PROTOZOA 423 



2. If Negri bodies cannot be found, examine the Gas:- 

 serian ganglia for cellular lesions. 



3. If the results from the examination for Negri bodies 

 and ganglion changes are negative, rabbits should be inocu- 

 lated in those cases where a late diagnosis will be of value. 

 Otherwise, animal inoculations should be omitted. 



Examination for Negri bodies. At least four prepara- 

 tions from each of the hippocampi, four from each of the 

 cerebra, and four from the cerebellum, should be carefully 

 examined before pronouncing the case negative. In making 

 the preparations for examination any one of the following 

 three methods may be employed. 



Smear preparations as described by Williams, of the New 

 York City Board of Health Research Laboratory. 



Impression preparations as described by Frothingham r 

 of Harvard University. 



Fixing the tissue and making sections. 



Either of the first two methods is preferable to the last r 

 although, occasionally the Negri bodies seem to be more clearly 

 differentiated in the section. Zenker's fluid is recommended 

 for fixing the tissue. It does not seem to be necessary to fix 

 for more than from four to six hours when the tissues are cut 

 in thin pieces. 



The stain to be employed for smear or impression prepara- 

 tions should be either Van Giessen's, or eosin and methylene 

 blue. If the tissue is fixed in acetone and sectioned, the stain- 

 ing method recommended by Mann or that proposed by Lentz 

 gives excellent results. If the tissue is fixed in Zenker's fluid, 

 eosin and methylene blue should be used. 



It is understood that in the application of any of these 

 methods, the greatest care should be taken relative to the 

 preparation, stain, the time of staining, and the variation in 

 the number and location of the Negri bodies in the brain. 

 Experience has shown that cases of rabies are exceedingly 

 rare which cannot be diagnosed accurately by the search for 

 Negri bodies. As a precaution, all reports that are negative 

 on microscopical and histological examination should state that 



