SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. 1 23 



None of these were affected by long standing diseases and none 

 showed a diminution in egg size greater than normal variation. 



It is clear that a diseased condition of a bird may cause a 

 decrease in the weight of each part of the egg without causing 

 a cessation of laying. It is also clear that other disturbances 

 sufficient to cause death may not affect the size of the egg pro- 

 duced on the day of death. 



iFere* studied the effect of morphine intoxication on the 

 weight of the egg. He found' that a stupefying dose caused a 

 diminution in the weight of the egg which was laid on the 

 day of the intoxication and which must have been nearly 

 formed at the time of the injection of the morphine. 



The effect of the morphine interrupted the laying for four 

 days and when it was resumed the first two or three eggs were 

 smaller than 'before the intoxication. This shows that an ex- 

 perimentally altered physiological condition may cause a dimi- 

 nution in the weight of the egg. 



It has been shown that, in general, the monthly mean egg 

 weight increases with the age of the bird, fluctuates with the 

 season of the year and is affected by the state of health. The 

 fact now to be considered is that during any month the eggs ot 

 each bird show a very considerable variation in egg weight and 

 in the weight of each of the egg parts. 



Before considering the nature of this variation in the weight 

 of the successive eggs it is important to notice the following 

 points in regard to the rate of production of the bird. 



1. Periods of production alternate with periods of non- 

 production. That is the bird lays in litters. 



2. The length of the periods of production and the number 

 of eggs laid in one litter vary at different seasons of the year. 



3. Throughout the warm months (April to September) the 

 period of non-production is typically a period of broodiness. 

 That is the instinct of the bird is to lay a litter of eggs and 

 then incubate them. While thirteen of the birds show this in- 

 stinct, nine were never broody. It is also interesting that 

 broodiness or non-broodiness is typical of the individual, for 



* Fere, M. Ch. Note sur la puissance toxiane et la puissance tera- 

 togene de la morphine sur le poulet. Bull, et mem. de la Soc. med. des 

 hop. de Paris, Vol. 14, series 3, pp. 608-617, 1897. 



