Generic Characters in the Coccaceae 159 



strongly developed in old cultures and on poor media like the 

 Nahrstoff agar. This character has not seemed to us of suflicient 

 diagnostic value to be included in our routine examinations. 



Involution and degeneration jorms. — In numerous examinations 

 of old cultures we found no involution forms of special significance. 

 As noted above, swollen and oval forms are more apt to occur in old 

 cultures of cocci, but they are not sufficiently definite to warrant 

 record. 



4. Cultural Characters. 



In a study of this sort we have necessarily included only those 

 tests which reveal definite and independent variable characters. 

 Most of the commonly observed cultural characteristics are the sec- 

 ondary results of a few fundamental properties which can be observed 

 on one medium as well as on several. For this reason we have elimi- 

 nated 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, except that agar has always markedly 

 more growth and potato often none. An organism producing 

 abundant chromogenic growth on agar will give good growth and 

 some pigment on the other media. The streptococcus growth (>n 

 agar gives restricted and veil-like growth on serum and Nahrst^ tf, 

 and usually no growth on potato. In other words, NahrstolT agar, 

 serum, and potato are simply poorer media than agar, and sh'nv no 

 specific characteristics other than those due to feebleness 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 is nowhere recorded in pubhshed 

 descriptions of the Coccaceae. In 25 out of 50 cultures grown on 

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

 coloration. These media have therefore been omitted. This action 

 is in accordance with the conclusions of the Committee on Standard 

 Methods (1905), in considering 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 forms studied form a surface pel- 

 licle or produce any characteristic odor. There remain to be ob- 

 served only two features — turbidity and sediment — which in our 



