Eggs of the Domestic Fowl (Gallus domesticus) have
been incubated by artificial means for many centuries,
this technique being of course ante -dated by the natural
method of the bird. Credit for the early introduction
of artificial incubation is generally given to the Chinese
and Ancient Egyptians who used, and still use, large
earthenware ovens, heated by burning d7y manure or rice
husks, to hatch chicks from fertile eggs. Landauer (1951)
has described in some detail the various methods of
incubation adopted in early times and has provided a very
interesting history of the development of artificial
incubation to modern times.
The phenomenon of a hatching egg has drawn the
attention of malty people through the ages for all have
wondered at the ability of this biologically distinct
entity to nurture within it an embryo which after the
process of incubation finally emerges from the egg as a
chick. Their interest has been accentuated by the fact
that some eggs hatch, others do not; most produce normal
chicks, some abnormal chicks. There is no knowing until
the eggs have ben incubated. The aura of mystery remains
but at least some of the conditions which determine the
fate of incubating eggs have been wholly or partly
elucidated and it is to this sphere of knowledge that the
present work endeavours to add. The results of previous
investigations concerning the whole aspect of hatchability
have been concisely reviewed by Landauer (1951) and Taylor
(1949) while previous work of special immediate interest
is reviewed in close associate with and under the headings
of the separate parts of this Thesis.
Surprisingly little is known of the conditions
prevailing in the Hen's nest and the obvious lack of interes
may be accounted for by the very great efficiency of
artificial incubators and the necessity for mass production
methods superimposing their influence and importance.
These issues dominate the present -day' scene and so it was
decided, having in mind the foregoing discussion, to
concentrate on the study of humidity and rate of turning
as applied in artificial incubation.
Arising out of this work a study of the significance
of embryonic orientation just before hatching on hatchability and the hatchability of some previously accepted
lethal Malpositions was carried out using a technique which
as far as can be determined had not been used previously.
The technique involved the X- raying of eggs prior to
hatching thus enabling the position of the embryo within
the egg to be observed without its sacrifice.