1. Seventy-four urease negative and twelve urease weakly positive strains were studied which, according to their biochemical properties, had to be considered as belonging to the Providence group. Thirty Proteus rettgeri and five anaerogenic Proteus species were examined concomitantly.

2. 668 strains of Enterobacteriaceae were tested for the P.P.A. reaction, of which only the 192 Proteus and the 86 Providence strains rapidly transformed phenylalanine into phenylpyruvic acid.

3. P.P.A. test, IMViC reactions, fermentation properties, smell, swarming are similar to those of the Proteus group, particularly P. rettgeri; it is therefore suggested that the Providence strains should be incorporated in the Proteus group.

4. For all purposes the P.P.A. reaction appears to be better suited than the urea test for differentiating strains of Enterobacteriaceae from the Proteus-Providence group.

The authors are grateful to Dr C. A. Stuart, Brown University, Providence, and Dr M. Greenstein, Sewage Disposal Works, Providence; to Dr W. H. Ewing, Communicable Disease Center, Chamblee, Georgia; to Prof. L. Olitzki, Hebrew University, Jerusalem; to Dr R. Mushin, University of Melbourne, Australia. We are especially indebted to Miss E. Salomon and Miss A. Engel for their valuable technical assistance.

Experiments on immunity produced by vaccine were carried out in mice with two strains of salmonella.

Against intraperitoneal challenge protection was such that 40–80 % of vaccinated mice survived a dose that killed almost all controls. This level of immunity appeared to be maintained with little change for at least 5–7 months. An explanation for this stability is suggested.

Against infection by the natural route, either by direct feeding or by exposure to infected animals, protection from vaccine was of a comparatively low order.

Resistance to infection by an artificial route was, therefore, not a measure of resistance to infection by the natural route.

The mortality patterns obtained with S. dublin injected intraperitoneally in both control and immunized mice could be described fairly well by curves of a simple Poisson type, based upon the assumption that the receipt of one or more organisms of a type capable of growing in the host resulted in death, and that both vaccination and passive protection simply reduced the proportion of this type.

A report is made of a total of 438 simultaneous blood serum and milk ring tests, and an attempt made to evaluate the milk ring test as a diagnostic aid in individual animals.

The ring test has been used to test the bulk milk from some 370 herds providing the greater part of the raw milk supply for Edinburgh.

The incidence of viable Br. abortus in raw milk samples taken in the Edinburgh area has been studied together with the ring test reaction of such samples.

The survey has shown that:

(1) The ring test is correct in some 93 % of cases in detecting cows whose blood serum will be found positive to the brucella agglutination test.

(2) The ring test, if carefully carried out, is a simple time-saving and accurate screening test for detecting herds possibly infected with brucella.

(3) A high proportion of herd milks (53 %) giving a positive reaction to the ring test is disclosed, and the probable effect of vaccination with strain 19 in giving rise to this figure is noted.

(4) The relatively high incidence (at least 10·5%) of Br. abortus in Edinburgh milk supplies is noted.

Thanks are tendered to Dr Bruhn of the Veterinary School, and Dr Bendtsen, Veterinary State Serum Institute, both of Copenhagen and to Dr Stableforth of the Ministry of Agriculture and Fisheries Laboratory at Weybridge, for providing samples of stained antigen. Thanks are also due to the Bacteriology Department, Edinburgh University, for providing material from guinea-pigs and for relevant information; to J. Norval, Esq., M.R.C.V.S., for permission to obtain samples from the slaughterhouse, and also to the dairies and farmers who granted facilities for taking samples and to Miss Elma Chapman for assistance in the laboratory studies and in taking samples.

1. By the dye test, toxoplasma antibodies in titres of 1/4 or more, were found in the sera of 25% of a sample of adult population of Sheffield.

2. Significantly higher, when strength as well as number was considered, were the reactions of the sera of veterinary surgeons and abattoir workers.

3. Still higher were the reactions of the sera of those who handled rabbits. Highest of all were those of rabbit trappers.

4. Toxoplasma antibodies active to a titre of 1/40 in the dye test were found in 34% of wild rabbits and, to a titre of 1/160, in 5%.

