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AUDIOVISUAL AIDS IN MEDICAL SCHOOLS
1315 that the corresponding antiBy increasing the number of original genetic determinants (A, B, and C in the table), it is evident that further cross-reactivity may lead to the postulation of a large number of subloci ". For example, with only four alleles, the possible number of subloci is already 14 if extensive cross-reactivity is at work. Nevertheless, only one locus (cistron)
antibodies, provided
we are aware
gens have structures in
common.
"
need be involved.
In the HL-A system there are more than four genetic determinants in each of two segregant series, and, since many of the corresponding antigens are cross-reacting, an "
"
impressive number of subloci may thus be postulated. Again the two series may still correspond to two loci. With these considerations in mind, we find it most likely that the existence of anomalous HL-A antigens in glomeruli merely reflects the presence of cross-reactive isoantibodies in the sera used in the absorption experiments. This is in agreement with the absorption patterns of glomeruli being identical with those observed with spleen lymphocytes. We believe that absorptions with peripheral-blood lymphocytes (or lymph-node lymphocytes) would have shown similar patterns. If this is confirmed, glomerular preparations are not necessary for HL-A typing of cadaver donors. However, we agree with Verrier
Jones and Moore that the extent and significance of cross-reactivity within the HL-A system need further investigation, so that we may eventually find a complete battery of truly monospecific lymphocytotoxic and/or complement-fixing platelet isoantisera which can be used for the typing of transplant donors and recipients. Blood Bank &
Blood-grouping Laboratory, University Hospital of Århus, 8000 Århus C, Denmark.
SIR,-In his account of this device (Dec. 5, p. 1166), Dr. Stoddart suggests that the incomplete saturation of the gas delivered to the patient results from the use of a " cold-water nebuliser " to humidify the oxygen, together with " dilution " with room air. In fact, however, the nebuliser used as a humidifier in the British Oxygen Company (B.O.C.) oxygen set slightly supersaturates the 1 gas passing through it at ambient temperature. This is shown by the fact that it delivers a visible cloud of extremely fine ( < 1 micron) droplets which would evaporate almost instantaneously if the atmosphere surrounding them were not supersaturated. A much more important factor is that, at 28 ° o, the oxygen is not merely diluted but makes up only about 9%of the volume delivered, so that even if fully saturated it can make only a small contribution to the total humidity. Since Dr. Stoddart’s device thus inevitably fails in one of its main objects, and also uses ten to fifteen times more oxygen than is necessary, it is difficult to see its advantages. A much more controllable arrangement would be to deliver air from a compressed-air supply through a flowmeter, and mix dry oxygen with it in the required proportion, using the B.O.C. flow-meter without the nebuliser. The combined flows could then be put through the nebuliser, which could be immersed in a heated water-bath if it were desired to raise the water content of the gas higher than can be obtained at room-temperature. The wet gas will lose comparatively little water in the connecting pipes, because most of the excess will be in the form of a fine aerosol. On the other hand, water carried as vapour in heated air from a hot-water humidifier is, as Dr. Stoddart
Wright, Wright,
B. M. Lancet, 1958, ii, 24. B. M. ibid. 1968, ii, 1392.
I
am
indebted
to
Dr.
J.
F. Nunn for valuable discussions.
Clinical Research Centre, Harrow, Middlesex.
B. M. WRIGHT.
AUDIOVISUAL AIDS IN MEDICAL SCHOOLS
SIR,-Professor Brooke’s commentary (Oct. 17, p. 817) stimulating some interesting letters, and Dr. J. R. F. Ingall (Nov. 21, p. 1087) is so right about " feedback neglect " and the need to improve the student-to-teacher relationship. Most students will applaud his enlightened philosophy, and it is significant that he should support Professor Brooke’s realistic plea " to work within our means and concentrate on audiotape with slides ". One day some Fairy Godmother may well provide the finance to establish (? at Milton Keynss) a National Centre as recommended in chap. x of the Brynmor Jones report. In the meantime, the " factory at Writtle working under the auspices of the Medical Recording Service Foundation is giving an excellent service; but can Mr. Charles Engel please tell us if there is as yet a comprehensive catalogue of the very many splendid 35 mm. slides, with and without is
"
A. SVEJGAARD F. KISSMEYER-NIELSEN.
VENTITUBE FOR PROVIDING OXYGEN-ENRICHED HUMIDIFIED AIR
1. 2.
