E. Hindle 
197 
gration. This reaction was found to be specific for each of the three 
strains investigated and constitutes one of the methods of distinguishing 
them. They may also be distinguished by means of the Pfeiffer 
phenomenon. When an animal was inoculated with OT c.c. of hyper¬ 
immune serum from a rat or rabbit, and then received 0‘5 c.c. of rat’s 
blood containing spirochaetes, if the latter were of the same strain as 
that used to produce the serum, they disappeared in about 10-30 
minutes; whereas, if the spirochaetes belonged to a different strain 
they persisted for several hours. 
Levaditi and Manondlian (1906,1907) as a result of their researches 
on this disease, came to the conclusion that the crisis of tick fever is 
“ un phenomene d’ordre purement phagocytaire,” thereby resembling 
that of European Relapsing Fever (Metschnikoff, 1887). During this 
period the mononuclear phagocytes of the spleen were found to ingest 
normal spirochaetes. The latter were said to occur only in the blood¬ 
stream and no intra-cellular stages were noticed. 
Levaditi and Roche (1907) investigated the mechanism of the crises 
and relapses of this fever, and found that the destruction of the 
spirochaetes at the crisis was not due to the presence of bacteriolysins 
or opsonins in the blood, but that these substances seemed to develop 
some hours later. The relapses were explained on the supposition that 
the spirochaetes which persist after the crisis, become resistant to the 
antibodies present in the blood, and then remultiply. According to 
these authors the resistance to antibodies, acquired at each relapse, is 
hereditary and therefoi’e cumulative ; and after the passage of a particular 
strain through three mice and two rats they were able to detect a 
difference in the resistance of the spirochaetes compared with that of 
the first infection. 
Manteufel (1907), however, came to a different conclusion with 
regard to the mechanism of immunity, and in opposition to the views 
of Levaditi and Manoueliau, showed that the parasiticidal agent is the 
serum, and that phagocytosis is only a symptom, not the cause of, 
immunity. 
Fraenkel (1907) found that the strain of relapsing fever from East 
Africa differed in its immunity reactions from that of the Congo, and 
considered that the two, for the present, must be regarded as distinct, 
Nuttall (1908) has provisionally proposed the name S. rossii for the 
spirochaete of East African Relapsing Fever, 8. duttoni being reserved 
for that of the Congo fever. 
