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HUMAN  BIOLOGY 

AND 

RACIAL  WELFARE 


C    i 


HUMAN  BIOLOGY 

AND 

RACIAL  WELFARE 


WALTER  B.  CANNON 
ALEXIS  CARREL 
EDMUND  V.  COWDRY 
EDWIN  GRANT  CONKLIN 
CHARLES  B    DAVENPORT 
JOHN  DEWEY 
HAVEN  EMERSON 
JOHN  F.  FULTON 
WILLIAM  KING  GREGORY 


Contributors 

WILLIAM  HEALY 
ALES  HRDLICKA 
ELLSWORTH  HUNTINGTON 
PAUL  A.   LEWIS 
ARCHIBALD  B.  MACALLUM 
ELMER  V.  McCOLLUM 
ROBERT  A.  MILLIKAN 
GEORGE  H.  PARKER 
HARRY  A.  OVERSTREET 


RAYMOND  PEARL 
EARLE  B.  PHELPS 
SIR  HUMPHRY  ROLLESTON 
HENRY  NORRIS  RUSSELL 
SIR  CHAS.  S.  SHERRINGTON 
WILLIAM  M.  WHEELER 
CLARK  WISSLER 
ROBERT  M.  YERKES 
HANS  ZINSSER 


Edited  by 

EDMUND  V.  COWDRY 

Professor  of  Cytology,  Washington  University,  St.  Louis 
WITH  AN  INTRODUCTION  BY 

EDWIN  R.  EMBREE 


SECOND  PRINTING 


PAUL  B  '  HOEBER  -  I^ 


NEW  YORK 


MCMXXX 


Copyright,  1930,  By  Paul  B.  Hoeber,  Inc. 
All  Rights  Reserved 


Published  February,  1930 
Reprinted  October,   1930 


Printed  in  the  United  States  of  America 


PREFACE 

Each  one  of  us  feels  in  his  own  experience  an  insistent 
urge  to  speciahze  in  order  that  he  may  do,  not  a  variety  of 
things,  but  a  few  things  better  and  more  quickly.  He  must 
swim  with  the  stream  or  he  will  not  survive.  It  is  true  in 
business  as  in  science.  In  one  way  this  concentration  is 
good,  and  in  another  it  is  bad.  It  is  good  since  it  is  the 
essence  of  progress  which  makes  the  world  a  better  place 
to  hve  in,  but  the  individual  suffers.  The  more  successful 
he  is  as  a  specialist,  the  more  difficult  it  is  for  him  to  avoid 
becoming  narrow-minded.  Because  he  does  not  understand 
the  hopes  and  aspirations  of  others  he  may  also  become 
intolerant.  He  may  adopt  a  condescending  attitude  toward 
his  fellows  whom  he  regards  as  less  favored. 

The  situation  has  not  been  helped  by  the  action  of  edu- 
cators in  permitting  speciaHzation  very  early  in  the  curricu- 
lum before  the  students  can  secure  a  broad  grasp  of  the 
problems  of  human  hfe  and  of  the  methods  of  attacking 
them.  Indeed  it  grows  worse  because  through  speciaHzation, 
advances  in  the  sciences  deahng  with  man  have  been  so 
phenomenal  that  each  has  come  almost  to  speak  in  a  lan- 
guage of  its  own  which  is  difficult  to  understand  without 
much  prehminary  study.  Thus,  barriers  are  erected  which 
prevent  breadth  of  view  and  which  breed  intolerance.  It  is 
really  a  vicious  cycle  which  hands  out  great  benefits  with 
one  hand  and  iron-bound  restrictions  with  the  other. 

The  purpose  of  this  book  is  to  play  a  small  part  in  breaking 
down  these  barriers  in  respect  to  the  group  of  sciences  which 
have  a  definite  bearing  on  human  welfare  and  are  referred 
to  collectively  as  "human  biology."  This  will  also  make  for 
progress  because  many  of  the  real  problems  he  between  the 
sciences  and  are  not  perceived  without  broad  knowledge. 
To  do  so  involves  team  work  by  many  speciahsts  with  the 
idea  of  describing  in  simple  language  the  goal  which  they 
are  striving  for.  It  is  also  a  kind  of  return  to  the  pubhc  for 
value  received  for  research  in  the  pure  sciences  is  never 
self-supporting.  There  must  be  "give"  as  well  as  "take." 


VI  PREFACE 


The  book  is  written  for  two  groups  of  readers.  First,  for 
students  who  are  about  to  specialize  and  can  do  so  more 
intelligently  after  they  have  seen  in  perspective  what  lies 
ahead.  This  appHes  particularly  to  medical  students  who 
in  order  to  be  good  physicians  must  above  all  be  good 
biologists.  A  knowledge  of  what  is  known  of  human  hfe 
past,  present  and  possible  future,  is  for  them  essential.  In 
the  second  place  it  is  hoped  that  the  book  will  be  of  interest 
to  readers  of  mature  years  occupied  both  in  science  and  in 
business  who  have  an  inquiring  turn  of  mind  and  wish  to 
look  a  little  below  the  surface.  In  this  way  it  may  assist  in 
the  movement  in  favor  of  "adult  education"  which  is 
gaining  momentum  within  the  United  States  and  is  destined 
to  spread. 

Valuable  suggestions  have  been  received  from  many 
quarters  not  only  by  the  Editor,  but  by  the  individual 
contributors  who  have  one  and  all  entered  enthusiastically 
into  the  spirit  of  the  enterprise  writing  on  their  own  re- 
sponsibility and  making  acknowledgment  when  necessary. 
The  editor,  however,  is  particularly  grateful  to  Dr.  Conklin, 
Mr.  Embree,  Dr.  Gregory  and  Mr.  Hoeber  for  their  con- 
tinued interest  and  advice. 

E.    V.    COWDRY. 

Washington  University, 

St.  Louis, 

January  2,1930. 


INTRODUCTION 

Edwin  R.  Embree 

IN  an  essay  entitled  "This  Simian  World"  Clarence  Day 
has  considered  what  kind  of  planet  this  might  be  if  some 
other  species  than  the  great  apes  had  evolved  into  mastery. 
He  plays  with  the  idea  of  the  dignity  and  wisdom  that 
might  have  been  displayed  if  children  of  elephants  had 
developed  into  leadership  instead  of  monkey-hke  animals; 
what  cleanness  and  cunning  would  have  marked  a  world 
ruled  by  super-cats;  what  poise  and  vision  might  have  come 
with  glorified  descendants  of  eagles.  But  as  a  matter  of  fact 
animals  akin  to  monkeys  were  the  ones  who  did  evolve; 
it  is  the  children  of  that  race  who  rule  the  earth  today. 
The  biology  derived  from  this  ancestry  governs  our  potential 
development  and  marks  its  ultimate  borders. 

We  inherit  some  very  great  habilities  from  these  animal 
forebears.  Our  bodies  are  weak  and  puny  as  compared  with 
the  magnificence  of  elephants.  The  grace  and  beauty  of 
the  great  cats  is  lacking  in  our  Simian  civihzation.  We  have 
httle  sense  of  personal  dignity  and  no  real  regard  for  privacy. 
We  congregate  in  hordes,  hve  together  crowded  into  tenements 
and  hovels.  We  are  unstable,  constantly  running  after  new 
toys  and  new  ideas,  rushing,  often  aimlessly,  up  and  down 
the  earth  as  our  ancestors  used  to  scuttle  chattering  among 
the  trees. 

But  we  inherited  in  common  with  our  monkey  cousins, 
one  great  talent,  namely  curiosity.  And  that  single  quality, 
probably  more  than  all  other  things  taken  together,  is 
responsible  for  the  phenomenal  progress  of  our  race.  We  have 
an  insatiable  hunger  to  know  all  about  everything.  This 
appetite  drives  us  to  avid  gossip  about  our  fellows;  to 
handhng  and  tinkering  with — "monkeying  with" — every 
object  or  idea  that  crosses  our  path;  to  rushing  hither  and 
yon  to  glimpse  a  dog  fight  or  view  an  aeroplane;  and  also 
to  deep  and  profound  study  of  intricate  problems  of  medicine 
and  physics. 

vii 


VllI  INTRODUCTION 

Two  Other  characteristics  have  helped  us  humans  in  our 
special  type  of  progress.  Our  chattering  forefathers  have 
given  us  a  love  of  talk.  We  are  forever  gabbhng;  we  have 
invented  great  systems  of  language;  we  even  pay  men  to 
talk  to  us  in  groups.  We  store  up  words  in  scrolls  and  books, 
and  build  huge  temples  called  hbraries  in  which  to  hoard 
this  preserved  chatter.  We  compel  children  to  devote  years  to 
the  study  of  talk  of  previous  generations.  We  have  invented 
devices  whereby  we  can  speak  to  our  friends  thousands  of 
miles  away,  and  machines  which  record  our  babble  and 
reproduce  it  from  black  metal  discs.  This  abihty  to  talk  and 
our  devotion  to  it  is  a  biological  character  of  our  species. 
It  enables  us  to  communicate  ideas  as  well  as  gossip  and  to 
pass  on  to  the  whole  race  our  accumulated  research  and 
experience. 

We  have  also  inherited  a  compulsion  to  action.  We  must 
always  be  busy;  we  rush  about,  we  build  and  tear  down 
and  build  again.  We  are  not  content  simply  to  inquire  and 
find  out  everything;  but  we  are  driven  to  do  something 
about  it  all.  And  this  again  while  it  means  a  lot  of  aimless 
motion  also  results  in  turning  our  knowledge  of  physics, 
for  example,  into  bridges  and  steam  trains  and  aeroplanes, 
and  our  knowledge  of  chemistry  and  medicine  into  pro- 
tection of  health;  into  prolonging  and  making  more  robust 
our  lives. 

These  are  simply  rather  picturesque  aspects  of  our  biologi- 
cal make-up.  Papers  in  the  present  volume  discuss  in  funda- 
mental terms  various  phases  of  the  biology  of  man  and  his 
environment.  Such  presentation  gives  an  approach  to 
intelligent  understanding  of  ourselves  in  our  present  state 
of  development  and  in  our  present  world. 

Our  inquiries  about  our  bodies  and  habits  have  for  many 
years  been  taking  new  directions.  From  passing  curiosity 
we  have  turned  to  deep  study  of  ourselves:  our  diseases 
and  how  these  may  be  cured  and  prevented,  our  intellects 
and  how  from  childhood  they  can  be  trained  into  ever  more 
masterful  tools,  our  emotions  and  how  they  may  offer  increas- 
ing pleasure  and  satisfaction  and  produce  less  distress  and 
conflict  and  distraction.  Being  members  of  a  group  living 
together  in  a  common  world,  we  are  also  beginning  to  study 


INTRODUCTION  IV 

our  group  activities  and  relations.  Students  of  the  social 
sciences  are  attempting  to  discover  and  explain  the  causes 
of  herd  action  and  that  of  individuals  with  respect  to  the 
group  and  also  to  formulate  suggestions  of  ways  by  which, 
if  we  wish,  we  may  change  or  modify  such  conduct  for  the 
well-being  and  happiness  both  of  the  individual  and  of  society. 

A  new  factor  is  transforming  world  relations.  Recent 
inventions  are  in  effect  causing  the  planet  to  shrink  rapidly. 
Curtiss,  Wright  and  Lindberg,  and  Marconi,  Edison  and  Bell 
have  between  them  practically  murdered  space.  We  have 
crossed  the  Atlantic  in  a  day  and  may  soon  be  flying  from 
New  York  to  Tokyo  in  less  time  than,  a  century  ago,  our 
fathers  moved  in  ships  from  Boston  to  New  Haven  or  in 
covered  wagons  from  Kansas  City  to  Topeka.  Individuals  are 
talking  between  Philadelphia  and  London  and  Berhn  as  read- 
ily as  our  forebears  conversed  about  the  village  store.  Each 
of  us  is  using  every  day  houses  and  clothes  and  machines 
and  toys  some  part  of  which  comes  from  Germany,  France, 
England  and  Japan.  Our  whole  world  of  1929  in  many 
ways  is  more  closely  packed  together  than  a  single  province 
of  France  or  county  of  England  two  or  three  centuries  ago. 

We  have  brilliantly  (although  not  yet  with  consistent 
thoroughness)  searched  out  the  secrets  of  the  world  about  us 
and  we  have  turned  this  knowledge  to  very  great  practical 
service  to  ourselves.  We  have  learned  much  about  our  own 
bodies  and  are  now  able  to  protect  them  against  many 
insidious  enemies:  germs,  harmful  foods,  improper  balance 
in  the  action  gf  glands,  unwholesome  emotions,  unsocial 
acts.  With  these  tentative  findings  in  our  possession  in 
physics,  medicine,  biology,  psychology  and  the  social 
sciences  and  with  more  accurate  knowledge  increasing 
steadily  (although  in  a  spotty  manner  and  along  an  irregular 
front),  the  question  arises  as  to  whether  it  may  not  now  be 
possible  to  make  another  great  push  forward  in  human 
evolution. 

It  is  beside  the  point  to  dispute  as  to  the  relative  impor- 
tance of  inheritance  and  education,  of  nature  vs.  nurture; 
for  any  great  advance  must  include  attention  to  both  the 
biological  and  the  social.  We  must,  for  instance,  find  some 
way  to  avoid  wars  if  the  race  is  not  to  destroy  itself  with  its 


X  INTRODUCTION 

ever-increasing  knowledge  of  physics  and  chemistry  which 
may  be  used  for  mutual  benefit  or  equally  for  world  destruc- 
tion. We  must  improve  beyond  recognition  by  present 
standards  both  the  significance  and  the  extent  of  our 
educational  system;  we  must  continue  to  protect  our  health 
and  hves  if  we  are  not  to  lose  irreparably  in  individual 
and  group  progress.  But  since  after  all  we  may  assume 
that  we  have  developed  from  a  definite  species  and  since  the 
limits  of  our  progress  are  involved  in  this  ancestry  and  in  the 
degree  to  which  we  have  evolved  from  it,  a  fundamental 
question  of  the  future  is:  Can  we  to  some  extent  control 
the  direction  of  the  evolution  of  the  race? 

THE    CONTROL   OF   NATURE 

Human  progress  has  been  a  series  of  triumphs  over 
natural  forces.  But  when  anything  new  is  proposed,  certain 
people  cry  out  that  this  is  a  perversion  of  nature.  Of  course 
it  is.  Man  rules  by  bending  the  world  to  his  will  and  to  the 
service  of  his  ends. 

Man  has  progressed  by  mastery  over  other  forces.  He 
rules,  insofar  as  he  does,  because  he  has  turned  nature  to 
his  service.  Natural  science  is  a  series  of  victories  over 
other  animals  and  over  inanimate  forces.  Coal,  which  in 
the  normal  "state  of  nature"  lies  in  deep  pockets  under- 
ground, he  has  mined  and  burned  to  keep  him  warm  and 
to  run  his  engines;  electricity,  which  naturally  is  jumping 
haphazard  about  the  universe,  he  has  harnessed  into  means 
for  communication  and  power.  He  has  exploited  the  tendency 
of  bees  to  store  up  honey  and  has  lured  these  busy  little  insects 
into  building  up  great  piles  of  this  sweet  food,  not  for 
themselves,  but  for  man.  Cows,  that  by  nature  furnish 
milk  for  their  young,  he  has  perverted  into  continuing  their 
supply  of  milk  long  past  the  need  of  their  calves  so  that 
it  may  be  poured  out  for  his  nourishment.  He  has  exploited 
the  seed-bearing  nature  of  fruits  and  grains  and  has  used 
this  super-abundance  of  seed  for  his  food;  he  has  crossed 
one  species  with  another  and  produced  such  hybrid  foods  as 
the  loganberry  and  the  tangelo  grapefruit  to  please  his 
palate,  and  new  varieties  of  flowers  for  his  enjoyment. 
He    has   developed    to   a   state   of   perversion   the   normal 


INTRODUCTION  XI 

tendencies  of  many  vegetables  so  that  larger,  richer  roots 
grow  on  Burbank  potatoes,  more  profuse  grain  on  many 
varieties  of  wheat  and  oats,  larger  and  more  succulent  stalks 
on  sugar  cane.  He  has  interfered  with  the  natural  reproduc- 
tion of  animals  in  order  to  breed  cattle  with  greater  quan- 
tities of  muscle  for  him  to  eat,  pigs  with  nutritious  fat  for  his 
table,  and  hens  with  a  penchant  for  laying  eggs.  He  has  pro- 
duced abnormalities  such  as  oxen  and  mules  where  these 
better  serve  some  special  purpose  of  his. 

Man  also  interferes  with  nature  when  he  kills  parasites 
which  might  otherwise  cause  his  illness  or  death,  when  he 
eradicates  mosquitoes  and  so  avoids  malaria  and  yellow 
fever,  or  when  he  sets  one  virus  to  fight  another  as  in  vaccina- 
tion against  smallpox.  He  changes  natural  processes  when 
he  gives  anesthetics  to  deaden  pain  and  when  he  aids 
childbirth  by  mechanical  means  or  by  caesarian  operation. 
The  whole  story  of  medicine  is  a  history  of  triumphs  over 
natural  forces.  Here  again,  man  is  beginning  to  take  an 
interest  in  even  more  vital  elements  of  control.  He  practices 
birth  control;  he  makes  it  impossible  for  certain  of  the  insane 
and  feeble-minded  to  reproduce  their  kind.  He  is  beginning 
to  inquire  about  the  possibihty  of  breeding  not  only  better 
horses  and  dogs,  but  even  a  finer  race  of  men.  Against  such 
proposals  many  cry:  "  It  is  a  perversion  of  nature. "  Certainly: 
but  no  more  so  than  flying  in  aeroplanes,  using  milch  cows, 
growing  grapefruit  or  wiping  out  the  cause  of  yellow  fever. 

What  has  been  done  is  nothing  compared  to  that  which 
may  be  just  ahead.  It  is  highly  important  that  in  such 
fundamental  matters  we  proceed  wisely,  cautiously  and  on 
the  basis  of  well  established  facts.  Any  constructive  activity 
in  human  biology  must  rest  upon  the  carefully  assembled 
findings  of  wise  research  and  must  be  supported  by  intelligent 
pubhc  opinion. 

THE    CONTENTS   OF   THIS   BOOK 

The  papers  presented  in  this  volume  report  the  results  of 
investigations  in  a  great  group  of  sciences  vitally  affecting 
man.  They  are  intended  not  only  to  give  a  general  back- 
ground and  perspective  to  students  of  special  sciences, 
but  also  to  give  to  the  average  intelHgent  layman  some 


XH  INTRODUCTION 


knowledge  of  the  present  state  of  learning  in  these  several 
branches  of  knowledge  and  to  give  him  some  idea  of  the 
bearing  of  the  various  specialties  upon  man  and  the  possibih- 
ties  of  his  further  development.  This  book  is  one  answer  to 
the  lament  of  H.  G.  Wells  when  he  says  "If  only  the 
scientists  would  tell  us  less  mumblingly  what  it  is  all  about!" 

We  hve  in  a  particular  world.  Our  life  and  activities  are 
hedged  in  and  controlled  by  the  nature  of  the  earth  and  the 
universe  of  which  it  is  a  part.  We  have  throughout  the  ages 
speculated  about  the  form  and  composition  of  our  world  and 
have  looked  wonderingly  at  other  spheres  which  seem  to 
our  unaided  eyes  but  tiny  specks  saihng  through  the  firmament 
of  space.  Great  telescopes  have  been  invented  to  enlarge  the 
reach  of  our  weak  eyes.  Through  these  we  explore  the 
heavens  and  in  other  ways  we  are  getting  shght  tentative 
knowledge  of  our  neighbor  worlds.  The  story  of  these 
explorations  into  the  far  reaches  of  the  universe  is  told  in 
Part  I,  with  special  attention  to  conditions  of  possible  Hfe, 
somewhat  similar  to  ours,  upon  the  other  spheres.  The  mag- 
nitude of  space  and  the  far  stretch  of  time  give  perspective 
to  any  consideration  of  man  and  his  world  today  and  in  the 
future. 

The  stream  of  hfe  upon  our  planet  leading  up  to  the  races 
of  man,  or  the  subdivisions  of  the  human  race,  is  discussed  in 
Part  II.  By  such  a  critical  examination  of  how  changes  and 
new  departures  in  organic  hfe  have  come  about  we  can  look 
to  the  future  with  at  least  scraps  of  knowledge  of  nature's 
precedents. 

In  addition  to  glimpses  of  the  past,  for  the  whole  record 
doubtless  will  never  be  unfolded,  we  need  an  understanding 
of  the  materials  nature  has  to  work  with  in  man:  the  structure 
of  the  human  body  and  the  ways  in  which  it  performs  its 
functions.  This  subject  is  presented  in  Part  in. 

As  biological  units  we  depend  upon  the  world  we  live  in 
for  food,  for  air  and  water  and  light  and  warmth.  We  are  on  a 
planet  teeming  with  multitudinous  life  in  the  form  of 
animals  both  large  and  microscopic  and  of  almost  infinite 
varieties  of  plants,  as  well  as  of  hundreds  of  millions  of 
other  human  beings.  We  must  snatch  the  means  of  living 
from  this  world;  we  are  constantly  influenced  by  heat  and 


INTRODUCTION  XIH 

cold,  light  and  darkness.  We  are  aided  by  certain  animals 
and  plants,  which  we  have  domesticated,  that  is,  trained  to 
tolerate  and  even  enjoy  being  exploited  for  our  food  and 
service.  Other  species  have  not  been  tamed:  hons  and  tigers 
are  still  fierce  enemies;  plants  of  the  jungle  and  undomesti- 
cated  herbs  which  we  call  weeds  fight  constantly  with  us  for 
possession  of  the  land.  A  notable  enemy  plant  is  the  prickly 
pear  which  is  conquering  thousands  of  acres  of  previously 
fruitful  land  every  month  in  Austraha.  The  microscopic  forms 
of  fife,  bacteria  and  protozoa,  threaten  us  today  more  than 
the  fierce  giants  of  old.  Part  iv  is  devoted  to  this  large 
subject  of  environment. 

Much  of  the  exact  knowledge  in  medicine  and  other  sciences, 
reported  in  Parts  in  and  iv  of  this  book,  has  been  obtained 
through  dissection  of  human  bodies  after  death  and  by 
cautious  experiments  on  Hving  beings — scientists  often  exper- 
imenting on  themselves  as  in  yellow  fever  and  typhus — and 
equally  cautious  work  on  animals.  The  information  obtained 
from  the  latter  source  is  usually  applicable  to  human  beings, 
since  we  have  many  similarities  to  other  animals.  Misguided 
people  called  "anti-vivisectionists"  have  attempted  to  tie 
the  hands  of  investigators  in  the  use  of  animals.  Women, 
wearing  furs  taken  from  animals  trapped  and  killed  with 
great  cruelty,  have  often  expressed  the  most  sentimental 
sympathy  for  animals  used  under  merciful  conditions  for 
experimental  work.  Such  people,  even  when  consistent  and 
actuated  by  the  best  of  motives,  are  often  unaware  of  the  use 
of  anesthetics  in  animal  experiments  and  of  the  care  with 
which  the  research  is  carried  out,  and  also  of  the  intensity  of 
human  suffering  which  such  experiments  tend  to  relieve 
or  prevent.  Dr.  W.  W.  Keen  has  suggested  that  agitators 
against  animal  experimentation  should  be  compelled  to 
watch  preventable  death  with  all  its  grimness  in  hospitals 
and  homes  or  be  confronted  with  a  dead  guinea  pig  and  the 
dead  body  of  one  of  their  friend's  children  and  be  asked  to 
choose  between  them. 

In  the  final  division,  Part  v,  the  future  is  discussed  on  the 
basis  of  facts  presented  earlier  and  of  studies  of  the  tendencies 
of  evolution  in  man  and  other  animals.  In  this  section  is 
included   a  tentative  report  on  the  inheritance  of  disease 


XIV  INTRODUCTION 

and  a  consideration  of  population  growth,  the  minghng  of 
races,  and  the  question  of  the  purposeful  improvement  of 
the  human  species. 

THE   PROPER   STUDY   OF   MANKIND   IS   MAN 

Studies  in  human  biology  are  now  for  the  first  time 
coming  into  their  own. .  With  a  basis  of  exact  science  in 
mathematics  and  physics  and  chemistry,  all  biology  begins 
to  have  a  firm  foundation.  It  will  always  be  difficult  to  make 
exact  observations  and  to  formulate  theories  which  govern 
hving  organisms  as  compared  to  the  accuracy  of  studies 
in  pure  mathematics  or  of  inanimate  matter.  It  is  more 
difficult  still  to  arrive  at  exactness  when  research  concerns 
human  beings  as  contrasted  with  simpler  forms  of  hfe. 
But  progress  is  being  made.  The  recent  advances  in  preven- 
tive medicine  are  among  the  great  triumphs  of  science  of 
all  time.  Knowledge  appHcable  to  man's  welfare  is  now 
coming  in  other  phases  of  biology.  Studies  in  physiology 
and  chemistry  are  giving  information  concerning  glands  and 
diet  that  have  direct  influence  upon  Hfe  and  health.  Biologists 
with  a  background  of  statistics  are  bringing  in  information 
concerning  wide  tendencies  in  disease  and  death,  in  population 
growth  and  potential  evolution.  Men  called  anthropologists 
are  searching  out  the  history  of  past  races  and  the  hfe 
and  habits  and  customs  of  living  peoples  in  diverse  parts 
of  the  earth,  and  by  putting  together  all  this  information 
they  give  us  some  idea  of  the  directions  in  which  we  are 
developing  and  of  ways  in  which  we  may  shape  the  course 
of  our  own  progress.  Sociologists  and  poHtical  scientists 
and  economists  are  beginning  to  glean  objective  evidence 
of  the  ways  we  hve  together  and  act  in  group  hfe.  Psycholo- 
gists and  psychiatrists  are  delving  into  our  minds — even  our 
subconscious  thoughts  and  emotions. 

Each  science  depends  upon  the  others.  It  is  largely  because 
of  the  progress  in  such  fundamental  disciphnes  as  physics 
and  chemistry  that  advance  is  now  possible  in  general 
biology  and  in  the  biological  aspects  of  man.  The  present 
volume  is  a  compendium  of  present  knowledge  in  the  several 
subjects  that  comprise  the  study  of  Man  as  an  Animal. 
It  should  serve  as  a  record  against  which  to  measure  the 
rapid  and  significant  advance  that  may  be  just  ahead. 


CONTENTS 


Page 

Preface v 

Introduction Edwin  R.  Embree  vii 

List  of  Contributors xvii 

PART  I 
Perspective 

Chapter 

I.  Life  IN  Space  AND  Time Henry  Norris  Russell       3 

PART  II 
The  Origin  of  Man 

II.  Evolution  Traced  Biochemically A.  B.  Macallum  35 

III.  The  Animal  Ancestry  of  Man William  K.  Gregory  53 

IV.  The  Evolution  of  the  Brain George  H.  Parker  91 

V.  Mental  Evolution  in  the  Primates.    .    .     Robert  M.  Yerkes  115 

VI.  Societal  Evolution W.  M.  Wheeler  139 

VII.  Human  Races Ales  Hrdli^ka  156 

PART  III 
Man  as  a  Physiological  Unit 

VIII.  The  Vital  Units  Called  Cells E.  V.  Cowdry  187 

IX.  The  Relation  of  Cells  to  One  Another.    .    .      Alexis  Carrel  205 

X.  The  Integrative  Action  of  the  Vascular  System 219 

W.  B.  Cannon 

XI.  Nervous  Integrations  in  Man 246 

J.  F.  Fulton,  Sir  C.  S.  Sherrington 
XII.  The  Integration  of  the  Sexes — Marriage  .    .  Clark  Wissler  266 

PART  IV 

Effects  of  Environment 

XIII.  The  Effect  of  Climate  and  Weather    Ellsworth  Huntington  295 

XIV.  The  Reaction  to  Food Elmer   V.    McColIum  331 

XV.  The  Influence  of  Urban  and  Rural  Environment   ....   348 

Haven  Emerson,  Earle  B.  Phelps 

XVI.  Antisocial  Behavior:  Delinquency  and  Crime 379 

William  Healy 

XVII.  Adjustment  to  Infectious  Disease Hans  Zinsser  406 

XVIII.  What  Medicine  Has  Done  and  Is  Doing  for  the  Race   .    .   428 

Sir  Humphry  RoIIeston 
XIX.  The  Relation  of  Science  to  Industry   .    .    R.   A.   Millikan  458 

XX.  The  Influence  of  Education John  Dewey  468 

XV 

37^70 


XVI  CONTENTS 

PART   V 

The  Futuke 

XXI.  The  Inheritance  of  Disease Paul  A.  Lewis  491 

XXII.  Some  Aspects  of  the  Biology  of  Human  Populations.    .    .    .   515 

Raymond  Pearl 

XXIII.  The  Mingling  of  Races Charles  B.  Davenport  553 

XXIV.  The  Purposive  Improvement  of  the  Human  Race 566 

Edwin  Grant  Conklin 

XXV.  The  Intentional  Shaping  of  Human  Opinion 589 

H.  A.  Overstreet 
Index 605 


LIST  OF  CONTRIBUTORS 

Cannon,  Walter  B.,  a.m.,  m.d.,  s.d.,  ll.d. 

George  Higginson  Professor  of  Physiology,  Harvard  Medical  School, 
Boston. 

Carrel,  Alexis,  m.d.,  sc.d.   Nobel  Prize,   1912. 

Member,  Rockefeller  Institute  for  Medical  Research,  New  York. 

CowDRY,  Edmund  V.,  ph.d. 

Professor  of  Cytology,  Washington  University,  St.  Louis. 

CoNKLiN,  Edwin  Grant,  ph.d.,  sc.d.,  ll.d. 

Research  Professor  of  Biology,  Princeton  University. 

Davenport,  Charles  B.,  ph.d. 

Director,  Department  of  Genetics,  Carnegie  Institution  of  Washington. 

Dewey,  John,  ph.d.,  ll.d. 

Professor  of  Philosophy,  Cohimbia  University,  New  York. 

Embree,  Edwin  R.,  m.a. 

President  of  the  Julius  Rosenwald  Fund,  Chicago. 

Emerson,  Haven,  m.d. 

Professor  of  Public  Health  Administration,  College  of  Physicians  and 
Surgeons,  Columbia  University,  New  York. 

Fulton,  John  F.,  ph.d.,  m.d. 

Research  Fellow  in  Natural  Science,  Magdalen  College,  Oxford;  Professor 
of  Physiology  (elect),  Yale  Medical  School,  New  Haven. 

Gregory,  William  King,  ph.d. 

Professor  of  Vertebrate  Palaeontology,  Columbia  University;  Curator 
of  the  Departments  of  Comparative  Anatomy  and  Ichthyology  and 
Research  Associate  in  Anthropology,  American  Museum  of  Natural 
History,  New  York. 

Healy,  William,  m.d. 

Director  of  Judge  Baker  Foundation,  Boston;  Director  of  Research, 
Institute  of  Human  Relations,  Yale  University,  New  Haven. 

Hrdlicka,  Ales,  m.d.,  Hon.  sc.d.  (Prague),  sc.d.  (Brno). 

Curator,  Division  of  Physical  Anthropology,  U.  S.  National  Museum, 
Smithsonian  Institution,  Washington. 

Huntington,  Ellsworth,  ph.d. 

Professor  of  Geography,  Yale  University,  New  Haven. 

*  Lewis,  Paul  A.,  m.d. 

Late  Associate  Member  of  the  Rockefeller  Institute. 

Macallum,  Archibald  B.,  ph.d.,  Hon.  sc.d.,  ll.d.,  f.r.s. 

Emeritus  Professor  of  Biochemistry,  McGill  University,  Montreal. 
*  Died  of  yellow  fever  at  Bahia,  Brazil,  on  June  30,   1929,  while  investi- 
gating the  cause  of  the  disease. 

xvii 


XVIII  LIST    OF   CONTRIBUTORS 


McCoLLUM,  Elmer  Verner,  ph.d.,  sc.d. 

Professor  of  Bio-Chemistry,  Johns  Hopkins  University,  School  of  Hygiene 
and  Public  Health,  Baltimore. 

MiLLiKAN,  Robert  A.,  ph.d.,  ll.d.,  sc.d.  Nobel  Prize,  1923. 

Director  of  Norman  Bridge  Laboratory  of  Physics,  and  Chairman  of 
Executive  Council,  Cahfornia  Institute  of  Technology,  Pasadena. 

Parker,  George  H.,  sc.d. 

Professor  of  Zoology  and  Director  of  the  Zoological  Laboratory,  Harvard 
University,  Cambridge. 

Overstreet,  Harry  A.,  d.sc.  (Oxon.) 

Head  of  the  Department  of  Philosophy,  College  of  the  City  of  New 
York;  Lecturer  in  Philosophy  at  the  New  School  for  Social  Research, 
New  York. 

Pearl,  Raymond,  ph.d.,  sc.d.,  ll.d. 

Directory  of  the  Institute  for  Biological  Research;  Research  Professor 
of  Biochemistry  and  Vital  Statistics,  School  of  Hygiene;  Professor  of 
Biology,  School  of  Medicine,  Johns  Hopkins  University,  Baltimore. 

Phelps,  Earle  B.,  b.s. 

Professor  of  Sanitary  Science,  College  of  Physicians  and  Surgeons, 
Columbia  University,  New  York. 

RoLLESTON,  Sir  Humphry,  Bart.,  g.c.v.d.,  k.c.b.,  m.d. 

Physician-in-Ordinary  to  H.  M.  The  King;  Regius  Professor  of  Physic, 
Cambridge,  England. 

Russell,    Henry    Norris,    a.m.,    ph.d.,    Hon.    d.sc.    (Dartmouth),    d.sc. 
(Harvard) 

Charles  A.  Young  Research  Professor  of  Astronomy  and  Director  of  the 
Princeton  University  Observatory,  Princeton. 

Sherrington,  Sir  Charles  S.,  m.d.,  o.m. 

Waynflete  Professor  of  Physiology;  Fellow  of  Magdalen  College,  Oxford. 

Wheeler,  William  Morton,  ph.d.,  s.d.,  ll.d. 

Professor  of  Entomology,  Harvard  University,  Associate  Curator  of 
Entomology,  Museum  of  Comparative  Zoology,  Cambridge. 

Wissler,  Clark,  ph.d.,  ll.d. 

Professor  of  Anthropology,  Yale  University,  New  Haven;  Curator-in- 
Chief,  Division  of  Anthropology,  American  Museum  of  Natural  History, 
New  York. 

Yerkes,  Robert  M.,  ph.d.,  Hon.  sc.d.,  Hon.  ll.d. 

Professor  of  Psychobiology,  Yale  University,  New  Haven. 

Zinsser,  Hans,  m.d. 

Professor  of  Bacteriology,  Harvard  University,  Boston. 


PART  I.  PERSPECTIVE 


HUMAN  BIOLOGY 

Chapter  I 

LIFE  IN  SPACE  AND  TIME 

Henry  Norris  Russell 

FEW  problems  arouse  more  widespread  interest  than 
those  of  the  extent  of  hfe  in  time  and  space.  "Are 
there  other  inhabited  worlds  than  ours?"  "How  long 
has  hfe  existed  in  this  world?"  "How  long  may  it  continue 
to  exist?"  These  are  far  from  easy  questions;  but,  by  patient 
accumulation  of  all  the  available  data,  a  more  definite 
approach  to  an  answer  may  now  be  given  than  seemed 
possible  a  decade  or  two  ago. 

We  must  first,  of  course,  define  our  terms.  "World" 
may  be  used  in  its  widest  sense,  to  denote  any  body  whose 
existence  can  be  observed,  or  rationally  conjectured,  within 
the  known  universe.  "Life,"  if  we  are  to  remain  in  the 
realm  of  science,  must  be  restricted  to  connote  organisms 
whose  chemistry  and  metabohsm  are  of  the  same  general 
nature  as  those  which  are  common  to  all  terrestrial  life, 
animal  and  vegetable.  Organisms  of  radically  different 
composition  and  structure  may  conceivably  exist;  but  our 
present  knowledge  of  nature  does  not  justify  any  extended 
speculation  concerning  them. 

Thus  specified,  our  problem  falls  naturally  into  successive 
parts:  First,  we  may  enumerate  those  physical  and  chemical 
conditions  which  appear  to  be  necessary  for  the  existence 
and  permanent  maintenance  of  life  of  the  kind  that  we 
know.  Second,  we  may  review  the  bodies  known  to  astron- 
omy, considering  which  of  them  pass  the  tests  just  laid 
down,  and  so  may  be  the  abodes  of  life,  and  what  evidence 
there  is  to  believe  that  any  of  them  actually  are  so.  Third, 
we  may  consider  the  evidence  which  bears  on  the  past 
duration  of  life  where  it  now  exists,  and  the  probable  interval 
during  which  it  may  continue  to  flourish.  Lastly,  we  have 
to  assess  the  probability  that  other  habitable  and  inhabited 

3 


(ujjLIBRARy 


4  HUMAN   BIOLOGY 

worlds,  not  accessible  to  present  means  of  observation,  may 
exist  within  the  known  universe. 

THE    CONDITIONS    NECESSARY    FOR    LIFE 

These  may  be  summarized  as  follows: 

(a)  The  Presence  oj  Those  Chemical  Elements  which  are 
Essential  Constituents  of  Living  Matter.  It  was  once  uncertain 
to  what  extent  this  condition  might  be  fulfilled,  and,  indeed 
whether  elements  unknown  on  earth  might  not  exist,  or 
even  predominate,  in  other  worlds.  The  evidence  of  the 
spectroscope  has  settled  the  matter.  Lines  which  reveal 
the  presence  of  familiar  terrestrial  elements  are  found  in  the 
spectra  of  the  remotest  observable  nebulae,  millions  of 
light-years  distant.  As  science  advances,  one  after  another 
of  the  groups  of  "unknown"  lines  which  were  supposed  to 
indicate  the  existence  of  strange  elements  have  been  iden- 
tified as  due  to  known  elements  under  new  conditions, 
until  hardly  anything  remains.  The  same  elements,  therefore, 
are  found  everywhere  in  the  universe.  What  is  more,  there 
is  good  evidence  that  they  are  everywhere  present  in  much 
the  same  proportions,  and  that  the  well-known  differences 
between  the  spectra  of  the  hotter  and  cooler  stars  arise  not 
from  differences  of  composition,  but  from  differences  in  the 
physical  conditions,  which  put  sometimes  certain  elements, 
and  sometimes  others,  into  a  condition  to  absorb  hues  in  the 
rather  limited  spectral  region  which  can  be  observed. 

Most  of  the  important  constituents  of  living  organisms: 
hydrogen,  carbon,  nitrogen,  oxygen,  magnesium,  calcium, 
iron,  are  shown  by  direct  evidence  to  be  widespread,  if  not 
ubiquitous.  For  a  few,  such  as  phosphorus  and  chlorine, 
evidence  is  lacking,  on  account  of  the  absence  of  suitable 
lines  of  these  elements  in  the  observable  part  of  the  spectrum; 
but  the  general  evidence  for  the  uniformity  of  nature  is  so 
impressive  that  there  can  be  no  doubt  that  these,  too,  are 
to  be  found  •  wherever  extensive  aggregations  of  matter 
exist. 

(b)  The  presence  of  certain  compounds  which  are  of  especial 
importance  to  life;  and,  most  of  all,  of  ivater  and  carbon 
dioxide.  The  relation  of  these  substances  and  their  properties 
to  life  has  been  so  ably  discussed  by  Professor  Henderson 


LIFE    IN   SPACE   AND  TIME 


as  to  make  repetition  superfluous.  But,  though  the  raw 
materials  for  these:  carbon,  oxygen,  hydrogen,  are  wide- 
spread, it  cannot  be  expected  that  the  compounds  them- 
selves will  be  found  everywhere.  It  is  well  known  that  a 
celestial  body  of  small  mass,  such  as  the  Moon,  cannot 
permanently  retain  an  atmosphere.  The  molecules  of  a 
gaseous  atmosphere  are  in  rapid  motion,  and  flying  about 
in  all  directions,  and  only  the  gravitational  attraction  of 
the  body  keeps  them  from  diffusing  away  into  the  practically 
perfect  vacuum  of  interplanetary  or  interstellar  space. 
For  a  body  no  larger  than  the  Moon  (and  at  ordinary  tem- 
peratures), gravity  is  not  strong  enough  to  keep  them  back, 
and  an  atmosphere,  even  if  one  were  artificially  supphed, 
would  escape  into  space.  Carbon  dioxide,  being  gaseous, 
would  escape  (though  more  slowly  than  the  hghter  gases) 
and  water-vapor  would  be  readily  lost,  so  that  hquid  water, 
too,  would  gradually  evaporate  away. 

The  Earth's  attraction  is  abundantly  sufficient  to  retain 
an  atmosphere,  and  as  we  shall  see  later.  Mars  is  also  able 
to  do  so.  For  bodies  roughly  similar  to  the  inner  planets 
of  our  system,  the  hmiting  size,  below  which  an  atmosphere 
and  ocean  cannot  be  retained,  appears  to  correspond  to  a 
diameter  of  about  3000  miles.  We  may  expect  smaller 
bodies  to  be  airless,  waterless,  and  hfeless,  while  on  those 
considerably  larger,  water  and  carbon  dioxide  are  hkely  to 
be  ubiquitous. 

(c)  A  Surface  Temperature  Below  the  Boiling  Point  of 
Water  at  All  Times,  and  Above  the  Freezing  Point  at  Least 
at  Regular  Intervals.  It  is  a  commonplace  that  liquid  water  is 
a  necessity  for  the  growth  and  reproduction  of  hfe,  though 
not  for  its  mere  existence  in  a  dormant  state.  Terrestrial 
experience  shows  that  life,  however,  may  persist  under 
alternations  of  temperature  with  a  very  low  minimum, 
provided  that  the  maximum  temperature  is  above  freezing 
and  lasts  long  enough.  If  this  condition  is  met,  the  lower 
Hmit  of  the  fluctuation  could  probably  descend  far  below 
any  observed  terrestrial  temperatures  without  making  Hfe 
impossible.  The  upper  hmit  appears  at  first  to  be  more 
sharply  defined,  for  even  temporary  boihng  appears  to 
be  fatal,  and  most  terrestrial  forms  succumb  at  temperatures 


O  HUMAN   BIOLOGY 

far  below  ioo°c.  It  is  noteworthy,  however,  that  some 
organisms,  such  as  the  algae  of  the  Yellowstone  hot  springs, 
maintain  themselves  at  temperatures  but  a  few  degrees 
below  the  boiling  point.  How  far  life  could  follow  the  rise 
of  boiling  point  with  higher  pressure,  we  do  not  know. 
It  might  even  be  that  some  resistant  spores,  or  their  equiv- 
alent, might  survive  evaporation  to  dryness;  but  the 
upper  limit,  as  stated  above,  may  serve  as  a  basis  for  our 
further  discussion. 

(d)  A  Supply  of  Light  Sufficient  for  Photosynthesis.  Whether 
this,  again,  is  an  absolute  requirement  is  hard  to  determine, 
for  it  is  conceivable  that  organisms  might  derive  their 
supplies  of  energy  from  chemical  reactions,  starting  with 
inorganic  materials;  but  the  presence  of  light  is  certainly 
highly  favorable  to  the  maintenance  of  Hfe,  and  probably 
to  its  origin  as  well.  Indeed,  it  has  recently  been  shown 
that  light  alone,  in  the  presence  of  inorganic  catalysts, 
suffices  for  the  photosynthesis  of  fairly  complex  compounds. 

Ultraviolet  light  needs  special  consideration.  The  shortest 
waves  transrnitted  through  the  Earth's  atmosphere  (from 
3500  to  3000  Angstrom  units)  are  very  potent  physiologically, 
and  on  the  whole,  highly  beneficial.  The  shorter  wave 
lengths  are  very  injurious,  indeed  lethal,  which  is  doubtless 
a  consequence  of  the  fact  that  terrestrial  organisms  are 
never  naturally  exposed  to  them.  That  different  limits  of 
tolerance  could  be  developed  under  different  conditions  is 
probable. 

The  last  two  conditions  demand  that  the  abode  of  life 
shall  be  a  planet,  revolving  at  an  appropriate  distance 
about  a  self-luminous  star,  from  which  it  derives  its  light 
and  heat. 

The  conditions  already  stated  appear  to  be  either  rigor- 
ously necessary,  or  at  the  least,  probably  so,  for  the  very 
existence  of  life  upon  a  planet.  Those  which  follow,  though 
perhaps  not  unconditionally  requisite  for  the  development 
and  maintenance  of  hfe,  are  so  much  in  its  favor  that  they 
should  be  added  to  the  list. 

(e)  The  Existence  of  Land  Areas.  On  a  planet  meeting  the 
other  conditions  of  habitability,  but  bathed  in  a  shoreless 
ocean,    life    of   suitable    terrestrial    forms    might   maintain 


LIFE    IN    SPACE    AND   TIME 


itself  indefinitely  if  transplanted  under  favorable  conditions. 
But  how  life  could  have  originated  on  such  a  planet  is  a 
hard  question.  Without  trespassing  on  the  field  of  the 
biologist,  reference  may  be  made  to  the  belief  that  the 
appearance  of  such  complex  systems  as  the  simplest  of 
hving  things  is  far  more  likely  to  occur  if  there  exists  a 
large  number  of  more  or  less  isolated  local  environments, 
such  as  would  be  provided  by  tide-pools  or  fresh-water 
ponds,  than  in  the  uniform  conditions  of  the  open  sea. 
Indeed,  in  a  sea  so  deep  that  no  hght  reached  the  bottom, 
it  is  very  hard  to  see  how  life  could  get  any  start.  The  pres- 
ence of  land,  that  is  the  absence  of  excess  of  water,  appears 
therefore  to  be  almost  a  necessary  condition. 

(f)  Rotation  of  the  Planet.  This  again  is  hardly  a  sine 
qua  non,  but,  nevertheless,  important.  The  regular  alterna- 
tion of  day  and  night,  and  the  seasonal  changes  which 
accompany  it  if  the  equator  is  inchned  to  the  plane  of  the 
orbit,  greatly  increase  the  area  of  the  planet's  surface  over 
which  favorable  temperature  conditions  are  attained,  and 
the  rhythmic  alternation  of  the  environment  is  pretty 
well  recognized  as  a  favorable  factor  in  evolution.  The 
effective  alternative  to  rotation  is  of  course  a  state  in  which 
the  planet  keeps  the  same  face  always  toward  its  primary — 
as  the  Moon  does  toward  the  Earth,  or  Mercury  toward 
the  Sun.  Under  these  conditions,  the  range  of  temperature 
from  one  side  of  the  planet  to  the  other  will  be  very  great, 
and  the  atmospheric  circulation  probably  very  violent, 
and  the  conditions,  though  not  necessarily  fatal  to  Hfe, 
will  be  clearly  unfavorable. 

(g)  Atmospheric  Oxygen.  Free  oxygen  is  a  prime  necessity 
for  animal  life,  and  a  waste  product  of  most  vegetable  forms. 
One  cannot  exist  without  consuming,  nor  the  other  without 
producing  it.  Yet,  though  it  is  so  intimately  associated  with 
the  higher  forms  of  life,  this  is  not  the  case  with  the  lower. 
Many  bacteria,  for  instance,  can  grow  only  in  its  absence. 
There  appears,  therefore,  to  be  no  sufficient  reason  for 
laying  down  the  presence  of  free  oxygen  as  a  prerequisite 
for  the  origin  of  life  upon  a  planet.  Other  chemical  reactions 
than  those  involving  direct  oxidation  might  have  provided 
the  primordial  forms  of  life  with  the  required  energy. 


8  HUMAN   BIOLOGY 

We  are  so  used  to  the  existence  of  free  oxygen  in  the 
atmosphere,  so  abjectly  dependent  on  it  in  fact,  that  it  is 
hard  for  us  to  realize  how  remarkable  it  is  that  a  gas  so 
chemically  active  should  be  present  in  large  proportions. 
Free  chlorine  would  be  only  a  httle  more  surprising.  There  are 
many  purely  inorganic  reactions  that  take  oxygen  out  of  the 
atmosphere,  and  that  on  a  very  large  scale,  and  no  known 
inorganic  processes  which  put  any  in.  Should  all  earthly 
hfe  perish,  while  geological  processes  went  on,  we  might 
expect  a  steady  depletion  of  the  atmospheric  oxygen. 
Practically  all  volcanic  rocks  contain  considerable  quantities 
of  the  ferrous  compounds  of  iron,  which  are  incompletely 
oxidized,  and  on  weathering  pass  into  the  ferric  state, 
with  absorption  of  oxygen.  Volcanic  gases,  moreover,  have 
never  been  found  to  contain  free  oxygen,  but  often  contain 
elements  avid  for  combination  with  oxygen,  so  that  they  are 
sometimes  actually  combustible.  The  evidence  indicates, 
indeed,  that  the  materials  of  the  Earth's  crust  as  a  whole, 
down  to  a  depth  of  say  twenty  or  thirty  miles,  are  definitely 
unsaturated  with  respect  to  oxygen.  If  the  whole  crust 
should  be  fused  and  thoroughly  mixed,  it  appears  very  prob- 
able that  all  the  oxygen  of  the  atmosphere  would  be 
absorbed  by  the  ferrous  iron  of  the  molten  lava,  and  might 
not  nearly  suffice  to  oxidize  it. 

There  is  little  reason  to  suppose  that  the  Earth  is  of  an 
exceptionally  unoxidized  composition  (especially  as  compared 
with  bodies  of  similar  density,  which  alone  can  be  planets 
with  land  and  water  areas),  and  it  does  not  therefore  seem 
probable  that  free  oxygen  should  be  an  initial  constituent  of 
a  planetary  atmosphere.  It  might  indeed  be  liberated  by 
inorganic  means,  for  example,  as  has  been  suggested,  by  the 
dissociation  of  water-vapor  at  a  high  temperature,  and  the 
escape  of  the  fast-moving  hydrogen  atoms  from  the  atmos- 
phere, leaving  oxygen  in  excess.  But  as  the  molten  mass 
cooled,  it  is  hard  to  see  how  this  oxygen  could  escape  chemical 
combinations  with  the  vast  mass  of  incompletely  oxidized 
lavas,  rendered  more  active  chemically  by  the  presence  of 
water  at  high  pressure  and  temperature. 

Vegetation,  on  the  other  hand,  is  continually  breaking 
up  carbon  dioxide,  and  pouring  oxygen  into  the  atmosphere, 


LIFE    IN    SPACE   AND   TIME 


and  under  terrestrial  conditions  a  certain  proportion  of 
the  carbonaceous  and  other  reduced  compounds,  which 
represent  the  other  side  of  the  equation,  are  buried  in 
sediments,  and  so  withdrawn  from  the  cycle  of  change. 

If  conditions  on  our  own  planet  can  be  taken  as  a  guide, 
it  would  appear,  therefore,  that  an  oxygenated  atmosphere 
may  be  regarded,  not  as  a  prerequisite  for  hfe,  but  as  its 
result,  and  as  strong  evidence  that  hfe  exists  upon  the 
planet,  or,  at  least,  has  existed  in  the  past,  within  an  interval 
comparable  with  geological  time. 

The  oxygen  of  the  Earth's  atmosphere  is  of  importance  to 
hfe  in  another  fashion,  less  widely  known.  High  in  the 
upper  air,  more  than  twenty  miles  from  the  surface,  a 
small  proportion  of  it  is  transformed  into  ozone,  probably 
by  the  influence  of  short-wave  radiation  from  the  Sun. 
Though  transparent  to  visible  hght,  ozone  has  a  remarkable 
power  of  absorption  for  the  ultraviolet  rays;  and,  owing 
to  its  presence,  no  radiations  of  wave-length  shorter  than 
2900  Angstrom  units  reach  the  surface,  though  the  Sun 
doubtless  emits  them  powerfully.  This  hmitation  is  a 
great  tribulation  to  the  spectroscopist;  but,  were  the  ozone 
removed,  the  short  waves,  whose  injurious  effects  are 
well  known,  would  have  a  most  disastrous  effect  upon 
hfe  at  the  surface.  A  very  small  quantity  of  oxygen  in  the 
atmosphere  would  however  probably  suffice  to  produce 
enough  ozone  to  afford  effective  protection. 

One  or  two  other  factors  may  perhaps  be  mentioned. 
The  superficial  gravity  of  the  planet,  though  it  would  have 
a  great  deal  to  do  with  the  limiting  size  which  could  be 
attained  by  land  animals,  appears  to  interpose  no  fatal 
obstacle  to  the  existence  of  life,  even  were  it  far  greater 
than  on  earth.  But  too  small  a  force  of  gravity  would  permit 
the  escape  of  atmosphere,  and  make  a  world  uninhabitable. 

Again  a  certain  minimum  atmospheric  pressure  is  necessary 
if  liquid  water  is  to  exist  at  all,  for  if  the  pressure  is  less 
than  3^f7o  that  which  prevails  at  the  Earth's  surface,  ice 
would  evaporate  directly,  at  a  temperature  below  its  melting 
point.  A  high  atmospheric  pressure  and  density  would 
presumably  greatly  influence  the  modes  of  respiration  and 
locomotion  of  animals;  but  the  only  hmit  which  can  be  set 


10  HUMAN   BIOLOGY 

corresponds  to  a  thickness  of  atmosphere  so  great  that, 
even  in  the  absence  of  haze,  little  or  no  light  from  without 
could  reach  the  planet's  surface.  An  atmosphere  many 
hundreds  of  times  as  thick  as  the  Earth's  would  be  required 
to  approach  this  hmit. 

THE    HABITABILITY   OF    KNOWN  ASTRONOMICAL  BODIES 

We  may  now  pass  briefly  in  review  the  bodies  known 
to  present-day  astronomy,  examining  whether,  and  to  what 
degree,  the  conditions  for  the  existence  of  hfe  upon  them 
are  met- 

When  it  is  realized  that  the  number  of  these  extra- 
terrestrial bodies  is  about  a  bilHon,*  this  sounds  hke  a 
formidable  project.  But  the  overwhelming  majority  of 
this  vast  multitude  may  be  dismissed  at  once.  Almost 
all  of  them  are  stars,  self-luminous  masses  of  incandescent 
gas  with  temperatures  which  rise  to  milhons  of  degrees  in 
the  interior,  and,  even  at  the  surface,  range  from  more 
than  20,ooo°c.  down  to  2000°c.  for  a  few  exceptionally  cool 
stars.  There  can  be  no  thought  of  hfe  here,  unless  in  poetic 
fancy,  such  as  that  which  makes  the  angel  in  Moody's 
"Masque  of  Judgment"  retire  to  ponder  on  deep  problems  of 
theology:  "Where  in  the  Sun's  core  hght  and  thought  are 
one. 

The  nebulae,  too  (the  only  other  bodies  which  are  visible 
at  interstellar  distances)  fade  from  our  hst  at  once.  Some, 
hke  that  in  Andromeda,  are  vast  clouds  of  stars,  so  remote 
that  their  very  hght  takes  a  miOion  years  or  more  to  reach 
us.  Others,  hke  that  in  Orion,  are  clouds  of  gas  and  dust,  so 
rarefied  that  there  is  no  more  matter  in  a  cubic  mile  of  their 
substance  than  in  a  cubic  inch  of  common  air. 

Comets,  too,  such  as  we  know  in  our  own  system,  are 
mere  "airy  nothings"  of  very  low  density,  and  incapable 
of  supporting  life. 

Planets  alone,  as  has  already  been  said,  can  be  habitable, 
and  here  the  limits  of  our  observing  powers  begin  to  be 
felt.  The  stars,  even  the  nearest  of  them,  are  so  remote 
that  planets  like  ours,  if  revolving  about  them,  would  be 

*  The  common  American  usage,  according  to  which  a  billion  =  lo'  = 
1,000,000,000,  requires  explicit  statement,  but  hardly  an  apology. 


LIFE    IN    SPACE    AND   TIME  I  I 

Utterly  invisible  with  the  greatest  telescopes  yet  built, 
or  even  dreamed  of;  nor  is  there  any  other  way  at  present 
known  to  science  by  which  their  existence  could  be  certainly 
detected.* 

We  are  thus  confined  perforce  to  the  consideration  of 
the  planets  of  our  own  solar  system,  and  the  number  of 
cases  which  we  have  to  deal  with  is  cut  down  from  a  bilhon 
to  a  Httle  over  a  thousand.  Most  of  these,  again,  drop 
out,  when  we  consider  that  the  asteroids,  which  number 
more  than  a  thousand,  are  without  exception  less  than 
500  miles  in  diameter,  and  far  too  small  to  retain  a  trace  of 
atmosphere.  The  same  can  be  said  of  the  26  satellites  of 
the  various  planets.  Two  or  three  of  the  largest  may  be 
a  httle  better  able  to  hold  an  atmosphere  than  the  Moon, 
but  none  of  them  can  actually  retain  one,  unless  they  are 
too  cold  to  be  habitable. 

Only  the  eight  principal  planets  now  remain.  One  of  these 
is  our  own  home,  and  out  of  the  contest.  Of  the  rest,  the 
four  major  planets:  Jupiter,  Saturn,  Uranus  and  Neptune, 
appear  to  be  hopeless.  All  four  are  of  low  mean  density, 
and  their  sohd  or  hquid  cores,  if  they  have  such,  must  be 
surrounded  by  atmospheres  thousands  of  miles  in  depth. 
Their  visible  surfaces  are  composed  of  clouds,  but  not  of 
clouds  such  as  those  with  which  we  are  famihar,  for  these 
surfaces  are  exceedingly  cold. 

It  is  only  within  recent  years  that  the  determination  of 
planetary  temperatures  by  observation  has  become  practi- 
cable. To  attempt  it,  we  must  be  able  to  measure  the  heat 
which  reaches  us  from  the  planet;  and  this  is  excessively 
small  in  amount.  With  a  thermopile  composed  of  wires  of 
brittle  alloy,  fine  as  hairs,  mounted  in  a  vacuum,  with  a 
great  reflecting  telescope  to  concentrate  the  radiation  of  the 
planet  on  such  an  instrument,  and  an  exceedingly  sensitive 
galvanometer  to  record  the  minute  currents  which  are  pro- 
duced in  it,  the  problem  has  been  solved,  and  extensive 
radiometric  observations  have  been  made  by  Coblentz  and 
Lampland  at  the  Lowell  Observatory,  and  by  Pettit  and 

*  The  partial  eclipse  of  a  small  star  by  a  very  large  planet  might  perhaps 
produce  an  observable  diminution  of  light;  but  this  test  would  not  distinguish 
between  a  cool  planet  and  a  faint  companion  star,  still  far  too  hot  to  be 
habitable. 


Martian 
date 

May  1 1 


May  29 


June  23 


July  31 


August  20 


LIFE    IN   SPACE   AND   TIME  I3 

Nicholson  at  Mt.  Wilson.  The  heat  which  reaches  us  from 
a  planet  is,  however,  of  two  kinds.  One  is  carried  by  the 
solar  rays  which  have  been  reflected  from  its  surface  or 
atmosphere,  along  with  the  hght  by  which  we  see  it.  The 
other  comes  from  the  solar  energy  which  has  been  absorbed 
by  the  planet's  surface,  has  heated  it  up,  and  is  then 
re-emitted  in  virtue  of  the  temperature  of  the  surface.  To 
distinguish  between  the  two  is  practicable,  because  the 
reflected  radiation  (speaking  broadly)  is  carried  by  short 
waves,  and  the  ''proper"  radiation  of  the  planet  by  waves 
ten  or  twenty  times  as  long.  A  suitable  screen,  such  as  a 
plate  of  glass,  or  a  cell  containing  water,  is  transparent  to 
waves  of  the  first  sort,  and  stops  those  of  the  second,  so  that 
the  efl"ects  of  the  two  can  be  separated.  From  the  observed 
percentage  of  transmission  it  is  possible  to  calculate  the 
temperature  of  the  planet's  surface  (with  some  reservations). 

When  this  process  is  apphed  to  Jupiter  or  Saturn,  it 
is  found  that  practically  all  the  heat  which  we  receive 
from  them  is  carried  by  the  reflected  sunhght.  Unless  the 
surface  temperature  is  more  than  ioo°  below  zero,  a  readily 
measurable  amount  of  planetary  radiation  would  be  super- 
posed upon  this;  where  we  find  hardly  any;  and  the  detailed 
computations  lead  to  a  temperature  of  about  —  i30°c.  for 
Jupiter,  and  —150°  for  Saturn.  These  are  but  little  above 
the  temperatures  at  which  the  radiation  of  the  Sun,  enfeebled 
by  distance,  would  suffice  to  keep  the  surface.  It  is  therefore 
clear  that,  whether  or  not  the  interior  of  the  planet  is  hot, 
very  little  heat  must  leak  out  to  the  surface.  Uranus  and 
Neptune,  being  farther  from  the  Sun,  are  doubtless  still 
colder,  and  direct  observations  of  the  former  indicate  that 
this  is  so. 

Higher  temperatures  may  prevail  in  the  sunless  interior, 
but  the  low  density  shows  that  this  interior  is  either  so  hot 

Fig.  I .  Mars.  Actual  photographs  of  planet  Mars  taken  through  large  telescope 
showing  successive  stages  of  development  during  Martian  summer.  Dates 
given  with  photographs  are  seasonal  dates  on  Mars  which  correspond  to  our 
calendar  dates.  Note  gradual  decrease  of  snow  at  pole  and  darkening  of 
planet's  tropics  with  advance  of  Martian  summer.  This  gradual  darkening 
of  certain  regions  of  planet  in  his  summer  season  and  their  subsequent  fading 
in  winter  are  best  explained  by  assuming  that  darkening  is  due  to  growth  of 
vegetation.  (By  E.  C.  Slipher,  Lowell  Observatory.) 


14  HUMAN    BIOLOGY 

as  to  be  gaseous,  or  else  the  core  of  the  planet  is  surrounded 
by  an  ocean  thousands  of  miles  deep. 

These  four  planets,  therefore,  are  in  all  probabiHty 
hfeless. 

The  case  of  Mercury  is  still  worse.  All  the  tests  show 
it  to  be  devoid  of  atmosphere  and  water.  One  face,  turned 
continually  towards  the  Sun,  reaches  a  temperature  of 
400°c.  (as  shown  by  the  radiometric  measurements).  The 
other,  in  permanent  darkness,  must  be  exceedingly  cold. 
No  more  inhospitable  world  could  be  imagined,  it  is  a  real 
Inferno. 

Two  worlds  only,  out  of  a  billion,  remain,  Venus  and 
Mars,  and  in  these  cases  the  conditions  are  more  favorable. 
Both  are  large  enough  to  retain  an  atmosphere,  and  both 
actually  possess  one;  one  is  hotter  than  the  Earth,  and 
the  other  colder,  but  neither  is  outside  the  limits  of  tolerance. 
They  and  they  alone,  need  discussion  in  detail. 

Venus,  until  a  few  years  ago,  appeared  the  most  favorable 
known  habitat  for  life  outside  the  Earth.  Though  she 
receives  twice  the  intensity  of  solar  radiation  that  we  do, 
the  reflecting  power  of  her  surface  is  high,  and  less  heat 
in  proportion  remains  upon  the  planet.  The  radiometric 
measures  indicate  a  temperature  of  about  6o°c.  for  the 
sunlit  side  (which,  though  rather  high,  is  not  out  of  the 
question),  and  —  20°c.  for  the  dark  side  (not  impossibly 
low).  The  existence  of  an  atmosphere  is  proved  conclusively 
by  the  appearance  of  twilight  when  we  see  the  planet  as  a 
thin  crescent.  Above  the  visible  surface,  this  atmosphere 
appears  to  be  less  extensive  than  the  Earth's;  but  this 
surface  may  well  be  composed  of  clouds.  The  uniform  white- 
ness of  the  surface,  and  the  absence  of  definite  markings 
have  long  been  recognized  as  favorable  to  this  view;  and  the 
remarkable  photographs  of  Ross  in  1927,  which  show  darkish 
spots  visible  by  ultraviolet  light  only,  and  changing  from 
night  to  night,  go  far  to  settle  the  matter. 

After  three  hundred  years  of  observation,  the  planet's 
rotation  period  is  still  unknown.  There  is  no  doubt  that 
it  is  much  longer  than  the  Earth's,  and  it  was  at  one  time 
supposed  that,  like  Mercury,  Venus  kept  one  face  always 
toward  the  Sun;  but  this  is  hardly  reconcilable  with  the 


LIFE    IN    SPACE    AND   TIME  1 5 

relatively  high  temperature  of  the  dark  side,  and  it  is 
probable  that  the  rotation  period  is  a  few  weeks  in  length. 

All  these  indications  are  favorable;  but  the  crucial  test 
remains,  i.e.  the  composition  of  the  atmosphere.  Fortunately 
oxygen  and  water  vapor  show  numerous  absorption  lines 
in  the  observable  region,  mainly  in  the  red,  and  can  be 
detected  by  spectroscopic  means.  The  application  of  this 
test  to  the  planets  is  hindered  by  the  fact  that  we  have 
to  observe  through  the  Earth's  atmosphere,  which  is  rich 
in  both  substances.  But,  if  the  planet  is  observed  when 
it  is  rapidly  approaching  the  Earth,  or  receding  from  it, 
the  "Doppler  shift"  due  to  this  motion  sets  the  hnes  pro- 
duced in  the  planet's  atmosphere  a  little  to  one  side  of 
the  stronger  ones  arising  in  that  of  the  Earth.  Even  if 
the  two  are  not  clearly  resolved,  measures  of  the  position 
of  the  resulting  blend  will  show  what  the  relative  intensities 
of  the  two  absorptions  are. 

This  ingenious  method,  devised  independently  by  Lowell, 
Campbell,  and  St.  John  at  the  three  great  observatories 
of  the  Western  United  States,  has  been  applied  to  Venus 
by  the  last-named  astronomer.  Not  the  slightest  effect 
due  to  the  presence  of  oxygen  on  the  planet  could  be  detected, 
though  the  lines  should  have  been  clearly  separated.  By 
comparison  with  laboratory  measures,  he  concludes  that 
the  quantity  of  oxygen  above  the  visible  surface  of  Venus 
must  be  less  than  Kooo  of  that  in  the  Earth's  atmosphere. 
This  test  is  apparently  decisive.  The  spectroscopic  test 
for  water  vapor  also  gave  a  negative  result;  but  it  is  much 
less  delicate,  and  a  small  quantity  might  escape  detection. 

It  would  seem  decidedly  improbable,  on  general  principles, 
that  Venus,  which  is  quite  as  much  like  the  Earth  in  size 
and  mass  as  one  of  a  pair  of  twins  is  usually  like  the  other, 
should  have  been  initially  entirely  devoid  of  water  while  the 
earth  had  so  much.  Escape  of  water  vapor  against 
the  planet's  gravitation  appears  to  be  out  of  the  question. 
The  cloud-like  forms  observed  with  ultraviolet  light  suggest 
condensations  of  vapor  of  some  sort,  and  nothing  else  than 
water  appears  to  be  at  all  plausible  in  the  connection. 
But  how  so  little  vapor  can  exist  above  the  clouds,  if  they 
are  really  composed  of  water,   at  a  relatively  high  tem- 


i6 


HUMAN   BIOLOGY 


perature,  is  hard  to  see.  The  stratosphere,  or  isothermal 
layer,  in  the  upper  part  of  the  Earth's  atmosphere,  is  almost 
free  from  water  vapor,  though  the  troposphere,  or  lower 
atmosphere,  is  full  of  it.  If  a  similar  demarcation  exists  on 
Venus,  and  if  the  lower  atmosphere  is  full  of  clouds  to  its 
very  top,  the  observed  phenomena  may  perhaps  be 
exphcable. 

The  absence  of  oxygen  cannot  be  similarly  explained, 
for,  not  being  subject  to  condensation,  it  would  diffuse 
freely  into  the  upper  atmosphere.  It  must  apparently  be 
accepted  that  Venus  is  devoid  of  oxygen,  and  this  points 
strongly  to  the  conclusion  that  neither  animal  nor  vegetable 
hfe  is  present  upon  the  planet.  Why  this  should  be  the 
case  is  a  matter  of  conjecture.  The  suggestion  has  recently 
been  made  by  Webster  that,  if  the  planet's  rotation  is 
slow,  and  the  difference  of  day  and  night  temperatures  as 
great  as  is  observed,  winds  of  great  violence  will  blow 
from  the  warmer  to  the  colder  regions,  and  it  may  well 
be  that  marine  erosion  has  more  than  overtaken  the  forces 
of  elevation,  so  that  the  planet  has  been,  for  the  most  of 
its  history,  covered  by  a  shoreless  sea,  in  which  life  had 
no  chance  to  arise;  nor  would  its  opportunity  have  been 
much  better  on  incessantly  storm-swept  coasts.  It  may  be, 
on  the  other  hand,  that  there  is  no  water  on  Venus,  in 
spite  of  the  a  priori  probability,  and  in  this  case  the  absence 
of  life  follows  necessarily. 

Though  much  remains  to  be  known  about  the  conditions 
which  prevail  upon  this,  the  nearest  of  the  planets,  the 
conclusion  that  life,  as  we  know  it,  is  not  to  be  found  on 
Venus  appears  to  rest  on  firm  foundations. 

So  we  come  finally  to  Mars,  and  to  a  situation  singularly 
contrasting  with  that  of  Venus.  Though  of  little  more 
than  half  the  Earth's  diameter.  Mars  has  a  surface-gravity 
38  per  cent  as  great  as  the  Earth's,  and  is  fully  able  to 
retain  an  atmosphere.  It  actually  possesses  one,  as  many 
things  prove,  but  one  less  extensive  than  ours.  The  amount 
of  atmosphere  above  a  square  mile  of  the  surface  appears 
to  be  between  one-tenth  and  one-half  as  much  as  on  the 
Earth,  which,  under  the  smaller  force  of  gravity,  would  give 
an    atmospheric    pressure    at    the    surface    lying    between 


LIFE    IN    SPACE   AND   TIME  1 7 

4  and  20  per  cent  of  that  under  which  we  find  ourselves. 
The  atmosphere  is  clear,  and  usually  permits  a  good  view 
of  the  planet's  surface,  especially  if  the  observations  are 
made  with  yellow  or  red  hght.  Clouds,  though  occasionally 
observed,  are  very  rare,  and  permanent  surface  markings 
are  numerous.  With  the  aid  of  these,  the  rotation  period 
has  been  accurately  determined  as  24*"  37""  22^  58,  only 
a  little  longer  than  the  Earth's,  while  the  equatoi  is  inchned 
to  the  orbit  by  25°,  which  leads  to  a  sequence  of  seasons 
very  Hke  our  own.  Noteworthy  seasonal  changes  have  been 
known  ever  since  the  planet  was  first  observed  telescopically. 
The  most  conspicuous  of  these  is  the  alternate  waxing 
and  waning  of  the  white  polar  caps,  which  shrink  in  summer 
and  form  again  during  the  winter  night,  exactly  as  snow- 
caps  might  be  expected  to  do.  Unhke  the  Earth's  polar 
snows,  however,  they  become  very  small  in  late  summer, 
the  northern  cap  diminishing  to  200  miles  in  diameter,  and 
the  southern  (which  has  its  summer  when  Mars  is  nearest  the 
Sun)  sometimes  vanishing  altogether.  That  these  caps 
are  formed  by  some  substance  which,  Hke  snow,  is  pre- 
cipitated from  the  atmosphere  in  cold  weather,  has  never 
been  doubted;  and  there  is  no  longer  any  question  that 
they  are  actually  composed  of  frozen  water. 

Radiometric  measures  of  temperature,  dealing  not  only 
with  the  planet  as  a  whole,  but  with  separate  regions  of 
the  disk,  were  made  extensively  during  the  favorable 
oppositions  of  1924  and  1926.  The  results  obtained  inde- 
pendently at  Flagstaff  and  Mt.  Wilson  show  that  the 
temperature  rises  at  noon  in  the  tropics  to  10°  or  i5°c. 
(50°  to  70°F.),  and  gets  almost  as  high  at  the  poles  in  the 
latter  part  of  the  long  summer  day  (which  endures  for 
almost  a  year  of  our  time).  At  night,  even  at  the  equator, 
it  falls  below  the  freezing  point,  and  the  polar  nights  must 
be  cold  indeed. 

This  is  exactly  the  right  temperature  range  for  the 
appearance  and  disappearance  of  snow  or  frost;  and  the 
conclusion  that  water  exists  on  the  planet's  surface  is  put 
beyond  doubt  by  spectroscopic  observations,  which  show 
that  there  is  water-vapor  in  the  atmosphere,  though  only 
to  about  5  per  cent  of  the  amount  present  in  the  Earth's. 


1 8  HUMAN   BIOLOGY 

The  amount  of  snow  in  the  polar  caps  can  be  roughly 
estimated  from  the  fact  that  the  heat  which  is  received 
fiom  the  Sun  during  the  season  is  sufficient  to  melt  and 
evaporate  it,  and  it  is  found  that  when  melted  they  would 
form  a  layer  of  water  averaging  only  a  few  inches  deep. 
All  the  water  resulting  from  the  melting  would  be  too 
little  to  fill  Lake  Erie,  and  it  is  evident  that  Mars,  as  a 
whole,  must  be  a  veiy  dry  planet,  and  that  desert  conditions 
must  prevail  over  most  of  its  surface. 

The  spectroscopic  test  reveals  oxygen,  too,  in  the  atmos- 
phere of  Mars.  The  Mt.  Wilson  observations  indicate  that 
the  quantity  of  this  gas,  above  a  square  mile  of  the  planet's 
surface,  is  about  15  per  cent  as  great  as  for  the  Earth. 
The  corresponding  partial  pressure  of  oxygen  at  the  surface 
is  6  per  cent  of  the  terrestrial  value,  too  little  to  support 
human  respiration  but  probably  within  the  limit  to  which 
life  could  adapt  itself.  The  presence  of  oxygen  appears  to 
be  intimately  connected  with  a  characteristic  of  the  planet, 
which  has  been  known  longer  than  any  other,  namely  its 
red  color.  The  greater  part  of  the  planet's  area  is  rather 
uniformly  of  this  hue  and  all  students  agree  in  the  belief 
that  in  these  portions  we  see  the  bare  surface  in  its  natural 
color.  Now  unweathered  igneous  rocks  are  not  usually  red, 
though  they  are  so  occasionally.  The  incompletely  oxidized 
ferrous  compounds  give  them  a  grayish  or  blackish  tone, 
sometimes  of  a  bluish  cast.  But  the  fully  oxidized  products  of 
weathering  of  such  rocks  are  usually  colored  yellow  or  red 
by  ferric  oxide.  Mars  shows  just  such  a  color,  while  among 
all  the  other  bodies  of  our  system  whose  bare  surfaces 
we  can  see  (Mercury,  the'  Moon,  and  the  asteroids  and 
satellites)  not  one  has  an  atmosphere,  nor  is  one  red.  The 
absence  of  red,  even  in  patches,  upon  the  airless  surface 
of  the  Moon  is  especially  noteworthy. 

The  most  interesting  of  the  Martian  markings  remain 
to  be  discussed.  The  dark  areas,  which  cover  about  35  per 
cent  of  the  surface,  are  of  a  greenish  or  bluish-gray  hue, 
in  contrast  to  the  reddish-yellow  of  the  rest.  They  were 
once  supposed  to  be  seas,  but  this  cannot  be  true,  for, 
if  they  were,  the  reflection  of  the  Sun  from  the  water  surface 
would  be  by  far  the  most  conspicuous  feature  upon  the 


LIFE    IN    SPACE    AND   TIME  ip 

planet.  They  show,  too,  conspicuous  differences  of  intensity, 
and  depth  of  color,  within  their  own  areas,  which  could 
hardly  occur  in  water  unless  it  was  very  shallow.  Most 
noteworthy  of  all,  they  exhibit  marked  seasonal  changes. 
Even  the  principal  markings,  though  of  fairly  permanent 
form  and  position,  vary  greatly  in  intensity,  being  at  times 
conspicuous,  and  again  almost  invisible. 

Speaking  broadly,  they  are  most  prominent  in  the  spring 
of  the  hemisphere  in  which  they  lie,  and  tend  to  fade  out 
in  the  autumn  and  winter,  at  which  season  the  color  some- 
times changes  from  greenish  to  yellow  or  brown.  These 
changes,  though  repeating  themselves  roughly  in  successive 
seasons,  show  considerable  irregularity. 

Crossing  the  lighter  regions  between  the  dark  areas,  and 
in  some  cases  the  latter  themselves,  are  the  finer  markings 
known  as  the  canals,  discovered  by  Schiaparelli  in  1877. 
No  doubt  remains  of  the  reality  of  such  markings,  for  many 
of  them  have  been  photographed  time  and  again.  The  photo- 
graphs show,  too,  that  the  canals  are  of  the  same  general 
color  as  the  dark  areas,  for,  like  the  latter,  they  come  out 
strongly  on  photographs  taken  with  red  light,  and  are 
inconspicuous  with*  blue  or  violet.  It  is  well  established, 
too,  that  they  show  seasonal  changes  in  visibility  which 
run  parallel  to  those  of  the  dark  areas. 

On  one  further  point  all  observers  of  the  canals  are 
agreed;  they  are  difficult  and  elusive,  and  can  be  well  seen 
only  at  those  favorable  times  when  the  incessant  turbulence 
of  the  Earth's  atmosphere,  which  produces  the  confusion 
of  the  telescopic  image  known  as  "bad  seeing,"  quiets 
down  for  a  few  moments  and  permits  a  relatively  clear 
view  of  the  planet.  Concerning  their  appearance,  when 
best  seen,  experienced  observers  are  in  extraordinary 
disagreement.  Some,  like  the  late  Percival  Lowell,  drew 
them  as  fine  sharp  lines,  following  great  circles  on  the 
sphere  for  hundreds  of  miles,  meeting  by  threes,  fours,  or 
more,  at  sharply  defined  points,  and  covering  the  whole 
planet  with  a  geometrical  network.  Others,  such  as  Barnard, 
described  instead  a  complex  mass  of  fine  detail,  appearing 
as  if  it  "had  been  painted  with  a  very  poor  brush,  producing 
a  shredded  or  streaky  and  wispy  efi'ect,"  but  failed  altogether 


20  HUMAN   BIOLOGY 


to  see  the  sharp  geometrical  network;  and  many  intermediate 
drawings  and  descriptions  exist. 

There  is  no  room  here  for  a  full  discussion  of  this  problem; 
but  it  may  be  said  in  brief  that  the  only  reasonable  explana- 
tion of  these  discrepancies  appears  to  he  in  what  astronomers 
call  "personal  equation."  The  process  of  recording,  by 
sketch  or  verbal  description,  details  which  can  be  seen 
only  by  ghmpses  of  a  few  seconds'  duration  when  the  air 
is  steady,  is  one  of  extreme  complexity;  and  psychological 
elements  in  the  report  which  the  eye  makes  to  consciousness 
are  apparently  important.  The  most  skilled  and  scrupulous 
observers  cannot  discriminate  between  the  objective  and 
subjective  elements  in  such  a  report  of  his  senses,  and  so  the 
discrepancies  arise. 

There  is  little  reason  to  hope  that  keener  eyes,  or  better 
atmospheric  conditions,  will  be  available  for  work  on  Mars 
in  the  future  than  there  have  been  in  the  past,  and  it  appears 
necessary  to  leave  the  question  of  the  exact  appearance  and 
arrangement  of  the  finer  Martian  markings  sub  judice, 
as  a  matter  not  at  present  determinable;  while  admitting 
their  reality.  The  photographs,  unfortunately,  cannot 
settle  the  question,  for  the  details  in  question  are  so  fine 
that  the  grain  of  the  plates  would  conceal  them,  even  if  no 
other  difficulties  existed. 

All  the  necessary  and  important  conditions  favorable 
to  life  appear  to  be  present  on  the  surface  of  Mars:  an 
adequate  temperature,  sunlight,  water,  atmospheric  oxygen, 
a  land  surface,  days  and  seasons.  The  force  of  gravity 
at  the  surface,  and  the  atmospheric  density,  though  less 
than  those  to  which  terrestrial  life  is  adapted,  appear 
to  be  well  within  the  limits  of  possible  adaptation. 

Two  independent  lines  of  evidence  point  toward  the 
actual  existence  of  vegetable  life  upon  the  planet.  The 
first  is  the  character  of  the  seasonal  changes  in  the  dark 
areas  and  canals.  The  brief  description  already  given  shows 
that  these  are  just  what  might  be  expected  from  the  growth 
of  vegetation,  as  the  temperature  rises  in  spring,  and  the 
water  locked  up  in  the  polar  cap  is  released,  and  its  dying 
down  in  the  cold  and  dryness  of  late  autumn  and  winter. 
The  fact  that  the  changes,   in  successive  Martian  years, 


LIFE    IN    SPACE    AND    TIME  21 


though  similar,  by  no  means  follow  exactly  the  same  routine, 
is  in  full  accord  with  this  view,  as  is  also  the  nature  of  the 
observed  variations  in  color. 

Though  the  hypothesis  of  vegetation  offers  a  sufficient 
explanation  of  the  observations,  it  is  by  no  means  a  necessary 
one.  Arrhenius,  for  example,  has  suggested  that  similar 
variations  in  appearance  would  be  presented  by  sahne 
deserts,  playas  as  they  are  called  in  the  Southwest,  which, 
in  the  rainy  season,  are  seas  of  dark  mud,  while  in  the 
dry  season  the  efflorescent  salts  come  to  the  surface  and 
the  color-tone  is  much  hghter.  Even  in  the  absence  of 
actual  rain,  the  absorption  of  moisture  by  hygroscopic 
salts  might  produce  a  similar  effect.  That  such  areas  should 
exist  in  a  desert  planet,  whose  surface  has  been  extensively 
weathered,  is  highly  probable,  and  the  seasonal  changes, 
alone,  can  hardly  be  regarded  as  decisive  evidence  in  favor 
of  vegetation. 

The  presence  of  a  considerable  amount  of  oxygen  in  the 
atmosphere,  however,  cannot  be  accounted  for  on  the 
salt-desert  theory,  while  it  is  an  immediate  consequence 
of  the  presence  of  vegetation.  Indeed,  as  has  already  been 
said,  it  is  hard  to  see  how  the  oxygen  could  have  got  into 
the  atmosphere  by  inorganic  processes,  or  remained  there 
permanently  if  it  had.  In  the  writer's  judgment,  the  com- 
bined evidence  makes  the  existence  of  vegetation  upon  the  sur- 
face of  Mars  highly  probable,  though  it  cannot  be  said  that  it 
estabhshes  it  beyond  all  doubt. 

Granting  this,  the  canals  are  simply  interpretable  in 
accordance  with  W.  H.  Pickering's  suggestion  that  they 
represent  narrow  strips  of  vegetation  along  valleys  or 
water-courses  of  some  sort,  where  there  is  more  moisture 
available  than  in  the  surrounding  deserts.  The  canals 
in  the  dark  areas,  whose  existence  appears  to  be  well  authen- 
ticated, would  then  be  bands  of  richer  vegetation  in  a  country 
of  sparse  growth,  and  the  seasonal  changes  in  the  canals 
are  immediately  exphcable. 

The  importance  of  such  a  conclusion  to  a  general  philos- 
ophy of  nature  is  obvious.  Life,  amazing  as  it  is  in  the 
complexity  and  dehcate  adjustment  of  its  processes,  is 
not  confined  to  our  world  alone,  where  we  might  suppose 


22  HUMAN    BIOLOGY 


its  origin  to  be  due  to  some  happy,  but  almost  infinitely 
improbable,  combination  of  favorable  conditions.  There 
are  but  three  bodies  in  our  system  upon  which  life  as  we 
know  it  could  have  the  least  chance  of  survival.  If  it  is 
present  upon  two  of  these  three,  it  is  reasonable  to  suppose 
that,  if  favorable  physical  conditions  exist  elsewhere  in  the 
universe,  fife  would  stand  a  good  chance  of  coming  into  being. 

Whether  animal  fife,  and,  still  more,  inteUigent  fife, 
exists  on  Mars  is  a  harder  question.  With  oxygen  to  breathe, 
and  vegetation  to  provide  food,  animal  life  might  well 
exist;  and  we  can  assign  no  reason  why  intelligence  should 
not  have  evolved.  But  to  obtain  evidence  of  the  existence 
of  such  life,  if  it  exists,  upon  a  planet  which  never  comes 
nearer  than  about  35,000,000  miles  would  be  a  hard  matter. 
As  is  well  known,  Lowell  believed  that  he  had  secured  such 
evidence,  and  his  arguments  were  of  a  thoroughly  scientific 
character  and  deserve  careful  consideration.  Briefly  stated, 
they  are  as  follows: 

The  network  formed  by  the  canals,  which  run  in  great 
circle  courses  across  hundreds  of  miles  of  desert,  suggests  a 
geometrical  diagram  far  more  than  a  map.  Accepting 
the  belief  that  they  are  water-courses,  or  rather  the  fertile 
land  on  each  side  of  these,  it  is  beyond  the  bounds  of  credulity 
to  suppose  that  a  system  such  as  is  shown  on  Lowell's 
drawings  is  the  product  of  geological  forces;  it  appears 
obviously,  indeed  glaringly,  artificial.  Hence  the  "canals" 
represent  strips  of  irrigated  land  flanking  artificial  water- 
courses, and  weie  laid  out  by  intelhgent  creatures  of  high 
engineering  skill.  As  the  polar  snows  recede,  the  canals 
darken  (vegetation  grows).  This  "quickening"  of  the 
canals  progresses  steadily  toward  the  equator  and  even 
beyond,  and,  in  some  cases,  half  a  Martian  year  later, 
it  has  been  seen  to  follow  the  same  canal  in  the  opposite 
direction.  Now  water  may  flow  down  hill  one  way,  but 
not  both  ways;  hence  it  is  carried  along  some  canals,  at 
least,  by  artificial  means;  it  is  pumped;  and  the  inhabitants 
who  made  the  canals  are  still  there  to  work  them.  Indeed 
the  orderly  and  world-wide  character  of  the  system  indicates 
a  degree  of  racial  organization  superior  to  the  present  state 
of  mankind. 


LIFE    IN    SPACE    AND   TIME  23 

The  intellectual  elegance  of  the  argument,  here  too 
briefly  sketched,  demands  admiration;  the  difficulties  with 
it  He  mainly  in  its  premises.  The  main  point  at  issue  is  the 
geometrical  character  of  the  canal  system,  which  is  doubted 
or  denied  by  the  majority  of  observers.  It  is  hardly  necessary 
to  say  that  no  question  as  to  the  trustworthiness  and 
integrity  of  any  of  the  distinguished  observers  who  have 
studied  the  planet  can  for  a  moment  be  raised;  each  faith- 
fully describes  what  the  subconscious  processes  of  his 
brain  report  to  his  consciousness.  But,  when  these  reports 
diff'er  so  widely,  with  respect  to  details  which  all  agree 
are  clearly  seen  only  by  ghmpses,  there  appears  to  be  no 
way  to  determine  which,  if  any,  of  the  drawings  of  various 
observers  most  resembles  what  we  would  see  if  the  planet 
were  ten  times  nearer,  and  its  details  observable  with 
certainty. 

Again,  the  progressive  "quickening"  of  the  canals  need 
not  necessarily  be  due  to  the  progress  of  water  along  them. 
Lau  has  suggested  that  as  the  polar  caps  melt,  the  atmos- 
phere may  become  foggy,  and  later  clear  up,  beginning 
in  high  latitudes.  The  growth  of  vegetation,  which  has 
proceeded  under  the  fog,  would  then  first  become  visible 
near  the  pole,  and  appear  to  progress  toward  the  equator 
as  the  fog  cleared.  This  effect  might  advance  northward 
or  southward  in  opposite  seasons,  without  any  water  having 
to  run  up-hill.  Indeed,  one  of  the  chief  difficulties  of  the 
hypothesis  of  artificial  irrigation  is  that  the  planet's  whole 
surface  must  be  assumed  to  be  extraordinarily  flat. 

In  view  of  these  considerations,  the  verdict  which  must 
at  present  be  rendered  upon  Lowell's  suggestion  is  the 
Scottish  one  of  '*not  proven."  There  is  too  much  uncertainty 
about  some  of  the  more  critical  data,  and  too  many  alterna- 
tive explanations,  to  justify  acceptance.  But  to  deny  that 
intelligent  life  exists  on  Mars  would  be  quite  unwarranted. 
Even  a  direct  proof  that  all  the  visible  features  of  the 
planet's  surface  were  of  "natural"  (as  distinguished  from 
artificial)  origin  would  obviously  be  no  evider  ce  at  all  for  the 
negative. 

The  question  must,  in  our  present  state  of  knowledge, 
be  left  open,  without  prejudice.  Animals,  indeed,  intelligent 


24  HUMAN   BIOLOGY 

animals,  may  exist  on  Mars;  but  we  have  no  reliable  evidence 
whether  or  not  they  do. 

It  is  interesting  to  consider  that,  if  Venus  had  intelHgent 
inhabitants,  who  could  observe  the  Earth  as  well  as  we 
can  study  Mars,  and  whose  instrumental  equipment  and 
scientific  knowledge  were  at  the  present  human  level, 
these  inhabitants  would  probably  come  to  just  the  same 
conclusion  regarding  the  Earth.  Seasonal  changes  on  our 
planet  would  be  conspicuous;  the  presence  of  oxygen  would 
be  spectroscopically  evident;  the  widespread  existence  of 
vegetation  might  be  inferred;  but  of  the  works  of  man,  even 
his  greatest,  nothing  could  be  seen  which  could  definitely 
be  distinguished  from  the  products  of  unconscious  forces. 
The  reahzation  of  this  is  wholesome,  for  us  the  self-styled 
"lords  of  creation." 

THE  AGE  OF  THE  EARTH  AND  OF  THE  STARS 

Geologists  have  long  been  able  to  arrange  the  strata 
in  order  of  their  relative  age,  and  to  distinguish  many 
successive  periods  by  their  characteristic  fossils;  but  it  is 
only  in  recent  times  that  the  geological  time-scale  has 
become  expressible  in  years. 

Estimates  based  upon  such  processes  as  the  date  of 
formation  of  sediments,  or  that  of  accumuLation  of  soluble 
salts  in  the  ocean  suffer  from  the  difficulty  that,  even 
though  the  present  rate  at  which  these  proceed,  and  the 
cumulative  effect  of  their  action  in  past  time,  were  accurately 
known,  we  have  no  security  that  their  rate  of  operation 
in  the  past  was  of  the  same  magnitude  as  at  present.  Calcula- 
tions based  on  the  coohng  of  the  Earth's  interior  once 
appeared  more  reliable,  but  they  have  been  completely 
upset  by  the  discovery  that  heat  is  generated  by  radioactive 
substances  in  the  superficial  layers.  Radioactivity,  however, 
has  furnished  us  with  what  is  apparently  a  trustworthy 
time-scale  in  place  of  these  dubious  ones. 

The  radioactive  elements  are  gradually  and  spontaneously 
disintegrating,  an  atom  of  one  sort  ejecting  a  part  of  itself 
and  changing  into  an  atom  of  another,  and  so  on  through 
a  long  sequence  of  transformations.  The  rate  of  these  trans- 
formations appears  to  be  quite  unaffected  by  any  external 


LIFE    IN    SPACE    AND   TIME  25 

conditions,  e.g.  pressure,  temperature,  and  the  like,  and 
presumably  depends  upon  the  structure  of  the  minute 
nuclei  of  the  atoms.  Radium  is  one  of  the  shorter-lived 
products  in  a  series  which  begins  with  uranium,  the  heaviest 
atom  known,  and  ends  with  lead;  but  the  lead  which  is 
so  formed  differs  in  atomic  weight  from  common  lead 
(206  instead  of  207)  and  can  therefore  be  identified  by  a 
careful  analysis.  If  lead  of  this  pecuHar  type  is  found  in  a 
uranium  mineral,  there  is  every  reason  to  beheve  that 
it  was  not  an  original  constituent,  but  has  been  formed 
in  situ  by  radioactive  change  in  the  crystal  where  it  is 
found.  The  rate  of  change  is  very  slow,  no  less  than 
66,000,000  years  being  required  for  the  transformation  of  i  per 
cent  of  the  uranium.  Hence,  if  we  find  lead  of  this  pecuHar 
sort  in  a  mineral,  amounting  to  15  or  20  per  cent  of  the 
weight  of  the  uranium  which  is  present,  it  is  evident  that 
it  must  have  Iain  undisturbed  in  the  rock  for  a  prodigious 
time  before  the  miner  and  the  chemist  broke  upon  its  rest. 
The  ages  of  minerals  in  many  eruptive  rocks  have  been  found 
in  this  way,  that  is,  the  time  since  the  rocks  themselves 
were  molten.  The  geological  period  during  which  the 
intrusion  of  the  mass  occurred  can  often  be  fixed,  which 
leads  to  the  determination  of  a  large  number  of  datum  points 
along  the  scale  of  geological  time.  Jeffreys  (1924),  reviewing 
the  evidence,  gives  the  following  summary: 

Period  Years 


Eocene 60,000,000 

Carboniferous 300,000,000 

Upper  Pre-Cambrian 550,000,000 

Lower  Pre-Cambrian 1,300,000,000 


Life  was  already  abundant  in  Cambrian  times,  and  had 
developed  a  multitude  of  highly  organized  forms,  so  that 
its  origin  must  be  placed  much  farther  back,  and  probably 
not  less  than  a  billion  years  ago.  Duiing  all  this  time, 
the  physical  conditions  on  the  Earth's  surface,  and,  in 
particular,  the  temperature,  must  have  been  very  similar 


26  HUMAN   BIOLOGY 

to  what  they  are  now.  The  evolution  of  living  forms  has 
been  continuous,  with  no  trace  of  a  serious  general  set-back. 
There  have  been  recurrent  epochs  of  glaciation;  but  at  no 
time  is  there  evidence  that  a  frigid  climate  prevailed  over 
the  whole  world;  and  it  is  quite  certain  that  the  temperature 
never  rose  anywhere  near  the  boiling  point,  even  for  a  single 
year.  The  Sun's  radiation  of  heat,  upon  which  the  Earth's 
surface  temperature  wholly  depends,  must  have  been  remark- 
ably constant  all  through  this  long  interval. 

But  radioactivity  tells  us  more  than  this  about  the 
history  of  our  planet,  it  enables  us  to  set  an  upper  hmit, 
as  well  as  a  lower,  to  its  age.  Uranium  still  exists  in  the 
Earth's  crust,  widely  disseminated  in  the  rocks,  though 
in  very  small  quantities,  averaging  about  one  part  in  140,000 
by  weight. 

There  must  have  been  more  uranium  in  the  past,  and, 
in  place  of  that  which  has  changed,  we  should  find  an 
equivalent  amount  of  lead.  Now  the  amount  of  lead  which 
is  now  present  in  the  crust  is  approximately  thrice  that 
of  the  uranium.  Aston's  recent  separation  of  common  lead 
into  isotopes  shows  that  about  30  per  cent  of  this  lead  has 
the  atomic  weight  206.  If  all  the  lead  of  this  sort  has  arisen 
from  disintegration  of  uranium,  a  simple  calculation  shows 
that  the  earth  would  be  4,800,000,000  years  old,  and  to 
account  for  any  considerably  greater  age  appears  to  be 
difficult. 

This  seems  at  first  sight  perilously  like  an  attempt  to 
date  the  Creation.  But  it  dates  not  the  origin  of  matter, 
but  the  formation  of  our  planet,  of  which  we  will  presently 
speak,  pausing  only  to  note  with  what  relatively  narrow 
limits  the  age  of  the  Earth  now  appears  to  be  definable, 
the  upper  limit  being  less  than  three  times  the  lower.  Future 
discoveries  may,  of  course,  give  reason  to  change  these 
estimates;  but,  in  the  present  state  of  knowledge,  the 
conclusion  that  the  Earth  is  more  than  two  and  less  than 
five  billions  of  years  of  age  appears  to  be  trustworthy. 

The  origin  of  the  solar  system  next  requires  consideration, 
and  the  limitations  of  space  compel  an  unwelcome  brevity. 
Our  system  possesses  an  extraordinary  dynamical  pecu- 
liarity. More  than  98  per  cent  of  the  angular  momentum 


LIFE    IN    SPACE    AND   TIME  27 

(a  quantity  whose  total  amount  cannot  be  altered  by  any 
processes  occurring  within  the  system)  is  at  present  pos- 
sessed by  the  planets,  which  form  but  3'foo  of  the  whole 
mass.  There  are  arguments  which  approach,  if  they  do 
not  actually  constitute,  a  proof  that  no  such  extreme 
segregation  of  the  angular  momentum  could  be  brought 
about  by  a  gradual  process  in  an  isolated  system;  and  it  is 
now  generally  admitted  that  here,  for  once,  the  catastrophic 
explanation  is  to  be  preferred  to  the  uniformitarian. 

Much  the  most  satisfactory  theory  of  the  origin  of  the 
planetary  system  is  that  which  attributes  it  to  a  close 
encounter  between  the  Sun  and  a  passing  star  whose  track 
almost  grazed  it.  Under  the  enormous  tidal  forces  huge 
eruptions  of  matter  would  take  place  from  both  bodies.  Much 
would  fall  back  on  the  Sun,  or  be  carried  away  by  the  star; but 
in  the  rest,  set  moving  sidewise  by  the  attraction  of  the 
star  as  it  receded,  we  may  see  the  raw  material  of  planets, 
asteroids,  satellites,  meteors  and  comets.  This  hypothesis 
was  first  advocated  by  Chamberlin  and  Moulton,  and 
has  been  modified  by  Jeans  and  Jeffreys.  Into  the  details 
of  the  controversy  between  the  "planetesimal"  and  "tidal" 
forms  of  the  theory  we  need  not  enter.  Many  of  the  details 
of  the  origin  of  our  system  are  still  obscure,  and  some 
very  puzzling;  but  the  general  theory  of  origin  by  an 
encounter  holds  the  field. 

During  the  earlier  stages  of  the  system,  when  much 
loose  matter  was  still  flying  about,  the  orbits  of  the  planets 
would  tend  to  become  nearly  circular  (as  they  actually 
are).  An  independent  estimate  of  the  age  of  the  system 
may  be  made  from  a  study  of  this  process.  Jeff"reys  reaches 
the  figure  of  7,000,000,000  years,  which  is  only  an  indica- 
tion of  the  order  of  magnitude,  and  theiefore  in  satisfactory 
agreement  with  the  radioactive  data.  Putting  all  this  in  a 
sentence,  it  appears  that  the  solar  system  was  probably 
formed  by  an  encounter  between  the  Sun  and  a  passing 
star,  sometime  about  four  billions  of  years  ago. 

How  does  this  compare  with  the  age  of  the  Sun  itself, 
or  of  the  other  stars?  This  question  refers,  of  course,  to 
their  age  as  stars  (luminous  bodies)  and  not  to  that  of  the 
matter  of  which  they  are  composed. 


28  HUMAN   BIOLOGY 

The  Sun  has  certainly  been  shining,  with  nearly  its 
present  brightness,  throughout  geological  time.  During 
this  interval  it  must  have  dissipated  into  space  an  amount 
of  energy  vastly  exceeding  the  whole  initial  store  of 
potential  energy  of  all  kinds  (gravitational,  chemical,  etc.) 
which  can  be  attributed  to  it  in  virtue  of  known  properties 
of  matter. 

All  investigators  are  therefore  now  agreed  that  some 
otherwise  unknown,  and  enormously  great,  source  of  energy 
exists  in  the  interior  of  the  Sun  and  of  the  stars,  where 
it  is  being  gradually  transformed  into  heat  and  radiated 
from  their  surfaces.  It  is  agreed,  too,  that  this  energy 
must  come  in  some  way  from  the  disintegration  of  atoms, 
though  the  details  of  the  process  are  still  in  debate.  According 
to  the  theory  of  relativity,  all  energy  possesses  mass,  and 
the  Sun  cannot  radiate  heat,  i.e.  energy,  without  diminishing 
in  mass.  To  a  single  pound  of  mass  corresponds  heat  enough 
to  raise  20,000,000  tons  of  rock  to  a  temperatuie  of  2000°c. 
and  convert  it  into  incandescent  lava;  yet,  measured  in 
this  way,  the  Sun's  total  radiation  corresponds  to  a  loss 
of  mass  of  4,600,000  tons  per  second.  This  is  a  truly  startling 
figure,  and  might  raise  alarm  concerning  the  future,  were 
it  not  that  calculation  shows  that  if  consumed  steadily 
at  this  rate,  the  Sun  would  last  for  15,000,000,000,000  years. 

To  what  degree  the  Sun's  actual  hfe  as  a  luminary 
approaches  this  figure  depends  upon  the  as  yet  unanswerable 
question  how  great  a  portion  of  its  mass  is  capable  of  trans- 
formation into  energy.  It  appears  probable,  in  view  of 
certain  properties  of  double  stars,  to  be  discussed  below, 
that  a  large  part  of  the  mass  is  transformable,  and  that 
the  fife  of  a  star  is  thousands  of  billions  of  years  in  length. 
It  is  well  established,  both  by  Eddington's  theory  and  by 
observation,  that  the  more  massive  stars  are  the  brighter. 
Ages  ago,  when  the  sun  was  more  massive,  it  was  doubtless 
brighter  and  hotter;  long  hence,  when  it  has  lost  mass 
perceptibly,  it  will  be  fainter.  It  should,  so  far  as  can  at 
present  be  estimated,  continue  to  supply  light  and  heat 
enough  to  maintain  life  on  the  Earth,  at  its  present  distance, 
for  tens  or  even  hundreds  of  billions  of  years.  The  past 
duration  of  terrestrial  life  appears  theiefore  to  be  but  a 


LIFE    IN    SPACE    AND   TIME  29 

snuiU  IVaction  ol"  that  which,  barring  accidents,  it  may  in 
future  enjoy. 

Only  one  type  of  physical  catastrophe  appears  to  threaten 
any  premature  termination  of  this  long  forecast.  Every 
now  and  then  a  star,  which,  so  far  as  we  can  tell,  has  pre- 
viously been  normal,  suddenly  blazes  out,  and  in  a  few 
days  becomes  ten  thousand  times  brighter  than  the  Sun,  or 
more,  appearing,  even  to  the  naked  eye,  as  a  conspicuous 
"new  star,"  or  nova.  Within  a  few  weeks  the  brightness 
fades,  and  in  a  decade  or  two  it  is  back  almost  where  it  was 
before.  Such  an  outburst  by  the  Sun  would  unquestionably 
destroy  all  earthly  Hfe,  except  possibly  that  in  the  cold  waters 
of  the  deep  sea,  and  even  this  would  probably  soon  perish 
for  lack  of  food;  and  we  may  be  sure  that  none  has  occurred 
since  Pre-Cambrian  times. 

Novae,  however,  are  by  no  means  rare  phenomena; 
one  is  seen  every  year  or  two,  and  many  more  must  escape 
discovery.  Allowing  one  nova  per  year,  which  is  too  few, 
and  ten  biUions  of  stars,  visible  and  invisible  (which  is 
a  great  many)  to  share  the  risks  of  catastrophe,  we  find 
that  an  average  star  is  likely  to  blow  up  once  in  ten  billion 
years,  at  the  longest.  An  interval  ten  times  shorter  would 
be  better  in  accordance  with  the  evidence. 

We  do  not  know,  however,  whether  such  calamities 
happen  to  stars  of  all  sorts,  or  only  to  those  of  certain 
special  characteristics,  nor,  in  the  latter  case,  whether 
the  Sun  belongs  to  a  susceptible  species.  In  any  case,  the 
possibility  is  remote  enough  to  be  eliminated  from  practical 
human  consideration. 

THE    POSSIBLE    EXISTENCE    OF    LIFE    IN    UNKNOWN   WORLDS 

Whether  other  stars,  as  well  as  the  Sun,  have  attendant 
planetary  systems  is  not  a  question  which  can  be  settled 
by  observation,  unless  our  present  powers  of  investigation 
should  be  increased  to  an  extent  which  now  appears  improb- 
able. To  assess  the  probability  that  such  systems  may 
exist  is  not,  however,  beyond  the  sphere  of  legitimate 
inference. 

If  planetary  systems  arise  from  close  encounters  between 
stars,  the  chance  of  their  birth  is  capable  of  calculation. 


30  HUMAN    BIOLOGY 

From  the  known  distances  which  separate  the  stars,  and 
their  rates  of  motion,  it  may  easily  be  shown  that,  on  the 
average,  a  star  should  approach  another  within  a  distance 
equal  to  that  which  separates  the  Earth  and  Sun,  only 
once  in  60,000,000,000,000  years,  and  a  much  closer  approach 
would  probably  be  necessary  to  produce  a  planetary  system. 
This  indicates  that  such  encounters  can  have  happened 
to  but  a  small  fraction  of  the  stars.  Evidence  that  encounters 
at  a  greater  distance  have  actually  happened  is  furnished 
by  the  binary  stars.  Such  a  pair  of  stars  moving  together 
through  space,  and  revolving  about  one  another  in  orbits, 
must  evidently  have  had  a  common  origin.  It  is  reasonable 
to  suppose  that  they  have  been  formed  by  the  division  of  a 
single  mass.  In  this  case,  the  original  orbit  must  have  been 
nearly  circular.  The  present  orbits  are  highly  eccentric; 
and  the  only  way  in  which  it  appears  to  be  possible  to 
account  for  this  is  by  the  effects  of  encounters.  A  passing 
star,  attracting  the  components  in  different  directions  and 
with  different  intensity,  would  disturb  their  motion  and 
convert  a  circular  orbit  into  an  elHpse.  To  account  for  the 
present  high  eccentricity  it  must  be  assumed  that  on  the 
average  a  binary  star  has  met  with  several  such  encounters. 
Jeans,  to  whom  this  argument  is  due,  has  shown  that  this  is 
possible,  provided  that  the  past  lives  of  the  stars  extend 
over  thousands  of  billions  of  years,  so  that  they  have  lost 
considerably  in  mass  since  their  formation. 

Encounters  close  enough  to  produce  planetary  systems 
should  be  much  less  probable  than  those  which  have  just 
been  discussed;  but,  even  so,  they  may  well  have  happened 
to  one  star  in  a  thousand,  or  more.  In  this  case  the  number 
of  planetary  systems  may  run  far  into  the  millions.  It  is 
not  in-  every  such  system  that  planets  would  be  found 
which  were  even  potentially  habitable;  but  the  number 
of  such  bodies  should  nevertheless  be  very  large.  Upon 
how  many  of  them  life  would  actually  be  found  is  not  so 
easy  to  estimate.  But  if  life  exists  in  two  out  of  three  of  the 
possible  places  in  our  system,  it  may  well  be  abundant 
elsewhere. 

All  told,  the  existing  evidence  indicates  that  the  number 
of  worlds  in  which  life  is  actually  to  be  found  within  the 


LIFE    IN    SPACE    AND   TIME  3 1 

known  universe  is  probably  to  be  counted  by  thousands, 
and  may  be  as  great  as  a  million.  In  how  many  of  these 
inteihgent  life  may  exist  we  are  hardly  able  to  conjecture, 
but  there  is  no  reason  for  supposing  that  our  world  is  unique 
even  in  this  respect. 

Only  one  characteristic  remains  by  which  our  system 
and  our  world  are  likely  to  be  distinguished.  It  is  not  at 
all  improbable  that  a  world  but  a  few  billions  of  years 
old  may  be  the  youngest  of  all.  Indeed,  encounters,  under 
present  stellar  conditions,  should  be  so  rare  that  it  appears 
improbable  that  even  one  should  have  happened,  anywhere 
among  the  stars  so  recently.  However,  as  Eddington  puts 
it,  these  few  billions  of  years  may  be  "the  interval  between 
the  event  itself  and  a  direct  consequence  of  this  event 
(viz.  the  evolution  of  beings  capable  of  speculating  about 
it.)"  Compared  with  the  inhabitants  of  the  older  worlds, 
our  race  may  be  primitive  indeed. 

REFERENCES 

Eddington,  A.  S.   1927.  Stars  and  Atoms.  New  Haven,  Yale  Univ.  Press. 
An  admirably  written  popular  account  of  recent  astrophysical  work. 
1926.  The  Internal  Constitution  of  the  Stars.  Cambridge  Univ.  Press. 

Henderson,  L.  J.  1913.  The  Fitness  of  the  Environment.  N.  Y.,  Macmillan. 
1917.  The  Order  of  Nature.  Cambridge,  Harvard  Univ.  Press.  Lucid  discus- 
sions of  the  general  physical  and  chemical  conditions  which  make  life 
and  evolution  possible. 

Jeans,  J.  H.  1919.  Problems  of  Cosmogony  and  Stellar  Dynamics.  Cambridge 
Univ.  Press. 

Jeffreys,  H.  1924.  The  Earth.  Cambridge  Univ.  Press. 

Russell,  H.  N.,  Dugan,  R.  S.  and  Stewart,  J.  Q.  1927.  Astronomy.  Bost. 
Ginn,  2  vols.  A  general  text  book  dealing  more  fully  with  most  of  the 
matter  here  mentioned. 


PART  11.  THE  ORIGIN  OF  MAN 


Chapter  II 

EVOLUTION  TRACED  BIOCHEMICALLY 

A.  B.  Macallum 

THE  cell,  animal  or  vegetable,  as  we  know  it,  is  a  com- 
plex and  highly  developed  chemical  mechanism, 
capable  of  continuing  its  Hfe,  as  it  has  done  in  a 
suitable  environment  through  eons  of  time,  and  transmitting 
to  its  descendants  the  endowments  of  a  far  past.  This  suitable 
environment  did  not  always  obtain  for  in  the  earliest  age 
of  the  earth  the  physical  conditions  on  its  surface  were 
vastly  different  from  what  they  have  been  since  and  are 
now.  This  at  once  suggests  the  question  how  and  when  did 
life  have  its  beginning. 

To  conceive  of  an  answer  to  this  question,  one  must 
concede  that  the  cell  has  in  its  history  undergone  an  evolution 
the  results  of  which  have  as  greatly  modified  its  structure  and 
characters  as  has  evolution  affected  the  multicellular  forms  of 
animal  and  vegetable  hfe.  The  units  of  primordial  hving 
matter  must,  therefore,  as  organisms,  have  been  much 
simpler  chemically  and  structurally,  and  smaller  in  volume, 
than  existing  ordinary  animal  and  vegetable  microorganisms. 
We  can,  from  what  we  know  of  the  latter,  predicate  what 
the  primordial  organism  lacked  as  compared  with  the 
Hving  unicellular  organism  of  today. 

First  of  all  there  was  no  nucleus  in  it.  There  are  cellular 
forms  of  hfe  in  which  no  nuclei  exist,  e.g.  the  blue-green 
algae  (Cyanophyceae),  the  moulds,  and  bacteria.  Nuclei  are 
also  wanting  in  certain  Protozoa  (e.g.  Dileptus  anser),  in 
certain  others  of  which  (Euplotes,  Ceratium,  Euglena,  etc.) 
the  types  of  mitosis  they  exemphfy  indicate  that  their  nuclei 
have  not  yet  acquired  the  special  characters  of  those  found 
in  typical  animal  and  vegetable  cells,  while  in  Calcituba 
mitosis  in  any  form,  rudimentary  or  otherwise,  does  not 
occur,  the  chromatin  of  its  nuclei,  when  cell  division  begins, 
segregating  in  a  pecuHar  fashion  into  a  large  number  of 
spherules   from   which   new   nuclei   are   formed.    Indeed   a 

35 


36  HUMAN   BIOLOGY 

comparative  study  of  the  nuclei  in  Protozoa  shows  that  the 
nucleus  is  not  an  original  organ  of  the  primordial  cell,  but 
developed  gradually  in  its  history,  and  very  probably  long 
before  the  evolution  from  the  primordial  form  of  Hfe,  the 
protocyte,  of  the  first  animal  and  vegetable  cells  had  begun. 
This  would  thus  explain  why  mitosis  is  so  similar  in  both. 
The  non-nucleated  animal  and  vegetable  cells  are  very 
probably  variant  special  survivals  of  descendants  of  the 
protocyte. 

There  was  no  superficial  envelope  for  the  protocyte  such 
as  we  find  enclosing  protozoan  and  protophytan  organisms  of 
today.  The  superficial  layer  of  its  mass  could  have  been 
but  what  the  superficial  layer  of  molecules  formed,  molecules 
kept  in  position  by  cohesive  or  molecular  forces  as  the  super- 
ficial molecules  of  a  drop  of  water  or  of  mercury  are  fixed 
in  their  position  through  the  action  of  surface  tension  forces. 
Such  an  envelope  is  found  in  many  protozoan  forms 
(Amoeba,  Pelomyxa,  etc.)  in  Myxomycetes  (the  slime 
moulds)  and  in  leucocytes,  and  it  is  through  decrease  at 
points  on  the  surface  of  the  tension  there  that  ameboid 
movement  occurs.  The  envelope  is  thus  so  labile,  physically, 
that  the  cell  can  take  in  solid  food  particles  and  even  other 
organisms.  This  type  of  surface  may,  because  of  its  general 
occurrence,  be  considered  as  primordial. 

It  had  not  differentiated  so  far  as  to  constitute  local 
condensations  in  its  interior  in  the  form  of  granules,  spherules 
or  chromidia.  The  protocyte  would  then  be  uniformly 
homogeneous  in  a  microscopic  sense  as  it  is  in  the  plasmodia 
of  slime  moulds  and  in  the  symplasms  (Lohnis)  of  bacteria. 

The  protocyte  must,  therefore,  have  been  a  simple  undif- 
ferentiated cytoplasmic  structure,  but  because  of  its  consti- 
tution, with  potentialities  for  chemical  transformation 
and  for  variations  in  structure  which  explain  the  origin 
and  development  of  the  cellular  organisms  which  have 
evolved  from  it.  It  must  have  been  very  minute,  much 
smaller  in  volume  than  the  cell  of  today  which  we  can  see 
with  the  microscope.  Fragmentation  of  it,  physically  or 
mechanically  engendered,  must  have  been  the  method  by 
which  it  multiplied  and  descendant  forms  arose  and  carried 
on  life. 


EVOLUTION   TRACED   BIOCHEMICALLY  37 

This  organism  must  have  been  capable  of  syntheses  which 
enabled  it  to  hve.  It  had  to  depend  on  the  inorganic  elements 
of  its  environment  for  these  syntheses.  Like  a  number  of 
plancton  organisms  and  bacteria  of  today,  it  was  capable 
of  combining  free  atmospheric  nitrogen  and  carbon  dioxide 
to  form  amino  acids,  the  integral  units  of  the  protein  mole- 
cules constituting  it,  for  after  a  time  the  primeval  atmos- 
pheric and  surface  waters  of  the  earth  contained  no  organic 
compounds  which  it  could  assimilate.  It  could,  therefore, 
live  and  reproduce  itself  in  an  absolutely  inorganic  world, 
and  its  metabohsm,  depending  wholly  on  its  power  to 
synthesize  from  inorganic  elements  its  proteins,  foreshadowed 
the  diatoms  and  desmids  as  well  as  the  Azotobacter 
of  today.  The  capacity  of  these  to  synthesize  from  carbon 
dioxide,  nitrogen,  oxygen,  phosphates  and  sulphates,  their 
organic  components  is  very  probably  inherited  from  the 
protocyte,  or  if  not  inherited,  then  due  to  a  constitution 
of  their  complexes  which  has  developed  to  assimilate  the 
inorganic  elements  of  their  environment. 

How  minute  such  an  organism  must  have  been  can  only 
be  inferred  from  what  we  know  of  the  minutest  organisms 
of  today.  These  are  invisible  under  the  highest  power  of  the 
microscope,  that  is,  they  are  less  in  diameter  than  o.  i  micron 
(a  micron  being  o.ooi  of  a  millimeter)  but  if  they  were 
not  transparent  they  could  be  revealed  with  the  ultrami- 
croscope.  They  can  pass  through  the  pores  of  a  Berkefeld 
filter  and  are  consequently  termed  "filtrable."  One  species 
causes  the  foot-and-mouth  disease,  another  smallpox, 
a  third  rabies,  and  a  fourth  the  mosaic  disease  of  the  tobacco 
leaf,  and  there  are  quite  a  number  of  others  which  are 
pathogenic.  Indeed  it  is  only  because  of  their  pathogenic 
character  that  we  have  any  knowledge  of  their  existence.. 
Whether  these  have  a  normal  habitat  of  their  own  and  are 
pathogenic  only  when  they  infect  animal  or  vegetable 
tissues,  or  whether  there  are  ultramicroscopic  organisms 
which  are  always  non-pathogenic  cannot  be  determined, 
for  there  are  no  methods  for  demonstrating  their  existence 
in  the  non-pathogenic  state.  Therefore,  it  cannot  be  known 
whether  there  are  non-pathogenic  ultramicroscopic  organisms 
which  can  and  do  constitute  proteins  for  their  own  complexes 


38  HUMAN   BIOLOGY 

from  free  nitrogen,  carbon  dioxide,  phosphates,  sulphates 
and  iron  of  their  environment. 

The  fact,  however,  that  there  are  such  ultramicroscopic 
organisms  is  an  indication  that  life  is  possible  in  exceedingly 
minute,  specially  constituted,  protein  complexes,  and  we  can, 
accordingly,  conceive  that  organisms  of  this  type  must  have 
been  the  very  first  to  appear  on  the  earth  when  its  surface 
conditions  favored  the  evolution  of  hfe.  The  fact  also  that 
such  organisms  multiply,  indicates  that  they  must  increase 
in  size  to  permit  this  muItipHcation.  Such  increase  in  size 
may  lead  to  variations  in  volume  and  eventually  to  the 
evolution  of  organisms  of  microscopic  size,  but  with  more 
or  less  undifferentiated  cytoplasm,  from  which  developed 
the  ancestor  of  all  the  cells,  animal  and  vegetable,  of  today. 

What  was  the  origin  of  such  a  primal  ultramicroscopic 
organism? 

There  have  been  advanced  a  number  of  theories  and 
hypotheses  to  account  for  the  origin  of  life  on  the  globe. 
Only  several  of  these  are  now  worthy  of  attention,  and  a 
brief  reference  to  the  character  of  such  may  be  made  here. 

There  was  first  of  all  the  theory  of  spontaneous  generation. 
This  theory,  first  definitely  advanced  by  Aristotle,  but 
held  in  a  more  or  less  inchoate  form  by  earlier  Greek 
philosophers  from  Thales  onward,  postulated  that  living 
organisms  can  arise  spontaneously  in  media  previously 
free  from  all  forms  of  life  whatever.  Lucretius  expressed 
this  view,  when  he  said  that  "the  earth  has  rightfully 
received  the  name  of  mother  since  all  things  are  begotten  of 
it  and  many  living  creatures  arise  out  of  it,  having  been 
generated  by  the  rains  and  the  warm  mists  formed  by  the 
sun."  Till  the  nineteenth  century  the  behef  in  spontaneous 
generation  was  almost  universal  and  it  was  not  an  unnatural 
result  of  observations  made  in  an  uncritical  age.  Some  of 
these  were  very  superficial.  One,  based  on  the  fact  that 
when  a  quantity  of  animal  tissue,  like  beef  muscle,  is  exposed 
to  the  free  air  and  sunshine  at  summer  temperature  larval 
forms  of  flies  and  other  insects  appear  in  it  in  a  few  days, 
was  explained  as  spontaneous  generation  of  these  in  putrefy- 
ing flesh.  This  explanation  was  everywhere  accepted  until 
Redi,  in  1668,  showed  that  when  meat  is  placed  in  a  wide- 


EVOLUTION  TRACED  BIOCHEMICALLY  39 

mouthed  jar  and  the  mouth  covered  w^ith  thin  gauze  per- 
mitting free  entrance  of  air  and  w^armth  but  excluding 
flies  and  other  insects,  no  larvae  of  any  form  made  their 
appearance  in  the  medium. 

The  results  of  similar  carefully  made  experiments  disposed 
of  a  number  of  instances  of  supposed  spontaneous  generation, 
but  the  theory  was  maintained,  nevertheless,  and  it  was 
generally  held  that  the  microorganisms  which  the  micro- 
scope revealed  to  observers  of  the  seventeenth  and  eighteenth 
centuries  did  not  arise  from  preexisting  forms,  a  view 
stoutly  maintained  by  Needham  and  Buffon.  Needham, 
when  he  heated  infusions  of  animal  and  vegetable  matter 
so  as  to  destroy  germs  existing  therein  and  kept  them  for  a 
few  days  at  room  temperature,  found  these  to  contain 
swarms  of  animalculae  which  he  concluded  must  have 
arisen  from  non-hving  matter.  Bufl'on  repeated  Needham's 
experiments  and  confirmed  his  results  and  conclusions. 
Spallanzani,  however,  found  that  no  organisms  appeared 
in  such  infusions  if  they  were  heated  for  half  an  hour  and 
kept  in  flasks  hermetically  sealed  by  fusing  their  necks  in  the 
flame.  This  result  was  regarded  as  decisive  until  after  the 
discovery  of  oxygen  by  Priestley  in  1774,  when  it  was 
maintained  that  from  Spallanzani's  infusions  oxygen  of  the 
air  was  excluded,  and  that  this  element  was  necessary 
there  to  permit  of  spontaneous  generation  of  organisms 
in  it.  The  discussion  on  the  subject  was  continued,  conse- 
quently, until  in  1856  Schroeder  and  von  Dusch,  and  finally, 
in  1859,  Schroeder,  found  that  in  infusions  treated  as  in 
Spallanzani's  experiments,  but  contained  in  flasks  closed 
by  plugs  of  cotton  wool  which  aUowed  free  access  of  air, 
but  no  air-borne  organisms,  to  the  infusions,  no  hving  forms 
developed  therein.  This  result  has  been  confirmed  a  countless 
number  of  times  in  the  last  seventy  years,  and  today  no 
one  beheves  that  Hving  forms  do  spontaneously  originate 
under  the  conditions  which  now  obtain  on  the  surface 
of  the  earth. 

This  turned  attention  to  other  possible  explanations  of 
the  origin  of  terrestrial  Hfe,  and  in  1871  Lord  Kelvin,  then 
Sir  William  Thomson,  advanced  the  view  that  hfe  began 
on    the    earth    when    fragments    of   shattered    hfe-bearing      


40  HUMAN   BIOLOGY 

planets  of  other  solar  systems  far  distant  in  space,  arriving 
as  meteors,  set  free  in  the  earth's  atmosphere  the  organisms 
they  carried  from  their  original  home,  and  that  thus  terres- 
trial hfe  began.  This  theory  involved  difficulties  which 
denied  a  general  acceptance  of  it.  Life  in  organisms,  meteor- 
borne,  would  have  to  be  maintained  for  an  impossible 
length  of  time,  for  a  meteor  derived  from  the  nearest  solar 
system,  that  of  which  a  Centauri  is  probably  the  sun, 
would  require  62,000,000  years  to  reach  the  earth,  moving 
at  the  rate  of  40  miles  per  hour  (Arrhenius),  and  when  it 
plunged  into  the  earth's  atmosphere  the  heat  thereby 
developed  would  sterihze  all  organisms  on  it,  even  if  they 
survived  ahve  after  so  incredibly  long  a  time. 

This  theory,  which  failed  to  win  acceptance,  was  again 
advanced,  but  with  an  important  modification,  in  1903  by 
Arrhenius,  who  used  the  then  recently  discovered  fact  of  the 
pressure  exercised  by  hght  and  other  radiations  to  maintain 
that  organisms  could  be  driven  by  it  through  space  inde- 
pendently of  meteors  and  with  a  velocity  enormously 
greater  than  the  latter  are  supposed  to  have.  This  pressure 
would,  according  to  the  calculations  of  Arrhenius,  reduce 
the  time  for  the  transportation  of  organisms  from  a  Centauri 
from  62,000,000  years  to  9000  years.  These  would  experience 
a  temperature  of  —  220°c.,  that  of  interstellar  space,  from 
the  beginning  to  the  end  of  their  course,  but  the  low  tem- 
perature, which  would  reduce  desiccation  almost  to  an 
absolute  minimum,  would  also  very  greatly  reduce  the  chem- 
ical activities  in  the  organisms  and  these  would  then  survive, 
as  it  were  in  a  latent  condition,  and  reach  the  earth's  atmos- 
phere, in  which,  because  of  their  enormous  velocity  (more 
than  800  miles  per  second)  friction  would  develop  a  tem- 
perature of  not  less  than  ioo°c.  This,  Arrhenius  held, 
would  not  necessarily  sterilize  them  for  the  protein  in  them, 
being  in  a  very  dry  state,  would  not  be  denatured  at  such  a 
temperature.  He  discounted  the  action  of  light  on  such 
organisms,  for  cultures  of  certain  bacteria  had  been  found 
unaffected  by  bright  sunlight  after  a  month  of  exposure 
to  it. 

This  theory,  in  the  present  state  of  our  knowledge  bearing 
on    the    facts    involved,    does    not    appear    tenable.    It   is 


EVOLUTION   TRACED   BIOCHEMICALLY  4 1 

scarcely  conceivable  that  the  high  temperature  of  120°  to 
300°c.  developed  on  contact  with  the  atmosphere  would 
leave  unaffected  the  living  complexes  of  these  organisms, 
and  that  the  intense  ultraviolet  light  from  the  sun,  a  great 
portion  of  which  does  not  penetrate  the  earth's  atmosphere, 
would  not  sterilize  the  organisms  before  they  reached  the 
outer  limit  of  the  atmosphere. 

The  theory  of  Arrhenius,  furthermore,  left  unexplained 
the  origin  of  life.  It  merely  postulated  that  hfe  originated 
somewhere  else  in  the  universe  than  on  the  earth  and  did  not 
attempt  to  explain  how.  If  life  originated  elsewhere,  what 
were  the  conditions  that  promoted  this  origin,  and  in  what 
respect  were  they  different  from  those  which  prevailed  on  the 
earth  at  some  time  in  Its  history? 

One ,  must,  accordingly,  turn  for  intellectual  satisfaction 
to  another  theory  which  does  not  avoid  the  cardinal  element 
of  the  problem  but  predicates  that  life  will  originate  any- 
where in  the  universe  where  the  conditions  favoring  its 
origin  obtain.  It  postulates  also  that  such  conditions  obtained 
on  the  earth  during  its  earliest  geological  age,  conditions 
which,  as  Huxley  expressed  it,  "it  can  no  more  see  again 
than  a  man  can  recall  his  infancy."  Among  those  who  have 
been  expositors  of  this  theory  during  the  last  fifty  years 
may  be  named  Pfliiger,  Moore,  Allen,  Sharpey-Schafer, 
and  Osborn,  and  in  19 10  the  author  gave  his  unreserved 
endorsement  of  it. 

This  theory  must  not  be  confused  with  that  of  spontaneous 
generation.  The  latter,  discredited  now,  as  already  indicated, 
implied  that  life  could  originate  de  novo  today  under  the 
conditions  which  ordinarily  prevail  on  the  earth's  surface. 
To  prevent  this  confusion  the  theory  now  to  be  discussed 
should  be  called  the  paleogenetic  theory. 

The  conditions  necessary  for  this  generation  of  living 
forms  must  have  prevailed  on  the  earth's  surface  when  the 
temperature  of  its  rock  crust  sank  below  ioo°c.  At  tem- 
peratures above  350°c.  all  the  water  later  forming  the 
oceans  was  then  as  water  vapor  in  the  atmosphere  which 
had  a  pressure  more  than  two  hundred  times  what  it  exercises 
today.  Countless  condensations  must  have  taken  place 
on  the  hot  rock  crust,  and  the  water  condensed  must  as 


42  HUMAN   BIOLOGY 

often  have  boiled  away  until  the  temperature  fell  to  about 
I20°c.,  when  permanent  deposits  of  water  were  formed, 
but  the  atmospheric  pressure,  because  of  the  still  large, 
though  now  reduced,  quantity  of  water  as  vapor  in  the 
atmosphere,  must  have  been  about  or  more  than  twenty 
times  as  great  as  it  is  today.  As  these  condensations  occurred 
almost  continuously  or  consecutively,  there  must  have 
been,  also  continuously,  electrical  discharges  of  enormous 
voltage  which  ionized  the  constituents  of  the  .atmosphere 
and  caused  the  formation  of  new  compounds  which  must 
have  played  a  part  in  later  syntheses,  especially  in  local 
condensations  of  water  which,  on  reduction  of  volume 
through  evaporation,  retained  them  as  solutes  more  or  less 
concentrated. 

What  were  these  constituents?  For  an  answer  we  must  go 
to  what  spectroscopy  has  revealed  regarding  the  con- 
stituents in  the  gaseous  envelopes  of  the  cooler  stars.  It 
has  been  found  that  in  stars  of  the  type  k*  (with  temperature 
of  not  more  than  4000°c.)  hydrocarbons  are  present,  and 
in  the  n  stars  (with  a  temperature  of  about  3000°c.)  and  the 
R  stars  (with  a  temperature  of  about  2300°c.)  carbon 
monoxide,  cyanogen,  methane,  oxygen  and  nitrogen  are 
found.  In  the  atmosphere  of  each  of  not  a  few  of  the  deriva- 
tions of  such  stars,  as  planets  are,  each  with  a  diameter  of 
more  than  4000  miles,  these  gases,  with  water  vapor,  must 
have  obtained,  and  thus  the  atmosphere  of  the  earth  in  the 
earliest  period  of  its  history  was  very  probably  so  constituted. 
What  the  proportion  of  each  gas  was  cannot  be  known, 
but  undoubtedly  carbon  dioxide  was  more  and  oxygen  less 
abundant  than  in  the  atmosphere  of  today,  for  the  carbon 
of  the  coal  deposits  was  then  combined  with  oxygen  as 
carbon  dioxide  from  which  it  was  set  free  by  vegetable 
life,  and  thus  the  oxygen  content  of  the  atmosphere  was 
increased.  Thus  the  earth  inherited  its  primeval  atmosphere. 

In  that  atmosphere  when  condensations  of  the  water 
vapor  began  there  must  have  been  other  inorganic  con- 
stituents, especially  the  chlorides  of  sodium  and  potassium, 
since  rain  water  today  carries  from  the  sea  these  salts  to  the 
land  surface,  for  M.  J.  Pierre  found  in  the  rain  water  collected 

*  Of  the  Harvard  classification. 


EVOLUTION    TRACED   BIOCHEMICALLY  43 

in  the  neighborhood  of  Caen  (see  Smith,  cited  by  Joly)  as 
much  as  1.23  tons  of  potassium  per  square  mile  per  year,  and 
this  indicates  that  other  salts  were  present.  Though  chlorides 
were  then  not  as  concentrated  as  they  are  in  the  ocean  today, 
some  of  what  the  first  condensations  dissolved  from  the 
hot  lithosphere  must  have  been  carried  into  the  water-laden 
atmosphere  of  the  time.  These  chlorides,  thus  present, 
must  have  been  to  a  great  extent  dissociated  (ionized) 
through  the  electric  discharges  accompanying  the  condensa- 
tions and  free  chlorine  would  thus  be  present  to  react 
with  the  other  constituents  of  the  atmosphere  and  promote 
the  formation  of  new  compounds.  With  the  first  condensa- 
tions the  water  acting  on  carbides  of  the  hot  rock  crust, 
such  as  those  of  calcium  and  iron,  would  set  free  methane 
and  other  hydrocarbons,  which  with  the  free  chlorine 
would  render  possible  other  syntheses. 

What  all  the  compounds  so  formed  were  one  cannot 
predicate  with  certainty,  but  one  may  reasonably  assume 
that  some  of  them  were  carbonyl  chloride  (COCI2),  carbonyl 
chloramide  (CIC0-NH2),  chlor-methane  (CHs-CI),  ethane 
(CH3CH3),  acetic  acid  (CH3COOH),  acetamide  (CH3CO- 
NH2),  amino-acetic  acid  (NH2-CHo-COOH),  propionic  acid 
(CH3-CH2-COOH),  amino-propionic  acid  (CH:,CH-NH2- 
COOH)  and  thio-amino-propionic  acid  (CH2SH-CH-NH2- 
COOH).  Such  would  be  condensed  with  the  water  vapor 
when  the  temperature  fell  below  ioo°c.,  and  in  small  bodies 
of  water,  which  by  evaporation  became  reduced  in  volume, 
they  would  become  concentrated  and  then  further  syntheses 
would  occur. 

From  these,  under  the  physicochemical  conditions  pre- 
vailing in  their  media,  in  which  were  contained  chlorides, 
phosphates  and  also  catalysts,  traces  of  iron  salts  for  example, 
peptides  and  even  polypeptides,  consisting  of  many  amino 
acid  links,  would  be  synthesized,  some  of  these  approaching 
in  composition  the  constitution  of  proteins. 

These  syntheses  would  take  place  countless  millions  of 
millions  of  times,  resulting  in  many  varieties  of  products 
until,  eventually,  there  would  be  formed  a  protein  complex 
of  ultramicroscopic  size,  endowed  with  the  constitution, 
and,    accordingly,    the    properties    of   an    ultramicroscopic 


44  HUMAN   BIOLOGY 

organism,  capable  of  synthesizing  its  own  complex  from 
the  carbon  dioxide,  nitrogen  and  other  constituents  of  its 
habitat,  thus  increasing  in  size,  which  would  at  length 
entail  divisional  fragmentation  and  reproduction.  So  would 
begin  the  long  reign  of  life  on  earth. 

At  what  temperature  of  the  primal  surface  water  of  the 
earth  this  synthesis  occurred  can  only  be  conjectured.  It 
must  have  been  not  above  8o°c.,  and  possibly  much  lower, 
for  although  certain  algae  live  and  multiply  in  the  waters 
of  hot  springs  at  temperatures  above  8o°c.,  and  bacteria 
of  the  thermophilic  class  can  be  cultivated  in  media  at 
8o°c.,  with  an  optimum  of  6^°  to  70°c.,  this  accommodation 
to  high  temperatures  may  be  a  later  adaptation.  When, 
of  course,  a  living  complex  is  formed  of  proteins  of  a  simple 
type  it  should,  one  may  suppose,  be  more  resistant  to  the 
action  of  heat,  but  many  of  the  proteins  which  we  can 
prepare  from  animal  and  vegetable  cells  are  "denatured" 
at  6o°c.,  and  at  8o°c.  all  are  so  altered  that  the  life  of  the 
organisms  yielding  them  or  formed  of  them  at  once  ceases. 
Indeed  there  are  few  organisms,  and  these  nearly  all  bacterial, 
which  can  survive  a  temperature  of  50°c.  maintained  for 
several  days.  Possibly  the  protocyte,  because  of  its  com- 
paratively simple  constitution,  may  have  been  able  to 
survive,  and  even  to  thrive,  at  8o°c.,  but  as  the  temperature 
of  its  media  fell  gradually  it  would  adjust  itself  accordingly, 
and  thereby  finally  develop  an  altered  protein  complex 
at  20°  to  30°c.,  which  at  higher  temperatures,  50°  to  70°c., 
would  be  "denatured,"  thus  ceasing  to  live.  In  this  adjust- 
ment it  is  possible  that  new  amino  acids,  those  with  cyclic 
atom  complexes  in  them  for  instance,  would  be  formed 
which,  entering  into  the  constitution  of  the  protein  complex, 
made  it  more  sensitive  and  more  readily  affected  by  higher 
temperatures. 

To  summarize:  the  primal  organism,  the  protocyte,  was 
ultramicroscopic  in  size,  was  of  comparatively  simple 
constitution,  and  began  as  a  product  of  the  union  in  a 
special  complex  of  a  number  of  amino  acids  which  were 
formed  from  constituents  of  the  atmosphere  when  the 
condensations  of  water  vapor,  at  or  below  ioo°c.,  were 
continuous,   and  when  also  evaporation  of  small  isolated 


EVOLUTION    TRACED   BIOCHEMICALLY  45 

bodies  of  water  concentrated  the  amino  acids  in  them 
and  rendered  the  synthesis  of  them  to  complexes,  millions  in 
number,  one  of  which,  of  special  constitution,  had,  to  use 
Tyndall's  expression,  "the  promise  and  potency  of  all 
terrestrial  hfe." 

The  animal  cell,  so  far  as  experimental  results  indicate, 
lacks  the  power  of  synthesizing  any  of  the  amino  acids 
except  the  simplest,  amino  acetic,  and  consequently  it 
must  depend  on  those  formed  by  vegetable  cells.  It  must 
then  have  evolved  later  from  cells  which  had  the  power  of 
synthesizing  their  own  amino  acids,  but  which  tended  to 
vary  and  to  develop  ultimately  a  dependence  for  these 
on  the  hydrolysis  of  the  proteins  of  vegetable  organisms  they 
invaginated.  The  Protozoa  of  today,  with  the  exception  of  a 
number  of  forms,  derive  their  amino  acids  from  the  hydrolysis 
of  the  organisms,  animal  and  vegetable,  which  they  ingest. 

This  variation  could  only  have  begun  after  the  cell 
nucleus  had  fully  developed,  for  mitosis  in  typical  animal 
cells  is  so  similar  in  its  character  to  mitosis  in  typical  vege- 
table cells  as  to  make  it  difficult  to  suppose  that  it  originated 
independently  in  both  kingdoms.  The  variation  could  not 
have  developed  except  after  a  long  time,  perhaps  millions 
of  years.  There  would  appear  to  be  today  descendants  of  a 
very  early  stage  in  this  variation,  for  Euglena,  Peridinium, 
Ceratium  and  other  flagellates,  which  at  times  contain 
chlorophyl  and  then  synthesize  from  inorganic  elements 
their  own  proteins  and  carbohydrates,  and  are  consequently 
regarded  by  some  as  vegetable  organisms,  are  also  by 
zoologists  generally  classed  as  animal  forms.  It  is  also 
remarkable  that  in  these  forms  the  mitotic  figure  in  all  its 
stages  is  so  different  from  what  it  is  in  typical  animal  and 
vegetable  cells,  and  so  rudimentary  in  character  as  to  suggest 
that  in  these  forms  are  still  repeated  the  nuclear  form  and 
structure  that  obtained  in  an  early  stage  of  the  evolution  of 
typical  mitosis. 

The  fact  that  the  flagellates  mentioned  could  alter 
with  the  conditions  of  their  environment  their  metabolic 
activities,  so  as  either  to  be  photosynthetic  or  to  depend  for 
their  nourishment  wholly  on  ingested  food  material,  is  an 
indication   that   the   primal   ancestors   of  the   animal   cell 


46  HUMAN   BIOLOGY 

could  have  arisen  from  variants  of  vegetable  organisms 
in  which  there  was  such  an  adjustment  in  their  metabohsm 
as  to  permit  eventually  the  development  of  the  animal 
type  of  nutrition. 

The  nucleus  of  the  animal  cell,  then,  harks  back  to  that 
of  the  vegetable  cell  when  mitosis  had  developed  and  become 
as  characteristic  as  it  is  in  the  typical  animal  and  vegetable 
cells  of  today.  The  transmission  of  mitosis,  unchanged, 
then,  through  hundreds  of  millions  of  years  from  the  time 
when  animal  organisms  had  not  yet  developed,  predicates 
an  incredibly  long  time  for  the  primal  vegetable  cells  to 
develop  mitosis  so  fixed  in  character  as  to  render  it  invariable 
in  its  characters  after  all  that  time. 

The  nucleus  then  must  be  an  organ  which  in  origin 
antedates  that  of  the  animal  cell.  This  prompts  the  question 
why  it  arose.  The  answer  is  not  at  hand,  but  one  may  refer 
to  some  facts  which  point  to  a  solution  of  it. 

The  life  of  the  protocyte  must  have  been  at  first  passed 
wholly  in  the  waters  of  the  globe  in  which  the  salts  dissolved 
from  the  rock  crust  must  have  been  of  low  concentration. 
Into  the  complex  of  the  protocyte  these  would  diffuse, 
and  it  would  adjust  itself  to  them.  If  any  chromatin  obtained, 
it  would  have  been  unaffected  by  them,  or,  if  affected,  only 
to  an  extent  that  would  have  produced  some  of  the  variations 
such  an  originally  undifferentiated  organism  would  undergo. 
The  concentration  of  the  salts  in  its  habitat  was,  however, 
slowly  increasing  as  it  has  done  ever  since,  till  now  in  the 
ocean  water  they  amount  to  3.5  per  cent.  This  increase  in 
concentration  must  have  begun  to  affect,  in  some  degree, 
the  chromatin,  rendering  it  uncertain  in  its  control  of  the 
metabolism  of  the  cell  and  also  of  the  transmission  of 
inherited  characters.  When  the  nucleus  developed,  it  was,  so 
to  express  it,  to  protect  the  chromatin  from  such  effects,  for 
inorganic  salts  are  wholly  absent  from  it  although  the  cyto- 
plasm of  the  cell,  animal  or  vegetable,  may  be  more  or  less 
densely  charged  with  them. 

The  nucleus,  on  this  conception  of  one  of  its  functions, 
therefore,  developed  when  the  concentration  of  the  salts  in 
the  cytoplasm  had  considerably  increased  and  when  it  was 
about  the  same  as  in  the  sea  water  of  the  period.  The  cyto- 


EVOLUTION    TRACED   BIOCHEMICALLY  47 

plasm  must  have  adjusted  itself  to  this  concentration,  which 
could  no  longer  affect  the  chromatin,  and  when  evolution 
had  produced  vertebrates  the  cells  of  such,  bathed  in  a 
plasma  with  constant  inorganic  composition,  must  have 
inherited  to  a  certain  extent  this  adjustment.  The  inorganic 
composition  of  such  cells  may  then  be  regarded  as  indicating 
the  composition  of  the  ocean  water  when  the  nucleus  had 
evolved. 

To  ascertain  what  this  composition  was,  one  must  take 
for  analysis  more  or  less  undifferentiated  cells  such  as 
amebae,  leucocytes  and  unfertihzed  ova  of  the  lower  verte- 
brates. Amebae  or  leucocytes  cannot  be  obtained  in  sufficient 
numbers  to  furnish  material  for  such  analyses,  but  ova 
can  be  used  and  analyses  of  those  of  the  common  herring 
gave,  in  per  cent: 

Na  K  Ca  Mg  CI 

0.08175  0.1795  0.00458       0.00138        0.2937 

The  excess  of  potassium  over  sodium  (Na:K  ::  100:219.9) 
is  in  contrast  with  what  obtains  in  the  ocean  today,  in  which 
the  sodium  is  to  the  potassium  as  100  is  to  3.61.  That  the 
ocean  water  of  the  earhest  geological  period  was  much  richer 
in  potassium  than  in  sodium  is  indicated  by  analyses  which 
have  been  made  of  the  waters  of  lakes  in  regions  where 
nearly  all  the  surrounding  surface  rocks  are  of  pre-Cambrian 
origin.  The  water  of  Reindeer  Lake,  situated  about  400 
miles  north  of  Winnipeg,  and  surrounded  wholly  by  Archean 
rocks,  contains  at  least  twice  as  much  potassium  as  sodium. 
So  also  do  the  waters  of  Rachel  See,  Wiirm  See  and  Ronig 
See,  of  the  Bavarian  Highlands.  The  ocean  water  of  the 
Archean  must  have  thus  been  richer  in  potassium  than  in 
sodium. 

The  salts  in  the  ova  amount  to  0.5609  per  cent,  or  less 
than  one-sixth  of  the  concentration  in  the  ocean  of  today. 
If  this  was  inherited,  then  the  animal  cell,  as  such,  evolved 
before  the  end  of  the  first  sixth  of  the  whole  geological 
part  of  the  history  of  the  earth. 

This  estimate  may  not  be  confirmed  when  analyses 
of  other  undifferentiated  animal  cells  have  been  made,  but 
so  far  it  is  of  interest  as  indicating  that  after  life  first  began 


48 


HUMAN   BIOLOGY 


on  earth  from  fifty  million  to  one  hundred  and  fifty  milHon 
years  had  passed  before  the  cell  nucleus  had  evolved  and 
become  fixed  as  an  organ. 

There  is  not  much  uncertainty,  if  any,  about  the  origin 
of  the  inorganic  composition  of  the  blood  plasma  and 
lymph  of  vertebrates.  The  first  circulatory  fluid  of  inverte- 
brates was  the  sea  water  in  which  they  lived,  as  it  is  today 
in  a  number  of  forms.  It  passed  through  openings  into  the 
channels  of  the  primitive  vascular  system,  and  when  in 
higher  forms,  as  they  developed,  this  system  became  closed 
off  from  the  exterior,  the  fluid  it  contained  was  still  sea 
water  of  that  early  period,  as  still  are,  in  the  composition 
and  concentration  of  their  salts,  the  blood  plasma  and  lymph 
of  vertebrates  of  today.  This  is  seen  on  comparison  of  the 
ratios  of  the  elements  in  it  with  those  in  the  sea  water  of 
today: 


Na 

K 

Ca 

Mg 

Ocean  water  of  today 

100 

3.6i 

3-91 

12.  I 

Human  plasma 

lOO 

6.75 

3-1 

0.7 

Mammal  plasma  (average) 

100 

6.6 

3-2 

0.76 

The  concentration  of  the  salts  in  the  plasma  of  mammals 
is  about  0.89  per  cent  (0.87  to  0.91  per  cent),  while  in  the 
ocean  they  amount  to  3.5  per  cent,  that  is,  really  four  times 
as  much  as  it  must  have  been  when  the  first  vertebrate, 
the  eovertebrate,  appeared.  The  Amphibia  and  Reptilia 
began  in  the  Carboniferous  Period  and  the  Mammalia 
began  in  the  Triassic.  As  these  were  chiefly  land  forms  they 
transmitted  to  their  descendants  the  inorganic  composition 
of  their  blood  plasma  derived  from  their  ancestors  of  the 
Cambrian  or  Ordovician. 

The  concentration  of  the  salts  in  the  ocean  has  ever 
been  increasing  steadily,  and  with  this  increase  there  has 
been  an  alteration  in  the  ratios  of  the  elements  therein  to 
each  other.  The  potassium  and  calcium  have  increased,  but 
not  proportionately,  for  the  former  has  been,  and  is,  con- 
stantly eliminated  to  form  the  mineral  glauconite,  scattered 
over  the  floor  of  the  ocean,  and  in  the  sedimentary  deposits 
of  various  periods,  while  of  the  calcium  always  added,  a 


EVOLUTION  TRACED  BIOCHEMICALLY 


49 


part  has  gone  to  form  the  Hmestone  deposits.  The  sodium 
and  magnesium  have  always  been  increasing  in  the  ocean, 
and  the  latter  relatively  more  rapidly  than  the  sodium. 
This  would  account  for  the  ratio  of  the  two,  lOo:  12.  i,  in  the 
ocean  water  of  today,  as  contrasted  with  the  ratio  of  100:0.8 
in  the  blood  plasma  of  mammals. 

On  the  concentration  of  salts  in  the  plasma  of  those 
vertebrates  which  have  had  a  marine  habitat  since  their 
origin,  the  gradually  increasing  concentration  of  the  salts 
in  the  sea  has  had  a  marked  effect.  This  is  seen  in  the  elasmo- 
branchs  (sharks,  dog  fishes  and  rays)  which  have  been 
marine  since  their  origin  in  the  Ordovician  or  early  Silurian. 
The  concentration  in  the  plasma  of  the  sand  shark,  Car- 
charias  littoralis,  was  found  to  be  1.938  per  cent,  slightly 
more  than  twice  that  in  the  blood  plasma  of  mammals. 
The  ratios  of  the  elements  to  each  other  are,  however, 
but  slightly  changed,  particularly  in  regard  to  magnesium, 
the  concentration  of  which  is  relatively  far  below  that  in  sea 
water. 

In  invertebrates  with  a  closed  circulation  which  have 
been  marine  as  long  as  the  elasmobranchs  have,  the  blood 
plasma  is  practically  sea  water.  This  is  the  case  in  the  horse- 
shoe crab  (Limulus),  which  has  always  been  marine  since 
the  close  of  the  Cambrian.  In  the  blood  of  this  the  concen- 
tration of  the  salts  found  was  2.98  per  cent,  whereas  in  the 
ocean  water  of  the  habitat  of  the  horseshoe  crabs  whose 
blood  was  analyzed,  it  ranged  from  2.9  to  3.12  per  cent. 
The  sea  water  thus  controls  the  composition  of  the  plasma 
in  Limulus.  It  does  so  also  in  the  case  of  the  lobster,  Homarus, 
descended  from  a  fresh  water  form  of  the  Cretaceous. 
The  concentration  of  the  salts  in  its  plasma  was  found 
to  be  2.852  per  cent,  practically  the  same  as  that  of  its 
habitat,  but  the  ratios  are  not  the  same,  as  may  be  seen : 


Na 

K 

Ca 

Mg 

Sea  water 

100 

3.61 

3-91 

12. 1 

Limulus 

100 

5.62 

4.06 

II. 2 

Homarus 

100 

3-73 

4.85 

1.72 

Carcharias 

100 

5-75 

2.98 

2.76 

Mflmmfll  fflverasre^      

100 

6.6 

3-2 

0.76 

50  HUMAN   BIOLOGY 

The  sea  water  has  dominated  ahnost  completely  the 
inorganic  composition  of  the  blood  plasma  in  Limulus,  less 
so  in  Homarus,  and  very  much  less  so  in  Carcharias,  although 
it  has  increased  therein  the  Na:Mg  ratio,  which,  however, 
is  only  about  one-fourth  that  in  the  blood  of  Limulus. 

The  circulatory  fluid  of  the  eovertebrate  must  have  been, 
therefore,  sea  water  of  the  time,  and  the  concentration  and 
proportion  of  the  salts  in  it  then  obtaining  were  maintained 
in  the  blood  of  the  vertebrates  which  exchanged  the  marine 
for  a  land  habitat  in  the  early  Carboniferous,  and  from 
which  later  mammals  developed.  The  blood  plasma  of  the 
latter  is,  on  its  inorganic  side,  then,  but  the  sea  water  of  the 
early  Cambrian,  when  the  ratios  of  the  elements  and 
the  concentration  of  these  were  different  from  what  they 
are  now. 

The  maintenance  of  these  through  hundreds  of  millions  of 
years  is  undoubtedly  a  function  of  the  vertebrate  kidney. 
There  is  in  invertebrates  no  organ  or  organs  having  this 
function,  for  the  coxal  glands  of  the  lobster,  which  are 
excretory,  maintain  the  ancient  ratios  of  the  inorganic 
elements  in  its  blood  plasma  but  do  not  control  the  concen- 
tration of  these,  and  in  consequence  the  salts  of  its  blood 
are  as  concentrated  as  those  of  its  habitat.  In  the  whales, 
the  Cetacea,  on  the  other  hand,  which  have  had  a  marine 
habitat  almost  as  long  as  the  lobster  (since  the  early  Eocene), 
the  concentrations  of  the  salts  and  the  ratios  of  the  elements 
therein  are  the  same  as  in  the  blood  plasma  of  the  horse 
and  pig,  which,  with  the  Cetacea,  were  derived,  it  is  held  by 
some  paleontologists,  from  a  mammal  form  of  the  Triassic. 

In  the  long  ages  the  kidney  has  ever  thus  performed 
functions  with  a  constancy  and  regularity  which  are  unri- 
valled in  the  world  of  life,  except  by  those  of  the  cell  nucleus 
which  is,  of  course,  of  vastly  more  remote  origin.  This 
constancy  contrasts  with  the  variations  in  functions  which 
other  organs  in  vertebrates  have  undergone.  It  has  made 
the  Vertebrata,  with  all  their  range  of  development,  possible, 
and  without  it  there  could  be  no  change  of  habitat  from 
sea  to  land  or  fresh  water  and  back  again  to  sea,  for  with 
each  such  change  there  would  be  a  variation  in  the  inorganic 
composition  of  the  internal  medium,  an  impossible  handicap 


EVOLUTION   TRACED   BIOCHEMICALLY  5  I 

to  overcome  in  the  evolution  of  vertebrates,  the  highest 
form  of  life  on  the  globe.  In  other  words,  without  this 
control  of  the  composition  of  the  internal  medium  there 
would  be  no  vertebrates. 

In  conclusion,  and  to  summarize,  there  were  three  great 
epochs  in  the  story  of  Hfe  on  the  earth. 

The  first  of  these  was  the  generation  of  hfe  itself  as 
an  ultramicroscopic  organism,  the  protocyte,  as  a  product 
after  many  milhons  of  syntheses  of  amino  acids,  derived 
from  the  first  constituents  of  the  atmosphere  and  water 
of  the  earth  in  the  beginning  of  geological  time,  had  achieved 
the  composition  of  a  complex  capable  of  repeating  itself  by 
syntheses  and  thus  initiating  the  long  reign  of  life  on  the 
globe. 

The  second  was  the  evolution  of  the  cell  nucleus  as  a 
sanctuary,  as  it  were,  to  protect  the  chromatin  from  the 
action  of  the  salts  of  the  sea  water  ever  increasing  in  con- 
centration and  ever  invading  the  cytoplasm  of  the  cell. 
This  protection  enabled  the  chromatin  to  transmit  to 
offspring  cells  and  organisms  inherited  characters,  and  thus 
to  render  evolution  from  stage  to  stage  possible. 

The  third  was  the  development  of  a  renal  organ  which 
controlled  and  stabilized  the  composition  of  the  internal 
medium,  the  blood  plasma,  bathing  the  cells  of  vertebrates 
and  thus  providing  for  constancy  in  the  primal  concentra- 
tions of  the  salts  in  the  cytoplasm  of  each,  inherited  from  the 
time,  when  the  cell  nucleus  was  evolved. 

REFERENCES 

Allen,  F.  J.  1899.  What  is  life?  Proc.  Birminghayn  Nat.  Hist.  &  Phil.  Soc, 

12:  44-67. 
Arrhenius,  S.    1907.   Das  Warden  der  Welten,  Trans,   from   Swedish  into 

German  by  L.  Bamberger,  Leipzig.  English  Trans,  by  H.  Borus,   1908. 
Huxley,  T.  H.   1870.  Pres.  Address,  Brit.  Ass.  Adv.  Science.  Report  Brit. 

Assn.  1870,  Lond.,  John  Murray. 
Kelvin,  Lord  (Sir  William  Thomson)  1871.  Pres.  Address,  Brit.  Ass.  Adv. 

Science,  Report  Brit.  Assn.  1871,  Lond.,  John  Murray. 
Macallum,  a.  B.  1910.  The  origin  of  life  on  the  globe.  Trans.  Can.  Inst.,  8: 

423-441. 
Macallum,  A.  B.  1926.  The  palaeochemistry  of  the  body  fluids  and  tissues. 

Physiol.  Rev.,  6:  316. 
Moore,  B.   1912.  The  Origin  and  Nature  of  Life.  Home  University  Library, 

62,  Lond.,  Willams  &  Norgate.    • 


52  HUMAN   BIOLOGY 

Needham,  T.  1748.  A  summary  of  some  late  observations  upon  the  generation , 

composition  and  decomposition  of  animal  and  vegetable  substances.  Pbil. 

Trans.  Roy.  Soc,  Lond. 
OsBORN,  H.  F.   1917.  Tlie  Origin  and  Evolution  of  Life.  N.  Y.,  Scribner's. 
Pfluger,  E.  1895.  Ueber  die  physiologische  Verbrennung  in  den  lebendigen 

Organismen.  Arch.  ges.  Physiol.,  10:  251. 
Redi,    F.    1 67 1.    Experientia   circa   Generationem    Insectorum.   Amsterdam. 

Trans,  into  English  by  N.  Bigelow,  1909. 
ScHROEDER,    H.   uud   VON   DuscH,  Th.    1 854.   Ueber   Filtration  der  Luft  in 

Beziehung  auf  Faulnis  und  Gahrung.  Ann.  d.  Cbem.  u.  Pbarm.,  89:  232. 
ScHROEDER,  H.   1 859.  Ucbcr  Filtration  der  Luft  in  Beziehung  auf  Faulnis, 

Gahrung  und  KrystalHzation.  Ann.  d.  Cbem.  u.  Pbarm., log:  35. 
Sharpey-Schafer,  Sir  E.  A.  1912.  Life:  its  nature,  origin  and  maintenance. 

Pres.  Address,  Brit.  Assn.  Adv.  Science.  Report  Brit.  Assn.  191 2.  Lond., 

John  Murray. 
Smith,  A.  Air  and  Rain.  Cited  by  Joly,  J.  1899.  An  estimate  of  the  geological 

age  of  the  earth.  Trans.  Roy.  Soc.  Dublin.,  s.  2,  7:  23. 
Spallanzani,  L.  1786.  Experiences  pour  Servir  a  I'Histoire  de  la  Generation 

des  Animaux  et  des  Plantes. 
Tyndall,  J.  1874.  Pres.  Address,  Brit.  Assn.  Adv.  Science.  Report  Brit.  Assn., 

1874,  Lond.,  John  Murray. 


Chapter  III 

THE  ANIMAL  ANCESTRY  OF  MAN 

William  K.  Gregory 

"know  thyself" 

THE  almost  hopeless  egocentrism  of  man,  his  deep 
prejudices  and  his  aversion  to  his  "poor  relations," 
the  apes  and  monkeys,  make  it  extremely  difficult  to 
secure  complete  and  ungrudging  acceptance  of  the  con- 
sequences of  man's  status  as  a  regular  member  of  the  order 
of  Primates.  To  this  day  the  discovery  of  man's  place  in 
Nature,  as  recognized  for  instance  by  Linnaeus  in  1759 
and  confirmed  since  then  by  thousands  of  separate  items  of 
proof,  remains  virtually  unknown  to  the  masses  of  the 
"educated"  and,  with  some  exceptions,  is  commonly 
ignored  by  college  presidents.  Even  the  word  Primates, 
except  as  apphed  to  certain  ecclesiastics,  is  not  to  be  found 
among  the  seventy  thousand  common  Engfish  words  fisted 
in  a  recent  abridged  edition  of  Webster's  dictionary.  Yet 
a  good  part  of  what  man  is  now,  even  many  of  his  parasites, 
diseases  and  structural  weaknesses,  to  say  nothing  of  his 
mental  characteristics,  come  to  him  by  way  of  his  primate 
ancestors.  When  we  give  up  the  traditional  method  of  the 
ostrich  in  deafing  with  such  unsavory  facts,  our  eyes  will 
be  open  to  the  wholesomeness  of  the  fruit  of  the  tree  of 
knowledge. 

It  is  therefore  the  object  of  the  present  chapter  to  indicate 
a  few  of  the  multitudinous  ways  in  which  man's  animal 
ancestry  conditions  his  present  biological  status,  to  trace 
the  main  stages  of  his  "ascent  to  Parnassus,"  and  at  the 
same  time  to  show  our  obligation  to  our  lowly  predecessors, 
each  of  which  did  his  share  in  testing,  rejecting  or  trans- 
mitting the  innumerable  "basic  patents,"  or  natural  adjust- 
ments, that  have  proved  requisite  for  our  survival  in  a  world 
of  inexorable  competitive'  tests. 

The  general  reader  may  ask  why  in  the  following  pages 
we  speak  so  confidently  of  the  "sequence  from  fish  to  man," 

53 


Fig.  I.  Genealogical  tree  of  animal  life. 
Figures  at  left  give  estimated  time  in  millions  of  years  from  beginning  of 
each  epoch  to  present,  according  to  Barrell's  estimates,  based  on  measure- 
ment of  rate  of  disintegration  of  radioactive  ores  since  they  were  crystallized 
at  different  geological  ages.  (After  Gregory,  Our  Face  from  Fisli  to  Man.  G. 
P.  Putnam's  Sons.) 

f54l 


THE  ANIMAL  ANCESTRY  OF  MAN  ^^ 

when  he  may  have  read  elsewhere  that  scientists  are  still 
disputing  whether  this  or  that  particular  fossil  is  or  is  not  the 
missing  link.  The  argument  may  be  compressed  into  the 
following  brief  statement:  When  we  study  the  recent  and 
fossil  vertebrates  as  a  whole,  and  when  we  study  at  the  same 
time  the  comparative  anatomy  of  their  organs,  we  fmd 
that  the  vertebrates  fall  into  larger  and  smaller  natural 
groups  which  may  be  arranged  in  the  form  of  a  tree,  with 
main  trunk,  boughs,  branches,  twigs  and  leaves.  Mankind, 
by  all  the  evidence  of  comparative  anatomy  and  kindred 
sciences,  belongs  on  one  of  the  small  twigs  nearest  to  the 
anthropoid  apes;  the  man-ape  branch  surely  belongs  in  the 
Old  World  or  catarrhine  division  of  the  Primates,  and  thus 
the  groups,  one  by  one,  may  be  traced  down  to  the  main 
vertebrate  trunk. 

Again,  the  record  of  fossilized  organic  remains,  or  palaeon- 
tology, imperfect  as  it  is,  offers  fully  concordant  evidence 
that  the  main  stages  of  ascent  from  fish  to  man  have  occurred 
in  the  following  order: 

I.  Proterozoic  ("Age  of  Primitive  Life") 

1.  Pre-Cambrian:  first  definite  traces  of  hfe  (algae, worm- 
tubes,  etc.). 

II.  Palaeozoic    ("Age    of    Invertebrates    and    Fishes") 

2.  Cambrian:  early  stages  of  main  phyla  of  invertebrates. 

3.  Ordovician:  first  traces  of  fish-like  forms. 

4.  Silurian:  earliest  well-known  fish-like  forms  (ostrac- 
oderms). 

5.  Devonian:  lobe-fmned,  air-breathing  fishes. 

6.  Lower  Carboniferous:  swamp-living  amphibians. 

7.  Upper  Carboniferous:  land-living  primitive  reptiles. 

8.  Permian:  mammal-like  reptiles  of  several  ascending 
grades. 

III.  Mesozoic    ("Age    of    Reptiles") 

9.  Triassic:  cynodont  reptiles  or  pro-mammals. 

10.  Jurassic:  archaic  insectivorous  mammals. 

11.  Cretaceous:  primitive  placental  insectivores. 

IV.  Caenozoic  ("Age  of  Mammals") 

12.  Eocene:  primitive  lemuroid  primates. 

13.  Oligocene:  proto-anthropoid  stock. 


§6  HUMAN   BIOLOGY 

14.  Miocene:  varied  anthropoids,  including  some  with 
pre-human  patterns  of  the  molar  teeth. 

15.  Pliocene:  probable  emergence  of  "tertiary  man." 
V.  Psychozoic  ("Age  of  Man") 

16.  Pleistocene:  primitive  man;  beginnings  of  modernized 
man. 

17.  Recent:  civihzed  man. 

It  is  true  that  there  are  larger  or  smaller  gaps  between 
each  of  these  stages  in  the  present  imperfect  state  of  our 
knowledge,  but  within  each  large  group  there  is  a  wide 
range  of  variation  in  particular  structures,  some  recalling 
the  previous  stage,  others  prophetic  of  later  stages.  It  is 
only  the  few  fortunate!}^  situated  persons  who  have  spent 
years  in  handhng  and  studying  the  original  materials  all 
along  the  hne  from  ostracoderms  to  man,  who  are  in  a 
position  to  appreciate  fully  the  weight  of  this  concordant 
testimony  of  systematic  zoology,  comparative  anatomy 
and  palaeontology  as  to  the  evolution  of  man;  but  even 
the  young  student  of  biology  quickly  reahzes  the  significance 
of  the  famous  blood-relationship  tests  and  of  the  embryo- 
logical  proof  that  man  resembles  other  mammals  in  the  basic 
features  of  his  development  and  in  his  subjection  to  the  laws 
of  heredity. 

man's  debt  to  the  earliest  organisms 

As  a  citizen  of  the  terrestrial  biota  man  inherits  all  the 
rights  and  privileges  but  also  the  responsibihties  and 
Habilities  of  his  status.  The  body  of  man,  as  a  mass  of  water, 
of  frothy  protoplasm  and  protoplasmic  by-products,  is  a 
labile,  combustible  mixture,  a  chemical  engine,  generating 
the  power  by  means  of  which  man  makes  a  place  for  himself 
in  the  world  of  hfe  (Martin).  Obviously  this  engine  must 
be  more  or  less  regularly  suppHed  with  water,  oxygen, 
nitrogen,  carbon  and  other  well-known  staples.  Hence 
perhaps  the  greater  part  of  man's  activity  is  devoted  to 
securing  and  consuming  these  necessities.  Again,  this  chemi- 
cal engine  will  work  efficiently  only  within  certain  limits  of 
temperature  and  pressure.  Hence  man,  like  other  organisms, 
seeks  those  parts  of  the  earth  in  which  the  temperatures 
and  pressures  are  most  conducive  to  his  welfare,  and  strives 


THE   ANIMAL   ANCESTRY   OF   MAN  -       57 

by  means  of  clothing,  houses  and  the  like,  to  protect  his 
chemical  engine  from  injurious  and  sudden  changes  in  the 
surrounding  medium. 

As  man  belongs  to  the  animal  rather  than  to  the  plant 
kingdom,  he  has  no  chlorophyl-bearing  leaves  to  store  up 
the  sun's  energy  for  his  use,  nor  can  he  derive  his  raw 
materials  directly  from  the  soil  or  from  the  atmosphere,  but 
in  common  with  all  other  animals  he  must  consume  simpler 
organisms  which  have  already  elaborated  the  raw  materials 
and  stored  up  the  energy  for  him. 

Man  is  a  many-celled  animal,  or  metazoan,  and  as  such 
each  human  being  consists  of  a  vast  and  shifting  democracy 
of  individual  cells,  which  are  organized  into  cooperative  and 
mutually  dependent  systems  of  organs,  tissues  and  the  like. 

We  need  not  discuss  fully  here  the  still  vexed  question  as  to 
what  group  of  invertebrates  the  oldest  chordate  ancestors 
of  man  were  derived  from.  It  will  be  sufficient  for  our  present 
purpose  to  note  that  if,  with  Professors  Patten  and  Gaskell, 
we  try  to  derive  them  from  the  common  stem  of  the  arach- 
nids (scorpions,  spiders,  etc.)  we  must  conceive  that  in  the 
transitional  stages  an  entire  reorganization  was  effected, 
involving  radical  displacements  and  transformations  of 
every  part  of  the  body.  Now  while  all  these  changes  are 
clearly  conceivable  under  the  terms  of  the  hypothesis,  the 
evidence  advanced  in  support  of  them  has  never  been  accepted 
by  the  majority  of  those  best  qualified  to  judge  of  its  value. 
On  the  other  hand,  if  we  hold  with  Professor  E.  B.  Wilson 
and  others  that  the  vertebrates  belong  to  that  great  division 
of  the  three-layered  animals  in  which  the  middle  embryonic 
layer,  or  mesoderm,  arises  from  pouches  lying  above  the 
enteron,  or  primitive  gut,  then  we  have  to  admit  that,  so 
far  as  known  at  present,  the  palaeontological  record  lacks 
the  transitional  stages  between  the  vertebrates  and  their 
assumed  sack-like  ancestors  and  that  the  vertebrates  and 
the  starfish  group  apparently  represent  two  widely  divergent 
end  stages  of  an  unknown  common  stem. 

CITIZEN    MAN    OF   THE    PHYLUM    CHORDATA 

At  any  rate,  the  "phylum  Chordata,"  to  which  man  and 
all  other  vertebrates  belong,  very  early  adopted  a  highly 


58  HUMAN   BIOLOGY 

efficient  type  of  locomotor  apparatus,  the  starting-point, 
as  we  shall  see,  of  a  long  series  of  successive  modifications, 
from  the  lancelet  to  man. 

The  developmental  history  of  Amphioxus  and  other 
lowly  chordates  (Delage)  indicates  that  at  a  very  early 
period  some  two-layered,  jellyfish-Iike  forms  gave  up  the 
free-floating  hfe  of  helpless  plankton  and  began  to  wriggle 
on  the  bottom  of  the  rich  inshore  feeding-grounds.  At  this 
time  perhaps  the  mesodermic  pouches  already  mentioned 
as  being  on  either  side  above  the  primitive  gut  became 
rhythmically  contractile,  hke  the  bell  of  a  jellyfish.  While 
the  details  are  quite  obscure,  it  is  plain  that  some  such 
stage  must  have  preceded  the  appearance  of  the  perfected 
muscle  pouch,  which  is  the  unit  of  the  locomotor  apparatus 
of  all  vertebrates  and  one  of  the  most  important  of  the 
basic  patents  to  which  all  vertebrates,  including  man,  owe 
the  possibility  of  their  subsequent  careers. 

These  primitive  contractile  pouches  probably  at  first 
surrounded  the  little  bags  of  potential  eggs  or  sperm  which 
had  been  derived  from  the  walls  of  the  primitive  gut;  even 
in  the  embryos  of  higher  vertebrates  (including  man)  the 
blocks  of  tissue  which  give  rise  to  the  body  muscles  and  to 
the  segments  of  the  backbone  first  appear  on  either  side, 
above  the  primitive  gut  and  above  the  longitudinal  strip 
of  tissue  that  gives  rise  to  the  eggs  or  sperm.  Meanwhile  at 
a  very  early  period  the  mesoderm  began  to  develop  a  median 
longitudinal  groove.  This  groove,  at  first  opening  below  into 
the  primitive  gut,  finally  became  closed  off  as  a  tube  filled  with 
clear  elastic  tissue  (Shumway).  Why  it  did  this  we  do  not 
know,  but  the  step  was  of  momentous  consequence  to  the 
future  history  of  the  race,  for  thereby  the  beginnings  of  a 
backbone  were  attained. 

Along  the  middle  of  the  back  behind  the  brain  and  above 
the  notochord  was  a  long  paired  groove  or  tube  forming  the 
main  nerve  cord,  with  lateral  branches,  the  spinal  nerves, 
leading  out  to  the  muscle  pouches,  which,  as  we  have  seen, 
had  already  budded  off  from  the  primitive  gut.  By  means  of 
these  primitive  "spinal  nerves"  and  of  the  spinal  cord  and 
brain,  the  contraction  of  the  segmental  muscle  pouches 
could  be  timed  and  integrated  effectively  into  cooperating 


THE    ANIMAL    ANCESTRY   OF    MAN 


59 


and  opposing  groups.  By  means  of  the  already  bewildering 
connection  systems  of  the  central  nervous  system,  stimula- 
tions of  the  primitive  sense  organs  (representing  the  senses 


B 


ecfoderm. 
nerirefube 

mesoderm 
noiochorc( 

enfoder?n 


ecfoderm 
nerireiube 
mesoder?72 
notochorcC 

entoderm. 


Fig.  2.  Lancelet  (Amphioxus),  lowest  existing  chordate. 

A.  Diagram  of  anatomy  of  adult  animal. 

(After  Marshall  and  Hurst,  Practical  Zoology.) 

B.  Section  of  embryo,  showing  relations  of  mesoderm  and  entoderm. 

(After  Cerfontaine,  from  Shumway's  Vertebrate  Embryology,  John  Wiley  &  Sons.) 

c.  Cross-sections  of  three  stages  of  development  in  frog,  showing  relations 
of  mesoderm  to  outer  and  inner  germ  layers. 

(After    Hyman,    Laboratory    Manual    for    Comparative    Vertebrate   Anatomy,    Chicago 
University  Press.) 

of  feehng,  taste,  smell,  sight,  balance,  bodily  position,  etc.) 
could  be  organized  and  directed  toward  successful  motor 
responses.  All  this  matter  hes  within  the  special  field  of  the 
neurologist  and  is  fully  dealt  with  elsewhere  in  this  book 
(Chaps.  Ill,  xi).  The  present  chapter  is  concerned  primarily 
with  the  muscular  and  skeletal  elements  of  the  vertebrate 
locomotor  apparatus  rather  than  with  the  nervous  mech- 
anism of  direction  and  control. 

At   a   very   early   period   the   primitive   muscle   pouches 
became   transformed  into  zigzag-shaped  muscle  segments. 


60  HUMAN   BIOLOGY 

or  myomeres,  arranged  in  a  closely  packed  series  on  either 
side  of  the  body,  quite  in  the  manner  of  the  fleshy  muscle 
flakes  in  modern  fish.  This  stage  is  fully  realized  in  Amphi- 
oxus,  the  very  lowest  of  the  fish-Hke  chordates  still  existing. 
In  normal  fish-like  vertebrates  that  move  through  the  water, 
the  body  is  "stream-lined,"  with  a  rapidly  widening  "enter- 
ing angle"  and  a  long  sloping  "run."  In  forward  locomotion 
the  muscle  segments  on  one  side,  immediately  behind  the 
head,  begin  to  contract  first  and  the  contraction  is  then 
passed  backward  toward  the  tail.  Meanwhile  the  muscle 
segments  on  the  opposite  side,  immediately  after  the  initial 
contraction,  begin  their  contraction,  so  that  the  head  is 
alternately  bent  slightly  from  one  side  to  the  other  as  the 
waves  of  contraction  run  along  the  body,  with  increasing 
ampHtude,  to  the  tail.  Presumably  the  continuous  notochord 
acts  as  an  axial  rod  or  spring.  At  first  the  wriggling  body 
does  not  need  any  accessory  steering  or  propelling  structures, 
but  in  later  stages  folds  of  skin,  originally  not  in  themselves 
movable,  grow  out  and  serve  as  keels  and  rudders.  From 
this  relatively  simple  beginning,  as  we  shall  presently  see, 
the  evolution  of  the  locomotor  apparatus,  at  least  in  its  main 
outlines,  from  fish  to  man  is  fairly  clear. 

But  before  proceeding  to  the  higher  stages  let  us  return 
to  the  basic  patent,  the  contractile  muscle  pouch.  Why  was 
it  contractile?  Each  muscle  segment  of  an  adult  fish  (Fig.  3) 
consists  of  a  zigzag  of  striped  muscle  fibers  fastened  at 
either  end  into  the  connective-tissue  septa  that  divide  the 
muscle  segments.  It  is  the  striped  muscle  fiber,  then,  that 
is  the  smaller  unit  of  contractility.  But  what,  in  turn,  makes 
it  contract?  Under  high  magnification  a  striped  muscle 
fiber  is  seen  to  be  composed  of  two  different  kinds  of  material, 
represented  by  the  dark  and  the  light-colored  cross-stripes. 
Physiologists  (Martin)  tell  us  that  when  a  muscle  swells 
out  and  shortens,  the  force  at  work  is  analogous  to  the 
force  of  surface  tension  and  that  the  frothy  nature  of  pro- 
toplasm supplies  a  relatively  enormous  surface  for  the 
operation  of  the  forces  of  surface  tension  exerted  between 
the  materials  of  the  dark  and  the  light  bands  of  the  muscle. 
But  how  does  the  nervous  discharge  from  the  central  nervous 
system  release  the  forces  of  surface  tension  which  had  up  to 


THE    ANIMAL   ANCESTRY   OF   MAN  6l 

that  moment  been  held  in  balance?  Here  we  come  to  a 
problem  with  which  the  physiologists  expect  to  be  strugghng 
for  a  long  time  to  come. 


Fig   3.  Arrangement  of  muscle  fibers  and  muscle  septa  (myosepta)  adherent 

to  inner  side  of  skin  of  a  modern  shark. 

(From  Gregory,  Proc.  Amer.  Pbilos.  Soc.) 

Meanwhile  we  may  emphasize  the  fact  that  from  the 
evolutionary  viewpoint  man  has  inherited  the  striped 
muscle  fiber,  which  is  the  smaller  unit  of  his  entire  locomotor 
system,  from  the  very  oldest  vertebrates,  and  that  a  large 
part  of  the  human  nervous  system,  like  that  of  other  verte- 
brates, is  concerned  with  the  regulation  of  the  locomotor 
organs  and  with  their  effective  coordination  with  other 
major  systems. 

The  known  record  of  fossihzed  remains  shows  that  the 
ostracoderms,  which  were  the  immediate  forerunners  of  the 
vertebrates,  were  already  in  existence  in  the  Ordovician 
and  Silurian  periods,  perhaps  half  a  bilHon  years  distant 
from  the  present  day.  Even  at  that  inconceivably  remote 
epoch  the  most  fundamental  problem  of  vertebrate  evolution 
had  already  been  solved  and  with  regard  to  the  ground-plan 
of  their  anatomy  the  ostracoderms  were  actually  far  nearer 
to  man  than  they  were  to  the  one-celled  starting  point  of  life. 
For  these  fish-Iike  chordates  were  already  bilaterally  sym- 
metrical, with  head  and  tail  and  the  ability  to  move  in  a  for- 
ward direction.  In  their  heads  they  had  paired  sense  organs 
representing  the  senses  of  smell,  vision  and  balance,  while 
the  main  divisions  of  their  brains,  as  shown  by  study  of  their 


62 


HUMAN   BIOLOGY 


fossilized  brain  casts,  were  of  the  primitive  vertebrate 
type;  the  mouth,  gill  chamber  and  digestive  tract  were 
beneath    the     brain    and    spinal    cord    and    the    primary 


Fig.  4.  Two  of  oldest  known  forerunners  of  backboned  animals. 
A.  Pharyngolepis  b.  Aceraspis. 

(After  Kiaer,  from  Greorgy,  Proc.  Amer.  Pbilos.  Soc.) 


locomotor  organs  consisted  of  a  closely  packed  series  of 
zigzag  muscle  segments  on  either  side  of  the  long  axis  of  the 
body.  Probably  also  they  possessed  a  notochord  or  elastic 
axial  rod  just  below  the  nerve  cord,  as  do  all  their  less 
modified  descendants. 

But  these  ostracoderms  were,  strictly  speaking,  not  yet 
vertebrates  for  the  reason  that  they  had  not  yet  acquired  a 
jointed  bony  vertebral  column,  or  backbone.  The  known 
ostracoderms,  according  to  the  convincingly  thorough 
studies  of  Stensio,  were  related  to  the  existing  class  of 
cyclostomes,  or  lampreys  and  hag-fishes,  rather  than  to  the 
true  fishes,  within  which  there  is  much  reason  to  suppose  the 
line  leading  to  Lind-Iiving  vertebrates  later  arose. 

In  the  ostracoderms,  according  to  Stensio's  evidence,  the 
mouth  opening  was  in  series  with  the  openings  leading  to  the 
gill  pouches,  as  it  is  in  the  embryos  of  all  higher  vertebrates. 
Thus  we  probably  should  not  have  tonsils  and  thyroid  and 
thymus  glands  any  more  than  we  shouki  have  had  a  tongue 


THE    ANIMAL   ANCESTRY   OF    MAN  63 

and  vocal  cords,  if  the  initial  steps  in  these  arrangements 
had  not  been  taken  by  our  eadiest  chordate  ancestors. 

Man  is  also  indebted  to  such  very  early  chordates  for 
another  "invention"  of  the  greatest  importance,  namely 
the  bone-cell.  Apparently  originating  in  the  deeper  layers 
of  the  skin,  the  bone-cells  later  invaded  the  connective- 
tissue  partitions  between  the  muscle  segments  and  ultimately 
gave  rise  to  the  internal  skeleton.  Perhaps  the  physiologists 
may  be  able  to  find  out  why  the  calcium  phosphate  and  cal- 
cium carbonate  w^re  deposited  in  the  Haversian  system  of 
capillaries  by  these  pecuhar  cells,  instead  of  being  cast  off 
by  the  excretory  system. 

Our  catalogue  of  debts  to  the  ostracoderms,  or  to  some  of 
their  contemporaries,  is  further  increased  by  the  fact  that 
they  seem  to  have  been  the  first  of  the  chordate  series  to 
develop  a  "head  shield,"  or  bony  mask  covering  the  entire 
gill  chamber  and  inner  brain-case.  In  the  more  typical 
ostracoderms  the  surface  head  shield  appears  to  have  been 
all  of  one  piece;  but  in  certain  of  the  anaspid  ostracoderms 
the  head  was  covered  by  small  dermal  plates,  somewhat 
after  the  fashion  that  was  adopted  by  our  own  ancestors. 

All  recent  evidence  tends  to  support  the  view  not  only 
that  the  modern  cyclostomes  are  the,  in  some  respects 
degenerate,  descendants  of  certain  of  the  ostracoderms 
but  that  Amphioxus  represents  a  still  further  degenerate 
derivative  of  the  same  stock. 

OUR  FOREBEARS  ATTAIN  THE  GRADE  OF  VERTEBRATES 

In  the  first  chordates  the  elastic  axial  tube,  or  notochord, 
as  seen  in  Amphioxus,  is  continuous  and  unsegmented;  but 
later  when  the  vertebrate  grade  of  organization  was  attained, 
rods  and  blocks  of  skeletal  tissue  began  to  be  secreted  under 
the  influence  of  the  muscle  segments,  and  as  these  blocks 
increased  in  importance  they  gradually  replaced  the  primary 
backbone,  or  notochord,  and  gave  rise  to  the  secondary 
backbone  or  vertebral  column.  In  the  ostracoderms  appar- 
ently only  a  notochord  was  present;  in  the  arthrodires  (a 
group  of  extinct  fishes  of  the  Devonian  period)  the  rods 
above  and  below  the  notochord  had  become  hard  enough 
in  the  tail  region  to  leave  their  imprints  in  the  surrounding 


64  HUMAN   BIOLOGY 

matrix;  in  the  early  ganoid  and  dipnoan  fishes  the  incom- 
plete blocks  or  half-rings  secreted  in  the  elastic  membrane 
around  the  notochord  may  be  seen  in  various  stages  of 
development;  in  the  oldest  amphibians  each  vertebra  was  a 
complex  of  eight  pieces;  and  it  is  only  in  the  higher  verte- 
brates that  they  become  reduced  in  number.  Meanwhile 
the  notochord  loses  its  functional  importance  in  the  adult 
but  may  always  be  identified  in  embryonic  stages. 

THE   ORIGIN   OF   JAWS   AND   TEETH 

The  internal  skeleton  of  the  mouth  and  gill  pouches  in  the 
ostracoderms  remained,  so  far  as  the  material  indicates,  in 
the  purely  cartilaginous  stage,  if  indeed  it  was  developed 
at  all.  In  the  sharks  these  cartilaginous  supports  of  the 
mouth  and  gill  arches  became  strengthened  by  the  deposition 
of  calcium  carbonate;  but  in  the  more  direct  Hne  of  forms 
leading  to  the  higher  vertebrates  the  primary  jaw  cartilages 
very  early  became  overlaid  by  bony  plates  bearing  teeth. 
These  teeth  at  first  were  nothing  but  minute  thorns  hke 
those  borne  by  the  skin  all  over  the  body  in  certain  ostraco- 
derms and  in  modern  sharks;  but  in  and  around  the  mouth 
these  dense  bone-hke  thorns  speciahzed  into  true  teeth; 
meanwhile  those  on  the  surface  of  the  body  gave  rise  to  the 
enamel-hke  scales,  while  those  on  the  top  and  sides  of  the 
head  fused  into  the  smooth  skull  and  jaw  plates  of  the  early 
ganoid  fishes. 

Thus  while  the  better  known  ostracoderms  appear  to  have 
been  approximately  ancestral  to  the  modern  Agnatha,  or 
so-called  **jawless"  cyclostomes,  some  remotely  related 
types  of  early  chordates  gave  rise  to  the  Gnathostomata, 
or  typically  jaw-mouthed  series  of  forms  including  the 
sharks  and  their  allies  the  crossopts,  or  lobe-fmned  ganoids, 
the  actinopts,  or  true  ganoids  (ancestral  to  the  modernized 
teleost  fishes)  and  finally  the  dipnoan,  or  double-breathing 
fishes. 

AN    IMPORTANT    EXPERIMENT    IN   BREATHING 

Very  early  in  the  history  of  the  lobe-fmned  ganoid  stock, 
which  seems  to  have  lived  in  swampy  streams  subject  to 
occasional  drying,  a  small  accessory  breathing  organ  was 


THE    ANIMAL    ANCESTRY    OF    MAN  6$ 

developed  in  the  shape  of  a  pouch  for  the  retention  of 
swallowed  air.  This  was  located  in  the  throat  behind  the 
gills  and  was  richly  siipphed  with  blood  vessels.   Perhaps 


p.„,»«sv.9<UMRSS^t^RSeHGI 


Fig.  5.  Lobe-fmned  fish  from  Devonian  of  Russia.  Restoration  of  Diplopterus 

by  Pander. 

it  was  derived  from  one  of  the  earHer  gill  pouches  which 
had  become  enlarged  for  the  reception  of  air  swallowed 
above  the  surface  of  the  water,  rather  than  for  the  extraction 
of  the  dissolved  air  from  the  water  passing  through  the 
other  gill  chambers.  However  that  may  be,  this  accessory 
breathing  organ  proved  to  be  of  incalculable  importance 
to  its  possessors  for  it  opened  up  to  them  the  possibility 
of  invading  the  dry  land  and  finally  of  disputing  its  posses- 
sion with  the  insects,  who  had  also  invaded  it  from  the 
water  but  at  an  earlier  date.  At  the  same  time  some  of  the 
lobe-finned  fishes  acquired  exceptionally  strong  and  fleshy 
fan-shaped  paired  fins,  by  means  of  which  their  still  more 
highly  evolved  descendants  were  enabled  to  complete 
their  conquest  of  the  dry  land.  Thus  man  owes  to  these 
ugly-looking  denizens  of  the  Palaeozoic  swamps  two  of  his 
most  indispensable  possessions,  namely  lungs  and  limbs, 
not  to  mention  many  other  improvements  that  they  ini- 
tiated, such  as  the  development  of  checker-like  bony 
centra  surrounding  the  primitive  notochord,  the  arrange- 
ment of  paired  bony  plates  on  the  roof  of  the  skull,  the 
development  of  a  double  shoulder  girdle  of  underlying 
and  surface  elements  and  the  production  of  a  pelvis  or  bony 
base  for  the  pelvic  fins,  dividing  the  musculature  of  the 
thorax  from  that  of  the  tail. 

THE  TETRAPODS  INVADE  THE  LAND 

The    earliest    four-footed    vertebrates    appear    to    have 
sprung   from   a  still   undiscovered   family   of  fishes  which 


THE    ANIMAL   ANCESTRY   OF    MAN  67 

combined  certain  characters  of  the  crossopt,  or  lobe- 
finned  fishes,  with  others  of  the  dipnoan  group,  while  avoiding 
the  pecuhar  specializations  of  either.  When  these  adven- 
turous pioneers  first  pushed  their  way  up  on  to  the  dry 
land  they  were  still  using  the  old  wriggling  movements  of 
the  body  invented  by  the  very  earhest  chordates.  In  some  of 
those  forms  in  which  the  body  was  very  long  and  the  paired 
paddles  were  relatively  small,  the  wriggHng  movements 
greatly  predominated  and  in  several  lines  the  incipient 
paired  hmbs  became  reduced  and  degenerate,  thus  giving 
rise  to  snake-hke  or  eel-hke  amphibians.  In  the  Hues  that 
were  more  nearly  related  to  our  own  ancestry,  on  the  con- 
trary, the  fore  and  hind  paddles,  corresponding  respectively 
to  our  arms  and  legs,  became  larger  and  stronger,  the  internal 
bony  rods  of  the  extremities,  due  to  the  new  stresses  of 
terrestrial  life,  became  shifted  and  modified  into  the  highly 
characteristic  five-rayed  hands  and  feet  which  were  safe- 
guarded by  all  the  later  stages  in  the  hne  of  ascent  to  man. 
Indeed  man  owes  to  these  earliest  amphibians  the  entire 
ground-plan  of  his  anatomy,  including  the  skeletal  and 
muscular  parts  of  his  locomotor  machinery.  Beneath  the 
successive  modifications  acquired  in  adaptation  to  later 
special  life  habits,  man  shares  this  tetrapodal  ground-plan 
with  tens  of  thousands  of  other  species  of  land-Hving  verte- 
brates of  the  great  classes  Amphibia,  Reptiles,  Birds  and 
Mammals,  which  are  collectively  bracketed  as  the  super- 
class Tetrapoda,  or  four-limbed  animals. 

Let  us  consider  a  little  more  in  detail  the  mechanism  of  the 
tetrapod  locomotor  machiner}^  especially  in  so  far  as  it  has 
served  as  'a  starting-point  for  that  of  man.  Even  in  the 
stage  of  the  air-breathing  fishes  the  simple  arrangement  of 
zigzag  muscle  segments  which  had  sufficed  to  produce  the 
wriggling  movements  of  earlier  forms  had  become  com- 
plicated, first  by  the  outgrowths  of  humps  of  the  body-wall 
surmounted  by  folds  of  skin  to  serve  as  keels  and  rudders, 
and  secondly  by  the  extension  of  buds  from  the  zigzag 
muscle  plates  into  the  bases  of  these  primitive  fins,  enabling 
the  fish  to  warp  them  and  finally  to  move  them  independently 
of  the  general  body  movements.  By  the  time  of  the  lobe- 
finned  fishes  the  fore  and  hind  pair  of  paddles  had  already 


68 


HUMAN    BIOLOGY 


acquired  a  set  of  muscles  which  served  to  raise,  lower,  bend 
or  warp  the  paddles  or.  to  move  them  forward  or  backward. 
When  some  of  these  fish  scrambled  out  on  land  the  muscles 


Fig.  7.  Musculature  of  fore  paddle  of  existing  lobe-finned  fish  Polypterus. 

(After  Klaatsch,  Die  Brustflosse  der  Crossopterygier.) 

of  the  paddles  became  further  strengthened  and  differ- 
entiated, so  that  soon  they  were  able  to  support  the  weight 
of  the  body  (Gregory,  1915). 

These  primitive  hmbs  were  at  first  short,  thick,  held  far 
out  from  the  body  and  sharply  bent  at  the  elbows  and 
knees.  The  serratus  muscles  on  either  side  of  the  neck  sent 
strips  to  the  inner  surfaces  of  the  shoulder  girdle  and  thus 
the  fore  part  of  the  body  was  slung  between  the  u-shaped 
shoulder  girdle,  which  had  been  inherited  from  the  fishes. 

