56  Comparative  Composition  of  Milks.      { AFebrXyfi908m' 
Hence,  it  has  come  to  pass  that  widely  varying  results  have  been 
obtained  by  different  workers.  The  chemical  work  was,  in  many 
instances,  undoubtedly  accurate,  but  the  samples  examined  were 
not  representative,  and  the  deductions  drawn  not  justified  by  the 
facts.  Chemical  data  alone  are  not  sufficient  to  properly  interpret 
analytical  findings,  in  the  study  of  milk  as  a  food  ;  they  must  be 
accompanied  by  the  consideration  of  physiological  principles,  also. 
It  has  been  with  this  thought  in  mind — -the  physiological  chem- 
ical point  of  view,  so  to  speak — that  the  writer  has  prepared  the 
following  chemical  data,  and  endeavored  to  interpret  their  physio- 
logical significance. 
PERCENTAGE  COMPOSITION  OF  HUMAN  MILK  DURING  THE 
ACT  OF  NURSING  (FORSTER) 
First  part  of  nurs- 
ing act 
Intermediate  part  of 
nursing  act 
Last  part  of  nurs- 
ing act 
Fat  
1.70 
2.77 
4.51 
Proteids  
1.13 
0.94 
0.71 
5.56 
5.70 
5.10 
Ash   
0.46 
0.32 
0.28 
Water  
90.24 
89.68 
87.50 
Colostrum,  the  milk  given  by  mammals  for  three  or  four  days 
after  the  birth  of  their  young,  differs  radically  in  composition  from 
normal  milk.  It  is  a  yellow,  oily  liquid  of  pungent  taste,  containing 
a  very  high  percentage  of  an  albumin  similar  to  blood  albumin, 
abundant  fat  globules,  and  numerous  large  circular  cells  called  colos- 
trum corpuscles. 
According  to  Chapin,  colostrum  contains  the  same  food  elements 
as  milk,  but  in  different  forms  ;  its  proteids  are  soluble,  and  its  sugar 
dextrose,  and  not  sugar  of  milk.  Its  function  is  to  furnish  readily- 
absorbable  nutriment  (since  the  stomach  of  the  infant  contains  no 
gastric  juice  during  the  colostrum  period)  and  to  stimulate  the 
development  of  the  absorptive  powers  of  the  digestive  tract. 
The  laxative  action  of  colostrum  in  removing  the  meconium  may 
be  due,  as  Rotch  claims,  to  a  disturbance  of  the  equilibrium  of  the 
mammary  glands,  and  of  the  digestive  tract  of  the  infant,  the  dis- 
turbances in  the  latter  amounting,  at  times,  to  acute  conditions  of 
fermentation  in  the  intestinal  tract,  with  laxation  (a  result  facilitated 
by  the  presence  of  the  readily  fermentable  sugar  dextrose)  ;  but,  it 
is  much  more  probably  due  to  the  high  percentage  of  fat  in  the 
fecal  residue. 
