530 PROTOZOAL DISEASES. 



of this drug. Good feeding and judicious exercise will favour his 

 chance of recovery. For further details of Lingard's special treat- 

 ment, I beg to refer the reader to my translation of Friedberger 

 and Frohner's " Pathologic." 



For intravenous treatment, see page 531. 



Tsetse Fly Disease {Nagana, Sleeping Sickness). 



CAUSE AND NATURE. — There are at least seven species of 

 the Tsetse-fly {Genus glossina), which is found throughout a large 

 portion of Central Africa, and has long been regarded as the cause 

 of horse traffic being impossible in the districts it inhabits. The so 

 called " true Tsetse '' {Glossina morsitans) is about half an inch 

 long, and somewhat resembles in appearance the common house 

 fly. It has a long thin proboscis ; chestnut thorax (chest), marked 

 longitudinally by four black lines ; and a yellowish-white abdomen 

 of five rings (A. Laboulb^ne). The points of attack which it 

 seems to prefer are the lower parl^ of the belly, insides of the 

 thighs and under the tail. The stricken anim.als become weaker 

 and weaker and finally die from debility after a variable period 

 of suffering which may extend from a few weeks to two or three 

 months. Sir David Bruce, who has investigated nagana {Zulu, 

 depressed in spirits) in its native abode, considers it to be surra; 

 as the microbes of both appear to be almost if not quite identical, 

 and the principal symptoms are the same. The microscopical 

 appearance of the flagellated trypanosome of nagana is almost 

 exactly similar to that of the surra microbe. The only difference 

 between the two seems to be that horned cattle are susceptible to 

 the "fly," but are nearly immune from surra. Bruce regards this 

 comparative immunity as a peculiarity of Ipdian cattle, which, if 

 his theory be correct, resemble Algerian sheep (p. 18) in their 

 freedom from anthrax. Dogs, mice and other animals are attacked 

 by both diseases. The dog is the most susceptible animal and the 

 on© in which the illness runs the quickest course. Bruce has found 

 that " the fly " is in no way virulent of itself ; but that it acts 

 simply as a carrier of the disease germ. " The fly " disease proves 

 fatal to all members and hybrids of the horse family except zebras 

 and to man. 



Theiler states that the tsetse fly is dependent for its existence on 

 big game, in the blood of which, Bruce frequently found trypano- 

 somata (the microbes of this disease) ; and that the more big game 

 are pressed back by the advance of white men, the more the disease 

 disappears. 



Human beings are liable to be affected by trypanosomiasis 

 (sleeping sickness), a disease closely akin to surra and nagana, as 



