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 yolk 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 egg 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 should 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 
