NOT DESCRIBED IN SECTIONS V. AND VI. 421 



old cultures kept at the room temperature the cells may be oval or 

 elongated. 



Biological Characters. An aerobic, non-liquefying micro- 

 coccus. Does not stain by Gram's method. Grows best in nutrient 

 agar. In stab cultures no growth is seen for several days. "At 

 length the growth appears as pearly-white spots scattered around the 

 point of puncture and minute, round, white colonies are also seen 

 along the course of the needle track"; these increase in size, and 

 after some weeks a rosette-shaped growth is seen upon the surface, 

 and the growth along the line of puncture has a yellowish-brown 

 color. At the end of nine or ten days, at 37 C., some of the colonies 

 on the surface of nutrient agar are as large as No. 4 shot; by trans- 

 mitted light they have a yellowish color at the centre, and the per- 

 iphery is bluish-white; by reflected light they have a milky- white 

 color. At 25 C. colonies first* become visible at the end of about 

 seven days, at 37 C. in three to four days. Does not grow upon 

 potato. Very scanty growth upon nutrient gelatin at 22 C. at the 

 end of a month. 



This micrococcus has usually been described as non-motile, but 

 Gordon has demonstrated that it has from one to four flagella, which 

 are difficult to demonstrate by the usual staining methods. 



Pathogenesis. Pathogenic for monkeys, which suffer from fever 

 as a result of subcutaneous inoculations and usually die in from thir- 

 teen to twenty-one days. The spleen is found to be enlarged and 

 contains the micrococcus. Not pathogenic for mice, guinea-pigs, 

 or rabbits. 



In man the micrococcus is found in large numbers in the spleen, 

 which is greatly enlarged. 



Widal Reaction. The blood serum of patients suffering from 

 Malta fever and of individuals who have recently recovered from the 

 disease causes the agglutination of Micrococcus melitensis in recent 

 cultures. According to Wright and Smith this reaction may be 

 manifested a year after recovery. Dilution of 1 : 1000 will in ex- 

 ceptional cases give a distinct agglutinating effect. 



