RABIES 



363 



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

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

 hydrophobias 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 Romanowsky 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. 

 Cerebellum, 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, 

 washed with water and covered with a stain made by adding 3 drops of Sat. ale. 

 sol. of basic fuchsin to 10 c.c. of distilled water and then adding 2 c.c. of Loffler's 

 methylene blue solution. The stain on the slide is then steamed gently and after- 

 ward washed with water and dried. 



FIG. 105. 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.) 



As their relation to the nerve-cell is more or less disturbed by such a method 

 it is preferable to fix brain tissue from the region of the cornu ammonis for five to 

 seven hours in Zenker's fluid, then to imbed in paraffin and make sections. These are 

 stained with Giemsa's stain and the Negri bodies are brought out as iliac-red bodies 

 in the blue cytoplasm of the nerve-cells. It is necessary to differentiate in 95% 

 alcohol. 



In the Lentz method the 3;* sections, after removal of the paraffin, are flooded 

 with absolute alcohol. They are then stained with a 1/2% solution of eosin in 60% 

 alcohol for one minute. Wash in water and next stain for one minute in Loffler's 

 methylene blue. Again wash in water. Apply Lugol's solution to the section for 

 one minute and then differentiate alternately in methyl alcohol and water until the 

 section is pink. After washing in water, again stain with Loffler's blue for one-half 

 a minute, then wash in water and dry carefully with filter-paper. Now differentiate 

 in alkaline alcohol (i drop of a 5% solution NaOH in 30 c.c. absolute alcohol) until 



