340 ARTIFICIAL INCUBATION 



oxygen than would be possible in the machine itself. The length 

 of time for cooling depends upon the temperature of the room 

 and the season of the year, and also upon the ventilation of the 

 machine. It is impossible to lay down definite rules; but it is safe 

 to begin cooling on the fifth day, and cool from four to five minutes 

 in a room heated to about 60. Do not let them cool any longer 

 than the time required for turning, in a room which is much cooler 

 than this. After the fifth day, the time for cooling should be 

 gradually increased, until, during warm weather and in the latter 



FIG. 160. Interior view of incubator cellar. Operator turning and cooling eggs. Water 

 is used on the floor to increase moisture in the incubators. 



part of the hatch, the eggs may be cooled from fifteen to twenty 

 minutes with very good results. The exact degree and process 

 of cooling are more or less disputed points, experiments proving 

 that environment varies so much that' no positive rule can be laid 

 down. It is evident that the eggs are considerably cooled during 

 turning, and that the machine also cools off somewhat while the 

 eggs are being taken out and replaced. Stop the cooling at the 

 same time that the turning is stopped, or about the eighteenth or 

 nineteenth day. 



Ventilation is essential in order that the gas liberated by the 

 embryo may be discarded. The problem is, how to supply fresh 



