STAPHYLOCOCCUS PYOGENES AUREUS 380 



for six to fourteen weeks when dried upon paper or cloth. 11 On 

 slant agar, staphylococci may be safely left for three or four months 

 without transplantation, and remain alive. 12 



The resistance of staphylococci to chemicals, a question of great 

 surgical importance, has been made the subject of extensive re- 

 searches, notably by Liibbert, 13 Abbott, 14 Franzott, 15 and many 

 others. According to Liibbert, inhibition of staphylococcus growth 

 is attained by the use of boric acid 1 in 327, salicylic acid 1 in 650, 

 corrosive sublimate 1 in 80,000, carbolic acid 1 in 800, thymol 1 in 

 11,000. Staphylococci are killed by corrosive sublimate 1 in 1,000 

 in ten minutes, by carbolic acid 1 per cent in 35 minutes, 3 per cent 

 in 2 minutes (Franzott). Ethyl alcohol, 16 even when absolute, is 

 not very efficient as a disinfectant. Nascent iodin, as split off from 

 iodof orm in wounds, is extremely powerful in . destroying staphy- 

 lococci. 



Pathogenicity. Separate strains of Staphylococcus pyo genes 

 aureus show wide variations in relative virulence. The most highly 

 virulent are usually those recently isolated from human suppurative 

 lesions, but no definite rule can be formulated in this respect. The 

 virulence of a given strain, furthermore, may be occasionally en- 

 hanced by repeated passages through the body of a susceptible 

 animal. Prolonged cultivation upon artificial media is liable to 

 decrease the virulence of any given strain, though this is not 

 regularly the case. There are, moreover, unquestionably, many 

 staphylococci constantly present in the air, dust, and water, which 

 although morphologically and culturally not unlike the pathogenic- 

 ally important species, may be regarded as harmless saprophytes. 



The susceptibility of animals to staphylococcus infection is, like- 

 wise, subject to extreme variations, depending both upon differences 

 between species and upon fortuitous individual differences in sus- 

 ceptibility among animals within the same species. Animals on the 

 whole are less susceptible to staphylococcus than is man. Among 

 the ordinary laboratory animals, rabbits are most susceptible to this 

 microorganism. Mice, and especially the white Japanese mice, show 



11 Deslong champs, Paris, 1897. 

 12 Passet, Fort. d. Med., 2 and 3, 1885. 

 "Liibbert, "Bipl. Untersuch.," Wurzburg, 1886. 

 14 Abbott, Medical News, Phila., 1886. 

 Franzott, Zeit. f. Hyg., 1893. 

 Hanel, Beit. z. klin. Chir., xxvi. 



