STRUCTURE OF EGGS.

New Zealand Herald, Volume LXIV, Issue 19731, 2 September 1927, Page 17

STRUCTURE OF EGGS.

BY G.H.

A REMARKABLE PROCESS. A MARVEL OF PERFECTION. ONE OF NATURE'S TRIUMPHS.

How many people stop to think about the structure of the egg ? Men who hatch thousands of birds every year are known to have displayed most appalling ignorance concerning egg structure. As we hold a fertile egg in our hand how seldom do we think that inside the shell lies a dormant body—the whole body of a fowl Hidden though it be, the germ is there, and i! needs only warmth to make it active, and a regular continuation of warmth to develop a living entity. What is known as a standard egg weighs two ounces. Of this one tenth is shell, and that is composed of carbonate of lime, the same substance that is found in mortar, chalk and marble. The hens get this from green bone and lucerne the most readily, for the reason that in this form of food it is most easily assimilated. Any feed carrying this form of lime in a dry state cannot be as valuable. This shell is delicately arranged, leaving minute pores through which moisture can evaporate and air be admitted. It is because of this pecularity of structure that an egg takes on flavours when left in a damp or dirty nest, or surrounded with musty or damaged neighbours. An egg in this respect is a good deal like a man; it absorbs from its surroundings, and is benefited or injured by its associates. Perfectly-Ordered Construction.

The particles of lime are most carefully arranged in systematic order, to give strength to the whole. No one can study the external covering of an egg without being made conscious of the perfect law and order in its construction, bet the lien be in perfect health, and the microscopic regularity and perfection of the structure of the shell will impress itself. An irregular, mis-shapen egg shell is an indication of ill-liealth. In the process of incubation the shell undergoes radical ch.mge, the lime softens and the chick breaks out into larger freedom with apparent ease. A little care and watchfulness, together with experience, will enable one to detect degrees of freshness in eggs simply by the feel and look of the shell.

Inside the shell or outer case of the egg is another called the membrane, which looks like a thin layer of skin, the purpose evidently being to hold the egg while the lime is being deposited. Instead of this being a single layer, it is double, composed of delicately traced fibres, interlacing and supporting each other, and separating at the larger end to form the air chamber. The circulation through these layers is by direct channels microscopic in size, yet perfect in adjustment. The white of the egg is almost pure albumen, the element that goes to make bones nerves, muscles, tendons, beak, claws, brain and feathers—down on the chick. Nature has made the white of the substance which makes growth, and the yolk of the substances that make vital energy, supplying each as it is needed by the embryo chick. An Indication of Freshness. One may note freshness by an examination of the air chamber at the top of the egg. When the egg is newly laid this air chamber is very small, and the membrane is quite close to the top of the egg, but as the moisture dries away by evaporation through the shell, it increases into one-quarter the size of the egg. Next we come to the albumen, a white, glutinous liquid, constituting .about one half the weight of the whole. Following a wellknown law of nature this albumen is not, as many suppose, one solid mass, but is divided up and deposited in delicate layers, the finest at the centre, which may easily be noted by cutting a hard-boiled egg carefully in two. As days pass, this material changes to structure, losing something of its cohesiveness and becoming more liquid. Here we find the most nutritious part of the egg. This is the nitrogenous portion and the part which enters so largely into many of the parts. The yolk, which forms the larger portion of the egg, is composed of oil and albumen, with other ingredients, such as soda, phosphorus, magnesia, iron, lime, etc. Of course, the different percentages of these are very minute, but the whole is completely mixed, so as to bo readily digested The yolk is designed by nature as the first food for the newly-hatched chick, and is drawn into the body during the last twenty-four hours of incubation. The yolk is enclosed in a very delicate membrane, which prevents its mixture with the albumen.

Many people are of the opinion that an egg constans a chick, every part of which is complete,, needing only incubation to resolve each part into its separate shape and place in the chick. This is true in a sense that the whole of the chick comes from the egg. but it is only the fertile eggs that contain embryo chicks. Process of Incubation. A fertile egg contains a living germ that lies dormant until warmed into life by the process of incubation. This germ is but a speck of a substance known as protoplasm, which is endowed with power to grow into a perfect chick. At first it is but a mere speck, not visible to the naked eye, but put it under a broody hen, or into an incubator, and it begins to grow and feed on the white of the egg, developing an arterial system, a nervous system, bones, flesh, muscles, brain, viscera, and finally a digestive system.

Day by day the different processes go on until "the period of incubation is completed and the chick is ready to come forth. The yolk, which up to this time has remained unchanged, is taken into the stomnch through the aperture at the navel and the aperture closes in a most wonderful manner. Once in the stomach, the yoik furnishes a supply of food for the chick for about forty-eight hours. The yolk largely carbonaceous, that is, composed of the elements that go to furnish animal heat, energy and the power to live, move and breathe.