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ARE VIRUSES ALIVE?

THE LANCET

LONDON: SATURDAY, JULY 3, 1937

When W. M. STANLEY announced two yearsago that he had isolated from Turkish tobacco

plants infected with mosaic disease a crystallineprotein having the characters of the virus, the

majority of virus workers received the news witha certain scepticism. Their doubt did not concernthe facts but their interpretation, for it seemedpossible that the virulence of this crystallinepreparation was due not to the protein but tomosaic virus present as an impurity. STANLEYhimself, who all along has shown commendablecaution in interpreting his findings, clearlyenvisaged this possibility. Since then events havemoved rapidly. His observations have been

repeated and confirmed in this country, BAWDENand his collaborators 1 at Cambridge havingisolated an identical protein from diseased Burleytobacco plants. STANLEY 2 has further obtainedthe same high-molecular-weight protein from

spinach and phlox plants infected with tobaccomosaic virus and BEALE has had similar successwith petunia plants. In every case the crystallineprotein was highly virulent.The fact that the same peculiar crystallisable

protein has been obtained from such divergentspecies of plants as phlox and tobacco and thata solution of this protein has always proved virulentin high dilution, is strong evidence in favour of,STANLEY’S view that this protein is the virus.But there is more. Tobacco mosaic virus has anumber of variants each of which produces symp-toms differing from those that characterise infectionwith the parent strain ; and from Turkish tobaccoplants infected with three of these variants-theyellow, the masked or symptomless, and the single-lesion mosaics—STANLEY 4 and LoRING s haveobtained heavy proteins which, though obviouslyrelated to STANLEY’S original preparation, havecharacteristics, both physical and chemical, thatdistinguish them from it and from one another.Thus when mosaic virus mutates the change isassociated with a change in the protein which thevariant produces in the plant that it infects.And when one adds that STANLEY has been unableto separate the heavy protein from a hypotheticalvirus impurity and that he has also shown thatchange produced in the protein is associated with

1 Bawden, F. C., Pirie, N. W., Bernal, J. D., and Fankuchen, I.,Nature, 1936, 138, 1051.

2 Stanley, W. M., Amer. J. Bot. 1937, 24, 59.3 Beale, H. P. (cited by Stanley) Ibid, 1937, 24, 59.

4 Stanley, W. M., J. biol. Chem. 1937, 117, 325.5 Loring, H. S., and Stanley, W. M., Ibid, p. 755.

a corresponding change in virus activity, it is noteasy to object to his conclusion that this high-molecular protein is the virus. A further advancecomes from the work of BERNAL and FANKUOHEN 6

who have been investigating at Cambridge thestructure of these crystalline proteins by means ofX ray photography and optical methods. Theyconfirm their previous opinion that STANLEY’Scrystals are of a liquid crystal nature ; they findthat though the crystals of different mosaic virusesshow the same intramolecular pattern there are

significant differences in intermolecular patternand they suggest the possibility of classifying theseviruses on the basis of X ray pattern.

It is difficult, then, to escape the conclusionthat these heavy proteins are the virus. Butsince they can be obtained in a crystalline formwithout loss of activity they appear to belong tothe non-living world. How are we to reconcilethis with the ability of viruses to multiply and tocause contagious diseases that spread like diseasesdue to living micro-organisms, and their abilityto give rise to variants ? But can there really beany sharp dividing line between the living and thenon-living ? As one passes downwards in the scaleof living things a point must be reached at whichit is extremely hard to say whether one is dealingwith the animate or inanimate, and it is possiblethat in the no-man’s land between the two worlds

agents will be found, like these viruses, whichpartake of the characters of both. As STANLEY

says, the enormous size of the molecules of thesevirus proteins may allow of sufficient complexityof structure for them to behave in some respectslike living organised beings. How many viruseswill prove eventually to be of the same nature asthese plant viruses it is impossible to predict, butalready evidence is adduced that one at least of theanimal viruses-that of the Shope rabbit papilloma-is a heavy protein. It seems fairly safe to

assume, on the other hand, that the large animalviruses, like the virus of psittacosis and the virusesof the pock diseases, are more highly organisedagents belonging more definitely to the living world.

DENTAL TREATMENT IN LONDON

A HANDBOOK recently issued by the LondonCouncil of Social Service, describing the facilitiesfor dental treatment in the L.C.C. area, is a usefulcontribution to an important aspect of public health.The information was collected by the studentsof the social science department of Bedford

College working under the direction of Mr. HENRYMESS and has been collated and checked by MissANNE TOPLEY. The survey suggests that thoughthe network exists for a scheme of dental treat-ment from early childhood to adult life, it is stilltoo fragmentary and incomplete to have its fullvalue as a means of combating dental disease.Thus there is provision for dental treatment for

6 Bernal, J. D., and Fankuchen, I., Nature, May 29th, 1937,p. 923.

7 Provision for the Dental Needs of the Working Classes inthe London County Council Area. Obtainable from theLondon Council of Social Service, 7, Bayley-street, W.C.1.1937. Pp. 22. 4d.