Page:Once a Week Jul - Dec 1859.pdf/79

68 reader knows,  is  simply  a mixture  of  twenty-one parte of  oxygen  gas  with  seventy-nine  parts  of nitrogen  gas. This air  was  introduced  into  a flask containing an  infusion  of  hay,  the  hay  having previously been  subjected  for  twenty  minutes  to a heat  of  100  degrees  Centigrade  (212  degrees Fahrenheit),  a temperature  which  would  destroy every germ. He thus  guarded  against  the  presence of any  germs,  or  animalcules,  in  the  infusion,  or in  the  air. The whole  was  then  hermetically sealed, so  that  no  other  air  could  gain  access. In spite of  these  precautions  cryptogamic  plants  and animalcules appeared  in  the  infusion. M. Pouchet repeated the  experiment  with  pure  oxygen  gas, instead of  air; and  with  similar  results.

In presence  of  such  statements  as  these,  only two courses  were  open  to  the  antagonists  of  Spontaneous Generation. They could  deny  or  disprove the facts; or  they  could  argue  that  the  precautions taken were  not  sufficiently  rigorous  to  exclude  the presence of  germs. I have already  said  how difficult it  is  for  the  modem  physiologist  to  admit Spontaneous Generation,  and  the  reader  will  be therefore  prepared  to  hear  that  M.  Pouchet  has roused immense  opposition; but  the  opponents have not  disputed  his  facts; one  and  all  they accept the  statements  as  he  makes  them,  and,  by criticism  and  counter-statement,  endeavour  to show  that  Spontaneous  Generation  is  just  as  inadmissible as  ever. These criticisms,  and  M. Pouchet’s  replies,  may  here  be  grouped  in  order, and  with  all  possible  brevity.

Milne-Edwards objected  to  the  conclusions  of M.  Pouchet,  saying: — There  is  no  proof  that the hay  itself  had  been  subjected  to  the  temperature of  100  degrees  Cent,  (or  the  boiling point  of  water),  it  being  very  probable  that although the  furnace  was  at  that  heat,  the  hay, which was  in  a glass  vessel  and  surrounded  with air at  rest,  was  not  at  anything  like  that  temperature.

To this  M.  Pouchet  replied,  that  he  and  M. Hougeau  ascertained  that  the  hay  was  at  the temperature of  100  degrees,  before  they  proceeded in their  experiments.

Milne-Edwards is  ready  to  grant  that  the  tem- perature may have  been  reached,  but  argues  that even that  would  not  suffice  for  the  destruction  of all  the  germs,  if  they  were  perfectly  dry. He refers to  the  observations  of  M.  Doyère,  which prove that  the  Tardigrada  (“water  bears,”  microscopic animals  common  in  stagnant  water),  when thoroughly desiccated,  preserve  their  power  of reviving  even  after  having  been  subjected  to  a temperature  of  140  degrees  Cent. (316 degrees Fahr.). If, therefore,  animals  of  so  complex  a structure  as  these  water-spiders  can  resist  the action of  so  high  a temperature,  there  is  no  reason for supposing  that  the  germs  of  the  simpler  ani- malcules would be  destroyed  by  it. Not content with this  argument,  which  is  sufficiently  forcible, Milne-Edwards narrates  an  experiment  of  his  own, which is  very  similar,  both  in  method  and  results, to one  I have  performed. Unhappily, it  is  an experiment  the  value  of  which  is  either  destroyed by the  argument  just  adduced,  or  else  it  destroys the argument. It is  this: In  two  tubes  a little water containing  organic  matter  is  placed,  one  of them  hermetically  sealed,  the  other  left  open  to the  air. They are  then  placed  in  a bath  of  boiling water and  kept  there  till  their  temperature  has reached that  point. After this  they  are  left  undisturbed for  a few  days. In the  tube  which  was exposed to  the  air  there  were  animalcules; in  the tube which  was  excluded  from  the  air,  before  the action of  heat  had  destroyed  all  the  germs,  not  an animalcule  could  be  seen.

Is not  this  something  like  a proof? “Why, no, sir,” as  Johnson  would  have  said. At least,  not if the  argument  previously  urged  is  worth  anything. Because every  one  will  see  that  if  it  be true,  as  Milne-Edwards  maintains,  that  the  temperature of  boiling  water  is  not  by  any  means high enough  to  destroy  the  organic  germs  of animalcules,  then  it  could  not  have  destroyed those germs  in  the  closed  tube,  and  animalcules ought to  have  made  their  appearance  there. If I could  lay  any  particular  stress  on  my  own  experiments (which  I do  not),  they  would  lead  to  the conclusion that  the  organic  germs  do  not  resist  the action of  boiling  water; for  I found  that  a piece of fish  divided  into  three,  and  placed  in  boiling water in  three  different  tubes,  one  closed  and excluded from  the  light,  the  second  closed  but exposed to  the  light,  and  the  third  open  and exposed to  the  light,  gave  me  no  animalcules  at all: had  there  been  any  germs  in  the  water  or meat,  these  must  have  been  destroyed. But all such observations  go  for  nothing  in  the  presence of M.  Pouchet’s  assertion  that  he  had  found animalcules in  the  infusion  after  subjecting  the organic matters  to  a temperature  of  250  degrees Cent. (546 degrees  Fahr.),  and  this,  too,  with artificial water. Unless the  germs  are  supposed to be  incombustible, it  is  difficult,  he  says,  to maintain,  after  this,  that  the  animalcules  were developed from  germs.

Milne-Edwards being  thus  disposed  of  by  M. Pouchet,  let  us  see  how  M.  Quatrefages  will  come off. He says,  that  having  examined  the  dust remaining on  the  filter  after  some  observations  on rain  water,  he  found  that  the  organic  elements presented a confused  assemblage  of  particles; and this continued  to  be  the  case  for  a few  minutes after their  immersion  in  water. But a few  hours afterwards, he  detected  a great  number  of  vegetable spores, infusoria,  and  those  minute  spherical  and ovoid bodies  familiar  to  microscopists,  which  inevitably suggest  the  idea  of  eggs  of  extremely small dimensions. He also  declares  that  he  has frequently seen  monads  revive  and  move  about after a few  hours  of  immersion. The conclusion drawn is,  that  the  air  transports  myriads  of dust-like  particles,  which  have  only  to  fall into the  water  to  appear  in  their  true  form  as animalcules.

The reply  of  M.  Pouchet  is  crushing. If the  air is  filled  with  animalcules  and  their  eggs,  they  will of  course  fall  into  any  vessel  of  water,  and  as  water is  their  natural  element,  will  there  exhibit  their vitality. But if  half  a dozen  vessels  of  distilled water, perfectly  free  from  animalcules,  be  left exposed  to  the  air,  beside  one  vessel  of  distilled water  containing  organic  substances  in  decay,  the half  dozen will  be  free  from  animalcules  and  eggs, but  the  one  will  abound  with  them. Now, it  is