View report page

6
Notification
of tuberculosis.
The number of "primary" cases of tuberculosis notified in London during 1918 (52 weeks) was
19,178, the corresponding figures for the years 1915-17 being 18,061, 17,031 and 18,735 respectively.
These figures do not relate exclusively to the civil population. Of.the total "primary" cases of
tuberculosis notified in 1918, 15,661 were pulmonary, and 3,517 were other forms of tuberculosis.

The Medical Research Committee's Report on the Epidemiology of Phthisis.
The Medical Research Committee issued in 1918 a report (No. 18, Special Report Series) embodying
the results of a statistical investigation by Dr. Brownlee into the epidemiology of phthisis in Great
Britain and Ireland. Dr. Brownlee premises that "in all diseases which are definite clinical entities the
curves of age-distribution follow definite laws." Applying this hypothesis to the age-incidence of phthisis
mortality he finds remarkable divergencies from a definite law in different areas of the United Kingdom ;
and he therefore concludes that phthisis is not one " definite clinical entity," but, so far as ages abo\e
10 years are concerned, a combination of three entities.
The three types of phthisis are thus differentiated by the contour of the curves representing the
age-incidence of mortality. Type I., predominant in Ireland and the Shetland Islands is characterised
by a sharp rise to a maximum between 20 and 25 years of age and then declines, and this is the " young
adult " phthisis. Type II. exemplified in the London mortality, has a maximum between 45 and 50years
of age, and is the " niiddle-age " phthisis. Type III. exhibited in the mortality rates of miners attains a
maximum incidence betw een 55 and 65 years, and is the " old age " phthisis.
Dr. Brownlee recognises that there may possibly be other means of accounting for the divergencies
observed in the phthisis mortality curves for different localities ; he refers to the need for considering
environment, occupation and climate, and also the effect of the elimination of susceptible persons by
natural selection, and proposes to discuss the influence of each of these conditions in a later note, but he
says, " at this moment it may be stated that none affords any adequate explanation of the phenomena
observed."
No mention, curiously enough, is made of the effect of movement of population upon the phthisis
mortality at different ages. In a paper on " The' Influence of Migration upon the Phthisis death-rate "
(Proc. of the Roy. Soc. Med. Vol. VI.), it was suggested that no inconsiderable influence upon phthisis
mortality had been exerted by migration. The growth of urban populations at the expense of surrounding
rural areas, and emigration in numbers to America and the Colonies, involve changes in the residual
populations not only in age and sex-constitution, but also in regard to vitality, since no stock can be
continuously depleted of its most virile elements without deterioration ; again, some countries have
sent away their phthisics, and of these in varying proportions some have died abroad and others have
returned to die at home.