352 BACTERIA PATHOGENIC TO MAN 



best fluid medium for the growth of the pneumococcus is Marmorek's 

 mixture, consisting of bouillon 2 parts and ascitic or pleuritic fluid 1 

 part. In this fluid pneumococci grow well, and cultures when preserved 

 in a cool place and prevented from drying retain their vitality and also 

 their virulence for a number of weeks. Lambert has found cultures 

 in this medium alive and fully virulent after eight months. 



Loeffler's blood-serum mixture is a good, solid tube medium for 

 making cultures, and is very convenient and useful at autopsies. One- 

 and-one-half per cent, fluid nutrient agar mixed with one-third its 

 quantity of warm ascitic fluid makes an excellent plate medium. 



Hiss SERUM MEDIA WITH AND WITHOUT INULIN. -These are very 

 useful. The inulin is fermented by typical pneumococci with coagula- 

 tion of the serum. While most streptococci fail to ferment the inulin. 

 This medium is, therefore, of considerable diagnostic value, 



Nutrient agar, with fresh rabbit blood smeared over it makes an 

 excellent medium for growth, but prevents the development of agglu- 

 tinable substance. On this medium, in a moist atmosphere at 36 C., 

 the cultures retain their viability and virulence for rabbits for months, 1 



CALCIUM BROTH WITH OR WITHOUT DEXTROSE. This medium has 

 proven of great value for the propagation of cultures where agglutina- 

 tion tests are to be carried out. The addition of a small piece of 

 marble to each tube of broth is the most satisfactory way of preparing 

 it. Marble broth for this purpose was suggested independently by 

 Bolduan and Hiss. 



RESISTANCE TO LIGHT, DRYING, AND GERMICIDAL AGENTS. On 

 artificial culture media the pneumococci tend to die rapidly. This is 

 partially due to the acid produced by their growth. In sputum they 

 live much longer. 



Pneumonic sputum attached in masses to clothes, when dried in the 

 air and exposed to diffuse daylight, retains its virulence, as shown by 

 injection in rabbits, for a period of nineteen to fifty-five days. Exposed 

 to direct sunlight the same material retains its virulence after but a 

 few hours' exposure. This retention of virulence for so long a time 

 under these circumstances is accounted for by the protective influence 

 afforded by the dried mucoid material in which the micrococci were 

 embedded. Guarnieri observed that the blood of inoculated animals, 

 w r hen rapidly dried in a desiccator, retained its virulence for months; 

 and Foa found that fresh rabbit blood, after inoculation and cultivation 

 in the incubator for twenty-four hours, when removed at once to a cool, 

 dark place, retained its virulence for sixty days. There a^re many con- 

 ditions, therefore, in which the virulence of the micrococcus is retained 

 for a considerable length of time. To germicidal agents pneumococci 

 are very sensitive. The fine spray expelled in coughing and loud speak- 

 ing soon dries so completely that no pneumococci usually survive after 

 two hours. The same is true for dust that remains suspended in the air. 



1 The green color produced by all pneumococci in blood-agar media, and showing especially well 

 in poured blood-agar plates is not diagnostic of this organism, as some strains of streptococci produce 

 .just as intense a green. 



