CHAPTER VI. 



THE GENUS ASCOCOCCUS. 



The generic name Ascococcus has had a long and 

 varied history. It was first used by Billroth (1874) in 

 his work on Coccobacteria septica, but was not applied by 

 him to a species or a genus. Billroth believed that un- 

 limited pleomorphism prevailed among the bacteria, and 

 his "Ascococcus" was merely the zooglcea form in general, 

 which he thought all bacteria might assume under proper 

 conditions. Cohn (1875), who had a more accurate con- 

 ception of the constancy of bacterial types, established the 

 name as a generic one. He defined the genus by mor- 

 phological characters alone, and included in it all forms 

 showing small spherical cells imbedded in lobed masses 

 of gelatinous matter. The species on which he founded 

 the genus, Asc. Billrothii, appeared in his laboratory, form- 

 ing a zooglcea layer on the surface of an ammonium 

 tartrate culture solution. Under this condition it devel- 

 oped an intense cheesy (butyric acid) odor and produced 

 a strongly alkalin reaction. No coccus has since been 

 found which will grow in such a manner on so simple a 

 medium; and it seems probable that Cohn was actually 

 working with a bacillus rather than a coccus. Many of 



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