240 BLOOD-VESSELS OF IVORY OR DENTINE. 



different shapes in different ani- 



FIG. 66. .111 



mals, so much so, indeed, as to be 

 regarded an important feature 

 in the classification of the animal 

 kingdom. But notwithstanding 

 the difference in shape, in the 

 \ ivory cells of different animals, 

 they all nevertheless have one 

 character in common, i. e. their 

 baccated (or headed) appearance 

 as seen in Fig. 65, A. The beads 

 represent the nuclei of the differ- 

 ent cells, which, as before stated, 

 consist of animal tissue, remain 

 as such, and, connected in a lin- 

 ear series, constitute the fibres 

 of the ivory, while around the 

 fibres, and within the cells, is 

 deposited the calcareous matter, 

 giving hardness, density, and 

 strength to the ivory. The fibres 

 themselves are also found to be 

 solid, instead of tubular as Ket- 

 zius thought, and the interfi- 



brous substance, instead of being structureless, to consist 



of organized cells. 



BLOOD-VESSELS OF DENTINE OR IVORY. 



The vascularity of dentine is generally denied by anat- 

 omists; but Fig. 66, taken from an injected specimen in 

 the possession of Professor Harris_, seems clearly to show 

 it has a circulation, and in his Principles and Practice of 

 Dental Surgery, he states that similar specimens are in the 

 possession of Dr. Maynard. In vol. 2 of the American 

 Journal of Dental Science, the doctor uses the following 

 language in explanation of the above figure, "the second 

 time he had the good fortune to make this discovery, it 

 was in the half of an inferior molaris, taken from the 



