198 GENETICS 



Hippocrates thought that sex of the offspring 

 depends upon the relative "vigor" of the parents, 

 while Sadler (1830) concluded that the relative ages 

 of the two parents is the determining factor. 

 Other writers, on the contrary, have thought that 

 the age of the mother at the time of childbirth deter- 

 mines the sex of the offspring, and Thury (1863), in 

 the days before the facts of maturation were known, 

 ascribed the determinative factor to the relative 

 degree of "ripeness" of the egg when fertilized. It 

 was once assumed also that the right ovary or the 

 right testicle is the seat of one sex and the left ovary 

 or left testicle of the other. Galen, who did the 

 biological thinking for several centuries of mankind, 

 asserted that the right side of the body, "being 

 warmer" than the left, consequently produces males. 

 Schenk cites a most amazing bit of folk-lore to the 

 effect that: "In Servia if a man has a stye on his 

 eyelid he comes to the conclusion that his aunt is 

 pregnant. If the stye is on the upper eyelid, the 

 child will be a male; if on the lower, a female." 



Modern theories of sex determination, like the 

 earlier speculations, may be resolved into two groups, 

 namely, those which depend upon controllable ex- 

 ternal or environmental factors such as food, climate, 

 chemical dosage and will power, and those which de- 

 pend upon internal factors at present beyond control. 



2. The Nutrition Theory 



Of external factors which may exert a moulding 

 influence upon the sex of the offspring, nutrition is 



