Abstract
When injected into the skin of rabbits, cultures of H. influenzœ can readily be distinguished from cultures of H. pertussis. While H. influenzœ causes slight inflammation, characterized by redness and swelling, H. pertussis produces bluish-violet discoloration in the involved part of the skin, frequently followed by necrosis. 1 , 2 The observations to be reported are concerned with the influence of intravenous injection of H. influenzœ and H. pertussis on the skin lesions caused by the intradermal injection of the respective organisms.
For our experiments H. influenzœ is cultivated on Levinthal agar, H. pertussis on Bordet-Gengou medium, containing 25% rabbit blood. Twenty-four or 48-hour cultures of H. influenzœ and 48-hour cultures of H. pertussis are suspended in saline. The bacterial content of the suspension varies between 2 to 4 billion microbes per cc. Rabbits are injected intradermally with 0.25 cc. each of suspensions of H. influenzœ and H. pertussis and reinjected intravenously 24 hours later with 1 to 2 cc. of a suspension of H. influenzœ. Three to 6 hours later the areas prepared intradermally with H. influenzœ are transformed into a bluish-black lesion, and necrosis follows. The influence of the intravenous injection on areas inoculated with H. pertussis is only moderate, mostly none. The intravenous injection of H. pertussis produces the same results as the intravenous injection of H. influenzœ. It also may lead to hemorrhagic-necrotic lesions in the areas of the skin previously inoculated with H. influenzœ, while the areas inoculated with H. pertussis are usually not affected. We have the impression, however, that the intravenous injection of H. influenzœ is more powerful than the injection of H. pertussis. It should be mentioned that in these experiments about one-third of the rabbits employed proved to be refractory.
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