564 PATHOGENIC AEROBIC BACILLI 
observed, or with the contents of a bubo, or with pieces of internal organs, 
or even with the contents of the intestine, they begin to become ill in from 
one to two days, according to the size of the animal. Their eyes become wa- 
tery, they begin to show disinclination for any effort, later they avoid their 
food, and hide quietly in a corner of the cage. The temperature rises to 
41.5° C., and with convulsive symptoms they die in from two to five days. I 
must observe that in Hong-Kong I could only obtain small guinea-pigs 
{weight from one hundred to one hundred and fifty grammes) and small 
rabbits (from two hundred to two hundred and fifty grammes). If I could 
have experimented upon larger animals it is possible that life would have 
been prolonged somewhat beyond the periods mentioned above. The parts 
around the point of inoculation are infiltrated with a reddish gelatinous 
exudation, the spleen is enlarged, sometimes there is a swelling of the lym- 
phatic glands, and in all the organs the bacilli are found. _ The results found 
after death in animals are very similar to those found in anthrax and in 
oedema malignum. Pigeons do not appear to be susceptible to the influence 
of the bacilli. I made experiments by feeding some mice and guinea-pigs 
with pure cultivations of the bacillus and with small pieces of the internal 
organs: the result was, such animals perished in a few days under the same 
symptoms as those which had been inoculated. In all the internal organs 
of animals so destroyed I found the bacilli. With the dust of dwelling- 
houses from which the plague-stricken had been removed, I made sev- 
eral experiments upon animals. Some of the animals died from tetanus. 
In one case only a guinea-pig died with plague symptoms, and in this ani- 
mal the same bacilli were found in the internal organs as in those of 
plague patients who had succumbed. These experiments with the dust from 
infected houses I shall certainly continue. Many rats and mice at present 
die spontaneously in Hong-Kong. I examined some of them. In the inter- 
nal organs of a mouse I discovered the same bacilli. : 
Experiments with Desiccation,—The contents of a bubo in which the 
bacilli were present in great numbers were wiped over cover glasses (per- 
fectly cleansed by heat and alcohol), and some of these cover-glasses were 
dried in the air of a room at a temperature ranging from 28° to 30°C. Oth- 
ers I exposed directly to the sun’s rays, and from among them, after an expo- 
sure of from one, two, and three hours up to six days, I removed some parts, 
putting such portions in beef-tea and placing them in the incubator. Those 
which had been standing in the room from one to thirty-six hours showed a 
pretty good growth in the incubator, but those which had been in the room 
for more than four days were unable to show any growth even after one 
week’sincubation. Those exposed directly to the sun were all destroyed after 
from three to four hours. Further cultivations on serum were treated 
exactly like the contents of the bubo with very similar results. 
Experiments with Heat.—Beef-tea cultivations which had been heated 
for thirty minutes ma water bath up to 80° C. were destroyed; at 100° C., in 
the vapor apparatus they were destroyed in a few minutes. 
Yersin reports that when fragments of the spleen or liver of 
animals which have died of the plague are fed to rats and mice they 
usually become infected and die, and the bacillus is found in their 
organs, lymphatic glands, and blood. He also demonstrated the pres- 
ence of the bacilli in dead rats found in the houses or streets of 
Hong-Kong. 
Without doubt rats play an important part in the propagation of 
the disease. Monkeys are also very susceptible to infection, and it is 
said that the disease has been known to occur as an epidemic among 
these animals. There is also good reason to believe that fleas have 
some influence in the propagation of the disease, by transferring the 
