METHODS OF HATCHING CHICKENS 315 



time, may not injure the hatch, but the best results can 

 only be secured when the temperature is kept steady. This 

 refers to temperature conditions in all parts of the egg 

 tray. The operator should test the machine by putting a 

 thermometer in each corner and one in the center of the 

 egg tray. 



The successful operator is not satisfied merely to hatch 

 a large percentage of the eggs ; he hatches them well. 

 Chicks may be hatched but not hatched right. The effect 

 of a wide range of temperature may not show much in the 

 number of chicks hatched, but it will probably show more 

 in the kind hatched, though this fact often escapes notice. 

 The danger from improper temperatures is not so much 

 in the loss of chicks that fail to hatch, as in those hatched 

 with low vitality. 



Ventilation. Not only the incubator room but the in- 

 cubator itself must have good ventilation in order to carry 

 out the impure air given off by the growing chick within 

 the shell and to supply the required amount of fresh air 

 or oxygen for proper development. The questions of 

 moisture and ventilation are closely related. The greater 

 the ventilation, the more moisture is required. Some in- 

 cubators are built on the principle that no moisture should 

 be supplied, the proper humidity being maintained by re- 

 stricting the ventilation. How much ventilation is neces- 

 sary, is the problem. More data is needed on this point. 

 It has been very clearly established, however, at the Oregon 

 Station, that increasing the ventilation without increasing 

 the moisture reduces the number of chicks hatched and 

 gives chicks of lower vitality. This is due to the extreme 

 dryness of the air surrounding the eggs, not to the greater 

 supply of fresh air. Under such conditions the chick does 

 not make a normal growth. When this excessive ventila- 

 tion, however, was supplemented with sufficient moisture 



