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in this country." A careful study of both Karl Pearson's and Sir Arthur Newsholme's statistical arguments
will not fail to convince everyone that he has given many sound reasons for showing that the
accuracy of Sir Arthur Newsholme's conclusions is open to very considerable doubt.
Karl Pearson considers that heredity flays the most important part in phthisis, and expresses the
opinion that the selection due to many years of heavy phthisis mortality has left us with a more immune
and resistant population, and goes on to say that if this is the explanation—and he believes it will be
found to be the ultimate explanation of the fall, especially the retarded fall, in the phthisis death.
rate—then infection is not the only factor worth investigating. He therefore suggests that " natural
selection may have done more for rac'al health in this matter than medical science."
" Evolution helps man better than he at present knows how to help himself, and possibly he
would learn to help himself better if he studied processes of racial selection a little more closely."
After a careful study of the various theories which have been put forward to explain the decline
of the tuberculosis death.rate during the latter half of the last century, the student may well be forgiven
for taking the view that not one of them can be said to afford an entirely satisfactory explanation.
Most of those who have studied the subject succumb to the temptation of starting a theory of their
own. I do not propose to say more than that in my opinion there are substantial grounds for the belief
that the data available for the study of the subject, particularly the certification of deaths from tuberculosis,
are not sufficiently reliable to enable one to make a fair comparison between such periods as
1850.1885 and 1885.1920. In the latter period the great advances which have taken place in the
facilities available for making a more accurate diagnosis of the presence of the disease, and therefore
its differentiation from other diseases, are sufficient to render any comparative study of the statistics
for the two periods very difficult. Furthermore, it always happens that when a disease attracts a great
deal more attention both from the medical faculty and the public that it is suddenly discovered to be
much more prevalent than was formerly thought to be the case. The only positive statement
therefore to which I should be inclined to commit myself at present would be that the general
improvement in the conditions of life of the working.classes, both at home and at work, and the
beneficial effects resulting from the better control of such important predisposing factors as the
contraction of the infectious fevers in early life, cannot have failed to produce decidedly favourable
influences upon the incidence, and progressively fatal character, of the disease.
The mortality from tuberculosis in the two sexes.—In connection with the decline of the death.
rate from tuberculosis it is an interesting fact that females have benefited more than males. The
difference in the first few years of life is in accordance with the general rule—viz., that the mortality
from all causes is greater during these years amongst male infants. After the early years of life the
position is reversed, and up to the age of twenty, girls are more liable to die of tuberculosis than boys.
The question has been asked whether this difference is due to some peculiar susceptibility of the tissues
of the female at this time of life or whether it is simply dependent upon the difference in the habits of
life of the two sexes ? In this connection it may be noted that amongst the working.classes young
girls often have the care of younger members of the family, and especially the babies, thus interfering
to a large extent with their freedom and natural physical development.
After the age of twenty, males die much more frequently of tuberculosis than females, and the
disparity increases until the age period fifty.five to sixty five is reached, and only slightly diminishes
thereafter. This difference depends in the main upon differences of occupation, for the great majority
of trades which predispose to tuberculosis are those followed, as a rule, almost exclusively by
men.
It is a significant fact that the comparative prevalence of fatal tuberculosis in the sexes, taking
all periods of life together, have been reversed since the modern development of industrialism, and that the
change has occurred earlier in those countries which first developed their industries. In England this
change began about 1868. In Scotland it was twenty.five years later. In Ireland females still continue
to suffer from Tuberculosis more than males. Furthermore in England and Wales the difference is
most marked in urban districts and least in rural, and it reaches its climax in certain towns—e.g., Birmingham
and Sheffield, where trades particularly liable to predispose to tuberculosis are largely carried on.
Industrialism has not increased the mortality from tuberculosis amongst adult males, but it has greatly
retarded the decline which has been taking place.
The role of the tubercle bacillus. Tuberculosis is generally described as an infections or contagious
disease and the tubercle bacillus as the causative organism. But authorities differ considerably as to
the importance to be attached to the role of the tubercle bacillus. Thus, one school of thought expresses
the view that inasmuch as tubercle bacilli are commonly present in the air we breathe and the food we eat,
that opportunities come frequently and almost constantly to all of us for acquiring the infection. Indeed,
there is ample evidence to show that the chances are that all of us become definitely infected at some
time or other during our lives, but in the ordinary course of events the disease becomes arrested in the
majority of us and leaves but a small trace behind in the form of a scar in the lung tissues or elsewhere.
Opportunities for infection, then, being admittedly so common, it is manifest that they can
count but little in the ultimate result. Some other factor, therefore, must determine whether the infection
is to lead to a progressive, and often fatal, result; and it has been suggested that this factor
can only be the power of resistance possessed by the individual. In other words, " the seed comes
to all of us; it is the soil which determines whether or no it shall germinate and grow to maturity."
It has been suggested that this view neglects to take any account of the possibility that the results of
infection may depend upon the size of the infecting dose. Much valuable information on the " influence
of dose " was gained by the Royal Commission on Tuberculosis as a result of numerous experiments.