244 BACTERIOLOGY FOR NURSES 



Pathogenesis. Tetanus under ordinary conditions affects only 

 man and horses; it can be produced, however, in other animals 

 by the injection of pure cultures on their toxin. 



The normal habitat of the tetanus bacilli is the intestinal tract 

 of herbivorous animals. In their dejecta the organisms find their 

 way into the soil and in the pulverized soil they are scattered 

 with the dust practically everywhere. Tetanus bacilli may be 

 found almost wherever man and domesticated animals have been. 

 In some localities they are much more numerous than in others, 

 and in certain parts of Long Island and New Jersey an unusual 

 number of cases have developed as a result of small wounds. 



When tetanus bacilli enter the body by way of the mouth 

 they are quite harmless. Passing into the intestines, they find 

 ideal anaerobic conditions and a temperature suitable to their 

 development, and they are able to multiply there without causing 

 any harm to their host. It is exceedingly curious that the horse, 

 which may almost be regarded as a tetanus " carrier," is the most 

 susceptible of all animals to tetanus toxin. Rats and birds are 

 only slightly susceptible and fowls scarcely at all. It is estimated 

 that an amount of tetanus toxin sufficient to kill a hen would kill 

 five hundred horses. 



Tetanus appears in man almost always as a wound complica- 

 tion, although the presence of tetanus spores in a wound does not 

 necessarily result in infection. It has been found by animal 

 experimentation that in a clean wound a few spores free from their 

 toxin do not give rise to the disease; they are in all probability 

 disposed of by the phagocytes. On the other hand, a lacerated or 

 contused wound made by a dirty, blunt instrument is a much more 

 favorable ground for their development, but even in such wounds 

 if mixed infection is prevented by prompt disinfection and conse- 

 quent killing of the associated bacteria, tetanus spores if present 

 in all probability will not develop. Symbiosis is perhaps the 

 main factor in determining whether or not the spores will be able 

 to germinate. The presence of other organisms, and especially the 

 pyogenic cocci, seem to facilitate their development. 



Not only traumatic tetanus but all other forms are now known 



