10 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
of the alveoli and ducts, as has been suggested, because 
when milk is drawn from the udder at the end of the 
first phase with a milk tube or catheter the composition 
of the first and last milk is about the same; but as soon 
as the teats are manipulated, thus beginning the second 
phase, the per cent. of fat is increased. The milk se- 
creted during the first phase contains a lower per cent. 
of fat than that formed in the second phase. The per 
cent. of other solids is nearly the same in the milk of 
both phases. The original ferments or enzymes, except 
oxydase, are present in greater quantity in milk of the 
second phase than in that of the first. The first milk 
drawn from the udder contains more oxydase than the 
end milk. 
