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.