In autumn and early winter certain ditches around Cambridge became offensive, and their water turned milky. This led to a grave suspicion of sewage contamination, which, however, was satisfactorily disproved. On the other hand certain bacilli with single flagella were isolated from the water of the ditches and found capable of giving off from their artificial cultures an odour comparable to that of the ditches. And to these bacilli, acting on the dead leaves which found their way into the water, and, probably, in conjunction with other anaerobic bacteria which were generating hydrogen disulphide, the sewage-like odour is attributed.

Certain patchy changes of colour in the leaves and wood immersed in the water are attributed to a chromogenic flagellate which was found growing on them.

Although much work on the epidemiology of plague has been done in many parts of the world since the discovery of the Bacillus pestis in 1894, the origin of the outbreaks in Eastern and Southern Russia has, until a short time ago, remained obscure. Transbaikalia, together with extensive areas of Northern Manchuria and North-east Mongolia that are conterminous with it, and, again, the region in Southern Russia which includes the Kirghese and Kalmuck steppes and especially that portion of it which lies between the lower reaches of the rivers Volga and Ural have long been known to contain endemic foci of plague, and have been the source of considerable outbreaks of pneumonic plague. Thus, in the winter of 1878–79, an outbreak of this type at Vetlianka, a Cossack village on the right bank of the Volga, caused alarm in Western Europe. Competent epidemiologists–British, French and German–visited the village after the event, and examined the circumstances that favoured the spread of the infection. Their observations were brought together and analysed by Netten Radcliffe (1881) in his memorandum on plague, which gives the first adequate description of a pneumonic plague epidemic. The more recent epidemics of pneumonic plague, namely, those of Manchuria in 1910–11 with 50,000 deaths, Middle China in 1917–18 with 15,000 deaths, and Manchuria in 1920–21 with 9000 deaths, owed their origin to ill-defined centres of infection in the immense tract of land which includes Transbaikalia and which is contiguous to the north-west boundary of China.

The list of bacteria recorded as causative agents in enteric fever and “food-poisoning” increases steadily, and the proved pathogens already number eleven types, of which three have been found in both continued fever and food-poisoning, three in continued fever alone, and five in food-poisoning alone. This list will undoubtedly be added to when cultural methods for the diagnosis of these conditions are more widely employed, especially in the tropics.

About a year ago the specific opportunity which our laboratories had been seeking presented itself. We were brought into touch with a farm on the outskirts of Vancouver engaged in the production of milk and the distributing of the same in the city. The proprietors of the farm, with at that time a herd of twenty-five grade cows, were endeavouring to supply a high grade milk, a milk having a low bacterial content, and secured from cattle giving a negative reaction to the tuberculin test. We approached the proprietors, Mr and Mrs Alexander Hill, and found that they were desirous of co-operating with us. At the same time their milk was obtaining a premium over the usual price obtained for market milk sold in the city. We made it clear that we were anxious to secure data which would be of use to milk producing farmers generally with respect to the possibility of producing a high quality milk; and they—Mr and Mrs Hill—assured us that they desired to have advice and help if the same could be forthcoming. Finally we made the following arrangement: (a) we were to be permitted to obtain samples of milk at any time deemed most suitable to ourselves, (b) these samples were to be examined for bacterial flora to the end that we might secure the data we needed, (c) no report on the examinations was to be sent from our laboratories until it became possible for us to publish the data as a whole, (d) the proprietors of the diary were to be given any information that was available from the laboratory data, but, under no circumstances, was the same to be used for publicity purposes, (e) we were to check up any of the procedures in vogue on the farm and dairy as far as proved to be possible without unduly interfering with the progress of our main project. The arrangement was agreed to mutually, and it is a matter of gratification to us that throughout the entire investigation the conditions detailed above were subscribed to loyally.

The method most commonly employed for the separation of antitoxic globulins is that by means of Ammonium Sulphate, and this was the process used in these laboratories for several years until, at the end of 1917, the supply of the necessary salt was cut off. We were then thrown back on Sodium Sulphate, a salt we had used before the War but which had not given us satisfactory results. A few fresh trials, however, showed us the faults of our previous technique and proved that Na2SO4 could satisfactorily replace Am2SO4 and so, since February 1918, we have used only the former salt. Changes in detail have been made from time to time and we have now established a routine method which has for some time given us satisfactory results.

In the course of investigations into outbreaks of typhoid in the county for which I act as Medical Officer, I have discovered a number of typhoid carriers whose histories seem worth placing on record as showing the extent to which the endemicity of the disease in rural areas is maintained by carriers. Of twenty-two found, four were identified in 1908, two in 1910, three in 1911, one in 1916, one in 1917, five in 1918, and six in 1919. Five were men and seventeen were women, giving a proportion of 77·3 per cent. of female carriers. Of the chronic typhoid carriers found by the German stations up to the close of 1907, 82 per cent. were women. All of my carriers were intestinal, one being a urinary carrier as well. As in every case attention was directed to the carriers owing to a case or cases of actual typhoid fever occurring; this experience indicates that, as is generally believed, faecal carriers are altogether in excess of urinary carriers, or that urinary carriers may not have the special malignancy commonly attributed to them.

1. The lesions produced by the different dusts employed in these experiments, and the conclusions to be derived thereform, have already been discussed in Section 6 of this paper (see p. 455, et seq.).

2. Plaque formation has been discussed. Evidence has been produced to show that the large plaques which tend to be formed in the parenchyma represent permanent pulmonary lesions. Small plaques, on the other hand, may be formed within the pulmonary lymphatics, in which case they may disintegrate in course of time. Such plaques have been termed “intralymphatic plaques.”

3. Evidence has been brought forward against the view that the degree of harmfulness of a dust is proportionate to the degree of angularity and sharpness of its consituent particles. Nor has the supposition that the dusts which stimulated phagocytosis were those which contained organic matter been confirmed experimentally. Although silica may be regarded as a cellpoison and that this may account for the inability of the phagocytes to remove it, there are probably other factors than this, since shale—universally admitted to be one of the least harmful dusts—contains from 55 per cent. to 60 per cent. of silica. As to why one dust is harmful, and another not, is a problem as yet unsolved.

4. The origin of the dust-cells has been studied. Reasons have been given to justify the belief that dust-cells are frequently derived from the alveolar epithelium. This, however, does not exclude the possibility of some participation of leucocytes or endothelial cells in the phagocytosis of dust particles.

5. The chief modes of elimination of dust from the lungs have been discussed. It has been shown that the dusts which stimulate phagocytosis tend to be eliminated from the lung by both bronchi and lymphatics, while such elimination as occurs of the dusts which elicit but a feeble phagocytic response is through the lymphatics rather than the bronchi.

The Standard Tetanus toxin sent out by the Hygienic Laboratory of the United States Public Health Service is in the form of a dry powder, and the required quantities have to be weighed out.