THE FILTERABLE MICROBES 389 



Bey in 1902, and is able to pass through the Chamberland "F" 

 filter. The virus resists drying for four days and remains active 

 for two or three months when spread on hay in a dark place. 

 It is destroyed by distilled water in five days, by glycerin in eight 

 days and rendered avirulent in a few hours by admixture of bile. 

 The disease is an acute febrije disorder characterized by severe 

 inflammation of the mucous membranes and rapid emaciation. 

 It is usually fatal. Immunity follows recovery and is induced 

 artificially by injecting the bile of infected animals under the 

 skin of the healthy cattle. In this way an active immunity is 

 acquired without an evident attack of the disease. 



The Virus of Rabies.^ — This organism exists in the central 

 nervous system, the peripheral nerves, the salivary glands, the 

 saliva and less frequently in other parts of the body of persons 

 or animals suffering from lyssa or rabies. The virus was filtered 

 by Remlinger in 1903. It may also be dialyzed through collodion 

 sacs.^ The virus is rendered inert by drying for two weeks, and 

 by heating at 55° C. for 30 minutes, by admixture of bile in a few 

 minutes, and by the gastric juice in 5 hours. It remains virulent 

 in glycerine for several months. Negri in 1903 described certain 

 bodies which seem to occur in the central nervous system in- 

 variably and exclusively in this disease. They are especially 

 numerous in the ammon's horn of the brain in cases of street 

 rabies. Preparations should be made from the gray matter of 

 the brain. A bit of this tissue is carefully spread on a slide by 

 exerting moderate pressure upon it with a second slide or a cover- 

 glass and at the same time moving it along the surface of the first 

 slide. The film is fixed in pure methyUc alcohol and stained with 

 Giemsa's solution, or it may be stained directly without fixation 

 with Leishman's stain. The Negri bodies are round and some- 

 what irregular in outline, from in to 27/i in diameter, and usually 

 inside the nerve cells. In the interior of the larger bodies, smaller 

 spherical structures of variable size and number may be seen. 

 The exact nature of the Negri bodies is uncertain. Some stu- 



' Poor and Steinhardt, Journ. Infect. Dis., 1913, Vol. XII, pp. 202-205. 



