Proceedings of the section of sciences - DWC - KNAW

( 792 )
have been reduced considel'ably, and c ihe 2 nc1 prcmolar more than
the first. Whel'e as the pl'ell10lars in thc uppel' jaw of all othe1'
Catarrhines possess thrce and in the lowel' jaw two fangs, the
pl'emolal's of man have normalHer one single fango That this
has originated from severa] , appcars from the grooves on the
s·urface. Now it is not without significance th at the fil'st pl'emolarshows
its origine of a form with several fange, by a dividing of the
point of the fango Sa P 2 is m'ore l'educed than P 1 with man. If
fmther the milkmolars, which temporarily pl'eeede the premolars
are eompared, we state that the milkmolars differentiate progressively
in the group of the ca,tarrhines, and this is especially the case with
the secOlld milkmolar . The progression concerns especially the erown
of the teeth, the number of roots is two in the lower jaw, three in
tIle uppel' jaw.
So if we for a moment fix our attention exclusively on 'fn
2 and
its replacing tooth P with man, it appears that the first is in
2
progl'ession, the seeond in regression, and that with man, the same
relation exists in l'egal'd to these two teeth as with ma and Pa of
the Platyrrhines. When man namely pushes out his ?n 2 and l'eplaces
it by P 2 , his set of teeth becomes functionally jnfel'ior, for instead
of a tooth with live or four lmobs on the crown and two or three
fangs there comes in its place a tooth with two cusps on the
smaller erown and only one root.
So we see, that the terminal element of the den tal band of
the second generation (P2) l'educe& with man. Still distinctly
may be seen the terminal l'eduction of the tooth band, of the
first gen eration , closing with J.11 a , fol' as is already mentioned our
Ma no longer even issues in ± 12 % of all cases, and is always
... behind in development, at least with more highly developed human
races. So the human set of teeth is characterized fi'om ihe catarrhine
Primaies by the following peculiarities; the last mol ar is on its way
of reduction, the last premolar is on its way of reduetlOn, the lasL
milkmolar 11as developed very progressively. So a trio ofphenomena
which are entirely homologiCc.9.1 to those, by which the catarrhine set
of teeth has originated from the platyrrhine. Only one phase is still
wanting to the process, namely the rel1laining persistent of the last
milkmolar and the sllppression of tile 1a&t premolar. And this phase
a180 is reached 110W and then indiv1dually. This among others
appears from what MAGlTOT says: La persistance des grosses mol aires
temporaÏl'es (m 2 ) s'observe très-souvent, concurl'emment avec
l'absence congénitale ou l'atrophie des secondes prémolaires (P 2 )
- 294 -