MOLARS OF SECOND DENTITION PERMANENT MOLARS. 39 



toward the inside and surrounding cavities, which are more 

 or less filled with cement ; to the anterior loop is attached a 

 small, secondary loop. The external border is always longer 

 than the internal. As the tooth wears and the table is estab- 

 lished, the cavities disappear. At first the imbedded portion is 

 hollowed by cavities, which reach the body of the tooth itself 

 and contain the papilla, or pulp, formed principally of blood- 

 vessels and nerves; later, these resolve into distinct roots, three 

 each for the first and sixth molars, and four each for the otliers. 

 According to Girard, these become distinct at five years of age. 



Fig. 27. 



Superior permanent molar (right side),— virgin tooth. E, external face ; 

 I, internal face ; E I, surface of contact. 



(Fig 27.) If the head is placed horizontally the first molar is 

 found imbedded in a vertical position, while the others incline 

 somewhat from below to above and from in front to behind. 



The superior molars are implanted in alveolar cavities, pris- 

 matic like the teeth, and separated from each other by bony 

 septa, whicli are thin at their free borders and thicker above. 

 The bottoms of the three last project into the maxillary sinuses, 

 while those of the three first are in the superior maxillary bone 

 itself In very old liorses the sinus may reach the root of the 

 third or even second tooth. 



