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Chapter IX
IncubationTo the casual observer, an egg consists roughly of three parts, but to the scientific investigator these are capable of several subdivisions. The shell, composed of lime, forms a protection; but it is not an impenetrable cover. It is very porous. It has between the particles of lime an innumerable number of very small holes, which allow the air to pass freely backward and forward during the process of incubation. Next is the white, the albumen. This is not all of one character; one portion is much denser than the other. The watery portion is placed around the outer surface next to the shell.
In the interior is the yolk, which in itself is, as a whole, lighter in density than the white, therefore its tendency is to come to rest upon the surface of the white. But the yolk is also differently constituted, one portion being a little heavier than another, with the consequence that the heavier portion moves downward and the lighter up. There is a good deal of misunderstanding about the very dense jellylike portions of white. Popular conception says the young chick is developed from them, but this is wrong. They simply consist of denser and more gelatinous albumen, and have acquired that twisted, corkscrew appearance and shape by the revolutions of the yolk in traveling down the ovary of the hen. But this twisting assists in keeping the light side up. It also prevents the yolk from being ruptured by sudden jar.Interior Structure of an Egg
Open a new-laid egg without breaking the yolk. Resting on its side, carefully remove part of the shell, and you will find a little white speck about one-eighth inch in diameter on the yolk next to the shell. This is the true germinal spot, known as the blastoderm, the minute nucleus of what is afterward to be the chick. The term blastoderm in itself is a very suggestive one; it means the sprouting skin. The blastoderm is present whether the egg is fertile or not, so that for all practical purposes, it is quite impossible to tell beforehand whether an egg will produce a chick. An infertile and a fertile egg to the naked eye present the same appearance. The difference is so minute that unless one uses a microscope it would be quite hopeless to place any faith upon conclusions.
Not only is it impossible to foretell fertility, but it is impossible to foretell the sex of the chick which any given egg will produce. During the first few days an egg is developing, the reproductive organs in the chick it contains are in duplicate, and until the process of incubation is pretty well advanced, both sets of organs are present. Then one set grows more prominent than the other. The rapidity with which the change is made will amaze any thoughtful person. The application of a few hours' warmth of the required temperature brings into activity all the power lying dormant from the time the egg was laid. After five or six hours, little finger-like processes begin to creep out from the blastoderm and gradually distribute themselves over the whole of the yolk.
Egg-turning cabinet. Series of rollers over which canvas is stretched. Each compartment tray removable with false bottom, a, which slips between canvas and tray frame. A, shows cabinet complete; B, detail construction.
At the end of 18 hours' incubation the head of the future chick, with the eyes enormously developed, and the spinal column, are plainly discernible under the microscope. After 40 hours there is a complete blood circulation, the heart is formed and beating has commenced, and the blood vessels have spread themselves over a considerable portion of the upper yolk. These are of a dual character; some are arteries, taking blood away from the embryo, some are veins bringing the blood back again. The heart commences pulsating about the second or third day. When the blood circulation commences, the necessity for another organ which has been developing next to the shell arises. There is another growth of vessels which follows the same course as the blood vessels. The natural reviver of impure blood is the oxygen in the air. There are no lungs in the shell, but this new organ, called the allantois, which lies next the shell, undertakes the work of breathing. Hence the necessity for the pores in the shell. If the shell were made non-porous the allantois would be useless. This has been proved with eggs which have had their pores filled with wax. When warmth is applied in the ordinary way, the first indication of growth appears, but the germ dies simply from want of fresh air.Why Exercise Care in Handling
Some people test their eggs, particularly white-shelled ones, on the fourth day, though a much better course is to test them on the seventh or eighth day. Perhaps a caution is needed against testing eggs too frequently. It is very hard for a beginner to refrain from handling his eggs, but knowing the delicacy of the blood vessels, which form a perfect maze of tracery over the yolks, and knowing that these and a further set busy absorbing the yolk are very highly sensitive, he will perceive that the less he interferes with the eggs the less likely he is to damage this fragile and delicate interior.
Another reason for not testing frequently is that in so doing the eggs are held up to the light in an unnatural position and some of these organs inside the egg are being twisted. Again, there is the light. To test eggs properly a very clear light is needed to pass through the egg. Therefore eggs should be tested only once, and that about the seventh or eighth day. If very doubtful about them, perhaps a second test might be given on the fourteenth day, not later, because between the tenth and eighteenth days is the most critical period in the life of the embryo.
