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may be treated, give very closely corresponding results. We have no
statistics fit to be submitted to critical analysis, nor shall we have so
long as we continue to " select " the cases which we recognize as able
to recover. There is little doubt that we are more accurate and more
refined in our recognition of infection at a much earlier stage in the
course of the disease than were our forefathers. When this increased
power of diagnosis is exercised we obtain a high percentage of
recoveries, but even by the most careful selection for sanatorium or
other treatment, about 25 per cent, of " early cases " progress to an
advanced condition under treatment. Even advanced cases on the
other hand may eventually become latent or arrested.
I am certain that a great number of people recover after infection,
and that this recovery, crippling though it may be, can occur after very
severe lesions to the lungs. Dr. T. D. Lister says that the resistance
of the individual patient may be likened to an elastic cord composed
of many threads, which resistance sustains the weight of the disease,
and the results of the administration of a toxin to a patient may be
compared to a series of dynamic phenomena. If one imagines such a
weight suspended by such a cord of many strands, and that the cord,
though moderately stretched, is suspending the weight in a fairly
stable position, the administration of a toxin such as Tuberculin could
be likened to the delivery of a tap or blow to the upper surface of the
weight. The effect of such a blow on a simple apparatus of this kind
would be that the weight would be depressed for a moment by the
increased stretching of the elastic cord, and then it would rebound to a
height slightly above its original position before coming to rest again
in its original position. If at the height of the rebound, we imagine
that an additional thread can be clipped in the cord, a stronger blow
(dose of anti-toxin) will be required to bring about a depression and a
rebound. By a series of such experiments one could imagine that the
cord would become too strong to be stretched by additional blows on
the weight, and to be capable of bearing an infinitely greater strain than
the original weight. One could also imagine the elastic cord stretched
to its utmost bearing capacity by the weight at the beginning, and that
any additional blow would merely break it without further stretching it.
Recovery or immunity implies elasticity of resistance. There are two
ways in which an individual can escape death by Tuberculosis, and
the first is by his being incapable of infection. Modern evidence seems
to show that this must be very rare. There may be such a thing as
hereditary immunity. The other way is by the energetic production