1. The virtual sterilization time (v.s.t.) has been used as a measure of the rate of disinfection of Bact. coli cultures by phenol under carefully standardized conditions. The relationship of this time to temperature at each of five phenol concentrations has been examined from a fresh point of view, since it has previously been shown (Jordan & Jacobs, 1946) that none of the commonly accepted temperature coefficients was satisfactorily constant.

2. The relationship is such that a minimum or threshold temperature exists for each concentration. A corresponding ‘maximum’ temperature has been fixed, defined as the temperature at which the v.s.t. is 10 min. The value of (v.s.t. – 10) thus varies from infinity to zero between these temperature limits.

3. Sigmoid curves are obtained when log (v.s.t. –10) is plotted against temperature for given phenol concentrations. These may be regarded as asymptotic to ordinates at the minimum and maximum temperatures.

4. The Pearl-Verhulst logistic equation gives a curve of the required sigmoid type, and this formula has been shown to fit the curves of log (v.s.t. – 10) against temperature very satisfactorily over the range of concentrations studied.

5. One of the constants of this formula partakes of the nature of a temperature coefficient, and it has, therefore, been possible to derive a truly constant temperature coefficient for each phenol concentration.

6. The values of this new temperature coefficient do not vary greatly with phenol concentration within the range studied, but it is not yet possible to establish whether it is essentially constant for all phenol concentrations with which it is possible to work.

From three patients suffering from gastro-enteritis, non-mannite-fermenting, dysentery-like organisms were isolated which showed marked serological relationship to X, Y and P119 strains of B. dysenteriae Flexner.

In carbohydrate peptone-water media the organism fermented glucose without production of gas. In Lemco broth, however, both acid and gas were produced from glucose. The only other carbohydrate which was fermented was saccharose, but fermentation was weak and occurred only when incubation was prolonged for several days.

The organism possesses the group antigen common to the whole Flexner group and also a new type specific antigen of its own. Therefore it must be regarded as a new, non-mannite-fermenting member of the Flexner group of dysentery organism.

This work was undertaken at the instigation of Prof. P. L. Sutherland, to whom I am indebted for assistance and advice in the preparation of this paper. My thanks are due to Mr S. J. Denyer, Chief Technician, who isolated the first strain and referred it for further examination. I also thank Mr Gordon Denton for technical assistance.

Subcultures of all three strains have been sent to the National Collection of Type Cultures in London. Samples of the specific antiserum may be obtained from this laboratory.

During the years 1943 and 1944 S. thompson, not hitherto reported in poultry in this country, has been isolated on forty-four occasions from thirty-one outbreaks in chicks, and two outbreaks in ducklings. Two extensive outbreaks are described in detail, and the epidemiology of the disease and its possible importance to public health are discussed.

We wish to record our appreciation of the help given by the late Dr R. B. Haines and by Miss E. M. L. Elliot, Ministry of Food, Department of Pathology, Cambridge, in the identification of some of the strains isolated from outbreak no. 1, and for the gift of a stock strain of S. thompson which was used in the typing of strains 2768 and 3845.

We also wish to thank Dr Joan Taylor, Emergency Public Health Laboratory, Oxford, for supplying us with factor 5 (absorbed) serum.

The Group I paracolon bacilli formed biochemically a stable group. They fermented glucose, maltose, mannite, and dulcite, but not saccharose. Most of them could be distinguished from Salmonella organisms by the late fermentation of lactose or the production of indole. Many resembled the Newcastle bacillus in being late-dulcite fermenters. Serologically 75% of the strains were identical, each containing the A antigen. Some formed a separate group containing the A antigen, and Bact. alkalescens antigen and the C antigen of some Group III strains. The A strains are probably identical with those of Dudgeon & Pulvertaft (1927), but their strains were described as being motile. All Group I strains had minor agglutinins in common with the dysentery bacilli, particularly when freshly isolated. Most of Dudgeon's strains were isolated from cases of urinary infection, but in the present investigation almost all were isolated from the discharges of infants with diarrhoea and enteritis. This organism may be regarded as pathogenic or facultatively so, and deserves a name. I suggest it would be appropriate to attach to it the name of Dudgeon, who was the first to call attention to it.

