278 Diseases of Poultry 



tion it is certain that some individual hens have an inherent 

 tendency to lay double-yolked eggs, while a great majority 

 of hens never lay anything but normal single-yolked eggs. 

 A bird with the tendency to double-yolked egg production 

 is more likely to produce double-yolked eggs when she is 

 quite young than later in her life. 



The two yolks of a double-yolked egg may enter the 

 oviduct simultaneously and pass the entire length of the 

 duct together receiving an entire common set of egg 

 envelopes, or they may come together at any level of the 

 oviduct from the funnel mouth to the beginning of the 

 isthmus. It is highly probable that the two ovulations 

 may be either simultaneous or that they may be separated 

 by any period up to the normal time which elapses between 

 ovulations. 



The production of a double-yolked egg is evidently seldom 

 caused by the simultaneous discharge of two normal separate 

 follicles into the oviduct. More often it is caused by the 

 successive discharge of separate follicles at times varying 

 from simultaneity to the normal period and by the subse- 

 quent union of the eggs in the duct due to a difference in 

 the rate of passage of the successive eggs. 



Inclusion in Eggs. — The number of different foreign sub- 

 stances which at one time or another have been found in- 

 closed in eggs is great. The list includes blood streaks or 

 spots, blood clots of firm consistency and often considerable 

 size, lumps of bacteria, worms, fecal matter, etc., etc. 



From the practical standpoint the only inclusions which 

 need consideration are blood spots. Many inquiries are annu- 

 ally received at this Station as to what causes these spots and 

 what to do to get eggs which will be free from them. These 

 inquiries are most frequent in the spring months. The 

 only thing which can be done in such cases is to candle the eggs 

 and sell only those lohich show no spots. Hens which are 



