﻿336 
  ANNUAL 
  EEPOET 
  SMITHSONIAN 
  INSTITUTION, 
  19 
  2 
  9 
  

  

  and 
  these 
  would 
  also 
  account 
  for 
  part 
  at 
  any 
  rate 
  of 
  any 
  local 
  inflam- 
  

   matory 
  response. 
  

  

  Such 
  an 
  explanation 
  would 
  do 
  quite 
  well 
  for 
  the 
  viruses 
  that 
  accom- 
  

   pany 
  infectious 
  diseases 
  and 
  would 
  cover 
  the 
  facts 
  for 
  the 
  bacterio- 
  

   phage. 
  But 
  phenomena 
  are 
  known 
  which 
  al"e 
  surely 
  more 
  or 
  less 
  

   analogous, 
  and 
  which 
  it 
  is 
  hardly 
  possible 
  to 
  regard 
  as 
  due 
  to 
  parasites 
  

   of 
  any 
  kind. 
  

  

  There 
  is, 
  for 
  instance, 
  the 
  agent 
  which 
  induces 
  cells 
  to 
  become 
  

   malignant, 
  indicated 
  years 
  ago 
  by 
  the 
  Imperial 
  Cancer 
  Research 
  

   Fund 
  (Haaland 
  and 
  Russell) 
  when 
  they 
  showed 
  that 
  close 
  contiguity 
  

   with 
  malignant 
  epithelial 
  cells 
  might 
  cause 
  normal 
  connective 
  tissue 
  

   to 
  grow 
  into 
  a 
  transplantable 
  sarcoma 
  — 
  one 
  of 
  the 
  great 
  discoveries 
  

   of 
  pathology. 
  People 
  had 
  known 
  that 
  they 
  met 
  with 
  tumors 
  occa- 
  

   sionally 
  which 
  seemed 
  to 
  be 
  mixtures 
  of 
  carcinoma 
  and 
  sarcoma; 
  

   they 
  knew, 
  too, 
  that 
  the 
  cells 
  at 
  the 
  edge 
  of 
  small 
  epitheliomas 
  looked 
  

   as 
  if 
  they 
  were 
  being 
  transformed 
  and 
  were 
  on 
  the 
  way 
  to 
  become 
  

   malignant, 
  though 
  the 
  prevalence 
  of 
  a 
  curious 
  dogma 
  to 
  the 
  effect 
  

   that 
  this 
  could 
  not 
  really 
  be 
  so 
  generally 
  prevented 
  them 
  talking 
  

   about 
  it. 
  The 
  experimental 
  mouse 
  work 
  explained 
  these 
  appearances; 
  

   without 
  it 
  they 
  could 
  have 
  carried 
  no 
  serious 
  inference 
  that 
  cancer 
  

   cells 
  might 
  influence 
  normal 
  cells 
  towards 
  malignancy. 
  Unless 
  we 
  

   suppose 
  that 
  tumor 
  cells 
  pervert 
  neighboring 
  normal 
  cells 
  by 
  argu- 
  

   ment, 
  persuasion, 
  example, 
  or 
  some 
  other 
  sort 
  of 
  immaterial 
  com- 
  

   munication, 
  we 
  naturally 
  assume 
  that 
  some 
  substance 
  passes 
  out 
  

   from 
  the 
  one 
  to 
  affect 
  the 
  other. 
  All 
  attempts 
  to 
  demonstrate 
  this 
  

   substance 
  in 
  dead 
  tumor 
  cells 
  or 
  in 
  extracts 
  of 
  them 
  uniformly 
  failed 
  

   untn 
  Rous 
  came 
  across 
  his 
  fowl 
  sarcoma 
  and 
  showed 
  that 
  it 
  could 
  

   be 
  transmitted 
  indefinitely 
  from 
  bird 
  to 
  bird 
  by 
  dried 
  dead 
  cells 
  or 
  

   by 
  filtrates 
  which 
  contained 
  nothing 
  that 
  could 
  be 
  seen 
  or 
  cultivated. 
  

   This 
  particular 
  tumor 
  produces 
  the 
  substance 
  in 
  a 
  form 
  so 
  stable 
  that 
  

   it 
  can 
  be 
  examined 
  and 
  played 
  with 
  when 
  it 
  is 
  detached 
  from 
  live 
  cells. 
  

   With 
  most 
  transplantable 
  tumors 
  it 
  is 
  present 
  in 
  such 
  small 
  amounts, 
  

   or 
  more 
  likely 
  in 
  such 
  a 
  labile 
  unstable 
  form 
  that 
  its 
  clear 
  demon- 
  

   stration 
  is 
  not 
  possible; 
  the 
  carcinoma-sarcoma 
  experiment 
  comes 
  

   off 
  only 
  with 
  a 
  minority 
  of 
  mouse 
  carcinomas. 
  Gye 
  has 
  shown 
  that 
  

   its 
  activity 
  may 
  be 
  modified, 
  enhanced, 
  or 
  depressed, 
  by 
  various 
  

   conditions, 
  which 
  helps 
  to 
  explain 
  the 
  difficulties 
  and 
  apparent 
  incon- 
  

   sistencies 
  which 
  are 
  met 
  with 
  in 
  its 
  experimental 
  investigation. 
  

   But 
  a 
  fair 
  number 
  of 
  tumors 
  have 
  now 
  been 
  transmitted 
  by 
  filtrates, 
  

   and 
  there 
  is, 
  I 
  think, 
  no 
  reason 
  to 
  doubt 
  that 
  the 
  production 
  of 
  this 
  

   carcinogenic 
  substance 
  is 
  a 
  common 
  property 
  of 
  all 
  malignant 
  growths. 
  

   We 
  believe 
  that 
  all 
  pathogenic 
  bacteria, 
  or 
  at 
  any 
  rate 
  all 
  the 
  larger 
  

   ones, 
  produce 
  extracellular 
  toxins; 
  there 
  is 
  no 
  other 
  way 
  in 
  which 
  they 
  

   can 
  injure 
  the 
  tissues. 
  But 
  in 
  man}^ 
  instances 
  they 
  are 
  so 
  unstable 
  

   that 
  it 
  is 
  at 
  the 
  best 
  difficult 
  to 
  demonstrate 
  their 
  presence 
  apart 
  

  

  