|The History Of Incubation|
There is nothing new under the sun. The modern poultry industry, with its production of millions of birds from centralized massive incubators, is not a new technology. The men who built the pyramids also built incubators. Even before the time of Moses, hatcheries with a capacity of ninety thousand were in full production. A few of these hatcheries are still operative, and even as late as the 1950s, were producing almost 90% of all the chicks in Egypt.
The design and construction of these hatcheries was ingenious but simple. The eggs lay on the floor of a cylindrical, brick building. Two to three feet above the eggs was a trough-like platform encircling the inner wall, within which burned a perpetual fire of camel dung. Air was drawn in through an opening at ground level, passed through the central hole in the ring of fire, and out through a hole in the dome-shaped roof.
Double rows of these incubating ovens faced on to a central corridor. Openings in the roof and ends of this corridor admitted light and ventilation.
The temperature of the eggs was measured by placing them against the eye-lids, and controlled by stoking or raking the fires. Humidity requirements and air cell size were judged by the sound made by rolling two eggs together in one hand.
Ancient records tell us that they custom hatched, returning two chicks for every three eggs brought in. their profit was all the hatch above 70%.
The Egyptians did not, however, have a monopoly on egg hatching. Their Chinese counterparts had developed two very successful methods by at least 1,000 B.C.
The first, and simplest, used the heat of rotting manure. The eggs were placed in a mixture of chopped straw and rice hulls on top of the manure; it appears to have been moderately successful.
The second method, more widely used and still functional today, was just as ingenious as the Egyptian hatchery. The basic structure was again a cylindrical building, but the fire was on the floor, with the eggs contained in an inverted cone above it, partially filled with ashes. Placed on the ashes were egg baskets made of woven straw. The eggs were contained in muslin bags, the whole being covered in an insulating layer of rice hulls. A straw thatch roof, shaped like the traditional coolie's hat, completed the insulation, and kept out the rain.
Every seven days a fresh bag of eggs was added to each basket, and the bags were continually moved about to turn the eggs. After the first three weeks of the hatching season, the fire was allowed to go out; the self-generative heat of the eggs kept the process going.
They had also developed the art of candling, for clear eggs were removed on the third day and sold for normal consumption.
The Greeks were not to be outdone, for Aristotle described in detail a method using rotting manure in 400 B.C. Several records exist of high-born Roman ladies foretelling the sex of their offspring by hatching an egg tucked under their breasts.
Numerous descriptions of methods using the heat of the human body are recorded throughout history and from all over the world. Philippine islanders paid their servants to lie on eggs. The eggs were laid between rows of sticks on a bed of ashes, and both servant and eggs were covered with blankets. South African farmers employed native girls to hatch ostrich eggs with body heat, when the feathers of these birds were in terrific demand.
Mechanical hatching did not come to the Western world until 1749, when Reamur in Paris developed the first mechanical box to hatch eggs. He used the ether capsule as a thermostat. In 1770, Campion was successful using a special room heated by the flues of his boiler.
The first successful commercial machine was the hot water incubator made by Hearson in 1881, and in 1895 Cypher put his 20,000 duck egg model on the market. The first all-electric automated machine did not appear until 1922.