Generic Characters in the Coccaceae 151 



Grow well on artificial media, producing abundant surface growths. 

 Planes of fission often at right angles; cells aggregated in groups, 

 packets, or zooglca masses. 



Genus 3, Micrococcus (Hallier) Cohn: Facultative parasites or 

 saprophytes. Cells in plates or irregular masses (never in long 

 chains or packets). Acid production variable. 



Genus 4, Sarcina (Goodsir) : Saprophytes or facultative para- 

 sites. Division under favorable conditions in three places, pro- 

 ducing regular packets. Sugars as a rule not fermented. 



Genus 5, Ascococcus (Cohn): Generally saprophytic and cells 

 imbedded in large, irregularly lobed masses of zooglea, in process 

 of carbohydrates. Acid usually formed. 



In the present investigation we have included representatives 

 of only three of these genera. The organisms belonging to the genus 

 Diplococcus do not lend themselves to comparative study on account 

 of the difficulty with which they may be cultivated, and representa- 

 tives of the genus Ascococcus occur, if at all, only in certain peculiar 

 habitats. We have limited our study to forms which can be found 

 in ordinary environments, and which may be cultivated on ordinary 

 laboratory media; that is, to the genera Streptococcus, Micrococcus, 

 and Sarcina. 



We have procured our cultures in approximately equal propor- 

 tions from five different sources: from the internal tissues of the dis- 

 eased human body, from the outer surfaces of the normal human 

 body, from water, from earth, and from air. Cultures classed under 

 Habitat I, the tissues of the diseased body, were obtained chiefly 

 from the Boston City Hospital, and the Massachusetts General 

 Hospital, of Boston, and the Johns Hopkins Hospital, of Baltimore. 

 We desire to express our cordial thanks to the bacteriologists of 

 these institutions for their courtesy in furnishing us with these organ- 

 isms. The cultures classed under Habitat II, surfaces of the normal 

 body, were obtained from three sources. A considerable number 

 were isolated from serum tubes, received by the Boston Board of 

 Health for diphtheria diagnosis. In this connection we desire to 

 acknowledge the courtesy of the bacteriologists of the Board. Only 

 those cultures which gave a negative diagnosis for diphtheria were 

 used. Another series of cocci was isolated from the hands of students 



