It has been estimated that 75% of typhoid epidemics are water-borne, and it is not surprising, therefore, that many attempts have been made to prove the presence of the specific bacillus in the suspected waters, although the bacteriological examination for this purpose has always been recognised as most difficult and uncertain.

The treatment which Dr A. E. Wright has advocated of certain chronic infections, by the injection of sterilised emulsions (vaccines) of the micro-organism causing the disease, is now well known, but a brief statement of its principles may make the following observations more clear.

As far as can be ascertained this sporozoon has not been described before as occuring in a monkey, though several cases have been recorded in man1 and in a number of other mammals.

At the present time when the parasitic protozoa found in the blood are receiving great attention, it may be interest to describe a form which appears not to have been noticed hitherto.

In a previous paper I referred to observations by Dr E. W. G. Masterman, on the prevalence of malaria in Jerusalem. Since that time Dr Masterman has searched various places for Anopheles in and near the city, and has found numerous larvae in the Birket Mamilla (or “Upper Pool of Gihon”) in winter, the water of which is conducted by covered conduits to Turkish baths in the city. The pool is dry in summer.

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.

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.

(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.

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.