98 SECTIONAL ADDRESSES 



before as well as after birth, it follows that since the secondary sex ratio 

 is 105 : 100, the primary sex ratio (that which obtains at conception) 

 must be higher than this, high enough, presumably, to allow for the 

 wastage that occurs. 



This suggested explanation of the difference between the primary and 

 secondary sex ratios and of the greater mortality of the male would seem 

 to accommodate every demand made upon it. Thus : abortion is far 

 more common than is usually recognised. Out of every 100 conceptions 

 only 78 can be expected to yield living offspring. The incidence of 

 abortion is higher during the earlier months of pregnancy. If, then, the 

 conditions which attend pregnancy are unfavourable to the embryo and 

 foetus, foetal death is made more probable, and if the male foetus is less 

 viable than the female, more males than females will perish. Under such 

 circumstances, the secondary sex ratio will be low. The sex ratio amongst 

 abortuses will be higher than that amongst still-births for the reason that 

 the differences in viability between male and female are greatest during 

 the earlier stages of intra-uterine development. Movements in the 

 secondary sex ratio can therefore be used as a measure of the success or 

 otherwise of the social services, of slum clearance, of the general health 

 of a community. The secondary sex ratio is lower in county boroughs 

 than in rural areas for the reason that abortion and still-birth are more 

 common in urban populations. The greater frequency of abortion 

 implies a higher male mortality, and therefore a lower sex ratio amongst 

 those who are born alive. The secondary sex ratio is thus a biological 

 yardstick with which town and country may be measured. It is highest 

 amongst first-born for the reason that the incidence of abortion and mis- 

 carriage is higher in large than in small families ; thus, in a dwindling 

 population, the secondary sex ratio will be high. It differs in different 

 countries for the reason that in them there are different standards of living 

 and of personal and public hygiene so that abortion and miscarriage are 

 commoner in one country than in another. It is influenced by migration 

 because of the reactions of the migrants to the new conditions. If the 

 migrants move from a relatively harsh environment to a relatively generous 

 one, so that the conditions associated with child-bearing are greatly im- 

 proved, it is to be expected that there will be fewer abortions and 

 miscarriages, and so relatively more male births and a high sex ratio. 

 This holds true of Northern European immigrants in the United States 

 of America. On the other hand, Southern European immigrants have 

 a lower sex ratio than their kin remaining in Europe for the reason that 

 the new conditions are to them less favourable than were those in 

 the countries from which they came. They reinforce the lowest social 

 categories, and a harsh European environment is replaced by one even 

 harsher. Thus the secondary sex ratio can, in such circumstances, be 

 used as an index of the success or otherwise of immigration. It is lower 

 amongst illegitimates than amongst legitimates for the reason that abortion 

 and still-birth are commoner amongst the former for very obvious 

 reasons. If it is not lower among illegitimates then it is to be assumed 

 that in that particular community illegitimacy is not regarded as an 

 unforgivable social error. It is lower amongst coloured people than 



