276 Seventeenth Annual Report of the 



Domestic animals, even of ;i kind little susceptible to the 

 disease, dogs, horses, mules, are apt to carry manure on their feet 

 and leg's, as are the wheels of wagons and the runners of sleighs. 



Toxins, antitoxins, serums, and infectious materials of reduced 

 virulence constitute a subtle means of infection, being employed to 

 lessen susceptibility, or produce immunity. Such products, repre- 

 senting a brand, furnished by a country where foot and mouth 

 disease exists, are likely to be contaminated by the germ of that 

 malady, as in the New England ease quoted above, and to become 

 the center of a new diffusion of the plague. A somewhat similar 

 experience is said to have been had at the inception of the Ameri- 

 can outbreak of 1908, and the next succeeding herd or section of 

 herd that was inoculated a little later in the same buildings and 

 yards came down with the disease. On the whole, this danger is 

 a very real one, and demands the most rigid legal restrictions in 

 the line of research on animal plagues and their products and, in 

 the preparation of immunizing and other serums, such control and 

 regulation as would render the terrible risks we now face an im- 

 possibility in lime to come. Tint we can never be free from such 

 dangers, so long ;is we import from countries that suffer from foot 

 and month disease, antitoxin, immunizing serums, vaccine lymph, 

 bovovaccine, bla< '> leg or anthrax lymph, or any one of the many 

 animal products used lor purposes of immunization and in the 

 preparation of which no real sterilization is practiced. 



For a similar reason, fresh hides, carcasses, bones, guts, hair, 

 bristles, wool or blood, from an infected country are pregnant 

 with danger. The same remark applies to clothes soiled with cow 

 manure, urine, milk, or other secretion or exudation, unless such 

 have been thoroughly soaked in a disinfectant, or subjected for a 

 length of time to a boiling temperature. 



symptoms in cattle 



There is first a period of incubation, shorter in hot than in cold 

 weather and varying from 36 hours to 6 days. Four days is the 

 average interval after a simple exposure. Exceptionally it appears 

 to extend to 15 days, but such prolonged incubations are, as a rule, 

 apparent rather than real, the virus remaining in contact with the 

 surface for some days before it, secures a means of entrance. The 



