In 1934 a committee on the eradication of bed-bugs appointed by the Minister of Health issued its report (Report on the Bed-bug, 1934) in which recommendations for research into the biology of Cimex lectularius L. were made. The committee was struck by the lack of precise information on certain aspects of the bionomics and habits of the insect and suggested work along the following lines:

The effect of food supply and starvation at different seasons and at different stages of development.

The periods of survival of bed-bugs and their eggs under different conditions.

The extent to which bed-bugs can subsist on the blood of birds, bats, mice, etc., when deprived of human blood.

The position and types of harbourages most favoured by bed-bugs under different conditions.

The distance which bed-bugs will travel, the factors (warmth, smell, etc.) which attract them, and whether they habitually return to the same harbourage.

We confirm the finding of Behnke, et al. (1935) that air at 8·6 atm. pressure has a somewhat intoxicating effect on human beings, and that this effect is due to nitrogen. The nitrogen effect reaches its maximum after about 3 min. There was no reduction of manual dexterity in the test used by us, but a considerable effect on performance of arithmetic, and on most practical activities. At 10 atm. these effects were somewhat enhanced, and manual dexterity was lowered in some cases. When helium or hydrogen was substituted for nitrogen there was no intoxication.

3–4% of carbon dioxide at atmospheric pressure caused no deterioration in manual or arithmetical skill, and in the two subjects tested, 6% of carbon dioxide caused no deterioration.

When air containing about 0·4% of carbon dioxide, and therefore with a partial pressure of about 4%, was breathed at 10 atm., there was a marked deterioration in manual dexterity, and a good deal of confusion. When breathing carbon dioxide at partial pressures of 6·6–9·7% at 10. atm., eight subjects lost consciousness in 1–5 min., but some could tolerate partial pressures of over 8% for 5 min. or more. With half an hour's exposure to a partial pressure of 6–7% of carbon dioxide, one subject lost consciousness after 7 min. at 10 atm. pressure, and another nearly did so.

We consider that the percentage of carbon dioxide in air at 10 atm. pressure should be kept below 0·3%. Exposure to high partial pressures of carbon dioxide at 10 atm. does not increase the liability to ‘bends’ or other symptoms due to rapid decompression.

Immersion in water below 40° F. did not enhance the effects of high-pressure air, or of carbon dioxide at atmospheric pressure, but somewhat enhanced those of high pressure and carbon dioxide together.

In certain breathing apparatus the resistance became so great at 10 atm. as to be intolerable.

Few subjects experienced serious trouble during compression, or during or after decompression. But one developed a unilateral pneumothorax.

It has long been recognized that there is a relationship between environment and health and examples of this association are easy to cite—overcrowding tends to spread infection. But our knowledge of the exact part played by occupational as distinct from economic and social environment is as yet imperfect.' The liability of the worker to ill-health, apart from any inborn constitutional weakness, is determined broadly by two factors. The first is the influence of the type of work directly upon the worker, an influence inherent in the actual occupation and the conditions under which the work is done. This might be regarded as the direct occupational risk. The second is the economic and social environment conditioned by the occupation followed: this might be termed the indirect occupational risk. This distinction was recognized by the Eegistrar-General who stated that both factors are essentially components of the total occupational risk since ' If a man is obliged by his place of work and his rate of pay to live in an insanitary area, the extra risk of death involved is, in a wider but very real sense, part of the occupational risk'. The purpose of the present paper is to try to disentangle the parts played by each in determining the occupational mortality from a specific disease like tuberculosis. The difficulty which previously presented itself was the absence of a standard which could be regarded as a measurement of the indirect occupational risks. The Registrar-General, in his last Occupational Mortality Supple-ment, has provided an approximate index, by publishing data on the mortality of males following particular occupations and also that of their wives. His viewpoint was.'. for no trade could longer be regarded as directly prejudicial to health if it were found to entail as much excess risk for the wife as for the husband. In such a case excess mortality would evidently be in the main attributable to the social conditions implied.' Greenwood likewise stated that ‘the wives share the social and geographical advantages of their husbands’ occupation but, with relatively ummportant exceptions, are not exposed to their specific occupational risks’. The purpose of the present paper is to try to disentangle the parts played by each in determining the occupational mortality from a specific disease like tuberculosis. The difficulty which previously presented itself was the absence of a standard which could be regarded as a measurement of the indirect occupational risks. The Registrar-General, in his last Occupational Mortality Supplement, has provided an approximate index, by publishing data on the mortality of males following particular occupations and also that of their wives. His viewpoint was. ‘..for no trade could longer be regarded as directly prejudicial to health if it were found to entail as much excess risk for the wife as for the husband. In such a case excess mortality would evidently be in the main attributable to the social conditions implied.’ Greenwood likewise stated that ‘the wives share the social and geographical advantages of their husbands’ occupation but, with relatively ummportant exceptions, are not exposed to their specific occupational risks'.

