Although the national statistics of the notifications of infectious diseases are defective with regard to age and sex, it has been established from the returns of London and other large towns that the mean age of attack from diphtheria has been increasing during the present century. The age shift has been from the pre-school to the school age. Several investigators have commented on the change in age incidence, Murphy (1907) reviewed the trend of mortality in London, and Chalmers (1913) the mortality of Scotland. Cheeseman, Martin & Russell (1939), as a result of an analysis of data kindly provided by the Medical Department of the London County Council, concluded that the change might be due to the decrease in size of family, especially in the more crowded districts. This would Jead to a decrease of morbidity at early ages and, as a consequence, a lower level of herd immunity at school ages, so that the epidemiological experience of the poorer districts would approximate to those of the middle-class districts. In this paper (pp. 188–9) reference was made to Turner's observation (1923) that both in London and Manchester the mean age of attack in epidemic years of scarlet fever was above the average, and it was shown that if the maximum weekly case rate of diphtheria in London (1897–1930) were correlated with the ratio of the number of cases at ages 0–4 to the number at 5–9, a significant negative value was reached. This finding was consistent with Turner's result, but it seemed of interest to apply a slightly more direct test by comparing years of heavy prevalence with adjacent years in which diphtheria was at a lower level.

1. The incidence of cross-infection with Str. pyogenes during a period of four months was compared in two blocks occupied by scarlet-fever patients. One block was nursed by the bed isolation method and the other by the ordinary method in current use for multiple-bed wards. 2. The rules for the bed isolation blook are given. 3. The incidence of cross-infection with Str. pyogenes among patients in the bed isolation block was 20·3%, that among patients in the ordinary block 22·6%. 4. We concluded that the bed isolation nursing technique practised was not effective in reducing cross-infection with Str. pyogenes among scarlet-fever patients. 5. A further test of bed isolation nursing was made for six months, using the extra precaution of vacuum-cleaning the floors. We found that crossinfection was still occurring, but the incidence could not be estimated since the Str. pyogenes strains isolated had to be destroyed at the outbreak of war. At this time the serological typing had not been completed. 6. The importance of dust-borne and droplet-borne infection in addition to that of contact infection is discussed. The type of investigation required to decide whether cross-infection in multiple-bed scarlet-fever wards can be eliminated by the methods at our present disposal is outlined.

A Proteus-like organism is described, which produced acid but no gas in carbohydrate media.

I wish to thank Dr W. D. Carruthers,. Medical Officer of Health of Staffordshire, for permission to publish this paper.

The question formulated in the introduction to this report can now be answered. Ozone in tolerable concentration is able to inactivate certain bacteria when these are present as unprotected singleton aerosol particles in atmospheres of 60–90% R.h. When such bacteria are covered with a protective coating of organic matter, however, as in aerosols naturally emitted during a sneeze or cough, then ozone in permissible concentration is without significant effect. Inactivation of such protected organisms can only be achieved by the use of ozone in decidedly higher concentrations, which must be deemed dangerous for prolonged spells of breathing. Bacteria that have settled on surfaces are generally more resistant to ozone than when in newly formed aerosols. Hence experimental evidence leads to the conclusion that ozone, in concentrations that can be breathed over long periods without irritation, cannot be expected to provide any effective protection against air-borne bacterial infection, through direct inactivation of the infectious carrier particles.

In Out original paper on germicidal aerosols (Twort, Baker, Finn & Powell, 1940) it was shown that the most satisfactory results were obtained with a solution of 10% hexyl resorcinol in propylene glycol together with a little alkali and wetting agent, the mixture being mechanically atomized into mist particles of appropriate size. Although it was confirmed by other workers that a high degree of lethal effectiveness on air-borne bacteria was achieved by the above procedure, objections were raised to its use in practice at the moment on the grounds that:

(1) The germicide base was difficult to obtain.

(2) The solvent was only manufactured in America, and not in bulk there.

(3) The mechanical apparatus advocated involved the use of metals now required for the making of war weapons.

1. Approximately 800 cultures of bacteria have been isolated from samples of water taken from lakes and from some of their inflowing waters. The morphology and Gram-staining reaction of the cultures have been determined together with the reactions in nutrient gelatin, dextrose broth, nitrate broth, and litmus milk.