At  this  stage  the  pelvis  had  no  direct  connection  with  the 
backbone.  In  front  view  it  was  v-shaped,  with  the  opposite 
femora  spreading  out  on  either  side  from  the  lower  part  of 


THE   ANIMAL   ANCESTRY   OF    MAN 


69 


the  V  and  with  the  backbone  lying  between  the  limbs  of  the 
V  but  connected  with  them  only  by  muscles.  In  side  view 
the  pelvis  as  a  whole  appeared  hke  an  inverted  y,  with  the 


Fig.  8.  Musculature  of  upper  arm  and  shoulder  girdle  of  crocodile. 

(After  Furbringer,  Zur  vergleichenden  Anatomic  des  Brustschulter-apparates  und   der 
Schulter-muskeln.) 

ihum,  or  inverted  stem  of  the  y  directed  upward  and  back- 
ward. As  a  whole  the  pelvis  lay  between  the  muscle  masses 
of  the  abdomen  and  those  of  the  tail  and  it  gave  attachment 
to  both  (Romer). 

When  such  an  animal  raised  itself  off  the  ground  the  body 
was  slung  Hke  a  suspension  bridge  between  two  piers,  the 
scapulae  of  the  pectoral  girdle  forming  the  front  pair  of 
piers  and  the  iha  of  the  pelvic  girdle  forming  the  rear  pair. 


Fig.  9.  Bridge-like  construction  of  primitive  tetrapod. 

(From  Gregory,  Proc.  Amer.  Pbilos.  Soc.) 

Between  these  the  ribs  and  backbone  formed  another 
superposed  jointed  cantilever  bridge  supporting  the  head 
and  the  viscera  and  acting  as  a  movable  base  for  the  most 
powerful  muscles  of  the  body.  In  general,  forward  progres- 
sion under  such  an  arrangement  involves  a  series  of  alternate 
and  rhythmical  extensions  and  flexions,  rockings,  bendings 
and  twistings.   For  instance,  while  the  right  hind  limb  is 


70 


HUMAN    BIOLOGY 


extending  and  pushing,  the  left  fore  limb  is  flexing  and 
pulling;  meanwhile  the  weight  is  swinging  between  the 
left  hind  limb  and  the  right  fore  limb,  the  pelvis  is  turned 


^"^^ 


r^l 


/M^ 

M^ 

q^  - 

...^^. 

a^ 


N, 


yz,u^ 


WTO 


■#k: 


Fig.  io.  Primitive  reptilian  and  primitive  mammalian  postures. 

A.  Primitive  reptile  {Seymour'xa)  of  Permocarboniferous  age. 

B.  Primitive  mammal  (opossum),  survivor  of  Cretaceous  marsupial  stock. 

(From  Gregory,  Proc.  Amtr.  Pbilos.  Soc.) 

slightly  toward  the  right,  while  the  pectoral  girdle  is  turning 
in  the  opposite  direction;  both  are  also  being  rocked  trans- 
versely in  opposite  directions. 


THE   ANIMAL   ANCESTRY    OF    MAN  Jl 

As  long  as  the  animal  crawls  with  the  belly  near  the 
ground,  the  lurching,  sinuous  movements  are  pronounced, 
but  by  the  time  of  the  higher  mammal-like  reptiles  of  the 
Triassic  period  a  notable  advance  toward  the  mammalian 
mode  of  locomotion  had  been  achieved,  in  that  the  body 
was  beginning  to  be  raised  further  from  the  ground  and  the 
feet  to  be  drawn  in  toward  the  mid-line.  Meanwhile  several 
of  the  ribs  in  the  sacral  region  of  the  backbone  became 
widened  out  at  the  farther  ends  and  attached  by  ligaments 
to  the  pelvis,  which  thus  began  to  assume  even  greater 
importance  in  the  mechanism  of  locomotion. 

OUR    ANCESTORS   BECOME    WARM-BLOODED 

At  this  point  let  us  turn  aside  from  the  consideration  of 
the  more  conspicuous  parts  of  the  locomotor  apparatus  in 
order  to  trace  the  internal  improvements  that  were  prereq- 
uisite for  its  fmal  development.  In  the  lower  vertebrates, 
including  the  fishes  and  reptiles,  the  body  temperature  is 
both  relatively  low  and  relatively  variable,  so  that  the 
animals  are  not  able  to  maintain  their  own  body  temperature 
and  vital  activities  at  a  high  level  during  severe  changes  in 
the  surrounding  medium.  The  mammals  are  able  to  do  this, 
not  only  because  their  red  corpuscles,  being  both  far  more 
numerous  and  smaller  than  those  of  the  lower  vertebrates, 
effect  a  quicker  and  larger  consumption  of  oxygen  in  a 
given  time,  but  also  because  they  have  more  efficient  lungs 
and  a  special  bellows-like  organ,  the  diaphragm,  which 
acts  in  a  way  like  a  forced  draught;  while  its  piston-like 
action,  described  by  Sir  Arthur  Keith,  no  doubt  accelerates 
the  circulation  and  consequent  metabolism.  Moreover  the 
body  is  covered  with  hair,  which  encloses  a  layer  of  non- 
conducting air,  and  the  skin  is  full  of  sweat  glands  and  oil 
glands,  which  further  assist  in  the  regulation  of  the  body 
temperature;  in  addition  to  these  are  the  complete  separation 
of  the  venous  and  arterial  blood  in  the  heart  and  several 
other  details  leading  to  more  rapid  aeration  of  the  blood 
and  a  greater  liberation  of  energy. 

The  higher  physiological  status  of  mammals  is  also  shown 
in  their  improved  methods  of  reproduction.  Whereas  with 
few  exceptions  reptiles  lay  large  eggs,  well  stored  with  yolk. 


72  HUMAN   BIOLOGY 


the  higher  mammals  retain  the  excessively  minute  eggs  within 
the  body  of  the  mother  and  nourish  the  young  till  birth 
by  means   of  the  placenta,   or   "afterbirth,"   after  which 


^Sj£^tj^5f5f£f: 


Fig.   II.  Cynognathus,  a  progressive  mammal-Iike  reptile  from  Triassic  of 
_       South  Africa.  Tentative  restoration  by  Gregory  and  Camp, 

they  feed  them  with  milk  from  the  maternal  mammary 
glands.  The  monotreme  mammals  of  Austraha  (including 
the  duckbill  platypus  and  the  spiny  anteater)  resemble 
the  reptiles  in  so  far  as  they  lay  large  eggs  well  supphed 
with  yolk,  as  well  as  in  the  ground-plan  of  their  reproductive 
organs  and  in  certain  characters  of  the  skeleton;  but  they 
feed  their  young  by  means  of  milk  secreted  by  the  mammary 
glands,  and  in  their  brains  and  many  other  organs  they 
are  true  mammals,  although  standing  as  the  lowest  surviving 
grade  of  that  class. 

The  superiority  of  the  mammahan  over  the  reptilian  grade 
of  organization  is  a  matter  of  direct  observation.  The  evolu- 
tion of  the  primitive  reptilian  to  the  promammahan  and 
thence  to  the  mammahan  grade,  which  is  so  plainly  indicated 
by  comparative  studies  of  recent  reptiles  and  mammals,  is 
supported  by  the  available  palaeontological  evidence, 
which  is  relatively  abundant  during  the  Permian  and 
Triassic  periods  when  the  mammal-hke  series  of  reptiles 
gradually  approached  the  mammahan  grade  (Figs,  ii,  i6 
D  and  e). 

The  fragmentary  fossil  history  of  the  mammahan  class 
itself  during  the  enormous  lapse  of  geologic  time  that  is 
represented  by  the  rocks  of  the  Triassic,  Jurassic,  Lower 
Cretaceous  and  Upper  Cretaceous  periods  is  preserved  in  a 
few  of  the  museums  of  the  world  in  the  form  of  small  collec- 
tions of  fossils  for  the  most  part  consisting  of  fragments  of 
jaws  containing  teeth,  all  of  which  are  of  priceless  value  as 
documents  (Simpson).  In  the  Triassic  certain  of  the  cynodont 


I  11  111  IV  V  vr  viT  viic  jx 

Fig.  12.  Structural  stages  in  evolution  of  upper  and  lower  molar  teeth  of  man. 

Scales  various. 
A-H,  upper  molars,  left  side. 

A.  Upper  Jurassic,  triangular  stage  (pantotherian). 

(After  G.  G.  Simpson.) 

B.  Cretaceous,  triangular  stage  (Deltatheridium). 

(After  Gregory  and  Simpson.) 

c.  Lov/er  Eocene  "tritubercular"  stage  (Didelphodus). 

(After  Gregory.) 

D.  Middle  Eocene,  transitional  stage  (Pronycticebus). 

(From  Gregory,  after  Grandidier.) 

E.  Upper  Eocene,  tubercular  stage  (Necrolemur). 

(From  Gregory,  after  Stehlin.) 

F.  Upper  Miocene,  primitive  anthropoid  (Dryoplthecus)  stage. 

(From   Gregory,   after  Pilgrim.) 

G.  Pleistocene,  primitive  man  (Le  Moustier)  stage. 

(After  Gregory.) 

H.  Recent,  human  stage, 
i-ix,  lower  molars,  right  side. 

I.  Jurassic,  tritubercular  stage,  with  incipient  heel  (Pantotherian). 

(After  G.  G.  Simpson.) 

II.  Cretaceous,  primitive  tuberculosectorial  stage  (Deltatheridium). 

(After  Gregory  and  Simpson.) 

III.  Lower  Eocene,  tuberculosectorial  stage,  with  low  heel  (Deltatherium). 

(After  Gregory.) 

IV.  Middle  Eocene,  transitional  stage  (Pronycticebus). 

(From  Gregory,  after  Grandidier.) 

V.  Upper  Eocene,  tubercular  stage  (Necrolemur). 

(From  Gregory,  after  Stehlin.) 

VI.  Lower  Oligocene,  five-cusped  proto-anthropoid  stage  (Propliopithecus). 

(From  stereoscopic  photograph  by  Prof.  J.  H.  McGregor.) 

VII.  Upper  Miocene,  five-cusped  anthropoid  stage  (Dryopithecus). 

(After  Gregory.) 

VIII.  Pleistocene,  primitive  human  stage  (Le  Moustier),  retaining  five  cusps. 

(After  Gregory.) 

IX.  Recent,  human  stage,  after  disappearance  of  fifth  cusp. 

(After  Gregory.) 


tt73l 


74  HUMAN   BIOLOGY 

reptiles  so  nearly  approached  the  mammalian  grade  in  so 
many  characters  of  their  dentition,  jaws,  skull,  backbone 
and  hmbs  that  they  almost  deserved  to  be  called  mammals. 
In  the  uppermost  Triassic  and  later  ages  the  Multituber- 
culates  flourished.  These  were  peculiarly  specialized  rodent- 
like forms,  probably  independently  derived  from  the  cyno- 
dont  grade  and  certainly  not  in  line  with  the  higher  mammals. 
Then  in  the  Jurassic  period  there  were  various  members 
of  at  least  seven  different  families  of  small  mammals  repre- 
senting early  experiments  along  mammalian  Hues.  Most 
of  these  famihes  left  no  recognizable  or  known  descendants 
in  later  ages,  but  in  one  of  them,  including  several  famous 
fossil  jaws  from  the  Lower  Jurassic  of  Oxford,  England,  to 
which  the  name  Amphitherium  was  applied,  the  lower 
molar  teeth  distinctly  foreshadow  the  "tuberculo-sectorial" 
type.  This  was  characteristic  of  the  earliest  placental  mam- 
mals of  the  Age  of  Mammals,  and  the  whole  science  of 
odontology  or  evolutionary  study  of  the  teeth  (Osborn,  1907; 
Gregory,  1922)  leads  us  to  predict  the  discovery  of  tuberculo- 
sectorial  lower  molars  in  the  Jurassic  forerunners  of  the 
placental  stock,  of  which  the  order  of  Primates  was  a  later 
outgrowth. 

Only  a  single  humerus  and  a  single  femur  belonging  to 
these  far-off  Jurassic  mammals  are  sufficiently  well  known 
to  have  been  closely  studied  but  even  although  it  is  not 
clear  as  to  which  kind  of  contemporary  jaws  and  teeth 
they  belong  with,  yet  again  they  are  of  great  value;  for,  as 
recently  shown  by  Dr.  G.  G.  Simpson,  the  precise  arrange- 
ment of  their  various  parts  and  processes,  in  the  light  of 
what  is  known  of  the  relations  of  bones  and  muscles  among 
recent  reptiles,  monotremes  and  typical  mammals,  shows 
that  these  limb  bones  of  Jurassic  mammals  were  intermediate 
in  details  between  the  cynodont  type  below  and  the  typical 
mammalian  grade  above.  In  other  words,  these  Jurassic 
mammals  were  raising  their  bodies  further  from  the  ground 
and  preparing  the  locomotor  apparatus  for  its  next  great 
conquest,  the  invasion  of  the  trees.  It  is  not  without  sig- 
nificance also  that  in  the  Cretaceous  period  preceding  the 
great  expansion  of  the  mammals  at  the  opening  of  the  Age 
of  Mammals  (Osborn,   19 10),  the  dominant  type,  so  far  as 


THE    ANIMAL   ANCESTRY   OF   MAN  75 

known,  was  closely  related  to  the  existing  opossums,  which 
are  arboreal. 

THE    PRIMATES    ASCEND    INTO    THE   TREES 

The  high  grade  of  vitahty,  the  relatively  advanced 
methods  of  reproduction  and  a  progressive  improvement 
in  brains  and  intelligence,  all  led  to  the  final  triumph  of  the 
placental  mammals  over  their  competitors  the  marsupial 
mammals,  which  were  for  the  most  part  crowded  into  far- 
away corners  of  the  world  auch  as  Patagonia  and  Australia. 
Possibly  this  higher  vitahty  of  the  primitive  insectivorous 
placentals,  joined  to  a  high  degree  of  variabihty  and  plas- 
ticity in  hereditary  characters,  early  enabled  them  to 
branch  out  and  adapt  themselves  for  many  methods  of 
locomotion  and  of  feeding,  according  to  the  w^ell-estabhshed 
principle  of  adaptive  radiation.  Unfortunately  the  fossil 
history  of  the  placentals  during  the  later  aeons  of  the  Age 
of  Reptiles  is  extremely  meager  but  early  in  the  Eocene 
epoch,  or  first  division  of  the  Tertiary  period  or  Age  of 
Mammals,  the  placental  stock  had  already  branched  out 
into  insectivores,  carnivores,  various  herbivorous  hoofed 
mammals,  rodents  and  so  forth.  The  direct  ancestors  of  the 
Primates  during  this  period  also  are  still  undiscovered  but 
the  fossils  from  early  Eocene  times  show  that  even  at  this 
immensely  remote  time  (estimated  by  geologists  as  perhaps 
fifty  or  sixty  milhon  years  ago)(BarreII)  the  order  of  Pri- 
mates had  already  begun  to  separate  into  several  of  its 
grand  divisions  as  we  know  them  today:  first,  there  were 
forerunners  of  the  modern  tree-shrews,  classed  by  many 
authors  under  the  more  ancient  and  primitive  order  Insec- 
tivora,  but  foreshadowing  the  Primates  in  many  features; 
secondly,  there  were  primitive  lemuroids,  structurally 
at  least  related  to  the  ancestors  of  the  varied  modern 
lemurs  of  Madagascar;  thirdly,  there  were  the  tarsioids, 
small  forms  with  much  enlarged  orbits,  related  to  the 
existing  spectral  tarsier  of  the  East  Indies. 

The  higher  primates  (including  the  platyrrhine,  or  New 
World  monkeys,  and  the  catarrhine,  or  Old  World  series 
of  tailed  monkeys,  anthropoid  apes  and  man)  do  not  begin 


76 


HUMAN   BIOLOGY 


to  appear  in  the  fossil  record  until  the  Oligocene,  or  second 
great  epoch  of  the  Tertiary  period,  and  so  far  as  present 
evidence  indicates  they  were  a  distinctly  later  series  than 


Fig.  13.   Incomplete  fossil  skeleton  of  very  primitive  primate  (Notharctus) 

from  Eocene  of  Wyoming. 
(After  Gregory.) 


the  early  Eocene  radiation  of  tree-shrews,   lemuroids  and 
tarsioids. 


THE   ANIMAL    ANCESTRY   OF   MAN  77 

Taken  collectively,  the  lower  Primates  were  represented  in 
Eocene  times  by  a  great  number  of  genera  and  species, 
founded  mostly  on  fragmentary  jaws  but  in  some  cases 
known  also  from  various  other  parts  of  the  skeleton.  In  the 
several  instances  in  which  the  structure  of  the  hind  feet 
is  known  the  great  toe  is  very  large,  provided  with  a  flat 
nail  and  set  off  at  an  open  angle  from  the  other  digits, 
which  were  long  and  slender.  In  all  the  recent  primates 
this  kind  of  great  toe  is  a  sign  of  tree-climbing  and  an  inten- 
sive study  of  the  skeleton  of  many  different  types  of  Primates 
from  Eocene  to  recent  times  can  lead  only  to  the  con- 
clusions that  the  ancestral  stock  of  the  entire  order  acquired 
many  of  its  peculiar  characters  in  the  trees  (Gregory,  1920, 
1927,  1928)  and  that  this  momentous  series  of  events,  of  far 
greater  importance  to  mankind  than  any  celebrated  in 
secular  history,  took  place  at  a  very  early  date  in  the  history 
of  the  placental  mammals,  perhaps  even  before  the  close 
of  the  Cretaceous  period. 

With  this  brief  review  of  the  earlier  fossil  records  of  the 
rise  of  the  Primates  before  us,  let  us  return  to  the  considera- 
tion of  the  evolution  of  their  locomotor  apparatus. 

In  such  a  specialized  swift-running  type  of  mammal 
as  the  horse,  the  limbs  have  become  modified  into  slender, 
suddenly  extensible  compound  levers,  and  in  full 
flight  the  body  is  catapulted  forward  by  the  sledge-hammer 
strokes  of  the  solid  hoofs.  In  this  case  the  middle  metacarpal 
bones  of  the  forefeet  and  the  middle  metatarsals  of  the 
hind  feet  become  greatly  elongated,  while  the  remaining 
metacarpals  and  metatarsals  become  more  or  less  reduced 
and  the  digits  below  these  have  even  disappeared  entirely. 
In  the  line  leading  to  man,  on  the  other  hand,  the  process 
of  digital  reduction  was  avoided,  because  long  before  the 
lateral  digits  could  be  reduced  through  running  on  the 
ground,  our  ancestors  took  to  the  trees,  where  all  five  digits 
of  the  hands  and  feet  were  needed  for  climbing.  It  is  also 
to  this  early  ascent  into  the  trees  that  the  Primates,  including 
man,  doubtless  owe  the  retention  of  other  relatively  primi- 
tive mammalian  features  in  many  parts  of  the  skeleton. 
For  although  arboreal  life  eventually  takes  its  toll  in  the 
way  of  specializations,  leading  finally  to  cul-de-sacs  from 


yS  HUMAN    BIOLOGY 

which  retreat  is  usually  impossible  and  in  which  extinction  is 
inevitable,  yet  it  is  an  easily  verifiable  fact  that  in  the  tree- 
shrews  and  lemurs  the  earlier  stages  of  arboreal  Kfe  conserved 
many  skeletal  characters  which  were  very  early  lost  by 
related  mammals  that  became  speciahzed  either  for  swift 
running,  or  leaping  on  the  ground,  or  digging,  or  swimming. 
We  are  now  in  a  position  to  consider  some  of  the  ways  in 
which  the  primitive  mammahan  skeleton  became  adapted 
for  arboreal  habits  (Morton).  When,  as  described  above, 
the  sacral  portion  of  the  vertebral  column  became  attached 
by  ligament  to  the  inner  sides  of  the  pelvis,  the  animal 
acquired  one  of  the  first  prerequisites  for  rearing  up  on  its 
hind  legs,  that  is,  by  contracting  the  longitudinal  dorsal 
muscles  the  creature  could,  so  to  speak,  raise  the  draw- 
bridge and  balance  it  upon  the  rear  pier  of  the  double 
suspension  bridge.  It  will  readily  be  seen  that  arboreal 
life  put  a  premium  upon  this  ability,  as  also  upon  the 
possession  of  limbs  that  were  equally  well  adapted  for 
pushing  and  for  pulling.  At  first  the  Primates  were  little 
more  than  quadrupeds  that  ran  along  the  tops  of  the  branches 
and  leaped  like  squirrels  from  branch  to  branch,  differing 
widely,  however,  from  normal  ground-living  quadrupeds 
in  their  grasping  hands  and  feet.  Such  indeed  are  the  tree- 
shrews  and  lemurs  of  the  present  time  and  such  were  their 
predecessors  in  Eocene  times.  Some  of  the  leaping  types, 
such  as  the  sifakas  and  indris  of  Madagascar  and  still  more 
the  galagos  and  spectral  tarsiers,  specialized  in  leaping  on  the 
long  hind  limbs,  rearing  the  forepart  of  the  body  as  described. 
In  these  hopping  forms  as  the  backbone  is  reared  upward, 
the  knee  is  bent  and  the  femora  are  directed  downward  and 
backward,  the  opposite  condition  to  that  which  took  place 
in  man  (Morton).  In  another  line  of  specialization  leading 
to  the  baboons,  the  animals  started  from  a  fully  developed 
monkey  stage;  spreading  from  the  forests  into  more  or 
less  open  savannahs,  they  spent  more  and  more  time  running 
on  the  ground  and  gradually  lost  the  typical  monkey-like 
configuration  of  the  body  and  became  more  or  less  dog-like, 
the  fore  and  hind  limbs  being  subequal  in  length,  the  hands 
and  feet  becoming  more  or  less  paw-like,  with  somewhat 
reduced  thumb  and  great  toe  and  slightly  enlarged  middle 


THE    ANIArAL   ANCESTRY   OF    MAN  79 

digits.  In  the  typical  South  American  monkeys,  on  the 
contrary,  the  skeleton  is  highly  speciahzed  for  arboreal  hfe. 
The  Hmbs  are  long,  giving  the  animal  a  long  reach  and  the 
long  cyhndrical  tail  is  unusually  thick  and  muscular,  com- 
prising many  spirally-wrapped  muscles  and  tendons  which 
enable  it  to  coil  up  hke  a  watch-spring  and  to  wrap  itself 
around  branches.  Its  flexible  tip  even  functions  as  a  sort  of 
fifth  hand.  In  general  the  skeleton  .of  the  South  American 
monkeys  is  radically  different  in  leading  features  from  that 
of  man  and  every  bone  of  it  is  readily  distinguished  from  its 
human  homologue. 

In  all  Primates  great  skill  in  balancing  the  body  and  in 
judging  distances  in  leaping  and  climbing  are  obviously 
necessary,  so  that  in  the  comparative  study  of  the  brains 
of  lemurs,  apes,  monkeys  and  man,  neurologists  have 
found  an  increasingly  high  degree  of  development  of  all 
those  parts  of  the  brain  that  serve  first  to  correlate  the 
sense  of  vision  with  the  senses  of  balance  and  of  bodily 
posture,  and  secondly,  to  initiate  the  appropriate  stimuli 
to  the  muscular  system  so  that  precision  of  movement  and 
balance  may  be  habitual. 

This  great  skill  in  balancing,  together  with  the  possession 
of  grasping  hands  and  feet,  early  led  both  the  New  World 
and  the  Old  World  divisions  of  the  Primates  to  use  one  or 
the  other  of  the  four  extremities  in  grasping  for  objects  of 
food,  while  the  remaining  three  were  employed  in  main- 
taining the  body  in  its  always  unstable  equihbrium.  The 
habit  of  sitting  upright,  which  enabled  both  hands  to  be 
used  in  the  manipulation  of  the  food,  led  in  the  Old  World 
division  to  the  development  of  special  pads  called  ischial 
callosities  at  the  hind  end  of  the  pelvis.  Again,  the  habit  of 
sitting  upright  in  the  ancestors  of  the  anthropoid  division 
of  the  Old  World  series,  together  with  the  increasing  length 
of  the  limbs,  finally  resulted  in  the  peculiar  method  of 
climbing  which  not  until  our  own  time  has  received  a  name, 
notwithstanding  its  literally  revolutionary  significance  in 
the  history  of  man.  This  habit  of  "brachiation"  (or  swinging 
by  the  arms),  as  it  was  aptly  named  by  Sir  Arthur  Keith, 
rescued  us  from  monkey-hood  and  by  turning  the  backbone 
of  our  ancestor  up  on  end  it  literally  set  him  on  his  feet 


80  HUMAN   BIOLOGY 

and  not  only  raised  his  face  toward  the  sky  but  encouraged 
him  to  use  his  hands  and  brains  in  working  out  his  own 
salvation.  Like  all  other  great  discoveries  which  disturb 
the  complacency  and  the  traditions  of  mankind,  this  one 
has  been  either  neglected,  waved  aside  or  ridiculed;  but  we 
shall  presently  see  that  when  the  masking  effect  of  man's 
present  hfe  habits  is  taken  into  account,  his  very  bones 
testify  and  his  inward  parts  reveal  the  signs  of  his  brachiating 
origin. 

In  the  present  imperfect  record  of  Primate  hfe  we  first 
come  upon  the  brachiating  habit  and  its  anatomical  corre- 
lates in  the  gibbons  of  Southeastern  Asia.  It  is  true  that 
some  feeble  attempts  at  brachiation  are  occasionally  offered 
by  some  of  the  longer-limbed  catarrhine  monkeys  or  even 
by  the  spider  monkeys  of  the  New  World  series.  But  these 
skilled  tumblers  are  mere  beginners;  their  performances, 
wonderful  as  they  are  when  considered  as  feats  in  balancing 
and  in  ballistics,  pale  in  comparison  with  the  dazzling 
exhibitions  of  the  gibbons,  which  are  the  true  virtuosi  of  the 
upper  branches  of  the  jungle.  With  all  the  abandon  due  to 
perfect  mastery  of  the  technical  details,  they  hurl  them- 
selves from  the  springing  bamboo  stalks,  keeping  them- 
selves upright  in  the  air  and  catching  the  next  hold  on  the 
branches  with  the  greatest  ease. 

Some  of  the  gibbons  of  the  genus  Hylobates  have  begun  to 
pay  a  price  for  this  virtuosity;  their  arms  and  hands  are 
excessivel}^  long  and  their  thumbs  considerably  enfeebled, 
since  Hke  a  trapeze  performer  they  tend  to  use  the  fingers  as 
hooks.  But  these  speciaHzations  are  less  pronounced  in  the 
hoolock  gibbons,  in  which  the  thumb  is  vigorously  developed. 
Moreover  the  single  known  fossil  femur  from  the  Miocene 
of  Germany  (named  Pliohylobates),  which  appears  to 
belong  to  a  primitive  gibbon,  is  distinctly  stouter  than  that 
of  its  modern  relatives.  It  is  a  reasonable  inference  therefore 
that  the  earhest  gibbons  were  somewhat  less  slender,  less 
fully  specialized  for  advanced  brachiating  habits  than  are 
their  modern  descendants,  and  in  view  of  the  various 
souvenirs  of  a  non-brachiating  catarrhine  ancestral  stock 
that  are  retained  even  in  the  modern  gibbon,  such  an 
inference  becomes  highly  probable.  Again,  the  small  fossil 


Fig.  14.  Skeleton  of  gibbon,  mounted  in  brachiating  pose. 
(Courtesy  of  The  American  Museum  of  Natural  History.) 


II81I 


82 


HUMAN    BIOLOGY 


jaw  from  the  Lower  Oligocene  of  Egypt,  to  which  the  name 
PropHopithecus  has  been  appHed  and  which  appears  to  be 
in  the  Hne  of  ascent  to  the  gibbons  also,  retains  all  or  nearly 
all  the  characters  which  might  be  predicated  of  the  jaw 
of  the  common  stem  form  of  all  the  anthropoid  series, 
including  man.  The  lower  teeth  in  this  jaw  are  each  more 
primitive,  that  is,  more  hke  those  of  still  older  primates, 
than  are  the  corresponding  parts  in  modern  gibbons.  Hence 
the  palaeontological  evidence,  slender  as  it  is,  lends  support 
to  the  conclusion  based  on  comparative  studies  of  the 
teeth,  skull  and  many  parts  of  the  anatomy  of  the  recent 
Primates,  namely,  that  the  later  specializations  of  brachia- 
tion  seen  in  the  gibbons  had  not  been  assumed  by  the  direct 
ancestors  of  the  higher  anthropoid  group. 

Nevertheless,  repeated  consideration  of  the  subject  must 
also  support  the  view  that  the  gibbons  on  the  whole  retain 
the  basic  features  of  the  earher  stages  of  brachiation,  namely, 
the  maintenance  of  an  upright  posture  at  right  angles  to  the 
general  plane  of  forward  motion,  that  was  also  prerequisite 
for  the  emergence  of  man.  The  relative  nearness  of  the 
oibbons  on  the  one  hand  to  the  ancestral  stock  of  the  anthro- 
poid-man  series,  and  on  the  other  hand  to  the  older  catar- 
rhine  stock,  has  been  recognized  by  all  authorities.  The 
gibbons  are  definitely  more  primitive  (that  is,  more  like  the 
lower  Primates)  than  any  of  the  great  apes  or  man  in  many 
characters  of  the  dentition,  of  the  skull,  vertebral  column, 
pelvis,  etc.,  as  well  as  in  the  brain  and  in  many  features  of 
the  viscera  (Keith).  Their  pelvis  is  remarkably  primitive; 
it  retains  clear  traces  of  the  ischial  expansions  characteristic 
of  the  Old  World  monkeys,  while  the  blade  of  the  ilium  is 
but  little  expanded  transversely. 

When  the  brachiating  gibbon  comes  down  on  the  ground, 
he  does  not  run  on  all  fours  like  a  monkey,  he  does  not 
swing  on  his  long  forearms  as  crutches  like  an  orang,  he 
does  not  walk  on  all  fours  with  bent  knuckles  as  do  the 
chimpanzee  and  the  gorilla;  on  the  contrary,  he  walks  or 
runs  upright  like  a  man,  with  his  femora  overextended,  so 
as  to  be  nearly  vertical  and  parallel  with  his  backbone. 
His  gait  on  the  ground  diflers  from  that  of  man  in  that  the 
arms  are  held  upward,  the  knees  turned  outward  and  the 


THE    ANIMAL   ANCESTRY   OF    MAN  83 

great  toe  inward.  In  such  a  position  the  gibbon  is  meeting 
and  solving  the  same  problem  of  balancing  the  whole  fore- 
part of  the  body  upon  the  pelvis  and  hind  limbs  that  is 
solved  more  completely  by  man.  Sir  Arthur  Keith,  in 
searching  for  the  early  history  of  man's  upright  posture, 
found  that  in  the  gibbon  the  arrangements  of  the  diaphragm, 
lungs,  pericardium,  and  many  other  internal  organs,  manifest 
many  characteristically  human  adjustments  to  upright 
posture,  and  he  concluded  that  man  had  derived  many  of 
his  structural  and  functional  adaptations  to  the  upright 
posture  from  an  older  brachiating  stage. 

In  conclusion,  the  annectant  position  of  the  gibbon 
between  the  lower  Old  World  Primates  and  the  great-ape- 
man  series  is  fully  documented  by  the  monographic  studies 
of  Tilney  on  the  brain  of  Primates  and  of  Keith  on  the 
viscera;  and  if  the  inference  were  made  that  because  the 
gibbon  is  specialized  in  a  few  features  his  basic  method  of 
brachiation  may  be  ruled  out  of  the  line  of  advance  leading 
to  man,  such  an  inference  would  appear  to  be  not  in  accord 
with  either  the  morphological  or  the  palaeontological 
evidence.  Quite  the  reverse,  while  the  brachiating  gibbon 
is  a  living  witness  of  the  ultimate  derivation  of  man  from 
an  arboreal  quadrumanal  monkey,  he  is  also  far  more  man- 
like than  monkey-like  in  many  features  of  his  viscera  and 
in  his  general  adaptation  to  the  upright  posture. 

MAN  EMERGES  ON  THE  GROUND 

Up  to  the  present  point  we  have  traced  in  outline  the 
general  history  of  the  vertebrate  locomotor  apparatus, 
showing  how  the  simplest  fish-like  forms  contain  the  poten- 
tiality and  the  ground-plan  of  the  sequence  of  animals  that 
emerged  from  the  swamps,  invaded  the  dry  land,  ascended 
into  the  trees  and  finally  turned  the  backbone  at  right 
angles  to  the  plane  of  progression  and  gave  rise  to  the  noble 
grade  of  brachiators.  All  the  existing  anthropoid  apes 
retain  clear  traces  of  derivation  from  a  primitive  brachiating 
stem  form,  perhaps  represented  by  some  of  the  various 
species  referred  to  Dryopithecus  and  allied  genera,  which 
roamed  over^Europe  and  India  during  the  Miocene  and 
Pliocene  times. 


84 


HUMAN   BIOLOGY 


Apparently  the  orang-utan  was  the  first  to  branch  off 
from  the  common  stock.  It  rapidly  attained  great  size, 
especially  the  old  males,  and  became  excessively  speciaHzed 


Fig.  15.  Structural  stages  in  rise  from  fish  to  man. 
Starting  from  upper  right-hand  corner,  "living  fossils"  form  a  series  that 
gradually  approaches  man  in  general  structural  plan.     Each  "living  fossil" 
is  also  a  surviving  witness  of  a  corresponding  stage  in  past  ages. 

for  arboreal  life,  using  chiefly  the  suspension  grasp  of  both 
the  hands  and  feet,  which  are  now  extremely  long  and  hook- 


THE    ANIMAL   ANCESTRY   OF    MAN  85 

like.  After  the  orang  had  begun  to  diverge,  the  common 
stock  contained  the  ancestors  of  the  chimpanzee,  gorilla, 
man  and  possibly  of  other  species  now  known  chiefly  from 
fossil  teeth  and  jaws  of  the  Dryopithecus  group.  The  common 
stock  was  probably  intermediate  in  size  between  the  siamang 
and  the  smaller  species  of  chimpanzee.  By  Upper  Miocene 
times  in  India  there  was  already  a  wide  range  in  size,  as 
indicated  by  the  fossil  teeth  of  anthropoids,  some  being 
but  httle  larger  than  those  of  siamangs,  others  nearly  as  big 
as  those  of  gorillas. 

The  known  African  anthropoids,  the  chimpanzee,  the 
gorilla  and  the  extinct  Australopithecus  (Dart),  show  the 
most  unmistakable  marks  of  close  kinship  with  each  other. 
Among  recent  forms  the  chimpanzee  on  the  whole  probably 
retains  the  greater  number  of  primitive  characters.  The 
range  of  variabihty  in  existing  chimpanzees  is  very  great, 
especially  in  regard  to  external  features,  details  of  skull 
form,  size  of  teeth,  degree  of  wrinkling  of  enamel  on  the 
molars,  and  many  other  characters.  In  some  chimpanzees 
the  basic  patterns  of  the  premolars  and  molars  rather 
closely]  approximate  the  primitive  human  type,  but  the 
canine  teeth  exhibit  the  opposite  tendency  toward  enlarge- 
ment. In  many  races  of  anthropoids  there  seems  to  be  a 
tendency  to  gigantism,  the  body  weight  mounting  to  many 
fold  greater  than  that  of  the  primitive  anthropoid  stock 
represented  by  the  tiny  fossil  lower  jaw  of  Propliopithecus. 
Very  heavy  bodies  are  not  favorable  for  extreme  agility 
in  the  trees  unless  a  cautious  swinging  movement  is  adopted, 
as  in  the  orang.  Hence  in  order  to  maintain  this  agility  it 
was  necessary  for  the  chimpanzee  to  acquire  a  surprisingly 
high  degree  of  muscular  strength. 

The  typical  chimpanzees  are  forest  animals  that  appar- 
ently spend  most  of  their  time  in  the  trees  and  have  therefore 
had  time  to  become  specialized  considerably  beyond  the 
stage  of  the  "common  ancestor"  of  the  higher  apes  and 
man.  For  instance,  at  least  in  many  chimpanzees  the  thumb 
is  reduced.  When  either  the  chimpanzee  or  the  gorilla  walks 
on  the  ground  it  commonly  assumes  a  position  which  is 
superficially  like  that  of  a  quadruped,  but  on  closer  inspec- 
tion we  see  that  these  animals  differ  profoundly  from  true 


86  HUMAN    BIOLOGY 

quadrupeds  in  the  fact  that  they  rest  the  weight  of  the 
forepart  of  the  body  not  upon  the  palms  of  their  hands 
but  upon  their  flexed  fingers,  a  souvenir  of  the  grasping 
action  of  the  hand  during  brachiation.  Usually  the  chim- 
panzees when  on  the  ground  stay  near  the  forests,  but 
explorers  have  sometimes  seen  them  crossing  wide  areas  of 
savannah  country  in  going  from  one  patch  of  forest  to 
another.  The  finding  of  the  fossil  skull  named  Australo- 
pithecus in  a  region  hundreds  of  miles  south  of  the  forest- 
Hving  anthropoids,  in  a  formation  of  which  the  hthologic 
characters  indicate  open  country  for  long  periods,  supports 
Dart's  view  that  the  most  man-Hke  known  member  of  the 
higher  ape  stock  was  already  in  course  of  invading  the 
open  country  as  did  the  ancestors  of  man. 

We  are  not  yet  sure  whether  man  branched  off  before  or 
after  the  gorilla  separated  from  the  common  stock.  The 
late  Professor  G.  Schwalbe  after  a  most  thorough  analysis 
concluded  that  man  branched  off  from  the  fork  that  also 
gave  rise  to  the  chimpanzee.  The  modern  old  male  gorilla 
has  become  extremely  un-manhke  in  its  excessive  body 
size,  huge  baboon-Hke  muzzle  and  teeth  and  certain  other 
features.  All  these  characters,  however,  may  have  been 
rapidly  acquired  after  the  gorilla  separated  from  the  main 
stock.  The  blood  tests,  the  brain  structure,  the  anatomy 
of  the  hands  and  feet  and  many  other  anatomical  characters 
indicate  that  the  relationship  between  gorilla  and  man  is  far 
closer  than  was  formerly  suspected.  The  ape-like  jaw  of  the 
Piltdown  skull  indicates  that  even  as  late  as  early  Pleistocene 
times  there  were  some  human  beings  with  strongly  ape-like 
characters  of  the  jaw  and  teeth. 

The  almost  human  hand,  foot  and  brain  of  the  gorilla 
suggest  that  a  secondarily^  quadrupedal,  ground-living  phase 
may  have  succeeded  the  purely  erect  arboreal  stage  and  pre- 
ceded the  erect  ground-walking  stage,  notwithstanding  the 
initial  mechanical  disadvantages  encountered  by  a  heavy- 
chested  form  in  assuming  the  erect  posture  (Morton). 
Even  now  in  spite  of  his  gigantism  or  of  his  short  hind  legs, 
the  young  gorilla  has  no  difficulty  in  standing  upright  or  in 
carrying  boxes  with  his  forearms  while  walking  in  the  erect 
position.   The   quadrupedal   gait   recorded   by   Hrdlicka   in 


THE    ANIMAL   ANCESTRY   OF    MAN  87 

babies  of  various  races  might  be  reminiscent  of  a  primitive 
quadrupedal  ground  phase  following  the  erect  aboreal  phase. 
But  on  the  whole  the  present  evidence  seems  to  favor  the 
view  that  when  man's  ancestors  came  down  out  of  the  trees 
they  held  the  body  erect  while  walking,  as  does  the  gibbon. 

While  there  are  hterally  thousands  of  items  of  evidence 
for  the  inference  that  man  is  a  speciahzed  pecuHar  offshoot 
of  the  anthropoid  stock,  the  exact  time  of  his  separation 
from  that  stock  and  the  more  precise  description  of  its 
anatomy  are  matters  of  inference  as  to  which  there  is  room 
for  differences  of  opinion.  Tlie  known  fossil  record  of  man's 
nearest  relatives,  while  very  meagre,  indicates  that  during 
the  Eocene,  or  first  grand  division  of  the  Age  of  Mammals, 
only  the  lower  grades  of  the  Primates  were  in  existence. 
By  the  time  of  the  Lower  OHgocene  the  short-jawed  pred- 
ecessors of  the  anthropoid  group  were  estabhshed.  In  the 
Miocene  and  Phocene  epochs  varied  species  of  anthropoid 
apes  roamed  over  Europe  and  India,  some  of  which  fore- 
shadowed man  in  the  patterns  of  their  molar  teeth.  Then 
there  is  a  blank  in  the  record  and  by  the  time  of  the  Upper 
Pliocene  and  Lower  Pleistocene  several  widely  different 
types  of  human  skull  were  already  in  existence.  There  is 
considerable  indirect  evidence  that  the  rate  of  evolution  in 
the  earlier  races  of  mankind  was  far  higher  than  it  was  in 
other  groups  of  animals  and  it  is  not  unlikely  that  the 
rapid  emergence  of  man  as  a  creature  of  the  open  plains 
took  place  in  the  vast  periods  of  time  represented  by  the 
Miocene  and  Pliocene  epochs. 

We  are  not  yet  informed  as  to  whether  this  emergence  took 
place  in  Asia,  Europe  or  Africa.  The  claims  of  the  high 
plateau  region  of  central  Asia  as  a  possible  center  of  dis- 
tribution of  the  nascent  Hominidae  have  been  urged  by 
Professor  Osborn  (1926),  and  several  fossil  teeth  of  unques- 
tionably human  type  have  been  found  imbedded  in  a  cave 
deposit  in  China  that  contained  other  fossil  mammals  of 
apparently  Pleistocene  age.  But  the  origin  of  man  from  the 
anthropoid  stem  must  be  sought  in  a  far  older  epoch,  perhaps 
the  Miocene,  so  that  there  would  be  plenty  of  time,  if  man 
originated  elsewhere,  for  him  to  have  reached  eastern  Asia 
by  Pleistocene  times.  Also  it  must  be  admitted  that  the  three 


K 


H 


^ 


^ 

'^ 


N,  U 


^Jf 


^ 


ABC  D  E  F  G 

Fig.  1 6.  Structural  stages  in  evolution  of  skull  from  fish  to  man. 

A.  (Lower  left).  Restoration  of  skull  of  Osteolepis,  a  Devonian  lobe-fmned 
fish.  Based  on  original  fossils  in  American  Museum  of  Natural  History  and  on 
Pander's  specimens. 

B.  Restoration  of  skull  of  Permocarboniferous  amphibian  (Trimerorhachis 
minor).  Based  on  fossil  specimens  in  American  Museum  of  Natural  History. 

C.  Permocarboniferous  primitive  reptile  (Captorhinus).  From  specimen  in 
American  Museum  of  Natural  History. 

D.  Permian  mammal-like  reptile  (Scymnognathus).  Restoration  of  skull 
based  on  fossil  specimens  in  American  Museum  of  Natural  History. 

E.  Triassic  mammal-like  reptile  (Cynognathus).  Restoration  of  skull  by 
Prof.  A.  S.  Romer,  based  on  fossil  specimens  in  British  Museum  (Natural 
History). 

F.  Recent  opossum,  "living  fossil"  mammal  type,  surviving  from  Cre- 
taceous period. 

G.  Eocene  lemuroid  primate  (Notharctus).  Restoration  based  on  fossil  skulls 
in  American  Museum  of  Natural  History. 

H.  (Top  row,  right).  Skull  of  recent  gibbon,  representing  little  modified 
survivor  of  Oligocene  proto-anthropoid  stock. 

I.  Immature  gorilla  skull,  representing  modified  descendant  of  Miocene 
anthropoid  stock. 

J.  Lower  Pleistocene  Pithecanthropus-  Cast  of  original  skull  top,  with  Prof. 
J.  H.  McGregor's  restoration  of  face.  Represents  one  of  primitive  human 
stages. 

K.  Upper  Pleistocene  Neanderthal  stage.  Restoration  of  skull  by  Prof.  J.  H. 
McGregor  from  original  fossil  specimens. 

L.  Recent  human  stage,  with  high  forehead  and  relatively  small  jaws. 

1881 


THE    ANIMAL   ANCESTRY   OF    MAN  89 

known  anthropoids  which  are  unquestionably  nearer  to 
man  than  any  others  are  the  three  African  forms,  the  chim- 
panzee, the  gorilla  and  the  extinct  Australopithecus.  Also 
the  European  fossil  species  Dryopithecus  rhenanus  and 
Dryopithecus  Jontani  in  the  detailed  patterns  of  their  molar 
teeth  appear  to  be  especially  related  to  the  African  group 
and  therefore,  according  to  the  evidence  of  blood  tests, 
etc.,  to  man. 

CONCLUSIONS 

In  conclusion,  the  theory  of  man's  derivation  from  lower 
vertebrates  according  to  the  general  sequence  of  stages 
outhned  in  this  article  may  claim  to  be  distinctly  more  than 
a  trial  hypothesis,  since  it  rests  upon  many  converging  lines 
of  evidence.  It  is  in  fact  an  outgrowth  of  the  general  advances 
of  the  past  half-century  in  vertebrate  palaeontology,  verte- 
brate zoology  and  taxonomy,  human  and  comparative 
anatomy,  anthropology,  embryology,  physiology  and  related 
sciences.  The  theory  of  the  brachiating  ancestry  of  man 
rests  in  the  first  place  upon  the  general  subject  of  the  classi- 
fication and  evolution  of  the  vertebrates  as  a  whole.  A  host 
of  zoologists  and  palaeontologists  have  estabhshed  the  fact 
of  man's  place  in  nature:  he  is  a  member  of  the  anthropoid- 
human  division  of  the  higher  Primates,  which  may  be 
traced  to  the  stem  of  the  order  of  Primates;  these  in  turn 
derive  from  primitive  placental  mammals  related  to  the 
existing  tree-shrews;  thence  we  pass  downward  through  the 
imperfect  records  of  the  Age  of  Reptiles  to  the  progressive 
mammal-hke  reptiles  of  the  Triassic;  downward  again  by 
plainly  recognizable  morphological  stages  to  the  theromorph 
stem  forms  in  the  Permian;  still  downward  to,  or  near  to,  the 
captorhinomorph  division  of  the  cotylosaurs;  and  thence  to 
the  horizon  of  the  varied  eotetrapods  of  the  Coal  Measures; 
in  the  Devonian  we  see  the  crossopterygian  and  dipnoan 
forerunners  of  the  Tetrapoda  and  below  that  a  long  gap  to 
the  varied  ostracoderms  of  the  Silurian,  which  show  us  the 
early  chordate  stem  in  various  guises.  Below  that  the  rest  is 
darkness,  except  that  comparative  morphology  throws 
considerable  hght  on  the  origin  of  the  basic  chordate  loco- 
motor apparatus  which  all  the  later  forms  inherited  in  part. 


90  HUMAN   BIOLOGY 

REFERENCES 

Barrell,  J.  1917.  Rhythms  and  the  measurements  of  geologic  time.  Bull.  Geot. 

Soc.  Amer.,  28:  745. 
Dart,  R.  A.  1926.  Taungs  and  its  significance.  Nat.  Hist.,  26:  No.  3,  315. 
Delage,  Y.,  and  Herouard,  E.   1898.  Traite  de  Zoologie  Concrete.  Vol.  8. 

Les  Procordes.  Paris,  Schleicher  Freres. 
Gaskell,    W.    H.    1895.    Origin  of  the  vertebrates.  Proc.  Cambridge  Pbilos. 

Soc,  9,  Pt.  I,  19. 
Gregory,  W.  K.   1915.  Present  status  of  the  problem  of  the  origin  of  the 

Tetrapoda.  Ann.  N.  Y.  Acad.  Sc,  26:  317. 
1920.  On  the  structure  and  relations  of  Notharctus,  an  American  Eocene 

primate.  Mem.  Amer.  Mus.  Nat.  Hist.,  n.s.,  3:  Pt.  11,  49. 
1922.  Origin  and   Evolution  of  the   Human  Dentition.  Bait.,  Williams  & 

Wilkins. 

1927.  How  near  is  the  relationship  of  man  to  the  chimpanzee-gorilla  stock? 
Quart.  Rev.  Biol.,  2:  No.  4,  549. 

1928.  Were  the  ancestors  of  man  primitive  brachiators?  Proc.  Amer.  Pbilos. 
Soc,  47:  No.  2,  129. 

1928.  The  upright  posture  of  man:  a  review  of  its  origin  and  evolution. 
Proc.  Amer.  Pbilos.  Soc,  47:  No.  4,  339. 
Hrdlicka,  a.  1927.  Quadruped  progression  in  the  human  child.  Am.  J.  Pbys. 
Anthrop.  10:  No.  3,  347. 

1927.  Children  on  "all  fours."  Additional  reports.  Am.  J.  Pbys.  Anthrop., 
11:  No.  I,  123. 

1928.  Children  running  on  all  fours.  Am.  J.  Phys.  Anthrop.,  11:  No.  2,  149. 
Keith,  A.    1923.   Man's  posture:  its  evolution  and  disorders.  Brit.  M.  J., 

pp.  451;  499;  545;  587;  624;  669. 
Martin,  H.  N.  1927.  The  Human  Body.  Ed.  11.  N.  Y.,  Henry  Holt. 
Morton,  D.  J.  1927.  Human  origin.  Am.  J.  Phys.  Anthrop.,  10:  No.  2,  165. 
OsBORN,  H.  F.  1907.  Origin  and  Evolution  of  the  Mammalian  Molar  Teeth. 

N.  Y.,  Macmillan. 
19 ID.  The  Age  of  Mammals  in  Europe,  Asia  and  North  America.  N.  Y., 

Macmillan. 
1926.  Why  Central  Asia?  Nat.  Hist.,  26:  No.  3,  263. 
Patten,  W.  1912.  The  Evolution  of  the  Vertebrates  and  Their  Kin.  Phila., 

Blakiston. 
RoMER,  A.  S.  1922.  The  locomotor  apparatus  of  certain  primitive  and  mammal- 

Hke  reptiles.  Bull.  Amer.  Mus.  Nat.  Hist.,  46:  Art.  10,  517. 
Shumwav,  W.  1927,  Vertebrate  Embryology.  N.  Y.,  John  Wiley. 
Simpson,  G.  G.  1928.  Catalogue  of  the  Mesozoic  MammaHa  in  the  Geological 

Department   of  the   British   Museum.    Publ.    by   Order  of  Trustees  of 

British  Museum. 
Stensio,  E.  a.  1927.  Downtonian  and  Devonian  Vertebrates  of  Spitsbergen. 

Pt.  I.  Family  Cephalaspidse.  Oslo,  Jacob  Dybwad. 
Tilnev,  F.  1928.  The  Brain  from  Ape  to  Man.  N.  Y.,  Hoeber. 
Watson,  D.  M.  S.   1926.   EvoUition  and  origin  of  the  amphibia.  Croonian 

lecture.  Pbilos.  Tr.  Roy.  Soc.  Lond.,  S.  b,  214:  189. 


Chapter  IV 

THE  EVOLUTION  OF  THE  BRAIN 

George  H.  Parker 

NO  organ  is  so  distinctive  of  man  as  his  brain.  Long 
recognized  as  the  seat  of  his  mental  hfe,  it  is  that 
portion  of  his  body  most  concerned  with  his  per- 
sonahty.  Here  take  place  those  changes  that  give  rise  to  his 
sensations,  his  memories,  his  voKtions;  here  arise  his  emo- 
tions, the  figments  of  his  imagination,  his  dreams;  and 
here  too,  in  abnormal  states,  appear  those  idiosyncracies 
and  moods  that  pass  over  step  by  step  into  insanity.  In 
short,  the  brain  is  the  organ  of  his  mind,  his  very  soul. 
Not  that  the  brain  alone  is  all  this,  for  this  organ  is  buried 
in  his  body,  which,  as  an  environment,  yields  among  other 
things  the  whole  range  of  internal  secretions  determining 
as  they  do  in  so  many  ways  the  setting  for  the  individual 
Hfe.  But  notwithstanding  the  importance  of  these  surround- 
ings, the  brain  harbors  what  is  one's  truest  self  and  in  this 
respect  no  other  organ  in  us  is  its  peer. 

Man's  brain  more  than  any  other  part  separates  him 
from  all  other  creatures.  Even  its  weight  shows  this.  Two 
hving  animals  only,  the  elephant  and  the  whale,  have 
brains  heavier  than  his.  The  elephant's  brain  weighs  about 
12  pounds,  that  of  a  large  whale  about  lo  pounds,  while 
man's  brain  turns  the  balance  at  almost  exactly  3  pounds. 
All  other  mammals  such  as  the  horse  and  the  cow  and  even 
giants  like  the  rhinoceros  and  the  hippopotamus  have 
smaller  brains  than  man.  The  gorilla,  a  close  relative  to 
man  and  slightly  heavier  in  body  than  he  is,  has  nevertheless 
a  brain  scarcely  one-third  as  large.  Thus  man  outstrips 
all  other  living  animals,  except  the  elephant  and  the  whale, 
in  the  absolute  weight  of  his  brain. 

Every  one  is  familiar  with  the  fact  that  the  size  of  an 
animal's  brain  is  roughly  proportional  to  that  of  its  body; 
the  elephant  has  a  gigantic  brain,  the  mouse  a  diminutive 
one.  But  it  is  not  so  commonly  known  that  large  animals 

91 


92  HUMAN   BIOLOGY 

have  disproportionately  small  brains  and  small  animals 
relatively  large  ones.  In  the  cat,  an  animal  of  medium  size 
and  therefore  appropriate  as  a  standard,  the  weight  of  the 
brain  is  about  i  per  cent  of  that  of  the  body.  In  the  Indian 
elephant,  whose  bodily  weight  may  be  from  6000  to  7000 
pounds,  the  brain,  large  though  it  is,  is  only  about  0.2  per 
cent  of  this  weight,  or  one-fifth  the  percentage  of  the  cat's 
brain.  The  condition  in  the  elephant  represents  fairly  well 
that  characteristic  of  most  large  mammals. 

The  opposite  extreme  is  clearly  illustrated  by  small 
animals  like  the  rats  and  the  mice,  whose  brains  are  large 
compared  with  their  bodies.  Thus  the  brain  of  the  harvest 
mouse,  whose  bodily  weight  is  about  7  grams,  represents 
over  5  per  cent  of  this  weight,  or  five  times  the  percentage 
of  the  cat's  brain.  Disproportionately  large  brains  are 
common  among  small  mammals.  The  same  seems  to  be 
true  of  birds;  witness  the  relatively  large  size  of  the  brain 
in  the  smallest  of  these,  the  humming  bird.  And  this  prin- 
ciple also  appears  to  apply  to  insects,  for  among  the  castes 
of  worker  ants  the  brain  is  rather  uniformly  large  even  when 
the  body  is  very  small. 

Apparently  each  phase  of  animal  life  requires  a  certain 
minimum  of  brain  wherewith  to  carry  on  its  nervous  and 
mental  activities,  and  when  for  one  reason  or  another  the 
body  as  a  whole  suffers  an  exceptional  reduction,  the  brain 
does  not  undergo  a  corresponding  decrease.  When  on  the 
other  hand  the  size  of  a  stock  of  animals  through  evolu- 
tionary growth  becomes  excessively  large,  as  in  the  case 
of  the  elephants  or  the  whales,  the  brain  follows  this  trend 
to  a  certain  extent,  in  response  to  increased  skin  surface  and 
musculature,  but  only  in  a  restricted  way,  for  the  sense 
organs  and  muscles  of  a  large  animal  are  after  all  not  much 
more  complicated  or  appreciably  more  numerous  than  those 
of  a  smaller  one.  Hence  the  necessity  of  proportional  increase 
in  the  central  nervous  organs  of  such  a  stock  does  not 
obtain.  Thus  in  such  an  evolutionary  growth  as  that  of  an 
elephant  or  any  other  large  creature,  the  central  nervous 
organs,  though  they  undergo  some  increase,  fall  noticeably 
behind  the  general  growth  of  the  animal  as  a  whole,  with  the 
result  that  the  proportional  size  of  these  organs  is  markedly 


THE    EVOLUTION   OF  THE   BRAIN  93 

less  than  what  might  have  been  expected.  In  both  sets  of 
changes,  decrease  and  increase,  the  brain  seems  to  lag 
behind  the  rest  of  the  animal,  and  gives  evidence  in  this 
way  of  a  degree  of  independence  not  commonly  associated 
with  animal  growth.  The  brain  in  its  evolution,  as  compared 
with  other  parts,  exhibits  what  may  be  described  as  an 
organic  conservatism  for  it  tends  to  maintain  its  size  irrespec- 
tive of  the  surrounding  flux. 

The  amount  of  brain  substance  in  different  animals 
is  often  taken  as  an  indication  of  their  intelhgence,  and  in  a 
measure  this  is  justified.  Thus  the  brain  weights  of  three 
animals  of  about  the  same  bodily  size,  a  very  large  dog, 
a  gorilla,  and  a  man,  are  respectively  135  grams,  430  grams, 
and  1360  grams,  a  rough  measure  of  their  comparative 
mental  powers.  Even  among  the  races  of  men  such  differ- 
ences are  not  unknown.  Thus  the  brain  of  the  Austrahan 
native  weighs  only  about  1185  grams,  an  amount  quite 
compatible  with  his  low  mentahty. 

But  such  measures  are  necessarily  of  only  very  general 
appHcabihty.  When  the  weights  of  various  human  brains  of 
European  stock  are  compared  great  individual  differences 
are  to  be  observed  from  the  extreme  of  microcephaly  to 
that  of  macrocephaly.  MicrocephaHc  brains  are  those  of 
1000  grams  or  less.  Such  brains  are  known  to  range  as  func- 
tional organs  down  to  a  httle  under  300  grams.  But  individ- 
uals possessing  brains  of  this  size  are  always  abnormal  and 
often  idiotic.  MacrocephaHc  brains  range  from  1500  to 
somewhat  over  1900  grams.  Individuals  thus  equipped  are 
by  no  means  always  geniuses,  but  in  many  cases  are  abnor- 
mal or  even  idiotic.  It  is,  however,  interesting  to  observe 
that  many  highly  intellectual  men  have,  if  not  macrocephahc, 
at  least  unusually  heavy  brains.  If  the  weight  of  the  average 
male  brain  of  European  stock  is  taken  as  1360  grams,  and  if 
the  weights  of  the  brains  of  male  European  intellectuals  are 
compared  with  this  as  a  standard,  it  is  found  that  the  brains 
of  the  majority  of  such  individuals  are  heavier  than  this 
standard.  Thus  of  46  brains  of  intellectuals,  33  were  heavier 
and  only  13  were  lighter  than  the  standard  brain.  The 
average  weight  of  these  46  brains  was  a  little  over  1440 
grams  or  80  grams  heavier  than  the  standard.  The  heaviest 


94  HUMAN    BIOLOGY 

brain  in  the  series  was  that  of  the  celebrated  French  zoologist 
Cuvier,  with  the  unusual  weight  of  1830  grams.  The  hghtest 
brain  was  that  of  the  recently  deceased  dean  of  French 
htterateurs,  Anatole  France,  who  reached  great  distinction 
notwithstanding  the  fact  that  his  brain  weighed  only  1190 
grams.  These  records  show  that  though  it  is  possible  to 
attain  high  intellectual  standing  with  a  brain  subnormal 
in  weight,  the  individual  whose  brain  is  above  the  average 
in  weight  has  on  the  whole  a  better  chance  at  such  attain- 
ment than  his  small-brained  competitor.  Nevertheless  it  is 
perfectly  clear,  when  all  the  facts  of  brain  weight  are  taken 
into  account,  that  beside  quantity  of  brain  there  are  other 
elements  concerned  with  intelligence.  Prominent  among 
these  without  doubt  is  the  organization  of  the  brain  materials, 
an  element  that  is  summarized  in  the  expression  quality 
of  brains,  and  for  which  a  physical  measure  is  difficult  to 
devise. 

In  the  human  species  the  brains  of  the  two  sexes  vary 
slightly.  The  weight  of  the  average  European  male  brain,  as 
already  stated,  is  1360  grams,  that  of  the  female  brain  1250 
grams,  a  difference  of  no  grams  or  about  4  ounces.  This 
difference  has  been  made  the  basis  of  an  unfavorable  com- 
parison of  the  sexes  in  man,  but  as  may  be  inferred  from 
what  has  already  been  said,  the  ground  for  such  a  comparison 
is  extremely  hazardous.  The  difference  in  the  weights  of  the 
brains  in  the  two  sexes  is  more  likely  correlated  with  the 
difTerences  in  the  weights  of  the  male  and  female  bodies  than 
with  different  orders  of  intelligence.  The  body  of  the  average 
European  male  weighs  about  70  kilograms  or  a  little  less 
than  155  pounds;  that  of  the  average  European  female 
about  ^^  kilograms  or  a  little  more  than  121  pounds,  a 
difference  of  15  kilograms  or  about  33  pounds.  This  differ- 
ence, which  implies  a  somewhat  larger  physical  task  on  the 
part  of  the  male  nervous  system  than  on  that  of  the  female 
is  probably  the  real  explanation  of  the  small  difference  in  the 
weights  of  the  two  classes  of  brains  rather  than  different 
degrees  of  intelligence.  From  another  standpoint  the  female, 
seems  to  have  the  advantage  over  the  male,  for,  assuming 
the  correctness  of  the  weights  of  the  brain  and  of  the  bodies 
male  and  female  given  in  this  paragraph,  the  brain  of  man  is 


THE  EVOLUTION  OF  THE  BRAIN  95 

only  about  1.9  per  cent  of  his  total  weight,  while  that  of 
woman  is  about  2.3  per  cent,  an  excess  of  a  fraction  of  i 
per  cent  in  her  favor. 

Roughly  speaking,  the  brain  of  man  is  about  2  per  cent  of 
his  total  weight  or  twice  the  corresponding  percentage  of  an 
average  animal  such  as  the  cat.  The  percentage  in  man, 
however,  does  not  by  any  means  reach  the  5  per  cent  attained 
in  such  small  mammals  as  mice.  Here  apparently  occur  the 
highest  percentages  known  between  brain  and  body  weights, 
a  condition  dependent  rather  upon  the  requirement  of  a 
minimum  amount  of  brain  substance  for  normal  function 
than  upon  excessive  mentahty. 

The  brain  is  the  most  comphcated  organ  in  the  vertebrate 
body.  It  is  a  most  intricate  arrangement  of  centers  and 
connections  that  far  exceeds  in  complexity  the  most  elaborate 
telephone  system.  It  is  at  once  the  despair  and  the  joy  of  the 
working  neurologist,  for  its  comphcations  seem  hmitless, 
while  the  problems  hidden  in  its  details  are  of  the  first  order. 

To  know  the  brain  we  cannot  consider  it  separately  from 
the  spinal  cord,  that  strand  of  nervous  tissue  which  stretches 
from  the  brain  backward  through  much  of  the  body.  In  the 
fishes  the  brain  is  only  a  fraction  of  the  weight  of  the  spinal 
cord.  In  the  frog  the  brain  and  cord  are  about  equal.  In  all 
higher  animals  the  brain  gains  over  the  cord  till  in  man  the 
cord  is  represented  by  a  rod  of  nervous  tissue  somewhat 
thicker  than  a  lead  pencil,  roughly  a  foot  and  a  half  long,  and 
with  a  weight  of  some  26  grams  or  about  a  fiftieth  that  of 
the  brain.  These  changed  relations  are  not  due  to  a  reduction 
in  the  cord  but  rather  to  an  excessive  development  of  the 
brain.  Starting  in  the  fishes  as  a  relatively  inconspicuous 
organ  the  brain  grows  in  proportionate  size  till  in  man  it  far 
overtops  all  other  parts  of  the  nervous  system. 

To  gain  some  acquaintance  even  in  a  superficial  way  with 
the  organization  of  the  human  brain,  it  is  best  to  look  first 
at  the  brain  of  some  simple  representative  vertebrate,  such 
for  example  as  that  of  a  frog.  The  brain  of  this  animal  lies 
in  a  bony  skull  and  upon  exposure  it  is  seen  to  consist  of  an 
elongated  stem  or  axis  which  expands  here  and  there  into 
special  prominences  or  lobes.  The  spinal  cord  of  the  frog, 
which  is  of  relatively  uniform  thickness,  gradually  enlarges 


96 


HUMAN   BIOLOGY 


where  it  passes  forward  into  the  head  and  thus  forms  the 
rear  section  of  the  brain,  the  medulla  oblongata  (Fig.  i). 
In  front  of  this  is  a  shght  tongue-hke  elevation,  the  cerebel- 


FlG.    I. 

Fig.  I.  Frog's  brain  seen  from  above. 

c,  cerebellum;  H,  hemispheres;  m,  medulla  oblongata;  o,  optic  lobes. 

Fig.  2.  Frog's  brain  opened  from  above  to  show  ventricles. 

c,  central  canal  of  spinal  cord;  h,  hemispheres;  m,  medulla  oblongata;  o, 
optic  lobes. 

lum,  which  is  followed  midway  on  the  length  of  the  brain  by 
a  pair  of  conspicuous  prominences,  the  optic  lobes,  on  the 
right  and  on  the  left.  A  httle  in  front  of  these  lobes  the  stem 
of  the  brain  branches  into  two  relatively  large  elongated 
bodies  which,  because  of  their  general  structural  agreement 
with  parts  in  the  brains  of  the  higher  animals,  are  called  the 
hemispheres.  These  lobes  terminate  the  brain  at  its  front 
end. 

If  a  transverse  section  of  the  frog's  spinal  cord  is  examined 
under  a  microscope  a  small  pore  can  easily  be  observed  near 
its  center.  This  pore  is  the  so-called  central  canal  which 
runs  lengthwise  in  the  cord.  The  cord  therefore  is  a  hollow 
structure  and  may  be  compared  not  inappropriately  to  a 
very  thick-walled  tube.  The  central  canal  of  the  cord  can  be 
traced  forward  into  the  brain  where  it  expands  into  a  suc- 
cession of  chambers  known  as  the  ventricles  of  that  structure. 
As  the  cord  enlarges  at  its  front  end  to  form  the  medulla 


THE    EVOLUTION   OF   THE   BRAIN  97 

oblongata  the  central  canal  enlarges,  giving  rise  to  the 
hindmost  ventricle  of  the  brain  (Fig.  2).  In  front  of  this  the 
canal  narrows  in  the  region  of  the  cerebellum  to  expand 
again  into  a  partially  paired  ventricle  in  the  optic  lobes. 
Again  it  narrows  and  then  once  more  enlarges  at  the  roots  of 
the  hemispheres  into  each  of  which  a  branch  passes  to 
expand  in  the  given  hemisphere  as  a  lateral  ventricle.  Thus 
both  cord  and  brain  are  hollow  structures,  tube-Hke  in 
character,  with  a  continuous  series  of  cavities  from  hind  end 
to  front.  The  group  of  animals  known  as  chordates,  namely 
the  vertebrates  or  back-boned  animals,  and  certain  closely 
related  invertebrates  such  as  the  sea-squirts,  are  all  charac- 
terized at  one  stage  or  another  by  the  possession  of  hollow 
central  nervous  organs  such  as  have  been  described  for  the 
frog.  This  condition  is  in  strong  contrast  with  that  of  the 
majority  of  invertebrates  such  as  the  insects,  crabs,  snails, 
clams,  worms  and  the  like,  all  of  which  have  central  nervous 
structures  formed  of  solid  masses  of  nervous  tissue  without 
ventricles  or  other  cavities.  The  cavities  of  the  vertebrate 
cord  and  brain  are  of  great  importance  in  facilitating  the 
exchange  of  nutritive  and  other  fluids  in  these  organs.  In 
animals  like  the  vertebrates  where  such  parts  come  to  be  of 
great  size  and  thickness  a  special  means  for  the  exchange  of 
fluids  is  necessary,  a  state  of  aff"airs  not  called  for  in  those 
more  lowly  organized  creatures  whose  bulk  of  nervous  tissue 
is  relatively  small. 

The  spinal  cord  and  brain  of  the  vertebrate  reflect  in  a 
general  way  the  conditions  of  the  animal's  body  immediately 
external  to  them.  The  cord  is  chiefly  concerned  with  the 
nervous  activities  of  the  trunk,  namely  the  whole  of  the 
body  exclusive  of  the  head.  The  trunk  is  relatively  uniform 
and  carries  upon  it  no  special  sense  organs  such  as  the  head 
does.  It  is  therefore  not  surprising  to  find  that  the  cord  is  of 
relatively  uniform  diameter  for  the  successive  nerves  that 
pass  out  from  it  are  distributed  each  to  nearly  equal  areas  of 
skin  and  masses  of  muscle  and  hence  duplicate  each  other 
step  by  step  along  the  length  of  the  animal.  Only  in  the 
trunk  of  higher  creatures  where  the  front  legs  and  hind  legs 
or  their  modifications,  wings  and  arms,  are  especially 
developed  does  the  cord  show  obvious  local  diff"erences.  In 


• 


98  HUMAN   BIOLOGY 

such  instances  the  highly  developed  extremity  with  its 
extra  skin  and  muscle  is  represented  by  a  slight  local  enlarge- 
ment in  the  cord  to  meet  the  increase  of  function.  Otherwise 
this  structure  is  extremely  uniform  throughout  its  length. 

Far  different  is  it  with  the  brain.  This  central  organ  Hes 
within  the  head  and  the  head,  as  is  well  known,  carries  the 
chief  sense  organs  of  the  body.  In  a  typical  vertebrate,  such 
as  the  frog,  there  are  three  pairs  of  these  organs,  the  nasal 
cavities,  the  eyes,  and  the  ears.  Of  these  the  foremost  are 
the  nasal  cavities,  the  nerves  from  which  enter  that  part 
of  the  brain  that  is  designated  the  hemispheres.  The  nasal 
cavities  being  chiefly  concerned  with  smell,  this  region  of  the 
frog's  nervous  system  may  therefore  be  designated  as  the 
olfactory  brain.  The  nerves  from  the  frog's  eyes  enter 
the  second  important  part  of  this  central  organ,  the  optic 
lobes,  and  hence  this  region  may  be  called  the  visual  brain. 
Finally  the  nerves  from  the  ears  terminate  in  the  anterior 
part  of  the  medulla  oblongata  in  close  proximity  to  the 
cerebellum.  This  region  might  therefore  be  supposed  to  be 
the  auditory  brain,  but  it  is  well  known  that  the  ears  of 
vertebrates  are  organs  of  a  complex  nature  and  that  they 
have  quite  as  much  to  do  with  enabling  the  animal  to 
maintain  an  upright  position  and  with  other  matters  of 
equilibrium  and  of  posture  as  they  do  with  hearing.  In 
fact  in  such  creatures  as  the  frog  where  the  sense  of  hearing 
is  in  a  relatively  undeveloped  state,  the  ears  are  in  all 
probability  more  concerned  with  positional  relations  than 
with  hearing.  Hence  this  portion  of  the  central  nervous 
organs  may  be  designated  as  the  positional  brain  without 
however  denying  to  it  a  number  of  other  functions,  one  of 
which,  for  instance,  is  hearing.  In  this  way  three  important 
functional  regions  may  be  distinguished  in  the  brain  of  the 
frog,  the  olfactory,  the  visual,  and  the  positional,  reflecting 
the  three  important  sense  organs,  the  nasal  cavities,  the 
eyes,  and  the  ears. 

On  first  inspection  scarcely  any  resemblance  can  be  seen 
between  the  brain  of  a  frog  and  that  of  a  man.  Instead  of  a 
stem  moulded  into  several  lobes  as  the  brain  of  the  frog  is, 
the  human  brain  seems  to  be  a  more  or  less  oval  mass 
covered  externally  by  a  most  intricate  system  of  convolutions 


THE    EVOLUTION   OF   THE   BRAIN  99 

(Fig.  3a).  On  closer  study,  however,  the  brain  of  man  reveals 
in  all  particulars  the  same  ground  plan  of  structure  as  that 
seen  in  the  frog,  the  chief  point  of  difference  being  the 
relative  development  of  its  several  parts.  If  the  cerebellum 
and  the  hemispheres  of  a  human  brain  are  cut  off,  the 
stem  that  is  left  reproduces  in  many  respects  the  essentials 
of  the  frog's  brain  (Fig.  3  b  and  c).  The  human  spinal  cord 
enlarges  at  its  front  end  to  form  in  the  brain  stem  of  man 
the  medulla  oblongata,  as  it  does  in  the  frog.  In  place  of  the 
small  tongue-like  cerebellum  in  the  frog  man  possesses  a 
complex  and  much  convoluted  cerebellum  of  relatively 
large  size.  The  medulla  and  the  cerebellum  in  man  together 
represent  a  positional  brain  as  they  do  in  the  frog.  Above 
this  section  of  the  brain  in  man  but  quite  hidden  from  view 
is  a  pair  of  optic  lobes  forming  a  part  of  the  so-called  corpus 
quadrigeminum  of  human  anatomy.  These  lobes  mark  the 
terminations  of  many  of  the  optic  nerve  fibers  and  represent 
the  visual  brain  of  the  frog.  In  front  on  the  underside  of  the 
hemispheres  of  the  human  brain  are  the  olfactory  tracts 
and  lobes  connected  by  nerves  with  the  nose.  They 
correspond  to  what  has  been  called  the  olfactory  brain  in  the 
lower  animals  and  are  entirely  overshadowed  in  man  by 
his  enormous  hemispheres. 

Thus  all  the  important  parts  in  the  brain  of  the  frog  recur 
in  proper  relations  in  the  stem  of  the  human  brain,  but  the 
human  brain  differs  from  that  of  the  frog  in  the  very  con- 
siderable development  of  its  cerebellum  and  particularly 
of  its  hemispheres.  This  excessive  growth  of  these  two 
parts  can  be  traced  step  by  step  in  the  animals  intermediate 
in  position  between  the  frog  and  the  higher  mammals. 
In  the  frog  and  its  relatives  the  stem  of  the  brain  and  the 
three  functional  regions  already  pointed  out  are  all  clearly 
open  to  view  from  above.  In  reptiles  the  cerebellum  and  the 
hemispheres  are  relatively  larger  than  in  the  frog,  but  they 
do  not  cover  up  in  any  important  way  the  stem  of  the  brain. 
In  the  lower  mammals,  such  as  the  rabbit,  the  cerebellum 
and  the  hemispheres  have  enlarged  sufficiently  to  cover 
most  of  the  stem  so  that  from  above  little  of  the  medulla 
oblongata  and  none  of  the  optic  lobes  can  be  seen.  Finally 
in  man  the  hemispheres  have  so  far  exceeded  in  growth 


Fig.  3.  Comparison  of  the  human  brain  (A  and  B)  with  the  frogs  brain  (C). 

A.  Human  brain  seen  from  side,  c,  cerebellum;  h,  hemispheres;  s,  stem  of 
brain. 

B.  Human  brain  cut  lengthwise  to  show  stem.  Dotted  outlines  show  cere- 
bellum, c,  and  hemisphere,  h.  Stem  of  brain  is  shown  in  solid  outhne.  m,  medulla 
oblongata,  positional  brain;  op,  optic  lobe,  visual  brain;  ol,  olfactory  lobe, 
olfactory  brain. 

C.  Frog's  brain  seen  from  side  for  comparison  with  human  brain,  c,  cere- 
bellum; H,  hemisphere;  m,  medulla  oblongata;  op,  optic  lobe;  ol,  olfactory  lobe. 


ttiool 


THE    EVOLUTION   OF  THE   BRAIN  10 1 

all  Other  parts  of  the  brain  that  they  have  covered  not  only 
the  stem  but  also  the  cerebellum  so  that  the  external  view 
of  the  human  brain  is  almost  entirely  that  of  its  hemispheres. 
Thus  the  brain  of  man  differs  from  that  of  the  frog  chiefly 
in  the  disproportionate  growth  of  two  of  its  parts,  the 
cerebellum  and  especially  the  hemispheres.  How  dispro- 
portionate this  growth  is  may  be  judged  from  the  fact  that 
in  man  the  stem  of  the  brain  represents  about  2  per  cent  of 
its  total  weight,  the  cerebellum  about  1 1  per  cent,  while  the 
hemispheres  account  for  87  per  cent.  The  distinguishing 
feature  of  man  as  an  organism  is  his  inteUigence  and  the 
distinguishing  feature  of  his  brain  is  the  relatively  enormous 
size  of  the  hemispheres.  Hence  it  is  natural  to  conclude 
that  the  hemispheres  are  that  part  of  his  brain  concerned 
with  his  intelhgence,  a  conclusion  confirmed  by  many 
other  hues  of  evidence. 

In  the  earher  part  of  this  chapter  the  statement  was  made 
that  the  brain  was  the  most  comphcated  organ  in  the  verte- 
brate body.  This  compHcation,  which  is  as  apparent  in  the 
spinal  cord  as  in  the  brain  itself,  is  due  to  the  enormously 
intricate  system  of  centers  and  connections  that  go  to  make 
up  the  structure  of  these  parts.  The  essential  element  in 
this  structural  complexity  is  the  nerve  cell  or  neurone. 
The  structure  of  these  nervous  units  is  discussed  in  chapterviii. 
The  cell  bodies  of  neurones  are  commonly  concerned  in  the 
formation  of  nerve  centers  and  their  processes,  the  nerve 
fibers,  are  the  means  of  connection  between  these  centers.  A 
true  nerve  cell  or  neurone  consists  not  only  of  a  cell  body 
but  also  of  such  nerve  fibers  as  grow  out  from  that  body 
and  since  in  some  instances  these  fibers  are  extremely  long 
the  spread  of  a  single  neurone  is  sometimes  very  considerable. 
Thus  in  the  hemispheres  of  the  human  brain  are  certain 
cell  bodies  whose  nerve  fibers  extend  downward  not  only 
through  the  brain  but  through  the  spinal  cord  almost  to  its 
lower  end.  Here  they  terminate  in  contact  with  a  second 
set  of  neurones  whose  nerve  fibers  may  extend  as  compo- 
nents of  one  of  the  nerves  of  the  leg  to  the  muscles  of  the 
toes.  Thus  the  first  neurone  has  its  origin  in  the  head  and 
the  second  terminates  in  the  toe;  together  they  represent 
a  length  about  equal  to  that  of  the  human  body.  When  it  is 


102  HUMAN   BIOLOGY 

remembered  that  most  animal  cells  are  of  microscopic 
proportions  and  quite  invisible  to  the  unaided  eye,  the 
extraordinary  character  of  the  nerve  cell  or  neurone  must  be 
evident. 

The  number  of  neurones  in  the  central  nervous  system  of 
man  is  inconceivably  great.  A  single  instance  will  suffice 
to  illustrate  this  statement.  The  gray  layer  that  covers  the 
exterior  of  the  human  hemispheres  is  of  great  uniformity  in 
thickness  and  in  structure  and  thus  lends  itself  easily  to  an 
estimation  of  the  number  of  neurones  contained  in  it.  This 
number  on  good  grounds  is  believed  to  be  nine  thousand 
two  hundred  and  eighty  millions  (9,280,000,000),  a  number 
which,  prodigious  as  it  is,  is  approximately  only  about 
one  three  thousandth  of  the  twenty-six  millions  of  millions 
(26  X  10^-)  of  cells  estimated  to  be  present  in  the  body 
of  the  adult  human  being.  It  is  clear  from  this  one  number 
alone  that  it  is  no  exaggeration  to  say  that  the  human  brain 
contains  millions  upon  millions  of  neurones.  The  interrela- 
tions of  these  elements  must  establish  a  system  whose 
intricacies  are  unbelievably  great. 

Notwithstanding  the  enormous  number  of  neurones  in  the 
central  nervous  organs  of  man,  these  elements  conveniently 
fall  in  accordance  with  their  functions  into  three  classes. 
These  classes  are  the  sensory  or  receptive  neurones,  the 
motor  or  effective  neurones,  and  the  communicating  or 
internuncial  neurones.  They  can  be  most  clearly  illustrated 
in  the  spinal  cord  where  nervous  relations  are  relatively 
simple  as  compared  with  the  brain. 

The  spinal  cord  gives  out  from  its  sides  right  and  left  a 
regularly  arranged  series  of  spinal  nerves.  As  these  nerves 
emerge  from  the  cord  they  are  seen  to  arise  by  two  independ- 
ent roots,  one  dorsal  and  the  other  ventral.  The  dorsal 
root  has  upon  it  an  enlargement  or  ganglion.  It  has  been 
known  now  for  somewhat  over  a  century  that  these  two 
roots  differ  in  the  kinds  of  fibers  that  comprise  them.  A 
dorsal  root  is  made  up  of  sensory  or  receptive  fibers.  These 
are  distributed  to  the  skin  and  to  the  sense  organs  concerned 
with  the  deeper  parts  of  the  body,  such  as  those  in  the 
muscles  and  the  tendons.  A  ventral  root,  on  the  other  hand, 
is  made  up  of  motor  or  effective  fibers  which  are  distributed 


THE    EVOLUTION    OF   THE   BRAIN  IO3 

to  the  voluntary  muscles  and  by  means  of  which  muscular 
movements  are  excited. 

The  cell  bodies  of  the  dorsal  fibers  are  contained  in  the 
gangha  of  the  dorsal  roots  and  the  fibers  themselves  pass 
from  these  cells  on  the  one  hand  to  the  regions  of  sensory 
termination  either  in  the  skin  or  among  the  muscles  and  on 
the  other  hand  into  the  spinal  cord,  where  they  branch 
and  extend  up  and  down  that  organ.  These  sensory  fibers 
are  as  numerous  as  to  give  rise  to  about  one-fourth  of  the 
substance  of  the  cord. 

The  cell  bodies  of  the  ventral  neurones  are  large  elements 
lodged  within  the  cord;  their  fibers  pass  directly  out  of  the 
cord  and  gather  into  bundles,  the  ventral  roots.  Each 
ventral  root  unites  with  a  dorsal  root  and  thus  constitutes  a 
spinal  nerve.  In  such  a  nerve  the  two  classes  of  fibers, 
sensory  and  motor,  retain  their  individuahty  though  they 
are  as  closely  apphed  one  to  the  other  as  are  the  wires  in  an 
electric  cable.  The  ventral  fibers  of  course  make  their  way  as 
motor  components  of  the  spinal  nerves  to  the  muscles  that 
they  control. 

These  two  classes  of  neurones,  sensory  and  motor,  together 
afford  the  basis  for  the  simplest  type  of  reflex  connection. 
When  the  foot  of  a  human  being  is  pricked  with  a  pin,  it  is 
instantly  withdrawn,  the  act  being  essentially  a  reflex.  The 
pricking  of  the  skin  stimulates  the  peripheral  branches  of  a 
sensory  neurone  and  thus  generates  a  nervous  impulse  that 
passes  over  the  sensory  fiber  to  the  cord.  Here  it  is  trans- 
ferred to  appropriate  motor  neurones  that  transmit  it  to  the 
muscles  by  which  the  foot  is  withdrawn.  Thus  these  two 
types  of  neurones  together  are  sufficient  to  carry  out  a 
simple  reflex  act.  It  is,  however,  an  open  question  whether 
in  man  such  simple  reflexes  ever  really  occur.  Certainly 
in  the  majority  of  reflex  arcs  more  than  two  neurones  are 
included.  These  intercalated  neurones  are  strictly  speaking 
neither  sensory  nor  motor.  They  represent  the  third  class  of 
elements  already  mentioned,  the  communicating  or  inter- 
nuncial  neurones,  which  are  characterized  by  the  fact 
that  they  connect  one  nerve  center  with  another  but  do 
not  extend  beyond  the  central  organ  of  which  they  form  a 
part.  Such  neurones  commonly  run  lengthwise  or  crosswise 


104  HUMAN   BIOLOGY 

in  those  organs  where  they  occur.  In  the  spinal  cord  of  man 
internuncial  neurones  make  up  fully  two-thirds  of  the  mass 
of  this  organ. 

The  conditions  that  obtain  in  the  human  cord  afford  a 
basis  for  the  understanding  of  those  in  man's  brain.  This 
organ  Hke  the  cord  is  provided  with  nerves  but  the  cranial 
nerves,  twelve  pairs  in  all,  are  very  individual  and  not  of  the 
same  uniform  character  as  the  spinal  nerves.  Some  of  the 
cranial  nerves,  such  as  the  olfactory,  are  purely  sensory 
but  most  of  them  are  mixed  motor  and  sensory  hke  the 
spinal  nerves.  The  majority  are  easily  reducible  to  the 
plan  of  a  spinal  nerve,  but  with  a  predominance  in  either 
sensory  or  motor  elements.  In  one  respect,  however,  they 
are  very  unhke  spinal  nerves.  They  contribute  to  the  forma- 
tion of  the  central  organ  with  which  they  are  connected  only 
a  relatively  small  amount  of  substance.  In  consequence  the 
mass  of  the  brain  is  made  up  ahnost  entirely  of  internuncial 
neurones.  In  fact,  entire  sections  of  the  brain  are  formed 
exclusively  of  this  type.  Thus  the  whole  of  the  cere- 
bellum is  internuncial  in  composition  and  the  same  is  true 
of  the  human  hemispheres.  Since  these  parts  together 
constitute  98  per  cent  of  the  weight  of  the  brain  and  because 
much  of  the  remaining  2  per  cent  is  also  composed  of  inter- 
nuncial material,  it  follows  that  the  human  brain,  in  contrast 
with  the  cord,  is  formed  almost  exclusively  of  this  type 
of  nerve  cell. 

When  the  evolutionary  history  of  the  sensory,  motor  and 
internuncial  neurones  is  traced,  an  interesting  sequence  is 
disclosed.  In  the  simplest  form  of  nervous  system  to  be  met 
with  such,  for  instance,  as  that  seen  in  the  tentacles  of 
sea-anemones,  the  only  nervous  element  present  is  a  sensory 
neurone  that  extends  directly  from  the  surface  of  the  animal 
to  the  subjacent  muscle.  By  means  of  such  a  nervous  element 
the  muscle  is  set  in  action  much  as  a  trigger  sets  off  a  gun. 
Since  this  type  of  nervous  organization  includes  only  one 
form  of  neurone  it  may  be  designated  mononeuronic. 
The  form  of  neurone  here  involved  is  most  akin  to  the 
sensory  neurones  of  higher  animals,  which  may  therefore 
be  looked  upon  as  approaching  most  nearly  the  primitive 
ancestral  type. 


THE    EVOLUTION    OF   THE    BRAIN  IO5 

The  second  evolutionary  stage  in  the  nervous  system  is 
that  seen  in  most  parts  of  the  sea  anemone's  body  and  in 
coral  animals  and  jellyfishes.  In  this  type  a  nerve  cell 
intervenes  betv^een  the  primitive  receptive  neurone  and  the 
muscles  and  represents  what  may  be  called  a  primitive 
motor  neurone.  This  motor  element  transmits  the  impulse 
received  from  the  sensory  neurone  to  the  many  muscle 
fibers  with  which  it  is  connected.  Such  a  type  of  nervous 
system,  since  it  is  composed  of  two  kinds  of  neurones,  has 
been  called  a  dineuronic  system. 

From  a  dineuronic  system  it  is  an  easy  step  to  a  system  in 
which  beside  the  sensory  and  the  motor  neurones  there  are 
intercalated  internuncial  neurones.  Indeed,  polyneuronic 
systems  are  found  in  the  worms,  the  crabs,  the  insects,  the 
snails,  and  all  higher  animals  including  man. 

When  representative  animals  possessing  this  kind  of 
nervous  system  are  examined  they  are  seen  to  exhibit  two 
important  phases  in  the  evolution  of  the  parts  concerned. 
These  phases  pertain  first  of  all  to  the  composition  of  the 
nervous  system  so  far  as  the  three  types  of  neurones  are 
involved  and,  secondly,  to  the  location  of  the  system  in  the 
animal. 

The  cellular  composition  of  the  polyneuronic  systems 
varies  in  different  animals.  In  the  worms  and  other  like 
forms  the  central  nervous  organs  are  composed  predomi- 
nantly of  sensory  and  motor  neurones  with  only  a  moderate 
number  of  internuncial  elements  present.  In  higher  animals 
such  as  the  crabs  and  insects  the  internuncial  neurones  show 
a  larger  increase  -than  the  sensory  and  motor  elements. 
This  increase  of  the  internuncials  becomes  excessive  in  the 
vertebrates  till  in  man  the  brain,  as  already  stated,  is  almost 
exclusively  internuncial.  Moreover  those  parts  of  the  human 
brain  which  are  most  important  to  man,  the  hemispheres 
proper,  are  entirely  internuncial. 

The  second  important  feature  of  the  polyneuronic  systems 
relates  to  their  location.  In  the  sea  anemones  and  jellyfishes 
the  nervous  system  is  for  the  most  part  a  thickened  portion 
of  the  outer  skin  and  thus  is  in  reality  a  part  of  the  outer 
covering  of  the  animal.  This  condition  is  also  realized  in 
some  worms  though  in  the  majority  of  these  animals  the 


I06  HUMAN   BIOLOGY 

nerve  strands  have  separated  from  the  skin  and  have  isunk 
into  deeper  situations  within  the  body.  In  higher  forms  such 
as  the  crabs,  insects,  snails,  and  back-boned  animals  the 
nervous  organs  with  their  growth  in  size  have  migrated 
well  away  from  the  skin  and  occupy  positions  relatively 
deep  in  the  body.  In  other  words,  the  nervous  system,  at 
first  simple  in  cellular  composition  and  later  complex, 
migrates  from  its  place  of  origin,  the  outer  skin,  to  a  deep 
situation  in  the  animal  where  it  is  at  once  in  closer  average 
proximity  to  the  various  parts  it  has  to  serve  and  where 
also  it  gains  protection  from  external  injury. 

In  the  embryonic  growth  of  the  human  being  few  changes 
are  more  interesting  and  significant  than  those  shown  by  the 
spinal  cord  and  brain.  These  organs  in  the  adult  are  deeply 
imbedded  in  the  interior  of  the  body  and  yet,  when  their 
development  is  followed,  they  are  found  to  arise  in  a  very 
different  region.  The  general  changes  seen  during  the  origin 
and  growth  of  these  parts  in  man  are  common  to  all  verte- 
brates and  in  fact  are  seen  more  clearly  and  easily  in  many 
of  the  forms  lower  than  man. 

If  the  developing  egg  of  the  common  frog  is  watched  from 
hour  to  hour  the  beginnings  of  the  spinal  cord  and  brain 
and  their  gradual  growth  and  migration  can  be  followed  with 
great  certainty.  This  is  more  easily  accompHshed  in  an 
animal  whose  egg  develops  freely  outside  the  body  as  the 
frog's  egg  does,  than  in  one  whose  embryonic  growth  takes' 
place  within,  as  in  man.  The  rate  of  development  in  the 
frog  is  largely  dependent  upon  the  temperature  of  the  water 
in  which  the  eggs  are  immersed,  but  in  ordinary  spring 
weather  the  first  traces  of  the  brain  and  spinal  cord  in  the 
frog's  eggs  begin  to  appear  about  two  days  after  the  eggs 
have  been  laid  and  fertihzed.  Once  the  nervous  system  has 
started  to  form  its  growth  is  relatively  rapid.  Within  a 
day  or  so  after  its  first  appearance  it  is  well  advanced  in  its 
separation  from  the  outer  skin  and  on  its  path  of  inward 
migration. 

It  is  important  for  our  present  purpose  to  follow  briefly  a 
few  of  the  details  of  this  developmental  process.  The  egg  of 
the  frog,  before  any  trace  of  central  nervous  organs  can  be 
seen  in  it,  is  a  small  sphere  composed  of  many  cells  which 


THE    EVOLUTION    OF   THE    BRAIN  IO7 

are  arranged  to  form  on  the  one  hand  a  partial  covering  or 
outer  skin  and  on  the  other  a  central  mass  of  rather  complex 
organization.  The  central  mass  eventually  gives  rise  to 
almost  all  of  the  internal  organs  of  the  frog.  The  outer 
skin  or  ectoderm,  as  it  is  technically  called,  sooner  or  later 
covers  the  growing  embryo  completely  and  becomes  in  the 
end  the  outer  skin  of  the  adult  frog.  But  before  this  happens 
other  transformations  occur. 

As  already  stated  the  first  changes  that  lead  to  the  forma- 
tion of  the  brain  and  spinal  cord  begin  about  two  days  after 
the  egg  is  laid.  These  changes  consist  of  a  thickening  of  the 
ectoderm  along  what  will  later  become  the  chief  axis  of  the 
embryo.  The  band  or  plate  of  thickened  ectoderm  thus 
formed  is  called  the  medullary  plate  (Fig.  4  a).  It  extends 
from  what  will  eventually  be  the  head  of  the  embryo  back 
to  its  hind  end.  During  the  formation  of  this  plate  its  right 
and  left  edges  rise  and  its  center  is  depressed  along  a  line 
corresponding  to  the  axis  of  the  future  animal.  In  this  way 
a  longitudinal  groove  or  ditch  is  produced  which  deepens 
as  the  plate  folds  upon  itself  and  sinks  into  the  embryo 
(Fig.  4  b).  As  the  groove  becomes  deeper  the  edges  on  either 
side  fold  over  and  meet,  thus  converting  the  longitudinal 
groove  into  a  longitudinal  tube,  the  medullary  tube,  whose 
walls  are  the  folded  plate  and  whose  cavity  once  com- 
municated freely  with  the  exterior.  Sooner  or  later  this  tube 
becomes  entirely  closed,  breaks  away  from  its  mother 
layer,  the  ectoderm,  and  sinks  still  deeper  into  the  body 
of  the  growing  embryo  (Fig.  4  c). 

The  fate  of  the  anterior  and  the  posterior  halves  of  this 
tube  is  very  different.  In  the  posterior  half  the  walls  thicken 
rather  uniformly  and  give  rise  to  the  materials  out  of  which 
the  adult  spinal  cord  is  formed.  In  this  process  the  cavity 
of  the  tube  diminishes  proportionally  and  becomes  the 
central  canal  of  the  adult  cord. 

The  anterior  half  of  the  embryonic  medullary  tube  is 
destined  to  become  th^  brain.  The  walls  in  this  part,  as  in 
the  other,  also  thicken  but  the  thickenings  in  the  brain 
region  are  very  local,  giving  rise  to  eminences  and  outgrowths 
such  as  the  cerebellum,  optic  lobes,  hemispheres,  and  the 
like  that  characterize  this  part  of  the  central  nervous  organs. 


io8 


HUMAN   BIOLOGY 


The  cavity  of  the  anterior  part  of  the  medullary  tube, 
as  might  be  expected,  changes  eventually  into  the  series 
of  brain  ventricles.  In  this  way  the  spinal  cord  and  brain 


B 


Fig.  4.  Three  stages  in  development  of  central  nervous  organs  as  seen  in 
sections  across  axis  of  embryo  frogs. 

A.  Early  stage  showing  medullary  plate,  p,  as  thickening  in  ectoderm,  e. 

B.  Later  stage  showing  depression  of  thickened  medullary  plate  to  form 
medullary  groove,  G. 

C.  Final  stage  showing  completed  medullary  tube,  t,  separated  from  outer 
ectoderm  or  embryonic  skin,  e. 

of  the  adult  frog  develop  from  the  outer  skin  or  ectoderm  of 
the  embryo  and  migrate  into  their  fmal  position  in  the 
deeper  part  of  the  body.  What  has  been  said  of  the  develop- 
ment of  the  central  nervous  organs  in  the  frog  holds  true 
for  all  other  vertebrates,  man  included,  for  even  in  us  these 
organs  have  an  external  origin. 


THE    EVOLUTION    OF   THE    BRAIN  lOQ 

This  truly  remarkable  growth  of  the  central  nervous 
system  of  man  and  other  vertebrates  from  the  ectoderm  of 
the  embryo  is  of  great  significance  when  the  stages  in  the 
evolution  of  the  nervous  system  in  the  lower  animals  are 
recalled.  It  will  be  remembered  that  in  the  simplest  animals 
in  which  a  nervous  system  occurs,  the  sea  anemones,  the 
coral  animals,  and  the  hke,  this  system  is  a  part  of  the 
outer  skin.  This  condition,  it  will  be  recalled,  is  also  reahzed 
in  certain  worms,  but  in  others  the  central  nervous  organs 
have  broken  away  from  the  outer  skin  and  have  migrated 
into  a  deeper  situation  where  they  regularly  occur  in  crabs, 
insects,  snails  and  other  higher  animals.  That  is  to  say  the 
brain  and  spinal  cord  in  the  developing  vertebrate  repeat  a 
series  of  changes  that  is  seen  in  the  successive  evolutionary 
steps  in  the  lower  animals.  They  illustrate  an  important 
principle  in  embryology,  namely,  the  so-called  law  of 
recapitulation  which  may  be  stated  briefly  as  follows: 
in  the  development  of  any  of  the  higher  animals  the  creature 
passes  temporarily  through  stages  that  are  permanent  con- 
ditions in  the  lower  forms.  Thus  in  the  early  stages  of 
embryonic  growth  in  vertebrates  the  nervous  system  is 
temporarily  a  part  of  the  outer  skin,  a  condition  that  is  per- 
manent for  this  system  in  sea  anemones,  coral  animals, 
and  others  of  the  same  general  type. 

The  evolution  of  the  vertebrate  brain  takes  place  on  lines 
quite  different  from  those  followed  by  the  cord.  This  is  well 
seen  in  the  sensory  relations  of  the  two  structures.  So  far 
as  our  conscious  life  is  concerned  the  spinal  cord  has  to  do 
chiefly  with  the  sensory  impulses  from  the  skin.  These 
impulses  enter  the  cord,  excite  reflexes  or  other  types  of 
movement,  and  make  their  way  to  the  brain  to  call  forth 
appropriate  sensation  such  as  touch,  pain,  cold,  hot,  and  the 
like.  Although  these  sensations  are  in  reality  resident  in 
the  brain  itself  we  refer  them  to  the  stimulated  spots  in  the 
skin.  If  we  prick  the  end  of  a  finger  with  a  needle,  we  have  a 
sensation  of  pain  and  we  think  of  the  pain  as  resident  in  the 
tip  of  the  finger  though  as  a  matter  of  fact  it  is  in  the  brain. 
This  is  the  common  rule  for  most  cord  sensations.  They 
are  referred  by  us  to  the  spot  on  the  surface  of  the  body 
where  the  stimulation  occurred.  This  reference  is  not  always 


no  HUMAN   BIOLOGY 


accurate  but  for  skin  sensations  it  is  commonly  so.  Deeper 
sensations  are  less  accurately  referred.  It  is  not  always  easy 
to  tell  exactly  which  tooth  aches  and  deeper  pains,  as  the 
physician  well  knows,  are  systematically  mislocated.  Never- 
theless the  reference  is  more  or  less  trustworthy  and  always 
to  some  spot  either  in  the  body  or  more  commonly  on  it. 
Since  most  of  our  daily  sensations  originating  through 
the  cord  are  skin  sensations  this  sensory  reference  is  usually 
to  organs  on  the  surface  such  as  those  of  touch  and  temper- 
ature. These  sense  organs  may  therefore  be  called  surface 
receptors.  All  the  skin  sense  organs  connected  with  the  cord 
belong  to  this  class  and  represent  a  primitive  and  very 
ancient  type  of  mechanism. 

In  strong  contrast  with  the  spinal  cord  and  its  surface- 
receptors  is  the  brain  with  its  sensory  equipment.  The  brain 
through  its  own  nerves  possesses  a  full  outfit  of  surface 
receptors  which  are  located  in  the  skin  of  the  face  as  the 
cord  receptors  are  in  that  of  the  trunk.  But  in  addition  to 
these  surface  receptors  the  brain  also  has  three  pairs  of 
special  receptors  of  its  own,  the  nasal  cavities,  the  eyes, 
and  the  ears.  In  all  these  the  sensory  activities  are  usually 
referred  not  to  the  bodily  locat  on  of  the  organ  itself  but 
to  some  distant  point  outside  the  body  and  commonly  far 
away.  The  odor  of  the  morning  coffee  is  not  referred  to  the 
nose  where  the  stimulation  occurs  but  to  the  coffee  percolator 
across  the  table.  Similarly  the  form  of  an  approaching 
friend  is  not  seen  in  the  eye  where  the  image  is  but  far  away 
down  the  street,  and  the  overture  played  by  the  orchestra 
is  not  heard  in  the  ear  but  as  coming  from  the  distant  band 
of  musicians.  All  these  sense  organs  differ  from  the  surface 
organs  in  that  the  sensations  called  forth  by  them  are 
referred  to  distant  points  far  beyond  the  body.  They  are 
therefore  called  distance  receptors  and  in  most  animals 
they  are,  as  in  man  and  other  vertebrates,  peculiar  to  the 
head.  They  are  undoubtedly  the  most  important  single 
factor  in  the  evolution  of  the  vertebrate  brain  for  without 
them  we  would  have  remained  simply  spinal-cord  animals. 

The  three  distance  receptors  in  the  vertebrates  have 
without  question  arisen  separately  and  at  quite  different 
times.  They  are  modified  surface  receptors  that  have  evolved 


THE    EVOLUTION    OF   THE    BRAIN  III 


in  complexity  hand  in  hand  with  the  growing  central  organs. 
The  original  state  from  which  they  arose  is  well  shown  in 
such  lowly  animals  as  the  earthworm.  This  creature  has  no 
nasal  cavities,  eyes,  or  ears  and  yet  it  responds  to  odors, 
Hghts,  and  sounds,  and  keeps  itself  oriented  to  gravity. 
All  these  funct  ons  are  carried  out  by  the  receptors  in 
its  skin,  but  its  responses  are  such  as  to  justify  the  view  that 
its  nervous  states  have  not  the  least  relation  to  distance 
reception  but  are  akin  to  surface  reception.  This  most 
probably  is  the  condition  that  characterized  the  ancestral 
vertebrate.  To  this  creature  every  sensory  stimulation, 
whether  it  was  from  trunk  or  head,  partook  of  the  nature 
of  surface  reception,  and  was  devoid  of  any  element  of 
distance.  From  this  state  of  primitive  surface  receptivity  the 
vertebrate  with  its  equipment  of  distance  organs  must  have 
developed. 

The  first  of  these  distance  receptors  to  appear  in  verte- 
brates was  the  organ  of  smell,  for  in  Amphioxus,  the  simplest 
of  the  fishes,  we  have  an  animal  with  a  well-developed 
olfactory  pit,  but  without  ears  or  eyes,  though  in  the  deeper 
parts  of  its  body  are  the  elements  out  of  which  eyes  could 
be  evolved.  Amphioxus  swims  without  orientation  to  gravity, 
it  responds  to  light  though  it  cannot  be  said  to  see,  and  it 
undoubtedly  senses  its  way  more  or  less  by  means  of  its 
olfactory  organ.  Like  the  celebrated  Nantucket  captain 
who  knew  the  sea  by  the  smell  of  the  lead,  this  primitive 
fish  probably  scents  its  way  about.  Its  brain  reflects  this 
meager  receptor  outfit,  for  it  is  scarcely  more  than  a  slight 
swelling  of  the  front  end  of  the  spinal  cord. 

All  fishes  higher  than  Amphioxus  and  all  other  verte- 
brates possess  ears  and  image-forming  eyes.  The  evidence 
from  the  lowest  of  these,  the  lampreys,  is  that  the  eyes 
evolved  in  advance  of  the  ears  because  the  ears,  entirely 
absent  from  Amphioxus,  exist  in  a  very  primitive  state  in  the 
lampreys,  whereas  the  eyes  which  were  already  foreshadowed 
in  Amphioxus  show  in  the  lampreys  evidence  of  high 
differentiation. 

As  a  distance  receptor  no  organ  is  more  important  to  the 
vertebrate  than  the  image-forming  eye,  for  by  its  means  an 
animal  can  respond  not  only  to  light,  as  the  earthworm  does. 


112  HUMAN   BIOLOGY 

but  to  the  details  of  a  luminous  field  as  the  higher  animals 
are  able  to  do.  With  the  growth  of  eyes  of  this  type  in  the 
early  vertebrates  came  the  concomitant  development  of  the 
optic  lobes  of  the  brain,  a  step  that  estabHshed  these  organs 
as  the  chief  receptor  centers  of  the  simpler  vertebrates. 

All  fishes  that  possess  eyes  also  have  the  so-called  ear 
sacs.  These  simple  ears  are  chiefly  concerned  with  positional 
relations,  equilibrium  and  the  like.  But  they  also  have  to  do 
with  hearing  and  both  functions  develop  hand  in  hand  in 
higher  forms  influencing  the  growth  of  the  brain  in  the 
region  of  the  cerebellum  and  the  medulla  oblongata.  Thus 
this  third  and  last  kind  of  distance  receptor  contributes  its 
share  to  brain  formation. 

In  this  way  the  evolutionary  growth  of  the  vertebrate 
brain  and  with  it  the  head  has  resulted  from  a  change  of  its 
primitive  surface  receptors  to  distance  receptors  whereby 
highly  specialized  nasal  cavities,  eyes,  and  ears  were  the 
external  products  and  an  olfactory,  a  visual,  and  a  positional 
brain  were  the  internal  results.  These  collectively  establish 
in  the  vertebrates  what  has  been  called  the  stem  of  the 
brain. 

But  this  stem  carries  with  it  more  than  the  three  sensory 
segments  just  accounted  for.  Of  the  additional  elements  in 
the  brain  stem,  the  chief  one  is  found  in  the  region  of  the 
hemispheres.  In  the  lower  vertebrates  the  two  lobes  at  the 
anterior  end  of  the  brain,  the  so-called  hemispheres,  are 
largely  concerned  with  olfaction.  This  sensory  activity, 
as  already  intimated,  is  the  first  to  develop  distance  recep- 
tion. It  is,  therefore,  not  surprising  to  find  that  in  verte- 
brate evolution  the  hemispheres  came  to  be  organs  of  unusual 
importance.  Not  only  did  distance  reception  for  the  olfactory 
function  reside  here,  but  the  hemispheres  developed  as 
centers  which  integrated  all  the  sensory  activities  including 
the  receptive  functions  of  the  skin,  of  the  organs  of  taste, 
of  sight  and  of  hearing.  Thus  the  hemispheres  of  the  higher 
vertebrates  came  to  represent  a  field  upon  which  was  reflected 
the  sensory  activities  of  the  whole  body.  Moreover,  to  this 
field  were  transferred  eventually  all  those  motor  centers 
which  we  ordinarily  associate  in  ourselves  with  volitional 
movements.  Thus  by  a  process  of  accretion  the  hemispheres 


THE    EVOLUTION   OF   THE   BRAIN  II3 

appropriated  by  evolutionary  steps  all  that  body  of  nervous 
activity  that  we  associate  with  conscious  Hfe  and  voHtional 
effort.  What  the  hemispheres  have  thus  taken  over  is  by 
no  means  all  of  our  nervous  doings.  The  lower  part  of  the 
brain  stem,  the  spinal  cord,  and  such  subsidiary  centers  as 
the  sympathetic  system  have  buried  within  them  an  untold 
mine  of  nervous  activity  that  never  really  reaches  this  upper 
level  but  that  nevertheless  has  potentialities  which  are  only 
beginning  to  be  appreciated  in  the  study  of  the  subconscious. 
That  which  has  emerged  in  the  course  of  the  differentiation 
of  the  hemispheres  in  the  higher  vertebrates  occupies  a 
place  quite  separate  from  that  of  the  original  olfactory 
centers  and  represents  in  a  measure  a  novel  system  super- 
imposed upon  the  older  olfactory  brain.  This  new  growth 
within  the  hemispheres,  chiefly  visible  in  the  mammals, 
is  astoundingly  expanded  in  man  in  whose  brain  it  is  repre- 
sented by  the  relatively  enormous  convoluted  surface  so 
characteristic  of  the  exterior  of  that  organ.  This  growth  is 
called  the  neopallium  and  in  the  higher  animals  it  has  so  over- 
grown and  overshadowed  the  ancient  brain  stem  as  to  have 
reduced  this  primitive  part  to  relative  inconspicuousness. 

In  the  neopallium  of  man  take  place  all  those  complicated 
activities  that  we  associate  with  personality.  Here  resides 
our  mental  life — our  sensations,  memories,  and  volitions; 
here  imagination  has  its  play,  and  here  too  when  maladjust- 
ments occur  moods  arise  and  insanity  may  reign.  Descartes 
believed  that  the  pineal  body  was  the  seat  of  man's  soul, 
but  modern  science  knows  that  the  neopallium  is  the  correct 
location.  Here  all  that  is  most  characteristic  of  us  takes 
place  and  in  fact  the  activity  of  the  region  is  in  all  prob- 
ability a  manifestation  of  our  real  inmost  selves. 

Thus  the  evolution  of  the  brain  of  man  finds  its  roots  in 
those  elemental  nervous  operations  connected  with  the 
muscular  responses  of  such  simple  animals  as  the  sea  anem- 
ones whence  have  sprung  the  differentiated  sense  organs  and 
central  nervous  organs  of  higher  animals.  By  the  conversion 
of  these  sense  organs  from  surface  receptors  to  distance 
receptors  and  by  the  simultaneous  growth  of  central  organs 
as  repositories  of  experience  there  has  been  established  in  the 
hemispheres  of  the  mammals  and  particularly  of  man  that 


114  HUMAN   BIOLOGY 

marvelous  organ,  the  neopallium,  which  is  at  once  the 
highest  center  of  nervous  differentiation  and  the  real  seat 
of  the  soul. 

REFERENCES 

Bayliss,    W.    M.    Ed.    4,    1924.    Principles    of  General   Physiology.   Lond., 

Longmans,  Green. 
Child,  C.  M.   192  i.  The  Origin  and  Development  of  the  Nervous  System. 

Univ.  Chicago  Press. 
Donaldson,  H.  H.  1895.  The  Growth  of  the  Brain.  Lond.,  Scott. 
Herrick,  C.  J.  1918.  Introduction  to  Neurology.  Phila.,  Saunders. 
1924.  Neurological  Foundations  of  Animal  Behavior.  N.  Y.,  Holt. 
1926.  Brains  of  Rats  and  Men.  Univ.  Chicago  Press. 
LoEB,  J.  1902.  Comparative  Physiology  of  the  Brain.  N.  Y.,  Putnam. 
LuciANi,  L.  1915.  Human  Physiology.  Vol.  3,  Muscular  and  Nervous  Systems. 

Lond.,  Macmillan. 
Lull,  R.  S.,  Ferris,  H.  B.,  Parker,  G.  H.,  Angell,  J.  R.,  Keller,  A.  G.,  and 

CoNKLiN,  E.  G.  1922.  The  Evolution  of  Man.  New  Haven,  Yale  Univ. 

Press. 
Parker,  G.  H.  1919.  The  Elementary  Nervous  System.  Phila.,  Lippincott. 
1922.  Smell,  Taste,  and  Allied  Senses  in  the  Vertebrates.  Phila.,  Lippincott. 
Sherrington, *C.  S    1906.  The  Integrative  Action  of  the  Nervous  System. 

N.  Y.,  Scribner. 


Chapter  V 
MENTAL  EVOLUTION  IN  THE  PRIMATES 
Robert  M.  Yerkes 

MANY  of  us  doubtless  would  be  profoundly  impressed 
if  by  watching  a  cinema  record,  run  backward,  we 
were  able  to  trace  to  their  prenatal  beginnings 
the  personality,  character,  temperament,  intellectual  traits, 
mannerisms  and  other  characteristic  modes  of  reaction  of  one 
of  our  intimate  friends.  Let  us  assume  that  the  pictorial  record 
adequately  represents  the  psychological  and  psychobiologi- 
cal  characteristics  of  our  friend  from  day  to  day  throughout 
a  half  century  of  existence,  and,  further,  that  in  the  picture 
the  physical  appearance  of  the  individual  is  so  far  con- 
ventionalized that  the  mental  appearances,  as  we  may  call 
them,  dominate  the  attention  and  interest  of  the  observer. 
Under  these  circumstances  what  is  likely  to  be  the  experience 
of  the  open-minded,  well-informed  layman  who  eagerly 
watches  the  retracing  of  mental  development?  With  con- 
siderable assurance  we  predict  the  following: 

The  first  few  years  of  the  story  will  yield  him  an  agreeable 
sense  of  famiharity  and  intelhgibihty.  The  friend  will  not 
only  be  definitely  recognized  in  the  pictorial  representation, 
but  there  may  appear  a  delightful  sense  of  intimacy  and 
understanding.  Gradually,  as  the  years  and  then  the  decades 
are  retraced,  the  feeling  of  familiarity  will  lessen  and  finally 
it  will  give  place  to  one  of  strangeness;  the  individual  is  no 
longer  identified  or  even  identifiable  as  one's  friend,  save 
perhaps  by  the  speciahst  in  psychobiology.  Instead,  the 
representation  is  that  of  a  more  or  less  obviously  typical 
human  mind  and  personality.  By  this  time  the  initial 
agreeable  glow  of  understanding  has  given  place  to  surprise, 
doubt,  and  the  observer  probably  looks  and  feels  puzzled. 
But  even  more  surprising  experiences  are  in  store  for  him,  as 
reaching  back  a  few  more  years  the  representation  gradually 
loses  its  resemblance  to  what  the  layman  knows  as  human 
behavior,  mentality,  and  personality,  and  comes  to  suggest 

115 


Il6  HUMAN   BIOLOGY 

quite  as  strongly  the  observed  psychobiological  character- 
istics of  some  other  type  or  types  of  organism.  The  chim- 
panzee, monkey,  or  in  accordance  with  personal  familiarity, 
the  horse,  dog,  or  cat  may  come  to  mind.  No  longer  then  is 
the  picture  distinctively  and  unmistakably  human.  "Why, 
it  might  perfectly  well  be  some  other  kind  of  being,"  exclaims 
the  amazed  onlooker. 

And  now  as  the  record  continues  to  unroll,  surprises 
crowd  one  another,  for  the  suggestion  or  definite  appearance 
of  the  behavioral  and  mental  characteristics  of  other  types  of 
animal  than  the  human  become  more  insistent,  and  doubt 
as  to  whether  the  record  really  represents  human  develop- 
ment gives  place  to  the  conviction  that  one  is  being  deceived 
and  that  the  picture  really  represents  some  stage  in  the 
psychobiological  development  of  a  yet  more  lowly  and 
primitive  mammal  than  the  chimpanzee,  monkey,  or  even 
the  lemur.  Presently  perhaps  the  behavior  of  the  fish  is  so 
definitely  suggested  that  the  observer  again  utters  exclama- 
tions of  amazement  and  increduhty. 

Although  such  a  pictorial  record  as  we  imagine  never 
has  been  made  and  could  be  obtained  only  with  extreme 
difficulty,  it  is  not  impossible.  Were  one  to  observe,  instead 
of  our  hypothetical  record  of  mental  development,  a  chrono- 
logically comparable  record  of  the  development  of  the  body, 
the  eff'ect  on  the  lay  observer  would  be  very  similar.  No 
description  of  the  evolution  of  the  human  mind  known  to 
us  is  more  incredible,  more  difficult  to  understand  as  natural 
process,  or  more  at  variance  with  certain  well-estabfished 
social  traditions,  including  befiefs  and  superstitions,  than 
is  the  actually  observable  series  of  events  between  the 
fertihzation  of  the  ovum  and  the  maturation  of  the  human 
personahty. 

Among  the  preconceptions,  superstitions,  or  inadequately 
founded  befiefs  which  we  should  brush  aside  in  order  fairly 
and  profitably  to  examine  the  evidences  of  genetic  relation 
among  different  types  and  conditions  of  mind,  is  the  assump- 
tion that  man  possesses  rational  intelfigence,  whereas  other 
animals  are  endowed  with  instinct.  Critical  and  sustained 
study  of  animal  behavior  indicates  on  the  contrary  that 
although  among  existing  primates  man  is  the  reasoner  par 


MENTAL    EVOLUTION    IN   THE    PRIMATES  II7 

excellence,  other  animals  also  are  intelligent  and  some  of  them 
at  least  exhibit  rational  forms  of  intelhgence.  For  the 
ancient  inadequate  formula,  "Man  is  rational;  brute, 
instinctive,"  the  present-day  psychobiologist  substitutes 
the  statement:  Every  living  organism,  by  virtue  of  inherited 
structures  and  developmental  tendencies,  is  instinctive  and 
also  in  widely  varying  degrees  capable  of  individual  adapta- 
tions which  are  more  or  less  definitely  intelhgent.  Within 
the  order  Primates,  to  which  we  shall  confine  our  discussion 
of  the  evolution  of  mind,  we  may  not  say  that  one*  type  is 
more  instinctive  than  another,  although  it  is  definitely 
estabHshed  that  intelhgence  differs  both  quantitatively  and 
quahtatively.  To  undertake  our  present  task  with  the 
conviction  that  man  is  mentally  unique  and  therefore 
without  genetic  relation  to  any  existing  or  extinct  type 
of  animal,  would  be  quite  as  prejudicial  to  the  discovery  of 
the  truth  as  would  be  initial  assumption  that  the  human 
mind  has  evolved  from  that  of  the  gorilla. 

Ignoring  technicahties  of  classification,  it  will  serve  our 
purpose  to  group  existing  primates  in  five  classes:  lemurs, 
tarsiers,  monkeys,  apes,  and  men.  We  shall  make  no  reference 
to  extinct  or  fossil  forms.  The  first  two  of  our  classes  are 
represented  today  by  animals  which  strike  the  layman  as 
squirrel-hke  rather  than  monkey-hke,  and  indeed  they 
resemble  the  flying  mammals.  Between  these  primitive  and 
often  called  pro-simian  creatures  and  the  distinctly  manhke 
primates  are  the  New  and  Old  World  monkeys  which, 
differing  extremely  in  appearance,  exist  in  many  genera 
and  species.  Most  closely  resembhng  man,  and  on  the 
whole  differing  httle  if  any  more  from  him  than  from  the 
monkeys,  are  the  four  primate  types  assigned  to  the  class  apes, 
or,  more  exphcitly,  anthropoid  apes:  the  gibbon,  orang-outan, 
chimpanzee  and  gorilla. 

As  in  turn  we  review  what  is  known  of  the  mode  of  fife, 
adaptive  capacity,  and  mental  traits  of  each  class  of  primate 
beginning  with  the  most  primitive,  we  discover  unmistakable 
evidences  of  increasing  resemblance  to  man  in  the  progress 
through  lemur,  tarsier,  monkey  and  ape.  To  the  speciafist 
in  psychobiology  this  is  no  less  impressive  and  no  less 
strongly  suggestive  of  genetic  relations  than  are  the  struc- 


Il8  HUMAN   BIOLOGY 

tural  resemblances  which  have  been  exhibited  in  the  earher 
chapters  of  this  volume.  We  presume  to  make  this  general 
statement  because  the  remainder  of  our  chapter  is  an 
exposition  of  the  facts  upon  which  it  rests. 

Standing  as  guide  posts  in  the  path  of  individual  develop- 
ment and  in  that  of  descent  are  certain  signally  important 
groups  of  psychobiological  phenomena.  They  include: 
(i)  receptivity,  or  the  psychobiological  relation  of  organism 
to  environment  through  the  senses;  (2)  behavioral  adap- 
tivity,  dr  the  adjustment  of  organism  to  environment,  (a) 
bhndly,  (b)  with  insight,  or  (c)  with  foresight — phenomena 
which  are  distinctively  organic  and  primarily  if  not  exclu- 
sively psychobiological;  (3)  ideational  processes,  creative 
imagination,  abstraction  and  generahzation,  as  conditions 
for  adaptation  through  modification  of  the  environment 
instead  of  by  self-adjustment- — a  long  step  in  primate 
evolution;  (4)  the  use  of  symbols,  the  growth  of  language, 
and  the  final  dominance  of  speech^ — phenomena  which, 
although  appearing  in  other  classes  of  primate,  become 
conspicuously  important  in  man;  (5)  inborn  reactive  tend- 
encies, emotions,  sentiments,  drives,  and  ideals,  and  (6) 
social  relations  in  experience,  organization,  and  institution. 

To  each  of  these  vast  assemblages  of  phenomena  in  the 
life  of  the  primate  we  shall  in  turn  briefly  attend,  for  together 
they  clearly  mark  the  main  highway  of  individual  develop- 
ment and  the  less  readily  followed,  because  less  direct, 
course  of  mental  evolution. 

RECEPTIVITY    AND    THE    PRESENT    DOMINANCE    OF    DISTANCE 

RECEPTORS 

It  is  observable  that  in  the  development  of  man  the  senses 
of  touch,  temperature,  smell  and  taste  become  functional 
prior  to  those  of  vision  and  hearing.  Likewise  among  the 
classes  of  primates  appear  diff^erences  in  the  senses  which 
roughly  correspond  to  those  of  individual  development. 
Crudely  put,  in  evolution  as  in  development  we  pass  from 
the  dominance  of  mechanical  and  chemical  stimulation  to 
that  of  vibrational.  The  observable  trend  is  from  sensitivity 
to  and  awareness  of  the  immediately  present  object  or  event 
to   that   of  the  spatially  or  temporally  distant.  For  touch 


MENTAL    EVOLUTION    IN   THE    PRIMATES  II9 

acquaints  the  animal  only  with  its  immediate  physical 
environment,  whereas  taste,  smell,  hearing  and  sight  bring 
it  into  relation  with  increasingly  remote  objects  and  events. 
As  we  develop  during  the  first  few  months  after  birth, 
we  are  rapidly  projected  into  environment,  and  the  physical 
self  is  enabled  to  sense  and  respond  to,  investigate  and 
adjust  to,  increasingly  numerous  and  distant  qualities  and 
objects  of  its  world. 

We  may  not  assert  it  as  fact,  but  the  evidences  strongly 
suggest  that  as  our  senses  develop,  so  also  have  they  evolved 
in  the  course  of  racial  history.  Like  our  embryonic  selves, 
our  early  ancestors  knew  the  world  chiefly  through  contacts 
and  chemical  changes.  But  our  less  remote  ancestors, 
monkey-like  creatures  perhaps,  and  our  infant  selves, 
lived  in  a  world  which  was  enriched  by  innumerable  sounds 
and  sights.  This  contrast  between  a  world  of  contacts  and 
tastes  and  one  predominantly  visual  and  auditory  transcends 
•our  present  powers  of  psychological  description. 

It  is  not  alone  by  addition  of  senses,  or  even  by  multiplica- 
tion of  qualities  within  a  sense  mode,  that  development 
and  evolution  proceed;  a  given  sense  may  become  either 
simpler  or  more  complex,  its  keenness  may  diminish  or 
increase  during  individual  or  racial  history.  Less  generally 
known  is  the  fact  that  the  functional  significance  of  a  sense 
may  change  tremendously  by  reason  of  integrative  psycho- 
biological  processes  which  enable  the  organism  to  perceive 
varied  aspects  and  relations  as  contrasted  with  simple 
qualities  of  objects,  and  which  thus  prepare  the  way  for  new 
types  of  behavioral  adaptation.  For  example,  in  individual 
development  and  in  evolution  vision  begins  with  awareness 
of  light.  Later  the  animal  comes  to  perceive  form,  size, 
texture,  distance,  spatial  relations,  color.  The  adult  sees 
both  more  and  differently  than  the  newly  born  infant; 
the  ape  sees  more  and  differently  than  the  lemur,  and  man 
sees  vastly  more  than  any  other  primate.  Observation 
indicates  that  the  trends  of  receptivity  in  development 
and  in  evolution  roughly  agree.  This  fact  is  peculiarly 
significant  because  we  may  follow  as  exactly  as  we  will 
the  story  of  development  and  by  the  results  may  be  guided 
in  our  search  for  phylogenetic  relations. 


120  HUMAN   BIOLOGY 

Among  existing  classes  of  primate  new  senses  have  not 
appeared,  but  the  distance  senses  of  hearing  and  sight  have 
greatly  increased  in  complexity  and  in  perceptual  value. 
Replacing  to  a  marked  degree  the  mechanical  and  chemical 
senses,  they  have  become  the  dominant  channels  of  com- 
munication between  the  primate  and  its  world.  The  degree 
of  dominance  of  visual  and  auditory  receptivity  and  percep- 
tion increases  from  lemur  to  man. 

PREEMINENTLY    IMPORTANT   ASPECTS   OF   BEHAVIORAL 

ADAPTATION 

An  animal  adapts  psychobiologically  to  its  world  as 
known.  If  its  knowledge  be  hmited  to  simple  awareness, 
through  contact,  chemical  action,  vibrations  in  air  or  ether, 
of  the  existence  of  media  about  it  and  of  objects  and  occur- 
rences in  those  media,  it  cannot  adapt  as  do  monkeys, 
apes  and  men.  There  must  be  perceptual  acquaintance 
with  objects  in  relation.  An  animal  obviously  cannot  respond 
to  an  apple  as  a  spherical  form  of  definite  size,  distance 
from  the  perceiver,  texture  and  color,  if  it  is  sensed  merely 
as  a  dark  spot  against  a  lighter  background.  Perceptual 
configurations  are  definitely  known  to  become  more  numer- 
ous, complex,  and  useful  as  bases  for  adaptive  behavior 
from  conception  to  maturity  in  human  life  and  from  lemur 
to  man  in  the  phylogenetic  series.  We  may  not  trace  the 
progress  step  by  step  in  either  case,  but  the  trend  toward 
increasing  richness  and  efficiency  of  perceptual  consciousness 
is  wholly  apparent. 

In  still  another  way  than  through  the  guiding  awareness 
of  the  presence,  qualities,  and  relations  of  objects  and  events, 
perceptual  consciousness  conditions  adaptive  ability.  It  is  a 
basis  of  motivation.  An  animal  strives  for  objectives  only 
within  the  limits  of  its  consciousness.  There  is  a  stage  in 
human  development,  as  there  are  stages  in  evolution,  when 
neither  the  quantity  nor  the  quality  of  an  objective  clearly 
influences  the  organism.  The  less  preferred  object  tends  to 
induce  the  same  response  as  the  more  preferred;  a  small 
bit  of  candy  or  fruit  tends  to  induce  as  strenuous  effort  to 
obtain  it  as  does  a  large  bit.  We  say  there  is  lack^of  dis- 


MENTAL   EVOLUTION   IN   THE    PRIMATES  121 

crimination  and  of  suitable  adaptation  to  certain  essential 
features  of  the  situation.  Either  the  subject  does  not  perceive 
the  differences  in  point  or  for  some  other  reason  it  is  incapable 
of  regulating  its  activities  in  accordance  with  them.  From 
lemur  to  man  no  less  obviously  than  from  infancy  to  maturity, 
motivation  becomes  increasingly  complex.  New  factors 
appear  and  adjustments  of  behavior  become  more  serviceable 
and  more  nearly  adequate. 

Behavioral  adaptation,  or  as  we  should  have  called  it  a 
few  years  ago,  habit-formation,  may  occur  with  or  without 
insight  and  foresight.  It  is  our  immediate  task  to  try  to 
trace  in  development  and  in  evolution  the  appearance  and 
history  of  different  types  of  adaptation.  We  shall  begin  with  a 
form  which  often  is  designated  as  "trial  and  error,"  but  we 
shall  use  the  expression  "bhnd  trial"  in  order  to  contrast 
it  with  insight  and  foresight. 

(a)  Blind  Trial.  A  box  containing  a  bit  of  candy  or  a 
rattle  is  presented  to  a  primate  subject.  The  only  way  to 
obtain  the  object  within  is  to  open  a  door  which  is  held  by  a 
hidden  mechanism  whose  release  may  be  effected  by  pushing 
a  lever  at  one  side  of  the  box.  This  is  a  type  of  problematic 
situation  which  many  investigators  have  presented  to 
animals  as  a  test  of  intelligence  or  of  abihty  to  profit  by 
experience.  Obviously,  insight  is  precluded  by  the  charac- 
teristics of  the  situation.  The  subject,  whether  lemur, 
monkey,  ape,  or  man,  manipulates  the  box  and  sooner  or 
later  by  happy  accident  operates  the  mechanism  of  release. 
Thereupon  it  obtains  the  desired  object,  and  thereafter  when 
the  same  problem  is  presented  it  may  exhibit  more  or  less 
perfect  adaptation.  This  type  of  experiment  has  been  cited 
as  one  in  which  solution  by  trial  is  inevitable. 

As  contrasted  with  situations  in  which  insight  is  either 
impossible  or  highly  improbable,  there  are  those  in  which  we 
should  naturally  expect  it  to  appear,  were  the  animal 
capable  of  it.  Such,  for  example,  is  the  milk-containing 
glass  bottle  whose  contents  the  primate  desires.  Observation 
reveals  that  neither  the  human  infant  nor  any  of  the  other 
primates,  with  the  possible  exception  of  certain  of  the 
anthropoid  apes,  is  likely  to  respond  to  this  situation  initially 
with   direct  and   perfect   adaptation.    Instead,   a   series   of 


122  HUMAN   BIOLOGY 


trials,  more  or  less  obviously  ineffective  and  wasteful, 
eventually  leads  to  skillful  manipulation  of  the  bottle 
and  the  drinking  of  its  contents. 

By  comparing  the  typical  performances  of  human  infants 
at  various  ages  and  of  representatives  of  the  various  classes 
of  primate  in  like  situations,  we  discover  that  adaptation  by 
trial  and  error,  in  other  words  bhndly  or  without  insight,  is 
characteristic  of  all  ages  and  types,  but  that  the  quickness  of 
adaptation  on  the  basis  of  blind  trial,  and  also  the  prob- 
ability of  indication  of  insight,  tend  to  increase  as  develop- 
ment progresses  and  also  as  we  progress  from  the  more 
primitive  toward  the  less  primitive  primate  type. 

(b)  Insight.  The  use  of  objects  as  instruments  in  con- 
nection with  behavioral  adaptation  is  peculiarly  significant 
of  insight.  Such  ability  is  virtually  unknown  in  the  lemurs 
and  tarsiers,  so  far  as  one  may  infer  from  observational 
report.  It  appears  in  the  monkeys,  and  is  obviously  more 
varied  and  important  in  the  anthropoid  apes  and  in  man. 
The  monkey  may  use  a  stick  to  draw  within  reach  objects 
which  are  not  otherwise  obtainable.  But  when  the  objective 
is  so  placed  that  the  stick  must  be  used  to  push,  direct 
and  pull  it  around  an  obstacle  through  a  devious  course 
which  sometimes  tends  away  from  and  again  toward  the 
subject,  the  monkey  fails  utterly,  whereas  the  ape  may 
succeed.  Herein  we  discover  a  contrast,  if  not  a  transition. 
Insightless  and  persistent  trial  and  error  may  ultimately 
result  in  success,  whatever  the  type  of  primate  in  question. 
But  ordinarily  it  is  not  difficult  for  the  observer  to  dis- 
tinguish between  blind  trial  and  that  which  is  guided  by 
perception  of  relation  of  means  to  end  and  of  the  desired 
object  to  the  waiting  hand  of  the  animal.  To  the  human 
adult  this  problem  of  a  roundabout  course  seems  extremely 
simple;  its  solution  is  grasped  instantly.  But  for  the  infant  it 
is  a  real  problem  which  prior  to  a  certain  stage  of  develop- 
ment, attained  only  after  several  months,  is  utterly  insolu- 
ble. Ability  to  handle  a  stick  deftly  and  to  direct  it  toward 
an  objective  does  not  assure  success:  there  must  in  addition 
be  a  measure  of  insight  into  spatial  relations,  and  the  sub- 
ject must  be  able  to  translate  its  perceptual  experience  and 
its  insight  into  adaptive  activity. 


MENTAL    EVOLUTION    IN    THE    PRIMATES  1 23 

In  a  metal  pipe,  or  elongated  wooden  box,  open  at  both 
ends  and  securely  fixed  in  position,  a  desired  object  is  so 
placed  as  to  be  beyond  the  reach  of  the  watching  subject. 
Nearby,  but  not  so  close  to  the  pipe  as  to  be  viewed  simul- 
taneousl}^  with  it,  is  a  stick  which  might  serve  as  instrument 
to  push  the  object  through  and  out  of  the  pipe.  The  situation 
presents  a  type  of  problem  appropriate  alike  for  infants, 
children,  and  the  various  classes  of  infrahuman  primate. 
As  in  the  case  of  the  problem  just  described,  the  human 
subject  must  develop  for  several  months  before  he  is  able  to 
solve  the  pipe  and  stick  problem.  Never,  so  far  as  we  have 
been  able  to  learn,  has  such  a  problem  been  solved  by  lemur- 
hke  primates  or  by  monkeys.  It  has,  however,  been  solved  in 
several  instances  by  the  chimpanzee,  under  conditions  which 
seemingly  precluded  the  possibility  of  chance  or  of  previous 
experience  with  a  similar  problematic  situation.  At  the  level 
of  the  apes  we  discover,  it  seems,  that  measure  of  selective 
adaptation  and  of  insight  which  renders  possible  prompt 
adjustment  to  this  type  of  novel  problem.  Man,  beyond  a 
certain  stage  in  childhood,  has  no  particular  difficulty  in 
understanding  and  adapting  to  such  a  situation. 

By  yet  another  simple  experiment  we  would  exhibit  the 
contrast  between  lemur  and  monkey,  on  the  one  hand,  and 
ape  and  man,  on  the  other.  If  food  or  other  desired  object  be 
suspended  beyond  the  reach  of  the  subject  and  a  number  of 
boxes  be  placed  within  easy  reach,  we  naturally  should 
expect  a  human  subject  to  solve  this  problem  promptly 
by  building  the  boxes  into  a  pyramid,  so  placed  that  from  it 
the  objective  can  readily  be  reached.  This  type  of  solution 
is  not  possible  to  the  human  infant,  but  appears  at  a  certain 
stage  of  childhood.  It  is  impossible,  so  far  as  we  know,  to 
monkeys  and  to  more  primitive  primates,  but  certain  at  least 
of  the  anthropoid  apes  succeed.  Indeed,  the  chimpanzee 
and  orang-outan  in  this  type  of  experiment  very  clearly 
manifest  their  adaptive  superiority  to  the  monkey,  to  the 
human  infant,  and  to  the  very  young  child. 

These  several  illustrative  experiments,  chosen  from  among 
scores  which  are  available  in  the  scientific  literature  or  in  our 
experience,  indicate  the  major  grounds  for  the  statement  that 
behavioral  adaptation  with  insight  or  partial  understanding 


124  HUMAN   BIOLOGY 

of  a  problem,  instead  of  being  limited  to  man  as  has  com- 
monly been  assumed  in  the  past,  is  shadowed  forth  in  the 
monkeys  and  definitely  and  convincingly  exhibited  by 
certain  of  the  anthropoid  apes.  Again,  it  is  clearly  indicated 
that  the  evolution  of  insight  in  the  primates  in  many  respects 
resembles  its  development  during  human  infancy  and 
childhood. 

(c)  Foresight.  Entirely  inadequately  we  have  described 
adaptation  with  bhnd  trial,  and,  by  contrast,  adaptation 
with  insight.  A  third  variety  of  behavioral  adjustment  may 
now  be  considered.  We  shall  call  it  foresight  or  preadapta- 
tion. It  begins  to  appear  during  human  childhood  and  becomes 
increasingly  conspicuous  with  progress  toward  maturity. 
Is  it  discoverable  in  other  types  of  primate?  The  brief  reply 
is:  111  the  lemur  and  tarsier  it  probably  does  not  appear; 
even  in  the  monkeys  it  has  not  been  definitely  estabhshed 
by  rehable  observation  and  the  chances  are  that  in  them,  if 
it  appears  at  all,  it  is  in  extremely  simple  form;  in  the 
anthropoid  apes  it  occurs,  but  much  less  frequently  and 
in  less  effective  form  than  in  man. 

Instances  of  ape  foresight  or  preadaptation  are  not 
abundant  in  the  Hterature,  nor  are  the  best  of  them  com- 
parable in  psychological  complexity  with  such  adjustments 
as  those  of  the  man  who  dons  a  raincoat  because  the  weather 
report  is  unfavorable.  On  the  other  hand,  the  action  of  the 
child  who  hides  forbidden  candy  so  that  its  mother  may  not 
confiscate  it  is  closely  paralleled  by  certain  adaptive  activities 
in  the  apes  which  obviously  imply  anticipation. 

According  to  trustworthy  reports,  an  ape,  after  observing 
the  prospective  work  of  the  day,  may  come  to  its  tasks 
eagerly  or  reluctantly.  When  confronted  with  a  situation 
which  demands  planning  and  proper  relating  of  a  succession 
of  acts,  it  may  behave  appropriately  and  successfully. 
Thus,  for  example,  in  the  absence  of  a  necessary  mechanism 
it  may  go  in  search  of  it  and  having  located  it  bring  it  into 
use.  There  are  indeed  in  the  systematic  experimental  litera- 
ture, as  well  as  among  miscellaneous  observations,  several 
peculiarly  interesting  examples  of  what  appears  to  be  antici- 
pation of  events  and  appropriate  preadaptation.  But 
manifestly  the  apes  differ  markedly  from  man  in  the  extent 


MENTAL    EVOLUTION    IN    THE    PRIMATES  1 25 

to  which  foresight  leads  to  preparedness  for  a  contingency. 
All  that  we  may  safely  say  Is  that  the  beginnings  of  foresight 
and  preadaptation  are  obviously  discoverable  In  the  anthro- 
poid apes. 

To  summarize,  adaptation  by  trial  and  error,  inslghtless 
effort,  appears  In  all  existing  types  of  primate  and  throughout 
the  course  of  Individual  development.  By  contrast,  adapta- 
tion with  Insight  has  not  been  discovered  in  the  lemur  or 
tarsler,  perhaps  Is  present  In  rudimentary  form  In  the 
monkeys,  clearly  manifests  Itself  In  the  man-Hke  apes,  and  is 
conspicuously  Important  in  adult  man.  Its  development 
may  be  traced  in  the  course  of  individual  history,  for  whereas 
the  newborn  Infant  is  incapable  of  selective  adaptation, 
the  young  child  commonly  exhibits  it,  and  the  manifestations 
of  Insight  become  increasingly  numerous  and  complex  as 
the  individual  approaches  maturity.  Likewise  there  is 
marked  contrast  from  type  to  type  and  from  stage  to  stage 
of  development  In  evidences  of  foresight  and  resulting  pre- 
adaptation. It  appears  reasonably  certain  that  this  mode  of 
behavioral  adaptation  does  not  appear  in  lemur,  tarsier,  or 
monkey,  that  it  is  discoverable  in  the  anthropoid  apes, 
and  from  this  evolutional  beginning  becomes  preeminently 
important  in  adult  man.  Like  selective  adaptation.  It  may  be 
traced  in  individual  development,  originating  during  infancy 
and  becoming  increasingly  conspicuous  through  child- 
hood and  maturity.  It  seems  Indeed  as  though  the  story  of 
our  own  development  were  traceable  through  the  following 
modes  of  adaptation  or  habit-formation:  From  the  "blind 
trial"  of  fetal  life  and  infancy,  through  the  selective  adapta- 
tions of  late  Infancy  and  childhood,  with  their  extending 
and  enriching  insights,  to  the  foresights  and  preadaptations 
of  adolescence  and  maturity. 

If  at  any  point  our  description  has  given  the  impression 
that  in  either  development  or  evolution  one  of  these  prin- 
cipal modes  of  adaptation  tends  to  replace  or  supplant 
another,  we  should  correct  it,  for  the  more  primitive  or 
simpler  type  always,  it  seems,  tends  to  persist  after  the 
appearance  of  a  psychoblologlcally  more  complex  and  more 
efficient  mode  of  adaptation. 


T26  HUMAN   BIOLOGY 

REPRESENTATIONAL   OR    IMAGINAL   PROCESSES 

For  ages  mankind  has  assumed  and  believed  that  ideation, 
thought,  and  reasoning  are  distinctively  and  probably 
exclusively  human.  But  recently  the  development  of  new 
techniques  and  the  accumulation  of  observational  data, 
through  the  comparative  study  of  psychobiological  phenom- 
ena in  the  primates,  have  essentially  altered  the  status  of 
knowledge.  It  is  now  legitimate  to  state  that  ideas,  simple 
thought  processes,  and  primitive  forms  of  reasoning  exist 
in  the  anthropoid  apes,  or  that  functional  equivalents  cause 
the  animals  to  act  as  though  experiencing  ideas  and  directed 
by  thoughts.  One  may  take  one's  choice  as  between  the 
natural  inference  that  similarity  in  adaptive  behavior 
implies  similarity  in  the  essentials  of  experience  or  that 
rationality  may  be  simulated  by  some  mechanism  which  is 
possessed  by  apes  but  not  by  men. 

Within  the  compass  of  a  few  paragraphs  typical  observa- 
tions or  evidences  of  representational  processes,  or  their 
functional  equivalents,  in  the  infrahuman  primates  may  be 
indicated  but  not  adequately  described.  In  accordance  with 
analysis  of  human  experience  these  processes  are  of  two 
principal  types:  the  reproductive  and  the  creative.  The 
former  are  usually  called  memory  processes;  the  latter, 
processes  of  constructive  or  creative  imagination.  Either 
type  of  process  may  involve  imagery,  and  if  the  subject  of 
observation  is  capable  of  experiencing  images  they  are 
almost  certain  to  appear  in  any  representational  process. 

Whereas  in  mammals  other  than  the  primates,  notably  in 
rats,  guinea  pigs  and  rabbits,  a  problematic  environmental 
situation  cannot  ordinarily  be  responded  to  appropriately 
for  more  than  a  few  seconds,  and  at  best  a  very  few  minutes, 
after  it  has  disappeared  from  view;  monkeys,  apes  and  men 
apparently  are  able  to  respond  adaptively  and  as  if  with 
definite  memory  of  the  situation  after  much  longer  intervals 
of  delay.  Typical  experiments  will  render  this  important 
psychological  contrast  clearer. 

The  subject  sits  before  three  doorways,  through  one  of 
which  when  released  it  may  pass  to  get  its  dinner.  Everything 
in  readiness,  the  experimenter  exhibits  for  a  moment  the 


MENTAL    EVOLUTION    IN   THE    PRIMATES  127 

prospective  food  and  permits  the  animal  to  see  it  placed 
beyond  a  particular  one  of  the  doorways.  Thereupon,  by 
use  of  a  suitable  screen  the  animal's  view  of  the  food  is  cut 
off,  and  the  three  doorways  or  reaction  areas  therefore 
appear  to  it  exactly  ahke.  For  a  definite  period,  say  ten 
minutes,  the  animal  awaits  opportunity  to  respond.  It  then 
is  released  and  makes  choice  among  the  doorways.  As  thus 
far  indicated  by  observations,  this  demand  for  response  on 
the  basis  of  prior  sensory  experience  is  more  easily  and 
successfully  met  by  the  monkey  than  by  the  rat;  by  the  ape 
than  by  the  monkey,  and  by  man  than  by  ape.  The  temporal 
span  of  memory,  or  period  during  which  the  animal  may  be 
kept  waiting  without  losing  its  power  of  correct  response, 
increases  very  rapidly  from  rat  to  man.  No  experiments  with 
lemurs  are  available,  so  we  refer  to  the  rat  instead.  Although 
further  observation  may  essentially  modify  the  findings,  it 
is  indicated  at  present  that  the  rat  ceases  to  respond  adap- 
tively  after  delays  exceeding  a  few  seconds,  whereas 
monkeys,  apes  and  men  may  succeed  after  many  hours. 

An  essentially  different  and  more  exacting  test  of  the 
existence  of  memory  processes  has  recently  been  employed 
to  exhibit  the  ability  of  various  primates.  The  subject 
faces  a  group  of  boxes  which  are  visually  alike  except, 
for  instance,  in  color.  Into  one  of  the  boxes  it  sees  food  put. 
A  screen  is  then  drawn  between  the  subject  and  the  boxes, 
and  the  latter  are  interchanged  so  that  the  food  container 
cannot  be  located  by  its  initial  position  but  must  instead 
be  identified  by  the  visual  quality  of  color.  After  a  stated 
interval  of  delay,  which  in  the  course  of  experimentation  has 
ranged  from  a  few  seconds  to  nearly  an  hour,  the  screen  is 
removed  and  the  animal  given  opportunity  to  seek  the  food. 
At  the  present  writing,  in  addition  to  man,  only  the  chim- 
panzee and  gorilla  have  demonstrated  their  ability  to  react 
successfully  in  this  type  of  situation  after  delays  of  at  least 
ten  minutes.  It  may  not  safely  be  inferred  that  all  other 
types  of  organism  are  incapable  of  such  response,  but  it  is 
safe  to  infer  tentatively  that  success  in  this  type  of  memory 
experiment  is  more  readily  and  more  frequently  achieved 
as  we  progress  from  the  various  orders  of  mammal,  through 
the  several  classes  of  primate  to  man. 


128  HUMAN   BIOLOGY 

i 

It  has  been  discovered  that  the  subject's  natural  basis 
of  choice  in  this  type  of  memory  test  is  the  position  of  the 
food  container.  When  absolute  position,  or  both  absolute 
and  relative  position  are  ehminated  and  correct  response 
depends  on  recognition  of  the  object  by  some  such  visual 
datum  as  color,  form,  size,  or  distance,  the  task  is  much  more 
difficult,  save  for  man,  who  is  able  to  recall  and  recognize  the 
food  container  by  reason  of  visual  or  kinesthetic-verbal 
imagery.  Whether  the  chimpanzee  or  gorilla  remembers 
and  recognizes  the  correct  box  through  the  functioning 
of  visual  images  or  otherwise  we  do  not  know,  but  at  least 
it  is  evident  that  there  is  closer  functional  resemblance 
between  what  may  legitimately  be  called  memory  responses 
of  ape  and  man  than  between  those  of  monkey  and  man  or 
monkey  and  other  mammals. 

To  the  question:  Do  memory  images  or  their  functionally 
equivalent  biological  processes  appear  at  certain  stages  in 
mental  evolution  and  in  certain  classes  of  primates,  and 
thereafter  become  increasingly  important  as  bases  of  adap- 
tive response  to  a  situation  which  is  not  continuously  present 
to  the  senses,  we  offer  our  opinion  that  the  observational  data 
now  available  justify  an  affirmative  reply,  but  they  justify 
also  emphasis  on  the  desirability  of  further  inquiry  and  the 
extreme  importance  of  additional  observations. 

Another  and  quite  different  but  equally  impressive  exhibit 
of  memory  response  is  provided  by  the  behavior  of  primates 
toward  individuals  intimately  known  but  from  whom  they 
have  been  separated  for  long  intervals.  We  are  familiar  with 
the  evidences  of  recognition  of  friends  by  dogs,  cats,  and 
other  domesticated  animals,  but  similar  intimacy  of  acquaint- 
ance with  the  behavior  of  monkeys  and  apes  is  limited  to  a 
few  individuals.  Yet  in  these  creatures  the  definiteness 
and  complexity  of  response  is  even  greater  than  in  the 
other  mammals,  and,  judging  by  the  reports  available,  it 
appears  after  prolonged  periods  of  separation.  There  are 
well-authenticated  statements  that  the  chimpanzee,  orang- 
outan,  and  gorilla  may  recognize  species  or  human  acquaint- 
ances after  many  months  of  separation,  and  at  least  one 
instance  has  been  recorded  of  the  recognition  of  a  man  by 
a   chimpanzee   after   separation   of  nearly   four   years.    In 


MENTAL   EVOLUTION    IN   THE    PRIMATES  1 29 

these  instances,  to  judge  from  our  own  experience,  the 
behavior  frequently  is  so  distinctive,  appropriate,  and 
indicative  of  identification  of  the  particular  individual  that 
one  is  not  tempted  to  question  the  existence  of  memory 
processes.  Whether  or  not  they  be  experiences  of  the  human 
order  we  shall  not  presume  to  say,  although  it  is  entirely 
clear  that  if  they  are  not  comparable  with  our  own  mental 
content  they  are  at  least  aspects  of  psychobiological  processes 
which  serve  the  same  purpose  as  does  reproductive  imagina- 
tion in  man. 

Creative  or  constructive  as  contrasted  with  reproductive 
imagination  has  seldom  been  sought  for  by  the  experimental 
student  of  animal  behavior,  but  by  various  authors  it  has 
been  suggested  that  the  use  of  environmental  objects  as 
tools  or  instruments  may  imply  the  presence  of  constructive 
imagination.  Such  activity  is  virtually  lacking  in  other 
mammals  than  the  primates:  it  appears  in  steadily  increasing 
variety  and  frequency  from  lemur  to  man.  Narrowly  limited 
in  the  monkeys,  to  judge  by  existing  information,  it  is  far 
more  conspicuous  and  serviceable  in  the  apes,  although 
even  in  them  markedly  less  well  developed  than  in  man. 

The  use  of  objects  as  aids  in  adaptation  marks  the  begin- 
ning of  behavioral  adaptation  through  modification  of 
environment  as  contrasted  with  the  process  of  self-adapta- 
tion. It  is  observable  that  whereas  most  existing  animals, 
more  or  less  rapidly  and  in  various  ways,  as  also  in  varying 
degrees,  adapt  to  their  environment,  man  is  distinguished 
by  the  extent  of  his  ability  to  shape  environment  to  his 
needs  and  desires.  Thus  he  extends  the  possibilities  of 
adaptation  and  enormously  increases  the  potentialities  of 
his  life.  It  is  by  virtue  of  his  constructive  imagination  and 
his  manual  dexterity  that  he  is  able  increasingly  to 
control  his  world. 

For  our  present  interest  in  adaptation  the  important 
question  is:  Are  there  evidences  in  ape,  monkey,  or  other 
primate  of  the  use  of  objects  as  tools  or  of  their  modification 
to  serve  as  such? 

Already  the  fact  of  occasional  use  of  sticks  and  other 
simple  objects  as  implements  has  been  recorded  by  us  for 
both  monkeys  and  apes.  The  latter,  however,  greatly  excel 


130  HUMAN   BIOLOGY 

the  former  in  the  variety  and  skill  of  instrumental  adapta- 
tions. When  it  comes  to  the  seeking  out,  creation,  or  con- 
struction of  tools,  pertinent  records  although  few  are 
obviously  important.  By  Kohler*  it  has  been  reported  for 
the  chimpanzee  that  a  branch  may  be  broken  from  a  con- 
venient tree  to  serve  as  means  of  reaching  and  securing 
distant  food.  This  author  also  reports  for  the  chimpanzee 
the  joining  of  two  sticks,  either  of  which  alone  was  too 
short  to  meet  the  animal's  need.  The  sticks  were  hollow  and 
they  were  of  such  size  that  it  was  possible  for  the  chimpanzee 
to  insert  the  end  of  one  into  the  aperture  of  the  other. 
In  this  instance  clearly  the  subject  had  at  hand  the  materials 
of  a  serviceable  tool,  but  except  as  brought  into  the  relation 
which  we  have  described  these  materials  remained  valueless 
as  aids  to  the  solution  of  the  problem  of  obtaining  food. 
Kohler  supphes  yet  another  type  of  observation  which 
clearly  belongs  in  this  category,  for  he  describes  a  chim- 
panzee as  reducing  the  size  of  one  end  of  a  stick  so  that  it 
might  be  inserted  into  the  hollow  end  of  another,  that  thus 
the  two  might  be  constituted  a  serviceable  instrument. 

All  of  these  adaptive  activities  may  be  classified  as  tool- 
making,  since  it  appears  that  the  ape  is  endeavoring  so  to 
manipulate  or  modify  a  portion  of  its  environment  as  to 
render  it  serviceable  in  the  solution  of  a  certain  practical 
problem.  As  we  intimated  above,  observations  of  this  sort 
are  relatively  few  and  we  may  only  tentatively  conclude 
that  the  anthropoid  apes  are  generally  capable  of  such 
expressions  of  what  in  ourselves  we  should  unhesitatingly 
call  constructive  imagination.  If  however  the  chimpan- 
zee, without  human  suggestion,  tuition,  or  other  definite  aid, 
modifies  environmental  objects  for  certain  definite  purposes, 
it  would  be  scarcely  more  reasonable  to  deny  constructive 
imagination  in  it  than  in  man.  Our  tentative  conclusion, 
based  largely  on  unpublished  data,  is  that  the  apes  possess 
creative  imagination. 

Investigation  of  memory  and  related  processes  in  monkeys 
and  apes  has  made  it  abundantly  clear  that  psychobiologi- 
cally  there  is  a  vast  gulf  between  lemur  and  ape  and  even 
between  monkey  and  ape,  for  it  is  only  in  the  latter  that 

*Chap.  4  and  5. 


MENTAL    EVOLUTION    IN   THE    PRIMATES  I3I 

clear  indications  of  reproductive  memory  images  or  their 
functional  equivalents  and  of  the  germs  of  constructive 
imagination  appear. 

Without  reproductive  imagination  an  animal  presumably 
cannot  adapt  selectively;  w^ithout  creative  imagination  it  is 
difficult  to  see  how  it  could  construct  tools.  It  is  our  tentative 
conclusion  from  such  observational  data  as  we  have  knowl- 
edge of,  that  man's  marvelous  power  of  adaptation  through 
control  of  his  environment  is  presaged  in  the  anthropoid 
apes.  He  is  not  the  sole  possessor  of  constructivity. 

Logically  this  discussion  should  be  extended  to  considera- 
tion of  behavioral  indications  of  the  evolution  of  the  processes 
of  abstraction  and  generaHzation,  but  for  practical  reasons 
this  is  undesirable.  Observational  data,  as  it  happens,  are 
few  and  of  uncertain  value.  Already  we  have  presented 
the  grounds  on  which  we  base  the  affirmation  of  the  existence 
of  both  reproductive  and  creative  imaginal  processes  in  the 
apes  and  with  less  certainty  in  the  monkeys.  We  do  not  feel 
justified  in  devoting  additional  space  to  this  section  by 
considering  such  evidences  of  the  beginnings  of  abstraction 
and  generalization  as  may  be  found  in  the  accounts  of 
primate  behavior.  It  must  suffice  to  state  that  not  only  are 
the  evidences  meager,  but  they  very  definitely  suggest  that 
no  existing  primate,  except  man,  is  capable  of  anything 
beyond  the  most  rudimentary,  or,  developmentally  con- 
sidered, the  most  primitive  forms  of  abstraction  and  generaH- 
zation. This  condition  is  so  importantly  related  to  our  next 
topic,  language  and  the  use  of  symbols,  that  it  will  neces- 
sarily receive  certain  further  attention  in  that  connection. 

LANGUAGE    AND    THE    FINAL   DOMINANCE    OF    SPEECH 

Thinking,  except  in  terms  of  concrete  experience,  depends 
upon  symbols  and  is  facihtated  by  them.  Doubtless  it  is 
beside  the  point  and  indicates  a  certain  limitation  of  insight 
to  inquire  whether  thinking  prepared  the  way  for  talking 
or  the  reverse — whether  function  anticipates  structure! 
Undeniably,  symboHsm  is  of  extreme  importance  in  human 
life.  It  therefore  is  necessary  to  ask  in  this  discussion  of 
evolutionary  process,  whether  there  appear  in  birds  or 
mammals   languages    comparable   in    functional   essentials, 


132  HUMAN  BIOLOGY 

if  not  in  degree  of  complexity  and  usefulness,  with  human 
speech,  and  whether  the  behavior  of  existing  primates 
suggests  or  definitely  indicates  the  evolution  of  ability  to 
use  symbols  and  the  presence  of  hnguistic  systems  of  expres- 
sion. The  first  of  these  questions  is  easily  answered;  the 
second  is  more  difficult. 

Intercommunication  evidently  occurs  in  various  types  of 
bird  and  mammal,  as  also  in  certain  classes  of  primate;  but 
in  most  instances  it  appears  to  be  primarily  affective, 
instead  of  serving  to  transfer  such  intellectual  processes  as 
those  of  perception  and  ideation,  inference  and  practical 
judgment.  Yet  precisely  these  forms  of  experience  are 
accompaniments  of,  and  presumably  essential  to,  behavioral 
adaptations  with  insight  and  foresight,  which  occasionally 
are  discoverable  in  the  apes.  The  use  of  symbols,  we  venture 
to  assert,  is  not  so  highly  developed  in  any  bird  or  mammal 
as  to  justify  the  application  of  the  term  language.  When  we 
direct  attention  to  the  apes  we  at  once  discover  diversity 
of  opinion  and  description,  for  there  are  those  who  attribute 
vocal  language  both  to  apes  and  monkeys,  whereas  more 
critical  and  conservative  authorities  assert  that  only  man 
may  properly  be  said  to  speak. 

The  following  should  bring  us  to  a  pause.  We  humans  are 
prone  to  consider  ourselves  the  measure  of  all  things.  Unre- 
flectingly we  accept  our  most  notable  psychobiological 
achievement,  language,  as  a  measure  of  the  development 
of  mind.  This  surely  is  indefensible,  for  it  may  be  that  such 
other  varieties  of  symbol  as  gesture,  facial  and  bodily  atti- 
tude, hmb  and  finger  movements,  are  more  naturally  and 
effectively  employed  by  a  particular  type  of  animal  than 
are  sounds.  Actually,  human  deaf  mutes  use  a  sign  language. 
Why  then  may  not  infrahuman  primates  exhibit  other  modes 
or  even  systems  of  linguistic  expression   than  the  vocal? 

Our  reply  is,  they  do.  Especially  in  monkeys  and  apes 
appear  evidences  of  intercommunication  through  transfer 
of  mental  state  by  such  behavioral  signs  as  we  have 
mentioned.  Although  we  should  hesitate  to  describe  it  as  lan- 
guage, we  must  nevertheless  recognize  its  functional  signifi- 
cance and  suggest  that  in  all  probability  there  is  no  greater 
contrast  between  the  status  of  the  use  of  symbols  by  ape 


MENTAL    EVOLUTION    IN   THE    PRIMATES  1 33 

and  by  man  than  in  their  respective  perceptual  experiences, 
creative  imagination,  insight,  foresight,  and  thought. 

It  is  said  that  apes  possess  a  vocal  mechanism  similar  to 
that  of  man  and  are  capable  of  producing  a  variety  of  sounds. 
The  fact  that  they  communicate  otherwise  than  by  talking 
possibly  should  be  attributed  to  lack  of  special  tendency  to 
reproduce  or  imitate  sounds  in  such  manner  as  to  facihtate 
the  growth  of  a  system  of  vocal  expressions.  Certain  it  is 
that  they  imitate  inteUigently  many  actions  that  they  see. 

Probably  the  most  important  single  difference  in  the 
intellectual  expressions  of  ape  and  man  is  the  hnguistic. 
For  whereas  our  ideas,  memories,  imaginings,  thoughts,  and 
intents  are  expressed  by  spoken  or  written  language,  the 
relatively  meager  and  simple  cognitive  experiences  of  the 
apes  gain  expression  through  bodily  attitude,  facial  expres- 
sion, gesture,  trunk  and  hmb  movements,  and  vocahzation. 
There  is  no  single  system  of  signs  or  symbols  comparable 
with  human  speech,  or  indeed  with  any  other  highly  organ- 
ized form  of  language.  One  must  grasp  and  understand 
or  interpret  the  total  picture  of  ape  behavior  instead  of 
depending,  as  is  possible  among  ourselves,  on  some  single 
form  or  aspect  of  behavior,  such  as  vocal  symbol.  It  may  not 
be  doubted,  however,  that  the  apes,  despite  their  hnguistic 
inferiority  to  man,  communicate  readily  and  to  an  eminently 
serviceable  degree. 

Scarcely  more  than  the  beginnings  of  symboKsm  have 
been  discovered  in  the  primates,  but  from  those  begin- 
nings, as  from  the  modes  of  behavioral  adaptation  which 
are  obse^rvable  in  monkeys  and  apes,  it  is  possible,  and  we 
think  probable,  that  human  symbolism  and  even  speech 
have  evolved.  The  subject  demands  and  richly  deserves 
more  systematic,  persistent,  ingenious,  and  determined 
investigation.  Curiously  enough,  for  every  unit  of  human 
energy  expended  on  observation  of  animal  symbohsm,  a 
hundred  have  been  used  for  surmise  and  speculative  dis- 
cussion. Why  is  man  so  ready  to  ignore  discoverable  fact 
and  to  indulge  in  vain  imaginings? 

Since  man  is  preeminently  and  undeniably  the  talking 
animal,  and  since  further  his  elaborate  system  of  vocal 
symbols  immeasurably  facihtates  both  self-adaptation  and 


134  HUMAN   BIOLOGY 

the  mastery  of  environment,  may  it  not  be  that  language 
is  his  most  important  single  behavioral  achievement,  and 
that  human  supremacy  is  due  to  linguistic  facihtation 
of  thought  and  intercommunication?  Probably  the  common 
ancestor  of  ape  and  man  used  symbols  very  simply  and 
seldom,  if  at  all.  The  human  hne  of  descent  tended  toward 
linguistic  development,  which  in  turn  furthered  the  accumu- 
lation of  a  vast  body  of  social  tradition.  The  ape  line, 
tending  by  contrast  toward  the  utiHzation  of  bodily  attitude 
instead  of  vocahzation  to  express  emotion  and  idea,  pro- 
gressed more  slowly,  haltingly,  and  without  the  accumula- 
tion of  racial  tradition  or  notable  mastery  of  environment. 

This  possible  general  contrast  between  the  distinctively 
human  and  non-human  directions  of  primate  evolution 
deserves  further  consideration,  because  it  appears  that 
survival  of  a  type,  its  geographical  distribution,  and  its 
multiplication,  are  conditioned  very  largely  by  its  ability 
to  control  environment.  While  the  apes  were  struggling 
to  adapt  themselves  to  unpredictable  variations  of  climate 
and  food  supply  and  failed  or  succeeded,  diminished  or 
increased,  in  accordance  with  circumstances  wholly  beyond 
their  control,  early  man  imagined  and  wrought  for  himself 
protective  coverings  and  shelters  from  heat  and  cold, 
from  sun  and  storm,  so  that  he  might  live  almost  anywhere 
on  earth,  whereas  other  primates  were  restricted  by  climate 
and  food  supply  to  certain  limited  areas.  Where  they  per- 
ished miserably  from  starvation  due  to  drought,  flood, 
or  devastating  storms,  he  has  sown  and  reaped,  with  fore- 
sight accumulated  and  stored  supplies,  and  multiplied 
both  sources  and  varieties  of  natural  and  artificial  prod- 
ucts, until  largely  independent  of  environmental  accidents. 
It  appears  that  during  the  era  of  differentiation  of  man 
from  other  types  of  man-like  ape,  progress  by  self-knowl- 
edge and  self-adaptation  was  more  narrowly  limited  and 
offered  fewer  opportunities  for  discovery  and  ingenious 
control  than  did  the  molding  of  environment  or  mutual 
adjustment  of  self  and  environment.  And  the  result,  not 
yet  completely  achieved,  although  clearly  indicated  in  its 
trend,  and  reasonably  predictable  from  the  present  status 
of  primates   on  the  earth,   is  the   failure  of  the  man-like 


MENTAL    EVOLUTION    IN    THE    PRIMATES  1 35 

apes  in  their  struggle  for  survival  and  their  eventual  dis- 
appearance from  the  earth,  and  the  steady  advance  of 
man  toward  perfection  of  Hfe  and  of  its  earthly  setting. 

EMOTIONS    AND   THEIR    EXPRESSIONS 

By  those  who  should  know,  it  is  said  that  the  chimpanzee 
more  strikingly  resembles  man  in  its  affective  hfe  than  in 
any  other  psychobiological  respect.  So  hke  the  human  are 
its  common  expressions  of  feehng,  emotion,  mood,  and 
sentiment,  that  the  observer  is  possessed  by  a  sense  of 
sympathetic  understanding.  We  have  advisedly  used  the 
terms  feehng,  emotion,  mood,  and  sentiment  because  the 
chimpanzee  exhibits  in  varying  degrees  these  several  forms 
of  affective  experience.  Probably  there  is  no  primary  human 
emotion  whose  counterpart  may  not  be  discovered  in  this 
organism,  or,  for  that  matter,  in  any  one  of  the  man-hke 
apes.  Only  apes  and  men  commonly  manifest  in  unmis- 
takable ways  joy,  elation,  anticipation  of  pleasure  or 
discomfort,  depression,  melancholy,  dread,  fear,  terror,  sus- 
picion, resentment,  anger,  dislike,  sympathy,  friendhness, 
sohcitude,  jealousy — the  hst  might  be  extended  almost  to 
the  hmit  of  human  experience.  To  those  who  are  intimate 
with  the  ways  of  the  anthropoid  apes,  their  actions,  whether 
emotional  or  cognitive,  are  as  meaningful  as  words. 

Even  to  the  relatively  inexperienced  observer  it  usually 
appears  that  the  affective  hfe  of  the  apes  is  more  nearly 
human  than  is  the  intellectual  or  cognitive.  Likewise  for 
the  scientist  it  is  a  commonplace  that  the  affective  expres- 
sions of  ape  and  man  are  remarkably  similar;  their  expres- 
sions of  cognitive  and  vohtional  experiences  markedly 
different.  Indeed,  the  two  widely  sundered  and  at  the  same 
time  similar  classes  of  creature  hve  in  sharply  contrasted 
perceptual  worlds  and  react  to  aspects  of  those  worlds  with 
extremely  different  interests  and  possibihties  of  insight  and 
foresight.  They  may  "feel"  ahke,  while  "acting"  differently! 

In  support  of  our  general  statements  we  present  a  single, 
but  we  beheve  typical,  instance  of  the  approach  of  primate 
to  human  affective  experience  and  expression.  We  have 
selected  the  appearance  of  sympathetic  relation  between 
mother  and  infant. 


136  HUMAN   BIOLOGY 

Among  existing  vertebrates  there  may  be  observed 
everything  from  total  lack  of  maternal  interest  in  offspring 
and  of  affection  and  sohcitude  for  them  to  its  obvious  and 
much  vaunted  degree  of  perfection  in  man.  Radical  differ- 
ences are  apparent  even  among  existing  classes  of  primate, 
for  the  sentiment  gains  in  strength  and  complexity  of 
expression,  persistence,  and  likewise  in  degree  of  resemblance 
to  the  human,  as  we  progress  from  lemur  to  ape. 

In  the  monkeys  the  phenomena  are  deeply  impressive 
and  irresistibly  suggestive  of  human  experience.  Only 
those  who  have  had  occasion  to  try  to  study  a  mother 
monkey  and  her  baby  can  appreciate  the  strength  of  her 
attachment.  She  is  continuously  watchful,  suspicious  of  all 
comers,  and  she  strenuously  resents  and  resists  every  attempt 
of  the  observer  to  approach  the  infant  or  to  separate  it 
from  her.  This  may  occur  even  when  she  is  on  terms  of 
friendly  intimacy  with  the  observer.  Of  the  chimpanzee, 
to  mention  only  that  anthropoid  ape  for  which  information 
is  most  nearly  adequate,  the  same  is  true.  If  the  infant  ape 
be  injured  or  taken  from  the  female,  maternal  distress  is 
commonly  indicated  by  violent  attempts  at  defense  or 
recovery,  by  extreme  restlessness  and  appearances  of 
anxiety,  and  by  grievous  crying  or  screaming. 

Evidently  parenthood  as  affective  experience  and  expres- 
sion more  closely  approaches  our  own  in  monkey  and  ape 
than  in  the  more  primitive  primates,  such  as  the  lemur  and 
tarsier,  or  in  any  other  inferior  mammal.  Unless  the  observer 
is  biased,  he  is  not  likely  to  escape  the  force  of  the  indications 
that  parental  sentiment  may  very  well  have  evolved  from 
the  relative  carelessness  of  the  lemur  to  the  intense  sym- 
pathetic attachment  and  solicitude  of  the  anthropoid  ape, 
and  thence  to  the  experiences  of  man. 

Important  also  is  the  fact  that  whereas  intimate  relations 
between  mother  and  infant  continue  for  only  a  few  hours 
or  days  in  most  mammals  and  are  said  to  be  relatively 
transient  even  in  the  primitive  forms  of  primate,  they 
last  for  weeks  and  months  in  the  monkeys,  and  even  for  years 
in  the  man-like  apes.  The  chimpanzee  may  and  often  does 
nurse  her  infant  for  two  years,  and  even  thereafter  she  may 
protect  and  train  or  instruct  it  and  attend  to  its  needs. 


MENTAL    EVOLUTION    IN    THE    PRIMATES  1 37 

SOCIAL    RELATION    AND    ORGANIZATION 

Human  social  relations  are  conditioned  by  sentiments, 
and  the  evolution  of  social  life  in  the  primates  almost 
certainly  has  paralleled  the  evolution  of  affective  experience 
and  expression.  Man  and  ant,  by  radically  different  evolu- 
tional change,  have  attained  highly  serviceable  forms  of 
social  relation  and  organization.  It  is  illuminating  to  con- 
trast the  social  hfe  of  these  two  types  of  creature.  Whereas 
human  social  evolution  is  characterized  by  the  enhancement 
of  the  value  of  the  individual  as  social  object,  that  of  the 
ant  is  similarly  marked  by  subordination  of  the  individual, 
through  speciahzation,  to  the  v^elfare  of  the  group.  Among 
men  and  apes  the  social  unit  is  the  family;  among  ants  it  is 
the  colony. 

Through  the  several  classes  of  primate  one  may  trace  the 
evokition  of  social  consciousness  and  its  behavioral  mani- 
festations toward  mutuality  of  interest,  self-subordination, 
cooperation  and  altruism. 

Were  we  to  pursue  further  the  topic  of  evolution  of  social 
consciousness  and  the  appearance  of  social  types  of  organiza- 
tion and  institution  in  the  primates,  we  should  encroach 
on  the  materials  of  the  next  chapter,  "Social  Evolution." 
Therefore  we  bring  to  a  close  this  brief  presentation  of 
evidences  of  mental  evolution  in  the  primates,  forthwith 
summarize  our  conclusions,  and  suggest  a  few  books  which 
the  interested  reader  may  find  helpful. 

CONCLUSIONS 

Critical  comparison  of  the  psychobiological  character- 
istics of  existing  classes  of  primate:  lemur,  tarsier,  monkey, 
ape,  and  man,  as  definitely  suggests  evolutional  changes 
during  descent  as  do  the  findings  of  comparative  anatomy 
and  embryology. 

Because  in  a  short  chapter  it  is  impossible  to  present 
the  varied  materials  and  evidences  of  mental  evolution 
systematically  and  completely,  we  have  selected  six  con- 
spicuously important  aspects  of  the  highly  complex  mental 
and  behavioral  life  of  the  primates  to  exemplify  materials 
and  degrees  of  resemblance  and  to  supply  typical  indications 
of  their  relation  in  descent. 


138  HUMAN    BIOLOGY 

The  selected  categories  are:  (i)  receptivity,  sensibility, 
and  the  transition  from  contact  to  distance  reception, 
which  finally  achieved  its  proximate  consummation  in 
human  vision;  (2)  modes  of  "habit-formation,"  "learning," 
or  behavioral  adaptation,  and  their  essential  forms  of 
experience,  which  seemingly  progressed  on  the  basis  of 
perceptual  configuration,  and  with  increasingly  complex 
motivation,  from  "trial  and  error,"  through  adaptation 
with  insight,  to  preadaptation  by  reason  of  foresight; 
(3)  representational  processes  and  the  correlated  behavior 
of  memory  and  imagination;  (4)  the  use  of  symbols,  the 
development  of  language,  and  the  final  dominance  of  speech 
in  man;  (5)  emotional,  or  more  generally  speaking,  affective 
experience  and  expression,  and  finally  (6)  social  experience, 
behavior  and  organization. 

In  each  of  these  spheres  of  psychobiological  interest 
the  observationally  determined  order  of  increasing  degree 
of  resemblance  to  man  is:  lemur,  monkey,  ape,  and  the  facts 
support  the  hypothesis  that  existing  primates  represent, 
in  some  instances,  steps  in  the  line  of  human  descent,  and 
in  others,  diverging  lines  of  evolution. 

REFERENCES 

Baldwin,  J.  M.  1902.    Development  and  Evolution.     N.  Y.,  Macmillan. 
lioBHouSE,  L.  T.  19 1 5.  Mind  in  Evolution.  Ed.  2.  Lond.,  Macmillan. 
Jones,  F.  W.  1926.  Arboreal  Man.  Lond.,  Edward  Arnold. 
KoHLER,    W.    1925.    The    Mentality   of  Apes.   Trans,  from  German  by  Ella 

Winter.  N.  Y.,  Harcourt  Brace. 
Morgan,  C.  L.  1914.  An  Introduction  to  Comparative  Psychology.  New  ed. 

Lond.,  Scribner. 
Romanes,   G.  J.    1883.   Mental   Evolution   in   Animals.  Lond.  Kegan  Paul, 

Trench.  1889.  Mental  Evolution  in  Man.  N.  Y.,  Appleton. 
Smith,  G.  E.  1924.  The  Evolution  of  Man.  Oxford  Univ.  Press. 
Tilney,  F.  1928.  The  Brain  from  Ape  to  Man.  2  vols.  N.  Y.,  Hoeber. 
Washburn,  M.  F.  1926.  The  Animal  Mind.  Ed.  3.  N.  Y.,  Macmillan. 
Yerkes,  R.  M.  1925.  Almost  Human.  N.  Y.,  Century. 
Yerkes,  R.  M.  and  A.  W.  1929.  The  Great  Apes.  Yale  Univ.  Press. 


Chapter  VI 

SOCIETAL  EVOLUTION 

W.  M.  Wheeler 

WHEN  as  children  we  first  escape  from  the  "big, 
buzzing,  booming  confusion,"  which  to  our  infantile 
consciousness  represents  the  surrounding  world, 
we  distinguish  an  indefinite  variety  of  different  things. 
Somewhat  later  we  notice  that  our  world  also  contains  a 
vast  number  of  very  similar  objects.  All  this  most  of  us 
take  for  granted  and  never  give  it  second  thought  during 
the  remainder  of  our  hves.  But  if  we  happen  to  become 
philosophers  or  scientists,  this  composition  of  reahty  strikes 
us  as  worthy  of  closer  study,  though  we  may  entertain  Kttle 
hope  of  learning  why  our  world  should  be  made  up  of  such 
an  extraordinary  number  of  similars  and  dissimilars.  As 
our  knowledge  increases,  we  observe  a  pronounced  tendency 
in  the  numerous  hke  objects  to  form  cohering  aggregates, 
and  this  tendency  seems  to  be  universal  in  its  range  from 
the  electrons  that  make  the  atoms,  the  atoms  that  make  the 
molecules,  the  molecules  that  make  the  masses,  from  sand 
dunes  and  oceans  to  planets  and  suns,  and  their  aggregates, 
the  constellations  and  nebulae.  When  we  turn  to  living 
things  we  find  the  tendency  even  more  pronounced  so  that 
the  like  entities  cohere  to  form  peculiar  integrated  systems 
known  as  organisms  which,  on  analysis,  reveal  themselves 
as  hierarchies  of  living  entities.  We  find  living  molecules, 
which  are  themselves  systems  of  inorganic  molecules, 
atoms  and  electrons,  organizing  themselves  to  form 
cells,  cells  to  form  persons,  persons  to  form  societies  consisting 
of  single  families  and  finally  multi-familial  or  group  societies 
like  the  one  into  which  we  are  born  and  in  which  we  are 
constrained  to  live  till  the  end  of  our  days. 

Yet  closer  observation  has  revealed  the  startling  fact, 
emphasized  only  within  recent  years,  that  the  similar 
entities  when  integrated  or  organized  as  wholes,  i.e.  as 
systems    or    organisms,    exhibit    new    and    unpredictable 

139 


140  HUMAN   BIOLOGY 

behavior  (qualities)  as  compared  with  the  behavior  of  their 
components.  Thus  when  sodium  and  chlorine  combine 
chemically  to  form  common  salt,  we  observe  that  it  behaves 
in  a  manner  very  different  from  either  of  its  constituent 
substances  in  isolation.  Similarly,  a  personal  organism 
behaves  very  differently  from  its  individual  cells.  A  new 
phenomenal  "level"  has  been  created,  so  to  speak,  which 
is  not  a  mere  sum  or  resultant  of  the  component  units  but  a 
novelty,  or  "emergent."  This  term,  like  the  noun  "emer- 
gence," has  in  this  connection  the  meaning  of  "emergency" 
and  is  not  to  be  understood  in  the  ordinary  sense  which 
implies  simply  a  manifestation  or  revelation  of  behavior, 
or  properties  previously  existing  in  the  components  of  the 
system  or  organism.  It  should  also  be  noted  that  in  order  to 
bring  this  consideration  into  harmony  with  present  physical 
theory,  we  must  not  regard  the  various  components  and 
emergent  wholes  (systems  and  organisms)  as  static  things, 
or  as  so  many  lumps  of  inert  matter,  but  as  activities  or 
movements,  albeit  of  very  various  velocities.  Such  an  atti- 
tude enables  the  scientist  to  avoid  the  embarrassing  con- 
tradictions and  inconsistencies  with  which  our  thinking 
has  been  seriously  infected  by  age-long  indulgence  in 
dualistic  (materialistic  and  spiritualistic)  notions  of  reality. 
Leaving  the  physicists,  chemists  and  astronomers  to  deal 
with  the  inorganic  aggregations  and  systems,  we  may  turn 
to  their  counterparts,  the  associations  and  societies  among 
living  things.  Here  the  cohesion  and  organization  of  like 
elements,  or  components,  is  indeed  astonishingly  diverse 
and  complicated.  Some  of  the  wholes  which  they  constitute 
are  very  loose  and  temporary  and  may  be  called  aggregations, 
like  the  swarms  of  dancing  midges  or  the  collections  of 
hibernating  lady-bird  bettles  in  the  mountains  of  the  Pacific 
States.  Others  are  very  persistent  and  consist  of  very 
interdependent,  and  therefore  very  intricately  organized, 
parts,  like  the  multicellular  bodies  of  most  plants  (Meta- 
phyta)  and  animals  (Metazoa).  Less  highly  organized  are 
the  wholes,  represented  by  the  colonies  of  the  social  insects, 
the  flocks  and  herds  of  birds  and  mammals,  and  the  societies 
of  man.  Table  i  enumerates  the  various  categories  of  associa- 
tions and  societies. 


SOCIETAL   EVOLUTION 


141 


Table  I 


TYPES  OF  ASSOCIATIONS  AND  SOCIETIES 


A.   Associations 

(Unstable,  temporary, 
incompletely  organ- 
ized wholes,  primarily 
dependent  on  environ- 
mental stimuli) 


,,  .  ,  .fa.  Homotypic 

1.  Mere  aggregations  or  agglomerations.     1  u  u 

2.  Breeding,  feeding,  hibernating,  sleeping,  f  a.  Homotypic 

lb.  He) 


eterotypic 

omotypic 

eterotypic 


Heterotypic 


Societies 

(More  nearly  per- 
manent, organized 
wholes  or  systems, 
primarily  dependent 
on  interindividual stim- 
uli) 


and  migratory  associations 

3.  Predatory  association. 

4.  Parasitic  association. 

5.  Symbiotic  or  mutualistic  association. 

6.  Mimetic  association. 

7.  Communities  (biocoenoses) 

1.  Persons       (multicellu- 
ar) 

2.  Mainly    nutritive    so- J  (Colonies,     corms, 
cieties  (closed)  \  etc.) 

Subsocial  insects 
Social  wasps 
Social  bees 
Ants 
Termites 

4.  Mainly  protective  so-  /  Flocks,      her  d  s  , 
cieties      (closed      and  1  schools,  etc. 
open) 

5.  Mainly  reproductive 
mixed        societies 
(closed) 


A.  Homotypic, 


Mainly     reproductive' 
societies  (closed) 


R.  Heterotypic 

Mainly  protective 
mixed  societies  (open)  , 
c.   Human  societies  (Group  societies) 


"Mixed  colonies" 
of  wasps 
Bumblebees 
Ants 

Flocks  of  different 
species  of  birds, 
herds  of  different 
ruminants,  etc. 


The  associations,  of  course,  vary  greatly  in  the  number 
of  their  component  individuals,  from, many  milHons  as  in 
the  migrating  swarms  of  locusts,  to  as  low  as  two,  in  most 
host  and  parasite  associations  among  insects.  Many  species 
often  assemble  to  form  aggregations  on  the  same  tree  or 
flower,  or  under  the  same  stone,  and  these  aggregations 
may  be  either  homotypic;  i.e.  consisting  of  members 
of  the  same  species,  or  heterotypic,  when  individuals  of 
more  than  one  species  assemble.  These  and  other  aggrega- 
tions may  also  result  from  very  important  or  urgent  activities 
of  the  individuals,  such  as  feeding,  breeding,  hibernating, 
sleeping  or  migrating.  Comprehensive  reviews  of  such 
cases,  with  citation  of  the  pertinent  hterature,  have  been 
recently  pubhshed  by  Deegener  (1918),  Allee  (1927)  and 
Brues  (1926).  Special  instances  of  the  very  small  associations 
are  also  seen  to  center  about  nutrition  in  the  cases  of  pred- 
ators, i.e.  carnivorous  animals  and  their  prey,  between 
parasites  and  their  hosts,  insects  and  the  plants  they  polli- 
nate, mimetic  organisms,  mainly  insects,  and  their  models 
and  in  what  are  known  as  the  communities,  or  biocoenoses, 


142  HUMAN    BIOLOGY 

which  are  great  heterotypic  associations  of  numerous  animals 
and  plants  occupying  the  same  type  of  environment  and 
entering  into  the  most  diverse  and  intricate  relations  with 
one  another,  e.g.  the  biota  (fauna  and  flora)  of  a  tropical 
rainforest  regarded  as  a  whole,  that  of  a  bog,  sand  dune, 
desert,  lake,  etc.  In  all  these  cases  the  associations  are  more 
or  less  unstable  and  temporary,  because  not  very  highly 
integrated.  Their  integration,  in  fact,  seems  to  be  largely 
determined  by  general,  extrinsic  or  environmental  stimuli. 

The  societies,  as  distinguished  from  the  associations, 
are  more  permanent,  organized  wholes  which  depend 
primarily  on  the  behavior  of  the  component  individuals 
towards  one  another.  In  order  to  be  with  its  fellows  the 
social  individual  will  not  infrequently  seek  to  adjust  itself 
even  to  a  harmful  or  fatal  environment  or  situation.  Hence 
societies,  as  a  rule,  can  be  established  only  between  indi- 
viduals of  the  same  species,  i.e.  of  the  same  genetic  origin, 
but  there  are  exceptions  in  which  individuals  of  two  or 
more  species  may  form  single  societies  (ants,  bees,  wasps, 
compound  flocks  and  herds  of  birds  and  mammals).  We  may 
therefore  distinguish  homotypic  and  heterotypic  societies. 
Human  societies  are  in  many  ways  so  peculiar  that  they 
may  be  assigned  to  a  third  category  by  themselves. 

Now  it  is  obvious  that  all  associations  and  societies 
are  merely  peculiar  expressions  of  the  most  general  and 
fundamental  activities  of  living  things,  namely  adaptation, 
and  it  is  also  apparent  that  the  associative  and  social 
adaptations  are  referable  to  the  basic  physiological  responses 
of  the  individual  organisms  to  stimuli  emanating  from  their 
fellows  or  their  general  environment.  We  may  roughly 
divide  these  responses  into  three  general  categories,  those 
which  satisfy  the  nutritive,  reproductive  and  protective 
(defensive  and  offensive)  needs  of  the  individual  organism, 
respectively.  The  different  societies  may  therefore  be  classi- 
fied according  to  the  preponderance  of  these  several  needs, 
in  their  behavior.  Thus  such  societies  as  the  human  person, 
which  consists  of  some  60,000,000,000,000  cells  and  such 
compound  organisms  as  the  Portuguese  man-of-war,  tape- 
worm, etc.  are  of  the  predominant  nutritive  type.  All 
their  individuals  are  in  contact  or  interconnected  in  such 


SOCIETAL   EVOLUTION  1 43 

a  manner  that  certain  ones,  specialized  lor  the  purpose, 
secure  and  distribute  nutriment  to  the  whole.  The  raison 
d'etre  of  the  society  seems  to  be  primarily  the  facihtation 
of  this  function.  In  other  societies,  however,  Hke  those  of  the 
social  insects  (wasps,  bees,  ants,  termites)  nutrition  seems 
to  be  subordinated  to  producing  and  rearing  as  many  young 
as  possible,  so  that  reproduction  and  all  that  it  implies 
would  appear  to  be  the  principal  adaptive  peculiarity  of 
such  societies.  Among  the  flocks  and  herds  of  birds  and 
mammals,  nutrition  and  reproduction  are  less  conspicuous 
than  the  forms  of  social  behavior  connected  with  protection. 
For  discussions  of  these  societies  the  reader  may  be  referred 
to  the  works  of  Espinas  (1924)  and  Petrucci  (1906)  and  the 
recent  volume  of  Alverdes  (1927).  As  would  be  expected, 
primitive  human  societies  have  their  closest  analogues 
among  certain  gregarious  mammals,  and  notably  among 
the  anthropoid  apes. 

The  problem  of  greatest  interest  to  the  student  of  animal 
associations  and  societies  is  concerned  with  the  precise 
nature  of  the  communal  bonds,  or  social  cohesion  which 
causes  the  individuals  to  assemble  and  remain  together  for 
a  longer  or  shorter  period.  The  aggregations  in  some  cases 
are  obviously  the  result  of  mere  accidental  .propinquity 
due  to  the  individuals  hatching  simultaneously  from  a 
batch  of  eggs  deposited  by  the  mother  organism  directly 
on  food  suitable  for  the  young.  Thus  the  larvae  of  such 
insects  as  the  gypsy  moth  and  potato  bettle  are  too  feeble 
to  stray  far  from  the  egg  cluster  from  which  they  hatch 
and  really  need  not  stray  far  from  one  another  because  they 
are  surrounded  by  an  abundant  supply  of  nutriment. 
The  same  is  true  of  plant  lice  which  are  born  alive  by  their 
feeble  wingless  mothers  and  the  sluggish,  legless  larvae 
of  Drosophila  and  blow  flies  which  hatch  from  numbers 
of  eggs  laid  almost  simultaneously  in  fermenting  fruit  or 
decomposing  flesh.  We  need  not  assume,  therefore,  that 
such  aggregations  of  larvae  are  due  to  fondness  for  one 
another's  company  or  are  kept  together  by  any  other  bond 
than  a  simple  chemotropic  response  to  their  common 
nutritive  environment.  But  some  aggregations  and  associa- 
tions undoubtedly  depend  on  stimuli  emanating  from  the 


144  HUMAN   BIOLOGY 

difTerent  individuals.  All  animals  give  oft  heat,  moisture, 
carbon  dioxide,  secretions  and  excretions  and  make  move- 
ments. Simple  tropistic  or  reflex  responses  to  these,  such 
as  those  designated  by  the  terms  thermotropism,  hygro- 
tropism,  chemotropism  and  stereotropism,  are  probably 
sufficient  to  account  for  many  aggregations  and  associations. 
Migratory  crickets  have  been  observed  to  huddle  together 
for  mutual  warmth  when  the  cool  of  evening  comes  on; 
slaters  (Oniscus)  are  induced  to  assemble  by  the  moisture 
which  they  give  off",  and  resting  locusts  may  be  stimulated 
to  flight  by  the  movements  of  their  feflows.  Rhythmic 
emission  of  hght  in  fireflies  or  of  chirping  in  crickets  may 
excite  rhythmic,  and  according  to  some  authors  synchronous, 
responses  of  the  same  kind  in  other  individuals  in  the  imme- 
diate neighborhood  ("physiological  sympathy"  of  Ribot). 
Some  simple  aggregations  are  evidently  the  result  of  a 
number  of  tropistic  responses.  One  example  will  suffice. 

The  larvae  of  the  common  blackfly  (SimuKum)  often 
congregate  in  dense  masses  on  stones  in  the  more  torrential 
parts  of  our  streams,  stand  erect  on  their  posterior  ends  and 
capture  with  their  out-spread,  rake-hke  mouthparts  diatoms 
and  other  microorganisms  as  they  float  past.  In  this  case 
we  may  distinguish  stereotropic  responses  of  the  larvae  to 
sohd  bodies  (the  stones),  rheotropic  responses  to  the  current 
and  probably  also  chemotropic  responses  to  the  higher 
oxygen  content  of  the  more  rapidly  moving  water.  It  wifl 
be  noticed  that  this  combination  of  tropistic  responses 
constitutes  an  exquisite  adaptation  because  it  places  the 
stationary  larvae  in  the  optimal  enviroment  for  securing  their 
food,  since  much  more  of  it  passes  within  their  reach  in  a  given 
time  in  the  torrential  than  in  the  sluggish  portions  of  the 
stream.  Although  aggregation  here  actually  brings  about  a 
competition  for  the  food  among  the  individuals,  this  dis- 
advantage is  more  than  compensated  by  the  increased 
supply  due  to  the  swiftness  of  the  stream.  There  is  an  exten- 
sive and  interesting  literature,  much  of  which  has  been 
reviewed  by  Allee,  dealing  with  the  effects  of  aggregations 
on  their  component  individuals,  but  the  subject  cannot  be 
further  elaborated  in  this  article. 


SOCIETAL    EVOLUTION  1 45 

Some  authors  have  endeavored  to  derive  the  societies 
from  the  associations,  but  it  is  difficult  to  find  any  cogent 
proof  of  their  contentions.  The  societies  really  represent 
very  different  emergent  levels  from  the  associations  and 
have  arisen  in  a  different  way,  though,  of  course,  ancient 
aggregative  or  associative  proclivities  may  have  been 
retained  by  many  species  and  may  serve  to  reinforce  their 
specifically  social  behavior.  The  members  of  societies,  as 
distinguished  from  the  associations,  are  primarily  concerned 
with  their  adaptations  to  one  another,  i.e.  with  neutralizing 
their  individual  antagonisms,  and  with  their  mutual  adjust- 
ment and  cooperation.  The  mass  of  stimuli  which  elicit 
these  adaptive  responses  may  be  called  the  social  medium. 
It  constitutes  a  very  complex  and  unstable  environment 
for  the  individuals,  and  successful  and  enduring  adjustment 
to  it  presupposes  a  high  sensitivity  and  considerable  behav- 
ioristic  plasticity  on  the  part  of  the  consociated  organisms, 
and  this  in  turn  presupposes  a  highly  organized  neuro- 
muscular apparatus.  It  is  clear  therefore  that  societies  can 
be  constituted  only  by  species  in  which  the  sense-organs, 
brain  and  muscular  system  have  attained  a  high  degree  of 
specialization,  and  not  by  animals  that  have  never  succeed- 
ed in  transcending  the  merely  tropistic  and  reflex  level. 
Social  life  demands  at  least  a  rudimentary  memory  and 
intelligence,  if  we  understand  by  the  latter  the  ability  to 
respond  adaptively  to  new  situations  on  the  basis  of  pre- 
vious experience,  or  in  other  words,  some  ability  to  learn. 
It  is  obvious,  moreover,  that  to  such  organisms  social  life 
furnishes  the  only  adequate  opportunity  for  much  further 
perfecting  of  the  intelligent  activities. 

