]4() PROF. DR. L. BOLK 



a superior (}ualit.y, but from a morphological and evolutionary 

 standpoint this object is a very valuable one because it is the 

 actual incorporation of all the theoretical and prophetical deduc- 

 tions at which we arrive in the foregoing paragraphs. Further- 

 more, the object does not at all impress one as a pathological 

 one. 



In the lower jaw analogous instances occur more frequently. 

 I recall that cases in which the second inilk molar persists and 

 the third molar is absent, are not extraordinarily rare in the 

 lower set. The reduction of the second incisor in the upper jaw 

 is an indication of the occurrence of a future denture in this jaw 

 more seldom than in the lower. In the former the reduction of 

 three elements must concur, in the lower only two, hence the 

 chance is greater in the latter than in the former. 



Finally, I wish to call attention to a very fine specimen in 

 my collection represented in figure 28. It is the lower jaw of 

 an adult (but still young) woman. In the right half of the jaw 

 the second milk molar persists and there are only two molars. 

 As the radiographical examination brought to light, there was 

 complete absence of the second premolar as well as the third 

 molar on this side. This half of the denture represents, there- 

 fore, the normal progressive state of dentition described in the 

 foregoing pages. The left half shows a very interesting peculi- 

 arity. The second milk molar persisted and the third molar 

 was lacking on the right side, and in this respect this half was 

 on the same level of progressive evolution as the right half. 

 However, there was a difference. The second premolar, absent 

 on the right side, was developed on the left, but obviously, 

 from some cause or other, had not pushed out the second milk 

 molar, and had erupted on the inner side of this tooth. It was 

 actually standing opposite the dental interstice between the 

 second milk molar and the first molar, thus illustrating the nor- 

 mal topographical relation between the elements of the first and 

 second dentition. 



A comparison of the conditions in the two halves of this 

 denture leads to the view that the left half may be considered 

 as an intermediate form between the normal condition and the 



