It does seem clear from the above series of results that of the factors examined in their relation to rickets, etc., the only one of substantial importance is differences in the manner of feeding. The absence of definite association with overcrowding is, certainly, surprising, in spite of the fact that we realise how crude is the measure of this factor which we have had to adopt. If, as we suggest, the personal factor is not a very serious one, the above findings afford at least prima facie evidence of the truth of the assertions made previously, and are certainly sufficient to warrant the prosecution of further field enquiries, on this line, but having greater regard to the obtaining of the necessary information in a form more suitable for detailed analysis.

In this section the influence of five possible factors on the weight of the child has been considered. No one of these can be shown to be of outstanding importance in this respect; but the efficiency of the mother shows the highest and most consistent relationship. Health of mother and those variations of feeding which are considered here as indiscretions have no appreciable influence on infant weight, but the remaining two variables, overcrowding and position of the infant in the family, seem to influence the weight of the child. In the case of overcrowding, the effect is small and only becomes substantial towards the end of the first year. Position of the infant in family, likewise, is of little moment; first and latest-born infants initially seem to have lower than average weights, but towards the end of the first year of life the weights of first-born infants tend to be over average, while those of infants born into already large families still show evidence of inferiority.

1. Opinions upon the relationship between anti-rabies immunity and the rabicidal power of rabies-immune serum have been stated.

2. The rabicidal antibody content of the sera of rabbits immunised with etherised virus, living fixed virus and carbolised virus has been determined while at its maximum and compared with the degree of immunity acquired after each method of treatment.

1. Normal “whole” blood and serum-leucocyte mixtures may exert a bactericidal effect when the serum (or plasma) is inactive in this respect, and may possess quantitatively greater bactericidal properties than serum (or plasma), when the latter is active per se, but such effects are relatively weak.

2. Leucocyte suspensions may exhibit an initial bactericidal action on certain bacteria, but this is usually weak and is followed by a pronounced growth-promoting influence on the surviving organisms.

3. Under certain conditions normal “whole” blood and serum-leucocyte mixtures are inferior to serum (or plasma) in bactericidal power. This is observed when the serum (or plasma) is strongly active per se and is due not merely to an inhibition of the bactericidal action of the leucocytes, but also to a lessened effect of the serum-bactericidins.

4. The comparative bactericidal power of normal “whole” blood or serumleucocyte mixtures on the one hand and serum or plasma on the other depends on the activity of the serum; when this is relatively weak, blood shows an enhanced action; when strong, blood is less active.

5. The above findings apply to a wide variety of bacteria irrespectively of biological species.

6. Bacterial extracts possess marked inhibitory properties on the bactericidal action of serum (or plasma), but not to any extent on the bactericidal properties of the leucocytes as evidenced by the approximately equal influence of such extracts on whole blood and serum respectively.

7. Dead bacteria in certain numbers produce inhibition of the bactericidal action of serum (or plasma), but exert a greater inhibitory influence on the reaction of “whole” blood.

8. It is suggested tentatively that when the serum is strongly bactericidal the killed organisms on being phagocyted along with living bacteria interfere with the intracellular destruction of the latter which at the same time are protected from the serum-bactericidins.

9. The paper also includes certain data regarding the time of maximum bactericidal action by serum towards various organisms and the occurrence of growth-promoting action following an initial bactericidal effect.

The granular “O” agglutination of human serums from eighty cases of typhoid and paratyphoid B fevers has been titrated with carefully selected killed typhoid “O” and paratyphoid B “O” suspensions of high sensitiveness.

In spite of a wide overlapping, due to common factors, a considerable specificity is shown, and this can be utilised in differential diagnosis, especially if due attention is paid to the different levels of “normal” agglutination for the two species.

1. “Normal” agglutinins for B. typhosus and B. paratyphosus B appear to be conclusively of the O type.

2. Such agglutinins appear to be of consistently low titre and are absent in many sera.

3. Normal agglutinins for B. paratyphosus A have not been encountered.

4. O agglutinins are readily produced by inoculation of a T.A.B. vaccine, and may rise to as high titres as those encountered during an enteric infection.

5. It is impossible to fix any limit for residual O agglutinins in inoculated persons.

6. The value of examining for O agglutinins in enteric cases is confirmed.

7. Some fallacies of a purely qualitative method are pointed out, and a plea is made for the inclusion of the principles of qualitative receptor analysis in a quantitative Widal.

1. Of 585 strains of lactose-fermenting aerobes each isolated from faeces of a different person, 501 did not utilise citrate or ferment cellobiose; 20 were citrate negative and cellobiose positive; 27 were cellobiose negative and citrate positive; and 37 were positive to both tests.

2. Almost 10 per cent, of the strains isolated were indol negative.

3. One culture was methyl-red negative and Voges-Proskauer positive. Two were positive to both tests. The rest were methyl-red positive and Voges-Proskauer negative.

4. It is concluded that the results are not favourable to the use of the citrate or the cellobiose test in routine water analysis.

5. A discussion of the taxonomy of the lactose-fermenting aerobes is given. Only two species, Bacterium coli (Escherich) L. and N., and Bacterium aerogenes (Escherich) Chester, are recognised.

