THE TEETH OF FOSSIL MAN 473 
in modern human races the width is equal to or greater 
than the length, although individual exceptions are not 
rare. In the Heidelberg molars the length slightly 
exceeds the width. Still, the narrowness of the Piltdown 
molars reminds us we are dealing with human teeth of a 
primitive form. 
Of late years a study of the pulp cavities of the teeth, 
of their roots, and of the manner in which the teeth are 
implanted in the jaws, has thrown quite a new light on 
some of the problems which relate to the origin of man. 
The introduction of X-rays as a means of transillumina- 
tion has made it possible for us to examine the buried 
parts of the teeth without destroying the mandibles in 
which they are implanted. It was the study of the pulp 
cavities and roots of the teeth of Neanderthal man which 
permitted Dr Adloff ^ to produce convincing evidence 
that this mid-Pleistocene race could not stand in an 
ancestral position to modern man, but represented a 
terminal offshoot from our ancestral stem. 
When the mandible and lower molars are examined by 
means of X-rays, the central cavities of the molar teeth, 
containing the sensitive living pulp tissue, are seen as 
comparatively clear spaces in the opaque bodies of the 
teeth (see fig. 6^, p. 191). In anthropoids, such as the 
gorilla and chimpanzee (fig. 174), the pulp cavities are 
comparatively shallow spaces between the crown above 
and upper ends of the roots below. The cavity is situated 
on a level with the neck of the tooth — the junction of 
the crown with the body of the tooth — the part formed 
by the fusion of the upper ends of the roots. In each 
of the three anthropoid molars the two roots diverge 
widely, especially in the chimpanzee (fig. 174). The 
roots of the second and third molar reach, or even pass 
beyond, the canal containing the dental nerve in the 
substance of the mandible. Two other points may be 
noted to complete an imperfect picture of the anthropoid 
lower molars : (i) on passing from the first to the third 
' For references to Dr Adloff's recent publications, see Anaf. An::. 
1913, vol. xlv. p. 191. 
