428 BIOLOGY OF THE LABORATORY MOUSE 



erythrocytes typically stain more intensely than those free in the plasma. 

 Other stains, such as hemotoxyhn, cresyl-blue, and azure II, stain them 

 poorly if at all. No motility has been noted by darkfield examination. 



E. dispar (32, 33, 37, 298), found in Mus minutus, Arvicola arvalis, and 

 Microtus pennsylvanicus, is predominantly discoid in its morphology but is 

 differentiated from E. coccoides chiefly by its animal pathogenicity. E. 

 coccoides does not infect Mus minutus and Arvicola arvalis, whereas E. dispar 

 fails to infect rats and white mice. 



Attempts to cultivate the organism have in most instances been unsuc- 

 cessful. Dinger (52) has reported cultivation on a coagulated egg medium in 

 Locke's solution. Although no ring forms were seen in the culture, inoculation 

 of a splenectomized mouse after three transfers produced the typical disease. 



Grahamella infection in mice. — In 1905, Graham-Smith (91) described a 

 new type of organism situated within the red blood cells of the mole. The 

 organisms stained blue with Giemsa's dye, and appeared as long or short, 

 curved, irregular rods, occasionally wedge- or club-like in shape. Dark 

 chromatin masses sometimes occurred at one or both ends of the rods. The 

 only pathological changes found were areas of focal necrosis in the livers of 

 the most severely infected animals. This observation was soon confirmed 

 by Thomson (272), who further noted that the bodies were non-acid-fast and 

 gram-negative. He could not transmit them to the rabbit, guinea pig, rat, 

 or mouse. Brumpt (31) in 191 1 proposed the generic name of Grahamella for 

 these organisms. Similar structures have subsequently been found in the 

 erythrocytes of the common laboratory and wild mice and related species 

 (212, 45, 21, 34, 36, 234). Classification of these organisms has not been 

 settled (31, 96, 141, 36), and probably will not be established until cultiva- 

 tion has been achieved. 



The incidence of the condition in mice may be high (34) , but no adequate 

 statistics are available. Infection does not result in clinically apparent 

 disease or in recognizable pathological changes. Splenectomy is without 

 pronounced effect (34). Examination of the blood of infected animals 

 reveals that the organisms are generally restricted to the erythrocytes 

 (45, 298) and may appear or disappear irregularly in a given animal (36). 

 The percentage of affected cells is low, even in heavy infections (34, 2, 122), 

 but the number of organisms in such cells is usually high, varying from about 

 5 to 20 or 30. The grahamellae differ from the bartonellae and eperythrozoa 

 in being more or less uniformly spaced within the erythrocyte. They are 

 considered to be non-pathogenic (2, 122), and attempts to transmit them to 

 other animals have failed (141, 36), although final evaluation must await 



