THE CHEMISTRY OF MILK. 
By Joseph H. Kastle, Chief Division of Chemistry , and Norman Roberts, Assistant 
Surgeon, Public Health and Marine-Hospital Service. 
PREFACE. 
In the following pages the attempt has been made to present suc- 
cinctly and yet sufficiently comprehensively for a thorough under- 
standing of the subject what is known to-day regarding the chemistry 
of milk, and to give the results of the analyses of the Washington 
milk supply, made in the division of chemistry of the hygienic labora- 
tory during a period of twelve weeks extending through July, August, 
and September, 1907. 
Part I of this communication deals with the chemical composition 
and general characteristics of milk. 
Part II deals with the chemical changes occurring in milk. Under 
this head are included changes in the composition of milk brought 
about, (1) by the action of heat and acids, (2) by the action of the 
enzymes of milk, (3) by the action of the digestive ferments, (4) 
by the action of bacteria and other micro-organisms, including the 
lactic acid fermentation and the abnormal fermentations of milk. 
Under this last section a few pages are also devoted to the subject of 
poisoning by milk, galactotoxismus. Under section 1 the destructive 
effect of heat on the milk enzymes is also considered. 
Part III is devoted to the consideration of legal standards governing 
the sale of milk in various localities. 
Part IV is devoted to the subject of milk adulteration, by skim- 
ming, watering, and the addition of foreign substances, including 
artificial coloring matters and milk preservatives. Some attention 
has been paid to the effect of artificial coloring matters and preserva- 
tives on the health of man. 
Part Y is devoted to the general consideration of the Washington 
milk supply. Under this head will be found, (1) a brief outline of 
the methods employed in milk analysis, (2) the results of our analyses 
of the Washington milk supply, (3) conclusions regarding the general 
character of the Washington milk supply. 
In the preparation of this communication we have drawn freely 
from the writings of numerous authors on the subjects herein con- 
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