A male Pariah-Irish terrier puppy, apparently about three months old, followed me home from the hospital in Krian. This was twelve months ago, so that the dog is now fifteen months old. Of his previous history I know nothing.

The parasite referred to in the preceding paper was found by Dr Gerrard in the polymorphonuclear leucocytes of a dog. As is stated by Dr Gerrard, the parasite is evidently similar to that discovered by Bentley and described by him, and afterwards by James, as the Leucocytozoon canis. Dr Gerrard sent some films, stained by him by Leishman's method, to Sir Patrick Manson, and they were handed on to me for description and identification. These films had faded in transit, they were therefore decolorised and restained by various methods. All the staining reactions mentioned in this description refer to these old films.

The origin and object of the following paper can be explained in a few words. In April, 1904, the writer published a series of 280 blood examinations (to which were added about 150 more) of natives of southern Angola (Portuguese West Africa) without recording a single instance of the presence either of trypanosomes or of spirochaetes in the circulation. Quite recently in the course of an investigation of the endemic malaria of the same district, 513 examinations made among the same people and with the same technique revealed 3 individuals harbouring trypanosomes and 4 showing spirochaetes in their blood. These observations, together with the fact that a year or so ago the natives reported no cases of Tick Fever, while recently statements are made by them that the Tick Fever of the upper Zambezi has reached Angola, and also the fact that Sleeping Sickness is reported to be advancing southward through the province, have led me strongly to suspect that these diseases have lately begun to spread markedly in my part of the colony, and that one or both of them may not inconceivably assume in the near future epidemic proportions.

Some months ago a bat flew into my house at Grahamstown and was captured. Unfortunately the animal was fatally injured. It was placed in a tobacco-box and on opening the box next day a lively insect like a common bed-bug (Acanthia lectularia) and emiting a similar odour was found in the fur behind the bat's neck. The bug was sent to Mr C. W. Mally, M. Sc., Entomologist to the Eastern Province, for identification and he kindly determined the species as being Acanthia pipistrelli Jenyns, adding that the specimen agreed very well with the description given by Jenyns. Mr Mally wrote, “In the absence of the Northern specimens of this species I cannot express an opinion as to varietal characters. This specimen is of especial importance because there is apparently no record of its occurrence in these parts, nor has the species of bat in connection with which it was first discovered been found at the Cape”. Through the kind intermediation of Mr Mally the bat was forwarded to Professor Duerdin of the Rhodes University, who determined the species to be Vespertilio capensis, “The Cape Serotine Bat”. Prof. Duerdin states it is “apparently one of the commonest of South African bats, but we do not seem to have many”.

In the samples of “blown” preserve tins examined by me, organisms of an intestinal type were present, which on reinoculation into sound tins gave rise to a gaseous decomposition.

No toxic symptoms were produced on feeding guinea-pigs with the contents of the “blown” tins.

It is usually accepted that in precipitin reactions a definite quantity of precipitin interacts with a definite quantity of homologous proteid, and further that in ordinary circumstances the interacting quantities combine to give rise to a precipitate, the precipitum. From this it follows that, if a known weight of serum containing precipitin be allowed to react with various weights of homologous proteid and if the quantities of proteid be sufficiently varied, certain reactions will be completed and others will be incomplete. The addition of precipitin and of homologous proteid to the superfluid of each reaction will determine the presence of excess of precipitin or of homologous proteid in such fluid. Conversely, if a known weight of the homologous proteid be allowed to interact with various weights of serum containing precipitin, it will be possible to determine in a similar manner those reactions which have been completed and those in which the homologous proteid or the precipitin is in excess. If the first stated proposition be correct, the results of these two series should coincide. A definite weight of serum containing precipitin should interact with a definite weight of proteid to from the precipitum.

1. A mixture of serum and its anti-serum has the property of fixing or deviating complement and thus interfering with haemolysis. In this there is a close analogy to the fixation of complements by cellreceptors in association with immune-bodies.

2. A large number of different complements may be fixed by the same combination of serum and anti-serum: some complements however may not be fixed.

3. The amount of homologous serum necessary to produce a distinct deviation of complement is extremely small—·000,01 c.c. and even less: as a rule it is many times less than the amount necessary to give a visible precipitate with the anti-serum.

4. When a precipitate forms, the deviating substance is present in the precipitate and may be so exclusively: precipitation is however not essential, as the deviation phenomenon may be given by an anti-serum without the formation of a precipitate.

5. The precipitin and deviation tests give results which are in great part in accord as regards specificity.

6. For any given amount of anti-serum there is an optimum amount of homologous serum which gives maximum deviation of complement: above as well as below the optimum the deviation diminishes.

7. The deviation phenomenon produces an effect similar to an “anti-complement” action and the views generally held with regard to anti-complements require revision. It is however still left an open question whether true anti-complements exist.

The experiments here recorded are not sufficiently numerous to justify any decided opinions as to the value of the tests with these various substances in differentiating certain bacilli which very closely resemble the diphtheria bacillus. They show, however, that most of the diphtheria-like organisms tested produce less acid than the diphtheria bacillus. Hofmann's bacillus and a diphtheria-like bacillus from the normal ear can be easily differentiated, since they from no acid. Any bacillus which acts on mannite or saccharose could also be easily differentiated.

