192 



ANNUAL REPORT OF THE 



OfiE. Doc. 



under oxaniinalion arc made by pressing a slide over a fresh cut 

 surface, usually of the hipi»ocampus major or cerebellum. The sec- 

 tion of the tissue, hijjpocampus major or cerebellum, is flattened 

 out widi a slide uuder jjressure. The slide raised from the tissue 

 will show a film on the slide which was in contact with the tissue, 

 and this lilm may be fixed and stained as smeais. In the film, the out- 

 line of the nerve cells and cellular structure taken up, is little dis- 

 turbed. In the impressions, the Negri bodies are not so apt to be 

 misj>laced or rubbed out of the nerve cell as the,y are in the smear 

 preparations. The stain for Negri bodies used by Harris^- has been 

 tried and found to take up more time in its application than the 

 Van Gieson stain, but at the same time the inner structure and the 

 differential stain are well brought out and the stain is recommended 

 in the examination of specimens iu which the Negri bodies are very 

 small in size, or inexceedingly small numbers. With good material, 

 Negri bodies may easily be demonstrated by either smear or im- 

 I>resions in seveial minutes. Fresh material is considered better 

 than decomposed, but in our experience Negri bodies are more easily 

 demonstrated in brain tissue from an animal dead 24 to 48 hours, 

 than in tissue examined Avithin a short time after death. The 

 changes that take place in the 24-48 hours after death appear to pre- 

 pare the tissue so that Negri bodies stand out more clearly, and 

 smears and impressions show clearer nerve cells. Decomposition 

 does not interefere very much in the examination until the outline of 

 the nerve cells is destroyed. Even when nerve cells are no longer 

 seen Negri bodies may be found, but it is not safe to venture a di- 

 agnosis on these extracellular bodies alone. Although it is believed 

 that Negri bodies can be demonstrated in from 97 to 99 per cent, of 

 animals afflicted with rabies that have been i)ermitted to die a 

 natural death, the results of the examination of the hippocampus 

 major and cerebellum, by means of smear preparations, as shown in 

 the following figures do not show this to be so: 



Hippocampus major 539, .. 

 (Smears for Negri bodies), 



393 Positive 

 Cases. 



349 (86.3%) + 



37 ( 9.6%)- 



7 ( 1.7%) S 



Cerebellum, 



(Smears for Negri bodies). 



341 Positive 

 Cases. 



301 (88.2%) + 



33 ( 9.67o)— 



7 ( 2.0%) S 



146 Negative 

 Oases. 



143 (97.9%)— 

 ( 0.0%) + 

 3 ( 2.0%) S 



145 Negative 

 Cases. 



141 (97.5%)— 

 ( 0.0%)+ 

 4 ( 2.7%) S 



+ Positive. 



-Negative. 



S-Suspicious. 



The high percentage 9.G per cent, of failures to demonstrate Negri 

 bodies in positive cases is unusual, and perhaps partially explained 

 in that many of the specimens examined were from animals killed 

 early in the onset of symptoms of the disease, and in that the speci- 

 mens examined have been in all stages of decomposition. Our 



