DEAD IN SHELL 291 
of pure air and moisture. When the chicks are alive in the egg 
they need an extra supply of oxygen, and if this is not forthcoming 
they either die quickly or become so enfeebled that they fail to 
hreak through the shell and ultimately succumb. Now chickens 
can put up with a great many troubles and inconveniences, and 
indeed the way they surmount difficulties borders on the miracu- 
lous, but there is one thing they cannot do without, and that is 
fresh air. The chick in shell has only the minute pores of the 
shell through which to imbibe its oxygen, and if that is not 
supplied in abundance the little flicker of life inside will gradually 
be snuffed out. 
Since writing the above I have come across some notes by 
Elizabeth Hepburne-Scott that fully confirm my suggestion that 
dead in shell may be to some extent increased by lack of oxygen. 
She says : 
““ The reason for ‘ dead in shell ’ is probably something so simple 
that we go beyond it in our endeavours to establish some great 
theory which, when gone into thoroughly, cannot possibly apply 
to every case. 
““My own idea is that we want more oxygen both in the in- 
cubators and in the room where the eggs are being aired. Pure 
air, not used-up air, where thirty or forty lamps are burning, and 
where the oxygen is absorbed as fast as it enters by the ventilators. 
««Come back to nature. The hen makes her nest out of doors, 
under hedgerows and bushes, out of the wind, but exposed to 
the fresh air. 
«How often one hears wonderful stories of deserted nests and 
cold eggs many hours before another hen can be found to cover 
the eggs—result, twelve chicks out of thirteen eggs; or thrilling 
stories of a friend who was miles from home when he had remem- 
bered he had left out the incubator drawer, and yet the result of 
his hatch was a record. Then one wonders why the careless often 
have such good luck. It may be that unconsciously the best 
thing was really taking place, and the embryo was receiving a 
greater proportion of fresh air than would have been the case had 
the printed regulations sent out with the incubator been followed. 
