380 PATHOGENIC BACTERIA. fatal issue. Meteorism and great tenderness of the abdo- men are observed. At the autopsy a sero-fibrinous or sero-purulent peritonitis is observed—sometimes hemor- rhagic. There is also generally a pleurisy, either serous or hemorrhagic. All the abdominal viscera are con- gested. The intestine is congested—contains an abun- dant mucous secretion. The Peyer patches are enlarged. The spleen is enlarged, blackish, and often hemorrhagic. In cases which are prolonged the liver is discolored. The kidneys are congested, the adrenals filled with blood. 4 4 In such cases the bacillus can be found upon the in- flamed serous membranes, in the inflammatory exudates, in the spleen in large numbers, in the adrenals, the liver, the kidneys, and sometimes in the lungs. The blood is also infected, but to a rather less degree. 4 c In cases described as chronic, the bacillus disappears completely in from five to twenty-four hours, and pro- duces but one lesion, a small abscess at the point of inoc- ulation. " Sanarelli has observed that if some of the poisonous products of the colon bacillus or the Proteus vulgaris be injected into the abdominal cavity of an animal recover- ing from a chronic case, it speedily succumbs to typical typhoid fever." Petruschkyl found that mice that recovered from sub- cutaneous injections of typhoid cultures frequently suf- fered from a more or less widespread necrosis of the skin at the point of injection. I experienced great difficulty in immunizing a horse to the disease, because every injection of virulent living organisms was followed by a necrosis equalling in size the distended area of subcutaneous tissue. Large quantities of filtered cultures produce symp- toms similar to those resulting from inoculation with the bacilli. The toxic product of the bacilli is, how- ever, practically insoluble, and, according to the ex- periments of Loffler and Abel and those of PfeifFer and 1 Zeitschrift fur Hygiene, Bd. xii., 1892, p. 261.