AX7THOR S ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, JUNE 1 



STUDIES ON INBREEDING 



II. THE EFFECTS OF INBREEDING ON THE FERTILITY AND ON THE 

 CONSTITUTIONAL VIGOR OF THE ALBINO RAT 



HELEN DEAN KING 



The Wistar Institute of Anatomy and Biology 



TWO CHARTS 



The present paper gives data showing the fertility and the 

 constitutional vigor in a strain of albino rats that was inbred, 

 litter brother and sister, for twenty-five successive generations. 

 Details regarding the manner in which these experiments were 

 conducted and data for the growth and variability in the body 

 weight of inbred rats have already been published (King, '18a). 



1. THE FERTILITY OF INBRED RATS 



As shown by a number of recent investigations (Pearson et 

 al., '99;Rommelland Phillips, '06; Pearl, '12, a, and Wentworth, 

 '16), fertility is undoubtedly a racial character that is transmitted 

 by inheritance, although it is influenced to a considerable extent 

 by a variety of extraneous factors. The mode of inheritance of 

 fertilit}^ in the rat is not discussed in the present instance, since 

 the effects of inbreeding on fertility is the chief subject under 

 consideration. 



Throughout this paper the word ' fertility' is used as defined by 

 Pearl and Surface ('02) to designate: "The total actual reproduc- 

 tive capacity of pairs of organisms, male and female, as expressed 

 by their ability when mated together to produce (i.e., bring to 

 birth) individual offspring." According to this view, fertility 

 depends upon and includes fecundity as well as a great number of 

 other factors. As Pearl and Surface state: "Clearly it is fertility 

 rather than fecundity which is measured in statistics of birth of 

 mammals." 



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THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 2 



