CHAPTER IV. 



INFECTIOUS DISEASES INVOLVING PRINCIPALLY 



THE NERVOUS SYSTEM. 



TETANUS. LOCKJAW. 



Definition. — Tetanus is an acute infectious disease due to an 

 anaerobic microorganism which produces in the body a toxic 

 product resembling strychnin in its physiological action. 

 The disease is characterized by tonic spasms of the muscles. 

 The mind of the patient remains undisturbed. 



Occurrence. — While tetanus has a wide general distribution 

 it is confined to infected districts. Where the soil has become 

 contaminated with the germ of the disease it is of common 

 occurrence. For this reason it is more prevalent in the 

 tropics than in northern climes; in some parts of the country, 

 commoner than in others. Horses, swine and sheep are more 

 often attacked than other domestic animals. The disease is , 

 more prevalent in the spring and fall than during other sea- 

 sons. Since the use of antiseptics has become more general, 

 tetanus is not as frequent as formerly. 



Etiology. — The disease is caused by the Bacillus tetani, an 

 anaerobic rod-shaped germ, usually carrying a spore at one 

 end. The germ occurs in the spore form in earth, putrifying 

 fluids 1 and manure. In infected districts tetanus spores are 

 normal inhabitants of the intestines of ruminants. 



Natural Infection. — Infection takes place through a fresh 

 wound into which the spores of the specific bacillus have 

 gained entrance. Obviously wounds so situated as to become 

 contaminated with soil or manure are most apt to become 

 infected. Therefore wounds in the feet, scrotum, umbilical 

 cord, compound fractures of the limb bones, tooth cuts and 

 eye wounds are most dangerous in this regard. As the original 

 wound may be very small and heal by first intention, it cannot 



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