(i) The theory of amoebic surveys and of related types of pathological surveys is discussed.

(ii) An inequality is derived,

where X is the total number of carriers and X1, X2 are the new carriers found at the first and second examinations.

(iii) Demonstrability is defined and several theoretical distributions of it are considered.

(iv) Demonstrability is shown not to be a constant in the populations considered.

(v) The danger of extrapolation is noted.

(vi) Life-table methods are introduced to treat some well-known published series.

(vii) A criterion for the adequacy of any estimate of the total carrier rate is given. The mean demonstrability of the outstanding carriers after successive examinations must form a decreasing series.

(viii) This criterion usually shows that the method of estimating the carrier rate for Entamoeba histolytica as three times the proportion of positives at a single examination, or as the total number of positives picked up in six examinations, both give too low a carrier rate.

(ix) It is suggested that the investigation of the ‘carrier’ rate may in certain cases be merely a measure of ‘demonstrability’.

(x) Possible future lines of investigation of the problem are noted.

Hoyle & Fairbrother (1937) showed that tissues infected with influenza virus contained two distinct particles, the infective virus elementary body, and a smaller particle, the soluble antigen, which could be demonstrated by complement-fixation tests.

A quantal response is one in which a certain event either happens or does not happen. If, in an animal experiment, we record merely whether or not the animal dies, we are measuring a quantal response. The type of data with which we are concerned here is familiar to all workers in biological assay, and occurs constantly in bacteriological and immunological experiments. A number of animals is divided randomly into several groups, and all the animals in each group are treated with the same dose of a certain substance. The doses differ from group to group, and are frequently arranged so that successive doses differ by a common dilution factor. At each dose the numbers of animals which respond positively and negatively are recorded. The potency of the substance may be measured by that dose which would in the long run produce a positive response in exactly 50 % of the animals, and the main statistical problem is how to estimate this dose (the LD 50) from the available data. It is assumed that any inaccuracies in measuring the doses are negligible in comparison with the sampling errors due to the inevitable differences between experimental animals.

1. In the spring of 1948 the health visitors of 422 authorities in Britain obtained information from 4683 mothers on accidental injuries sustained by their young children during the first 2 years of life. This study formed part of a questionnaire inquiry into the health and development of these young children, who had all been born in one week, 3–9 March 1946.

2. The mothers seem to have remembered accurately the more serious accidents which received professional treatment during the 2 years under review. It is possible that some of the minor injuries which had not been treated were not recalled or entered on the questionnaires.

3. The rate for all serious injuries which received professional care was 79·6 per 1000 children in the sample. Treated cuts were almost as frequent as treated burns or scalds, each being sustained by about 37 per 1000 children. There were only 7·5 fractures per 1000 children. The sum of the rates for each type of injury (81·3 per 1000) slightly exceeds the combined rate for all children injured (79·6 per 1000). This is due to the fact that in calculating the former rates eight children who were each involved in two serious accidents of different types were counted twice, i.e. once under each type of injury sustained.

4. In 1946–8 treatment of young children for burns or scalds and for serious cuts was most frequently given by general practitioners. Children under 2 years of age were admitted to accident wards of hospitals chiefly for the treatment of serious burns or scalds. Fractures were usually treated at out-patients’ departments.

5. Although almost all accidents occurred at home, variations in housing conditions, as measured by crowding and the domestic facilities available, had little effect on the incidence of accidents among children under 2 years of age. Accidents happened most frequently when the children were beginning to walk and becoming inquisitive, and most injuries occurred either because they were not steady on their feet or because they had not developed ‘heat-sense’.

6. Since domestic help was rare, most children had to play in the kitchen or living room while their mothers were doing the housework, cooking and laundry. In these circumstances, they were often exposed to the risk of injury.

1. Five generations of guinea-pigs bred successfully on diet 18 supplemented with crystalline ascorbic acid but without fresh green food.

2. No difference in reproductive performance was found between these animals and those of the normal breeding colony receiving unlimited supplies of fresh abbage.

3. Symptoms of vitamin E deficiency appeared among some young of the fourth and fifth generations, showing that diet 18 alone contained barely enough of this factor for continuous reproduction througy many generations.

4. Diet 18, supplemented by hay and fresh green food to supply vitamin C and additional vitamin E, provides all the essential factors required by the guinea-pig.

1. Thirty-four vaginal Corynebacteria have been grouped and subgrouped according to their cultural and biochemical characters. Owing to their instability and to the rigid taxonomy of the Corynebacteria, the exact identity of many of the strains is uncertain, but their characters have been compared with some of the Corynebacteria which have been given specific rank.

2. The majority of strains were carbohydrate-fermenters and many were of the hyperacid type. These may be associated in some way with a normal high vaginal acidity.

3. Many instances of resemblances to C. diphtheriae in morphology, in staining reactions, and in cultural appearances relating to the different dissociative phases, were encountered in the examination of these strains, and, in fact, some of the cultural types seen were analogous to those of C. diphtheriae described by Mcleod.

4. Intradermal tests on rabbits showed that many of these strains, including some from each group, were capable of inciting inflammatory reactions in their tissues, and it is suggested that they may play a secondary part in some infections.

A technique for carrying out the anti-globulin test with Salm. typhi O suspension in described; this technique has been used to examine a number of human sera. The degree of amplification of agglutinin titre and the final titres obtained were appreciably greater in the sera of individuals with a history of Salm. typhi infection, some of whom were carriers, than in the sera of normal individuals.

The recorded mortality from tuberculosis has fallen greatly in England and Wales since the middle of the nineteenth century when records were first available. The fall in rate has not occurred uniformly in all age groups however, and one result of this is that the maximum mortality rate in males is now occurring at a much later period of life than formerly.