INFECTIOUS DISEASES 193 



having all instruments, bottles, and so on, sterile, and of 

 having environments that are conducive to asepsis. The 

 immune swine that are to be hyperimmunized should be 

 kept in a pasture or yards that are concreted to prevent 

 undue filthiness. The virus used may be obtained from 

 the field, that is, from natural outbreaks of cholera, or it 

 may be produced by injecting healthy, susceptible pigs 

 with one to two cubic centimeters of virus. A pig 

 weighing from sixty ro ninety pounds is usually used. 

 The virus pigs should be carefully observed, and tempera- 

 ture records maintained. If susceptible pigs have been 

 injected with a virulent virus there will be evidence of 

 the disease in four to seven days, and from the seventh 

 to the ninth day the temperature of the pig will probably 

 range from 105 to 108 degrees Fahrenheit, and is then 

 prepared for slaughter by thoroughly washing and apply- 

 ing some disinfectant to the skin of the venter surface of 

 the body. In addition to these precautions the inferior 

 cervical region is shaved. The entire pig is shrouded with 

 moist, antiseptic gauze to prevent any particles of dust 

 from dropping into the vessels used in collecting the virus. 

 The vessels are severed, and the blood is collected in a 

 sterile vessel and the fibrin whipped and removed; the 

 remainder of the blood is filtered through gauze, and con- 

 stitutes the virus blood. The virus pig is then autopsied, 

 and if lesions of cholera are not found, or if lesions of 

 other diseases are found, the collected virus blood is 

 discarded. The collection of field virus requires the same 

 precaution. 



Hyperimmunizing may be accomplished by the intra- 

 peritoneal, intravenous, or intramuscular injections of virus. 

 The quantity of virus employed depends upon the method 

 used, that is, the slow or quick method. For the intravenous 

 and intramuscular methods five cubic centimeters of virus 

 are used to the pound weight of the hog that is being hyper- 

 immunized. This quantity is divided and given in two 

 injections in the slow process and as a single injection in 

 the quick process. In the intravenous method the 

 injection is made in an ear vein after properly cleaning and 



