Questionnaire survey of the drift mines of the British Isles revealed that the presence or absence of rat infestations could be related to the size of the mine in terms of manpower, large mines being more commonly infested than small ones. In addition, various features of drift mines and their surroundings, i.e. the presence of urban areas, nearby rat concentration points, canteen and surface stables, horses, the absence of buildings and the type of surface sanitation are all related to infestation. Field survey has shown that the extent of dilapidation and piling of waste material assists infestation. It has also indicated that the greater infestation of pits with large numbers of workmen is due to some extent to the extra cover provided by the greater number of surface buildings, these being few or lacking altogether in small pits.

At a mine at which changes in the rat population were studied it was seen that unsuccessful poisoning could leave a breeding nucleus of rats, but that there could also be a speedy re-invasion even after successful poison treatments. Whilst the surface rat population in the buildings of this mine was controlled there were no underground infestations. It appears, therefore, that regular inspection and control of surface infestations should in most cases prevent underground infestation.

This work was carried out under a research grant from Safety in Mines Research Establishment, Ministry of Power, and I am indebted to the Ministry for permission to publish the results. I should like to express my gratitude to the several members of the staff of the Safety in Mines Research Establishment, Sheffield, for the help they gave, in particular Mr C. S. W. Grice. I should like also to thank Prof. L. E. S. Eastham in whose department the work was carried out, Dr E. T. B. Francis who supervised it, Miss B. B. Jones of the Ministry of Agriculture, Fisheries and Food, and the many employees of the National Coal Board who assisted at various times.

An investigation of Salm. saint-paul infection in England and Wales in 1959 is described. In one-third of the human incidents the infection was attributed to home-produced meat coming from two infected abattoirs.

Animal infection was demonstrated and was probably due to contaminated imported animal feedingstuffs.

The clinical histories of 55 of the 89 cases reported during the year were studied. There was one death. In ten patients the illness commenced with fever and malaise and diarrhoea was absent or did not occur until 24–48 hr. later. One patient developed meningitis and another an abdominal abscess.

A village epidemic of brucellosis, due to Brucella melitensis, contracted from infected sheep and goats owned by the vifiagers is described. Of the 309 inhabitants eighty-four became infected and seventy-nine were clinically ill with brucellosis. The investigation covered 232 of the total population and nearly all those not examined belonged to the age group, 0–5 years, not directly exposed to infection by contact with diseased animals.

The population of the village was made up of forty-six families, only nine of which escaped infection. In the affected families, the incidence varied from one to seven in each case. The size of the family varied from three to eleven but there was no correlation between the size of the family and the number contracting brucellosis, neither did sex play any part in the incidence. All age groups were susceptible but the morbidity increased with age and this was correlated with increased risk of exposure to infection of the older age groups.

There was considerable variation in the severity of the clinical illness but there were no fatiities and all patients responded to antibiotic therapy.

Brucella melitensis was isolated from twenty-eight of the thirty-six patients subjected to blood culture and specific agglutinins at an acceptable level were demonstrated in all but three of those with a clinical illness.

The number of persons without evidence of clinical brucellosis who possessed significant brucella agglutinins was very small and the assumption that in an endemic area the number of infected persons is much greater than the number clinically ill was not borne out in the outbreak described here.

Persistence of specific agglutinins up to 2 years after recovery from the clinical illness is recorded.

We wish to pay tribute to the late Professor J. Gurevitch for his constant interest and helpful advice.

Thanks are due to Prof. M. Ruiz Castaneda for providing us with the Castaneda bottles for blood culture work, to Dr E. Neeman of the Government Brucella Reference Laboratory for supplying the Standard Brucella Antigen and for examining the strains of Brucella isolated, and to Colonel H. J. Bensted for his interest and help in preparing the paper. Finally, we are indebted to Mrs Aliza Abut Kayner, social worker in the village health centre, for her valuable help in gathering statistical data.

Either triplicate or paired sewer swabs put down at sixty manholes were examined after 24, 48 or 72 hr. periods of enrichment at 37° C. in a standard tetrathionate medium (medium C) and in two new tetrathionate modifications—medium A being a combination of tetrathionate broth and ingredients of Wilson and Blair's medium, and medium B similar but containing only half the amount of the Wilson and Blair's ingredients, and in addition 1% sodium lauryl sulphate.

Salmonellae were isolated from thirty-nine sites: there were three double isolations of salmonellae.

