قراءة كتاب Being Well-Born: An Introduction to Eugenics
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Being Well-Born: An Introduction to Eugenics
a child’s fate in life is frequently decided long before birth, and that no amount of food or hospital service or culture or tears will ever wholly make good the deficiencies of bad “blood,” or in the language of the biologist, a faulty germ-plasm, and the conviction must surely be borne home to the intelligent members of society that one thing of superlative importance in life is the making of a wise choice of a marriage mate on the one hand, and the prevention of parenthood to the obviously unfit on the other.
In the present volume it is intended to examine into the natural endowment of the child. And since full comprehension of it requires some understanding of the nature of the physical mechanism by which hereditary traits are handed on from generation to generation, a small amount of space is given to this phase. Then, that the reader may appreciate to their fullest extent the facts gathered concerning man, a review of the more significant principles of genetics as revealed through experiments in breeding plants and animals has been undertaken. The main applications of these principles to man is pointed out in a general discussion of human heredity. Finally, inasmuch as all available data indicate that the fate of our very civilization hangs on the issue, the work concludes with an account of the new science of eugenics which is striving for the betterment of the race by determining and promulgating the laws of human inheritance so that mankind may intelligently go about conserving good and repressing bad human stocks.
In order to eliminate as many errors as possible and to avoid oversights I have submitted various chapters to certain of my colleagues and friends who are authorities in the special field treated therein. While these gentlemen are in no way responsible for the material of any chapter they have added greatly to the value of the whole by their suggestions and comments. Thus I am indebted to Professor Leon J. Cole for reading the entire manuscript; to Professors A. S. Pearse and F. C. Sharp for reading Chapter VII; to Professor C. R. Bardeen for reading special parts; to Doctor J. S. Evans for reading Chapter VI and part of V; to Doctor W. F. Lorenz, of the Mendota Hospital, for reading Chapter VIII; to Judge E. Ray Stevens for reading Chapter IX, and to Helen M. Guyer for several readings of the entire manuscript.
Grateful acknowledgment is made to all of these readers, to various publishers and periodicals for the use of certain of the illustrations, to the authors of the numerous books and papers from which much of the material in such a work as this must necessarily be selected, and to my artist, Miss H. J. Wakeman, for her painstaking endeavors to make her work conform to my ideas of what each diagram should show.
M. F. G.
CONTENTS
| CHAPTER | PAGE | |
| I | Heredity | 1 |
| Blood heritage—Kind determined by origin—Ancestry a network—Ancestry in royalty—Offspring derived from one parent only—Dual ancestry an aid in studying heredity—Reversion—Telegony—Prenatal influences apart from heredity—Parent body and germ not identical—A hereditary character defined—Hereditary mingling a mosaic rather than a blend—Determiners of characters, not characters themselves, transmitted—Our knowledge of heredity derived along three lines—The method of experimental breeding—The statistical method—Galton’s law of regression—Correlations between parents and offspring—The biometrical method, statistical, not physiological—Mental as well as physical qualities inheritable. | ||
| II | The Bearers of the Heritage | 20 |
| The cell the unit of structure—Unicellular organisms—Importance of cell-theory—Heredity in unicellular forms—Reproduction and heredity in colonial protozoa—Conjugation—Specialization of sex-cells—The fertilized ovum—Advancement seen in the Volvox colony—Natural death—Specialization in higher organisms—Sexual phenomena in higher forms—Cell-division—Chromosomes constant in number and appearance—Significance of the chromosomes—Cleavage of the egg—Chief processes operative in building the body—The origin of the new germ-cells—Significance of the early setting apart of the germ-cells—Individuality of chromosomes—Pairs of chromosomes—Reduction of the number of chromosomes by one-half—Maturation of the sperm-cell—Maturation of the egg-cell—Parallel between the two processes—Fertilization—Significance of the behavior of the chromosomes—A single set of chromosomes sufficient for the production of an organism—The duality of the body and the singleness of the germ—The cytoplasm in inheritance—Chromosomes possibly responsible for the distinctiveness of given characters—Sex and heredity—Many theories of sex determination—The sex-chromosome—Sex-linked characters in man—In lower forms. | ||
| III | Mendelism | 67 |
| New discoveries in the field of heredity—Mendel—Rediscovery of Mendelian principles—Independence of inheritable characters—Illustration in the Andalusian fowl—The cause of the ratio—Verification of the hypothesis—Dominant and recessive—Segregation in the next generation—Illustrated in guinea-pigs—Terminology—The theory of presence and absence—Additional terminology—Dominance not always complete—Modifications of dominance—Mendel’s own work—Dihybrids—Getting new combinations of characters—Segregations of the determiners—Four kinds of gametes in each sex—The 9:3:3:1 ratio—Phenotype and genotype—The question of blended inheritance—Nilsson-Ehle’s discoveries—Such cases easily mistaken for true blends—Skin-color in man—Questionable if real blends exist—The place of the Mendelian factors in the germ-cell—Parallel between the behavior of Mendelian factors and chromosomes—A single chromosome not restricted to carrying a single determiner. | ||
| IV | Mendelism in Man | 97 |
| Probably applicable to many characters in man—Difficult to get correct data—A generalized presence-absence |