250 Diseases of Poultry 



When it enters the egg in this way it is much more fluid 

 than the thin albumen of the laid egg. The fluid albumen 

 added in this way dissolves some of the denser albumen al- 

 ready present, and so brings about the dilution of the latter 

 in some degree. At the same time, by this process of diffu- 

 sion, the fluid layer is rendered more dense, coming finally 

 to the consistency of the thin layer of the laid egg. The 

 thin albumen layer, however, does not owe its existence in 

 any sense to this dilution factor, but to a definite secretion 

 of a thin albumen by the glands of the isthmus and uterus. 



The addition of albumen to the egg is completed only after 

 it has been in the uterus from five to seven hours. Before 

 the acquisition of albumen by the egg is completed a fairly 

 considerable amount of shell substance has been deposited 

 on the shell membranes. For the completion of the shell 

 and the laying of the egg from twelve to sixteen, or excep- 

 tionally even more, hours are required.^ 



The main factor in propulsion of the ovum along the oviduct 

 appears to be the peristaltic movements of the latter ; it 

 is probable that the cilia which line the cavity have some- 

 thing to do with the rotation of the ovum on its chalazal 

 axis. 



With this account of the anatomy and physiology of the 

 female organs of reproduction in hand we may proceed to 

 a consideration of their diseases. These diseases fall at 

 once into two classes : (a) those affecting the ovary, and (b) 

 those affecting the oviduct. 



1 The foregoing account is based upon that given by Pearl and Cur- 

 tis, Jour. Exper. ZooL, Vol. 12, pp. 123 and 124, 1912. 



