PREPAEATION OF VACCINES 119 



surgical treatment of the lesions. Cases of this kind 

 are chronic suppurating sinuses — as poll evil, fistu- 

 lous withers, pyorrhcea alveolaris, or suppurating 

 periodontitis. In this latter disease there are gener- 

 ally numerous organisms present, and a polyvalent 

 vaccine should therefore be employed. Chronic in- 

 flammation of the eye, such as conjunctivitis caused 

 by pyogenic organisms, yields readily to vaccine 

 treatment or antistreptococci serum. 



Preparation of Vaccines. — For all practical pur- 

 poses vaccines may be regarded as suspensions 

 containing intracellular toxins in combination with 

 bacterial protoplasm, and the results obtained by 

 their employment depend upon the activity of these 

 toxins and the quantity present in the vaccine. Such 

 vaccines may contain (a) dead bacteria, now commonly 

 called "bacterins " — the bacteria are destroyed either 

 by heat or chemical reagents; (h) bacteria in the 

 " living " condition, now spoken as " true vaccine," 

 either unaltered, attenuated, or ** sensitised " by 

 combination with the homologous immune body. A 

 vaccine may be " autogenous " — that is, prepared from 

 the particular strain of bacterium already producing 

 the infection in the patient; or "stock" — that is, 

 one prepared from another bacterium of the same 

 species, but already stored in the laboratory. How- 

 ever, a few general principles may at once be laid 

 down with regard to their preparation. In the first 

 place there is a consensus of opinion that as the passage 

 of an organism through the body of each individual 