Though  a  rather  highly  developed  neuromuscular  system 
is  a  sine  qua  non  of  social  life,  it  is  far  from  true  that  all  ani- 
mals thus  equipped  must  become  social.  Tigers,  hawks, 
spiders  and  tiger-beetles  are  richly  endowed  organisms, 
but  they  do  not  live  in  societies.  Moreover,  when  we  study 
the  positions  of  social  species  in  the  animal  hierarchy  we 
find  that  they  are  confined  to  certain  sporadic  groups  of 
species  and  that  they  often  differ  externally  in  no  respect 
from  the  most  closely  related,  highly  specialized,  non- 
social  forms.  A  worker  honey-bee  or  hornet  is  quite  unable 


146  HUMAN   BIOLOGY 

to  live  except  in  a  society,  and  yet  no  one  could  infer  this 
fact  from  their  structure,  which  differs  in  no  essential 
character  from  that  of  their  soHtary  congeners.  It  would 
seem,  therefore,  that  some  other  pecuhar  condition  in 
addition  to  the  high  development  of  the  neuromuscular 
system  is  essential  to  the  formation  of  true  societies.  This 
I  beheve  to  be  the  development  of  the  family.  So  long  as  its 
members  remain  together,  a  family  is,  of  course,  a  rudimental 
society,  with  reproductive,  nutritive  and  protective  functions 
and  an  unmistakable  differentiation,  or  division  of  labor 
in  its  components.  All  the  societies  of  insects  are  hierely 
single  families  in  origin  though  they  may  become  very 
populous  and  acquire  an  extraordinary  differentiation  of 
their  members.  The  family  origin  of  the  flocks  and  herds 
of  birds  and  mammals  and  hordes  and  tribes  of  primitive 
man  is  also  apparent;  though  in  these  societies  the  family 
is  open  and  not  closed  as  in  insects  and  there  is  a  retention 
in  the  flocks,  herds  and  hordes  of  primitive  aggregative  or 
associative  tendencies  which  seem  to  hark  back  to  the 
ancestral  fish  and  tadpole  stages.  This  retention  is  apparent 
in  important  further  developments  to  be  briefly  considered 
in  a  later  paragraph. 

The  family  impHes  the  vital  aflihation  of  the  off"spring 
with  the  parents  and  this  can  only  be  accompHshed  on  the 
condition  that  the  adult  hfe  of  the  parents  is  sufficiently 
prolonged  to  admit  of  rearing  the  off"spring  to  maturity. 
This  increase  in  parental  longevity  also  permits  a  corre- 
sponding extension  of  the  care  of  the  off'spring  and  gives  the 
latter  time  for  a  more  complicated  development  and  greater 
opportunities  for  learning  and  therefore  of  preparation 
for  adult  life.  The  latter  consideration  has  been  often 
discussed  by  sociologists,  psychologists  and  educators, 
but  the  increase  of  the  adult  life  of  the  parents  as  a  prereq- 
uisite to  that  of  the  young  has  been  overlooked.  It  is  just 
this  latter  condition  which  enables  us  to  account  for  the 
beginnings  and  further  development  of  the  families  which 
become  the  elaborate  closed  societies  of  the  ants,  wasps, 
bees  and  termites.  Most  mother  insects  die  soon  after 
oviposition  and  the  young  are  left  to  shift  for  themselves, 
but   in   certain   groups,   owing   to   peculiarities   of  food   or 


SOCIETAL    EVOLUTION  I47 

environment,  the  adult  life  of  the  mother  or  of  both  parents  is 
considerably  prolonged  so  that  it  overlaps  the  larval  period 
or  even  a  part  or  the  whole  of  the  adult  Hfe  of  the  offspring 
and  thus  furnishes  an  opportunity  for  close  relations  between 
the  members  of  two  successive  generations.  I  find  these 
conditions  reahzed  in  at  least  thirty  insect  groups,  which 
are  often  so  remotely  related  to  one  another  or  related  in 
such  a  manner  that  the  family  must  be  supposed  to  have 
arisen  independently  (polyphyletically)  on  at  least  as  many 
separate  occasions  during  the  long  racial  history  of  the 
Hexapoda,  which  extends  over  some  300,000,000  years 
from  the  Upper  Carboniferous  to  the  present  time.  These 
famihes  vary  greatly  in  complexity  and  stabihty.  In  most 
cases  the  parents  are  deserted  by  the  progeny  while  the 
latter  are  still  young,  and  the  rudimentary  society  dissolves, 
a  condition  observed  in  what  I  have  called  the  subsocial 
insects  (certain  beetles,  wasps,  bees,  Embiids,  earwigs,  etc.). 
In  the  termites,  ants,  higher  wasps  and  bees,  however,  the 
affiliation  of  the  progeny  with  the  mother  (Hymenoptera) 
or  with  both  parents  (termites)  becomes  much  more  intimate 
and  prolonged,  so  that  at  least  the  worker  caste,  which 
constitutes  the  great  majority  of  the  personnel  of  the 
society,  never  dissolves  its  consociation  with  the  parents. 
The  single  family  is  thus  enabled  to  remain  a  society, 
though  capable  in  some  cases  of  growth  to  a  population  of 
hundreds  of  thousands  of  individuals.  This  is  accompHshed 
by  partial  starvation  of  most  of  the  offspring  so  that  they 
fail  as  larvae  to  develop  their  reproductive  organs  (ahmen- 
tary  castration)  and  even  as  adults,  in  their  capacity  as 
nurses,  inhibit  the  further  development  of  their  gonads 
by  starving  themselves  as  a  result  of  feeding  the  successive 
broods  of  larvae,  the  queen  and  the  other  adult  members 
of  the  colony  (nutricial  castration). 

In  the  foregoing  account  of  insect  societies  nothing  is 
said  about  the  nature  of  the  bonds  which  unite  the  parents 
and  offspring  and  thus  initiate  the  family  or  about  the 
nature  of  the  social  medium  which  regulates  the  social 
behavior.  I  beheve  that  we  may  detect  these  recondite 
factors  in  what  I  have  called  "trophallaxis,"  or  exchange 
of  food. 


148  HUMAN   BIOLOGY 

The  larvae  of  many  social  insects  (ants,  wasps  and  ter- 
mites) are  not  only  fed  by  the  adult  members  (parents  and 
workers)  of  the  colony,  but  may  in  turn  feed  their  nurses 
with  sahvary  or  other  secretions.  The  young  are  therefore 
a  source  of  food  for  the  adults  and  vice  versa,  and  the  ''fond- 
ness" of  the  social  insects  for  their  young  proves  to  be  not 
some  altruistic  "instinct,"  such  as  love  or  affection,  but 
the  hunger  of  the  individual  and  therefore  an  egoistic 
appetite.  There  is  also  a  trophallactic  relation  between  the 
adult  members  of  the  colony,  which  are  constantly  feeding 
one  another  with  regurgitated  hquid  foods  (ants)  or  with 
regurgitated  semisoHd  foods  or  feces  or  substances  (exudates) 
secreted  from  the  surfaces  of  their  own  bodies  (termites). 
So  powerful  is  this  habit  that  it  is  extended  even  to  many 
of  the  heterogeneous  insects  which  have  managed  to  hve 
in  the  nests  of  the  social  species,  i.e.  to  the  true  guests 
among  the  myrmecophiles,  which  hve  with  ants,  and  the 
highly  speciahzed  guests  of  termites  (termitophiles).  Further- 
more, since  the  senses  of  taste  and  smell  are  not  differentiated 
in  insects  as  they  are  in  the  higher  vertebrates,  and  since, 
in  the  former,  we  may  therefore  more  properly  speak  of  a 
single  chemical  sense,  we  are  justified  in  including  under 
trophallaxis  also  an  exchange  of  odors  as  one  of  the  important 
cohesive  bonds  in  insect  societies.  There  are,  in  fact,  indi- 
vidual, colonial  and  nest  odors,  which  the  social  insects  are 
able  to  recognize  and  distinguish  and  therefore  serve  to 
determine  many  of  their  reactions  and  much  of  their 
behavior.  Both  the  food  and  the  odors  thus  constitute  a 
regulative,  circulating  social  medium  which  not  only  func- 
tions as  a  social  cohesive,  but  in  the  case  of  the  food,  furthers 
the  growth  and  maintenance  of  the  society  in  a  manner 
analogous  to  the  circulating  blood  stream  in  the  body  of  a 
higher  animal,  which  is  also  a  society  of  cells.  Of  course, 
the  word  "food"  is  here  used  in  a  general  physiological 
sense,  both  as  nutriment  and  as  a  stimulant,  or  excitant, 
because  the  amounts  of  the  substances  exchanged  may  be 
extremely  small  though  of  such  a  chemical  composition  as  to 
produce  pronounced  reactions,  just  as  a  very  small  amount 
of  alcohol  may  produce  much  more  violent  reactions  in 
some  people  than  large  quantities  of  rice  or  potatoes. 


SOCIETAL   EVOLUTION  1 49 

The  flocks,  packs  and  herds  of  the  higher  vertebrates 
constitute  peculiar  societies,  quite  unhke  those  of  insects, 
and  might  more  properly  be  called  peoples,  populations  or 
"peuplades,"  to  use  Espinas'  term.  They  may  consist  of  a 
number  of  associated  famihes,  of  individuals  of  one  or  both 
sexes  or  of  the  young  only.  They  may  be  loosely  or  intensively 
organized,  temporary  or  more  permanent,  and  either  closed 
or  open,  to  use  the  classification  of  Alverdes,  i.e.  they  may 
either  repel  outsiders  or  admit  them,  even  when  they 
belong  to  ahen  species,  and  permit  them  to  become  members 
of  the  society  in  good  standing.  Our  knowledge  of  these 
pecuhar  organizations  is  far  from  complete,  but  some  of 
them  have  been  recently  studied  with  results  that  seem  to 
have  important  bearings  on  human  societies,  which  are 
really  of  the  same  fundamental  structure.  The  peuplades 
are  held  together  by  what  has  been  usually  called  the  gre- 
garious, or  herd  instincts,  but  the  investigations  to  which 
I  have  just  referred  seem  to  show  that  the  cohesion  may  be 
due  to  more  concrete  and  observable  behavioristic  factors. 

In  their  studies  of  birds,  Schjelderup-Ebbe,  Katz  and 
Fischel  have  shown  that  the  flocks  are  organized  according 
to  a  pecuhar  "pecking  order,"  in  which  each  individual  has 
its  own  status  depending  on  whether  it  may  peck  other 
individuals  or  submit  to  being  pecked  by  them.  To  quote 
Alverdes,  "Schjelderup-Ebbe  has  shown  how  an  order  of 
precedence  comes  into  existence  within  societies.  A  flock 
of  fowls  in  a  fowl  run  is  not  exclusive  in  the  sense  that  its 
members  make  common  cause  against  a  new  arrival,  leaving 
the  latter  isolated.  The  new  comer  may  safely  attach  itself 
to  the  flock,  but  the  position  it  is  to  hold  therein  must 
first  be  won  by  fighting.  For  no  two  hens  ever  hve  side  by 
side  in  a  flock  without  having  previously  settled,  either  for 
the  time  being,  or  for  good,  which  is  the  superior  and  which 
the  inferior;  the  "pecking  order"  thus  estabHshed  decides 
which  of  the  birds  may  peck  the  other  without  fear  of  being 
pecked  in  return.  Similar  pecking  codes  exist,  according  to 
Schjelderup-Ebbe,  among  sparrows,  wild  ducks,  and  possibly 
among  many  other  kinds  of  animals.  Pecking  among  cocks 
is  governed  by  the  same  rules  as  among  hens,  except  that 
the  cocks  exhibit  greater  ferocity.  Such  "pecking  orders" 


150  HUMAN   BIOLOGY 

give  the  society  concerned  a  certain  degree  of  organization." 
This  "pecking  order"  which  would  seem  to  be  the  cohesive 
among  the  peuplades,  corresponding  to  the  very  different 
cohesive,  trophallaxis,  among  the  societies  of  insects,  leads 
naturally  to  a  complex,  organized  hierarchy  of  individuals, 
depending  on  their  age,  sex,  vigor,  and  blufFmg  capacity. 
It  is  so  suggestive  of  human  communities,  in  which  we  have 
a  similar  hierarchy  of  social  status  based  on  the  bivalent 
self-assertion  and  self-abaserrfent,  or  sadistic  and  masochistic 
motives  of  the  individual,  that  the  results  of  further  investi- 
gations on  the  peuplades  of  other  Vertebrates  will  be  awaited 
with  interest.  Perhaps  what  we  call  government  in  human 
societies  is  really  only  a  glorified  "pecking  order !"^ 

When  we  turn  to  the  societies  of  man  we  are  confronted 
with  an  emergent  level  so  much  higher  and  so  much  more 
compHcated  than  that  of  any  of  the  other  social  animals 
that  it  seems  to  transcend  analysis.  Biologically  it  is  obvious 
that  it  consists  of  a  great  number  of  genetically  related 
families,  and  though  there  is  among  the  individuals  of  each 
of  these  a  division  of  labor  essentially  like  that  of  the  animal 
family,  there  is  superadded  a  more  elaborate  division  of 
labor  which  traverses  the  families  and  is  quite  unlike  that 
of  the  unifamilial  society  of  insects,  since  it  is  a  product  of 
learning  and  custom  and  has  not  become  hereditary.  Further- 
more, his  much  more  highly  developed  neuromuscular 
system,  intelligence,  memory,  and  language  have  enabled 
man  to  create  and  transmit  from  generation  to  generat'on 
vast  accumulations  in  the  form  of  stores  of  knowledge, 
elaborate  institutions,  constructions,  mores,  arts,  sciences, 
etc.,  which  the  animals,  restricted  to  their  Hmited  hereditary 
endowments  and  feeble  individual  plasticity  of  response  to 
their  inorganic  and  living  environment,  could  neither  develop 
nor  transmit.  This  tradition,  or  social  memory,  has  therefore 
been  regarded  as  the  leading  pecuharity  of  human  societies, 
but  it  must  be  admitted  that  there  are  some  very  rudimental 
indications  of  it  even  in  the  social  insects. 

^  In  this  connection  it  is  interesting  to  note  that  the  domestication  of 
animals  depends  on  a  similar  order.  Nearly  all  our  domestic  animals  belong 
to  social  species  and  their  successful  subjugation  implies,  so  to  speak,  a  realiza- 
tion on  their  part  of  their  defenseless  inferiority  in  the  presence  of  man. 


SOCIETAL    EVOLUTION  I5I 

Naturally  the  question  as  to  what  brings  about  the  cohe- 
sion of  the  individuals  is  far  from  being  as  easily  answered  in 
human  as  in  animal  societies.  To  this  question,  which  also 
involves  the  causes  of  the  maintenance  or  continuation  as 
well  as  the  origin  of  human  societies,  the  philosophers  and 
sociologists  of  the  past  have  given  a  number  of  different 
answers.  These  are  all  hypothetical,  and  none  of  them  is 
altogether  satisfactory.  Several  of  them,  in  fact,  are  quite 
inadequate  and  at  present  obsolete,  but  it  may  be  of  interest 
to  consider  them  seriatim. 

1.  The  earliest  hypothesis,  if  it  deserves  so  dignified 
a  name,  is,  of  course,  that  of  Genesis,  according  to  which  the 
male  of  our  species  was  made  out  of  clay  by  divine  fiat  on  the 
sixth  day  and  the  female  from  his  rib  by  the  same  process 
somewhat  later.  This  statement  has  some  extraordinary 
implications,  only  two  of  which  need  be  mentioned.  First, 
man  having  been  created  complete,  he  was  necessarily  a 
social  being  from  the  beginning,  and  inquiry  into  the  causes 
of  society  must  be  useless.  Secondly,  owing  to  his  special 
creation,  man  is  definitively  set  over  against  the  other 
animals  and  Nature  in  general.  This  is  the  view  still  taken 
for  granted  by  many  theologians  so  that  for  them  all  inquiry 
into  social  evolution  and  cohesion  in  a  biological  sense  must 
be  meaningless. 

2.  Some  of  the  Greek  philosophers,  including  Plato, 
entertained  a  similar  supernatural  view  of  the  origin  of  man 
and  his  society,  mainly  on  ethical  grounds.  But  Plato  seems 
also  to  have  been  inclined  to  regard  society  as  having  had  a 
natural  origin  and  growth  and  this  view  was  definitively 
developed  by  Aristotle  and  much  later  by  other  philosophers, 
including  de  Maistre  and  Kant. 

3.  In  the  seventeenth  and  eighteenth  centuries  an  hypoth- 
esis of  the  origin  of  human  society  was  expounded  by 
Hobbes,  Locke  and  Rousseau,  which  seems  very  strange  to 
us.  These  philosophers  imagined  that  men  had  formed  and 
continued  to  maintain  their  society  by  mutual  agreement, 
or  compact.  That  anything  like  society  could  owe  its  begin- 
ning and  cohesion  to  such  frail  intellectual  motives  was 
quite  in  harmony  with  the  thinking  of  those  centuries. 
Of  course,  the  corollary  that  men  might  dissolve  by  intellec- 


152  HUMAN   BIOLOGY 

tual  agreement  what  they  had  built  up  by  the  same  means 
was  one  of  the  arguments  in  favor  of  the  French  Revolution. 
At  the  present  time  the  doctrine  has  no  sociological  impor- 
tance, except  possibly  to  a  certain  type  of  reformer. 

4.  Another  intellectuahstic  hypothesis  of  societal  origins 
was  excogitated  by  Starcke  who  beheved  that  early  man  took 
up  social  life  because  he  had  observed  its  advantages  among 
the  social  insects  in  his  environment.  Similar  fanciful  notions 
have  been  occasionally  advanced  to  account  for  more  modest 
human  inventions,  e.g.  the  supposition  that  the  Australian 
aborigines  derived  the  boomerang  from  observing  the 
circular  paths  described  by  the  falling  sickel-shaped  leaves 
of  certain  species  of  Eucalyptus.  While  this  latter  hypothesis 
cannot  be  dismissed  as  altogether  improbable,  Starcke's 
notion  becomes  absurd  when  we  consider  that  man  must 
have  been  a  social  animal  long  before  he  had  sufficient 
intelligence  to  observe  and  imitate  the  social  insects  and 
that,  even  had  he  conceived  society  as  the  result  of  such 
casual  observations,  that  fact  would  not  have  enabled  him 
to  maintain  it  throughout  his  whole  subsequent  racial 
history  in  all  parts  of  the  world. 

5.  Darwin's  hypothesis  of  evolution  through  natural 
selection  is,  of  course,  quite  a  different  matter.  According  to 
it,  social  origins  are  really  accidental,  but  when  men  had 
once  established  social  relations  with  one  another,  the 
advantages  accruing  would  lead  to  the  survival  of 
the  individuals  that  adhered  to  the  social  habit,  while 
those  who  reverted  to  a  solitary  mode  of  life  would  be 
eliminated.  Naturally,  from  a  human  point  of  view,  the 
advantages  of  society  are  enormous,  and  existing  man  has 
never  experienced  any  other  mode  of  life,  but  the  selection 
hypothesis,  though  logical,  does  not  go  to  the  root  of  the 
matter.  The  merely  evolutionary,  or  transformist  core  of 
the  hypothesis,  however,  is  immensely  important.  We 
should  not  be  wrong  in  stating  that  evolution  may  be  more 
easily  demonstrated  in  ethnology,  archeology,  and  history 
than  in  the  study  of  living  and  extinct  organisms. 

6.  If  we  revert  to  the  principle  of  emergence,  briefly 
considered  in  the  introduction  to  this  chapter,  we  might  say 
that    human    society    arose    rather    suddenly    and    discon- 


SOCIETAL   EVOLUTION  1 53 

tinuously  when  the  primitive  family  expanded  by  some 
natural  process  of  growth,  affiliation  and  differentiation  of 
individuals  into  the  clan  or  tribe,  but  even  this  leaves  us  in 
the  dark  in  regard  to  the  actual  factors  which  brought  about 
the  expansion  and  still  maintain  the  soHdarity  of  the  indi- 
viduals in  the  great  societies  of  the  present  time. 

7,  Psychologists,  psychopathologists  and  sociologists  are 
now  unanimous  in  maintaining  that  social  cohesion,  or  what 
some  have  called  the  "social  mind,"  must  be  constituted 
by  the  wealth  of  non-rational  behavior  which  has  been 
variously  designated  as  the  appetites,  cravings,  instincts, 
interests  and  emotions  of  the  individual.  Some  have  postu- 
lated a  special  "herd  instinct"  (Trotter)  or  "gregarious 
instinct"  (Drever),  while  others  have  based  human  soli- 
darity on  "consensus"  (Comte),  synergy,  or  cooperation 
(Spencer),  on  altruism,  sympathy,  affection  or  even  egoism 
(Le  Dantec).  It  will  be  seen  that  all  of  these  bonds  are  of  a 
physiological  or  primitively  psychological  character  and 
therefore  quite  different  from  those  which  we  call  intellectual, 
or  rational.  They  are,  no  doubt,  fundamentally  the  same  as 
the  primitive  associative  tendencies  which  we  observe  in  the 
uniform  members  of  the  flocks  and  herds  of  birds  and  mam- 
mals, and  may  therefore  be  traceable  to  the  instinctive 
bonds  which  unite  the  members  of  the  family. 

8.  Durkheim,  while  accepting  these  tendencies  as  the 
basis  of  social  cohesion  in  the  more  primitive  human  societies, 
has  pointed  out  that  as  society  develops,  the  strongest 
bonds  are  those  produced  by  the  continued  action  and 
intensification  of  the  social  division  of  labor.  The  associated 
individuals  necessarily  become  more  and  more  heterogeneous 
psychically,  and  therefore  more  and  more  interdependent. 
This  increase  in  interdependence  brings  about  both  the 
cooperation  and  the  constraint  which  are  such  conspicuous 
features  in  highly  developed  societies.  Cooperation  is  not, 
therefore,  a  primitive  condition,  but  supervenes  after  a 
certain  differentiation  has  been  developed  by  division  of 
labor,  or  speciahzation  among  the  individuals;  and  the 
constraint,  restraint,  inhibitions  and  repressions  which  the 
social  unit  is  bound  to  exercise  and  endure  have  had  much 
to  do  with  the  creation  of  the  traditions  (social  heredity). 


154  HUMAN   BIOLOGY 

mores,  laws,  religious  institutions,  etc.  which  in  turn  con- 
strain their  creators.  Durkheim's  view  has  the  advantage  of 
referring  the  integration,  or  solidarity  of  society,  to  a 
principle  which  is  universal,  not  only  in  all  animal  societies, 
but  also  in  all  multicellular  organisms.  This  principle,  the 
division  of  labor,  was  first  recognized  and  named  by  the 
economist  Adam  Smith  and  only  later  introduced  into 
biology  by  Milne-Edwards. 

The  very  significant  role  of  the  primitively  psychological 
and  the  relative  insignificance,  even  in  our  present  civiliza- 
tion, of  the  specifically  intellectual  processes  have  been  most 
impressively  set  forth  by  Pareto  in  his  "Traite  de  Sociologie" 
and  by  Sumner  and  Keller  in  their  "Science  of  Society." 
A  study  of  these  works  might  be  said  to  constitute  a  Hberal 
education.  Pareto  designates  the  irrational  foundations  of 
social  behavior  as  the  "residues,"  the  rationahzations  of 
them  in  which  we  are  constantly  indulging,  as  the  "deriva- 
tions." Sumner  and  Keller's  remarkable  picture  of  the  mores 
and  of  their  fundamental  significance,  stability,  and  tenacity, 
based  on  exhaustive  ethnological  studies,  forms  an  admirable 
background  for  Pareto's  contentions,  which  he  illustrates 
mainly  with  materials  drawn  from  the  ancient  and  con- 
temporary history  of  European  peoples.  Both  works  are 
important  also  because  they  lift  sociology  entirely  out  of  the 
valuative  and  moralizing  slough,  in  which  it  has  long 
floundered,  onto  the  scientific  plane.  The  strange  light  which 
these  and  many  other  similar  studies  of  human  society 
cast  on  our  zealous  social  reformers  and  propagandists 
enables  us  to  appreciate,  on  the  one  hand,  the  impulsive, 
irrational,  wishful  thinking  which  is  the  true  drive  of  their 
own  activities  and,  on  the  other  hand,  the  extraordinary 
magnitude  and  inertia  of  the  behavior  they  are  trying  to 
control  and  reform. 

REFERENCES 

Allee,  W.  C.  1927.  Animal  aggregations.  Quart.  Rev.  Biol.,  2:  267-398. 

Alverdes,  F.  1927.  Social  Life  in  tlie  Animal  World.  N.  Y.,  Harcourt  Brace. 

Brues,  C.  T.  1926.  Remarkable  abundance  of  a  cistelid  beetle,  with  observa- 
tions on  other  aggregations  of  insects.  Amer.  Natural.,  60:  526-545. 

Deegener,  p.  19 18.  Die  Formen  der  Vergesellschaftung  im  Tierreiche. 
Leipzig,  Veit. 


SOCIETAL    EVOLUTION  1 55 

DuRKHEiM,  E.  1922.  De  la  Division  du  Travail  Social.  Paris,  Alcan. 
EsPiNAS,  A.  1924.  Des  Societes  Animales.  Ed.  3.  Paris,  Alcan.  (Ed.  i,  1877.) 
Ferriere,  a.  1915.  La  Loi  du  Progr^s  en  Biologic  et  en  Sociologie  et  la  Ques- 
tion de  rOrganisme  Social.  Paris,  Giard  &  Brieve. 
FiscHEL,  W.    1927.  Beitrage  zur  Sociologie  des  Haushuhns.  Biol.  Zentralbl. 

47:  678-696. 
Katz,   D.    1922.  Tierpsychologie  und  Soziologie  des  Menschen.  Zeitscbr.  J. 

Psychol.  88. 
1926.  Socialpsychologie  der  Vogel.  Ergebn.  der  Biol.,  i :  447-477. 
Le  Dantec,  F.  191 1.  L'Egoisme  seule  base  de  toute  Societe.  Paris,  Flammarion. 
Pareto,  V.  191 7.  Traite  de  Sociologie  Generale.  French  ed.  by  P.  Boven. 

2  vols.  Paris,  Payot  &  Co. 
Petrucci,  R.  1906.  Origine  Polyp Iiyletique,  Homotypie  et  Noncomparabilite 

des  Societes  Animales.  Fasc.  7.  Notes  et  Mem.  Inst.  Solvay. 
Schjelderup-Ebbe,  T.  1922.  Beitrage  zur  Sozialpsychologie  des  Haushuhns. 

Ztscbr.  J.  Psychol,  88. 
Das  Leben  der  Wildente  in  der  Zeit  der  Paarung.  Psychol.  Forscb.,  3. 
Sumner,  W.  C.  and  Keller,  A.  G.  1927.  The  Science  of  Society.  4  vols.  New 

Haven,  Yale  Univ.  Press. 
Wheeler,  W.  M.  1923  Social  Life  Among  the  Insects.  N.  Y.,  Harcourt  Brace. 
1928.  Emergent  Evolution  and  the  Development  of  Societies.  N.  Y.,  Norton. 
1928.  Insect  Societies,  their  Origin  and  Evolution.  London,  Keegan  Paul. 


Chapter  VII 

HUMAN  RACES 

Ales  Hrdlicka 

ONE  of  the  plainest  facts  regarding  man  is  that  he  differs, 
physically  as  well  as  otherwise.  Physically  he  differs 
so  that,  except  in  the  rare  cases  of  "identical"  or 
one-egg  twins,  every  individual  may  readily  be  told  apart 
from  all  others.  This  is  individual  variation,  which,  while 
general  to  all  living  forms,  is  most  pronounced  in  man. 

In  every  human  community,  however,  from  the  larger 
family  groups  or  "hnes"  onward,  there  are  evidences  of  the 
formation  of  strains,  the  individuals  of  which  approach  or 
resemble  each  other  in  pigmentation,  stature,  build,  and 
more  or  less  even  in  physiognomy.  The  larger  the  human 
group  the  more  such  strains  there  usually  are,  and  the 
more  some  of  these  tend  to  become  established,  both  soma- 
tologically  and  territorially.  Such  strains  now  form  types, 
which,  if  allowed  further  to  develop  and  multiply  and  segre- 
gate, begin  to  assume  the  status  of  races;  which,  with  time, 
develop  again  their  own  strains  and  types  and  perhaps 
races. 

Thus  human  variation  and  differentiation  go  on;  and  thus 
they  have  gone  on  since  the  beginnings  of  man,  producing 
various  races,  most  of  which  perished  in  the  long  struggle 
of  human  ascent.  But  others  persist  to  this  day,  and  it  is 
the  study  and  classification  of  these  surviving  as  well  as 
their  daughter  races  that  have,  long  since,  been  one  of  the 
serious  concerns  of  Anthropology,  and  that  will  be  succinctly 
dealt  with  in  the  following  pages. 

MAN   AND    SPECIES 

In  biological  classification  man  constitutes  the  ultimate 
distinct  genus  of  the  Primates,  the  genus  Homo.  The  com- 
ponents of  this  most  widely  distributed  genus  present 
extensive  physical  variation,  and  this  variation  occurs  in 
numerous  more  or  less  distinct  strains,  the  larger  and  better 

156 


HUMAN   RACES  1 57 

established  of  which  are  known  as  the  human  races.  These 
races  differ  much  in  age  as  well  as  in  distinctiveness;  and  the 
oldest  and  most  distinct  have  appeared  to  some  students  to 
deserve  the  term  of  species  rather  than  races. 

The  question  hinges  largely  on  the  concept  of  a  "species." 
This  concept  and  its  definition  have  never  been  made  as 
clear  as  one  would  wish.  A  perfect,  universally  valid  defini- 
tion of  a  species  seems  in  fact  impossible.  A  species  may 
merely  be  said  to  be  a  well-defined,  autonomous  and  per- 
sistent organic  unit,  living  in  a  free  state  of  nature,  not 
grading  freely  into  any  other  unit,  and  generally  of  less 
perfect  fecundity  outside  than  inside  of  its  limits.  A  species 
moreover  differs  from  all  other  species  not  only  morphologi- 
cally, but  also  in  its  physiological  manifestations,  and  in  its 
"psychic"  behavior. 

When  we  apply  such  a  concept  and  definition  to  man, 
we  fail  to  estabhsh  separate  species  in  this  genus.  Even 
man's  most  distinct  strains  intergrade  very  substantially 
with  others,  somatologically,  physiologically  and  in  mental 
behavior;  they  interbreed  freely  and,  under  normal  con- 
ditions, rear  normal  lastingly  fecund  progency;  and 
all  are  changeable  in  the  direction  of  other  units  of  the 
group,  under  altered  conditions.  There  is  therefore,  as 
well  recognized  already  by  Darwin  and  many  other  eminent 
older  students  of  the  question,  no  justification  for  the 
assumption  within  the  human  genus  of  more  than  one  true 
species,  and  the  different  strains  of  man  may  properly 
be  regarded  as  just  subspecies,  varieties,  or,  most  simply 
and  intelligibly,  as  races. 

ORIGIN    OF    HUMAN    RACES 

The  phenomenon  of  raciation,  i.e.  of  differentiation  into 
races,  is  common  to  all  living  organisms.  It  is  an  important, 
and  in  higher  organic  forms  probably  necessary,  step 
towards  speciation,  or  the  formation  of  species. 

The  formation  of  races  in  any  geographically  extensive 
group  is  more  or  less  continuous,  according  to  circumstances 
such  as  environmental  differences,  isolation,  in-breeding 
and  mix-breeding.  Judging  from  analogies  among  the 
existing  anthropoid  apes,  it  is  safe  to  assume  that  there 


158  HUMAN    BIOLOGY 

were  distinct  races  already  among  the  human  precursors, 
and  that  more  or  less  different  races  were  present  throughout 
the  existence  of  man.  It  is  not  impossible,  even,  that  more 
than  one  race  of  precursors  were  evolving  simultaneously 
towards  man,  though  only  the  most  successful  of  such 
possible  separate  developments  appears  to  have  survived. 

It  may  therefore  legitimately  be  said  that  from  the  earhest 
times  of  its  existence  humankind  was  tending  to  differentiate 
into  races;  and  that  racial  differentiation  in  man  is  a  con- 
tinuous, general  hfe  process,  without  sharply  demarkable 
beginnings  or  end.  Its  causes  are  organic  variability,  adapt- 
abiHty  to  changed  conditions,  eventual  heredity  of  the 
newly  developed  and  sustained  characters,  and  prolonged 
segregation  of  the  new  groups. 

Nascent  Races 

Whenever  a  human  group  of  some  magnitude  and  geo- 
graphical extent  begins  to  assume  lasting  somatological 
characters  that  tend  to  differentiate  it  plainly  from  other 
groups  of  man,  it  may  justly  be  regarded  as  a  nascent  race. 
Whether  such  a  race  becomes  successful,  i.e.  prevails  and 
becomes  established,  will  depend  on  conditions. 

The  tendency  towards  the  development  of  new  human 
races  may  be  observed  in  many  parts  of  the  world  today. 
Its  chief  present  factors  are,  on  one  hand,  the  basic  human 
qualities  or  functions  of  variability  and  blending;  and  on  the 
other  hand  intermixture,  with  unification  of  activities. 

Wherever  two  or  more  racial  elements  come  into  such 
contact  as  will  bring  on  free  intermarriage,  there  will  before 
long  begin  to  form  an  intermediary  type  or  progressive 
blend.  In  most  cases  such  a  blend,  through  circumstances, 
becomes  dissolved  into  one  or  more  of  the  parent  bodies, 
or  is  so  influenced  by  the  predominance  of  one  or  another  of 
these  that  it  fails  to  reach  any  distinct  status  of  its  own. 
But  in  favorable  cases,  which  are  those  of  mixtures  within 
large  political  units,  there  will  be  formed  a  "nation,"  which 
with  time  advances  towards  uniformity  of  language  and 
habits.  And  such  a  unit,  if  immigration  is  not  great,  will 
show  ever  more  of  physical  resemblances. 


HUMAN    RACES  1 59 

Precisely  such  phenomena  took  place  within  all  the  large 
political  units  or  nations  that  exist  today.  Every  one, 
without  exception,  is  the  resultant  of  the  merging  of  various 
racial  elements,  and  each  one  may  now  be  seen  to  be 
approaching,  more  or  less,  a  recognizable  new  type  of  its 
own,  e.g.  the  Spanish,  Italian,  French,  German,  English, 
and  even  the  American.  These  new  types  are  of  the  order 
of  nascent  races.  Could  any  of  these  nations  exist  for  some 
milleniums  without  further  material  accretions  from  the 
outside,  the  strong  probability  is  that  a  definite  new  second- 
ary race  would  be  established. 

Human  raciation  of  the  present  is  one  of  the  plainest 
and  most  generalized  evidences  of  continuing  human 
evolution. 

RACE   CHARACTERS 

The  characters  that  distinguish  human  races  are  morpho- 
logical, physiological,  chemical,  psychological,  and  even 
pathological.  They  occur  in  more  or  less  of  correlations,  but 
there  are  numerous  and  in  instances  important  exceptions 
in  this  respect. 

The  principal  physical  differences  in  human  races  are 
those  of  color,  nature  of  the  hair,  characteristics  of  the 
skull,  face,  eyes  and  nose,  stature,  relative  lengths  of  the 
long  bones,  and  of  teeth,  especially  incisors.  Important 
differences  exist  in  the  brain,  internal  organs  and  many 
other  parts,  but  these  largely  await  further  investigation. 

The  main  Junctional  racial  differences,  so  far  as  known, 
are  those  in  pulse,  temperature  and  eruption  of  the  teeth. 
There  are  doubtless  many  others;  but  here  once  more  a  great 
deal  remains  to  be  learned  through  further  research.  Demo- 
graphic differences  belong  to  this  section. 

Chemical  racial  differences  are  manifest  in  the  blood,  in 
sweat,  and  inferentially  in  the  various  immunities.  Almost 
nothing  is  known  as  yet  of  probable  differences  in  the  various 
internal  secretions,  and  elsewhere.  Here  too  remains  a  great 
field  for  future  studies. 

The  mental  differences  between  the  races,  numerous  and 
in  some  cases  important,  elude  thus  far  direct  and  precise 
specification    or   determination.    Sensory   differences    exist. 


l60  HUMAN   BIOLOGY 

but  their  exact  nature  and  degrees  remain  to  be  established. 
There  are,  between  the  more  distinct  races  at  least,  appar- 
ently substantial  differences  in  the  higher  psychical  processes, 
but  they  have  not  yet  been  precised;  their  study  is  much 
comphcated  by  what  are  merely  mental  habits. 

The  pathological  racial  differences  are  in  the  main  those  of 
"predispositions"  and  immunities.  They  are  mostly  environ- 
mental, and  local  rather  than  racial,  in  character.  They 
directly  correlate  but  little  with  other  racial  features;  but 
in  their  indirect  effects,  survival  or  ehmination,  range 
among  the  basic  factors  in  human  evolution.  Among  patho- 
logical conditions  largely  pecuhar  to  some  races  may  be 
mentioned  the  transient  nutritional  disorder  in  childhood 
that  leads  to  the  frequent  premature  occlusion  of  the 
sagittal  suture,  with  consequent  scaphocephaly,  in  the  negro; 
the  pecuhar  psychoses  of  the  Malays;  the  neurasthenias, 
various  skin  disorders,  etc.,  among  the  whites;  etc. 

The  differences  in  all  these  Hues  are  in  every  human  group 
associated  with  astonishing  similarities  to  identities,  pointing 
strongly  to  a  common  derivation  of  all  the  existing  human 
varieties. 

INSTABILITY 

All  the  racial  characters,  of  whatever  order,  appear  in 
more  or  less  wide  ranges  of  individual  and  of  group  variation, 
and  the  extremes  of  the  group  variation  as  a  rule  largely 
overlap  or  interdigitate  with  those  of  other  racial  units. 

None  of  the  characters  in  any  group  may  be  regarded  as 
wholly  set  and  stable.  A  few  examples  will  here  suffice. 

Color 

Color  oj  Skin.  In  the  "white"  race  the  color  of  the  skin 
ranges  from  light  bluish-white  or  pinkish,  as  in  the  Nordic 
blond  or  red-haired,  to  all  shades  of  tan  (many  Mediter- 
raneans), or  brown  (some  Arabs,  Egyptians,  Abyssinians, 
etc.),  to  almost  black  (some  Abyssinians,  some  Hindus). 

It  varies  from  almost  white  to  dark  brown  (solid  chocolate) 
in  the  Chinese  and  Japanese,  from  that  of  old  leather  to 
dark  brown  in  the  American  Indian. 


HUMAN    RACES  l6l 

It  is  absolutely  black  in  many  Australians,  whose  hair 
may  be  nearly  straight  and  features  almost  like  those  of  a 
White.  It  may  be  brown  in  an  Aino  with  a  physiognomy 
much  like  that  of  a  Russian.  It  may  be  light  tan  in  a  dark- 
haired  Nordic,  or  resplendently  white  in  a  Mediterranean 
or  a  Semitic  brunette. 

It  ranges  from  the  blackest  through  dark  brown  and  red 
brown,  to  that  of  old  leather,  in  the  Negroes  (including  the 
Bushmen). 

Color  oj  Eyes.  This  varies  in  white  races  from  pale  blue,  or 
greenish,  or  greyish,  to  dark  brown;  among  the  Asiatics, 
aboriginal  Americans,  Polynesians  and  Malays,  from  medium 
to  very  dark  brown;  and  among  the  negroes  from  dark 
brown  to  black.  There  are  more  or  less  marked  age  changes 
in  the  color  of  the  eyes  in  every  individual. 

Color  of  Hair.  The  hair  varies  from  almost  colorless,  or 
golden,  or  red,  through  all  shades  of  brown,  to  jet  black,  in 
whites;  from  dark  reddish  brown  to  jet  black,  in  the  yellow- 
browns;  from  tow-yellow  to  coal  black  in  the  Australian; 
from  coal-  or  jet-black  to  soot-  or  greyish-black,  in  the 
negroes.  It  may  vary  from  very  light  to  dark  brown  between 
the  childhood  and  later  adult  life  in  the  same  individual 
among  the  whites,  or  from  sandy  to  black,  as  among  some  of 
the  Melanesians. 

Character  of  Hair 

The  hair  is  straight  to  decidedly  curly  in  whites;  it  is 
straight  to  loosely  wavy  in  yellow-browns;  is  straight  to 
bushy-curly  or  frizzly  in  the  Australians;  and  presents 
bushy  curls  to  scant  spirals,  in  the  negroes.  The  degree  of 
curliness  or  wave  may  differ  during  the  life  of  the  same 
individual. 

In  cross-section,  on  the  average,  the  hair  of  the  white|is 
oval,  that  of  the  yellow-browns  round,  that  of  the  true 
negro  elliptic;  but  there  is  much  variation  and  overlapping 
throughout. 

The  Skull 

The  whole  gamut  of  cephalic  index,  and  also  that  of  skull 
height,   is   found  among  the  whites;  similarly  among  the 


1 62  HUMAN   BIOLOGY 

yellow-browns;  while  general  dolicho-  to  meso-cephaly, 
but  reaching  in  individuals  and  in  some  central  tribes  to 
brachycephaly,  prevails  in  the  African  negro.  Even  the 
full-blood  Australian  reaches  from  extreme  dolichocephaly 
to  the  border  of  brachycephaly,  and  from  low  skull  to  high 
(see  Hrdlicka,  1924). 

The  skull  shape  changes  between  birth  and  the  adult 
stage;  differs  in  the  two  sexes;  is  affected  slightly  by  stature; 
and  has  within  historic  times  been  observed  to  gradually 
change  in  the  same  people,  particularly  in  the  direction  of 
brachycephaly  (Austria,  Bohemia,  Germany,  England, 
etc.),  but  also  in  the  opposite  direction  (the  Eskimo). 

The  most  distinct  and  least  varied  skull,  on  the  whole,  is 
that  of  the  African  negro.  Yet  it  also  shows  some  marked 
differences,  as  in  the  "Boskop"  type,  which  may  here  and 
there  be  observed  among  the  living  unmixed  negroes  in 
South  Africa.  And  individual  negro  features  occur  now  and 
then  in  the  crania  of  all  other  races,  without  admixture. 
In  some  respects,  such  as  the  nose,  and  prognathy,  the 
African  negro  skull  is  on  the  whole  the  most  primitive;  yet 
it  will  occasionally  be  exceeded  even  in  these  features  by  an 
Australian  or  Melanesian;  and  in  some  points,  such  as  the 
reduction  of  the  jaws  and  particularly  that  of  the  supraorbital 
ridges,  it,  on  the  average,  exceeds  these.  In  the  reduction 
of  the  brow  ridges  it  surpasses  (which  means  that  it  is 
evolutionally  more  advanced)  even  the  skull  ofthe  white  man. 

Other  Racial  Differences 

Much  the  same  conditions  of  indefmiteness,  or  imperfect 
stability,  and  overlapping,  apply  to  all  other  characters, 
of  whatever  nature,  that  are  better  known  in  man  at  large. 
Nothing  is  fully  set,  nothing  immutable,  nothing  wholly 
apart  from  the  rest.  Wherefore  the  conclusion  that  man  is 
represented  today  by  but  one  species,  and  that  his  sub- 
divisions deserve  no  farther  reaching  designation  than  that 
of  races,  seems  the  only  justifiable  conclusion. 

Changes  in  Racial  Characters 

Races  are  more  or  less  definite  hereditary  complexes. 
Their   characters   may   be   viewed  as  so  many  acquisitions 


HUMAN    RACES  1 63 

in  the  course  of  the  history  of  each  race.  These  acquisitions, 
correlated  and  harmonized  with  the  rest,  have  become 
"fixed"  and  hereditary.  The  older  and  more  important  they 
are  to  the  system,  the  greater  may,  in  general,  be  said  to  be 
their  fixity.  But  none  are  absolutely  permanent;  so  far  as 
perceivable  all  can  change,  and  probably  even  be  lost, 
under  new  conditions  favoring  or  demanding  a  change  or  a 
loss.  Races  are  therefore  not  permanent  but  changeable. 

Examples  of  changes  in  somatic  racial  characters  are  more 
or  less  clearly  perceivable  in  many  cases. 

The  Aryans  who  have  immigrated  into  India  since  per- 
haps 2000  B.C.  now  often  present  color  so  nearly  black  that 
nothing  hke  it  exists  in  any  other  late  branch  of  the  white 
race.  The  Ethiopians  of  Semitic  derivation  stand  next  in  this 
respect.  The  unmixed  Arabs  in  Arabia  and  Egypt  show  not 
seldom  a  rich  full  reddish  brown  color  of  their  whole  body, 
fully  equaling  that  of  the  American  Indian;  while  among 
higher  class  Arabs  the  skin  may  be  practically  white.  On  the 
other  hand  the  Lapp,  the  Eskimo  and  the  northwest  coast 
American  Indian  show  more  or  less  depigmentation  of  the 
skin,  particularly  of  the  body.  Without  mixture  some  of  these 
skins  approach  those  of  the  whites.  And  a  similar  phenom- 
enon is  manifest  here  and  there  among  the  upper  classes  of 
Japan  and  China. 

The  cephalic  index,  as  shown  by  Matiegka,  v.  Luschan, 
Parsons,  Fleure,  has  in  general  been  slowly  rising  dui'ing  the 
present  millenium  in  the  Slavs,  Germans,  the  English  and 
others.  The  average  stature  is  increasing  in  Holland,  Den- 
mark, Sweden,  Japan,  and  especially  in  the  United  States 
(See  Hrdlicka,  1925).  The  bulk  of  the  supraorbital  ridges, 
the  prominence  and  size  of  the  malars  and  angles  of  the 
lower  jaw,  the  size  of  the  jaws  and  teeth  as  a  whole,  are 
diminishing  in  the  civilized  races.  The  character  of  the  hair, 
the  nose,  orbits,  physiognomy,  the  bulk  of  the  body,  the 
relative  proportions  of  the  trunk  and  the  lower  limbs,  all  are 
changeable,  and  change  appreciably  here  or  there  within 
historic  times. 

Many  physical  features  are  slowly  changing  now  in  some 
peoples    as    may    perhaps    best    be    witnessed    among    the 


164  HUMAN   BIOLOGY 

American  whites,  but  also  among  the  American  Indians, 
and  probably  even  in  the  American  negroes. 

All  the  changes  of  racial  characters  observable  in  man 
appear  to  be  essentially  of  the  nature  of  adaptations  and 
responses  to  the  environment,  to  altered  habits,  to  abundance 
of  nutrition  and  to  favorable  or  unfavorable  hygienic 
conditions.  The  changes  as  a  rule  are  gradual.  There  is  no 
record  in  man  of  any  important  sudden  mutation. 

The  changeability  of  race  in  accord  with  conditions,  is  a 
fact  of  much  practical  importance.  It  shows  that  man  is  still 
quite  plastic,  and  that  he  therefore  is  capable  of  further 
favorable  evolution;  and  that  it  depends  largely  on  the 
conditions  to  which  he  is  subjected  as  to  whether  he  is  to 
advance,  and  what  direction  this  advance  is  to  take.  All 
of  which  is  of  basic  value  to  the  social  sciences  and  eugenics, 
as  well  as  to  anthropology. 

CLASSIFICATION    OF    HUMAN    RACES 

Attempts  at  a  classification  of  the  human  races  by  their 
physical  peculiarities  date  doutbless  to  times  when  men 
began  to  be  more  precisely  acquainted  with  types  of  human- 
kind different  from  themselves.  The  old  Egyptians,  as  shown 
by  Petrie  and  others,  recognized  and  depicted  on  their 
monuments  the  pygmy  and  the  regular  Negro,  the  Semites, 
Aryans,  and  some  Mongoloids.  The  Jews  and  the  Phoeni- 
cians, the  Greeks  of  Herodotus  and  especially  Alexan- 
der, and  surely  the  Romans  of  Caesar,  Tacitus,  Diodore, 
and  Pliny,  as  well  as  the  Chinese,  were  acquainted  with 
various  races  of  man  and  left  more  or  less  intelligible  accounts 
of  them;  while  the  Negroes,  Tartars  (''Huns")  and  Mongols, 
besides  various  secondary  strains,  have  been  well  known, 
since  Roman  times,  to  Europe  in  general. 

The  Christian  era  was  not  favorable  to  studies  of  man; 
but  a  fresh  impetus  to  these  was  given  by  the  reports  of 
various  travelers  in  distant  lands,  such  as  Marco  Polo, 
and  above  all  by  the  discovery  of  America,  particularly 
when  this  became  known  to  be  a  separate  continent,  occupied 
by  separate  people.  Yet  even  then  there  was  nothing  like  a 
serious  attempt  at  a  scientific  classification  of  the  human 


Homo  sapiens 


HUMAN    RACES  1 65 

races  until  near  the  middle  of  the  eighteenth  century. 
There  are  essays  by  Bernier  (1684),  and  Bradley  (1721), 
but  they  are  too  imperfect  to  have  any  real  value. 

The  first  effective  scientific  classification  of  humankind 
is  that  of  Linnaeus  and  appears  in  his  great  work  "Systema 
naturae"  (10  editions,  1735-60),  Man  belongs  to  the  class 
of  Mammals,  order  Primates;  he  forms  but  one  species, 
the  Homo  sapiens;  and  he  is  divided  into  the  following  races: 

Americanus 

Europaeus  • 

Asiaticus 
Asser  (Negro) 

Two  other  "races"  are  mentioned,  the H.  Jerus  (savage) 
and  the  H.  monstruosus  (monstrous),  which  probably 
connect  with  some  pecuhar  notions  of  the  past;  otherwise 
the  substance  of  the  classification  holds  true  to  this  day. 

The  next  most  important  racial  classification  is  that  of 
Blumenbach  (178 1).  This  is  based  on  that  of  Linnaeus, 
but  leaves  out  the  "savage"  and  the  "monstrous"  varieties, 
and  adds  the  Malay.  Blumenbach  recognized  five  main 
races,  the  Caucasian,  Mongoloid,  Malay,  American,  and 
Negro.  His  classification  prevailed  until  recent  time;  it 
has,  in  fact,  an  influence  to  this  day. 

Yet  even  Blumenbach' s  views  did  not  prove  entirely 
satisfactory,  as  a  result  of  which  there  arose  in  the  course 
of  time  almost  as  many  schemes  of  classifications  of  the 
races  of  man  as  there  were  students  of  the  question.  These 
schemes  differ  widely  as  to  the  number,  names  and  distinc- 
tions of  the  races.  As  to  number,  Virey  (1801)  recognized 
but  two  main  races  or  "species;"  for  Morton  (1839)  there 
were  twenty-two,  for  Huxley  (1870)  nineteen,  for  Topinard 
(1885)  nineteen,  for  Deniker  (1901,  1926)  twenty-nine,  for 
Burke  sixty-three.  (See  Waitz,  1863;  Tuttle,  1866;  Darwin, 
1871;  Topinard,  1885;  and  Deniker,  1901,  1926.) 

PRESENT   CLASSIFICATION 

The  classification  to  be  given  here  is  based  wholly  on 
somatology.  It  is  the  result  of  a  careful  consideration  of  the 


1 66 


HUMAN   BIOLOGY 


views  of  Others,  but  also  of  extensive  personal  knowledge  of 
peoples,  and  that  of  both  the  living  and  the  skeletal  remains. 
It  is  restricted  to  the  essentials. 


S" 


^^ 


o 


^^^ 


WHITES 

OR 

CAUCASOID 


< 

< 

o 

H 

O 


LAST  GLACIAL 
Fig.    I. 

The  Main  Races  or  Stems 

There  are  three  primary  Stems  or  Races  of  Man.  They  are 
the  White,  the  Yellow-brown,  and  the  Black;  or  the  Caucas- 
oid,  the  Mongoloid,  and  the  Negroid.  The  terms  are  all 
more  or  less  unsatisfactory,  but  they  are  the  best  we  have 
and  the  most  generally  understood.  (Fig.  i.) 

Characterization.  These  three  primary  stems  differ  from 
each  other  in  a  great  number  of  items,  but  no  feature, 
except  in  its  advanced  development,  is  the  exclusive  property 


HUMAN    RACES 


167 


of  any  one.  The  whites  and  the  negroes  stand  in  general  the 
farthest  apart.  The  yellow-browns  are  more  or  less  inter- 
mediate, but  mostly  nearer  to  the  white  than  to  the  negro. 
The  more  obvious  and  better  known  differences  of  the  three 
stems  are  given  in  Table  i : 


Table  i 
principal  characteristics  of  the  main  human  stems  or  races 


Whites 
(Caucasoid) 


Yellow-browns 
(Mongoloid) 


Blacks 
(Negroid) 


Color  of  skin  (in  the 
living) 


Color  of  hair . 


Color  of  eyes  (iris)  . 


Conjunctiva. 


Hair  of  the  head  .  .  . 


Beard . 


Hair  over  Body. 


Hair  in  Axillae  and 
on  Pubis 

Stature 


Head     (and    skull): 
Cephalic  index 


Height  of  Vault. 


Shape       (aside       of 
cephalic  index) 


Size     (relatively     to 
Stature) 


Essentially  "white" 
(bluish  or  pinkish 
white,  to  tan,  brown, 
and  even  near  black) 


Lightest  flax  to 
golden,  or  red, 
through  all  shades  of 
brown,  to  coal  black 


Pale  blue  to  deep 
blue,  greenish,  grey, 
and  all  grades  of 
brown 


Bluish  white  to  pearly 
white 


Rich,  long,  medium 
to  fine,  straight  to 
wavy,  to  curly. 

Cross-section  oval. 

In  males  tendency  to 
baldness  (under  nor- 
mal conditions). 

Tendency,  both  sexes, 
to  early  greying,  and 
greyness  often 

extreme  (pure  white) 


Moderate  to  rich  and 
long,  slightly  wavy 
to  loosely  curly, 
grows  plentifully  on 
sides  of  face 


Moderate       to       pro- 
nounced 


Moderate      to 
nounced 


pro- 


Moderate  to  tall   (no 
pygmies) 


Moderate  dolicho- 
cephaly  to  marked 
brachycephaly 


Moderate     to      high, 
(rarely  low) 


Great  variation 


Small  to  very  large 


Essentially  "yellow- 
brown"  (near- 
white,  to  leather  yel- 
low and  all  shades  of 
brown) 


Dark  reddish  black  to 
coal  black 


Medium  to  very  dark 
brown 


Yellowish     white     to 
reddish  dirty  yellow 


Rich,  long,  medium 
to  somewhat  coarse, 
straight,  to  slightly 
wavy. 

Cross-section  round- 
ish. 

Slight  tendency  to 
baldness. 

Greyness  but  moder- 
ate and  later  (than 
in  whites),  and  grey- 
ness generally  in- 
complete (yellowish- 
grey) 


Scanty  to  moderate, 
straight  to  slightly 
wavy,  no  beard  on 
sides  of  face 


None  or  slight 


None  to  moderate 


Short  to  tall  (occa- 
sional approach  to 
pygmies) 

Moderate  dolicho- 
cephaly  to  marked 
brachycephaly 


Low  to  high 


Considerable 
ation 


Small  to  large  (in 
many  groups  some- 
what smaller  than  in 
whites) 


Essentially  "black" 
(yellowish  brown,  to 
various  shades  of 
brown  to  full  shiny 
black) 


Coal  black  to  greyish 
black 


Darkbrown  to  black 


Yellowish  white  to 
very  reddish  dirty 
yellow 

Bushy  to  scant, 
medium  to  somewhat 
coarse,  thick  curls  to 
scattered  spirals. 

Cross-section  elliptic. 

None  or  but  slight 
tendency  to  baldness. 

Greyness  but  moder- 
ate and  later  (than 
in  whites),  and  grey- 
ness generally  incom- 
plete (iron-grey  or 
yellowish  grey) 


Moderate  to  fair, 
loosely  to  closely 
curly,  grows  moder- 
ately on  sides  of  face 


Slight   to   pronounced 
Moderate 


Very  short  to  very 
tall  (pygmies) 

Pronounced  dolicho- 
cephaly  to  meso- 
cephaly,  rarely 
brachycephaly 

Low  to  moderate 
(rarely  above  moder- 
ate) 


Form  characteristic, 
variation  limited 

Small  to  moderate 
(smaller  than  in 
whites) 


1 68 


HUMAN   BIOLOGY 


Table  i 

[Continued) 

Whites 
(Caucasoid) 

Yellow-browns 
(Mongoloid) 

Blacks 
(Negroid) 

Deformities  (Patho- 
logical) 

Rare  (mostly  various 
plagio-      and      acro- 
cepnalies) 

Very      rare      (mostly 
approaching       acro- 
cephaly) 

Frequent  (premature 
occlusion  of  sagittal 
suture,  with  conse- 
quent scapho- 
cephaly) 

Forehead 

Medium  to  high 

Generally    double, 
lateral 

Low  to  above  medium 

Low  to  medium 

Frontal  eminences. . 

Generally    double, 
lateral,    but    mostly 
less  marked  than  in 
whites 

Generally  single, 
median  _  (especially 
marked  in  children) 

Supraorbital    ridges 
(in  males) 

Submedium    to    pro- 
nounced 

Submedium    to    pro- 
nounced 

Slight  to  medium 

Glabellar  region 

Medium 

In  large  Asian  groups 
characteristically 
flattened 

Medium  to  beetling 

Nasion      Jcpression 
(in  males) 

None  to  deep,  mostly 
well  defined 

Shallow    to    medium, 
now    and    then    ill- 
defined 

Submedium  to_  deep 
"line"  depression 

Eyes:  Fissures 

Horizontal  to  slightly 
oblique 

Oblong,  more  or  less 
spindle-shaped 

Slightly  to   markedly 
oblique 

Horizontal  to  some- 
what oblique 

Eyes:  Visible  part  of 
eye-balls 

Oblong,     spindle     to 
almond  shaped 

More  rounded  (than 
in  whites  or  yellow- 
browns) 

Nose:       Height 
(prominence       of 
bridge) 

Medium  to  high 

Submedium  to  above 
medium 

Low  to  submedium 

Nose:  Breadth 

Medium  to  narrow 

Medium 

Broad 

Nasal  Index 

Lepto      (mostly)      to 
mesorhine 

Mesorhine,  in  general, 
Leptorhine          occa- 
sional (Eskimo) 

Mostly  mildly  dull 

Platyrhine 

In       skull:       Nasal 
borders 

Sharp 

Mildly  dull  to  very 
dull,  to  gutters 

In  skull:  Nasal  spine 

Well  developed  (espe- 
cially in  height) 

None   to   submedium 
(especially  in  height 

Moderate  to  small 

Malars 

Subdued      to      above 
medium 

Above      medium      to 
bulky  or  prominent 

Submedium   to   above 

medium 

Facial    prognathism 

None 

None  to  slight 

Slight  to  very  marked 

Alveolar        progna- 
thism 

None  to  moderate 

Moderate  to  marked 

Above  medium  to  very 
pronounced 

Lids 

Medium  to  thin 

Medium    to    slightly 
above 

Thick    to    very    thick 

and  more  or  less 
everted 

Teeth 

Small  to  medium 

Hoe-shaped      (mildly 
concave  buccally) 

Medium  to  large 

Medium  to  large 

Upper  incisors 

Shovel-shaped  (deeply 
concave    and    later- 
ally   bordered    buc- 
cally) 

Hoe-  to  occasionally 
shovel-shaped 

Chin 

Moderate    to    promi- 
nent 

Light       to       strongly 
developed 

Medium 

Medium    to    subdued 

Jaws. 

Medium       to       very 
strongly  developed 

Submedium     to     me- 

dium 

Face  as  a  whole 

Mostly  relatively  nar- 
row,  with   moderate 
cheek-bones          and 
angles 

Mostly   relatively 
broad,    with    promi- 
nent cheek-bones 

Breadth  and  features 
mostly  subdued 

Neck 

Medium  to  long 
In  prime,  shapely 

Medium 
Less  shapely 

Medium  to  long 

Body 

In     prime,      excellent 

proportions 

Hemispherical            to 
semi-conical 

Conical       to       semi- 
conical,      to      hemi- 
spherical   (espec.    in 
Malay) 

Conical,       to       rarely 

semi-conical 

Buttocks 

Shapely,  to  moderate 
steatopygy 

Less    shapely,     never 
steatopygy 

Shapely,   to   occasion- 

ally pronoun  ced 
steatopygy 

HUMAN   RACES 


169 


Table  i 

(Continued) 

Whites 
(Caucasoid) 

Yellow-browns 
(Mongoloid) 

Blacks 
(Negroid) 

Genitals:  Male 

Medium 
Nothing  special 

Medium 
Nothing  special 

Frequently            more 
muscular  than  stout, 
less  shapely,  and  will 
not  always  come  to 
apposition  in  stand- 
ing 

Less    shapely    and  of- 
ten slender 

Above  medium 

Genitals:  Female 

Occasional  hyper- 
trophy of  nymphae 

Thighs  (in  females) . 

Stout     and     shapely, 
and  in  standing  are 
in  apposition 

Mostly  less  stout  to 
lanky,  and  in  many 
of  the  more  slender 
not,  or  not  fully, 
in  apposition  when 
standing 

Shapely  and  full 

Mostly  moderate,  and 

less  shapely  than  in 
whites 

Hands     (relate 
largely  to  size  of 
body,     length     of 
limbs,       and       to 
function) 

Small  to  large 

Small  to  medium 

Predominantly  large 
(in  the  taller  negroes) 

Feet  (do.) 

Small         to         large, 
well  developed  arch 

Small  to  medium  well 
developed  arch 

Tend  to  large,  (in  the 

taller  negroes)  arch 
low,  tendency  to  nor- 
mally flat  feet 

Bones  of  the  skele- 
ton 

Bones  of  forearm  and 
leg    relatively    short 
to  medium 

Relative      length      of 
bones  of  forearm  and 
leg  medium  to  above 
medium      (as  _  com- 
pared with  whites) 

Curvatures   generally 
medium  ' 

Bones  of  forearm  and 
leg  relatively  long 

Curvatures     of     long 
bones      in      general 
medium 

Long  bones  mostly 
remarkably  straight 

Special 

Platymery  and  platy- 
cnaemy  rare 

Platymery  and  platy- 
cnaemy          frequent 
(espec.  in  the  Ameri- 
can Indian)  and  pro- 
nounced 

No       platymery       or 

platycnaemy 

AH    bones,    especially 
in    senility,    inclined 
to  arthritic  exostoses 

Rachitis  not  rare 

Less     inclination     to 
arthritic       exostoses 
than  in  whites 

Bones  marked  by  free- 
dom from  exostoses 
of  all  kinds 

Rachitis        rare        to 
absent 

Rachitis  rare  in  wild, 
frequent  in  semi- 
civilized    and    mixed 

Brain:  Size 

Medium  to  large 

Submedium  to  large 

Small      to       medium. 

rarely  above 

Brain:  Cerebral  con- 
volutions 

Medium  to  rich  and 
deep 

Submediumto   occa- 
sionally     rich      and 
deep 

Relatively  simple  and 
shallow,  to  but 
fairly  complex  and 
deep 

Disti  nguishing 
Mental      Charac- 
teristics     (to      be 
taken  with  reser- 

Nervous   as    well    as 
physical        vivacity; 
temperamental 

Mostly  less  vivacious 
and  temperamental 

Active  and  jolly, 
rather  than  ner- 
vously vivacious;  not 
very    temperamental 

vation,  urtil  more 
scientifically 
determined) 

Strong  ambitions  and 
sassions;        idealism 
lighly  developed 

Love    of    all    amuse- 
ment; love  of  sport, 
exploration,     adven- 
ture 

Ambitiousness        less 
developed;  emotions 
and      passions      less 
apparent,  even  when 
strong;    idealism    in 
general  moderate  to 
good 

Not  very  ambitious; 
emotions  and  pas- 
sions strong  but  jess 
rational;  idealism 
rather  weak 

Love  of  sport,  less  so 
of    exploration    and 
adventure 

Love  of  amusement 
and  sport  strong,  of 
exploration  weak,  of 
adventure  moderate 

Artistic 

Artistic 

Artistic  qualities 
above  moderate  in 
few  lines  only,  mainly 
pictorial,  decorative, 
and  industrial 

1 70 


HUMAN    BIOLOGY 


Table  i   (Continued) 


Whites 
(Caucasoid) 


Yellow-browns 
(Mongoloid) 


Blacks 
(Negroid) 


I  Music    highly    devel- 
I     oped 


Poetry   highly   devel- 
oped 

Egoism  and  individu- 
ality strong 


Subject  to  cares  and 
worries 


Industrious 


Religious    life    highly 
varied  and  developed 


Much  subject  to 
psychoses  and  other 
brain  affections 


Music  subdeveloped 


Poetry  subdeveloped 

Egoism  and  individu- 
ality less  pronounced 


Less,  in  general,  sub- 
ject _  to  cares  and 
worries 


Very    industrious 


Less  varied  or  intense 


Moderately  subject  to 
psychoses  and  brain 
affections 


Musical  ability  well 
represented,  but  not 
of  high  intellectual 
order 


Poetry  of  low  order 

Egoism  and  individu- 
ality not  strong 


Rather  careless  and 
free  from  lasting 
worries,  but  ridden 
by  superstitious  fears 

Not  very  or  steadily 
industrious 


Little  variety  or  devel- 
opment 

Moderately  subject  to 
psychoses 


MAIN    SECONDARY   RACIAL   GROUPS 

Besides  the  three  main  racial  stems,  there  are  four  large 
and  important  racial  groups  which  next  demand  attention. 
They  are  the  Austrahans,  the  Papuans,  the  Polynesians  and 
the  Finno-Ugrians  or  Semimongoloids. 

The  Australians  (and  related  Tasmanians)  are  a  fairly 
well-defined  race,  which,  according  to  all  indications,  is  an 
old  derivative  of  the  late  glacial  man  of  western  Asia. 
Notwithstanding  their  black  color  and  other  important 
features  their  basic  relation  is  with  the  white  stem,  though 
in  its  early  and  primitive  stages.  Outside  of  the  mixture  with 
late  Papuans  and  further  back  possibly  even  some  Negrito, 
their  hair,  beard,  physiognomy  and  even  their  blood  are 
closest  to  those  of  whites,  particularly  perhaps  those  of  the 
Dravidian  type,  though  often  much  more  primitive  somatolog- 
ically.  The  Tasmanians  may  safely  be  classed  now  as  a 
moderate  variant  of  the  Austrahans.^ 

The  Papuans  and  related  Melanesians  are  in  all  prob- 
abihty  of  mixed  origin.  Though  at  present  quite  typical, 
they  disclose  now  and  then  features  which  point  in  two 
main  directions:  to  an  old  type  such  as  that  of  the  original 
Australian,  and  to  the  Negrito.  There  seems  to  appear 
in  Melanesia  also  an  evidently  later,  perhaps  much  more 

'  (See  Cat.  Crania,  U.  S.  Nat.  Mus.,  No.  3,  1928.) 


HUMAN    RACES 


171 


recent  and  smaller  element  of  the  true  tall  negro.  Anthropo- 
logical knowledge  of  the  Melanesians  is  as  yet  far  from  as 
comprehensive  or  satisfactory  as  is  needed. 


WHITES 


Fig.  2. 

The  Polynesians,  though  also  of  a  mixed  origin,  constitute 
a  fairly  well-defined  secondary  race.  They  show  clear  marks 
of  a  large  caucassoid,  a  small  mongoloid  (Malay?),  and  a 
still  smaller  negroid  (Negrito?)  element  in  their  composition. 
In  Hawaii  there  is  also  some  late  admixture  with  the  tall 
negro,  and  throughout  there  is  considerable  recent  introduc- 
tion of  white  blood. 

The  Semimongoloids  {Finno-Ugrian  or  Ural-Altaic  peo- 
ples), occupied  sparsely,  until  the  tenth  century  a.d.,  a 
vast  territory  between  true  whites  and  the  true  Mongoloids, 
taking  in  most  of  European  Russia  and  the  large  parts  of 
Siberia  and  central  Asia.  They  embraced  the  original 
Finnish  tribes  along  the  Baltic,  the  old  natives  of  the  Volga, 
the  Huns,  possibly  the  original  Bulgars,  the  Tartars,  and 
various  more  or  less  nomadic  "Turanian"  or  "Turcic" 
units  in  Siberia  and  the  Turkestans.  According  to  various 
indications  they  possibly  included,  also,  the  original  Koreans, 


172  HUMAN   BIOLOGY 

and  may  have  been  related  to  the  pre-Japanese  populations 
of  Japan. 

This  vast  stock  has  never  hitherto  been  segregated  as  a 
separate  racial  unit,  yet  it  appears  to  necessitate  such  a 
separation.  Its  constituents  can  neither  legitimately  be 
classed  as  full  whites,  nor  as  full  mongoloids.  They  are 
intermediary,  but  evidently  not  mixbloods  merely. 
They  may  be  conceived  as  later  waves  of  evolving  humanity, 
than  those  of  the  truer  yellow-browns,  advancing  from 
Europe  eastward  during  the  late  Paleolithic  and  early 
Neolithic  times. ^ 

This  vast  and  loose  stock  has  become  greatly  thinned 
out  and  admixed  partly  with  whites,  partly  with  mongols, 
until  today  in  many  parts,  such  as  the  Baltic  States,  Hun- 
gary and  Bulgaria,  in  the  interior  of  Russia,  and  in  many 
parts  of  Siberia  as  well  as  in  central  Asia,  it  shows  mere 
remnants  or  traces. 

The  probable  relation  of  these  four  secondary  large  racial 
groups  to  the  main  stems  or  races,  is  shown  in  Figure  2. 

DAUGHTER-RACES 

Each  of  the  three  human  stems  or  main  races,  and  in  a 
smaller  measure  also  each  of  the  main  secondary  groups, 
has  in  the  course  of  time  differentiated  into  a  number  of 
newer  well-established  racial  units,  the  daughter-races. 

The  better  established  daughter-races  of  the  White  stem 
are,  in  brief:  The  Hamitic;  the  Semitic;  the  Mediterranean; 
the  Alpine;  and  the  Nordic.  Besides  these  truer  races  there 
are  several  additional  strains  in  this  large  stem,  such  as  the 
Dinaric,  East  Baltic,  Armenoid,  Turcic,  etc.,  but  these 
as  yet  are  not  sufficiently  well  defined  and  deserve  the  term 
of  sub-races  or  types  rather  than  races.  And  in  each  of  the 
larger  groups  there  are  a  smaller  or  larger  number  of  national- 
istic or  local  groups  that  represent  more  or  less  advanced 
nascent  types  or  races,  races  in  the  process  of  formation. 

The  main  daughter-races  of  the  Yellow-Brown  stem  are: 
The  Mongolic;  the  Malay;  and  the  American.  There  are 
also  a  number  of  subraces  and  of  old  mixture-types,  such  as 

^  See  Hrdlicka,  A.  The  peopling  of  Asia,  Trans.  Am.  Pbilos.  Soc,  60  : 
525   et.  seq,  1921;  9180.  The  peopling  of  the  earth,  ibid.,  65:  isoet.  seq.,ig26. 


HUMAN    RACES 


173 


the  palaeo-Asiatic  or  Americanoid,  the  Tungusic,  the  Aino, 
the  Khmer,  etc.,  in  Asia,  and  the  Eskimoan,  the  Maya- 
Toltecan,    and    the    Lagoa    Santa — Algonquian    (or    Uto- 


MEDITERRANEAN 


WHITES 
Fig.  3. 


Aztecan),  etc.,  in  America;  and  there  are  important  nation- 
alistic types  such  as  that  of  the  Chinese,  Japanese,  etc. 
Much  here  remains  to  be  cleared  and  defined  through  further 
studies. 

The  Negro  stem  occurs  in  two  main  races,  the  negroes 
proper,  and  the  pygmies,  and  the  latter  are  divided  into 
three  racial  groups,  namely  the  negrito,  the  negrillo,  and  the 
Bushmen-Hottentots. 

An  interesting  question  is  which  one  of  the  two  main 
subdivisions  of  the  negroid  stem  is  the  parental  one.  As  there 
are  no  indications  of  pygmies  in  the  human  ancestry,  it 
would  seem  that  these  short  peoples  are  secondary;  on  the 
other    hand    their    marked    subdivisions    and    the    greater 


MONGOLIC 


YELLOW-BROWNS 

Fig.  4. 


SIOUAN 


AMERICANS 


Fig.  5. 

fi74l 


HUMAN    RACES  I  75 

homogeneity  of  the  regular  negroes  point  to  a  greater 
antiquity  of  the  short  strains.  The  probabihty  is,  however, 
that  both  are  developments  from  an  older  stock  of  near 

NEGRITO  NEGRILLO  BUSHMEN  6C 

HOTTENTOTS  NEGRO 


NEGROIDS 

Fig.  6. 

medium  stature  and  less  pronounced  characteristics  than 
either  of  these  speciahzations. 

There  are  several  types  distinguishable,  but  not  well 
defined  as  yet,  among  the  regular  negro. 

Concluding  Remarks:  The  foregoing  gives  the  gist  of  human 
classification.  To  go  into  further  details  would  in  this  place 


176  HUMAN   BIOLOGY 

be  unprofitable,  and  also  more  or  less  uncertain.  There  is  a 
need  of  much  further  study  in  this  field,  and  that  by  experts. 
The  subraces  and  types  and  nascent  racial  entities  must  be 
determined  scientificially  country  by  country,  which  will 
take  yet  a  long  time  to  be  accomplished.  Within  late  years 
there  was  a  hope  that  the  agglutinin  tests  of  the  blood 
might  be  helpful,  if  not  decisive,  in  racial  classification, 
but  that  hope  has  in  a  large  measure  failed.  Recently  new 
and  more  thorough  chemical  tests  of  the  blood  (See  Am. 
J.  Phys.  Anthrop.,  1927.)  have  been  devised  and  may 
effect  more  in  this  direction.  Though  it  must  always  be 
remembered  that  human  races  are  variable  and  unstable 
units,  much  admixed,  merging  more  or  less  with  other 
racial  groups,  and  without  any  true  lines  of  demarcation, 
in  blood  or  any  other  particular. 

MIXTURE   OF   RACES 

Human  races  without  exception  are  freely  miscible,  which 
has  always  been  one  of  the  stronger  arguments  against  their 
being  true  species.  Human  intermarriage  has  now  been 
observed  in  all  parts  of  the  world,  and,  barring  cases  due  to 
purely  individual  causes,  there  are  no  instances  of  sterility, 
weakness  of  the  offspring,  or  eventual  extinction  of  the 
mixed  bloods. 

A  popular  fallacy  met  with  occasionally  to  this  day  in  the 
more  southern  parts  of  the  United  States,  is  that  the  prog- 
eny of  the  white  and  the  negro  will  not  survive  or  breed 
beyond  the  quadroon  or  at  most  the  octoroon.  Actual 
observation  has  completely  failed  to  sustain  these  opinions. 
It  may  be  said  unreservedly  that,  except  where  disease 
enters  into  the  case,  there  is  no  known  limit  to  the  fecundity 
of  the  white-black  progeny.  And  the  same  applies  apparently 
to  the  mixbloods  of  any  other  two  or  more  races. 

Another  widely  held  view  outside  of  science  is  that  the 
results  of  race  mixture  are  generally  bad.  This  view,  also, 
is  not  sustainable  by  critical  observation.  It  may  be  said, 
as  a  rule,  that  the  results  of  a  normal  union  of  two  healthy 
units  of  whatever  races,  followed  by  a  wholesome  care  to  the 
children,  will  result  in  a  normal  and  healthy  progeny.  If 
such  a  union  occurs  between  two  mentally  unequal  races, 


HUMAN    RACES  1 77 

such  as  the  white  and  black,  the  children  are  generally  an 
improvement  on  the  belated  parent,  though  not  equaling  the 
more  gifted  one.  But  the  case  is  not  seldom  comphcated  by 
prejudice,  social  ostracism,  poverty,  and  other  factors,  which 
may  .act  adversely  on  the  progeny  of  such  a  union.  In  many 
cases  affecting  the  whites  and  negroes  in  the  United  States, 
moreover,  the  union  has  been  a  clandestine  one,  between 
inferiors  of  both  sides,  and  frequently  aggravated  by  intoxi- 
cation; the  child  is  not  desired,  and  whether  at  home  or  in  an 
institution  is  brought  up  under  unfavorable  conditions.  It  is 
these  social  and  disgenic  agencies  that  frequently  affect  the 
negro-white  of  mixed  blood  and  give  him  a  complex  of 
inferiority. 

When  the  question  of  mixture  of  parts  of  the  same  main 
race,  such  as  the  White,  is  approached,  it  may  be  said  most 
positively  that  science  has  n^er  been  able  to  detect  any 
ill  results,  except  again  in  individual  instances  and  there 
through  collateral,  social  and  economic,  and  especially 
pathological  conditions. 

All  the  larger  units  of  the  white  race  are  composites.  The 
English  have  the  blood  of  their  neolithic  ancestors,  of  the 
Bronze  Age  invaders,  of  the  Mediterraneans,  etc.,  brought 
in  by  the  legions  of  Rome,  of  the  western  Germanic  immi- 
grants, of  the  Normans,  of  the  Gallic  and  other  French,  and 
of  all  the  later  immigration.  The  Germans  are  a  third 
Nordic,  third  Slav  and  third  Alpine.  The  French  are  a 
mixture  of  Gauls,  Alpines,  Iberians,  Mediterraneans  in 
general,  Franks,  Brythons,  Goths,  Basques,  etc.  The 
Spanish  have  Iberian,  Gallic,  Suabian,  Vandal,  Moor  and 
Basque  blood.  Even  in  Sweden  and  Norway  there  is  plain 
evidence  of  more  than  one  population.  A  wholesale  racial 
(white)  mixture  has  been  going  on  for  centuries  in  Europe 
and  in  many  other  parts  of  the  world,  above  all  and  more 
recently  in  America,  without  any  trace  of  damage.  To  look 
upon  such  mixtures  as  detrimental,  in  this  or  any  other 
country,  is  scientifically  unjustifiable.  The  biological  indica- 
tions, under  normal  conditions,  are  more  in  favor  of  than 
against  such  mixtures.  And  what  is  true  in  this  respect  of 
the  whites  applies  equally  to  the  yellow-browns  and  the 
blacks.  One  of  the  most  mixed  of  the  yellow-brown  groups 


lyS  HUMAN   BIOLOGY 

are  the  Japanese,  yet  they  are  about  the  most  virile  people 
of  the  Far  East. 

Extensive  and  what  may  be  called  normal  mixture  between 
the  negro  and  various  elements  of  the  white  race  (Egyptians, 
Arabs,  etc.)  has  taken  place  in  north  Africa,  from  Abyssinia 
to  Morocco  and  south  of  the  Sahara.  In  none  of  these 
territories  is  there  apparent  any  degeneration,  physical  or 
mental,  as  a  result  of  the  mixture.  Mentally  the  progeny 
shows  a  general  improvement  on  the  negro,  though  it  does 
not  evidently  reach  the  standard  of  those  who  have  admixed 
with  him. 

;;;  "equality"    of    RACES 

The  sum  of  the  average  characters,  physical,  physiological, 
and  psychological,  of  a  given  group  of  people,  whether  a 
family,  a  nation,  or  a  race,  forms  the  complex  standard  or 
general  quahty  of  the  group.  They  involve  the  normal 
appearance,  behavior,  and  all  other  manifestations  of  the 
group. 

These  standards  differ  from  race  to  race,  and  between 
some  races  they  are  very  material.  Their  study  has  occupied 
anthropology  from  its  very  beginnings,  yet  they  are  not 
yet  clearly  and  completely  determined  in  any  group. 
Which  is  especially  true  of  the  more  subtile  differences 
that  are  difficult  of  exact  evaluation,  the  foremost  among 
which  are  those  of  mentality. 

Due  to  these  defects  in  our  knowledge,  it  is  impossible  as 
yet  to  exactly  weigh  the  qualities  of  races  and  compare  them 
with  anything  approaching  precision.  And  it  is  due  to  this 
impossibihty  that  wide  differences  of  opinion  as  to  the 
equivalence  of  the  races  exist  and  can  not  easily  be  settled. 

The  general  and  most  deeply  ingrained  view  is  that  races 
are  no  more  equal  in  mentality  than  they  are  in  physique. 
This  opinion  is  partly  due  to  egoism  and  ignorance,  partly 
to  more  or  less  subconscious  feelings  due  to  accumulated 
bias  and  experiences,  and  only  slightly  and  exceptionally  to 
actual  thorough  scientific  investigation.  Aside  from  the 
universal  "group  spirit"  of  egoism,  the  matter  is  greatly 
complicated  by  the  social,  language,  religious  and  habit 
differences,  through  economic  factors,  and  by  the  universal 


HUMAN    RACES  1 79 

distrust  of  the  less  known.  Nevertheless  an  "intuitive" 
feehng  of  inferiority  or  superiority,  subjective  and  obj-ective, 
if  generahzed  and  based  on  a  prolonged  direct  experience 
of  one  group  with  another,  deserves  careful  attention. 

The  scientific  study  of  the  relative  values  of  races  has  two 
separate  resources.  The  first  is  the  circumstantial  and 
indirect  observations,  the  second  that  of  direct  evidence 
and  examination. 

The  circumstantial  and  indirect  evidence  of  a  race  is  that 
of  its  origin  and  antiquity;  of  its  environmental  history; 
of  its  cultural  past  and  present;  and  of  its  relative  position 
in  regard  to  and  esteem  by  other  races.  The  direct  evidence 
is  that  of  the  demography,  pathology,  character,  and 
potentiahties  of  the  race,  as  shown  under  trained  and 
unbiased  observation;  while  the  examinations  are  those  of 
modern  anthropology  and  psychology. 

The  indirect  evidence  leads  to  suggestive  inductions,  some 
of  which  are  already  known  to  be  facts. 

Races  that  have  been  subjected  for  a  long  time  in  their 
past  to  malarial  or  other  infections  and  survive,  must  have 
acquired  more  or  less  of  immunity  against  these  infections 
which  is  lacking  in  other  races — and  such  Medicine  has  found 
to  be  the  case.  Such  races  have  therefore  gained  a  certain  vital 
advantage,  but  this  only  at  the  cost  of  prolonged  suffering 
which  was  adverse  to  intellectual  advance.  It  is  an  old 
truism  that  a  malarial  region  breeds  few  talents;  and  the 
same  may  be  applied  to  all  chronic  blood  infections.  It  could 
not  be  expected  therefore  that  two  human  groups,  one 
living  in  a  wholesome  and  the  other  in  a  malarial  region  could 
progress  equally  and  retain  the  same  standards.  The  affected 
group  would  become  belated. 

The  development  of  intellectual  differences  would  similarly 
be  favored  by  non-pathological  factors  which,  on  one  side, 
would  lastingly  be  of  stimulative  or  favorable  nature, 
while  in  the  other  case  the  stimulation  would  be  largely 
lacking,  to  which  might  be  joined  unfavorable  affects  of 
various  nature,  such  as  the  development  of  repressive  Ideas 
and  habits  (superstitions,  slavery,  cannibalism,  etc.). 

All  these  conditions  have  been  realized,  particularly  as 
between  the  races  of  the  northern  temperate  zone  and  those 


l80  HUMAN   BIOLOGY 

of  the  tropics;  and  the  results  could  not  possibly  be  equahty, 
physical,  physiological,  or  intellectual.  In  broad  Hnes  it  is 
legitimate  therefore  to  speak  of  "advanced"  and  "belated" 
human  groups  or  races.  And  the  cultural  and  other  indirect 
evidence  sustains  this  assumption. 

As  to  direct  scientific  determination  of  the  differences 
between  races,  what  has  thus  far  been  accompHshed  is  in  the 
physical  hne.  Comparative  racial  physiology,  chemistry 
and  psychology  are  only  in  their  beginnings.  Of  the  physical 
studies  the  most  relevant  in  this  connection  are  those  of  the 
brain  and  the  skull,  or  the  head  in  the  Hving.  These 
researches,  too,  are  far  from  finished;  but  enough  has  already 
been  done  for  some  vaHd  conclusions.  These  are,  in  broad 
hnes  once  more,  that  within  the  same  stem  what  differences 
there  are  are  essentially  individual;  but  that  between  the 
moderate  zone  peoples  and  those  of  the  tropics,  or,  more 
particularly,  between  the  whites  and  the  blacks,  there  are 
differences  that  sustain  the  conclusions  arrived  at  through 
other  considerations. 

The  point  is  raised,  now  and  then,  that  what  differences 
there  are  between,  for  instance,  the  white  and  the  negro, 
are  differences  in  accomphshments  and  education,  rather 
than  those  of  potentiahties.  Should  this  mean  that  the  brain 
of  the  belated  group  is  capable  of  development,  the  prop- 
osition could  readily  be  assented  to  for  there  is  no  evidence 
or  probabihty  to  the  contrary.  But  there  appears  to  be  no 
possibility  of  estabhshing  the  thesis  that  the  brains  of  the 
belated  human  groups,  such  as  the  negro,  the  negrito,  the 
Bushmen-Hottentot,  the  Melanesians,  the  Australo-Tas- 
manians,  the  Veddahs,  the  Fuegians,  is  of  equal  potentiahty 
with  those  of  the  Old  American,  the  English,  Scotch,  Irish, 
French,  Germans,  etc.,  and  that  the  only  differences  are  in 
training,  enlightenment  and  opportunity. 

A  serious  question  with  which  anthropology  is  frequently 
confronted,  is:  What  are  the  indications  as  to  the  future 
of  the  belated  groups?  This  question  involves  much  more 
than  physical  anthropology,  more  even  than  anthropology 
in  general.  It  involves  pathology,  economics,  competition, 
adaptation.  The  answers  are  to  be  seen  wherever  the 
advanced  come  into  direct  contact  with  the  really  belated. 


HUMAN    RACES  l8l 


RACE    DEGENERATION 


Races  do  not  live  forever.  Just  as  the  whole  so  the  parts 
of  humankind  change.  They  differentiate  into  newer,  or 
daughter-races;  they  end  through  exhaustion  by  wars, 
famine,  disease,  the  remnant  merging  with  some  stronger 
group;  or  they  assimilate  so  much  of  other  blood  as  to  be 
changed  into  a  new  unit;  or  they  degenerate  mentally  and 
sink  into  long  dormant  states  in  which  they  may  perish,  or 
from  which  they  may  r.evive  for  a  further  course  of  active 
existence. 

In  human  history,  "race"  after  "race"  has  risen  to 
power  and  cultural  prominence,  only  sooner  or  later  to  go 
down  before  some  stronger  group.  This  up-hnger-and-down 
phenomenon  has  in  fact  up  to  the  recent  time  been  the 
invariable  rule.  Its  principal  cause  has  often  been  believed 
to  be  "race  degeneracy." 

If  mentahty  be  excluded,  no  such  degeneracy  in  any 
instance  can  be  detected  by  anthropologists.  The  physique 
of  the  purer  remnants  of  the  Old  Egyptians,  Syrians,  Arabs, 
Persians,  Greeks,  Romans,  Gauls,  Mongols  and  Mayas, 
is  seen  on  direct  examination  into  the  matter  to  be  as  good 
as  it  ever  was.  There  has  been  no  perceptible  physical 
degeneracy  in  any  of  these  cases.  Even  the  mixtures  left  by 
these  peoples  fail  as  a  rule  to  show  degeneracy. 

This  unexpected  reahzation  leads  to  the  search  for  somatic 
degeneracy  in  man  elsewhere,  which  leads  to  interesting 
results.  Physical  deterioration  appears  to  be  rare  and  hmited 
to  localized  groups.  It  seems  to  affect  mainly  the  stature 
and  bulk  of  the  body,  occasionally  also  the  strength. 

The  foremost  examples  of  stature  and  bulk  diminution, 
though  without  relative  weakening,  are  probably  the 
various  pygmy  groups,  particularly  the  negrillo  and  the 
negrito.  As  no  dwarfs  are  known  in  human  ancestry 
the  pygmy  condition  may  be  looked  upon  as  secondary.  But, 
while  its  origin  may  have  Iain  in  disgenic  influences,  the 
result,  that  is  the  pygmy  status  of  the  body,  may  perhaps 
be  conceived  more  properly  as  adaptation  or  speciahzation, 
than  degeneration.  There  are  many  analogies  to  this  in  the 
animal  kingdom.  And  the  same  principle  apphes  probably 


1 82  HUMAN   BIOLOGY 

to  Other  dwarf  or  shortened-stature  groups,  such  as  those 
of  America  (Mexico,  Venezuela,  Brazil).  For  outside  of 
their  smaller  stature  and  mass  these  groups  are  quite 
fecund,  and  able  to  cope  with  their  special  environments. 

Nevertheless  deterioration  proper  may  occasionally  be 
observed,  as  for  example  among  the  native  populations  of 
Java,  in  the  southern  Bushmen  and  Hottentots,  in  some  of 
the  Alpine  and  Appalachian  populations  in  Europe  and 
America,  in  parts  of  China  and  especially  of  central  and 
southern  India,  among  some  of  th^  American  Indian  tribes 
in  transitional  stage,  such  as  the  Osage,  southern  Ute,  and 
others  and  among  some  at  least  of  the  negro  communities 
in  America. 

In  all  these  instances  the  deterioration  is  seen  not  to  be 
"racial"  or  general,  but  to  apply  only  to  such  groups  and 
famihes  as  have  become  subject  to  unfavorable,  physically 
and  otherwise  degrading  conditions. 

Race  deterioration  is  therefore  a  conception  that  is  not 
sustained  by  science.  Deterioration,  where  present,  is  seen 
to  be  a  phenomenon  of  locahty  and  of  conditions,  but  not 
of  a  race.  It  may  extend  to  a  geographic  group,  a  social 
class,  a  tribe  perhaps,  but  never  as  far  as  discoverable  now, 
to  a  whole  race. 

A  temporary  deterioration  of  human  groups,  as  that  of 
individuals,  is  moreover,  mostly  "curable,"  and  is  often 
cured,  on  the  one  hand,  through  natural  ehmination  of 
those  affected  most  seriously,  and,  on  the  other,  through 
restitution  and  new  adaptations  of  the  remainder.  The 
beneficial  vis  mediatrix  naturae  acts  evidently  on  groups  as  it 
does  on  individuals,  and  where  deterioration  does  not 
surpass  the  limit  of  the  curable  it  slowly  restores  and 
strengthens,  until  a  "normal"  status  is  reached  once  more, 
adapted  to  and  mastering  the  particular  place  and  conditions. 

One  of  the  peoples  in  whom  such  restitution  under  more 
favorable  conditions  may  best  be  studied,  and  that  in 
various  parts  of  the  world,  are  the  Jews. 

A  physical  degeneration  of  a  race  is  therefore  a  notion  for 
which  it  is  difficult  to  find  a  substantial  foundation.  If 
traced  closely  the  supposed  degeneracy  resolves  itself 
generally  into  mental  affects  and  states,  which  in  cases  may 


HUMAN    RACES  I 83 

amount,  without  physical  concomitants,  to  actual  general- 
ized deterioration. 

REFERENCES 

Darwin,  C.  1871.  The  Descent  of  Man.  Num.  ed.,  Lond.  &  N.  Y. 
Deniker,  J.  190 1.  The  Races  of  Man.  Lond. 

1926.  Les  Races  et  les  Peuples  de  la  Terre.  Paris,  Masson. 
Haddon,  a.  C.  1925.  The  Races  of  Man,  and  Their  Distribution.  N.  Y.Milner. 
Hrdlicka,  a.  1924.  Catalogue  of  Crania.  U.  S.  N.  M.,  Nos.  i,  2,  3. 

1925.  Old  Americana.  Bait.,  Williams  and  Wilkins. 
NoTT,  J.  C,  and  Gliddon,  G.  R.  1871.  Types  of  Mankind;  and  Indigenous 

Races  of  the  World.  Num.  ed.,  Phila.,  1 854-1 871. 
Topinard,  p.  1885.  Elements  d'AnthropoIogie  gen.  Paris. 
TuTTLE,  H.  1866.  Origin  and  Antiquity  of  Physical  Man.  Boston. 
Waitz,  T.  1863.  Anthropologic  der  Naturvolker.  Esp.  in  augmented  English: 
Introduction  to  Anthropology,  Lond. 


PART  III.  MAN  AS  A  PHYSIOLOGICAL  UNIT 


Chapter  VIII 
THE  VITAL  UNITS  CALLED  CELLS 

E.    V.    COWDRY 

THE  human  body  is  made  up  of  a  mass  of  living  units, 
which  are  known  as  cells.  The  term,  cell,  is  a  misnomer 
and  a  relic  of  the  past,  yet  it  is  sanctioned  by  usage. 
Vital  units  are  not  empty  spaces,  as  the  word  suggests,  but 
filled  with  a  fluid  substance  called  protoplasm,  which  is  the 
basis  of  all  vital  activity.  Recognition  of  their  existence 
dates  back  almost  one  hundred  years.  The  cell  theory  intro- 
duced by  Schleiden  and  Schwann  (1838),  according  to  which 
all  living  things  are  built  up  of  cells,  has  played  a  funda- 
mental role  in  biology  and  medicine  comparable  in  impor- 
tance only  to  the  conception  of  the  existence  of  organic 
evolution. 

SIZE    AND    SHAPE    OF    CELLS 

In  size,  the  cells  of  our  bodies  are  very  small.  Among  the 
most  minute  are  the  white  blood  cells,  or  leucocytes,  about 
3^20  of  3,n  inch  in  diameter  and  altogether  too  tiny  to  be 
seen  with  the  naked  eye.  Human  eggs  are  the  largest  (3'^o 
inch)  and  are  just  visible  when  artificially  stained.  Since 
they  are  so  minute  the  number  of  these  vital  units  which 
make  up  the  body  of  a  man  weighing  about  155  pounds  is 
legion.  It  has  been  calculated  (Donaldson)  that  there  are 
about  26,500,000,000,000. 

The  shape  of  cells  is  highly  variable.  We  can  study  their 
form  in  several  ways.  One  method  is  to  examine  them  with 
the  microscope  in  the  still  living  state.  A  red  blood  cell 
which  carries  the  respiratory  pigment  called  hemoglobin, 
and  a  leucocyte,  viewed  in  this  way,  are  represented  diagram- 
matically  in  Figure  i  (a  and  b).  The  former  is  rather 
lens  shaped  but  looks  circular.  Within  the  leucocyte  may 
be  seen  an  irregular  lobated  structure,  known  as  the 
nucleus,  which  will  be  referred  to  again.  Some  cells  are 
much  elongated,   like  the  muscle  cell   (d),   and  the  nerve 

187 


i88 


HUMAN   BIOLOGY 


cell  (e).  If  the  conductile  process  of  the  latter  were  hkewise 
magnified  700  times  it  would  extend  downward  beyond 
the  hmits  of  the  page,  a  distance  of  1568  feet. 


Fig.  I.  Diagrams  to  illustrate  the  shape  of  different  kinds  of  cells. 
A.  Red  blood  corpuscle.  B.  Leucocyte,  c.  Flattened  cells  of  skin.  d.  Muscle 
cell.  E.  Nerve  cell.  f.  Group  of  pancreatic  cells.  (Magnified  700  times.) 

Another  method  is  to  preserve  the  cells,  cut  them  into 
very  thin  shces,  or  sections,  and  stain  them.  Such  sections 
can  be  made  1/25,000  inch  in  thickness.  A  section  through 
the  skin  is  illustrated  at  c  in  Figure  i.  It  shows  how  the 
cells  become  flattened  as  the  surface  is  approached.  Diagram 
F  illustrates  the  grouping  of  secreting  cells  in  the  pancreas. 

CELLS   BEHAVE    LIKE    INDIVIDUALS    IN    A    LARGE    COMMUNITY 

Despite  their  microscopic  dimensions,  the  cells  of  the 
body  have  a  certain  measure  of  independence  like  individuals 
in  a  large  community,  a  comparison  originally  made  by 
Virchow  (1858).  While  they  are  members  of  this  community 
they  grow,  reproduce  their  kind,  die  and  are  destroyed  by 


THE   VITAL    UNITS    CALLED    CELLS  1 89 

their  neighbors  or  by  the  fluids  surrounding  them.  Some 
by  virtue  of  their  occupations  have  a  shorter  life  than  others. 
There  is  reason  to  believe  that  the  hfe  of  leucocytes  in  the 
blood  stream  is  Hmited  to  a  few  days,  perhaps  even  to  a 
few  hours.  The  average  age  of  red  blood  cells  is  placed  at 
between  fifteen  and  forty  days,  while  nerve  cells  usually 
remain  alive  during  the  whole  Hfe  of  the  individual. 

During  the  life  of  any  man  or  woman  a  continual  replacement 
of  dead  cells  by  Hving  cells  is  provided  for.  The  rate  of  this 
replacement  is  naturally  conditioned  by  the  length  of  life 
of  the  cells  in  question.  Since,  as  we  have  said,  the  nerve 
cells  may  remain  functionally  active  as  long  as  the  individual 
lives  no  arrangement  is  normally  necessary  for  this  replace- 
ment, which  explains  the  lasting  injury  resulting  from  the 
death  of  nerve  cells  in  various  forms  of  paralysis  and  in 
organic  diseases  of  the  nervous  system.  The  expectation  of 
life  of  blood  cells  being  short  they  are  replaced  relatively 
quickly  by  the  production  of  new  cells,  chiefly  in  the  bone 
marrow  and  lymph  glands. 

But  one  of  the  most  interesting  reservoirs  of  new  life  (or 
rather  of  more  life)  in  the  body  is  found  in  the  deeper  layers 
of  the  epidermis.  Here  the  cells  multiply  rapidly  and  new 
cells  are  supplied  from  within  to  take  the  place  of  the  dying 
and  dead  cells  on  the  surface  which  are  continually  being 
cast  off".  It  is  a  true  saying  that  "while  we  are  in  life  we  are 
in  death"  because  this  protective  investment  of  dead  cells 
is  held  like  a  shield  between  the  living  delicate  tissues 
beneath  and  the  environment  outside.  It  is  a  kind  of  shock 
absorber. 

This  insulation,  however,  if  it  were  complete,  would  make 
us  totally  inert  and  unresponsive.  We  may  regard  the  cells 
of  our  sense  organs  as  sentinals  looking  out  through  specially 
constructed  windows  in  our  skin  so  that  they  may  perceive 
what  occurs  without,  and  signal  the  results  to  the  entire 
body  through  the  activity  of  certain  nerve  cells,  devoted  to 
conduction,  which  group  themselves  in  series  like  the  relay 
stations  in  a  telegraph  system.  The  analogy  is  a  close  one,  for, 
with  the  passage  of  each  nervous  impulse,  slight  electrical 
variations  take  place.  Happily  for  our  peace  of  mind  the 
receptive  cells  are  only  attuned  to  certain  changes  in  our 


1 90  HUMAN   BIOLOGY 

environment.  Sounds  occur  which  we  do  not  hear,  and 
hght  waves,  notably  the  ultraviolet,  strike  us  which  we 
cannot  see,  yet  influence  us  profoundly. 

The  cells  of  our  lungs  are  adapted  to  the  taking-up  of 
oxygen  and  the  giving-off"  of  carbon  dioxide.  The  cells  of  the 
ahmentary  tract  take  in  foods  and  those  of  the  kidney 
throw  out  waste  products.  Muscle  cells  enable  us  to  move  and 
work.  As  we  have  intimated,  some  cells  are  stationary  and 
others  highly  motile.  Sperms  in  search  of  eggs  to  fertihze 
may  travel  relatively  long  distances.  Leucocytes  in  the  blood 
stream  are  washed  hither  and  thither  but  may  actively 
migrate  through  the  vessel  walls  to  attack  invading  bacteria 
and  other  harmful  agencies.  They  may  be  likened  to  the 
policemen;  the  fat  cells  (which  store  potential  energy),  to 
the  bankers;  the  muscle  cells,  to  the  laborers;  the  gland 
cells  to  the  manufacturers;  and  so  on,  while  the  nerve  cells 
form  an  hereditary  ruling  class. 

Cells,  like  individuals,  through  their  special  tempera- 
mental activities  affect  their  surroundings.  In  the  body 
they  are  bathed  in  fluids  the  character  of  which  they  modify. 
These  fluids  are  comparable  to  the  atmosphere,  often 
polluted,  in  which  we  live.  Important  physiological  changes 
take  place  in  this  watery  environment  so  that  the  activity 
of  the  body  cannot  be  regarded  merely  as  the  unrelated 
sum  total  of  those  of  the  component  cells.  An  element  of 
integration  is  added  through  which  elements,  themselves 
diff"erent,  by  association  may  produce  something  wholly 
new,  the  character  of  which  could  not  have  been  forseen, 
just  as  oxygen  and  hydrogen,  two  gases,  on  combination 
make  a  different  substance,  water.  The  medium  about  the 
cells  may  not  remain  fluid,  but  may  be  converted  by  the 
cells  into  various  substances,  among  which  is  bone,  without 
which  we  would  be  spineless  creatures  indeed.  Cells  of  like 
character  are  grouped  into  what  we  call  tissues,  such  as 
cartilage.  The  tissues,  in  turn,  are  often  combined  to  form 
organs,  as,  for  example,  the  thyroid  gland,  which  on 
enlargement  produces  a  goiter. 

The  behavior  of  cells  is  dependent  upon  their  ancestry, 
their  environment  (or  training)  and  their  age.  Thus  the 
blood-forming  organs  produce  blood   cells  and  the  deeper 


THE   VITAL    UNITS    CALLED    CELLS  I9I 

layers  of  the  epidermis,  skin  cells,  not  muscle  cells  or  sex 
cells.  But  to  explain  all  the  differences  existing  between 
fully  developed  cells  on  the  basis  of  what  is  known  of  their 
heredity  is  difficult  because  all  of  them,  except  the  sex 
cells,  are  known  to  inherit  the  same  chromosome  complex. 
Here,  as  in  the  case  of  individuals,  it  is  customary  to  fall 
back  upon  the  environment  to  which  the  cells  must  become 
adapted  if  they  are  to  survive.  Young  cells  are  more  adaptable 
than  older  ones  and  are  immune  to  a  lot  of  degenerative 
changes  by  which  the  older  ones  are  afflicted;  they  are  also 
better  behaved;  fewer  of  them  become  criminals. 

It  is  a  kingdom  rather  than  a  democracy  because  the 
nerve  cells,  though  dependent  for  their  position  and  all  their 
worldly  goods  upon  the  others,  are  born  to  this  station,  not 
elected  to  it.  They  also  control.  The  arrangement  is  in  many 
respects  almost  Utopian. 

The  division  of  labor  leaves  nothing  to  be  desired.  There 
is  always  an  excess  of  willing  hands  (or  cells)  for  every 
basic  industry,  which  we  call  the  "physiological  reserve." 
This  is  exemplified  by  the  observation  that  we  can  live 
with  one  lung,  one  kidney  or  a  third  of  our  liver  substance. 
Yet  normally  there  is  no  unemployment.  The  labor  is 
equally  spread  among  the  cells  in  each  organ.  To  live,  the 
cells  must  work;  otherwise  like  individuals  they  atrophy 
from  disuse  and  die  as,  for  example,  when  labor  is  denied 
them  by  the  ruhng  class  of  nerve  cells.  When  the  task 
becomes  harder  they  increase  in  size  and  power,  again  like 
individuals.  But  this  happy  state  of  affairs  does  not  last 
forever.  Inevitably  the  kingdoms  rise  and  wane.  Death 
for  the  individual,  made  up  of  the  kingdom  of  cells,  is  a 
normal  process. 

Internal  disintegration  may  come  in  different  ways 
which  we  cannot  discuss  here.  Reference  may  be  made, 
however,  to  the  fact  that  the  cells  do  not  always  attend  to 
their  duties  as  they  should  do.  When  the  kingdom  has 
attained  the  height  of  its  efficiency  and  is  on  the  downward 
path  (middle  life  and  old  age)  some  of  the  cells  show  an 
alarming  tendency  to  shake  off  the  community  control 
which  has  been  molded  by  nature  during  millions  of  years, 
as  laws  have  been  formulated  by  the  experience  of  the  race. 


192  HUMAN   BIOLOGY 

Like  criminals  (see  Chapter  xv)  they  become  antisocial.  They 
grow  unrestrictedly,  invade  the  territory  belonging  to  the 
other  cells,  pilfer  their  food,  which  they  can  ill  afford  to 
lose,  and  so  completely  disrupt  established  conditions  that 
community  life  is  no  longer  possible.  But,  again  like  crim- 
inals, the  cells  do  not  embark  upon  this  mad  career  merely 
out  of  perversity.  Beforehand  they  are  injured  in  some 
way  which  we  do  not  at  all  understand.  They  are  the  victims 
of  some  intangible  kind  of  misfortune.  They  have  been 
designated  "anarchists"  by  tumor  specialists.  As  a  result 
of  their  activity  one  in  every  seven  of  us  dies  of  cancer 
(see  Chap,  xviii). 

It  is  a  curious  fact  that  although  death  in  one  way  or 
another  is  thus  inevitable  for  the  individual,  there  is  reason 
to  suppose  that  it  is  apparently  not  so  for  special  groups  of 
cells  removed  from  the  body.  Carrel  has  found  that  when 
cells  known  as  fibroblasts  are  taken  from  the  body  and 
cultivated  in  appropriate  media,  which  are  changed  at 
stated  intervals,  they  will  live  as  far  as  we  can  tell  at  present 
forever. 

MICROSCOPIC   STRUCTURE   OF   CELLS 

The  properties  of  living  cells  are  so  challenging  that  it  is 
not  surprising  that  many  attempts  have  been  made  to 
ascertain  the  structural  basis  of  life.  The  problem  is  obvi- 
ously a  difficult  one.  Thus  far  a  beginning  has  hardly  been 
made,  although  it  has  been  possible  to  recognize  certain 
elements  within  the  cell. 

A  gland  cell  of  the  stomach,  for  example,  when  magnified 
about  4000  times,  is  represented  in  Figure  2.  It  possesses  a 
very  flexible  and  delicate  cell  membrane  by  which  is  enclosed 
a  mass  of  watery  material.  In  it  may  always  be  seen  a  large 
oval  or  spherical  structure,  the  nucleus,  which  we  mentioned 
at  the  beginning  of  the  chapter.  It  was  discovered  by  the 
Englishman,  Robert  Brown,  in  1831.  The  fluid  contents  of 
the  cell,  other  than  the  nucleus,  are  known  as  the  cytoplasm. 
In  addition,  one  may  observe  various  granules  in  this  case 
consisting  of  mucus,  or  slime,  which  is  about  to  be  poured 
into  the  cavity  of  the  stomach. 


THE  VITAL   UNITS    CALLED   CELLS 


193 


All  other  cells  present  the  same  structural  pattern  in  so 
far  that  a  cell  wall  enclosing  liquid  material  may  be  dis- 
tinguished. The  nucleus  and  the  mitochondria  are  likewise 


o  ^o^-T^o 


Cell  membpdne 


tlitochondpiA 


-NucleAP  membrane 
Naclcap  contents 
■Nucleolus 


Fig.  2.  Diagram  of  mucus-secreting  cell  of  stomach.  (Magnified  about  1500 

times.) 

invariably  present.  Various  special  components  are  found, 
in  certain  kinds  of  cells.  Among  these  may  be  mentioned 
secretion  in  gland  cells,  droplets  of  fat,  contractile  fibrils 
in  muscle  cells,  and  pigment  in  the  cells  of  the  eye  and  often 
in  those  of  the  skin. 


THE    CELL    IS   BUILT    LIKE    AN    ENGINE 

We  can  liken  the  cell  to  an  engine  although  it  is  in  every 
respect  a  more  efficient  mechanism.  Despite  its  small 
size  it  is  able  to  bring  about  chemical  and  physical  changes, 
the  majority  of  which  it  is  impossible  to  repeat  outside  the 
body  even  with  the  aid  of  the  most  delicate  and  complicated 
apparatus. 

The  cell  takes  in  crude  materials  and  makes  them  into 
finished  products  (e.g.  adrenalin)  which  influence  other 
industries  or  tissues,  themselves  composed  of  cells.  As  a 
great  engine  is  organized  in  space  so  is  the  cell.  Gland  cells, 
for  instance,  devote  a  special  part  of  their  circumference  to 
the  reception  of  substances  from  the  blood  stream,  just  as 


194  HUMAN   BIOLOGY 

an  engine  has  a  mechanism  for  the  intake  of  materials  to  be 
used  in  it.  Gland  cells  discharge  from  their  opposite  extrem- 
ities the  products  which  they  make  (see  Fig.  2).  Engines 
have  attachments  for  the  utiHzation  of  the  power  generated. 
This  polar  organization  of  the  cell,  providing  for  intake  and 
output  and  other  attributes  which  it  is  unnecessary  to 
mention  here,  is  referred  to  as  polarity. 

The  motive  power  for  the  cell  and  the  engine  is  derived 
from  the  combustion,  or  burning,  of  material  coming  from 
without.  Both  of  them  are  transformers,  for  energy  is  not 
"created"  anywhere  in  the  known  universe,  it  is  merely 
changed  from  one  form  to  another.  Sunhght  acting  upon 
the  green  coloring  matter  of  plants  causes  in  some  mysterious 
way  the  hberation  of  oxygen  and  the  formation  of  compounds 
high  in  carbon  and  hydrogen.  These  substances  are  the 
fuel.  They  are  present  in  abundance  in  food  and  wood, 
coal  and  oil.  Combustion  is  brought  about  by  the  addition 
of  oxygen  from  the  air.  The  energy  developed  through  this 
process  of  oxidation  is  much  more  economically  used  in  the 
cell  than  in  the  engine,  for  in  the  latter  a  large  part  of  it  is 
lost  by  heat  radiation.  An  impulse  passing  along  a  nerve 
fiber  generates  heat,  but  only  to  about  1/1,000,000  of  a 
degree. 

Waste  is  discharged  from  the  cells  into  the  surrounding 
body  fluids  (see  Chap,  xi)  and  is  finally  eliminated  through 
the  lungs,  kidneys,  digestive  tract  and  skin.  In  the  engine 
it  is  carried  away  in  smoke  and  disposed  of  as  ashes.  If 
such  products  accumulate  instead  of  being  removed  in.  an 
orderly  way  both  machines  become  clogged  and  cease  to 
function. 

Electrical  forces  are  harnessed  in  the  cell  and  by  the 
engine.  Without  them  life  would  be  impossible.  In  cells 
they  are  usually  barely  detectable,  but  in  rare  instances 
these  vital  units  are  grouped  together  to  form  organs  which 
are  highly  charged  and  are  capable  of  giving  a  dangerous 
electrical  shock,  or  when  appropriately  connected  up,  to 
ring  a  bell  vigorously.  This  can  be  done  by  the  electrical 
organs  of  some  fishes.  Though  most  cells  are  rhythmical 
or  periodic  in  their  action  they  are,  as  we  have  intimated, 
never  electrically  at  rest.  By  rest  is  here  meant  complete 


THE   VITAL    UNITS    CALLED    CELLS  1 95 

inactivity,  which  would  be  death.  In  the  same  way  an 
engine,  or  any  mechanical  contrivance,  must  be  used  or  it 
will  deteriorate  and  become  unworkable. 

Cells  compare  favorably  with  engines,  especially  chemical 
ones,  in  still  another  respect,  namely,  the  much  greater 
speed  at  which  they  perform  their  duties.  Like  so  many 
things  connected  with  the  cell  we  understand  this  quahty 
but  imperfectly.  It  is  known,  however,  that  the  rate  of 
chemical  reactions  is  hastened  by  pecuhar  substances 
termed  enzymes,  which  are  of  many  kinds  and  are  widely 
distributed  in  Hving  matter.  While  they  accelerate  chemical 
changes  thej^  have  the  property  of  maintaining  their  integrity 
so  that  they  are  not  lost  in  the  process,  but  may  play  their 
part  again  and  again.  Catalysts  are  widely  used  in  industry. 

ObviousI}^  some  internal  mechanism  for  the  separation 
and  integration  of  chemical  changes  is  essential  for  the  cell 
and  the  engine.  If  the  contents  of  a  cell  are  stirred  up  and 
mixed  together  it  dies,  just  as  the  efficiency  of  any  engine 
would  be  destroyed  if  all  parts  of  it  were  thrown  together  into 
one  vast  heap.  Although  such  organization  undoubtedly 
exists  in  the  cell,  how  it  is  brought  about  in  a  space  so  small 
that  we  cannot  see  it  with  the  naked  eye  is  a  mystery. 

A  certain  amount  of  localization  and  separation  of  chemi- 
cal reactions  is,  however,  made  possible  by  the  elements 
which  are  microscopically  visible  in  the  cell.  Some  results 
of  recent  investigations  point  to  the  conclusion  that  chemical 
and  physical  changes  of  great  variety  are  prone  to  occur  at 
surfaces  of  separation  between  materials  of  different  char- 
acter. Referring  back  to  Figure  2,  it  will  be  seen  that  we 
have  to  consider  in  this  connection:  (i)  the  surface  of  the 
cell  itself;  (2)  the  surface  of  the  mitochondria;  and  (3) 
the  surface  of  the  nucleus.  The  contents  of  the  nucleus  are, 
in  addition,  shut  off  from  the  surrounding  fluid  cytoplasm 
in  which  it  is  embedded.  It  is  within  the  nucleus  that  the 
physical  basis  of  inheritance  is  mainly  concentrated.  This 
feature  of  segregation  and  protection  is  very  important  in 
the  preservation,  without  continual  modification,  of  heredi- 
tary characteristics  (see  Chap.  11).  The  nucleus  is  the  most 
acquisitive  living  element  known  to  us.  It  "hoards  like  a 
raven."  This  will  be  briefly  considered  later. 


196  HUMAN   BIOLOGY 

But  this  measure  of  organization  is  very  inadequate  to 
explain  even  in  a  halting  way  the  capabihty  of  the  cell  to 
manufacture  materials  and  to  live.  It  will  be  noted  that 
comparatively  large  stretches  of  the  cytoplasm  occur 
between  the  components  which  we  have  enumerated  in  which 
no  trace  of  structure  can  be  made  out,  notwithstanding  the 
fact  that  great  improvements  have  recently  been  made 
in  our  microscopes.  These  parts  are  marked  "x"  in  Figure  2 
and  constitute  what  is  known  as  the  ground  substance. 
It  is  made  up  largely  of  materials  in  the  colloidal,  or  glue- 
hke,  state.  They  are  of  gelatinous  consistency  and  hold  a 
great  deal  of  water.  Indeed  Hving  material  contains  about 
85  per  cent  of  water. 

LIMITS    OF    MICROSCOPIC  VISIBILITY 

With  ordinary  white  hght  and  direct  illumination  we 
can  distinguish  particles  about  1/250,000  of  an  inch  in 
diameter  provided  that  they  are  colored;  or  that  the  hght 
rays  when  passing  through  them  are  shghtly  deflected, 
in  other  w^ords,  that  they  exhibit  a  different  refractive 
index  from  the  ground  substance  of  the  cell  in  which  they 
are  observed.  We  can  push  back  the  limits  of  visibihty  a 
httle  further  (to  approximately  1/11,000,000  of  an  inch) 
by  employing  an  ultramicroscope.  The  principle  of  this 
piece  of  apparatus  is  that  the  hght  is  so  arranged  that  it 
strikes  the  cell  at  an  angle  to  the  direction  of  observation. 
We  recall  how  particles  of  dust,  otherwise  invisible,  flash 
out  in  the  presence  of  a  beam  of  hght  entering  a  darkened 
room. 

The  ultramicroscope  often  permits  us  to  detect  in  these 
"x"  areas  the  reflections  of  many  extremely  tiny  bodies 
which  often  dance  about  actively,  Hke  httle  twinkhng  stars, 
in  the  field  of  vision.  But  there  remain  regions  of  the  ground 
substance  in  which  even  these  particles  are  not  seen.  Methods 
of  ultraviolet  photography,  now  in  their  infancy,  may  even- 
tually help  us,  but  it  seems  unhkely.  Thus,  the  ground 
substance  in  which  these  various  structural  difi"erentiations 
are  formed  is  quite  beyond  our  ken.  Basically  it  must  be 
structurally  organized,  also,  but  we  have  only  nebulous  and 
ifl-conceived  theories  concerning  it  which  it  is  unprofitable 


THE   VITAL    UNITS    CALLED    CELLS  1 97 

to  mention  here.  This  much,  however,  we  do  know:  that 
the  cell  itself  is  a  complete  and  indivisible  unit.  Attempts 
to  distinguish  hving  and  non-living  elements  in  it  are  futile 
and  irrational. 

MULTICELLULAR  AND   UNICELLULAR  ORGANISMS    CONTRASTED 

Thus  far  we  have  stressed  one  of  the  principal  tenets  of 
the  cell  theory,  which  is  indeed  an  estabhshed  fact,  namely, 
that  the  body  is  a  sort  of  kingdom  of  cellular  units.  This 
apphes  not  only  to  man  but  to  almost  all  living  animals 
and  plants.  The  word  almost  is  inserted  because  forms  of 
hfe  exist  which  are  themselves  single  cells,  not  combinations 
of  cells.  We  at  once  think  of  the  bacteria  and  of  certain 
unicellular  animals,  the  Protozoa.  As  an  example  of  the 
latter,  the  parasite  of  malaria  is  cited.  There  is  a  distinct 
difference  between  the  life  of  a  unicellular  organism  and  a 
cell  inhabiting  our  own  body. 

Perhaps  this  may  be  made  clear  by  reference  to  Figure  3. 
A  unicellular  organism  like  an  ameba  (a)  has  'to  adjust 
itself  only  in  respect  to  its  own  environment  (e).  A  cell 
of  the  intestine  (i),  on  the  other  hand,  must  shape  its 
behavior  not  only  in  response  to  the  character  of  the  contents 
of  the  intestine  (e)  but  also  in  respect  to  neighboring  cells 
(c)  and  the  fluids  of  the  body  (f).  In  the  case  of  epithelial 
cells  of  the  skin  the  contact  with  adjacent  cells  is  often 
not  merely  the  close  approximation  of  like  surfaces.  There 
may  be  continuity  of  living  substance  across  specially 
developed  bridges  which  pass  from  one  cell  to  another. 
Cellular  activity  may  also  be  governed  by  nerve  fibers 
terminating  on  their  surfaces  so  that  stimuli  originating 
in  other  parts  of  the  body  impinge  upon  them.  The  associa- 
tion with  the  body  fluids  is  a  complex  matter  involving  the 
transport  of  substances  of  many  kinds  to  and  from  the  cell. 
It  is  interesting  to  note  that  we  have  among  these  the 
so-called  chemical  messengers,  or  hormones,  produced  by  the 
ductless  glands,  and  probably  by  other  cells  not  recognized 
as  glandular  in  nature.  Through  their  action  one  cell  may 
influence  another  far  removed  from  it.  A  free  living  pro- 
tozoan or  a  bacterium  is,  therefore,  not  strictly  homologous  ^GilC/O 

OS 


198 


HUMAN    BIOLOGY 


to  a  cell  existing  in  a  multicellular  aggregate.  It  has  more 
individuality  and  is  less  bound  down  by  the  conventions 
under  which  it  lives. 


Fig.  3.  Comparison  of  amcba  and  cell  of  intestine. 

An  ameba  (a)  must  adjust  itself  to  its  environment  (e).  A  cell  of  intestine 
(i)  must  react  to  its  environment  (e),  neighboring  cells  (c  and  c')  and  fluids 
of  body  (f). 


ALL    CELLS    ARE    SAID   TO    DEVELOP    FROM    PRE-EXISTING 

CELLS 

Another  postulate  of  the  cell  theory  is  that  all  cells 
originate,  or  develop,  only  from  preexisting  cells.  No 
exception  to  this  generalization  has  ever  been  observed. 
But  its  unqualified  acceptance  involves  the  further  assump- 
tion that  life  commenced  at  some  very  remote  epoch  when 
the  primordial  cell  was  first  built  up  from  presumably 
lifeless  components  and  that  cells  do  not  arise  in  this  way 
at  the  present  time.  As  Wilson  has  clearly  said  life  "is  a 
continuum,  a  never  ending  stream  of  protoplasm  in  the  form 
of  cells,  maintained  by  assimilation,  growth  and  division. 
The  individual  is  but  a  passing  eddy  in  the  flow  which 
vanishes  and  leaves  no  trace,  while  the  general  stream  of 
life  goes  forward."  Though  this  is  what  is  always  observed, 
it  is  conceivable  that  exceptions,  quite  unsuspected,  may  in 


THE   VITAL   UNITS    CALLED   CELLS  1 99 

rare  cases  occur.  If  it  is  literally  true  that  life  once  "evolved" 
and  that  the  process  of  creation  has  never  been  repeated 
the  most  primitive  cells  now  known  to  us  or  their  descendants 
must  have  persisted  without  evolutionary  change  for  a  very 
long  time.  This  would  mean  that  they  constitute  a  self- 
perpetuating  reservoir  of  Hving  forms  arising  from  others 
hke  them  which  is  not  replenished  by  the  creation  of  new 
forms  from  inanimate  material. 

It  is  interesting  to  note  that  certain  disease-provoking 
agents  exist  which  are  not  cellular  in  structure.  Some 
investigators  believe  them  to  be  living,  while  others  think 
them  to  be  dead.  In  this  category  are  placed  the  iruses 
(literally  poisons)  of  chicken  pox,  rabies,  common  warts 
and  certain  other  infective  diseases.  They  are  too  small  to 
be  seen,  yet  hke  living  cells  they  are  capable  of  unhmited 
multiphcation,  or  more  correctly,  of  increase  in  amount, 
if  each  ultimate  particle  is  not  an  individual  unit  susceptible 
of  division  to  form  two  others  like  it.  The  viruses  have  never 
thus  far  been  found  to  develop  de  novo,  that  is  to  say  in 
the  absence  of  preexisting  viruses.  They  can  only  increase 
in  intimate  association  with  hving  cells,  from  which  they 
may  have  arisen  in  the  first  place.  To  determine  just  what 
they  really  are  is  one  of  the  most  captivating  problems  in 
cytology. 

CELLULAR   BASIS    OF    INHERITANCE 

But  it  is  in  cell  multiphcation,  and  in  the  associated 
phenomena  of  inheritance,  that  we  have  one  of  our  greatest 
riddles.  It  would  seem  a  simple  matter  to  ascertain  why  a 
cell  divides  to  form  two  others  like  it,  but  it  is  not  so.  Some 
of  the  changes  that  occur  we  can  observe  though  we  cannot 
begin  to  explain  them.  They  are  not  always  alike  and  there 
is  still  some  difference  of  opinion  in  regard  to  details  but 
the  general  process  is  represented  very  diagramatically  in 
Figure  4. 

A.  A  cell  just  before  division  is  represented.  In  it  the 
distinctive  nuclear  material,  chromatin,  is  illustrated  dis- 
tributed in  the  space  within  the  nuclear  membrane.  Just 
above  the  nucleus  two  granules  may  be  seen,  usually  referred 


200 


HUMAN   BIOLOGY 


to  together  as  a  diplosome.  The  cytoplasmic  material  tends 
to  be  radially  arranged  about  the  diplosome  which  must  be  a 
dynamic  center  of  some  kind. 


Fig.  4.  Schematic  representation  of  cell  division. 

A.  Resting  cell  with  diplosome  just  above  nucleus,  b.  Separation  of  two 
centrosomes  of  diplosome.  Spireme  formation  within  nucleus,  c.  Longitudinal 
division  of  spireme,  d.  Chromosomes  formed  from  each  half  of  spireme  arranged 
on  opposite  sides  of  equator,  e.  Groups  of  chromosomes  migrate  apart  and 
lose  tiieir  distinct  outhnes.  Groove  appears  about  equator  of  cell.  f.  Groove 
deepens  and  pinches  originally  single  cell  into  two. 


B.   The   first  change  consists  of  a  concentration  of  the 
chromatic  substance  into  a  long  and  tortuous  thread  or 


THE   VITAL    UNITS    CALLED   CELLS  201 

spireme.  At  the  same  time  the  diplosome  divides  giving 
rise  to  two  centrosomes  which  separate  and  migrate  in 
opposite  directions. 

c.  The  spireme  sphts  longitudinally  throughout  its  length. 
This  is  important  because,  if  the  hereditary  determinants 
occupy  a  definite  Hnear  arrangement  in  the  substance  of 
the  spireme,  as  they  appear  to  do,  it  provides  for  their 
quahtatively  equal  separation  into  two  parts. 

D.  The  double  spireme  now  becomes  segmented  into  a 
series  of  pairs  of  rod-Hke  bodies  called  chromosomes.  The 
nuclear  membrane  disappears;  the  centrosomes  move  further 
apart.  The  chromosomes  become  disposed  in  such  a  way 
that  those  formed  from  each^half  of  the  spireme  are  placed 
on  opposite  sides  of  a  plane  known  as  the  equator  of  the 
cell  and  represented  by  a  dotted  hne. 

E.  The  groups  of  chromosomes  separate  and  then  fuse 
together  losing  their  discrete  outhnes.  A  circular  groove 
appears  around  the  equator  of  the  cell  and  gradually  deepens. 

F.  Finally  the  masses  formed  from  the  chromosomes 
become  enclosed  in  nuclear  membranes  and  the  groove 
pinches  the  originally  single  cell  into  two  cells  which  are 
qualitatively  similar  as  far  as  their  nuclear  components 
are  concerned. 

DETERMINATION   OF    SEX 

A  fundamental  difference  has  been  discovered  in  the 
chromosomes  of  male  and  female  sex  cells.  The  former 
originally  contain  one  x,  or  sex,  chromosome  which  is  often 
larger  than  the  others  and  easily  identified;  while  the  latter 
possess  two  of  them.  As  the  sperms  and  eggs  mature  the 
number  of  chromosomes  in  each  is  reduced  by  one  half, 
because  they  are  later  to  combine  to  produce  tissue  cells 
with  the  whole  number.  This  means  that  half  of  the  males 
contain  an  x  chromosome  and  that  the  other  half  do  not, 
further,  that  each  and  every  female  has  now  one,  in  place  of 
the  original  two.  On  fertilization  there  are  two  possibilities 
expressed  by  the  following  equations. 

1 .  Egg  X  +  Sperm  x  =  individual  2X,  a  female 

2.  Egg  X  +  Sperm  =  individual  ix,  a  male 


202  HUMAN   BIOLOGY 

The  first  is  that  the  egg  is  fertihzed  by  a  sperm  carrying 
one  X  chromosome  so  that  an  individual  results  which  has 
two  X  chromosomes  and  is  a  female.  The  second  is  that  the 
egg  is  fertilized  by  a  sperm  with  no  x  chromosome,  so  that 
the  resulting  individual  possesses  only  the  one  x  chromosome 
contained  in  the  egg  and  is  therefore  a  male. 

The  determination  of  sex  is,  however,  not  so  simple  as  it 
appears  to  be  from  these  equations.  Many  factors  enter  in  to 
modify  the  process  which  we  do  not  understand.  Some  of 
them  may  be  environmental  and  nutritional.  Gradations 
between  maleness  and  femaleness  occur  and  some  individuals 
may  be  both,  that  is  hermaphrodites.  Though  the  chromo- 
somes may  contain  the  physical  basis  of  heredity  we  are 
profoundly  ignorant  as  to  what  it  actually  is.  Modern  chem- 
istry does  not  enhghten  us  on  this  point.  Inheritance  of 
some  characters  through  the  cytoplasm  of  the  egg  is  a 
possibiHty  that  has  been  much  discussed. 

THE    SCIENCE    OF   CYTOLOGY 

The  science  which  deals  with  cells  is  called  appropriately 
cytology.  The  cytologist  is  concerned  with  the  smallest 
visible  things,  the  astronomer  with  the  largest.  Yet  in  a  sense 
this  science  stands  at  the  head  of  the  hst  because  it  is  a 
kind  of  superstructure  built  upon  the  other  sciences,  which 
are  said  to  be  more  fundamental.  The  cytologist  must 
avail  himself  of  advances  in  the  more  easily  studied  fields 
of  physics  and  chemistry,  but  in  doing  so  he  has  to  b^  very 
cautious  because  there  is  always  the  question  as  to  how  far 
discoveries  in  these  sciences  may  be  applied  in  the  inter- 
pretation of  vital  processes  occurring  largely  out  of  his 
reach  in  living  cells.  But  the  reverse  does  not  hold;  the 
physicist  and  the  chemist  may,  and  often  do,  forge  right 
ahead  in  their  researches  without  taking  into  consideration 
in  the  least  the  activities  of  living  matter.  It  is  almost 
invariably  dead  material,  the  reactions  of  which  are  more 
definitely  predictable,  to  which  they  give  exclusive  attention. 

Cytology  is  also  the  meeting  place  or  the  center  of  integra- 
tion of  related  sciences.  The  biologist  and  the  bacteriologist, 
the  physiologist  and  the  pathologist  all  contribute  material 
of  the  utmost  importance  to  our  knowledge  of  cells.  Evidently 


THE   VITAL    UNITS    CALLED    CELLS  203 

the  cytologlst  must  be  broadminded  and  friendly  cooperation 
is  essential  for  his  success.  He  is  obhged  to  invoke  assistance 
on  all  sides.  Through  experience  he  usually  acquires  a  pro- 
found respect  for  the  capabilities  of  these  vital  units  and  an 
appreciation  of  the  saying  that  "Nature  moves  in  mysterious 
ways  her  v^onders  to  perform."  He  is  distrustful  of  the 
simple  cut  and  dried  explanations  sometimes  offered  by 
his  colleagues  in  other  branches  of  science.  It  is  a  curious 
paradox  that  those  investigating  vital  phenomena,  faced 
as  they  always  are  by  the  unknown  and  unpredictable, 
are  much  less  ready  to  accept  bhndly  the  existence  of  super- 
natural deities  or  controlhng  powers  than  are  the  astrono- 
mers, physicists  and  mathematicians.  When  committees 
are  appointed  to  report  on  the  relation  of  science  and  reli- 
gion it  is  almost  invariably  workers  in  the  exact  sciences 
who  take  the  lead  in  assuring  the  laity  that  the  two  Hnes 
of  thought  and  action  are  fully  compatible  and  reconcilable. 

For  those  who  would  understand,  even  in  a  halting  way, 
what  hfe  is,  enough  has  perhaps  been  said  to  indicate  the 
interest  which  attaches  to  these  elementary  vital  units 
which  are  the  highly  adaptable  building  stones  of  the  bodies 
of  all  plants  and  animals.  To  the  practical  minded  it  may 
be  worth  while  to  cite  a  few  examples  of  how  profoundly 
the  study  of  cytology  has  influenced  human  welfare. 

Of  all  the  cells  of  the  body  the  most  easily  examined  are 
those  of  the  blood.  Reference  was  made  at  the  beginning 
of  this  chapter  to  the  white  blood  cells,  or  leucocytes. 
A  few  minutes  devoted  to  their  study  is  often  sufficient  to 
return  a  definite  verdict  as  to  whether  an  operation  for 
appendicitis  should  be  undertaken.  Similarly  observation 
of  the  red  blood  cells  gives  information  which  helps  to  tell 
whether  a  patient  is  suffering  from  a  simple  secondary 
anemia  or  from  the  dreaded  disease  known  as  pernicious 
anemia,  which  latter  is  now  happily  greatly  improved  by 
the  administration  of  liver  extract.  When  a  tumor  is  dis- 
covered and  the  surgeon  while  operating  comes  to  suspect 
that  it  may  be  a  cancer,  all  he  has  to  do  is  to  arrange  for 
the  cytological  examination  of  a  small  fragment.  In  a  few 
minutes,  while  the  patient  remains  under  anesthesia,  he 
is  told  with   considerable   accuracy,    from   the   appearance 


204  HUMAN   BIOLOGY 

of  the  cells,  whether  the  overgrowth  is  benign  or  mahgnant. 
In  the  latter  case  he  is  dealing  with  a  cancer  and  he  must 
remove  in  addition  to  the  mass  itself  a  large  amount  of 
the  surrounding  tissue  to  prevent  recurrences  if  at  all 
possible.  Cytological  studies  on  certain  parts  of  the  pancreas, 
termed  the  islands  of  Langerhans,  in  human  diabetes  and 
particularly  in  the  same  disease  experimentally  produced 
in  animals  led  directly  to  the  recent  discovery  of  insulin,  a 
substance  which  has  given  a  new  lease  of  life  and  usefulness 
to  thousands  of  sufferers  whose  future  otherwise  would  have 
been  hopeless.  In  fact  nothing  further  need  be  said  in  favor 
of  well-regulated  animal  experimentation.  Persons  who 
really  desire  to  influence  human  reactions  for  the  better 
both  in  health  and  disease  will  readily  understand  how 
important  it  is  not  to  study  the  body  as  a  whole  vaguely, 
but  rather  to  base  the  investigations  upon  the  behavior 
of  the  constituent  vital  units  of  which  the  body  is  built, 
in  other  words  to  get  down  to  fundamentals. 

REFERENCES 

CowDRY,  E.  V.   (Editor)    1924.  General  Cytology.  Univ.  Chicago  Press.  A 

cooperative  book  written  by  13  authors.  General  principles  underlying 
cellular  structure  and  function. 
CowDRY,  E.  V.  (Editor)  1928.  Special  Cytology.  N.  Y.,  Hoeber.  A  cooperative 

book  written  by  35  authors.  Special  activities  of  the  cell  in  health  and 

disease. 
Sharp,  G.  L.  1927    Introduction  to  Cytology.  Ed.  2.,  N.  Y.  McGraw  Hill. 

Written  chiefly  from  the. botanical  point  of  view. 
Wilson,  E.  B.  1925.  The  Cell  in  Development  and  Inheritance.  Ed.  3.,  N.  Y., 

Macmillan. 


Chapter  IX 
THE  RELATION  OF  CELLS  TO  ONE  ANOTHER 

Alexis  Carrel 

BIOLOGY  deals  with  problems  of  a  far  more  complex 
nature  than  those  of  any  other  natural  science. 
The  solution  of  some  of  these  problems  is  not  yet  in 
sight.  As  their  subject  matter  hes  on  difficult  and  dangerous 
grounds  at  the  frontier  of  science  and  philosophy,  it  cannot 
easily  be  brought  into  the  experimental  field.  Such  is  the 
question  of  the  manifoldness  and  the  unity  of  the  organism. 
We  know  that  every  human  being  is  composed  of  bilHons 
of  cells  aggregated  into  tissues  and  organs,  and  that  each 
cell  is  constituted  of  an  immense  number  of  smaller  elements. 
As  the  number  of  permutations  possible  between  the  minute 
components  of  the  cells  and  between  the  cells  themselves 
is  practically  infinite,  every  individual  differs  from  any 
other  individual  who  has  ever  lived,  and  is  an  unique 
event  in  nature.  In  spite  of  his  extreme  complexity,  the 
human  individual  is  an  harmonious  whole.  His  specific 
characteristics  come  from  the  enormous  development  of  the 
cerebral  system  and  the  appearance  of  the  mind.  Memory, 
conscience,  and  personality  are  the  ultimate  expressions  of 
the  highest  organization  that  a  cell  community  has  ever 
evolved.  It  is  through  the  association  of  myriads  upon 
myriads  of  nervous  cells  that  the  most  prodigious  form 
of  energy  existing  in  the  world  manifests  itself. 

The  processes  which  bring  about  and  maintain  the  whole- 
ness of  the  organism  seem  to  be  purposeful.  This  character- 
istic is  apparent,  not  only  in  the  formation  of  the  body 
from  the  ovum,  but  also  in  the  regenerative  mechanisms 
which  cause  a  lost  part  of  an  organ  to  grow  again  or  a  wound 
to  heal.  It  is  also  present  in  the  processes  which  reestablish 
the  equilibrium  of  the  body  after  it  has  been  disturbed. 
These  adaptive  mechanisms  are  numerous.  For  instance, 
if  one  kidney  is  removed,  the  other  enlarges.  When  the 
axis  of  a  limb  is  modified  by  the  defective  repair  of  a  fracture, 

205 


206  HUMAN   BIOLOGY 

the  architecture  of  the  bone  itself  becomes  changed,  and  the 
trabeculae  orient  themselves  according  to  the  new  Hnes  of 
stress.  Through  a  more  complex  process,  the  bacterial 
invasion  of  the  body  is  opposed  by  substances  which  develop 
within  the  tissues  and  lead  to  the  destruction  of  the  foreign 
elements.  It  appears  that  any  factor  tending  to  disturb  the 
physiological  equilibrium  determines  a  reaction  which 
opposes  this  factor,  as  happens  in  the  inorganic  world, 
according  to  the  Le  Chateher  principle.  Formative,  regenera- 
tive and  adaptive  processes  bring  about  or  maintain  the 
wholeness  of  the  organism,  as  if  the  building-up  and  preser- 
vation of  this  wholeness  were  their  end.  They  are  probably 
the  different  aspects  of  a  single  principle.  This  principle  seems 
to  group  and  direct  in  a  purposeful  way  the  processes  which 
are  instrumental  in  producing  the  unity  of  the  organism.  Each 
event  is  mechanically  related  to  an  antecedent  event  which 
we  may  call  its  c^se.  But  the  causal  events  themselves 
appear  to  be  linked  together  in  a  teleological  manner. 
The  Aristotelian  conception  of  efficient  and  final  causes 
satisfactorily  expresses  what  seemingly  happens  in  the 
organism. 

It  is  obvious,  however,  that  this  conception  does  not  help 
us  to  understand  the  mechanism  of  the  simultaneous 
plurality  and  unity  of  the  organism.  The  nature  of  the 
purposeful  processes,  at  which  students  of  nature  have 
wondered  for  ages,  has  remained  utterly  unknown.  In 
spite  of  the  great  difiiculty  of  the  problem,  we  are  irresistibly 
compelled  to  delve  into  the  mystery  of  the  constitution  of 
the  body  and  the  semblance  of  a  driving  intellect  within 
a  community  of  tissue  cells.  So  far,  this  search  has  been  in 
vain.  But  it  will  never  cease,  because  human  beings  will 
again  and  again  attempt  to  unveil  the  secrets  of  their  nature. 
Even  if  the  ultimate  goal  is  never  reached,  such  a  study 
may  become  of  practical  significance.  It  is  well  known 
that  the  quality  of  a  human  being  depends  largely  on  the 
perfection  with  which  his  component  parts  are  coordinated. 
If  the  factors  that  control  the  building-up  of  organs  and 
tissues  during  embryological  development  and  also  those 
that  determine  the  hereditary  characteristics  were  discovered, 
it  would  become  possible  artificially  to  improve  the  quality 


THE    RELATION   OF    CELLS   TO   ONE   ANOTHER  207 

of  human  beings.  Such  knowledge  would  be  still  more 
important  for  the  future  progress  of  medicine.  Today,  the 
cure  of  disease  depends  almost  entirely  on  the  spontaneous 
power  of  the  organism  to  repair  itself.  The  object  of  thera- 
peutics is  chiefly  to  set  in  motion  by  appropriate  means 
some  of  these  natural  mechanisms.  Should  we  discover  the 
nature  of  the  factors  which  are  instrumental  in  the  repair 
of  a  diseased  body,  we  could  probably  activate  the  cicatriza- 
tion of  wounds,  the  healing  of  fractures,  and  the  cure  of  any 
disease.  For  these  reasons,  it  appears  to  be  not  only  of 
philosophical  but  also  of  practical  significance  to  look  into 
the  mechanisms  that  make  a  unity  from  the  cell  aggregates 
composing  the  body  of  the  higher  animals. 

However,  it  should  be  clearly  understood  that  for  the 
biologist  the  problem  is  purely  scientific  and  should  be 
dealt  with  exclusively  by  the  experimental  method.  The 
temptation  is  great,  in  the  presence  of  a  very  complex 
problem,  to  build  up  hypotheses  and  to  assume  that  they 
are  the  expressions  of  reality.  In  this  manner,  almost  every- 
thing can  be  explained  and,  in  fact,  has  been  explained.  But 
each  succeeding  generation  has  to  demolish  the  systems 
created  by  the  preceding  one,  and  no  real  progress  in  knowl- 
edge is  made.  On  the  contrary,  if  we  realized  that  natural 
truth  can  be  apprehended  only  in  fragments  and  by  the 
strict  application  of  the  scientific  method,  we  would  not 
try  to  develop  a  formula  disposing  of  the  more  complex 
biological  problems  in  a  logical  manner.  In  the  course  of 
investigation,  philosophy  and  biology  should  not  be  mixed. 
Biology  is  in  one  realm  and  philosophy  in  another.  Scientific 
explanation  and  philosophic  explanation,  as  Needham 
said,  are  two  distinct  foods  of  the  soul,  and  they  are  confused 
only  at  great  peril.  Biology  is  full  of  such  confusions,  and 
has  suffered  markedly  from  them.  It  is  obvious  that  hypoth- 
eses are  necessary.  But  only  hypotheses  susceptible  of 
experimental  verification  must  be  constructed.  We  have  to 
be  purely  empirical.  It  is  time  to  discard  mere  logical 
concepts.  The  concepts  required  for  the  building-up  of  an 
experimental  science  must  be  such  that  they  remain  true, 
whatever  future  experience  may  be  in  store.  Modern  physi- 
cists widely  use  concepts  which  are  equivalent  to  a  set  of 


208  HUMAN   BIOLOGY 

operations.  In  his  remarkable  essay  on  the  logic  of  physics, 
Bridgman  shows  that  a  concept  must  involve  as  much  as, 
and  nothing  more  than,  the  set  of  operations  by  which  it  is 
determined.  Concepts  can  be  defined  only  in  the  range  of 
actual  experiments,  and  when  they  cannot  be  so  defined, 
they  are  meaningless. 

If  meaningless  and  useless  questions  were  banished  from 
natural  sciences,  the  road  to  progress  would  be  freer.  Biolo- 
gists have  more  or  less  entangled  themselves  in  philosophic 
and  scientific  systems.  Those  who  belong  to  the  vitalistic 
school  believe  that  the  integrating  principle  that  makes 
a  whole  of  the  organism  cannot  be  expressed  in  physico- 
chemical  terms.  The  mechanisms  responsible  for  the  organic 
unity  would  be  directed  by  an  independent  agent,  a  govern- 
ing idea,  analogous  to  that  of  an  architect  in  the  construction 
of  a  building.  The  more  eminent  exponent  of  vitalism, 
Driesch,  teaches  that  certain  classes  of  natural  facts  are  not  of 
the  physicochemical  type,  but  possess  an  autonomy  of  their 
own.  The  autonomous  agent  at  work  in  the  vital  processes, 
called  entelechy  by  Driesch,  is  something  that  is  non- 
physicochemlcal.  However,  it  is  not  psychical.  It  is  of  a 
non-energetic  character  and  cannot  create  energy.  It  is 
concerned  only  with  the  arrangement  of  the  manifoldness. 
This  definition  of  entelechy  shows  that  it  is  quite  outside 
of  the  realm  of  positive  investigation.  The  hypothesis  of  a 
non-physicochemical  force  within  the  organism  and  at  the 
same  time  independent  of  the  organism  cannot  inspire 
any  new  line  of  research.  It  is  a  pure  mental  construct, 
impossible  to  reach  and  to  measure.  It  will  contribute  no 
more  to  the  finding  of  new  biological  laws  than  the  belief  in 
Naiads  presiding  over  the  fate  of  springs  has  helped  in  the 
discovery  of  the  laws  of  hydrodynamics.  Although  it  may 
be  of  real  philosophical  interest,  such  a  concept  should  be 
discarded  by  biologists  as  being  meaningless.  The  classical 
mechanisticism  that  has  superseded  vitalism  does  not 
express  a  sounder  intellectual  attitude.  It  claims  that  the 
application  of  the  scientific  method  exhausts  the  content 
of  natural  phenomena,  and  that  all  physiological  processes 
can  be  explained  in  terms  of  the  present  laws  of  physico- 
chemistry.  These  pretensions  are  obviously  unwarranted. 


THE    RELATION    OF    CELLS   TO   ONE    ANOTHER  209 

It  is  impossible  to  know  whether  the  phenomena  that  take 
place  at  a  given  scale  of  magnitude  will  occur  at  a  very 
much  smaller  scale.  Can  the  second  law  of  thermodynamics 
express  what  is  going  on  in  cell  organs  less  than  o.  i  micron 
in  diameter?  Helmholtz  doubted  it,  and  Guye,  in  his  remark- 
able essay  on  physicochemical  evolution,  has  discussed 
how,  at  such  a  magnitude,  the  statistical  laws  of  physics 
are  possibly  replaced  by  the  laws  of  the  individual  action 
of  molecules,  atoms  and  electrons.  As  long  as  the  phenomena 
that  take  place  in  minute  cell  structures  have  not  been 
investigated,  they  cannot  be  assumed  to  follow  the  known 
laws  of  physical  chemistry.  The  affirmations  of  mechanis- 
ticists  on  this  subject  must  be  considered  as  useless  and 
meaningless.  The  neomechanistic  school  has  assumed  a 
more  sensible  attitude.  It  makes  almost  no  philosophical 
claims,  but  merely  asserts  the  universal  dominion  of  scientific 
method  over  natural  phenomena.  However,  it  is  still  unsound 
as  it  limits  science  to  the  realm  of  phenomena  which  can  be 
studied  quantitatively  and  expressed  mathematically. 
Science  should  not  be  identified  with  measurement  and,  as 
Gilbert  Lewis  said,  one  must  have  no  patience  with  any 
definition  of  the  scientist  that  would  exclude  a  Darwin,  a 
Pasteur,  and  a  Kekule.  After  all,  it  seems  that  the  best 
possible  intellectual  attitude  for  biologists  is  to  follow  the 
advice  of  Claude  Bernard  and  "reject  all  scientific  and 
philosophical  systems  in  the  same  manner  as  they  would 
break  the  chains  of  intellectual  bondage." 

The  problem  of  the  unity  and  manifoldness  of  the  organ- 
ism has  then  to  be  attacked  with  only  the  help  of  the  experi- 
mental method.  Our  concepts  of  the  integrating  principle 
must  not  be  logical  constructs,  but  the  mere  expression  of 
the  manner  through  which  they  are  acquired.  How  can  we 
bring  into  the  field  of  experimental  analysis  the  purposeful 
processes  of  the  living  organism?  It  is  obvious  that  such  an 
attempt  would  be  unthinkable  if  the  teleological  agent  were 
an  entelechy  independent  of  the  body.  In  that  case,  the 
subject  should  be  dismissed  from  the  laboratory  and 
entrusted  to  the  philosopher.  However,  we  may  reasonably 
assume  that  the  purposeful  factors  reside  within  the  units 
themselves,  and  not  within  the  organism  as  a  whole.  While 


210  HUMAN   BIOLOGY 

no  experiment  can  be  made  on  a  non-physicochemical  agent 
distinct  from  the  body,  it  is  entirely  feasible  to  measure  an 
impulse  toward  organization  present  in  a  small  group  of 
cells.  It  has  recently  been  discovered  that  cells  removed 
from  their  normal  surroundings  and  caused  to  hve  as 
independent  units  begin  at  once  to  manifest  their  innate 
properties.  The  analysis  of  these  properties,  which  remain 
hidden  in  normal  hfe,  may  explain  the  mechanism  of  some 
of  the  formative  and  regenerative  processes.  Such  an  investi- 
gation can  be  made  on  embryonic  as  well  as  on  adult  organ- 
isms. It  is  well  known  that  the  prospective  value  of  any 
group  of  embryonic  cells  is  far  greater  than  its  real  value. 
When  a  blastula  is  cut  into  two  parts,  each  develops  an 
embryo.  This  experiment  indicates  that  the  fate  of  a  cell 
is  a  function  of  its  position.  The  egg  is  an  equipotential 
harmonious  system,  as  Driesch  has  named  it.  Each  element 
appears  to  be  able  to  play  diflerent  parts  equally  well  in 
the  formation  of  the  totahty.  What  factors  are  responsible 
for  the  actuahzation  or  non-actuahzation  of  its  potential- 
ities? Probably  certain  chemical  substances  set  free  by  the 
cells  themselves.  The  epidermis  of  amphibia  produces  the 
lens  of  the  eye  under  the  influence  of  a  formative  stimulus 
from  the  primary  optic  vesicles.  The  analysis  of  the  nature 
of  such  a  stimulus  is  impossible  when  the  tissues  are  parts 
of  a  living  organism.  But  it  would  become  feasible  if  the 
physicochemical  conditions  that  may  determine  the  trans- 
parency of  epidermis  were  ascertained  in  vitro,  and  if  the 
substances  set  free  by  optical  vesicles  were  studied  under 
the  same  conditions. 

Should  the  principles  determining  organization  reside 
within  the  elements  composing  the  body,  they  would  become 
apparent  if  tissue  cells  of  various  types  were  isolated  and 
maintained  in  vitro  in  a  condition  of  active  and  free  life. 
With  this  object  in  view,  we  have  developed  elaborate 
physiological  techniques  during  the  last  few  years  by  which 
tissues  and  blood  cells  can  be  separated  from  the  body  and 
caused  to  show  their  natural  tendencies  toward  organization 
and  the  elemental  properties  underlying  formative,  regenera- 
tive and, adaptive  stimuli.  The  application  of  the  method  of 
tissue  culture  in  its  modern  form  to  embryonic  and  adult 


THE    RELATION    OF    CELLS    TO   ONE    ANOTHER  211 

tissues  of  birds  and  mammals  has  revealed  some  of  their 
fundamental  properties. 

1.  Unlimited  Proliferative  Potentialities  oj  Tissue  Cells. 
When  fibroblasts  or  epithelial  cells  are  removed  from  the 
body  of  an  animal  and  kept  in  a  nutrient  medium  under 
proper  conditions,  their  multiphcation  goes  on  indefinitely 
at  the  same  rate.  As  long  as  waste  products  are  ehminated 
and  food  material  is  supplied,  they  synthesize  new  proto- 
plasm from  the  constituents  of  their  medium.  A  strain  of 
tissue  cells  is  immortal,  if  maintained  in  a  proper  state 
outside  of  the  body.  Within  the  organism,  tissue  cells 
actuahze  only  a  small  part  of  their  potentiaKties.  But  the 
proHferative  capacity  always  remains  present,  even  in  old 
age,  when  the  cells  are  still  capable  of  unhmited  multiph- 
cation in  vitro. 

2.  Dependence  of  Cell  Activity  on  the  Composition  oj  the 
Medium.  Tissues  taken  from  an  embryo  or  from  a  pure 
culture  of  embryonic  cells  and  placed  in  a  medium  containing 
inorganic  salts  and  glucose,  but  no  nitrogenous  substances, 
stop  growing  after  a  few  days  and  die.  In  a  medium  contain- 
ing inorganic  salts  and  lacking  glucose,  death  occurs  almost 
immediately.  On  the  contrary,  fibroblasts  or  epithehal 
cells  cultivated  in  embryonic  proteins  immediately  increase 
their  rate  of  multiphcation.  After  a  few  days,  the  mass  of 
the  tissue  doubles  in  size  every  forty-eight  hours  and  the 
velocity  of  prohferation  remains  stationary.  Under  such 
conditions,  the  cells  accumulate  reserves.  Then,  if  they 
are  deprived  of  food,  they  go  on  multiplying  for  several 
days.  Connective  tissue  cells  removed  from  an  adult  animal 
rejuvenate  at  once  and  begin  to  multiply  again  when  they 
are  placed  in  embryonic  proteins,  although  they  may  have 
been  in  a  dormant  condition  for  several  years.  After  a  few 
weeks,  they  cannot  be  distinguished  from  embryonic  cells. 
These  experiments  led  to  the  important  conclusion  that  the 
prohferation  of  a  cell  depends  on  the  composition  of  the  fluid 
in  which  it  is  placed.  The  state  of  rest  or  of  proliferation  of  a 
tissue  in  the  adult  animal  is  a  function  of  the  quality  and 
quantity  of  the  food  material  at  its  disposal.  A  tissue  cell 
has  no  spontaneous  activity  or  energy.  It  is  like  a  motor 
which  does  not  run  when  it  lacks  fuel.  The  reason  for  cell 


212  HUMAN   BIOLOGY 


multiplication  must  always  be  sought  in  the  nature  of  the 
surrounding  fluid.  The  growth  energy  of  a  cell  at  a  given 
instant  is  a  function  of  its  inherent  growth  energy  at  the 
preceding  instant  and  of  the  concentration  of  growth- 
promoting  and  growth-inhibiting  substances  in  its  medium. 

3,  Diversity  of  Growth-Promoting  Factors  According  to  Cell 
Types.  Pure  strains  of  epithehal  cells  or  fibroblasts,  when 
placed  in  a  medium  composed  of  embryonic  proteins,  or  of 
proteoses,  peptones,  and  peptides,  begin  at  once  to  multiply. 
Adult  as  well  as  embryonic  cells  respond  in  identical  ways 
to  the  presence  of  these  substances.  The  rate  of  growth 
depends  both  on  their  nature  and  their  concentration.  But 
fibroblasts,  epithelial  cells,  and  macrophages  do  not  behave 
in  the  same  manner  toward  a  given  substance.  In  embryonic 
proteins,  the  rate  of  proliferation  of  epithelium  is  always 
slower  than  that  of  connective  tissue.  Thyroid  cells,  and 
iris  or  Malpighian  epithelium  in  pure  cultures  grow  much 
less  actively  than  fibroblasts.  Moreover,  these  cell  types  do 
not  utilize  serum  proteins.  When  cultivated  in  such  a 
medium,  they  die  within  a  few  weeks  while,  on  the  other 
hand,  blood  and  tissue  macrophages  proliferate  rapidly  in 
serum.  The  latter  also  multiply  when  fed  on  muscle  frag- 
ments or  protein  precipitates.  They  remain  in  the  localities 
where  these  particles  are  present  and  increase  in  size,  as 
w^ell  as  in  number.  But  in  digests  from  proteins  and  in  con- 
centrated solutions  of  embryonic  proteins,  they  do  not 
multiply,  and  often  die.  If  such  an  investigation  were 
extended  to  other  cell  types,  differences  doubtless  would 
be  discovered  also  in  the  nature  and  concentration  of  the 
substances  w^hich  promote  their  growth.  The  innate  prop- 
erties of  the  various  cell  types  account  for  the  specific 
response  of  the  tissues  within  the  organism  toward  a  given 
nutrient  substance.  Their  activity  is  automatically  and 
differentially  determined  by  the  quantity  and  the  quality 
of  the  food  supply. 

Some  nutrient  substances  may  be  manufactured  by  the 
tissues  themselves.  For  instance,  tissue  cells  cultivated  in  a 
flask  set  free  in  their  fluid  medium  growth-activating 
substances.  When  leucocytes  are  multiplying  actively  in  a 
plasma  coagulum,  the  medium  acquires  the  power  of  pro- 


THE   RELATION   OF   CELLS   TO   ONE   ANOTHER  21 3 

moting  the  multiplication  of  fibroblasts  and  of  epithelial 
cells.  This  phenomenon  must  be  attributed  to  the  production 
of  either  embryonic  proteins,  or  of  proteoses  and  peptones. 

4.  Specific  Growth-Inhibiting  Factors  for  Various  Cell 
Types.  When  fibroblasts  and  epithelial  cells  are  placed  in  a 
medium  composed  of  diluted  plasma,  they  go  on  multiplying 
for  a  few  days,  but  their  rate  of  multiphcation  is  less  active 
than  in  Tyrode  solution.  The  significant  fact  is  thus  brought 
to  hght  that  not  only  is  plasma  not  a  nutrient  substance  for 
these  cells,  but  that  it  inhibits  their  multiphcation.  This 
effect  increases  progressively  with  the  age  of  the  animal  that 
supplies  the  blood.  It  is  not  due  to  a  special  condition  of  the 
proteins  during  adult  and  old  age.  Once  isolated,  these 
proteins  have  no  inhibiting  or  activating  effect  on  cell 
proliferation.  But  quite  the  reverse,  the  lipoids  that  can  be 
extracted  from  plasma  possess  a  very  marked  inhibiting 
effect  on  the  growth  of  fibroblasts.  The  plasma  of  an  old 
animal  contains  a  large  amount  of  lipoids,  and  they  are 
more  toxic  for  tissue  cells.  However,  the  substances  exerting 
such  a  marked  effect  on  fibroblasts  and  epithelial  cells  do 
not  prevent  the  multiplication  of  macrophages.  Macrophages 
proliferate  in  the  blood  of  an  old  animal,  although  the 
multiplication  is  slower  than  when  they  are  cultivated  in  the 
plasma  of  a  young  animal. 

5.  Morphological  Effect  oj ■  Nutritional  Changes.  When 
cells  endowed  with  definite  morphological  characteristics 
are  placed  in  a  medium  where  their  nutrition  becomes 
modified,  marked  changes  occur  in  their  appearance.  Blood 
monocytes  cultivated  in  a  medium  containing  some  red 
blood  corpuscles,  or  particles  of  protein  precipitate,  or 
fragments  of  muscle  killed  by  heat,  increase  rapidly  in  size. 
After  a  few  days,  they  may  be  ten  times  longer  than  they 
were  originally,  and  closely  resemble  tissue  macrophages. 
In  fact,  they  cannot  be  distinguished  from  them  by  any 
known  morphological  criteria.  Inversely,  tissue  macrophages 
cultivated  in  a  medium  containing  only  a  minute  amount  of 
nutrient  substances  decrease  progressively  in  size  and  lose 
their  large  neutral  red  vesicles.  The  mitochondria  shrink 
and  the  nucleus  itself  becomes  smaller.  The  cells  assume  an 
appearance  analogous  to  that  of  blood  monocytes.  A  similar 


214  HUMAN   BIOLOGY 

phenomenon  is  observed  when  the  food  supply  of  fibroblasts 
is  modified.  It  is  known  that  such  cells  growing  from  frag- 
ments of  adult  connective  tissue  contain  a  small  segregation 
apparatus  and  a  few  slender  mitochrondria.  After  they 
have  been  fed  well  for  a  few  days  on  embryonic  proteins,  the 
segregation  apparatus  grows  much  larger  and  the  nucleus 
and  mitochondria  become  similar  to  those  of  embryonic 
fibroblasts. 

It  is  obvious  that  the  anatomic  constitution  of  a  cell  is 
modified  by  its  nutritional  state.  Cell  morphology  depends, 
in  some  respects,  on  the  nature  and  the  concentration  of  the 
substances  which  are  free  in  the  surrounding  medium. 
Moreover,  the  effect  of  the  medium  may  be  more  radical 
and  lead  to  a  transformation  of  the  cell  type  itself.  When  blood 
monocytes  become  crowded  in  a  plasma  coagulum,  they 
die  or  transform  themselves  into  fibroblasts,  that  is,  into  a 
type  whose  physiological  properties  are  very  different. 
Secretory  activity  also  depends  on  the  nature  of  the  peri- 
cellular fluid.  A  pure  culture  of  iris  epithehum  in  embryonic 
proteins  gives  rise  to  rapidly  developing  cells  which  contain 
very  few  dark  granulations.  On  the  contrary,  when  the 
rate  of  growth  is  decreased  by  the  presence  of  blood  serum, 
a  large  amount  of  pigment  is  produced  and  the  cultures 
become  almost  entirely  black. 

6.  Effort  toward  Organization  of  Isolated  Tissue  Cells. 
Tissue  cells  isolated  from  the  body  for  several  years  retain 
certain  habits  in  the  formation  of  colonies.  They  attempt 
to  join  together  by  building  up  tissues  of  the  same  architec- 
ture as  were  found  within  the  parent  organism.  Fibroblasts 
never  scatter  through  the  medium  of  the  flask,  but  rather 
pack  themselves  closely  together  in  an  intricate  manner, 
forming  a  felt-hke  tissue  which  resembles  young  embryonic 
tissue.  Epithehal  cells,  on  the  other  hand,  practically 
always  unite  by  their  edges  and  form  a  kind  of  pavement. 
If  fibroblasts  are  placed  close  to  a  pure  culture  of  iris  epithe- 
lium, they  quickly  surround  the  epithehal  cells  which  con- 
gregate in  acinus-like  formation,  as  indeed  Fischer  has  shown. 
Although  living  far  removed  from  the  body  in  artificial 
media,  epithelial  cells  have  a  tendency  to  unite  as  they  are 
wont  to  do  in  the  organism.  A  pure  strain  of  Ehrlich  car- 


THE    RELATION    OF    CELLS    TO    ONE    ANOTHER  215 

cinoma  sends  forth  into  the  medium  buds  and  sinuous 
branches  composed  of  densely  packed  cells  and  grows 
to  resemble  an  alveolar  carcinoma,  without  any  connective 
tissue  to  fill  the  spaces  between  the  alveoh.  Thyroid  cells 
may  also  form  alveoH  in  which  secretory  substance  is 
observed.  Evidently,  therefore,  cells  isolated  from  the  body 
show  a  bhnd  tendency  to  form  organs  even  when  there  is  no 
organism  and  no  object  for  such  formation.  This  purposeless 
organization  is  clearly  the  expression  of  certain  fundamental 
properties  of  the  cells.  Blood  monocytes,  on  the  contrary, 
never  congregate  as  a  tissue.  When  they  are  cultivated  in  a 
flask,  they  scatter  all  over  the  coagulum.  It  is  only  when 
they  have  reached  its  edges  that  they  begin  to  grow  in  a 
denser  formation.  But  the  cells  never  come  in  contact  on 
their  sides.  Sometimes  they  unite  in  a  chain,  but  it  is  never 
a  constant  and  definitive  structure.  If  compelled  to  aggre- 
gate in  a  mass,  they  generally  die.  Their  scattering  through 
the  body  is  the  expression  of  an  elementary  property  and 
not  of  an  impulse  to  protect  the  organism  against  the  invasion 
of  bacteria  or  the  accumulation  of  dead  cells  or  foreign 
bodies. 

7.  Production  by  the  Cells  Themselves  of  Certain  Conditions 
of  their  Environment.  It  is  very  probable  that  the  fluids  of 
the  body,  such  as  interstitial  lymph  and  blood  serum,  are 
entirely  the  result  of  cell  activity.  But  the  mechanisms 
governing  the  formation  of  interstitial  lymph  by  the  tissues, 
and  the  eff'ect  of  the  lymph  on  the  tissues  are  still  unknown. 
Nevertheless,  it  has  become  possible  to  investigate  the 
manner  in  which  groups  of  cells  may  modify  their  immediate 
environment.  When  a  fragment  of  pure  culture  of  fibroblasts 
is  placed  in  a  coagulum  stained  with  phenol  red,  it  quickly 
surrounds  itself  with  an  orange-yellow  crown,  and  a  piece 
of  spleen  creates  for  itself  a  still  more  acid  atmosphere. 
Colonies  of  blood  monocytes  do  not  produce  any  local  change 
in  the  color  of  the  medium,  but  they  progressively  modify 
the  hydrogen  ion  concentration  of  the  entire  coagulum. 
When  fragments  of  spleen  are  being  transformed  into 
sarcoma  by  Rous  virus,  the  production  of  acid  becomes  more 
active.  In  composite  tissues  made  of  normal  and  sarcomatous 
fibroblasts  living  in  symbiosis,  golden-yellow  spots^on  an 


2l6  HUMAN   BIOLOGY 

orange  background  characterize  the  presence  of  malignant 
islands  within  the  normal  tissue.  Cells  also  modify  their 
medium  by  the  production  of  larger  or  smaller  amounts  of 
proteolytic  ferment,  growth-activating  substances,  etc. 
A  fragment  of  leucocytic  film  placed  beside  a  pure  culture 
of  fibroblasts  causes  an  increase  in  the  rate  of  proliferation 
of  the  latter.  This  effect  is  due  to  the  setting  free  of  a  growth- 
activating  substance  in  the  medium.  Certain  malignant 
fibroblasts  attract  wandering  cells  and  receive  from  those 
cells  the  substances  which  determine  cell  multiplication. 
The  substances  may  belong  to  the  class  of  embryonic 
proteins,  such  as  are  contained  in  very  young  cells.  They 
may  also  be  protein  split  products.  It  is  evident  that  tissues 
possess,  in  some  measure,  the  power  to  manufacture  the 
medium  in  which  they  live. 

The  application  of  such  a  new  method  to  a  very  old  prob- 
lem has  brought  to  light  some  of  the  hitherto  unsuspected 
properties  of  living  tissues  which  are  instrumental  in  building 
up  unity  from  manifoldness.  These  properties  until  recently 
have  remained  hidden  because  cells  had  always  been  studied 
as  independent  units  without  consideration  of  their  environ- 
ment. It  is  imperative,  on  the  other  hand,  to  apprehend  the 
concrete  event  of  a  living  cell  and  not  merely  the  abstrac- 
tions on  which  classical  cytology  is  based.  Tissue  and  blood 
cells  never  escape  the  influence  of  their  environment  with- 
out, as  well  as  within,  the  organism.  When  removed  from 
the  body  of  the  embryonic  or  adult  animal,  they  manifest 
almost  at  once  their  latent  potentialities.  They  are  seen  to 
be  endowed  with  attributes  which  compel  them  to  respond 
in  a  certain  manner  to  given  chemical  substances.  Even 
when  they  have  been  separated  from  the  organism  for 
several  years,  they  keep  elementary  characteristics  which 
induce  them  to  organize,  despite  the  fact  that  there  is  no 
organism  to  be  formed.  They  are  apparently  endowed  with 
instincts  which  continue  to  manifest  themselves,  even  when 
they  have  become  purposeless. 

The  elements  of  the  body,  therefore,  do  not  appear  to  be 
integrated  by  a  central  principle.  Ontogenic  or  regenerative 
stimuli  cannot  be  likened  to  the  driving  impulse  of  the 
mind  of  a  sculptor  carving  a  statue.  There  is  no  need  of  an 


THE    RELATION    OF    CELLS    TO   ONE    ANOTHER  217 

architect  to  direct  the  execution  of  the  plan,  because  the 
hving  units  themselves  understand  the  requirements  of  the 
whole  and  act  according  to  it,  through  a  process  which  has 
no  analogy  in  nature.  Cells  can  be  compared  to  stones  which 
might  have  the  magical  power  of  setting  themselves  in  order 
and  making  a  wall,  even  when  there  is  no  house  to  be  erected 
and  no  mason  to  build  it.  Possibly  there  is  some  remote 
analogy  between  the  behavior  of  tissue  elements  and  that 
of  ants  or  bees  which  bhndly  work  for  the  interest  of  the 
community.  But  the  manner  in  which  final  causes  seem  to 
act  upon  efficient  causes  is  as  mysterious  in  the  case  of 
insects  as  in  that  of  cells.  Biology  is  not  at  present  in  a 
position  to  give  any  general  explanation  of  organization 
and  of  the  teleological  processes  responsible  for  it.  We  must 
patiently  bring  into  the  experimental  field  the  mechanisms 
which  cause,  partly  at  least,  the  unity  of  the  body.  After  an 
extensive  analysis  of  the  elementary  processes,  the  horizon 
may  broaden,  and  the  veil  may  be  lifted.  But  all  is  still 
very  dark.  Even  if  the  ultimate  mystery  of  organic  unity 
should  never  be  understood,  this  investigation  of  the  inte- 
grating principles  will  be  far  from  useless.  It  is  bound  to 
supply  medicine  with  most  important  information  about  the 
mechanisms  which  are  involved  in  the  formation  and 
maintenance  of  the  wholeness  of  the  body,  and  to  increase 
its  power  for  curing  diseases  and  improving  the  quality 
of  human  beings. 

REFERENCES 

Bridgman,  p.  W.  1927.  The  Logic  of  Modern  Physics.  N.  Y.,  Macmillan. 
Carrel,  A.   1923.  A  method  for  the  physiological  study  of  tissues  in  vitro. 
J.  Exper.  Med.,  38:  407. 
1924.  Tissue  culture  and  cell  physiology.  Physiol.  Rev.,  4:  i. 

1927.  La  cytologic  nouvelle.  Cornpt.  rend.  Soc.  bioL,  96:  1198. 

1928.  Modern  techniques  of  tissue  culture  and  results.  Archiv.  J.  exp. 
Zelljorscb.,  6:  70. 

Carrel,  A.,  and  Ebeling,  A.  H.  1926.  The  fundamental  properties  of  the 
fibroblast  and  the  macrophage,  i.  The  fibroblast.  J.  Exper.  Med.,  44:  261. 

1926.  II.  The  macrophage.  J.  Exper.  Med.,  44:  285. 

1928.  III.  The  malignant  fibroblast  of  sarcoma  10  of  the  Crocker  Foundation. 
J.  Exper.  Med.,  48:  105. 

1928.  IV.  The  malignant  fibroblast  of  Jensen  sarcoma.  J.  Exper.  Med., 
48:  285. 


2l8  HUMAN   BIOLOGY 

Fischer,  A.   1927.  Gewebeziichtung:  Handbuch  der  Biologic  der  Gewebe- 

zellen  in  Vitro.  Miinchen,  MuIIer  &  Steinicke. 
GuYE,  C.  E.  1922.  L'EvoIution  Physico-Chimique.  Par.,  Etienne  Chiron. 
Lewis,  G.  N.  1926.  The  Anatomy  of  Science.  New  Haven,  Yale  Univ.  Press. 
Needham,  J.  1928.  Recent  developments  in  the  philosophy  of  biology.  Quart. 

Rev.  Biol.,  3:  77. 


1 


i 


Chapter  X 

THE   INTEGRATIVE  ACTION  OF 
THE  VASCULAR  SYSTEM 

W.  B.  Cannon 

A  FLOWING  stream  of  water  brings  to  the  simple 
organisms  fixed  on  the  rocks  of  the  stream  bed  the 
food  and  oxygen  needed  for  existence  and  carries 
away  the  waste.  These  single-celled  creatures  can  five  only 
in  watery  surroundings;  if  the  stream  dries  they  die  or  enter 
a  dormant  state.  The  same  conditions  prevail  for  the  incal- 
culable myriads  of  cells  which  constitute  our  bodies.  We 
ordinarily  think  of  ourselves  as  inhabitants  of  the  air.  In 
fact,  however,  every  part  of  us  that  is  ahve  is  in  contact  with 
fluid.  The  surfaces  of  the  body  are  either  dead,  as  the  horny 
layer  of  the  skin,  or  are  covered  with  moisture,  as  the  eyes 
and  the  nose  and  mouth.  Within  these  surfaces  are  the  vast 
multitudes  of  minute  Hving  elements  or  cells  which  compose 
our  muscles,  glands,  brain,  nerves  and  other  parts.  Each 
cell  has  needs  similar  to  those  of  the  single  cell  in  the  flowing 
stream.  But  the  body  cells  are  shut  away  from  any  chances 
to  obtain  food,  water  and  oxygen  from  the  environment  or  to 
discharge  the  waste  materials  resulting  from  activity.  To 
provide  these  necessities  moving  streams  of  fluid  have  been 
developed  to  take  from  the  moist  surfaces  of  the  body  food, 
water  and  oxygen  which  they  dehver  to  the  cells  in  the 
remotest  nooks  of  the  organism,  and  from  the  cells  they 
bring  back  to  the  moist  surfaces  the  useless  waste  to  be 
discharged.  The  streams  which  form  a  fluid  matrix  for  our 
body  cells  are  the  blood  and  the  tissue  fluid  or  lymph. 
They  are  related  to  each  other  somewhat  as  the  water  in  a 
rivulet  is  related  to  the  more  stagnant  water  in  the  swamp 
through  which  it  flows.  The  blood  passes  rapidly  along 
fixed  courses  in  tubular  vessels;  the  tissue  fluid,  which 
fifls  the  chinks  and  crannies  outside  the  vessels  until  it  too 
is  gathered  in  its  own  channels,  is  shifted  slowly  from  place 
to  place.  We  are  to  examine  the  nature  of  these  fluids  and  the 

219 


220  HUMAN   BIOLOGY 

ways  in  which  the  internal  environment  of  the  cell  is  made 
favorable  by  keeping  them  on  the  move  and  constantly 
fresh  and  uniform. 

The  Nature  of  Blood  and  Tissue  Fluid.  The  blood,  con- 
stituting about  8  per  cent  of  the  body  weight,  is  a  remarkable 
substance  consisting  of  immense  numbers  of  red  corpuscles 
(a  drop  of  blood  contains  millions  of  them)  and  also  minute 
motile  white  corpuscles,  floating  in  a  thickish  watery 
solution  of  salts,  sugar  and  albuminous  material,  the  plasma. 
The  plasma  constitutes  somewhat  more  than  half  of  the 
total  blood  mass.  The  red  corpuscles  are  able  to  take  on 
very  quickly  in  the  lungs  a  load  of  oxygen,  which  is  more 
or  less  unloaded  in  other  parts  of  the  body  where  the  cells 
are  in  need  of  it.  On  the  way  back  from  these  cells  to  the 
lungs  the  red  corpuscles  carry  one  of  the  waste  products  of 
activity,  the  carbon  dioxide  which  results  from  oxidation 
or  burning,  a  process  that  yields  heat  and  mechanical  work 
in  the  activities  of  the  organism.  The  motile  white  corpuscles 
serye  as  scavengers  and  protectors  against  inert  foreign 
particles  and  invading  germs  which,  if  they  should  accumu- 
late, would  pollute  the  stream.  The  plasma  is  a  conveyor 
of  all  manner  of  food  materials  provided  by  the  fmal  digestive 
processes  in  the  intestines.  These  materials  are  carried,  like 
oxygen,  to  the  remote  cells  for  use  in  case  of  need  or  to 
special  places  where  they  are  stored  for  future  use.  The 
plasma  also  carries  from  the  cells  the  waste  materials, 
apart  from  carbon  dioxide,  which  result  from  the  wear  and 
tear  of  activity,  and  delivers  them  to  the  kidneys  through 
which  they  are  discharged  from  the  body. 

The  plasma  also  has  the  extraordinary  capacity  to  change 
from  a  fluid  to  a  jelly  when  it  comes  into  contact  with  an 
injured  region.  If  the  blood  vessels  are  damaged,  for  example, 
and  there  is  danger  of  loss  of  blood  through  the  opening, 
the  jellifying  or  clotting  of  the  plasma  forms  a  plug  which 
more  or  less  promptly  closes  the  opening  and  prevents  what 
might  be  a  serious  bleeding. 

The  tissue  fluid  diff'ers  from  blood  chiefly  in  containing  no 
red  corpuscles  and  less  albuminous  material  than  the 
plasma.    It  does   contain,   however,   white   corpuscles,   and 


THE    INTEGRATIVE   ACTION   OF   THE   VASCULAR   SYSTEM       221 

also  sugar  and  salts.  And  it  is  capable  of  clotting,  though 
the  clot  is  less  firm  than  that  formed  by  the  blood  itself. 
Since  the  tissue  fluid  Hes  between  the  blood  vessels  and 


Lymph  vessel 


T^lqhT  heart 

ArTerles 
Fig.  1.  Diagram  of  circulation. 

Left  heart  chamber  pumps  blood  out  into  arteries  which  distribute  it  to 
capillaries.  Venous  blood  is  collected  from  capillaries  and  returned  to  right 
heart  chamber  by  veins.  Thence  it  is  pumped  to  lungs  and  onward  to  left 
heart  chamber.  Tissue  fluid,  exuded  through  capillary  walls,  is  collected  in 
lymph  vessels  and  returned  to  veins  near  heart. 

(Modified  from  Paton.) 

the  tissue  cells,  all  the  materials  exchanged  between  the 
cells  and  the  flowing  blood  must  pass  through  it.  It  is, 
therefore,  the  direct  intermediator  for  that  exchange. 

The  Circulation  of  Blood  and  Tissue  Fluid.  Because  these 
fluids  are  limited,  the  only  way  for  them  to  serve  con- 
tinuously as  carriers  between  the  secluded  cells  and  the 
body  surfaces  is  by  being  used  over  and  over  again.  They 
must  circulate  (see  Fig.  i).  The  blood  is  forced  through  the 
vessels  by.  the  contractions  or  "beats"  of  the  heart — 
essentially  a  powerful  hollow  muscle  with  two  chambers, 
right  and  left.  Each  chamber  has  inlet  and  outlet  valves. 
The  nature  of  the  muscle  requires  it  to  rest  after  each  beat 
before  it  can  beat  again.  During  the  rest  period  blood 
flows  into  the  chambers  of  the  muscle  through  the  inlet 
valves,  into  the  right  chamber  from  all  the  remote  parts 
of  the  body,  into  the  left  chamber  from  the  lungs.  When 
the  muscle  contracts  on   its  contents,  these  valves  close. 


222  HUMAN   BIOLOGY 

preventing  a  back-flow;  the  pressure  on  the  contents  rises 
until  it  opens  the  outlet  valves,  whereupon  the  blood  is 
driven  forth  through  these  valves  into  the  outleading 
vessels,  from  the  right  chamber  into  vessels  distributing 
to  the  lungs,  from  the  left  chamber  into  the  great  main 
vascular  trunk  of  the  body,  the  aorta.  The  heart  then 
relaxes,  and  when  the  pressure  within  it  becomes  less  than 
that  in  the  vessels,  the  outlet  valves  close.  Thus  the  heart 
is  emptied,  and  made  ready  for  being  recharged. 

The  vessels  leading  away  from  the  heart  are  hke  the 
elaborate  branchings  of  a  thickly  growing  tree.  The  major 
trunk  is  the  aorta.  Large  minor  trunks  reach  out  to  the  arms 
and  legs,  to  the  head  and  to  the  organs  of  the  abdomen,  e.g. 
the  stomach,  the  hver  and  the  intestines.  In  each  of  these 
regions  the  minor  trunks  ramify  again  and  again  into  smaller 
and  smaller  twigs  until  every  part  of  the  body  is  supphed. 
The  vessels  leading  away  from  the  heart  are  the  arteries, 
and  this  intricate  branching  system  is  sometimes  called 
the  "arterial  tree."  The  arteries  have  relatively  thick 
elastic  walls,  and  because  provided  with  muscle  their 
capacity  can  be  varied.  When  the  heart  discharges  its 
load  into  the  arteries  it  starts  a  distending  wave  along  their 
contents,  which  can  be  felt  in  any  superficial  branch,  e.g. 
in  the  wrist  at  the  base  of  the  thumb,  as  a  "pulse." 

We  must  remember  always  that  the  virtue  of  the  cir- 
culating blood  is  to  serve  the  cells  which  are  far  removed 
from  the  sources  of  supply  and  from  the  conveniencies  for 
voiding  their  rubbish.  It  is  clear  that  this  service  must  be 
performed  through  the  walls  of  the  vessels.  The  arterial 
walls  are  too  thick  to  permit  the  passage  of  material  to  and 
fro.  The  process  of  exchange  occurs  through  the  walls  of 
capillaries,  extremely  minute  tubules  with  walls  so  exceed- 
ingly tenuous  that  gases,  such  as  oxygen  and  carbon  dioxide, 
and  sugar  and  salts  in  solution,  pass  readily  through  them. 
The  capillaries,  about  1/4000  of  an  inch  in  diameter,  form  a 
rich  and  intricate  network,  intimately  insinuated  between 
the  layers  and  masses  of  the  cells  everywhere  in  the  body. 
Into  this  network  the  fine  twigs  of  the  arterial  tree,  the 
arterioles,  pour  the  blood;  and  from  it  the  blood  is  gathered 
into  the  fine  twigs  of  another  tree,  the  tree  of  veins.  From 


THE    INTEGRATIVE    ACTION    OF   THE   VASCULAR    SYSTEM        223 

the  venules  the  blood  passes  to  larger  and  larger  veins  with 
thicker  and  stronger  walls  until  the  main  trunks  are  reached 
which  pour  the  blood  accumulated  from  all  parts  of  the 
body  into  the  right  chamber  of  the  heart. 

Many  of  the  veins  He  just  beneath  the  skin  where  they 
may  be  so  prominent  at  times  that  they  are  clearly  seen. 
On  the  back  of  the  hand,  for  example,  they  are  usually 
evident  as  a  coarse  network.  By  pressing  on  one  with  the 
tip  of  a  finger  and  sweeping  out  the  blood  toward  the  wrist 
with  the  thumb,  a  valve  (a  cup-shaped  sac  attached  at  the 
side  of  the  vein)  can  be  demonstrated  which  does  not 
permit  a  back  flow.  Wherever  the  veins  are  rhythmically 
pressed  upon,  as  by  the  muscles  in  walking,  the  valves 
require  the  blood  within  them  to  be  forced  towards  the 
heart.  This  pumping  action  on  the  veins  may  aid  greatly 
in  hastening  the  circulation. 

A  similar  system  of  arteries  and  veins  connects  the 
capillaries  of  the  lungs  with  the  heart.  It  is  important  to 
note  that  in  the  lungs,  as  in  all  other  parts,  the  flow  of  blood 
through  the  capillaries  is  the  essential  process.  Only  in  the 
capillary  region  do  the  necessary  exchanges  occur.  AH 
of  the  rest  of  the  circulatory  system  exists  to  maintain  the 
flow  in  that  region  where  it  is  serviceable. 

Tissue  fluid  is  produced  by  the  filtering  of  a  portion  of 
the  plasma  through  the  capillary  wafl.  In  some  parts  of 
the  body,  e.g.  in  the  hver,  the  capillaries  are  so  "permeable" 
that  the  process  of  filtration  occurs  continuously;  in  other 
parts,  e.g.  in  the  limbs,  it  occurs  only  when  the  parts  are 
active.  Under  such  conditions  the  fluid  may  be  formed  more 
rapidly  than  it  can  be  carried  away,  and  therefore  the  part 
may  become  perceptibly  larger. 

The  tissue  fluid  is  returned  to  the  blood  in  two  ways. 
It  may  pass  back  in  part  through  the  capillary  wall  when 
the  activity  of  the  part  ceases,  or  it  may  enter  a  definite 
system  of  thin-walled  tubes,  the  so-called  "lymphatics," 
and  be  conducted  through  them  to  a  large  vein  near  the 
heart  where  the  lymph  is  delivered  as  a  stream  into  the 
blood.  The  larger  lymphatic  vessels,  like  the  veins,  are 
provided  with  valves  and  in  consequence  every  little  pres- 
sure exerted  on  them  pushes  the  lymph  onward  to  the  exit. 


224  HUMAN   BIOLOGY 

In  their  course  the  lymphatics  are  interrupted  by  nodes  or 
"glands,"  which  act  as  sieves  and  hold  back  small  particles, 
e.g.  bacteria  and  cancer  cells,  and  keep  them  from  being 
widely  spread  through  the  rest  of  the  body.  When  protecting 
the  body  in  this  way  they  become  enlarged  and  can  then  be 
felt.  Thus,  when  the  tonsils  are  inflamed  the  lymph  glands 
of  the  neck  may  be  swollen  and  tender. 

The  multitudes  of  fmely  branched  arterioles  which  the 
blood  must  pass  through  on  its  way  to  the  capillaries  offer  a 
considerable  frictional  resistance.  When  the  heart  beats 
and  discharges  its  contents,  it  must  develop  a  pressure 
which  will  drive  the  blood  not  only  past  this  resistance, 
but  also  through  the  capillary  net  and  the  veins.  With  each 
fresh  delivery  of  blood  from  the  heart  the  elastic  arteries 
stretch  to  accommodate  the  extra  contents,  and  while 
the  heart  is  resting  and  filling  behind  the  outlet  valves  the 
elastic  recoil  of  the  arterial  walls  presses  the  blood  contin- 
uously onward.  Measurements  show  that  the  blood  in  the 
arteries  is  under  a  high  head  of  pressure,  equal  (in  young 
adults)  to  a  column  of  about  120  millimeters  of  mercury 
(about  5  inches)  at  the  peak  of  the  cardiac  discharge  into 
them,  and  to  about  80  millimeters  (about  3  inches)  just 
before  the  next  discharge.  In  the  capillaries  the  pressure 
has  fallen  to  about  25  millimeters  (about  i  inch),  and  it 
falls  progressively  in  the  veins  until  its  lowest  point  is  found 
as  the  blood  enters  the  right  chamber  of  the  heart. 

Clearly  the  same  amount  of  blood  must  pass  through 
the  heart,  the  lungs,  arteries,  capillaries  and  veins  at  the 
same  time,  or  otherwise  the  circulation  could  not  continue. 
Since  the  total  bed  of  the  capillaries  is  much  greater  than 
the  cross-area  of  the  aorta  or  the  large  veins,  the  blood 
moves  much  more  slowly  in  the  capillaries  than  in  either 
the  arterial  or  venous  trunks.  This  slow  flow  in  the  capillaries 
provides  time  for  the  important  exchanges  which  occur  in 
this  region. 

As  we  shall  soon  see,  the  circulation  must  vary  greatly 
in  its  service  to  the  needy  cells,  according  to  their  degree 
of  activity.  The  adjustments  are  brought  about  through 
nervous  control  of  the  heart  and  blood  vessels.  The  heart 
can  be  made  to  beat  rapidly  or  slowly  by  action  of  two 


THE  INTEGRATIVE  ACTION  OF  THE  VASCULAR  SYSTEM   225 

sets  of  nerves,  the  vagus  nerves  which  hold  the  heart  rate 
in  constant  check  and  the  sympathetic  nerves  which  make 
the  rate  faster.  Interestingly,  the  constant  moderate  action 
of  the  vagus  nerves  can  be  used  to  speed  up  the  heart;  it  is 
only  necessary  to  remove  the  check  which  they  exert.  The 
blood  vessels,  especially  the  arterioles,  can  be  made  smaller 
here  and  larger  there,  also  by  action  of  the  sympathetic 
nerves,  thus  hmiting  the  flow  to  one  part  and  distributing 
a  larger  volume  to  another  part  as  need  arises;  indeed,  the 
mass  of  the  blood  can  be  largely  shifted  from  one  region 
of  the  body  to  other  regions  in  special  emergencies. 

The  Constancy  of  the  Internal  Environment.  One  of  the 
most  striking  features  of  the  more  highly  developed  organ- 
isms is  their  independence  of  their  surroundings.  They  can 
go  long  without  water  and  food,  they  can  endure  extremes 
of  outer  temperature,  they  can  Hve  equally  well  at  the 
seashore  or  on  the  mountain  tops.  Lower  organisms  have 
not  these  capacities.  They  have  been  developed  by  remark- 
able automatic  arrangements  whereby,  in  spite  of  external 
changes  and  in  spite  of  bodily  activities  which  tend  to 
disturb  the  internal  conditions,  the  fluid  matrix  of  the  body 
is  kept  constant.  The  great  French  physiologist,  Claude 
Bernard,  stated  fifty  years  ago  that  it  is  the  fixity  of  the 
milieu  interieur  which  is  the  condition  of  free  and  independent 
hfe.  "All  the  vital  mechanisms,"  he  wrote,  "however  varied 
they  may  be,  have  only  one  object,  that  of  preserving 
constant  the  conditions  of  Hfe  in  the  internal  environment." 
We  shall  now  examine  some  of  the  ways  in  which  this  con- 
stancy is  maintained. 

The  Constancy  of  Blood  Sugar.  Grape  sugar  or  glucose 
is  the  form  into  which  starchy  food  is  changed  for  use  in 
the  body.  Of  all  energy-yielding  materials  supphed  by  the 
food,  glucose  is  the  most  readily  serviceable.  When  it  is 
provided  in  abundance  it  is  preferably  utilized;  the  burning 
of  fat  is  almost  completely  stopped.  Furthermore,  according 
to  present  views,  glucose  or  its  storage  precursor,  glycogen, 
is  essential  for  muscular  contraction.  The  substance  is 
continually  being  used,  therefore  (even  during  sleep  the 
heart  muscle  and  the  muscles  of  respiration  are  consuming 
glycogen)  and  it  can  be  renewed  only  periodically.  How  is 


226  HUMAN    BIOLOGY 

the  problem  met  of  delivering  a  continuous  supply  of  this 
important  material  to  the  active  cells? 

The  problem  is  more  complex  than  at  first  appears. 
Ordinarily  the  concentration  of  circulating  glucose  is  lOO 
miUigrams  in  lOO  cubic  centimeters  of  blood  (commonly 
expressed  as  lOO  mg.  per  cent).  If  the  concentration  rises 
to  about  1 80  mg.,  the  glucose  will  be  lost  by  escape  through 
the  kidneys;  if  it  falls  to  about  45  mg.,  convulsions  are 
Hkely  to  occur,  which  may  be  followed  by  coma  and  death. 
The  sugar  supply,  consequently,  must  not  only  be  con- 
tinuous, but  cannot  vary  beyond  certain  hmits  without 
danger  of  Joss  or  serious  disturbance. 

