﻿338 
  ANNUAL 
  EEPORT 
  SMITHSONIAN" 
  INSTITUTION, 
  1929 
  

  

  cultivated 
  apart 
  from 
  live 
  cells, 
  it 
  multiplies 
  only 
  under 
  conditions 
  

   where 
  its 
  specific 
  activity 
  is 
  displayed, 
  its 
  inactivation 
  by 
  chloroform 
  

   and 
  other 
  protoplasmic 
  poisons 
  does 
  not 
  take 
  it 
  nearer 
  life 
  than 
  are 
  

   toxins 
  or 
  enzymes 
  or 
  indeed 
  simple 
  metallic 
  catalysts, 
  and 
  its 
  reten- 
  

   tion 
  of 
  activity 
  after 
  the 
  drastic 
  methods 
  of 
  purification 
  recently 
  

   described 
  by 
  Murphy 
  seems 
  to 
  definitely 
  exclude 
  it 
  from 
  "live." 
  As 
  

   to 
  its 
  origin, 
  all 
  the 
  evidence 
  seems 
  to 
  concur 
  in 
  indicating 
  that 
  the 
  

   Rous 
  virus 
  arises 
  de 
  novo 
  in 
  each 
  tumor. 
  There 
  is 
  no 
  epidemio- 
  

   logical 
  evidence 
  that 
  cancer 
  comes 
  into 
  the 
  body 
  from 
  outside; 
  

   everything 
  we 
  know 
  supports 
  the 
  classical 
  view 
  that 
  it 
  is 
  a 
  local 
  

   autochthonous 
  disease. 
  Most 
  of 
  the 
  experimental 
  work 
  with 
  the 
  

   virus 
  has 
  started 
  with 
  an 
  actual 
  tumor, 
  and 
  it 
  is 
  therefore 
  just 
  possible 
  

   that 
  an 
  agent 
  might 
  be 
  carried 
  along 
  through 
  the 
  whole 
  series 
  which 
  

   originated 
  somewhere 
  else 
  than 
  in 
  a 
  tumor. 
  But 
  experimental 
  

   sarcomas 
  produced 
  by 
  embryo 
  extract 
  and 
  indol, 
  arsenic, 
  or 
  tar 
  have 
  

   been 
  transmitted 
  by 
  filtrates, 
  and 
  if 
  others 
  have 
  failed 
  to 
  reproduce 
  

   Carrel's 
  results 
  I 
  would 
  only 
  remark 
  that 
  in 
  a 
  question 
  like 
  this 
  one 
  

   positive 
  experiment 
  is 
  worth 
  more 
  than 
  a 
  great 
  many 
  negative 
  ones. 
  

   Epitheliomas 
  are 
  easily 
  produced 
  in 
  mice 
  by 
  tar 
  and 
  in 
  men 
  by 
  

   chronic 
  irritation, 
  and 
  if 
  we 
  believe 
  that 
  all 
  malignant 
  tumors 
  contain 
  

   more 
  or* 
  less 
  of 
  a 
  carcinogenic 
  agent 
  akin 
  to 
  the 
  Rous 
  virus, 
  it 
  follows 
  

   that 
  we 
  can 
  with 
  a 
  considerable 
  degree 
  of 
  certainty 
  stimulate 
  normal 
  

   tissues 
  to 
  produce 
  virus. 
  It 
  is, 
  therefore, 
  not 
  very 
  remarkable 
  that 
  

   Murphy, 
  Leitch, 
  and 
  Brebner 
  have 
  at 
  any 
  rate 
  occasionally 
  demon- 
  

   strated 
  a 
  carcinogenic 
  agent 
  in 
  preparations 
  of 
  normal 
  tissues 
  (testes, 
  

   pancreas, 
  and 
  embryo 
  plus 
  placental 
  extract). 
  

  

  It 
  is 
  difficult 
  to 
  escape 
  the 
  conclusion 
  that 
  the 
  Rous 
  virus 
  arises 
  in 
  

   the 
  tumor. 
  There 
  is 
  no 
  doubt 
  that 
  it 
  is 
  a 
  means 
  by 
  which 
  a 
  tumor 
  

   may 
  be 
  experimentally 
  dispersed 
  through 
  any 
  number 
  of 
  available 
  

   animals, 
  and 
  it 
  is 
  apparently 
  responsible 
  for 
  some, 
  at 
  any 
  rate, 
  of 
  the 
  

   metastases 
  which 
  occur 
  in 
  the 
  course 
  of 
  the 
  natural 
  disease. 
  But 
  

   there 
  is 
  no 
  evidence 
  that 
  such 
  a 
  virus 
  ever 
  naturally 
  causes 
  a 
  fresh 
  

   tumor, 
  and 
  we 
  learn 
  the 
  important 
  lesson 
  that 
  the 
  means 
  by 
  which 
  a 
  

   disease 
  is 
  propagated 
  may 
  not 
  be 
  the 
  same 
  as 
  that 
  by 
  which 
  it 
  was 
  

   originally 
  started. 
  

  

  This 
  consideration 
  becomes 
  particularly 
  interesting 
  when 
  we 
  try 
  to 
  

   bring 
  a 
  frankly 
  infectious 
  disease 
  such 
  as 
  foot-and-mouth 
  disease, 
  mea- 
  

   sles, 
  or 
  smallpox 
  into 
  comparison. 
  Brought 
  up 
  as 
  we 
  all 
  have 
  been 
  in 
  

   the 
  heyday 
  of 
  bacteriology, 
  it 
  is 
  a 
  little 
  difficult 
  for 
  us 
  to 
  get 
  an 
  unprej- 
  

   udiced 
  view 
  of 
  the 
  situation. 
  Because 
  an 
  agent 
  is 
  constantly 
  asso- 
  

   ciated 
  with 
  and, 
  as 
  we 
  believe, 
  is 
  the 
  cause 
  of 
  a 
  disease 
  very 
  similar 
  

   to 
  others 
  which 
  we 
  feel 
  assured 
  are 
  caused 
  by 
  bacteria, 
  we 
  naturally 
  

   assume 
  that 
  its 
  natural 
  history 
  is 
  more 
  or 
  less 
  similar 
  to 
  that 
  of 
  bac- 
  

   teria. 
  We 
  might 
  have 
  been 
  in 
  a 
  better 
  position 
  to 
  take 
  a 
  just 
  view 
  of 
  

   the 
  facts 
  if 
  we 
  had 
  lived 
  in 
  prebacteriological 
  days, 
  or 
  if 
  we 
  could 
  put 
  

  

  