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YOU and HERE DTT Y

by AMRAM SCHEINFELD

assisted in the genetic sections by MO RONG Deis GriW HIER) Ph.D:

RESEARCH GENETICIST, CORNELL UNIVERSITY MEDICAL COLLEGE

PLEUS ERATE DEBBY. TinE AU THOR

With four color-plates and seventy-five draw- ings, maps and diagrams

Including an original study of The Inheritance of Musical Talent cite

ey NENTS AY pat ge Oo]

GARDEN CITY PUBLISHING CO, INC. Garden City, New York Bp y |

a fi}

CopPpyYRIGHT, 1939, BY AMRAM SCHEINFELD

All rights reserved. No part of this work may be reproduced without the written permission of the publishers.

H \/ JI3dO S

we, |

To MY FATHER AND

THE MEMORY OF

MY MOTHER

GarDEN City Pus.isHiNnc Co. Reprint Edition, 1945, by special arrangement with J. B. LIPPINCOTT Co.

Gh Ga \ 2 Printed in the United States of America

/

PREFACE

Mosr books on scientific subjects addressed to the general public are written from the inside looking out—that is to say, from the viewpoint of the scientist looking out, and not infrequently down, to the reader.

This book is written from the outside looking in—from the view- point of a layman peering into the laboratories of the scientists (in this case those concerned with the study of human heredity) and reporting back to others what he has seen, heard and learned.

The two viewpoints differ in many respects, and especially is this true of the subject here dealt with. The scientist studying heredity is preoccupied chiefly with the processes by which the findings in his field were achieved and which pave the way for future discoveries. When, and if, he stops to consider the practical aspects of his science in relation to human life, he is inclined to think in terms of broad averages, of large masses and many gen- erations, and of individuals as mere fragments in a limitless mosaic.

But the layman is interested primarily in himself and in the im- mediate application of the scientific findings to his own life and to his own little world which will come to an end when he passes on.

The difference in viewpoints underlies the motivation and, I hope, the justification for this book. Had any scientist made easily available to me all the facts about human heredity which I wished to know, and which many years of writing for the general public have taught me that others wish to know, this book would never have been written, nor should I have had the temerity to think of writing it. When I began my study of the subject, it was solely with the practical purpose of utilizing some facts about human heredity in a projected work of fiction. Before very long I discovered that the findings in this field so completely shattered my own precon- ceived notions and the ideas held by all but an initiated few, as to

obliterate my original plans. I became convinced that the most in- Vii

Vili PREFACE

teresting and important task before me was to acquire as thorough a knowledge of this subject as I could and then, in some way, to communicate what I had learned to others.

The subsequent steps included my enrolment (at a mature age; for a college course in genetics and the setting aside of all other activity for several years to devote myself to further study and re- search. The first fruits came with a series of articles on human heredity which I wrote for a popular magazine. These proved to my own satisfaction that the subject could be expounded to laymen without putting them through the technical mazes of meiosis and mitosis, the formation of spindle fibers and polar bodies, of linkage, cross-over, nondisjunction of chromosomes, tetraploidy, etc., all con- sidered essentials in almost every college course and treatise’ on genetics.

From the articles grew the plan for a book, but even when the contract for it was signed with my publishers, nothing like the present work was contemplated. That it did grow to its present proportions was due to many factors, not the least of which was the quite unexpected aid and encouragement given it by the very scientists and other authorities who, I had feared, would look askance at such a project undertaken by one outside their fold.

Thus, well aware that a layman writing on a scientific subject must, like Caesar’s wife, be~or try to be—above suspicion, I am heartened by the thought that in every phase of this book I have had expert counsel and guidance, and that, as a happy consequence, my acknowledgments of indebtedness are many.

In my toddling steps I was aided by Dr. Henry J. Fry of the New School For Social Research. Later, as the necessity for an ac- tive scientific associate grew imperative, through the friendly offices of Prof. Donald C. Lancefield, then of Columbia University and now of Queens College, I was brought in touch with Dr. Morton D. Schweitzer of the Cornell University Medical College.

