322 RABIES 



pleteh' prostrated, the only evidence of life being a slight res- 

 piratory movement. The head occupies different positions. 

 In some it is drawn backward as in tetanus ; in others it is 

 drawn down with the nose near the fore legs and in still 

 others it is extended as if the animal were sleeping. The 

 period of this complete paralysis varies from a few hours to a 

 few days, but ordinarily it has not exceeded twenty-four 

 hours. Although these animals are unable to move volun- 

 tarilv there is a refiex action of the limbs until a very short 

 time before death. 



During the period of incubation the temperature of the 

 rabbits is normal. As the time approaches for the first symp- 

 toms to appear there is an elevation of temperature of from i 

 to 2 degrees, which continues for a variable length of time, 

 but rarely longer than two days. This is followed by a grad- 

 ual or usually a more rapid drop to the subnormal, which con- 

 tinues to the end. 



The differential diagnosis in experimental animals is not 

 difficult. Rabbits inoculated with several varieties of patho- 

 genic bacteria frequently exhibit symptoms of paralysis for a 

 brief period preceding death. In cases of injury to the brain 

 or spinal cord there may also be paralysis, which in the 

 absence of the history of the case might be taken for that of 

 rabies. In these cases, however, the symptoms appear very 

 soon after inoculation. This is especially true when the par- 

 alysis is due to mechanical injur}' of the brain or to irritation or 

 septic substances and in the case of the pathogenic bacteria if 

 paralysis occurs at all it is almost invariably preceded by 

 marked disability. This method of diagnosing rabies requires 

 that the inoculated animals remain apparently well for a con- 

 siderable length of time after the subdural inoculation and 

 before the paralytic symptoms appear. 



The lesions found on the post-mortem examination are 

 also of much assistance in making a diagnosis. If the animal 

 died from septicaemia or brain injurj? there will be lesions 

 almost invariably recognizable in the brain or viscera. In the 

 case of septicaemia a bacteriological examination will reveal 

 the presence of microorganisms. If the death was caused by 



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