INCUBATOR (Lat. incubator, one who lies in a place, from ineubare, to lie within, to incu bate, from in, in ± Marc, to lie). A tern, ap plied in poultry-raising to devices used for artificial incubation or the hatching of eggs. Arti ficial incubation was successfully practiced in very ancient times in Egypt and China, and prob ably other countries. The methods and ap pliances still used in China are quite simple, and even crude, but are employed with great skill and success. Iii".aumur, the eminent French physi cist, used successfully a very crude form of in cubator, consisting of a barrel heated with fer menting, manure: but he encountered much criti cism and opposition on the ground that chickens so hatched "were unfit for human food because they tasted of the heating material, and that such chickens were absolutely sterile, and if the proc ess were fx.rsisted in the race of fowls would necessarily die out." Similar prejudice against incubator chicks has persisted until within com paratively recent years; but artificial incubation has become so firmly established, and, the experb mental stages having long been passed, the meth. ods and appliances have been made so simple and practical, that it is considered absolutely twee. sary in the rearing of fowls in large numbers. There were, of course, many failures in the early attempts to devise a practical incubator, al though in the first application for a patent on such a device in this country, in 1847, some of the principles on which incubators should be constructed were stated with remarkable clear ness and accuracy. Practical success with modern incubators may be said to date from the Paris Exposition of 1877, at which Rouillier and Arnoult exhibited their 'hydro incubator.' "This incubator," says Beale, "has a very large tank, holding about fourteen gallons of water, which is divided into three hori zontal compartments, each communicating with the others by means of a few small holes. This tank is placed in a wooden ease, and surrounded on all sides save the bottom (under which is the egg-drawer) by an inch or more of felt, or some other non-conducting material, tightly pressed down. When this tank is filled with hot water, it is found that the water loses only from two to five degrees every twenty-four hours, according to the temperature of the place where it is kept. If the water in the top compartment only be drawn off, and that in the lower ones be left un disturbed. the former being again filled with boil ing water, the heat from this will gradually af fect the [temperature of the] lower body, and pre vent, its going down. By repeating this every twelve hours, the heat in the egg-drawer can be maintained at almost any degree of temperature, with a scarcely perceptible variation." Notwith standing the simplicity and efficiency of incuba tors of this type, attempts to devise a practical automatic, self-regulating incubator were per sisted in until incubators of this kind have been brought to a high state of perfection, and havo been generally adopted. Incubators of the auto matie type are of two main classes—hot-water and hot-air. The advantages and disadvantages of the better makes of the two classes are very evenly balanced. There are hundreds of different makes of incubators on the market, many of them very efficient when properly handled. An average hatch of over 80 per cent. of fertile eggs is secured by experienced poultrymen, but experi ence, skill, and careful attention to details are essential to such success.
The essentials of a good incubator are an egg chamber uniformly heated, preferably from above; a self-regulating source of heat, controlled by a thenno-regulator, the actuating arm of which is situated in the egg-chamber, and which is sensitive to 1°, or preferably above or below the desired temperature; and provisions for the ventilation of the egg-chamber, and for maintaining the proper degree of humidity there in. In addition to these, says Watson, "a con 1•Lnient appliance for turning the eggs, positive in action, should accompany each incubator. This
may be an extra tray that is to be placed bottom side up over the tray of eggs and held firmly in this position while both trays are turned, thus completely transferring the eggs from one tray to another without, jar. The different machines have very different appliances • for accomplishing this result." The object sought in artificial in cubation is to imitate as closely as possible the conditions of heat, air, moisture. etc., which ob tain in natural incubation under the hen. The temperature is carefully maintained at about 100° F. or only a few degrees above by placing the incubator in a basement, cellar, or other mom where the temperature is stable, and by using a sensitive thermo-regulator to control the heat applied; the moisture of the air in the egg chamber is carefully controlled, so that evapora tion from the eggs proceeds as under normal conditions: and a sufficient amount of fresh air is supplied to the chamber to carry off the harm ful gases which may accumulate and kill the in cubating chick. The frequent turning of the eggs during the earlier stages of incubation is believed to have an analogy in the practice of the hen. However, it is not considered advisable to disturb the eggs after the eighteenth day, or to open the incubator thereafter until the hatch is complete, and the chicks dry. As the success of incubation depends so largely upon maintaining the proper moisture conditions in the air of the egg-cham ber, some reliable means of controlling these conditions is essential. It has been proposed to use the normal loss of weight of eggs during incu bation under brooding hens as a guide for this purpose. The West Virginia Agricultural' Ex periment StatiOn found that the eggs which hatched under hens lost on an average 16.5 per cent. of their weight in nineteen days. The in fertile eggs and those which did not hatch lost from 1 to 2 per cent. less. The normal loss of weight of 100 eggs under natural incubation was fcund to be about 10 ounces in 6 days, 20 cunees in 12 days, and 31 ounces in 18 days. By weighing the eggs in the tray at the beginning of incubation, and at intervals during the process, the progress of evaporation (loss of weight) may be determined, and the ventilation and humidity so controlled as to make the loss of weight conform to the normal figures. Except in very dry climates there is said to he more danger of over-saturation than under-saturation of the air. A humidity of 45 per cent. saturation is considered safe. as a rule.
If artificial incubation is practiced, some pro vision must be made for the care of the chicks when they leave the incubator. Variously arti ficially heated devices known as brooders are used for this purpose. These may be very simple and cheap, or elaborate and expensive. Almost all manufacturers of inenbators also make brood ers, and there is consequently a great variety of forms to choose from. The requisites of a good brooder are that it should be: (I) Warm (90° 100° during the first week, with gradually lower ing temperature thereafter), and economical of heat,which is preferably applied mainly from the sides or above; (2) clean. dry, and well-venti lated; (3) simple in construction, and so ar ranged that the chicks may be seen. The brooder should be so constructed that the chicks may go out for exercise, and return at will.
BIBLIOGRAPHY. The literature of the subject Bibliography. The literature of the subject is voluminous. All up-to-date treatises on poul try-raising explain the processes of artificial incubation, and describe methods and appliances. Among the books which may be consulted are: Watson, Farm Poultry (New York, 1901) ; Beale, Profitable Poultry Keeping (New York, 1895) ; Stoddard, The New Egg Farm (New York, 1906) : Cyphers, Incubation and Its Natural Laws (Bos ton, 1894) ; Incubators and Chicken-Raising Ap pliances (London. 1899) ; Fiske. Poultry Appli ances and Handicraft (New York, 1902). See FOWL.