RABIES 649 



dehydrated as usual in graded alcohols, embedded in paraffin, and 

 sectioned. The sections are best stained by the method of Mann, as 

 follows: 



The sections, attached to slides in the usual way, are immersed in the follow- 

 ing solution for from twelve to twenty-four hours: 



Methylene-blue (Gruebler OO), 1 per cent 35 c.c. 



Eosin (Gruebler BA), 1 per cent 35 c.c. 



Distilled water 100 c.c. 



They are then differentiated in: 



Absolute alcohol 30 c.c. 



Sodium hydrate, 1 per cent in absolute alcohol -5 c.c. 



In this solution blue is given off and the sections become red. After about five 

 minutes the sections are removed from this solution, are washed in absolute alco- 

 hol, and are placed in water where they again become faintly bluish. It is of ad- 

 vantage to immerse them, now, in water slightly acidified with acetic acid. Follow- 

 ing this they are dehydrated with absolute alcohol and cleared in xylol, as usual. 



In preparations made in this way, the nerve cells are stained a pale 

 blue, and in their cytoplasm, lying either close to the nucleus or near the 

 root of the axis-cylinder process, are seen small oval bodies stained a deep 

 pink. The bodies are variable in size, measuring from 1 to 27 micra in 

 diameter. They are round or oval, show a more deeply stained periph- 

 eral zone which has been interpreted as a cell membrane, and, in their 

 interior, often show small vacuole-like bodies. There may be more than 

 one, often as many as three or four, in a single cell. 



The rapid demonstration of Negri bodies in smears of brain tissue 

 has recently been advocated by many observers and has been extensively 

 used for diagnosis. It is carried out, according to Van Gieson, 1 in the 

 following way: A small pin-head-sized piece of brain tissue from the 

 regions indicated above, is placed on one end of a slide under a cover- 

 glass and the cover is gently squeezed with the finger until the tissue is 

 flattened out into a thin layer. The glass cover is then gently shifted 

 across the slide until the brain tissue is smeared along the entire surface. 

 These smears may be fixed in methyl alcohol and stained by the Giemsa 

 method, as described in the chapter on Spirochaeta pallida (see page 

 592). 



Stained in this way, the Negri bodies are stained light blue, in con- 

 trast to the darker and more violet cell-bodies. 



1 Van Gieson, Proc. of N. Y. Pathol. Soc., N. S., iv, 1906. 



