268 ADOLF H. SCHULTZ. 



The excess of male stillbirths is ascribed by most authors to the 

 more difficult labor attendant upon the greater size of the male, 

 especially the circumference of the head. In regard to this 

 question Button ('10) is of the opinion that at the time of birth 

 the bones of the male skull are as a rule more firmly ossified than 

 those of the female. In this connection he states also that with 

 the advance of civilization the pelvic development in women is 

 not proportionate to the cephalic development which is taking 

 place in infants. This perhaps explains the fact shown by Bluhm 

 ('12) that the relative number of induced premature births is on 

 the increase. That labor in cases of male children more often 

 demands artificial aid from the obstetrician is shown by Prinzing, 

 according to whom 6.18 per cent, of male births in Wiirttemberg 

 called for operative measures, as compared with 4.67 per cent, 

 in the births of female children. The process of labor itself is 

 the cause of only a small percentage of stillbirths, the majority 

 dying before labor sets in. 1 Therefore, the greater size of the 

 male cannot in itself be held responsible for the high sex-ratio of 

 stillborn. According to Treichler ('95) 29.6 per cent., and ac- 

 cording to Prinzing ('07) 32.6 per cent, of all stillbirths are pre- 

 mature, and in the sex-ratio of these size plays but little part. 



Frequently sex-ratio has been studied in relation to the pelvic 

 diameters of the mother. The results are somewhat conflicting. 

 Hoffmann ('87), Dohrn ('88) and Orschansky ('94) may be 

 mentioned, according to whom the sex-ratio in children of mothers 

 with narrow pelves is small; in contrast to this, Linden ('86) 

 states it to be 133 in 360 births in which the mothers had narrow 

 pelves. In case the size of the pelvis really has an influence, this 

 can be exerted only upon the secondary sex-ratio in the way of 

 elimination. In the same manner it seems evident that many of 

 the factors which apparently affect the sex-ratio do not change 

 it at conception, that is, they do not have any sex-determining 

 effect, but by their influence upon intrauterine mortality they 

 change only the sex-ratio of births. The well-known fact that 

 the secondary sex-ratio among Jews is relatively high is explained 

 by Du'sing on the ground of incest, blood marriages being of 



1 According to Ladame ('04) those dying during labor amounted to 36.4 per 

 cent, of all the stillbcrn in Switzerland in 1900. 



