METHODS OF HATCHING CHICKENS 311 



of 85. A wet bulb temperature, therefore, of about 88 

 degrees seems to indicate the best humidity conditions of 

 the incubator. 



It is not assumed that it is necessary to supply moisture 

 to the incubator to maintain the proper humidity conditions 

 of the egg chamber. Further experiments showed that 

 different incubators required varying amounts of moisture 

 to maintain the same readings of the wet bulb thermometer, 

 one incubator requiring double the amount of another. The 

 explanation is that the ventilation in the one machine was 

 greater than in the other. The humidity conditions there- 

 fore are strongly influenced by the amount of ventilation. 

 Again it was demonstrated that by cutting off the ventila- 

 tion, the proper wet bulb temperature could be maintained 

 without supplying any moisture. 



Moisture and Carbonic Acid Gas. An explanation, or 

 partial explanation, of the results obtained from supplied 

 moisture was discovered in another experiment. Carbonic 

 acid gas with moisture decomposes calcium carbonate. The 

 egg shell is 93.7% calcium carbonate. Eggs emptied of 

 their contents were put in glass fruit jars, some with water 

 and some without. The jars were then put in an incubator 

 for 21 days, and a strong current of carbonic acid gas was 

 forced through them. At the end of the incubation period, 

 the egg shells in jars containing water in the bottom were 

 broken down or dissolved, while those without the moisture 

 in the jars were unaffected and apparently as strong and 

 hard as at the start. From this it appeared that the shell 

 is something more than a mere covering to preserve the 

 egg. A German experimenter found that there was a loss 

 of lime in the shell during incubation. 



What becomes of it? Chemical investigations at the 

 Oregon Station showed that the chick as it was developing 

 within the shell was drawing upon the shell for nutrition ; 



