1. A complement fixation test has been developed to measure the minor antigenic differences which occur between strains of the virus of foot-and-mouth disease of the same immunological type.

2. Strain-specific sera were prepared from each of the virus strains examined and then titrated with each of the antigens.

3. The amounts of complement fixed in each reaction were measured in the region of maximal fixation where the antigen and antibody were present in optimal proportions.

4. Heterologous antigen-antibody reactions were compared with the homologous reaction in each test and expressed as cross-fixation ratios.

5. Pairs of antigens could then be compared by taking the product of their cross-fixation ratios one with the other. The values of cross-fixation product so obtained ranged from 1·0 between identical strains to 0·01 between strains of different immunological type.

6. Strains of virus which exhibit cross-fixation products of 0·5 or more with one another have been classified within subtype groups.

I wish to acknowledge the guidance and encouragement of Dr J. B. Brooksby, Director of the Animal Virus Research Institute, Pirbright, and the technical assistance of Mr E. Scoates.

Infected human thyroid tissue cultures have been found to yield free V-Z virus on ultrasonic disintegration and some virus is also present in the fluid phase of intact tissue cultures, while the yield of virus from infected human amnion cells is very low and no free virus is found in the fluid phase. Thyroid cultures are more susceptible to infection with V-Z virus, and the infected cultures are a better source of complement-fixing antigen, than are amnion cultures.

The lack of free virus in infected amnion tissue cultures cannot be attributed to protection by interferon. It also seems likely that if any infectious virus were released it would be more likely to be adsorbed to normal cells than to be inactivated, but as no secondary foci appear in amnion monolayers we conclude that infective virus is not released into the medium.

It is suggested that the virus in thyroid cells is present in a more complete form than that in amnion cells.

We are grateful to Dr R. M. Rawcliffe of Birkenhead General Hospital and Dr F. Whitwell of Broadgreen Hospital, Liverpool, for arranging the supply of thyroid tissue.

A virus was isolated from fifteen of nineteen children living in an infants' home during an outbreak of diarrhoea. The virus possesses many of the characteristics of the enterovirus group but is serologically distinct from any of the accepted members of this group. It is non-pathogenic for unweaned mice, non-cytopathic in tissue cultures of monkey kidney, but is rapidly cytopathic for tissue-cultured cells of human origin. It is serologically similar to virus Hu 659 isolated by Abrahams in the United States (personal communication).

I should like to thank the Director-General of Public Health and State Psychiatric Services, New South Wales, for permission to publish.

Since the original epizootic of myxomatosis in this country (1953–55) carcasses of rabbits from outbreaks of the disease have been sent regularly to the Central Veterinary Laboratory, Weybridge, but no detailed investigations have been carried out on outbreaks of disease in natural populations in Great Britain since 1954 (Armour & Thompson, 1955). In July 1962 a rabbit was sent from the East Riding of Yorkshire and as a matter of routine this establishment was informed of the outbreak. The population of rabbits concerned was large and occupied an area of approximately 200 acres. The strain of virus causing the outbreak was attenuated and when this was discovered efforts were made to secure samples for as long as the outbreak lasted.

1. The first chronic carrier in western Norway was discovered in 1918. Since then 147 individuals have been found to be chronic carriers, 84 being carriers of S. typhi and 63 of S. paratyphi B.

2. Of the 147 chronic carriers 23 were males and 124 females. Most of the carriers were elderly folk, 96 over the age of 50 and 37 over the age of 70 when their carrier state was discovered. There is a considerable rise in the incidence of gall-stones among women around the age of 50, while a similar rise comes at a higher age in men. This sex difference may be a contributory cause of the larger number of female carriers.

3. Operations were performed on 66 chronic carriers with a view to curing the carrier state. In 2 cases, only cystotomy could be performed because of the state of the gall-bladder. In one of these the carrier state was cured, while it persisted in the other.

4. The gall-bladders of 64 chronic carriers were removed by operation with the following results: 2 died as a result of the operation, 9 remained carriers, and 53 are considered cured. The operation was therefore successful in four-fifths of the cases.

The gall-bladders of 2 individuals who remained carriers were found at operation to be sterile and perfectly normal, without stone formation. Two other individuals who remained carriers have later died, 1½ and 7 years after their operations. In both cases S. paratyphi B was cultivated from the common bile duct and the hepatic duct. The specific process may therefore in a few cases be situated at a higher level in the bile passages of the liver.

5. The interval between infection and operation varied from 3 months to 50 years. The 2 carriers who had the longest interval are both cured.

6. Indications for operation are given on the basis of the experiences provided by the present material.

Leptospirosis is a zoonosis that causes appreciable ill health and economic loss in North Queensland. Fourteen serotypes of Leptospira were known to infect man in the area, and information on their local distribution and seasonal and occupational incidence had been obtained. The next step in the investigation was to determine the reservoir hosts and estimate their significance.

Wild animals examined comprised 5 monotremes, 643 marsupials, 2355 rodents, 67 bats, 30 birds, 28 reptiles, and 21 toads. Evidence of leptospiral infection was obtained from 223 marsupials, 309 rodents, and 6 fruit-bats. Analysis indicated that the principal maintaining hosts were: Peremeles nasuta—of L. kremastos (and possibly L. mini) in canefields and rain forest.

Isoodon macrourus—of L. broomi, L. mini, and L. kremastos in canefields.

Rattus rattus, R. norvegicus (focal), and Mus musculus (focal)—of L. zanoni in town and canefields.

Rattus sordidus conatus—of L. australis in canefields.

