Experiments are reported in which the bactericidal effect of α-, β- and γ-rays of radium, X-rays of various wave-lengths, and neutrons, has been observed, particularly on Bact. coli and spores of B. mesentericus. It is shown that the survival curves are exponential and that the lethal dose is independent of the intensity of the radiation and of the temperature during the irradiation. The lethal dose varies for different radiations, being, in the case of vegetative bacteria, greatest for those radiations, particularly α-rays, which produce their ionizations close together.

These experimental facts can all be explained on the view that the “lethal” action of radiation is really the production of lethal mutations. It is deduced that the number of “genes” in Bact. coli is of the order of 1000.

1. The distribution of coliform bacteria in lakes and streams has been studied. Weekly samples have been collected from different depths from the north and south basins of Windermere, from Thirlmere, and Bsthwaite Water, dnd from streams flowing into these lakes. Nearly 300 cultures have been isolated from positive tubes of MacConkey broth and their relationship to the coliform group has been studied and considered.

2. In relatively unpolluted streams the counts of coliform bacteria and the plate counts on sodium casemate agar tended to fluctuate in the same direction as river level, but in polluted streams the increased flow of water accompanying a higher river level reduced the numbers of bacteria per unit volume. Counts of coliform bacteria were, in general, much higher in summer than in winter, despite the lower rainfall in summer.

3. During the winter period of circulation of the water, samples of water from different depths in the lakes gave approximately the same count for coliform bacteria. When stratification of the water became established numbers of coliform bacteria in the hypolimnion (the lower stratum) dropped to very low figures and remained fairly constant; much higher counts were found in the epilimnion (the upper stratum).

Large fluctuations in numbers of coliform bacteria which occurred from week to week in the lakes were related to fluctuations in plate counts at only one of the seven sampling points, and were not related to previous rainfall. The count of coliform bacteria was greatest in summer and autumn, a phenomenon that was by no means entirely a result of the bacteria which were washed in being concentrated in the epilimnion. It is suggested that temperature may have affected viability and proliferation.

4. Of the total number of coliform organisms producing acid and gas from lactose at 37° C, approximately 70% were Bact. coli types I and II, and the remainder were members of the I.A.C. group. In the relatively pure waters of Thirlmere and its inflows Bact. coli, type I, made up 86 and 98% respectively of the total coliform cultures isolated, whereas in the relatively impure waters of Windermere and Esthwaite Water the percentages were 39 and 37 respectively. The differences were due to the greater proportions of Bact. aerogenes, type I, and of intermediate and irregular types in the impure waters. The significance of greater proportions of the I.A.C. group in polluted rather than in unpolluted water is discussed. The actual counts of coliform bacteria were very much lower in Thirlmere than in the other lakes examined.

5. Of the total cultures isolated from positive tubes of MacConkey broth 27% did not produce acid and gas in MacConkey broth at 37° C. Approximately one-half of these cultures, however, fermented lactose at 30° C, and gave varied results with the standard differential tests. The majority of these cultures could, by gradually increasing the incubation temperatures of successive inoculations, be “trained” to ferment lactose at 37° C but not at 40° C. They were more frequently isolated from the polluted lakes and inflows than from unpolluted waters. The remaining organisms isolated proved to be non-lactose-fermenting species belonging to the genera Proteus, Salmonella, Eberthella and Alkaligenes (Bergey).

1. The existence of an anaerogenic strain of Bact. paratyphosum C is recorded in Egypt.

2. It was isolated in August 1937, together with an aerogenic strain, from the urine of a patient suffering from enteric fever.

3. Biologically the anaerogenic strain was identical with the aerogenic except that it did not produce gas from any “sugar”.

4. The anaerogenic strain retained its inability to produce gas from “sugars” for the three years during which tests were carried out, subculturing on various fluid media containing different sugars failing to cause any gas production.

