PHOBLEMS OF HUMAN DENTITION 99 



molar. The development of the teeth proceeds very ref2;ulai'ly up 

 to awell-defiiied date, but as soon as the formation of the first per- 

 manent molar, inmiediately after that of the second milk molar, 

 has commenced, further development is stopped during nearly 

 a full year. This fact is in complete accord with the funda- 

 mental idea of my hypothesis, that our first permanent molar 

 originally was a deciduous tooth, belonging to the milk dentition. 



To form a just judgment of the argument advanced it is 

 essential to keep in view the fact that the germ of our first i)er- 

 manent molar emerges from the dental lamina at a nuich earlier 

 date, not only than that of the immediately preceding perma- 

 nent tooth, the second premolar, but even earlier than the germ 

 of the first permanent incisor. This irregularity seems very 

 difficult to understand, since the succession in which the germs 

 of the elements of both dentitions are formed by the dental 

 lamina is a very regular one. First the germ of the first 

 incisor appears, afterward that of the second incisor, then that 

 of the canine, and so on. If the generally accepted opinion 

 that our first permanent molar belongs to the second dentition 

 be correct, one must wonder why the germ of a tooth in the 

 middle of the row arises even relatively long before that of the 

 foremost tooth of this row, in contradiction to the general rule. 

 From my point of view, there is not the least difficulty in under- 

 standing this phenomenon, our first permanent molar not being 

 a tooth in the middle of the row of the second dentition but the 

 hindmost tooth of our milk dentition. And viewed in this light, 

 the succession in the outgrowth of the different enamel-organs 

 from the dental lamina proceeds regularly. 



To this argimient, taken from embryology, I will add one of 

 a morphological nature, viz. : the resemblance of our second 

 milk molar to our first j^ermanent molar. As a rule, the form 

 and cusp differentiation of Mi shows more likeness to those of 

 the second temporary molar than to those of the second perma- 

 nent molar. The great difference in the type of our first and 

 second permanent molars is never found in conqiaring AIi with 

 nio. Our first permanent molar always seems to l)e a repro- 

 duction of the second milk molar on an enlarged scale. These 



