472 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



After the tests are completed, the product is distributed under aseptic 

 conditions, in small, sterile, capillary tubes or upon sterile, ivory points, 

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

 to tropical countries. Under the average climatic conditions the product 

 should remain active for a period of about three months. 



BLACKLEG VACCINE. The production of blackleg vaccine depends 

 upon the use of a virulent culture of B. anthracis symptom atici. A 

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

 symptoms 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 outside 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 re- 

 moved from the body under aseptic precautions. This material is taken 

 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 until the 

 mass becomes pasty or putty-like in consistency, the material placed in 

 small shallow pans and attenuated by drying at a 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 devitalization and probable death of any extraneous 

 vegetative forms during the attenuation process. 



The blackleg vaccine is tested relative to the degree of attenuation by 

 the injection of one dose for cattle into each of a series of several guinea- 

 pigs. The number of guinea-pigs which die indicates the degree of 

 virulence of the tested material. Another test consists in the injection 

 of three series of guinea-pigs with the attenuated virus, each pig of each 

 of the three series receiving, respectively, one-third, one-half and three- 

 fourths of the usual dose for cattle. When the results are correct those 



