TEETH OF DIPIIYODONTS. 



327 



The dentinal tubes, d, d, send off ramuli into the inter-tubular 

 tissue, and terminate either by anastomotic loops, or in the 

 irregular vacuities or cells at the periphery of the dentine. The 

 dentinal compartments, or indications of the original cells of the 

 dentinal pulp, are shown at «, h ; the modified peripheral layer of 

 the dentine, remarkable for its superior sensibility, at g. The 

 layer of cement, h, which covers the dentine of the fang, is seldom 

 so thick as to show a bone-cell, in human teeth. The structure of 

 the dentine relates, in regard to the curvilinear compartments, 

 a, b, to the steps in its formation ; and, in regard to its tubular 

 columns, to the strength of the tooth and its vitality ; the latter 

 important property depending on the percolation of the plasma 

 through the delicate cellular sructure of the filamentary pro- 

 longations of the pulp, so far as they may extend along the tubuli. 

 The sensibility of the dentine is due to concomitant productions 

 of neurine ; but the distinct tubules are not large enough to 

 admit capillary vessels with red particles of blood, and the tissue 

 above described 



has consequently 2 <>o 



been termed ' un- 

 vascular dentine.' 

 G. Carnivora. — 

 The feline denti- 

 tion is the best for 

 flesh-food. The 

 canines, fig. 260, 

 c, are of great 

 strength, deeply 

 implanted in the 

 jaw, with the fangs 

 thicker and longer than the enamelled crown; this part is 

 conical, slightly recurved, sharp-pointed, convex in front, with 

 one or two longitudinal grooves on the outer side, almost 

 flat on the inner side, and with a sharp edge behind. The 

 lower canines pass in front of the upper ones when the mouth 

 is closed. The incisors, six in number on both jaws, form a trans- 

 verse row ; the outermost above, ib. i, is the longest, resembling 

 a small canine ; the intermediate ones have broad and thick 

 crowns indented by a transverse cleft. The first upper premolar, 

 p 2, is rudimental ; there is no answerable tooth in the lower jaw. 

 The second, p 3, in both jaws, has a strong conical crown sup- 

 ported on two fangs. The third upper tooth, p 4, has a cutting or 

 trenchant crown divided into three lobes, the last being the largest, 



Dentition of Lion. 



