THE EFFECTS OF SEMI-SPAYING AND OF SEMI- 

 CASTRATION ON THE SEX RATIO OF THE 

 ALBINO RAT)MUS NORVEGICUS ALBINUS.) 



HELEN DEAX KING 



The Wistar Institute of Anatomy and Biology 



The widely accepted view of a hundred years ago that the sex 

 of an individual depends entirely upon which of the ovaries sup- 

 plied the egg is generally credited to Hippocrates (460-377 B. C). 

 In spite of a considerable amount of adverse evidence, this theory 

 was revived by von Seligson in 1895, and very recently it has been 

 advocated by Dawson ('09) and by Calhoun ('10). The first 

 two of these recent advocates of the theory are physicians, and 

 much of the evidence that they offer in support of their views is 

 derived from clinical cases that have come under their own obser- 

 vation. Calhoun's conclusions are the results of an investigation 

 of stock breeding on a western ranch. 



Medical literature contains descriptions of many cases of one- 

 sided ovariotomy which show that eggs capable of developing 

 into individuals of either sex are produced in each ovary. Authen- 

 tic records indicate that in man, as well as in cattle, the removal 

 of one testicle does not lead to the production of offspring of 

 one sex only. Evidence of this kind, however, is either ignored 

 entirely by von Seligson, Dawson and Calhoun, or its authentic- 

 ity is questioned. 



Among the first to make an experimental investigation of 

 the cause of sex in mammals was Henke (1786). This investi- 

 gator operated upon pigs, dogs and rabbits, removing an ovary 

 or a testicle from each of the individuals used in the experiments. 

 The results reported as having been obtained when these animals 



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