Nov.  2,  1896.] 
Supplement  to  the  Tropical  Agriculturist.'" 
36.^ 
No  absolute  distinction,  however,  could  be  drawn 
respecting  the  activity  possessed  by  the  bacteiia 
of  nodules  of  different  families  of  leguminous 
plants.  For  it  was  one  only  of  degree.  Pure 
cultivations  of  unlike  origin  represented  not  special 
kinds  but  only  adopt  able  forms  ; these  w’ere  able 
in  a weaker  degree  to  enter  into  symbiosis  with 
all  the  families  ; these  were  the  neutral  bacteria. 
If  one  such  form  entered  a leguminous  root  and, 
W’hile  forming  nodules  in  it,  increased,  its  de- 
scendants would  be  influenced  by  the  parent  plant 
so  energetically  that  they  would  only  po.=sess 
the  full  power  of  working  in  the  case  of  legu- 
minous families  of  the  same  kind,  but  they  would 
loo.se  it  more  or  less  for  all  others.  On  sowing, 
therefore,  in  any  particular  soil,  nodules  can 
only  be  formed  with  certainty  when  the  neutral 
bacteria  or  the  form  of  bacteria  adopted  for 
the  particular  kind  of  plant  in  question  are 
present  in  sufficient  quantity.  If  in  a soil  already 
exhausted  more  or  less,  by  heavy  leguminous 
cropping  of  its  neutral  bacteria,  there  be  put  in 
another  leguminous  plant  which  is  not  closely 
related  to  the  previous  one,  there  will  no  longer 
be  the  conditions  present  for  ihe  formation  of 
nodules,  or  else  this  formation  will  be  so  meagre 
that  it  has  but  little  value  for  the  nitrogenous 
nourishment  of  the  plant.  Hence,  wherever  there 
are  no  nodule-bacteria  in  soils,  or  these  are  present 
only  in  small  quantity,  the  lacking  bacteria  should 
be  artificially  supplied  by  inoculation  of  the  soil 
through  the  medium  of  the  proper  “Nitragin’’ 
for  the  crop  in  question. 
In  preparing  ‘‘Nitragin’'  for  commercial  use, 
Nobbe  and  Hiltner  took  the  “pure  cultivation” 
obtained  as  already  described,  transferred  it, 
with  suitable  precautions,  to  a glass  bottle  holding 
8 to  10  oz.,  and  containing  at  the  bottom  a 
small  quantity  of  agar-gelatine  on  which  it  was 
then  allowed  to  grow’ ; the  bottle  was  sealed  and 
the  contents  kept  from  the  light.  In  this  form 
the  “ Nitragin  ”,  is  available  for  use,  and  can 
now' be  purchased  by  anyone  desirous  of  trying  it. 
MILK  AND  MILK  PRODUCTS. 
(By  Mb.  James  Mollison), 
Superintendent  Government  Farms,  Bombay. 
Milk  sours  so  quickly  in'lndia  that  in  order  to 
get  fresh  cream  the  use  of  a De  Laval  Separator 
becomes  almost  compulsory.  The  separator  will 
be  found  economical  in  other  ways.  By  means 
of  a separator  the  milk,  so  soon  as  it  is  milked, 
can  be  separated  into  its  two  jjroducts — cream 
and  separated  milk.  The  latter  soon  sours,  but 
the  former  must  be  kept  to  ripen  before  it  can 
be  made  into  good  butter.  The  separation  of 
whole  milk  by  mechanical  power  makes  a large 
dairy  unnecessary,  for  no  room  is  required  for 
the  numerous  vessels  otherwise  needed  lor  setting 
the  milk.  If  it  is  found  necessary  to  raise  cream 
by  the  ordinary  milk-setting  jirocess  in  India, 
the  quicker  the  cream  is  made  to  rise  the  better 
the  results  will  be ; because  even  under  the 
most  favourable  conditions  it  is  improbable  that 
all  the  cream  can  be  skimmed  off  before  the 
milk  has  thickened  by  turning  sour.  The  loss 
can  be  avoided  if  the  milk  is  maintained  at  an 
artificially  low  temperature  by  means  of  ice. 
