194 ANNUAL REPORT OF THE Off. Doc. 



5. AVliere Negri bodies are not demonstrated and slight prolifera- 

 tion changes are seen in the plexil'orm ganglion, it is reported that 

 the microscopic examination is negaglive, and that the diagnosis 

 mnst rest upon the result of the animal inoculation test. 



AMlh those specimens from animals destroyed shortly after the 

 first symptoms are noted and suspected of having rabies, the ex- 

 amination and diagnosis is made as follows: 



1. Smeais are made and examined for Negri bodies, and as soon 

 as the bodies are found, the examination is discontinued and a di- 

 agnosis of rabies is made. 



2. When Negri bodies are not found in the smears, sections of 

 those structures are examined b^^ the smear method, and if Negri 

 bodies are found, the examination is discontinued and a diagnosis 

 of rabies is made. 



3. In those cases where the brain tissue is entirely destroyed and 

 only the ganglia are obtained, the presence of well marked character- 

 istic Van Gehuchten-Nelis changes in the plexiform ganglion is con- 

 sidered sufficient to base a diagnosis of rabies upon. 



4. Where Negrgi bodies are not demonstrated and well marked 

 Van Gehuchten-Nelis changes are found, a diagnosis of rabies is 

 made and the animal inoculation test is carried out to verify the 

 diagnosis. 



5. Where Negri bodies are not demonstrated and no proliferation 

 changes are seen in the plexiform ganglion, it is reported that the 

 microscopic examination is negative and that the diagnosis must 

 rest upon the result of the animal inoculation test. 



As soon as the result of the animal inoculation test is obtained, 

 it is reported. All experimental animals are kept for a period of 100 

 days, and if at the end of that time they show no symptoms, the ani- 

 mal inoculation test is considered negative. 



In the routine examination of the specimens suspected of rabies 

 in the laboratory of the Pennsylvania State Livestock Sanitary 

 Board during 190.5-1906 inclusive, 914 were included, as shown in 

 Table No. IT, the animal inoculation test was resorted to in 198 

 cases, 87 of which proved positive and 111 negative. 



Specimens from a fairly large variety of animals have been ex- 

 amined and attention is called to the fact that Negri bodies were 

 demonstrated in each of the species, including three human beings. 

 The rabbits and guinea pigs tabulated are some of the experimental 

 animals in which it was necessary to examine the brain tissue for 

 Negri bodies. The brains of all the rabbits and guinea pigs that 

 died within the usual period of incubation, were examined and the 

 diagnosis was made on the Negri bod}' in each instance. 73.9 per 

 cent, of all the specimens examined were found positive, 22,9 per 

 cent, remained suspicious and 2.9 per cent were too far decomposed 

 for examination. The percentage of positive cases may be somewhat 

 higher than is the experience of other laboratories, which must be 

 attributed to purely local conditions. 



In Pennsylvania, the State Livestock Sanitary Board prefers 

 the confirmation by a laboratory examination of all epizootics as 

 they arise in a new locality and not infrequently a rapid success 

 of positive cases, make their appearance in the laboratory. 



