Eight explosive outbreaks of food poisoning, occurring in school canteens in England during 1953 and affecting 1190 known cases, are described. The clinical features were characteristic of the toxin type of illness. No deaths occurred.

The food causing all of these outbreaks was prepared from spray-dried skim milk powder. It was not subsequently heat-treated and was usually consumed 3–4 hr. after preparation.

The spray-dried milk powder proved to contain a high content of bacteria, including large numbers of Staph. aureus, of a phage pattern often associated with food poisoning. The assumption was therefore made that these outbreaks were caused by staphylococcal enterotoxin.

Because the food was often consumed within 3–4 hr. of reconstitution of the milk powder—before, in fact, the staphylococci had had time to grow—it is concluded that the poisoning must have been due mainly to pre-formed toxin.

Consideration is given to the opportunities for the formation of toxin in a spray-drying plant, and reasons are brought forward for believing that it is formed mainly in the balance tank where the warm milk is kept, sometimes for several hours, before passing into the final drying chamber.

The processing of the milk and the precautions for preventing contamination of the finished product are discussed.

1. Plasma heated to 56° C. for 4 min. is not clotted by staphylococcal coagulase or thrombin, but when heated in the presence of glycine remains sensitive to the action of these clotting agents.

2. With glycine, plasma no longer clots after heating at 62° C.

1. If lysogenicity is used in conjunction with sensitivity to a set of phages aa a tool for phage-typing, a further subdivision of the phage types of Salm. paratyphi B becomes possible, and also the types fall into a number of natural groups. When lysogenicity is tested by growth of two types in mixed culture, phages are produced which by their characteristic host ranges reveal a subdivision of types, parallel and complementary to the subdivision found by a study of lysogenicity. These phage reactions therefore possess a biological significance not entirely empirical.

2. The method of Craigie & Yen, which made possible a great advance in phage typing of Salm. typhi by means of preparations derived by adaptation from a single phage, has not yet been shown to be applicable to the typing of Salm. paratyphi B (Felix & Callow, 1951). As some of the typing phages used in the Felix & Callow system are identical with certain ‘natural’ phages derived from lysogenic strains, the lysogenic character of the types they reveal may be used in conjunction with these sensitivity tests as characteristics of phage types, if the set of phages is increased by addition of a few, shown in Table 1. This suggestion was made to the International Committee for Enteric Phage Typing in 1952.

3. In addition to the demonstration by the direct method of phages carried by lysogenic strains of Salm. paratyphi B, phages derived from mixed cultures of different types are characteristic of some phage types. Further development of the use of such phages and study of their nature and origin demand further research. Until further investigations have been made, the subdivision of phage types which they reveal must be regarded as tentative.

4. Strains from a large outbreak of paratyphoid fever, which could not be typed reliably by the method of Felix & Callow, possessed peculiar lysogenic properties which, together with certain phage reactions, justify their designation as a new type, ‘Sittard’. These strains can be identified if phages derived from tests of lysogenic power are used in addition to those of the Felix & Callow system. A number of strains from other sources, diagnosed as type ‘Sittard’ by their sensitivity to phages, were shown to possess lysogenic properties characteristic of the type.

5. A few other strains, shown in a similar way to represent new types, are described.

1. The serum proteins of calves from birth to weaning, and the maternal colostral whey have been examined with the ‘classical’ Tiselius electrophoresis apparatus. Differences were shown between calves fed colostrum and those partially deprived of colostrum.

2. A study of the pre-colostral calf serum showed the presence of albumin and of two major components with mobilities similar to the α and β globulins of adult serum. A component forming approximately 1·4 % of the total serum proteins and with a mobility similar to that of γ1 or fibrinogen represented the γ1 globulin. This globulin component was not unconverted fibrinogen and may be autogenous γ globulin or γ globulin passively acquired in utero.

3. Autogenous γ globulin was evident in colostrum-fed and colostrum-deprived calves shortly after birth. The γ1 and γ2 components could be distinguished by the 10th day after birth, at which time the γ1 globulin was the greater. By the 30th day the γ2 globulin exceeded the γ1 globulin and a smaller component termed the γ3 globulin could usually be detected between the γ2 and the salt boundary.

