W. W. C. Topley

The Spread of Bacterial Infection. The Problem of Herd-Immunity.

In our previous studies on the spread of bacterial infection among mice, the resistance of the host has not been especially investigated; although the importance of this factor has been repeatedly referred to in discussing the experimental results obtained.

The Value of Mixed Vaccines in the Prevention of the Common Cold

Although the common cold may appear to form a relatively trivial constituent of the mass of acute respiratory disease, which presents the student of preventive medicine with one of his most difficult and pressing problems, the total sickness and incapacity to which it gives rise is by no means small; and there are adequate reasons for regarding it as the occasional precursor of far more serious troubles. It is, therefore, not without interest to enquire, whether or no those procedures, which are commonly recommended as possessing prophylactic value, can make good their claim when submitted to an adequate test. The enquiry here recorded suffers from the fact that the total number of individuals at risk was relatively small; but the answer to the main question posed is so unambiguous, and accords so well with the results obtained in the only other adequate tests of which we have knowledge, that it seems desirable that it should be briefly recorded. It is possible, also, that some little interest attaches to the figures of frequency, duration and severity of common colds within a particular community

Immunisation and Selection as Factors in Herd-Resistance

It has been suggested (Topley and Wilson, 1923) that the general problems of immunity and resistance have been studied too exclusively from the point of view of the individual, and that their reconsideration from the point of +7iew of the herd would probably yield results of some interest. It is clear, for instarlce, that the herd possesses at least one method of acquiring resistance that is not at the disposal of the individual. If natural resistance be in any degree a variable character, the average herd resistance will be augmented by a simple sorting process during the spread of any epidemic infection associated with specific deaths among the population at risk, quite apart from any possible increase in the resistance of surviving individuals svithin that population.

The Excretion of B. enteritidis (aertrycke) in the Faeces of Mice after Administration by Mouth.

In the preceding report (Topley and Ayrton, 1923 a) we have described a technique by which measurements may be obtained of the excretion of B. enteritidis (aertrycke) 1 in the faeces of mice.