i)2  Dain/  Cattle  and  the  Butter  Test. 
The  percentage  of  fat  in  sample  13  is  exceptionally  high 
and  inquiry  elicited  the  fact  that  this  sample  had  been 
obtained  independently  of  the  remainder,  and  did  not  fairly 
represent  the  bulk. 
Table  I. — Analyses  of  Milk  Samples. 
No. 
Sample 
Fat 
1 
Shorthorn  ....... 
per  cent. 
307 
2 
Lincoln  Bed  Shorthorn  ..... 
3-32 
3 
Devon  ........ 
3-43 
4 
South  Devon  ....... 
2-72 
5 
Longhorn  ....... 
4-66 
6 
Bed  Poll 
2-99 
7 
Ayrshire  ......... 
3-79 
8 
Jersey  ........ 
4-29 
9 
Guernsey  ....... 
4-47 
10 
Kerry  ........ 
4T3 
11 
Dexter  ........ 
4-87 
12 
Gloucester  ....... 
4-92 
13 
Welsh 
7-20 
Physical  Investigations. 
In  order  to  determine  the  numbers  and  relative  sizes 
of  the  globules  in  different  samples  (see  Figs.  1-13), 
photomicrographs  of  thin  films  of  the  undiluted  milks  at  a 
magnification  of  1,000  diameters  were  obtained.  A single 
drop  of  the  milk  was  taken  from  a well-shaken  sample  by 
means  of  a standard  platinum  wire  loop  such  as  is  used  for 
inoculating  the  tubes  of  nutrient  broth  in  a Rideal-Walker 
germicide  test.  The  drop  was  placed  on  a glass  slip  and 
covered  with  a five-eighths  inch  circular  cover  glass,  the  latter 
being  carefully  lowered  into  position  with  no  pressure  other 
than  that  of  its  own  weight  ; the  preparation  was  then  ringed 
round  with  vaseline  to  prevent  evaporation. 
On  account  of  the  very  considerable  oscillation  (Brownian 
movement)  of  the  finer  globules,  very  short  exposures  only 
were  found  to  be  admissible,  and  by  the  use  of  very  rapid 
plates  the  exposure  was  reduced  to  one-fiftieth  of  a second. 
Prints  of  fields  representing  an  area  of  0T55  mm.  by  OTl  mm. 
were  thus  obtained  ; all  the  globules  in  each  field  were 
counted  and  measured,  and  from  the  numbers  and  sizes  so 
obtained.  Table  II.,  representing  the  percentage  numbers  of 
different  sizes  of  fat-globules  in  the  thirteen  different  breeds 
was  computed. 
