E. Hindle 
195 
and Todd (1905) mention an instance in which out of twenty men that 
contracted the disease in one caravan, ten of them died. 
Treatment. Up to the present there are no records of any treatment 
having been successfully used to cure the disease in its natural host, 
man; but it seems probable that “606” will cure the disease. The 
following experiments have been made on the treatment of the disease 
in laboratory animals :— 
Vassal (1907) found that the benzidine colours had an effect upon 
S. duttoni. In the case of rats infected with the spirochaete, the 
injection of certain of these colours, 2-3 days after the inoculation of 
the disease, was often followed by the disappearance of the parasites 
within 24 hours. Moreover if the colour was injected together with the 
spirochaete the course of the disease was always retarded and sometimes 
prevented. 
J. McIntosh (1910) found that the injection of 0005 gm. of 
dioxydiamidoarsenobenzol (“606”) into each of a number of rats infected 
with relapsing fever, caused the parasites to disappear within 6-18 
hours. Moreover the rats were then immune to any further infection. 
YakimofF and Kohl-Yakimoff (1910) have carefully investigated the 
treatment of S. duttoni in mice and rats. When mice infected with 
S. duttoni were injected with “ 606 ” on the first, second, or third day 
after the appearance of spirochaetes in the blood, the majority of the 
animals were cured, and in every case the parasites were driven out of 
the circulation. In a few cases, however, the spirochaetes reappeared 
in the blood. An injection of “ 606 ” administered 24 hours previously 
to the inoculation of the disease, immunised both rats and mice 
against infection. 
These investigators also found that the injection of benzidine colours 
into infected animals caused the spirochaetes to disappear for 6-21 days, 
but then they reappeared. They also found that injections given 
24 hours previously to the inoculation of the disease prevented any 
infection. 
In a later paper (1911) Yakimoff and Kohl-Yakimoff confirm their 
previous results on the treatment of this fever by “ 606.” From their 
experiments it seems possible that this drug will prove successful in the 
treatment of this disease in human patients. 
Immunity, etc. The fact that recovery from African Relapsing Fever 
is followed by a certain degree of immunity from further attacks was 
first noted by Sir John Kirk on the Zambesi, and later by Daniels 
(Manson, 1903) who observfed the disease in Nyasaland. 
