﻿334 
  AlSTNtfAL 
  REPORT 
  SMITH 
  SOliTlAl^ 
  INSTITUTION, 
  192 
  9 
  

  

  There 
  is 
  indeed 
  no 
  evidence 
  that 
  viruses 
  contain 
  or 
  produce 
  poisonous 
  

   substances 
  as 
  do 
  so 
  many 
  bacteria. 
  

  

  We 
  can 
  not, 
  therefore, 
  affirm 
  that 
  viruses 
  differ 
  radically 
  in 
  com- 
  

   position 
  from, 
  e. 
  g., 
  the 
  typhoid 
  baccillus 
  — 
  nor 
  that 
  they 
  do 
  not. 
  We 
  

   probably 
  "have 
  no 
  business 
  to 
  make 
  an 
  assumption 
  either 
  way. 
  

  

  Metabolism. 
  — 
  The 
  attempts 
  which 
  have 
  been 
  made 
  to 
  demonstrate 
  

   the 
  production 
  of 
  carbon 
  dioxide 
  by 
  viruses 
  have 
  failed, 
  but 
  the 
  quanti- 
  

   ties 
  involved 
  are 
  small 
  and 
  the 
  technical 
  difficulties 
  large, 
  so 
  that 
  we 
  

   can 
  not 
  regard 
  the 
  evidence 
  as 
  conclusive. 
  It 
  seems, 
  however, 
  that 
  

   if 
  they 
  have 
  any 
  respiratory 
  exchange 
  it 
  must 
  be 
  at 
  a 
  much 
  slower 
  rate 
  

   per 
  infective 
  dose 
  than 
  that 
  of 
  ordinary 
  bacteria. 
  

  

  Stability 
  and 
  resistance 
  to 
  harmful 
  agents. 
  — 
  Some 
  viruses 
  at 
  any 
  rate 
  

   can 
  retain 
  their 
  activity 
  in 
  vitro 
  for 
  several 
  years. 
  Some 
  bacterio- 
  

   phages 
  endure 
  for 
  a 
  long 
  time 
  in 
  bacteria-free 
  ffitrates; 
  the 
  Rous 
  tumor 
  

   virus 
  can 
  be 
  kept 
  almost 
  indefinitely 
  in 
  dried 
  tumor 
  tissue. 
  Others 
  

   are 
  more 
  labile 
  and 
  are 
  difficult 
  to 
  keep 
  over 
  a 
  period 
  of 
  days. 
  There 
  

   is 
  much 
  the 
  same 
  variability 
  as 
  there 
  is 
  with 
  bacteria 
  and 
  bacterial 
  

   toxins; 
  viruses 
  as 
  a 
  class 
  are 
  not 
  characteristically 
  unstable, 
  evanescent 
  

   things. 
  

  

  A 
  good 
  deal 
  has 
  been 
  made 
  from 
  time 
  to 
  time 
  of 
  their 
  resistance 
  to 
  

   heat 
  and 
  protoplasmic 
  poisons. 
  Here 
  again 
  the 
  results 
  are 
  very 
  

   various 
  and 
  differ 
  with 
  the 
  sort 
  of 
  virus 
  and 
  the 
  conditions 
  of 
  experi- 
  

   ment; 
  there 
  are 
  no 
  general 
  rules. 
  But 
  there 
  are 
  a 
  remarkable 
  number 
  

   of 
  instances 
  of 
  viruses 
  which 
  have 
  resisted 
  temperatures 
  up 
  to 
  75° 
  C, 
  

   and 
  treatment 
  with 
  chloroform, 
  alcohol, 
  ether, 
  toluol, 
  phenol, 
  acids, 
  

   alkalies, 
  and 
  so 
  forth. 
  Formalin 
  destroys 
  many 
  of 
  them 
  quickly, 
  

   which 
  is 
  curious, 
  for 
  its 
  action 
  in 
  coagulating 
  proteids 
  is 
  much 
  slower 
  

   than 
  that 
  of 
  alcohol, 
  which 
  they 
  often 
  resist. 
  As 
  a 
  whole 
  they 
  are 
  

   certainly 
  more 
  resistant 
  than 
  vegetative 
  bacteria, 
  but 
  it 
  is 
  not 
  certain 
  

   that 
  they 
  differ 
  markedly 
  from 
  bacterial 
  spores. 
  In 
  several 
  parti- 
  

   culars 
  this 
  resistance 
  recalls 
  that 
  of 
  enzymes, 
  and 
  their 
  peculiarities 
  

   may 
  be 
  another 
  reason 
  for 
  suspecting 
  that 
  they 
  are 
  not 
  made 
  of 
  quite 
  

   ordinary 
  proteids. 
  There 
  is 
  nothing 
  in 
  their 
  size 
  per 
  se 
  which 
  should 
  

   protect 
  them. 
  

  

  Capacity 
  Jor 
  independent 
  life 
  and 
  multiplication. 
  — 
  There 
  is 
  no 
  con- 
  

   vincing 
  evidence 
  that 
  any 
  virus 
  has 
  grown 
  and 
  multiplied 
  in 
  artificial 
  

   culture, 
  though 
  successes 
  have 
  been 
  reported, 
  and 
  the 
  observations 
  

   of 
  the 
  Maitlands 
  on 
  vaccinia 
  are 
  difficult 
  to 
  explain 
  away; 
  they 
  would 
  

   have 
  been 
  more 
  impressive 
  if 
  animal 
  cells 
  could 
  have 
  been 
  kept 
  out 
  of 
  

   the 
  medium 
  altogether. 
  Living 
  cells 
  are 
  in 
  all 
  cases 
  necessary, 
  which 
  

   may 
  be 
  supplied 
  by 
  living 
  bacteria, 
  hving 
  animals 
  or 
  plants 
  or 
  tissue 
  

   cultures. 
  That 
  they 
  really 
  do 
  multiply 
  under 
  these 
  conditions 
  seems 
  

   beyond 
  question; 
  indefinite 
  serial 
  passage 
  of 
  an 
  infective 
  virus 
  (e. 
  g., 
  

   foot-and-mouth 
  disease) 
  through 
  experimental 
  animals 
  (e. 
  g., 
  guinea 
  

   pigs), 
  indefinite 
  subculture 
  of 
  the 
  bacteriophage, 
  quantitative 
  tissue 
  

  

  