THE PATHOGENIC RHIZOPODA 303 



smallpox, and the Negri bodies of rabies, as protozoan organisms of the 

 nucleophaga type. 



Neuroryctes hydrophohicB, Williams, the "Negri body," offers the 

 best evidence of the rhizopod affinities of these intracellular inclu- 

 sions, the mammalian brain cells, better than the skin cells, lending 

 themselves to rapid fixation and study. 



When Pasteur and his immediate followers were working on the 

 antirabic serum in connection with the cure of hydrophobia, they 

 were obliged to wait from two to three weeks to tell whether the treat- 

 ment they were giving a supposed victim was necessary or not. This 

 was due to the fact that many days were required for the disease to 

 develop in laboratory animals inoculated with the virus of the sus- 

 pected animal, and, as may be imagined, it was a period of great 

 suspense for all concerned. In 1898 the inoculation period was 

 shortened to about nine days by Wilson's substitution of guinea-pigs 

 for rabbits, these animals taking the disease more quickly than rabbits 

 as used by Pasteur. Still, the time was far too long for diagnosis. 

 Today it is possible to determine rabies in "mad" animals off the 

 street in one-half hour. This wonderful practical advance in technical 

 methods of the laboratory is due to the discovery by Negri, in 1903, 

 of minute, characteristic inclusions in nerve cells of brain and spinal 

 cord of animals with rabies, and by a special "smear" method of 

 demonstrating them devised by A. W. Williams in 1904. The value 

 of the Negri bodies in diagnosis was quickly recognized by pathologists 

 throughout the world, and contributions confirming and extending 

 Negri's discovery poured into the press. At the present time it is 

 recognized that these characteristic structures occur in 100 per cent, 

 of definite cases of street rabies, and that they are found nowhere else 

 in diseased tissues. "What claims have these specific structures to be 

 regarded as organisms, and if organisms, where do they belong? 



Negri regarded them as protozoa belonging to the class sporozoa, but 

 was not particularly clear as to their classification. Previous observers, 

 notably Di Vestea, in 1894, and Grigoriew, in 1897, had mentioned 

 structures in the nervous system of rabic animals and had described 

 them as protozoa, but the things observed were apparently quite unlike 

 the Negri bodies. Others, notably Volpino, in 1904, followed Foa, 

 Schaudinn, and Prowazek in their interpretation of the Guarnieri 

 bodies in smallpox, in believing that the real organism of hydrophobia 

 is the granule, more often multiple, found in the substance of the 

 "body," while the bulk of the "body" consists of material secreted by 

 the cell (hence Prowazek's term " chlamydozoa") about the parasite. 

 Williams' and Lowden's work, in 1906, and Negri's later papers leave 

 no grounds for such an interpretation, the former believing that the 

 granules represent distributed chromatin so characteristic of many 

 forms of protozoa, and placing the Negri bodies as protozoa in" the 



