THE ALIMENTARY CANAL AND ITS APPENDAGES 159 



Man's adoption of a more delicate diet, those degenerating first 

 which were the last to be added to form the compound tooth, 

 In the upper jaw this is the posterior lingual and in the 

 lower the posterior unpaired cusp. In the third molar, the 

 so-called wisdom tooth, the process of reduction may go so far 

 that finally, instead of a tooth with four or five cusps, a vestigial 

 stump alone appears. In a relatively large number of cases, 

 indeed, no wisdom tooth at all appears, it being either not 

 formed, or, if formed, retained within the gum. 



Repeated investigations on this subject have all tended to 

 show that these signs of degeneration, so marked in Europeans, 

 are found in non-Europeans also, but not at all to the same 

 extent as among the Aryan race. Quite apart from patho- 

 logical cases, upper molars with three cusps, lower molars with 

 four, and reduced wisdom 'teeth, occur more frequently in 

 Europeans than in Negroes, Mongolians, or native Australians. 

 The low race last named, in its dental formula, appears least 

 removed from the hypothetical original type ; for in it are still 

 found complete rows of splendid teeth with powerfully developed 

 canines and molars, the latter being either uniform, or even 

 increasing, in size, as we proceed backwards, in such a way 

 that the wisdom tooth is the largest of the series. This is 

 decidedly a pithecoid character, which is always found in Apes. 

 The upper incisors of the Malay, apart from their prognathous 

 disposition, have occasionally a distinctly pithecoid form, their 

 anterior surface being convex, and their lingual surface slightly 

 concave. The ancestors of the Europeans seem to have had the 

 same form of teeth, for the oldest existing fragments of skulls 

 from the Mammoth age (e.g. the jaws from la Naulette and 

 Schipka) reveal tooth forms which must be classed with those 

 of the lowest races of to-day. 



Apart from those variations in the human dentition, which 

 tend to approximate it to that of Anthropoids, still more 

 startling ones are occasionally found. For example, the 

 appearance of a third premolar is not very rare. In the Freiburg 

 anatomical museum there is an upper jaw with three well- 

 developed premolars on each side, thus showing the dental 

 formula of the New "World Apes. An increase in the number of 

 molars is also not very rare in both Man and the Anthropoids. 

 A fourth molar, in a more or less perfect form, is to be met with 

 in every large collection of skulls. Zuckerkandl has shown that 

 the epithelial germ of a fourth molar is not infrequently present 



