142 JouKXAL OF THE MiTCHELL SociE.TY [^September 



eggs beside tlie incubator, whicb was started at the same time. 

 Marked eggs were taken from the hen nest every day and weighed on 

 a chemical balance. The same number of eggs from the incubator 

 were weighed each day. The average loss in weight of fertile eggs 

 from the hen nest at the close of the eighteenth day was found to be 

 11.4%. The average loss of weight of the fertile eggs taken from the 

 incubator was 18.5%. By proper adjustment of moisture in this 

 particular incubator it was possible to carry through hatches with loss 

 of between 11 and 1^%, which we presume must be correct. This 

 adjustment of moisture improved the hatch, but did not cut down the 

 loss in marked degree. 



Turning and cooling the eggs were studied with similar results. 



A personal experience of the author led to the present attempt to 

 solve the problem. He was in the center of a large auditorium in 

 Atlanta, not noted for good ventilation. The air which he was breath- 

 ing was coming to him after being used by the gTcat throng on the 

 floor below. After suffering great discomfort he arose to leave the 

 auditorium, and found himself so weak he was scarcely able to walk. 

 The sense of relief experienced when fresh air was reached can never 

 be forgotten. By fortunate coincidence, an incubator was hatching 

 that night, and the author's mind reverted to those little chicks in the 

 shell preparing for the supreme struggle of their lives, when they 

 were by sheer strength to break their way into this world. Certainly 

 if they were seized with the weakness just described they must fail in 

 their struggle and die exhausted. The conditions in the incubator 

 were so similar that on careful deliberation it was believed that lack 

 of oxygen was the principal cause of death. Incorrect moisture might 

 produce great discomfort and be a sufficient reason for good ventila- 

 tion, but with this exactly right the lack of oxygen might well pro- 

 duce extreme weakness. Animals are supplied with a marvelous 

 nerve mechanism controlled by centers in the brain which speed up or 

 slow down respiration according to the demands of the body for 

 oxygen, but any one who has on a mountain top experienced conditions 



