10 
In studies upon the cause of spotted (tick) fever I had the opportu- 
nity of examining the blood, both fresh and stained, in a number of cases. 
Two cases were in hospital in Missoula, and daih^ examinations were 
made. In the fresh blood a few cells were found to contain parasites. 
Three forms were seen. The most common was a single ovoid body, 
retractile, situated within the cell, usualh^ near its edge. lYhen the 
slide is warmed this bod}" possesses the power of projecting quite rap- 
idly pseudopodia and a slight change of position. This form, which 
is apparently an early or young form, is about 1.5 to 2 micra in 
length, and 0.5 to 1 micron in width at its widest part. It closely 
resembles the earliest intracorposcular parasites of jestivo-autumnal 
malaria. (See PI. II, figs, d, 5.) 
Another form, not so common, was larger, being about 2 to 2.5 by 
I to 1.5 micra, larger at one end and showing in the larger end a dark 
granular spot; this was also amoeboid, (See PI. II, fig. 6.) 
The third form noted was arrang'ed in pairs, distinctly pyriform, 
with the smaller end approaching, and in two cases a fine thread unit- 
ing the small ends was seen. Motion was not observed in this form, 
but the spot mentioned in the second form was seen. (See PI. II, 
%• ^ 
Great difficulty was experienced in staining the organism. A num- 
ber of stains were used, but the most satisfactoiy results were 
obtained by the use of lAright’s stain, followed by Loeffler’s blue. 
Carbolized Unna’s polychrome methylene blue also gave fair results, 
heat fixation at 120° C. for twenty minutes being used. 1 was unable 
to find the paired forms in stained preparations, though Drs. Wilson 
and Chowning informed me that they had no difficulty in doing so. 
By a reference to PI. I, figs. 1 and 2, it will be seen that the parasite 
takes the stain more deeply at one end and is onh" faintly outlined in its 
periphery. Sometimes it has onW a central stained spot surrounded 
by a clear unstained space. (See PL I, fig. 3.) 
The parasites are never found in veiy large numbers, it being usu- 
ally necessary to search several fields of the slide to find one. Some- 
times they occur in groups, two or three infected cells being found in 
one field. In both fresh and stained preparations extracorpuscular 
bodies closeW resembling the small single intracorpuscular form were 
seen. I was unable to definiteW decide the character of these bodies, 
but am strong!}" inclined to think that they are the young form of the 
parasite which has not }"et invaded the red cells. 
I had the opportunit}^ to examine the fresh and stained blood from 
cases in the Bitter Eoot Valle}^ of smallpox, typhoid fever, measles, 
scarlet fever, rheumatic fever, pneumonia, pernicious anemia, some 
surgical cases, and from healthy persons, but did not note in an}" of 
them any bodies, either intra oi* extra corpuscular, resembling in any 