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.

In 1931 Cummins, Weatherall & Waters investigated the adsorption of tuberculin by anthracite dust and the subject was further investigated by Cummins & Williams in 1938. After the publication by Kettle (1934) of his observation that the intra-tracheal inoculation of kaolin dust mixed with dead tubercle bacilli gave rise to a much greater reaction than did the inoculation of kaolin alone, the result of the mixture being comparable to an early silicotic lesion, the author, thinking that this effect might have been due to adsorption of the products of the bacilli on to the dust, tried the same experiment with a number of other dusts, met with in mines, such as those of silica, sericite and anthracite. He obtained comparable results with all of them, though of different degrees according to the dust used (Cummins, 1940b).

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. Certain appearances of the colonies and some biochemical reactions of forty strains of B. dysenteriae Sonne have been investigated.

2. In thirty-five strains definite raised papillae occurred on parent colonies after 3–5 days' growth on MacConkey's medium or ordinary agar.

3. Papillae were produced both by strains that fermented lactose in fluid culture and those that did not; in the former case they were pink, in the latter pale.

4. Papilla-producing and other strains could not be differentiated by various biochemical reactions or by straight agglutination tests.

The susceptibility of the field vole to experimental infection with bovine, human and avian bacilli respectively was the subject of a previous paper (Griffith, 1939).

In a previous paper (Twort, Baker, Finn & Powell, 1940) we were able to show that the bactericidal properties of phenolic -aerosols were correlated with their physical characters, though our experiments were not sufficiently numerous or varied to enable us to estimate separately the effect of the different factors operative. Here we propose to describe similar tests which we have carried out on the germicidal smokes used by Twort & Baker (1940, 1941), namely, those produced by smouldering cardboard impregnated with potassium nitrate, and by dropping incense and Peru balsam on to hot metal surfaces. There were also used mixtures obtained by distilling Peru balsam under reduced pressure: fraction I, b. p. 109–110° C; fraction II, b. p. 120–138° C; fraction III, bp 148–155° C, at 3 mm. Hg, and the residue from this operation.

Subcutaneous inoculations: Two strains of human origin were tested, one was of eugonic human type from the sputum of an English case of pulmonary tuberculosis; the other was of dysgonic human type obtained by Dr J. A. Young from a native in Nigeria. Both strains produced typical general tuberculosis in the hamster, the lesions on the whole showing less caseation than those set up by bovine bacilli (vide 1939).

The vole strain of bacillus gave rise to generalized disease resembling tuberculosis. The duration of life of the animal was, however, prolonged and though the bacilli were abundant in the lesions there was no necrosis or caseation. Similar results in two hamsters were reported in 1939.

The avian bacillus was the least pathogenic of the four types. Of the three hamsters inoculated only one (H. 17, dose 5·0 mg.) showed macroscopic foci in the liver and spleen; as these were not seen microscopically in sections it is doubtful if they were due to the action of tubercle bacilli. It is unfortunate that the specimens of Hamster 17, which died in my absence from the laboratory, were badly fixed; a smear preparation of the spleen was not made. In the others tubercle bacilli were found in the organs, but were not numerous. The peculiar result after 5·0 mg. of avian bacilli—enormous multiplication of bacilli in spleen, liver and a local gland without macroscopic tuberculous lesions—described in the first paper was not reproduced.

Feeding: The four different types of bacilli were given by the mouth to six hamsters, the dose in each instance being 10 mg. of culture. Two of the hamsters, one fed with a potato culture of the vole strain, the other with a human strain, escaped infection. The remaining four hamsters, each fed with one of the four types of bacilli, developed disease, the severity of which in each instance was in harmony with that following subcutaneous inoculation of the type.

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.

A Technique for drying serum proteins from the frozen state has been described by Greaves & Adair (1939). For war requirements the procedure has been to dry in 12 oz. medical flats into each of which is put 200 c.c. of serum. The bottles are then placed in a −20° C. cold room on shelves slightly inclined to the horizontal. The inclination is to allow the maximum quantity of serum to be dried consistent with the exposure of a reasonable surface area from which to dry. This method of freezing produces a wedge-shaped block of serum in the bottle (Fig. 1) and is very efficient. Large amounts of serum for the use of the Army have been dried in this manner by Greaves and his colleagues.

Human serum was dried in this department at the outbreak of war with a view to its possible use as a stable substitute for whole blood for transfusion purposes. In the absence of any definite knowledge of dosage, the arbitrary unit of 200 c. c. was chosen, because this was approximately the amount of serum which could be obtained from a pint of clotted blood, and also because this amount of serum could conveniently be frozen before drying in 12 oz. medical-flat bottles. The technique of freezing was to place the bottles of serum on racks in a cold-room maintained at –20° C, the racks being slightly inclined from the horizontal so that the serum froze in a wedge, thus giving a reasonably large surface from which evaporation could occur during the drying process. Large amounts of human serum have been dried by sublimation from the frozen state on apparatus based on the experimental model described by Greaves & Adair (1939), after prefreezing by this simple technique.

