102 LICE AND THEIR MENACE TO MAN 



thrown into waves which are nearly in the same 

 plane, like those of a swimming eel, so that it is 

 not a true spiral. When stained in microscope 

 preparations it is seen to have a core of material 

 which takes a deeper coloration than the envelop- 

 ing outer sheath. It has, however, no definite 

 nucleus as most Protozoa have. It swims actively 

 about backwards or forwards by means of a cork- 

 screw movement or in waves. It multiplies by 

 splitting either along its whole length or across the 

 middle. At times at one end a small granular 

 swelling is seen, or the whole organism appears 

 to split up into granules. It is considered that 

 these granules represent a stage in the life-history 

 and that they grow again into typical spirochaetes, 

 but the actual change has not been observed. 

 The spirochaete which is the cause of relapsing 

 fever is known as Spirochaeta recurrentis, this 

 name being given to it as it cannot be found in 

 the blood between the bouts of fever but recurs 

 when the disease relapses. The parasite is found 

 not only free in the blood but also in the cells of 

 certain tissues, including the white cells of the 

 blood and sometimes in the red cells. 



Shortly after Obermeyer reported his discovery 

 it was shown that if the blood of a relapsing fever 

 patient was injected into a healthy man the latter 

 developed the disease. Following on this it was 

 found that the disease could be transmitted 

 similarly to monkeys, rats, and several other 

 animals, and that the parasite could be demon- 



