58 PRIMITIVE TREPHINING IN PERU [ETH. ANN. 16 
Sumunarily, it appears that the three processes of incising, elevating, 
and rasping were commonly and perhaps invariably employed in defi- 
nite sequence in producing a complete operation; in general, the treat- 
ment began with exploratory scraping or cutting and proceeded to 
definite incision; at a stage determined by the conditions the operator 
had recourse to elevation and thereby forcibly and often violently dis- 
severed the button; as the operation approached completion the edges 
of the bone were reduced by rasping or scraping. There are only one 
or two eases in which there is not either direct or strong presumptive 
evidence of the process of incising; in most of the cases also there is 
either direct or strongly presumptive evidence of elevating, and in 
every suitably conditioned case there is conclusive evidence of rasping. 
INSTRUMENTS 
More than half of the specimens indicate with considerable clearness 
the character of the incising instrument and somewhat less clearly the 
nature of the rasping instrument, while there is little indication con- 
cerning the instrument used as an elevator. 
The incising instrument evidently possessed a single rather blunt 
point, without shoulders or other device to limit the depth of cutting; 
the bluntness is indicated by the width of the bottom of the kerf, which 
is always rounded or concaye for a width ranging from 0.5 mm. to 1.5 
mm.; the fact that the point was single is indicated by the frequency 
with which it slipped toward the termini of the incisions and by the 
character of the scratches thereby produced, while the absence of 
shoulder is indicated by the variability in depth of the incisions and by 
the freedom of the margins of the incisions from striation or other marks 
of friction in every case in which the details of the operation are clear. 
In addition to bluntness at the tip, the instrument thickened rapidly 
in the body, as attested by the somewhat flaring V-shape of the inci- 
sions, which are frequently as wide, and never less than half as wide, as 
deep. The form in plan, section, and longitudinal profile of every well- 
preserved incision indicates that the single point was operated by a 
reciprocal motion, so as to form a single-tooth saw, sufficient downward 
pressure being exercised to cause it to “bite” the bone, and thus pro- 
duce a kerf having a width determined by the thickness of the instru- 
ment, and a length and longitudinal profile determined by the length of 
stroke and the center of partial revolution of the instrument in the 
hand of the holder; for in most cases in which the kerf is well pre- 
served the longitudinal profile is more or less concave, indicating that 
the tip of the instrument moved through a longer radius than its head. 
Also the well-preserved incisions indicate that the instrument was not 
only blunt-tipped but rough-sided, for the sides of the kerfs are striated 
longitudinally, though somewhat irregularly. 
There is nothing to suggest in any case that the point of the instru- 
ment was round or square, and decisive indications in many cases that 
