families of Europe, the environment is as good as knowledge and wealth can make it. No child dies for lack of plenty of food and the best medical care, even if his father or mother died young. And the members of this caste are not exposed to any such unsanitary conditions, or such economic pressure as could possibly cause both parent and child to die prematurely. If the association between longevity of parent and child mortality holds for the royal families of Europe and their princely relatives, it can hardly be regarded as anything but the effect of heredity,—of the inheritance of a certain type of constitution.
Dr. Plœtz studied the deaths of 3,210 children in European royalty, from this viewpoint. The following table shows the relation between father and child:
Length of Life of Fathers and Child-mortality of Their Children in Royal and Princely Families, Plœtz' Data
| Year of life in which fathers died | At all ages | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 16-25 | 26-35 | 36-45 | 46-55 | 56-65 | 66-75 | 76-85 | 86-up | ||
| No. of children. | 23 | 90 | 367 | 545 | 725 | 983 | 444 | 33 | 3210 |
| No. who died in first 5 years | 12 | 29 | 115 | 171 | 200 | 254 | 105 | 1 | 887 |
| Per cent. who died | 52.2 | 32.2 | 31.3 | 31.4 | 27.6 | 25.8 | 23.6 | 3.0 | 27.6 |
Allowing for the smallness of some of the groups, it is evident that the amount