DEVELOPMENT OF CITY MILK SUPPLY PROBLEMS 43 
small expense for laboratory equipment.®® Among its limita- 
tions the fact that it is not readily applicable to milk of low 
germ content nor to pasteurized milk are the most important. 
As acid formation is the most prominent objectionable 
feature in milk of poor keeping quality it has been suggested 
as a measure of keeping quality. Studies of acid develop- 
ment in milk show that at the temperatures to which milk 
is ordinarily exposed during delivery and in the household, 
changes in acidity occur at first so slowly as to appear of 
little significance but that later acidity imereases very 
rapidly.° As a result milk at the time of delivery may be 
so little changed as to show on titration a normal acidity and 
yet be sour before the lapse of twenty-four hours. 
A simple and on the whole fairly satisfactory test of keep- 
ing quality may be made by holding a sample of milk at a 
definite temperature for a definite time and then examining 
for acid and flavors. This test has the merit of not requiring 
apparatus more complicated than a good ice chest and facili- 
ties for the titration of acidity. It is a test which is within 
the financial possibilities of any municipality which has suf- 
ficient funds to provide an inspector to collect and observe 
milk samples. 
Tue PROBLEM OF INSPECTION 
Attention has already been drawn to the fact that a city 
can learn little about the actual condition of its milk supply 
until it provides some form of inspection, but much of the 
value of such information depends upon the form of in- 
spection provided. 
Until about 1900 city milk inspection consisted almost ex- 
clusively of the collection and examination of samples within 
the municipality. At succeeding periods attention was 
focused upon skimming and watering as affecting the food 
32, S. Reed and J. D. Brew, Counting Bacteria by Means of the Mi- 
croscope, Tech. Bul. 49, N. Y. Agr. Exp. Sta., 1916. 
40, G. Hastings and A. C. Evans, 4 Comparison of the Acid Test and 
the Rennet Test for Determining the Condition of Milk for the Cheddar 
Type of Cheese, Cire. 210, U. S. D. A., Bureau of A. I., 1913. 
