12 SCIENCE IN AFRICA 



in stock husbandry must be reviewed. Since the arrival of the 

 European, the number of large and small stock has increased 

 beyond measure. This has naturally reflected upon the condition 

 of the grazing and thereby has formed a vicious circle by removing 

 the vegetation and stimulating soil erosion in a way closely com- 

 parable with the effects of shifting cultivation. In an effort to 

 replace the superfluous numbers of native stock by fewer animals 

 of better quality, European science is causing another marked 

 change in the African environment. The experiments have not 

 extended widely in purely native areas, but they will make them- 

 selves felt in the next quarter of a century. Efforts are directed 

 primarily to producing better animals for the dual purpose of 

 milk production and draught, and have been closely connected 

 with attempts to introduce mixed farming as an alternative to 

 shifting cultivation. 



Meanwhile animal diseases, which were formerly important 

 agents in keeping down the numbers of domestic animals, have 

 been reduced by the introduction of European science. Rinder- 

 pest, for example, was introduced to Africa in the latter half of 

 last century, and was spread throughout most of the continent 

 partly by the migrations of wild animals, many of which, particu- 

 larly buffalo, are very susceptible to the disease. Intensive study, 

 stimulated by its occurrence in epizootic form, has led to the per- 

 fecting of vaccination. The results in changing the environment 

 for stock may be gauged from the fact that to-day almost every 

 animal in the Fulani herds of Northern Nigeria is inoculated 

 against rinderpest before it is a year old. In a similar way east 

 coast fever, a tick-borne disease which is indigenous throughout 

 eastern and southern Africa is being brought under control by the 

 compulsory dipping of animals at regular intervals to destroy the 

 ticks. This and related diseases provide an interesting example of 

 a measure of control which is employed by native pastoralists, even 

 though they do not fully understand the part played by ticks : the 

 habit of burning pastures during the dry season not only stimulates 

 the growth of young nutritious grass, but also destroys the ticks 

 which find their home in the old grass. This custom, in so far as it 

 contributes to the increase of the herds, plays its part in the vicious 

 circle of overgrazing and soil erosion, and hence is a cause of much 



