ry5 SCIENCE IN AFRICA 



tropical Africa. They can, of course, be cured by nutritional 

 methods where medical aid is available, as a result of fundamental 

 research carried out in Europe and in the East during the last 

 twenty years. There may, however, be a number of local deficiency 

 diseases whose presence is masked by the numerous better-known 

 diseases from which natives suffer. To mention one example, in 

 Nigeria a disease involving blindness has been evident among 

 people who feed largely on cassava. It has been noticed particu- 

 larly in school children among whom the disease has been cured 

 by feeding with cod-liver oil. Similar complaints have been ob- 

 served in other parts of Africa and the value of vitamin A as a 

 protection from infection has been stressed by Fox (1933). The 

 blindness in Nigeria may be a disease known in European coun- 

 tries to be a direct result of vitamin A deficiency, but opinion is 

 divided and some authorities consider it to result from some toxin 

 in the food. Dr. Clarke investigated this question in Nigeria 

 during 1935 and 1936 under a grant made by the Medical Re- 

 search Council and Colonial Medical Fund, and his conclusions 

 give weight to the view that poisonous substances occur in appreci- 

 able quantities in cassava and coco yam. Thus the avitaminosis is 

 probably caused by food toxins which do not allow the vitamins 

 to be used properly by the body. 



The relation between nutrition and resistance to disease was the 

 subject of an important discussion by the British Association in 

 1935- The opinion is often expressed that susceptibility to parasitic 

 worms is enhanced by malnutrition. There is, in fact, some experi- 

 mental evidence in animals in support of this view, discussed by 

 Miss P. A. Clapham (1933). Nearly every native has worms of one 

 kind or another, and a recent work on the zoological content of 

 male and female natives' intestines, though at present based on 

 small numbers, indicates that women have considerably fewer 

 worms than men. It has been suggested that this is due to the 

 more varied diet of women, but it is also possible that infestation 

 by helminths depends on the facilities which the parasites have for 

 distribution from host to host rather than on the food of their 

 hosts. If susceptibility to worm parasites is partly a result of mal- 

 nutrition it is important to remember that the converse is probably 

 true, that infestation with intestinal parasites favours the develop- 



