18 A MANUAL OF DENTAL ANATOMY. 



basal cusp of the canine and the inner cusp of the bicuspid 

 are the same thing, differing only in degree, while it is 

 interesting to note that the pulp chamber in the bicuspid 

 has hardly any prolongation towards the small inner cusp, 

 so that the resemblance between the two teeth is thus made 

 more complete. 



This close relationship of canines and bicuspids will be 

 again considered in the chapter on the Homologies of the 

 Teeth ; for our present purpose it will suffice to merely point 

 out its existence. The transition from the bicuspids to the 

 molars is more abrupt ; at least it is not so easy to point 

 out exactly how a modification of the one would arrive at 

 the form of the other. But it merely needs an exaggera- 

 tion of the differences existing between a canine and a first 

 bicuspid to make a good imitation of a second bicuspid. 



If any one will take the trouble to make mental note of 

 the deviation in form which he meets with in teeth, he will 

 find that they almost invariably consist of approaches to- 

 wards the form of the teeth on either side of them ; and 

 will infallibly be led to the conclusion that incisors, canines, 

 and bicuspids are not three patterns of teeth perfectly 

 distinct, and each sui generis, but that they are modifications 

 of one and the same pattern. I may add, that comparative 

 odontology teaches us the same thing, and demonstrates 

 clearly the substantial identity of the three forms, as also 

 of the true molars. 



Upper molar teeth have crowns of squarish form, the 

 angles being much rounded off. It may be premised that 

 the first molar is more constant in shape than the second, 

 and this latter than the third ; with this proviso the first 

 and second may be described together. 



The masticating surface carries four subequal cusps, two 

 labial or external and two lingual or internal ; the anterior 

 internal cusp is distinctly the largest, and it is connected 

 with the posterior external cusp by a thick oblique ridge 



