410 INFECTION AND IMMUNITY. 



association with organisms which are known to 

 favor its growth. When incrusted in solid ma- 

 terial and accompanied by suitable saprophytes it 

 may readily find the anaerobic conditions which 

 are demanded for germination of the spores. 

 Resistance. The spores are very resistant. In one instance 

 they remained virulent for eleven years on a splin- 

 ter of wood. They may be killed in six days by 

 direct sunlight. In comparison with non-spore- 

 forming organisms they are very resistant to anti- 

 septics. Kitasato found that they were killed in 

 five minutes by steam, in fifteen hours by a 5 per 

 cent, carbolic acid, in two hours by 5 per cent, 

 carbolic acid to which 0.5 per cent, of hydro- 

 chloric acid was added, in three hours by 1 to 1000 

 corrosive sublimate and in thirty minutes by the 

 same solution to which 0.5 per cent, hydrochloric 

 acid had been added. 



infection Tetanus is conspicuously a wound infection and 

 that it develops so frequently from wounds which 

 are contaminated with earth is readily understood 

 from the distribution of the organisms as cited 

 above. Considering, however, the great number of 

 such wounds and the prevalence of the bacillus, 

 the rarity of the disease is remarkable. In expla- 

 nation of this fact investigations have shown that 

 the organism is not a vigorous parasite, that it 

 demands special conditions for its development in 

 the tissues. According to Vaillard and Eouget, 

 the spores when washed free of toxin do not cause 

 tetanus, but rather are taken up and destroyed by 

 leucocytes. 



Anaerobic The bacillus, furthermore, is a strict anaerobe, 



ai wounai demanding for its development a wound from 



which the air is largely excluded. It is well known 



