1. In the course of the examination of sputum from cases of lobar pneumonia, observations have been made on the incidence of the chief types of pneumococci. In the district from which the material was obtained, there was an apparent local diminution in the number of cases of lobar pneumonia due to Type II; the figures were 32·6 per cent. of Type II cases in the period 1920–22, and only 7·4 per cent. in the period 1924–27. The incidence of Type I was approximately the same in the two periods, the percentages being 30·6 and 34·3.

2. Several different serological varieties of pneumococci have been obtained from the sputum of each of several cases of pneumonia examined at various stages of the disease. This has occurred most frequently in cases of pneumonia due to Type I, and in two instances four different types of Group IV were found in addition to the chief types. The recovery of different types is facilitated by the inoculation of the sputum (preserved in the refrigerator), together with protective sera corresponding to the various types in the order of their appearance.

3. Two interesting strains of Group IV pneumococci have been obtained from pneumonic sputum.

One was an R strain which produced typical rough colonies, yet preserved its virulence for mice and its capacity to form soluble substance. This R pneumococcus developed a large capsule in the mice, which died of a chronic type of septicaemia. A strain producing smooth colonies was obtained from it in the course of a prolonged series of passage experiments.

The second strain, which was proved not to be a mixture, agglutinated specifically with the sera of two different types. In the peritoneal cavity of the mouse the specific soluble substance of each type was produced.

4. A method of producing the S to R change through ageing of colonies on chocolate blood medium containing horse serum is described. After two to three days' incubation small rough patches appear in the margins of the smooth colonies, and from these pure R strains can be isolated.

5. It has been shown that the R change is not equally advanced in the descendants of virulent pneumococci which have been exposed to the action of homologous immune serum. Some R strains form traces of soluble substance in the peritoneal cavity of the mouse; these revert readily to the virulent S form and, in addition, are able to produce active immunity. Others show no evidence of S antigen; spontaneous reversion takes place with difficulty, if at all, and they are incapable of producing active immunity. The stronger the immune serum used, the more permanent and complete is the change to the R form.

6. Restoration of virulence to an attenuated R strain, with recovery of the S form of colony and of the original serological type characters may be obtained by passage through mice. The change from the R to the S form is favoured by the inoculation of the R culture in large doses into the subcutaneous tissues; but the most certain method of procuring reversion is by the inoculation of the R culture, subcutaneously into a mouse, together with a large dose of virulent culture of the same type killed by heat.

Incubation of such a mixture in vitro does not induce reversion.

7. Reversion of an R strain to its S form may occasionally be brought about by the simultaneous inoculation of virulent culture of another type, especially when this has been heated for only a short period to 60° C., e.g. R Type II to its S form when inoculated with heated Type I culture.

8. Type I antigen appears to be more sensitive to exposure to heat than Type II antigen, since the former loses the power to cause reversion when heated to 80° C, whereas Type II culture remains effective even after steaming at 100° C.

9. The antigens of certain Group IV strains appear to be closely related to that of Type II, and are equally resistant to heat. Steamed cultures of these Group IV strains cause the R form derived from Type II to revert to its S form, while they fail to produce reversion of the R form derived from Type I.

10. The inoculation into the subcutaneous tissues of mice of an attenuated R strain derived from one type, together with a large dose of virulent culture of another type killed by heating to 60° C., has resulted in the formation of a virulent S pneumococcus of the same type as that of the heated culture.

The newly formed S strain may remain localised at the seat of inoculation, or it may disseminate and cause fatal septicaemia.

The S form of Type I has been produced from the R form of Type II, and the R form of Type I has been transformed into the S form of Type II.

The clear mucinous colonies of Type III have been derived both from the R form of Type I and from the R form of Type II, though they appear to be produced more readily from the latter. The newly formed strains of Type III have been of relatively low virulence, and have frequently remained localised at the subcutaneous seat of inoculation.

Virulent strains of Types I and II have been obtained from an R strain of Group IV.

11. Heated R cultures injected in large doses, together with small doses of living R culture have never caused transformation of type, and only rarely produced a reversion of the R form of Type II to its virulent S form.

12. The results of the experiments on enhancement of virulence and on transformation of type are discussed and their significance in regard to questions of epidemiology is indicated.

The remarkable paper by Fred. Griffith on the significance of pneumococcal types, reproduced in the preceding pages of this Journal, in which it was first published 38 years ago (Griffith, 1928), describes a series of careful and painstaking experiments which show beyond doubt that the ability to produce a polysaccharide capsule can regularly be restored to ‘rough’ (R) strains of pneumococci which have lost it, by the subcutaneous inoculation of mice with a mixture of a small number of the living R bacteria and an excess of heat-killed, capsulated (S) virulent bacteria. The inoculated mice frequently died from septicaemia and virulent, capsulated S organisms could be isolated from the blood. On the other hand, in control experiments, the injection of suspensions of heat-killed S bacteria alone never yielded living organisms, while recovery of virulent S organisms by (mutational) reversion, following inoculation of living R bacteria alone, was a rare event. Griffith called this phenomenon ‘transformation’ and, at least in the field of bacterial genetics, this name is still specifically used to describe it.

Opaque colonies of group A streptococci, detected on clear agar plates with obliquely transmitted light, are composed of extremely long chains of cocci. The mucopeptide layer of the cell-wall is involved in the formation of enhanced intercellular bridges. It is suggested that this exaggerated chaining results in an altered growth pattern which gives the appearance of granular opacity to surface colonies.

