1. Second attacks of typhoid fever are uncommon. In the literature this has been taken to imply that an attack of typhoid fever confers a high degree of immunity which, nevertheless, may be overcome by such factors as re-infection by a large dose, an organism of a different strain, or one of high virulence.

2. Two large outbreaks of typhoid fever in the same community within 5 months produced eleven examples of second attacks. Clinical descriptions of four of these are given.

3. Details are given of the population at risk and the attack rates in various groups.

4. The evidence of these facts and figures, though inconclusive, suggests that an attack of typhoid fever does not confer more than a moderate degree of specific immunity. The influence of chloramphenicol upon immunity remains sub judice.

Purified tuberculin in concentrations equivalent to 1x/20 standard Old Tuberculin had no apparent effect on the outgrowth in vitro of liver and kidney epithelium derived from sensitized guinea-pigs.

Acknowledgement is made with thanks to Miss Florence Taylor for technical assistance, and to Mr L. Jones for help with the microphotography.

1. When coagulase-positive staphylococci are grown on nutrient agar containing fresh mammalian serum and haemoglobin, discrete areas of clearing appear in the medium near to the growth.

2. These ‘plaques’ are due to proteolysis, the haemoglobin acting as a chromoprotein indicator substrate. For convenience the effect is referred to as ‘proteoclast’.

3. The effect is due to the interaction of a diffusible product of the staphylococci with constituents of normal sera. The staphylococcal factor has been obtained in a bacterium-free filtrate and its interaction with serum studied quantitatively. It resists boiling.

4. The number of plaques produced under defined conditions showed a linear correlation with the amount of serum used, but not with the amount of filtrate.

5. By means of serial filtration through Gradocol membranes it was shown that one factor in normal serum required for the proteoclast effect is particulate, having a size of the order 20–70 m μ diameter.

6. It was found that a third factor present in fresh sera was also required.

7. Serum was rendered inactive by conditions of heating and ultra-violet irradiation similar to those required to sterilize vegetative bacteria and viruses.

8. It is suggested that the proteoclast effect is due either to a non-pathogenic virus, or to a hitherto unrecognized particulate enzyme precursor present in sera and activated by the staphylococcal factor.

A description is given of the topography, type of farming carried out, and the living conditions of the agricultural community of a district in South Wales where a survey was made of the infection rate of rats with Leptospira icterohaemorrhagiae.

Leptospires were seen in stained sections of the kidneys of eighty-two of the 357 rats examined (23%). With a single exception, all the infected rats were adult, but no difference in sex-incidence was found.

Weil's disease occurs in this area, but no cases in man or cattle had been reported from this particular locality. Blood samples taken from six persons living on two heavily infested farms contained no anti-leptospiral agglutinins.

1. Glycine, alanine, and several isomers of alanine, DL-glutamic acid and DL-aspartic acid, when added to fresh guinea-pig serum and allowed to stand on the bench for half an hour, will protect the complement of this serum from destruction by heating at 55 and 56° C. for half an hour, but most of the complement activity is destroyed by heating at 57° C. and it is completely destroyed at 58° C. after half an hour.

2. Derivatives of glycine do not have any protective effect.

3. Various substances of high molecular weight, that might be described as ‘protective colloids’ do not have any protective effect.

4. How these amino-acids when added to serum alter the heat-lability of the complement is not understood.

The investigation of 10,436 fermented tubes arising in the presumptive coliform examination of samples of water at six laboratories in England and Wales has shown that, with unchlorinated supplies, the unconfirmed presumptive test gives sufficiently accurate results. Full confirmation of all presumptive positive tubes of these waters is impracticable as a routine and ‘colony-confirmation’ gives a correction of only 0·5%. With chlorinated waters, however, ‘colony-confirmation’ discloses an error of 5·5%, largely due to the presence of anaerobes. This error can also affect the faecal coli (44° C.) count and may be so large in individual samples that assessment of chlorinated supplies should not be based on the presumptive test until this has been checked at least by plating.

In three cattle vaccination experiments, with three strains of the virus of foot-and-mouth disease, it was shown that virus passaged in culture in cattle tongue epithelial tissue was as effective an antigen as virus passaged in cattle.

With two virus strains, the virus content of the culture at the peak of infectivity was about the same as that of vesicle epithelium from the tongues of reacting cattle. Variable and less satisfactory results were obtained with the third strain, but one culture passage yielded tissue of sufficiently high virus content for the preparation of vaccine of adequate potency.

No modification in the antigenic behaviour of the strains was detected as a result of passage in culture.

It is a pleasure to acknowledge the technical assistance given by Mr W. J. Brownsea.

1. A study of factors involved in the transmission of haemolytic streptococci has been made by experiments with healthy carriers and individuals whose upper respiratory passages were contaminated with Chromobacterium prodigiosum.

2. The following conclusions were reached: (a) Expulsion of haemolytic streptococci in droplet spray is determined by the nature of the expiratory activity (Fig. 1), the concentration of the organism in the saliva (Table 3) and the volume of salivary flow (Fig. 6).

(b) Droplets and droplet-nuclei are less important vehicles of transmission because of the extremely low content of haemolytic streptococci in them (Figs. 2–5)

(c) Dust particles carrying haemolytic streptococci and liberated by agitation of handkerchiefs more effectively pollute the air than violent expiratory activities (Figs. 4 and 5).

(d) Hands and clothing readily become contaminated by heavy nasal carriers (Table 4) and the former serve as the principal means of contaminating the environment and other individuals.

3. A diagram showing probable mechanisms of transmission is given (Fig. 7) in which hand contact is represented as a more important pathway of spread than air-borne dust which, in turn, is more important than either droplets or droplet-nuclei.

This investigation has been concerned with the changes that occur in the coliform and faecal coli content of water samples on storage at room and refrigerator temperatures for 6 hr. as compared with those occurring after 24 hr. storage.

The examination was conducted by a 70-tube method using twofold diminishing volumes.

The percentages of samples showing a significant change corresponding to at least a doubling or halving of the coliform content on storage were: (a) at room temperature after 6 hr. 24.7%, and after 24 hr. 38.3%; (b) at refrigerator temperature after 6 hr. 25.0%, and after 24 hr. 33.9%. The percentages of samples showing a significant change in the faecal coli content on storage were: (a) at room temperature after 6 hr. 18.7%, and after 24 hr. 34.6%; (b) at refrigerator temperature after 6 hr. 10.4%, and after 24 hr. 25.0%. The changes were preponderantly decreases and most of the large changes occurred after 24 hr.

The investigation has shown that fewer changes occur after 6 hr. storage than after 24 hr. storage, and that storage for 6 hr. at refrigerator temperature is preferable to storage for 6 hr. at room temperature. Even so, some samples show significant changes after 6 hr. storage at refrigerator temperature; the coliform content is significantly altered in 25% of samples and the faecal coli content in 10% of samples.

Samples of water should, therefore, be examined as soon as possible after collection, certainly within 6 hr., and during the period of transport to the laboratory they should be kept cold, if possible by ice.

A quantity of 0.1 ml. of a 3% solution of crystalline sodium thiosulphate in a 6 oz. bottle is sufficient to neutralize up to 5 p.p.m. of residual chlorine; the use of large quantities of thiosulphate is unnecessary, except possibly for some swimming-bath samples. The investigation has shown that this amount of thiosulphate has no significant effect on the coliform or faecal coli content of non-chlorinated water samples during 6 hr. storage at refrigerator temperature. There therefore appears to be no disadvantage in adding this amount of thiosulphate to all water sampling bottles.