“Professor Karl Person, than whom there is no higher authority on biologic statistics, finds that his researches on the incidence of pulmonary tuberculosis rather favor the presumption of hereditary being a leading if not a dominant factor. It is impossible, he admits, to assume, with the present insufficient data that any disease is inherited in the same sense that physical and mental characteristics are inherited, but if inheritance of a consumptive tendency or diathesis is not assumed, it is difficult to explain the facts, or to see how any one escapes with the actual universal distribution of the infection, especially in dense populations. Few individuals, he says, who lead a moderately active life can escape an almost daily risk of infection. Another fact pointing the same way is that the average age at the onset of the disease is practically the same in all cases, whereas with the infection theory, pure and simple, it should occur earlier when a constant possibility of infection exists, as, for instance, in families where some members is a sufferer from the disease. Statistics show only an insignificant difference in such cases. The present tendency to magnify the infection factor at the expense of the formerly more generally accepted view of the importance of heredity in the spread of pulmonary tuberculosis is, we think, largely based on a prior grounds. When consumption was demonstrated to be due to microbic infection there seemed to be little need of invoking any other agency. Another thing favoring the change of view was the apparent better prognosis afforded, and further, we may perhaps consider the advocacy of the infection theory as some what prompted by ideas of expediency as falling more readily in line with the active campaign against ‘the great white plague.’
“For a biometric authority like Professor Pearson to magnify the importance of heredity in tuberculosis is, however, significant and should tend to modify some of the radical utterances that consumption is not and can not be, in any proper sense, hereditary. Another fact brought out by Professor Pearson is that, while the offspring of consumptives are not less fertile and in all probability are even more fertile than those of normal heredity, the fact that.
