1. Animals susceptible and naturally immune to plague—Bombay rats and white mice—were infected with Past, pestis and supravital study of white blood cells from the peripheral blood stream carried out. Similar studies were made on white mice injected with (a) pure envelope serum, (b) pure somatic serum, and (c) whole antiplague serum.

2. Different experimental conditions produced different cell pictures with different behaviours of individual cell types, especially the polymorpho-nuclears, the monocytes and the clasmatocytes. These abnormalities were found to bear distinctive relationship to (a) active immunity, (b) passive immunity, and (c) susceptibility on the part of the experimental animal.

3. The value of immunological inferences from this study in relation to plague-serum therapy and plague prophylaxis has been emphasized.

4. The possibility of a better understanding of host-parasite relationships from similar studies in other bacterial infections has been pointed out.

Our thanks are due to Lt.-Col. S. S. Sokhey, I.M.S., Director Haffkine Institute, for his interest in this investigation.

The experimental method for, and analysis of, more than 300 determinations of air influx rates into two unheated ‘closed rooms’ of opposite aspects each fitted (a) with wall grating, or (b) with flue, are described. The average relative efficacy for all observed wind velocities of (a) of 50 sq.in. to (b) of 15 sq.in., so far as facilitating natural ventilation in the rooms used, is found to be 1·0. The analysis reveals definite and complex relations between influx rate and wind velocity. A correlation is made with data from other sources, principally photographs of the flow forms of air streaming past grounded house models, and a theory is advanced to explain the broad features of the observations. Comparison with similar published work is made, and the fundamental necessity of simultaneous measurement of the speed and direction of the main wind stream is stressed. The advantage of the flue and the importance of openings, other than those in the room concerned, are pointed out.

The author wishes to record that the investigation was commenced at the instigation of Mr Dean Chandler, to whom he is indebted for en-couragement to publish the results of the further examination of the data obtained. He desires also to acknowledge the enthusiastic interest in the experimental work which his colleagues of the Physical Laboratory displayed throughout the investigation.

The measurements of the wind velocity, so essential to the completeness of the observations, frequently necessitated the scaling of roofs in snow, rain and gale, yet at no time were they neglected.

The author thanks Dr E. V. Evans, General Manager and Director of the South Metropolitan Gas Co., for granting permission to publish the paper.

Measurement of ventilation, is of importance both in the design and control of heating and ventilating systems. In addition, the rates of ventilation actually obtaining constitute an important factor in any quantitative studies of air-borne infection. Measurements of ventilation have, however, not been made as often as was desirable: partly, at least, owing to the lack of a convenient method.

The process of removal of bacteria from the air of a room of which part only is irradiated with ultra-violet light is discussed.

Formulae are derived for the rate of disappearance of bacteria from the air in such circumstances and for The equilibrium levels reached when bacteria-carrying particles are being continuously introduced into the air at a constant rate. These formulae include terms for the effect of simultaneous ventilation and for the effect of sedimentation of the bacteria-carrying particles.

The results of a short series of tests are compared with those calculated from these formulae and the two found to agree reasonably well on the assumption that the air within both the irradiated and nonirradiated zones is effectively mixed.

Figures are given over a range of humidities for the sensitivity of salivary organisms to ultra-violet irradiation when suspended as small particles in the air.

A chart is presented for the evaluation of the mean radiation intensity within a rectangular volume produced by a point source situated within or on the boundaries of the volume.

This account of an outbreak of food poisoning may prove interesting, as its origin is attributed to a somewhat unusual source.

The organisms described as Bacillus wakefield and considered to be members of the Flexner group are not dysentery bacilli. They are paracolon bacilli containing α-antigen.

1. Out of 221 horses tested 34·8 % showed natural diphtheria antitoxin to the extent of 0·02 unit or more per c.c. of serum.

2. Amongst the horses in which no natural circulating antitoxin was detected, a much larger number failed to respond to stimulus than amongst those having circulating antitoxin. But, amongst the animals that did show appreciable response to primary stimulus, there was not much difference in degree of response between the horses with and those without natural circulating antitoxin.

The extensive epidemic of mumps which prevailed in Copenhagen in the winter of 1941–2 will presumably serve to establish whether Helge Petersen's (1941) general formula for epidemic curves for direct infectious diseases applies to mumps.

The enormous increase in the number of children* eating their mid-day dinners at school canteens came at a time when enlargement of school buildings was impossible and when equipment was difficult to obtain. The following report on meals served in nine canteens illustrates the success that has been achieved in providing adequate meals in spite of great difficulties of preparation and service. The schools were chosen to represent different conditions of environment and type of canteen. Sample meals were analysed and an attempt was made to assess the home food of the children.

1. Iodine vapour at a readily tolerable concentration of 0·1 mg./cu.ft. of air gives a rapid kill of freshly sprayed salivary organisms at humidities above 50 %.

2. At the same concentration dry bacteria are not as readily killed, the killing rate only becoming appreciable above 70 % R.H.

1. The Tworts' potency measures correlate highly with all the reasonable alternative single measures of potency which have been examined.

1. Section A of this report is introductory; Section B deals with the correlations between the Tworts' measures of carcinogenic potency and certain alternative measures, and their use in testing the significance of differences between the potencies of different oils. Section C deals with the relation of potency to physical characteristics and place of origin of the oil. Section D deals with the relations between the saturation, refractivity, carcinogenic potency and place of origin of oils.