4. Albumin concentrations generally fluctuated inversely to changes in the total serum globulins.

5. The α globulins associated with fetuin declined shortly after birth in the colostrum-fed group. In the deprived group α globulin first rose and then fell. In both groups minimum α globulin values were reached at about the 30th day, when the α1 globulin, although initially the major component in pre-colostral calf serum, was more depleted than the α2.

6. The β globulin frequently showed a transient though marked increase when the α globulins were at their lowest values.

7. No changes in the electrophoretic mobilities of the major serum proteins were detected as the calves matured, and no significant difference was found between the mobilities of the electrophoretic components of calf and adult sera.

8. The electrophoretic examination of colostral whey, colostral lacto-globulin fractions and calf serum immediately after suckling usually showed one lacto-globulin component. The relationship between the serum γ globulins and the lacto-globulin. is discussed.

The author wishes to thank Dr M. Robertson, F.R.S., and Sir Alan Drury, F.R.S. for their interest and encouragement during the course of this work, Dr W. R. Kerr for his co-operation in supplying most of the serum and colostrum samples, and Dr A. W. Stableforth and Dr J. S. Paterson for making certain cattle available for these experiments.

A passive protection test with brucella antibodies, based on the spleen counts technique, has been described. This test has been found more sensitive than that based on lethal challenge.

Normal human sera have been shown to possess marked protecting power.

Protective activity of human sera was considerably increased following vaccination with living streptomycin-dependent brucellae, or after natural disease.

The bearing of these findings on several brucellosis problems has been briefly discussed.

The author wishes to express his thanks to Prof. A. L. Olitzki for constant advice and encouragement; to Dr H. V. Muhsam, Department of Statistics, the Hebrew University, for generous help in the statistical analysis; and to Miss R. Avraam for technical assistance.

Field observations supplemented by laboratory tests were carried out on the occurrence of myxomatosis at two sites with contrasting environments near the northern limit of rabbit infestation in Australia, during the period May 1952 to April 1953.

In spite of the very low incidence of cases of myxomatosis observed in wild rabbits during that period great reductions in the rabbit population occurred.

Analysis of the results of serum surveys indicates that myxomatosis was present and caused minor unobserved epizootics during this period, The overlap in this area of rabbit breeding and active transmission of myxomatosis probably led to a high death rate in the sub-adult rabbit population.

In spite of continued reintroduction of fully virulent standard virus into the areas, all strains of virus recovered were somewhat attenuated. There was a suggestion that at Texas the degree of attenuation increased during the study period.

Sex ratios and data on reproduction are presented for the 1488 rabbits shot at the two areas. Recovery from myxomatosis appeared to have no adverse effect on the fecundity of the female rabbit.

1. The lacto-globulin in bovine colostral whey, and the γ globulin in the serum contain the normal and induced agglutinins to the protozoon Trichomonas foetus.

2. A decline in γ globulin in sera from cattle approaching calving may be associated with the concentration of the lacto-globulin in the udder.

3. The elimination of the passive normal and induced agglutinins acquired by the neonatal calf was logarithmic. The autogenous production of γ globulin by the calf occurred soon after birth, resulting in an apparent decline in the rate of elimination of the lacto-globulins.

4. The autogenous production of γ globulin was not necessarily accompanied by that of detectable normal agglutinin.

5. Calves injected with T. foetus antigen within the first 3 weeks of life, and in which there was evidence of autogenous γ globulin, developed normal autogenous but not induced agglutinins.

6. Calves which received colostrum containing maternal induced and normal agglutinins, calves partially deprived of colostrum, and calves immunized in early life, produced the normal autogenous agglutinin between the 30th and 60th days, reaching the normal adult titre of 1/48–1/96.

7. The properties of the normal agglutinins were investigated. They possess some characteristics significantly different from those of the induced agglutinins. These suggested that the normal agglutinins were γ globulin molecules with an ‘accidental’ genetic configuration complementary to T. foetus.

The author wishes to thank Dr M. Robertson, F.R.S., and Sir Alan Drury, F.R.S. for their interest and encouragement during the course of this work, and Dr R. C. Campbell for the statistical analysis.

Four red cell antigen-antibody systems in the rabbit are described.

Three of these systems, Z, Y and W, appear to be inherited as an allelomorphic series. The fourth is inherited independently.

