354 MEDICAL BACTERIOLOGY 



EXERCISE 106. DIAGNOSIS OF RABIES. 



A. Microscopical Diagnosis. 



a. The head of the animal is opened and the brain removed. 

 In case the animal is some distance from the laboratory it is best to 

 cut off the head, pack in ice and ship by express. 



h. Thin pieces of the various parts of the brain, such as 

 Ammon's horns, cerebellum, cerebrum and medulla are fixed in 

 equal parts of formalin and 95% alcohol for 12 to 18 hours. They 

 are then treated as follows: 



1. 95% alcohol, 14 hour. 



2. 95% alcohol again for i/^ hour. 



3. Anilin oil until clear; one hour is usually sufficient. 



4. Xylol 15 to 30 minutes. 



5. Melted paraffin, 2I/2 hours. 



6. Cut to 3 or 4 microns. 



7. Stain in hematoxylin and eosin. 



Cell inclusions known as negri bodies, which are usually found 

 most abundant in Ammon's horns, are the evidence of rabies. 



The medulla is searched for infiltrations around the blood ves- 

 sels. These changes are found in a few conditions other than 

 rabies. 



B. Smear Method.^ 



a. Small pieces of the various parts of the brain are crushed out 

 between two clean slides and treated as follows : 



1. Fix the smears while still wet in methyl alcohol (neutral- 



ized with sodium carbonate) to which •jV% of picric 

 acid has been added. Blot off excess of fixative. 



2. Stain smears as follows : 



Saturated alcoholic solution of fuchsin, 3 cc. 

 Saturated alcoholic solution of methylene blue, 2 cc. 

 Distilled water, 30 cc. 



Heat the .slide over a flame until it steams, wash in tap 

 water and blot. The stain does not keep long. 



'■Williams, Amer. Jonr. of Public Hygiene, Feb., 1908. 



