On reading the excellent paper on the parasites of the Culicidae recently published by Dr Léon Dyé, I was struck by the fact that several of the organisms mentioned by him had been seen and described by me long ago in the course of my original studies on malaria and mosquitoes carried out in India during 1895–1899. My observations were, however, recorded for the most part in Indian medical publications, which are little accessible to European readers, and have been so far forgotten that some of the parasites of mosquitoes seen by me have been recently rediscovered by various observers. It may therefore be of interest—perhaps not alone from the historical point of view—to resuscitate these old records and compare them with more recent and exact work. I may add that attempts were made by me to infect men with two of the organisms which I observed. My writings on the subject were contained in the following publications, which are here numbered for reference:—

In view of the great interest attached to the questions discussed in the preceding paper, and the doubt expressed therein regarding the accuracy of Schaudinn's observations on the relationship between Halteridium and Trypanosoma, it seems expedient to reprint the following short papers by Novy, MacNeal, and Torrey, and Novy and Knapp, which appeared on February 9th, 1906, in Science (vol. 23, pp. 207–208).

In a previous paper on Bird Trypanosomes it was pointed out that these organisms grew readily in the test-tube on blood agar and that the resulting forms resembled the flagellates which Schaudinn found in the gut of mosquitoes which had fed on owls infected with Halteridium and with H. Ziemanni. In other words, the position taken was that the flagellates observed in the mosquitoes did not represent stages in the life-history of intracellular parasites but were actually cultures in vivo of trypanosomes present in the blood of the birds used. In confirmation of this position it was desirable to show that trypanosomes could actually grow and multiply in the gut of mosquitoes and that such forms actually did correspond to those which would be obtained in vitro.

In general, it may be said that bacteria once introduced into a culture of trypanosomes tend to outgrow and check the development of the flagellates. In exceptional instances, however, the bacteria thus introduced exert little of no interference and may be even apparently beneficial. While in the former case the trypanosomes soon die out, in the latter instance the mixed cultures may be kept for six months or longer.

1. Cultures of Gärtner's bacillus grown on broth do not excrete any large amount of toxin into the fluid medium.

2. Suspension in broth made from ordinary agar cultures and killed by means of heat (30 mins. at 60°C.) are fairly toxic.

3. The most toxic preparations were obtained by autolysis of the bacilli, especially in the presence of toluol.

4. Cultures grown on agar and killed by means of chloroform vapour lose their toxicity to a considerable extent.

5. Autolysis takes place best in the presence of distilled water or of normal saline.

6. Autolysed material sterilised by heat is more toxic than the filtrate obtained from the same digest.

7. Shaking the bottles during the process of autolysis increases the yield of toxic substances.

8. Gärtner toxin withstands heating to 100°C. for 30 mins.

9. Paratyphoid B. bacillus cultures on autolysis yield a filtrate quite as toxic as those from the Gärtner bacillus itself.

10. Paratyphoid toxin is also heat resistant (100° for 30 mins.).

11. A colon bacillus gave a toxin which was fatal to mice. It was not heat resistant.

12. Feeding experiments with Gärtner-infected meat, both cooked and uncooked, proved successful.

13. So far as the present experiments go the connection between virulence and toxicity does not appear to be very definite.

14. The Gärtner bacillus contains a toxin of the endotoxin type as is shown in comparing results 1 and 3. This toxin gives rise to very definite clinical symptoms of which the gluing together of the eyelids and the prolonged narcosis before death are the most notable. The post-mortem signs have much in common with those arising from other intestinal intoxications.

The undoubted fact that milk may act as a vehicle for the transmission of a number of diseases has directed considerable attention to the Bacteriological and Public Health aspects of milk. Yet it cannot be said, tuberculosis excepted, that the bacteriological examination of milk has afforded in the past much assistance in the prevention of disease, while only very occasionally has a subsequent examination served to elucidate the cause and origin of a milk-spread epidemic. A survey of the literature of the subject will show that although extensive work has been carried out upon the bacteriology of milk, the subject is so large and many-sided that what is known is but an insignificant proportion of what requires to be ascertained. A great deal of the work done has been in relation to tuberculosis. Almost all the milk examinations have been carried out with mixed milk samples, and not with quite fresh milk from individual cows.

