RABIES 567 



rabies is a demonstration of Negri bodies. If they are found the 

 diagnosis is complete. Failure to find them does not necessarily 

 exclude a diagnosis of rabies, and an emulsion prepared from the 

 central nervous system, using the gray substance as far as possible, 

 is injected subdurally into an experimental animal for a final diag- 

 nosis. The method of animal inoculation, while slower than the 

 microscopic examination of the brain, is the final test in doubtful 

 cases. Of course, treatment should not await the results of animal 

 inoculation if there is suspicion that a patient has been bitten by a 

 rabid dog, especially if the hands, face or other unprotected surface 

 be the site of the wounds. 



Staining Negri Bodies. Williams and Lowden 1 have developed a 

 technic for the rapid demonstration of Negri bodies, which is widely 

 followed at the present time. A small piece of the gray substance 

 from the region of the hippocampus major and from the cerebellum 

 of the animal is placed upon a clean glass slide and covered with a 

 clean coverglass. Pressure is applied to the latter until the tissue is 

 flattened and spread uniformly. The pressure is now shifted to one 

 edge of the coverglass and the flattened tissue is forced along the 

 slide, leaving a thin film as it passes. Fixation with neutral absolute 

 methyl alcohol (Merck reagent) containing about 0.1 per cent, picric 

 acid (about ten minutes are required) is followed by removal of the 

 fixing agent with filter paper. 



A small amount of a freshly prepared staining mixture, made in 

 the proportions of 30 c.c. of distilled water, 10 c.c. of a saturated alco- 

 holic solution of methylene blue and 0.5 c.c. of a saturated alcoholic 

 solution of basic fuchsin is poured over the slide, warmed till steam 

 arises, then poured off. The excess stain is removed in running water 

 and the preparation is carefully dried with filter paper. The prepara- 

 tion is examined with an oil immersion lens. 



Negri bodies, which vary in size from about 1 micron to 25 microns 

 in diameter, are stained magenta with blue granules by this process; 

 the cytoplasm of the nerve cells is pale blue; the nuclei of the nerve 

 cells are colored a darker blue. 



The Pasteur Treatment for Rabies. Pasteur 2 made the very important 

 observation that the virus of rabies as it exists in rabid dogs (street 

 virus) could be so attenuated by repeated passages through rabbits 

 that it lost much of its original virulence for the dog. This change in 



1 Loc. cit. t 2 Loc. cit. 



