389 
PART V. THE WASHINGTON MILK SUPPLY. 
So far as our experimental work on this subject is concerned, 
the principal object has been to determine the general character 
of the milk at present supplied to the consumer in Washington and 
the District of Columbia. With this in view, routine chemical anal- 
yses have been made of milk offered for sale by various milk dealers 
in the city of Washington and the District of Columbia, from the 
5th of July, 1907, to the 27th of September, 1907, inclusive. So 
much has been written on the subject of the routine analysis of 
milk, and the methods at present employed are generally so well 
understood, that only a few words concerning the methods em- 
ployed in this investigation are required. For further details con- 
cerning methods of milk analysis, the reader is referred to the follow- 
ing standard works on this subject, viz, Modern Methods of Testing 
Milk and Milk Products, Van Slyke, New York, 1907; and Food 
Inspection and Analysis, Leach, New York, 1907. The chemical 
examination of the Washington milk supply has included the deter- 
mination of specific gravity, total solids, fat, sugar, ash, acidity, 
refractometer reading, quantity of dirt by volume, and tests for 
preservatives. During the month of September special attention 
was paid to the examination for preservatives, and during this time 
the determination of sugar and total solids was omitted. The latter 
were calculated from the specific gravity and the percentage of fat 
according to Babcock’s rule. The samples submitted for examin- 
ation were collected by certain inspectors of the health office, and 
as soon as collected were put on ice and kept there until delivered 
at the Hygienic Laboratory, and until the chemical examinations 
were completed. As soon as the sample was brought into the 
laboratory, the acidity of the milk was determined on 50 cubic 
centimeters of the sample. The specific gravity and the percentage 
of fat and also the refractometer reading (the latter on the milk 
serum) were also determined practically as soon as the sample reached 
the laboratory, especially in those cases in which owing to lack of 
time the total solids were not determined by weighing, and in the 
event that these determinations indicated that any particular 
sample was below standard' the total solids on this particular sample 
were determined by weighing in the manner described in the fol- 
lowing: . 
Specific gravity .-^-The specific gravity of the milk was determined 
either by means of the Westphal balance or by means of the Que- 
venne lactometer. 
Total solids and ash . — The total solids and ash were determined by 
the method recommended by Leach (1). This method consists in 