Cream  rises  quickest  in  a falling  temperature 
and  to  expedite  the  process  on  practical  lines 
in  India  I should  recommend  that  shallow  vessels 
be  used,  that  these  be  placed  in  pans  containing 
the  coolest  well  water  procurable,  or  that  water 
be  cooled  specially  for  the  purpose  by  allowing 
it  to  filter  through  a series  of  earthenware 
chatties.  It  is  well  enough  known  that  if  porous 
earthenware  vessels  aie  placed  on  a stand  one 
above  the  other  so  that  the  water  passes  from 
one  to  the  other,  even  though  the  temperature 
of  the  atmosphere  is  high,  evaporation  takes  place 
which  lowers  the  temperature  of  the  water  so 
that,  that  which  collects  in  the  lowest  vessel 
is  comparatively  cool  and  is  ordinarily  of  suffi- 
ciently low  temperature  to  rapidly  lower  the 
temperature  of  new  milk,  provided  the  milk 
is  set  in  its  vessel  in  the  water.  This  is  a 
cheaper  method  of  rapidly  cooling  milk  than 
the  use  of  ice.  There  is  however  one  objection. 
If  milk  is  cooled  below  the  temperature  of  the 
surrounding  air,  it  will  (like  any  other  cold 
substance)  condense  the  moisture  of  the  surround- 
ing air  and  along  wdth  this  moisture  it  will 
absorb  any  taint  or  odour  existing  in  that  at- 
mosphere. Impure  air  under  these  conditions 
will  certainly  injure  milk.  The  point  therefore 
to  be  sure  of  is  that  the  dairy  is  thoroughly 
ventilated  and  that  the  air  which  circulates 
through  it  is  pure.  If  on  the  other  hand  milk 
at  a comparatively  high  temperature  is  exposed 
to  air  of  a lower  temperature  the  latter  will 
cei’tainly  be  the  absorbent.  These  statements 
tend  to  show  that  the  refrigerator  in  common 
use  in  dairies  is  of  great  value.  The  refrffierator 
is  designed  to  aerate  milk  and  at  the  same 
time  to  cool  it.  The  refrigerator  is  essentially 
a continuous  tube  ranged  like  a “ worm  ” inside 
a frame.  Cold  water  is  made  to  circulate  throimh 
the  continuous  tube  w’hilst  the  milk  passes  as 
a thin  firm  over  the  metal  frame;  the  milk  is 
cooled  and  at  the  same  time  is  throughly  e.vposed 
to  the  atmosphere  so  that  the  animal  odour 
which  invariably  impregnates  new  milk  is  driven 
off.  It  is  at  the  same  time  thoroughly  expo.ed  to 
the  oxidizing  influence  of  pure  air.  This  refri- 
gerating process  is  employed  to  prepare  milk  for 
conveyance  by  road  or  rail  in  closed  vessels  to 
considerable  distances  and  the  milk  is  un- 
doubtedly all  the  better  for  the  treatment. 
I have  found  that  in  hot  weather  milk  so 
treated  is  further  preserved  against  any  fermen- 
tative change  if  the  vessels  are  covered  with 
hoods  of  wet  canvas.  The  heat  of  the  sun  or  of 
the  air  evaporates  the  water  from  the  hood  and 
the  heat  necessary  for  volatilization  of  water  is 
derived  partly  from  the  milk  which  is  of  course 
further  cooled. 
A cool  well  ventilated  dairy  kept  scrupulously 
clean  is  as  necessary  in  India  as  elsewhere.  A 
well  planned  and  well  arranged  dairy  should,  in 
India,  have  high  walls  with  a considerable  airspace 
between  the  ceiling  and  the  double  tiled  roof. 
Either  a cement  concrete  floor  or  a stone  floor 
does  very  well,  but  the  joints  of  the  latter  should 
be  well  cemented.  The  walls  also  should  be 
plastered  with  cement  to  a height  of  three  or 
foui  feet  or  tiled,  and  there  should  be  no  under- 
ground drain.  Milk  must  necessarily  be  spilled 
from  time  to  time  on  the  dairy  floor,  and  if 
there  are  crevices  in  the  floor  or  walls,  small 
