130 R. F. SOGNNAES 



occurring at the neck of the teeth in combination with other post- 

 mortem changes. Investigators have in the past expressed doubts 

 as to the intra \'itam nature of caries-hke cavities observed in the 

 enamel of prehistoric teeth. It would seem from our observations 

 that cavities in the enamel proper observed by gross inspection of 

 prehistoric and ancient teeth mav with some confidence be attributed 

 to intra vitam pathologv, hvpoplasia, or caries, and, when doubts 

 exist, the differential diagnosis mav be established by histologic ex- 

 amination, as indicated above and elsewhere. 



Acid soil would be expected to give a generalized surface etching 

 all over the tooth, but this is rarelv seen. The demarcated decalcifica- 

 tion zones in the tooth surface are suggestive of a localized cause. 

 In the case of the external tooth surfaces it seems logical to assume 

 that the postmortem destruction would be favored by the aerobic 

 conditions in the upper layer of the soil within a relatively short 

 period after death, before bacterial and gaseous products of putre- 

 faction become predominant. This does not, however, satisfactorily 

 explain the location of the destruction in the internal parts of the 

 teeth. The production of these defects would require longer periods. 



Finally, one should perhaps not overlook the possibility that the 

 defects described above may occasionally have been produced after 

 exhumation of the skulls and teeth, in cases where the specimens, 

 when stored, were covered with wet ground, in which case condi- 

 tions would prevail similar to those reported by Wedl. For the 

 major defects, however, this would seem to be a somewhat remote 

 possibility, because the postmortem destruction has often been 

 grossly evident at the time of exhumation, sometimes to an extent 

 where only the caps of enamel remained. Such destruction is ob- 

 viously not produced during life, but must occur sometime after 

 death and before exhumation. 



Experimental Demineralization and Rf:mineralization 



In view of the fact that the dissolution of calcium phosphate looms 

 so significantly in the mechanisms of vertebrate hard tissue destruc- 

 tion, a few experimental observations (largely unpublished and 



