PNEUMONIA. 283 



solution beyond the neutral point determined with rosalic 

 acid, to each liter. The agar-agar is first streaked with 

 sterile rabbit's blood, then inoculated. The cultures are 



\'\c. 62. — Diplococcus pneumoniae : colony twenty-four hours old upon gelatin ; 

 x 100 (Frankel and Pfeiffer). 



kept at 37. 5 C. Not only is this true, but ordinarily 

 they seem to be unable to accommodate themselves to a 

 purely saprophytic life, and unless continually trans- 

 planted to new media die in a week or two, sometimes 

 sooner. 



Kinyoun recommended to the writer that virulence 

 could be retained for a considerable time by keeping 

 blood from an infected rabbit, in a hermetically sealed 

 glass tube, on ice. This plan seems to work admirably 

 if the blood is not kept too long. 



The colonies which develop at 24 C. upon 15 per 

 cent, gelatin plates are described as small, round, cir- 

 cumscribed, finely granular white points which grow 

 slowly, never attain any considerable size, and do not 

 liquefy the gelatin (Fig. 62). 



If, instead of gelatin, agar-agar be used and the plates 

 kept at the temperature of the body, the colonies which 



