300 



INFECTIOUS DISEASES 



germ spreads from the wounds through the nerves and cen- 

 tral nervous system. The disease-producing organisms are 

 present in great numbers in the nerve-tissue and saliva. 



The period of incubation varies from a few days to several 

 months. It is usually from ten to seventy days. 



The symptoms diifer in the different species. There are two 

 forms of the disease: the furious and 

 jr^A^^dumh. The former is more common. 

 .f.^-^- In the dog, the symptoms may he 

 divided into three stages. The first, or 

 melancholy stage, usually lasts from 

 twelve to forty-eight hours. The ani- 

 mal's behavior is altered and it becomes 

 sullen, irritable and nervous. Some- 

 times it is friendly and inclined to lick 

 the hand of its master. An inclination 

 to gnaw or swallow indigestible objects is 

 sometimes noted. Frequently a certain 

 part of the skin is rubbed or licked. 



The second, or furious stage, may last 

 several days. Violent nervous or rabid 

 sjTuptoms are manifested, and the dog may leave home and 

 travel long distances. The animal usually shows a strong inclina- 

 tion to bite. It may move about snapping at imaginary objects in 

 its delirium, and may bite any person or animal with which it 

 comes in contact. The Ijark is peculiar, the appetite is lost and 

 the animal becomes weak and emaciated. 



In the third, or paralytic stage, the dog may present an emaci- 

 ated, dirty, ragged appearance. The lower jaw may drop, the 

 tongue hangs from the lips and the eyes appear sunken and 

 glassy. > Paralysis of the hind parts may be present. 



In the dumb form, the paralytic s^Tuptoms predominate and 

 the disease pursues a short course. Rabies terminates in death 

 in from four to ten days. 



Fia. 105.- 



■^1 



-Negri bodies in nerve- 

 tissue. 



