120 THE PLAGUE 



effect may be an enlargement of the cervical glands, or the mucous 

 membrane of the stomach and small intestine may become inflamed and 

 hemorrhagic and the mesenteric and other glands may be enlarged. 

 Either form of the disease may develop and in any case the disease 

 terminates fatally. When a dilute culture is painted on the mucous 

 membrane of the nose carefully to avoid abrasion or dropped into the 

 conjunctival sac, general infection, the pneumonic or the bubonic form, 

 develops. 



McCoy found that the ground squirrel and the rock squirrel of 

 California are quite as susceptible as the rat. Strong and others in the 

 study of the Manchurian outbreak place the Siberian marmot in the 

 same list. All these animals develop epidemics of the plague. 



The guinea-pig is slightly less susceptible than the above named 

 animals to the plague bacillus on inoculation. No outbreak of the 

 plague in the guinea-pig in its native state is recorded, but there was 

 an epidemic among these animals in the Zoological Garden at Sydney 

 in 1902. Both gray and white mice are susceptible and may acquire 

 the disease by feeding on infected material. Rabbits are somewhat 

 less susceptible than guinea-pigs and mice. They are killed by sub- 

 cutaneous inoculations, but are not affected by feeding. Cats may 

 acquire the disease through eating infected mice or rats. Hunter 

 reports such cases from Hongkong. Ferrets, also used in destroying 

 rats, may succumb when the feeding is long continued. Hyenas, 

 jackals and dogs are only slightly susceptible, especially by way of the 

 mouth. According to Toyama, the Japanese bat is quite susceptible. 

 Wilson reports an epidemic among hogs in Hongkong. Cattle, sheep, 

 goats and horses are not susceptible. Subcutaneous inoculations in 

 these animals are followed by local reactions, but general infection 

 does not result. The testimony concerning the susceptibility of birds, 

 reptiles, amphibians and fish is conflicting, but it seems to be safe to 

 say that these animals play no part in the distribution of the disease. 



In his early work, Yersin observed that an unusual number of the 

 flies in his workroom died and later Nuttall showed that the fly may 

 be infected, fatally to itself and may distribute the disease. The 

 plague bacillus has been found in ticks, ants and lice. The role played 

 by the flea in this disease will be discussed later. 



