1. The tuberculin reaction is based on an hypersusceptibility of the skin and is an expression of an altered reaction capacity of the tissues, following an initial infection with the tubercle bacillus.
2. The strength of allergy fluctuates with the activity of the lesion and with the presence of certain qualifying factors.
3. It seems possible by quantitative examination to find a critical threshold which will usually establish a diagnosis in active tuberculous cases, although it must be considered that this evidence is only presumptive for osseo-articular disease until all other possible active foci have been ruled out.
4. In cases of bone or joint disease where the allergy falls below the critical threshold, and in the absence of certain modifying factors, active tuberculosis can, with fair degree of certainty, be eliminated in the diagnosis.