TURNING 339 



Turning. — The turning of eggs during artificial incubation is 

 a process designed to duplicate the motion which the hen gives to 

 the eggs in natural hatching. The effect of the turning is to 

 change the position of the germ; for, owing to the high tempera- 

 ture, the albumin has a tendency to break up, the j^olk rising 

 higher and higher, allowing the germ to come in contact with 

 the shell. Turning is also necessary to supply oxygen to the grow- 

 ing embryo, for the germ absorbs oxygen from the albumin, and 

 the albumin in turn gets oxygen from the air cell or through the 

 shell of the egg. If the €'gg is not turned, especially during the 

 later stages, the embryo will not be of the right shape or in the 

 right position in the egg, and therefore is unable to hatch. 



The following is a comprehensive rule for turning. Begin turn- 

 ing on the evening of the third day, continue this process each 

 day, morning and evening, until the evening of the eighteenth 

 or nineteenth day, or until the eggs show signs of pipping. Then 

 prepare the machine for hatching, and do not remove the tray 

 for any purpose. 



Several methods are recommended for turning, and a number 

 of appliances come with different machines. The most common 

 of these is the turning frame, the eggs being placed between the 

 slots, the theory being that when this frame is moved back and 

 forth the eggs are rolled about. As a matter of fact, however, 

 many of the eggs, especially if of different sizes, are found to be 

 in the same position, and the small ones are apt to be cracked. 

 The best method, undoubtedly, is that of hand turning, which 

 consists in placing the palm of the hands on some of the eggs from 

 the centre, and moving them about the tray, trying, so far as 

 possible, to put them into a different position. If the hands are 

 pressed firmly on the eggs, this method promotes uniformity, and 

 very few, if any, eggs are cracked or broken. It is unnecessary to 

 mark the eggs and turn them halfway over each time; this re- 

 quires extreme care, and the amount of time and labor expended 

 is not productive of any better results. If the incubator is of the 

 double-tray type, the trays shpuld be shifted before replacing them 

 after turning, and the ends reversed twice daily, thus counteract- 

 ing any variation in temperature in the different parts of the 

 machine (Fig. 160). 



Cooling takes place during the process of turning, the object 

 again being to imitate nature. It not only allows the egg to cool 

 off, but at the same time permits it to secure a greater amount of 



