1. Heat at 70°C. destroys the form of the flagella and their ability to combine with flagellar agglutinins but it does not destroy their antigenic nature since they can still generate flagellar agglutinins in the animal body.
2. Heat at 70°C. and even at 120°C. in the autoclave does not destroy the forms of the bacilli themselves nor their ability to become agglutinated and to absorb agglutinins.
3. Somatic agglutinins are destroyed to a considerable extent by heat at 70°C. and completely destroyed by heat at 75°C.
4. Heat at 70°C. causes little or no destruction of flagellar agglutinins but a temperature of 75°C. changes the agglutinins so that they react more slowly and produce a slightly lower reaction with a zone of inhibition in the stronger dilutions.