Dr. Schweitzer’s participation in this enterprise proved one of the happiest events that could have befallen it. To him fell the task of gathering most of the material for the chapters dealing with hereditary diseases and defects, and of preparing the data for the extensive “black” gene lists; of working out genetic ratios for the

PREFACE ix

various “forecast” tables and other parts involving genetic pre- dictions; and in general, of casting a trained eye over all the facts and statements in the book coming within the scope of his knowl- edge as a geneticist. I can say unreservedly that without his en- thusiastic cooperation, painstaking research and meticulous editing, this book would have fallen short of such scientific validity as it may now possess.

Because human genetics is correlated with all other sciences deal: ing with human beings, it was necessary to seek further for in- formation and counsel from physicians, sociologists, psychologists, anthropologists and various other experts. This aid was so gra- ciously and generously given wherever sought that every part of this book can be said to have had the benefit in its preparation of careful reading, discussion, criticism or editing by some qualified expert. With both pride and gratitude I therefore acknowledge my great indebtedness to the following:

Prof. Lancefield, for reading all the first twenty chapters; Dr. George W. Henry, Associate Professor of Psychiatry at Cornell University Medical College, for reading and discussing “Sick Minds,” “The Twilight Sexes” and “Sexual Behavior”; Dr. Walter Bromberg, Senior Psychiatrist, Bellevue Psychiatric Hospital, and Psychiatrist of the New York Criminal Courts, for editing the afore- mentioned three chapters and “Enter the Villain”; Dr. Alfred J. Lotka, of the Metropolitan Life Insurance Company, for editing and aiding, with members of his staff, in the preparation of charts for “How Long Will You Live?”, and to Prof. Ray- mond Pearl, of Johns Hopkins University, for reading and dis- cussing that chapter; Dr. Dwight F. Chapman, of the Department of Psychology, Columbia University, for helpful criticisms and sug- gestions regarding “The Battle of the IQ’s” and “Personality”; Prof. Carl E. Seashore, of the University of Iowa, for reading “Musical Talent” and giving pertinent advice regarding the original study presented therein; Dr. Gene Weltfish, of the Department of An- thropology, Columbia University, for her suggestions regarding “Race” and her invaluable aid in the preparation of maps for that chapter; and to Frederick Osborn, Associate in Anthropology, American Museum of Natural History, for reading and discussing

x PREFACE “Ancestry,” “The Giddy Stork,” “Eugenics: Negative” and “Pro-

gram for Tomorrow.”

(In all of these acknowledgments no responsibility is implied on the part of the individuals named for any errors of fact or judgment that may still have survived in the text. The responsibility for any failings of commission or omission, or for any opinions expressed in this book, I accept fully as my own.)

On behalf of Dr. Schweitzer, as well as on my behalf, thanks are extended to the following who discussed with him special phases of disease inheritance: Dr. James Ewing, Director of the Memorial Hospital for the Treatment of Cancer; Dr. May Wilson, Associate Professor of Pediatrics at Cornell University Medical College (child- hood rheumatism); Dr. Eugene Opie, Professor of Pathology at Cornell (tuberculosis); and also to Drs. William Schmidt, Harold Aaron, Emanuel Klein, Nathan Kaliss and Emil Smith.

Overseas our thanks go to Prof. J. B. S. Haldane of the University of London who, in editing this book for British publication, made many important suggestions by which we have profited. For several other corrections we may thank Prof. S. J. Holmes of the University of California.

For discussion of problems relating to intelligence I am indebted to Prof. Gertrude H. Hildreth of Teachers College, Columbia University; Dr. Beth L. Wellman of the University of Iowa; Dr. Donah B. Lithauer, Psychologist of the Hebrew Orphan Asylum, New York; and Dr. I. Newton Kugelmass.