Thanks are due to the hundreds of volunteers who made the survey possible. The Medical Officers of Health of Sheffield, Leeds and Manchester and the veterinary officers, superintendents of markets and food inspectors in these cities made admirable arrangements, which are gratefully recorded, for the obtaining of specimens. Valuable advice and help in obtaining samples from rabbits were given by officers of the Pests Control Division of the Ministry of Agriculture and Fisheries and by their trappers. Dr Marmion supplied some of the sera from veterinary surgeons. The assistance of the technical staff of the Bacteriology Department, University of Sheffield, is gratefully acknowledged. The work was assisted by a grant to C.P.B. from the Medical Research Council.

An account is given of experiments designed to study the spread of myxomatosis in populations of rabbits living under natural conditions on a number of sites in the Eastern Riverine Plain of south-eastern Australia. In five different trials the disease spread from inoculated rabbits, but failed to gain momentum and died down within a few weeks of its introduction.

In December 1950, when the disease was persisting at low incidence on one test site and seemed to have died out in the others, an epizootic broke out in the neighbourhood which spread, in a few months, over the greater part of south-eastern Australia. The only factor, apart from climatic ones, which could account for this sudden change in the activity of the disease was the development of large populations of two rabbit-feeding mosquitoes, Anopheles annulipes and Culex annulirostris. A close correlation was demonstrated, on the flats bordering the Murray River, between the distribution of these insects and myxomatosis activity.

The author is indebted to Mr F. N. Ratcliffe, officer-in-charge, Mr J. le G. Brereton, Mr J. Calaby, and Dr R. Mykytowycz, all of the Wildlife Survey Section, Commonwealth Scientific and Industrial Research Organization, for assistance given during the course of the work and to Mr Ratcliffe, and Prof. F. Fenner of the Australian National University, for guidance in the presentation of the results.

1. The production of weaned young from pairs or groups of three, four and five mice, each containing one male, has been compared.

2. For long-term large-scale production, small breeding groups of one male with two females are proposed.

I should like to thank Dr A. S. Parkes, F.R.S., for much helpful criticism, and Dr Walter Perry for the statistical tests.

Salmonella typhi or S. paratyphi B were found in very large numbers in the faeces of enteric carriers. Of twenty-four carriers, four were found negative by the fullest examination. Of the twenty found positive almost all harboured many millions of bacilli per gram of faeces.

A minute inoculum of one drop (1/50 ml.) of a 1:1000 dilution of faeces on a culture plate only rarely failed to reveal all the positives without the use of an ‘enrichment’ medium and the result of such a procedure was a culture plate with virtually a pure culture of the pathogen.

I am grateful to the Medical Superintendents of the Mental Hospitals at Cardiff, Bridgend and Denbigh, and the Medical Officer of Health for Brecon for submitting specimens for examination.

Bacteriological surveys of beach pollution were made at a seaside resort before and after the installation of a new sewer outfall.

The presumptive coliform count on samples of sea water was found to be a satisfactory index of contamination, and showed good agreement with sanitary survey and with the results of float-test observations. The faecal coli count was in general constantly related to the results of the presumptive test, but there was some indication that coliform bacilli of the I.A.C. groups persisted or multiplied in the sand around the outfall.

The degree of contamination of the sea water at a given sampling point was shown to depend not only on its distance from the outfall but on various meteorological and tidal factors.

For bacteriological surveys of beach pollution, it is suggested that a large series of tests by a relatively simple technique is preferable to a more limited investigation by more complex methods.

The possibility of laying down bacteriological standards for bathing beaches is discussed. An upper permitted limit of the order of 1000 coliform organisms per 100 ml. would discriminate between areas on the beach investigated which were unsatisfactory by sanitary survey before and after the installation of the new sewerage scheme, and those parts of the beach which were apparently not subject to serious pollution with sewage.

I am greatly indebted to Lt.-Col. J. M. Linton Bogle, consulting engineer responsible for the sewerage scheme described, for his interest in and practical help with this investigation; to members of the staff of the local authority concerned for help with sampling, and to Dr A. F. Ollerenshaw and Mr A. Partridge, who were in local charge of the temporary laboratory where the presumptive tests were carried out, in 1950 and 1948 respectively.

A technique is presented for the titration of the virus of foot-and-mouth disease in culture in surviving epithelial tissue from the tongues of cattle. The cultures are incubated in cups on Perspex plates, and the detection of virus multiplication is by a complement-fixation test made on the culture in each cup.

