THE PLAGUE 121 



Apes resemble man in their susceptibility to plague, developing 

 both the pneumonic and bubonic forms. Epidemics among these ani- 

 mals have been reported. 



Modes of Infection. According to Dieudonne and Otto there are 

 five geographical foci where the plague is endemic and from which 

 it is spread to diverse parts of the earth. Four of these are in Asia 

 and one in Africa. The first lies in the Kwen-Fun mountains in the 

 Eastern Himalayas. From this place the plague extended in 1893 to 

 Cochin China and Hongkong. The second is in the southwestern foot- 

 hills of the Himalayas. From this place the disease spread over 

 India, reaching Bombay in 1896 and at the same time it traversed 

 Persia and reached the Black sea, invading Russia by way of Samar- 

 kand. This focus has a population of about one million, and English 

 physicians have reported thirty smaller or larger epidemics in this 

 region between 1823 and 1897. Many of these resembled the black 

 death of the middle ages and were certainly the pneumonic form of 

 the plague. These epidemics affected both men and rats. Among the 

 latter there exists a chronic plague which serves to keep the bacillus 

 alive and virulent. 



The third region is the most extensive, covering northern Mongolia 

 and the Kirghiz Steppes. From this locality the plague in highly 

 virulent form spread over Manchuria in the winter of 1910-11. The 

 infection of this region was first investigated in 1895 by two Russian 

 physicians who discovered what has since been known as the "tara- 

 bagan" plague. The tarabagan or Siberian marmot is a small animal, 

 widely distributed in the mountains about Lake Baikal and over the 

 high table-land of Western Siberia. It lives in large families in 

 excavations which they make and which are several feet deep. They 

 leave their homes in great numbers in the fall in search of food. They 

 are valuable on account of their fur and many of them, being ill with 

 the plague, are easily captured. It has long been known that men 

 become infected with a highly fatal disease in skinning the animals. 

 The bacillus, having found a human host, is spread from man to man. 

 The crowded life in small huts during the winter favors the spread of 

 the infection. Whole communities are wiped out and in fear many 

 flee to adjacent territory, carrying the disease with them. The mar- 