easily lost by cooling and condensation, unless the connecting tubes are lagged or heated. With the arrangement suggested, a small storage bag, with a non-return valve if rebreathing were contraindicated, would greatly reduce the air and gas requirements, so that the air could be supplied with a portable blower and the oxygen consumption reduced to a reasonable level. As well as giving complete and easy control of oxygen content and humidity, the method would be economical to run and thus suitable for less sophisticated environments than an intensive-therapy unit. notes,
which have been made in our medical schools ? can he say what channels are now available for a clinical tutor to obtain these on loan in the U.K. at a nominal charge ?
audiotapes,
Furthermore,
Harrogate.
STUART MEATCHEM.
CONCEPTIONS OF MEDICAL CARE
SIR,-Professor Rhodes’s admirable article on the conflict between the claims of the individual and those of society (Oct. 24, p. 870) puts the problem in a nutshell. He asks whether we should have individual-based medicine or species-based medicine. anger, and anxiety seem be rife ... in the National Health Service " but new attitudes and the problems which they engender are not peculiar to Great Britain. Professor Rhodes says that those who opt out of the struggle emigrate or turn to hobbies, gardening, and golf. As one who has done all these things, I find myself still involved, willy nilly, in the struggle.
Undoubtedly " Frustrations,
to
Professor Rhodes may have in mind some secret ShangriLa which the rest of us do not know about, but in most of the world the winds of change are blowing at gale force. The shape of medical practice abroad is being moulded by the same socioeconomic factors which bedevil the N.H.S. Emigration may merely deliver the doctor from his native frying-pan into a foreign one, if not into the fire itself. For instance, in the U.S.A. we may well end up with something worse than Britain’s N.H.S. (pace those of your correspondents who think we have it already). If the emigrating doctor is more missionary than capitalist he fares no better by selecting a backward country. Even as recently as twenty years ago a strong character might have been able to carve out a little medical empire in an off-thebeaten-track place like Lambarene or Deschapelles. There
antibodies, provided
we are aware
gens have structures in
common.
"
need be involved.
In the HL-A system there are more than four genetic determinants in each of two segregant series, and, since many of the corresponding antigens are cross-reacting, an "
"
impressive number of subloci may thus be postulated. Again the two series may still correspond to two loci. With these considerations in mind, we find it most likely that the existence of anomalous HL-A antigens in glomeruli merely reflects the presence of cross-reactive isoantibodies in the sera used in the absorption experiments. This is in agreement with the absorption patterns of glomeruli being identical with those observed with spleen lymphocytes. We believe that absorptions with peripheral-blood lymphocytes (or lymph-node lymphocytes) would have shown similar patterns. If this is confirmed, glomerular preparations are not necessary for HL-A typing of cadaver donors. However, we agree with Verrier
Jones and Moore that the extent and significance of cross-reactivity within the HL-A system need further investigation, so that we may eventually find a complete battery of truly monospecific lymphocytotoxic and/or complement-fixing platelet isoantisera which can be used for the typing of transplant donors and recipients. Blood Bank &
Blood-grouping Laboratory, University Hospital of Århus, 8000 Århus C, Denmark.
