_Lungs._--The alveoli were filled with homogeneous masses, containing but few degenerated epithelial cells and leucocytes. The blood-vessels were dilated, particularly in the subpleural part of the organ. In some places capillary mycotic emboli with subsequent hemorrhage were encountered. The large blood-vessels and bronchi were normal. _Salivary Glands._--Those glands attached to the primary bubo showed the normal structure of a combined mucous and serous gland. _Liver._--There was considerable congestion. The centres of the acini showed parenchymatous and fatty degeneration. The cells on the periphery of the acini exhibited typical fatty infiltration. The large blood-vessels and small ducts were without change. _Kidney._--The cells of the kidney showed various degrees of degeneration, ranging from parenchymatous to fatty infiltration. There were a few capillary hemorrhages and hyaline casts present. _Suprarenals._--These showed slight degeneration. _Spleen._--This organ showed congestion, a few hemorrhages, and bacterial emboli; otherwise normal. The bacteriological examination of the material from this cat gave the following results: 1. _Smears:_ _a._ From the buboes showed degenerated leucocytes, many lymphocytes, and numerous bacteria, some of which resembled _Bacillus pestis_ in their polar staining. _b._ From the spleen showed numerous plague-like, polar-stained bacilli. Round involution forms were present. 2. _Cultures:_ _a._ From the buboes were badly contaminated with _Bacillus coli_ and _Bacillus pyocyaneus_ colonies. _b._ From the spleen: A few scattered colonies of _Bacillus pyocyaneus_ developed on the surface of the agar. Between the large colonies a scanty growth of dewy appearance was noticed. Smears made from this growth revealed plague-like bacilli of the cultural type, showing a few club-shaped involution forms. Subcultures were made in order to secure pure culture. They showed a pure growth of _Bacillus pestis_ as indicated by the morphology of bacilli and shape of the colonies. Agglutination with plague-immune serum was positive. 3. _Inoculation experiments (vaccination method):_ _a._ One guinea-pig was inoculated with the material from the left bubo, another one with material from the right bubo. They died of plague on the third and fifth days, respectively. _b._ One guinea-pig was inoculated with the material from the spleen. It died of plague on the third day. _c._ One guinea-pig was inoculated with material from the nostrils obtained by swab. The animal survived, showing no indication of plague. _d._ One guinea-pig was inoculated with material from the rectum obtained by swab. It died of plague on the fifth day.