The three experiments with which this report deals were undertaken with the object of re-examining the conversion factor 1600 which had been provisionally allotted by the Second International Conference on Vitamin Standardization (1934) for converting the results of spectrophotometric tests for vitamin A into international units.

The size of the mortality sex ratio from pneumonia depends upon several factors which exert varying pressure with age, since it was shown for the London boroughs that the relative male risk was not high or low throughout life but displayed considerable variations.

In infancy social conditions have little effect upon the ratio, and there was no association with the degree of urbanization. In London the correlations with the indices of density became insignificant when the infant death-rate from pneumonia was kept constant. The male infant risk increases with the prevalence of the disease, and significant correlations were obtained when the indices of overcrowding were kept constant.

In childhood the size of the mortality sex ratio is not related to urbanization. The conditions operating for a high male mortality in childhood varies from those in infancy, since, for the eighty-three county boroughs, there was no correlation between the two ratios.

For the age group 15–65, in which the male pneumonia rate was twice that for females, there was a distinct association with degree of urbanization. In the London boroughs the mortality sex ratio was unrelated to social and economic conditions when the usual indices, the proportion of the population living more than two to a room, and the proportion of males in social class V were used. That environmental conditions had little effect on the ratio is also suggested by the experience of the mining communities which showed little difference in the mortality sex ratio between the county boroughs and urban districts. The rural mining areas were in agreement with the urban when allowance was made for the agricultural workers in these districts. In London there was a small significant correlation between the sex ratio and the pneumonia mortality sex ratio, indicating that the residential or industrial character of the borough was associated with the mortality ratio. Some support for this is given by the county boroughs where high ratios were found in the industrial towns and low ratios in the residential towns. Some occupations involve a direct risk of pneumonia, i.e. furnacemen, rollermen, etc., and others have a more indirect risk, e.g. inn-keepers, hotel-keepers, etc. Although the prognosis of pneumonia is affected by previous indulgence in alcohol, the effect of this factor can only be a matter of speculation. The mortality sex ratio from pneumonia in the three occupations in which a higher proportion of heavy drinkers are found than in the general population, inn-keepers, hotel-keepers, etc., barmen, etc., makers of alcoholic drinks, all of which have a high standardized mortality ratio from pneumonia, form an interesting progression. These values were 247, 394, and 1200, but the number of deaths among wives in the last two groups, 5 and 2, was so small that the ratios are really of no value. Yet there is, perhaps, an indication that as the opportunity for the wives to indulge in heavy drinking decreases with each class the mortality sex ratio from pneumonia increases. This factor of alcoholic indulgence probably operates in most occupations, and since the proportion of heavy drinkers is larger among men than among women, it would be necessary for only a small proportion of men to carry a heavy risk of pneumonia mortality to effect a large increase in the mortality sex ratio. It seems that the factors responsible for the relatively high male mortality from pneumonia, in this age group, were an occupational risk and the habits of the males.

In old age, as with the young age groups, there was no association with degree of urbanization. The mortality sex ratios of the London boroughs showed evidence of a geographical distribution. This was apparently a local characteristic, since the ratio of the county boroughs did not show any tendency to vary geographically.

A pleomorphic, Gram-negative organism, apparently the cause of purulent meningitis, is described. Reasons for regarding it as a Neisseria are adduced.

The experiments here described proved that preparations made from widely different classes of bacteria are capable of inducing immunity in mice against pneumococci. The success of these preparations was found to depend on the differential separation of an active immunizing antigen from another bacterial constituent—an ‘opposition factor’—which interferes with immunization. Further investigation and comparison depend largely on the discovery of a really effective method for the isolation and purification of the active antigen. Until its chemical nature is determined, the identity of the pneumococcal species antigen with similarly acting substances found in other bacteria remains unproved.

Pathogenic bacteria depend for their virulence and invasiveness on certain products individual to the species or type, and specific immunity is due to the development of the appropriate antibodies. But chemotherapy, as in the case of the sulphonamides, interferes with a less specialized metabolic process of the microbes and is neither species nor type specific in action. It is reasonable to infer that bacteria may possess in common a vital process associated with the presence of a common constituent which may be antigenic. ‘Species antigen’ may be a substance of this nature.

