THE MOUTH, AND ITS TREATMENT. 275 



or several, or even the entire set. The periosteum, 

 being largely composed of fibrous tissue, is not 

 very prone to take on inflamation, but its situation 

 is most unfavourable to recovery from an attack 

 when it has been set up. The double fold of 

 membrane lies between two bony surfaces, which 

 only yield to the membrane as it thickens (one of 

 the changes it imdergoes during the inflammatory 

 process) in one direction, and that eminently cal- 

 culated to increase the evil. By this thickening 

 the tooth is raised in its socket above its fellows, 

 and consequently first receives the pressure of 

 the opposing jaw. It thus becomes driven back 

 upon the membrane, and so the mischief is greatly 

 increased. During the early stage of this affection, 

 the momentary relief derived fi:'om clenching the 

 jaws together, tempts the individual in whom it 

 occurs fi'equently to do so, until, from the pro- 

 gress of the attack, the membrane becomes so 

 excessively tender that the slightest touch of the 

 tooth gives pain. 



The symptoms of periostitis are pain, heat, 

 and swelling, confined more or less to the affected 

 part. I say more or less, because sometimes the 

 pain shifts its position, rendering it difficult to 

 decide with confidence where the mischief really is. 

 These symptoms undergo aggravation at night, 

 the reclining posture, the greater warmth of the 

 body in bed, and certain physiological changes 

 which occur at this period of the twenty-four 



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