Biochemically Group III bacilli resembled Group I strains but differed in fermenting saccharose. Some were motile. The metabolic and biochemical properties examined were stable. Serologically many (40%) possessed the A antigen, but also possessed a type-specific antigen, E. Others (37%) possessed both C and D antigens, usually C but sometimes D was dominant. These strains are related to the dysentery bacilli by the possession of common, minor antigens. A group of serologically heterogeneous strains remained (23%), generally unrelated to the dysentery bacilli.

Most Group II bacilli were stable biochemically, but some were not. Many strains of Group IV were unstable. Serologically, Groups II and IV were mostly heterogeneous, although 24% were included in the A, B, C, D, E pattern. Together they formed but a minority of all the paracolon bacilli.

Further serological investigation is required to discover new antigens and to link up the paracolon bacilli isolated from various sources.

This work was carried out under a whole-time grant from the Medical Research Council of Ireland to whom I am indebted.

I wish to record my very best thanks to my director, Prof. R. A. Q. O'Meara, for his continuous interest and invaluable advice at all times and without whose aid this research would not have been possible. My gratitude and thanks are due to my colleague, Dr J. St L. O'Dea, for his unfailing co-operation, particularly in obtaining all the specimens so quickly, in assisting at the post-mortems, and for many other services too numerous to mention.

Thanks are also due to the authorities, doctors and nurses of St Ultan's Hospital, Temple Street Hospital, St Kevin's Hospital, Clonskeagh Fever Hospital, Cork Street Hospital, and the Child Welfare Clinics in Dublin, particularly to Dr F. N. Elcock and Dr T. Murphy for their support and co-operation; to the ‘Diarrhoea and Enteritis’ Committee of the Department of Local Government and Public Health for their supervision of the research; and to the staff of the Department of Bacteriology, Trinity College, Dublin, where the research was carried out, for the help and facilities given.

I would like to thank all those general practitioners in Dublin who co-operated by the early notification of cases and in other ways. Finally, I wish to record my appreciation to the Statistics Branch, Department of Industry and Commerce, for their interest and kindness in furnishing a valuable report.

1. Solubility of a germicide in the medium (water or air) in which it is operating appears often to be the most important physical characteristic governing degree of activity on bacteria (partition law).

2. Evidence of the importance of solubility has only been derived from a study of the action of phenols and glycols, a high bactericidal activity never being registered unless solubility was low.

3. Other types of germicide were exceptional in that high solubility coincided with high bactericidal activity: iodine and maleic anhydride in the air; mercuric chloride and many organic acids in the test-tube.

4. Mixtures of germicide and bacteria as used in the test-tube were sprayed into the air, the bactericidal effect being usually increased or decreased according as to whether it was originally low or high in the test-tube.

5. The vapour pressures of most of the germicides used were deduced from the Clausius and Clapeyron formula, the boiling-points being determined by the bubbling method.

6. When the amount of a phenol used in the air is approximately proportional to the vapour pressure, the bactericidal effects of the different samples are more nearly parallel when the degree of saturation of the air is low than when it is high.

7. No phenol with a vapour pressure lower than 0·0021- mg. Hg, and tested at full saturation, sterilized the air during the first minute of the experiment, while all samples with, at least, 10 times this vapour pressure did so when at 12·5 % saturation.

8. Among the phenols tested, especially those having low vapour pressures, the concentration (w/w) in air is very much less than the concentration in water in the respective experimental conditions, where but few survivors is the criterion of efficacy. Owing to a number of different factors, the rapid decline in the initial concentration is more likely to be met with under air than under test-tube conditions.

1. By means of phage typing of Bact. typhosum, the source of infection in a boy who drank water from a polluted stream was traced backwards via water, sewage effluent, crude sewage and faecal specimens to unsuspected typhoid carriers in a large institution.

