Writers have devoted a good deal of attention to this subject, and we have been shown statistics, reports of imbecile asylums, etc., for the purpose of proving that the marriage of cousins results in the production of idiots, and other defectives; but the results of more careful examinations of the subject invalidate the views heretofore held, and it must be acknowledged that when both parties are healthy there is no more liability of mental incompetency in the children of cousins, than in the offspring of persons more remotely related. It must be added, however, that there are other reasons why the marriage of cousins is not to be generally recommended. Besides the fact that the feeling existing between cousins is often only that which is felt by brothers and sisters for each other, there is the still more important fact that on account of the blood relation, unions of this kind are more apt than others to bring together persons having similar morbid tendencies. _4. Persons having serious congenital deformities should not marry._ The reason for this rule is obvious. Persons suffering with serious congenital defects, as natural blindness, deafness, deformity of the limbs, or defective development of any part, will be more or less likely to transmit the same deformities or deficiencies to their children. There are, of course, cases of natural blindness, as well as of disability in other respects, to which this rule does not apply, the natural process of development not being seriously defective. It has even been observed that there is a slight tendency to the reproduction in the offspring, of deformity which has been artificially produced in the parents, and has existed for a long time. Many ancient nations observed this rule. Infants born cripples were strangled at birth or left to die. A Spartan king was once required by his people to pay a heavy fine for taking a wife who was inferior in size. _5. Criminals should not marry._