16 
This investigation and the work of the Department of Agriculture 
concerning the milk supply at the farms were referred to in a letter 
to the President, June 11, 1907, by Dr. G. Lloyd Magruder, of Wash- 
ington, in which it was suggested that the Bureau of Public Health 
and Marine-Hospital Service be directed to make an investigation of 
the milk industry in the District of Columbia from the farm to the 
consumer, with the cooperation of other departments.® 
The Surgeon-General, being called upon by the President for an 
opinion as to whether such an investigation should be made, replied 
affirmatively, with detailed reasons therefor, and with special recom- 
mendations as to cooperation of the several bureaus in the Depart- 
ment of Agriculture, and the President and the Secretary of the 
Treasury thereupon directed the said investigation. 
In order to properly study the subject as it exists in the District 
of Columbia, it was deemed necessary to treat the matter from a 
broad point of view ; that, to study the local aspect of a world-wide 
problem, the findings and experiences of others must necessarily be 
considered. In many respects the Federal Government has peculiar 
advantages for the study of these problems which, strictly speaking, 
are not confined to any one locality, but are national in scope. It is 
therefore incumbent on the National Government to assume its re- 
sponsibilities and attempt the solution of scientific questions of this 
character influencing the lives and health of its citizens. Because of 
the relation the Public Health and Marine-Hospital Service bears to 
the conservation of the public health it was determined to make this 
investigation of such a character that, in addition to being of local 
value, it would also be of assistance to health officers at large, and 
especially to those not as yet provided with the necessary laboratory 
facilities and corps of workers such as can be afforded only by the 
richer and more densely populated centers. 
It has been the object to include in this volume all available data 
showing the influence of milk as a carrier of infection, its chemical 
composition, the contaminations found therein, their influence upon 
it as an article of food, and the measures necessary in its produc- 
tion and handling to prevent such contamination. 
Milk in the udder of a healthy cow is rarely sterile, but with 
proper methods can occasionally be removed in small quantities free 
from micro-organisms. In this condition it may theoretically be 
considered normal milk, and as such has been kept for over two years. 
But this is not the milk of commerce. In the healthy cow, milk may 
contain organisms while still in the udder, or receive its initial con- 
tamination with the omnipresent microphyte in its passage through 
the ducts of the animal’s teats. This may be considered its first point 
of contact with the outer world, for these organisms in the healthy 
animal have gained access to the ducts from without. At every other 
°Annual Report, Public Health and Marine-Hospital Service, 1907, p. 35. 
