662 THE TEETH. 



corpuscles, or by a fermentation process ; with regard to the former, it is 

 conceivable that the amoaboid movements of the pus-corpuscles might wear 

 away the dental substances ; in the latter case, the generation of an organic 

 acid might be assumed. In chronic cases, the eroded portions are covered by 

 a thin membrane of connective tissue or by a layer of granulation tissue." 

 u Sometimes, on the other hand, the inflammation spreads from the root-mem- 

 brane to the socket of the tooth ; when this occurs, the canals of the latter in 

 the vicinity of the focus of suppuration become expanded; excavations, in the 

 form of pits and grooves, are found in it, and, finally, there ensues a partial 

 resorption of the alveolus, which process is induced by the proliferation of 

 the elementary organs of the connective tissue." u ln addition to the senile 

 form, a hypertrophy occurs as a sequel of chronic affections of the root- 

 membrane, consisting essentially in a thickening, and a more or less 

 advanced callous formation. The generally straight bundles of fibrous tissue 

 often pursue a radiating course for the most part i. e., they extend from the 

 outer surface of the cementum toward the alveolar wall, forming a series of 

 closely packed arches, and are inserted, by a fan-shaped expansion, into the 

 osseous trabeculae." "The bundles of connective tissue, especially in cases of 

 very irregular hypertrophy, interlace one with another in various directions, 

 forming a sort of felted work of bundles, which penetrate the enlarged fora- 

 mina in the alveolar wall. 



Charles S. Tomes * says : " The general direction of the fibers (of the alve- 

 olo-dental membrane) is transverse that is to say, they run across from the 

 alveolus to the cementum without break of continuity, as do also many capil- 

 lary vessels; a mere inspection of the connective-tissue bundles, as seen in a 

 transverse section of a decalcified tooth in its socket, will suffice to demon- 

 strate that there is but a single ' membrane,' and that no such thing as a 

 membrane proper to the root and another proper to the alveolus can be dis- 

 tinguished. At that part which is nearest to the bone the fibers are grouped 

 together into conspicuous bundles ; it is, in fact, much like any ordinary 

 fibrous membrane. On its inner aspect, where it becomes continuous with 

 the cementum, it consists of a fine net-work of interlacing bands, many of 

 which lose themselves in the surface of the cementum. But, although there is 

 a marked difference in histological character between the extreme parts of the 

 membrane, yet the markedly fibrous elements of the outer blend and pass 

 insensibly into the bands of the fine net-work of the inner part, and there is 

 no break of continuity whatever. I have never seen the fibers, whether 

 in longitudinal or in transverse sections, pass straight in the shortest possible 

 line from the bone to the cementum, but they invariably pursue an oblique 

 course, which probably serves to allow for slight mobility of the tooth with- 

 out the fibers being stretched or torn." 



Ecsults. The results of my researches may be summed up in the following 

 points : 



(1) Pericementum is a layer of connective tissue between the root of the tooth 

 and the wall of the alveolus, and common to both. This connective tissue in the 

 juvenile condition is myxomatous, rich in bioplasson bodies. In the adult it is 

 fibrous, scantily supplied with plastids the so-called connective-tissue cells. The 

 bundles of the connective tissue are continuous with those of the gum and those of 

 the periosteum of the alveolus. 



* " A Manual of Dental Anatomy," Philadelphia, 1876. 



