196 TROPICAL MEDICINE AND HYGIENE 



interdependence between the presence of spirochaetes 

 and the different phases of relapsing fever. An early 

 view was that the fever resulting from the presence of 

 the parasite in the blood caused its destruction and 

 that relapses were due to the development of further 

 generations of spirilla from spores. The existence 

 of spores of S. obermeieri has, however, not been 

 demonstrated. The blood of a patient during the 

 apyrexial intervals will still infect monkeys if injected 

 into them. Another view attributed the disappearance 

 of spirilla to the formation in the blood of some bacteri- 

 cidal agent at the crisis, while a more modern view is that 

 the spirilla are destroyed by phagocytosis, this destruction 

 occurring chiefly in the spleen. The lengthening periods 

 of interruption and the mildness of relapses is by others 

 attributed to the acquirement by the patient of increas- 

 ing degrees of immunity. This view is consistent with 

 the probable protozoal nature of the parasite. The 

 spirillum or S. obermeieri is one of a class of organisms 

 of which many pathogenic species are known. These 

 mentioned in the order of their discovery include 

 S. anserini, the cause of septicaemia of geese ; S. theileri f 

 affecting cattle in South Africa ; S. gallinarum, causing 

 fever in fowls in Brazil, the Sudan, and elsewhere, and 

 S. duttoni, the cause of African tick fever. These organ- 

 isms resemble each other in their general morphology 

 and active motility. They all occur free in the circu- 

 lating blood during the febrile paroxysm and are no 

 longer found after the temperature has fallen. In the 

 intervals between the attacks of fever small actively motile 

 bodies containing chromatin are found in some of the 

 red cells. 



It has furthermore been demonstrated that certain of 

 them are conveyed by the bite of certain ticks; thus, 

 S. gallinarum is transmitted by Argas persicus, S. theileri 

 by Boophilus decoloratus, and S. duttoni by Ornithodorns 

 moubata. No such demonstration has been made in the 

 case of Indian and European relapsing fever, but a tick 



