HfiRIC. 

 UBRARY 



INTRODUCTION 



In co-operation with the Department of Poultry Husbandry this 

 work was begun under the direction of Professor G. W. Cavanaugh. 



Poultrymen have noted that the chickens hatched from the eggs of 

 some hens are much stronger and more vigorous than those hatched 

 from the eggs of other hens. Even with hens apparently of the same 

 vigor, fed and housed in the same pen, mated with the same cock, and 

 the eggs incubated under similar conditions, we will find some hens 

 of the pen laying eggs hatching chickens in large percentages, while 

 other hens of the pen will give most contrary results. 



This condition may be attributed to one of three different causes; 

 namely, the inherited constitutional vigor of the hen transmitted to 

 the chick, the influence of the cock, or a difference in the proportionate 

 chemical composition of the egg. 



To determine, if possible, the relation of the vitality of the chick 

 to the chemical composition of the egg, and, if this relation be found, 

 to attempt to control the composition of the egg, this work was begun. 



It is evident, at once, that this problem involves an examination 

 of the egg before incubation, and a study of the changes taking place 

 during incubation, together with an examination of the young chick. 

 Also in the feeding experiments, examination of the eggs must be 

 made while the hens are in normal condition, on their normal rations, 

 and then at intervals as the feeding is changed. 



