Inoculation of Rabbits 371 



later be found. Other parts cut from the appropriate areas of the 

 brain tissue are placed in fixative to prepare for sectioning should 

 that later become desirable. 



Williams and Lowden* devised a new technic of examination for 

 Negri bodies that has been of considerable advantage to those en- 

 gaged in looking for them for assisting in the diagnosis of rabies, as 

 well as in studying the bodies themselves. It may be called the 

 " smear method" to differentiate it from the older and less certain 

 "section method." Briefly, the method is as follows: 



Glass slides and cover-glasses are washed thoroughly with soap and 

 water and heated in a flame to get rid of oily substances. A small 

 bit of the gray substance of the brain chosen for examination is 

 placed upon 'one end of a slide, a cover-glass placed upon it and 

 pressed down so as to spread out the nervous tissue in a thin layer, 

 when the cover is slowly moved to the opposite end of the slide 

 spreading out the nerve-cells and distributing them over the surface. 

 The tissues selected for examination should come from at least three 

 different parts of the gray matter of the central nervous system, first, 

 from the cortex of the brain in the neighborhood of the fissure of 

 Rolando, or in the region corresponding to it; second, from Ammon's 

 horn; third, from the cerebellum. 



The smears are dried in the air and then stained as stated above. 



Formerly an examination of the spinal sympathetic ganglia was 

 made, and the diagnosis made from what was found in them. This 

 constitutes the least important and most rarely pursued form of diag- 

 nostic procedure at the present time. However, we will suppose 

 some sympathetic ganglia secured. The remainder of the animal's 

 head can then be destroyed. With the material thus secured we 

 make the following diagnostic tests: 



1. Examination for the Negri bodies. 



2. Inoculation of rabbits. 



3. Examination for histological changes in the ganglia. 



1. The Negri Bodies. As now generally conceded, the discovery 

 of these bodies in the cells of the central nervous system may be 

 taken as positive evidence of the existence of rabies in its transmis- 

 sible stage. 



2. The Inoculation of Rabbits. This is only necessary in highly 

 suspicious cases in which no Negri bodies are found, or in which the 

 investigator is not satisfied that such bodies are specific indications 

 of the disease. 



The glycerinated or fresh nervous tissue can be employed. A bit of 

 the tissue is made into a creamy suspension, under aseptic precau- 

 tions, by adding physiological salt solution, crushing and grinding 

 in a small agate mortar. When it is ready a rabbit is anesthetized, 

 the hair is pulled out over one side of the skull (or if it be preferred, 



* "Jour, of Infectious Diseases," 1906, in, 452. 



