BACTERIAL EXAMINATION OF EGGS 467 
shell by being heated in the flame. The expulsion of the albumin into 
the second flask should be done slowly and watched closely. As soon 
as the yolk appears in the hole the heating is interrupted and the egg is 
tilted from one side to the other to allow the rest of the albumen to run 
out. In the same manner the yolk is expelled in two portions. The 
success of this method depends largely on the size of the hole. If this 
is too small, it is hard to separate the white from the yolk; if it is too 
large, it is difficult to expel the yolk in two separate portions. Some- 
times the yolk obstructs the hole before all of the albumen is obtained. 
If the yolk does not retract after cooling, the egg is inverted for a 
moment. Often the vitelline membrane will not rupture, and the yolk 
will come out in one piece. This can be prevented by puncturing the 
membrane with a sterile platinum needle. In this manner four flasks 
are obtained from each egg, two of them containing albumin and two 
of them containing yolk. The flasks are repeatedly shaken to mix the 
contents well. It is of advantage to have tall flasks because the con- 
tents can be mixed more easily without wetting the cotton plug. Two 
flasks, one with albumin and one with yolk, are incubated at 38° C. for 
forty-eight hours, and the other flasks are incubated at 20° C. for five 
days. After this period of development subcultures on agar slants are 
made to determine if growth has taken place. 
Rettger’s Method for the Bacterial Examination of Eggs. The 
egg to be examined is placed small end up, in an egg cup or holder. 
The upper half of the egg is flamed with a Bunsen burner, the cup being 
turned constantly so that every part of the upper half of the shell is 
brought into brief contact with the flame. While the egg is held in 
one hand the upper end of the shell is removed with sterile scissors, 
leaving an opening about 1 in. in diameter. The white is poured out, 
care being taken to prevent it from running down the side of the shell. 
At this point the edge of the opening is flamed after which the entire 
yolk is poured out into a wide-mouthed flask, or better still, a large 
tube especially designed for this work by Rettger. Previous to intro- 
ducing the yolk, definite amounts of nutrient bouillon are placed in the 
flasks (25-50 c.c.) or tubes (25 c.c.) which are plugged with cotton and 
sterilized. The yolk and bouillon should be thoroughly mixed. In 
case the test tube is used this process is greatly facilitated by the pres- 
ence of a small glass rod about 1$ in. in length. The tubes should then 
be placed in the 37° C. incubator and after seventy-two hours’ incuba- 
tion agar streaks made from them. These should be incubated for 
from twenty-four to forty-eight hours. 
