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, when 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 toa 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 
