HEALTH AND POPULATION 565 



to compare the health conditions of a considerable population 

 in the Bas Congo from year to year since 1931. The results 

 (FOREAMI 1 93 1 -5, A.R., Trolli 1934, TroUi and Dupuy 1934) 

 provide what is probably the most detailed piece of demographic 

 work yet undertaken in Africa. The twenty-five doctors erft- 

 ployed make medical examinations of some 350,000 individual 

 natives, men, women, and children, every six months. By this 

 means the prevalence and spread or regression of the principal 

 diseases have been established, and full data on such subjects as 

 infant and maternal mortality have been collected. Perhaps the 

 most striking results concern the sex-ratio. In European countries 

 the births of boys exceed those of girls in the proportion of 105 or 

 106 to 100. Among the Bakongo, however, the ratio is apparently 

 reversed, since there were 93-7 boys to 100 girls born in 1932, 

 99-1 in 1933, and 99-4 in 1934. This apparent reversal of the 

 biological law that more males are born than females, is attributed 

 by Trolli (1934) to the matriarchal society of the Bakongo, which 

 leads to girls being more sought after than boys. This factor must 

 clearly affect the survival rate of boys, but it is difficult to see how 

 it can affect the birth rate. In the same paper Trolli advances 

 another explanation that the mortality of males is greater before 

 birth and the first few weeks of life. M. P. Ryckmans (1933) now 

 Governor-General of the Congo, suggested that there may have 

 been errors in collecting the data sufficient to account for the 

 abnormality, but Trolli points out that the data were obtained 

 each year by seven censuses by different members of the staff 

 working in separate districts. 



During the period from birth to 3 years the female sex still 

 predominates over the male among the Bakongo, but the domi- 

 nance becomes progressively less until from 3 to 15 years the 

 proportion is reversed and there are more boys than girls, perhaps 

 a result of an emigration of girls. A second reversal of sex-ratio 

 occurs among adults, there being more adult women than men, 

 a result of higher death rate and emigration of men. This differ- 

 ence is exaggerated among old people of 45 years and more, 

 among whom the low figure of about two men to three women 

 is the average. Figures and graphs showing the remarkable change 

 in sex-ratio are published separately for the seven districts of the 