2. A nurse in the institution contracted typhoid fever, caused by the same phage type (C) of Bact. typhosum as was found (a) in the stools of typhoid carriers in the wards in which she was on duty, (b) in the crude sewage and sewage effluent from the institution, (c) in the stream into which the sewage effluent discharged, and (d) in the stools of the boy who drank the stream water. The nurse's sister, who had had an attack of typhoid fever a few months earlier, was infected with a different type (E 1) of Bact. typhosum and was therefore not the source of her sister's infection.

3.The laboratory technique is described for the examination of (a) samples of water, sewage effluent and crude sewage, using different selective and enrichment media, (b) large numbers of faecal specimens for enteric organisms by a preliminary pooling of specimens in batches of six or seven, and further examination of the individual specimens comprising a positive batch, thus effecting a saving of time and economy of media.

We wish to thank the Medical Officers of Health, sanitary inspector and the medical and nursing staff of the institution for their enthusiastic co-operation in the investigation.

This account of an outbreak of food poisoning may prove interesting, as its origin is attributed to a somewhat unusual source.

In a discussion of a series of tests connected with the fastness of colours on textile fibres, Villavecchia (1918) mentions the use of neutral ammonium acetate or common salt solution for measuring the colour resistance to perspiration. Thus in the case of coloured cotton, this is immersed for 10 min. alongside an equal quantity of white cotton yarn in a 0·1% aqueous ammonium acetate at 80°C., and the extent of colouring of the yarn as well as the degree of stripping of the coloured sample noted after drying without rinsing. An odd number of degrees of fastness is arbitrarily assigned to the coloured specimen according to the result, e.g. V degrees if neither the original tint nor the whiteness of the yarn is changed. Similarly with linen, hemp and ramie. For coloured wool both methods are used, viz. with sodium chloride and with ammonium acetate. In the former case, the alteration in colour is noted after simply dipping the wool in salt solution and allowing to air-dry out at room temperature. In the latter case, an equal quantity of white zephyr wool in addition to the white cotton is present. V degrees in all cases are stated to be conventionally adopted between industrial associations and dyestuff manufacturers for materials which are fast enough to reveal no change whatever in the testing bath. For coloured silk there are no precise data, and usually it is immersed in distilled water for several days to ascertain if any colour is lost.

This paper embodies the findings in all proven cases of diphtheria admitted to the Hull City Hospital during the years 1938–43 inclusive. All cases during those 6 years were typed and the clinical and bacteriological findings correlated. Since 1932 all severe cases had been typed and in the winter of 1932–3 a consecutive series of 313 cases was investigated and the results published (Leete, McLeod & Morrison, 1933). The 1933 paper showed a high gravis incidence of 59% and an associated high case fatality rate. Not until the end of 1937 was it again possible to type every case admitted but since then we have done so, and the series now presented embodies observations on 2039 infections, the great majority of which were clinical cases.

1. Avian tubercle bacilli were grown in hanging-drop cultures in embryo extract prepared as for tissue culture, but diluted to 25–5% of its usual concentration.

2. Microscopic branching colonies of pseudomycelia developed in the surface film of the hanging drops during the first few days of incubation, after which growth declined.

3. The development of these colonies was studied on the warm stage and proceeds as follows:

(a) The original rods elongate into filaments.

(b) The filaments multiply by ordinary fission and also by forming fine, pin-like terminal sprouts which grow into independent bacilli.

(c) After division the daughter filaments usually remain in contact at the site of fission; their terminal growth continues at an angle to the former cleavage plane and the colony thus acquires its characteristic branching structure.

(d) The colony enlarges and ramification becomes increasingly complex until about the fifth day of incubation when growth declines. The bacilli remain filamentous.

4. When transferred to embryo extract of normal concentration the pseudomycelial colonies revert to the ‘standard’ type of development characteristic of the more concentrated medium, i.e. they pass through a phase of filamentous proliferation followed by disintegration of the filaments into short discrete rods.

