TREATMENT OF SCABIES

917 TREATMENT OF SCABIES To the Editor of THE LANCET SiR,-Seeing that Dr. Kingston’s excellent article on this subject in THE LANCET of Oct. 12th confirms the experiments which I myself made about 20 years ago, but failed to publish, I feel that I must now support his findings, and congratulate him on drawing attention to the fact that whereas the " sulphur treatment " has been handed down from one textbook to another as a so-called cure for this condition, this is far from being the case as is so commonly thought. The " cure while you wait system," as used in some hospitals, where the patient is given a sulphur bath, thoroughly scrubbed with a nailbrush and sulphur ointment applied, is I am sure doomed to failure. Much may depend upon the efficiency of the scrubbing and thereby opening up the burrows made by the acarus, but it must not be forgotten that if only one of these escapes (and I am convinced that many more than this must do so), and if only one acarus is left behind under the skin, eggs will be produced at the rate of 2 or 3 a day for 14 days. The acarus may lay as many as 50 eggs. These take 14 days to hatch, so that it would take about six weeks before the last eggs are hatched. This surely is the cause of so many recurrences after so-called immediate cures. My contention is that every case treated should be examined weekly for at least six weeks before one can affirm that a cure has been effected, and yet how seldom is the trouble taken to carry out this routine. In a large hospital, such as a mental hospital, it is practically impossible to eradicate this trouble unless some such routine is adopted. In support of the findings which Dr. Kingston has recorded I would add that I have found the acarus in a burrow after the patient had had the recognised sulphur bath treatment, followed by daily applications of sulphur ointment for 14 days. I have also found the live acarus in the burrow under the skin of a patient who had had the sulphur bath treatment followed by applications of sulphur ointment twice a week for four weeks, and in many cases after shorter periods of similar treatment. Further, in a wax cell on a slide under a cover-slip I found that the acarus would live for 24 hours immersed in water, 48 hours crawling about over sulphur ointment, and as long as seven days in a cell such as described with nothing else in it. I am naturally pleased to see that Dr. Kingston has taken the trouble to make somewhat similar investigations and that his results so closely agree with my own. But surely it is time that medical students were taught that the sulphur bath and ointment, as described in most text-books, is not a cure, and that repeated trials and examinations must be made to prevent the relapse and further spread of this condition, which once left unrecognised and improperly dealt with becomes a source of untold trouble in any large institution. I am, Sir, yours faithfully,

R. EAGER,

Oct. 15th.

Medical Superintendent, The Hospital, Exminster.

GERMICIDAL PROPERTIES OF MERCURY PREPARATIONS To the Editor of THE LANCET SIR,-In the annotation entitled Skin Disinfection in your last issue (p. 838) you refer to the well-known fact that the germicidal properties of mercury preparations as determined. by different methods vary

enormously. We think that the following simple experiments throw a great deal of light on the causes of the discrepancies. When the carbolic-acid coefficient of mercury preparations is determined, a loopful of the bacterial culture, after contact with a known concentration of the mercury compound, is removed after a known interval of time, and is subcultured into a given quantity of nutrient broth. If no growth subsequently occurs in this broth it has been assumed that the bacteria in the treated culture were killed when the loopful was removed. Usually this assumption is correct, but in the case of mercury preparations the assumption is purely fallacious. The refusal to develop is due to the bacteriostatic action of the accompanying mercury salt carried over with the loopful into the broth. If instead of plain nutrient broth, broth containing 0’2 c.cm. of a sterile 5 per cent. solution of sodium sulphide per 5 c.cm. of broth is employed, an entirely different picture of the facts is obtained. The sulphide inactivates the mercury which is carried over, and the supposedly dead germs are found to be alive and unharmed. The differences between the real and the apparent germicidal properties of a few mercury preparations are seen in the following Table :Real carbolicMercury Apparent carbolic acid coefficient. coefficient. preparation. 0’15 800 Mercuric chloride.. 25 Mercuric cyanide.. Less than 0’1 1300 Mercuric iodide 7 N.B.-The mercuric chloride in the strong solutions that were necessary was dissolved with the help of sodium chloride and the mercuric iodide with the help of potassium iodide. The actual coefficient of mercuric cyanide could not be determined because a 10 per cent. solution (which is actually a supersaturated solution at 180 C.) failed to kill the bacteria after 10 minutes’ contact. ....

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We think we can now give a reasonable explanation of the germicidal failures of mercury preparations under clinical conditions. For instance, the Departmental Committee of Maternal Mortality and Morbidity in their final report (1932, p. 113) showed that a 1 in 1000 solution of mercury perchloride did not kill haemolytic streptococci on the hands nor did it prevent reinfection after a time. From the above table it will be seen that mercury perchloride is actually a much weaker germicide than pure carbolic acid, and a 1 in 1000 solution is a very feeble one bactericidally. When such a solution is applied to the skin, the mercury compound tends to combine slowly with the excretions of the sweat glands to form insoluble compounds, and as the bacteria have not been killed they can subsequently be removed in the living condition. It is only when some soluble uncombined mercury compound is removed with the bacteria that fictitious results are obtained. The germicidal ineffectiveness of soluble mercury compounds in the presence of pus and blood is too well known to require special comment. WA

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W. C. REYNOLDS, S. N. H. STOTHART.

Hull, Oct. 15th.

PARIS

(FROM

OUR OWN

CORRESPONDENT)

THE SURGICAL CONGRESS

Francaise de Chirurgie held its congress in Paris from Oct. 7th to 12th, these dates being chosen so that it might coincide with the motor show. In his opening address, Prof. Gaston Michel, of Nancy, courageously faced the dangers threatening the medical profession at the present time, as much from within as from without. He pleaded for scientific probity, and a critical attitude towards " too beautiful statistics " and towards those who THE Association

forty-fourth