INFECTIOUS DISEASES 197 



and this should be encouraged, as a cleaner product and 

 one that is more easily injected is produced. The blood 

 obtained from hyperimmune swine by either process is 

 preserved by adding a small percentage of phenol or 

 trikresol and properly sealed and placed in storage at a 

 temperature of about 50 degrees Fahrenheit. Before the 

 serum is used it is tested. First, second, third, and fourth 

 bleedings from different hyperimmunes, or the blood from 

 different hyperimmunes obtained by slaughtering, are 

 mixed up to quantities of 80,000 cubic centimeters. This 

 amount constitutes a series, and therefore each series is 

 a composite serum. For a test sample a proportionate 

 quantity is taken from each separate quantity that makes 

 up a series. The sample should be obtained immediately 

 after bleeding, thus obviating reopening of the bottles. 



For the test eight healthy, susceptible pigs, weighing 

 from sixty to ninety pounds each, are selected. These 

 pigs are maintained in four separate pens of two each. 

 The test is made as follows: Each of the eight pigs is 

 injected with two cubic centimeters of virus; pigs No. 1 

 and No. 2 receive twenty-five cubic centimeters of serum; 

 pigs Nos. 3 and 4 receive twenty cubic centimeters of 

 serum; pigs No. 5 and 6 receive fifteen cubic centimeters 

 of serum; and pigs Nos. 7 and 8 receive the virus only. 

 Pigs Nos. 7 and 8 are designated check pigs, and they 

 should show visible symptoms and die of typical cholera 

 within twelve to eighteen days. A temperature record 

 is maintained for twenty days, and from observing this 

 record the virulency of the virus and the potency of the 

 serum can in a measure be determined. The following 

 chart is the record of a serum test: (See p. 198.) 



This test is not absolute, but it is of value as an indi- 

 cator. The test should be repeated if the following con- 

 ditions arise. First, if the check pigs should not show 

 any evidence of cholera within ten to fifteen days; sec- 

 ond, if the check pigs or any of the other six should show 

 a constant high temperature beginning on the second, 

 third, or fourth day after the test begins; third, if either 