Special thanks, which I am sure will be echoed by all music lovers, are due to the scores of musicians and singers who con- tributed data for the study of the Inheritance of Musical Talent, to their concert managements and personal representatives who aided in enlisting their cooperation, and to Ernest Hutcheson, President of the Juilliard Institute; also, for the auxiliary study of Voice Types, to Miss Rose Held and members of the Schola Cantorum.

To Prof. Gregory G. Pincus and to the Anatomical Record I am indebted for permission to reproduce the photograph of the human ovum; to Dr. Seymour F. Wilhelm, of Beth Israel and Montefiore Hospitals, New York City, for the slide from which the spermato- zoa photograph was made; to Prof. Lewis M. Terman of Stanford University and to the McGraw-Hill Company, for permission to

PREFACE xi

use material from “Sex and Personality”; and to the Macmillan Company for permission to quote from “Human Heredity,” by Baur, Fischer and Lenz.

My memory has undoubtedly failed me with regard to others who have been of great help. Also, while I do not name them, mem- bers of my family and many friends know how deep is my grati- tude for innumerable services and considerate acts which con- tributed toward the production of this book.

Finally, I wish to acknowledge my debt to all the many geneti- cists, scientists and research workers from whose painstaking studies I have gleaned, and in the conveyance of whose findings my role has been merely that of a reporter. It is my hope that the indebtedness will be repaid in some measure by. such added in- terest as this book may stimulate in their work.

To acknowledge my great debt to my publishers would be superfluous, for the make-up of this book itself will speak for their faith in this enterprise and the unlimited support and encourage-

ment which they gave it. AMRAM SCHEINFELD

New York City, June 1, 1939.

Ristty! n é a4 \ esas ¥ Se pach of

As . i} Pie tate

wy u?

CHAPTER

II. III.

IV.

VI. VII. VIIl.

IX.

XI. XII. XIII. XIV. xv. XVI. XVII. XVIII. XIX. XX. XXI. XXII. XXIII. XXIV.

XXV.

CONTENTS

PREFACE

- A NEW SCIENCE .

LIFE BEGINS AT ZERO

THE ETERNAL GERM-PLASM WHAT WE “DON’T”? INHERIT MYTHS OF MATING

THE MIRACLE OF “YOU” . THE PERILOUS ROAD TO BIRTH “BOY OR GIRL?”

SUPER CHAIN-GANGS .

PEAS, FLIES AND PEOPLE .

EYE COLOR . : n : *

HAIR COLOR SKIN COLOR : é . THE FEATURES

BODY FORM AND STRUCTURE

WHAT WILL YOUR CHILD LOOK LIKE?

WHAT MAKES US TICK DUPLICATED HUMANS THE DIONNES

THE “BLACK” GENES . OUR PRINCIPAL ENEMIES . FOR MEN ONLY . STRUCTURAL DEFECTS SICK MINDS

HOW LONG WILL YOU LIVE?

Xili

PAGE Vil

II 17 22 27 3 I 37 44 49

55 62

70 80

97

oe 107 114 119g 130 130 150

158

XIV

CHAPTER XXVI. XXVII. XXVIII. XXIX. XXX. XXXI. XXXII. XXXIII. XXXIV. XXXV. XXXVI. XXXVII. XXXVIII. XXXIX. XL. STs XLII.

XLIII.

CONTENTS

THE TWILIGHT SEXES “BLACK” GENE ROLL-CALL

HOW DO YOU KNOW THE BABY’S YOURS? ACHIEVEMENT: BIRTH OR LUCK?

THE BATTLE OF THE “IQ's”

MUSICAL TALENT: PART I

MUSICAL TALENT: PART II

FROM APTITUDE TO GENIUS

PERSONALITY) soe Iho sn ae

ENTER THE VILLAIN .

