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EXPERIMENTAL GENERAL SCIENCE 



portions of the skin. In fact, the teeth, though considerably 

 harder than bone, are really hardened portions of the skin. 

 In man there are two sets of teeth, the first set or "milk teeth" 

 being twenty in number and the second or permanent set 

 containing thirty-two. There are the same number of teeth 

 in each jaw and the same number on each side of the jaw. The 

 first set consists of four chisel-like incisors in front in each 

 jaw. Back of these on each side is a single strong canine 



FIG. 88. The temporary teeth. The rudiments of the permanent teeth are 

 seen enclosed in the bones. (Gorgas.) 



(cuspid) tooth and back of the canines two teeth with flattened 

 surfaces for grinding and called molars in consequence. The 

 milk teeth fall out one by one and are succeeded by stronger 

 teeth of the same kind. In this permanent set, three larger 

 grinding teeth or "back teeth" make their appearance further 

 back on each side of the jaw. The last of these are sometimes 

 called wisdom teeth. All the teeth are firmly set in the jaw 

 and all are supplied with nerves and blood vessels which run 



