DIAGNOSIS 605 



inoculation, that is, when the virus has become of the fixed type, 

 only the smallest bodies are seen. The classification of these bodies, 

 to which Williams has given the zoological name neuroryctes hydro- 

 phobia, cannot yet be regarded as established, and Calkins states 

 that we are not yet justified in classifying them as sporozoa, because 

 their variable form, their uninucleate condition, leading to chromatin 

 distribution and budding, though found in other protozoa, are not 

 characteristic for sporozoa. Williams and Lowden, whose careful 

 researches of the Negri bodies have contributed much to our know- 

 ledge, describe them as follows: "They measure in size from 0.5 



FIG. 214 



* 



I 



10. 





 



"Negri bodies," or Neuroryctes hydrophobias, in different stages of chromatin distribution. 



(After Negri.) 



to 18 micra (Negri saw some as large as 25 micra); no very large 

 forms are found in the early stages of the disease, and in the fixed 

 virus infection only the very small forms are found. They vary 

 much in shape, from mere irregular points to larger, round, oval, 

 or elongated bodies. They are generally inside of the large ganglion 

 cells, but in smear preparations (see below) they may be found 

 squeezed out of the cells. Whatever the variety of species of animals 

 infected the bodies preserve their same general characteristic structure, 

 namely, a hyaline cytoplasm with an entire margin, and with one or 



