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more of the patients had extracapsular spread at the timeof diagnosis. They believe that 57% of their control grouphad distant metastases when the primary tumour wasremoved, and, if this was also true of the group treatedwith chemotherapy, then actinomycin D was important inthe reduction of the mortality-rate in this second group.The long survival of some of the patients in this groupsuggested that the metastases were destroyed rather thanmerely suppressed by the drug. Fembach and Martynassume, however, that this drug inhibits only the smalland poorly established metastases, though it is capable ofpreventing new metastases from developing once treatmentis started.

There are good reasons, therefore, for further trial ofactinomycin D under carefully controlled conditions, andwith suitably large doses. Fernbach and Martyn do notrecommend preoperative radiotherapy except perhaps toreduce a very large tumour to a size convenient forremoval. Their data make it clear that invasion of thevessels and infiltration of the capsule can happen at anyage, so age alone is no reason for neglecting radiotherapy ofthe tumour bed.The success of a further trial depends largely on enough

patients being available for treatment and assessment, andthis can be achieved only by the concentration of patientsin a few centres where a consistent plan of treatment canbe ensured by the cooperation of paediatricians, surgeons,pathologists, and hxmatologists. After accidents malignanttumours are the second most important cause of death inchildhood, and the organisation of their treatment on aregional basis, with regional and national facilities, is longoverdue.

MICRO ’66

IN 1866 the London Microscopical Society, established27 years earlier, was granted it Royal Charter. To markits centenary the Royal Microscopical Society last weekheld an international exhibition and conference-" Micro ’66 "-at Imperial College, London. The exhi-bition, opened on Monday by the Duke of Edinburgh,surveyed the microscope " yesterday, today and tomor-row ". The historical section included some fine examplesof late-17th-century instruments made by those " fathersof the microscope " Robert Hooke and Antoni van

Leeuwenhoek. " Today " was largely represented by atrade fair, but the most interesting exhibits were themodels illustrating recent achievements and possiblefuture applications of electron microscopy-direct visual-isation of virus/antibody interaction (an influenza virusparticle, magnified 1,500,000 times, was shown with anti-body molecules attached to its surface spikes); combina-tion with biochemical techniques to reveal details of

collagen structure; and investigations of retinal pathways,which seem to allow sophisticated coding of photoelectricinformation despite apparent structural limitations.The Royal Microscopical Society-the largest and most

influential society of its kind in the world-can look backon 127 years of useful and active life, But centenariesseem to bring new vigour, and the Society is continuallywidening its aims. It now has well over a thousandmembers, mostly in Europe and the United States, and ameeting in Bethesda, Maryland, in 1963, was so successfulthat another American meeting is to be held next month-this time in Chicago. In these days of ever-increasing

specialisation, the Society is providing a useful service forits members with its occasional " survey lectures ", inwhich a subject of wide general interest is reviewed anddiscussed by a recognised authority. One importantactivity of the Royal Microscopical Society has been theintroduction of short courses of instruction in the basic

principles of optical microscopy. These courses havebecome very popular; and-with expensive instruments insome research establishments lying unused for monthssimply through lack of trained personnel ’-they deserveto be more widely known. Commenting on Micro ’66,Dr. J. R. Baker, the Society’s chairman, said he was confi-dent it would make " a positive and long-lasting contri-bution to the development of microscopy throughout theentire world". That is certainly true of the RoyalMicroscopical Society.

OVERDOSES FROM LINEAR ACCELERATOR

ON Feb. 11 this year a fault in the control system of the8 MeV linear accelerator at Hammersmith Hospitalcaused an overdose to be given to three patients undergoingelectron-beam therapy.2 The effects on two of the patientswere severe; in the third case, the effects were slight. Astatement from the committee of inquiry, issued last week,does not say anything more about the condition of thepatients or the illnesses for which they were being treated,but we understand that the two severely affected patientsare still in hospital. The rapidity with which the electronbeam is extinguished after it enters the skin makes it

particularly suitable for the treatment of mycosis fungoidesand skin reticulosis, and it has also been used inexfoliative dermatitis. Large areas of the body can bequickly and uniformly irradiated.3The inquiry into the accident discloses that the

coincidence of two rare events led to the failure of a control

system that had operated without mishap since 1958. Theoutput of the electron gun which feeds the accelerator iscontrolled by varying the current through its filament; butthe variations required are normally very small, and theradiographers are not permitted to alter the filamentcurrent by more than a slight amount-except after a newfilament has been fitted (which is about once a year), whenfor 3 or 4 days a higher current is needed to give the sameoutput from the accelerator. That was the situation onFeb. 11, and unhappily on that day there was also a partialfailure in the dosemeter which monitors the electron beam

emerging from the accelerator. If the failure had beentotal (as it usually is when a dosemeter goes wrong), itwould have been noticed at once. As it was, a transientfault in a capacitor produced a false low reading in thedosemeter, and the radiographers raised the filamentcurrent still further, thus causing the overdoses. Thoughthey knew that a higher current was to be expected, theradiographers were not satisfied and, after treating thethree patients, they called in the engineer and the physicistto test the machine. By then the capacitor had righteditself and the accelerator was working normally, so it wasnot until 3 days later, when two of the patients reportedsimilar symptoms, and the capacitor finally failed, that itbecame clear that overdoses had been given.

Thus, a control system which had been very carefully1. Guardian, April 7, 1966.2. See Lancet, 1966, i, 535.3. Szur, L., Silvester, J. A., Bewley, D. K. ibid. 1962, i, 1373.