Theories of localized tuberculosis other than of the lungs are quite plausibly worked out. Of course, the pulmonary variety of tuberculosis is pretty generally conceded to come from inspiring infected air, or from taking the germ into the stomach with food. The bacilli introduced by the inspired air ingraft themselves in the apices of the lungs. The reason for this particular localization is attributed to the limited expansion of this part of the chest, and especially the weakness of the expirating movement. The natural sciences--especially mechanics--are frequently used by medical science in reinforcing a theory; but the student should not allow plausible argument to paralyze his real effort at getting at the truth.

If the theories of scientific medicine regarding tuberculosis were true, there could be no plausible reason given why tuberculosis, syphilis, or a fatal contagion had not depopulated the earth; and certainly, if the theories of bacteriology were true, there could be no good reason given why germs had not prevented the populating of the earth.

The fatal weakness about all the germ science is that it cannot give a good reason why man is not extinct, if its theories of causation are true; and, on the other hand, if all it boasts of its great art and science be true, why disease is not stamped out.

Why do not all people who inhale bacilli develop the corresponding disease? Why are there people who cannot be made to take tuberculosis, and why are there a small percentage: who cannot be prevented from taking the disease? The answer to these questions will give a good working hypothesis on which to base a rational theory of causation.

The theories advanced in the various chapters in this book certainly are plausible, and the fact that, when applied, they work is all the proof that rationality needs. Bigotry and prejudice have never been, nor ever will be, convinced that the other fellow is not an ignoramus.

The theories of diathesis, enervation, and autotoxemia, when applied to tuberculosis, work out and rationally explain the cause, and certainly give the only depend prevention or immunization.

The various types of tubercular diseases--the classified tubercular diseases--are easily explained when it is known that this infection cannot be made to infect a gouty diathesis, but that it is easy to cultivate all types of tubercular affections--graft them, so to speak--on the tubercular diathesis.