SEXUAL BEHAVIOR

EVOLUTION: CHICKEN OR EGGP

RACE (2s oR epee ask @ Bane Ver: ANCESTRY) 5" ntect ited Reanim Pala eat in THE ‘GIDDY (STORK its ae ee EUGENICS: NEGATIVE APA Cg PROGRAM FOR TOMORROW . .. YOU ‘AND: HEREDITY 12 7) eee yk tee APPENDIX eMedia stu sics kloan CM a een

INDEX . . . ° ° ¢ e e

PAGE 172

184 205 214 Stig a 256 279 289 300 BEL oa) 335 255, 366

373

396 409 423

LIST OF ILLUSTRATIONS

Parents and offspring (color plate). . . . . Frontispiece

The human egg and human sperms (from a photograph) facing

The homunculus

Fertilization i Hee

Human dhiearmeree as hey radi nck if Ait it in pairs

Human chromosomes, as they look under the microscope

Genes, or section of chromosome

The heredity process

How a fertilized egg-cell aan

How sperms are produced .

Compatibility in mating

F ingers representing chromosomes .

“Finger” chromosomes in combinations .

Conception

Fertilized human egg (eee)

Relationship between mother and ide

How sex is determined

Our “chain-gangs” (chromosomes and genes)

One of Mendel’s experiments with peas .

Diagram of the eye

What makes your eye color Ge plate) uirict paindeeeny What makes your hair color (color plate) . . . facing esin, color (color plate) . genie eimirey joao) Yl facing

How the “nose-bridge” gene works . Nose-shapes, “dominance” and “recessiveness” “Eye-shape” genes . “Hairdresser” genes Head shapes

PAGE

4 5 6 6 7 8

10 12 14 25 28 ay 32 33 34 40 46 50 56 56 62 68 72 2B 75

77 83

XVi LIST OF ILLUSTRATIONS

The laws of. chance

Homely parents: beautiful child. Eanes Parente Herel

child . How twins are produced Mirror-imaging How triplets may be precited” The Dionne quintuplets (diagram) . How the Dionne quintuplets were ed ced Tuberculosis and environment . “Sex-linked” inheritance Pattern baldness How baldness is inherited . The ductless glands Hand abnormalities Negro albinos (from a photograph) The human life span As incomes drop, deaths of Rabie rise Death and occupations . Females live longer! Oddities in sex How a gynandromorph may ae poner Human intersexes . “Black” gene symbols (Key to “Black” Gene Tables) Your blood type ; IQ’s of children in relavion't to father’ s status . IQ differences in twins, unrelated children, etc. . Kirsten Flagstad’s musical pedigree . The Toscanini family (diagram) How musical talent may be inherited Talent results from various matings

facing

The late Leopold Auer (from a sketch by the nisthor) bane Heredity or training? Samuel Reshevsky, chess champion

(from a photograph) es The Dionnes (from a photograph) . Homicides—United States and other countries

facing facing

PAGE

89 96

101 104 106 108 110 127 132 134 136 140 142 146 160 164 166 168 175 177 179 187 207 221 225 261 267 268 269 278

284 298 302

Lust OF TLEUS TRATIONS XV

PAGE

Raine “Map OritierWiited later ys a gure y tes) had Masculine and feminine characteristics (table) . . beats The “ink-blot” tests for “masculinity” and “femininity” . . 313 “Masculinity” and “femininity” in men and women by occu- Patlons aye. A aH Nh REAR AGRA 9) NITE Sex characteristics in fesike Sa ig ACA, MOR RE i ae i a be 22 MCD Caincetiist’ Chickenlomer otro Mimrti le) pune lama eee 2b) SiierCVOLOLION OL Inala OPO pine Mmm nt, hy ide ee amanaceh 2a0 he orci of races.( map yo... 0D A) Sp Rae ae AA The melting pots of Europe (series of Tee) . 344 Birth, American: Culture, Chinese (from a Bho aay facing 354 Oldiconceptopancesttvagn cer ape Wanna gars Hire by ital cite OR The Kallikak family tree... sla lay: cada Mri Ba The birth-rate “differential” aran\is SEE, ae RARNY henge 200 Wittstemication comadraccomplish yin tal vol Glo mensiwnoen Wih 870

Dest toler traits iy AVOMeTENae HU CR Vite, PW men ee Ale ME sey

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ee ee Wr aes oe

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CHAPTER I A NEW SCIENCE

Srop and think about yourself:

In all the history of the world there was never any one else exactly like you, and in all the infinity of time to come there will never be another.

