652 THE TEETH. 



C. S. Tomes* says : " The pulp may be described as being made up of 

 a nmeoid, gelatinous matrix, containing cells in abundance, which are espe- 

 cially numerous near its periphery. In it some fibrous connective tissue is dis- 

 coverable. The odontoblast layer is sometimes called the membrana eboris. 

 The odontoblasts are furnished with three sets of processes," etc., like Wal- 

 deyer. " The exact nature of the terminations of the nerve-fibers is not 

 known." 



Adolph Witzelt asserts that the odontoblasts, at their free extremities, 

 exhibit thick prolongations, and in their finely granular protoplasm contain 

 one or two nuclei. The new formations of dentine are composed of a finely 

 granular or lamellated basis-substance, in which dentinal canaliculi are pres- 

 ent, etc. 



THE PERICEMENTUM. BY C. F. W. BODECKER, D. D. S., M. D. S. t 



(A) Forms and Development. The pericementum (root-membrane or alveolo- 

 dental periosteum, etc.) is a formation of connective tissue, identical with the 

 periosteum which covers all bones. It consists of a layer interposed between 

 the roots of the teeth and their corresponding bony alveoli, and is common to 

 both. It is continuous with the connective tissue the so-called submucous 

 layer of the gum and with the periosteum of the maxillae. Its fibers are 

 connected with the cementum of the root as well as with the wall of the alve- 

 olus. A few writers have described the pericementum as a double membrane, 

 one of which belongs to the root, the other to the alveolus ; but I have not 

 been able to see anything that justifies such a separation. Only in a few 

 specimens have I seen, close around the root, a thin layer of very dense and 

 fine fibers, the general direction of which was not fully identical with that of 

 the connective tissue which produces the main mass of the pericementum. 



The course taken by the connective-tissue bundles is slightly wavy and 

 oblique, starting from the cementum and running upward toward the alveolus. 

 The bundles of this tissue are very dense, without many decussations. The 

 parallel direction of the bundles begins to change into a diverging one at 

 about the height of the border of the socket, where the bundles become 

 coarser, decussate, and thus produce the elastic connective-tissue cushion 

 termed the gum. 



From the anatomical disposition of the pericementum conclusions may be 

 drawn as to its physiological action. It is obvious that the relatively soft and 

 elastic layer between the two bony formations cementum and alveolus is 

 designed to lessen the concussion upon the jaw-bones during mastication. 

 The oblique direction of the connective-tissue bundles is the most favorable 

 for the suspension of the tooth within its socket, as the bundles correspond to 

 the funnel shape of the socket, in the center of which is situated the conical 

 root of the tooth. The elasticity of the layer of pericementum admits of a 

 slight degree of motion of the roots ; hence we understand the formation of 

 facets on the proximate surfaces of the crowns of the teeth in crowded maxil- 

 lary arches. 



My specimens represent two varieties of pericementum one of a reticu- 



" Manual of Dental Anatomy," Philadelphia, 1876. 

 " Die aiitiseptische Behamllung der Pulpa-Kraiikheiten," Berlin, 1879. 

 * Extracted from the essay, " Oil Pericementum and Periceinentitis." The Dental Cosmos, 

 Philadelphia, 1879-80. 



