RABIES. 145 



Longer periods have been observed. Dr. George H. Hart, of 

 the United States Department of Agriculture, reports an 

 instance in a dog in which the period was fully one year. 

 Shorter periods of incubation than fifteen days have been 

 reported, but they are very unusual. In cows the period of 

 incubation varies from 14 to 70 days, in horses from 20 to 45 

 days, in cats from 15 to 60 days, in goats, sheep and swine 

 from 14 to 60 days, in rabbits from 9 to 7.8 days, in guinea 

 pigs from 12 to 50 days. 



In man the period of incubation is alleged to vary more. 

 Fourteen to sixty-four days are usually given, but it is reported 

 to be shorter, and also much longer, in some instances. 



In an act approved March 27th, 1903, the State Live Stock 

 Sanitarv,' Board was empowered to control rabies in Pennsvl- 

 vania, and dogs known to have come in contact with dogs 

 with rabies in the locality where "abies exists are placed under 

 restraint for 100 days, which means that the dog is either con- 

 fined or muzzled. 



The virus contained in saliva from a dog with rabies has 

 been successfully removed by filtration through a fine porce- 

 lain filter, proving that the causative agent is a solid body. 

 Its activity is readily destroyed by heat, light and by drying. 

 A five per cent, solution of carbolic acid, or a i : 1000 solu- 

 tion of corrosive sublimate destroys it in five minutes. Xitric 

 acid and citric acid or lemon juice is said to kill it ver\' 

 quickly. The virus may V^e preserved in neutral glycerine 

 unchanged for some time. It is quite resistant to putrefaction. 



Galtiers found that the brain of rabbits dead of rabies 

 buried twenty-three days still contained the virus. 



The danger of man actually developing rabies when bitten 

 by an animal depends upon the following : — 



First — The animal inflicting the bite must have rabies. 

 This has given rise to the opinion that the disease may appear 

 spontaneously and that it is an intrinsic part of the dog's 

 being which may creep out at any time under various extra- 



