196 COMPARATIVE DENTAL ANATOMY 



a rule have good, strong teeth, but their physical 

 organization is also sometimes degenerated by 

 lack of nourishment or by disease. Their teeth 

 also then partake of the general deficiency, and 

 become deteriorated in structural integrity also. 

 This fact shows that dental degeneracy and dis- 

 ease is due to deficiency of general structure, 

 strength, and integrity, for the teeth are among 

 the first of the tissues to be affected by disturb- 

 ance of the nutritive supply. 



The teeth of civilized man are much reduced 

 in size as well as structure, and also the strength 

 of their supporting environments, by disuse. 

 The gradual lessening of the function of mastica- 

 tion, and the reduction of the force and variety 

 of jaw movements has led to a marked weakening 

 and degradation of the dental mechanism in Man. 

 Growth force has been reduced by disuse, and the 

 whole apparatus has become more or less rudi- 

 mentary, in accordance with the law of economy 

 of growth in the unused parts. The jaws are 

 much contracted through disuse, — so much so 

 that there is often lack of space for the teeth to 

 erupt in proper position. This produces irregu- 

 larity of the arrangement of the teeth, and, in 

 the case of the third molars, leads to serious dis- 

 turbances, owing to the shortening of the jaws 

 and lack of room for them to come into place. 

 The teeth are also disappearing through economy 



