THE HYGEINE OF MARRIAGE: CONCEPTION AND CHILDBIRTH FERTILIZATION AND BIRTH OF TWINS
After fertilization has taken place, the cell formed by the union of the spermatozoon and the ovum begins to grow and descends into the uterus, where it is nourished if the uterus is prepared to perform this function. Once growth has begun, it usually goes on to the completion of a normally formed infant. Malformations or abnormalities of any sort may be due to: (1) defect in the ovum or spermatozoon; (2) mechanical causes, such as interference with circulation in a limb by a fold or twist in the membranes surrounding the child's body; or (3) a venereal disease acquired in the uterus of the mother. Birthmarks and other deformities are to be looked upon as accidents in the pre-natal growth of the infant. They are never due to any shock or perturbed mental state of the mother. The belief that an experience undergone by the pregnant mother can "mark" her child is superstition.
The general reader is often curious as to the cause of the birth of twins. This happens in two ways. If the twins are identical, they are the result of a division of a single fertilized ovum in such a way that two infants develop instead of one. In other cases twins are due to the fertilizations of two ova at the same time, just as in the case of some animals it is usual for a litter to be born instead of only one offspring. The ability to have twins is apparently a survival of this capacity possessed by our animal ancestors, and is hereditary.
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