1. A review of the few studies so far made on the high mortality from tuberculosis among elderly men, and a consideration of the available statistics, indicate that urbanization is one of the principal factors responsible.

2. In the present inquiry, which was confined to London, 445 newly diagnosed cases of tuberculosis in men over 40, together with the same number of paired controls, were studied by means of a questionnaire and of personal interview.

3. It was found that the tuberculous patients differed significantly from the controls in the following characteristics; Scots, Irish, Welsh, or foreign nationality; single, widower or divorced; resident in common lodging houses or hostels; inadequate or special diet; history of gastrectomy; a winter cough; shortness of breath; insufficient sleep; and heavy drinking and smoking. On the other hand, overtime or night work, diabetes, rheumatoid arthritis, asthma, and mental illness were distributed fairly evenly in the two groups.

4. Unfortunately no group of elderly women exists in this country living under the same sort of conditions as the elderly men studied here, so that it was impossible to determine how far the various factors considered were responsible for the high rate of late adult male tuberculosis. A study, however, of a population of established civil servants living under ordinary conditions revealed little difference between the observed rates of tuberculosis and those expected on the basis of national notification figures for men and women in the older age groups.

5. It appears that a low standard of personal hygiene, associated especially with heavy smoking and drinking and residence in loading houses, predispose to the development of tuberculosis in the elderly male. Part of the evil effect of living in common lodging houses in particular may be due to the increased risk of exposure to tuberculous infection that it entails.

6. It is tentatively concluded that the casual workers of an urbanized community are one of the principal reservoirs of tuberculous infection in large towns, and since there is no numerically comparable female population, this group, and its immediate male contacts, account in large measure for the difference between the male and female tuberculosis rates in the older age groups.

This work was initiated during the tenure of a Prophit Scholarship of the Royal College of Physicians, and completed with the aid of a grant from the Medical Research Council.

I am indebted to members of the Prophit Committee of the Royal College of Physicians for their support and encouragement, and most particularly to Dr G. S. Wilson, Director of the Public Health Laboratory Service, under whose guidance the work was carried out. Figures relating to the incidence of tuberculosis in the Civil Service are published by kind permission of Dr W. E. Chiesman, Treasury Medical Adviser, and Dr M. C. W. Long, Dr J. W. Parks, and Dr H. Stannus Stannus, whose departmental records were used to compute the figures.

I am greatly indebted to the consultants and staff of the seventeen chest clinics who co-operated in the investigation, for their interest and help in tracing patients, and to the medical superintendents of numerous sanatoria and chest hospitals, and to the surgeons who permitted me to interview patients under their care as controls.

I should like also to acknowledge the assistance received from the medical officers of health of the metropolitan boroughs who kept me informed of notifications from lodging houses in their areas, and supplied information about the accommodation.

Two units, within a mouse-breeding colony, with different breeding systems, have been compared from the point of view of general healthiness of the breeding stock. In one unit the monogamous-pair system, involving post-partum oestrus mating, was employed and in the other the harem system, with isolation of the pregnant females for each litter-down until after the post-partum oestrus. The two units were housed separately and had different staffs. The monogamous-pair unit was accommodated in four small rooms not directly connected; the harem unit in two larger connecting rooms. The methods of cageing, bedding, feeding, watering, care, culling and subsequent procedures were identical for both units and the same system of recording individual detailed information relating to health and breeding was followed for the two units. The size of the two populations studied was 1198 and 1024, respectively, the larger number belonging to the harem unit in which the mice were retained for a significantly longer period. These mice were moved more frequently and handled much more often.

Apart from a small outbreak of Tyzzer's disease (in the harem-bred unit) and sporadic cases in both units spread over the whole period of the survey—some 3–4 years—the general health of the two units was good. There were no cases of salmonella infection, mousepox, pasteurellosis or other serious infections. Throughout the period both units maintained a high standard of productivity and there was no evidence that the mating of the monogamous pairs at the post-partum oestrus led to any weakness or ill health. As would be expected, however, the losses from death and culling were greater among the females in both units.

