Turning our attention to human heredity we find that many well-marked hereditary abnormalities run in families, A. dominant character is banded down regardless of sex, only by an affected' individual and to about half of his or her children, Instances of this are certain malter: mations, like brachydactyly (absence of one bone in each Anger), They may prove very serious in marriage between close relatives. Thus a marriage between cousins with a hereditary shortening of one finger may produce a child without hand and feet, Another great group of abnoralities are sex-linked recessives, These are much commoner in males than in females. They are not, however, directly passed by the affected males to their children but their daughters pass the character on to half of their sons. The best known and most serious condition pro Pawated in this manner is haemo-Dhilin, a failure of the blood to clot to serious often fatal, itosomal recessive anomalies are most likely to result from union between near relatives incestuous unions, marriages tween cousins) sit ice both partners are likely to carry the same recess sive gene. Examples are deaf mutism, certain "eye or skin affections, several discases of metabolism,
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