The  problem  of  constancy  of  sugar  in  the  blood  is  solved 
by  storage.  When  food  containing  much  starch  and  sugar 
is  eaten,  the  glucose  which  results  from  digestion  is  stored 
locally  in  the  muscles  and  for  general  use  in  the  cells  of  the 
liver,  as  glycogen.  The  general  reserve  in  the  liver  can  be 
built  up,  however,  only  by  collaboration  of  the  pancreas. 
In  that  organ  are  groups  or  "islands"  of  cells  that  elaborate 
a  peculiar  substance  which  they  discharge  into  the  blood 
stream  as  an  internal  secretion.  When  it  is  lacking,  sugar  is 
not  stored  in  the  liver,  is  not  normally  used  by  the  tissues, 
and  may  accumulate  in  the  blood  until  it  has  a  concen- 
tration there  of  300  mg.  per  cent  or  higher.  If  under  these 
circumstances  an  extract  of  the  island  cells  (insulin)  is 
injected  into  a  vein,  the  blood  sugar  is  promptly  reduced 
both  by  storage  and  by  use.  There  is  evidence  that  normally 
an  increase  of  blood  sugar  causes  impulses  to  be  discharged 
through  the  vagus  nerves  to  the  island  cells;  they  then  secrete 
natural  insulin  into  the  circulating  blood,  and  this  sub- 
stance carried  about  the  body  induces  both  the  building-up 
of  the  glycogen  reserves  and  the  more  efficient  utilization 
of  glucose. 

The  stored  glucose  is  needed  when  extra  combustion  or 
special  muscular  activity  is  demanded  in  the  organism,  for 
example,  on  exposure  to  cold  or  in  severe  and  prolonged 
physical  struggle.  Under  these  circumstances  the  glycogen 
in  the  liver  cells  is  changed  to  soluble  glucose,  is  discharged 
into  the  blood,  and  is  distributed  to  all  parts  of  tbe  body. 
The  mechanism  by  which  glucose  is  thus  increased  in  the 


THE    INTEGRATIVE   ACTION    OF   THE    VASCULAR    SYSTEM        227 

circulation  is  similar  to  that  operating  when  it  is  stored; 
it  is  a  combination  of  nervous  action  and  an  internal  secre- 
tion. Just  above  each  kidney  is  an  organ  about  the  size  of 
the  end  of  the  thumb,  the  adrenal  gland.  The  mid-portion 
of  this  gland  is  called  the  medulla,  the  outer  portion,  the 
cortex.  The  cells  of  the  adrenal  medulla  are  controlled 
by  sympathetic  nerves,  i.e.,  nerves  which  are  excited  by 
exposure  to  cold,  by  strenuous  muscular  efforts  and  by 
strong  emotions,  such  as  fear  and  rage.  The  substance 
which  these  cells  pour  into  the  blood  stream,  when  they  are 
stimulated  by  the  nerve  impulses,  has  the  remarkable  power 
of  producing  in  all  parts  of  the  body  the  same  effects  that 
are  produced  by  the  sympathetic  nerve  impulses  them- 
selves. These  impulses  not  only  cause  a  discharge  of  adrenin 
into  the  circulating  blood,  they  also  call  forth  glucose  from 
the  stores  in  the  hver.  But  the  secreted  adrenin  can  do 
hkewise.  Thus  the  sympathetic  impulses  and  the  secreted 
adrenin  cooperate  to  mobilize  the  reserves  of  energy-yielding 
material  when  the  cells  are  hkely  to  be  in  need  of  it. 

Fat  is  stored  in  fat  cells,  and  there  is  evidence  that  protein 
is  stored  in  Hver  cells.  After  a  considerable  period  of  fasting 
the  blood  still  has  a  normal  fat  and  protein  content;  the 
fat  and  protein  reserves  have  been  reduced,  however, 
and  yet  organs  of  prime  importance,  e.g.  the  heart  and  the 
brain,  show  no  signs  of  any  weakness  or  decrease  of  weight. 
They  are  maintained  at  the  expense  of  the  reserves  and 
of  less  important  structures.  The  conditions  which  govern 
the  laying-by  of  fat  and  protein  reserves  and  which  bring 
them  out  for  use  when  they  are  needed  are  still  largely 
unknown. 

The  Constancy  of  the  Water  Content  oj  the  Blood.  As  we 
have  seen,  the  blood  plasma  and  the  tissue  fluids  are  watery 
solutions  of  salts,  sugar  and  albuminous  materials.  The 
sap  of  cells  is  also  a  watery  solution  of  hke  materials.  Between 
this  sap  and  the  tissue  fluid  everywhere  is  the  cell  membrane 
through  which  water  and  certain  of  the  dissolved  substances 
can  readily  pass.  Ordinarily  the  water  of  the  plasma  is 
balanced  against  that  in  the  tissue  fluid,  and  that  in  turn 
is  balanced  against  the  water  in  the  cells.  If  the  water  of  the 
plasma   is   increased    it   disturbs   the   balance,    and,   when 


228  HUMAN   BIOLOGY 

excessive,  results  in  headache,  nausea,  dizziness  and  other 
effects  attributable  to  an  altered  state  of  the  brain.  On  the 
other  hand,  if  the  water  of  the  plasma  is  decreased  the 
blood  becomes  thickened,  the  blood  pressure  falls,  fluid 
passes  out  of  the  cells  and  the  temperature  of  the  body 
rises  in  a  fever.  The  constancy  of  the  water  content  of  the 
plasma,  therefore,  is  of  primary  importance  for  the  normal 
life  of  the  organism. 

Water  is  being  continuously  lost  from  the  body.  It  floats 
away  as  vapor  in  every  breath  we  expel.  Even  when  we  are 
quiet  it  is  lost  through  the  skin  at  the  rate  of  about  a  quart 
a  day.  And  it  goes  out  through  the  kidneys  with  waste 
products  which  must  be  kept  in  solution.  To  replace  this 
continuous  loss  water  can  be  taken  only  periodically  and 
then  it  may  be  taken  in  excess  of  the  immediate  require- 
ment. Under  the  circumstances  how  does  the  plasma  fare? 

Experiments  have  shown  that  its  consistency  is  kept 
constant  in  spite  of  most  exacting  tests.  Over  five  quarts 
of  water  have  been  drunk  in  six  hours  (indeed,  the  volume 
of  water  exceeded  by  one-third  the  estimated  volume  of 
the  blood  in  the  man  who  performed  the  feat)  and  yet  it 
was  absorbed  into  the  body,  was  carried  to  the  kidneys 
and  by  them  discharged,  without  at  any  time  causing  a 
dilution  of  the  blood  which  could  be  detected  by  studying 
a  change  of  its  color.  On  the  other  hand,  total  deprivation 
of  water  for  as  long  as  three  days  may  be  endured  without 
any  detectable  change  in  the  concentration  of  the  plasma 

The  remarkable  uniformity  of  the  water  content  of  the 
blood  is  maintained  by  storage  and  overflow.  When  much 
water  is  introduced  into  the  body  it  is  stored  in  muscles 
and  other  organs  and  in  the  skin.  Since  muscles  constitute 
nearly  half  of  the  body  weight  only  a  very  small  accumula- 
tion in  each  muscle  cell  results  in  a  large  reserve.  And  in  the 
skin  is  a  peculiar  form  of  tissue,  with  innumerable  miteuo 
spaces,  in  which  water  and  the  substances  dissolved  in  it 
(sugar  and  salts)  can  be  retained.  If  the  water  intake  is  not 
great  or  too  rapid  to  be  accommodated  in  these  stores  it 
pours  over  the  dam  in  the  kidneys  and  is  discharged  from 
the  body.  The  kidneys  must  be  remarkably  sensitive  to  a 
slight  change  in  the  concentration  of  the  blood  or  there 


THE  INTEGRATIVE  ACTION  OF  THE  VASCULAR  SYSTEM   229 

would  be  easily  detected  alterations  after  the  drinking  of 
large  volumes  of  w^ater  such  as  described. 

When  need  arises  water  is  withdrawn  from  the  stores. 
After  bleeding  there  is  a  sudden  demand.  The  largest  amount 
of  the  released  fluid  comes  from  the  muscles  (though  they 
lose  only  }i  of  i  per  cent  of  their  weight)  and  the  next 
largest  amount  comes  from  the  skin.  Other  parts  give  up 
their  reserve  as  well.  Among  the  other  organs  are  the  sahvary 
glands.  The  saliva  which  they  produce  is  more  than  98  per 
cent  water.  When  the  water  supply  fails,  therefore,  they 
cannot  provide  an  adequate  amount  of  saliva  to  keep  the 
throat  moist.  In  consequence  disagreeable  sensations  of 
dryness  and  stickiness  arise  from  that  region,  sensations 
which  we  call  thirst.  This  leads  to  the  drinking  of  water 
and  thus  to  restoration  of  the  normal  supplies  in  the  body 
and  to  resumption  of  the  normal  service  of  the  salivary 
glands. 

The  Constancy  of  Temperature.  One  of  the  most  striking 
and  easily  observed  constants  of  the  internal  environment 
is  that  of  the  temperature  in  the  "warm-blooded"  animals. 
Although  there  is  a  daily  swing  from  a  low  point  about 
4  A.M.  to  a  high  point  about  4  p.m.,  the  variation  is  hardly 
more  than  a  degree  in  the  Fahrenheit  scale.  The  constancy 
is  so  reliable  that  the  thermometer  makers  can  stamp 
98.6°  on  the  scale  with  assurance  that  it  will  mark  closely 
the  temperature  of  the  normal  person  everywhere.  The 
value  of  uniform  temperature  is  demonstrated  by  comparing 
the  influence  of  cold  on  ourselves  and  on  lower  animals 
without  a  regulatory  mechanism.  As  the  weather  becomes 
cold  the  frog,  for  example,  becomes  more  and  more  sluggish, 
until  finally  he  sinks  inactive  to  the  bottom  of  his  pool  and 
thus  remains  unless  he  is  warmed  again.  This  behavior  is 
determined  by  the  direct  dependence  of  the  speed  of  chemical 
processes  in  the  body  on  the  degree  of  heat.  The  "cold- 
blooded" animals,  having  the  temperature  of  their  surround- 
ings, can  act  with  speed  only  when  the  weather  is  warm; 
the  warm-blooded,  maintaining  a  fairly  fixed  high  tempera- 
ture in  spite  of  external  cold,  can  act  with  speed  at  all  times. 
There  is  no  better  illustration  than  this  of  the  value  of  the 
even  tenor  of  our  internal  environment  as  a  condition   for 


230  HUMAN    BIOLOGY 

freedom  from  changes  in  the  external  environment.  How 
is  this  valuable  independence  achieved? 

To  understand  regulation  of  temperature  we  must  reahze 
first  that  heat  is  continuously  being  produced  in  the  body 
by  every  variety  of  activity  that  occurs.  All  the  energy 
of  the  heart  is  turned  to  heat  inside  us,  about  three-fourths 
of  the  energy  of  our  muscles  appears  necessarily  as  heat, 
the  processes  in  the  hver  are  accompanied  by  large  heat 
production.  As  the  circulating  blood  passes  through  the 
specially  active  regions,  heat  flows  from  the  warmed  cells 
to  the  cooler  blood  and  is  thus  distributed  to  other  regions. 
An  important  service  which  the  circulation  performs, 
therefore,  is  that  of  equalizing  the  temperature  in  different 
parts  of  the  body.  It  also  plays  an  essential  role  in  the 
management  of  heat  loss  through  the  skin. 

Let  us  suppose  that  there  is  a  tendency  for  the  body 
temperature  to  rise  because  a  large  amount  of  heat  has  been 
produced  by  muscular  work.  The  heat  will  go  to  the  colder 
outer  air  by  radiation  and  conduction  if  it  is  brought  to 
the  skin,  which  is  in  contact  with  the  air.  Under  these 
circumstances  the  nerves  governing  the  size  of  the  surface 
arterioles  relax  their  grip,  the  vessels  dilate,  and  the  blood 
flows  through  them  and  through  the  capiflaries  to  which 
they  contribute,  in  much  greater  abundance.  In  consequence 
the  skin  becomes  red.  Thus  the  extra  heat  is  deHvered  to  the 
surroundings  and  a  rise  of  body  temperature  is  prevented. 
If  the  outer  air  is  too  warm  to  permit  the  heat  to  pass  to  it, 
however,  another  process  is  resorted  to;  heat  is  lost  by 
evaporation.  When  water  evaporates,  as  much  heat  is 
taken  from  the  surroundings  as  would  be  required  to  cause 
the  water  to  evaporate.  The  greater  deHvery  of  warm  blood 
to  the  skin  can  be  combined  with  pouring  of  sweat  on  the 
skin  surface.  As  the  sweat  evaporates  the  surface  is  cooled 
and  Hkewise  the  flowing  blood.  If  the  air  is  dry,  large  amounts 
of  heat  may  be  lost  in  this  way,  and  thereby  high  external 
temperatures  may  be  withstood  (e.g.,  by  stokers  and 
foundry  workers).  Occasionally  the  sweat  glands  fail  to 
develop  or  they  degenerate.  Persons  thus  afflicted  may  have  to 
wet  their  garments  in  order  to  endure  hot  weather,  or  they 
may  pant,  as  a  dog  does  (having  inefficient  swxat  glands). 


THE    INTEGRATIVE   ACTION   OF   THE   VASCULAR    SYSTEM       23 1 

and  lose  moisture  from  the  surfaces  of  the  respiratory 
passages.  The  highly  uncomfortable  experience  which  we 
have  on  a  day  which  is  not  only  hot  but  muggy  is  due  to  the 
interference  with  free  evaporation  by  the  moisture  already 
in  the  air. 

If  the  body  temperature  tends  to  fall,  an  interesting  series 
of  adjustments  occurs,  all  directed  towards  preservation 
of  the  steady  state.  First,  heat  which  is  being  lost  is  con- 
served: perspiration  is  reduced  to  a  minimum,  the  surface 
vessels  are  contracted  and  thus  the  warm  blood  from  the 
interior  is  not  exposed  to  the  cold  surroundings,  and  in 
animals  provided  with  hair  or  feathers  these  appendages 
of  the  skin  are  elevated  so  that  a  thicker  layer  than  usual 
of  insulating  air  is  enclosed  in  their  meshes.  In  us  only 
futile  "gooseflesh"  remains  of  this  last  protective  reaction, 
and  we  resort  therefore  to  extra  clothing  to  prevent  too 
great  heat  loss. 

If  the  check  on  the  outflow  of  heat  is  not  sufficient  to 
protect  against  a  fall  of  body  temperature,  more  heat  must 
be  produced.  The  first  step  in  that  direction  is  a  discharge 
of  adrenin  from  the  adrenal  medulla.  This  remarkable 
substance  not  only  collaborates  with  the  sympathetic 
impulses  which  are  constricting  the  surface  vessels,  but  it 
has  the  power  to  accelerate  the  processes  of  combustion  in 
all  parts  of  the  organism.  Its  discharge  is  like  opening  the 
dampers  of  a  furnace:  burning  goes  on  more  rapidly  and  the 
heat  production  quickly  mounts.  But  even  this  extra  heat 
may  not  be  enough  to  match  the  losses.  In  that  event 
muscular  activity  is  automatically  started,  i.e.,  shivering 
occurs.  The  greater  production  of  heat  with  which  we  are 
familiar  when  we  run  or  play  vigorous  games  then  results; 
indeed,  shivering  may  more  than  double  the  rate  of  heat 
development  in  the  body.  And  if  shivering  does  not  suffice 
to  keep  up  the  normal  temperature  we  are  hkely  to  be 
impelled  to  engage  in  such  strenuous  physical  exertion  that 
heat  flows  to  the  blood  from  many  large  muscle  masses 
engaged  in  the  eff"ort  and  is  dehvered  promptly  to  all  parts 
of  the  body  by  the  streaming  blood. 

It  is  noteworthy  that  not  only  are  there  arrangements 
which  check  a  shift  of  body  temperature  in  one  direction 


232  HUMAN   BIOLOGY 

or  the  other,  but  that  there  are  successive  Hnes  of  defense 
set  up  against  the  shift.  If  dilatation  of  the  skin  vessels 
does  not  stop  the  rise  of  body  temperature,  sweating  super- 
venes; if  conservation  of  heat  is  not  enough  to  stop  the 
fall  of  temperature,  a  second  Hne  of  defense  appears  in  the 
action  of  the  sympathico-adrenal  mechanism,  and  a  third 
in  shivering.  Of  course  extreme  conditions  can  break  down 
these  defenses,  and  a  person  may  die  of  heat  stroke  or  of 
freezing.  Within  a  wide  range  of  temperature  variations 
in  the  external  environment,  however,  we  maintain  the 
temperature  of  the  internal  environment  at  an  astonishingly 
uniform  level. 

The  dedicate  control  of  the  body  temperature  indicates 
the  operation  of  a  sensitive  thermostat.  The  location  of 
this  part  of  the  regulatory  apparatus  is  in  the  base  of  the 
brain,  in  the  so-called  thalamic  region.  If  the  blood  going 
to  that  region  is  warmed,  the  surface  vessels  are  relaxed 
and  sweating  takes  place;  if  the  blood  is  cooled,  shivering 
results.  When  that  region  is  destroyed,  regulation  is  lost 
and  the  animal  is  changed  to  the  cold-blooded  type,  i.e., 
its  temperature  now  follows  the  changes  of  its  surroundings. 
Anesthetics,  such  as  ether  and  chloroform,  and  also  excessive 
amounts  of  alcohol,  have  similar  effects.  In  fever  the  ther- 
mostat is  set  for  a  higher  temperature  level. 

Adjustments  for  Maintaining  an  Adequate  Oxygen  Supply. 
The  cells  of  the  body  are  more  closely  dependent  on  oxygen 
than  on  any  other  substance  obtained  from  the  outer 
world.  We  can  hve  without  food  for  weeks,  and  without 
water  for  days,  but  there  are  important  nerve  cells  in  the 
brain  which  cannot  live  without  oxygen  for  longer  than 
about  eight  minutes.  These  differences  appear  to  be  due  to 
differences  of  storage  of  these  substances  in  the  organism. 
Food  and  water  are  stored,  as  we  have  seen,  but  since 
oxygen  is  present  all  about  us,  as  one-fifth  part  of  the 
atmosphere,  there  is  no  need  for  storage  and  to  a  note- 
worthy degree  there  is  none.  The  problem  in  times  of  need, 
therefore,  is  that  of  conveying  the  oxygen  to  the  cells  from 
the  surrounding  supply. 

Although  such  need  arises  after  profuse  hemorrhage, 
for  example,  or  in  poisoning  by  illuminating  gas  or  auto- 


THE    INTEGRATIVE   ACTION   OF   THE   VASCULAR   SYSTEM       233 

mobile  exhaust,  these  may  be  regarded  as  unnatural  states. 
The  problem  is  best  presented  and  is  best  met  during 
vigorous  muscular  exertion.  The  oxygen  requirement  of  a 
man  of  average  size  may  be  only  0.25  to  0.30  hter  (quart) 
per  minute  when  he  is  at  rest;  but  very  rigorous  exertion 
may  raise  the  requirement  to  15  liters  per  minute  or  more. 
Even  in  most  favorable  circumstances  hov^ever,  the  maximal 
intake  of  oxygen  is  at  a  rate  less  than  4  Kters  per  minute. 
Thus  during  highly  strenuous  effort  the  intake  may  be 
from  10  to  12  times  what  it  is  during  rest  and  yet  be  far 
short  of  what  is  needed.  When  this  situation  arises  the 
lactic  acid  which  attends  muscular  contraction  is  not 
burned  to  carbon  dioxide  and  it  accumulates  in  the  muscles. 
Contraction  can  continue,  but  with  decreasing  efficiency 
because  of  increasing  concentration  of  the  acid.  Thus  an 
"oxygen  debt"  is  incurred;  and  even  though  activity 
ceases,  extra  oxygen  must  be  delivered  to  the  muscles  to 
burn  in  part  the  lactic  acid,  until  the  debt  is  paid  and  the 
resting  state  is  restored.  Various  and  complex  adjustments 
of  the  respiratory  and  circulatory  systems  are  made,  each 
tending  to  supply  an  amount  of  oxygen  sufficient  to  meet 
the  need  of  the  laboring  parts  or  to  pay  the  oxygen  debt 
if  the  need  has  not  been  met  during  the  period  of  labor. 

The  respirations,  first  of  all,  are  deeper  and  more  frequent. 
This  change  occurs  at  the  very  start  of  a  muscular  effort, 
too  soon  to  be  caused  by  any  other  agency  than  the  nerve 
impulses  which  initiate  the  effort  itself.  Thereafter  the 
greater  volume  of  breathing,  which  we  have  all  noted  when 
exercising  vigorously,  is  due  to  an  increase  of  carbon  dioxide 
(and  perhaps  lactic  acid  in  addition)  in  the  blood.  As  this 
increase  develops,  the  portion  of  the  brain  which  governs 
the  respiratory  movements  becomes  more  active  and  by 
ampHfying  and  accelerating  these  movements  it  brings 
about  a  much  greater  pulmonary  ventilation  than  before. 
This  carries  away  the  carbon  dioxide  which  is  given  off 
from  the  circulating  blood  into  the  myriads  of  Httle  sacs  or 
alveoh  of  the  lungs.  At  the  same  time  the  greater  ventilation 
maintains  the.  percentage  of  oxygen  in  these  alveoh.  By 
this  double  process  the  blood  unloads  its  volatile  waste 
(carbon  dioxide)  and  is  promptly  loaded  with  oxygen  for 


234  HUMAN   BIOLOGY 

delivery  to  the  active  organs.  The  respiratory  adjustments, 
therefore,  maintain  in  the  lungs  an  adequate  supply  of 
oxygen  in  spite  of  the  extra  demand,  and  they  minimize 
the  accumulation  of  carbon  dioxide  there  in  spite  of  the 
larger  deposit  from  the  blood. 

To  understand  the  circulatory  adjustments  we  must 
remember  that  the  carriage  of  oxygen  and  carbon  dioxide 
is  dependent  on  the  red  blood  corpuscles  of  the  blood  and 
that,  although  their  number  can  be  increased  in  emergencies, 
it  is  nevertheless  hmited.  In  such  conditions  the  only  way 
to  increase  the  carriage  of  these  gases  is  to  increase  the  use 
of  the  carriers;  in  other  words,  to  multiply  the  number  of 
trips  wh'ch  the  carriers  make  between  the  lungs  and  the 
active  parts.  This  in  fact  takes  place,  but  in  addition 
the  processes  of  loading  and  unloading  are  facilitated  at  the 
two  stations.  We  shall  now  consider  these  adjustments  in 
detail. 

First,  in  order  that  there  shall  be  a  larger  output  of  blood 
from  the  heart  there  must  be  a  larger  return  of  blood  to 
the  heart  through  the  veins.  This  effect  is  achieved  by  a 
variety  of  actions  when  we  engage  in  muscular  effort. 
The  nerves  governing  the  size  of  the  blood  vessels  in  the 
capacious  vascular  area  of  the  stomach  and  intestines 
cause  these  vessels  to  contract.  In  consequence  much  of 
the  blood  is  driven  out  of  them  and  into  the  vessels  of  the 
muscles,  which,  as  we  shall  see,  have  a  greatly  enlarged 
capacity  when  the  muscles  are  at  work.  Now  the  contracting 
muscles  press  more  or  less  rhythmically  on  the  vessels, 
especially  on  the  small  veins,  and  since  there  are  valves 
which  permit  only  an  onward  flow  of  the  blood  towards 
the  heart,  the  rhythmic  pressure  necessarily  promotes 
that  flow.  If  the  left  wrist  is  grasped  firmly  by  the  right 
hand,  and  the  left  hand  is  then  rapidly  and  repeatedly 
clenched  and  relaxed,  the  quick  filling  of  the  veins,  as  seen 
on  the  back  of  the  hand,  can  be  readily  demonstrated. 
Another  type  of  pumping  action  on  the  veins  occurs  in  the 
functioning  of  the  great  dome-shaped  muscle  of  respiration, 
the  diaphragm,  which  separates  the  chest  from  the  abdomen. 
When  it  contracts,  it  flattens,  and  thereby  it  somewhat 
increases  the  pressure  on  the  great  vein  which  leads  the 


THE    INTEGRATIVE    ACTION    OF   THE   VASCULAR    SYSTEM        235 

blood  upward  through  the  abdomen  from  the  legs.  Since 
valves  prevent  the  backward  flow  of  the  blood  into  the 
legs  the  pressure  favors  the  onward  flow.  At  the  same  time 
that  the  pressure  in  the  abdomen  is  increased  by  contraction 
of  the  diaphragm,  the  pressure  on  the  veins  in  the  chest  is 
decreased.  The  result  is  that  with  each  inspiratory  act 
conditions  are  estabhshed  which  promote  the  flow  of  a 
larger  volume  of  blood  into  the  heart.  During  expiration 
the  returning  venous  blood  accumulates  in  the  veins  outside 
the  chest,  in  the  arms,  neck  and  abdomen.  At  the  next 
inspiration,  however,  the  conditions  just  described  recur 
and  the  accumulated  blood  is  driven  to  the  heart.  Thus  to 
the  pumping  action  of  the  limb  muscles  is  added  the  pumping 
action  of  the  diaphragm  as  a  factor  favoring  the  greater 
utilization  of  the  blood.  Note  that  the  bodily  organization 
is  such  that  the  contracting  muscles,  which  need  extra 
oxygen  because  of  their  contractions,  automatically  favor 
the  securing  of  the  needed  oxygen  by  returning  the  blood 
which  carries  it;  and  that  the  diaphragm,  which  is  made  to 
pump  more  vigorously  during  exercise,  not  only  maintains 
the  oxygen  supply  for  loading  the  oxygen  carriers,  but  also 
aids  to  speed  up  the  circulation  of  the  carriers. 

Although  the  capacity  of  the  heart  chambers  can  be 
enlarged,  that  adaptation  is  limited.  The  greater  return 
of  blood  to  the  heart  in  a  given  time  resulting  from  the 
pump-like  actions  just  described  must  be  received  and 
sent  forth,  therefore,  by  a  heart  that  beats  faster.  As  with 
the  red  corpuscles,  limitation  is  compensated  for  by  more 
rapid  service.  The  faster  heart  beat  is  brought  about  and 
maintained  by  a  variety  of  agencies.  We  have  noted  that 
the  very  act  of  making  a  motion  is  accompanied  by  increase 
of  respiration,  because  nerve  impulses,  attending  the  act, 
excite  the  respiratory  center  in  the  brain.  Similarly  when 
we  start  to  move,  the  heart  beats  faster  because  vagus 
nervous  influences,  which  are  continuously  holding  the 
heart  in  check,  are  more  or  less  suppressed.  These  are  devices 
for  prompt  adjustment  to  need,  that  appear  in  two  diff"erent 
systems  which  are,  however,  clearly  related  in  their  coopera- 
tive functions.  The  pump-like  action  of  the  limb  muscles 
and    of  the   diaphragm,    that   drives    onward   the   venous 


236  HUMAN   BIOLOGY 

blood,  causes  an  increase  of  pressure  in  the  veins  (note  the 
prominence  of  the  veins  beneath  the  skin  during  exertion). 
This  increased  pressure  continues  and  accentuates  the 
nervous  effects  just  mentioned,  for  when  it  is  appHed  to  the 
right  side  of  the  heart,  it  starts  a  reflex  which  suppresses 
still  more  the  vagus  check  on  the  heart  rate  and  thereby 
the  beat  becomes  still  faster.  The  sympathetic  nerves, 
also,  which  are  known  to  be  excited  when  muscular  exertion 
is  very  strenuous  and  especially  when  emotional  excitement 
accompanies  the  eff"ort,  as  in  competitive  games,  may  play 
an  important  part  in  making  the  heart  contract  more 
rapidly.  All  these  influences  working  in  harmony  provide 
for  adequate  reception  of  the  greater  volume  of  blood 
flowing  back  through  the  veins,  for  adequate  delivery  of 
the  blood  to  the  lungs  where  the  deeper  ventilation  cares 
for  the  larger  exchange  of  the  respiratory  gases  (oxygen 
and  carbon  dioxide),  and  for  adequate  driving  of  the  oxygen- 
laden  blood  into  the  great  "arterial  tree." 

The  more  ample  discharge  from  the  heart  into  the  arteries 
is  attended  by  a  rise  of  pressure  in  the  arteries.  In  tests 
made  on  a  man  riding  a  stationary  bicycle  the  arterial  blood 
pressure  rose  at  the  start  from  130  millimeters  of  mercury 
to  180,  and  during  the  continuation  of  the  exercise  it 
remained  high,  between  165  and  170  millimeters  (i.e.  at 
about  7  inches  instead  of  the  resting  level,  about  5  inches). 
The  value  of  the  increased  pressure  we  can  best  appreciate 
when  we  consider  that  there  is  a  dilation  of  the  arterioles 
and  capillaries  in  the  active  muscles.  If  the  arterial  pressure 
were  barely  sufficient  to  keep  the  blood  in  circulation,  a 
widening  of  the  vessels  in  one  region  would  provide  such  a 
way  of  escape  for  the  blood  from  the  arteries  into  the  veins 
that  it  would  run  through  them  and  thus  would  leave  other 
regions  without  an  adequate  supply.  The  increased  arterial 
pressure  not  only  prevents  any  such  failure  of  the  delivery 
of  blood  to  quiet  regions,  but  it  also  assures  rapid  flow 
through  the  dilated  vessels  of  active  regions,  i.e.  where 
the  need  for  the  materials  which  the  blood  carries  is  greatest. 

The  dilation  of  the  blood  vessels,  arterioles  and  capillaries 
in  active  muscles  is  one  of  the  most  remarkable  adjustments 
for  bringing  supplies  to  the  cells  and   for  carrying  away 


THE    INTEGRATIVE   ACTION    OF  THE   VASCULAR   SYSTEM       237 

their  waste  in  an  emergency.  Careful  studies  have  shown 
that  when  a  muscle  is  at  rest  many  of  its  capillaries  are  not  in 
use  or  that  they  have  shifts  of  service,  one  opening  here  for  a 
time  and  then  closing  down  so  that  no  blood  runs  through 
it,  while  another  near-by  capillary  opens  and  serves  its 
neighborhood.  Only  the  capillaries  which  contain  blood  are 
visible.  When  an  active  muscle  from  one  side  of  the  body  is 
compared  with  the  corresponding  muscle,  inactive,  of  the 
other  side,  the  astonishing  fact  appears  that  the  number  of 
open  capillaries  in  the  muscle  at  work  may  range  from  40  to 
100  times  the  number  in  the  muscle  at  rest.  What  causes 
the  capillaries  to  dilate  is  not  yet  clear;  lack  of  oxygen, 
increase  of  carbon  dioxide,  or  possibly  some  subtle  substance 
resulting  from  the  wear  and  tear  of  the  muscle  as  it  pulls, 
may  open  the  vessels.  However  they  may  be  opened,  the 
great  importance  of  their  being  open  should  not  be  over- 
looked. It  is  in  the  capillary  region  of  the  circulatory  system 
that  the  exchanges  between  the  blood  and  the  fixed  cells 
occur.  Here  all  the  adjustments  of  that  system  during 
physical  work  that  we  have  been  considering  have  their 
significance.  The  blood  is  bearing  sugar  and  oxygen  which 
the  laboring  muscles  require,  it  can  bear  away  the  carbon 
dioxide  and  water  which  result  from  the  burning  that 
attends  contraction.  The  nearer  the  flowing  blood  can  be 
brought  to  the  muscle  cells  in  their  need  for  both  these 
services,  the  more  efficiently  will  the  muscular  work  be 
performed.  The  extraordinary  unfolding  of  the  unused 
capillaries  assures  intimate  relations  between  the  cells 
and  the  blood  stream. 

We  may  now  complete  the  circuit  of  adaptive  changes 
in  the  circulatory  system.  It  is  clear  that  when  the  muscles 
are  rhythmically  contracting  and  massaging  the  vessels 
within  and  between  them  they  are  pressing  on  a  greater 
volume  of  blood  than  is  present  when  the  muscles  are  at 
rest.  In  other  words  the  laboring  muscles  act  as  if  they 
were  outlying  hearts,  receiving  more  blood  when  they  work 
and  pumping  that  blood  back  to  the  central  heart  and  to 
the  lungs  for  a  new  service. 

Still  another  remarkable  relation  remains  to  be  mentioned : 
that  of  the  facilitation  of  the  gas  exchanges  in  the  capillaries 


238  HUMAN   BIOLOGY 

of  the  lungs  and  of  the  muscles.  We  have  seen  that  the 
adjustments  in  the  circulation  when  work  is  being  done  are 
all  directed  towards  increasing  the  number  of  trips  of  the 
red  blood  corpuscles  from  lungs  to  muscles  and  from  muscles 
to  lungs  again  in  a  given  time.  Although  the  blood  flow 
in  the  capillaries  is  slower  than  anywhere  else  in  the  circuit, 
when  the  rate  is  increased  it  is  increased  in  the  capillaries 
as  well  as  elsewhere.  That  means,  of  course,  that  less  time 
is  allowed  for  the  carriers  to  unload  carbon  dioxide  in  the 
lungs  and  take  on  oxygen  and  to  perform  the  reverse  proc- 
esses in  the  muscles.  The  beautiful  fact  has  been  discovered 
that  excess  of  carbon  dioxide  hastens  the  unloading  of 
oxygen  from  the  corpuscles  and  that  excess  of  oxygen  hastens 
the  unloading  of  carbon  dioxide.  When  the  muscles  work, 
therefore,  and  produce  extra  carbon  dioxide  and  need  more 
oxygen,  the  extra  carbon  dioxide  forces  the  unloading  of 
oxygen  from  the  corpuscles  more  rapidly  at  a  time  when 
the  faster  flow  through  the  muscle  capillaries  requires  a  more 
rapid  unloading.  And  when  the  corpuscles,  laden  with  carbon 
dioxide,  reach  the  lungs,  the  higher  concentration  of  oxygen 
there  drives  out  the  carbon  dioxide  more  rapidly  when  the 
faster  flow  through  the  pulmonary  capillaries  requires  a 
more  rapid  unloading.  In  each  place  the  gas  which  drives 
the  other  out  seizes  the  vacated  place  in  the  carrier  for  itself 
and  holds  it  until  it  in  turn  is  driven  out.  There  is  no  more 
fascinating  interplay  of  processes  than  this  in  any  part  of 
the  organism. 

One  more  striking  provision  for  assuring  an  adequate 
delivery  of  oxygen  in  case  of  need  is  seen  in  the  sudden 
rise  in  the  number  of  red  blood  corpuscles  when  muscular 
exertion  is  vigorous.  This  is  the  only  aspect  of  the  adaptation 
of  the  organism  to  oxygen  want  that  resembles  a  resort  to 
the  supply  depots.  As  we  have  seen,  when  muscular  exertion 
is  severe  and  prolonged,  glucose  is  mobilized  from  the  liver 
stores  and  distributed  by  the  blood  for  use  wherever  required. 
There  is  a  store  of  red  blood  corpuscles  in  the  spleen;  the 
concentration  of  the  corpuscles  there  may  be  as  much  as 
twice  that  in  the  general  circulation.  In  strenuous  exercise 
the  spleen  is  made  to  contract  by  sympathetic  nerve  impulses 
and   squeeze  out  its   contents.   The   addition   of  the    con- 


THE    INTEGRATIVE    ACTION    OF   THE   VASCULAR    SYSTEM        239 

centrated  blood  thus  made  to  that  in  the  vessels  may  increase 
the  number  of  circulating  corpuscles  by  20  per  cent  or  more. 
These  corpuscles,  of  course,  promptly  become  carriers  of 
oxygen  and  carbon  dioxide,  at  a  time  when  their  services 
are  in  demand. 

It  is  of  interest  to  note  that  many  of  the  changes  in  the 
circulation  described  are  a  part  of  the  bodily  changes  occur- 
ring in  profound  emotional  excitement.  Respiration  deepens, 
the  heart  beats  more  rapidly,  the  arterial  pressure  rises, 
the  blood  is  shifted  aw^ay  from  the  stomach  and  intestines 
to  the  heart  and  central  nervous  system  and  the  muscles, 
sugar  is  freed  from  the  reserves  in  the  liver,  the  spleen 
contracts  and  adrenin  is  discharged  from  the  adrenal 
medulla.  The  key  to  these  marvelous  transformations  in 
the  body  is  found  in  relating  them  to  the  natural  accom- 
paniments of  fear  and  rage:  running  away  in  order  to  escape 
and  attacking  in  order  to  be  dominant.  Whichever  the 
action,  a  hfe-or-death  struggle  may  ensue.  The  emotional 
responses  may  be  regarded  as  preparatory  for  that  struggle, 
adjustments  which  so  far  as  possible  put  the  organism  in 
readiness  for  meeting  the  demands  which  will  be  made 
upon  it.  The  secreted  adrenin  not  only  collaborates  with 
the  sympathetic  impulses,  to  the  degree  that  they  are 
engaged  in  the  adjustments,  but  it  has  the  property  of 
extending  the  ability  of  fatigued  muscle  to  continue  at  work. 
All  these  wonderful  arrangements  which  operate  when  we 
engage  in  hard  muscular  exercise,  and  particularly  when 
there  is  attendant  excitement,  we  can  best  understand  by 
reference  to  racial  history.  For  myriads  of  generations  our 
ancestors  have  had  to  meet  the  exigencies  of  existence  by 
physical  effort,  perhaps  in  supreme  effort.  The  struggle 
for  existence  has  been  a  nerve  and  muscle  struggle.  The 
organisms  in  which  the  adjustments  were  most  rapid  and 
most  perfect  had  advantages  over  their  opponents  in  which 
the  adjustments  w^re  less  so.  The  functional  perfections 
had  survival  value,  and  we  may  regard  the  remarkable 
arrangements  for  mobilizing  the  body  forces,  which  are 
displayed  when  intense  muscular  activity  is  required  or 
anticipated,  as  the  natural  consequences  of  a  natural 
selection. 


240  HUMAN   BIOLOGY 

The  Constancy  oj  the  Neutrality  of  the  Blood.  The  foregoing 
edscription  has  repeatedly  called  attention  to  the  release 
of  lactic  acid  and  carbon  dioxide  (which  in  watery  solution 
forms  carbonic  acid)  during  muscular  work.  Besides  these 
and  other  acids  which  may  be  developed  in  the  body,  acid 
foods  may  be  eaten  and  absorbed  and  they  also  tend  to 
render  the  blood  acid.  On  the  other  hand,  the  food  may  be 
alkaline  in  reaction,  or  there  may  be  a  loss  of  acid  from  the 
body  by  its  secretion  in  the  gastric  juice,  or  the  carbon 
dioxide  may  be  "pumped  out"  of  the  blood  to  a  considerable 
degree  by  prolonged  deep  breathing;  each  of  these  conditions 
tends  to  render  the  blood  alkaline.  It  is  of  the  greatest 
importance  to  the  existence  and  proper  action  of  the  cells 
that  the  reaction  of  the  blood  and  tissue  fluid  shall  not  become 
either  acid  or  alkaline.  If  the  blood  becomes  too  acid,  coma, 
or  unconsciousness,  is  likely  to  occur;  if  too  alkahne,  con- 
vulsions may  take  place.  If  the  fluid  supplied  to  the  heart 
is  too  acid,  the  muscle  relaxes  and  ceases  to  beat;  if  too 
alkaline,  it  again  ceases  to  beat,  but  usually  stops  in  the 
contracted  state.  These  are  only  two  examples  out  of  many 
that  could  be  cited  to  show  the  dangers  of  a  shift  of  the 
chemical  reaction  of  the  blood  too  far  away  from  the  neutral 
point  between  acidity  and  alkalinity.  Within  a  narrow  range 
of  variation  the  nervous  system  will  operate  perfectly,  with 
no  signs  of  coma  or  spasmodic  discharges,  and  the  heart 
will  go  on  beating  continuously.  But  the  reaction  must  be 
kept  within  that  narrow  range. 

The  complete  account  of  the  mechanisms  by  which  the 
reaction  of  the  blood  is  kept  close  to  neutrality,  in  spite 
of  external  and  internal  conditions  which  are  constantly 
acting  to  push  the  reaction  away  from  that  point,  would 
require  elaborate  and  detailed  consideration  of  highly 
involved  processes.  We  shall  regard  only  the  simpler  aspects 
of  the  mechanisms.  Dissolved  in  the  blood  plasma  is  a 
compound  of  the  elements  sodium  (symbolized  by  the 
letters  Na),  hydrogen  (H),  carbon  (C)  and  oxygen  (O) 
in  three  parts  (ordinary  cooking  soda).  This  compound 
is  known  chemically  as  sodium  bicarbonate  (NaHCOs). 
The  symbol  of  carbonic  acid,  which  results  from  dissolving 
carbon  dioxide  (CO2)  in  water  (HoO),  is  H2C0i.     Now  the 


THE    INTEGRATIVE    ACTION    OF   THE    VASCULAR    SYSTEM        24 1 

reaction  of  the  blood  is  determined  by  the  relation  of  H2CO3 
to  NaHCOs  existing  in  the  blood.  If  the  carbonic  acid  is 
increased  the  blood  is  more  acid;  if  the  carbonic  acid  is 
decreased,  as  it  may  be  by  excessive  voluntary  ventilation  of 
the  lungs  and  consequent  removal  of  carbon  dioxide  from 
the  blood,  the  blood  is  more  alkahne.  If  a  non-volatile 
acid,  such  as  hydrochloric  acid  (HCl)  is  added  to  the  blood, 
it  unites  with  the  sodium  of  some  of  the  sodium  bicarbonate 
and  drives  off  carbon  dioxide,  according  to  the  following 
equation: 

HCI  +  NaHCOs  =  NaCI  +  H^O  +  CO2 

The  NaCl  is  common  salt,  a  neutral  harmless  substance. 
The  H2O  and  CO2  form  the  famihar  carbonic  acid,  which 
is  volatile.  The  addition  of  the  strong  acid  (HCI)  has,  to  be 
sure,  made  the  blood  more  acid  by  increasing  the  H2CO3, 
but,  as  we  have  seen,  this  stimulates  the  respiratory  mechan- 
ism and  thus  the  extra  carbon  dioxide  is  quickly  and  readily 
reduced.  And  when  it  is  reduced  the  normal  ratio  of  H2CO3 
to  NaHCOs  returns,  the  neutrahty  of  the  blood  is  restored, 
and  the  deeper  breathing  stops. 

The  sodium  bicarbonate  has  served  to  protect  the  blood 
from  becoming  acid  in  the  circumstances  just  described, 
and  because  of  its  capacity  to  perform  that  function  it  is 
called  a  "buffer"  salt.  Another  buffer  salt  existing  in  the 
blood,  especially  in  the  red  blood  corpuscles,  is  alkaline 
sodium  phosphate  (Na2HP04).  When  acid  is  added  to  blood, 
not  only  is  it  "buffered"  by  sodium  bicarbonate  but  also 
by  the  alkaline  sodium  phosphate,  according  to  the  following 
equation: 

Na2HP04  +  HCI  =  NaH2P04  +  NaCl 

Again  note  that  common  salt  (NaCl)  is  formed  and  acid 
sodium  phosphate.  It  happens  that  both  "alkaline"  and 
"acid"  sodium  phosphate  are  almost  neutral  substances. 
The  strong  hydrochloric  acid  (HCI)  has,  therefore,  not 
altered  the  reaction  of  the  blood  to  an  important  degree  by 
changing  the  alkahne  to  the  acid  form  of  the  sodium  phos- 
phate. The  acid  phosphate  has,  however,  a  slightly  acid 
reaction  and  it  must  not  be  permitted  to  accumulate  in  the 


242  HUMAN   BIOLOGY 

blood.  Unlike  carbonic  acid  it  cannot  be  breathed  away. 
It  is  eliminated  by  being  discharged,  along  with  excess 
of  NaCI,  by  way  of  the  kidneys.  If  large  amounts  of  non- 
respirable  acid  appear  in  the  blood,  ammonia,  which  is 
alkaline  and  which  is  ordinarily  changed  to  a  neutral  prod- 
uct, urea,  is  utilized  to  render  the  acid  harmless  and  to 
carry  it  away  in  the  urine. 

A  modification  of  these  processes  occurs  when  the  blood 
tends  to  become  alkaline.  Let  us  suppose  that  a  sharp  pain 
has  caused  unusually  deep  breathing.  The  carbon  dioxide 
percentage  in  the  lungs  is  thereby  reduced  and  in  consequence 
it  is  reduced  also  in  the  blood.  The  ratio  of  H2CO3  to  NaHCOs 
is  lowered,  i.e.  the  reaction  shifts  towards  the  alkaline  side 
of  neutrality.  Under  these  conditions  respiration  may  cease 
altogether  for  a  time.  In  the  absence  of  breathing  the  carbon 
dioxide,  which  is  continuously  being  produced  by  the 
beating  heart  and  other  persistent  activities,  accumulates 
in  the  blood  until  the  normal  ratio  of  H2CO3  to  NaHCOa 
returns,  whereupon  the  rhythmic  ventilation  of  the  lungs 
begins  again.  And  if  the  reaction  of  the  blood  is  for  some 
time  shifted  towards  alkalinity,  alkaline  sodium  phosphate 
is  excreted  by  the  kidneys  until  neutrality  is  assured. 

In  the  main  the  delicate  balance  between  a  dangerous 
acid  and  an  almost  equally  dangerous  alkaline  reaction  is 
maintained  by  the  extraordinary  sensitiveness  of  the  respira- 
tory center  in  the  brain  and  of  the  kidneys  to.  even  slight 
alterations  in  the  blood.  We  may  think  of  these  sentinels  as 
being  continuously  on  the  alert,  ready  at  the  first  indications 
of  a  change  to  act  in  such  a  way  as  to  prevent  a  harmful 
swing  away  from  the  normal  steady  state  of  neutrality. 

Other  Integrative  Services  oj  the  Circulating  Blood.  We  have 
been  considering  the  blood  and  lymph  as  the  fluid  matrix 
of  the  body  and  noting  the  various  devices  which  work 
towards  the  maintenance  of  constancy  of  the  supplies 
and  of  the  working  conditions  which  it  provides  for  the 
living  cells.  Among  the  devices  for  regulating  the  storage 
and  mobilization  of  sugar,  it  will  be  recalled,  the  adrenal 
medulla  and  the  islands  of  the  pancreas  were  mentioned. 
These  are  examples  of  glands  of  internal  secretion,  or  endo- 
crine   glands,    organs    which    elaborate    special  substances 


THE    INTEGRATIVE   ACTION    OF   THE   VASCULAR    SYSTEM        243 

and  on  occasion  discharge  their  products  into  the  blood 
stream  for  distribution  to  all  parts  of  the  body.  The 
profound  influence  w^hich  these  internal  secretions  have  on 
the  organism  cannot  be  overemphasized.  In  general  they 
affect  the  rate  and  nature  of  the  chemical  changes  in 
the  body,  sex  functions  and  characteristics,  and  the  processes 
of  growth. 

We  have  seen  that  adrenin  produced  by  the  adrenal 
medulla,  when  discharged  in  extra  amount,  is  capable  of 
accelerating  heat  production.  Another  gland  which  affects 
the  speed  of  combustion  is  the  thyroid,  which  is  located 
in  the  neck.  When  it  is  deficient,  the  processes  of  burning 
in  the  body  may  be  so  slow  that  the  heat  output  may  be 
reduced  30  per  cent  or  more  below  the  normal  level.  Natu- 
rally enough  persons  afflicted  with  this  condition  are  espe- 
cially sensitive  to  cold  weather.  When  the  substance 
produced  by  the  thyroid  is  delivered  to  the  blood  in  excess, 
the  heat  production  may  be  doubled  in  rate.  More  food 
must  be  eaten  in  order  to  keep  up  the  normal  weight,  the 
skin  is  flushed,  and  sweating  is  prominent,  for  the  extra 
heat  must  be  eliminated  if  normal  temperature  is  to  be 
maintained.  It  is  possible  that  the  thyroid  plays  a  role  in 
adjusting  the  body  to  alterations  in  the  external  temperature, 
acting  like  the  adrenal  medulla  but  in  a  less  ready  and  a 
more  persistent  manner. 

The  sex  glands,  the  testes  and  ovary,  produce  substances 
which,  given  into  the  blood  stream,  bring  forth  the  typical 
features  of  the  male  and  female  respectively.  The  influence 
of  the  testes  in  this  respect  has  long  been  known.  The 
striking  transformations  which  occur  in  the  boy  at  puberty: 
the  growth  of  hair  on  the  face  and  other  parts  of  the  body, 
the  deeper  voice,  the  development  of  physical  vigor,  the 
assertiveness  and  sense  of  power,  all  these  fail  if  the  testes  are 
absent.  Analogous  changes  occur  in  the  young  girl  at 
puberty  and  are  lacking  if  the  ovaries  are  removed.  The 
outer  part  (the  cortex)  of  the  adrenal  gland  also  has  a 
remarkable  relation  to  the  development  of  superficial 
sex  appearances.  If  tumors  of  this  portion  of  the  adrenal 
gland  appear  in  young  boys,  maturing  occurs  at  an  early 
age;   the   phenomenon    is    sometimes    referred    to    as    the 


244  HUMAN   BIOLOGY 

"infant  Hercules"  type.  In  woman  such  tumors  have  the 
extraordinary  effect  of  giving  the  female  some  of  the  male 
characters,  e.g.  a  deep  voice  and  a  beard,  and  removing  a 
number  of  the  typical  features  of  the  female. 

The  endocrine  glands  which  especially  influence  growth 
are  the  thyroid  and  the  pituitary  which  is  at  the  base  of  the 
brain.  If  the  thyroid  is  deficient  from  birth  the  condition 
of  cretinism  results.  Unless  treated  the  child  remains  a 
dwarf,  hideous  in  appearance,  and  furthermore  an  idiot. 
Such  monsters  are  now  rare,  for  it  is  commonly  known  that 
by  giving  a  preparation  of  the  thyroid  gland  it  is  possible 
to  bring  about  a  natural  development  of  body  stature 
and  of  the  nervous  system.  The  transformations  thus 
wrought  seem  nothing  short  of  miraculous.  If  there  is 
deficiency  of  the  front  part  of  the  pituitary  gland,  dwarfism 
results,  but  the  dwarf  is  not  idiotic.  He  is  unusually  fat, 
especially  about  the  hips,  he  has  an  infantile  body  form, 
and  there  is  failure  of  development  of  the  reproductive 
organs.  When  this  portion  of  the  pituitary  gland  is  over- 
developed and  overactive  in  youth,  growth,  especially  of 
the  long  bones,  is  excessive.  The  result  is  a  giant.  The 
large  growth  of  the  pituitary  body  enlarges  the  bony  pocket 
in  which  it  rests,  and  with  the  x-rays  it  is  possible  to  see 
in  the  skulls  of  living  giants  the  evidence  of  the  cause  of  their 
abnormality.  Recent  experiments  indicate  that  the  growth- 
principle  of  this  gland  has  been  isolated  and  can  be  used 
eff^ectively  in  promoting  growth  during  adolescence. 

The  foregoing  references  to  the  functions  of  the  endocrine 
glands  should  be  regarded  as  merely  illustrative.  In  each 
instance  it  is  clear  that  an  organ  in  one  part  of  the  body 
has  remote  effects  on  parts  far  removed  from  it.  The  connect- 
ing agency  is  not  the  nervous  system,  but  the  other  great 
integrating  system  of  the  organism,  the  circulating  blood 
and  tissue  fluids. 

REFERENCES 

Bainbridge,  F.  a.  1923.  The  Physiology  of  Muscular  Exercise.  Ed.  2,  Lond., 
Longmans,  Green. 

Cannon,  W.  B.  1926.  Some  general  features  of  endocrine  influence  on  metab- 
olism. Am.  J.  Med.  Sc,  171:  1-20. 


THE    INTEGRATIVE    ACTION    OF   THE   VASCULAR    SYSTEM        245 

1929.   Bodily  Changes  in  Pain,   Hunger,   Fear  and  Rage.   Ed.   2,   N.  Y., 
Appleton. 
Haldane,   J.   S.    191 7.   Organism   and   Environment  as   Illustrated   by   the 

Physiology  of  Breathing.  Yale  Univ.  Press. 
Hill,  A.  V.  1926.  Muscular  Activity.  Bait.,  Williams  &  Wilkins. 
Howell,  W.  H.  1927.  A  Textbook  of  Physiology,  Ed.  10.  Phila.,  Saunders. 
RowNTREE,  L.  G.  1922.  The  water  balance  of  tlie  body.  Physiol.  Rev.,  2:  116. 
Sharpey-Schafer,  E.  1924.  The  Endocrine  Organs.  Lond.,  Longmans,  Green. 


Chapter  XI 

NERVOUS  INTEGRATIONS  IN  MAN 

J.  F.  Fulton  and  C.  S.  Sherrington 

IT  has  to  be  remembered  that  of  the  cells,  which  in  their 
multitudes  compose  the  body,  whether  animal  or 
human,  each  one  leads  its  individual  Hfe,  is  individually 
born,  feeds  and  breathes  for  itself,  and  is  destined  for 
individual  death.  This  book  has  described  already  these 
microscopic  hving  units,  and  their  arrangement  and  com- 
bination into  differentiated  systems  and  aggregates  called 
tissues  and  organs.  These  pages  have  also  told  how  from  those 
systems  and  organs  is  constructed  the  unified  individual, 
for  instance  the  human  being.  With  the  differentiation  of  the 
cell  systems  have  gone  division  of  labor  and  specialization 
of  function,  and  a  crowning  part  in  the  integration  of  the 
total  individual  is  played  by  the  system  of  differentiated 
nerve  cells,  the  nervous  system. 

NERVOUS    integration 

The  system  provides  speedy  communication  between  one 
part  of  the  body  and  another  part,  by  message  sending. 
One  of  its  main  offices  is  to  "operate"  the  muscles.  It  has 
been  commonly  and  permissibly  hkened  to  an  electric 
installation  with  connected  central  exchanges  whither  run 
wires  from  receiving  stations  and  whence  issue  wires  to 
outlying  motor  machines.  Through  it  a  single  receiving 
station  has  touch  with  many  of  the  motor  machines.  The 
exchanges  are  the  nerve  centers  in  spinal  cord  and  brain; 
the  motor  machines  are  the  muscles,  the  receiving  stations 
are  the  sense  organs,  and  the  wires  are  the  nerve  fibers 
connecting  all  these  into  a  system.  The  central  exchanges 
are  so  contrived  that  a  wire  from  a  receiving  station  can 
put  these  or  those  motor  machines  into  action  and  likewise 
stop  or  restrain  others  which  would  impede  or  conflict  with 
them. 

The  receiving  stations  are  commonly  called  sense  organs; 
through  them  light,  sound,  or  other  external  stimuh  excite 

246 


NERVOUS    INTEGRATIONS    IN    MAN  247 

in  the  central  exchanges  a  reaction  which  often  documents 
itself  to  the  mind  as  a  perceptual  experience.  But  that 
sensual  result  accrues  only  when  the  central  reaction 
involves  certain  sets  of  the  central  exchanges.  The  central 
reaction  taken  as  a  whole  consists  of  much  that  does  not 
document  itself  to  the  mind.  Therefore  it  is  better  in  speaking 
of  the  receiving  station  to  replace  the  term  "sense  organ" 
by  the  broader  and  simpler  term  "receptor."  This  latter 
is  suitable  for  the  receiving  station  in  respect  of  both  of  its 
two  central  results,  the  non-mental  "reflex"  and  the  sensual 
or  other  mental  result;  whereas  "sense  organ"  is  a  misnomer 
for  the  receiving  station  in  respect  of  its  purely  reflex  and 
non-mental  function.  This  distinction  is  the  more  important 
because  the  pure  reflex  central  reaction  occurs  sometimes 
by  itself,  and  can  in  experiment  be  cut  off  from  the  mental 
by  taking  advantage  of  the  partial  separateness  of  the 
central  exchanges  for  the  two,  although  the  nerve  from  the 
receptor  leads  to  both.  The  conducting  paths  to  the  "mental" 
nerve  centers  run  for  the  most  part  through  the  "reflex" 
nerve  centers. 

The  "exchanges"  or  "centers"  consist  of  extensively 
branched  nerve  cells  "holding  hands"  with  each  other  in 
many,  but  precisely  restricted,  directions,  these  communica- 
tions being  for  the  most  part  capable  of  being  opened  or 
closed  as  circumstances  may  require.  The  "lines"  entering 
and  leaving  the  exchanges,  and  traversing  them  en  route  for 
others,  are  built  of  long  living  threads  (nerve  fibers)  each 
one  an  extension  from  some  nerve  cell,  and  by  it  kept 
alive.  The  cells  and  their  fibers  when  followed  in  the  direction 
of  their  linkage  can  be  traced  as  chains  of  which  each  link 
is  a  living  nerve  cell  with  its  nerve  fibers.  Along  these  living 
chains  travel,  when  a  stimulus  excites  them  at  any  point, 
"nervous  impulses,"  transient  waves  of  physicochemical 
change.  A  receptor  acting  on  the  nerve  fibers  which  connect 
it  with  its  next  nerve  centers  thus  excites,  when  it  is  stimu- 
lated, nervous  impulses  which  run  into,  and  in  various  direc- 
tions along,  the  central  nervous  system.  Everywhere  and 
whatever  the  receptor,  whether  the  retina  reacting  to  light, 
the  ear  to  sound,  or  the  skin  to  touch,  the  nervous  impulses 
generated  seem  to  be  alike.   Each  is  a  brief  disturbance 


248  HUMAN   BIOLOGY 

lasting  about  3^:500  of  a  second,  and  travelling  about 
88  yards  a  second  along  the  conducting  paths.  Each 
impulse  leaves  the  conductor  behind  it  in  a  state  incapable 
of  transmitting  another  impulse  for  about  the  same  period. 

Similarly  the  messages  issuing  from  a  nervous  center 
whatever  they  have  to  effect,  whether  to  cause  a  gland  to 
secrete,  a  muscle  to  contract,  or  the  heart  to  slacken,  consist 
solely  of  nerve  impulses  hke  those  generated  by  the  receptors 
at  the  beginnings  of  their  entrant  paths.  Some  of  the  nerve 
fibers  are  thicker  than  others,  and  in  these  their  impulses 
travel  sHghtly  faster  than  those  of  the  smaller.  Otherwise 
the  only  difference  observed  between  impulses,  wherever 
occurring  in  the  nervous  system,  hes  not  in  the  individual 
impulse  itself  but  in  the  time-grouping  of  the  impulses,  so 
that  concomitant  with  intensity  of  actions  go  impulse  trains 
of  higher  frequency  (although  each  impulse  in  each  train  is  still 
quite  discrete) ,  so  that  the  number  of  successive  impulses  arriv- 
ing or  leaving  by  a  particular  pa1^h  is  per  second  greater. 

But  impulses  are  not  the  sole  form  of  functional  reaction 
exhibited  by  the  nervous  system.  Consisting  as  it  does  of 
chains  of  conducting  cells  laid  end  to  end,  the  impulse 
after  propagating  itself  along  one  cell  has  then  to  excite 
the  next.  All  points  of  hnkage  between  cell  and  cell  in  the 
system  are  confined  to  nerve  centers.  It  is  in  nerve  centers 
that  functional  study  finds  evidence  of  forms  of  reaction 
which  summate,  that  is  can  add  themselves  together  both 
in  space  and  in  time,  which  nervous  impulses  cannot  do. 
These  reactions  which  can  show  summation  do  so  chiefly 
in  regard  to  the  excitation  of  one  cell  by  the  next  cell  or 
cells  down  stream  from  or  collateral  to  it  in  the  cell  chain 
as  followed  in  its  functional  direction.  Further  at  these 
neurone  junctions  (synapses),  which  always  lie  within  the 
nervous  centers,  a  process  which  is  the  polar  opposite  of 
excitation  is  found,  i.e.,  inhibition.  It,  like  excitation  just 
mentioned,  gives  evidence  of  summation,  but  has  for  result 
the  prevention  or  diminution  or  suppression  of  excitation. 
There  is,  however,  no  evidence  that  it  can  suppress  impulses 
once  started  to  traverse  the  nerve  fiber.  These  processes 
of  excitation  and  inhibition  can  much  exceed  in  duration 
the  brief  nervous  impulse  itself. 


NERVOUS    INTEGRATIONS    IN    MAN  249 

Speed  of  communication  and  of  reaction  of  one  part  of 
the  body  to  happenings  at  another  seems  to  be  part  of  the 
"purpose"  of  this  Hving  telephone  system.  Although  its 
microscopic  structure  and  its  elemental  unit  reactions 
exhibit  an  almost  monotonous  uniformity  and  process,  the 
results  which  are  their  outcome  are  strikingly  various  and 
bear,  as  do  so  many  of  the  body's  reactions  (but  these  even 
more  obviously  than  most)  the  feature  of  "purpose." 
Thus,  by  their  means  a  speck  of  dust  in  the  eye  sends 
messages  thence  far  and  wide  over  the  body,  all  of  them 
conducive  to  an  obvious  purpose.  Its  messages  evoke  (i) 
protective  movement  of  the  eyelids,  (2)  protective  secretion 
of  tears,  (3)  protective  coming  of  the  hand  to  the  assistance 
of  the  eye  and  indeed  a  whole  train  of  motor  acts  toward 
relief  of  the  situation.  Finally  (4)  that  situation  is  reinforced 
and  therefore  protectively  accentuated,  until  relief  has 
come,  by  superadded  mental  experience,  i.e.,  pain;  the  pain 
we  note  is  hkewise  and  nr  less  than  the  rest  of  the  train 
of  reactions  a  sequel  to,  a  product  and  accompaniment  of, 
the  neural  reaction,  mysterious  though  the  relation  between 
it  and  the  material  processes  still  remains. 

The  nervous  system  throughout  the  whole  great  class  of 
animals  known  as  vertebrate  exhibits  the  same  broad  plan  of 
construction,  the  same  character  of  unit  cells  or  neurones 
arranged  in  chains  and  with  conductive  thread-like  fibers, 
and  the  same  fundamental  reactions,  namely  impulse 
conduction  and  the  two  opposed  processes  of  excitation  and 
inhibition.  In  man  it  does  not  depart  from  that  plan  or 
from  those  characters  but  merely  offers  the  highest  and 
most  complex  example  of  them. 

It  was  said  above  that  a  main  function  of  the  nervous 
system  is  to  enable  quick  appropriate  reaction,  by  movement 
for  the  most  part,  to  environmental  events  significant  for 
the  organism,  for  example  escape  from  being  made  a  prey,  or 
the  securing  of  prey  or  other  food.  The  primitive  nervous 
system  of  the  more  primitive  vertebrates  secures  this  end, 
within  usually  a  more  restricted  range  of  circumstances  than 
in  the  higher  vertebrates,  and  so  far  as  we  can  Judge  by 
little  else  than  pure  reflex  action. 


250  HUMAN   BIOLOGY 

INTEGRATION    BY   PURE    REFLEX   ACTION 

In  the  lower  vertebrates  the  spinal  cord  forms  relatively 
to  the  brain  a  much  larger  portion  of  the  whole  central 
nervous  organ.  Spinal  reactions  unaided  by  the  brain  operate 
a  much  larger  part  of  the  acts  of  the  animal  than  in  higher 
forms.  There  is  no  evidence  that  mental  experience  enters 
into  any  of  this  spinal  operation;  its  reactions  appear  to 
follow  mechanically  and  automatically,  and  for  that  very 
reason  are  termed  reflex.  This  "spinal"  life  concerns  itself 
in  these  animals  with  attitude,  locomotion,  breathing  move- 
ments, movements  for  grooming  the  skin,  and  defending 
it  from  parasites,  movements  of  escape  from  local  injury, 
the  actual  swallowing  of  food,  and  so  on.  The  reflex  actions 
thus  exhibited  are  themselves  of  various  grades  of  com- 
plexity. Reflex  actions  of  various  grades  such  as  obtain  in 
animals  make  up  also  a  large  part  of  the  functioning  of  the 
nervous  system  of  man.  Integration  by  reflex  action  is  a 
part  of  the  integration  which  his  nervous  system  effects 
for  man,  and  an  important  part.  His  reflexes  perform  many 
sorts  of  useful  acts  for  him  throughout  his  waking  day,  not 
to  speak  of  some,  such  as  his  reflex  breathing,  which  continue 
during  his  profoundest  sleep.  This  "reflex"  life  of  man 
is  sufficiently  many-sided  to  reheve  the  mental  portion  of 
his  nervous  system  from  much  that,  were  matters  not  so, 
would  occupy  it  and  preclude  his  attention,  one  would 
suppose,  from  higher  things. 

Of  this  reflex  life  one  field  which  is  particularly  primitive 
is  that  concerned  with  the  viscera,  particularly  the  digestive, 
and  their  movements.  Such  movements,  though  rather 
complex,  occur  with  digestive  periodicity,  largely  regulated 
by  lower  and  primitive  centers  of  the  nervous  system, 
and  during  health  they  pass  practically  unperceived,  indeed 
the  mind  cannot  by  any  eff"ort  of  attention  attain  perception 
of  them.  Another  related  primitive  reflex  or  set  of  reflexes 
concerns  the  movements  which,  ventilating  the  lungs,  are 
indispensable  for  breathing.  These,  although  themselves 
in  essence  purely  automatic,  illustrate  the  close  touch  which 
can  obtain  between  the  "reflex"  and  the  "mental."  We  can 
hardly    think    about    our    respiratory    movements    without 


Fig.  I. 

I.  Reflex  arc  with  two  elements,  receptor  and  effector. 

II.  Reflex  arc  with  one  receptor  and  two  effectors,  illustrating  how,  through 
branching  in  center,  one  sensory  neurone  may  influence  more  than  one 
motor  neurone.  , 

III.  Reflex  arc  consisting  of  two  receptors  and  one  effector,  illustrating 
principle  of  convergence;  axone  of  motor  neurone  is  referred  to  as  final  common 
path. 

IV.  Diagram  showing  interaction  of  two  separate  reflex  arcs  through  associ- 
ation neurones  a. 

In  all  four  figures  letters  indicate  following:  r,  receptor;  s,  surface  of  body; 
E,  effector  (skeletal  muscle);  i,  ganglion  cell  of  receptor;  2,  axone  of  effector; 
c,  central  nervous  system,  e.g.,  center  in  spinal  cord;  fcp,  final  common  path; 
A,  association  neurone  in  central  nervous  system. 


125  il 


252 


HUMAN   BIOLOGY 


altering  them,  although  they  are  reflex.  This  touch  attains 
its  closest  in  instances  where  as  in  man  the  expiratory 
movement  is  regulable  by  the  higher  and  so-called  volitional 


Fig.  2.  Schematic  cross  section  of  spinal  cord,  illustrating  control  which 
may  be  exerted  by  a  receptor  over  effectors  on  two  sides  of  body.  One  motor 
neurone  may,  through  peripheral  branching,  supply  many  muscle  fibers. 


centers  in  order  to  serve  the  vocal  organ  for  speech,  man's 
language  having  become  a  supreme  mode  of  expression  for 
his  mental  experience. 

Turning  next  to  acts  in  which  we  employ  the  muscles 
which  are  famihar  to  us  as  moving  our  bony  frame 
in  trunk  and  Hmbs,  much  of  the  reflex  activity  of  the  nervous 
system  is  devoted  to  exploiting  this  field  for  many  purposes 
of  Hfe.  Regarding  these  muscles  it  is  to  be  noted  that  although 
we  have  already  Hkened  them  to  motor  machines  at  the 
disposal  of  nerve  centers  driving  them  from  without,  they 
are  in  fact  instruments  not  purely  passive  under  that  drive, 
for  they  possess  receptors  of  their  own  intrinsic  within  them- 
selves, and  can  report  and  send  messages  on  their  own 
behalf  into  the  central  exchanges.  They  have  some  voice  in 
their  own  conditions  of  service,  and  the  messages  by  which 
they  thus  express  themselves  are  termed  proprioceptive. 
The  proprioceptive  reflexes  are  peculiarly  remote  from 
mental  experience  and  lie  quite  beyond  our  self-examination 
by  any  eff"ort  of  introspection.  But  they  habitually  exert  a 
self-regulation  upon  the  muscular  activity  not  only  during 


NERVOUS    INTEGRATIONS    IN    MAN  253 

purely  reflex  acts  initiated  from  receptive  sources  outside 
the  active  muscles  themselves,  but  during  the  execution 
of  even  highly  volitional  acts.  One  set  of  the  proprioceptive 
reflexes  arising  intrinsically  in  muscle  reinforces  the  muscular 
contraction.  A  pull  upon  a  muscle,  whether  passively  given 
or  occasioned  by  the  active  contraction  of  the  muscle  itself 
stimulates  tension  organs  in  the  muscle  and  its  tendon 
and  these  receptors  tend  to  excite  reflex  contraction  of  the 
muscle  and  can  reinforce  contraction  already  present. 
Active  contraction  itself  stimulates  certain  other  end-organs 
within  the  muscle  connected  with  the  muscle  fibers  them- 
selves, and  these  again  exert  a  reflex  influence  on  the  driving 
.nervous  center.  The  intrinsic  reflex  (proprioceptive)  influence 
developed  by  the  muscle  itself  on  the  nerve  center  imme- 
diately driving  it  consists  probably  of  opposed  influences 
of  excitation  and  inhibition  in  various  degrees  of  balance. 
This  is  a  fundamental  factor  in  the  normal  behavior  of  our 
muscles  and  its  loss  by  disease  may  cause  grave  impair- 
ment of  posture  and  movement,  and  especially  of  skilled 
acts. 

Among  the  acts  which,  using  these  partially  self-regulated 
muscles,  the  nervous  system  of  man,  like  that  of  many 
lowlier  organized  beings,  .  integrates  essentially  reflexly, 
is  that  of  maintenance  of  the  erect  position.  How  essentially 
reflex  this  act  is  becomes  evident  from  the  competent  way 
in  which  in  its  two  habitual  forms  of  standing  and  stepping 
it  goes  on  without  making  any  continuous  demand  upon 
our  mental  attention.  Conversation  may  seem  to  engross 
the  mind  wholly  while  we  stand  or  walk.  Aristotle  and  his 
peripatetics  promenaded  while  discussing  philosophy.  In 
the  reflex  basis  of  standing  and  stepping  the  nervous  reactions 
of  man  resemble  fundamentally  those  of  the  animals,  save 
for  the  important  detail  that  in  man  the  vertebral  column 
is  balanced  vertically  and  the  forelimbs  are  free  of  the 
ground.  The  essence  of  the  reaction  seems  to  be  that  the 
superincumbent  weight  of  the  body  tends  to  put  tension 
upon  and  thus  to  stretch  certain  of  the  muscles,  so  exciting 
them  through  their  own  reflex  arcs  to  reflex  contraction. 
A  widely  distributed  set  of  muscles  so  placed  as  to  antagonize 
gravity  in  the  erect  attitude  of  the  body  is  found  to  be 


254  HUMAN   BIOLOGY 

especially  sensitive  to  this  proprioceptive  stimulation  by 
passive  stretch.  This  antigravity  reaction  of  the  muscles 
themselves  is  reinforced  by  adjuvant  reflexes  operated  by 
pressure  of  the  foot  upon  the  ground.  The  whole  many- 
muscled  reflex  is  further  modified  by  reflexes  originated  by 
two  tiny  gravity  organs  lying  in  the  bony  wall  of  the  skull, 
and  forming  part  of  the  inner  ear,  though  not  themselves 
auditory.  These  Kttle  sacs  contain  small  crystaHine  "stones" 
loosely  attached  to  sensitive  nerve  patches.  According 
to  the  position  of  the  head  the  stones  press  or  drag  upon 
the  nerve  bed  in  this  or  that  direction  and  to  this  or  that 
degree.  These  cranial  gravity  sacs  have  through  their 
nerves  and  the  lower  nervous  centers  the  power  of  modifying 
the  gravity  reflexes  of  the  antigravity  muscles. 

It  is  abundantly  shown  by  experiment  in  the  higher 
animals  that  the  standing  posture  and  stepping,  walking 
or  running  can  be  executed  after  destruction  of  all  the 
higher  parts  of  the  brain  and  certainly  after  removal  of 
all  that  part  which  may  be  termed  the  "mental  organ." 
Not  only  does  the  purely  reflex  animal  stand  and  step, 
but  it  can  when  displaced  from  the  erect  position  reflexly 
regain  it  and  restore  itself,  head,  body  and  limbs  and  all 
to  that  posture.  A  remarkable  manoeuvre  exhibited  by 
the  cat  is  that  when  inverted  and  let  fall  from  a  short 
height,  it  rights  itself  in  the  air  and  alights  on  its  feet. 
This  manoeuvre  is  executed  perfectly  by  reflex  action  after 
removal  of  the  animal's  entire  higher  brain;  cinemato- 
graph analysis  of  the  act  shows  that  it  is  then  performed 
exactly  in  the  same  way.  Observations  upon  human  infants 
with  congenital  non-development  of  the  higher  brain  have 
revealed  in  them  also  righting  reflexes  resembhng  those 
of  animals. 

To  these  reflexes  of  habitual  attitude  and  locomotion 
can  be  added  a  number  which  bear  the  purpose  of  self- 
protection.  Thus  the  reflex  quadruped  will,  if  it  hurts 
one  foot,  go  on  three  legs  with  the  hurt  foot  held  up  out 
of  further  harm's  way.  The  ear  of  the  purely  reflex  cat  will 
flick  and  throw  ofl'  the  fly  which  settles  there,  not  less 
promptly  than  does  that  of  a  normal  cat.  So  too  the  dog 
scratches  itself,  grooming  its  coat  by  a  rhythmic  movement 


NERVOUS    INTEGRATIONS    IN    MAN  255 

of  the  hind  foot,  and  this  occurs  after  severance  of  the 
spinal  cord.  The  shoulder-skin  irritated  by  parasites  then 
evokes  still  the  same  scratching  movement  of  the  hind 
Hmb,  although  both  the  skin  and  the  muscles  are  beyond 
means  of  appeal  to  any  portion  of  the  brain.  The  scratching 
thus  performed  as  a  pure  spinal  reflex  does  however  often 
lack  the  precision  of  direction  which  higher  and  cerebral 
control  can  give  it.  Instances  in  normal  man  of  simple 
protective  reflexes  are,  besides  the  closure  of  the  eyelids 
against  a  blow,  the  expiratory  movements,  cough  and 
sneeze,  which  remove  irritants  from  the  respiratory  passage; 
also  the  involuntary  holding  of  the  breath  against  an  irritant 
vapor.  The  purposive  character  of  reflexes  is  evident. 

In  man  severance  of  the  spinal  cord  is  followed  imme- 
diately by  a  period  of  depression  of  function  in  that  part  of 
the  cord  cut  off"  from  connection  with  the  brain.  This  period 
of  shock  lasts  for  weeks  or  months.  It  is  as  though  in  man  the 
higher  nervous  centers  so  greatly  contribute  to  the  driving 
of  the  spinal  (lower)  mechanisms  that  the  removal  of  that 
drive  upsets  the  spinal  mechanisms  for  a  long  time.  In 
most  animals  this  is  far  less  so,  e.g.  dog;  but  the  monkey 
in  this  respect  resembles  man.  In  man  the  spinal  reflexes 
released  from  higher  control  tend  to  be  mainly  flexor  in 
type.  There  is  a  spread  from  one  spinal  center  to  another, 
so  that  contraction  of  the  bladder,  and  profuse  sweating 
may  accompany  flexion  of  both  legs;  this  generalized  spinal 
reflex  response  is  termed  the  "mass  reflex." 

The  Decerebrate  Animal.  We  may  now  pass  from  the 
spinal  condition  in  man  to  a  more  highly  integrated  state, 
usually  referred  to  as  the  decerebrate  condition.  The 
condition,  which  is  brought  on  by  removal  of  the  nervous 
organ  anterior  mid-brain  is  well  recognized  in  animals 
and  has  been  thoroughly  investigated.  (See  Chapter  iv.) 
A  decerebrate  animal  is  capable  of  standing  albeit  the 
posture  is  an  exaggerated  caricature.  Movements  are  well 
coordinated  and  graded  so  long  as  the  cerebellum  remains 
intact.  The  decerebrate  condition  is  also  characterized 
by  a  series  of  striking  reactions  known  as  the  neck  and 
labyrinthine  reflexes.  Rotation  of  the  head  to  the  left, 
for  example,  causes  increase  in  tonus  of  the  extensor  muscles 


2^6  HUMAN    BIOLOGY 

on  the  left  side,  so  that  if  the  animal  chooses  to  seize  an 
object  to  the  left  of  him  the  hmbs  on  that  side  are  ready 
to  support  his  weight  when  he  takes  off  with  his  right  foot. 
The  same  reactions  are  exhibited  by  human  beings  when 
in  a  decerebrate  condition.  Indeed,  to  the  neurologist  the 
occurrence  of  neck  and  labyrinthine  reflexes  in  man  is  an 
important  diagnostic  sign.  These  reactions  off"er  still  another 
instance  of  the  more  comphcated  field  of  integration  which 
one  encounters  on  examining  the  higher  levels  of  the  brain 
stem. 

The  Cerebellum  and  Bulb.  Lying  over  the  bulb  in  intimate 
anatomical  association  with  it  is  the  large  convoluted 
organ  known  as  the  cerebellum.  If  this  is  removed,  the 
rest  of  the  brain  stem  being  allowed  to  remain  intact, 
orderly  locomotion  and  dehcately  adjusted  skilled  move- 
ments become  forever  impossible.  Extirpation  of  the  cere- 
bellum, however,  produces  no  eff"ect  upon  the  mind.  The 
wildly  incoordinated  character  of  the  movements  which 
result  from  a  cerebellar  lesion  is  usually  referred  to  as 
"cerebellar  ataxia."  The  way  in  which  the  cerebellum 
operates  to  secure  delicate  adjustments  of  the  voluntary 
muscles  is  still  to  some  extent  a  mystery.  No  reflex,  for 
instance,  is  known  to  occur  in  normal  animals  which  does 
not  also  take  place  after  the  cerebellum  is  removed.  The 
anatomical  relations  of  the  cerebellum,  however,  provide 
important  information  as  to  its  probable  mode  of  action. 
It  is  known  that  the  great  proprioceptive  system  of  sensory 
nerves  arising  within  the  skeletal  muscles  (tendon  organs 
and  muscle  spindles)  send  large  fiber  tracts  which  pass 
up  the  spinal  cord  and  into  the  cerebellum,  eventually 
terminating  within  the  cerebellar  cortex  as  do  other  large 
groups  of  fibers  which  descend  from  the  cerebral  hemispheres. 
Emerging  from  the  cerebellum  are  other  fiber  tracts  which 
descend  via  the  red  nucleus  to  the  motor  neurones  of  the 
spinal  cord,  immediately  subserving  the  skeletal  muscle 
fibers.  Electrical  stimulation  of  the  cerebellum  sometimes 
causes  excitation,  and  sometimes  inhibition  of  the  voluntary 
musculature,  but  more  often  a  mixture  of  both  in  the  mus- 
culature as  a  whole.  Consequently,  one  may  conclude 
that  the  cerebellum  can  bring  to  bear  both  excitatory  and 


NERVOUS    INTEGRATIONS    IN    MAN 


257 


Inhibitory  influence  and  that  by  virtue  of  its  rich  receipts 
from  the  sensory  endings  in  muscle  it  exerts  an  influence 
appropriate  to  the  particular  reaction  in  progress,  so  securing 


CEREBELLUM 


OPTIC  CHIASN/l 


PITUITARY  3T^LK 

HYPOTH/\L^MUS 


PONS 


MEDULLA 


Fig.  3.  Median  sagittal  section  of  human  brain,  showing  position  beneath 
cerebral  hemispheres  of  cerebellum,  medulla  and  hypothalamus. 


an  orderly  adjustment  of  the  movement.  When  movements 
are  initiated  through  activity  of  the  cerebral  hemispheres, 
the  cerebellum,  through  its  cerebro-ponto-cerebellar  con- 
nections, is  notified  of  the  intended  act,  and  adjustments 
are  automatically  made  to  bring  about  its  harmonious 
execution.  The  adjustments  facihtated  by  the  cerebellum 
involve  regulation  of  the  reciprocal  activity  of  antagonistic 
muscle  groups  as  well  as  of  the  so-called  synergic  muscles. 

The  activity  of  the  cerebellum  is  not  confined  to  the 
skeletal  muscles;  it  exerts  also  a  regulatory  influence  over 
the  eye  muscles,  the  vocal  cords,  and  the  muscles  of  deglu- 
tition. Destruction  of  the  cerebellum  causes,  for  example, 
characteristic  changes  in  the  voice,  the  speech  becoming 
thick,  monotonous  and  slurring  (ataxia  of  the  laryngeal 
muscles),  and  swallowing  usually  becomes  to  some  extent 
impaired  though  not  impossible.*  It  may  be,  however,  that 
the  dysphagia  of  cerebellar  lesions  is  due,  not  to  destruction 
of  the  cerebellum,  but  to  injury  of  the  subjacent  centers  of 
the  medulla  (bulb). 


258  HUMAN   BIOLOGY 

The  nervous  organ  (the  bulb)  which  immediately  directs 
and    executes    swallowing    is    a    lower    non-mental    center 
Hke  the  cerebellum  and  the  spinal  cord.  The  mental  organ, 
however,  is  able  to  get  into  touch  with  the  bulbar  organ. 
The  swallow,  moreover,  is  unlike  the  previous  steps  in  the 
train  of  behavior  directed  toward  obtaining  food,  since  it 
cannot  be  initiated  by  the  mental  organ  per  se.  We  cannot 
swallow  unless  we  have  something  to  swallow;  the  act  is 
essentially  a  reflex  and  requires  a  local  stimulus.  Further, 
when  once  initiated  it  cannot  be  arrested  by  the  mental 
organ;  it  must  take  its  course,  hence  the  bitter  powder  once 
placed  at  the  back  of  the  child's  tongue  is  safe  from  refusal  if 
the  swallow  starts.   And  the  final  step  of  transit  down  the 
gullet  is  so  wholly  reflex,  and  the  nervous  system  which  it 
involves  is  so  remote  from   mentality  that  ordinarily  we 
cannot  sense  it  at  all,  let  alone  voluntarily  initiate  or  arrest 
it.  The  swallow  is  thus  a  reaction  which,  dealing  with  an 
object  (food)  which  has  formed  the  aim  and  goal  of  a  whole 
train  of  mentally  operated  and  supervised  acts  involving 
the  central  nervous  organs,   finally  takes  the  object  thus 
acquired    and    dismisses    it    abruptly    from    all    commerce 
with  mind.  Although  within  the  body,  it  will  under  normal 
circumstances  never  again  come  within  the  ambit  of  cogni- 
zance of  the  mental  organs.  A  dog  comes  to  the  platter, 
and  seizes  the  food;  or  in  the  case  of  man,  he  serves  himself 
with  his  hand  and  some  tool  to  pass  the  food  to  his  mouth. 
Experiment  shows  that  this  stage  of  the  act  is  impossible 
to  the  dog  after  destruction  of  that  part  of  the  brain,  the 
cortex  cerebri,  which  is  the  mental  organ;  similarly  with  man 
where  lesions  (e.g.  tumors)  of  the  cerebral  hemispheres  may, 
if  extensive,  cause  a  state  of  apraxia  in  which  the  individual, 
though  unparalyzed,  is  quite  unable  to  feed  himself  or  to 
do  so  simple  an  act  as  to  strike  a  match.  A  further  phase 
in  the  chain  of  nervous  reactions  associated  with  feeding 
is  the  treatment  of  the  food  within  the  mouth  by  tongue 
and  teeth,  its  mastication  and  its  mixing  with  saliva.  Experi- 
ment teaches  that  after  removal  of  the  whole  "mental  organ" 
these  processes  still  occur.  This,  as  a  preliminary  act  to  the 
swallow,  an  elaborately  adjusted  movement  which  transfers 
the  food  from  the  mouth  across  the  entrance  to  the  windpipe 


NERVOUS    INTEGRATIONS    IN    MAN  259 

to  the  gullet,  and  so  to  the  stomach,  this  despite  its  com- 
plexity, can  go  forward  after  removal  of  all  of  the  higher 
parts  of  the  brain  and  the  whole  of  that  portion  which 
we  have  termed  mental. 

The  Hypothalamus.  If  the  brain  stem  is  transected  so  as 
to  leave  intact  a  few  millimeters  of  the  base  of  the  brain, 
known  as  the  hypothalamus,  the  preparation  being  other- 
wise the  same  as  that  used  for  study  of  the  decerebrate 
condition,  one  observes  a  most  striking  series  of  phenomena. 
The  animal  is  restless  and  exhibits  periodic  outbursts  which 
have  been  appropriately  termed  "sham  rage."  The  pupils 
become  dilated,  eyes  protruded,  fur  erect  and  the  animal 
may  snarl,  growl  and  show  his  teeth,  and  exhibit  in  addition 
periodic  running  movements.  Occasionally,  if  gently  patted 
the  animal  may  purr  and  wag  its  tail  inordinately  and  show 
other  evidence  of  intense  pleasure.  In  the  small  area  of  the 
hypothalamus  there  he  the  centers  for  emotional  expression, 
and  when  these  are  released  from  higher  control  the  thresh- 
old for  ehcitation  of  emotional  responses  is  lowered. 

In  man  one  sees  the  direct  counterpart  of  such  a  state 
under  the  influence  of  certain  drugs,  notably  ether,  alcohol 
and  "laughing"  gas,  when  vigorous  expressions  of  rage  or  of 
exceptional  delight  may  alternate  with  surprising  rapidity. 
Symptoms  of  acute  mania  associated  with  outbursts  of 
activity  •  of  the  sympathetic  nervous  system  akin  to  the 
sham  rage  or  to  the  expression  of  pleasure  seen  in  hypothal- 
amic animals  have  been  observed  in  man  after  injuries 
to  the  base  of  the  brain.  From  this  and  other  evidence  the 
hypothalamus  has  come  to  be  looked  upon  as  the  chief 
ganglion  of  the  sympathetic  system,  and  the  region  of  the 
brain  chiefly  concerned  with  emotional  expression.^ 

HIGHEST    NERVOUS    CENTERS 

The  supreme  outcome  of  nervous  integration  is  mind, 
and  in  man  mind  dominates  the  organism.  Could  we  look 
quite  naively  at  the  body  as  indwelt  by  mind  we  might 
perhaps  suppose  mind  diff'used  throughout  it,  not  locahzed 
in  any  one  particular  portion  at  all.  That  it  is  locahzed  and 

1  The  relation  of  the  hypothalamus  to  emotional  expression  has  lately  been 
(fealt  with  at  length  by  W.  B.  Cannon  (1927)  and  by  his  pupil  P.  Bard  (1928). 


26o  HUMAN   BIOLOGY 

that  its  localization  is  in  the  nervous  system — can  we  attach 
meaning  to  that  fact? 

Taking  as  manifestations  of  mind  those  ordinarily  received 
as  such,  mind  does  not  seem  to  attach  to  life,  however  complex, 
where  there  is  no  nervous  system,  nor  even  where  that  system 
though  present  is  quite  scantily  developed.  The  nervous 
system  is  that  system  whose  special  office  from  its  earher 
appearance  onward  throughout  evolutionary  history  has 
been  more  and  more  to  weld  the  body  into  one  consolidated 
mechanism  reacting  as  a  unity  to  the  changeful  world  about 
it.  Mind  becomes  more  recognizable  the  more  developed 
the  nervous  system.  Hence  one  difficulty  in  tracing  mind 
to  its  origin  is  the  twiht  emergence  of  mind  from  no  mind, 
which  is  repeated  even  in  the  individual  Hfe-history.  But 
that  in  this  system  mind  as  we  know  it  has  had  its  beginning 
and  has  progressively  with  it  step  by  step  developed,  is 
significant  of  the  system.  In  the  nervous  system  itself  there 
is  locahzation  of  function,  relegation  of  different  work  to 
the  system's  different  parts.  This  locahzation  shows  men- 
taHty  not  distributed  broadcast  throughout  the  nervous 
system,  but  restricted  to  a  certain  portion  of  it.  And  this 
particular  portion  to  which  mind  transcendently  attaches 
is  exactly  that  where  are  carried  to  their  highest  pitch  the 
nerve  actions  which  manage  the  individual  as  a  whole, 
especially  in  his  reactions  to  the  external  world,  animate 
and  inanimate,  outside  himself.  This  part  moreover  is  a 
comparatively  modern  structure  superposed  on  the  non- 
mental  and  more  ancient  other  nervous  parts.  The  mental 
portion  is  so  placed  that  its  commerce  with  the  body  and 
with  the  external  world  can  occur  only  through  the  medium 
of  the  archaic  non-mental  nervous  parts.  This  perhaps 
makes  more  intelligible  the  common  and  well-recognized 
experience  that  acts  essentially  reflex,  such  as  standing  and 
walking,  are  initiated  and  controlled  by  processess  with 
mental  accompaniments  although  not  actually  run  by  them. 
Thus,  just  as  plants,  for  instance  the  pine  tree  on  the  rock 
side,  orientate  themselves  to  the  hne  of  gravity  (geotropism) 
so,  with  greater  speed  and  nicety  of  movement,  does  the 
animal,  for  instance  the  dog  as  it  stands,  runs,  and  so  forth. 
It  maintains  the  erect  attitude;  and  as  mentioned  earlier 


NERVOUS    INTEGRATIONS    IN    MAN  26 1 

it  does  so  essentially  by  a  pure  reflex,  a  geotropic  reflex. 
The  erect  posture  is  the  normal  basis  both  in  ourselves 
and  in  the  dog  for  much  of  all  the  active  reaction  to  the 
w^orld  that  hfe  and  its  behavior  demand.  Its  observance 
and  maintenance  are  therefore  of  eminent  and  fundamental 
importance  to  the  organism.  Maintaining  the  erect  attitude 
is  indeed  nothing  less  than  keeping  right  side  up  to  the 
world  in  v^hich  it  hves.  What  is  the  relation  of  the  highest 
centers,  the  mental  organ  proper,  to  this  great  basic  act  of 
animal  hfe  of  keeping  itself  right  side  up?  As  already  stated 
the  animal  without  its  mental  organ  still  stands  and  walks, 
runs  and  even  jumps,  and  further  can,  if  its  erect  attitude  be 
disturbed,  regain  it.  It  is  therefore  less  true  to  say  that  the 
animal  under  direction  of  its  mind  keeps  itself  right  side 
up  than  to  say  that  the  animal  body  by  automatic  mechanism 
is  kept  right  side  up.  From  the  animal's  point  of  view,  as  a 
sentient  being,  for  itself  to  be  right  side  up  to  the  world  is,  of 
course,  for  the  world  to  be  right  side  up  to  it.  In  other  words, 
the  body's  automatism  ensures  that  the  mind  looking,  so  to 
speak,  out  from  the  body,  finds  the  world  right  side  up. 
This  relation  is  maintained  by  physiological  reflex  processes 
seemingly  as  non-mental  as  is  the  digestive  secretion  of 
the  bile.  Hence,  this  right-side-upness  being  settled  without 
mind,  and  indeed  prior  to  mind,  and  naive  mind  being, 
whatever  else  it  is,  utilitarian,  the  situation  has  not  invited 
and  not  had  consideration  from  naive  mind.  Mind  has  not 
troubled  because  it  has  not  needed,  so  to  say,  to  think  about 
a  relation  already  established  and  given  it  from  the  outset. 
This  enables  us  therefore  to  trace  how,  in  the  make-up  of 
mind,  right-side-upness  of  the  world  comes  as  an  innate 
unargued  dictum,  an  immediate  intuition,  largely  eluding 
mental  analysis  because  there  is  wanting  direct  sense 
experience  of  its  origin  and  of  its  elemental  processes, 
although  confusion  in  mental  space  results  when  its  elements 
conflict.  William  James,  with  characteristic  picturesqueness, 
wrote  that  "our  prehistoric  ancestors  discovered  the  com- 
mon-sense concepts,"  among  them  as  he  says  "one-space." 
With  that  latter  we  may  set  "world  right-side-upness;" 
but  we  must  date  its  discovery  further  back  than  to  our 
prehistoric  ancestors.  It  is  an  immediate  intuition  and  must 


262  HUMAN   BIOLOGY 

date  back  not  merely  to  the  prehistoric  but  to  the  entirely 
prehuman. 

The  portion  of  the  human  brain  which  on  account  of 
much  and  well-established  evidence  must  be  regarded  as  the 
material  seat  of  man's  mind  is  that  great  surface  structure 
rooted  in  the  forebrain  and  a  relatively  new  excrescence 
from  it  known  as  the  cortex  and  its  fibers;  and,  probably 
subsidiarily  to  that,  the  thalamus  deep  underlying  the 
cortex,  and  of  far  older  evolutionary  history.  The  thalamus 
forms  a  relay  station  for  practically  all  of  the  nerve  paths 
ascending  to  the  cortex.  The  cortex  itself  is  for  the  most 
part  of  comparatively  late  evolutionary  history.  The  pre- 
mammalian  vertebrates  possessed  merely  a  trace  of  it  or 
none  at  all.  The  higher  mammals,  especially  the  monkey, 
possess  it  in  large  proportions.  In  man  it  is  so  greatly  devel- 
oped that  even  in  brute  bulk  it  dwarfs  the  whole  of  the  rest 
of  the  nervous  system.  From  the  biological  point  of  view  it 
represents  the  very  culmination  of  integration  of  the 
animal  organism.  It  consists  of  two  broadly  symmetrical 
hemispheres,  one  right  and  one  left.  The  relation  with  the 
voluntary  muscles  is  for  each  hemisphere  a  crossed  one,  so 
that  it  is  the  left  hemisphere  which  is  concerned  with  the 
skilled  acts  of  the  right  hand.  A  curious  fact  is  that  in  right- 
handed  persons  the  left  hemisphere  is  functionally  the  more 
important  mentally.  Medical  experience  shows  that  small 
lesions  of  certain  parts  of  the  left  hemisphere  destroy  speech 
and  even  memory,  while  similar  lesions  of  the  right  hemis- 
phere may  pass  for  years  unnoticed  because  productive  of 
no  obvious  defect  or  symptoms.  In  fact  the  recent  experience 
of  brain-surgeons  dealing  with  malignant  growths  indicates 
that  the  entire  right  cerebral  hemisphere  of  a  right-handed 
human  being  may  be  removed  without  there  ensuing  mental 
defects  that  are  recognizable  (Dandy),  though  of  course 
the  patient  becomes  in  result  of  such  an  operation  paralyzed 
on  the  left  side. 

This  supreme  development  of  the  brain,  the  cerebral 
cortex,  has  the  property  of  relatively  quickly  adjusting 
its  reactions  to  meet  various  conditions.  It  can  establish 
new  functional  habits  requiring  new  functional  connections. 
A  dog  secretes  saliva  when  food  is  placed  in  its  mouth; 


NERVOUS    INTEGRATIONS    IN    MAN  263 

that  is  a  reflex  innate  and  characteristic  of  the  species. 
But  a  dog  customarily  fed  by  the  same  person  may  secrete 
sal  va  when  it  sees  that  person  come  at  the  accustomed  time. 
This  latter  is  a  reaction  for  which  it  has  been  shown  the 
cortex  is  needful.  The  cortex  has  the  means  of  attaching 
the  reactive  act,  e.g.  sahvation,  innately  resulting  from  a 
particular  stimulus,  e.g.  food  in  the  mouth,  to  another 
stimulus,  e.g.  visual  image  of  a  platter,  if  this  latter  stimulus 
has  occurred  for  even  a  few  times  closely  precurrent  to  the 
innately  eff"ective  one.  Individual  experience  with  its  repeti- 
tions during  daily  life  of  stimuli  habitually  closely  associated 
in  time  finds  the  cortex  therefore  an  educable  nervous 
organ,  by  which  the  organism  acquires  numbers  of  adapted 
reactions  meeting  the  vicissitudes  of  the  environment. 
Man  experiencing  these  reactions  in  himself  is  aware  that 
accompanying  these  adapted  and  adaptable  trains  of  acts 
and  behavior  there  occur  in  him  mental  events  which  he 
distinguishes  in  some  measure  one  from  another  as  memorial, 
■  aff"ective,  conative,  etc.  This  mental  activity  is  so  important 
to  man  that  from  our  point  of  view  it  would  seem  the 
coping  stone  of  the  integration  of  the  individual.  It  is  there- 
fore to  the  psychologist  we  must  turn  for  fuller  study  of  the 
final  contribution  made  by  the  nervous  system  to  the 
integration  of  man. 

But  to  pass  from  a  nerve  impulse  to  a  psychical  event 
is  to  step  as  it  were  from  one  world  to  another.  We  might 
expect  then  that  at  the  places  of  transition  from  its  non- 
mental  to  its  mental  regions  the  brain  would  exhibit  some 
striking  change  of  structures.  But  no;  in  the  mental  parts 
of  the  brain  still  nothing  but  the  same  old  structural  ele- 
ments, with  essentially  the  same  old  features,  set  end-to-end 
in  neurone  chains  as  elsewhere,  and  evidently  just  as  before 
serving  as  lines  for  travel  of  nerve  impulses,  and  nodal 
points  for  their  convergence  and  irradiation,  their  further 
launching  by  excitation,  and  their  restriction  by  inhibition. 
We  are  here  faced  in  perhaps  its  sharpest  form  with  the 
age-old  ever  unsolved  problem  of  the  nexus  between  matter 
and  life  and  mind. 


264  HUMAN   BIOLOGY 


REFERENCES 

General  Features  of  Reflex  Action 

Forbes,  A.  1922.  The  interpretation  of  spinal  reflexes  in  terms  of  present 

knowledge  of  nerve  conduction.  Physiol.  Rev.,  2:  361-414. 
Fulton,   J.    F.    1926.   Muscular   Contraction   and   the   Reflex   Control   of 

Movement.  Bait.,  Williams  &  Wilkins. 
Sherrington,  C.  S.  1906.  The  Integrative  Action  of  the  Nervous  System. 

New  Haven:  Yale  Univ.  Press.,  Lond.,  Humphrey  Alilford. 
Postural  Contraction 

LiDDELL,  E.  G.  T.,  and  Sherrington,  C.  S.  1924-1925.  Reflexes  in  response 

to    stretch   (myotatic  reflexes).  Proc.  Roy.  Soc,  96B:  212-242;  97B: 

267-283. 
Magnus,  R.  1924.  Korperstcllung.  Berl.,  Springer. 
Sherrington,  C.  S.   191 5.   Postural  activity  of  muscle  and  nerve.  Brain, 

38:  191-^34- 

1924.  Problemsof  muscular  receptivity.  Nature,  1 13: 732;  892-894:924-932. 
Rademaker,   G.  G.  J.    1926.   Die  Bedeutung  der  Roten   Kerne  und  des 

iibrigen  Mittelhirns  fiir  Muskeltonus,  Korperstellung  und  Labyrinth- 
reflexe.  Berl.,  Springer. 
1927.  Onthephysiology  of  reflex-standing.  Proc.  Konin.  Akad.  Wet.  Amster- 
dam, 30:  796-810. 
Cerebellum  and  Bulb 

Bremer,  F.  1924.  Physiologic  du  cervelet  chez  le  pigeon.  Compt.  rend.  Soc. 
de  Biol.,  90:  381-384. 

1925.  Le  cervelet  et  la  physiopathologie  du  tonus  musculaire.  J.  Neurol,  et 
Psychiat.,  25:  520-525. 

Denny-Brown,  D.,  Eccles,  J.  C,  and  Liddell,  E.  G.  T.  1929.  Observa- 
tions on  the  responses  to  stimulation  of  the  cerebellum.  Proc.  Roy.  Soc, 
104B:  518-536. 

Holmes,  G.  19 17.  The  symptoms  of  acute  cerebellar  injuries  due  to  gunshot 
injuries.  Brain,  40:  461-535. 

Ingvar,  S.  1923.  On  cerebellar  localization.  Brain,  46:  301-335. 

Miller,  F.  R.  1926.  The  physiology  of  the  cerebellum.  Physiol.  Rev.,  6: 
124-159. 

Miller,  F.  R.,  and  Sherrington,  C.  S.  1915.  Some  observations  on  the 
bucco-pharyngeal  stage  of  reflex  deglutition  in  the  cat.  Quart.  J.  Exper. 
PbysioL,  9:  147-186. 

Rademaker,  G.  G.  J.,  and  Winkler,  C.  1928.  Annotations  on  the  physi- 
ology and  the  anatomy  of  a  dog,  living  38  days,  without  both  hemispheres 
of  the  cerebrum  and  without  cerebellum.  Proc.   Konin.  Akad.  Wet. 
Amsterdam,  31:  332-338. 
Hypothalamus 

Bard,  P.  192S.  A  diencephalic  mechanism  for  tlie  expression  of  rage  with 
special  reference  to  the  sympathetic  nervous  system.  Amer.  J.Physiol., 
84:  490-515;  see  also  Arch.  Neurol.  &  Psychiat.,  22:    230-246,  1929. 

Beattie,  J.,  Long,  C.  N.  H.,  and  Brow,  G.  R.  1929.  Physiology  of  the  hypo- 
thalamus. Proc.  Roy.  Soc.  (In  press.) 

Cannon,   W.   B.    1927.   The  James-Lange  theory  of  emotions:  a   critical 
examination    and   an  alternative  theory.  Arn.  J.  Psyc/jo/.,  39:  106-124. 
1928a.  Neural  organization  for  emotional  expression.  Feelings  and  Emotions, 
pp.  257-269. 


NERVOUS    INTEGRATIONS    IN    MAN  265 

19286.  The  mechanism  of  emotional  disturbance  of  bodily  functions.  New 
Eng.  J.  Med.,  198:  877-884. 

Fulton,  J.  F.,  and  Bailey,  P.  1929.  Contribution  to  the  study  of  tumors 
in  the  region  of  the  third  ventricle:  their  diagnosis  and  relation  to  patlio- 
logical  sleep.  J.  Nerv.  &"  Ment.  Dis.,  69:  1-25;  145-164;  261-277. 
The  Hemispheres 

Berry,  R.  J.  A.  1928.  Brain  and  Mind  or  the  Nervous  System  of  Man. 
N.  Y.,  Macmillan. 

Dandy,  W.  E.  1928.  Removal  of  right  cerebral  hemisphere  for  certain  tumors 
with  hemiplegia.  Prelim.  Report.  J.  A.  M.  A.,  90:  823-825. 

GoLTZ,  F.  1892.  Der  Hund  ohne  Grosshirn.  Pfluger's  Arch.,  51:  570-614. 

Head,  H.  1926.  Aphasia  and  kindred  disorders  of  speech.  2  vols.,  Cambridge 
(Eng.)  Univ.  Press. 

Leyton,  a.  S.  F.,  and  Sherrington,  C.  S.  1916.  Observations  on  the  excit- 
able cortex  of  the  chimpanzee,  orang-utan,  and  gorilla.  Quart.  J.  Exper. 
Physiol.,  11:  135-227. 


Chapter  XII 
THE  INTEGRATION  OF  THE  SEXES— MARRIAGE 

Clark  Wissler 

ONE  of  the  most  difficult  problems  man  faces  is  the 
understanding  of  his  own  community  hfe.  Modern 
society  has  proved  so  baffling  that,  in  despair,  many 
have  turned  to  the  study  of  primitive  hfe,  assuming  that 
there  the  fundamentals  may  be  found  in  high  rehef.  Something 
has  been  gained  by  such  study  of  primitive  communities, 
but  the  result  is  rather  disappointing,  since  experience 
proves  it  Httle  less  difficult  to  penetrate  the  complexity  of 
a  savage  community  than  to  comprehend  a  present-day 
town.  Nevertheless,  a  Httle  has  been  gained  in  the  way  of 
perspective,  and  looking  at  human  community  life  in  the 
large,  the  integration  of  the  sexes  is  seen  as  the  core  of 
the  structure.  In  the  social  science  of  the  past,  stress  was 
laid  upon  the  family,  or  the  biological  pair,  which  was 
considered  the  fundamental  social  unit.  According  to  this 
conception,  a  community  is  an  aggregation  of  mated  pairs, 
engaged  even  in  reproduction  and  the  rearing  of  their  offspring. 
In  time,  however,  students  of  society  came  to  feel  that  this 
was  too  narrow  a  view;  there  is  still  universal  agreement 
that  the  rearing  of  children  is  the  chief  business  of  these 
mated  pairs,  but  it  nevertheless  appears  that  a  community 
is  something  more  than  a  mere  aggregation  of  such  pairs. 
Everything  we  know  of  primitive  man  indicates  that  he  is 
by  nature  a  camp  dweller,  which  is  to  say,  that  he  Hves  in 
communities,  or  groups.  Further,  these  communities  are, 
in  constitution,  groups  of  cooperating  mated  pairs,  with 
their  children.  One  often  meets  the  statement  that  in 
primitive  communities  there  is  no  speciahzation  in  labor 
or  social  function,  that  each  individual  does  everything  for 
himseff.  This  is  contrary  to  the  observed  facts,  because 
we  encounter  individual  speciahzation  in  handicraft  and 
organized  team  work,  a  savage  camp  presenting  in  outhne  a 
rephca  of  a  civihzed  community.  So  we  can  feel  on  safe 

266 


THE    INTEGRATION   OF   THE   SEXES — MARRIAGE  267 

ground  in  assuming  that  one  of  the  distinguishing  charac- 
teristics of  the  species  Homo  sapiens  is  his  biological  equip- 
ment for  group  life.  We  may  also  agree  with  those  who 
regard  human  community  Hfe  as  an  expression  of  man's 
original  nature.  Of  course,  it  is  not  the  mere  matter  of 
Hving  in  a  community  that  distinguished  man,  since  some 
other  Hving  forms  maintain  such  group  hfe;  rather  should 
we  bear  in  mind  that  the  human  community  is  in  many 
respects  unique,  at  least,  easily  distinguishable  from  others. 
Looked  at  from  the  outside  a  savage  community  is  an 
inbreeding,  self-contained,  group  of  human  beings.  The 
number  of  males  rarely  differs  markedly  from  the  number 
of  females,  on  the  average  scarcely  at  all.  In  the  discussion 
of  the  sex  ratio,  the  relatively  small  differences  between 
the  number  of  males  and  females  is  given  its  due,  but 
considered  from  the  standpoint  of  our  problem,  we  are 
justified  in  ignoring  these  smaller  constant  and  local  differ- 
ences, at  least  for  the  present.  So,  one  of  the  primordial 
biological  conditions  in  group  life  is  the  division  of  the 
community  into  halves,  one  of  which  is  male  and  the  other 
female.  It  is  now  quite  the  fashion  to  insist  that  rationaliza- 
tion is  something  unreal  and  that  it  plays  no  part  in  the 
shaping  of  social  affairs;  so  we  shall  not  say  that  savage 
man  rationalized  on  this  matter.  What  we  do  propose  is 
that  there  is  in  anatomy,  physiology,  and  behavior,  such 
an  objective  cleavage  between  the  sexes,  that  human  beings, 
being  what  they  are,  could  not  help  responding  to  it.  Nor 
could  they  well  ignore  what  was  always  present  and  observ- 
able. It  appears,  then,  that  sex  is  one  of  the  most  natural 
objective  lines  of  cleavage  in  a  community.  Consistent  with 
this  are  the  sharply  defined  distinctions  between  what 
women  and  men  may  or  may  not  do.  The  line  of  sex  cleavage 
cross-sections  the  life  of  the  community,  and,  whether 
rationalized  or  not,  it  functions.  In  one  way,  it  seems  that 
man  has  improved  upon  nature  by  widening  the  gap  between 
the  sexes,  by  such  secondary  developments  as  costume, 
division  of  labor,  and  social  procedure.  On  the  other  hand, 
there  are  evidences  everywhere  of  more  or  less  successful 
integration  of  function  within  the  group.  One  form  of  such 
integration  is  marriage,  the  mated  pair,  and  it  is  the  knitting 


268  HUMAN   BIOLOGY 

of    these    pairs    into    a    cooperating   group   that   forms   a 
community. 

FORMS  OF  MARRIAGE 

We  are  often  told  that  society  has  but  two  alternatives: 
marriage  or  promiscuity.  We  are  also  told  that  promiscuity 
would  prevail  if  it  were  not  for  the  restraining  hand  of 
society.  These  statements  do  not  reveal  the  true  status 
of  the  human  sex  problem,  but  they  do  bring  before  us 
points  of  regard  in  contemporary  thought.  Taking  up, 
first,  the  matter  of  marriage,  we  may  select  for  study  any 
one  of  several  aspects  of  the  subject,  confining  our  discussion 
to  it  alone.  Thus,  we  may  look  upon  marriage  as  a  biological 
phenomenon,  solely.  On  the  other  hand,  we  may  regard 
it  as  a  social  institution;  again,  as  an  economic  adjustment 
to  living  conditions.  Shifting  our  interest,  we  may  take 
the  ethnography  of  marriage  as  our  task  and  so  concern 
ourselves  with  describing  existing  forms  of  marriage  and 
stating  in  what  parts  of  the  world  they  occur.  This  can  be 
narrowed  somewhat,  by  making  it  an  anthropological  investi- 
gation, and  thus  limiting  the  study  to  primitive  peoples. 
Finally,  one  may  consider  only  the  history  of  marriage,  and 
with  the  data  available,  attempt  to  discover  the  tinie  order 
in  which  each  form  of  marriage  appeared.  Also  one  may 
specialize  in  the  history  of  divorce  in  Europe  and  America, 
the  history  of  legislation  regarding  marriage,  the  rights  of 
property  in  the  marriage  relation,  etc.  All  of  which  shows 
how  complex  marriage  is  and  how  deeply  rooted  in  society. 
It  is  not  a  simple  phenomenon  and  there  is  no  ground  for 
expecting  its  cause  to  lie  in  a  single  controlling  factor. 

Naturally,  a  great  deal  has  been  written  and  said  on  the 
subject,  too  much  to  be  summarized  here,  but,  for  purposes 
of  orientation,  we  may  enumerate  a  few  of  the  important 
contributions  so  far  made.  Turning  first  to  marriage  as  a 
social  institution,  we  cite  Westermarck's  definition:  "a 
relation  of  one  or  more  men  to  one  or  more  women  which  is 
recognized  by  custom  or  law  and  involves  certain  rights 
and  duties  both  in  the  case  of  the  parties  entering  the  union 
and  in  case  of  the  children  born  of  it."  While  no  definition 
can  fully  cover  all  examples  of  marriage,  this  one  does  meet 


THE    INTEGRATION    OF   THE    SEXES— MARRIAGE  269 

the  situation  with  respect  to  the  sex  and  number  of  the 
persons  concerned.  If,  on  the  other  hand,  we  consider  the 
whole  marriage  complex,  all  its  ramifications  in  society, 
then  varieties  may  be  discovered  that  fall  outside  the 
range  of  this  definition,  but  at  that  it  is  a  good  working 
definition  of  marriage  as  a  social  institution.  Yet,  before  we 
go  far  afield,  it  may  be  advantageous  to  consider  the  number 
of  possible  ways  in  which  it  is  conceived  the  sexes  be  paired 
in  marriage;  these  possibifities  of  union  are  as  follows: 

1.  One  man  to  one  woman  at  a  time — monogamy. 

2.  One  man  and  two  or  more  women  simultaneously — 
polygyny. 

3.  One  woman  and  two  or  more  men  simultaneously — 
polyandry. 

4.  Two  or  more  men  and  two  or  more  women  simul- 
taneously— group  marriage. 

So,  taking  marriage  to  mean  matings  of  appreciable 
duration,  formally  sanctioned  by  the  community,  this 
list  exhausts  the  possibifities.  That  is,  if  the  group  maintains 
a  definite  marriage  system,  that  system  must,  in  general 
outfine,  conform  to  one  of  these  four  types  of  matings. 
Now,  as  everyone  knows,  these  four  forms  of  marriage 
do  occur  in  the  world  of  today;  an  important  fact  to  bear 
in  mind,  for  those  who  contend  that  marriage  is  something 
invented  by  man,  will  give  great  weight  to  this  exhaustion 
of  the  possibifities.  They  will  say  that  here  is  proof  that 
the  form  of  marriage  adopted  is  a  choice  on  the  part  of  the 
community.  There  are,  however,  certain  relations  between 
these  four  forms  of  marriage  that  discourage  so  simple  an 
explanation. 

It  is  sometimes  assumed  that  these  four  marriage  systems 
are  mutually  exclusive,  which  in  practice  would  mean  that 
when  a  community  adopts  one,  it  frowns  upon  the  other. 
To  some  extent  this  is  the  case.  Highly  organized  govern- 
ments legislate  the  national  form  of  marriage,  which,  in 
case  of  Christian  nations,  is  monogamy.  The  other  three 
forms  of  marriage  are  thus  made  illegal  and  punishments 
are  provided  for  those  who  attempt  such  unions.  On  the 
other  hand,  certain  non-Christian  nations  legafize  polygyny 
and  so  outlaw  polyandry  and  group  marriage,  but  curiously 


270  HUMAN   BIOLOGY 

enough,  they  do  not  outlaw  monogamy.  This  is  consistent 
in  one  way,  because  it  is  the  woman  who  is  restricted  to  a 
union  with  one  man,  not  the  man  who  is  limited  to  one 
woman.  Long  ago,  Westermarck  demonstrated  that  mono- 
gamy was  tolerated  everywhere,  which  he  considered  proof 
that  monogamy  was  the  original  natural  union  of  mankind. 
That  this  does  prove  it  rrtay  be  doubted,  because  a  man 
usually  marries  one  woman  at  a  time;  so  he  would  first 
be  monogamous,  even  though  later  polygynous.  In  the 
same  way  the  first  step  in  polyandry,  the  form  of  marriage  in 
which  a  woman  marries  several  men,  may  be  monogamous, 
later  polyandry  and  eventually  group  marriage.  It  appears 
then  that  the  forms  of  marriage  are  not  mutually  exclusive 
in  community  practice,  and  that  in  dealing  with  the  subject 
it  would  be  fairer  to  regard  the  ideal  of  the  community 
or  nation  rather  than  to  count  all  the  forms  of  union  observed 
at  a  given  time.  A  monogamous  tribe  would  then  be  one  in 
which  other  forms  of  marriage  were  frowned  upon;  a  poly- 
gynous tribe  one  in  which  that  form  of  marriage  was  the 
objective,  even  though  a  number  of  men  had  but  one  wife 
each.  Looked  at  in  this  way,  a  census  of  the  world  may  be 
taken  to  see  what  form  of  marriage  prevails. 

First,  we  may  inquire  as  to  what  peoples  live,  or  have 
been  observed  to  live,  without  marriage  of  any  kind.  For 
such  examples  the  records  of  explorers  have  been  searched 
without  success.  Everywhere,  marriage  as  a  social  institution 
is  recognized  and  enforced,  so  we  can  say,  with  confidence, 
that  marriage  is  universal.  Westermarck  and  others  made 
this  clear  long  ago.  It  would  seem  then  that  marriage  as  a 
social  institution  is  very  old,  probably  the  oldest  surviving 
social  complex.  Not  a  few  social  philosophers  and  historians, 
as  well,  have  regarded  it  as  the  foundation  to  the  whole 
social  structure.  Whether  this  is  a  justifiable  hypothesis 
or  not,  we  need  not  pause  to  consider,  but  may  return  to  the 
question  of  universality.  As  we  have  stated,  there  are  four 
forms  of  marriage,  all  of  which  exist  at  the  present  time 
and  that  a  savage  community  or  a  nation  consistently 
approves  one  of  these  and  frowns  upon  the  antagonistic 
forms.  In  a  world  survey  of  marriage  forms  monogamy  may 
appear  dominant  because  it  is  the  form  followed  by  Christian 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  27 1 

nations  whose  civilization  is  spreading  over  the  world,  and 
the  tendency  for  all  nations  taking  over  this  type  of  civihza- 
tion,  whether  Christianized  or  not,  is  to  adopt  monogamy, 
for  example,  Turkey.  So  it  is  clear  that  monogamy  is  asso- 
ciated with  a  dominant  contemporary  world  culture,  and 
is  being  carried  along  with  it.  If  we  disregard  this  recent 
phenomenon  and  review  the  pagan  and  non-Christian 
peoples  of  the  world,  a  different  picture  greets  us.  Polygyny 
now  far  exceeds  other  forms.  Monogamy  is  next,  however, 
after  which  come  polyandry  and  group  marriage.  It  is 
difficult  to  be  exact,  because  of  the  varying  nature  of  our 
information,  but  there  seems  httle  doubt  that  polygyny 
leads  by  a  wide  margin.  On  this  ground,  the  views  of  Wester- 
marck  are  opposed  by  some  authorities  who  claim  that  not 
monogamy,  but  polygyny,  was  the  original  and  is  still  the 
natural  form  of  marriage.  They  say  that  "by  nature  man 
is  a  polygynous  animal."  Yet,  origins  to  human  customs 
are  for  the  most  part  past  finding  out.  Some  have  sought 
the  answer  in  man's  mammalian  background,  but  some 
animals  are  monogamous,  some  polygynous,  and  some 
promiscuous.  Our  knowledge  of  the  gorilla  and  other  primates 
is  not  very  specific  on  family  matters,  but  there  is  reason  to 
suspect  them  to  be  polygynous  when  conditions  permit. 

The  one  thing  we  can  be  sure  of  is  that  marriage  is  univer- 
sal. Each  nation  and  primitive  community  not  only  works 
toward  the  standardization  of  a  marriage  system,  but  gives 
its  sanction  to  each  marriage  in  a  fixed  procedure.  This  is 
the  marriage  rite  or  ceremony.  It  occurs  in  the  presence 
of  the  relatives  of  the  contracting  parties,  at  least  those  of 
the  bride,  who  have  given  their  assent  to  the  procedure. 
It  is  the  business  of  those  present  to  see  that  the  require- 
ments of  the  group  as  to  eligibility  have  been  met  by  the 
candidates.  Marriage  is  so  intricately  meshed  into  the 
life  of  the  community  that  the  situation  is  always  complex, 
but  one  function  the  ceremony  serves  is  to  give  notice  to 
the  community  that  a  marriage  has  been  entered  into. 

PROMISCUITY 

At  the  outset  we  cited  promiscuity  as  the  antithesis  of 
marriage.  True  promiscuity  implies  no  union  other  than  the 


272  HUMAN   BIOLOGY 

most  casual,  the  sexes  remaining  absolutely  free.  The  group 
form  of  marriage,  previously  noted,  would  approach  promis- 
cuity, provided  every  woman  in  the  community  was 
married  to  every  man;  but  group  marriages  as  found  do  not 
include  the  whole  tribe,  instead  a  small  number  of  men  and 
women  constitute  a  family.  So,  as  previously  stated,  no 
where  in  the  world  do  we  fmd  a  community  living  in  absolute 
promiscuity.  Yet,  there  was  a  time  when  the  view  prevailed 
that  a  state  of  promiscuity  preceded  marriage;  that  one  of 
the  important  steps  in  the  evolution  of  society  was  taken 
when  marriage  appeared.  Everyone  assumes  that  marriage, 
like  other  social  institutions,  had  a  beginning,  or  that 
marriage  was  preceded  by  a  state  of  no-marriage.  But 
we  have  seen  that  marriage  as  a  social  institution  may  have 
been  preceded  by  restricted  mating  similar  to  what  is 
observed  among  many  other  mammals.  The  weakness  of  the 
promiscuity  theory  lies  in  the  assumption  that  promiscuity 
is  the  only  possible  antecedent  to  marriage  as  a  social  institu- 
tion. There  is  every  reason  to  believe  that  the  biological 
family  functioned  a  long  time  before  the  form  of  society 
we  now  know  came  into  existence.  However,  one  of  the 
strongest  supporters  of  original  promiscuity  was  Lewis  H. 
Morgan,  who  arrived  at  this  interpretation,  not  by  free 
speculation,  but  by  empirical  observation.  Discovering 
that  primitive  peoples  had  peculiar  methods  of  reckoning 
relationship  which  took  the  mother  into  account,  but  did 
not  distinguish  between  the  father  and  other  men  of 
similar  age,  Morgan  believed  this  to  be  a  survival  of  an 
earlier  form  of  human  society  in  which  the  father  was 
unknown  and  so  indicated  an  antecedent  stage  of  promis- 
cuity. It  is  now  believed  that  there  are  other  interpretations 
to  this  phenomenon  more  consistent  with  the  observed 
facts.  However,  Morgan  seems  to  have  been  the  only 
student  of  marriage  offering  a  theory  of  promiscuity  based  upon 
objective  observations,  and  since  this  theory  has  not  stood 
the  test  of  time,  we  may  consider  the  case  as  not  proved. 

MARRIAGE    AS    A    REGULATOR    OF    SEX    LIFE 

[Our  own  social  viewpoint  encourages  the  inference  that 
the  primary  function  of  marriage  is  to  regulate  sex  life. 


THE    INTEGRATION    OF   THE    SEXES — MARRIAGE  273 

For  one  thing,  we  place  a  high  value  on  the  virginity  of  the 
bride,  the  chastity  of  the  groom,  and  the  strict  observance 
of  the  marriage  tie.  AH  other  peoples  seem  to  put  equal 
stress  upon  the  fidehty  of  the  married  woman,  but  many, 
if  not  most,  primitive  peoples,  care  httle  for  pre-nuptial 
abstinence.  In  fact,  not  a  few  primitive  peoples  look  upon 
virginity  among  the  unmarried  as  abnormal,  or  at  least 
antisocial;  whereas  the  irregularities  of  a  married  woman  are 
vigorously  condemned.  There  is  then  some  justification  in  the 
notion  that  marriage,  of  whatever  form,  is  a  regulator  of  sex 
hfe,  though  often  preceded  by  an  initial  period  of  approved 
hcense,  and  accompanied  by  varying  degrees  of  laxity. 

Among  advanced  nations  a  belief  prevails  that  early 
sex  activity  and,  naturally,  early  marriage,  is  injurious  to 
the  mother,  as  well  as  the  child.  This  tends  to  postpone 
marriage  several  years  after  puberty.  On  the  other  hand, 
primitive  people  regard  the  appearance  of  the  menses  as 
evidence  that  the  girl  is  of  marriageable  age.  Thus,  the 
primitive  base  their  procedure  upon  definite  biological 
evidence  which  is  somewhat  in  contrast  to  the  civilized 
method  of  legahzing  an  arbitrary  age  in  terms  of  the  calendar. 
When  a  girl  in  a  primitive  community  begins  to  menstruate, 
the  event  is  publicly  solemnized  by  a  ceremony  and  thus 
it  becomes  known  that  she  is  sexually  mature.  After  this, 
marriage  may  follow  at  any  time.  Reliable  statistics  as  to 
the  age  of  marriage  among  primitive  people  are  not  available, 
chiefly  because  they  have  no  means  of  accurately  recording 
age,  but  it  is  safe  to  say  that  few  girls  reach  the  age  of 
fifteen  and  remain  unmarried,  many  of  them  becoming 
mothers  at  an  earlier  age.  Yet,  it  is  not  only  primitive 
peoples  who  indulge  in  early  marriages,  for  we  find  them 
everywhere,  in  China,  India,  and  to  a  slightly  less  degree 
in  Europe.  The  laws  of  the  United  States  also  permit  mar- 
riage at  early  ages  under  restricted  conditions.  Public  opinion, 
on  the  other  hand,  now  discourages  such  marriages,  espe- 
cially among  those  above  the  average  economic  level.  Our 
educational  practice  may  accentuate  this  attitude,  since 
the  national  ideal  is  to  furnish  a  public  high  school  education 
to  every  girl,  to  attain  which  she  must  remain  in  school 
until  about  seventeen  years  old.  If  we  add  to  this  the  ideal 


274  HUMAN   BIOLOGY 

of  college  training,  to  which  a  large  minority  in  our  popula- 
tion aspire,  we  see  how  the  approved  marriageable  age  for 
girls  is  advanced  another  four  years.  We  all  know  how  the 
ideals  of  the  upper  levels  filter  down  to  the  lower,  and  so 
may  expect  in  the  country  at  large  a  rising  average  of 
marriageable  age  for  women. 

However,  early  marriage  is  frequently  opposed  on  biologi- 
cal grounds.  Medical  opinion  seems  to  condemn  both  early 
and  late  marriages  as  injurious  to  the  mother,  as  well 
as  to  the  child;  but,  as  in  many  cases  of  this  kind,  satis- 
factory statistics  are  wanting.  To  furnish  some  objective 
data  on  this  question  Miss  Stoner  collected  maternity  records 
from  hospitals  in  the  United  States.  In  these  data  the 
ages  of  mothers  range  from  thirteen  to  forty-three,  but,  so 
far,  the  records  fail  to  show  any  important  differences  in 
the  health  of  the  infants  or  of  the  mothers,  except  a  slightly 
unfavorable  average  for  those  below  seventeen  years. 
However,  the  number  of  cases  below  that  age  is  small, 
rendering  even  this  result  somewhat  uncertain.  Primitive 
girls  are  believed  to  mature  earlier  than  European  girls, 
but  in  such  biological  matters  as  this,  it  is  the  physiological 
age  of  the  individual  that  counts.  At  least  until  it  is  shown 
that  menstruation  appears  at  different  stages  of  bodily 
growth  among  different  races,  there  is  no  reason  for  assuming 
that  early  marriage  will  be  less  favorable  in  one  race  than  in 
another.  Anyway  man  has  survived,  suggesting  that  the 
danger  in  early  motherhood  cannot  be  great,  though  it 
does  follow  that  the  mortality  rate  might  be  lowered  by 
raising  the  marriageable  age  to  seventeen. 

So  far  we  have  not  considered  the  marriageable  age  of 
the  male.  It  is  generally  assumed  that  boys  mature  later 
than  girls,  but  there  is  no  certain  proof  of  this.  Baldwin 
reports  spermato;zoa  appearing  in  the  urine  of  some  boys 
at  eleven  years,  suggesting  an  earlier  maturity  than  usually 
supposed.  However  this  may  be,  it  seems  that  among 
civilized  countries  the  average  age  of  grooms  exceeds  that  of 
brides  by  two  or  three  years.  Some  observations  among 
primitive  peoples  suggest  a  somewhat  greater  disparity, 
estimated  by  Pitt-Rivers  at  seven  to  fourteen  years.  Where 
polygyny  prevails  and  the  tendency  is  for  the  older  men  to 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  275 

claim  the  young  girls,  the  disparity  of  age  will  be  greater 
still.  On  the  other  hand,  the  scarcity  of  available  brides 
may  be  so  great  that  a  number  of  young  men  will  marry 
women  much  older  than  themselves.  In  general,  however, 
the  tendency  is  for  the  age  of  the  groom  to  exceed  that  of 
the  bride,  whatever  the  state  of  society. 

The  term,  child  marriage,  recently  given  wide  pubhcity 
in  "Mother  India,"  suggests  the  marriage  of  immature 
girls  to  adult  men.  Such  a  marriage  custom  is  found  in 
India,  where  infant  marriages  are  frequent  and  in  cases 
where  the  male  reaches  maturity  many  years  in  advance, 
grave  abuses  may  occur.  Child  betrothal,  however,  is 
widespread;  usually  it  is  found  to  some  degree  in  all  polygy- 
nous  countries  where  competition  for  the  marriageable 
women  is  keen.  On  the  whole,  however,  society  frowns  upon 
the  consummation  of  marriage  before  puberty,  even  the 
crudest  of  peoples  regarding  such  practices  as  abnormal 
and  injurious. 

POSSIBLE   BIOLOGICAL    CONTROL   OF    MARRIAGE 

In  any  consideration  of  social  behavior  and  sex  functions, 
it  is  well  not  to  forget  that  whatever  form  institutions 
take,  they  rest  upon  a  biological  foundation.  As  we  have 
stated,  a  discussion  of  marriage  involves  both  biological 
and  social  factors,  between  which  we  cannot  always  clearly 
distinguish.  It  may  be  that  the  two  are  always  in  process 
of  integration,  the  result  being  community  hfe  as  we  find 
it.  Some  of  the  biological  factors  involved  are  obvious,  as 
the  external  sex  characters,  the  physiology  of  reproduction, 
the  urges  that  express  themselves  as  interest  in  the  opposite 
sex,  love  of  sex  companionship,  jealousy,  etc.  Participation 
in  sex  Hfe,  as  the  functioning  of  the  biological  organism,  may 
be  said  to  involve  psychological  as  well  as  physiological 
activities,  more  or  less  integrated.  It  is  usual,  however,  to 
consider  anything  beyond  the  most  temporary  association 
of  the  human  pair  as  not  a  biological  matter,  but  a  social 
or  conventional  one,  to  which  the  term  marriage  is  apphed. 
Here  is  the  parting  of  the  ways  in  the  interpretation  of 
human  sex  hfe.  If  one  takes  a  birdseye  view  of  the  hterature 
of  the   subject,    from    Morgan,    McLennan,    Westermarck, 


276  HUMAN   BIOLOGY 

to  the  most  ultramodern  advocate  of  promiscuity,  certain 
assumptions  are  stated  or  implied.  One  of  these  is  that,  if 
biological  factors  alone  ruled,  all  sex  unions  would  be 
transitory,  or  promiscuous;  the  converse  being  that,  when 
human  sex  Hfe  is  observed  to  be  otherwise,  the  conventions 
of  the  group  bar  the  way.  In  other  words,  every  individual 
would  be  promiscuous,  if  he  were  permitted.  The  alternative 
assumption,  and  one  stoutly  defended,  is  that  biologically 
man  is  monogamous;  that  the  association  of  one  man 
and  one  woman  tends  to  be  of  long  duration,  that  occasional 
promiscuity  and  plural  unions  are  social  developments.  It  is 
observable  that,  in  either  case,  the  appeal  is  made  to  biolog- 
ical factors  as  determiners.  It  may  be  profitable,  therefore,  to 
consider  some  of  the  possible  ways  in  which  biological  factors 
may  control  marriage,  rather  than  the  reverse.  Our  usual 
way  of  approaching  problems  of  control  is  to  consider  biology 
the  offender  and  society  the  discipHnarian.  The  danger 
here  is  in  taking  too  much  for  granted. 

Thus,  polygyny  has  been  explained  as  due  to  an  excess 
of  women,  or  to  a  variation  in  the  sex  ratio. 

THE    SEX    RATIO 

At  the  outset  we  assumed  that  in  a  normal  community 
the  sexes  would  be  approximately  equal,  but  careful  investi- 
gations of  the  sex  ratio  in  man  indicates  a  shght  tendency 
for  males  to  predominate  at  birth.  Here,  however,  we  are 
concerned  with  the  sex  ratio  at  marriageable  age,  or  the 
survival  sex  ratio.  Even  the  birth-rate  ratio  for  males  and 
females  is  a  survival  ratio,  for  many  die  in  embryo,  con- 
cerning which  rehable  statistics  are  wanting.  Again,  the 
infant  mortahty  tables  for  some  national  populations  show 
sex  differences  in  the  survival  rate,  and  vital  statistics, 
in  general,  a  difference  in  the  death  rate,  the  summation  of 
which  gives  a  higher  survival  ratio  for  women.  This  is 
evident  in  the  census  tables  for  Great  Britain,  United  States, 
France,  Germany,  Sweden,  and  some  other  countries. 
In  all  of  these  countries  monogamous  marriages  are  enforced, 
from  which  it  would  appear  that  an  excess  of  marriageable 
women  is  accumulating.  This  is  undoubtedly  true,  but  to 
see  the  relation  of  this  excess  to  marriage  calls  for  a  careful 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  277 

analysis  of  census  data  according  to  age.  However,  our 
present  interest  is  as  to  whether  plural  marriages  result 
from  an  excess  of  women.  Or,  to  state  the  case  in  general 
terms,  can  it  be  shown  that  an  excess  of  one  sex  over  the 
other  determines  the  form  of  marriage? 

On  logical  grounds,  assuming  that  every  sexually  mature 
individual  will  seek  a  mate,  a  system  of  monogamy  could 
be  followed  only  when  the  number  of  mature  females 
approximates  that  for  males.  Otherwise,  the  enforcement 
of  monogamy  would  meet  with  resistance  on  the  part  of 
the  minority.  Should  there  be  a  marked  excess  of  females, 
then  polygyny  would  be  the  most  probable  social  adjust- 
ment. If,  however,  the  males  outnumbered  the  females, 
polyandry  might  be  the  solution.  While,  at  first  reading, 
such  a  causal  relation  may  seem  obvious,  the  weak  point 
in  it  is  that  the  regulation  of  marriage  is  a  social  matter, 
and  there  are  still  other  solutions.  For  example,  a  monog- 
amous community  may  be  reasonably  successful  in  pre- 
venting plural  and  random  matings;  another  may  be 
polygynous,  without  excess  of  females,  the  minority  of 
unmarried  males  living  cehbate  or  in  irregular  polyandry. 
Merely  casting  up  the  possibihties  will  not  help  us  here;  to 
find  to  what  extent,  if  any,  the  sex  ratio  influences  marriage, 
we  must  approach  the  question  empirically.  One  obvious 
procedure  is  to  compare  sex  ratios  among  monogamous, 
polygynous,  and  polyandrous  peoples. 

Such  a  comparison  is  rendered  difficult  for  want  of  data, 
since  good  statistics  are  available  for  monogamous  countries 
only.  Nevertheless,  we  have  some  information  worth 
considering.  Buxton  reported  for  the  New  Hebrides  island 
population  a  marked  excess  of  males,  amounting  in  one 
island  to  more  than  lo  per  cent.  Similar  reports  come  from 
New  Guinea  and  other  islands  in  the  Melanesian  area, 
suggesting  that  whatever  may  be  the  sex  ratio  at  birth, 
Melanesia  as  a  whole  tends  to  a  marked  excess  of  male 
survivals.  The  marriage  systems  for  these  islands  vary 
somewhat,  but  on  the  whole  tend  to  be  polygynous,  the 
older  men  claiming  the  young  women.  On  the  other  hand, 
the  Navajo  Indians  of  the  United  States  are  also  largely 
polygynous,  but  the  females  are  in  excess.  The  best  known 


278  HUMAN   BIOLOGY 

polyandrous  peoples  are  the  Todas  of  India,  among  whom 
the  males  are  markedly  in  excess  of  the  females.  These  are 
fair  samples  of  the  data  available  and  what  we  observe 
is  that  polygyny  may  flourish  in  an  excess  male  population 
as  well  as  in  the  reverse  condition.  But  even  should  the 
correlation  be  regular,  we  should  hesitate  to  regard  the 
sex  ratio  as  the  determiner  of  the  marriage  system,  since  by 
infanticide  and  other  means  the  community  may  so  regulate 
the  survival  sex  ratio  as  to  conform  to  the  marriage  ideal. 

The  studies  of  Pitt-Rivers  indicate  no  direct  relation 
between  the  sex  ratio  and  the  form  of  marriage,  but  show 
that  a  declining  population,  regardless  of  the  form  of  mar- 
riage, is  accompanied  by  an  excess  of  male  survivals,  and 
an  increasing  population  by  parity,  or  an  excess  in  females. 
In  the  cases  cited,  the  populations  in  the  New  Hebrides 
and  that  of  the  Toda  country  are  declining,  and  that  of 
the  Navajo  increasing,  which  is  consistent  with  the  con- 
clusions of  Pitt-Rivers.  While  it  may  be  wise  to  reserve 
decision  as  to  the  general  validity  of  this  theory,  it  is  clear 
that  the  sex  ratio  can  no  longer  be  considered  an  important 
initial  factor  in  determining  the  form  of  marriage. 

PROMISCUITY   AND   THE   BIRTH    RATE 

Having  shown  that  the  sex  ratio  has  in  itself  no  claim  as  a 
determiner  of  the  marriage  form,  we  may  consider  the 
relation  between  birth  rate  and  marriage.  It  is  conceivable 
that  if  a  form  of  marriage  is  highly  unfavorable  to  a  parity 
of  the  sexes,  the  groups  practicing  it  will  either  die  out,  or 
be  socially  demoralized,  and  that  in  this  way  it  should  come 
about  that  one  or  two  of  the  possible  forms  of  marriage 
would  dominate.  Thus,  it  has  been  said  that  polyandry 
leads  to  extinction  because  the  birth  rate  is  low;  but  many 
groups  of  primitive  people  having  other  forms  of  marriage 
are  dying  out  equally  fast.  Further,  data  upon  the  birth 
rate  of  primitive  peoples  are  scarcely  obtainable  because 
mothers  do  not  accurately  recall  the  number  of  children 
they  have  borne.  The  attempts  recently  made  to  check 
up  on  the  birth  rates  for  Eskimo  and  American  Indians  are 
not  conclusive,  but  as  far  as  they  go,  indicate  a  birth  rate 
as  high  as  that  of  White  Americans  in  colonial  days.  This 


THE    INTEGRATION   OF  THE    SEXES — MARRIAGE  279 

should  encourage  caution  in  dealing  with  the  statements 
found  in  ethnographic  Hterature.  One  of  the  arguments 
against  polygyny  is  that  it  tends  to  reduce  the  birth  rate, 
but  studies  in  native  Africa  and  elsewhere  suggest  that 
when  economic  and  social  conditions  are  similar,  the  birth 
rate  for  monogamous  marriages  is  the  same  as  for  polygy- 
nous.  In  this  respect,  then,  monogamy  and  polygyny  are 
upon  the  same  level.  The  case  for  polyandry  is  not  so  good, 
but  there  is  still  reason  for  doubting  that  the  birth  rate  is 
seriously  impaired  by  this  form  of  marriage;  for  one  thing, 
it  seems  to  have  existed  in  certain  parts  of  the  world  for  a 
long  time. 

On  the  other  hand,  promiscuity  is  under  suspicion.  It  is 
generally  beheved  that  the  few  females  in  modern  society 
who  are  promiscuous  are  rarely  mothers.  In  many  primitive 
populations  a  period  of  promiscuity  precedes  marriage  and 
it  is  the  behef  of  observers  that  pregnancies  are  rare  during 
this  interval.  This  imphes  that  in  a  state  of  promiscuity,  the 
birth  rate  will  be  near  the  vanishing  point.  Yet,  too  great 
weight  should  not  be  given  this  evidence,  because  such 
approximate  sterihty  seems  to  result  from  intense  sexual 
activity,  stimulated  by  special  conditions,  whereas  advancing 
age  and  preoccupation  with  the  affairs  of  life  might  be 
expected  to  ehminate  excessive  unions  and  so  approximate 
the  normal  conditions  favoring  reproduction.  Prostitution 
is  not  pecuhar  to  modern  monogamous  society,  but  occurs 
regardless  of  the  form  of  marriage.  Even  in  primitive  com- 
munities prostitutes  are  to  be  found.  The  number  of  women 
so  engaged  is  always  small  and  though  this  number  may 
rise  and  fall  with  the  changing  social  complex  of  the  group, 
it  rarely  rises  above  a  negligible  minority,  and  so  cannot 
materially  affect  the  birth  rate  as  a  whole.  If  then,  a  condition 
of  absolute  promiscuity  should  prevail,  there  is  some  reason 
to  expect  a  lowered  birth  rate,  which  in  turn  might  militate 
against  promiscuity  in  favor  of  marriage.  Also,  there  is 
some  reason  to  believe  that  promiscuity  would  be  incom- 
patible with  stable  group  life  and  would  materially  interfere 
with  the  proper  care  of  children.  So,  on  the  whole,  it  seems  a 
justifiable  conclusion  that  there  are  biological  obstacles  to 
general  promiscuity  in  favor  of  unions  of  reasonable  stability 


28o  HUMAN   BIOLOGY 

and  duration.  In  other  words,  the  community  that  does  not 
maintain  a  well-ordered  system  of  marriage  is  in  danger  of 
extinction. 

THE    PERIOD    OF    INFANCY 

So  far  we  have  looked  upon  marriage  as  primarily  a  matter 
of  mating,  whereas  the  biological  necessity  in  human  life 
is  the  rearing  of  children.  It  is  a  reasonable  expectation, 
then,  that  both  the  biological  and  the  social  aspect  of  mar- 
riage will  be  adapted  to  the  child;  hence,  it  would  appear 
that  marriage  is  primarily  a  social  adjustment  to  the  bearing 
and  rearing  of  children,  rather  than  to  sex  life.  That  primitive 
peoples  have  given  thought  to  the  child,  there  is  abundant 
evidence.  A  child  born  out  of  wedlock  is  looked  upon  as 
abnormal,  but  not  necessarily  for  the  same  reason  that  we 
assign  to  such  happenings.  In  defence  of  these  practices, 
they  insist  that  the  child  and  the  mother  need  the  care  of  a 
man,  and  where  there  is  a  child  there  should  be  both  a  wife 
and  a  husband.  So  taking  account  of  the  way  even  primitive 
peoples  react  toward  the  child  bearing  and  rearing  cycle, 
it  appears  that  any  serious  consideration  of  marriage  must 
recognize  children  as  an  important,  if  not  the  important 
element  in  the  social  complex. 

The  child,  also,  is  a  probable  factor  in  the  duration  of 
marriage.  In  contrast  to  the  young  of  other  mammals,  the 
child  grows  slowly,  causing  an  overlapping  of  childhood 
in  the  family.  If  the  child  matured  in  a  season,  unions  of 
short  duration  might  suffice;  but  since  a  woman  may 
bear  children  at  short  intervals  for  approximately  thirty 
years,  their  childhoods  will  so  overlap  that,  during  this 
whole  period  one  or  more  will  be  dependent.  So  the  long 
growing  period  of  the  child,  as  a  biological  factor,  puts  a 
condition  upon  tribal  marriage  practice. 

We  have  called  attention  to  the  reports  of  observers 
that  some  primitive  tribes  permit  unmarried  unions  to 
continue  until  a  child  is  born  and  it  is  usual  to  assume  the 
truth  of  what  is  implied,  viz.,  that  the  custom  is  for  no 
marriage  to  take  place  until  a  child  is  born.  If,  however,  it 
were   the    custom   to   postpone   marriage,   then   an   earlier 


THE    INTEGRATION    OF   THE    SEXES — MARRIAGE  281 

marriage  would  be  irregular  and  so  frowned  upon,  if  not 
dealt  with  in  harsh  fashion.  But  a  look  back  over  the  htera- 
ture  scarcely  warrants  such  a  statement.  We  may,  therefore, 
entertain  serious  skepticism  concerning  the  prevalence 
of  marriage  only  when  a  child  is  born,  until  a  more  searching 
investigation  makes  it  clear  that  such  a  custom  does  prevail 
in  a  large  number  of  tribes.  This  is  offered  as  a  caution, 
for  there  is  sufficient  evidence  that  the  ever  present  and 
necessary  children  are  an  important  consideration  in  mar- 
riage, without  falHng  back  upon  such  assumed  universal 
practices  as  the  initiation  of  marriage  only  after  children 
are  born.  It  may  well  be,  that  all  such  cases  are  social 
demands,  or  that  what  the  group  feels  should  be,  is  marriage 
as  anticipatory  to  the  rearing  of  children.  Even  so  inter- 
preted, however,  they  are  evidences  of  the  universahty  of 
the  belief  that  children  and  marriage  are  complementary. 

Some  alarm  has  been  felt  over  such  proposals  as  trial 
marriage,  contract  marriage,  companionate  marriage,  etc., 
all  of  which  have  been  proposed  as  checks  upon  the  rising 
frequency  of  divorce.  The  ideas  underlying  these  proposals 
are  not  new,  but  seem  to  have  been  tried  one  time  and 
another.  In  Scotland,  we  are  told  that  prior  to  the  Reforma- 
tion, there  was  a  custom  known  as  "hand-fasting,"  which 
was  a  trial  marriage  not  to  exceed  a  year,  at  the  end  of  which 
period  the  couple  married  or  separated  as  they  desired. 
The  reader  of  ethnographic  literature  is  well  aware  that 
among  many  primitive  peoples  the  prospective  bride  and 
groom,  preliminary  to  marriage,  live  together  as  man  and 
wife,  often  in  the  hut  of  the  parents  of  one  of  the  contracting 
parties.  Such  a  trial  marriage  tests  two  important  qualifica- 
tions of  the  pair,  fecundity  and  ability  to  support  them- 
selves economically. 

In  conclusion,  then,  it  appears  that  a  much  stronger 
claim  can  be  made  for  the  long  period  of  infancy  as  a  deter- 
mining factor  in  marriage,  than  for  any  other  biological 
factor  so  far  considered.  Slow  growth  is  also  characteristic 
of  the  higher  primates  and  one  may  expect  more  exact 
observations  on  the  gorilla  and  the  chimpanzee  to  give  us 
further  light  upon  this  hypothesis. 


282  HUMAN   BIOLOGY 

SPONTANEOUS   ATTRACTIONS   AND   AVERSIONS 

Among  the  more  intangible  factors  in  human  sex  hfe  are 
the  spontaneous  attractions  and  aversions  between  the 
sexes.  Romantic  love  is  supposed  to  be  pecuhar  to  cultured 
nations,  but  something  hke  it  turns  up  among  the  most 
primitive.  Elopements  are  frequent  among  the  Austrahan 
natives  and  in  Africa  the  warrior  is  said  to  go  into  battle 
singing  of  his  lady  love.  Aversions  on  the  one  hand  and 
spontaneous  attachments  on  the  other  seem  everywhere 
to  result  in  the  breaking  of  law  and  custom  and  these  unions 
are,  for  a  time,  monogamous.  Here  may  be  a  reassertion  of 
the  basic  behavior  that  forms  the  biological  background  to 
marriage.  With  these  factors  go  jealousy  and  the  effort  to 
maintain  the  exclusive  relationship  set  up,  which  also  seem 
to  be  natural  responses.  In  this  way  it  seems  possible  to 
arrive  at  a  behavioristic  view  of  marriage,  or  at  least  to 
justify  it  as  a  social  necessity  in  the  harmonious  functions 
of  community  life. 

So  far  we  have  not  referred  to  the  aversion  known  as 
"incest."  Though  a  great  deal  of  thought  has  been  given 
the  subject  there  is  still  no  unanimity  of  opinion  as  to  whether 
incest  is  instinctive  or  conventional.  All  peoples  make  a 
distinction  between  an  incestuous  group  and  those  among 
whom  sex  relations  may  be  established,  but  these  distinc- 
tions, while  eminently  practicable,  are  variable  and  arbitrary. 
If  incest  is  an  instinct,  it  is  difficult  to  see  what  biological 
use  it  serves.  The  old  idea  that  inbreeding  was  destructive 
has  met  with  little  support  from  experimental  biology, 
though  some  doubt  is  expressed  as  to  how  incest  would  work 
in  a  small  savage  tribe  which  is,  for  the  most  part,  inbreeding. 
In  such  cases  incest  would  serve  as  the  only  check  to  free 
mating.  But  the  inbreeding  argument  is  so  weak  that  most 
supporters  of  the  instinct  theory  of  incest  fall  back  upon 
aversion  toward  those  with  whom  one  is  closely  associated, 
as  parents  and  children,  brothers  and  sisters.  Psychologists, 
on  the  other  hand,  are  disposed  to  regard  the  incest  aversion 
as  a  result  of  repression.  A  survey  of  primitive  practice 
reveals  a  universal  taboo  on  unions  of  mother  and  son; 
the  case  for  father  and  daughter  is  not  so  strong,  because 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  283 

there  are  existing  forms  of  relationship  which  strongly  hint 
of  a  time  when  fathers  regularly  married  their  daughters. 
RecaUing  that  under  primitive  conditions  the  biological 
relation  of  the  husband  to  the  daughter  of  his  wife  is 
uncertain,  such  union  may  or  may  not  be  incest  as  we  use 
that  term.  It  is  also  true  that  brother  and  sister  marriages, 
though  unusual,  are  found  among  a  few  peoples.  Cousin 
marriage,  on  the  other  hand,  occurs  in  many  parts  of  the 
world.  However,  most  primitive  groups  set  up  arbitrary 
divisions  between  which  the  incest  taboo  holds.  These 
rules  are  equally  binding  upon  the  married  and  the  unmar- 
ried, the  young  and  the  old.  In  many  cases  death  is  the 
penalty  for  transgression.  So,  as  a  controller  of  sex  activity, 
incestuous  prohibitions  are  often  more  effective  than  mar- 
riage, even  when  so  clumsily  formulated  as  to  be  inconsistent 
with  biological  relationship.  It  is  this  inconsistency  in 
primitive  incest  regulations  that  makes  it  difficult  to  explain 
incest  as  an  instinct. 

ECONOMIC  CONTROL  OF  THE  FORM  OF  MARRIAGE 

Suppose  at  this  point  we  turn  aside  to  consider  marriage 
as  the  economic  integration  of  the  sexes;  perhaps  that  is  too 
high-sounding  a  term,  but  society  does  seem  to  have  an 
economic  cornerstone.  There  'is  a  school  of  thought  which 
teaches  that  humanity  sweetens  the  course  of  fife  by  pre- 
tending that  the  stern  unpleasant  realities  do  not  exist; 
perhaps  that  is  why  so  many  people  reject  the  idea  that 
society  has  an  economic  side.  Their  excuse  is  that  such  a 
statement  is  rank  materiahsm  and  they  further  profess 
horror  at  the  suggestion  that  marriage,  the  acme  of  senti- 
ment, could  have  grown  up  as  an  economic  adjustment. 
But  when  we  face  the  reahties  of  fife,  the  truth  of  the 
old  Chinese  proverb  comes  to  mind  with  special  force, 
"After  food  and  clothing  are  sufficient,  honor  and  disgrace 
can  be  distinguished.  After  a  regular  stipend  is  guaranteed, 
good  manners  can  be  appreciated."  One  might  with  equal 
truth  say  that  after  the  family  is  housed,  clothed,  and  fed,  the 
future  looks  bright.  Anyway,  the  most  serious  business 
that  confronts  a  social  group,  or  a  tribe,  is  to  feed  itself, 
and  close  upon  the  heels  of  this  need  are  shelter  and  clothing. 


284  HUMAN   BIOLOGY 

Even  the  most  thorough-going  ideaUst  admits  as  much  and 
there  is  Httle  need  to  do  more  than  remind  the  reader  of  these 
homely  facts.  It  is  well,  also,  to  remember  that  a  primitive 
community  is  self-contained,  but  that  it  can  only  be  so 
through   differentiation   of  labor   and   orderly  cooperation. 

We  have  considered  the  force  of  certain  biological  factors 
in  the  shaping  of  marriage,  but  it  is  conceivable  that  economic 
factors  also  play  a  part.  The  researches  of  Hobhouse  and 
others  indicate  that  polygyny  is  far  more  frequent  among 
pastoral  and  agricultural  peoples  than  among  hunters.  This 
is  attributed  in  part  to  differences  in  individual  wealth  and 
in  part  to  the  need  for  labor.  Instead  of  a  retinue  of  female 
servants  the  head  of  the  family  acquires  wives  whose 
children  are  also  a  labor  asset.  Monogamy,  on  the  other  hand, 
is  almost  non-existent  among  pastoral  peoples.  The  economic 
relation  is  even  clearer  when  we  turn  to  such  practices  as 
"wife  purchase,"  the  custom  being  rare  among  hunters,  but 
very  frequent  in  pastoral  and  agricultural  states.  In  general, 
then,  we  can  say  that  economic  factors  in  the  life  of  the 
community  do  bear  upon  the  form  of  marriage.  Wife  purchase, 
of  course,  results  in  regarding  women  as  property,  something 
particularly  abhorent  to  our  culture.  Yet  the  male  tendency  to 
possess  is  fundamental,  and  the  last  thing  a  man  is  disposed 
to  release  is  his  woman.  Modern  communistic  reformers  seem 
to  sense  marriage  as  the  bulwark  of  private  property,  and  so 
usually  try  to  set  up  communism  in  sex,  so  far  without 
success. 

When  we  take  into  account  the  sharp  distinctions  primitive 
people  make  between  the  work  of  men  and  women,  it  appears 
that  one  outstanding  feature  of  modern  life  is  the  degree  to 
which  the  sexes  are  integrated.  Step  by  step,  industrially, 
politically,  socially  and  intellectually,  the  women  of  the 
civilized  world  are  advancing  to  equal  rights  of  participation 
in  national  life.  This  is  a  matter  of  current  history  and  a 
subject  with  which  the  reader  is  familiar.  Nor  can  it  be  said 
that  the  change  has  been  wholly  irrational  or  unconscious, 
because  there  have  been  and  exist  today,  organizations  of 
women,  laboring  to  bring  about  further  specific  adjustments 
in  their  favor.  Even  the  slogan  "all  sex  distinctions  must  go" 
is  familiar.  Presumably,  what  is  meant  by  "sex  distinctions" 


THE    INTEGRATION    OF   THE    SEXES — MARRIAGE  285 

are  conventions,  social  attentions,  legal  discriminations, 
political  privileges,  and  obliteration,  for  the  most  part,  of 
the  objective  "sex  tags"  society  places  upon  the  individual. 
Women  sometimes  charge  industrial  and  poHtical  systems 
with  being  man  made,  demanding  that  society  be  revamped  so 
that  a  woman  can  automatically  take  the  place  of  a  man  and 
the  reverse.  The  major  premise  of  this  syllogism  has  the 
appearance  of  soundness,  and  once  granted,  it  would  follow 
that  the  complete  social  integration  of  the  sexes  calls  for  a 
new  system  in  which  biological  sex  distinctions  are  to  be 
ignored. 

We  may,  however,  appraise  this  ideal  of  modern  woman  by 
looking  back  upon  our  ancestors  and  upon  living  savages 
who  resemble  them.  The  popular  idea  of  savage  life  is  a 
social  order  in  which  the  women  do  all  the  work  and  are 
barred  from  all  pleasures  of  life;  but  upon  closer  inspection, 
this  is  not  a  fair  characterization  of  the  part  woman  plays  in 
savage  society.  However,  our  concern  at  this  moment  is  not 
so  much  with  the  amount  and  kind  of  work  savage  women 
did,  as  with  the  degree  of  specialization  of  labor  with  respect 
to  sex.  It  does  appear  that  in  savage  society  the  distinctions 
are  sharp;  few  tasks  are  looked  upon  as  appropriate  for  both 
sexes.  If  the  women  make  baskets,  the  men  leave  them  alone; 
if  the  women  hoe  the  fields,  the  men  stay  away,  and  vice 
versa.  We  are  often  told  that  modern  industrialism  deprives 
woman  of  her  aboriginal  occupations.  Thus,  the  baking  of 
bread  gradually  passed  into  the  hands  of  men;  weaving  and 
spinning,  the  ancient  and  honored  work  of  woman,  was  grad- 
ually driven  from  the  home  to  the  factory  dominated  by  man, 
and  so  on.  But  too  much  should  not  be  made  of  this  analogy, 
for  there  is  evidence  that  even  in  savage  society  shifts 
occurred  from  one  sex  to  the  other;  the  question  of  importance 
is,  as  to  how  successful  society  has  been  in  keeping  vocations 
open  to  the  sexes  on  equal  terms.  In  modern  savage  society, 
as  we  have  hinted,  there  are  few,  if  any,  specialized 
vocations  without  sex  discrimination.  On  the  contrary, 
these  distinctions  are  so  emphasized  that  they  frequently 
rise  to  the  level  of  taboos,  and  anything  that  is  closely 
associated  with  one  sex  is  approached  by  the  other  with 
caution.  Every  reader  of  primitive  lore  knows  how  rigidly 


286  HUMAN   BIOLOGY 

woman  Is  excluded  from  the  preparation  for  the  hunt  and 
for  war;  the  explanation  usually  given  is  that  men  fear  she 
will  magically  contaminate  their  weapons  and  offend 
their  guardian  spirits.  But  this  is  probably  putting  the 
explanation  before  the  thing  to  be  explained;  the  chances 
are  that  the  segregation  of  the  sexes  is  deep  set  in  savage 
society  and  that  these  superstitions  are  afterthoughts  in 
defence  of  the  practice. 

The  adult  who  attempts  to  justify  a  social  convention  to  a 
questioning  child  uses  such  secondary  explanations,  and 
those  who  recall  such  experiences  can  the  better  understand 
the  savage  mind.  Yet  this  is  of  httle  moment  at  present, 
since  we  find  savage  society  marked  by  what  seems  to  us 
extreme  segregation  of  the  sexes,  and  the  failure  of  any 
savage  to  conform  to  the  tribal  patterns  of  segregation  would 
be  frowned  upon  as  a  matter  of  course.  What  our  women  com- 
plain of  is  this  same  savage  exclusiveness  on  the  part  of 
modern  man.  It  is  this  old  attitude,  they  say,  which  attempts 
to  bar  women  from  industry  and  from  pohtical  hfe.  If,  how- 
ever, this  segregation,  this  resistance  to  integration,  is  as  old 
as  the  race,  we  are  justified  in  suspecting  a  biological  basis. 
Recent  studies  of  primates  present  in  clear  outhne  a  dis- 
tinction in  behavior  patterns  between  the  males  and  the 
females.  Female  primates  adjust  themselves  to  a  new  situa- 
tion by  attitudes  and  movements  of  one  kind,  the  males  of 
the  same  species  by  another.  These  respective  attitudes  are 
seen  in  the  adults  of  the  species  in  purposeful  association, 
not  only  in  sex  activity,  but  in  other  lines  of  action.  This 
suggests  that  submerged  in  the  organism  of  the  human 
species  are  sex  patterns  which  tend  to  segregate  the  sexes. 
In  simpler  terms,  men  have  a  group  of  response  patterns 
peculiar  to  themselves,  by  virtue  of  which  they  draw  apart 
from  women.  Women,  on  their  part,  are  thrown  together 
for  similar  reasons.  The  process  is  automatic,  or  at  least 
subconscious.  One  or  two  women  may  readily  adjust  them- 
selves to  a  group  of  men,  or  be  harmoniously  tolerated,  and 
vice  versa;  but  when,  as  in  a  normal  human  community, 
the  number  of  each  sex  Is  about  the  same,  each  tends  to 
respond  en  bloc,  and  thus  they  pull  apart.  This  Is  much  like 
what  happens  when  dark  and  white  races  attempt  to  live 


THE    INTEGRATION   OF   THE   SEXES — MARRIAGE  287 

together,  a  small  minority  will  not  be  disturbing,  but  a  bloc 
will  take  form  if  this  minority  becomes  formidable.  The 
question  then  is,  in  how  far  can  modern  society  overcome 
this  tendency? 

In  industrial  life,  from  time  to  time,  new  lines  of  work  are 
opened  to  women,  but  we  may  ask,  to  what  extent  do  men 
and  women  work  at  the  same  thing  in  the  same  place  and 
time?  More  than  once,  it  has  been  remarked  that  when 
women  constitute  a  respectable  minority  in  any  trade  or  pro- 
fession, men  tend  to  shift  to  other  hnes.  The  usual  explana- 
tion for  this  is  economic,  viz.,  wage  competition,  but  the 
subject  has  not  been  studied  searchingly  enough  to  make  it 
certain  that  this  is  the  only  factor  or  even  the  primary  one, 
since  it  is  possible  that  the  segregation  tendency  is  reassert- 
ing itself.  As  we  have  noted,  even  the  most  primitive  of 
communities  gets  on  by  coordinating  the  segregated  labors 
of  the  sexes,  rather  than  by  attempting  wholesale  integration; 
and  there  are  signs  that  something  like  this  is  going  on  in 
modern  industry. 

Noting  then ,  how  segregation  of  the  sexes  with  respect  to 
work  has  been  the  rule  in  the  past,  we  may  consider  how  far 
biological  factors  control  the  kinds  of  work  performed  by 
women  and  by  men.  From  the  first,  we  see  men  handling  the 
more  violent  tasks  of  life,  women  the  routine  work.  Even 
primitive  woman  seems  to  have  had  leisure  to  indulge  in 
basketry,  pottery,  and  other  like  occupations,  as  a  visit  to  a 
museum  will  show.  Altogether,  she  had  a  varied  life,  but  in 
modern  industry,  she  specializes  in  what  was  formerly  con- 
sidered man's  work.  Yet,  on  the  whole,  we  seem  to  find 
modern  woman  in  industry  engaged  in  occupations  which 
require  less  muscular  exertion  and  which  otherwise  remind  us 
of  her  primitive  labors.  Nevertheless,  again,  we  advise  cau- 
tion, because  this  subject  has  not  received  the  attention  it  de- 
serves, but  the  suggestion  is  that  biological  factors  are  operat- 
ing now  as  in  the  past,  to  differentiate  the  work  of  men  and 
women. 

Some  alarm  is  felt,  however,  because  the  organized 
woman's  movement  decries  all  distinctions,  and  seeks  to  put 
women  into  all  kinds  of  work.  The  fear  is  that  injury  to 
health  and   offspring  will   result.   Space  does  not  permit  a 


288  HUMAN   BIOLOGY 

review  of  what  has  been  written  on  the  biological  fitness  of 
women  to  do  man's  work,  but  from  the  very  first,  she  has 
shown  a  capacity  for  hard  work,  and  while  on  the  average 
not  so  strong  as  man,  she  can,  if  need  be,  come  sufficiently 
near  that  average  to  satisfy  most  requirements.  Anyhow, 
modern  society  gives  so  much  concern  to  the  health  and 
well-being  of  employes,  that  the  danger  here,  if  any,  will  be 
transitory;  the  expectation  being  that  segregation  will 
reassert  itself  along  favorable  lines.  Again,  the  increasing 
economic  independence  of  women  is  believed  to  impede 
marriage,  to  encourage  divorce,  and  to  stimulate  birth  con- 
trol. If  this  be  true,  economic  factors  are  not  only  controlling 
marriage  as  a  social  institution,  but  also  exercising  a  control 
over  the  biological  factors  of  reproduction  as  well. 

DIVORCE 

Current  discussion  of  divorce  often  leaves  one  the  im- 
pression that  the  practice  is  something  new.  On  the  contrary 
it  is  as  old  as  marriage  itself,  for  while  a  few  primitive 
peoples  are  said  to  consider  marriage  insoluble,  as  do 
orthodox  Hindus,  these  are  exceptions.  Hobhouse  examined 
the  data  for  271  independent  tribes,  finding  that  in  about  72 
per  cent  of  these  the  parties  could  separate  at  will,  24  per 
cent  could  do  so  under  stated  conditions,  while  in  only  4  per 
cent  was  divorce  barred.  From  this  it  appears  that  divorce 
is  recognized  almost  as  widely  as  marriage.  As  to  the  fre- 
quency with  which  these  people  exercise  the  option  of  divorce, 
one  cannot  be  definite  for  want  of  statistics,  but  the  casual 
observations  of  travelers  indicate  that  divorce  among  them 
frequently  exceeds  the  civilized  rate.  However,  not  being 
able  to  determine  these  frequencies,  we  cannot  say  in  how 
far  they  are  due  to  economic  conditions.  Yet,  we  can  correlate 
the  degree  of  divorce  toleration  with  the  economic  type  of 
culture ;  thus,  the  271  tribes  just  referred  to  were  about  equally 
distributed  between  pastoral  peoples,  hunters  and  agricultur- 
ists, and  these  types,  in  turn,  manifested  the  same  degree  of 
tolerance  toward  divorce.  It  would  follow,  then,  that  neither 
denial  nor  freedom  of  divorce  depends  upon  the  economic 
status  of  a  people.  This  is  consistent  with  certain  recent  stud- 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  289 

ies  which  show  no  economic  control  over  the  divorce  rate 
in  the  United  States. 

We  have  expressed  doubt  that  the  integration  of  sexes  in 
industry  was  destined  to  be  reahzed.  On  the  other  hand,  our 
people  have  achieved  a  measure  of  success  in  educational  and 
social  integration.  Such  integration  seems  to  work  well  in  the 
secondary  school  and  the  college,  and  we  should  add,  in 
church  functions,  social  gatherings,  and  so  on.  In  short, 
recreations,  theaters,  lectures,  radio  programs,  newspapers, 
etc.,  are  all  enjoyed  by  the  sexes  in  companionship.  This  is  in 
sharp  contrast  to  primitive  and  most  oriental  peoples  among 
whom  men  and  women  rarely  go  about  companionably  or 
participate  equally  in  social  activities.  We  also  regard  this 
joint  companionable  participation  as  an  ideal  to  be  striven 
for,  and  so  endeavor  to  bring  about  more  complete  integra- 
tion. One  pecuharity,  however,  is  that  all  these  activities  are 
something  apart  from  one's  daily  work,  and  are  not  in  that 
sense  governed  by  economic  factors. 

Further,  it  is  ideal  companionship  of  this  kind  that  is 
usually  cited  as  the  objective  in  marriage,  and  there  is  reason 
to  suspect  that  the  high  standards  of  companionship  thus  set 
up  are  responsible  for  part  of  the  increase  in  the  divorce  rate. 
Again,  as  we  noted  above,  the  postponement  of  marriage 
and  the  reaHzation  of  a  high  standard  of  education,  may 
increase  the  difficulty  in  deciding  upon  a  mate  and  even 
develop  an  aversion  to  sex  fife.  Also,  the  statistics  on  divorce 
indicate  that  separations  are  relatively  frequent  among 
marriages  in  which  brides  are  under  twenty-two  and  grooms 
under  twenty-five,  and  that  the  younger  the  one  or  the  other, 
the  more  frequent  the  divorce.  Also,  marriages  after  twenty- 
nine  and  thirty-four,  respectively,  show  a  higher  divorce  rate, 
increasing  with  age.  This  means  that  the  most  stable  unions 
are  those  for  women  of  twenty-two  to  twenty-nine  and  for 
men  of  twenty-five  to  thirty-four.  No  doubt  these  data  need 
rechecking,  but  they  are  fairly  consistent  with  the  logic  of  the 
situation.  Women  advocates  declaring  for  the  aboHtion  of 
marriage  and  the  economic  independence  of  women  say  that 
in  such  an  ideal  society,  women  will  become  mothers  when- 
ever they  are  ready;  but  if  motherhood  is  postponed  until 
woman  is  economically  in  a  position  to  support  children,  she 


290  HUMAN   BIOLOGY 

may  find  the  necessary  responses  fully  inhibited.  Such 
radical  proposals,  however,  are  always  upon  the  assumption 
that  men  will  be  non-resistant  and  that  all  women  will  be 
ruled  by  the  head  rather  than  otherwise,  something  biologi- 
cally improbable.  To  return  to  our  subject,  it  appears,  then, 
that  divorce  occurs  in  all  states  of  society,  regardless  of 
econortii''  status  and  that  a  number  of  factors  must  be  con- 
sidered in  assigning  causes  to  the  modern  trend  in  divorce, 
the  chances  being  that  economic  factors  are  the  least  of 
them.  Man}^  students  of  tiie  subject  now  regard  maladjust- 
ments in  sex  life  and  failure  to  realize  the  new  ideal  of 
companionable  integration  as  the  factors  disturbing  the 
stability  of  the  marriage  relation. 

THE  MARRIAGE  OF  THE  FUTURE 

However,  so  complex  a  matter  as  the  integration  of  the 
sexes  cannot  be  treated  adequately  in  a  brief  sketch,  for 
there  are  many  other  aspects  of  the  subject  to  be  considered 
before  one  can  form  a  properly  balanced  view.  Since,  however 
it  appears  that  a  change  in  the  degree  and  direction  of  sex 
integration  is  now  under  way,  one  is  justified  in  trying  to 
form  some  notion  of  the  direction  in  which  modern  society  is 
moving.  The  increasing  economic  independence  of  women,  or 
economic  integration,  has  no  doubt  contributed  something 
to  reduce  the  economic  aspect  of  marriage,  and  anything 
that  so  tends  throws  the  emphasis  more  and  more  upon 
child  rearing  and  otherbiological  relations.  At  the  same  time 
our  social  drift,  as  shown  in  education  and  companionship 
ideals,  has  emphasized  the  intellectual  and  emotional 
integration  of  the  sexes  generally,  encouraging  free  associa- 
tion in  recreation  and  uplift  pursuits.  The  suggestion  is, 
therefore,  that  the  future  marriage  in  our  society  will  be  a 
readjustment  to  biological  rather  than  to  economic  factors. 

REFERENCES 

Briffault,  R.  1927.  The  Mothers.  A  Study  of  the  Origins  of  Sentiments  and 

Institutions.  3  vols.  London,  George  Allen  &  Unwin. 
Carr-Saunders,  a.  M.   1922.  The  Population  Problem.  Oxford,  Clarendon 

Press. 
Ellis,  H.  Man  and  Woman:  A  Study  of  Human  Secondary  Sexual  Characters. 

Ed.  5,  N.  Y.,  Scott. 


THE    INTEGRATION    OF   THE    SEXES MARRIAGE  29 1 

Groves,  E.  R.,  and  Ogburn,  W.  F.  1928.  American  Marriage  and  Family 

Relations.  N.  Y.,  Henry  Holt. 
HoBHOuSE,  L.  T.,  Wheeler,  G.  C.,  and  Ginsberg,  M.  1915.  The  Material 

Culture  and  Social   Institutions  of  the  Simpler  Peoples.  An  Essay  in 

Correlation.  London,  Chapman  &  Hall. 
Langdon-Davies,  J.  1927.  A  Short  History  of  Women.  N.  Y.,  Viking. 
LiNDSEY,  B.  B.,  and  Evans,  W.  1927.  The  Companionate  Marriage.  N.  Y., 

Boni  &  Liveright. 
Malinowski,  B.  1927.  Sex  and  Repression  in  Savage  Society.  N.  Y.,  Harcourt, 

Brace. 
Pitt-Rivers,  G.  H.  L.  F.  1927.  The  Clash  of  Culture  and  the  Contact  of 

Races.  London,  Routledge. 
Stoner,   E.   R.    1927.  The  eugenic  aspect  of  early  and  late  child-bearing. 

Eugenical  News,  12:  111-112. 
Thomas,  W.  L  1907.  Sex  and  Society.  Studies  in  the  Social  Psychology  of 

Sex.  Univ.  Chicago  Press. 
Westermarck,  E.  1926.  A  Short  History  of  Marriage.  London,  Macmillan. 


PART  IV.  EFFECTS  OF  ENVIRONMENT 


Chapter  XIII 

THE  EFFECT  OF  CLIMATE  AND  WEATHER 

Ellsworth  Huntington 

THE    climatic    FACTORS 

WEATHER,  as  everyone  knows,  is  the  natural 
atmospheric  changes  from  day  to  day;  climate  is 
the  sum  total  of  the  weather  year  after  year.  In 
studying  their  combined  physiological  effects  it  is  advisable 
to  begin  with  the  individual  factors  of  which  they  are 
composed.  Temperature  is  the  most  important  of  these. 
Ordinary  experience  gives  some  idea  of  how  temperature  may 
influence  human  health  and  activity.  It  is  not  so  easy,  how- 
ever, to  appreciate  the  effect  of  changes  of  temperature,  for 
changes  often  produce  effects  totally  different  from  what  the 
actual  temperature  as  measured  by  the  thermometer  would 
lead  one  to  expect.  Humidity  probably  comes  next  in 
importance,  but  it  is  difficult  to  differentiate  between  the 
direct  effect  of  atmospheric  moisture  itself  upon  the 
skin,  nerves,  mucous  membrane  and  the  like,  and  its 
indirect  effect  upon  the  sensible  or  "feelable"  temperature. 
When  the  thermometer  reads  70°f.,  unmoving  air  that  is  satu- 
rated with  water  feels  warm,  for  its  sensible  temperature  is 
high,  but  perfectly  dry  air  feels  cool  because  evaporation 
causes  the  sensible  temperature  to  be  too  low  for  comfort. 

The  effects  of  wind  are  even  harder  to  isolate  than  those  of 
humidity.  That  the  movement  of  the  air  has  a  direct 
physiological  effect  in  addition  to  its  cooling  power  is 
evident  to  anyone  whose  eyes  have  watered  in  a  high  wind. 
The  wind  also  does  much  harm  by  carrying  dust  and  other 
impurities.  Yet  its  most  important  physiological  effect  is 
tojower  the  sensible  temperature.  Sunlight,  the  fourth  great 
climatic  factor,  resembles  both  humidity  and  wind  in 
being^highly  important  because  of  its  effect  on  our  feelings  of 
warmth  or  the  reverse,  and  yet  in  producing  its  own 
individual  effects  of  quite  a  different  kind.  The  moment  the 
sun's  rays  are  intercepted  we  feel  cooler,  but  the  complete 


269  HUMAN    BIOLOGY 

effect  of  sunlight  depends  on  how  much  radiation  we  receive 
from  the  red  end  of  the  spectrum  with  its  long  heat  waves  and 
how  much  from  the  blue  end  with  its  short-waved,  highly 
active  ultraviolet  hght  whose  chemical  effects  upon  rickets 
and  the  hke  have  recently  been  much  discussed. 

No  study  of  climatic  factors  is  complete  unless  it  includes 
atmospheric  pressure  and  electricity,  but  we  shall  mention 
them  only  to  dismiss  them.  Time  and  again  inexperienced 
investigators  think  that  they  detect  a  close  relationship 
between  barometric  pressure  and  physiological  activities. 
Such  a  relationship  is,  indeed,  very  evident  when  the 
low  pressure  on  high  mountains  is  compared  with  the 
normal  pressure  at  sea  level,  but  thus  far  the  most  pains- 
taking investigators  have  had  little  success  in  isolating  any 
clear-cut  effects  of  the  barometric  variations  at  any  one 
place.  Supposed  effects  of  this  kind  appear  to  be  due  almost 
wholly  to  the  accompanying  changes  in  temperature, 
relative  humidity,  winds  and  sunlight.  As  to  atmospheric 
electricity,  many  little  scraps  of  evidence  suggest  that  it 
may  exert  an  important  influence  upon  human  well-being. 
People  appear  to  feel  stimulated  after  thunder  showers,  or 
in  factories  where  electric  sparks  are  active,  but  no  one  yet 
knows  whether  the  supposed  effects  are  really  electrical  or 
are  due  to  special  combinations  of  temperature,  humidity, 
and  wind. 

THE    LAW    OF    CLIMATIC    LIMITS 

The  physiological  effects  of  temperature,  humidity, 
atmospheric  movement,  and  sunlight  can  best  be  understood 
in  the  light  of  two  fundamental  laws,  those  of  climatic 
limits  and  climatic  optima.  Although  both  laws  are  almost 
self-evident,  they  are  rarely  understood  or  consciously 
used  as  the  basis  of  adjusting  mankind  to  his  environment. 

The  law  of  limits  may  be  stated  thus:  Almost  every 
environmental  factor  may  be  so  extreme  that  it  is  fatal  to  the 
individual,  or  prevents  reproduction  and  is  thus  fatal  to  the 
species.  Sometimes  there  are  both  upper  and  lower  limits, 
and  sometimes  only  one.  Every  form  of  life  is  subject  to  two 
limits  of  temperature.    A  rise  of  100°  in  the  temperature  at 


I 


THE    EFFECT   OF    CLIMATE    AND    WEATHER  297 

the  earth's  surface  would  destroy  most  forms  of  life  excep 
near  the  poles.  Some  bacteria  do  indeed  live  in  hot  springs, 
while  dormant  seeds  and  spores  can  endure  still  higher 
temperatures  provided  the  air  be  dry,  but  even  in  the 
lowest  organisms  reproduction  appears  never  to  take  place 
unless  the  temperature  is  well  below  the  boiling  point  of 
water.  As  for  man,  the  obvious  limit  is  a  temperature  such 
that  the  cooling  mechanism  of  the  sw^eat  glands,  skin,  lungs 
and  circulation  is  no  longer  able  to  prevent  the  body  tempera- 
ture from  rising  permanently  above  normal.  Experiments 
indicate  that  even  when  healthy  persons  are  at  rest  and 
practically  unclothed,  a  temperature  of  93°f.  in  saturated  air 
is  likely  to  cause  the  body  temperature  to  rise  as  much  as  5°  in 
two  hours — a  genuine  fever  which  would  presumably  increase 
and  soon  prove  fatal  if  the  atmospheric  conditions  were  pro- 
longed. In  dry  air  a  higher  temperature  can  of  course  be  en- 
dured; a  century  and  a  half  ago  bold  experimenters  remained 
uninjured  in  temperatures  as  high  as  262°f.  but  even  seven 
minutes  of  such  air  raised  the  pulse  from  the  normal  of  about 
70  to  144  beats  per  minute. 

In  Death  Valley  in  southern  California,  a  summer  tempera- 
ture ranging  up  to  120°  or  130°  each  day  for  several  months 
is  practically  unendurable,  even  though  the  air  is  very  dry. 
A  single  season  of  such  weather  has  been  known  to  drive 
people  crazy,  and  almost  no  one  can  endure  two  summers. 
A  very  strong  woman  might  possibly  bear  healthy  children 
in  such  a  place  and  the  children  might  grow  up,  but  it  is 
extremely  doubtful  whether  any  kind  of  human  beings 
could  stand  the  summer  heat  if  it  continued  all  the  year. 

As  for  the  lower  limit,  many  forms  of  life  die  promptly  if 
the  temperature  reaches  freezing.  Some  fairly  high  forms 
however,  such  as  cold-blooded  vertebrates  like  frogs,  can 
be  frozen  stiff  and  yet  recover  completely  when  melted.  No 
one  knows  exactly  how  low  a  temperature  they  can  endure, 
but  so  long  as  they  are  frozen  and  dormant,  there  can  be  no 
reproduction  and  they  are  as  good  as  dead.  Hence  for 
plants  and  cold-blooded  animals  a  freezing  temperature  is 
practically  the  lower  limit  for  the  reproduction  of  the  species. 
Warmblooded  animals  can  reproduce  at  lower  temperatures, 
and  man  seems  able  to  withstand  the  lowest  temperature  of 


298  HUMAN   BIOLOGY 

all.  But  if  the  human  race  were  not  protected  by  clothing, 
shelter  and  fire,  it  would  almost  certainly  fail  to  reproduce 
itself  wherever  the  temperature  falls  far  below  the  freezing 
point  for  any  great  length  of  time. 

The  Hmits  imposed  by  humidity  are  clear  enough  at  high 
temperatures,  but  fade  away  at  the  most  favorable  tem- 
peratures. If  warm  air  is  completely  saturated,  the  absence 
of  evaporation  and  the  consequent  difficulty  which  the 
body  experiences  in  coohng  itself  make  it  doubtful  whether 
the  human  species  could  keep  on  reproducing  itself  even 
though  other  conditions  were  propitious  and  the  temperature 
no  higher  than  90°f.  In  Japan  at  the  end  of  the  hot  damp 
summer  the  conceptions  which  result  in  living  births  are  less 
numerous  than  the  deaths.  How  much  of  this  is  due  to  high 
temperature  and  how  much  to  excessive  humidity  it  is 
impossible  to  say,  but  humidity  is  of  decisive  importance, 
for  similiar  temperatures  with  moderate  humidity  do  not 
produce  any  such  results.  If  humidities  and  temperatures 
like  those  of  the  summers  in  Japan  and  along  the  coast  of 
South  China  persisted  indefinitely  the  inhabitants  would 
presumably  diminish  in  numbers  until  natural  selection 
had  eliminated  all  who  were  unable  to  endure  extreme 
humidity  at  the  ordinary  summer  temperatures.  Slightly 
higher  temperature  and  humidity  might  easily  prevent 
all  reproduction. 

We  are  not  yet  sure  whether  man  is  excluded  from  any 
part  of  the  earth  by  the  direct  effect  of  a  lower  limit  of 
humidity,  although  he  is  obviously  excluded  by  the  indirect 
effects  upon  water  supplies  and  vegetation  in  places  like 
the  uninhabited  southern  part  of  the  Arabian  interior. 
In  Death  Valley,  even  when  one  does  not  feel  uncomfortably 
hot,  the  dryness  of  the  air  makes  one  uncomfortably  thirsty 
practically  all  the  time.  One  drinks  till  his  stomach  is 
seriously  distended,  and  yet  is  never  satisfied,  for  the  moisture 
content  of  the  tissues  cannot  be  kept  normal.  Whether  such 
conditions  would  permanently  prevent  the  reproduction 
of  the  human  race  we  do  not  know.  At  lower  temperatures 
the  bad  effects  of  extreme  aridity  diminish  and  there  is  no 
evidence  that  even  complete  dryness  would  in  itself  prevent 
human  existence,  provided  food  and  water  were  available. 


THE    EFFECT   OF    CLIMATE    AND    WEATHER  299 

If  the  earth  should  be  deprived  of  sunlight  all  hfe  would 
soon  perish,  and  the  same  thing  would  happen  if  the  sunhght 
were  sufliciently  intense.  Thus  there  must  be  both  lower 
and  upper  Hmits  of  sunhght,  but  neither  appears  to  be 
reached  naturally  on  any  part  of  the  earth's  surface.  The 
dwellers  in  dense  forests  and  in  the  Arctic  region  with  its 
long  night  seem  at  first  thought  to  get  as  httle  hght  as 
anyone,  but  as  a  matter  of  fact  such  people  at  certain 
times  or  seasons  get  a  great  deal  of  Hght  either  directly 
from  the  sky  or  by  reflection  from  the  snow.  The  people  who 
really  approach  the  lower  hmit  appear  to  be  the  poorest 
workers  in  the  factories  of  our  smokiest  cities.  In  some 
places  such  people  may  be  slowly  dying  for  lack  of  sunhght, 
even  if  other  conditions  are  not  intolerable.  As  to  the  upper 
limit,  Woodruff,  in  an  interesting  book  on  "Tropical  Light," 
maintained  that  the  hght  within  the  tropics  approaches  the 
upper  hmit  for  the  white  man,  but  experiments  on  both 
men  and  monkeys  indicate  that  much  of  the  ill  effect  which 
he  ascribed  to  hght  is  really  due  to  heat.  Yet  the  intensity 
of  the  hght  may  reduce  human  efficiency  in  the  great 
tropical  deserts.  Long  experience  has  convinced  the  Arabs 
that  they  need  heavy,  opaque  clothing  and  headgear 
to  keep  out  the  sunhght.  How  far  this  is  for  protection 
against  heat  and  how  far  against  sunlight  is  not  clear,  but 
the  trouble  which  such  people  experience  from  the  desert 
glare  is  enough  to  show  that  the  light  is  too  strong. 

The  limits  of  atmospheric  movement  include  almost  com- 
plete quiescence  at  one  extreme  and  intolerable  gales  at 
the  other.  If  the  air  should  become  absolutely  quiet,  the 
exhalations  from  plants  and  animals,  and  from  man  and  his 
works,  would  soon  contaminate  it  to  a  degree  that  can 
scarcely  be  appreciated.  Evaporation  would  saturate  the 
the  lower  atmosphere  with  vapor,  thus  intensifying  the  ill 
effects  of  the  gases  and  odors.  Life  would  become  intolerable. 
An  approach  to  such  conditions  is  found  in  a  few  sheltered 
and  undrained  valleys  where  volcanic  gases  temporarily 
accumulate,  and  in  the  streets  and  tunnels  of  great  cities 
where  the  fumes  from  factories,  automobiles  and  other 
sources  poison  the  air.  On  the  other  hand,  if  the  wind  were  to 
blow  constantly  with  hurricane  force,  the  larger  forms  of  life 


300  HUMAN   BIOLOGY 

would  doubtless  disappear  by  reason  of  starvation,  exhaus- 
tion or  failure  to  reproduce.  The  nearest  approach  to  a  hmit 
imposed  by  the  wind  is  probably  found  in  western  Tierra 
del  Fuego.  There  the  winds  of  the  "Roaring  Forties"  make 
hfe  one  long,  cold,  miserable  struggle.  A  handful  of  lowly 
Ahkaluf  do  indeed  manage  to  survive  in  the  more  protected 
spots,  but  even  they  cannot  Hve  everywhere.  In  eastern 
Persia  the  almost  equally  violent  "Wind  of  a  Hundred 
and  Twenty  Days"  prevents  the  growth  of  trees  and  makes 
hfe  scarcely  worth  hving  throughout  the  summer,  though 
it  does  not  prevent  the  existence  of  a  fairly  abundant  and 
moderately  civilized  population.  But  such  a  wind  throughout 
the  year,  in  the  cold  winter  as  well  as  the  hot  summer, 
might  render  the  region  uninhabitable. 

Although  the  various  kinds  of  chmatic  hmits  are  not 
always  sharply  drawn,  I  have  dwelt  on  them  because  the 
physiological  relationships  of  all  types  of  inhabited  chmates 
can  best  be  grasped  by  thinking  of  them  as  lying  between  the 
hmits  and  the  optimum;  we  do  n-ot  know  of  any  chmate 
which  enjoys  the  optimum  in  all  respects.  Thus  every 
chmate  is  more  or  less  unfit,  a  fact  which  entails  most 
serious  consequences  as  to  health  and  progress.  Another 
important  generalization  concerning  man's  climatic  limits  is 
that  in  practically  all  cases  they  fall  not  far  from  the  most 
extreme  conditions  that  now  exist  upon  the  earth.  Perhaps 
this  merely  means  that  man's  mentality  has  enabled  him  to 
overcome  most  of  the  climatic  handicaps  which  he  has 
yet  encountered.  Presumably  the  limits  can  be  pushed  back 
still  farther,  but  for  thousands  of  years  to  come  they  are 
likely  to  be  a  vital  factor  in  human  existence.  This  becomes 
more  obvious  when  we  remember  that  there  are  at  least  three 
great  sets  of  limits — individual,  racial  and  cultural.  Even  in 
the  earth's  uninhabited  chmatic  borderlands  such  as  the  ice 
sheets  of  Greenland  and  Antarctica  and  the  hot  desert  of 
southern  Arabia,  individual  members  of  the  human  race  can 
undoubtedly  survive  indefinitely;  therefore  such  regions 
are  not  beyond  the  outer  climatic  limits,  but  whether  they 
are  beyond  the  limits  where  healthy  children  of  our  own  race 
can  grow  up  is  by  no  means  so  certain.  And  even  if  they  lie 
within  the  racial  limits,  does  the  physiological  handicap  of 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  3OI 

the  extreme  climate  leave  the  people  enough  energy  for  the 
advancement  of  civiHzation?  Both  history  and  geography 
seem  to  answer  in  the  negative,  for  the  intrusions  of  civihzed 
people  in  such  regions  are  sporadic  and  temporary  and  the 
permanent  inhabitants  invariably  stand  very  low  in 
civihzation. 

The  Onas  of  Tierra  del  Fuego,  the  Indians  of  the  moistest 
Amazon  forests,  the  primitive  pre-Arabic  people  of  central 
Arabia,  the  most  northerly  Ostiaks  and  Samoyedes  of  Siberia, 
and  the  shepherds  of  the  highest,  coldest  parts  of  Tibet  illus- 
trate the  two-fold  effect  of  hfe  near  the  chmatic  Hmits.  Such 
people  are  kept  in  a  low  stage  of  civihzation  partly  by  their 
inabihty  to  wrest  from  their  poor  environment  a  sufficient  sur- 
plus of  food  and  other  commodities  to  give  them  the  leisure 
to  make  new  inventions  and  devise  new  modes  of  hfe,  and 
partly  by  their  tremendous  physiological  handicap.  They  must 
indeed  be  constitutionally  vigorous  in  order  to  survive,  but  a 
large  part  of  their  vigor  is  consumed  in  resisting  extremes  of 
chmate.  Bitter  cold,  intense  heat,  over-powering  sunshine, 
or  hot,  enervating  humidity  may  not  kill  a  man  or  even 
make  him  sick,  but  they  diminish  his  surplus  energy.  He 
uses  up  so  much  of  his  strength  in  keeping  his  blood  at  the 
right  temperature  and  so  often  fails  to  do  this  that  in  his 
leisure  moments  he  is  tired  and  sleepy,  and  rarely  possesses 
the  extra  energy  which  enables  men  in  better  climates  to 
advance  civilization.  Thus  the  climatic  limits  of  civilization 
or  progress  seem  to  be  much  narrower  than  those  of  the 
human  race  as  a  whole,  and  those  of  the  race  are  narrower 
than  those  of  the  individual. 

CLIMATIC   OPTIMA 

I.  Temperature.  Interesting  and  important  as  are  climatic 
limits,  they  do  not  concern  us  so  closely  as  do  chmatic 
optima.  The  optimum  or  most  favorable  condition  for  each 
climatic  factor  varies  in  accordance  with  the  other  factors, 
but  if  those  other  factors  remain  constant,  the  optimum 
for  any  one  factor  can  be  fairly  accurately  determined. 
The  optimum  temperature  for  various  living  organisms 
is  shown  in  Figure  i.  Low  temperature  is  represented  on  the 
left  and  high  on  the  right;  the  vertical  height  of  each  curve 


302 


HUMAN   BIOLOGY 


indicates  the  efficiency  of  the  life  process  at  any  given  tem- 
perature. At  the  bottom  the  generahzed  curve  for  the 
growth  of  plants  indicates  that  at  50°f.  the  ordinary  plant 


O'F 5'  10'  15'  Z.0' Z5' 30'-3S'  W  45' so' SS' (O'  ts' 70'  JS' ^O' S5' ?0' ^S  lOO'F 


Mental 
Energy 


Mental  and 
Physical    Energy 
Combined 


Physical    Energy 
Health 


Absorption   of 

Oxygen  by 

Crayfish 


Rate  of  Fission 
of  Infusoria 


Growth  of 
Plants 


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Fig.  I.  Mean  Temperature  and  Vital  Processes. 

(From  Huntington's  Civilization  and  Climate,  ed.  3,  Yale  Univ.  Press.) 

makes  no  growth;  at  S5°  growth  is  very  shght,  and  at  60° 
slow;  but  at  higher  temperatures  it  rapidly  increases  and 
reaches  a  maximum  at  85°.  Above  that  level  the  rate  of 
growth  rapidly  diminishes  and  the  plants  die  if  the  tem- 
perature for  night  and  day  together  averages  above  ioo°f. 
In  this  curve,  as  in  the  others  of  Figure  i,  all  conditions  of 
humidity,  air  movement  and  sunHght  have  been  averaged 
together,  so  that  they  neutrahze  one  another,  and  the 
resultant  curve  represents  only  the  effect  of  temperature. 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  303 

The  second  curve  from  the  bottom  in  Figure  i  shows  Prof. 
L.  L.  Woodruff's  measurements  of  the  rate  of  fision  among 
the  lowly  one-celled  infusorians  known  as  paramoecium. 
At  40°  no  fision  and  hence  no  reproduction  take  place, 
higher  temperatures  are  accompanied  by  increasingly 
rapid  fision  until  the  optimum  is  reached  between  80° 
and  85°.  In  a  still  warmer  environment  reproduction  dimin- 
ishes rapidly  and  finally  ceases  at  about  95°.  The  total 
activity  of  animals  like  the  crayfish  may  be  measured  by 
their  absorption  of  oxygen  as  shown  in  the  next  curve. 
Here  the  phenomena  are  almost  the  same  as  in  the  other 
cases,  with  an  optimum  at  about  74°. 