The health record of the monogamous-pair bred unit was consistently higher than that of the harem-bred unit. There were more cases of Tyzzer's disease in the harem-bred mice and more evidence generally of ill health in this unit. Infertility was three times greater with the harem-bred mice as compared with those in the monogamous-pair unit.

Details of the two systems are discussed and although the records maintained for the two may not be strictly comparable it is concluded that, under the conditions obtaining, the monogamous-pair breeding system yielded a healthier colony of mice than the harem breeding system.

I should like to thank Dr J. S. Patterson and Mr R. Cook for placing many of their records at my disposal, Mr S. Peto and his staff for carrying out much of the tedious compilation of data, and Dr D. W. Henderson, F.R.S., for affording me facilities for this work. To these I am especially grateful for their interest, advice and assistance.

When the manifold system of freeze-drying is used the practice of plugging the tubes containing the product to be dried would seem to be necessary. It should be emphasized that a loose plug implies teased out cotton-wool and not just a loosely fitting one. Virus was recovered from the drying apparatus under various conditions when unplugged tubes were used. No virus contamination could be demonstrated when the tubes were plugged.

A special cabinet was designed to protect the operator, during post-mortem examinations on animals infected with pathogenic organisms, against the risk of enhaling infected material and the surrounding area from becoming contaminated. The cabinet was suitable for small animals including mice and guinea-pigs.

The National Institute for Water Research of the South African Council for Scientific and Industrial Research has been engaged on extensive research into the conservation of water supplies and into the reclamation of industrial and sewage effluents. Within the framework of this programme, a comparative study of the efficiency in the reduction of bacterial numbers by existing conventional sewage treatment plants has been carried out. The numerical decreases in bacterial populations after primary sedimentation, biological filtration, the activated sludge process, secondary sedimentation (humus tank), and final sand filtration have been compared with the reduction in bacterial numbers attained by the treatment of sand-filter effluent, humus tank effluent, and primary biological filter effluent in units for further biological purification.

Various types of units for this purpose have been investigated, and from available results it appears perfectly feasible to consider the suitability of effectively purified sewage effluents as sources for raw water supplies for industrial and domestic use. Sewage effluents after final further biological purification could be admitted for unrestricted discharge into rivers. The possibility of objections from the point of view of public health and future use is completely ruled out by the fact that the quality of the final effluent is as good as that of river water.

A variety of experimental units for further biological purification of sewage effluents have been studied, and a comparison of the results obtained from grass-plots, artificial vleis (a natural vlei in South Africa is a marshy or swampy depression in the ground in which water collects and which supports a standing vegetation), algal beds, artificial model rivers, and maturation or oxidation ponds have shown that maturation ponds, possibly a number of ponds in series, with an established microflora and microfauna of their own, may provide the final solution of the problem. Further biological purification will play an important role in the conservation of water supplies and will contribute to the raw water sources available for industrial and domestic use.

In parallel with these studies, the effect of the discharge of sewage effluents from conventional treatment plants into a river system has been investigated together with the fate of the sewage bacteria after admission to a natural environment. The manifestations of self-purification have been recorded, and the additional or superimposed effect of run-off and drainage from populated and unpopulated areas, as well as the admission of storm-water, have been considered together with the effects of seasonal variations due to climatic conditions.

The author wishes to express his gratitude to his assistants who bravely bore the burden of the routine work involved, and wishes to thank the S.A. Council for Scientific and Industrial Research for permission to publish this paper.

The distribution of salmonella agglutinins among 2117 normal sera from 1054 male and 1063 female adult population of Ibadan is described, and the relation of the distribution of the agglutinins with the antigens of salmonella strains isolated over 2-year period in a hospital in Ibadan, Nigeria, is discussed.

We wish to thank Prof. B. G. T. Elmes and Dr J. B. Lawson for their help with the collection of specimens. Our thanks are due to Mr R. J. Leeming, F.I.M.L.T. for his technical assistance.

