Quantitative methods have been used in several investigations by Kabat and his colleagues (1945–50) in the study of serological relations of various preparations of blood-group substances. The investigations have taken twoforms: (1) the amounts of antibody nitrogen precipitated from a standard volume of an antiserum by varying amounts of the blood-group substances have been plotted against the amount of blood-group substance added; (2) the hexosamine has been measured in the precipitates formed with antiserum in the zone of antibody excess and the ratio of hexosamine precipitated to hexosamine in the blood-group substance added has been calculated; the amount of methyl-pentose precipitated has also been measured (Kabat, Baer &Knaub, 1949) and the ratio of methyl-pentose precipitated to methyl-pentose added hasbeen calculated.

In a previous communication on the bacteriology of dehydrated fish (Shewan, 1945), data were presented concerning various aspects of the drying process, and their bearing upon commercial production was discussed. This communication reports further work, done mainly during the war, on the effect of storage conditions on the bacterial flora of various kinds of dehydrated fish products.

1. The effects of poison treatments on the rat populations of two sample districts of heavily infested sewers in a London borough were studied.

2. Each district had a maximum rat population represented by a census figure of about 10,000 g. wheat eaten per day, corresponding to at least 400 rats.

3. Poison treatments after prebaiting, at intervals of 6 months, reduced the rat population of each district to less than 10% of the maximum. A rapid restoration of the population followed, and the level reached in 6 months was near the maximum.

4. In both areas, direct poisoning with sodium monofluoroacetate ‘1080’ was as effective as a prebaiting treatment. Direct poisoning with zinc phosphide was relatively unsuccessful.

5. When both areas received double treatments, consisting of direct poisoning with sodium monofluoroacetate followed by a prebaiting treatment, the estimated population of one district was reduced to about 3% of the maximum. In the other area, rain made the second poisoning ineffective.

6. The rate at which the population was restored from the 3% level was even higher than the rates previously observed, and was probably too high to be accounted for solely by breeding. Evidently, invasion from the surface played a part.

7. No relationship could be established between the estimated sewer rat population densities within each district, and the known sites of surface infestation.

We are grateful to the Council and officers of the Borough in which the work was done, for unstinted help throughout the inquiry. We also owe thanks to H. V. Thompson for help in the early stages; to him and to Miss M. D. A. Lawrence for discussing the work during its progress; to Miss M. M. Spencer for help in the analysis of the records and in checking calculations; and to A. G. Jenson for mapping the districts and for drawing the figures.

Suspensions of Strep. pyogenes, Staph. aureus, Ps. pyocyanea and micrococci in serum, distilled water, saline and oleic acid solution were allowed to dry on cover-slips. The numbers of bacteria surviving after periods of exposure were estimated from viable counts of extracted cover-slips.

All the organisms tested showed after drying a fall in viable count that was absent in aqueous suspensions not allowed to dry. Ps. pyocyanea was shown to have a lower survival rate on drying than the other organisms.

Serum afforded moderate protection to the suspended organisms during the period of drying.

0·1 mg./ml. oleic acid caused a rapid destruction of Strep. pyogenes and a significant destruction of Ps. pyocyanea as well as of Staph. aureus and micrococci in drying films of these organisms. The similarity of the fate of Staph. aureus and micrococci during drying in low concentrations of oleic acid is in contrast to the previously reported greater sensitivity of Staph. aureus to higher concentrations of oleic acid (1–10 mg./ml.) in the test-tube.

The implications of these findings are discussed in relation to skin and wound flora, and to environmental hygiene.

The complement-fixation technique described in this paper was designed as a simple and rapid micro-method. It is derived from the method published by Fulton & Dumbell (1949), but a number of modifications have rendered it less laborious to perform and more flexible in application. Using rabbit, human and guinea-pig antisera, this technique has been successfully applied to the serological examination of the viruses of influenza, vaccinia and Newcastle disease, and experience with other materials, such as gonococcal antigen and extracts of chorio-allantoic membrane and mouse lung, suggests that it is of general application.

1. The lysis of Bact. coli by glycine is inhibited completely by various treatments: (a) by heating the bacteria at 65 or 100° C.; (b) by the action of Cr, Fe, and Al salts at concentrations which cause agglutination of the organisms, (c) by various heavy metals, including particularly Hg and Ag salts, at low concentrations (d) by lethal concentrations of formaldehyde and phenol.

