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METRIC SYSTEM IN PRACTICE
617 was found in an individual also exhibiting the XXY Klinefelter syndrome. A mother carrying a balanced 22/13 translocation
gave birth to a classical mongol with 47 normal chromosomes and 3 no. 21 chromosomes, and without the maternal translocation. The fact that translocations seem to increase the probability of non-disjunction in other chromosomes invests the discovery of a translocation in an apparently healthy individual with eugenic significance. The diagnostic interest of translocations is mainly dependent on their phenotypic consequences. For example, all the healthy carriers of the different 21/13 varieties with a balanced 45-chromosome genotype have been reported to be normal. The " exceptional 46-chromosome mongols" are phenotypically indistinguishable from classical trisomics. A possible conclusion would be that the loss of satellites does not have harmful effects, because of the low
genic content of these segments. By contrast the two varieties of the 22/13 type seem harmful. In the first case (multiple vertebral dysgenesis) ’vertebral deformities and mental and physical retardation were observed. The second example,8 observed in a mother and in 4 of her children, determined various degrees of speech defect and mental retardation, ranging from very severe in the children to normality in the mother. These intrafamilial variations between carriers of the same variety demonstrate the influence of the rest of the genotype. But the interfamilial variation between different varieties of the same type could be attributed to the extent of change in each variety-i.e., the eliminated fragments could differ. If the effect of position is ignored, at any rate in a preliminary survey, a sample of, say, 20 varieties of the 22/13 type could yield much information about the genic content of the eliminated fragment. For example, if it was observed that 2 characters, which are sometimes independent, are always accompanied by a 3rd, when both are present together, a threepoint linkage map would be obtained; and its spatial relationship to the centromeres could be established. To determine whether the eliminated fragment belonged to no. 22 or to no. 13 would depend upon comparisons between types 22/13 and
centigrammes the usual numeral writing can be used, but it is safer instead of relying on the simple point-usually invisible -to write a zero with a comma after it thus: 0,50 (not -50). Accidents cannot occur with the metric system when care is taken; but the apothecaries’ system leads to many accidents, either through bad design of the symbols or, more frequently, when preparing solutions of powerful drugs and endeavouring to change grains per pint into milligrammes per litre. The metric system is safer. A. P. CAWADIAS. POSITIONING FOR GALLBLADDER SURGERY SIR,-The letter from Mr. Fauset Welsh (Feb. 11) prompts me to suggest an alternative method which has been appreciated by the surgeons with whom I have worked during the past ten years. The method is to place 2 large firm pillows lengthways over the upper two-fifths of the operating-table, one on top of the other, with the"lower a few inches further towards the feet, thus forming a step " which supports the lumbar curve. The unconscious patient on his canvas is then placed supine on the table so that the lower edge of the top pillow lies directly beneath a point about two inches below the xiphisternum. A 3rd pillow is placed under his knees. The table should be tilted foot down about 10° and given a 5° left lateral tilt: this encourages the liver and other abdominal organs to fall away from the thorax towards the left pelvic cavity. The upper pillows open the thoracic outlet without the backbreaking effect of the old-fashioned producing " bridge "; the pillow under the knees is an asset to any intra-abdominal procedure-it produces upward rotation of the pelvis, which besides increasing abdominal relaxation permits the spinal column to rest fully supported, so minimising the postoperative backache " one associates with overstretched spinal ligaments " carrying the can " for curarised spinal supporting muscles. The weight of the patient’s legs is also supported over a wider area, making thrombosis of the calf vein less likely. "
Royal East Sussex Hospital, Hastings.
22/15. The method is limited by the shortness of the analysable fragment. This is due to the harmful effect of autosomal deletions. Some types in which the deleted fragments are genetically quite inactive could very well be transmitted unknowingly in our species. Thus, a possible polymorphism of the karyotype 1 among apparently normal people, even though very rare, cannot be ruled out.
This discussion of cytogenetic mapping of chromosegments would probably have been considered unrealistic a year ago. But with the worldwide expansion of research in cytogenetics, the requisite sample of many varieties of the same type is likely to be obtainable fairly some
soon.
