200 POULTRY BREEDING 
with a view to getting this out of the egg-chamber as 
rapidly as it was formed. Then Graham of Canada, Nix 
of Pennsylvania, and Dryden of Utah (now of Oregon), 
began to experiment, and they discovered that there is a 
greater percentage of carbon dioxide under a sitting hen 
than there is in any incubator, and they concluded that 
carbon dioxide was necessary to a good hatch in some 
way not yet understood. 
Later experiments leave the whole subject in much 
doubt, but have brought out some facts that seem to 
indicate the proper methods by which vigorous chicks 
may be hatched with vitality enough to live and mature 
normally. We know that we can now hatch chicks that 
are perfectly normal, and this is the point at which in- 
cubator operators have been aiming all these years. It 
seems at this time that scientists were going to get back 
to very nearly the ancient mud-oven conditions before 
they get to the place where the greatest success will be 
achieved with artificial incubation. 
Some diseases seem particularly likely to attack chicks 
hatched in an incubator, and it is now well known that 
infection may be conveyed through the shell of an egg 
or even exist in it before it is laid, thus carrying to the 
embryo chick the germs that lead to its early death. To 
prevent this, the best practice of the latest investigators 
is thoroughly to disinfect the eggs and the incubator be- 
fore hatching is begun. To accomplish this the eggs are 
wiped with a cloth dampened in alcohol and the incubator 
is washed with a solution of some antiseptic, such as creo- 
lin, every part of the inside and the egg trays washed and 
then set in the sun to dry. 
The process of incubation is interesting, although sim- 
ple in its essentials. An egg is a very complicated piece 