The richest growths of salinonellae were obtained from medium B and the poorest from medium C. Medium C however yielded more isolations from the smaller sewers than medium B: the converse held true in the trunk sewers.

An optimal 48 hr. enrichment time for sewer swabs was demonstrated in the case of medium A. No optimal time was found for either of the other two media. Platings at the optimal enrichment time from medium A yielded more salmonella isolations than the combined 24 and 48 hr. platings from medium C.

A survey has been made of a sample of children aged 0–5 years in a number of areas in England and Wales for the presence of symptomless excreters of poliomyeitis virus.

The investigation covered a 2-year period from the spring of 1957 to the summer of 1959.

Altogether 28, 797 specimens were examined of which 140 were positive for Type 1 virus, 24 for Type 2, and 44 for Type 3, the corresponding rates being 4·85, 0·83, and 1·53 per 1000 specimens respectively.

It is estimated that for every notified case of poliomyelitis there were about 140 symptoinless excreters of Type 1 virus. No accurate estimates of this ratio were possible for the other two types, but it was certainly much higher.

The incidence of positive specimens was 15 per 1000 in the first and 2·6 per 1000 in the second year of the survey, but there were considerable local variations.

Type 2 virus was not isolated during the second year. Most specimens were examined for the presence of salmonellae and shigellae which both had a frequency of about 2 per 1000. The salmonellae were mainly S. typhimurium, and all the shigellae were Sh. sonnei.

Some information was obtained on the prevalence of other viruses. Coxsackie B virus was the most commonly isolated and in the second year was commoner than poliomyelitis virus. Its seasonal incidence was roughly the same as that of polio myelitis virus.

Adenoviruses were isolated in about 6 per 1000 specimens and were most common in the winter. ECHO viruses were about half as common as adenoviruses and the maximum incidence was in the autumn.

The limitations of the sampling method used and the problems of analysis of the results are discussed.

The nasal carriage of 407 mothers before, during and after admission to a maternity hospital and that of their babies during and after hospital stay was investigated together with the nasal carriage by the hospital staff.

The nasal carrier rate among mothers admitted to hospital was 38%, 40% of these strains being resistant to penicillin.

The nasal carrier rate among the nursing staff was 38 and 72% of these were resistant to penicillin.

If a population is swabbed only once approximately 25% of the carriers will be missed. Those showing slight carriage were no more likely to be missed than those showing heavy carriage. The concentration of organisms in the nose is evidently varying continuously.

Heavy carriers are no more likely to transmit than light carriers and it is therefore not right to report on the profusion or otherwise of growth if that implies a greater chance of transmission.

The biggest increase in resistance among nursing staff strains occurred in the non-typable group which could be explained by resistance to phage developing concurrent with resistance to antibiotics.

The difference in phage-distribution between patient and staff strains centred in group II which formed 19% of patient strains but only 7% of hospital strains.

The carrier rate was no higher for those with a history of hospital admission within 12 months or without a history of staphylococcal sepsis.

Those giving a history of penicillin therapy had the same resistance rate as those without a history of such therapy.

Observations are reported on the mechanism of transmission of a neurotropic strain of Newcastle disease virus from infected to normal baby chicks. Infection appeared to be mediated mainly by large or very labile air-borne particles. Other factors examined were the time of maximum infectivity of chicks, the effects of duration of contact, of the social habits of the chicks and of the type of cage used to house them.

Results obtained by contact experiments were supported by tests in which settling virus particles were collected in Petri dishes placed at various distances from infected chicks.

The virulence of strains of the three types of poliovirus have been examined by the subcutaneous injection of monkeys. The strains used were the Sabin attenuated Types 1, 2 and 3, Cox attenuated Types 1, 2 and 3, the Brunenders Type 1 partially attenuated strain, MEF-1, Type 2 and Saukett, Type 3.

The results obtained indicated that the subcutaneous route of injection offers a promising method for comparing and characterizing strains of poliovirus.

1. Two methods of injecting monkeys intraspinally are compared.

2. It has been shown that the technique of inserting the needle through the cord and withdrawing it 1–2 mm. before injection (Sabin's technique) gives a less widespread distribution of inoculum than the alternative method of making the injection as soon as the tip of the needle is within the substance of the spinal cord (‘standard technique’).

3. When attenuated Type 3 poliovirus is injected into cynomolgus monkeys by Sabin's technique, the incidence of paralysis and poliomyelitis lesions observed is less than when it is injected by the ‘standard technique’.

