MANUFACTURE OF VACCINES 729 



The absence of symptoms in the treated animals shows that no tetanus 

 toxin has been elaborated in the culture medium and therefore that 

 the vaccine does not contain B. tetani. 



After the tests are completed, the product is distributed under 

 aseptic conditions, in small, sterile, capillary tubes sealed in sterile, 

 glass containers, properly labeled, dated and kept in the refrigerator 

 until placed upon the market. 



If kept in a cold dark place, smallpox vaccine retains its protective 

 activity for a considerable period. Under the influence of heat and light 

 it rapidly deteriorates. For this reason it is difficult to ship the vaccine 

 to tropical countries. Under suitable conditions the product should 

 remain active for a period of about one year. 



BLACKLEG VACCINE. The production of blackleg vaccine depends 

 upon the use of a virulent culture of B. anthracis symptomatici (B. 

 chauvai, B. gangraena emphysematosa) . A heifer s inoculated with 

 a small portion of the virus and rapid, acute symptoms are usually 

 produced. Death usually supervenes in about three days. The car- 

 cass and ward are thoroughly disinfected, the body of the animal is 

 suspended, and, after again carefully disinfecting the outside of the 

 body, portions of the skin are removed and the muscular tissue is in- 

 spected. Those areas of the muscles which show the dark color, gas- 

 eous formation and characteristic lesions of blackleg, are removed to the 

 laboratory and examined microscopically for the presence of the specific 

 organisms. After the muscle is freed from the gross connective tissue, 

 it is suspended in strips or finely chopped, and allowed to dry spon- 

 taneously. It is then ground and sterile water is added until the mass 

 becomes pasty or putty-like in consistency,. after which the material is 

 placed in small shallow pans and attenuated by drying at tempera- 

 ture of 85 to 100 for six or seven hours. In preparing the "single 

 vaccine" most laboratories attenuate the virus by drying at an average 

 temperature of about 90 for six hours. In addition' to the aseptic 

 precautions observed in conducting the above processes, microbial 

 contamination is practically eliminated by the devitalization and 

 probable death of any extraneous vegetative forms during the attenua- 

 tion process. 



Blackleg vaccine (single) is tested, according to the method recom- 

 mended by the Bureau of Animal Industry, U. S. Dept. of Agriculture, 

 as follows: A series of eight guinea pigs are injected intramuscularly 