1. Spore formation in eight typical members of the genus Bacillus has been studied.

2. Three of these strains, including one species of B. anthracis, have been found to be practically asporogenous under the experimental conditions. In general the following statements hold good for the sporogenous races studied.

3. Spore formation is almost, or entirely, inhibited by cultivation on media rich in amino acids, such as tryptic digests of casein or meat. Similar inhibition results following cultivation on a medium containing reasonably high concentrations of a mixture of amino acids and asparagine.

4. When such media are suitably diluted with standard inorganic salt solutions the percentage of spores formed is greatly increased, and frequently at least 99 per cent. of spores are formed if the dilution is sufficiently high.

5. When simple nitrogenous compounds such as amino acids are added to a dilute casein digest medium in which sporulation is almost complete, a definite decrease in the percentage of spores present is observed. Asparagine, which is probably readily assimilated, apparently completely hinders spore formation in most cases. Other amino acids do not exert so pronounced an effect, and ammonium phosphate does not appreciably inhibit the formation of spores.

6. The fact that the addition of glycine suppresses growth markedly when it is added to a dilute casein digest medium, but does not appreciably hinder sporulation, suggests that the formation of spores is not due to any toxic effect of added compounds, or compounds already present in the medium.

7. Sporulation is almost complete in a “synthetic” medium in which low concentrations of ammonium phosphate and sucrose represent the sources of nitrogen and carbon, respectively. However, frequent transfers in such a medium may inhibit spore formation partially or entirely in certain instances. This effect probably depends upon the enhanced ability of the culture in question to utilise sucrose as a source of carbon when cultivated constantly in its presence.

8. It is concluded, from the above data, that endospore formation in aerobic bacilli bears an inverse relationship to the amount of available nutrient material present in the culture medium.

I am indebted to Prof. Sir F. G. Hopkins and Miss M. Stephenson for their constant encouragement during the progress of this work. My thanks are due to Mr Pirie of this Department who kindly furnished me with several of the amino acids employed, and to Dr Miles of the Department of Pathology for his kindness in supplying me with certain of the cultures.

1. A simple blood-tellurite medium has been described which is absolutely selective for C. diphtheriae and the diphtheroids. In many cases diagnosis at sight of the colonies is possible after 24 hours' incubation. The medium is especially useful for the isolation of carriers when diphtheria bacilli are present in very scanty numbers.

2. The existence of two main types of C. diphtheriae has been confirmed.

1. Human and guinea-pig sperms are susceptible to the most diverse chemicals to almost the same degree.

2. There exists a substance in human semen which protects both human and guinea-pig sperms against certain chemicals, especially sodium oleate, orthovanillin and potassium borotartrate.

3. When perfectly fresh human semen is not available, the spermicidal powers of substances may be tested by using guinea-pig sperms suspended in human semen which has been kept cool.

An examination of some 10,000 tumour-bearing mice appertaining to 240 experiments comprising 24,000 animals has been made to find whether there was any difference in sensitiveness of the skin to our carcinogenic agents, according to colour of coat and eyes. Methods involving only elementary arithmetic have been utilised as we have, unfortunately, no statistical mind on our staff, and thus we have, presumably, failed to derive full benefit from the data available. We have ventured, however, to draw the following tentative conclusions as regards the particular animals under discussion, they being obtained from varied sources:

1. Self-coloured animals (excluding pure white) were more sensitive to petroleum oils (weak agents) than the corresponding piebald. (That is, a black was more sensitive than a black and white, etc.)

2. When tars (strong agents) were utilised instead of petroleum oils an opposite state of affairs existed, the self-coloured animal being more resistant than its piebald companion. This reversal may be explained on the grounds of cell tolerance.

3. Pink-eyed animals (excluding pure white) had a greater all-over sensitiveness of the skin to our agents than pigmented-eye animals.

4. On the whole the most sensitive animal was the pink-eyed fawn.

5. The frequency of hyaline degeneration of the spleen and marked thyroid enlargement was greater among pink-eyed animals, especially when fawn coloured, than among pigmented-eye animals.

A study has been made of the bacterial flora in the sewage supplied to, and the effluent from, the bacteria beds which deal with the liquors produced at the Coventry gasworks. A high count in the effluent from the beds of bacteria containing an oxidase system, or a relatively large increase in the viability of such organisms when compared with the original sewage, has been found to be concurrent with good purification in the beds, and vice versa.

The bacterial flora undergoes considerable modification in the beds, and also when mixed with 4 per cent, of its volume of spent liquor in the laboratory. The total viable count of the treated sewage is reduced under these conditions, but the count of those bacteria which give the direct oxidase reaction and therefore catalyse the oxidation of catechol is relatively increased.

A gram negative vibrio (strain 0 1) is the only bacterium isolated which has proved capable of breaking down monohydric phenols. It has been constantly isolated from the effluent liquors.

Gasworks' ammonia liquor in the relatively high concentrations used exerts a markedly toxic action on all types of sewage bacteria, and the purification of this liquor by the beds is not so satisfactory. The toxicity is probably caused by the highly alkaline reaction of the liquor.