4. The relative merits of the two techniques are discussed.

1. Bacterial infection of amoebic hepatic abscess is a relatively uncommon event.

2. Investigations to demonstrate a possible bactericidal effect of liver pus in vitro indicated that small inocula, especially of young cultures, of Sh. sonnei, Staph. pyogenes and an organism of pseudomonas species were rendered sterile. Organisms such as Esch. coli, Saim. typhi, Saim. typhimurium, Sh. boydii and Strep.faecalis showed a drop in viable count during the first few hours of incubation followed by a logarithmic increase. The strain of A. aerogenes, on the other hand, was not decreased in numbers during the first few hours of incubation and showed a prolonged lag phase followed by a logarithmic increase in numbers. Shigella sonnei, Staph. pyogenes, Sh. boydii and Strep. fascalis attained to maximum population densities which were less than those obtained in control broth tubes and less than those of other organisms in liver pus.

3. It is suggested that secondary bacterial infection of amoebic liver abscess is often endogenous in origin, occurring after primary aspiration due to disinte gration of the lining wall of the cavity, allowing the entrance of portal blood containing organisms from the damaged bowel.

A modification of the metabolic inhibition test for titrating poliomyelitis antibody is described. The method depends on the substitution of galactose for glucose in the initial medium to eliminate colour change during the period of virus activity. Neutralization is detected by the addition of glucose at the end of the period, when the usual colour changes associated with this type of test occur. A statistical analysis of the results obtained is given.

This method can also be used for titrating antibodies to other enteric viruses.

Thanks are due to Dr Hélène Mair, Dr D. R. Gamble and Dr A. D. Macrae for strains of enteroviruses, and to Miss Patricia Jerram, for valuable technical assistance in the early days of this work.

1. A study of the various aspects of passive tetanus immunization and combined active and passive immunization in different animal species has been undertaken.

2. The criteria on which conclusions have been based consisted of titration of antitoxin serum levels and mouse and guinea-pig protection tests using a challenge of 20 M.L.D. of tetanus toxin.

3. A study of the rate of elimination of heterologous tetanus antitoxin in normal and sensitized animals showed that the latter eliminated antitoxin more rapidly from circulation after subcutaneous injection but no difference could be detected following intravenous administration. More important is the profound loss of serum antitoxin in both animal groups from the seventh day onwards.

4. The rate of elimination in humans receiving 1500 units of horse antitoxin subcutaneously was approximately the same in normal subjects and those who had been previously exposed to horse serum.

5. The interference of an active primary immune response by the simultaneous injection of antitoxin in rabbits was consistently more marked with fluid toxoid than with adsorbed toxoid. Thus, combined active and passive immunization of persons who have never been actively immunized, is not recommended, especially with fluid toxoid.

6. Administration of adsorbed toxoid 7 days or more after passive immunization with heterologous antitoxin does not interfere with the primary immune response.

7. Comparison of the immunizing potency in rabbits of fluid and adsorbed toxoids showed that the latter was far superior.

8. Homologous antitoxin was demonstrated in man and animals to be immunologically superior to the heterologous type in every respect. It persisted unchanged in a therapeutically active concentration for at least 3 weeks in humans and its protective action in guinea-pigs was at least 100 times greater than heterologous antitoxin. Since homologous antitoxin can be used in low doses it will not interfere with the primary immune response in combined immunization.

9. A recommended prophylactic dose of homologous antitoxin for man would be 200–250 units.

Experiments have been described in which mice were infected by the inhalation of a mono-dispersed aerosol of Salm. typhimurium. The disease so produced was characterized by a specific primary pneumonia. The lethal dose was very much smaller than that required by ingestion, and was approximately equal to the intraperitoneal lethal dose. Possible implications have been discussed.

The authors wish to thank Mr S. Peacock for his invaluable help in the operation of the Henderson apparatus, and Messrs A. V. Lowle and C. M. R. Pitman for technical assistance. We also wish to thank Dr J. S. Paterson for supplying some of the bacterial strains, and for much advice and encouragement.

1. In our hands the assay of a plague vaccine, in terms of its power to protect mice against what was hoped to be a standard challenge, was found to be impracticable.

2. Assay by mouse protection tests in terms of a Standard vaccine was found to be possible, but it proved to be a very time-consuming procedure and demanded the use of an almost prohibitively large number of mice for a sufficient number of replicate tests which are required to offset the variability in the method. Theoretically a single test might be adequate if the numbers of immunized mice were very large, but there are obvious limitations to the numbers of mice that can be included in a single test of this nature.

