1. A method is described for the experimental investigation of aerosol systems formed by the atomization of suspensions of viruses into the atmosphere. Observations on the physical properties of such systems have been made, and an experimental approach found to certain practical problems connected with air-borne virus infections, particularly counter measures involving the use of ultra-violet light and aerosols of chemical antiseptics.

2. Mice, placed in an atmosphere into which the respective virus had been atomized, have contracted the diseases of influenza and infectious ectromelia in a manner closely analogous to naturally occurring air-borne infection.

3. The infection resulting from the inhalation of virus is described. The suggestion is made that this method of infection may be used with advantage ( a )in studying in detail the histology of lung lesions, and (b) in obtaining more uniform infection of large batches of mice.

4. The two methods of experimental infection, (i) intranasal instillation under anaesthesia, and (ii) normal inhalation, have been compared and contrasted. It is deduced from the evidence available that as little as 1 % only of the virus may reach the lungs of mice breathing normally in an atmosphere containing dispersed nuclei of influenza virus.

We gratefully acknowledge the assistance we have received from Miss Dora Lush.

The experiments show that rapid and effective sterilization of atmospheres containing atomized particles of influenza and vaccinia viruses, and probably also of herpes simplex virus, can be obtained by ultra-violet radiation of wave-length 2537 A. At least 99 % and probably more of an aerosol of influenza virus was killed by exposure for 6 sec. at. a distance of 2 cm. from either a Hanovia lamp or a G.E.C. ‘Sterilamp’. These findings confirm the work of Wells and his associates who first demonstrated the susceptibility of this virus to ultra-violet radiation (Wells & Brown, 1936; Wells & Henle, 1941). At the same distance the ‘Sterilamp’ produced more than a 99 % kill of vaccinia virus with an exposure of 1 sec. and about a 90 % kill in 0·5 sec. The experiments with herpes were less satisfactory but suggested a similar sensitivity. These results support the view that ‘germicidal’ lamps are likely to be useful in reducing the infectivity of air contaminated with particles from persons suffering from virus infections of the respiratory tract.

We wish to acknowledge our indebtedness to the late Sir Patrick Laidlaw who, although his name does not appear as author, largely inspired the investigation and took an active part in it until his death.

Substantial reduction in the bacterial content of the air of an empty room after infection with B. prodigiosus (or with Staphylococcus albus or a diphtheroid bacillus) has been effected by means of hypochlorites introduced into the air by atomization from a Dynalysor or by spraying from a flit gun.

The ‘normal’ variation of the bacterial content of the air of an occupied (crowded) room has been described.

Repeated spraying of a solution containing 1% of sodium hypochlorite or of a 1·3% suspension of water-sterilizing powder (bleaching powder) from a flit gun has been shown to reduce materially the bacterial content of the air of the occupied room.

Similar sprayings of water have been shown to have no appreciable effect on the bacterial content of the air of the occupied room and the action of the hypochlorite was, therefore, not merely a mechanical removal of bacteria from the air.

Methods have been devised for assessing the degree of disinfection per individual spraying of hypochlorite, and, although the methods are mainly of comparative value, it may be stated that the reduction in the total bacterial content of the air of the occupied room for a single spraying of hypochlorite Y (≡1% sodium hypochlorite) was of the order of 33%, or more. The percentage reduction of potentially pathogenic bacteria which may have been present was almost certainly greater than the reduction of the total bacterial content, which included resistant saprophytic bacteria. The average concentration of hypochlorite Y used in these experiments was 0·38 c.c. per million c.c. of air (i.e. less than 11·0 c.c. per 1000 cu. ft. of air) per spraying, i.e. was exceedingly small, and even smaller concentrations were equally effective when the hypochlorite was atomized into the air by means of the Dynalysor.

Rather less consistent results were obtained with the chemically less active bleaching powder suspension than with hypochlorite Y in the flit-gun experiments.

The relative humidity of the air has been shown to be a factor of great importance, and in the experiments described in this paper effective air disinfection was not obtained at low relative humidities at temperatures ranging from 54 to 74° F. The need for accurate determination of the critical lower limit of relative humidity is stressed.

Tobacco smoke has been shown to reduce the efficiency of hypochlorite sprays but the experimental evidence was insufficient for any definite conclusion to be drawn.

The advantages and disadvantages of hypochlorites as air disinfectants have been discussed and the conclusion reached that repeated (every 20 or 30 min.) spraying of the air of an occupied room with a 1% solution of hypochlorite (e.g. hypochlorite Y) constitutes a simple, practical, inexpensive and efficient method of air disinfection, and, provided simple precautions are observed, there are no serious objections to such a procedure.

Sample frequency distributions are given of height and weight measurements of London elementary school children made during the period 1935–8. In addition these measurements have been analysed in order to determine the seasonal fluctuation in rates of growth. The rate of increase in height appears to reach a maximum in the latter part of spring and a minimum in the middle of autumn. The rate of increase in weight appears to reach a maximum in the latter part of autumn and a minimum in the middle of spring. Tables and graphs are given showing, for each sex, the variation in the rates of growth throughout the calendar year. I wish to thank the County Medical Officer of Health, W. Allen Daley, M.D., F.R.C.P., for permission to publish this paper and for encouragement in its preparation; Mr L. Coward, F.I.A., and Mr E. Lewis Faning, Ph.D., for statistical criticism; and Mr J. H. Farrar for drawing the diagrams.

The London County Council takes no responsibility for the views expressed in this paper which are personal only.

Signs and symptoms attributed to a disturbed function of the parathyroid glands as a result of the protracted action of small quantities of fluorine have been described elsewhere (Spira, 1942c). It was shown that the lesions on the teeth known as ‘mottled enamel’ were frequently accompanied by lesions on the skin and its appendages, the nails and hair. The object of the present communication is to give some details of the changes produced in the finger- and toe-nails in chronic fluorine poisoning (fluorosis).

In continuation of previous work involving accentuated effects of perspiration on chrome upper leather, the present paper records observations of such effects in more complicated conditions.

Thus, effects were studied at varying temperatures and pH of tans, buffered tans, buffered perspiration, buffered perspiration coupled with tans, buffering material itself and soap solutions.

Particular reference is made to the influence of basicity on the stability of the chrome complex against perspiration in such buffered chemical systems. Brown grain leathers are considered as well as box and willow calf.

A method is evolved for minimizing spueing risks or the formation of Glauber's salts in the vamps of worn footwear, by appropriate treatment of the skins before cutting up into shoe upper components.

Finally, some foot-bath experiments and the dark, cracky grain of worn insoles are discussed from the general point of view of perspiratory action on footwear.

The writer acknowledges with thanks the assistance of Messrs L. P. Huggett, B.Sc., A.I.C., and W. H. F. Jackman, B.Sc., A.I.C., in the routine analytical work. His best thanks are also due to the Director and Council of the Research Association for permission to publish.