How little the increasing mortality of the later born children up to the tenth child is based on a biological law is shown in Figure C 53. +Numerical position of birth and infant mortality up to the age of five in princely families+, by Ploëtz; 463 seventh to ninth children show the same mortality as the 614 first born.
Pearson endeavored to prove a high degree of inferiority in the first born, physically and intellectually as well as morally. But his results are very open to attack, as Weinberg has recently shown; one is reminded of Pearson's results in Crzellitzer's Figure C 54--first and later born. Crzellitzer writes thus about this--"A +high degree of myopia+ is +more frequent amongst first born+ than among later children. The disadvantage of the first born in respect of myopia is based on a greater hereditary taint and on no other factor. Where there is no hereditary taint about one quarter to one-third are affected, no matter whether first, second, third, etc., born. Also in well-to-do families, where the age of fathers at the time of procreation is materially higher, the first born are more frequently myopic than their brothers or sisters."
Percentage of Frequency of Extreme Short-sightedness.
Child 1st 2nd 3rd 4th 5th 6th 7th 8th ============================== ==== ==== ==== ==== ==== ==== ==== ==== 1,246 children from 216 working-class families. 46.4 33.7 31.4 26.6 26.5 26.0 15.5 18.7
1,246 children from 216 working-class families, classified according to presence or absence of inherited tendency to short-sightedness.
With inherited tendency 61.6 34.9 27.7 25.5 31.5 32.0 10.5 6.7 Without inherited tendency 35.9 33.7 34.3 24.6 25.0 22.2 19.0 23.3
206 children from 45 well-to-do families. 63.1 36.1 36.0 36.0 20.0
A large amount of material has been treated by W. Weinberg, in which tuberculous and non-tuberculous families are compared.
Figure C 55--+influence of numerical position of birth on infant mortality+ and Figure C 56--+mortality of the first and later born+. Weinberg writes concerning these: "The parallelograms in the first row indicate for each position in order of birth how many children out of every hundred die before the age of 20. On this, however, the difference in the mortality in families with different numbers of children has an influence. To counteract this, it has been calculated how many children in each position would die if within each family the number of children had no influence, and the actual number of deaths expressed as a percentage of the expectation calculated in this way gives parallelograms to the second row. After eliminating the influence exercised by the size of the family, the increase of the mortality with the higher birth number appears considerably smaller. Figure C 56, which compares the mortality of the first and last born children, is to a certain extent a test of this. This shows clearly a considerably higher death rate in the last born. Both figures indicate that children of the same numerical position of birth show a higher mortality, if from tuberculous families."