By ultracentrifugation of emulsions of brains from suckling mice infected with the MEF1 strain of poliomyelitis virus, infective virus can be separated from a non-infective soluble antigen. The soluble antigen which remains in the supernatant fluid is serologically specific and is responsible for most of the complement fixation shown by such brain emulsions.

Soluble antigen is not demonstrable in the brains of adult mice infected with a strain of the virus which has not been adapted to sucklings.

The soluble antigen is heat stable and resists treatment with organic lipoid solvents such as acetone, ether and chloroform.

Against the concept that starch is inert immunologically and, therefore, an ideal substrate for in vitro studies on leucocytes, the results here recorded demonstrate that there are at least two components of serum which are specifically required for phagocytosis of starch. The available evidence suggests that the heat-labile component is C′, and the heat-stable component is specific Ab. The latter, which is a serum globulin, conforms to the definition of Ab from three standpoints: (1) it is adsorbed to the starch granule at low temperature and cannot be eluted by washing with saline at pH 7–0; (2) although it is found in ‘normal’ serum, it appears in increased quantities in the serum of animals injected with starch; and (3) once combined with the starch granule, it exerts three in vitro immunological effects, i.e. opsonization, induction of immuneadherence, and agglutination. As evidence that the latter reactions are due to specific Ab, the enhancement of phagocytosis and the induction of immune-adherence are manifested only in the presence of C′.

The measurement of Ab or C′ has been complicated by the finding that fresh normal serum to be employed as C′ has invariably contained Ab to starch. This situation is similar to that which exists with a variety of micro-organisms, e.g. Micrococcus aureus, against which the majority of normal animals and human beings possess circulating Ab. To obtain C′ free of Ab, fresh guinea-pig serum was adsorbed in the cold with starch. Despite the low temperature which would be expected to reduce the C′ fixation, about 30–40% of C′ activity was lost during adsorption for 60 min. at 0° C. When the adsorption was performed in the absence of Mg2+ and Ca2+, the loss of C′ was lessened considerably. This is interpreted to mean that at least two factors contributed to the loss of C′ cited above: (1) the specific fixation of some or all components of C′ to the starch-Ab complex, which requires the presence of Mg2+ and Ca2+, and which occurs even in the cold; and (2) the non-specific action of starch in adsorbing C′, or perhaps destroying C′, which does not require Mg2+ or Ca2+.

1. Pival at 0·025% is somewhat less toxic than warfarin at 0·005% to R. norvegicus when ingested for periods up to 72 hr. It is also less acceptable in a dry cereal bait.

2. Pival and warfarin at 0·025 % are about equally toxic and equally acceptable to R. rattus.

3. Young R. rattus appear to be more resistant than heavier rats to both Pival and warfarin.

4. The fungicidal properties of Pival are discussed.

The evidence presented supports the hypothesis that the experimental form of anthrax induced by depositing a cloud of single spores on lung epithelium is initiated in the lymphatic regions and not in lung tissue.

Proportionately few of the deposited spores reach the lymph glands. The majority remain inactive in so far as induction of disease is concerned. Slowly, however, they seem to go through the first stages of germination but do not multiply and therefore die. This is probably the major factor operative in their disappearance from the lung.

Effective prophylactic measures are suggested for dealing with an unimmunized host exposed to anthrax infection by the pulmonary route.

The LD50 dose of Past. pestis is much greater when tested by the respiratory route than by subcutaneous challenge. This is probably due to trauma inflicted on the airborne particles.

Two forms of plague, both originating in the respiratory tract of the guinea-pig, can develop according to the size of the particle containing Past. pestis presented to the host. Small particles initiate a broncho-pneumonia which leads to septicaemia and death. Large particles establish a septicaemia, and death results more quickly without the development of a pneumonia.

Cross-infection to normal animals occurs irregularly when they are exposed to others developing plague by the respiratory route. Such incident is rare when the initially infected animals are exposed to large particles. Cross-infected animals suffer from the disease characteristic of exposure to large particles. Attempts to establish an epizootic by cross-respiratory infection were abortive, probably due, in some measure, to the type of disease developing in first cross-infections.

