650 DISEASED CAUSED BY FILTRABLE VIRUS 



The smears may also be stained by a method originated by Van 

 Gieson, which gives an excellent contrast stain and reveals more clearly 

 the inner structure of the Negri bodies. Van Gieson's stain is prepared 

 as follows : 



Distilled water 10 c.c. 



Saturated alcoholic solution of rosanilin violet 2 drops. 



Saturated aqueous solution of methylene-blue diluted one-half 



with water 2 drops. 



This method has been modified by Williams and Lowden, 1 who add 

 to 10 c.c. of distilled water 3 drops of saturated alcoholic basic fuchsin 

 and 2 c.c. of Loeffler's methylene-blue. The slides are fixed in methyl 

 alcohol, washed in water, and covered with the freshly prepared stain. 

 The slide is held over the flame until the solution steams and is then 

 rinsed in water and dried. The Negri bodies assume a brilliant hue and 

 contain in their interior darkly stained, irregular particles which have 

 been interpreted as chromatin bodies. As to the nature of the Negri 

 bodies opinions are still divided. Their constant presence in rabic 

 brain tissue is unquestioned and their diagnostic significance well 

 established. Cultivation experiments, however, have been uniformly 

 unsuccessful. A number of observers, Negri himself, Calkins, 2 Williams 

 and Lowden, 3 and others, believe these bodies to be protozoa. The 

 last-named authors base this opinion upon the definite morphology of 

 the bodies, and their staining properties, which in many respects are 

 similar to those of protozoa. These observers also claim that the mor- 

 phology of the bodies shows a number of regular cyclic changes which 

 are found accompanying different stages of the disease; these changes 

 correspond, according to these workers, to similar cycles occurring 

 among known protozoa of the suborders of the class Sporozoa. Many 

 pathologists still look upon them as specific degenerations of the nerve 

 cells similar to the changes observed by Babes. 



It is not possible to decide absolutely from the facts at present at our 

 disposal whether or not the Negri bodies should be regarded as parasites 

 or as specific degeneration products. Their constant presence in rabic 

 animals, and their apparent absence from normal brains and the brains 

 of animals dead of other diseases, would tend to favor the parasitic 

 view. To us it would seem that added to this the clear outlines, apparent 

 regularity of structure, and curiously consistent grouping of the darkly 



1 Williams and Lowden, Jour. Inf. Dis., 3, 1906. 



2 Calkins, Discussion, Proc. N. Y. Pathol. Soc., N. S., vol. vi, 1906. 

 8 Williams and Lowden, loc. cit. 



