METHODS OF USING ANTI-HOG-CHOLERA SERUM 157 



rums are the same, and we offer the observation 

 for what it is worth. 

 Follow-up treatment is indicated: 



1. For very valuable hogs where the greatest 

 possible safety is required. 



2. When the following conditions coexist in the 

 same animal or herd : 



A. Immediate protection is imperative. 



B. Ultimate permanent immunity is desired. 



C. Conditions render immediate simultaneous 

 treatment dangerous. 



Follow-up treatment is contra-indicated in all 

 cases in which it appears 'that serum alone or si- 

 multaneous treatment will be equally effective. 



It is in immunizing hogs with resistance obvi- 

 ously below normal, and in maintaining immune 

 herds under somewhat adverse conditions that 

 follow-up treatment renders greatest service. In 

 practice, especially in the East, we constantly en- 

 counter the three conditions we have enumerated 

 above, and follow-up immunization relieves us 

 from the necessity of choosing between serum 

 alone which will not produce a permanent immu- 

 nity, and simultaneous treatment which is posi- 

 tively dangerous at the time when immediate pro- 

 tection is required. In a succeeding chapter the 

 adaptations of follow-up treatment will receive 

 further attention in connection with specific con- 

 ditions which we meet in the field. 