3. The Ouchterlony plate technique proved to be useful in indicating the antigens present in a particular vaccine, but not on a strictly quantitative basis.

4. The vaccine prepared from the virulent human strain of P. pestis was found to protect mice more efficiently than those prepared from avirulent strains and when the protective potency was expressed in terms of content of antigen and high molecular weight substances the vaccine prepared from the virulent culture was found to be even more potent than the Standard acetone-dried vaccine.

5. The use of formalin as a preservative results in some loss of potency of a vaccine but, provided the strain of P. pestis used for the preparation of the vaccine is highly virulent, this need not be serious and is offset by a number of advantages.

By means of a complement-fixation test of the sera of laboratory rats and mice, the immunological response of these animals to both naturally occurring and induced PPLO infections was determined, and the presence and extent of infection in the animals determined by culture.

PPLO antibodies specific for the infecting strain were demonstrable in rats and mice from which PPLO were isolated.

The amount of serum antibody rises with the extent and severity of the infection. Thus, young rats with PPLO infections confined to the nasopharynx had little or no antibody whereas the oldest rats with consolidated lungs had the highest titres. In mice too, the sera of those with pneumonia had the highest titres.

The comparatively low titres found in rat bronchiectasis together with the failure to isolate PPLO from the spleen and other organs, suggest that the chronic form of the disease remains localized. This is in contrast to infections with rat polyarthritis and related PPLO in which the organisms can be isolated from the lymph nodes and other organs and in which antibody is present in high titre.

In view of the high degree of correlation between the presence of antibodies to PPLO in the blood and the presence of PPLO in the tissue of rats and mice, it is suggested that specific antibody found in man is a significant indicator of PPLO infection.

A tissue culture system using chick embryo cells gave bacteria-free vaccinia virus suspensions of sufficient potency to use as a vaccine. Clinical trials with vaccines prepared by this method gave similar results to those with sheep lymph vaccine.

The number and some characteristics of the colds experienced by office workers in London and Newcastle upon Tyne are described.

Age was the only factor found to be strongly associated with the number of colds experienced by an individual. Female staff suffered only 10–15% more colds than male staff. The presence of children in the household had little or no effect. The daily use of public transport also appears to be unrelated to the number of colds suffered.

We are grateful to the Ministry of Pensions and National Insurance for affording us the facilities necessary for the carrying out of this investigation, and particularly to the staffs of the offices who collaborated with us in providing the records and to the members of the Establishment Department and to the staff representatives for their help in the organization of the study. We are also indebted to the Medical Department of the Ministry for their interest and advice. We also wish to record our gratitude to the Shell Petroleum Company, its officers and staff, and particularly the chief medical officer, for their assistance and collaboration, to the management and staffs of the two other London offices studied and to the nurses, Mrs E. Hodgson, Miss M. Petts, Miss L. Waddell and Mrs E. A. Wilson, who collected the records.

In 1959, 69 cases of aseptic meningitis were admitted to various hospitals in Scotland—all apparently due to a Hitherto unrecognized virus. This agent had the characteristics of an ECHO virus but differed from the 28 ECHO viruses at present recognized. Seventy-five strains of the virus were isolated, and human thyroid and human amnion tissue cultures proved much superior to monkey kidney tissue cultures for its isolation.

1. Some of the biological and physical properties of one member (FES) of an inter-related group of viruses were examined and compared with the Saukett strain of poliovirus Type 3.

2. The accumulated data of particle size, immunological relationship, and host tissue and cell tropism indicates that this is a naturally occurring non-neurotropic strain of poliovirus Type 3. It shows a slight immunological difference from Saukett, and also differs from it in temperature stability.

3. The significance of four different isolations of this agent in a brief period is discussed.

1. Field trials suggest that 3-monthly operations against rats in sewers using either 0·25% sodium fluoracetate or 2% fluoracetamide as a direct poison are more effective than 6-monthly treatments with 2·5% zinc phosphide or 10% arsenious oxide using the pre-baiting method.

2. In six paired trials 2% fluoracetamide gave better results (an apparent 100% clearance in five instances) than 0·25% sodium fluoracetate.

3. There is no evidence, at present, that direct poisoning treatments with 2% fluoracetamide or 0·25% sodium fluoracetate are improved by the addition of mould inhibiting substances to the bait.

The work described above was made possible only by the co-operation of a large number of local authority councils and their staffs, to whom we are therefore much indebted. We wish to thank also, Mr J. D. Riley who gave considerable help during the early stages of the trials.