214 POULTRY PRODUCTION 



on a normal egg, tlie proper depth of the air cell on the eight 

 clay of incubation was 5# of an inch. On the fonrteenth day 

 it was about 15 of an inch, and on the nineteenth day it was 

 f^- of an inch. This means approximately a little less than 

 a third of the contents of the egg is taken i\\) by the air cell 

 on the eighth day, a little over one-third on the fom-teenth 

 and about two-fiftlis on the nineteenth day. 



Best Means of Supplying Moisi.ure. — Dryden' found that 

 a tray of moist sand placed in the bottom of the nursery 

 was more efficient in limiting the evaporation of eggs during 

 incubation than was a tray of the same size and location 

 filled with water. 



The average loss of weight by evaporation was 1G.13 per 

 cent when no sand was used and but 12.2S per cent when 

 it was used. This seems to indicate that the sand furnishes 

 a more efficient evaporating surface for moisture than does 

 the unbroken surface of the water. 



I'earl- reports that "The most satisfactory way to supply 

 this extra moisture where sand trays are not an integral part 

 of the incubator, has been found to be by sjtrinkling the 

 eggs with warm water twice a day. The water is warmed 

 to a temperature of from 104° to inS° F. . . . The 

 a])])lication of moisture is begun as soon as the eggs go into 

 the machine, and is continueil until the eighteenth day. 

 Since ado]3ting this ])rocedure a A'cry considerable reduction 

 in the mortality of chicks in the shell has beel^ effected." 



Dryden^ has shown that when water is present it dissolves 

 carbon dioxide which is normally ])rcsent in an inculxitor. 

 This tends to weaken the shells of the eggs ma.king the 

 exclusion of the cliick easier, the calcium of the shell being 

 soluble in water containing carbon dioxide. This niay be a 

 factor in Pearl's results. 



Ventilation. — The cjuestion of what constitutes proper 

 ventilation for an incubator is one upon which there is little 

 satisfactory experimental evidence. Yet restricting or aug- 



' Utah Bulletin No. 102. 



^Poultry Management at the Main Statiuu, lUl.'i. 



' Utah Biillelin, No. 92. 