Whether or not you attach any importance to that fact, undoubt- edly you have often wondered what made you what you are; what it was that you got from your parents and your ancestors and how much of you resulted from your own efforts or the effects of en- vironment; and finally, what of yourself you could pass on to your children.

Until comparatively recently, all this was a matter of theory and speculation. Not until the dawn of this century was anything definitely established about the mechanism of heredity, and for some years thereafter the most important points were bandied about like footballs among the biologists. Then, dramatically climaxing a series of some of the most remarkable experiments in all scientific history, the whole field of genetics (the study of heredity and variation among living things) became brilliantly illumined, and what had been theory became fact.

With American geneticists, led by the Nobel Prize winner, ~ Thomas Hunt Morgan, in the vanguard, the work has been pro- ceeding on many broad fronts throughout the world. New data are - pouring in with increasing volume from geneticists, pathologists, and other scientists. Experiments are repeated countless times, state- ments checked and rechecked. If the reader is inclined to be skeptical regarding some of the conclusions, let him be advised that no greater skeptics can be found than the geneticists themselves. Their rigid determination to take nothing for granted, and to

subject the reports of even their most brilliant colleagues to the I

2 YOU AND HEREDITY

severest tests, has made genetics one of the most exact of all biologi- cal sciences.

Thus it can be said with assurance that the mechanism of heredity—among humans as among other living and growing things—now stands clearly revealed. While all of its intricacies are by no means laid bare, the basic principles are as unmistakably clear as the workings of a watch. Problems of heredity that con- founded the greatest thinkers and scientists of the past, from Aristotle to Darwin, have been solved. Long-standing mysteries about birth and development have been unraveled. Endless popular beliefs, theories and superstitions have been completely discredited. Existing social philosophies have been called into question and the way pointed to a reconstruction of humanity itself.

And yet, vitally important as all this is, very little of it has so far seeped through to the general public. If nobody believes in the stork any more, it is astonishing what people still do believe about heredity. The fault, however, is not that of the layman. Develop- ments in the field of genetics have been too rapid and recent to reach widespread circulation, and most of the published reports have been of so technical a nature as to have little appeal for the average reader. Even where isolated phases of the subject are popu- larly treated in newspapers and magazines, the layman is generally left confused through lack of sufficient understanding of the basic principles.

So we come to the purpose of this book, which is:

1. To sift out from the genetics laboratories and research fields the outstanding facts about heredity directly applicable to human beings.

2. To present these facts in clear-cut, untechnical language, dia- grams and illustrations.

3. To point out what their significance may be to the individual . and to society, leaving the reader to draw his own conclusions.

The steps and processes by which these findings were arrived at will be largely omitted. It is assumed that you, the reader, do not care two raps about the love life of sea urchins or about the inter- action of hereditary factors for coat colors in mice, or what happens when a yellow-bodied Drosophila melanogaster (fruit-fly) with

A NEW SCIENCE 3

double-bar eyes and vestigial wings is crossed with a gray-bodied, long-winged, normal red-eyed one. True, without laborious study of these lowlier creatures the geneticists could never have arrived at the facts about human beings, for not the least of their amazing discoveries has been that the mechanism of heredity is almost the same in all living things.

Nevertheless, the facts about the laboratory creatures can wait. What you probably wish to know, as directly as possible, are the answers to the innumerable questions about your own heredity and that of your fellow humans. These questions we hope have been anticipated and answered in the following pages.

