Carbon Dioxide Under Sitting Hens. 
By H. D. EpMoND. 
The following experiments were carried on to determine 
the carbon dioxide content of air in incubators and under sit- 
ting hens. Certain manufacturers of incubators have made 
extravagant claims for their machines because they contain a 
large amount of carbon dioxide during the incubation period 
and that they approximated the conditions in this respect as 
found under the hen. Whether carbon dioxide is essential to 
a perfect hatch and vitality in a chick is still an open question. 
This work is not complete enough to settle the question and 
there is very little data to be found on this subject. It is true, 
as shown by the following tables, that there is a much larger 
percentage of carbon dioxide under a sitting hen than in an 
‘ncubator and it is also true that a hen hatches chickens with 
greater vitality than an incubator. Judging from the amount 
of carbon dioxide found under a hen it seems probable that it 
has no ill effect on the growth of the embryo chicken. It may 
have a retarding effect for it is known that eggs hatch about 
24 hours sooner in an incubator than under a hen. This extra 
time may allow the yolks to become properly absorbed, thus 
producing a chicken of stronger vitality. 
