40 4 SCIENCE PROGRESS 



was no safe guide to the form of the glenoid cavity, since it 

 is clear that a precisely similar result of wear may accrue 

 whether the glenoid cavity is deep, as in the human skull, or 

 shallow, as in the chimpanzee. 



And now as to the canine. Mr. Miller's arguments to prove 

 that Dr. Smith Woodward is entirely wrong in his view that 

 this is the right lower canine are founded upon assumptions 

 for which no warrant can be found on an appeal to fact. " In 

 all living great apes," he remarks, " the postero-internal 

 surface of the lower canine is convex." This is true only of 

 the tooth in transverse section : in a longitudinal section 

 it is concave. Nor is he more happy in his statement that 

 " No matter how long a lower canine may have been in use 

 it never assumes the form seen in Eoanthropus , nor does it 

 lose all trace of the original convexity of its inner portion." 

 Mr. Miller's experience of worn canines in the chimpanzee 

 is evidently limited, or he would not have failed to find examples 

 which flatly contradict him when he says that all traces of the 

 original convexity of the inner surface of the tooth are never 

 lost. How largely he has substituted " intuition " for investi- 

 gation is shown by his assurance that " a mechanical inter- 

 relation of the teeth, such as would produce a worn sur- 

 face " presenting a wide shallow concavity directly back- 

 wards and inwards, "is not only unknown among primates, 

 but (in a lower canine) I have never been able to find any 

 mammal with the upper and lower teeth so arranged that it 

 could exist." This may very well be true, so far as Mr. Miller 

 is concerned, but in the British Museum are two chimpanzee 

 jaws (1.8.9.4. and 1.8.9. 10.), m tne collection of Lord Roth- 

 schild is a third, and in the Royal College of Surgeons' Museum 

 is a fourth, achieving Mr. Miller's standard of the impossible. 

 In the British Museum specimens the worn surfaces, how- 

 ever, present a slight twist, recalling that of a propeller, but 

 in that in Lord Rothschild's museum the resemblance to 

 the Piltdown tooth is extraordinarily close. In studying 

 the worn surfaces of these teeth in the great apes the aspect 

 which most impresses one is not the similarity, but the re- 

 markable dissimilarity, they present, a phenomenon due to 

 variations in their size, and the angle at which they stand 

 in the socket, for these vary the incidence of wear by the 

 opposing teeth. In some cases attrition is caused, not by the 



