THE NEGRI BODIES 661 



may assume two forms the raging and the paralytic 

 The latter is not met with in man, unless certain rare 

 forms of acute ascending paralysis (e.g. Landry's) be 

 manifestations of it. In the dog either may occur, but 

 in rodents the paralytic form is almost always the one 

 assumed. The incubation period in man is very variable ; 

 it is never less than about twenty days, and possibly may 

 be as long as two years, or even more ; it is usually 

 about seven to ten weeks. In the dog it is usually two 

 to three months, and in the rabbit, after inoculation 

 from the dog, about two to three weeks. After onset, the 

 disease is invariably fatal in the course of a few days. 



The virus resides in the central nervous system, as was 

 shown by Pasteur, in the saliva and salivary glands, in 

 the lachrymal glands and adrenals, and to some extent 

 in the spleen, but the lymph glands, blood and tissues 

 generally are non-infective. 



Emulsions of brain, etc., filtered through a porcelain 

 filter are usually non-infective, but Remlinger found that 

 after very complete trituration the virus may pass 

 through such a filter. 



No micro-organism has been demonstrated with cer- 

 tainty in rabies. Negri described the constant presence 

 of structures the Negri bodies particularly in the 

 grey matter of the hippocampus major, which he regards 

 as protozoa. They are of varying size, apparently encap- 

 suled, taking a pink colour in smears stained with eosin 

 and methylene-blue, the smallest spherical and structure- 

 less, larger ones with a central granule or nucleus, the 

 largest, round, ovoid or elongated, containing several 

 (as many as eight) granules (Fig. 64, 6). They occur 

 abundantly in animals suffering from chronic rabies, 

 but in the acute type are scanty, though still to be 

 found ; in " fixed virus " (p. 664) they are very small. 

 So constantly are the Negri bodies present in rabies, and 



