BACTERIAL ANALYSIS OF EGGS 469 
Hadley and Caldwell’s Method. The egg shell should be thor- 
oughly disinfected before any opening is made. This may be accom- 
plished by first washing the egg, if soiled, with soap and water and a 
wad of cotton, then immersing for ten minutes in 1 : 5000 mercuric 
chloride solution, containing either citric acid or ammonium chloride 
to merease the penetrating power. The egg may then be plunged 
into 95 per cent alcohol, removed, drained and ignited to dry the sur- 
face. ‘These operations can be carried on in a suitably constructed 
wire rack in which the eggs can await examination, being meanwhile 
protected from air contamination. 
Next, as a final precaution, the egg should be well flamed at the end 
opposite the air space until a very thin layer (1-2 mm.) of the albumen 
lying close to the shell is coagulated. The amount of heating required 
can be ascertained by experience. After this, by means of sterile forceps, 
a hole about 2 cm. in diameter is made at the flamed end and the white 
poured into a tube or flask containing 25 c.c. of the desired medium. 
Next, the opening in the shell is enlarged to about 3 em. The yolk is 
cently allowed to run out of the shell onto a circle of sterile filter paper 
(kept in a small pile under the bell jar). The paper is then so inclined 
that the yolk rolls about until the white is entirely removed by the paper, 
after which the yolk is rolled off the edge of the paper into a tube or 
flask containing at least 25 c.c. of culture medium, an amount some- 
what greater than the volume of the average yolk. Great care must, 
of course, be taken not to rupture the yolk membrane before the yolk 
is poured into the tube. The yolk may then be broken by means of a 
sterile glass rod and mixed with the broth. 
The preparation is now ready for incubation which may be carried 
on for forty-eight hours at 37° C., followed by forty-eight hours at 20° C. 
The white may be mixed with the broth and grown in the same manner. 
At the end of the period of incubation the tubes should be again mixed 
by rotation to insure distribution of the bacteria, and a small amount 
on a straight needle transferred from each to ordinary tubes contain- 
ing broth. The broth tubes are incubated at 37° and at 20° C., as were 
the original tubes and examined for growth at the end of four days. In: 
case growth appears plate cultures are made.* 
*Tn addition to the points of technique mentioned above, minor details can per- 
haps best be worked out by the individual investigator. For instance, cotton plugs 
in the large tubes are unwieldy. They may be replaced by close-fitting glass covers, 
coming well down over the tops of the egg tubes. The breaking of the yolk and the 
mixing with the broth may be accomplished by means of broken glass placed in 
the tubes with the broth, rather than by means of glass rods, a procedure which 
may favor contamination from the air. Wire cages or racks of various sizes and 
