174 PRACTICAL BACTERIOLOGY. 



pyogenes aureus have an unpleasant smell, like sour 

 decomposing paste. 



These bacteria are pretty easily stained with most 

 aniline dyes, but their coloration is not intense. It is 

 therefore best to use more powerful staining solutions. 

 Gram's method is particularly suitable, the micrococci 

 becoming permanently stained. Faultless prepara- 

 tions may be obtained if the fixed cover-glass prepara- 

 tions are allowed to float for twenty-four hours upon 

 the surface of a very dilute solution of fuchsine (50 

 com. of water, 10 drops of concentrated alcoholic 

 solution of fuchsine), after which they should be 

 thoroughly rinsed with water. 



With the microscope we see irregularly arranged 

 small roundish cells (see Plate I., Fig. 1), a little less 

 than ToVo mm. in diameter. If they are closely packed 

 together, they form heaps ; but if they have been very 

 much separated, they lie either singly or in twos or 

 threes; sometimes they are grouped as diplococci, 

 sometimes as short three-celled threadlets, at others 

 as three-celled pyramids, or tetrads ; it never happens 

 that chains of more than three or at most four 

 cells are formed. In the tissues and in the pus they 

 may occur singly or in groups, and it is in conse- 

 quence of its manner of growth that it has been 

 included in the genus Staphylococcus. Its manner 

 of growth in cultivations cannot afford us any real 

 specific characteristics, since it is so various. For 



