17 
Chapter III. 
NATURAL INCUBATION. 
Before proceeding to give our readers advice on the management of the sitting hen, we will explain in as 
few words as possible the composition and structure of the egg. On analysis the shell is found to be com- 
posed of carbonate of lime, perforated by minute holes, which can be seen by the aid of the microscope, 
Nature making a wise provision by this means in providing the recjuired amount of air to the embryo chicken, 
and for the purpose of evaporation. If the egg is covered with a coating of grease, or if a pin-hole is pricked 
in the top or large end of the egg, it will effectually prevent the egg hatching. Thus many hatches are 
spoilt by one egg being broken in the nest, and covering the others with the contents. 
The freshness or staleness of an egg can be tested by the size of the air chamber, which in a new-laid 
egg is very small, becoming larger and larger the staler the egg, until at last in a very stale egg it occupies 
nearly one-third of the whole inside space in the shell. This is caused by the evaporation of the moisture in 
the air chamber, and outside air taking its place. 
The white, or albumen, of the egg is that from which the future chicken is formed — not the yolk, as is 
often erroneously supposed. The yolk is also composed of albumen, coloured chiefly by iron, and is en- 
closed in a fine membrane or skin to prevent admixture with the white. The yolk supplies to the embryo 
chicken the necessary nourishment while going through the different stages of incubation, and for some time 
after hatching this is absorbed through the navel, and traces may be found in the intestines, on dissection, 
for some days after being hatched. Attached to the outside of the yolk, in appearance like a small dark 
speck, is the germ, which always floats uppermost, no matter in what position the egg is laid down. This is a 
wise provision made by Nature, allowing the germ to be kept nearest in contact with the heat of the hen's 
body, and which is studied by all makers of modern incubators in providing heat downwards to the egg. 
The length of time occupied by the chickens in obtaining admission to the outside world varies to a great 
extent, depending chiefly on the vigor of the chicken, or thickness of the shell. The beak is provided with a 
small horny covering at the top, to assist the chicken to break the shell, which it does with a star like fracture, 
at first gradually, working right round in a nearly straight line, cutting off the top of the shell in the form of a 
lid, then with a few vigorous stretches is free. It is not wise to assist them out of the shell, Nature sees to 
this much better than man can do, and if a chicken is not strong enough to get out of its own accord it will 
rarely do any good in after life, and the whole of the yolk should be absorbed into the abdomen, otherwise 
they rarely live. Chickens are frequently found dead in the shell ; the causes of this are many and various. 
It may be that the eggs have been badly fouled at some time during the process of incubation ; that the 
chickens may be wanting in constitution or stamina ; that the eggs become cold at a critical time ; or from 
want of moisture, or bad ventilation if hatched in incubators. There are many causes likely to arise during the 
different stages of their development which pjove fatal, and often cannot be avoided. The chickens when 
first hatched present a miserable appearance, but after a few hours' warming look most attractive. 
In selecting eggs for incubation, if a hen is used for hatching, eggs can be kept for a fortnight or three 
weeks, and even a longer period, if they are placed large end downwards in a box covered with stout cardboard 
or zinc, in which holes have been cut in size to accommodate the eggs, and stored in a moderately cool place, 
which is not higher than 70 to 80 degrees Fahrenheit in summer. A higher temperature, such as 90 to 95 
degrees Fahrenheit, will invariably spoil the eggs for incubation. Severe frost will have the same effect, so 
eggs intended for hatching should be placed in some place where a fairly moderate uniform temperature can 
be obtained. 
B 