The fact has not been overlooked that many readers may already know more or less about the subject of heredity; but for the sake of the many others to whom this is all quite new, it is our plan to presuppose no previous knowledge whatsoever. And so, in the vernacular, we are going to start from “scratch.”

CHAPTER II

LIFE BEGINS AT ZERO

A sperm and an egg: You, like every other human being and most other animals, began life as just that.

A single sperm enters a single egg and a new individual: is started on its way.

Leaving aside for the present the part played by the ie we know that a father’s rdle in his child’s heredity is fixed the moment that it is conceived. Whatever it is that the father passes on to his child must be contained within that single sperm.

But to find out exactly what that sperm contains has not been so simple a matter.

Consider, first, its size:

One hundred million sperms may be present in a single drop of seminal fluid. Two billion sperms—two thousand million, as many as were needed to father all the people in the world today— could be comfortably housed in the cap of a small-sized tube of toothpaste!

The microscope had to be well perfected before a sperm could be even seen. Then, in the first flush of discovery, carried away by their desire to believe, just as children and lovers imagine that they see a man in the moon, some scientists (circa 1700 a.D.) reported excitedly that every sperm contained a tiny embryonic being. With professional gravity they gave it the name of “homunculus” (little man), and scientific papers appeared showing careful drawings of the little being in the sperm—although there was some dispute as to whether it had its arms folded or pressed against its side, and whether or not its head had any features.

Presently, however, it became apparent that imagination had run away with scientific perspicacity. The head of the sperm—in which interest rightfully centered, as the tail was merely a means for

4

Photographed from a slide prepared by Dr. Seymour F. Wilhelm.

Magnification about Behe same as egg above, showing rela- tive size of a single sperm compared with the humanegg.

THE HUMAN EGG

HUMAN SPERMS

A two-day old un- fertilized human ovum, photograph- ed by Dr. Gregory G. Pincus.

Magnification and enlargement about 600 diameters, or millions of times by volume.

The black spot at

upper center is the region of the nu- cleus.

LIFE BEGINS AT ZERO 5

propelling it—proved to be a solid little mass that defied all attempts at detailed study. Even the great Darwin, who was so right about many things, could never more than guess at what the sperm head. _comprised—and his guess was a. wrong one. Many scientists thought it was hopeless to try to find out. Others concluded that if the

sperm head itself could never be dissected and its contents exam- ined, they might still find out what it carried if they could learn what happened after it entered the egg. And in this they were right.

Crowning years of painstak- ing study, we know at last that what a human sperm carries— the precious load that it fights so desperately to deliver—are twenty-four minute things called chromosomes.

When the sperm enters the

egg, and penetrates its substance, the head begins to unfold and reveal itself as having been made up of the twenty-four closely packed chromosomes. As they represent everything that enters the egg, we know beyond any doubt that these chromo-

“CRANIAL

“UMBILICAL CORD”

A)

THE HOMUNCULUS (or Manikin) which early scientists believed was contained in the sperm.

After drawings by (a) Hartsoeker—1694 (b) Dalempatius—1699

somes must comprise all the hereditary material contributed by the

father.

What of the egg? Although many thousands of times larger than the sperm, the egg is yet smaller than a period on this page, barely visible to the naked eye. Under the microscope we see that it consists largely of foodstuffs with the exception of a tiny globule, or nucleus. What that contains we see when the sperm head enters the egg and releases its chromosomes. Almost at the Same time, the egg nucleus breaks up and releases tts twenty-four

6 YOU AND HEREDITY

similar chromosomes—the contribution ofthe mother to the child’s

heredity. eee @ = > NUCLEUS FERTILIZATION (A) Sperm-head enters egg (B) Sperm-head and nucleus

of egg each release their chromosomes.

Thus, the new individual is started off with forty-eight chromo- somes.

