Grassi has repeatedly asserted that the geographical distribution of the genus Anopheles in Italy coincides with that of malaria. Even in his most recent publication he lays special stress upon the coincidence, and considers that what he claims will probably hold true all over the world.

The importance of malaria as a disease affecting vast numbers of the human race renders it essential that we should study most completely all that affects the etiology of the disease. Through the brilliant researches of Ross, Grassi, Bignami and Bastianelli, and others we know that several species of Anopheles serve as definitive hosts of human malarial parasites, and that when these insects are infected they are capable of communicating the parasite to man. As far as the evidence goes these insects appear to be the only means by which the disease is spread. The sexually mature parasites circulating in man's blood gain access to the insect when it feeds upon this fluid. After a period of 7 to 8 days, under suitable conditions of temperature, the parasites appear in the insect's saliva, and when this occurs the latter is capable of producing infection by the act of biting. The highly interesting literature on this subject has been considered elsewhere by one of us, as also by Lühe, and the reader is referred to these publications for particulars1.

Milk, as every bacteriologist knows, is not only a universal and excellent food-stuff for human beings, but a medium admirably adapted for the growth and multiplication of microbes. For the latter reason milk deserves every attention at the hands of the hygienist, it being incontestably established that it may serve as a vehicle of disease agents. How well natural milk is adapted to this purpose, viz. to serve as nutritive medium for bacteria, is clear from its alkaline condition, and from its containing all ingredients required for the growth and multiplication of bacteria: proteid, fat, carbohydrate, and a large percentage of the essential mineral matters. It is a matter of common experience that all milk, however carefully it may be collected, however clean and aseptic may be the vessels into which it is received, will on standing, or after being handled in the way usual between collection and distribution, be found to teem with various kinds of bacteria. This fact is confirmed by the bacteriological examination of the milk sold in London shops, milk which, normal though it may be in appearance, chemical analysis, and taste, is usually found to contain hundreds of thousands of bacteria per cubic centimeter; bacteria which belong to various species and some of which when grown separately in sterile milk cause rapid changes and alter profoundly the character of the milk, e. g. Bacillus lactis, Proteus vulgaris, Bacillus coli, Bacillus mesentericus, spores of Bacillus enteritidis, etc. If allowed to stand, the milk containing the above mixture of bacteria exhibits even at ordinary temperatures, but in a more marked degree at temperatures of 70° F. and above, those profound changes which are popularly expressed as ‘going bad,’ changes caused by the rapid multiplication of one or other of the above microbes.

The principal data which form the basis of the present paper were tabulated by the writer for the Annual Report of the Chief Inspector of Factories for 1899, and were obtained as a result of an enactment in the Factories and Workshops Act of 1895. This enactment requires every medical practitioner attending on or called in to visit a patient whom he believes to be suffering from lead poisoning, contracted in a factory or workshop, to notify the case forthwith to the Chief Inspector of Factories at the Home Office; and a similar obligation is imposed on the occupier of a factory or workshop to send written notice of every such case to the Certifying Surgeon and Inspector of Factories for the district.

In almost all investigations relating to ventilation of inhabited buildings determinations of the carbonic acid present in the air are essential. The method in common use is that of Pettenkofer, or some modification of it. This method has, however, the disadvantage that the determinations necessitate the carrying to and from the laboratory of large bottles, and take a considerable time. To overcome these drawbacks several methods capable of being conveniently applied on the spot have been devised, but their accuracy is hardly sufficient for practical purposes, hence they have not come into general use.

When fresh meat, or blood, is boiled the colour changes from the red of oxyhaemoglobin to a dull, brownish colour. The change of colour is due to splitting up of oxyhaemoglobin into coagulated proteid and haematin, which are precipitated. The dark colour of haematin, mixed with the white of coagulated proteid, gives the dull brown. When, however, meat has been salted, it has a characteristic red colour when cooked. It is evident, therefore, either that ordinary haematin is not split off from the oxyhaemoglobin, or that the colour of the haematin is masked by the presence of another pigment.

The opinion has recently been expressed1 that the poisonous action of ordinary coal-gas and carburetted water-gas is probably in part due to the “Illuminant” hydro-carbons, of which ethylene is the chief, and not simply to carbonic oxide. In consequence of the doubt existing on this point one of us was asked by the recent Departmental Committee of the Home Office on Water-Gas to investigate the matter, and the results of the experiments which we were then able to make appeared in the Committee's Report2. In the main series of observations the animal was placed in a respiration chamber through which a current of air was passing at a known rate. With the current, before it entered the chamber, a known percentage of coal-gas or carburetted water-gas was mixed. It was found that whether ordinary coal-gas or carburetted water-gas was used the symptoms observed were those of carbonic oxide poisoning, and corresponded exactly to the percentages of carbonic oxide present. We also found that Benzene, which is one of the “illuminants,” is present in proportions far too small to contribute to the toxic effects of coal-gas or carburetted water-gas. Finally, we endeavoured to investigate separately the action of ethylene. The ethylene we then used was prepared in the ordinary way from sulphuric acid and alcohol, and when about 10% of the gas was mixed with air and supplied to an animal very distinct toxic symptoms were produced.

Whatever may be the final form of the theories of Ehrlich as to the constitution of the bacterial toxines and as to the essential nature of immunity there can be no doubt of the stimulus they have given and are likely to give to inquiries relating to these subjects. As the present paper is intended to give a preliminary account of some researches bearing on the reactions of certain toxines it may be useful to recall the main features of the theories in question so far as they relate to the toxines investigated.

There have not been wanting those who have alleged that isolation hospitals have failed to fulfil the object for which they were erected, inasmuch as scarlet fever has during the last few years been prevalent to an exceptional extent. Those who argue thus, are in favour of diminishing expenditure on the erection and maintenance of isolation hospitals, and consider that we must trust to “improved sanitation” for diminishing and possibly in the end annihilating infectious diseases.