116 HOG CHOLEEA 



mils of 5 per cent aqueous solution of carbolic acid 

 for each 95 mils of blood. The pigs used to pro- 

 duce simultaneous virus must meet the same es- 

 sential requirements as are met by those used to 

 produce hypering virus; that is, they must show 

 ample evidence that they are suffering with acute 

 hog cholera at the time they are bled, and they 

 must be free of all other infectious diseases trans- 

 missible through their blood. 



Hog cholera virus is sometimes heated at 50 C. 

 for twelve hours before being sent out, in which 

 case a virulence test is necessary before it can 

 be released for field use. In our own work we 

 greatly prefer unheated virus. 



Keeping qualities. Like protective serum, hog 

 cholera virus must be kept in a dark, cool place. 

 Bureau of Animal Industry regulations allow it 

 to be used not more than sixty days subsequent to 

 the date of drawing, but wherever a thirty-day 

 limit is practicable, we believe it is safer. There 

 are times when an inactive virus may result in as 

 heavy losses as are sometimes charged to impo- 

 tent serum. 



Labeling. The virus label should include: 



1. Eelease tag and license number if the labora- 

 tory is operated under federal license. 



2. Name and address of manufacturing firm or 

 institution. 



3. Dosage table. 



