CHAPTER XT. 



THE GENUS SARCINA. 



A PECULIAR microscopic plant, made up of colorless 

 spherical cells, arranged in packet groups of eight, was 

 described by Goodsir in 1842 (Goodsir, 1842) and named 

 by him Sarcina ventriculi. The generic name Sarcina 

 has since been applied to all cocci which show this cell 

 grouping. Migula (1900) defines the genus by the pres- 

 ence of spherical cells, which divide in three planes at 

 right angles to each other, non-motile and lacking spores. 



The genus Sarcina, as thus defined, is much more homo- 

 geneous than Migula's genus Micrococcus: it includes 

 no such parasitic forms as those which we have separated 

 from Micrococcus in our genera Diplococcus, Aurococcus, 

 and Albococcus. Five red pigment formers, however, are 

 classed by Migula in the genus Sarcina. Cocci of the latter 

 type, growing in packets and producing red pigment, are 

 frequently found in nature. In their biological characters 

 these forms correspond closely to the red pigment formers 

 which do not occur in packets, rather than to the yellow 

 sarcinae. In their almost invariable negative reaction 

 to the Gram stain, in their marked and peculiar action 

 on nitrates (forming in a large proportion of cases nitrites, 



but not ammonia), and in their rare and slight action 



226 