5. Serologically there was no indication of any antigenic difference between the anaerogenic and the aerogenic strains.

6. The anaerogenic strain contained the Vi antigen and retained it for three years when kept at room temperature.

1. A short synopsis of research upon application of hypochlorites to airpurification is given.

2. A short review of the most recent work on this subject shows that:

(a) Of the “nebulizers” employed by Baker, Finn & Twort (1940) the “Atmozon” is incapable of consistent atomizing of hypochlorites, whilst the “Aerograph” has an efficiency much below that of modern atomizers.

(b) The data obtained by them, after due allowance for defective technique, can be interpreted as fully confirming the view that HOCl gas is the active germicide in hypochlorite spraying. Sterility can be approximately attained (99·75% reduction) by HOCl gas with a volumetric concentration in air, of not more than (3·5 × 109)−1.

(c) The application of the “Aerosol” theory is discussed and reasons given for its non-applicability to hypochlorite spraying.

(d) Alleged drawbacks to this practical application of hypochlorite air disinfection are discussed and shown to be of no practical importance.

1. The paper records the result of a study of the serological types of haemolytic streptococci in scarlatina, puerperal fever, erysipelas, ear infections, tonsillitis, erythemas, etc., and normal throats, and their epidemiological relationships.

2. Tables and charts are given showing statistical records of scarlatinal cases which occurred over a period of 16 months in Edinburgh, a city with a population of about half a million inhabitants. In all there were 2287 cases. Of these 2169 were treated in an infectious diseases hospital, and were thus readily accessible for investigation. 1364 of the cases were school children. The strains of haemolytic streptococci from 1664 of the hospital-treated cases were serologically examined.

3. During an epidemic of scarlatina certain schools practically escaped, but in these there was a proportionately greater number of cases the following year, as compared with those schools which had suffered heavily the previous season.

4. Depending on the types of haemolytic fltreptococci isolated, scarlatina patients have been divided into three main categories: (1) pupils or school children, (2) “pupil-contacts” (families of pupils), and (3) “non-pupil-contacts” (famines without children of school age). The types of haemolytic streptococci found in these three groups have been correlated. There was a similarity in the types found in pupils and “pupil-contacts”, but not in those of pupils and “non-pupil-contacts”. Those types obtained from “pupil-contacts” and “non-pupil-contacts” were related. These features have been discussed.

5. Certain types of haemolytic streptococci predominated in the pupil cases. These were for the most part the epidemic types. The non-epidemic types, sporadic in appearance, were found mostly in “non-pupil-contacts”. “Pupil-contacts” occupied an intermediate position.

6. One main epidemic type ran through the three classes of patients. It was later replaced by another type.

7. The majority of cases of scarlatina which occurred in a school at a particular time were due to one type. It tended to persist despite the sporadic occurrence of other types. On occasions two types were present concurrently, but usually the one disappeared, and afterwards the other produced most of the cases.

8. The types of haemolytic streptococci in scarlatina, erysipelas, otitis media and mastoiditis, tonsillitis, and other streptococcal infections have been compared and the findings discussed. For the most part there was a correlation of types among all these conditions, and these types appeared to be responsible for a single epidemic of streptococcal infections.

9. The major epidemic types found simultaneously in the City of Edinburgh and in a small community, 12 miles distant, differed.

10. The types of haemolytic streptococci isolated from the throats of nurses in a general hospital bore little relationship to those isolated from medical officers and nurses in an infectious diseases hospital. The common epidemic types were present in the latter.

11. Correlations were shown to exist between the types of haemolytic streptococci in scarlatina patients, and those isolated from various members of their families, in 50% of the occasions in which the organisms were found.

12. The rapid change in the types occurring in the nasopharynx and the problem of immunity have been investigated and discussed in the case of a person exposed to massive infections with haemolytic streptococci.

13. Haemolytic streptococci on the handkerchiefs of scarlatina patients were viable after 4 weeks in most cases and after 7 weeks in two cases. After 15 weeks they were all dead.

14. Haemolytic streptococci were isolated from toys and fruit taken from scarlatina patients.