During the course of our experiments on the lethal effectiveness of organic smokes to bacteria in the air (Baker & Twort, 1940, p. 587), we experienced, as time went on, more and more difficulty in obtaining satisfactory results, whereas in the early days of these investigations our findings were relatively consistent. In the first place, our charcoal-incense ‘candles’, when smouldered, failed to give the results expected, and in-seeking an explanation for the failure it was thought possible that the temperature of smouldering was too high and that there was pyrolysis of the emitted smoke as it passed over the glowing point of the candle. Attempts were made to elucidate the matter by (1) smouldering the ‘candle’ inverted, and (2) heating the crushed ‘candle’ on a hot plate of regulated temperature. Both methods gave somewhat improved results, but these still remained very poor, and our next procedure was to examine the effect of the smokes obtained from incense supplied from different sources. The results were irregular, as they were with several other substances which were re-tested. Only Peru balsam continued to give good ‘kills’ for some time, but, finally, we were unable to reproduce our original results even with this product. While there seemed to be evidence that the smoke, generated by smouldering on a hot plate such substances as cardboard and the incense-charcoal mix, was somewhat more lethally effective than when generated by smouldering as a ‘candle’ or strip, the experimental results as a whole had, by this time, become consistently bad.

Intravenously injected into a goat in a single dose of 50·0 mg. b.c.g. caused the death of the animal from pneumonia in 9 days and was demonstrated in the blood until the day of death, though in progressively diminishing numbers.

Intravenously injected into a goat on successive occasions, the dose on each being 10·0 mg., b.c.g. was filtered from the blood by the tissues within 3–5 days. There was little or no evidence that b.c.g. disappeared from the blood more quickly after previous injection of that micro-organism. b.c.g. was not excreted into the milk cisterns of this goat or, if excreted, the bacilli did not long survive.

Intramammarily injected b.c.g. produced inflammatory reactions in the mamma with formation of caseo-pus and ultimate destruction of the gland as a secretory organ. The micro-organisms, however, did not remain alive for any lengthy period in the mamma and in the two instances reported were not viable after about 15 weeks.

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.

In 1930 the author (Graham-Smith, 1930) showed that of spores of B. anthracis inoculated on 7 July 1907, on to dry, sterile pieces of canvas, measuring about 0·5 × 0·5 in., which were kept in a Petri dish in a cupboard with a glass door in the laboratory and therefore exposed to diffuse daylight at room temperature in a dry atmosphere, large numbers were capable of germinating in ordinary laboratory media after 10 years and progressively smaller numbers after 17 and 20 years. Very few germinated after 22 years and none after 22½ years.

Papillary variation includes all heritable changes of character which take place in the papillae of bacterial colonies and the corresponding variations in liquid media.

The following is a short summary of what is known about these variations. Papillary variation was first observed in B. coli-mutabile, and other coliform bacteria show the same variations. This race forms white colonies on lactose neutral-red plates. After 1–5 days’ incubation minute papillae, which become red and increase in size, appear on their surfaces. Subcultures from thesepapillae give colonies of two kinds, white and red. The white colonies continue to throw red, the reds breed true (Neisser, 1906; Massim, 1907). Similar variation to different sugars occurs in other related bacteria: B. dysentenae Sonne varies to lactose, B. dysentenae Mexner to maltose, B. paracolon to saccharose, B. coh-mutabile, B. acidi-lactici and B. typhosus to dulcite (Twort, 1907; Reiner Miiller, 1909; Burn, 1910; Stewart, 1926, 1927). Vacation takes place only on the sugar concerned, but, once it has taken place, the character remains fixed, even after long growth on other media. Variation is not determined by length of exposure to the sugar. It occurs at (or after) the end of the logarithmic phase. If this phase is kept going by daily subculture (in the appropriate sugar) the bacteria of the chain carried on from culture to culture do not vary, however long they are exposed (Stewart, 1927; Deere, Dulaney & Michelson, 1939). On the other hand, if the logarithmic phase is curtailed by heavy inoculation of a culture, variation occurs early (Stewart, 1927). If the bacterium is grown on a plate without sugar until the colonies are well formed and the sugar is then added, with care not to disturb the colonies, variants appear after very short exposure (Stewart, 1927, 1928). A variation 33–2 may be completed in, two distinct steps; thus a race of B. typhosus formed white colonies on dulcite with pink papillae, subcultures from which gave white and pink colonies; the pink colonies formed dark red papillae from which on subculture came pink and dark red colonies, the latter bred true.