In view of the wide distribution of ‘species antigen’ among bacteria generally, it is probable that this constituent has already been separated and named in accordance with its presence in a particular species, but irrespective of its potential immunizing capacity.

So far as pneumococci are concerned, there is good evidence that species antigen may be identical with the species C carbohydrate. Tillett (1927) found that rabbits injected with successive courses of heat-killed pneumococci, whether of types I, II, III or of avirulent rough strains, developed an equal increase of resistance to infection by type III Pneumococcus. In 1936 Enders, Wu & Shaffer varied the procedure, and by injections of rough pneumococci prepared an antiserum which gave passive protection to rabbits against infection by type III Pneumococcus. This antiserum lost its protective power after absorption with the species C carbohydrate.

1. Serological methods for the determination of smallpox immunity are briefly discussed, and it is concluded that they are unlikely to provide a diagnostic method of sufficient accuracy.

2. Experimental work is recorded which shows certain differences in the response of previously vaccinated individuals, revaccinated simultaneously with a standard vaccine lymph and an elementary body suspension (vaccinia) of high potency. The significance of these differences is discussed.

3. The results indicate that although the advantage of the e.b. suspension over vaccine lymph is relatively insignificant, that of two insertions over one is very marked. In revaccination the routine use of one insertion only may result in a certain number of semi-immunes (vaccinoids) being erroneously reported as immunes.

4. It is concluded that if the two insertion technique be practised, persons showing immune reactions (negatives) may be considered, in all probability, as possessing full immunity to vaccinia-variola virus.

1. A general survey of diphtheria in Glasgow during 1934–42 has been made. Over 11,000 strains of C. diphtheriae have been typed and the incidence of the types is recorded.

2. The period has been marked by a change in the predominant type of organism from intermedius to gravis, and gravis infections are now responsible for most of the mortality, though the average case fatality rate due to them is not high.

3. Diphtheria on the whole has been mild and complications relatively few, but some shift in the death-rate incidence to the higher age periods with increase in the corresponding case fatality rate has taken place. A small shift in the age incidence of diphtheria is noted.

4. Some account of the effect of immunization is given.

5. Comment is made upon colony variation among the types of C. diphtheriae.

A form of Pirani vacuum gauge is described for obtaining a continuous record of the total residual pressure in a high-vacuum serum-drying cylinder of the Greaves-Adair type. The circuit incorporates an automatic relay which breaks the electric current heating the frozen serum if the pressure rises to a dangerous level, and so delays materially the onset of fusion of the serum.

Experiments on the bactericidal properties of mists were performed in a closed room of 850 cu. ft. capacity. The test organism was sprayed into the room through an Atmozon nebulizer operated from a mechanically driven Austin diaphragm compressor; the pressure was maintained at 7 lb./sq. in. Air to the compressor was taken through rubber tubing from an adjoining room to avoid accidental admixture of antiseptics into the air used to atomize the bacteria. The output of the nebulizer was 0·22 c.c./min. In the majority of the experiments the test organism was sprayed for 2 min. To ensure that an adequate mist was being emitted, the culture was nebulized in the dark against a dark background, and examined frequently with a light beam. Even distribution of the mist in the room was ensured by convection currents from a large hot-water pipe which ran along the length of two walls about 2 ft. from the floor, and by a small electrically driven fan placed immediately behind the nebulizer.

In seven years 176 cases of Q fever have been diagnosed in Queensland. Nearly all the 129 patients who lived in Brisbane were associated with meat works. Most of the forty-seven country patients worked on dairy farms.

Investigation of native animals, cattle and ticks, has indicated in outline the natural history of Q fever, which is set out diagrammatically in Fig. 1. (Several steps in this outline need confirmation and much detail remains to be filled in.)

First there is a basic cycle of infection with the bandicoot (and probably other bush animals) as reservoir, and Haemaphysalis humerosa (and probably Ixodes holocyclus) as vector. A bush worker may interrupt this cycle and get Q fever from the attack of Ixodes holocyclus.

Cattle become infected, probably through Ixodes holocyclus and perhaps through other ticks. It is possible that there is a secondary cycle: cattle-Haemaphysalis bispinosa-cattle.

Ticks on the cattle (Boophilus annulatus microplus or Haemaphysalis bispinosa) are probably the source of human infection. It is suggested that inhalation of tick faeces is the likely mode of entry of Rickettsia burneti.