BUBONIC PLAGUE. 439 adrenals congested. There are often sero-sanguinoleiit effusions into the serous cavities. Klein 1 states that the intraperitoneal injection of the bacillus into guinea-pigs is of diagnostic value, produc- ing in twenty-four to forty-eight hours a thick cloudy peritoneal exudate rich in leukocytes and containing characteristic chains of the plague bacillus. Animals fed upon cultures or upon the flesh of other animals dead of the disease became ill and died with typical symptoms. When Klein inoculated animals with the dust of dwelling-houses in which the disease had occurred, some died of tetanus, one from plague. Many rats and mice in which examination showed the charac- teristic bacilli died spontaneously in Hong-Kong. Yersin showed that flies also die of the disease. Mace- rating and crushing a fly in bouillon, he not only suc- ceeded in obtaining the bacillus from the medium, but infected an animal with it Nuttall,2 in reviewing Yersin's fly-experiment, found the statement true, and showed that flies fed with the cadavers of plague-infected mice died in a variable length of time. Large numbers of plague bacilli were found in their intestines. He also found that bed-bugs allowed to prey upon infected animals took up large numbers of the plague bacilli and retained them for a number of days. These bugs did not, however, infect healthy animals when allowed, subsequently, to feed upon them. Nuttall is not, however, satisfied that the number of his experiments upon this point was great enough to 'be conclusive. Ogata found that the plague bacillus existed in the bodies of fleas found upon diseased rats. One of these he crushed between sterile object-glasses and introduced into the subcutaneous tissues Of a mouse, which died in three days with typical lesions of the plague, a con- trol-animal remaining well. Some guinea-pigs taken 1 Centralbl f. Bakt. u. Parasitenk., xxi., No. 24, July 10, 1897, p. 849. 2 Ibid., Aug. 13, 1897.