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pointed tooth: so that we may draw a surest ion tVoni this fact 

 that all the teeth of the series at one time were pointed. 



It is moreover true that wherever we tind these pointed teeth 

 they are present in the jaw in large numbers, sometimes sixty or 

 seventy on one side and usually running far back into the mouth, 

 and it is this fact which led to the suggestion of the theory of 

 " concrescence " in the formation of molar teeth. 



The 



You might at this stage be not inclined to take this " concrescence 

 theory " seriously, but my address has been suggested largely by the 

 fact that it lias been taken very seriously by some well-known 

 anatomists in Germany : as seen in the position of Professor Schwalbe, 1 

 in a recent article, in which he reviews the entire literature in 

 regard to the formation of teeth published during the past fourteen 

 or fifteen years, and concludes that in the concrescence theory 

 and the differentiation or cusp addition theory the evidence is so 

 evenly balanced that he cannot decide between them. It is, therefore, 

 a question xnl judiu 1 , and worthy of the attention of odontologists. 

 As to the source of this theory, it was proposed simultaneously by 

 two Germans, both of whom claim the credit of originating it. One 

 is Dr. Carl Rose, a physician of Freiburg, a man of fine powers of 

 research and great energy, since he has, during the past few years, 

 issued in rapid succession a series of valuable papers on the embryo- 

 logical development of the teeth, which place him in the front rank 

 of students of this subject in this decade. The other is Professor 

 W. Klikenthal, of Jena, whose views sprang principally from the 

 study of the teeth of whales. While these two writers are in doubt 

 as to which should enjoy the precedence, I find, in correspondence 

 with my friend Dr. Ameghino, of the Argentine Republic, also 

 originally a physician and now a distinguished palaeontologist, that 

 he promulgated this theory as far back as 1884. In a work which 

 he published at that time, entitled Filogenia he says : ''' For the 

 reasons we are about to give it is evident that all mammals which 

 possess compound teeth have in past periods possessed a very 

 much larger number of teeth, but of quite simple conical form, 

 like those of the modern dolphin. The most primitive mammals 

 must also have had a number of very elevated teeth, but it is dim- 

 cult at the present time to determine how large this number was. 

 Nevertheless, if we take as an example a mammal in which the 

 dentition is complete, as in the Macrauchenia z or in the horse, and 



1 " Ueber Theorien tier Dentition," Anatomischer Anzeiger Central-Mat t, 1894. 



2 This is one of the peculiar extinct South American hoofed animals. 



