HUMAN DENTITION. 463 



of the dentinal pulp, when the cusps are yet distinct from each 

 other, they constitute so many distinct radiating systems of den- 

 tinal tubes, and the crown of a molar seems to be formed by the 

 basal confluence of three, four or five simple teeth. At the circum- 

 ference of the crown of both premolar and molar teeth, the tubes 

 incline more and more towards the horizontal direction as they 

 approach the fangs. In the upper premolars in which the pulp- 

 cavity divides and is continued in the form of two linear fissures 

 along the connate fangs,(!) each fissure is the centre of divergence 

 of radiating tubes, having the same primary and secondary curva- 

 tures, as in the single fang of the incisor and canine. When a 

 molar is implanted by only two broad and compressed fangs the 

 pulp-cavity usually divides in each ; and when the last molar is 

 implanted by an undivided root, the dentinal tubes of that part radiate 

 also from two distinct pulp-canals. In the base of three-fanged and 

 four-fanged molars there are as many radiating systems of dentinal 

 tubes. The terminations of the tubes in the fangs are more fre- 

 quently resolved into fine branches than in the crown, and the 

 communications between these branches and the analogous minute 

 tubes from the radiated cells of the cement are numerous and plain. 



The dentinal cells of the human tooth (2) are sub-circular, about 

 3^th of an inch in diameter ; they seem most numerous from being 

 most conspicuous, near the periphery of the dentine, as origi- 

 nally described by me in the dentine of the Crocodile. (3) They 

 are best seen in sections of the crown of a permanent tooth 

 before it has come into place. In a longitudinal section the peri- 

 pheral boundary of the cell, or that next the enamel, is most 

 conspicuous ; it describes a slight curve : the lateral boundaries form 

 a very open angle : the posterior boundary is formed generally by 

 the convex curve of the posterior cell which appears slightly to 

 over-lap the one in front, and in this view of the cells their 

 transverse diameter exceeds the longitudinal one. In a transverse 

 section of the dentine the cells' boundaries are, for the most part 

 hexagonal, with the angles feebly marked. From the difl?erences 



(1) PI. 122, v, v. (2) PI. 123, fig. 1, t?, (?. 



(3) Report of British Association, 1838, p. 144. 



