504 BACTERIOLOGY. 



As to its duration of life outside the body, the 

 researches of Bordoni-Uffreduzzi throw some light. 

 He found that pneumonic sputum attached to clothes, 

 when dried in the air and exposed to diffuse day- 

 light, retained its virulence, as shown by injection 

 in rabbits, for a period of nineteen to fifty-five days. 

 Exposed to direct sunlight the same material retained 

 its virulence after twelve hours' exposure. This reten- 

 tion of virulence for so long a time under these circum- 

 stances is accounted for by the protective influence 

 afforded by the dried albuminous material in which the 

 micrococci were embedded. Thus, Guarnieri observed 

 that the blood of inoculated animals, wheu rapidly dried 

 in a desiccator, retained its virulence for months; and 

 Foa found that fresh rabbit blood, after inoculation and 

 cultivation in the incubator for twenty-four hours, 

 when removed at once to a cool, dark place, retained 

 its virulence for sixty days. There are many condi- 

 tions, therefore, in which the virulence of the micro- 

 coccus is retained for a considerable length of time. 



The Source of Infection. Although, as we have just 

 seen, the pneumococcus may retain its virulence in 

 dried sputa for considerable lengths of time, still such 

 pneumococci are not the only source of contagion, for 

 in the throat secretions of many healthy persons, and 

 in the bronchial and lung discharges of nearly all cases 

 of chronic pulmonary diseases, we have the pneumo- 

 cocci abundantly present. 



Pathogenesis. The micrococcus lanceolatus is quite 

 pathogenic for some animals viz., mice and rabbits 

 less so for others. In mice and rabbits the subcutaneous 

 injection of small quantities of pneumonic sputum in 

 the early stages of the disease, or of a pure, virulent 



