PNEUMOCOCCUS 



147 



Cultures. On gelatine plate it produces very minute colonies 

 after quite a length of time. On glycerine agar it grows better, 

 but the colonies are small and difficult to see. In both, the colo- 

 nies are whitish, with a pearly lustre. On blood serum it grows 

 in transparent colonies. On blood agar the colonies are tiny and 



FIG. 37. Diplococcus pneumonias, from the heart's blood of a rabbit. X 

 1,000. (Frankel and Pfeiffer.) 



of a greenish color, lying on a brown base due to production of 

 methemoglobin. In bouillon it grows feebly, with a whitish 

 sediment, and in the form of chains. Here the growth is inhibited 

 by the products of its own metabolism, i.e., lactic acid. If this 

 is neutralized by putting chalk into the bouillon the growth 

 becomes luxuriant and the bouillon becomes thick. On potato it 