5. The development of a pseudo-mycelium is compared with the three common types of growth previously seen in more concentrated embryo extract.

6. The results of this investigation shed light on the controversial question of whether the ‘mycelial’ form of the tubercle bacillus is a single individual formed by ‘true’ lateral budding or a composite structure produced by the terminal, angular growth of coherent but independent bacilli. Our observations on the living organisms have shown that under appropriate experimental conditions both these forms may develop.

In the present work it is suggested that the sterilization of bacterial suspensions by mercurial antiseptics is a reflexion of a possible stoichiometrical relation between the mercuric compound and the thiol receptors in the bacterial cells.

This has been verified experimentally by studying the times of survival of suspensions of B. typhosum mixed with multiples and submultiples of the quantity of antiseptic theoretically equivalent to the thiol content of the suspension, as estimated by iodometric titration.

The considerable differences observed in the time of survival of suspensions mixed respectively with more and with less than the thiol equivalent of antiseptic, and the absence of any marked effect of dilution of the mixture, show that there is a quantitative relationship between the amounts of substrate and the quantity of antiseptic capable of sterilizing it.

Since Green & Mellanby (1928, 1930) reported that vitamin A protected the body against infection, this problem has been studied by various authors (Verder, 1928; Lassen, 1930, 1931; Seidmon & Arnold, 1931–2; Boynton & Bradford, 1931; McClung & Winters, 1932; Stryker & Janota, 1941). In general, the results showed that A avita-minotic animals were more susceptible to spontaneous or experimental infections than controls kept on a normal diet. However, in so far as we know, no experimental work has been done on the inverse problem—the effect of infection on vitamin A metabolism.

The organisms described as Bacillus wakefield and considered to be members of the Flexner group are not dysentery bacilli. They are paracolon bacilli containing α-antigen.

1. A series of lactic streptococci which were almost all capable of clotting milk in 24 hr. at 22°C. were divided into two groups on the basis of a few simple biochemical and morphological tests. The two groups corresponded to what some workers consider to be the species Str.lactis and Str.cremoris.

2. A series of phage races were tested for their action on the streptococci under various temperature and growth conditions.

3. The characteristics of phage attack on the organisms tended to confirm the division into Str.lactis and Str.cremoris species. Each of the strains of the long-chained cremoris type was attacked by only a few phages at the most, sometimes by a single phage only, whereas each of the lactis (short-chained) strains was attacked by a variety of phages. Furthermore, with two exceptions, the phage attacking the cremoris types on the one hand and the lactis types on the other formed quite separate and distinct groups.

4. None of the phages acted upon the several available strains of Str.faecalis and other group D (Lancefield) streptococci.

5. The evidence obtained from the phage sensitivity tests seems to justify the division of the lactic streptococci into two species, Str. lactis and Str. cremoris.

The author is indebted to Dr H. R. Whitehead for his interest in this work, and for helpful criticism and advice.

In experiments at this Station designed to find the most appropriate methods for the dehydration of fish, it was early recognized that bacteriological control would be necessary in order to ensure the safety of the final product. Many preliminary experiments were performed before a suitable method was found for commercial production. In these experiments data were obtained and are given here to illustrate the general argument, although most of the results are concerned largely with the method finally adopted.

1. Early blood culture is the best method of laboratory diagnosis in the inoculated case of enteric fever, but agglutination tests may give useful information.

2. In inoculated cases of enteric fever O and Vi agglutinins may be absent or present only at low titres. Steadily rising titres are not the rule and the titres more often fluctuate.

3. Complete agglutination at titres over 1: 80 for TO, over 1: 40 for AO, or over 1: 10 for Vi is suggestive but not diagnostic of an active infection.

4. Non-specific stimulation of the O and Vi agglutinins in the inoculated affects mainly the lower range of titres which are probably of little diagnostic significance.

5. Previous inoculations increase the proportion of people with residual O agglutinins within 6 months of the last inoculation but do not affect the Vi agglutinins.

