1. 52·6% of marmots placed in contact with marmots infected with plague by inhalation developed pulmonary plague and died within 4–6 days.

2. Marmots suffering from pneumonic plague are infective at an early stage of the disease and the animals which such marmots infect acquire plague after a short incubative period.

3. Pulmonary plague can be readily transmitted to the small marmot (Spermophilus citellus Linn.), and these animals, when suffering from pulmonary plague, are in turn capable of transmitting the same type of plague through the respiratory passages.

4. Septicaemic plague can be developed in marmots very easily as a result of respiratory infection and also by direct subcutaneous inoculation with small amounts of culture.

5. The marmot can acquire plague by way of the alimentary tract and spread the disease by feeding on plague-infected carcases. The histological appearances observed in the lesions of these cases are characteristic.

We have already considered, in previous papers, the influence of parental age, on birth, marriage, sex, susceptibility, and reaction to bacterial invasion, evidence having been produced which lends support to the belief that this factor does modify the organism in its behaviour with respect to the attributes considered. It is therefore reasonable to extend the enquiry, and examine whether these variations are accompanied by modifications in structural attributes. In the present paper the characters studied are, eye-colour, stature and intelligence.

We were recently consulted by an officer serving on the Western Front as to the significance attaching to ordinary bacteriological methods of gauging the potability of waters. He wished to know what was the probability that a given water supply did not contain more than a certain proportion of bacteria in the unit volume, it having been found that particular samples tested showed no growth while, perhaps, larger samples had done so, or that so many out of a series of samples of the same size had given positive results. Having obtained what seemed to us a reasonable solution of the particular problem proposed, we thought that the results might interest other officers and bacteriologists who have to do similar work. A survey of the criteria actually used by bacteriologists when they form an opinion as to the purity of waters seems to us to emphasise the need for some discussion.

The results obtained point to a consistent relationship between lipolytic activity and bacteriolytic power on tubercle bacilli.

The least bactericidal extract was lung extract; the most powerful was pancreas extract.

Liver, thymus and lymphatic glands were strongly bactericidal.

Other organs, suprarenal glands, pig and cat spleen, human and cat kidney, human and ox brain, ox thyroid, cat lung, ox bone marrow and ox pituitary glands were found to be bactericidal to a lesser degree.

The human skin extract examined for bactericidal properties was fatty and cloudy in appearance and exceptionally rich in esterases1.

Even if exceptional in its esterase activity this sample of skin bears out the relationship between lipolysis and bacteriolysis of tubercle bacilli in a striking way, as it was also extremely bactericidal.

No difference was noticed between bovine and human tubercle bacilli in susceptibility to any gland extract examined.

Other acid-fast bacilli, though on the whole less susceptible than tubercle bacilli to the influence of these extracts, were bacteriolysed by them. They were also killed by one lung extract (pig's) which contained an unusually large amount of olein lipase and which had no effect on tubercle bacilli.

I wish to express my thanks to Dr W. Cramer for his kind advice and encouragement, to Dr Cobbett for his kindly criticism, to Professor Shennan and Dr Miller for human material, and to Dr Wang for several strains of tubercle bacilli.

The expenses of this Research were met in part by a grant from the Earl of Moray Trust.

It was desired to determine the minimum amount of acid which would kill tubercle and other acid-fast bacilli, incidentally to note any distinction between human and bovine tubercle bacilli and between tubercle and other acid-fast bacilli in respect to sensitiveness to acid, and to find whether inorganic acid were more powerful in action than organic acid, and whether insoluble fatty acids were also effective.

In the preceding reports on infant mortality in counties during 1908 (Cd. 5263), in 241 urban areas in 1907–10 (Cd. 6909), and in Lancashire (Cd. 7511), the chief environmental circumstances favouring excessive infant mortality have been enumerated and to some extent discussed.

Ledingham and Penfold have shown that during the lag-phase of growth of B. coli in a nutrient medium the time and bacilli are connected by an equation of the form Xn=K log Y where n and k are constants (the initial seeding = 1). It has been pointed out in this communication that there is a relationship between n and k, and that the above equation can be put in the form

The advantage of this new equation is that K remains of the same value throughout the whole series of experiments.

In the case investigated by Ledingham and Penfold the constant of unrestricted growth is approximately equal to 2K.

The equation can also be put in the form

where Z is the “constant” of growth at a time X. By suitably adjusting n and a this equation can be made to represent not only the lag-phase of growth but also the logarithmic phase, and the special phase of retarded growth when the X − Y curve is rectilinear. When cell-death occurs the bacteria usually perish at such a rate that the X − Y curve is logarithmic; the general equation therefore also covers this case.