RABIES 291 



specially fine filters, and an inoculation with the filtrate has successfully 

 reproduced the disease. 



In 1903 Negri found both in inoculated and rabid street dogs, in certain 

 parts of the cerebral nervous system, particularly in the horns of the amnion, 

 in the Pur kin je cells of the cerebellum, in the nerve cells of the pons, in the 

 cord and the central cortex, when sections of these parts were stained by 

 Mann's method, (methyl blue-eosin), certain bodies which took up the 

 stain, and appeared a brick red, these bodies being round or slightly 

 oval, periform, or even irregular triangles, and varying greatly in size, 

 from 1 to 27 tx; either isolated or grouped in the cells. These were found 

 in dogs affected with rabies, as well as other rabid animals and man. 

 They retain their characteristics even when the cadaver was in a 

 state of advanced putrefaction and remain perfect in glycerine. Negri 

 regards these as the various stages of evolution of a parasite which 

 should be classed with the "protozoa" and claims these as the true 

 excitors of rabies. It is true that for some time before Negri had an- 

 nounced his theory, a number of observers thought that the origin of rabies 

 must be due to the protozoa, particularly Dijestal, who had described 

 having seen in the spine and ganglionic nerves, small bodies like 

 protozoa. 



These bodies are to-day generally known as Negri's corpuscles or 

 bodies, (see plate) , and have since been observed and described by a num- 

 ber of other observers, and studied particularly with regard to their 

 minute structure ( Volpino, Williams, Bohn) , and it must be admitted that 

 they are found with great regularity in rabid dogs and their presence is 

 regarded as diagnostic. 



In 1903 to 1905, 457 dogs suspected of rabies were examined 

 by Italian scientists; 297 were proved by inoculation to be rabid and in all 

 but nine the corpuscles of Negri were found. 



The claim of Negri that this specific parasite (protozoon) is the true 

 and only cause of rabies is a question that is opposed by those observers 

 who have filtered the emulsified brain substance of an affected animal 

 and the filtrate reproduced the disease by inoculation; there is a possibility, 

 however, that certain of these corpuscles may be so infinitesimal as to 

 pass through the filter and so small as to be beyond the power of the 

 microscope to render them visible. 



Pasteur has demonstrated that a rabid brain loses its infectious 

 virulence only when that part has become partially decomposed, that is 

 to say, after four or five days; while it remains virulent in air-tight tubes 

 or in moistened carbolic gauze. Neustube found that the brain of a 

 rabid dog retained its virulent properties when kept under a slightly 

 elevated temperature for ten or twelve days. Mergel found the virulence 

 as strong as ever in the putrid brain of a rabid wolf fourteen days after 



