In a previous communication the authors drew attention to the occurrence of complement-fixation by normal serum along with various non-antigenic substances, and recorded the results of a study of this phenomenon with particular reference to the serum principle or principles concerned in the reaction (Mackie and Finkelstein, 1928). Though no conclusive interpretation of the results could be offered, a close analogy was established between the reacting agent of the serum and a natural antibody, e.g. a natural haemolysin, and the observations appeared to be of significance in relation to natural immunity phenomena.

1. An outbreak is described of fatal epidemic enteritis due to B. dysenteriae Sonne which occurred in the autumn, 1928, in the infant wards of a hospital in Glasgow.

2. The clinical histories of two fatal cases are given.

3. The bacteriological and immunological examination of two strains of B. dysenteriae Sonne is described.

4. The results are given of a series of animal inoculations undertaken to study the virulence of B. dysenteriae Sonne and the nature of the lesions which it produces. To these are added the results of certain feeding experiments.

Three cases of continued fever are described in which the Salmonella type “Dublin” was isolated from the blood. The cultural and serological behaviour of the three strains so obtained are compared with those of 34 strains of typical S. enteritidis (Gärtner) (including strains from commercial rat virus) and with those of 12 other strains of S. dublin (including six from calf-dysentery in Denmark). The suggestion is made that the “Dublin” type is of bovine habitat and that cows' milk is the vehicle of human infection.

1. Analysis of a series of 135 strains of B. aertrycke indicates that at least four well-defined types may be recognised on the basis of morphology, colonial formation, virulence to mice, and to a less extent agglutination by salt, serum, and acids. These types comprise: (i) type A—the normal smooth virulent form; (ii) type B—a smooth form of low virulence; (iii) type C—a roughish, so-called ichthyotic, form of low virulence; (iv) type D—the really rough avirulent form. Between these well-defined types certain transitional forms may sometimes be recognised, the virulence of which is frequently of an order intermediate between that of the A type on the one hand, and the B, C, or D types on the other.

2. Evidence is brought to show that if a virulent strain is sub-cultured daily, under conditions known to lead to a fall in virulence of the whole culture, a gradual replacement occurs of the virulent type A bacilli by the avirulent B, C or D types. So long as an adequate proportion, which is very small, of type A bacilli persists in the culture the virulence of the whole culture remains fairly high; but when all type A bacilli have been replaced by bacilli of the B, C or D types the virulence of the whole culture falls considerably.

1. Three hundred and two samples of sera from normal people, and 847 samples from cases suspected of enteric, or from contacts, have been examined for heat labile agglutinins against B. typhosus and allied organisms.

2. Sera from the “not normals” show a higher percentage of agglutinins against nearly all the organisms tested than sera from the “normals.”

3. In the contact group of the “not normals” the incidence of agglutinins is practically the same as in the “normal” group.

4. Sera from inoculated persons show a higher percentage of agglutinins against those organisms included in the T.A.B. vaccine used during the late war, than the sera from non-inoculated persons.

5. There is a higher percentage of agglutinins for B. typhosus, B. paratyphosus A and B. paratyphosus B among males than among females, especially in the age groups 20–30 and 30–40.

6. The proportion of normal males whose sera agglutinate B. typhosus, B. paratyphosus A and B. paratyphosus B and the group suspension is significantly lower than corresponding proportion noted in an investigation recorded by Rosher and Fielden in 1922. The proportion of agglutinating sera for these strains among normal females is substantially the same in our findings as in theirs.

7. The associations between ability to agglutinate different pairs of organisms are shown to be statistically significant in those cases which might arise from T.A.B. inoculation.

8. For these reasons it seems likely that the present distribution among the adult male population of agglutinins for B. typhosus, B. paratyphosus A, B. paratyphosus B and for Salmonella strains allied to B. paratyphosus B when in the group phase, was largely determined, in the period 1925–6, by the results of T.A.B. inoculation carried out during the war. It is probable that this effect is slowly disappearing.

9. Statistically significant associations were found between certain other pairs of organisms, which could not be explained as resulting from inoculation with T.A.B. vaccine, or as a result of any common antigenic stimulus. These associations were found mainly in the “not normal” group; and their meaning, at the moment, remains obscure. It may be noted that the number of sera agglutinating these particular pairs of suspensions was, in most cases, small.

10. Our results, so far as they yield any information on this point, do not suggest that infection with any one of the organisms studied by us increases the probability of the patient's serum agglutinating some other bacterium, with which the infecting organism is not antigenically related.

11. High titres were found chiefly in sera from the “suspected of enteric” group. The normal group usually gave low titres.

It is an undisputed fact that various diseases have been transmitted by the water of swimming baths, and although such cases have not been very frequently recorded it is nevertheless important that steps should be taken to prevent their occurrence. This can only be done by maintaining a standard of purity of the bath water similar to drinking water.

It is evident that the water of swimming ponds cannot be kept pure by the fill and empty system, but should be subjected to a process of continuous filtration combined with aeration and chlorination.

In order to maintain the standard of purity thus obtained it is necessary that a strict supervision should be made of the bathers, and those who have any infectious condition should not be permitted to use the pond.

Regulations similar to those suggested by the American Public Health Association should be made and enforced.

It is greatly to be desired that the causes of the decline of tuberculosis, which has been so striking a feature in the history of that disease in recent times, should be clearly ascertained; for only through an understanding of their nature and relative importance can our efforts to accelerate that decline hope to succeed.

Summarising the results of this investigation, those set out in the first part of the paper are, on the whole, very gratifying. Making due allowances for difficulties of comparison, there is little doubt that entrants now are in a better condition than they were twenty years ago. The characters, e.g. general nutrition and state of teeth, for which there has been no improvement or actually a set back in recent years are those which might be expected to have been influenced by transitory conditions due to the war and are also those the measurement of which most closely depends upon the standard adopted; this standard has probably risen.

In the second part of the paper, I have shown that there is an intimate relation between various defects which develop before, sometimes long before, school age and defects or disabilities which are of grave importance during school life. How far one is dealing with environmental effects and how far with inborn weaknesses cannot, of course, be ascertained without further data; but it is clear that the care of the child before admission to school is a matter deserving as much attention as possible, even with respect to shortcomings often attributed to factors only coming into play during school age.