6. Vi agglutinins may be present in normal inoculated persons who are not carriers.

General immunological principles appear to be of wide if not univeral application, and can be applied equally to the hyperimmunization of horses for the production of therapeutic sera, or to human immunization against diphtheria and tetanus. A wider knowledge of the results obtained in animals, chiefly guinea-pigs, rabbits and horses, can help in a better understanding of all that is involved in the immunization of children against diphtheria.

The response of an animal to an antigenic stimulus depends almost entirely on its previous experience of that antigen. If it has had no previous experience, antibody is produced slowly and in small amounts. If it has had previous experience, a change occurs in its antibody-producing mechanism which enables it on further stimulation to produce anti-body more rapidly and in larger amounts. To produce this effect the early experience must be adequate and followed by a sufficient period of rest. It is shown that the normal antitoxic values of animals can give considerable information on their previous experience of antigen; that this information can be made use of in the hyperimmunization of horses; and that inadequate primary stimuli and failure to provide adequate rest may lead to the production of antitoxins of low value and poor quality.

Two things are necessary for defence against toxins: circulating antitoxin and a high reactivity of the antibody-producing mechanism (potential immunity). Methods of immunization should be chosen so as to provide both these essentials.

Green & Mellanby (1928, 1930) were the first to direct attention to a specific relationship between vitamin A deficiency and infection. They studied the occurrence of spontaneous infections in vitamin A-deficient rats and concluded that animals fed on a diet deficient in vitamin A, but complete in all other respects, develop multiple infective lesions and die. Since then vitamin A has become known as the ‘anti-infective’ vitamin.

1. Out of 221 horses tested 34·8 % showed natural diphtheria antitoxin to the extent of 0·02 unit or more per c.c. of serum.

2. Amongst the horses in which no natural circulating antitoxin was detected, a much larger number failed to respond to stimulus than amongst those having circulating antitoxin. But, amongst the animals that did show appreciable response to primary stimulus, there was not much difference in degree of response between the horses with and those without natural circulating antitoxin.

1. The sizes of the droplets and droplet-nuclei produced by sneezing, by coughing and by speaking, were studied by the microscopic measurement of 12,000 droplet stain-marks found on slides exposed directly to mouth-spray, and of 21,000 stain-containing droplet-nuclei recovered from the air on to oiled slides exposed in the slit sampler.

2. From these measurements it was calculated that the original diameters of the respiratory droplets ranged from 1 to 2000 μ, that 95 % were between 2 and 100 μ and that the most common were between 4 and 8 μ. Similar size distributions were exhibited by the droplets produced in sneezing, in coughing and in speaking, except that, in the case of sneezing, the smaller droplets were relatively more numerous.

3. The respiratory droplet-nuclei were found to range in diameter from ¼ to 42 μ; 97 % had diameters between ½ and 12μ; the commonest diameter was between 1 and 2 μ.

4. The proportion of droplets of each size which will contain bacteria, whether commensal or pathogenic, is determined by the size of the droplets and by the numbers of bacteria in the secretions atomized. Calculations made on the basis of the size distributions obtained in this investigation indicated that few of the smaller droplets, and thus few of the droplet-nuclei, are likely to contain pathogenic organisms. Droplet-spray is unlikely to give rise directly to true airborne infection unless very large numbers of pathogenic organisms are present in the secretions of the anterior mouth.

5. The persistence of droplet-nuclei in the air of a 1700 cu.ft. room and of a 70 cu.ft. chamber was investigated by sampling the air with the slit sampler at intervals following sneezing.

6. When the air was not artificially disturbed by a fan, the time taken for the disappearance from the air of 90% of the bacteria-carrying droplet-nuclei varied from 30 to 60 min.; the nuclei larger than 8 μ in diameter usually disappeared within 20 min., and the nuclei larger than 4 μ within 90 min.; the smaller nuclei, few of which contained bacteria, remained airborne for much longer periods, on one occasion for at least 30 hr. When a fan was run throughout the experiment, the nuclei disappeared from the air much more rapidly.