In order to reveal the otherwise colorless chromosomes special dyes have to be applied. When this is done, they appear as colored bodies. Hence their name “chromosomes” (color-bodies).

But almost immediately another remarkable fact becomes ap- parent. We find that the chromosomes are of twenty-four different kinds as to shape, size, etc., with one of each kind contributed

by each parent. If we could arrange all the pairs in a line they would look like this:

KARUCDALAVOHHOGREHD OM

ABCDEFGHIJKLMNOPQRSTUVWHH

How human chromosomes would look if arranged in pairs.

These forty-eight chromosomes comprised all the physical heritage with which you began your life.

By a process of division and redivision, as we shall see in detail later, these initial forty-eight chromosomes are so multiplied that

LIFE BEGINS AT ZERO nile (7

eventually every cell in the body contains an exact replica of each and every one of them. This is not mere theory. If you were will- ing to lend yourself to a bit of dissection, an expert could: take some of your own cells and show you the chromosomes in them looking just about like those pictured here.

As we viewed them up to this point, the chromosomes are in their compressed form. But at certain times they may stretch out into filaments ever so much longer, and then we find that what they consist of appar- ently are many gelatinous beads closely strung together.

These beads either are, in themselves, or contain the paves wandstt ts-the genes which, so far as science can now establish, are the ultt- mate factors of heredity. Un- der the most powerful mag- nification, differences are ap- parent among these chromo- some sections in size, depth of shading, and patterns of striping. But whether or not differences are revealed to the eye, we know beyond any question that each gene has a definite function in the creation and develop- ment of the individual.

Of all the miraculous particles in the universe, one can hardly conceive of anything more amazing than these infinitesimally tiny units. We say again “infinitesimally tiny” for want of another. and better expression. Think of the microscopic size of a sperm. Then recall that the head of a sperm alone contains twenty-four chromo- somes. And now consider that strung in a single chromosome might be anywhere from scores to hundreds of genes—with a single gene, in some cases, able to change the whole life of an’ indi- vidual! |

To grasp all this you must prepare yourself for a world’ in

HUMAN CHROMOSOMES

As they look under the microscope.

8 YOU AND HEREDITY

which minuteness is carried to infinity. Contemplating the heavens, you already may have adjusted yourself to the idea of an infinity of bigness. You can readily believe that the sun is millions of miles away, that stars, mere specks of light, may be many times larger than the earth; that the light from a star which burned up six thousand years ago, is reaching us only now; that there are bil- lions of stars in the space beyond space which our most power-

THE GENES

A. Section of a chromosome Cy stretched out. The beads are & the genes or contain the ‘SS genes. ‘2 S O | 4 C. The whole string, or chromosome, | B. The same section much compressed | with the genes and dyed, as it | drawn together. looks under the |

microscope.

ful telescopes cannot yet reveal. This is the infinity of bigness out- side of you.

Now turn to the world inside of you. Here there is an infinity of smallness. As we trace further and further inward we-come to the last units of life that we can distinguish—the genes. And here with our limited microscopes, we must stop, just as we are stopped in our exploration of the stars by the limitations of our telescopes. But we can make some pretty good guesses about what the genes are from what we already know about what they can do.

You believe the astronomer when he tells you that, on October 26, in the year 2144, at thirty-four minutes.and twelve seconds past twelve o’clock noon there will be a total eclipse of the sun. You believe this because time and again the predictions have come true.

LIFE BEGINS AT ZERO 9

You must now likewise prepare yourself to believe the geneticist when he tells you that a specific gene, which cannot yet be seen, will nevertheless at such and such a time do such and such things and create such and such effects—under certain specified condi- tions. The geneticist must make many more reservations than the astronomer, for genetics as a science is but a day-old infant com- pared to astronomy, and the genes are living substances whose action is complicated by innumerable factors. But despite all this, so much has already been established about our gene workings that we must stand in greater awe than ever at this latest revelation of how fearfully and wonderfully we are made.

