CYPRINOIDS, 151 



cell or nascent tube appears to project from the surface of the pulp 

 in a pyramidal form at the base of each tube, and to pass by a con- 

 tracted apex into its cavity; this is, however, a deceptive appearance, for 

 its walls are in continuity with the transparent calcified walls of the 

 dental tube, and the more opake cavity of the cell alone communicates 

 with the corresponding cavity of the calcified tube. The true diame- 

 ter of the calcigerous tube, including its transparent parietes with it& 

 sub-opake cavity, nearly equals that of the superficial elongated cell, 

 at the expense of which it is about to be developed. 



From the circumstance of the section, here figured, including two 

 or three layers of the calcigerous tubes, their interspaces are made to 

 appear smaller and their decussation to commence sooner and to be 

 more frequent than is really the case in any given layer. 



In fully formed teeth calcification proceeds in the Ugamentous 

 basis of the pulp from the circumference towards the centre ; the union 

 of the tooth to the pharyngeal bone takes place in the laniariform 

 teeth, as in those of the barbel, by numerous slender, wavy, subcylin- 

 drical processes, corresponding with the former fasciculi of the liga- 

 mentous substance ; these calcified processes are implanted, like piles, 

 into the subjacent bone, slightly diverging as they penetrate it, and 

 gradually exchanging in it their dentinal for an osseous texture. The 

 centripetal course of calcification proceeds more rapidly at the basis 

 than in the body of the tooth, and the pulp-cavity thus becomes 

 closed below, (excepting at a small central aperture for the passage of 

 the nerve and vessels) , while it remains widely open in the body of the 

 tooth. A section of part of the base of a pharyngeal tooth of the 

 barbel, exhibiting the numerous roots or fangs by which it is anchy- 

 losed to the bone, and the widely open pulp-cavity at the base of the 

 projecting body of the tooth, is represented, as seen by a moderately 

 magnifying power (1 inch focus of Ross's compound achromatic) in 

 plate 58, fig. 2 : the figure is in the situation of the pulp-cavity : 

 opposite the right hand is a portion of the thin dentinal wall of the 

 base of the exserted part of the tooth, in which the transverse course 

 of the calcigerous tubes is indicated. 



