1. Four mouse lines have been tested for “H” and “O” antibody production following inoculation with Salmonella typhi murium and S. enteritidis; two of these lines had been selected for resistance and susceptibility but not inbred; two, D and E, had been brother-sister inbred for over thirty generations but not selectively as far as resistance is concerned.

2. After immunization with S. typhi murium:

(a) Female mice, in all four lines, tend to give higher “H” and “O” titres than do males, a positive correlation between ability to produce antibody and resistance to infection being thus established.

(b) Interline differences exist for both these antibodies. Those concerned with “H” antibody may be correlated with resistance. In the case of “O” antibody, no correlation is suggested.

3. After immunization with S. enteritidis:

There appears to be no correlation sexually or interlineally between resistance and antibody production. That genetic differences exist, in respect of this organism also, is shown by the fact that the pure lines, D and E, give a better antibody response than the selected lines A and B. When tested for immunizability by subsequent infection with S. enteritidis no useful information could be obtained with strain A or B owing to their great internal variation. Strains D and E both showed a gain in expectation of life following immunization. The more resistant strain D showed a significantly greater gain than did E, the strain with a lower natural resistance.

4. The titres of normal “O” enteritidis-antibody found in the four lines indicates that there may be a negative correlation between the titre of these antibodies and resistance to infection with S. enteritidis.

5. The significance of the above findings is discussed and it is stressed that a significant correlation between resistance and antibody formation does not imply that the two phenomena are causally related.

6. It is pointed out that strains that have been inbred even without selection react far more homogeneously in the infection experiments here described than do strains that have been selected but not intensively inbred.

1. The description of a strain which behaves as a pure Vi variant of S. typhi is given. Complete absence of H antigen from it is demonstrated. The non-interference in its Vi agglutinating activity by the very small amount of O antigen contained in it is shown. This strain has been designated “Vi 1”.

2. With the help of this strain, the practical applicability of Vi agglutination as a reliable method for the routine serological diagnosis of typhoid infection and for the detection of typhoid carrier condition, in preference to O and H types of agglutination, is stressed.

The object of this paper is to describe the immunizing procedures that have proved to be the most suitable up to the present time for preparing a potent serum from the horse for the treatment of typhoid fever. The principles on which the methods are based have their origin in the studies of Felix and his collaborators on the antigenic structure of Salmonella typhi. The technical details that follow will, we hope, assist those who are interested in the preparation of the serum as a therapeutic agent to obtain products which maintain a consistently high level of potency. This objective is not readily attained, but is of paramount importance, because the clinical use of products that fall below the permissible limits of potency would tend to bring discredit upon the serum as a specific remedy owing to insufficient dosage. The adoption of standards of potency that are prescribed by an official authority is an obvious desideratum and would guard against this risk, but in the meantime we shall be pleased to help by providing the requisite cultures and serological reagents.

This investigation was initiated when twelve miners who were working in a certain part of the Mill Close Lead Mine complained of smarting of the eyes associated with marked congestion of the conjunctivae. They also suffered from a stinging sensation in the nose and throat. The particular area in which they were working differed from other parts of the mine in that there was a strong smell of sulphuretted hydrogen present. After recovery, and when the ventilation had been improved, the men were able to continue working in that area without experiencing further discomfort. The interesting part of the investigation was tracing the origin of the sulphuretted hydrogen. The odour proceeded from collections of mine water which the miners very appropriately called “stink water”. In this there was a deposit of sulphur mixed with black sludge which also smelt strongly of H2S. The sludge consisted of slightly gelatinous black masses mixed with a whitish felt work of a filamentous organism. On microscopical examination the filaments were seen to contain sulphur globules, and often to arise from a mass of black material. This black material consisted of sulphur and inorganic salts in a slimy matrix, the black colour being due to the presence of ferrous sulphide. On further examination these masses were found to be teeming with other bacteria, Gram-negative bacilli and spirilla, both of which were motile, the spirilla being actively so.

No case of transformation (in vivo) of the “xylose-positive” typhoid bacillus to the “xylose-negative”, or vice versa, has been observed in any of the material dealt with at the State Serum Institute, Copenhagen.

On the other hand, the types of paratyphoid B bacilli that can be established on the basis of their relation to rhamnose and inositol did not prove to be absolutely constant; actual or apparent transformation of one type to the other having been observed in several cases.

In this connexion the suggestion is made that Bitter's rhamnose reaction be omitted; the distinction between types R1 and R2 would thus disappear.

