358 AGEICULTTJEAL AND INDUSTRIAL BACTEBIOLOGY 



Cidtural Characters. — The fact that Clostridium tetani 

 is an obligate anaerobe makes its isolation in pure culture 

 somewhat difficult. Colonies grown in gelatin are usually- 

 woolly. Bouillon is clouded and a sediment is formed. 

 Blood serum is liquefied and milk more or less completely 

 digested. Brain medium is blackened as a result of the 

 development of hydrogen sulphide in the presence of iron. 



Physiology. — The organism grows best at body tem- 

 perature but readily likewise at room temperatures. It 

 requires for the best development almost complete exclusion 

 of oxygen. It will grow readily in mixed cultures with 

 some organism which is an obligate aerobe. The spores are 

 quite resistant and will withstand drying indefinitely. High 

 temperatures maintained for considerable periods of time 

 are requisite for certain destruction of the organism. Gas 

 and acid are produced in small quantities from carbo- 

 hydrates. 



Pathogenesis. — The tetanus bacillus usually produces 

 disease as a result of its inoculation into the tissue of a 

 wound under conditions favoring the exclusion of air. The 

 fact that it is not an obligate pathogen is well illustrated by 

 the fact that when its washed spores are injected into the 

 tissues, they usually do not produce tetanus, but are even- 

 tually destroyed by the body. It is usually only when this 

 organism is associated with dirt and is to some extent pro- 

 tected that it multiplies and produces its characteristic 

 toxin and symptoms of disease. It will also produce fatal 

 results when injected in pure culture together with a little 

 of the medium (containing toxin) in which it has been 

 growing. 



The Clostridium tetani when growing in a wound pro- 

 duces a powerful toxin. This travels apparently through 

 two channels to the central nervous system. Some of the 

 toxin passes into the blood stream and is absorbed from it 

 by the central nervous system. Other portions travel along 



