MICROBIAL DISEASES OP MAN AND DOMESTIC ANIMALS 79 1 



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 



Fig 166 — Tetanus baciUi showing end spores. {After Kolle and Wassermann from 



Slill.) 



through porcelain filters. 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, s 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 sufl&ce to kill mice and 

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