It would be beneficial if authors working in this field gave as much attention to precise phenotypic description as to accurate chromosome analysis. Institut de Progenèse, RAYMOND TURPIN Hôpital Trousseau, Paris, 12e.
JÉRÔME LEJEUNE.
METRIC SYSTEM IN PRACTICE SiR,—The possible error Dr. Dawkins (March 4) mentions, due to shifting the decimal point in the wrong direction when using the metric system, is avoided by following the advice given in many foreign pharmacology books-i.e., writing out in full the dose in milligrammes. Thus not -010 g., but ten milligrammes is written in full on the prescription, and also the words, half, a quarter, &c., are spelt out. This also has the advantage of concentrating the attention of the prescriber on the dosage. When we deal with
W. R. MURPHY.
RADIOACTIVE DRINKING-WATER AND CANCER
SiR,—There has been little comment on the suggested link between " unexpected variations in cancer incidence apparently related to water-supplies "and high radioactivity in West Devon drinking-water.22 Although an " intensive integrated programme of measurements both of radioactivity and trace elements ... with a social survey " is being carried out in West Devon, is there not an urgent necessity to support this work by similar surveys elsewhere-for the following reasons ? (1) The Devon work suggests that natural radioactivity in drinking-water, which has been regarded as very small and negligible " (2% of " natural background 11),3 may be a significant cause of cancer of all types. (2) Some cancer may possibly be prevented by substituting drinking-water of low radioactivity. (3) As a precautionary measure all the appreciably radioactive water-supplies in West Devon have been cut off and replaced by inactive supplies."2 Is this not necessary "
"
elsewhere ? (4) Four of the nine examinations of West Devon reservoir water samples showed high radioactivity. Is water no longer being drunk from these reservoirs ? (5) Devonian geological strata (" old red sandstone "), from which the highly radioactive water comes in West Devon, is widely found in South Devon, Cornwall, Somerset (Exmoor and the Quantocks), a large area of South Wales, the southern 1. Allen-Price, E. D. Lancet, 1960, i, 1235. 2. Abbatt, J. D., Lakey, J. R., Mathias, D. J. ibid. 1960, ii, 1272. 3. Hazards to Man of Nuclear and Allied Radiations. Report to the Medical Research Council. H.M. Stationery Office, 1956.
gave birth to a classical mongol with 47 normal chromosomes and 3 no. 21 chromosomes, and without the maternal translocation. The fact that translocations seem to increase the probability of non-disjunction in other chromosomes invests the discovery of a translocation in an apparently healthy individual with eugenic significance. The diagnostic interest of translocations is mainly dependent on their phenotypic consequences. For example, all the healthy carriers of the different 21/13 varieties with a balanced 45-chromosome genotype have been reported to be normal. The " exceptional 46-chromosome mongols" are phenotypically indistinguishable from classical trisomics. A possible conclusion would be that the loss of satellites does not have harmful effects, because of the low
genic content of these segments. By contrast the two varieties of the 22/13 type seem harmful. In the first case (multiple vertebral dysgenesis) ’vertebral deformities and mental and physical retardation were observed. The second example,8 observed in a mother and in 4 of her children, determined various degrees of speech defect and mental retardation, ranging from very severe in the children to normality in the mother. These intrafamilial variations between carriers of the same variety demonstrate the influence of the rest of the genotype. But the interfamilial variation between different varieties of the same type could be attributed to the extent of change in each variety-i.e., the eliminated fragments could differ. If the effect of position is ignored, at any rate in a preliminary survey, a sample of, say, 20 varieties of the 22/13 type could yield much information about the genic content of the eliminated fragment. For example, if it was observed that 2 characters, which are sometimes independent, are always accompanied by a 3rd, when both are present together, a threepoint linkage map would be obtained; and its spatial relationship to the centromeres could be established. To determine whether the eliminated fragment belonged to no. 22 or to no. 13 would depend upon comparisons between types 22/13 and
