
THE CHIMPANZEE AND ORANG UTAN. 361 
of the Hare, viz. one behind the other, with the chance of being dislodged, together 
with the contiguous bicuspis, by the great laniary tooth, which threatens to undermine 
and sap their attachment to the jaw. But such is the orderly action impressed upon 
the agents of growth, that all obstacles are removed, and the necessary expansion of 
the jaws takes place in due succession in all the requisite directions, and perfect regu- 
larity in the ultimate position of the adult teeth is the result. It may, then, be reason- 
ably asked, How does it happen that in Man, in whom the difference in the size of the 
deciduous and adult teeth is comparatively so inconsiderable, and where, therefore, the 
chances of disarrangement are so much fewer, malposition of the permanent teeth should 
be so frequent an occurrence, and an object of such common solicitude among parents? 
The answer obviously is, that in most cases it arises from a mischievous interference 
with the agents to which the necessary changes have been entrusted. The means by 
which the growth of the permanent teeth is kept in due restraint are too often prema- 
turely removed by anticipating the natural period of shedding the temporary teeth. 
The act of extraction accelerates the growth of the concealed teeth, both by the removal 
of the check which nature had imposed upon it, and by the irritation induced in the 
surrounding parts; and their full development being consequently acquired before the 
jaws have been sufficiently enlarged, they occupy more or less of the relative position 
which they had when half formed within their bony cavities. 
In the drawings of the Pongo’s skull (Plates LIII. and LIV.), figures of the rudiments 
of the permanent teeth taken from the jaws of a young Simia Satyrus are added, so that 
a detailed account of their points of correspondence is here unnecessary. It will be ob- 
vious that the difference that exists depends on the proportions of the teeth which have 
been worn away in the adult skull. 
The only instance which I have found recorded of a Simia Satyrus having been ob- 
served of that age when part of the anterior permanent teeth had been acquired, is in the 
account given by Dr. Jeffries of the dissection of an Orang, which measured 3 feet and 
6 inches in height'!. The permanent incisors had advanced to their proper place, and 
the middle ones of the upper jaw are stated to have measured ths of an inch in length 
and 2ths in breadth ; now the same teeth in the Pongo precisely correspond in the latter 
dimensions, and their excess in regard to length obviously results from the completion 
of the fang. 
The os hyoides has a broader body and shorter cornua than in the human subject, 
but the body is not hollowed out as in the Chimpanzee. 
I have already alluded to the simple form and great length of the spines of the cer- 
vical vertebre in the Orang. The conditions of their superior development are obvi- 
ously the backward position of the occipital foramen, the disproportionate development 
of the face, and the general anterior inclination of the vertebre themselves. The atlas 
' See Webster and Treadwell’s Boston Journal of Philosophy, vol. ii. p. 570; and Philosophical Magazine, 
vol. Ixvii. p. 186, 1826. 
