DIPLOCOCCUS PNEUMONIA 359 



more profuse is its growth, and the greater its viability, both qualities 

 going hand in hand with its diminishing parasitism. The length of life 

 of these bacteria may be much increased by their preservation at a low 

 temperature, in the dark, and by the exclusion of air. By far the best 

 medium for keeping pneumococci alive is the previously mentioned 

 calcium-carbonate-infusion broth. Grown in this medium and kept in 

 the ice-chest, cultures may often remain alive for months. 



In sputum the viability of pneumococci seems far to exceed that 

 observed upon culture media. The studies of Guarnieri,' Bordoni- 

 Uffreduzzi,^ and others have shown that pneumococci slowly dried in 

 sputum may remain not only alive but virulent, after from one to four 

 months, when protected from light; and as long as nineteen days 

 when exposed to diffused light at room temperature. Experiments by 

 Ottolenghi ^ have, in the main, confirmed these results; the virulence 

 seems, in Ottolenghi's experiments, to have become considerably attenu- 

 ated before the death of the cocci occurred. More recent studies by 

 Wood,^ whose attention was focused chiefly upon pneumococcus viabil- 

 ity in finely divided sputum — in a condition, in other words, in which in- 

 halation transmission would be possible — have shown that pneumococci 

 in finely sprayed sputum survive for only about one and one-half hours, 

 under ordinary conditions of light and temperature. Exposed to strong 

 sunlight pneumococci die off within an hour, often within a few minutes. 



Low temperatures are well borne by pneumococci, temperatures 

 slightly above zero being even conducive to the prolongation of life and 

 the preservation of virulence. 



The resistance of the pneumococcus to heat, on the other hand, is 

 low, 52° C. destroying it within ten minutes.^ To germicidal agents, 

 carbolic acid, bichlorid of mercury, permanganate of potassium, etc., 

 the pneumococcus is extremely sensitive, being destroyed by weak solu- 

 tions after short exposures. 



The disinfection of sputum, offering considerable difficulties because 

 of the protective coating of the secretions about the bacteria, has been 

 recently made the subject of a spec al study by Wadsworth." The con- 

 clusions reached by this writer indicate that pneumococci in exudates 



1 Guamieri, Att. della R. Acad. Med. di Roma, iv, 1888. 

 ' Bordoni-Uffreduzzi, Arch. p. 1. sc. med., xv, 1891. 

 3 Ottolenghi, Cent. f. Bakt., xxv, 1889. 

 ' Wood, Jour. Exp. Med., vii, 1905. 

 'Sternberg, Cent. f. Bakt., xii, 1891. 

 ' Wadmorth, Jour. Inf. Disej^ses, iii, 1906. 



