the community would, therefore, seem relevant in this context.
In a paper2 first published in 1915, Freud described " the bewilderment and the paralysis of energies " felt by noncombatants in the 1914-18 war, a state which he attributed to a general feeling of disillusionment with civilisation and an altered attitude towards death that the war had imposed. Freud claimed that the conventionally civilised man sought to avoid the whole issue of death both in himself and in others, whether friend or foe, and he always laid stress on the fortuitous nature of the whole event. In this way, man endeavoured " to modify the significance of death from a necessity to an accident". According to Freud, the attitude of our unconscious, however, was totally different, in that, like primitive man, it does not believe in its own death; it behaves as if immortal", whilst readily acknowledging and desiring the death of an enemy. Freud believed that war swept away the conventional attitudes towards death, exposing the primitive and unconscious feelings but substituting no positive alternative in men’s minds. "
1. Zbl. Bakt. 1960, 179, 433. 2. Freud, S. Thoughts for the Times
War and Death. 1915.
Surely, such a conflict could not but have repercussions and be a contributory factor in the rising incidence of neurotic illness at the present day ? North Wales Hospital,
SIR,-In general it is often hard to decide which method is most suited for routine use in a clinical laboratory, and we believe that the choice will mostly depend in the first place on personal experience and background of the various laboratories. Apart from this, we should like to comment on the letters of Dr. Blanchaer (Jan. 20) and Dr. Latner and Mr. Skillen (Feb. 3) concerning the methods of separating isoenzymes. In our opinion starch-gel electrophoresis is an excellent research procedure, and in many investigations agar-gel electrophoresis can perhaps not replace this technique. Latner states that some isoenzymes, such as those of alkaline phosphatase, apparently require the molecular sieve effect of starchgel for their separation. In this respect it must, however, be mentioned that glutamate dehydrogenase on the contrary cannot be separated in starch-gel 1 though this is without difficulty in agar-gel. In this way both methods are complementing each other. Furthermore it seems from the discussion that the various methods of demonstrating L.D.H. activity using agar-gel electrophoresis as separating technique 3-6 can lead to different conclusions. So Blanchaer 4 did not succeed in demonstrating glucose-6-phosphate dehydrogenase isoenzymes in agar-gel; but good results are obtained by the method of van der Helm.’ On the other hand, we can agree with Blanchaer that the agar-gel technique according. to Wieme is a very practical method of separating L.D.H. isoenzymes. The resolution of the different fractions is excellent, and albumin has no influence on the so-called fraction L.D.5 (heart fraction, in our nomenclature L.D.I). Moreover, we have no reason to believe that the tetrazolium staining technique on starch-gel gives better results than on agar-gel. The sensitivity is first of all dependent on the quality of the tetrazolium salt used. Some preparations of nitro-B.T. do not give any colour at all, but with a good quality and the slightly modified procedure of van der Helm, we are now able to demonstrate five L.D.H. bands in every normal as well as pathological serum. An example is shown in the accompanying figure, and it is apparent that these results are in no way inferior to the patterns illustrated by Latner.
L.D.H. pattern (in duplicate) of patient with myocardial infarction (L.D.l and L.D.2 greatly elevated) and simultaneous liver damage (L.D.5 increased as well) during shock. S.G.O.T. 140 E. S.G.P.T. 150 E. L.D.H. 1420 E.
Finally, to illustrate the relative ease of the method of van der Helm (staining with nitro-B.T. instead of M.T.T. as mentioned in Latner’s preliminary communication) we should like to give some figures concerning the application of this method in a general hospital with a busy routine clinical laboratory. About 1500 L.H.D.-isozymograms of serum, urine, cerebrospinal fluid, and other body fluids, together with several tissue homogenates, were made in the past six months. Sera from all kinds of patients, including 75 with myocardial infarction, were investigated. 4 specimens were run simultaneously, 2 on each of two agar slides; but, if so desired, 1. Markert, C. L., Møller, F. Proc. Nat. Acad. Sci. 1959, 2. van der Helm, H. J. Neurochem. (in the press). 3. Wieme, R. J. Clin. chim. acta, 1959, 4, 46. 4. Blanchaer, M. C. ibid. 1961, 6, 272. 5. van der Helm, H. J. Lancet, 1961, ii, 108. 6. van der Helm, H. J. Clin. chim. acta, 1962, 7, 124. 7. van der Helm, H. J. Personal communication.
863 this number can without difficulty be extended to, say, 9 (3 on each of three slides) with exactly the same apparatus and in the same time. During a morning it is thus possible to investigate more than 60" samples. From the viewpoint of economy, needed for the incubation is the amount of substrate chemicals used (D.P.N. of the because expensive important, and tetrazolium salt). In our hands, the cost in this respect is less than 6d. per estimation. When dry, the isozymograms can be kept indefinitely, they can be projected as lantern slides, and they are ideally suited for scanning. Apart from the question of true quantitativeness, results can thus be expressed in reproducible figures. For this purpose we now have in use a Beckman Spinco Analytrol with micro-attachment, which automatically plots and integrates the patterns. It is our opinion that agar-gel electrophoresis is superior to starch-gel electrophoresis for separating L.D.H. isoenzymes in a routine clinical laboratory, the more so since this method of electrophoresis is already the method of choice in many laboratories in Europe for separating
conjugated catecholamines, Department of Cardiology, Royal Infirmary, Edinburgh. Department of Medicine, Loma Linda University, Los Angeles, U.S.A.
proteins and for immunoelectrophoresis. Clinical Chemical Laboratory, St. Elisabeth’s Hospital, Haarlem, Holland.
