1. T Vi-coated rabbit erythrocytes, when injected into rabbits, stimulate the production of a (pure) Vi antiserum.

2. The T Vi extract was found to be heat-stable with respect to antigenicity and agglutinability, as shown by means of coated erythrocytes.

3. By means of cross-absorption tests it was shown that the Vi antigen of S. typhi differs from the Vi antigen of the Ballerup organism.

4. The need for caution in relying on resistance to heat as a character of groups of antigens is emphasized.

We wish to thank Dr P. R. Edwards, of the Communicable Disease Centre, U.S.P.H.S., and Dr Alcor S. Browne, California State Department of Health, for supplying certain of the cultures and specimens of typing serum used in these studies.

The present communication completes the series of war-time studies (Shewan, 1945, 1953) on the dehydration of fish, and is concerned with certain aspects of the bacteriology of the small-scale commercial production of dehydrated fish (herring, kipper, fresh and smoked cod), carried out in the summers of 1944 and 1945 by the Ministry of Food in a factory at Aberdeen. During these commercial trials, samples of fish were taken each day for a routine bacterial count and examined for the presence of food-poisoning pathogens. Several other tests were made from time to time in order to elucidate special points, such as the adequacy of the cooking procedure and the occasional incidence of high bacterial counts. The following is a summary and review of these results; with some recommendations for future production.

In a previous paper (Bailey, 1953a) I discussed the distribution of the total size of a stochastic epidemic, involving both infection and removal, in a given group of homogeneously mixing susceptibles. The model employed was of the ‘continuous infection’ type, according to which infected individuals continue as sources of infection until removed from circulation by recovery, death or isolation. This may be contrasted with the chain-binomial type of model which entails short periods of high infectivity and approximately constant incubation periods (see, for example, Greenwood, 1931, 1949; Lidwell & Sommerville, 1951; Bailey, 1953b). The basic assumptions are that, with x susceptibles and y infectious persons in circulation, the chance of one new infection taking place in time dt is βxy dt, while the chance of a removal is γy dt, where β and γ are the infection and removal rates, respectively.

Investigation of the viricidal effect of a mixture of ethylene oxide and carbon dioxide on two viruses, Columbia SK and vaccinia, yielded favourable results. Since ethylene oxide also exerts a germicidal effect, it offers simple and inexpensive disinfection of certain materials, especially those of low thermostability.

A bacteriological study of burned patients and of the staff and environment in a burns unit was made with the purpose of discovering the principal reservoirs and routes of transfer of Ps. pyocyanea.

Infected burns appeared to be the most important reservoirs. About 3 % of the stools of normal subjects and of patients with intestinal symptoms carried the organism, which was also isolated from the nose, throat, nasopharynx, skin and ear of a small proportion of patients and staff in the burns wards.

The hands of nurses in the wards were often contaminated with Ps. pyocyanea, and presented a likely vector in the transfer of the organism by contact—e.g. from the bandages of infected patients, and from furniture and other objects near to their beds.

It was shown by slide agglutination that a new type of Ps. pyocyanea admitted to one of the wards spread freely in that ward but hardly at all to the other ward. Since patients from both wards used the same dressing station and operating theatres, it seemed from this finding that a large proportion of the cross-infection occurred in the wards.

Polymyxin dusting powder was shown in a controlled trial to protect exposed burns against contamination by Ps. pyocyanea.

These results are discussed in relation to the mechanism of transfer of the organism and the methods of preventing cross-infection. The need to use several methods concurrently is emphasized, since none of those which have been investigated contributes more than a partial effect. Cubicle wards are advocated, since much cross-infection is shown to occur in open wards.

We are much indebted to Dr G. T. Cook for kindly letting us use results obtained by him at the Oxford Public Health Laboratory. We also wish to thank Prof. J. F. D. Shrewsbury of Birmingham University and our colleagues at the Birmingham Accident Hospital for their valuable co-operation, and Dr A. C. Cunliffe of King's College Hospital for information on the typing of Proteus from patients in our wards.

Teepol, sodium hydroxide, and Dettol failed to exert a viricidal effect on Columbia SK virus. The same virus was inactivated by 90% propylene glycol after exposure for 24 hr. at 4° C. The viricidal effect of propylene glycol was neutralized by 0·2% furacine.

An account is given of the examination by biochemical and serological methods of 800 strains of brucella sent for identification to the Brucella Reference Laboratory of the Public Health Laboratory Service.

Most of the strains were isolated from milk in Great Britain, but strains from other countries, and from cases of undulant fever, were also examined.

Of 738 strains from milk in Britain, 680 were Br. abortus, of which sixty-two (9·1 %) were of a type inhibited by all the usual test-dyes in their customary concentrations. Thirty strains of Br. melitensis, behaving typically in all laboratory tests, were obtained from milk from individual cows, herds or bulk sources. Br. melitensis has now been identified from twenty-four separate farms and one Tuberculin Tested bulk supply in this country. Eighteen strains behaved like Br. abortus in biochemical tests, but serologically like Br. melitensis.

Of the relatively small number of strains isolated from patients with undulant fever in Britain, all those from persons infected in this country were Br. abortus, with the exception of two laboratory infections with Br. melitensis. The organisms isolated in Britain from patients infected abroad comprised three strains of Br. melitensis, one strain behaving biochemically like Br. abortus and serologically like Br. melitensis, and two behaving biochemically like Br. melitensis and serologically like Br. abortus. One of the latter was from a patient infected in southern Italy, and the examination of nineteen strains from that country showed that thirteen were of this type. The thionin-resistant type of Br. abortus was identified several times, from undulant fever cases in Rhodesia, Kenya and Italy. No strains of Br. suis were observed.

