SOME RECENT EXPERIMENTS IN INCUBATION 



BY JAMES DRYDEN 



There are evidently some fundamental differences between natural and 

 artificial incubation. 



Believing that the hen held the secret of incubation, our first work was 

 to investigate the hen to discover, if possible, the fundamental differences. 



When we began incubation work, the theory was widely prevalent, that 

 the failure of incubators to hatch satisfactorily was due to improper 

 ventilation in the machine. About that time a poultryman in Massa- 

 chusetts wrote me a letter in which he discussed this point and gave it as 

 his opinion, that an excessive amount of carbonic acid gas in the incubators 

 was responsible for poor results in hatching. He thought better ventilation 

 was needed to carry off the carbonic acid gas. He further stated that 

 where incubators were used for hatching chicks, he knew of no poultry 

 farms in his section of the country that had been successful for more than 

 three years in succession. 



We set about investigating this point. This was at the Utah Station. 

 The first thing to do was to find out how much carbonic acid gas accumu- 

 lated under sitting hens and in incubators during incubation. After the 

 chemist had made a long series of tests, it was discovered that instead of 

 there being an injurious amount of carbonic acid gas in the incubators, 

 there was actually less than was found under sitting hens. This started a 

 new line of investigation. Is there less ventilation under the hen than in 

 the incubator; and is carbonic acid gas a benefit instead of an injury? 

 What is the function, if any, of carbonic acid gas in incubation? 



It was demonstrated in the first experiment that carbon dioxide 

 with moisture will decompose the egg shell. Eggs emptied of their 

 contents and sealed up in bottles highly charged with carbon dioxide 

 were kept moist in the incubator, throughout the incubation period. 

 When taken out they were either broken down or readily crumbled to pieces 

 between the fingers. Other eggs under the same conditions, but without 

 any moisture in the bottles, showed no signs of disintegration, the shells 

 being apparently unchanged. They were hard to cut with a pen knife. 

 Another egg emptied of its contents, filled with water and sealed up in a 

 bottle, but with no water in the bottle, was decomposed and dissolved. 



The conclusion is that carbon dioxide will weaken or decompose the shell 

 when it comes in contact with water, either on the outside or inside of the 

 shell. It looks as though carbonic acid gas has an important function to 



