MANUFACTURE OF VACCINES 565 



removed by filtration and the filtrate is injected into guinea-pigs. 

 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 or upon sterile, ivory 

 points, 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 difiScult 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 symptomaiici. A heifer 

 is inoculated with a small portion of the virus and rapid, acute symp- 

 toms are usually produced. Death usually supervenes in about three 

 days. The carcass and ward are thoroughly disinfected, the body of 

 the animal is suspended, and, after again carefully disinfecting the out- 

 side of the body, portions of the skin are removed and the muscular 

 tissue is inspected. Those areas of the muscles which show the dark 

 color, gaseous 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 spontaneously. It is then ground and sterile water is 

 added untU the mass becomes pasty or putty-hke in consistency, after 

 which the material is placed in small shallow pans and attenuated 

 by drying at temperature 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 

 devitahzation and probable death of any extraneous vegetative forms 

 during the attenuation 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 



