Pathogenesis. Anatomical Cliang-es. Symptoms. 13 



natural infection. According to the amount inoculated, the 

 animals die after twenty-four hours or after eight to thirty 

 days. Intramuscular inoculation leads to death in twenty-seven 

 to thirty days. Intravenous injection of a bouillon culture only 

 leads to a transitory elevation of temperature. 



Natural infection occurs by the introduction of the bacilli 

 through the nose. Since bacillus pyocyaneus is a common sap- 

 rophyte, found especially in manure, straw, feces, etc., it easily 

 gets into the noses of hogs in rooting. The inoculation experi- 

 ments of Koske admit also the possibility of different portals 

 of entrance. If the disease has once made its appearance it is 

 spread by the nasal secretions of the sick animals. 



Young animals are especially susceptible to natural infec- 

 tion. 



Pathogenesis. After gaining access to the nasal mucosa, 

 the bacilli multiply rapidly and soon get into the upper portions 

 of the nasal cavities and into the ethmoid bone. They form 

 powerful toxins and these produce, in the nasal mucosa and 

 particularly in that of the ethmoid bone, a hemorrhagic inflam- 

 mation which subsequently spreads to the meninges. Bacterial 

 toxins, absorbed into the i)lood, soon cause a general elevation 

 of temperature and petechias and ecchymoses in various por- 

 tions of the body. Koske showed experimentally that the toxins 

 of the bacillus pyocyaneus can by themselves produce a typical 

 picture of the disease. 



Anatomical Changes. The nasal mucosa is deep purplish 

 red and the intensity of the redness is, according to Imminger, 

 somewhat decreased upward. If the disease takes a short course 

 one finds blood coagula in the ethmoidal cells ; if the course has 

 been more protracted a hemorrhagic purulent exudate is evi- 

 dent ; there may be deviation and atrophy of the bony lamella. 

 The frontal sinuses usually contain a serous fluid. Hemor- 

 rhages are seen under the periosteum of the ethmoid and vomer, 

 as well as in the sheaths of the olfactory and optic nerves. The 

 congested vessels of the meninges show lilood extravasation; 

 blood is also seen between the convolutions of the brain, some- 

 times in the shape of blood coagula. The substance of the brain 

 appears edematous and the ventricles contain a red-tinged 

 though clear fluid. Sometimes blood coagula are deposited on 

 the choroid plexuses. While Imminger did not And any other 

 changes, Koske found a turbid, reddish fluid in very small 

 amounts in the peritoneal cavity, here and there diffuse red- 

 dening of the intestinal mucosa, streaky reddening of the cor- 

 tical portion of the kidney, subserous hemorrhages and paren- 

 chymatous degeneration of the internal organs. 



Symptoms. The disease is ushered in by a febrile elevation 

 of temperature up to 41° and above and a diminution of appe- 



