HEREDITY OF DISEASES. 37 



The same author says : " Childbearing by an im- 

 mature mother is popularly held to be dangerous to 

 the continued general health of the mother, and to 

 prevent her complete development in size and beauty. 

 I have no positive evidence to adduce in favor of this 

 generally-entertained notion, which my own experi- 

 ence appears to me to confirm. ... In its corrobora- 

 tion, however, I can adduce the ample experience of 

 eminent breeders of the lower animals. I have had 

 this opinion expressed to me, especially in regard to 

 mares, cows, ewes, and bitches." l 



Many other authorities might be cited to the same 

 effect, were it not that the influence of early breeding 

 in arresting the development of the mother is so often 

 observed by intelligent breeders as to render it unne- 

 cessary. 



In oviparous animals it has been observed, not 

 only that the eggs of very young females are less in 

 number and smaller than those produced at maturity, 

 but that a larger proportion are not fertile, the yelk 

 being frequently wanting or imperfect. And also, in 

 other groups of animals, that the number of young 

 produced at a birth is less with young mothers than 

 with those that are fully developed. 3 



Geyelin says: "It has been ascertained that the 

 ovarium of a fowl is composed of six hundred ovules, 

 or eggs; therefore a hen, during the whole of her 

 life, cannot possibly lay more eggs than six hundred, 

 which, in a natural course, are distributed over nine 

 years, in the following proportions : 



1 Dr. Duncan, " Fecundity, Fertility, and Sterility," p. 392. 



2 Ibid., pp. 38, 65, 70. 



