844 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



develop in an atmosphere of carbon dioxide. Media for the cultivation of the 

 bacillus should be slightly alkaline and should contain for best growth about 2 

 per cent of glucose or 1.5 per cent sodium formate. The addition of pieces of fresh 

 raw sterile tissue is valuable. On agar at 37 colonies appear in forty-eight hours 

 which show microscopically, a mass of tangled threads resembling colonies of B. 

 subtilis or Bact. anthracis. In broth a cloudiness is produced in twenty-four to 

 thirty-six hours with the development of gas and a very disagreeable odor. In 

 gelatin the colonies develop more slowly than on agar and show liquefaction. In 

 old stab cultures a pine tree growth occurs. Gas is usually produced. In milk 

 growth occurs without coagulation. Acid is produced in some carbohydrate media. 

 Gas is produced during the action upon protein and consists chiefly of carbon dioxide 

 but also of hydrogen sulphide and certain volatile organic compounds commonly 

 found in putrefactions. The tetanus bacillus forms two soluble toxins, tetano- 

 lysin, and tetano-spasmin. The former is less stable and dissolves red blood- 

 corpuscles. The latter produces the characteristic spasms of the muscles. This 

 poison may be obtained after one to two weeks' growth in slightly alkaline salt- 

 peptone-bouillon under anaerobic conditions at 37.5 and separated by filtration 

 through porcelain niters. When taken by the mouth the toxin is ineffective, given 

 intravenously it produces a generalized tetanus, while after subcutaneous injection 

 the disease begins with local spasms. The central nervous system is reached by 

 ascent of the toxin along the motor nerves nearest the point of inoculation. A 

 dose of toxin injected directly into the nerve trunk of an animal may produce a 

 fatal result when it is innocuous intravenously. The spores often withstand 80 

 for one hour and live steam for about ten minutes. Direct sunlight destroys them 

 in time. They survive drying for several years and resist the ordinary disinfectants 

 for a considerable length of time, i : 1000 mercuric chloride for three hours, 5 per 

 cent carbolic acid for about ten hours. 



Practically all mammalia are susceptible to tetanus though rats are 

 but slightly so. Very minute doses of toxin suffice to kill mice and 

 guinea-pigs. Birds show but little susceptibility and the hen is said 

 to be three hundred thousand times more resistant to tetanus toxin 

 than the horse. Reptiles and amphibians are practically immune to 

 very large doses when kept at low temperature. 



Natural infections probably do not occur without the presence of 

 other microorganisms. The bacillus and its associated material gains 

 entrance through some break in the tissues. The organism is prac- 

 tically confined to the site of inoculation, but it is sometimes found in 

 the blood and internal organs after death. 



Against toxin-freed cultures phagocytosis is probably the process 

 which overcomes infection. The toxin is highly antigenic and animals 

 can be immunized against it in a manner similar to that for diphtheria 

 toxin. 



