SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. 123 
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. 
Fere* 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 
clay 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. 