The infectivity of Brucella suis for the guinea-pig by the respiratory route has been studied. Br. Suis was dispersed in airborne particles of various sizes from single organisms to 12μ in diameter, and it was found that the infectivity decreased 600-fold with increasing particle size within this range. It is suggested that this is due to the ability of Br. Suis to multiply rapidly on the surface of the lower reaches of the respiratory tract.

1. The 6 hr. soluble antigen production test for comparing the infectivity of influenza virus preparations is described in detail. Dilutions of the preparations are inoculated intra-allantoically into groups of fertile eggs, and after 6 hr. of incubation the amounts of soluble antigen formed in their chorio-allantoic membranes are determined. Reproducible results can be obtained.

2. The similar test, in which haemagglutinins in the chorio-allantoic membranes are measured 6 hr. after inoculation of seed virus, is less accurate and less sensitive.

3. Eggs of different ages of incubation form different amounts of soluble antigen in their chorio-allantoic membranes in 6 hr. when inoculated with the same amounts of virus.

1. After inoculation of eggs with a large dose (108·6 ID50) of influenza virus, chorio-allantoic membranes harvested from the 3rd to at least the 21st hr. (but not at the 1st or 2nd hr.) gave rise to large amounts of soluble antigen in 6 hr. in the chorio-allantoic membranes of sub-inoculated eggs (6 hr. soluble antigen production test). These amounts were larger than resulted from inoculation of equivalent numbers of ID50 of standard allantoic fluid virus. By the conventional 72 hr. test, the infectivity of the chorio-allantoic membranes increased 1 hr. later, at the 4th hr. after inoculation.

2. Allantoic fluids and chorio-allantoic membranes harvested from passages of very large and of small amounts of influenza virus were tested by 6 hr. soluble antigen production. The relative amounts of soluble antigen formed by different seeds appeared to be determined by their ID50: HA ratios, irrespective of whether they were allantoic fluid or chorio-allantoic membrane preparations. Larger amounts of soluble antigen were formed in 6 hr. per ID50 inoculated by preparations having lower ID50: HA ratios, i.e. containing larger amounts of ‘incomplete’ virus, and vice versa.

3. It is suggested that high infectivity in the 6 hr. soluble antigen test per ID50 inoculated is due to a content of ‘incomplete’ virus, or of virus precursors: possibly these are in fact the same.

4. More particles of an incomplete virus preparation than of standard allantoic fluid virus must be inoculated to produce a given amount of soluble antigen in 6 hr. It is suggested that a process resembling multiplicity reactivation must occur in cells infected with more than one particle of ‘incomplete’ virus.

Six strains of bluetongue virus were compared by cross complement-fixation tests performed on Perspex sheets according to the method of Fulton & Dumbell using antigens derived from crude saline extracts, and acetone and ether extracts, of infected suckling mouse brains. Only minor differences were encountered with the former and no significant differences with the latter. The reasons for this are discussed.

In the neutralization tests important differences were demonstrated between strains.

There is evidence that the soluble antigen is composed of particles of varying size, that the smaller particles are responsible for the marked overlapping in the complement-fixation tests, and that increasing complexity associated with increasing particle size may be concerned with increasing serological specificity.

1. An M-producing strain of Streptococcus pyogenes type-12 was shown to be carried on the surface of apparently healthy tonsils for at least 3 years.

2. Loss of M substance in a strain of type-3 in a tonsillar carrier was shown to be by gradual replacement of matt forms by glossy variants. This pair of naturally occurring variants showed very different growth rates as mixtures in liquid media.

3. Under suitable conditions, glossy variants regularly appeared and replaced the M-producing strain from which they were derived in these and all other strains of type-3 and type-12 tested from a wide variety of sources.

4. It is suggested that the selection of variants by the differential nutrient value of the micro-environment is the deciding factor in carrier strains showing loss of M substance.

No evidence was obtained to support the hypothesis that the observed reduction in numbers of coliform bacteria during sewage treatment was due to the action of bacteriophage.

