DIPLOCOCCUS PNEUMONIA 359 



others have shown that pneumococei slowly dried in sputum may re- 

 main alive and virulent for 1 to 4 months, when protected from light; 

 and as long as nineteen days when exposed to diffused light at room 

 temperature. Experiments by Ottolenghi l have confirmed these re- 

 sults; the virulence seems, in Ottolenghi's experiments, to have become 

 considerably attenuated before death of the cocci. Recent studies by 

 Wood, 2 whose attention was focused chiefly upon pneumococcus viability 

 in finely divided sputum in a condition in which inhalation transmission 

 would be possible have shown that pneumococei survive for only about 

 one and one-half hours, under ordinary conditions of light and tempera- 

 ture. Exposed to strong sunlight pneumococei die off within an hour. 



Low temperatures slightly above zero are conducive to the pro- 

 longation of life and the preservation of virulence. 



The resistance of the pneumococcus to heat is low, 52 C. destroying it 

 in ten minutes. 3 To germicidal agents, carbolic acid, bichlorid of mer- 

 cury, permanganate of potassium, etc., the pneumococcus is sensitive, 

 being destroyed by weak solutions after short exposures. 



The disinfection of sputum, difficult because of the protective coat- 

 ing of the secretions about the bacteria, has been recently studied by 

 Wadsworth. 4 The conclusions reached by this writer indicate that 

 pneumococei in exudates are most rapidly destroyed by twenty per cent 

 alcohol, other and stronger disinfectants being less efficient, probably 

 because of slighter powers of diffusion. 



Virulence and Pathogenicity. The virulence of pneumococei is sub- 

 ject to much variation, depending upon the length of time during which 

 it has been cultivated. It has been mentioned above that under condi- 

 tions such as those prevailing in dried sputum or blood 5 the virulence of 

 pneumococei may be preserved for several weeks. Ordinarily, the 

 virulence diminishes as the cocci adapt themselves to life upon artificial 

 media. Upon media containing animal albumin, such as ascitic fluid or 

 blood agar, this attenuation is less rapid than upon the simple meat- 

 infusion preparations. 



In the blood of rabbits dead of a pneumococcus infection, taken 

 directly into sterilized tubes, sealed and kept in the dark, Foa 6 has been 

 able to preserve the virulence of pneumococei for as long as forty-five 

 days. Preservation in the spleen of animals dead of pneumococcus 

 infection, as practiced by Neufeld, has been mentioned above. Whether 



1 Ottolenghi, Cent. f. Bakt., xxv, 1889. 2 Wood, Jour. Exp. Med., vii, 1905. 

 3 Sternberg, Cent. f. Bakt., xii, 1891. 4 Wadsworth, Jour. Inf. Diseases, iii, 1900. 

 6 Guarnieri, loc. cit. 6 Foa, Zeit. f . Hyg., iv, 1888. 