I wish to thank the numerous bacteriologists who sent cultures and provided details of their isolation. A few submitted large numbers of strains and enabled a general picture of the prevailing types to be obtained. I am grateful to these and to the other bacteriologists who provided information about the herds from which Br. melitensis was isolated, in particular Dr P. H. Martin and Dr J. A. Sykes (Ipswich), Dr L. M. Dowsett (Norwich), Dr J. Kennedy (Newcastle, then at Stafford), Dr J. H. C. Walker (Luton), Dr E. H. Gillespie and Dr N. S. Mair (Leicester) and Dr J. E. Jameson (Brighton). I have also to acknowledge the help of Dr A. W. Stableforth, Director of the Ministry of Agriculture and Fisheries Veterinary Laboratory, who provided much bacteriological and veterinary information about the infected herds.

1. The normal agglutinin (n.a.) for Trichomonas foetus found in all normal adult cattle has a titre of 1:48 to 1:96. N.a. appears to be specific for T. foetus and cannot be absorbed by other flagellates such as T. vaginalis or even completely by the heterologous serological variety of T. foetus itself. The n.a. appears to be a native constituent of the serum and not to be induced by an exogenous antigen.

2. The n.a. passes into the serum of the calf from the maternal colostrum during the first 24 hr. of life. The elimination of the passive n.a. and the development of the autogenous newly formed n.a. in the calf are traced. The passive n.a. disappeared from the 17th to the 55th day and the autogenous n.a. began to appear as a rule from the 35th to the 60th day and was fully established by the 63rd to the 113th day.

3. The elimination of the maternal, induced antibody acquired passively from the colostrum took place logarithmically. The rate measured by the half-life ranged from 14 to 20 days, but in one animal which took a very large amount of colostrum it was 57 days.

4. The intramuscular injection of T. foetus antigen into very young calves up to 4 weeks old induced no antibody. When the doses were relatively small the animal produced antibody to antigen given at a later period. When a very large amount was injected in this early period the subsequent capacity to respond to the same antigen but not to other antigens was seriously impaired.

The personal encouragement of Prof. H. G. Lamont and the support afforded by the Ministry of Agriculture, Northern Ireland, are gratefully acknowledged.

1. Immuno-conglutinin production by auto-stimulation was attempted in guinea-pigs, pigs, donkeys, rats and mice by the intravenous injection of a suspension of Gram-negative bacteria. The attempt was successful in rats and mice.

2. Experiments were carried out to elucidate the lack of response in guinea-pigs.

The author would like to thank Mr N. H. Hole of the Ministry of Agriculture Veterinary Laboratories at Weybridge, who inoculated and bled the donkeys used in these experiments.

1. When the D.S.P. strain of influenza virus A is grown in eggs into which 100 μc. of radioactive inorganic phosphate has been introduced the virus incorporates 32P into its structure.

2. Some 20–25% of the virus 32P is found in the virus phospholipid; the remainder is combined with the virus protein and is probably present in the virus nucleic acid.

3. When the virus is disintegrated by ether treatment with the liberation of separate red-cell agglutinating and complement-fixing ‘soluble antigen’ particles the non-lipid 32P is found to be associated with the soluble antigen fraction and not with the haemagglutinin.

4. It is suggested that the complement-fixing soluble antigen is a nucleoprotein while the haemagglutinin is a phosphorus-free protein.

In the period following the last war a large acceleration has occurred in the rate of decline of the death-rates of the younger age groups. The oldest age groups have not shared in this improvement. This course of the death-rates is in striking contrast to the predictions of two decades ago when it was thought that any substantial improvement in the age specific rates was most likely to occur at the older ages. A large part of the fall at younger ages has been due to the decrease in mortality from infectious diseases and tuberculosis. The death-rates at ages 5–24 are now probably almost at a minimum and if a further appreciable improvement is to be made in them the death-rate from violence must be reduced. Violent deaths account for roughly one-third of all deaths in this age range.

An attempt has been made to establish the nature of the ringworm flora of Birmingham, comprising: (1) the species encountered; (2) their relative concentration; (3) their distribution.

A marked increase in the number of cases due to fungi of animal origin has been demonstrated.

It has been shown that the main reservoir of infection in the city is centred upon Sparkbrook and Balsall Heath, with a rather smaller focus in the Hockley–Lozells area.

The ability of four species of trichomonads to withstand freezing was investigated with a view to storage of stock cultures. Of the conditions investigated the most satisfactory was found to be storage at – 79° C. following slow freezing, the protozoa being suspended in medium containing 10% glycerol. T. gallinae was the most easily preserved and survived even without glycerol for 6 months. No observations on survival beyond this period have yet been made so the possible maximum time of survival is not known.

T. vaginalis remained viable for four months but deteriorated in storage and had died out after 6 months. The sample of T. hominis containing 10 % glycerol was still viable after 6 months at – 79° C., but in the presence of 5 % glycerol survival was not observed beyond 4 months. T. foetus could not be preserved under any of the conditions tested. The possible implications of these results are discussed.

By the inoculation of suspensions of mosquitoes on the chorio-allantoic membrane of chick embryos, seven pock-producing viruses have been isolated. The mosquitoes were collected in a small area of the Murray Valley situated in the north-western corner of Victoria and southern New South Wales. Six of the viruses were isolated from pools of C. fatigans and one from a pool of C. annulirostris. Five of the viruses were found to be members of the bird pox group and related to fowl-pox virus. Two of the viruses differed in the type of pock they produced on the chorio-allantoic membrane and appeared to be serologically unrelated to the other five.

The interest and criticism of Sir Macfarlane Burnet, F.R.S., throughout the conduct of this work is gratefully acknowledged.