Consanguineous parentage | 79 | 53.2 = 208
Parents cousins | 70 | 50.0 = 195
Parents uncle and niece | 9 | 66.7 = 261
--------------------------------------------------
4. Imbecility and Idiocy | 16,416 | 28.7 = 100
Consanguineous parentage | 237 | 43.0 = 150
Parents cousins | 211 | 43.1 = 150
Parents uncle and niece | 26 | 38.5 = 134
--------------------------------------------------

Table XXI gives the proportion of the mentally defective who are the
offspring of consanguineous marriages. The term "cousin" in both
these tables probably means first cousins. It will be remembered that
Prussian statistics of consanguineous marriages are very imperfect,
but that at least 6.5 in every thousand are consanguineous (first
cousins or nearer).

TABLE XXI.[73]
_Parentage of Mental Defectives in Prussia._
-----------------------------------------------------
| Consan- | |Uncle and
|guineous.|Cousins.| Niece.
-----------------------------------------------------
1. Insanity (simple) | 6.5[A] | 5.8[A]| .64[A]
Hereditary | 14.2 | 12.5 | 1.6
Not hereditary | 3.0 | 2.7 | .22
-----------------------------------------------------
2. Paralytic Insanity | 4.1 | 3.8 | .35
Hereditary | 11.1 | 9.6 | 1.48
Not hereditary | 2.9 | 2.5 | .11