Rabbits immunized with whole streptococci of group B, type II, produce two immunologically distinct type-specific antibodies which are essentially equal by weight in protecting mice against infection with homologous type strains.

The capsular antigen with which these antibodies react is a polysaccharide containing galactose, glucose, glucosamine, and a labile component which has not been chemically identified. Extraction of the bacteria with TCA yields this ‘complete’ antigen, whereas extraction with HCl yields a partial antigen without the labile component. This degraded antigen can also be derived from the TCA antigen by treating the latter with hot HCl, and is indistinguishable from that extracted directly from the bacteria with HCl.

One of the antibodies produced, the TCA antibody, is directed against the labile component of the polysaccharide. The other, the HCl antibody, is directed against a β-d-galactoside determinant; and the precipitin reaction with this antibody is not masked in the ‘complete’ TCA antigen by the presence of the labile component.

The group-specific polysaccharide, which is located in the cell-wall, is also extracted with either TCA or HCl but can be eliminated from the preparations by fractional precipitation with ethanol. Although it is known that the type-specific polysaccharide is located in the streptococcal capsule, it is not at present clear in what form this substance occurs in the living streptococcal cell. It may be present partially as the degraded HCl form, or possibly wholly as the intact TCA form. Further immunological and chemical studies of these type-specific polysaccharides are in progress, and will be presented in another communication.

1. Streptococci causing neonatal infection in piglets have been identified serologically as belonging to group D.

2. Glycerophosphate, glucose and xylose have been identified as components of the group substance isolated from these micro-organisms.

3. The streptococci isolated from piglets with this disease in England appear to belong to a single serological type characterized by a capsular polysaccharide.

4. Glucose, glucosamine and galactosamine have been identified as components of the type-specific substance.

5. It is suggested that these streptococci should be designated Capsular Type 1 in Streptococcus suis, a new subgroup in group D.

1. In streptococcal infection of piglets the causative agent (PM streptococcus) was isolated from the throats of a high proportion of infected animals and from their apparently healthy litter-mates.

2. The PM streptococcus was isolated from the noses of three out of forty-three normal sows. In one sow the streptococcus was also isolated from the throat.

3. Bacteriaemia was induced in piglets up to the age of 17 days by inoculating into the nose and throat broth cultures of the PM streptococcus. Blood cultures were usually positive within 24 hr., and secondary involvement of the joints and meninges frequently occurred during the ensuing few days.

4. Serum taken from piglets 5 weeks after experimental infection and administered subcutaneously protected susceptible piglets against subsequent infection with PM streptococci.

5. The possibility of preventing streptococcal infection in piglets by active immunization of the sow is discussed.

A method of controlling outbreaks of streptococcal infection of the upper respiratory tract in communities such as boarding schools is described.

It is suggested that, in a search for carriers, nose and mouth swabs should be taken in place of the customary nose and throat swabs. These swabs will detect those who are dispersing streptococci into the environment, as distinct from the carriers who are not dispersers. It is essential that infections of the skin and ears should also be looked for.

It is recommended that all dispersers, whether nose or mouth positive, should receive sulphanilamide insufflation in both nostrils twice daily for a week, or longer if necessary, without exclusion from school. In addition, penicillin lozenges for 2 days may be recommended for the mouth positives only.

The history is considered to be an important factor in deciding the extent of the initial investigation, and examples are given to illustrate this. When mass swabbing is considered necessary, it is highly desirable that the whole community should be swabbed at the same time, as early as possible in the outbreak. It is also desirable that bacteriological follow-up should be available to check that control has been effected.

The sensitivity of quantal and graded responses to mouse-adapted bluetongue virus for the detection of neutralizing antibody was compared using probit and rankit analysis. The graded response, based on survival times, allowed the demonstration of antibody in highly dilute serum, in which antibody was not detected by the quantal response recording percentage death.

Quantal responses to bluetongue virus variants were compared with theoretical dose-response curves constructed according to the Poisson distribution for the random variation of virus particles in inocula. Of these theoretical curves the first term in the Poisson distribution gave the best approximation to the experimental data but the fit to normal distribution curves was better. The quantal responses to bluetongue virus did not appear to reflect the random variation of one-or-more infectious virus particles in inocula.

In graded responses to bluetongue virus, a rectilinear relationship was observed between reciprocal harmonic means of survival times and log virus dilutions.

1. Faeces from apparently healthy Bantu children from schools in Soweto township near Johannesburg were examined eight times at fairly regular intervals over a period of 1 year.

2. Only fifty-five children were present for all eight investigations and, of these, 36·4% yielded salmonellae and 9·1% shigellae. Taking the group as a whole, 26·2% of the children had salmonella infections and 6·2% shigella infections.

3. Parasites were shown to be present in sixty-four of the 130 children during the period of the investigation.

4. As in other surveys, there were more isolations in summer than in winter.

5. S. labadi and S. typhimurium were most frequently isolated, with the group B–E constituting 75% of the total isolations. S. typhi, S. paratyphi A, B and C were not found.

6. Water supplied to each house by the Johannesburg municipality was of good quality, yet it did not affect the incidence of salmonellosis and shigellosis.

7. In spite of better socio-economic conditions the incidence of salmonellosis is comparable to the two previously mentioned surveys. These findings indicate a lack of instruction on personal hygiene and the importance of public health measures.