Am.  Jour.  Phaim.l 
December,  1900.  J 
Substitute  Infant-Feeding. 
583 
insist  upon  their  observance  on  the  part  of  dairymen,  the  problem 
of  a  proper  milk-supply  will  be  largely  solved. 
The  prompt  and  rapid  aeration  and  the  cooling  of  milk  are  mat- 
ters of  importance.  The  temperatures  at  which  bacteria  in  milk 
grow  most  rapidly  are  those  near  body  heat.  There  is  practically 
no  growth  when  the  temperature  is  below  500  F.  It  has  been 
proved  that  bacteria  which  increased  two  hundred  fold  in  four  hours, 
at  930  F.,  increased  only  eight  fold  at  55 0  F.;  so  the  necessity  of 
cooling  the  milk  immediately  after  milking  will  be  apparent. 
Combined  aerators,  strainers  and  coolers,  suitable  for  use  with 
well-water  or  ice-water,  can  be  had  at  any  dairy-supply  house,  at  a 
small  cost.  By  using  one  of  these,  the  cow  odor,  the  animal  heat, 
and  most  of  the  dirt  can  be  removed  from  milk  in  a  few  minutes. 
The  milk  of  a  herd  of  cows  can  then  be  mixed  and  bottled,  or  canned 
and  packed  in  ice,  or,  as  is  often  done,  lowered  into  a  well  or  set  in 
a  cool  spring.  Such  milk  will  keep  well,  while  milk  "  warm  from 
the  cow  "  soon  spoils. 
Sometimes  dairymen  add  preservatives  to  their  milk,  to  keep  it 
sweet.  The  articles  most  commonly  used  are  boric  acid,  borax  and 
formaldehyde.  Formaldehyde  is  particularly  objectionable,  as  it 
renders  the  curds  exceedingly  tough.  It  can  be  detected  by  adding 
to  a  small  quantity  of  slightly  diluted  milk  an  equal  quantity  of 
commercial  sulphuric  acid.  Pour  the  milk  into  a  test-tube  or  flask, 
and  then  allow  the  acid  to  run  in,  so  as  not  to  mix  with  the  milk. 
A  violet  color  will  appear  at  the  junction  of  the  two  liquids  if  for- 
maldehyde is  present,  and  the  curd  of  the  milk  will  dissolve  slowly 
when  the  tube  is  shaken. 
In  selecting  cow's  milk  for  infant-feeding,  that  which  is  clean, 
aerated,  cooled  and  bottled  immediately  after  milking,  and  kept 
below  6o°  F.,  until  delivered,  is  the  article  to  be  chosen  by  the 
physician.  The  richness  of  milk  and  cream  depends  upon  the  breed 
of  cattle  supplying  the  milk.  In  most  of  the  States  that  have  dairy 
laws  the  minimum  amount  of  'butter  fat  allowed  in  the  milk  is  3  per 
cent.  In  actual  practice  milk  varying  between  3  and  5  per  cent, 
butter  fat  will  be  met. 
In  reference  to  the  production  of  butter  fat,  cows  may  be  roughly 
divided  into  three  classes:  (1)  Fancy,  full-blooded  Guernseys  and 
Jerseys,  giving  milk  containing  5  per  cent,  and  over;  (2)  ordinary 
Jerseys  and  Guernseys,  known  as  "butter  cows,"  giving  milk  contain- 
