GENERAL CONSIDERATION OF FILTRABLE VIRUS 905 



brains and the brains of animals dead of other diseases, would tend 

 to favor the parasitic view. To us it. would seem that added to 

 this the clear outlines, apparent regularity of structure, and curiously 

 consistent grouping of the darkly staining inclusions would add 

 weight to such an assumption. We have triturated rabic tissue 

 and shaken it up in anti-formin and seen many free Negri bodies 

 apparently enucleated from the cells in consequence. Such com- 

 plete extrusion from the cell also is seen in the ordinary smear 

 preparations. It is at least unlikely that a cell-degeneration area 

 would be expelled from the cytoplasm in so clearly outlined and 

 morphologically unaltered a form. The fact that the virus is filtrable, 

 as shown by Remlinger, 27 Poor and Steinhardt, 28 and others, would 

 on the other hand seem to contradict the etiological importance of 

 the Negri bodies unless, with some of the observers named, we 

 assumed them to represent a large stage in the life-cycle of a 

 protozoan parasite, which also occurred in smaller forms. It is a 

 curious fact, also, that Negri bodies are scarce or absent in the 

 spinal cord and cerebrum, though these areas are as virulent or 

 more so than the hippocampus and cerebellum. They are small and 

 hard to find in virus fixe, largest and most plentiful in cases in which 

 the incubation period has been prolonged as with street-virus in- 

 fection. Much can be said on both sides, but in analyzing the present 

 experimental facts, it seems fair to say that neither point of view 

 is certain, though the parasitic nature of the Negri bodies seems 

 very likely. 



The cultivation of parasites from rabic tissues has of course been 

 attempted by most bacteriologists who have studied the disease since 

 Pasteur. In all attempts, until very recently, either no results were 

 obtained or else the parasites described could be shown to be present 

 because of extraneous contamination. Recently Noguchi announced 

 that he has been able to cultivate the virus by employing a technique 

 similar to his methods of cultivating Treponema pallidum and 

 poliomyelitis virus. Into high tubes filled with ascitic fluid a bit of 

 fresh sterile rabbit kidney and a small piece of rabic virus were 

 placed. The ascitic fluid was covered with sterile oil and the tubes 

 incubated at 37.5 C. After five days' incubation cloudiness ap- 

 peared and with it, minute globoid bodies not unlike those seen in 





^Eemlinger, Ann. de Pinst. Past., xvii, 1903. 



28 Poor and tfteinltardt, Jour, of Inf. Dis., xii, 1913. 



