EXAMINATION -OF FROZEN EGG PRODUCTS. ~ 89 
water may be added, if necessary, to obtain an even distribution. 
Dry in the air on a level surface. Make three such slides from each 
subsample. 
Immerse the slides carrying the dried egg films in xylol or benzol 
for 1 minute. Again dry, and place in 1 per cent carbolic methylene 
blue for from 10 to 20 minutes. The object is to stain the bacteria 
deeply, and to stain fat, débris, and background as lightly as possible. 
To do this, wash off the excess of stain in water, and immerse in 50 to 
60 per cent alcohol until only a faint blue is visible. This decolorizing 
is quickly done. Failure to decolorize is followed by serious errors 
in results. | 
Dry, and examine with the microscope, counting 20 fields along the 
diagonals of each slide. 
A desirable optical combination to employ is that which is used in 
the direct microscopic examination of milk. The microscope should 
have an oil immersion objective and an ocular giving the field desired, 
and should be fitted with a mechanical stage. ‘To standardize the 
microscope, place upon the stage a stage micrometer, and on the dia- 
phragm of the ocular place an eyepiece micrometer, with a circular 
ruling, 8 mm. in diameter, and divided mto quadrants. Adjust the 
draw tube until the inner circle of the eyepiece micrometer has a diam- 
eter of 0.146 mm. Record the necessary adjustment of the draw 
tube. By this adjustment, the inner circle will cover i/7,200,000 ce. 
of the undiluted egg, giving a factor of 7,200,000. ‘This means that 
the number of bacteria in a single field shouid be multiplied by 
7,200,000, or, if 60 fields ate counted, the total number should be 
multiplied by 120,000, to obtain the number of bacteria in 1 ce. of the 
original egg material. If any variation from this procedure is used, 
the factor must be calculated. 
CHEMICAL HXAMINATION.! 
Start the chemical examination immediately after the taking of 
subsamples, and make ail determinations in duplicate. Thaw the 
subsamples by partially immersing the containers in warm water, the 
temperature of which should not be above 50° C. Then thoroughly 
mix them, preferably with an eiectric stirrer. In the absence of such 
an instrument in the laboratory, the mixing may be quite satisfactorily 
accomplished by sucking the meited subsample several times through 
a Gooch crucible containing no asbestos, using very moderate suction. 
Examine this mixed composite sample by the following methods: 
TOTAL SOLIDS. 
Weigh approximately 5 grams of the sample into a tared lead dish 
of 24 to 3 inches diameter, and dry in a vacuum of not less than 25 
inches at 55° C., until there is no further loss in weight. This drying 
1 The analytical methods described were very largely devised or adapted to egg analysis by N. Hendrick 
son, formerly of the Food Research Laboratory. 
