CONTENTS
| CHAPTER | PAGE | |
| [I] | Heredity | [1] |
| Blood heritage—Kind determined by origin—Ancestry a network—Ancestry in royalty—Offspringderived from one parent only—Dual ancestry an aid in studying heredity—Reversion—Telegony—Prenatal influences apart from heredity—Parentbody and germ not identical—A hereditary character defined—Hereditary mingling a mosaic rather than a blend—Determinersof characters, not characters themselves, transmitted—Our knowledge of heredity derived along three lines—The method ofexperimental breeding—The statistical method—Galton’s law of regression—Correlations betweenparents 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—Heredityin unicellular forms—Reproduction and heredity in colonial protozoa—Conjugation—Specializationof sex-cells—The fertilized ovum—Advancement seen in the Volvox colony—Natural death—Specialization in higher organisms—Sexualphenomena in higher forms—Cell-division—Chromosomes constant in number and appearance—Significance of the chromosomes—Cleavageof the egg—Chief processes operative in building the body—The origin of the new germ-cells—Significance of the early settingapart of the germ-cells—Individuality of chromosomes—Pairs of chromosomes—Reduction of the number of chromosomes by one-half—Maturationof the sperm-cell—Maturation of the egg-cell—Parallel between the two processes—Fertilization—Significance of the behaviorof the chromosomes—A single set of chromosomes sufficient for the production of an organism—The duality of the body and the singlenessof the germ—The cytoplasm in inheritance—Chromosomes possibly responsible for the distinctiveness of given characters—Sexand 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—Independenceof inheritable characters—Illustration in the Andalusian fowl—The cause of the ratio—Verification of the hypothesis—Dominantand recessive—Segregation in the next generation—Illustrated in guinea-pigs—Terminology—The theory of presence and absence—Additionalterminology—Dominance not always complete—Modifications of dominance—Mendel’s own work—Dihybrids—Getting new combinationsof characters—Segregations of the determiners—Four kinds of gametes in each sex—The 9:3:3:1 ratio—Phenotype and genotype—Thequestion of blended inheritance—Nilsson-Ehle’s discoveries—Such cases easily mistaken for true blends—Skin-color in man—Questionableif real blends exist—The place of the Mendelian factors in the germ-cell—Parallel between the behavior of Mendelianfactors 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 generalizedpresence-absence formula—Indications of incomplete dominance—Why after the first generation only half the children may show the dominantcharacter—Eye-color in man—Hair-color—Hair-shape—Irregularities—Digital malformations—Eye defects—Other defects inheritedas dominants—Recessive conditions more difficult to deal with—Albinism—Other recessive conditions in man—Breeding out defects—Otherinheritable conditions in man. | ||
| [V] | Are Modifications Acquired Directly by the Body Inherited? | [121] |
| Which new characters are inherited?—Examples of somatic modifications—Use and disuse—The problemstated—Special conditions in mammals—Three fundamental questions—External influences may directly affect the germ-cells—Such effectsimprobable in warm-blooded animals—Poisons may affect the germ-plasm—How can somatic modifications be registered in germ-cells?—Persistence of Mendelianfactors argues against such a mode of inheritance—Experiments on insects—On plants—On vertebrates—Epilepsy in guinea-pigs—Effectsof mutilations not inherited—Transplantation of gonads—Effects of body on germ, general not specific—Certain characters inexplicableas inherited somatic acquirements—Neuter insects—Origin of new characters in germinal variation—Sexual reproduction in relationto new characters—Many features of an organism characterized by utility—Germinal variation a simpler and more inclusive explanation—Analysisof cases—Effects of training—Instincts—Disease—Reappearance not necessarily inheritance—Prenatal infection not inheritance—Inheritanceof a predisposition not inheritance of a disease—Tuberculosis—Two individuals of tubercular stock should not marry—Specialsusceptibility less of a factor in many diseases—Deaf-mutism—Gout—Nervous and mental diseases—Other disorders which havehereditary aspects—Induced immunity not inherited—Social, ethical and educational significance of non-inheritance of somatic modifications—Nocause for discouragement—Improved environment will help conserve superior strains when they do appear. | ||
| [VI] | Prenatal Influences | [159] |
| All that a child possesses at birth not necessarily hereditary—The myth of maternal impressions—Injuriousprenatal influences—Lead poisoning—The expectant mother should have rest—Too short intervals between children—Expectant mothersneglected—Alcoholism—Unreliability of most data—Alcohol a germinal and fetal poison—Various views of specialists on the effects ofalcoholism on progeny—The affinity of alcohol for germinal tissue—Innate degeneracy versus the effects of alcohol—Experimental alcoholismin lower animals—Further remarks on the situation in man—Much inebriety in man due to defective nervous constitution—Factors to be reckoned within the study of alcoholism—Venereal diseases—The seriousness of the situation—Infantile blindness—Syphilis—Some of the effects—A bloodtest—Many syphilitics married—Why permit existing conditions to continue?—Ante-nuptial medical inspection—The perils of venereal diseasemust be prevented at any cost—Bad environment can wreck good germ-plasm. | ||
| [VII] | Responsibility for Conduct | [195] |
