PLAGUE. 203 



the frightful frequency with which plague prevails among 

 the lower classes in Bombay. 



Plague adheres obstinately to human habitations. It 

 does not extend in an explosive manner over large portions 

 of the same city, but passes from house to house. In addi- 

 tion to human intercourse, an important part is played by 

 the remarkable relations that exist between rats and simi- 

 lar vermin and bubonic plague, as was already recognized in 

 the middle ages. From numerous sources the German 

 Plague-commission was informed that the outbreak of the 

 epidemic was preceded by a pestilential disease among rats, 

 with an enormous mortality. The natives believe so firmly 

 in the connection between the plague of rats and that of 

 human beings that some of them will at once leave their 

 houses if they find a dead rat present. After great effort 

 the German Plague-commission succeeded in obtaining the 

 fresh cadaver of a rat that had been infected, and in it they 

 found numerous plague -bacilli.* Yersin has made the note- 

 worthy statement that he found the plague-bacillus in the 

 dust and the filth of plague-houses. 



Experiments on Animals. The animal most suscepti- 

 ble to plague is the rat. Minimal amounts of a culture 

 suffice on cutaneous inoculation to cause death regularly. 

 The same result may be attained by application of the 

 plague-bacilli to the mucous membrane of the eye or of the 

 nose. Rats die after eating quite small amounts of plague- 

 infected food, or after gnawing the bodies of other rats dead 

 of plague. The latter circumstance especially is of great im- 

 portance. It explains the incredibly rapid spread of rat- 

 plague, and also renders it probable that rats are responsible 

 for the extension of the disease from house to house. 

 Next to the rat in susceptibility to the plague is the gray 

 ape. Plague-bacilli are pathogenic for the usual labora- 

 tory-animals in general ; pigeons alone form an exception. 

 At the autopsy a mucous, at times hemorrhagic, exudate 

 is found at the point of injection. The nearest glands are 

 most enlarged, and they undergo suppuration but seldom. 

 The blood and the internal organs contain the bacilli, the 

 former, however, in but small amount. Kolle calls atten- 

 tion to a more protracted course for the disease, which 

 takes place if rats and guinea-pigs are inoculated with cul- 



* It is believed that squirrels and monkeys also may be infected by plague 

 and act as disseminators of the disease. A. A. E. 



