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X.]   DISEASE.   186

at large, than there is in a group of consumptive families. It would be quite fair to estimate the value

of n at least as low as 0.8.

We have thus three values of n to try ; viz. 1, 0.9, and 0.8, of which the first is scarcely possible and the last is much the more suitable of the other two. The corresponding values of 0.73 divided by n, are + 0.73, -I- 0.81, and + 0.91. Referring to Table 8 we find the Grades corresponding to those deviations to be 69, 71, .and 73. We should therefore expect 69, 71, or 73 per cent. of the Co-Fraternity to be non-consumptive, according to the value of n we please to adopt, and the complement to those percentages, viz. 31, 29, or 27, to be consumptive. Observation (p. 173), gave the value of 26 by one method of calculation, and of 28 by another.

Too much stress must not be laid on this coincidence, because many important points had to be slurred over, as already explained. Still, the prima facie, result is successful, and enables us to say that so far as this evidence goes, the statistical method we have employed in treating consumptivity seems correct, and that the law of heredity found to govern all the different faculties as yet examined, appears to govern that of consumptivity also, although the constants of the formula differ slightly.

Data for Hereditary Diseases.-The knowledge of the officers of Insurance Companies as to the average value of unsound lives is by the confession of many of