THE TEETH. 639 



those of bone-tissue. Only exceptionally have I seen within the lamellae bio- 

 plasson formations analogous to bone-corpuscles. (See Fig. 278.) 



In the specimen from which I have selected a spot for illustration, the 

 lamellated systems were developed in a most marked manner ; and the blood- 

 vessels in the center of these systems were so regular that they suggested the 

 query whether or not we had here to deal with vaso-dentine, so common in 

 the teeth of fish. These formations occurred in the apex of the root, some 

 of them in the middle of regular dentine, while the lowest systems, without 

 any distinct boundary, were connected with the cementum, which latter, here 

 and there, also exhibited medullary canals. 



In a large number of specimens of secondary dentine I was struck by the 

 presence of bay-like excavations on the boundary of the pulp, filled with 

 medullary elements or multinuclear bodies (myeloid bodies or myeloplaxes). 

 The pulp-tissue exhibited all the features of inflammation, to which also the 



EP 



SD 



FlG. 278. OSTEO-DENTINE, THE THIRD VARIETY OF SECONDARY DENTINE. 



D, primary dentine; SD, secondary dentine; SL, system of lamellae, resembling those of 

 Haversian systems of bone ; MC, medullary canal filled with bioplasson ; BC, small plastids, 

 identical with bone-corpuscles ; EP, erosions of osteo-dentine due to pulpitis. Magnified 600 

 diameters. 



bay-like excavations in the secondary dentine were doubtless due. If we con- 

 sider the formation of secondary dentine as the result of a slight but long- 

 continued irritation, we readily understand that such an irritation may 

 occasionally terminate in an inflammatory process so-called pulpitis. The 

 newly formed dentine, partly at least, will be destroyed by the inflammation, 

 and thus produce a combination of both formative and destructive processes, 

 so common in inflammation of bone-tissue. The presence of inflammation 

 would also explain the pain which sometimes accompanies the formation 

 of secondary dentine. 



