798 
PROCEEDINGS OF SECTION I. 
been mainly directed, oneway or another, against the tubercle bacillus 
itself. If these efforts have not so far been attended with any great 
measure of success, it is not, as the bulky literature of the subject 
shows, owing to any lack of effort or ingenuity on the part of those 
who have Deen engaged in them. The mere mention of the methods 
that have been advocated and tried would be quite beyond the scope 
of this paper. But the “plan of campaign” against the Bacillus 
tuberculosis as hitherto carried out may be considered as roughly 
consisting of two parts- — the one of defence, the other of attack. 
In the way of defence, it has been sought in various ways to 
strengthen the natural existence of the organism invaded, for there 
exists in the blood and tissues of all healthy animals a certain, though 
varying, degree of resistance to every kind of bacterial infection. To 
this end hygienic surroundings — general and climatic — pure air, sun- 
light, good food, galvanism, physical exercises, oils, and innumerable 
drugs of the “ tonic’ * kind have been advocated. 
In the way of attack there has been, perhaps, more activity — cer- 
tainly more innovation. The total destruction of the bacillus and its 
spores by some substance deadly to it, but harmless to the animal in 
whose tissues it is imbedded, is doubtless an ideal method of attack, 
but it is, unfortunately, for very obvious reasons, impossible to 
administer any substance of the “ germicide” or “antiseptic” class — 
such as carbolic acid or corrosive sublimate — in quantity sufficient to 
destroy the bacillus without at the same time destroying or seriously 
injuring its host. Nevertheless, a vast number of substances of this 
class have been employed, not for the most part with the idea of 
directly destroying the bacillus, but in the hope of impairing its 
vitality, diminishing its toxic power, neutralising its poisonous 
products, or limiting its reproductive activity (spore formation), and 
in these ways indirectly helping the organism to resist it. 
The introduction of Koch’s tuberculine in 1890 marks a new 
departure. Tuberculine is essentially the poison (or poisons) elabo- 
rated by tubercle bacilli in artificial cultivation, freed from the 
bacilli by filtration. Its effect when injected into a tuberculous 
subject is to destroy the morbid (tubercular) tissue in which the 
bacilli are imbedded. This destruction of tissue is accompanied by a 
rise in temperature, a fact which makes tuberculine of the greatest 
value as a means of diagnosis. It has certainly not fulfilled the hopes 
that were entertained at the time of its introduction; nor, I venture 
to think, is it reasonable to anticipate any great benefit so far as its 
destruction of tubercular tissue is concerned. It has, however, in 
all probability, other effects upon the system which, judging from 
analogy and by the light of recent investigations, may yet prove of 
paramount importance in the treatment, and perhaps even prevention, 
of tuberculosis. 
The researches to which I refer are those relating to the natural, 
acquired, or artifically produced immunity to bacterial diseases, 
particularly those of Ehrlich, and of Behring and Kitasato. 
It has long been known that persons who have recently suffered 
from a zymotic disease, such as smallpox or typhoid, are for a time, 
and, in some cases, for a very long time, proof against the same 
disease. And the same phenomenon is observed amongst animals, as, 
notably, in the case of anthrax. The aim of “vaccinations” and 