The  other  four  lines  in  Figure  i  represent  human  activity. 
The  lower,  marked  "Health"  is  based  on  the  work  of  the 
National  Research  Council's  Committee  on  "Atmosphere 
and  Man."  In  shows  the  daily  deaths  of  persons  five  years 
of  age  and  over  in  New  York  City  on  and  immediately 
after  days  having  the  temperatures  indicated  at  the  top. 
It  has  been  inverted  so  that  the  high  portions  mean  good 
health  and  low  portions  poor  health.  The  resemblance  of 
this  curve  to  those  for  plants  and  animals  in  unmistakable. 
The  only  important  difference  is  that  the  left-hand  portion 
tends  to  become  horizontal  at  a  level  much  higher  than 
that  to  which  the  other  end  descends.  This  merely  indicates 
that  in  cold  weather  mankind  protects  himself  against  low 
temperature  in  a  way  that  is  impossible  for  other  creatures. 
At  high  temperatures  how^ever,  he  does  not  protect  himself 
and  therefore  his  health  diminishes  just  as  does  that  of 
animals  and  plants.  The  highest  point  or  optimum  comes 
when  the  temperature  for  day  and  night  together  averages 
66°  to  70°.  Numerous  other  investigations  give  a  similar 
result  except  that  the  optimum  appears  on  an  average  to  be 
slightly  lower,  namely  an  average  of  64°  or  6^°  for  the 
entire  twenty-four  hours. 

The  next  curve,  "Physical  Energy,"  shows  the  amount 
of  piece-work  accomplished  by  five  hundred  men  and  women 
in  Connecticut  factories  on  days  with  various  mean  tempera- 
tures. Its  resemblance  to  the  line  for  "Health"  need  hardly 
be  pointed  out.  There  is  the  same  tendency  toward  levelness 
on  the  left,  and  the  same  rapid  falling  off  at  high  tempera- 


304  HUMAN   BIOLOGY 

tures.  The  chief  difference  is  that  the  most  rapid  work  is 
done  when  the  outside  temperature  averages  60°  for  day 
and  night  together  instead  of  66°  to  70°.  One  reason  for  this 
lower  optimum  is  doubtless  that  when  people  are  at  work 
they  warm  themselves  at  least  a  httle  and  therefore  prefer  a 
temperature  somewhat  lower  than  that  which  is  most 
favorable  for  people  who  are  inactive,  and  for  those  who  are 
ill.  Perhaps,  too,  the  lower  optimum  means  that  in  the 
work  of  factory  operatives  not  only  physical  energy  but 
mental  activity  is  required  so  that  this  curve  tends  some- 
what to  approach  the  mental  curve  which  lies  just  above. 
The  optimum  for  football  is  obviously  much  lower  than  for 
factory  work. 

The  curve  for  "Mental  Energy"  represents  the  scholar- 
ship records  of  about  sixteen  hundred  students  at  West 
Point  and  Annapolis.  It  resembles  the  curves  for  health 
and  physical  energy  except  that  the  optimum  lies  at  about 
38°  and  there  is  a  plateau  from  that  point  to  the  physical 
optimum  at  6§°.  Although  the  reliability  of  this  curve  is 
not  so  great  as  that  of  the  others,  several  investigations 
confirm  the  general  thesis  that  the  optimum  temperature 
for  mental  activity  under  our  conditions  of  clothing,  housing, 
and  diet  is  lower  than  that  for  physical  activity. 

Taken  as  a  whole.  Figure  i  illustrates  the  laws  of  both 
climatic  limits  and  climatic  optima  so  far  as  temperature  is 
concerned.  It  suggests  that  for  every  living  creature  there 
is  a  distinct  degree  of  activity  for  every  condition  of  tem- 
perature. The  activity  is  highest  at  the  optimum;  with 
lower  temperatures  it  falls  off  rapidly  at  first  and  then  more 
slowly  until  the  lower  limit  is  reached.  Above  the  optimum 
the  activity  tends  to  decline  rapidly  and  under  all  cir- 
cumstances appears  to  cease  at  least  by  the  time  a  mean 
temperature  of  about  100°  is  reached.  The  exact  position 
of  the  optimum  appears  to  vary  from  one  individual  or  race 
to  another,  but  the  general  law  is  of  universal  application. 

The  four  upper  curves  of  Figure  i  illustrate  the  further 
law  that  the  optimum  temperature  varies  according  to  the 
type  of  activity.  When  taken  together  they  suggest  that 
so  far  as  temperature  is  concerned  the  best  climate  for 
people  of  European  ancestry  who  live  under  our  conditions 


THE    EFFECT   OF    CLIMATE   AND   WEATHER  305 

of  clothing,  housing  and  diet  is  one  where  the  summer 
months  are  close  to  the  physical  optimum  and  average 
about  6^°  with  daily  maxima  of  70°  to  75°  and  night  tem- 
peratures of  ^s°  to  60°,  while  the  winters  approach  the 
mental  optimum  with  midday  temperatures  of  45°  to  50° 
and  mild  frosts  at  night.  London  and  the  southern  end  of 
Puget  Sound  approach  this  as  closely  as  almost  any  places; 
Oakland  in  Cahfornia,  Santiago  in  Chile,  WelHngton  in 
New  Zealand,  and  the  Austrahan  seacoast  south  of  Mel- 
bourne also  come  near  to  it,  although  a  httle  too  warm  in 
winter.  But  not  even  London  or  Puget  Sound  has  an  ideal 
chmate,  for  other  factors  as  well  as  temperature  must  be 
considered. 

2.  Humidity.  In  attempting  to  determine  the  optimum 
humidity  it  is  essential  to  employ  a  method  such  that  the 
overwhelming  effect  of  temperature  does  not  hide  the 
effect  of  humidity.  One  excellent  way  is  by  means  of  climo- 
graphs.  A  climograph  is  one  form  of  what  I  have  called  an 
isograph,  which  is  a  general  name  for  a  kind  of  diagram  in 
which  two  variables  are  represented  by  the  horizontal 
and  vertical  ordinates  and  a  third  by  isopleths  or  lines 
representing  equal  degrees  of  intensity.  A  contour  map  is  a 
familiar  kind  of  isograph.  On  such  a  map  one  variable  is 
latitude  which  we  measure  up  and  down,  or  along  the 
vertical  ordinates  as  the  mathematician  puts  it;  another 
is  longitude  which  we  measure  east  and  west,  or  along  the 
horizontal  ordinate;  the  third  is  altitude  which  were  represent 
by  sinuous  contour  lines.  All  points  along  the  coastline 
are  at  sea  level,  or  on  the  zero  contour;  all  points  a  thousand 
feet  above  sea  level  lie  along  the  thousand-foot  contour, 
and  so  on  until  a  small  area  of  the  highest  land  may  be  enclosed 
by  the  twenty-thousand-foot  contour  hne.  By  coloring  the 
space  between  sea  level  and  the  thousand-foot  contour  dark 
green,  the  space  between  the  thousand-  and  two  thousand- 
foot  lines  pale  green,  and  so  on  with  different  shades  up  to 
dark  brown  for  high  altitude,  we  get  a  map  which  gives  a 
general  picture  of  the  height  of  the  land. 

A  climograph  is  simply  another  form  of  isograph.  In  the 
one  given  in  Figure  2  latitude  is  replaced  by  temperature, 
longitude  by  relative  humidity,  and  height  above  sea  by  the 


306  HUMAN   BIOLOGY 

death  rate.  In  other  words  chmatic  conditions ,  regardless 
of  their  geographic  location,  take  the  place  of  distances 
east  and  west  or  north  and  south,  and  excess  or  deficiency 
of  deaths  is  substituted  for  height  of  the  land  above  or 
below  sea  level.  Figure  2  illustrates  how  the  matter  works 
out  for  3,700,000  deaths  in  the  cities  of  France  and  Italy. 
In  the  upper  left  hand  corner  the  number  31.6  is  located 
at  the  high  monthly  temperature  of  82°  to  83°  and  the  low 
relative  humidity  of  45  to  50  per  cent.  It  is  based  on  all 
months  with  that  kind  of  weather  no  matter  what  city  or 
year  they  occurred  in.  For  each  month  the  death  rate  for 
the  city  in  question  is  first  expressed  as  a  percentage  of 
the  normal  death  rate,  that  is,  of  the  rate  to  be  expected 
in  that  city  in  that  particular  year  when  due  allowance 
is  made  for  the  steady  improvement  in  medical  methods. 
In  the  case  before  us  the  percentages  for  several  months  in 
several  cities  averaged  31.6  higher  than  the  normals  for  the 
places  and  years  of  their  occurrence. 

Run  down  the  figures  below  31.6.  The  relative  humidity 
remains  constant,  but  the  temperature  becomes  lower. 
The  percentages  hkewise  diminish  steadily,  then  they 
begin  to  have  minus  signs;  and  finally  at  a  temperature  of 
67°  to  68°  the  deaths  average  7.8  less  than  the  normal. 
Skip  now  to  the  next  column  and  begin  with  —9.4  at  a 
temperature  of  about  64°  and  a  relative  humidity  of  50 
to  S5  pel'  cent.  Passing  from  this  number  to  the  right,  we 
maintain  the  same  temperature  but  reach  higher  degrees 
of  atmospheric  humidity.  The  death  rate  steadily  diminishes 
until  at  a  relative  humidity  of  85  to  90  per  cent  it  averages 
14  per  cent  less  than  the  normal. 

Now  that  we  understand  what  the  figures  on  our  isograph 
mean,  we  can  draw  isopleths  which  will  be  like  contour 
lines.  Each  will  pass  through  all  points  having  a  given 
departure  of  the  death  rate  from  the  normal.  The  central 
solid  line  in  Figure  2  is  the  isopleth  indicating  10  per  cent 
less  than  the  normal  number  of  deaths;  the  lines  above  and 
below  represent  5  per  cent  less  than  normal,  then  come  two 
solid  lines,  the  normal.  Beyond  that  the  dotted  lines  indicate 
a  greater  and  greater  excess  of  deaths  above  the  normal. 
In  spite  of  some  irregularities  on  the  edges  where  the  number 


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Fig.  2.  Climograph  of  3,700,000  Deaths  in  France  and  Italy,  1899-1913. 
(From  Huntington's  World  Power  and  Evolution,  Yale  Univ.  Press.) 


f307l 


308  HUMAN   BIOLOGY 

of  months  is  small  because  the  weather  conditions  are 
extreme,  the  general  degree  of  regularity  in  Figure  2  is  high. 
The  optimum  temperature  is  evidently  64  to  6^°  which  is 
close  to  that  which  we  found  in  New  York  City.  At  that 
temperature  the  best  condition  of  humidity  appears  to  be 
80  to  85  per  cent.  Thus  the  main  climatic  optimum  for  the 
cities  of  France  and  Italy  is  an  average  monthly  tempera- 
ture of  64°  to  65°  and  an  average  relative  humidity  of  85  to 
90  per  cent. 

As  one  departs  from  the  optimum  in  any  direction,  the 
death  rate  increases,  slowly  along  the  hne  indicating  the 
optimum  temperature,  most  rapidly  where  the  temperature 
and  humidity  both  become  unfavorable.  Low  temperature 
is  bad  even  if  the  air  is  moist,  but  very  bad  if  the  air  is  dry. 
The  worst  figure  on  the  chmograph  is  an  excess  of  42.5  per 
cent  with  a  humidity  of  §s  to  60  per  cent  and  a  temperature 
of  40°.  Under  the  very  hot,  dry  conditions  shown  in  the 
upper  left  hand  corner  of  Figure  2,  the  death  rate  Hkewise 
rises  very  high,  being  31.6  per  cent  above  normal.  Under 
hot  moist  conditions  the  rate  might  be  still  higher,  but 
France  and  Italy,  with  their  dry  summers  except  in  the 
cool  north,  are  free  from  such  conditions. 

Turn  now  to  Figure  3,  representing  921,000  deaths  from 
non-contagious  diseases  among  white  people  in  the  cities 
of  the  eastern  United  States  from  19 12  to  1915.  It  is  hke 
Figure  2  except  that  the  numbers  have  been  omitted,  the 
isopleths  have  been  smoothed  to  remove  irregularities, 
and  shading  has  been  added  so  that  good  conditions  are 
dark  and  bad  conditions  hght.  The  general  aspect  of  the 
chmograph  is  almost  identical  with  that  of  Figure  2.  The 
best  health  and  fewest  deaths  occur  with  a  temperature  of 
approximately  6^°  and  a  relative  humidity  of  80  to  85  per 
cent.  Poor  health  and  many  deaths  prevail  when  the  weather 
is  hot  and  dry  and  especially  when  it  is  cold  and  dry. 

Many  other  investigations  give  similar  results.  Under 
most  conditions  fairly  moist  air  is  better  than  dry,  and  this 
is  true  even  when  the  optimum  temperature  prevails.  In 
both  very  hot  and  very  cold  weather,  however,  extreme 
humidity  is  less  favorable  than  more  moderate  conditions. 
In  cold  weather  this  must  be  partly  due  to  the  exposure 


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Deaths   in  Relation  to   Temperature 
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J. 


Fig.  3.  Climograph  of  921,000  Deaths  of  White  People  in  the  Cities  of  the 

United  States,  1912-1915. 

(From  Huntington's  World  Power  and  Evolution,  Yale  Univ.  Press.) 

I3O9I 


310 


HUMAN   BIOLOGY 


which  occurs  in  storms,  but  it  may  be  connected  with  the 
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Fig.  4.  Post-operative  Death  Rate  at  Boston  in  Relation  to  Humidity  and 

Temperature. 
(From  Huntington's  Civilization  and  Climate,  ed.  3,  Yale  Univ.  Press.) 

reverse  is  true.  In  hot  weather  the  excess  of  deaths  at  high 
humidities  represents  the  discomfort,  weakness  and  ultimate 
illness  which  are  often  the  direct  result  of  heat  combined 
with  moisture,  as  in  cases  of  sunstroke.  It  should  be  noted 
however,  that  even  in  tropical  countries  damp  heat  does 
less  harm  than  dry  heat.  Thus  in  India  and  similar  countries 
the  death  rate  reaches  a  maximum  during  the  excessively 
hot  dry  weather  of  the  spring  months  and  systematically 
falls  as  soon  as  the  rains  begin.  Part  of  this  is  unquestionably 
due  to  somewhat  lower  temperature,  but  the  more  favorable 
conditions  of  humidity  also  appear  to  be  important.  Never- 
theless, if  the  summer  air  in  India  should  approach  satura- 
tion all  the  time,  which  is  by  no  means  the  case,  the  conditions 
would  be  almost  unendurable.  The  exact  state  of  affairs  is 
illustrated  in  Figure  4  showing  the  relative  number  of 
deaths  following  surgical  operations  performed  in  Boston 
hospitals  on  days  with  various  temperatures  and  humidities. 
When  the  temperature  at  8  a.m.  is  below  70°f.,  the  number 


THE    EFFECT   OF    CLIMATE   AND    WEATHER  3II 

of  deaths  declines  steadily  as  the  humidity  increases,  as 
appears  in  the  dotted  lines,  but  when  the  8  a.m.  temperature 
is  above  70°  it  is  very  dangerous  to  submit  to  a  surgical 
operation  if  the  relative  humidity  is  either  very  low  or  very 
high,  whereas  with  a  humidity  of  ^^  to  60  per  cent  the 
chances  of  survival  are  excellent.  In  this  particular  case 
other  factors  such  as  the  change  of  temperature  from  day  to 
day  are  doubtless  concerned,  but  abundant  other  evidence 
shows  that  at  high  temperatures  there  is  a  decided  optimum 
of  humidity  which  is  far  more  favorable  than  either  extreme. 

Optima  Determined  by  Laboratory  Experiments.  The 
conclusion  that  there  are  very  definite  cHmatic  optima  is 
supported  by  numerous  experiments  as  well  as  by  the 
statistical  methods  already  described.  At  the  Pittsburgh 
Laboratory  of  the  U.  S.  Bureau  of  Mines  hundreds  of 
persons  have  been  tested  in  experimental  chambers  where 
the  temperature,  humidity  and  movement  of  the  air  can  be 
controlled  with  great  accuracy.  The  following  table  sum- 
marizes the  results  thus  obtained  at  various  temperatures 
in  saturated  air  with  subjects  who  are  very  Hghtly  clad. 
The  pulse  rate,  body  temperature  and  metabolism  are  all 
influenced.  With  ordinary  clothing  and  for  persons  absolutely 
at  rest,  the  most  comfortable  temperature  in  satural^ed  air 
appears  to  be  not  far  from  70°,  but  when  work  is  done  the 
most  comfortable  temperature  is  lower. 

Another  way  of  representing  the  same  experiments  appears 
in  Figure  5.  There  temperature  is  measured  horizontally 
from  low  on  the  left  to  high  on  the  right;  the  amount  of 
moisture  in  the  air  is  measured  vertically,  the  bottom  of 
the  diagram  representing  absolutely  dry  air  and  the  top 
300  grains  of  moisture  per  100  pounds  of  air;  the  curved 
fines  show  percentages  of  relative  humidity.  The  heavy 
"comfort  fine"  indicates  that  when  people  are  normally 
dressed  and  absolutely  at  rest,  the  most  comfortable  tem- 
perature in  motionless  saturated  air  is  64°.  A  departure  of  a 
single  degree  from  this  condition  is  at  once  perceptible.  In 
unsaturated  air  an  equal  degree  of  comfort  is  felt  at  all  other 
points  along  the  comfort  fine.  Thus  the  feefing  of  comfort 
at  68°F.  and  60  per  cent  humidity  is  the  same  as  at  64°f. 
and  100  per  cent,  or  at  76°f.  and  10  per  cent  or  any  other 


312 


HUMAN   BIOLOGY 


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THE    EFFECT   OF    CLIMATE    AND    WEATHER 


313 


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as  when  it  is  moist.  In  similar  fashion  along  each  of  the  other 
lines  parallel  to  the  comfort  line  the  atmospheric  conditions 
are  at  all  points  equally  comfortable,  although  the  degree  of 
comfort  diminishes  as  one  recedes  from  the  comfort  line. 
Nevertheless  the  effect  on  health  varies  along  each  line  in 
accordance  with  the  humidity. 

The   most   significant   fact   about   the   experiments   just 
described  is  their  close  agreement  with  the  statistical  results 


314  HUMAN   BIOLOGY 

already  given.  The  absolute  optimum  appears  to  be  a 
temperature  of  d^'^  or  66°  and  a  relative  humidity  of  about 
80  per  cent.  Such  conditions  are  Hke  those  which  prevail  in 
cool  greenhouses,  the  kind  which  have  a  springlike  freshness 
and  in  which  one  feels  neither  hot  nor  cold  and  can  either 
work  or  rest  without  discomfort. 

3.  Air  Movement.  Thus  far  we  have  considered  only  still 
air.  That  is  by  far  the  most  important  condition  because 
most  civilized  people  spend  much  of  their  time  where  the 
air  moves  only  shghtly.  Nevertheless  the  movement  of  the 
air  is  so  important  that  Dr.  Leonard  Hill  and  others  have 
made  vigorous  efforts  to  devise  an  instrument  which  will 
measure  the  combined  effect  of  temperature,  relative  humid- 
ity, and  movement  of  the  air.  The  resultant  instrument  is 
known  as  the  katathermometer.  A  large  wet-bulb  ther- 
mometer is  heated  to  ioo°f.,  or  approximately  the  tem- 
perature of  the  body,  and  exposed  to  the  air.  Its  rate  of 
coohng  depends  on  all  three  atmospheric  conditions.  Thus 
the  time  required  for  the  katathermometer  to  drop  from 
100°  to  95°  gives  an  approximate  measure  of  the  coohng 
power  exerted  by  the  air  upon  the  human  skin.  That  is  one 
of  the  best  measures  of  the  extent  to  which  the  air  is  com- 
fortable and  healthful.  It  is  by  no  means  a  perfect  measure 
however,  for  hot,  dry  air  may  have  as  great  a  coohng  power 
as  moist  air  of  moderate  temperature,  but  it  is  by  no  means 
so  healthful. 

The  relation  between  movement  of  the  air  and  tem- 
perature is  illustrated  in  Figure  6.  Here  the  reading  of  the 
dry  bulb  thermometer  is  indicated  on  the  left,  and  of  the 
wet  bulb  thermometer  on  the  right.  The  lower  curved  hne 
above  the  words  "Effective  Temperature"  indicates  the 
degree  of  heat  or  cold  experienced  at  any  given  temperature 
when  the  air  is  at  rest  and  is  saturated  with  moisture.  The 
greatest  degree  of  comfort  is  found  of  course  at  66°  where 
the  effective  temperature  hne  joints  comfort  hne.  At  both 
higher  and  lower  temperatures  discomfort  increases  until 
the  hmits  are  reached  and  death  ensues. 

The  other  long  curved  hues  indicate  the  conditions  when 
the  air  moves  with  velocities  such  as  100,  200,  or  more  feet 
per  minute.  The  faster  the  movement  of  the  air  the  higher 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  315 

the  temperature  at  which  any  given  condition  produces  a 
specified  coohng  effect.  Thus  when  the  air  moves  700  feet  a 
minute,  saturated  air  with  a  temperature  of  70°  feels  as 
cool  as  still  air  with  a  temperature  a  trifle  below  60°.  If  the 
air  is  not  saturated,  the  dry  and  wet  bulbs  of  course  stand  at 
different  levels,  and  the  effect  of  atmospheric  movement  is 
increased,  as  is  indicated  by  the  example  which  accompanies 
the  chart. 

At  temperatures  above  that  of  the  body,  as  appears  from 
the  crossing  of  the  wind  velocity  lines,  any  movement  of  the 
air  increases  the  feeling  of  discomfort.  The  reason  for  this  is 
that  after  still,  hot  air  has  touched  the  body  and  thereby 
been  cooled,  it  acts  as  a  sort  of  blanket  to  keep  away  still 
hotter  air.  But  when  the  air  is  in  motion  new  air  keeps 
touching  the  body,  thus  tending  to  heat  the  body  more 
and  more. 

In  both  Figures  5  and  6  we  may  well  think  of  a  comfort 
zone  lying  on  either  side  of  the  comfort  line.  This  zone  is 
practically  identical  with  the  areas  of  heaviest  shading  in 
our  climographs.  It  likewise  represents  the  atmospheric 
conditions  under  which  factory  accidents  are  least  numerous, 
and  various  other  human  conditions  are  most  favorable. 
Thus  from  whatever  side  we  approach  the  matter  we  find 
the  optimum  at  a  temperature  of  6^  or  66°  and  a  relative 
humidity  of  approximately  80  per  cent  in  still  air,  or  else 
under  other  atmospheric  conditions  which  give  the  air 
essentially  the  same  cooling  power.  Nevertheless  high  wind, 
like  great  dryness,  is  not  so  desirable  a  means  of  securing 
the  right  cooling  power  as  is  the  correct  temperature.  The 
best  combination  of  all  is  probably  air  at  about  6j°¥.  and  80 
per  cent  relative  humidity,  with  a  barely  perceptible  move- 
ment. A  departure  from  these  conditions  in  any  direction 
diminishes  people's  comfort,  reduces  their  capacity  to  work, 
presumably  increases  their  susceptibility  to  disease,  and 
unquestionably  raises  their  death  rate. 

4.  Variability.  Even  yet  we  have  not  reached  a  final 
definition  of  the  optimum  climate.  Variability  must  also  be 
considered.  Experiments  show  that  plants  kept  uniformly 
at  their  optimum  temperature  grow  faster  than  if  kept 
uniformly    at    any    other    temperature,    but    not    so    well 


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Fig.  6.  The  Effect  of  Temperature,  Air  Motion  and  Humidity  on  Human 

Comfort. 
(From  Sayers  and  Davenport,  U.  S.  Public  Health  Rep.,  1927.) 


I316I 


THE    EFFECT    OF   CLIMATE   AND   WEATHER  317 

as  when  the  temperature  varies  above  and  below  the 
optimum.  In  other  words  the  most  favorable  condition  is  a 
variable  temperature  whose  average  is  the  optimum.  Similar 
experiments  have  not  yet  been  performed  upon  human 
beings  to  any  appreciable  degree,  but  studies  of  factory 
work  and  death  rates  indicate  that  man  is  benefitted  by 
variabihty  quite  as  much  as  are  plants. 

The  daily  deaths  in  New  York  City  illustrate  the  matter. 
At  all  seasons,  summer  and  winter  alike,  a  drop  of  tem- 
perature is  systematically  accompanied  by  a  drop  in  the 
death  rate.  It  is  reasonable  enough  that  in  summer  a  drop 
from  a  high  temperature  toward  the  optimum  should  reduce 
the  death  rate,  but  how  can  a  drop  downward  away  from  the 
optimum  in  winter  produce  the  same  result?  Although  the 
exact  physiological  processes  are  not  yet  known,  the  answer 
appears  to  be  that  the  conditions  are  analogous  to  those  of  a 
cold  bath.  A  healthy  adult  can  take  a  dip  in  cold  water  and 
emerge  with  a  decided  glow  of  warmth  and  with  a  stimulus 
to  activity  and  health  which  lasts  for  hours.  But  let  that 
same  person  stay  in  water  with  a  temperature  of  50°  for 
an  hour  or  two,  and  he  may  be  so  chilled  that  he  will  not 
recover  for  days. 

The  analogy  of  the  hot  bath  perhaps  applies  to  the 
seemingly  unreasonable  proposition  that  even  in  winter  a 
rise  of  temperature  is  accompanied  by  an  immediate  rise 
in  the  death  rate,  but  the  case  is  not  clear.  If  bath  water 
of  almost  any  temperature  is  gradually  warmed,  a  feeling  of 
relaxation  generally  ensues,  which  perhaps  means  less 
power  to  resist  disease.  A  less  speculative  cause  of  a  rising 
death  rate  associated  with  a  rise  of  temperature  even  when 
the  temperature  thereby  approaches  the  optimum  is  found 
in  the  almost  universal  tendency  for  houses  to  be  greatly 
heated  on  days  when  the  outside  temperature  is  rising  or 
has  just  finished  rising.  We  cannot  seem  to  make  our  fur- 
naces and  our  windows  keep  pace  with  the  weather.  If  we 
were  able  to  do  this,  much  of  the  rise  in  the  death  rate 
because  of  a  rise  in  the  winter  temperature  might  possibly 
be  eliminated.  Each  month  in  the  year  the  same  conditions 
are  manifest:  many  deaths  when  the  temperature  rises, 
few  when  it  falls. 


3l8  HUMAN   BIOLOGY 

In  this  connection  the  question  at  once  arises  whether 
the  good  effect  of  falHng  temperature  is  completely  counter- 
acted by  the  bad  effect  of  rising  temperature.  Among 
plants,  as  we  have  seen,  this  is  not  the  case;  the  net  effect 
of  the  two  types  of  change  is  stimulating.  Among  men  the 
most  extensive  of  the  few  investigations  along  this  hne 
is  that  of  the  Committee  on  the  Atmosphere  and  Man  in 
New  York  City.  There  during  a  six-year  period,  a  very 
systematic  relationship  was  found  between  the  average 
change  of  temperature  from  one  day  to  the  next  during 
ten-day  periods  and  the  deaths  at  the  end  of  such  periods. 
If  the  variability  is  small,  no  matter  whether  the  temperature 
be  high  or  low,  the  death  rate  is  high.  When  the  average 
variability  amounts  to  3°  during  most  of  the  year,  or  to  4° 
or  5°  during  the  winter,  the  death  rate  is  at  a  minimum. 
If  the  variabihty  rises  higher,  the  death  rate  likewise  rises, 
but  even  with  the  most  extreme  variabihty  it  is  not  so 
high  as  with  extreme  uniformity.  In  New  York  variabihty 
appears  to  have  more  effect  on  health  than  does  humidity 
and  about  half  as  much  as  mean  temperature.  If  such  a 
relationship  is  universal,  as  appears  to  be  indicated  by  many 
scattered  bits  of  evidence,  variabihty  must  be  of  the  utmost 
importance  in  determining  man's  health  and  energy  all 
over  the  world. 

Other  things  being  equal,  extreme  uniformity  of  tem- 
perature from  day  to  day  is  decidedly  undesirable;  extreme 
variabihty  is  also  undesirable,  but  to  a  less  degree;  and 
between  the  two  extremes  hes  the  optimum.  From  this 
point  of  view  the  chmate  of  Newport  in  Rhode  Island  appears 
to  approach  the  ideal  quite  closely,  while  chmates  with 
great  uniformity  as  in  southern  Cahfornia  or  very  violent 
changes  as  in  central  Siberia  are  far  from  the  optimum. 
Apparently  the  moderately  variable  type  of  chmate  is 
good  by  reason  of  its  changes  not  only  in  temperature,  but 
in  humidity,  sunshine,  and  wind. 

This  is  as  far  as  we  can  carry  our  study  of  climatic  optima. 
We  may  hazard  the  guess  that  the  optimum  atmospheric 
pressure  is  found  within  one  or  two  thousand  feet  of  sea  level, 
and  that  the  optimum  conditions  of  sunhght  are  found  in 
different  latitudes  according  to  the  pigmentation  of  the  skin. 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  319 

CLIMATIC    DIFFERENCES    OF    RACE 

Up    to    this    point    our    data   have  appHed   only   to  the 
European  branch   of  the  white   race.    But  do  other  races 
react  Hke  the  white  man?  What  little  exact  evidence  is  yet 
available  suggests  distinct  differences  in  the  cHmatic  optima 
of  different  races  or  of  the  same  race  when  living  in  different 
chmates,   but   it   also   suggests   that   these   differences   are 
shght.   In  Japan  the  optimum  appears  to  be  ahiiost  the 
same  as  in  the  United  States.  At  Osaka  for  example,  the 
126,000  deaths  from  19 13  to  19 17  indicate  an  optimum  of 
approximately  66°f.  and  70  to  80  per  cent  relative  humidity. 
Among  Cuban  cigar-makers  in   Florida  the  best  work  is 
done  when  the  temperature  averages  from  65°  to  70°  which 
is  somewhat  higher  than  among  the  factory  workers  of  New 
England.   The   conditions   among   Negroes   in   the   United 
States   are   illustrated   in    Figure  7  which  is  hke  Figure  3 
except  that  it  is  based  on  167,000  colored  people  instead  of 
921,000  white  people.  Although  the  cities  were  the  same  in 
both   cases,   the   colored   people  are  mainly   found   in  the 
more  southerly  of  them  so  that  Figure  7  represents  a  some- 
what more  southerly  region  as  w^ell  as  a  more  tropical  race 
than    Figure   3.    Nevertheless   the   two   figures   are   almost 
identical.  The  only   important  difference   is  that  the  opti- 
mum temperature  for  the  Negroes  is  about  4°  higher  than  for 
the  whites,  and  the  optimum  relative  humidity  also  a  trifle 
higher. 

Fortunately  we  are  not  limited  to  the  American  Negro 
for  our  knowledge  as  to  the  climatic  optimum  of  tropical 
people.  In  Java  the  Dutch  have  gathered  exact  statistics 
for  a  race  that  has  lived  close  to  the  equator  for  many 
centuries.  Of  course  there  are  no  low  temperatures  even  in 
the  towns  at  greatest  altitudes,  but  so  far  as  they  go  the 
Javanese  data  agree  closely  with  those  for  whites  and 
Negroes.  Although  the  dark-skinned  Javanese  have  lived 
close  to  the  equator  for  so  long,  their  optimum  temper- 
ature appears  to  be  near  70°f.  or  only  about  5°  above  that  of 
the  white  race;  and  their  optimum  humidity  does  not  seem  to 
differ  materially  from  that  of  the  Europeans.  Morever,  what 
little  evidence  we  have  suggests  that  mild  changes  of  tem- 
perature are  just  as  stimulating  to  tropical  people  as  to  the 


SO^ 


so^ 


70^ 


60" 


V 

^< 
3 

g     50° 


a 


40° 


S0° 


20"     _ 


10" 


50'/o 

— r— 


60% 


70% 


80% 


Colored   Hon- contagious 
United  States  (1912-1915) 

167  000  deaths 


-5 


»o% 

— ] — 


-10 


-10 


Deaths  in  Relation  to  Temperature 
and  Humidity, 


± 


Fig.  7.  Climograph  of  167,000  Deaths  of  Negroes  in  the  Cities  of  the  United 

States,  1912-1915. 

(From  Huntington's  World  Power  and  Evolution.  Yale  Univ.  Press.) 


l[32ol 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  32 1 

rest  of  US.  II  all  this  is  true  it  puts  a  wholly  new  aspect  on 
the  problems  of  acclimatization  and  the  geographic  location 
of  the  origin  of  man. 

THE    GEOGRAPHIC    DISTRIBUTION    OF    HEALTH    AND    ENERGY 

The  data  now  before  us  enable  us  to  gain  an  approximate 
idea  of  the  effect  of  climate  upon  health  throughout  the 
world.  Hundreds  of  experiments,  the  work  of  thousands  of 
factory  hands,  and  the  deaths  of  millions  of  persons,  as  we 
have  seen,  enable  us  to  determine  the  approximate  degree  of 
health  and  energy  under  any  given  combinations  of  tem- 
perature, humidity  and  variability.  On  the  basis  of  weather 
records  it  is  therefore  possible  to  construct  a  map  showing 
the  approximate  degree  of  health  that  would  be  enjoyed  by 
the  white  race  in  any  part  of  the  world  if  climate  were  the 
sole  determinant  of  health.  Such  a  map.  Figure  8,  shows  two 
main  areas  where  the  climate  approaches  the  optimum, 
namely  the  northeastern  quarter  of  the  United  States  from 
the  Atlantic  to  beyond  the  Mississippi  River,  and  the 
parts  of  Europe  centering  around  the  North  Sea.  Other 
minor  centers  are  the  Pacific  Coast  of  the  United  States,  New 
Zealand,  Japan,  and  probably  Chili,  although  the  South 
American  portion  of  the  map  is  not  very  rehable.  The 
whole  map  is,  indeed,  tentative  and  should  be  revised  as 
soon  as  possible.  Nevertheless  there  is  no  reason  to  expect 
any  important  charge  in  the  main  outlines. 

In  a  similar  map  for  tropical  people  the  optimum  areas 
would  be  located  a  little  nearer  the  equator  than  in  Figure  8, 
but  the  general  aspect  of  the  map  would  be  changed  only  a 
little.  The  tropical  regions  and  continental  interiors  would 
still  be  low  and  the  warmer  parts  of  the  stormy  temperate 
zone  would  be  high.  Another  and  highly  significant  feature 
would  also  still  be  evident,  namely  the  decline  of  health  and 
energy  toward  the  centers  of  the  continents  even  in  the  most 
favorable  latitudes.  The  reason  for  this  is  partly  the  dryness  of 
the  interiors  and  their  extreme  changes  of  temperature  at 
certain  times  coupled  with  other  periods  of  very  little  change 
from  day  to  day.  These  latter  conditions  apply  especially  to 
central  Asia  because  of  its  relative  lack  of  cyclonic  storms 


32  2 


HUMAN   BIOLOGY 


such  as  give  to  the  northeastern  United  States,  northwestern 
Europe  and  Japan  a  constant  but  moderate  variabihty  from 
day  to  day  at  all  seasons. 


180    150     120    90    60    SO  0   30    CO     90  120 150 180 


150    120 


Fig.  8.  World  Map  of  Climatic  Energy. 
(From  Huntington's  Business  Geography,   ed.  2,  John  Wiley  &  Sons,  Inc.) 


It  cannot  be  too  strongly  emphasized  that  Figure  8  is  a 
purely  chmatic  map  showing  the  degree  to  which  the  chmate 
probably  departs  from  the  optimum  for  health  and  activity. 
Nevertheless  this  map  of  chmatic  energy  is  almost  identical 
with  maps  of  both  health  and  civihzation.  The  interpretation 
of  this  threefold  agreement  is  clear  in  the  hght  of  our 
previous  discussion  of  hmits  and  optima.  The  chmatic  map 
must  be  the  foundation,  for  neither  health  nor  civihzation 
can  possibly  produce  any  appreciable  effect  upon  the  dis- 
tribution of  chmate.  Hence  it  appears  that  in  the  world  today 
the  primary  control  of  the  distribution  of  health  and  civihza- 
tion is  chmate.  The  way  the  matter  works  appears  to  be  as 
foHows : 

The  more  nearly  the  chmate  approaches  the  optimum  the 
greater  the  degree  of  health  and  energy.  The  greater  the 
degree  of  energy,  the  more  hkely  people  are  to  make  advances 
in  civihzation.  But  an  advance  in  civihzation  means  improve- 
ment in  health  by  reason  of  new  knowledge,  and  improved 
health  in  turn  helps  toward  still  further  advance  in  civihza- 


THE   EFFECT   OF   CLIMATE   AND   WEATHER  323 

tlon.  The  gap  between  the  regions  that  He  near  the  climatic 
optima  and  those  lying  near  the  cHmatic  Hmits  becomes 
steadily  greater. 

The  only  serious  objection  to  such  a  connection  between 
the  distribution  of  chmate  and  civilization  is  found  in  a 
comparison  of  the  past  with  the  present.  Everyone  knows 
that  ancient  civilizations  reached  their  height  in  regions 
where  the  chmate  is  of  only  medium  quahty  according  to 
Figure  8.  Does  not  this  prove  that  whatever  may  be  the  fact 
today  the  chmate  of  the  past  cannot  have  been  a  main  factpr 
in  the  distribution  of  civihzation?  This  question  has  been 
carefully  studied  but  is  still  in  dispute. 

Two  points  however  seem  clear.  The  first  is  that  the 
chmatic  optimum,  as  has  been  imphed  in  previous  pages, 
varies  according  to  people's  stage  of  progress.  For  unclothed 
people  a  higher  temperature  and  a  lower  degree  of  vari- 
abihty  are  required  than  for  people  who  wear  clothes.  The 
same  is  true  when  people  without  fire  are  compared  with 
those  who  have  that  marvelous  means  of  keeping  warm. 
Houses,  stoves,  furnaces  and  various  other  methods  of 
keeping  warm  have  also  tended  little  by  little  to  lower  the 
optimum  temperature  and  increase  the  optimum  variability. 
This  tendency  in  itself  is  enough  to  account  for  a  considerable 
part  of  the  shift  in  the  centers  of  civilization. 

In  addition  to  this  a  second  point  needs  emphasis  before  we 
can  understand  the  relation  of  climate  to  civilization. 
Geologists  universally  agree  that  25,000  or  30,000  years  ago 
great  ice  sheets  covered  large  sections  of  North  America  and 
Europe  where  civihzation  today  stands  very  high.  The 
climatic  change  which  caused  the  ice  sheets  to  disappear  has 
taken  place  irregularly,  sometimes  proceeding  rapidly,  then 
slowly,  and  even  reversing  itself.  Even  during  the  historic 
period  similar  climatic  pulsations  appear  to  have  taken  place 
on  a  smaller  scale.  For  centuries  the  climate  has  swung  in  one 
direction  and  then  for  centuries  in  the  other,  just  as  during 
shorter  periods  it  swings  first  one  way  for  a  few  years  and 
then  the  other.  Yet  on  the  whole  dry  lands  like  western  Asia 
and  the  southwestern  United  States  appear  to  have  been 
somewhat  drier  during  the  last  one  or  two  thousand  years 
than  during  the  previous  period. 


324  HUMAN   BIOLOGY 

One  feature  of  these  climatic  pulsations  has  undoubtedly 
been  a  certain  change  in  mean  temperature,  but  changes  of 
this  sort  have  evidently  been  slight.  Even  at  the  height  of 
the  .Glacial  Period  the  average  temperature  of  the  earth  was 
probably  not  more  than  15°  or  20°f.  lower  than  now  and 
since  the  dawn  of  civilization  the  temperature  has  pre- 
sumably not  fluctuated  more  than  perhaps  a  tenth  or  at 
most  a  fifth  as  much  as  this,  far  too  httle  to  be  readily  evident 
either  from  the  ordinary  historic  records  or  from  the  known 
facts  as  to  plants  and  animals.  On  the  other  hand  the  amount 
of  storminess  has  apparently  varied  considerably  from 
century  to  century.  Part  of  the  evidence  is  found  in  ruins, 
irrigation  ditches,  and  traces  of  old  fields  in  areas  where  the 
water  supply  is  now  utterly  inadequate;  another  part  appears 
in  the  level  of  salt  lakes,  the  location  of  ancient  roads,  the 
rate  of  growth  of  ancient  trees,  and  many  other  features 
which  indicate  a  greater  water  supply  during  some  centuries 
than  during  others.  Such  evidence,  be  it  noted,  applies 
mainly  to  the  drier  parts  of  the  world,  where  even  a  slight 
change  in  rainfall  may  produce  serious  results. 

This  is  not  the  place  to  discuss  the  matter  in  detail,  but 
greater  rainfall  appears  to  indicate  greater  humidity  and 
greater  storminess;  and  greater  storminess  means  more 
frequent  changes  of  temperature.  Thus  although  the  average 
temperature  of  any  given  part  of  the  earth  has  probably 
changed  very  little  during  historic  times,  the  degree  of 
humidity  and  still  more  the  degree  of  variability  from  one 
day  to  the  next  appear  to  have  varied  considerably.  All  this 
means  that  during  the  Glacial  Period  the  optimum  climate 
was  located  much  nearer  to  the  equator  and  to  the  great 
deserts  than  at  present.  Since  then  it  has  moved  poleward 
and  at  the  same  time  toward  the  margins  of  the  continents,  but 
the  movement  has  been  irregular.  During  the  historic  period 
for  centuries  at  a  time,  especially  in  the  era  ending  with 
the  time  of  Christ,  the  optimum /or  the  stage  of  human  culture 
then  existing  appears  to  have  been  located  in  the  dry  lands 
around  the  Mediterranean  and  in  western  Asia  where 
ancient  civilization  made  its  greatest  progress.  The  cen- 
turies of  greatest  storminess  when  the  climate  most  nearly 
approached   the  optimum   appear  to  have  been  periods  of 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  325 

progress;  the  centuries  of  diminishing  storminess  when  the 
optimum  swung  northwestward  appear  to  have  been  times 
of  distress  and  decline. 

This  conclusion  is  by  no  means  universally  accepted.  In 
fact  many  able  people  assail  it  vigorously  and  even  ridicule  it. 
They  say  that  such  an  hypothesis  is  unnecessary  because 
other  historic  and  cultural  conditions  afford  a  full  explanation 
of  the  rise  and  fall  of  civilization.  They  also  say  that  the  facts 
on  which  the  hypothesis  is  based  are  scanty  and  are  subject 
to  various  interpretations.  Therefore  it  is  wise  to  suspend 
judgment,  but  it  is  highly  significant  to  see  the  way  in 
which  independent  lines  of  investigation  dovetail.  One  line, 
the  earliest,  suggests  that  the  great  centers  of  ancient 
civilization  rose  to  their  highest  levels  when  their  climates 
were  more  moist  and  variable,  and  hence  nearer  to  the 
physiological  optimum  than  at  present.  Another  shows 
that  the  optimum  varies  according  to  the  degree  of  civilization, 
and  man's  consequent  ability  to  protect  himself  from  low 
temperature  and  excessive  dryness.  A  third  indicates 
that  at  present  the  distribution  of  civilization  and  progress  is 
almost  identical  with  that  of  climatic  energy.  All  three 
together  suggest,  although  they  do  not  prove  that  in  the  past 
as  at  present,  the  distribution  of  civilization  has  been  closely 
determined  by  the  physiological  effect  of  climate. 

CLIMATE    AND    RACIAL    CHARACTERISTICS 

This  brings  us  to  the  vexed  question  of  the  relation  of 
climate  to  racial  characteristics.  So  far  as  external  character- 
istics are  concerned,  the  case  is  fairly  clear.  In  general  the 
pigmentation  of  the  races  of  the  world  varies  according  to  the 
intensity  of  the  sunlight,  for  pigment  appears  to  be  primarily 
a  protection  against  ultraviolet  light.  The  center  of  the  fair 
Nordics  today,  and  we  know  not  how  long  in  the  past,  is 
Scandinavia  where  the  sunlight,  especially  in  its  shorter  ultra- 
violet wave  lengths,  is  never  very  strong.  The  blackest  races 
are  all  found  in  low  latitudes.  Here  and  there  to  be  sure, 
we  find  relatively  fair  people  in  low  latitudes  and  moderately 
dark  tribes  in  high  latitudes,  but  in  most  cases  this  is  the 
obvious  result  of  migration.  When  once  a  race  has  acquired 
a  given  pigment,  it  presumably  requires  a  long  time  for  a  new 


326  HUMAN   BIOLOGY 

environment  to  induce  any  important  change,  unless  the 
pigmentation  is  so  unfavorable  that  the  race  tends  to  die  out. 
If  mutations  occur  on  a  large  scale,  a  rapid  change  is  of 
course  possible,  but  barring  that  a  moderately  fair  race,  if  it 
lives  out  of  doors  and  becomes  well  tanned,  can  presumably 
subsist  in  a  tropical  region  for  thousands  of  years,  provided  it 
is  adapted  to  the  environment  in  other  ways  and  is  not  in 
competition  with  a  darker  race. 

Other  forms  of  adaptation  can  be  scarcely  more  than 
mentioned.  One  is  the  condition  of  the  sweat  glands  of  the 
skin.  Among  Negroes  and  other  dark  races  the  sweat 
glands  are  more  numerous,  smaller,  and  less  active  than 
among  white  people.  They  flood  the  skin  with  fine  droplets  of 
moisture,  but  do  not  pour  out  such  streams  of  perspiration  as 
do  the  glands  of  the  white  man.  Another  apparent  adaptation 
is  found  in  the  form  of  the  nose.  Among  northern  races  the 
nostrils  tend  to  be  small  and  relatively  round,  not  admitting 
a  large  amount  of  air  at  one  time,  and  forcing  the  air  to  pass 
through  a  relatively  long  passage  where  it  is  warmed  before 
reaching  the  throat.  Among  Negroes  on  the  other  hand,  the 
nostrils  are  short,  and  wide  open  so  that  large  amounts  of  air 
can  be  taken  in  at  once.  Such  a  condition  is  favorable  in  a 
warm  climate  where  the  heat  often  compels  rapid  breathing 
even  when  people  are  at  rest.  But  is  decidely  disadvantageous 
where  the  temperature  ranges  far  below  zero,  and  may  be  an 
important  reason  why  colored  people  do  no  thrive  in  regions 
like  the  most  northerly  parts  of  the  United  States. 

The  relation  of  mental  characteristics  to  climate  is  not  so 
obvious  as  that  of  physical  characteristics.  Most  biologists 
believe  that  there  are  mental  as  well  as  physical  differences 
among  races;  many  say  that  the  brain,  being  the  most 
recently  evolved  organ,  is  likewise  the  most  variable.  Yet  an 
important  group  of  anthropologists  and  psychologists  deny 
this ;  all  mental  differences  which  others  call  racial,  so  they  say, 
are  due  to  training  and  social  inheritance.  Although  the 
brain  varies  in  size  and  intricacy  from  race  to  race  and  in  that 
respect  is  like  the  skin,  sweat  glands,  nose  and  other  organs, 
it  is  assumed  to  be  uniform  in  its  functions.  A  more  reasonable 
view  seems  to  be  that  the  powers,  aptitudes  and  functioning 
of  the   brain  vary   like  those  of  any  other  organ  and  are 


THE    EFFECT    OF    CLIMATE    AND    WEATHER  327 

similarly  subject  to  climatic  influences.  According  to  this 
interpretation  a  biological  process  of  selection  weeds  out 
certain  types  in  certain  regions.  Occupations  are  often  the 
basis  of  selection,  but  occupations  in  turn  depend  largely  on 
climate,  especially  in  primitive  communities.  Thus  where  rice- 
culture  prevails  the  family  which  cannot  force  itself  to 
undergo  the  degree  of  steady  work  required  to  plant  the  rice, 
guard  it,  and  keep  up  the  little  canals  and  dikes  needed  for 
irrigation  is  almost  sure  to  be  either  poorly  nourished,  so  that 
it  does  not  raise  many  children,  or  else  to  be  forced  into 
another  group  which  gets  a  hving  in  some  other  way. 

The  most  far-reaching  of  all  chmatic  factors  in  producing 
deep-seated  mental  differences  appears  to  be  the  seasons.  In 
warm  moist  fands  some  sort  of  food  can  be  procured  at 
almost  any  season.  Where  a  long  dry  season  occurs  this  is 
not  so  easy,  and  where  there  is  a  cold  winter  practically  no 
food  can  be  procured  for  many  months  except  by  hunting. 
Under  these  latter  circumstances  an  agricultural  population 
can  scarcely  survive  unless  it  possesses  sufficient  foresight 
to  see  that  in  summer  suppHes  of  food,  skins  and  the  like 
are  laid  by  for  winter.  It  must  also  possess  sufficient  intelli- 
gence to  plan  for  such  supplies,  sufficient  energy  to  gather 
far  more  than  is  needed  for  immediate  use,  and  sufficient 
self-control  to  husband  the  suppfies  through  the  whole  of  the 
period  of  scarcity.  In  a  tropical  climate  many  people  can 
survive  without  these  qualities;  in  a  region  with  well- 
defined  winters,  such  mental  weaklings  tend  to  be  weeded 
out,  leaving  only  the  more  intelligent,  energetic  and  self- 
controlled.  That  such  selection  is  the  primary  cause  of  the 
apparent  biological  difference  in  the  mental  powers  of 
tropical  and  non-tropical  races  has  never  been  positively 
proved,  and  perhaps  never  will  be.  Yet  as  a  working  hypothe- 
sis it  seems  to  fit  the  facts  extremely  well. 

ACCLIMATIZATION 

Our  last  topic  in  connection  with  climate  is  acclimatization, 
especially  as  it  concerns  the  white  man  in  the  tropics.  The 
materials  for  an  intelligent  opinion  as  to  this  much-debated 
problem  have  already  been  presented.  Mankind  presumably 
originated  in  one  or  more  climatic  provinces  which  were 


328  HUMAN   BIOLOGY 

moderately  warm,  although  probably  not  tropical.  One  of 
the  chief  arguments  for  this  viewpoint  is  that  the  optimum 
chmate  for  tropical  races,  as  we  have  seen,  is  almost  the  same 
as  for  others.  Thus  it  seems  probable  that  all  races,  if 
obhged  to  Hve  with  little  or  no  clothing  and  with  unwarmed 
shelters,  would  find  their  optimum  where  the  average  tem- 
perature for  the  summer  does  not  run  much  above  75°,  and 
that  of  winter  not  much  below  ^^°,  or  let  us  say  an  extreme 
range  from  80°  in  the  hottest  summer  month  to  50°  in  the 
coldest  winter  month.  If  such  a  chmate  were  blessed  with 
frequent  but  not  too  extreme  variations  of  temperature, 
it  would  be  well-nigh  ideal  for  almost  any  race  which  did  not 
have  our  modern  means  of  protecting  itself  against  the  cold. 
The  seacoasts  of  southern  Palestine  and  northern  Florida 
come  close  to  having  such  temperatures.  But  if  conditions 
of  this  kind  really  come  so  near  to  being  the  optimum  for 
all  races  in  the  primitive  state,  we  are  perhaps  justified  in 
assuming  that  they  may  not  be  very  different  from  those 
of  the  climate  in  which  man  originated  and  in  which  he 
became  stamped  with  a  climatic  relationship  which  he  has 
never  been  able  to  eliminate. 

From  some  such  region  then  we  may  suppose  that  man  has 
spread  into  regions  as  hot  as  the  southern  end  of  the  Red  Sea, 
as  warm  and  moist  as  the  Amazon  Basin,  as  windy  as 
Tierra  del  Fuego,  as  cold  and  snowy  as  Greenland,  and  as 
mild  and  even  as  Hawaii.  In  each  of  these  places  he  has 
become  sufficiently  acclimated  to  survive  even  if  he  cannot 
prosper,  and  yet  in  each  of  them  he  is  still  far  from  being 
perfectly  acclimated,  for  nowhere  does  he  find  the  perfect 
optimum. 

This  gives  us  a  clue  to  white  acclimatization  in  the 
tropics.  If  mankind  is  derived  from  one  original  stock  and 
yet  can  live  comfortably  in  so  great  a  variety  of  climates, 
there  is  every  reason  to  believe  that  the  white  man  might 
become  acclimated  in  the  tropics,  provided  he  subject 
himself  to  a  sufficiently  rigid  process  of  selection. 

The  secret  of  the  matter  seems  to  lie  in  selection.  Today 
the  white  people  who  live  permanently  in  tropical  countries 
and  especially  those  who  bring  up  children  there  are  an 
extremely  highly  selected  group.  They  themselves  may  not 


THE    EFFECT   OF    CLIMATE    AND    WEATHER  329 

realize  it  when  they  tell  how  well  the  tropical  climate  agrees 
with  them.  Yet  for  every  individual  who  goes  to  the  tropics 
as  a  sojourner,  a  large  number  have  thought  of  doing  so  but 
have  refrained  because  of  limitations  of  health.  Again, 
among  those  who  actually  go  to  tropical  countries  a  large 
proportion  leave  after  a  few  years  because  they  do  not  like 
the  climate  or  because  some  member  of  their  family 
suffers  from  it.  The  few  who  remain  permanently  and 
bring  up  families  are  in  most  cases  persons  of  a  peculiar  type 
of  constitution  which  adapts  them  to  the  tropical  climate. 
By  means  of  such  selection  for  generation  after  generation 
a  strain  of  white  people  could  probably  be  produced  which 
would  be  able  to  stand  the  tropical  climate  quite  as  well  as 
do  any  of  the  present  tropical  races. 

If  the  specific  tropical  diseases  like  malaria  and  hookworm 
could  be  eliminated,  the  chances  are  that  such  people 
could  live  in  comparative  health  and  comfort.  They  might 
also  maintain  their  present  stage  of  civilization  and  go  on  to 
a  higher  stage  provided  they  could  overcome  the  tremendous 
handicap  of  contact  with  tropical  races  of  lower  standards. 
There  is  not,  however,  the  slightest  reason  to  believe  that 
such  tropical  white  people  would  change  their  climatic 
optimum  any  more  than  the  Javanese  have  changed  theirs. 
They  would  of  course,  be  better  adapted  to  tropical  con- 
ditions than  are  the  ordinary  white  people  of  Europe  and 
the  United  States,  but  they  would  presumably  still  be 
living  in  a  climate  which  departs  far  from  their  optimum 
and  in  which  it  is  much  harder  to  overcome  the  departures 
than  is  the  case  in  cooler  climates. 

Perhaps  some  day  some  race  will  learn  to  guard  itself 
against  high  temperature,  high  humidity,  and  undue  monot- 
ony, but  that  is  likely  to  prove  far  harder  than  to  guard  against 
low  temperature  and  undue  dryness.  Low  temperature  is 
the  easiest  of  all  climatic  handicaps  to  conquer,  for  fire, 
houses,  clothing  and  exercise  are  all  methods  of  overcoming 
its  effects.  Undue  dryness  too  can  be  overcome  to  a  con- 
siderable extent  by  clothing  which  keeps  the  skin  moist. 
But  high  temperature,  excessive  humidity  and  excessive 
monotony  present  a  problem  of  far  greater  complexity 
especially  because  those  conditions  predispose  the  individual 


330  HUMAN   BIOLOGY 

toward     inertia     whereas     cold     and     dryness    predispose 
toward  activity. 

Thus  our  final  conclusion  is  that  although  it  is  probably 
possible  for  selected  portions  of  the  white  race  to  become 
as  well  adapted  to  the  tropics  as  are  the  Javanese  for  example, 
it  is  far  from  probable  that  they  will  maintain  a  degree  of 
energy  and  progress  equal  to  that  of  similarly  selected 
people  of  the  same  race  in  a  better  cHmate.  Always,  it 
would  seem,  the  people  who  Hve  near  the  chmatic  hmits 
will  be  at  a  disadvantage,  while  those  who  Hve  near  the 
chmatic  optima  will  be  the  most  healthy,  energetic  and 
progressive. 

REFERENCES 

Balfour,  A.  1923.  Sojourners  in  the  tropics  and  problems  of  acclimatization. 
Lancet,  204:  1 329-1 334;  205:  84-87,  243-247. 

Castellani,  a.,  and  Chalmers,  A.  J.  1929.  Manual  of  Tropical  Medicine. 
Ed.  4,  N.  Y.,  Wood,  pp.  39-146  (esp.  127-146). 

EijKMAN,  C.  1924.  Some  questions  concerning  the  influence  of  the  tropics  on 
man.  Lancet,  206:  887-893. 

Hoffman,  F.  L.  1924.  Problems  of  mortality  and  acclimatization  in  the 
Central  American  tropics.  In:  International  Conference  on  Health 
Problems  in  Tropical  America,  pp.  657-708. 

Huntington,   E.   1924.  Civilization  and  Climate.  Ed.  3.  New  Haven,  Yale 
Univ.  Press. 
World  Power  and  Evolution.  New  Haven,  Yale  Univ.  Press. 
Climate  and  the  evolution  of  civilization.  In:  The  Evolution  of  Earth  and 

Men.  New  Haven,  Yale  Univ.  Press. 
Weather  and  Health.  Wash.,  Carnegie  Inst. 

Sayers,  R.  R.,  and  Davenport,  S.  J.  1927.  Review  of  literature  on  the  physio- 
logical effects  of  abnormal  temperatures  and  humidities.  U.  S.  Public 
Health  Rep.,  42:  Pt.  i,  933-996  (Reprint  No.  1150). 

Sundstroem,  E.  S.  Contributions  to  tropical  physiology.  Univ.  Calif.  Publ. 
in  Physiol.,  6:  1-216. 

Trcwartha,  G.  T.  1926.  Recent  thought  on  the  problem  of  white  acclimatiza- 
tion in  the  wet  tropics.  Geograph.  Rev.,  16:  467-478. 


Chapter  XIV 
THE  REACTION  TO  FOOD 

Elmer  V.  McCollum 

PHILOSOPHERS  in  all  ages  have  given  thought  to  the 
nature  of  foods  and  of  nutritional  processes.  Spallan- 
zani  ( 1 729-1 799)  who  occupied  himself  with  many 
experiments  on  the  digestion  of  foods,  was  of  the  opinion 
that  there  was  but  one  kind  of  food  or  ahment.  This  view 
had  seemed  satisfactory  to  some  early  Greek  philosophers, 
but  by  the  beginning  of  the  nineteenth  century  the  eminent 
French  physiologist  Magendie  reached  the  conclusion  that 
there  are  several  kinds  of  nutrient  principles  in  a  chemical 
sense.  Even  as  late  as  1835,  when  Dr.  Wilham  Beaumont, 
a  surgeon  in  the  U.  S.  Army,  was  writing  about  his  famous 
experiments  on  digestion  conducted  with  Alexis  St.  Martin 
as  a  subject,  he  expressed  the  view  that  there  wais  but  one 
kind  of  nutrient  principle  or  aliment.  He  beheved  that  this 
ahment  was  contained  in  all  the  many  varieties  of  foodstuffs 
consumed  by  man  and  animals  and  that  the  process  of 
nutrition  involved  dissolving  out  this  principle  by  the 
digestive  juices  and  converting  it  into  a  salt-like  derivative 
of  a  substance  which  he  called  gastrite,  forming  gastrite  of 
ahment.  This  he  beheved  with  shght  modifications  entered 
the  blood  and  served  with  little  change  for  the  upbuilding  or 
repair  of  tissues. 

During  the  nineteenth  century  much  knowledge  accumu- 
lated concerning  the  nature  of  proteins,  carbohydrates, 
fats  and  the  inorganic  or  mineral  constituents  of  foodstuffs. 
About  1865  a  method  was  formulated  and  adopted  by  the 
Association  of  Agricultural  Chemists  as  official  for  the 
analysis  of  foods.  In  this  method  proteins,  digestible  car- 
bohydrates, cellulose,  fats  and  mineral  constituents  were 
separately  estimated  with  a  fair  degree  of  accuracy.  The 
behef  became  almost  universal  among  students  of  nutrition 
that  these  four  classes  of  nutrients  were  all  that  were  necessary 
for  the  support  of  animal  nutrition. 

331 


332  HUMAN   BIOLOGY 

After  1865  there  was  an  era  of  enthusiasm  for  the  study, 
with  both  human  and  animal  subjects,  of  the  protein 
requirements  and  energy  requirements  of  the  individual 
as  influenced  by  age  and  condition  of  Hfe.  Such  studies  were 
carried  on  by  Prof.  Carl  Voit  of  Munich,  and  his  students 
extended  his  studies  in  many  countries.  W.  A.  Atwater  was 
the  great  exponent  of  nutrition  work  of  this  kind  in  the  United 
States  prior  to  1 900.  He  thought  that  nutrition  would  be  placed 
upon  a  strictly  scientific  basis  when  all  the  ordinary  foodstuffs 
had  been  analyzed  chemically,  their  energy  values  and 
digestibility  determined,  and  the  cost  of  production  of  each  of 
our  important  farm  crops  had  been  studied.  Atwater  spent  the 
active  period  of  his  life  in  the  collection  of  data  along  these 
lines. 

The  results  of  the  chemical  analysis  of  foods  showed 
striking  differences  in  their  composition.  Meats,  eggs,  and 
the  flesh  of  poultry  and  fish  consist  in  great  measure  of 
water,  protein,  fat  and  inorganic  salts.  Milk  in  a  dry  state 
contains  in  addition  to  a  large  amount  of  protein  much 
carbohydrate  (milk  sugar)  and  a  relative  abundunce  of  fat 
as  well  as  the  various  inorganic  elements  found  on  the 
ashing  of  an  animal  body.  Among  the  vegetable  foods,  peas 
and  beans  contain  extraordinary  amounts  of  proteins,  very 
little  fat,  but  a  moderate  amount  of  carbohydrate,  and  an 
ash  of  characteristic  composition.  Cereal  grains  contain 
much  less  protein  and  relatively  much  more  carbohydrate 
and  starch,  and  but  a  little  fat.  The  nuts,  with  the 
exception  of  the  chestnut  which  contains  starch, 
contain  almost  no  carbohydrate,  large  amounts  of  protein, 
and  are  exceedingly  rich  in  fats.  Fruits  and  some  of  the 
tuber  and  root  vegetables  are  exceedingly  rich  in  water, 
so  that  in  the  form  in  which  they  are  ordinarily  purchased 
their  energy  and  protein  values  appear  quite  low  in  contrast 
with  many  other  foods.  It  is  not  surprising  that  in  the  era 
of  enthusiasm  over  the  analysis  of  foods,  the  striking  differ- 
ences in  composition  should  have  raised  great  expectations  in 
the  minds  of  investigators  concerning  their  ultimate  value  in 
the  planning  of  diets.  Atwater  cherished  the  hope  that 
when  his  elaborate  plan  of  study  was  complete  it  would 
be  possible  to  advise  the  housewife  concerning  the  most 


THE    REACTION    TO    FOOD  333 

economical  choice  of  food,  and  that  the  farmer  could  readily 
calculate  the  most  economical  combinations  of  feeding 
stuffs  which  would  supply  the  necessary  protein  and  energy 
for  animal  production,  milk  and  egg  production,  etc. 
Soon  after  1900  it  became  possible  to  begin  the  appHcatlon 
of  this  Hne  of  reasoning  in  the  feeding  of  farm  animals,  and 
the  fact  came  to  light  that  two  diets  might  have  the  same 
chemical  composition  so  far  as  analysis  can  show,  yet  one 
might  be  highly  satisfactory  and  the  other  a  complete  failure 
from  the  physiological  standpoint.  It  became  evident,  there- 
fore, that  the  chemical  procedure  in  analyzing  foods  has 
distinct  hmltatlons  and  that  there  are  qualities  in  foods  which 
even  the  most  searching  analysis  cannot  reveal. 

As  early  as  1843  Pereira  in  a  book,  "A  Treatise  on  Food 
and  Diet,  "called  attention  to  the  fact  that  there  must 
be  other  principles  than  aqueous,  saccharine,  albuminous, 
and  oleaginous  principles  in  lemon  juice,  which  was  known 
to  be  a  valuable  food  in  the  treatment  of  scurvy,  for  he 
pointed  out  that  it  did  not  owe  this  property  to  any  of  the 
principles  recognized  by  chemists. 

As  early  as  1881  Lunin  in  Germany  had  attempted  to 
feed  laboratory  animals  on  mixtures  containing  exactly 
those  principles  which  the  chemist  determines  in  his  analysis, 
proteins,  carbohydrates,  fats,  and  a  mixture  of  those  min- 
eral salts  known  to  be  normal  constituents  of  the  animal 
body.  He  made  the  interesting  and  unexpected  discovery 
that  such  diets  were  inadequate,  although  from  a  standpoint 
of  chemical  analysis  they  appeared  to  be  complete.  It  was 
many  years  before  this  subject  was  again  studied  in  an 
effective  way.  Wide  publicity  was  given  to  Lunin's  results 
In  a  much  used  textbook  by  Bunge,  and  these  doubtless 
led  to  many  speculations  by  physiologists. 

In  1905  Pekelharing  in  Holland  published  experiments 
comparable  to  those  of  Lunin.  He  fed  white  mice  on  a  bread 
of  casein,  albumin,  rice  flour,  lard  and  a  mixture  of  all  the 
salts  which  ought  to  be  found  in  their  food,  and  gave  them 
water  to  drink.  He  observed  that  they  all  starved  to  death, 
even  though  they  ate  greedily  of  the  food  In  the  beginning. 
He  further  showed  that  if  instead  of  water  they  were  given 
milk  to  drink  they  continued  to  thrive.  He  established  the 


334  HUMAN   BIOLOGY 

fact  that  something,  which  was  lacking  in  his  basal  diet,  was 
contained  in  the  whey  from  which  the  casein  and  fat  had 
been  ehminated.  He  states:  "My  intention  is  only  to  point 
out  that  there  is  a  still  unknown  substance  in  milk  which  even 
in  very  small  quantities  is  of  paramount  importance  to 
nourishment.  If  this  substance  is  absent  the  organism  loses 
the  power  properly  to  assimilate  the  well-known  principal 
parts  of  food,  the  appetite  is  lost,  and  with  apparent  abundance 
the  animals  die  of  want.  Undoubtedly  this  substance  not  only 
occurs  in  milk  but  in  a  series  of  foodstuffs  both  of  vegetable 
and  animal  origin. " 

The  following  year  Hopkins  in  England  described  exper- 
iments almost  identical  with  those  of  Pekelharing  and  drew 
the  same  deductions. 

After  1900  rapid  progress  was  made  in  the  study  of  the 
chemical  properties  of  individual  proteins  isolated  from 
many  foods,  and  it  soon  became  apparent  that  proteins 
are  of  many  kinds,  and  that  they  yield  varying  proportions 
of  their  several  digestion  products. 

Interest  was  greatly  stimulated  in  the  study  of  nutrition 
by  a  series  of  experiments  conducted  between  the  years  1906 
and  191 1  at  the  University  of  Wisconsin.  In  these  experiments 
animals  were  fed  diets  restricted  as  to  source,  certain  ones 
being  fed  solely  upon  corn  products,  others  upon  oat  prod- 
ucts, and  still  others  on  wheat  products,  etc.  In  the  case  of 
cattle,  the  leaf,  stem  and  seed  were  all  included  in  the  ration, 
but  in  the  case  of  mammahan  animals,  such  as  farm  pigs  and 
rats,  diets  of  a  yet  simpler  character  were  tested.  The  curious 
discovery  was  made  that  none  of  the  cereal  grains,  such  as 
whole  wheat,  rolled  oats,  corn  meal,  either  singly  or  collect- 
ively were  adequate  for  the  support  of  growth  and  the  promo- 
tion of  well-being  in  animals  when  they  formed  the  sole  source 
of  nutrient.  It  was  later  found  that  even  diets  of  great 
complexity,  the  components  of  which  were  derived  solely 
from  cereal  grains,  peas,  beans,  tubers,  starchy  roots  and 
fruits,  proved  insufficient  for  the  promotion  of  satisfactory 
growth  or  for  the  maintenance  of  prolonged  physiological 
well-being.  At  one  time  a  diet  containing  23  articles,  all 
known  by  experience  to  be  wholesome  components  of 
the  diet,  was  tested  on  young  rats  and  found  inadequate. 


THE    REACTION    TO    FOOD  335 

On  the  other, hand,  so  simple  a  mixture  as  70  or  75  per  cent 
of  rolled  oats,  and  30  or  35  per  cent  of  a  flour  prepared 
from  a  broad  leaf  such  as  clover,  alfalfa,  turnip,  celery,  etc., 
induced  very  good  growth,  some  reproduction,  rearing  of 
young,  and  the  repetition  of  the  hfe  cycle  in  the  family 
restricted  to  this  diet. 

Little  rats  have  grown  from  soon  after  weaning  to  maturity 
with  capabihty  to  reproduce  when  fed  nothing  but  hard  boiled 
egg  yolk.  It  is  evident  that  neither  monotony  nor  restriction 
as  to  source  is  the  determining  factor,  but  rather  the  unique 
constitution  of  the  diet  in  a  chemical  sense  which  determines 
its  quaHty. 

The  most  significant  investigation  in  nutrition  leading 
to  the  modern  era  of  research  was  that  of  Eijkman,  who  in 
1897  at  Batavia,  Java,  discovered  that  fowls  fed  solely 
upon  pohshed  rice  develop  a  disease  characterized  by 
multiple  neuritis  which  was  recognized  as  the  analogue  in 
the  bird  of  a  disease  long  common  among  the  rice  eaters 
of  the  Orient  under  the  name  beri-beri.  Eijkman  showed 
that  various  extracts  of  plant  products  including  rice 
pohshings,  produced  a  spectacular  cure  in  birds  which  were 
within  a  few  hours  of  death.  He  demonstrated  that  the  dose 
of  active  material  necessary  to  produce  such  a  cure  was 
extraordinarily  small.  His  experiments  attracted  httle 
attention  for  a  decade,  but  were  discovered  and  repeated 
about  1910  by  Funk,  who  confirmed  Eijkman's  results 
and  coined  the  term  "vitamine"  to  designate  the  active 
principle,  a  lack  of  which  causes  the  development  of 
polyneuritis  in  both  man  and  animals.  In  19 12  the  first 
of  the  fat-soluble  vitamins,  now  known  as  vitamin  a,  was 
discovered  in  butter  fat.  Up  to  this  time  it  had  been 
accepted  that  all  foods  have  essentially  the  same  fuel  or 
calorific  value  and  approximately  the  same  digestibility, 
hence  the  same  nutritional  value.  It  was  clearly  demon- 
strated by  McCoIlum  and  Davis,  and  by  Osborne  and 
Mendel,  that  butter  fat,  egg  yolk  fat,  and  cod  liver  oil  had 
growth  and  health-promoting  properties  not  possessed  by 
such  foods  as  lard,  olive  oil,  almond  oil,  etc.  In  19 12  Hoist 
and  Froelich  of  Norway  conducted  experiments  with  guinea 
pigs    in   which   they   produced   experimentally   the   lesions 


336  HUMAN   BIOLOGY 

characteristic  of  scurvy  in  man.  They  showed  that  scurvy 
would  develop  in  guinea  pigs  confined  to  dried  or  cooked 
foods  and  that  scurvy  was  prevented  by  the  inclusion  of  small 
additions  of  fresh  green  foods  such  as  dandehons.  Their 
experimental  work  placed  upon  a  scientific  footing  the  knowl- 
edge of  the  etiology  of  scurvy  which  had  been  vaguely 
recognized  since  the  appearance  of  a  book  on  this  disease 
written  by  James  Lind  in  1754.  Lind  recognized  the  impor- 
tance of  fresh  uncooked  vegetable  foods  in  the  diet  for  the 
prevention  or  cure  of  scurvy,  and  his  advice  was  acted  upon 
for  many  years  in  the  rationing  of  soldiers,  sailors  and 
prisoners  before  any  clear  concept  was  gained  as  to  the  nature 
of  the  substance  in  certain  foods  which  prevented  this 
disease. 

In  1922  it  was  demonstrated  that  there  is  a  special  vitamin, 
now  designated  as  d,  in  cod  liver  oil  which  plays  a  special 
role  in  bone  growth  and  is  a  protective  agency  in  the  pre- 
vention or  cure  of  rickets  in  infants  and  animals.  In  1922 
Evans  and  Bishop  discovered  the  existence  of  a  vitamin 
which  plays  a  special  part  in  fertihty.  It  may  be  explained 
that  a  system  of  nomenclature  was  adopted  in  1916  whereby 
the  class  of  nutrient  principles  typified  by  that  discovered 
by  Eijkman  in  1897,  of  which  very  small  amounts  in  the 
diet  suffice  for  the  promotion  of  health,  are  designated  by 
the  first  letters  of  the  alphabet.  They  are  now  known  as 
vitamins  a,  b,  c,  d,  e  and  f.  Vitamin  F,  the  most  recently 
discovered  of  these  principles,  was  demonstrated  by  Smith 
and  Hendrick,  and  later  shown  by  Goldberger  to  be  con- 
cerned in  the  etiology  of  pellagra,  which  is  now  generally 
beheved  to  be  a  vitamin-deficiency  disease. 

As  our  knowledge  now  stands  it  is  accepted  that  vitamin  a 
when  lacking  in  the  diet  causes  damage  especially  to  cells  of  the 
epithelial  type.  Glandular  structures  such  as  the  lacrymal  glands, 
sahvary  glands,  and  digestive  glands,  suffer  injury  and  partial  or 
total  loss  of  function.  As  a  result  of  such  injury  to  the  lacrymal 
glands  eye  secretion  is  interfered  with,  and  the  consequent  drying 
of  the  eyes  together  with  the  bacterial  growth  which  freely  takes 
place  in  the  conjunctival  sac  results  in  profound  injury  and 
eventually  in  destruction  of  the  eye.  This  is  so  characteristic 
that    observations    on    the   appearance   of  ophthalmia   under   a 


I 


THE    REACTION    TO    FOOD  337 

controlled  dietary  regimen  are  accepted  as  a  qualitative  test  for 
vitamin  a. 

The  term  "vitamin  b"  now  designates  the  principle  discovered 
by  Eijkman  which  is  the  etiological  agent  in  beri-beri.  When  this 
substance  is  lacking  from  the  diet  the  motor  nerve  cells  in  the 
cord  are  damaged  and  peripheral  neuritis  followed  by  atrophy  of 
those  groups  of  muscles  whose  motor  nerves  are  injured  develops. 

In  vitamin  c  deficiency  the  walls  of  the  capillary  vessels  of  the 
vascular  system  are  especially  injured,  but  it  is  not  known  with 
certainty  whether  the  endothelial  cells  suffer  the  principal  damage 
or  whether  the  cement  substance  holding  them  together  is 
destroyed.  Certain  it  is  that  hemorrhage  due  to  rupture  of  the 
capillaries  is  the  most  striking  feature  of  scurvy  but  resolution  of 
bone  substance  is  also  quite  marked. 

Vitamin  d  is  concerned  with  the  deposition  of  calcium  and 
phosphorus  in  the  bones.  It  regulates  in  some  way  the  concen- 
tration of  phosphorus  and  to  a  lesser  degree  the  calcium  of  the 
blood.  In  the  absence  of  vitamin  d  the  amount  of  phosphorus  falls 
to  a  surprisingly  low  level  so  that  the  soIubiHty  product  of  calcium 
X  phosphorus  is  not  great  enough  to  permit  of  the  precipitation 
of  tricalcium  phosphate  for  deposition  in  the  osseous  system. 

Vitamin  e  functions  in  some  manner  not  yet  understood. 
Sterihty  is  produced  alike  in  males  and  females  by  a  deficiency 
of  this  principle  but  the  manifestation  of  a  deficiency  of  vitamin  e 
in  the  two  sexes  differs  considerably.  In  males  atrophy  of  the 
germinal  epithelium  and  consequent  loss  of  the  power  of  spermato- 
genesis is  seen.  In  females  ovulation  tends  to  remain  normal  but 
death  of  the  young  in  prenatal  life  and  their  resorption  constitutes 
the  mode  of  termination  of  an  incomplete  gestation. 

Vitamin  f,  originally  called  by  Goldberger  p-p  to  designate  its 
pellagra-preventive  properties,  is  now  believed  to  be  the  etiological 
agent  in  pellagra.  According  to  such  data  as  exist,  a  deficiency  of 
this  principle  promotes  the  development  of  changes  in  the  skin 
which  result  in  a  characteristic  erythemia,  bronzing,  injury  to  the 
mucosa  of  the  mouth  and  digestive  tract,  chronic  diarrhea  and 
the  nervous  symptoms  characteristic  of  that  disease. 

Vitamin  a  is  found  abundantly  in  fish  liver  oils,  fats  from 
mammalian  livers,  butter  fat,  egg  yolk,  yellow  pigmented 
vegetables  and  leaves  of  plants  generally.  It  is  absent  or 
nearly  so  from  vegetable  foods  of  all  kinds,  white  varieties 
of  fruits  and  vegetables  and  in  fact  all  fruits  and  vegetables 
not  containing  yellow  pigments.  Thus,  red  beets,  red  and 


338  HUMAN    BIOLOGY 

blue  varieties  of  corn,  etc.  do  not  contain  it.  It  is  nearly 
absent  from  cereals  and  absent  from  such  refined  cereal 
products  as  white  flour,  corn  meal,  pohshed  rice,  etc. 

Vitamin  b  is  most  abundant  in  yeast,  wheat  germ,  rice 
pohshings,  and  various  leaves  of  plants.  It  is  relatively 
abundant,  however,  in  whole  grains,  peas,  beans,  tubers, 
roots,  and  fruits  of  all  kinds.  It  is  less  abundant  in  milk 
and  scarcely  present  in  muscle  types  of  meats,  although 
abundant  in  glandular  organs,  such  as  liver,  kidney,  etc. 
It  is  essentially  lacking  in  the  refined  cereal  products. 

Vitamin  c  is  contained  in  fresh  raw  fruits  and  vegetables 
of  all  kinds,  but  is  especially  abundant  in  the  juice  of  lemons 
and  other  citrus  fruits,  and  fresh  green  leaves  such  as 
cabbage,  lettuce,  etc.  It  is  found  in  small  amount  in  winter 
milks,  is  more  abundant  in  summer  milks,  is  nearly  lacking 
in  lean  meats  but  the  raw  glandular  organs  contain  it  in 
fair  abundance.  No  dry  grains  or  other  plant  seeds  contain 
the  principle  but  it  is  rapidly  generated  in  liberal  amounts 
when  seeds  are  germinated  or  caused  to  sprout.  During 
cooking,  vitamin  c  is  destroyed,  principally  because  of  its 
ready  oxidizability.  It  can  be  heated  to  fairly  high  tempera- 
tures provided  oxygen  is  excluded.  In  the  process  of  canning 
the  smothering  of  the  fruit  or  vegetable  in  syrup  or  juice  dur- 
ing the  interval  while  the  cans  are  in  the  exhaust  box  causes 
them  to  undergo  a  gradual  heating  process  which  accelerates 
for  a  time  the  rate  of  internal  respiration,  which  tends 
rapidly  to  use  up  the  oxygen  dissolved  in  the  tissues.  After 
this  is  efi^ected  subsequent  heating  does  not  tend  to  destroy 
vitamin  c.  Canned  goods,  therefore,  are  superior  generally  in 
this  respect  to  foods  of  all  kinds  which  are  cooked  under  ordi- 
nary kitchen  conditions;  the  latter  tend  to  destroy  practically 
completely  all  of  the  antiscorbutic  vitamin  c. 

Vitamin  d  is  found  in  large  quantities  only  in  the  liver 
oil  of  fishes.  It  is  most  abundant  in  pufl"er  liver  and  slightly 
less  so  in  the  liver  of  the  cod  and  the  haddock.  These  two 
fish  oils  furnish  the  principal  source  of  this  vitamin. 

There  is  growing  evidence  that  vitamin  d  is  a  modification 
of  some  sterol,  a  relative  of  cholesterol.  Ergosterol,  from 
ergot,  yeast  and  other  fungi,  is,  when  irradiated,  the  most 
active  substance  known  in  the  prevention  or  cure  of  rickets. 


THE    REACTION   TO    FOOD  339 

Doses  of  0.00 1  mg.  daily  suffice  to  cause  the  healing  of  a 
rachitic  lesion  in  little  rats.  It  appears,  however,  that  other 
substances  among  the  sterols  are  capable  of  possessing  the 
vitamin  d  property.  The  sterols  which  can  acquire  vitamin 
potency  are  activated  by  exposure  to  ultraviolet  irradiations. 
It  appears  that  in  the  tropics  where  there  is  much  ultra- 
violet energy  from  the  sun,  the  rays  with  certain  frequencies 
activate  the  pro-vitamin  d  contained  in  the  skin.  This  is 
then  transported  throughout  the  body  and  becomes  a 
regulating  agency  in  bone  calcification.  In  those  parts  of 
the  world  where  radiant  energy  from  the  sun  is  low,  or  for 
long  periods  non-existent  as  in  the  polar  regions,  this  defi- 
ciency must  be  made  good  by  the  consumption  of  oils 
from  marine  sources.  In  the  north  temperate  zone  where 
the  great  centers  of  population  subsist  in  a  climate  where 
little  of  the  skin  surface  can  be  exposed  to  light  during  the 
colder  parts  of  the  year,  and  where  only  small  quantities 
of  marine  food  are  eaten,  rickets  among  children  and  animals 
is  most  prevalent.  An  important  factor  appears  to  be  the 
smokiness  of  the  atmosphere  of  cities  which  tends  to  filter 
out  much  of  the  radiant  energy  of  a  frequency  capable  of 
activating  the  pro-vitamin  d.  It  is  for  this  reason  that  the 
practice  has  now  become  established  throughout  the  United 
States  and  much  of  Europe  of  giving  cod  liver  oil  to  infants 
as  a  routine  measure  of  protection  against  the  development 
of  rickets. 

A  substitute  for  cod  liver  oil  is  now  much  promoted  in 
the  form  of  radiant  energy  derived  from  the  quartz  mercury 
vapor  lamp  which  is  rich  in  wave  lengths  of  frequencies 
necessary  for  the  activation  of  pro-vitamin  d.  While  there 
can  be  no  doubt  of  the  effectiveness  of  this  physical  sub- 
stitute for  the  chemical  principle,  vitamin  d,  there  is  little 
justification  for  the  extraordinary  enthusiasm  shown  by 
many  physicians  and  lay  persons  for  treating  all  manner 
of  ailments  with  the  ultraviolet  lamp.  No  evidence  has 
yet  been  brought  forward  which  indicates  that  the  ultra- 
violet lamp  is  effective  in  any  other  condition  than  in 
safeguarding  skeletal  development. 

Vitamin  f  has  much  the  same  distribution  as  vitamin  b, 
but  is  apparently  considerably  more  abundant  in  lean  meat 


340  HUMAN    BIOLOGY 

than  is  the  antlneuritic  vitamin  b.  Vitamin  f  is  much  more 
stable  to  heat  than  vitamin  b,  a  fact  which  was  instrumental 
in  bringing  about  its  discovery.  Yeast,  lean  meats,  leafy 
vegetables  and  milk  are  among  the  common  foods  available 
in  abundance  which  are  potent  in  vitamin  f,  the  most 
important  being  the  fir'st  named.  Other  common  foodstuffs 
cannot  yet  be  classified  as  to  their  values  in  preventing 
pellagra. 

During  the  last  fifteen  years  Dr.  Simmonds  and  the 
writer  have  given  much  attention  to  the  study  of  human 
dietaries  in  different  parts  of  the  world.  The  results  can 
be  furnished  briefly  as  follows:  Successful  human  dietaries 
are  found  in  three  types  of  geographic  environment.  In  the 
coldest  parts  of  the  earth  mankind  subsists  essentially 
upon  a  carnivorous  diet.  The  Eskimos  of  Northwest  Green- 
land hve  mainly  upon  birds,  eggs  and  seals.  They  eat  no 
land  animals  and  fish  only  for  a  few  weeks  in  mid-summer. 
Although  small,  they  are  very  hearty  people  and  have 
held  their  own  under  the  most  unfavorable  conditions  of 
chmate  through  many  generations.  It  is  interesting  that 
they  have  excellent  bones  and  that  their  teeth  rarely  decay. 
It  should  be  emphasized  that  they  eat  glandular  organs  as 
well  as  other  parts  of  the  creatures  which  serve  as  food. 

In  the  warmest  regions  of  the  world,  which  are  also 
characterized  in  general  by  excess  of  wetness,  live  the  rice- 
eating  peoples.  Their  diet  is  in  the  main  vegetarian  and 
consists  of  rice  as  the  principal  cereal,  with  additions  of 
soy  beans,  various  tubers  and  root  vegetables,  and  large 
amounts  of  leafy  vegetables  of  many  kinds.  These  include 
Chinese  cabbage,  leaves  of  sweet  potato,  bamboo  sprouts, 
water  cress,  spinach  and  other  similar  vegetables.  The 
leaf  of  the  plant  is  superior  to  the  seed,  tuber,  root  or  fruit 
In  its  dietary  properties.  In  fact,  the  edible  leaf  is  in  itself 
complete  from  the  standpoint  of  its  dietary  principles. 

In  19 1 5  the  writer  and  Miss  Davis  described  a  procedure 
consisting  of  a  properly  planned  series  of  feeding  experiments 
in  which  a  single  natural  food  is  supplemented  singly  or  in  a 
multiple  fashion  with  known  nutrient  principles,  such  sup- 
plementing increasing  in  complexity  as  the  series  is  extended 
until  it  Is  discovered  what  constitutes  the  fewest  additions 


THE    REACTION   TO    FOOD  34 1 

of  known  nutrient  principles  which  just  suffice  to  complete 
the  food  in  question  and  form  an  adequate  diet.  This  system 
is  known  as  the  "biological  method"  for  the  analysis  of  a  food- 
stuff. We  now  have  a  great  body  of  knowledge  based  upon 
the  application  of  this  procedure  to  all  our  more  important 
natural  foods. 

Many  kinds  of  grazing  animals  subsist  well  solely  upon 
leaves  of  grass  or  other  forage  crops.  The  importance  of 
the  leafy  type  of  vegetable  in  the  diet  of  the  rice-eating 
peoples  cannot  be  overestimated.  Because  of  the  density 
of  population,  milk-producing  animals  are  not  kept  in  the 
rice-eating  regions  so  these  people  have  never  had  a  supply 
of  dairy  products.  Their  only  food  of  animal  origin  is  eggs, 
poultry  and  pork,  which  are  eaten  somewhat  sparingly, 
but  in  some  places  considerable  amounts  of  fish  are  available. 
People  on  such  a  dietary  regimen  are  very  successful  in 
their  physical  development  and  compare  in  the  most  favored 
districts  with  the  best  specimens  of  the  human  race  any- 
where to  be  found. 

A  third  type  of  diet  which  is  satisfactory  is  found  in  use 
in  the  dryest  regions  of  the  world.  On  the  margins  of  the 
Sahara  and  Arabian  deserts,  and  in  the  great  dry  belt 
extending  across  Asia  from  Arabia  to  Mongolia,  the  inhabit- 
ants subsist  only  through  the  conversion  of  pasturage  into 
human  food  through  the  agency  of  flocks  and  herds.  Here 
the  only  article  fit  for  human  consumption  which  is  likely 
to  be  available  in  abundance  is  milk,  which  ordinarily 
sours  quickly  because  of  the  contamination  of  the  containers 
with  remnants  of  sour  milk  and  the  absence  of  means  of 
refrigeration.  In  Arabia  the  typical  diet  of  the  native 
consists  mainly  of  sour  milk,  but  this  is  supplemented  with 
a  small  amount  of  barley  bread,  dates,  and  with  meat 
approximately  once  a  month.  Even  under  the  trying  condi- 
tions of  desert  life  people  live  and  maintain  surprising 
vitality  on  such  a  simple  regimen.  There  are  certain  char- 
acteristics about  the  diet  of  people  in  the  great  centers  of 
culture  in  the  north  temperate  zones,  which  include  the 
United  States,  Canada,  and  Central  Europe,  that  tend  to 
induce  malnutrition.  The  significance  of  this  could  not  be 
appreciated   until   research   on   quality   in    foods   and   the 


342  HUMAN    BIOLOGY 

nutritive  requirements  of  the  body  had  progressed  to  a 
suitable  stage.  For  example,  although  refined  bolted  flour 
has  been  manufactured  to  some  extent  from  time  immemorial 
its  use  never  became  general  until  after  1879,  ^^  which  year 
the  roller  mill  process  for  making  white  flour  was  invented. 
Considerations  of  commerce,  the  great  distance  to  the 
centers  of  population  in  the  eastern  United  States  from  the 
great  grain  growing  regions  in  the  west,  and  the  inevitable 
transport  of  flour  for  long  distances  by  ship  or  rail,  necessitate 
keeping  qualities  in  flour  which  were  entirely  unnecessary 
two  generations  ago  when  the  milling  industry  was  a  neigh- 
borhood one  and  the  stock  of  flour  relatively  unrefined  was 
replenished  at  intervals  of  two  to  three  weeks.  We  are 
now,  therefore,  eating  highly  refined  white  flour,  deger- 
minated  corn  meal,  and  polished  rice,  in  diff'erent  parts 
of  the  country  in  amounts  never  before  approached. 

At  present  the  annual  consumption  of  sugar  per  person 
per  year  in  the  United  States  is  115  lbs.  The  consumption 
has  increased  about  ten  times  in  a  century  and  now  con- 
stitutes as  much  as  8  or  10  per  cent  of  the  total  energy 
supply  of  many  people,  who  are  likewise  consuming  a  high 
intake  of  refined  cereal  products.  For  some  years  I  have 
described  the  typical  American  diet  as  a  white  bread, 
muscle  meat,  sugar  and  potato  combination.  Such  a  mixture 
is  a  failure  in  animal  experiments  and  would  be  a  failure 
in  human  experience  if  it  were  not  for  the  regular  addition 
of  small  amounts  of  certain  foods  which  have  the  property 
of  enhancing  the  quantity  of  the  principal  articles  of  the 
diet.  These  are  especially  of  two  classes,  namely,  the  leafy 
type  of  vegetable,  and  milk  and  other  dairy  products. 

From  what  has  already  been  said  it  will  be  appreciated 
that  on  certain  kinds  of  diets  the  so-called  deficiency  diseases 
due  to  lack  of  one  or  another  vitamin  will  develop.  Beri-beri 
is  the  most  widespread  of  these  but  at  times  in  the  past 
scurvy  was  also  of  common  occurrence.  Epidemics  of  vitamin 
A  deficiency  have  in  general  affected  smaller  groups  of 
people.  Pellagra  has  in  certain  regions  reached  the  pro- 
portions of  a  scourge.  As  many  as  200,000  people  were 
reported  sufl"ering  from  this  disease  in  the  United  States 
alone  in   191 7.   From  then  until  the  flood  of  1927  in  the 


THE    REACTION    TO    FOOD  343 

Mississippi  Valley  the  incidence  of  the  disease  has  been 
considerably  less,  but  it  rose  again  on  that  occasion. 

A  common  defect  in  the  diet  of  Americans  and  Europeans 
is  that  of  a  deficiency  of  calcium  together  with  an  excess  of 
phosphorus  in  the  food  supply.  It  has  been  clearly  demon- 
strated that  an  unfavorable  ratio  between  these  two  elements 
in  the  food  tends  to  disturb  the  metabohc  processes  in  the 
bones.  The  disease  known  as  rickets  can  readily  be  produced 
in  animals  in  either  of  two  ways:  by  feeding  a  diet  low  in 
calcium  and  disproportionately  rich  in  phosphorus,  or 
deficient  in  phorphorus  and  disproportionately  rich  in 
calcium.  In  either  case  in  order  to  have  the  disease  develop 
there  must  be  a  paucity  of  sunHght  containing  radiations 
of  ultraviolet  wave  length,  and  also  of  vitamin  d.  Marked 
deficiency  of  protein  in  the  diet  over  a  considerable  period, 
as  when  the  population  is  at  war  or  approaching  famine 
conditions  and  is  forced  to  subsist  upon  a  diet  of  cabbage, 
lettuce  and  other  green  foods  has  been  observed  to  cause 
epidemic  dropsy. 

The  idea  prevails  in  many  minds  that  so  long  as  people 
escape  developing  the  characteristic  syndromes  of  the 
deficiency  diseases,  the  diet  may  be  said  to  be  adequate.  This 
rests  upon  a  failure  to  appreciate  nice  distinctions  in  physio- 
logical well-being.  In  experimental  work  with  animals  it  has 
been  found  readily  possible  to  distinguish  a  number  of  grades 
of  malnutrition.  Diets  which  are  very  badly  constituted  may 
result  in  total  failure  of  young  creatures  to  grow,  or  the 
diet  may  be  sufficiently  good  so  that  growth  may  take 
place  but  at  two-thirds  of  the  normal  rate,  the  animals 
eventually  presenting  the  appearance  of  runts.  Again  the 
diet  may  be  good  enough  to  induce  growth  at  the  normal 
rate  until  adult  size  is  attained  and  yet  be  inadequate 
for  the  support  of  physiological  well-being  throughout  the 
normal  span  of  life. 

We  have  often  recorded  the  chronological  age  at  which 
distinct  signs  of  seniHty  appear  in  comparatively  young 
animals  as  evidence  of  the  quahty  of  the  diet.  Again,  crea- 
tures have  been  observed  to  develop  in  a  manner  apparently 
normal  and  in  adult  fife  appear  to  be  well-nourished,  yet 
fail  in  one  or  another  way  in  fertihty:  (a)  having  no  young, 


344  HUMAN   BIOLOGY 

(b)  producing  young  but  failing  to  secrete  a  milk  supply  for 
their  nutrition,  (c)  producing  a  milk  supply  inadequate  in 
quality  such  that  the  young  do  not  thrive,  (d)  developing 
cannibalistic  tendencies  leading  the  mother  to  destroy  the 
young. 

Recent  studies  of  Koessler  lend  strong  support  to  the 
view  that  chronic  underfeeding  with  respect  to  vitamin  a 
can  produce  pernicious  anemia.  The  trend  of  events  in  the 
history  of  such  patients  includes  digestive  disturbances 
followed  by  decreased  acid  secretion  in  the  stomach,  resulting 
eventually  in  achlorhydria.  Under  such  conditions  bacteria 
frequently  develop  in  the  stomach,  while  peptic  digestion 
fails.  The  periodic  inundation  of  the  duodenum  with  badly 
infected  food,  or  half-digested  bacterially  contaminated 
food,  results  in  seeding  the  entire  small  intestine  with 
putrefactive  organisms.  The  mucosa  of  both  the  stomach 
and  intestine  is  believed  to  be  impaired  in  respect  to  secre- 
tion and  absorption,  so  that  the  body  tends  to  be  injured  by 
failure  of  its  food  supply  because  of  faulty  digestion,  and 
also  through  intoxication  caused  by  absorbing  the  products 
of  putrefaction  which  are  produced  under  such  circumstances 
in  extraordinary  amounts.  These  substances  are  in  the  main 
destroyed  in  the  process  of  absorption  in  normal  individuals 
but  the  impaired  intestinal  mucosa  appears  to  promote 
their  passage  directly  into  the  blood  stream  where  they 
tend  to  destroy  the  corpuscles  and  also  to  injure  the  blood- 
forming  tissues.  One  of  the  most  notable  discoveries  of 
recent  years  is  the  extraordinarily  beneficial  effect  of  feeding 
liver  to  patients  suffering  from  pernicious  anemia. 

Since  in  recent  years  the  tendency  in  the  United  States 
has  been  in  the  direction  of  subsisting  upon  a  diet  derived 
from  refined  cereals,  such  as  white  flour,  degerminated 
corn  meal,  polished  rice  and  other  similar  products,  meats 
of  a  muscle  type,  potatoes,  and  sugar,  the  author  has  for  a 
decade  offered  what  appears  to  be  the  simplest  advice  as  to 
how  the  diet  may  be  greatly  improved  in  quality  without 
interfering  with  our  established  dietary  practices.  Milk 
and  the  leafy  type  of  vegetables  are  the  only  calcium-rich 
foods,  and  both  of  these  are  so  constituted  as  to  have  proteins 
peculiarly   effective   in   supplementing   the   rather   inferior 


THE    REACTION    TO    FOOD 


345 


proteins  of  many  vegetable  foods,  and  are  otherwise  appro- 
priately constituted  with  respect  to  the  vitamins  and  mineral 
salts.  For  this  reason  the  writer  has  designated  these  as 
"protective  foods"  and  has  urged  the  planning  of  the  daily 
diet  so  as  to  include  more  hberal  amounts  of  both  than  are 
ordinarily  eaten.  The  recognition  of  the  Hkehhood  of  taking 
a  diet  which  consists  too  largely  of  cooked  or  dried  foods, 
with  consequent  deprivation  of  vitamin  c,  justifies  our 
emphasizing  the  importance  of  including  in  each  day's 
ration  some  article  known  to  contain  vitamin  c,  the  anti- 
scorbutic principle.  This  is  especially  important  in  the 
feeding  of  infants  whose  milk  supply  is  pasteurized,  because 
pasteurization  destroys  practically  all  of  the  vitamin  c. 
The  regular  administration  of  fruit  juices,  especially  orange 
and  tomato  juice,  has  practically  caused  infantile  scurvy 
to  disappear  in  the  United  States.  In  out  of  the  way  places, 
especially  during  the  winter,  potato  juice,  cabbage  juice, 
or  turnip  juice  are  often  to  be  had  and  form  an  excellent 
substitute  for  orange  or  tomato  juice.  As  has  already  been 
said,  certain  foods  canned  by  modern  processes  are  also  a 
fairly  good  source  of  vitamin  c.  Reduced  to  the  simplest 
possible  terms,  the  best  advice  as  to  how  to  insure  an 
adequate  daily  diet  is  as  follows:  The  daily  diet  should  be 
built  up  around  the  consumption  of  approximately  one 
quart  of  milk  a  day.  This  will  afford  about  800  calories  of 
energy  and  will  constitute  from  ^^  to  J-^  of  the  total  energy 
intake  of  most  individuals.  There  should  be  one  serving  of 
leafy  vegetables  such  as  cabbage,  spinach,  Brussel's  sprouts, 
cauliflower  or  other  greens,  and  two  servings  of  salad  each 
day.  It  would  be  logical  to  always  eat  these  at  the  end  of 
the  meal  because  of  the  detergent  properties  of  raw  lettuce, 
celery,  apples,  cabbage,  and  other  raw  fruits  or  vegetables 
which  may  constitute  part  of  the  salad.  This  custom  would, 
however,  be  difficult  to  establish.  The  salads  are  of  special 
importance  in  furnishing  vitamin  c.  After  these  simple 
regulations  are  complied  with  the  rest  of  the  diet  may  be 
selected  to  satisfy  the  appetite  and  may  include  any  of  the 
refined  cereal  products,  sugar-rich  foods,  etc. 

In  general  the  greatest  amount  of  injury  through  mal- 
nutrition results  from  a  diet  which  is  poorly  constituted 


346  HUMAN   BIOLOGY 

with  respect  to  several  nutrient  principles,  so  that  the 
individual  is  brought  into  a  condition  of  chronic  injury  from 
lack  of  one  or  another  of  the  vitamins,  or  from  an  inappro- 
priate supply  of  mineral  elements.  The  most  advertised 
inorganic  deficiency  in  recent  years  is  that  of  iodine  depriva- 
tion in  its  relation  to  the  development  of  simple  goiter. 
It  is  now  known  that  a  lack  of  sufficient  iodine  will  result 
in  a  certain  type  of  thyroid  enlargement  which  is  very 
common  in  so-called  goiter  areas  of  which  there  are  several 
in  the  United  States  and  Canada.  To  offset  this  deficiency 
enterprising  salt  manufacturers  have  put  upon  the 
market  iodized  salt  which  is  said  to  contain  approximately 
4  ounces  of  potassium  iodide  to  a  ton  of  salt.  At  the  present 
time  there  is  some  difference  of  opinion  regarding  the  sound- 
ness of  the  practice  of  offering  iodine  to  a  population  in  this 
manner.  The  truth  appears  to  be  that  almost  all  people  in 
goitrous  districts  would  be  benefitted  by  taking  iodized 
salt.  On  the  other  hand,  a  small  number  who  suffer  from 
adenomatous  thyroid  are  likely  to  be  injured  by  taking 
more  than  the  very  minimum  of  iodine  upon  which  health 
can  be  maintained.  It  is  always  wise,  therefore,  for  one  with 
thyroid  disease  to  secure  the  advice  of  a  specialist  concern- 
ing the  procedure  to  be  adopted. 

A  few  words  concerning  the  danger  from  spoiled  food 
should  be  added.  There  is  considerable  carelessness  in  the 
household  in  the  matter  of  odd  remnants  of  food  which 
are  often  kept  for  many  hours  or  several  days  in  ineffective 
refrigerators.  Foods  which  become  contaminated  with  certain 
kinds  of  organisms  are  very  dangerous  indeed.  What  is 
still  frequently  called  "ptomaine"  poisoning — a  word  which 
has  tended  to  fall  into  disuse  in  recent  years,  the  term 
"food  poisoning"  having  taken  its  place — is  in  general 
poisoning  from  paratyphoid  infected  food.  It  appears  also 
that  other  kinds  of  spoilage,  especially  that  in  which  the 
proteins  tend  to  undergo  decomposition,  may  cause  severe 
and  often  fatal  illness.  It  is  therefore  never  safe  to  serve 
poorly  preserved  remnants  of  food.  If  any  taint  is  suspected 
food  should  be  discarded,  and  should  never  be  eaten  except 
after  re-heating  for  some  minutes  at  boiling  temperature. 
Another  type  of  food  poisoning  is  due  to  the  growth  of  the 


THE    REACTION   TO    FOOD  347 

botuliiius  organism.  The  Bacillus  bolulinus  does  not  grow 
at  body  temperature,  therefore  it  does  not  develop  in  the 
alimentary  tract.  It  becomes  dangerous  when  food  contami- 
nated with  its  spores  is  canned  without  the  application  of 
sufficient  heat  to  kill  the  spores.  Under  such  conditions  the 
organism  develops  at  room  temperature  and  in  the  course 
of  time  produces  an  extremely  toxic  product.  Even  taking 
a  small  taste  of  such  spoiled  canned  food  has  resulted  in 
death.  Owing  to  the  gravity  of  botulinus  poisoning  the 
commercial  canners  have  for  years  made  a  thorough  study 
of  the  conditions  which  they  must  meet  in  order  to  render 
their  products  safe  and  wholesome.  For  this  reason  com- 
mercially canned  foods  are  now  safe  in  respect  to  botulism, 
but  home  canned  foods,  especially  those  canned  by  the 
so-called  cold  pack  method,  which  was  so  greatly  in  vogue 
for  some  years,  are  a  source  of  danger.  Those  who  preserve 
foods  at  home  by  canning  should  secure  advice  from  the 
U.  S.  Department  of  Agriculture  or  from  the  National 
Canners  Association,  as  to  methods  which  are  safe. 

REFERENCES 

McCoLLUM,  E.  v.,  and  Simmonds,  N.  1925.  The  Newer  Knowledge  of  Nutri- 
tion. Ed.  3,  N.  Y.  Macmillan. 
Food,  Nutrition  and  Health.  Published  privately.  A  popular  book  on  the 
application   of  modern   nutrition   studies  to   the   personal   problems  of 
those  suffering  from  malnutrition. 

Sherman,  H.  C.  1926.  The  Chemistry  of  Food  and  Nutrition.  Ed.  3,  N.  Y., 
Macmillan. 


Chapter  XV 

THE  INFLUENCE  OF  URBAN  AND  RURAL 
ENVIRONMENT 

Haven  Emerson  and  Earle  B.  Phelps 

IS  the  city  or  the  country  proving  the  better  place  for 
man  to  live  in?  Are  there  advantages  in  the  urbs,  a 
place  of  strength  with  walls,  beyond  those  of  the  rus,  a 
region  of  broad  lands?  Has  human  adjustment  to  the 
congregate  existence,  implying  compromise  and  sacrifice, 
resulted  also  in  biological  adaptation,  or  success  in  a  new 
relationship  between  the  individual  and  his  material  and 
social  environment? 


life  in  cities 

Cities  are  an  experiment  for  man.  He  blundered  and 
wasted,  lost  and  suffered  in  them  for  centuries  before 
sanitation  made  cities  safe  for  hving,  as  they  had  long  before 
become  relatively  safer  than  the  country  for  material 
possessions. 

Only  within  the  last  hundred  years  have  the  changes  come 
which  made  the  city  dominate  national  and  even  continental 
populations,  at  least  in  the  number  of  inhabitants. 

The  London  of  the  Saxons  held  hardly  20,000  people. 
From  the  time  of  Richard  i  to  that  of  Henry  vii,  about 
three  hundred  and  eleven  years,  the  population  fluctuated 
between  40,000  and  50,000.  Between  1700  and  1800  there 
was  a  growth  of  6§  per  cent  and  in  the  next  hundred  years 
an  increase  of  over  600  per  cent.  The  extraordinary  growth 
of  London  did  not  begin  until  after  1850.  Similarly  New 
York  with  under  80,000  in  1800  and  about  600,000  in  1850, 
has  increased  tenfold  in  the  past  seventy-eight  years. 

And  this  is  not  exceptional  either  in  the  national  or 
continental  sense,  for  the  same  influences  and  resource, 
economic,  social  and  scientific  have  prevailed  widely,  at 
least  in  Europe  and  the  Americas. 

348 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT       349 

111  1890  only  33  per  cent  of  the  people  of  the  United 
States  hved  in  cities,  but  the  shift  from  farm  to  factory, 
from  village  to  town  has  been  at  an  increasing  rate  until 
today  not  less  than  ^^  per  cent  of  our  total  population  of 
120,000,000  are  city  dwellers.  Among  the  eleven  and  a 
half  milhon  people  of  the  State  of  New  York,  85  per  cent 
are  classed  as  urban.  In  Dakota  86.4  per  cent  of  the  people 
are  rural. 

What  is  the  effect  on  human  life  of  moving  from  farm, 
forest  and  shore,  where  a  square  mile  of  continental  United 
States  shelters  and  supports  17.3  persons  (40  per  square  mile 
for  total  urban  and  rural)  to  the  metropolitan  area  of 
New  York  where  there  are  14,438  persons  in  the  same  unit 
of  area,  and  where  there  are  in  many  regions  of  the  city 
300  to  400  persons  living  on  the  acre,  or  224,000  on  the 
square  mile  area? 

It  is  the  very  best,  not  merely  the  average,  quality  of 
life  which  we  strive  for,  as  well  as  for  a  greater  length  or 
quantity.  It  is  the  satisfactions  of  human  life,  the  function 
of  enjoyment,  not  merely  the  status  of  material  existence 
or  survival  we  try  to  attain.  Any  index  of  success  in  man's 
gradual  or  forced  adaptation  from  his  so-called  natural, 
his  primeval  or  ancient  manner  of  life  to  the  prevailing 
trial  or  test  of  existence  in  great  community  aggregations 
will  prove  incomplete  and  inadequate  unless  it  includes  a 
spiritual  as  well  as  a  physical  element.  However  successful 
the  historians  and  philosophers  of  tomorrow  may  be  in 
evaluating  the  relative  merits  of  our  present  preference  for 
mass  existence  as  distinguished  from  the  family  or  unitary 
life  of  our  but  recent  ancestors,  we  can  at  least  relate  today 
those  differences  and  similarities  of  record  which  characterize 
the  lives  and  deaths  of  city  and  country  residents. 

MODERN    MUNICIPAL    SANITATION 

It  was  not  until  such  alert  and  analytical  citizens  as 
Chadwick  in  England  and  Shattuck  and  Stephen  Smith  in 
Massachusetts  and  New  York  began  to  study  the  balance 
sheet  of  their  fellow  citizens  that  the  desperate  plight  of  the 
town  dweller  was  made  known.  Cities  could  not  grow  or 


350  HUMAN   BIOLOGY 

even  survive  when  the  death  rate  exceeded  the  birth  rate. 
Immigration  from  the  land  and  from  other  countries  could 
not  long  make  good  the  losses  from  disease  when  half  of  all 
the  babies  born  died  within  the  year.  Even  with  birth  rates 
almost  twice  as  high  as  those  prevaiHng  in  our  cities  today, 
the  annual  death  rates  of  London  and  New  York  in  the 
middle  of  the  nineteenth  century  not  infrequently  exceeded 
them. 

The  alarm  raised,  together  with  the  constant  evidence 
on  all  sides  that  the  wealth  and  influence,  the  commerce 
and  industry  of  the  cities  were  at  stake,  created  a  pubHc 
opinion  which  was  finally  responsible  for  the  era  of  modern 
municipal  sanitation. 

Seventy-five  years  ago  the  large  cities  of  Europe  and 
America  were  unsafe  for  human  habitation.  Death  rates  of 
30  per  thousand  of  the  population  were  not  uncommon  and 
the  loss  of  child  Hfe  was  appalhng.  Extinction  was  prevented 
by  the  organization  of  services  and  facihties  for  disposal 
of  human  waste,  the  provision  of  safe  food  and  water, 
some  control  of  housing  and  work  places,  and  specific 
measures  for  Hmiting  the  spread  of  the  communicable 
diseases. 

There  are  cities  in  the  United  States  today  where  the 
Negro  fraction  of  the  population,  constituting  from  10 
to  20  per  cent  of  the  total,  shows  an  excess  of  deaths  over 
births.  The  urbanized  Negro,  the  most  primitive  of  the 
races  engulfed  in  city  industrial  fife,  sufl'ers  as  the  white 
races  of  England  and  America  did  in  our  cities  of  1850, 
from  factors  which  are  not  solely  those  of  educational  and 
economic  disadvantages. 

Everywhere  the  Jew  exhibits  a  superiority  to  other  races 
in  his  abihty  to  survive  the  city  handicaps,  possibly  as  a 
result  of  the  long  centuries  of  enforced  ghetto  existence 
in  many  lands,  and  his  thriftiness,  his  intelhgent  use  of 
professional  and  communal  services  for  his  health  protection. 

Municipal  sanitation  saved  the  hfe  of  the  city.  The  city 
would  now  be  king.  In  fact  the  balance  of  power  not  only  of 
wealth,  but  of  actual  numbers  of  our  population  has  shifted 
to  these  artificial  environments  we  have  created.  The 
city  seems  now  to  supply  to  the  majority  of  our  people  those 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT      35 1 

satisfactions   that   constitute   the   object   of  Hfe   in    larger 
measure  than  does  the  country. 

How  nearly  has  man  overcome  the  handicaps  he  has 
created  by  crowding  together?  What  has  he  acquired  which 
can  be  considered  a  biological  asset? 

COMPARATIVE    DEATH    RATES 

In  its  simplest  terms  the  truth  appears  to  be  that  the 
death  rate  is  higher  and  the  expectation  of  hfe  is  less  in 
city  than  among  rural  populations.  Differences  of  age,  sex 
and  race  composition  of  the  populations  cannot  wholly 
explain  the  disadvantage  of  the  city  people.  Either  the 
greater  prevalence  and  severity  of  diseases  or  the  lower 
resistance  of  the  people  in  the  city  seems  to  be  responsible. 

Perhaps  the  best  single  index  of  the  relative  hygienic 
value  of  hving  conditions  in  city  and  country  is  to  be  found 
in  the  death  rate  from  tuberculosis,  a  disease  which  expresses, 
certainly  in  comparable  racial  aggregates,  the  sum  of 
environmental,  social  and  economic  conditions  which  we 
speak  of  as  the  standard  of  living.  When  due  regard  is 
given  to  the  place  of  origin  of  the  disease  as  distinguished 
from  the  place  of  death  of  the  patient  we  see  emphasized  in  a 
striking  way  the  advantages  of  rural  over  urban  conditions. 

The  residential  death  rates  from  tuberculosis  in  New 
York  State  as  analyzed  for  the  year  1926  by  J.  V.  DePorte 
show  them  to  be  consistently  higher  among  city  dwellers 
than  among  rural  residents.  Thus  the  tuberculosis  death 
rate,  computed  on  the  basis  of  resident  deaths  for  New 
York  City  irrespective  of  the  place  of  death  in  the  State 
was  102.5  per  100,000  of  population  and  for  the  rest  of 
the  State  it  was  74.3. 

Similarly  the  resident  tuberculosis  death  rate  for  the  urban 
part  of  New  York  State  outside  New  York  City  was  83.2 
per  100,000  population,  while  that  of  the  rural  portion  of 
the  State  was  59.4. 

This  same  difference  is  maintained  throughout  all  classes 
of  cities  when  compared  with  the  rural  areas  of  their  respec- 
tive counties,  whether  we  deal  with  cities  of  large  sizes 
or  with  those  of  100,000  to  250,000,  50,000  to  100,000, 
25,000  to  50,000,  or  places  of  10,000  to  25,000.     These  differ- 


352  HUMAN    BIOLOGY 

ences  cannot  be  explained  satisfactorily  on  any  basis  of 
selective  race,  age,  sex,  occupational  or  economic  differences 
among  the  11,318,734  people  dealt  with  in  this  study.  As 
Dr.  DePorte  well  says:  "Among  the  several  important  causes 
of  death,  the  element  of  residence  is  perhaps  of  greatest 
weight  in  mortahty  from  tuberculosis." 

Turning  now  to  the  death  rates  of  the  registration  area  of 
the  United  States  in  19 10  and  1920  we  find  not  only  in  the 
rate  for  all  causes  combined,  but  for  a  goodly  number  of 
the  more  common  causes  of  death,  higher  rates  among  the 
city  people  than  among  the  rural.  The  following  table  gives 
not  only  the  differences  between  urban  and  rural  rates, 
but  the  trend  and  the  consistency  of  the  differences  over  that 
decade  during  which  the  shift  of  population  to  the  cities  took 
on  the  highest  speed,  to  be  exceeded  in  all  probability, 
however,  by  the  period  since  1920.  No  similar  period  of 
time  has  been  characterized  in  this  country  by  a  greater 
improvement  in  general  health  conditions  in  both  city  and 
rural  regions.  At  no  previous  period  have  the  services  of 
science  and  of  the  medical  profession  and  public  health 
workers  been  more  nearly  similar  in  value  for  the  great 
majority  of  rural  communities  as  well  as  for  the  cities. 

Various  parts  of  the  country,  notably  in  the  states  of 
New  England  and  in  northern  New  York  where  extreme 
changes  have  occurred  in  the  age  grouping  and  rural  pro- 
portion of  the  populations  concerned,  there  has  been  observed 
during  the  past  fifty  years  an  increasing  inadequacy  in 
the  number  and  distribution  of  physicians  to  meet  the 
desires  or  necessities  of  small  and  widely  scattered  village 
and  farm  groups.  Physicians  distribute  themselves  very 
much  as  other  people  do,  on  the  basis  of  more  advantageous 
economic  and  social  conditions  for  themselves  and  their 
families.  They  too,  therefore,  have  gravitated  to  city 
centers  where  hospitals,  laboratories,  libraries  and  schools 
are  available.  While  one  physician  to  seven  hundred  people 
was  a  reasonable  ratio  in  the  era  of  the  horse  and  buggy 
and  dirt  roads,  today  with  no  more  effort  or  time,  a  physician 
can  readily  serve  a  thousand  people  as  well  or  better,  even 
if  they  are  as  scattered  and  distant,  as  were  their  ancestors. 
There  would  seem  to  be  no  evidence  that  health  protection  or 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT      353 

care  of  the  sick  in  rural  areas  has  yet  been  sacrificed  to 
any  degree  by  the  cityward  trend  of  country  folk  and  physi- 
cians, although  within  the  next  twenty  years,  failure  of 
medical  services,  if  determined  exclusively  on  an  individual 
preference  or  competitive  basis  by  physicians,  is  likely  to 
develop,  especially  where  the  clearing  of  the  roads  in  winter 
cannot  be  relied  upon.  The  local  county  or  crossroads 
hospital  available  for  all  patients  and  for  all  physicians  is 
likely  to  prove  a  sufficient  advantage  to  attract  the  young 
physician  again  to  enter  rural  practice.  In  the  sparsely 
settled  mountain  regions  of  the  Carolinas,  Kentucky  and 
Tennessee  there  never  has  been  any  self-supporting  basis 
upon  which  adequate  medical  services  could  be  provided, 
and  a  retrograde  condition  both  physical  and  mental 
has  prevailed. 

The  active  public  health  movement,  encouraged  by  funds 
from  private  philanthropy,  which  has  already  resulted 
in  the  provision  of  full-time  health  officers  for  more  than 

Table  i 

urban  and  rural  death  rates  by  principal  causes  per  100,000  of 

population  in  the  united  states  registration  area 

(u.  s.  census  bureau,  mortality  rates,   i918-i920) 


•9 

10 

1920 

Urban 

Rural 

Urban 

Rural 

All  causes 

1590.0 

1340.0 
142. 1 

7-2 

1411 .0 
168. 1 

1 194.0 

Diseases  of  the  Heart 

157-6 

133- 1 

Appendicitis 

14.0 

19.2 

7.  4 

Pneumonia  (all  forms) 

171. 2 

109-5 

127.4 

76.5 
70.1 

168.5 

1 07 . 0' 

Tuberculosis  (all  forms) 

179-5 

118. 5 
100.2 

99-8 
7.8 

80.5 

19-4 
52.2 
18.9 

108.2 

Nephritis  and  Brights'  Disease 

III. 3 

81.5 

8.1 

72.3 
16.8 

78.0 

Cancer,  Malignant  Tumors 

68.0 

Puerperal  Septicemia 

5.8 

5-4 

Cerebral  Hemorrhage 

80.0 

81.4 

Diabetes 

13.5 

13-1 

Diarrhea  and  Enteritis  (under  2  years)   

118. 0 

77-3 
15.9 

35-1 

Diphtheria  and  Croup 

25.8 
13-4 

12. 1 

Measles 

II. 5 

10.3 

7-4 

Typhoid  fever 

22.4 

233 

8.2 

5  5 

5.4 

9.6 

Scarlet  Fever 

14.2 

3-9 

354  HUMAN   BIOLOGY 

12  per  cent  of  all  the  counties  of  our  states,  promises  to  be  of 
increasing  value  in  carrying  the  benefits  of  the  appHed 
medical  sciences  of  today  to  remote  homes  and  small  villages. 
Rapid  increases  in  means  of  communication  and  transporta- 
tion and  wider  spread  of  reliable  information  about  per- 
sonal health  will  continue  to  bring  benefits  to  the  rural 
family  which  have  up  to  this  time  been  available  only  in 
large  centers  of  population. 

It  will  be  noted  that  the  crude  general  death  rates  from 
all  causes,  without  adjustments  for  age,  sex  and  racial 
differences  in  the  populations  (first  line  of  table)  are  higher 
for  city  populations  for  each  of  the  years  by  almost  exactly 
the  same  degree,  i.e.  about  i8  per  cent.  The  improvement 
in  health  and  security  of  life  has  been  at  the  same  rate 
during  the  decade  19 10-1920  in  both  city  and  country 
populations,  and  still  we  find  that  the  city  rate  in  1920  is 
not  yet  as  low  as  the  rural  rate  in  19 10. 

Apparently  the  disadvantage  of  city  existence  as  compared 
with  rural,  for  the  population  groups  as  they  are  constituted 
today,  in  the  United  States,  is  represented  by  approximately 
2.2  deaths  per  thousand  per  annum,  which  for  the  estimated 
65,000,000  people  classified  as  urban  dwellers  amounts  to  a 
total  of  143,000  deaths  per  year. 

The  chief  racial  differences  of  population  are  in  favor  of 
the  city  group  since  the  negroes  are  to  be  found  in  larger 
proportion  in  rural  than  in  urban  populations  and  it  is  their 
presence  which  always  raises  a  general  death  rate.  Any 
correction  made  on  the  basis  of  proportion  of  white  and 
colored  races  would  result  in  a  greater  disadvantage  in 
urban  death  rates. 

Similarly  in  the  matter  of  age  differences  the  result  of 
adjustment  would  be  to  raise  and  not  lower  the  city  rates. 
It  will  be  seen  from  Table  11,  summary  of  age  groups  of  the 
urban  and  rural  populations  in  the  State  of  New  York, 
that  the  city  population  has  a  greater  proportion  of  younger 
persons. 

Again  in  the  matter  of  differences  in  the  proportions  of 
the  sexes  in  the  two  groups  of  population,  the  city  contains 
a  generally  higher  ratio  of  women  than  does  the  country, 
as  for  example  in  the  metropolitan  area  of  Boston  there  are 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT      355 


Table  ii 
age  groups  in  new  york  state  population 


Age  (years) 

Urban 
(per  cent) 

Rural 
(per  cent) 

Under  I'i 

27.9 

27.8 

I  <;— 24, 

17.2 

14.5 

2-?— ^zl          

18.8 

13.8 

■2  «— 4,4 

15. 1 

13-4 

Ai  and  over 

21 .0 

30.5 

Total 

100. 0 

100  0 

just  over  80  males  for  every  100  females,  v^^hile  in  Massachu- 
setts as  a  whole  there  are  found  to  be  96  males  for  each  100 
females.  The  death  rates  of  females  are  in  general  lower 
than  those  of  males,  and  their  hfe  expectancy  on  the  whole 
two  or  three  years  longer  than  that  of  males  for  the  various 
decades  of  life. 

The  upshot  is  that  when  we  adjust  and  correct  city  and 
rural  death  rates  by  taking  into  account  the  differences  of 
race  and  age  and  sex,  the  resulting  city  rate  is  higher  and 
the  rural  rate  lower.  When  this  process  is  carried  out  for 
New  York  City  as  compared  with  the  rest  of  the  State, 
the  city  death  rate  is  raised  at  least  one  point  per  thousand 
and  that  of  the  state,  preponderantly  rural,  correspondingly 
lowered.  The  disadvantage  of  city  existence  as  compared 
with  rural  for  similarly  constituted  population  groups, 
therefore,  would  be  materially  greater  than  has  been  indi- 
cated above,  and  the  comparative  death  rates  of  Table  i 
uncorrected  for  age,  sex  and  race  differences,  represent  a 
distinctly  conservative  statement  of  that  disadvantage. 

How  much  of  this  excess  is  chargeable  to  the  environment, 
physical  and  social,  of  the  city,  and  how  much  to  the  trades 
and  occupations,  which  are  now  conducted  in  the  city  and 
which  might  if  carried  on  in  rural  communities  cause  at  least 
as  much  loss  of  Hfe,  we  have  no  way  of  knowing. 

Much  evidence,  however,  for  the  essential  hazards  of 
city  life  per  se  as  compared  with  rural  can  be  had  from  a 
study  of  individual  causes  of  death  among  young  and  old, 
and   from   factors  not  primarily  or  necessarily  related  to 


356 


HUMAN   BIOLOGY 


occupations.  Particular  death  rates  for  the  principal  causes 
are  with  few  exceptions  higher  for  urban  than  for  rural 
populations  (Table  i). 


THE    EXPECTATION    OF    LIFE 


More  satisfying  than  death  rates  in  picturing  the  relative 
healthfulness  of  groups  of  people  is  the  Hfe  expectancy  table 
in  which  we  see  reflected  the  experience  of  the  past  in  terms 
of  probabihty  of  survival  of  those  now  living.  It  may  be 
explained  that  the  "expectation  of  hfe"  is  the  average  length 
of  life  remaining  to  all  persons  alive  at  the  beginning  of  a 
specified  year  of  age.  For  our  present  purpose  we  can  quote 
as  applicable,  with  a  high  degree  of  probability,  the  experience 
of  the  white  race  in  the  original  registration  states  (New 
England,  New  York,  New  Jersey,  Indiana,  Michigan  and 
District  of  Columbia).  The  rural  population  described  is  that 
part  of  the  people  living  in  communities  of  10,000  or  less. 


Table  hi 
expectation  of  life  for  the  white  population  of  the  original 

REGISTRATION  STATES  (iQOp,  IQIO,  Ipll) 

(Bureau  of  the  Census,  U.  S.  Life  Tables,  1910) 


Years  remaining: 

Male 

Female 

1  Urban     Rural 

Urban 

1 
1 

Rural 

At  birth   

'  47-32  !   5506 

!    51.39 

57-35 

At  ase  10. . 

49.13      54.53 

52.22        55.54 

20. 

40.51      45.92 

43.51      46 . 86 

30. 

32.61       38. I 

'  35  52      39- 05 

40.. 

25.32      30.20 

27.88  i  31.15 

ro     

18.59      22.43 

20.53         2^.27 

There  Is  then  no  exception  to  the  advantage  at  every 
age  group  of  the  rural  as  compared  with  the  city  dweller 
in  the  average  length  or  expectancy  of  life. 

This  does  not,  however,  tell  the  whole  story  any  more 
than  one  can  get  all  the  truth  from  the  death  rates  of  an 
individual  year.  These  figures  mean  that  under  a  uniform 
condition  as  to  death  rates  at  each  age  group,  equal  to  that 
of  the  period  1909-1911,  a  male  child  born  and  continuing 


THE    INFLUENCE    OF    URBAN    .\ND    RURAL    ENVIRONMENT      357 

to  live  in  the  country  will,  on  the  average,  Hve  nearly 
eight  years  longer  than  a  male  child  similarly  born  and 
Hving  in  the  city.  The  difference  for  a  female  child  is  about 
six  years.  These  advantages  of  the  country  decrease  numeri- 
cally with  advancing  years,  until  at  the  age  of  fifty  they 
are  about  one-half  the  initial  value. 

The  Hfe  tables  deal  with  death  rates  at  each  specific 
year  of  hfe  and  hence  the  results  are  automatically  cor- 
rected for  any  disparity  in  age  grouping  as  between  city 
and  country.  It  cannot  be  assumed,  however,  that  the 
generally  greater  expectation  of  hfe  enjoyed  by  the  country 
dweller  is  due  wholly  to  his  physical  environment. 

Table  iv 

life  expectancy  in  the  original  u.  s.  registration  states 

(Bureau  of  the  Census,  U.  S.  Life  Tables,  19 10) 

White  Males 


Age 

0 

10 

20 

30 

40 

50 

1901 

Urban 

44.0 

47.5 

39-1 

31-9 

25.1 

18.6 

Rural 

Difference    in    favor    of 
rural 

54.0 
10. 0 

54.4 

6.9 
49-1 

46.0 
6.9 

38.4 
6.5 

30.5 

22.8 

5.4 

4.2 

1910 

Urban 

47-3 

40.5 

32.6 

253 

18.6 

Rural 

Difference 

55.1 

54-5 

45.9 
5.4 

38.1 

30.2 
4.9 

22.4 

7.8 

5-4 

1.6 

0. 1 

-1-5 

5-5 

3-8 

Change 

Urban 

3.3 

1. 1 

1.4 
-o.ij 

-1-5 

0.7 

0.2 

0 

1901-1910 

Rural 

-0.3 

-0.3 

—  0.4 

Difference 

—  2.2* 

-I.O 

-0.5 

-0.4 

White 

Females 

1 90 1 

Urban 

Rural 

Difference 

47.9 

50.3 

41.9 
46.  I 

34-5 

27-3 

20.3 

55 

4 

54.4 

38.8    31.2 

23.5 

7 

5 

4.1 

4.2 

4-3 

3.9 

3-2 

1910 

Urban 

Rural 

Difference 

51 

4 

52.2 

43-5 

46.9 

3-4 

35-5 
39-1 

27.9 

20.5 

57 

4 

55-5 
3-3 

31.2 

233 

6 

0 

3-6 

3-3 

2.8 

Change 

Urban 

3 

5 

1.9 
1. 1 

1.6 

1.0 

0.6 

0.2 

Rural 

2 

0 

0.8 

0.3 

-0.7 

0.0 

—0.2 

Difference 

—  I 

5 

-0.8 

-0.8 

-0.6 

-0.4 

*  Difference  in  favor  of  rural  is  decreasing. 
X  Rural  expectancy  decreased. 


358  HUMAN   BIOLOGY 

By  comparison  of  the  life  expectancy  tables  of  1901  with 
those  of  19 10  it  appears  that  by  this  criterion  there 
has  been  a  gradual  reduction  of  the  disadvantage  of  the 
city  dweller.  While  the  rural  population  still  (1910)  enjoyed 
a  substantially  longer  hfe  expectancy  at  every  decade  of 
from  four  to  eight  years,  than  did  his  city  friend,  the  gains 
of  the  city  man  and  woman  have  been  a  little  greater;  thus 
the  difference  has  been  reduced.  There  is  good  reason  to 
believe  that  there  has  been  a  continued  reduction  in  the 
handicap  of  the  urban  population  since  19 10,  but  the  life 
expectancy  tables  have  not  yet  been  officially  issued  since  then. 

A  white  male  born  and  continuing  to  live  in  the  country 
had  an  expectation  of  hfe  at  birth,  in  1901,  10  years  greater 
than  that  of  a  similar  male  child  in  the  city.  At  the  age  of 
fifty  this  advantage  had  decreased  to  4.2  years.  Similar 
values  for  white  females  are  7.5  years  and  3.2  years. 

In  19 10  the  actual  expectancy  of  a  male  child  had  increased 
in  the  city  by  3.3  years  and  in  the  country  by  i.i  years  so 
the  advantage  in  favor  of  the  country  had  been  reduced 
2.2  years,  that  is  from  ten  years  to  7.8  years.  At  the  age  of 
fifty  the  expectation  was  unchanged  in  the  city  and  0.4 
years  less  in  the  country,  reducing  the  country  advantage 
from  4.2  to  3.8  years. 

Turning  now  from  the  quite  convincing  evidence  that, 
taken  as  a  population  group,  city  people  die  earfier  and  at  a 
higher  rate  from  the  principal  causes  than  do  country 
people,  we  have  many  elements,  entirely  apart  from  those 
of  heredity,  race,  age,  sex  and  a  possible  social  selection, 
any  one  of  which  may  have  a  share  in  causing  the  disadvan- 
tages, and  which  are  worthy  and  possible  of  analysis. 

In  the  environment  of  the  city  dweller,  compared  with 
that  of  the  rural  family,  we  appreciate  difi"erences  of  atmos- 
phere, water,  food,  clothing,  fighting,  insects  and  personal 
contacts,  each  a  possible  factor  in  modifying  the  safety  of 
life. 

While  there  seems  to  be  almost  no  fimit  to  the  adaptations 
of  fife  to  diff'erences  of  environment  in  permitting  these  to 
occur  without  sacrifice  of  the  individual,  there  is  some  reason 
to  befieve  that  we  have  not  caught  up  with  the  rapid  changes 
which    have    accompanied    the    artificial    environment    we 


THE    INFLUENCE   OF   URBAN   AND   RURAL   ENVIRONMENT       359 

have  created  in  our  cities.  We  are  largely  in  control  of 
environment  but  we  do  not  yet  know  w^ith  certainty  the 
lengths  to  which  we  can  safely  go  in  modifying  it  for  our 
convenience,  comfort  or  pleasure. 

THE    ATMOSPHERE 

The  atmosphere  is  man's  most  intimate  physical  environ- 
ment. Physiologically  it  has  two  primary  functions:  It 
provides  for  the  necessary  respiratory  exchange,  oxygen 
being  taken  into  the  system,  and  carbon  dioxide  being  given 
out.  It  also  provides  for  the  removal  of  heat  from  the  body 
surfaces,  lungs  and  skin,  by  processes  of  convection  and 
evaporation.  Except  under  conditions  of  asphyxiation, 
smothering  or  drowning,  the  respiratory  exchange  function 
seldom  fails.  The  modern  problems  of  ventilation  concern 
themselves  to  a  large  extent  with  the  second  or  heat-remov- 
ing properties  of  the  air. 

As  has  been  previously  suggested,  the  air  provides  a 
chmate,  and  under  our  present-day  habits  of  hfe,  especially 
in  the  cities,  we  deal  largely  with  an  artificial  chmate. 
In  addition  to  the  temperature,  humidity  and  movement  of 
the  air,  its  three  significant  physical  properties  affecting 
comfort  and  health,  the  atmosphere  has  quahties  that 
determine  the  character  and  extent  of  solar  radiation  reach- 
ing the  earth's  surface.  It  is  in  fact  a  selective  screen  through 
which  the  sun's  rays  pass  with  more  or  less  modification. 
Of  the  hght  of  the  visible  spectrum,  "hght"  in  the  common 
use  of  the  word,  about  20  per  cent  is  absorbed  by  a  clear 
atmosphere  at  sea  level.  The  rate  of  absorption  increases 
with  decreasing  wave  length  so  that  only  a  small  part  of  the 
total  ultraviolet  radiation  of  the  sun  ever  reaches  the  earth's 
surface,  while  a  large  proportion  of  the  infra-red  spectrum 
and  the  heat  rays  do  come  through.  This  selective  screening 
effect  is  of  course  modified  by  the  thickness  of  the  air 
layer  (altitude  of  the  place)  and  by  the  clouds,  fog,  smoke  and 
dust. 

Another  property  of  the  atmosphere,  concerning  the 
effect  of  which  we  know  but  httle,  is  its  electrical  property. 
We  hve  in  a  strong  potential  gradient  by  reason  of  which 
an   electric   current   is   always   passing   between   the   earth 


360  HUMAN   BIOLOGY 

and  the  air.  The  amount  of  this  current  is  dependent  upon 
the  ionization  of  the  atmosphere,  which  in  turn  is  affected 
by  the  presence  of  radio-active  substances,  by  ultraviolet 
radiation  and  probably  by  the  penetrating  radiation  recently 
studied  by  Millikan.  The  relation  of  these  electrical  prop- 
erties of  the  air  to  health  and  comfort  offers  an  interesting 
held  of  study.  At  present  our  knowledge  concerning  this  is 
imperfect. 

As  regards  urban  and  rural  atmospheres,  great  differences 
are  at  once  apparent.  The  physical  properties,  temperature, 
humidity  and  movement,  are  determined,  of  course,  by 
latitude,  altitude  and  relation  to  seashore  and  mountains, 
but  under  otherwise  equivalent  conditions,  the  "open  air" 
of  the  country  has  advantages,  especially  in  the  summer 
time. 

A  characteristic  of  large  cities  is  the  mass  of  heated  brick, 
stone  and  concrete  that  reflects  much  of  the  sun's  heat 
back  upon  the  dwellers  and  retains  what  heat  is  absorbed, 
giving  it  out  in  the  night  hours,  preventing  the  natural 
coohng  that  comes  in  the  country  with  the  setting  of  the 
sun.  Air  movement  is  lessened  by  tall  buildings,  and  the 
human  output  of  humidity  and  heat  becomes  a  distressing 
factor  in  crowded  places. 

Whereas  in  the  city  the  radiant  heat  of  the  summer  sun, 
striking  the  masonry  of  buildings  and  paved  streets,  is  either 
reflected,  adding  to  the  immediate  discomfort,  or  absorbed 
and  stored,  to  be  returned  during  the  night-time,  in  the 
country  it  is  to  a  large  extent  absorbed  and  neutrahzed 
by  green  fohage.  The  full  significance  of  this  phenomenon 
can  best  be  shown  by  a  brief  mathematical  computation. 

It  has  been  estimated  (Bailey)  that  an  acre  of  beech 
trees,  400  to  600  trees,  will  evaporate  about  2,000,000 
pounds  of  water  during  the  season,  or  let  us  say  10,000 
pounds  per  day.  The  heat  absorbed  by  this  amount  of 
evaporation  amounts  to  6^  small  calories  per  square  centi- 
meter per  day. 

The  solar  constant,  as  defined  by  the  Smithsonian  Insti- 
tution, represents  the  quantity  of  heat  that  would  be  received 
from  the  sun  if  there  were  no  atmosphere.  On  a  clear  day, 
at  sea  level,  the  actual  heat  received  is  of  the  order  of  90 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT       36 1 

calories  per  square  centimeter  per  hour,  on  a  surface  facing 
the  sun.  On  surfaces  inchned  to  the  sun's  rays  the  heat 
received  is  less  according  to  the  cosine  of  the  angle  of  inchna- 
tion.  The  earth's  surface  is  more  or  less  inchned  first  accord- 
ing to  latitude  and  season,  and  again  according  to  the 
hour  of  the  day. 

At  latitude  42°  the  sum  of  the  hourly  values  of  the  cosine 
of  the  angle  of  inchnation  is  7.61  for  the  15  hours  of  sunhght 
at  the  summer  solstice,  and  5.67  during  the  12  hours  at  the 
equinoxes.  These  values  then  represent  the  equivalent 
hours  of  normal  exposure  during  each  day,  and  their  mean 
value,  6.6,  may  be  taken  as  a  fair  representation  of  the 
average  daily  number  of  hours  of  normal  exposure  during 
the  summer.  The  average  daily  amount  of  heat  received, 
therefore,  on  a  square  centimeter  of  surface  does  not  exceed 
the  value  for  normal  exposure,  90  calories  per  hour  times  6.6 
hours  or  594  calories  per  day.  It  is  always  less  than  this 
by  the  proportion  of  cloudiness,  and  by  the  amount  of  heat 
intercepted  by  fog,  smoke  and  dust.  In  the  vicinity  of  Nev^^ 
York  City,  the  cloudiness  alone  diminishes  the  sunshine  to 
60  per  cent  of  its  possible  value  during  the  summer  months. 

The  computed  absorption  by  trees,  6^  calories,  is  1 1  per 
cent  of  the  total  heat  received  over  the  forest  area  through 
clear  and  dry  air,  and  a  much  greater  proportion  of  the 
actual  radiation  through  the  average  atmosphere.  The 
significance  of  this  value  will  be  appreciated  if  it  be  noted 
that,  taking  in  the  hours  of  normal  exposure  as  computed, 
the  diff'erence  between  the  summer  solstice  and  the  equinoxes 
amounts  to  only  25  per  cent  of  the  former. 

It  will  be  noted  in  Table  i  that  the  death  rate  from 
diarrhea  and  enteritis  under  two  years  of  age  was  48  per 
cent  higher  in  the  urban  than  in  the  rural  populations  (52.2 
urban,  35.1  rural)  in  1920,  and  in  1910,  53  per  cent  higher. 
While  diarrheal  disease  of  infants  has  generally  in  the  past 
been  thought  to  be  due  chiefly  to  the  spoilage  of  food, 
to  bacterial  contamination  of  milk  and  water  and  to  lack 
of  care  in  washing  and  clothing  infants,  strong  evidence  has 
recently  been  presented  by  Arnold  suggesting  that  such 
high  effective  temperatures  as  commonly  prevail  in  our 
cities  in  summer  are  a  definite  predisposing  cause  to  this 


362 


HUMAN    BIOLOGY 


disease.  The  city  child  suffers  more  from  diarrhea  and 
enteritis  probably  because  the  environment  of  brick,  stone, 
concrete  and  asphalt  prevents  his  adjusting  to  temperature, 
humidity  and  air  motion,  as  favorably  as  he  does  where 
fohage  is  present.  Carelessness  in  the  city  household  in  many 
of  the  minor  details  of  cleanhness  and  care  of  children  may 
result  from  the  general  demoralization  which  commonly 
accompanies  spells  of  hot  weather.  Even  among  cities  there 
are  differences  in  the  unfavorableness  of  environment.  For 
instance,  in  Washington,  where  the  expectancy  of  hfe  is 
the  highest  of  all  the  cities  of  500,000  and  over  in  the  regis- 
tration area,  and  in  Pittsburgh,  where  it  is  lowest,  we  have  the 
extremes  of  abundant  foliage,  parks  and  spacious  streets 
in  one  place  and  an  almost  treeless,  parkless  city  of  bare 
streets  in  the  other.  Pittsburgh's  death  rate  from  diarrhea 
and  enteritis  under  two  years  of  age  has  for  many  years 
ranged  from  two  and  a  half  to  four  times  as  high  as  that 
of  Washington,  for  the  white  population,  although  much 
of  this  difference  is  doubtless  due  to  differences  in  age, 
sex  and  social  elements.  In  view  of  all  these  facts,  it  seems 
not  improbable  that  the  atmospheric  environment  of 
Washington  is  responsible  in  considerable  measure  for  the 
advantages  which  its  children  enjoy  in  a  low  death  rate 
from  this  chief  cause  of  infant  mortahty. 


DIARRHEA    AND    ENTERITIS 

Table  v 

under  2  years  of  age: 
white  population 

DEATH    RATE   PER    100,000 

Year 

Washington 

Pittsburgh 

1911 

55-4 

132.0 

1912 

312 

116. 0 

1913 

34-9 

138.0 

1914 

18.9 

106.7 

1915 

26.3 

100.6 

1916 

27.5 

123.6 

1917 

35-3 

130.8 

1918 

35-5 

121. 2 

1919 

28.6 

89.2 

1920 

22.6 

75-5 

THE    INFLUENCE    OF    URBAN   AND    RURAL    ENVIRONMENT      363 

Most  of  the  large  cities  have  ordinances  designed  to  prevent 
the  smoke  nuisance,  but  strict  enforcement  has  generally 
been  tempered  by  a  knowledge  of  the  difficulties  involved, 
especially  in  the  combustion  of  soft  coal.  The  railroads 
are  among  the  worst  offenders  and  a  recent  survey 
in  New  York  has  indicated  that  the  harbor  boats  are  fre- 
quent and  serious  offenders. 

In  certain  of  the  larger  mid-western  cities,  determined 
efforts  have  been  made  to  abate  what  was  rapidly  becoming 
a  most  serious  nuisance.  In  Pittsburgh,  in  particular,  it 
was  decided  to  clean  up  the  atmosphere,  for  the  nickname 
of  the  "smoky  city"  was  not  one  to  be  proud  of,  nor  did  it 
confer  commercial  advantage.  Quantitative  measures  of 
the  actual  pollution  of  the  atmosphere  have  indicated  a 
very  great  improvement  since  the  active  campaign  of 
abatement  was  begun,  and  the  improvement  is  obvious 
to  the  regular  visitor.  Many  other  of  the  great  industrial 
cities  of  the  Middle  West  have  had  similar  experiences, 
although  present  conditions  in  most  of  them  are  still  bad 
according  to  the  standards  of  the  eastern  cities,  where 
soft  coal  is  not  used  to  so  great  an  extent. 

In  New  York,  on  the  other  hand,  the  tendency  has  been 
in  the  opposite  direction  during  recent  years.  Labor  troubles 
in  the  anthracite  coal  regions  have  led  to  a  relaxing  of  the 
rules  against  bituminous  coal  and  the  taxpayers  are  becoming 
accustomed  to  a  gradually  increasing  load  of  atmospheric 
pollution.  The  efforts  of  the  health  department  to  prevent 
the  growing  evil  have  so  far  had  little  or  no  result  apparent 
to  the  dwellers  in  certain  sections,  although  it  cannot  be 
denied  that  the  strong  presence  of  attempted  law  enforce- 
ment has  partially  stemmed  the  tide  of  growing  disregard 
of  the  sanitary  code.  A  most  suggestive  aspect  of  the  situation 
has  recently  been  recorded  in  a  report  of  the  Committee  of 
the  Merchants'  Association  of  New  York.  They  show  a 
definite  and  very  large  economic  injury  to  merchants, 
manufacturers  and  others,  due  to  the  increasingly  smoky 
atmosphere.  As  soon  as  we  begin  a  scientific  evaluation  of 
the  economic  losses  resulting  from  the  unrestricted  use  of 
soft  coal,  probably  conservatively  expressed  at  $20.00 
per  capita  per  annum,   it  will  no  longer  be  necessary  to 


364.  HUMAN   BIOLOGY 

meet  the  strong  economic  argument  Jor  soft  coal  by  the 
less  definite  and  oft-questioned  statements  of  possible 
health  hazards  against.  When  economic  gain  meets  economic 
loss  on  even  terms,  health  and  comfort  and  civic  pride  may 
ultimately  determine  the  issue. 

Atmospheric  pollution  with  smoke  and  dust,  and  the  fog, 
which  is  increased  by  the  presence  of  both  of  these  in  the 
air,  is  greater  over  cities  than  in  the  country,  with  a  resulting 
reduction  of  the  permeabihty  of  the  air  by  those  valuable 
short  rays  of  fight  which  are  known  to  be  preventive  and 
curative  for  rickets.  While  rickets  may  occur  in  any  latitude 
if  there  is  interference  with  the  metabofic  processes  which 
determine  normal  development,  particularly  of  the  soft 
growing  ends  of  the  long  bones  of  the  body,  it  is  found  most 
abundantly,  and  indeed  almost  universally,  among  babies 
in  their  first  year  of  fife  in  the  large  northern  cities  of  Europe 
and  America.  Here,  in  addition  to  the  fimitations  of  the 
sun's  rays  by  low  incfination  and  cloud,  children  are  housed 
unsuitably  as  to  fight  and  fed  unsuitably  as  to  antirachitic 
elements  of  diet. 

Rickets  is  but  rarely  found  as  a  direct  cause  of  death, 
but  its  harmfulness  if  reflected  in  increased  susceptibifity 
of  children  to  bronchitis  and  pneumonia,  and  in  the  difficulty 
of  childbearing  in  women  whose  pelves  have  been  deformed 
by  rickets  in  childhood.  Even  with  the  widespread  use  of 
cod  liver  oil  and  artificial  sunlight  to  correct  and  prevent 
the  rickets  of  infants  in  the  cities  of  the  United  States 
there  was  even  as  late  as  1920  a  ratio  of  1.75  cases  per  child 
population  in  cities  to  every  one  among  country  children. 

While  many  elements  go  to  make  up  the  causes  of  death 
from  bronchitis  and  pneumonia,  it  is  worth  noting  that 
in  the  registration  area  of  the  United  States  the  city 
rates  were  far  above  those  of  the  country  as  shown  in 
Table  vi. 

In  those  areas  of  our  cities  where  rickets  prevails  among 
children,  for  example  where  Negroes  and  Italians  live  in 
crowded  tenements,  the  death  rates  of  children  from  pneu- 
monia and  bronchitis  are  found  to  be  from  two  to  three 
times  as  high  as  in  the  rural  areas  of  the  same  latitude. 
The  same  races  that  exhibit  rickets  most  abundantly  in 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT       365 

Table  vi 
BRONCiirris  AND  pneumonia:  death  rates  i'ek   100,000  I'oi'iJLAiioN,    1910 

AND    1920 

(U.  S.  Registration  Area) 


1910 

1920 

Urban     Rural 

Urban 

Rura 

Acute  Bronchitis 

16.8 

10.7 

9-7 

SQ 

Broncho-pneumonia 

61.0  1     28.9 

69.9 

40.2 

Pnpiimonia              .       

no. 2 

80.6 

98.6 

66.8 

Total                

1 87 . 0      1 1 0 . 2 

178.2  1   1 12.0 

northern  congested  city  quarters,  where  sunhght  and  even 
sky-shine  is  difficult  to  get  for  many  months  in  the  year,  are 
entirely  free  from  rickets  in  southern  chmates  and  in  rural 


regions. 


Children  of  school  age  show  consistent  differences  in  the 
prevalence  of  acute  respiratory  tract  disease,  "colds  and 
coughs,"  which  betrays  one  of  the  apparent  and  perhaps 
temporary  superiorities  of  city  environment.  From  the 
studies  of  the  New  York  Ventilation  Commission  in  regard 
to  heating  and  ventilating  schools,  with  every  factor  con- 
trolled as  far  as  was  humanly  possible,  it  was  found  that 
the  acute  respiratory  disease  rate  among  children  of  rural 
Cattaraugus  County  resulted  in  an  absence  rate  of  23  per 
cent  of  possible  days  of  school  attendance,  while  among 
the  urban  children  of  Syracuse  this  absence  rate  was  9.9 
to  II. 7  per  cent  for  the  same  school  year  (1926-1927), 
with  the  experience  in  New  York  City  in  other  years  almost 
identical  with  that  of  Syracuse.  In  cities  the  inclemencies 
of  weather  are  much  less  of  a  hazard,  because  of  nearness 
of  the  child  to  school,  the  freedom  of  the  pavements  from 
snow,  slush  and  water,  and  the  quicker  drying  of  hard, 
drained  street  pavements.  Wet  feet,  wet  clothing,  long 
distance  in  wind  and  rain  and  snow  seem  to  have  been 
among  the  important  factors  to  the  disadvantage  of  country 
children,  all  of  which,  however,  are  nowadays  being  offset 
to  a  great  degree  by  the  concrete  or  hard  surfaced  country 


366  HUMAN   BIOLOGY 

highway,  and  automobile  transportation  between  home  and 
school. 

While  the  aesthetic  and  economic  dangers  of  a  city 
atmosphere  polluted  by  smoke,  dusts,  industrial  gases, 
fumes  and  odors  is  easily  determined  and  measured,  it  is  a 
matter  of  great  difficulty  to  prove  that  the  fouHng  of  the 
air  in  cities  is  the  direct  or  contributing  cause  of  important 
groups  of  sicknesses  and  deaths. 

Where  evergreen  trees,  vines,  shrubs  and  the  sturdy 
grasses  and  flowering  plants  cannot  survive  the  deposit  of 
tar,  ash,  sulphur  and  the  hmitation  of  sunhght  even  in  the 
open  yards  and  park  spaces  of  cities,  we  may  assume  that 
the  area  is  not  fit  for  the  human  child.  City  environment  as 
sketched  here  is  common  in  many  American  cities.  In  all 
such  city  quarters  we  find  the  poorest  paid,  least  intelhgent  or 
certainly  the  most  underprivileged  of  our  unskilled  laboring 
population  and  the  high  sickness  and  death  rates.  It  is 
impossible  to  be  sure  what  part  of  the  poor  hygiene  is 
properly  chargeable  to  the  bad  city-made  physical  environ- 
ment and  what  is  the  share  of  ignorance,  poverty,  foreign 
birth  and  unstable  economic  status. 

WATER    SUPPLIES 

From  the  point  of  view  of  our  present  study,  water 
represents  one  of  the  essential  contacts  between  man  and 
his  environment.  It  extends  the  range  of  the  environment 
and  makes  it  possible  for  an  adverse  condition,  such  as  a 
typhoid  case  or  carrier,  at  some  rural  point,  to  affect  the 
individual  or  a  large  part  of  the  population  in  a  distant 
city  community.  The  prime  essential  in  a  domestic  water 
supply  is  freedom  from  pathogenic  bacteria,  and  this 
in  general  means  freedom  from  human  pollution.  Typhoid 
fever  is  the  disease,  in  this  country  at  least,  most  frequently 
associated  with  polluted  water  and  the  typhoid  fever 
statistics  of  cities  before  and  after  they  have  undertaken 
the  purification  of  an  impure  water  supply  furnish  clear 
evidence  of  this  association.  In  the  city  of  Pittsburgh,  for 
example,  filtration  was  begun  in  1908,  although  portions 
of  the  city  continued  to  drink  unfiltered  river  water  for  the 
next  two  years.  The  typhoid  fever  death  rate  for  the  period 


THE    INFLUENCE    OF    URBAN    AND    RURAL    ENVIRONMENT       367 

1900-1908  averaged  133  per  100,000  population.  In  the 
period  1911-1915  the  average  rage  was  15.9.  For  comparison, 
Boston  showed  rates  of  16.0  and  8.0  for  the  five  year  periods 
before  and  after  19 10  without  change  in  its  fairly  satis- 
factory water  supply. 

At  Columbus,  Ohio,  the  typhoid  fever  death  rate  had 
averaged  over  'ji^  and  had  frequently  been  in  excess  of  100. 
The  filtration  plant  was  completed  in  the  fall  of  1908. 
The  two  years  following  showed  rates  of  20  and  18,  and 
during  the  next  five  years,  the  rates  averaged  15.8.  Similar 
instances  could  be  multiplied  to  almost  any  extent,  for 
in  the  whole  field  of  sanitary  science  there  is  no  clearer 
proof  of  the  adequacy  of  any  measure  taken  for  the  pro- 
tection of  the  public  health  than  is  to  be  found  in  the  reduc- 
tion of  typhoid  fever  through  water  purification. 

As  a  general  thing  the  water  supphes  of  cities  are  of  satis- 
factory quahty.  This  is  one  advantage  enjoyed  by  a  large, 
congested  population  over  a  smaller  one.  New  York  City, 
for  example,  has  been  compelled  by  the  gradually  increasing 
density  of  population  in  its  environs  to  extend  its  water 
supply  catchment  further  and  further  afield,  until  today  it 
reaches  into  the  Catskills  and  appropriates  water  at  a 
distance  of  135  miles  from  the  city.  The  sources  of  this 
water  are  carefully  protected  and  controlled;  it  is  submitted 
to  the  purifying  action  of  storage  in  great  reservoirs,  and  is 
protected  against  any  small  remaining  chance  of  pollution 
by  chlorination  at  several  points  in  the  system.  The  result 
is  a  water  supply  that  in  point  of  view  of  safety  and  general 
desirability  is  all  that  can  be  asked  for  and  is  excelled  by 
few  if  any  large  city  supplies. 

The  reason  this  amount  of  effort  can  be  expanded  to 
procure  a  satisfactory  water  supply  is  the  astonishingly  low 
per  capita  cost  to  the  city  dwellers.  The  cost  of  collecting, 
storing,  protecting,  purifying  and  conveying  from  the  moun- 
tains and  delivering  to  the  people  of  the  city  their  individual 
daily  allowance  of  a  hundred  and  thirty  gallons  of  a  safe, 
attractive,  palatable  water  is  about  three-quarters  of  a 
cent  a  day  in  New  York  City. 

The  smaller  town  supplies  are  proportionately  more 
expensive,  and  cannot  afford  the  same  degree  of  protection. 


368 


HUMAN    BIOLOGY 


The  difliculty  of  supervising  a  water  supply  and  of  supplying 
water  which  is  safeguarded  and  not  merely  passively  "safe" 
increases  with  diminishing  size  of  community,  and  reaches 
its  hmit  at  the  farm  well. 

A  modern  water  plant  for  the  farm,  including  adequate 
protection  of  the  well  and  a  pumping  outfit  with  storage 
tank,  will  cost  more  per  capita  than  the  New  York  City 
supply,  both  as  to  installation  and  for  operation  and  main- 
tenance. In  general  the  rural  supply  is  inadequately  pro- 
tected. On  the  other  hand  it  has  the  advantage  of  isolation. 
Many  dangerously  pollutable  wells  are  harmless  because  of 
the  absence  of  disease  among  the  immediate  members  of 
the  family. 

Both  the  typhoid  fever  and  dysentery  rates  confirm  the 
opinion  as  to  relative  safety  of  urban  and  rural  water  supplies 
in  the  United  States,  based  upon  sanitary  and  engineering 
information. 


Table  vii 
typhoid  fever  and  dysentery:  death  rates,  u.  s.   registration  area, 

I9IO-I92O 


1910 

1920 

Urban      Rural 

Urban 

Rural 

Typhoid  fever 

22.4        23.3 
4.4          8.3 

5-5 
1     2.0 

9.6 

Dysentery 

5-9 

The  typhoid  fever  death  rate  has  fallen  75  per  cent  in 
cities  during  the  ten  year  period  and  that  of  rural  popula- 
tions, 59  per  cent.  The  city  populations  have  an  advantage 
in  security  against  communicable  diseases  transmitted 
through  discharges  from  the  bowel,  because  they  have 
used  their  combined  resources  to  buy  engineering  skill  to 
dispose  of  human  wastes  in  a  sanitary  manner  and  for  the 
protection  of  their  communal  water  supplies.  It  has  been 
stated  that  nine-tenths  of  the  problem  of  rural  sanitation 
consists  in  protecting  the  water  supply  of  the  household 
from  pollution  by  its  own  human  wastes. 


THE    INFLUENCE    OF    URBAN   AND    RURAL    ENVIRONMENT      369 


FOODS 


Foods  are  properly  considered  from  the  sanitary  point 
of  view  a  factor  of  environment  only  less  immediately  or 
momentarily  essential  to  life  processes  than  water  and  air. 
Through  foods  our  contact  with  physical  environment  is 
most  widely  extended.  Entirely  apart  from  the  quality 
and  relative  proportions  of  the  essentials  of  human  nutri- 
ment expressed  in  protein,  fat,  carbohydrate,  salts  and 
vitamines  (discussed  in  Chap,  xiv)  there  are  in  the  processes 
of  production,  transport,  storage,  preparation  and  serving 
of  foods,  factors  in  the  cause  of  preventable  diseases  of  the 
communicable  and  nutritional  groups  affecting  in  different 
ways  and  to  different  degrees  urban  and  rural  residents. 

Variety,  range,  freshness  and  cost  of  foods  used  to  be  all 
to  the  advantage  of  the  country  family,  but  today  the 
control  of  food  supplies,  through  the  power  of  demand  by 
cities,  has  so  far  altered  the  situation  that  in  fact  even  the 
family  of  small  means  in  the  city  may  supply  its  nutritional 
needs  more  reliably  throughout  the  seasons  and  often  at 
less  expense  than  can  the  dweller  on  farm  or  in  rural  village. 

The  greater  buying  power  of  the  city  permits  a  degree  of 
supervision  over  the  sanitary  safety  of  foods  quite  impossible 
for  scattered  rural  households.  Today  the  city  dweller 
commands  a  range  of  foods,  of  higher  standard,  and  better 
guarded  against  the  hazards  of  contamination  by  disease 
than  does  the  rural  householder.  Federal  inspection  of 
meats  is  one  of  the  great  central  sanitary  services  which 
protects  city  food  consumers  to  a  degree  quite  lacking  for  those 
who  use  almost  entirely  locally  butchered  and  'distributed 
meats. 

Foods  from  all  parts  of  the  world  are  found  in  our  city 
markets,  those  from  even  distant  lands  being  delivered 
fresh  on  our  tables  by  virtue  of  the  superior  character  of 
ventilation,  chilling  and  speed  in  transportation,  while  the 
canning,  desiccation  and  cold  storage  of  foods  makes  it 
possible  to  have  all  the  year  round  diets  adapted  to  every 
reasonable  need  or  taste,  and  appropriate  to  age  and 
occupation. 

If  there  is  advantage  in  food  supplies  today,  it  probably 
lies  with  the  city  dweller,   particularly  during  the  winter 


370  HUMAN   BIOLOGY 

season,  but  certainly  unfavorable  distinctions  are  fast 
breaking  down. 

However,  in  regard  to  fluid  milk  and  fresh  milk  products, 
the  greater  hazard  of  the  distant  city  consumer  has 
demanded  a  degree  of  protection  which  has  so  far  not  been 
equally  available  in  the  regions  of  milk  production. 

The  milk  supply  of  cities  in  particular  required  and  has 
received  more  attention  from  the  health  authorities  than  any 
other  food.  Milk  has  long  been  recognized  as  a  possible 
cause  of  disease,  coming  directly  from  the  cow  (e.g.  bovine 
tuberculosis  and  streptococcus  sore  throat  where  this  is 
due  to  an  inflamed  udder  discharging  pus  in  the  milk)  or 
indirectly  from  the  handler  (e.g.  typhoid  fever,  diphtheria, 
septic  sore  throat,  when  this  is  due  to  sore  throat  in  the 
milker,  etc.),  and  has  in  fact  been  a  prohfic  source  of 
epidemics. 

Of  the  776  epidemic  outbreaks  of  disease  traced  to  milk 
in  the  United  States  in  recent  years,  as  reported  by  Armstrong 
and  Parran  of  the  United  States  Public  Health  Service, 
613  were  of  typhoid  fever,  7  of  paratyphoid,  6  of  dysentery 
and  diarrhea,  42  of  septic  sore  throat,  6^  of  scarlet  fever 
and  43  of  diphtheria.  Probably  only  a  low  percentage  of 
tuberculosis  in  humans  (less  than  5  per  cent)  is  due  to  the 
bovine  tuberculosis  conveyed  by  milk  or  its  products. 

By  pasteurization  and  central  bacteriological  control  of 
the  milk  supply,  cities  have  learned  to  protect  themselves 
against  the  hazards  of  disease  germs  introduced  into  the 
milk  during  its  production  or  distribution.  All  forms  of 
pathogens  'likely  to  be  found  in  milk  are  destroyed  at  a  tem- 
perature of  140°  in  twenty  minutes.  Commercial  pasteuriza- 
tion applies  this  treatment.  Because  of  numerous  possibilities 
of  milk  escaping  the  full  treatment  intended,  the  equipment 
must  be  carefully  designed  and  operated.  Legal  definitions 
of  pasteurization  differ.  New  York  City  requires  143°  for 
thirty  minutes.  At  about  145°  in  thirty  minutes  definite 
physical  change  begins,  the  fat  globules  become  dispersed 
and  cream  does  not  rise  as  completely.  At  higher  temper- 
atures a  more  definite  chemical  change  occurs. 

Pasteurization  is  little  practiced  in  the  country  and 
small  town.  Here  again  isolation  is  a  safeguard.  Suppose 


THE    INFLUENCE    OF    URBAN   AND    RURAL    ENVIRONMENT      37 1 

one  farmer  supplies  ten  families,  two  persons  only  handling 
the  milk.  Each  member  of  those  ten  famihes  is  exposed  to 
the  possibiHty  of  infection  from  two  persons.  But  if  fifty 
farmers  bring  milk  to  a  central  plant  where  it  is  mixed, 
stored  and  sent  out  to  500  famihes,  a  total  of  150  persons 
handhng  the  milk  at  various  stages,  the  exposure  of  each 
individual  user  to  a  possible  source  of  infection  is  now 
increased  seventy-five  fold,  and  a  large  outbreak  of  disease 
now  becomes  a  definite  possibility.  Nevertheless,  the  general 
use  of  unpasteurized  milk  in  the  rural  districts  is  doubtless 
one  of  the  factors  contributing  to  the  higher  rural  typhoid 
fever  and  dysentery  rates. 

A  secondary  result  of  the  higher  and  more  uniform 
standards  of  safety  of  the  milk  in  cities  is  the  increase  of  the 
per  capita  consumption  of  it  by  city  residents.  The  more 
rehable  the  city  milk  supply  the  more  does  it  enter  into 
the  dietaries  of  the  people,  and  the  city  dweller  is  approach- 
ing an  optimum  use  of  milk,  with  resultant  benefits  to  his 
health  and  economy  for  his  pocketbook. 

It  is  evident  from  study  of  the  prevailing  diseases  of  the 
Porto  Ricans  and  of  our  native  American  Indians  that  in 
spite  of  favorable  rural  environmental  factors  in  other 
respects,  they  are  suffering  severely  from  the  lack  of  milk, 
particularly  for  their  children. 

LIGHT 

Light  as  a  factor  of  environment,  quite  apart  from  the 
accompanying  effects  of  warmth,  or  radiation,  or  specific 
nutritional  effects,  bears  directly  upon  the  differences  of 
urban  and  rural  life,  the  dweller  in  towns  submitting  to 
physiological  disadvantages  from  the  use  of  articificial 
lights  to  which  the  human  eye  is  not  fully  adapted,  which 
the  rural  resident  does  not  have  to  suffer.  We  have  no 
information  which  can  carry  us  at  present  beyond  the  stage 
of  general  impression,  but  it  would  seem  that  the  artificial 
conditions  of  lighting  that  prevail  indoors,  in  transit,  in 
factory  and  office,  in  kitchen,  nursery  and  school,  in  church, 
theater  and  club,  in  cities  constitute  a  physiological  handicap 
to  the  function  of  vision  even  if  no  other  harmful  effect 
can  be  determined. 


372  HUMAN   BIOLOGY 

Progress  in  illumination  engineering  has  probably  reduced 
the  injury  to  the  clerk,  the  factory  operative,  the  student 
by  more  nearly  approaching  an  optimum  quality  and 
quantity  of  light  upon  the  near  object  or  throughout  the 
hail  and  shop,  so  that  a  tendency  towards  equahzation 
of  this  factor  as  a  selective  city  disadvantage  is  undoubtedly 
occurring. 

INSECTS 

One  further  environmental  factor  not  included  under 
the  term  social  or  human  relations  is  that  of  insects  which 
serve  as  a  means  of  transmitting  disease.  Cities  are  certainly 
at  present  favored  beyond  their  country  neighbors  in 
relative  freedom  from  the  fly  and  mosquito.  This  is  due  to 
the  reduction  in  the  number  of  horses  in  cities  following  the 
advent  of  motor  transportation,  to  the  great  pains  taken  to 
prevent  fly  breeding  in  and  about  stables  and  garbage  dumps, 
and  to  the  inevitable  destruction  of  mosquito  breeding  places, 
when  low  land  is  fifled  and  drained  in  the  process  of  reclama- 
tion for  housing,  parks  and  industry. 

The  urban  malaria  death  rate  in  1920  in  the  United 
States  was  0.9  per  100,000  population  and  the  rural  was  5.9. 

The  body  louse  and  the  rat  flea  are  potentially  greater 
hazards  in  cities  than  in  rural  regions  but  both  are  so 
readily  controlled  by  cleanliness  and  suitable  building 
construction  and  maintenance  for  the  exclusion  of  vermin 
that  we  may  properly  ignore  them  as  environmental  factors, 
at  least  in  the  United  States.  It  is  true,  of  course,  that  in 
many  rural  counties  of  California  and  adjacent  states 
the  distribution  of  the  flea  {X.  cheopsis)  by  the  ground  squirrel 
and  possibly  other  rodents  constitutes  a  rural  danger, 
and  it  is  recalled  that  typhus  fever  is  widely  reported  from 
small  town  and  rural  regions  of  Georgia  and  Alabama, 
pointing  to  some  still  undetermined  insect  conveyor  of 
disease  which  apparently  operates  as  well  in  small  as  in 
large  communities. 

PERSONAL   CONTACT 

Certainly  with  the  communicable  diseases,  particularly 
those    transmitted    by    discharges    through    the    nose    and 


THE    INFLUENCE   OF    URBAN   AND    RURAL   ENVIRONMENT      373 

throat,  a  chief  determining  factor  is  the  frequence  and 
intimacy  of  personal  contact,  especially  if  this  is  uncon- 
trollable, as  in  the  stores,  conveyances,  pubhc  streets, 
eating  places,  and  industries  of  many  cities.  From  the 
experience  of  the  United  States  it  would  appear  that  the 
acute  communicable  diseases  of  childhood  are  acquired 
earher  in  life  in  cities,  that  they  cause  a  higher  death  rate 
for  this  very  reason  among  children  and  that  adult  city 
populations  are  more  generally  immune  to  measles,  mumps 
diphtheria  and  scarlet  fever  than  are  country  people  of  the 
same  ages. 

It  has  been  noted  in  army  experience  in  many  countries, 
in  the  course  of  enhstment  for  obhgatory  routine  mihtary 
training,  and  in  the  emergency  of  mobihzationi  for  w^ar, 
that  young  men  from  the  cities  are  less  likely  to  develop 
the  acute  communicable  diseases  than  are  those  coming 
from  rural  regions.  Only  recently  has  the  science  of  immu- 
nology advanced  to  the  point  v^here  proof  of  immunity  can 
be  given,  in  tv^o  of  the  diseases  in  question,  i.e.,  diphtheria 
and  scarlet  fever,  and  it  is  found  that  the  prevalence  of 
immunity  to  these  diseases  is  greater  among  city  children 
than  in  rural  children  even  when  there  has  been  no  history 
of  attacks  of  the  diseases  in  question.  There  is  good  cir- 
cumstantial evidence  to  suggest  that  by  the  very  process 
of  widespread  exposure  to  those  contacts  through  which 
communicable  diseases  are  spread,  many  children  in  cities 
acquire,  possibly  through  unrecognized  mild  attacks  of 
infection  and  carrier  stages,  an  active  and  fairly  permanent, 
if  not  absolute,  immunity,  which  serves  as  an  important 
protection  to  them  earher  in  hfe  and  more  commonly  than 
to  children  relatively  isolated  in  rural  households  who  meet 
a  smaller  play  and  school  and  work  group.  In  other  words, 
there  are  some  compensations  in  the  form  of  immunity 
for  the  higher  death  rates  for  these  diseases  now  generally 
recorded  in  urban  communities. 

In  spite  of  our  inadequate  reporting  of  the  venereal 
diseases  and  the  uncertainty  as  to  certificate  of  deaths 
from  these  causes,  all  the  experience  with  both  white  and 
colored  populations  in  the  United  States  tends  to  show 
their  much  wider  prevalence  and  higher  mortahty  in  cities 


374 


HUMAN   BIOLOGY 


Table  viii 

measles,  scarlet  fever,  diphtheria  and  croup:  death  rates  per  100,000 
population,  u.  s.  registration  area 


1910 

1920 

Urban 

Rural 

Urban 

Rural 

Measles 

134 

II. 5 
8.2 

10.3 

5.4 

18.9 

34-6 

7.4 

Scarlet  fever 

14.2 

3-9 

Diphtheria  «&  croup 

25.8 

15.9 
35-6 

12. 1 

Comhined     

53-4 

22.4 

than  in  rural  regions.  The  mortality  rates  serve  as  a  prob- 
able rehable  index  of  the  degree  of  difference.  In  19 lo  the 
urban  rate  from  syphihs  was  7.3,  the  rural  3.0,  while  in 
1920  these  were  11.9  and  6.0  respectively.  Similarly  for 
gonococcus  infection  the  urban  rate  was  0.5,  the  rural 
o.i  in  1910,  and  1.2  and  0.4  respectively  in  1920.  Some  of 
the  difference  may  be  due  to  the  greater  proportion  of 
persons  of  the  earher  decades  of  life  in  the  cities. 

All  differences  in  the  mortahty  and  morbidity  of  city 
and  rural  populations  cannot  be  explained  on  the  bases  of 
risks  of  infection,  nor  yet  by  the  alternations  from  optimum 
in  the  factors  of  physical  environment.  The  marked  and 
consistently  higher  death  rates  from  diabetes  and  appen- 
dicitis in  cities  are  in  all  probabihty  related  to  the  manner 
of  Hfe,  with  superalimentation  and  the  decreasing  necessity 
for  bodily  exertion  in  the  ordinary  conduct  of  life  as  the 
major  causes. 

While  there  is  an  obvious  tendency  towards  a  similarity 
in  the  physical  equipment  of  life  and  labor  of  the  country 
and  city  households,  there  remains  the  fundamental  differ- 
ence between  the  closed  places  of  work  and  the  nature  of 
work  under  unfavorable  atmospheric  conditions  in  cities, 
and  the  outdoor  occupations  of  the  rural  family  which 
more  nearly  approach  a  favorable  biological  opportunity 
for  both  survival  and  development. 

There  is  no  controlled  mass  of  information  upon  the 
relative  frequency  of  mental  and  nervous  diseases  among 
city  and  rural  populations  except  in  the  matter  of  such 
advanced,  serious  or  terminal  conditions  as  are  of  necessity 


THE    INFLUENCE   OF    URBAN   AND   RURAL    ENVIRONMENT      375 

provided  for  in  state  hospitals  for  mental  disorders.  While 
to  persons  of  sensitive  and  intellectual  type,  Hving  in  the 
great  city,  the  hurly-burly,  racket,  turmoil  and  press  of 
persons,  the  constant  pressure  of  contacts  neither  sought 
nor  desired,  the  bombardment  upon  one's  sensations  through 
all  the  senses  of  strong  stimuli,  even  the  mere  physical 
presence  of  streams  of  fellow-beings,  the  necessary  rapidity 
of  reactions,  all  combine  to  cause  a  sort  of  spiritual  fatigue 
or  social  nausea,  probably  the  great  mass  of  people  are 
happier  when  going  along  in  a  crowd  than  when  self-reliance 
and  independence  are  required  and  where  lonehness  is  the 
one  great  horror  of  their  hves.  If  noise  and  crowding  were 
causes  of  disease,  boiler  makers,  pneumatic  drill  operators, 
traffic  police  and  motor  truck  drivers  should  provide  us 
with  abundance  of  chnical  material,  and  the  rate  of  mental 
and  nervous  disease  would  mount  rapidly  as  we  enter  the 
homes  on  metropohtan  thoroughfares  where  underground, 
surface  and  elevated  traffic  vie  with  each  other  in  one  great 
competitive  inferno  of  noise  and  smell,  speed  and  crowding. 

With  the  exception  of  those  mental  diseases  which  follow 
alcoholism  and  syphilitic  infection,  diseases  r,ecognized  as 
more  frequent  in  the  city  than  in  the  country  there  is  no 
evidence  in  the  admissions  to  state  mental  disease  hospitals 
that  the  city  offers  a  worse  environment  than  the  country. 
In  fact,  quite  the  reverse  conclusion  can  be  drawn  from  the 
reports  of  several  of  our  states.  Loneliness,  lack  of  recreation, 
the  drudgery  of  farm  and  housework,  the  monotony  of 
life  unrelieved  by  visitors  or  visits,  all  combine  to  create 
disorders  of  personality  and  eccentricities  of  character 
which  lead  to  such  extremes  of  conduct  as  to  call  for  medical 
protection  and  guidance  among  rural  families. 

Like  other  elements  of  his  most  complicated  and  elaborate 
being,  man's  mind  and  senses  are  apparently  more  apt  to 
remain  healthy  if  they  are  in  use  than  if  atrophy  or  stagna- 
tion are  permitted.  The  confirmed  city  dweller  may  suffer 
nervously  from  the  eternal  quiet  of  the  open  spaces,  as 
the  country  wife  may  find  her  head  confused  where  the  city 
noises  never  cease.  There  may  be  effects  of  noisy  hurried 
city  life  upon  heart,  digestion,  or  other  tissues  and  functions, 
so  obscure  that  we  cannot  detect  them  or  isolate  the  factors 


376  HUMAN   BIOLOGY 

of  human  crowd  or  noisy  street  as  in  any  way  causative 
of  the  premature  degenerations  or  decay  of  tissues  that 
we  rather  thoughtlessly  attribute  to  the  tension  of  city 
life  rather  than  admit  that  they  follow  perhaps  more  intimate 
and  personal  factors  of  individual  hygiene. 

Our  study  of  man  in  relation  to  the  environment  of  city 
and  country  is  directed  towards  the  structure  and  function 
of  his  organs  and  their  reactions  to  external  stimuh.  We 
see  him  adapting  himself  with  remarkable  success  to  a  wide 
variety  of  physical  and  emotional  environments.  We  express 
the  lag  in  his  adjustment  to  the  artificiahty  of  the  city  by 
increased  death  rates  from  many  causes,  some  of  which" 
we  know  to  be  preventable  and  to  be  related  to  man-made 
conditions. 

The  conditions  of  hfe,  particularly  in  cities,  have  been 
changing  with  increasing  rapidity  during  the  recent  decades 
in  which  the  shift  of  population  has  also  been  strongly  to 
cities.  Our  problem  as  socially  organized  units,  our  communal 
difficulty,  is  so  to  modify  the  results  of  our  human  aggrega- 
tion that  we  shall  approach  most  nearly  the  condition  of 
safety  for  hfe  which  we  find  still  in  greater  measure  in  the 
country. 

Man's  mastery  of  his  environment  is  one  of  his  distinc- 
tions from  the  brute,  which  can  adjust  to  but  not  control 
its  surroundings.  There  seems  to  be  no  reason  to  doubt 
that  the  will  to  maintain  unpolluted  air,  suitable  hght, 
water  and  food  can  be  expressed  almost  as  effectively  in 
the  city  as  in  the  country.* 

Man  will  remain  his  own  greatest  hazard  in  the  cities, 
partly  from  the  diseases  he  spreads  and  knows  not  how  to 
control,  partly  from  his  ambition  in  the  satisfaction  of 
which,  as  expressed  in  wealth,  luxury  and  power,  he  deprives 
his  fellows  of  some  of  the  indispensable  quaHties  of  environ- 
ment. While  the  spirit  and  urge  is  upon  man  to  seize  and 
enjoy  those  quahties  and  substances  of  Hfe  which,  he  beheves, 
are  found  only  in  the  city,  he  will  make  sacrifices  of  his 
health  and  that  of  his  children  to  acquire  them.  He  will 
demand  from  the  sciences  and  arts  every  possible  adjustment 
which  will  bring  him  in  the  city  the  guarantees  of  survival 
which  nature  has  abundantly  provided  in  the  open  spaces. 


THE    INFLUENCE    OF    URBAN   AND   RURAL    ENVIRONMENT      377 

When  speed,  and  change  and  power  over  material  things 
seem  less  valuable  than  those  quahties  and  properties  of 
life  which  man  holds  always  within  himself,  regardless  of 
his  place  of  residence,  we  shall  see,  or  our  inheritors  will, 
a  redistribution  of  people  where  less  effort  will  go  to  the 
creation  of  a  safe  environment  by  artifice,  in  an  intimate 
and  abundant  contact  with  the  invigorating  reahties  of 
outdoors. 

CONCLUSIONS 

Apparently  we  pay  and  pay  heavily  in  terms  of  loss  of 
Hfe  for  our  inchnation  or  rather  determination  to  live  in 
increasing  numbers  in  cities.  We  have  been  for  at  least  fifty 
years  reducing  the  discrepancy  between  rural  and  urban 
death  rates.  Whether  we  shall  ourselves  be  so  modified  or 
adapted  that  we  can  tolerate  or  survive,  on  equal  terms  with 
our  country  cousins,  the  conditions  so  far  inherent  in  city 
environment,  or  whether  we  shall  so  alter  and  command  the 
contacts  and  physical  setting  of  our  urban  life  that  these 
no  longer  constitute  a  handicap,  only  the  future  can  tell. 
But  as  long  as  the  rush  of  people  cityward  continues,  social 
and  medical  science  will  be  concerned  with  watching  end 
results  and  trends,  with  analyzing  material,  social  and 
psychical  elements  of  city  hfe,  until  man  can  be  sure  of 
control  of  his  environment  regardless  of  place  and  association 
with  his  fellows,  so  that  there  may  be  no  hindrance  or  limit 
to  his  choice  of  place  or  manner  of  life  in  seeking  to  satisfy 
his  reasonable  ambition  to  live  to  the  limits  of  his  inherited 
capacities. 

The  city  dweller  is  in  the  majority.  He  will  command  and 
perhaps  dominate  as  fanatically  as  the  farmer  often  has 
ruled  the  city  in  the  past.  After  the  city  dweller  has  learned 
to  bend  material  things  to  his  wishes  with  entire  safety 
and  to  accommodate  his  body  and  life  to  the  pressing  throngs 
about  him  in  street  and  store  and  factory,  he  will  still  require 
in  all  probability  to  make  and  keep  contact  with  the 
elements,  a  relation  which  no  amount  of  associations  with 
similar  men  can  replace.  He  will  always  need  the  sweetening 
influence  of  the  uncontrollable  sun  and  wind  and  rain  which 


378  HUMAN   BIOLOGY 

he  has  been  at  such  pains  to  ward  off  and  hmit  In  his  urban 
hfe. 

REFERENCES 

Arnold,  L.  1927.  Diarrhea  in  infants.  Arab.  Pediat.,  44:  71. 

Bailey,  L.  H.  1925.  Standard  Cyclopedia  of  Horticulture.  N.  Y.,  Macmillan. 

Chapin,  C.  V.  191 2.  Sources  and  Modes  of  Infections.  N.  Y.,  Wiley. 

De  Porte,  M.  V.  1928.  Recorded  and  resident  death  rates  from  tuberculosis 

in  New  York  State,  1926.  Am.  Rev.  Tuberc,  17:  634-662. 
DoANE,  R.  W.  1910.  Insects  and  Disease.  N.  Y.,  Holt. 
Dublin,  L.  I.  1928.  Health  and  Wealth.  N.  Y.,  Harper. 

Gruenberg,  B.  C.  1926.  Modern  Science  and  People's  Health.  N.  Y.,  Norton. 
Hazen,  a.  1914.  Pure  Water  and  How  to  Get  It.  N.  Y.,  Wiley. 
McCoLLUM,  T.  1925.  TIae  Newer  Knowledge  of  Nutrition.  N.  Y.,  Macmillan. 
Newsholme,  Sir  A.  1923.  Vital  Statistics.  N.  Y.,  Appleton. 
Phelps,  E.  B.  1925.  Public  Health  Engineering.  N.  Y.,  Macmillan. 
Weber,  A.  F.  1899.  The  Growth  of  Cities.  N.  Y.,  Macmillan. 
Winslow,  C.  E.  a.  1926.  Fresh  Air  and  Ventilation.  N.  Y.,  Dutton. 


Chapter  XVI 

ANTISOCIAL  BEHAVIOR: 
DELINQUENCY  AND  CRIME 

William  Healy 

IT  is  not  possible  to  discuss  scientifically  antisocial 
behavior,  such  as  crime  and  delinquency,  according 
to  the  ordinary  terms  of  social  facts.  What  do  we  mean 
when  we  speak  of  crime,  delinquency,  criminal,  delinquent? 
For  the  sake  of  sound  generalizations  there  is  very  great 
need  of  good  definitions  and  discriminations  in  this  field. 

It  seems  to  be  taken  for  granted  by  most  writers  that 
crime  is  behavior  easily  differentiated  and  quite  set  apart 
from  all  other  conduct,  so  much  so  that  very  few  have 
conceived  that  there  is  any  necessity  for  defining  it.  But 
some  do  pay  attention  to  this  point,  notably  Garafalo,  the 
jurist  and  criminologist.  He  cites  many  instances  of  laws 
making  crimes  of  behavior  which  at  other  periods  and 
under  other  circumstances  has  not  been  considered  crime. 
To  kill  during  a  war  is  not  criminal,  and  yet  killing  at 
other  times,  perhaps  from  much  the  same  motives,  is  a 
crime.  In  one  place  bribery  is  hardly  an  off'ense;  in  another 
country  it  is  a  serious  one. 

Garafalo  calls  for  understanding  of  what  constitutes  a 
real  or  "natural"  crime;  behavior  that  would  be  recognized 
anywhere  and  among  all  peoples  as  really  crime,  which,  as 
such,  may  be  contrasted  with  legal  or  made  crime.  Real 
or  "natural"  crime  is  a  violation  of  the  fundamental  altruistic 
sentiments,  namely,  those  of  pity  and  probity,  in  the  average 
measure  in  which  they  occur  in  civilized  humanity.  How- 
ever, as  Ferri  suggests,  it  should  be  remembered  that  social 
sentiments  have  changed  during  the  ages;  they  have  been 
and  are  being  evolved,  together  with  alterations  in  social 
conditions.  Colajanni  very  well  says  that  punishable  acts 
are  those  which,  determined  by  individual  and  antisocial 
motives,  disturb  the  conditions  of  existence  and  shock 
the  average  morality  of  a  given  people  at  a  given  moment. 

379 


380  HUMAN    BIOLOGY 

The  ordinary  dictionary  definitions  of  crime  are:  "An 
omission  of  a  duty  commanded,  or  the  commission  of  an 
act  forbidden,  by  pubHc  law."  "Gross  violation  of  human 
law — in  distinction  from  a  misdemeanor  or  trespass  or  other 
shght  offense."  Procedure  under  the  criminal  law  generally 
makes  no  attempt  to  define  crime,  but  the  New  York  Penal 
Code  says  that  a  crime  is  an  act  or  omission  forbidden  by 
law  and  punishable  by  death,  imprisonment,  fine,  or  removal 
from  office.  Delinquency,  as  the  term  is  used  in  America, 
means  offense  against  the  law  committed  by  an  individual 
of  juvenile  court  age,  up  to  seventeen  or  eighteen  years  in 
most  states. 

One  of  the  most  important  points  for  consideration  by 
those  who  study  delinquents  and  criminals  scientificially 
for  the  purpose  of  correlating  physical  or  mental  peculiarities 
with  special  conduct  proclivities  is  that  criminals,  after 
all,  are  only  the  caught  and  convicted  offenders  against  the 
law.  Who  or  what  are  those  who  commit  crime  and  remain 
for  long  or  even  permanently  undetected,  hence  figuring 
very  little  or  not  at  all  in  any  studies  of  persons  rated  as 
criminals?  Some  suggestion  of  what  the  answer  to  this 
might  be  is  in  the  following:  I  remember  once  in  the  Juvenile 
Court  of  Chicago  a  mentally  defective  boy  appeared  in 
court  for  the  third  or  fourth  time,  having  been  readily 
apprehended  each  time  after  a  minor  burglary  in  his  neigh- 
borhood. Next  came  two  active  high  school  boys  who 
together  had  perpetrated  some  fifty  or  sixty  burglaries  or 
larcenies  without  apprehension.  They  had  hugely  enjoyed 
their  adventures;  their  stories  were  corroborated  by  dis- 
covered loot. 

Then,  next,  for  the  sake  of  more  fundamental  considera- 
tions in  the  science  of  human  nature,  it  is  worth  everything 
steadily  to  insist  on  the  very  plain  fact  that,  compared  to 
crime,  much  that  is  not  rated  as  crime  is  as  injurious,  or 
even  more  injurious,  and  bespeaks  as  much  deviation  from 
the  ideals  of  social  welfare.  Those  who  have  to  deal  with 
the  problems  of  family  life  come  to  know  of  many  cases  of 
frightful  misbehavior  that  are  not  punished  and  that  are 
hardly  punishable  under  the  law.  Cruel  dominations  and 
frictions  in  the  family  that  bring  about  great  unhappiness, 


ANTISOCIAL   behavior:    DELINQUENCY    AND    CRIME  38 1 

resulting  in  life  failures  and  in  mental  upsets,  are  some 
examples  of  what  I  mean.  Or  injuries  done  to  one's  fellow 
beings  in  more  public  ways  often  represent  behavior  that  is 
worse  than  crime.  We  may  remember  Shakespeare's  "He 
that  robs  me  of  my  good  name"  as  a  case  in  point. 

This  is  a  matter  of  vast  importance  if  we  are  really  to 
get  at  the  relationship  of  antisocial  conduct  to  biological 
conditionings.  Injurious  to  the  person  and  rights  of  others  is, 
for  example,  the  action  of  the  landlord  who  maintains 
premises  conducive  to  immorality  and  ill-health,  or  the 
attitude  of  employers  who  have  such  wage  scales  that 
decent  standards  of  living  cannot  be  upheld  by  their 
employees.  Then  what  witness  we  could  give,  from  hundreds 
of  case  histories,  to  the  harm  done  by  extreme  moral  neglect 
of  young  boys  and  girls,  or  by  pernicious  teachings,  resulting 
not  only  in  sex  misconduct  but  also  in  other  forms  of  delin- 
quency, the  real  offender  not  being  convicted  or  perhaps 
convictable  by  legal  process.  Or  to  go  to  history  for  rep- 
resentative examples  of  terrible  misconduct  to  be  contrasted 
to  legal  crime,  what  a  huge  material  is  available,  ranging  from 
the  kiss  of  Judas  to  the  wholesale  slaughterings  of  Napoleon. 

It  becomes  plain  enough  that  the  portrayal  of  the  causes 
in  human  nature  of  tendencies  towards  antisocial  conduct, 
one  artificially  differentiated  variety  of  which  is  called 
crime,  must  be  undertaken  upon  a  much  larger  canvas  if 
the  true  perspectives  and  backgrounds  of  antisocial  conduct 
are  to  be  shown. 

In  considering  statements  of  what  criminals  are  in  terms 
of  human  nature,  it  is  an  important  point  to  remember  the 
differences  in  the  laws  and  in  the  facilities  for  detection 
and  apprehension  of  offenders  in  various  countries,  and 
even  in  different  parts  of  our  own  country.  It  appears  highly 
probable  that  the  undetected  and  unapprehended  may 
represent  in  average  make-up  a  very  different  group  from 
those  who  relatively  easily  fall  into  the  toils  of  the  law. 
There  are  a  hundred  ways  in  which  we  might  suggest  possible 
differences;  a  very  picturesque  comment  on  the  whole 
problem  is  afforded  by  the  immediate  situation  in  this 
country  with  regard  to  murder.  Apropos  of  the  recent  so- 
called  gangster   murders,   we  are   informed   by  the   press. 


382  HUMAN   BIOLOGY 

probably  with  some  approach  to  correctness,  that  in  the 
last  two  years  there  have  been  over  two  hundred  such 
murders  in  Chicago  alone,  with  almost  none  of  the  murderers 
brought  to  trial.  While  this  is  an  outstanding  example  of 
the  main  point  we  have  in  mind,  in  regard  to  less  lurid 
offenses  almost  equally  baffling  conditions  confront  one 
who  would  generalize  about  human  nature  as  related  to 
criminahstic  behavior. 


CRIMINOLOGICAL    THEORIES 

For  our  own  orientation,  some  mention  of  older  concep- 
tions of  criminology  will  be  advantageous.  Any  outlining 
of  the  various  ideas  that  have  been  held  in  this  field  leads 
to  the  realization  that  they,  all  of  them,  are  bare  theories. 
Even  the  concepts  of  the  law,  based  though  they  are  upon 
"the  accumulation  of  human  wisdom  during  the  centuries" 
are  but  theories  concerning  the  fitness  of  certain  punish- 
ments and  the  eff'ectiveness  of  deterrency  and  reformation. 
It  shows  that  only  the  first  beginnings  of  the  application  of 
scientific  method,  of  experiment  and  the  observation  of 
results,  are  as  yet  discernible  in  the  treatment  of  criminals. 

Until  some  fifty  years  ago  the  generally  held  notion  in 
regard  to  crime  was  that  it  always  results  from  a  fiat  of 
the  individual's  free  will.  Nothing  further  was  needed  by 
way  of  essential  explanation,  nothing  pertaining  to  specific 
biological  or  sociological  features  concerning  the  individual 
or  his  environment.  The  latter  part  of  the  last  century 
witnessed  the  rise  of  the  biological  and  sociological  schools 
of  criminology,  captained  respectively  by  Lombroso  and 
Ferri.  They  and  their  followers  constituted  the  Positivist 
or  Italian  school  of  criminology,  as  set  over  against  the 
earlier  classical  school  whose  tenets  have  been  mentioned. 
Enrico  Ferri  drew  up  the  following  orienting  diagram  of 
theories: 

Crime  is  a  phenomenon  of  either: 

A.  Normality:  biological  or  social 

B.  Biological  abnormality: 

(a)  Atavistic:  organic  plus  psychic,  or  psychic 

(b)  Pathological:  neurosis,  neurasthenia,  or  epilepsy 


ANTISOCIAL   behavior:    DELINQUENCY    AND    CRIME  383 

(c)  Degeneracy 

(d)  Defect  of  nutrition  of  the  central  nervous  system 

(e)  Defect  of  development  of  the  inhibitive  centers 

(f)  Moral  anomaly 
c.   Social  abnormality: 

(a)  Economic  influences 

(b)  Juridicial  inadaptability 

(c)  Complex  social  influences 
D.  Biologicosocial  abnormality. 

