904 DISEASES 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, 24 who add 

 to 10 c.c. of distilled water three 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 red 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, 25 Williams and Lowden, 26 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 morphology 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 



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



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

 56 Williams and Lowden, loc. cit. 



