Occurrence, Etiology. 465 



Russia is heavily infected as is indicated by the frequent introduction of the 

 disease into Germany and Austria (in 1908 there were 7,253 cases in 4,060 com- 

 munities). 



The disease is also frequently found in Servia, Bulgaria and in Roumania 

 (273 cases in 1908; in 1906, 142 mad dogs were brought to the veterinary institute 

 of Bucharest), while it is observed more rarely in Turkey. 



In Belgium there were 123 cases in 1908, in Italy 525, in Switzerland 2. In 

 Holland 41 cases of rabies were observed in 1907, and in Spain the disease also 

 seems to appear frequently, but Denmark, Sweden and Norway have for years 

 been free from the disease. 



In North America rabies is very common (Frothingham) and has been in- 

 creasing in prevalence during the last ten years (Hart). In the United States 

 230 human beings were the victims of rabies in 73 cities from 1890 to 1900, while 

 in the District of Columbia 91 eases of rabies in animals were reported from 

 1893 to 1900. 



In Africa, the disease is also known, and in Asia it appears very frequently, 

 while Australia has thus far been free from it. 



Etiology. Eemlinger and Riffat-Bey produced typical 

 rabies in 6 out of 19 rabbits with a filtrate of highly diluted 

 virulent, brain emulsion which passed through a fairly porous 

 Berkefeld filter. According to the results of these experiments, 

 which were later confirmed by Di Vestea, Schriider, Bertarelli 

 & Volpino and others, the virus of rabies must belong to the 

 filterable microorganisms. The attempts at cultivation which 

 have thus far been unsuccessful, justify the supposition that 

 it multiplies only in the tissues and fluids of the body. The 

 purest and most concentrated virus is secured -in the central 

 nervous system of the diseased animals; it is also found in 

 the salivary glands and their secretions, and sometimes in other 

 glands of similar structure (lachrymal glands, pancreas, mam- 

 mary glands), while in the aqueous humor (Gibier, Pasteur, Al- 

 banesi, Courmont & Nicolas), in the cerebro-spinal fluid (Pas- 

 teur), and in the blood (Marie) the virus is found only in excep- 

 tional cases, and in the flesh not at all. (Konradi found it in the 

 blood of guinea pigs, but only in small quantities.) 



Negri Bodies. In 1903 Negri found in dogs and rabbits inoculated 

 with either street or fixed virus, and also in animals which had died 

 or had been killed after natural infection small, round, oval or three 

 cornered inclusions in the large ganglion cells of the hippocampus 

 major, in the Purkinje cells of the cerebellum, in the ganglion cells 

 of the cerebral cortex, pons, and medulla oblongata, and sometimes 

 also in the nerve cells of the spinal ganglia and spinal cord. These 

 structures now known as Negri bodies, are 1 to 27 /* long, 1.5 to 5 a* 

 broad and appear red in color when stained with methylene blue- 

 eosin '(the Mann method of staining) . These cell inelosures (see Plate I) 

 contain in their interior very small, strongly retractile, and sharply 

 outlined granules. Negri believes that these bodies, which have been 

 found exclusively in rabid animals and persons are the parasites 

 (protozoa) of rabies, because among other reasons they appear in the 

 nerve cells only 14 to 23 days after artificial infection, and resist both 

 putrefaction and the effect of glycerin. 



These findings have later been confirmed by Volpino, Beck, Bosc, 

 Ernst, Bohne, Lentz, and others, and tiie structure of the bodies has 

 also been subjected to a closer study. According to Volpino 's investiga- 

 tions, the large bodies consist of a hyaline ground substance, in which 



Vol. 1—30 



