114 THE ACUTE SELF-LIMITED INFECTIONS 



bacillus upon the central nervous system. This 

 poison, like that of the diphtheria germ, is separable 

 or extracellular. It is produced by the bacteria, 

 absorbed along the motor nerves, and carried to the 

 brain and cord. Tetanus bacilli enter the body almost 

 invariably by punctured or lacerated wounds. They 

 multiply in the deep, covered position afforded by such 

 wounds, but are not themselves taken up by the blood 

 to be distributed throughout the body, only their 

 poisons being absorbed. The bacteria are common in 

 soil, manure, dust from covered places, wood, and the 

 like. Their vitality is considerable, due to the forma- 

 tion of resistant spores. 



Wounds carry the germs beneath the skin, where 

 they lie covered and hidden in the deeper tissues. 

 They do not grow in the presence of oxygen (anaerobic), 

 so that a secluded place in the depths of wounds favors 

 their development and that of their toxin. Simple 

 uncomplicated, open wounds are probably never the site 

 of development for tetanus bacilli. If other germs are 

 introduced the tissues are further devitalized by them, 

 and they absorb any available free oxygen, so that 

 favorable conditions for tetanus are increased. Either 

 spores or vegetating germs may be introduced on rusty 

 nails, splinters of wood or glass, blank-cartridge plugs, 

 or the grinding of dirt into wounds. Tetanus some- 

 times appears in the newborn or in the puerperal 

 mother, particularly after instrumental delivery. Ordi- 

 nary gelatin, sometimes injected under the skin to 

 arrest hemorrhage, is said to often contain spores. 



Between the time of introduction of the germs 

 and the outbreak of symptoms a period of incubation 



