608 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
from infection during collection and transportation. Under some 
conditions the protection of the consumer against milk-borne infec- 
tion may be best brought about by compulsory pasteurization of that 
portion of the milk supply which can not otherwise be raised to proper 
standard. Whatever method of control be adopted, it is certain 
that any genuine improvement in the character of a milk supply 
will be followed in the long run by a lessening in the amount of 
typhoid fever, diphtheria, scarlet fever, and to some extent tuber- 
culosis. The early detection of a single case of typhoid fever or 
scarlet fever on a dairy farm may be the means not only of preventing 
an extensive epidemic, but of avoiding the formation of scores of new 
foci which can in turn serve to light up subsequent cases for many 
years. Proper pasteurization of milk has been followed in many 
cities, as in Glasgow, Liverpool, and London, by an immediate and 
material reduction in the amount of typhoid fever. In other words, 
the connection between an expenditure of public money and a direct 
return in prevention of disease can be more clearly demonstrated 
in the case of milk-supply control than in some other of the usual 
municipal health department activities. 
~ The question whether the quality of a city milk supply can be more 
favorably influenced by inspection and supervision at thé source, or 
by generally enforced and controlled pasteurization is one upon 
which there is still some difference of opinion among experts. There 
is little doubt, however, that simply as a matter of economy of 
administration much is to be said at present in favor of centralized 
pasteurization of a large portion of the supply. Viewed as a method 
for preventing a large number of cases of infectious disease at rela- 
tively small expenditure the pasteurization of milk certainly ranks 
high among effective health measures. 
One of the important bacteriological advances of the last few years 
has been the discovery that a considerable number of healthy persons, 
convalescents, or others, harbor disease germs and that these persons 
are important agents in spreading disease. The detection and 
*proper treatment of disease-germ carriers, particularly in the more 
serious diseases and before or in the early stages of an epidemic, is 
now recognized as an important although difficult task. The whole 
question of the control of germ carriers is one that needs more careful 
study with a view to determining the actual results of the methods 
adopted. From this point of view, inspection of school children, 
especially at the beginning of the school year, is probably to be 
classed as a highly profitable activity, although it is to be wished 
that fuller and better-studied statistics were available. 
Inspection of school children is highly valuable, also, in detecting 
various common congenital or acquired defects. If the defects are 
remediable, their early discovery may avoid development into per- 
