2.  Saccharomyces    rosaceus    (Pink    torula). — Growth     on    sterilised

potato  which  had  been  inoculated  from  a  colony  contaminating  a  plate-
cultivation.  This  yeast  develops  a  coral-pink  colour,  but  does  not  grow
so  luxuriantly  as  the  chromogenic  bacteria.
*  The  term  "attenuation"  is  applied  also  to  a  virus,  in  the  sense  of
weakening  or  modifying  its  effect.  To  avoid  confusion  the  term  mitigation
might  be  employed  exclusively  to  express  this,  and  attenuation  used  only
in  the  sense  indicated  above.
XXIV  DESCRIPTION    OF    PLATES.
PLATE  XVI.  (Folhioing  Plate  XV.}

1.  Bacillus  anthracis  (Bacteridie  du  charbon  ;  Bacillus  of  splenic  fever,

wool-sorter's  disease,  or  malignant  pustule],  —  The  bacillus  of  anthrax
grows  very  rapidly  on  sterilised  potato,  especially  when  placed  in  the
incubator  at  the  temperature  of  the  blood.  The  growth  forms  a
creamy-yellow  layer,  with  copious  spore-formation.
2.  Bacterium  indicum   (Micrococcus  indicus,   Koch;  Bacillus  indicus,

Fliigge).  —  Sterilised  potato  inoculated  with  a  pure  growth  obtained  by
successive  cultivations.  Unless  the  growth  is  quite  free  from  the
presence  of  other  bacteria,  the  brilliant  red  colour  is  not  obtained.
PLATE  XVII.  (Following  Plate

i  and  2.  Bacillus  cyanogenus  (Bacterium  syncyanum  ;  Bacillus  of  blue
milk}.  —  Potato  inoculated  from  a  cultivation  in  nutrient  gelatine.  In
three  days  a  peculiar  bluish-green  growth  develops  on  the  surface  of
the  potato,  and  in  nine  days  it  has  a  heaped-up  margin  of  a  bluish-
green  colour,  while  the  central  portion  has  turned  almost  black.
PLATE  XVIII.  (Facing  page  104.)

1.  Bacillus  tuberculosis.  —  Pure  cultivation  of  the  tubercle-bacillus  on

blood-serum  solidified  obliquely.
2.  Pure  cultivation  on  solid  blood-serum  in  a  glass  capsule.
3.  The  same  as  Fig.  2,  examined  under  a  low  power  of  the  microscope,  x  80.
4.  Impression-preparation   showing   the   peculiar   serpentine   growth  of  the

colonies  on  blood-serum,      x  700.
