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content of 11 lice does not produce trench fever when rubbed into 

 the broken skin ; (10) infection probably does not take place by the 

 mouth or by inhalation ; (11) the excreta of lice are not normally 

 capable of producing trench fever ; (12) hce infected with trench fever 

 do not transmit the disease to their offspring ; (13) there is a possibility 

 of some attacks of trench fever being afebrile throughout ; (14) the 

 percentage of individuals naturally immune to trench fever is exceed- 

 ingly small ; (15) old age is no bar to infection ; (16) such immunity 

 as results from an attack of trench fever is not permanent, and may 

 only persist for so long as the individual shows evidence of the disease ; 

 (17) even as late as the 79th day of disease a patient's blood may 

 remain infective, and be capable of infecting lice fed on such a patient 

 while febrile ; (18) the different varieties of trench fever result from 

 differences in the persons infected rather than in the source of infection. 

 Some of these findings may be modified by future work, as the number 

 of experiments made has been but small. 



Since trench fever is conveyed by lice, there is the possibility of 

 its being carried to all parts of the world where conditions favour 

 the spread of louse-borne disease. A map has been compiled showing 

 the distributiou throughout the world of the three louse-borne diseases, 

 typhus exanthematicus, relapsing fever and trench fever. Strict 

 accuracy is not claimed, however, owing to the scantiness of informa- 

 tion from the less civilised parts of the world, and to doubt concerning 

 the nature of certain epidemics ; and further, no account has been 

 taken of the war epidemics, information about these being too 

 fragmentary. 



Typhus fever is now very rare in Western Europe, though once 

 common and still lingering in endemic form in parts of Ireland, 

 Brittany and possibly southern Portugal. It occurs frequently in 

 Austria, especially Galicia, is very prevalent throughout Russia and 

 the mainland of Asia from about 25° N. latitude, and before the War, 

 was often met with in Turkey. In Japan, and Asia south of 25° 

 N. latitude, it is less frequent, being apparently absent from Central 

 and Southern India, the East Indies, the Malay Peninsula, and 

 Australasia, with the exception of Celebes. In Africa, it is very 

 prevalent north of the Sahara, and south of this, it is epidemic in parts 

 of Cape Colony. It has occurred as localised outbreaks in Canada 

 and the United States, being generally traceable to Irish immigrants, 

 but has never become endemic there. In Mexico and the South 

 American Andes it flourishes on the high groimd in both endemic 

 and epidemic form, and has been recorded from the greater part of 

 South America, but not recently in Guiana or the West Indies. 



In Europe and northern Africa the distribution of recurrent fever 

 corresponds exactly to that of typhus. In Asia it is less prevalent 

 to the east of the Obi and Ural rivers than to the west of them, while 

 it has not been definitely reported from Japan, the East Indies, Malay 

 Peninsula and Australasia (with the possible exception of a single 

 death in W. Australia). It has been reported from the greater part 

 of India, and, as spasmodically occurring, over the greater part of 

 North America. The form occurring in Central and South America 

 is possibly tick-borne, as is also that occurring in Africa south of the 

 Sahara, Ornithodorus moubata being the vector. 



