THE GENUS SARCINA 233 



eleven strains corresponded with Aurococcus rather than 

 with Swcina. They were generally Gram-positive, acid- 

 forming, actively liquefying forms. We are, therefore, 

 inclined to consider orange packet formers as exceptional 

 aurococci, which grow in packets, rather than as members 

 of the genus Sarcina, which have acquired the biochem- 

 ical characters of the parasitic genus. Other aberrant 

 forms allied to this type are S. casei and S. butyrica, 

 both isolated by Migula from cheese. These organisms 

 are characterized by slimy growth masses and by the 

 production of a strong acid reaction in milk. In the 

 absence of further evidence they may be considered as 

 exceptional variants of S. flava which have acquired cer- 

 tain fermentative powers. 



The second important type among the sarcinas differs 

 from the first by possessing the power of reducing nitrates. 

 It corresponds in general, therefore, to M. citreus. Thirty- 

 four of our one hundred and thirty-seven strains belong to 

 this type. As with Aur. mollis and M. citreus, some cultures 

 form ammonia, and some, nitrites, while a few show both. 

 All are for the present included under a single type. In re- 

 gard to their action on gelatin, too, these organisms resemble 

 Aur. mollis and M. citreus. Most of them liquefy quite 

 actively, but a few strains (nine of our thirty-four) fail to 

 produce liquefaction. As in the previous cases, we have 

 felt it best to recognize the more numerous liquefying 

 form as a distinct type center, and to leave the question 

 of the existence of another type center, of non-liquefying 



