r^yS SCIENCE IN AFRICA 



Uganda^ for instance, has been very considerably reduced by the 

 institution of a varied dietary particularly rich in vitamin A, as 

 pointed out by Owen and Mitchell (1931). Again, the Medecin- 

 en-Chef of the Belgian Congo, discussing cases of beri-beri and 

 rickets in his annual report for 1931, notes that 'les avitaminoses 

 sont essentiellement des maladies des camps des travailleurs et des 

 prisons'. Now that the source of the trouble is recognized, the 

 position has been much improved, as shown by Dr. Trolli (1936) 

 for the Belgian Congo and Dr. A. J. Orenstein (1936) for the Wit- 

 watersrand gold mines. 



Deficiency of certain minerals, especially those containing cal- 

 cium and phosphorus, is common all over the continent and natives 

 go to great pains to make good the lack. Everywhere salt, par- 

 ticularly natural salt, which contains a variety of constituents in 

 addition to sodium chloride, is a most valued article of trade, 

 and natives sometimes travel great distances to obtain supplies for 

 themselves and their stock, or drive their stock periodically to salt 

 licks. In many places earth from special areas rich in salts is regu- 

 larly eaten and in some cases, especially among nursing mothers, 

 young children, and people suffering from intense infestation by 

 parasitic worms, the desire for special earths as food develops into 

 pica, or a depraved craving, as described by J. W. Foster (1927) 

 for East African natives. Often Africans obtain meagre supplies 

 of mineral salts, especially calcium, from the tissues of plants; thus 

 in parts of Rhodesia, Kenya, and Uganda reeds are burnt and 

 salt obtained from the ashes by a process of solution and reprecipi- 

 tation. In Nigeria the leaves of the baobab tree, which chemical 

 analysis shows to have a peculiarly high calcium content, are 

 crushed and eaten in soups. The latter case provides a striking 

 illustration of the dietetic value of a customary native practice. 

 Precautions are always taken to avoid direct sun on the leaves 

 during the drying process, a practice for which a very sound reason 

 has been elucidated by laboratory analysis and experiment: it has 

 been shown that sun-drying as opposed to shade-drying destroys 

 the vitamin content of the leaves. 



Examples such as this show the importance of full understanding 

 of traditional native attitudes towards different articles of native diet 

 and their preparation, as a preliminary to measures of improve- 



