698 INFECTION AND IMMUNITY. 



are specific for rabies, and of great diagnostic- 

 value. Against the hypothesis that these bodies 

 are the cause of hydrophobia, the following points 

 are cited : The distribution of the jSTegri bodies 

 does not correspond with the greatest concentra- 

 tion of the virus in the nervous tissue, the latter 

 being most abundant in the medulla and pons 

 where the Negri bodies are encountered rarely. They 

 present certain analogies with "protoplasmic in- 

 clusions" seen in other conditions, as in carcinoma, 

 variola, etc. Eemlinger found that the virus 

 passes through appropriate Berkefeld filters, and 

 for this reason Schiider holds that the bodies of 

 Negri, being too large for filtration, can not be 

 considered as the specific organism. The view of 

 Schiider may be criticized, since the smallest 

 ISTegri bodies are so minute that their filtration 

 would seem to be possible. Nevertheless, it must 

 remain doubtful whether bodies one micron in di- 

 ameter, the proliferation of which has not been 

 proved, may be considered as parasites. The hy- 

 pothesis of Negri is hardly on a satisfactory basis 

 at present. Remlinger considers the bodies as 

 "involution forms" of the tissue cells which have 

 been invaded by the true parasite. 



The filterability of the virus argues for its ultra- 

 microscopic size. By means of filtration one may 

 isolate it even from Drains which are badly decom- 

 posed, and the method renders it possible to ob- 

 tain pure cultures for purposes of immunization. 

 Inoculation with filtered virus is sometimes fol- 

 lowed by a prolonged incubation period which may 

 depend on the retention of many of the organisms 

 by the filter. A similar effect was produced by 

 Hogyes by inoculating with diluted virus. 



