434 POULTRY CULTURE 



There is a greater loss, with the haphazard methods under 

 which most incubators are run, than where the eggs are placed 

 under hens for hatching. 



Extreme dryness and extreme humidity are both detrimen- 

 tal. The range between the temperature of the incubator 

 and that of the room influences the humidity in the egg trays of 

 the machine. The difference of the temperature of the two 

 bodies of air — the one in the machine and that outside — causes 

 a circulation of air through the machine. As the difference in 

 temperature decreases, there is less circulation and higher 

 humidity in the machine. A machine set in a corner where 

 there is dead air will have insufficient circulation of air, and 

 there is likely to be a poor hatch. To maintain a uniform 

 humidity, note must be made of the range of temperature, and 

 the supply of moisture must be governed accordingly. A wet 

 bulb thermometor kept at a temperature of about 88° gives 

 the most favorable results. 



Carbon dioxid is given off from the embryo through the 

 egg shell. Atwood has shown that the loss of carbon dioxid 

 during the last five days of incubation is about five-eighths of 

 the total loss of carbon dioxid, twice as much as is given off ia 

 the third five days, ten times as much as in the second five 

 days, and almost fifty times as much as in the first five days. 

 In an incubator this carbon dioxid must be kept below 150 parts 

 in 10,000. One hundred fertile eggs will require 165 cubic feet 

 of fresh air to be passed over and around them on the twentieth 

 day to keep the embryos from asphyxiating. 



Standardizing the Incubator. — Proper moisture, it is found, 

 will result in as much as 35 per cent, difference in hatching 

 of the eggs; therefore the incubator trays should be standard- 

 ized by the following rule : 



Rate of evaporation depends to a certain extent on amount 

 of ventilation; therefore it will be necessary to observe just 

 how much ventilation you have in applying moisture. The 

 difference between the temperature of the body of air in the 

 room and that of the incubator makes the exchange of air in 

 the incubator possible, and the greater this difference the faster 

 the two bodies of air will exchange. 



Calcium salts are absorbed from the shell during the chick's 



