STRANGLES 91 



ill producing passive immunity in the animals which 

 have not become affected, if it be prepared from the 

 particular strain of organism responsible for the out- 

 break of the disease. Thus if the serum of animals 

 recovered from the disease be used to protect the 

 healthy in-contact ones, good results can be hoped for. 

 However, this immunity is of short duration. 



Vaccines prepared from killed cultures of strepto- 

 cocci have been used to give active immunisation, but 

 the results are very indifferent. An autogenous 

 vaccine should give much better results in treatment, 

 as obviously an outbreak in a stable is caused by the 

 same strain of organism ; this latter vaccine is 

 especially useful in chronic conditions or in attacks 

 which run an irregular course, such as abscess forma- 

 tion in regions remote from the primary seat of the 

 affection. A method now extensively used in human 

 practice, both in the treatment of affections due to the 

 various pyogenic cocci and for production of active 

 immunisation against other infections, is the use of 

 sensitised vaccines. An autogenic vaccine is prepared, 

 and either before or after its sterilisation the bacterial 

 emulsion is mixed with its specific antiserum, the anti- 

 serum being previously heated to 56° to destroy the 

 complement. This mixture is then allowed to stand 

 for twelve hours, when it can be shown that the 

 bacilli have entered into combination with their 

 specific amboceptor. The bodies of the bacteria are 

 then washed free from serum in several changes of 

 physiological saline solution and standardised in the 



