COMPARATIVE STUDY OF THE COCCI 65 



to grow without air give abundant aerobic growths. 

 Therefore, for purposes of classification we have con- 

 sidered the study of the aerobic surface growth a suffi- 

 cient measure .of the relation to free oxygen, as well as 

 of general vigor. The five grades of surface growth 

 correspond to five grades of aerobiosis, including all 

 variations from forms which are anaerobic and faculta- 

 tively aerobic to forms which should be classed as strong 

 aerobes. 



Temperature relations. There are two points of special 

 importance which ought to be determined in studying 

 temperature relations — the optimum temperature and 

 the high death-point. The death-point at extreme low 

 temperatures is too indefinite to be attempted, and the 

 extreme limits of growth may be omitted as far less 

 important than the other two properties. 



For the determination of the optimum temperature 

 we first made a series of preliminary studies by com- 

 paring agar cultures grown at 10, 20, 37, 45, and 56 

 degrees. Two cultures grew better at 20 degrees, 18 

 developed equally well at 20 and 37 degrees, 22 showed 

 an optimum at 37 degrees, two grew equally well at 37 and 

 45 degrees, and four grew best at 45 degrees. These 

 conclusions refer only to the amount of growth, — color 

 production being generally most active at 20 degrees. 

 From these results we concluded that the information 

 to be gained by cultures grown below 20 degrees and 

 above 37 degrees would be scarcely commensurate with 



