114 THE PATHOGENIC MICROCOCCI. 



cultures showing growth only at the end of several days. 

 The colonies appear as pearly-white spots scattered around 

 the points of puncture, and as minute round white colonies 

 along the course of the needle-track, which increases in size, 

 and after some weeks a rosette-shaped growth is seen upon 

 the surface. Along the line of puncture the growth assumes 

 a yellowish-brown color. 



At 35 C. the colonies become visible only at the end of 

 seven days ; at 37 C. they are seen in three or four days. 



It does not grow on potato. 



Pathogenesis. This micrococcus is not pathogenic for mice, 

 guinea-pigs, or rabbits, but subcutaneous injections in mon- 

 keys have induced fever, the animal dying in from thirteen 

 to twenty-one days. At the autopsy the spleen is found 

 enlarged and contains the micrococcus. 



In man the micrococcus is found in the enlarged spleen in 

 great numbers. 



Agglutination. Recent cultures of Micrococcus melitensis 

 are agglutinated by the blood-serum of patients suffering 

 from Malta fever, and occasionally with some this reaction 

 is manifested a year after recovery. This agglutinating effect 

 has been obtained in a dilution as high as 1 in 1000. 



QUESTIONS. 



Give the several names of the Micrococcus pneumonix ; by whom and how 

 was it discovered? 

 Where is it found ? 

 What is its morphology? 

 How does it stain ? 



How does it behave with regard to oxygen ? 

 Does it possess flagella? 

 Is it motile ? 



In what media and at what temperature does it grow? 

 What is its thermal death-point? 



How does it grow in bouillon, gelatin, agar, blood-serum? 

 What protects animals from inoculations with virulent cultures? 

 What animals are susceptible? 



What are the effects of subcutaneous and intrathoracic injection of animals? 

 What is the synonym of the pneumococcus? 

 Is it a coccus ? 

 By whom was it discovered ? 

 Where is it found ? 

 Give its morphology. Its staining properties. Give its principal bio- 