THE HEREDITY PROCESS

EVERY MAN and EVERY WOMAN At conception received 24 Chromosomes from Each parent

or 48 in all 22 In mating ~ “4 Each passes —I on half OA \ Poea ixelrantres eye Te er, her J j a chromosomes d ait aGs f ay , Be) axe IW We —> —7 <—— Cat Q vay |

The FATHER'S role 24 (24 —The MOTHER,

is merely that of SPs Wy although she also

passing on half eS Ye) acts as incubator otf his Chromosomes AN a, and nourisher for 4

by way of a les vy : the egg .con- cola “| These 48 chromo.[) SIVuSe> Re mores somes comprise co the child =

heredity than ackareninea tee | doce ne Father heredity of the child

CHAPTER III

THE ETERNAL GERM-PLASM

No less important than knowing what heredity is, is knowing what it zs not. Before we examine the chromosomes and their genes in detail, let us first find out how the sperms or eggs which carry them are produced in the parent. That in itself will clear away much of the deadwood of the past with innumerable false theories, beliefs and superstitions about the life processes.

Not so long ago the most learned of scientists believed that whatever it was that the sperms or eggs contained, these were products of the individual, in which were incorporated in some way extracts of themselves. That is to say, that each organ or part of a person’s body contributed something to the sperm or egg. Darwin, a proponent of that theory, called these somethings “gem- mules.” |

By the “gemmule” theory, all the characteristics of both parents could be transmitted to the child, to be blended in some mysteri- ous way within the egg and reproduced during development. A child would therefore be the result of what its parents were at the time it was conceived. As the parents changed through life, so would their eggs or sperms, and the chromosomes in them, also change. All that is what scientists believed not so long ago, and what the vast majority of people today still believe—erroneously.

The theory that sperms or eggs change as the individual changes has now been upset. Because we have learned finally that the chromosomes which they contain are not new products of the in- dividual and are most certainly not made up of “gemmules” or contributions from the various parts of the body.

As we have seen, a human being starts life as just a single cell containing forty-eight chromosomes. That initial cell must be

multiplied countless times to produce a fully developed person, If

12 YY O°U ASN(D2 EE REE Diletta

HOW A FERTILIZED EGC-CELL MULTIPLIES ) oP

(1) Original cell. (Only four (2) Each chromosome splits in chromosomes shown, for sim- half, lengthwise plification )

» ZO)\GO

(3) The halved chromosomes go » (4) The halved chromosomes to opposite sides and wall grow to full size, resulting in forms between them as cell two cells, each a replica of begins to divide the original

and this is accomplished by a process of division and redivision, as shown in the accompanying illustration.

Continuing in the same way, the two cells become four, the four eight, and this goes on into the billions—the material with which to make the cells, after that in the egg is exhausted, coming from the mother.

But the cells do not all remain the same, by any means. After the earliest stages, when they are still very limited in number, they begin “specializing.” Some give rise to muscle cells, some to skin, blood, brain, bone and other cells, to form different parts’ of the body. But a certain number of cells remain aloof.

They take no part in building the body proper, and at all odds

ee eee ee ee ee

THE ETERNAL GERM-PLASM 13

preserve their chromosomes unchanged and unaffected by any- thing that happens outside of them—short of death itself.

These “reserve” cells are the germ cells, dedicated to posterity. It ts from these cells that the sperms or eggs are derived.

When a boy is born, he already has in his testes all the germ cells out of which sperms will eventually be produced. When he reaches puberty, a process is inaugurated that will continue throughout his life—or most of his life, at any rate. In the same way that billions of cells grew from one, millions of more germ cells are manufactured from time to time by division and re division. Up to a certain point the process is the same as that pre. viously explained—but just before the sperms themselves are to be formed, something different occurs. The chromosomes in the germ cell remain intact and the cell merely splits in half, each half getting only twenty-four chromosomes, or one of every pair.