74 BACTERIOLOGY 



inoculable into laboratory animals, is very commonly present 

 as a saprophyte in earth, especially in cultivated soil which has 

 been manured with horse- or cow-dung. In the faeces of the 

 former animal it is said to be practically normally present, and 

 therefore not only garden and farm soil but also street- and 

 road-dust usually contain tetanus bacilli ; and the disease can 

 easily be experimentally produced by inoculating mice or rabbits 

 with a little material obtained from such sources. The organ- 

 ism is an actively motile, slender rod, varying much in length, 

 and most easily recognised when spore-bearing, the spore being 

 terminal and more or less spherical, giving the typical " drum- 

 stick" appearance illustrated in Fig. 10, b. In its active 

 vegetative form, it possesses numerous flagella, stains readily, 

 and is Gram-positive. 



From its habitat, it is usually mixed with numerous other 

 organisms, often anaerobic like itself ; and with these it may 

 be introduced into a wound and give rise to the disease. 

 Foreign substances such as splinters of wood, grit, and dirt, 

 by the irritation which they produce, may assist its action. 

 As mentioned in a previous chapter, wounds with garden or 

 farm-implements, especially if penetrating deeply even though 

 comparatively small or with much contusion or laceration of 

 the tissues, are most liable to be followed by tetanus. In addi- 

 tion to the more usual methods by which the disease is 

 contracted, cases of tetanus may follow the bite of an insect, 

 bullet-wounds, burns, dental operations, infection of the 

 umbilical cord in newly-born children, and even from the 

 therapeutic injection of commercial gelatin if not previously 

 thoroughly sterilised. 



Although growing well under anaerobic conditions, the 

 organism is a difficult one to separate in pure culture from the 

 other anaerobes along with which it is usually found. Anaerobic 

 plate cultures may be made ; or the mixed culture may be 

 heated, say at 80 C. for an hour, or at 100 C. for from a half 

 to ten minutes or more, in the hope of killing off the less- 

 resistant non-sporing organisms. It grows best at body tem- 

 perature, but it also grows at ordinary room temperature. In 

 stab-cultures in glucose gelatin, or agar it grows best at the 

 deepest part of the thrust, i.e. farthest away from the air, 

 sometimes sending off delicate lateral offshoots, diminishing 

 towards the upper part of the growth, and producing the so- 

 called " bottle-brush " appearance. It causes slow liquefaction 

 of gelatin. 



Both in culture and in the living body it produces very 

 active toxins, of which there may be present in a single cubic 

 centimetre of an actively virulent broth-culture, enough to 



