Natal, which has been considered of recent years to be a malaria-free country, has been visited in the past six months by an extensive epidemic of this disease.

The following notes on trypanosomes which I have observed in certain mammals, birds, and goldfish obtained in the neighbourhood of Elstree in Hertfordshire appear worthy of publication, for the reason that our knowledge regarding the geographical distribution of trypanosomes is far from complete. No description has as yet been given of the trypanosomes found in bats by various observers, and a species encountered by me in the mole is, I believe, new.

IN view of a previous failure1 to produce a skin infection with Ankylostoma, it seems worth while to put on record the present successful case. Dr J. B. Leathes very kindly offered himself as the subject of experiment. It is important to note that he has never, either before or during the course of the experiment, had anything to do with any Ankylosotoma material except that deliberately applied to his person for the purpose of this experiment, nor has he been to any infected place or even worked in the part of the Institute where the cultures of Ankylosotoma larvae have been kept. On March 21st a small quantity of water containing encapsuled larvae of A. duodenale, hatched artificially from infected faeces from Cornwall, and 13 days old, was applied to the forearm. After five minutes the arm was bandaged up and left for two hours, at the end of which time the wrappings were removed and the arm throughly cleansed. The purpose of the experiment and the precautions necessary were fully appreciated by the subject, and there is no doubt that there was not the slightest possibility of a mouth infection.

As is only too well known by those who have undertaken the task, the work of constructing a Life-Table by an extended method, even when “graphic” means are employed for lightening the labour, is long and wearisome.

In a previous paper a record of the distribution of Anopheles in Great Britain was given, the localities mentioned including Cambridge and the surrounding country. Since 1901, Anopheles imagines have been searched for in cellars and houses during the winter, in places where they were known to congregate. During the summer a yearly search for larvae was made in various collections of water in the vicinity of Cambridge with a view to securing material for purposes of study and instruction. It appears worthy of note that there has been a notable decrease in the number of imagines caught in cellars, etc. in the winter months. The insects were fairly numerous in my own house during 1901–1902, as many as 60–100 being found hibernating in the cellar. In 1903–1904 there were fewer, only about 6 being caught. Not a single imagine has been caught in the house since that winter. Whereas Anopheles were frequently caught in houses during 1901–1903 in the warmer months, very few were encountered in 1904, and I have not found a single specimen this year. The common Anopheles in this region is A. maculipennis, as I have already recorded, A. bifurcatus being less frequently encountered. Apparently corresponding results have to be recorded with regard to Anopheles' larvae. These were certainly very numerous during the period 1900–1903, and they have become scarcer since, being apparently quite absent in certain waters where they formerly abounded. That the Anopheles are not extinguished is certain, for I have found a few larvae (A. maculipennis) in the river Cam this summer, and my friend Mr Pearce has brought me an imago from Grantchester (close to Cambridge), in addition to larvae of A. bifurcatus which must have hibernated there. Hibernating larvae of this species have twice been found by me since I first recorded their presence about Cambridge.

The object of this paper is to record briefly the result of certain observations and experiments on a disease of the rat, which is chiefly interesting from the close resemblance it bears to leprosy in the human subject. Not only are the lesions similar in their macroscopical and microscopical appearances, but the causal bacillus closely resembles the Bacillus leprae in its morphological characters, distribution in the tissues, staining reactions, and refusal to adopt a saprophytic habit of life.

It is generally recognised that, in certain diseases, recovery mainly depends upon the prompt and efficient reaction of the tissues forming antibodies, such as bacteriolysins, antitoxins, and the like, and it is possible that these peculiar. biological responses may be influenced by the administration of drugs.

Many years ago while making in the laboratory of the late Prof. Carnelley in Dundee, by Pettenkofer's method, a series of Carbonic Acid determinations, in which turmeric paper was used as the indicator, I observed that the last few brown rings made on the paper as the solution approached neutralization showed a tendency to become decolorized in a relatively short space of time, the final ones being seen to vanish even as one looked at them. This at the time—and subsequent observation has confirmed the truth of the conclusion—was ascribed to the CO2 of the air rapidly neutralizing the solution of baryta, which getting more and more dilute as the solution of oxalic acid was gradually added, finally reached a degree of dilution that was all but instantly neutralized by the amount of CO2 present in an ordinary atmosphere. Even then I came to the conclusion that the phenomenon depended on a principle which might probably be made the basis of a rapid method of estimating the amount of CO2 in air generally, but it is only recently that I have had time to adjust the details of the method which I now propose. It will readily be understood that a long series of experiments other than those of which the results are now recorded were carried out before finality was reached on many points of the method. These need not be detailed here, though some of them will be alluded to as occasion arises. It may be stated that the method has been found to give results which approximate to the truth—at least as tested by Pettenkofer's method—much more closely than was at first anticipated.

In the last number of the Journal of Hygiene we described an improved method of calculating birth-rates, by means of which exact correction can be made, in comparing the birth-rates of two communities or of the same community at different periods, for variations in the proportion of married women at childbearing ages, and for the different fertility-rates at different ages of childbearing life. The value of this method consists in the fact that by its means true differences in childbearing can be discovered, the differences due to variations of age or marital condition being eliminated.

