lyG 



POULTRY DISEASES AND THEIR TREATMENT. 



material is far less common than it used to be; over-feeding or 

 over-stimulation probably more so." 



Small, Yolkless Bggs. These little eggs, variously called 

 "wind-eggs," "cock eggs," "witch eggs," "luck eggs," etc., are 

 familiar to every poultry keeper. They contain no definitely 

 formed yolk, and to the casual observer seem to consist of 

 nothing but a small shell filled with white. The laying of one 

 of these eggs is popularly supposed to mark the end of a laying 

 period. This belief is without foundation in fact. They may 

 be produced at any time. Unpublished data collected over a 

 period of years at this Station in regard to such eggs indicate 

 that three factors are fundamentally concerned in their pro- 

 duction. These are : — 



1. The bird must be in an active laying condition; the more 

 pronounced the degree of physiological activity of the oviduct 

 the more likely are these eggs to be produced. 



2. There must be some foreign body, however minute, to 

 serve as the stimulus which shall start the albumen glands se- 

 creting. This foreign body may be either a minute piece of 

 hardened albumen, a bit of coagulated blood, a small piece of 

 yolk which has escaped from a ruptured yolk, etc. 



3. It seems likely, though this is a point not yet definitely 

 settled, that ovulation (i. e., the separation of a yolk from the 

 ovary) must precede the secretion of albumen around the for- 

 eign body to form one of these eggs. 



Double and Triple Yolked Bggs. Eggs with two yolks are, 

 of course, quite common. They result from a disturbance of 

 the time relations of ovulation, of such nature that two yolks 



Fig. 42. Triple yolked es 



(Original). 