2. The lysis is not inhibited by sodium fluoride, potassium cyanide, or sodium monoiodoacetate at concentrations which suppress the action of certain enzymes.

3. This evidence on the whole supports the rejection of the view that a simple physical process is responsible for lysis by glycine, but does not yet enable us to distinguish between the other possible mechanisms of the lysis because the treatments used might equally interfere either with the structural proteins of the bacteria, or with the hypothetical enzymes which might be concerned in producing the lysis.

1. Among infants attending Child Welfare Clinics there was a steady decline in the incidence of nasal carriage of Staph. aureus over the first year of life.

2. Infants born in hospital showed a much higher incidence of Staph. aureus in the first 2 months of life than infants born at home. A similar difference was also very distinct in the later part of the first year of life.

3. Mothers delivered 2 weeks to 2 months previously had a higher incidence of nasal carriage of Staph. aureus when delivered in hospital than when delivered at home. After this interval the incidence was similar in all groups of mothers throughout the rest of the year.

4. In the first few months of life there was a tendency for carriage in infants to be associated with carriage in the mother, but towards the end of the year there was no such relationship. This association appeared most clearly in infants born at home and in infants 2–5 months old born in hospital F.

5. A very high proportion (25 out of 30) of the strains tested from infants born in hospital F less than 5 months previously were penicillin-resistant. Infants born at home had a much lower incidence of resistant strains.

6. A high proportion of strains of Staph. aureus isolated from mothers delivered in hospital F were resistant throughout the first year. Strains from mothers delivered in hospital C or at home showed a much lower proportion of resistant strains.

7. Phage-typing showed a great variety of types, but those found among the penicillin-resistant strains were rather less varied than among the sensitive strains. When Staph. aureus was found both in infant and mother, although the same phage type was commonly present in both, in 16 out of 35 couples different types were found.

8. Investigation in maternity hospitals C and F showed a high proportion of penicillin-resistant strains of Staph. aureus among the nurses and infants and in the dust of the nurseries, but not among the mothers. There was no important difference between the two hospitals as regards the incidence of resistant strains isolated from nurses and infants in spite of the differences found in babies from the two hospitals when swabbed at the clinics.

9. The significance of these results is discussed.

Experiments to determine the role of particle size in the infectivity of anthrax spores are described. Clouds of homogeneous particles were produced. The mortality-dosage curves for guinea-pigs and monkeys are given for clouds of various particle sizes. Data are given on the effect of time in the concentration-time relationship. The results are compared with those recorded by other workers on the relationship of particle size to respiratory retention.

Infectivity was highest with single-spore clouds, falling off as particle size increased. Reasons are given for attributing this effect to difference in site of deposition of different-sized particles.

1. Outbreaks of mild food poisoning have been investigated in which heat-resistant Cl. welchii appeared to be the causative organism. The outbreaks were characterized by colic and diarrhoea without vomiting, commencing 8–20 hr. after ingestion of the contaminated food.

2. The strains of Cl. welchii concerned are only feebly toxigenic, and apart from the heat-resistance of their spores, and some colonial characters, fit well into Cl. welchii Type A. The toxin production and the serology of the strains is uniform within an outbreak.

3. Mild food poisoning similar to that seen in natural epidemics has been produced in volunteers by ingestion of cultures of heat-resistant Cl. welchii isolated from contaminated meat.

4. Infection is almost invariably due to meat which has been boiled, steamed, braised, stewed or insufficiently roasted, allowed to cool slowly, and eaten the next day, either cold or reheated.

5. Outbreaks of this kind should be prevented by cooking meat immediately before consumption; or, if this is impossible, by cooling the cooked meat rapidly and keeping it refrigerated until it is required for use.

Thomas & Van den Ende (1941) and Puck and his collaborators (Puck, Hamburger, Robertson & Hurst, 1945; Puck, Robertson, Wise, Loosli & Lemon, 1946) have shown that the application of small amounts of oil to bedclothes reduces the quantities of dust and bacteria liberated during bedmaking. Joyce Wright in her first investigation (Wright, Cruickshank & Gunn, 1944) found that oiling bedclothes was, consequently, effective in reducing the incidence of cross-infection, but this was not confirmed in her later work (Wright, Begg & Smellie, 1947), or by Krugman & Ward (1951). Barnard (1952), however, has recently shown that cross-infection can possibly arise by interchange of bacteria in blankets during laundering. Oiling of bedclothes may, therefore, be a very useful hygiene measure.

