METHODS OF EXAMINING MILK 267 
an unwarranted impression of accuracy. For example, 
when the numbers are in millions no figures smaller than 
the millions have any significance in the routine analysis 
of milk. In making the report raise the number to the 
next highest round number, but never lower it. 
“In no case shall the count of a single plate be re- 
garded as sufficient for the purpose of grading milk. If 
a single sample of milk only is to be tested there should 
be at least three plates counted before a report is made.” 
MICROSCOPIC METHOD 
The apparatus required for this method consists of 
a microscope, a supply of ordinary glass slides, and a 
straight capillary pipette marked to deliver 1/100 c.c., 
with the graduation mark 114 to 2% inches from the tip. 
The calibration should be tested by weighing on chemical 
balances the quantity of milk delivered when the pipette 
is filled to the mark. One pipette may be used for a num- 
ber of samples of milk provided it is kept clean. This 
may be done by rinsing the interior with clean water 
after each sample and wiping the exterior with a clean 
towel. 
Preparation of Smears.—“ One one-hundredth c.c. 
of milk or cream is deposited upon a clean glass slide by 
means of the pipette above described. By the use of a 
clean stiff needle this drop of milk is spread over an 
area of one square centimetre. This may be most con- 
veniently done by placing the slide upon any glass or 
paper ruled into areas one centimetre square. These 
marks showing through the glass serve as guides. After 
uniform spreading the preparation is dried in a warm 
place upon a level surface. In order to prevent notice- 
able growth this drying must be accomplished within 
