34 SOME MINUTE ANIMAL PARASITES 



tively free from flies, while their dark companions 

 harbour numerous flies whose tint strongly resembles 

 that of their hosts. White clothing also seems to 

 repel the flies. When there is much wind or the 

 sky is very overcast, the flies abandon man and 

 invariably seek cover. 



Various attempts have been made to find some 

 ointment noxious to the fly but harmless to man. 

 Among the African natives the juices of certain 

 herbs rubbed on the body are said to deter the flies, 

 but when put to the test these are of little use for 

 any length of time. Various preparations have been 

 used by Europeans, but practically none of them 

 have been of effect after about an hour. Among 

 some of the substances advocated, but which need 

 to be renewed at frequent intervals, are eucalyptus 

 oil, turpentine, oil of bergamot, clove oil, oil of 

 origanum, thymol or carbolic acid in weak solution, 

 and citronella oil, the latter seemingly being the 

 best. Bird-lime made from mistletoe and other 

 berries has been used for trapping flies, but is of 

 very local service. 



Regarding treatment of sleeping sickness, little 

 can be said with certainty except that drugs contain- 

 ing arsenic are of most value, and that their efficacy 

 is multiplied tenfold if the patient can be treated as 

 soon as possible. Unfortunately, the date when a 

 person has been bitten cannot always be determined 

 with certainty, and the difficulty of medical treat- 

 ment is intensified in consequence. 



The earlier workers on the treatment of sleeping 

 sickness used mixtures containing arsenious acid or 