(Part of the material upon which this paper is based is included in a thesis for submission for the Cambridge M.D. degree by one of us (D.M.).)

1. Bacteriological surveys of more than forty popular bathing beaches around the coasts of England and Wales have been made during the past 5 years. The great majority of the beaches studied were subject to contamination with sewage.

2. A rough grading of the beaches studied gave a similar ranking order whether the results of the presumptive coliform test or faecal coli counts were used as the basis of grading.

3. Grading of beaches was valid only when surveys were carefully planned to ensure representative sampling from the areas on the beaches concerned where bathing actually took place.

4. The coliform test as used in the bacteriological examination of drinking waters was the main test procedure used but had certain limitations. Promising results with plate counts on relatively non-inhibitory media were obtained.

5. Various salmonella serotypes, notably Salm. paratyphi B, were isolated in small numbers from a high proportion of sea-water samples. The proportion of positive results for salmonella isolation increased from 13·3% in samples with less than 1000 coliform organisms per 100 ml. to 40·1% in samples with over 10,000 coliforms per 100 ml. Comparison of the numbers of salmonellae isolated with what is known of the minimum infective doses of these organisms suggested that very large volumes of sea water would require to be ingested for infection to occur.

6. Poliovirus was not isolated from a small series of sea-water samples examined. Because of the very large dilution factor, special concentration procedures would probably be required to isolate this virus from sea water.

7. Four cases of paratyphoid fever probably due to bathing were recorded. Surveys of the two associated beaches had given median presumptive coliform counts of more than 10,000 per 100 ml., and both showed gross macroscopic pollution with sewage.

8. A statistically controlled study of the bathing histories of 150 poliomyelitis cases in children living permanently by the seaside gave no evidence that bathing had played any part in causing the disease.

1. The question of a possible eclipse phase during the first week of experimental mouse tuberculosis has been examined.

2. Using fluorescence microscopy to examine sections and to perform counts of stainable bacilli for comparison with counts of culturable bacilli in the lungs it was found that bacilli multiplied very slowly during the first 5 days, and rapidly from about the sixth day onwards.

3. At all times there was close agreement between stainable and culturable bacilli in the lungs.

4. During the lag phase, the bacilli occurred as widely scattered, often weakly acid-fast cells that were difficult to defect by Ziehl–Neelsen staining.

5. Active removal of bacilli by phagocytes is believed not to be important at this stage.

6. After 5 or 6 days, clusters of bacilli, rapidly increasing in number and size and strongly acid fast, were readily detected in the lungs.

Ambient temperature profoundly affects the mortality rate and symptomatology in rabbits infected with an attenuated strain of myxoma virus. Simulated summer temperatures allowed at least 70% of infected rabbits to recover, whereas only 8% recovered when held at simulated winter temperatures. Similar fluctuating high temperatures did not reduce the lethality of rabbitpox or of a highly virulent strain of myxoma virus.

On the chorio-allantoic membrane of developing chicken embryos the proliferation of myxoma virus was almost completely inhibited at 39° C., but the yield of rabbitpox virus was not reduced at this temperature.

The serological response and viraemia in rabbits held under different conditions of ambient temperature were investigated. Low temperatures resulted in high titres of circulating virus and soluble antigens, whereas at high temperatures anti-body appeared early. Haemolysin production was not affected by ambient temperature.

The widely variable response of rabbits infected with the attenuated strain of myxoma virus when held at mild temperatures indicates that there is a considerable variation in the innate resistance of the host to the invasion of the virus. This resistance is enhanced by high and reduced by low ambient temperatures, so that the host response is relatively uniform under these conditions. The precise nature of this innate resistance has not been elucidated.

Now that attenuated strains of virus are common and many rabbits exhibit enhanced genetic resistance, seasonal temperatures will have an important influence on the mortality rate in epizootics of myxomatosis.

It is a pleasure to acknowledge the skilled technical assistance of Mr A. Brand.