Two antigens, probably polysaccharide in nature, were extracted from smoothgonococci.

One of these could be adsorbed on to red cells and sensitized these cells to the action of a gonococcal antiserum. The factors concerned in this adsorption were investigated. The antigen, which was shown by a mirror absorption technique to be of two distinct types, was lost with the S-R change.

The second antigen was detected by its ability to fix complement in the presence of an immune serum.

It is suggested that these two antigens form a complex which determines the nature of the surface of the smooth gonococcus.

I wish to thank Dr J. C. Thomas, Provincial Pathologist, for the facilities for carrying out these investigations; Prof. M. van den Ende and Dr A. Kipps for helpful and constructive criticism; and Miss E. Bennett, Miss B. Jefferies, Mr L. Heitman, Mrs S. Maddison, and Mr G. C. Buckle for technical assistance.

If A is the average density of virus particles per unit volume and am(a)l, m= 2, 1,0, 1,2,) are the dilution levels, the proportion of eggs remaining sterile at dilution am (if eggs are used as the material to be infected) will be e~Xam if the ordinary assumptions of dilution assay are valid. In many cases this is not true because the eggs vary amongst themselves in their infectibility. If p is the probability of any one particle (when present) being infective for an individual egg, and if p does not vary from particle to particle the probability of the egg remaining sterile is e~pXam. If p varies from egg to egg so that it has a probability distribution/(p), the probability of an egg chosen at random remaining sterile is

Of the outbreaks of severe human encephalitis which have been recorded in Australia, five conformed to one clinical and epidemiological type. The disease was designated Australian X disease in 1917, 1918, 1922 and 1925 and Murray Valley encephalitis (MVE) in 1951. The causal virus was transmitted to laboratory animals during 1917, 1918 and 1925, but was not retained for later comparison with other viruses. The virus was isolated again during 1951 and identified as a new member of the arthropod-borne encephalitides, closely related to, but distinct from, Japanese B encephalitis virus.

Under the conditions of our experiments, the local potentiation of immunity to influenza reported by FazekasdeSt Groth and Donnelley could not be demonstrated.

We should like to thank Dr C. H. Andrewes and Dr A. Isaacs for their advice and criticism, and Messrs E. Owen and D. Eade for their technical assistance.

1. One hundred and eighty-seven freshly isolated strains of Haemophilus pertussis, together with ten laboratory strains and eleven strains of H. parapertussis were submitted to tests of their morphological, biochemical and antigenic properties in relation to their virulence to mice.

2. The naturally occurring H. pertussis strains form a single antigenic type differing from that of the attenuated laboratory strains.

3. H. parapertussis forms, as previously claimed, a distinctive type with characteristic properties closely related to H. pertussis.

Our thanks are due to Col. H. J. Bensted, Prof. J. W. McLeod and Drs A. Beck, D. G. Evans, G. Eldering, J. Marks, M. T. Parker, M. Pittman and H. Proom for supplying strains used in this investigation.

Strains of Staphylococcus pyogenes able to grow in 0·1 unit/ml. of penicillin produced penicillinase and were regarded as resistant. The majority of the remaining strains had the same sensitivity as the standard sensitive staphylococcus.

Five hundred and three strains were isolated from pre-clinical medical students from 1950 to 1953, and 24% were penicillin-resistant. Two per cent were streptomycin-resistant and none were resistant to chloromycetin, aureomycin or terra-mycin. Two hundred and forty-six of the strains were isolated from persistent and intermittent carriers, but only 14% were penicillin-resistant.

Another 183 strains were isolated from persons unattached to hospital, and 14% were resistant to penicillin. Only one strain was streptomycin-resistant; one was chloromycetin-resistant and none were resistant to the other antibiotics.

Among persistent and intermittent carriers, more than 7 times as many penicillin-resistant strains were isolated from those who had had previous penicillin therapy as from those who had not.

It was concluded that the administration of antibiotic increases the number of resistant strains in the community.

Staphylococcal α- and β-toxins inhibited the spontaneous activity of isolated rabbit intestine, the former leading to an increase in tone and the latter to a decrease. The γ-toxin and δ-haemolysin had no effect in concentrations likely to be met in extracts of cultures, nor did δ-lysin enhance the action of β-toxin. Culture extracts in which the haemolytic toxins had been neutralized by antiserum sometimes produced an increase in tone or amplitude or both, which was moderate in degree but rapid in onset. This stimulation was more common with strains isolated from food-poisoning outbreaks than from infective lesions. It was occasionally observed with coagulase-negative strains and was therefore considered to be unrelated to enterotoxin. No effect on intestine was observed which could be considered specific for food-poisoning strains.

We are indebted to Dr R. E. O. Williams of the Central Public Health Laboratory, Colindale, for providing food-poisoning strains of staphylococci, to Dr H. W. Smith for strain CN, and the Wellcome Research Laboratories for gifts of sera.

1. When toxic filtrates derived from coagulase-positive staphylococci including twelve food-poisoning strains, thirty pyogenic strains of human and twelve of animal origin were applied to isolated rabbit gut in vitro, two characteristic responses were obtained, associated with the α- and β-lytic titres respectively, and abolished by the corresponding antisera. They were independent of the origin of the strains.

2. A non-specific response is also described which is thought to be due to the peptone in the medium.

3. No effect that could be attributed to enterotoxin, such as was reported by Anderson (1953), was observed and it is concluded that isolated rabbit gut is unlikely to prove a useful indicator of its presence.

We are indebted to Drs Mary Barber, J. M. Talbot, F. C. O. Valentine and H. Williams Smith for strains; to Dr R. E. O. Williams for strains and bacteriophage typing; to Prof. C. E. Dolman and Messrs Burroughs Wellcome for strains and antisera; to Mr F. Crisp of the Division of Experimental Biology, National Institute for Medical Research, Medical Research Council, for rabbit gut; and Dr H. O. Schild for continued interest and practical help.

1. Straight-chain α-amino-acids are all equally effective in causing the lysis of Bact. coli.

2. Various modifications of this structure always result in a decrease of this lytic activity.

3. The optical isomers of α-amino-acids are equally effective in causing lysis.

4. There is a correlation between the lytic and the bactericidal powers of the amino-acids and their derivatives.

Desert rodents often have been used successfully as laboratory animals in parasitology (Abdel Azim & Cowper, 1950; Adler & Feldman-Muhsam, 1952; Delanoe, 1929; Kuntz & Malakatis, 1954; Nicolle, Anderson & Colas-Belcour, 1927; Sergent & Poncet, 1951 a, b) and virology (Durand & Laigret, 1932; Gear & Davis, 1942; Noury, 1948; Snyder, Zarafonetis & Liu, 1945; Van Rooyen & Danskin, 1944; Zarafonetis, 1945). However, with the exception of investigations into the role of some of these animals as mammalian reservoirs of plague (Ristorcelli, 1938; Tikhomirova, 1934; Wassilieff, 1933), no reports have been found of their use for experimental bacterial infections.

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.

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.

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.

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.