The God of Nature has said from the beginning that man and wife are one flesh, and He has repeated it in the Christian dispensation. There is such a union of bloods by marriage that cannot be separated. Sanguinity is established by consanguinity, or the "uniting together of two bloods," so that the woman imparts her sanguinity to the man, and the man his to the woman—they become one flesh.
If so, as it surely seems to be by the law of God as laid down in Scripture, then in the case we have before us of marriage with a deceased wife's sister or marriage with a sister's husband, the woman, being of the same sanguinity as her sister, cannot marry the husband of her sister, because that sister has, in the union of blood or flesh, united her sanguinity to her husband. Consequently, marriage with a deceased wife's sister is illegal, owing to the union of blood, according to the law of God and therefore nature—"Man and wife are one flesh."
The study of physiology has made one decided step in advance towards acknowledging the reality of union of bloods in marriage. It says now that, only when offspring commences, consanguinity, which is a union of two bloods, occurs.
Man and wife are only one flesh, then, by offspring, we may say. Before, although married, they were two as it were, and not considered one
