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in vaccinating those who desire to be vaccinated, butby persuading all those with whom his work brings himin contact-and especially the parents or guardians ofunvaccinated children-to have the operation performedwithout delay.As no country can be said to be free from invasion

in the presence of a pandemic disease, legislationshould be possible to prevent the passage of personsfrom one country to another unless freedom from com-municable disease is assured. Such a principle shouldapply particularly to aliens seeking labour in tropicalcountries and the guarantee be required of recentvaccination. Colonel King further draws attention to thenecessity of the British Empire awaking to the importanceof the example in force in the public health service ofAmerica, by placing special officers at the chief foreignports, and elsewhere trusting to consuls, to maintain touchof diseases throughout the world. Professor E. W. Hopein this connexion is quoted as forcibly proclaiming theerror of ignoring the necessity for bringing the pandemicdisease of small-pox within the scope of an internationalconvention. Such a step can alone rouse us from thesense of false security, short of a severe and wide-

spread outbreak for which the increasing number ofunvaccinated persons in this country and elsewhere issmoothing the way.

THE ROYAL SOCIETY CONVERSAZIONE.

WHILE the exhibits at the conversazione of the RoyalSociety, held on Wednesday evening, May 12th, were notso numerous as on pre-war occasions, they were ofconsiderable interest, covering many scientific fields,though medicine was represented in few direct ways.Pure science seems to have held first claim to parade,but the opportunity seems to have been missed of

presenting examples of the fruits of advice given by theSociety to the Government through the war. Nor werethere any illustrations of the advances made by acooperation of university activities with those of thefactory.

Fluorescence, Osmotic Processes, and Synthetics.A very fascinating demonstration was that of

fluorescence in Lepidoptera by ultra-violet radiationby Dr. J. C. Mottram and Dr. E. A. Cockayne. Theseinvestigators employed filtered light from a mercury-vapour lamp, using only radiations of certain wave-lengths. When exposed to these rays and viewed, ofcourse, in the dark, the fluorescence of the wings ofbutterflies and moths was most remarkable, some morebrilliant than others resembling a bright opal matrixunder the most favourable conditions. This curiousanalysis of light (we must remember white light is acomposite of primary colours) can be exhibited to someextent in a solution of the wings of certain species inglacial acetic acid.

Close by, an interesting document was shown: theoriginal letter of Priestley which in 1779 announced thediscovery that plants give off oxygen:Osmosed clay easily enough may have medical

significance. Specimens of this were shown by theOsmosis Company, Ltd. So far the process has beenapplied to the purification and decolorising of chinaclay for the manufacture of paper and clean fire-clays,and the results are of the most encouraging description.The process is based on an electrolytic selective action.The only exhibit illustrating a captured industry was

that of Messrs. J. Crosfield and Sons, Ltd., who showedan attractive series of synthetic products for perfumeryformerly elaborated entirely in foreign countries. Themanufacture was installed owing to the difficulty, insome cases impossibility, of obtaining such productsduring the war.

Bacterial Photog7.ap3a, JJ.Iites, Fleas, and b’itamines.There was an interesting series on view in the Council

Room of photomicrographs obtained by means of ultra-violet light by Mr. J. E. Barnard. An importantadvantage of employing ultra-violet light for thispurpose in microscopical work is that biological pre-

parations, particularly bacteria and other micro.,

organisms, are rendered sufficiently opaque to ultra-violet light of suitable wave-length to render stainingunnecessary. This appears to open up a very promisingfield of investigation, for by this method micro-organismscan be photographed in the living state.Professor R. Newstead exhibited samples of mite-

infested fiour, which illustrates the importance of

preventing mite invasion. When this happens the flouris ruined, and develops a most unpleasant odour andbecomes discaloured owing to the quantities of excre-’ment with which it is charged. A high moisture’content invites invasion.Professor G. H. F. Nuttall and Dr. D. Keilm.,

exhibited microscopic specimens illustrating herm,,aphrodites of inter-sexual type in Pediculus human1ts:: zThe exhibit comprised a complete series of forms fromthose of male type to those of female type, the coexist-ing characters of both sexes being present to a varyingdegree. It is pointed out that the inter-sexual formswhich occur among pediculi in nature are derived fromthe crossing of the races of P. humanus-i.e., capitis andcorporis. Some of these crosses yield up to 20 per cent.of hermaphrodites, and the appearance of hermaphro-dites in a given stock is always accompanied by agreat decrease or almost complete disappearance offemales.Professor E. Mellanby, whose work on the subject is

familiar to our readers through our columns, gavestriking illustrations of the effect of the absence of anaccessory food factor (probably fat-soluble A) in thediet of puppies which developed rickets. The investi-gation by Mrs. Mellanby also demonstrated that dietsdeficient in an accessory food factor, possibly fat-soluble A, produce teeth defectively calcified and moreor less irregularly placed in soft jaws. Referring toteeth, Dr. J. H. Mummery, in a demonstration of thenerve end-cells in the pulp of the human tooth, pointedout that the mode of distribution of sensory nerves inthe pulp of the tooth was not met elsewhere in the

body.Frog 31el,,,,,o,,Thosis, Plant Respira-tton, and Wireless

Telephony.The influence of thyroid feeding on the frog was

instanced in the exhibit of Mr. Julian Huxley andMr. Lancelot T. Hogben. There were examples of

(1) acceleration of a frog’s metamorphosis by thyroidfeeding ; (2) metamorphic changes induced by iodine;and (3) metamorphosis of amblystoma by thyroidfeeding with a control.A quite interesting demonstration of an ingenious

apparatus recording the rate at which air under slightlyreduced pressure is drawn through the pores of a leafwas given under the direction of the Botany Depart-ment of the Imperial College of Science and Technology.This recording porometer gives a measure of the size ofthe pores, which varies for different leaves. It is ofinterest also to mention the system de3cribed by Mr.Edwin Edser of concentrating minerals and coal byfroth flotation. Shortly, this is done by adding waterto the low-grade mineral, which is reduced to a finestate, then forcing a stream of minute bubbles of airthrough the fluid, which brings the valuable material tothe surface, which can be skimmed off. The barrenmaterial, rock or slate, is not floated.Lastly should be mentioned as a modern wonder the

demonstration of wireless telephony given in the

meeting room. The audience here heard plainly inall parts of the room a musical performance beinggiven 30 miles away (Chelmsford). The loud-speakingtelephone had no communication with that placeexcept by the all-pervading ether ; there were no wires,no pipes-in a word, no visible means of transmissionat all.

Sir J. J. Thomson, the President, received a largecompany of distinguished guests.

DONATIONS AND BEQUESTS.-The Chelsea Hospitalfor Women has received a grant of JE400 from the trustees ofthe Zunz Bequest.-The Royal Dental Hospital of Londonhas received a donation of X500 from the trustees ofSmith’s (Kensington Estate) Charity. -