302 MANUAL OF BACTERIOLOGY. 



about forty-eight hours, appearing as minute, whitish, trans- 

 lucent, circular growths. 



As a means of differentiation between the pneumococcus on the one hand 

 and the streptococcus on the other, Hiss* devised a medium consisting of 

 nutrient agar to which inulin is added. Hiss showed that the pneumococcus 

 ferments this substance in sugar free media, while streptococcus does not fer- 

 ment it. In fact there is a group of organisms morphoiogically and culturally 

 like the pneumococcus which do not ferment indulin. Ruedigerf has made 

 use of Hiss inulin agar for the isolation of the pneumococcus, and he gives the 

 following directions for its preparation and use: 



(a) Peptone (Witte) lo c.c. 



Agar-agar 15 c.c. 



Sugar-free broth (neutral) 1,000 c.c. 



Dissolve by boiling for one hour, adding water from time to time to com- 

 pensate for evaporation. Heat in the autoclave for 15 or 20 minutes, clarify 

 with egg, filter through cotton and rhake up to 800 c.c. with distilled water. 



(b) Dissolve 15 grams of pure inuUn in 200 c.c. of distilled water, mix this 

 solution with (a), add 20 of a 5 per cent, solution of litmus (Merk's highest 

 purity), tube and sterilize in the autoclave under 10 pounds' pressure for 15 

 minutes. Some stains of pneumococcus will not grow in this medium; it may 

 be improved by adding i c.c. of ascetic fluid to each tube before use. In 

 this medium the pneumococcus in 24 to 96 hours at 37° C. show red colonies 

 agiinst a blue background. 



Berryt concludes from her investigations that the pneumo- 

 coccus undergoes decided changes under artificial cultivation, 

 among others in its loss of power of fermenting inulin. These 

 changes may be permanent or they may return under favorable 

 conditions. The change in morphology is seen in a tendency 

 toward a streptococcus type. Loss of virulence is always 

 lost on artificial media, but is enhanced by passage through 

 animals. Berry concludes in regard to the inulin reaction that 

 too much reliance should not be placed upon it, and that a 

 negative result is not sufficient to exclude the pneumococcus, 

 particularly where the organism tested has been cultivated for 

 a long ti.me on artificial culture media. 



*Journ. Experimental Medicine. 1Q05, No. 7, p. 317. 

 ^Journ. Infectious Diseases. Vol. III., 1906, p. 317. 

 JBerry. Journ. Inject. Dis. Vol IV., 1907, pp. 93-107. 



