Comparative anatomy of the bands of Schreger.

Abstract

This is a comparative anatomical study of the bands of Sch re g e r in mammalian enamel. The observation was made on meridional ground section of the crown. The ground surface was stained with hematoxy lin.Through the investigation it was established that the mentioned structure of the enamel has a characteristic feature specific to each kind of animal. The pattern of the bands of S chr eger can therefore be useful as one of the taxonomic criteria.The zonial patterns can be classified into following main categories:1) Carnivora type: The bands are conspicuous because the diazoniae consisting of cross sections of the enamel rods are bounded clearly against the parazoniae which are cut mostly in longitudinal direction and oriented parallel to the course of the bands. They stand verticalupon the dentine surface and describe rather a streight course. me indifferent bright layer under the enamel surface is relatively thin.2) Primate type: The bands are relatively broad and each of them consists of 5-15 rods in its width. They stand oblique to the dentoenamel junction and run in more or less curved course. Leaving a thin indifferent layer above the dentine they vanish into a thicker bright layer under the enamel surface. The parazoniae are also composed with curved, oblique sections of the enamel rods so that the boundary of the dia- against the parazoniae is rather transitional.3) Ungulate type: The bands are considerably long and the indifferent zones are broad in accordance with the thick enamel of the order. They stand oblique to the dento. enamel junction and are more or less curved. The boundary between para- and diazoniae is still more obscure than that in the Primate type. Even in the parazoniae a parallel arrangement of the longitudinally cut rods is scarcely to encounter. The rods in the diazoniae are arranged in rows.4) Rodent type: The para- and diazoniae are in most Rodents bounded sharply against each other and no transition of the rods from a band to the adjacent one can be seen. They are straight and consist of rather small number of enamel rods, mostly of a single row of them. The Leporidae and Caviidae have, however, their own patterns of the bands of Schrege r. In general the molar teeth of the Rodents show zonial structures more or less modified from those found in the incisors.