SOME PROBLEMS OF RESEARCH 3 



(XI, XII, XIII). Again, studies of forestry and agriculture are 

 relevant to the problems created by the native practice of shifting 

 cultivation. They are connected with soil science through the 

 effects of excessive destruction of pests and intensive cultivation 

 upon soil erosion, and with meteorology through the interaction 

 of these factors with the rainfall. 



All the animal kingdom, whether wild, domestic, fish, insects, or 

 man himself, must depend directly on plants for food, since plants 

 are the only agents for building inorganic into organic substances. 

 Thus all the upward-pointing arrows in the upper part of the 

 diagram represent food relations. There are also, however, back- 

 ward effects: the wild animals (Zoology, VIII) and domestic 

 animals (Animal Industry, XIV) affect the wild and domestic 

 plants by consuming them and by manuring the soil in which they 

 grow; aquatic animals (Fisheries, IX) have similar relations with 

 the flora of the ocean, lakes, and rivers; and insect pests (Entomo- 

 logy, X) affect not only man and animals, but forest trees and 

 crops. Finally the study of man himself (XV-XVII) is related to 

 that of every aspect of the environment, either through the con- 

 ditions of health and nutrition which it imposes on him or through 

 activities such as agriculture, forestry, and mining by which he 

 modifies it. 



Although in setting forth the recent advances in these subjects, 

 the individual sciences have to be treated separately, it cannot be 

 too strongly urged that their interrelations have important prac- 

 tical applications; progress in one field may often be hampered 

 through neglect of related studies. 



Africa as a field for pure as opposed to applied science, if such 

 a distinction can be drawn, is almost infinite, and only the boun- 

 daries have yet been explored. In a work of this nature but little 

 space can be devoted to fundamental problems of science such as 

 the shape and structure of the earth, the processes by which the 

 continents have reached their present configuration, the mecha- 

 nism of evolution, or the early ancestry of man. Africa has already 

 contributed its quota to the solution of such questions, and 

 references to the work accomplished have been incorporated 

 where possible. 



