Cha,.. vii.] Til E FACE. 117 



the case of a man who was much troubled by a 

 carious tooth in the lower jaw (supplied by the third 

 division of the fifth), and who developed a patch of 

 grey hair over the region supplied by the auriculo- 

 temporal nerve (a branch also of the third division). 



The muscles of mastication are often attacked 

 by spasm. When the spasm is clonic the chattering 

 of the teeth is produced that is so conspicuous a 

 feature in rigor. When the spasm is tonic the mouth 

 is rigidly closed, and the condition known as trisnius, 

 or lockjaw, is produced. Trismus is among the tirst 

 symptoms of tetanus. It is also very apt to be pro- 

 duced by irritation of any of the sensory branches 

 of the third division of the fifth, since the motor nerve 

 supply of the muscles themselves is derived from that 

 trunk. Thus trismus is very common in caries of the 

 lower teeth, and during the "cutting" of the lower 

 wisdom tooth. It is much less common in affections 

 of the upper set of teeth, since they are supplied by 

 a more remote division of the fifth nerve. 



Teeth. As a test of age the following periods 

 for the eruption of teeth are given by Mr. C. Tomes : 

 Temporary teeth : Lower central incisors, six to nine 

 months ; upper incisors, ten months ; lower lateral 

 incisors, and four first molars, a few months later ; 

 then, after a rest of four or five months, the canines ; 

 and, lastly, the second molars ; the whole being in place 

 by the end of the second year. Permanent teeth : First 

 molars, sixth or seventh year ; next in order the 

 lower central incisors, then the upper central incisors, 

 and a little later the laterals, the eighth year ; first, 

 bicuspids, ninth or tenth year ; second bicuspids and 

 canines, about the eleventh year, the lower preceding 

 the upper ; the second molars, the twelfth or thirteenth 

 year ; the wisdom teeth, eighteen to twenty-five or later. 



An alveolar abscess is an abscess about the 

 fang of a tooth. In the case of single-fanged teeth 



