BACTERIA IN CROUPOUS PNEUMONIA. 



407 



but especially to the dependent portions of the body. Occasionally there is 

 a little pus near the puncture, but usually death occurs before the'cellulitis 

 reaches the point of producing pus. The subcutaneous connective tissue 

 contains a quantity of bloody serum, which possesses virulent properties and 

 which contains a multitude of micrococci. There is usuc lly more or less in- 

 flammatory adhesion of the integument to the subjacent tissues. The liver 

 is sometimes dark-colored and gorged with blood, but more frequently it is 

 of a lighter color than normal and contains much fat. The spleen is either 

 normal in appearance or enlarged and dark-colored. Changes in this organ 

 are more marked in those cases which are of the longest duration. 



' ' The blood commonly contains an immense number of micrococci, usually 

 joined in pairs and having a diameter of about 0.5 /*. These are found in 

 blood drawn from superficial veins, from arteries, and from the cavities of 

 the heart immediately after death, and in a few cases their presence has been 



FIG. 93. Micrococcus pneumonias crouposae in blood of rabbit inoculated with pneumonic spu- 

 tum. X 1,000. 



verified during life. Observations thus far made, however, indicate that it 

 is only during the last hours of life that these parasites multiply in the cir- 

 culating fluid, and in a certain proportion of the cases a careful search has 

 failed to reveal their presence in the blood in post-mortem examinations 

 made immediately after the death of the animal." 



In animals which are not examined until some hours after death 

 a considerable increase in the number of micrococci occurs post mor- 

 tem. The fact that this micrococcus varies very much as to its 

 pathogenic power, as a result of conditions relating to the medium in 

 which it develops, was insisted upon in my first published paper, and 

 has been fully established by later researches (Frankel, Gameleia). 

 Susceptible animals inoculated with attenuated cultures acquire an 

 immunity against virulent cultures. 



In dogs subcutaneous injections usually give a negative result, 

 or at most a small abscess forms at the point of inoculation. In a 



