1. The Introduction (pp. 67–73) describes the course of infant mortality in England and Wales over the past century, and critically reviews arguments advanced to prove that variations in the infant mortality rate (i.m.) are caused by genetic differences with respect to viability.

2. The i.m. in county boroughs shows a 2-yearly cycle of variability, affecting places with high mortalities.

3. We have devised and tested various social indices and have selected five which gave the highest joint covariance with infant mortality in county boroughs during the 11 years 1928–38. These indices are:

H, percentage of families living more than 1 person per room.

U, percentage of men unemployed.

P, percentage of occupied males in the Registrar-General's Social Classes IV and V.

F, percentage of women employed on manufacturing processes.

L, latitude.

4. We have computed multiple regression equations involving i.m. and the five indices for each of the 11 years, and two summarizing equations. The regressions plus sampling variance account for about 80% of the total variance in infant mortality. The regression is linear.

5. Latitude does not affect infant mortality in Class I. For this and other reasons we regard the latitude effect as expressing miscellaneous poverty indices omitted from our equations.

6. The regression equations enable us to divide the population into various strata with characteristic average infant mortality rates. These include:

‘Better off’ (all poverty indices = 0) i.m.=23·1

Overcrowded poor i.m. = 108

Unemployed overcrowded poor i.m. = 153

Babies whose mothers work in industry suffer an additional mortality risk of at least 35 per 1000, and possibly more. The figure 23·1 is the i.m. rate that would prevail if our five poverty symptoms could be eliminated.

7. In county boroughs two-thirds of infant deaths would be avoided by the abolition of conditions defined by our indices. Of the preventable deaths, one-third are associated with overcrowding, one-quarter with low-paid occupations, one-fifth with unemployment, and one-eighth with industrial employment of women. In England and Wales, over 250,000 deaths in 11 years, about 63% of the total, can be attributed to adverse social conditions.

We have to thank the Rockefeller Foundation for a personal grant to one of us (J. W.) out of an allocation for research work in Prof. Lancelot Hogben's Department, and the Halley Stewart Trust for a grant for mechanical computing equipment. Our thanks are also due to the various members of the Zoology Department in the University of Birmingham who assisted in computing at various times, and especially to Prof. Hogben for his unfailing interest, advice and support.

Changes of nuclear structure in bacteria have been studied by means of the hydrochloric acid-Giemsa method which produces brilliantly stained specimens and can be carried out with almost the same ease as some of the ordinary routine staining techniques.

The nuclear changes in the four spore-bearing organisms studied are outlined in Text-fig. III, to which the following numbers refer. The dumbbell bodies which are dispersed in the cells of the young growth (1) become alined in the long axis of the cell (2) where they eventually fuse into an axial nuclear cylinder (3, 4). These cells divide up into fusion cells of approximately the same length (5). The development of the ‘chromosome’ stage (1) into the fusion cell (5) is the first step in the process of sporulation. During its further development the fusion cell or spore mother cell divides twice (6, 7), with the result that it is segregated into four structures which often assume dumbbell shape. Therefore the chromatin cylinder of the individual spore mother cell seems to be equivalent to four nuclear elements one of which functions as the spore ‘chromosome’ (‘nucleus’?), whereas the remaining three disintegrate (8, 9). The ripe spore (9) representing, as it does, the smallest cell unit contains one nuclear structure only.

Therefore the two main features in spore formation of bacteria appear to be (1) a fusion of the dumbbell bodies into an axial chromatin rod (‘autogamy’?), (2) a reduction partition which is reminiscent of, though not corresponding to, the more complicated phenomenon of meiosis in the higher organisms. The sporulation, as outlined in this paper, gives new proof of the important part played by the chromatinic dumbbell bodies (‘chromosomes’) in the developmental cycle of spore-bearing organisms. The fusion cell with its axial chromatin cylinder has for the first time been proved to have a progressive functional significance as a stage in a nuclear cycle. The particular mode of fusion followed by reduction partition suggests that the chromatinic dumbbell bodies may be concerned with the transmission of the hereditary characters in bacteria.

1. A study has been made of different types of coliform bacteria with particular reference to (a) their ability to ferment lactose in MacConkey broth at different temperatures, and (b) the effect of using different temperatures of incubation for the indol, methyl-red, V.P., and citrate tests.

2. It was found that 97% of the cultures of Bact. coli (indol positive, methyl-red positive, V.P. negative, citrate negative) examined could ferment lactose with production of acid and gas between 40 and 44° C. The number was not appreciably reduced at 45° C. but was markedly reduced at 46° C. 28% of the cultures of Bact. coli (indol negative, methyl-red positive, V.P. negative, citrate negative) and 15% of Bact. aerogenes (indol negative, methyl-red negative, V.P. positive, citrate positive) were found to be positive at 44° C.

3. The adoption of a temperature of incubation of 30°C. for the V.P. test as advocated by Levine (1941) and the use of O'Meara's test showed that many cultures previously regarded as unable to produce acetylmethylcarbinol were in fact able to do so. Employing a temperature of 30°C. for 5, or in some cases 7, days for the methyl-red test, it was found that with nearly all the cultures tested there was an inverse correlation between the results of the methyl-red test and those of the V.P. test. With these modifications in technique some cultures originally designated as Intermediate type I were found to have reactions corresponding with those of Bact. aerogenes type I. Similarly, many cultures originally classified as Intermediate type II should have been typed as Bact. aerogenes type II.

4. It was found that all cultures of Intermediate type I classified as such by the new technique were incapable of using the nitrogen of uric acid for growth, but that the majority produced hydrogen sulphide. Cultures of Bact. aerogenes type II, on the other hand, grew well in uric acid medium, but produced no hydrogen sulphide.

The investigation described in this paper was carried out by the Freshwater Biological Association, as part of the programme of the Water Pollution Research Board of the Department of Scientific and Industrial Research. The paper is published by permission of the Department.

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.

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.

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.

The bodies of pneumococci contain a constituent of protein origin which interferes with immunization.

This constituent can not only counteract the immunizing action of the species antigen, but reduce the immunity response to the type-specific antigen.

In heat-killed pneumococci (ordinary bacterial vaccine) the coagulation of the protein renders the anti-immunity factor relatively insoluble and minimizes its action.

In solutions of pneumococci the anti-immunity factor is liberated and reduces the immunity response to the type-specific antigen.

The immunizing effect of a small dose of heat-killed pneumococci can be abolished if the cocci be dissolved before injection. But a larger dose of dissolved vaccine produces immunity, the effect of the antigen predominating.

The anti-immunity factor is heat resistant at acid pH, but is destroyed by alkaline heat. In these respects it resembles the immunizing antigens.