Rattus assimilis—of foci of L. australis, a variant of L. pomona, and probably of L. hyos in rain forests.

Random infections were also encountered, but the maintaining hosts of the other serotypes known to infect man in the area (icterohaemorrhagiae, canicola, bindjei, robinsoni, bratislava, grippotyphosa, medanensis, celledoni) were not determined.

Domestic animals examined included 137 cattle, 54 pigs, 7 sheep, 34 dogs, 31 cats, and a dairy herd in which there was an epizootic of pomona leptospirosis. Again, there was a wide scatter of infection, but, apart from the long-known association of L. pomona and L. hyos with cattle and pigs, there was no evidence of maintaining hosts in this series.

As indicated in the Introduction, the work reported here was part of a planned investigation into the epidemiology of leptospirosis. Some of the early material was collected by Dr M. J. Mackerras, Dr R. L. Doherty, Mrs D. G. Delamoir, and Miss C. J. Ross, who had previously been stationed at the Institute's Field Station, and we are indebted to Mr D. W. Lavers, Mr S. G. Knott, and Mr R. E. Dunham, of the Queensland Department of Agriculture and Stock, for a number of sera from domestic animals. Many of the mammals were identified by Dr W. A. McDougall, of the Queensland Department of Agriculture and Stock, Mr E. le G. Troughton, then of the Australian Museum, Sydney, Mr B. J. Marlow, then of the C.S.I.R.O. Wildlife Section, Canberra, and by Dr J. L. Harrison, Dr M. J. Mackerras, and Mr R. Domrow of the Institute. We are indebted also to Mrs M. Macgregor, Librarian of the Institute, for considerable help with the literature.

Investigations in the Mossman districts of North Queensland showed the maintaining hosts of leptospiral serotype medanensis to be Perameles nasuta and Isoodon macrourus in canefields, secondary woodland and rain forest. Rattus sordidus conatus is the maintaining host of grippotyphosa in canefields. The host range of six serotypes was extended by the cultural studies.

We would like to express our thanks to Dr G. Alberts, superintendent of Mossman District Hospital, for his co-operation, and also to Miss H. MacDonald and Mr A. Wood for technical assistance.

A chemically defined fluid medium—improved formate lactose glutamate—is described of which the cost is less than a quarter that of standard MacConkey broth and which is at least equally suitable for routine bacteriological examination of water. It has actual advantages in that the medium after fermentation is clearer and that, therefore, acid and gas production is more easily seen; moreover more isolations of both coliform bacteria and of Esch. coli are obtained with fewer false positive reactions. Trials with a solid version of the medium suggest that the relative freedom from false positive reactions arises from the failure of the medium to grow Cl. welchii—one of the commonest causes—and enterococci, another suspected participant. In fact, without any inhibitory agent the medium appears to be virtually specific for the coliform group and particularly favours Esch. coli. It remains to be seen whether certain aerobic spore-bearers found from time to time in surface waters may, to some slight extent, interfere with the almost complete specificity so far discovered.

The medium is recommended in place of MacConkey broth and other peptonecontaining media, not only for the prospect of better results, in that suppression of the coliform group does not occur, but also for cheapness and for freedom from the inevitable variability associated with media incorporating peptone and, particularly, bile salt. It is hoped that this medium will shortly become available commercially in dehydrated form at a price still considerably less than that required to make up MacConkey broth from its constituents.

Some labour-saving curtailments in the routine of water examination are also suggested.

It is hoped not only that the fluid medium will supplant MacConkey broth for the dilution method of water analysis but that the solid medium, without material alteration, will also prove suitable for water examination by membrane filtration.

I am deeply grateful to my laboratory staff, particularly Mr J. H. Evans, F.I.M.L.T., and Mr G. H. Lowe, F.I.M.L.T., for undertaking so much of the work when routine work was particularly heavy, and for many valuable suggestions. My thanks in addition are due to Mrs Peggy Johnson and Mrs Marilyn Childs, who made up the medium, and also to the directors of the participating P.H.L.S. laboratories not only for having the work carried out but for helpful comments.

Polyvinyl-pyrrolidone-iodine complex (PVP-I) was shown to have a rapid disinfectant activity in vitro against vegetative bacteria and fungi and against vegetative Trichomonas. The presence of organic matter had a slight delaying effect on the killing time. Bacterial spores survived in PVP-I for 17 hr. and fungal spores for 1½ hr. Used as an agent for pre-operative preparation of the skin, PVP-I was more efficient than others tested, rendering the skin surface sterile even when heavily contaminated, and keeping it so for 1 hr. None of the staining characteristics of iodine were noted since PVP-I was easily removed by water. Two individuals, known to be iodine sensitive, developed mild iodism after application of PVP-I.

The authors are indebted to the staff of the hospital for their co-operation; and to Berk Pharmaceuticals Limited for supplies of PVP-I, manufactured by them as Betadine (Povidone-iodine B.P.).

A variety of surfaces was tested for self-disinfecting action against Staph. aureus and Esch. coli at a humidity of 42%. Surfaces which had been treated with disinfectants sometimes reduced the survival when the organisms were applied subsequently in drops of broth, but the reduction was very small unless the surface was able to absorb appreciable amounts of disinfectant and the drop of inoculum spread. When the inoculum was applied dried in cotton dust, only surfaces which evolved formaldehyde showed any activity against the bacteria. These surfaces also reduced the survival of bacteria in liquid inocula.

We would like to record our thanks to Dr O. M. Lidwell for much helpful advice.