In selecting eggs for hatching use only those that are of uniform size and color, with smooth, strong shells. Abnormal eggs are likely to produce weak or crippled chicks. The eggs should be stored in a room where the temperature ranges from 50 to 60 degrees. It has been a prevailing idea that eggs for hatching should be turned daily. Several men of authority claim that this is not necessary, but the case is not definitely proved. Eggs kept for a week or more should be turned at least twice a week. It can do no harm and may prove beneficial. Never set dirty eggs; if they are dirty, carefully wipe them with a damp cloth until all spots are removed.Shipping Eggs for Hatching
The three most important points to be considered in packing and shipping eggs for hatching are: First, the boxes and filling should be as light as possible consistent with strength and rough handling; second, the handles of boxes must be so constructed that freight cannot be piled on top and thus crush them; third, the eggs must be prevented from jarring, and yet must not be packed so tightly as to cause breakage from pressure.
Light wooden boxes have proved most satisfactory with many poultrymen. They should be of enough depth to insure an inch of excelsior below the lowest layer. When used they are packed about as follows: A layer of corrugated pasteboard cylinders rests on a piece of pasteboard next to the excelsior. Each of these cylinders contains an egg, small end down. The corrugations of the paste-board come on the inside of the cylinder, and thus take up any jar. Over this is placed a second paste-board, then a layer of excelsior, and at the top a board lid, which is screwed down with little screws. If more than one layer of eggs is to go in a box, a pasteboard is placed between the two layers of the cylinders.
The handle of the box must remain upright. A split-wood, rounded handle clearing the top of the box about 2 inches and fastened securely on both sides so it cannot move backward or forward, is excellent. It is best to have the handle fastened to the sides of the box and not to the lid, because there might be a strain on the latter, and the screws might give way, especially if 100 eggs are being shipped at a time. Some men stamp each egg with their initials and seal the lid to the box with a printed label pasted on. Then the customer can tell if the eggs have been changed in transit. The label gives the name and address of the poultryman and the name of the breeds of poultry raised printed on it. The name and address of the consignee are written on the blank. Last, but most important, a stamp or a label should always be applied on the lid, saying, "Eggs for Hatching, Handle With Care."
Many people object to the box for shipping eggs. The principal objection is that expressmen are more likely to throw boxes than they are the baskets. For this reason ordinary splint baskets with handles are very popular. In packing them a layer of excelsior is placed on the bottom and around the sides. In this the eggs are carefully wrapped in excelsior or paper and the basket filled with excelsior and gently pressed down to prevent any possible shifting of the eggs from their positions. Cheesecloth or cotton is now tacked over the top and the words "eggs for hatching" painted or stenciled on the cloth itself. The label is fixed to the handle. Baskets, it is claimed, can be shipped with more certainty of their safe arrival than boxes. Upon receipt of a package or a basket of eggs for hatching, the eggs should not be removed unless the hen or the incubator is ready to receive them. Until hatching can be started the basket or the package should be turned over daily.Classes of Incubators
There are two very distinct types of incubators on the market; the hot-water tank and the hot-air machine. Perhaps the latter is really far more ancient than the former, but until a few years back there were no hot-air machines that could approach the hot-water tank. After giving both systems a very long and exhaustive trial, generally speaking results have proved satisfactory from both. There are certainly indifferent and bad examples in each kind to be obtained, and experiences vary accordingly. A great deal, then, depends upon the incubator purchased. It may be taken as a general rule that any machine which has a reputation of some years' standing has been found to answer very well in the hands of reasonable people.