For some years past a careful record has been kept of the method of feeding, not only of all children dying of epidemic diarrhoea, but also of all babies under one year of age in the houses of the working classes, which are visited year by year in the course of routine house-to-house inspections by the sanitary inspectors in my department. It is impossible to ask the necessary questions at every house, but in most houses information has been given without difficulty, and it may be taken as certain that the 1259 babies living in 10,308 houses who are classified in the first four columns of Table I belong approximately to the same social stratum as the 121 babies dying from diarrhoea who are classified in the four last columins of the same table.

In the month of June, 1905, no fewer than 99,518 natives were employed on mines and works in the labour districts of the Witwatersrand, and the neighbouring mining areas of Klerksdorp, Heidelberg, and Vereeniging. In addition to these there were also working on the gold mines over 45,000 Chinese labourers. This vast industrial army is recruited from many and in great measure from very distant sources. Of the natives employed during the year ending June, 1905, the whole of British South Africa furnished only just over 32%: less than 2% came from British Central Africa: 60% were drawn from the Southern Portuguese East Coast provinces; and 3.6% from the Portuguese provinces north of latitude 22°. German South-West Africa contributed under 1%, but this area has latterly ceased to be a source of supply.

It is well known that the air of wells, mines, &c. is sometimes capable of extinguishing a flame, and recent researches have shown that this is almost always due to deficiency of oxygen, accompanied by the presence of a considerable percentage of CO21. The extinctive atmosphere is popularly known as “choke-damp” or “black-damp.” The source of the CO2 is not necessarily the same in all cases. If oxidisable organic matter is present it is reasonable to suppose that the CO2 may be derived from the carbon in this organic matter by the action on it of air; but the derivation remains a supposition. Carbonaceous materials may be oxidised and yet give no CO2. The other obvious source of CO2 is the decomposition of carbonates by an acid, the acid being produced by some process of oxidation. The commonest mineral which will yield an acid by oxidation with air is pyrites, and if direct oxidation of carbonaceous matter be ruled out, it may be assumed that the occurrence of CO2 is ultimately referable to pyrites in an easily oxidisable form, for example as marcasite.

Since the publication of the Indian Plague Commission in 1901, with the exception of a short paper by Hankin (1905), comparatively little has been published in scientific journals dealing with the spread of plague in India from an epidemiological view-point. Not that this has been lost sight of in India, for there are many very valuable reports in existence in the archives of the various local Governments, containing most interesting observations made by officers of the Indian Medical Service who have dealt personally with the epidemics; but as these reports are, in the nature of things, not available for reference by the public, it has been thought advisable and useful to compile a digest of them for publication.

In 1898 Arloing and Courmont published the results of experiments made by them on the agglutination produced by the serum of tubercular patients. For this purpose they used a strain of the tubercle bacillus isolated by the former, which produced a uniform turbidity when grown in glycerine broth. With this culture, serum from tubercular patients gave reactions at dilutions of 1 in 5, 10 or 20 in a large percentage of cases, and that from normal individuals only in a much smaller percentage and then not very strongly. From this they concluded that the agglutination reaction was likely to be of considerable use in the diagnosis of tuberculosis.

The “graphic” method of constructing a Life-Table which is ably and lucidly expounded in the paper by Drs Newsholme and Stevenson (published in the Journal of Hygiene, vol. III. No. 3, pp. 297—324), is one way of dividing up foundation figures of population and deaths, given in groups of ages, into numbers belonging to each separate year of age, so that, either directly by the fraction , or indirectly by first obtaining , and then finding the value of , the series of px values is obtained forming the connecting link between the data and the results of the Life-Table.