60 of the degree of airway obstruction. Pa02 cannot therefore be used to predict D.L.CO. Moreover, because the alveolar oxygen tension is mainly depen...

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60 of the degree of airway obstruction. Pa02 cannot therefore be used to predict D.L.CO. Moreover, because the alveolar oxygen tension is mainly dependent in these subjects on the alveolar carbon-dioxide tension (which is equivalent to PaC02), and Paco2 also did not correlate with D.L.CO, it is clear that the alveolar-arterial oxygen gradient cannot be used to oredict D.L.CO. K. N. V. PALMER University Department of Medicine, M. L. DIAMENT. Aberdeen AB9 2 ZD. Foresterhill,

failure-rate1 of mechanical means its efficacy is considerable -in addition to the special groups of patients which I have already detailed (June 21, p. 1262). Long-term information which will appear in due course will further confirm the suggestion that the risk of thromboembolism attached to oestrogen-containing preparations may well have been removed with this progestin-only oral contraceptive. Syntex Pharmaceuticals Ltd., G. A. CHRISTIE. Maidenhead.

XYY KARYOTYPE IN MONOZYGOTIC TWINS SIR,-The current interest in the nature of the behaviour disturbances associated with the extra Y chromosome prompts us to report the first case, to our knowledge, of a pair of monozygotic twins concordant for XYY karyotype. These boys of mixed Negro-White ancestry have been followed by us since infancy, both having had febrile convulsions between the ages of 3 and 6 years. One of the twins also had petit-mal seizures; the other had surgical correction of an undescended testicle at the age of 10. During childhood the twins preferred to be with each other rather than their peers and were generally passive, although on occasion they demonstrated physical violence toward other children. At age 14, first one twin and then the other manifested sudden aggressive outbursts, which, in at least one of the twins, were preceded on each occasion by a premonitory abdominal sensation, and followed by relaxation and somnolence. Because of these episodes it was decided to examine their chromosomes. Both twins are now, at the age of 15 years, 73 in. (185 cm.) tall, and in a special class of slow learners. A detailed investigation of the patients and their family is in progress. Department of Medical Genetics, JOHN D. RAINER New York State Psychiatric Institute and LISSY F. JARVIK College of Physicians and Surgeons, SYED ABDULLAH Columbia University, TAKASHI KATO. New York 10032.


*** Dr. Butler and Dr. Hill send the following reply.-

CHLORMADINONE ACETATE AS ORAL CONTRACEPTIVE SIR,-Dr. Butler and Dr. Hill (June 21, 1962) have not answered the crucial question whether they specifically checked by tablet-counting that their patients had indeed taken all their tablets; and they include the statement that method-failure pregnancies became more common with increasing months of use. I have analysed our method and total failure rates, month by month, for up to two years, and find that the method-failure rate does not vary significantly over the entire period, whereas the total-failure rate does increase slightly-suggesting that, as patients become more familiar with the preparation, so their tablet-taking becomes less dependable. Dr. Butler and Dr. Hill inquire whether the women in our worldwide series were of the same ethnic group, stature, and weight as the patients used by the F.P.A., without indicating these details for their own patients. The fact that the trials were carried out in the U.K. does not preclude the possibility of inclusion of patients of other races-thus comparison cannot be given. Certainly in our trials, which include considerable experience in European women, none of these factors influenced the pregnancy-rate. Dr. Butler and Dr. Hill raise the question of women being of proven fertility. In a series of patients, identical to those used in the Mexican contraceptive trials, contraceptive placebos (lactose tablets) were used to establish the incidence of placebo side-effects. The Pearl index (method failure) was 260, proving that these women were truly fertile. The place of chlormadinone acetate in contraception should be as an elegant, more dependable, and safer alternative to mechanical means-and compared with the high

SIR,-Dr. Christie’s questions can be answered briefly. Counting pills-no; daily record of pill-taking and other

consecutively complete-yes; ethnic groups-overwhelmingly Caucasian ; 70% weighed over 120 lb. We hoped Dr. Christie would welcome the suggestion that better results might be obtained by prescribing a larger dose to bigger-built British women. facts

The hard fact is that in our series 13 out of 208 became pregnant in the space of less than 2 years. Council for the Investigation of Fertility Control, London W.1.



DO PREGNANT WOMEN TAKE THEIR IRON? SIR,-Dr. Bonnar and his colleagues2 demonstrated by repeated tests that 32% of 60 pregnant women did not take their iron, and further emphasised the value of testing the stools for therapeutic iron before diagnosing any anxmia of pregnancy as refractory. Our own experience in 1966 was similar. We also used a simple filter-paper technique, but employed the prussian-blue reaction. We found, in random sampling of 483 antenatal patients in hospital and domiciliary practice, that 28% were not taking their iron.3 Kilpatrick labelled the tablets with a marker, and found that only 60-70% of Cardiff schoolgirls took their iron tablets regularly.4 It is unfortunate that Dr. Bonnar and his colleagues ixnplied that this lack of cooperation in women in taking iron had merely been " suspected ", when they quoted previous workers including Kilpatrick and ourselves. The similarity of the results obtained by three groups working in different parts of the British Isles is remarkable. It suggests that any of these simple tests may be helpful in the hxmatological management of iron deficiency. Lambeth and St. Thomas’s London.


London Hospital, E.1.


NATIONAL SOCIETY FOR TRANSPLANT SURGERY Mr. R. E. WESTERMAN (Chairman of the Board of Trustees, The National Society for Transplant Surgery, 11 Alma Road, Cardiff CF2 5BD) writes: " This society was registered as a charity in March, 1968, the principal objectives being the enrolment of voluntary donors to bequeath organs for cadaveric transplantation surgery, the raising of funds for research and facilities in transplant surgery, and the education of potential donors to an awareTo ness of the interdependence of mankind in this sphere. ensure legal clarity and to avoid unnecessary distress each bequest is countersigned by the next of kin. We believe our expanding register of donors to be the largest in the world and wish to make details available to interested transplantationsurgery units. We seek guidance on how best to place our services at the disposal of the medical profession."

Peel, J., Potts, M. Textbook of Contraceptive Practice; p. 47. London, 1969. 2. Bonnar, J., Goldberg, A., Smith, J. A. Lancet, 1969, i, 457. 3. Afifi, A. M., Banwell, G. S., Bennison, R. J., Boothby, K., Griffiths, P. D., Huntsman, R. G., Jenkins, G. C., Lewin Smith, R. G., McIntosh, J., Qayum, A., Ross Russell, I., Whittaker, J. N. Br. med. J. 1966, i, 1021. 4. Kilpatrick, G. S. Proc. R. Soc. Med. 1966, 59, 1220. 1.