Page:Collier's New Encyclopedia v. 04.djvu/84

LEFT EUGENICS 58 may improve or impair the racial qual- ities of future generations either physi- cally or mentally." It is based upon genetics or the study of heredity, a science open to experimental methods, in which great advance in knowledge has been attained; eugenics seeks to apply this knowledge to the improvement of the human stock by selection in mating. The study of genetics has shown that the qualities which influence heredity are contained in the chromatin of the nucleus of the male and female germ cell; that in fertilization there is intermingling of the chromatin, and the ovum from which the development of the embryo proceeds contains the qualities of both parents. The substances contained in chromatin and which influence development are called determinants and in certain direc- tions their influence is predictable. There are certain unit characters such as color and form of hair in animals, color in flowers, etc., which are transmitted to the off"spring with certainty, appearing in the first generation, when they are termed dominant or in the second genera- tion when they are termed recessive. White and black guinea pigs when mated produce black offspring, the black being dominant, and in the second generation one in every four of the offspring will be white, the white color being recessive. This is known as Mendelian inheritance, and was described by Mendel in 1865, whose work remained unknown until 1906, when the law and the former pub- lication of Mendel were rediscovered. There are similar unit characters in man which are transmitted with equal cer- tainty and if it were desirable to produce a race marked by excessive fingers (poly- dactylism) or webbed fingers (syndac- tylism) it would be possible by selective mating to do so. There are also certain unit characters which are linked with sex, appearing in males and transmitted by females who do not have the condition which is recessive. Thus hssmophilia, or tendency to bleeding, affects males only, but is transmitted by females. In addi- tion to this Mendelian inheritance in which there is no blending of chai-acter, there is another form in which char- acters such as general body size, stature, skin color, are blended in the offspring. Great results have been attained in the breeding of domestic animals, strains being developed marked by certain qual- ities which are desirable, such as milk production, fat formation, wool produc- tion, etc. All these animals are bred •under strictly artifical conditions, and it is not probable that the qualities arrived at would be advantageous for animals in a natural state. It has also been ascer- tained that only the qualities resident in EUGENICS the germ affect heredity and that qual- ities which are acquired and due to en- vironment are not inherited. While this is true, environmental conditions are probably of equal importance for the im- provement of a race, with the character of the germ plasm, for a good environ- ment may render possible the develop- ment of qualities which in another en- vironment might be suppressed. The most important qualities which affect man in his social relations are the mental, such as general mental ability, temperament, memory, musical, literary, artistic and mathematical ability, and these are un- doubtedly subject to inheritance, but to an unknown extent. With regard to the inheritance of disease there is a surer foundation. There is no inheritance of the infectious diseases, though there may be infection of the male or female germ cell or infection of the foetus by the mother before birth, re- sulting in congenital disease. Or dis- ease of the parents may affect not the germinal material of the germ cell, but the general character of the cellular ma- terial, resulting in a general imperfection of offspring. Syphilis may affect the off- spring in any of these ways and it should constitute a bar against mating. Great interest attaches to the inheritance of such conditions as insanity, epilepsy, and feeble-mindedness. These may be due to conditions which are acquired and are not inheritable, but when due to a congenital imperfection of the nervous material they are inheritable to a high degree. These diseases are of such enor- mous social importance in increasing the number of defectives which burden a state that mating among them should be forbidden. Certain states have passed laws requiring the sterilization of males and females so affected, but it is difficult to have such laws carried out, and they are opposed to the moral sense of the people. Segregation with separation of the sexes is much more desirable, but in asylums it is difficult or impossible to have this so effectively done as to include the milder forms of these diseases which may be just as disadvantageous for breeding. There are certain forms of criminality which depend upon qualities which may be transmitted, and breeding from these should be prohibited, but the interdiction should not include all those who come under the ban of the law. A fine population has arisen from the crim- inals whom England formerly trans- ported to her colonies. The desire to im- prove the race is a laudable one, but there is great uncertainty as to mea- sures. The prevention of descent from those with such defects of both mind and body as are inheritable and disad-