2. Many organisms grew poorly on artificial media, and were unable to grow in either dextrose or nitrate broth. In general the cultures showed weak physiological activity, particularly in litmus milk and in dextrose, though gelatin liquefaction was fairly common. Colonies produced on solid media were frequently pigmented, shades of yellow being particularly common. A significant feature was that most of the bacteria (95%) were rod-shaped, and though many cultures showed considerable variation in cell length and were consequently difficult to classify, short rods were in general more prevalent than long. Coccus forms made up less than 1 % of the toal number considered.

3. When the cultures were grouped according to their biochemical activities no consistent differences were observed between the types from near the surface and from near the bottom of a lake, nor between the lake and the inflow, but differences were observed in samples taken from the same lake on different occasions. Some types were common to both the lake and the inflows, while others occurred in only one of those habitats. Some types were found both near the surface of the lake and near the bottom, whilst others were confined to one depth.

4. A comparison of the types of bacteria isolated from waters with those found by other workers in soils shows that the main difference in the bacterial flora is the absence in water of the Gram-positive pleomorphic forms of the genera Mycobacterium and Corynebacterium and of Bact. globiforme Conn.;, all of which are common in soils of very widely different agricultural types.

5. In the discussion it is pointed out that, in common with soil types bacteria isolated from water cannot be adequately classified by the usual tests in carbohydrates; in dextrose broth, for instance, the reaction is often only a slight change in pH value.

1. V strains of Bact. typhosum can be sterilized by means of merthiolate or colloidal silver without destructive effect on either the Vi or O antigens.

2. Suspensions in physiological saline sterilized and preserved by the addition of either merthiolate or silver retain their property of stimulating Vi antibody formation in the rabbit for at least one year if stored at 0–2° C, but when stored at 23–25° C. this property is lost after 4 months' storage.

3. The Vi antibody-stimulating property of a merthiolate-killed and preserved suspension in physiological saline is almost completely destroyed by an exposure of 5 days at 37° C. or 4 hr. at 60° C.

4. Bact. typhosum bacilli killed with merthiolate or alcohol, and dried with acetone, show no loss of Vi antigen when stored in the dry state for 1 year at 23–25° C, or after 3 months at 37° C.

5. Suspensions sterilized and preserved with merthiolate in 32% saline will withstand 50 days' storage at 37° C, or 7 months at 23–25° C, without significant loss of their Vi antibody-stimulating properties.

6. Suspensions in 32% saline can be sterilized by an exposure to 60° C. for 2 hr., and even after 4 hr. exposure at this temperature, show no loss of Vi antigen content.

7. Suspensions killed by merthiolate or alcohol, and preserved by the addition of 25% alcohol in physiological saline, failed to stimulate Vi antibody formation in the rabbit after being stored for 20 days at 37° C.

8. The application of these findings to the production of a stable T.A.B.C. vaccine of enhanced immunological qualities is discussed.

9. The effect of mixing Bact. typhosum with tetanus formol-toxoid has been examined, and the advisability of employing heat-killed-phenolized vaccine mixed with tetanus formol-toxoid for combined immunization against tetanus and typhoid infections is discussed.

10. A suggested technique for the preparation, supply, and administration of two new types of T.A.B.C. vaccine is described.

1. Examination of samples of soil from 106 localities by enrichment culture technique gave 37% toxic samples, the percentage containing Clostridium botulinum ranging from a certain 5% to a possible 14%.

2. Cl. botulinum type A was shown to be present in four of the five positive samples, type B in one. Characteristics of a pure culture of type A are given.

3. Incidental data on the occurrence of some other toxigenic anaerobes are given.

In a recent paper Withell (1942) has shown that for a wide range of microorganisms and disinfectants or poisons the logarithms of the survival times are approximately normally distributed. Even when the number of survivors is adequately represented by an exponential function of the time (e−kt) say, the former hypothesis still gives approximately correct results. This suggests that in many cases the data are not good enough to distinguish between the two hypotheses (1) of a constant force of mortality k and (2) of a normal distribution of the logarithms of survival times. It is worth while, therefore, to examine the form of the distribution of the logarithms of survival times when the exponential law is true, and to see how nearly normal it is. We shall show that except for the position of the mean, this distribution is independent of k.

Chlorine at the rate of 5 and 10 parts per million of available chlorine in the form of Milton significantly increased the reduction time of milk samples.

Observed increases varied from −0·50 to + 1·25 hr.

At this level of chlorination the increase in R.t. is not correlated with the initial plate count and also occurs at all levels of R.t.