THE INCUBATION OF THE EGG 181 



hatch. He further noted the fact that in laying, the average 

 time spent on the nest was approximately sixty minutes. 

 As a result of two years' work, he found that by placing 

 eggs, being held for hatching for a considerable tim6, under 

 hens for sixty minutes daily during the holding period, he 

 increased the number of vigorous chicks by 10 per cent. 



He states that he "noticed further in handling eggs in 

 incubators both years, that the embryos of the warmed 

 eggs, after being placed in the incubator, presented a dis- 

 tinctly different appearance from those eggs not warmed, 

 being more clear cut, larger in size at the same period of 

 incubation, more active, and giving every appearance of being 

 stronger and more vigorous. 



" Considering both tests, it seems apparent that there is no 

 particular gain to be secured from warming eggs that are 

 to be held for a period of not more than ten or twelve days, 

 although this requires further investigation. Apparently 

 the vitality of the embryo suffers when held for a longer 

 period." 



Jackson suggests no practical method of warming eggs held 

 for hatching purposes, and no good method has been devised. 



A possible partial explanation of the above may be had 

 in the findings of Bushnell and Maurer,^ who report that 

 bacteria found in normal eggs do not develop readily at 

 blood (or incubating) temperatures, but dp develop at ordi- 

 nary room temperatures. As they suggest, when eggs are 

 kept for hatching at ordinary temperatures, enough develop- 

 ment of the organisms may take place during the time 

 intervening between the laying of the eggs and their incuba- 

 tion, to bring about decomposition enough to injure the 

 delicate embryo chick by vitiating its food-supply. Infertile 

 eggs presumably frequently infected do not decompose when 

 kept at incubator temperatures for three weeks. 



Disinfecting Purchased Eggs. — Because of the prevalence of 

 certain chick diseases, and the fact that their germs are found 

 adhering to the shells, many poultrymen are disinfecting 

 their eggs by dipping them in 92 per cent, alcohol or in a 



' Unpublished data of Kansas Experiment Station. 



