Major Greenwood

On the Statistical Measure of Infectiousness.

We all recognise that some diseases are more “catching” than others. Every mother knows that measles is very catching and most people set aside a group of common complaints, measles, mumps, whooping-cough, scarlet fever, diphtheria—perhaps roughly in that order—as catching complaints. Then again, still keeping ourselves within the circle of ideas of educated non-medical people, one has such complaints as common colds or influenza which one thinks of as running through a house indeed but does not put quite into the measles category, as one feels that factors determine the spread other than mere proximity to a sick person. Lastly, one has some illnesses, gonorrhoea would be a fair example, which everybody recognises to be spread wholly by contagion, almost always by a particular method of contagion, but does not regard as catching at all in the sense that measles and whooping-cough are catching. When we enquire into the reasons of these opinions they will be found, I think, to be these.

A further Contribution to the Experimental Study of Epidemiology.

In the Goulstonian Lectures, delivered in 1919, one of us (W. W. C. T.) discussed the possibility of attacking epidemiological problems by the method of direct experiment, and reported a few preliminary observations on the spread of enteric infection among mice. Since then a series of reports have been published dealing with the investigation of particular problems along these lines (Topley, 1921 a and b , 1922 a and b , 1923, Topley and Wilson, 1923 a and b , Topley and Ayrton, 1924 a, b and c , Topley, Ayrton and Lewis, 1924 a and b , Topley, Wilson and Lewis, 1925).

Contributions to the Experimental Study of Epidemiology: The Effect of Vaccination on Herd Mortality.

In several previous reports we have described the behaviour of communities of mice, submitted over long periods of time to the risks attendant on the epidemic prevalence of a bacterial infection. These communities have been recruited in ways varying both as regards the rate of immigration and the nature of the immigrants.

The Relation between the Cancer and Diabetes Death-rates.

Early in 1912 Professor E. C. C. Baly, F.R.S., acting on behalf of Mr Jessup, brought one of us a collection of Swiss statistics and requested that it should be analysed, with the object of measuring the relation between the death-rates of cancer and diabetes. In the course of this work we have been led to consider many problems of theoretical and practical interest, bearing partly on the method of analysis and partly on the results yielded; it would not be possible to deal with all these in a single paper and the present memoir is devoted to a study of the problem first suggested, viz. the relation between the cancer and diabetes death-rates. Since, however, this may be the first paper of a series, it will be convenient to deal at some length with the nature of the investigation and the motives which led us to undertake it.

William McDougall, 1871 - 1938

William McDougall, son of Isaac Shimwell McDougall, a manufacturing chemist of Higher Broughton, and his wife Rebekah née Smalley, was born at Chadderton, Lancs, on 22 June 1871, and died November, 1938. McDougall described his father as a typical dark Highlander and his mother as of pure Saxon type. He represented, he said, “that blend of the Mediterranean and Nordic races which has produced the English people”. He was sent at the early age of five to a private school and at fourteen to Weimar where he attended a Real-Gymnasium for a year. From the age of fifteen he attended for four years courses in the University of Manchester; he graduated with first class honours and specialized in geology in his last year. He came up to St John’s College, Cambridge, in May 1890, was admitted Scholar on 21 June 1892 and Fellow 9 November 1897. He was placed in the first class in both parts of the Natural Sciences Tripos, taking Physiology and Human Anatomy with Physiology in Part II. He graduated B.A. in 1894, M.B., B.Chir., and M.A. in 1897

The Epidemic Potency of Strains of Bact. aertrycke of varying virulence: A Report to the Medical Research Council.

ONE of the questions, to which the experimental study of epidemics has as yet given no decisive answer, is the possible significance of variations in bacterial virulence. The experiments here recorded relate to this problem, in the particular case of mouse-typhoid spreading within a closed community. Webster and his co-workers (Webster, 1923, a, b, c, d; 1924, a, b; Webster and Pritchett, 1924) would regard the virulence of any single strain of Bact. aertrycke, the causal organism concerned, as but little variable. While admitting (Webster and Burn, 1928, a, b, c) that variations in virulence may occur in bacteria belonging to this group under the influence of a bacteriophage, they consider that any single strain maintains a constant level of virulence for an indefinite period of time, under any of the usual methods of cultivation, and that variations in virulence are difficult, if not impossible, to induce by any of the methods usually adopted. In particular, they believe that such variations play no significant part in the epidemic spread of disease. Our own experiments, and those of our colleagues (Lockhart, 1926), many of which have not yet been recorded, have convinced us that Bact. aertrycke, when cultivated in the laboratory under various conditions, varies in virulence to a greater degree, and more frequently, than Webster and his colleagues suppose; although our own experience is in accord with theirs, in so far as we have found that a single strain, maintained by massive subculture in a solid medium, and at infrequent intervals, usually maintains its virulence unaltered over months or years. This aspect of the problem will, however, be dealt with more fully in subsequent reports. The present series of experiments is concerned with the epidemic behaviour of strains of appreciably different virulence. With regard to the origin of these strains, we would merely note that they are all derived from strains isolated during the course of the experimental epidemics which we have studied during the past 10 years, and are, so far as we can tell, descendants of the original strain with which we started. Their after-history, as regards the time during which they have been maintained in subculture, and the

The Effect of Withdrawing Mice from an Infected Herd at Varying Intervals.

In a recent report (Greenwood et al. 1936) we included a short discussion of the few scattered observations that we had made on the effects of the dispersal of an infected herd (pp. 189–92). Briefly, we had found that the division of a herd, in which an epidemic due to Bact. typhi-murium was under way, into small isolated groups was followed by a greatly decreased rate of mortality in those groups when the dispersal was carried out at the beginning of the beginning of the epidemic period. Reaggregation of the groups resulted in a fresh spread of the disease, but the final mortality was lower than in a similar herd which had not been dispersed during the earlier stages of cage life (Topley, 1922). In a subsequent experiment (Topley & Wilson, 1925) dispersal was carried out at a later stage of epidemic spread, and very different results were obtained. For the first three weeks or so after division into small groups there was no material difference between the mortality experienced by the dispersed and not-dispersed mice. But at about the 25th day the death-rate in each of the dispersed herds showed a definite decline, while that in the undispersed herds continued unabated for some further length of time.

William Whiteman Carlton Topley, 1886 - 1944

William Whiteman Carlton Topley, the eldest of the three sons (the other children, two, died young) of William Henry and Mary Ann Morland Topley was born in Lewisham on 19 January 1886. Topley’s father, who died suddenly in 1916 from coronary disease, at the age of sixty-three was a man of wide intellectual interests and Topley’s uncle, William Topley (1841-1894) was elected into this Society in 1888. William Topley entered the Royal School of Mines in 1858 and was appointed an assistant geologist on the Geological Survey of the United Kingdom in 1862. According to the obituary notice (Proc. Roy. Soc. 59, lxx (1896)) his early memoir ‘On the superficial deposits of the Medway, with remarks on the denudation of the Weald’, published in 1865, ‘did much towards settling a long debated point in geological speculation’.

The Mortality of a Herd of Mice under "Normal" Conditions.

For the purpose of assessing the effects of exposure to a special environment on a herd of mice, one naturally desires a control series, viz. a herd not exposed to a specific risk but otherwise in pari materia with our colonies under experiment.

On the Mechanisms by which protection against Infectious Disease is acquired in “Natural” Epidemics

The problem which we shall discuss in this communication is of great importance, is perhaps the most important of all epidemiological problems, and we are far indeed from supposing that we have solved it. We think, however, that the work we have done is certainly useful in enabling us, and others, to state the problem correctly, and possibly useful in suggesting a first approximation to its solution.