CHAPTER XXVI 

 THE FILTERABLE MICROBES 



The Virus of Foot-and-mouth Disease.^ — This filterable or- 

 ganism occurs in the vesicles present in the mouth and on the 

 feet of the diseased animals, and also in the milk of cows suffering 

 from foot-and-mouth disease. The virus was shown to be filter- 

 able- by Loffler and Frosch in 1898. It is jendered inert by heat- 

 ing to 50° C. for 10 minutes. Animals are immune after recovery 

 from the disease. Cattle and swine are naturally susceptible 

 and a few cases of the disease have occurred in man. Nothing 

 definite is known concerning morphology or cultures. The in-- 

 fection seems to be transmitted with the food as well as by 

 inoculation. 



The Virus of Bovine Pleuro-pneumonia. — This organism is 

 present in the affected lungs and in discharges from the respira- 

 tory tract of cattle suffering from pleuro-pneumonia. Nocard 

 filtered the virus through a Chamberland "F" filter in 1899. It 

 is rendered inert by heating at 58° C, but retains its virulence in 

 glyceriiie for weeks and resists freezing. Cultures have been 

 obtained by the collodion-sac method byNocard and Roux. The 

 organisms in such cultures are extremely minute and variable in 

 form. Some of them are spirals and others approximately spher- 

 ical. Immunity follows recovery from the disease, and has been 

 induced artificially by inoculation with cultures and also by inocu- 

 lation with virulent exudate from the lung of a dead animal into 

 the subcutaneous tissue of the tail of the animal to be immunized.^ 



The Virus of Cattle Plague (Rinderpest). — This organism 

 occurs in the blood, organs and excretions of cattle suffering from 

 the disease. It was shown to be filterable by Nicolle and Adil- 



' KoUe and Wasserman, Handbuch, 1012. Bd. I. S. 028. 



