is the primary factor and that good environment, euthenics, is the secondary one.
For this purpose we augment the 100 families of the preceding section by the addition of 240 more families like them, and we examine each family history to find how many of the children died before completing the fourth year of life. The data are summarized in the following table:
Child Mortality in Families of Long-lived Stock, Genealogical Record Office Data
| Size of family | No. of families investigated under 5 years | No. of families showing deaths | Total no. of deaths | |
|---|---|---|---|---|
| 1 | child | 6 | 0 | 0 |
| 2 | children | 6 | 0 | 0 |
| 3 | " | 38 | 4 | 5 |
| 4 | " | 40 | 6 | 7 |
| 5 | " | 38 | 4 | 4 |
| 6 | " | 44 | 12 | 13 |
| 7 | " | 34 | 8 | 11 |
| 8 | " | 46 | 13 | 18 |
| 9 | " | 31 | 14 | 20 |
| 10 | " | 27 | 14 | 14 |
| 11 | " | 13 | 6 | 9 |