THE ORGANISMS OF SUPPURATION. 179 



the growth is more considerable ; under these circum- 

 stances the colonies unite along the strokcj forming 

 a thin, whitish, transparent coating, which is scarcely 

 visible at its edges. The growth upon potatoes is 

 hardly perceptible ; indeed the organisms never really 

 develop properly. The streptococcus thrives best in 

 bouillon, in which, in a. few days, if the temperature 

 of 37° C. be maintained, a flocculent sediment is 

 formed, whilst tlie colour remains unchanged. 



It may be stained in the same way as the Staphylo- 

 coccus pyogenes aureus ; it is permanently stained if 

 treated according to Gram's method. If especially 

 perfect preparations are required, it is well to use 

 more dilute fuchsine solutions, and, while frequently 

 changing this solution, and rinsing the cover-glass, to 

 allow at least two days to the organisms to absorb 

 the stain. In this manner preparations are produced 

 in which the individual cells stand out especially dis- 

 tinctly ; if stronger solutions are used, the outlines 

 are less distinct, and the resemblance to a string of 

 pearls is not so evident. An indistinct gelatinous 

 substance-:^the swollen outer membranous covering of 

 the cell — is apt to become stained also ; and as its 

 colour is intenser internally than externally, the cells 

 appear to have no sharp outline, but to run into one 

 another, thus forming a thread. Clear outlines can 

 only be obtained if the preparations are gradually 

 stained with very dilute solutions. 



