Seven more carriers, all possessing appreciable quantities of Vi agglutinins, are added to those already known.

Vi agglutination tests performed on 2526 inhabitants of the Transvaal, both native and white, showed that 5·3 % had similar quantities of Vi agglutinins.

A fair number of these positive reactors were further examined for the presence of typhoid bacilli in their excreta, but the number of positive findings was very small.

It is argued that there are a large number of typhoid faecal carriers who are such minimal excreters that the typhoid bacilli in their stools escape detection.

We wish to thank Dr T. Lötter, Acting Medical Officer of Health of Pretoria, and his staff, for their kindly help in collecting the material for this paper. Our special thanks are due to Lieut.-Col. H. Nelson, Medical Officer of Health of Pretoria, now on active service, for his never-failing interest in our work which has been such a great encouragement.

1. A weekly examination for haemolytic streptococci was made of the dust of two hospital wards; observations lasted in each ward for about six months. The wards chosen were a combined ear, nose and throat and eye ward used for adult patients, and a children's ward.

2. It was found that on an average for the whole period the dust of the former ward contained 300,000 haemolytic streptococci per gram and the dust of the latter 250,000 per gram.

3. Representative colonies of haemolytic streptococci grown from each sample of dust were examined serologically to determine their group. About 33% of those isolated from the E.N.T. Eye ward were group A and about 80% of those from the children's ward.

4. In order to determine the relationship of the streptococci in the dust to streptococcal infection among patients and staff, throat swabs and swabs from septic lesions were regularly examined.

5. In the children's ward 27·8% of 270 patients were found to be infected with haemolytic streptococci either on admission or at some time during their stay in hospital. The incidence of infection acquired in hospital was more than 12·2%. About two-thirds of these infections were latent.

6. Group A streptococci isolated from the dust and swabs were identified serologically according to type. It was noted that the occurrence of a particular type in the dust often resulted from the presence of one or more infected persons in the ward.

7. It was, however, frequently noted that a particular type made its first appearance in the dust when it could not be cultured from any of the swabs. It is possible that these strains were introduced to the ward by visitors, such as patients' relatives and friends or patients from other wards coming for septic dressings.

8. No conclusive example of a hospital cross-infection conveyed by dust was noted.

I wish to thank Dr T. J. Hennelly and Dr D. G. Morgan, Medical Superintendents of the two hospitals, for giving me the facilities to carry out the investigation; also Dr S. T. Crowther and Dr Duncan Davies, and the sisters and nursing staff for their assistance and co-operation. I am especially indebted to Dr V. D. Allison for his helpful advice and criticism.

Results are given of the typing (by biochemical fermentation tests) of 290 strains of Bact. paratyphosum B isolated during an epidemic in the north of Scotland. Of these strains 283 were of type R3I1. Seventy-four strains isolated in or around Edinburgh later in the same year, and 107 strains from three patients were also typed. Some variation (2·4 % in the north and 4 % in Edinburgh) was observed, but, in general, typing by the fermentation of rhamnose and inosite is of epidemiological significance.

I am indebted to Dr Kirkpatrick for supplying strains of Bact. paratyphosum B and providing access to the necessary records, to Dr Seiler for epidemiological notes on the Edinburgh cases, and to Prof. Mackie for his valuable advice and encouragement.

Experiments on the bactericidal properties of mists were performed in a closed room of 850 cu. ft. capacity. The test organism was sprayed into the room through an Atmozon nebulizer operated from a mechanically driven Austin diaphragm compressor; the pressure was maintained at 7 lb./sq. in. Air to the compressor was taken through rubber tubing from an adjoining room to avoid accidental admixture of antiseptics into the air used to atomize the bacteria. The output of the nebulizer was 0·22 c.c./min. In the majority of the experiments the test organism was sprayed for 2 min. To ensure that an adequate mist was being emitted, the culture was nebulized in the dark against a dark background, and examined frequently with a light beam. Even distribution of the mist in the room was ensured by convection currents from a large hot-water pipe which ran along the length of two walls about 2 ft. from the floor, and by a small electrically driven fan placed immediately behind the nebulizer.

1. The antigenicity of batches of T.A.B.C. vaccine after mixture with tetanus toxoid and held at 18–25° C. for 6–7 weeks, 12–13 months and 16 months was tested in groups of adult males in whom the pre-inoculation titres for the various antigens were strictly comparable.

2. The batch used within 6–7 weeks of production produced the greatest effect, but the older batches were not greatly reduced in potency.

3. Within the limitations imposed by the restricted investigation, the more effective result following the use of the 16 months vaccine as compared with the 12–13 months vaccine indicates that factors in addition to that of time were concerned in the deterioration of antigenic power.

