158 
DK. J. CLELAND ON THE VAKIATIONS OE THE HUMAN SKULL. 
to what deficient curvature would ; and thus it happens that projection forwards and 
elongation downwards of the face are liable to be confused together in judging of pro- 
gnathism. The Kafir skull 68 and the Australian 73 may be taken as illustrations of 
these two kinds of facial prominence. Not only in judging of dry skulls, but also with 
respect to skulls clothed with the integuments and during life, the elongation of the 
face downwards may be mistaken for projection forwards ; for this seems to have been 
done by Virchow in the instance of the adult Cretin head already referred to. So also 
the appearance simulating prognathism, extremely common in the rustic population of the 
west of Ireland, is certainly not the result either of prognathous dentition or large orbito- 
nasal angle, but reaches its maximum when there is a heavy dentition in the upper jaw, 
and the lower jaw is so small that the chin fails to come forward into a straight line below 
the upper incisors. 
In column 67 of the General Table it has been sought to express by a single measure- 
ment, termed index-angle of prognathism, the gross amount of prognathism, whether 
dependent on projection or length of face, or on deficient cranial curvature. It is the 
angle between two lines, both starting from the alveolar process between the middle 
incisors, and one of them passing to the fronto-nasal suture, while the other touches the 
lowest part of the base in the diagram, which in most instances is the back of the fora- 
men magnum, but in some foetuses is the front of that foramen. The angle exhibits a 
great deal of individual variation in the nations in which several specimens have been 
examined, the variation in the German skulls amounting to 14° ; still the order in which it 
arranges the nations is worth noting. The most orthognathous skulls are the Greek, and 
after them come Scotch, French, Irish, German, Kanaka, Hindoo, Esquimaux, Peruvian, 
Kafir, Australian, Negro, and lastly, most prognathous of all, the compressed and flat- 
tened Americans. 
A much more precise comparison, however, than can be made either by this index- 
angle or by division of skulls into prognathous, orthognathous, and opisthognathous, 
may be made by distinguishing the different points which together combine to consti- 
tute prognathism. 
First. Prognathous dentition can be easily detected with the unassisted eye. 
Secondly. The size of the orbito -nasal angle should be distinguished. 
Thirdly. The cranial curvature ought to be considered quite apart from the preceding- 
characters, although the following may be taken in lieu of it. 
Fourthly. As the curvature of the cranium is continued in the face, and in most cha- 
racteristically prognathous skulls the facial part of the curve is unusually slight even 
when the proper cranial curve appears fully developed, it is well to take account of the 
whole curve which is expressed by the retreating angle contained between the long dia- 
meter of the foramen magnum and a line from the back of the palate to the alveolar 
process between the middle incisors. This may be termed the foramino-palatal angle. 
The foramin o-palatal angle (column 31) gives results not very dissimilar from those 
