THE MISSING LINK 283 



sapiens, the view was possible that the two stocks which 

 to-day blossom and display themselves the one as the 

 human race, the other as the man-like apes (gorilla, 

 chimpanzee, orang, and gibbons), became separated 

 from one another in long past geologic ages, and that 

 they have undergone each an independent development 

 from a creature so unlike both as seen to-day, that we 

 cannot speak of it as a missing link or a link at all. 

 That view must be considerably modified by the dis- 

 covery of the Piltdown jaw the jaw of Eoanthropus 

 Dawsoni which is not that of a " man," that is not of 

 the genus Homo, but must, in my judgment, be con- 

 sidered as one of the family Hominidae a Hominid, as 



Description of Fig. 24. 



FIG. 24. Diagrams of the lower surface of the lower jaw of A, man ; B, 

 the Eoanthropus of Piltdown (the left half reconstructed) ; and C, the 

 Chimpanzee. 



The jaws are supposed to be immersed in sand, so as to conceal all but the 

 lower surface. The narrowness of the actual inferior margin of the jaw 

 in man, A, a, b, contrasts with the breadth and flatness of this same 

 border in Eoanthropus, B, a, b, and the Chimpanzee, C, a, b. 



In the human jaw A we see behind the narrow front border a the large semi- 

 circular excavations for the attachment of the digastric muscles right and 

 left. They pass from here to the hyoid bone. From the spine (double 

 in origin) between the two digastric impressions passes a pair of muscular 

 slips, called the genio-hyoid muscles, also to the hyoid bone, and from 

 the pair of spines marked^/ a pair of muscles, called the genio-glossals, 

 pass to the tongue. These inferior and superior mental spines and the 

 digastric impressions, much smaller in size than in man, are seen in the 

 chimpanzee's jaw, C, but are rubbed or partly broken and partly rubbed 

 awayjin the Piltdown half-jaw, B. In the figures A and C the size of the 

 digastric impressions and mental spines is exaggerated, but their relatively 

 much greater size in man than in the chimpanzee is correctly given, and 

 this greater size is connected with the greater control of the tongue and 

 the floor of the mouth in man, possibly connected with speech. 



Reference Letters. a, Broad, upwardly and forwardly sloping surface, reduced 

 in man ; b, lower border of the jaw-bone ; x, front margin of the digastric 

 "impression" of the right side. Dig, digastric impression ; y, superior 

 mental spine of the left side ; Fr., fractured edge of the Piltdown jaw, 

 and corresponding region in that of the chimpanzee. 



