Most  complex  fluids,  including  milk,  undergo  chemical
changes  on  standing  or  on  keeping,  also  with  much  shaking
or  jolting.  Although  the  precise  nature  of  the  changes  is
not  known,  there  is  evidence  that  stale  milk,  even  if  not
soured,  has  undergone  changes.  Many  housewives  rightly
make  a  practice  of  heating  their  milk  for  the  household  as
soon  as  it  has  been  delivered.  If  milk  which  has  been
pasteurised  is  sold  as  raw  milk  it  will  be  heated  again  in
many  houses  and  will  thus  have  been  heated  twice  before
consumption.  Of  recent  years,  with  the  introduction  of
pasteurisation  on  a  large  scale,  it  has  been  found  that  milk
which  has  been  heated  twice  is  not  a  suitable  food  for  infants,
having  a  tendency  to  induce  infantile  scurvy.  It  is  not
known  how  far  such  tendencies  are  due  to  the  long  interval
which  will  almost  certainly  have  elapsed  between  the
drawing  of  the  milk  and  its  consumption,  or  how  far  the
second  heating  may  be  the  detrimental  factor.  More
precise  knowledge,  while  of  interest,  does  not  affect  the
general  point,  and  it  should  be  clearly  borne  in  mind  that
artificially  fed  infants,  whose  sole  food  is  milk,  should  not
be  given  milk  which  has  been  heated  on  two  separate
occasions.
If  pasteurised  milk  is  sold  as  raw  milk  there  is  a  very
good  chance  that  it  will  be  again  heated  in  the  home  before
being  given  to  the  infant,  which  is  most  undesirable.  There
can  be  no  doubt  that  milk  delivered  for  infants  should  be
delivered  raw,  both  in  order  to  ensure  that  it  is  as  fresh  as
may  be  possible,  and  also  to  prevent  a  second  heating.
272  HYGIENE

The  American  regulations  for  the  sale  of  milk  very  rightly
insist  on  such  milk  being  regarded  as  unfit  for  infants.
