6 BULLETIN 391, U. S. DEPARTMENT OF AGRICULTURE. 
The eggs composing sample No. 41645 were low-grade seconds 
and cracked eggs sorted from April storage packed eggs. Although 
the bacterial findings in these eggs are extreme, they afford a good 
example of what happens when undergrade stock, particularly 
cracked eggs, is held in storage for several months. Other investi- 
gations confirm the bacterial findings in these grades of eggs. 1 
While the actual number of eggs in these two samples is small, 
they represent grades of eggs which come with more or less frequency 
to all egg-breaking plants. It is evident that it is not possible to 
prepare from them a uaiformly high-grade product. 
The results obtained from the examination of these eggs, as pic- 
tured graphically in figure 1, show the condition in which the eggs 
under observation, which had been candled as fit for food purposes, 
would have reached 
2,OS2 7~Q7XL /Vl/A/BSR Of £GGS £X4/Y//V£~D the consumer had 
9HBH99^HRHHH9BHHHIwllJUH they boon sold in the 
&G.S- jRf/? Cf/vr, p/wcr/CALLY sr&?//.£ ~ shell. In other words 
WB^BBB^MB .._ SB they show the limita- 
\/3.S0£~/? CfAfT, CO/V7X//V/A/G &ACT£/?/A tions of candling as 
the only method for 
l^.&Pf/? C£/VZ, COMZX/M/A/G B. COL/. determining the con- 
dition of market eggs- 
Fig .1. — Results of bacteriological examination of candled breaking Tf Trnl 1 smrjear Subse- 
stock. 
quently to what ex- 
tent the grading of eggs out of the shell is of assistance in the separa- 
tion of sterile eggs from nonsterile eggs. 
EFFECT OF CONDITION OF SHELL UPON BACTERIAL CONTENT OF EGG. 
DESCRIPTION OF THE EGG SHELL. 
The contents of an egg is protected by a shell and two membranes. 
The shell, which is composed largely of lime salts, is porous and is 
coated with a mucilaginous material which gives the bloom charac- 
teristic of newly laid eggs. The two elastic membranes which line 
the shell consist of microscopic fibers very closely interlaced. The 
outer tissue is much heavier than the inner. The two separate at the 
large end of the egg and form the upper and lower walls of the air 
cell. Nature has thus provided a protective porous covering through 
which the respiration of the chick, during its embryonic develop- 
ment, may proceed. If the shell is not cracked it offers a very 
effective barrier against mold and bacterial penetration. If it is 
cracked, however, bacteria can more readily penetrate the two mem- 
branes. Egg handlers are familiar with the growth of mold in the 
crevices of a cracked shell. 2 In a large number of examinations 3 
of eggs containing molds, bacteria were found to be present in almost 
all instances, usually in large numbers. The contents of leaking eggs, 
i Unpublished results. 2 TJ. S. Dept. Agr. Bui. 51, pi. VI. 3 u. S. Dept. Agr. Bui. 51, pp. 33-^8. 
