430 



RABIES 



iline 



2. The Gumming Method. In this the brain is emulsified in saline 

 and dialyzed. In this method the virus is so attenuated that injec- 

 tions do not produce rabies on intracranial inoculation. 



3. In the Hogyes method the fresh virulent cord is injected but s 

 diluted in strength that it acts as does an attenuated virus. 



In the diagnosis of rabies in dogs it is preferable to preserve the animal so that 

 the development of the symptoms may be observed. 



In case the dog has been killed, it may be possible to make a diagno- 

 sis by means of the Negri bodies. These are round or oval bodies from 



FIG. 112. Two nerve cells of hippocampus major (smear preparation) showing 

 Negri bodies. A, Negri bodies; B, inner bodies within the Negri bodies. (After 

 Reichel, American Veterinary Review.) 



i to 2o/x in diameter, which may be found in the nerve-cells, especially 

 those of the cornu ammonis (Hippocampus major). 



These bodies were first described by Negri in 1903. In street rabies large ame- 

 boid forms from 18 to 2$n may be found, while in the nerve tissues of animals with 

 "fixed" virus only minute forms, 0.5/1 or less, may be detected. The fact that the 

 virus will pass through a Berkefeld filter is no argument against its protozoal 

 nature. Calkins considers it to be of rhizopod affinity. The name Neuroryctes 

 hydrophobia has been given it. The bodies are present four to seven days before 

 the onset of symptoms. They may be demonstrated by staining smears of gray 

 brain substance by some Romano wsky method, especially by the Giemsa stain. 

 The smears should be made by mashing the thin slice of gray matter taken from i. 

 Cornu ammonis, 2. Region of fissure of Rolando in dog crucial sulcus or 3. Cere- 

 bellum, with a cover-glass against the slide. Afterward the cover-glass is gently 

 drawn along the slide. 



The smear on the slide is then fixed in methyl alcohol for two to three minutes, 







I 



