In a recent paper Withell (1942) has shown that for a wide range of microorganisms and disinfectants or poisons the logarithms of the survival times are approximately normally distributed. Even when the number of survivors is adequately represented by an exponential function of the time (e−kt) say, the former hypothesis still gives approximately correct results. This suggests that in many cases the data are not good enough to distinguish between the two hypotheses (1) of a constant force of mortality k and (2) of a normal distribution of the logarithms of survival times. It is worth while, therefore, to examine the form of the distribution of the logarithms of survival times when the exponential law is true, and to see how nearly normal it is. We shall show that except for the position of the mean, this distribution is independent of k.

Salmonella strains isolated in Palestine from camels could not be differentiated from a human strain isolated in the same country. The Palestine strains differ from S. kentucky by lower fermenting activities, but are antigenically identical with it.

1. Loaves were baked from three types of wheaten flour made from the same grist; a straight run white flour of 73% extraction, a finely ground wholemeal (100% extraction) and a medium ground wholemeal (100% extraction). Bread from each was consumed by six persons for periods of 11–12 days. The daily consumption was 530–630 g. dry weight of bread and, in addition, 37 g. margarine, 284 c.c. milk, 72 g. marmalade jelly and 284 c.c. of mild ale.

2. The total energy, nitrogen and fibre of the food consumed and of the faeces excreted over a period of 7 days were determined. Assuming that the foods other than bread were wholly digestible, the average percentage absorption of energy, nitrogen and fibre from the white bread was 96·1, 91·1, and 65·8 respectively; from the fine wholemeal bread it was 86·9, 85·3 and 14 respectively and from the coarser ground wholemeal 87·1, 85·7 and 9·7 respectively.

3. The nitrogen intake per 100 g. of the wholemeal bread eaten, was 2·91; of the white bread 2·70 g. This advantage was, however, neutralized by the greater amount of nitrogen lost in the faeces when wholemeal was taken, so that the average net gain of nitrogen to the body was 2·46 and 2·49 respectively per 100 g. dry weight of bread consumed.

4. The loss of 9% more of the energy of the bread in the faeces from wholemeal than from white bread is largely accounted for by the undigested cell envelopes and woody fibre in the bran. The greater utilization of the fibre of the white bread is in accordance with the observations of Rubner who showed that the cell membranes of the endosperm were of different composition from those of the bran cells and were more readily attacked by bacteria in the gut.

5. The range of individual variations in the utilization of the energy of the breads were: for white bread 95·4–96·8% and for wholemeal 85·4–88·7%. In the utilization of nitrogen these were: for white bread 88·2–94·1%, and for wholemeal 78·5–89·6%. The same subjects showed the better utilization of both energy and nitrogen.

6. The fineness of grinding of the wholemeal within the range used made no significant difference to the utilization of either energy or nitrogen.

At the beginning of the war, the London County Counoil issued a report by Sir Frederick Menzies, their late School Medical Officer, on the average heights and weights of London elementary school children in 1938. The report is based on the measurements of about 100,000 children, and is probably the most important contribution to the anthropometry of childhood that has appeared in this country for many years.

Quantitative observations were made on the rate of disinfection of Bacterium coli and of the spores of Bacillus subtilis by caustic soda at different temperatures and different concentrations. The tests were carried out in the presence of 1/1000 milk. It was found that:

(1) With Bact. coli the concentration coefficient n was about 2·7, and the temperature coefficient θ10°C. about 2.

(2) With B. subtilis spores the concentration coefficient n was about 1·75 and the temperature coefficient θ10°C. about 1·5.

(3) With Bact. coli the values for the reaction velocity constant k tended to be irregular at 40° C. and with B. subtilis spores at 70° C, suggesting that at these temperatures some additional factor, presumably heat coagulation of the protein, was beginning to affect the results.

(4) With both organisms the value of the reaction velocity constant k was relatively slow at the start and tended to increase progressively during the course of disinfection. Whether it diminished again as sterility was approached could not be ascertained for technical reasons.

(5) With both organisms the presence of 1/1000 milk did not seem to affect the rate of disinfection as compared with distilled water.

(6) One experiment with Bact. coli suggested that the rate of disinfection was affected appreciably by the number of organisms present. Increasing the number of organisms in the suspension 100 times diminished the value of k by about one-third.

(7) The value of k was about 3,000,000 times greater with Bact. coli than with B. subtilis spores.

(8) If the mean value of n is taken as 2·2, it follows that doubling the concentration of caustic soda increases the reaction velocity by 4·6 times. If, for example, with a given concentration of caustic soda sterility was reached in 9 min., then doubling the concentration would reduce this time to 2 min., while halving the concentration would increase it to about 40 min.

(9) If the mean value of θ10°C. is taken as 1·75, it follows that a rise of 10° C. in the temperature increases the reaction velocity 1·75 times. If, for example, with a given temperature sterility was reached in 9 min., then raising the temperature 10° C. (18° F.) would reduce this time to about 5 min., while lowering the temperature 10° C. would increase it to about 15 min. With temperatures, however, of over 40° C. (104° F.) the rate of destruction of yegetative organisms, and with temperatures of over 70° C. (158° F.) the rate of destruction of sporing organisms in the presence of caustic soda is probably increased by the effect of the heat itself.

(10) A comparison of our figures for caustic soda with those of Chick for phenol shows that a 0°05% solution of caustic soda at 20° C. destroyed Bact. coli about five times as fast as a 0°5% solution of phenol at 20° C. destroyed Bact. paratyphosum B, and that a 5% solution of caustic soda at 30° C. destroyed B. subtilis spores nearly three times as fast as a 5 % solution of phenol at 33·3° C. destroyed anthrax spores. The superiority of caustic soda over phenol, particularly at concentrations likely to be used in practice, is manifest.

(11) Discussing the standardization of disinfectants, we conclude that the value of k taken in the middle stage of the reaction, or from the beginning of disinfection to about the end of the middle stage, affords the most suitable measure of comparison. This is essentially the same conclusion as that reached by Withell (1942), who uses as his index the time necessary to destroy 50% of the organisms.

Chlorine at the rate of 5 and 10 parts per million of available chlorine in the form of Milton significantly increased the reduction time of milk samples.

Observed increases varied from −0·50 to + 1·25 hr.

At this level of chlorination the increase in R.t. is not correlated with the initial plate count and also occurs at all levels of R.t.

1. The six ‘viruses’, Liverpool, Danysz, London, Ready Rat Relief, Institut Pasteur and Ratin, which are the principal bacterial cultures at present employed for anti-rodent control in Great Britain, have been examined. 2. By means of reciprocal absorption tests all these six strains were found to be serologically identical with S. enteritidis Gaertner, antigenic structure, IX:gom:—. 3. From the results of the fermentation tests, which may be used to subdivide this serological type, Liverpool, Danysz, Ready Rat Relief and Ratin were assigned to the var. danysz subgroup; while the London and Institut Pasteur strains could not be distinguished from the classic S. enteritidis type. 4. Both of these subgroups are pathogenic for man, and evidence is cited which shows quite clearly that human cases of gastro-enteritis have been caused by the use of virus preparations. There are, also, reasonable grounds for believing that these bacterial types may be pathogenic for a number of domestic animals, including some poultry.