GROUP OF PYOGENIC COCCI. 



49 



trance to the lungs -by way of the circulating blood. 

 Infection of the lungs by direct invasion through the 

 respiratory tract is improbable. The popular idea 

 that pneumonia is the direct result of taking cold is 



Fig. 5. Diplococcus pneumonise in the heart's blood of a rabbit. 

 X 1000. (After Frankel-Pfeiffer.) 



erroneous. While it is true that exposure to cold 

 may so lower the resistance as to favor the infection 

 of the lungs, pneumonia rarely follows a simple cold. 

 The infection in pneumonia is general, that is, a sep- 

 ticemia in which the manifestations are localized 



