56 A MANUAL OF DENTAL ANATOMY. 



the same point, bend abruptly at an angle, and give oft 

 numerous branches. The meshwork produced by the cross- 

 ing of the tubes at all sorts of angles in the inner part of 

 the enamel is so complicated as to render it impracticable 

 to reproduce it in a drawing. That portion of enamel next 

 to the dentine is without canals. Von Boas (Zeits. f. wissen. 

 Zoolog. Bd. xxxii.), describing the similarly constructed 

 enamel of scaroid fishes, says that I was in error in sup- 

 posing that the canals open upon the outer surface of the 

 enamel. But I do not understand his reasons for dissenting 

 from my opinion, which re-examination of many specimens 

 has tended to confirm. I have not been able to satisfy 

 myself whether the tubes occupy the interspaces of the 

 enamel prisms, or their axes. 



It would appear also as if these tubes were empty during 

 life, as in sections they appear to be more or less blocked up 

 with dirt. The existence of the prisms at all is not certain, 

 and this led Kolliker to say that true enamel does not 

 appear to exist in fishes (Mik. Anat. p. 114) ; the enamel of 

 fish is, however, developed from an enamel organ homologous 

 with, and exactly like, that of amphibia and reptiles, so 

 that these anomalous tissues must be regarded as being un- 

 questionably enamel. 



DENTINE. 



THE greater part of every tooth is made up of dentine, 

 which thus, even after the removal of the other tissues 

 would preserve somewhat its characteristic form. Several 

 varieties of dentine exist in which those peculiarities of 

 structure which differentiate it from bone become less 

 marked, so that a point is sometimes reached at which it 

 is hard to say whether a particular structure should more 

 rightly be regarded as dentine, or as bone. It will be most 

 convenient to commence with the description of that variety 



