BACTERIA IN CROUPOUS PNEUMONIA. 319 



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 hlood 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. 



FIG. 9). Micrococcus pneumonias crouposae in blood of rabbit inoculated with pneumonic spu- 

 tum, x 1,000. 



In dogs subcutaneous injections usually give a negative result, 

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

 single experiment, however, the writer has seen a fatal result in a 

 dog from the injection of one cubic centimetre of bloody serum from 

 the subcutaneous connective tissue of a rabbit recently dead. This 

 shows the intense virulence of the micrococcus when cultivated in 

 the body of this animal. Pneumonia never results from subcutane- 

 ous injections into susceptible animals, but injections made through 

 the thoracic walls into the substance of the lung may induce a typi- 

 cal fibrinous pneumonia. This was first demonstrated by Talamon 

 (1883), who injected the fibrinous exudate of croupous pneumonia, 

 obtained after death, or drawn during life by means of a Pravaz 

 syringe from the hepatized portions of the lung, into the lungs of 



