8TAPHTLOCOCCU8. 941 



of gelatin, and other cultural properties. The 

 Staphylococcus alb us differs from the Staphylo- 

 coccus aureus only in its inability to form pig- 

 ment, and it cannot he made to acquire this prop- 

 erty. Pigment is formed most abundantly on 

 potato, whereas little is formed on blood serum. 

 Other pigment-forming varieties are: 8. eereus 

 flacus, 8. pyogents citreus, S. scarlatinas and 

 Micrococcus kematodfs. The S. epidtrmidis albu* 

 of Welch is of low virulence. Weichselbaum 

 obtained a S. endocardUUis rugatus from a case 

 of endocarditis. Xot all of these varieties produce 

 soluble toxins. The pigment of . aureus is an 

 excretion product which is formed only in the 

 presence of oxygen. It is insoluble in water, sol- 

 uble in alcohol and ether, and gives the reaction 

 of a lipochrome (L e.. the pigment may be saponi- 

 fied and gives the lipoc-yanin reaction in which the 

 pigment turns blue when treated with concentra- 

 ted sulphuric acid). 



Aside from wide individual variations, the re- 

 sistance of staphylococci to heat depends on the * 

 concentration of the suspension, the nature of the 

 medium (whether water, gelatin or pus), and 

 whether the test is a dry or wet one (Xeisser and 

 Lipstein). Eighty degrees centigrade for one-half 

 to one hour kills them under all conditions, and 

 60 C. for one-half hour kills many strains when 

 suspended in bouillon. They are not killed by re- 

 peated freezing and thawing, and are very resist- 

 ant to desiccation. When in the form of fine dust 

 they die in twenty-eight days (Kirstein). Resist- 

 ance to the action of sunlight is variable; some 

 strains are killed in from three to five hours. 



