DISEASES OP THE OX AND SHEEP. 297 



gradually becomes shorter, and after about twenty-five trans- 

 missions from rabbit to rabbit, the period of incubation at length 

 becomes one of only about eight days. After another twenty- 

 five transmissions, the period of incubation drops to seven days, 

 and continues to be seven days, even if the virus is passed on 

 from rabbit to rabbit even to the number of ninety of those 

 animals. Now, the marrow of these rabbits, when carefully 

 suspended in a very dry atmosphere, gradually becomes less 

 virulent, the rate and degree of diminution depending upon 

 the thickness of the particles and the external temperature. 

 The lower the temperature, the longer the virulence is main- 

 tained. 



M. Pasteur's method is somewhat as follows : — Every day a 

 piece of marrow freshly taken from a rabbit which has died of 

 rabies contracted after an incubation of seven days is suspended 

 in a series of flasks. The air contained in the flask is kept dry 

 by placing fragments of potassium in the bottom of it. Each 

 day a dog is inoculated with the contents of a syringe full 

 of *' bouillon," with which a small quantity of the marrow 

 which has been longest in the flasks has been mixed. On the 

 next day the same operation is performed, but with fresher and 

 more virulent matter, and so on until at length the very virulent 

 matter which has only been in the flask for a day or two is used. 

 By these means the dog is rendered incapable of being attacked 

 with rabies, even if the virus be injected under the skin, or even 

 into the surface of the brain by means of the operation of 

 trepanning. M. Pasteur succeeded in rendering fifty dogs of 

 various ages and breeds incapable of taking the disease, and did 

 not fail in a single case. 



Upon the 6th day of July 1885 three persons from Alsace 

 Called at M. Pasteur's laboratory. Of these one was Theodore 

 Vone, a grocer at Meissengalt, near SchlesLadt, and he had been 

 bitten on the arm two days previously by his own dog, which 

 had gone mad. Another was Joseph Meister, a boy nine years 

 of age, who had been bitten by the same dog on the same day. 

 The dog had pinned him to the ground, and had bitten him so 

 badly about the hands, legs, and thighs, in fourteen different 

 places that the boy experienced great difficulty in walking. 

 When picked up, he was covered with foam and blood. At 

 about twelve hours after the accident, the bites had been 



