292 MY POULTRY DAY BY DAY 
“To make a practical suggestion, I would like to see an experi- 
ment carried out by those who have the money, and manager who 
could give his time to the work, of using pure oxygen from a 
cylinder every day in the incubator-room, preferably just before 
the eggs were taken out of the machines to be aired. The chicken 
at all stages would benefit, but it requires the pure air more than 
any other period on the nineteenth day, when most of the ‘ dead 
in shell’ can be traced as being alive up to that time. It is a 
critical day; the head of the bird is turning, and the air cell 
must be filled with pure air for the lungs to imbibe and so give 
strength for the final effort of hatching. 
“Temperature, moisture and ventilation all play their part 
in the life history of the embryo, but as oxygen is necessary to 
life, it is probably of first importance. It is not so much a matter 
of airing for a long time, but that the air itself is pure. 
“Tf I have not already written too much, may I tell a story of 
my personal experience which may amuse some, but, at any rate, 
prove that I have had this question of ‘dead in shell’ under my 
observation for some years, although I have never been situated 
where I could carry out my theories for very long. 
“While poultry-farming in South Africa I was much bothered 
with ‘dead in shell,’ and I suppose it got on my brain, for one 
night I dreamt I was in a market town in Cumberland and a 
woman was standing at the door of the market hall selling a small 
bradawl, and calling out: ‘No more dead in shell; pierce the 
air-cell on the nineteenth day!’ I was so much impressed by 
this dream that for two or three seasons I used to prick a hole in 
the eggs with a strong needle, and I was quite convinced that I 
had better hatching results than I had previously.” 
While I am disposed to believe that the increase of dead in 
shell may be partly owing to lack of pure air, I can only look upon 
it as a secondary or contributory cause of death, and it is probably 
not the primary reason for the increased pre-natal mortality that 
we all so much deplore. 
Another suggested cause is bad fertilising—known as weak 
germs—and while bad fertilising may account for part of the 
