952 DISEASES CAUSED BY FTLTRABLE VIRUS 



the ears are often inflamed, and in white rabbits thrombosed vessels in 

 the ears can be seen. 



Monkeys are susceptible arid usually die at the end of seven days. 



Etiology. The lesions in the blood vessels in animals and man 

 indicate the presence of the causative agent in these locations. Wol- 

 bach 49 who studied histological material from this point of view, 

 found within the endothelial cells of the vascular lesions, in smooth 

 muscle cells of the media, as well as occasionally in detached en- 

 dothelial cells present in thrombi extremely minute small "diplo- 

 coccmlike" organisms. These, he states, stain with eosin-methylene- 

 blue. The organisms were best stained with Giemsa solution with 

 which they appear as slender pale blue rods. There was a distinct 

 contrast between the appearance of these organisms and that of 

 accidentally introduced bacteria, in that the shape of the former 

 was vaguely outlined and less sharp than that of the bacteria. 

 Ricketts 51 had described similar organisms in the blood of man and 

 guinea-pigs which he described as "lanceolate chromatin-staining 

 bodies" in sets of two, a small amount of eosin-staining substance 

 appearing between the two individuals. The same organism was 

 seen in smears of the intestinal contents of ticks. Wolbach has also 

 seem them in smear preparations made from the eggs of infected 

 ticks. 



In the case of these bodies, as well as in those described in 

 connection with typhus fever, definite conclusions cannot be reached 

 as yet. A careful analysis of the entire subject will be found in 

 Wolbach 's paper of 1919. The organisms, if they are organisms, 

 probably belong to the class of Rickettsia. They have not been 

 cultivated. 



The prevention of the disease depends largely upon the preven- 

 tion of tick bites and the suppression of the wood tick, a matter 

 which is very difficult in the countries in which they abound. 



51 Eicketts, Jour. A. M. A., 47, 1906, 33 ; Jour. A. M. A., 47, 1906, 358 ; Jour. 

 A. M. A., 47, 1906, 1067; Jour. A. M. A., 49, 1907, 1278; Jour. Infec. Dis., 4, 

 1907, 141; Jour. A. M. A., 49, 1907, 24; Trans. Chicago Path. Soc., 1907; Jour. 

 Infec. Dis., 5, 1908, 221; Jour. A. M. A., 52, 1909, 379; Medical Record, 76, 

 1909, 842. 



