. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . quefied, and the staphylococciform a golden-yellow or orange-colored deposit at the bottom of thetube. Under unfavorable conditions the Staphylococcus aureus gradu-ally loses its ability to make pigment and to liquefy gelatin. Theliquefi cation is due to a ferment called gelatinase formed by the staphy-lococci. It may be separated from the cocci by filtration (Loeb). Growth on Agar.—In streak and stab cultures on agar a whitishgrowth is at first produced, and this at the end of a few days becomesa
. Pathogenic microörganisms; a practical manual for students, physicians, and health officers . quefied, and the staphylococciform a golden-yellow or orange-colored deposit at the bottom of thetube. Under unfavorable conditions the Staphylococcus aureus gradu-ally loses its ability to make pigment and to liquefy gelatin. Theliquefi cation is due to a ferment called gelatinase formed by the staphy-lococci. It may be separated from the cocci by filtration (Loeb). Growth on Agar.—In streak and stab cultures on agar a whitishgrowth is at first produced, and this at the end of a few days becomesa faint to a rich golden yellow on the surface. The yellow pigmentationis produced only in the presence of oxygen; colonies formed at thebottom of a stab culture or under a layer of oil remain —^Milk is coagulated at the end of from one to eight —^The staphylococci grow readily on potato and produceabundant deep colored pigment. Growth on Lofflers Solidified Blood Serum.—Growth vigorous, withfairly good pigment production. Some varieties slowly liquefy the Fig. 1100 diameters. THE STAPHYLOCOCCI 247 Growth on Blood Agar.—^If nutrient agar to which a Httle animalblood has been added is streaked with staphylococci there appears, atthe end of twenty-four hours at 35° C, about the growth a clear zone,owing to the hemolytic effect of the staphylococcus products. Acids Produced.—In media containing carbohydrates there is, as aresult of the growth of the Staphylococcus aureus, a production of acidin considerable quantities, consisting chiefly of lactic, butyric, andvalerianic acids. These acids have been supposed to play a part in theproduction of pus, in which, according to some observers, they are oftenpresent. No gas is formed. Resistance.—^The staphylococcus is distinguished from most othernon-spore-bearing pathogenic bacteria by its greater power of resistanceto outside influences, desiccation, etc., as well as to chem
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