142 BACTERIA IN THE SOIL 



microscopical preparation. Like other spores, they are extremely 

 resistant to heat, desiccation, and antiseptics.* 



As we have seen, this bacillus is a strict anaerobe, growing only 

 in the absence of oxygen. The favourable temperature is 37 C., and 

 it will only grow very slowly at or below room temperature. The 

 organism is readily stained by the ordinary stains and by Gram's 

 method. 



An excellent culture is generally obtainable in glucose gelatine. 

 The growth occurs only in the depth of the medium, and appears as 

 fine threads passing horizontally outwards from the track of the 

 needle. At the top and bottom of the growth these fibrils are 

 shorter than at the middle or somewhat below the middle. For 

 extraction of the soluble products of the bacillus, glucose broth may 

 be used. (For isolation and detection of the B. tetani, see Appendix, 

 p. 481.) 



In some countries, and in certain localities, the bacillus of tetanus 

 is a very common habitant of the soil, and when one thinks how 

 frequently wounds must be more or less contaminated with such 

 soil, the question naturally arises, How is it that the disease is, 

 fortunately, so rare? Probably we must look to the advance of 

 bacteriological science to answer this and similar questions at all 

 adequately. Much has recently been done in Paris and elsewhere to 

 emphasise the relation which other organisms have to such bacteria 

 as those of typhoid and tetanus. In tetanus, Kitasato, Vaillard, and 

 others have pointed out that the presence of certain other bacteria, 

 or of some foreign body, is necessary to the production of the disease. 

 The common organisms of suppuration in particular appear to 

 increase the virulence of the bacillus of tetanus. How these 

 auxiliary organisms perform this function has not been fully 

 elucidated. Probably, however, it is by damaging the tissues and 

 weakening their resistance to such a degree as to afford a favourable 

 multiplying ground for the tetanus bacillus. Some authorities hold 

 that they act by using up the surrounding oxygen, and so favouring 

 the growth of the germ of tetanus. In any case it is now generally 

 held that in natural infection the presence of some foreign body or 

 suppurative bacteria is necessary to produce the disease. 



Quarter-Evil and Malignant (Edema 



Quarter-Evil (or symptomatic anthrax) is a disease of animals, 

 produced in a manner analogous to tetanus. It is characterised by 

 a rapidly-increasing swelling of the upper parts of the thighs, sacrum, 

 etc., which, beginning locally, may attain to extraordinary size and 



* Atlas and Principles of Bacteriology, by Lehman n and Neumann, part ii., 

 pp. 330-337. 