The distribution of inhaled bacterial aerosols has been studied in guinea-pigs, monkeys and mice, using Bacillus subtilis spores labelled with radiophosphorus. Particle sizes from about 1 to 12μ have been used.

The guinea-pig shows the expected change of distribution with particle size; the proportion retained in the head increases with increased particle size. The figures correspond closely with those for man. Monkeys show similar results but are more irregular.

The subsequent fate of the retained particles has been studied and accords with what is known about ciliary removal.

The work is intended to link with parallel investigations of respiratory infection in closely similar conditions, and its implications are discussed in a paper on that subject (Druett et al. 1953).

1. Australian wild rabbits which had recovered from myxomatosis acquired in the field contained in their serum antibodies which could be detected by complement-fixation or neutralization tests for a long period (more than 18 months) after their recovery. The titre of complement-fixing antibody fell fairly rapidly during the first few months, and remained at a steady level thereafter. No change could be detected in the titre of neutralizing antibodies throughout the observation period.

2. Inoculation of such rabbits with myxoma virus was sometimes followed by the development of a local lesion at the inoculation site, and in these rabbits the titre of complement-fixing antibody rose, but there was no alteration in the neutralizing power of the serum. In other animals no lesion developed and there was no change in the antibody titre.

3. Serum was collected from a total of 824 wild rabbits from seventeen localities in eastern Australia with varying histories of myxomatosis since December 1950. Examination of 135 of these sera by both neutralization and complement-fixation tests showed that the results obtained by the two methods were in close agreement.

4. In many areas in which the disease was absent in the summer of 1950–1 and produced a violent epizootic in 1951–2, the majority (70–90 %) of the sera collected from rabbits 2–5 months after the height of the epizootic contained antibody to myxoma virus, i.e. the majority of the survivors had recovered from the disease.

5. Counts of the rabbit population before and after a violent epizootic in the summer of 1951–2, and the proportion of immune animals amongst the survivors in these areas showed that the case-mortality rate was between 99·4 and 99·8%.

6. Consideration of the results obtained in the serological surveys showed that the case-mortality rate was probably of this order (about 99·5%) in all areas in which there had been no disease or a negligible outbreak in 1950–1, whether they had a grade I or grade II kill in 1951–2.

7. In certain other areas, in which a grade I outbreak in 1950–1 was followed by a grade II or poorer kill in 1951–2, the observed immune rate was considerably higher than would be expected if the case-mortality rate (assuming that the whole rabbit population was susceptible) was 99·5%. The possible causes of this are discussed. Survival of immune survivors from the first epizootic through the second may be a factor of some importance, but it is probably not the only factor involved.

8. The areas just mentioned were exceptional. In most places there was either no build-up of population after the 1950–1 epizootic, or a second effective epizootic destroyed the majority of rabbits in the small population which had developed by reproduction of the survivors of the first outbreak.

1. Antibodies to the flagellar antigens of salmonellae are frequently present in the urine of Egyptians.

2. In many individuals, who are not urinary carriers but have schistosomiasis and have received T.A.B. vaccine, these urinary antibodies are derived from the plasma due to exudation or bleeding into the urinary tract.

3. In urinary enteric carriers, the urinary antibodies are due, at least in part, to the local production or release of antibodies within the urinary tract, as shown by the ratios of urine titre to serum titre with different H suspensions.

4. The production of antibodies within the urinary tract is considered to be an example of production or liberation of antibody by cells at, or close to, the site of infection.

1. An investigation has been carried out into the conditions necessary for the production of immuno-conglutinin in rabbits.

2. The inoculation of complement adsorbed on sensitized cells stimulates the production of immuno-conglutinin. We have called this procedure hetero-stimulation.

3. Immuno-conglutinin also results from the inoculation of untreated but killed bacteria. This procedure for its production we call auto-stimulation. Gram-negative bacteria appear to be more effective stimulants than Gram-positive bacteria. Soluble antigens did not appear to be as effective as bacterial suspensions.

4. The necessity for clarifying the part played by immuno-conglutinin in in vivo immune processes has been stressed.

The authors would like to thank the following for gifts of experimental materials: Mr H. I. Field, strains of S. pullorum; Dr J. Boissard, strain of C. hofmanni; Dr C. H. Lea and Dr R. S. Hannan, purified casein; Miss Dunkerley, Bence Jones protein. Cx polysaccharide for testing acute phase protein in rabbit serum was made available by the kindness of Dr McCarty of the Hospital of the Rockefeller Institute for Medical Research, New York; and much of the work on this aspect was done in consultation with Dr H. C. Anderson, to whom we are most grateful.

