186 STUDIES ON PATHOLOGIC OVA. 



in the rate of travel of the two types of sperm, or that a disease process, or a factor 

 such as alcoholism, might affect one type to a greater degree than the other. 



Hertwig (1912) attributes sex determination to the ovum or the degree of its 

 maturation, an advanced stage of maturation producing males. In this way he 

 attempts to explain the difference in sex-ratio according to social class. Thury 

 (1863) proposed the idea that ova which are fertilized late may produce more 

 males. Thus he explained the high sex-ratio among Jews who, on religious grounds, 

 refrain from intercourse for 7 days following menstruation. Here may also be 

 mentioned the recent investigations by Siegel on the relation of menstruation to 

 sex, according to which coitus from the first to the eighth day after menstruation 

 yields 86 per cent males; from the ninth to the fifteenth day it results in 65 per 

 cent females; from the sixteenth to the twenty-second day, 85 per cent of con- 

 ceptions are females, and in the remaining premenstrual period woman is prac- 

 tically sterile. Pryl and Jaeger, working independently, have confirmed Siegel's 

 observations. 1 These findings contradict, in a way, those of Hertwig and Thury. 



Lorenz (1898), Lenhosse'k (1903), and Orschansky (1903) are of the opinion 

 that sex is sujbect to hereditary influences, inasmuch as they found families in 

 which males predominated and those in which females appeared in excessive 

 numbers. Newcomb (1904), Woods (1906), and Heron (1906) deny this and show 

 that inheritance plays no part in the sex-ratio. Numerous authors attribute its 

 variation to the absolute and relative ages of the parents. According to Rosenfeld 

 (1900), there is a decided preponderance of male children born to young and old 

 fathers, as compared with those of middle age. Francke, from the statistics of 

 Norway, found this to be true in respect to young fathers, but reached an opposite 

 conclusion as regards old ones. Dumont (1894) found for Paris a sex-ratio of 

 101.9 when the fathers were from 18 to 25 years, 104.2 when the fathers were 

 between 25 and 50 years, and 97.5 when they were over 51 years. According to 

 E. Bidder (1878), the sex-ratio of births by mothers under 18 and over 40 years 

 is especially high, and Specht (1916) reports that the large majority of births 

 by mothers under 16 years are male. Sadler (1830) stated that the relative ages of 

 the parents determine the sex-ratio. The latter is 86.5 when the father is younger 

 than the mother, 94.8 when both are of equal age, and reaches 163.2 when the 

 father's age exceeds that of the mother by 16 or more years. Kollman (1890) ob- 

 tained an opposite result, drawing the conclusion, which was based on extensive 

 material, that the sex-ratio is high when the father is younger and low when he is 

 older than the mother. At the same time he opposes the view that the absolute 

 age of the mother has any influence whatever upon sex-ratio. Stieda, on the basis 

 of his investigations, came to the conclusion that any influence on the part of the ab- 

 solute ages of the parents is out of the question, as he noted the highest sex-ratio 

 when the parents were of equal age. Numerous other authors have occupied 

 themselves with the question of parental age as an influence upon sex-ratio, but 

 only two additional ones will be mentioned, Boudin (1862) and Stadler (1878). 

 The conflicting views which have been presented suffice to show that nothing 



'These papers could not be obtained by the author, but are discussed by Nilsson. 



