TETANUS 325 



in soil, and is found in the large intestine of horses and 

 cattle. Heavily manured soils and those with a high con- 

 tent of organic matter seem to contain the bacilli in greater 

 numbers than soils lower in humus. The bacillus is an an- 

 aerobe that forms very resistant spores. The toxin it pro- 

 duces is one of the most poisonous substances known, when it 

 is introduced into the tissues of an animal. A man weighing 

 One hundred and seventy-five pounds will be killed by 0.23 

 of a milligram. Toxins have been made of such potency 

 that 0.00,000,002 gram is fatal to a white mouse. An or- 

 ganism capable of producing such a substance does not need 

 to grow extensively in the body of an animal in order to 

 cause injury. 



The tetanus bacillus is usually introduced into the tissues 

 through a puncture wound by some object that carries the 

 infective material into the deeper lying tissues. Puncture 

 wounds made by rusty, dirty nails are most dangerous. 

 Horses, especially, become infected in this manner. Punc- 

 ture wounds bleed but little, and therefore the foreign mat- 

 ter is not likely to be washed out by the blood; nor is it 

 easy to cleanse the wound by washing, as may be done with 

 a more superficial abrasion. The infection may occur in 

 such operations as dnrUinir, castration, and through the 

 umbilical cord of foals. The more frequent occurrence of 

 the disease in horses, as compared to other domestic animals, 

 is apparently due to the greater susceptibility of the horse 

 to the toxin. It is estimated that the horse is twelve times 

 as sensitive as the mouse and 360,000 times as sensitive as 

 the fowl to this toxin. 



In man a large proportion of the disease is due to the 

 wounds produced by Fourth of July accidents. The filling 

 of many forms of fireworks is earth, which may contain 

 the extremely resistant spores of the tetanus bacillus. Some 

 portion of the filling may be blown into the skin by the 