1. Elementary body suspensions of vaccinia virus placed on the chorio-allantoic membrane of the developing chick embryo showed immediately an enhanced infectivity which may amount to a several-fold increase in titre.

2. In studying the growth curve of vaccinia virus in the chorio-allantois the distribution of virus between the liquid and the membrane had to be taken into account.

3. Some virus disappeared after inoculation, but this did not necessarily indicate a non-infective phase in a growth cycle.

4. Virus began to increase in 4–5 hr. and proceeded without stepwise increments, reaching a maximum in about 36 hr.

5. Haemagglutinin and complement-fixing ‘soluble’ antigen were formed during the growth of virus, and the titre of each was directly related to the amount of virus. They were detectable when the titre of virus reached respectively 106.5–10.70 and 105.5–106.0 pocks per ml.

6. Haemagglutinin may have been acting as a complement-fixing antigen.

7. Neither haemagglutination nor complement-fixation provided evidence for the occurrence of a non-infective phase of virus as part of a growth cycle.

Vaccinia virus inoculated on the chorio-allantois and causing infection spread to the uninoculated part of the membrane, the embryo, the allantoic and amniotic fluids and the yolk within 1 day.

The virus grew in the embryo and possibly in the uninoculated part of the chorio-allantois, but in the latter no macroscopic lesions were detected.

Virus increased in amount in the allantoic fluid and may have grown in the lining of the allantoic sac; it did not increase in the amniotic fluid; it was present in yolk and increased slightly but its local growth was doubtful.

The presence of haemagglutinin and complement-fixing antigen was related to the amount of virus.

Allantoic fluid from infected eggs could be a ready source of antigen for complement-fixation.

1. Eleven thousand two hundred and twenty-eight sera from persons, mostly blood donors, living in Kent and seven counties in East Anglia, have been tested and 379 (3·4%) found to have complement-fixing antibody to Rickettsia burneti at a serum titre of 1/10 or greater.

2. A group of 396 donors in Kent and East Anglia, composed of 190 donors with antibody, and 206 donors from those without antibody to serve as controls, were interviewed, and an epidemiological history was obtained on the possible ways in which they had been exposed to R. burneti during the period 1942–53.

3. A comparison of the epidemiological histories of the positive and negative donors showed that donors in Kent who had constant occupational exposure to cattle and sheep including unprocessed materials from them, or who had had a raw milk supply to their homes for all or part of the period 1942–53, more frequently had antibody than those donors without such qualities. In East Anglia the positive serological state among donors was associated only with the use of raw milk and not with occupational exposure to animals. There were suggestive findings among Kentish donors that those who visited farms or other potentially infectious places, either during the course of their job or during their leisure, also experienced greater risk of infection.

4. In general, these findings of infection from occupational exposure, from visits to infectious localities, or from the use of raw milk in the home, confirmed the tentative epidemiological conclusions drawn from a previous investigation of patients with Q fever. It was not found in this survey, however, that residence near dairy farms, receipt of objects from potentially infectious localities, or contact with persons from such localities was associated with a special risk of infection.

5. No association was found between the donors' serological state and the keeping of dogs, cats, poultry, pigs, rabbits, psittacine birds in the vicinity of the home or its infestation by mice, rats or mosquitoes.

The complement-fixing antigen activity of canine hepatitis virus is due to particles which are estimated to measure from 70 to 105 mμ and which probably can form larger aggregates. The active particles in the original virus tissue suspension were of sizes similar to those in the purified preparations, their serological properties being identical. The chemical properties of the antigen are those of protein, probably ribonucleoprotein. No evidence has been obtained to explain the association of a high concentration of the antigen with the presence of numerous intranuclear inclusion bodies in the lesions. It is evident, however, from these experiments that the inclusion bodies are not just deposits of the serologically active material. Since the intranuclear inclusion bodies and also the antigen are probably composed of ribonucleoprotein, it is possible that they both represent certain stages in the formation of virus protein by a catalytic reaction from the denatured host proteinogen.