We are indebted to the Medical Officers in charge of the Training Establishments concerned, Surgeon Captain H. F. Briggs, M.B., Ch.B, F.R.C.S. (Ed.), R.N., Surgeon Captain W. P. Vicary, M.R.C.S., L.R.C.P., R.N., and Surgeon Commander H. A. Shellwell, M.R.C.S., L.R.C.P., R.N.V.R., for their ready and valuable co-operation.

1. Certain strains of lactose and non-lactose-fermenting coliform bacilli have been found to possess a common agglutinogen. This antigen is found in both motile and non-motile smooth strains and appears to be distinct from ‘H’, ‘O’ and rough antigens, and from the X antigen described by Topley & Ayrton. In certain respects it seems to resemble the Vi antigen of Felix & Pitt, notably in the inhibitory effect it exerts on ‘O’ agglutination. It is, however, not associated with virulence and is of relatively wide distribution.

2. The strains, when inoculated into rabbits, stimulate the production to high titre of an agglutinin which can be absorbed out completely by any one of the strains.

3. Subculture of the strains under certain conditions results in the loss of the antigen and the development of specific variants.

4. Agglutinins to these strains have been found in certain diagnostic sera and may prove a possible source of error, particularly if slide agglutination is relied on for identification.

We take this opportunity of expressing our thanks to Prof. G. S. Wilson for the loan of Bact. typhi-murium ‘X’ antiserum.

1. A series of cases of repeated accidental vaccinal infections of vaccinia and vaccinoid types in subjects possessing strong or complete vaccinal immunity, is presented.

2. It is suggested that there is a similarity between such cases and the repeated infections on the hands of farm workers and milkers handling cows naturally infected with cowpox.

3. It is difficult to fit satisfactorily such facts into the framework of the modern theory of vaccinal immunity, but no explanation of the apparent discrepancy can be suggested.

The α-naphthol modification of the Voges-Proskauer (v.-p.) test described by Barritt (1936) has proved satisfactory for the examination of the coli-aerogenes group in the hands of several workers, including Harold (1936), Vaughn, Mitchell & Levine (1938), Kluyver & Molt (1939), Iyer & Raghavachari (1938–9), and Batty-Smith (1941).

1. The basic observations of Piekarski (1937–40) and F. Neumann (1941) on Feulgen-positive, chromatinic structures, going through a regular cycle of division, in the cells of Bact. coli and Proteus vulgaris are confirmed and the view that these structures are nuclear in nature is accepted.

2. The chromatinic structures in bacteria from old cultures, although usually distinguishable from the cytoplasm, are too small to be resolved accurately. After transfer to a fresh nutrient medium the chromatinic structures increase in size and give rise to short, often dumbbell shaped, rods (chromosomes) which multiply by splitting lengthwise in a plane more or less parallel with the short axes of the bacterium.

3. The chromatinic structures of Bacl. coli and of Proteus vulgaris are essentially the same as those previously described in myxobacteria and actinomycetes (Badian, 1930, 1933, 1936) and in various well-known aerobic spore-forming bacteria (Badian, 1933, 1935; Robinow, 1942).

4. A single cell of Bact. coli or Proteus vulgaris contains one chromatinic body or one or two pairs of these, representing primary and secondary division products.

5. Few bacteria from young cultures are single cells. When fixed through the agar with Bouin's mixture and stained briefly with Giemsa's solution, bacteria from young growing cultures of Bact. coli, Proteus vulgaris, B. mesentericus and B. megatherium assume a banded appearance indicating that each bacterium consists of two, three or four separate cells.

6. A plasmolysing treatment has been applied to B. megatherium which provides direct proof of the composite structure of this bacillus by inducing its component protoplasts to shrink away independently from the outer supporting cell wall.

I wish sincerely to thank Dr H. B. Fell for the hospitality offered to me at the Strangeways Laboratory, for her sustained interest in this investigation and for her help in preparing the manuscript for the press. I have also pleasure in admitting my indebtedness to Prof. E. G. Pringsheim for much helpful criticism and advice in matters relating to the bacterial cell wall.

In seven years 176 cases of Q fever have been diagnosed in Queensland. Nearly all the 129 patients who lived in Brisbane were associated with meat works. Most of the forty-seven country patients worked on dairy farms.

Investigation of native animals, cattle and ticks, has indicated in outline the natural history of Q fever, which is set out diagrammatically in Fig. 1. (Several steps in this outline need confirmation and much detail remains to be filled in.)

First there is a basic cycle of infection with the bandicoot (and probably other bush animals) as reservoir, and Haemaphysalis humerosa (and probably Ixodes holocyclus) as vector. A bush worker may interrupt this cycle and get Q fever from the attack of Ixodes holocyclus.

