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been removed. If we concede that small fragmentsmay have been overlooked, we should still expect con-siderable temporary improvement, as in thyrotoxicosisafter inadequate thyroidectomy.

I suggest that improvement might well be due not tothymectomy, but to the accidental removal of para-thyroids in some patients. This would set up a stateof latent tetany, counteracting the myasthenia. Thefavourable action of large doses of guanidine shows thattetany corrects the myoneural disorder of myasthenia.The well-known anatomical aberrations of the para-thyroids, which may be found in the thymus and atother sites in the mediastinum and at the base of theneck, exposes them to injury or removal in some patientsduring thymectomy.

If this suggestion is correct, the serum calcium shouldbe low in the patients who improve, and within thenormal range when the operation fails. As I am un-likely to have an adequate number of patients to testthis hypothesis, I bring it to the notice of those who’have suitable opportunities. If investigation confirmsmy suggestion deliberate parathyroidectomy shouldobviously supersede thymectomy in the treatment ofmyasthenia gravis.

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Basingstoke. L. P. E. LAURENT.

RELIGIO MEDICI

SiR,—In Dr. Douglas Guthrie’s excellent and informa-tive tercentenary tribute (in your issue of Oct. 9) to theauthor of the first " Religio Medici " there are two pointson which I would like to comment.

Firstly, Dr. Guthrie states that the book was trans-lated into several languages including Italian. It istrue that in a letter to the antiquary, John Aubrey, dated14 March, 1672-3, Sir Thomas Browne stated that he44 write- Religio Medici in English, which was sincetranslated into Latin, French, Italian, High and LowDutch." But up to the present time no contemporaryedition in Italian has ever been seen, and it seems thatBrowne was himself under a misapprehension about this.The statement did not, in fact, become true until the’appearance of Professor Piccoli’s translation in 1931.

Secondly, Dr. Guthrie states that " of the closing yearsof Browne’s life we have little information." Thisappears to me to be the very opposite of the truth. Thelater years of Browne’s life are much more fully docu-mented than any other period by the voluminous andinteresting correspondence which has survived. Most ofthe letters are addressed to his son, Dr. Edward Browne,FRS, and they provide a detailed picture of Brownepursuing his medical practice and scientific interests inNorwich.

London, N.W.3. GEOFFREY KEYNES.

THE SIZE OF INFLUENZA A VIRUS

SiR,-In the kindly notice of my Pelican book Beyondthe Microscope, in your issue of Oct. 2, you stigmatise as" rash " my acceptance as " an established fact ’’ of theAmerican estimate of 15 mft as the diameter of theinfluenza virus particle, against the English estimate of100 lift. May I, as briefly as possible, attempt to justifymy apparent rashness ?

The’two most recent American papers on the size ofthe influenza virus particle are those by Chambers andHenle (J. exp. Med. 1943, 77, 251) and Chambers, Henle,Lauffer and Anderson (Ibid, p. 265) and I quote freelyfrom them. It would, I think, be agreed that thepresence of cell components in a virus preparation castsdoubt on all measurements of virus particle size unlessthe possibility of adsorption of virus on- the largerparticles is eliminated. Now the English work on thesize of influenza virus was carried out on mouse-lungtissue and the American work on mouse-lung tissue andthe extra-embryonic fluids of chicks. The followingare the relevant facts :

1. Both infected and normal mouse lung tissue containparticles of 100 mlt.

2. The infectious unit from tissue suspensions is about100 mit in diameter and is of the same chemical compositionas particles of the same size and abundance separated fromnormal tissue by an identical procedure.

3. Particles 100 my in diameter separated from normallung tissue can adsorb the virus completely from the egg fluid

and thereby acquire the infective property. Moreover theantigenic properties of the particles from infected lungextracts are similar to those of the normal lung particles anddiffer only in the superimposition of the antigenic structureof the virus as it occurs in chick allantoic fluid.

4. Extra-embryonic fluid of chicks infected with the virusof influenza A contained the virus in high concentration, butthe virus frequently could not be sedimented from such fluidby speeds which would remove all virus activity from mouse-lung filtrates. These authors spun a mixture of tobacco-mosaic virus and influenza virus from allantoic fluid andfound that while the tobacco-mosaic virus was almost com-

pletely sedimented under their conditions, about, half theinfluenza virus actively remained in the supernatant.Tobacco-mosaic virus sediments with about the same velocityas a spherical particle of 50 mft of the same density as mostviruses.

5. Ultrasonic vibrations increased the infectivity of lung-tissue sediments by 10-30 fold, thus suggesting that aggre.gates were being broken up by this means.

6. The infectivity of some of Chambers and Henle’s pre.parations was such that if the infective units were 100 min diameter, infection could be obtained with considerably lessthan one particle.

7. Electron micrographs of the isolated virus proteinindicate that the pradominating unit is roughly spherical inshape and has a particle diameter of about 11 met.

It seems to me that this evidence is at least as good asmuch of that which supports the estimates of other virussizes accepted as established facts.

Plant Virus Research Station,Cambridge. KENNETH M. SMITH.

TREATMENT OF BURNS AT FIRST-AID POSTS

SiB,—Would it not be wise to insist on the masking ofall dressers who treat. burns at first-aid posts ? In yourissue of May 29 Leonard Colebrook describes a case fromwhose burn haemolytic streptococci were cultivated fourhours after it was sustained. Masking of all attendantson this case might well have prevented the infection andresultant delay in healing. Recently I had the chanceof hearing of a community of 120 who had nose andthroat swabs taken. No less than 70 of these werecarriers ; all were feeling healthy and carrying out theirroutine duties A burn case attended by one of these 70would probably have been infected. The masking of allnurses attending confinements is no longer an innovation.It is a routine standard to ensure a satisfactory puer-perium.’ No-one need suggest the old bogy of frighten-ing the patient; it just does not exist. In my opinionall first-aiders and all dressers and nurses in the hospitalcasualty departments should automatically mask beforeattending to burns.Smethwick. C. KIRBY.

CHILLED KAOLIN POULTICE

SIR,-From time to time methods of treatment aredescribed which involve the local application of lowtemperatures.1 I would suggest that some attentionshould be paid to the value of the local application ofchilled kaolin poultices, as this preparation will maintaina low temperature over a long period in the same waythat it will maintain a high temperature. The detailsof the method are as follows :

I

I

Kaolin poultice is spread on lint to an even thickness of aquarter of an inch. The exposed surface is covered with alayer of gauze to obviate sticking. Three such " cold poul-tices " are prepared and cut to shape. They are packed inlarge envelopes or flat X-ray film tins and are chilled in adomestic refrigerator. The poultices are applied one at atime, and are held in place by bandage over a thick layer ofcotton-wool. Each is left on until it no longer feels cold ;it is then replaced by a newly chilled one and the discardedone is repacked in its tin or envelope and returned to therefrigerator for re-chilling.

This method is described with some diffidence as

its use is limited to certain definite indications. But Ihave used " cold kaolin " since 1938 and am convincedof its value as a simple and easily available means ofobtaining a local application of low temperature over a1UU tdIUtl.

W. S. PARKER.

1. Ungley, C. C. Lancet, 1943, i, 681 ; Allen, F. M. Ibid, p. 723.