54 RELATIONSHIPS OF THE COCCACE^E 



except that agar always has markedly more growth, 

 and potato often none. An organism producing abun- 

 dant chromogenic growth on agar will give good growth 

 and some pigment on the other media. The streptococci 

 on the other hand form a restricted and veil-like growth 

 on serum and Nahrstoff, and usually no growth on 

 potato. In other words, with the organisms studied 

 by us, Nahrstoff agar, serum, and potato showed no 

 specific characteristics other than those due to feeble- 

 ness of growth. Blood serum may be useful in other 

 groups to show a special type of liquefaction, but in a 

 preliminary study of 50 of our cultures we never found 

 this to occur; and it has been very rarely and doubtfully 

 recorded in published descriptions of the Coccaceae. In 

 twenty-five out of fifty cultures inoculated on potato no 

 growth occurred, and in no case have we observed dis- 

 coloration. These media have therefore been omitted; 

 and the action is in accordance with the conclusions of 

 the Committee on Standard Methods (1905) in consider- 

 ing their value for general diagnostic use. 



Nutrient broth. In the group of the cocci we have not 

 found that any information of definite value could be 

 derived from a study of broth cultures. None of the 

 cultures examined form a surface pellicle or produce 

 any characteristic odor. There remain to be observed 

 only two features — turbidity and sediment — which, in 

 our judgment, depend directly on other properties, such 

 as the general vigor of growth and the size of the cell 



