54-1 BUKEAU OF ANIMAL INDUSTRY. 



Perhaps no disease in medicine has been the object of move contro- 

 versy than rabies. Certain medical men of prominence have even 

 doubted the existence ' of the disease. Many medical men have 

 claimed for it a spontaneous origin. The experience, however, of 

 ages has shown that contagion can be proved in the great majority of 

 cases, and, l)y analog}' with other contagious diseases, we maj'^ onl}' 

 believe that the development of one case requires the preexistence 

 of a case from which the virus has been transmitted. M. Pasteur 

 has further added to our knowledge of the disease by showing that 

 a virus capable of cultivation exists in the nervous system, espe- 

 cially in the lower part of the brain (medulla oblongata) and in the 

 anterior part of the spinal column. M. Pasteur has further shown 

 that that portion of the nervous S5^stem which contains the virus, the 

 exact nature of which has not yet been demonstrated, will retain it 

 for a very long time if kept at a very low temperature or if left sur- 

 rounded b}^ carbonic acid; but if the nerve matter, which is virulent at 

 first, is exposed to the air and is kept from putrefaction by substances 

 which will absorb the surrounding moisture, it will gradualh' lose 

 its virulence and become inoffensive in about fifteen daj's. He has 

 further shown that the action of a weak virus on an animal will pre- 

 vent the development of a stronger virus, and from this he has formu- 

 lated his method of proph3^1actic treatment. This treatment consists 

 in the successive inoculation of portions of the nerve matter contain- 

 ing the virus from a rabid animal which has been exposed to the 

 atmosphere for thirteen days, ten days, seven days, and four days, 

 until the virulent mattor which will produce rabies in any unprotected 

 animal can be inoculated with impunit}'^. A curious result of the 

 experiments of M. Pasteur is that an animal which has first been inocu- 

 lated with a virus of full strength can be protected by subsequent 

 inoculations of attenuated virus repeated in doses of increasing 

 strength. 



Symjjtoms. — From the moment of inoculation l)y the bite of a rabid 

 dog or other rabid animal or b}' otiier means, a variable time elapses 

 before the development of anj^ symjjtoms. This time may be eight 

 days or it may be several months; it is usuall}^ about four weeks. 

 The first symptom is an irritation of the original wound. This 

 wound, which mav have healed completely, commences to itch until 

 the horse rubs or bites it into a new sore. The horse then becomes 

 irritable and vicious. It is especially susceptible to moving objects; 

 excessive light, noises, the entrance of an attendant, or any other dis- 

 turbance will cause the patient to be on the defensive. It apparently 

 sees imaginary objects; the slightest noise is exaggerated into threaten- 

 ing.violence; the approach of an attendant or another animal, espe- 

 cially a dog, is interpreted as an assault and the horse will strike 

 and bite. The violence on the part of the rabid horse is not for a 