The  scholarship  of  this  diagram  is  substantiated  by  the 
citation  of  some  forty  authorities.  Ferri  himself  is  the  pro- 
ponent of  the  biologicosocial  abnormahty  theory  which 
holds  that  the  criminal  tendency  is  conditioned  by  elements 
in  both  the  individual  and  his  environment. 

From  our  present-day  standpoint,  we  reahze  that  the 
anthropological  observations  upon  which  earher  theories 
are  founded  represent  not  only  merely  caught  off"enders  but 
very  partial  studies  of  human  individuals.  The  mental  Hfe, 
as  it  is  viewed  by  modern  psychiatry  and  psychology,  was 
almost  entirely  neglected.  The  work  of  Lombroso  and  his 
adherents,  for  example,  with  their  discriminations  and 
measurements  of  the  physical  structure,  and  particularly 
of  physical  anomalies,  represents  one  pole  of  investigaton. 
To  my  thinking  the  greatest  weakness  of  their  findings  is  in 
lack  of  any  correlations  of  such  physical  findings  with  the 
study  of  mental  capacities.  It  seems  very  likely  that  the 
Lombrosians  were  often  dealing  with  essentially  feeble- 
minded individuals,  who,  because  of  certain  social  circum- 
stances, became  criminals.  This  might  account  for  the 
well-recognized  difference  between  their  findings  and  those 
in  other  countries  where  mental  defectives  have  from  early 
life  been  taken  care  of  in  institutions.  As  representing  the 
opposite  pole  of  investigatory  method,  we  might  take  the 
recent  studies  of  Bjerre,  the  Swedish  lawyer,  who  constructs 
pictures  of  the  motives  and  characteristics  of  criminals 
through  prolonged  and  repeated  interviews  with  them  in 
prison,  an  intensive  piece  of  interpretive  work  with  little 
attention  to  the  theoretical  consideration  of  the  schools  of 
criminology. 


384  HUMAN    BIOLOGY 

THE    PLACE    OF    SCIENCE    IN    THIS    FIELD 

It  is  certainly  pertinent,  after  this  cursory  review  of 
theoretical  criminology,  to  ask  by  what  right,  or  for  what 
reason,  science  invades  this  field.  At  least  one  may  inquire 
why  the  biological  or  psychological  sciences  should  play 
any  part  in  the  study  of  treatment  of  offenders  against 
society.  It  will  readily  be  granted  that  sociology  is  involved; 
indeed,  the  law  itself  as  social  regulation  belongs  to  the 
data  of  sociology.  Or  put  it  otherwise,  why  not  leave  the 
whole  matter  of  dealing  with  antisocial  conduct,  particularly 
crime,  to  the  law  and,  in  order  to  meet  the  needs  of  society, 
call  for  a  finer  development  of  legal  procedure? 

One  answer  to  this  is  that  individuals  showing  certain 
deviations  from  the  norm,  such  as  mental  defect,  nervous 
disease,  or  mental  instability,  more  easily  succumb  to 
influences  conducive  to  antisocial  behavior  than  the  ordinary 
run  of  mankind.  There  are,  then,  some  definite  correlations 
between  what  biological  science  can  discern  and  the  exhibi- 
tion of  specific  conduct  tendencies,  making  for  some  pre- 
dictabilities which  may  be  the  bases  of  good  social 
therapeutics  and  prophylaxis. 

A  second  answer  might  be  that  the  law,  in  undertaking 
measures  for  the  protection  of  society,  is  provably  a  very 
considerable  failure  in  what  it  essays  to  accomplish.  If  it 
be  argued,  in  turn,  that  it  is  only  the  modern  and  more 
humanitarian  law  and  the  weakness  of  modern  judges  that 
prevents  the  law  from  being  successful,  we  have  only  to 
consult  the  annals  of  history  and  find  that  the  harshness  of  a 
Lord  Jeffries,  or  hangings  for  sheep  steahng,  or  lopping  off" 
ears  and  hands,  by  no  means  stamped  out  crime.  Statistics 
of  recidivism  (repetition  of  offense  after  the  law  has  dealt 
with  the  individual),  wherever  they  are  available,  show  that 
penalties  inflicted  by  the  law  are,  very  commonly,  no  effec- 
tive deterrent  to  criminal  proclivities  on  the  part  of  the 
offender  punished.  Few  figures  are  available  for  the  United 
States  because  of  the  backwardness  of  any  attempt  on  our 
part  to  look  with  scientific  spirit  into  what  is  accomplished 
with  criminals,  but  it  is  well  known  that  the  amount  of 
recidivism  is  appalling;  a  tremendous  number  of  those  who 
are  punished  have  been  punished  before.  An  English  jurist, 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  385 

Justice  Rhodes,  some  twenty  years  ago  turned  to  the 
medical  profession  in  an  article  in  the  British  Medicaid ournal 
and  asked  whether  this  deahng  with  offenders  was,  after 
all,  altogether  a  job  for  the  law.  Do  not  the  facts  of  recidivism 
prove  that  it  is  for  scientists  to  cure  criminal  propensities? 
He  quoted  Enghsh  criminal  statistics,  showing  that  in  an 
ordinary  year  upwards  of  10,000  of  those  convicted  had 
been  previously  convicted  more  than  twenty  times  each, 

SIZE    AND    COST    OF   THE    CRIME    PROBLEM 

And  perhaps  another  reason  why  scientists  should  be 
interested  in  crime  is  the  enormous  size  of  it  as  an 
unanswered  problem  in  our  civihzation,  especially  in  our 
modern  American  hfe. 

If  we  reckon  costs  in  terms  of  money  the  Missouri  Crime 
Survey  is  worth  considering,  a  careful  piece  of  work  showing 
that  the  bill  for  crime  in  that  state  is  about  $100,000,000 
a  year,  and  Missouri  is  probably  fairly  representative,  not 
much  better  or  worse  than  other  states.  Mr.  Prentiss  of  the 
National  Crime  Commission  estimates  the  direct  cost  of 
law  enforcement  alone  at  $4,000,000,000  a  year  in  the 
United  States.  If  we  need  to  say  anything  more  about  the 
cost  of  actual  crime,  we  could  generahze  and  state  that  in 
times  of  peace  the  greatest  pubhc  expense,  next  to  that  of 
education,  is  by  far  that  of  combating  crime,  and  this  cost 
does  not  take  into  account  the  various  big  losses  sustained 
through  crime. 

Notwithstanding  the  enormous  number  of  criminals  who 
are  not  apprehended  or  convicted,  over  ^o  oi  i  per  cent 
of  the  population  of  this  country  at  any  given  time  is  under 
commitment  for  dehnquency  and  crime.  That  certain  crimes 
form  almost  a  national  pastime  with  us  is  shown  by  such 
proportionate  figures  as  the  following:  During  19 19  in  St. 
Louis  there  were  1087  highway  robberies,  and  in  Chicago 
1862  were  recorded.  In  the  whole  of  France  that  year,  it 
is  said  there  were  but  29  such  robberies.  Homicides  with  us 
have  been  statistically  treated  by  Hoffman  who  shows 
their  enormous  relative  occurrence,  not  only  in  Chicago, 
which  figures  so  greatly  in  our  newspapers  as  a  center  of 


386  HUMAN   BIOLOGY 

crime,  but  also  in  other  American  cities,  some  of  which 
show  greater  proportionate  figures.  The  average  of  28 
American  cities  for  a  number  of  years  showed  about  9  homi- 
cides per  100,000  inhabitants,  while  in  England  there  were 
only  0.7.  Prentiss  calculates  that  12,500  persons  were 
murdered  in  1926;  he  estimates  that  there  are  2,000,000 
criminals  in  this  country;  he  states  that  the  pohce  and  other 
law  enforcing  bodies  employ  400,000  persons. 

Our  daily  reading  makes  it  rather  banal,  perhaps,  to  offer 
the  observation  that  the  amount  of  space  given  to  crime 
in  the  newspapers  proves  the  extent  of  crime.  Parenthetically 
one  might  speak  of  the  definite  advertisement  of  crime  and 
the  fact  that  it  has  no  mean  value  for  newsgatherers. 

NATIONAL   COMPARISONS 

The  well-known  fact  that  in  several  European  countries  the 
crime  problem  is  vastly  less  in  proportion  than  with  us  in 
America  requires  for  its  explanation  much  more  than  is 
usually  offered.  Those  who  propose  remedies  for  our  crime 
troubles  usually  cite  some  one  possible  cause,  in  line  with 
their  own  interests  or  views,  as  explanatory  of  the  better 
conditions  in  several  of  the  older  countries.  But  the  fact  is 
that  everywhere  the  social  background  involves  complexities 
that  have  to  be  taken  into  account  when  considering  the 
incidence  of  any  social  problem  or  the  results  of  dealing  with 
it.  For  example,  legalists  are  prone  to  attribute  the  relative 
lesser  amount  of  crime  in  England  to  the  swiftness  with 
which  offenders  are  brought  to  trial  and  disposed  of.  While 
we  have  no  doubt  that  this  is  one  factor,  certain  other 
immensely  important  considerations  are  forgotten  in  any 
such  reasoning.  The  total  situation  is  entirely  different 
from  ours  because  of  such  conditions,  among  many  variations 
from  our  national  circumstances,  as  the  following:  Vastly 
greater  homogeneity  of  population;  politics  playing  no  part 
in  most  appointments,  whether  of  judges  or  other  ofTicials 
dealing  with  offenders,  the  police  and  indeed  whole  city 
administrations  being  free  from  politics;  the  national 
government  representing  an  integrated  regime  so  that  laws 
concerning  crime  are  the  same  for  the  entire  country  and 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  387 

there  is  a  centralized  effort  to  know  and  deal  with  crime  and 
criminals,  identification  of  criminals  being  vastly  easier 
on  account  of  this;  the  temper  of  the  people  in  general  being 
totally  different  with  regard  to  its  feehng  about  law  breaking, 
a  more  subtle  but  a  most  important  factor.  Or  if  we  take 
Germany,  another  country  where  crime  is  much  less  a  prob- 
lem than  with  us,  we  have  conditions  similar  to  those  of 
England,  plus  such  facts  as  the  universal  registration  of 
population  and  the  development  of  a  specially  well-trained 
poHce  force. 

From  the  foregoing,  it  should  be  clear  that  our  own 
national  situation  with  regard  to  crime  and  dehnquency  is 
sui  generis,  and  that  the  extent  of  crime  with  us  can  be 
accounted  for  by  some  conditions  and  sets  of  conditions 
that  are  conceivably  modifiable  and  by  some  that  are 
not.  As  a  matter  of  social  environment,  we  might  think 
of  our  present  immense  handicap  of  politics  as  in  so  many 
places  it  permeates  the  field  of  dealing  with  crime,  and 
consider  whether  or  not  this  might  be  changed.  And  then 
the  facts  that  our  judges  are  so  untrained  in  criminalistics, 
that  there  are  great  weaknesses  in  our  police  systems,  that 
there  is  so  much  ineffective,  half-spirited  and  uninstructed 
parole  and  probation  work  which  should  be  constructive 
and  preventive,  that  there  exist  miserable  moral  contagions 
in  prison  life — these  are  to  be  pondered  over.  Are  they 
alterable,  if  a  different  spirit  were  breathed  into  our  national 
combat  against  crime? 

But  on  the  other  hand,  we  cannot  change  the  fact  of  the 
newness  of  our  civilization,  nor  immediately  modify  traits 
and  habits  of  the  various  races  and  nationalities  that  make 
up  our  population,  traits  and  habits  that  among  a  mixed 
people  so  readily  engender  antisocial  behavior,  nor  can  we 
easily  diminish  the  spirit  of  restlessness  and  recklessness  that  is 
inevitable  in  a  fast  growing  country,  so  rich  in  its  resources 
that  many  opportunities  are  given  for  changing  occupations 
and  moving  about.  Then  the  size  of  our  country  is  an 
unescapable  circumstance,  bearing  on  the  crime  problem, 
especially  in  this  age  of  rapid  transportation  and  easy 
chance  for  flight,  in  most  important  ways.  The  independence 
of  our  separate  states  in  dealing  with  crime  and  criminals 


388  HUMAN   BIOLOGY 

is  another  cause  for  the  extent  of  crime,  which,  very  plainly, 
at  least  through  national  registration  and  identification, 
must  be  met  by  centralized  federal  effort. 

The  facts  of  criminology,  even  those  belonging  to  biology 
and  psychology,  certainly  include  environmental  conditions 
as  they  exist  in  any  particular  community.  Crime  is  conduct- 
reaction  of  a  given  person  to  a  given  environment.  The  crime 
problem,  whether  of  any  individual  or  of  a  statistical 
series,  includes  variables  of  personality  and  environment. 
In  etiological  studies,  the  latter,  as  well  as  the  former,  is 
bound  to  have  its  place. 

Indeed  this  is  so  true  that  the  influences  which  make  for 
crime  in  one  city  and  state  may  be  found  to  be  utterly 
unlike  those  in  another  part  of  the  country,  and  differences 
of  racial  origins  may  be  insufficient  to  account  for  this. 
In  our  own  comparative  studies  of  Chicago  and  Boston 
offenders  we  discovered  most  notable  contrasts  in  crime 
tendencies,  even  among  peoples  of  the  same  racial  standards, 
such  as  the  southern  Italians.  Concerning,  for  example, 
these  Italians,  in  Boston  there  is  the  comparatively  stabili- 
zing influence  of  police  and  court  work  almost  entirely  free 
from  politics,  and  much  social  effort  of  other  sorts.  This 
is  challenging  in  its  results  and  may  be  compared  to  what 
has  so  unfortunately  met  the  same  type  of  immigrants 
and  their  children  in  the  other  city. 

With  many  things  similar  in  two  communities,  there  are, 
nevertheless,  great  possible  differences  in  influences  in  the 
same  country  and  under  the  same  laws.  By  investigating 
the  after-careers  of  420  boys,  repeated  offenders,  handled 
in  the  Juvenile  Court  of  Chicago,  it  was  ascertained  that 
no  less  than  209  of  them  were  in  court  as  adult  offenders  for 
the  more  serious  offenses,  and  157  were  committed  to  adult 
penal  institutions;  at  least  13  (possibly  16)  of  these  became 
murderers,  and  3Q  are  known  habitual  or  professional 
criminals.  Coming  to  the  Juvenile  Court  of  Boston  during 
the  same  years  were  400  young  repeated  offenders  who 
produced  only  84  appearing  in  the  adult  court  and  with 
offenses  relatively  so  minor  that  only  25  were  sent  to  adult 
penal  institutions;  there  were  no  murderers,  and  almost 
none  became  habitual  criminals. 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  389 

These  are  facts  which  must  make  us  for  some  of  the 
explanations  of  crime  turn  from  theoretical  considerations, 
whether  of  the  schools  of  criminology  or  of  the  legahsts,  to 
these  very  practical  issues  which  confront  our  civihzation. 
Some  of  the  causations  he  right  in  the  spirit  of  the  com- 
munities themselves,  as  exemphfied  by  their  patterns  of 
pohtical  and  other  community  behavior,  and  in  the  different 
modes  of  treatment  of  offenders.  The  social  environment  is  a 
very  large  part  of  the  story  of  crime. 

LAW   VERSUS    SCIENCE    IN    TREATMENT    OF    CRIME 

The  lack  of  understanding  between  science  and  the  law 
with  regard  to  the  knowledge  of  and  treatment  of  the  prob- 
lems of  crime  has  not  been  very  favorable  to  the  develop- 
ment of  any  satisfactory  haison  between  the  two.  Jurists 
and  other  legally  trained  people,  so  far,  have  shown  but 
shght  awakening  to  the  possibility  of  the  apphcation  of 
scientific  method  to  the  great  task  of  protecting  society 
from  criminahsm.  Indeed,  one  can  fairly  say  that  there 
has  not  been  the  introduction  of  even  any  business-hke 
methods  of  taking  account  of  profits  and  losses,  successes 
and  failures,  that  accrue  through  treatment  of  crime  by  the 
methods  in  vogue  under  the  law.  One  has  yet  to  see  any 
study  coming  from  a  jurist  which  undertakes  to  set  forth 
the  results  of  what  has  been  accomplished  by  what  he  has 
prescribed.  Such  a  tracing  of  results  or  outcomes  is  funda- 
mental, of  course,  in  the  sciences  which  aim  to  have  control 
of  material  or  of  situations,  but  since  the  law  has  grown  to 
what  it  is  through  slowly  developing  theory  and  tradition, 
it  has  found  no  reason  for  introducing  the  methods  of 
business  or  science. 

On  the  other  hand,  science  has  never  advanced  to  the 
stage  of  undertaking  any  thorough-going  treatment  of 
offenders  with  the  aim  of  ascertaining,  perhaps  by  experi- 
ment, what  can  be  accomplished  through  any  treatment. 
Very  meager  attempts  have  been  made  here  and  there 
to  do  something  concerning  some  one  feature  of  the  total 
situation  in  individual  cases,  such  as  attention  to  the  health 
or  to  trade  training  of  offenders,  but  there  have  been  practi- 
cally no  well-rounded  efforts  to  check  the  careers  of  criminals 


390  HUMAN   BIOLOGY 

through  attention  to  all  the  comphcating  factors  of  causa- 
tion which  will  have  to  be  met,  even  in  individual  cases. 
Science,  up  to  the  present,  has  been  concerned  mostly  with 
theorizing  about  criminals  and  the  causations  of  criminality, 
and  almost  nowhere  has  entered  into  the  effort  for  control 
of  the  crime  situation. 

It  is  true  that  in  the  Germanic  countries  and  in  Italy 
the  training  for  jurists  to  administer  the  criminal  law  has 
included  acquaintance  with  what  of  science  has  been 
developed  under  the  head  of  criminology,  and  this  is  a 
step  in  advance  of  anything  that  goes  on  in  this  country. 
Here,  even  in  most  law  schools  there  is  no  training  in 
criminology.  Elected,  or  in  a  few  places  appointed,  to 
positions  where  they  have  to  deal  with  delinquents  or 
criminals,  we  have  judges  who  are,  almost  all  of  them, 
totally  unacquainted  with  the  principles  of  any  science 
that  makes  for  the  understartding  of  human  nature.  I 
have  never  even  heard  of  a  conference  of  jurists  and  scientists 
in  this  country  on  the  important  subject  of  how  best  to 
deal  with  criminals.  Regularly  in  Germany,  judges,  psycholo- 
gists, and  psychiatrists  gathered  for  such  conferences 
which  were  found  to  be  most  valuable.  Nowadays  we  should 
also  include  sociologists. 

The  only  time  when  any  science  of  human  nature  comes 
in  close  contact  with  the  bench  in  regard  to  criminal  affairs 
is  when  the  question  of  mental  disease  that  bears  upon 
responsibility  is  to  the  front.  With  the  introduction  of 
alienists  in  criminal  cases,  testifying  from  an  ex  parte  stand- 
point, a  not  inconsiderable  and  very  understandable  distrust 
of  mental  science  on  the  part  of  the  legal  profession  has 
grown  up.  Yet  when  specific  attempts  have  been  made  to 
better  the  situation,  the  legal  profession  has  often  stood  in 
the  way,  as  in  the  celebrated  Leopold-Loeb  case.  In  this 
instance,  the  psychiatrists  who  studied  at  great  length 
the  young  offenders  and  the  causes  of  their  terrible  deed 
were  willing  to  put  every  bit  of  information,  including  their 
knowledge  of  many  other  crimes  committed  by  the  accused, 
into  the  hands  of  the  experts  retained  by  the  state.  The 
latter  were  willing,  and  indeed  made  a  st;rong  effort  to  go 
on  with  the  case  on  the  basis  of  such  a  consultation,  one  of 


ANTISOCIAL   behavior:    DELINQUENCY   AND   CRIME  39 1 

them  making  the  notable  statement  that  if  all  in  conference 
had  the  same  facts  there  would  be  no  reason  for  disagreement. 
(Incidentally,  it  should  be  remembered  that  the  psychiatrists 
were  not  acting  merely  as  aHenists.  The  question  of  insanity 
was  not  brought  up  in  the  court,  and  indeed  under  the  law 
it  is  the  jury  in  IHinois  which  decides  the  question  of  insanity, 
that  is,  properly  speaking,  legal  irresponsibihty.  But  there 
was  no  jury  in  this  case,  and  no  trial.  It  was  merely  a  hearing 
before  the  judge,  after  the  plea  of  guilty  had  been  made.) 
The  state's  attorney  refused,  probably  on  account  of  possible 
criticism  of  his  office,  to  allow  the  experts  he  had  engaged 
to  enter  into  such  an  arrangement  and  consultation.  Here 
came  out  in  strong  demarcation  the  difference  between  the 
standpoints  of  the  law  and  of  science:  Any  appearance  in 
court  is  regarded  as  high  contest,  there  is  short  shrift  for 
any  idea  that  digging  out  the  whole  truth  for  the  sake  of 
society  is  an  end  to  be  aimed  at.  The  usual  procedure  is 
that  the  prosecutor  seeks  to  prove  guilt,  the  defending 
lawyer  to  prove  innocence  or  as  near  it  as  possible,  and 
neither  seeks  to  establish  the  exact  truth.  What  might  have 
been  a  historical  event  of  importance  for  progress  was 
blocked  in  the  above  case  by  legaHsm,  science  was  not 
allowed  to  have  fair  play  in  the  situation.  It  is  only  through  a 
fair-minded  attempt  to  study  the  total  situation  and  present 
it  in  court  (it  was  finally  very  largely  done  in  the  above 
case  by  the  psychiatrists)  that  respect  for  what  science  has 
to  offer  in  criminology  will  grow  among  the  legal  profession. 
The  main  points  to  be  made  are  that  American  judges  and 
other  officials  of  the  law  are  very  slightly  indeed  acquainted 
with  criminology.  Secondly,  the  older  criminology,  repre- 
sented by  many  volumes  on  library  shelves  is  mainly 
theoretical  and  by  no  means  well  developed  from  the 
standpoint  of  treatment  of  offenders.  In  consequence  of 
both  these  facts  the  application  of  the  modern  methods  of 
science  to  the  individual  case  is  exceedingly  limited  as 
affairs  now  stand.  This  appears  surpassingly  strange, 
since  treatment  is  the  one  big  issue:  how  to  protect  society, 
how  to  handle  the  offender  so  that  he  will  cease  his  criminal- 
istic tendencies.  The  legal  therapeutist  who  prescribes 
some  treatment,  such  as  a  period  in  jail,  has  little  or  no 


392  HUMAN   BIOLOGY 

notion  of  what  this  will  do  for  the  offender  or  for  society. 
I  am  warranted,  from  what  I  know,  in  saying  that  many  a 
judge  has  never  been  inside  the  institution  to  which  he 
sends  offenders,  and  practically  no  judges  have  any  knowl- 
edge of  the  effects  of  the  regime  to  which  they  consign 
offenders.  This  chasm  between  prescribing  treatment  and 
diagnosis  followed  by  the  observation  of  results  is  anti- 
science;  the  law  appears  to  be  very  little  concerned  with 
results,  and  if  obtaining  results  is  not  the  main  business  of 
the  law,  then  it  is  a  strange  phase  of  human  endeavor. 

But  this  statement  of  lack  of  cooperation  between  science 
and  the  law  in  criminal  affairs  must  not  stand  alone  and  be 
taken  merely  at  its  face  value.  As  we  said  above,  there  is  no 
real  distinction  between  crime  and  delinquency ;  the  fact  is  that 
the  delinquent  is  an  offender  against  society  who  has  committed 
offenses  of  just  the  same  nature  as  the  criminal,  only  at  an 
age  arbitrarily  determined  as  juvenile.  Now,  in  connection 
with  the  study  of  dehnquents  as  such,  and  working  hand 
in  hand  with  juvenile  court  authorities,  science  has  been 
playing  recently  a  very  considerable  part.  Medical,  psychi- 
atric, psychological,  and  social  investigations  of  dehnquents 
have  been  growing  apace,  undertaken  in  scores  of  places  by 
well-organized  chnics.  Sometimes,  and  very  properly, 
this  extends  beyond  the  mere  examination  of  the  offender  to 
study  of  the  etiology  of  the  offense.  It  is  true,  however,  that 
science  has  had,  even  in  connection  with  these  chnics, 
very  Kttle  to  do  with  the  treatment  under  the  law.  Perhaps 
one  reason  for  this  is  that  science  has  not  advanced  far 
enough  to  be  able  to  offer  enough  to  create  confidence  in 
what  it  might  do.  However,  its  chances  for  carrying  out 
experimental  therapy,  such  as  science  everywhere  under- 
takes, have  been  so  shght  that  lack  of  progress  in  discovering 
eflPective  treatment  is  readily  understandable.  The  next 
step  must  certainly  be  therapy  scientifically  prescribed 
and  administered,  with  close  observation  of  results.  It 
would  seem  easy  enough  to  command  the  resources  of 
probation  departments  and  state  correctional  institutions 
for  dehnquents  in  order  to  demonstrate  the  possibihties  of 
therapy  and  estabhsh  the  causes  and  remedies  of  the  weak- 
nesses that  now  exist. 


ANTISOCIAL   behavior:    DELINQUENCY   AND   CRIME  393 

Treatment  of  any  kind,  either  legal  or  scientific,  applied 
to  juvenile  delinquents,  must  be  understood  to  have  very 
direct  relationship  to  the  whole  crime  problem.  This  is 
provable  through  many  findings  in  all  civihzed  countries 
that  the  careers  of  habitual  criminals  in  the  great  majority 
of  cases  begin  during  youth  and  even  childhood.  This  is  an 
enormously  significant  fact,  one  that  has  not  yet  been  fully 
recognized  in  its  importance  for  the  lav^  and  also  for  science. 

Lest  there  be  a  mistake,  it  must  be  stated  that  a  few 
courts  and  institutions  dealing  with  adult  criminals  employ 
psychologists  and  psychiatrists,  but  this  is  almost  entirely 
from  a  discriminatory  standpoint,  separating  the  sheep 
from  the  goats,  mental  defectives  and  those  showing  aberra- 
tional characteristics  from  the  more  normal.  The  "Briggs 
Law,"  providing  in  Massachusetts  for  the  psychiatric 
examination  and  classification  of  those  convicted  of  felonies, 
is  the  most  advanced  provision  for  this  type  of  work.  So 
far,  only  very  hmited  modifications  of  treatment  are  offered 
as  the  outcome  of  such  examinations.  As  an  example  of 
the  tendency  to  a  modern  scientific  approach,  we  may  take, 
however,  the  work  done  with  adults  in  the  probation  depart- 
ment of  the  New  York  City  Court  of  General  Sessions 
where  attempt  at  social  and  individual  diagnosis  is  regarded 
as  prerequisite  to  treatment. 

DOES    CRIMINALITY   BETOKEN    ABNORMALITY 

The  reader  of  a  work  on  human  biology  is,  naturally, 
interested  to  know  what  statement  science  has  to  offer 
concerning  the  essential  nature  of  those  who  are  offenders 
against  society.  Is  crime,  or  dehnquency,  the  reaction  of  an 
individual  pecuHar  or  abnormal  in  any  way  to  an  environ- 
ment that  is  either  normal  or  abnormal?  The  preceding 
pages  contain  material  essential  for  consideration  before 
this  question  is  answered.  They  offer  fundamental  criticisms 
of  the  data  and  conclusions  that  have  been  published  under 
the  title  of  criminology.  It  is  hardly  necessary  to  recapitulate 
the  several  points;  such  as  the  fact  that  only  caught  offenders 
are  studied;  that  what  is  designated  as  crime  does  not 
differ  in  any  respect  from  much  other  antisocial  conduct; 


394  HUMAN  BIOLOGY 

that  only  very  recently  have  the  immensely  important 
studies  of  mental  capacities  and  aberrations  and  the  more 
dynamic  elements  of  mental  hfe  been  introduced;  that 
sociological  science,  as  correlated  with  psychiatric  work, 
is  only  just  beginning  and  was  almost  entirely  wanting  in 
the  picture  presented  by  earher  theoretical  criminology. 

Noting  the  Hmitations  which  observations  of  incarcerated 
criminals  represent,  yet  we  find  that  recent  better  studies 
of  them  go  far  towards  deciding  for  or  against  some  crimino- 
logical theories.  And  studies  of  juvenile  delinquents,  a 
goodly  proportion  of  whom  go  on  to  adult  criminaKty, 
as  we  indicated  above,  offer  a  very  much  better  range  of 
facts  upon  which  to  base  conclusions. 

In  considering  the  theory  that  "the  criminal"  is  a  peculiar 
type  of  individual  from  a  biological  standpoint,  "a  degen- 
erate," "an  atavistic  phenomenon,"  etc.,  it  can  be  said 
at  once  that  with  practical  scientific  workers  in  the  field 
this  older  idea  finds  almost  no  place.  The  anthropometric 
investigations  of  Goring  in  England  on  a  large  group  of 
inmates  of  a  prison  of  the  penitentiary  type  seem  quite 
to  upset  the  notion  that  the  criminal,  even  the  caught 
criminal,  represents  an  abnormal  type  biologically.  Having 
been  educated  in  the  Lombroso  tradition,  I  myself  undertook 
a  very  careful  survey  of  young  offenders  as  they  came  to 
us  in  the  Chicago  Juvenile  Court,  many  of  them  very  serious 
definquents,  from  the  standpoint  of  biological  anomahes. 
To  my  utter  surprise,  I  found  nothing  in  the  least  corrobora- 
tive of  the  biological  theory.  Indeed,  the  proportion  of 
stigmata  of  degeneracy  among  these  offenders  appeared 
fittle,  if  any,  greater  than  among  the  general  population. 
It  is  true  that  if  one  observes  the  inmates  of  certain  peni- 
tentiaries fifing  past,  one  certainly  sees  an  inordinate  number 
of  pecufiar  appearing  men,  but  again  I  assert  that  these 
are  highly  selected  groups.  We  cannot  fairly  draw  conchisions 
concerning  criminals  in  general,  to  say  nothing  of  the  make- 
up of  those  who  are  otherwise  serious  social  offenders,  by 
observing  such  a  group.  Without  any  idea  of  being  merely 
cynical,  I  insist  that  penitentiary  sentences  are  being  served 
for  the  most  part  by  those  not  endowed  with  shrewdness 
enough  "to  get  away  with"  crime,  not  well  enough  off  to 


ANTISOCIAL   behavior:    DELINQUENCY   AND   CRIME  395 

have  good  legal  defense,  not  energetic  enough  to  move  olF 
to  another  state  after  they  have  committed  a  crime,  and 
that,  above  all,  they  probably  represent  an  undue  pro- 
portion of  mental  defectives,  as  compared  to  criminals 
in  general.  That  biological  anomaly  exists  among  mental 
defectives  in  greater  proportion  than  among  the  mentally 
normal  is  an  acknowledged  and  easily  observable  fact. 
Taking  up  mental  defect  next  as  possibly  representing  a 
biological  anomaly  (perhaps  imperfect  structure  or  func- 
tioning power  of  brain  cells)  correlated  with  criminahty, 
we  may  say  that  here,  too,  we  are  at  once  introduced  to 
complexities  far  greater  than  were  earher  seen.  Some  critics 
have  recently  called  attention  to  the  ludicrous  differences 
in  findings  of  mental  defect  among  groups  of  dehnquents 
and  criminals  as  made  by  various  examiners.  This  is  thought 
by  Sutherland  to  be  due  largely  to  the  varieties  of  attitudes 
and  training  of  the  mental  examiners,  showing  that  mental 
tests  are  not  yet  to  be  utihzed  as  entirely  safe  criteria.  I 
hardly  think  he  is  on  safe  ground  in  this  opinion  because 
different  groups  as  selected  for  imprisonment,  for  example 
in  different  communities,  vary  tremendously  according  to 
the  attitude  of  the  community  toward  probation,  reforma- 
tion, and  other  modes  of  treatment,  and  may  thus  well 
vary  in  average  mentality.  But  still  one  must  acknowledge 
that  probably  the  earlier  large  statements  of  the  proportion 
of  mental  defect  among  delinquents  and  criminals  was 
the  result  of  unskilled  and  uncritical  work  by  mental  testers. 
(As  a  matter  of  fact,  the  significance  of  good  mental  testing 
rests  largely  on  the  frequency  with  which  findings  are 
corroborated  by  different  examiners,  perhaps  in  different 
institutions  and  at  later  periods.)  At  any  rate,  the  upshot 
of  the  whole  matter  seems  to  be,  fairly  stated,  that  among 
caught  delinquents  and  criminals,  there  is,  undoubtedly,  a 
much  greater  proportion  of  mental  defect  than  among  the 
ordinary  population.  Suppose  we  say  that  i  to  3  per  cent 
of  the  population  would  rate  as  defective  according  to  the 
standard  age-level  tests  now  in  vogue;  then  we  find  by  the 
same  criteria  from  10  to  15  per  cent  of  delinquents  defective 
as  they  appear  in  the  juvenile  court.  As  might  be  supposed, 
there  is  at  once  a  process  of  selection  going  on.  In  the  correc- 


39^  HUMAN   BIOLOGY 

tfonal  institutions  for  juvenile  offenders  there  is  a  much 
larger  proportion  of  defectives.  But  the  curious  discovery 
was  made  by  Doll,  a  very  careful  investigator,  that  in  the 
penal  institutions  in  New  Jersey  there  is  a  smaller  pro- 
portion of  mental  defectives  than  in  the  juvenile  correctional 
schools. 

The  essence  of  the  figures  now  available  from  many  sources 
is  that  while  mental  defect  in  an  undue  proportion  is  found 
among  inmates  of  prisons  and  correctional  institutions  of  the 
several  types,  nevertheless  we  cannot  conclude  that  feeble- 
mindedness is  at  all  the  large  factor  in  the  causation  of 
criminahty  that  at  one  time  was  supposed. 

To  come  back,  as  we  must  in  scientific  spirit,  to  the  problem 
of  antisocial  conduct  in  general  as  not  differing  funda- 
mentally from  crime,  we  can  easily  beheve  that  no  such 
biological  defect  as  may  be  imphed  by  feeblemindedness 
plays  any  great  part  in  it.  Further,  in  the  discussion  of 
crime  itself,  we  are  bound  to  consider  those  who  commit 
larcenies  and  other  crimes,  but  who  "get  away  with  it." 
The  thieving  that  goes  on  from  transportation  companies 
and  warehouses  in  this  country,  amounting,  if  Prentiss  is 
right,  to  over  $100,000,000  a  year,  is  certainly  crime,  but 
as  I  have  already  said,  extraordinarily  few  of  those  who 
commit  such  offenses  are  taken  into  custody.  Can  anyone 
suppose  that  in  a  criminal  practice  apparently  as  common 
as  this,  the  perpetrators  represent  much  else  than  the  average 
run  of  the  population,  that  they  are  individuals  pecuhar 
from  any  biological  standpoint? 

But  another  important  problem  of  biological  import 
has  to  be  met  concerning  criminals.  Among  them  is  there 
not  an  undue  proportional  representation  of  other  varieties 
of  deviations  from  the  mental  norm?  We  can  at  once  say 
that  some  exceedingly  important  facts  bearing  on  this  matter 
have  been  brought  to  hght  recently  as  we  have  gained 
better  knowledge  of  certain  types  of  such  deviations.  I 
speak,  particularly,  of  the  finding  that  among  dehnquents 
and  criminals  there  are  many  cases  of  what,  in  general 
terms,  might  be  called  abnormal  personahty.  The  interest 
in  abnormal  personality  Hes  not  only  in  the  statistical 
findings,  but  also  in  the  facts  of  the  incorrigibility  of  this 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  397 

type  of  offenders,  the  continuity  of  their  careers,  and  the 
severity  of  the  offenses  they  perpetrate.  Psychiatry  is 
gradually  coming  to  know  better  this  class  of  individuals, 
which  comprises  several  sub-types,  and  to  be  challenged 
by  the  eccentricities  of  their  mental  and  characterial  devia- 
tions, by  the  possible  biological  bases  of  the  condition, 
by  the  curious  mental  dynamics  exhibited  in  lack  of  inhibi- 
tory powers  which  lead  to  impulsive  dehnquency  and 
criminahty,  with  evidence  in  some  instances  of  an  under- 
lying feeling  of  a  strange  need  for  punishment. 

With  what  we  have,  even  so  far,  gained  in  understanding 
of  abnormal  personaHties,  there  has  come  about  much 
better  appreciations  of  the  part  they  play  in  crime.  Birnbaum 
in  Berlin  has  for  some  years  been  calHng  attention  to  the 
terrific  offenses  and  the  long  careers  of  the  constitutional 
psychopathic  inferiors,  as  he  designates  them,  among 
offenders.  Many  recent  studies  in  the  United  States  call 
attention  to  similar  types  of  individuals  and  to  their  anti- 
social conduct  tendencies.  However,  while  our  classifications 
and  our  definitions  remain  on  the  loose  footing  that  they 
now  are,  with  different  observers  using  terms  in  very  different 
ways,  we  are  not  in  any  position  to  give  percentages  of  the 
abnormal  personaHties  among  offenders.  But  it  is  very 
significant  that  psychiatrists,  working  systematically  in 
the  large  penitentiaries  of  lUinois,  classify  from  60  to  90 
per  cent  of  the  inmates  as  showing  traits  of  abnormal 
personahty.  One  cannot  here  open  the  question  whether 
the  characteristics  these  observers  speak  of  may  or  may 
not  have  been  induced  by  environmental  experiences  of  any 
kind,  or  by  the  absorption  of  any  one  of  several  toxic  sub- 
stances which  may  have  caused  malfunctioning  of  nervous 
cells.  But  it  is  highly  probable  that  in  a  not  inconsiderable 
share  of  the  cases  of  this  kind  a  biological  anomaly  was 
present.  Birnbaum  attributes  nearly  all  of  the  trouble  to 
defective  germ  plasm,  but  apparently  without  good  proof 
on  his  part,  especially  since  there  are  encountered  nowadays 
effects  of  a  very  similar  sort  upon  character  and  conduct 
that  are  the  after-result  of  encephalitis  lethargica  (a  disease 
occurring  or  only  recognized  as  such  in  the  last  decade  or  so 
in  America)  and  of  some  cases  of  concussive  brain  injury. 


398  HUMAN   BIOLOGY 

No  Students  of  conduct  deviations  can  afford  to  forget 
that  very  many  mental  defectives  have  sound  and  wholesome 
character  traits,  the  result  of  good  upbringing.  On  the  other 
hand,  we  have  to  recognize  that  in  instances  of  abnormal 
personahty,  arising  as  the  result  of  anyone  of  the  several 
biological  causes  mentioned,  the  influence  of  attempts  at 
educative  control  are  often  very  slight  indeed.  Our  own 
experience  with  treatment  of  individual  cases  shows  this, 
and  the  careful  regime  undertaken  for  a  group  of  post- 
encephalitic conduct  disorder  cases  at  the  Pennsylvania 
Hospital  also  proves  it. 

The  part  that  mental  disease  as  ordinarily  spoken  of 
plays  in  criminality  is,  statistically  considered,  not  great. 
But  the  borderline  between  abnormal  personality  and  mental 
disease  is  not  easy  to  draw,  and  psychiatry  has  not  yet 
entered  into  enough  researches  on  personality  problems 
to  have  said  its  last  word  on  the  subject.  Some  of  the  most 
notorious  murder  trials  have  centered  about  this  question 
of  what  constitutes  mental  disease;  the  problem  sometimes 
has  arisen  because  of  the  vague  but  obvious  mental  or 
personality  abnormality  of  the  murderer.  Coming  under 
the  head  of  the  ordinary  groupings  of  the  psychoses,  there 
are  comparatively  few  inmates  of  penal  institutions,  and 
almost  none  among  those  in  juvenile  correctional  schools. 

Our  own  years  of  study  in  the  field  of  conduct  disorders 
have  led  me  and  my  co-workers  to  perceive  very  plainly 
that  if  we  are  to  discuss  at  all  the  relationship  of  the  biologi- 
cal make-up  of  individuals  to  their  conduct  tendencies, 
we  must  include  not  only  inferiorities,  weaknesses,  and 
degeneracies,  but  also  superiorities  of  physical  structure 
and  deviations  from  the  norm  in  the  way  of  overdevelop- 
ment and  physical  precocity.  A  very  real  cause  of  "breaking 
over  the  traces"  socially  and  committing  offenses,  in  our 
particular  era,  is  to  be  found  in  unusual  and  premature 
general  strength  and  development,  as  well  as  more  rarely 
in  unusually  early  sex  maturity  which  may  or  may  not 
accompany  precocious  or  unusual  general  structural  develop- 
ment. Anent  this,  we  may  cite  the  fact,  well  known  by  this 
time,  that  girls  appearing  in  the  juvenile  court  for  sex 
offenses  tend   to  be   larger   for  their  age  than  the  norm. 


ANTISOCIAL    behavior:    DELINQUENCY    AND    CRIME  399 

Our  findings  on  this  seem  conclusive,  and  indeed,  it  has 
been  noted  as  a  common  sense  observation  by  various 
judges  in  juvenile  courts.  The  implications  of  such  over- 
development are  obvious.  The  girl's  over-size  or  over-develop- 
ment of  secondary  sex  characteristics  plays  its  part  in  her 
own  mental  and  emotional  hfe,  as  w^ell  as  in  her  social 
situation.  Precocious  puberty,  taken  alone,  is  much  less  a 
factor  than  this  one  of  structural  development,  the  posses- 
sion of  an  unusually  good  physique. 

Any  student  of  young  offenders  comes  to  know  the  incen- 
tives to  social  misconduct  that  there  are  in  the  possession 
of  a  strong  body  without  sufficient  chances  for  satisfactory 
outlets  in  exercise,  adventure  and  excitement.  With  the 
increasing  development  of  our  close  urban  Hfe,  the  correlation 
between  delinquent  activity  and  the  need  for  physical 
adventure  and  excitement  becomes  very  apparent.  It  is 
safe  to  say  that  many  of  the  criminal  offenses  of  later 
adolescence,  even  some  of  the  more  desperate  ones,  are 
due  to  need  for  activity  and  adventure  on  the  part  of  young 
men.  The  biological  background  of  this  situation  is  plain 
to  us  in  many  cases,  particularly  where  the  individual  has 
a  physical  structure  displaying  more  than  ordinary  energy 
and  development. 

EMOTIONAL    LIFE   AS    RELATED   TO    CRIME 

The  part  which  the  emotional  hfe  plays  in  the  production 
of  antisocial  behavior  of  many  sorts  is  entirely  under- 
standable. It  has  become  a  matter  of  deep  interest,  not 
only  for  the  psychologist  and  psychiatrist,  but  also  for  the 
physiologist.  Something  of  the  biological,  structural  as  well 
functional,  foundations  of  emotional  life  are  becoming  known 
through  researches  of  great  import.  The  work  of  Head, 
Cannon  and  others,  for  example,  in  demonstrating  the  optic 
thalamus  as,  at  least,  one  center  of  emotional  activity,  is 
immensely  important  for  understanding,  not  only  the  human 
body,  but  also  the  human  personality. 

Endocrinology,  to  the  front  so  much  just  now,  has  made 
great  claims  in  explanation  of  personality  characteristics 
and  conduct  trends.  There  seems  to  be  a  modicum  of  truth 
in  the  enthusiasm.  Conservative  scientific  endocrinologists 


400  HUMAN   BIOLOGY 

who  have  undertaken  very  careful  and  prolonged  special 
examinations  of  offenders  for  us,  in  their  reports  account  for 
very  Httle  indeed  of  the  antisocial  behavior,  and  in  spite 
of  the  existence  of  the  much-advertised  and  much  used 
extracts  of  glands,  offer  very  few  suggestions  for  treatment. 
I  have  come  to  the  conclusion  that  the  environmental  hfe 
and  experiences,  which  all  biologists  must  include  when 
they  are  studying  an  organism,  are  too  often  left  out  of 
account  in  the  enthusiasm  for  endocrinology.  Perhaps  this 
is  because  many  of  these  environmental  experiences  are 
only  to  be  known  at  all  through  analysis  of  the  mental 
life  and  content. 

Some  of  us  who  are  a  bit  older  have  seen  rise  and  fall 
many  biological,  particularly  medical,  theories  concerning 
the  causation  of  criminahty.  We  may  remember  that  it 
has  been  successively  regarded  as  a  manifestation  of  epilepsy, 
of  degeneracy,  of  feeblemindedness,  of  abnormal  intracranial 
pressure  which  was  to  be  relieved  through  opening  the  skull. 
Then  trauma  of  the  hypothetical  moral  center  was  held 
responsible,  and  so  were  tonsils  and  adenoids,  and  more 
recently,  focal  infections,  while  to  be  really  up-to-date,  we 
must  include  abnormal  functioning  of  the  glands  of  internal 
secretion. 

HEREDITY   AND    CRIMINALITY 

Readers  in  biology  should  very  properly  have  the  matter 
of  heredity  presented  to  them,  even  here  in  our  section  on 
hum.an  conduct.  Behavior  disorders,  though  having  such 
a  muItipHcity  of  possible  causation  factors,  are  regarded 
often  by  the  laity  and  sometimes  by  scientific  men,  perhaps 
because  they  are  not  brought  face  to  face  with  all  the  facts  in 
individual  case  studies,  as  proof  of  an  outbreak  of  inherited 
tendencies.  In  contrast  to  this  it  is  interesting  to  note  that 
everywhere  in  actual  cHnical  work  with  delinquents  and 
criminals,  very  httle  explanation  is  offered  in  terms  of 
heredity.  Discussions  on  this  topic  have  been  undertaken 
mainly  without  careful  scientific  work  being  offered  in 
proof  that  there  is  any  such  thing  as  the  inheritance  of 
criminal  tendencies.  Again,  neglect  of  the  deeper  influences  of 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  4OI 

the  environment,  particularly  the  social  and  mental  environ- 
ment, constitutes  the  main  weakness  in  any  such  attempt 
to  draw  conclusions  about  the  origin  of  dehnquent  or  criminal 
behavior. 

Actual  experiments  with  dehnquents,  such  as  we  detail 
in  a  recent  study,  show  that  individuals  removed  to  better 
community  conditions  from  an  environment  easily  seen 
to  be  productive  of  criminaHsm,  with  very  great  frequency 
change  their  conduct  tendencies,  if  they  are  normal  in 
mental  make-up.  From  our  findings  we  see  no  reason  for 
offering  a  bad  prognosis  to  child-placing  agencies  in  cases 
even  of  severely  delinquent  children  because  there  has  been 
criminalism  in  the  forbears.  Even  in  studying  the  outcomes 
of  our  Chicago  series  of  youthful  recidivists,  for  the  most 
part  very  inadequately  or  poorly  treated  cases,  we  could  see 
no  reason  for  regarding  inheritance  of  criminalistic  tendencies 
as  playing  any  known  part  in  careers.  Looking  in  any  way 
at  the  findings  when  statistics  of  other  factors  are  taken  into 
account,  heredity,  except  of  abnormal  mentality,  seems  to  be 
of  little  significance.  For  example,  among  either  the  failures 
or  the  successes,  nearly  as  great  a  percentage  came  from 
criminalistic  as  from  normally  behaving  families. 

We  may  not  want  to  go  as  far  as  the  ultra-behaviorists 
do  and  allege  that  given  an  infant  one  can  make  either  saint 
or  sinner  out  of  him  but  it  does  seem  certain  from  our 
observations  that  what  influences  the  mental  life,  even 
among  the  feebleminded,  vastly  out-weighs  in  effect  on 
conduct  tendencies  anything  that  we  know  that  comes 
through  inheritance.  It  still  remains  that  the  conclusions  of 
Spaulding,  who  showed,  in  working  with  a  large  series  of  our 
cases,  that  there  was  no  proof  of  the  inheritance  of  criminal 
tendencies  as  such,  hold  good. 

IDEATIONAL    LIFE    AND    CRIME 

Adding  to  the  foregoing  suggestions  of  the  richness  of  the 
field  that  is  ploughed  up  if  case  after  case  of  conduct  disorder 
is  carefully  studied,  we  are  led  further  to  make  perhaps  the 
most  important  observation  concerning  the  more  positive 
and  constructive  aspects  of  investigation  into  the  causative 


402  HUMAN   BIOLOGY 

background  of  antisocial  behavior.  It  cannot  be  too  strongly 
stated  that  the  dynamics  of  conduct  tendencies  within  the 
human  individual  include  not  only  the  emotional  and  affec- 
tive phenomena  which  we  have  already  discussed,  but  even 
more  strongly  center  in  his  ideational  hfe.  More  provocative 
of  conduct  and  more  directly  causatively  antecedent  to  it 
than  anythmg  else  are  ideas.  This  is  a  fundamental  con- 
sideration. The  nature  of  the  ideational  Hfe  or,  at  least,  of 
parts  of  it  and  the  manner  in  which  certain  ideas  are  handled 
by  the  individual,  these  are  what  immediately  create  conduct 
norms  and  deviations.  It  is  to  the  mental  content,  then, 
to  what  notions  or  ideas  are  held  by  the  individual,  and  to 
what,  through  his  emotional  life,  he  does  with  his  ideas  that 
we  must  essentially  turn  for  understanding  his  delinquent  or 
criminal  activities. 

All  conduct,  as  being  behavior  related  to  one's  fellow 
beings,  is  a  social  phenomenon.  All  conduct  is  the  direct 
result  of  mental  life.  These  are  truisms  too  often  neglected. 
Whether  as  the  result  of  sudden  impulse  or  deliberate 
intent,  human  action,  which  is  called  conduct,  follows  upon 
mental  representation.  The  idea  is  there  before  the  act. 
The  biologist  perceives  that  some  physical  deviations  or 
pathologies,  structural  or  functional,  particularly  in  the 
central  nervous  system,  are  conducive  in  some  measure  to 
antisocial  conduct,  but  it  is  to  be  noted  that  even  in  such 
cases  the  path  to  action  must  lead  through  the  ideational 
field  of  mental  life.  It  is  these  considerations  that  lead  us  to 
see  clearly  that  delinquency,  crime,  and  antisocial  conduct 
in  general  are  psychosocial  phenomena. 

METHODOLOGICAL    CONTRIBUTIONS 

At  this  point  it  may  be  fairly  asked:  What  have  the 
sciences  of  human  nature  so  far  mainly  contributed  to  the 
understanding  of  antisocial  conduct,  or  more  particularly, 
to  the  understanding  of  delinquency  and  crime?  The  best 
answer  seems  to  me  to  be  that  they  have  contributed  a  new 
methodology,  based  on  case  studies.  The  earlier  general 
theorizings  when  brought  face  to  face  with  the  special 
problems  in  an  individual  case  generally  failed  entirely  to 


ANTISOCIAL   behavior:    DELINQUENCY   AND    CRIME  403 

answer  them.  This  is  because  the  factors  producing  the 
results  always  proved  to  be  many  more  than  any  theory 
suggested.  One  of  the  greatest  of  medical  cHnicians  used  to 
say  that  for  therapy  it  is  generally  not  so  important  to  know 
that  a  man  had  some  particular  disease  as  to  know  what 
particular  man  had  the  disease.  Just  so  for  the  effective 
handling  of  conduct  disorder;  only  it  is  necessary  to  go  a 
step  further  and  to  ascertain,  if  possible,  not  merely  what 
was  the  special  make-up  of  this  given  individual  who 
committed  the  offense,  but  also  under  what  environmental 
conditions  he  hves  or  has  Hved,  and  what  have  been  and 
what  are  his  mental  experiences.  Now,  reactions  between  the 
individual  and  his  environment,  back  and  forth,  are  not  so 
simple,  and  involve  an  immense  amount  of  circular  response, 
that  phenomenon  so  famihar  to  biologists.  It  becomes  a 
highly  complicated  affair  when  the  mental  life  and  conduct 
tendencies  of  human  beings,  under  the  complex  conditions 
of  the  human  social  environment,  are  the  matters  under 
consideration. 

The  methodology  which  is  evolving  in  the  modern  case 
studies  of  antisocial  behavior  takes  the  best  possible 
cognizance  of  the  structural  and  functional  physical  make-up 
of  the  individual;  his  mental  make-up  from  the  standpoint 
of  normality  versus  defect  or  aberrational  tendency;  his 
ideational  life;  his  outer  circumstances,  present  and  past; 
his  many  mental  and  emotional  experiences  derived  through 
family  life,  education,  companionship;  and  the  inciting 
circumstances  of  the  special  antisocial  offense  which  may 
be  the  immediate  problem. 

It  is  a  far  cry  from  the  many  theories  of  crime  and  classi- 
fications of  criminals  to  modern  case-study  methods,  and 
from  general  assumptions  concerning  treatment,  such  as 
have  led  to  the  building  of  institutions  and  whole  penal 
systems,  to  careful  observation  of  the  outcomes  of  different 
forms  of  treatment  in  series  of  differentiated  cases.  The 
latter  represents  the  approach  of  science  to  any  problem 
of  control.  To  develop  remedies  for  crime  and  delinquency  we 
need  adequate  diagnoses  and  research  into  etiology,  case  by 
case,  and  the  closest  study  of  results.  Beginnings  of  this 


404  HUMAN   BIOLOGY 

are  to  be  seen  already  in  work  with  juvenile  delinquents, 
but  even  here  science,  so  far,  is  having  very  httle  chance  for 
trying  different  plans  of  treatment.  The  best  of  correctional 
institutions  receive  a  motley  aggregation  of  individuals, 
and  in  the  main,  treat  them  without  regard  to  individual 
diagnosis  and  etiology.  These  institutions  are  really  hospitals 
or  colonies  for  the  treatment  of  delinquency,  the  social 
disease,  but  in  their  regime  and  after-care,  which  is  as 
important,  and  in  some  cases  more  so,  than  detention, 
they  are  not  awakened  to  the  advantages  of  a  scientific 
methodology.  Anyone  acquainted  with  the  ordinary  manage- 
ment of  our  public  affairs  knows  plenty  of  reasons  for  this, 
but  with  a  better  understanding  of  the  possibilities  and  a 
more  educated  public  sentiment  the  situation  certainly 
should  be  alterable. 

In  present  day  endeavors  to  get  better  understandings, 
there  are  healthy  signs  of  much  cooperation  between 
sociologists,  psychiatrists,  psychologists,  with  here  and  there 
other  medical  men,  anthropologists  and  educators  taking  some 
part.  Already  nothing  stands  out  any  clearer  than  that  the 
more  effective  handling  of  the  problems  of  antisocial  conduct, 
an  end  so  utterly  desirable,  depends  upon  the  extension  of 
scientific  method  in  this  field.  Observing  the  demonstrable 
high  values  of  the  case  method  study  of  juvenile  delinquents, 
the  diagnoses  made,  the  uncovering  of  the  varied  etiological 
factors,  the  adequacy  of  well  directed  treatment  based  on 
scientific  fact,  observing  these  things  no  one  can  doubt 
the  possibilities  of  checking  very  many  anti-social  careers. 
The  main  effort  should  be  in  the  direction  of  applying  this 
early  therapy.  While  the  bent  twig,  the  older  offender, 
presents  a  harder  problem  we  may  be  assured  that  coordinate 
methods  more  scientifically  constructed,  could  vastly  better 
protect  society  from  delinquency  and  crime. 

REFERENCES 

Bjerre,  a.  1927.  The  Psychology  of  Murder.  Lend.,  Longmans,  Green. 

Brasol,  B.  1927.  Elements  of  Crime.  Oxford  Univ.  Press. 

Burt,  C.  1925.  The  Young  Delinquent.  Univ.  of  London  Press. 

CooLEY,  E.  J.  1927.  Probation  and  Delinquency.  Catholic  Charities  of  N.  Y. 

Garafalo,  R.  1914.  Criminology.  Boston,  Little,  Brown. 

Healy,  W.  1915.  The  Individual  Delinquent.  Boston,  Little,  Brown. 


ANTISOCIAL   behavior:    DELINQUENCY   AND   CRIME  405 

Healy,  W.,  and  Bronner,  A.  F.   1927.  Delinquents  and  Criminals,  Their 

Making  and  Unmaking.  N.  Y.,  Macmillan. 
1923.  Case  Studies,  Series  i.  Boston,  Judge  Baker  Foundation. 
Healy,  W.,  Bronner,  A.  F.,  Baylor,  and   Murphy.  1929.  Reconstructing 

Behavior  in  Youth.  N.  Y.,  Knopf. 
Sutherland,  E.  H.  1924.  Criminology.  Phila.,  Lippincott. 
Tarde,  G.  1913.  Penal  Philosophy.  Boston,  Little,  Brown. 
Addams,  J.,  et  al.  1924.  The  Child,  the  Clinic,  and  the  Court.  N.  Y.  New 

Republic  Pub.  Co. 


Chapter  XVII 
ADJUSTMENT  TO  INFECTIOUS  DISEASE 

Hans  Zinsser 

WHEN  one  living  unit  implants  itself  on  the  surface 
or  within  the  tissues  of  another,  the  result  of  the 
association  must  be  either  a  mutual  adaptation, 
degrees  of  which,  are  spoken  of  as  "commensulism"  and 
"symbiosis,"  or  a  struggle  determining  the  deftruction  of 
one  or  the  other  of  the  reacting  organisms.  The  processes 
which  are  initiated  and  by  which  the  invaded  unit  depends 
itself  have  been  analyzed  particularly  in  connection  with 
infectious  diseases  of  man  and  animals.  But  in  order  to 
understand  them  properly  it  is  important  to  remember 
that  the  powers  of  adjustment  and  defense  which  are  set 
in  motion  have  a  biological  significance  far  broader  than  its 
apphcation  to  the  accidents  of  infection.  They  represent  a 
deep-seated  emergency  mechanism  latent  in  the  normal 
body,  an  ancient  heritage  of  the  cytoplasm  by  which  living 
cells  and  tissues  are  enabled  to  meet  abnormal  metabolic 
conditions  of  any  kind  and  to  preserve  themselves  from 
injury  by  the  entrance  into  their  substance  of  any  materials 
that  cannot  be  utilized  nutritionally.  Since  many  of  these 
methods  of  defense  are  shared  in  common  by  the  higher 
animals  and  plants  and  the  simplest  Kving  units  like  pro- 
tozoa, Ehrlich  has  picturesquely  spoken  of  them  as  Uralte 
Protoplasma  Weisheit. 

Infection  is  in  itself  a  distinctly  abnormal  process,  or 
perhaps  better,  an  accident  in  the  plan  of  nature.  The 
term  "normal,"  when  applied  to  the  physiological  processes 
of  the  higher  animals,  is  of  course,  like  "infinity"  in  mathe- 
matics, an  entirely  abstract  conception.  Nevertheless,  it 
is  necessary  to  formulate  it  as  a  working  basis,  for  the  purpose 
of  properly  defining  deviations.  Thus,  it  is  a  normal  ten- 
dency in  nature  to  preserve  the  integrity  of  biological  units, 
and  the  parasitism  of  one  living  individual  upon  the  sub- 
stance of  another  may  be  regarded  as  an  abnormal  occur- 
rence which  implies  either  struggle  or  adaptation;  and  here, 

406 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  4O7 

as  in  human  economic  relations,  the  parasite,  if  the  con- 
dition becomes  habitual,  pays  for  the  situation  by  the  loss 
of  one  or  more  of  the  functions  no  longer  needed,  a  sort  of 
biological  degradation.  If  the  cohabitation  becomes  mutually 
advantageous,  as  in  the  root  tubercles  of  the  leguminosae, 
in  the  symbiosis  of  green  algae  and  certain  flagellates,  or 
perhaps  in  the  case  of  colon  bacilli  and  various  animals, 
there  is  a  sort  of  shrewd  metabolic  opportunism  in  which 
the  loss  of  biologic  liberty  pays  for  the  comforts  of  pre- 
digestion,  or  in  other  words  civilization.  Such  perfect, 
even  mutually  helpful  adaptation,  however,  is  relatively  rare 
and  in  most  instances  the  entrance  of  one  living  unit  into 
the  substance  of  another  is  either  entirely  prevented,  or 
resented  by  the  initiation  of  a  struggle,  as  a  result  of  which 
one  or  the  other  participant  is  destroyed.  Little  is  known 
regarding  the  conditions  which  ordinarily  prevent  such 
invasion  except  that  it  is  intimately  bound  up  with  the 
property  of  life  and  closely  associated  with  the  activities  of 
the  various  enzymes  by  which  the  host  maintains  his 
metabolic  equilibrium  and  by  which  the  invader  attacks  the 
substance  of  the  host.  It  is  not,  at  any  rate,  the  unsuitability 
of  the  environment  within  the  jelly  of  a  mass  of  frog's  eggs 
which  keeps  the  bacteria  in  the  puddle  from  swarming  into 
it;  for,  let  a  sudden  frost  kill  the  eggs  over  night  and,  as 
Bail  has  pointed  out,  the  mass  swarms  with  invaders  before 
the  following  morning.  In  general,  then,  Hving  things, 
though  surrounded  by  innumerable  other  living  things  which 
could  readily  make  use  of  their  body  substances,  are  pre- 
served during  life  from  such  invasion. 

The  majority  of  microorganisms,  of  the  same  classes  and 
orders  as  those  which  can  cause  fatal  infection,  are  eco- 
nomically independent,  living  on  dead  organic  and  inorganic 
materials,  and  delicately  adapted  to  many  diff'erent  types  of 
environment.  A  relatively  small  group  have  developed  the 
capacity  of  living  in  or  upon  the  animal  body,  and  the 
nasopharynx,  the  intestines,  the  conjunctivae  and  other 
parts  of  the  accessible  body  have  all  developed  their  charac- 
teristic flora.  It  is  out  of  these  in  most  cases  that  the  patho- 
genic or  disease-producing  groups  have  arisen,  a  process  of 
evolution  which  it  is  easier  to  conceive  in  the  case  of  bacteria 


408  HUMAN   BIOLOGY 

than  in  other  living  forms,  because  the  artificial  production  of 
changes  or  mutations,  both  as  to  growth  characteristics 
and  infectious  power,  can  be  easily  and  rapidly  accomphshed 
in  the  laboratory. 

As  a  matter  of  actual  observation  we  may  subdivide 
bacteria  into  definite  classes  according  to  the  degree  to 
which  they  developed  parasitic  properties,  as  follows: 

1.  Those  which  under  no  circumstances  will  grow,  except  in  the 
saprophytic  state,  upon  dead  organic  and  inorganic  materials. 

2.  Those  which  have  become  adapted  to  an  environment 
supplied  on  the  physiologic  exterior  of  the  bodies  of  other  forms 
where  the  reaction  and  the  substance  of  secretions  and  waste 
products  supply  them  with  a  suitable  environment. 

3.  Those  which,  living  on  the  exterior  of  the  body,  may  produce 
powerful  poisons  by  which  the  host  is  injured  both  locally  and 
generally.  To  this  class,  which  still  may  be  regarded  as  purely 
saprophytic,  belong  some  of  our  important  pathogenic  organisms, 
the  diphtheria  and  the  tetanus  bacilli,  which  do  not  actually 
enter  the  tissues  and  may  therefore  be  spoken  of  accurately  as 
pathogenic  saprophytes.  Unless  the  toxin  production  in  these 
forms  is  in  some  way  related  to  the  creation  of  suitable  metabolic 
conditions  for  the  organism  itself,  its  biological  purpose  is  quite 
obscure.  It  is  not  impossible  that  by  the  destruction  of  hving 
tissues  these  toxins  create  the  conditions  that  permit  development. 

4.  Bacteria  which  ordinarily  lead  a  purely  saprophytic  existence 
but  which,  given  suitable  circumstances,  may  invade  the  tissues 
of  another  form.  This  is  the  most  widely  distributed  class  of  the 
pathogenic  organisms,  and  includes  most  of  the  ordinary  intestinal 
infectious  agents  and  many  of  the  so-called  surgical  infections; 
and  the  bacteria  of  this  class,  because  of  their  saprophytic  attri- 
butes, are  easily  cultivated  on  artificial  media. 

5.  The  relatively  strict  parasites  which  cannot  be  cultivated  at 
all,  or  only  by  the  use  of  specially  adapted  methods,  and  which 
seem  to  have  developed  a  more  or  less  strict  parasitism  for  the 
conditions  prevailing  in  the  living  bodies,  often  of  a  particular 
animal  species. 

Any  classification  of  this  kind  must  be  regarded  as  repre- 
senting points  on  a  curve  along  which  many  gradations 
of  saprophytism  and  parasitism  are  recorded.  In  regard  to 
speed  and  delicacy  of  biological  adaptation,  there  is  no  class  of 
living     things    more   worthy   of  study   than   the   bacteria. 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  409 

Every  species  of  higher  animal  has  its  pecuHar  invaders, 
which  rarely  or  never  cause  spontaneous  infections  in 
other  species.  Many  diseases  of  man  cannot  be  inoculated  to 
any  animals  except  the  higher  apes;  and  domestic  animals 
suffer  from  fatal  infections  which  often  have  no  power  what- 
ever to  invade  man.  Moreover,  in  certain  instances,  rabies 
for  example,  where  an  invader  can  afflict  many  different 
species,  continued  passage  through  one  type  of  host  (rabbits) 
will  increase  the  virulence  for  this  one,  considerably 
diminishing  its  invasive  power  for  man.  Organisms  Hke  the 
gonococcus,  which  spontaneously  infect  man  only,  exhibit 
a  distinctly  nutritive  adaptation  by  refusing  to  grow  on 
anything  but  human  protein  in  the  first  generations  of 
artificial  cultivation,  rapidly  losing  this  fastidiousness  after 
a  short  time  of  test-tube  existence. 

While  these  and  many  other  examples  that  might  be 
given  illustrate  the  dehcacy  of  adaptation  to  the  invasive 
from  the  saprophytic  condition,  still  more  remarkable  is 
the  speed  and  ease  with  which,  in  the  laboratory,  we  can 
increase  or  decrease  the  virulence  or  invasive  powers  of 
certain  bacteria  by  the  simplest  expedients.  With  the 
pneumococcus,  for  instance,  we  can  readily,  by  successive 
mouse  passage,  enhance  virulence  until  one-miflionth  of  a 
broth  culture  wifl  kill;  and  by  properly  manipulating  this 
same  culture,  we  can  obtain  individual  so-called  "rough" 
colonies,  which  are  typical  in  most  of  their  biological  proper- 
ties, but  win  no  longer  kiO  mice  except  in  large  doses.  It  is 
becoming  increasingly  apparent  that  the  study  of  bacterial 
mutation  is  promising  to  develop  facts  of  profound  biological 
importance  since,  together  with  the  loss  of  virulence,  changes 
may  occur  in  cefl  chemistry  and  immunological  properties. 

Since  every  infection  is  of  course  a  process  in  which  the 
two  chief  variables  concerned  are  the  pathogenic  micro- 
organism and  the  host,  it  has  been  necessary  to  discuss 
briefly  the  factors  influencing  the  invader.  We  are  chiefly 
concerned  in  this  chapter,  however,  with  the  conditions  of  the 
host  by  which  invasion  is  either  permitted  or  prevented. 
The  higher  animals  all  possess  in  their  normal  state  a 
so-called  "natural"  resistance  against  many  bacteria. 
This  natural  resistance  can  to  some  extent  be  analyzed  into 


410  HUMAN   BIOLOGY 

a  cooperation  of  the  blood  plasma,  the  circulating  nucleated 
cells  and  certain  fixed  cells  largely  represented  by  units 
of  the  reticulo-endotheial  system,  so  that  even  when  con- 
siderable amounts  of  bacteria  which  cannot  by  themselves 
gain  entrance  are  experimentally  injected  into  such  animals, 
they  are  promptly  disposed  of  by  a  process  not  identical  with, 
but  similar  to  that  which  is  active  in  acquired  immunity. 

Many  possible  balances  in  the  reaction  between  the  in- 
vader and  the  host  are  conceivable,  and  for  this  reason  it  is 
not  surprising  that  in  the  natural  evolution  of  infectious 
disease  many  different  types  of  relationship  have  been  estab- 
hshed.  Thus,  when  hemolytic  streptococci,  pneumococci, 
anthrax,  plague  or  typhoid  baciUi,  or  many  other  bacteria, 
invade  the  body,  they  set  up  a  violent  reaction — an  expres- 
sion partly  of  their  own  toxic  properties,  partly  of  the  ener- 
getic effort  of  the  host  to  get  rid  of  them — and  these  together 
constitute  disease.  In  other  cases  such  as  the  treponema 
pallidum  of  syphilis,  the  organism,  probably  because  it  has 
for  centuries,  been  directly  passed  from  body  to  body, 
without  intermediate  external  existence,  is  so  perfectly 
adapted  to  the  tissues  of  man  that  it  creates  little  acute 
disturbance.  Injury  is  manifest  only  after  considerable 
accumulation,  and  we  have  a  chronic  and  slowly  destructive 
disease.  This  state  of  affairs  approaches  the  quasi  sym- 
biotic conditions  observed  in  certain  sarcosporidial  and 
spirochetal  diseases  in  mice  and  in  trypanosome  infections 
in  rats,  in  which  it  may  be  said  that  infection  has  developed 
into  an  adaptation  so  perfect  that  the  host  no  longer  reacts, 
and  manifest  disease  does  not  follow.  At  opposite  ends  on  the 
series,  then,  we  may  have  disease  without  infection,  as  in 
diphtheria  and  tetanus,  where  the  bacteria  do  not  invade 
but  manufacture  externally  a  toxin  which  is  absorbed;  and 
infection  without  disease,  as  in  the  last  cases  mentioned. 

When  bacteria  that  are  capable  of  causing  a  fatal  infection 
in  an  animal  or  in  a  human  being  enter  the  body,  immediately 
a  struggle  is  set  up  in  which  the  bacteria  grow  and  elaborate 
any  poisonous  substances  which  they  are  capable  of  produc- 
ing. Both  b}^  their  presence  in  the  intercellular  spaces  and 
by  the  toxic  inflammatory  effects  of  their  constituents  and 
products,  they  injure  the  cells  of  the  immediate  neighbour- 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  4 II 

hood  in  which  they  are  lodged,  as  well  as  remote  areas  to 
which  their  toxic  products  are  carried.  The  body  responds 
by  a  process  which,  in  its  main  Hnes  of  strategy,  includes 
both  a  neutrahzation  of  the  bacterial  poisons  and  a  destruc- 
tion of  the  invading  cells  by  the  blood  plasma  and  by  the 
phagocytic  action  of  the  white  blood  cells  and  of  certain 
fixed  tissue  cells.  If  the  body  survives,  a  subsequent  invasion 
of  the  same  bacteria  encounters  a  considerable  enhance- 
ment of  all  these  properties,  which  results  in  a  much  more 
rapid  disposal  of  the  invaders.  When  we  say  that  the  reaction 
is  "specific,"  we  approach  the  most  mysterious  biological 
fact  in  the  process,  and  mean  thereby  that  this  entire  train 
of  events  is  strengthened  by  the  first  infection  only  in  regard 
to  the  same  or  to  closely  related  infectious  agents. 

The  simple  observation  that  a  body  which  has  survived  an 
infection  is  thereafter  resistant  to  reinfection  by  the  same 
agent  for  periods  from  fractions  of  a  year  to  the  remainder 
of  life,  is  as  old  as  history,  was  known  in  ancient  China  and 
India,  was  recorded  by  Thucydides  in  regard  to  the  plague 
in  Athens,  and  was  generally  familiar  to  clinicians  when 
Jenner  applied  it  experimentally  in  smallpox.  It  was  scien- 
tifically formulated  by  Pasteur  with  bacteria,  and  its  analysis 
has  constituted  the  material  of  the  science  of  immunology. 

Briefly  summarized,  the  basic  facts  of  the  analysis,  as  far 
as  it  has  gone,  are  as  follows:  Normal  animals,  whether  they 
possess  a  demonstrable  degree  of  resistance  or  no  resistance 
whatever  to  a  given  infectious  agent,  may  be  rendered 
highly  resistant,  sometimes  even  completely  immune,  by  a 
variety  of  methods.  These  are: 

1.  The  survival  from  an  infection  with  the  particular  micro- 
organism administered  either  in  small  doses  or  in  an  attenuated 
(weakened)  form. 

2.  Systematic  dosage  with  the  dead  organisms. 

3.  Similar  treatment  with  the  products  of  the  organism  (toxins). 

When  the  resistance  has  been  achieved,  the  animal  has 
changed  profoundly  in  its  reaction  to  this  particular  infection 
and  to  no  other,  and  its  immunity  can  to  a  large  extent  be 
referred  to  the  blood  plasma  and  to  certain  special  cells. 
If,  as  in  diphtheria  or  tetanus,  the  toxins  are  the  important 


412  HUMAN   BIOLOGY 

factors  of  injury,  treatment  with  the  toxins  alone  will 
induce  the  formation  within  the  animal  of  a  neutralizing 
constituent  in  the  blood,  the  specific  antitoxin,  which  will 
not  only  protect  the  tissues  of  the  immunized  animal  from 
injury  by  any  absorbed  or  injected  toxin,  but  can  be  used, 
by  taking  the  serum  from  such  an  animal,  to  protect  others, 
i.e.,  antitoxin  treatment.  And  to  emphasize  that  these  so- 
called  bacterial  toxins  are  merely  a  special  group  of  a  larger 
class  of  similar  things  in  nature,  it  is  well  to  state  here  that 
what  we  have  said  about  bacterial  toxins  applies  as  well  to 
snake  poisons,  spider  poisons,  the  vegetable  poisons  (ricin, 
crotin  and  abrin)  and  to  certain  enzymes. 

In  cases  in  which  the  invasive  power  of  the  bacteria 
is  relatively  more  important  than  their  toxin  production  the 
immunity  is  antibacterial  rather  than  antitoxic,  and  the  blood 
serum  of  the  animal  treated  with  the  attenuated  or  dead 
bacterial  bodies  acquires  a  substance  which  specifically  unites 
with  the  bacteria  (sensitizat  on)  and  alters  them  so  that  they 
are  more  susceptible  to  a  number  of  destructive  effects. 
Bacteria  mixed  with  such  an  immune  serum  will  rapidly  clump 
into  masses,  precipitating  to  the  bottom  of  the  tubes.  By 
suitable  experiments  (absorption  tests)  it  can  be  shown  that 
in  the  course  of  this  phenomenon  the  bacteria  have  absorbed 
out  of  the  serum  the  substance  responsible  for  the  reaction. 
Also,  it  can  beshown  that  the  actual  clumping  of  the  bacteria 
is  due  to  the  fact  that  union  with  this  immune  constituent  of 
the  serum  has  rendered  the  cells  susceptible  to  electrolytes  in 
the  fluid,  probably  altering  their  suspension-equilibrium,  so 
that  they  are  precipitated  by  the  electrolytes  just  as  are  col- 
loidal suspensions.  At  the  same  time  the  union  with  this  anti- 
body or  "sensitizer,"  as  it  is  called,  has  rendered  the  bacteria 
susceptible  to  an  enzyme-like  normal  constituent  of  the 
serum,  the  "alexin"  or  "complement,"  which  can  often 
kill  sensitized  bacteria  of  varieties  which  it  cannot  injure  in 
the  unsensitized  state.  Again,  the  wandering  and  fixed 
phagocytic  cells  of  the  body,  leucocytes  and  various  endothelial 
cells,  can  take  up  and  destroy  virulent  bacteria  much  more 
effectively  after  their  union  with  the  serum  antibody  than 
in  their  native  condition.  Thus  the  immunization  has  induced 
the  formation  of  a  specific  reaction  body  which  becomes  free 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  4I3 

in  the  serum,  which  has  a  specific  capacity  for  union  with  the 
particular  bacteria  and  which,  by  uniting  with  them,  changes 
them  so  that  they  are  more  easily  destroyed  and  removed. 

There  are,  of  course,  many  other  factors  involved,  but  for 
the  purpose  of  making  thoroughly  clear  the  remarkable 
capacity  of  the  body  to  adjust  itself  to  an  abnormal  condition 
which  threatens  its  destruction,  it  is  best  to  follow  only  the 
main  Hnes  of  occurrence,  rather  than  to  confuse  the  primary 
issue  by  an  abundance  of  less  important  detail.  This  dormant 
capacity  of  the  body  to  meet  specifically  an  abnormal 
condition  which  threatens  its  survival  would  be  difficult  to 
understand  if  the  described  train  of  events  were  confined  to 
infection.  But,  although  the  "antibody"  mechanism  was 
discovered  first  in  connection  with  infectious  diseases  and, 
in  this  relation,  has  its  most  immediate  practical  interest, 
it  is  important  to  realize  that  this  inherent  capacity  of 
specific  response  applies  broadly  to  the  entrance  of  a  multi- 
tude of  extraneous  materials,  of  which  bacteria  are  only 
a  small  and  relatively  unusual  class.  To  make  this  clear 
it  will  be  necessary  to  consider  the  processes  that  go  on  in  the 
metabolism  of  higher  animals  and  the  chemical  nature  of  the 
substances  which  normally  penetrate  within  the  physiological 
interior  of  the  body. 

In  the  lower  forms  of  animal  life  digestion  is  intracellular, 
and  within  specialized  vacuoles  solid  particles  of  the  foreign 
substances  are  broken  down  into  forms  in  which  they  can 
be  incorporated  into  the  protoplasm  of  the  cell.  In  the  lower 
metazoa  the  digestive  process  remains  intracellular,  but  is 
gradually  being  relegated  to  special  endothelial  cells.  Through- 
out the  upward  scale  of  the  animal  kingdom  there  is  a  gradual 
substitution  of  extracellular  for  intracellular  digestion. 
In  the  higher  forms  of  animal  life  normal  digestion  is  so  exclu- 
sively the  task  of  certain  specialized  intestinal  enzymes 
that  the  materials,  which  eventually  enter  the  circulation 
and  are  distributed  to  the  cell  units  for  assimilation,  have 
been  converted  into  diffusible  form,  chemically  adjusted 
to  cellular  needs.  Thus,  it  is  likely  that  in  the  completely 
normal  body,  a  condition  which  probably  never  exists  except 
for  short  periods,  no  foreign  fats,  proteins  or  complex  car- 
bohydrates penetrate  into  the  circulation,  the  fats  being  split 


414  HUMAN    BIOLOGY 

in  the  intestine  to  fatty  acids  and  glycerine,  the  proteins  to 
amino-acids  and  the  carbohydrates  to  simple  sugars. 
Should  unaltered  fats  of  foreign  origin  get  into  the  circulation, 
abnormal  conditions  may  ensue  of  which  we  are  more  or  less 
in  ignorance  but  which,  at  any  rate,  have  no  bearing  on 
processes  of  immunity  to  infection.  The  same  is  true  of 
most  of  the  carbohydrates,  except  certain  speciaHzed  ones 
produced  by  bacteria.  In  regard  to  the  proteins,  however, 
conditions  are  different.  Complete  proteins,  including  the 
materials  of  the  bacterial  body,  form  a  class  of  substances 
which  cannot  enter  the  circulation  and  come  into  contact 
with  the  tissues  of  the  higher  animals  without  arousing 
reactions  by  which  these  tissues  are  specifically  and  in  all 
probability  permanently  changed.  For  this  reason,  these 
materials  are  grouped  together  and  designated  by  the  word 
antigen. 

Since  the  purpose  of  this  chapter  is  to  explain  a  rather 
complex  state  of  affairs  with  as  little  use  of  technical  phrase- 
ology as  possible,  we  may  be  permitted  to  explain  the  term 
"antigen"  in  greater  detail.  It  is  a  functional  term  which, 
irrespective  of  chemical  structure,  designates  any  substance 
which  can  arouse  tissue  cells  to  this  specific  reaction.  If 
materials  of  this  class,  whether  animal  or  vegetable  proteins, 
bacteria,  or  various  poisons,  or  enzymes  are  administered  to 
the  animal  body  in  such  a  manner  that  preliminary  digestion 
is  avoided,  for  instance  by  injection  with  the  hypodermic 
syringe,  there  appear  after  a  time,  in  the  circulation  of 
the  treated  animal,  substances  which  specifically  react  with 
the  injected  "antigen."  Almost  the  entire  structure  of  the 
science  of  immunology  consists  in  the  detailed  elaboration 
of  this  simple  law  of  antigens.  Thus,  to  illustrate  by  an 
ordinary  example,  horse  serum  fed  to  a  normal  individual  is 
broken  up  in  the  stomach  and  upper  intestine  into  its 
component  amino-acids,  and  these  are  absorbed,  distributed 
and  utilized  by  the  cells.  The  same  horse  serum,  obtaining 
unchanged  access  to  the  circulation,  may  be  demonstrated  in 
the  blood,  unchanged  but  gradually  diminishing  in  amount, 
for  a  considerable  time — days  and  weeks.  As  it  disappears, 
however,  the  blood  serum  of  the  injected  individual  acquires 
a  property  not  previously  possessed,  namely,  of  specifically 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  4I5 

precipitating  horse  serum.  By  "specificity"  in  such  a  case  we 
imply  that  the  serum  of  an  individual  so  treated  precipitates 
horse  serum  only,  and  not,  to  any  extent,  any  other  protein. 
Since  the  precipitating  property  appears  to  depend  upon 
some  newly  produced  cellular  product,  it  has  been  assumed 
that  the  blood  contains  a  substance  absent  from  the  animal 
originally,  conveniently  spoken  of  as  an  "antibody,"  in 
this  case  "precipitin." 

That  there  is  an  actual  substance  in  the  serum  upon 
which  these  reactions  depend  and  that  they  are  not  merely 
the  consequences  of  a  change  of  state  is  made  apparent 
by  the  fact  that  the  antigenic  substances  absorb  out  of 
the  serum  their  individual  reaction  bodies.  Thus,  if  an 
agglutinating  or  a  precipitating  serum  is  mixed  with  the 
bacteria  or  other  antigen  upon  which  this  serum  exerts  its 
action,  the  supernatant  fluid  of  such  a  mixture  will  be 
deprived  of  the  capacity  to  produce  the  particular  eff"ect, 
and  this  power  can  be  shown  to  have  been  transferred  to 
the  precipitate.  For  to  some  extent  the  precipitate  can  be 
washed,  its  unit  combinations  partially  dissociated  and  the 
so-called  "antibodies"  recovered. 

It  is  this  property  possessed  by  substances  of  a  given 
chemical  and  physical  structure  to  arouse  a  specific  response 
on  the  part  of  the  tissue  cells  which  constitutes  the  basic  fact 
of  immunology.  For  the  bacterial  body  and  many  of  the 
bacterial  products,  toxic  or  otherwise,  belong  to  this  class  of 
antigenic  substances,  and  an  infection  is  therefore  nothing 
more  than  the  entrance  of  an  antigen  into  the  physiological 
interior  of  the  body,  diff'ering  from  a  similar  penetration  of 
undigested  egg  white,  milk  or  any  other  protein  chiefly  in 
that,  in  the  case  of  bacteria,  the  antigen  is  a  living  cell  which 
can  multiply  at  the  expense  of  the  host  and  often  possesses 
general  and  specific  toxic  properties,  together  with  selective 
powers  of  localizing  or  penetrating  particular  organs  or 
tissues  of  the  host.  These  diff"erences  from  ordinary  antigens 
and  the  fact  that,  in  regard  to  these  variables,  no  two  species 
of  bacteria  are  entirely  alike,  has  of  course  necessitated  the 
assembhng  of  a  formidable  volume  of  precise  information,  a 
good  deal  of  which  is  of  practical  value  in  diagnosis  and 
treatment.  The  science  of  immunology,  therefore,   is  one 


4l6  HUMAN    BIOLOGY 

which  has  developed  innumerable  intricate  ramifications. 
But  when  all  is  said  and  done,  they  all  take  ultimate  root  in 
the  antigenic  properties  of  bacterial  materials — just  as  the 
chemical  sciences  are  basically  founded  on  the  electrical 
laws  governing  atomic  and  molecular  structure,  except 
that  we  know  considerably  less  about  the  antigens  and  their 
reactions. 

In  regard  to  the  nature  of  the  antigenic  substances  and 
in  an  analysis  of  the  responses  aroused  by  them  in  the  cells  of 
the  body  we  must  therefore  seek  for  light  concerning  one  of 
the  most  fundamental  laws  of  function  of  the  living  cell, 
physiological  in  the  sense  that  it  is  possessed  by  all  of  the 
higher  animals  as  a  latent  capacity  and  in  that  it  invariably 
is  called  into  play  in  one  way  or  another  in  the  hfe  of  any 
individual;  abnormal  only  in  the  sense  that  it  is  probably 
never  in  action  under  conditions  of  perfect  metabolism,  a 
state  which,  however,  cannot  be  expected  to  prevail  except 
for  short  periods  in  the  course  of  any  existence.  Whether 
this  emergency  reaction  capacity  should  be  regarded  as  a 
survival  of  the  more  primitive  properties  of  a  less  specialized 
cellular  cooperation,  or  a  function  acquired  to  meet  the 
inevitably  frequent  entrance  of  foreign  proteins  into  the 
animal  body  is  an  interesting  subject  for  speculation,  but 
quite  unanswerable  at  the  present  time. 

Although  the  term  "antigen"  was  first  devised,  on  an 
erroneous  etymological  construction,  to  designate  all  sub- 
stances which  were  capable  of  inciting  the  animal  body  to 
the  production  of  antibodies,  there  is  little  doubt  that 
the  meaning  of  the  word  should  be  more  comprehensive  than 
this.  At  the  time  when  it  was  introduced  investigations 
upon  "hypersensitiveness"  were  in  their  infancy  and  the 
power  of  a  foreign  substance  to  arouse  a  specific  reaction 
in  the  cells  of  the  body  was  recognized  only  by  the  discovery 
of  antibodies  in  the  circulating  blood,  either  by  the  tech- 
nique of  agglutination,  precipitation  or  "sensitization"  to 
complement.  It  has  since  become  clear  that  many  substances 
may  alter  the  specific  reaction  capacity  of  the  cells  without 
actually  leading  to  the  formation  of  circulating  antibodies. 
The  recognition  of  this  state  of  affairs  has  come  largely 
through  investigations  of  the  strange  phenomena  of  "ana- 


ADJUSTMENT    TO    INFECTIOUS    DISEASE  417 

phylaxis"  and  "allergic  hypersensitiveness."  These  occur- 
rences can  best  be  explained  by  examples.  Antigenic 
substances  like  horse  serum  and  egg  albumen  when  injected 
into  normal  guinea  pigs  may  cause  no  reactions  whatever, 
though  given  in  considerable  amounts.  The  material  itself 
is  entirely  inocuous.  If,  however,  the  first  administration  is 
followed  in  the  course  of  two  or  three  weeks  by  a  second 
injection  of  the  same  material,  severe  injury  of  the  animal 
may  result.  Since  the  original  material  was  harmless,  it  is 
obvious  that  some  change  was  brought  about  in  the  animal 
as  a  result  of  the  first  contact;  and  the  state  reached  is 
known  as  "specific  hypersensitiveness"  or,  in  the  case  of  the 
complete  proteins,  "anaphylaxis."  An  animal  so  sensitized 
will  react  only  to  the  particular  material  with  which  it  has 
been  prepared.  If,  for  instance,  one  guinea  pig  is  given  egg 
white  and  another  horse  serum,  a  subsequent  injection  of 
horse  serum  into  the  "egg  white  animal"  will  be  entirely 
uneventful,  and  vice  versa.  But  a  repetition  of  the  identical 
material  into  the  same  animal  will  arouse  a  response  apparent 
both  by  local  edema,  possibly  tissue  destruction,  and  by 
systemic  symptoms  which  may  cause  death  within  a  few 
minutes.  It  is  quite  impossible  to  summarize  these  reactions 
by  any  generalization  since  they  vary  with  the  several 
animal  species  and  are  subject  to  differences  dependent  upon 
dosage  and  the  intervals  between  injections.  Physiologically 
the  poirit  of  attack  appears  to  lie  chiefly  in  the  capillary 
endothelium,  which  is  rendered  permeable  as  a  result  of 
the  reaction,  and  there  is  reason  to  believe  that  the  further 
complex  train  of  events  which  is  set  in  motion  in  other, 
parts  of  the  body  is  secondary  to  this  primary  injury. 

But  while  there  is  much  that  is  obscure  about  the  actual 
causes  of  injury  and  death  in  such  cases,  it  is  quite  clear 
that  the  process  is  set  in  motion  by  union  of  the  reinjected 
antigen  with  antibodies  that  were  formed  in  the  animal  as  a 
result  of  the  first  injection.  These  antibodies,  remaining  to 
some  extent  incorporated  in  the  cells  that  formed  them, 
have  acquired,  in  consequence,  a  greatly  enhanced  capacity 
for  union  with  the  antigen;  and  this  sudden  introduction  of  a 
foreign  protein  into  or  upon  the  surface  of  the  tissue  cells, 
particularly   of  the   reticulo-endothelial   system,   results   in 


4l8  HUMAN   BIOLOGY 

injury.    We    can,    for    instance,    inject    antibodies    against 
horse  serum  into  a  normal  guinea  pig  and,  allowing  time  for  a 
penetration  of  these  reaction  bodies  into  the  cells,  render  the 
an  mal  "passively'    sensitive  to  horse  serum.  Quantitative 
exper  ments  indicate  that  the  power  of  an  "antihorse  serum" 
thus  to  sensitize  a  normal  animal  "passively"  is  propor- 
tionate to  the  contents  of  "antihorse"  antibodies.  And  it  is 
a  logical  deduction,  therefore,  that,  knowing  the  reactions 
to  be  cellular,  the  cells  have  absorbed  the  specific  antibodies, 
now  containing,  in  the  jargon  of  our  trade,  "sessile  receptors 
or  antibodies"   for  horse  serum.    For  many   reasons   it  is 
clear  that  a  similar  mechanism  underlies  most  of  the  other 
forms  of  hypersensitiveness  which  are  concerned  in  important 
pathological  conditions  of  man,  namely,  asthma,  hay  fever, 
serum   sickness   and   perhaps   drug   idiosyncrasies.   And   in 
many  of  these  conditions,  although  the  fundamental  phe- 
nomena are  identical  with  those  encountered  in  hypersensi- 
tiveness  to    horse    serum    and    other   proteins,    circulating 
antibodies  have  not  been  demonstrable.  For  many  reasons 
which  it  is  quite  impossible  to  analyze  in  this  connection, 
it  seems  probable  that  in  several  of  these  conditions  the 
antigen  is  quite  capable  of  arousing  a  specific  change  in 
the  reaction  capacity  of  the  cells  analogous  in  every  way  to 
that  aroused  by  the  proteins  but  not  followed  by  the  pro- 
duction of  circulating  antibodies.  We  would,  accordingly, 
define  the  term  "antigen"  today  not  as  representing  only 
substances  that  lead  to  antibody   formation,   but  as  any 
material  which,  introduced  into  the  physiological  interior  of 
the   body,   leads   to   a   specific  alteration   of  the   reaction 
capacity  of  the  cells,  detectable  now  not  only  by  the  presence 
of  antibodies,  but  by  the  development  of  local  or  general 
hypersensitiveness  to  the  particular  substance.  Nevertheless, 
while  it  is,  of  course,  important  to  recognize  that  there  is  a 
difference    between    those    foreign    substances    which    give 
rise  to  antibodies  and  those  for  which  no  circulating  anti- 
bodies appear,  it  is  quite  as  necessary  to  remember  that 
the  fundamental  occurrences  in  all  forms  of  hypersensitive- 
ness   are    alike    in    indicating    specific    alterations    in    cell 
responses,    identical    in    all    phases  except  in  those  which 
depend   upon   the   presence   of  the   circulating   antibodies. 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  419 

The  change  in  cell  capacity  therefore  is  the  essential  fact 
and  the  discharge  of  the  reaction  substances  into  the  cir- 
culation purely  secondary,  depending  in  some  manner 
upon  the  chemical  and  physical  properties  of  the  particular 
antigen. 

The  most  perfect  antigenic  substances  are  the  proteins 
and  it  is  from  the  study  of  these  that  most  of  our  knowledge 
is  derived.  It  would  appear  that  the  antigenic  function  may 
be  in  some  manner  related  to  non-difFusibiHty,  since  the 
nature  and  molecular  size  of  antigenic  substances  seem  to 
imply  reaction  with  the  cell  surfaces.  Teleologically  regarded, 
this  may  mean  that  substances  that  can  penetrate  into  the 
cells  and  undergo  intracellular  digestion  may  not  require 
the  development  of  a  special  antibody  mechanism.  The 
second  criterion  necessary  to  the  possession  of  antigenic 
function  seems  to  be  an  inability  of  the  healthy  body  to 
eliminate  these  substances  promptly  by  the  ordinary 
means  of  excretion.  Take  the  case  of  egg  white.  This  antigen 
is  eliminated  by  monkeys  almost  quantitatively  within  a 
few  hours,  little  or  no  antibody  is  formed  and  hypersensi- 
tiveness  develops  only  to  a  slight  degree.  And  when  in 
animals  like  rabbits,  or  even  in  man,  antibodies  are  studied  in 
response  to  the  injection  of  horse  serum,  the  horse  seru*m 
may  be  found  circulating  for  days,  disappearing  only  grad- 
ually as  antibodies  begin  to  form.  Thus,  the  most  effective 
antigens  are  substances  which  are  not  easily  eliminated, 
which  are  not  removed  from  the  circulation  with  facility  and 
which,  presumably  on  this  account,  form  a  slow  union  with 
the  cells  of  the  body. 

It  seems  quite  clear  that  the  antigenic  proteins,  besides 
possessing  the  essential  physical  properties  mentioned  above 
must  undergo  a  very  definite  chemical  union  of  some  kind 
with  the  responding  cells,  which  is,  indeed  an  inevitable 
conclusion  from  investigations  on  the  nature  of  specificity. 

It  is  in  this  matter  of  specificity  that  the  immunological 
reactions  illustrate,  more  than  any  other  physiological 
phenomena,  the  exquisite  powers  of  adjustment  of  the  animal 
cell.  In  no  other  group  of  biological  observations  is  speci- 
ficity so  finely  differential  and  so  manifold.  The  response  of 
any  given  species  of  animal  in  essential  mechanism  to  the 


420  HUMAN   BIOLOGY 

injection  of  all  foreign  proteins  is  alike.  But  in  every  case, 
limited  only  by  the  available  number  of  protein  antigens, 
the  response  is  specific  for  the  particular  variety  injected. 
Thus  the  immunological  response  is  so  exact  differentially 
that  the  antibodies  elicited  by  the  several  proteins  vary 
with  every  animal  and  plant  species  from  which  the  antigens 
are  derived  and,  in  their  overlapping,  follow  with  consider- 
able accuracy  zoological  and  botanical  relationships.  Anti- 
bodies to  horse  serum,  for  example,  react  partially  with 
that  of  zebra,  mule  and  donkey,  and  the  kinship  of  man 
with  the  higher  apes  may  be  more  fundamentally  determined 
by  the  similarity  of  the  serum  antigens  than  by  any  of  the 
more  superficial  characteristics. 

Of  the  greatest  importance  to  the  biological  principles 
we  are  discussing  are  the  investigations  planned  to  reveal 
the  properties  of  the  various  protein  molecules  which  deter- 
mine specificity,  and  which  have  been  authoritatively 
reviewed  by  Wells  who  himself  has  added  much  to  the 
understanding  of  these  conditions.  There  is  no  longer  any 
question  about  the  fact  that  immunological  specificity  is  a 
function  of  the  chemical  structure  of  the  particular  protein 
antigen.  Immunological  similarity  is,  as  Wells  has  repeatedly 
shown,  based  on  chemical  similarity,  while  immunological 
differences  are  coordinate  with  chemical  differences. 

While  the  protein  nature  of  the  substance  as  a  whole 
seems  essential  to  its  antigenic  function,  it  is  nevertheless 
not  the  entire  molecule  which  determines  the  specificity. 
This  has  been  variously  demonstrated  by  Pick,  Landsteiner, 
Wells  and  others  who  have  shown  that  by  the  introduction 
of  simple  radicals,  e.g.  iodine,  diazo  and  nitro  groups  which 
combine  with  the  aromatic  ring  of  certain  amino  acids,  or 
even  by  alteration  of  certain  salt-forming  groups  of  the 
protein,  the  specificity  of  the  particular  protein  may  be 
shifted  from  its  original  species  relationship  to  another 
depending  on  the  chemical  change.  In  this  way  an  iodized 
horse  serum  produces  antibodies  that  react  with  other 
iodized  proteins,  but  not  as  well,  at  least,  with  the  original 
native  horse  serum.  It  is  quite  beyond  the  scope  of  this 
chapter  to  enlarge  upon  this  most  important  phase  of 
immunology,  and  the  reader  whose  interest  has  been  aroused 


ADJUSTMENT   TO    INFECTIOUS   DISEASE  421 

had  best  consult  the  thorough  and  critical  discussions  of 
this  subject  by  Wells  in  his  "Chemical  Aspects  of  Immunity." 
The  chemical  facts  which  we  have  outlined  make  it  quite 
plain  that  in  stimulating  the  cellular  responses  the  so-called 
antigenic  substances  unite  primarily,  because  of  their 
non-diffusibihty,  with  the  cell  surfaces;  but  it  is  rendered 
hkely  by  a  number  of  experiments  that  the  antigenic  sub- 
stance may  secondarily  be  incorporated  in  the  cell  sub- 
stance. Since,  as  we  have  seen,  a  relatively  small  part  of 
the  protein  molecule  is  associated  with  the  specificity, 
it  may  well  be  that  the  union  with  the  cell  is  something 
like  an  orientation  of  the  foreign  protein  molecule  in  the 
cell  membrane,  reacting  through  the  group  which  carries 
its  specific  affinity  for  the  cell  substance.  What  happens 
after  this  is  entirely  mysterious.  That  the  cell  should  be 
capable  of  responding  by  an  individually  different  reaction 
product  to  almost  any  number  of  foreign  proteins  and,  in 
addition  to  this,  to  a  large  variety  of  chemically  altered 
products  of  each  of  these  proteins  is  an  easily  demonstrable 
fact  for  which  no  theory  is  at  present  adequate.  The  only 
explanation  of  this  state  of  affairs  which  has  ever  been 
ventured  is  the  side  chain  theory  of  Ehrlich,  which  is  actually 
nothing  more  than  a  restatement,  in  theoretical  language, 
of  the  fundamental  observations.  It  states,  in  substance,  that 
after  the  antigen  has  united  with  the  cells,  the  particular 
radicles  of  the  protoplasm  which  possessed  the  specific 
affinity  for  the  antigen  are  thrown  out  of  action  and  must  be 
reproduced  by  the  cell  for  its  functional  purposes.  It  is 
assumed  that  continuous  stimulation  of  the  cell  in  this 
manner,  by  repeated  saturation  of  the  particular  cell  con- 
stitutents  involved,  leads  to  an  overproduction  of  these 
substances,  which  finally  takes  place  to  such  a  degree  that 
they  are  discharged  into  the  circulation.  These  so-called 
"cell  receptors"  become  the  circulating  antibodies.  Since 
they  possess  a  specific  affinity  for  the  antigen,  they  now 
unite  with  it  in  the  circulating  blood.  The  theory  is  spoken 
of  as  the  "side  chain  theory"  because,  by  analogy  with 
organic  chemistry,  Ehrlich  conceived  the  cell  receptors  as 
"side  chains"  of  the  protoplasm  which  could  cover  many 
specificities  because  of  the  great  complexity  of  this  material. 


422  HUMAN   BIOLOGY 

It  would  be  quite  impossible  to  follow  the  intricate  rami- 
fications into  which  this  theory  has  led  and  which,  though 
not  demonstrable  in  many  of  its  details,  is  still  the  most 
inteIHgent  analysis  of  the  conditions  that  has  been  offered. 

The  body  cell  is,  of  course,  a  complex  laboratory  in  which 
a  great  many  different  chemical  processes  can  take  place 
side  by  side.  Bayhss,  summarizing  the  activities  of  the  cell, 
describes  it  as  "a  complex  of  substances  of  varying  chemical 
natures  and  in  various  states  of  aggregation,  associated 
together  by  forces  of  surface  tension  electrically  charged, 
etc.  In  these,  the  liquid  state  enables  an  elaborate  play  of 
forces  to  take  place.  Chemical  reactions  can  effectively 
proceed  simultaneously  in  different  parts  of  the  cell,  so 
that  there  is  some  mechanism  by  which  one  part  is  tem- 
porarily isolated  from  another."  It  is  quite  conceivable,  of 
course,  that  a  great  many  complex  reactions  of  entirely 
different  nature  may  take  place  in  a  heterogeneous  system 
of  this  kind,  separated  from  each  other  by  semi-permeable 
surface  layers,  but  it  is  hard  to  conceive  the  mechanism  for 
a  train  of  events  in  which,  let  us  say,  a  molecule  of  horse 
serum  will  arouse  a  specific  antibody  response  which  in 
principle  is  exactly  like,  but  in  specificity  distinctly  separate 
from  that  aroused  by  a  molecule  of  horse  serum  into  which  a 
methyl  or  a  diazo  group  has  been  introduced.  Moreover, 
it  must  be  remembered  that  after  the  reaction  is  over, 
after  antibodies  have  been  produced,  have  circulated  and,  in 
time,  have  disappeared  from  the  blood  stream,  the  cell 
still  retains  an  increased  reaction  capacity  for  the  particular 
protein  molecule  with  which  it  has  once  reacted.  This  it  is 
impossible  to  explain  on  a  physicochemical  basis,  and  yet  is 
most  easy  to  demonstrate.  For  instance,  a  human  being 
once  injected  with  horse  serum  will,  years  later,  on  the 
intracutaneous  administration  of  a  minute  amount  of 
horse  serum,  react  with  a  rapid  formation  of  a  large  wheal, 
whereas  in  the  perfectly  normal  subject  no  reaction  whatever 
may  take  place.  And  guinea  pigs  sensitized  with  horse 
serum  by  a  single  injection  may  retain  a  hypersensitiveness 
that  will  result  in  severe  distress  of  breathing,  and  perhaps 
convulsions,  months  after  the  first  injection  of  horse  serum, 
which  in   the  normal  guinea  pig  had  no  effect  whatever, 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  423 

though  given  in  large  amounts.  This  latent  reaction  capacity 
with  or  without  formation  of  antibodies  is  a  mystery. 
Its  recognition  has  explained  many  abnormal  conditions 
in  man  and  has  led  to  much  exact  analysis,  but  it  has 
remained  in  its  fundaments  utterly  unexplained. 

In  order  to  obtain  a  proper  physiological  understanding 
of  infectious  processes,  therefore,  it  is  simplest  to  remember 
that  the  body  cells  of  bacteria  are  composed  of  protein 
materials,  largely  nucIeoprotein-Hke  substances,  which  pos- 
sess this  antigenic  function.  As  soon  as  bacteria  that  have 
become  biologically  adapted  to  entrance  and  survival  in 
the  animal  body  have  invaded  either  through  the  skin,  the 
respiratory  or  intestinal  tracts,  and  have  penetrated  into 
the  physiological  interior  they  become  foreign  antigenic 
substances  in  the  same  sense  in  which  this  would  apply  to 
egg  white  or  horse  serum  which  had  been  experimentally 
injected.  In  the  case  of  bacteria,  however,  the  antigen  is  a 
living  cell  which,  because  of  its  development  of  parasitic 
properties,  is  capable  of  increasing  in  quantity  at  the  expense 
of  the  host.  Also,  these  bacterial  invaders  often  produce 
poison  which,  in  different  bacteria,  possess  varying  selective 
pharmacological  affinities  for  definite  parts  of  the  body; 
and  these  poisons  often  are  in  themselves  antigens.  The 
nature  of  the  disease,  therefore,  depends  upon  the  manner 
of  entrance,  the  amount  of  local  inflammation  aroused  at 
the  point  of  entrance,  the  distribution  of  the  organisms  in  the 
body  and  the  particular  tissues  of  the  host  which  are  selec- 
tively injured  by  the  poisons.  Upon  these  factors  depend  the 
manner  of  infection,  the  incubation  period  and  the  nature  of 
the  symptoms;  and  if  we  know  what  the  biological  prop- 
erties of  the  various  bacteria  are  in  these  respects,  we 
have  a  logical  basis  for  diagnosis  and  can  often  state  by 
which  particular  microorganism  or  type  of  microorganism 
the  disease  is  caused. 

The  antigenic  substances  which  are  liberated  from  the 
bacteria  and  come  in  contact  with  the  cells  give  rise  to  the 
specific  increase  of  reaction  capacity  for  this  particular 
antigen.  In  some  cases  this,  let  us  call  it  "increased  specific 
irritability,"  remains  purely  a  cellular  function  and  may  be 


424  HUMAN    BIOLOGY 

observed  by  various  methods,  the  most  important  of  which 
we  can  illustrate  best  in  connection  with  tuberculosis. 

When  an  animal  or  a  human  being  is  tuberculous  and  we 
reinfect  the  skin  with  tubercle  bacilh  or  inject  a  small 
amount  of  tubercuhn,  the  tuberculous  animal  will  react 
with  a  violent  inflammation  to  a  dose  which  would  have 
aroused  little  or  no  response  in  the  normal.  This  means  that 
the  body  is  on  a  hair  trigger  in  regard  to  the  specific  response 
which  is  set  in  motion  by  contact  with  this  antigen,  and 
many  of  us  believe  that  this  specifically  irritable  condition 
is  a  direct  manifestation  of  the  protective  armament  of  the 
cells. 

In  most  cases,  however,  the  specific  reaction  aroused  by 
the  antigen  expresses  itself  not  only  by  an  increased  cell 
reaction,  but  by  the  appearance  in  the  circulation  of  cell 
products  which  we  speak  of  as  antibodies.  Efforts  have  been 
made  to  isolate  these  antibodies  and  although  we  have  no 
definite  knowledge  of  either  their  exact  chemical  nature  or 
structure,  we  do  know  that  they  are  associated  with  the 
globulins  of  the  blood  plasma.  We  know  them  by  their 
activities  rather  than  by  their  chemical  and  physical  prop- 
erties, in  that  we  can  easily  demonstrate,  by  test-tube 
experiment,  that  in  the  serum  of  an  immunized  animal  the 
particular  bacteria  with  which  the  animal  has  been  treated 
undergo  certain  changes;  and  that  by  contact  with  the 
bacteria  the  serum  loses  this  particular  property,  that  is, 
the  bacteria  specifically  absorb  these  substances. 

The  changes  which  contact  with  an  immune  serum  pro- 
duces in  bacteria  as  a  consequence  of  this  union  are  simple 
and  easily  described: 

Bacteria  which  will  remain  finely  suspended  in  a  normal 
serum  will  aggregate  in  clumps  in  a  homologous  immune 
serum. 

Similarly,  an  extract  of  bacteria  filtered  clear  and  added  to 
a  normal  serum  will  leave  the  serum  entirely  unclouded, 
whereas  a  similar  extract  of  the  same  bacteria  added  to  a 
homologous  immune  serum  will  give  rise  to  the  formation 
of  a  flocculent  precipitate. 

In  both  of  these  cases  an  analysis  of  the  mechanism  has 
shown   that   by   union   of  the   antibody   and   the  bacterial 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  425 

substance  the  molecular  equilibrium  of  the  bacterial  sus- 
pension is  altered,  so  that  precipitation  occurs,  just  as 
many  colloidal  suspensions  may  be  precipitated  in  the 
presence  of  electrolytes.  If  we  allow  bacteria  to  absorb 
their  particular  antibody  out  of  a  serum  and  wash  this 
united  complex  in  distilled  water,  these  so-called  "sensitized" 
bacteria  will  remain  unprecipitated;  but  add  an  electrolyte 
by  resuspending  them  in  salt  solution  and  rapid  precipitation 
or  agglutination  will  occur. 

Furthermore,  by  the  absorption  of  the  antibodies  the 
bacteria  become  vulnerable  to  two  effective  influences  in 
the  body.  One  is  an  enzyme-like  constituent  in  the  circulat- 
ing blood  which  is  easily  destroyed  by  heat  and  deteriorates 
on  standing,  but  which  is  always  present  in  fresh  blood. 
It  is  called  by  immunologists  "alexin"  or  "complement." 
This  active  serum  constituent  of  normal  animals  exerts  a 
destructive,  sometimes  even  a  solvent  eff"ect  upon  bacteria, 
relatively  slight  in  the  case  of  normal  bacteria,  but  materi- 
ally enhanced  after  the  bacteria  have  in  some  manner  been 
changed  by  the  union  with  their  antibodies. 

Again,  there  are  in  the  bodies  of  all  animals  definite  cells 
usually  spoken  of  as  the  "white  blood  cells"  and  certain 
wandering  cells  of  the  reticulo-endothelial  system  (clas- 
matocytes  and  phagocytic  endothelial  cells  of  various  kinds) 
which  have  retained  the  primitive  capacity  for  intracellular 
digestion.  These  take  up  foreign  particles  that  gain  access 
to  the  body.  The  particular  type  of  these  cells  that  we  are 
capable  of  studying  in  the  test  tube,  namely,  the  leucocytes  of 
the  blood,  will  not  take  up  bacteria  to  any  extent  if  washed 
leucocytes  are  brought  together  with  bacteria  in  physiological 
salt  solution.  In  the  presence  of  normal  serum  they  can 
take  up  many  bacteria  of  the  less  virulent  varieties,  but  will 
often  entirely  fail  to  ingest  bacteria  of  very  virulent  strains, 
like  pneumococci  or  virulent  anthrax  bacilli.  After  such 
bacteria,  however,  have  united  with  antibody,  they  are  so 
altered  that  the  phagocytes  can  take  them  up  and  destroy 
them  actively  and  in  large  numbers. 

The  mechanism  by  which  the  union  with  specific  antibody 
modifies  bacteria  is  still,  to  a  great  extent,  obscure.  By 
the  absorption  of  antibody  there  is  a  reduction  of  electrical 


426  HUMAN   BIOLOGY 

charge  and,  as  far  as  agglutination  is  concerned,  Northrup 
has  shown  that  there  is  both  a  decrease  of  potential  (below 
13  milHvoIts)  and  a  reduction  of  cohesive  force  by  the 
combined  action  of  the  serum  constituents  and  the  salts. 
There  is  undoubtedly  a  surface  change  in  the  bacteria 
as  a  consequence  of  their  union  with  the  specific  serum 
constituent  which  profoundly  alters  their  relationship  to 
the  environment.  But  this  we  know  empirically  rather 
than  by  any  clear  understanding  of  the  mechanism. 

It  is  therefore  plain  that  the  specific  response  of  the 
cells  stimulated  by  contact  with  the  bacterial  antigen  has 
resulted  in  the  formation  of  substances  which  render  the 
cell  itself  more  sensitive  to  the  antigen.  Free  in  the  cir- 
culation, these  antibodies  can  unite  with  the  homologous 
bacteria  and  thereby  change  them.  By  agglutination,  the 
bacteria  are  caught  in  the  finer  capillaries  and  more  easily 
ingested  by  endothelial  phagocytic  cells,  such  as  the  Kupffer 
cells  in  the  liver,  and  functionally  similar  cells  in  other 
organs.  At  the  same  time,  an  increased  susceptibility  to  the 
destructive  action  of  the  complement  or  alexin,  and  an 
increased  susceptibility  to  phagocytosis  (processes  quite 
actively  defensive)  are  initiated. 

It  must  not  be  assumed  that  by  the  analysis  of  the  relation- 
ship of  antigen  to  the  production  of  circulating  antibodies 
we  have  covered  the  entire  story  of  the  adjustment  of  the 
body  to  infection.  It  is  quite  clear  from  numerous  observa- 
tions that  in  addition  to  this  mechanism  there  is  also  a 
more  deep-seated  resistance  of  the  cells  of  the  tissues,  and  a 
capacity  for  bacterial  destruction  by  such  cells,  which  cannot 
be  brought  into  relationship  with  antibody  production. 
There  are,  in  naturally  immune  animals,  cellular  activities 
like  inflammatory  response  and  phagocytosis,  which  seem 
to  go  on  independent  of  the  presence  of  antibodies.  And 
in  animals  that  have  been  immunized  and  allowed  to  rest 
until  all  antibodies  have  disappeared  there  remains  a 
powerful  capacity  on  the  part  of  the  tissues  to  respond  to 
infection  in  which,  again,  no  cooperation  of  antibodies  can 
be  demonstrated.  Moreover,  animals  that  have  been  non- 
specificially  rendered  resistant  by  the  injection  of  broth  or 
ptopene    solutions    into    the    peritoneal    or    pleural    cavity 


ADJUSTMENT   TO    INFECTIOUS    DISEASE  427 

some  time  before  the  administration  of  virulent  organisms 
may  be  shown  to  react  with  an  energetic  formation  of 
inflammatory  granulation  tissue  which  protects  them 
in  a  manner  fundamentally  different  from  that  involved 
in  the  antigen-antibody  mechanism  which  we  have  described. 
Too  httle  is  known  about  the  nature  of  these  reactions  to 
make  it  possible  to  discuss  them  inteUigently,  but  it  must 
not  be  forgotten  that  they  exist  and  that  while  they  are 
much  more  difficult  to  investigate,  gradual  progress  is 
being  made  in  their  comprehension. 

It  is  hardly  necessary  to  state  that  no  adequate  presenta- 
tion of  the  problems  of  immunology  can  be  made  in  the 
brief  space  available.  The  study  of  the  adjustment  of  the 
human  body  to  infection  is  in  that  transitional  stage  in 
which  a  great  volume  of  insufficiently  correlated  information, 
much  of  it  purely  empirical,  must  be  subjected  to  a  more 
definite  analysis  by  physiological  and  chemical  methods. 
It  must  be  clear,  however,  even  from  the  superficial  review 
which  we  have  presented  that,  in  its  broader  conception, 
the  study  of  infection  offers  data  and  material  that  are  far 
more  significant  for  the  investigation  of  cell  reactions  than 
is  indicated  by  their  relationship  to  infectious  disease.  The 
phenomena  outhned  represent  deep-seated  capacities  of 
cell  adjustment  which  should  receive  as  much  attention  from 
the  general  physiologist  as  they  do  from  the  immunologist. 

REFERENCES 

Bail,  O.  191  i.  Das  Problem  der  Bakteriellen  Infektion.  Leipzic,  Klinkhardt. 
BoRDET,  J.  1920.  Traite  de  rimmunite.  Paris,  Alasson. 
Jordan,  E.  O.  1920.  General  Bacteriology.  Ed.  8,  Pliila.,  Saunders. 
Metchnikoff,   E.    1901.   Immunity  dans  les   Maladies   Infectueuses.   Paris, 

Masson. 
Park,   W.   H.,   Williams,  A.   W.,   and   Krumwiede,   C.    1924.   Pathogenic 

Microorganisms.  Ed.  8.,  Phila.,  Lea  &  Febiger. 
Wells,  H.  G.  1920.  Chemical  Pathology.  Ed.  4,  Phila.,  Saunders. 

1925.  Chemical  Aspects  of  Immunity.  N.  Y.,  Chemical  Catalogue. 
Zinsser,  H.  1928.  Textbook  of  Bacteriology.  Ed.  7,  N.  Y.,  Appleton. 

1923.  Infection  and  Resistance.  N.  Y.,  Macmillan. 
Note.  For  obvious  reasons  no  attempt  has  been  made  to  give  references  to 
any  but  the  larger  treatises  and  summaries  which  deal  with  this  subject. 


Chapter  XVIII 

WHAT  MEDICINE  HAS  DONE  AND  IS  DOING  FOR 

THE  RACE 

Sir  Humphry  Rolleston 

IN  the  past  medical  men,  being  those  chiefly  interested  in 
natural  science,  played  no  insignificant  part  in  the  spread 
of  general  culture.  This  is  hardly  surprising  for  the 
doctor  is  or  should  be  a  biologist,  and  medical  science  is 
practically  synonymous  with  human  biology.  Although  at 
one  time  medicine  came  within  the  province  of  the  ency- 
clopedic scholar,  the  scholar-physicians  were  not  without 
their  influence  on  classical  learning;  Thomas  Linacre  (1460- 
1524)  was  largely  responsible  for  the  introduction  of  the 
study  of  Greek  into  Great  Britain,  and  by  founding  the 
Royal  College  of  Physicians  of  London  in  15 18  encouraged 
the  pursuit  and  raised  the  standard  of  learning  among  its 
Fellows,  who  as  scholarly  physicians  set  an  example  in 
extending  the  cult  of  the  classics.  Since  the  birth  of  phys- 
iology in  1628,  when  William  Harvey  published  his  discovery 
of  the  circulation  of  the  blood,  the  observations  and  the 
needs  of  medicine  have  illustrated  and  stimulated  research 
in  physiology  and  chemistry;  though  medicine  owes  an 
ever-increasing  debt  to  these  sciences,  the  account  is  not 
entirely  one-sided:  statistical  science  too  owes  much  to  the 
stimulus  given  by  the  requirements  of  medicine,  as  realized 
and  carried  out  in  its  earliest  days  by  Sir  William  Petty 
(1623-1687)  and  later  by  Dr.  William  Farr  (1807-1883). 

In  primitive  races  the  priesthood  supervised  the  care  of 
the  body  as  well  as  the  cure  of  souls,  a  combination  with  an 
evil  influence  in  fostering  superstition  and  engendering 
belief  in  magic;  but  the  advice  given  then  and  by  medical 
men  since  with  regard  to  manner  of  life,  the  use  of  alcoholic 
stimulants  and  of  narcotics,  and  sexual  conduct  has  made 
for  good  morals.  The  medical  missionary,  the  modern  suc- 
cessor in  the  functions  of  the  primitive  priest-doctor,  gains 
potential  leverage  for  his  moral  and  religious  teaching  from 

428 


WHAT    MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      429 

his  reputation  in  relieving  the  ills  of  the  body.  As  a  general 
rule  far-reaching  medical  reforms  tend  to  bring  about  social 
reforms  and  improvement  in  the  material  and  moral 
condition  of  the  people;  the  healthy  body  favors  a  healthy 
state  of  the  mind;  the  destruction  of  insanitary  and  over- 
crowded slums  and  the  substitution  of  well-lighted  and 
properly  drained  tenements,  as  the  result  of  the  Medical 
Officer  of  Health's  activities,  must  help  the  poor  to  a  more 
happy  as  well  as  a  more  healthy  hfe;  freedom  from  epidemics 
and  chronic  disabihty  enables  self-respecting  work  to  be 
done  and  thus  banishes  worry,  discontent  and  starvation. 
As  Medicine  became  more  rational  and  entered  on  a  scientific 
stage  it  gradually  freed  itself  from  gross  superstitions, 
behef  in  the  supernatural  origin  of  disease,  demoniac  posses- 
sion, and  magic;  in  this  way  it  influenced  mankind  to  take 
a  logical  view  of  natural  phenomena. 

Passing  from  these  general  ways  in  which  medicine  has 
influenced  humanity  to  its  more  obvious  and  special  effects: 
the  death  rate  of  England  and  Wales  fell  from  20.6  per  1000 
living  in  1868  to  11. 7  in  1928,  and  the  infant  mortality  rates 
from  155  to  6^  per  1000  during  the  same  period.  Further  in 
1854  the  expectation  of  life  at  birth  for  males  was  39.9  and 
for  females  41.85  years,  whereas  in  1922  the  corresponding 
figures  were  ^^.6  and  59.58  years.  Other  European  countries 
show  changes  on  the  same  lines,  which  in  the  main  must  be 
ascribed  to  improved  conditions  of  sanitation  and  the 
influence  of  medical  science.  As  was  proved  in  the  European 
War  (1914-1918)  the  practical  apphcations  of  advances  in 
medicine  and  surgery,  sanitary  precautions,  a  pure  water 
supply,  and  generally  in  preventive  medicine  diminished  in 
an  unprecedented  degree  the  toll  of  disease  and  life  exacted 
by  war  and  pestilence.  Medicine  has  of  course  greatly 
influenced  veterinary  practice  and  thereby  improved  the 
comfort  and  well-being  of  mankind. 

Unfortunately  the  art  of  healing  may  lag  long  behind  the 
scientific  milestones;  thus  Harvey's  discovery  of  the  cir- 
culation of  the  blood  in  1628  was  not  followed  by  any 
modification  in  practical  medicine  for  many  years;  for 
example,  transfusion  of  blood,  first  performed  in  the  seven- 
teenth century,  did  not  become  a  routine  practice  until  thg. 


430  HUMAN    BIOLOGY 

Great  European  War  (191 4-1 91 8),  and  the  intravenous 
injection  of  drugs,  originated  by  Christopher  Wren  about 
1656,  did  not  come  into  general  use  until  Ehrhch's  arsphena- 
mine  was  employed  about  19 10;  Humphry  Davy's  discovery 
in  1799  of  laughing  gas  (nitrous  oxide)  as  an  anesthetic, 
though  demonstrated  again  in  the  following  year  at  Guy's 
Hospital  by  W.  Allen,  remained  unutilized  until  Crawford  W. 
Long  (1842),  and  the  dentists  Horace  Wells  (1845)  ^^^ 
WilHam  Morton  (1846)  employed  ether  as  an  anesthetic, 
and  James  Y.  Simpson  of  Edinburgh  introduced  chloroform 
in  1847.  James  Lind  showed  in  1754  how  scurvy,  which  was  a 
constant  and  most  serious  cause  of  incapacity  on  long 
voyages,  could  be  prevented,  but  it  was  not  until  1795 
that  this  simple  means  was  put  into  general  use  in  the 
Royal  Navy  of  Great  Britain  and  at  once  banished  this 
ancient  scourge.  Herbert  Spencer  instanced  this  long  delay 
of  forty-one  years  which  the  Admiralty  allowed  to  elapse 
before  acting  on  Lind's  recommendation  as  an  apt  illustration 
of  the  inertia  and  torpor  of  administrative  bodies.  Some 
years  passed  before  Lister's  (1827-19 12)  antiseptic  method 
(1868)  conquered  the  conservative  opposition  in  his  own 
country  and  transformed  surgery,  so  that  it  may  be  regarded 
as  the  greatest  material  benefit  ever  conferred  on  humanity. 
The  fight  against  childbed  or  puerperal  fever,  begun  by 
Charles  White  of  Manchester  in  1773,  Alexander  Gordon  of 
Aberdeen  in  1795,  Ohver  Wendell  Holmes  of  Boston  in 
1843,  ^^d  I-  P-  Semmelweis  of  Vienna  in  1861,  has  saved 
many  Hves  and,  with  the  later  knowledge  of  infection  and 
how  to  avoid  it,  should  certainly  be  more  successful  in  the 
future.  The  last  fifty  years  have  seen  the  most  notable 
changes  that  have  ever  occurred  in  the  history  of  surgery; 
as  the  result  of  Lister's  work  operations  on  parts  of  the  body 
which  previously  were  seldom  attempted  have  become 
commonplace,  and  the  gain  to  humanity  in  freedom  from 
suffering  and  imminent  death  has  been  incalculable,  for 
example  in  conditions  such  as  appendicitis,  gallstones, 
other  abdominal  diseases,  and  brain  tumors,  which  were 
previously  too  dangerous  to  remove  and  therefore  were 
treated  by  palliative  measures  only. 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR   THE    RACE      43 1 

Specialism.  During  the  same  period  the  intensive  study 
of  diseases  of  certain  parts  of  the  body,  such  as  the  eye, 
the  throat,  the  nose  and  ear,  the  genitourinary  organs, 
and  the  skin,  to  mention  a  few  only  of  the  numerous  speci- 
alties, has  greatly  increased  the  efficiency  of  the  heahng 
art,  for  sudb  speciahsts  acquire  a  degree  of  technical  skill 
which  is  otherwise  impossible.  In  addition  to  the  instances 
just  mentioned  the  benefit  derived  from  prolonged 
experience  in  manipulative  and  dehcate  operative  pro- 
cedures is  seen  in  some  other  branches  of  surgery,  such  as 
orthopedics  and  plastic  operations  by  which  deformities 
and  cripphng  due  to  congenital  malformations,  injury  or 
disease  are  remedied.  The  utihzation  of  natural  agencies  in 
the  treatment  of  disease  and  disabiHty  has  been  much 
extended;  thus  rest,  fresh  air,  and  sunhght  (hehotherapy)  or, 
when  the  latter  is  not  available,  artificially  produced  ultra- 
violet rays,  have  largely  superseded  the  previous  routine 
surgical  methods  in  tuberculous  disease  of  bone  and  joints. 
Massage  and  re-education  by  exercises  and  gymnastics  in  old 
injuries,  particularly  in  stiff  joints,  though  not  unknown  to 
the  Greeks  and  Romans,  have  been  much  expanded.  Treat- 
ment by  baths,  douches  and  sprays  (hydrotherapy),  long 
employed  at  spas,  has  been  elaborated  and  is  being  placed  on 
a  more  scientific  basis  much  to  the  advantage  of  patients 
with  chronic  arthritis  and  allied  affections. 

THE  BENEFITS  FROM  KNOWLEDGE  OF  THE  CAUSES  OF  DISEASE 

By  recognizing  the  existence  of  separate  diseases  (diag- 
nosis) in  the  first  place,  and  then  discovering  their 
respective  causes  (disposing  and  immediate  or  directly 
responsible)  medicine  has  supplied  the  means  for  their 
prevention  or,  if  it  is  too  late  for  this,  for  their  cure  or  relief. 
An  accurate  knowledge  of  this  branch  of  medical  science 
(etiology)  is  essential  for  any  but  the  empirical,  namely 
that  derived  from  experience,  treatment. 

The  disposing  causes  of  disease  render  the  individual 
liable  to  contract  an  illness,  such  as  influenza,  which  he 
might  otherwise  escape;  thus  an  unhealthy  environment, 
such  as  foul  air,  working  in  ill-ventilated  rooms,  improper 
food,    alcoholism,    worry,    insufficient    sleep    and    exercise, 


432  HUMAN   BIOLOGY 

may  reduce  the  bodily  resistance;  an  inherited  constitution 
may  render  the  onset  of  certain  diseases,  such  as  those  of  the 
kidneys,  heart  and  blood  vessels,  or  lungs,  a  definite  danger; 
and  one  disease  may  favor  the  onset  of  another,  for  example 
measles  and  diabetes  melhtus  may  both  be  followed  by 
tuberculosis  (see  Chap.  xx).  Realization  of  thtse  various 
tendencies  enables  precautionary  steps  to  be  taken.  Epidem- 
iology, or  the  study  of  the  conditions  responsible  for  the 
great  epidemics,  such  as  bubonic  plague  and  cholera,  has 
provided  knowledge  bearing  on  the  prevention  and  control 
of  their  occurrence,  as  is  shown  by  their  practical  dis- 
appearance from  civilized  countries  where  preventive  meas- 
ures are  adopted,  and  by  their  occurrence  in  India  and  China. 
Investigation  of  the  factors  favoring  the  onset  of  chronic 
disabling  disease,  such  as  was  advocated  and  begun  by  the 
late  James  Mackenzie,  still  awaits  completion.  In  order  to 
understand  and  remove  the  disposing  factors  an  exhaustive 
study  must  be  made  not  only  of  the  earliest  symptoms  and 
signs  of  disease,  but  of  the  patient's  environment;  circum- 
stances in  the  patient's  life  which  are  unfavorable  to  a 
healthy  existence  may  be  obvious  to  the  medical  man,  who 
may  thus  be  able  to  benefit  other  members  of  the  family. 
'  The  earliest  indications  of  disease,  such  as  undue  fatigue 
or  a  sense  of  ill-being,  are  manifestations  of  disordered 
function,  and  often  precede  any  gross  structural  change 
which  can  be  detected  by  ordinary  physical  examination 
of  the  patient.  In  the  past  the  decision  whether  or  not  there 
was  anything  the  matter  with  a  person  largely  turned  on  the 
presence  or  absence  of  gross  physical  changes.  The  study  of 
functional  efficiency  of  different  organs  of  the  body  has 
much  advanced  the  recognition  and  treatment  of  disease; 
chemical  examination  of  the  contents  of  the  stomach  after  a 
test-meal  may  show  absence  of  the  hydrochloric  acid  nor- 
mally present  and  necessary  for  the  digestion  of  proteins 
(meaty  foods)  and  this  deficiency  should  be  corrected  by 
acid  given  by  the  mouth.  Chemical  analyses  of  the  blood, 
the  air  expired  from  the  lungs,  the  urine  and  the  excreta 
provide  evidence  of  the  manner  in  which  the  changes  in 
the  living  body  producing  heat  and  energy  (metabolism) 
are  being  carried  out;  examination  of  the  blood  will  show 


WHAT    MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      433 

whether  or  not  the  kidneys  are  doing  their  work  properly 
and  so  decide  whether  or  not  it  is  safe  for  the  patient  to 
undergo  certain  operations,  such  as  the  removal  of  an 
enlarged  prostate;  examination  of  the  amount  of  sugar  in  the 
blood  may  reveal  a  tendency  to  diabetes  mellitus;  the 
functional  efficiency  of  the  kidneys  and  of  the  liver  can  be 
estimated  by  their  ability  to  deal  with  certain  dyes;  grad- 
uated exercises  throw  light  on  the  efficiency  and  reserve 
power  of  the  heart  and  on  the  state  of  general  physical 
fitness. 

Microscopical  examination  of  the  blood  may,  by  revealing 
an  increase  in  the  number  of  the  white  corpuscles  (leuco- 
cytosis),  make  it  highly  probable  that  the  infection  in  a 
case  of  fever  is  due  to  a  microorganism  likely  to  cause  an 
abscess.  By  the  bacteriological  method  of  blood-culture 
the  bacteria  causing  some  infective  diseases,  such  as  septi- 
cemia and  pyemia  (commonly  spoken  of  as  blood  poisoning), 
can  be  isolated;  further,  special,  so-called  serological, 
reactions  point  to  the  presence  of  certain  infective  diseases, 
such  as  typhoid  fever  (Widal's  reaction),  Malta  fever, 
syphilis  (Wassermann  reaction);  by  means  of  a  somewhat 
similar  method  it  is  possible  to  decide  whether  a  blood- 
stain is  due  to  human  or  animal  blood.  By  examination  of  the 
blood  (Hijmans  van  den  Bergh  reaction)  a  distinction  can 
be  drawn  between  some  forms  of  jaundice  and  so  a  decision 
can  be  made  whether  or  not  the  cause  can  be  removed  by 
operation.  Examination  of  the  blood  is  also  essential  in  the 
recognition  of  diseases  of  the  blood-forming  organs,  and 
differentiates  the  various  forms  of  anemia  and  leukemia. 

A  new  development  auxiliary  to  the  diagnosis  and  treat- 
ment of  the  poor,  especially  those  attending  hospitals,  is  the 
medical  social  service;  by  investigation  of  the  environmental 
conditions  in  the  patient's  own  home  much  light  may  be 
thrown  on  the  factors  responsible  for  early  disease  and  so 
indicate  the  lines  on  which  efficient  treatment  should  be 
carried  out.  In  order  to  treat  the  ailing  child  or  mother 
without  any  evidence  of  gross  organic  disease,  knowledge 
of  the  home  conditions  is  most  important.  Further,  in  the 
case  of  infectious  maladies,  such  as  tuberculosis,  other 
sufferers  may  be  detected;  the  factors  lying  at  the  root  of 


434  HUMAN   BIOLOGY 

functional  neuroses  and  early  mental  disorder  can  thus  be 
elucidated;  mental  hygiene  is  a  branch  of  the  preventive 
medicine  which  is  essential  in  connection  with  the  neuro- 
logical and  psychiatric  out-patient  clinics  of  a  hospital. 

The  immediate  or  directly  responsible  causes  of  disease 
include  the  numerous  infections,  the  various  forms  of 
mechanical  injury,  and  negative  factors  such  as  the  absence 
of  an  internal  secretion  or  of  a  vitamin  essential  to  the 
maintenance  of  health.  The  knowledge  of  the  immediate 
exciting  causes  of  the  infectious  diseases  is  due  to  the 
sciences  of  bacteriology  and  later  of  protozoology,  and  is  one 
of  the  greatest  milestones  in  the  history  of  medicine.  In 
the  sixteenth  century  Hieronymus  Fracastorius  of  Verona 
spoke  of  the  "seeds"  of  contagion  passing  from  one  person  to 
another,  and  was  the  first  to  compare  infection  with  vinous 
fermentation;  but  the  real  founder  of  bacteriology  was 
Louis  Pasteur  (1822- 1895)  a  chemist  and  not  a  medical 
man,  and  with  his  the  name  of  Robert  Koch  (1843-1910)  of 
Berlin  will  always  be  associated  as  a  pioneer  in  its  advance 
and  in  the  methods  of  specific  treatment  for  diseases  due  to  a 
known  microbe.  The  epoch-making  discoveries  of  the 
microorganisms  responsible  for  diphtheria,  tetanus  and 
typhoid  fever,  and  so  of  measures  for  their  prevention  and, 
to  take  a  more  modern  instance,  the  successful  elaboration 
of  insulin  in  the  treatment  of  diabetes  mellitus,  would 
have  been  impossible  without  animal  experiments.  Yet 
many  well-meaning  but  ill-advised  people,  unmindful  of 
our  Lord's  words  "Ye  are  of  more  value  than  many  spar- 
rows," have  bitterly  opposed  the  practice  of  vivisection;  it  is 
perhaps  best,  and  certainly  most  charitable,  to  assume  that 
they  know  not  what  they  do,  and  will  not  realize  the  truth 
until  it  is  revealed  to  them  by  seeing  their  young  child 
gasping  for  breath  and  dying  for  want  of  antidiphtheritic 
serum.  Pasteur  did  not  see  the  virus  of  canine  rabies  or 
human  hydrophobia,  but  following  in  the  footsteps  of 
Edward  Jenner  (1749- 1823),  who  in  1798  made  public  the 
vaccination  with  the  material  of  cowpox  (vaccinia)  as  a 
protection  against  human  smallpox,  he  gave  an  emulsion  or 
vaccine  of  the  virus  of  rabies,  at  first  weakened  or  attenuated 
and  then  gradually  intensified,  to  persons  bitten  by  mad  dogs 


WHAT   MEDICINE    HAS   DONE   AND    IS    DOING    FOR    THE    RACE      435 

and  still  in  the  incubation  stage,  namely  the  interval  that 
elapses  between  the  bite  and  the  onset  of  symptoms,  and  so 
averted  the  distressingly  fatal  disease  hydrophobia.  The 
success  of  protective  vaccination  with  the  killed  micro- 
organisms responsible  for  typhoid  and  paratyphoid  fevers 
was  shown  in  the  European  War  ( 19 14-19 1 8)  by  the  freedom 
from  these  diseases,  unparalleled  in  previous  wars,  by  the 
troops  treated  with  the  vaccine  originally  introduced  by 
Almroth  Wright.  These  are  outstanding  instances  of  infec- 
tive diseases  in  which  a  scientific  knowledge  of  the  exciting 
cause  has  enabled  prevention  or  cure  to  be  effected. 

Tropical  medicine  provides  some  of  the  most  impressive 
examples  of  the  beneficial  results  of  scientific  investigation 
in  the  prevention  of  disease.  In  1877  Patrick  Manson  dis- 
covered that  mosquitoes  carry  and  convey  from  man  to 
man  the  parasite  of  filarial  disease,  which  while  in  the 
mosquito  undergoes  a  cycle  in  its  hfe  history,  so  that  the 
mosquito  is  the  intermediate  host  necessary  for  the  develop- 
ment of  the  filarial  organism  and  the  spread  of  this  parasitic 
disease.  The  idea  that  blood  sucking  and  biting  flies  play  a 
part  in  infecting  man  is  not  new;  it  was  a  behef  among 
savages,  and  Beauperthuy  (i  807-1 871)  thought  it  respon- 
sible for  malaria  and  yellow  fever;  Manson's  suggestion 
that  the  mosquito  was  the  vector  of  malarial  infection  was 
proved  to  be  correct  by  Ronald  Ross  working  under  his 
direction,  and  in  1900  Walter  Reed  (1851-1902)  and  his 
colleagues  proved  the  correctness  of  Beauperthuy  and  C.  J. 
Finlay's  hypothesis;  this  was  the  necessary  step  to  the 
control  and  prevention  of  malaria  and  yellow  fever.  Similarly 
the  African  sleeping  sickness  has  been  shown  to  be  due  to 
infection  with  an  animal  parasite  Trypanosoma  gambiense 
transmitted  by  the  tsetse  fly.  The  proof  that  bubonic  plague, 
due  to  the  Bacillus  pestis,  is  conveyed  to  man  by  the  bites 
of  fleas  carried  by  rats,  and  that  typhus,  formerly  known 
as  gaol  fever,  is  due  to  a  rickettsia  carried  by  lice,  provided 
an  obvious  guide  to  the  prevention  of  these  diseases.  Hydatid 
disease  of  the  Hver  and  other  parts  (which  is  not  a  tropical 
disease)  is  due  to  the  entrance  into  the  alimentary  canal  of 
human  beings  of  the  ova  of  a  tape  worm  common  in  the 
intestines  of  dogs. 


436  HUMAN   BIOLOGY 

Malaria  is  probably  the  commonest  and  most  disabling 
disease  in  the  tropics;  in  India  alone  more  than  four  million 
victims  apply  annually  for  treatment  on  this  account.  The 
mortality  and  economic  loss  thus  produced  are  enormous  and 
now'^fortunately  are  preventable.  The  deteriorating  effect  on 
national  health  and  morale  is  very  real,  and  W.  H.  S.  Jones 
has  brought  together  evidence  to  show  that  the  decadence  of 
Magna  Graecia  in  400  B.C.  was  largely  due  to  the  prevalence 
of  malaria.  Cinchona  or  Jesuit's  bark,  which  contains 
quinine,  owes  its  name  to  its  successful  use  in  the  treatment 
of  the  Countess  of  Cinchon  in  1638,  and  is  said  to  have  been 
accidentally  discovered  by  the  natives  of  South  America 
before  the  Spanish  invasion  of  1 630-1 640.  Writing  in  1897 
Sir  William  Osier  (1849-1919)  regarded  its  introduction  as 
not  only  one  of  the  greatest  events  in  medical  history  but 
as  one  of  the  great  factors  in  the  civiHzation  of  the  world. 
It  did  much  to  cure  the  disease  and  to  mitigate  the  evils  of 
the  disease  by  destroying  the  parasite  when  it  has  gained 
entrance  to  the  circulation,  and  small  doses  may  protect 
persons  from  becoming  affected.  In  1880  a  French  military 
surgeon  C.  L.  A.  Laveran  (1845- 1922),  ^^st  observed  the 
malarial  parasite;  in  1894  Patrick  Manson  (1844- 1922) 
applied  to  malaria  the  hypothesis,  based  on  his  previous 
discovery  that  mosquitoes  conveyed  the  filarial  parasite  to 
man,  and  in  1898  Ronald  Ross  proved  that  mosquitoes 
conveyed  the  malarial  parasite  to  man.  It  thus  became 
evident  that  mosquito-borne  diseases  could  be  prevented 
by  making  it  impossible  for  mosquitoes  to  bite  human  beings; 
this  can  be  done  by  keeping  the  mosquitoes  off  by  netting 
and  screening,  but  the  most  satisfactory  means  is  the 
complete  irradication  of  mosquitoes.  Anti-malarial  cam- 
paigns for  the  destruction  of  mosquitoes  by  various  methods 
have  in  many  places,  as  was  notably  shown  in  Havana  and 
the  Panama  Canal  area  under  General  W.  C.  Gorgas'  (1854- 
1920)  direction,  entirely  changed  the  sanitary  conditions  in 
tropical  regions  previously  deserving  the  epithet  of  "the 
white  man's  grave."  As  already  mentioned,  yellow  fever, 
which  formerly  levied  a  terrible  toll  of  human  life,  is  also 
conveyed  to  man  by  the  bites  of  a  mosquito,  Aedes  aegypti 
or  Stegomyia  Jasciata,  and  has  now  been  almost  completely 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR   THE    RACE      437 

suppressed;  it  Is  indeed  one  of  the  best  examples  in  medical 
history  of  an  acute  infectious  disease  which  can  be  prevented 
by  scientific  sanitation. 

Prognosis,  or  forecasting  what  will  happen,  is  a  very  impor- 
tant function  of  medical  men,  as  it  supplies  what  everyone  is 
anxious  to  know  when  illness  overtakes  them  or  their 
relatives.  The  power  of  predicting  the  duration  and  outcome 
of  a  given  case  of  disease  depends  on  several  data:  first  an 
accurate  knowledge  of  the  nature  of  the  illness  (diagnosis), 
secondly  on  knowledge  of  its  natural  history,  course  and 
significance,  of  the  comphcations  that  may  occur,  the 
sequelae  or  results  that  may  follow,  and  how  far  treatment 
can  influence  it  beneficially,  and  thirdly  on  acquaintance  with 
the  individual  patient's  constitution,  family  history,  inherited 
characters,  mental  traits,  previous  health  and  habits  of 
life.  Prognosis  thus  involves  problems  all  of  which  may  not 
be  capable  of  solution,  particularly  during  the  initial  stages, 
and  is  probably  the  most  difficult  part  of  medicine.  It  may 
be  vitally  important  for  a  man  with  many  responsibilities  to 
know  if  he  must  face  death  at  no  long  interval,  and  in  these 
circumstances  he  should  share  the  medical  man's  honest 
opinion,  but  a  fatal  prognosis  must  be  given  only  when 
there  is  absolute  evidence.  In  cases  of  doubt  an  optimistic 
view  is  better  for  all  concerned,  and  even  when  there  is  every 
reason  to  anticipate  the  worst,  the  unasked  warning  may  be 
harmful,  and  many  patients  know,  though  they  do  not  really 
wish  to  be  told,  what  is  before  them.  Of  course  reticence 
must  not  delay  or  interfere  with  the  proper  medical  or 
surgical  treatment  of  the  disease.  The  foretelHng  of  the 
physical  future  of  the  individual  is  not  confined  to  conditions 
of  illness,  for  a  medical  survey  is  an  essential  part  of  life 
insurance,  and  apart  from  this  there  is  much  to  be  said  for 
the  wisdom  of  a  periodic  overhaul  of  the  man's  body  as  well 
as  of  his  business  affairs  and  stock,  so  that  he  may  be  warned 
in  time  of  any  early  indications  which  make  it  desirable  to 
change  his  manner  of  life. 

As  a  result  of  the  application  of  statistical  methods 
the  occurrence  of  epidemics  can  in  certain  instances  be  fore- 
told so  that  preparations  can  be  made  in  advance.  Thus 
J.  Brownlee  (1868- 1927)  pointed  out  that  after  a  pandemic  of 


438  HUMAN   BIOLOGY 

influenza,    recurring    outbreaks    may    be    anticipated    at 
intervals  of  thirty-three  weeks,  provided  that  the  thirty- 
third   week   does   not   fall    between   June   and    December. 
Measles  tends  to  recur  every  two  years  in  large  communities 
or  three  years  in  small  communities,  apparently  depending 
on  the  accumulation  of  susceptible  children.  Protective  meas- 
ures, such  as  education  of  the  public  to  pay  special  attention 
to  colds  in  children  under  three  years  of  age  and  to  call  in 
medical  men  at  once,  to  segregate  all  contacts  of  cases,  and 
the    offer   to    immunize    young    and    delicate    children    by 
the  injection  of  the  blood  serum  from  a  convalescent  patient, 
can  then  be  taken  to  prevent  the  spread  of  disease  and  min- 
imize the  mortality.  The  study  of  epidemics  of  infectious  dis- 
eases artificially  induced  and  experimentally  controlled  in 
laboratory  animals  carried  out  by  Simon  Flexner  at  the  Rock- 
efeller Institute  in  America  and  Topley  in  England  may  be 
confidently  expected  to  throw  much  further  light  on  the  fac- 
tors influencing  the  occurrence  of  epidemics,  and  thus  to  point 
the  way  to  their  prevention.  This  again  is  an  example  of  the 
value  of  animal  experiments  as  a  means  of  providing  the 
knowledge  necessary  to  diminish  human  disease  and  suffering. 
Protective  Vaccination  against  Diseases.  Edward  Jenner's 
discovery  in  1798  that  smallpox,  a  disease  which  in  the  past 
levied  a  heavy  toll  in  death  and  disfigurement,  could  be 
prevented  by  introducing  under  the  skin  material  obtained 
from  cows  with  the  modified  disease  of  cowpox   (vaccinia) 
was  a  great  improvement  on  the  previous  method  of  inducing 
an  attack  of  smallpox  by  inoculation  of  healthy  persons  with 
material  from  patients  suffering  from  actual  smallpox  in  the 
hope  that  by  producing  a  mild  attack  further  risk  from  a 
virulent  form  would  be  obviated.  Jenner's  discovery  laid 
the  foundation  of  protective  immunization  against  infectious 
disease;  this  method  arouses  the  same  defensive  mechanisms 
that   ordinarily   follow   a   non-fatal   attack   of    the   disease 
but  without  actually  making  the  inoculated  person  ill  with 
the   ordinary   manifestations   ot   that  disease.   Such   active 
immunization  was  employed  with  complete  success  by  Pasteur 
in  the  prevention  of  hydrophobia  in  human  beings  who  had 
already  been  bitten  by  a  mad  dog,  and  would  after  a  latent  or 
incubation    period    have    developed    this    constantly    fatal 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      439 

disease.  Its  adoption  against  infection  with  enteric  (typhoid 
and  paratyphoid)  fever,  due  to  the  work  of  Almroth  Wright, 
was  as  already  mentioned,  crowned  by  phenomenal  success 
in  the  Great  European  War  (1914-1918)  and  has  been 
employed  in  other  diseases. 

Prophylactic  or  protective  serums  render  the  individual 
into  whom  they  are  hypodermically  injected  immune  to  the 
diseases  caused  by  the  viruses  which  have  set  up  changes 
in  the  animals  from  which  the  serum  is  obtained.  The  blood 
serum  of  the  animals  thus  treated  contains  so-called 
antibodies  which  antagonize  the  toxins  or  poisons  pro- 
duced by  the  viruses;  in  this  way  passive  immunity  is 
produced,  and  contrasts  with  the  active  immunity  which 
results  when  vaccines  or  emulsions  of  dead  viruses  are 
injected,  the  tissues  of  the  person  so  vaccinated  being  thus 
stimulated  to  produce  the  specific  (i.e.  corresponding  to  the 
particular  virus)  antibodies.  Antidiphtheritic  and  anti- 
tetanic  serums  are  well-estabhshed  examples.  Various  other 
serums  have  been  used  in  the  same  way  (see  Chap,  xvii). 

An  important  step  is  the  method  of  being  able  to  determine 
whether  or  not  an  individual  is  susceptible  to  certain 
infections,  and  therefore  hkely  to  contract  them  when 
exposed  to  them.  This  immunological  reaction  is  in  practical 
use  in  diphtheria  (the  Schick  test)  and  in  scarlet  fever 
(the  Dick  test),  and  can  be  applied  to  the  inmates  of  schools; 
those  children  who  are  thus  found  to  be  unprotected  against 
either  of  these  two  diseases  can  then  be  injected  with 
antidiphtheritic  or  antiscarlatinal  serum,  and  so  rendered 
immune  to  these  infections  for  a  time.  In  this  way  epidemics 
in  schools  can  be  prevented.  • 

Curative  Antitoxic  Serums.  The  cure  of  diphtheria  by  the 
subcutaneous  injection  of  the  blood  serum  of  an  animal, 
usually  the  horse,  previously  immunized  or  rendered 
insusceptible  to  the  bacillus  of  diphtheria,  has  largely 
robbed  the  disease  of  its  terrors.  This  remedy  was  the 
result  of  careful  bacteriological  research  involving  animal 
experiments  by  Behring.  Antitetanic  serum,  produced  in  an 
analogous  way  by  Kieasato,  is  the  best  method  of  treating 
tetanus.  Cerebrospinal  fever  (meningococcic  meningitis)  and 
one  form  of  pneumonia  (that  due  to  type  i  pneumococcus 


Wilhelm  Konrad  Roentgen  (1845-1923). 


I440I 


WHAT   MEDICINE    HAS    DONE   AND   IS   DOING    FOR   THE    RACE     44 1 

are  infections  which  have  more  recently  been  treated  with 
success  by  the  corresponding  antitoxic  serums. 

X-rays,  discovered  by  Professor  W.  K.  von  Roentgen 
(1845-1923)  at  Wiirzberg  in  November  1895,  now  constitute 
an  essential  aid  not  only  in  diagnosis  or  the  detection  of 
what  is  the  matter  with  patients,  especially  those  with 
internal  complaints  of  otherwise  obscure  nature,  but  also  in 
treatment,  particularly  that  of  skin  diseases  and  cancerous 
growths.  First  employed  mainly  to  determine  the  exact 
position  of  foreign  bodies,  such  as  bullets  and  needles,  in  the 
body  and  of  the  ends  of  fractured  bones,  its  use  was  extended 
to  the  detection  of  disease  in  the  organs  of  the  chest  and 
abdomen  and  the  skull;  by  the  introduction  of  substances, 
such  as  salts  of  bismuth  and  barium  and  more  recently  of 
tetraiodophenolphthalein,  opaque  to  x-rays,  the  position, 
size,  shape,  and  movements  of  the  hollow  viscera  can  be 
studied  in  Hfe,  and  thus  is  obtained  knowledge  which  pre- 
viously could  be  suppHed  only  by  an  exploratory  opera- 
tion. While  medicine  has  benefited  enormously  by  the  help 
of  radiology,  surgery,  which  was  made  painless  by  the 
introduction  of  anesthetics,  safe  by  the  adoption  of  Lister's 
antiseptic  methods  and  asepsis,  has  been  assisted  by  the 
accurate  locaHzation  of  disease  provided  by  x-rays.  The 
rays  of  radium  are  employed  for  the  treatment  of  skin 
conditions  and  especially  small  cancerous  growths  there 
and  in  some  other  accessible  positions  with  great  success. 

INTERNATIONAL   HEALTH   ORGANIZATIONS 

The  Health  Section  of  the  League  of  Nations  is  an  inter- 
national organization  in  the  interests  of  the  control  of 
disease  throughout  the  world,  in  which  more  than  fifty 
nations  are  cooperating.  By  this  means  early  information 
about  epidemics  is  broadcasted,  and  much-needed  data  about 
tropical  diseases  are  made  available.  In  addition  there  are 
governmental,  commercial,  and  privately  endowed  agencies 
active  in  the  fight  against  disease  and  the  resul-ting  economic 
loss.  The  International  Health  Board  of  the  Rockefeller 
Foundation  (established  in  1909)  which  cooperates  with 
government  agencies  and  thus  acts  on  the  principle  of 
helping  those  who  can  and  will  help  themselves,  has  carried 


442  HUMAN   BIOLOGY 

on  an  extensive  campaign  against  hookworm  disease  in  the 
Southern  States  of  North  America  and  elsewhere,  and 
against  malaria  and  yellow  fever  in  an  international  manner. 
Not  only  do  these  campaigns  diminish  the  diseases  against 
which  they  are  directed  and  so  are  of  great  humanitarian 
and  economic  value,  but  by  their  educational  influence  in 
inculcating  sound  principles  of  sanitation,  for  example  in 
hookworm  disease  the  erection  of  latrines  and  the  disposal 
of  excreta,  lead  to  improved  health  and  a  decrease  in  the 
incidence  of  other  diseases,  such  as  typhoid  fever  and 
dysentery.  Hookworm  disease  occurs  in  agricultural  laborers, 
the  parasite  gaining  its  entrance  through  the  unbroken  skin; 
it  can  be  prevented  by  wearing  shoes,  even  when  the  soil  is 
heavily  contaminated  by  fecal  polkition;  the'  infected 
individuals  can  be  cured  by  the  oral  administration  of  new 
drugs,  such  as  chenopodium,  carbon  tetrachloride,  and 
ascidol. 

ORTHODOX   AND    IRREGULAR   MEDICINE 

One  of  the  duties  of  the  British  Minister  of  Health,  as 
defined  by  the  Ministry  of  Health  Act  19 19,  is  "the  avoidance 
of  fraud  in  connection  with  alleged  remedies;"  this  cautiously 
worded  sentence  brings  up  for  consideration  the  relation  of 
orthodox  medicine  and  the  medical  man  to  quackery  and 
their  obHgation  to  protect  the  public  from  exploitation  by 
irregular  practitioners  out  purely  for  gain  at  the  expense  of 
the  patient  regardless  of  any  harm  which  he  may  suffer.  The 
problem  is  delicate,  for  a  new  method  employed  by  a  man 
without  any  qualification  to  practise  and  little  knowledge  of 
medicine  may  be  good  in  virtue  of  special  knowledge, 
experience,  or  manipulative  skill  in  one  direction;  and  on  the 
other  hand  quackery  may  be  practised  by  a  graduate  in 
medicine.  Individually  medical  men  can  and  do  protect 
their  patients  against  fraudulent  methods  of  treatment,  but 
concerted  action  has  not  been  general.  In  North  America, 
where  cults  of  medicine,  such  as  Christian  Science,  osteopathy, 
chiropractic,  and  patent  medicines  with  flaunting  advertise- 
ments are  much  in  evidence,  action  has,  as  far  as  is  possible 
in    the    circumstances    of   the    legislature's    arrangements, 


WHAT    MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      443 

been    taken    by    the    American    Medical    Association    and 
other  bodies. 

SPECIAL    FORMS    OF    DISEASE 

Tuberculosis,  called  by  John  Bunyan  "the  Captain  of  the 
Men  of  Death"  and  more  recently  "the  white  plague,"  has 
greatly  diminished  in  its  mortahty;  thus  in  England  and 
Wales  tuberculosis  of  the  lungs  in  1847  carried  off  3189  of 
every  milhon  Hving,  whereas  in   1928  this  death  rate  had 
fallen  to  755.  Many  factors  have  played  a  part  in  this  change: 
improved  conditions  of  living  and  more  wholesome  food, 
better   ventilation,   more   open-air   hfe,   less   overcrowding, 
education  of  the  public  in  general  hygiene  and  in  particular  as 
regards  the  risk  of  spread  of  infection.  The  control  of  milk 
from    tuberculous   cows   is   most   important   in   preventing 
infection  of  infants  and  young  children  with  the  bovine 
form    of    tuberculosis.    The    open-air    treatment,    though 
advocated  in   1840  by  G.   Bodington  of  Sutton  Coldfield, 
Warwickshire,    England,    and    by    Henry    MacCormac    of 
Belfast  in  1855,  and  put  in  practice  by  BrehmeratGobersdorf 
in  Silesia  in  1859  and  by  E.  L.  Trudeau  in  the  Adirondacks  in 
1884,  did  not  meet  with  general  adoption  in  Great  Britain 
until  the  end  of  the  last  century,  long  after  the  fall  in  the 
tuberculosis  mortality  had  begun.  Its  influence  in  educating 
tuberculous  persons  in  a  proper  manner  of  life  has  been  most 
beneficial,  but  otherwise  it  has  its  limitations;  it  is  not  easy 
to  get  the  poor  to  go  to  sanatoriums  in  the  earliest  and  most 
curable  stages,  and  it  must  be  realized  that  in  order  to 
consohdate    the    cure    begun    at    sanatoriums    tuberculous 
patients  should  continue  to  lead  a  protected  life  in  a  colony  or 
village    settlement   where   they    carl    earn    their    living    in 
hygienic    workshops    and    other    favorable    conditions;    a 
beginning  in  the  establishment  of  such  permanent  industrial 
colonies   for   ex-sanatorium   tuberculous   persons   has   been 
made  at  Papworth  Hall  near  Cambridge  and  at  Preston  Hall 
near  Maidstone,  Kent,  in  England,  under  the  direction  of  Dr. 
P.  C.  Varrier-Jones  who  has  organized  industries  on  a  self- 
supporting  basis.  During  the  years  that  the  Papworth  Colony 
has  been  in  existence  no  case  of  tuberculosis  has  occurred  in 
the    children    living    in    the    cottages    with   their    formerly 


444  HUMAN   BIOLOGY 

actively  tuberculous  fathers.  Numerous  associations,  such  as 
the  American  National  Tuberculosis  Association  organized 
by«=E.  L.  Trudeau  in  1904  and  the  National  Association  for  the 
Prevention  of  Tuberculosis  founded  in  Great  Britain  in  1898, 
have  undertaken  antituberculosis  campaigns  for  the  education 
of  the  public  so  as  to  prevent  infection  and,  if  this  has  already 
occurred,  to  popularize  treatment  at  the  earliest  possible 
time;  by  way  of  propaganda  they  have  arranged  travelling 
exhibits,  lectures,  and  cinema  films,  such  as  that  of  the 
American  National  Tuberculosis  Association  which  toured 
all  the  States  east  of  the  Mississippi  from  1906  to  19 12. 
It  is  satisfactory  to  notice  that  the  death  rate  from  tuberculo- 
sis in  the  United  States,  which  was  201  per  100,000  in  1900, 
has  been  reduced  to  86.6  in  1925.  These  campaigns,  especially 
by  their  insistence  on  the  gospel  of  open-air,  have  also  led, 
as  a  kind  of  by-product,  to  improvement  in  the  general 
health  of  the  human  race. 

In  1882  Robert  Koch  demonstrated  the  microorganism, 
the  tubercle  bacillus,  responsible  for  widespread  disability 
and  death,  and  thus  opened  the  way  to  the  prevention  of 
infection,  both  from  human  and  animal  sufferers,  for  example 
by  inhalation  of  the  expectoration  and  by  ingestion  of  milk 
containing  bovine  bacilli.  Thus  the  spread  of  "the  seed"  can 
be  minimized  by  education  of  the  public,  laws  against  spitting, 
and  special  care  and  measures  to  be  taken  about  those 
with  the  fully  developed  disease,  such  as  destruction  of 
their  expectoration,  efficient  ventilation  and  disinfection. 
The  importance  of  preventing  the  spread  of  tuberculosis 
by  milk  from  cows  suffering  from  the  disease  has  already 
been  mentioned.  Without  "the  seed,"  or  the  tubercle 
bacillus,  the  disease  of  course  cannot  occur,  but  it  is  so 
ubiquitous  that  in  towns  avoidance  of  exposure  to  its 
infection  cannot  be  insured,  and  yet  it  is  comparatively 
few  who  fall  victims  to  its  obviously  evil  effects.  The  factor 
of  the  "soil"  or  constitutional  power  of  resistance  of  the 
individual  was  somewhat  cast  into  the  background  in  the  early 
days  of  bacteriology  when  much  was  hoped  from  the  dis- 
covery of  the  responsible  germ  and  specific  treatment  by 
tuberculin;  but  its  importance  is  now  fully  recognized  in  the 
hygiene  and  open-air  methods  of  treatment  and  in  the  care  of 


* 
WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      445 

delicate  children.  Systematic  surveys  of  school  children  thus 
act  as  a  prophylactic  measure  by  providing  a  remedial 
change  of  air  and  rest  to  those  in  a  pretuberculous  or  in  a 
very  early  stage;  and  further,  by  the  detection  and  segrega- 
tion of  children  so  affected  as  to  be  a  source  of  infection  to 
others,  these  surveys  by  medical  men  combat  the  insidious 
spread  of  the  disease. 

Venereal  Disease.  Of  the  two,  syphilis  and  gonorrhea, 
the  first  is  more  far-reaching  and  devastating  in  its  effects; 
whereas  gonorrhea  is  locally  more  effective  in  causing 
sterihty  and  chronic  ill-health  in  women,  and  in  infants 
ophthalmia  and  bhndness  from  infection  at  the  time  of  birth, 
syphilis  may  attack  any  and  every  part  of  the  body,  and  is 
now  known  to  be  the  cause  of  locomotor  ataxia,  general 
paralysis  of  the  insane  and  other  disabling  conditions  which 
supervene  years  after  the  original  infection  has  been  thought 
to  be  cured.  Statistics  show  that  the  mortality  from  loco- 
motor ataxia  and  general  paralysis  has  recently  diminished — 
a  result  which  may  fairly  be  correlated  with  the  knowledge 
that  they  are  late  results  of  syphilis  and  with  the  improved 
and  earlier  treatment  of  syphilis.  By  means  of  a  blood  test, 
the  Wassermann  reaction,  introduced  in  1906,  the  existence 
of  syphilis,  although  there  may  not  be  any  other  evidence 
of  its  responsibility,  can  be  determined,  and  thus  point 
the  way  to  curative  treatment  which  has  been  made  much 
more  complete  and  effective  in  the  last  twenty  years.  Syphilis 
is  a  killing  disease  not  only  of  adults  but  of  innocents  yet 
unborn,  and  is  a  most  potent  cause  of  abortion,  miscarriage, 
still-birth,  and  infantile  mortality;  it  is  said  that  one  third 
of  all  syphilitic  infants  die  before  birth,  and  that  of  the 
remainder  34  per  cent  succumb  during  the  first  six  months 
of  life — an  appalling  total  mortality  of  77  per  cent  (Kasso- 
witz) ;  but  fortunately  treatment  of  pregnant  women  with  the 
disease  prevents  these  fatalities.  In  England  and  Wales 
the  establishment  of  free  treatment  centers  for  venereal 
disease,  of  which  in  1928  there  were  188,  was  at  once  followed 
by  diminished  incidence;  in  1920  85,531  persons  were 
treated  and  in  1924  54,380,  the  progressive  diminution  in  the 
number  of  new  cases  being  due  to  the  successful  treatment 
of  syphilis.  But  in  1928  there  were  65,931  new  cases.  Schau- 


446  HUMAN   BIOLOGY 

(Jinn's  discovery  in  1905  of  the  Treponema  pallidum,  the 
cause  of  syphilis,  rendered  it  possible  to  make  a  certain 
and  early  diagnosis  of  this  enemy  of  human  hfe  and  efficiency. 
By  treatment  with  Ehrlich's  (1854-19 15)  organic  arsenical 
preparations  (salvarsan,  arsphenamine,  "606")  and  by 
drugs  of  an  analogous  nature,  the  infective  power  of  the 
primary  sore  is  rapidly  abohshed,  and  thus  the  spread 
is  prevented  of  a  disease  which  otherwise  damages  or 
destroys  the  individuals  who  have  contracted  it  and  also  their 
unborn  offspring.  Not  only  is  the  propagation  of  the  disease 
prevented  but  a  well-marked  curative  effect  obtained  in  the 
individual. 

The  ideal  of  EhrHch's  chemotherapy  is  that  by  means  of 
a  drug  the  virus  of  a  disease  should  be  destroyed  in  the  body 
of  a  patient  without  doing  any  harm  to  the  patient.  Although 
the  second  essential  has  not  been  entirely  achieved,  the  out- 
standing success  of  organic  arsenic  preparations  in  protozoan 
infections  of  man  is  a  great  tribute  to  Ehrlich's  labors;  thus 
the  treatment  of  syphilis  by  arsenobenzol  preparations 
(arsphenamine),  of  trypanosomiasis  by  analogous  drugs, 
and  of  amebic  dysentery  by  emetine  has  revolutionized  the 
aspect  of  these  killing  diseases. 

*  Acute  rheumatism  or  rheumatic  fever  has  long  been  recog- 
nized as  a  most  serious  cause  of  crippling  heart  disease, 
especially  in  children,  and  of  early  death.  Campaigns  to 
educate  the  public  and  so  to  diminish  its  effects  are  actively 
maintained;  the  objects  are  to  remove  its  causes,  such  as  bad 
teeth  and  infected  tonsils,  which  may  be  summed  up  as  focal 
sepsis,  to  obviate  the  disposing  environmental  circumstances, 
such  as  damp  dwellings,  and  to  bring  rheumatic  children 
under  medical  observation  at  an  early  stage.  Experience  has 
shown  that  the  cardiac  damage  due  to  acute  rheumatism  in 
children  may  be  minimized  by  prolonged  rest  in  bed.  Before 
the  introduction  of  treatment  by  salicylates  in  1877  rheumatic 
fever  tortured  its  victims  for  six  weeks;  now  the  fever  and 
pain  can  be  banished  in  a  few  days,  but  salicylates  cannot  be 
relied  upon  to  prevent  the  heart  complications. 

Chronic  arthritis  (rheumatoid  arthritis),  fibrositis,  and 
chronic  rheumatism  exact  an  enormous  toll  of  disability  and 
economic  loss  mainly  from  adults,  though  the  heart  is  not 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      447 

damaged,  as  in  rheumatic  fever.  These  chronic  rheumatic 
affections  are  in  large  measure  due  to  focal  sepsis  somewhere 
in  the  body,  a  state  of  affairs  which  naturally  tends  to  become 
more  frequent  with  the  passage  of  years.  The  prevention 
of  such  causes  by  attention  to  dental  disease  and  infected 
tonsils  is  therefore  on  the  same  hnes  as  in  rheumatic  fever, 
but  other  methods  of  treatment,  such  as  that  at  spas  and 
forms  of  radiant  heat  and  hght,  have  recently  been  more 
widely  employed. 

Malignant  Disease.  While  infant  mortaHty  has  fallen  in  a 
most  remarkable  manner,  many  epidemic  and  infectious 
diseases  have  been  controlled,  and  the  average  duration  of 
hfe  greatly  increased,  there  is  much  yet  to  be  accomphshed 
in  the  conquest  of  disease.  This  was  shown  by  the  pandemic 
of  influenza  in  1918-1919,  by  the  outbreak  of  encephahtis 
epidemica,  practically  a  new  disease,  in  19 17,  and  by  the 
lack  of  efficient  control  over  acute  poIiomyeHtis,  known 
since  1840.  Perhaps  the  outstanding  example  is  cancer, 
the  mortaHty  from  which  is  increasing,  though  this  may 
in  part  be  due  to  the  survival  of  a  larger  number  of  people,  as 
a  result  of  improved  hygienic  conditions,  to  the  age  when 
mahgnant  disease  most  commonly  occurs.  The  British  figures 
of  the  mortaHty  from  cancer  and  tuberculosis  are  instructive 
in  this  connection:  in  1884  the  annual  mortaHty  rate  per 
miHion  persons  Hving  was  563  for  cancer  and  2574  for 
tuberculosis,  whereas  in  1928  the  corresponding  figures  were 
1425  for  cancer  and  755  for  tuberculosis.  Cancer  occurs  in 
aH  parts  of  the  world,  no  country  or  race  is  exempt,  for  the  old 
statements  that  primitive  unciviHzed  tribes  are  not  affected 
were  due  to  want  of  accurate  knowledge;  it  has  been  estimated 
that  I  out  of  every  7  persons  reaching  the  age  of  thirty  years 
win  die  of  cancer.  The  urgency  of  the  prevention  of  cancer  has 
led  to  intensive  investigation  in  special  institutions  aH  over 
the  civiHzed  world  of  the  various  problems  concerned,  and  an 
enormous  amount  of  information  bearing  on  its  causation, 
pathology,  incidence  and  statistics  has  been  accumulated; 
but  so  far  the  essential  cause  has  not  been  indubitably 
established,  and  until  this  much  sought  for  discovery  is 
made,  the  means  of  prevention  is  yet  to  seek.  But  although 
this  final  fichievement  has  not  been  accomplished,  the  way  has 


448  HUMAN    BIOLOGY 

been  prepared,  and  in  the  meanwhile  much  has  been  done; 
conditions  which  favor  the  incidence  of  cancer,  such  as 
chronic  irritation  and  inflammation,  have  been  recognized 
and  so  can  be  obviated,  such  as  irritation  of  the  tongue 
by  a  sharp  tooth  or  of  the  skin  by  materials  such  as  soot, 
paraffin  and  other  agents  in  industrial  occupations.  To  take  an 
example  in  which  medical  men  have  been  the  main  sufferers: 
more  than  a  hundred  radiologists  have  now  died  from  cancer 
of  the  skin  caused  by  x-rays;  standardized  methods  of 
protection  against  the  dangers  of  x-rays  and  radium  expo- 
sures have  now  been  formulated,  so  as  completely  to  obviate 
them. 

Educative  campaigns  to  instruct  the  pubHc  about  the 
importance  of  seeking  medical  advice  about  the  earliest 
symptoms  of  possible  mahgnant  disease,  so  that  if  present  a 
growth  may  be  removed  at  a  period  when  cure  can  be 
obtained,  have  done  much  good.  The  progress  of  diagnostic 
methods,  such  as  x-rays,  enabling  a  decision  to  be  made  at 
a  stage  not  previously  possible,  has  given  the  sufferers  the 
benefit  of  cure  by  early  operation;  the  improvement  of 
surgical  technique  and  x-ray  and  radium  therapy  are  other 
advances  which  have  been  of  service  in  the  treatment 
of  cancer.  Before  1890  the  operative  removal  of  tissues  and 
lymphatics  around  malignant  tumors  was  not  sufficiently 
wide,  and  as  a  result  recurrences  were  more  frequent  than 
after  the  more  complete  and  extensive  operations  now 
performed. 

One  of  the  great  triumphs  of  applied  physiology  was  the 
exact  localization  of  tumors  in  the  brain  so  as  to  indicate 
the  exact  position  where  the  surgeon  should  trephine  the 
skull  for  their  removal. 

Diseases  oj  the  Heart  and  Blood  Vessels.  Except  aneurysm, 
or  pathological  dilatation  of  the  arteries  of  the  limbs  with 
a  tendency  to  rupture  which  was  known  to  Galen  (130-200  a. 
D.),  little  in  connection  with  the  circulatory  system  was 
recognized  until  long  after  Harvey's  publication  of  the 
circulation  of  the  blood  (1628).  The  reason  for  this  was  that 
the  methods  of  physical  examination  of  the  heart  were  not 
practised  until  the  beginning  of  the  nineteenth  century  when 
J.N.  Corvisart  (1755-1821)  in  1 808  resuscitated  Auenbrugger's 


WHAT   MEDICINE    HAS   DONE   AND    IS    DOING    FOR   THE    RACE      449 

(1722- 1 809)  neglected  discovery  of  percussion  and  R.T.H. 
Laennec  (1781-1826)  in  1819  published  his  classical  work  on 
auscultation.  The  alterations  of  the  heart  sounds  (murmurs) 
which  characterize  valvular  disease  were  elaborated  through- 
out most  of  the  nineteenth  century,  and,  as  is  now  apparent, 
attention  was  directed  too  much  to  the  more  obvious 
evidence  of  valvular  disease  and  not  sufficiently  to  the  condi- 
tion of  the  muscular  efficiency  of  the  heart.  The  signs  of 
cardiac  disease  were  regarded  as  far  more  important  than 
the  patient's  symptoms  and  sensations.  The  new  cardiology 
began  with  James  Mackenzie's  (1853-1925)  elucidation  of 
the  irregularities  of  the  pulse,  and  the  more  accurate  indica- 
tions for  the  use  of  digitalis  in  cardiac  affections,  derived 
from  instrumental  investigation;  this  advance  was  con- 
tinued by  Thomas  Lewis'  observations  with  the  electrocardi- 
ograph. By  these  means  the  actual  changes  in  the  heart 
revealed  by  special  methods  were  correlated  with  more 
obvious  signs;  the  latter  have  thus  in  most  instances  be- 
come a  reliable  guide  to  the  underlying  condition  without 
recourse  to  the  more  elaborate  methods  of  the  original  pio- 
neers. More  accurate  knowledge  of  the  causes  of  heart 
disease,  such  as  acute  rheumatism,  infections  and  especially 
syphilis  have  made  curative  treatment  more  rational  and 
successful,  and  prevention  more  possible.  The  accurate 
instrumental  estimation  of  blood  pressure  which  enables  its 
abnormal  characters  to  be  detected  before  symptoms  have 
made  their  appearance,  is  most  valuable  as  a  warning  to 
start  preventive  treatment  in  an  early  stage. 

A  brief  reference  should  be  made  to  the  advances  made 
in  the  recognition  and  treatment  of  the  various  diseases  oj 
the  blood-forming  organs.  Anemia  may  be  due  to  many  causes; 
one  form  is  due  to  the  presence  of  a  parasite  in  the  alimentary 
canal,  as  in  hookworm  disease  (see  p.  442) ;  the  destruction  of 
these  worms  or  better  the  prevention  of  this  infection  is  the 
logical  and  successful  sequel  of  this  new  knowledge.  Another 
form  of  grave  anemia,  the  pernicious  or  Addisonian,  has  now 
been  shown  to  be  benefited  by  an  administration  of  liver 
substance  which  also  has  a  most  satisfactory  influence 
on  the  tropical  disease  known  as  sprue.  Anemia  due  to  loss  of 
blood,  such  as  occurs  as  the  result  of  disease,  wounds  or 


450  HUMAN   BIOLOGY 

operation,  can  be  most  successfully  remedied  by  introducing 
into  the  patient's  veins  the  blood  of  a  hke  nature,  previously 
tested  to  show  that  it  is  compatible,  from  another  and  healthy 
person  (the  donor);  blood  transfusion  is  an  old  idea,  but 
it  is  only  within  the  last  twenty  years  that  its  technique 
has  been  so  improved  as  to  make  it  safe.  Anemia  may  be 
due  to  the  action  of  substances  used  in  industries,  such  as 
lead,  benzole,  some  explosives,  or  of  x-rays  or  radium  in 
persons  exposed  to  their  influence  for  long  periods  in  the 
course  of  their  occupation;  knowledge  of  the  causes  makes  it 
comparatively  easy  to  anticipate  and  prevent  regrettable 
results  by  periodical  inspection  of  the  employees.  Another 
form  of  anemia  associated  with  enlargement  of  the  spleen, 
known  as  chronic  splenic  anemia,  has  been  proved  to  be 
curable  by  surgical  removal  of  the  spleen,  an  operation 
which  has  also  been  found  to  be  an  effective  cure  for  chronic 
hemolytic  jaundice. 

NEUROLOGY 

The  remarkable  progress  in  physiology  since  the  second 
half  of  the  last  century  has  influenced  the  practice  of  medicine 
in  many  directions,  but  probably  in  none  more  than  in 
bringing  about  a  clearer  insight  into  disorders  and  diseases 
of  the  nervous  system.  Morbid  physiology,  which  is  part  of 
pathology,  has  thrown  much  light  on  the  causes  of  nervous 
diseases,  as  have  the  new  developments  in  psychology; 
thus  it  has  become  possible  to  apply  more  rational  and 
effective  treatment  to  functional  disorders  (neuroses, 
psychoneuroses)  as  well  as  to  structural  diseases  of  the  brain, 
spinal  cord  and  nerves.  The  needs  of  the  numerous  cases  of 
war  neuroses  led  to  much  psychotherapeutic  practice,  and 
the  experience  thus  gained  has  borne  fruit  and  modified  in 
some  respects  previous  conceptions.  The  recognition  of  the 
effect  of  syphilis  in  producing  degenerative  diseases  of  the 
nervous  system  has  emphasized  the  urgency  for  thorough 
early  treatment.  Recently  one  of  these  diseases,  general 
paralysis  of  the  insane,  has  been  much  benefited  by  the 
artificial  production  of  malaria.  The  importance  of  heredity 
in  mental  disorders  has  aroused  eugenic  activities  for  the 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR   THE    RACE      45 1 

protective  segregation  of  the  mental  defectives  and  limita- 
tion of  their  propagation. 

Reform  in  the  Treatment  of  the  Insane.  The  efforts  of 
Pinel  (1745- 1 826)  in  France  from  1792,  John  Connolly  (1840), 
the  Tukes  and  others  in  Britain  led  to  the  abandonment  of 
barbarous  methods,  a  rehcof  the  time  of  demoniac  possession, 
and  changed  the  character  of  asylums  from  that  of  prisons  to 
that  of  mental  hospitals.  By  the  modern  study  of  the  factors 
responsible  for  mental  disorder  and  the  early  treatment  of 
mental  instabihty  great  benefit  has  been  effected  in  both 
preventive  and  curative  directions.  This  movement  of 
mental  hygiene  has  been  an  actively  efficient  method  of 
correcting  faulty  habits  of  life,  removing  injurious  environ- 
mental influences,  and  of  correcting  abnormahties  of  conduct, 
and  thus  preventing  deliquency  and  mental  disorder.  By 
the  arrangements  made  for  the  care  and  segregation  of  the 
mentally  defective,  their  well-being  has  been  promoted  and 
the  liability  of  their  multiplying  has  been  minimized. 

ENDOCRINE    DISEASES 

Certain  glands  in  the  body  pour  their  secretions  into  the 
circulating  blood  and  are  spoken  of  as  the  ductless  or 
endocrine  glands  or  glands  of  internal  secretion  (see  Chap.  x). 
The  substances  they  supply  are  necessary  for  the  normal 
functioning  of  the  body  and  are  called  hormones  and  spoken 
of  as  chemical  messengers.  Absence,  deficiency,  excess,  or 
alteration  of  these  hormones  upsets  the  so-called  endocrine 
balance  and  produces  various  disorders  of  health  or  dis- 
eases. The  secretion  of  the  thyroid  gland  contains  the 
active  principle,  thyroxin,  which  can  now  be  artificially 
made  or  synthetized  in  the  chemical  laboratory;  it  is  a 
stimulant  and  increases  the  changes,  or  metabolism,  of  the 
body  so  that  they  take  place  more  rapidly.  If,  as  the  result 
of  disease  or  removal  of  the  thyroid  gland,  the  secretion  of 
thyroxin  is  absent,  the  individual  becomes  apathetic,  slow 
in  body  and  mind,  puffy  and  somew^iat  fat;  when  this 
occurs  in  an  adult  it  is  known  as  myxedema,  when  in  a  baby 
as  cretinism  and  then,  although  the  years  pass,  the  individual 
remains  in  an  infantile  state.  These  patients  can  be  restored 
to  practically  a  normal  condition  by  the  administration  of 


452  HUMAN   BIOLOGY 

the  extract  of  the  thyroid  gland  of  an  animal;  but  this  substi- 
tution treatment  must  be  continued  indefinitely  as  the 
individual's  own  thyroid  cannot  supply  the  hormones. 
Excessive  and  probably  also  altered  secretion  of  the  thyroid 
gland  causes  a  condition  (exophthalmic  goiter  or  Graves' 
disease)  which  is  the  opposite  of  myxedema  and  is  character- 
ized by  extreme  nervousness,  protrusion  of  the  eyes,  enlarge- 
ment of  the  thyroid  gland  (goiter),  sweating,  palpitation 
and  rapid  action  of  the  heart;  this  disease  is  greatly  benefited 
by  removal  of  part  or  almost  the  whole  of  the  gland,  and  is, 
at  any  rate  temporarily,  improved  by  the  administration  of 
iodine.  The  thyroid  gland  is  concerned  with  the  metaboHsm 
(or  changes  connected  with  the  presence)  of  iodine  in  the 
body,  just  as  the  small  parathyroid  glands  in  its  immediate 
neighborhood  regulate  the  metaboHsm  of  calcium.  In  certain 
regions,  such  as  the  basin  of  the  Great  Lakes  and  the  valley 
of  the  Mississippi  in  North  America,  parts  of  Switzerland, 
and  some  valleys  of  the  Himalayas,  enlargement  (goiter)  of 
the  thyroid  gland  is  endemic;  this  has  long  been  connected 
with  the  water  supply.  According  to  McCarrison  simple 
goiter  is  due  to  a  number  of  causes,  viz.  deficiencies  and 
excesses  in  food,  polluted  water,  gastrointestinal  infection, 
insanitary  conditions  of  fife,  and  deficiency  of  iodine.  This 
simple  goiter,  which  is  not  accompanied  by  the  symptoms  of 
Graves'  disease,  occurs  much  more  frequently  in  young  girls 
than  in  males,  and  according  to  D.  Marine  is  due  to  a  lack 
of  iodine;  he  has  found  that  it  can  be  prevented  by  the 
administration  of  small  doses  of  iodine  twice  a  year,  a 
striking  demonstration  of  scientific  preventive  medicine. 
The  pituitary  gland  at  the  base  of  the  brain  exerts  a  well- 
marked  influence  on  physical  growth;  deficiency  of  its 
internal  secretion  leads  to  a  form  of  obesity,  with,  in  children, 
arrest  of  development  so  that  the  changes  of  puberty  do  not 
appear.  Overactivity  of  the  anterior  lobe  of  the  pituitary 
causes  excessive  growth  which  in  early  fife  is  responsible 
for  giants,  and  in  older  people,  whose  bones  can  no  longer 
grow  in  length,  for  a  characteristic  increase  in  size  of  the 
extremities  known  as  acromegaly.  An  extract  of  the  posterior 
lobe  of  the  pituitary  has  been  found  to  prevent  for  some 
hours  the  excessive  excretion  of  urine  which  so  disturbs  the 


WHAT    MEDICINE    HAS    DONE    AND    IS    DOING    FOR    THE    RACE      453 

rest  of  the  subjects  of  diabetes  insipidus;  but,  just  as  in 
myxedema  and  cretinism,  and  in  diabetes  mellitus,  in  which 
the  injection  of  insulin  temporarily  transforms  the  patient 
into  a  normal  person,  so  also  must  this  form  of  treatment  be 
continued,  for  the  relief  is  not  permanent  and  therefore  not  a 
cure.  The  adrenal  or  suprarenal  glands,  which  He  in  close 
contact  with  the  kidney  but  are  not  concerned  in  the  excre- 
tion of  urine,  are,  hke  the  pituitary,  composed  of  two  parts; 
the  internal  or  medulla  has  an  internal  secretion,  adrenahne 
or  epinephrine,  which  is  a  tonic  to  the  vascular  system, 
maintains  the  blood  pressure  by  constricting  the  arteries, 
and  so  is  much  used  in  the  arrest  of  bleeding.  It  is  also 
employed  for  the  rehef  of  asthma.  It  can  be  manufactured 
in  the  chemical  laboratory.  Other  glands,  such  as  the  para- 
thyroids and  gonads  (the  sex  glands),  have  internal  secretions 
which  keep  the  body  in  a  normal  condition,  and  when  altered 
bring  about  morbid  manifestations. 

An  international  agreement  as  to  a  standard  composition 
of  therapeutic  substances  (including  endocrine  preparations, 
serums,  and  vaccines)  has  been  a  valuable  measure  in 
insuring    their    proper    preparation,    strength    and    purity. 

Advances  in  medical  science  dealing  with  diet  have  so 
greatly  promoted  human  welfare  that  a  whole  chapter 
(Chap,  xiv)  is  devoted  to  their  discussion. 

PREVENTIVE   MEDICINE 

Towards  the  true  ideal  of  medicine^ — the  prevention 
rather  than  the  cure  or  relief  of  disease — there  has  been  more 
advance  in  the  last  fifty  years  than  in  any  similar  period  of 
the  world's  history.  Preventive  medicine  is  closely  bound 
up  with  the  practical  application  of  physiology,  for,  as  Sir 
George  Newman  points  out,  it  must  deal  with  the  causes  of 
health  so  as  to  be  able  to  discover  the  causes  of  disease,  and 
thereby  effect  the  "removal  of  the  occasion  of  disease  and 
physical  inefficiency  combined  with  the  husbanding  of  the 
resources  of  the  individual." 

According  to  G.  E.  Vincent,  President  of  the  Rockefeller 
Foundation,  the  activities  of  public  authorities  can  prevent, 
wholly  or  in  part,  not  more  than  20  per  cent  of  the  diseases 
causing  death  or  disablement;  there  is  therefore  the  most 


454  HUMAN    BIOLOGY 

urgent  need  for  education  of  the  lay  public  in  "the  laws  of 
physiological  righteousness;"  for  if  the  people  do  not  know  or 
understand  properly  the  principles  of  personal  hygiene,  they 
will  neglect  them  or  carry  them  out  imperfectly,  in  fact  "the 
people  perish  for  want  of  knowledge."  Sir  George  Newman 
has  insisted  that  health  education  is  an  essential  part  of  any 
national  health  policy,  that  instruction  should  be  given  in 
schools,  and  has  faciHtated  this  by  the  issue  from  the  Board 
of  Education  of  "A  Handbook  of  Suggestions  on  Health 
Education."  In  this  education  medical  men  have  taken 
the  pioneer  part,  and  for  its  right  guidance  and  success  must 
continue  to  give  this  service. 

Infant  Welfare.  As  about  80  per  cent  of  the  population 
are  born  free  from  disease,  it  is  obviously  most  important  to 
protect  them  against  the  various  dangers  in  the  way  of 
infection,  improper  feeding,  and  neglect  that  may  assail 
them.  Antenatal  care  and  instruction  of  the  mothers,  infant 
welfare  centers,  and  infant  treatment  clinics  provided  by  the 
state  are  obviously  of  great  value  in  this  respect.  In  1871- 
1880  out  of  every  thousand  infants  149  died  during  the  first 
year  of  life,  in  1928  this  number  had  fallen  to  6§.  The  infant 
welfare  centers  should  continue  to  supervise  the  health  of 
the  young  up  to  the  age  of  school  life. 

The  school  medical  service,  started  in  1907  in  England  and 
Wales,  is  part  of  the  public  health  service  of  the  country, 
and  employs  more  than  1800  medical  men  and  women.  This 
step  in  preventive  medicine  has  been  followed  by  a  substan- 
tial degree  of  physical  and  mental  improvement. 

Disease  of  the  teeth,  pyorrhea  alveolaris  and  dental  caries, 
are  an  extremely  common  cause  of  ill  health,  rheumatism 
and  fibrositis,  neuritis,  disease  in  the  abdomen  and  other 
parts.  The  frequency  of  dental  disease  may  have  increased 
with  the  cooking  of  civilized  hfe,  but,  be  this  as  it  may,  the 
great  importance  of  oral  sepsis,  including  tonsilhtis,  in 
causing  widespread  bodily  disease,  especially  rheumatic  fever 
and  heart  disease,  has  only  recently  been  fully  recognized. 
The  institution  of  dental  clinics  for  the  inspection  of  school 
children,  as  part  of  the  systematic  school  medical  service  in 
Great  Britain,  is  a  most  valuable  element  in  preventive 
medicine.  Logically   a   similar  periodical  medical  exainina- 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR   THE    RACE    '4^^ 

tion  of  adults  should  be  available  in  order  to  give  timely 
warning  of  the  tendency  to  disease  and  to  detect  the  early 
evidence  of  insidious  disorders  of  which  there  may  not  be  any 
conscious  suspicion,  such  as  high  blood  pressure,  kidney  or 
nervous  affections.  Comparatively  few  consult  their  medical 
attendants  in  the  same  way  that  they  visit  their  dentists  in 
order  to  anticipate  trouble.  But  that  this  is  worth  while  has 
been  shown  by  the  action  of  some  American  Life  Insurance 
Companies  in  offering  their  pohcy-holders  periodical  medical 
examinations  by  the  Life  Extension  Institute;  the  results 
have  shown  that  it  is  a  good  business  proposition,  for  there 
was  a  substantially  lower  death  rate  among  those  who 
availed  themselves  of  the  offer  as  compared  with  the  policy- 
holders who  did  not.  If  this  step  is  economically  sound  from 
the  statistical  point  of  view,  it  is  surely  worth  consideration 
by  the  individual. 

Preventive  Physiological  Tests.  A  recent  example  of  the 
application  of  physiology  and  psychology  to  practical  life  is 
seen  in  the  examination  of  candidates  for  aviation  work,  and 
periodically  of  pilots  to  see  if  they  are  fit  to  continue  or 
need  rest.  The  tests  evolved  during  the  European  War  proved 
of  great  value  in  deciding  questions  which  an  ordinary 
medical  examination  cannot  do  with  such  certainty.  The 
human  machine  has  to  adapt  itself  to  the  changing  conditions 
of  temperature  and  oxygen  tension  depending  on  rapid 
alterations  of  altitude;  and  to  estimate  the  capacity  of  the 
individual  in  these  respects  and  to  determine  the  state  of  the 
nervous  system  and  the  sense  organs  special  methods  of 
testing  are  necessary.  By  these  tests  loss  of  life  and  disabling 
crashes  were  diminished. 

Preventive  Bacteriology.  The  comparatively  new  knowledge 
that  otherwise  normal  people  may  carry  in  their  bodies  the 
germs  of  disease,  such  as  typhoid  fever,  pneumonia,  diph- 
theria, and  cerebrospinal  fever, *and  thus  unconsciously  give 
the  disease  to  others,  explains  the  apparently  spontaneous 
outbreaks  of  disease.  The  detection  of  these  "carriers"  by 
bacteriological  means  supplies  the  obvious  way  of  preventing 
disease,  namely  isolation  of  the  carrier. 

Preventive  Surgery.  Examples  of  the  preventive  influence 
of  internal  medicine  are  mentioned  elsewhere  in  this  chapter. 


456  HUMAN   BIOLOGY 

and  it  is  therefore  unnecessary  to  repeat  them.  But  attention 
should  be  drawn  to  the  way  in  which  surgery  acts  in  a 
similar  way;  the  removal  of  local  centers  of  bacterial  infection 
or  septic  foci,  such  as  an  inflamed  vermiform  appendix  or  a 
small  abscess  on  the  finger,  may  prevent  a  severe  peritonitis 
or  a  general  infection  which  would  otherwise  prove  fatal. 
Complete  removal  of  a  cancerous  growth  is  another  obvious 
example. 

Dentistry,  which  until  the  end  of  the  last  century  was 
mainly  mechanical  in  its  conceptions,  is  now  recognized  as 
a  most  eff"ective  means  of  preventing  general  ill-health  and 
disease  in  other  parts  of  the  body,  such  as  rheumatism. 

