64 THE STRUCTUEE OF MAN 



maxillary, and also in the relation of the former to the posterior 

 edge of the hard palate. 



As a rule, the transverse palatine suture runs right across 

 the palate, i.e. the two horizontal plates of the palatine bones 

 have a more or less straight anterior edge (Fig. 44, A). Not 

 infrequently, however, the median portions of these plates are 

 more prolonged anteriorly, the course of the transverse palatine 

 suture being correspondingly irregularly oblique on either side, as 

 depicted in Fig. 44, B. 



I find the latter condition to be still more marked in the 

 Orang-Utan (Fig. 44, C), and the same may be true, as Waldeyer 

 has already shown, of other Mammals. [By analogy to the lower 

 vertebrata] we have here an index of a low grade of organisation. 



The proximal end of the first visceral skeletal arch (Meckel's 

 cartilage) (I, mk., Fig. 45), which developmentally precedes the 

 bony lower jaw (md.~), 1 is continued into the middle auditory 

 chamber of the embryo as a cartilaginous enlargement. This 

 becomes twice constricted to form the incus (in.} and the malleus 

 (ml.} Some authorities homologise these with the quadrate 

 and articular elements of the mandible of the lower Yertebrata, 

 [but according to others they are structures sui generis distinct 

 in origin from the embryonic lower jaw. The value of these 

 elements is one of the most vexed problems in comparative 

 morphology. All investigators are, however, agreed that they 

 are the representatives of an apparatus, at least in part functional 

 in lower Vertebrates, in effecting the indirect articulation of the 

 jaw apparatus upon the skull, and that in Man and the Mammals, 

 in which this articulation has become direct, this apparatus, under 

 associated change of function, has entered secondarily into con- 

 nection with the organ of hearing] (cf. Figs. 45 and 46). 



A trace of the embryonic connection between the malleus 

 and Meckel's cartilage is long retained, in the so-called prpcessus 

 gracilis of the malleus, which passes towards the lower jaw 



1 The prognathous type of skull has been assumed to be reversionary to a pithe- 

 coid condition ; but this consideration is by no means a simple one. The cousins 

 Sarasin have pointed out that the lowest forms of human skulls, e.g. those of 

 Veddahs, Andaman Islanders, and Bushmen, are of the orthognathous or (Andaman 

 Islanders) mesognathotis type. The orthoguathous type may thus have been 

 attained by human beings at a very early period, and subsequently lost. If this be 

 the case (but it is doubtful) the prognathous condition of Negroes and Melanesians, 

 and the great projection of the jaw in some woolly and straight-haired races, must 

 be a secondary condition, which has been preceded by orthognathy. In this case 

 the orthognathy once more attained by Europeans must be regarded as a third 

 phylogenetic phase in the evolution of the skull (Sarasin). 



