Incubation 1851 



temperature, moisture, and ventilation 

 Temperature 



After the eggs have been placed in the incubator, the temperature 

 will drop and will remain low for several hours; it will then gradually 

 rise, taking perhaps twelve to fourteen hours to reach the desired degree. 

 The operator should not attempt to increase the heat too rapidly, but 

 should allow it to increase gradually. When the correct degree of 

 temperature is reached, there should be only slight variations of tem- 

 perature during the period of incubation. Although it is best to maintain 

 an even temperature, it is not always possible to do so, and an occasional 

 variation of one half degree, or slightly more, will not result seriously 

 if the average temperature is correct. A high temperature should be 

 avoided, especially at the beginning of incubation. The temperature 

 should be read through the glass door of the incubator, and this door 

 should be opened as few times as possible. 



Temperature during the first week of incubation. — The position of the 

 thermometer should always be considered in determining the proper 

 degree of temperature to be maintained. If the thermometer hangs 

 above the trays of eggs, as it does in some incubators, thereby registering 

 the temperature of the air and not that of the eggs, the actual temperature 

 of the eggs is i to i| degree lower during the first week than the registered 

 temperature of the egg chamber. Therefore, in order to give the eggs 

 the proper amount of heat during the first week, if hanging thermometers 

 are used, it is necessary to keep the temperature at 102.5° or 103° F.; 

 if contact thermometers are used, the temperature should be 102° F. 

 Contact thermometers should always be placed between two fertile eggs. 



Temperature during the second week of incubation. — The temperature 

 within the incubator is less influenced b}^ that outside after the first week, 

 owing to the increasing amount of animal heat given off by the growing 

 embryos. If hanging thermometers are used, the mercury should be 

 held at 103° F.; if contact thermometers are used, the heat should be 

 increased to 103° F. 



Temperature during the third week of incubation. — -The temperature 

 should be maintained as near 103° F. as possible until about the eighteenth 

 day, when it may be allowed to rise to 104° F.^ 



Moisture and ventilation 



Oxygen is essential for the normal development of the embryo chick, 

 the amount required increasing with the growth of the embryo. Eggs 

 that are being incubated give off carbon dioxide, which is formed in the 



5 Directions for controlling the temperature after the eighteenth day are given under the heading "The 

 hatching period." 



