TEXAS FEVER 121 



spleen, two to three per cent, in blood of left heart and lung, 

 very few in marrow of sixth rib and in skeletal muscles. At post- 

 mortem examination the corpuscles have a rounded form. Free 

 forms of the parasite were not observed by Smith and Kilbourne 

 in the peripheral blood; but were found in the blood from the 

 heart. 



In the mild type of the disease the parasites are as a rule in- 

 visible in fresh blood, rarely one may be observed on the edge 

 of a corpuscle as a pale spot about 0.5/x in diameter. In prepara- 

 tions stained by alkaline methjdene blue, the}' appear as round 

 coccus like bodies 0.2-0.5/a in diameter, situated within red cor- 

 puscles. Ordinarily but one is found in a corpuscle. In many cases 

 division of the parasite was observed into two (Smith and Kil- 

 bourne). This form of the parasite is characteristic of the mild 

 autumnal form of the disease. Smith and Kilbourne found that 

 three groups of animals have this type of the disease, (1) those 

 exposed late in the season (October and November), (2) those 

 that have passed through an acute attack earlier in the season; 

 the second attack or relapse in October or November, (3) those 

 that contract the mild form during or previous to the season of 

 the acute form of the disease. In groups 1 and 2 the disease is 

 mild and may pass unnoticed. Infected corpuscles appear in the 

 blood as the number of red corpuscles begin to diminish and dis- 

 appear as the number of red corpuscles begin to increase. Rarely 

 a corpuscle containing a large pyriform parasite is found. A few 

 animals (group 3) showed infected corpuscles several weeks before 

 fever appeared, the disease changing into the acute type with 

 pyriform parasites instead of those of the coccus form. In the 

 mild type of the disease there may be five to 50% of the red cor- 

 puscles in the circulatory blood infected for a period of one to 

 five weeks. 



Changes in the blood. — There is a progressive loss of red cor- 

 puscles until an extreme oligocythemia is reached. In some cases 

 as high as 1,000,000 corpuscles have been lost per day. In many 

 cases the count of red corpuscles decreases nearly to 1,000,000 

 to 2,000,000 per cmm. Counts, taken from Smith and Kilbourne, 

 are given of two cases, — one fatal, the other recovering. With 

 the reduction in the number of corpuscles marked changes are 

 found in their size and staining. When the number of corpuscles 



