198 TROPICAL MEDICINE AND HYGIENE 



others found in the mouth, in smegma, in tropical ulcers, 

 and in certain tumours in mice. Whether the last two 

 have any pathological significance is not known. Spiro- 

 chaetes may be found in large numbers in the faeces in 

 some cases of diarrhoea and in the expectoration in some 

 forms of bronchitis. 



The question as to whether spirochaetes are protozoa or 

 bacteria cannot be fully discussed here. Formerly they 

 were considered to be bacteria. As long ago, however, 

 as 1888, Tamilensky suggested that the S. obermeicri might 

 be only a stage of a haemocytozoon, and since 1904, when 

 Schaudinn suggested that spirochaetes should be con- 

 sidered as protozoa, this view has been generally accepted. 

 More recently (1906) Novy and Knapp have disputed 

 Schaudinn's conclusions, asserting that he was mistaken 

 in his observations, and reclassifying the spirochaetes 

 as bacteria. 



The question must for the present, therefore, be con- 

 sidered an open one, but it is of interest to note that the 

 known pathogenic species have certain features strikingly 

 resembling those of organisms concerning the inclusion 

 of which among the protozoa there can be no dispute. 

 These features are the constancy and intensity of the 

 blood infection, and, in the case of some at least, the 

 transmission by alternative hosts. 



A remarkable feature in the etiology of relapsing fever 

 is the fact that although its local infectivity is very marked 

 it does not spread widely except among populations living 

 under uncleanly conditions. Thus, when outbreaks 

 occurred in English towns, they were almost entirely 

 confined to the Irish, and in the Bombay epidemics 

 described by Vandyke Carter, the disease only affected 

 overcrowded localities. It may, however, spread to 

 other patients in a moderately well arranged insti- 

 tution or hospital in the Tropics. 



At one time famine was considered to play such an 

 important part in the etiology of this disease as to give 

 it the name of " famine fever." While, however, famine- 



