110 



Biological Therapy 



formation in others. For these reasons vaccines should he 

 used on only perfectly healthy animals. 



3. Bacterins are suspensions of killed bacteria in a 

 suitable vehicle, usually normal saline solution, to which 

 is added phenol or trikresol as a preservative. Bacterins are 

 successfully used for the prevention and treatment of a large 

 number of acute and chronic diseases. For successful use 

 of bacterins the etiological factor responsible for the disease 

 should be known and the bacterin to be used for its preven- 

 tion or treatment should contain this organism or organisms, 

 as the case may be. This is referred to as specific treatment 

 and the greater the specificity of the product the better the 

 results which follow its use. 



Bacterins are known as stock and autogenous. In the 

 case of the former, the product is prepared in advance and 

 is available when required. It contains bacteria ordinarily 

 associated with a given condition and the results from the 

 use of stock bacterins are generally entirely satisfactory. 



Autogenous bacterins are, strictly speaking, prepared 

 from the individual on which they are to be used. In vet- 

 erinary practice this term is also used to describe a product 

 containing bacteria isolated from one individual and in- 

 tended for use in other members of the same herd or flock. 

 In exceptional cases stock bacterins fail to accomplish their 

 purpose either because of the presence of some organism 

 not ordinarily associated with such cases or because of un- 

 usual virulence possessed by some organism present in the 

 individuals under treatment. In such cases bacterins which 

 contain the specific bacteria present in the case may be 

 prepared. These are referred to as autogenic bacterins. It 

 is fortunate that in most cases stock bacterins are entirely 

 efficacious since the preparation of autogenous products re- 

 quires time which may be urgently needed for treatment and 

 since their production is naturally somewhat expensive. 



At Pitman-Moore Biological Laboratories great care is 

 given to the preparation of autogenous bacterins. The or- 

 ganisms are carefully studied by our staff of bacteriologists 

 and only bacteria having etiological significance are placed 

 in the finished product. See page 114 for discussion regard- 

 ing bacterins. 



4. Filtrates and Bacterial By-Products. These consist 

 of the purified and sterile by-products of bacterial growth. 