The best incubator, of course, is the one which approaches in its work the closest to Nature. In studying natural incubation there is, in the first place, top heat. Heat rising from below would never do, as it would evaporate the moisture from the eggs too quickly. The next point is steady warmth; when a hen is brooding, her temperature is invariable. The temperature of a brooding hen is about 104 degrees, and that does not vary a great deal during the time she is sitting. Therefore, in order to have a successful incubator, a machine capable of developing a top heat of 104 degrees to the eggs and keeping it steady there, is needed. Of course, the eggs under the hen will vary in temperature according to the position they take; that is to say, those under the breast will be rather warmer than those on the outside. But they are changed in position now and again. Each machine must possess a sufficiency of ventilation; fresh air is a perpetual necessity.Moisture Essential
Another very greatly discussed question is that of moisture. Hot-air incubators are usually non-moisture machines, whereas the tank machines require added moisture. Perhaps there has been no bigger bone of contention between the manufacturers than this question of moisture or non-moisture. Within reasonable limits, both systems are satisfactory. A great many people overdo the moisture. Some manufacturers even advise that if chicks do not come out freely to dip the eggs in water. That is a ridiculous practice. Eggs do not require a lot of added moisture. The amount that should be passed through the machine should be just about sufficient to keep a check upon the amount of evaporation. An egg contains about 85 per cent water, the body of a chick about 80 per cent, therefore a slight drying out is wanted and not an atmosphere always saturated.
Methods of Management
Every reputable maker sends out instructions with his machine, and the purchaser should follow these implicitly. If he does not, he is running a risk for his own pocket, and he is not doing justice to the maker of the machine. He must also bear in mind that the instructions sent out with any machine are the result of experience with that particular make, and as the manufacturer's interest lies in obtaining satisfactory hatching, so the directions are to that end, and should be valued.
The incubator should be placed in a sunless room or cellar, or any place where the temperature is equable day and night, or fairly so. It is not an indication of good working in a machine if one running gets perhaps 80 per cent and on the next occasion only 50 per cent. There is something wrong somewhere. It has been rather the rage with advertisers to make a great fuss about 100 per cent results. Novices thinking about taking up the incubator must not be misled; 100 per cent results are exceedingly rare. If one gets 80 per cent on a six months' working, he may conclude that he made a very profitable deal in his machine.
One may have as good a machine as it is possible to get, but unless the eggs are right he cannot hatch them. Eggs must not only be fresh, but they must contain all the elements and the germs that go toward making good, strong chicks. Unless they are carefully selected from stock birds kept in such a manner as to insure a certain amount of animal vitality, they cannot turn out strong, lusty chicks.Record Card for Incubator
Click here for bigger image
Record card for incubator. This form shows a very convenient method of taking notes of hatches. Data secured in this way are often invaluable because they may lead to the detection of faulty management at weak points in the hatching methods practiced.
Always get eggs from the best sources. Enough directions are not given about changing the position of the eggs in the drawer. Manufacturers say that the heat is the same all over the drawer, but not one machine in 1,000 will give the same heat in every part. Therefore, it is advisable to shift the eggs from place to place in the drawer.Incubator Management
One of the most important factors in successful incubation is an abundant supply of oxygen, which the developing embryos must obtain only from sweet, fresh air. To get an abundance of fresh air where the incubator cellar is partly below ground is much more difficult than when the hatching room is level with the earth.
During the past few years there has been a considerable amount of controversy with regard to the operation of incubators with or without moisture. Poultrymen are generally agreed that moisture in some form is necessary. Two experiment stations have published bulletins showing that the machines which had moisture supplied gave larger hatches, and stronger chicks than the machines operated without being supplied with more moisture than is contained in the atmosphere. The publication of this work has led some large incubator manufacturers to equip their machines with automatic moisture regulators, and there is no doubt that this is a great improvement on the non-moisture machines. The conditions under which a machine is operated has everything to do with the success of the hatch. By his expert operation the experienced man may secure a good hatch from an inferior incubator; on the other hand, an inexperienced man may, through lack of knowledge make a complete failure with even one of the best machines.
If the machine has just been purchased, it should be removed from the crate and assembled, care being exercised to follow the manufacturers' directions for putting the various parts together. In choosing a room, select one that will allow for ample ventilation without a direct draft on the machine. Do not place the machine in front of a window, as the direct rays of the sun will make it difficult to control the temperature. A cellar that can be ventilated and that is not too damp makes an excellent place for the machine.
Colony houses combined. In winter colony houses brought end to end thus may serve for general coop. Building paper tacked over ends.
For best results see that the machine is perfectly level; otherwise it will not distribute the heat evenly to all parts of the egg chamber. The lamp should be cleaned and filled with a good grade of kerosene, which will insure a steady flame and no smoke. The lamp should be lighted and placed in position, as it will require several hours to dry and warm the woodwork thoroughly. When the mercury in the thermometer registers 100 degrees, it will be necessary to read the thermometer every 15 or 20 minutes in order to adjust the thumbscrew on the regulator. When the thermometer registers 102 degrees adjust the thumbscrew so the tin disk on the regulator arm will be just trembling on the rise. The machine should be run for at least 24 hours before putting the eggs in. This will give an opportunity to study the regulator and see that the temperature remains steady.