Cattle become infected, probably through Ixodes holocyclus and perhaps through other ticks. It is possible that there is a secondary cycle: cattle-Haemaphysalis bispinosa-cattle.

Ticks on the cattle (Boophilus annulatus microplus or Haemaphysalis bispinosa) are probably the source of human infection. It is suggested that inhalation of tick faeces is the likely mode of entry of Rickettsia burneti.

We have investigated, with the most satisfactory results, the possibility of using sulphur dioxide (Williams, Waterman, Keresztezy & Buchman, 1935) for the selective destruction of thiamin in foodstuffs.

1. The action of phenol on Bact. coli has been studied quantitatively in detail under such conditions that unfavourable circumstances other than the presence of the germicide were as far as possible eliminated. Briefly, this involved the addition of phenol solution directly to a large volume of culture developed under rigidly standardized conditions.

2. When the mortality exceeded 95% the variation between the numbers of colonies on replicate plates, when determining the numbers of survivors, was often excessive.

3. Under the conditions used the death-rate was not constant. First, there was a phase (1) of slow but increasing death-rate which merged gradually into a phase (2) of approximately constant rate which was also the maximum for a given phenol concentration. There are indications that the death-rate may decline towards the extreme end of the disinfection process.

4. The virtual extinction time (the time taken for the survivors to fall to 1 per ml. as determined by extrapolation of the log survivors-time curve) increased as the phenol concentration decreased, as also did the duration of phase 1. The latter occupied about 60% of the virtual extinction time when the concentration was 3·48 g. phenol per 1., but with rising concentration its duration decreased at a greater rate than the virtual extinction time so that at about 7 g. per 1. phase 1 was very short though still detectable. The standard errors of the virtual extinction times varied between ± 1·5% and ± 5·43%.

5. Using the probit method it has been shown that at low concentrations of phenol the distribution of resistance of Bact. coli is approximately normal when the resistance is measured in terms of the survival times.

6. The distribution of resistance was found to be normal at all concentrations of phenol used, when that resistance was measured in units of the logarithms of the survival times, with the exception that at the lower concentrations there was a sudden change in the slope of the probit-log survival-time line at about 20% mortality. This change became less marked with rising concentration and was probably absent at 8·00 g. phenol per 1.

7. After conversion into the dosage-mortality form, the data reveal that about 70% of the cells show an approximately normal distribution of resistance when the latter is expressed in terms of the dosage survived for a fixed time, provided that the exposure time is less than 50 min.

8. The distribution tends to be normal for longer exposure times when the resistance is measured in terms of the logarithms of the dosages survived. On this basis a change of slope of the probit-log dosage line is observed as in the case when resistance is measured in terms of the logarithms of survival times.

Homogenization of activated sludge greatly increased the apparent bacterial count obtained by plating on a solid medium, and for this reason facilitated the isolation of the predominant flora by liberating the bacteria from the interior of the sludge flocs. The ordinary domestic cream-making machine was found to be quite effective for this purpose.

The high counts obtained indicated that there are probably several hundred thousand million bacteria per gram of dry matter in activated sludge.

Aeration of sewage was found to result in an increase in the total count of bacteria, and a high count was maintained for a considerable time. After aeration for several days fairly rapid and apparently fairly complete separation of the sludge occurred on allowing the liquid to stand, but the supernatant liquor contained large numbers of bacteria. When a fresh quantity of sewage was added to the small quantity of sludge which settled and a second period of aeration commenced, the bacteria were found to associate more quickly with the sludge than they had during the first aeration. Coliform bacteria and spore-forming aerobes formed only a small fraction of the total number of micro-organisms concerned in these changes, and moulds and yeasts never accounted for a large proportion. The predominant bacteria did not produce acid from glucose.

Various media were tested in investigating the bacteriology of activated sludge. None showed any superiority to nutrient agar. Coliform bacteria and aerobic spore-formers were encountered in negligible numbers. The morphological and physiological characters of seventy-one strains of the predominant bacteria were determined. The majority were Gram-negative rods with no action on carbohydrates and were members of the genera Achromobacterium, Chromobacterium, and Pseudomonas. Those isolated from activated sludge soon after its formation from aerated sewage were found to be non-proteolytic, but a proteolytic flora was established after the sludge had been built up for a period of 4 weeks. The characters of the predominant bacteria indicate that they are water types derived from the water supply or the drainage water which enters sewage. Intestinal bacteria appear to be unimportant.

The experiments described in this paper were carried out as part of the programme of the Water Pollution Research Board of the Department of Scientific and Industrial Research, and the results are published by permission of the Department.