In this report are included a series of a thousand cases examined from Jan. 1910 to Jan. 1911, the tests being made weekly at the R. N. Hospital, Haslar. Most of the cases were under observation in the hospital when their clinical characters could be recognised; in many of the cases several tests were applied, week after week, thus making the results obtained of greater value.

Although typhoid bacilli were liberally supplied to larvae of Musca domestica, all attempts to demonstrate B. typhosus in the pupae or imagines were unsuccessful, until recourse was had to disinfection of the ova. After this preliminary disinfection both larvae and pupae gave pure growths of B. typhosus but hitherto it has not been possible to examine the imagines.

In the experiments with unsterilised ova great difficulty was experienced in determining whether B. typhosus was present in MacConkey plates owing to the almost invariable occurrence of the colourless typhoid-like colonies of the Bacillus “A” which was evidently an organism throughly adapted to the conditions prevailing in the interior of the larvae, pupae and imagines.

The fact also that this organism like B. typhosus fermented mannite without the production of gas, rendered the search for B. typhosus still more difficult.

By the employment of sorbite—in place of lactose-media, a preliminary differentiation might have been possible but was not considered practicable in the first place owing to the expense of sorbite, and secondly owing to the fact that the fermentation of sorbite by B. typhosus though constant, is sometimes delayed. The most satisfactory plan was to pick off as many colonies as possible and inoculate them on litmus-milk. Bacillus “A” invariably rendered litmus-milk intensely alkaline.

From the practical point of view the main conclusion to be drawn from the experiments detailed in this communication is that the typhoid bacillus can lead only a very precarious existence in the interior of larvae or pupae which possess, at least in so far as these investigations warrant, a well-defined bacterial flora of their own.

Even under the highly artificial conditions of the final series of experiments, it was not possible to decide whether the B. typhosus though recoverable from the pupa was really actively multiplying in the pupal interior or gradually dying out. There was some indication that the latter was the case, as the typhoid colonies recovered from the pupa in the one successful instance, were extremely few in number, while the larvae which had been feeding on B. typhosus contained enormous numbers as evidenced both by cultural and microscopical examination.

Since the above experiments were concluded, some further researches by Graham-Smith (1911) on the carriage of bacteria by flies have appeared in the form of a Local Government Board Report. This author has succeeded in recovering B. anthracis from blow-flies bred from larvae fed on meat infected with spores of this organism, but has failed to recover B. typhosus or B. enteritidis under similar experimental conditions.

The digestion of solidified blood-serum by certain sporing bacilli is well known, and Bienstock (1899) and Rettger have shown that B. putrificus and other obligate anaerobic sporing bacteria destroy protein and cause putrefactive changes. Hardly any observations have been made, however, to determine whether aerobic, non-sporing bacilli and cocci have any power to break down proteid, although it is often assumed they can do so. Rettger (1906) found that bacilli of the colon group did not set up putrefactive changes in a mixture of egg and meat protein; he made no quantitative experiments as to whether any destruction of protein took place, and Dr C. J. Martin informed me that he has for long noticed that preparations of pure proteins, when left exposed to air, did not appear to be broken down by bacteria, although moulds were able to grow in them.

On February 10th, 1911, the attention of the Medical Officer of Health was called by the practitioner in charge to an outbreak of diarrhoea in a family named R. residing in Paddington. The note made at the interview was to the effect that cases had occurred on the 8th, 9th, and 10th (2 cases) of the month, the four patients having violent diarrhoea and passing much blood. The onset was quite sudden in every case. It was thought that “food poisoning” could be excluded, and the main object in directing attention to the outbreak was to ascertain if any defective drainage existed at the house. Incidentally it may be remarked that the house drainage, etc. had been completely overhauled in 1907 and that no defects existed in February last except one leaky joint on a waste pipe.

The organisms examined have been killed, (a) by temperatures which should not have destroyed the reducing enzyme, (b) by sodium fluoride and four other antiseptics, derivatives of phenol, and (c) by acetone. In each case there has been total destruction of the reducing power, any apparent production of nitrite from nitrate being too slight to justify the assumption that it is due to anything more than experimental error. Filtrates of fluid cultures have also failed to reduce. The results may be summed up as follows:

(1) The reduction of nitrite by certain dysentery bacilli is not due to a soluble extra-cellular enzyme.

(2) Dysentery bacilli and B. coli killed by a minimal degree of heat have little if any effect in reducing nitrites.

(3) Organisms killed by antiseptics or by acetone do not reduce nitrates and nitrites.

(4) Even where all the organisms are not dead, reduction may be prevented by antiseptics.

(5) The high antiseptic value of tetrachlor-o-biphenol, tetrabrom-o-kresol, p-chlor-m-kresol and hexabrom-dioxy-diphenyl-carbinol has been established for the organisms of the dysentery group.

