The subject of the following remarks is the mode of spread of bubonic plague in epidemic form as deduced from observations made during the outbreak at Sydney. The nature of the disease, and the whole of the circumstances which accompanied its appearance, having been described at length in my official report, only those points which have a direct bearing on the subject just defined are here mentioned; but a brief preliminary statement of certain local conditions is necessary.

Elkton, the county seat of Cecil county, Maryland, is a town of 2542 inhabitants, built upon a red clay soil, rather flat as to surface, but sloping gently toward the Elk river. This small stream is not navigable, is but slightly influenced by the tides, and is only about 25 feet below the highest part of the town.

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 death of Professor von Pettenkofer, which was briefly alluded to in the last issue of the Journal of Hygiene, has removed one who was everywhere acknowledged as a great leader among the workers in our science, and as the pioneer who has been mainly instrumental in bringing about the recognition of Hygiene, particularly on its experimental side, as a separate subject of investigation and university instruction.

Both boric acid and borax are extensively used as food preservatives, and much interest attaches to the question of their influence if any upon the general nutrition of the consumer, especially children. Although this method of preserving food has existed for a comparatively long period there seems no agreement as to the harmfulness or otherwise of these substances when taken with a mixed diet.

The object of the experiments detailed below, which were made at the suggestion of Dr W. Hunter, was to ascertain whether media containing neutral-red afford a rapid means of detecting Bacillus coli in water and estimating the number present.

The want of success which has so persistently attended the efforts of most bacteriologists to isolate the B. typhosus from water supplies suspected to have caused enteric fever, suggested a study of the varieties of B. coli which are associated with the B. typhosus in the dejecta of patients suffering from enteric fever. It was hoped that the organisms in question might show cultural characteristics or reactions to specific sera, which would enable them to be distinguished from the varieties of B. coli present in the dejecta of healthy people; so that even if the B. typhosus were not detected, the presence of these special organisms might afford reasonable grounds for the belief that the water under examination had been fouled by the specific dejecta of cases of enteric fever. With this object in view 150 organisms have been examined; of these 80 were isolated from the stools of cases of enteric fever and 70 from the stools of healthy men. The enteric fever cases were five in number, one being a severe relapse, and the other four severe cases which terminated fatally. The stools were obtained during the third and fourth weeks of the disease and also, in the fatal cases, from the intestines after death had occurred.

The momentous discovery of the part played by Anopheles in the propagation of malaria necessitates careful local inquiries into the prevalence of this genus, in order to ascertain how far the different methods of lessening the amount of malaria which have recently been proposed can be profitably applied to the circumstances met with. In no country are such studies more essential than in India on account of the radical differences in the topographical and climatic conditions of different provinces of this vast and densely populated country, ranging from the waterless deserts of Sind to the steamy, waterlogged marshes of Lower Bengal.

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.

It is well known that fresh sewage always contains large numbers of the common colon bacillus. It is also true that when a water source is polluted with any considerable quantity of fresh sewage it is usually possible to demonstrate the presence of the colon bacillus in such water. Upon these familiar facts have been based various methods and conclusions of greater or less value to public hygiene.

Formic aldehyde, the simplest possible aldehyde, is a substance possessed of considerable biological and chemical interest. Its biological interest consists in the fact that it has long been regarded as forming the first product of plant assimilation, and has recently been actually demonstrated as such in plants. The ease with which this substance undergoes polymerisation resulting in the formation of sugars, under the influence of simple reagents, justifies the assumption that formic aldehyde is an essential link in the building-up of complex carbohydrates by plants. In addition to this it has recently been requisitioned as the only possible source of proteid anabolism. Its interest to the physiological chemist is that it combines energetically with proteids, and to a less extent with carbohydrates, effecting considerable alteration of their physical and physiological properties. This behaviour seems to be directly antagonistic to the biological rôle ascribed to the substance above. This apparent anomaly of the same substance being both a poison and an essential physiological constituent of living cells is discussed by Loew. It seems to depend upon the fact that what may be termed the biological formic aldehyde is present in small quantities (dilute solutions) and is quickly used up, owing to the ease with which it polymerises or forms innocuous compounds. This last property has an immediate bearing upon the subject of this inquiry in so far as it may serve to explain the results obtained by the administration of small quantities of formic aldehyde to man in his food. It is in this connection that formic aldehyde is of interest to us, and the importance of this subject is in our opinion sufficient to justify us in reviewing somewhat exhaustively the results of other observers with regard to the chemical and physiological properties of this substance.

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 research which follows was undertaken with the object of determining how far the neutral-red reaction described by Rothberger could be utilised for the purpose of detecting Bacillus coli in water-supplies.

The following contribution to the aetiology of cerebrospinal meningitis is published with a view to calling attention to the possible part played by dust in the causation of this disease. The strong connection between dusty occupations and cases of cerebrospinal fever, as here detailed afford, it is believed, a prima facie presumption that dust may be one of the vehicles of the specific germ.

Towards the end of October 1900 the Sanitary Authorities of Cambridge and Chesterton found themselves face to face with a serious outbreak of diphtheria; the first official notification had been on October 14th, and by October 23rd eleven cases had been notified, of which four terminated fatally, on October 15th, 21st, 22nd and 26th respectively. These four were all children attending the Infants' Department of a certain Higher Grade School, and the other seven cases were either children of this school or persons closely associated with them.

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.

Before proceeding to describe the imago of Anopheles, we wish to record some observations regarding the hibernation of the larvae of various Culicidae. Grassi (1900, p. 47)1 considered that A. bifurcatus hibernated chiefly in the larval form, for he found the larvae of this species in midwinter in Southern and Central Italy, the imagines being rarely encountered. It was quite different with A. maculipennis. In this case the imagines congregated in houses, huts, caverns, etc., whereas no larvae could be found during the winter. Though he assumed that it was so, his finding the larvae in midwinter in the first instance did not prove that they hibernated, for they might well have been derived from late-laid eggs.

During the thirteen years which have elapsed since the publication of my researches upon the bactericidal properties of the blood and other fluids of the body, a large amount of most valuable knowledge has been acquired regarding the blood both in health and disease. Through the work of many investigators the complicated subject of immunity is gradually being solved, and we are beginning to understand the way in which the body combats or is protected against the inroads of disease. We have learnt of the existence of specific antitoxic, agglutinative, haemolytic, bactericidal and cellulicidal properties in the blood-serum, etc., as also of a number of neutralizing bodies to these. The quite recent discovery of specific precipitins, which act upon various bacterial products, milks, peptone, egg-albumin, and upon human blood and its derivates, has opened a wide field for investigation, which cannot fail to ultimately yield results of the greatest importance. We have to thank bacteriological investigation for the greater part of the advances which have been made, although a considerable portion properly belongs in the domain of physiology.