Patients with symptoms of diseases of the liver and biliary system and also chronic carriers were represented in greater numbers for type R3I1 than for type R2I1, but it is doubtful whether this observation can be taken as a general one. Apart from this, the behaviour of these two types was very uniform as to the clinical course of the infections they produced. The cases of infection with the rarer types, also, did not seem to vary clinically from those with the more frequent types. On the other hand, the difference between the clinical course of paratyphoid B and the infection with Salmonella typhi murium was very marked.

1. The more recent literature on the experimental methods employed in variola or alastrim-vaccinia variation is reviewed and briefly discussed.

2. An account is given of attempts to produce a vaccinia variant from variola of the virulent type and a successful result, by employing the method of intratesticular passage, has been described.

3. The reasons for accepting this as a genuine variation and not a vaccinial contamination are discussed.

4. An attempt has been made to analyse some possible factors underlying the discrepancies in the literature, and a plea is made for more co-operation in future work on the subject.

Two new Salmonella types are described. S. minnesota was isolated from a turkey. Its antigenic formula is XXI: b ⇋ enx. S. worthington was found both in a chicken and in a turkey. Its antigenic formula is I XIII XXIII: Iw ⇋ z…. Transfers of each type have been deposited in the National Collection of Type Cultures of Great Britain and in the American Type Culture Collection.

The investigation deals with the bacteriological examination of 386 samples of water from Manchester swimming baths where the method of purification could be studied.

There were 339 samples from chlorinated pools of which 160 gave acid and gas in MacConkey broth at 37° C. and 2130 strains were isolated. The remaining forty-seven samples were from untreated open-air pools. Thirty of these samples were positive and 270 strains were isolated. The strains were classified according to Wilson's method into the coli, intermediate, aerogenes and irregular groups, and only 1·78% of the total were found to be irregular. Both series of samples included more than 72% which contained coli, and among the chlorinated samples no less than 70% yielded aerogenes and nearly 49% intermediate type, while among the non-chlorinated baths there were 43% with aerogenes and 40% with intermediate type. There was a similar difference in the proportions of coli, aerogenes and intermediate type in chlorinated and in non-chlorinated baths when the results were considered on the basis of strains (Table II).

Since these differences in proportion were considered significant, and since the chief variation in conditions between outdoor and indoor baths consists of chlorination, a series of experiments was devised to test the effect of chlorine on pure cultures of coli, aerogenes, and intermediate type. There was very little change after adding 0·1 part of chlorine per million, but the addition of 0·3 and 0·5 part was followed by very rapid reduction in numbers with diminution in free chlorine. This reduction was on the whole least with aerogenes. The numbers continued to fall for about 48 hr. until all trace of chlorine had disappeared and then regrowth occurred. This regrowth was most vigorous and most rapid with aerogenes (see figures) but was very slow in all cases.

The survival rate, p, of a measured inoculum of Staph. aureus in a standard volume of denbrinated blood, is a reliable quantitative measure of the bactericidal power of blood. The number of viable organisms in the inoculum and in the blood-bacterium mixture may be estimated with the necessary accuracy by counts of colonies developing from measured volumes of the fluids let fall on to the surface of solid media. Fildes' agar was the most suitable medium for this surface-viable count, and was selected on the basis of four criteria; of the media tested it yielded the highest counts, and the counts conformed most closely to a Poisson series; and on it the mean colony size was maximum, and the coefficient of variation of colony size was minimum. On this medium, the close conformity of the separate count values to a Poisson series enabled the standard error of the survival rate to be determined from a simplification of the general expression for the standard error of a ratio.

The number of colonies growing from a sample of a blood-bacterium mixture may be reduced, not by killing of the individual cocci, but as a result of their aggregation either by agglutinins in the blood, or in the cytoplasm of leucocytes that are phagocytic but not bactericidal. It appears that these mechanisms are unlikely to operate in blood-bacterium mixture containing relatively few organisms; in such mixtures the survival rate is a reflexion of the killing power only.

The immunological significance of p has not been investigated, but the range of values for healthy human adults differs significantly from that for sufferers from chronic staphylococcal infection. Moreover, by the technique employed differences may be detected between individual values of p that cannot reasonably be attributed to technical or sampling errors.

An account has been given in a previous paper of the immunizing procedures now employed in the preparation of anti-typhoid serum in the horse for therapeutic use in man (Felix & Petrie, 1938). The object of the present communication is to describe the methods used for the titration of the serum.