106 HOG CHOLEEA 



and at the same time, 20 mils each of the sample 

 of serum to be tested. The other two receive no 

 serum, but are employed as controls to determine 

 the virulence of the virus. Daily observations are 

 made and temperatures are recorded as required, 

 preferably once a day. The essential require- 

 ments for a satisfactory test are that both pigs 

 which receive virus only shall sicken during the 

 test period (21 days) and that at least one of them 

 shall sicken between the fourth and seventh days 

 subsequent to injection, and shall before the fif- 

 teenth day suffer from hog cholera in a degree 

 sufficient to cause death. As an additional con- 

 dition, no more than one of the pigs that receive 

 serum and virus shall show visible illness, and in 

 case one should sicken it must be completely re- 

 covered before the twenty-first day following the 

 beginning of the test. 



Bureau of Animal Industry regulations govern- 

 ing the interpretation of tests will be found in the 

 Appendix. In general, tests are classified accord- 

 ing to results as ' ' satisfactory, " "unsatisfac- 

 tory" or "no test," the latter giving indefinite 

 results. The satisfactory test has already been 

 described; the unsatisfactory test is usually re- 

 ferred to impotent or contaminated serum; re- 

 tests are indicated when the serum-treated pigs 

 or more than one of the virus pigs sicken before 

 the fourth day, when the control pigs do not sicken 



