9 
5. AGE. 
Persons from 15 to 50 years of age more often contract the disease, 
as during- that period they are more actively engaged in outdoor work. 
The vouno-est case was 18 months and the eldest 71 years old. 
0. SEX. 
In 121 cases, 76 were males and 15 females, the ditference being 
probably due to the greater liability to exposure of men on account 
of occupation. 
7. THE PARASITE. 
In the spring of 1902 Dr. A. P. Longeway, secretary of the Mon- 
tana State Board of Health, engaged the services of Drs. L. B.AYilson 
and IV. M. Chowning, of the Universit}^ of Minnesota, to investigate 
the ‘‘spotted (tick) fever” then prevailing in the Bitter Root Talley. 
These gentlemen published the results of their work in the Journal 
of the American Medical Association July 19. 19U2, and in the 
report of the Montana State Board of Health for 1901-2. 
Surgeon-General IV^mian, of the Marine-Hospital Service, detailed 
Surg. J. O. Cobb to also investigate the disease, and his report was 
published in the Public Health Reports, volume 17. Xo. 33, August 
15, 1902. 
The same year Dr. F. F. lVesl)rook, of the L^niversiH of Minne- 
sota, visited Missoula and conlirmed the tindings of Drs. Wilson and 
Chowning. His report will be found in the Ihennial report of the 
Minnesota State Board of Health for 19(M-2. 
IVilson and Chowning noticed ovoid intracorpuscular bodies in 
stained preparations of the blood from their earlier cases. They did 
not determine the character or signihcance of these bodies until the}^ 
examined the fresh blood of case Xo. 91, when they found ovoid intra- 
corpuscular bodies showing amoeboid movements. These observations 
the}^ confirmed in all the later cases which they examined. To IVilson 
and Chowning, then, belongs the credit of discovering a parasite which 
is yevy jjro7jaNi/ the cause of spotted (tick) fever. 
Parasites in the red-blood cells are rather common in the animal 
kingdom. The two which I desire to mention especially are those of 
malaria and of Texas cattle fever. The parasite found in the red- 
blood corpuscles of persons suffering from spotted fever apparently 
lies between these two. Unlike most malarial parasites, it is not pig- 
mented, but, like them, it shows amoeboid movements, thus differing 
from the Pyrosoma higeminum^ which is nonpigmented and without 
motion. Again, one form of the parasite found in spotted fever is 
arranged in pairs in the red- blood cells, closely resembling the double 
form of Pyrosoma higeminura. 
