SOME PROBLEMS OF RESEARCH I5 



has shown that this disease is not restricted to the endemic centres 

 on the west coast, but extends in a dormant form throughout 

 large tracts of Africa as far east as Uganda and the Sudan. It 

 has been pointed out recently by medical authorities that these 

 potential centres offer opportunities, through the agency of air 

 transport, for the spread of the disease to huge populations not 

 only in eastern and southern Africa but even in a wider area. 



Slower transport by road, rail, and ship can create similar prob- 

 lems. For example, sleeping sickness is caused by small organisms 

 in the blood, of which there are probably many local strains. A 

 population accustomed to one strain and having developed a cer- 

 tain degree of immunity may wander into the realm of another 

 strain, and thereby suffer from a violent epidemic. This has prob- 

 ably occurred in many parts of Nigeria, where the environmental 

 conditions both inside and outside man differ so widely from north 

 to south, and where it is believed that sleeping sickness has increased 

 during the last quarter of a century. In estimating the increase or 

 decrease of disease, it must be remembered that in the absence of 

 comparable statistics, figures of incidence depend in a large degree 

 on the activity of doctors. 



In this sketch of the changes now proceeding in the African 

 environment, the principle of the cinematograph has been adopted 

 rather than that of the snapshot. Although this volume as a whole 

 attempts to depict a cross-section of present-day scientific activity, 

 the cross-section is only made possible by imagining the process of 

 change to be temporarily suspended for examination. The picture 

 really presented by Africa is one of movement, all branches of 

 physical, biological and human activity reacting on each other, to 

 produce what biologists would refer to as an ecological complex. 



LAND PLANNING 



Every branch of human activity, including cultivation, grazing, 

 forestry, game preservation, mining, and administration, involves 

 the utilization of land, and the claims of the various activities often 

 come into conflict. An analysis of the existing utilization and poten- 

 tiality of land is therefore of great significance. The policies which 

 have been followed in defining rights to land are discussed in An 



