. Oral pathology and practice. A text-book for the use of students in dental colleges and a hand-book for dental practitioners. se communicating lacunae is called a lamella, and the nutritivecurrents are thus in relation with all the tissue cells through thecanaliculi. (See Fig. 24.) The first modification, or differentiation, is found in the ce-mentum, which has all the distinguishing features of bone, if weexcept alone the lamellae. The lacunae are present, and the canal-iculi ; even the Haversian canals are sometimes found. Thev are THE PATHOLOGY OF DENTAL CARIES. 97 not as constant as in t
. Oral pathology and practice. A text-book for the use of students in dental colleges and a hand-book for dental practitioners. se communicating lacunae is called a lamella, and the nutritivecurrents are thus in relation with all the tissue cells through thecanaliculi. (See Fig. 24.) The first modification, or differentiation, is found in the ce-mentum, which has all the distinguishing features of bone, if weexcept alone the lamellae. The lacunae are present, and the canal-iculi ; even the Haversian canals are sometimes found. Thev are THE PATHOLOGY OF DENTAL CARIES. 97 not as constant as in true bone, but even in that they are not alwayspresent. The lamellar, concentric arrangement of the lacunae aboutthe Haversian canals is alone lacking, and this is the case evenwhen these vascular canals are found in the cementum. The pro-portion of animal and earthy matter has been but slightly changed,the variation between different bones being sometimes greater thanthat between bone and cementum. Cementum, then, essentiallydiffers from bone only in the loss of the lamellar arrangement ofthe cells. (See Fig. 8.) Fig. d- Transverse Section of Bone, showing Lamellar Arrangement of the Lacunae aboutthe Nutritional , Haversian canals, b, c, d, Lacunae with branching canaliculi. (Gray.) The next step in the differentiation is found in the dentine,,which has lost the lacunal corpuscles that distinguish cementumand bone. As these contain the greater proportion of the livingmatter, we naturally anticipate a considerable reduction in thatelement, and analyses show that it has but about four-fifths theamount found in bone, while the earthy salts are correspondinglyincreased. In its physical structure, then, dentine retains but thecanaliculi of bone, and these appear in their analogues, the dentinalfibrillar Instead of being the channel of communication betweenthe lacunar, as in bone and cementum, they serve to connect thepulp, the analogue of the medulla of bone, with the
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