1392 The Cornell Reading-Courses 



ventilation throughout incubation, or at first to check ventilation and then 

 to increase it as this becomes necessary. With either method it is essential 

 that moisture be present to prevent undue evaporation. When the 

 ventilation is checked it is not considered so necessary to supply moisture, 

 because evaporation takes place much more slowly when the change of air 

 in the egg chamber is lessened than when it is increased. The amount of 

 evaporation of the egg contents may be controlled very successfully by 

 maintaining a proper degree of humidity in air that is taken into the 

 machine. The humidity under a sitting hen usually registers about 60°. 

 If a non-moisture machine is operated in a room in which the air is dry 

 owing to climatic conditions, or in which several incubators are being 

 operated, it may be necessary to supply moisture. 



Supplying moisture. — Unless the manufacturers so direct, moisture 

 should never be supplied in an incubator.* If non-moisture machines 

 are operated in a dry place, the floor of the room may be kept wet unless 

 it is of wood, in which event pans containing water may be placed under 

 the machines. The amount of moisture exhaled from a surface in a given 

 space of time is governed by the extent of the surface and not by the 

 depth of the receptacle. This principle should be remembered when 

 supplying moistiire in a room or in an incubator. With machines in 

 which arrangements have been made for supplying moisture, certain days 

 should be set for looking after the supply in order to avoid a possible 

 chance of the moisture receptacle becoming dry. Moisture on the glass 

 at pipping time usually indicates a good hatch, being due to the large 

 amount evaporated from the chicks. 



Controlling ventilation. — In some cases ventilation is controlled by slides 

 over the ventilator openings, which are usually in the bottom of the incu- 

 bator. With such machines it is a good practice to restrict ventilation the 

 first week by keeping the slides closed, opening them gradually from the 

 seventh day until they are wide open. The temperature of the room 

 must be considered in regulating the ventilators, and the warmer the 

 weather the wider they may be opened. Generally it is advisable to close 

 the slides the nineteenth day. They may be opened again as soon as the 

 hatch is completed, to admit plenty of fresh air. Some machines have 

 additional ventilators to be opened only after the chicks are through hatch- 

 ing; these must not be mistaken for the ventilators to be used during 

 incubation. Constant ventilation is provided in some types of incubators 

 that are not fitted with slides. Such machines should never be tampered 

 with. The necessity of following the manufacturers' directions in regard 

 to ventilation cannot be too strongly impressed on the mind of the novice. 



* The same amount of moisture placed above the eggs that is often placed underneath them would 

 cause complete saturation and damage the hatch in most machines; hence, the manufacturers' directiona 

 should always be followed. 