centigrammes the usual numeral writing can be used, but it is safer instead of relying on the simple point-usually invisible -to write a zero with a comma after it thus: 0,50 (not -50). Accidents cannot occur with the metric system when care is taken; but the apothecaries’ system leads to many accidents, either through bad design of the symbols or, more frequently, when preparing solutions of powerful drugs and endeavouring to change grains per pint into milligrammes per litre. The metric system is safer. A. P. CAWADIAS. POSITIONING FOR GALLBLADDER SURGERY SIR,-The letter from Mr. Fauset Welsh (Feb. 11) prompts me to suggest an alternative method which has been appreciated by the surgeons with whom I have worked during the past ten years. The method is to place 2 large firm pillows lengthways over the upper two-fifths of the operating-table, one on top of the other, with the"lower a few inches further towards the feet, thus forming a step " which supports the lumbar curve. The unconscious patient on his canvas is then placed supine on the table so that the lower edge of the top pillow lies directly beneath a point about two inches below the xiphisternum. A 3rd pillow is placed under his knees. The table should be tilted foot down about 10° and given a 5° left lateral tilt: this encourages the liver and other abdominal organs to fall away from the thorax towards the left pelvic cavity. The upper pillows open the thoracic outlet without the backbreaking effect of the old-fashioned producing " bridge "; the pillow under the knees is an asset to any intra-abdominal procedure-it produces upward rotation of the pelvis, which besides increasing abdominal relaxation permits the spinal column to rest fully supported, so minimising the postoperative backache " one associates with overstretched spinal ligaments " carrying the can " for curarised spinal supporting muscles. The weight of the patient’s legs is also supported over a wider area, making thrombosis of the calf vein less likely. "
Royal East Sussex Hospital, Hastings.
22/15. The method is limited by the shortness of the analysable fragment. This is due to the harmful effect of autosomal deletions. Some types in which the deleted fragments are genetically quite inactive could very well be transmitted unknowingly in our species. Thus, a possible polymorphism of the karyotype 1 among apparently normal people, even though very rare, cannot be ruled out.
This discussion of cytogenetic mapping of chromosegments would probably have been considered unrealistic a year ago. But with the worldwide expansion of research in cytogenetics, the requisite sample of many varieties of the same type is likely to be obtainable fairly some
soon.
It would be beneficial if authors working in this field gave as much attention to precise phenotypic description as to accurate chromosome analysis. Institut de Progenèse, RAYMOND TURPIN Hôpital Trousseau, Paris, 12e.
JÉRÔME LEJEUNE.
METRIC SYSTEM IN PRACTICE SiR,—The possible error Dr. Dawkins (March 4) mentions, due to shifting the decimal point in the wrong direction when using the metric system, is avoided by following the advice given in many foreign pharmacology books-i.e., writing out in full the dose in milligrammes. Thus not -010 g., but ten milligrammes is written in full on the prescription, and also the words, half, a quarter, &c., are spelt out. This also has the advantage of concentrating the attention of the prescriber on the dosage. When we deal with
W. R. MURPHY.
RADIOACTIVE DRINKING-WATER AND CANCER
SiR,—There has been little comment on the suggested link between " unexpected variations in cancer incidence apparently related to water-supplies "and high radioactivity in West Devon drinking-water.22 Although an " intensive integrated programme of measurements both of radioactivity and trace elements ... with a social survey " is being carried out in West Devon, is there not an urgent necessity to support this work by similar surveys elsewhere-for the following reasons ? (1) The Devon work suggests that natural radioactivity in drinking-water, which has been regarded as very small and negligible " (2% of " natural background 11),3 may be a significant cause of cancer of all types. (2) Some cancer may possibly be prevented by substituting drinking-water of low radioactivity. (3) As a precautionary measure all the appreciably radioactive water-supplies in West Devon have been cut off and replaced by inactive supplies."2 Is this not necessary "
"
elsewhere ? (4) Four of the nine examinations of West Devon reservoir water samples showed high radioactivity. Is water no longer being drunk from these reservoirs ? (5) Devonian geological strata (" old red sandstone "), from which the highly radioactive water comes in West Devon, is widely found in South Devon, Cornwall, Somerset (Exmoor and the Quantocks), a large area of South Wales, the southern 1. Allen-Price, E. D. Lancet, 1960, i, 1235. 2. Abbatt, J. D., Lakey, J. R., Mathias, D. J. ibid. 1960, ii, 1272. 3. Hazards to Man of Nuclear and Allied Radiations. Report to the Medical Research Council. H.M. Stationery Office, 1956.