166 TEXT-BOOK OF BACTERIOLOGY. 



however, possess special interest, and it is hardly worth our while 

 to consider them here, although many have been exactly described 

 and their peculiarities carefully investigated. 



We will only mention a few of the sarcinae which occur in the 

 air, because they display the peculiar cell-division characteristic of 

 this class of bacteria, in which the segmentation proceeds equally in 

 all directions. 



YELLOW SARCINA. 



The yellow sarcina derives its name from the beautiful sulphur 

 or lemon coloring matter which its cultures display. 



The separate cells are colorless. They are somewhat large, 

 globular, or slightly-flattened cells, always occurring in the well- 

 known bale-like or packet- like arrangement. They stain readily, 

 yet in the colored preparations the peculiar form of the bundle 

 often becomes indistinguishable. 



On the gelatin plate the colonies of the yellow sarcina grow but 

 slowly. They appear under the microscope as roundish, slightly- 

 granulated sulphur-colored masses. 



In the test-tube cultures the yellow sarcina grows freely only 

 at the surface, where it forms a moderate-sized yellowish accumu- 

 lation, which is continued a short distance down into the puncture 

 in the shape of clearly-isolated granules. A little lower down their 

 size and frequency greatly diminish, and lower still no growth at 

 all takes place. In older cultures a very slow and slight liquefac- 

 tion of the culture medium is generally perceptible. 



On oblique agar the yellow sarcina soon produces a thickish 

 coating of a canary-yellow color. 



On potatoes it grows slowly and very gradually produces small 

 yellow spots and grains. 



The yellow sarcina is a strictly aerobic bacterium; it also thrives 

 in the incubator. 



The white sarcina differs from the yellow one only in the ab- 

 sence of the coloring matter; no other differences have been re- 

 marked. 



The orange sarcina is distinguished by its forming a golden- 

 yellow pigment, as well as by its somewhat intense liquefaction of 

 gelatin. Further, the separate colorless cells are perceptibly 

 smaller than those of the yellow sarcina. 



On the glass plate it grows in the form of round granular 

 colonies with clearly-defined edges and orange-yellow color, which 

 liquefy the gelatin if they are on the surface. 



In the test-tube the gelatin is softened throughout the whole 



