DISEASES PRODUCED BY ULTRA-MICROSCOPIC ORGANISMS 479 



and claim to have secured more favorable results than by the 

 older method. Nocard has also produced a curative and pro- 

 phylactic serum by the hyperimmunization of animals by the 

 injection of increasing doses of pure culture until six liters have 

 been used. In doses of 40 c.c. it served as an efficient prophylactic, 

 and, in larger amounts, as a curative agent in the early stages of the 

 disease. 



Transmission. The method of natural spread of the disease 

 is not certainly known. It is probably through inhalation of the 

 causal organism. 



Virus of Foot-and-mouth Disease 



Disease Produced. Foot-and-mouth disease, aphthous fever, 

 Maul- and Klauenseuche in cattle and other bovines, sheep, goats, 

 swine, deer, and occasionally horses, dogs, cats, and man. 



The disease has been known for over a century in Europe. 

 Loffler and Frosch, in 1897, Hecker, in 1898, and others since 

 that time have shown that the virus of foot-and-mouth disease 

 may pass through Chamberland and Berkefeld filters, but not 

 through the thicker Kitasato filter. 



Distribution. The disease is known from most of Europe, 

 Asia, and Africa. It has been introduced several times into the 

 United States, but has been stamped out. It has also been 

 reported from Argentina. 



Nature of the Virus. All efforts at observation and culture of 

 the organism have failed. The facts given above show it to be 

 a filterable virus and probably ultramicroscopic. 



Pathogenesis. The disease may be produced by the inocula- 

 tion of susceptible animals with the filtrate through a porcelain 

 filter. It is characterized by an acute fever, the appearance of a 

 vesicular eruption on the mucous membranes of the mouth, on 

 the feet and between the toes. It is commonly not fatal, but is 

 so contagious, and leads to such losses in flesh and milk, that it is 

 among the most feared of cattle diseases. 



Immunity. Vaccination by intentional infection of animals has 

 sometimes been practised in an effort to " get it over with " as 

 quickly as possible when it breaks out in a herd. An animal 

 recovered is relatively immune. Such methods are attended by 