IN GENERAL PRACTICE
SlR,—To live in and attend the practice of a hospital, supporting a good local postgraduate teaching centre, for a week or two would be well worth while for any general practitioner. I believe, therefore, that these projected centres should have suitable hostels. Dr. Levitt (April 7) rightly stresses the value of informal contacts in postgraduate education; and they are far more likely to be made when living in. Anyway to spend a short period in a student atmosphere again is a uniquely stimulating experience. Moreover, visits from postgraduates from far and wide would prevent a local postgraduate centre from becoming parochial.
S. H. p S. F. HOWARD. ITOWARD.
ADRENAL MEDULLARY SECRETION IN HYPERTHYROIDISM
SIR,-Dr. Harrisonand Dr. Durlachhave drawn attention to the problem of adrenal medullary function in hyperthyroidism, and Dr. Durlach has suggested that the thyroid and adrenal medulla may be mutually antagonistic. We have recently studied this problem in man by insulintolerance/adrenaline-excretion tests.3 In this test, one-hour specimens of urine are collected two hours after intravenous insulin, and the adrenaline excretion estimated by a fluorometric method. It was found that if the level of circulating thyroid hormone was increased above normal by administration of dessicated thyroid, lxvo-thyroxine or dextro-thyroxine, the adrenaline excretion following insulin hypoglycxmia resembled that reported by others in adrenalectomised patients.4 In untreated hypothyroid patients, the excretion of adrenaline following insulin was significantly reduced, but the pattern of excretion resembled that in normal individuals and was quite unlike that in adrenalectomised patients. Further, the low adrenaline excretion in hypothyroid patients could be corrected by thyroxine. These studies suggest, therefore, that high concentrations of thyroid hormone may block the release of adrenaline from the adrenal medulla, while low concentrations may cause a simple depression of adrenal medullary function. This study did not take into account possible changes in the excretion of
before, and for
1. Harnson, T. S. Lancet, 1961, ii, 1311. 2. Durlach, J. ibid. April 7, 1962, p. 747. 3. Leak, D., Brunjes, S., Johns, V. J., Starr, P. (in preparation). 4. Von Euler, U. S., Ikkos, D., Luft, R. Acta endocr., Copenhagen, 1961,
DAVID LEAK. SHANNON
pH: A SIMPLER DEFINITION SIR,-While accepting Dr. Moran Campbell’s strictures
pH, may I make another comment, for the benefit of any stubborn enough to go on using it ?
log of the reciprocal of the is sometimes described to hydrogen-ion concentration ", students as " the log of the hydrogen-ion concentration with the minus sign omitted ". This version is false unless the pH happens to be a whole number, for it neglects the fact that in the log of a number less than one, only the characteristic (the part to the left of the decimal point) is negative, the mantissa being always positive. In an N/5 solution of HCL for example, the hydrogen-ion concentration is 0-2 g. per litre. 0-7. The pH therefore = -log 0-2 = -(1-3) = +1-0-3 If we simply removed the minus sign from the log of [H]+, we should arrive at 1-3, which is incorrect. A simpler name for " the reciprocal of the hydrogen-ion concentration " is " the number of litres which contain 1 gramme of hydrogen-ions ". It is therefore suggested that a definition of pH altogether easier to grasp and to teach is pH is the log of the number of litres of a solution which contain 1 gramme of hydrogen-ions ". as
H. A. ZONDAG.
and this is
SIR,-Your annotation of March 31 illustrates the complete confusion of modern orthopaedic teaching on this subject. I wish that those who share your views would obtain a baby with feet like those illustrated and take a good look at it. They will notice that: (1) Though you call the deformity equinovarus, the toes pointing upwards in calcaneus. (2) The outer sides of the feet correspond exactly to the concavity of the uterine wall. (3) The skin over them is thinned and adherent. (4) The peroneal muscles are almost entirely paralysed, as
would occur if there had been pressure on the outer side of the leg. (5) The deformity on one side is greater than that on the other, suggesting that the worse foot has had more pressure on it, as if it had been the outer one in a crosslegged malposition. If they cannot see this now, it will become abundantly obvious when they treat the case. (6) The abduction of the hips is greater than usual, and consequently congenital dislocation of the hip is unknown with feet of this kind. The converse-that congenital dislocation is very common in association with valgus mouldings of the feet -has been noticed, but not explained. These observations may tempt them to question the present ban by orthopaedic surgeons on the study of the mechanical conditions in which the baby has spent the previous nine months. If they dare to trespass into the obstetricians’ domain, they will find that there is a perfectly simple explanation for the various mouldings of the feet (" talipes " is a term that is never defined), for congenital dislocation of the hip, for " idiopathic " scoliosis, and for the distinct conditions of two-limbed and four-limbed arthrogryposis. If, finally, they should be tempted to investigate the results that can be obtained by what I call controlled movement, I shall be happy to demonstrate them. DENIS BROWNE. London, W.1.