INCUBATOR, a machine employed for the artificial hatching of chickens from eggs. Such devices were known to mankind from early ages. Pliny says that the Egyptians thus hatched 100,000,000 chickens a year. While artificial incubation was introduced into France and England during the 18th century, the in cubator was brought to greatest perfection in the United States in the 19th century. The first patented invention of the modern incubator was in 1847, but any practical success in such ma chines cannot be met with before 1877, when Rouillier and Arnoult exhibited their hydro-in cubators at the Paris Exhibition.
There are two general classes of incubators, those in which hot air is used for the mainte nance of heat aritt--the application of it to the eggs, the other in which hot water serves this purpose. An automatic incubator of first-class make it equally efficient whichever of these two heating mediums is employed, but there are many different types of machine offered for sale, and the struggle between cheapness and efficiency sometimes leads to the sacrifice of the latter. There are certain essentials to an in cubator which must be attained at any cost, and the machine that is deficient in any one of these is a failure, which means that it cannot guar antee to yield of living chicks at least 80 per cent. The following may be enumerated as absolute requisites in a good incubator : (1) An egg chamber heated at a uniform temperature. It is best that the heat should come from above, when it is likely to be reverberated from the floor of the chamber and to more evenly affect the eggs, and may at once strike the germinal vesicle which from its lightness always rises to the upper surface of the yolk. (2) A source of heat which is self-regulative. The therm°, regulator in general use is actuated by an arm thrust within the egg chamber, and must be sensitive to an atmosphere of 54° or at most 1° above that which is desired. (3) Good ventilation within the egg chamber, with some provision by which a certain degree of moisture may be maintained in the air. (4) Added to this, is a good turning apparatus. There are very many devices for effecting this purpose; perhaps the best is that of a tray fitting exactly over the tray in which the eggs are laid, and by the turning of which the eggs may be replaced in a reversed position in the applied tray.
Of course the aim of a true incubator is to reproduce as accurately as possible by arti ficial means the conditions of natural hatching under a setting hen. Thus the supply of heat
and air must be conformable to a fixed standard. The temperature is to be kept unchanged at 100° F., or a little above that, by placing the incubator in a room not exposed to draughts. To make accident in this respect impossible, a cellar, or specially built chamber, should be used, where no access of colder air may cause a fall in temperature, and a sensitive thermo-regu lator furnish automatic means of preventing ex cessive heat from destroying the vitality of the eggs. Moisture must be preserved in the air of the egg chamber that the eggs may not be shriveled by excessive evaporation. There must also be adequate ventilation, that no harmful gases sicken or kill the hatching chick. The turning of the eggs is considered necessary, be cause the sitting fowl has the habit of so doing, but the eggs should not be disturbed after the 18th day, nor the incubator be opened after that date, until the hatch is completed. With regard to the moisture of the air, it has been considered proper after studying the progress of evapora tion, as reckoned from the loss of weight in a fertile egg during the process of hatching, that a humidity of 45 per cent is the safest degree of saturation.
Various ways have been resorted to of tak ing care of the chickens after they leave the in cubator. They must at first be kept in an atmosphere of from 90° to 100°, at least for the first week, and heated places of shelter, known as brooders, must be prepared for them. There are many patterns and kinds of brooders, which are manufactured by the same firms as those which make incubators. The requisites for brooders are: (1) The temperature of the first week, as given above should be gradually low ered. (2) The greatest diligence should be applied to secure and maintain cleanliness, dry ness and good ventilation. (3) Their construc tion should be such that newly-hatched chickens may always be in view. As the chicks grow to ward fledging, facilities should be afforded them to leave the brooder for exercise. See also POULTRY. Consult Cooke, P., 'Successful In cubxtion) (Los Angeles 1911);