The Greeks who were fond of philosophical disputations used to argue about how many stones make a heap. One is not a heap, nor two or three; five or six certainly are a heap. Where is the border line? So too it is implicit in any series which runs from a definite positive at one end to a definite negative at the other that there must be a point of transition somewhere in the series in which there is certain to be an error in evaluation of 50%. This is simple mathematics and applies to the reading of x-ray films of the chest in the appraisal of tuberculous lesions as well as to anything else.
The first part of this document is related to the evaluation of tuberculosis in soldiers, especially with reference to x-ray diagnosis of early lesions. The writers scratch their heads and worry about different observers differing