266 
Spirochaetosis 
and it was at the bases of two of these pillars in the room used as 
a dining room that I noticed the ticks in the year 1896 or about that 
time. For several years I continued to live in the same house and 
suffered no harm from them. In more recent years, that is, about 1903 
or 1904, both Europeans and natives have suffered from •'Tick Fever’ 
(Spirillum) in houses which were built on either side of the site on 
which my old house stood. It has been affirmed that the ticks in these 
houses are the cause of the fever; I can only conclude that in previous 
years they were innocuous and that they have become nocuous since 
1896.” I do not know of any similar observation having as yet been 
recorded. 
The disease has repeatedly been transmitted to experimental animals, 
rats, mice and monkeys, by means of infected ticks, and in a number of 
cases unwittingly to experimenters in European laboratories. I may, in 
this connection, instance the case of Mr Merriman, in my laboratory, 
who suffered from the disease in ’consequence of being bitten by two 
0. mouhata (first-stage nymphs) whose biology be was studying. He 
did not know he had been bitten by the ticks until after two days when 
he showed me two characteristic bites upon his forearm. His attack 
followed 16 days after the bites were inflicted, the incubation period 
being four to six days longer than is usual. 
Of 25 monkeys with which Mollers experimented in Berlin no less 
than 20 died of spirochaetosis. There is, therefore, uo possible doubt 
about the tick being the carrier of the disease. 
Mollers’ observations were of fundamental importance in relation to 
the etiology of the disease. He proved that ticks continue to harbour 
the parasite even after repeated feeds upon clean animals: thus ten out 
of 12 monkeys were infected in succession by one lot of ticks which 
were fed upon them. His stock of ticks had died down to a low point 
toward the end of the series or the positive results would doubtless have 
continued longer. A tick may remain infective a year-and-a-half or 
longer after its initial infective meal of blood. He proved, moreover, 
that the parasites in the tick are transmitted hereditarily to the third 
generation when the ticks were fed throughout upon clean animals. 
Another observation possessing considerable interest is that of Manteufel 
(1910) that the ticks apparently acquire immunity to spirochaetal 
infection. Hindle has since found that about 30 “/o of the mouhata sent 
to me from Uganda failed to become infected. It is conceivable that 
the stage of the disease or of the spirochaete’s development at which the 
tick imbibes the para.sites may have some influence upon the number 