Bile and the bile salts are substances of great importance in connection with typhoid fever. On the one hand, they are extensively used in differential media for the isolation of B. typhosus from the excreta, and in media designed to cultivate the bacillus from the blood; while on the other, the survival of the organism in the gall bladder and its association with gall stones and cholicystitis indicate that bile may play an important rôle in the etiology of the disease. It would appear therefore that a study of the mode of action of bile in culture media for the isolation of B. typhosus might, apart from its bearing on bacteriological technique, incidentally throw light on the far more important question of typhoid fever and the production of typhoid carriers.

1. A study of the natural bacterial flora of the house-fly appears to be essential in forming a correct estimate of the part played by flies in transmitting pathogenic bacteria.

2. The house-fly may carry at least 27 varieties of Bacillus coli, by far the most frequent of which are B. coli communis and MacConkey's bacillus No. 71.

3. As far as can be judged from the character of these colon bacilli the house-fly derives its bacterial flora equally from excremental matter and from other sources.

4. Certain non-lactose fermenting bacilli appear to be capable of multiplying in the intestine of the house-fly. Of these Morgan's bacillus No. 1 is a not infrequent inhabitant of the fly's intestine and B. paratyphosus β has been found on two occasions.

All the non-biting flies examined, C. erythrocephala, M. domestica, S. carnaria, F. canicularis, L. caesar and O. anthrax, possess a filtering apparatus situated in the pseudo-tracheae of the suctorial disc. The anatomy and action of this filter have been most thoroughly studied in C. erythrocephala. The suctorial disc is grooved by pseudo-tracheae which end near its centre in closed collecting channels. The latter open into furrows or gutters formed by the peculiar disposition of the prestomal teeth on the walls of the prestomal cavity. The opening of the mouth is situated at the base of the cavity. During natural feeding the lobes of the suctorial disc are pressed together so that the lumen of the prestomal cavity is obliterated, and no food can enter the mouth except through the collecting tubes. The pseudo-tracheae are channels kept open by chitinous rings situated in their walls. Each ring has one bifid extremity, enclosing between the horns the “interbifid space”, which forms an opening of definite size into the pseudo-trachea. A fold in the cuticle, the “interbifid groove”, leads to each interbifid space.

The fluid food is sucked first along the interbifid grooves through the chitin-lined interbifid spaces into the pseudo-tracheae. Particles of larger diameter than the interbifid spaces (·006 mm.) are usually prevented from entering the mouth and are rejected. The fluid and smaller particles are drawn along the pseudo-tracheae, through the collecting channels and gutters between the prestomal teeth into the mouth. By means of strong suction two opposite interbifid grooves may be made to communicate with each other owing to the lateral fissures connecting with the longitudinal pseudo-tracheal fissure being forced open, and consequently a few larger particles, up to ·02 mm. in diameter, may be drawn into the pseudo-tracheae.

Certain relatively large and very attractive objects, such as the ova of tape-worms, too large to pass through the filter, may occasionally be swallowed. Such objects probably pass directly into the mouth, when the prestomal cavity is open, during the prolonged sucking efforts made by the flies.

The large number of experiments which have been made leave little room for doubt that under natural conditions, especially when the fly is feeding on a thin film of moisture, the filtering apparatus works with a high degree of efficiency.

The occurrence of non-virulent strains of bacilli, which are indistinguishable except by animal experiment from virulent diphtheria bacilli, makes it especially interesting to investigate the varying pathogenicity of this bacillus. Owing to their complete lack of pathogenicity for laboratory animals, the exact relationship of the non-virulent types of B. diphtheriae to the virulent forms of this organism, cannot yet be considered as settled, although Arkwright (1910) has succeeded in obtaining a slight but very definite development of antitoxin in the blood of a horse immunised with non-virulent strains.

(1) The young of parents both of which have been injected with an immunising mixture of diphtheria toxin and antitoxin, show immunity of the same order as that of young from similarly treated mothers and normal fathers.

(2) The injection of certain foreign substances into a female guinea-pig appears to have a direct effect on the offspring in diminishing their resistance to diphtheria toxin, shown equally well by the young of mothers injected, (a) before the attainment of sexual maturity, (b) during pregnancy, and (c) after birth during the period of lactation.

(3) A single injection of diphtheria toxin may give rise to a condition of active immunity (as tested by the resistance of the young) in guinea-pigs possessing hereditarily transmitted passive immunity. Should this injection of toxin give rise to great constitutional disturbance, the young may show lowered resistance, whereas, if it give rise to but slight constitutional disturbance, the young show a high degree of immunity. These effects appear to be accentuated if similar injections are repeated in the next generation.