478 BACTERIOLOGY. 



quently exceed their fellows greatly in size, especially 

 in old cultures, when this may be considered to be the 

 result of involution forms. (See Figs. 61, 62, 63, and 

 64.) 



They stain readily by aniline colors and by Gram's 

 method. 



FIG. 63. FIG. 64. 



?TT> 



T#\v?<& 



..'jj^fv^,* 



v^^i^'l 



Streptococci from solidified serum cul- Streptococcus growing in long 

 ture appearing mostly as diplococci. chains in bouillon culture. X 1000 

 X 1000 diameters. diameters. 



Biological Characters. Streptococci grow readily in 

 various liquid and solid culture media. The most 

 favorable temperature for their development is from 

 30 to 37 C., but they multiply freely at ordinary 

 room- temperature 18 to 20 C. They are faculta- 

 tive anaerobes, growing both in the presence and ab- 

 sence of oxygen. 



Growth on Gelatin. Tubes of gelatin which have 

 been inoculated with streptococci by puncture with the 

 platinum needle show on the surface no growth beyond 

 the point of entrance. In the depth of the gelatin on 

 the second or third day a distinct, tiny band appears, 



