64 MICROSCOPIC ANATOMY OF THE TEETH 



afforded by teased preparations will, we think, leave little 

 doubt that, at all events in many areas of the enamel, such 

 an arrangement of the prisms exists. Von Ebner expresses 

 his surprise that the observations of Smreker have not been 

 more generally recognized, and concludes that the necessity 

 of preparing very thin sections by grinding and the great 

 difficulties encountered in the microscopic examination of 

 enamel have been the cause of this neglect. Smreker 

 prepared very thin ground sections which were carefully 

 polished, some being treated with silver nitrate and some 

 not. 



It will be said that the obvious explanation of this appear- 

 ance in transverse section is that the prisms are viewed 

 obliquely, one prism appearing to slightly overlap another 

 of the same form, for if a circular disk is overlapped by 

 another it would cause an appearance of concavity in the 

 underlying disk, and, similarly, if one disk is overlapped 

 by two the lower one would have a double concave margin. 

 It would be very difficult to prove that this was not the 

 explanation by the examination of sections alone, but 

 teased preparations, in which the enamel prisms are separated 

 and isolated, would indicate if there were really any such 

 structure as that which these authors describe. 



Von Ebner, who was at first inclined to think that the 

 appearances were due to the obliquity of the sections, 

 endeavoured to prove the point by this method. Fragments 

 of enamel were scraped from a tooth and allowed to fall 

 into water or glycerine, where they were separated and 

 broken up with needles and examined under the microscope. 

 Such preparations showed separated prisms with grooves 

 running the whole length of the detached portion, and other 

 separated fragments were seen in cross -section with a con- 

 cavo-convex figure. These observers also describe other 

 appearances in both teased preparations and sections, as 

 the Flugelfortsatze or wing processes of the prisms (Plate III, 

 fig. 14) and connecting processes between the columns of 

 prisms, called by Von Ebner the intercolumnar bridges. 



The wing processes of the prisms may often be observed 

 in teased preparations of mammalian enamel. These are 

 projections from the prisms, appearing sometimes 



