﻿210 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  vessels 
  containing 
  the 
  milk 
  are 
  placed 
  in 
  water 
  and 
  brought 
  

   to 
  a 
  temperature 
  of 
  150 
  to 
  1">"> 
  F., 
  and 
  then 
  cooled 
  and 
  

   kept 
  cool 
  until 
  used. 
  This 
  method 
  kills 
  most 
  of 
  the 
  bacteria 
  

   in 
  milk 
  and 
  makes 
  less 
  change 
  otherwise 
  than 
  does 
  boiling. 
  1 
  

  

  Bacteria 
  are 
  important 
  in 
  connection 
  with 
  many 
  other 
  in- 
  

   dustries. 
  The 
  formation 
  of 
  acetic 
  acid 
  (the 
  acid 
  of 
  vinegar) 
  

   is 
  due 
  to 
  the 
  growth 
  of 
  several 
  kinds 
  of 
  bacteria. 
  I'art 
  or 
  

   all 
  of 
  the 
  processes 
  of 
  curing 
  tobacco, 
  tanning 
  leather, 
  pre- 
  

   paring 
  plant 
  fibers 
  (as 
  llax 
  and 
  hemp), 
  and 
  making 
  butter 
  

   and 
  cheese 
  depend 
  upon 
  the 
  growth 
  processes 
  of 
  different 
  

   kinds 
  of 
  bacteria. 
  

  

  196. 
  Bacterial 
  diseases 
  of 
  plants 
  and 
  animals. 
  Although 
  

   many 
  bacteria 
  grow 
  constantly 
  upon 
  and 
  within 
  other 
  plants 
  

   and 
  animals, 
  these 
  are 
  usually 
  not 
  disease-producing 
  bacteria. 
  

   Sometimes, 
  however, 
  malconditions 
  in 
  the 
  host 
  plant 
  or 
  ani- 
  

   mal 
  are 
  produced 
  by 
  bacteria, 
  and 
  disease 
  and 
  death 
  of 
  the 
  

   host 
  may 
  result. 
  2 
  

  

  Brief 
  reference 
  to 
  a 
  few 
  kinds 
  of 
  bacterial 
  disease 
  will 
  af- 
  

   ford 
  illustrations 
  of 
  some 
  of 
  the 
  effects 
  produced 
  upon 
  plants 
  

   and 
  animals 
  (fig. 
  170). 
  In 
  the 
  case 
  of 
  black 
  rot 
  of 
  cabbage 
  

   the 
  bacteria 
  enter 
  the 
  cabbage 
  leaf 
  through 
  the 
  leaf 
  pores. 
  

   Once 
  within 
  the 
  leaf, 
  they 
  grow 
  rapidly, 
  and 
  brown 
  or 
  black 
  

   spots 
  appear 
  on 
  the 
  leaf 
  as 
  outward 
  evidence 
  of 
  the 
  inward 
  

   ravages 
  of 
  the 
  parasites. 
  These 
  leaves 
  may 
  become 
  shriveled. 
  

   The 
  disease 
  may 
  spread 
  throughout 
  the 
  plant 
  and 
  result 
  in 
  

   destruction 
  of 
  the 
  entire 
  head 
  of 
  cabbage. 
  

  

  ' 
  Pear 
  blight" 
  is 
  a 
  disease 
  which 
  often 
  seriously 
  affects 
  the 
  

   leaves, 
  young 
  twigs, 
  and 
  fruit 
  of 
  the 
  pear 
  and 
  apple. 
  The 
  

   bacteria 
  cannot 
  live 
  under 
  long 
  exposure 
  to 
  direct 
  sunlight 
  

  

  1 
  "Care 
  of 
  Milk 
  on 
  the 
  Farm,'' 
  Farmer*' 
  Hull! 
  tin 
  63, 
  U.S. 
  Dept. 
  Apr., 
  1000. 
  

   " 
  liacteria 
  in 
  Milk." 
  Farmers' 
  1 
  Bulletin 
  ,'^,v, 
  U.S. 
  Dept. 
  Agr., 
  looo. 
  

  

  " 
  Sources 
  of 
  Bacteria 
  in 
  Milk," 
  Bulletin 
  51, 
  Storrs 
  Agr. 
  Exp. 
  Sta., 
  Storrs, 
  

   Conn., 
  1008. 
  

  

  "Milk 
  and 
  its 
  I'mdnets 
  as 
  Carriers 
  of 
  Tuberculosis 
  Infection," 
  Bul- 
  

   letin 
  143, 
  Bureau 
  of 
  Animal 
  Industry, 
  U.S. 
  Dept. 
  A.^r.. 
  1000. 
  

  

  2 
  A 
  few 
  diseases 
  are 
  caused 
  by 
  small 
  animal 
  parasites, 
  but 
  since 
  these 
  are 
  

   not 
  bacterial 
  diseases, 
  they 
  are 
  not 
  included 
  in 
  this 
  discussion. 
  

  

  