This investigation was commenced by one of us (F. C. H.) in conjunction with Dr Allan C. Monkhouse, who was at the time Research Chemist to the Liquor Effluents Sub-Committee of the Institution of Gas Engineers. Dr Monkhouse accepted another appointment shortly after the commencement of the work, and was therefore unable to assist further, but we should like to express our indebtedness to him during the initial period. We are also indebted to Prof. J. W. McLeod and Prof. J. W. Cobb for their kindly interest and encouragement, and to Mr P. N. Langford, Engineer and Manager of the Coventry Gas Department, for the facilities he so generously placed at our disposal at Coventry.

One of us (F. C. H.)is in receipt of grants from the Medical Research Council, and would again express his thanks to that body.

One of us (A. K.) is indebted to the Liquor Effluents and Ammonia Sub-Committee of the Institution of Gas Engineers for permission to publish this work.

1. Whooping cough is now in London the most important epidemic disease of childhood in causing physical suffering, loss of school attendance, impairment of physique and mortality.

2. The mean annual incidence of whooping cough in children under 10 in Battersea during the quinquennium 1925–9 is estimated to have been about 60 per 1000 living, and the fatality rate 1·26 per 100 cases. The fatality rates in the first two years of life were estimated to be 4·0 and 3·3 respectively, at ages 2 to 5, 0·7 and at ages 5 to 10, 0·2 per 100 cases.

3. Epidemics of whooping cough in Battersea and Greenwich tend to have a biennial periodicity; a summer epidemic is often immediately followed by or merges into a winter epidemic subsiding by midsummer, and then follows a year of low incidence, so that the total incidence of cases in successive years from midsummer to midsummer shows an alternation of epidemic and interepidemic years.

4. Epidemics do not always run concurrently in areas of London separated by several miles; the spread is checked to some extent by barriers to free communication and small districts thus occasionally escape an epidemic, or an interval of several months may separate the epidemic peaks in districts a mile or so apart.

5. The view that the epidemic cycle in whooping cough can be explained by a periodic reduction of the proportion of children not previously attacked below some critical limit, is shown to be untenable. Both the termination of epidemics and their periodicity can be explained by the occurrence of a latent immunisation of contacts as in measles, such immunity only lasting about 1 year instead of 2 or 3.

6. The occurrence of such a transient latent immunisation is indicated by (a) measurement of the rise and fall of apparent infectiousness of cases to other children in the same house during 6 years in Battersea, (b) measurement of the frequency of second cases in houses after different intervals of time during a decade in Greenwich, and (c) analysis of the attack rates amongst home contacts in Holborn and Battersea during several years following exposure to infection as compared with those among control groups of children. These phenomena would be difficult to explain as resulting from a “cycle of activity” of the organism.

7. In London as a whole a special enquiry into the previous histories of school entrants proves that 44 per cent. of children have an attack of whooping cough before their fifth birthday. According to Battersea records 27·7 per cent. are notified or reported to the Public Health authority as having whooping cough by this age, and 42·3 per cent. by the tenth birthday. It is concluded that in that borough about 60 per cent. of the true incidence is notified at ages under 4, about 72 per cent. at age 4, and 90 per cent. at ages 5 to 10 when school supervision is fairly complete. At all ages under 10 the recorded incidence in Battersea represents about 70 per cent. of the true incidence.

8. It follows that about 60 per cent. of London children have whooping cough by the tenth year, and about 61 per cent. at some time during life, this proportion being rather lower than estimates made from histories given by parents in a group of American towns. The bulk of the remaining 40 per cent. must escape attack by virtue of some kind of immunity rather than by avoidance of contact with infection through life, and a part of these no doubt escape by the repeated acquisition of transient latent immunity during epidemics, and the remainder by virtue of an inherent immunity to the disease.

9. During the year following an epidemic the proportion of children under 10 who are susceptible is approximately doubled and again halved during the next epidemic. This must be mainly due to temporary latent immunisation during an epidemic of x children to each one attacked, the value of x lying between the limits 1 and 4, this depending upon the unknown proportion who are inherently immune. If the bulk of the two-fifths of all children who escape attack have inherent immunity, as is suggested but not proved by the data, then the ratio of latent to recognisable infections lies between 1 and 2.

10. Superposed upon the gradual rise and fall of infectiousness believed to be due to these immunity changes, there occurs a sudden rise at the commencement of an epidemic which must be attributed to an enhanced real infectiousness. This probably arises from a sudden increase in activity of the organism itself under seasonal influences setting in at the moment when the herd immunity becomes insufficient to withstand the infection pressure, so that the balance is upset and the epidemic begins.

11. These findings are similar to those for measles, the chief differences being, (i) epidemics are usually spread over a year instead of 6 months; (ii) latent immunity apparently lasts about a year instead of 2 or 3; (iii) about 60 per cent. of children are attacked at some time during life instead of about 90 per cent.; (iv) there is probably inherent immunity in a certain proportion, but not in measles; (v) the ratio of latent to manifest infections is lower.

We are indebted to Miss M. Kirby for drawing the diagrams in this paper. Towards the expenses of this research a grant was made by the British Medical Association.