| All mental process accompanied by neural process—Gradations in nervous response from lower organisms to man—Behavior of manyanimals often an automatic adjustment to simple external agents—Tropisms—Certain apparently complex volitions probably only tropisms—Complicatingfactors—Many tropic responses apparently purposeful—Tropisms grade into reflex actions and instincts—Adjustability of instinctsopens the way for intelligent behavior—Modification of habits possible in lower animals—Some lower vertebrates profit byexperience—Rational behavior—Conceptual thought probably an outgrowth of simpler psychic states—The capacity for alternative actionin higher animals—The elemental units of the nervous system are the same in lower and higher animals—Neuron theory—Establishmentof pathways through the nervous system—Characteristic arrangements of nerve cells subject to inheritance—Different parts of the cortexyield different reactions—Skill acquired in one branch of learning probably not transferred to another branch—Preponderance of cortex inhighest animals—Special fiber tracts in the spinal cord of man and higher apes—Great complexity in associations and more neuronsin the brain of man—The nervous system in the main already staged at the time of birth—Many pathways of conduction not yet established—Theextent of the modifiable zone unknown—Various possibilities of reaction in the child—Probable origin of altruistic human conduct—Trainingin motive necessary—Actual practise in carrying out projects important—Interest and difficulty both essential—The realizationof certain possibilities of the germ rather than others is subject to control—We must afford the opportunity and provide the properstimuli for the development of good traits—Moral responsibility. | ||
| [VIII] | Mental and Nervous Defects | [228] |
| Prevalence of insanity—Imperfect adjustments of the brain mechanism inheritable—Many mental defectivesmarried—Disproportionate increase in number of mental defectives—Protests voiced by alienists—Examples of hereditary feeble-mindedness—Difficultto secure accurate data—Feeble-mindedness and insanity not the same—Many types of insanity—Not all insanities of the same eugenicalsignificance—Difficulties of getting genealogies of specific forms of insanity—Certain forms of insanity seem to behave as Mendelian recessives—Gradesof feeble-mindedness—About two-thirds of feeble-mindedness inherited—Some results of non-restraint of the feeble-minded—Not allcases of mental deficiency inherited—Epileptics—Feeble-mindedness probably a recessive—Many apparently normal people are carriers ofneuropathic defects—Tests for mental deficiency—The backward child in school—The exceptionally able child—Cost of caring for ourmentally disordered—Importance of rigid segregation of the feeble-minded—Importance of early diagnosis of insanity—Opinion of competentpsychiatrists essential—Some insanities not hereditary—Importance of heredity in insanity not appreciated. | ||
| [IX] | Crime and Delinquency | [263] |
| Heredity and environment in this field—Feeble-mindedness often a factor—Many delinquent girls mentallydeficient—Institutional figures misleading—Many prisoners mentally subnormal—Inhibitions necessary to social welfare—The high-grade morona difficult problem—Degenerate strains—Intensification of defects by inbreeding—Vicious surroundings not a sufficient explanation in degeneratestocks—Not all delinquents defectives—No special inheritable crime-factor—What is a born criminal?—Epileptic criminal especially dangerous—Themental disorders most frequently associated with crime—Bearing of immigration on crime and delinquency—Sexual vice—School instructionin sex-hygiene—Mere knowledge not the crux of the sex problem—Early training in self-restraint an important preventive of crimeand delinquency—Multiplication of delinquent defectives must be prevented. | ||
| [X] | Race Betterment Through Heredity | [289] |
| Questionable charity—Past protests—An increasing flood of defectives—Natural elimination of defectivesdone away with—Why not prevent our social maladies?—Eugenics defined—Improved environment alone will not cure racial degeneracy—Heredityand environment—Inter-racial marriage—Human conservation—Kindness in the long run—The problem has two phases—Constructive eugenics must bebased on education—Inferior increasing more rapidly than superior stocks—An unselected population may contain much valuable material—Thelack of criteria for judging fitness—The college graduate—Native ability, independence and energy eugenically desirable—Four childrento each marriage required to maintain a stock—Factors contributing to low birth-rate in desirable strains—The educated public mustbe made to realize the situation—Utilization of family pride as a basis for constructive eugenics—The tendency for like to marry like—Publicopinion as an incentive to action—Choosing a marriage mate means choosing a parent—The best eugenic marriage also a lovematch—The elimination of the grossly unfit urgent—Suggested remedies—Inefficacy of laws which forbid marriage of mental defectives—Systemsof mating impracticable in the main—Corrective mating presupposes knowledge of eugenics—Segregation has many advocates—Sterilizationas a eugenic measure—To what conditions applicable—In insanity—In feeble-mindedness—In cases of epilepsy—Sterilizationlaws—Social dangers in vasectomy—Our present knowledge insufficient—Sterilization laws on trial—An educated public sentiment themost valuable eugenic agent—The question of personal liberty—Education of women in eugenics needed—Much yet to be done—A workingprogram—Which shall it be? | ||
| Glossary | [343] | |
| References for Further Reading and Study | [355] | |
| Index | [361] |
BEING WELL-BORN
CHAPTER I
HEREDITY
It is a commonplace fact that offspring tend to resemble their parents. So commonplace, indeed, that few stop to wonder at it. No one misunderstands us when we say that such and such a young man is “a chip off the old block,” for that is simply an emphatic way of stating that he resembles one or the other of his parents. The same is true of such familiar expressions as “what’s bred in the bone,” “blood will tell,” and kindred catch phrases. All are but recognitions of the same common fact that offspring exhibit various characteristics similar to those of their progenitors.
Blood Heritage.—To this phenomenon of resemblance in successive generations based on ancestry the term heredity is applied. In man, for instance, there is a marked tendency toward the reappearance in offspring of structures, habits, features, and even personal mannerisms, minute physical defects, and intimate mental peculiarities like those possessed by their parents or more remote forebears. These personal characteristics based on descent from a common source are what we may call the blood heritage of the child to discriminate it from a wholly different kind of inheritance, namely, the passing on from one generation to the next of such material things as personal property or real estate.