184 



BACTERIOLOGY OF THE EYE 



Pneumococci will only grow at a temperature over 22 C. ; their 

 optimum is 35 C. They require a faintly alkaline medium ; different 

 strains vary in their sensitiveness to acidity. The media must be 

 moist and not too old. On agar and blood- serum the colonies are 



seen as fine, clear, round 

 surface drops, faintly 

 opalescent in transmitted 

 light ; sometimes they are 



FIG. 30. SECRETION FROM A PNEUMOCOCCAL 

 CONJUNCTIVITIS. 



FIG. 31. PXEUMOCOCCAL Pus 

 FROM A RABBIT'S INOCU- 

 LATED CORNEA, SHOWING 

 INVOLUTION FORMS. 



minute elevations resembling colonies of Streptococci, but not so sharply 

 marked. In a few days the colonies may become practically invisible. 

 Single colonies of Pneumococci on moist media may be so slightly raised 

 above the surface that their presence can only be demonstrated by ex- 

 amining the surface moisture which has been removed with a platinum 



FIG. 32. VARYING APPEARANCE OF PNEUMO- 

 COCCI ON GLYCERINE AGAR (UHTHOFF 

 AND AXENFELD). 



c, Elongated bacillary forms. 



FIG. 33. CHAIN FORMATION IN 

 BOUILLON AND ON GLYCERINE 

 AGAR (UHTHOFF AND AXEN- 

 FELD). 



loop. (In order to increase the bacterial contents of such material, 

 Romer has recommended that it be first put into a mixture of fluid 

 blood-serum of a young rabbit with one-third its volume of glycerine.) 

 It often occurs that many agar media which are otherwise quite useful 

 cannot be used for Pneumococci. When obtained from the conjunctiva 



