COMPARATIVE STUDY OF THE COCCI 53 



1904); but even with them it varies markedly with the 



medium used for cultivation. We cultivated certain 



selected organisms in broth at 20 degrees and at 37 



degrees, on nutrient gelatin, acid gelatin, alkalin gelatin, 



anaerobic gelatin, and Nahrstoff-Heyden agar; and 



examined them at intervals by Welch's staining method. 



In every case capsules^ were apparent at some stages, 



being most strongly developed in old cultures and on 



poor media like the Nahrstoff agar. This character 



has not seemed to us of sufficiently promising diagnostic 



value to be included in routine examinations outside 



the genus, Diplococcus. 



Involution and degeneration forms. In numerous 



examinations of old cultures we found no involution 



forms of special significance. As noted above, swollen 



and oval cells are more apt to occur in old cultures of 



cocci, but they are not sufficiently definite to warrant 



record. 



Cultural Characteristics. 



In this study we necessarily included only those 

 tests which reveal definite and independent variable 

 characters. Most of the commonly observed cultural 

 characteristics are the secondary results of a few funda- 

 mental properties, which can be observed on one medium 

 as well as on several. For this reason we have eliminated 

 a number of the ordinary media from our routine. 

 The general character of the growth is approximately 

 the same on agar, blood serum, potato, or Nahrstoff, 



