INFECTIOUS DISEASES OF MICE 431 



an "unhealthy, bristhng" appearance. The tendency of the infection 

 seemed to be towards recovery. Spread occurred by contact. 



Examination of hairs from the periphery of the lesions after treatment 

 with potassium hydroxide revealed chains of spores in the medulla of the 

 hairs. Individual spores were oblong or square with rounded corners, and 

 measured 3 to 6 ^t in diameter. After about 3 days of cultivation on 

 Sabauraud's maltose agar, tufts of growth appeared, enlarging to form white 

 disks with a chalky, central opaque mass and a large powdery areola. After 

 subculture, the margins presented uneven, ray-like prolongations and the 

 reverse side of the colonies was brownish-red in color. The disease was 

 reproduced experimentally by rubbing cultures into depilated and scarified 

 skin. Further studies on transmission and immunity were terminated 

 because of infection in the laboratory attendants. Ringworm of a different 

 type was discovered in 4 of several hundred mice from a different stock, 

 housed in another department of the laboratory. 



Spirochetosis and Leptospirosis in Mice 



Spiral organisms are not of significance as the etiological agents of fatal 

 disease in mice. They are of importance, however, because mice may be 

 carriers of the organisms which, in turn, may manifest themselves during the 

 course of experimental or diagnostic procedures. Spirochetes have been 

 found in spontaneous and transplanted tumors of mice (27, 294, 86, 41), and 

 in the blood of animals inoculated with trypanosomes (334, 30, 99). The 

 identity of these strains has not been estabUshed satisfactorily and various 

 names have been applied to them: Spirochaeta miiris or BorreUa muris (22), 

 S. mlcrogyrata var. Gaylordi, 5. laverani, S. naganophilia, and others. Some 

 of the organisms encountered probably were identical with Spirillum minus; 

 others may have been saprophytic intestinal forms, or strains introduced by 

 contamination of blood or tissue used for inoculation. Two forms, namely 

 Spirillum minus and Leptospira icier ohemorr ha giae, are worthy of further 

 discussion because of their relationship to human disease. 



Spirillum minus. — This organism, which was first found in a rat by 

 Carter in 1887, has subsequently been shown to cause one type of rat-bite 

 fever. It is identical with Spirochaeta morsus muris, and probably with 

 5. laverani and S. muris. Varying figures have been given for the occurrence 

 of the organism in laboratory (221) and wild mice. It has been found in the 

 blood of one of two field mice (38), in the mammary glands of 31 of ^^ 



