Licence: Public Domain Mark
Credit: A manual of dental anatomy : human and comparative / by Charles S. Tomes. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
31/614 (page 17)
![Their i)atlis are not, liowcver, either perfectly straiglit or perfectly parallel, for alternate layers appear to be inclined in ojjposite directions, while they are also wavy, forming several curves in their length. The curvature of the enamel prisms is most marked upon the masticating surface ; while the lavere, alternating in the direction of their inclination as just described, are in planes transverse to the long axis of the crown, and con-espond to the fine strife on the surface of the enamel, which appear to be caused by their outcrop. The curvatures take place in more than one plane ; in other words, tlie course of the individual prism is more or less a spiral. Altiiongh most prisms run through the whole thickness of the enamel, yet inasmuch as the area of the outer is much larger than that of the inner surface of the enamel, and tlie individual prisms do not undergo any alteration in size as they pass outwards, many supplemental fibres are present in the outer portions which do not penetrate far inwards. The individual fibres are to all appearance structureless in perfectly formed human enamel, but a faint transverse striation, fainter, but otherwise not unlike that of voluntary nuiscle. is so general that it cannot be regarded as patlio- logical, although it is most strongly developed in imperfect brownisli enamel. The striation in <iuestion may be seen even in a single isolated fibre, and is not necessarily con- tinuous over adjacent fibres, though it often is so ; it is rendered more ap])arent by the sliglit action of diluted acids upon the fibre. Very various interpretations of this appear- ance have been given. It has been attributed to an inter- mittent calcification of the enamel fibre (Hertz), but is with more probability referred to varicosities in tlie indi- vidual fibres (Kolliker, VValdoyer) ('). It is very marked in (') The striation of voluntary muscle liitK Ijccn alle^'ed to lie ilue lu this same can.se (Dr. Haycraft, I'rocoeding.-i of Royal Society, Feb. 1881). A, I](https://iiif.wellcomecollection.org/image/b21932025_0031.jp2/full/800%2C/0/default.jpg)
