64 THE STRUCTURE 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, ze. 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.),’ is continued into the middle auditory 
chamber of the embryo as a cartilaginous enlargement. This 
becomes twice constricted to form the. incus (77.) and the malleus 
(ml.) Some authorities homologise these with the quadrate 
and articular elements of the mandible of the lower Vertebrata, — 
[but according to others they are structures suc 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 processus 
eracilis 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) mesognathous type. The orthognathous 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). 
