BACTERIUM PNEUMONIA. 331 



monly found in the mouths of healthy individuals as 

 well as in other conditions. 



Inspection of the seat of inoculation usually reveals 

 a local reaction. " This may be of a serous, fibrinous, 

 hemorrhagic, necrotic, or purulent character. Fre- 

 quently we may find combinations of these conditions, 

 such as fibro-purulent, fibrino-serous, or sero-hemor- 

 rhagic." ' The most conspicuous naked-eye change 

 undergone by the internal organs will be enlargement 

 of the spleen. It is usually swollen, but may at times 

 be normal in appearance. It is sometimes hard, dark 

 red, and dry ; or it may be soft and rich in blood. Fre- 

 quently there is a limited fibrinous exudation over por- 

 tions of the peritoneum. 



Except in the exudations, the organisms are found 

 only in the lumen of the bloodvessels, where they are 

 usually present in enormous numbers. In the blood 

 they are practically always free, and are but rarely found 

 within the bodies of leucocytes. 



In stained preparations from the blood and exudates 

 a capsule is not infrequently seen surrounding the organ- 

 isms. (Fig. 63.) This, however, is not constant. 



1 1' a drop of blood from the dead animal be intro- 

 duced into the tissues of a second animal (mouse or 

 rabbit), identically the same conditions will be repro- 

 duced. 



If the organism be isolated in pure culture from the 

 blood of the animal, and a portion of this culture be 

 introduced into the tissues of a susceptible animal, 

 we shall see again the same pathological picture. 



It must be remembered, however, that this or- 



1 Welch : Johns Hopkins Hospital Bulletin, December, 1892, vol. iii. 

 No. 27. 