The eggs are now placed in the machine and one must not be alarmed if the mercury in the thermometer recedes from sight. This is easily accounted for by the fact that the eggs are cold, and it will require several hours before the thermometer will again register 102 degrees. The eggs should not be disturbed until the third day. The only work required is cleaning and filling the lamp each evening. On the evening of the third day the eggs should be turned and cooled for five minutes. Be sure there is no grease on the hands when turning the eggs. After the third day turn and cool the eggs morning and evening, gradually increasing the amount of cooling as the hatch progresses.Testing the Eggs
The eggs should be tested on the seventh and fifteenth days. This may be done during the day if a dark room is available; if not, at night. The testing of the eggs is very easy and after a little practice one should experience no difficulty in distinguishing the good from the bad. When held to the light, a fertile egg can be distinguished by a small, dark center (the heart) from which blood vessels radiate in every direction. The infertile or sterile eggs will be perfectly clear when held up to the light. Eggs that contain dead germs can be distinguished by a small, dark center, though sometimes this is lacking, surrounded by an irregular circle and the absence of blood vessels.
When the eggs are tested on the fifteenth day those that contain live chicks will appear, when held to the light, to be filled with a dark mass, which in reality is the developing embryo. The infertile eggs should be saved and used in feeding the young chicks for the first few days; they may also be used for baking purposes, as a slight evaporation is the only change that has resulted from incubation. The eggs should not be turned or cooled after the eighteenth day. Close the machine and do not disturb it, except to fill and trim the lamp, until the hatch is complete. While the eggs are hatching, the temperature of the machine may go as high as 105 or even 107 degrees; this is caused by the animal heat given off by the chicks and no attempt should be made to lower the temperature if the machine has been running properly just previous to hatching.
Before resetting, the machine should be cleaned and disinfected thoroughly, a new wick put in the lamp, and operated for a day or more in order to adjust the regulator properly.Care of the Incubator
Many incubators are short-lived. The owners complain of unsatisfactory results after the first season or two, but the trouble is more often due to improper care of the machine during the idle season than to defectiveness. More of the life of an incubator depends upon care when not in use than upon any other one thing. The main thing to guard against is dampness, but exposure to weather conditions of any kind is always harmful. The aim, therefore, should be not merely to keep the machine dry, but where it will be as little influenced by outside conditions as possible.
A cellar, no matter how dry, is not a desirable place to store an incubator between seasons. An attic, a loft, or an upstairs airy room not in use are far better. Prior to being stored, the tank if a hot-water machine is used, should be drained while the water is still hot. Both the cap and the faucet should then be left open and the lamp burning with a very low flame until the tank has become thoroughly dry, because of the circulation of air through the faucet and cap. The flame, if allowed to burn for an hour or two, should dry the machine well. The egg chamber should previously be thoroughly cleansed, scrubbed if necessary. No wood parts should be wetted, because where the wood is unprotected with varnish it will swell and shrink more or less. If the inside must be scrubbed, this should be done while the machine is still warm and the doors left open until everything is dry.
Side hill coop. Legs in front make roosts come level when coop is set on hillside.
All removable parts should be taken off the outside and stored in the egg chamber. The lamp should be emptied, the wick removed, and everything thoroughly washed. The burner should be cleaned and stored separately from the lamp, the chimney wrapped in cotton to insure against breakage, the thermometer packed in a little box of cotton, the egg tester, wrench, screw driver and other accessories also stored in the egg chamber. With everything possible removed from the outside, the machine may be stored in small space without danger of parts being broken; in fact, several machines may stand one upon another. As a further protection, they should be covered with cloths and kept so until needed the following spring.
Several weeks prior to starting the new hatch, the parts should be assembled, the machine set up and run to see that everything is in good order, so that any necessary new parts can be secured before the hatching season actually arrives. By such care, however, there should be no losses of parts, and the only thing that one should need would be wicks, an occasional new burner, and extra lamp chimneys to take the place of those that break through any accident.
Next: Chapter X
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