INDUSTRIAL   MEDICINE 

In  preventing  disease  among  those  employed  in  various 
occupations,  which  were  formerly  known  as  dangerous  trades, 
medicine  has  done  much  and  is  progressively  doing  more  for 
the  well-being  of  the  race.  In  Great  Britain  as  long  ago  as 
1832  Dr.  Turner  Thackrah  and  in  1857  Dr.  E.  H.  Grecnhow 
enquired  into  the  influence  of  industrial  occupations  on 
health,  and  since  then  these  problems  have  been  widely  and 
intensively  investigated;  since  19 17  a  special  section  of 
the  physiological  department  at  Harvard  University,  Boston, 
Massachusetts,  has  been  devoted  to  scientific  research  into  the 
causation  of  industrial  diseases  under  the  direction  of 
Dr.  C.  K.  Drinker.  The  poisonous  eff'ects  of  lead  which 
attend  a  number  of  industries,  such  as  white  lead  workers, 
printers,  potters,  have  long  been  known,  and  as  the  result  of 
carefully  planned  protective  measures,  including  periodical 
examination  of  the  employees,  based  on  investigations  of  the 
circumstances  of  the  industry,  the  evil  effects  have  been 
largely  obviated.  But  other  metals,  such  as  nickel,  zinc, 
manganese,  copper,  and  mercury  (in  hatters,  thermometer 
and  mirror  makers)  may  be  responsible  for  industrial 
poisoning.  A  number  of  occupational  diseases  are  due  to  the 
inhalation  of  dust,  especiaUy  among  miners,  as  in  the 
"gold-miners  phthisis"  in  which  particles  of  sihca  are 
particularly  harmful. 

As  examples  of  the  value  of  arresting  the  incidence  of 
toxic  effects  from  dangerous  occupations,  reference  may  be 


WHAT   MEDICINE    HAS    DONE    AND    IS    DOING    FOR   THE    RACE     457 

made  to  the  rapid  effect  of  skilled  medical  advice  in  con- 
nection with  the  occurrence  of  jaundice  and  hepatic  disease 
in  aeroplane  workers  who  used  tetrachlorethane  ("dope")  to 
paint  the  wings  of  aeroplanes  in  England  at  an  early  stage  of 
the  Great  War,  and  later  on  in  the  War  in  the  care  of  workers 
in  munition  factories  where  trinitrotoluene  ("t.n.t.")  was  used. 
It  may  be  pointed  out  that  the  exigencies  of  the  War  stimu- 
lated efforts  in  the  direction  of  industrial  hygiene.  The  practical 
apphcation  of  experimental  psychology,  which  investigates 
the  responses  of  individuals  to  definite  prescribed  condi- 
tions, has  proved  to  be  of  great  economic  value  in  increasing 
the  output  of  work  in  factories  and  workshops  by  modifying 
the  conditions  of  work,  particularly  by  the  introduction  of 
intervals  of  rest,  maintaining  good  atmospheric  conditions 
so  as  to  obviate  fatigue,  and  by  minimizing  monotony  and 
boredom. 

REFERENCES 

Dana,  C.  L.  1928.  The  Peaks  of  Medical  History.  Ed.  2,  N.  Y.,  Hoeber. 

Garrison,  F.  H.  1929.  An  Introduction  to  the  History  of  Medicine.  Ed.  4, 
Phila.,  Saunders. 

GuNTHER,  R.  T.  1925.  Early  Science  in  Oxford.  Oxford  Univ.  Press,  vol.  3, 

Masters,  D.  1925.  The  Conquest  of  Disease.  Lond.,  Lane. 

McCarrison,  R.  1928.  The  Simple  Goitres.  Lond.,  BailHere,  Tindall  &  Cox. 

Myers,  C.  S.  1926.  Industrial  Psychology  in  Great  Britain.  Lond.,  Cape. 

Newman,  G.  1926.  An  Outline  of  the  Practice  of  Preventive  Medicine.  Min- 
istry of  Health  Publ.,  Lond. 
Annual  Reports  of  the  Chief  Medical  Officer  of  the  Ministry  of  Health,  and 
of  the  Board  of  Education,  Lond. 

Newsholme,  a.  1925.  The  Ministry  of  Health.  N.  Y.,  Putnam. 

Osler,  W.  1921.  The  Evolution  of  Modern  Medicine.  Silhman  Lectures,  Yale 
Univ.,  191 3,  Yale  Univ.  Press. 

Rockefeller  Foundation,  Annual  Rep.,  N.  Y. 


Chapter  XIX 
THE  RELATION  OF  SCIENCE  TO  INDUSTRY 

R.  A.  MiLLlKAN 

A  WELL-KNOWN  public  speaker  of  fifty  years  ago 
once  remarked  ruefully  after  disastrous  consequences 
had  followed  misplaced  humor,  "I  rose  by  my  gravity 
and  fell  by  my  levity." 

I  use  this  incident  as  an  introduction  to  my  chapter 
for  the  sake  of  calhng  attention  to  the  fact  that  what  is 
absurd  or  ridiculous  today  was  perfectly  good  science,  or 
at  least  good  philosophy,  not  more  than  350  years  ago, 
that  the  very  existence  of  the  "law  of  gravity"  was  discov- 
ered as  late  as  1650  a.d.  and  that  "levity"  and  "levitation" 
have  through  all  recorded  history  up  to  Newton  been  just  as 
acceptable  scientific  ideas  as  gravity  and  gravitation,  so 
recently  have  we  begun  to  understand  just  a  httle  about  the 
nature  of  the  world  in  which  we  live. 

Nor  do  I  need  to  go  back  300  years  to  make  my  point  as  to 
the  newness  of  our  knowledge.  It  is  within  the  memory  of 
every  man  of  the  age  of  sixty  that  in  the  great  Empire  State 
of  New  York  the  question  could  be  seriously  debated,  and 
in  the  most  intelligent  of  her  communities  too,  as  to  whether 
Archbishop  Usher's  chronology,  computed  by  adding  Adams 
930  years  to  Enoch's  365  years  to  Methuselah's  969  years, 
etc.  gave  the  correct  date  of  creation.  Recent  election 
returns  from  Arkansas  indicate  that  the  same  debate  is  at 
this  very  moment  going  on  there. 

But  what  has  this  to  do  with  "Science  and  Industry?" 
Everything!  For  mankind's  fundamental  behefs  about  the 
nature  of  the  world  and  his  place  in  it  are  in  the  last  analysis 
the  great  moving  forces  behind  ail  his  activities.  Hence 
the  enormous  practical  importance  of  correct  understandings. 
It  is  his  behefs  about  the  nature  of  his  world  that  determine 
whether  man  in  Africa  spends  his  time  in  beating  tomtoms  to 
drive  away  evil  spirits,  or  in  Phoenicia  in  building  a  great 
"burning  fiery  furnace"  to  Moloch  into  which  to  throw  his 

458 


THE    RELATION    OF    SCIENCE    TO    INDUSTRY  459 

children  as  sacrifices  to  his  God,  or  in  Attica  in  making  war 
on  his  fellow  Greeks  because  the  Delphic  Oracle,  or  the 
flight  of  birds,  or  the  appearance  of  an  animal's  entrails 
bids  him  do  so,  or  in  medieval  Europe  in  preparing  for  the 
millennium  to  the  neglect  of  all  his  normal  duties  as  he  did  to 
the  extent  of  bringing  on  a  world  disaster  in  the  year  looo, 
or  in  burning  heretics  in  Flanders  or  drowning  witches  in 
Salem,  or  in  making  perpetual  motion  machines  in  Phila- 
delphia, or  magnetic  belts  in  Los  Angeles,  or  soothing  syrups  in 
New  England. 

The  invention  of  the  airplane  and  the  radio  are  looked 
upon  by  everyone  as  wonderful  and  pre-eminently  useful 
achievements,  and  so  they  are,  perhaps  one-tenth  as  useful 
as  some  of  the  discoveries  in  pure  science  that  I  shall  pres- 
ently discuss  and  hence  worthy  of  a  moment  or  two  of 
consideration. 

As  I  listened  in  Pasadena  to  the  Presidential  candidates 
presenting  in  their  own  easily  recognizable  voices  from  the 
platform  in  Madison  Square  Garden  to  the  people  of  the 
United  States  the  issues  of  the  election,  or  at  least  its  shib- 
boleths, I  found  myself  aglow  with  enthusiasm  for  the  future 
of  representative  government.  The  few  thousand  citizens  of 
Athens  gathered  about  the  Acropolis  to  hear  the  problems 
of  the  city  discussed  and  then  to  cast  their  ballots.  The 
120  million  citizens  of  the  United  States  in  this  recent 
election  had  precisely  the  same  opportunity  and  in  my  judg- 
ment they  used  it  judiciously.  These  public  discussions 
addressed  to  the  ears  of  the  nation  represent,  I  think,  a 
stupendous  advance.  No  such  step  forward  in  public  edu- 
cation has  been  taken  since  the  invention  of  printing. 

But  this  new  achievement  of  the  race,  this  new  capacity 
for  education  was  after  all  only  an  inevitable  incident  in  the 
forward  sweep  of  pure  science,  which  means  simply  knowl- 
edge, knowledge  of  the  nature  and  capacities  of  the  physical 
world,  the  ethereal  world  (to  which  the  radio  belongs j,  the 
biological  world  and  the  intellectual  world;  for  this  knowl- 
edge, as  man  acquires  it,  necessarily  carries  applied  science 
in  its  wake. 

Look  for  a  moment  at  the  historic  background  out  of 
which  these  modern  marvels,  as  you  call  them,  the  airplane 


460  HUMAN   BIOLOGY 

and  the  radio,  have  sprung.  Neither  of  them  would  have 
been  at  all  possible  without  200  years  of  work  in  pure  science 
before  any  bread  and  butter  applications  were  dreamed  of, 
work  beginning  in  the  sixteenth  century  with  Copernicus 
and  Kepler  and  Gahleo,  whose  discoveries  for  the  first  time 
began  to  cause  mankind  to  gHmpse  a  nature,  or  a  God, 
whichever  term  you  prefer,  not  of  caprice  and  whim  as  had 
been  all  the  Gods  of  the  ancient  world,  but  instead  a  God 
who  rules  through  law,  a  nature  which  can  be  counted 
upon  and  hence  is  worth  knowing  and  worth  carefully 
studying.  This  discovery  which  began  to  be  made  about 
1600  A.D.  I  call  the  supreme  discovery  of  all  the  ages,  for 
before  any  application  was  ever  dreamed  of,  it  began  to 
change  the  whole  philosophical  and  religious  outlook  of  the 
race,  to  effect  a  spiritual  and  an  intellectual,  not  at  first  a 
material  revolution,  this  was  to  come  later.  This  new  knowl- 
edge was  what  began  at  this  time  to  banish  the  monastic 
ideal  which  had  led  thousands,  perhaps  millions  of  men,  to 
withdraw  themselves  from  useful  lives.  It  was  this  new 
knowledge  that  began  to  inspire  man  to  know  his  universe  so 
as  to  be  able  to  live  in  it  more  rationally. 

As  a  result  of  that  inspiration  there  followed  200  years 
of  the  pure  science  involved  in  the  development  of  the 
mathematics,  and  ofthe  celestial  mechanics,  necessary  merely 
to  understand  the  movements  of  the  heavenly  bodies,  useless 
knowledge  to  the  unseeing,  but  all  constituting  an  indispen- 
sable foundation  for  the  development  of  the  terrestrial 
mechanics  and  the  industrial  civilization  which  actually 
followed  in  the  nineteenth  century;  for  the  very  laws  of 
force  and  motion  essential  to  the  design  of  all  power  machines 
of  every  sort  were  completely  unknown  to  the  ancient  world, 
completely  unknown  up  to  Galileo's  time. 

Does  the  practical  man  of  today  fully  realize  that  the 
airplane  was  only  made  possible  by  the  development  of  the 
internal  combustion  engine,  that  this  in  its  turn  was  only 
made  possible  by  the  development  of  the  laws  governing 
all  heat  engines  (the  laws  of  thermo  dynamics)  through  the 
use  for  the  hundred  preceding  years  of  the  steam  engine, 
that  this  was  only  made  possible  by  the  preceding  200 
years  of  work  in  celestial  mechanics,  that  this  was  only  made 


THE    RELATION    OF    SCIENCE   TO    INDUSTRY  46 1 

possible  by  the  discovery  of  the  laws  of  force  and  motion 
by  Gahleo  and  Newton.  That  states  the  relationship  of 
pure  science  to  industry.  The  one  is  the  child  of  the  other. 
You  may  apply  any  blood  test  you  wish  and  you  will  at 
once  establish  the  relationship.  Pure  science  begat  modern 
industry. 

In  the  case  of  the  radio  art,  the  commercial  values  of  which 
now  mount  up  to  many  billions  of  dollars,  the  parentage 
is  still  easier  to  trace.  For  if  one's  vision  does  not  enable 
him  to  look  back  300  years,  even  the  shortest-sighted  of  men 
can  scarcely  fail  to  see  back  eighteen  years.  For  the  whole 
structure  of  the  radio  art  has  been  built  since  1910,  definitely 
and  unquestionably  upon  researches  carried  on  in  the  pure 
science  laboratory  for  twenty  years  before  anyone  dreamed 
that  there  were  immediate  commercial  applications  of  these 
electronic  discharges  in  high  vacuum. 

It  is  precisely  the  same  story  everywhere  in  all  branches 
of  human  progress.  I  suspect  it  would  be  difficult  to  find  a 
single  exception.  Here  is  the  latest  illustration  that  came  to 
my  attention  less  than  a  week  ago  in  a  letter  from  the  Air  Re- 
duction Sales  Company.  It  reads  as  follows:  "We  take  pleasure 
in  handing  you  herewith  a  complete  set  of  luminescent  tubes, 
each  containing  in  the  pure  state  one  of  the  elements  of  the 
air,  namely,  nitrogen,  oxygen,  argon,  hydrogen,  neon,  helium, 
krypton  and  xenon.  It  seems  to  us  worthy  of  note  that  at 
the  beginning  of  this  century  these  gaseous  elements  as 
such  had  practically  no  commercial  significance.  Today 
the  estimated  value  of  the  plants  and  equipment  that  have 
been  created  either  to  manufacture  or  to  use  and  handle  these 
gases  in  industry  amounts  to  three  hundred  million  dollars. " 

The  writer  of  this  letter  might  have  added  that  the  chain 
of  discovery  which  led  up  to  this  result  started  in  the  most 
"useless"  of  all  sciences,  astronomy;  for  helium,  as  its  name 
implies  and  as  everyone  knows,  was  first  discovered  in  the  sun 
with  the  aid  of  the  spectroscope,  and  thirty  years  later  it  was 
its  discovery  in  minute  amounts  in  our  atmosphere,  also  with 
the  aid  of  the  spectroscope,  that  set  us  looking  for  the  other 
inert  gases  of  which  the  letter  speaks  and  which  have 
recently  found  such  enormous  application  in  neon  tubes  and 
the  like. 


462  HUMAN   BIOLOGY 

But  why  continue  these  recitals,  for  no  intelhgent  man 
today  needs  to  be  convinced  that  our  material  prosperity  rests 
wholly  upon  the  development  of  our  science.  It  is  as  to  the 
broader  values,  intellectual  and  spiritual,  that  even  intelhgent 
men  sometimes  express  doubt.  Let  me  then  start  with  the 
foundations  that  I  have  already  laid  and  try  to  show  to  what 
these  beginnings  are  leading,  whither  we  are  going,  not 
materially,  but  as  feehng,  thinking  and  wilhng  beings. 

Was  Pasteur  only  a  scientific  enthusiast  when  he  wrote:  "  In 
our  century  science  is  the  soul  of  the  prosperity  of  nations  and 
the  hving  source  of  all  progress.  Undoubtedly  the  tiring 
discussions  of  pohtics  seem  to  be  our  guide^ — empty  appear- 
ances! What  really  leads  us  forward  is  a  few  scientific 
discoveries  and  their  apphcation. " 

Or  was  H.  G.  Wells,  himself  not  a  scientist  at  all,  merely 
talking  nonsense  when  he  wrote:  "When  the  intellectual 
history  of  this  time  comes  to  be  written,  nothing,  I  think,  will 
stand  out  more  strikingly  than  the  empty  gulf  in  quahty 
between  the  superb  and  richly  fruitful  scientific  investigations 
that  are  going  on,  and  the  general  thought  of  other  educated 
sections  of  the  community.  I  do  not  mean  that  scientific 
men  are,  as  a  whole,  a  class  of  supermen,  deahng  and  thinking 
about  everything  in  a  way  altogether  better  than  the 
common  run  of  humanity,  but  in  their  field  they  think  and 
work  with  an  intensity  and  integrity,  a  breadth,  a  boldness, 
patience,  thoroughness,  fruitfuhiess,  excepting  only  a  few 
artists,  which  puts  their  work  out  of  all  comparison  with 
any  other  human  activity.  In  these  particular  directions  the 
human  mind  has  achieved  a  new  and  higher  quality  of 
attitude  and  gesture,  a  veracity,  a  self  detachment,  and 
self-abrogating  vigor  of  criticism  that  tends  to  spread  out 
and  must  ultimately  spread  to  every  other  human  affair. " 

These  ma}^  be  extravagant  statements,  most  of  us  scientists 
are  sure  they  are,  but  I  should  like  to  attempt  to  picture  a 
little  of  what  I  think  was  in  the  back  of  the  minds  of  their 
authors  when  they  made  them.  I  shall  do  it  by  drawing  an 
analogy  between  the  life  of  mankind  as  a  whole  and  the  life 
of  man  as  an  individual.  But  first  let  me  answer  the  question 
as  to  what  we  know  about  the  duration  of  the  life  of  mankind. 
A  hundred  years  ago  we  knew  practically  nothing  about  it,  as 


THE    RELATION    OF    SCIENCE   TO    INDUSTRY  463 

my  opening  remarks  on  Archbishop  Usher's  chronology 
showed.  But  since  then  we  have  made  some  scientific 
discoveries,  discoveries  that  are  not  usually  hsted  as  of 
industrial  importance  at  all,  but  which  in  my  opinion 
outweigh  by  far  in  practical  value  to  the  race,  either  the 
invention  of  the  airplane  or  of  the  radio,  and  that  simply 
because  they  change  fundamentally  our  ideas  about  the 
nature  of  the  outside  world,  and  hence  change  also  the 
nature  of  our  acting  in  relation  to  it. 

We  have  learned  within  the  past  half  dozen  years  through 
studies  in  radioactivity  that  this  world  of  ours  has  in  all 
probabihty  been  a  going  concern,  in  something  hke  its  present 
geological  aspects  as  to  crustal  constituents,  temperatures, 
etc.  for  more  than  a  bilHon  years,  and  hence  that  the  human 
race  can  probably  count  on  occupying  it  for  a  very  long  time 
to  come,  say  another  billion  years;  and  further,  that  mankind 
has  been  doing  business  on  it  in  something  hke  his  present 
shape  for  about  20,000  years,  perhaps  50,000,  but  in  any  case 
a  time  that  is  neghgibly  small  in  comparison  with  the  time 
that  is  behind  and  also  that  is  presumably  ahead  of  him; 
in  other  words,  we  have  learned  that  mankind,  speaking 
of  him  as  an  individual  human  being,  is  now  just  an  infant  a 
few  months  old  at  the  most,  an  infant  that  up  to  about  a 
minute  ago,  for  the  300  years  since  GaHIeo  are  but  a  minute 
in  the  geological  time-scale,  had  been  lying  in  his  crib  spend- 
ing his  waking  hours  playing  with  his  fingers,  wigghng  his 
toes,  shaking  his  rattle,  in  a  word,  in  simply  becoming 
conscious  of  his  own  sensations  and  his  functions,  waking  up, 
as  he  did  amazingly  in  Greece,  to  his  own  mental  and 
emotional  insides.  Just  one  minute  ago  he  began  for  the  first 
time  to  peer  out  through  the  slats  in  his  crib,  to  wonder  and  to 
begin  to  try  to  find  out  what  kind  of  an  external  world  it  is 
that  lies  around  him,  what  kind  of  a  world  it  is  in  which  he 
has  got  to  live  for  the  next  billion  years.  The  answers  to  that 
question,  even  though  never  completely  given,  are  henceforth 
his  one  supreme  concern.  In  this  minute  of  experience  that 
he  has  already  had  he  has  tumbled  down  in  his  crib,  bumped 
his  head  against  the  slats,  and  seen  stars,  real  ones  and  unreal 
ones,  and  he  has  not  yet  learned  to  distinguish  with  certainty 
between  those  that  actually  exist  and  those  that  only  seem  to 


464  HUMAN   BIOLOGY 

exist  because  his  eye-balls  have  received  a  blow,  and  so  he 
is  reaching  out  his  hands  part  of  the  time  trying  to  grasp 
illusions,  and  yet  slowly,  painfully  learning,  bit  by  bit, 
that  there  is  an  external  world,  physical  and  biological,  that 
can  be  known,  that  can  be  counted  upon  when  it  has  once 
become  known,  to  act  consistently,  not  capriciously,  that 
there  is  a  law  of  gravity  and  that  it  is  not  necessary  to  be 
covered  with  bruises  all  the  time  because  he  forgets  it, 
that  there  is  a  principle  of  conservation  of  energy,  and  that 
all  constructive  and  worth-while  effort  everywhere  must 
henceforth  take  it  into  account  and  be  consonant  with  it,  that 
it  is  not  worth  while  to  spend  much  time  with  sentimental- 
ists who  wish  that  that  law  did  not  exist  and  sometimes 
try  to  legislate  it  out  of  existence,  that  again  there  are  facts 
of  heredity  that  it  is  utterly  futile  to  enveigh  against,  that 
our  whole  duty  is  rather  to  bend  every  energy  to  know  what 
they  are  and  then  to  find  how  best  to  live  in  conformity 
with  them,  that,  in  a  single  sentence,  there  is  the  possibility 
ahead  of  mankind  of  learning  in  the  next  billion  years  of 
its  existence  to  live  at  least  a  million  times  more  wisely 
than  we  now  live.  This  is  what  Pasteur  meant  when  he 
said,  "What  really  leads  us  forward  is  a  few  scientific 
discoveries  and  their  applications. "  This  is  what  Wells  meant 
when  he  contrasted  the  result  of  the  objective  method  of 
learning  used  in  the  pursuit  of  science  with  what  he  calls 
"the  general  thought  of  other  educated  sections  of  the 
community."  The  one  guesses  and  acts  upon  its  hunches  or 
its  prejudices,  the  other  tries  at  least  to  know,  and  succeeds 
in  knowing  part  of  the  time. 

We  need  science  too  in  education,  and  much  more  of  it 
than  we  now  have,  not  primarily  to  train  technicians  for 
the  industries  which  demand  them,  though  that  may  be 
important,  but,  much  more,  to  give  everybody  a  little  glimpse 
of  the  scientific  mode  of  approach  to  life's  problems,  to 
give  everyone  some  familiarity  with  at  least  one  field  in 
which  the  distinction  between  correct  and  incorrect  is  not 
always  blurred  and  uncertain,  to  let  him  see  that  it  is  not 
always  true  that  "one  opinion  is  as  good  as  another,"  to 
let  everyone  understand  that  up  to  Galileo's  time  it  was 
reputable  science  to  talk  about  gravity  and  levity,  but  that 


THE    RELATION    OF    SCIENCE    TO    INDUSTRY  465 

after  Galileo's  time  the  use  of  levity  became  limited  to  the 
ridiculous,  that  "the  town  that  voted  the  earth  was  flat,  flat 
as  my  hat,  flatter  than  that,"  had  a  perfect  right  to  exist 
before  1400  a.d.,  but  not  after  that  date,  that  we  are  learning 
slowly  through  the  accumulated  experience  and  experiment- 
ing of  the  centuries,  especially  since  1600  a.d.,  more  about  the 
eternal  laws  that  govern  in  the  world  in  which  we  hve.  And 
for  my  own  part  I  do  not  beHeve  for  a  moment  that  these 
eternal  laws  are  Hmited  to  the  physical  world  either.  Less 
than  sixty  years  ago,  to  take  one  single  iUustration,  there 
existed  a  large  poHtical  party  in  the  United  States  caUed  the 
Greenback  Party  which  Jumped  at  conclusions  and  which 
conducted  campaigns  to  induce  our  government  to  go  over 
to  a  fiat  money  basis.  I  do  not  suppose  such  a  party  could 
exist  today  unless  it  be  in  states  that  passed  anti-evolution 
laws,  for  there  are  some  laws  that  have  become  established, 
even  in  the  field  of  finance. 

This  brings  me  to  a  brief  discussion  of  the  current  opposi- 
tion to  the  advance  of  science,  an  opposition  participated 
in  even  by  some  intelligent  people,  on  the  ground  that 
mankind  cannot  be  trusted  with  too  much  knowledge,  by 
others  on  the  ground  that  beauty  and  art  and  high  emotion 
are  incompatible  with  science.  Now,  fear  of  knowledge  is 
as  old  as  the  Garden  of  Eden  and  as  recent  as  Dr.  Faust,  and 
there  is  no  new  answer  to  be  made  to  it.  The  old  answer  is 
merely  to  point  to  what  the  increase  in  knowledge  has  done 
to  the  lot  of  mankind  in  the  past,  and  I  think  that  answer 
is  sufficient,  for  it  has  certainly  enfranchised  the  slave  and 
given  every  man,  even  the  poorest,  such  opportunities  as 
not  even  the  prince  of  old  enjoyed.  Who  would  go  back  to 
the  Stone  Age  because  Stone-age  man  had  no  explosives? 
Of  course  every  new  capacity  for  beauty  and  joy  and  for 
accomplishment  brings  with  it  the  possibility  of  misuse  and 
hence  a  new  capacity  for  sorrow. 

But  it  is  our  knowledge  alone  that  makes  us  men  instead  of 
lizards,  and  thank  God,  we  cannot  go  back  whether  we  would 
or  no.  Our  supreme,  our  Godlike  task,  is  to  create  greater 
beauty  and  fuller  joy  with  every  increased  power  rather  than 
to  turn  our  weeping  eyes  toward  the  past  and  fling  ourselves 
madly,  unreasoningly  athwart  the  path  of  progress.  Beauty 


466  HUMAN    BIOLOGY 

« 

in  the  ameba's  house  disappeared  when  man  cleaned  up  the 
miasmic  swamp,  but  it  was  only  because  the  ameba  had  not 
the  capacity  to  adapt  itself  to  modern  sanitation. 

No,  the  only  real  question  in  a  nation  like  ours  is  not 
whether  science  is  good  for  us  materially,  intellectually, 
esthetically,  artistically.  Of  course  it  is,  for  science  is  simply 
knowledge  and  all  knowledge  helps.  The  only  real  question  is 
how  the  forward  march  of  pure  science,  and  of  applied  science 
which  necessarily  follows  upon  its  heels,  can  best  be  maintained 
and  stimulated,  for,  as  Pasteur  said,  "It  is  this  alone  that 
really  leads  us  forward." 

The  answer  to  that  question  will  depend  upon  the  nature 
of  one's  whole  social  philosophy.  If  you  think  that  social 
progress  is  best  brought  about  by  a  paternalistic  regime  of 
some  kind,  by  throwing  upon  a  few  elected  or  hereditary 
officials  the  whole  responsibility  for  social  initiative  of  all 
sorts,  then  you  will  say,  "Let  the  government  do  it  all;  let  it 
establish  state  universities  and  state  research  laboratories 
and  state  experimental  projects  of  all  kinds  as  it  has  done  in 
most  countries  in  Europe,  and  let  the  whole  responsibility  for 
our  scientific  progress  lie  in  these  institutions.  But  if  you 
believe  with  the  makers  of  our  nation  in  the  widest  possible 
distribution  of  social  responsibility,  in  the  widespread 
stimulation  of  constructive  effort,  in  the  nearest  possible 
approach  to  equality  of  opportunity,  not  only  for  rising  to 
wealth  and  position,  but  for  sharing  in  community  service, 
if  you  believe  with  President  Hoover  that  government 
should  only  step  in  where  private  enterprise  fails,  that  it 
should  act  only  as  a  stimulant  to  private  initiative  and  a 
check  to  private  greed,  then  the  industries  in  the  United 
States  which  are  themselves  the  offspring  of  pure  science, 
will  join  in  a  great  nation-wide  movement  to  keep  alive  the 
spirit  of  science  all  over  this  land  of  ours  through  keeping 
pure  science  going  strong  in  universities,  its  logical  home,  and 
applied  science  going  strong  in  the  private  industrial  labora- 
tories where  it  thrives  best.  No  country  ever  had  such  an 
opportunity  as  ours,  such  a  widespread  stimulation  of 
initiative,  such  a  large  number  of  citizens  who  had  learned  to 
treat  financial  power  as  a  public  trust,  such  resources  to 
command,  such  results  to  anticipate.   With  our  American 


THE    RELATION    OF    SCIENCE   TO    INDUSTRY  467 

Ideals  American  industry  cannot  fail,  I  think,  to  realize  this 
opportunity  and  to  support  and  keep  in  the  finest  possible 
condition  "the  hen  which  lays  her  golden  egg."  That,  is 
my  conception  of  the  relation  of  science  and  industry  in  the 
United  States. 


Chapter  XX 
THE  INFLUENCE  OF  EDUCATION 

John  Dewey 

PROBABLY  man's  pidest  tradition  about  himself  is 
that  he  is  different  in  kind  from  all  other  animals,  so 
different  that  according  to  the  version  current  in  the 
Christian  world  he  and  he  alone  is  made  in  the  divine  image. 
That  this  tradition  is  deep-seated  and  supremely  cherished  is 
made  evident  in  the  bitter  opposition  aroused  by  the  theory 
of  his  animal  descent.  This  theory  is  a  challenge  to  behef  in 
his  unique  status  among  creatures  on  earth.  The  conception 
was  not  arbitrary  in  its  origin.  There  is  a  mass  of  facts 
which  taken  at  their  face  value  support  the  behef  that  a 
great  gulf  divides  man  from  the  animals.  He  alone  is  ca- 
pable of  morals,  religion  and  science,  invents  tools,  devel- 
ops arts,  employs  language,  transmits  culture  and  envelops 
himself  in  institutions.  His  possession  of  ideals  and  of  the 
sense  of  right  and  wrong,  his  consciousness  of  laws,  are  alone 
enough  to  give  rise  to  the  notion  that  his  kinship  to  other 
animals  is  at  most  physical.  Realization  that  these  differ- 
ences are  due  to  the  fact  that  man  alone  is  an  educable  being 
in  a  pre-eminent  sense  of  the  word  is  the  most  extraordinary 
and  complete  proof  of  the  significance  of  education.  Of 
all  the  various  definitions  that  can  be  given  of  man,  that  he 
is  the  educable  being  is  that  which  goes  deepest. 

Man  is  not  only  educable  but  he  educates.  He  has  not 
only  potentialities  for  the  extraordinay  modifications  which 
seem  to  put  him  in  a  class  far  above  other  animals,  but  he  has 
the  constant  desire  to  transmit  all  accomplished  transforma- 
tions to  others.  He  is  a  propagandizing  (to  use  the  word 
for  once  in  a  good  sense)  animal  as  well  as  a  propagating 
one.  His  zeal  in  social  and  moral  reproduction  matches  that 
in  physical  reproduction.  The  course  of  culture  has  been 
slow  and  tortuous,  exposed  to  accident  and  destruction. 
But  it  would  have  been  still  more  so  if  man  had  remained 
merely  a  being  capable  of  education  but  without  the  energetic 

468 


THE    INFLUENCE    OF    EDUCATION  469 

tendency  to  train,  instruct  and  form  others  of  his  kind. 
Nor  has  the  desire  and  abihty  been  limited  to  his  own  kind. 
The  history  of  civilization  would  have  been  very  different 
without  the  domestication  of  animals;  this  domestication 
marks  an  extension  of  training  to  other  species.  In  the  case 
of  his  own  kind,  however,  the  need  to  educate  is  itself 
biologically  imperative.  Much  has  been  said  by  John  Fiske 
and  others  of  the  effect  of  the  prolongation  of  infancy  in 
the  human  animal  in  developing  care  of  others  and  the 
reflex  effect  of  this  necessary  care  upon  the  growth  of  moral 
sentiments  and  ideas.  But  it  testifies  also  to  the  fact  that 
the  young  require  education  by  others  to  an  extent  not 
paralleled  among  other  animals. 

EDUCATION    A   BIOLOGICAL    NECESSITY 

The  human  being  is  born  feeble,  impotent,  needy  in 
the  extreme.  He  cannot  survive  without  the  attention  and 
nurture  of  others  who  are  capable  and  who  supply  his 
wants.  Food  and  protection  must  be  extended  to  him  by 
others;  this  not  a  matter  of  choice  but  of  necessity  if  he  is  to 
hve  more  than  a  day  or  two.  But  the  matter  does  not 
terminate  there.  He  has  to  learn  to  do  and  fend  for  himself; 
he  has  to  pass  from  the  status  of  dependence  to  one  of 
independence.  And  this  he  can  do  only  as  he  learns  from 
others.  His  native  tendencies  demand  manifestation;  he  has 
eyes,  ears,  hands  and  vocal  organs.  Even  these  he  has  to 
learn  to  use.  Much  of  their  development  is  due  to  an 
intrinsic  maturing  of  the  organism  itself.  To  that  extent 
the  young  teach  themselves.  But  such  organic  development 
does  not  take  them  far.  Indeed,  without  direction  from 
others,  it  leads  to  arrested  development.  Fortunately, 
although  also  in  some  respects  unfortunately,  others,  more 
experienced  and  more  initiated  into  the  acquired  habits 
and  resources  of  a  community,  have  an  interest  in  giving 
native  aptitudes  direction.  They  see  to  it  that  natural 
tendencies  are  directed  toward  certain  objects  and  attached 
to  certain  ideas  and  ideals.  Interest  in  this  process  springs 
from  sources  over  and  above  such  affection  for  the  young 
as  may  be  entertained.  For  since  death  is  as  sure  as  birth, 
social   institutions,    behefs   and   skills   can   be   perpetuated 


470  HUMAN    BIOLOGY 

only  as  they  are  renewed;,  the  customs  of  a  group  and 
civilization  must  be  integrated  into  the  habits  of  at  least 
enough  of  the  young  to  ensure  their  continuing  reproduction. 
Not  only  does  this  general  force  operate,  but  that  of  direct 
utihty;  indeed,  the  latter  is  often  more  intense.  The  demand 
for  aid  and  cooperation  in  carrying  on  the  occupation  of  the 
group,  whether  tribe  or  family,  is  urgent.  Children  and 
youth  are  taught  so  they  may  be  of  assistance;  their  help 
is  needed  in  savage  tribes,  for  example,  in  the  hunt  and  war, 
in  making  baskets,  utensils,  clothing,  etc.  The  immature 
can  be  of  use  only  as  they  learn  the  skills  their  elders  possess. 
In  multitudes  of  ways,  the  affection,  the  social  interest 
and  loyalty  and  the  desire  for  direct  aid  interact  with  the 
dependence  and  the  native  tendencies  of  children  to  educate 
the  latter.  All  the  words  that  express  the  operation  tell 
the  same  story,  to  rear,  raise,  form,  nurture,  cultivate. 

If,  then,  one  wished  to  sum  up  briefly  the  influence 
of  education  one  can  only  say  that  it  is  a  process  of  civihz- 
ing;  of  transforming  a  biological  heritage  into  beliefs,  abili- 
ties and  aspirations  consonant  with  sharing  in  social  life,  and 
this  through  the  medium  of  what  has  already  been  achieved  in 
the  group  and  culture  into  which  the  young  are  born.  Or,  from 
the  standpoint  of  mankind  instead  of  that  of  the  individ- 
ual, the  eff'ect  of  education  is  to  secure  the  perpetuation  of 
culture  in  all  the  various  phases  in  which  the  anthropologist 
uses  that  word,  material,  intellectual,  moral  and  institutional. 
It  is  education  that  makes  the  diff'erence  between  the  mere 
original  animal,  in  which  respect  the  human  being  is  inferior 
to  most  other  vertebrates,  and  the  human  being  with 
whatever  of  culture  and  civilization  he  possesses.  If  this 
claim  for  education  is  doubted,  it  is  because  education  is 
taken  too  narrowly,  being  identified  with  schooling.  Of 
education  in  the  sense  of  schooling,  the  statement  is  of 
course  not  true.  But  the  education  of  the  schools  represents  a 
specialized  mode;  education  itself  is  synonymous  with  all 
the  ways  in  which  native  biological  tendencies  are  shaped 
into  formed  abilities,  attitudes  and  dispositions. 

Before  we  consider  the  specialized  mode  (a  consideration 
that  is  the  main  concern  of  this  contribution)  it  is  advisable 
to  mention  some  questions,  more  or  less  controversial,  that 


THE    INFLUENCE    OF    EDUCATION  47 1 

grow  directly  out  of  the  relation  of  biological  and  cultural 
factors.  One  of  them  is  that  of  the  re'ation  of  heredity  and 
environment,  or  as  it  better  stated  since  the  days  of  Galton, 
of  nature  and  nurture. 

THE  fundamentals:  nature  and  nurture 

It  is  not  necessary,  fortunately,  to  raise  the  question 
in  its  full  scope.  For  in  the  practice  of  educative  training  it 
is  necessary  that  the  two  factors  should  cooperate  and  not  be 
set  over  against  each  other.  In  other  words,  they  are  fac- 
tors, and  the  factors  of  education.  The  most  ardent  devotee 
of  the  importance  of  original  nature  cannot  deny  the  necessity 
of  the  surrounding  medium  as  the  means  of  developing 
native  capacities  and  giving  them  direction.  The  acquisition 
of  language  is  a  striking  instance.  Without  a  hereditary  or 
"natural"  equipment,  an  individual  cannot  learn  to  speak. 
But  his  speech  would  remain  a  mere  babbhng  and  lisping, 
mere  cries  probably  not  even  well  articulated  and  certainly 
without  sense  and  meaning,  except  for  the  nurture  given  by 
interaction  with  other  previously  educated  human  beings. 
When  we  come  to  written  language  and  Hterature,  dependence 
upon  nurture  by  social  environment  is  even  more  obvious. 
Although  even  then  native  capacities  of  the  hand  and  brain  are 
involved,  education  signifies  the  process  of  using  them  in 
certain  definite   ways,  ways  that  are  expressed  in  nurture. 

Thus  with  respect  to  education  the  problem  reduces 
itself  to  one  of  greater  or  less  emphasis.  Some  magnify  one 
factor,  some  the  other.  None  can  deny  the  necessity  of  both. 
As  a  rule,  the  particular  emphasis  given  depends  upon  arbi- 
trary conditions;  in  part,  personal  temperament  and  previous 
training  decide;  in  part,  social  creeds.  Anyone  who  has  read 
the  literature  on  the  subject  is  aware,  for  example,  that 
those  who  incline  to  favor  political  aristocracy  emphasize 
original  hereditary  differences  as  the  dominant  force;  those 
inclined  to  a  democratic  faith  put  more  emphasis  upon  the 
force  of  environment  and  its  nurture.  Ardent  social  reform- 
ers and  revolutionists  have  often  gone  to  the  point  of 
asserting,  as  did  Helvetius,  the  omnipotence  of  education 
when  that  is  taken  in  its  widest  sense.  Extremists  in  the 
other  direction  hold  that  as  you  cannot  make  a  silk  purse  out 


472  HUMAN   BIOLOGY 

of  a  sow's  ear,  so  education  can  never  seriously  modify  and 
transform  original  capacities.  Their  plea  is  always  for 
recognition  of  individual  differences  of  native  ability  and  for 
selection  (for  anything  beyond  training  for  elementary 
utihties)  of  those  inherently  of  superior  gifts. 

The  issue  thus  raised  is  too  complex  and  controverted  to 
go  into  here.  But  it  is  something  to  recognize  that  we  must 
have  both  factors  in  some  measure.  In  addition,  the  testi- 
mony of  biology  to  native  differences  is  a  valuable  contri- 
bution to  the  educative  process  and  is  destined  to  become 
more  so.  But  most  persons  who  approach  the  matter  from 
the  side  of  education  would  utter  a  warning  against  too 
ready  identificacion  of  native  differences  of  traits  with  differ- 
ence of  ability.  Sympathizing  personally  with  this  view,  I 
suggest  three  considerations  in  support  of  it.  In  the  first 
place,  standards  or  norms  of  abihty  are  much  affected  by 
convention.  A  strictly  intellectual  and  professional  class 
would  take  to  measure  abihties  quite  different  capacities 
from  those  which  would  be  taken  by  not  only  executive  and 
mechanically  minded  persons,  but  also  by  those  of  strong 
esthetic  tastes.  Every  social  culture  tends  to  exaggerate  the 
value  of  certain  qualities  and  minimize  that  of  others. 
When  we  take  school  education  into  account,  even  more 
conventional  factors  come  into  play.  The  abilities  that 
happen  to  be  especially  cultivated  in  the  schoolroom  are 
treated  as  if  they  were  a  universal  measure.  In  short,  while 
persons  may  be,  in  theory  at  least,  compared  with  one 
another  with  respect  to  certain  traits,  determination  of 
how  these  traits  themselves  stand  with  reference  to  a  scale  of 
superiority  and  inferiority  of  personality  is  a  radically 
different  matter.  The  latter  involves  judgments  of  values 
in  respect  to  what  sort  of  a  person  is  to  be  socially  desired  and 
prized.  And  such  judgments  are  exposed  to  all  kinds  of 
artificial  influences. 

In  the  second  place,  and  as  the  counterpart  of  the  first 
point,  individuals  are  marked  by  all  kinds  of  characteristics 
which  do  not  form  a  straight  one-way  series.  A  person 
may  be  highly  musical  and  not  highly  developed  in  some 
other  respects;  he  may  have  conspicuous  philosophical 
ability  and  be  deficient  in  practical  capacity.  Children  who 


THE    INFLUENCE    OF    EDUCATION  473 

are  judged  at  school  to  be  laggards  are  found  sometimes  at 
home  to  be  more  helpful  than  their  brothers  and  sisters  more 
adept  in  studies.  Are  not  these  traits  worthy  of  recognition 
in  education?  In  any  case,  what  is  wanted  as  an  educational 
product  is,  barring  very  unusual  cases,  a  balanced  person- 
ahty,  and  balance  is  as  a  rule  much  more  a  product  of 
nurture  than  it  is  of  original  nature. 

Finally,  contact  and  interaction  between  those  more 
gifted  and  those  less  gifted  is  a  normal  condition  of  normal 
education,  for  one  class  as  much  as  for  the  other.  It  takes  all 
kinds  of  people  to  make  the  world,  and  as  long  as  society  at 
large  is  such  an  intermixture  as  it  is,  it  is  dangerous  not  to 
give  all  a  chance  to  develop  to  the  limit  of  their  capacities. 
One  can  appreciate  the  force  of  this  point  by  imagining 
himself  as  an  adult  confined  to  a  circle  of  other  adults  all 
superior,  and  all  selected  because  of  native  superiority. 
Most  persons  would,  I  think,  dread  the  thought  of  such  an 
exclusive  companionship.  To  recognize  all  kinds  of  abilities 
and  to  give  them  all  opportunity  is  desirable,  but  specializa- 
tion on  what  is  regarded  at  a  particular  time  as  superiority 
would  be  likely  to  develop  a  set  of  conceited  prigs,  who  for 
lack  of  suitable  contacts  and  knowledge  of  average  human 
nature  would  be  most  unsuited  for  the  task  of  leadership. 

The  conclusion  at  which  these  remarks  are  directed  is 
that  the  greatest  knowledge  which  can  be  obtained  of  native 
tendencies,  endowments  and  shortcomings  is  of  genuine 
importance  to  the  educator,  but  it  is  something  to  be  used 
within  the  educational  scheme  in  determining  proper  meth- 
ods and  materials  for  each  boy  and  girl,  not  something  which 
can  be  employed  in  a  general  way  to  decide  the  scope  and 
limits  of  education.  The  great  value  of  such  knowledge  is, 
first,  that  it  shows  what  education  has  to  build  with  and  upon; " 
the  recognition  of  native  endowments  is  the  perception  of 
educative  capital.  Without  knowledge  of  them  education 
tends  to  become  an  external  and  hit  and  miss  imposition. 
With  such  knowledge,  the  educator,  parent  or  teacher,  can 
cooperate  with  traits  and  forces  that  already  exist.  Secondly, 
such  knowledge  is  a  precondition  of  individualization  of 
education;  it  is  a  safeguard  against  mechanical  uniformity, 
and  regimentation.  Thirdly,  while  original  gifts  constitute  the 


474  HUMAN   BIOLOGY 

initial  forces  that  make  education  possible,  and  also,  it  may 
be  admitted,  set  a  limit  to  what  is  possible  in  individual 
cases,  yet  our  educational  processes  are  still  so  defective  that 
every  normal  individual  has  more  capacities  than  as  yet 
we  know  how  to  discover  and  develop  by  adequate  educa- 
tional methods.  Moreover  since  only  experimentation  can 
discover  just  where  the  limits  are  located,  it  is  fatal  to  define 
hmitations  rigidly  in  advance.  Too  many  children  have  been 
judged  dull  and  stupid  merely  because  the  right  methods  and 
materials  were  not  presented  and  have  later  been  aroused 
when  rightly  approached,  to  enable  us  safely  to  act  upon  the 
basis  of  antecedent  judgments  of  inferiority. 

INFLUENCE  OF  BIOLOGY  ON  EDUCATION 

Increased  biological  knowledge  has  conferred  on  education 
the  priceless  boon  of  necessity  of  knowledge  of  original 
capital  stock  and  of  individual  differences;  it  has  also  led  to 
a  specific  study  of  definite  original  tendencies,  impulses  and 
"instincts."  The  significance  of  instincts  for  education  is 
still,  however,  a  controverted  question.  The  theory  that 
intelhgence  may  be  regarded  as  an  organization  of  instincts 
cannot  be  maintained  in  the  face  of  facts.  The  helplessness 
of  human  infancy  is  itself  a  sign  that  in  human  beings  the 
definite  organization  of  instinctive  powers  in  lower  animals 
has  broken  down,  and  it  must  also  be  recognized  that  even 
in  them  instincts  are  not  as  fixed  and  rigid  as  they  were 
formerly  supposed  to  be.  Biologically,  intelligence  is  con- 
ditioned by  failure  of  instincts  to  meet  the  needs  of  human 
life;  it  represents  the  method  of  supplementation  of  their 
inadequacy  for  the  work  of  life.  To  educate  simply  or  mainly 
on  the  basis  of  original  instinctive  tendencies  means  at  best 
and  most  only  to  secure  specialized  practical  skills,  not  a 
development  of  intelligence  itself.  In  reality,  therefore,  the 
study  of  instincts  is  not  a  study  of  fixed  educational  founda- 
tions but  is  a  way  of  making  knowledge  of  individual  poten- 
tialities more  definite  and  accurate.  Instincts  do  not  set  the 
ends  of  education,  but  indicate  in  a  more  accurate  manner 
materials  to  be  dealt  with.  The  educative  problem  is  what 
may  and  should  be  done  with  them;  what  may  and  should 
be  made  out  of  them;  and  to  find  an  answer  to  these  ques- 


THE    INFLUENCE    OF    EDUCATION  475 

tions  we  have  to  go  outside  of  instincts  to  judgments  of 
their  relation  to  esthetic,  cognitive  and  moral  values  as  ends. 
Finally,  in  this  connection,  our  modern  knowledge  of 
biological  equipment  defines  one  of  the  fundamental  unsolved 
problems  of  education.  All  our  knowledge  goes  to  show  that 
man  is  not  fitted  by  his  biological  heritage  to  Hve  success- 
fully in  civihzation.  The  more  complex  a  civiHzation,  the 
more  "artificial,"  biologically  speaking,  are  the  conditions 
imposed  upon  its  constituent  members,  and  the  greater  the 
strain  to  which  they  are  subjected.  Statistics  of  disease  and 
of  nervous  and  mental  disorders  reveal  their  increase  under 
modern  conditions  of  Hfe.  It  is  for  this  reason  that  the  prob- 
lem of  deahng  with  the  organism  so  that  it  may  adjust  itself 
to  take  advantage  of  the  resources  of  civihzation  is  said  to  be 
an  unsolved  fundamental  problem.  While  there  is  constantly 
increased  attention  paid  to  the  body  and  its  education,  it 
cannot  be  asserted  even  by  the  most  optimistic  that  its 
results  as  yet  even  offset  the  maladjustments  created  by 
our  school  practices,  to  say  nothing  of  providing  a  positive 
and  constructive  basis  for  a  general  efficient  and  healthful 
meeting  of  the  conditions  of  present  civihzation. 

We  now  return  to  a  consideration  of  the  relation  which 
the  incidental  education  given  to  the  young  in  early  societies 
bears  to  intentional  nurture,  defining  for  our  purposes 
"incidental"  and  "intentional"  by  the  absence  or  presence  of 
schools. 

EDUCATION   AND    CIVILIZATION 

Lack  of  systematic  organization  of  educative  processes 
was  no  doubt  one  cause  of  the  slow  progress  of  early  society. 
As  long  as  the  process  of  transmission  by  nurture  was  acci- 
dentally carried  on,  much  that  was  gained  was  inevitably  lost. 
Yet  knowledge  of  primitive  societies  discloses  that  even  in  them 
there  was  a  certain  amount  of  dehberate  instruction  given. 
There  were  even  solemn  ceremonies  set  apart  for  induction  of 
the  young  into  the  most  cherished  traditions  and  rites  of 
their  group.  The  perpetuation  of  such  culture  as  existed  was 
not  left  at  the  mercy  of  accident.  Although  there  were  no 
schools,  education  was  a  conscious  function,  definitely  and 
rehgiously  taken  care  of. 


476  HUMAN   BIOLOGY 

The  next  stage  of  development  appeared  when  tribal 
life  became  complicated  because  of  marked  divisions  of  labor, 
each  demanding  some  special  mode  of  skill  and  knowledge. 
Without  going  into  detail,  we  may  point  out  that  there  was  a 
division  in  two  directions.  On  the  one  hand,  there  were  the 
medicine  men,  later  differentiated  into  physicans  and  the 
priesthood,  and  on  the  other  hand,  the  secular  useful  arts. 
The  former  possessed  the  "higher  learning;"  they  were  the 
guardians  of  the  mysteries  upon  which  depended  personal 
health  and  the  well-being  and  prosperity  of  the  group. 
All  the  data  show  what  pains  were  taken  to  select  the 
young  men  who  showed  special  aptitude  for  these  callings, 
and  the  careful  discipline  they  underwent.  The  other  phase 
gradually  developed  into  regular  apprenticeship  by  which 
skill  in  making  needed  tools,  utensils,  furnishings  weapons, 
etc.,  was  transmitted.  Even  this  brief  account  would  be 
incomplete,  however,  if  we  did  not  note  that  the  division  of 
labor  between  men  and  women  brought  about  a  marked 
differences  in  the  training  of  boys  and  girls. 

This  bare  outline  is  intended  merely  to  indicate  how  progress 
in  civilization  went  hand  and  hand  with  and  depended 
upon  a  corresponding  advance  in  educational  instrumen- 
talities; because  in  indicating  the  background  out  of  which 
schools  finally  developed  at  least  among  the  peoples  from 
whom  we  derive  our  own  culture,  it  suggests  how  recent  and 
new  are  the  agencies  we  today  associate  with  the  word 
"education."  For  no  estimate  of  the  possible  influence  of 
education  can  be  made  that  does  not  start  from  the  fact 
that  education  as  we  know  it  today  is  an  affair  of  almost  the 
last  century.  The  custom  of  apprenticeship  in  the  mechanical 
and  utilitarian  arts  for  the  mass,  the  reservation  of  higher 
education  to  the  select  few,  the  influence  of  "the  mysteries" 
upon  higher  education,  the  sharp  separation  of  educational 
aims,  methods  and  subject-matter  as  between  men  and 
women,  persisted  almost  to  our  own  day.  The  idea,  of 
educational  agencies  and  opportunities  for  everybody,  having 
a  common  content,  and  the  idea  of  an  educational  ladder  by 
which,  in  theory  at  least,  all  could  come  to  share  in  the  higher 
skills  and  knowledge  is  a  new  thing  in  human  history. 
Recollection  of  this  fact  would  quiet  some  of  our  impatient 


THE    INFLUENCE   OF    EDUCATION  477 

and  harsh  criticisms  of  the  defects  of  our  educational 
system.  What  is  much  more  important,  the  fact  has  tremen- 
dous implications  as  to  the  future  influence  of  education.  It 
justifies  hopes  which  otherwise  might  seem  to  be  extravagant 
dreams. 

From  these  considerations  there  emerges  a  rough  defini- 
tion of  education,  but  one,  it  is  hoped,  adequate  for  our  pur- 
pose. Education  consists  of  all  the  influences  which  operate 
during  the  hfe  of  an  individual  to  form  and  transform  his  atti- 
tudes and  dispositions,  whether  of  thought,  behef  or  conduct. 
This  statement,  made  from  the  side  of  the  individual,  has  a 
counterpart  in  social  and  collective  terms.  So  considered, 
education  consists  of  all  the  agencies  and  instrumentalities  by 
which  society,  through  forming  the  mind  and  behavior  of 
individuals,  transmits  its  own  cultural  attainments  and 
prepares  the  way  for  its  own  improvement.  As  already  noted, 
the  educative  influences  are  of  two  kinds,  the  relatively 
informal,  and  those  that  operate  through  schools  as  a 
formal  medium.  Schools  have  not  existed  at  most  more  than 
a  few  thousand  years  of  the  hundred  of  thousands  of  human 
history;  while,  if  we  contract  the  entire  span  to  the  measure 
of  a  day,  public  and  universal  schooling  occupies  hardly 
more  than  a  moment  of  that  day.  The  latter  feature  is  that 
most  characteristic  of  our  time,  and  to  its  influence,  actual 
and  potential,  the  discussion  will  now  be  directed. 

THE  EDUCATION  OF  THE  FUTURE 

Under  the  first  heading  may  well  be  put  the  increas- 
ing importance  attached  to  those  distinctive  capacities  that 
constitute  individuality,  the  powers  and  interests  that  mark 
off  one  person  from  another.  As  we  have  already  noted,  educa- 
tion until  comparatively  recently  was  a  class  education.  This 
fact  meant  that  in  practice  the  kind  of  education  received  was 
decided  chiefly  by  the  status  in  the  social  and  economic  scale 
of  the  families  from  which  children  came.  Individuality  was 
submerged  in  status.  It  was  a  virtue  for  persons  to  be  content 
with  the  station  In  which  It  had  pleased  God  to  place  them. 
Because  there  was  no  little  opportunity  for  individuals  to  put 
into  action  the  capacities  that  they  possessed,  they  were 


478  HUMAN    BIOLOGY 

naturally  subordinated  in  education  to  meet  the  requirements 
of  the  class  to  which  the  persons  in  question  belonged.  The 
development  of  pubhc  common  schools  marked  the  beginning 
of  a  change.  The  idea  of  universal  education  imphes  that  all 
persons  shall  have  at  least  the  elements  of  an  opportunity  to 
develop  whatever  potentialities  they  individually  have. 

In  some  European  countries,  it  is  true  that  even  with 
universal  schooling  there  are  at  least  two  types  of  schools, 
designed  from  almost  the  first  grade,  for  members  of  two  dif- 
ferent social  classes  who  are  thus  regarded  as  predestined  to 
different  spheres  of  life.  But  in  this  country  because  of  the 
conditions  under  which  the  country  was  settled  this  idea  never 
obtained.  There  were  the  same  elementary  and  secondary 
schools  for  all.  Different  types  of  courses  were  developed  in  the 
high  school,  but  a  youth  found  his  place  in  one  or  another 
according  to  his  own  abilities  and  preferences  rather  than 
because  of  any  external  class  standard.  Economic  status  still 
largely  decides  how  far  in  the  educational  scale  individuals 
will  proceed.  But  by  the  development  of  municipal  colleges, 
training  schools  for  teachers  and  especially  state  universities, 
an  educational  ladder  was  erected;  the  parts  of  it  were  so 
articulated  that  it  was  made  easier  for  individuals  of  capacity 
to  rise  through  its  entire  length.  This  tendency  was  reinforced 
by  generous  provision  of  scholarships;  in  many  of  our 
larger  cities  there  are  now  organizations,  some  municipal,  the 
greater  number  private,  that  make  it  possible  for  children  of 
unusual  ability,  coming  from  homes  that  are  not  well  off,  to 
continue  in  school;  these  associations  select  promising  children 
in  the  elementary  schools  and  take  them  on  into  secondary 
education,  when  otherwise  they  would  be  obliged  to  go  to 
work.  By  means  of  legislation  raising  the  years  of  necessary 
school  attendance  and  forbidding  child-labor  under  these 
years,  the  ideal  of  equal  educational  opportunities  for  all 
approaches  more  nearly  a  reality.  The  fruits  of  this  policy 
are  beginning  to  be  seen  in  the  extraordinary  fivefold 
multiplication  of  the  number  of  pupils  in  high  schools, 
colleges  and  professional  schools  within  the  last  thirty  years. 
It  is  impossible  to  judge  the  extent  of  release  and  development 
of  individual  abilities  that  would  otherwise  be  lost  to  the 
world,  due  to  this  policy.  < 


THE    INFLUENCE    OF    EDUCATION  479 

The  point  just  made  refers  particularly  to  the  external 
and  administrative  side  of  education  and  its  influence.  It  is 
quite  true  that  provision  on  this  side  is  far  from  covering  the 
whole  ground  of  the  discovery,  selection  and  release  of  individ- 
ual capacities.  Within  the  schools,  in  spite  of  the  opportunity 
they  furnish,  it  is  still  possible  for  lock-step,  mass  instruction 
to  persist.  But  there  has  nevertheless  been  a  constant 
multiphcation  both  of  types  of  schools  and  a  multiphcation 
of  courses,  which  render  possible  a  closer  approximation 
of  education  to  individual  needs  and  powers.  What  is  more 
important  is  the  fact  that  in  the  more  progressive  schools, 
there  is  much  greater  attention  than  there  was  even  a 
generation  ago  to  individuals  as  such,  even  when  they  are  all 
together  in  the  same  school  class.  A  definite  effort  is  made  to 
provide  not  merely  a  varied  program  of  studies  so  that  each 
pupil  shall  have  scope  for  any  special  abilities  he  may 
possess,  but  to  diversify  material  and  methods  even  in  the 
same  study,  so  as  to  supply  occasion  for  individual  attack 
and  response.  While  relatively  this  tendency  is  still  backward, 
there  is  much  evidence  that  its  fermentation  will  gradually 
leaven  the  whole  lump  of  mass  education.  In  administration, 
the  former  quasi-military  regimentation  is  quite  generally 
giving  way  to  a  more  liberal  policy  in  such  matters  as 
discipline  and  promotions. 

The  second  point  under  this  heading  is  closely  connected 
with  that  just  made.  In  the  better  schools,  personal  initi- 
ative is  prized  and  encouraged  as  it  never  used  to  be.  Of  course 
the  main  tradition  of  the  school  has  been  that  of  passivity. 
Minds  were  treated  as  blank  pieces  of  paper  on  which  informa- 
tion was  to  be  stamped.  Or  they  were  empty  reservoirs 
into  which  knowledge  was  to  be  poured  by  means  of  conduit 
pipes  from  text  books  and  the  teachers'  words.  Recitations 
and  examinations  were  calculated  merely  to  test  and  record 
the  amount  that  had  been  poured  in  and  not  leaked  out. 
Or,  to  vary  the  metaphor,  the  mind  was  like  a  gramophone 
plate  where  memory  retained  what  was  impressed,  and  the 
recitation  and  examination  periods  were  times  when  the  plate 
was  set  in  motion  to  give  out  what  it  had  taken  in.  Not  even 
the  most  optimistic  would  hold  that  this  tradition  has  died 
out  in  our  schools;  its  baleful  consequences  in  suppression 


480  HUMAN   BIOLOGY 

of  intellectual  and  moral  individuality  remain.  But  it  is 
generally  weakening.  Educational  reformers  from  an  early 
date  have  denounced  the  procedure.  While  perhaps  their 
influence  has  not  been  great,  the  inherent  development  of 
universal  education  has  worked  against  it.  The  more  pupils 
ther-e  are  in  schools,  the  greater  the  heterogeneity  among 
them,  and  the  greater  the  difficulty  in  impressing  the  same 
stamp  upon  tKem  all  and  in  securing  a  uniform  response. 
The  disregard  of  personal  individualized  mental  activity 
resulted  in  creating  aversion  to  study.  Mobile,  active 
children  rebelled  against  constant  external  imposition  and 
mechanical  repetition.  Actual  results  were  not  correspondent 
with  the  eff"orts  put  forth.  The  conflict  between  the  active 
nature  of  most  children  and  the  enforced  passivity  of  study 
was  so  unfavorable  to  genuine  learning  that  the  idea  arose, 
and  still  persists,  that  the  mind  is  actually  averse  to  learning. 
Intelligent  teachers,  perceiving  the  unsatisfactory  result 
and  perhaps  themselves  bored  and  nervously  strained  by  the 
artificial  monotony  and  uniformity  sought  out  almost 
unconsciously  methods  that  would  invoke  more  active 
reactions  from  pupils.  The  idea  of  utilizing  the  interest 
of  pupils  in  education  may  be  degraded  to  the  level  of  mere 
amusement,  but  in  its  reality  it  marks  the  sound  principle 
of  enlisting  the  active  cooperation  of.  pupils  in  what  they  are 
doing  in  school.  Under  such  conditions  of  personal  mental 
activity,  it  is  found  that  most  children  like  to  go  to  school 
and  enjoy  learning. 

As  far  as  elementary  schools  are  concerned  the  chief 
stimulus  to  a  more  active  curriculum  undoubtedly  proceeded 
upward  from  the  kindergarten.  In  higher  education,  it  was 
promoted  by  the  development  of  scientific  laboratories  in 
which  methods  of  inquiry  and  discovery  took  the  place  of 
memorizing  authoritative  statements  imposed  from  without. 
The  method  gradually  spread  to  such  subjects  as  literature 
and  history  where  increasing  emphasis  was  put  upon  col- 
lateral readings  and  library  research.  As  kindergarten 
methods  worked  upwards,  university  methods  worked 
downwards  until  they  tended  to  meet.  Aside  from  the 
general  influence  of  scientific  method  in  furthering  a  change 
from  passive  to  active  learning,  the  specific  efl'ect  of  a  more 


THE    INFLUENCE    OF    EDUCATION  48 1 

scientific  study  of  psychology  should  be  noted.  The  older 
psychology  that  was  in  the  intellectual  air  and  that  was 
definitely  taught  in  training  schools  for  teachers,  was  a 
psychology  of  the  reception  of  sensations  and  impressions 
from  without,  and  of  faculties  inhering  in  the  mind  by  which 
the  material  thus  received  was  worked  over.  The  entire 
development  of  psychology  has  been  to  reverse  both  these 
conceptions.  On  the  one  hand,  the  motor  side  of  hfe  has  been 
brought  to  attention  and  the  connection  of  sensory  impres- 
sions with  active  motor  adaptations.  On  the  other  side  the 
whole  hierarchy  of  ready-made  faculties  has  been  relegated 
to  the  scientific  scrap-basket.  With  it  has  gone  the  vogue  of 
the  notion  of  "formal  discipline"  which  was  the  theoretical 
foundation  of  the  old  idea  of  mental  training  by  means  of 
mechanical  exercises  constantly  repeated.  If  attention  and 
memories  were  "faculties,"  it  was  logical  to  hold  that  they 
would  be  developed  and  strengthened  by  a  series  of  gymnas- 
tic exercises.  What  was  attended  to  or  memorized  made 
httle  difference.  If  the  mind  was  only  kept  at  it,  the  inherent 
faculties  of  attention  and  memory  would  be  built  up. 
Moreover  as  mental  faculties,  they  had  an  existence  and 
mode  of  operation  quite  independent  of  any  bodily  activity, 
which  indeed  was  thought  of  as  hostile  to  their  manifesta- 
tion. The  quieter  the  child  was  kept,  the  more  prospect  was 
there  that  his  mental  faculties  would  come  into  play  as  he 
was  kept  pouring  over  his  text-books.  It  is  hardly  too  much 
to  say  that  every  teacher  in  every  training  school  is  now 
taught  a  radically  different  psychology.  He  learns  that 
the  young  child  is  primarily  a  sensory-motor  being,  and  that 
his  intellectual  development,  corresponding  to  the  function 
of  his  cerebral  structures,  is  brought  about  as  coordinations 
and  cross-connections  are  built  up  among  sensory-motor 
activities.  Psychology  has  been  so  revolutionized,  in  a 
biological  direction,  that  the  significance  of  the  body  and 
of  organic  activity  is  coming  into  its  own.  For  the  idea  of 
faculties  capable  of  separate  training,  obtained  by  means  of 
set  and  uniformly  repeated  exercise,  has  been  substituted 
the  idea  of  the  total  engagement  and  response  of  the  whole 
being  in  effective  learning.  Teachers  indeed  meet  with^many 
obstructions  and  embarrassments  when  they  try  to  put  their 


482  HUMAN    BIOLOGY 

theoretical  psychology  into  effect  in  the  classroom.  But  it  is  a 
great  advance  to  have  destroyed  the  theory  that  underlay 
and  justified  the  old  procedures.  Gradually  there  will  come 
about  such  a  transformation  of  actual  schoolroom  conditions 
and  equipment  as  will  make  it  possible  to  carry  the  new 
scientific  conceptions  into  practice.  In  the  best  schools,  much 
progress  in  this  direction  has  already  been  made. 

OBSTACLES  TO  BE  OVERCOME 

A  difficulty  which  amounts  to  an  obstruction  is  the 
persistence  of  older  scholastic  traditions  after  the  actual 
situation  as  respects  knowledge  has  radically  changed.  It 
was  inevitable  at  a  certain  time  that  chief  emphasis  should 
be  given  to  the  acquisition  of  the  tools  of  learning.  This 
tradition  took  possession  of  elementary  schools  during  their 
formative  period  in  our  own  country.  For  under  pioneer 
conditions  mastery  of  the  three  R's  (reading,  'riting,  'rithme- 
tic)  was  the  key  to  all  educational  opportunity.  Homes  and 
neighborhoods  were  scantily  supplied  with  reading  material; 
letter  writing  was  a  special  event,  and  so  on.  Moreover  the 
school  and  neighborhood  provided,  in  demands  made  upon 
the  young,  full  opportunities  for  immediate  contact  with 
raw  materials  of  nature  and  with  such  industrial  techniques 
as  existed.  Now  the  situation  is  largely  reversed,  at  least 
in  urban  and  semi-urban  communities  which  have  constantly 
grown  at  the  expense  of  rural  districts.  Yet  upon  the  whole  the 
tradition  persists  which  makes  the  acquisition  of  the  three  R's, 
together  with  a  somewhat  miscellaneous  body  of  information 
in  history  and  geography  and  perhaps  nature  study,  the  main 
•  business  of  the  eight  years  of  the  grades,  that  is,  of  the  entire 
schooling  which  the  mass  of  children  receives.  The  case  is 
made  worse  by  the  multiplication  of  bodies  of  learning. 
Modern  languages  now  make  their  claim;  to  the  new  develop- 
ment of  the  physical  sciences  are  added  new  and  important 
social  studies.  The  result  is  congestion  of  the  curriculum, 
and  a  consequent  superficial  touching,  in  the  higher  elemen- 
tary grades,  the  high  school  especially'  and  even  the  college, 
upon  a  multitude  of  subjects  with  mastery  of  none.  There 
is  not  even  enough  of  any  one  of  them  to  leave  behind  a 


THE    INFLUENCE    OF    EDUCATION  483 

taste  and  thirst  which  will  secure  continuing  development  in 
some  intellectual  line  after  school  days  are  ended. 

Ideas  formed  in  the  days  when  it  was  reasonably  possible 
for  a  man  who  had  been  studiously  through  the  schools 
to  master  the  sum  total  of  learning  too  largely  control  the 
schools  today.  Complaints  of  lack  of  thoroughness  and  of 
intellectual  disciphne  go  back  to  this  cause.  Nothing  which 
may  be  of  importance  at  some  time  in  hfe  but  finds  its  way 
into  "courses"  and  textbooks.  Meantime  books  and  printed 
material  have  increased  enormously,  and  it  is  possible  for 
the  adult  to  find  information  when  he  needs  it  with  a  mini- 
mum of  trouble.  Also  opportunities  for  amusement  and, for 
culture  have  muItipHed  outside  of  school.  The  result  is  not 
merely  congestion,  overstrain  and  superficiaHty,  but  distrac- 
tion. The  burden  is  increased  because  well-meaning  organ- 
izations who  have  some  cause  to  serve  seize  upon  the  schools 
as  the  easiest  way  to  reach  the  pubhc  and  promote  opinion 
favorable  to  their  causes. 

In  consequence,  the  most  serious  of  problems  today  as  far 
as  the  course  of  study  is  concerned  is  that  of  reduction  and 
simpHfication.  Unfortunately  attempts  made  in  this  direction 
are  often  atavistic.  What  is  urged  by  way  of  simpHfication  is 
merely  return  to  some  curriculum  of  the  past,  simpler  in  the 
sense  that  it  consists  of  a  smaller  number  of  studies,  but 
irrelevant  to  present  conditions  and  conceived  still  in  the 
encyclopedic  spirit  as  far  as  it  goes.  What  is  actually  indi- 
cated is  surrender  of  the  ideal  of  "covering  the  ground," 
and  a  substitution  for  full  treatment  of  all  subjects  of  hmited 
groups  of  material  that  are  typical,  with  a  view  to  developing 
independent  method  of  thought  and  inquiry  on  the  part  of 
students,  instead  of  the  now  hopeless  task  of  inculcating  a 
vast  mass  of  information,  which  in  any  case  is  readily 
accessible  in  an  up-to-date  form  in  books  and  periodicals 
when  needed.  In  short,  nothing  but  a  revolution  in  aim  would 
appear  to  meet  the  requirements  of  the  situation.  Such  a 
revolution  would  make  supreme  the  development  of  definite 
intellectual  interests  sufiiciently  varied  to  protect  students 
from  premature  one-sidedness  and  sufficiently  powerful  to 
communicate  to  the  minds  of  learners  an  impetus  to  go 
further.  For  one  of  the  tragedies  of  present-day  instruction. 


484  HUMAN   BIOLOGY 

even  in  colleges,  is  the  extent  to  which  subjects  studied  are 
dropped  about  as  soon  as  the  courses  devoted  to  them 
are  scholastically  terminated.  Along  with  the  formation  of 
such  active  and  enduring  tastes  would  go  experience  to 
inform  students  as  to  proper  sources  of  information  and 
abihty  to  utihze  them.  As  long  as  the  idea  of  subject-matter 
for  its  own  sake  persists,  instead  of  subject-mastered  for 
the  sake  of  developing  inherent  intellectual  interest  and 
method,  no  thoroughgoing  reformation  of  instruction  seems 
to  be  probable. 

At  present  the  conservatism  of  schools  contrasts  strangely 
with  the  readiness  to  scrap  old  machinery  in  industry, 
old  behefs  in  science,  and  old  practices  in  the  professions, 
when  new  conditions  render  better  ones  available.  It  cannot  be 
truly  stated  that  schools  have  not  made  an  effort  to  re-adapt 
themselves  to  new  social  conditions.  For  the  converse  is  true. 
But  the  adaptation  has  been  made  largely  by  procedures  that 
defeat  the  purpose.  For  it  has  been  attempted  mainly  by 
addition,  with  the  result  already  mentioned.  What  is  needed 
is  a  change  of  attitude  and  aim  that  takes  advantage  of  the 
non-scholastic  resources  that  have  developed,  and  that  recog- 
nizes that  method  which  enables  the  mind  to  deal  with  prob- 
lems as  they  manifest  themselves  is  now  more  important  in 
life  than  accumulation  and  cold  storage  of  subject-matter.  It 
would  be  absurd  of  course  to  suppose  that  method  can  be 
acquired  except  in  actual  deahng  with  subject-matter.  But  if 
the  thought  and  energy  that  now  go  into  a  vain  effort  to  record 
subject-matter  and  keep  up  with  its  growth  were  spent  in 
selecting  Hmited  fields  that  are  typical  of  present  methods  of 
intellectual  inquiry  and  mastery  the  outcome  would  be  very 
different.  As  long  as  the  issue  is  regarded  as  lying  ahiiost 
exclusively  between  the  hmited  and  thorough  curriculum  of 
the  past  in  classics  and  mathematics  and  spreading  over  the 
whole  content  of  present-day  knowledge  and  interest,  the 
present  situation  of  confusion  will  continue. 

The  large  degree  of  failure  to  obtain,  by  our  present 
system,  fundamental  intellectual  achievement  is  seen  in  two 
marked  traits  of  the  popular  mind:  undue  deference  to  any 
one  who  obtains  popular  prestige  as  an  "authority"  in  any 
field,  and  an  accompanying  credulity  of  mind  that  undis- 


THE    INFLUENCE   OF    EDUCATION  485 

criminatingly  accepts  for  a  time  anything  offered,  only 
to  turn  soon  to  some  newer  topic.  For  the  older  tradition  of 
universal  scholarship  has  affected  even  the  teaching  of 
science,  short  of  the  small  number  who  become  capable  of 
independent  speciahzation.  The  essentials  of  scientific 
method,  of  a  certain  way  of  looking  at  things  and  seeking 
and  weighing  evidence,  in  short  the  development  of  judgment, 
are  swamped  in  the  acquisition  of  information,  all  the  items 
of  which  stand  on  the  same  level  and  are  equally  subject  to 
belief  or  unbelief.  The  mind  is  left  more  ready  to  seek  for 
signs  and  wonders,  and  more  ready  to  grasp  at  and  swallow 
whatever  is  presented  in  print.  The  mere  mass  of  what 
is  offered  daily,  monthly  and  yearly,  overpowers  inde- 
pendent judgment  and  creates  a  state  of  intellectual  impo- 
tence; the  mind  is  oppressed  rather  then  enlightened.  Perhaps 
the  most  encouraging  signs  of  improvement  are  now  found 
in  various  branches  of  professional  education.  These  have  to 
deal  with  the  problem  presented  by  the  enormous  growth 
material  in  both  bulk  and  complexity,  and  are  correspond- 
ingly forced  by  the  necessities  of  the  situation  to  simplify, 
and  to  simplify  not  by  arbitrary  limitation  to  traditional 
portions  of  the  field,  but  by  emphasis  upon  subject-matter 
that  is  strategic  in  developing  command  of  method. 

There  are  many  who  are  pessimistic  regarding  the  ability 
of  intelligence  to  take  any  considerable  part  in  social  direction. 
After  a  period  in  which  psychology  was  conceived  almost 
exclusively  in  intellectualistic  terms,  a  marked  reaction  has 
set  in.  This  is  due  in  part  to  the  influence  of  biology  on 
psychology.  For  the  former  has  revealed  the  large  role  of 
non-rational  factors  in  the  human  make-up.  Instinct, 
impulse,  emotion,  desire,  habit  occupy  the  position  once 
held  by  intellect.  Anthropological  knowledge  has  disclosed 
the  role  of  non-rational  factors  in  the  whole  course  of  human 
life  on  earth.  Study  of  mental  disorders,  great  and  small, 
has  shown  the  extent  to  which  what  presents  itself  as  reason 
is  in  fact  an  ex  post  facto  rationalization  dictated  by  desire 
and  having  only  the  semblance,  the  form,  of  rationality 
without  its  substance.  This  reaction  has  occurred  during 
a  period  in  which  the  need  of  direction  by  informed  intelli- 
gence of  social  affairs  has  enormously  increased.  It  is  only 


486  HUMAN   BIOLOGY 

necessary  to  point  to  the  rise  of  democracy  that  has  brought 
the  masses  into  possession  of  political  power;  the  disturbance 
of  old  habits  and  institutions  produced  by  new  technological 
developments  in  industry  and  commerce;  the  elimination 
of  distance  and  the  barriers  that  formely  kept  peoples 
apart  which  has  produced  an  interminghng  and  contact  of 
peoples  and  races  not  prepared  to  understand  one  another, 
and  so  on.  The  effect  has  been  both  an  immense  expansion  of 
educational  facihties,  and,  as  greater  responsibihties  were 
thrown  upon  the  schools,  a  growing  scepticism  regarding 
what  it  is  possible  for  education  to  accomplish. 

In  this  connection  the  remarks  made  earher  about  the 
newness  of  universal  education  find  their  pertinency.  We  are 
at  only  the  beginning,  not  the  maturity,  much  less  the  chmax, 
of  the  experiment  of  affecting  social  fife  and  giving  it  guidance 
through  intentional  education.  And,  as  been  summarily 
indicated,  the  experiment  is  still  in  large  measure  affected  by 
customs  and  traditions  that  hang  over  from  an  earlier 
period.  In  consequence  the  problem  of  educational  recon- 
struction by  which  these  hang-overs  will  be  ehminated 
and  materials  and  methods  introduced  which  will  develop 
the  type  of  mind  and  character  adapted  to  contemporary 
movements  is  far  more  than  a  scholastic  problem.  It  is  the 
fundamental  problem  of  society  itself. 

It  is  no  part  of  this  chapter  to  try  to  tell  in  detail  the 
nature  of  the  reconstruction  that  is  demanded.  Three  condi- 
tions of  its  achievement  may,  however,  be  properly  indicated. 
The  new  knowledge  of  psychology  indicates  the  need  of  much 
more  attention  to  emotional  factors  than  they  have  received. 
Upon  the  whole,  education  has  so  far  been  concerned  with 
forming  practical  skills  and  giving  information,  with  inci- 
dental training  of  intellectual  habits.  The  emotional 
factors  that  determine  the  set  and  channels  of  operation  of 
practical  abilities  and  of  knowledge  have  been  largely 
neglected.  Such  questions  as  more  and  better  esthetic 
education,  instruction  in  sexual  matters,  the  place  of  religion, 
the  formation  of  minds  emancipated  from  racial  and  inter- 
national prejudice,  moral  teaching  that  is  vital  and  not 
merely  formal,  all  find  their  proper  place  in  this  connection. 


THE    INFLUENCE    OF    EDUCATION  487 

Secondly,  the  basic  role  of  financial  considerations  in 
every  serious  attempt  at  successful  execution  of  the  great 
experiments  must  be  recognized.  All  competent  observers  have 
testified  that,  aside  from  sheer  inertia,  the  chief  obstacle 
in  the  way  of  introducing  into  the  school  methods  and 
materials  that  are  known  to  be  desirable  is  the  matter  of 
financial  support.  Instruction  through  the  medium  of  books, 
reinforced  by  blackboards  and  a  few  maps,  is  the  cheapest 
possible  system.  Introduction  of  shops,  laboratories,  etc., 
doubles  the  expense.  And  this  is  not  the  end.  In  order  that 
they  may  be  utilized  successfully,  the  numbers  in  classes 
must  be  reduced.  This  fact  requires  more  and  better  trained 
teachers.  In  order  to  attract  and  hold  the  type  of  person  as 
teacher  who  can  initiate  and  direct  genuinely  educative 
methods,  pecuniary  reward  and  compensation  by  way  of  social 
recognition  and  prestige  must  be  increased;  and  meeting  the 
second  condition  depends  largely  upon  fuIfiHing  the  first.  In 
spite  of  the  great  growth  of  pubhc  expenditures  for  schools 
(it  is  estimated  that  the  annual  cost  of  schools  in  the  United 
States  is  now  two  bilHon  dollars),  much  remains  to  be  done 
to  awaken  the  attention  of  the  pubHc  to  the  necessity  of 
greatly  increased  financial  support. 

The  third  condition  is  closely  alhed.  What  is  called  "aca- 
demic freedom"  is  much  more  than  academic  matter.  In 
fact,  it  is  in  the  higher  institutions  about  which  the  question 
is  usually  raised  that  there  exists  at  present  the  most  freedom 
of  thought  and  discussion.  Influences  which  tend  to 
suppression,  are  most  powerful  in  lower  schools  where  the 
larger  number  receive  their  training.  Objective  discussions  of 
social  conditions,  especially  in  their  economic  imphcations,  is 
rare  and  difficult.  The  result  of  this  virtual  tabu  on  free  and 
independent  thinking  on  the  part  of  both  teacher  and  student 
is  twofold.  On  one  hand,  an  added  premium  is  put  on  the 
formal  and  mechanical  elements  in  training.  Drill,  practice  to 
achieve  skills,  and  inculcation  and  absorption  of  information, 
are  what  remain  when  inquiry  and  reflection  are  excluded. 
Or,  if  there  is  thinking  it  is  confined  to  specialized  technical 
fields.  On  the  other  hand,  students  are  sent  out  into  hfe 
without  that   kind   of  intelligent   understanding   of  needs, 


488  HUMAN   BIOLOGY 

conditions  and  possibilities  that  is  indispensable  to  social 
direction;  confusion  automatically  piles  up. 

The  foregoing  bare  outHne  emphasizes  the  point  originally 
made.  The  standing  problem  of  education  is  interaction 
of  biological  native  factors  with  the  factors  that  constitute 
culture  in  its  broad  sense:  that  is,  the  achievements  and 
aspirations  that  actually  obtain  in  the  society  within  and 
for  which  individuals  are  educated.  The  essential  point  is 
that  instead  of  conceiving  nature  and  nurture  as  competitive 
rivals,  we  should  treat  nurture  as  the  means  by  which  nature 
and  culture  are  brought  into  the  fullest  harmonious  relation- 
ship with  each  other.  This  problem,  which  is  the  problem 
of  securing  the  free  satisfaction  of  individuals  together 
with  social  order  and  progress,  is  equally  that  of  both 
social  hfe  and  education. 

REFERENCES 

Galton,  Sir  F.  1883.  Inquiries  into  Human  Faculty  and  its  Development. 

N.  Y.,  Macmillan. 
FiSKE,  J.  1899.  Essay  on  The  Part  Played  by  Infancy  in  Human  Evolution. 

In:  A  Century  of  Science,  and  Other  Essays.  Bost.,  Houghton,  Mifflin. 
Thorndike,  E.  L.  1913.  Educational  Psychology.  N.  Y.,  Teachers  College. 

3  vols.,  see  especially  the  first:  The  Original  Nature  of  Man. 
Dewey,  J.  19 16.  School  and  Society.  Univ.  Chicago  Press. 

1916.  Democracy  and  Education,  N.  Y.,  Macmillan. 
KiLPATRiCK,  W.   H.    1927.   Education  for  a  Changing  Civilization.  N.  Y., 

Macmillan. 
Hart,  J.  K.  1918.  Democracy  in  Education.  N.  Y.,  Century. 
Bode,  B.  H.  1927.  Modern  Educational  Theories.  N.  Y.,  Macmillan. 

1920.  Fundamentals  in  Education.  Macmillan. 
Miller,  H.  L.,  and  Hargreaves,  R.  T.  1922.  The  Self-Directed  School.  N.  Y., 

Scribner's. 


PART  V.  THE  FUTURE 


Chapter  XXI 
THE  INHERITANCE  OF  DISEASE 
Paul  A.  Lewis* 

CONSIDERED  in  a  broad  and  untechnical  sense,  an  in- 
dividual's inheritance  means  all  those  attributes  both 
actual  and  potential  received  at  or  before  birth  from 
the  parents.  This  usage  has  of  late  years  been  given  up 
by  scientific  men  in  favor  of  a  more  circumscribed  one,  name- 
ly, that  the  inheritance  consists  of  those  attributes  actual  and 
potential  acquired  at  the  moment  of  conception  due  to  the 
intrinsic  properties  of  the  germ  cells. 

This  distinction  is  of  real  importance  to  a  clear  under- 
standing of  the  relations  between  inheritance  and  disease. 
The  bibhcal  dictum  that  the  sins  of  the  fathers  are  visited 
on  their  offspring  for  generations  has  been  considered  in 
recent  times  to  be  particularly  apphcable  to  one  contagious 
disease,  syphilis.  Children  suffering  severely  from  this  disease 
are  frequently  brought  into  the  world  at  or  before  the  normal 
birth  period.  It  is  now  considered  a  certainty  that  in  these 
cases  the  child  is  infected  at  some  point  in  its  fetal  life 
definitely  subsequent  to  its  conception.  In  any  event, 
it  is  infected  with  an  extraneous  microorganism  carried  by 
one  or  both  parents.  Many  other  similar  and  less  obnoxious 
instances  of  "intra-uterine  infection"  might  be  cited  from 
our  knowledge  of  human  and  animal  diseases.  On  the  other 
hand,  it  is  known,  by  animal  experiment  at  least,  that  the 
offspring  of  an  immune  mother  are  apt  to  show  more  than 
the  usual  resistance  to  certain  diseases  for  some  time  after 
birth.  This,  it  is  recognized,  is  due  to  the  transfer  of  pro- 
tective substances  in  a  passive  way  from  the  mother  either 
through  the  membranes  separating  the  fetal  from  the  maternal 
circulation  in  utero  or  in  the  milk  during  the  first  days  of  life. 
Under  the  older  definition,  these  instances  would  be  con- 
sidered to  be  cases  of  inherited  disease  or  inherited  immunity 

*  Died  of  yellow  fever  at  Bahia,  Brazil,  on  June  30,  1929,  while  investigating 
the  cause  of  the  disease. 

491 


492  HUMAN   BIOLOGY 

respectively,  but  are  not  so  regarded  under  the  more  rigid 
definition  of  inheritance. 

Even  the  circumscribed  definition  of  inheritance  as  here 
given  may  not  be  wholly  accurate.  There  is  much  reason  to 
beheve  that  injury  to  the  parents  by  long-continued  exposure 
to  certain  poisons  such  as  alcohol  or  lead  may  affect  the 
offspring  unfavorably  and  it  is  also  probable  on  the  basis  of 
animal  experiments  that  exposure  of  the  parents  to  roentgen 
rays  may,  under  certain  conditions,  result  in  altered  if  not 
abnormal  descendants.  In  so  far  as  these  influences  may  be 
manifest  through  action  on  the  male  parent  it  can  only 
be  by  some  affection  of  the  germ  cell  itself  and  it  would 
probably  be  impossible  to  frame  an  entirely  adequate  defi- 
nition of  inheritance  in  which  these  preconceptual  influences 
are  justly  accounted  for.  These  may  for  purposes  of  definition 
be  recognized  and  passed  over. 

The  outstanding  achievement  of  genetic  study  has  been  to 
show  that  as  a  broad  biological  principal  the  most  diverse 
general  characters  can  be  analyzed  into  an  infinity,  almost, 
of  combinations  of  less  inclusive  specific  unit  characters 
which  are  inherited  independently  in  principal.  Actually 
they  are  inherited  either  separately  or  in  small  and  apparently 
"chance  constituted"  linkage  groups.  There  is  every  reason 
to  suppose  that  the  mechanism  of  human  inheritance  com- 
pletely conforms  to  this  "Mendelian"  scheme.  That  it 
does  so  has  been  demonstrated  for  a  considerable  number 
of  characteristics. 

"Disease"  is  a  general  concept  sufficiently  defined  for  many 
purposes  as  any  condition  of  body  or  mind  which  departs 
from  "perfect  health."  A  precise  definition  which  shall  be 
more  critical  than  this  and  cover  all  the  manifestations  of 
morbid  processes  is  extremely  difficult  to  formulate.  It 
would  greatly  simplify  this,  and  many  other  discussions  of  a 
similar  nature,  if  an  all-inclusive  definition  could  be  framed, 
but  the  attempt  would  be  hopeless  and  misleading  in  the 
nature  of  the  facts.  It  is  well  to  recognize  this  clearly  at 
this  point  because  there  is  a  very  general  assumption  or 
belief  that  people  are  quite  definitely  divided  into  two 
classes,  those  who  are  born  healthy  and  of  sound  constitu- 
tion,  and  those  who  come  into  the  world  otherwise.  All 


THE    INHERITANCE   OF    DISEASE  493 

such  conceptions,  it  should  be  clearly  seen,  are  in  fact  untrue. 
A  healthy  person  is  one  who  has  no  gross  anatomical  or 
physiological  defects  and  enough  normal  general  health  to 
get  on  with.  Any  refinements  of  definition  must  be  entirely 
with  reference  to  some  ideal  standard  which  will  doubtless 
change  with  time  and  future  evolution  or  achievements. 

In  fact  the  great  progress  made  by  medicine  as  an  art 
and  a  science  from  the  dawn  of  civihzation  down  to  today  is 
based  on  the  steadily  developed  recognition  of  the  infinite 
complexity  and  relative  nature  of  the  phenomena  included 
in  the  general  term  "disease."  And  especially  the  remarkable 
progress  of  the  last  two  centuries  is  due  to  the  extension  of 
this  general  principle  into  the  study  of  particular  diseases. 
Even  the  most  simple  (apparently)  of  abnormal  conditions 
is  found  on  closer  scrutiny  to  be  of  the  utmost  complexity. 
A  common  boil  is  spoken  of  in  scientific  terms  as  a  simple 
inflammation  and  even  moderately  informed  lay  people 
know  it  as  the  result  of  some  "germ"  getting  into  an  insignifi- 
cant scratch.  In  reahty  the  processes  are  complex  far  beyond 
our  present  understanding.  Essentially  the  same  process  in 
the  lungs  gives  rise  to  the  acute  and  often  fatal  disease, 
pneumonia.  But  when  pneumonia  is  examined,  even  in  the  hght 
of  our  present  imperfect  knowledge,  attention  being  paid  to 
the  particular  germ  giving  rise  to  the  infection,  and  the 
quahties  and  distribution  of  the  reaction  material  in  the 
lungs,  it  is  easy  to  discriminate  more  than  ten  essentially 
independent  kinds  of  extensive  and  severe  inflammations  of 
the  lungs,  which  would  be  properly  designated  by  the  prac- 
ticing physician  as  pneumonia. 

It  will  readily  be  understood,  therefore,  that  when  as 
in  this  chapter  an  attempt  is  made  to  deal  with  the  points  of 
contact  and  mutual  influence  of  two  such  all-inclusive 
and  infinitely  complex  assemblies  of  phenomena  as  those 
of  inheritance  and  of  disease,  it  cannot  profitably  be  done 
solely  with  reference  to  general  principles.  Nor  would  it  be 
useful  in  this  place  to  attempt  a  very  detailed  account  of 
what  is  known.  The  plan  adopted  is  to  try  to  give  an  out- 
hne  of  principles  where  these  are  discernible  and  to  illustrate 
them  with  such  concrete  examples  as  may  be  most  informing 
to  the  general  reader. 


494  HUMAN   BIOLOGY 


INFECTIOUS   DISEASES 


As  previously  pointed  out  there  is  in  the  rigid  sense  no 
such  thing  as  the  positive  inheritance  of  an  infectious 
disease.  This  hes  in  the  nature  of  the  case  since  the  impelling 
incident  in  such  a  disease  is  the  entry  of  an  agency:  germ, 
bacterium  or  protozoan,  from  the  environment.  None  the  less, 
the  inheritance  is  of  very  vital  significance  and  within 
certain  hmits  absolutely  controls  the  prevalence  of  these 
diseases.  This  is  true  when  we  approach  the  question  from 
a  wide  biological  viewpoint,  regarding  species  Hues.  It  then 
becomes  in  truth  a  matter  of  common  knowledge.  It  is 
probably  quite  correct  to  state  that  each  distinct  species 
of  animal  or  plant  has  certain  diseases  which  are  peculiar 
to  it,  and  neither  naturally  nor  artificially  transmissible 
to  any  other  species.  Influenza  and  malaria  are  fair  examples 
of  such  diseases  of  human  beings.  Asiatic  cholera  is  another. 
Many  cases  may  be  cited  in  which  species  lines  are  not 
rigidly  respected  and  are  yet  very  influential.  Smallpox  is 
such  a  human  disease.  It  may  spread  .to  milch  cattle  under 
suitable  conditions,  but  in  them  produces  a  modified  type 
of  disease  similar  to  the  naturally  occurring  cowpox.  Rabies 
is  widely  disseminated  among  the  domestic  animals,  is  very 
frequently  transmitted  to  man  but  is  not  known  as  a  disease 
of  birds. 

The  questions  at  issue  really  become  debatable  when  we 
consider  the  relation  of  the  racial,  familial  or  individual 
inheritances  within  the  species.  It  is  now  clear  that  here 
the  lines  are  much  less  rigid.  There  are  very  certain  instances, 
particularly  among  plants,  where  families  or  strains  within 
the  race  are  quite  immune  to  a  particular  disease  from  which 
the  race  as  a  whole  suffers  most  severely.  The  rust-resistant 
varieties  of  wheat  and  asparagus  are  familiar  cases.  Similar 
cases  can  be  made  out  among  animals.  There  is  no  certain 
instance  of  an  infectious  disease  affecting  one  or  more 
races  of  the  human  species  and  leaving  another  untouched. 
There  are  a  number  of  instances  when  it  seems  that  certain 
races  are  less  susceptible  than  others  to  particular  diseases 
but  even  here  it  is  impossible  in  the  present  state  of  knowl- 
edge to  be  sure  of  the  significance  of  the  cases.  Racial  habits 
as  to  diet,  for  example,  and  the  continued  state  of  contact 


THE    INHERITANCE    OF    DISEASE  495 

with   the   disease  are   apparently   influential    factors   about 
which  there  is  as  yet  insuflicient  information. 

When  we  turn  from  the  race  to  the  individual,  vision 
apparently  becomes  clearer,  for  there  can  be  no  doubt 
that  with  reference  to  most  infectious  diseases  there  are 
wide  individual  variations  in  resistance.  These  are  made 
manifest  in  several  ways.  Most  certainly  perhaps  in  the 
varying  severity  of  the  effects  of  an  established  infection, 
but  also  in  all  reasonable  probability  in  the  "take  or  no  take" 
as  a  result  of  approximately  equal  grades  of  exposure.  It 
is  again  remarked  that  the  matter  is  apparently  clearer 
when  the  individual  is  considered.  It  is  meant  that  the 
differences  in  resistance  are  more  definitely  discernible, 
they  are  in  fact  unmistakable.  But  in  the  individual  case 
it  is  always  open  to  question  whether  the  exposure  has 
in  fact  been  equal;  whether  more  or  less  immunity  has  been 
acquired  from  the  mother,  or  actively  accumulated  through  a 
succession  of  abortive  exposures;  or  whether  a  previous 
mild  attack  of  the  disease  may  not  have  passed  unnoticed 
and  given  an  effective  vaccinal  protection.  The  great 
advance  in  medical  science  in  the  past  fifty  years  consists 
in  considerable  part  in  the  acquisition  of  the  understanding  of 
these  fundamental  features  of  the  body's  reaction  to  infections. 
It  has  seemed  to  many,  perhaps  to  most,  thoughtful  physicians, 
in  recent  years  that  these  near  at  hand  factors  were  sufficient 
to  account  for  all  the  differences  in  individual  resistance. 

But  if  we  go  back  for  a  moment  to  an  earlier  period  we 
find  a  fixed  and  universal  opinion  that  certain  infectious 
diseases  follow  family  lines  to  a  considerable  extent.  This 
is  not  true  of  measles  or  smallpox.  It  seems  conspicuously 
true  of  tuberculosis.  Most  of  us  can  doubtless  call  to  mind 
families  in  which  severe  illnesses  and  deaths  from  tuberculosis 
have  been  common,  and  other  families  in  which  they  have 
been  rare.  Large  groups  of  family  histories  have  been 
collected  and. submitted  to  the  best  available  mathematical 
analysis  and  these  have  also  given  evidence  of  some  difference 
in  the  inheritance.  But  it  is  also  known  that  under  conditions 
of  universal  exposure  as  in  crowded  cities,  practically  all 
individuals  have  some  tuberculosis  at  some  time  or  other. 
The  disease  is  one  which  often  lasts  in  individual  cases  for 


496  HUMAN   BIOLOGY 

years  or  even  through  a  long  lifetime.  There  is  obviously 
unusual  opportunity  for  infection  to  follow  a  family  in 
which  it  is  established.  In  the  face  of  such  considerations 
on  the  contrary  side,  it  cannot  be  maintained  that  such 
studies  of  human  family  histories  as  have  been  made  abso- 
lutely decide  the  matter.  They  do  give  evidence,  however, 
that  familial  differences  in  resistance  exist. 

Some  light  has  been  thrown  on  this  case  by  animal 
experimentation.  Guinea  pigs  are  very  susceptible  to 
inoculation  tuberculosis.  These  animals  have  also  been 
favored  as  subjects  for  genetic  experiments.  There  exist  a 
few  families  of  the  species  which  have  been  propagated  for 
years  by  the  closest  possible  inbreeding.  With  regard  to  cer- 
tain characters,  color,  growth  rates,  fertility,  etc.,  the  family 
characters  are  distinctive  beyond  question.  It  has  also 
been  possible  to  show  that  the  families  differ  in  their  suscepti- 
bility to  inoculation  tuberculosis.  The  differences  are  of 
degree  only.  That  is,  all  are  susceptible,  but  the  disease 
advances  much  more  rapidly  in  some  families  than  in  others. 
Animal  experiments  cannot  in  general  be  transferred  to  the 
interpretation  of  human  phenomena  without  scrupulous 
consideration.  But  the  laws  of  inheritance  have  been  proved 
in  other  cases  to  be  among  the  most  fundamental  of  biological 
phenomena.  Wherever  there  is  sexual  reproduction  the  laws 
of  Mendel  have  been  found  to  govern  the  inheritance. 
And  wherever  a  certain  quality  has  been  found  to  be  definitely 
inherited  in  any  species  it  is  found  to  be  inherited  in  other 
species  possessing  the  quality.  The  details  governing  the 
inheritance  of  the  quality  may  differ  from  species  to  species, 
but  this  only  means  that  the  relative  importance  of  certain 
qualities  may  be  found  to  vary  in  relation  to  other  qualities 
which  may  or  may  not  be  definitely  heritable.  The  quality, 
to  repeat,  if  subject  to  inheritance  in  one  species  will  be 
similarly  controlled  in  any  other  in  which  it  may  occur, 
although  it  may  be  a  much  more  important  and  significant 
quality,  in  the  one  species  than  in  the  other.  Also  it  may  be 
considered  certain,  that,  in  its  fundamentals,  inoculation 
tuberculosis  in  the  guinea  pig  reproduces  the  condition  of 
spontaneous  tuberculosis  in  man.  There  are  doubtless 
important  departures  in  the  intimate  nature  of  the  disease 


THE    INHERITANCE   OF   DISEASE  497 

in  the  various  species  but  these,  however  significant,  must 
still  be  regarded  as  differences  in  detail.  It  would  seem 
proper  to  consider  therefore  that  the  results  of  the  animal 
experiments  may  safely  be  applied  to  the  interpretation 
of  what  has  been  observed  of  the  inheritance  of  the  human 
disease  to  the  extent,  at  least,  that  we  should  for  the  future 
be  ready  to  accept  the  statistics  and  familial  observations 
at  the  significance  thay  carry  on  their  face,  rather  than 
straining  all  points  of  possible  criticism  and  reservation. 
In  other  words,  it  seems  established  in  all  reasonable 
probabihty  that  important  factors  influencing  the  incidence 
of  tuberculosis  and  the  development  of  the  disease  in  the 
individual  are  inherited. 

The  studies  of  human  material  from  the  pathological 
standpoint  show,  as  has  been  said,  that  most  individuals 
become  infected  with  tuberculosis  at  one  time  or  another 
and  it  may  therefore  be  concluded  that  neither  in  kind  nor 
degree  are  the  inherited  factors  capable  of  preventing 
infection.  They  must,  therefore,  be  exerted  on  the  progress 
of  the  disease  after  the  body  is  invaded  by  Bacillus  tuber- 
culosis. The  direct  evidence  at  present  available  from  human 
sources  does  not  carry  us  beyond  this  point. 

What  we  know  of  the  pathology  of  human  tuberculosis, 
experience  derived  from  animal  experimentation  with  this 
disease,  and  consideration  of  our  knowledge  of  other  infec- 
tious diseases  enables  us  to  set  up  a  series  of  surmises  or 
hypotheses  with  regard  to  the  possible  nature  of  the  inher- 
itable factors  involved  but  it  would  be  difficult  if  not  impos- 
sible to  check  these  effectively  by  direct  studies  of  the  human 
disease.  It  has  been  possible  to  make  a  beginning  in  this  direc- 
tion on  the  basis  of  the  guinea-pig  experiments  just  mentioned. 

It  is  found  in  the  first  place  that  there  are  a  number  of 
inherited  factors  involved.  At  least  three  and  possibly  four 
separately  inherited  factors  or  factor  groups  are  indicated 
by  the  results  with  the  available  guinea-pig  families.  It 
cannot  be  assumed  that  these  families  assembled  by  chance 
for  other  purposes  present  all  the  possible  variants.  Nor 
can  it  be  assumed  that  the  most  complete  collection  of 
guinea-pig  material  would  accurately  portray  and  relatively 
evaluate  the  human  factors.  What  is  presented  is  a  minimum 


498  ■  HUMAN    BIOLOGY 

Statement  of  the  number  of  factors  involved  and  an  indica- 
tion of  the  way  they  may  exert  their  effects. 

In  the  guinea  pig  it  is  found  that  there  are  inherited 
factors  which  influence  the  quantity  of  antibodies  (antitoxic 
substances)  which  are  produced  in  response  to  a  given 
stimulus.  There  are  other  inherited  factors  which  influence 
the  severity  and  precise  quahty  of  the  ulceration  which  the 
tubercle  bacillus  and  some  other  irritating  agents  produce 
in  the  skin,  and  in  the  character  of  the  tuberculous  inflamma- 
tion in  the  lymphatic  vessels  and  glands.  There  is  aIso]^an 
indication  of  another  group  of  separately  inherited  factors 
affecting  the  nature  of  the  reaction  to  dietary  deficiencies. 

Granted  that  there  are  inheritable  factors  influencing  the 
character  of  tuberculosis  in  the  individual,  any  clue  as  to 
their  dominant  or  recessive  quality  is  a  matter  of  great 
interest.  Unfortunately  the  human  material  lacks  the 
precision  of  detail  necessary  for  an  answer  to  such  a  question. 
The  guinea-pig  material  suggests  that  where  all  of  the 
characters  favorable  to  resistance  are  combined  in  a  family 
it  presents  a  dominant  combination.  The  first  generation 
crossbreds  are  as  resistant  as  the  most  resistant  family.  In 
the  actual  observations  they  somewhat  surpass  this  mark, 
indicating  the  operation  of  those  forces  which  make  for 
heterosis  or  hybrid  vigor.  Where  crosses  are  made  between 
families  of  less  than  the  maximum  resistance  the  result 
varies.  Some  crosses  produce  offspring  as  resistant  as  the 
better  family,  another  produces  an  intermediate  resistance. 
In  general,  dominance  of  resistance  prevails  but  it  is 
imperfect. 

The  available  information  from  all  sources  with  respect  to 
the  inheritance  of  a  variable  degree  of  resistance  to  tubercu- 
losis suggests  some  further  comment  in  relation  alike  to 
its  medical  aspects  and  to  the  genetic  point  of  view. 

Belonging  essentially  to  the  prebacterlologlcal  era  of 
pathology  Is  the  conception  that  susceptibility  to  infectious 
disease  is  more  or  less  definitely  related  to  fundamental 
Inheritable  qualities  which  find  expression  In  physical 
conformation,  that  is,  "physical  type,"  and  in  peculiarities 
of  function,  that  is  "'Constitution."  The  terminology  was  on 
the  whole  very  loose  and  Interchangeably  employed.  Con- 


THE    INHERITANCE    OF    DISEASE  499 

stitution  also  was  often  thought  to  be  expressed  in  physical 
characteristics.  When  functional  characteristics  were  thought 
of  as  directly  related  to  disease  the  term  "diathesis"  was 
frequently  used.  Thus  people  of  a  certain  inherited  "con- 
stitution" were  regarded  as  especially  Hable  to  tuberculosis, 
particularly  to  that  of  the  lymphatic  glands  on  the  basis  of 
a  "scrofulous  diathesis." 

When  ideas  were  crystalhzed  during  and  after  the  classical 
bacteriological  studies  of  the  latter  quarter  of  the  last 
century  the  conception  of  the  scrofulous  diathesis  was  first 
amphfied  in  an  attempt  to  harmonize  it  with  new  observa- 
tions, and  then  almost,  if  not  quite  discarded,  as  being  at 
best  inadequately  grounded.  The  considerations  advanced 
in  amplification  of  the  conception  are  of  considerable  interest 
in  the  present  connection. 

It  was  first  shown  that  the  lymphatic  lesions  characteris- 
tically associated  with  the  diathesis  were  tuberculous  and 
that  they  had  in  general  the  same  etiology  as  pulmonary 
tuberculosis.  It  was  soon  very  evident  that  it  was  difficult, 
if  not  impossible,  to  discriminate  between  those  physical 
characteristics  that  might  be  preexistent  and  possibly 
reflect  predisposing  causes,  and  those  that  were  the  con- 
sequences of  long-continued  chronic  disease  transmitted  by 
contact  infection  from  generation  to  generation  and  often 
persisting  in  the  individual  from  earhest  childhood  to  old 
age.  It  also  appeared  that  the  other  lesions,  particularly  those 
of  the  skin,  that  had  frequently  been  regarded  as  evidences 
of  a  scrofulous  diathesis  were  not  tuberculous  but  were  due 
to  casual  infection  with  staphylococci,  streptococci  and 
probably  other  microorganisms. 

This  recognition  of  many  of  the  appearances  as  "con- 
sequences" greatly  weakened  the  whole  conception.  The 
further  evidence  that  if  there  was  a  constitutional  pre- 
disposition it  was  not  strictly  specific  for  tuberculosis  but 
involved  other  inflammatory  processes  as  well,  put  the 
question  out  of  touch  with  the  progressive  thought  of  the 
time,  which  was  primarily  engaged  in  establishing  specific 
relationships,    either  of  etiology  or  immunity. 

With  the  coincident  and  tremendous  improvement  in 
hygienic   conditions   and   nutritional   well-being   in   Europe 


500  HUMAN   BIOLOGY 

and  especially  in  America,  tuberculosis  and  the  minor 
infections  referred  to  have  a  greatly  diminished  prevalence. 
It  is  now  to  be  accepted  that  practically  all  of  the  aforetime 
ability  to  segregate  a  type  of  people  having  the  scrofulous 
diathesis  (if  such  there  are)  was  dependent  on  the  continued 
manifestation  of  the  infections  to  which  they  are 
susceptible. 

It  is  of  interest  and  significance  that  an  experimental 
approach  to  the  question  with  suitable  material  develops  a 
picture  which  fits  so  well  with  the  conception  of  a  scrofulous 
diathesis  as  it  stood  at  about  the  beginning  of  the  present 
century.  There  is  observed  in  the  guinea-pig  experiments 
already  outhned  an  inherited  group  of  reactive  quahties 
that  are  related  to  susceptibility  to  tuberculosis,  and  also 
find  expression  in  the  character  of  the  tissue  changes  in 
tuberculosis  and  in  some  simple  inflammatory  reactions. 
Respecting  the  hmitations  imposed  by  species  differences 
this  would  seem  to  be  as  close  as  it  could  be  hoped  to  come  to 
an  experimental  definition  of  the  scrofulous  diathesis. 

A  generation  ago  the  general  conception  of  the  funda- 
mental nature  of  inheritance  was  that  it  was  a  blending  or 
fusing  of  the  parental  characteristics,  stronger  characters 
being  diluted  by  weaker.  The  cases  which  such  a  blend  did 
not  explain  were  regarded  as  unaccountable  exceptions. 
Then  the  work  of  Mendel  was  revived  and  it  was  seen  that 
when  inherited  quahties  were  sufficiently  analyzed  into 
their  component  parts  the  blended  was  rather  the  exceptional 
occurrence.  But  instances  of  blending  inheritance  could  not 
be  gotten  over  or  disregarded  and  it  seemed  to  some  students 
that  there  must  be  two  principal  forms  of  inheritance.  These 
views  have  been  quite  completely  harmonized  by  further 
study.  In  the  obvious  Mendehan  case  a  particular  character, 
which  to  famihar  scrutiny  is  simple  and  definite,  is  controlled 
by  the  presence  or  absence  of  a  single  inheritable  unit  known 
as  the  gene.  Color  in  animals,  eye  color  in  man,  tallness  or 
dwarfness  in  the  garden  pea  are  such  characters  and  their 
study  clearly  defined  the  Mendelian  principle  in  inheritance. 
Skin  color  in  man  if  albinism  is  contrasted  with  the  presence 
of  any  pigment  is  similarly  controlled. 


THE    INHERITANCE    OF    DISEASE  5O I 

But  skin  color  among  the  pigmented  of  the  human  species, 
tallness  or  shortness  in  the  human  race  (excepting  particular 
types  of  dwarfism),  the  weight  or  ear  length  in  rabbits  and 
innumerable  other  conditions  are  at  first  sight  not  so  con- 
trolled. The  result  of  a  cross  between  individuals  of  widely 
different  character  is  usually  a  "blended"  or  intermediate 
state  in  the  offspring.  While  it  was  difficult  at  first,  as  has 
been  said,  to  fit  these  cases  to  the  Mendehan  hypothesis  it  is 
now  apparent  that  blended  inheritance  means  that  the 
character  as  expressed  in  the  individual  is  the  resultant  of 
the  combined  and  overlapping  functional  expression  of  the 
action  of  two  or  more  genes.  It  now  is  the  consensus  of 
opinion  among  students  of  heredity  that  this  is  the  true 
significance  of  blended  inheritance.  Mendehan  principles  are 
as  strictly  apphcable  as  in  the  more  obvious  instances  but 
more  than  one,  often  many,  unit  characters  are  involved 
in  the  make-up  of  the  observable  quality.  This  is  evidently 
the  condition  underlying  the  inherited  factors  in  resistance 
to  tuberculosis. 

The  guinea-pig  material  submitted  to  analysis  with  this 
principle  in  mind  gives  the  following  provisional  result: 
For  each  of  the  five  famihes  there  is  a  characteristic  grade  of 
resistance.  This  could  be  accounted  for  by  the  action  of  two 
separately  inherited  unit  characters  but  not  by  one.  The 
study  of  the  crosses  between  the  families  indicates  that 
there  are  operative  not  less  than  three  and  possibly  four  unit 
characters.  The  study  of  the  physiological  reactions  shows 
suggestive  relations  in  such  widely  separated  functional 
activities  as  the  immunological  reactions,  the  tissue  reactions, 
and  responses  to  dietary  changes,  with  an  observable  inde- 
pendence between  them.  This  would  also  justify  the  assump- 
tion of  at  least  three  characters.  The  tissue  reactions  when 
further  analyzed  are  found  to  be  complex,  involving  at  the 
least  two  characters.  The  other  types  of  reaction  are  obvi- 
ously blended  and  must  involve  at  least  two  characters.  The 
results  at  hand  then  must  be  assumed  to  involve  at  least  six 
and  possibly  eight  separately  inherited  unit  characters. 
Probably  the  matter  is  much  more  comphcated  than  this  in 
the  guinea  pig,  and  even  more  so  in  the  human. 


502  HUMAN   BIOLOGY 

Now  for  the  color  inheritance  in  these  same  families  of 
guinea  pig,  Wright  has  made  out  the  operation  of  at  least 
seven  separate  characters  and  he  calculates  that  the  possible 
recombinations  of  these  would  lead  in  this  stock  alone  to  no 
less  than  25,000  color  varieties  of  guinea  pig.  There  is,  as 
suggested  previously,  no  apparent  reason  for  assuming  that 
tuberculosis  resistance  is  determined  (in  so  far  as  it  is  depend- 
ent on  inheritance)  in  any  other  or  more  simple  way  than  this 
in  either  guinea  pigs  or  humans,  and  we  are  led  to  beheve 
that  the  possible  varieties  of  humans  from  the  point  of  view 
of  their  behavior  with  respect  to  tuberculosis  must  actually 
number  in  the  thousands.  In  fact  it  appears  rather  remark- 
able on  this  bas'S  that  famihal  characters  are  ever  recogniz- 
able even  though  the  assumption  of  an  inheritable  influence 
were  uncontested.  One  is  incHned  to  think  that  there  must  be 
favored  associations  of  characters  which  divert  the  results 
into  fairly  well-defmed  main  channels  in  many  cases.  How- 
ever this  may  be,  and  allowing  all  possible  latitude  for 
famihal  association  of  inheritable  quahties,  it  is  plain  that 
under  the  systematic  outcrossing  which  is  the  rule  in  human 
matings,  the  observed  fact  that,  taken  by  and  large,  the 
individual  variations  in  resistance  to  tuberculosis  are  more  in 
evidence  than  the  family  hkenesses  is  what  one  would  expect. 

In  no  other  infectious  disease  of  man  has  it  been  made  so 
evident  that  inherited  quahties  are  influential  in  either  the 
prevalence  or  character  of  the  disease  in  the  individual. 
Instances  are  reported  among  animals,  both  in  reference 
to  spontaneous  epidemics  and  inoculation  diseases  where 
the  result  is  as  definite  or  more  so,  and  where  the  inheritance 
of  the  controlhng  factors  is  less  comphcated.  The  nature 
of  these  factors  is  undetermined  in  these  cases  and  their 
consideration  therefore  would  not  at  this  time  throw  addi- 
tional light  on  human  problems. 

It  shouki  of  course  be  held  constantly  in  mind  that 
inheritance  can  be  but  one  of  the  important  influences 
determining  the  incidence  of  any  infectious  disease.  In  the 
case  of  tuberculosis  as  already  outhned  the  factors  we  are 
dealing  with  do  not  determine  the  absolute  level  of  the 
racial  resistance.  Such  are  at  present  intangible.  What  is 
determined  is  the  degree  and  kind  of  individual  variation 


THE    INHERITANCE    OF    DISEASE  5O3 

in  the  resistance.  Calculation  of  the  results  with  the  guinea 
pigs  has  shown  that  such  factors  as  age,  abihty  to  gain 
weight  on  a  mixed  diet,  absolute  weight,  etc.,  factors  in 
part  determined  by  the  inheritance  and  in  part  by  environ- 
mental conditions,  can  account  for  something  less  than  lo 
per  cent  of  the  observed  variation.  Factors  of  direct  influences 
and  directly  dependent  on  the  inheritance  account  for 
somewhat  over  30  per  cent  of  the  variation.  There  remain  50 
or  60  per  cent  of  the  observed  differences  between  individuals 
at  present  not  accounted  for.  Such  factors  as  differences  in 
kind  and  amount  of  food  consumed,  "accidents"  incident 
to  the  spread  of  the  disease  within  the  animal  (implantation 
in  particular  organs,  etc.)  are  doubtless  to  be  included  in 
this  category.  Essentially  it  is  to  be  counted  as  an  accompKsh- 
ment  that  we  may  at  present  be  quite  certain  that  inheritance 
does  play  a  recognizable  part  in  the  prevalence  of  an  infectious 
disease. 

CANCER   AND   OTHER    MALIGNANT   TUMORS 

In  general  the  state  of  our  knowledge  of  the  factors 
underlying  the  occurrence  of  malignant  tumors  is  not 
dissimilar  to  that  with  regard  to  tuberculosis.  The  evidence 
from  human  sources  is  of  about  the  same  order  but  less 
significant  on  the  whole.  Tumors  have  been  alleged  to 
frequent  occasionally  certain  families  while  others  remain 
quite  untouched.  In  the  mass  there  is  the  sporadic,  occasional 
appearance  of  a  tumor  case  in  most  family  histories.  Cancer 
is  not  believed  by  most  authorities  to  be  an  infectious 
disease  although  the  fact  that  it  can  apparently  be  initiated 
in  man  and  animals  by  chronic  irritation  with  various 
substances,  even  by  various  parasites,  creates  many  resem- 
blances between  tumors  and  infections.  If  the  tumors 
classified  as  sarcomata  are  included  there  are  cases  in  which 
the  utmost  consideration  of  detail  fails  to  reveal  any  precise 
reason  why  they  should  not  be  accepted  as  infections; 
and  yet  because  of  that  fact  that  these  appearances  suggesting 
infection  are  the  exception  rather  than  the  rule,  most 
scientists  hold  in  reserve  the  thought  that  even  in  these  cases 
it  is  more  than  possible  that  some  other  explanation  will 


504  HUMAN   BIOLOGY 

be  found,  that  eventually  it  will  appear  that  all  the  true 
malignant  tumors  (including  most  forms  now  classed  as 
such)  will  be  found  to  originate  in  causes  resident  within 
the  body. 

Tumors  bear  a  certain  resemblance  to  infection  in  that 
those  which  originate  in  animals  are  often  transferable  to 
other  animals  of  the  same  species  by  a  succession  of  trans- 
plantations of  the  tumor  tissue,  or  in  some  instances  by 
extracts  of  this  tissue  containing  no  intact  body  cells.  The 
conditions  governing  the  transplantation  are  such  as  to 
make  the  influence  of  inheritance  very  apparent.  These 
tumors  are  never  transferable  outside  the  species  of  animal 
in  which  they  originate.  For  instance,  mouse  tumors  can  only 
be  propagated  in  mice.  Within  the  species  they  are  transfer- 
able with  great  difficulty  when  at  all,  from  one  race  to 
another.  It  is  quite  likely  that  this  line  is  as  rigid  as  the  species 
line,  but  it  is  impossible  to  be  sure  because  in  the  domesticated 
mice,  rats,  and  fowls  which  are  available  for  experimentation, 
racial  lines  have  been  hopelessly  confused  by  repeated 
intercrossings.  However  this  may  be,  it  has  been  the  common 
experience  that  when  transplants  of  a  spontaneous  tumor 
are  attempted  they  succeed  in  but  a  small  percentage  of 
the  subjects  unless  by  chance  the  subjects  are  the  immediate 
relatives  of  the  animal  bearing  the  original  tumor,  when  the 
percentage  of  success  may  be,  and  often  is,  greater.  It  is 
evident  that  a  racial  and  familial  variation  in  the  suscepti- 
bility-resislance  ratio  is  operative  in  the  tumor  transplanta- 
tion experiments. 

This  variation  in  resistance  has  been  the  subject  of 
thorough  genetic  experimentation  and  analysis  in  certain 
instances.  When  the  Japanese  waltzing  mouse  and  the 
common  tame  mouse  were  compared  it  was  found  that  their 
differences  with  respect  to  tumor  transplantability  across  the 
race  line  must  be  under  the  influence  of  at  least  twelve 
separately  inherited  unit  characters.  The  reasoning  applied 
to  the  case  of  tuberculosis  in  the  preceding  paragraphs 
holds  here.  We  should  expect  the  familial  evidence  for 
inheritability  in  the  human  race  to  appear  only  very  occa- 
sionally. Even  less  is  known  about  the  fundamental  nature  of 
the  inherited  characters  in  tumors  than  in  tuberculosis. 


THE    INHERITANCE   OF   DISEASE  5O5 

There  is  also  a  great  deal  of  evidence  that  the  incidence 
of  spontaneous  mahgnant  tumors  in  animals  is  quite  depend- 
ent on  the  inheritance. 

DISEASES   BASED   ON    ABNORMAL    SENSITIZATION 

A  number  of  disease  conditions,  all  troublesome  and  some 
very  serious,  asthma,  hay  fever,  and  various  "idiosyncrasies" 
against  particular  articles  of  food  or  particular  drugs  have 
been  found  to  have  certain  features  in  common.  They  are 
ahke  in  that  they  are  all  unusual  reactions  to  particular 
substances  found  in  the  environment  which  do  not  affect 
most  people  in  any  harmful  way.  Of  those  suffering  from 
the  condition  some  react  only  to  a  single  substance,  others 
are  affected  by  many  substances.  The  diseases  are  so  common 
as  to  be  famihar  to  most  people  and  place  need  not  be 
given  here  to  any  detailed  description  of  them.  The  simplest, 
and  in  many  ways  most  characteristic,  is  uticaria,  or  hives. 
Most  people  suffer  at  one  time  or  another  from  this  trouble. 
Some  people  always  have  it  as  a  consequence  of  eating  a 
particular  food,  e.g.  strawberries,  eggs.  The  skin  becomes 
blotched  and  irregular  wheals  are  raised  above  the  general 
level  of  the  skin  surface  by  reason  of  the  fact  that  the  skin  in 
these  areas  is  swollen.  The  swelHng  is  due  to  fluid  in  these 
areas  having  left  the  blood  vessels  and  stagnated  in  the  tissue 
spaces.  In  asthma  the  same  general  process  occurs  but 
the  area  affected  by  the  sweHing  is  the  smaller  air  tubes 
in  the  lungs  and  these  are  partly  closed,  making  breathing 
difficult.  In  hay  fever  it  is  the  mucous  membranes  of  the 
eyes  and  nose  which  are  affected. 

Inquiry  has  disclosed  a  well-marked  famihal  influence  in 
these  conditions.  They  are  in  some  measure  inherited.  The 
inheritance  seems  to  be  based  on  recessive  characters  in  the 
Mendehan  sense.  There  is  a  certain  difficulty  in  this  inter- 
pretation, however,  in  that  not  all  the  offspring  of  matings 
with  both  parents  diseased  are  afflicted.  This  is  susceptible 
of  alternative  explanations.  It  may  be  that  the  inheritance  is 
dependent  on  multiple  factors  in  which  case  the  line  between 
dominant  and  recessive  is  not  necessarily  clean  cut.  Some 
characters  may  be  dominant,  others  recessive  and  the  actual 
behavior  of  the  individual  is  the  result  of  a  kind  of  balance. 


506  HUMAN   BIOLOGY 

Another  possible  explanation  is  that  the  disease  itself  is 
not  inherited  but  only  the  Hability  to  contract  it.  That  is  to 
say,  an  individual  potentially  sensitive  by  reason  of  inherit- 
ance may  escape  the  influence  of  the  environmental  factor 
and  never  reveal  his  latent  tendencies. 

It  may  well  be  remarked  that  in  spite  of  a  very  great  deal 
of  experimental  work  many  of  the  factors  in  the  state  of 
hypersensitiveness  are  not  yet  understood.  For  example, 
some  of  the  most  striking  and  disastrous  instances  are  those 
of  people  sensitive  to  horse  serum  as  determined  by  their 
reactions  to  the  injection  of  diphtheria  antitoxin.  Those  in 
whom  the  sensitiveness  is  most  acute  have  usually  also  been 
subject  to  attacks  of  asthma  when  the  dust  from  horses 
has  been  inhaled.  But  many  people  injected  with  antitoxin 
become  very  sensitive  to  further  injections  of  horse  serum 
without  showing  any  tendency,  so  far  recognized,  to  develop 
asthma  on  contact  with  horses.  It  is  apparent  that  the 
inheritance  is  but  one  of  the  factors,  even  though  an  impor- 
tant one,  which  must  be  considered  when  we  try  to  understand 
disease  conditions. 

DISORDERS  AND  DEFECTS  OF  THE  CENTRAL  NERVOUS  SYSTEM 

Popular  interest  in  inheritance,  ahke  of  normal  and 
abnormal  quahties,  naturally  reaches  its  highest  when  the 
nervous  system  is  considered.  From  the  medical  point  of 
view  we  are  here  deahng  with  the  diseases  referable  to  a 
single  organ.  Gross  defects  of  development  occur  and  are 
likely  to  be  lethal  before  their  general  effects  on  function 
can  become  manifest.  Finer  defects  in  structure  may  well 
be  common  but  may  escape  recognition.  The  brain  and 
spinal  cord  are  affected  in  the  course  of  infectious  diseases 
which  are  to  be  considered  as  general  infections,  and  also 
are  the  seat  of  infections  primary  in  or  affecting,  chiefly 
themselves,  e.g.  pohomyeHtis,  encephahtis  lethargica,  and 
cerebrospinal  meningitis.  With  reference  to  these  what  has 
been  said  with  regard  to  the  inheritance  of  immunity  or 
susceptibility  to  infectious  disease  generally  doubtless  has 
some  appHcation  in  principle  but  we  have  no  specific  knowl- 
edge of  inherited  influences  in  the  particular  cases.  The 
functional  disorders  of  the  nervous  system  are  manifest  in 


THE    INHERITANCE   OF    DISEASE  5O7 

almost  infinite  variety  and  the  study  of  them  has  gradually 
become  a  very  intricate  specialty.  From  our  present  point 
of  view  only  certain  outstanding  selections  can  be  considered 
for  purposes  of  illustration. 

Feeblemindedness  has  a  peculiar  interest.  The  condition 
(one,  it  may  be  supposed,  of  Hmited  development)  rests  in 
some  instances  on  an  inherited  basis  as  made  evident  by 
careful  and  competent  scientific  investigation.  Is  feeble- 
mindedness a  disease?  Obviously  it  may  be  so  regarded  in 
the  social  sense,  since  on  a  purely  practical  basis  a  highly 
developed  society  is  forced  to  maintain  large  institutions  for 
the  care  of  such  of  its  offspring  as  are  unable  to  maintain  the 
pace.  From  the  pathological  standpoint  it  is  hardly  to  be 
looked  upon  as  a  disease  except  in  the  most  extreme  or 
particular  instances.  But  when  one  begins  to  discriminate 
on  a  quantitative  basis  all  the  standards  must  be  arbitrarily 
chosen.  The  question  clearly  becomes  an  academic  one 
when  purely  practical  standards  are  disregarded.  The  same 
may  be  said  of  many  types  of  insanity.  The  discrimination 
between  sane  and  insane  in  ^neral  is  possible  on  a  legalistic 
and  practical  basis,  however  difficult  decision  in  particular 
cases  may  be.  A  perfectly  sharp  borderline  in  the  scientific 
sense  can  hardly  be  drawn. 

But  insanity  presents  another  aspect,  in  that  there  are 
certain  disorders  of  the  nervous  system  characterized  by 
definite  symptomatic  behavior  which  clearly  define  them 
without  reference  to  their  severity  or,  in  other  words, 
whether  the  sufferer  is  incapacitated  or  not.  The  most  widely 
illustrative  perhaps  is  the  disease  known  as  essential  epilepsy. 
Those  most  slightly  affected  may  not  only  be  not  incapaci- 
tated but  may  be  mentally  quite  normal  or  unusually 
brilliant  people.  Those  most  severely  affected  are  or  fre- 
quently become  unquestionably  insane.  In  its  mildest  forms 
or  in  its  most  severe,  the  symtomatology  is  characteristic. 
The  difficulties  of  recognition  in  the  mild  cases  are  due  to 
the  fact  that  the  slight  symptoms  long  pass  unnoticed.  This 
disease  is  inherited  in  many  cases,  and  apparently  usually 
as  a  Mendelian  recessive.  There  are  indications  of  sex 
linkage  in  some  instances  and  it  sometimes  appears  as  a 
dominant.   Multiple   factors  are  probably  involved.   Other 


508  HUMAN   BIOLOGY 

forms  of  insanity  equally  well  characterized  are  recognized 
and  some  are  probably  inheritable. 

A  great  mass  of  suspected  and  uncertain  material  is 
presented  for  consideration  in  this  field  which  has  usually, 
and  doubtless  some  times  properly,  been  explained  by 
assuming  that  what  is  inherited  is  not  any  specific  disease 
but  a  general  instability  of  the  nervous  system  on  the  basis 
of  which  variously  classifiable  disorders  and  diseases  are 
developed.  This  is  the  kind  of  assumption  which  has  in  the 
past  frequently  been  made  for  other  conditions  and  has  as 
often  been  replaced  with  advancing  knowledge. 

LONGEVITY 

It  has  been  increasingly  recognized  of  late  that  the  length 
of  life  of  the  individual  is  a  measurable  biological  phenome- 
non, the  analysis  of  which  might  uncover  very  interesting 
facts.  It  is,  of  course,  a  common  impression  that  length  of 
life  is  determined  in  considerable  measure  by  inheritance. 
Some  families  are  thought  to  be  notably  long  lived.  That 
the  condition  is  counter-balaqced  by  equally  well-marked 
short  hved  families  is  possible  but  this  is  in  the  nature  of  the 
case  less  easy  to  be  sure  about.  When  an  individual  lives  a 
long  time  we  think  naturally  of  his  constitution  as  a  respon- 
sible factor  and  when  his  ancestry  and  immediate  relatives 
also  survive,  the  constitutional  factor  becomes  more  and 
more  apparent.  But  when  an  individual  dies  young,  the 
disease  of  which  he  died  or  the  accident  of  fate  which  carried 
him  off  is  the  impressive  feature.  Suffice  to  say  that  observa- 
tions on  selected  families  of  animals,  fruit  flies  and  guinea 
pigs  particularly,  have  shown  that  length  of  life  whether 
short  or  long  is  a  definite  family  characteristic  and  have 
given  us  some  clues  regarding  its  hereditary  transmission. 

It  has  not  been  sufficiently  recognized  that  this  matter  is 
definitely  related  to  the  broad  question  of  the  inheritance  of 
disease.  To  make  it  plain  that  there  must  be  such  an  intimate 
relationship  it  is  only  necessary  to  point  out  that  when  the 
individual  dies  it  is  most  usually  from  some  definite  and 
immediate  disease.  There  are,  it  is  true,  some  instances,  and 
these  in  the  long  lived  exclusively,  where  death  comes  in 
such  a  way  that  the  rational  description  of  it  is  comprised  in 


THE    INHERITANCE    OF    DISEASE  5O9 

the  Statement  that  the  bodily  machine  was  worn  out,  that 
there  was  a  general  functional  disintegration.  Even  here 
complete  knowledge  would  be  hkely  to  show  that  some 
particular  functional  failure  was  really  responsible,  for  the 
evidence  from  tissue  culture  work  is  to  the  effect  that  given 
a  suitable  environment,  muscle  cells,  cartilage,  aud  many 
other  tissue  cells  are  capable  of  indefinitely  reproducing 
themselves  and  presumably  of  thus  perpetuating  their  proper 
function  in  a  way  indicative  of  potential  immortality. 

But  on  the  whole,  death  is  due  to  particular  and  recogni- 
zable causes.  And  those  people  who  die  young  are  carried 
away  by  infectious  processes  taking  form  as  definite  diseases, 
tuberculosis,  acute  lobar  pneumonia,  malaria,  etc.  Whereas 
those  who  live  through  this  period  succumb  to  cancer, 
degenerative  disease  of  the  organs  (nephritis,  arteriosclerosis, 
etc.)  or  less  well  characterized  infections  such  as  broncho- 
pneumonia. These  facts  permit  of  interpretation  in  the  sense 
that  certain  individuals  and  their  relatives  are  more  suscep- 
tible than  the  average  to  the  diseases  of  early  life,  i.e.  take 
them  more  severely  than  others  and  oftener  succumb  to 
them.  At  present  for  want  of  sufficiently  precise  information 
we  are  unable  to  assign  values  to  the  different  factors  in  this 
very  complex  matter.  Hypothetically  if  the  human  race 
were  comprised  exclusively  of  those  we  know  as  long  lived 
such  diseases  as  tuberculosis  and  typhoid  fever  would  be 
unknown  or  would  be  recognized  as  disorders,  disturbing  but 
not  especially  dangerous  to  life.  Whereas  if  the  population 
were  exclusively  of  the  short  lived,  cancer,  arteriosclerosis 
and  many  other  diseases  would  be  practically  unknown. 

ASSEMBLAGE  OF  CHARACTERS  AND  QUALITIES 

Throughout  this  presentation  it  has  been  evident  that  the 
essential  characters  on  the  inheritance  of  disease  depends  are 
separately  transmissible  units  of  an  almost  endless  variety. 
In  some  few  instances  one  such  unit  may  completely  control 
a  disease  condition.  But  in  most  cases  not  only  is  the  disease 
itself  only  partly  influenced  by  the  inheritance  but  even  that 
part  is  controlled  by  a  number  of  separately  inheritable  unit 
characters.  Our  present  knowledge  fails  completely  in  so  far 


510  HUMAN   BIOLOGY 

that  ill  no  single  instance  does  it  furnish  a  pertect  insight 
into  the  fundamental  nature  of  even  one  of  these  inheritable 
units.  The  task  for  the  future  is  obviously  enormous  if  we  are 
to  gain  a  usable  understanding  of  the  inheritance  of  disease 
on  the  basis  of  rational  knowledge.  We  require  to  know  for 
the  different  disease  conditions  the  precise  part  played  by 
the  inheritance  in  toto;  the  number  of  unit  characters  in- 
volved for  each  case,  and  their  structural  or  functional  nature. 
It  may  well  be,  however,  that  the  obstacles  which  intervene 
between  our  present  understanding  and  a  much  more  perfect 
and  useful  one  are  lessened  by  some  favoring  circumstances 
which  may  be  sketched. 

While  it  is  considered  fundamental  that  unit  character  is 
distinct  in  inheritance,  certain  definite  instances  are  known 
where  diverse  characters  are  usually  inherited  together.  This 
is  termed  Hnkage.  Thus  in  hemophiha  (which  is  manifest 
by  failure  of  the  blood  to  clot,  so  that  those  affected  are 
"bleeders,")  the  disease  condition  is  finked  with  the  factors 
determining  the  sex.  It  is  also  true  that  a  single  unit  character 
is  sometimes  known  to  be  concerned  with  a  variety  of 
structures  or  functions  although  the  author  is  unable  to  point 
out  an  example  of  this  nature  with  reference  to  any  disease 
condition. 

From  the  point  of  view  of  pathology,  also,  there  are  rather 
clearly  outfined  associations  between  certain  structural 
pecufiarities  and  disease  conditions,  excluding  cases  pre- 
viously outfined  where  the  disease  is  directly  dependent  on  a 
particular  fault  of  structure.  There  are  also  recognizable 
tendencies  for  individuals  and  famifies  to  suft'er  from  or  be 
relatively  immune  to  groups  of  diseases.  Thus  the  tafi,  thin, 
flat-chested  type  of  man  is  befieved  to  be  more  fiable  to 
acquire  tuberculosis.  People  who  suffer  from  rheumatism 
and  gout  are  befieved  to  be  less  fiable  than  the  average  to 
acquire  tuberculosis.  Most  of  these  relationships  are,  as  at 
present  recognized,  of  the  uncertain  order  resting  on  the 
impressions  of  successive  generations  of  physicians.  Yet 
recent  approaches  to  the  subject  on  the  basis  of  careful 
measurements,  accurately  recorded  case  histories  and 
adequate  statistical  analysis  lend  credence  to  the  befief  that 
there  is  a  real  and  traceable  set  of  associations  here  which  it 


THE    INHERITANCE   OF    DISEASE  5II 

will  be  worth  while  to  develop  by  further  studies.  Up  to  now 
the  interest  has  chiefly  centered  on  recognizing  certain 
anatomical  types  of  people  and  trying  to  correlate  with  these 
the  diseases  from  which  they  have  suffered.  The  recent  work 
of  Draper  who  approached  the  question  by  taking  typical 
cases  of  certain  diseases  and  studying  the  physical  conforma- 
tion seems  to  promise  more  definite  results.  Of  similar  import 
and  carrying  even  greater  suggestion  of  future  interest  are 
observations  indicating  that  the  blood  grouping,  a  functional 
inheritable  manifestation  developed  under  definite  conditions 
between  the  blood  cells  and  the  blood  serum,  is  associated  in 
the  inheritance  with  the  natural  immunity  to  diphtheria 
toxin  or  with  the  capacity  to  be  immunized  against  this 
poison. 

It  is  quite  within  the  bounds  of  possibihty  that  tracing 
such  relationships  as  have  here  been  outhned  may  make  it 
possible  to  trace  resistance  factors,  themselves  intangible, 
through  their  frequent  association  with  other  characters 
more  easily  recognizable. 

Sunburn  as  an  Illustration.  It  is  somewhat  curious  that  much 
of  what  we  know  of  the  principles  of  the  inheritance  of 
disease  can  be  quite  well  illustrated  by  a  critical  con- 
sideration of  simple  sunburn.  The  following  paragraphs 
about  this  condition  may  well  serve  as  a  summary  of  the 
main  features  developed  in  the  preceding  discussion  of 
more  serious  diseases  and  defects. 

1.  The  effect  commonly  known  as  sunburn  is  pathologically 
closely  related  to,  but  not  identical  with,  effects  produced  by 
heat  rays,  roentgen  rays,  acids  and  some  other  chemical 
agents.  Burning  is  a  property  of  the  sun's  rays,  particularly 
those  of  a  portion  of  the  ultraviolet  region  of  the  spectrum. 
A  rather  common  type  of  disease  is  thus  induced  by  a  highly 
speciahzed  and  particular  agency. 

2.  A  number  of  environmental  conditions  must  be 
observed  in  order  that  the  injury  may  be  produced.  These 
conditions  need  not  be  enumerated  in  detail  here  since  they 
relate  to  the  fact  that  ultraviolet  rays  are  at  a  threshold 
level  in  sunlight  as  it  reaches  the  earth  and  only  reach 
burning  intensity  under  clear  skies,  summer,  high  altitude, 
and  other  favoring  circumstances. 


512  HUMAN   BIOLOGY 

3.  Individuals  of  the  human  species  vary  widely  in 
their  susceptibiHty  to  this  injury.  These  differences  are 
largely  dependent  directly  on  the  surface  pigmentation 
although  it  is  not  unhkely  that  other  quahties  of  the  skin 
may  be  of  definite  influence. 

4.  All  of  the  diff"erences  in  pigmentation  which  are 
commonly  recognized  as  characteristic  of  the  various  races 
and  intraracial  types  of  the  human  species  are  of  significance 
for  this  disease.  The  most  highly  colored  race  (the  negro)  is 
supposed  to  be  absolutely,  and  doubtless  is  practically, 
insusceptible  to  this  injury  or,  in  other  words,  possesses  a 
complete  natural  immunity.  The  most  completely  blond 
types  are  most  susceptible.  Since  there  is  entirely  satisfying 
evidence  that  the  pigmentary  variations  are  controlled 
by  the  inheritance  in  accordance  with  Mendehan  principles 
it  may  with  propriety  be  said  that  susceptibility  to 
sunburn  (or  per  contra,  natural  immunity  against  it)  is 
inherited. 

5.  Many  of  the  less  extreme  blonds  and  all  of  the  lighter 
grades  of  the  positively  pigmented  types  develop  increased 
pigmentation  (tan)  under  repeated  exposure.  The  capacity 
for  tanning  varies  enormously  and  many  rather  complete 
blonds  seem  to  be  entirely  lacking  in  it.  The  tanning  is  in 
effect  an  acquired  immunity  to  a  specific  injury.  And  it  is 
proper  to  say  that  many  individuals  who  under  ordinary 
conditions  are  very  susceptible  to  sunburn  may  by  treatment 
be  given  a  very  perfect  immunity  against  it,  while  others  are 
not  only  naturally  very  susceptible  but  lack  certain  capacities 
and  consequently  cannot  be  rendered  immune.  From  the 
point  of  view  of  the  inheritance  we  are  here  concerned  with 
the  same  mechanism  that  was  considered  in  the  preceding 
paragraph,  i.e.,  the  inherited  pigmentary  control,  and  we  may 
accordingly  consider  that  we  have  not  only  an  inherited 
natural  immunity  but  a  variable  inherited  capacity  to 
acquire  an  artificial  immunity. 

6.  The  natural  pigmentation  is  transmitted  as  a  blending 
type  of  inheritance,  that  is,  it  is  controlled  by  multiple  unit 
characters  in  the  Mendelian  sense.  The  same  may  naturally 
be  said  of  the  susceptibility  to,  and  the  capacity  to  acquire  an 
immunity  against,  sunburn. 

7.  Finally,  not  to  strain  the  illustration  it  may  be  pointed 


THE    INHERITANCE    OF    DISEASE  513 

out  that  the  pigment  when  present  is  carried  by  a  special 
type  of  cell  with  no  other  known  function  than  that  of 
producing  and  locahzing  the  coloring  matter.  The  pigment 
is  produced  by  the  oxidation  (presumably  by  the  associated 
activities  of  particular  ferments)  of  a  particular  colorless 
substance.  The  final  color  depends  on  the  amount  of  pigment 
and  the  distribution  of  the  cells  which  carry  it.  There  are 
evidently  various  points  at  which  the  controlhng  factors 
which  genetic  theory  postulates  as  multiple  unit  characters 
could  be  operative.  Complete  absence  or  reduction  in 
number  of  the  chromophore  cells,  variations  in  their  general 
functional  activity,  or  differences  in  any  of  the  particular 
chemical  (fermentative)  activities  underlying  the  pro- 
duction and  "ripening"  of  the  characteristic  pigment  are 
obvious  and  distinct  loci  where  controlhng  factors  might  well 
exert  their  force.  One  of  the  tasks  for  the  future  is  to  analyse 
and  locate  these  factors  in  precise  terms  with  reference 
to  general  and  particular  structures  and  functions. 

Other  chapters  have  given  consideration  to  the  more 
general  aspects  of  inheritance  and  its  social  significance. 
This  one  may  well  be  concluded  by  explicit  reiteration  of 
the  rather  obvious  fact  that  any  application  of  our  knowledge 
of  the  inheritance  of  disease  to  the  broad  purposes  of  race 
betterment  must  be  through  the  development  of  ability 
to  control  particular  and  individual  cases.  Our  general 
culture,  our  freedom  from  certain  infectious  diseases  may 
alike  be  immediately  and  largely  a  matter  of  social  inheri- 
tance. Our  liability  to  those  diseases,  defects,  and  dis- 
comforts which  are  controlled  by  the  physical  inheritance 
must  always  be  based  directly  on  the  qualities  of  the  germ 
plasm  transmitted  from  father  and  mother  to  their  children 
and  so  to  their  grandchildren. 

We  can  perhaps  sterilize  certain  obvious  defectives  and  so 
minimize  the  economic  burden  imposed  by  the  maintenance 
of  institutions  for  their  care.  But  we  cannot  so  durably  solve 
the  problems  imposed  by  the  fact  that  disabling  defects, 
diseases  and  tendencies  to  the  development  of  disease  are 
inherited.  The  faulty  germ  plasm  considering  the  multitude 
of  distorted  conditions  is  too  widespread  for  this.  The 
ancients  when  they  wished  to  completely  subjugate  a 
conquered    enemy    people    "decimated"    the    population. 


514  HUMAN   BIOLOGY 

This  seems  to  be  the  ultimate  which  cold-blooded  immediate 
destructive  human  purpose  can  achieve.  It  is  doubtful 
if  we  shall  ever  be  persistent  enough  to  interfere  radically 
with  the  propagation  of  lo  per  cent  of  the  defectives  even 
in  cases  where  there  is  complete  agreement  as  to  the  need 
for  such  measures. 

Recognizing  the  wide  distribution,  the  completely  individ- 
ualistic character  of  the  faults  in  the  germ  plasm,  it  seems 
that  most  rapid  progress  can  be  made  through  the  develop- 
ment of  the  individual  understanding  and  conscience. 
The  appeal  to  family  pride  has  been  a  most  potent  force 
in  the  past,  and  one  which  it  may  be  feared  the  present 
unduly  loses  sight  of.  From  the  present  point  of  view  this 
force  has  too  often  been  misdirected,  the  pride  has  been 
in  the  concealment  of  existing  defects  so  far  as  possible. 
This  is  equivalent  to  making  contracts  under  false  pretenses 
and  in  an  informed  society  must  come  to  be  regarded  as 
criminal. 

Family  pride  is  likewise  regarded  as  undemocratic.  But 
in  terms  of  generations  we  can  pass  to  our  descendants  as 
we  choose  a  democracy  of  the  unfit  or  one  of  the  highest 
personal  and  social  accomplishment.  To  the  development 
of  this  end  the  study  of  the  detailed  manner  in  which 
diseases  or  the  influences  controlling  disease  incidence 
are  transmitted  in  inheritance  is  likely  to  prove  an  increas- 
ingly useful  and  stimulating  force.  At  present  and  doubtless 
in  the  end  the  practical  guide  to  individual  judgment 
would  appear  ta  he  in  the  item  of  longevity.  A  short  lived 
strain  may  be  fundamentally  healthy,  a  long  lived  one  must 
be  at  least  superior.  When  this  complex  of  physical  attributes 
is  balanced  with  the  knowledge  of  the  presence  or  absence 
of  certain  particular  diseases  in  the  strain  and  the  whole 
weighed  with  a  rating  for  success  with  the  business  of  life, 
the  basis  for  the  intelligently  prideful  propagation  of  the 
family  may  be  well  laid. 

REFERENCES 

Castle,  W.  E.  1924.  Genetics  and  Eugenics.  Cambr.,  Harvard  Univ.  Press. 

Crew,  F.  A.  E.  1927.  Organic  Inheritance  in  Man.  London,  Oliver  &  Boyd. 

Draper,  G.  1924.  Human  Constitution.  Phila.,  Saunders. 

Lewis,  P.  A.,  and  Loomis,  D.  1928.  J.  Exper.  Med.,  47;  437,  449. 

Martins,  F.  1914.  Konstitution  und  Vererbung.  Berlin. 

Stockard,  C.  R.  1926.  Medicine,  5:  105. 

Wright,  S.,  and  Lewis,  P.  A.  1921.  Am.  Naturalist,  55:  20. 


Chapter  XXII 

SOME  ASPECTS  OF  THE  BIOLOGY  OF 
HUMAN  POPULATIONS 

Raymond  Pearl 

A  POPULATION  may  be  defined  as  an  aggregation  of 
individual  organisms  of  the  same  species,  living 
together  in  a  hmited  and  defined  universe.  In  the  case 
of  human  beings  the  limits  of  the  "universe"  of  a  particular 
population  are  commonly  defined  either  geographically  or 
politically.  We  thus  speak  intelligibly  of  the  "population  of 
the  United  States,"  meaning  the  aggregation  of  human  beings 
Hving  together  within  the  geographical  boundaries  of  the 
United  States  of  America. 

The  problems  presented  by  human  populations  are  many 
and  diverse.  The  economic  conditions  prevaifing  within  any 
particular  population,  its  social  organization,  its  racial 
composition,  and  so  on,  all  suggest  many  questions  to  which 
the  answers  are  generally  either  not  known  at  all,  or  only 
vaguely  and  imperfectly.  But  underlying  all  such  questions 
are  still  more  basic  ones,  which  have  to  do  with  the  biology  of 
human  populations.  Man  is  an  animal.  However  civihzed 
he  is  or  may  become,  what  it  is  that  after  all  keeps  him 
present  and  voting,  as  the  phrase  goes,  is  the  basic  fact  that 
he  is  an  organism,  which,  in  the  aggregate,  must  be  nourished, 
must  reproduce,  and  must  finally  die.  The  fundamental 
characteristics  of  those  groups  of  human  beings  that  we  call 
populations  necessarily  depend  upon  these  basic  biological 
attributes  and  actions  of  the  individuals  which  compose 
them.  But  recent  research  has  demonstrated  that  a  complete 
account  of  the  biology  of  a  population  will  require  something 
more  than  an  examination  of  the  biology  of  each  separate 
individual  composing  it.  The  group  behaves  biologically  in 
certain  ways  as  a  whole.  For  the  adequate  study  of  such 
phenomena  there  is  rapidly  developing  a  separate  division 
of  science,  which  is  called  "group  biology,"  or  the  biology  of 
populations.  It  is  to  the  discussions  of  the  biology  of  human 
populations  that  this  chapter  will  be  chiefly  devoted. 

515 


5l6  HUMAN   BIOLOGY 

Before  embarking  upon  the  consideration  of  the  biological 
characteristics  and  problems  of  human  populations  it  will 
be  desirable  to  have  before  us  some  broad  statistical  facts 
about  such  populations. 

So  far  as  anyone  knows,  the  curious  animal  which  Linnaeus 
perhaps  ironically  designated  Homo  sapiens  Hves  only  upon 
one  planet,  the  Earth  (see  chapter  i).  Nobody  knows 
exactly  how  many  human  beings  are  Hving  on  this  planet  at 
this  moment,  or  how  many  have  been  ahve  upon  it  at  any 
other  moment.  Theoretically  it  should  be  a  simple  matter 
to  count  them.  Practically  such  a  task  is  beset  with  diffi- 
culties. What  then  actually  happens  is  that  at  intervals  of 
five  or  ten  year<5  as  accurate  counts  as  possible  are  made  of 
all  those  people  whose  aggregate  state  of  civihzation  is  such 
that  any  counts  are  feasible.  Estimates  are  then  made  of 
the  numbers  of  the  others.  Roughly  speaking  the  numbers 
of  persons  hving  on  the  earth  in  1927  were  of  the  order  shown 
in  Table  i. 

Table  i  furnishes  a  good  deal  of  interesting  information 
about  the  number  and  kinds  of  people  who  are  spread  over 
the  earth's  surface.  It  is  seen  that  while  Europe  is  only  about 
a  fifteenth  part  of  the  land  area  of  the  globe,  shghtly  more 
than  a  quarter  of  all  the  people  in  the  world  hve  there. 
Oceania  has  about  the  same  area  as  Europe,  but  less  than  a 
two-hundredth  part  of  all  the  people  hve  there.  Asia  covers 
less  than  a  third  of  the  globe  but  has  more  than  half  the 
people.  Africa  and  North  America  have  respectively  about 
a  fifth  and  a  seventh  of  the  area,  but  each  has  rather  less 
than  a  twelfth  of  the  people. 

Plainly  if  Europe  and  Asia  are  to  be  regarded  as  normally 
populated,  then  the  rest  of  the  world  is  greatly  under- 
populated. Or,  conversely,  if  North  America  is  held  to  have 
something  like  an  optimum  population  then  Europe  and 
Asia  are  enormously  overpopulated.  But  there  is  scarcely  a 
country  in  Europe  which,  at  the  present  moment,  is  not 
at  least  talking  about  the  desirability  of  larger  populations. 
And,  on  the  other  hand,  a  great  deal  is  heard  in  the  United 
States  about  the  wisdom  which  will  inhere  in  sharply 
restricting   the    future   growth   of  our   population.    In   fact 


SOME   ASPECTS    OF   THE   BIOLOGY    OF    HUMAN    POPULATIONS    5I7 


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5l8  HUMAN   BIOLOGY 

there  is  now  in  operation  a  law  recently  passed  which  greatly 
reduces  the  increase  in  our  population  from  immigration. 

These  broad  facts  suggest  that  it  would  be  difficult  to  draw 
up  at  this  moment  a  definition  of  an  optimum  population 
for  any  given  area,  to  which  everybody  would  agree.  Par- 
ticularly those  people  already  inhabiting  the  area  in  question 
are  almost  sure  to  have  views  about  what  is  the  best  popula- 
tion size  for  them,  which  will  be  different  from  those  reached 
by  other  groups,  or  by  dispassionate  students  of  population 
problems  in  general.  For  after  all  to  speak  of  an  "optimum" 
population  implies  a  criterion  of  what  is  best.  And  tastes 
do  differ  so.  In  a  brilliant  paper  read  before  the  World 
Population  Conference  in  Geneva  in  the  summer  of  1927 
Prof.  H.  P.  Fairchild  took  the  position  that  the  determining 
element  in  discussing  optimum  size  of  population  should 
be  "material  well-being,  or  "standard  of  living."  To  this 
it  is  difficult  to  urge  any  specific  theoretical  objection. 
But  there  is  a  very  considerable  and  real  practical  one, 
and  it  is  again  simply  that  tastes  do  differ  so.  The  radio, 
the  movie,  the  automobile,  canned  peaches,  and  Eskimo  pie 
are  clearly  evidences  of  a  high  standard  of  living,  in  the  sense 
of  "material"  well-being.  But  there  are  a  great  many  people 
in  the  world  who  do  not  care  for  these  things,  not  in  the  very 
least.  On  Professor  Fairchild's  definition,  as  on  any  other 
conceivable  one,  what  will  seem  to  one  group  of  people  an 
optimum  population  will  not  strike  another  group  at  all 
that  way.  The  point  is  beautifully  illustrated  in  the  attitude 
of  the  city  man  and  the  country  man  towards  each  other's 
dwelling  places  and  standards  of  living.  Each  really  thinks 
the  other  a  bit  simple,  not  to  say  feebleminded,  for  living  as 
he  does,  when  after  all  he  does  not  have  to.  But  the  truth 
merely  is  that  each  likes  his  own  way  of  living  better  than 
another  way.  Europe  had  more  than  twice  as  many  persons 
per  square  mile  as  Asia  (roughly  127  as  against  60).  Perhaps 
both  have  long  since  passed  their  optimum  populations. 
But  this  can  hardly  be  true  elsewhere  because  in  all  the  rest 
of  the  world  taken  together,  except  Europe  and  Asia  (and  the 
Polar  Regions),  there  are,  on  the  average,  only  about  12 
persons  per  scjuare  mile. 


SOME   ASPECTS    OF   THE   BIOLOGY   OF   HUMAN    POPULATIONS    519 

Has  there  been  any  tremendous  dashing  ofF  of  Europeans 
to  populate  the  unused  lands  of  the  world?  There  has  not. 
One  example  must  suffice.  Since  the  war  Great  Britain  has 
been  of  all  European  countries  perhaps  the  one  from  which 
one  would  be  most  hkely  to  want  to  move,  if  motives  of 
"material  well-being"  and  "standard  of  living"  were  the 
only  important  ones  to  be  considered.  Taxes  are  enor- 
mously high,  the  national  debt  is  large,  'amounting  to 
something  of  the  order  of  £  1 80  per  capita  of  population,  there 
are  many  unemployed  (1,180,290  on  Sept.  22,  1924)  and  so 
on.  But  in  1924  only  371,306  persons  left  Great  Britain  for 
other  than  European  destinations.  In  that  same  year  253,542 
persons  from  other  parts  of  the  world  than  Europe  decided 
that  they  wanted  to  come  and  live  in  Great  Britain.  So 
that  the  net  departure  was  of  only  117,766  people.  This 
constituted  only  about  one  person  in  each  400  of  the  popula- 
tion. And  the  proportion  of  net  emigrants  to  unemployed 
(who  surely  are  enjoying  a  low  standard  of  living)  was 
only  about  i  in  10.  There  seems  no  escape  from  the  con- 
clusion that  the  vast  majority  of  people  who  five  in  Great 
Britain  do  so  because  they  want  to.  They  may  be  having  a 
bad  time  of  it,  but  even  so  they  do  not  want  to  move.  Why 
they  do  not  is  fundamentally  because  they  are  not  merely 
units  of  economic  and  sociological  discussion,  but  instead 
are  human  beings,  full  of  prejudices,  peculiar  hkes  and 
disfikes  all  their  own.  Such  things  are  fundamental  biological 
attributes  of  human  beings.  Any  science  of  mankind  which 
neglects  them  will  not  be  human  biology,  whatever  else  it 
may  be. 

There  is  finally  a  general  point  which  needs  emphasizing 
about  the  discussion  of  optimal  population.  Because  the 
word  "optimum"  by  its  very  definition,  implies  a  matter  of 
taste,  feeling  or  emotion,  it  in  so  far  removes  the  discussion 
outside  the  field  of  exact,  objective  science.  Much  sociology  is 
filled  with  discussion  of  moral  or  other  "values"  overtly  or 
otherwise.  Many  writers  on  population  talk  at  length  about 
what  is  "good,"  or  "better,"  or  "best,"  or  "bad,"  "worse," 
or  "worst"  in  respect  to  population.  But  surely  the  path  to 
an  exact  science  of  population  does  not  lie  in  these  directions. 
What  the  subject  needs  is  a  Pareto  rather  than  evangelists. 


520  HUMAN    BIOLOGY 

Going  back  again  to  Table  i,  it  is  interesting  to  note  that 
of  all  the  people  in  the  world  just  under  37  per  cent  are 
Christians,  and  just  over  63  per  cent  are  not.  This  should  be 
encouraging  to  missionaries.  So  also,  perhaps,  should  be 
the  fact  that  no  other  single  rehgious  faith  has  anything  Hke 
as  large  a  proportion  of  the  people  on  the  earth  as  has 
Christianity.  The  nearest  is  Confucianism  and  Taoism, 
with  19  per  cent. 

Again,  however  it  is  clear  that  mere  size  is  not  all. 
There  are  more  fundamental  biological  considerations. 
The  Jews  constitute  less  than  i  per  cent  of  the  people  of  the 
earth.*  Is  there  anyone  who  would  venture  the  assertion 
that  their  proportionate  influence  in  human  affairs  is  of 
the  order  of  i  per  cent?  Whether  "chosen  "  or  not  they  are  as  a 
people  differentiated,  in  a  statistical  sense,  from  the  rest 
of  mankind  by  the  most  objective  of  tests,  success  in  life 
and  influence  and  power  in  the  control  of  human  affairs  on  a 
world-wide  scale.  And  it  is  equally  plain  that  the  basis  of 
their  differentiation  must  be  constitutional  in  the  biological 
sense.  Theirs  has  never  been  an  easy  environment,  physical 
or  biological.  A  differentiated  tenth  of  any  herd  is  never 
hkely  to  have  an  easy  time.  The  crowd  is  against  them. 
And  it  is  a  big  and  rough  crowd. 

There  is  perhaps  room  for  legitimate  pride  on  the  part  of 
somebody  that,  on  the  record,  the  people  of  North  America 
seem  to  be  most  tolerant  of  differences  in  rehgious  faith  of 
any  in  the  world.  For  whereas  96  per  cent  of  the  people  in 
Europe  are  Christians,  and  only  4  per  cent  Non-Christian, 
and  whereas  97  per  cent  of  the  people  of  Asia  are  Non- 
Christian  and  only  3  per  cent  Christian,  in  North  America 
approximately  i  person  in  every  5  is  not  even  technically  a 
Christian.  In  this  80  per  cent  Christian  population  there  are 
inchided  also,  and  mainly  without  prejudice,  an  appreciable 
number  of  devotees  of  every  main  brand  of  exotic  faith  except 

*  No  one  can  discuss  the  Jews  realistically  without  being  accused,  either  by 
Jew  or  by  Gentile,  of  having  confused  race  and  religion.  The  merits  of  this 
controversy  seem  to  be  few  and  slight.  For  the  purpose  of  the  present  discussion 
it  is  sufficient  to  state  the  fact  that,  of  the  persons  who  are  set  down  in  Table  i 
above  as  Jews,  an  overwhelmingly  large  proportion  are  biologically  differ- 
entiated in  a  whole  series  of  respects,  anatomical,  physiological  and  psycho- 
logical from  the  rest  of  mankind.  Whether  they  are  called  a  race,  or  are  not 
so  called,  is  of  no  importance  in  the  present  connection. 


SOME   ASPECTS   OF   THE   BIOLOGY   OF    HUMAN    POPULATIONS    52 1 

Shintoism.  The  same  thing  is  not  true  of  any  other  continent 
except  Asia,  and  there  to  a  much  smaller  degree 
quantitatively. 

In  addition  to  such  a  birdseye  picture  of  the  number  of 
different  kinds  of  people  who  inhabit  the  earth  as  is  given  in 
Table  i,  it  is  also  desirable  that  the  reader  have  some  idea 
of  the  age  and  sex  distribution  of  human  populations.  To 
this  end  Table  ii  has  been  prepared.  In  this  table  some  29 
different  human  populations  are  arranged  in  descending 
order  according  to  the  proportion  of  males  aged  fifteen  to 
forty-nine  to  the  whole  male  population.  Thus  55.4  per  cent 
of  the  hving  male  population  of  Belgium  fall  in  age  some- 
where between  fifteen  and  forty-nine  years  inclusive.  This 
is  a  higher  proportion  than  any  other  of  the  populations 
hsted  shows.  Therefore  Belgium  stands  at  the  head  of  the 
table.  Russia  has  only  39.6  per  cent  of  its  Hving  male  popula- 
tion between  the  ages  of  fifteen  and  forty-nine  inclusive, 
and  stands  at  the  bottom  of  the  table. 

Table  11  also  shows  the  number  of  females  hving  in  each  of 
three  broad  age  groups,  per  100  males  hving  at  the  same  ages. 

This  table  has  been  computed  from  data  given  in  a  recent 
paper  by  Moine. 

Let  us  consider  first  the  proportion  of  the  sexes.  It  is 
apparent  from  the  table  that  the  general  rule  is  that  in  the 
first  period  of  fife,  up  to  age  fifteen,  males  are  somewhat 
in  excess  in  the  hving  population.  The  only  exceptions 
to  this  rule  among  the  populations  hsted  in  Table  11  are 
France,  Canada,  Greenland  and  Russia  (in  Europe). 

In  the  period  of  vigorous  adolescent  and  adult  hfe,  between 
the  ages  of  fifteen  and  forty-nine  inclusive,  the  general  rule 
is  for  females  to  be  a  httle  in  excess  of  males  in  the  hving 
population,  but  there  are  fairly  frequent  exceptions.  In 
Table  11  the  countries  having  fewer  females  than  males 
at  these  ages  are:  Samoa,  United  States,  Union  of  South 
Africa  (both  natives  and  whites),  Austrahan  Confederation, 
Canada,  British  India,  Japan  and  Brazil.  These  are  all 
populations  in  which  either  there  is  a  considerable  immigra- 
tion of  young  adult  males  for  industrial  reasons,  or  in  which 
the  female  is  under  something  of  a  handicap  in  the  general 
social  scheme  of  things. 


522 


HUMAN   BIOLOGY 


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SOME    ASPECTS    OF   THE    BIOLOGY   OF    HUMAN    POPULATIONS    523 

In  the  last  period  of  life,  from  age  fifty  on,  females  are 
rather  considerably  in  excess  of  males  in  most  hving  popula- 
tions. The  exceptions  to  this  rule,  among  the  populations 
listed  in  Table  ii  are  Samoa,  United  States,  Australia, 
Canada,  Union  of  South  Africa  (whites),  British  India, 
Brazil  Bulgaria.  The  fact  that,  in  general,  females 
have  a  greater  longevity  than  males  accounts  for  their 
usually  greater  frequency  in  the  living  population  at  ages 
from  fifty  years  on. 

Turning  now  to  the  age  distribution  of  living  populations 
it  appears  that,  on  the  average,  approximately  a  half  of  the 
population  of  living  males  falls  between  the  ages  fifteen  and 
forty-nine  inclusive.  Thirty  five  per  cent  are  under  fifteen 
years  of  age  and  15  per  cent  are  fifty  years  of  age  or  over. 
For  females  the  corresponding  average  percentages  are 
51,  33,  and  16. 

Among  the  different  populations  the  greatest  variation  is 
found  in  the  percentage  of  the  total  population  under  fifteen 
years  of  age.  In  this  age  group  the  effects  of  differences  in 
both  natality  and  mortality  are  directly  felt. 

The  age  distribution  of  living  populations  has  much  more 
than  merel}^  statistical  interest.  Figure  i  shows  in  graphic  form 
the  average  situation  documented  in  Table  11. 

Practically  no  children  below  the  age  of  fourteen  are 
completely  self-supporting  by  their  own  effort.  A  large 
proportion  of  persons  above  fifty  also  are  not,  by  their  own 
efforts  at  those  ages.  The  half  of  the  population  between  the 
ages  of  fifteen  and  forty-nine  has  to  support  a  large  part 
of  the  rest  of  the  population  as  well  as  themselves.  This 
burden  includes  both  direct  expenditure  at  the  time,  that  is 
while  they  are  under  fifty,  and  also  savings  for  their  own 
old  age,  when  they  can  no  longer  work.  This  extraordinary 
overlapping  of  generations  characterizes  human  populations 
to  an  extent  perhaps  not  equalled  in  any  other  living  form. 
It  is  a  factor  of  profound  importance  in  their  biology.  The 
tremendous  burden  depicted  in  Figure  i  is  borne  by  mankind 
for  reasons  in  part  emotional.  We  (in  a  statistical  sense) 
care  for  our  offspring  and  our  parents  beyond  the  time 
limits  of  biological  necessity  in  good  part  because  we  want  to. 
But  for  this  satisfaction  we  pay  a  high  price. 


524 


HUMAN   BIOLOGY 


In  these  facts  is  to  be  found  unquestionably  one  of  the 
basic  reasons  for  the  practice  of  contraception  or  birth 
control  in  countries  having  what  we  are  pleased  to  regard  as 


THE  LIVIHG  POPU^L^TIOri 


Tlie 

50  6'Ovef 


Fig    I.    Approximate     average     distribution     of     living     human     population 

Frequencies    are  depicted  as  areas. 

a  "high"  state  of  civilization  (see  chapter  xxii).  As  the 
burden  becomes  more  and  more  clearly  recognized  the 
natural  tendency  is  to  attempt  to  reduce  it  by  limiting  the 
number  of  children.  But  this  hope  is  in  some  degree  illusory, 
because  what  frequently  happens  is  merely  that  the  distribu- 


SOME    ASPECTS    OF   THE    BIOLOGY   OF    HUMAN    POPULATIONS    525 

tioii  of  the  burden  is  altered,  not  its  total  drag.  Consider,  for 
example,  the  population  of  France,  which  is  not  far  from 
the  condition  technically  called  "stationary"  by  statisticians. 
France  has  shghtly  less  than  a  quarter  of  its  living  population 
under  fifteen,  in  place  of  the  average  35  per  cent.  But  on  the 
other  hand  she  has  almost  exactly  25  per  cent  of  her  popula- 
tion aged  fifty  or  over.  So  once  more  each  of  the  potentially 
actively  working  fifty  per  cent  has  one  extra  mouth  to  feed 
besides  his  or  her  own,  in  whole  or  in  part. 

Consider  another  case.  The  native  population  of  Greenland 
is  not  particularly  soHcitous  about  keeping  its  old  people 
aHve  after  they  are  unable  to  fend  for  themselves  and  earn 
their  own  keep.  Eskimos  of  advanced  age  are  hard  to  find, 
on  the  testimony  of  all  Arctic  travellers.  But  does  this  materi- 
ally reduce  the  burden  in  total  on  the  workers?  It  does  not. 
For  while,  according  to  the  figures  of  Table  11,  only  about 
8.5  per  cent  of  the  living  population  of  Greenland  is  fifty 
years  or  over  in  age,  something  over  40  per  cent  are  children 
under  fifteen. 

The  figures  of  Table  11  give  us  a  glimpse  of  one  of  the 
most  important  elements  of  the  biology  of  human  groups 
or  populations.  This  is  the  principle  of  self-regulation. 
Self-regulation  of  the  individual  organism,  in  its  regeneration 
and  in  its  physiological  and  morphological  processes  gener- 
ally, has  long  been  familiar  to  the  student  of  biology.  It  is 
also  one  of  the  most  striking  and  important  phenomena  in 
group  biology,  or  the  biology  of  populations. 

In  the  next  section  we  shall  consider  this  matter  more 
particularly. 

THE    SELF-REGULATION    OF    HUMAN    POPULATIONS    IN    SIZE 

The  primary  biological  variables  involved  in  the  growth 
of  population  are  two  in  number;  natality,  measured  by  the 
birth  rate,  on  the  one  hand;  and  mortality,  measured  by 
the  death  rate,  on  the  other  hand.  These  primary  elements 
are  fundamental  to  the  discussion  of  the  growth  of  popu- 
lations of  any  and  all  organisms  whatever,  from  ameba  to 
man.  In  most  of  the  lower  organisms  hving  in  a  state  of  nature, 
whether   plant   or   animal,   these   are   the   only   first-order 


526  HUMAN   BIOLOGY 

variables  which  have  to  be  taken  into  account  in  discussing 
the  problem. 

In  most  human  populations,  especially  those  inhabiting 
large  geographical  areas,  a  third  factor  may  influence 
directly  the  size  of  the  population  at  any  given  moment, 
in  greater  or  less  degree.  This  third  factor  is  migration,  and 
it  is  theoretically  to  be  regarded  as  a  primary  variable  in 
determining  the  growth  of  such  human  populations.  While 
theoretically  a  first-order  variable,  migration  is,  in  large 
population  aggregates,  practically  always  much  less  important 
in  its  purely  quantitative  effects  upon  population  size 
than  are  the  basic  variables,  natality  and  mortality.  The 
growth  of  the  population  of  the  United  States  is  a  case  in 
point.  If  one  plots  the  census  counts  of  this  population 
(as  in  Fig.  5  injra  )  from  1790  to  1920  inclusive  it  is  impossible 
to  detect  in  the  curve  of  growth  any  separate  or  disturbing 
effect  of  immigration.  Unfortunately  it  is  impossible  to 
analyze  the  effect  of  immigration  upon  the  population 
of  the  United  States  in  detail,  for  the  reason  that  net  immigra- 
tion figures,  which  take  account  of  departures  as  well  as 
arrivals,  are  available  only  since  1908.  But  some  general 
facts  are  available  and  illuminating.  In  the  years  between  1830, 
when  records  began  on  the  point,  and  1870,  the  total  number 
of  immigrants  into  the  country  was  7.3  millions.  The  total 
population  of  the  country,  as  given  by  the  census  in  1870 
was  38.6  millions.  So  that  if  all  the  immigrants  who  came  into 
the  country  had  stayed  here,  and  none  had  died  in  the 
meantime  (both  assumptions  being,  of  course,  far  from  the 
real  facts)  the  total  immigration  in  the  period  would  have 
constituted  only  19  per  cent  of  the  total  population.  For 
the  census  years  beginning  with  1870  and  coming  down  to 
1920,  numbers  of  immigrants,  in  gross  (i.e.,  without  deduc- 
tion of  emigrants)  in  the  year,  per  thousand  of  population 
existing  in  the  same  year  are  as  follows: 


SOME   ASPECTS   OF   THE   BIOLOGY   OF    HUMAN    POPULATIONS    527 

Table  hi 


Year 

Annual  Immigration  into  the 
United  States  Per  1000 
Population 

1870 

lO.O 

1880 

9.1 

1890 

7-2 

1900 

5-9 

1910 

"•3 

1920 

4.1 

1926 

..6 

Richmond  Mayo-Smith  and  Thomas  Allan  Ingram  give 
the  following  corresponding  figures  for  emigration  from 
Great  Britain  and  Ireland,  with  the  comment  that:  "Even 
taking  Great  Britain  and  Ireland  together,  the  loss  by 
emigration  per  annum  has  not  been  very  large. " 


Table 

V 

Period 

Annual  emigration  per  1000  of 
the  average  population  of 
Great  Britain  and  Ireland 

1853-1855 

8.4 

I 856- I 860 

4-3 

1861-1870 

5.2 

1871-1880 

5.1 

1881-1890 

7-1 

1891-1895 

5-1 

1 896- 1 900 

3-7 

1901-1905 

5-5 

Besides  the  three  primary  biological  factors  of  natahty, 
mortahty  and  migration  which  influence  the  observed 
growth  of  human  populations  there  are  various  secondary 
environmental  factors  which  may  play  a  part  in  determining 
the  final  result.  These  are  such  things  as  food  supply, 
the  economic  situation  in  general  and  particular,  social 
forces  of  various  sorts,  and  perhaps  others.  But  it  should 
always  be  kept  in  mind  that  these  are  all  secondary  factors 
from  a  biological  point  of  view.  They  produce  whatever 


528  HUMAN   BIOLOGY 

eflect  they  may  have  upon  the  final  result,  namely  the  size 
of  the  population  at  any  given  moment,  by  acting,  more  or 
less  powerfully  as  the  case  may  be,  upon  one  or  more  of  the 
three  primary  biological  variables,  natahty,  mortality  and 
migration.  Thus  an  economic  depression  in  a  particular 
country  may  affect  adversely  the  birth  rate  of  that  country, 
or  even  the  death  rate  if  the  degree  of  the  depression  is 
sufficiently  great  or  its  duration  sufficiently  prolonged. 
These  effects  will,  in  greater  or  smaller  degree,  reflect 
themselves  finally  in  the  size  of  the  population.  This  final 
effect  upon  the  growth  of  the  population  may,  however, 
be  extremely  slight,  and  difficult  or  even  impossible  of 
separate  statistical  recognition  or  measurement,  because 
of  compensating  influences  at  work  at  the  same  time. 
Logically,  however,  the  operation  of  these  secondary  factors 
must  always  be  recognized.  But  from  the  point  of  view  of 
the  theory  of  population  growth  their  influence  is  always  a 
second  order  one.  They  can  produce  any  effects  upon 
population  only  by  operating  upon  the  primary  biological 
forces  of  natality,  mortality  and  migration. 

The  net  effect  of  the  two  important  variables,  natality  and 
mortality,  upon  population  may  be  studied  in  various  ways. 
One  of  the  most  illuminating  is  by  the  use  of  a  constant 
which  has  been  called  the  "vital  index"  of  a  population. 
It  has  this  form: 

,,.     ,  .    ,  Births  X  100 

Vital  index  =        t^ ^f 

Ueatris 

The  vital  index  gives  an  accurate  picture  of  the  net 
biological  status  of  a  population  as  a  whole  at  the  moment  of 
its  calculation.  If  the  ratio  100  births:  deaths  is  greater  than 
100  the  population  if  growing  naturally,  and  is  in  so  far 
biologically  healthy.  If  the  ratio  is  less  than  100  the  popula- 
tion is  not  exhibiting  natural  growth,  however  sound  it 
may  be  in  other  respects.  There  may  be  a  sufficient  amount 
of  immigration  to  compensate  the  deficiency  in  births, 
so  that  there  is  no  actual  depopulation.  But  the  condition  is 
fundamentally  unsound  biologically. 

The  vital  indices  of  the  population  of  the  United  States 
have  been  extensively  studied  by  the  writer  (1924,  Chaps. 


SOME    ASPECTS    OF   THE    BIOLOGY   OF    HUMAN    POPULATIONS    529 

III  and  ix).  Sweeney  has  made  an  interesting  and  com- 
prehensive examination  of  the  vital  indices  of  all  the  popula- 
tions of  the  world  for  which  records  of  births  and  deaths 
exist. 

Using  the  vital  index  as  a  measure  of  the  phenomena  we 
may  now  discuss  two  examples  of  autonomic  regulation 
in  a  human  population.  The  first  concerns  the  population  of 
England  and  Wales.  For  each  quarter  of  each  year  from 
1838  to  1920  inclusive  the  vital  index  of  the  population  was 
computed.  Grouping  the  data  in  five-year  periods  gives  the 
results  shown  in  Table  v. 


Table  v 
grouped  data  for  vital  index  and  crude  birth  rate  of  england  and 

WALES 


Period 

100  births 
deaths 

General  birth  rate 
per  10,000 

1 838- 1 839 

140.28 

310 

1840- I 844 

148.04 

322 

1 845-1 849 

13961 

326 

I 850- I 854 

151.69 

339 

1 855- 1 859 

15523 

343 

I 860- I 864 

157-30 

349 

1 865- 1 869 

157. II 

353 

I 870- I 874 

161.35 

355 

1 875-1 879 

167.69 

356 

I 880- I 884 

171. 81 

1                      338 

1885-1889 

1                  169.85 

1                      320 

I 890- I 894 

1                  161.48 

1                      305 

I 895- I 899 

1                 I 66 . 40 

1                      296 

I 900- I 904 

1                 171.25 

1                      285 

I 905- I 909 

1                 177-40 

1                      267 

1910-1914 

1                 175-09 

1                      242 

1915-1919 

1                 134-95 

1                      208 

1920- 

205.48 

255 

The  immediately  striking  feature  of  this  table  is  the 
general  smoothness  of  the  trend  of  the  values  of  the  vital 
index  as  one  runs  down  the  column.  In  order  to  appreciate 


530 


HUMAN   BIOLOGY 


this  fact  fully,  however,  it  is  necessary  to  resort  to  graphical 
presentation.  The  vital  index  and  birth  rate  data  from  Table 
V  are  shown  graphically  in  Figure  2. 


■ 

— 1 

1 

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360 


320 


280 


210 


200 


i60 


i20 


80 


40 


18^0  50     60     70     SO     90  1900   10     20 

Years 

Fig.   2.  Trend  of  vital   index   (lOO  births:  deaths)   and  crude  birth  rate  in 
England  and  Wales,    1838-1920,  inclusive. 

It  is  at  once  apparent  that  the  ratio  of  births  to  deaths  in 
England  and  Wales  had  but  a  slow  but  on  the  whole  even 
and  steady  tendency  to  increase  from   1838  to   19 14.  This 


SOME   ASPECTS   OF   THE   BIOLOGY   OF    HUMAN    POPULATIONS    53 1 

Steady  progress  was  interrupted  to  a  degree  sufficient  to 
be  apparent  upon  only  two  occasions  during  the  three 
quarters  of  a  century.  These  were  in  1847- 1849  ^^^  1890- 
1892.  These  fluctuations,  which  only  shghtly  aff"ected  the 
even  upward  trend  of  the  curve,  were  apparently  due  to 
the  influenza  pandemics  of  1847- 1848  and  1 890-1 891. 

The  broad  result  is  perfectly  clear  and  outstanding.  The 
population  of  England  and  Wales  is  today  exhibiting  a 
greater  purely  biological  survival  value  as  a  whole  population 
than  it  was  three-quarters  of  a  century  ago.  Whether  it  is  a 
mentally,  morally  or  anthropometrically  fitter  population 
does  not  now  concern  us.  We  are  dealing  here  solely  with  the 
fact  that,  taking  the  people  of  England  and  Wales  as  a 
whole,  slightly  over  two  babies  were  born  for  every  death 
per  year  in  1920,  as  against  1.4  babies  per  death  per  year  in 

1838-1839; 

Now  this  result  will  strike  any  one  informed  as  to  the 
sociological  and  eugenical  literature  of  the  last  two  decades 
as  curiously  at  variance  with  the  pessimistic  tenor  of  that 
literature,  taken* as  a  whole.  It  has  been  pronounced  from 
high  places  that  the  general  trend  of  British  people  was 
biologically  downwards,  that  they  were  in  fact  becoming 
a  decadent  race.  Abundant  quotations  in  support  of  this 
contention  could  be  cited,  were  space  available  and  were  it 
necessary.  This  gloomy  view  has  had  its  foundation  mainly 
upon  the  fact  that,  since  the  quinquennium  1875-1880, 
the  birth  rate  in  England  and  Wales  has  been  falling  rather 
rapidly,  as  is  clearly  shown  in  Figure  2.  This  fact  has  been 
studied  by  Miss  Elderton  in  great  detail. 

But  from  a  purely  numerical  viewpoint,  what  matters  a 
falling  birth  rate  if  the  death  rate  falls  even  more  rapidly, 
so  that  the  net  survivorship  at  any  instant  of  time  is  con- 
stantly getting  higher?  To  this  it  will,  of  course,  be  answered 
at  once  by  those  who  view  with  alarm  the  declining  birth  rate 
that  the  real  crux  of  the  matter  is  in  the  diff"erential  change  in 
fertility.  Nowadays  the  "best"  people  are  said  not  to  produce 
their  due  share  of  progeny,  while  the  "worse"  people  are 
alleged  to  overproduce.  In  the  American  population,  how- 
ever, the  writer  (1924  Chap,  viii)  has  shown  that  the  element 
perhaps  least  effectively  integrated  socially  with  the  rest  of 


532 


HUMAN   BIOLOGY 


the  population,  the  negro,  has  the  lowest  survival  value  as  a 
group  (vital  index  generally  less  than  lOo).  Measured  by 
this  same  test  the  population,  as  a  whole,  of  England  and 


1901    03    05    07     09     11      13     15     17     19     21     23    25 

Yec^rs 

Fig.  3.  Vital  index  (100  births:  deaths)  of  population  of  France  during  20th 

century. 

Wales  is  today  more  vigorous  than  it  was  in  1838.  This  is 
a  plain  fact.  Whether  this  fact  is,  sociologically  or  eugeni- 
cally  considered,  a  bad  thing  or  a  good  thing,  is  the  kind 
of  question  which,  as  has  already  been  pointed  out,  has 
no  place  in  an  objective,  quantitative  science  of  human 
group  biology. 

For  this,  our  present  point  of  view,  the  interesting  and 
important  feature  of  the  case  is  the  extraordinary  self- 
regulation  of  the  population  growth  during  this  long  period, 
by  intercorrelated  changes  in  birth  rates  and  death  rates. 
During  the  period  under  review  the  birth  rate  steadily  rose 


SOME   ASPECTS   OF   THE   BIOLOGY   OF   HUMAN    POPULATIONS    533 

for  more  than  thirty  years,  and  then  even  more  decisively 
fell.  But  the  concurrent  changes  in  the  death  rates  were  such 
that  no  sensible  alteration  in  the  general  trend  upward  of 
the  vital  index  was  produced  by  this  change  in  the  course 
of  the  birth  rate. 

The  second  example  of  the  self-regulation  of  human  pop- 
ulation size  is  afforded  by  the  vital  index  of  the  population 
of  France.  Figure  3  shows  a  plot  of  this  index  for  the  years 
1900  to  1926  inclusive.  The  abscissal  points  of  plotting 
are  taken  as  mid-year  points. 

What  the  diagram  shows  is  that  during  the  period  from 
1900  to  the  outbreak  of  the  World  War  in  1914  the  birth- 
death  ratio  in  France  had  maintained  a  level  somewhere 
between  100  and  no,  with  fluctuations  which  occasionally, 
brought  it  a  little  below  the  dead  line  of  survival  at  100 
per  cent.  With  the  onset  of  the  war  the  vital  index  fell  to 
unprecedentedly  low  values.  But  immediately  upon  the  cessa- 
tion of  hostilities  the  vital  index  rose  at  an  even  more  rapid 
rate  than  that  of  its  previous  fall,  reaching  in  1920  a  higher 
value  than  it  had  attained  at  any  time  during  the  century. 

Again  the  magnitude  and  speed  of  action  of  the  size- 
regulating  powers  of  a  human  population  are  strikingly 
demonstrated. 

THE  GROWTH  OF  HUMAN  POPULATIONS 

It  is  observed  that  the  growth  of  populations  of  the  most 
diverse  organisms  follows  a  regular  and  characteristic  course. 
The  population  at  first  grows  slowly,  but  gains  impetus 
as  it  grows,  passing  gradually  into  a  stage  of  rapid  growth, 
which  finally  reaches  a  maximum  of  rapidity.  After  this 
stage  of  most  rapid  growth  the  population  increases  ever 
more  and  more  slowly,  until  finally  there  is  no  perceptible 
growth  at  all.  In  short,  the  populations  of  various  forms 
of  life  first  wax  in  this  speed  of  growing  and  then  wane. 

The  equation  to  the  curve  which  has  been  found  by  exper- 
iment and  observation  to  be  descriptive  of  population 
growth  in  a  wide  variety  of  organisms  as  first  discovered  by 
the  Belgian  mathematician  Verhulst  in  1838.  His  pioneer 
work  was  forgotten,  and  consequently  overlooked  by  most 
subsequent  students  of  the  population  problem.  In  1920  th 


534 


HUMAN   BIOLOGY 


present  writer  and  his  colleague,  Lowell  J.  Reed,  without 
any  knowledge  of  Verhulst's  prior  work,  independently  hit 
upon  the  same  equation. 


1 
1 

Logistic 

Curve  and 

ITS    First   Derivative    Curve 
Asymptote 

> 

' 

/ 

K 

1 

o 

o 

TiMF                                                                1 

1                          b 

' 

Fig.  4.  Logistic  curve  and  its  first  derivative. 

Verhulst  called  his  curve  "logistic."  This  usage  we  shall 
follow.  The  characteristic  appearance,  and  some  of  the 
mathematical  properties  of  the  logistic  curve  are  shown  in 
Figure  4.  The  equation  to  the  simple  logistic  used  by  Verhulst 
is: 


y  = 


I  +e 


a-\-hx 


The   generahzed   logistic,   developed   by   the  writer  and 
Reed,  has  the  form 

k 


y 


J    _!_   pa<s  +  <iiX-'ratx'^-\-  ,  .  .Onx" 


SOME    ASPECTS    OF   THE   BIOLOGY   OF    HUMAN    POPULATIONS    535 


In  these  equations  y  denotes  population  size  and  x  denotes 
time. 

It  has   been   demonstrated  statistically  that  populations 


o 


/oo 


75 


50 


-J 


25 


United  States 

) 

t 

/ 

r 

/ 

A 

/ 

J 

-rn^ 

f 

1800   20     40     60     80   1900  20 

Year 

Fig.  5.  Observed  and  calculated  growth  of  population  of  United  States. 

of  human  beings  have  grown  according  to  the  logistic  curve, 
so  far  as  may  be  judged  from  the  available  census  records, 
in  at  least  the  following  countries:  Sweden,  United  States  of 
America,  France,  Austria,  Belgium,  Denmark,  England 
and  Wales,  Hungary,  Italy,  Norway,  Scotland,  Servia, 
Japan,  Java,  Phihppine  Islands,  Baltimore  City,  New  York 
City,  and  the  world  as  a  whole. 

In  illustration  of  this  statement  three  cases  are  presented 
graphically   here.   These   are   the   United   States    (Fig.   5), 


536 


HUMAN   BIOLOGY 


France  (Fig.  6),  and  the  world  as  a  whole  (Fig.  7).  In  these 
diagrams  the  circles  give  the  census  counts  (or,  in  the  case 
of  the   world    as   a   whole,   estimates)    of  the   populations 


5:: 


w 


30 


^    20 

I 

/o 


France 

J. 

/ 

/" 

^ 

^ 

f 

IQOO  25      50     75    1900 

Year 

Fig.  6.  Observed  and  calculated  growth  of  population  of  France. 

existing  at  the  given  dates,  while  the  smooth  curves  are  the 
fitted  theoretical  curves  of  population  growth. 

In  the  case  of  the  demographic  units  listed  above  the 
census  records  do  not  extend  over  a  sufficiently  long  time 


SOME   ASPECTS   OF   THE   BIOLOGY  OF   HUMAN    POPULATIONS    537 


to  make  the  case  conclusive  that  population  growth,  if 
undisturbed,  would  follow  in  human  groups  the  complete 
course  of  one  cycle  of  a  logistic  curve.  The  available  data 


JGOO 

:d  12.00 


s? 

World               ^ 

s 

^ 

/ 

^ 

/ 

A 

f 

^ 

0- 

r" 

^  woo 

g    800 

^  eoo 

^  400 
200 


1750    75     ISOO    25      50      75     1900 

Year 

Fig.  7.  Observed  and  calculated  growth  of  population  of  world. 

only  make  such  a  conclusion  in  some  degree  probable.  And 
one  cannot  conduct  experiments  with  human  beings  on 
this  point,  as  can  be  done  with  lower  organisms.  But  for- 
tunately it  has  been  possible  to  find  one  group  of  human 
beings,  the  indigenous  population  of  Algeria,  in  which  a 
cycle  of  population  growth  has  been  practically  completed 
during  the  period  for  which  census  records  are  available. 


538 


HUMAN   BIOLOGY 


these  having  been  carefully  made  by  the  French.  In  this 
case  the  human  population  followed  in  its  whole  cycle  of 
growth  a  simple  logistic  curve.  This  case  has  been  fully 


1^ 


■< 

Q 


UPPER     ASyMPTOT£  =    S.379 

>- 

^ 

f 

^ 

5 

C 

^1 

)T£  = 

< 
3 

< 

4 

►         i 

— ^n 

» 

■MPTC 

1856    le&l     1866    1871     1876    1381      1886     1891     1896    1901     1906     1911      1916      1921     I9JZ6    193/ 

YEAR 

Fig.  8.  Observed  and  calculated  growth  of  indigenous  native  population  of 

Algeria. 

described  and  analyzed  in  the  writer's  book  "The  Biology 
of  Population  Growth"  and  is  illustrated  here  in  Figure  8. 

The  logistic  curve,  which  is  found  by  actual  experience 
to  describe  accurately  the  course  of  population  growth  in  a 
wide  variety  of  organisms,  constitutes  a  valuable  first  step, 
but  only  a  first  step,  towards  reaching  an  understanding 
of  the  biology  of  the  process.  What  we  want  to  know  is  how 
the  biological  forces  of  natality  and  mortality  are  so  inte- 
grated and  correlated  in  their  action  as  to  lead  to  a  final 
result  in  size  of  population  which  follows  this  particular 
curve    rather    than    some    other    one. 

In  the  laboratory  a  series  of  investigations,  experimental 
mathematical,  and  statistical,  has  been  carried  out  for  the 
purpose  of  throwing  light  on  the  problem.  Limitations  of 
space  make  it  impossible  to  do  more  here  than  give  a  brief 
resume  of  the  results  to  date.  A  full  account  of  these  investi- 
gations is  given,  however,  in  certain  of  the  references  listed 


SOME    ASPECTS    OF   THE   BIOLOGY    OF    HUMAN    POPULATIONS    539 

at  the  end  of  this  chapter  Pearl,  1925,  19276  and  other 
papers  cited  in  the  sources  referred  to. 

In  brief  what  is  found  is  that  both  of  the  fundamental 
first-order  population  variables,  natahty  and  mortahty, 
are  directly  and  markedly  influenced  by  density  of  popula- 
tion above  a  certain  magnitude.  The  sense  of  this  influence 
is  that  fecundity  rates  are  markedly  lowered  by  small 
increases  in  density  at  relatively  low  densities,  while  after  a 
certain  density  is  passed  further  increases  produce  only 
shght  decreases  in  birth  rates  down  to  an  asymptotic  limit; 
and,  second,  that  death  rates  are  insignificantly  aff"ected  by 
increasing  density  at  relatively  low  densities,  while  after  a 
certain  density  is  passed  death  rates  markedly  increase 
with  increasing  density  up  to  an  asympototic  limit. 

In  short  it  is  possible  to  account  for  all  the  main  features 
of  the  growth  of  experimental  populations  of  the  fruit-fly, 
by  a  simple  hypothesis  as  to  the  correlated  behavior  of 
three  variables,  natality  mortahty,  and  density.  There  is 
some  evidence  that  the  situation  is  similar  in  human  popula- 
tions, in  its  fundamental  biology,  although  there  the  influence 
of  other  second-order  variables  comphcates  the  situation. 

THE     COMPOSITION    OF     POPULATIONS    AND    DIFFERENTIAL 

FERTILITY 

The  total  size  of  a  population  is  of  course  only  one  of  its 
attributes.  There  are  others  of  great  biological  interest, 
notably  the  composition  of  a  population  in  respect  of 
diff"erent  kinds  of  individuals.  All  societies,  whether  of  ants 
or  men,  tend  to  difl^erentiate  into  castes,  each  performing 
a  different  function  in  the  whole  integrated  group.  Wheeler 
has  particularly  discussed  this  phenomenon. 