On the basis of comparative titrations in culture and in cattle, the method has been found to be as sensitive for the detection of virus as the titration by intradermal inoculation of the tongue of cattle. The method can also be applied in the detection of antibody in neutralization tests.

We wish to record our thanks to Messrs E. Scoates and P. Mitchell for their technical assistance, and to Messrs H. M. Smith, R. H. Compton and R. L. Jackson for their part in the design and fabrication of various bottle rotators, plate shakers, Perspex lids and the inoculating box.

1. T Vi-coated rabbit erythrocytes, when injected into rabbits, stimulate the production of a (pure) Vi antiserum.

2. The T Vi extract was found to be heat-stable with respect to antigenicity and agglutinability, as shown by means of coated erythrocytes.

3. By means of cross-absorption tests it was shown that the Vi antigen of S. typhi differs from the Vi antigen of the Ballerup organism.

4. The need for caution in relying on resistance to heat as a character of groups of antigens is emphasized.

We wish to thank Dr P. R. Edwards, of the Communicable Disease Centre, U.S.P.H.S., and Dr Alcor S. Browne, California State Department of Health, for supplying certain of the cultures and specimens of typing serum used in these studies.

An account is given of the examination by biochemical and serological methods of 800 strains of brucella sent for identification to the Brucella Reference Laboratory of the Public Health Laboratory Service.

Most of the strains were isolated from milk in Great Britain, but strains from other countries, and from cases of undulant fever, were also examined.

Of 738 strains from milk in Britain, 680 were Br. abortus, of which sixty-two (9·1 %) were of a type inhibited by all the usual test-dyes in their customary concentrations. Thirty strains of Br. melitensis, behaving typically in all laboratory tests, were obtained from milk from individual cows, herds or bulk sources. Br. melitensis has now been identified from twenty-four separate farms and one Tuberculin Tested bulk supply in this country. Eighteen strains behaved like Br. abortus in biochemical tests, but serologically like Br. melitensis.

Of the relatively small number of strains isolated from patients with undulant fever in Britain, all those from persons infected in this country were Br. abortus, with the exception of two laboratory infections with Br. melitensis. The organisms isolated in Britain from patients infected abroad comprised three strains of Br. melitensis, one strain behaving biochemically like Br. abortus and serologically like Br. melitensis, and two behaving biochemically like Br. melitensis and serologically like Br. abortus. One of the latter was from a patient infected in southern Italy, and the examination of nineteen strains from that country showed that thirteen were of this type. The thionin-resistant type of Br. abortus was identified several times, from undulant fever cases in Rhodesia, Kenya and Italy. No strains of Br. suis were observed.

I wish to thank the numerous bacteriologists who sent cultures and provided details of their isolation. A few submitted large numbers of strains and enabled a general picture of the prevailing types to be obtained. I am grateful to these and to the other bacteriologists who provided information about the herds from which Br. melitensis was isolated, in particular Dr P. H. Martin and Dr J. A. Sykes (Ipswich), Dr L. M. Dowsett (Norwich), Dr J. Kennedy (Newcastle, then at Stafford), Dr J. H. C. Walker (Luton), Dr E. H. Gillespie and Dr N. S. Mair (Leicester) and Dr J. E. Jameson (Brighton). I have also to acknowledge the help of Dr A. W. Stableforth, Director of the Ministry of Agriculture and Fisheries Veterinary Laboratory, who provided much bacteriological and veterinary information about the infected herds.

1. When the D.S.P. strain of influenza virus A is grown in eggs into which 100 μc. of radioactive inorganic phosphate has been introduced the virus incorporates 32P into its structure.

2. Some 20–25% of the virus 32P is found in the virus phospholipid; the remainder is combined with the virus protein and is probably present in the virus nucleic acid.

3. When the virus is disintegrated by ether treatment with the liberation of separate red-cell agglutinating and complement-fixing ‘soluble antigen’ particles the non-lipid 32P is found to be associated with the soluble antigen fraction and not with the haemagglutinin.

4. It is suggested that the complement-fixing soluble antigen is a nucleoprotein while the haemagglutinin is a phosphorus-free protein.