BY JAMES DRYDEN 87 



Fourth That the chick when it emerges from the shell, has more lime in 

 its body than was originally in the contents of the egg. 



Fifth That the hen-hatched chick has more lime than the incubator 

 chick. 



Sixth That supplying artificial carbon dioxide to incubators apparently 

 injures the hatch. 



Another point of difference, possibly of great importance, was brought 

 out in recent experiments at the Oregon Station. Chemical determinations 

 showed the presence of oil on egg shells. A small amount was found on 

 fresh eggs. About the same amount was found on eggs that had been 

 incubated artificially for two weeks, while on eggs incubated by the hen 

 for two weeks there was about seven or eight times the amount of oil. 

 What is the function of this oil? Does it hold the secret of sitting hens? 

 We have not been able to determine what part this oil plays in incubation, 

 owing to difficulties in applying oil artificially. We have found further 

 that by taking eggs from under a sitting hen and putting them in an incuba- 

 tor, the oil on the shell disappears in large part. 



Let me mention another point where incubators and hens differ. Eight 

 or nine years ago in the Utah Station, we found by weighing a great many 

 eggs at stated periods during incubation, that the incubator eggs lost more 

 weight than eggs under the hen; in other words, incubators dried the eggs 

 more than did the hen. This, I believe, was later confirmed by the 

 Guelph Station. The W r est Virginia Station reported some results that 

 were contradictory. However, at the Oregon Station it was found that 

 there was a greater loss in incubators than under hens. 



This fact led to experiments on the use of moisture in incubators, and 

 as a result, most incubator makers have modified their directions as to 

 moisture. By adding moisture to the machine the evaporation of the 

 eggs was checked and by checking the evaporation with moisture, it was 

 found that the chicks, when hatched, had greater weight. 



Now about the oil that the hen puts on the egg. Oil on the shell will 

 check evaporation. It may serve the purpose of moisture so far as evapora- 

 tion is concerned. This no doubt explains why eggs under hens 

 lose less weight than incubator eggs. 



This raises another question. At Guelph there was found what was 

 claimed to be conclusive evidence that there is a greater circulation of 

 air under the sitting hen than in the incubator, but the fact that there was 

 less evaporation from eggs under the hen, could hardly be reconciled with 

 the fact that there was greater air circulation under the hen. It seems 

 to me that the presence of oil explains this point. The hen gives plenty 

 of ventilation and the oil prevents too great evaporation; but the oil 

 may have other important functions about which as yet, we know nothing. 



