THE INCUBATION OF THE EGO 205 



take up room in the egg tray, thus reducing the egg capacity 

 of the machine, break fully as many eggs as is done by hand- 

 turning, and save little if any labor (see Fig. 94). 



Principles of Operation. — So far as present knowledge 

 indicates, successful incubation depends primarily upon four 

 conditions. These are (1) temperature, (2) moisture, (3) 

 ventilation, and (4) position. The principles involved in 

 the operation of incubators have to do with making these 

 conditions favorable. 



Place of Operation. — ^The place of operation has much to 

 do with furnishing proper incubating conditions. It is 

 highly desirable (1) that it shall not be subject to frequent 

 or sudden changes in temperature; (2) that an abundance 

 of fresh air may be admitted, while the heavy gases near 

 the floor and the light gases near the ceiling have means of 

 escape; (3) that the relative humidity be rather high; (4) 

 that it be impossible for the sunlight to strike the incubator 

 at any time of day. 



A cellar, and particularly a cave cellar, having a grade 

 entrance and a top ventilator, will come about as near meeting 

 these conditions as any room found on the farm. Outside 

 changes do not quickly affect it, it is likely to be reasonably 

 damp, does not admit the sunlight, allows the light gases 

 to escape above and the heavy ones that have settled to the 

 floor to flush out every time the door is opened. 



Temperature. — The temperature at which eggs are incu- 

 bated naturally depends primarily upon the temperature 

 of the setting hen. As will be seen in Table XX, this 

 temperature is quite variable between different hens on the 

 same day and for the same hen on different days. This 

 table was made by Eycleshymer^ from observations made 

 by placing thermometers in nests, so that they would come 

 in contact with the body of the setting hens. The Roman 

 numerals designate the hens, while the arable numerals 

 indicate the days of incubation. 



Eycleshymer^ also made observations of eggs in relation 

 to the temperature of the setting hen. The temperature 



> Piologioal Bulletin, May, 1907, ' li)i4, 