Some of the serological properties which allow these sera to be recognized are described and attention is drawn to a property of rabbit red cells, manifested by a variation in their susceptibility to agglutination by homologous antisera, which can complicate the separation of a mixture of antibodies in one serum.

1. Rabbit cells show a marked variation in agglutination when reacting with apparently homologous iso-antisera.

2. This phenomenon has been investigated in two ways:

(a) Samples of apparently homologous antisera have been absorbed with (i) strongly agglutinating cells, (ii) poorly agglutinating cells. It was found that strongly agglutinating cells absorbed the antibody completely and rapidly from the serum, whilst poorly agglutinating cells, though they absorbed it completely, did so much more slowly. Also, when a serum which had been absorbed with poorly agglutinating cells until these no longer reacted with it was titrated against strongly agglutinating cells, these were still strongly agglutinated. This showed a source of serious error when investigating new sera by absorption techniques and when using weak antisera for grouping purposes.

(b) Poorly agglutinating cells were injected into rabbits, and the antisera so obtained were examined against strongly agglutinating cells and against the poorly agglutinating cell used as the antigen. The antibody response was poor; two out of eight rabbits developed an antibody, and strongly agglutinating cells reacted more strongly with these antisera than the poorly agglutinating cells which had been used as the antigen.

3. Three hypotheses for this variation in agglutination have been put forward and discussed:

(a) That the variation is due to cross reactions between numbers of closely related antigen-antibody systems. The results of the investigations 2 (a) and 2(b) suggest that this is unlikely.

(b) That the disposition of antigen sites on the surface of the red cell is a factor determining the agglutinability of the cell. It is considered that this might play a subsidiary role in the phenomenon as it is shown in the rabbit.

(c) That rabbit red cell agglutinability is mainly determined by the number of antigen sites on the cell available to the antibody. The experimental results can be explained on this hypothesis, and it is suggested that this may be the main factor accounting for the behaviour of rabbit red cells. It is pointed out that supporting evidence for this is afforded by measurements with radio iodinated antisera.

Dilution series of viruses often do not fit the exponential curve which they should fit if the usual assumptions of the theory of dilution series were true. Suppose the density of the virus suspension is λ, the average number of virus particles per unit volume of the inoculum (we suppose that unit volume is the amount actually used in inoculating the egg or other test material). Let C be the proportion of infective virus so that Cλ is the effective density of virus particles, and X is a factor depending on the dilution used such that CλX is the expected number of infective particles in the inoculum.

1. The in vitro properties of 214 strains of Proteus organisms isolated from dogs, cats, cattle, pigs, birds and other domestic and captive wild animals were examined.

2. The majority of strains were P. mirabilis, 23% being P. vulgaris and 4·7% P. morganii.

3. P. vulgaris was found more frequently in pigs and cattle than in other animals.

4. Biochemical varieties of the Proteus group occurring in man have been found in animals.

5. The action of Proteus strains on red blood cells was examined and strain differences observed.

Two new statistical methods—one parametric, the other non-parametric—are developed to compare the slopes of quantal infectivity curves.

Ten influenza strains were examined with the aid of these tests, and the results show that virus yielded by the von Magnus phenomenon (i.e. containing ‘incomplete’ particles) and standard infective virus do not differ in the slope of their infectivity curves.

It is concluded that the von Magnus phenomenon yields a mixture of infective and non-infective particles; on this evidence Fulton's suggestion of uniformly changed virulence is untenable.

I am greatly indebted to Prof. P. A. P. Moran for helpful discussions of theory, and frequent corrections of statistical technique.

1. An apparently pure rabbit iso-antibody marked with 131I has been shown to adsorb specifically to a greater extent on some rabbit cells than on others. This accords with previous evidence that the same iso-antibody exhibits a higher titre with the cells which are shown here to absorb more marked antibody than with those which adsorb less.

2. Saturation of two of these red cell types by repeated application of fresh quantities of the 131I iso-antibody until no more is specifically adsorbed, suggests that the number of functional antigenic sites is six or seven times greater on the one than on the other cell.

3. There is no apparent difference in the amount of 131I iso-antibody adsorbed by any one type of rabbit cell in comparative titrations using 3·3 % MgSO4.7H2O medium instead of normal saline.

1. Coliform and paracolon β strains agglutinated to a high titre with OB antisera from two strains of Escherichia coli O111B4H2.

