,<'. \HIES 



531 



FIG. 163 



This is the so-called rabies of the streets. Wolves, cats, foxes, dogs, 

 horses, cows, and deer may contract the disease; monkeys, rabbits, and 

 guinea-pigs are all inoculable with it, as, indeed, are all warm-blooded 

 animals. Rabies occurs in almost all parts of the world; it is most 

 common in Russia, France, and Belgium; it is not infrequent in Austria 

 and in those parts of Germany bordering on Russia, and in England. In 

 this hemisphere it is comparatively rare, yet it occurs occasionally in 

 various parts of the United States, in Mexico and South America. It 

 is extremely rare in North Germany, Switzerland, Holland, and Den- 

 mark, owing to the wise provision that all dogs shall be muzzled; and 

 in Australia it has not been known to occur. 



Etiology and Pathogenesis. Until recently all of the numerous re- 

 sea rehes in regard to the specific cause of rabies gave negative results. 

 The latest studies of this disease, however, make it seem probable that 

 hydrophobia may be added to the growing list of diseases caused by 

 protozoa. In 1903 Negri described certain bodies 

 in the large nerve cells throughout the central 

 nervous system of animals dying of this disease. 

 He found them in largest numbers in animals 

 dying after the fourteenth day of the disease, and 

 especially numerous in the cells of the gray matter 

 of Ammon's horns. He did not attempt to study 

 the bodies very minutely. Besides demonstrating 

 them in dogs, he found them in rabbits, in a cat, 

 and in a human being. He considers the bodies 

 protozoa and the cause of rabies. In our labo- 

 ratory we have fully corroborated Negri 's results. 

 There is no doubt as to the presence of the 

 bodies in large numbers in animals in which the 

 -disease has progressed somewhat slowly. In 

 animals dying quickly of fixed virus we have 

 also found many, but the forms are very small, 

 so that thev may easily be overlooked in poorly 



i * -\\~ i 11* ii 



prepared specimens. We have seen bodies small 

 enough to pass a Berkefeld, thus accounting for 

 the positive results obtained by some observers after the inoculation of 

 filtrates obtained from Berkefeld filters. We have found the larger forms 

 especially numerous in the brains of guinea-pigs inoculated with street 

 virus. Since the discovery of these bodies Poor, in the Health Depart- 

 ment laboratory, has examined 23 cases of "street rabies," 17 in dogs, 

 3 in horses, and 2 in human beings. In all of these cases he demon- 

 strated the presence of the Negri bodies in sections of the central 

 nervous system. All of these cases were subsequently proven to be 

 hydrophobic by animal inoculation. In a number of suspicious cases, 

 which were afterward proven to be non-rabic, no bodies were found. 



The smallest bodies in the sections seem to be structureless, taking 

 a homogeneous purplish stain with eosin and methylene blue. As the 

 bodies become larger they present a definite structure. A central grannie 



Negri bodies within nerve 

 cell of cornu ammonis in 

 (Schematic.) 



