216 



KNOWLEDGE. 



June, 1913. 



this poison which ultimately killed the animal or 

 person — a theory that at basis was almost right. 



But all these theories, and many others, have 

 been exploded completely by the discovery of the 

 trypanosome in the blood of sleeping - sickness 

 patients, and which long since has been proved to 

 be the cause of the disease. 



An interesting idea was that the European was 

 less prone to sleeping-sickness than the native, but 

 so far as his susceptibility to the disease is con- 

 cerned the idea is entirely wrong. There is some 

 truth, however, in the statement that a smaller pro- 

 portion of Europeans than natives are attacked ; but 

 this is probably, in part, due to the fact that most 

 Europeans are not subjected to the same risk, living, 

 more or less, indoors during the day, when the 

 tsetse-fly is at the height of its activities. On the 

 other hand the natives are in the open all day and 

 always subject to the fly's attentions. 



There is, nevertheless, a curious thing that has 

 often been noticed, and which undoubtedly has a 

 good deal of bearing on this subject, and that is the 

 tsetse-fly's marked aversion to settling on anything 

 white. It is the prevailing fashion, of course, for 

 the Europeans of tropical parts to dress in white 

 duck, and it has been observed that when a 

 European so dressed and natives have gone to a 

 spot where flies are abundant, the natives are 

 attacked most mercilessly, while the European is 

 comparatively unmolested. That this is due to the 

 colour of his clothes has been proved by tacking a 

 square of black cloth over, say, one arm, when 

 instantly, under the same conditions, the flies will 

 settle on the square. It is probably that the fly 

 instinctively will not settle on white owing to its 

 becoming then conspicuous. 



Notwithstanding this, all things being equal, the 

 European quite as readily falls a victim to sleeping- 

 sickness, and he possesses no natural immunity. 



Nagana, or the African " fly-sickness " of cattle, is 

 produced, as has been mentioned before, by T. brucei, 

 a trypanosome very similar in some of its phases to 

 T. gambiense, but which at other times is met with 

 as a small trypanosome of tadpole-like shape, having 

 neither undulating membrane of any width nor 

 " free flagellum." Besides cattle it attacks dogs and 

 cats, while it is pathogenic to most small animals as 

 well. It is harmless, however, to man, and it is found 

 in the blood of wild antelopes and other big game, 

 in which it seems to cause no ill-effects, strangely 

 enough. 



Nagana constitutes one of the great cattle plagues 

 of Africa, and has done untold harm to the develop- 

 ment of the country for stock-raising ; for it is 

 impossible to keep even domestic stock where this 

 disease occurs. Its effects on the animals it attacks 

 are essentially similar to the effects produced by T. 

 gambiense, with only minor differences. " Nagana " 

 is a Zulu name, and means " breaking, or withering 



up," and this name describes the course of the 

 disease very well, since the animals present a most 

 lamentable appearance of utter weakness. 



The tsetse-fly responsible for the spread of 

 Nagana is Glossina morsitans, a tsetse - fly 

 resembling G. palpalis in many ways, but its body 

 is of a lighter brown colour, and has characteristic 

 markings on the abdomen. Morsitans is the 

 commonest of the tsetse-flies, and is widely spread 

 over Africa ; moreover it is not confined in its haunts 

 to water-tracts. 



Treatment. 



Now we come to the last consideration, namely, 

 the cure of trypanosome diseases. A great deal of 

 work has already been done in this direction, but 

 there is a vast amount more needed yet. There is 

 practically no cure whatever, although there have 

 been rare cases of apparent recovery, which, quite as 

 likely, were due- to the patient's own bodily strength 

 as to the success of any " treatment " he mav have 

 had. 



The drugs known as atoxyl and arsacetin* and 

 other arsenic-containing compounds may be said to 

 be the standard drugs used in the treatment, but an 

 enormous number of substances of all kinds have 

 been tried. 



All the drugs like atoxyl are violent poisons, and 

 so have to be used with extreme caution, or the 

 " remedy " becomes worse than the disease, and, in 

 the case of atoxyl, blindness is very easily produced 

 in the patient by the slightest overdose. 



Although these drugs do not produce permanent 

 good, they seem to have a beneficial effect some- 

 times, and if cure meant only the ridding of the 

 patient's blood from trypanosomes, they would 

 indeed be admirable cures. Their effect in this way 

 may be quite remarkable, for while the patient's 

 blood may be swarming with trypanosomes, a dose 

 of atoxyl will completely free it from the parasites 

 in the course of an hour or two. Moreover, it may 

 remain free for months actually, but sooner or later 

 the trypanosomes will reappear, and the course of 

 the disease is not interrupted in reality. What 

 happens to the trypanosomes under the influence of 

 atoxyl nobody knows exactly. It has been said 

 that they " hide " in the bone-marrow or form 

 invisible spore forms, but all the same nobody knows 

 perfectly where they go or what they do in the 

 meantime. 



Apart from the drug treatment there is another 

 way of fighting the disease which, while it does not 

 aim at curing people who have already contracted 

 sleeping-sickness, does nevertheless aim at a decided 

 check to the spread of the disease. This consists in 

 removing the natives away from watercourses and 

 areas that the tsetse-fly inhabits, in confining all 

 people suffering from the disease to isolation-camps, 

 in destroying the undergrowth of river and lake 



/NH, /NH.CO.CH:, 



Atoxyl = CcH 4 <f Arsacetin = C C H 4 \ 



X AsO.(OH).ONa X AsO . (OH) . ONa 