The majority of sedentary lightly clad acclimatized European men and women in Singapore are reasonably comfortable in relation to their indoor thermal environment provided the effective temperature does not exceed 78° F. or fall below 73° F.

European women, who were, however, older as a group than the other subjects, preferred rather cooler conditions than European men or Asian men and women.

There were considerable variations between individuals in their comfort tolerance for various levels of warmth, but the average opinion of one individual was usually consistent provided sufficient votes were collected to provide an adequate sample at each level of warmth.

When the dry-bulb temperature was above 83° F., increasing the average air movement from a still to a more turbulent condition added to the comfort of the majority of European men and women. When the temperature was below 83° F. for men and 81° F. for women, moderately good air movement was rather less comfortable than slight air movement; whereas below 77° F. still air was more comfortable than slight or moderate air movement. Increasing the air movement within a compartment can thus be used for combating thermal discomfort only within a limited range of warmth, but within that range it is extremely useful.

Two groups of naval ratings who had been living in a warship in a tropical climate were reasonably comfortable at similar levels of warmth to the men in Singapore, but they were less tolerant of levels of warmth above the comfort zone.

During the investigation of a number of epidemics of Clostridium welchii food poisoning (Hobbs, Smith, Oakley, Warrack & Cruickshank, 1953) the opportunity arose of examining some 500 different strains of Cl. welchii for toxigenicity. Work on so large a scale made it essential to develop a routinefor this purpose, and after several trials we devised the folio whig sequence of tests, which have proved entirely satisfactory in our hands, and may be of interest to others.

The stock diet for rats and mice, diet 41 cubed, can be rendered sterile to broth by autoclaving at 15 lb./sq. in. for 20 min. without impairment of the nutritive value for breeding mice.

1. Antibody occurs in the uterus and can be withdrawn by irrigation. Intrauterine antibody results from the introduction of antibody into the lumen of the uterus.

2. Neither free antibody nor the sensitization of the uterus has been produced by intramuscular injection of antigen, even when antibody has circulated in the bloodstream for periods from a few weeks to many months.

3. Active sensitization of the uterus follows upon the repeated introduction of antigen into the uterus.

4. It is concluded that antibody can be produced locally by some of the cells in the uterus when T. foetus antigen is present.

5. The uterus of the cow can be sensitized passively in vivo by the instillation of bovine anti-trichomonas serum so that the instillation 6–10 days later of Trichomonas antigen will produce the characteristic local anaphylactic reaction.

1. An electrophoretically homogeneous antigen preparation extracted from a strain (LII) of Pseudomonas aeruginosa by trichloracetic acid inhibits four phages active against this strain, and two phages (5 and 14) to which it is resistant but which attack a mutant strain LIII–3 bi.

2. An extract prepared in the same way from strain LIII–3 bi has no antigenic or inhibitory properties. Lysis of LIII–3 bi organisms by chloroform, however, yields a potent inhibitor active against several phages.

3. TCA extracts from immunologically distinct Ps. strains AII, BII and GII also inhibit phages 5 and 14 to which these strains are resistant.

4. The effect of a third phage (13) on Ps. LIII–3 bi is activated by the extract from strain LII which normally inhibits phages 5 and 14. Prolonged contact with very dilute solutions of the extract also causes activation of phage 5. Activation of phage 14 has not been observed.

5. The above findings are discussed in relation to current theories of phage action and phage inhibition.

Cases of paratyphoid fever are often not diagnosed until the second, third or subsequent weeks of illness. When calculating clearance rates of a series of cases the calculations must be based only on the numbers known to be positive at the week under consideration. If based throughout on the total number of cases the rates of clearance in the early weeks are greatly reduced.

Cases for which laboratory records are incomplete must not be entirely rejected when calculating clearance rates but must be retained in the population for as long as they were known to be positive.

Analyses designed to show the duration of infection in paratyphoid fever can only be made with accuracy under the most favourable conditions.

A large number of cases of paratyphoid fever were repeatedly examined bacteriologically to establish the duration of the infection as distinct from the clinical illness. After an initial lag the proportion of cases remaining infected fell logarithmically until the carriers revealed themselves.

We are grateful to many medical officers for information about their cases, and to Dr Lewis Fanning and Dr Ian Sutherland for much helpful criticism.