During my bacteriological investigations on the enlarged prostate gland which I am carrying out in conjunction with Mr Cuthbert Wallace, I have isolated a bacillus which presents the following characteristics and which appears to be, so far as I can ascertain, an organism which has not previously been met with.

H. Smidt in a recent note on the reduction of methylene blue by means of milk confirmed the results of Schardinger that a mixture of formaldehyde and methylene blue is decolorised by the action of milk. This reaction depends on the presence of a ferment—a catalase—in the milk, and, as this ferment is readily destroyed by heat, serves as a very simple method of determining whether a given sample of milk is “raw” or not. By way of conclusion Smidt stated that he thought this test might be of still further utility in that it might be possible to estimate the degree of bacterial contamination of the milk by its means. If such a comparatively simple test could be employed, in an easy and effective fashion, it would be of immense service, as, owing to the rapidity with which it can be carried out, the milk could be examined before distribution.

Phthisis (pulmonary tuberculosis) is distinguished from nearly all other infectious diseases by its protracted duration and by the prolonged disability which it imposes upon enormous numbers of the total working population. It is further distinguished by the complexity of the influences which are regarded as affecting its spread or capable of controlling its prevalence. It is therefore of the first importance that the relative values of measures for controlling phthisis should be closely studied, and that special attention should be given to those which promise the greatest yield for a given expenditure. In particular it is important to be aware of any which can be set to work without the delay and expense involved in creating a new service. The present paper is intended as a contribution to this study. The facts collected in it and others of a similar kind deserve more extended investigation than it has been possible for me to give them in the intervals of official work. They are put forward here without any illusions as to the inevitable shortcomings of their presentation but with a conviction that from the economic standpoint they are of fundamental importance in the prevention of phthisis.

With ordinary care and cleanliness it is possible to obtain milk which, when freshly drawn, contains less than 1500 organisms per cubic centimetre.

Freshly drawn milk should not contain gas-forming organisms in at least 50 c.c.

Gas-forming organisms are present in milk owing to contamination with faecal material. Of these organisms the B. oxytocus perniciosus, the B. neapolitanus and the B. coli communis occur in greatest number in fresh milk, while the B. cloacae and B. lactis aerogenes appear at a later stage.

Out of 107 non-chromogenic lactose fermenters isolated from milk only one bacillus gave the reactions of the B. acidi lactici (Hüppe); while the B. Grünthal, B. pneumoniae (Friedländer), and the B. coscoroba have not been met with once.

Finally, I desire to enter a plea for the substitution of certain fermentation reactions in the place of some of the tests now usually employed, in the routine examination of water and food-stuffs, to identify these organisms. At present bacteriologists make use of some, or all, of the following tests:

1. Morphology.

2. Motility.

3. Staining by Gram's method.

4. Character of the growth on nutrient gelatin.

5. Liquefaction of gelatin.

6. Action on milk.

7. Foemation of indol.

8. Fermentation of glucose.

9. Fermentation of lactose.

10. Fermentation of cane sugar.

11. Action on neutral-red.

All the organisms mentioned in Tables I and II produced clotting in milk, fermented glucose, gave the neutral-red reaction, had much the same morphology, and the growths on agar and gelatin did not afford any assistance towards differentaniting between them.

I would therefore suggest that instead of five of the tests, Nos. 4, 6, 7, 8, and 11, we should substitute the following:

Fermentation of dulcit,

Fermentation of adonit,

Fermentation of inulin,

Vodes and Proskauer's reaction, as by so doing we should get a finer differentiation without increase in work and we should not be classing as B. coli organisms which may have little in common with, and have a distribution entirely different from that of the B. coli communis.

The use of earthenware as a filtering material for the purification of water is probably of very ancient origin, but the modern modification, the porcelain filter, according to Gautier (1890), is due to Nadaud de Buffon (1861). Earthenware filters in general serve the useful purpose of aërating the water and retaining suspended matter and are therefore valuable in rendering boiled and rain water clear and palatable. The first application of bacteriological methods of examination by pupils of Robert Koch showed, however, that the great majority of these and other water filters gave no protection against disease organisms. Hesse (1885–6) found that clays and asbestos retained micro-organisms to a marked extent, and, although Plagge (1886) confirmed this observation he demonstrated that but few filters prevented the direct transmission of bacteria and that even the best after a few days contaminated the filtrates indirectly. This indirect contamination Plagge attributed to the growth of micro-organisms within the filter mass and so pronounced is its influence that porcelain filters after being a few days in action give filtrates richer in germs than the original water. Schäfer (1893) states that porcelain filters do not allow organisms to grow through them when the water filtered is of such a character that the organisms cannot multiply in it. He points out that the waters usually filtered for domestic purposes do not allow B. typhosus and V. cholerae to grow, and that in such cases porcelain filters are efficient. Unfortunately, however, drinking waters do occur in which these organisms can multiply, and then indirect contamination is inevitable if the filter be allowed to act more than a few days without sterilisation.