The  writer  has  recently  studied  one  aspect  of  this  matter  in 
the  population  of  the  United  States  (1927a).  In  a  recent 
report  on  natahty  from  the  United  States  Census  Bureau 
(Birth  Statistics,  1924)  there  is  a  table  (numbered  10,  pp. 
1 71-18 1)  which  makes  available  some  new  and  welcome  data 
regarding  difl"erential  fertihty  in  this  country. 

The  data  apply  to  the  United  States  birth  registration 
area  exclusive  of  Delaware,  Maine,  Massachusetts,  New 
Hampshire,  Rhode  Island  and  Indiana. 


540  HUMAN   BIOLOGY 

The  original  table  provides  the  following  information: 
The  births,  number  of  children  born,  and  living,  and  average 
number  born  and  hving  to  mothers  of  1923,  by  occupation 
and  age  of  father  The  occupations  of  the  fathers  are  grouped 
into  the  following  main  classes,  with  a  number  of  smaller 
subdivisions  in  each  main  class: 

1.  Agriculture,  forestry,  and  animal  husbandry. 

2.  Extraction  of  minerals. 

3.  Manufacturing  and  mechanical  industries. 

4.  Transportation. 

5.  Trade. 

6.  Pubhc  service  (not  elsewhere  classified). 

7.  Professional  service. 

8.  Domestic  and  personal  service. 

9.  Clerical  positions. 

When  one  considers  carefully  the  subdivisions  under 
these  nine  main  heads  the  usual  difficulty  with  official  vital 
statistics  is  at  once  encountered.  Economically  and  socially 
differentiated  groups  are  included  in  some  particular  general 
class  from  the  remainder  of  which  they  are,  in  these  respects, 
sharply  set  apart,  in  reality.  But  it  is  reasonably  obvious 
that  economic  and  social  factors  and  forces  are  among  the 
most  important  elements  in  determining  the  biologically 
significant  environment  of  human  beings,  as  they  exist 
here  and  now.  Relative  wealth  virtually  determines  the 
character  of  the  immediate  physical  environment  in  which 
men  live.  Furthermore,  economic  and  social  position  are 
significantly  correlated  with  the  amount  of  physical  labor 
which  individuals  perform,  and  this  has  been  shown  (Pearl, 
1924,  Chap,  xi)  to  be  biologically  important. 

In  view  of  these  considerations  it  was  deemed  necessary 
to  reconstitute  the  main  occupational  classes,  as  given  in 
the  original  document  cited,  so  that  they  might  conform  at 
least  somewhat  more  closely  to  significant  reality.  The 
general  plan  followed  in  this  reconstitution  of  the  classes 
has  been  described  in  detail  (Pearl,  1927a)  and  need  not 
be  repeated  here.  The  net  upshot  of  the  manipulation  is  to 
leave  all  the  main  occupational  classes  except  7  (professional 
service)  composed  chiefly  of  laborers,  more  or  less  skilled, 
but    still    persons    whose    living   depends    upon    the    daily 


SOME   ASPECTS    OF  THE   BIOLOGY   OF    HUMAN    POPULATIONS    54 1 

performance  of  more  or  less  routine  tasks,  in  contrast  to 
the  persons  composing  the  reconstituted  class  7,  who,  in  the 
large,  get  their  Hving  rather  more  by  the  exercise  of  their 
wits  than  of  their  muscles. 

In  order  that  there  may  be  no  misunderstanding  the 
names  of  the  main  occupational  classes  which  have  been 
altered  by  the  described  procedure  will  be  printed  in  italic 
type  throughout.  This  typographical  usage  will  serve  to 
indicate  that  the  statistics  so  printed  are  for  the  reconstituted 
classes,  and  not  for  the  classes  originally  so  named  in  the 
official  report. 

The  next  and  final  point  of  method  to  be  considered 
before  coming  to  the  results  is  that  of  age.  The  ideal  in 
all  studies  of  fertihty  is,  of  course,  the  completed  family. 
In  the  present  case  this  ideal  cannot  be  precisely  attained 
from  the  available  data.  General  consideration  of  the 
problem,  and  careful  examination  of  all  the  figures  them- 
selves as  given  in  the  original  report,  led  finally  to  the 
decision  to  deal  analytically  with  the  data  for  fathers  aged 
forty-five  and  over.  This  procedure  will  probably  give  as 
close  an  approximation  as  it  is  possible  to  get,  from  these 
or  similar  records  extracted  from  the  official  standard 
birth  certificate  of  the  United  States,  to  the  unknown 
average  size  of  completed  family  for  the  different  occupational 
classes. 

Table  vi  represents  the  first  set  of  basic  data  which  we 
shall  need  in  the  discussion. 

Before  discussing  at  all  the  results  of  this  table,  it  is 
necessary  to  consider  some  of  the  important  peculiarities 
of  the  data.  In  the  first  place,  if  the  figures  of  column  d 
could  be  regarded  as  representing  exclusively  completed 
famihes,  which  they  almost  but  not  quite  can,  they  would 
still  give  an  erroneous  impression  of  the  gross  fertility  of  the 
several  occupational  classes,  for  the  following  simple  reason. 
All  the  data  in  the  table  are  derived  from  the  experience  of 
women  who  were  mothers  in  1923.  That  is  to  say,  they 
were  women  who  were  fertile  in  that  particular  year.  No 
other  women  are  included.  No  sterile  matings  appear, 
and  no  matings  of  generally  low  fertility  throughout  the 
mated  Hfe,  except  the  few  in  which  the  female  chanced  to 


542 


HUMAN   BIOLOGY 


Table  vi 

children  born  to  mothers  of  i923,  by  fathers  aged  forty-five  years  or 
over,  by  occupation  of  father,  in  reconstituted  general  classes 

or    OCCUPATIONS 


Occupation  of  Father 


en 


O 

H 
(a) 


1 

^ 

1 

^ 

►T! 

-C 

JS 

u 

U 

u 

0 

<4-l 

e*H 

<4-l 

i« 

0 

mber  c 
living 

0 

0 

0 

mber 
r  born 

mber 
r  born 

number 
iving 

3  0 
C  > 

^S 

^> 

^S 

<u 

CJ 

>— . 

-o 

Total 
dren 

Total 
child 

Mean 
dren 

Mear 
dren 

Mean 
dren 

(b) 

(c) 

(d) 

(e) 

(0 : 

c 

11 

IS 


c 
u 


(g) 


Agriculture,  forestry  and  ani- 
mal husbandry 

Extraction  of  minerals 

Manufacturing  and  mechanical 
industries 

Transportation 

Trade 

Public  service 

Professional  service 

Domestic  and  personal  service. 

Clerical  occupations 

Totals 


41,825  289,1401  251,833 
4,117    32,677     26,6og 


i7g,6oi 
22,gg7 
30,38g 

4,374 
21,672 
10,799 

6,296 


100,946 


32,875 

2i6,gg6 

4,480 

27,002 

6,771 

34,885 

949 

5,i8g 

5,828 

24,386 

2,424 

12,820 

1,677 

7,149 

650,244 


6.91  6.02 

7.g4  6.46 


60  5.46 
03  5.13 


15 
47 
18 
29 
26 


554,570 


4-49 
4.61 
3.72 
4.46 
3-75 


0.89 

1.48 

1 .  14 
o.go 
0.66 
0.86 
0.46 
0.83 
0.51 


6.445.490.91  54.8 

I    I 


12.9 
18.6 


17.3 
14-9 
12.8 
15.7 
II  .0 
15.7 
12.0 


have  a  baby  in  1923.  That  there  are  very  few  of  such  low 
fertlHty  matings  included  is  evident  if  it  is  recalled  that  we 
here  are  deahng  only  with  famihes  in  which  the  father  was 
forty-five  years  of  age  or  over  in  1923.  In  general  the  vast 
bulk  of  men  who  engender  a  baby  when  they  are  forty-five 
years  old,  or  over  that  age,  are  probably  persons  whose  whole 
marital  history  has  been  characterized  by  relatively  high 
fertihty,  as  compared  with  the  rest  of  their  same  social  class. 
The  net  result  is  that  the  values  in  columns  d  and  e  of 
Table  iv  somewhat  exaggerate  the  true  average  fertihty 
of  the  whole  population  of  the  same  age  in  the  various 
occupational  classes.  The  figures  represent  the  average 
size  of  family  of  a  selected  sample  only  of  the  total  popula- 
tion in  each  class,  the  basis  of  the  selection  being  high  and 
probably  historically  continued  fertility.  This  means  that,  in 
the  best  case,  we  can  only  discuss  from  these  data  relative 
and  not  absolute  fertihty  values.  But  there  seems  no  reason 


SOME   ASPECTS    OF   THE    BIOLOGY    OF    HUMAN    POPULATIONS    543 


to  suppose  that  the  relative  fertihties  of  the  most  fertile  por- 
tions of  the  populations  in  the  several  main  occupational 
classes,  as  given  by  these  data,  are  not  safely  comparable. 


Public  Service 


Manufacturing 
Agriculture 


Extraction  of  Minerals 
J I I I I I I I      ' 


0    0J2  0.4  0.6  0.8  1.0  iJi   lA  1.6   1.8  ;i.o 
Relative  Size  of  Family 

Fig.  9.  Bar  diagram  showing  relative  average  size  of  family  experienced  by 
mothers  of  1923  in  their  reproductive  lives  up  to  that  date,  according  to 
occupation  of  fathers  who  were,  in  1923,  forty-five  years  of  age  or  over. 

The  only  essential  difficulty  with  the  figures  is  that  the  uni- 
verse of  discourse  which  they  encompass  is  a  definitely 
limited  one,  and  we  cannot  safely  generalize  beyond  these 
bounds. 


544 


HUMAN   BIOLOGY 


In  the  portion  of  the  population  here  under  discussion,  the 
figures  show  that  when  the  average  size  of  family  produced 
by  a  mother  of  1923  in  her  total  reproductive  hfe  up  to 


12 


10 


a 


0 


# 


In 

I 

Q: 


4- 


\ 


\ 


\ 


;/ 


Profess-  Clerical  Trade  Dom-  Public  Transpor-Manufact-Agri-  Mining 
ional  estic  tation     uring  culture 

Fig.  10.  Relative  population  and  fertility  by  occupational  classes. 


that  time,  by  a  father  who  fell  in  the  Professional  class  and 
was  forty-five  years  of  age  or  over  in  1923,  is  taken  as  i.o, 
the  average  size  of  family  reproduced  from  mothers  of  1923 
by  fathers  who  fell  in  the  occupational  class  Extraction  oj 
minerals,  and  similarly  aged  torty-five  years  or  over  in  1923, 

was  1.9. 

The  professional,  capitalistic  group  exhibits  the  lowest 
average  size  of  family,  and  the  labor  groups,  whether  in 
factories,  farms  or  mines,  the  highest.  The  facts  are  shown 
graphically  in  Figure  9. 

Let  us  now  examine  the  relation  between  fertility,  the 
number  ot  more  fertile  families,  and  the  total  population 
of  occupied  males,  in  the  several  reconstituted  occupational 
classes.  This  is  done  graphically  in  Figure  10,  on  the  basis 


SOME    ASPECTS    OF   THE   BIOLOGY   OF    HUMAN    POPULATIONS    545 

that  for  each  of  these  variables  the  condition  in  the  Pro- 
fessional class  is  taken  as  i  .0. 

Broadly  what  Figure  10  shows  is  that: 

I.  For  each  male  forty-five  years  or  over  in  the  class 
Projessional  service  in  1920,  there  was  0.34  of  a  male  of 
corresponding  age  in  Clerical  occupations;  1.60  in  Trade; 
0.47  in  Domestic  and  personal  service;  0.23  in  Public  service; 
and  0,79  in  Transportation.  In  these  six  occupational  classes 
more  fertile  families,  as  defined  above,  occurred  in  about 
the  same  proportions  relative  to  the  Projessional  service 
class  taken  as  i.oo  in  both  instances,  as  the  dash  hne  of 
Figure  10  shows.  This  means  that  in  these  six  occupational 
groups  more  fertile  famihes  are  represented  in  about  the 
same  relative  proportions  to  each  other,  as  occupied  males 
of  corresponding  age  in  the  classes  as  a  whole.  This  is  only 
approximately  true,  because  the  population  figures  are 
for  1920,  and  those  for  more  fertile  famihes  are  for  1923. 
But  the  general  consonance  of  the  relative  figures  for  the 
six  classes  named  will  probably  not  be  significantly  disturbed 
by  this  consideration. 

2.  For  every  male  forty-five  or  over  engaged  in  Pro- 
fessional service  in  1920,  there  were  3.22  workers  of  cor- 
responding age  in  Manufacturing  and  mechanical  industries; 
3.04  in  Agriculture;  and  0.27  in  Extraction  of  minerals. 
But  for  every  more  fertile  family,  as  here  defined,  in  the 
Projessional  service  class,  there  were  5.64  such  famihes  in  the 
Manufacturing  class;  7.18  in  the  Agriculture  class;  and  0.71 
in  the  Extraction  oj  minerals  class.  What  these  results 
mean  is  that  famihes  of  more  than  average  total  fertihty 
occurred  in  these  three  classes,  in  proportion  to  the  male 
population  of  corresponding  age,  taking  the  Projessional 
class  as  i.oo,  from  two  to  three  times  as  often  as  they  did 
in  any  of  the  six  occupational  classes  discussed  above. 

3.  The  relative  total  number  of  children  ever  born,  up  to 
and  including  1923,  in  the  more  fertile  famihes  is  not  widely 
different  from  the  proportion,  always  relative  to  the  Pro- 
jessional group  as  I.oo,  in  which  the  several  occupations 
are  represented  in  the  general  male  population,  so  far  as 
concerns  the  first  six  occupations.  This  means  that  in  these 
six  occupations  the  total  fertihty  up  to  1923,  in  the  more 


546 


HUMAN   BIOLOGY 


fertile  group  with  which  we  are  deahng,  was  nearly  in  simple 
proportion  to  the  size  of  the  groups  themselves,  having 
regard  to  age,  and  when  the  Professional  service  group  is 


40 


■45 
40 
3S 
30 
Z5 
ZO 
15 
10 
5 


I  Population        \^More -fertile  Families  ||  Children 


ill     B-^     it] 


Professional  Clerical         Trade      Domestic      Public    Transporiat'ion  Manufacture  Agriculture  Mining 
Fig.  1 1.  Graph  of  the  three  percentage  columns  of  Table  vii. 

taken  as  i.oo  in  each  instance.  But  in  the  three  occupational 
classes  Manufacturing,  Agriculture,  and  Mining  the  case 
is  quite  different.  Whereas  there  were  3.22  times  as  many 
males  aged  forty-five  and  over  in  the  Manufacturing  class 
in  1920  as  in  the  Professional  class,  the  females  mated  to 
males  in  the  Manufacturing  class  had  produced,  up  to  and 
including  1923,  8.9  times  as  many  children  as  had  the 
females  mating  to  the  corresponding  portion  of  the  males  in 
the  Professional  class,  in  the  same  period.  In  1920  there 
were  3.04  times  as  many  males  forty-five  years  of  age  and 
over  in  the  Agriculture  class  as  they  were  in  the  Professional. 
But  the  total  production  of  children  up  to  and  including  1923, 
by  the  more  fertile  moieties  in  the  classes,  had  been  11.86 
times  as  great  in  the  Agriculture  class  as  it  had  been  in  the 
Professional.  In  the  Extraction  of  minerals  class  there  were 
only  0.27  as  many  males  forty-five  years  of  age  and  over  as 
there  were  in  the  Professional  class.  But  the  production  of 
children  up  to  1923  had  been  1.34  times  as  great  in  the 
former  class  as  in  the  latter. 

So  far  we  have  considered  the  populations,  more  fertile 
families,  and  total  children  ever  born,  of  th^  several 
occupational  classes,  only  in  relation  to  the  Professional 
group  taken  as  i.oo.  This  procedure  gives  a  correct  picture 
of  the  situation  so  far  as  strictly  interclass  comparisons  of 


SOME   ASPECTS    OF   THE    BIOLOGY    OF    HUMAN    POPULATIONS    547 


the  unit  elements  are  concerned.  But  it  does  not  permit 
entirely  correct  conclusions  to  be  drawn  in  respect  of  the 
important  question  as  to  the  proportionate  contribution  of 
each  occupational  group  to  the  total  population  of  the  next 
generation. 

The   figures  necessary   to  permit  the  discussion  of  this 
point  are  given  in  Table  vii,  and  are  shown  graphically  in 


Figure  1 1 


Table  vii 
fertility  of  the  occupational  groups  relative  to  the  total 

population 


Occupational  class  (Reconstituted) 


Per  cent 

in  each 

class  in 

1920  of 

males  45 

and  over 


(a) 


Per  cent 
of  more- 
fertile 
families  in 
1923 


(b) 


Professional  service 

Clerical  occupations 

Trade 

Domestic  and  personal  service . 
Public  service 


Transportation 

Manufacturing  and  mechanical  industries. 
Agriculture,    forestry,    and    animal    hus- 


bandry. 


Extraction  of  minerals. 


Totals. 


9 

66 

3 

33 

9 

69 

4 

59 

2 

19 

7 

43 

31 

13 

29 

•39 

2 

1 

■S9 

100 

00 

S-77 
1.66 
6.71 
2.40 
0.94 
4.44 
32.57 

41-43 
4.0^ 


100.00 


Per  cent 

of  total 

children 

ever  born 

to  families 

in  column 

(b) 

(c) 


5 
1 

5 
I 

o 

4 
33 

44 
5 


75 
10 
56 

97 
So 

15 

37 

47 
05 


100.00 


While  the  general  trend  of  Figure  1 1  is  similar  to  that  of 
Figure  lo,  as  it  is  in  fact  bound  to  be,  Figure  ii  brings  out 
an  additional  bit  of  information  that  is  not  shown  by  Figure 
10.  What  Figure  ii  shows  is  that  in  the  first  six  occupa- 
tional groups  {Professional,  Clerical,  Trade,  Domestic, 
Public,  and  Transportation)  the  more  fertile  famihes  in  each 
group  form  a  smaller  percentage  of  the  total  number  of 
more  fertile  famihes  than  the  males  forty-five  years  of  age 
and  over,  in  that  same  group  do,  of  the  total  number  of 


548  HUMAN   BIOLOGY 

occupied  males  of  the  same  ages.  The  single  cross-hatched 
column  is  shorter,  in  every  one  of  these  first  occupational 
groups,  than  is  the  solid  column.  Similarly  in  these  same  six 
occupational  groups  the  number  of  children  ever  born  in 
each  group  forms  a  still  smaller  percentage  of  the  total 
number  of  children,  than  do  either  the  males  forty-five 
years  and  over  or  the  more  fertile  families  in  each  group  of 
their  respective  columns.  The  double  cross-hatched  columns 
in  these  six  occupational  classes  are  shorter  than  either  the 
solid  or  the  single-hatched  columns.  These  results  mean  that 
the  men  aged  forty-five  and  over  in  these  occupational 
classes  have  not  contributed  to  the  next  generation  in  as  high 
a  proportion  as  their  own  representation  in  this  generation. 

The  case  is  quite  difi"erent  for  the  last  three  occupational 
groups  {Manufacturing,  Agriculture,  and  Extraction  of 
minerals).  In  these  three  groups  the  percentage  of  children 
ever  born,  and  the  percentage  of  more  fertile  families  is 
higher  than  the  percentage  of  males  forty-five  years  of  age 
and  over  in  the  total  population  of  occupied  males.  In  each 
of  these  three  occupational  groups  the  double  cross-hatched 
column  is  taller  than  the  single  cross-hatched  columns, 
which  in  turn  is  taller  than  the  solid  column.  The  men  aged 
forty-five  and  over  in  these  three  occupational  classes  have 
contributed  to  the  next  generation  more  than  their  own 
proportionate  representation  in  this  generation.  The  excess 
contribution  is  particularly  marked  in  the  case  of  the 
farmers. 

Summing  the  whole  case  up  it  appears  that  the  great 
laboring  groups.  Manufacturing,  Agriculture  and  Mining, 
not  only  have  a  higher  proportion  of  more  fertile  famihes  per 
unit  of  population  so  occupied,  than  do  the  other  occupa- 
tional! groups,  but  also  they  have  a  much  larger  average 
number  of  children  per  family.  Put  in  another  way  it  comes 
to  this;  In  our  population  it  appears  that  the  Professional, 
Clerical,  Trade,  Domestic  and  personal  service.  Public 
service,  and  Transportation  occupational  classes  are  reproduc- 
ing themselves  in  such  a  manner  as  not  to  maintain  in  quite 
its  present  status  their  relative  representation  in  the  popula- 
tion. But  the  heavy  laboring  classes.  Manufacturing, 
Agriculture,    and   Mining,   are   reproducing   themselves   in 


SOME  ASPECTS  OF  THE  BIOLOGY  OF  HUMAN  POPULATIONS  549 

excess  of  their  representation  in  the  population.  From  this 
excess  must  necessarily  be  supplied  the  deficiencies  in  the 
first  six  classes  in  the  next  generation,  if  these  classes  are 
to  maintain  about  the  same  representation  in  the  total 
population  that  they  exhibit  in  the  present  generation. 

In  a  theoretically  ideal  social  organization  there  would 
presumably  be  a  constant  relative  number  of  persons 
engaged  in  each  of  the  numerous  differentiated  occupations, 
which  when  integrated  together  are  essential  to  the  well- 
being  and  survival  of  the  society  as  a  whole.  There  is  theoreti- 
cally a  fixed  proportion  of  teachers,  lawyers,  store-keepers, 
laborers,  soldiers  and  so  on,  necessary  to  the  most  economic 
functioning  of  the  whole  social  organism.  But  in  actual 
human  societies  there  is  no  extraneous  autocratic  determina- 
tion of  these  occupational  classes.  Instead  the  actual  existing 
number  is  determined  by  a  process  of  natural  selection, 
in  which  processes  economic  factors  are  probably  the  most 
important  element. 

But  another  factor  comes  also  into  the  case.  The  human 
units  wear  out  faster  in  some  occupations  than  in  others, 
and  therefore  need  to  be  replaced  faster.  Also  this  is  not 
only  an  industrial  country,  but  a  country  in  which  the 
increase  of  prosperity  and  well-being  is  apparently  almost 
solely  dependent  now,  has  been  for  some  time  in  the  past, 
and  presumably  will  be  for  some  time  in  the  future,  upon 
the  continued  growth  of  industry. 

In  order  to  permit  the  population  to  increase  roughly 
two  and  a  half  times,  and  enjoy  the  standards  of  living 
which  prevail  at  the  present  time,  it  has  been  necessary  to 
increase  coal  and  pig  iron  production  from  50  to  70  times,  the 
cotton  production  20  times,  the  railway  mileage  3000  fold, 
and  so  on.  It  is  only  because  the  organization  of  industrial 
processes,  inventions,  and  scientific  discoveries  have  made 
possible  the  growth  of  industry  of  all  sorts  at  the  rates 
indicated  that  human  beings  have  been  able  to  enjoy  the 
standard  of  living  that  they  have  and  do,  and  at  the  same 
time  permit  the  population  to  grow  as  it  has. 

These  facts  suggest  further  that  all  along  there  has 
had  to  be  an  increasing  production  of  laborers,  skilled 
and    unskilled,    in    the    manufacturing     and     mechanical 


550  HUMAN    BIOLOGY 

industries.   Machinery  alone  does   not   make  a  profitable 
factory.  There  must  be  workmen  to  run  the  machines. 

It  is  possible  that  the  findings  regarding  fertihty  in  this 
country  are  not  widely  divergent  from  what  theoretically 
ought  to  be  if  our  society  is  to  continue  in  general  prosperity 
and  well-being,  and  continue  to  grow  in  these  respects.  In 
short  do  we  not  need  to  have  laborers  reproduce  faster  than 
the  first  six  occupations  on  our  Hst,  in  order  first  to  take  up 
the  greater  human  wastage  in  the  laboring  classes,  and  second 
to  permit  of  continued  industrial  growth  and  prosperity? 
Possibly  a  sound  economic  structure  of  the  country  as  a 
whole  is  in  a  very  real  and  considerable  sense  dependent 
upon  just  this  relationship. 

The  facts  set  forth  in  Table  vii  plainly  mean  that  some  part 
of  the  next  generation's  supply  of  professors,  doctors, 
lawyers,  bankers,  railroad  presidents,  and  the  like,  will  have 
to  be  recruited  among  the  sons  of  the  farmers  and  factory 
laborers  of  this  generation.  But  what  of  it?  Just  precisely 
this  relationship  has  always  been  true  so  far  in  the  history 
of  the  world  and  probably  will  be  for  a  long  time  to  come.  And 
furthermore  from  just  the  same  sources  will  have  to  be 
recruited  some  of  the  clerks,  typists,  small  tradesmen, 
job-holders,  brakemen,  motormen  and  various  other  citizens. 

In  the  United  States  the  agricultural  group  has  for  a 
long  time  produced  far  more  than  enough  children  to  main- 
tain its  own  industry.  These  farm  boys  have  contributed  in 
no  small  measure  to  the  highest  intellectual,  social,  and 
economic  classes  of  our  population.  In  fact  the  agricultural 
class  has  demonstrated  an  especial  fitness  to  contribute 
sound  stock  to  other  occupational  classes.  It  is  possible 
that  time  will  show  that  the  industrial  class  in  our  large 
cities  is,  in  already  measurable  and  probably  increasing 
degree,  doing  the  same  thing. 

The  falling  birth  rate  and  death  rate  and  the  type  of 
occupational  differential  fertility  discussed  here  may  perhaps 
be  regarded  as  adaptive  regulatory  responses,  that  is  biolog- 
ical responses,  to  alterations  in  the  environment  in  which 
human  society  lives.  In  this  environment  the  economic 
element  is  perhaps  the  most  significant  biologically. 


SOME   ASPECTS    OF   THE   BIOLOGY  OF    HUMAN    POPULATIONS    55 1 

Additional  evidence  relevant  to  this  discussion  is  afforded 
by  an  examination  of  the  immigration  statistics.  In  the  year 
ending  June  30,  1926,  the  net  immigration  (immigrants 
minus  emigrants)  of  persons  who  had  some  occupation 
amounted  to  133,752  persons.  This  figure  is  arrived  at 
after  deducting  from  the  total  net  immigration  93,744  net 
immigrant  persons  of  "no  occupation,"  who  were  chiefly 
women  and  children. 

Among  the  133,725  immigrants  having  an  occupation  the 
percentage  distribution  was  as  follows: 

Percentage  oj  total  net  irnmigrajits 
Occupational  class  having  an  occupation 

Professional 6.8 

Clerical 1 1 . 9 

Agriculture iQ-  i  1 

Skilled  laborers  (chiefly  manufacturing)   23.3  |-  50.2 

Laborers 7-8j 

Servants 19.5 

Fifty  per  cent  of  the  net  immigration  falls  in  the  three 
occupational  classes  at  the  extreme  right-hand  end  of  Figures 
10  and  II.  These  classes  not  only  have  the  greatest  fertility 
but  they  are  the  classes  into  which  immigration  is  most 
heavily  attracted.  All  this  is  a  part  of  the  picture  of  a  pre- 
dominantly industrial  type  of  social  organization.  It  needs 
all  the  time  more  and  more  workers  if  it  is  to  continue  to 
maintain  or  increase  the  average  standard  of  living  of  its 
inevitably  growing  population. 

CONCLUSION 

In  this  chapter  I  have  attempted  to  discuss  a  few  of  the 
many  biological  problems  presented  by  human  population 
from  the  viewpoint  of  objective,  quantitative  science.  Some 
of  the  points  discussed  are  the  subject  of  major  controversy 
from  the  sociological  and  humanitarian  viewpoints.  But  with 
such  controversies  human  biology,  if  it  expects  to  be  regarded 
as  a  science,  can  have  no  concern.  Its  primary  objective 
must  be  to  describe  the  phenomena  accurately  and  in 
quantitative  terms,  and  not  to  attempt  to  justify  them,  or 
deplore  them,  or  get  alarmed  about  them,  or  have  any 
emotional  reactions  about  them  whatever.  Perhaps  when  a 
clear,    comprehensive    and    precise    understanding    of   the 


552  HUMAN    BIOLOGY 

phenomena  of  human  group  biology  has  been  achieved 
man  can  do  something  effective  about  purposefully  altering 
some  of  its  elements,  if  he  then  still  desires  to  do  so. 

REFERENCES 

Carr-Saunders,  a.  M.  1922.  The  Population  Problem.  Oxford,  Clarendon 

Press. 
Dublin,  L.  I.   (Ed.)    1926.  Population  Problems  in  the  United  States  and 

Canada.  Boston,  Houghton  Mifflin. 
East,  E.  M.  1923.  Mankind  at  the  Crossroads.  N.  Y.,  Scribners. 

1927.  Heredity  and  Human  Affairs.  N.  Y.,  Scribners. 
Farr,  W.   1885.  Vital  Statistics:  A  Memorial  Volume  of  Selection  from  the 

Reports  and  Writings  of  William  Farr,  m.d.,  d.c.l.,  c.b.,  f.r.s.  Ed.  by 

Noel  A.  Humphreys.  Lond. 
Lotka,  a.  J.  1925.  Elements  of  Physical  Biology.  Bait.,  WiUiams  and  Wilkins. 
Malthus,  T.  R.  Essay  on  the  Principle  of  Population  as  it  Affects  the  Future 

Improvement  of  Society.   (The   Everyman  Library  edition,  which  is  a 

reprint  of  the  seventh  edition  of  the  original  work,  is  perhaps  the  most 

easily  available.) 
Pearl,   R.    1924.  Studies  in  Human  Biology.  Bait.,  Williams  and  Wilkins. 
1925.  The  Biology  of  Population  Growth.  N.  Y.,  Knopf. 
1927  (a).  Differential  fertility.  Quart.  Rev.  Biol.  2:  102-118. 
1927  (6).  The  growth  of  populations.  Ibid.,  pp.  532-548. 
Rivers,  W.  H.  R.   (Ed.)    1922.  Essays  on  the  Depopulation  of  Melanesia. 

Cambridge  Univ.  Press. 
Sweeney,  J.  S.  1926.  The  Natural  Increase  of  Mankind.  Bait.,  Williams  and 

Wilkins. 
Yule,  G.  U.  1925.  The  growth  of  population  and  the  factors  which  control 

it.  J.  Roy.  Stat.  Soc,  88:  1-58. 


Paul  B.  Hoeber,  Inc.,  76  Fifth  Avenue,  New  York 


Chapter  XXIII 

THE  MINGLING  OF  RACES 

Charles  B.  Davenport 

RACES  are  groups  of  individuals  within  a  species  which 
differ  by  one  or  more  well-marked  characters.  Thus, 
in  the  human  species,  we  have  the  white,  negro  and 
Asiatic  races;  and,  in  the  European  group,  we  distinguish  the 
blue-eyed,  blond  race  of  the  Northwest;  the  brunette, 
long-headed  race  of  the  Mediterranean  and  the  short-headed 
race  that  extends  from  the  Alpine  region  eastward. 

Wherever  two  races  come  to  inhabit  the  same  country 
they  tend  to  hybridize.  The  question  that  arises  is  what 
about  the  children?  Do  they  take  after  one  race  or  the  other 
or  do  they  show  a  mixture  of  the  unhke  traits  of  the  two  races 
or  will  the  traits  blend  in  them?  Will  any  mental  differences 
in  the  two  races  be  inherited?  Will  the  hybrids  be  socially 
equal,  or  superior,  to  the  pure  races  from  which  they  are 
derived? 

In  the  last  quarter  of  a  century  more  research  has  been 
made  on  race  crossing  in  animals  and  plants  than  ever 
before.  Certain  principles  have  come  about  through  this 
genetical  research  and  we  may  well  inquire  in  how  far  they 
apply  to  man.  The  first  genetical  principle,  which  we  may 
test  in  man,  is  the  principle  of  dominance.  When  two  crossed 
races  differ  in  that  one  possesses  a  trait  that  the  other  lacks, 
then  one  of  three  things  may  happen.  Either  the  trait  may 
appear  in  the  offspring,  in  which  case  it  is  said  to  be  dominant, 
or  it  may  disappear  in  the  first  hybrid  generation,  in  which 
case  it  is  said  to  be  recessive,  or  it  may  show  a  blend  between 
the  parental  conditions,  in  which  case  it  is  beheved  to  be 
of  a  genetically  complex  nature.  Where  the  inherited  trait 
depends  upon  a  single  dominant  gene  in  the  second  hybrid 
generation,  resulting  from  a  mating  of  the  Fi  hybrids,  the 
dominant  trait  will  ordinarily  appear  in  three-quarters  of 
the  offspring,  the  other  quarter  being  of  the  recessive  type. 
In  the  case  where  the  trait  is  not  simple  but  compound,  the 

553 


554  HUMAN   BIOLOGY 

proportion  of  pure  dominants,  or  recessives,  in  the  second 
hybrid  generation  will  be  changed.  Thus,  instead  of  one- 
quarter  showing  the  recessive  condition,  only  one  in  i6  may 
show  it  fully  developed,  or  even  one  in  64.  In  these  cases  all 
sorts  of  intermediate  grades  between  presence  and  absence 
will  appear. 

The  phenomenon  of  segregation  appears  in  the  second 
hybrid  generation,  as  stated  in  the  last  paragraph,  for  some 
of  the  individuals  show  a  trait  and  some  do  not  show  the 
trait.  Actually,  in  any  hybrid  population,  we  do  not  have  the 
experimental  conditions  set  down  in  the  foregoing  paragraph 
for  first  hybrid  generation  individuals  do  not  exchisively, 
or  regularly,  mate  with  each  other.  In  most  of  the  hybrid 
populations  that  we  know  there  are,  besides  the  crossing  of 
first  generation  hybrids,  back  crossing  with  the  parental 
types,  second  hybrid  generations  mated  with  second  hybrid 
individuals,  also  with  first  hybrid  generations,  or  the  parental 
types.  After  three  or  four  generations,  the  hybrid  generation 
is  a  great  mixture  of  all  conceivable  combinations  of  hybrid 
generations  of  various  degrees  with  each  other  and  with  the 
parental  stocks.  In  such  a  population,  minghng  by  chance,  we 
expect  no  definite  proportions  of  individuals  possessing  any 
particular  trait,  or  any  particular  blend,  but  rather  a  great 
variabihty  in  respect  to  the  trait  in  question,  some  individ- 
uals being  characterized  by  its  presence,  some  by  its  absence 
and  others  by  various  grades  between  these  extremes.  The 
standard  deviation  of  the  trait  in  question  is  thus  high  in  a 
hybrid  population. 

HETEROSIS 

When  two  races  are  crossed  it  sometimes  happens  that 
the  first  generation  hybrids  show  a  character  that  is  not 
favorable  in  either  of  the  parental  races.  This  result  is 
ordinarily  found  in  the  case  where  a  trait  is  dependent  upon 
two  factors  for  its  expression.  One  of  these  factors,  a,  may 
be  carried  by  the  one  race  in  which  the  trait  does  not  appear 
phenotypically,  the  other  factor,  b,  may  occur  in  the  other 
race  which  is  also  phenotypically  without  the  factors.  The 
combination,  a  b,  will  bring  together  the  two  essential 
factors  and  the  trait  is  expressed  phenotypically.  To  cite 


I 


THE    MINGLING    OF    RACES  §^^ 

an  example  from  poultry,  two  races  of  white  birds  may  be 
crossed  and  produce  a  bird  with  the  full  pigmentation  of 
the  jungle  fowl.  This  is  because  one  of  the  races  is  white, 
through  the  absence  of  factor  b,  the  other  through  the 
absence  of  factor  a,  and  the  hybrid  brings  together  the  two 
factors  essential  to  full  coloration. 

One  of  the  commonest  expressions  of  this  law  is  seen  in 
the  union  of  races  both  of  which  are  unable  phenotypically 
to  express  their  full  developmental  potentiahties,  due  to  the 
absence  from  each  of  some  developmental  factor.  When  this 
factor  is  different  in  the  two  races  their  union  may  result  in 
the  hybrid  possessing  more  development-stimulating  factors 
than  either  of  the  parental  races  possessed.  Accordingly, 
the  hybrid  may  show  an  exceptional  capacity  for  growth. 
This  result  is  known  as  hybrid  vigor,  or  heterosis.  We 
naturally  look  for  evidence  of  heterosis  in  the  first  generation 
hybrid  between  two  races. 

In  later  generations  some  of  the  individuals  possess  both 
of  the  developmental  factors  in  question.  Others  possess 
neither  and  others  will  possess  one  or  the  other  so  that  we 
should  expect  in  a  later  hybrid  population  to  find  a  great 
variabihty  in  capacity  for  growth. 

The  case  of  hybrid  vigor  is  well  illustrated  in  maize. 
When  any  variety  of  maize  is  inbred  it  tends  to  produce 
dwarfed  offspring.  Indeed,  the  ears  developed  on  such 
self-fertiHzed  plants  produce  a  small  proportion  of  viable 
seeds.  If,  on  the  other  hand,  any  female  flower  is  poUinated 
with  any  other  plant  the  large  ears  are  produced  and  these, 
when  planted,  develop  into  vigorous  offspring.  If  two 
depauperate  products  of  inbreeding  are  mated  in  corn  the 
offspring  show  this  hybrid  vigor. 

Coming  now  to  the  traits  of  human  races  the  first  question 
that  we  have  to  consider  is  whether  any  of  them  are  inherit- 
able. It  would  seem  to  be  foolish  to  raise  this  question,  but  we 
do  so  because  such  inheritance  has  been  denied. 

On  the  physical  side  we  know  of  not  a  few  traits  that  are 
inherited  in  accordance  with  simple  Mendelian  laws.  Thus 
brown  eye  color  is  dominant  over  the  absence  of  brown 
pigmentation  in  the  iris,  as  exhibited  by  blue  eyes.  The  first 
generation  shows  a  dominance  of  the  brown  eye  color  and  in 


^^6  HUMAN    BIOLOGY 

later  generations  browns  and  blues  appear,  with  the  browns 
in  greater  number,  as  we  would  expect  in  a  dominant  trait. 
In  a  hybrid  population,  derived  originally  from  Nordic  and 
South  European  stock,  we  get  in  the  same  family  brown  and 
blue-eyed  children  in  varying  proportions.  This  is  because 
the  germ  cells  of  the  parents  are  dissimilar,  due  to  the  hybrid 
origin  of  their  parents. 

In  some  other  cases,  inheritance  is  more  compHcated, 
as  in  skin  color.  It  has  been  shown  that  in  the  first  generation 
hybrid  between  white  and  a  black-skinned  negro  the  children 
are  of  an  intermediate  color,  as  we  see  in  the  mulatto.  When 
two  mulattoes  are  mated  their  offspring  are  partly  mulatto; 
sometimes  they  have  a  darker  color  to  which  the  term  "Sambo" 
is  apphed;  sometimes  the  lighter  color  of  the  quadroon.  If, 
indeed,  a  large  number  of  the  children  of  such  first  generation 
hybrids  are  examined  it  will  be  found  that  in  every  sixteen 
there  is,  on  the  average,  one  white  child  and  one  full  black. 
This  is  the  basis  for  the  conclusion  that  the  brown  or 
black  skin  color  depends  upon  two  pairs  of  factors  a  and  b. 
In  the  negro  these  two  pairs  are  both  active  in  the  mulatto; 
the  A  and  b  factors  are  both  present  but  unpaired.  Of  the 
germ  ceils  of  the  hybrids  some  carry  the  factor  a  only,  some 
the  factor  b  only,  some  neither  factor  and  some  both  factors 
A  and  B.  When  two  germ  cells,  both  carrying  a  and  b,  unite, 
the  full  black  color  is  restored;  but  when  two  others  unite, 
neither  of  which  possesses  A  and  b,  the  offspring  will  be 
white.  Other  combinations  will  give  brown  to  black  skin 
color. 

Still  other  traits  are  even  more  complicated  in  their 
inheritance,  partly  because  there  seem  to  be  more  than  two 
pairs  of  factors  involved  and  partly  because  the  development 
of  the  trait  is  to  a  considerable  extent  influenced  by  environ- 
mental conditions.  Thus  it  is  known  that  a  tendency  to  be 
over-fat  is  inherited  so  that  we  may  speak  of  an  inherited 
factor  in  the  building  of  the  body.  We  have  reason  for 
believing  that  slender  parents  are  such  by  virture  of  the 
absence  of  factors  that  promote  the  laying  on  of  fat.  In 
two  such  slender  parents,  especially  if  of  slender  stock, 
all  of  their  offspring  remain  slender.  Through  excessive 
feeding  or  inactivity  these  offspring  may  lay   on    fat   but 


THE    MINGLING    OF    RACES  557 

they  do  not  lay  it  on  readily,  or  are  easily  disturbed  in 
their  alimentary  functions  by  overfeeding,  and  return 
readily  to  their  normal  weight  after  the  super-feeding, 
which  they  generally  find  distasteful,  has  ceased.  On  the 
other  hand,  persons  derived  from  a  union  of  two  famihes 
in  which  fleshiness  is  common  often  find  (i)  that  they  have 
fairly  large  appetites  and  (2)  that  they  tend  to  lay  on  flesh, 
even  with  moderate  feeding,  (3)  that  they  are  tolerant  of 
large  amounts  of  food  and,  (4)  that  dieting  and  exercise  are 
able  to  reduce  their  build  only  slowly  and  with  great  difficulty. 
Nevertheless,  the  fact  that  variations  in  food  ingestion 
play  some  part  in  body  build  comphcates  the  study  of 
inheritance  of  this  trait. 

Not  only  physical  traits,  hke  eye  color,  skin  color,  body 
build  and  such  characters  as  stature,  color  and  form  of  the 
hair,  proportions  of  facial  features  and  many  others  are 
inherited  in  race-crosses  but  also  mental  traits.  This  is  a 
matter  which  is  often  denied,  but  the  apphcation  of  methods 
of  mental  measuring  seem  to  have  produced  indubitable 
proof  that  the  general  intelHgence  and  specific  mental 
capacities  have  a  basis  and  vary  in  the  different  races  of 
mankind.  Thus  it  has  been  shown,  by  standard  mental  tests, 
that  the  negro  adolescent  gained  lower  scores  than  white 
adolescents  and  this  when  the  test  is  made  quite  independent 
of  special  training  or  language  differences  and  also  when 
the  children  tested  have  a  similar  amount  of  schooling. 
Not  only  the  psychological  examination  in  the  army  but 
also  the  special  studies  made  by  Mayo  and  others,  working 
in  the  Department  of  Psychology  at  Columbia,  and  many 
other  investigations  are  agreed  in  this  result.  On  the  other 
hand,  it  seems  probable  that,  in  the  matter  of  sense  percep- 
tion and  discrimination,  the  negro  race  is,  in  general, 
superior  to  the  whites.  Tests  made  on  whites  and  negroes  in 
Jamaica  indicate  that  the  negroes  are  superior  in  their 
ability  to  discriminate  slight  differences  in  musical  pitch, 
intensity  and  time.  There  is  no  doubt,  in  view  of  the  studies 
of  Dr.  Hazel  M.  Stanton,  that  differences  in  capacity  for 
such  discriminations  are  inherited  and  we  can,  therefore, 
understand  the  more  readily  how  they  may  become  racial 
traits. 


7^^:r^^^ 


558  HUMAN   BIOLOGY 

Not  only  in  respect  to  physical  traits  and  mental  traits  do 
races  of  mankind  differ,  but  also  in  regard  to  temperament. 
Common  observation  shows  that  the  emotional  output  of 
different  peoples  is  very  different.  We  note  that  the  North 
American  Indian  is  httle  given  to  emotional  expression. 
On  the  other  hand,  the  African  negro  expresses  his  emotions 
copiously.  In  Europe  the  Scotch  Highlanders  are  character- 
ized by  a  prevaihngly  somber  tendency,  while  the  South 
Itahans  are  characterized  by  lightness  of  spirit.  Now  there 
can  be  no  question  that  temperament  is  inherited,  though  in  a 
rather  compHcated  fashion.  This  was  worked  out  some 
years  ago  by  the  author,  who  found  a  factor  for  excitability 
which  is  possibly  a  simple  Mendehan  dominant  and  a  factor 
for  cheerfulness  which  may,  or  may  not,  be  combined  with 
excitabihty.  The  combination  of  these  two  factors  results 
in  persons  who  are,  on  the  one  hand,  both  cheerful  and 
excitable  and,  on  the  other  hand,  in  those  who  are  cheerful 
and  somewhat  stolid;  those  who  are  of  a  depressed  tempera- 
ment and  easily  aroused  and,  finally,  those  who  are  both 
depressed  and  unresponsive  to  stimuli.  These  conditions 
are  inherited  and  show  definitely  that  when  one  parent 
exhibits  excitability,  at  least  half  of  the  children  will 
show  a  similar  trait.  Where  both  parents  are  depressed, 
all  of  the  offspring  will  show  a  general  depression.  The 
differences  in  temperament  of  different  peoples  are  not  to  be 
ascribed  to  their  environment  but  to  differences  in  bodily, 
physiological  functions  which  determine  unrestricted  output 
of  the  emotions  on  the  one  hand,  or  inhibitions  of  output 
on  the  other. 

Not  only  in  temperament  but  also  in  instincts  do  the  races 
of  mankind  differ.  For  example,  it  is  well  known  that  most 
of  the  races  of  Europe  are  fairly  stable  and  domestic,  engaged 
in  agriculture  or  industry.  However,  from  eastern  Europe 
and  western  Asia  have  come  forth  races  of  mankind  with 
a  strong  tendency  to  wander  over  the  face  of  the  earth. 
Such  are  the  Gypsies  which  have  run  through  Europe  and 
America  and  such  are  some  nomadic  peoples  who  are  scat- 
tered across  the  face  of  Asia  and  Northern  Africa  and  who  even 
before  the  time  of  Livingstone  had  penetrated  into  the  heart 
of  Equatorial  Africa.  Now  the  instinct  to  wander,  or  nom- 


THE    MINGLING    OF    RACES  559 

adism,  is  one  that  has  an  hereditary  basis.  This  has  been 
worked  out  in  some  detail  by  the  author  and  the  results  of  his 
investigation  have,  so  far,  not  been  disproved.  We  have 
evidence  also  that  other  instinctive  quahties  are  characteris- 
tic of  the  different  races  of  mankind  and  have  Hkewise  an 
hereditary  basis. 

A  race  is  more  than  a  haphazard  collection  of  individual 
traits.  Each  well-estabhshed  race  which  has  persisted  for  many 
generations  in  the  same  locahty  has  gained  in  the  course  of 
these  generations  an  adjustment  to  the  particular  environ- 
mental conditions  in  which  it  Hves.  This  adjustment  to 
environment  has  been  brought  about  in  man  by  a  different 
method  from  that  employed  with  domestic  animals.  A 
breeder  of  dogs,  let  us  say,  finds  a  mutation  which  offers 
certain  advantages  to  the  possessor  for  particular  purposes. 
He  seizes  upon  this  advantageous  trait;  succeeds  in  repro- 
ducing it  by  breeding  and  then  seeks  to  place  the  dog,  or 
the  new  breed  of  dogs,  in  a  position  where  it  can  make  use 
of  this  trait.  It  will  be  observed  that  the  new  mutation  is  not, 
from  the  beginning,  better  or  worse,  but  it  is  better  or  worse 
for  a  particular  environment  in  which  the  animal  is  to  be 
placed.  It  remains,  in  order  that  the  mutation  should  be 
advantageous,  that  the  dog  should  come  to  find  an  environ- 
ment for  which  this  new  trait  pecuharly  fits  it.  Thus,  in  the 
course  of  time,  there  have  come  into  existence  many  races  of 
dogs  which  differ  from  each  other  in  form  or  in  temperament 
or  in  instincts,  and  for  each  of  these  differences  some  niche 
has  been  found  which  has  made  it  possible  to  preserve  the 
particular  strain  of  dogs  as  a  useful  race. 

So,  also,  in  mankind  the  races  that  have  survived  have 
been  those  which  have  become  possessed  of  one  or  more 
traits  that  have  pecuharly  fitted  them  for  the  environments 
in  which  they  arose  or  which  have  enabled  the  possessor  to 
find  an  environment  in  which  the  new  traits  would  give 
him  a  special  advantage.  The  adjustment  of  races  to  their 
environments  depends  first  upon  the  possibiHty  of  mutation. 
The  experience  of  geneticists  in  the  last  twenty-eight  years 
has  demonstrated  that  such  mutations  are  constantly 
present  in  all  species  of  animals  and  plants.  The  problem  is 
no  longer  how^  mutations  arise  but  rather  how  it  comes  about 


560  HUMAN   BIOLOGY 

that  a  species  can  maintain  for  a  long  time  its  specific 
characteristics  in  the  midst  of  such  widespread  mutation. 
One  answer  to  the  last  question  is  that  so  many  mutations 
are  lethal,  or  disadvantageous,  that  their  possessors  are 
eliminated.  If  all  the  traits  that  arise  through  mutation  are 
not  disadvantageous  they  do  not  handicap  the  possessor 
and  may  persist.  If  they  give  the  possessor  an  advantage  in 
his  environment  or  in  some  other  environment  to  which  he 
may  migrate  then  he  will  have  a  peculiar  opportunity  to 
survive  and  perpetuate  these  advantageous  qualities.  An 
important  principle  then  is,  to  recapitulate,  that  each  race 
that  has  inhabited  an  environment  for  a  long  time  has 
become  adjusted  to  that  environment  by  the  acquisition  of 
certain  favorable  mutations. 

The  question  at  once  arises,  what  happens  in  the  case  of 
hybrids  who  are  representatives  of  two  such  adjusted  races? 
Will  the  new  combination  of  characters  that  arises  in  the 
progeny  be  more  or  less  fitting  for  the  hybrids  in  the  situation 
in  which  they  find  themselves? 

With  these  general  principles  in  view  we  proceed  now  to  a 
more  or  less  systematic  survey  of  the  principal  groups  of 
human  hybrids  that  have  been  produced. 

I.  Indian-European  Crosses.  A  crossing  between  the 
American  Indian  and  the  white  man  has  frequently  taken 
place  in  the  Americas.  In  South  America  the  early  Spanish 
conquerors  were  young,  single  men,  some  of  whom  estab- 
lished themselves  in  America  and  produced  large  families  of 
hybrids  with  the  Indians.  Some  of  the  descendants  of  these 
unions  are  among  the  leaders  in  South  America.  They  have 
more  ambition  than  the  average  Indian  and  they  are  better 
acclimated  to  the  tropical  conditions  met  with  in  certain 
parts  of  the  west  coast  of  South  America,  than  are  the 
Europeans.  In  the  early  days  of  North  America  also,  French 
adventurers  penetrated  in  large  numbers  into  Canada  and 
left  a  numerous  hybrid  progeny.  These  were  often  character- 
ized by  great  vigor  and  activity  and  ability  to  withstand  the 
hardships  of  frontier  life.  Precise  measurements  of  intelli- 
gence of  Indians,  Mexicans  and  mixtures  between  them  by 
Garth  (1922)  leads  to  the  conclusion  that  the  mixed  bloods 
are  the  most  intelligent  of  the  groups. 


THE    MINGLING    OF    RACES  56 1 

2.  Negro-white  Crosses  in  America.  Many  crosses  were  made 
in  Brazil  between  Portugese  and  negroes,  producing  a  race 
known  as  the  Metis  which  is  not,  in  general,  characterized 
by  hybrid  vigor.  Tuberculosis  is  said  to  be  common  among 
them.  They  show  dissatisfaction  with  agricultural  life  and 
have  often  proved  to  be  unreHable  in  matters  of  trust.  Many 
of  them  are  keenly  intelligent  but  generally  are  fond  of 
display,  rather  than  of  sohd  achievement.  There  has  been 
no   social   barrier   to   their   progress   and   they    frequently 

.  achieve  high  pohtical  office. 

The  negro-white  hybrid  of  North  America  and  of  the 
United  States  results  from  a  cross  between  two  races  that 
resemble  each  other  in  stature,  though  they  differ  in  their 
proportions,  for  the  negro  has  longer  legs  than  the  white. 
In  the  mulatto  hybrid  the  skin  color  is  intermediate;  the 
form  of  the  nose,  the  prognathism  and  other  facial  features 
are  blends  of  the  two  races.  In  body  build  the  mulattoes  are, 
on  the  average,  shghtly  superior  to  the  whites,  at  least  this 
was  true  of  the  white  and  negro  soldiers  returning  from 
France  in  19 19.  The  negro  has,  on  the  average,  many 
advantages  in  physical  quahties  over  the  white.  He  is  much 
less  apt  to  suffer  defects  of  the  spine;  and  goiter,  obesity, 
deaf-mutism,  deafness  and  most  important  diseases  of  the 
eyes  and  nasal  fossae  and  throat  are  less  common  in  his  case 
than  among  whites.  The  mulattoes  exhibit  many  of  the 
excellent  physical  quahties  of  the  negro,  but  on  the  other 
hand,  they  have  an  extraordinarily  high  incidence  of  tuber- 
culosis and  the  venereal  disease  rate  is  several  times  higher 
than  among  the  whites.  The  mulatto,  however,  is  more 
restless,  on  the  whole,  than  the  negro  and  less  easily  satisfied 
with  his  lot.  This  is  possibly  due  to  a  disharmony  introduced 
by  the  cross.  In  the  United  States  the  colored  population 
has  a  crime  rate  of  between  two  and  three  times  that  of 
the  white. 

3.  Hottentot  and  Dutch.  Hybrids  between  the  Hottentots 
and  Dutch  of  South  Africa  have  been  extensively  studied  by 
Professor  E.  Fischer.  He  finds  that  the  bastard  males  show 
some  evidence  of  hybrid  vigor  but  they  are  said  not  to  be 
more  variable  than  the  Dutch  in  respect  to  stature  and  some 
other  qualities.  However,  the  bastard  stock  contained  few 


562  HUMAN    BIOLOGY 

pedigreed  individuals.  Perhaps  the  general  low  variability 
found  by  Fischer  in  various  traits  may  be  due  to  a  mate 
selection  of  an  intermediate  type,  the  extremes  being 
ehminated.  Fischer  finds  these  hybrids  between  phlegmatic, 
industrious,  thrifty,  Dutch  stock  and  thi  Hottentot  stock, 
on  the  average,  honest  and  faithful.  They  are  serious, 
without  being  melancholy.  They  show  a  good  deal  of 
curiosity.  They  lack  energy,  pertinacity,  foresight  and 
prudence.  They  do  not  properly  control  their  strong  taste 
for  alcohol.  We  have,  here,  evidence  of  a  composite  of  the 
behavior  of  the  parental  stocks.  Seriousness  is  a  Dutch 
trait.  Curiosity  is  a  trait  of  primitive  peoples  to  whom 
a  strange  sound  or  unexplained  object  may  mean  a  lurking 
cause  of  death.  Curiosity  is  an  intense  desire  to  know; 
knowledge  is  a  necessary  prehminary  to  defense.  Extreme 
energy  in  pushing  through  undertakings  against  difficulties 
is  a  European  and  not  an  African  trait  and  this  the  bastards 
do  not  get.  The  need  of  alcohol  is  associated  with  a  serious, 
mildly  depressed  temperament  which  finds  reHef  in  the  effect 
of  spirits.  This  need  may  result,  also,  from  a  feehng  of 
insufficiency,  a  reflection  of  an  internal  conflict  of  instincts. 

4.  Polynesian  Hybrids.  The  Polynesians  of  Hawaii  have 
been  extensively  hybridized.  The  native  Hawaiians  have  been 
crossed  with  Nordic  Europeans,  Portuguese,  Chinese  and 
Philippinos.  The  results  of  these  crosses  have  been  described 
by  Porteus  (1926)  and  by  Dunn  (1928).  The  Chinese 
coolies  are  thrifty  and  frugal  and  have  a  strong  sense  of 
family  duty  and  responsibility.  They  are  individualistic 
and  secretive  and  show  a  marked  tendency  to  murder. 
The  Chinese-Hawaiian  hybrids  stand  first  among  all  of 
the  hybrids  in  industry  and  self  support  and  are  sought  for 
in  positions  of  responsibility.  The  docile  temperament  of  the 
Hawaiian  and  the  intellectual  elements  of  the  Chinese  are 
combined.  The  excellent  home  training  afforded  by  the 
Chinese  fathers  is  largely  responsible  for  the  high  ideals 
of  their  offspring.  In  the  Hawaiian-white  union,  the  restless, 
ambitious,  individualistic  temperament  ofthe  white  appears  to 
be  dominant.  A  study  of  physical  features  of  the  hybrids 
between  Hawaiians  and  Europeans  has  been  made  by  Dunn. 
The  shorter  head  ofthe  Hawaiians  is  inherited  as  a  dominant 


THE    MINGLING    OF    RACES  563 

in  the  hybrids.  The  broader  noses  of  the  Hawaiians  also 
reappear  in  the  hybrids.  The  darker  hair  color,  the  wave 
of  the  hair,  the  dark  eye  and  skin  of  the  Hawaiians  are, 
at  least,  partially  dominant  in  the  offspring.  Much  varia- 
bihty  is  found  among  the  hybrids  of  the  second  and  later 
generations. 

5.  The  Philippinos  of  Luzon.  The  Phihppino  has  come  in 
contact  with  the  Chinese,  Japanese,  Negrito  and  Caucasian 
and  has  in  himself  their  united  and  commingled  bloods. 
The  result  is  an  over-emotional,  weakly  inhibited  hybrid. 
Transported  to  the  Hawaiian  Islands  the  Philippinos,  though 
constituting  only  about  lo  per  cent  of  the  population, 
are  responsible  for  over  42  per  cent  of  the  murders  and  43  per 
cent  of  the  sex  offenses.  Porteus  explains  their  impulsiveness, 
noisy  self-expression,  alternating  obstinacy  and  suggesti- 
bleness,  as  due  to  a  conflict  of  dissimilar  temperaments. 
Ordinary  education  is  not  suitable  for  them.  "An  education," 
he  states,  "that  stimulates  an  unattainable  ambition  is 
cruelty." 

6.  The  Dutch  East  Indies.  In  the  neighborhood  of  the 
Straits  extensive  race  crossing  has  taken  place  from  early 
times.  The  Chinese  have  penetrated  into  the  East  Indian 
islands  in  great  numbers.  Their  children  are  comely  of  form 
and  possess  excellent  manners.  This,  again,  may  be  in 
part  due  to  the  disciphne  of  the  Chinese  fathers.  However, 
hybrids  with  the  Dutch  are  hkewise  possessed  of  much 
beauty  and  grace  so  that  the  traits  of  the  native  Malays 
have  contributed  much  to  the  high  quahty  of  their  offspring. 
In  Sumatra  the  hybrids  between  the  Dutch  and  the  native 
women  enjoyed  the  status  of  the  Europeans  and  many  of 
these  hybrids,  after  European  training,  have  come  to  fill 
offices  of  distinction  in  the  islands.  Thus,  in  the  Dutch 
East  Indies,  we  find  httle  adverse  effect  on  the  progeny 
resulting  from  hybridization. 

7.  Eurasians.  In  India  hybrids  between  native  women  and 
European  men  have  been  produced  in  considerable  numbers. 
These  are  called  Eurasians.  While  able  to  endure  the  chmate 
of  India  better  than  the  Europeans  they  are  said  to  lack 
in  industry  and  perseverance.  They  are  less  useful  as  clerks 
than   the  natives  because  they  often  decline  to  learn  the 


564  HUMAN   BIOLOGY 

native  language  and  are,  thus,  cut  off  from  transacting 
business  with  the  natives.  Serious  temperamental  conflicts 
seem  to  occur  in  their  emotional  life. 

8.  Scandinavian-Lapp.  Among  the  European  races,  one 
crossing  that  has  been  most  thoroughly  studied  is  that 
between  the  Lapps  and  the  Scandinavians.  Mjoen  finds  that 
the  hybrids  are  non-resistant  to  tuberculosis,  feebly  inhibited 
to  alcohol  and  show  an  unusual  amount  of  psychic  dis- 
turbance and  criminaHstic  behavior.  Dr.  Halfdan  Bryn, 
the  anthropologist,  hkewise  states  that  he  has  a  firm 
impression  that  crossing  between  Lapps  and  Norwegians  is 
especially  bad  for  both  parties.  He  cites  the  large  number 
of  cases  of  congenital  dislocation  of  the  hip  and  suggests  that 
this  is  due  to  disharmony  between  the  pelvis  and  the  head 
of  the  femur.  Lundborg  also  finds  the  Lapp-Swedish  crosses 
to  be  especially  susceptible  to  tuberculosis. 

This  survey  of  the  results  of  race  crossing  leads  to  the 
conclusion  that  there  is  no  single  rule  that  applies  to  all 
racial  hybrids.  Some  of  them,  like  the  French  Canadian- 
Indian  hybrids  and  the  Chinese-Hawaiian  seem  to  show 
hybrid  vigor;  others,  like  the  Eurasians,  show  an  enfeeble- 
ment.  Some  are  devoid  of  beauty  of  form  and  figure  while 
others,  like  the  Javanese-European  crosses,  are  characterized 
by  comeliness  and  grace.  The  most  widespread  physical 
defect  seems  to  be  a  liability  to  tuberculosis,  although  it  is 
possible  that  this  is  due  to  a  persisting  lack  of  resistance, 
inherited  from  the  more  primitive  race,  and  contact  with 
European  carriers  of  the  disease.  The  most  serious  defect 
found  in  hybrids  is  perhaps  the  bad  behavior  of  Philippino 
hybrids  and  the  negro-white  crosses,  apparently  due  to 
conflicting  instincts. 

In  regard  to  variability  of  hybrids,  there  has  come  to  be  a 
difference  of  opinion.  Herskovits  has  found  a  low  variability 
of  the  negro-white  hybrids  in  respect  to  stature,  height  of 
nose  and  cephalic  index.  These  are,  however,  characteristics 
in  which  the  negroes  and  the  whites  are  not  strikingly 
dissimilar  and,  therefore,  a  high  degree  of  variability  is  not 
necessarily  to  be  expected.  On  the  other  hand,  it  is  clear  that 
in  features  which  are  most  unlike  in  the  parental  races, 
hybrids  are  most  variable;  as,  for  instance,  in  the  skin  color 


THE   MINGLING   OF   RACES  $ۤ 

and  nose  breadth  that  show  such  great  variability  in  the 
mulattoes.  Fischer  also  refers  to  the  low  variabihty  in  the 
bastards  of  South  Africa  and  Rodenwaldt  is  surprised  by 
the  same  phenomenon  in  the  hybrids  of  Kisar.  Here,  again, 
the  disappointment  is  perhaps  due  to  expecting  a  generally 
greater  variability  of  hybrids.  The  greater  variabihty  of  the 
hybrid  is  to  be  found  only  in  those  traits,  if  any,  which  are 
strikingly  dissimilar  in  the  parental  stocks. 

As  a  result  of  this  rapid  survey  of  race  crossing  we  are 
led  to  the  conckision  that  there  is  no  universal  rule  as  to  the 
physical  or  social  consequences  of  race  crossing.  Sometimes 
the  progeny  are  superior  to,  sometimes  equal  to,  sometimes 
inferior  to  the  parental  stocks.  In  the  absence  of  any  uniform 
rule  as  to  the  consequences  of  race  crossing  and  in  view  of  the 
disharmony  shown  by  many  hybrids  it  is  well  to  discourage 
hybridization  between  extreme  types,  except  in  those  cases 
where,  as  in  the  Chinese-Hawaiian  cross,  it  clearly  produces 
superior  progeny.  The  negro-white  and  the  Phihppino- 
European  crosses  seem,  on  the  other  hand,  of  a  type  that 
should  be  avoided. 

REFERENCES 

Davenport,  C.  B.,  and  Danielson,  F.  H.  1913.  Heredity  of  Skin  Color  in 

Negro-White  Crosses.  Publ.  No.  188,  Carnegie  Inst,  of  Wash. 
Davenport,  C.  B.,  and  Love,  A.  G.  192 1.  Army  Anthropology.  Med.  Dept.  U. 

S.  A.  in  World  War.  Vol.  15,  Statistics. 
Fischer,  E.  19 13.  Die  Rehobother  Bastards  und  das  Bastardierungs-problem 

beim  Menschen.  Jena,  G.  Fischer. 
Herskovits,  M.  J.  1928.  The  American  Negro:  A  Study  in  Racial  Crossing. 

N.  Y.,  Knopf. 
LuNDBORG,  H.,  and  Linders,  F.  J.  1926.  The  Racial  Character  of  the  Swedish 

Nation.  Uppsala;  Swedish  State  Inst,  for  Race  Biology. 
PoRTEus,  S.  D.,  and  Babcock,  M.  E.  1926.  Temperament  and  Race.  Boston, 

Badger. 
Ripley,   W.  Z.    1900.  The   Races  of  Europe.   Lond.   Kegan   Paul,   Trench, 

Triibner  &  Co. 
Rodenwaldt,  E.  1927.  Die  Mestizen  auf  Kisar.  Batavia,  Mededeelingen  van 

den  Dienst  der  Volksgezondheid  in  Nederlandsch-Indie. 
Spiller,  G.  191 1.  Paper  on  Interracial  Problems,  communicated  to  the  First 

Universal  Race  Congress,  London.  Boston,  World  Peace  Foundation. 


Chapter  XXIV 

THE  PURPOSIVE  IMPROVEMENT  OF  THE 

HUMAN  RACE 

Edwin  Grant  Conklin 

THAT  the  human  race  is  physically,  mentally  and 
socially  far  from  perfect  and  that  there  is  great  need 
for  improvement  in  each  of  these  regards  is  universally 
admitted.  The  armies  of  defective  and  delinquent  persons 
in  every  nation  and  race,  the  crowded  hospitals,  asylums. 
Jails  and  penitentiaries  in  almost  every  country,  the  enor- 
mous cost  of  caring  for  this  human  wreckage  and  wastage, 
all  testify  to  the  fact  that  there  is  urgent  need  for  improve- 
ment. Indeed  it  is  merely  a  question  of  how  long  civilization 
can  continue  to  carry  this  ever-increasing  burden  of  the 
bungled  and  botched,  of  paupers,  feebleminded  and  insane, 
of  bums,  thugs  and  criminals.  In  the  United  States  it  is 
said  that  the  cost  of  maintaining  public  custodial  institutions 
for  these  social  parasites  is  from  one-third  to  one-seventh  of 
all  the  public  revenues  of  the  several  states,  while  the  direct 
and  indirect  cost  of  crime  in  this  country  has  been  estimated 
from  three  and  one-half  billion  dollars  each  year  at  the 
lowest  figure  to  twenty  billions  at  the  highest  (Prentiss, 
1927).  There  is  no  doubt  that  the  human  race,  in  America  as 
well  as  in  other  countries,  stands  in  the  utmost  need  of 
improvement,  if  civilization  is  to  endure  and  progress. 

But  is  there  any  possibility  of  checking  this  tide  of 
degeneracy  and  of  turning  it  in  the  direction  of  racial 
improvement?  Is  it  one  of  the  inevitable  results  of  civilization 
that  progress  for  the  few  means  degeneration  for  the  many, 
and  that  in  the  end  the  weeds  must  necessarily  choke  out  the 
wheat?  The  histories  of  many  great  civilizations  of  the 
past  would  seem  to  confirm  the  opinion,  sometimes  expressed, 
that  civilization  itself  is  a  disease  which  ends  in  suicide. 
But  on  the  other  hand  our  greater  knowledge  of  nature 
and  of  man  places  in  our  hands  the  power  to  combat  the 
evils   which   have  overthrown   former   civilizations   and   to 

566 


THE    PURPOSIVE    IMPROVEMENT   OF   THE    HUMAN    RACE        567 

turn  the  current  of  human  evolution  from  degeneracy  to 
progress.  Already  we  know^  how  to  improve  the  breeds  of 
domestic  animals  and  cultivated  plants;  we  know  that  man 
also  is  a  hving  creature  and  that  all  the  principles  of  heredity 
and  development,  of  progress  or  degeneration,  of  hfe  or 
death  apply  to  man  as  well  as  to  the  humblest  animal  or 
plant.  Mankind  could,  if  it  would,  breed  a  healthier,  more 
intelHgent,  more  ethical  type  than  the  general  average  of  the 
existing  race.  Exactly  the  same  principles  which  are  used 
so  successfully  in  the  improvement  of  horses  or  cattle  or 
crops  would  produce  corresponding  results  if  apphed  to 
human  reproduction  and  development. 

PRINCIPLES    OF    GOOD   BREEDING 

What  are  these  principles  of  good  breeding  which  have 
doubled  the  best  speed  of  horses,  the  best  weight  of  cattle, 
the  best  yield  of  wheat  during  the  past  century?  They 
may  be  summed  up  under  two  general  heads:  (i)  improved 
heredity  through  selective  breeding:  (2)  improved  environ- 
ment through  better  food,  nurture,  training.  No  successful 
breeder  neglects  either  of  these  factors. 

The  only  Hving  bond  between  one  generation  and  the 
next  is  found  in  the  germ  cells,  and  whatever  is  inherited  must 
be  carried  in  these  cells.  Of  course  no  adult  characters  are 
present  in  germ  cells,  but  certain  genes  or  inheritance  factors 
are  contained  in  those  cells  and  by  the  interaction  of  these 
factors  on  one  another  and  by  their  reactions  to  environmental 
stimuli  the  adult  characters  gradually  develop.  Every 
developed  character  is  the  result  of  many  factors  or  causes, 
some  of  which  are  inherited  (that  is  they  are  present  in  the 
germ  cells)  and  others  are  environmental.  For  example,  there 
are  multitudes  of  factors  both  hereditary  and  environmental 
involved  in  the  development  of  the  eye;  most  of  these  are 
common  to  all  eyes  and  hence  are  non-differential,  but  as 
between  a  blue  eye  and  a  brown  one  there  must  be  at  least 
one  differential  factor  and  if  this  factor  is  located  in  the  germ 
plasm,  as  it  is,  the  eye  color  is  said  to  be  inherited  in  spite 
of  the  fact  that  many  of  the  factors  in  the  production  of 
this  character  are  environmental.  However,  if  the  differential 


568  HUMAN    BIOLOGY 

cause  of  any  character  is  found  in  conditions  outside  of  the 
germ  plasm,  as  for  example  in  the  production  of  bhndness 
by  drinking  wood  alcohol,  the  character  is  plainly  environ- 
mental. When  such  environmental  factors  act  at  an  early 
stage  of  development,  and  especially  before  birth,  it  is  often 
difficult  to  distinguish  them  from  hereditary  ones.  But 
whenever  a  particular  trait  appears  in  several  individuals 
of  the  same  family  or  confraternity,  it  is  generally  safe  to 
say  that  its  differential  cause  is  inherited.  On  the  other  hand, 
if  it  occurs  but  once  or  rarely  its  cause  may  be  either  heredi- 
tary or  environmental  and  in  such  a  case  only  the  study 
of  the  progeny  of  such  individuals,  preferably  under  experi- 
mental conditions,  will  reveal  which  is  the  differential 
factor. 

Even  the  development  of  inherited  characters  may  be 
modified  by  environment,  especially  if  it  acts  at  an  early  stage 
in  development,  and  consequently  the  breeder  must  select 
not  only  good  seed  or  stock  but  he  must  also  provide  good 
soil,  food  and  care  if  he  is  to  produce  superior  plants  or 
animals.  Heredity  and  environment  are  not  contestants 
but  cooperators  in  making  or  destroying  breeds  or  races  or 
civihzations.  Heredity  furnishes  the  materials,  environment 
shapes  and  uses  them;  heredity  is  the  mechanism,  environ- 
ment is  the  stimulus  which  sets  it  in  action;  heredity  fixes 
the  possibihties  of  development,  environment  determines 
which  of  these  possibihties  shall  become  reahties. 

As  apphed  to  man  these  principles  of  good  breeding 
are  known  as  eugenics  and  euthenics.  They  are  never  in 
conflict,  though  this  cannot  be  said  of  all  eugenicists  and 
euthenicists.  Both  principles  are  indispensable  in  all  develop- 
ment whether  it  be  that  of  the  body  or  of  the  mind,  of 
the  individual  or  of  society,  and  where  two  factors  are  in- 
dispensable it  is  useless  to  debate  which  is  the  more 
important. 

But  while  we  cannot  match  these  factors  against  each 
other  we  can  point  out  some  of  their  contrasts.  In  general 
heredity  is  more  constant,  environment  more  variable; 
heredity  more  specific,  environment  more  general;  heredity 
less  easily  controlled,  environment  more  easily  controlled. 
Therefore  in  efforts  for  human  betterment  more  attention  has 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        569 

been  paid  to  euthenics  than  to  eugenics.  Indeed  almost  all 
the  agencies  that  have  been  employed  for  the  betterment  of 
mankind  have  been  aimed  at  the  improvement  of  the 
environment.  Among  these  are  government,  education, 
rehgion,  art,  Hterature,  science,  medicine,  sanitation, 
engineering*;  and  practically  everything  which  we  include 
in  that  social  complex  which  we  call  civihzation. 

Only  eugenics,  which  is  the  attempt,  or  rather  the  proposal, 
by  man  to  breed  from  the  fit  rather  than  the  unfit,  and 
natural  selection,  which  is  this  same  objective  attained  by  the 
slow  and  wasteful  processes  of  overproduction  and  the 
ehmination  of  the  unfit  in  the  struggle  for  existence,  are 
directed  to  the  improvement  of  heredity.  And  yet  for 
continuous  and  lasting  human  progress  there  must  be 
improvement  of  heredity  as  well  as  of  environment.  As  the 
motto  of  good  photography  is  "Get  it  in  the  negative," 
so  the  motto  of  good  breeding  is  "Get  it  in  the  blood. " 

The  only  known  method  of  improving  heredity  pur- 
posively  is  by  selective  breeding,  that  is  by  mating  individuals 
that  come  of  good  stock  and  that  show  good  quafities,  and  by 
the  prevention  of  the  breeding  of  poor  stock  and  of  defective 
individuals.  No  method  is  known  by  which  inheritance 
factors  can  be  improved  directly.  Very  rarely  such  factors 
may  undergo  change,  or  what  is  called  mutation,  but  such 
changes  are  generally  for  the  worse  rather  than  for  the 
better  and  their  causes  are  almost  wholly  unknown.  Neither 
the  experience  of  breeders  nor  the  principles  of  genetics 
holds  forth  any  hope  that  bad  inheritance  factors  can 
ever  be  purposively  changed  into  good  ones.  The  only 
practicable  method  of  improving  heredity  is  by  selection 
of  the  best  and  ehmination  of  the  worst. 

And  yet  there  can  be  no  progress  apart  from  favorable 
environment,  and  human  progress  is  pecuharly  dependent 
upon  it.  Man's  environment  is  more  extensive  and  more 
varied  than  that  of  any  other  hving  creature  and  its  effects 
on  his  development  and  activity  are  correspondingly  greater. 
In  addition  to  the  same  sort  of  environment  which  he 
shares  with  other  organisms,  he  is  pecuharly  affected  by  intel- 
lectual and  social  stimuh.  By  means  of  language,  institutions 
and  education,  the  experiences  of  men  in  all  countries  and 


570  HUMAN    BIOLOGY 

ages  may  be  a  part  of  his  environment.  Furthermore,  by 
intelHgence  and  social  cooperation,  men  are  able  to  control 
their  environment  as  no  other  creatures  can.  Indeed  it  may 
be  granted  at  once  that  the  only  possibiHty  of  the  purposive 
improvement  of  the  race  hes  in  the  control  of  environment, 
using  this  term  in  its  broadest  sense,  and  thus  including  the 
selective  agency  in  propagating  good  stock  and  ehminating 
bad.  For  even  the  improvement  of  heredity  must  rest  upon 
science,  education  and  social  cooperation  and  all  of  these  are 
parts  of  human  environment. 

The  great  importance  of  environment  in  human  hfe  and 
progress  has  led  some  environmentahsts  to  minimize  the 
importance  of  heredity.  They  sometimes  assert  that  it 
determines  only  unimportant  physical  traits  such  as  the 
color  of  the  eyes  or  hair,  and  that  environment  determines 
all  the  rest.  But  of  course  there  is  a  basis  in  the  germ  cells 
for  everything  that  will  ever  develop  out  of  those  cells 
and  in  many  instances  this  germinal  basis  is  the  differential 
cause  of  many  important  characters.  It  is  needless  to 
say  this  to  biologists,  but  there  are  some  psychologists, 
sociologists  and  apostles  of  human  equality  who  still  main- 
tain, in  the  realm  of  theory  but  not  in  actual  practice, 
that  "all  men  are  born  equal"  and  that  the  differences  be- 
tween races  and  classes  and  individuals  are  caused  only  by 
differences  in  environment,  and  not  by  differences  in  heredity. 

Of  course  the  major  differences  that  distinguish  one 
species  from  another  are  inherited;  each  "produces  seed  after 
his  kind."  Men  differ  from  horses  or  dogs  primarily 
because  they  come  from  different  kinds  of  germ  cells.  In  the 
same  incubator  and  under  practically  identical  conditions, 
a  hen's  egg  develops  into  a  chick,  a  duck's  egg  into  a  duckling. 
Similarly  racial  traits,  such  as  those  that  characterize 
different  breeds  of  dogs  or  horses  or  men,  are  inherited.  This 
is  true  not  only  of  physical  but  also  of  psychical  character- 
istics; the  bull  dog,  or  pointer,  or  hound  inherits  not  only  his 
physical  but  also  his  mental  and  temperamental  traits; 
the  European,  the  Asian,  or  the  African  inherits  not  only 
his  skin  color,  hair  form,  shape  of  eyes,  nose,  lips.  Jaws  and 
skull,  but  also  many  of  his  mental,  emotional  and  social 
peculiarities. 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        57 1 

Likewise  traits  that  occur  repeatedly  in  the  same  family 
and  under  various  environmental  conditions  are  certainly 
inherited,  and  this  is  true  not  only  of  physical  traits  but 
also  of  psychical  ones.  In  the  case  of  dogs  the  type  of  behavior 
characteristic  of  different  breeds  is  as  certainly  inherited 
as  is  their  physical  form.  There  is  good  evidence  that  the 
same  is  true  of  different  breeds  of  men.  Some  famiHes  are 
predominantly  highly  emotional,  others  stohd;  some  intel- 
lectually brilhant,  others  stupid;  some  contain  many  feeble- 
minded individuals,  others  many  that  are  insane.  Where 
such  traits  are  repeated  in  several  members  of  a  family 
and  under  various  environmental  conditions  there  can 
be  no  doubt  that  they  are  inherited.  By  the  very  defini- 
tion of  racial  or  family  traits  they  are  inherited;  otherwise 
they  are  not  racial  or  family  traits. 

It  is  only  when  we  come  to  the  individual  differences 
that  appear  in  members  of  the  same  race  or  family  that 
questions  arise  as  to  whether  they  are  hereditary  or  environ- 
mental. Children  of  the  same  family  may  be  male  or  female, 
tall  or  short,  hght  or  dark,  cheerful  or  morose,  wise  or  foohsh. 
and  therefore  it  was  formerly  held  that  such  individual 
differences  must  be  the  results  of  differences  in  early  environ- 
ment, since  all  children  of  the  same  parents  were  once 
supposed  to  have  the  same  heredity.  But  since  the  redis- 
covery of  Mendel's  law  in  1900  we  know  that  each  parent 
transmits  only  half  of  his  or  her  inheritance  factors  to  children 
and  ahnost  never  the  same  combination  of  factors.  Of 
course  parents  can  never  transmit  factors  which  they 
do  not  possess  and  consequently  "the  inherited  nature 
of  the  offspring  is  determined  by  that  of  the  parents  until 
men  gather  grapes  of  thorns  or  figs  of  thistles."  (Bateson, 
192 1). 

Individual  differences,  therefore,  may  be  caused  by 
new  combinations  of  inheritance  factors  and  very  rarely 
by  new  mutations  of  those  factors,  or  by  modifications 
of  the  environment;  sometimes  only  a  study  of  large  numbers 
of  individuals  of  the  same  stock  and  under  varying  environ- 
mental conditions  will  reveal  whether  these  differences  are 
hereditary  or  environmental. 


572  HUMAN   BIOLOGY 

DOES    GOOD    ENVIRONMENT    OR  TRAINING  IMPROVE  HEREDITY? 

It  has  long  been  an  article  of  faith  with  extreme  environ- 
mentahsts  that  improvement  of  environment  will  improve 
not  only  development,  but  also  heredity  itself.  Doubtless 
inheritance  factors  can  be  modified  in  rare  instances  by 
changes  in  environment.  It  has  been  shown  that  such 
modifications  can  be  produced  by  x-rays,  though  these  are 
almost  always  of  a  degenerative  sort.  But  there  is  no  satis- 
factory evidence  that  good  environment  will  produce 
improvements  in  heredity  or  bad  environment,  bad  heredity: 
no  evidence  of  the  inherited  effects  of  use  or  disuse  or 
training.  A  given  kind  of  wood,  such  as  pine,  oak  or  mahog- 
any, may  be  shaped  into  chairs,  tables  or  doors  by  the  tools 
and  forces  that  act  upon  it,  but  the  wood  itself  does  not 
change  its  nature.  Similarly  a  given  kind  of  egg,  such  as 
that  of  a  fish  or  frog  or  bird  may  have  its  development 
shaped  and  modified  to  a  certain  extent  by  the  environ- 
ment that  acts  upon  it,  without  changing  its  fundamental 
nature  or  heredity. 

In  the  mental  and  social  fields,  as  well  as  in  the  physical, 
there  is  no  satisfactory  evidence  that  the  effects  of  use  or 
disuse  are  inherited  in  the  biological  sense.  Numerous  claims 
of  such  modification  of  heredity  have  been  made.  One  of  the 
most  important  of  these  was  announced  in  1923  by  the 
distinguished  Russian  physiologist  Pavlov  who  found  that 
it  took  about  300  trials  to  teach  the  first  generation  of  white 
mice  with  which  he  experimented  to  come  to  food  on  the 
ringing  of  a  bell,  the  second  generation  came  in  about  100 
trials,  the  third  in  30,  the  fourth  in  10,  and  the  fifth  genera- 
tion in  5  trials.  Here  was  apparently  an  amazingly  rapid 
inheritance  of  the  effects  of  training,  indeed  it  was  so  at 
variance  with  all  other  experience  in  animal  training  and  in 
human  education  that  it  was  generally  discredited  in  spite  of 
the  scientific  standing  of  the  author.  Recently  Pavlov  has 
admitted  that  his  results  were  based  on  errors  and  he  with- 
draws his  claims  as  to  the  inheritance  of  the  effects  of  train- 
ing (McDougall,  i927).ThepsychologistWm.McDougall,has 
recently  (1927)  published  the  results  of  a  very  careful  and 
extensive  study  of  the  inherited  effects  of  the  training  of 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        573 

white  rats  through  twelve  to  seventeen  generations.  He  is 
convinced  that  there  is  some  evidence  that  such  training 
does  shghtly  affect  heredity,  but  such  modification  is  so 
shght  and  slow  that  he  honestly  admits  the  improbabihty 
of  greatly  improving  the  human  race  by  the  inherited  effects 
of  good  environment,  good  training  or  good  education. 
Other  investigators,  notably  Bagg  (1920)  and  MacDowell 
(1924)  have  found  no  evidence  that  the  training  of  ancestors 
facihtates  the  learning  of  the  descendants  in  the  case  of 
mice  and  rats. 

Of  course  good  environment,  training  and  education 
greatly  improve  individual  development  but  in  spite  of  the 
fact  that  no  one  has  ever  proved  conclusively  that  they 
improve  heredity  or  that  the  effects  of  use  or  disuse  are 
inherited,  this  doctrine  of  "the  inheritance  of  acquired 
characters"  is  still  maintained  by  many  persons  who  feel 
that  it  ought  to  be  true  even  if  it  is  not,  and  who  sometimes, 
by  hook  or  crook,  attempt  to  make  nature  agree  with  their 
theories.  So  many  persons  have  gone  wrong  morally  in 
maintaining  that  acquirements  are  inherited,  from  the 
patriarch  Jacob  in  his  deahngs  with  his  father-in-law  Laban 
down  to  a  few  real  scientists  and  many  pseudo-scientists  of 
the  present  day,  that  an  interesting  article  might  be  written 
on  "The  influence  on  moral  character  of  the  doctrine  of  the 
inheritance  of  acquired  characters."  If  the  inheritance  of 
acquired  characters  were  as  important  a  factor  in  human 
progress  as  some  persons  suppose,  it  would  not  be  necessary 
to  make  a  minute  search  for  it  in  every  hole  and  corner,  it 
would  occur  frequently  and  indubitably,  but  even  its  defend- 
ers must  admit  that  it  occurs  rarely  and  doubtfully  if  at  all. 
All  human  experience  teaches  that  children  still  have  to  learn 
their  mother  tongue,  that  they  still  have  to  be  "house- 
broken,"  that  they  still  have  to  be  taught  good  habits,  that 
they  still  must  be  taught  what  is  right  and  what  is  wrong, 
although  such  training  has  been  going  on  for  countless 
generations.  In  these  and  in  a  thousand  other  instances  the 
universal  experience  of  mankind  confirms  the  conclusions  of 
the  biologists  that  the  effects  of  training  are  not  inherited. 

But  while  the  acquirements  and  experiences  of  former 
generations  are  not  passed  on  to  descendants  through  the 


574  HUMAN   BIOLOGY 

germ  cells,  they  are  passed  on  through  many  forms  of  social 
communication,  through  imitation,  signs,  language,  writing, 
education,  customs  and  institutions.  This  has  been  called 
"social  inheritance,"  but  it  is  not  inheritance  at  all  in  the 
biological  sense  but  rather  a  part  of  the  social  environment. 
By  means  of  social  continuity  each  generation  is  bound  to 
every  other  one,  each  later  generation  builds  on  the  work  of 
earher  ones.  Thus  science,  art,  government  and  culture  in 
general  advance  from  age  to  age:  whereas  in  germinal 
inheritance  later  generations  begin  almost  where  earlier  ones 
began  and  not  where  they  ended.  It  is  this  immensely 
important  difference  between  germinal  and  social  inheritance 
that  makes  biological  progress  so  slow  as  compared  with 
social  progress.  It  is  this  which  causes  knowledge  to  outrun 
performance,  and  ideals  to  point  the  way  to  realizations. 
It  is  this  continuity  and  development  of  society  from  genera- 
tion to  generation  which  makes  possible  such  a  topic  as 
"the  purposive  improvement  of  the  human  race."  And  it  is 
this  contrast  between  the  rapid  improvement  of  environment 
and  the  slow  improvement  of  heredity  that  causes  many 
persons  to  seek  some  short  cut  to  the  desired  haven  of  a  more 
perfect  human  inheritance.  Unfortunately  no  such  short  cut 
has  ever  yet  been  found  and  so  far  as  we  know  at  present 
the  only  possible  method  of  improving  heredity  is  by  the 
method  of  selective  breeding. 

APPLICATION  OF  BIOLOGICAL  PRINCIPLES  TO  HUMAN 

BETTERMENT 

These  are  the  fundamental  principles  that  govern  individ- 
ual and  racial  development  and  any  program  for  the  improve- 
ment of  the  human  race  must  rest  upon  these  principles. 
In  what  practicable  manner  can  these  principles  be  utilized 
and  controlled  for  race  betterment? 

The  tremendous  improvements  that  have  been  effected 
in  almost  all  breeds  of  domestic  animals  and  cultivated 
plants  by  the  method  of  selective  breeding  have  led  certain 
enthusiastic  eugenicists  to  predict  that  corresponding 
improvements  in  the  human  race  could  be  made  in  a  rela- 
tively short  time  by  the  same  method,  and  many  persons 
have   looked   forward   to  a   eugenic  paradise  in   which   all 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        575 

physical  deformity,  mental  defect  and  moral  delinquency 
would  be  abolished  and  "men  hke  gods"  would  people  the 
earth.  But  a  more  careful  and  cautious  appraisal  of  the 
difficulties  involved  has  led  many  biologists  to  the  conclusion 
that  while  the  principles  of  good  breeding  apply  to  man  as 
much  as  to  any  other  organism,  the  practical  difficulties  in 
the  way  of  utihzing  these  principles  are  so  great  that  it  is 
hopeless  to  expect  any  rapid  improvement  of  the  heredity  of 
the  race  under  existing  social  conditions  or  under  any  others 
that  are  hkely  to  be  reahzed  within  the  next  few  centuries. 
Under  popular  forms  of  government,  the  great  mass  of 
mankind  cannot  be  expected  to  observe  the  laws  of  good 
breeding  and  to  ehminate  from  reproduction  all  but  the 
very  best  hereditary  lines,  and  the  most  that  can  be  expected 
from  the  prevention  of  the  breeding  of  defectives  is  that  the 
race  may  be  saved  from  further  deterioration.  If  some  wise 
and  benevolent  despot,  or  if  some  superhuman  intelligence 
and  power,  were  to  control  the  breeding  of  men  as  man 
controls  his  flocks  and  crops,  the  same  sort  of  improvement 
could  be  brought  about  in  the  human  race  as  has  been 
accomplished  in  the  case  of  domestic  animals  and  cultivated 
plants.  In  a  certain  sense,  society  has  such  power  and  it 
can  impose  all  sorts  of  restrictions  and  inhibitions  on  individ- 
uals, but  it  is  more  than  doubtful  whether  it  has  superhuman 
intelligence  or  benevolence.  Under  these  conditions,  the 
whole  program  of  human  eugenics  is  reduced  to  an  attempt 
to  prevent  or  reduce  the  breeding  of  the  worst  lines,  to 
promote  the  breeding  of  the  best  types  and  to  leave  the 
great  mediocre  mass  of  mankind  to  people  the  earth  as  it 
has  always  done  in  the  past.  How  inefficient  such  a  program 
is  can  be  appreciated  if  one  compares  it  with  the  rigid 
elimination  from  reproduction  of  all  but  the  best  lines  in 
modern  stock  breeding.  And  how  long  it  would  take  markedly 
to  improve  the  entire  human  race  by  such  a  feeble  measure 
can  be  left  to  those  who  deal  with  geological  ages  and 
light-years. 

The  difficulty,  or  rather  the  impossibility,  of  any  more 
radical  program  of  eugenics  than  that  indicated  above, 
namely  the  gradual  reduction  of  the  fecundity  of  the  worst 
human  types  and  the  encouragement  of  greater  fecundity 


576  HUMAN   BIOLOGY 

in  the  best  types,  makes  it  extremely  improbable  that  any 
great  or  rapid  improvement  in  the  inherited  nature  of  the 
human  race  can  be  produced  by  this  method.  It  is  relatively 
easy  for  the  breeder  of  animals  or  plants  to  choose  the  types 
which  he  wishes  to  propagate  and  to  make  new  combinations 
oi  desirable  traits,  but  the  case  is  far  different  in  man  where 
in    the  main    restrictions    on    reproduction    must   be    self- 
imposed,  where  there  is  httle  uniformity  of  opinion  among 
different  people  and  in  different  ages  as  to  what  is  the  best 
human  type,  and  where  social  and  moral  customs  are  at 
variance    with    the    best    genetical    procedure.    Alexander 
Graham  Bell  (1914),  who  was  greatly  interested  in  human 
eugenics  and  who  was  also  a  skillful  breeder  of  sheep,  once 
contrasted  the  differences  in  the  technique  of  sheep-breeding 
with  the  social  conditions  governing  human  reproduction, 
by   supposing  that  the  sheep  breeder  were   compelled  to 
observe  human  customs,  namely  (i)  all  must  be  allowed  to 
breed    and    none    must    be    sterilized,    (2)    weaklings    and 
deformed  individuals  must  receive  special  care  and  must  be 
permitted  to  propagate,  (3)  polygamous  and  consanguineous 
unions  must  not  be  permitted,   (4)  every  individual  must 
be  allowed  to  choose  its  own  mate  and  for  life.  Under  such 
conditions,  he  says,  no  improvement  in  a  flock  would  be 
possible,    and   as    long   as   these   social   conditions   prevail 
among  men  no  hereditary  improvement  in  the  human  stock 
will  be  possible.   But  already  the  first  and  second  of  the 
social   customs    named   are   being   changed,    and   we   may 
confidently  look  forward  to  the  time  in  the  near  future  when 
all  civilized  societies  will  prevent  the  propagation  of  the 
worst   forms   of  bodily   defect,   mental  disease   and   moral 
degeneracy  that  are  known  to  be  inherited.  But  even  for 
the  purpose  of  breeding  a  race  of  supermen  mankind  will 
probably  never  consent  to  abolish  marriage  and  monogamy 
and  adopt  the  morals  of  the  farmyard  and  the  breeding 
pen,   for  by  such  methods  more  of  social  value  would  be 
lost  than  could  be  gained  biologically. 

IS   THE   PROGRAM   OF   EUGENICS   BIOLOGICALLY   SOUND? 

These    and    other    practical   difficulties    in    the    way    of 
eugenical  progress  have  been  pointed  out  by  many  biologists 


I 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        577 

as  well  as  by  popular  writers.  Long  ago  (1872- 1873),  Darwin 
expressed  to  Galton  his  doubt  as  to  the  feasibility  of  any 
satisfactory  method  of  selecting  the  best  human  stocks  and 
Huxley  (1894)  indicated  the  difficulties  and  dangers  of 
permitting  any  individual  or  class  of  individuals  to  decide 
which  human  famihes  were  most  fit.  Recently  several 
leading  students  of  genetics  have  criticised  many  phases  of 
current  eugencial  propaganda.  Bateson  (192 1),  in  his 
Galton  Lecture  before  the  Eugenics  Education  Society,  while 
endorsing  the  fundamental  principles  of  eugenics,  said  that 
we  know  altogether  too  httle  of  the  ways  in  which  heredity 
and  environment  cooperate  to  produce  genius  to  justify 
at  present  any  extensive  interference  with  human  reproduc- 
tion. He  pointed  out  that  eugenic  caution  might  have  lost 
to  the  world  Beethoven,  Keats,  perhaps  even  Francis  Bacon, 
and  to  these  names  he  might  have  added  many  others, 
such  as  Schubert,  Faraday,  Lincoln  and  a  host  of  others 
in  whom  democracy  glories.  Still  more  recently,  Jennings 
(1925)  and  Pearl  (1927)  have  stressed  the  difficulty,  if  not  the 
impossibihty,  of  deciding  who  are  the  fittest  and  the  real 
danger  that  any  attempted  decision  of  this  kind  might  be 
made  on  the  basis  of  family,  class  or  race  pride  and  arrogance. 
Both  of  these  authorities  also  emphasize  the  fact  that  good 
and  bad  heredity  are  so  mixed  in  all  men,  in  short  that 
man  is  such  a  mongrel  or  heterozygote,  that  no  one  can 
predict  with  any  degree  of  accuracy  what  the  individual 
characteristics  of  the  children  of  any  particular  mating 
will  be,  and  both  insist  that  social  distinction  may  depend 
more  upon  environment  than  upon  heredity. 

All  modern  geneticists  approve  the  segregation  or  sterih- 
zation  of  persons  who  are  known  to  have  serious  hereditary 
defects,  such  as  hereditary  feeblemindedness,  insanity,  etc., 
but  they  very  properly  object  to  the  extravagant  proposals  to 
sterihze  all  persons  who  are  socially  dehnquent.  Bateson  says 
that  the  sterihzation  of  habitual  criminals,  which  has  been 
mooted  in  America,  might  ehminate  many  with  good  inherit- 
ance as  well  as  those  with  hereditary  defects.  Morgan  (1925) 
says  that  the  segregation  of  defectives  is  now  attempted 
on  a  somewhat  extensive  scale  in  asylums  of  the  insane  and 
feebleminded,  but  that  he  "would  hesitate  to  recommend  the 


578  HUMAN   BIOLOGY 

incarceration  of  all  their  relatives  if  the  character  is  suspected 
of  being  recessive."  In  view  of  the  fact  that  East  (191 7)  has 
estimated  that  feeblemindedness  is  carried  as  a  recessive  in  one 
person  out  of  fourteen  in  the  entire  population  of  the  United 
States,  this  hesitancy  on  Morgan's  part  is  more  than  justified. 

As  contrasted  with  some  of  the  extravagant  proposals 
of  propagandists,  against  which  these  scientists  have  pro- 
tested, should  be  cited  the  actual  proposals  of  legislation 
regarding  sterihzation  which  have  been  made  by  the  Ameri- 
can Eugenics  Society:  "State  authorization  by  approved 
physicans  to  sterilize  a  person  who  is  insane,  feebleminded, 
epileptic,  one  with  inherited  blindness  or  deafness  or  other 
very  serious  inherited  defect,  when  desired  by  such  persons 
or  guardians.  The  approval  of  such  proposed  operation 
and  operator  by  a  deputy  appointed  by  the  State  Board  of 
Health  for  such  purpose  is  required."  Can  any  serious 
objection  be  urged  against  such  a  law? 

Many  students  of  heredity  have  criticised  the  condem- 
nation of  a  whole  race  or  class  as  being  genetically  inferior 
and  have  insisted  upon  the  democratic  principle  that  persons 
should  be  measured  by  their  own  worth.  Morgan  (1925) 
very  truly  says:  "If  it  is  unjust  to  condemn  a  whole  people, 
meaning  thereby  a  political  group,  how  much  more  hazardous 
is  it,  as  some  sensational  writers  have  not  hesitated  to 
do,  to  pass  judgment  as  to  the  relative  genetic  inferiority 
or    superiority    of   different    races  ...  A    little    good-will  „ 

might    seem    more    fitting    in    treating    these    complicated  * 

questions  than  the  attitude  adopted  by  some  of  the  modern 
race-propagandists. " 

While  these  criticisms  of  the  more  extreme  advocates 
of  race  superiority  or  of  the  "human  thoroughbred"  are 
fully  justified,  they  do  not  properly  apply  to  the  more 
sober  and  scientific  advocates  of  eugenics.  Admittedly 
it  is  difficult  to  decide  which  human  traits  and  stocks  are 
best,  especially  when  one  considers  the  needs  of  a  distant 
and  unknown  future,  but  it  is  much  easier  to  decide  which 
are  better  and  which  worse.  To  anyone  who  has  first-hand 
knowledge  of  the  many  forms  of  inherited  human  defects,  of 
the  great  differences  between  the  feebleminded  and  the 
highly  intelligent,  between  the  insane  and  the  sane,  between 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        579 

bums  or  thugs  and  useful  members  of  society,  this  alleged 
difficulty  of  deciding  between  the  better  and  the  worse 
appears  to  be  a  purely  academic  matter.  Of  course  eugenicists 
should  avoid  indiscriminate  condemnation  of  whole  races 
or  classes;  real  eugenics  is  as  democratic  as  the  Mendelian 
law  and  recognizes  good  qualities  wherever  they  occur. 
Of  course  eugenicists  should  manifest  the  good-will  which 
Morgan  commends,  but  they  would  be  recreant  to  duty 
and  false  to  truth  if  they  should  affirm  that  "all  men  are 
born  equal"  in  respect  of  bodily  efficiency,  intellectual 
capacity,  or  social  value  and  that  either  west  or  "east  of 
Suez  the  best  is  fike  the  worst. " 

Most  of  these  criticisms  have  been  aimed  at  extravagant 
statements  of  propagandists  and  not  at  the  fundamental 
principles  of  eugenics  proposed  by  Galton  and  his  followers, 
but  Pearl  (1927,  1928)  has  recently  attacked  the  fundamental 
principle  "that  superior  people  will  have,  in  the  main, 
superior  children,  inferior  or  defective  ones,  inferior  or 
defective  children,  and  therefore  that  the  former  should  be 
encouraged  to  have  large  families,  the  latter  small  ones  or 
none  at  all."  By  an  examination  of  all  biographies  that 
occupy  at  least  one  full  page  in  the  Encyclopedia  Britannica, 
he  finds  that  of  the  214  greatest  philosophers,  poets  and 
scientists  who  have  ever  lived,  only  ten  had  superior  or 
distinguished  parents  and  that  95  per  cent  came  of  mediocre 
or  inferior  stock.  "Ordinary  people,"  he  says,  "have  pro- 
duced nineteen  times  as  many  of  the  greatest  human  beings 
•  •  •  as  have  people  in  some  degree  distinguished."  These 
results,  he  admits,  are  objectively  much  the  same  as  Galton's  in 
that  in  his  investigation  of  the  English  judges,  the  latter  ( 1 892) 
found  that  about  nine  times  as  many  distinguished  men  were 
produced  by  mediocre  people  as  were  produced  by  eminent 
people.  But  while  Galton  concluded  that  the  incidence  of 
distinction  was  proportionally  far  greater  in  distinguished 
families  than  in  the  whole  population,  and  indeed  that 
the  chances  that  a  distinguished  man  would  have  a  distin- 
guished son  were  at  least  five  hundred  times  greater  than  that 
an  unknown  man  would  have  such  a  son.  Pearl  maintains 
this  conclusion  is  not  true  biologically  since  it  was  based  upon 
Galton's   so-called    "law   of  ancestral   inheritance,"   which 


580  HUMAN   BIOLOGY 

has  now  been  replaced  by  the  "law  of  Mendel."  Furthermore, 
he  says  that  early  environment  rather  than  heredity  may 
determine  this  greater  incidence  of  distinction  in  distin- 
guished families.  Finally,  Pearl  concludes  that  even  if  the 
argument  of  Galton  and  Pearson  were  completely  true 
biologically,  its  social  apphcation  would  be  questionable,  for 
even  if  the  average  of  the  race  were  raised,  and  modern 
genetics  offers  no  guarantee  of  this,  95  per  cent  of  the  great- 
est men  who  have  ever  lived  ^^ would  never  have  been  horn 
because  the  people  who  were  in  fact  their  parents  would  not 
have  been  allowed  to  breed  under  such  a  regime." 

This  is  the  most  destructive  criticism  of  the  fundamental 
principles  of  eugenics  that  has  ever  come  from  a  distinguished 
geneticist.  Other  criticisms  have  dealt  largely  with  the 
extravagances  of  certain  popular  writers  on  eugenics,  but 
these  criticisms  strike  at  the  very  foundations  of  eugenics 
and  if  they  are  true  indictments,  eugenics  must  go  to  the 
scrap-heap  along  with  astrology  and  other  pseudosciences. 
But  the  eugenicist  may  well  examine  critically  these  criti- 
cisms before  proclaiming  with  Othello  his  occupation  gone. 
It  is  true  thatGalton's"  law  of  ancestral  inheritance"  has  been 
replaced  by  Mendelism  when  dealing  with  the  mechanism  of 
the  hereditary  transmission  of  inheritance  factors,  but  when 
deahng  with  average  results  of  inheritance  in  a  general 
population,  Galton's  law  is  still  true.  It  is  true  that  in 
individual  instances  "hke  does  not  produce  hke,  but  only 
somewhat  like"  as  Brooks  (1899)  expressed  it,  but  on  the 
whole  and  as  an  average  of  mass  results  it  is  true  that  "like 
produces  Hke"  to  such  an  extent  that  this  principle  has  for 
ages  past  furnished  a  valuable  basis  for  selective  breeding; 
how  much  can  be  accomplished  by  such  a  method  is  shown 
by  the  improvements  in  the  breeds  of  domestic  animals  and 
cultivated  plants  in  all  the  period  before  the  discovery  of  the 
Mendehan  principle. 

With  regard  to  Pearl's  conclusion  that  "ordinary  people 
have  produced  nineteen  times  as  many  of  the  greatest  human 
beings  ...  as  have  people  in  some  degree  distinguished,"  it 
is  only  necessary  to  say  in  reply  that  ordinary  people  are  at 
least  several  million  times  as  numerous  as  distinguished 
people  when  measured  by  Pearl's  standard  of  distinction. 


THE    PURPOSIVE    IMPROVEMENT   OF   THE    HUMAN    RACE        58 1 

namely  mention  in  the  Encyclopedia  Britannica.  Of  the 
two  hundred  fourteen  philosophers,  poets  and  scientists 
whose  biographies  occupy  at  least  one  full  page  of  that 
Encyclopedia,  ten  had  parents  of  such  distinction  as  to  merit 
independent  mention.  These  names  are  drawn  from  all 
countries  and  periods  during  the  past  twenty-five  hundred 
to  three  thousand  years  and  during  that  time  it  would  seem 
to  be  a  safe  guess  that  there  must  have  been  in  all  civilized 
countries  at  least  one  billion  parents.  If  all  of  these  had  pro- 
duced great  personages  in  the  ratio  of  1:21,  as  in  the  cases 
cited  by  Pearl,  there  would  have  been  nearly  fifty  million 
persons  instead  of  two  hundred  fourteen  whose  biographies 
would  have  occupied  a  full  page  each  in  the  Encyclopedia. 

Finally  when  Pearl  says  that  95  per  cent  of  the  world's 
greatest  men  would  never  have  been  born  if  reproduction 
had  been  limited  to  distinguished  persons,  it  must  be  granted 
that  this  is  true  but  only  in  the  sense  that  not  a  person  in  the 
world  would  ever  have  been  born  the  same  person  if  he 
had  had  different  parents.  Beethoven  would  not  have  been 
Beethoven  if  his  father  had  been  Haydn,  but  who  can  say 
that  he  might  not  have  been  replaced  by  an  even  greater 
musical  genius? 

Modern  genetics  does  not  support  the  idea  that  genius 
comes  more  frequently  from  mediocrity  than  from  superiority, 
except  in  the  sense  of  the  old  conundrum:  "Why  do  white 
sheep  eat  more  than  black  ones?"  Answer:  "Because  there 
are  more  of  them. "  Genius  has  natural  causes  and  one  of  the 
most  important  of  these  is  heredity.  There  is  no  reason  for 
regarding  it  as  miraculous  in  origin  nor  as  belonging  to  the 
"Order  of  Melchizedek,  who  had  neither  father  nor  mother, 
pedigree  nor  posterity."  Owing  to  extraordinarily  fortunate 
combinations  of  good  genes  and  of  stimulating  environment, 
good  things  may  sometimes  come  out  of  Nazareth  and  world 
leaders  from  poor  stock,  but  the  fundamental  principles  of 
eugenics  are  absolutely  sound  and  Galton's  conclusion  that 
genius  is  hereditary  has  been  abundantly  proved  by  Pearson 
and  his  school,  by  Gowen  (1925),  Terman  (1916,  1915)  and 
practically  by  all  who  have  seriously  studied  this  subject. 
No  doubt  environment  is  very  important  in  the  development 
of  human  personality,  but  the  study  of  identical  twins  by 


582  HUMAN   BIOLOGY 

Galton  and  of  school  children  and  college  students  by  Terman 
and  by  Gowen  have  shown  that  Galton's  conclusion  is 
well  founded  that  "nature  prevails  enormously  over  nur- 
ture when  the  differences  of  nuture  do  not  exceed  what  is 
commonly  to  be  found  among  persons  of  the  same  rank  of 
society  and  in  the  same  country." 

WHAT    ARE   THE    PROBABILITIES    OF    RACE    IMPROVEMENT? 

The  Hmitations  of  eugenics  as  a  means  of  race  improve- 
ment lie  in  the  field  of  practical  appHcation  rather  than  of 
genetical  principles.  Some  of  these  practical  difficulties  in 
the  path  of  eugenic  progress  can  be  overcome  with  an 
aroused  social  conscience,  and  with  increased  knowledge  of 
human  inheritance  and  development  the  time  may  soon 
come  when  all  highly  civilized  nations  will  prevent  by 
segregation  or  sterilization  the  propagation  of  the  worst 
elements  in  society.  This  is  already  being  done  in  many 
states  and  nations  by  the  segregation  of  the  feebleminded, 
insane  and  criminals  in  asylums  and  prisons.  It  is  doubtful 
whether  it  will  ever  be  possible  to  segregate  or  sterilize 
normal  persons  who  are  known  to  come  of  tainted  stock  and 
hence  may  carry  inherited  defects  as  recessive  factors.  By 
means  of  simpler  and  more  effective  means  of  sterilization 
and  especially  by  methods  of  preventing  conception  such 
persons  may  choose  to  be  childless,  and  in  a  stationary 
population,  which  we  may  except  within  a  few  centuries, 
public  sentiment  may  be  a  great  aid  in  restricting  the 
reproduction  of  the  unfit.  Indeed  sentiment  and  custom  are 
much  more  potent  in  such  matters  than  are  legal  enactments. 
Already  the  practice  of  voluntary  birth  control  is  wide- 
spread and  is  rapidly  solving  the  population  problem,  and 
it  is  not  improbable  that  it  will  also  help  to  solve  the  problem 
of  the  propagation  of  hereditary  defects,  for  people  with 
even  a  modicum  of  intelligence  would  prefer  to  have  no 
children  rather  than  to  have  defective  ones. 

More  important  and  still  more  difficult  of  accomplish- 
ment than  such  measures  of  negative  eugenics  are  the 
perpetuation  and  increase  of  the  best  elements  in  human 
society,  or  the  promotion  of  positive  eugenics.  As  civilized 
society  is  at  present  organized  the  most  intelleuctal,  progres- 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        583 

sive  and  ambitious  members  of  society  are  most  heavily  handi- 
capped in  reproduction.  The  long  period  of  education, 
intensive  application  to  preparation  for  a  career,  luxurious 
ideals  of  family  life  and  unwillingness  to  be  burdened  with 
children  have  greatly  reduced  the  fertility  or  have  completely 
sterihzed  some  of  the  best  human  stocks.  Some  silly  aspects 
of  modern  feminism  which  put  individual  freedom  and 
personal  pleasure  before  family  and  racial  duties,  which 
teach  that  social  success  is  a  more  worthy  aim  than  mother- 
hood, and  that  the  devoted  mother  of  a  large  family  is 
to  be  pitied  or  even  ostracised  are  contributing  mightily 
to  race  deterioration.  If  the  heredity  of  the  race  is  to  be 
improved  such  dysgenic  social  customs  must  be  changed  and 
a  premium  put  upon  the  reproduction  of  the  most  fit.  Many 
suggestions  have  been  made  looking  to  this  end  but  appar- 
ently the  only  ones  that  hold  much  promise  of  success  are 
better  education  regarding  eugenics  and  an  awakening  of 
religious  fervor  in  behalf  of  race  betterment. 

While  many  peoples  of  the  western  world  are  cultivating  a 
spirit  of  race  suicide  among  the  most  intelligent  and  progres- 
sive elements  of  society,  the  peoples  of  the  Orient  still  regard 
reproduction  as  a  supreme  duty  to  the  family  and  the  race. 
The  ancient  cry  of  Rachel,  "Give  me  children  or  I  die"  is 
still  the  cry  of  the  great  mass  of  women  of  the  East,  where 
the  most  honorable  salutation  to  a  woman  is,  "May  you  be 
the  mother  of  many  sons!"  Many  eastern  and  some  western 
countries  are  already  overpopulated  and  the  need  of  the 
whole  world  is  not  for  more  people  of  the  mediocre  or  inferior 
sorts  but  rather  more  of  the  better  and  fewer  of  the  worse 
varieties.  To  what  extent  this  spirit  of  the  East  can  be 
Hmited  to  the  better  portion  of  the  population,  and  whether 
any  similar  spirit  may  be  aroused  in  the  western  world  is 
doubtful,  but  upon  such  a  differential  between  the  better 
and  the  poorer  lines  the  whole  program  of  eugenics  depends. 

In  the  meantime  environment  can  be  and  will  be  greatly 
improved.  There  is  now  much  greater  opportunity  for  every 
person  to  develop  his  innate  potentialities  than  ever  before  in 
the  world's  history.  Education  and  social  cooperation  are 
more  widespread  than  ever  before.  Science  is  discovering 
means  of  preventing  disease,  prolonging  life  and  increasing 


584  HUMAN   BIOLOGY 

efficiency.  While  these  improvements  of  environment  and 
of  development  do  not  directly  improve  heredity  they  do 
open  the  way  to  an  indirect  attack  upon  that  problem. 
Whatever  is  accompHshed  in  the  way  of  eugenics  or  euthenics 
must  be  through  inteUigence,  education  and  social  coopera- 
tion and  of  these  three  factors  education  is  the  one  that  can 
be  most  readily  controlled.  Education  in  the  broadest  sense 
is  the  chief  hope  of  human  progress. 

THE  DISTANT  FUTURE  , 

When  one  looks  back  upon  a  billion  years  of  hfe  upon 
this  planet  and  forward  to  another  possible  billion  years, 
he  cannot  fail  to  inquire  whether  there  is  likely  to  be  any 
such  evolutionary  progress  in  the  future  as  there  has  been 
in  the  past.  Will  the  human  race  persist  and  become  more 
perfect  in  body,  mind  and  society,  or  will  it  also  go  the  way 
of  every  species  of  former  geological  ages?  Of  course  one  can 
only  speculate  about  such  questions,  but  there  are  certain 
scientific  data  that  may  serve  as  a  basis  for  such  speculations. 

In  the  past,  progressive  evolution  has  led  to  increasing 
specialization  and  integration  of  increasing  numbers  of 
living  units;  to  increasing  complexity  and  perfection  of 
structures,  functions  and  adaptations;  to  increasing  respon- 
siveness, capacity  of  profiting  by  experience,  intelligence, 
control  over  environment,  freedom.  The  pressure  of  over- 
production of  individuals  and  variations  has  forced  living 
things,  like  plastic  clay,  into  every  possible  crack  and 
cranny  and  way  of  escape.  Whenever  in  the  past  evolution 
has  gone  as  far  as  possible  in  any  single  line,  some  other  path 
of  outflow  has  been  found.  Organisms  have  probably  already 
explored  every  path  that  was  possible  to  them.  But  in  the 
course  of  past  ages  new  paths  have  been  made  possible  not 
only  by  changes  in  environment  but  also  by  changes  in  the 
organisms  themselves. 

One  of  the  most  important  lines  of  evolution  in  the  past 
was  the  path  of  multicellularity,  by  which  multitudes  of 
cells  are  integrated  into  tissues,  organs,  systems,  persons, 
thus  affording  means  of  progress  in  size  and  in  differentiation 
and   perfection   of  structures,    functions   and   adaptations, 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        585 

But  progress  in  most  if  not  all  of  these  lines  long  ago  reached 
its  possible  Hmits  within  a  single  individual. 

Another  Hne  of  evolution  w^as  found  by  a  few  animals 
in  the  combination  of  persons  into  societies  which  are  the 
highest  and  most  complex  type  of  organization  that  has  yet 
appeared  on  earth.  It  is  very  probable  that  this  path  has  not 
yet  been  fully  explored,  certainly  there  seem  to  be  many 
opportunities  for  further  advance  along  this  line  both  for 
animals  and  man. 

Finally  the  path  of  increasing  responsiveness,  capacity 
of  profiting  by  experience,  intelhgence,  control  over  environ- 
ment and  consequent  freedom,  represents  the  most  important 
outlet  that  is  now  open  to  the  highest  organisms. 

In  all  of  these  paths  man  has  made  great  progress.  But 
there  does  not  seem  to  be  much  if  any  improvement  to  be 
expected  from  further  increase  in  the  size  or  complexity  of 
his  body;  in  this  direction  his  progress  has  practically  come 
to  an  end. 

In  social  speciahzation  and  cooperation,  mankind  is 
at  present  making  its  most  important  advance  and  the  end 
in  this  direction  is  not  yet  in  sight.  The  same  is  true  of  the 
advance  in  intelhgence  and  control  of  environment.  The 
most  rapid  and  significant  advance  in  human  evolution  has 
passed  on  from  individual  cells  to  persons,  then  to  social 
organizations,  and  it  now  takes  in  the  environment,  for  man  is 
now  adding  to  his  own  individual  powers  the  inimitable  forces 
of  the  universe.  In  such  a  brief  sketch  one  may  catch  a 
ghmpse  of  the  general  course  of  past  and  present  evolution 
and  of  its  probable  future. 

Certain  human  famihes  and  stocks  are  now  becoming 
extinct  and  in  the  distant  future  this  may  extend  to  some  of 
the  primary  races  of  mankind,  but  it  seems  probable  that 
some  of  these  disappearing  races  will  be  incorporated  in  the 
surviving  ones.  By  extensive  intercommunication  and 
hybridization,  it  is  probable  that  the  distinction  between 
existing  races  will  gradually  disappear.  In  this  process 
it  is  possible  that  new  types  may  arise  which  may  ultimately 
replace  the  older  types,  and  thus  human  evolution  may 
go  on.  But  so  far  as  one  can  now  foresee  there  is  no  likelihood 
that  the  entire  human  race  will  become  extinct  before  other 


586  HUMAN   BIOLOGY 

higher  animals  do,  and  therefore  there  is  httle  probabihty 
that  man  will  disappear  and  leave  the  lead  to  some  other 
type  of  animal.  Already  man  controls  his  environment  to 
such  an  extent  that  it  is  almost  inconceivable  that  his 
race  should  be  wiped  out  and  leave  other  forms  of  hfe 
persisting  which  are  so  much  more  the  slaves  of  environment 
than  he  is. 

There  is  no  probabihty  that  the  human  race  will  ever 
become  perfect  in  body,  mind  or  society;  no  doubt  there  will 
always  be  room  for  improvement.  There  may  be  a  reduction 
in  the  relative  amount  of  degeneracy,  a  decrease  in  the 
numbers  of  the  bungled  and  botched,  the  feebleminded  and 
insane,  the  antisocial  and  the  brutal,  but  probably  without 
any  prospect  of  ehminating  all  degeneracy.  There  may  be 
an  increase  in  the  relative  number  of  really  superior  persons 
until  the  general  level  may  be  more  nearly  that  of  the  best 
specimens  of  the  present  race,  but  there  is  no  likehhood  that 
the  entire  race  can  be  made  illustrious  or  perfect. 

Possibly  new  mutations  may  occur  that  may  lead  to 
the  production  of  individuals  superior  to  any  that  have 
appeared  hitherto,  superior  in  physical  vigor  and  length  of 
Hfe,  in  mental  capacity  and  performance,  in  social  and 
moral  quahties.  But  if  such  mutants  should  appear,  they 
would  have  to  be  preserved  and  perpetuated  by  intelligent 
social  selection  rather  than  by  natural  selection,  for  man  is  no 
longer  the  slave  of  his  environment  or  the  helpless  victim  of 
circumstance.  To  a  large  extent  he  shapes  his  own  environ- 
ment and  to  that  extent  he  controls  his  own  destiny. 

Consequently  great  secular  changes,  such  as  changes 
of  climate,  the  coming  of  another  ice  age,  the  formation  of 
deserts,  or  the  rising  or  falling  of  continents  would  never 
again  affect  the  human  race  as  greatly  as  they  did  in  the 
past.  Changes  in  climate  might  cause  extensive  migra- 
tions, another  ice  age  might  make  tropical  resorts  popular, 
formation  of  deserts  might  necessitate  extensive  irrigation 
projects,  changes  in  the  land  and  water  areas  of  the  globe 
might  necessitate  extensive  migrations  but  they  would 
probably  not  greatly  change  the  human  type,  for  man  now  is 
able  to  control  his  environment  rather  than  permit  it  to 
control  him.  And  the  more  he  is  able  to  control  the  condi- 


THE    PURPOSIVE    IMPROVEMENT    OF   THE    HUMAN    RACE        587 

tions  of  his  life,  the  less  chance  will  there  be  for  natural 
evolution. 

In  large  part  the  future  evolution  of  man  will  be  self- 
directed  and  his  progress  will  be  an  approach  to  his  own 
ideals.  One  of  the  chief  joys  of  life  is  growth,  one  of  the 
deepest  desire  of  the  entire  human  race  is  for  progress.  But 
in  spite  of  these  emotions  and  desires,  human  beings  would 
not  willingly  abandon  their  humanity  in  order  to  become 
superhuman.  Their  ideals  are  not  of  some  other  more 
perfect  species  but  rather  of  a  more  perfect  humanity. 
Even  his  gods  have  always  been  created  in  man's  own  image. 
Even  the  most  ecstatic  visions  of  a  new  heaven,  a  new  earth 
and  a  new  humanity  are  still  in  specific  type  the  old  heaven 
and  earth  and  humanity  slightly  remodelled.  Our  highest 
ideals  are  merely  new  combinations  of  the  most  perfect 
conditions,  traits  and  beings  that  we  have  known.  In  his 
vision  of  the  future  triumphs  of  the  race,  Whittier  describes: 

A  dream  of  man  and  woman 
Diviner  but  still  human, 
Solving  the  riddle  old, 
Shaping  the  Age  of  Gold. 

And  all  the  visions  and  aspirations  of  poets,  prophets  and 
seers  cannot  picture  any  more  ideal  being  than  man  released 
from  his  imperfections  and  limitations.  If  the  future  evolution 
of  man  will  be  largely  self-directed  and  if  the  goal  toward 
which  he  would  go  is  merely  a  more  perfect  humanity, 
it  follows  that  there  is  no  probability  that  the  human  race 
will  ever  in  the  future  give  rise  to  other  orders  or  genera  or 
species  of  superior  beings,  no  prospect  that  the  future 
evolution  of  man  will  duplicate  the  tremendous  advances  of 
his  past  evolution.  By  his  knowledge  and  power  man 
has  in  a  measure  risen  above  nature,  he  has  eaten  of  the  fruit 
of  the  tree  of  knowledge  and  has  become  as  the  gods, 
knowing  good  and  evil,  and  now  it  remains  to  be  seen 
whether  in  future  ages  his  race  may  secure  the  fruit  of  the 
tree  of  life  and  become  immortal. 

REFERENCES 

Bagg,  H.  J.  1920.  Individual  differences  and  family  resemblances  in  animal 
behavior;  a  study  of  habit  formation  in  various  strains  of  mice.  Arch. 
Psychol.,  No.  43,  1-63. 


588  HUMAN    BIOLOGY 

Bateson,   W.    1921-22.   Common   sense   in   racial   problems.   Eugenics  Rev., 

13: 325-338. 
Bell,  A.  G.  1914.  How  to  improve  the  human  race.  J.  Heredity,  5:  1-7. 
Brooks,  W.  K.  1899.  The  Foundations  of  Zoology.  N.  Y.,  Macmillan. 
CoNKLiN,   E.  G.    191 5.   Heredity  and  Environment  in  the  Development  of 

Men.  Princeton  Univ.  Press. 
1923.  The  Direction  of  Human  Evolution.  N.  Y.,  Scribner. 
Darwin,  F.  1903.  More  Letters  of  Charles  Darwin.  Vol.  2.  N.  Y.,  Appleton. 
East,  E.  M.  19 17.  Hidden  feeble-mindedness.  J.  Heredity,  8:  215-217. 
Galton,  F.  1914.  Hereditary  Genius.  Lond.,  Macmillan. 
GoDDARD,  H.  H.   191 1.  Heredity  of  feeble-mindedness.  Cold  Spring  Harbor, 

N.  Y. 
GowEN,  J.  W.,  and  Gooch,  M.  S.    1925.  Mental  Attainments  of  College 

Students  in  Relation  to  Previous  Training,  Environment,  and  Heredity. 

Univ.  of  Maine  Studies,  S.  2,  No.  5;  1-22. 
Huxley,  T.  H.  1894.  Evolution  and  Ethics,  Prolegomena.  (Collected  essays, 

Vol.  9,  N.  Y.,  Appleton.) 
Jennings,  H.  S.  1925.  Prometheus.  N.  Y.,  Dutton. 
McDougall,  W.   1927.  An  experiment  for  the  testing  of  the  hypothesis  of 

Lamarck.  Brit.  J,  Psychol.,  17:  267-304. 
MacDowell,  E.  C.  1924.  Experiments  with  rats  on  the  inheritance  of  training. 

Science,  59:  302-303. 
Morgan,  T.  H.  1925.  Evolution  and  Genetics.  Princeton  Univ.  Press. 
Pavlov,   L   P.    1923.   New  researches   on   conditioned    reflexes.   Science,  58: 

359-361. 
Pearl,  R.  1927.  The  biology  of  superiority.  Am.  Mercury,  12:  257-266. 

1928.  The  Present  Status  of  Eugenics.  Hanover,  N.  H.,  Sociological  Press. 
Prentiss,  M.  O.   1927.  The  Cost  of  Crime.  Manufacturers  Record,  Feb.  24. 

(Quoted  from  Huntington  and  Whitney,  1927,  The  Builders  of  America. 

N.  Y.  Morrow.) 
Terman,  L.  M.  1916.  The  Measurement  of  Intelligence.  Boston,  Houghton. 


Chapter  XXV 

THE  INTENTIONAL  SHAPING  OF  HUMAN 

OPINION 

H.  A.  OVERSTREET 

WHAT  seems  most  significant  about  our  human  order 
of  life  is  that  we  can  intentionally  reshape  our 
fundamental  behavior  patterns.  In  the  lower  orders 
these  patterns:  food-getting,  shelter,  sex,  group-hving,  etc., 
appear  to  be  almost  entirely  fixed.  Generation  follows 
generation  with  no  changes  save  those  slowly  wrought  by 
the  impersonal  forces  of  Nature.  We,  on  the  contrary,  seem 
able  to  take  thought;  and  while  we  cannot  thereby  add  a 
cubit  to  our  stature,  we  can  so  alter  our  ways  of  doing 
things  as  to  create  for  ourselves  successively  more  adequate 
worlds.  On  the  level  of  humankind,  in  short,  we  seem  to 
discover  a  type  of  causal  agency,  thought,  which,  for  the 
first  time,  with  a  degree  of  obvious  power,  makes  itself  felt 
in  the  evolutionary  process. 

What  thought  is,  still  remains  so  much  a  matter  of  con- 
troversy that  it  need  not  detain  us  here.  But  that  thought 
actually  exists  and  that  it  is  productive  of  far-reaching 
changes  in  our  behaviors  ought  to  be  so  obvious  as  to  need  no 
defense.  And  yet  there  are  those  who  take  but  small  stock 
in  the  power  of  thought  to  change  our  fundamental  behav- 
iors. They  are  the  behevers  in  the  inborn  and  unchangeable 
character  of  human  nature.  They  point  to  the  basic  instincts, 
of  pugnacity,  food-getting,  sex,  etc.,  and  assert  that  these 
are  what  govern  and  will  always  govern  man's  hfe.  But  they 
fail  to  make  a  distinction.  Sex  may  be  a  fundamental  bio- 
logical pattern,  but  the  ways  in  which  the  sex  life  can  operate 
will  be  as  different  as  that  between  the  savage  who  drags 
his  wife  home  with  a  club  and  the  modern  urbanite  who  goes 
a-wooing  in  his  motor  car.  Food-getting  may  be  fundamental, 
but  the  ways  will  differ  from  the  crude  hunting  of  the 
primitive  to  the  organized  husbandry  of  the  modern.  No 
doubt  the  raw  material  of  human  life  remains  steadfast,  but 

589 


590  HUMAN    BIOLOGY 

the  ways  in  which  that  raw  material  is  shaped  and  reshaped 
are  as  multitudinous  as  the  generations  of  man. 

The  really  significant  processes  of  human  hfe,  in  fact, 
would  seem  to  be  marked  by  the  passage  from  one  powerful 
thought  system  to  another.  At  the  present  time,  two  such 
thought-transitions  are  apparent.  The  first  has  to  do  with  the 
so-called  instinct  of  pugnacity.  For  a  number  of  centuries 
the  thought  governed  mankind  that  war  was  both  a  natural 
and  an  honorable  mode  of  setthng  differences  between 
poHtical  units.  That  thought  is  beginning  to  lose  its  undis- 
puted power.  It  seems  not  extravagant  to  predict  a  time 
when  the  thought  of  setthng  pohtical  conflicts  by  kilhng 
people  will  appear  so  monstrously  absurd  as  to  be  relegated 
to  barbarism. 

During  the  centuries  in  which  the  war  point  of  view 
prevailed,  a  thousand  and  one  behaviors  resulted.  War 
departments  were  organized,  war  leaders  trained,  armies 
were  enlisted,  navies  built,  guns  were  manufactured,  schools 
of  strategy  were  maintained,  defensive  patriotism  was 
taught,  war  heroes  were  lauded.  The  war-idea,  in  short, 
was  the  powerful  cause  which  generated  a  vast,  mutually 
supporting  system  of  behaviors.  On  the  other  hand,  let  the 
thought  once  begin  to  prevail  that  war  is  a  monstrous 
absurdity,  and  the  ground  is  cut  away  from  all  these  modes 
of  behavior.  Other  behavior-patterns  will  begin  to  be  shaped. 
Departments  for  mutual  cooperation  will  succeed  depart- 
ments for  mutual  annihilation;  armies  will  be  devoted  to  the 
conquest  of  Nature  instead  of  the  conquest  of  men.  In  short, 
the  typical  institutions  and  the  typical  heroisms  will  come  to 
be  those  which  contribute  to  the  upbuilding  rather  than 
to  the  destruction  of  life. 

In  another  respect  also  the  western  world  is  passing  from 
one  powerful  thought  system  into  another.  In  this  case  it  is 
in  connection  with  the  basic  pattern  of  food-getting.  In  the 
early  nineteenth  century  the  invention  of  steam-driven 
machinery  opened  up  unexpected  opportunities  for  accumu- 
lating wealth.  Up  to  that  time  the  feudal  thought-system 
had  built  up  characteristic  behavior-patterns.  Chief  among 
these  was  the  obligation  for  life-long  service  on  the  part  of 
retainers   and  responsibility   for  defense  and  livelihood  on 


THE    INTENTIONAL    SHAPING    OF    HUMAN    OPINION  59 1 

the  part  of  the  overlords.  The  invention  of  steam-driven 
machinery  swept  away  this  feudal  point  of  view,  bringing 
in  its  place  the  new  generating  idea  of  free  competitive 
enterprise.  With  the  new  idea-system  came  the  independence 
of  the  worker,  but  also  the  release  of  the  overlord  from 
responsibility  for  the  support  of  his  retainers.  We  all  know 
the  fairly  tragic  story  of  what  happened  as  the  feudal  idea 
began  to  fade  out  and  the  free-enterprise  idea  began  to 
prevail.  There  came  the  "masterless"  man,  the  wage-earner; 
there  came  the  ruthless  misuse  of  the  Hves  of  the  workers; 
there  came  a  new  kind  of  poverty,  city  slums  and  regimented 
factory  slaves.  Then  slowly,  as  we  know,  two  new  ideas 
began  to  emerge.  On  the  one  hand,  there  was  the  thought 
that  the  pohtical  order  must  now  take  some  of  the  respon- 
sibihty  hitherto  assumed  by  the  feudal  chiefs.  Factory 
legislation  was  born.  On  the  other  hand,  the  idea  developed 
among  the  workers  that  they  must  now  stand  together  in 
their  own  defense.  The  trade  union  was  born,  with  the 
alleviating  and  reconstructive  results  that  we  know. 

At  the  present  time,  the  alert  mind  easily  senses  the  fact 
that  the  economic  world,  being  still  far  less  than  perfect  in 
its  organization,  is  in  transition.  Poverty  has  been  dimin- 
ished, but  fear  remains.  Factory  slavery  is  less  degrading  but 
drabness  rules.  The  State  has  assumed  obhgation,  but  riches 
flaunt  their  opportunities  in  the  face  of  labor.  At  the  present 
time,  western  civihzation  is  apparently  fumbhng  forward 
to  a  new  underlying  idea  that  will  enable  it  to  produce, 
exchange  and  consume  without  the  fairly  tragic  waste  of  hfe 
entailed  by  the  present  system. 

From  the  foregoing  we  may,  I  think,  properly  conclude 
that  the  really  significant  history  of  mankind  is  the  history 
of  the  change  of  its  governing  thoughts  about  things.  What 
we  call  progress,  in  brief,  would  seem  to  be  the  substitution 
(however  caused)  of  a  thought-system  which  generates  more 
adequate  for  one  which  generates  less  adequate  satisfactions. 

CAN  GOVERNING  IDEAS  BE  INTENTIONALLY  CHANGED? 

If  this  is  true,  then  the  most  important  question  which 
human  life  could  seem  to  ask  itself  would  be:  How  can  we 


592  HUMAN   BIOLOGY 

intentionally  change  our  less  adequate  governing  ideas? 
Back  of  that,  of  course,  is  the  previous  question:  Can  we 
intentionally  change  our  present  governing  ideas?  Are  not 
the  ideas  that  rule  our  behavior  themselves  the  creatures  of 
circumstances,  generated  in  us  by  impersonal  forces  that 
are  beyond  our  conscious  control?  To  return  to  our  examples, 
was  it  not  steam-driven  machinery  which  brought  the  new 
idea  of  free-enterprise,  and  was  it  not  the  exigencies  of 
poverty  and  the  misuse  of  hfe  which  forced  the  ideas  of 
factory  legislation  and  collective  bargaining?  Again,  was  it 
not  the  unspeakable  horror  of  the  late  international  slaughter 
which  made  the  war-idea  so  monstrous  that  it  had  to  be 
cast  away?  Do  men  ever  intentionally  shape  new  ruhng 
ideas?  Are  we  not  in  this,  as  in  all  matters,  in  the  grip  of 
forces  greater  than  ourselves? 

The  answer  to  such  questions  is  difficult  to  obtain  and 
even  when  we  have  ventured  one  answer,  there  will  still  be 
doubt.  It  may  help  to  clear  the  issue,  however,  if  we 
examine  a  case  of  idea-change  which  we  seem,  in  a  measure, 
to  be  able  to  trace  to  conscious  beginnings. 

Perhaps  the  most  profound  of  the  idea-changes  which 
have  been  effected  among  us  is  the  development  of  the 
scientific  habit  of  thought.  In  many  regions  of  hfe,  to  be  sure, 
and  about  a  multitude  of  matters,  that  habit  of  thought  is 
still  not  developed,  but  in  most  of  our  western  world,  in 
all  that  concerns  physical  matters,  the  scientific  habit  of 
thought  now  rules  with  a  fair  degree  of  universality. 

To  illustrate  by  contrast,  let  me  recall  a  pathetically 
amusing  case  which  happened  recently  in  a  small  town  near 
New  York.  An  Italian  boy  had  been  taken  ill.  The  sister, 
who  was  a  university  student,  suggested  calling  a  doctor. 
But  the  peasant  mother  would  have  none  of  it.  She  sent  for  an 
old  woman  who  was  reputed  to  cure  by  magic.  When  the 
old  woman  came,  she  directed  that  all  the  dishes  in  the 
house  be  brought  into  the  boy's  room  and  spread  about 
him.  Then  she  poured  a  drop  of  oil  into  each  plate,  pro- 
nouncing as  she  did  so  an  incantation.  Then  the  plates  were 
gathered  up,  more  incantations  were  pronounced,  and  she 
left.  In  the  course  of  time,  the  boy,  being  a  fairly  healthy 
youngster  and   suffering   only   from   an   over-dose   of  food 


THE    INTENTIONAL   SHAPING   OF   HUMAN   OPINION  593 

recovered.  For  the  mother  there  was  not  the  slightest  doubt 
that  the  magic  of  the  old  woman  had  turned  the  trick. 

Here  was  a  fundamental  idea  governing  the  behavior  of 
this  Itahan  woman,  an  idea  which,' one  suspects,  it  would  be 
difficult  to  find  among  the  average  folk  of  our  modern 
western  world.  Formerly,  of  course,  the  Italian  mother's 
attitude  was  universal.  How  came  it  that  the  change  was 
made  from  the  magic-idea  to  the  now  prevaihng  physical- 
cause-and-effect  idea? 

The  story  goes  back,  of  course,  into  ancient  history  when 
men  hke  Thales,  Democritus,  Leucippus,  Archimedes, 
Hippocrates,  and  others  refused  to  follow  the  prevaihng 
ignorances  and  superstitions  and  made  their  independent 
observations  of  the  world.  But  the  most  dramatic  episode  in 
the  story,  I  venture  to  beheve,  occurred  about  three  hundred 
years  ago  when  the  young  Itahan  Gahleo  made  his  starthngly 
simple  experiment  from  the  top  of  the  Tower  of  Pisa.  That 
experiment  was  a  direct  challenge  to  the  older  truth-tech- 
nique, which  had  rehed  upon  tradition  and  authority  and  had 
made  no  effort,  by  observation,  experimentation  and 
calculation,  to  discover  the  actual  relationships  existing  in 
the  physical  world.  Out  of  Gahleo  as  we  know,  and  largely 
because  of  his  actual  experimentation,  there  grew  the 
brilhdnt  activity  of  the  succeeding  three  hundred  years, 
which  included  such  men  as  Newton,  Huyghens,  Hehnholtz, 
Faraday,  Clerk  Maxwell,  Einstein,  and  the  rest,  and  which 
generated  a  way  of  thinking  about  the  world  and  of  doing 
things  in  it  and  with  it  wholly  new  in  human  history. 

The  examination  of  what  actually  happened  in  this 
case  may  perhaps  give  us  a  helpful  clue  to  the  question: 
How  can  we  intentionally  reshape  our  governing  thought- 
systems? 

HOW    OUR    GOVERNING    THOUGHTS    MAY   BE    RESHAPED 

Starting  with  Galileo,  let  us  look  for  the  widening  influence 
of  his  challenging  idea.  In  the  first  place,  there  was  the 
individual,  himself,  product,  no  doubt,  of  his  environment, 
but  bringing  into  his  environment  something  that  was  not 
already  there.  What  was  this  so-called  environment?  In  one 


594  HUMAN   BIOLOGY 

sense  it  was  the  same  as  that  of  the  traditionahsts  who 
opposed  him.  In  another  sense  it  was  different.  His  selective 
mind  saw  things  that  they  did  not  see.  Also,  he  read  what 
they  did  not  read  and  pondered  the  things  he  read  in  ways 
to  which  they  were  not  accustomed.  In  short,  Gahleo  was 
not  simply  a  product  of  his  environment.  He  was  a  selective 
mind  which  in  large  measure  shaped  its  own  environment. 

This,  it  seems  to  me,  is  the  first  fundamental  factor.  Back 
of  all  these  three  centuries  of  brilliant  transformation  stands 
a  mind  looking  out  independently  at  its  world. 

But  there  was  a  second  important  factor.  Galileo's  mind 
was  associated  with  other  minds.  First  there  was  his  associa- 
tion with  minds  that  had  gone  before,  the  minds  kept 
alive  on  the  printed  page.  In  the  second  place  there  was  the 
association  with  contemporary  minds  of  like  interest  and 
similar  intelligence.  Out  of  this  association  there  arose  that 
mutual  give  and  take  of  ideas,  that  checking  up,  that  recog- 
nition of  unity  in  diversity  which  seems  to  be  essential  to  all 
effective  thinking. 

Then  there  came  a  third  stage.  Those  who  were  fired  by 
the  same  interests  came  to  the  laboratories  of  Galileo  and 
the  other  masters  to  watch  them  work  and  to  work  with 
them.  Also  there  grew  up  the  need  for  new  modes  of  scientific 
communication.  Where  formerly  the  few  masters  could 
write  personal  letters  to  one  another,  accounts  of  experiments 
now  began  to  be  printed  and  exchanged  among  the  investiga- 
tors. The  scientific  Journal  was  born.  Books  were  printed  for 
those  who  were  expert  in  the  field. 

Generations  passed  while  these  things  were  taking  place. 
Galileo  and  the  first  masters  died,  and  others  followed. 
Then  came  the  fourth  stage.  Research  began  to  be  widespread, 
workshops  of  investigation  were  accepted  as  essential  for 
truth-seeking,  journals  and  books  were  widely  issued. 
Discoveries  followed  discoveries.  Above  all,  practical  use 
was  made  of  the  discoveries.  Whereat  we  enter  the  fourth 
stage — of  teaching  the  results  to  the  non-expert.  The  school 
master  conveyed  the  scientific  information  to  his  pupils. 
Books  and  journals  were  written  now  not  for  expert  alone, 
but  for  the  non-expert,  e.g.  the  children  in  the  schools,  the 
youth  in  the  colleges,  and  for  the  older  folk.  What,  in  short. 


THE    INTENTIONAL    SHAPING    OF    HUMAN   OPINION  595 

began  in  the  brain  of  one  man  finally  reached  the  masses  of 
the  population. 

The  story,  of  course,  thus  briefly  sketched,  was  far 
from  brief  in  its  unrolling.  Nor  was  its  unrolling  quite  as 
smooth  as  we  have  seemed  to  indicate.  But  in  the  end 
Galileo's  challenge  won.  Hated  in  his  time  by  the  priests 
and  the  academic  traditionalists,  forced  even  to  recant,  his 
fundamental  idea  now  rules  so  securely  that  any  thought  of 
going  back  to  the  attitudes  and  procedures  of  his  tormentors 
is  completely  out  of  the  question. 

CAN    SCIENTIFIC-MINDEDNESS   BECOME    THE    GOVERNING 
THOUGHT    IN    OUR   WORLD    OF    SOCIAL  VALUES? 

I  have  chosen  this  example  for  the  reason  that  if  one  were 
asked  what  idea-habit  most  needs  to  be  developed  in  the 
modern  world  the  answer,  it  seems  to  me,  would  run  some- 
thing as  follows:  In  the  physical  world,  Galileo  and  his  suc- 
cessors have  won;  in  the  world  of  individual  and  social  values, 
they  still  remain  largely  defeated.  And  the  question  forces 
itself,  can  the  type  of  thinking  which  has  so  powerfully 
transformed  our  physical  world  become  the  ruling  type  of 
thinking  in  our  world  of  human  values?  We  need  not 
elaborate  upon  the  comparative  rarity  of  scientific-mindedness 
in  matters  political,  economic  and  social.  The  question 
which  needs  answering  is,  what  can  be  done  to  generate 
scientific-mindedness  in  these  deplorably  unscientized 
regions?  Can  the  modern  world  deliberately  set  itself  to 
building  a  Galilean  habit  of  thought  in  the  social  as  well  as 
the  physical  areas  of  its  life? 

The  answers  usually  given  to  this  question  are  fairly 
discouraging.  How,  it  is  said,  can  we  ever  expect  a  newspaper- 
fed,  movie-debauched,  prejudice-ridden  mass  of  people  to 
regard  all  human  questions  with  the  detachment  and  the 
generous  all-roundness  of  the  scientific  mind?  The  thing 
seems  inconceivable.  And  yet  is  it  so?  May  it  not  be  that  in 
this  matter,  as  in  the  case  of  Galileo,  the  mills  of  the  gods 
grind  slowly,  but  they  do  somehow  grind? 

It  seems  worthwhile  to  go  back  to  our  first  fundamental. 
There  was  Galileo,  the  individual  thinker.  But  more  than 
that  there  was  Galileo  the  experimenter.  This,  it  seems  to  me, 


596  HUMAN   BIOLOGY 

is  crucial.  Galileo  did  not  simply  talk  about  what  he  beheved 
to  be  true.  He  cHmbed  to  the  tower's  top  and  did  some- 
thing that  could  be  accurately  verified.  That,  doubtless, 
in  the  end,  was  why  he  won.  The  experiment  he  performed 
carried  its  own  persuasion. 

In  the  field  of  social  values,  it  is  at  once  apparent,  there 
are  many  thinkers  but  few  experimenters.  These  thinkers 
would  hke  to  ehminate  poverty,  would  like  to  have  a  warless 
world,  would  like  to  develop  a  citizenry  of  tolerant  and 
growing  minds,  would  like  to  put  color  and  adventure 
into  the  human  scene.  For  the  most  part  they  write  books 
about  these  matters.  In  other  words,  they  use  the  fairly 
easy  technique  of  verbal  persuasion  instead  of  the  much 
more  difficult  but  far  more  powerful  technique  of  persuasion 
by  experiment. 

Can  experimentation  be  introduced  into  the  field  of  human 
values?  There  are,  I  think,  at  least  two  outstanding  examples 
which  are  worth  examining.  The  first  has  to  do  with  a  pro- 
found change  of  ideas  about  what  education  means.  In 
this  case  the  Tower  of  Pisa  was  at  the  University  of  Chicago, 
and  the  Galileo  in  question  was  a  professor  of  philosophy, 
John  Dewey.  Dewey  believed  that  the  basic  ideas  then  pre- 
vailing in  education  were  in  error.  He  seemed  to  find  in  the 
schools  no  effort  to  tie  up  the  material  of  instruction  with 
the  actual  life  of  the  children  in  such  manner  as  to  make 
it  both  significant  and  vitally  effective.  He  might  have 
expounded  the  matter  to  his  students  and  gone  no  further. 
On  the  contrary,  convinced  of  the  idea  that  education  must 
in  every  respect  be  vital  to  each  age-period  and  must 
actually  function  in  the  life  of  the  child,  he  established  a 
school  in  which  to  try  out  his  ideas.  As  the  school  began 
to  show  results,  interested  educators  came  to  observe. 
Some  of  these  went  away  and  established  other  schools.  A 
wider  circle  of  teachers  observed  and  carried  the  methods 
into  their  classrooms.  Articles  began  to  be  written.  That 
was  in  1896.  Today,  only  a  little  more  than  thirty  years 
later,  the  Dewey-idea  of  education  has  become  so  powerful 
among  the  progressives  in  education  that  it  not  only  begins 
to  circle  the  globe  but  it  bids  fair  to  penetrate  and  transform 
the  traditional  system  of  instruction. 


THE    INTENTIONAL   SHAPING    OF    HUMAN    OPINION  597 

Let  me  cite  a  second  example.  In  the  middle  of  the  nine- 
teenth century  the  peasantry  of  Denmark  were  in  a  fairly 
deplorable  condition.  They  were  ignorant,  and  economically 
they  were  almost  bankrupt.  An  idea  was  born  in  the  mind 
of  a  thinking  individual,  N.  F.  S.  Grundtvig.  It  was  the  idea 
that  what  the  Danish  peasantry  needed  was  responsible 
inteUigence  and  that  through  responsible  intelligence  they 
could  raise  the  status  of  their  own  and  their  country's 
life.  But  he,  too,  did  not  simply  preach  his  behef.  He  tried 
the  experiment  of  gathering  a  group  of  young  men  about 
him  and  of  starting  with  them  the  process  of  self-education. 
That  was  the  beginning  of  the  Danish  Folk  High  School. 
Today,  in  a  small  country  less  than  half  the  size  of  Indiana, 
there  are  over  sixty  of  these  schools  for  adults.  But  what 
is  more  noteworthy  is  that,  directly  as  a  result  of  this 
ideal  developed  in  the  brain  of  one  man  and  growing  stronger 
through  widening  circles  of  followers,  the  Danish  farmer 
as  a  class  is  today  probably  the  most  enhghtened,  coopera- 
tive and  prosperous  in  the  world. 

VALUE  OF  CONSTRUCTIVE  IDEAS  CAPABLE  OF 
EXPERIMENTAL  TEST 

These  two  examples  will  be  sufficient  to  serve  our  present 
purpose,  although  a  number  of  others  might  be  cited.  From 
these  examples  it  seems  possible  to  assert  that  intentional 
reshaping  of  the  basic  thought-systems  of  man  can  be 
accomplished.  And  it  also  seems  clear  what  factors  are 
essential.  Fundamental  to  the  process,  apparently,  is  the  pres- 
ence of  an  individual  with  a  constructive  idea  capable  of 
being  put  to  experimental  test. 

No  doubt  the  calling  forth  of  such  a  constructive  idea  will 
often  be  brought  about  by  the  exigencies  of  situations.  It  is, 
however,  probably  untrue  to  hold  that  the  exigencies  of 
situations  will  themselves  generate  new  ideas.  We  seem 
forced  to  believe  that  the  thinking  and  experimenting 
individual  is  the  prime  essential. 

Granted  this,  and  granted  also  the  slow  widening  of 
influence,  I  think  we  have  the  clue  to  the  process  of  inten- 
tionally reshaping  our  human  behavior-patterns.  At  the 
present  time,  one  such  reshaping  seems  to  be  in  its  early 


598  HUMAN   BIOLOGY 

stages.  We  have  already  spoken  of  the  change  taking  place 
in  the  war-idea.  Let  us  note  how  it  fits  into  the  foregoing 
description.  Before  the  Great  War  there  was  a  tolerably 
widespread  feeling  against  the  mutual  slaughter  of  men. 
Conferences  on  peace  had  been  held  with  a  fair  degree  of 
frequency.  Nevertheless,  despite  the  growing  sentiment  of 
humaneness,  the  Great  War  swept  us  into  its  horrors. 
What  is  significant  about  practically  all  post-war  peace 
talk  is  that  it  insists  upon  one  or  another  experiment  being 
made  in  the  art  of  hving  together  internationally.  The 
outstanding  experiment  is  the  League  of  Nations,  conceived 
in  the  mind  of  a  constructively  thinking  individual.  The 
average  person  is  as  yet  hardly  aware  of  what  is  happening  in 
Geneva.  But  so,  in  hke  manner,  the  average  person  in  Italy 
or  Germany  or  England  was  quite  unaware  of  the  profoundly 
reconstructive  event  that  was  happening  in  Pisa.  It  is 
probably  true,  however,  that  as,  in  the  international  atmos- 
phere of  Geneva,  case  after  case  of  poHtical  conflict  is 
resolved,  a  new  habit  of  mind  will  develop  among  the 
citizens  of  the  world,  the  habit  of  expecting  reasonable  dis- 
cussion before  a  resort  to  arms.  War  will  doubtless  disappear 
when  the  new  idea-system  becomes  so  firmly  formed  in  us 
that  the  older  idea-system  will  vanish  by  reason  of  its  utter 
absurdity. 

Another  reshaping  seems  also  to  be  in  its  early  stages. 
Who  the  individual  was  who  first  caught  the  idea  we  do  not 
know.  But  at  the  present  time,  a  large  number  of  individuals 
are  possessed  of  the  idea  that  the  habit  of  straight  and 
responsible  thinking  in  matters  that  still  lie  outside  the 
range  of  exact  science  can  best  be  developed  by  the  process 
of  discussion  among  adults.  At  the  present  time,  discussion- 
groups  are  being  formed  all  over  the  world.  In  these  groups — 
experiments  in  thinking  together — the  essential  intent  is  to 
overcome  the  one-sidedness  and  the  intolerant  finality  of 
the  kind  of  thinking  that  considers  no  point  of  view  save  its 
.own. 

One  may  safely  predict,  I  think,  that  a  new  behavior 
pattern  is  here  in  process  of  being  formed.  As  it  takes  shape, 
many  things  will  change,  for  example,  the  habit  of  reading 
only    one    partian    newspaper,    of  being  content   to   make 


THE    INTENTIONAL   SHAPING    OF   HUMAN    OPINION  599 

judgments  on  hearsay  or  on  tradition,  of  judging  issues 
solely  from  a  single  national  or  racial  point  of  view.  In  their 
stead  will  be  increasingly  developed  the  habit  of  viewing 
debatable  matters  from  all  sides  and  with  all  possible 
consideration. 

SWEEPING  CHANGES  ARE  TAKING  PLACE  IN 
THOUGHT-HABITS 

We  have  referred  to  two  examples  or  experiments  which 
would  seem  to  promise  changes  in  our  thought-habits. 
A  brief  reference  to  a  number  of  institutions  may  emphasize 
the  fact  that  a  far  more  widespread  modification  of  thought- 
habits  is  in  process  than  we  are  ordinarily  accustomed  to 
beheve.  Within  the  last  thirty  years  the  public  hbrary  has 
become  an  estabhshed  part  of  our  hfe.  Where  formerly  all 
of  us,  with  the  exception  of  a  favored  few,  were  cut  off  from 
the  accumulated  heritage  and  the  growing  inteUigence  of 
the  world,  today  access  to  the  wisdom  of  humankind  has 
been  intentionally  provided.  No  doubt  the  effect  of  this  in 
another  generation  will  be  profound. 

Again,  within  Kttle  more  than  a  decade,  one  entire  sex 
has  emerged  to  a  condition  of  Hfe  in  which  it  has  the  right 
to  be  effectively  intelHgent.  Almost  overnight  a  type  of 
women's  organization  of  a  new  kind,  the  kind  where  serious 
study  and  discussion  are  carried  on,  has  developed,  with 
the  result  that  a  fairly  vast  population  of  new  readers  and 
thinkers  has  been  added  to  our  country  and  is  being  added 
to  the  world  at  large. 

Another  sign  of  the  times  is  the  formation  of  what  have 
come  to  be  called  child  study  groups.  Where  formerly 
parenthood  was  taken  for  granted,  and  little  or  no  effort 
was  made  to  become  intelligent  in  the  highly  significant 
function  of  child-rearing,  the  effort  among  parents  to  incor- 
porate for  their  use  the  best  that  modern  science  has  to  offer 
is  becoming  widespread.  Again,  parents  are  no  longer,  as  in 
previous  generations,  supposed  to  hold  aloof  from  the 
educational  processes.  In  the  formation  of  associations  of 
parents  and  teachers,  the  thought  begins  to  prevail  that  the 
basis  of  the  education  of  the  child  lies  in  an  intelligent 
cooperation  between  the  home  and  the  school. 


600  HUMAN   BIOLOGY 

Another  development  is  the  public  forum,  where  the  effort 
is  made  to  develop  the  many-sided  outlook  which  is  the 
beginning  of  all  true  thinking.  Still  another  development 
is  the  adult  school.  Sometimes  it  is  an  evening  high  school 
where  adults  make  up  for  educational  opportunities  lost  in 
youth;  sometimes  it  is  a  school  which  offers  the  adult  the 
privilege  of  continuing  his  education  on  a  level  of  mature 
insight  impossible  in  the  days  of  school  and  college. 

These  things  are  all  still  in  their  beginnings.  But  back  of 
them,  apparently,  is  a  single  idea,  namely,  that  freedom 
among  human  beings  and  elevation  of  life  can  be  gained 
only  by  searching  out  and  applying  such  truths  as  humans 
are  progressively  able  to  discover.  It  is  that  single  idea  which 
seems  increasingly  to  be  on  the  way  to  becoming  the  govern- 
ing thought-habit  of  our  life. 

THE  GRAFTING  OF  IDEAS  GOOD  AND  BAD 

But  there  is  one  further  significant  point  to  notice.  The 
modern  age  differs  from  the  ages  preceding  by  the  swiftness 
with  which  it  can  universalize  an  idea.  Had  Galileo  lived 
today,  his  Pisa  experiment  would  doubtless  have  been  front 
page  news,  and,  overnight,  it  would  have  reached  scientists 
at  the  ends  of  the  earth.  Ideas  have  always  been  powerful, 
but  much  of  their  energy  has  had  to  be  wasted  in  the  sheer 
effort  to  cross  barriers.  Now  an  idea  can  go  with  the  swiftness 
of  the  lightning,  girdling  the  earth  in  an  instant  of  time. 

This  means  that,  once  an  idea  is  conceived  and  put  to  the 
test,  it  has  a  power  to  launch  itself  never  before  possessed. 
Ghandi's  passive  resistance  in  India  affects  the  attitudes  of 
hundreds  of  thousands  of  persons  throughout  the  world. 
Russia's  effort  to  free  herself  from  ignorance  and  oppression, 
however  faulty  the  methods  may  be,  helps  to  inspire  new 
hopes  for  mankind  in  regions  thousands  of  miles  away.  The 
western  world's  emancipation  of  an  entire  sex  from  bondage 
helps  to  remove  the  veil  from  the  Turkish  woman.  The 
eight-hour  day  in  England  and  America  begins  to  raise  the 
industrial  status  of  the  labor-slaves  of  India  and  China. 

But  unfortunately  the  thing  works  both  ways.  The  shot 
fired  at  Sarajevo  inflamed  a  world  to  slaughter.  Lying 
propaganda  swung  whole  peoples  into  fanatic  hatred.  The 


THE    INTENTIONAL    SHAPING    OF    HUMAN    OPINION  6o  I 

communiques  of  a  state  department  can  still  be  counted 
upon  to  turn  a  freedom-loving  people  into  oppressors  of  the 
weak.  Both  parties,  in  short,  the  hberal  and  the  reactionary, 
have  equal  access  to  swiftness  and  universahty  of  com- 
munication. What  bearing  is  this  hkely  to  have  upon  the 
progress  of  ideas? 

As  a  matter  of  fact,  in  the  past  centuries,  the  chief  agencies 
for  the  communication  of  ideas  have  invariably  been  in  the 
control  of  those  who,  to  say  the  least,  have  not  been  eager 
for  a  departure  from  the  estabhshed  ways.  The  priesthood 
and  the  pohtical  state  have  been  guardians  of  the  status  quo, 
not  explorers  of  the  new.  Doubtless  it  will  always  be  so. 
Certainly,  in  the  present  day,  the  chief  agencies,  newspaper, 
school,  church,  and  state,  are,  as  often  as  not,  opponents  of 
new  ideas.  Or,  to  express  it  in  positive  terms,  they  are  dehber- 
ate  propagandists  for  the  estabhshed  thought-systems. 
With  the  swift  and  wide-reaching  devices  of  communication 
at  their  command,  they  have  a  power  which  was  never 
before  possessed  by  governing  groups. 

This  must  halt  us  in  our  first  thought  that  with  swift 
communication  the  rate  of  progress  in  human  opinion  will 
be  more  rapid.  As  a  matter  of  fact,  the  greater  the  power 
that  progressive  ideas  now  have  to  move  over  the  face  of  the 
earth,  the  greater  is  the  power  of  reactionary  ideas  to  outstrip 
them  and  neutrahze  their  effects. 

Is  there  any  hope  of  breaking  the  preponderant  power  of 
the  neutrahzing  influences?  There  would  seem  to  be  one, 
perhaps  only  one:  namely,  the  development  among  the 
citizenry  of  the  world  of  an  increasing  abihty  to  be  critical- 
minded,  to  think  for  themselves  instead  of  taking  their  ideas 
predigested.  Is  that  development  possible?  There  are  three 
ways  in  which  it  is  already  taking  place.  The  first  has  to  do 
with  advertising.  A  generation  ago,  advertising  was  unblush- 
ingly  the  art  of  more  or  less  clever  deception.  It  had  unhin- 
dered scope  to  deceive  a  people  too  naively  uncritical  to 
know  that  they  were  being  deceived.  Today,  however,  a 
widespread  critical  scepticism  has  developed  with  the 
result  that  advertising,  in  the  main,  has  been  compelled 
to  be  honest,  in  accordance  with  the  old  adage,  "honesty 
is  the  best  pohcy." 


602  HUMAN   BIOLOGY 

The  second  instance  applies  to  newspapers.  As  a  matter 
of  fact,  while  we  still  read  our  newspapers  for  the  news  and 
accept  such  coloring  of  the  news  as  is  skillfully  foisted  upon 
us,  there  is  a  conspicuous  absence  of  confidence  in  newspapers 
as  purveyors  of  social  and  political  Judgments.  Outstanding 
cases  are  on  record  in  which  the  citizenry  of  municipalities 
have  deliberately  voted  against  the  candidates  and  the 
policies  supported  by  the  newspapers. 

A  third  case  of  critical  scepticism  applies  to  politicians. 
About  a  generation  ago  it  began  to  be  bruited  about  that 
politicians  served  "special  interests."  Politicians  are  now 
known  for  what,  in  large  measure,  they  are,  a  special  kind 
of  business  men  making  profits  for  their  own  group.  With 
such  widespread  skepticism,  the  politician  is  finding  it 
increasingly  difficult  to  orate  his  way  into  easy  power. 

Critical  skepticism  can,  indeed,  be  developed.  Is  there 
anything  that  can  be  done  to  accelerate  the  development 
of  critical-mindedness  among  us?  The  schools,  hitherto,  have 
applied  themselves  to  this  need  in  far  smaller  measure  than 
it  would  seem  they  ought.  They  have  developed  adults  apt 
with  the  tools  of  life,  arithmetic,  spelling,  geography,  and  the 
rest.  They  have  actually  done  far  too  little  to  inculcate  that 
power  of  critical  questioning  which  is  the  essence  of  good 
Judgment.  An  outstanding  instance  is  the  teaching  of 
history.  Practically  nowhere  is  history  taught  in  the  critical 
spirit  of  seeking  out  all  the  possible  points  of  view.  It  should 
be  obvious,  however,  that  the  history  of  America,  to  take 
a  single  example,  studied  solely  out  of  American  textbooks 
can  hardly  give  the  student  that  access  to  divergent  points 
of  view  which  is  the  prime  essential  for  critical  Judgment 
and  of  a  truly  liberal  education. 

Is  there  any  way  of  setting  for  the  schools  this  more 
adequate  goal  of  critical-mindedness?  Since  it  is  the  adults 
who  must  set  the  standards  for  the  schools,  one  suspects  that 
no  way  will  be  found  save  through  the  eventual  development 
of  critical-minded  grown-up  people.  Are  we  here  in  a  vicious 
circle?  How  are  uncritical-minded  grown-ups  to  demand 
an  education  in  critical-mindedness  for  their  children? 

It  is  at  this  point  that  the  new  and  growing  interest  in  the 
continuing    education    of   the   adult   becomes    of   essential 


THE    INTENTIONAL   SHAPING    OF    HUMAN   OPINION  603 

significance.  To  many  persons  it  has  seemed  an  astounding 
fact  that  while  fairly  rich  provision  has  been  made  for  the 
training  of  juvenile  minds,  no  systematic  provision  has  ever 
made  for  the  training  of  the  adult  mind.  And  yet  it  is  obvious 
that  in  the  juvenile  years  most  of  the  matters  that  are  of 
importance  in  the  social,  political  and  economic  conduct  of 
Hfe  are  still  beyond  the  level  of  immature  intelligence  since 
they  require  experience  of  things  as  they  are.  To  an  increasing 
number  of  persons  throughout  the  world,  then,  it  seems  of 
primary  importance  that  a  new  idea  of  education  be  con- 
ceived and  put  into  effect,  the  idea,  namely,  that  adulthood 
is  the  period,  not  when  education  ends,  but  when  the  deeper 
and  far  more  essential  education  in  inteUigent  judgment 
really  begins.  No  doubt  this  is  an  idea  which  will  be  of  most 
constructive  value  for  the  future.  It  may  take  another  three 
hundred  years  to  get  it  thoroughly  domesticated.  Neverthe- 
less, since  it  is  most  fundamental  of  all  to  the  progress  of 
human  thinking,  it  would  seem  to  be  a  major  idea  worth 
pushing  into  effective  reahzation. 

INFLUENCE  OF  INVENTION  ON  GOVERNING  HABITS 

In  the  foregoing,  we  have  considered  only  the  intentional 
shaping  of  human  opinion.  There  is,  of  course,  one  powerful 
factor  which  is  constantly,  but  unintentionally  shaping  ideas 
and  attitudes.  This  factor  is  invention.  The  invention  of 
electric  Hghts  has  unquestionably  developed  reading  habits 
and  amusement  habits  never  before  possible.  The  invention 
of  the  automobile  has  developed  travel  habits,  not  to  speak 
of  financial  habits,  which  were  not  found  in  the  older  days  of 
slow-moving  vehicles.  The  invention  of  the  moving  picture 
helped  to  break  the  saloon-habit  of  mind.  It  has  hkewise 
broken  into  the  ignorances  and  provinciahsms  and  has 
served  to  bring  the  most  distant  and  colorful  experiences 
within  the  compass  of  the  average  life.  Also,  it  has  developed 
a  new  and  perhaps  questionable  habit  of  erotic  interest. 

But  the  inventor,  as  we  know,  does  not  deliberately  set 
himself  to  bring  about  these  things.  They  happen  along  with 
the  new  device.  Nevertheless,  it  is  significant  to  note  that 
inventions  do  change  the  ideas  and  attitudes  of  individuals 
and  groups.  It  is  even  possible  to  beheve  that,  knowing  this, 


604  HUMAN   BIOLOGY 

one  might  with  deliberate  intent  set  about  to  make  the  type 
of  invention  which  would  serve  in  an  intended  way  to  reshape 
the  mind-habits  of  men. 

Summing  up  the  whole  matter,  then,  it  would  seem 
wholly  within  reason  to  assert  that  there  are  ways  of  shaping 
human  opinion,  ways  that  are  intentional  and  ways  that  are 
unintentional.  Back  of  both  ways,  we  seem  always  to  fmd 
the  thinking  individual,  the  individual  able  to  challenge 
things-as-they-are,  able  to  ask  pointedly  whether  things-as- 
they-are  must  forever  be  as  they  are,  able  above  all  through 
the  power  of  imaginative  insight  to  transform  untried 
possibihties.  The  most  important  event  in  the  world  would 
seem  to  be  the  planting  of  a  new  idea.  The  next  important 
would  seem  to  be  its  nurture  and  propagation. 

REFERENCES 

Dewey,  J.  1927.  The  Public  and  its  Problems.  N.  Y.,  Holt. 
HoLLiNGWORTH,  H.  L.  1913.  Advertising  and  Selling.  N.  Y.,  Appleton. 
LiPPMAN,  W.  1922.  Public  Opinion.  N.  Y.,  Harcourt,  Brace. 
Macpherson,  W.  1920.  The  Psychology  of  Persuasion.  Lond.,  Methuen. 
Ogburn,  W.  F.,  1922.  Social  Change.  N.  Y.,  Huebsch. 
Overstreet,  H.  a.  1925.  Influencing  Human  Behavior.  N.  Y.,  Norton. 
Robinson,  J.  H.  1923.  The  Humanizing  of  Knowledge.  N.  Y.,  Doran. 
RouTZAHN,  M.  S.,  and  E.  E.  1928.  Publicity  for  Social  Work.  N.  Y.,  Russell 

Sage  Found. 
Scott,  W.  D.  192  i.  The  Psychology  of  Advertising  in  Theory  and  Practice. 

Bost.,  Small,  Maynard. 
Sedgwick,  W.  T.,  and  Tyler,  H.  W.  1917.  A  Short  History  of  Science.  N.  Y., 

Macmillan. 
Smith,  T.  V.  1926.  The  Democratic  Way  of  Life.  Univ.  Chicago  Press. 


INDEX 


Academic  freedom,  487 
Acute  rheumatism,  446 
Adaptation,  behavioral,  120-125 
Adenin  (adrenalin),  227,  453 
Adjustment    to    infectious    disease, 

406-427 
Adolescence,  244 
Adrenal  gland,  227,  453 
Adrenalin,  see  adenin 
Age,  and  fertility,  542 

in   different   populations,   522-524 
Air  movement,   physiological  effects 

of,  314 
Allergy,  417 
American  races,  174 
Anaphylaxis,  417 
Andromeda,  10 
Anemia,  449 

in  industrial  workers,  450 

pernicious,  344 
Antibodies,  415 
Antigens,  416,  419 
Antisocial  behavior,  see  crime 
Apes,  anthropoid,  ^^ 
Associations,   contrasted   with   socie- 
ties, 142 
Asteroids,  1 1 
Astronomy,  influence  on  pure  sciences, 

461 
Atmosphere,  5 

influence  on  life  in  cities,  359-366 
Atmospheric  movement,  269-301 
Atmospheric  pressure,  9 
Attractions,  spontaneous  in  relation 

to  marriage,  282 
Australians,  170 
Aversions,  spontaneous  in  relation  to 

marriage,  282 

Bacteria,  classification  of,  408 

immunity  to,  411 

invasion  by,  409,  412 

toxins  of,  410 
Bacteriology,  preventive,  455 
Beaumont,  experiments  by,  331 
Behavior,  antisocial,  see  crime 
Behavioral  adaptations,  120-125 

summary,  125 


Biology,  influence  on  education,  474 

of  human  populations,  515-552 
Birth-rate,  529-533 

and  occupation,  540-551 

and  promiscuity,  278-280 

influenced  by  war,  533 
Black  races,  characteristics  of,   167- 

170,  173,  175 
Bleeders,  510 
Bleeding,  effect  of,  229 
Blind  trial,  121 

Blood,  as  an  integrating  mechanism, 
242 — 244 

circulation,  221-225 

constancy  of  neutrality,  240-242 

constancy  of  sugar  in,  225-227 

constancy  of  temperature,  229-232 

constancy  of  water  in,  227-229 

examination  of,  433 

nature  of,  220 

oxygen  supply  in,  232-239 
Blood  plasma,  inorganic  composition 

of,  48-51 
Blood  vessels,  diseases  of,  448 
Blood-forming  organs,  diseases  of,  449 
Blood-relationship  test,  56,  176 
Bone,  "invention  of,"  63 
Botulism,  347 
Brain,  and  personality,  118 

development,  106-108 

evolution  of,  91-114 

human,  256-263 

human  compared  with  frog,  98-101 

inheritance  of  disease  of,  506-508 

sexual  diff^erences,  94 

weight  of,  91-95 
Breeding,  principles  of  good,  567-574 

Caenozoic,  ^^ 

Calcium,  in  sea  water,  48 

Cancer,  192 

inheritance  of,  503-505 
see  also  malignant  disease 

CapiHaries,  221,  237 

Carbon  dioxide,  238 

Cell  division,  199-201 

Cell  membrane,  192 

Cells,  as  laboratories,  422 


605 


6o6 


INDEX 


Cells,  as  vital  units,  187-204 

behave  like  individuals  in  a  com- 
munity, 188-192 

built  like  engines,  193-196 

contrasted  with  protozoa,  196 

cultivated  outside  the  body,  2 1 0-2 1 6 

dependence  of  activity  upon  envi- 
ronment, 21 1 

developed   from   pre-existing  cells, 
198 

electrical  forces  in,  194 

environment  within  the  body,  219 

influenced  by  nutritional  changes, 
213 

inorganic  composition  of,  47   . 

microscopic  structure    192 

origin  of,  35-43 

relation  to  one  another,  205-217 
Cells,  response  to  growth  promoting 
factors,  212 

size  and  shape,  187 

unlimited  growth  of,  211 
Cellular  basis  of  inheritance,  199-201 
Cephalic  index,  163 
Cerebellum,  256 
Chicago,  crimes  in,  385 
Chinese,  see  yellow-brown  races 
Christian  world,  468 
Christianity  and  monogamy,  269-271 
Christians,  number  of,  520 
Chromosomes,  201 
Chronic  arthritis,  446 
Circulation,  diagram  of,  221 
Cities,  life  in,  348-378 

atmosphere,  359-366 

comparative  death  rates,  351-356 

conclusions,  377 

expectation  of  life,  356-359 

foods,  369-371 

insects,  372 

light,  371 

municipal  sanitation,  349-35 1 

personal  contact,  372-377 

water  supplies,  366-368 
Civilization,  and  education,  475-477 
Climate,  effects  of,  295-330,  340-342 

factors  in,  295 
Color,  of  eyes,  161 

of  hair,  161 

of  skin,  160 
Comets,  10 


Communal  bonds,  143 
Communistic   reform   in   relation   to 

marriage,  284 
Companionate  marriage,  281 
Constitution,  498 
Contract  marriage,  281 
Conversation,  influence  of,  viii 
Country  life  and  city  life  compared, 

348-378 
Cousins,  marriage  of,  283 
Crime,  379-404 

and  emotional  life,  399 

and  ideational  life,  401 

and  methodological  contributions, 
402 

criminality  and  abnormality,  393- 

399 

heredity,  400 

law  versus  science,  389-391 

national  comparisons,  386-389 

scientific  study,  384 

size  and  cost  of  crime,  385,  568 

theories,  382-383 
Cytology,  science  of,  202-204,  216 
Cytoplasm,  192 

Dead  cells  replaced   by  living  ones, 

189 
Death  rate,  and  climate,  306-310 

comparative     (urban    and     rural), 
35 1 -356 _ 

reduced  with  fall  of  temperature, 

317 
Decerebrate  animal,  254 

Defectives  and  delinquents,  cost  of,  584 
Deficiency  diseases,  342-346 

thyroid  enlargement,  346 
Degeneration  of  race,  1 81-183 
Delinquency,  see  crime 
Dewey,  contribution  of,  596 
Diarrhea  of  infants,  361 
Diet,  331-347 

and  fertility,  336-343 
Digestion,   intracellular   replaced   by 

extra-cellular,  413 
Diseases,  acute  rheumatism,  446 

adjustment  to  infectious,  406-427 

chronic  arthritis,  446 

deficiency,  342-346 

definition  of,  492 

diarrhea  of  infants,  361 

enteritis  of  infants,  361 

inheritance  of,  491-514 


INDEX 


607 


Diseases,  malignant,  447 

mental,  in  urban  and  rural  environ- 
ments, 375 

of  blood  forming  organs,  449 

of  heart  and  blood  vessels,  448 

of  teeth,  454 

pernicious  anemia,  344 

thyroid  enlargement,  346 

tuberculosis,  351,  443-445 

typhoid,  366-368 

vaccination  against,  438 

venereal,  445 
Distance  receptors,  1 1 1 

present  dominance  of,  1 18-120 
Division  of  labor  among  cells,  191 
Divorce,  288-290 

Ductless  glands,  diseases  of,  451-453 
Dutch  East  Indies,  563 
Dutch-Hottentot  crosses,  561 

Earth,  age  of,  24-29 

future  of,  30,  31 
Education,     a     biological    necessity, 

469-471 

and  civilization,  475-477 

changes  in,  596 

influence  of,  468-488 

influence  of  biology  in,  474 

nature  and  nurture,  471-474 

obstacles  to  be  overcome,  482-487 

of  adults,  597 

of  the  future,  477-482 

role  of  science  in,  464 
Electrical  forces  in  the  cell,  194 
Elementary  schools,  480 
Emotional  life  and  crime,  399 
Emotions,  and  their  expressions,  135, 
136 

center  of  in  brain,  259 

efi"ect  on  respiration,  239 
Endocrine  diseases,  451-453 
Energy,  from  intake  of  food,  345 

geographic  distribution  of,  321-325 
Enteritis  of  infants,  361 
Environment,  and  heredity,  572-574 

determined       by      cell      activity, 
2 1 5-2 1 7 

efi"ects  of,  295-330 

influence  of  urban  and  rural,  348- 

internal,  225 
mastery  of,  376 


Environment,  and  heredity,  when  life 

began,   35,   41-44 
"Equality  of  races,"  178-180 
Eugenics,  568-584 

and  euthenics,  568 

control  of,  572 

criticism  of,  580 

environment  and,  570 

limitations  of,  582 

program  of,  574 

sterilization,  577 
Eurasians,  563 
Evolution,  climate  in,  327 

conclusions  regarding,  51,  89 

dominance   of  distance   receptors, 
1 18-120 

memory  in,  128 

mental  in  primates,  1 15-138 

of  brain,  91-114 

path  of  multicellularity,  584 

role  of  language  in,  1 31-135 

social  organization,  137 

societal,  139-154 

traced  anatomically,  84 

traced  biochemically,  35-51 
Exercise,  eff^ect  on  circulation,  238 
Expectation  of  life,  356-359 
Experimentation  with  animals,  204, 

496 

Familial,  influence  in  disease,  505 

pride,  514 
Family,  relation  of  off"spring  to,  146, 
148 

size  of,     in  diff"erent  occupations, 

543-551 
Fat,  storage  of,  227 
Fathers,     occupation    and     fertility, 

540-550 
Feeble-mindedness,  503 
Female    acquiring    male    characters, 

244  _ 
Feministic  movement,  284 
Fertility,  and  age,  542 

and  occupation,  540-551 

diff"erential  in  human  populations, 

539-551 
Filtrable  viruses,  37 
Food,  in  cities  and  in  the  country, 

369-371 
influence  of,  331-347 
Food  poisoning,  346 
Foresight,  124 


6o8 


INDEX 


France,  population  of,  536 

Gaileo,  contribution  of,  593-595 
Genes,  definition  of,  567 
Genius,  and  brain  weight,  93 

and  inheritance,  581 
Gibbons,  80-83 
Gonorrhea,  445 
Gorilla,  86 

Great  Britain,  immigration  into,  519 
Group  marriage,  269-271 
Growth-inhibiting  factors,  213 
Growth-promoting  factors,  212 

Hair,  character,  161 

color,  161 
Health,  geographical  distribution  of, 
321-325  ♦ 

international  organizations,  441 
Heart,  221,  234-239 

diseases  of,  448 
Heredity,  and  environment,  572-574 

modification  ©f,  572 
Hottentot-Dutch  crosses,  561 
Human  behavior-patterns,  597 
Human  opinion,  changes  in  thought 
habits,  599-600 

experimental  tests,  597-599 

governing  ideas,  591-593 

grafting   of  ideas,   good   and   bad, 
600-603 

influence  of  invention,  603-604 

intentional  shaping  of,  589-604 

re-shaping  of  governing  thoughts, 

593-595 

scientific-mindedness,  595-596 
Human  populations,  5^5~552 

composition    of,     and    difTcrential 
fertility,  539-551 

conclusions,  551 

fundamentals,  515-525 

growth  of,  533-539 

self-regulation,  525-533 
Human  races,  156-183 

classification,  164-172 

daughter  races,  172-176 

degeneration,  181-183 

"equality"  of  races,  178-180 

mixture  of  races,  176-178 
Humidity,    physiological    effects    of, 

296-301,  305-311 
Hypersensitivity,  416 
Hypothalamus,  259 


Imagination,  126 

Immunology,  science  of,  427 

"Incest,"  282 

Indian-European  crosses,  560 

Industry,  relation  to  science,  458-467 

Infant  welfare,  454 

Infectious  diseases,  494-503 

Inheritance,  and  genius,  581 
cellular  basis  of,  199-201 
of  disease,  491-514 
of  unusual  ability,  579 

Inheritance  in  diseases,  491-514 
abnormal  sensitization,  505-506 
cancer  and  other  malignant  tumors, 

503-505 
central  nervous  sytem,  506-508 
characters  and  qualities  in,  509-5 14 
fundamentals  in,  491-503 
longevity,  504-505 

Insane,  treatment  of,  451 

Insects,  in  urban  and  rural  environ- 
ments, 372 

Insight,  122-124 

Integrative     action,     of     glands     of 
internal  secretion,  242-244 
marriage,  266-290 
of  nervous  sytem,  246-263 
of  vascular  system,  219-244 

Intelligence  and  race  mixture,  559 

Intra-uterine  infection,  491 

Invertebrates,  age  of,  S5 

Iodine,  influence  on  thyroid,  346 

Japanese,  see  yellow-brown  races 
Jaws,  origin  of,  64 
Jews,  number  of,  520 

survival  in  cities,  350 
Juvenile  court,  388 

Kidney,  function  of,  50,  51 

Language,  role  in  evolution,  1 31-135 
Law  of  climatic  limits,  296-301 

acclimitization,  327-330 

and  racial  characteristics,  325-327 

climatic  differences  of  race,  319-321 

climatic  optima,  301-319 

geographic   distribution   of   hcaltli 
and  energy,  321-325 
Life,  arriving  on  meteors,  40 

conditions  necessary  for,  4-10 


INDEX 


609 


Life  .definition  of,  3 

expectation  of,  356-^59 

geneological  tree  of,  54 

in  cities,  348 

in  various  geological  epochs,  5$,  56 

light  requirements,  6 

on    known    astronomical     bodies, 
10-24 

oxygen  requirement,  7 

"reflex,"  250 

synthetic  processes  in,  37 

temperature  requirements,  5 
Light,   in  urban  and   rural   environ- 
ment, 371 

necessary  for  life,  6 
Living  matter,  constituents  of,  4 
Locomotor  apparatus,  origin  of,  65-71 

reflexes  of,  255 
Longevity,  508-509 
Lungs,  221 
Lymph,  inorganic  composition  of,  48 

Magnesiumj  increasing  in  ocean,  49 
Malaria,  436 
Malignant  disease,  447 
Mammals,  age  of,  55 

contrasted  with  reptiles,  72 
Mammary  glands,  origin  of,  72 
Man,  age  of,  55-57 

citizen  of  phylum  chordata,  57-63 

color  of  skin,  160 

emerges  on  the  ground,  83-89 

influenced  by  food,  331-347 

instabihty,  160 

nascent  races,  158 

origin  of,  35-5 1 

origin  of  races,  157 

race  characters,  159 

races  of,  156-183 

societies     biologically     considered, 
150 

species  of,  156 
Marriage,  and  promiscuity,  271 

and  sex  ratio,  276-278 

as  integration  of  the  sexes,  266-290 

as  regulator  of  sex  Hfe,  272-275 

contract,  281 

divorce,  288-290 
Marriage,  economic  control  of,  283- 
288 

effect  of  period  of  infancy,  280,  281 

effective  early,  273-275 

forms  of,  268-271 


Marriage,  of  cousins,  283 

of  the  future,  290 

possible  biological  control  of,   275 

spontaneous  attractions  and  aver- 
sions, 282 
Mars,  12,  13 

canals,  19 

possibility  of  life  on,  16-24 
Medicine,  industrial,  456 

influence  on  the  race,  428-457 

knowledge    of   causes    of   disease, 
413-441 

orthodox  and  irregular,  442 

preventive,  453-456 

prognosis,  437 

specialism  in,  431 

tropical,  435-437 
Melanesians,  170 
Memory,  as  factor  in  evolution,  128 

nervous  center  of,  262 
Mendel,  on  inheritance,  500-502 
Mendelian  laws,  555 
Mental  defect  and  crime,  395-398 
Mental  disease,  and  crime,  398 

and  insanity,  451 
Mental     energy     and     temperature, 
302,  304 

other  climatic  factors,  327 
Mentality,  development  of,  115,  116 
Mercury,  rotation  of,  7 

temperature  of,  14 
Mesozoic,  55 

Metabolism  and  temperature,  312 
Microscopic  visability,  196 
Milk,  purification  of,  370 
Mind,  centers  of,  259-263 

evolution   and   primates,    11 5-1 37 
Mingling  of  races,  553-565 

Dutch-East  Indians,  563 

Eurasians,  563 

fundamentals  in,  553 

heterosis  (hybrid  vigor),  554 

Indian-European  crosses,  560 

Hottentot-Dutch  crosses,  561 

Negro-White  crosses,  561 

Philippinos,  563 

Polynesian  hybrids,  562 

Scandinavian-Lapp,  564 
Missouri  crime  survey,  385 
Mitochondria,  193 
Mixture  of  races,  176-178 
Monkeys,  see  primates 
Monogamy,  269-271 


6io 


INDEX 


"Mother  India,"  275 
Multicellular  and  unicellular  organ- 
isms contrasted,  197 
Muscle,  contraction  of,  60 
Mutations,  586 

Nascent  races,  158 

National  Crime  Commission,  385 

Nature  versus  nurture,  ix 

control  of,  x,  471-474,  488 
Nebulae,  10 
Negro,  see  black  races 
Negroes  and  whites,  contrasted,  180 

crosses,  561 

in  respect  to  climate,  319 

in  urban  and  rural  populations,  354 
Neomechanistic  school,  the,  209 
Nerve  cells  (neurones),  102,  248 
Nervous  integrations  in  man,  246-263 
Neurology,  progress  in,  450 
Neutrality    of  blood,   constancy    of, 

240-242 
Nucleus,  as  a  sanctuary,  51,  195 

in  primitive  forms,  35,  45~47 

structure  of,  192 
Nurture  versus  nature,   ix,  471-474, 

488 
Nutritional  changes,  effect  on  cells, 

213 

Ocean,  change  in  composition  of,  47. 
48 

increase  in  magnesium,  49 

increase  in  sodium,  49 
Opinion,  see  human 
Organisms,  the  most  minute,  37 

origin,  38 

primitive,  44 

survival  of,  469-471 

unity  of,  205 
Orion,  10 
Ovaries,  243 
Oxygen,  absent  on  Venus,  16 

atmospheric,  7-10 

chemotropic  responses  to,  144 

in  earth's  crust,  8 

maintenance  of  supply,  232-239 

present  on  Mars,  18 
Ozone,  in  atmosphere,  9 

Palaeozoic,  s^ 
Papuans,  170 
Pernicious  anemia,  344 


Personal   contact,   in   spread   of  dis- 
ease, 372-374 
Personality,  development  of,  115,  116 

scat  of,  1 1 3 
Philippinos,  563 
Philosophy,  social,  466 
Pituitary  gland  and  gigantism,  244, 

452 
Planet,  as  abode  of  life,  6 
atmospheric  oxygen  of,  7 
rotation  of,  7 
superficial  gravity  of,  9 
Poisoning  from  food,  346 
Polyandry,  269-271 
Polygyny,  269-271 
Polynesian-hybrids,  562 
Polynesians,  171 
Population,  see  human 
Potassium,  proportion  to  sodium,  47 
Preventive  medicine,  453-456 
Primates,  become  arboreal,  75,  78 
classification,  107 
emotions  in,  135,  136 
language  in,  131,  132 
memory  in,  128 
mental  evolution  in,   11 5-1 38 
skill  in  balancing,  79 
social  organization  in,  137 
Primitive  life,  age  of,  55 
Progressive  education,  468-488 
Promiscuity,  268-271 
Proterozoic,  s^ 

Psychology,  revolution  in,  481,  485 
Psychozoic,  56 
Puberty,  243 
Pulse-rate  and  temperature,  3 1 2 

Rabies,  37 

Race,  and  crime,  388,  563 

and  temperament,  558 

what  medicine  has  done   for,  428 
Race  characters,  159 

changes  in,  162-164 

in    respect    to    climate,    319-321, 
325-327 
Race  crossing  and  improvement,  565 
Race    improvement,    application    of 
biological  principles,  574-576 

the  distant  future,  584-587 

improvement  in  heredity,  572-574 

principles  of  good  breeding,   567- 
571 


INDEX 


6ll 


Race      improvement,      program      of 
eugenics,  576-582 

probabilities,  582-584. 

purposive,  566-587 
Race  suicide,  583 
Races  of  men,  157 
Races,  mingling  of,  553-565 
Racial  susceptibility,  504 
Reflex,  defined,  247 
Reflexes,  103,  246,  250-255 

diagrams  of,  251,  252 
Regulation,  of  blood  sugar,  225-227 

of  oxygen  supply,  232-239 

of  temperature,  229-232 

of  water  content  of  blood,  227-229 
Reptiles,  age  of,  ^s 
Respiration,     and     oxygen     supply, 
232-239 

origin  of,  64 
Reticulo-endothelial  system,  425 
Righthandedness,  262 
Rural     environment,     influence     of, 

348-378 

Saint  Louis,  crimes  in,  385 
Scandinavian-Lapp  crosses,  564 
Schools,  conservatism  of,  484 
Science,   pure   development   of,   460, 
461 

relation  to  industry,  458-467 
Semimongoloids,  171 
Sense  organ  defined,  247 
Sex,  determination  of,  201 

in  different  populations,  522 
Sex  cleavage,  in  the  community,  267 
Sex  life  regulated  by  marriage,  272- 

275 
Sex  ratio,  276-278 
Sexes,  segregation  of,  287 
Sexual  diff"erences,  brain  weight,  94 

chromosomes,  202 
Skin,  as  a  protection,  189 
Skull,  evolution  of,  88 

racial  characters,  161,  162 
Smallpox,  37,  492 
Smoke  nuisance,  363 
Societal  evolution,  139-154 
Societies,  classification,  141,-143 

contrasted  with  associations,  142 

hypotheses  concerning,  151-154 
Sodium,  increasing  in  ocean,  49 

proportion  to  potassium,  47 


Sodium     bicarbonate,     influence     in 

blood,  240-242 
Solar  system,  origin  of,  26-29 
Soul,  seat  of,  114 
Species  and  man,  156 
Spectra,  of  stars,  4 
Speech,  dominance  of,   in  evolution, 

131-135 

nervous  center  for,  262 
Spinal  cord,  97 
Spinal  nerves,  102 
Spontaneous  generation,  in  origin  of 

life,  39 
Stars,  age  of,  24-29 

gaseous  envelopes  of,  42 
Sterilization,  of  defectives,  513,  577 
Sugar,  and  muscular  activity,  226 

constancy  in  blood,  225-227 

storage  of,  242 
Sun,  age  of,  27-29 

source  of  ultra-violet  light,  9 
Sunburn,  51 1-5 13 
Sunlight,     physiological     effects     of, 

269-301 
Surgery,  preventive,  455 
Sweat  glands,  function  of,  230,  326 
Syphilis,  445 

Teeth,  diseases  of,  454 

origin  of,  64,  73 
Temperature,  constancy  of,  229-232 

necessary  for  life,  5,  44,  296-299 

physiological  effects  of,  296-301 
Testicles,  243 
Thyroid  gland,  243 

disease  of,  452 

enlargement  of,  346 
Tissue  culture,  210-216 
Tissue  fluid,  220,  223 
Tobacco,  mosaic,  37 
Trees,  influence  of,  360 
Trial  and  error,  125 
Trial  marriage,  281 
Tuberculosis,  443-445 

and  race  mixture,  564 

inheritance  of,  495-500 

urban  and  rural  death-rates,  35 1 
Typhoid  fever,  366-368 

Ultra-microscope,  196 
Ultraviolet   light,   absorption   of,   in 
atmosphere,  9 


6l2 


INDEX 


United     States,     immigration     into, 
526,  527 

population  of,  535 
Unity  of  the  organism,  205 
Urban    environment,     influence     of, 

348-378 

Vaccination,    against   diseases,    438- 

441 
Vascular   system,   integrative   action 

of,  219-244 
Venereal  disease,  445 
Venus,  14-16 

devoid  of  oxygen,  16 
Vertebrates,  evolution  ot,  63 
Vital  index,  of  population,  528 
Vital  units,  called  cells,  187-204 
Vitalism,  208 
Vitamine  C,  345 
Vitamines,  discovery  of,  336 

properties  of,  337-340 
Vivisection,  xiii,  434 


War,  influence  on  birth-rate,  533 
War-idea,  598 

Warm-blooded  forms,  evolution  of,  71 
Water  content  of  blood,  227-229 
Water  supplies,  366-368 
Weather,  effects  of,  295-330 

see  climate 
White  races,  characteristics  of,  167- 

170,  173 
White-Negro  crosses,  556,  561 
Woman,  in  primitive  and  advanced 

societies,  284-288 
Women,  and  industrial  life,  287 
World,  age  of,  31 

definition  of,  3 

population  of,  517,  537 
Worlds  unknown,  29-31 

X-rays,  discovery  and  use  of,  441 

Yellow-brown    races,    characteristics 
of,  167-170,  172,  174 


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