Pathogenesis 



593 



kept at 37 C., some of the colonies have a diameter of 2 to 3 

 mm. They are round in form, have an even contour, are 

 slightly raised above the surface of the agar-agar, and are 

 smooth and shining in appearance. On examining the 

 colonies by transmitted light, the center of each is seen to 

 be yellowish, while the periphery is bluish- white in color. 

 The same colonies by reflected light appear milky white in 

 color. Colonies on the surface of the agar-agar are found 

 to be no larger than hemp-seed after a couple of months 

 of cultivation. 



When kept at 25 C., no colonies become visible to the 



Fig. 173. Micrococcus melitensis (Muir and Ritchie). 



naked eye before the seventh day; at 37 C., before the 

 third or fourth day. 



Scarcely any growth takes place in gelatin, and no lique- 

 faction of the medium occurs. 



No growth takes place on boiled potato. 

 Plate cultures are not adapted to the study of the organism 

 because of its extreme slowness of growth: 



The thermal death-point given by Dalton and Eyre* is 

 57-5 C. 



Pathogenesis. The micro-organism is not pathogenic 

 for mice, guinea-pigs, or rabbits, but is fatal to monkeys 



* "Jour, of Hyg.," 1904, iv, p. 157. 

 33 



