PATHOGENIC PROTOZOA 41 1 



Schaudinn regards Entamoeba coli as a harmless commensal, but 

 Entamoeba histolytica as a definite tissue-destroying parasite, a faculty 

 which gives to this form of tropical dysentery its pernicious and often 

 fatal characteristic. 



Rabies Furiosa 



From dysentery to hydrophobia seems a long jump and yet we may 

 find that these two diseases and with them others apparently as diverse, 

 as small-pox, sleeping sickness, etc., owe their malignancy to the de- 

 structive action of protozoa on different tissues of the body. I take up 

 rabies next because the organism of hydrophobia agrees in many of its 

 characteristics with that of dysentery, and belongs, as I believe, on the 

 present evidence, in the group of rhizopods. 



Peculiar structures have been known for several years in the brain 

 and nerve cells of animals with rabies. Negri, however, in 1904 was 

 the first to suggest that these are as distinctive of hydrophobia as 

 Plasmodium is of malaria, and he and his assistants succeeded in 

 establishing the conviction that these ' Negri ' bodies are sufficiently 

 characteristic to afford a quick and safe diagnosis of rabies. Beyond 

 the suggestion that these bodies are organisms comparable to the small- 

 pox organism as described by Councilman and his collaborators, Negri 

 did not attempt to outline their systematic position. From the ap- 

 parent absence of nuclei and other structures in the Negri bodies, 

 pathologists have been inclined to interpret them as secretions, or 

 degenerations of a specific type, and very few have been hardy enough 

 to regard them as protozoa. Among these few, however, is Dr. Anna 

 W. Williams, of New York, who spent a summer at Woods Hole three 

 years ago, working on protozoa, and who has done a great deal on 

 pathogenic protozoa; and to her belongs the credit of establishing the 

 protozoon nature of these enigmatical structures. 



One of the curious features of pathogenic protozoa is that they are 

 very refractory to the ordinary cytological stains, and do not behave 

 like other cells under hematoxylin or methylin blue, etc. This is why 

 the organism of syphilis was overlooked until last year, and this is why 

 Negri failed to get any evidence of cell structure in his rabies organism. 

 In all of his preparations and figures the bodies appear as highly 

 vacuolated structures with no sign of nucleus or differentiated cell body. 

 Dr. Williams, using the Giemsa stain, a method that has been singularly 

 successful in staining delicate pathogenic protozoa, showed that not 

 only do these Negri bodies have a definite structure with nucleus and 

 cytoplasm, but also that a series of nuclear metamorphoses occur 

 which are identical in their consecutive phases with the typical free- 

 living rhizopods. Nuclear fragmentation takes place until as in 

 Entamoeba or Centropyxis or Amoeba, etc., the cell is filled with chro- 



