ANIMAL INDUSTRY 453 



cies in diet, and recent work on intestinal worms has shown that 

 susceptibihty is reduced by improved diet, though in some infec- 

 tions it has to be remembered that modern methods in which well- 

 fed animals are herded together on improved pasture may increase 

 the opportunities for the distribution of parasites. Nutrition is also 

 of great importance in the cases of dormant infection: for example, 

 the breeds of native cattle which are usually immune to trypano- 

 somiasis carry trypanosomes in their systems when in infected 

 areas, and a reduction in the quantity and quality of their food 

 often leads to the parasites getting the upper hand. For these 

 reasons the study of African pastures, much of which forms part 

 of the work of departments of veterinary research or animal hus- 

 bandry, has been described in some detail in Chapter VI. 



HIDES AND SKINS 



The trade in hides and skins from various parts of Africa offers 

 considerable scope for improvement and expansion. Certain 

 prevalent insect or fungal parasites, though not seriously affecting 

 the vitality of their host animals, do great damage by penetrating 

 or affecting the skins and thereby reducing their market value. 

 For example, bot-flies damage cattle hides by their boring action 

 on escaping from the tissues belov/ the skin, and the value of goat- 

 skins is much reduced by the borings of the mite, Demodex folli- 

 culorum. For the control of the latter special research appears 

 necessary, since dipping and other established practices have no 

 effect on the parasites. Opportunity is thereby offered for im- 

 proving the hide and skin trade by direct control of parasites. 



An easier and more far-reaching means of increasing the value 

 of hides is by improving the methods of flaying and drying. In 

 many parts of Africa hides are seriously cut in the flaying process 

 and are subsequently dried in the sun, which means that high- 

 quality leather can never be produced from them. Accordingly 

 efforts are being made by many agricultural and veterinary depart- 

 ments to institute systems of shade-drying and better flaying. In 

 this the local departments have received help and co-operation 

 from the hides and skins committee of the Imperial Institute, and 

 from the British Leather Workers Research Association. 



