HOG-TRIBE. 00/ 



young Sus scrofa. I could find no germ of a successor to the 

 small anterior deciduous molar (ib. cl. 2) ; and we have seen that 

 the lower jaw of the nearly full-grown Phacochere presented only 

 one premolar (PL 140, fig. 4, p 4). The germ of this tooth is shown 

 in PI. 141, fig. I, p4: the first true molar (ib. m 1 has already 

 lost half its crown by the wear of mastication, and its early loss, 

 with the obliteration of its alveolus, as in PI. 140, fig. 4, accounts 

 for its having hitherto escaped the notice of the Naturalists who have 

 paid most attention to the remarkable dentition of the Phacocheres. 



The single permanent incisor in each intermaxillary of the 

 Phacochcerus jEliani is preceded by a deciduous and more simple 

 incisor. 



199. Microscopic structure. — The dentine of the teeth of the 

 common Hog is dense, unvascular, susceptible of a bright polish. In 

 a vertical section of the second premolar the calcigerous tubes radiate 

 from the pulp-cavity, passing from its summit into the crown in 

 almost straight lines, and with a flexuous course from its sides : the 

 strongest curve is at their commencement, but it is short, and they 

 then proceed straight towards the enamel, with a few dichotomous 

 acute-angled divisions, the terminal third part of the thus divided 

 tubes bending gently from the grinding surface in curves which di- 

 verge slightly from the centre of each tubercle ; the ultimate divisions 

 at the outer surface of the dentine are extremely numerous, fine, 

 and plexiform. The diameter of the tubes at the middle straight 

 part of their course is g^oth of an inch, and here they are separated 

 by interspaces equal in diameter to the breadth of nearly two tubes : 

 they gradually diminish as they approach the enamel. Fine ramuli 

 are sent off from the sides of the main-tubes, which curve across 

 the interspaces, and are mostly lost in the compartments of the 

 basal substance. 



The dusky yellow-coloured osteo-dentine, into which sub- 

 stance the pulp is finally converted, presents a much more flexuous 

 arrangement of dentinal tubes, the ramuli of which not unfrequently 

 dilate into angular calcigerous cells ; these in the osteo-dentine of the 

 base of the teeth are numerous, and present in some parts a con- 

 centric arrangement. 