2. The presence of β antigen in some strains of Esch. coli O111B4H2 has been shown and therefore such strains should be classified as plus β forms. This factor could not be demonstrated by agglutination tests but was evident by its ability to produce and absorb β antibodies.

3. The dissociation and complex nature of β forms was discussed.

The writer wishes to express her thanks to Prof. S. D. Rubbo for his helpful criticism of the manuscript.

1. The diphtheria antitoxin titres of several thousand samples of cord blood have been analysed with relation to the histories of the mothers.

2. Among mothers without histories of diphtheria or of immunization those born in 1933 or later showed a higher degree of natural immunity.

3. The distribution of antitoxin titres among mothers who had suffered from diphtheria was similar to the average distribution among the unimmunized.

4. The differences in proportions with any antitoxin in different groups of unimmunized mothers were almost entirely made up of those with titres above 0·04 and below 1·0 unit per ml.

5. Among the artificially immunized mothers there were many more with low titres, i.e. below 0·04, and a few more with high titres, i.e. over 1·0, than among the unimmunized.

6. Mothers immunized between the ages of 9 and 14 with the peak at 11 or 12 years showed the highest immunity rate.

7. The greatest number of high titres occurred among recovered cases subsequently immunized.

The results of experiments designed to determine the threshold values for various thermal stimuli have been reported. The threshold increments in the intensity of radiation in ‘still’ air were determined first for several areas of exposure. In further experiments the effects of simultaneous changes in both the speed and temperature of the air, and the air speed and radiation intensity, were examined.

The data from these experiments were then used to estimate the relation between the temperature and speed of the air on the rate of heat loss by convection. The findings were shown to be in good accord with previously published data.

During the discussion of a paper presented by the author to the Society for Water Treatment and Examination at Sheffield in 1952, it was noted that several water bacteriologists were confirming, with a high degree of success, presumptive positive tubes in the coliform test as Bacterium coli type I after incubation for 6 hr. only in MacConkey broth at 44° C. (Taylor, 1952).

Groups of guinea-pigs were passively immunized against diphtheria toxin with homologous antitoxic serum so that their sera contained, at the start of the experiment, 1·0, 0·1, 0·01 or 0·001 unit/ml, respectively. They were then actively immunized with one, or two spaced, injections of 0·1 Lf of A.D.F. Two control groups were included, one passively immunized only and the other actively immunized only.

Passively produced serum titres of 0·01 and 0·001 unit/ml. did not interfere with active immunization in any demonstrable way.

A titre of 0·1 unit/ml. did interfere with active immunization, markedly 4 weeks after the primary, slightly 2 weeks after the secondary, and markedly 14 weeks after the secondary, stimulus.

A titre of 1·0 unit/ml. interfered with active immunization, markedly 4 weeks after the primary, and 2 and 14 weeks after the secondary, stimulus. This titre, however, did not completely annul the effect of the primary stimulus. The highest observed serum titre was obtained at the 32nd, instead of at the 4th week, as in the guinea-pigs actively immunized only.

In large measure the results confirm those of Barr and her colleagues who found that, in human babies, an initial ‘passive’ titre of 0·04 unit/ml. serum did not interfere with active immunization, whereas a titre of 0·1 unit/ml, led to unsatisfactory immunization.

A micro-drying method is described, which is simple, rapid and reproducible. It has been shown to give results in reasonable agreement with the Karl Fischer method, and with the vapour-pressure method. The results on samples of low moisture content are, however, considerably higher than those by the so-called American standard method. The method has been in routine use for over 3 years.

The effect of two chelating agents, sodium diethyldithiocarbamate and 8-hydroxy-quinoline (oxine), on 70 strains of brucellae (24 Br. abortus, 22 Br. melitensis and 28 Br. suis) has been examined.

The pattern of growth and inhibition of the three species as it appears in the carbamate test described by Renoux is of some value in the differentiation of species. Br. suis is more resistant to carbamate than the other two species.

The three species also differ in their sensitivity to oxine, and strains of Br. suis from various sources were consistently more resistant than the other species. This observation may be of use in the identification of Br. suis.

My thanks are due to Prof. Adrian Albert and Dr J. H. Marshall for helpful discussion of the chemical aspects of this work, and to Mr B. Madge, A.I.M.L.T., for technical assistance.