SIR,-In his account of this device (Dec. 5, p. 1166), Dr. Stoddart suggests that the incomplete saturation of the gas delivered to the patient results from the use of a " cold-water nebuliser " to humidify the oxygen, together with " dilution " with room air. In fact, however, the nebuliser used as a humidifier in the British Oxygen Company (B.O.C.) oxygen set slightly supersaturates the 1 gas passing through it at ambient temperature. This is shown by the fact that it delivers a visible cloud of extremely fine ( < 1 micron) droplets which would evaporate almost instantaneously if the atmosphere surrounding them were not supersaturated. A much more important factor is that, at 28 ° o, the oxygen is not merely diluted but makes up only about 9%of the volume delivered, so that even if fully saturated it can make only a small contribution to the total humidity. Since Dr. Stoddart’s device thus inevitably fails in one of its main objects, and also uses ten to fifteen times more oxygen than is necessary, it is difficult to see its advantages. A much more controllable arrangement would be to deliver air from a compressed-air supply through a flowmeter, and mix dry oxygen with it in the required proportion, using the B.O.C. flow-meter without the nebuliser. The combined flows could then be put through the nebuliser, which could be immersed in a heated water-bath if it were desired to raise the water content of the gas higher than can be obtained at room-temperature. The wet gas will lose comparatively little water in the connecting pipes, because most of the excess will be in the form of a fine aerosol. On the other hand, water carried as vapour in heated air from a hot-water humidifier is, as Dr. Stoddart
Wright, Wright,
B. M. Lancet, 1958, ii, 24. B. M. ibid. 1968, ii, 1392.
I
am
indebted
to
Dr.
J.
F. Nunn for valuable discussions.
Clinical Research Centre, Harrow, Middlesex.
B. M. WRIGHT.
AUDIOVISUAL AIDS IN MEDICAL SCHOOLS
SIR,-Professor Brooke’s commentary (Oct. 17, p. 817) stimulating some interesting letters, and Dr. J. R. F. Ingall (Nov. 21, p. 1087) is so right about " feedback neglect " and the need to improve the student-to-teacher relationship. Most students will applaud his enlightened philosophy, and it is significant that he should support Professor Brooke’s realistic plea " to work within our means and concentrate on audiotape with slides ". One day some Fairy Godmother may well provide the finance to establish (? at Milton Keynss) a National Centre as recommended in chap. x of the Brynmor Jones report. In the meantime, the " factory at Writtle working under the auspices of the Medical Recording Service Foundation is giving an excellent service; but can Mr. Charles Engel please tell us if there is as yet a comprehensive catalogue of the very many splendid 35 mm. slides, with and without is
"
A. SVEJGAARD F. KISSMEYER-NIELSEN.
VENTITUBE FOR PROVIDING OXYGEN-ENRICHED HUMIDIFIED AIR
1. 2.
easily lost by cooling and condensation, unless the connecting tubes are lagged or heated. With the arrangement suggested, a small storage bag, with a non-return valve if rebreathing were contraindicated, would greatly reduce the air and gas requirements, so that the air could be supplied with a portable blower and the oxygen consumption reduced to a reasonable level. As well as giving complete and easy control of oxygen content and humidity, the method would be economical to run and thus suitable for less sophisticated environments than an intensive-therapy unit. notes,
which have been made in our medical schools ? can he say what channels are now available for a clinical tutor to obtain these on loan in the U.K. at a nominal charge ?
audiotapes,
Furthermore,
Harrogate.
STUART MEATCHEM.
CONCEPTIONS OF MEDICAL CARE
SIR,-Professor Rhodes’s admirable article on the conflict between the claims of the individual and those of society (Oct. 24, p. 870) puts the problem in a nutshell. He asks whether we should have individual-based medicine or species-based medicine. anger, and anxiety seem be rife ... in the National Health Service " but new attitudes and the problems which they engender are not peculiar to Great Britain. Professor Rhodes says that those who opt out of the struggle emigrate or turn to hobbies, gardening, and golf. As one who has done all these things, I find myself still involved, willy nilly, in the struggle.
Undoubtedly " Frustrations,
to
Professor Rhodes may have in mind some secret ShangriLa which the rest of us do not know about, but in most of the world the winds of change are blowing at gale force. The shape of medical practice abroad is being moulded by the same socioeconomic factors which bedevil the N.H.S. Emigration may merely deliver the doctor from his native frying-pan into a foreign one, if not into the fire itself. For instance, in the U.S.A. we may well end up with something worse than Britain’s N.H.S. (pace those of your correspondents who think we have it already). If the emigrating doctor is more missionary than capitalist he fares no better by selecting a backward country. Even as recently as twenty years ago a strong character might have been able to carve out a little medical empire in an off-thebeaten-track place like Lambarene or Deschapelles. There