20 
8. METHOD OF IXFECTIOX. 
The life history of the organisms of malaria and Texas fever natu- 
rally suggested that some insect was concerned in the transmission of 
the disease. On investigation it Avas found that the ticks appeared in 
the A^alleA^ about the last of February, but were inacth'e until the 
middle of March or first of April, the first cases of feA^er appearing 
about the last of March.' The ticks begin to diminish greatly in 
number from about June 1, and after the middle of July Axry few are 
seen; the cases of fever also begin to diminish about June 1, the latest 
date on which the disease has been known to occur being’ July 20. 
' Mosquitoes do not appear in the A'alley until after the first cases of 
feA^er develop, and remain some time after the last cases appear. 
Bedbugs and other house insects, I think, were well excluded, by the 
fact that there has neA’er been known an instance in which two cases 
occurred the same year in the same house. 
On a closer study of the cases of spotted (tick) feA'er it Avas always 
found that there was a historA' of tick bites about one week before the 
onset. In four cases there was a history of a single bite two, three, 
five, and seA^en days, respectiA^ely, before the initial symptoms'. The 
usual time between the bite and the onset of the feA^er is about seA’en 
daA’S. If the tick transmits the disease, it inaA’ be asked, WhA^ do not 
more persons become infected, and Avhy is the infection confined to 
the west bank of the Bitter Root RAer ? I think this may be answered 
bA" the A^ei’A^ obvious fact that the tick is unable to traAxd aiiA^ great 
distance, unless carried on some person or object. Again, it is A'ery 
unusual for a tick to bite a person and not be discoA'ered in a short 
while, and the result is the death of the tick. If, as in Texas feA^er, 
the deA’elopment of the parasite takes place in the female tick and the 
voung ticks transmit the infection, the A’ei’A^ small number of ticks 
which escape detection on persons explains the small number of infected 
ticks. Where do the female ticks get their infection ? I examined a 
recoA’ered case twenty -four days after discharge by the physician and 
had no trouble in finding the parasite in the fresh blood. This child 
had been out of doors for OA’er two weeks, and if a female tick (ticks 
were quite numerous near the house) had bitten her and escaped 
destruction the parasites in the blood taken in bA^ the tick would haAX 
undergone development and the young ticks, when hatched out, would 
be ready to infect prospectAe Auctims. 
AVhile the aboA'e facts and conclusions tend strongly to the belief 
that the ticks are necessarv for the transmission of the disease, the 
actual fact can not be proA’ed scientifically until carefully controlled 
experiments are made on nonimmune persons. 
