21 
interpretations, this ‘‘working’ hypothesis” was most natural, and 
thoroughh" justified, and they show (see above, p. 13) that they thor- 
oughly understood that certain experimental studies were called for 
in connection with this theory. 
Arriving in Missoula this season (1901), it required but a few da}^s 
to see the zoological points involved and to understand that an experi- 
ment with ticks and rabbits was the most important work to be con- 
sidered, especially as the strictl}^ medical side of the disease was less 
important to me than the zoological features, leading to its prevention. 
As stated above (p. 19), 1 injected blood from three patients into rab- 
bits, but failed to convince myself of the presence of any Plrojolasma 
in the inoculated rabbits. Not being able, so far as 1 could see, to 
transmit the disease to rabbits, my tick experiment on these rodents 
had no further purpose. 
Quite a number of points have been advanced in support of the tick 
theory. I have considered these arguments in detail, from the zoo- 
logical point of view, and have prepared a lengthy discussion covering 
them. There are, however, so many points of difference of findings 
and opinion between the supporters of the tick theoiy and m}^self that 
three of my friends, to whom I submitted this manuscript for criticism, 
have felt that the discussion might be open to a possible interpretation 
which was most foreign to m}^ mind. On this account I have omitted 
from the manuscript all points except the following: 
8. All of the patients, 23, coming under observation during this investigation had 
been bitten by ticks. In 14 cases a history was given of severe tick bites two to 
eight days before the onset of the disease. In a number of other cases an apparently 
clear history of severe tick bites immediately preceding the onset of “spotted fever” 
was vouched for by the recovered patients or their friends. — Wilson and Chowning, 
1904a, page 52. 
In connection with this point it will be necessaiy to refer to some of 
the cases. 
It must be admitted as very striking that so man}- cases of “spotted 
fever” have been preceded by a tick bite, still in a region where it is 
almost exceptional to go into the woods or fields without being bitten 
by ticks, it is not . excluded that this is a mere coincidence. On 
account of this latter possibilit}", the greatest- reserve should be exer- 
cised in order not to draw a “post hoc, propter hoc” conclusion. 
As the valley was thoroughly worked up this }"ear (1904) upon the 
subject of ticks and as people kept a close lookout for anything 
resembling a tick or a tick bite, negative evidence obtained from the 
cases of 1904 is of more value than that obtained prior to 1903. Let 
us therefore turn to a consideration of the cases which occurred in 
1904: 
Case 1 . — Mr. R., patient of Doctor Buckley; fatal case. History of 2 tick bites in 
right inguinal region, each surrounded by an undurated inflammatory zone; patient 
was apparently infected in Grant Creek, namely, outside of the regular district. 