1. The hypotheses of Pfeiffer, Emmerich and Löw, attributing agglutination to a vital paralysis due to the action of a bacteriolytic enzyme, and those of Gruber, Dineur, and Nicolle, which ascribe the action to the glutinous nature of the membranes or cilia, are insufficient to account for the observed phenomena.

2. The views of Paltauf and Duclaux that a specific precipitate is formed in the medium which mechanically carries the bacilli together are sufficient, but probably do not account fully for the agglutination of washed bacilli.

3. Arrhenius's assumption that the gas laws are applicable to the partition of agglutinin between bacilli and medium is improbable since the conditions under which these laws can be applied are absent.

4. The formula given by Arrhenius for the partition of agglutinin seems to be a special case of a general formula holding for the absorption of substances from solution by substances with highly developed surfaces, e.g., the adsorption of iodine from solution by charcoal. A superficial analogy between the gas partition law and the adsorption partition law for equilibria is to be expected, likewise an equally superficial analogy between reactions in true solutions and colloidal solutions, e.g., of agglutinin, for the velocity of reaction.

5. The special formula given by Arrhenius does not apply to the entire range of agglutinin solutions and the change which must be made in the constants is incompatible with the application of the gas laws, but agrees with the view that the fixation of agglutinin is due to adsorption.

6. The fixation of agglutinin from two different typhoid immune sera by living typhoid bacilli did not correspond to the partition law deduced by Arrhenius from the experiments of Eisenberg and Volk.

7. The rate of addition of bacillary suspension to agglutinating serum is a factor determining the amount of agglutinin fixed by the bacilli. By adding the suspension in parts more agglutinin is removed than in the case where the whole amount of suspension is added at once. This points to the equilibria belonging to the class met with in absorption.

8. Similar adsorption equilibria are obtained by experiments on staining.

9. The cell contents probably play an important part in agglutination as the washed membranes are but slightly agglutinated.

10. Motile cultures of B. typhosus grown at 37°C., and non-motile cultures grown at 42°C., agglutinated equally well, the agglutinable substance probably being unchanged.

11. The law governing the fixation in B. typhosus, heated to 58°C. for 30 minutes, is probably different to that holding for living cultures owing to modification of the agglutinable substance.

DURING the last six years (1899—1904) some fifteen thousand examinations of material from throats for the diphtheria bacillus have been made at the Lister Institute. The localities from which this material has been derived have naturally been widespread and varied; much of the work however has been done for local authorities in and near London, and the sources of origin of the major part of the material have not varied very much during the whole period under review.

(1) The lactose-fermenting organisms of faeces may be divided into two groups according to the molecular ratio alcohol/acetic acid produced from glucose under specified conditions.

(a) Those which produce alcohol and acetic acid in approximately equal molecular proportions.

(2) Those which produce more than 2·5 molecular proportions of alcohol to 1 of acetic acid.

(3) The members of the first of these groups comprise the Groups 1, 2, 3, and 4 (1) suggested provisionally by MacConkey from the consideration of the action of these organisms on cane-sugar and dulcite. The members of the second of the groups correspond with Group 4, Sub-groups 2 and 3, of MacConkey' provisiosnal classification.

(4) B. lactis aerogenes acts upon glucose in a totally different manner from B. coli communis and is therefore to be regarded as a distinct organism.

The aim of the following investigations was to ascertain the limits within which men can continue to exist normally, and to work, when the air temperature is abnormally high: also to study the abnormal phenomena which are produced when these limits are exceeded.

Plague was introduced into Queensland from Sydney in 1900, and every subsequent year has been marked by an outbreak in Brisbane. In both towns the authorities are unsparing in their efforts to eradicate the factors contributing to its maintenance, but in both places the infection of the rats and their haunts is so extensive that the disease may now be looked upon as endemic in the two cities. The probabilities are, however, that the pest will be harder to eradicate in Sydney, where the buildings are substantially built, and not as in Brisbane light structures of wood which more easily lend themselves to treatment and are comparatively temporary in their character.

The subject-matter of this paper is a study of the relationship which exists between the natural immunity enjoyed by an individual to any disease, and the capacity which he possesses of acquiring immunity if attacked. Most of the facts discussed are moderately well known. They are furnished by the statistics of the acute infectious diseases which have accumulated since the middle of last century. These statistics are in many respects very defective for the purpose required, but they refer to very considerable numbers of cases, and thus afford a basis for the estimation of different degrees of immunity with some accuracy. The most numerous collection of statistics relates to small-pox among the vaccinated and unvaccinated. These have been dealt with in an earlier paper1, and the results alone will be referred to here. This group of statistics unfortunately practically exhausts the whole data concerning acquired immunity. The next statistics of importance are those referring to the different outbreaks of typhus, relapsing, and enteric fever, and of a few other less common diseases. Last must be placed those regarding the diseases which chiefly affect children. These for several reasons, however, afford less definite data.

The following experiments were begun with the object of ascertaining the distribution in nature of certain lactose-fermenting organisms which are by some grouped under the name Bacillus coli, but by others are regarded as belonging to a different class of organisms; a difference of opinion which is most probably the principal factor in causing the value of B. coli as an index of pollution to be such a vexed question among bacteriologists. The investigation, however, resolved itself into a search for the B. lactis aerogenes principally, and secondarily for the other lactose fermenters. Incidentally certain other points are referred to which it was thought might prove of interest though not actually pertaining to the subject of the paper.