R. J. Anderson, Note on a Diastema between Molars and Premolars etc. 207 



question it has scarcely reached the level of the second premolar and 

 the pair are much fresher than any of the other molar teeth. 



Taking the teeth of a jaw, at random, in which the mouth is 

 "full", I find that the teeth are approximately the same, in their 

 antero-posterior diameters, throughout the molar series. The third 

 molar a little more and the second a little less than the jaw with 

 the gap. The first molars measure the same from front to the back 

 of the crowns. The third premolars are exactly the same in diameter 

 from before back. Taking the age as six years, it seems probable 

 that during the interval between the emergence of the third Premolar 



and the first Molar of the lower jaw the second Premolar emerged, 

 which is somewhat narrower than the corresponding tooth in another 

 jaw under examination whilst Premolar III is the same. If the second 

 Molar Milk were small, the third permanent Molar might come to 

 occupy then a space farther forwards perhaps than it naturally has. 

 Another explanation is there might be a primary elongation of the 

 dental groove and dislocation of Sacs, so as to throw the range of 

 Molars farther back. In two mandibles amongst several examined a 

 slight fissure was observed. As a specimen for teaching purposes it 

 is particularly convenient. The crescentic groove external to the gap 

 is bounded by a ridge that reaches from the middle of the third Pre- 

 molar to the middle of the first Molar. 



