HEALTH AND POPULATION 577 



ment of malnutrition and food deficiency by interfering with 

 digestion and absorption. 



The dependence of teeth on diet is another question of striking 

 interest. Sir Edward and Lady Mellanby have pointed out that 

 dental caries among Kikuyu natives in East Africa is more preva- 

 lent in towns and mission stations, where natives wear clothes, than 

 among untouched members of the same tribe living a rural life. 

 They attribute this partly to the deficiency of calcium and vitamin 

 D in the diet, but also to lack of sunshine directly on the body, and 

 to the shortened period of breast-feeding which results from town 

 life. This conclusion was confirmed by Oranje, Noriskin, and 

 Osborn (1935) for the South African Bantu. 'The percentage of 

 Bantu having carious teeth', they state, 'and the average number 

 of caries per individual are lower in relatively primitive Bantu 

 than in those who have had a closer contact with Europeans by 

 working on farms, in mines, or in towns.' Dr. Osborn is continu- 

 ing this study on a larger scale in the native territories of South 

 Africa and the Johannesburg mine compounds. On the other 

 hand, there is reason to suppose in some areas that natives in the 

 reserves have bad teeth as a result of food deficiency, but in towns 

 the varied diet results in improvement. The deficiencies which are 

 involved in causing dental decay, either singly or in various com- 

 binations, are those of calcium, phosphorus, vitamins A, D, and C, 

 and lack of oral hygiene likewise plays its part. A study of these 

 factors among both urban and rural natives offers a great oppor- 

 tunity for research. 



The monotony of native diet has been found to be of great 

 importance, since it means that deprivationof any constituent, even 

 if normally taken in very small quantities, may result in the com- 

 plete absence of some essential substance. This monotony is 

 perhaps most strongly marked among pastoral peoples such as the 

 Masai. It is less obvious in agricultural tribes whose diet changes 

 during the year, and who use an astonishing variety of relishes. 

 The diet of cultivators, however, though varied, is seldom well 

 balanced, and it seems probable that a series of deficiencies occurs 

 throughout the year as the food changes from month to month. In 

 labour camps and prisons, the effects of monotony in diet have 

 sometimes been very serious. The high mortality of prisoners in 



