GENERAL CONSIDERATION OF FILTRABLE VIRUS 903 



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

 following solution for from twelve to twenty-four hours : 



Methylene-bluc (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 alcohol, and are placed in water where they again become faintly 

 bluish. It is of advantage to immerse them, now, in water slightly acidified 

 with acetic acid. Following 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, measur- 

 ing from 1 to 27 micra in diameter. They are round or oval, show 

 a more deeply stained peripheral 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, 23 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. 



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

 contrast to Hie darker and more violet cell-bodies. 



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



